Nitric oxide involvement in pancreatic β cell apoptosis by glibenclamide

Glibenclamide as a second-generation compound of sulfonylurea has widely been used in the treatment of type 2 diabetes patients. It has been shown that it induces apoptosis in β cells, which is partially mediated by Ca2+ influx. Here, we investigated the role of nitric oxide (NO) and nitric oxide synthase (NOS) isoforms on glibenclamide-induced apoptosis in rat insulinoma cells. Our results showed that glibenclamide induces NO generation (measured as nitrite) that is accompanied with decrease of cell viability in a defined concentration of glibenclamide. The effects of glibenclamide on cell viability were partially inhibited after treatment with NG-nitro-l-arginine methyl ester (l-NAME), inhibitor more selective for constitutive nitric oxide synthase, and in the presence of D600— a blocker of voltage-gated L-type Ca2+ channels inhibited Ca2+ influx into β cells, whereas aminoguanidine (AG), a preferential inhibitor of inducible NOS, was significantly less effective. Analysis of DNA fragmentation by electrophoresis and staining with Hoechest 33342 and propidium iodide showed that l-NAME, but not AG, prevented DNA fragmentation and decreased the number of cells with condensed and fragmented nuclei. It revealed that the effects of glibenclamide on apoptosis were partially inhibited by treatment with l-NAME. In conclusion, we have shown that NO production in glibenclamide treated cells may be involved in the induction of apoptotic cell death in pure β cell line and it may be due to Ca2+ dependent activation of constitutive NOS isoforms.