Investigation of the protective effects of carnosine in methotrexate-induced liver injury in rats

Methotrexate (MTX) is an antimetabolite widely used in clinical practice and is known to exert toxic effects on the liver. Previous studies have reported that MTX may induce hepatotoxicity by triggering oxidative stress, inflammation, and apoptosis. This study aimed to investigate the potential protective effects of carnosine (CAR) against MTX-induced liver injury. In our study, 32 male Wistar albino rats were divided into four groups: Control, MTX, MTX+CAR, and CAR. Rats in the MTX+CAR and CAR groups received carnosine (CAR) intraperitoneally at a dose of 100 mg/kg/day for 24 days. On day 21 of the experiment, rats in the MTX and MTX+CAR groups were administered methotrexate (MTX) intraperitoneally at a dose of 20 mg/kg. The Control group received an equivalent volume of saline intraperitoneally, similar to the CAR-treated groups. Biochemical analysis of rat serum samples revealed that MTX administration significantly increased serum AST and ALT levels. A similar increase was observed in TNF-α levels in liver tissue. Gene expression analysis demonstrated that MTX elevated BAX mRNA expression while reducing NRF2, HO-1, and BCL-2 expression levels in liver tissue. Immunohistochemical evaluation showed a marked increase in Caspase-3 immunoreactivity in the MTX group. Among oxidative stress parameters, TOS and OSI levels were elevated in the MTX group, whereas TAS, an indicator of antioxidant capacity, was decreased. Carnosine (CAR) administration largely reversed these MTX-induced alterations. Following CAR treatment, serum AST, ALT, and TNF-α levels as well as BAX, Caspase-3, TOS, and OSI levels decreased, while BCL-2, NRF2, and HO-1 expression levels increased. Histopathological findings were consistent with and supported the biochemical and molecular results. Considering the results of our study, we suggest that CAR may serve as a potential protective agent against MTX-induced hepatotoxicity through its anti-apoptotic, antioxidant, and anti-inflammatory effects. However, further advanced and comprehensive studies are required to clarify the optimal dose, duration of administration, and detailed molecular mechanisms underlying the protective effects of CAR. Keywords: Carnosine, Hepatotoxicity, Inflammation, Methotrexate, Oxidative Stress