NADPH oxidase contributes to coronary endothelial dysfunction in the failing heart

Mechanisms and clinical implications of endothelium-dependent vasomotor dysfunction in coronary microvasculature

Coronary microvascular disease (CMD), which affects the arterioles and capillary endothelium that regulate myocardial perfusion, is an increasingly recognized source of morbidity and mortality, particularly in the setting of metabolic syndrome. The coronary endothelium plays a pivotal role in maintaining homeostasis, though factors such as diabetes, hypertension, hyperlipidemia, and obesity can contribute to endothelial injury and consequently arteriolar vasomotor dysfunction. These disturbances in the coronary microvasculature clinically manifest as diminished coronary flow reserve, which is a known independent risk factor for cardiac death, even in the absence of macrovascular atherosclerotic disease. Therefore, a growing body of literature has examined the molecular mechanisms by which coronary microvascular injury occurs at the level of the endothelium and the consequences on arteriolar vasomotor responses. This review will begin with an overview of normal coronary microvascular physiology, modalities of measuring coronary microvascular function, and clinical implications of CMD. These introductory topics will be followed by a discussion of recent advances in the understanding of the mechanisms by which inflammation, oxidative stress, insulin resistance, hyperlipidemia, hypertension, shear stress, endothelial cell senescence, and tissue ischemia dysregulate coronary endothelial homeostasis and arteriolar vasomotor function.

Coronary blood flow in heart failure: cause, consequence and bystander

Heart failure is a clinical syndrome where cardiac output is not sufficient to sustain adequate perfusion and normal bodily functions, initially during exercise and in more severe forms also at rest. The two most frequent forms are heart failure of ischemic origin and of non-ischemic origin. In heart failure of ischemic origin, reduced coronary blood flow is causal to cardiac contractile dysfunction, and this is true for stunned and hibernating myocardium, coronary microembolization, myocardial infarction and post-infarct remodeling, possibly also for the takotsubo syndrome. The most frequent form of non-ischemic heart failure is dilated cardiomyopathy, caused by genetic mutations, myocarditis, toxic agents or sustained tachyarrhythmias, where alterations in coronary blood flow result from and contribute to cardiac contractile dysfunction. Hypertrophic cardiomyopathy is caused by genetic mutations but can also result from increased pressure and volume overload (hypertension, valve disease). Heart failure with preserved ejection fraction is characterized by pronounced coronary microvascular dysfunction, the causal contribution of which is however not clear. The present review characterizes the alterations of coronary blood flow which are causes or consequences of heart failure in its different manifestations. Apart from any potentially accompanying coronary atherosclerosis, all heart failure entities share common features of impaired coronary blood flow, but to a different extent: enhanced extravascular compression, impaired nitric oxide-mediated, endothelium-dependent vasodilation and enhanced vasoconstriction to mediators of neurohumoral activation. Impaired coronary blood flow contributes to the progression of heart failure and is thus a valid target for established and novel treatment regimens.

Nutraceutical, Dietary, and Lifestyle Options for Prevention and Treatment of Ventricular Hypertrophy and Heart Failure

Although well documented drug therapies are available for the management of ventricular hypertrophy (VH) and heart failure (HF), most patients nonetheless experience a downhill course, and further therapeutic measures are needed. Nutraceutical, dietary, and lifestyle measures may have particular merit in this regard, as they are currently available, relatively safe and inexpensive, and can lend themselves to primary prevention as well. A consideration of the pathogenic mechanisms underlying the VH/HF syndrome suggests that measures which control oxidative and endoplasmic reticulum (ER) stress, that support effective nitric oxide and hydrogen sulfide bioactivity, that prevent a reduction in cardiomyocyte pH, and that boost the production of protective hormones, such as fibroblast growth factor 21 (FGF21), while suppressing fibroblast growth factor 23 (FGF23) and marinobufagenin, may have utility for preventing and controlling this syndrome. Agents considered in this essay include phycocyanobilin, N-acetylcysteine, lipoic acid, ferulic acid, zinc, selenium, ubiquinol, astaxanthin, melatonin, tauroursodeoxycholic acid, berberine, citrulline, high-dose folate, cocoa flavanols, hawthorn extract, dietary nitrate, high-dose biotin, soy isoflavones, taurine, carnitine, magnesium orotate, EPA-rich fish oil, glycine, and copper. The potential advantages of whole-food plant-based diets, moderation in salt intake, avoidance of phosphate additives, and regular exercise training and sauna sessions are also discussed. There should be considerable scope for the development of functional foods and supplements which make it more convenient and affordable for patients to consume complementary combinations of the agents discussed here. Research Strategy: Key word searching of PubMed was employed to locate the research papers whose findings are cited in this essay.

