The real estate of NOS signaling: location, location, location.

Although the combined use of hydralazine and isosorbide dinitrate confers important clinical benefits 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 rats, to test the hypothesis that hydralazine (HYD) alone or in combination with nitroglycerin (NTG) or isosorbide dinitrate 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 with wild type myocytes. Both sarcomere length shortening and intracellular Ca(2+) transient (Δ[Ca(2+)]i) responses in NOS1(-/-) cardiomyocytes were augmented by HYD in a dose-dependent manner. NTG 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 the heart failure rat model. HYD alone or in combination with NTG reduced sarcoplasmic reticulum (SR) leak, improved SR Ca(2+) reuptake, and restored SR Ca(2+) content. HYD and NTG at low concentrations (1 μm), scavenged superoxide in isolated cardiomyocytes, whereas in cardiac homogenates, NTG inhibited xanthine oxidoreductase activity and scavenged NADPH oxidase-dependent superoxide more efficiently than HYD. Together, these results revealed that by reducing SR Ca(2+) leak, HYD improves Ca(2+) cycling and contractility impaired by nitroso-redox imbalance, and NTG enhanced contractile efficiency, restoring cardiac excitation-contraction coupling.

Nitric oxide (NO) plays a central role in the regulation of cardiovascular homeostasis and is involved in the regulation of vascular tone and cardiac contractility as well as gene expression and cell proliferation. Furthermore, NO modulates renin secretion and salt and fluid reabsorption in the kidney.1 Three isoforms of NO synthase (NOS) have been identified, the neuronal NOS (nNOS or NOS I), the inducible NOS (iNOS or NOS II), and the endothelial NOS (eNOS or NOS III). While all of these enzymes potentially affect blood pressure, only eNOS-deficient mice are hypertensive.2,3 Although nNOS is expressed in cardiac myocytes,4,5 as well as in vascular smooth muscle cells,6–8 relatively little is known about the role played by nNOS-derived NO in cardiovascular homeostasis. Both pro- and antihypertensive actions have been attributed to nNOS, and selective inhibitors of this isoform have been reported to normalize blood pressure,9 as well as to attenuate flow-induced vasodilatation in eNOS−/− mice.8 The regulation of nNOS activity, like that of eNOS, is determined by phosphorylation of the enzyme as well as by its association with a number of regulatory proteins.10 One protein that associates with nNOS in human embryonic kidney (HEK293) cells and is reported to play a major role in regulating the activity of the Ca2+-dependent enzyme, is the plasma membrane Ca2+/calmodulin-dependent Ca2+-ATPase (PMCA).11 The ATPase binds to nNOS via an interaction between its carboxyl terminus and the PDZ domain of nNOS. Increasing expression of the PMCA4b isoform markedly attenuates NO synthesis by nNOS, an effect not observed in cells overexpressing a mutant PMCA that was devoid of Ca2+-transporting activity.11 Thus, …

Nitric oxide (NO) stimulates soluble guanylyl cyclase and, thus, enhances cyclic guanosine monophosphate (cGMP) levels. It is a currently prevailing concept that NO inhibits platelet activation. This concept, however, does not fully explain why platelet agonists stimulate NO production. Here we show that a major platelet NO synthase (NOS) isoform, NOS3, plays a stimulatory role in platelet secretion and aggregation induced by low doses of platelet agonists. Furthermore, we show that NOS3 promotes thrombosis in vivo. The stimulatory role of NOS is mediated by soluble guanylyl cyclase and results from a cGMP-dependent stimulation of platelet granule secretion. These findings delineate a novel signaling pathway in which agonists sequentially activate NOS3, elevate cGMP, and induce platelet secretion and aggregation. Our data also suggest that NO plays a biphasic role in platelet activation, a stimulatory role at low NO concentrations and an inhibitory role at high NO concentrations.

