Activation of mitochondrial ATP-sensitive potassium channels increases cell viability against rotenone-induced cell death

We recently showed that activation of ATP-sensitive potassium (K-ATP) channels in PC12 cells induces protection against the neurotoxic effect of rotenone, a mitochondrial complex I inhibitor. In this study, we sought to determine the locus of the K-ATP channels that mediate this protection in PC12 cells. We found that pretreatment of PC12 cells with diazoxide, a mitochondrial K-ATP channel selective opener, dose-dependently increases cell viability against rotenone-induced cell death as indicated in trypan blue exclusion assays. The protective effect of this preconditioning is attenuated by 5-hydroxydecanoic acid (5-HD), a selective mitochondrial K-ATP channel antagonist but not in the presence of HMR-1098, a selective plasma membrane K-ATP potassium channel antagonist. In contrast, P-1075, a selective plasma membrane K-ATP channel opener, does not induce protection. Using specific antibodies against SUR1 and Kir6.1, we detected immunoreactive proteins of apparent molecular masses 155 and 50 kDa, corresponding to those previously reported for SUR1 and Kir6.1, respectively, in the mitochondria-enriched fraction of PC12 cells. In addition, whole cell patch-clamp studies revealed that inward currents in PC12 cells are insensitive to P-1075, HMR-1098, glibenclamide and diazoxide, indicating that functional plasma membrane K-ATP channels are negligible. Taken together, our results demonstrate for the first time that activation of mitochondrial K-ATP channels elicits protection against rotenone-induced cell death.