Use of Dithiothreitol Assay to Evaluate the Oxidative Potential of Atmospheric Aerosols

Oxidative potential (OP) has been proposed as a useful descriptor for the ability of particulate matter (PM) to generate reactive oxygen species (ROS) and consequently induce oxidative stress in biological systems, which has been recognized as one of the most important mechanisms responsible for PM toxicity. The dithiothreitol (DTT) assay is one of the most frequently used techniques to quantify OP because it is low-cost, easy-to-operate, and has high repeatability. With two thiol groups, DTT has been used as a surrogate of biological sulfurs that can be oxidized when exposed to ROS. Within the DTT measurement matrix, OP is defined as the DTT consumption rate. Often, the DTT consumption can be attributed to the presence of transition metals and quinones in PM as they can catalyze the oxidation of DTT through catalytic redox reactions. However, the DTT consumption by non-catalytic PM components has not been fully investigated. In addition, weak correlations between DTT consumption, ROS generation, and cellular responses have been observed in several studies, which also reveal the knowledge gaps between DTT-based OP measurements and their implication on health effects. In this review, we critically assessed the current challenges and limitations of DTT measurement, highlighted the understudied DTT consumption mechanisms, elaborated the necessity to understand both PM-bound and PM-induced ROS, and concluded with research needs to bridge the existing knowledge gaps.

Isolevuglandin scavenger attenuates pressure overload-induced cardiac oxidative stress, cardiac hypertrophy, heart failure and lung remodeling

Increased levels of reactive isolevuglandins (IsoLGs) are associated with vascular inflammation and hypertension, two important factors affect heart failure (HF) development. The role of IsoLGs in HF development is unknown. Here we studied the role of IsoLG scavenger 2-hydroxybenzylamine (2-HOBA) in transverse aortic constriction (TAC) induced heart failure. We observed that TAC caused a significant increase of IsoLG protein adducts in cardiac and lung tissues in mice. Both IsoLG scavenger 2-hydroxybenzylamine (2-HOBA) and its less reactive isomer 4-hydroxybenzylamine (4-HOBA) significantly attenuated the left ventricular (LV) and lung IsoLGs in mice after TAC. 2-HOBA and 4-HOBA attenuated TAC-induced LV hypertrophy, heart failure, and the increase of lung weight in mice, and also improved TAC-induced LV dysfunction. Moreover, both 2-HOBA and 4-HOBA effectively attenuated LV cardiomyocyte hypertrophy, lung inflammation, lung fibrosis. These findings suggest that methods to reduce IsoLGs may be useful for HF therapy.

Carnosine protects cardiac myocytes against lipid peroxidation products

Endogenous histidyl dipeptides such as carnosine (β-alanine-L-histidine) form conjugates with lipid peroxidation products such as 4-hydroxy-trans-2-nonenal (HNE and acrolein), chelate metals, and protect against myocardial ischemic injury. Nevertheless, it is unclear whether these peptides protect against cardiac injury by directly reacting with lipid peroxidation products. Hence, to examine whether changes in the structure of carnosine could affect its aldehyde reactivity and metal chelating ability, we synthesized methylated analogs of carnosine, balenine (β-alanine-N^τ-methylhistidine) and dimethyl balenine (DMB), and measured their aldehyde reactivity and metal chelating properties. We found that methylation of N^τ residue of imidazole ring (balenine) or trimethylation of carnosine backbone at N^τ residue of imidazole ring and terminal amine group dimethyl balenine (DMB) abolishes the ability of these peptides to react with HNE. Incubation of balenine with acrolein resulted in the formation of single product (m/z 297), whereas DMB did not react with acrolein. In comparison with carnosine, balenine exhibited moderate acrolein quenching capacity. The Fe²⁺ chelating ability of balenine was higher than that of carnosine, whereas DMB lacked chelating capacity. Pretreatment of cardiac myocytes with carnosine increased the mean lifetime of myocytes superfused with HNE or acrolein compared with balenine or DMB. Collectively, these results suggest that carnosine protects cardiac myocytes against HNE and acrolein toxicity by directly reacting with these aldehydes. This reaction involves both the amino group of β-alanyl residue and the imidazole residue of L-histidine. Methylation of these sites prevents or abolishes the aldehyde reactivity of carnosine, alters its metal-chelating property, and diminishes its ability to prevent electrophilic injury.

Myocardial metabolism in diabetic cardiomyopathy: potential therapeutic targets

SIGNIFICANCE

Cardiovascular complications in diabetes are particularly serious and represent the primary cause of morbidity and mortality in diabetic patients. Despite early observations of cardiac dysfunction in diabetic humans, cardiomyopathy unique to diabetes has only recently been recognized.

RECENT ADVANCES

Research has focused on understanding the pathogenic mechanisms underlying the initiation and development of diabetic cardiomyopathy. Emerging data highlight the importance of altered mitochondrial function as a major contributor to cardiac dysfunction in diabetes. Mitochondrial dysfunction occurs by several mechanisms involving altered cardiac substrate metabolism, lipotoxicity, impaired cardiac insulin and glucose homeostasis, impaired cellular and mitochondrial calcium handling, oxidative stress, and mitochondrial uncoupling.

CRITICAL ISSUES

Currently, treatment is not specifically tailored for diabetic patients with cardiac dysfunction. Given the multifactorial development and progression of diabetic cardiomyopathy, traditional treatments such as anti-diabetic agents, as well as cellular and mitochondrial fatty acid uptake inhibitors aimed at shifting the balance of cardiac metabolism from utilizing fat to glucose may not adequately target all aspects of this condition. Thus, an alternative treatment such as resveratrol, which targets multiple facets of diabetes, may represent a safe and promising supplement to currently recommended clinical therapy and lifestyle changes.

