Neurotoxicology and Teratology 22 (2000) 565–572 0892-0362/00/$ – see front matter © 2000 Elsevier Science Inc. All rights reserved. PII: S0892-0362(00)00082-9 Biochemical and morphological effects of fumonisin B 1 on primary cultures of rat cerebrum Oh-Seung Kwon a, * ,1 , William Slikker Jr. a,b , David L. Davies c a Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA b Division of Neurotoxicology, National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR 72079, USA c Department of Anatomy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA Received 2 August 1999; accepted 5 April 2000 Abstract Chronic dietary consumption of the mycotoxin fumonisin B 1 (FB 1 ) is associated with leukoencephalomalacia and neuronal degeneration, but identification of the cellular mechanisms underlying this neurotoxicity is difficult due to concurrent adverse systemic changes. For this reason, the present investigation used an in vitro approach to assess the short-term consequences of direct FB 1 (0.5–75 M) exposure on astrocytes and oligodendrocytes in primary cultures of rat cerebrum. Beginning at 5 days in vitro, the cultures were exposed to FB 1 at five concentrations (0.5–75 M), and the cultures were evaluated at 10 and 15 days in vitro. The levels of the sphingolipid-associated constituents sphingosine and sphinganine were determined with a high-performance liquid chromatography. Relative to untreated cultures, exposure to FB 1 diminished the levels of sphingosine at 15 days in vitro, whereas FB 1 -exposed cultures showed significantly increased sphinganine levels and sphinganine/sphingosine ratios. In addition to these changes in sphingolipid constituents, FB 1 -exposed (0.5–75 M) cultures exhibited a two-fold increase in the number of process-bearing cells by 15 days in vitro. Also, the activity of 2',3'-cyclic nucleotide 3'-phosphohy- drolase, an enzyme associated with myelin and oligodendrocytes, was increased in FB 1 -treated cultures. This study suggests that short- term exposure to FB 1 may modify the proliferation or differentiation of glial cells. © 2000 Elsevier Science Inc. All rights reserved. Keywords: Fumonisin B 1 ; Glia; Leukoencephalomalacia; Mycotoxin; Oligodendrocyte; Sphinganine; Sphingosine 1. Introduction The mycotoxin fumonisin B 1 (FB 1 ), a major metabolite of the fungus Fusarium moniliforme, is a worldwide contam- inant in dietary corn [17,32]. Experimental administration of pure FB 1 to horses causes equine leukoencephalomalacia; the principal brain lesions are edema and necrosis in white matter [14,37]. Pharmacokinetic studies demonstrate that FB 1 is rapidly eliminated from plasma [27], and that FB 1 is not extensively distributed within the body after intravenous administration of 14 C-FB 1 [34]. FB 1 is structurally similar to sphinganine (Sa) and sphingosine (So), the long-chain base backbones of sphingomyelin, cerebrosides, sulfatides, and gangliosides that are important constituents of myelin [18]. Consequently, FB 1 modulation of sphingolipid biosynthesis is considered to result from inhibition of Sa N-acyltrans- ferase both in vivo [23,24] and in vitro [15,35]. The mechanism whereby FB 1 impairs white matter is un- known. In cell culture studies in which the concentration of FB 1 is controlled, FB 1 (10 M) inhibits axonal outgrowth from hippocampal neurons, and decreases cellular sphin- golipids [8]. Aggregating brain cell cultures exposed to FB 1 (3–40 M) for 10 days show decreases in both the total content of myelin basic protein and immunoreactivity of the oligo- dendrocyte membrane marker galactocerebroside (GalC) in the absence of general cytotoxicity [16]. However, another oligodendrocyte marker 2',3'-cyclic nucleotide 3'-phospho- hydrolase (CNP) activity was not altered in this system. Our previous in vivo studies indicate that multiple subcuta- neous dosing of developing rats with FB 1 significantly reduces body and brain weights, and also causes hypomyelination accompanied by altered sphingolipid metabolism in the central nervous system [11,12]. The present study investigated the influence of FB 1 exposure on sphingolipid metabolism in primary glial cultures. Because this model contains a heter- ogenous population of glia, it allows for oligodendrocyte– astrocyte interactions known to influence oligodendrocyte development [2,19]. Furthermore, it excludes confounding systemic variables associated with FB 1 -treated rodents such 1 Present address: Bioanalysis and Biotransformation Research Center, Korea Institute of Science and Technology, no. 39-1 Hawolgok-dong, Sungbuk-gu, Seoul 136-791, Republic of Korea. * Corresponding author. Tel.: +82-2-958-5184; fax: +82-2-958-5059. E-mail address: oskwon@kistmail.kist.re.kr (O.S. Kwon).