ATP-sensitive K+ channels contribute to the protective effects of exogenous hydrogen sulfide against high glucose-induced injury in H9c2 cardiac cells

Hyperglycemia, as well as diabetes mellitus, has been shown to impair ATP-sensitive K+ (K-ATP) channels in human vascular smooth muscle cells. Hydrogen sulfide (H2S) is also known to be an opener of K-ATP channels. We previously demonstrated the cardioprotective effects exerted by H2S against high-glucose (HG, 35 mM glucose)-induced injury in H9c2 cardiac cells. As such, we hypothesized that K-ATP channels play a role in the cardioprotective effects of H2S against HG-induced injury. In this study, to examine this hypothesis, H9c2 cardiac cells were treated with HG for 24 h to establish a model of HG-induced insults. Our findings revealed that treatment of the cells with HG markedly decreased the expression level of K-ATP channels. However, the decreased expression of K-ATP channels was reversed by the treatment of the cells with 400 mu M sodium hydrogen sulfide (NaHS, a donor of H2S) for 30 min prior to exposure to HG. Additionally, the HG-induced cardiomyocyte injuries, including cytotoxicity, apoptosis, oxidative stress and mitochondrial damage, were ameliorated by treatment with NaHS or 100 mu M diazoxide (a mitochondrial K-ATP channel opener) or 50 mu M pinacidil (a non-selective K-ATP channel opener) for 30 min prior to exposure to HG, as indicated by an increase in cell viability, as well as a decrease in the number of apoptotic cells, the expression of cleaved caspase-3, the generation of reactive oxygen species (ROS) and the dissipation of mitochondrial membrane potential (MMP). Notably, treatment of the H9c2 cardiac cells with 100 mu M 5-hydroxydecanoic acid (5-HD, a mitochondrial K-ATP channel blocker) or 1 mM glibenclamide (Gli, a non-selective K-ATP channel blocker) for 30 min prior to treatment with NaHS and exposure to HG significantly attenuated the above-mentioned cardioprotective effects exerted by NaHS. Notably, treatment of the cells with 500 mu M N-acetyl-L-cysteine (NAC, a scavenger of ROS) for 60 min prior to exposure to HG markedly reduced the HG-induced inhibitory effect on the expression of K-ATP channels. Taken together, our results suggest that K-ATP channels play an important role in the cardioprotective effects of exogenous H2S against HG-induced injury. This study also provides novel data demonstraring that there is an antagonistic interaction between ROS and K-ATP channels in HG-exposed H9c2 cardiac cells.