FUTURE DIRECTIONS

Elucidation of the mechanisms underlying the initiation and progression of diabetic cardiomyopathy is essential for development of effective and targeted treatment strategies. Of particular interest is the investigation of alternative therapies such as resveratrol, which can function as both preventative and mitigating agents in the management of diabetic cardiomyopathy.

What can we learn about treating heart failure from the heart's response to acute exercise? Focus on the coronary microcirculation

Coronary microvascular function and cardiac function are closely related in that proper cardiac function requires adequate oxygen delivery through the coronary microvasculature. Because of the close proximity of cardiomyocytes and coronary microvascular endothelium, cardiomyocytes not only communicate their metabolic needs to the coronary microvasculature, but endothelium-derived factors also directly modulate cardiac function. This review summarizes evidence that the myocardial oxygen balance is disturbed in the failing heart because of increased extravascular compressive forces and coronary microvascular dysfunction. The perturbations in myocardial oxygen balance are exaggerated during exercise and are due to alterations in neurohumoral influences, endothelial function, and oxidative stress. Although there is some evidence from animal studies that the myocardial oxygen balance can partly be restored by exercise training, it is largely unknown to what extent the beneficial effects of exercise training include improvements in endothelial function and/or oxidative stress in the coronary microvasculature and how these improvements are impacted by risk factors such as diabetes, obesity, and hypercholesterolemia.

CPUY11018, an azimilide derivative, ameliorates isoproterenol-induced cardiac insufficiency through relieving dysfunctional mitochondria and endoplasmic reticulum

Objectives

Deterioration of cardiac performance under stress may be partly mediated by dysfunctional mitochondria and endoplasmic reticulum (ER) that is likely related to an activation of NADPH oxidase (NOX) and an increase in pro-inflammatory factors. We investigated if a new compound CPUY11018 (CPUY) derived from Azimilide could ameliorate the stress impaired cardiac performance.

Methods

Forty-eight male Sprague Dawley rats were randomly divided into six groups and were injected with isoproterenol (ISO, 1 ml/kg, s.c.) for 10 days. Cardiac myocytes and fibroblasts from neonate rats were incubated with ISO. CPUY was employed and compared with apocynin (APO) – an inhibitor of NOX.

Key findings

In ISO-treated group, the compromised haemodynamics and cardiac remodelling were significant with dysfunctional mitochondria indicated by decreased MnSOD and mitochondrial membrane potential, and an enhanced reactive oxygen species genesis. Downregulation of FKBP12.6, CASQ2 and SERCA2a was also remarkable in vivo and in vitro implying an abnormal ER. Upregulated Nox4, p22phox and p47phox were significant, associated with upregulation of Src, IκBβ and NFκB, and downregulation of pAMPK/AMPK and Cx40 in vivo and in vitro. These abnormalities were relieved by CPUY and APO.

Conclusions

CPUY is potential in managing cardiac insufficiency through normalizing mitochondria and ER in the affected heart.

Cardioprotective effects of melatonin against myocardial injuries induced by chronic intermittent hypoxia in rats

Obstructive sleep apnea (OSA) associated with chronic intermittent hypoxia (CIH) increases the morbidity and mortality of ischemic heart disease in patients. Yet, there is a paucity of preventive measures targeting the pathogenesis of CIH-induced myocardial injury. We examined the cardioprotective effect of melatonin against the inflammation, fibrosis and the deteriorated sarcoplasmic reticulum (SR) Ca(2+) homeostasis, and ischemia/reperfusion (I/R)-induced injury exacerbated by CIH. Adult male Sprague Dawley rats that had received a daily injection of melatonin (10 mg/kg) or vehicle were exposed to CIH treatment mimicking a severe OSA condition for 4 wk. Systolic pressure, heart weights, and malondialdehyde were significantly increased in hypoxic rats but not in the melatonin-treated group, when compared with the normoxic control. Levels of the expression of inflammatory cytokines (TNF-α, IL-6, and COX-2) and fibrotic markers (PC1 and TGF-β) were significantly elevated in the hypoxic group but were normalized by melatonin. Additionally, infarct size of isolated hearts with regional I/R was substantial in the hypoxic group treated with vehicle but not in the melatonin-treated group. Moreover, melatonin treatment mitigated the SR-Ca(2+) homeostasis in the cardiomyocyte during I/R with (i) Ca(2+) overloading, (ii) decreased SR-Ca(2+) content, (iii) lowered expression and activity of Ca(2+) -handling proteins (SERCA2a and NCX1),and (iv) decreased expressions of CAMKII and phosphorylated eNOS(ser1177). Furthermore, melatonin ameliorated the level of expression of antioxidant enzymes (CAT and MnSOD) and NADPH oxidase (p22 and NOX2). Results support a prophylactic usage of melatonin in OSA patients, which protects against CIH-induced myocardial inflammation and fibrosis with impaired SR-Ca(2+) handling and exacerbated I/R injury.

