[Frontiers in Bioscience 14, 237-262, January 1, 2009]

Role of xanthine oxidoreductase in cardiac nitroso-redox imbalance

Konstantinos Tziomalos, Joshua M. Hare

Interdisciplinary Stem Cell Institute and Division of Cardiology, Leonard M. Miller School of Medicine, University of Miami

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. XOR - biochemistry and function
4. XOR is upregulated in HF
5. Effects of XOR in myocardial contractility
5.1. Ex vivo studies
5.2. In vivo studies
5.3. Mechanisms involved in the negative inotropic action of XOR
5.3.1. Myocardial energetics
5.3.2. Ca2+ cycling
5.3.3. Structural changes in the myofilaments
6. Cardiac remodeling - the role of XOR
6.1. Hypertrophy
6.2. Apoptosis
6.3. Alterations in matrix structure
7. Ischemic cardiomyopathy - the role of XOR
8. Diastolic dysfunction and XOR
9. Interaction of XOR with other sources of ROS in HF
10. Interaction of XOR with antioxidant systems in HF
11. Cross-talk of oxidative and nitrosative pathways in HF - the role of XOR
12. Peripheral effects of XOR inhibition in HF
13. XOR and adipogenesis
14. Clinical studies of XOR inhibition in HF
15. Perspective
16. Acknowledgements
17. References

1. ABSTRACT

Emerging evidence supports the importance of nitroso-redox balance in the cardiovascular system. Xanthine oxidoreductase (XOR) is a major oxidative enzyme and increased XOR activity, leading to both increased production of reactive oxygen species and uric acid, is implicated in heart failure. Within the heart, XOR activity stimulates cardiomyocyte hypertrophy, apoptosis, and impairs matrix structure. The underpinnings of these derangements can be linked not solely to oxidative stress, but may also involve the process of nitroso-redox imbalance. In this regard, XOR interacts with nitric oxide signaling at numerous levels, including a direct protein-protein interaction with neuronal nitric oxide synthase (NOS1) in the sarcoplasmic reticulum. Deficiency or translocation of NOS1 away from this microdomain leads to increased activity of XOR, which in turn impairs excitation-contraction coupling and myofilament calcium sensitivity. There is a mounting abundance of preclinical data supporting beneficial effects of inhibiting XOR, but translation to the clinic continues to be incomplete. A growing understanding of XOR and its role in nitroso-redox imbalance has great potential to lead to improved pathophysiologic insights and possibly therapeutic advances.

2. INTRODUCTION

Heart failure (HF) is an important cause of morbidity and mortality worldwide (1, 2), and currently represents the leading cause of hospitalization in individuals older than 65 years (2, 3). Despite the significant progress in its management, 5-year mortality rates are still as high as 50% and are even greater in the more advanced stages of the disease (1, 2). The prevalence of HF increases with age and therefore the number of patients with HF is expected to rise with the progressive aging of the population (3). The improved survival of patients with myocardial infarction (MI) is an added driver of the increasing prevalence of HF (1, 4).

The regulated production of reactive oxygen species (ROS) is crucial for cellular homeostasis (5). In this regard, there is accumulating evidence that ROS play signaling roles and participate in the regulation of many cellular functions (5). However, oxidative stress denotes a state of imbalance between the production of ROS and antioxidant mechanisms in which the former prevail over the latter (6). Oxidative stress is intimately involved in the pathogenesis of HF, regardless of its underlying cause (coronary heart disease or non-ischemic cardiomyopathy) (7). Elevated levels of a variety of markers of oxidative stress have been reported in both plasma and pericardial fluid in patients with HF and positively correlate with the degree of left ventricular dilation and the severity of HF (8-11).

The imbalance between ROS production and antioxidant mechanisms leads to myocyte dysfunction, injury and necrosis resulting in the development and progression of HF (7). ROS reduce Ca+2 entry in the cardiomyocytes, attenuate myocardial contractility, and augment cardiomyocyte apoptosis (5, 12). Oxidative stress also contributes to the development of HF by inducing heart remodeling (13). ROS are potent stimulators of matrix metalloproteinases (MMP), which in turn mediate left ventricular (LV) remodeling (13-19).

A variety of sources contribute to the increased ROS production in HF, including xanthine oxidoreductase (XOR) (20, 21), the mitochondria (22, 23), nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (24-26) and uncoupled nitric oxide synthase (NOS, both neuronal (NOS1) and endothelial (NOS3)) (27, 28) (Figure 1). In contrast, reduced levels of antioxidant mechanisms have been reported in these patients and are inversely associated with the stage of HF (11, 20, 29).

Among oxidative enzymes, XOR has been the focus of significant research as a principal culprit participating in the propagation of oxidative stress in HF (20). Here we review existing data on the role of XOR in the pathogenesis of HF and cardiac remodeling, and address the potential therapeutic implications of XOR inhibition.

3. XOR - BIOCHEMISTRY AND FUNCTION

Among oxidative enzymes, XOR is a key regulator of oxidative stress (30). XOR belongs to the molybdoenzyme family and exists as a homodimer in 2 potentially interconvertible forms, xanthine dehydrogenase (XDH) and xanthine oxidase (XO) (30, 31). Each monomer consists of a molybdenum center, 2 distinct iron-sulfur centers and a flavin adenine dinucleotide (FAD) center (30, 31) (Figure 2). XOR catalyzes the conversion of hypoxanthine to xanthine and xanthine to uric acid (30). During XOR reoxidation, both hydrogen peroxide (H2O2) and superoxide (O2-) are produced (30) (Figure 3). XO appears to be more potent ROS generator than XDH since both can react with either NAD+ or molecular oxygen but the reactivity of XO toward NAD+ is negligible (32). However, XDH can be converted to XOR either by a reversible process involving thiol oxidation or by proteolytic cleavage (30).

O2- was identified as a product of XOR activity in 1968 and is a potent free radical produced by the 1-electron reduction of molecular oxygen (33). Except from its direct effects, O2- can also transform to other potent ROS (5, 34). O2- can react with H2O2 leading to the formation of hydroxyl radicals (OH-) (Haber-Weiss reaction) (34). Production of OH- through this reaction has also been demonstrated in the failing myocardium (35). O2- can also generate peroxynitrite by interacting with NO (5). O2- is converted by superoxide dismutase (SOD) to H2O2, which is less potent but can also exert cardiotoxic effects (5, 36). H2O2 can also convert to OH- through the Fenton reaction (H2O2 + Fe2+ OH- + OH- + Fe3+) and this conversion was shown to occur in myocardial tissue obtained from animal models of heart failure (22, 36).

4. XOR IS UPREGULATED IN HF

An upregulation of cardiac XOR expression and activity has been consistently reported in various animal models of HF (28, 37-40) and in humans with HF (21). This upregulation could be a result of the activation of the renin-angiotensin system - a hallmark of HF (41) - since angiotensin II appears to stimulate XOR (42). Moreover, HF is characterized by increased circulating levels of proinflammatory cytokines (43, 44), which could also augment XOR activity (45, 46). Hypoxia also stimulates XOR activity (47-49) and might therefore play a role in XOR upregulation in HF, particularly in patients with ischemic cardiomyopathy.

5. EFFECTS OF XOR IN MYOCARDIAL CONTRACTILITY

5.1. Ex vivo studies

Whether XOR is implicated in the pathogenesis of HF and the specific mechanisms involved have been evaluated in several studies. XOR-produced O2- diminishes maximal Ca2+-activated force in isolated cardiac myofilaments (50). Moreover, XOR inhibition with allopurinol augments contractile force (51). A XOR-induced decrease in the Ca2+ sensitivity of cardiac myofilaments could help explain this negative inotropic effect of XOR (51-53). Furthermore, XOR reduces myofibrillar Ca2+-ATPase activity (54). An increase in the maximal force-generating capacity of cardiomyocytes may also contribute to the positive inotropic action of XOR inhibition (55). Maximal force-generating capacity is greatly reduced in ventricular muscle isolated from rats with HF (56). It should also be noted that allopurinol had no significant effect in the contractility of ventricular trabeculae isolated from normal hearts (55). This finding supports the importance of XOR upregulation in HF in the pathogenesis of myocardial dysfunction (55). In addition to O2-, OH-, produced by the interaction of O2- with H2O2, can also reduce myocardial contractility (13, 57).

5.2. In vivo studies

The negative inotropic effects of XOR in the in vitro studies were also assessed in animal models of HF. In an early experiment from our lab, acute inhibition of XOR with allopurinol (200 mg infused as 3.3. mg/min in the right atrium) improved myocardial contractility in dogs with pacing-induced HF (38). These observations were subsequently reproduced by other investigators (58). In accordance with the results of the ex vivo studies, allopurinol did not substantially modulate the contractility of normal hearts (38, 58).

In order to decipher the mechanisms accounting for these beneficial actions of XOR inhibition, we compared the effects of allopurinol (200 mg given as 6.6. mg/min intravenously for 30 min) with intravenously administered vitamin C - an antioxidant agent - in dogs with pacing-induced HF (28). Allopurinol exerted a positive inotropic effect to a degree equivalent to vitamin C (28). In addition, when allopurinol was infused immediately after vitamin C, it had no additional effect on myocardial contractility (28). These findings supported the idea that XOR-induced oxidative stress is primarily responsible for the detrimental effects of XOR on myocardial systolic function and that the latter effects can be abrogated with allopurinol treatment (28).

In a genetic model of dilated cardiomyopathy, the spontaneously hypertensive/HF (SHHF) rat, oxypurinol - the active metabolite of allopurinol - when administered po for 4 weeks (1 mmol/l in drinking water) improved fractional shortening and increased LV ejection fraction (LVEF) (59). Again, these effects of oxypurinol appeared to result from the amelioration of XOR-induced oxidative stress (59). Indeed, SHHF rats showed an increase in oxidative stress and more specifically, in the production of O2- in their cardiomyocytes; this altered redox state was restored with oxypurinol treatment (59). We also observed that oxidative stress was primarily due to increased XOR activity whereas NADPH oxidase activity was similar in HF and control rats (59).

5.3. Mechanisms involved in the negative inotropic action of XOR

Overall, there is now considerable evidence supporting the importance of XOR in the impairment of myocardial contractility in HF. XOR-induced oxidative stress emerges as the principal mechanism of this effect of XOR. We will next discuss in more detail the putative mechanisms that could contribute to this negative inotropic action of XOR-induced oxidative stress. We will schematically divide them in effects on myocardial energetics, Ca+2 cycling and structural changes in the myofilaments.

5.3.1. Myocardial energetics

XOR could contribute to the development of HF through its adverse effects on myocardial energetics (60). Phosphocreatine (PCr) is the principal energy reserve molecule in the heart (61). Creatine kinase (CK) uses PCr as a substrate in order to produce ATP, the cellular energy "currency" (61). HF is characterized by a depletion of both ATP and PCr and the reduction in the levels of these energy molecules correlates directly with the severity of HF (62). The PCr/ATP ratio is also reduced in HF, suggesting an imbalance between energy demand and supply (63). In patients with dilated cardiomyopathy, the decreased PCr/ATP ratio represents an independent predictor of mortality (64). Energy depletion in the failing myocardium appears to result principally from a reduction in CK activity (65, 66). In turn, inhibition of CK activity in isolated rat hearts diminishes contractile reserve (67, 68) and it has been proposed that the same may apply in the failing human heart (61). Therefore, a tight link appears to exit between energy starvation in the failing myocardium and the development and progression of heart failure (61).

A number of ex vivo studies supports a role for XOR in the impairment of myocardial energetics in HF (36, 57). XOR reduces CK activity in rat hearts in vitro through the production of O2- (36). H2O2 also suppressed CK activity in the same report (36). Moreover, OH- reduced the ATP content of cardiomyocytes in vitro (57).

There are preliminary findings that suggest that XOR inhibition can prevent the deterioration of myocardial energy status and thus prevent the development of HF. Treatment with either allopurinol or oxypurinol (0.5. mmol/l and 1 mmol/l in the drinking water for 4 weeks, respectively) after the induction of MI in mice prevented the decrease in the PCr/ATP ratio (60). This resulted in attenuation of ventricular dilation and of the fall in LVEF (60).

It has been proposed that energy depletion in the failing human heart has also deleterious consequences on mechanical efficiency (61). In isolated rat hearts, inhibition of CK activity induces mechanoenergetic uncoupling (67, 68). Mechanoenergetic uncoupling is a core characteristic of HF and refers to a mismatch between the depressed myocardial contractility and the energy consumption, which is disproportionately high (38, 69). The pivotal role of XOR in the regulation of myocardial energetics is supported by the findings of several studies that evaluated the effects of XOR inhibition on mechanical efficiency. We showed that allopurinol consistently improves mechanical efficiency in animal models of HF (28, 38). In dogs with pacing-induced HF, acute inhibition of XOR with allopurinol increased myocardial contractility; at the same time, a reduction in myocardial oxygen consumption was observed and therefore an improvement in mechanical efficiency was achieved with allopurinol treatment (38). Again, attenuation of XOR-induced oxidative stress appears to be implicated in this improvement in myocardial energetics with allopurinol treatment (28). Indeed, in dogs with pacing-induced HF, allopurinol and vitamin C ameliorated mechanoenergetic uncoupling to a similar extent (28). In addition, when allopurinol was infused immediately after vitamin C, it did not yield any further improvement in cardiac mechanical efficiency (28).

The amelioration of myocardial energetics with allopurinol appears paradoxical in view of its positive inotropic action. Conventional positive inotropic agents disproportionately increase myocardial energy consumption and further aggravate the mechanoenergetic uncoupling in the failing heart (69). In dogs with HF, we reported that dobutamine improves contractility but at the same time induces a significant increase in myocardial oxygen consumption culminating in a decrease in mechanical efficiency (38) (Figure 4). A similar effect in humans was theorized as an explanation for the increased morbidity and mortality of patients with HF treated with positive inotropic agents (70, 71). The Ca2+-sensititizing effect of XOR-inhibition was proposed to account for the improvement in mechanoenergetic uncoupling with allopurinol despite the increase in contractility (39).

5.3.2. Ca2+ cycling

Perturbations in physiological cardiomyocyte Ca+2 cycling might be involved in the pathogenesis of HF (39, 72). The major players in Ca+2 cycling are the cardiac calcium release channel (ryanodine receptor, RyR), the sarcoplasmic reticulum (SR) Ca2+-ATPase 2alpha (SERCA2alpha)/phospholamban (PLB) complex and the Na+-Ca+2 transporter (NCX) (72) (Figure 5). RyR is responsible for the release of Ca+2 from the SR in response to the influx of Ca+2 through the L-type (or voltage dependent) Ca+2 channels (LTCC) (72). SERCA2alpha controls Ca2+ uptake in to the SR during diastole after its release from the myofilaments (72). SERCA2alpha activity is directly associated with cardiac contractility (72). PLB is another integral protein of the SR and plays an important role in the regulation of cardiac contractility (72). PLB inhibits SERCA in the unphosphorylated state; in contrast, phosphorylation of PLB is associated with enhanced SERCA activity (72). NCX participates in diastolic Ca2+ extrusion in the extracellular space (72).

HF is characterized by abnormalities in the abundance and/or the activity of all major Ca+2 cycling proteins. More specifically, impairment in the RyR function has been reported in human HF resulting in uncoupling with the LTCC (73). SERCA2alpha levels and activity are reduced in human HF and result in both systolic and diastolic dysfunction (74, 75). In addition, PLB phosphorylation is impaired in HF and this leads to a further suppression of SERCA2alpha function (75). Regarding NCX, an upregulation in its expression has been reported in the failing human myocardium (74). It has been hypothesized that the subsequent increased Ca2+ extrusion in the extracellular space combined with a reduced SR Ca2+ uptake contributes to the pathogenesis of HF (76).

XOR appears to affect Ca2+ cycling. Early studies showed that XOR inhibition blunts Ca2+ amplitude (51). It was suggested that this effect might stem from increased binding of Ca2+ to the myofilaments and that this decrease in intracellular Ca2+ concentration may be beneficial (51). More recent studies offer new insights in the interaction of XOR with Ca2+ cycling proteins. We found that SERCA levels decrease whereas NCX levels increase in SHHF rats during the development of HF; more importantly, oxypurinol normalized NCX levels and blunted the reduction in SERCA levels (59). In order to identify the level where XOR controls the synthesis of Ca2+-cycling proteins, we studied the effects of XOR inhibition in dogs with pacing-induced HF (77). Allopurinol treatment (100 mg po daily) during the HF-induction period attenuated the decrease in myocardial contractility (77). In accordance with our earlier findings in mice, allopurinol attenuated the increase in NCX mRNA and protein levels in dogs as well (77). Furthermore, allopurinol prevented the upregulation of PLB mRNA and protein levels and the fall in phosphorylated PLB levels (77). In rats with established diastolic HF, XOR inhibition with oxypurinol also increased phosphorylated PLB levels (40). Therefore, it is intriguing to speculate that XOR-derived ROS could influence transcription of genes encoding the synthesis of Ca2+-cycling proteins. In addition, it controls Ca2+-cycling by post-translational mechanisms as well, such as the regulation of PLB activity by affecting its phosphorylation.

