c-Myc promotes tubular cell apoptosis in ischemia-reperfusion-induced renal injury by negatively regulating c-FLIP and enhancing FasL/Fas-mediated apoptosis pathway

c-Myc plays an important role in cell proliferation,differentiation,and cell apoptosis.FasL/Fas pathway is a key regulator of cell apoptosis.This study was aimed to investigate the effects of c-Myc on the FasL/Fas pathway in ischemia-reperfusion(I/R)-induced renal injury.Rats were objected to bilateral renal ischemia for 60 min and reperfused for 24 or 48 h.NRK-52 E cells were treated with hypoxia-reoxygenation(H/R)or FasL.Immunohistochemistry was used to identify the distribution of c-Myc.Cell apoptosis was assessed by TUNEL staining.Ad-c-Myc and recombinant pcDAN 3.0 were used to overexpress c-Myc and c-FLIP,respectively.ChIP assay and luciferase assay were used to detect the binding of c-Myc to c-FLIP promoter.In I/R rats,c-Myc was increased significantly and mainly located in renal tubular epithelial cells;meanwhile,c-FLIP was decreased,cleaved caspase-8,cleaved caspase-3 and TUNEL-positive staining cells were increased.Treatment of I/R rats with c-Myc inhibitor 10058-F4 significantly attenuated the decrease in c-FLIP,the increase in cleaved caspase-8,cleaved caspase-3,TUNEL-positive cells,Scr and BUN in I/R rats.In NRK-52 E cells,hypoxia and reoxygen induced the increase in c-Myc and decrease in c-FLIP.ChIP and luciferase assay results indicated that cMyc binds to the promoter region of c-FLIP gene.Overexpression of c-Myc markedly decreased c-FLIP.Overexpression of c-FLIP inhibited the increase in cleaved caspase-8 and caspase-3 induced by FasL.Data indicated that c-Myc is increased in kidneys of I/R rats and negatively regulates the expression of c-FLIP,then enhanced FasL-induced cell apoptosis in I/R stress.