Mitochondrial reactive oxygen species are the intracellular mediators of the increase in cardiac contractility induced by endothelin-1

. AIELLO EA,; DE GIUSTI VC,; CORREA MV; VILLA-ABRILLE MC; YEVES AM; CHIAPPE DE CINGOLANI GE; CINGOLANI HE

New London, New Hampshire, EEUU

Congreso; Gordon Research Conference, Cardiac Regulatory Mechanisms; 2008

Gordon Research Conference,

Mitochondrial reactive oxygen species are the intracellular mediators of the increase in cardiac contractility induced by endothelin-1. Aiello EA, De Giusti VC, Correa MV, Villa-Abrille MC, Yeves AM, Chiappe de Cingolani GE, Cingolani HE. Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, UNLP, La Plata, Argentina.Reactive oxygen species (ROS) have been implicated in different deleterious cardiovascular actions. However, in recent years, it was shown that moderate concentrations of ROS can act as intracellular signaling molecules playing important roles in different physiological mechanisms. Thus, the objective of the present work was to evaluate the role and source of ROS generation in the positive inotropic effect of a physiological concentration of endothelin-1 (ET-1, 0.4 nM).  Isolated cat ventricular myocytes were used to measure sarcomere shortening with a video-camera, superoxide anion (.O2-) with chemiluminescence, and ROS production and intracellular pH (pHi) with epifluorescence.  The ET-1-induced positive inotropic effect (40.4±3.1 %, n=10, p<0.05) was associated to an increase in ROS production (105±29 fluorescence units above control, n=6, p<0.05). ET-1 also induced an increase in .O2- production that was inhibited by the NADPH oxidase blocker, apocynin, and by the blockers of mitochondrial ATP-sensitive K+ channels (mKATP), glibenclamide and 5 hydroxydecanoic acid. The ET-1-induced positive inotropic effect was inhibited by apocynin (0.3 mM; 6.3±6.6 %, n=13), glibenclamide (50 mM; 8.8±3.5 %, n=6), 5 hydroxydecanoic acid (500 mM; 14.1±8.1, n=9), and by scavenging ROS with MPG (2 mM; 0.92±5.6 %, n=8). ET-1 enhanced proton efflux (JH) carried by the Na+/H+ exchanger (NHE) after an acid load, effect that was blocked by MPG. Consistently, the ET-induced positive inotropic effect was also inhibited by the NHE selective blocker HOE642 (5 mM; 9.37±6.07 %, n=7). The data suggest that ET-1 stimulates the NADPH oxidase, forming .O2- which opens mKATP and releases mitochondrial ROS, which in turn activates the NHE and triggers an increase in contractility.