5.3.3. Structural changes in the myofilaments

XOR upregulation in HF also has detrimental effects on myofilament structure that apparently contribute to its negative inotropic action. In mice with ischemic cardiomyopathy, allopurinol reduced the levels of 4-hydroxy-2-nonenal (HNE)-modified myocardial proteins (39). HNE is a lipid peroxidation product that can disrupt the structure of myocardial proteins (78, 79). In another study, transgenic mice with truncated troponin I, a model of dilated cardiomyopathy, exhibited a 3-fold increase in XOR activity compared with wild type littermates (80). These transgenic mice showed excessive oxidative damage in myofibrillar proteins, particularly actin, that was attenuated with allopurinol treatment (26 mg/dl in the drinking water for 2 months) (80). In the same report, XOR inhibition with allopurinol restored cardiac muscle force in isolated cardiac muscle and prevented LV dilation (80). These findings support the notion that the myofibrillar damage induced by XOR is implicated in the pathogenesis of contractile dysfunction in HF.

6. CARDIAC REMODELING - THE ROLE OF XOR

Cardiac remodeling is the intermediate step in the development of overt HF regardless of its underlying cause (81). The principal mechanisms leading to remodeling are cardiomyocyte hypertrophy and apoptosis as well as alterations in matrix structure (81). Oxidative stress is intimately implicated in the development of cardiac remodeling by stimulating all 3 pathways (13). Among the various sources of ROS, XOR is a key factor in the development of remodeling. Several studies showed that allopurinol prevents LV remodeling both after experimental MI in mice (39, 60, 82) as well as in established HF (59, 83).

We will next briefly discuss the pathophysiologic mechanisms culminating in cardiac remodeling, with a specific focus on the existing data implicating XOR in these pathways.

6.1. Hypertrophy

Cardiac hypertrophy represents, to some extent, a physiological adaptive response to hemodynamic stress (84). However, it might also progress to overt HF and is associated with increased cardiovascular morbidity and mortality in the general population (84, 85). Significant progress has been made during the last decade in elucidating the signaling pathways involved in the pathogenesis of myocardial hypertrophy (86). In this labyrinth of interacting control mechanisms, the mitogen-activated protein kinase (MAPK) pathway appears to have a prominent role (86). The final effectors in this system are p38, c-Jun N-terminal kinases (JNK) and extracellular signal-regulated kinases (ERK) (86). Among these, ERK was proposed to be particularly significant in terms of regulating cardiac hypertrophy (86, 87).

Recent studies propose a role for XOR in the stimulation of ERK-induced myocardial hypertrophy (Figure 6). In isolated rat cardiomyocytes exposed to hypoxia-reoxygenation, there was an upregulation of XOR activity and the resulting oxidative stress induced ERK phosphorylation (88). In addition, allopurinol dose-dependently reduced this ERK activation (88). OH- also induce myocardial hypertrophy after experimental MI in mice (13). In Dahl salt-sensitive hypertensive rats with established diastolic HF, an increase in ERK phosphorylation was noticed that was attenuated with oxypurinol treatment (40). In SHHF rats, we also reported an increased phosphorylated/unphosphorylated ERK ratio and a restoring of this imbalance with oxypurinol (59). More importantly, in the same study, XOR inhibition induced a regression in cardiomyocyte hypertrophy and reduced LV mass (59) (Figure 7). These preliminary observations implicate XOR in the pathophysiology of cardiac hypertrophy through the activation of ERK.

Cardiac hypertrophy is also characterized by an upregulation of a series of genes that is collectively characterized as the fetal gene program and includes atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), beta-isoform of myosin heavy chain (beta-MHC) and the alpha skeletal muscle isoform of actin (alphaSA) (89). This overexpression might represent a causative agent for myocardial hypertrophy (89). We found that mRNA levels of all these genes are increased in SHHF rats with established HF; we also showed that oxypurinol blunted the upregulation of ANP and alphaSA and completely normalized BNP and beta-MHC expression (59).

6.2. Apoptosis

In animal models of heart failure, apoptotic cardiomyocyte death is a precursor of overt heart failure (90). Increased apoptosis of cardiomyocytes is also frequently observed in patients with HF and may play a role in its progression (91, 92). Our knowledge of the signaling routes that regulate cardiomyocyte apoptosis has increased exponentially during the last decade (84). These routes are often identical or tightly linked to the ones controlling myocardial hypertrophy (84, 86). Thus, apoptosis signal-regulating kinase 1 (ASK1), which stimulates cardiomyocyte apoptosis and contributes to the pathogenesis of LV remodeling (93, 94), belongs to the above-mentioned MAPK family and is a selective upstream activator of p38 and JNK (86, 93, 95). Both p38 and JNK have also been implicated as apoptosis-promoting kinases, although the existing data are conflicting (86, 96). The final effectors of apoptotic cell death are caspases, a group of proteolytic enzymes, which are under the control of the Bcl-2 family of proteins (97, 98). The Bcl-2 family includes members with both pro- and anti-apoptotic actions (97, 98). Among the former, the Bax subfamily was recently shown to interact with p38 resulting in the induction of cardiomyocyte apoptosis (99).

Oxidative stress is intimately involved in the stimulation of apoptotic death of cardiomyocytes (12, 90). XOR was also shown to stimulate apoptosis of rat cardiomyocytes in vitro by increasing Bax mRNA levels (100). Oxidative stress was also shown to activate ASK (95, 101) and ASK appears to be essential for the oxidative stress-induced apoptotic cell death (94, 95). In Dahl salt-sensitive hypertensive rats with established diastolic HF, an increase in ASK1 phosphorylation has been reported and was reversed with oxypurinol treatment (40). Moreover, XOR inhibition prevented LV dilation and improved the survival rate in the same study (40). It is apparent that more studies are necessary in order to clarify the role of ASK in XOR-mediated prevention of cardiac remodeling.

6.3. Alterations in matrix structure

In the heart, extracellular matrix is not a static skeleton but a dynamic system (102-104). In contrast, it has become clear that altered matrix turnover is an active component of the process of cardiac remodeling (102-104). MMP is a family of enzymes that includes more than 20 members (collagenases, gelatinases and stromelysins) and is the major regulator of extracellular tissue breakdown (102-104). In this context, it is of interest that XOR activates MMP-2, MMP-9 and MMP-13 in cardiac fibroblasts and vascular smooth muscle cells in vitro (16, 17). OH- is also a major player in the pathogenesis of post-MI remodeling in mice, possibly by activating MMP-2 (13). Interestingly, myocardial MMP-2, MMP-9 and MMP-13 protein levels and activity are elevated in patients with HF compared with controls (19, 105, 106). In addition, in animal models, non-selective inhibition of MMP activity prevented the development of cardiac remodeling (15, 18). MMP-9 knockout mice are protected from post-MI remodeling (107) whereas transgenic mice overexpressing MMP-2 develop advanced remodeling (108). Preliminary studies in humans also suggest that suppression of MMP-2 and MMP-9 expression in patients with acute MI prevents remodeling (109). Therefore, the in vitro stimulatory effects of XOR on MMP-2, MMP-9 and MMP-13 could be implicated in the beneficial effects of XOR-inhibitions on cardiac remodeling.

7. ISCHEMIC CARDIOMYOPATHY - THE ROLE OF XOR

The impact of XOR inhibition in ischemic cardiomyopathy deserves special mention, since this is the commonest cause of HF (4, 110). There is considerable evidence suggesting that allopurinol preserves myocardial contractility and improves survival after experimental MI in mice (39, 60, 82) (Figure 8). Interestingly, an increased XOR activity was also demonstrated in the remote LV myocardium in these reports (39, 82). Even more importantly, in rats with established ischemic HF, chronic administration of allopurinol (50 mg/kg/day po for 10 weeks) induced reverse remodeling and decreased LV weight and fibrosis (83). Therefore, XOR inhibition seems not only to prevent the development of HF after MI but is also effective in stimulating reverse remodeling in established ischemic HF.

8. DIASTOLIC DYSFUNCTION AND XOR

It has already been mentioned that XOR inhibition exerts a Ca2+ sensitizing action in cardiac myofilaments (39, 51-53). One could anticipate impairment in diastolic relaxation as a result of this effect; indeed, other Ca2+ sensitizing agents induce diastolic dysfunction by lowering the threshold of (Ca2+)i where myocardial contraction is activated (111). In contrast, XOR inhibition does not shift the range of Ca2+ activation and can actually improve diastolic dysfunction (39, 40). In an early study in mice with post-MI HF, allopurinol improved diastolic relaxation (39). In a more recent report, Dahl salt-sensitive hypertensive rats with established diastolic HF were treated with oxypurinol (40 mg/kg per day for 4 weeks) (40). XOR inhibition reduced interstitial fibrosis, prevented LV dilation and the survival rate of rats treated with this agent was significantly (p < 0.01) greater than rats given vehicle (0.5% carboxymethyl cellulose) (40) (Figure 9). As already mentioned, a reduction in ERK and ASK1 phosphorylation, an augmentation in PLB phosphorylation and an attenuation in cardiomyocyte apoptosis were observed with oxypurinol treatment and could explain its beneficial effects (40). The role of renin-angiotensin system inhibition in patients with systolic HF is well established and they might also be useful in diastolic HF (4). It is thus of interest that the beneficial effects of candesartan in this study were mediated through its effects on cardiac XOR (40). Therefore, XOR inhibition might partly contribute to the salutary effects of angiotensin receptor blockers in patients with HF.

9. INTERACTION OF XOR WITH OTHER SOURCES OF ROS IN HF

NADPH oxidases are family of 5 enzymes that transfer electrons from NADPH to molecular oxygen leading to the formation of O2-. Similar to XOR, NADPH oxidases are also stimulated - among other agonists - by cytokines and angiotensin II (112). We recently showed that NADPH oxidase activity is similar in HF and control rats (59). In the same study we observed an upregulation of the NADPH oxidase subunits Gp91phox and p67phox in HF rats whereas p22phox and p47phox did not change significantly (59). However, NADPH oxidase activity is increased in the failing human myocardium (26, 113, 114) and may promote the development of cardiac hypertrophy, remodeling and ultimately HF (112, 115). It should be noted that there appears to be a cross-talk between NADPH and XOR in that the former increases the production of O2- from the latter by inducing the conversion of XDH to XO (116).

The mitochondria might also generate ROS in the failing heart (22). This was attributed to a decreased activity of complex I leading to an impairment in electron transport (22). However, the mitochondria also represent the main energy source through oxidative phosphorylation and this essential function is disrupted by XOR-produced O2- (117).

10. INTERACTION OF XOR WITH ANTIOXIDANT SYSTEMS IN HF

SOD converts O2- to H2O2 and exists in 3 isoforms, cytosolic or copper-zing SOD (SOD1), manganese SOD (SOD2, localized in mitochondria) and extracellular SOD (SOD3) (118). A relative deficit of SOD appears to be implicated in the development and progression of HF (23, 100, 119). Heart/muscle-specific SOD2-deficient mutant mice demonstrate increased production of O2- leading to HF (23). In humans, a polymorphism in the SOD2 gene that reduces the antioxidant activity of SOD also increases the risk of developing HF (119). Regarding the implicated mechanisms, inhibition of SOD1 and SOD3 induced apoptosis of rat cardiomyocytes in vitro and increased Bax mRNA levels (100). SOD2-deficient mutant mice showed suppressed oxidative phosphorylation and decreased levels of ATP in the heart (23). These detrimental consequences of the deficiency of SOD, the principal superoxide-inactivating antioxidant enzyme, further support the pivotal role of O2- in the pathogenesis of HF.

11. CROSS-TALK OF OXIDATIVE AND NITROSATIVE PATHWAYS IN HF - THE ROLE OF XOR

Since its original description as endothelium-derived relaxing factor in the pivotal experiments of Furchgott and Zawadski in 1980 (120), intense interest has been focused on the nitric oxide (NO) signaling pathway (5). Prototypically, NO exerts signaling by activation of guanylyl cyclase, which in turn converts guanosine triphosphate (GTP) to cyclic guanosine monophosphate (cGMP), an important second messenger (121). However, another mechanism of action of NO has been the topic of intensive research during the last decade, namely S-nitrosylation, which is the covalent attachment of NO to cysteine thiol (5). This ubiquitous signaling mode represents a post-translational modification system akin to phosphorylation, and is regulated and capable of tight molecular regulation by virtue of its reversibility. An important corollary to the molecular regulation exerted by SNO, is that NOSs are frequently found in signaling modules participating in protein-protein interactions with effector proteins. This is particularly true in the cardiomyocyte in which NOSs are compartmentalized in various key organelles (122). NOS1 is situated in the SR and mitochondria and NOS3 in specialized sarcolemmal signal-transducing domains termed caveolae (123-125). In this context, it is also important to stress that, in HF, NOS1 redistributes from the SR to the cell membrane (126) and this could have important implications in NO signaling in the failing myocardium (122).

NO is an important modulator of excitation/contraction coupling and myocardial energetics (127, 128) (Figure 5). NO regulates all major Ca+2 cycling proteins. NOS1 progressively activates RyR, possibly by S-nitrosylation (129, 130). NOS1 inhibits SERCA (123). NOS3 inhibits the LTCC in a cGMP-dependent way; however, it can also regulate it through S-nitrosylation and whether it exerts stimulatory or inhibitory actions depends on the redox milieu (131, 132).

Overall, NO appears to protect against the development of myocardial hypertrophy (133, 134). However, it has been reported that NO activates the hypertrophy-inducing MAPK, ERK1/2, in animal and human cell lines (135, 136). More specifically, NO activates Ras through S-nitrosylation and this leads to ERK1/2 activation (137). It was also suggested that NO mediates the stimulating effect of vascular endothelial growth factor (VEGF) on ERK1/2 in human endothelial cells; this effect was cGMP-dependent (138, 139). This is controversial as others did not observe effects of NO on ERK1/2 in murine macrophages (140). More recent studies reported that NOS1 inhibits Ras activity by S-nitrosylation and impairs downstream activation of RAF and ERK1/2 (141).

Besides these effects of NO on hypertrophy-regulating kinases, NO modulates the activity of specific phosphatases that are implicated in myocardial hypertrophy. Calcineurin is a Ca+2-activated phosphatase that dephosphorylates nuclear factor of activated T-cells (NFAT), which then translocates to the nucleus and stimulates hypertrophic gene expression (142). In cardiomyocytes and in vascular smooth muscle cells, NO prevents the activation of calcineurin and exerts anti-hypertrophic actions by regulating Ca+2 concentration (143, 144). This was mediated through a cGMP-dependent inhibition of Ca+2 entry via the LTCC (144).

NO can both induce and inhibit apoptosis depending on its concentration, cell type and redox status (145). It has already been mentioned that XOR can activate ASK-1, which then stimulates p38 and JNK resulting in increased apoptosis. In contrast, NO inhibits ASK-1 through S-nitrosylation (146). It was also recently reported that NOS inhibition induces cardiomyocyte apoptosis in wild type mice but not in ASK-1 deficient mice (147). These findings highlight the significance of ASK-1 inhibition in the anti-apoptotic actions of NO. Despite the inhibitory action of NO on ASK-1, the effects of NO on the downstream effectors of ASK-1 in the MAPK pathway, p38 and JNK, might promote apoptosis. Thus, NO activates p38 in various cell lines resulting in pro-apoptotic effects (135, 136, 140, 148). NO-induced p38 activation is both cGMP-dependent and independent (149, 150). Regarding the effect of NO on JNK, both inhibitory and stimulating actions have been reported, depending on the cell line assessed (136, 140, 151-153). Again, these actions of NO were either mediated through the guanylyl cyclase pathway or through S-nitrosylation (151-153). Overall, the effects of NO on both the apoptosis-stimulating (p38/JNK) and the hypertrophy-inducing branches (ERK1/2) of the MAPK pathway are complex and require further study.

ROS and NO interact in multiple levels (Figure 1). On one hand, XOR has multiple effects on NO-signaling pathways. As previously mentioned, O2- interacts with NO to form peroxynitrite; thus, elevated O2- levels decrease NO bioavailability (5). XOR also appears to regulate the S-nitrosylation pathway. In recent years it has become clear that nitrosative and oxidative pathways share similar targets and therefore compete for the same binding sites (5). Moreover, the modification of a protein by one signaling route could alter this protein's susceptibility to the effects of the other route (5). It was also shown that XOR reduces S-nitrosothiols and particularly S-nitrosoglutathione (GSNO), leading to the regeneration of glutathione, the enzyme that reduces SNO moieties in proteins and preserves the S-nitrosylation equilibrium (154). Interestingly, the reduction of GSNO by XOR depends on the production of O2- (154). However, XOR can also augment NO production by catalyzing nitrite reduction, particularly in ischemic conditions (155).

