MPC2 Mediates Mitochondrial Dysfunction And Apoptosis In High Glucose-treated Podocytes

Background and objective:Diabetic kidney disease(DKD)is the most common microvascular disease in diabetes patients,and is also an important cause of end stage renal disease(ESRD).Podocytes play an important role in the development of DKD.Glomerular hypertrophy and podocyte depletion are the glomerular characteristics of progressive DKD,and the degree of podocyte loss is related to the severity of the disease.Podocyte injury and its reduction have important roles in the pathogenesis of proteinuria.Mitochondria are the source of energy for cell survival,and mitochondrial abnormalities have been shown to contribute to podocyte injury in DKD.In high glucose(HG)-treated podocytes,mitochondrial function and dynamics are abnormal,and intracellular metabolism is often disrupted.However,the molecular mechanism is still unclear.Mitochondrial pyruvate carrier(MPC)is localized on the inner mitochondrial membrane and is composed of two subunits,MPC1 and MPC2.It mediates pyruvate transport from the cytoplasm to the mitochondrial matrix,which determines the cellular energy supply and cell survival.Previous studies have found that abnormal expression of MPC protein can cause abnormal mitochondrial function.Here,we hypothesize that MPC2 damages mitochondria and induces apoptosis in HG-treated podocytes.The purpose of this study is to provide a theoretical basis for the treatment of podocyte injury in DKD.Methods:Western blotting,immunofluorescence and immunoprecipitation were used to detect the expression of MPC2 in HG-treated podocytes.Pyruvate levels were measured to evaluate metabolic station.Mitochondrial membrane potential(MMP)was measured by inverted fluorescence microscopy and flow cytometry.Mitochondrial morphology was assayed by Mito Tracker Red staining,and cellular apoptosis was examined by flow cytometry.Furthermore,podocytes were treated with UK5099 and MPC2 si RNA to assess the outcomes of UK5099 treatment and MPC2 knockdown.Results:Intracellular pyruvate was accumulated,the mitochondria were damaged and cellular apoptosis increased in podocytes cultured with HG compared to that in control podocytes.MPC2 acetylation was significantly increased in HG-treated podocytes.Furthermore,the mitochondrial morphology changed,the MMP decreased,and cellular apoptosis increased.Inhibition of MPC2 function by UK5099 and MPC2 knockdown by si RNA exhibited the same effects as those caused by HG treatment.Conclusion:MPC2 mediates mitochondrial dysfunction in HG-treated podocytes,ultimately leading to cell apoptosis.