Loureirin B Attenuates Methotrexate-Induced Liver Injury Associated with Oxidative Stress, SIRT1 Alterations, and TGF-β/SMAD3-Related Profibrotic Responses.

Background

Methotrexate-induced oxidative stress is mechanistically linked not only to hepatocellular injury but also to DNA damage, indicating that oxidative stress, hepatotoxicity, and genotoxicity represent interconnected manifestations of the same antifolate-driven toxic cascade. Methotrexate (MTX)-induced hepatotoxicity is characterized not only by oxidative stress, but also by progressive fibrotic remodeling driven by activation of the TGF-β/SMAD signaling pathway.

Objective

We aimed to examine the hepatoprotective effects of Loureirin B, with a particular focus on its anti-fibrotic potential and underlying molecular mechanisms in MTX-induced liver injury.

Methods

Thirty female Wistar rats were assigned to normal control, MTX, and MTX + Loureirin B groups. Liver injury was induced with a single intraperitoneal MTX dose (20 mg/kg), followed by oral administration of Loureirin B (50 mg/kg/day) for 10 days. Biochemical, molecular, and histopathological analyses were performed, including ALT, AST, ALP, MDA, SIRT1, TGF-β, SMAD3, hydroxyproline, and VEGF levels, alongside the evaluation of necrosis, fibrosis, and inflammatory infiltration.

Results

MTX induced significant hepatic injury characterized by elevated serum ALT, AST, and ALP levels, increased oxidative stress, suppression of SIRT1, and increased TGF-β and SMAD3 levels, accompanied by elevated collagen-associated markers. Loureirin B treatment significantly reduced the serum liver enzyme levels and oxidative stress, partially restored SIRT1 levels, and decreased fibrosis-associated markers, including hydroxyproline and VEGF. Although the TGF-β levels were significantly reduced following Loureirin B treatment, the reduction in SMAD3 levels did not remain statistically significant after correction for multiple comparisons. Histopathological findings further demonstrated attenuation of fibrosis-associated changes and partial improvement in hepatic architecture.

Conclusions

Loureirin B may exert protective effects against methotrexate-associated liver injury through the modulation of oxidative stress, partial restoration of SIRT1 levels, attenuation of profibrotic alterations associated with the TGF-β/SMAD pathway, and modulation of VEGF-related responses.