Agonistic antibody to angiotensin II type 1 receptor accelerates atherosclerosis in ApoE-/- mice

This study aimed to investigate the effects of agonistic antibody to angiotensin II type 1 receptor (AT1-AA) on atherosclerosis in male ApoE-/- mice which were employed to establish the animal models of AT1-AA in two ways. In the first group, mice were injected subcutaneously with conjugated AT1 peptide at multiple sites; in the second group, mice were infused with AT1-AA prepared from rabbits that were treated with AT1 peptide intraperitoneally. Mice in each group were further randomly divided into five subgroups and treated with AT1 peptide/AT1-AA, AT1 peptide/AT1-AA plus valsartan, AT1 peptide/AT1-AA plus fenofibrate, AT1 peptide/ AT1-AA plus pyrrolidine dithiocarbamate (PDTC) and control vehicle, respectively. Antibodies were detected in mice (except for mice in control group). Aortic atherosclerotic lesions were assessed by oil red O staining, while plasma CRP, TNF-α, nuclear factor-kappa B (NF-κB) and H2O2 were determined by ELISA. CCR2 (the receptor of MCP-1), macrophages, and smooth muscle cells were detected by immunohistochemistry. P47phox, MCP-1 and eNOS were detected by RT-PCR, while P47phox, NF-κB and MCP-1 were detected by Western blot assay. The aortic atherosclerotic lesions were significantly increased in AT1 peptide/AT1-AA treated mice, along with simultaneous increases in inflammatory parameters. However, mice treated with valsartan, fenofibrate or PDTC showed alleviated progression of atherosclerosis and reductions in inflammatory parameters. Thus, AT1-AA may accelerate aortic atherosclerosis in ApoE-/- mice, which is mediated, at least in part, by the inflammatory reaction involving nicotinamide-adenine dinucleotide phosphate oxidase, reactive oxygen species, and NF-κB. In addition, valsartan, fenofibrate and PDTC may inhibit the AT1-AA induced atherosclerosis.

Diabetic cardiomyopathy: mechanisms and new treatment strategies targeting antioxidant signaling pathways

Cardiovascular disease is the primary cause of morbidity and mortality among the diabetic population. Both experimental and clinical evidence suggest that diabetic subjects are predisposed to a distinct cardiomyopathy, independent of concomitant macro- and microvascular disorders. 'Diabetic cardiomyopathy' is characterized by early impairments in diastolic function, accompanied by the development of cardiomyocyte hypertrophy, myocardial fibrosis and cardiomyocyte apoptosis. The pathophysiology underlying diabetes-induced cardiac damage is complex and multifactorial, with elevated oxidative stress as a key contributor. We now review the current evidence of molecular disturbances present in the diabetic heart, and their role in the development of diabetes-induced impairments in myocardial function and structure. Our focus incorporates both the contribution of increased reactive oxygen species production and reduced antioxidant defenses to diabetic cardiomyopathy, together with modulation of protein signaling pathways and the emerging role of protein O-GlcNAcylation and miRNA dysregulation in the progression of diabetic heart disease. Lastly, we discuss both conventional and novel therapeutic approaches for the treatment of left ventricular dysfunction in diabetic patients, from inhibition of the renin-angiotensin-aldosterone-system, through recent evidence favoring supplementation of endogenous antioxidants for the treatment of diabetic cardiomyopathy. Novel therapeutic strategies, such as gene therapy targeting the phosphoinositide 3-kinase PI3K(p110α) signaling pathway, and miRNA dysregulation, are also reviewed. Targeting redox stress and protective protein signaling pathways may represent a future strategy for combating the ever-increasing incidence of heart failure in the diabetic population.

The TNF-α/sphingosine-1-phosphate signaling axis drives myogenic responsiveness in heart failure

Heart failure (HF) is hallmarked by an increase in total peripheral resistance (TPR) that compensates for the drop in cardiac output. While initially allowing for the maintenance of mean arterial pressure at acceptable levels, the long-term upregulation of TPR is prone to compromise cardiac performance and tissue perfusion, and to ultimately accelerate disease progression. Augmented vasoconstriction of terminal arteries, the site of TPR regulation, is cooperatively driven by mechanisms such as: (i) endothelial dysfunction, (ii) increased sympathetic activity and (iii) enhanced pressure-induced myogenic responsiveness. Herein, we review emerging evidence that the increase in myogenic responsiveness is central to the long-term elevation of TPR in HF. On a molecular level, this augmented intrinsic response is governed by an activation of the tumor necrosis factor-α (TNF-α)/sphingosine-1-phosphate signaling axis in microvascular smooth muscle cells. The beneficial effect of TNF-α scavenging strategies on tissue perfusion in HF mouse models adds to the gaining momentum to revisit the use of anti-TNF-α treatment modalities in discrete HF patient populations.

Cardiac inflammation after local irradiation is influenced by the kallikrein-kinin system