The roles of nitric oxide (NO) in the heart have been studied intensely ever since the first report nearly 2 decades ago showing that endogenous NO modulates cardiac myocyte function.1 All 3 NO synthase (NOS) isoforms have been found in mammalian heart tissues (see reviews in Massion et al2 and Belge et al3). A complex array of myocyte and nonmyocyte cells in the heart express NOS isoforms, and the local generation of NO2,3 and reactive oxygen species (ROS)4 may exert both autocrine and paracrine effects on cellular function. Not only is the endothelial isoform of NOS (eNOS, or NOS3) robustly expressed in the endothelial cells of the cardiac vasculature, but eNOS is also present within cardiac myocytes, where the enzyme associates with the scaffolding/regulatory protein caveolin-3 in T tubules in plasmalemmal caveolae.5 The neuronal NOS (nNOS, or NOS1) is also expressed in cardiac myocytes, where the enzyme appears to be localized in the sarcoplasmic reticulum and modulates phospholamban phosphorylation.6 Although both eNOS and nNOS appear to be physiologically expressed in cardiac tissues, the inflammation-related NOS isoform (iNOS, or NOS2) only appears in the heart after immunoactivation; iNOS may modulate the decline in myocardial function seen in sepsis.7 There have been innumerable studies of the cardiac effects of various NOS inhibitors, NO-donating drugs, and NO itself.2 The cardiac phenotypes of NOS “knockout” mouse models have been characterized extensively, and mice lacking 1, 2, or all 3 NOS isoforms have been generated and characterized.8 In addition, the roles of NOS substrates, cofactors, and allosteric modulators have been explored exhaustively in diverse cardiac model systems. Emerging from this broad range of experimental evidence is an increasingly clear view that NO and NOS are key determinants of cardiac function. Yet the molecular mechanisms and …

In heart failure, the amplitude and rate of decay of both contraction and the underlying systolic Ca2+ transient are reduced. A current debate concerns the mechanism of these alterations of calcium handling. One theory invokes decreased activity of the sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA)1 while another focuses on alterations in the SR Ca2+ release channel (ryanodine receptor, RyR).2 A significant contribution to this debate is made by Jiang et al3 in this issue of Circulation Research . Calcium that activates contraction comes from two sources: (1) the extracellular fluid, largely via the L-type Ca2+ current ( I Ca); and (2) the SR, by release through the RyR. Because the latter is generally larger and the amplitude of I Ca is not consistently altered in failure (see review4), work has focused on release from the SR. Release occurs via calcium-induced calcium release (CICR) whereby Ca2+ entry increases the probability of opening of a closely apposed RyR (see general reviews5,6⇓). Relaxation requires that [Ca2+]i be lowered by the combined effects of SERCA and Na+-Ca2+ exchange (NCX). The activity of SERCA is depressed by the accessory protein phospholamban and this inhibition is removed by phosphorylation, providing a mechanism whereby sympathetic stimulation can increase SR Ca2+ content and hence Ca2+ release from the SR. Importantly, depression of SERCA activity will not only decrease the amplitude of the Ca2+ transient (by decreasing SR content) but will also directly slow the rate of decay. The RyR can be phosphorylated,7 and there is an important interaction between an auxiliary protein (FKBP), phosphorylation, and RyR opening. Briefly, FKBP stabilizes interactions between RyRs such that …

The purpose of the study was to demonstrate the presence of nitric oxide (NO) synthase (NOS) isoforms (neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS)) and the role of NO in the ovary of Heteropneustes fossilis. In one half of the ovary collected during different reproductive stages, NOS isoforms were localized immunohistochemically in paraffin sections whereas the other half was processed for NOS and NO quantification using western blot followed by densitometry and nitrate/nitrite assay respectively. The role of NO on oocyte maturation was studied by examining the effect of NO donor (sodium nitroprusside; SNP) and NOS inhibitor (Nomega-nitro-l-arginine methyl ester) on 17alpha,20beta-dihydroxy-4-pregnen-3-one (17alpha,20beta-P)-induced germinal vesicle breakdown (GVBD) in the cultured oocyte collected during prespawning phase. NOS immunostaining was predominantly localized in previtellogenic follicles, with nNOS detected in the nucleus and cytoplasm of oocytes whereas iNOS and eNOS localized in granulosa, theca cells, and cytoplasm of oocytes. The NOS expression was higher in previtellogenic phase when compared with vitellogenic phase. The nitrate/nitrite concentrations in ovary showed gradual increase from recrudescence (4.9+/-0.19 nM/mg protein) to late previtellogenic phase (7.02+/-0.53 nM/mg protein), but showed a sharp decline during the vitellogenic phase (0.41+/-0.053 nM/mg protein). Serum and ovarian nitrate/nitrite level showed a close association during the reproductive cycle. The results showed an increase in NOS activity and nitrate/nitrite concentrations as the follicle grow suggesting involvement of NO in follicular development. SNP significantly inhibited 17alpha,20beta-P-induced GVBD in fish oocytes. Thus, it is concluded that the fish ovary possesses NOS/NO system and a possibility that NO has a role in follicular development and regulation of oocyte maturation in fish, H. fossilis.

