Acute Simvastatin Inhibits KATP Channels of Porcine Coronary Artery Myocytes

Background: Statins (3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitors) consumption provides beneficial effects on cardiovascular systems. However, effects of statins on vascular KATP channel gatings are unknown. Methods: Pig left anterior descending coronary artery and human left internal mammary artery were isolated and endothelium-denuded for tension measurements and Western immunoblots. Enzymatically-dissociated/cultured arterial myocytes were used for patch-clamp electrophysiological studies and for [Ca2+](i), [ATP](i) and [glucose](o) uptake measurements. Results: The cromakalim (10 nM to 10 mu M)- and pinacidil (10 nM to 10 mu M)-induced concentration-dependent relaxation of porcine coronary artery was inhibited by simvastatin (3 and 10 mu M). Simvastatin (1, 3 and 10 mu M) suppressed (in okadaic acid (10 nM)-sensitive manner) cromakalim (10 mM)-and pinacidil (10 mu M)-mediated opening of whole-cell K-ATP channels of arterial myocytes. Simvastatin (10 mu M) and AICAR (1 mM) elicited a time-dependent, compound C (1 mu M)-sensitive [H-3]-2-deoxy- glucose uptake and an increase in [ATP](i) levels. A time (2-30 min)- and concentration (0.1-10 mu M)-dependent increase by simvastatin of p-AMPK alpha-Thr(172) and p-PP2A-Tyr(307) expression was observed. The enhanced p-AMPK alpha-Thr(172) expression was inhibited by compound C, ryanodine (100 mu M) and KN93 (10 mu M). Simvastatin-induced p-PP2A-Tyr(307) expression was suppressed by okadaic acid, compound C, ryanodine, KN93, phloridzin (1 mM), ouabain (10 mu M), and in [glucose](o)-free or [Na+](o)-free conditions. Conclusions: Simvastatin causes ryanodine-sensitive Ca2+ release which is important for AMPK alpha-Thr(172) phosphorylation via Ca2+/CaMK II. AMPK alpha-Thr(172) phosphorylation causes [glucose](o) uptake (and an [ATP](i) increase), closure of K-ATP channels, and phosphorylation of AMPK alpha-Thr(172) and PP2A-Tyr(307) resulted. Phosphorylation of PP2A-Tyr(307) occurs at a site downstream of AMPK alpha-Thr(172) phosphorylation.