Role of reactive oxygen species in the regulation of cardiac contractility

Increased production of reactive oxygen species (ROS) has been linked to the pathogenesis of contractile dysfunction in heart failure. However, it is unclear whether ROS can regulate physiological cellular processes in the myocardium. Here, we characterized the role of endogenous ROS production in the acute regulation of cardiac contractility in the intact rat heart. In isolated perfused rat hearts, endothelin-1 (ET-1, 1 nmol/L) stimulated ROS formation in the left ventricle, which was prevented by the antioxidant N-acetylcysteine and the NAD(P)H oxidase inhibitor apocynin. N-acetylcysteine, the superoxide dismutase mimetic MnTMPyP, and apocynin significantly attenuated ET-1-mediated inotropic effect, which was accompanied by inhibition of extracellular signal regulated kinase 1/2 (ERK1/2) phosphorylation. Moreover, the mitochondrial KATP channel blocker 5-HD, and the mitochondrial large conductance calcium activated potassium channel blocker paxilline, but not the sarcolemmal KATP channel blocker HMR 1098 attenuated the inotropic response to ET-1. However, ET-1-induced ROS generation was not abolished by inhibiting mitochondrial KATP channel opening. In contrast to ET-1 stimulation, the positive inotropic effect of β1-adrenergic receptor agonist dobutamine (250 nmol/L) was significantly augmented by N-acetylcysteine and apocynin. Moreover, dobutamine-induced phospholamban phosphorylation was markedly enhanced by apocynin. In conclusion, NAD(P)H oxidase-derived ROS play a physiological role in the acute regulation of cardiac contractility in the intact rat heart. Our results reveal that ET-1-induced increase in cardiac contractility is partially dependent on enhanced ROS generation, which in turn, activates the ERK1/2 pathway. On the other hand, β-adrenergic receptor-induced positive inotropic effect and phospholamban phosphorylation is enhanced by NAD(P)H oxidase inhibition.

Research Highlights
► Positive inotropic effect of ET-1 is partly dependent on NAD(P)H oxidase derived ROS.
► ROS mediate the ET-1-induced increase in ERK1/2 activity.
► NAD(P)H oxidase derived ROS limit the positive inotropic effect of dobutamine.
► NAD(P)H oxidase inhibition enhances dobutamine-induced phospholamban phosphorylation.
► ROS play a physiological role in the acute regulation of cardiac contractility.