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The purpose of this study was to determine the effect of sulfinpyrazone on fumonisin B1-induced elevation of free sphingoid bases in LLC-PK1 cells. Fumonis ins are a family of mycotoxins produced by the fungi Fusarium moniliforme which is common contaminant in corn. Fumonisins are also potent inhibiors of sphingosine and sphinganine N-acyltransferases (ceramide synthases), key enzymes in sphingolipid metabolism resulting in the elevation of free sphinganine. The cytosolic concentration of fumonisin B1 was known to be closely proportional to the elevation of free sphinganine in LLC-PK1 cells [Yoo, H.-S., Norred, W.P., Wang, E., Merrill, A.H., Jr., and Riley, R.T. (1992) Toxicol. Appl.Pharmacol. 114. 9-15]. Sulfinpyrazone, an anion transport inhibitor, reduced the elevated level of free sphinganine resulting from fumonisin B1 inhibition of de novo sphingolipid biosynthesis. Fumonisin B1 at a concentration of 20mcM showed approximately 120pmol/106 cells relative to 3-10pmol/106 cells in control cultures, and sulfinpyrazone at a concentration of 200mcM partially reversed the increased level of free sphinganine induced by fumonisin B1 down to normal level after exposure to fumonisin B1 for 8 to 24hr. However, the reduced effect of sulfinpyrazone on the fumonisin B1-induced elevation of intracellular sphinganine was not shown after 24hr. Fumonisin B1 exposure to LLC-PK1 cells for 36 and 48hr showed approximately 74 and 80pmol per 106 cells relative to 82 and 76pmol,respectively, in fumonisin B<1SUB>1 plus sulfinpyrazone-treated cultures. Sulfinpyrazone-induced less elevation of free sphinganine in confluent cells after exposure to fumonisin B1 suggested that either sulfinpyrazone may block the availability of fumonisin B1 to cells or act on the fumonisin B1 interaction with ceramide synthase.
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