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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Toxicology & Mycotoxin Research » Research » Publications at this Location » Publication #327302
Title: Elevated nuclear sphingoid base-1-phosphates and decreased histone deacetylase activity after Fumonisin B1 treatment in mouse embryonic fibroblasts

Author
item GARDNER, NICOLE - Creighton University
item Riley, Ronald
item Showker, Adele
item Voss, Kenneth
item SACHS, ANDREW - Creighton University
item MADDOX, JOYCE - Creighton University
item GELINEAU-VAN WAES, JANEE - Creighton University

Submitted to: Toxicology and Applied Pharmacology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2016
Publication Date: 5/1/2016
Citation: Gardner, N., Riley, R.T., Showker, A.J., Voss, K.A., Sachs, A., Maddox, J., Gelineau-Van Waes, J. 2016. Elevated nuclear sphingoid base-1-phosphates and decreased histone deacetylase activity after Fumonisin B1 treatment in mouse embryonic fibroblasts . Toxicology and Applied Pharmacology. 298:56-65.

Interpretive Summary: Fumonisins are toxins made by molds that are commonly found in corn. They cause diseases in animals. Fumonisin B1 (FB1), the most abundant fumonisin, causes neural tube defects in mice and is a suspected risk factor for these serious birth defects in humans consuming fumonisin-contaminated corn-based foods as a dietary staple. The biological mechanisms involved in neural tube defect induction by FB1 are poorly understood. Experiments were done using mouse embryonic fibroblast cells exposed to FB1 in culture. Significant amounts of sphinganine-1-phosphate, an important signaling molecule in cells, were found in the cells’ nuclear fraction. FB1 exposure also led to a change (increased acetylation) in the structure of nuclear proteins known as histones, a change that is potentially important because acetylation status of histones influences gene expression. The increased histone acetylation in FB1 exposed cells was reversed when the accumulation of sphinganine-1-phosphate in the nuclear fraction was inhibited by co-exposing the cells to compounds that interfere with sphinganine-1-phosphate production. The results are important because they suggest that inappropriately high levels of sphinganine-1-phosphate resulting from FB1 exposure influence the expression of genes, including those involved in proper neural tube closure. As such, the findings provide insight about biomolecular mechanisms that might be critical for neural tube defect induction by FB1.

Technical Abstract: Fumonisin B1 (FB1) is a mycotoxin produced by a common fungal contaminant of corn. Administration of FB1 to pregnant LM/Bc mice induces exencephaly in embryos, and ingestion of FB1-contaminated food during early pregnancy is associated with increased risk for neural tube defects (NTDs) in humans. FB1 inhibits ceramide synthase enzymes in sphingolipid biosynthesis, causing sphinganine (Sa) and bioactive sphinganine-1-phosphate (Sa1P) accumulation in blood, cells, and tissues. Sphingosine kinases (Sphk) phosphorylate Sa to form Sa1P. Upon activation, Sphk1 associates primarily with the plasma membrane, while Sphk2 is found predominantly in the nucleus. In cells over-expressing Sphk2, accumulation of Sa1P in the nuclear compartment inhibits histone deacetylase (HDAC) activity, causing increased acetylation of histone lysine residues. In this study, FB1 treatment in LM/Bc mouse embryonic fibroblasts (MEFs) resulted in significant accumulation of Sa1P in nuclear extracts relative to cytoplasmic extracts. Elevated nuclear Sa1P corresponded to decreased histone deacetylase (HDAC) activity and increased histone acetylation at H2BK12, H3K9, H3K18, and H3K23. Treatment of LM/Bc MEFs with a selective Sphk1 inhibitor, PF-543, or with ABC294640, a selective Sphk2 inhibitor, significantly reduced nuclear Sa1P accumulation after FB1, although Sa1P levels remained significantly increased relative to basal levels. Concurrent treatment with both PF-543 and ABC294640 prevented nuclear accumulation of Sa1P in response to FB1. Other HDAC inhibitors are known to cause NTDs, so these results suggest that FB¬1-induced disruption of sphingolipid metabolism leading to nuclear Sa1P accumulation, HDAC inhibition, and histone hyperacetylation is a potential mechanism for FB1-induced NTDs.