Pharmacological antagonism of fumonisin B1 cytotoxicity in porcine renal epithelial cells (LLC-PK1):: A model for reducing fumonisin-induced nephrotoxicity in vivo

Fumonisin B-1 is a mycotoxin commonly found on corn. It is hepatotoxic and nephrotoxic in domestic and experimental animals, and causes equine leukoencephalomalacia and porcine pulmonary oedema. It is a potent inhibitor of ceramide synthase. Inhibition leads to accumulation of free sphingoid bases in cells and tissues. In pig kidney epithelial cells (LLC-PK1), fumonisin B-1 induces increased tumour necrosis factor alpha (TNFalpha) expression independent of the accumulation of sphingoid bases. The objective of this study was to investigate pharmacological approaches for intervening in fumonisin B-1 toxicity using the LLC-PK1 cell model. The toxicity of fumonisin B-1 was assayed using cell viability and lactate dehydrogenase (lactate dehydrogenase) release. Pretreatment of cells with myriocin, preventing sphinganine accumulates, prevented the fumonisin B-1-induced decrease in cell viability and increased lactate dehydrogenase release. Modulation of adenosine receptor activity did not reduce the fumonisin B-1 cytotoxicity. As with myriocin, silymarin pretreatment prevented the fumonisin B-1-induced effects on cell viability and lactate dehydrogenase release. When added 6 or 24 hr after treatment of cells with fumonisin B-1, both myriocin and silymarin reversed the decreased cell viability and suppressed the increased lactate dehydrogenase release. Myriocin, but not silymarin, blocked the accumulation of sphinganine in fumonisin B-1-treated cells. Silymarin, unlike myriocin, induced expression of TNFa to an extent similar to fumonisin 131, but pretreatment with silymarin decreased the fumonisin B-1-induced TNFalpha expression in LLC-PK1 cells. Results suggest that the mechanisms by which myriocin and silymarin protect renal cells are different, and silymarin potentially prevents fumonisin B-1-induced toxicity by modulating TNFalpha expression or signals downstream of the inhibition of ceramide synthase.