Loganin Ameliorates Cholestatic Liver Fibrosis by Inhibiting Hepatic Stellate Cell Autophagy and Activation Through EGFR Signaling.

Liver cirrhosis represents the irreversible end-stage of various chronic liver diseases, whereas hepatic fibrosis, characterized by hepatic stellate cell (HSC) activation, constitutes the critical pathological intermediate in this progression. In this study, we investigated the antifibrotic effects of loganin, a natural iridoid glycoside, and elucidated its underlying mechanisms in bile duct ligation (BDL)-induced cholestatic liver injury and hepatic fibrosis and in TGF-β1-stimulated HSCs. Sprague-Dawley rats subjected to BDL surgery received loganin for 14 days, resulting in marked amelioration of hepatomegaly, inflammatory infiltration, hepatocyte necrosis, and collagen deposition, alongside restoration of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin (T-BIL) levels and suppression of fibrogenic gene expression (collagen type I alpha 1 chain [COL1α1], alpha-smooth muscle actin [α-SMA], and fibronectin). Moreover, loganin attenuated hepatic autophagy, as evidenced by reduced Beclin-1 expression and LC3B-II/I ratio, with decreased colocalization of α-SMA and LC3B. Bioinformatics analysis and molecular docking indicated that epidermal growth factor receptor (EGFR) may be the target protein through which loganin exerts its antifibrotic effect. Experimental validation demonstrated that loganin suppressed BDL-induced EGFR phosphorylation in vivo. In TGF-β1-activated HSC-T6 cells, loganin inhibited cell activation, downregulated fibrosis markers, impaired autophagic flux, and suppressed TGF-β1-induced upregulation of Beclin-1 and LC3B-II/I. Critically, cotreatment with the EGFR agonist EGF reversed the autophagy-inhibitory and antifibrotic effects of loganin, whereas the EGFR inhibitor AG-1478 mimicked loganin's actions, confirming EGFR signaling as the functional mediator. Overall, these results indicated that loganin could alleviate liver injury and hepatic fibrosis in BDL rats by inhibiting autophagy and activation of HSCs, and this protective effect is mediated by the EGFR pathway.