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.