The free radical gas nitric oxide (NO) is produced by 3 isoforms of nitric oxide synthase (NOS). All of them are present in the heart: NOS1 (nNOS, “neuronal” NOS) has been detected in cardiac conduction tissue and intracardiac neurons; NOS2 (iNOS, “cytokine-inducible” NOS) can be expressed by virtually all cells in the heart, often in conjunction with the expression of inflammatory cytokines; and finally, NOS3 (eNOS, “endothelial-constitutive” NOS) is expressed in coronary endothelium, endocardium, and cardiac myocytes. NOS3 regulates the tone of vascular smooth muscle cells; the permeability and platelet adhesion of endothelial cells; and the receptor-effector coupling, energetics, contractility, and apoptosis of cardiomyocytes.1,2 Since the original demonstration of myocardial NOS2 activity in idiopathic dilated cardiomyopathy,3 a negative inotropic effect of NO frequently was hypothesized to contribute to the depressed contractile function of failing myocardium. This hypothesis was inspired by the simultaneous publication of experimental results that showed a depressed contractile response of isolated cardiomyocytes to β-adrenergic agonists after NOS2 induction by lipopolysaccharides.4 See p 2318 To further explore this depressant action of NO on myocardial contractility, numerous experimental and clinical studies were performed, but they yielded apparently conflicting results on the inotropic effect of NO from either endogenous or pharmacological sources.2 As reported in this issue of Circulation , Cotton et al5 tackled the question of the inotropic action of NO by measuring left ventricular (LV) performance in normal control subjects and in patients with dilated cardiomyopathy during intracoronary infusion of the NOS inhibitor NG-monomethyl-l-arginine (L-NMMA). During L-NMMA infusion, Cotton et al5 observed a modest drop (14%) in LV dP/dtmax in the control group and no change in LV dP/dtmax in the cardiomyopathy group, despite myocardial expression of NOS2 in their patients. They concluded that the small …

nitric oxide (NO) plays an important role in intracellular signaling, and stole the limelight in 1992 by winning science's equivalent of an “Oscar”: Science magazine's “Molecule of the Year.” Subsequently, the importance and versatility of its known roles has expanded. Furthermore, this

