Lupus-prone NZBWF1/J mice, defective in cytokine signaling, are resistant to fumonisin hepatotoxicity despite accumulation of liver sphinganine

Abstract

Fumonisin B 1 (FB 1) is a mycotoxin produced by Fusarium verticillioides, commonly present in corn and other cereals. Exposure to FB 1 causes organ-specific diseases in various species, e.g., equine leukoencephalomalacia and porcine pulmonary edema; in mice the response is hepatotoxicity. We earlier reported that ceramide synthase inhibition by FB 1, the initial biochemical effect of this mycotoxin, results in modulation of cytokine network in response to accumulated free sphingoid bases. In the current study we used NZB/NZW-F1 (NZBW) mice that have modified cytokine expression and develop lupus beginning at 5 months of age. The NZBW and C57BL/6J (CBL) mice (appropriate control) were given five daily subcutaneous injections of either saline or 2.25 mg FB 1/kg/day and euthanized 24 h after the last treatment. Peripheral leukocyte counts were higher after exposure to FB 1 in CBL but not in NZBW. FB 1 treatment caused increases of plasma alanine aminotransferase and aspartate aminotransferase activity in CBL mice indicating hepatotoxicity; no elevation of circulating liver enzymes was recorded in NZBW mice. Hepatotoxic responses were confirmed by microscopic evaluation of apoptotic cells. The FB 1-induced proliferation of cells observed in CBL strain was abolished in NZBW animals. The sphinganine accumulation in liver after FB 1 was equal in both strains of mice. The NZBW strain lacked the FB 1-induced increases in the expression of liver tumor necrosis factor α, interferon γ, receptor interacting protein (RIP), and tumor necrosis factor α-related apoptosis-inducing ligand (TRAIL), observed in CBL. Results confirmed our hypothesis that initial altered sphingolipid metabolism caused by FB 1 leads to perturbation of liver cytokine network and ultimate cellular injury; the mice deficient in cytokine signaling are refractory to FB 1 hepatotoxicity.