Myocardial mineralocorticoid receptor activation by stretching and its? functional consequences

DÍAZ RG; PÉREZ NG; MORGAN PE; VILLA-ABRILLE MC; CALDIZ CI; PORTIANSKY EL; NOLLY MB; ENNIS IL; CINGOLANI HE

HYPERTENSION

LIPPINCOTT WILLIAMS & WILKINS

Lugar: Philadelphia; Año: 2014 vol. 63 p. 112 - 118

0194-911X

Mineralocorticoid receptor (MR) antagonists decrease morbidity and mortality in heart failure patients for whom oxidative stress is usual; however, the underlying mechanism for this protection is unclear. Since aldosterone stimulates reactive oxygen species (ROS) production in several tissues, we explored its effect and the intracellular pathway involved in the rat myocardium. Aldosterone dose-dependently increased O2.- production in myocardial slices. At 10 nmol/L, aldosterone increased O2.- to 165±8.8 % of control, effect prevented not only by the MR antagonists eplerenone and spironolactone (107±7.8 and 103±5.3 %, respectively) but also by AG1478 (105±8.0%), antagonist of the EGF receptor (EGFR). Similar results were obtained by silencing MR expression through the direct intramyocardial injection of a lentivirus coding for a siRNA against the MR. The aldosterone effect on O2.- production was mimicked by the mKATP channel opener diazoxide and blocked by preventing its opening with 5-HD and glibenclamide, implicating the mitochondria as the source for O2.- . Inhibiting the respiratory chain with rotenone or the permeability transition pore (PTP) with cyclosporine also cancelled aldosterone-induced O2.- production. In addition, aldosterone effect depended on NADPH oxidase and phosphoinositide 3-kinase activation, as apocynin and wortmannin, respectively, inhibited it. EGF (0.1µg/mL) similarly increased O2.-, although in this case MR antagonists had no effect, suggesting that EGFR transactivation occurred downstream from MR. Inhibition of mKATP channels, the respiratory chain, or PTP did not prevent Akt phosphorylation, supporting it happened upstream of the mitochondria. Importantly, cardiomyocytes were confirmed as source of aldosterone induced mitochondrial ROS production in experiments performed in isolated cardiac myocytes. These results allow us to speculate that the beneficial effects of MR antagonists in heart failure may be related to a decrease in oxidative stress.