7-ketosterol Induced Pancreatic β-cell Apoptosis Via Endoplasmic Reticulum Stress Pathway

Background:Impairment of pancreatic β-cell function is one of the important pathophysiology factors which leading to type 2 diabetes,and its risk factors and mechanism have not yet completely clear.Clinical observation indicated that the concentration of cholesterol oxidation products is related with the onset of type 2 diabetes,but the specific mechanism remains poorly understood.There are studies showing that ER stress and its downstream proapoptotic molecule,C/EBP homologous protein(CHOP),plays an important role in pancreatic β-cell apoptosis,but whether and how ER stress signaling takes part in 7-KC induced pancreatic β-cell apoptosis is not determined.Methods:MTS measurement was used to detect the survival condition of pancreatic β-cell cell in different concentration and time of 7-KC.Western blot analysis was used to detect the expression of cleaved-caspase 3 and the BCL protein family,as well as ER stress level.4-PBA was used to explore adverse effect of 7-KC.Results:The 7-KC group showed a significant reduced survival rate(P<0.05).Western blot analysis indicated that 7-KC can significantly increase the expression of leaved-caspase 3 in pancreatic β-cells.Western blot analysis showed that the expression of ER stress sensors,p-PERK,p-IRE1α and ATF6,were significantly higher than control group,pointing out that 7-KC increased the levels of ER stress in(P<0.05),and it can be inhibited by ER stress protector 4-PBA.Western blot analysis also showed a significant increase of the expression of p-eIF-1α,ATF4 and CHOP than control group(P<0.01),which can be inhibited by 4-PBA,and elevated CHOP expression in 7-KC induced pancreatic β-cells was linked to activation of cleaved-caspase 3.However,the administration of ER stress protector 4-PBA could significantly reduce apoptosis in 7-KC induced pancreatic β-cells.Conclusion:7-KC influenced pancreatic β-cells survival and promoted apoptosis in these cells.It induced pancreatic β-cells apoptosis in which ER stress and its downstream transcription factor CHOP proapoptotic pathways played an important role.So our study provided a new strategy for type 2 diabetes mellitus pathogenesis and treatment.