EDITORIAL FOCUSNO control: nitric oxide directly regulates substrate delivery to NOS. Focus on "Nitric oxide can acutely modulate its biosynthesis through a negative feedback mechanism on l-arginine transport in cardiac myocytes"Craig GattoCraig GattoSchool of Biological Sciences, Illinois State University, Normal, IllinoisPublished Online:01 Aug 2010https://doi.org/10.1152/ajpcell.00191.2010This is the final version - click for previous versionMoreSectionsPDF (135 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations although the amino acid arginine is commonly associated with nitric oxide (NO) production via NO synthase (NOS), it also participates in the synthesis of urea, creatine, creatinine, agmatine, polyamines, as well as overall protein synthesis. Furthermore, it also influences hormone release (insulin, prolactin, and others) and synthesis of pyrimidine bases. Thus, physiologically arginine participates in disposal of protein metabolic waste, muscle metabolism, vascular regulation, immune system function, neurotransmission, RNA synthesis, and hormone-mediated signaling (4). More importantly, although all cells require arginine, not all cells possess the metabolic capacity to produce it and thus must obtain arginine via the circulation. In cells that must acquire l-arginine exogenously, it seems logical that there would be regulatory mechanisms in place to moderate the rate of l-arginine uptake via cationic amino acid transporters (CATs). Surprisingly, there are few reports that address CATs as possible metabolic sites of regulation.In light of limited information, the report from Zhou et al. (28), the current article in focus (published in this issue of American Journal of Physiology-Cell Physiology), is particularly important. Their article describes findings from freshly isolated rat ventricular cardiomyocytes that endogenously produced NO negatively regulates l-arginine uptake (28). Functionally, this l-arginine transport appears to be mediated via the cationic amino acid transporters 1 and 2 (CAT-1 and CAT-2A; human genes SLC7A1 and SLC7A2, respectively) (25). This important observation extends previous work from the Peluffo laboratory functionally identifying CAT-1 and CAT-2A as equal contributors to l-arginine uptake in cardiac muscle (15, 18). These observations identify a critical regulatory role for CATs in NO signaling and thus contribute to cardiac muscle physiology and pathophysiology.CAT structure-function.The CAT proteins, a subgroup of the solute carrier family 7, function as the predominant entrance pathway for cationic amino acids in nonepithelial cells. Four members of the CAT family have been functionally characterized (CAT-1, CAT-2A, CAT-2B, and CAT-3), and all are glycosylated plasma membrane proteins that contain 14 putative transmembrane spans. (Recently, a fifth member, CAT-4, has been identified but remains poorly understood.) The four isoforms display similar substrate specificity for cationic amino acids. The transport process for all four members is driven by the electrochemical gradient of the transported amino acid and is Na+ independent.CATs belong to the system y+ subgroup of the cationic amino acid transporters (4). The system y+ transporters are highly selective for cationic amino acids with a preference for a long carbon backbone, e.g., homoarginine > arginine ≈ lysine > ornithine > 2,4-diamino-n-butyric acid (2, 18). However, separate isoforms do display different apparent affinities and rates of transport for these substrates. For example, CAT-1 and CAT-2B transport l-arginine with relatively high apparent affinity (0.07–0.25 mM) and low capacity, whereas CAT-2A has a higher maximal velocity and lower apparent affinity (2–5 mM) for this amino acid (4). CAT-mediated transport is stereospecific; that is, d-isomers are not substrates for system y+ transporters. CAT-2A and CAT-2B are mutually exclusive splice variants of the SLC7A2 gene that only differ by a 42 amino acid stretch encompassing the putative TM8–TM9 hairpin, which includes the fourth intracellular loop (4). Subsequent studies identified two amino acids within this 42 amino acid segment in CAT-2A (i.e., Arg369 and Ser381) that contribute to the significantly lower apparent substrate affinities in this isoform (9).Members of the system y+ transporter family can also recognize l-arginine analogs that are methylated at the guanido group such as NG-nitro-l-arginine methyl ester (l-NAME), an inhibitor of constitutive NOS (5). Also, system y+ CATs are sensitive to the sulfhydryl reagent N-ethylmaleimide (NEM), which inhibits members of system y+ at concentrations nearly tenfold lower than is required to block other proteins (3, 15, 18). In red blood cells, 200 μM NEM blocked system y+ transporters, whereas system y+L transporters also present in these cells were not NEM sensitive (19). System y+L transporters move cationic amino acids in an uncoupled manner, as well as neutral amino acids coupled with Na+.NO regulates cardiac CATs.The important role that constitutively produced NO plays in myocardial function has been reviewed recently by Seddon et al. (22). It has been three decades since Furchgott and Zawadzki (7) reported on endothelium-derived relaxation factor (subsequently identified as NO) (11, 17), and since then, NO signaling has been described in many tissues in addition to smooth muscle. Indeed, most cell types contain one or more NOS isoforms, with the predominant isoforms being NOS-1 (neuronal NOS) and NOS-3 (endothelial NOS), both of which are in cardiac muscle (1). The third isoform, NOS-2, is an inducible form (iNOS), so named for its increased synthesis during an inflammatory response. NO is a reactive free radical gas formed by oxidation of the guanidine group of l-arginine to produce NO and l-citrulline (8). Given that NO can readily diffuse through membranes and the highly reactive nature of free radicals, free cytosolic NO has an extremely short half-life. However, there is increasing support for the notion that nitrosothiols may serve as a NO reservoir for subsequent release and signaling (14).In any case, initial NO production depends directly on the availability of l-arginine to NOS. The NOS enzymes are some of the most highly regulated enzymes known, and in this issue of the Journal, Peluffo and colleagues make a compelling argument that, at least in cardiac myocytes, regulation extends upstream to the control of substrate availability by decreasing l-arginine uptake via CAT-1 and CAT-2A (28) (Fig. 1). Indeed, the bioavailability of NO has been linked to a reduced rate of l-arginine uptake in congestive heart failure. This decreased l-arginine uptake was concomitantly associated with lower CAT-1 mRNA levels (12). Given that cardiac myocytes, like most cells, must import l-arginine from the circulation, NO production and CATs are intimately linked. Thus, the observation by Zhou and colleagues (28) that NO directly decreases l-arginine uptake by CATs is quite novel in that it demonstrates a direct link between NOS and CATs, as opposed to a signaling induced (e.g., cGMP-mediated phosphorylation) phenomenon.Fig. 1.Schematic diagram of key nitric oxide (NO) autoregulatory sites. In cardiac myocytes, l-arginine (l-Arg) substrate is supplied to NO synthase (NOS) solely via cationic amino acid transporters 1 and 2A (CAT-1 and CAT-2A). Direct modulation of NO signaling via NO-mediated S-nitrosylation of NOS and soluble guanylate cyclase (sGC) to reduce their activities has been reported (Refs. 20 and 21, respectively). In the figure, NO binding and stimulation are depicted by a green arrow, whereas inhibition via NO S-nitrosylation is depicted by a red blunted line. The findings of Zhou et al. (28) now extend NO autoregulation upstream to CAT-1 and CAT-2A, the sources of l-arginine supply.Download figureDownload PowerPointThe next big question is how CAT-1 and CAT-2A are modulated by NO. Here again, the thorough experimental approach provides compelling, albeit circumstantial, evidence for direct NO-mediated S-nitrosylation of these CATs (28). That is, in general, the actions of NO are thought to be mediated through stimulation of soluble guanylate cyclase (sGC) and elevation of cGMP levels, which in turn activates cGMP-dependent protein kinases (6). Alternatively, many effects of NO are attributed to S-nitrosylation, i.e., the covalent modification of cysteine -SH groups by NO to generate S-nitrosothiol. For example, nitric oxide can increase the open probability of ryanodine receptor channels through this mechanism, contributing to positive inotropy (24, 27). Indeed, NO S-nitrosylation has been reported to modify several important proteins within the cardiovascular system: 1) The duration of β-adrenergic stimulation is reciprocally regulated in the endothelium and myocardium by S-nitrosylation of β-arrestin 2 which enhances β-adrenergic receptor downregulation (16) and G protein-coupled receptor kinase which prolongs β-adrenergic receptor desensitization (26). 