Distinct generation, pharmacology, and distribution of sphingosine 1-phosphate and dihydrosphingosine 1-phosphate in human neural progenitor cells

In vivo and in vitro studies suggest a crucial role for Sphingosine 1-phosphate (S1P) and its receptors in the development of the nervous system. Dihydrosphingosine 1-phosphate (dhS1P), a reduced form of S1P, is an agonist at S1P receptors, but the pharmacology and physiology of dhS1P has not been widely studied. The mycotoxin fumonisin B1 (FB1) is a potent inhibitor of ceramide synthases and causes selective accumulation of dihydrosphingosine and dhS1P. Recent studies suggest that maternal exposure to FB1 correlates with the development of neural tube defects (NTDs) in which the neural epithelial progenitor cell layers of the developing brain fail to fuse. We hypothesize that the altered balance of S1P and dhS1P in neural epithelial cells contributes to the developmental effects of FB1. The goal of this work was first to define the effect of FB1 exposure on levels of sphingosine and dh-sphingosine and their receptor-active 1-phosphate metabolites in human embryonic stem cell-derived neural epithelial progenitor (hES-NEP) cells; and second, to define the relative activity of dhS1P and S1P in hES-NEP cells. We found that dhS1P is a more potent stimulator of inhibition of cAMP and Smad phosphorylation than is S1P in neural progenitors, and this difference in apparent potency may be due, in part, to more persistent presence of extracellular dhS1P applied to human neural progenitors rather than a higher activity at S1P receptors. This study establishes hES-NEP cells as a useful human in vitro model system to study the mechanism of FB1 toxicity and the molecular pharmacology of sphingolipid signaling.This article is part of a Special Issue entitled ‘Post-Traumatic Stress Disorder’.

► Exposure of human neural progenitors to the toxin FB1 increases dh-sphingosine levels.
► S1P receptor-active dhS1P also accumulates, increasing the dhS1P:S1P ratio.
► dhS1P is more potent than S1P for Smad activation and cAMP inhibition in progenitors.
► These distinctions reflect differences in cellular uptake, not receptor selectivity.
► dhS1P signaling may contribute to neural progenitor cells’ response to FB1 exposure.