Baricitinib Mitigates Methotrexate-Induced Liver Fibrosis Model via YAP Pathway

<i>Background and Objectives</i>: Liver fibrosis, a chronic process caused by various pathogenic factors, including drug toxicity, metabolic disorders, and chronic inflammation, is associated with liver-related mortality rates worldwide. It has been established that methotrexate (MTX), a pharmaceutical agent utilised in the treatment of numerous diseases, induces hepatic fibrosis. Currently, there is still a paucity of clinically efficacious antifibrotic drugs for the management of hepatic fibrosis. Thus, the present research sought to evaluate the antifibrotic effects of baricitinib in a rat model of MTX-induced liver fibrosis through the yes-associated protein (YAP) pathway. <i>Materials and Methods</i>: A total of 36 Wistar rats were assigned to three groups (<i>n</i> = 12) randomly: a control group, an MTX-induced liver fibrosis group, and a baricitinib-treated group, which received 20 mg/kg/day of baricitinib following fibrosis induction. All treatments were administered for 10 days. <i>Results</i>: Biochemical analyses revealed significant increases in plasma alanine aminotransferase (ALT), cytokeratin-18 (CK-18), and malondialdehyde (MDA) levels, as well as liver transforming growth factor-beta (TGF-β), YAP1, and MDA levels, in the MTX-induced fibrosis group in comparison to the control group (<i>p</i> < 0.05). Notably, baricitinib addition significantly reduced these biomarkers (<i>p</i> < 0.05). A histopathological evaluation further confirmed a marked reduction in fibrosis, hepatic necrosis, and cellular infiltration in the baricitinib-treated group relative to the MTX-induced fibrosis group. <i>Conclusions</i>: Accordingly, our findings suggest that baricitinib mitigates MTX-induced liver fibrosis, potentially through its anti-inflammatory and antifibrotic effects mediated by the suppression of the YAP signalling pathway. These results highlight that baricitinib could be a potential treatment option for patients with liver fibrosis.