Postischemic recovery and oxidative stress are independent of nitric-oxide synthases modulation in isolated rat heart.
ABSTRACT During myocardial ischemia and reperfusion, nitric oxide ((.)NO) was shown to exert either beneficial or detrimental effects. Uncoupled (.)NO synthases (NOS) can generate superoxide anion under suboptimal concentrations of substrate and cofactors. The aim of our study was to investigate the role of NOS modulation on 1) the evolution of functional parameters and 2) the amount of free radicals released during an ischemia-reperfusion sequence. Isolated perfused rat hearts underwent 30 min of total ischemia, followed by 30 min of reperfusion in the presence of N(G)-nitro-D- or L-arginine methyl ester (NAME, 100 microM) or of D- or L-arginine (3 mM). Functional parameters were recorded and coronary effluents were analyzed with electron spin resonance to identify and quantify the amount of alpha-phenyl-N-tert-butylnitrone spin adducts produced during reperfusion. The antioxidant capacities of the compounds were determined with the oxygen radical absorbance capacity test. L-NAME-treated hearts showed a reduction of coronary flow and contractile performance, although neither L-NAME nor L-arginine improved the recovery of coronary flow, left end diastolic ventricular pressure, rate pressure product, and duration of reperfusion arrhythmia, compared with their D-specific enantiomers. A large and long-lasting release of alkyl/alkoxyl radicals was detected upon reperfusion, but no differences of free radical release were observed between D- and L-NAME or D- and L-arginine treatment. These results may indicate that, in our experimental conditions, cardiac NOS might not be a major factor implicated in the oxidative burst that follows a global myocardial ischemia.
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ABSTRACT: l-Arginine (l-Arg) is a conditionally essential amino acid in the human diet. The most common dietary sources of l-Arg are meat, poultry and fish. l-Arg is the precursor for the synthesis of nitric oxide (NO); a key signaling molecule via NO synthase (NOS). Endogenous NOS inhibitors such as asymmetric-dimethyl-l-Arg inhibit NO synthesis in vivo by competing with l-Arg at the active site of NOS. In addition, NOS possesses the ability to be "uncoupled" to produce superoxide anion instead of NO. Reduced NO bioavailability may play an essential role in cardiovascular pathologies and metabolic diseases. l-Arg deficiency syndromes in humans involve endothelial inflammation and immune dysfunctions. Exogenous administration of l-Arg restores NO bioavailability, but it has not been possible to demonstrate, that l-Arg supplementation improved endothelial function in cardiovascular disease such as heart failure or hypertension. l-Arg supplementation may be a novel therapy for obesity and metabolic syndrome. The utility of l-Arg supplementation in the treatment of l-Arg deficiency syndromes remains to be established. Clinical trials need to continue to determine the optimal concentrations and combinations of l-Arg, with other protective compounds such as tetrahydrobiopterin (BH4 ), and antioxidants to combat oxidative stress that drives down NO production in humans.Molecular Nutrition & Food Research 06/2013; · 4.31 Impact Factor
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ABSTRACT: Small amounts of carbon monoxide (CO) are continuously produced in mammals. The intracellular levels of CO can increase under stressful conditions following the induction of HO-1 (heme oxygnase-1), a ubiquitous enzyme responsible for the catabolism of heme. Unlike nitric oxide, which is a free radical, CO does not contain free electrons but may be involved in oxidative stress. The carbonate radical has been proposed to be a key mediator of oxidative damage resulting from peroxynitrite production, likewise, the precursor of the carbonate radical anion being bicarbonate and carbon dioxide. We report herein some of the transcription factors and protein kinases involved in the regulation of vascular HO-1 expression. Beyond its widely feared toxicity, CO has revealed a very important biological activity as a signaling molecule with marked protective actions namely against apoptosis and endothelial oxidative damage. Abnormal metabolism and function of CO contribute to the pathogenesis and development of cardiovascular diseases. Important results have been reported in which CO and CO-releasing molecules (CO-RMs) prevent intimal hyperplasia by arresting hyperproliferative vascular smooth muscle cells and increased mobilization and recruitment of bone-marrow-derived progenitor cells. Clinical studies have demonstrated beneficial properties of CO-RMs in transplantation. The anti-inflammatory properties of CO and CO-RMs have been demonstrated in a multitude of animal models of inflammation, suggesting a possible therapeutic application for inflammatory diseases. The development of a technology concerning CO-RMs that controls the delivery and action of CO under different pathological conditions represents a major step forward in the development of CO-based pharmaceuticals with therapeutic applications.Pharmacology [?] Therapeutics 09/2012; · 7.79 Impact Factor
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ABSTRACT: Nitric oxide ((•)NO) is synthetized enzymatically from L-arginine (L-Arg) by three NO synthase isoforms, iNOS, eNOS and nNOS. The synthesis of NO is selectively inhibited by guanidino-substituted analogs of L-Arg or methylarginines such as asymmetric dimethylarginine (ADMA), which results from protein degradation in cells. Many disease states, including cardiovascular diseases and diabetes, are associated with increased plasma levels of ADMA. The N-terminal catalytic domain of these NOS isoforms binds the heme prosthetic group as well as the redox cofactor, tetrahydrobiopterin (BH4) associated with a regulatory protein, calmodulin (CaM). The enzymatic activity of NOS depends on substrate and cofactor availability. The importance of BH4 as a critical regulator of eNOS function suggests that BH4 may be a rational therapeutic target in vascular disease states. BH4 oxidation appears to be a major contributor to vascular dysfunction associated with hypertension, ischemia/reperfusion injury, diabetes and other cardiovascular diseases as it leads to the increased formation of oxygen-derived radicals due to NOS uncoupling rather than NO. Accordingly, abnormalities in vascular NO production and transport result in endothelial dysfunction leading to various cardiovascular disorders. However, some disorders including a wide range of functions in the neuronal, immune and cardiovascular system were associated with the over-production of NO. Inhibition of the enzyme should be a useful approach to treat these pathologies. Therefore, it appears that both a lack and excess of NO production in diseases can have various important pathological implications. In this context, NOS modulators (exogenous and endogenous) and their therapeutic effects are discussed.Pharmacology [?] Therapeutics 07/2013; · 7.79 Impact Factor