Unveiling the role of Pafah1b3 in liver fibrosis: A novel mechanism revealed.

Liver fibrosis is a common outcome of various chronic hepatic insults, characterized by excessive extracellular matrix (ECM) deposition. The precise mechanisms, however, remain largely undefined. This study identified an elevated expression of platelet-activating factor acetylhydrolase 1B3 (Pafah1b3) in liver tissues from both carbon tetrachloride (CCl4)-treated mice and patients with cirrhosis. Deletion of Pafah1b3 significantly attenuated CCl4-induced fibrosis, hepatic stellate cell (HSC) activation, and activation of transforming growth factor-β (TGF-β) signaling. Mechanistically, PAFAH1B3 binds to mothers against decapentaplegic homolog 7 (SMAD7), disrupting SMAD7's interaction with TGF-β receptor 1 (TβR1), which subsequently decreases TβR1 ubiquitination and degradation. Pharmacological inhibition using 3-IN-P11, a specific Pafah1b3 inhibitor, conferred protective effects against CCl4-induced fibrosis in mice. Furthermore, Pafah1b3 deficiency reduced hepatic inflammation. Overall, these results establish a pivotal role for Pafah1b3 in modulating TGF-β signaling and driving HSC activation.