Curcumin Interferes With Renal Interstitial Fibrosis

Objective To study the effect of curcumin on proliferation,tubular epithelial-myofibroblast transdifferentiation,secretion of extracellular material,and TGF-β/Smad signal transduction pathway of human renal tubular epithelial cells HK-2 induced by transforming growth factor-β₁(TGF-β₁),and further to explore the mechanism of curcumin on the prevention and treatment of renal interstitial fibrosis.Methods The HK -2 cells were cultured by DMEM/F12(1:1) with 10%fetal bovine serum in 37℃and 5%CO₂.After being cultured 24 hours by free serm,cells were divided into the control group,TGF-β₁ group(TGF-β₁ 10 ng/mL),curcumin low dose therapy group (TGF-β₁ 10 ng/mL +Cur 1μmol/L),curcumin median dose therapy group(TGF-β₁ 10 ng/mL +Cur 5μmol/L),and curcumin high dose therapy group(TGF-β₁ 10 ng/mL +Cur 10μmol/L). Then the HK-2 cell morphology were observed through the microscope.The cell proliferation were tested by MTT assay after being treated for 24 hours,48 hours and 72 hours.The expression ofα-SMA and E-cadherin of HK-2 were tested by indirect immunohistochemical staining after being treated for 24 hours.And the concentration of typeâ… collagen,typeâ…¢collagen and FN in culture medium supernatant were detected by ELISA after being treated for 24 hours,48 hours and 72 hours.And the expression of mRNA of typeâ… collagen,typeâ…¢collagen were tested after being treated for 24 hours.And the expression of protein of TβRâ… ,TβRâ…¡,smad2,Smad 3,P-Smad 2/3 and smad7 were detected after being treated for 24 hours.Results We found that TGF-β₁ could stimulate HK-2 cells proliferation time-dependently compared with the control group,and there was significant difference(P＜0.05).But the cell proliferation was inhibited after treated by curcumin(P＜0.05),and the cells morphology could be maintained by curcumin.Secondly,we found that the expression ofα-SMA of HK-2 cultured with TGF-β₁ was much notable than the control group,but significantly attenuated after treated by curcumin(P＜0.05).And the expression of E-cadherin was markedly decreased after treated by TGF-β₁ alone,but recovered after treated by curcumin(P＜0.05).Thirdly,we also found that the secretion of typeâ… collagen,typeâ…¢collagen and FN were markedly inhibited in the culture medium supernatant treated by curcumin(P＜0.05).At the same time the expression of mRNA of typeâ… collagen,typeâ…¢collagen also attenuated.Finally,we found that TGF-β₁ could enhance the expression of TβRâ… ,TβRâ…¡,smad2,Smad3,P-Smad 2/3,and attenuate the expression of smad7,but after treated by curcumin,the expression of TβRâ… ,TβRâ…¡,smad2,Smad3,P-Smad 2/3 were down-regulated obviously,and the expression of smad7 were up-regulated(P＜0.05).Conclusion We obtained that TGF-β₁ could induce tubular epithelial cells proliferation, lead to tubular epithelial-myofibroblast transdifferentiation,and increase the amount of extracellular matrix,such as typeâ… collagen,typeâ…¢collagen and FN.In addition,it could activate TGF-β/Smad signal transduction pathway.All these results confirmed that TGF-β₁ is the key factor in development of renal interstitial fibrosis,and this is consistent with previous reports.At the same time,we also obtained that curcumin at given concentrations could inhibit the tubular epithelial cells proliferation,and inhibit tubular epithelial-myofibroblast transdifferentiation,and reduce synthesis and secretion extracellular matrix.In addition, curcumin could obstruct the TGF-β/Smad signal transduction pathway.So we concluded that curcumin could prevent the development of renal interstitial fibrosis to a certain extent.And this would provide evidence for later clinical application.