On the other hand, NO regulates XOR activity. Earlier biochemical studies showed that NO can inhibit both XO and XDH (156, 157). More specifically, NO reacts with an essential sulphur in the molybdenum center of XOR and removes it (156). Furthermore, NOS1 deficiency augments the production of O2- by XOR in the cardiomyocytes; in contrast, NOS3 deficiency has no impact on XOR expression (52, 158, 159). This effect of NOS1 deficiency is due to an increase in XOR activity whereas XOR mRNA and protein levels are not affected; this suggests that NOS1 via a post-translational effect (very possibly S-nitrosylation) constrains XOR activity (52, 159). NOS1 deficiency also results in increased activation of p38 kinase, and it has been proposed that the latter could activate XOR by phosphorylation (158). It is also of interest that XOR and NOS1 coimmunoprecipitate in the SR of cardiomyocytes, suggesting a direct protein-protein interaction (52). The co-localization of XOR and NOS1 could also stem from an attachment to a common adapter protein (52). Therefore, inside the cardiomyocytes, this NO-XOR interaction appears to be NOS1-specific and spatially confined to the SR (52). It is also of interest that NOS3 suppresses NADPH activity conferring cardioprotection (160) whereas NADPH-generated O2- can induce NOS3 uncoupling thereby augmenting O2- production and reducing NO bioavailability (161). It is apparent that the cross-talk between oxidative and nitrosative pathways is not limited to XOR and NOS1 but extends to other major players of these systems.

The NO-XOR interplay is an important regulator of myocardial function (5, 162). It has been already mentioned that S-nitrosylation progressively activates RyR; however, oxidation hampers this regulatory action by inducing irreversible activation of RyR (129, 130). In addition, the effect of NOS3 on LTCC depends on the redox status (131, 132). Peroxynitrite, the product on NO and O2- reaction, suppresses myocardial contractility by impairing Ca+2 responsiveness of myofilaments (57). This was attributed to a reduction in the activity of NCX resulting in an increase in intracellular Ca+2 concentration (57). Peroxynitrite also inhibits mitochondrial function and this could result in a reduction in ATP levels that could also be implicated in its negative inotropic actions (163). Besides systolic function, peroxynitrite increases resting tension in isolated heart muscle and this could potentially result in impairment in diastolic function (164). The suppressing effects of peroxynitrite on myocardial contractility could also be related to its proapoptotic actions on cardiomyocytes (165). In addition, peroxynitrite also triggers the cell death of endothelial cells (165) and this might adversely affect coronary vasculature, myocardial perfusion, and inotropy.

Overall, these findings suggest that XOR has an important role in the interplay between oxidative and nitrosative mechanisms and the preservation of nitroso-redox balance (6). In vivo studies lend further support to this hypothesis. In dogs with HF, we showed that pretreatment with the non-specific NOS-inhibitor NG-monomethyl-L-arginine (L-NMMA) prevents the increase in myocardial contractility and the improvement in mechanoenergeting uncoupling induced by allopurinol (28). This finding implies that suppression of O2- production is not sufficient to restore myocardial function but additionally requires an intact NO-signaling pathway (28). We extended these findings by studying NOS1 knockout mice; these mice exhibited impaired contractility that was reversed by allopurinol (52). This suggests that part of the positive inotropic effects of allopurinol stem from a reduction in O2- levels-induced rise in the bioavailability of NO (52). In addition, in dogs with normal heart function, L-NMMA increased myocardial oxygen consumption and depressed myocardial efficiency and this effect was alleviated by either vitamin C or allopurinol coinfusion (28). These findings suggest that a physiological NO signaling is essential for the control of XOR-induced oxidative stress in normal hearts and prevents XOR from depressing cardiac efficiency (28).

The pivotal role of nitroso-redox balance in cardiovascular homeostasis and more specifically in HF is also supported by clinical studies showing that combined administration of nitrates and hydralazine reduced mortality in HF regardless of its severity (166, 167). Since nitrates act as NO donors (168) and hydralazine scavenges ROS and is implicated as possibly inhibiting NADPH oxidases (169, 170), it is attractive to contemplate that their beneficial effects in HF are mediated through the restoration of nitroso-redox balance (162).

12. PERIPHERAL EFFECTS OF XOR INHIBITION IN HF

Even though XOR is located in cardiomyocytes and exerts a multitude of autocrine effects as delineated above, the liver and small intestine show the most abundant expression of this enzyme in humans (30). In addition, XOR is expressed in endothelial cells and can also be released in the circulation (30). Therefore, apart from the direct effects of XOR on myocardial structure and function, peripheral mechanisms may also be implicated in the XOR-induced impairment of myocardial function. In dogs with pacing-induced HF, allopurinol treatment (100 mg po daily during the pacing period) attenuates the increase in arterial elastance, an index of afterload, as well as the decrease in ventricular elastance, a marker of contractility (37). Together these effects lead to the preservation of ventricular-vascular coupling ratio (ventricular/arterial elastance) and subsequently to an improved systolic function compared with the placebo group (37). Similar results were observed with both acute (5-day) and chronic (10-week) administration of allopurinol in rats with left coronary artery ligation-induced HF (83).

Studies in both animals and humans have shown that oxidative stress plays a role in the development of endothelial dysfunction (ED) in HF (171). ED is frequently present in HF and correlates with its severity ( (172-177). Endothelium-bound XOR has a critical role in the pathogenesis of ED in these patients since it is more than 2-fold more active in HF and its activity strongly correlates with the degree of ED (20). In addition, several studies showed an improvement in ED in patients with HF with XOR inhibition (178-180). It must be emphasized that systemic ED is associated with arterial stiffening and increased vascular tone which in turn increase afterload and lead to HF progression (181-183). In addition, ED in the coronary circulation might compromise myocardial oxygenation and could also contribute to the worsening of myocardial function (184, 185). More importantly, prospective studies showed that ED in HF represents an independent risk factor for readmission with worsening HF, heart transplantation and mortality (186-188). Therefore, it is reasonable to assume that the salutary effects of XOR inhibition on ED could translate into long-term clinical benefits in patients with HF; however, this remains to be established in prospective studies.

Another important aspect of XOR inhibition is the reduction in serum uric acid (SUA) levels. Uric acid per se is a powerful ROS-scavenger (189) and also activates other endogenous antioxidant systems, particularly SOD (190). Interestingly, uric acid is metabolized by uricase in most mammals whereas in humans the uricase gene is non-functional (191). It has thus been proposed that this might confer a survival advantage to humans due to increased antioxidant defense (192). However, uric acid can also promote the development of cardiovascular disease since it has proinflammatory actions (193-195), activates platelets (196), stimulates the growth of vascular smooth muscle cells (197, 198) and induces ED (199). Prospective studies suggested that elevated SUA levels represent an independent risk factor both in the general population (200-202) and in patients with established cardiovascular disease, including coronary heart disease (203, 204) and acute stroke (205). Elevated SUA levels are frequently observed in patients with HF and directly correlate with its severity (206-208). The upregulation of XOR in HF might contribute to this phenomenon; decreased renal excretion and increased XOR substrate resulting from enhanced ATP breakdown are other putative explanations (209). Elevated SUA levels in HF reflect - to a certain degree - the activation of the XOR oxidative pathway; however, uric acid per se may also contribute to HF pathophysiology (209). In patients with HF, elevated SUA levels are associated with systemic inflammation (207), increased peripheral vascular resistance (210, 211), decreased functional capacity (206) and with the presence of diastolic dysfunction (212). More importantly, prospective studies showed that elevated SUA levels in HF independently predict mortality and the need for transplantation (213-215). Interestingly, elevated SUA levels also predict allograft vasculopathy in cardiac transplant recipients (216). In addition, in the Losartan Intervention For Endpoint reduction in hypertension (LIFE) study, a losartan-induced reduction in SUA levels in patients with left ventricular hypertrophy reduced cardiovascular morbidity and mortality (217). Therefore, by reducing SUA levels, XOR inhibition might offset an important risk factor in patients with HF.

13. XOR AND ADIPOGENESIS

Our knowledge of the mechanisms through which XOR contributes to the pathogenesis of cardiovascular disease continues to expand. A recent study showed that XOR can stimulate adipogenesis and that this effect is mediated through a XOR-induced increase in the activity of peroxisome proliferator-activated receptor gamma (PPARgamma) (218). PPARgamma is an important regulator of adipose differentiation and when activated, enhances adipogenesis through the induction of transcription of specific adipogenic genes (219). In the same study, a reduction in adipose mass was observed in XOR null mice, further supporting the importance of XOR in adipogenesis (218). Interestingly, XOR null mice do not live more than 40 days (220) and this is additional evidence that XOR serves important physiological roles.

If the association of XOR with adipogenesis is confirmed in humans, XOR inhibition could emerge as a promising strategy in the management of obesity and obesity-related disorders, including type 2 diabetes mellitus and the metabolic syndrome. Paradoxically, obesity is associated with improved survival in patients with HF, a phenomenon termed reverse epidemiology (221). However, it appears that obesity is not truly protective but merely reflects a lower inflammatory response in obese patients with HF (221). HF is increasingly being recognized as an inflammatory state and increased inflammation contributes to the development and progression of HF (222). Clearly, more studies are required to unravel the complex links between obesity and HF and the potential role of XOR in this interplay.

14. CLINICAL STUDIES OF XOR INHIBITION IN HF

The beneficial effects of XOR inhibition in the above-mentioned studies in a variety of animal models of HF support the pivotal role of XOR in the pathogenesis of HF. They also suggest that XOR inhibition might represent a valuable adjunct in the treatment of HF in humans as well. Based on these promising results, a number of studies have evaluated the effect of this treatment strategy in the clinical setting. In a preliminary study from our group in patients with dilated cardiomyopathy, intracoronary infusion of allopurinol (0.5., 1.0. and 1.5. mg/min, each administered for 15 min) decreased myocardial oxygen consumption without affecting myocardial contractility (21). Therefore, XOR is involved in the pathogenesis of mechanoenergetic uncoupling in HF i.e. the discordance between impaired LV work and myocardial energy consumption, which impairs the mechanical efficiency of contraction (21).

In another study assessing acute XOR inhibition, a single intravenous dose of oxypurinol (400 mg) significantly reduced LV end-systolic volume and increased LVEF (p = 0.03 and p = 0.003, respectively) in patients with ischemic cardiomyopathy (223).

Short-term XOR inhibition has also been evaluated in HF. In a randomized placebo-controlled trial (n = 50), allopurinol (300 mg/day po for 3 months) significantly (p = 0.035) reduced plasma BNP concentrations (224). It is well established that elevated BNP concentrations represent a strong and independent risk factor in HF (225, 226). In another randomized placebo-controlled trial (n = 60), oxypurinol (600 mg/day po for 1 month) induced a non-significant increase in LVEF (p = 0.08) (227). However, when patients with baseline LVEF £ 40% were analyzed separately, there was a significant (p < 0.02) improvement in LVEF with oxypurinol treatment (227) (Figure 10).

The largest study of the effects of an XO inhibitor in HF patients is the Oxypurinol Therapy for Chronic HF study (OPT-CHF) (228, 229). In this double-blind study, 405 patients with NYHA class III-IV heart failure were randomized to receive either oxypurinol 600 mg/day or placebo for 24 weeks (229). Overall, there was no difference beween groups in the composite endpoint comprising CHF morbidity, mortality, and quality of life (229). However, in a post-hoc exploratory analysis oxypurinol improved the outcome of patients with elevated SUA levels at baseline (> 9.5. mg/dl) (229). This cutoff value was selected on the basis of a previous study in patients with CHF which showed that these SUA levels are the best for predicting mortality (213). In addition, within the entire oxypurinol group, a larger decrease in SUA levels was associated with a better outcome (229). These data strongly support the concept that patients with CHF and elevated SUA levels, potentially a surrogate for increased XOR activity, might benefit the most from XOR inhibition. Finally, in the placebo group of the OPT-CHF study, baseline SUA levels were associated with adverse outcome, further supporting earlier reports on the predictive role of SUA levels in CHF and other cardiovascular disorders (213-216).

It should be noticed that the effects of XOR inhibition in the aforementioned studies were observed in the context of standard pharmacological treatment for HF, including beta-blockers and rennin-angiotensin system inhibitors (223, 227, 229). Therefore, it appears that XOR inhibition can provide additive benefits to those of current drug therapy for HF.

An important limitation of all studies employing allopurinol treatment is that this agent has other effects besides XOR inhibition, including antioxidant action, copper chelation, inhibition of lipid peroxidation and down-regulation of heat shock protein expression (230). Allopurinol can also directly scavenge OH- (231). Therefore, not all effects of allopurinol can be attributed to XOR inhibition. On the other hand, it has been suggested that cell-associated XOR may be less susceptible to allopurinol inhibition (232). This finding could imply that the effects of allopurinol administration cannot totally capture the significance of XOR.

15. PERSPECTIVE

XOR is intimately involved in the pathophysiology of HF and exerts regulatory actions in multiple levels of both ROS and NO signaling pathways. Preclinical studies and preliminary clinical studies assessing XOR inhibition showed promising findings. Given the rising burden of HF and its high morbidity and mortality rates, there is a clear rationale for pursuing further prospective, large-scale clinical studies designed to evaluate the potential therapeutic role of XOR inhibition in these patients. Finally, in this emerging era of individualized medicine, identifying and targeting specific subgroups of patients - such as patients with elevated SUA levels as the OPT-CHF study suggests - might also maximize the benefits of XOR inhibition in the management of HF.

16. ACKNOWLEDGEMENTS

Joshua M. Hare is supported by grants NIH 2RO1 HL-65455-05, NIA RO1 AG025017, NIH U54HL081028-01 and NIH/NHLBI R01HL084275. Konstantinos Tziomalos is supported by a grant from the Hellenic Antihypertensive Society. Joshua M. Hare serves as a consultant to Cardiome Pharma Corporation.

17. REFERENCES

1. M. Tendera: The epidemiology of heart failure. J Renin Angiotensin Aldosterone Syst 5 Suppl 1, S2-S6 (2004).

doi:10.3317/jraas.2004.020
http://dx.doi.org/10.3317/jraas.2004.020

2. American Heart Association: Heart disease and stroke statistics; 2005 update., 2007.

 

3. F. A. Masoudi, E. P. Havranek and H. M. Krumholz: The burden of chronic congestive heart failure in older persons: magnitude and implications for policy and research. Heart Fail Rev 7, 9-16 (2002).

doi:10.1023/A:1013793621248
http://dx.doi.org/10.1023/A:1013793621248

4. S. A. Hunt, W. T. Abraham, M. H. Chin, A. M. Feldman, G. S. Francis, T. G. Ganiats, M. Jessup, M. A. Konstam, D. M. Mancini, K. Michl, J. A. Oates, P. S. Rahko, M. A. Silver, L. W. Stevenson, C. W. Yancy, E. M. Antman, S. C. Smith, Jr., C. D. Adams, J. L. Anderson, D. P. Faxon, V. Fuster, J. L. Halperin, L. F. Hiratzka, A. K. Jacobs, R. Nishimura, J. P. Ornato, R. L. Page and B. Riegel: ACC/AHA 2005 Guideline Update for the Diagnosis and Management of Chronic Heart Failure in the Adult: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Update the 2001 Guidelines for the Evaluation and Management of Heart Failure): developed in collaboration with the American College of Chest Physicians and the International Society for Heart and Lung Transplantation: endorsed by the Heart Rhythm Society. Circulation 112, e154-e235 (2005).

doi:10.1161/CIRCULATIONAHA.105.167586
http://dx.doi.org/10.1161/CIRCULATIONAHA.105.167586

5. J. M. Hare and J. S. Stamler: NO/redox disequilibrium in the failing heart and cardiovascular system. J Clin Invest 115, 509-517 (2005).

doi:10.1172/JCI200524459
http://dx.doi.org/10.1172/JCI200524459

6. J. M. Zimmet and J. M. Hare: Nitroso-redox interactions in the cardiovascular system. Circulation 114, 1531-1544 (2006).

doi:10.1161/CIRCULATIONAHA.105.605519
http://dx.doi.org/10.1161/CIRCULATIONAHA.105.605519

7. M. Seddon, Y. H. Looi and A. M. Shah: Oxidative stress and redox signalling in cardiac hypertrophy and heart failure. Heart 93, 903-907 (2007).

doi:10.1136/hrt.2005.068270
http://dx.doi.org/10.1136/hrt.2005.068270

8. Z. Mallat, I. Philip, M. Lebret, D. Chatel, J. Maclouf and A. Tedgui: Elevated levels of 8-iso-prostaglandin F2alpha in pericardial fluid of patients with heart failure: a potential role for in vivo oxidant stress in ventricular dilatation and progression to heart failure. Circulation 97, 1536-1539 (1998).

