Fumonisin B₁ alters sphingolipid metabolism and disrupts the barrier function of endothelial cells in culture

Fumonisins are responsible for at least two diseases of veterinary importance (equine leukoencephalomalacia and porcine pulmonary edema) and are carcinogenic for experimental animals and, perhaps, humans. They have been found to disrupt sphingolipid metabolism in many types of cells, including hepatocytes, neurons, and renal cells. In this study, endothelial cells from porcine pulmonary arteries were cultured on micropore filters as a model for the endothelial barrier, and barrier function was quantitated as the movement of albumin across the endothelial monolayers. Fumonisin B₁ increased the amount of free sphinganine by 20- to 30-fold within 3 hr, as expected for inhibition of sphinganine (sphingosine) N-acyltransferase by this mycotoxin. At 30 to 50 μM, fumonisin B₁ doubled the rate of albumin transfer across endothelial monolayers; however, there was no loss of cell viability based on morphology or trypan blue exclusion. When 15 μM D-erythro-sphinganine was added to the cells, the rate of albumin transfer also doubled (after 24 hr incubation) without a loss of viability; however, this treatment increased the cellular level of sphinganine by >100-fold. Addition of 25 μM sphinganine caused even greater albumin transfer, but also resulted in significant cell death. These results establish that fumonisin B₁ and D-erythro-sphinganine allow accelerated passage of macromolecules across the endothelium. Fumonisin B₁ alters sphingolipid biosynthesis with an elevation of sphinganine in the cells which may, at least in part, explain the observed disruption of endothelial barrier function.