Radiotherapy of intrathoracic and chest wall tumors may lead to exposure of the heart to ionizing radiation, resulting in radiation-induced heart diseases (RIHD). The main manifestations of RIHD become apparent many years after treatment and include cardiomyopathy and accelerated atherosclerosis. This study examines the role of the kallikrein-kinin system (KKS) in RIHD by investigating the cardiac radiation response in a kininogen-deficient Brown Norway Katholiek (BN/Ka) rat model. BN/Ka rats and wild-type Brown Norway (BN) rats were exposed to local heart irradiation with a single dose of 18 Gy or 24 Gy and were observed for 3 to 6 months. Examinations included in vivo and ex vivo cardiac function, histopathology, gene and protein expression measurements, and mitochondrial swelling assays. Upon local heart irradiation, changes in in vivo cardiac function were significantly less in BN/Ka rats. For instance, a single dose of 24 Gy caused a 35% increase in fractional shortening in BN rats compared with a 16% increase in BN/Ka rats. BN rats, but not BN/Ka rats, showed a 56% reduction in cardiac numbers of CD2-positive cells, and a 57% increase in CD68-positive cells, together with a 52% increase in phosphorylation of extracellular signal-regulated kinase 1/2 (Erk1/2). Local heart irradiation had similar effects on histopathology, mitochondrial changes, and left ventricular mRNA levels of NADPH oxidases in the two genotypes. These results suggest that the KKS plays a role in the effects of radiation on cardiac function and recruitment of inflammatory cells. The KKS may have these effects at least in part by altering Erk1/2 signaling.

Increased NADPH oxidase-derived superoxide is involved in the neuronal cell death induced by hypoxia-ischemia in neonatal hippocampal slice cultures

Neonatal brain hypoxia-ischemia (HI) results in neuronal cell death. Previous studies indicate that reactive oxygen species, such as superoxide, play a key role in this process. However, the cellular sources have not been established. In this study we examine the role of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex in neonatal HI brain injury and elucidate its mechanism of activation. Rat hippocampal slices were exposed to oxygen glucose deprivation (OGD) to mimic the conditions seen in HI. Initial studies confirmed an important role for NADPH oxidase-derived superoxide in the oxidative stress associated with OGD. Further, the OGD-mediated increase in apoptotic cell death was inhibited by the NADPH oxidase inhibitor apocynin. The activation of NADPH oxidase was found to be dependent on the p38 mitogen-activated protein kinase-mediated phosphorylation and activation of the p47(phox) subunit. Using an adeno-associated virus antisense construct to selectively decrease p47(phox) expression in neurons showed that this led to inhibition of both the increase in superoxide and the neuronal cell death associated with OGD. We also found that NADPH oxidase inhibition in a neonatal rat model of HI or scavenging hydrogen peroxide reduced brain injury. Thus, we conclude that activation of the NADPH oxidase complex contributes to the oxidative stress during HI and that therapies targeted against this complex could provide neuroprotection against the brain injury associated with neonatal HI.

Family-based association studies for next-generation sequencing

An individual's disease risk is determined by the compounded action of both common variants, inherited from remote ancestors, that segregated within the population and rare variants, inherited from recent ancestors, that segregated mainly within pedigrees. Next-generation sequencing (NGS) technologies generate high-dimensional data that allow a nearly complete evaluation of genetic variation. Despite their promise, NGS technologies also suffer from remarkable limitations: high error rates, enrichment of rare variants, and a large proportion of missing values, as well as the fact that most current analytical methods are designed for population-based association studies. To meet the analytical challenges raised by NGS, we propose a general framework for sequence-based association studies that can use various types of family and unrelated-individual data sampled from any population structure and a universal procedure that can transform any population-based association test statistic for use in family-based association tests. We develop family-based functional principal-component analysis (FPCA) with or without smoothing, a generalized T(2), combined multivariate and collapsing (CMC) method, and single-marker association test statistics. Through intensive simulations, we demonstrate that the family-based smoothed FPCA (SFPCA) has the correct type I error rates and much more power to detect association of (1) common variants, (2) rare variants, (3) both common and rare variants, and (4) variants with opposite directions of effect from other population-based or family-based association analysis methods. The proposed statistics are applied to two data sets with pedigree structures. The results show that the smoothed FPCA has a much smaller p value than other statistics.

Nitroso-redox balance in control of coronary vasomotor tone

Reactive oxygen species (ROS) are essential in vascular homeostasis but may contribute to vascular dysfunction when excessively produced. Superoxide anion (O(2)(·-)) can directly affect vascular tone by reacting with K(+) channels and indirectly by reacting with nitric oxide (NO), thereby scavenging NO and causing nitroso-redox imbalance. After myocardial infarction (MI), oxidative stress increases, favoring the imbalance and resulting in coronary vasoconstriction. Consequently, we hypothesized that ROS scavenging results in coronary vasodilation, particularly after MI, and is enhanced after inhibition of NO production. Chronically instrumented swine were studied at rest and during exercise before and after scavenging of ROS with N-(2-mercaptoproprionyl)-glycine (MPG, 20 mg/kg iv) in the presence or absence of prior inhibition of endothelial NO synthase (eNOS) with N(ω)-nitro-L-arginine (L-NNA, 20 mg/kg iv). In normal swine, MPG resulted in coronary vasodilation as evidenced by an increased coronary venous O(2) tension, and trends toward increased coronary venous O(2) saturation and decreased myocardial O(2) extraction. These effects were not altered by prior inhibition of eNOS. In MI swine, MPG showed a significant vasodilator effect, which surprisingly was abolished by prior inhibition of eNOS. Moreover, eNOS dimer/monomer ratio was decreased after MI, reflecting eNOS uncoupling. In conclusion, ROS exert a small coronary vasoconstrictor influence in normal swine, which does not involve scavenging of NO. This vasoconstrictor influence of ROS is slightly enhanced after MI. Since inhibition of eNOS abolished rather than augmented the vasoconstrictor influence of ROS in swine with MI, while eNOS dimer/monomer ratio was decreased, our data imply that uncoupled eNOS may be a significant source of O(2)(·-) after MI.

