Inducible nitric oxide synthase in severe human heart failure: impact of mechanical unloading

Inflammation in Heart Failure-Future Perspectives

Chronic heart failure is a terminal point of a vast majority of cardiac or extracardiac causes affecting around 1-2% of the global population and more than 10% of the people above the age of 65. Inflammation is persistently associated with chronic diseases, contributing in many cases to the progression of disease. Even in a low inflammatory state, past studies raised the question of whether inflammation is a constant condition, or if it is, rather, triggered in different amounts, according to the phenotype of heart failure. By evaluating the results of clinical studies which focused on proinflammatory cytokines, this review aims to identify the ones that are independent risk factors for heart failure decompensation or cardiovascular death. This review assessed the current evidence concerning the inflammatory activation cascade, but also future possible targets for inflammatory response modulation, which can further impact the course of heart failure.

Cardioprotective Effect of Resveratrol in a Postinfarction Heart Failure Model

Despite great advances in therapies observed during the last decades, heart failure (HF) remained a major health problem in western countries. In order to further improve symptoms and survival in patients with heart failure, novel therapeutic strategies are needed. In some animal models of HF resveratrol (RES), it was able to prevent cardiac hypertrophy, contractile dysfunction, and remodeling. Several molecular mechanisms are thought to be involved in its protective effects, such as inhibition of prohypertrophic signaling molecules, improvement of myocardial Ca²⁺ handling, regulation of autophagy, and the reduction of oxidative stress and inflammation. In our present study, we wished to further examine the effects of RES on prosurvival (Akt-1, GSK-3β) and stress signaling (p38-MAPK, ERK 1/2, and MKP-1) pathways, on oxidative stress (iNOS, COX-2 activity, and ROS formation), and ultimately on left ventricular function, hypertrophy and fibrosis in a murine, and isoproterenol- (ISO-) induced postinfarction heart failure model. RES treatment improved left ventricle function, decreased interstitial fibrosis, cardiac hypertrophy, and the level of plasma BNP induced by ISO treatment. ISO also increased the activation of P38-MAPK, ERK1/2^{Thr183-Tyr185}, COX-2, iNOS, and ROS formation and decreased the phosphorylation of Akt-1, GSK-3β, and MKP-1, which were favorably influenced by RES. According to our results, regulation of these pathways may also contribute to the beneficial effects of RES in HF.

Analysis on mechanism of ATP-sensitive K+ channel opener natakalim improving congestive heart failure after myocardial infarction

The action mechanism of natakalim, a novel ATP-sensitive potassium channel opener, was studied in ameliorating the congestive heart failure (CHF) after myocardial infarction. A total of 25 healthy Wistar male rats (age, 10 weeks; average weight, 300 g) were selected, and the CHF models after acute myocardial infarction (AMI) were prepared by ligation of left anterior descending branch. They were randomly divided into the sham operation group, the model group and the groups of 1, 3 and 9 mg/kg/day natakalims. Each group had 5 mice that were sacrificed after 8 weeks. We compared left ventricular end-diastolic diameter (LVEDD), left ventricular ejection fraction (LVEF), N-terminal prohormone of brain natriuretic peptide (NT-proBNP), left ventricular mass index, myocardial cell cross-sectional area, myocardial collagen content, plasma endothelin-1 (ET-1) and endothelial nitric oxide synthase (eNOS) levels. Compared with the sham operation, the LVEDD and NT-proBNP in the model group and each natakalim group were elevated. LVEF decreased significantly, while the left ventricular mass index, myocardial cell cross-sectional area, myocardial collagen content, plasma ET-1 and eNOS levels increased. Natakalim intervention improved the above changes and the improvement effect of 3 mg/kg/day group was the highest. The mechanism of natakalim against the endothelin system can be explained by the fact that inhibiting ET-1 synthesis can reduce the ET-1 levels in circulation leading to the release of NO and PGI2. Inhibition of the vasoconstriction effect of ET-1 can improve the hemodynamics of high-load status and ameliorate the cardiac systolic and diastolic functions. In conclusion, natakalim can improve the ventricular remodeling of CHF after AMI, and 3 mg/kg/day was the most effective dose.

Venous congestion, endothelial and neurohormonal activation in acute decompensated heart failure: cause or effect?

