12-O-Tetradecanoylphorbol-13-Acetate Inhibits TGF-β1-Induced Proliferation and Fibrosis in LX-2 Hepatic Stellate Cells by Regulating both YAP and AKT ActivitiesOA

Background:Although transforming growth factor-β(TGF-β)drives hepatic stellate cell activation and fibrogenesis,the mechanisms by which 12-O-tetradecanoylphorbol-13-acetate(TPA)modulates these processes in TGF-β1-activated hepatic stellate cells remain to be determined.Therefore,we investigated whether TPA alleviates fibrosis in TGF-β1-treated hepatic stellate cells and regulates both canonical and non-canonical pathways.Further,we assessed whether inhibitors of these pathways similarly affect proliferation and fibrosis in LX-2 cells.Methods:LX-2 hepatic stellate cells were used as the experimental model.Cells were treated with TPA,TGF-β,or TGF-β plus TPA,and Yes-associated protein(YAP)and protein kinase B(PKB;AKT)phosphorylation,as well as YAP intracellular localization,were assessed.PKC-δ involvement was examined using the pan-PKC inhibitor Go 6983,and the roles of YAP and AKT in TGF-β1-activated LX-2 cells were evaluated using verteporfin and AKTI-1/2,respectively.Results:TPA significantly increased YAP phosphorylation and reduced its nuclear translocation,resulting in decreased LX-2 cell proliferation and fibronectin(FN1)production.Although TPA also inhibited AKT phosphorylation,FN1 expression was primarily regulated by YAP inhibition.Notably,proliferation in TGF-β1-treated LX-2 cells was suppressed only upon co-administration of both inhibitors.Our results suggest that coordinated regulation of YAP and AKT activity is essential for controlling fibroblast proliferation and ECM production.Conclusions:These findings suggest that in TGF-β-activated hepatic stellate cells,YAP simultaneously controls proliferation and fibrosis,and AKT regulates only proliferation.Therefore,TPA,which regulates both YAP and AKT activity,may be a promising therapeutic candidate for liver fibrosis treatment by simultaneously controlling proliferation and fibrosis in hepatic stellate cells.