NADPH oxidase-dependent oxidative stress in the failing heart: From pathogenic roles to therapeutic approach

Heart failure (HF) occurs when the adaptation mechanisms of the heart fail to compensate for stress factors, such as pressure overload, myocardial infarction, inflammation, diabetes, and cardiotoxic drugs, with subsequent ventricular hypertrophy, fibrosis, myocardial dysfunction, and chamber dilatation. Oxidative stress, defined as an imbalance between reactive oxygen species (ROS) generation and the capacity of antioxidant defense systems, has been authenticated as a pivotal player in the cardiopathogenesis of the various HF subtypes. The family of NADPH oxidases has been investigated as a key enzymatic source of ROS in the pathogenesis of HF. In this review, we discuss the importance of NADPH oxidase-dependent ROS generation in the various subtypes of HF and its implications. A better understanding of the pathogenic roles of NADPH oxidases in the failing heart is likely to provide novel therapeutic strategies for the prevention and treatment of HF.

β-Adrenergic receptors desensitization is not involved in exercise-induced cardiac fatigue: NADPH oxidase-induced oxidative stress as a new trigger

Prolonged strenuous exercise (PSE) induces transient left ventricular (LV) dysfunction. Previous studies suggest that β-adrenergic pathway desensitization could be involved in this phenomenon, but it remains to be confirmed. Moreover, other underlying mechanisms involving oxidative stress have been recently proposed. The present study aimed to evaluate the involvement of both the β-adrenergic pathway and NADPH oxidase (Nox) enzyme-induced oxidative stress in myocardial dysfunction in rats following PSE. Rats were divided into 4 groups: controls (Ctrl), 4-h exercised on treadmill (PSE), and 2 groups in which Nox enzyme was inhibited with apocynin treatment (Ctrl APO and PSE APO, respectively). We evaluated cardiac function in vivo and ex vivo during basal conditions and isoproterenol stress. GSH/GSSG ratio, cardiac troponin I (cTnI) release, and lipid peroxidation (MDA) were evaluated. PSE induced a decrease in LV developed pressure, intrinsic myocardial contractility, and relaxation associated with an increase in plasma cTnI release. Our in vivo and ex vivo results demonstrated no differences in myocardial response to isoproterenol and of effective dose 50 between control and PSE rats. Interestingly, the LV dysfunction was reversed by apocynin treatment. Moreover, apocynin prevented cellular oxidation [GSH/GSSG ratio: PSE APO rats vs. PSE rats in arbitrary units (au): 1.98 ± 0.07 vs. 1.35 ± 0.10; P < 0.001]. However, no differences in MDA were observed between groups. These data suggest that myocardial dysfunction observed after PSE was not due to β-adrenergic receptor desensitization but could be due to a signaling oxidative stress from the Nox enzyme.

Cystatin C levels are associated with the prognosis of systolic heart failure patients

BACKGROUND

Cystatin C, which has long been regarded as a biomarker that indicates kidney functions, has recently been recognized as an inflammatory marker in the human body.

AIM

To elucidate how cystatin C is related to the prognosis of systolic heart failure patients.

METHODS

Patients with systolic heart failure who were admitted to the fourth affiliated hospital of Harbin Medical University between January and April 2008 were enrolled in this study. Serum homocysteine, high-sensitivity C-reactive protein (hs-CRP) and cystatin C levels were determined and all the patients received an average of 2 years of follow-up for occurrence of death, heart transplantation or readmission with worsening heart failure.

RESULTS

Of 138 patients enrolled, those who experienced adverse outcomes (e.g. cardiac death, heart transplantation or progressive heart failure) (n = 21) had considerably higher mean levels of serum homocysteine (28.6 ± 13.4 vs 14.4 ± 6.3mg/L; P < 0.01), hs-CRP (17.5 ± 14.1 vs 6.4 ± 7.7 μmol/L; p < 0.01) and cystatin C (1.63 ± 0.81 vs 0.91 ± 0.27 mg/L; P < 0.01) than those without adverse outcomes (n = 117). Furthermore, the Cox proportional hazards model demonstrated that serum homocysteine, hs-CRP and cystatin C are all independent predictors of adverse outcomes.

CONCLUSIONS

Cystatin C, together with hs-CRP and homocysteine, is an independent risk factor that is important in the prognosis of patients with systolic heart failure.

Medroxyprogesterone acetate aggravates oxidative stress and left ventricular dysfunction in rats with chronic myocardial infarction

The role of estrogens during myocardial ischemia has been extensively studied. However, effects of a standard hormone replacement therapy including 17β-estradiol (E2) combined with medroxyprogesterone acetate (MPA) have not been assessed, and this combination could have contributed to the negative outcomes of the clinical studies on hormone replacement. We hypothesized that adding MPA to an E2 treatment would aggravate chronic heart failure after experimental myocardial infarction (MI). To address this issue, we evaluated clinical signs of heart failure as well as left ventricular (LV) dysfunction and remodeling in ovariectomized rats subjected to chronic MI receiving E2 or E2 plus MPA. After eight weeks MI E2 showed no effects. Adding MPA to E2 aggravated LV remodeling and dysfunction as judged by increased heart weight, elevated myocyte cross-sectional areas, increased elevated left ventricle end diastolic pressure, and decreased LV fractional shortening. Impaired LV function in rats receiving MPA plus E2 was associated with increased cardiac reactive oxygen species generation and myocardial expression levels of NADPH oxidase subunits. These results support the interpretation that adding MPA to an E2 treatment complicates cardiovascular injury damage post-MI and therefore contributes to explain the adverse outcome of prospective clinical studies.

