Nicorandil Protects Cardiac Microvascular Endothelial Cells From Advanced Glycation End Products Induced Cytotoxicity Via Promoting Autophagy

Microvascular dysfunction, as a major comorbidity of Diabetes mellitus, is mainly induced by advanced glycation end products (AGEs). We hypothesized that the anti-angina medicine nicorandil protects cardiac microvascular endothelial cells (CMECs) subjected to AGEs and investigated themechanisms regarding to autophagy regulation. Cellular viability and migration were analyzed to determine the effects of nicorandil or pathway inhibitors. Western blot, monodansylcadaverine (MDC) staining, adenovirus expressing mCherry - green fluorescent protein light chain 3 (LC3)transfection, transmission electron microscopy and confocal microscopy were used to elucidate autophagy and its regulation. Nicorandil at 100 mu M ameliorated the AGE-induced cytotoxicity. LC3-II upregulation and increased autophagosome formation were found in the nicorandil-treated groupscompared with the AGE groups, which were suppressed by wortmannin or chloroquine. Wortmannin or chloroquine attenuated cellular protection of nicorandil. AGEs promoted phosphorylation of I kappa B kinase beta (IKK beta), I kappa B alpha and p65, the target proteins in the nuclear factor-kappaB (NF-kappa B) signaling pathway. Inactivating the NF-kappa B pathway by pyrrolidine dithiocarbamate (PDTC) or nicorandil increased the level of LC3-II or the formation of MDC-labeled autophagosome. Confocal microscopy revealed that nicorandil as well as PDTC promoted autophagic flux inAGEs treated CMECs. The study suggests that nicorandil exerts cytoprotective effects on CMECs from AGEs by inducing autophagy, partly through inhibiting the NF-kappa B signaling pathway.