Effect and mechanism of protein kinase C δ on cell cycle blockage and apoptosis in human umbilical vein endothelial cells induced by high glucose

Objective To investigate the effect of protein kinase C(PKC) δ on high glucose-induced cell cycle blockage and apoptosis in human umbilical vein endothelial cells(HUVECs),and explore its underlying mechanism.Methods HUVECs were divided into five groups:non-transfected+normal glucose(NG group,D-glucose 5.6mmol/L),transfected with Ad5-null+normal glucose(NN group),non-transfected+high glucose(HG group,D-glucose 25mmol/L),transfected with Ad5-PKCδ+high glucose(PHG group),and transfected with Ad5-PKCδ and high glucose treated with rottlerin(PHR group,10μmol/L rottlerin).The distribution of PKCδ was detected by confocal microscopy.Cell cycle and apoptotic rate of HUVECs were evaluated by flow cytometry.In addition,protein expression of phosphorylated forkhead box O1(FOXO1)(S256) and P27kip1 were detected by Western blotting.Results Compared with NG group,the empty vector transfection showed no biological influence on cell cycle in NN group(P0.05).Again,compared with NG group,the protein expression of PKCδ in HUVECs was up-regulated,the cytosol/nuclei ratio of PKCδ was decreased,cell cycle was blocked in G0/G1 phase,the apoptosis increased significantly,and the protein content of p-FOXO1(S256) and P27kip1 increased(P0.05) in both HG and PHG group.Compared with PHG group,the cytosol/nuclei ratio of PKCδ was increased,cell cycle was blocked in G0/G1 phase,the apoptosis was ameliorated,and the protein expression of p-FOXO1(S256) and P27kip1 decreased in PHR group after rottlerin treatment(P0.05).Conclusion High glucose can increase PKCδ expression and partly activate the translocation into nucleus in HUVECs,and induces blockage of the cell cycle G0/G1 phase by PKCδ→p-FOXO1(S256)→P27kip1 pathway,thus enhances cell apoptosis.