2) S-nitrosylation has been shown to stimulate and inhibit the function of cardiac L-type Ca2+ channels, which can directly affect cardiac contractility (10, 23). 3) Significant reductions in myocardial injury following coronary artery occlusion and ischemia have also been attributed to S-nitrosylation. Specifically, S-nitrosylation of hypoxia-inducible factor-1α promotes myocardial capillary synthesis via increases in vascular endothelial growth factor (13). Many other proteins contributing to cardiac pathophysiology have also been reported to contain levels of S-nitrosylation (14).In addition, NO has been reported to modulate its own signaling via S-nitrosylation of NOS itself (20), as well as downstream effectors of cGMP signaling, such as sGC (21). Therefore, it stands to reason that S-nitrosylation may also play a critical role in upstream regulation of NO signaling as well. Although one cannot rule out the involvement of additional protein mediators without direct experimental evidence, the simplest and most direct explanation for the observations of Zhou et al. (28) is consistent with NO-mediated S-nitrosylation of CAT-1 and CAT-2A. In particular: 1) Incubation with the exogenous NO producers sodium pentacyanonitrosyl ferrate(III) dehydrate (SNP) or S-nitroso-N-acetyl-dl-penicillamine (SNAP) decreased currents stimulated by 10 mM l-arginine (and l-lysine) in whole cell voltage-clamped myocytes. 2) Although application of an exogenous NO producer might inhibit CAT-mediated transport via cGMP production and subsequent G-kinase phosphorylation of the transporter, this does not appear to be the case because both SNP and SNAP decreased l-lysine fluxes in vesicle preparations, which do not contain cytosolic sGC and G-kinase. 3) They observed a biphasic behavior of l-arginine-induced currents, indicative of l-arginine entry and subsequent NOS conversion to NO and l-citrulline, with this endogenously produced NO then acting back on CAT to decrease l-arginine inward currents. This plausible mode of action was supported pharmacologically by inclusion of the ubiquitous NOS inhibitor l-NAME, which eliminated the inhibitory component of the l-arginine currents. In contrast, the sGC inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), was without effect. Taken together these data strongly support that there is a direct NO-mediated inhibition of CAT transport in cardiac myocytes.In conclusion, the article by Zhou et al. (28) brings to light new relevant understanding of NO signaling, which now must include regulation of its own synthesis by downregulation of substrate delivery via CATs. The cationic amino acid transporters CAT-1 and CAT-2A are now tentative new participants in this scenario and if confirmed, these transporters could be targets for drug development for the treatment of some cardiac insufficiencies. We are all aware that cardiac excitation-contraction coupling involves a diverse team of players, which now appears to include the plasma membrane cationic amino acid transporters CAT-1 and CAT-2A.GRANTSThe author's work is supported by National Institutes of Health Grants GM-061583 and DK-83859 and National Science Foundation Grant MCB 0347202.DISCLOSURESNo conflicts of interest, financial or otherwise, are declared by the author.ACKNOWLEDGMENTSI thank Drs. Pablo Artigas and Charles Costa for comments on the manuscript.REFERENCES1. Bredt DS. Nitric oxide signaling specificity - the heart of the problem. J Cell Sci 116: 9–15, 2003.Crossref | PubMed | ISI | Google Scholar2. Closs EI , Boissel JP , Habermeier A , Rotmann A. Structure and function of cationic amino transporters (CATs). J Membr Biol 213: 67–77, 2006.Crossref | PubMed | ISI | Google Scholar3. Deves R , Angelo S , Chavez P. N-ethylmaleimide discriminates between two lysine transport systems in human erythrocytes. 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Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factor. Nature 327: 524–526, 1987.Crossref | PubMed | ISI | Google Scholar18. Peluffo RD. l-Arginine currents in rat cardiac ventricular myocytes. J Physiol 580: 925–936, 2007.Crossref | PubMed | ISI | Google Scholar19. Pola E , Bertran J , Roca A , Palacin M , Zorzano A , Testar X. Sensitivity of system A and ASC transport activities to thiol-group-modifying reagents in rat liver plasma membrane vesicles. Evidence for a direct binding of N-ethylmalemide and iodoacetamide on A and ASC carriers. Biochem J 271: 297–303, 1990.Crossref | PubMed | ISI | Google Scholar20. Ravi K , Brennan LA , Levic S , Ross PA , Black SM. S-nitrosylation of endothelial nitric oxide synthase is associated with monomerization and decreased enzyme activity. Proc Natl Acad Sci USA 101: 2619–2624, 2004.Crossref | PubMed | ISI | Google Scholar21. Sayed N , Baskaran P , Ma X , van den Akker F , Beuve A. Desensitization of soluble guanylyl cyclase, the NO receptor, by S-nitrosylation. Proc Natl Acad Sci USA 104: 12312–12317, 2007.Crossref | PubMed | ISI | Google Scholar22. Seddon M , Shah AM , Casadei B. Cardiomyocytes as effectors of nitric oxide signaling. Cardiovasc Res 75: 315–326, 2007.Crossref | PubMed | ISI | Google Scholar23. Sun J , Picht E , Ginsburg KS , Bers DM , Steenbergen C , Murphy E. Hypercontractile female hearts exhibit increased S-nitrosylation of the L-type Ca2+ channel alpha-1 subunit and reduced ischemia/reperfusion injury. Circ Res 98: 403–411, 2006.Crossref | PubMed | ISI | Google Scholar24. Sun J , Yamaguchi N , Xu L , Eu JP , Stamler JS , Meissner G. Regulation of the cardiac muscle ryanodine receptor by O2 tension and S-nitrosoglutathione. Biochemistry 47: 13985–13990, 2008.Crossref | PubMed | ISI | Google Scholar25. Verrey F , Closs EI , Wagner CA , Palacin M , Endou H , Kanai Y. CATs and HATs: the SLC7 family of amino acid transporters. Pflügers Arch 447: 532–42, 2004.Crossref | PubMed | ISI | Google Scholar26. Whalen EJ , Foster MW , Matsumoto A , Ozawa K , Violin JD , Que LG , Nelson CD , Benhar M , Keys JR , Rockman HA , Koch WJ , Daaka Y , Lefkowitz RJ , Stamler JS. Regulation of β-adrenergic receptor signaling by S-nitrosylation of G-protein-coupled receptor kinase 2. Cell 129: 511–522, 2007.Crossref | PubMed | ISI | Google Scholar27. Xu L , Eu JP , Meissner G , Stamler JS. Activation of the cardiac calcium release channel (ryanodine receptor) by poly-S-nitrosylation. Science 279: 234–237, 1998.Crossref | PubMed | ISI | Google Scholar28. Zhou J , Kim DD , Peluffo RD. Nitric oxide can acutely modulate its biosynthesis through a negative feedback mechanism on l-arginine transport in cardiac myocytes. Am J Physiol Cell Physiol (May 26, 2010). doi:10.1152/ajpcell.00077.2010.Link | ISI | Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: C. Gatto, School of Biological Sciences, Illinois State Univ., 210 Julian Hall; Campus Box 4120, Normal, IL 61790-4120 (e-mail: [email protected]edu). Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation Cited ByEffects of L-arginine supplementation on biomarkers of glycemic control: a systematic review and meta‐analysis of randomised clinical trials10 January 2021 | Archives of Physiology and Biochemistry, Vol. 16Oral L-Arginine Administration Improves Anthropometric and Biochemical Indices Associated With Cardiovascular Diseases in Obese Patients: A Randomized, Single Blind Placebo Controlled Clinical Trial29 December 2015 | Research in Cardiovascular Medicine, Vol. 5, No. 1 More from this issue > Volume 299Issue 2August 2010Pages C213-C215 Copyright & PermissionsCopyright © 2010 the American Physiological Societyhttps://doi.org/10.1152/ajpcell.00191.2010PubMed20505043History Published online 1 August 2010 Published in print 1 August 2010 Metrics