Predictors of oxidative stress in heart failure patients with Cheyne-Stokes respiration

PURPOSE

Cheyne-Stokes respiration during sleep is associated with increased mortality in heart failure. The magnitude of oxidative stress is a marker of disease severity and a valuable predictor of mortality in heart failure. Increased oxidative stress associated with periodic breathing during Cheyne-Stokes respiration may mediate increased mortality in these patients. We hypothesized that the presence of Cheyne-Stokes respiration is associated with oxidative stress by increasing the formation of reactive oxygen species in patients with heart failure.

METHODS AND RESULTS

Twenty-three patients with heart failure [left ventricular ejection fraction 30.2 ± 9% (mean ± standard deviation)] and 11 healthy controls underwent nocturnal polysomnography. Subjects with obstructive sleep apnea were excluded. The majority (88%) of patients with heart failure had Cheyne-Stokes respiration during sleep. The intensity of oxidative stress in neutrophils was greater in patients with heart failure (4,218 ± 1,706 mean fluorescence intensity/cell vs. 1,003 ± 348 for controls, p < 0.001) and correlated with the duration of Cheyne-Stokes respiration. Oxidative stress was negatively correlated with SaO(2) nadir during sleep (r = -0.43, p = 0.039). The duration of Cheyne-Stokes respiration predicted severity of oxidative stress in patients with heart failure (beta = 483 mean fluorescence intensity/cell, p < 0.02).

CONCLUSIONS

Levels of oxidative stress are increased in patients with heart failure and Cheyne-Stokes respiration during sleep compared with healthy controls. The duration of Cheyne-Stokes respiration predicts the magnitude of oxidative stress in heart failure. Increased oxidative stress may mediate increased mortality associated with Cheyne-Stokes respiration in patients with heart failure.

NADPH oxidase inhibition ameliorates cardiac dysfunction in rabbits with heart failure

Increased NADPH oxidase activity is found in both experimental and clinical HF. Here, we investigated the effects and mechanisms of NADPH oxidase inhibition on cardiac function in rabbits with HF. HF was induced by combined volume and pressure overload. Rabbits with HF or sham operation were randomized to orally receive apocynin, an inhibitor of NADPH oxidase (15 mg per day) or placebo for 8 weeks. Echocardiography was performed to examine the cardiac function and structure of the rabbits. Cardiac fibrosis was evaluated by masson's trichrome staining. The transforming growth factor-beta (TGF-β), connective tissue growth factor (CTGF), matrix metalloproteinase-2 (MMP-2), and matrix metalloproteinase-9 (MMP-9) expression were measured by real-time PCR. The expression of SERCA2a and phospholamban (PLB) was detected by reverse transcription-polymerase chain reaction and Western Blot. SERCA2a activity was evaluated by measuring the Pi liberated from ATP hydrolysis. Rabbits with HF exhibited cardiac dysfunction and fibrosis. These changes were associated with significant increases in myocardial NADPH oxidase activity and oxidative stress. Compared with sham-operated rabbits, the TGF-β, CTGF, MMP-2, and MMP-9 mRNA expression significantly increased, the expression of SERCA2a and PLB dramatically decreased, and the SERCA2a activity was lower in HF rabbits. Apocynin reduced NADPH oxidase activity and oxidative stress, decreased TGF-β, CTGF, MMP-2, and MMP-9 expression, attenuated cardiac fibrosis, increased SERCA2a and PLB expression, restored SERCA2a activity, and thereby ameliorated cardiac dysfunction. Thus, chronic NADPH oxidase inhibition ameliorated cardiac dysfunction by decreasing cardiac fibrosis and preserving SERCA2a expression and activity.

Involvement of reductive stress in the cardiomyopathy in transgenic mice with cardiac-specific overexpression of heat shock protein 27

Oxidative stress plays an important role in cardiac diseases, which has been well demonstrated, whereas the role of reductive stress has been poorly investigated. We and others have shown previously that heat shock protein 27 (Hsp27) plays a role as an antioxidant. To investigate whether overexpression of Hsp27 could lead to reductive stress and result in cardiomyopathy, we generated transgenic mice with different expression levels of Hsp27. We observed that transgenic mice with high levels of Hsp27 developed cardiomyopathy. The myopathic hearts were under reductive stress, which was evidenced by an increased ratio of reduced glutathione/oxidized glutathione and a decreased level of reactive oxygen species. In addition, upregulated glutathione peroxidase 1 and decreased iron content were revealed in the myopathic hearts. More importantly, inhibition of glutathione peroxidase 1 significantly attenuated the development of cardiomyopathy. The data indicate that the Hsp27-induced cardiomyopathy could be attributed to, at least in part, upregulation of glutathione peroxidase 1. Our findings suggest that reductive stress plays an important role in the development of cardiomyopathy and that Hsp27 may serve as a potential target for the treatment of patients with cardiomyopathy.

