Background and aims: Lysyl oxidase-like 1 (LOXL1) proteins are amine oxidases that play a crucial role in extracellular matrix remodeling due to their collagen cross-linking and intracellular functions. The role of LOXL1 in cholestatic liver fibrosis remains unexplored.
Methods: We measured LOXL1 expression in two murine models of cholestasis (Mdr2 knockout [Mdr2-/-] and bile duct ligation [BDL]). We used adeno-associated virus (AAV) serotype 6-mediated hepatic delivery against LOXL1 (AAV2/6-shLoxl1) to investigate the therapeutic efficacy of targeting LOXL1 in cholestatic liver fibrosis. NIH-3T3 murine fibroblasts were used to investigate the function and regulatory mechanisms of LOXL1 in vitro.
Results: LOXL1 expression was significantly upregulated in Mdr2 -/- and BDL mice compared to their corresponding controls, predominantly in collagen-rich fibrous septa and portal areas. AAV2/6-shLoxl1 significantly reduced LOXL1 levels in Mdr2-/- and BDL mice, mainly located in desmin-positive hepatic stellate cells (HSCs) and fibroblasts. Concomitant with reduced LOXL1 expression, there was reduced ductular reaction, inflammation, and fibrosis in both Mdr2 -/- and BLD mouse models. Additionally, Loxl1 intervention decreased Ki-67 positive cells in the desmin-positive areas in both Mdr2 -/- and BDL mice. Overexpression of LOXL1 significantly promoted fibroblast proliferation by activating the platelet-derived growth factor receptor and extracellular signal-regulated kinase signaling pathways in vitro.
Conclusion: Our findings demonstrated that selective inhibition of LOXL1 derived from HSCs/fibroblasts attenuated cholestatic liver/biliary fibrosis, inflammation, ductal reaction, and HSC/fibroblast proliferation. Based on our findings LOXL1 could be a potential therapeutic target for cholestatic fibrosis.
Keywords: ECM; LOXL1; cholestatic; fibrosis; hepatic stellate cell.