Infiltration of Inflammatory Cells Plays an Important Role in Matrix Metalloproteinase Expression and Activation in the Heart during Sepsis

Nitric oxide (NO) is an important second messenger, involved in the implementation of various cell functions. It regulates various physiological and pathological processes such as neurotransmission, cell responses to stress, and neurodegeneration. NO synthase is a family of enzymes that synthesize NO from L-arginine. The activity of different NOS isoforms depends both on endogenous and exogenous factors. In particular, it is modulated by oxidative stress, induced by photodynamic therapy (PDT). We have studied the possible role of NOS in the regulation of survival and death of neurons and surrounding glial cells under photo-oxidative stress induced by photodynamic treatment (PDT). The crayfish stretch receptor consisting of a single identified sensory neuron enveloped by glial cells is a simple but informative model object. It was photosensitized with alumophthalocyanine photosens (10 nM) and irradiated with a laser diode (670 nm, 0.4 W/cm2). Antinecrotic and proapoptotic effects of NO on the glial cells were found using inhibitory analysis. We have shown the role of inducible NO synthase in photoinduced apoptosis and involvement of neuronal NO synthase in photoinduced necrosis of glial cells in the isolated crayfish stretch receptor. The activation of NO synthase was evaluated using NADPH-diaphorase histochemistry, a marker of neurons expressing the enzyme. The activation of NO synthase in the isolated crayfish stretch receptor was evaluated as a function of time after PDT. Photodynamic treatment induced transient increase in NO synthase activity and then slowly inhibited this enzyme.

