H2S preconditioning-induced PKC activation regulates intracellular calcium handling in rat cardiomyocytes

The present study was aimed to investigate the regulatory effect of protein kinase C (PKC) on intracellular Ca2+ handling in hydrogen sulfide (H2S)-preconditioned cardiomyocytes and its consequent effects on ischemia challenge. Immunoblot analysis was used to assess PKC isoform translocation in the rat cardiomyocytes 20 h after NaHS (an H2S donor, 10(-4) M) preconditioning (SP, 30 min). Intracellular Ca2+ was measured with a spectrofluorometric method using fura-2 ratio as an indicator. Cell length was compared before and after ischemia-reperfusion insults to indicate the extent of hypercontracture. SP motivated translocation of PKC alpha, PKC epsilon, and PKC delta to membrane fraction but only translocation of PKC epsilon and PKC delta was abolished by an ATP-sensitive potassium channel blocker glibenclamide. It was also found that SP significantly accelerated the decay of both electrically and caffeine-induced intracellular [Ca2+] transients, which were reversed by a selective PKC inhibitor chelerythrine. These data suggest that SP facilitated Ca2+ removal via both accelerating uptake of Ca2+ into sarcoplasmic reticulum and enhancing Ca2+ extrusion through Na+/Ca2+ exchanger in a PKC-dependent manner. Furthermore, blockade of PKC also attenuated the protective effects of SP against Ca2+ overload during ischemia and against myocyte hypercontracture at the onset of reperfusion. We demonstrate for the first time that SP activates PKC alpha, PKC epsilon, and PKC delta in cardiomyocytes via different signaling mechanisms. Such PKC activation, in turn, protects the heart against ischemia-reperfusion insults at least partly by ameliorating intracellular Ca2+ handling.