Curcumin Modulates Autophagy On High Glucose-treated Podocytes To Protect Them From Damage

Objective: Diabetic nephropathy(DN)account for a great proportion in causes of end stage renal disease(ESRD).It will threat patients' life with a high prevalence and increasing mortality.Many patients appear to show renal dysfunction in early time despite the comprehensive clinical treatment including rigorous blood pressure and glycemic control,as well as the inhibition of renin-angiotensin-aldosterone system.Up to now,the exact pathophysiological mechanisms of DN are unclear because of the complexity,and DN has not been treated well yet.Thus,there is an urgent need for improving mechanistic understanding of DN and then developing new and effective therapeutic drugs to delay the progression of DN.Our study aims to investigate the effects and underlying mechanisms of curcumin induced autophagy on high glucose-treated podocytes in vitro.To ex plore the role of curcum in in protecti ng renal podocy tes from damage in the development of diabetic nephropathy.Methods: Cell viability was determined by MTT Assay after curcumin pretreatment with different concentration.Finally we determine the concentration of curcumin is1 umol,5umol,10 umol.Podocytes were pretreated with curcumin(1,5,10 u M)for 1h and then incubated with HG(30u M)for 24 h in vitro.Cultured mouse podocytes(MPC5)were divided into six groups: Control group(Normal Glucose,5.5 mmol/L,High glucose group(High Glucose,30mmol/L),Curcumin group(High Glucose+Curcumin,1,5and 10umol/L)),Rapamycin group(High Glucose+Rapamycin,10nmol/L).The expression of autophagy-related factors and podocyte structure and functional markers,including LC3 B,Beclin-1,Synaptopodin,Nephrin,were measured by Western blotting analysis.Cultured mouse podocytes(MPC5)were divided into six groups: Control group(Normal Glucose,5.5 mmol/L),High glucose group(High Glucose,30mmol/L),Curcumin group(High Glucose+Curcumin,1,5and 10 umol/L)),LY294002 group(High Glucose+LY294002,10umol/L).The expression of the phosphorylation of Akt and m TOR were examined by Western blotting analysis.Results: 1.Effects of curcumin on the expression levels of autophagy-related factors.Western blot showed the expression levels of LC3?/I and Beclin-1 in high glucose group were significantly dropped compared with the control group;but were noticeably attenuated in curcumin-treated group and rapamycin group compared with the high glucose group;Curcumin induced substantial increase in expression of LC3 II in a dose-dependent manner.2.Curcumin maintain the expression levels of podocyte marker protein under high glucose conditions.The results showed that the protein expression levels of synaptopodin and nephrin in high glucose group were decreased compared with the control group.Furthemore,there was a increase in protein expression of synaptopodin and nephrin in podocytes treated with curcumin and rapamycin compared with podocytes under high glucose incubation.3.Curcumin activate the autophagy of podocytes via inhibiting the PI3K/Akt/m TOR signaling pathway.Western blot showed the expression levels of p-m TOR in curcumin-treated group had a significant decrease in a dose-dependent manner compared with the high glucose group.But the expression levels of LC3 II,which is known as a downstream molecule of the PI3K/Akt/m TOR signaling pathway,were markedly increased.There was a noticeable decrease in protein expression of p-Akt in podocytes treated with curcumin compared with the high glucose group.However,the results showed that the treatment with curcumin led to a increase of the levels of Beclin-1,which is known as the target of Akt.Conclusions: 1.Curcumin pretreatment can attenuate high glucose-induced podocyte injury by regulating the autophagy activities,and the beneficial effect is dose-dependent.2.Curcumin can keep normal function of podocytes under high glucose condition,as revealed by the protection of podocytes and amelioration of renal function.This sudy demonstrated that curcumin-induced autophagy could be a potential treatment strategy for diabetic nephropathy.3.The mechanism of curcumin mediated beneficial effects is related to the inhibition of the PI3K/Akt/m TOR signaling pathway.