 

9. J. J. Belch, A. B. Bridges, N. Scott and M. Chopra: Oxygen free radicals and congestive heart failure. Br Heart J 65, 245-248 (1991).

doi:10.1136/hrt.65.5.245
http://dx.doi.org/10.1136/hrt.65.5.245

10. M. Nonaka-Sarukawa, K. Yamamoto, H. Aoki, H. Takano, T. Katsuki, U. Ikeda and K. Shimada: Increased urinary 15-F2t-isoprostane concentrations in patients with non-ischaemic congestive heart failure: a marker of oxidative stress. Heart 89, 871-874 (2003).

doi:10.1136/heart.89.8.871
http://dx.doi.org/10.1136/heart.89.8.871

11. M. Keith, A. Geranmayegan, M. J. Sole, R. Kurian, A. Robinson, A. S. Omran and K. N. Jeejeebhoy: Increased oxidative stress in patients with congestive heart failure. J Am Coll Cardiol 31, 1352-1356 (1998).

doi:10.1016/S0735-1097(98)00101-6
http://dx.doi.org/10.1016/S0735-1097(98)00101-6

12. J. M. Hare: Oxidative stress and apoptosis in heart failure progression. Circ Res 89, 198-200 (2001).

 

13. S. Kinugawa, H. Tsutsui, S. Hayashidani, T. Ide, N. Suematsu, S. Satoh, H. Utsumi and A. Takeshita: Treatment with dimethylthiourea prevents left ventricular remodeling and failure after experimental myocardial infarction in mice: role of oxidative stress. Circ Res 87, 392-398 (2000).

 

14. K. Kameda, T. Matsunaga, N. Abe, H. Hanada, H. Ishizaka, H. Ono, M. Saitoh, K. Fukui, I. Fukuda, T. Osanai and K. Okumura: Correlation of oxidative stress with activity of matrix metalloproteinase in patients with coronary artery disease. Possible role for left ventricular remodelling. Eur Heart J 24, 2180-2185 (2003).

doi:10.1016/j.ehj.2003.09.022
http://dx.doi.org/10.1016/j.ehj.2003.09.022

15. J. T. Peterson, H. Hallak, L. Johnson, H. Li, P. M. O'Brien, D. R. Sliskovic, T. M. Bocan, M. L. Coker, T. Etoh and F. G. Spinale: Matrix metalloproteinase inhibition attenuates left ventricular remodeling and dysfunction in a rat model of progressive heart failure. Circulation 103, 2303-2309 (2001).

 

16. S. Rajagopalan, X. P. Meng, S. Ramasamy, D. G. Harrison and Z. S. Galis: Reactive oxygen species produced by macrophage-derived foam cells regulate the activity of vascular matrix metalloproteinases in vitro. Implications for atherosclerotic plaque stability. J Clin Invest 98, 2572-2579 (1996).

 

17. D. A. Siwik, P. J. Pagano and W. S. Colucci: Oxidative stress regulates collagen synthesis and matrix metalloproteinase activity in cardiac fibroblasts. Am J Physiol Cell Physiol 280, C53-C60 (2001).

 

18. F. G. Spinale, M. L. Coker, S. R. Krombach, R. Mukherjee, H. Hallak, W. V. Houck, M. J. Clair, S. B. Kribbs, L. L. Johnson, J. T. Peterson and M. R. Zile: Matrix metalloproteinase inhibition during the development of congestive heart failure : effects on left ventricular dimensions and function. Circ Res 85, 364-376 (1999).

 

19. C. V. Thomas, M. L. Coker, J. L. Zellner, J. R. Handy, A. J. Crumbley, III and F. G. Spinale: Increased matrix metalloproteinase activity and selective upregulation in LV myocardium from patients with end-stage dilated cardiomyopathy. Circulation 97, 1708-1715 (1998).

 

20. U. Landmesser, S. Spiekermann, S. Dikalov, H. Tatge, R. Wilke, C. Kohler, D. G. Harrison, B. Hornig and H. Drexler: Vascular oxidative stress and endothelial dysfunction in patients with chronic heart failure: role of xanthine-oxidase and extracellular superoxide dismutase. Circulation 106, 3073-3078 (2002).

doi:10.1161/01.CIR.0000041431.57222.AF
http://dx.doi.org/10.1161/01.CIR.0000041431.57222.AF

21. T. P. Cappola, D. A. Kass, G. S. Nelson, R. D. Berger, G. O. Rosas, Z. A. Kobeissi, E. Marban and J. M. Hare: Allopurinol improves myocardial efficiency in patients with idiopathic dilated cardiomyopathy. Circulation 104, 2407-2411 (2001).

doi:10.1161/hc4501.098928
http://dx.doi.org/10.1161/hc4501.098928

22. T. Ide, H. Tsutsui, S. Kinugawa, H. Utsumi, D. Kang, N. Hattori, K. Uchida, K. Arimura, K. Egashira and A. Takeshita: Mitochondrial electron transport complex I is a potential source of oxygen free radicals in the failing myocardium. Circ Res 85, 357-363 (1999).

 

23. H. Nojiri, T. Shimizu, M. Funakoshi, O. Yamaguchi, H. Zhou, S. Kawakami, Y. Ohta, M. Sami, T. Tachibana, H. Ishikawa, H. Kurosawa, R. C. Kahn, K. Otsu and T. Shirasawa: Oxidative stress causes heart failure with impaired mitochondrial respiration. J Biol Chem 281, 33789-33801 (2006).

doi:10.1074/jbc.M602118200
http://dx.doi.org/10.1074/jbc.M602118200

24. F. J. Giordano: Oxygen, oxidative stress, hypoxia, and heart failure. J Clin Invest 115, 500-508 (2005).

doi:10.1172/JCI200524408
http://dx.doi.org/10.1172/JCI200524408

25. H. Mollnau, M. Oelze, M. August, M. Wendt, A. Daiber, E. Schulz, S. Baldus, A. L. Kleschyov, A. Materne, P. Wenzel, U. Hink, G. Nickenig, I. Fleming and T. Munzel: Mechanisms of increased vascular superoxide production in an experimental model of idiopathic dilated cardiomyopathy. Arterioscler Thromb Vasc Biol 25, 2554-2559 (2005).

doi:10.1161/01.ATV.0000190673.41925.9B
http://dx.doi.org/10.1161/01.ATV.0000190673.41925.9B

26. C. Heymes, J. K. Bendall, P. Ratajczak, A. C. Cave, J. L. Samuel, G. Hasenfuss and A. M. Shah: Increased myocardial NADPH oxidase activity in human heart failure. J Am Coll Cardiol 41, 2164-2171 (2003).

doi:10.1016/S0735-1097(03)00471-6
http://dx.doi.org/10.1016/S0735-1097(03)00471-6

27. L. J. Dixon, D. R. Morgan, S. M. Hughes, L. T. McGrath, N. A. El Sherbeeny, R. D. Plumb, A. Devine, W. Leahey, G. D. Johnston and G. E. McVeigh: Functional consequences of endothelial nitric oxide synthase uncoupling in congestive cardiac failure. Circulation 107, 1725-1728 (2003).

doi:10.1161/01.CIR.0000066283.13253.78
http://dx.doi.org/10.1161/01.CIR.0000066283.13253.78

28. W. F. Saavedra, N. Paolocci, M. E. St John, M. W. Skaf, G. C. Stewart, J. S. Xie, R. W. Harrison, J. Zeichner, D. Mudrick, E. Marban, D. A. Kass and J. M. Hare: Imbalance between xanthine oxidase and nitric oxide synthase signaling pathways underlies mechanoenergetic uncoupling in the failing heart. Circ Res 90, 297-304 (2002).

doi:10.1161/hh0302.104531
http://dx.doi.org/10.1161/hh0302.104531

29. Y. Chen, M. Hou, Y. Li, J. H. Traverse, P. Zhang, D. Salvemini, T. Fukai and R. J. Bache: Increased superoxide production causes coronary endothelial dysfunction and depressed oxygen consumption in the failing heart. Am J Physiol Heart Circ Physiol 288, H133-H141 (2005).

doi:10.1152/ajpheart.00851.2003
http://dx.doi.org/10.1152/ajpheart.00851.2003

30. C. E. Berry and J. M. Hare: Xanthine oxidoreductase and cardiovascular disease: molecular mechanisms and pathophysiological implications. J Physiol 555, 589-606 (2004).

doi:10.1113/jphysiol.2003.055913
http://dx.doi.org/10.1113/jphysiol.2003.055913

31. Y. Kuwabara, T. Nishino, K. Okamoto, T. Matsumura, B. T. Eger, E. F. Pai and T. Nishino: Unique amino acids cluster for switching from the dehydrogenase to oxidase form of xanthine oxidoreductase. Proc Natl Acad Sci U S A 100, 8170-8175 (2003).

doi:10.1073/pnas.1431485100
http://dx.doi.org/10.1073/pnas.1431485100

32. J. S. Olson, D. P. Ballou, G. Palmer and V. Massey: The mechanism of action of xanthine oxidase. J Biol Chem 249, 4363-4382 (1974).

 

33. J. M. McCord and I. Fridovich: The reduction of cytochrome c by milk xanthine oxidase. J Biol Chem 243, 5753-5760 (1968).

 

34. B. Halliwell and J. M. Gutteridge: Oxygen toxicity, oxygen radicals, transition metals and disease. Biochem J 219, 1-14 (1984).

 

35. T. Ide, H. Tsutsui, S. Kinugawa, N. Suematsu, S. Hayashidani, K. Ichikawa, H. Utsumi, Y. Machida, K. Egashira and A. Takeshita: Direct evidence for increased hydroxyl radicals originating from superoxide in the failing myocardium. Circ Res 86, 152-157 (2000).

 

36. S. Genet, R. K. Kale and N. Z. Baquer: Effects of free radicals on cytosolic creatine kinase activities and protection by antioxidant enzymes and sulfhydryl compounds. Mol Cell Biochem 210, 23-28 (2000).

doi:10.1023/A:1007071617480
http://dx.doi.org/10.1023/A:1007071617480

37. L. C. Amado, A. P. Saliaris, S. V. Raju, S. Lehrke, M. St John, J. Xie, G. Stewart, T. Fitton, K. M. Minhas, J. Brawn and J. M. Hare: Xanthine oxidase inhibition ameliorates cardiovascular dysfunction in dogs with pacing-induced heart failure. J Mol Cell Cardiol 39, 531-536 (2005).

doi:10.1016/j.yjmcc.2005.04.008
http://dx.doi.org/10.1016/j.yjmcc.2005.04.008

38. U. E. Ekelund, R. W. Harrison, O. Shokek, R. N. Thakkar, R. S. Tunin, H. Senzaki, D. A. Kass, E. Marban and J. M. Hare: Intravenous allopurinol decreases myocardial oxygen consumption and increases mechanical efficiency in dogs with pacing-induced heart failure. Circ Res 85, 437-445 (1999).

 

39. L. B. Stull, M. K. Leppo, L. Szweda, W. D. Gao and E. Marban: Chronic treatment with allopurinol boosts survival and cardiac contractility in murine postischemic cardiomyopathy. Circ Res 95, 1005-1011 (2004).

doi:10.1161/01.RES.0000148635.73331.c5
http://dx.doi.org/10.1161/01.RES.0000148635.73331.c5

40. E. Yamamoto, K. Kataoka, T. Yamashita, Y. Tokutomi, Y. F. Dong, S. Matsuba, H. Ogawa and S. Kim-Mitsuyama: Role of xanthine oxidoreductase in the reversal of diastolic heart failure by candesartan in the salt-sensitive hypertensive rat. Hypertension 50, 657-662 (2007).

doi:10.1161/HYPERTENSIONAHA.107.095315
http://dx.doi.org/10.1161/HYPERTENSIONAHA.107.095315

41. R. W. Schrier and W. T. Abraham: Hormones and hemodynamics in heart failure. N Engl J Med 341, 577-585 (1999).

doi:10.1056/NEJM199908193410806
http://dx.doi.org/10.1056/NEJM199908193410806

42. E. M. Mervaala, Z. J. Cheng, I. Tikkanen, R. Lapatto, K. Nurminen, H. Vapaatalo, D. N. Muller, A. Fiebeler, U. Ganten, D. Ganten and F. C. Luft: Endothelial dysfunction and xanthine oxidoreductase activity in rats with human renin and angiotensinogen genes. Hypertension 37, 414-418 (2001).

 

43. P. Aukrust, T. Ueland, F. Muller, A. K. Andreassen, I. Nordoy, H. Aas, J. Kjekshus, S. Simonsen, S. S. Froland and L. Gullestad: Elevated circulating levels of C-C chemokines in patients with congestive heart failure. Circulation 97, 1136-1143 (1998).

 

44. G. Torre-Amione, S. Kapadia, C. Benedict, H. Oral, J. B. Young and D. L. Mann: Proinflammatory cytokine levels in patients with depressed left ventricular ejection fraction: a report from the Studies of Left Ventricular Dysfunction (SOLVD). J Am Coll Cardiol 27, 1201-1206 (1996).

doi:10.1016/0735-1097(95)00589-7
http://dx.doi.org/10.1016/0735-1097(95)00589-7

45. P. Ferdinandy, H. Danial, I. Ambrus, R. A. Rothery and R. Schulz: Peroxynitrite is a major contributor to cytokine-induced myocardial contractile failure. Circ Res 87, 241-247 (2000).

 

46. K. C. Flanders, A. R. Bhandiwad and T. S. Winokur: Transforming growth factor-betas block cytokine induction of catalase and xanthine oxidase mRNA levels in cultured rat cardiac cells. J Mol Cell Cardiol 29, 273-280 (1997).

doi:10.1006/jmcc.1996.0272
http://dx.doi.org/10.1006/jmcc.1996.0272

47. P. M. Hassoun, F. S. Yu, A. L. Shedd, J. J. Zulueta, V. J. Thannickal, J. J. Lanzillo and B. L. Fanburg: Regulation of endothelial cell xanthine dehydrogenase xanthine oxidase gene expression by oxygen tension. Am J Physiol 266, L163-L171 (1994).

 

48. W. B. Poss, T. P. Huecksteadt, P. C. Panus, B. A. Freeman and J. R. Hoidal: Regulation of xanthine dehydrogenase and xanthine oxidase activity by hypoxia. Am J Physiol 270, L941-L946 (1996).

 

49. Y. Hoshikawa, S. Ono, S. Suzuki, T. Tanita, M. Chida, C. Song, M. Noda, T. Tabata, N. F. Voelkel and S. Fujimura: Generation of oxidative stress contributes to the development of pulmonary hypertension induced by hypoxia. J Appl Physiol 90, 1299-1306 (2001).

 

50. N. G. MacFarlane and D. J. Miller: Depression of peak force without altering calcium sensitivity by the superoxide anion in chemically skinned cardiac muscle of rat. Circ Res 70, 1217-1224 (1992).

 

51. N. G. Perez, W. D. Gao and E. Marban: Novel myofilament Ca2+-sensitizing property of xanthine oxidase inhibitors. Circ Res 83, 423-430 (1998).

 

52. S. A. Khan, K. Lee, K. M. Minhas, D. R. Gonzalez, S. V. Raju, A. D. Tejani, D. Li, D. E. Berkowitz and J. M. Hare: Neuronal nitric oxide synthase negatively regulates xanthine oxidoreductase inhibition of cardiac excitation-contraction coupling. Proc Natl Acad Sci U S A 101, 15944-15948 (2004).

doi:10.1073/pnas.0404136101
http://dx.doi.org/10.1073/pnas.0404136101

53. W. D. Gao, Y. Liu and E. Marban: Selective effects of oxygen free radicals on excitation-contraction coupling in ventricular muscle. Implications for the mechanism of stunned myocardium. Circulation 94, 2597-2604 (1996).

 

54. C. Ventura, C. Guarnieri and C. M. Caldarera: Inhibitory effect of superoxide radicals on cardiac myofibrillar ATPase activity. Ital J Biochem 34, 267-274 (1985).

 

55. H. Kogler, H. Fraser, S. McCune, R. Altschuld and E. Marban: Disproportionate enhancement of myocardial contractility by the xanthine oxidase inhibitor oxypurinol in failing rat myocardium. Cardiovasc Res 59, 582-592 (2003).

doi:10.1016/S0008-6363(03)00512-1
http://dx.doi.org/10.1016/S0008-6363(03)00512-1

56. N. G. Perez, K. Hashimoto, S. McCune, R. A. Altschuld and E. Marban: Origin of contractile dysfunction in heart failure: calcium cycling versus myofilaments. Circulation 99, 1077-1083 (1999).

 

57. H. Ishida, C. Genka, Y. Hirota, Y. Hamasaki and H. Nakazawa: Distinct roles of peroxynitrite and hydroxyl radical in triggering stunned myocardium-like impairment of cardiac myocytes in vitro. Mol Cell Biochem 198, 31-38 (1999).

doi:10.1023/A:1006989826711
http://dx.doi.org/10.1023/A:1006989826711

58. T. Ukai, C. P. Cheng, H. Tachibana, A. Igawa, Z. S. Zhang, H. J. Cheng and W. C. Little: Allopurinol enhances the contractile response to dobutamine and exercise in dogs with pacing-induced heart failure. Circulation 103, 750-755 (2001).

