Silymarin protects against liver damage in BALB/c mice exposed to fumonisin B1 despite increasing accumulation of free sphingoid bases

Fumonisin B-1 (FB1) is a mycotoxin produced by Fusarium verticillioides found on corn and corn-based foods. It causes equine leukoencephalomalacia, porcine pulmonary edema, and liver and kidney damage in most animal species. Fumonisin B-1 perturbs sphingolipid metabolism by inhibiting ceramide synthase activity, leading to the production of cell signaling factors including tumor necrosis factor alpha (TNF-alpha). The signal pathways of TNF-alpha are important factors in the pathogenesis of FB1 hepatotoxicity. In the present study, female BALB/c mice were treated daily with 750 mg/kg silymarin by gavage and 2.25 mg/kg FB1 subcutaneously for 3 days. Then, 1 day after the last FB1 injection, the mice were euthanized and blood and tissues were sampled for analyses. Silymarin significantly diminished FB1-induced elevation of plasma alanine aminotransferase and aspartate aminotransferase activities and the number of apoptotic hepatocytes, while it augmented hepatocyte proliferation indicated by an increase in proliferating cells. Silymarin dramatically potentiated FB1-induced accumulation of free sphinganine and sphingosine in both liver and kidney. Silymarin itself slightly increased expression of hepatic TNF-alpha; however, it prevented the FB1-induced increases in TNF-alpha, TNF receptor 1, TNF receptor-associated apoptosis-inducing ligand, lymphotoxin beta, and interferon gamma. The induction of transforming growth factor beta1 expression in liver following FB1 treatment was not affected by silymarin. These findings suggest that silymarin protected against FB1 liver damage by inhibiting biological functions of free sphingoid bases and increasing cellular regeneration.