Hypotonic Swelling Promotes Nitric Oxide Release in Cardiac Ventricular Myocytes: Impact on Swelling-Induced Negative Inotropic Effect.

GONANO L, MORELL M.; DE GIUSTI VERONICA, AIELLO ALEJANDRO; BURGOS JUAN IGNACIO, VILA PETROFF M; DULCE RAUL, HARE JOSHUA

CARDIOVASCULAR RESEARCH

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2014 p. 456 - 466

0008-6363

Aims: Cardiac myocyte swelling occurs in multiple pathological situations and has been associated with contractile dysfunction, cell death and enhanced propensity to arrhythmias. We investigate whether hypotonic swelling promotes NO release in cardiac myocytes and whether it impacts on swelling-induced contractile dysfunction. Methods and results: Superfusing rat cardiac myocytes with a hypotonic solution (HS; 217 mOsm), increased cell volume, reduced myocyte contraction and Ca2+ transient and increased NO-sensitive DAF-FM fluorescence. When cells were exposed to HS + 2.5 mM of the NO synthase inhibitor L-NAME, cell swelling occurred in the absence of NO release. Swelling-induced NO release was also prevented by the NOS1 inhibitor, Nitroguanidine, and significantly reduced in NOS1 knockout mice. Additionally, Colchicine (inhibitor of microtubule polymerization) prevented the increase in DAF-FM fluorescence induced by HS indicating that microtubule integrity is necessary for swelling-induced NO release. The swelling-induced negative inotropic effect was exacerbated in the presence of either L-NAME, Nitroguandine, the guanylate cyclase inhibitor, ODQ, or the PKG inhibitor, KT5823, suggesting that NOS1-derived NO provides contractile support via a cGMP/PKG-dependent mechanism. Indeed, ODQ reduced Ca2+ wave velocity and both ODQ and KT5823 reduced the HS-induced increment in ryanodine receptor (RyR2, Ser2808) phosphorylation suggesting that in this context, cGMP/PKG may contribute to preserve contractile function by enhancing SR Ca2+ release. Conclusions: Our findings suggest a novel mechanism for NO release in cardiac myocytes with putative pathophysiological relevance determined, at least in part, by its capability to reduce the extent of contractile dysfunction associated with hypotonic swelling.