 

59. K. M. Minhas, R. M. Saraiva, K. H. Schuleri, S. Lehrke, M. Zheng, A. P. Saliaris, C. E. Berry, L. A. Barouch, K. M. Vandegaer, D. Li and J. M. Hare: Xanthine oxidoreductase inhibition causes reverse remodeling in rats with dilated cardiomyopathy. Circ Res 98, 271-279 (2006).

doi:10.1161/01.RES.0000200181.59551.71
http://dx.doi.org/10.1161/01.RES.0000200181.59551.71

60. A. V. Naumova, V. P. Chacko, R. Ouwerkerk, L. Stull, E. Marban and R. G. Weiss: Xanthine oxidase inhibitors improve energetics and function after infarction in failing mouse hearts. Am J Physiol Heart Circ Physiol 290, H837-H843 (2006).

doi:10.1152/ajpheart.00831.2005
http://dx.doi.org/10.1152/ajpheart.00831.2005

61. J. S. Ingwall and R. G. Weiss: Is the failing heart energy starved? On using chemical energy to support cardiac function. Circ Res 95, 135-145 (2004).

doi:10.1161/01.RES.0000137170.41939.d9
http://dx.doi.org/10.1161/01.RES.0000137170.41939.d9

62. M. Beer, T. Seyfarth, J. Sandstede, W. Landschutz, C. Lipke, H. Kostler, M. von Kienlin, K. Harre, D. Hahn and S. Neubauer: Absolute concentrations of high-energy phosphate metabolites in normal, hypertrophied, and failing human myocardium measured noninvasively with (31)P-SLOOP magnetic resonance spectroscopy. J Am Coll Cardiol 40, 1267-1274 (2002).

doi:10.1016/S0735-1097(02)02160-5
http://dx.doi.org/10.1016/S0735-1097(02)02160-5

63. M. A. Conway, J. Allis, R. Ouwerkerk, T. Niioka, B. Rajagopalan and G. K. Radda: Detection of low phosphocreatine to ATP ratio in failing hypertrophied human myocardium by 31P magnetic resonance spectroscopy. Lancet 338, 973-976 (1991).

doi:10.1016/0140-6736(91)91838-L
http://dx.doi.org/10.1016/0140-6736(91)91838-L

64. S. Neubauer, M. Horn, M. Cramer, K. Harre, J. B. Newell, W. Peters, T. Pabst, G. Ertl, D. Hahn, J. S. Ingwall and K. Kochsiek: Myocardial phosphocreatine-to-ATP ratio is a predictor of mortality in patients with dilated cardiomyopathy. Circulation 96, 2190-2196 (1997).

 

65. W. Shen, M. Spindler, M. A. Higgins, N. Jin, R. M. Gill, L. J. Bloem, T. P. Ryan and J. S. Ingwall: The fall in creatine levels and creatine kinase isozyme changes in the failing heart are reversible: complex post-transcriptional regulation of the components of the CK system. J Mol Cell Cardiol 39, 537-544 (2005).

doi:10.1016/j.yjmcc.2005.05.003
http://dx.doi.org/10.1016/j.yjmcc.2005.05.003

66. L. Nascimben, J. S. Ingwall, P. Pauletto, J. Friedrich, J. K. Gwathmey, V. Saks, A. C. Pessina and P. D. Allen: Creatine kinase system in failing and nonfailing human myocardium. Circulation 94, 1894-1901 (1996).

 

67. R. Tian and J. S. Ingwall: Energetic basis for reduced contractile reserve in isolated rat hearts. Am J Physiol 270, H1207-H1216 (1996).

 

68. B. L. Hamman, J. A. Bittl, W. E. Jacobus, P. D. Allen, R. S. Spencer, R. Tian and J. S. Ingwall: Inhibition of the creatine kinase reaction decreases the contractile reserve of isolated rat hearts. Am J Physiol 269, H1030-H1036 (1995).

 

69. H. Ishihara, M. Yokota, T. Sobue and H. Saito: Relation between ventriculoarterial coupling and myocardial energetics in patients with idiopathic dilated cardiomyopathy. J Am Coll Cardiol 23, 406-416 (1994).

 

70. M. Packer, J. R. Carver, R. J. Rodeheffer, R. J. Ivanhoe, R. DiBianco, S. M. Zeldis, G. H. Hendrix, W. J. Bommer, U. Elkayam, M. L. Kukin, G. I. Mallis, J. A. Sollano, J. Shannon, P. K. Tandon and D. L. DeMets: Effect of oral milrinone on mortality in severe chronic heart failure. The PROMISE Study Research Group. N Engl J Med 325, 1468-1475 (1991).

 

71. C. M. O'Connor, W. A. Gattis, B. F. Uretsky, K. F. Adams, Jr., S. E. McNulty, S. H. Grossman, W. J. McKenna, F. Zannad, K. Swedberg, M. Gheorghiade and R. M. Califf: Continuous intravenous dobutamine is associated with an increased risk of death in patients with advanced heart failure: insights from the Flolan International Randomized Survival Trial (FIRST). Am Heart J 138, 78-86 (1999).

doi:10.1016/S0002-8703(99)70250-4
http://dx.doi.org/10.1016/S0002-8703(99)70250-4

72. F. del Monte and R. J. Hajjar: Targeting calcium cycling proteins in heart failure through gene transfer. J Physiol 546, 49-61 (2003).

doi:10.1113/jphysiol.2002.026732
http://dx.doi.org/10.1113/jphysiol.2002.026732

73. S. O. Marx, S. Reiken, Y. Hisamatsu, T. Jayaraman, D. Burkhoff, N. Rosemblit and A. R. Marks: PKA phosphorylation dissociates FKBP12.6 from the calcium release channel (ryanodine receptor): defective regulation in failing hearts. Cell 101, 365-376 (2000).

doi:10.1016/S0092-8674(00)80847-8
http://dx.doi.org/10.1016/S0092-8674(00)80847-8

74. R. Studer, H. Reinecke, J. Bilger, T. Eschenhagen, M. Bohm, G. Hasenfuss, H. Just, J. Holtz and H. Drexler: Gene expression of the cardiac Na(+)-Ca2+ exchanger in end-stage human heart failure. Circ Res 75, 443-453 (1994).

 

75. U. Schmidt, R. J. Hajjar, P. A. Helm, C. S. Kim, A. A. Doye and J. K. Gwathmey: Contribution of abnormal sarcoplasmic reticulum ATPase activity to systolic and diastolic dysfunction in human heart failure. J Mol Cell Cardiol 30, 1929-1937 (1998).

doi:10.1006/jmcc.1998.0748
http://dx.doi.org/10.1006/jmcc.1998.0748

76. B. O'Rourke, D. A. Kass, G. F. Tomaselli, S. Kaab, R. Tunin and E. Marban: Mechanisms of altered excitation-contraction coupling in canine tachycardia-induced heart failure, I: experimental studies. Circ Res 84, 562-570 (1999).

 

77. A. P. Saliaris, L. C. Amado, K. M. Minhas, K. H. Schuleri, S. Lehrke, M. St John, T. Fitton, C. Barreiro, C. Berry, M. Zheng, K. Kozielski, V. Eneboe, J. Brawn and J. M. Hare: Chronic allopurinol administration ameliorates maladaptive alterations in Ca2+ cycling proteins and beta-adrenergic hyporesponsiveness in heart failure. Am J Physiol Heart Circ Physiol 292, H1328-H1335 (2007).

doi:10.1152/ajpheart.00461.2006
http://dx.doi.org/10.1152/ajpheart.00461.2006

78. I. E. Blasig, T. Grune, K. Schonheit, E. Rohde, M. Jakstadt, R. F. Haseloff and W. G. Siems: 4-Hydroxynonenal, a novel indicator of lipid peroxidation for reperfusion injury of the myocardium. Am J Physiol 269, H14-H22 (1995).

 

79. P. Eaton, D. J. Hearse and M. J. Shattock: Lipid hydroperoxide modification of proteins during myocardial ischaemia. Cardiovasc Res 51, 294-303 (2001).

doi:10.1016/S0008-6363(01)00303-0
http://dx.doi.org/10.1016/S0008-6363(01)00303-0

80. J. G. Duncan, R. Ravi, L. B. Stull and A. M. Murphy: Chronic xanthine oxidase inhibition prevents myofibrillar protein oxidation and preserves cardiac function in a transgenic mouse model of cardiomyopathy. Am J Physiol Heart Circ Physiol 289, H1512-H1518 (2005).

doi:10.1152/ajpheart.00168.2005
http://dx.doi.org/10.1152/ajpheart.00168.2005

81. M. Jessup and S. Brozena: Heart failure. N Engl J Med 348, 2007-2018 (2003).

doi:10.1056/NEJMra021498
http://dx.doi.org/10.1056/NEJMra021498

82. N. Engberding, S. Spiekermann, A. Schaefer, A. Heineke, A. Wiencke, M. Muller, M. Fuchs, D. Hilfiker-Kleiner, B. Hornig, H. Drexler and U. Landmesser: Allopurinol attenuates left ventricular remodeling and dysfunction after experimental myocardial infarction: a new action for an old drug? Circulation 110, 2175-2179 (2004).

doi:10.1161/01.CIR.0000144303.24894.1C
http://dx.doi.org/10.1161/01.CIR.0000144303.24894.1C

83. V. Mellin, M. Isabelle, A. Oudot, C. Vergely-Vandriesse, C. Monteil, B. Di Meglio, J. P. Henry, B. Dautreaux, L. Rochette, C. Thuillez and P. Mulder: Transient reduction in myocardial free oxygen radical levels is involved in the improved cardiac function and structure after long-term allopurinol treatment initiated in established chronic heart failure. Eur Heart J 26, 1544-1550 (2005).

doi:10.1093/eurheartj/ehi305
http://dx.doi.org/10.1093/eurheartj/ehi305

84. V. P. van Empel and L. J. De Windt: Myocyte hypertrophy and apoptosis: a balancing act. Cardiovasc Res 63, 487-499 (2004).

doi:10.1016/j.cardiores.2004.02.013
http://dx.doi.org/10.1016/j.cardiores.2004.02.013

85. D. Levy, R. J. Garrison, D. D. Savage, W. B. Kannel and W. P. Castelli: Prognostic implications of echocardiographically determined left ventricular mass in the Framingham Heart Study. N Engl J Med 322, 1561-1566 (1990).

 

86. J. Heineke and J. D. Molkentin: Regulation of cardiac hypertrophy by intracellular signalling pathways. Nat Rev Mol Cell Biol 7, 589-600 (2006).

doi:10.1038/nrm1983
http://dx.doi.org/10.1038/nrm1983

87. O. F. Bueno, L. J. De Windt, K. M. Tymitz, S. A. Witt, T. R. Kimball, R. Klevitsky, T. E. Hewett, S. P. Jones, D. J. Lefer, C. F. Peng, R. N. Kitsis and J. D. Molkentin: The MEK1-ERK1/2 signaling pathway promotes compensated cardiac hypertrophy in transgenic mice. EMBO J 19, 6341-6350 (2000).

doi:10.1093/emboj/19.23.6341
http://dx.doi.org/10.1093/emboj/19.23.6341

88. S. M. Kang, S. Lim, H. Song, W. Chang, S. Lee, S. M. Bae, J. H. Chung, H. Lee, H. G. Kim, D. H. Yoon, T. W. Kim, Y. Jang, J. M. Sung, N. S. Chung and K. C. Hwang: Allopurinol modulates reactive oxygen species generation and Ca2+ overload in ischemia-reperfused heart and hypoxia-reoxygenated cardiomyocytes. Eur J Pharmacol 535, 212-219 (2006).

doi:10.1016/j.ejphar.2006.01.013
http://dx.doi.org/10.1016/j.ejphar.2006.01.013

89. G. W. Dorn, J. Robbins and P. H. Sugden: Phenotyping hypertrophy: eschew obfuscation. Circ Res 92, 1171-1175 (2003).

doi:10.1161/01.RES.0000077012.11088.BC
http://dx.doi.org/10.1161/01.RES.0000077012.11088.BC

90. D. Cesselli, I. Jakoniuk, L. Barlucchi, A. P. Beltrami, T. H. Hintze, B. Nadal-Ginard, J. Kajstura, A. Leri and P. Anversa: Oxidative stress-mediated cardiac cell death is a major determinant of ventricular dysfunction and failure in dog dilated cardiomyopathy. Circ Res 89, 279-286 (2001).

doi:10.1161/hh1501.094115
http://dx.doi.org/10.1161/hh1501.094115

91. J. Narula, N. Haider, R. Virmani, T. G. DiSalvo, F. D. Kolodgie, R. J. Hajjar, U. Schmidt, M. J. Semigran, G. W. Dec and B. A. Khaw: Apoptosis in myocytes in end-stage heart failure. N Engl J Med 335, 1182-1189 (1996).

doi:10.1056/NEJM199610173351603
http://dx.doi.org/10.1056/NEJM199610173351603

92. G. Olivetti, R. Abbi, F. Quaini, J. Kajstura, W. Cheng, J. A. Nitahara, E. Quaini, C. Di Loreto, C. A. Beltrami, S. Krajewski, J. C. Reed and P. Anversa: Apoptosis in the failing human heart. N Engl J Med 336, 1131-1141 (1997).

doi:10.1056/NEJM199704173361603
http://dx.doi.org/10.1056/NEJM199704173361603

93. H. Nagai, T. Noguchi, K. Takeda and H. Ichijo: Pathophysiological roles of ASK1-MAP kinase signaling pathways. J Biochem Mol Biol 40, 1-6 (2007).

 

94. O. Yamaguchi, Y. Higuchi, S. Hirotani, K. Kashiwase, H. Nakayama, S. Hikoso, T. Takeda, T. Watanabe, M. Asahi, M. Taniike, Y. Matsumura, I. Tsujimoto, K. Hongo, Y. Kusakari, S. Kurihara, K. Nishida, H. Ichijo, M. Hori and K. Otsu: Targeted deletion of apoptosis signal-regulating kinase 1 attenuates left ventricular remodeling. Proc Natl Acad Sci U S A 100, 15883-15888 (2003).

doi:10.1073/pnas.2136717100
http://dx.doi.org/10.1073/pnas.2136717100

95. K. Tobiume, A. Matsuzawa, T. Takahashi, H. Nishitoh, K. Morita, K. Takeda, O. Minowa, K. Miyazono, T. Noda and H. Ichijo: ASK1 is required for sustained activations of JNK/p38 MAP kinases and apoptosis. EMBO Rep 2, 222-228 (2001).

doi:10.1093/embo-reports/kve046
http://dx.doi.org/10.1093/embo-reports/kve046

96. R. A. Kaiser, Q. Liang, O. Bueno, Y. Huang, T. Lackey, R. Klevitsky, T. E. Hewett and J. D. Molkentin: Genetic inhibition or activation of JNK1/2 protects the myocardium from ischemia-reperfusion-induced cell death in vivo. J Biol Chem 280, 32602-32608 (2005).

doi:10.1074/jbc.M500684200
http://dx.doi.org/10.1074/jbc.M500684200

97. J. M. Adams and S. Cory: Life-or-death decisions by the Bcl-2 protein family. Trends Biochem Sci 26, 61-66 (2001).

doi:10.1016/S0968-0004(00)01740-0
http://dx.doi.org/10.1016/S0968-0004(00)01740-0

98. K. M. Regula and L. A. Kirshenbaum: Apoptosis of ventricular myocytes: a means to an end. J Mol Cell Cardiol 38, 3-13 (2005).

doi:10.1016/j.yjmcc.2004.11.003
http://dx.doi.org/10.1016/j.yjmcc.2004.11.003

99. S. Dhingra, A. K. Sharma, D. K. Singla and P. K. Singal: p38 and ERK 1/2 MAPkinases mediate interplay of TNF- and IL-10 in regulating oxidative stress and cardiac myocyte apoptosis. Am J Physiol Heart Circ Physiol 293, H3524-3531 (2007).

doi:10.1152/ajpheart.00919.2007
http://dx.doi.org/10.1152/ajpheart.00919.2007

100. D. A. Siwik, J. D. Tzortzis, D. R. Pimental, D. L. Chang, P. J. Pagano, K. Singh, D. B. Sawyer and W. S. Colucci: Inhibition of copper-zinc superoxide dismutase induces cell growth, hypertrophic phenotype, and apoptosis in neonatal rat cardiac myocytes in vitro. Circ Res 85, 147-153 (1999).

 

101. M. Saitoh, H. Nishitoh, M. Fujii, K. Takeda, K. Tobiume, Y. Sawada, M. Kawabata, K. Miyazono and H. Ichijo: Mammalian thioredoxin is a direct inhibitor of apoptosis signal-regulating kinase (ASK) 1. EMBO J 17, 2596-2606 (1998).

doi:10.1093/emboj/17.9.2596
http://dx.doi.org/10.1093/emboj/17.9.2596

102. G. L. Gallagher, C. J. Jackson and S. N. Hunyor: Myocardial extracellular matrix remodeling in ischemic heart failure. Front Biosci 12, 1410-1419 (2007).

doi:10.2741/2157
http://dx.doi.org/10.2741/2157

103. A. M. Deschamps and F. G. Spinale: Pathways of matrix metalloproteinase induction in heart failure: bioactive molecules and transcriptional regulation. Cardiovasc Res 69, 666-676 (2006).

doi:10.1016/j.cardiores.2005.10.004
http://dx.doi.org/10.1016/j.cardiores.2005.10.004

104. F. G. Spinale: Matrix metalloproteinases: regulation and dysregulation in the failing heart. Circ Res 90, 520-530 (2002).

doi:10.1161/01.RES.0000013290.12884.A3
http://dx.doi.org/10.1161/01.RES.0000013290.12884.A3

105. P. Sivakumar, S. Gupta, S. Sarkar and S. Sen: Upregulation of lysyl oxidase and MMPs during cardiac remodeling in human dilated cardiomyopathy. Mol Cell Biochem 307, 159-167 (2008).

doi:10.1007/s11010-007-9595-2
http://dx.doi.org/10.1007/s11010-007-9595-2

106. Y. Y. Li, A. M. Feldman, Y. Sun and C. F. McTiernan: Differential expression of tissue inhibitors of metalloproteinases in the failing human heart. Circulation 98, 1728-1734 (1998).