Animal studies have suggested that nitric oxide (NO) synthases (NOS) play a role in the regulation of protein metabolism in endotoxemia. We therefore investigated the role of inducible NOS (NOS2) on intestinal protein and neuronal NOS (NOS1) and endothelial NOS (NOS3) on amino acid metabolism. Three groups of mice were studied: 1) wild-type (WT), 2) NOS2 knockout (NOS2-KO), and 3) NOS2-KO + N(omega)-nitro-l-arginine methyl ester (NOS2-KO + l-NAME), both in nonstimulated and LPS-treated conditions. By infusion of the stable isotopes l-[phenyl-(2)H(5)]Phe, l-[phenyl-(2)H(2)]Tyr, l-[guanidino-(15)N(2)]Arg, and l-[ureido-(13)C; (2)H(2)]citrulline (Cit), intestinal protein, amino acid, and Arg/NO metabolism were studied on the whole body level and across intestine. In nonstimulated situations, NOS2 deficiency increased whole body protein turnover and intestinal Gln uptake and Cit production. In NOS2-KO + l-NAME, the above-mentioned changes were reversed. After LPS in WT, whole body NO and Cit production increased. In contrast to this, LPS decreased net intestinal Gln uptake, whole body NO, and Cit production in NOS2-KO mice. Treatment of NOS2-KO + l-NAME with LPS was lethal in eight of eleven mice (73%). The surviving mice in this group showed a major drop in intestinal protein breakdown and synthesis to almost zero. Thus both in baseline conditions and during endotoxemia, the absence of NOS2 upregulated NOS1 and/or NOS3, which increased intestinal metabolism. The drop in intestinal protein metabolism in the endotoxemic NOS2-KO + l-NAME group might play a role in mortality in that group.