Particulate air pollution and coronary heart disease

PURPOSE OF REVIEW

Air pollution poses a significant health risk. The article focuses on the adverse effects of air pollution on the cardiovascular system.

RECENT FINDINGS

Short-term and long-term studies clearly indicate that relatively modest exposures to particulate matter in the ambient air are associated with increased morbidity and mortality due to coronary heart disease. In humans, inhalational exposure to particulate air pollutants decreases heart rate variability, causes ST-segment depression and endothelial dysfunction, increases blood pressure and blood coagulability, and accelerates the progression of atherosclerosis. Mechanisms of air pollution-induced cardiotoxicity include increased generation of reactive oxygen species followed by activation of proinflammatory and prothrombotic pathways. In experimental settings, ultrafine air pollutants instilled directly into the cardiac vasculature depress cardiac contractility and decrease coronary flow. Both effects are attenuated by the use of a free radical scavenger.

SUMMARY

Reactive oxygen species-related mechanisms of air pollution cardiotoxicity might become a valid target in developing new pharmacological strategies aimed at decreasing adverse effects of air pollution during extreme episodes (fires, earthquakes, industrial accidents, acts of terrorism). Educating patients and the general population on the negative cardiovascular effects of air pollution might be helpful in decreasing the risk of developing air pollution-related coronary heart disease.

CPU228, a derivative of dofetilide, relieves cardiac dysfunction by normalizing FKBP12.6, NADPH oxidase and protein kinase C ε in the myocardium

Objectives

The aim of this study was to determine if CPU228, a derivative of dofetilide, is more effective than dofetilide in attenuating isoproterenol-induced heart failure by recovering downregulated FK506 binding protein (FKBP12.6), and suppressing oxidative stress, upregulated NADPH oxidase and protein kinase C ε (PKCε) hyperphosphorylation in the myocardium.

Methods

Heart failure was induced by isoproterenol (1 mg/kg s.c. for 5 days) in male Sprague-Dawley rats. Intervention with either CPU228 or dofetilide (2 mg/kg on Days 3–5) was then conducted in vivo and in vitro.

Key findings

Isoproterenol produced compromised left ventricular systolic pressure, left ventricular pressure rise (dp/dtmax) and fall (dp/dtmin), and left ventricular end-diastolic pressure, associated with oxidative stress, abnormal FKBP12.6, NADPH oxidase p67phox and PKCε in the myocardium. CPU228 was more effective in attenuating these changes than dofetilide in vivo. Dofetilide produced a prolonged QTc to replace a shortened one. In primary neonatal cardiomyocytes, cultured with isoproterenol and treated with either CPU228 or dofetilide at 10−8, 10−7 and 10−6 mol/l, isoproterenol produced a hyperadrenergic state characterized by downregulated FKBP12.6, upregulated NADPH oxidase p67phox and PKCε in vitro. CPU228 was more effective than dofetilide in recovering these changes in a dose-dependent manner without a prolonged QTc.

Conclusions

CPU228 was more effective than dofetilide in attenuating heart failure by normalizing isoproterenol-induced changes, including downregulation of FKBP12.6, upregulation of NADPH oxidase and PKCε hyperphosphorylation in vivo and in vitro.

Isoproterenol disperses distribution of NADPH oxidase, MMP-9, and pPKCepsilon in the heart, which are mitigated by endothelin receptor antagonist CPU0213

AIM

Spatial dispersion of bioactive substances in the myocardium could serve as pathological basis for arrhythmogenesis and cardiac impairment by beta-adrenoceptor stimulation. We hypothesized that dispersed NADPH oxidase, protein kinase Cepsilon (PKCepsilon), early response gene (ERG), and matrix metalloproteinase 9(MMP-9) across the heart by isoproterenol (ISO) medication might be mediated by the endothelin (ET) - ROS pathway. We aimed to verify if ISO induced spatially heterogeneous distribution of pPKCepsilon, NAPDH oxidase, MMP-9 and ERG could be mitigated by either an ET receptor antagonist CPU0213 or iNOS inhibitor aminoguanidine.

METHODS

Rats were treated with ISO (1 mg/kg sc) for 10 days, and drug interventions (mg/kg) either CPU0213 (30 sc) or aminoguanidine (100 ip) were administered on days 8-10. Expression of NADPH oxidase, MMP-9, ERG, and PKCepsilon in the left and right ventricle (LV, RV) and septum (S) were measured separately.

RESULTS

Ventricular hypertrophy was found in the LV, S, and RV, in association with dispersed QTc and oxidative stress in ISO-treated rats. mRNA and protein expression of MMP-9, PKCepsilon, NADPH oxidase and ERG in the LV, S, and RV were obviously dispersed, with augmented expression mainly in the LV and S. Dispersed parameters were re-harmonized by either CPU0213, or aminoguanidine.

CONCLUSION

We found at the first time that ISO-induced dispersed distribution of pPKCepsilon, NADPH oxidase, MMP-9, and ERG in the LV, S, and RV of the heart, which were suppressed by either CPU0213 or aminoguanidine. It indicates that the ET-ROS pathway plays a role in the dispersed distribution of bioactive substances following sustained beta-receptor stimulation.