 

107. A. Ducharme, S. Frantz, M. Aikawa, E. Rabkin, M. Lindsey, L. E. Rohde, F. J. Schoen, R. A. Kelly, Z. Werb, P. Libby and R. T. Lee: Targeted deletion of matrix metalloproteinase-9 attenuates left ventricular enlargement and collagen accumulation after experimental myocardial infarction. J Clin Invest 106, 55-62 (2000).

 

108. M. R. Bergman, J. R. Teerlink, R. Mahimkar, L. Li, B. Q. Zhu, A. Nguyen, S. Dahi, J. S. Karliner and D. H. Lovett: Cardiac matrix metalloproteinase-2 expression independently induces marked ventricular remodeling and systolic dysfunction. Am J Physiol Heart Circ Physiol 292, H1847-H1860 (2007).

doi:10.1152/ajpheart.00434.2006
http://dx.doi.org/10.1152/ajpheart.00434.2006

109. T. Fujiwara, T. Matsunaga, K. Kameda, N. Abe, H. Ono, T. Higuma, J. Yokoyama, H. Hanada, T. Osanai and K. Okumura: Nicorandil suppresses the increases in plasma level of matrix metalloproteinase activity and attenuates left ventricular remodeling in patients with acute myocardial infarction. Heart Vessels 22, 303-309 (2007).

doi:10.1007/s00380-007-0975-z
http://dx.doi.org/10.1007/s00380-007-0975-z

110. M. Gheorghiade and R. O. Bonow: Chronic heart failure in the United States: a manifestation of coronary artery disease. Circulation 97, 282-289 (1998).

 

111. R. J. Hajjar, U. Schmidt, P. Helm and J. K. Gwathmey: Ca++ sensitizers impair cardiac relaxation in failing human myocardium. J Pharmacol Exp Ther 280, 247-254 (1997).

 

112. C. E. Murdoch, M. Zhang, A. C. Cave and A. M. Shah: NADPH oxidase-dependent redox signalling in cardiac hypertrophy, remodelling and failure. Cardiovasc Res 71, 208-215 (2006).

doi:10.1016/j.cardiores.2006.03.016
http://dx.doi.org/10.1016/j.cardiores.2006.03.016

113. C. Maack, T. Kartes, H. Kilter, H. J. Schafers, G. Nickenig, M. Bohm and U. Laufs: Oxygen free radical release in human failing myocardium is associated with increased activity of rac1-GTPase and represents a target for statin treatment. Circulation 108, 1567-1574 (2003).

doi:10.1161/01.CIR.0000091084.46500.BB
http://dx.doi.org/10.1161/01.CIR.0000091084.46500.BB

114. C. Nediani, E. Borchi, C. Giordano, S. Baruzzo, V. Ponziani, M. Sebastiani, P. Nassi, A. Mugelli, G. d'Amati and E. Cerbai: NADPH oxidase-dependent redox signaling in human heart failure: relationship between the left and right ventricle. J Mol Cell Cardiol 42, 826-834 (2007).

doi:10.1016/j.yjmcc.2007.01.009
http://dx.doi.org/10.1016/j.yjmcc.2007.01.009

115. F. Qin, M. Simeone and R. Patel: Inhibition of NADPH oxidase reduces myocardial oxidative stress and apoptosis and improves cardiac function in heart failure after myocardial infarction. Free Radic Biol Med 43, 271-281 (2007).

doi:10.1016/j.freeradbiomed.2007.04.021
http://dx.doi.org/10.1016/j.freeradbiomed.2007.04.021

116. J. S. McNally, M. E. Davis, D. P. Giddens, A. Saha, J. Hwang, S. Dikalov, H. Jo and D. G. Harrison: Role of xanthine oxidoreductase and NAD(P)H oxidase in endothelial superoxide production in response to oscillatory shear stress. Am J Physiol Heart Circ Physiol 285, H2290-H2297 (2003).

 

117. Z. Makazan, H. K. Saini and N. S. Dhalla: Role of oxidative stress in alterations of mitochondrial function in ischemic-reperfused hearts. Am J Physiol Heart Circ Physiol 292, H1986-H1994 (2007).

doi:10.1152/ajpheart.01214.2006
http://dx.doi.org/10.1152/ajpheart.01214.2006

118. F. M. Faraci and S. P. Didion: Vascular protection: superoxide dismutase isoforms in the vessel wall. Arterioscler Thromb Vasc Biol 24, 1367-1373 (2004).

doi:10.1161/01.ATV.0000133604.20182.cf
http://dx.doi.org/10.1161/01.ATV.0000133604.20182.cf

119. L. Valenti, D. Conte, A. Piperno, P. Dongiovanni, A. L. Fracanzani, M. Fraquelli, A. Vergani, C. Gianni, L. Carmagnola and S. Fargion: The mitochondrial superoxide dismutase A16V polymorphism in the cardiomyopathy associated with hereditary haemochromatosis. J Med Genet 41, 946-950 (2004).

doi:10.1136/jmg.2004.019588
http://dx.doi.org/10.1136/jmg.2004.019588

120. R. F. Furchgott and J. V. Zawadzki: The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine. Nature 288, 373-376 (1980).

doi:10.1038/288373a0
http://dx.doi.org/10.1038/288373a0

121. F. Murad: Shattuck Lecture. Nitric oxide and cyclic GMP in cell signaling and drug development. N Engl J Med 355, 2003-2011 (2006).

doi:10.1056/NEJMsa063904
http://dx.doi.org/10.1056/NEJMsa063904

122. J. M. Hare: Spatial confinement of isoforms of cardiac nitric-oxide synthase: unravelling the complexities of nitric oxide's cardiobiology. Lancet 363, 1338-1339 (2004).

doi:10.1016/S0140-6736(04)16083-2
http://dx.doi.org/10.1016/S0140-6736(04)16083-2

123. K. Y. Xu, D. L. Huso, T. M. Dawson, D. S. Bredt and L. C. Becker: Nitric oxide synthase in cardiac sarcoplasmic reticulum. Proc Natl Acad Sci U S A 96, 657-662 (1999).

doi:10.1073/pnas.96.2.657
http://dx.doi.org/10.1073/pnas.96.2.657

124. O. Feron, L. Belhassen, L. Kobzik, T. W. Smith, R. A. Kelly and T. Michel: Endothelial nitric oxide synthase targeting to caveolae. Specific interactions with caveolin isoforms in cardiac myocytes and endothelial cells. J Biol Chem 271, 22810-22814 (1996).

doi:10.1074/jbc.271.37.22810
http://dx.doi.org/10.1074/jbc.271.37.22810

125. A. J. Kanai, L. L. Pearce, P. R. Clemens, L. A. Birder, M. M. VanBibber, S. Y. Choi, W. C. de Groat and J. Peterson: Identification of a neuronal nitric oxide synthase in isolated cardiac mitochondria using electrochemical detection. Proc Natl Acad Sci U S A 98, 14126-14131 (2001).

doi:10.1073/pnas.241380298
http://dx.doi.org/10.1073/pnas.241380298

126. T. Damy, P. Ratajczak, A. M. Shah, E. Camors, I. Marty, G. Hasenfuss, F. Marotte, J. L. Samuel and C. Heymes: Increased neuronal nitric oxide synthase-derived NO production in the failing human heart. Lancet 363, 1365-1367 (2004).

doi:10.1016/S0140-6736(04)16048-0
http://dx.doi.org/10.1016/S0140-6736(04)16048-0

127. R. M. Saraiva and J. M. Hare: Nitric oxide signaling in the cardiovascular system: implications for heart failure. Curr Opin Cardiol 21, 221-228 (2006).

doi:10.1097/01.hco.0000221584.56372.dc
http://dx.doi.org/10.1097/01.hco.0000221584.56372.dc

128. J. M. Hare: Nitric oxide and excitation-contraction coupling. J Mol Cell Cardiol 35, 719-729 (2003).

doi:10.1016/S0022-2828(03)00143-3
http://dx.doi.org/10.1016/S0022-2828(03)00143-3

129. L. Xu, J. P. Eu, G. Meissner and J. S. Stamler: Activation of the cardiac calcium release channel (ryanodine receptor) by poly-S-nitrosylation. Science 279, 234-237 (1998).

doi:10.1126/science.279.5348.234
http://dx.doi.org/10.1126/science.279.5348.234

130. J. P. Eu, J. Sun, L. Xu, J. S. Stamler and G. Meissner: The skeletal muscle calcium release channel: coupled O2 sensor and NO signaling functions. Cell 102, 499-509 (2000).

doi:10.1016/S0092-8674(00)00054-4
http://dx.doi.org/10.1016/S0092-8674(00)00054-4

131. D. L. Campbell, J. S. Stamler and H. C. Strauss: Redox modulation of L-type calcium channels in ferret ventricular myocytes. Dual mechanism regulation by nitric oxide and S-nitrosothiols. J Gen Physiol 108, 277-293 (1996).

doi:10.1085/jgp.108.4.277
http://dx.doi.org/10.1085/jgp.108.4.277

132. J. Sun, E. Picht, K. S. Ginsburg, D. M. Bers, C. Steenbergen and E. Murphy: Hypercontractile female hearts exhibit increased S-nitrosylation of the L-type Ca2+ channel alpha1 subunit and reduced ischemia/reperfusion injury. Circ Res 98, 403-411 (2006).

doi:10.1161/01.RES.0000202707.79018.0a
http://dx.doi.org/10.1161/01.RES.0000202707.79018.0a

133. L. A. Barouch, T. P. Cappola, R. W. Harrison, J. K. Crone, E. R. Rodriguez, A. L. Burnett and J. M. Hare: Combined loss of neuronal and endothelial nitric oxide synthase causes premature mortality and age-related hypertrophic cardiac remodeling in mice. J Mol Cell Cardiol 35, 637-644 (2003).

doi:10.1016/S0022-2828(03)00079-8
http://dx.doi.org/10.1016/S0022-2828(03)00079-8

134. T. P. Cappola, L. Cope, A. Cernetich, L. A. Barouch, K. Minhas, R. A. Irizarry, G. Parmigiani, S. Durrani, T. Lavoie, E. P. Hoffman, S. Q. Ye, J. G. Garcia and J. M. Hare: Deficiency of different nitric oxide synthase isoforms activates divergent transcriptional programs in cardiac hypertrophy. Physiol Genomics 14, 25-34 (2003).

 

135. S. J. Kim, J. W. Ju, C. D. Oh, Y. M. Yoon, W. K. Song, J. H. Kim, Y. J. Yoo, O. S. Bang, S. S. Kang and J. S. Chun: ERK-1/2 and p38 kinase oppositely regulate nitric oxide-induced apoptosis of chondrocytes in association with p53, caspase-3, and differentiation status. J Biol Chem 277, 1332-1339 (2002).

doi:10.1074/jbc.M107231200
http://dx.doi.org/10.1074/jbc.M107231200

136. H. M. Lander, A. T. Jacovina, R. J. Davis and J. M. Tauras: Differential activation of mitogen-activated protein kinases by nitric oxide-related species. J Biol Chem 271, 19705-19709 (1996).

doi:10.1074/jbc.271.33.19705
http://dx.doi.org/10.1074/jbc.271.33.19705

137. H. M. Lander, D. P. Hajjar, B. L. Hempstead, U. A. Mirza, B. T. Chait, S. Campbell and L. A. Quilliam: A molecular redox switch on p21(ras). Structural basis for the nitric oxide-p21(ras) interaction. J Biol Chem 272, 4323-4326 (1997).

doi:10.1074/jbc.272.7.4323
http://dx.doi.org/10.1074/jbc.272.7.4323

138. J. Hood and H. J. Granger: Protein kinase G mediates vascular endothelial growth factor-induced Raf-1 activation and proliferation in human endothelial cells. J Biol Chem 273, 23504-23508 (1998).

doi:10.1074/jbc.273.36.23504
http://dx.doi.org/10.1074/jbc.273.36.23504

139. A. Parenti, L. Morbidelli, X. L. Cui, J. G. Douglas, J. D. Hood, H. J. Granger, F. Ledda and M. Ziche: Nitric oxide is an upstream signal of vascular endothelial growth factor-induced extracellular signal-regulated kinase1/2 activation in postcapillary endothelium. J Biol Chem 273, 4220-4226 (1998).

doi:10.1074/jbc.273.7.4220
http://dx.doi.org/10.1074/jbc.273.7.4220

140. C. D. Jun, C. D. Oh, H. J. Kwak, H. O. Pae, J. C. Yoo, B. M. Choi, J. S. Chun, R. K. Park and H. T. Chung: Overexpression of protein kinase C isoforms protects RAW 264.7 macrophages from nitric oxide-induced apoptosis: involvement of c-Jun N-terminal kinase/stress-activated protein kinase, p38 kinase, and CPP-32 protease pathways. J Immunol 162, 3395-3401 (1999).

 

141. K. W. Raines, G. L. Cao, E. K. Lee, G. M. Rosen and P. Shapiro: Neuronal nitric oxide synthase-induced S-nitrosylation of H-Ras inhibits calcium ionophore-mediated extracellular-signal-regulated kinase activity. Biochem J 397, 329-336 (2006).

doi:10.1042/BJ20052002
http://dx.doi.org/10.1042/BJ20052002

142. J. D. Molkentin, J. R. Lu, C. L. Antos, B. Markham, J. Richardson, J. Robbins, S. R. Grant and E. N. Olson: A calcineurin-dependent transcriptional pathway for cardiac hypertrophy. Cell 93, 215-228 (1998).

doi:10.1016/S0092-8674(00)81573-1
http://dx.doi.org/10.1016/S0092-8674(00)81573-1

143. S. J. Li and N. L. Sun: Regulation of intracellular Ca2+ and calcineurin by NO/PKG in proliferation of vascular smooth muscle cells. Acta Pharmacol Sin 26, 323-328 (2005).

doi:10.1111/j.1745-7254.2005.00049.x
http://dx.doi.org/10.1111/j.1745-7254.2005.00049.x

144. B. Fiedler, S. M. Lohmann, A. Smolenski, S. Linnemuller, B. Pieske, F. Schroder, J. D. Molkentin, H. Drexler and K. C. Wollert: Inhibition of calcineurin-NFAT hypertrophy signaling by cGMP-dependent protein kinase type I in cardiac myocytes. Proc Natl Acad Sci U S A 99, 11363-11368 (2002).

doi:10.1073/pnas.162100799
http://dx.doi.org/10.1073/pnas.162100799

145. S. V. Raju, L. A. Barouch and J. M. Hare: Nitric oxide and oxidative stress in cardiovascular aging. Sci Aging Knowledge Environ 2005, re4 (2005).

doi:10.1126/sageke.2005.21.re4
http://dx.doi.org/10.1126/sageke.2005.21.re4

146. H. S. Park, J. W. Yu, J. H. Cho, M. S. Kim, S. H. Huh, K. Ryoo and E. J. Choi: Inhibition of apoptosis signal-regulating kinase 1 by nitric oxide through a thiol redox mechanism. J Biol Chem 279, 7584-7590 (2004).

doi:10.1074/jbc.M304183200
http://dx.doi.org/10.1074/jbc.M304183200

147. T. Yamashita, E. Yamamoto, K. Kataoka, T. Nakamura, S. Matsuba, Y. Tokutomi, Y. F. Dong, H. Ichijo, H. Ogawa and S. Kim-Mitsuyama: Apoptosis signal-regulating kinase-1 is involved in vascular endothelial and cardiac remodeling caused by nitric oxide deficiency. Hypertension 50, 519-524 (2007).

doi:10.1161/HYPERTENSIONAHA.107.092049
http://dx.doi.org/10.1161/HYPERTENSIONAHA.107.092049

148. S. Ghatan, S. Larner, Y. Kinoshita, M. Hetman, L. Patel, Z. Xia, R. J. Youle and R. S. Morrison: p38 MAP kinase mediates bax translocation in nitric oxide-induced apoptosis in neurons. J Cell Biol 150, 335-347 (2000).

doi:10.1083/jcb.150.2.335
http://dx.doi.org/10.1083/jcb.150.2.335

149. D. D. Browning, M. P. McShane, C. Marty and R. D. Ye: Nitric oxide activation of p38 mitogen-activated protein kinase in 293T fibroblasts requires cGMP-dependent protein kinase. J Biol Chem 275, 2811-2816 (2000).

doi:10.1074/jbc.275.4.2811
http://dx.doi.org/10.1074/jbc.275.4.2811

150. O. J. Han, K. H. Joe, S. W. Kim, H. S. Lee, N. S. Kwon, K. J. Baek and H. Y. Yun: Involvement of p38 mitogen-activated protein kinase and apoptosis signal-regulating kinase-1 in nitric oxide-induced cell death in PC12 cells. Neurochem Res 26, 525-532 (2001).