Venous congestion and endothelial and neurohormonal activation are known to occur in acute decompensated heart failure (ADHF), yet the temporal role of these processes in the pathophysiology of decompensation is not fully understood. Conventional wisdom presumes congestion to be a consequence of worsening cardiovascular function; however, the biomechanically driven effects of venous congestion are biologically plausible contributors to ADHF that remain largely unexplored in vivo. Recent experimental evidence from human models suggests that fluid accumulation and venous congestion are not simply consequences of poor cardiovascular function, but rather are fundamental pro-oxidant, pro-inflammatory, and hemodynamic stimuli that contribute to acute decompensation. The latest advances in the monitoring of volume status using implantable devices allow for the detection of venous congestion before symptoms arise. This may ultimately lead to improved treatment strategies including not only diuretics, but also specific, adjuvant interventions to counteract endothelial and neurohormonal activation during early preclinical decompensation.

Overexpression myocardial inducible nitric oxide synthase exacerbates cardiac dysfunction and beta-adrenergic desensitization in experimental hypothyroidism

BACKGROUND

Altered nitric oxide synthase (NOS) has been implicated in the pathophysiology of heart failure (HF). Recent evidence links hypothyroidism to the pathology of HF. However, the precise mechanisms are incompletely understood. The alterations and functional effects of cardiac NOS in hypothyroidism are unknown. We tested the hypothesis that hypothyroidism increases cardiomyocyte inducible NOS (iNOS) expression, which plays an important role in hypothyroidism-induced depression of cardiomyocyte contractile properties, [Ca(2+)]i transient ([Ca(2+)]iT), and β-adrenergic hyporesponsiveness.

METHODS AND RESULTS

We simultaneously evaluated LV functional performance and compared myocyte three NOS, β-adrenergic receptors (AR) and SERCA2a expressions and assessed cardiomyocyte contractile and [Ca(2+)]iT responses to β-AR stimulation with and without pretreatment of iNOS inhibitor (1400 W, 10(-5)mol/L) in 26 controls and 26 rats with hypothyroidism induced by methimazole (~30 mg/kg/day for 8 weeks in the drinking water). Compared with controls, in hypothyroidism, total serum T3 and T4 were significantly reduced followed by significantly decreased LV contractility (EES) with increased LV time constant of relaxation. These LV abnormalities were accompanied by concomitant significant decreases in myocyte contraction (dL/dtmax), relaxation (dR/dtmax), and [Ca(2+)]iT. In hypothyroidism, isoproterenol (10(-8)M) produced significantly smaller increases in dL/dtmax, dR/dtmax and [Ca(2+)]iT. These changes were associated with decreased β1-AR and SERCA2a, but significantly increased iNOS. Moreover, only in hypothyroidism, pretreatment with iNOS inhibitor significantly improved basal and isoproterenol-stimulated myocyte contraction, relaxation and [Ca(2+)]iT.

CONCLUSIONS

Hypothyroidism produces intrinsic defects of LV myocyte force-generating capacity and relaxation with β-AR desensitization. Up-regulation of cardiomyocyte iNOS may promote progressive cardiac dysfunction in hypothyroidism.

Natakalim improves post-infarction left ventricular remodeling by restoring the coordinated balance between endothelial function and cardiac hypertrophy

Endothelial dysfunction can lead to congestive heart failure and the activation of endothelial ATP-sensitive potassium (K_ATP) channels may contribute to endothelial protection. Therefore, the present study was carried out to investigate the hypothesis that natakalim, a novel K_ATP channel opener, ameliorates post-infarction left ventricular remodeling and failure by correcting endothelial dysfunction. The effects of myocardial infarction were assessed 8 weeks following left anterior descending coronary artery occlusion in male Wistar rats. Depressed blood pressure, cardiac dysfunction, evidence of left ventricular remodeling and congestive heart failure were observed in the rats with myocardial infarction. Treatment with natakalim at daily oral doses of 1, 3 or 9 mg/kg/day for 8 weeks prevented these changes. Natakalim also prevented the progression to cardiac failure, which was demonstrated by the increase in right ventricular weight/body weight (RVW/BW) and relative lung weight, signs of cardiac dysfunction, as well as the overexpression of atrial and brain natriuretic peptide mRNAs. Our results also demonstrated that natakalim enhanced the downregulation of endothelium-derived nitric oxide, attenuated the upregulation of inducible nitric oxide synthase-derived nitric oxide (NO), inhibited the upregulated endothelin system and corrected the imbalance between prostacyclin and thromboxane A₂. Overall, our findings suggest that natakalim prevents post-infarction hypertrophy and cardiac failure by restoring the coordinated balance between endothelial function and cardiac hypertrophy.

