Article

Hydralazine and Organic Nitrates Restore Impaired Excitation-Contraction Coupling by Reducing Calcium Leak Associated with Nitroso-Redox Imbalance

Miller School of Medicine, University of Miami, United States
Journal of Biological Chemistry (Impact Factor: 4.6). 01/2013; 288(9). DOI: 10.1074/jbc.M112.412130
Source: PubMed

ABSTRACT Although the combined use of hydralazine and isosorbide dinitrate has provided surprising beneficial outcomes in patients with heart failure, the underlying mechanism of action is still controversial. We used two models of nitroso-redox imbalance, neuronal NO synthase deficient (NOS1(-/-))mice and spontaneously hypertensive heart failure (SHHF) rats, to test the hypothesis that hydralazine alone or in combination with nitroglycerin or isosorbide dinitrate (ISDN) restores Ca(2+) cycling and contractile performance and controls superoxide production in isolated cardiomyocytes. The response to increased pacing frequency was depressed in NOS1(-/-) compared to wild type (WT) myocytes. Both sarcomere length shortening and Δ[Ca(2+)](i) responses in NOS1(-/-) cardiomyocytes were augmented by hydralazine in a dose-dependent manner. Nitroglycerin alone did not affect myocyte shortening but reduced Δ[Ca(2+)](i) across the range of pacing frequencies and increased myofilament Ca(2+) sensitivity thereby enhancing contractile efficiency. Similar results were seen in failing myocytes from SHHF rats. Hydralazine alone or in combination with nitroglycerin reduced SR Ca(2+) leak, improved SR Ca(2+) reuptake and restored SR Ca(2+) content. Both, hydralazine and nitroglycerin at concentrations as low as 1 μM, scavenged superoxide in isolated cardiomyocytes, whereas in cardiac homogenates, nitroglycerin inhibited xanthine oxidoreductase activity and scavenged NADPH oxidase-dependent superoxide more efficiently than hydralazine. Therefore, we revealed that by reducing SR Ca(2+) leak, hydralazine improved Ca(2+) cycling and contractility impaired by nitroso-redox imbalance, and nitroglycerin enhanced the contractile efficiency, restoring cardiac excitation-contraction coupling.

0 Followers
 · 
230 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The origins of the hydralazine/isosorbide dinitrate (H+ISDN) combination therapy are rooted in the first large-scale clinical trial in heart failure: V-HeFT I. Initially utilized for the balanced vasodilatory properties of each drug, we now know there is "more to the story." In fact, the maintenance of the nitroso-redox balance may be the true mechanism of benefit. Since the publication of V-HeFT I 30 years ago, H+ISDN has been the subject of much discussion and debate. Regardless of the many controversies surrounding H+ISDN, one thing is clear: therapy is underutilized and many patients who could benefit never receive the drugs. Ongoing physician and patient education are mandatory to improve the rates of H+ISDN use.
    Heart Failure Clinics 01/2014; DOI:10.1016/j.hfc.2014.07.001 · 1.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Excessive oxidative stress in the heart results in contractile dysfunction. While antioxidant therapies have been a disappointment clinically, exercise has shown beneficial results, in part by reducing oxidative stress. We have previously shown that neuronal nitric oxide synthase (nNOS) is essential for cardioprotective adaptations caused by exercise. We hypothesize that part of the cardioprotective role of nNOS is via the augmentation of the antioxidant defense with exercise by positively shifting the nitroso-redox balance. Our results show that nNOS is indispensable for the augmented anti-oxidant defense with exercise. Furthermore, exercise training nNOS knockout mice resulted in a negative shift in the nitroso-redox balance resulting in contractile dysfunction. Remarkably, overexpressing nNOS (conditional cardiac-specific nNOS overexpression) was able to mimic exercise by increasing VO2max. This study demonstrates that exercise results in a positive shift in the nitroso-redox balance that is nNOS-dependent. Thus, targeting nNOS signaling may mimic the beneficial effects of exercise by combating oxidative stress and may be a viable treatment strategy for heart disease. Copyright © 2015. Published by Elsevier Ltd.
    Journal of Molecular and Cellular Cardiology 01/2015; 81. DOI:10.1016/j.yjmcc.2015.01.003 · 5.22 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Rationale: While nitric oxide (NO) signaling modulates cardiac function and excitation-contraction coupling, opposing results due to inconsistent experimental conditions, particularly with respect to temperature, confound the ability to elucidate NO signaling pathways. Here we show that temperature significantly modulates NO effects. Objective: Test the hypothesis that temperature profoundly impacts nitroso-redox equilibrium, thereby affecting sarcomeric reticulum (SR) Ca(2+) leak. Methods and Results: We measured SR Ca(2+) leak in cardiomyocytes from wild-type (WT), NO/redox imbalance (NOS1(-⁄-)), and hyper S-nitrosylation (GSNOR(-⁄-)) mice. In WT cardiomyocytes, SR Ca(2+) leak increased as temperature decreased from 37°C to 23°C, whereas, in NOS1(‒/‒) cells, the leak suddenly increased when the temperature surpassed 30ºC. GSNOR(‒/‒) cardiomyocytes exhibited low leak throughout the temperature range. Exogenously added NO had a biphasic effect on NOS1(‒/‒) cardiomyocytes; reducing leak at 37ºC but increasing it at sub-physiologic temperatures. Oxypurinol and Tempol diminished the leak in NOS1(-⁄-) cardiomyocytes. Cooling from 37° to 23°C increased ROS generation in WT but decreased it in NOS1(-⁄-) cardiomyocytes. Oxypurinol further reduced ROS generation. At 23°C in WT cells, leak was decreased by tetrahydrobiopterin, an essential NOS cofactor. Cooling significantly increased SR Ca(2+) content in NOS1(-⁄-) cells but had no effect in WT or GSNOR(-⁄-). Conclusions: Ca(2+) leak and temperature are normally inversely proportional, whereas NOS1 deficiency reverses this effect, increasing leak and elevating ROS production as temperature increases. Reduced denitrosylation (GSNOR deficiency) eliminates the temperature dependence of leak. Thus, temperature regulates the balance between NO and ROS which in turn has a major impact on SR Ca(2+).
    Circulation Research 10/2014; 116(1). DOI:10.1161/CIRCRESAHA.116.305172 · 11.09 Impact Factor