Nitroxyl (HNO) Stimulates Soluble Guanylyl Cyclase to Suppress Cardiomyocyte Hypertrophy and Superoxide Generation

Abstract

BackgroundNew therapeutic targets for cardiac hypertrophy, an independent risk factor for heart failure and death, are essential. HNO is a novel redox sibling of NO• attracting considerable attention for the treatment of cardiovascular disorders, eliciting cGMP-dependent vasodilatation yet cGMP-independent positive inotropy. The impact of HNO on cardiac hypertrophy (which is negatively regulated by cGMP) however has not been investigated.MethodsNeonatal rat cardiomyocytes were incubated with angiotensin II (Ang II) in the presence and absence of the HNO donor Angeli's salt (sodium trioxodinitrate) or B-type natriuretic peptide, BNP (all 1 µmol/L). Hypertrophic responses and its triggers, as well as cGMP signaling, were determined.ResultsWe now demonstrate that Angeli's salt inhibits Ang II-induced hypertrophic responses in cardiomyocytes, including increases in cardiomyocyte size, de novo protein synthesis and β-myosin heavy chain expression. Angeli's salt also suppresses Ang II induction of key triggers of the cardiomyocyte hypertrophic response, including NADPH oxidase (on both Nox2 expression and superoxide generation), as well as p38 mitogen-activated protein kinase (p38MAPK). The antihypertrophic, superoxide-suppressing and cGMP-elevating effects of Angeli's salt were mimicked by BNP. We also demonstrate that the effects of Angeli's salt are specifically mediated by HNO (with no role for NO• or nitrite), with subsequent activation of cardiomyocyte soluble guanylyl cyclase (sGC) and cGMP signaling (on both cGMP-dependent protein kinase, cGK-I and phosphorylation of vasodilator-stimulated phosphoprotein, VASP).ConclusionsOur results demonstrate that HNO prevents cardiomyocyte hypertrophy, and that cGMP-dependent NADPH oxidase suppression contributes to these antihypertrophic actions. HNO donors may thus represent innovative pharmacotherapy for cardiac hypertrophy.

HNO/cGMP-dependent antihypertrophic actions of isopropylamine-NONOate in neonatal rat cardiomyocytes: potential therapeutic advantages of HNO over NO˙

“…It has also been suggested that HNO may mediate, at least in part, some of the biological effects traditionally attributed to endogenous NO˙(2, 26). It is thus now apparent, however, that HNO offers considerable advantages in the treatment of cardiovascular disease (26,31,38,44).In addition to these aforementioned protective cardiovascular actions, the distinct pharmacology of HNO gives rise to a spectrum of unique properties that potentially position HNO-based pharmacotherapies even more favorably than their NO˙-based counterparts. HNO, in direct contrast to NO˙, resists scavenging by superoxide (30,36), is resistant to vascular tolerance development (23, 25), and enhances myocardial contractility (39, 40).…”

“…It has also been suggested that HNO may mediate, at least in part, some of the biological effects traditionally attributed to endogenous NO˙(2, 26). It is thus now apparent, however, that HNO offers considerable advantages in the treatment of cardiovascular disease (26,31,38,44).…”

“…NO˙and HNO share several common cardiac and vascular protective actions, ranging from potent vasodilator (2, 10, 12-14, 22, 23, 59) and antiplatelet actions (3,4) to, more recently, antihypertrophic actions in cardiomyocytes (31). These actions are all mediated predominantly via sGC (10,22,23,31,47,59) and a subsequent increase in cGMP (14,23,31,47). It has also been suggested that HNO may mediate, at least in part, some of the biological effects traditionally attributed to endogenous NO˙ (2,26).…”

“…The rapidly vanishing therapeutic efficacy of organic nitrates such as glyceryl trinitrate after continuous application, however, hampers the clinical utility of traditional nitrosovasodilators for long-term use (20,25). Interestingly, we have recently provided evidence that the prototypical HNO donor Angeli's salt (sodium trioxodinitrate) elicits antihypertrophic and superoxide-suppressing actions in cardiomyocytes (31). The alternative conventional available HNO donor isopropylamine-NONOate (IPA-NO) has the advantage over Angeli's salt, in that it does not elicit corelease of nitrite (NO 2 Ϫ ) concomitantly with HNO (35,38), but its antihypertrophic actions have not previously been examined.…”

“…All materials used for cardiomyocyte isolation were of tissue culture grade. Cardiomyocytes were isolated from neonatal (1-to 2-day-old) SpragueDawley rats using serial enzymatic digestion as previously described (28,31). Cardiomyocytes were suspended in sterile DMEM, supplemented with 100 U/ml penicillin, 100 g/ml streptomycin, and 10% FCS.…”