Anatomic distribution of nitric oxide synthase in the heart

In the last decade, a great deal of attention has been focused on adenoviral-mediated gene transfer into somatic cells as a possible therapeutic approach. Somatic gene transfer into postmitotic cells (such as cardiomyocytes) provides a very powerful means to deliver the protein of interest, which is either functionally defective or missing because of loss of gene expression. In recent years, gene therapy for heart failure has gained considerable interest, mainly because of improvements in vector technology, cardiac gene delivery, and a better understanding of the molecular basis of heart failure.1 2 Heart failure provides an attractive candidate for gene therapy, because several targets have been identified as either functionally impaired or defective. Studies using animal models and failing human hearts have identified several abnormalities that affect excitation-contraction coupling. In particular, changes at the level of sarcolemmal/sarcoplasmic reticulum Ca2+ transport and contractile proteins are thought to contribute to depressed contractile function. Cardiomyocytes from failing animal and human hearts reveal abnormal Ca2+ homeostasis, such as reduced sarcoplasmic reticulum (SR) Ca2+ release, elevated diastolic Ca2+, and reduced rate of Ca2+ removal.3 4 5 There is strong evidence that reduced expression or activity of the SR Ca2+ ATPase (SERCA) and increased expression of Na+-Ca2+ exchanger are key changes contributing to alterations in calcium homeostasis in the heart.6 7 8 9 10 It is also believed that abnormalities in calcium cycling are responsible for blunting of the frequency potentiation of contractile force in the failing human heart.11 Thus, SR Ca2+ ATPase plays a dominant role in removing cytosolic Ca2+ and is the main mechanism for restoring SR Ca2+ load. The Na+-Ca2+ exchanger, on the other hand, transports calcium outside the cell and is a competitor …

Nitric Oxide and Septic Vascular Dysfunction