The Role And Mechanism Of Uncoupling Protein 2(UCP2)in Septic Acute Kidney Injury

BackgroundSepsis is increasingly considered as a global healthare issue due to a high rate of morbidity and mortality,along with considerable costs.Acute kidney injury(AKI)is a frequent and serious complication of sepsis,which is well-known as an independent risk factor for increased mortality of sepsis.Recent studies have revealed that mitochondrial dysfunction is profoundly involved in the pathophysiology of sepsis as well as septic AKI,which might be a promising target of intervention.UCP2,the most well-known protein of Uncoupling proteins(UCPs),which is located in the mitochondrial inner membrane,can regulate numerous metabolic processes,such as ATP and ROS production,mitochondrial calcium balance,MMP stabilization and glucose control,in addition to regulation of immunity and multiple pathologies,such as sepsis,diabetes,and cancer.Our previous studies have shown that UCP2 plays a protective role in myocardial mitochondrial damage under septic condition orinsepticacuteliverinjuryorin sepsis-associated encephalopathy.However,the pathological function of UCP2 was found to be tissue-and disease-specific.The functional role of UCP2 in septic AKI remains to be determined.Objective1.To detect the expression level of UCP2 during septic AKI and analysis the relation between the UCP2 expression level and the development of septic AKI in mice.2.To investigate the impact and mechanism of inhibiting the expression of UCP2 by genipin during the septic AKI in mice.3.To investigate the impact and mechanism of up-or downregulation of UCP2 expression by UCP2 recombinant lentiviral(LV5-UCP2)or si-UCP2 transfection during the septic AKI in HK-2 cells.MethodsIn vivoTo construct a septic AKI animal model,LPS were intraperitoneally injected into C57BL/6 mice.Mice were divided into the following groups:control LPS-treated(LPS 6h 12h 24h)and LPS(24h)+genipin-treated(Genipin).Part ?:Renal function,histopathology,UCP2 level were compared between control group and LPS(6h?12h?24h)grops in vivo.Part ?:The UCP2 level,renal function,histopathology,inflammation,mitochondrial function and ultrastructure,oxidative stress and apoptosis were compared between LPS(24h)group and Genipin group in vivo.In vitroTo construct a septic AKI cell model,HK-2 cells were exposed to LPS(100?g/ml).Cells weredivided into the following six groups:control,LPS,LV5-NC-transfected+LPS(LV5-NC+LPS),si-NC-transfected+LPS(si-NC+LPS),LV5-UCP2-transfected+LPS(LV5-UCP2+LPS),and si-UCP2-transfected+LPS(si-UCP2+LPS).Part ?:The UCP2 level,cell viability,inflammation,mitochondrial function and ultrastructure,oxidative stress and apoptosis were respectively measured among all groups in vitro.ResultsPart ?1.After LPS exposure,the serum BUN,NGAL,KIM-1 levels at all time points and the serum Cr level at 12h and 24h were increased significantly compared with control group.2.LPS resulted in serious renal pathological damage at all time points.3.After LPS exposure,the UCP2 mRNA and protein expression levels at all time points were increased significantly compared with control group.Part ?1.Genipin resulted in a significant blockade of the LPS-induced upregulation of the UCP2 mRNA and protein expression levels.2.Genipinaggravated the LPS-induced renal injury,inflammation,macrophages infiltration,mitochondrial dysfunction,oxidative stress and apoptosis.Part ?1.UCP2 overexpression protected HK-2 cells from LPS-induced injury by suppression of inflammation,oxidative stress,MMP loss,ROS production and apoptosis,increase of ATP production and mtDNA content,amelioration of damage to the mitochondrial ultrastructure.2.UCP2 knockdown resulted in decreased HK-2 cell resistance to LPS toxicity,as shown by increased inflammation,mitochondrial dysfunction,oxidative stress and apoptosis.Conclusion1.Our study successfully created septic model induced by LPS.2.UCP2 may protect LPS-induced AKI by ameliorating mitochondrial dysfunction,anti-inflammation,antioxidative activities and promoting autophagy,ultimately inhibiting tubule epithelial cell apoptosis,and that increasing the UCP2 content in mitochondria constitutes a new therapeutic approach for septic AKI.