Cholesterol Depletion Activate Hepatic Stellate Cells Mediated Through SREBP‐2 Signaling

Liver fibrosis is one of the leading cause of death worldwide. In liver, hepatic stellate cells are the primary cell type that gets activated during fibrosis. LX-2 cells are human-derived hepatic stellate cell lines typically employed for studying liver fibrosis mechanisms and screening anti-fibrotic lead molecules. Although LX-2 cells are partially activated in culture conditions, numerous stimuli including TGF-β, H₂O₂, hypoxia, LPS were reported to activate LX-2 cells. In this study, for the first time, the effect of cholesterol depletion on LX-2 cells was studied. Under cholesterol-depleted conditions, the mRNA and protein expression of HSC activation markers (α-SMA, GFAP) were significantly increased. Also, the expression of SREBP-2, HMGCR were significantly upregulated in response to cholesterol depletion. Treatment with fatostatin, a reported SREBP inhibitor abolished nuclear SREBP-1 and SREBP-2 expression and regulated the SREBP signaling. Transmission electron microscopic imaging showed distinct ultrastructural changes in response to cholesterol depletion. Furthermore, cholesterol depletion did not affect the cell-cycle profile of LX-2 cells compared with untreated while fatostatin treatment induced G2 cell-cycle arrest. Overall, cholesterol depletion activated LX-2 cells mediated by SREBP-2 signaling and therefore could be further employed as stimuli for LX-2 activation and screening lead molecules targeting SREBPs.