doi:10.1023/A:1010917129951
http://dx.doi.org/10.1023/A:1010917129951

151. H. S. Park, S. H. Huh, M. S. Kim, S. H. Lee and E. J. Choi: Nitric oxide negatively regulates c-Jun N-terminal kinase/stress-activated protein kinase by means of S-nitrosylation. Proc Natl Acad Sci U S A 97, 14382-14387 (2000).

doi:10.1073/pnas.97.26.14382
http://dx.doi.org/10.1073/pnas.97.26.14382

152. D. S. Park, L. Stefanis, C. Y. Yan, S. E. Farinelli and L. A. Greene: Ordering the cell death pathway. Differential effects of BCL2, an interleukin-1-converting enzyme family protease inhibitor, and other survival agents on JNK activation in serum/nerve growth factor-deprived PC12 cells. J Biol Chem 271, 21898-21905 (1996).

doi:10.1074/jbc.271.36.21898
http://dx.doi.org/10.1074/jbc.271.36.21898

153. H. S. So, R. K. Park, M. S. Kim, S. R. Lee, B. H. Jung, S. Y. Chung, C. D. Jun and H. T. Chung: Nitric oxide inhibits c-Jun N-terminal kinase 2 (JNK2) via S-nitrosylation. Biochem Biophys Res Commun 247, 809-813 (1998).

doi:10.1006/bbrc.1998.8788
http://dx.doi.org/10.1006/bbrc.1998.8788

154. M. Trujillo, M. N. Alvarez, G. Peluffo, B. A. Freeman and R. Radi: Xanthine oxidase-mediated decomposition of S-nitrosothiols. J Biol Chem 273, 7828-7834 (1998).

doi:10.1074/jbc.273.14.7828
http://dx.doi.org/10.1074/jbc.273.14.7828

155. H. Li, A. Samouilov, X. Liu and J. L. Zweier: Characterization of the magnitude and kinetics of xanthine oxidase-catalyzed nitrite reduction. Evaluation of its role in nitric oxide generation in anoxic tissues. J Biol Chem 276, 24482-24489 (2001).

doi:10.1074/jbc.M011648200
http://dx.doi.org/10.1074/jbc.M011648200

156. K. Ichimori, M. Fukahori, H. Nakazawa, K. Okamoto and T. Nishino: Inhibition of xanthine oxidase and xanthine dehydrogenase by nitric oxide. Nitric oxide converts reduced xanthine-oxidizing enzymes into the desulfo-type inactive form. J Biol Chem 274, 7763-7768 (1999).

doi:10.1074/jbc.274.12.7763
http://dx.doi.org/10.1074/jbc.274.12.7763

157. P. M. Hassoun, F. S. Yu, J. J. Zulueta, A. C. White and J. J. Lanzillo: Effect of nitric oxide and cell redox status on the regulation of endothelial cell xanthine dehydrogenase. Am J Physiol 268, L809-L817 (1995).

 

158. S. Kinugawa, H. Huang, Z. Wang, P. M. Kaminski, M. S. Wolin and T. H. Hintze: A defect of neuronal nitric oxide synthase increases xanthine oxidase-derived superoxide anion and attenuates the control of myocardial oxygen consumption by nitric oxide derived from endothelial nitric oxide synthase. Circ Res 96, 355-362 (2005).

doi:10.1161/01.RES.0000155331.09458.A7
http://dx.doi.org/10.1161/01.RES.0000155331.09458.A7

159. R. M. Saraiva, K. M. Minhas, S. V. Raju, L. A. Barouch, E. Pitz, K. H. Schuleri, K. Vandegaer, D. Li and J. M. Hare: Deficiency of neuronal nitric oxide synthase increases mortality and cardiac remodeling after myocardial infarction: role of nitroso-redox equilibrium. Circulation 112, 3415-3422 (2005).

doi:10.1161/CIRCULATIONAHA.105.557892
http://dx.doi.org/10.1161/CIRCULATIONAHA.105.557892

160. R. S. Smith, Jr., J. Agata, C. F. Xia, L. Chao and J. Chao: Human endothelial nitric oxide synthase gene delivery protects against cardiac remodeling and reduces oxidative stress after myocardial infarction. Life Sci 76, 2457-2471 (2005).

doi:10.1016/j.lfs.2004.11.028
http://dx.doi.org/10.1016/j.lfs.2004.11.028

161. L. Kalinowski and T. Malinski: Endothelial NADH/NADPH-dependent enzymatic sources of superoxide production: relationship to endothelial dysfunction. Acta Biochim Pol 51, 459-469 (2004).

 

162. J. M. Hare: Nitroso-redox balance in the cardiovascular system. N Engl J Med 351, 2112-2114 (2004).

doi:10.1056/NEJMe048269
http://dx.doi.org/10.1056/NEJMe048269

163. R. Radi, M. Rodriguez, L. Castro and R. Telleri: Inhibition of mitochondrial electron transport by peroxynitrite. Arch Biochem Biophys 308, 89-95 (1994).

doi:10.1006/abbi.1994.1013
http://dx.doi.org/10.1006/abbi.1994.1013

164. S. B. Digerness, K. D. Harris, J. W. Kirklin, F. Urthaler, L. Viera, J. S. Beckman and V. Darley-Usmar: Peroxynitrite irreversibly decreases diastolic and systolic function in cardiac muscle. Free Radic Biol Med 27, 1386-1392 (1999).

doi:10.1016/S0891-5849(99)00184-7
http://dx.doi.org/10.1016/S0891-5849(99)00184-7

165. P. Pacher, J. S. Beckman and L. Liaudet: Nitric oxide and peroxynitrite in health and disease. Physiol Rev 87, 315-424 (2007).

doi:10.1152/physrev.00029.2006
http://dx.doi.org/10.1152/physrev.00029.2006

166. J. N. Cohn, D. G. Archibald, S. Ziesche, J. A. Franciosa, W. E. Harston, F. E. Tristani, W. B. Dunkman, W. Jacobs, G. S. Francis, K. H. Flohr, S. Goldman, F. R. Cobb, P. M. Shah, R. Saunders, R. D. Fletcher, H. S. Loeb, V. C. Hughes and B. Baker: Effect of vasodilator therapy on mortality in chronic congestive heart failure. Results of a Veterans Administration Cooperative Study. N Engl J Med 314, 1547-1552 (1986).

 

167. A. L. Taylor, S. Ziesche, C. Yancy, P. Carson, R. D'Agostino, Jr., K. Ferdinand, M. Taylor, K. Adams, M. Sabolinski, M. Worcel and J. N. Cohn: Combination of isosorbide dinitrate and hydralazine in blacks with heart failure. N Engl J Med 351, 2049-2057 (2004).

doi:10.1056/NEJMoa042934
http://dx.doi.org/10.1056/NEJMoa042934

168. L. J. Ignarro, C. Napoli and J. Loscalzo: Nitric oxide donors and cardiovascular agents modulating the bioactivity of nitric oxide: an overview. Circ Res 90, 21-28 (2002).

doi:10.1161/hh0102.102330
http://dx.doi.org/10.1161/hh0102.102330

169. T. Munzel, S. Kurz, S. Rajagopalan, M. Thoenes, W. R. Berrington, J. A. Thompson, B. A. Freeman and D. G. Harrison: Hydralazine prevents nitroglycerin tolerance by inhibiting activation of a membrane-bound NADH oxidase. A new action for an old drug. J Clin Invest 98, 1465-1470 (1996).

 

170. A. Daiber, M. Oelze, M. Coldewey, K. Kaiser, C. Huth, S. Schildknecht, M. Bachschmid, Y. Nazirisadeh, V. Ullrich, A. Mulsch, T. Munzel and N. Tsilimingas: Hydralazine is a powerful inhibitor of peroxynitrite formation as a possible explanation for its beneficial effects on prognosis in patients with congestive heart failure. Biochem Biophys Res Commun 338, 1865-1874 (2005).

doi:10.1016/j.bbrc.2005.10.106
http://dx.doi.org/10.1016/j.bbrc.2005.10.106

171. B. Hornig, N. Arakawa, C. Kohler and H. Drexler: Vitamin C improves endothelial function of conduit arteries in patients with chronic heart failure. Circulation 97, 363-368 (1998).

 

172. S. H. Kubo, T. S. Rector, A. J. Bank, R. E. Williams and S. M. Heifetz: Endothelium-dependent vasodilation is attenuated in patients with heart failure. Circulation 84, 1589-1596 (1991).

 

173. H. Drexler, D. Hayoz, T. Munzel, B. Hornig, H. Just, H. R. Brunner and R. Zelis: Endothelial function in chronic congestive heart failure. Am J Cardiol 69, 1596-1601 (1992).

doi:10.1016/0002-9149(92)90710-G
http://dx.doi.org/10.1016/0002-9149(92)90710-G

174. S. D. Katz, L. Biasucci, C. Sabba, J. A. Strom, G. Jondeau, M. Galvao, S. Solomon, S. D. Nikolic, R. Forman and T. H. LeJemtel: Impaired endothelium-mediated vasodilation in the peripheral vasculature of patients with congestive heart failure. J Am Coll Cardiol 19, 918-925 (1992).

 

175. S. D. Katz, M. Schwarz, J. Yuen and T. H. LeJemtel: Impaired acetylcholine-mediated vasodilation in patients with congestive heart failure. Role of endothelium-derived vasodilating and vasoconstricting factors. Circulation 88, 55-61 (1993).

 

176. A. Y. Chong, A. D. Blann, J. Patel, B. Freestone, E. Hughes and G. Y. Lip: Endothelial dysfunction and damage in congestive heart failure: relation of flow-mediated dilation to circulating endothelial cells, plasma indexes of endothelial damage, and brain natriuretic peptide. Circulation 110, 1794-1798 (2004).

doi:10.1161/01.CIR.0000143073.60937.50
http://dx.doi.org/10.1161/01.CIR.0000143073.60937.50

177. Y. Ishibashi, T. Shimada, T. Sakane, N. Takahashi, T. Sugamori, S. Ohhata, S. Inoue, H. Katoh, K. Sano, Y. Murakami and M. Hashimoto: Contribution of endogenous nitric oxide to basal vasomotor tone of peripheral vessels and plasma B-type natriuretic peptide levels in patients with congestive heart failure. J Am Coll Cardiol 36, 1605-1611 (2000).

doi:10.1016/S0735-1097(00)00920-7
http://dx.doi.org/10.1016/S0735-1097(00)00920-7

178. W. Doehner, N. Schoene, M. Rauchhaus, F. Leyva-Leon, D. V. Pavitt, D. A. Reaveley, G. Schuler, A. J. Coats, S. D. Anker and R. Hambrecht: Effects of xanthine oxidase inhibition with allopurinol on endothelial function and peripheral blood flow in hyperuricemic patients with chronic heart failure: results from 2 placebo-controlled studies. Circulation 105, 2619-2624 (2002).

doi:10.1161/01.CIR.0000017502.58595.ED
http://dx.doi.org/10.1161/01.CIR.0000017502.58595.ED

179. C. A. Farquharson, R. Butler, A. Hill, J. J. Belch and A. D. Struthers: Allopurinol improves endothelial dysfunction in chronic heart failure. Circulation 106, 221-226 (2002).

doi:10.1161/01.CIR.0000022140.61460.1D
http://dx.doi.org/10.1161/01.CIR.0000022140.61460.1D

180. J. George, E. Carr, J. Davies, J. J. Belch and A. Struthers: High-dose allopurinol improves endothelial function by profoundly reducing vascular oxidative stress and not by lowering uric acid. Circulation 114, 2508-2516 (2006).

doi:10.1161/CIRCULATIONAHA.106.651117
http://dx.doi.org/10.1161/CIRCULATIONAHA.106.651117

181. F. A. Lopez and S. Casado: Heart failure, redox alterations, and endothelial dysfunction. Hypertension 38, 1400-1405 (2001).

doi:10.1161/hy1201.099612
http://dx.doi.org/10.1161/hy1201.099612

182. H. Drexler: Endothelium as a therapeutic target in heart failure. Circulation 98, 2652-2655 (1998).

 

183. K. Tziomalos, V. G. Athyros, A. Karagiannis and D. P. Mikhailidis: Endothelial function, arterial stiffness and lipid lowering drugs. Expert Opin Ther Targets 11, 1143-1160 (2007).

doi:10.1517/14728222.11.9.1143
http://dx.doi.org/10.1517/14728222.11.9.1143

184. K. Arimura, K. Egashira, R. Nakamura, T. Ide, H. Tsutsui, H. Shimokawa and A. Takeshita: Increased inactivation of nitric oxide is involved in coronary endothelial dysfunction in heart failure. Am J Physiol Heart Circ Physiol 280, H68-H75 (2001).

 

185. A. F. van den Heuvel, D. J. van Veldhuisen, E. E. van der Wall, P. K. Blanksma, H. M. Siebelink, W. M. Vaalburg, W. H. van Gilst and H. J. Crijns: Regional myocardial blood flow reserve impairment and metabolic changes suggesting myocardial ischemia in patients with idiopathic dilated cardiomyopathy. J Am Coll Cardiol 35, 19-28 (2000).

doi:10.1016/S0735-1097(99)00499-4
http://dx.doi.org/10.1016/S0735-1097(99)00499-4

186. S. D. Katz, K. Hryniewicz, I. Hriljac, K. Balidemaj, C. Dimayuga, A. Hudaihed and A. Yasskiy: Vascular endothelial dysfunction and mortality risk in patients with chronic heart failure. Circulation 111, 310-314 (2005).

doi:10.1161/01.CIR.0000153349.77489.CF
http://dx.doi.org/10.1161/01.CIR.0000153349.77489.CF

187. T. Heitzer, S. Baldus, Y. von Kodolitsch, V. Rudolph and T. Meinertz: Systemic endothelial dysfunction as an early predictor of adverse outcome in heart failure. Arterioscler Thromb Vasc Biol 25, 1174-1179 (2005).

doi:10.1161/01.ATV.0000166516.52477.81
http://dx.doi.org/10.1161/01.ATV.0000166516.52477.81

188. D. Fischer, S. Rossa, U. Landmesser, S. Spiekermann, N. Engberding, B. Hornig and H. Drexler: Endothelial dysfunction in patients with chronic heart failure is independently associated with increased incidence of hospitalization, cardiac transplantation, or death. Eur Heart J 26, 65-69 (2005).

doi:10.1093/eurheartj/ehi001
http://dx.doi.org/10.1093/eurheartj/ehi001

189. W. S. Waring, D. J. Webb and S. R. Maxwell: Systemic uric acid administration increases serum antioxidant capacity in healthy volunteers. J Cardiovasc Pharmacol 38, 365-371 (2001).

doi:10.1097/00005344-200109000-00005
http://dx.doi.org/10.1097/00005344-200109000-00005

190. H. U. Hink, N. Santanam, S. Dikalov, L. McCann, A. D. Nguyen, S. Parthasarathy, D. G. Harrison and T. Fukai: Peroxidase properties of extracellular superoxide dismutase: role of uric acid in modulating in vivo activity. Arterioscler Thromb Vasc Biol 22, 1402-1408 (2002).

doi:10.1161/01.ATV.0000027524.86752.02
http://dx.doi.org/10.1161/01.ATV.0000027524.86752.02

191. R. J. Johnson, D. H. Kang, D. Feig, S. Kivlighn, J. Kanellis, S. Watanabe, K. R. Tuttle, B. Rodriguez-Iturbe, J. Herrera-Acosta and M. Mazzali: Is there a pathogenetic role for uric acid in hypertension and cardiovascular and renal disease? Hypertension 41, 1183-1190 (2003).

doi:10.1161/01.HYP.0000069700.62727.C5
http://dx.doi.org/10.1161/01.HYP.0000069700.62727.C5

192. B. N. Ames, R. Cathcart, E. Schwiers and P. Hochstein: Uric acid provides an antioxidant defense in humans against oxidant- and radical-caused aging and cancer: a hypothesis. Proc Natl Acad Sci U S A 78, 6858-6862 (1981).

doi:10.1073/pnas.78.11.6858
http://dx.doi.org/10.1073/pnas.78.11.6858

193. M. G. Netea, B. J. Kullberg, W. L. Blok, R. T. Netea and J. W. van der Meer: The role of hyperuricemia in the increased cytokine production after lipopolysaccharide challenge in neutropenic mice. Blood 89, 577-582 (1997).

 

194. J. Kanellis, S. Watanabe, J. H. Li, D. H. Kang, P. Li, T. Nakagawa, A. Wamsley, D. Sheikh-Hamad, H. Y. Lan, L. Feng and R. J. Johnson: Uric acid stimulates monocyte chemoattractant protein-1 production in vascular smooth muscle cells via mitogen-activated protein kinase and cyclooxygenase-2. Hypertension 41, 1287-1293 (2003).

doi:10.1161/01.HYP.0000072820.07472.3B
http://dx.doi.org/10.1161/01.HYP.0000072820.07472.3B

195. D. H. Kang, S. K. Park, I. K. Lee and R. J. Johnson: Uric acid-induced C-reactive protein expression: implication on cell proliferation and nitric oxide production of human vascular cells. J Am Soc Nephrol 16, 3553-3562 (2005).

doi:10.1681/ASN.2005050572
http://dx.doi.org/10.1681/ASN.2005050572

196. M. H. Ginsberg, F. Kozin, M. O'Malley and D. J. McCarty: Release of platelet constituents by monosodium urate crystals. J Clin Invest 60, 999-1007 (1977).

