Prevention of Fumonisin B1-Induced Neural Tube Defects by Folic Acid T.W. SADLER, 1 * ALFRED H. MERRILL, 2 VICTORIA L. STEVENS, 3 M. CAMERON SULLARDS, 2 ELAINE WANG, 2 AND PING WANG 1 1 Department of Cell and Developmental Biology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599-7090 2 Department of Biochemistry, Emory University, School of Medicine, Atlanta, Georgia 30335-3050 3 Department of Radiation Oncology, Emory University, School of Medicine, Atlanta, Georgia 30335-3801 ABSTRACT Background: The mycotoxin fumonisin B1 (FB1) inhib- its sphingolipid synthesis, blocks folate transport, and has been associated with increased incidences of can- cer and neural tube defects. Results from reproductive studies in animal models in vivo and in vitro have demonstrated toxicity in some cases, but no specific terata after fumonisin exposure. No information is avail- able about folic acid’s potential to protect against this toxicity. Methods: Neurulating mouse embryos were exposed to fumonisin or folinic acid in whole embryo culture and assessed for effects on growth and development. Results: Fumonisin exposure inhibited sphingolipid synthesis, reduced growth, and caused cranial neural tube defects in a dose dependent manner. Supplemen- tal folinic acid ameliorated the effects on growth and development, but not inhibition of sphingolipid synthe- sis. Conclusion: Fumonisin has the potential to inhibit em- bryonic sphingolipid synthesis and to produce embryo- toxicity and neural tube defects. Folic acid can reverse some of these effects, supporting results showing that fumonisin disrupts folate receptor function. Teratology 66:169 –176, 2002. © 2002 Wiley-Liss, Inc. INTRODUCTION Fumonisins are mycotoxins produced by the molds Fusarium moniliforme and F. proliferatum that are found throughout the world. More than 10 types of fumonisins have been identified with the most preva- lent being fumonisin B1 (FB1), which is also the most toxic (Thiel et al., ’92; Musser and Plattner, ’97). FB1 is found in contaminated corn and high levels are associ- ated with periods of hot dry weather that are followed by high humidity (Shelby et al., ’94). In animals ex- posed to fumonisins, liver and kidney damage occur (Merritt et al., ’97) and chronic feeding results in can- cer in mice and rats (Gelderblom et al., ’91, Gelderblom et al., 92; Norred et al., ’98). These mycotoxins also cause porcine pulmonary edema (Harrison et al., ’90; Haschek et al., ’92; Osweiler et al., ’92) and equine leukoencephalomalacia (Kellerman et al., ’90). Expo- sures in humans have been associated with esophageal and liver cancer (Marasas et al., ’88; Sydenham et al., ’90; Rheeder et al., ’92; Chu and Li, ’97) and high levels of FB1 and its metabolites in corn and tortillas have been correlated with increased incidences of neural tube defects in parts of Texas (Hendricks, ’99), Guate- mala (Filmore et al., ’99), and South Africa (Viljoen et al., ’95). This association has led to the hypothesis that fumonisins may cause embryotoxicity and birth defects (Hendricks, ’99). FB1 has been shown to alter sphingolipid synthesis, by inhibiting the enzyme ceramide synthase (sphin- gosine N-acetyltransferase), resulting in increased pro- duction of sphinganine and decreased production of downstream products, including ceramide, which may alter cell signaling (Wang et al., ’91). Altered sphingo- lipid synthesis also disrupts cell membrane integrity and affects receptor function, including transport of folic acid by the folate receptor (Stevens and Tang, ’97). Because of these biochemical effects, and the associa- tion with disease and poor reproductive outcomes in animals and humans, fumonisins have been tested in laboratory animals for their potential as reproductive toxins. Results from these studies have varied depend- ing on the species and experimental paradigm em- ployed. For example, extracts from Fusarium cultures and purified FB1 have been shown to be embryotoxic to hamsters (causing increased resorptions and fetal death) (Floss et al., ’94a, b), mice (Gross et al., ’94; Reddy et al., ’96), rats (Lebepe-Mazur et al., ’95; Collins et al., ’98a,b), chicks (Javed et al., ’93; Zacharias, ’96), and rabbits (LaBorde et al., ’97). With exception of studies with hamsters and chicks, however, affects on Grant sponsor: NIH R01, HD29495, GM46368; Grant sponsor: March of Dimes, 1 FY00-802. *Correspondence to: T.W. Sadler, University of North Carolina, De- partment of Cell and Developmental Biology, 108 Taylor Hall, CB #7090, Chapel Hill, NC 27599-7090. E-mail: tsadler@med.unc.edu Received 24 July 2001; Accepted 9 April 2002 Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tera.10089 TERATOLOGY 66:169 –176 (2002) © 2002 WILEY-LISS, INC.