CathepsinB Induces Islet Beta Cell Inflammatory Response Through Apoptosis-independent Autophagy Overexpression

After cardiovascular disease and cancer,type 2 diabetes has become the third threat to people’s health and lives of non-communicable diseases.It bring physical and mental pain for patients and their families,and its high cost of treatment to patients and has tremendous pressure to their families.According to incomplete statistics,the number of China’s existing diabetes is more than 40 million,with 120 million new patients per year,of which 95%are type 2 diabetes.But so far,the pathogenesis of type 2 diabetes is not yet clear,it also needs further investigation.T2DM is a chronic inflam,matory process,and it is gradually recognized,accepte inflammation hypothesis of type 2 diabetes.Inflammation plays a role in pathogenesis of type 2 diabetes.Elevated levels of cytokine was show in the T2DM patients,and an increased risk of developing the T2DM disease was found in individuals with higher blood levels of Il-1β,IL-6 or MCP-1.Recent research suggests autophagy is involved in the pathological process of inflammation in type 2 diabetes.Autophagy is a lysosome-mediated degradation pathway in eukaryotic cells.It is an important mechanism for recycling of cytoplasmic components and cells self-protective mode.It maintains cell survival、updatereuse of material and homeostasis through degradation of damaged protein and dysfunctional intracellular organelles.Defective autophagy is associated with many diseases.However,recent studies indicate that autophagy may have a dual role,it may have a harmful side.We speculate that excessive autophagy could be harmdul in disease development.The study is aimed to investigate the influence of excessive autophagy for inflammation in INS-1 cells.We treated INS-1 cells with saturated fatty acid.We first sought to determine which of the proper concentration of PA to casue proper levels of apoptosis and significantly levels of autophagy.The effect of Four PA concentrations(0,0.25,0.5 and 1.OmM)on INS-1 cells at an incubation time of’ 12h on cell viability and autophagy activation was evaluated by western blot and DAPI.The results showed that the concentration of 0.5mM PA met the experiments requirements.We next investigated the effects of autophagy overexpression in transfected INS-1 cells with Atg7-inserted pCMGAC-GFP plasmid.Levels of mRNA of the inflammatory cytokines by QPCR were detected.The results showed that the protein level CathepsinB and levels of mRNA of inflammatory cytokines IL-1 β,MCP-1,TNF-αand IL-6 were significantly increased.CathepsinB inhibitor CA074-Me suppressed the increased mRNA levels of inflammatory cytokines under autophagy overexpression condition.Blocking Caspase-3 activity with Z-DEVD-FMK significantly blocked apoptosis but did not affect the inflammatory response.These results indicate that Cathepsin B-mediated excessive autophagy expression induced inflammatory response independent of apoptosis in INS-1 cells.This finding will provide a novel vision of the pathogenesis of type 2 diabetes and a new theoretical basis for treatments of T2D.