Pemetrexed ameliorates Con A-induced hepatic injury by restricting M1 macrophage activation

Autoimmune hepatitis (AIH), characterized by immune-driven liver destruction and cytokine production, is a progressive inflammatory liver condition that may progress to hepatic cirrhosis or tumors. However, the underlying mechanism is not well understood, and the treatment options for this disease are limited. Pemetrexed (PEM), a clinically used anti-folate drug for treating various tumors, was found to inhibit the nuclear factor (NF)-κB signaling pathways that exert an important role in the development of AIH. Here, we investigated the impact of PEM on immune-mediated hepatic injuries using a murine model of Concanavalin A (Con A)-induced hepatitis, a well-established model for AIH. Mice received intraperitoneal PEM injections 3 times at 12-hour intervals, and two hours later, they were challenged with Con A. Liver samples and serum were collected after 10 h. The results indicate that PEM significantly improved mouse survival rates and lowered serum transaminase levels. Moreover, PEM effectively alleviated oxidative stress, reduced histopathological liver damage, and mitigated hepatocyte apoptosis. Notably, it reduced the activation of M1-type macrophages in the liver. The expression of proinflammatory cytokines and genes associated with M1 macrophages, such as tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, IL-12, IL-1β, and inducible nitric oxide synthase (iNOS), was also decreased. Finally, the results indicated that PEM regulates M1 macrophage activation by modulating the NF-κB signaling pathways. Overall, these results demonstrate that PEM effectively guards against immune-mediated hepatic injuries induced by Con A by inhibiting M1 macrophage activation through the NF-κB signaling pathways and indicate the potential of PEM as a practical treatment option for AIH in clinical settings.