Alleviation Of Hepatotoxicity Caused By Overactivation PPARA Through PPARA-inducible MiR-181a2 And Regulation Of Epithelial-Mesenchymal Transition By MiR-126-5p Targeting GSK3B In Hepatic Stellate Cells

Micro RNAs(miRNAs)are genomically encoded,evolutionarily conserved,nonprotein-coding,20-23 nucleotide single-stranded RNAs that negatively regulate gene expression by interacting with the 3' UTR of protein-coding m RNA.In recent years,overwhelming evidence has demonstrated the crucial regulatory roles of miRNAs in liver physiological or pathological processes.Our results revealed that alleviation of hepatotoxicity caused by overactivation PPARA through PPARA-inducible miR-181a2 and regulation of epithelial–mesenchymal transition by miR-126-5p targeting GSK3 B in hepatic stellate cells.According to the results,we concluded that: 1.Alleviation of hepatotoxicity caused by overactivation PPARA through PPARA-inducible miR-181a2.Widely varied compounds,including certain plasticizers,hypolipidemic drugs(e.g.Ciprofibrate,fenofibrate,WY-14643 and clofibrate),agrochemicals and environmental pollutants,are peroxisome proliferators(PPs).Appropriate dose of PPs causes a moderate increase in the number and size of peroxisomes and the expression of genes encoding peroxisomal lipid metabolizing enzymes.However,high dose PPs causes varied harmful effects.Chronic administration of PPs to mice and rats results in hepatomegaly and ultimately carcinogenesis.Nuclear receptor protein peroxisome proliferator-activated receptor-?(PPARA)was shown to be required for this process.However,biological adaptations to minimize this risk are poorly understood.In this study,we found that(1)miR-181a2 expression was significantly induced by high dose PPARA-specific agonists.(2)The Hsa-miR-181a2 promoter region contains putative PPRE in pre-miR-181a2 and is directly trans-activated by PPARA.(3)Overactivation of PPARA causes cytotoxicity.(4)Exogenous expression of miR-181a-5p dramatically alleviated the cell toxicity caused by high dose PPARA-specific agonists.Conclusion: This study identified a feed-back loop between miR-181a2 and PPARA,which allow biological systems to approach a balance when PPARA is overactivated.Such a balancing mechanism would assist the establishment of meaningful human risk assessments and also aid the rational design of drugs.2.Regulation of epithelial–mesenchymal transition by miR-126-5p targeting GSK3B in hepatic stellate cells.Various chronic liver injuries,including viral infection,alcoholic liver disease and NASH,lead to hepatic fibrosis which associated with reduced liver function,and eventual liver failure.Fibrosis is typically characterized by accumulation of extracellular matrix(ECM)deposited by myofibroblasts.Although hepatic fibrosis causes evident morbidity and mortality in chronic diseases,the lack of detailed knowledge about specific molecular contributors mediating fibrogenesis hampers the design of effective antifibrotic therapies.It has been reported that hepatic stellate cells(HSCs)are responsible for 90% of the myofibroblast population in hepatic fibrosis in transgenic mice.The activation of HSCs is considered to be the central event in the process of liver fibrosis.As a supplement to the ?canonical principle? of hepatic fibrogenesis,a series of studies strongly suggested that epitheliale-mesenchymal transition(EMT)is an important contributor to the progression of hepatic fibrosis.Upregulation of hepatocyte nuclear factor 4a(HNF4a)could ameliorate liver fibrosis and function with the inhibition of EMT in activated HSCs in rats.It has been reported that the expression of miR-126 was significantly changed after the activation of HSCs.However,the specific function and mechanism of miR-126 in HSCs has not been studied.In this study,we found that(1)Exogenous expression of miR-126-5p induced the activation and EMT in hepatic stellate cells.(2)The m RNA and protein levels of EMT-related transcription factor ZEB1 were significantly increased after exogenous expression of miR-126-5p.(3)miR-126-5p directly targeted the GSK3 B 3' UTR and supressed the protein level of GSK3 B.(4)Exogenous expression of miR-126-5p up-regulated B-catenin expression by depressing GSK3 B.(5)Exogenous expression of GSK3 B inhibited EMT induced by miR-126-5p.Conclusion: This study identified that miR-126-5p as an inducer of EMT in HSCs by targeting GSK3 B and then turning on Wnt/B-catenin signaling pathway.miR-126-5p may be used as a molecular target for antifibrosis in the future.