Left Ventricular Assist Devices: An Evolving State of the Art

Heart failure is a disease of increasing prevalence around the world. The treatment options for patients suffering from this ailment range from pharmacologic to surgical. Heart failure, however, continues to harbor a dismal prognosis despite conventional treatments. The high mortality rate among this patient population has spawned interest in alternative therapies. Mechanical circulatory support has emerged as a treatment option for patients with refractory heart failure. Over the past years a number of studies have highlighted the effectiveness of left ventricular assist devices (LVAD’s) in improving patient’s outcomes. The technologies that support these devices have evolved and provide new opportunities to manage patients suffering from this debilitating disease. Heart transplantation continues to generate the most reproducible survival benefit to patients with advanced heart failure, but is limited by a lack of donors. It is therefore the goal of mechanical assist therapy to improve patient survival and quality of life in heart failure in light of the limitations of heart transplantation. In this article we examine the evolving utility of LVAD’s in the treatment of heart failure.

Cytokines in HIV-associated cardiomyopathy

Among the multiple cardiac manifestations occurring in HIV-infected patients, cardiomyopathy is one of the most challenging. Its incidence has only slightly decreased since the introduction of highly active antiretroviral therapy (HAART). Also, its pathogenesis remains relatively unclear. Although several studies demonstrated the presence of HIV genome in the heart of patients, more recent developments found that viral infection plays an indirect role only, as well as they recognized the contribution of proinflammatory cytokines in the progression of the disease. Experimental studies on animals and cultured myocytes have established the signalling pathway triggered by proinflammatory cytokines in heart failure and cardiomyopathy. Tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) and IL-6 promote expression of inducible nitric oxide synthase (iNOS) in cardiomyocytes through activation of p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor kappaB (NFkappaB). TNF-alpha and high concentrations of NO also induce cardiomyocyte apoptosis by TNF type 1 receptor activation. This biological framework, which is also involved in progression of cardiomyopathy in humans, is more pronounced in HIV-infected patients, in whom proinflammatory cytokines TNF-alpha, IL-1 and IL-6 are increased, resulting in an enhanced expression of cardiac iNOS, especially in patients with a low CD4 T cell count. This may account for the worse outcome of heart failure in HIV-infected patients. However, there are only few data today to support future therapeutic implications of cytokines antagonism in treatment of HIV-infected patients with cardiomyopathy. Whether modulation of TNF production or selective inhibition of p38 MAPK pathway could be useful approaches remains uncertain.

Left ventricular assist device and drug therapy for the reversal of heart failure

BACKGROUND

In patients with severe heart failure, prolonged unloading of the myocardium with the use of a left ventricular assist device has been reported to lead to myocardial recovery in small numbers of patients for varying periods of time. Increasing the frequency and durability of myocardial recovery could reduce or postpone the need for subsequent heart transplantation.

METHODS

We enrolled 15 patients with severe heart failure due to nonischemic cardiomyopathy and with no histologic evidence of active myocarditis. All had markedly reduced cardiac output and were receiving inotropes. The patients underwent implantation of left ventricular assist devices and were treated with lisinopril, carvedilol, spironolactone, and losartan to enhance reverse remodeling. Once regression of left ventricular enlargement had been achieved, the beta2-adrenergic-receptor agonist clenbuterol was administered to prevent myocardial atrophy.

RESULTS

Eleven of the 15 patients had sufficient myocardial recovery to undergo explantation of the left ventricular assist device a mean (+/-SD) of 320+/-186 days after implantation of the device. One patient died of intractable arrhythmias 24 hours after explantation; another died of carcinoma of the lung 27 months after explantation. The cumulative rate of freedom from recurrent heart failure among the surviving patients was 100% and 88.9% 1 and 4 years after explantation, respectively. The quality of life as assessed by the Minnesota Living with Heart Failure Questionnaire score at 3 years was nearly normal. Fifty-nine months after explantation, the mean left ventricular ejection fraction was 64+/-12%, the mean left ventricular end-diastolic diameter was 59.4+/-12.1 mm, the mean left ventricular end-systolic diameter was 42.5+/-13.2 mm, and the mean maximal oxygen uptake with exercise was 26.3+/-6.0 ml per kilogram of body weight per minute.

CONCLUSIONS

In this single-center study, we found that sustained reversal of severe heart failure secondary to nonischemic cardiomyopathy could be achieved in selected patients with the use of a left ventricular assist device and a specific pharmacologic regimen.