Investigation Of Taurine Protection Against As₂S₃-induced Autophagy In Livers Of Offspring Rats Through PPARγ Pathway

Objective: Chronic exposures to arsenic have been associated with various noncancerous diseases,including metabolic diseases.Peroxisomeproliferatoractivated receptor gamma（PPARγ）,a nuclear receptor and ligand-dependent transcription factor,regulates metabolism.In our previous study,we have found that arsenic induced autophagosome formation and caused autophagic cell death in INS-1 cells through reactive oxygen species（ROS）pathway.Whether arsenic exerts hepatotoxicity and the precise molecular mechanisms of arsenic-induced hepatotoxicity are not completely elucidated.Taurine was nonessential amino acids,mainly in the liver.Taurine had the effect of antioxidant and involved in the protective effect of cell metabolism.Previous studies had found that taurine could reduce arsenic-induced hepatotoxicity,but whether it could prevent arsenic-induced hepatotoxicity through PPARγ pathway intervention is unclear.In this study,we investigated the protective mechanism of taurine on arsenic-induced hepatotoxicity of offspring rats.Method: To investigate the effects of As₂O₃ on offspring rats,the pregnant Wistar rats were randomly divided into five groups,and the rats were treated with 0 mg/kg BW⁸ mg/kg BW As₂O₃,the group 5 was given 8 mg/kg BW As₂O₃ after pretreatment with taurine.The rats were given by gavage once a day to the offspring weaning.The offsprings was treated as its mother until sexual maturity,totally 57 days.We measured the body weight and liver organ coefficient of the offspring rats,and observed the morphology of rat liver by HE staining.To observe the formation of autophagosome in liver cells of offspring rats,we used the electronic microscopy and counted the number of the autophagosome.The expressions of PPARγ,LC3 and p62 protein in the liver of offspring rats were detected by Western blot.We used RT-PCR to detect the expression of PPARγ gene.To investigate the hepatotoxicity induced by arsenic and the protective effects of taurine,we used HepG2 cells exposed in 1μM As₂O₃ for 24 h.RNA interference was used to measure whether arsenic-induced autophagy was the major cause of the cell death.MTT method was used to measure the cells viability after the cells were pretreatment with taurine and PPARγ activator respectively.The expressions of PPARγ,LC3 and p62 protein in the liver of offspring rats were detected by Western blot.Results: After exposed to different concentrations of arsenic the liver organ coefficient of offspring rats was increased significantly,and after pretreatment with taurine the liver organ coefficient decreased significantly.HE staining showed that,the size of liver cells was significantly reduced with the increase of the concentrations of arsenic and after treatment with taurine the size of the cell was increased.Quantification of the autophagosomes numbers per cell demonstrated that As₂O₃ increased autophagosomes number significantly and in a dose-dependent manner.The number of autophagosomes in As₂O₃-treatedrats was obviously decreased after pretreatment with taurine.The level of LC3-II was increased dramatically and the level of P62 was decreased in As₂O₃-treated livers.After pretreatment with taurine,the expression of LC3-II was decreased and the expression of P62 was increased dramatically in As₂O₃-treatedcells.The expression of PPARγ protein and gene was decreased in offsprings’ livers.Taurine could reverse arsenic-inhibited PPARγ and inhibit autophagy.We found that As₂O₃ caused autophagic cell death in HepG2 cells.HepG2 cell were pretreatment with Tau and PPARγ activator Rosiglitazone（RGS）respectively before treatment with As₂O₃.We found that autophagy was inhibited after pretreatment with RGS in As₂O₃-treated cells.After pretreatment with Tau,the level of PPARγ was improved dramatically and the autophagy was inhibited in As₂O₃-treated cells,suggesting that taurine could protect hepatocytes against As₂O₃ through modulating PPARγ–autophagy pathway.Conclusion: As₂O₃ could induce autophagy in offspring livers;the inhibition of PPARγ contributed to the As₂O₃–induced autophagy in offspring livers;Taurine protects against As₂O₃-induced autophagy in livers of rats through PPARγ pathway.