 

197. D. H. Kang, L. Han, X. Ouyang, A. M. Kahn, J. Kanellis, P. Li, L. Feng, T. Nakagawa, S. Watanabe, M. Hosoyamada, H. Endou, M. Lipkowitz, R. Abramson, W. Mu and R. J. Johnson: Uric acid causes vascular smooth muscle cell proliferation by entering cells via a functional urate transporter. Am J Nephrol 25, 425-433 (2005).

doi:10.1159/000087713
http://dx.doi.org/10.1159/000087713

198. G. N. Rao, M. A. Corson and B. C. Berk: Uric acid stimulates vascular smooth muscle cell proliferation by increasing platelet-derived growth factor A-chain expression. J Biol Chem 266, 8604-8608 (1991).

 

199. W. S. Waring, D. J. Webb and S. R. Maxwell: Uric acid as a risk factor for cardiovascular disease. QJM 93, 707-713 (2000).

doi:10.1093/qjmed/93.11.707
http://dx.doi.org/10.1093/qjmed/93.11.707

200. M. J. Bos, P. J. Koudstaal, A. Hofman, J. C. Witteman and M. M. Breteler: Uric acid is a risk factor for myocardial infarction and stroke: the Rotterdam study. Stroke 37, 1503-1507 (2006).

doi:10.1161/01.STR.0000221716.55088.d4
http://dx.doi.org/10.1161/01.STR.0000221716.55088.d4

201. J. Fang and M. H. Alderman: Serum uric acid and cardiovascular mortality the NHANES I epidemiologic follow-up study, 1971-1992. National Health and Nutrition Examination Survey. JAMA 283, 2404-2410 (2000).

doi:10.1001/jama.283.18.2404
http://dx.doi.org/10.1001/jama.283.18.2404

202. L. K. Niskanen, D. E. Laaksonen, K. Nyyssonen, G. Alfthan, H. M. Lakka, T. A. Lakka and J. T. Salonen: Uric acid level as a risk factor for cardiovascular and all-cause mortality in middle-aged men: a prospective cohort study. Arch Intern Med 164, 1546-1551 (2004).

doi:10.1001/archinte.164.14.1546
http://dx.doi.org/10.1001/archinte.164.14.1546

203. V. G. Athyros, M. Elisaf, A. A. Papageorgiou, A. N. Symeonidis, A. N. Pehlivanidis, V. I. Bouloukos, H. J. Milionis and D. P. Mikhailidis: Effect of statins versus untreated dyslipidemia on serum uric acid levels in patients with coronary heart disease: a subgroup analysis of the GREek Atorvastatin and Coronary-heart-disease Evaluation (GREACE) study. Am J Kidney Dis 43, 589-599 (2004).

doi:10.1053/j.ajkd.2003.12.023
http://dx.doi.org/10.1053/j.ajkd.2003.12.023

204. V. G. Athyros, D. P. Mikhailidis, E. N. Liberopoulos, A. I. Kakafika, A. Karagiannis, A. A. Papageorgiou, K. Tziomalos, E. S. Ganotakis and M. Elisaf: Effect of statin treatment on renal function and serum uric acid levels and their relation to vascular events in patients with coronary heart disease and metabolic syndrome: a subgroup analysis of the GREek Atorvastatin and Coronary heart disease Evaluation (GREACE) Study. Nephrol Dial Transplant 22, 118-127 (2007).

doi:10.1093/ndt/gfl538
http://dx.doi.org/10.1093/ndt/gfl538

205. A. Karagiannis, D. P. Mikhailidis, K. Tziomalos, M. Sileli, S. Savvatianos, A. Kakafika, T. Gossios, N. Krikis, I. Moschou, M. Xochellis and V. G. Athyros: Serum uric acid as an independent predictor of early death after acute stroke. Circ J 71, 1120-1127 (2007).

doi:10.1253/circj.71.1120
http://dx.doi.org/10.1253/circj.71.1120

206. F. Leyva, S. Anker, J. W. Swan, I. F. Godsland, C. S. Wingrove, T. P. Chua, J. C. Stevenson and A. J. Coats: Serum uric acid as an index of impaired oxidative metabolism in chronic heart failure. Eur Heart J 18, 858-865 (1997).

 

207. F. Leyva, S. D. Anker, I. F. Godsland, M. Teixeira, P. G. Hellewell, W. J. Kox, P. A. Poole-Wilson and A. J. Coats: Uric acid in chronic heart failure: a marker of chronic inflammation. Eur Heart J 19, 1814-1822 (1998).

doi:10.1053/euhj.1998.1188
http://dx.doi.org/10.1053/euhj.1998.1188

208. M. M. Kittleson, M. E. St John, V. Bead, H. C. Champion, E. K. Kasper, S. D. Russell, I. S. Wittstein and J. M. Hare: Increased levels of uric acid predict haemodynamic compromise in patients with heart failure independently of B-type natriuretic peptide levels. Heart 93, 365-367 (2007).

doi:10.1136/hrt.2006.090845
http://dx.doi.org/10.1136/hrt.2006.090845

209. J. M. Hare and R. J. Johnson: Uric acid predicts clinical outcomes in heart failure: insights regarding the role of xanthine oxidase and uric acid in disease pathophysiology. Circulation 107, 1951-1953 (2003).

doi:10.1161/01.CIR.0000066420.36123.35
http://dx.doi.org/10.1161/01.CIR.0000066420.36123.35

210. W. Doehner, M. Rauchhaus, V. G. Florea, R. Sharma, A. P. Bolger, C. H. Davos, A. J. Coats and S. D. Anker: Uric acid in cachectic and noncachectic patients with chronic heart failure: relationship to leg vascular resistance. Am Heart J 141, 792-799 (2001).

doi:10.1067/mhj.2001.114367
http://dx.doi.org/10.1067/mhj.2001.114367

211. S. D. Anker, F. Leyva, P. A. Poole-Wilson, W. J. Kox, J. C. Stevenson and A. J. Coats: Relation between serum uric acid and lower limb blood flow in patients with chronic heart failure. Heart 78, 39-43 (1997).

 

212. M. Cicoira, L. Zanolla, A. Rossi, G. Golia, L. Franceschini, G. Brighetti, P. Zeni and P. Zardini: Elevated serum uric acid levels are associated with diastolic dysfunction in patients with dilated cardiomyopathy. Am Heart J 143, 1107-1111 (2002).

doi:10.1067/mhj.2002.122122
http://dx.doi.org/10.1067/mhj.2002.122122

213. S. D. Anker, W. Doehner, M. Rauchhaus, R. Sharma, D. Francis, C. Knosalla, C. H. Davos, M. Cicoira, W. Shamim, M. Kemp, R. Segal, K. J. Osterziel, F. Leyva, R. Hetzer, P. Ponikowski and A. J. Coats: Uric acid and survival in chronic heart failure: validation and application in metabolic, functional, and hemodynamic staging. Circulation 107, 1991-1997 (2003).

doi:10.1161/01.CIR.0000065637.10517.A0
http://dx.doi.org/10.1161/01.CIR.0000065637.10517.A0

214. H. Sakai, T. Tsutamoto, T. Tsutsui, T. Tanaka, C. Ishikawa and M. Horie: Serum level of uric acid, partly secreted from the failing heart, is a prognostic marker in patients with congestive heart failure. Circ J 70, 1006-1011 (2006).

doi:10.1253/circj.70.1006
http://dx.doi.org/10.1253/circj.70.1006

215. E. A. Jankowska, B. Ponikowska, J. Majda, R. Zymlinski, M. Trzaska, K. Reczuch, L. Borodulin-Nadzieja, W. Banasiak and P. Ponikowski: Hyperuricaemia predicts poor outcome in patients with mild to moderate chronic heart failure. Int J Cardiol 115, 151-155 (2007).

doi:10.1016/j.ijcard.2005.10.033
http://dx.doi.org/10.1016/j.ijcard.2005.10.033

216. M. M. Kittleson, V. Bead, M. Fradley, M. E. St John, H. C. Champion, E. K. Kasper, S. D. Russell, I. S. Wittstein and J. M. Hare: Elevated uric acid levels predict allograft vasculopathy in cardiac transplant recipients. J Heart Lung Transplant 26, 498-503 (2007).

doi:10.1016/j.healun.2007.01.039
http://dx.doi.org/10.1016/j.healun.2007.01.039

217. A. Hoieggen, M. H. Alderman, S. E. Kjeldsen, S. Julius, R. B. Devereux, U. De Faire, F. Fyhrquist, H. Ibsen, K. Kristianson, O. Lederballe-Pedersen, L. H. Lindholm, M. S. Nieminen, P. Omvik, S. Oparil, H. Wedel, C. Chen and B. Dahlof: The impact of serum uric acid on cardiovascular outcomes in the LIFE study. Kidney Int 65, 1041-1049 (2004).

doi:10.1111/j.1523-1755.2004.00484.x
http://dx.doi.org/10.1111/j.1523-1755.2004.00484.x

218. K. J. Cheung, I. Tzameli, P. Pissios, I. Rovira, O. Gavrilova, T. Ohtsubo, Z. Chen, T. Finkel, J. S. Flier and J. M. Friedman: Xanthine oxidoreductase is a regulator of adipogenesis and PPARgamma activity. Cell Metab 5, 115-128 (2007).

doi:10.1016/j.cmet.2007.01.005
http://dx.doi.org/10.1016/j.cmet.2007.01.005

219. R. M. Evans, G. D. Barish and Y. X. Wang: PPARs and the complex journey to obesity. Nat Med 10, 355-361 (2004).

doi:10.1038/nm1025
http://dx.doi.org/10.1038/nm1025

220. T. Ohtsubo, I. I. Rovira, M. F. Starost, C. Liu and T. Finkel: Xanthine oxidoreductase is an endogenous regulator of cyclooxygenase-2. Circ Res 95, 1118-1124 (2004).

doi:10.1161/01.RES.0000149571.96304.36
http://dx.doi.org/10.1161/01.RES.0000149571.96304.36

221. K. Kalantar-Zadeh, G. Block, T. Horwich and G. C. Fonarow: Reverse epidemiology of conventional cardiovascular risk factors in patients with chronic heart failure. J Am Coll Cardiol 43, 1439-1444 (2004).

doi:10.1016/j.jacc.2003.11.039
http://dx.doi.org/10.1016/j.jacc.2003.11.039

222. A. Yndestad, J. K. Damas, E. Oie, T. Ueland, L. Gullestad and P. Aukrust: Systemic inflammation in heart failure--the whys and wherefores. Heart Fail Rev 11, 83-92 (2006).

doi:10.1007/s10741-006-9196-2
http://dx.doi.org/10.1007/s10741-006-9196-2

223. S. Baldus, K. Mullerleile, P. Chumley, D. Steven, V. Rudolph, G. K. Lund, H. J. Staude, A. Stork, R. Koster, J. Kahler, C. Weiss, T. Munzel, T. Meinertz, B. A. Freeman and T. Heitzer: Inhibition of xanthine oxidase improves myocardial contractility in patients with ischemic cardiomyopathy. Free Radic Biol Med 41, 1282-1288 (2006).

doi:10.1016/j.freeradbiomed.2006.07.010
http://dx.doi.org/10.1016/j.freeradbiomed.2006.07.010

224. A. D. Gavin and A. D. Struthers: Allopurinol reduces B-type natriuretic peptide concentrations and haemoglobin but does not alter exercise capacity in chronic heart failure. Heart 91, 749-753 (2005).

doi:10.1136/hrt.2004.040477
http://dx.doi.org/10.1136/hrt.2004.040477

225. R. Latini, S. Masson, I. Anand, M. Salio, A. Hester, D. Judd, S. Barlera, A. P. Maggioni, G. Tognoni and J. N. Cohn: The comparative prognostic value of plasma neurohormones at baseline in patients with heart failure enrolled in Val-HeFT. Eur Heart J 25, 292-299 (2004).

doi:10.1016/j.ehj.2003.10.030
http://dx.doi.org/10.1016/j.ehj.2003.10.030

226. B. Stanek, B. Frey, M. Hulsmann, R. Berger, B. Sturm, J. Strametz-Juranek, J. Bergler-Klein, P. Moser, A. Bojic, E. Hartter and R. Pacher: Prognostic evaluation of neurohumoral plasma levels before and during beta-blocker therapy in advanced left ventricular dysfunction. J Am Coll Cardiol 38, 436-442 (2001).

doi:10.1016/S0735-1097(01)01383-3
http://dx.doi.org/10.1016/S0735-1097(01)01383-3

227. H. E. Cingolani, J. A. Plastino, E. M. Escudero, B. Mangal, J. Brown and N. G. Perez: The effect of xanthine oxidase inhibition upon ejection fraction in heart failure patients: La Plata Study. J Card Fail 12, 491-498 (2006).

doi:10.1016/j.cardfail.2006.05.005
http://dx.doi.org/10.1016/j.cardfail.2006.05.005

228. R. S. Freudenberger, R. P. Schwarz, Jr., J. Brown, A. Moore, D. Mann, M. M. Givertz, W. S. Colucci and J. M. Hare: Rationale, design and organisation of an efficacy and safety study of oxypurinol added to standard therapy in patients with NYHA class. Expert Opin Investig Drugs 13, 1509-1516 (2004).

doi:10.1517/13543784.13.11.1509
http://dx.doi.org/10.1517/13543784.13.11.1509

229. J. M. Hare, B. Mangal, J. Brown, C. Fisher, R. S. Freudenberger, W. S. Colucci, D. L. Mann, P. Liu, M. M. Givertz and R. P. Schwarz: Impact of Oxypurinol in Patients with Symptomatic Heart failure: Results of the OPT-CHF Study. J Am Coll Cardiol (2008). In press.

 

230. P. Pacher, A. Nivorozhkin and C. Szabo: Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol. Pharmacol Rev 58, 87-114 (2006).

doi:10.1124/pr.58.1.6
http://dx.doi.org/10.1124/pr.58.1.6

231. P. C. Moorhouse, M. Grootveld, B. Halliwell, J. G. Quinlan and J. M. Gutteridge: Allopurinol and oxypurinol are hydroxyl radical scavengers. FEBS Lett 213, 23-28 (1987).

doi:10.1016/0014-5793(87)81458-8
http://dx.doi.org/10.1016/0014-5793(87)81458-8

232. E. E. Kelley, A. Trostchansky, H. Rubbo, B. A. Freeman, R. Radi and M. M. Tarpey: Binding of xanthine oxidase to glycosaminoglycans limits inhibition by oxypurinol. J Biol Chem 279, 37231-37234 (2004).

doi:10.1074/jbc.M402077200
http://dx.doi.org/10.1074/jbc.M402077200

Abbreviations: ANP : atrial natriuretic peptide; aSA : a skeletal muscle isoform of actin; ASK1 : apoptosis signal-regulating kinase 1; ß-MHC : ß-isoform of myosin heavy chain; BNP : brain natriuretic peptide; cGMP : cyclic guanosine monophosphate; CK : creatine kinase; ED : endothelial dysfunction; ERK : extracellular signal-regulated kinases; GTP : guanosine triphosphate; HF : heart failure; HNE : 4-hydroxy-2-nonenal; JNK : c-Jun N-terminal kinases; L-NMMA : NG-monomethyl-L-arginine; LTCC : L-type Ca+2 channels; LV : left ventricular; LVEF : left ventricular ejection fraction; MAPK : mitogen-activated protein kinase; MI : myocardial infarction; MMP : matrix metalloproteinases; NADPH : nicotinamide adenine dinucleotide phosphate; NCX : Na+-Ca+2 transporter; NFAT : nuclear factor of activated T-cells; NO : nitric oxide; NOS : nitric oxide synthase; NOS1 : neuronal nitric oxide synthase; NOS3 : endothelial nitric oxide synthase; PCr : Phosphocreatine; PLB : phospholamban; PPARgamma : peroxisome proliferator-activated receptor gamma; ROS : reactive oxygen species; RYR : ryanodine receptor; SERCA : sarcoplasmic reticulum Ca2+-ATPase; SOD : superoxide dismutase; SR : sarcoplasmic reticulum; SUA : serum uric acid; VEGF : vascular endothelial growth factor; XDH : xanthine dehydrogenase; XO : xanthine oxidase; XOR : xanthine oxidoreductase

Key Words: Xanthine Oxidoreductase, Nitric Oxide, Nitroso-Redox Imbalance, Heart Failure, S-nitrosylation, Review

Send correspondence to: Joshua M. Hare, Clinical Research Building, Room 1124, P.O. Box 019132 (C-205) Miami, FL 33101, Tel: 305-243-1998, Fax: 305-243-1894, E-mail:JHare@med.miami.edu