Subchronic toxic effects of Fusarium moniliforme and fumonisin B1 in rats and mice

Fumonisin B1 exposure increases Hsp70 expression in the lung and kidney of rats without inducing significant oxidative stress

The objective of this experiment was to determine whether fumonisin B₁ (FB₁) added to the diet of rats in a dose of 50 mg/kg changes the production of heat shock protein 70 (Hsp70) in the lungs and kidney of rats. We also studied the effect of this mycotoxin on the antioxidant system of the body. Mature (8 weeks old) male Wistar Crl:WI BR rats (n = 6/group) were fed the toxin-containing diet for 5 days. FB1 resulted in a 7% body weight reduction without significantly changing the feed intake. Western blot analysis of the lungs and kidney demonstrated a substantial (1.4-fold and 1.8-fold, respectively) increase in Hsp70 expression. Alterations could not be detected in the clinical chemical parameters (total protein, albumin, total cholesterol, glucose, creatinine and urea concentrations, and aspartate aminotransferase activity). There was no statistically significant change in malondialdehyde concentrations and the measured antioxidant parameters (the amount of reduced glutathione, GSH and glutathione peroxidase activity, GPx) in the blood plasma, lung and kidney tissue. Thus, it can be concluded that FB₁ did not induce oxidative stress in the lungs and kidney, but increased Hsp70 production.

Biodegradation of Mycotoxins: Tales from Known and Unexplored Worlds

Exposure to mycotoxins, secondary metabolites produced by fungi, may infer serious risks for animal and human health and lead to economic losses. Several approaches to reduce these mycotoxins have been investigated such as chemical removal, physical binding, or microbial degradation. This review focuses on the microbial degradation or transformation of mycotoxins, with specific attention to the actual detoxification mechanisms of the mother compound. Furthermore, based on the similarities in chemical structure between groups of mycotoxins and environmentally recalcitrant compounds, known biodegradation pathways and degrading organisms which hold promise for the degradation of mycotoxins are presented.

Mycotoxins: cytotoxicity and biotransformation in animal cells

Mycotoxins are secondary metabolites produced by many microfungi. Hitherto, over 300 mycotoxins with diverse structures have been identified. They contaminate most cereals and feedstuffs, which threaten human and animal health by exerting acute, sub-acute and chronic toxicological effects, with some considered as carcinogens. Many mycotoxins at low concentrations are able to induce the expression of cytochrome P450 and other enzymes implicated in the biotransformation and metabolization of mycotoxins in vivo and in vitro. Mycotoxins and their metabolites elicit different cellular disorders and adverse effects such as oxidative stress, inhibition of translation, DNA damage and apoptosis in host cells, thus causing various kinds of cytotoxicities. In this review, we summarize the biotransformation of mycotoxins in animal cells by CYP450 isoforms and other enzymes, their altered expression under mycotoxin exposure, and recent progress in mycotoxin cytotoxicity in different cell lines. Furthermore, we try to generalize the molecular mechanisms of mycotoxin effects in human and animal cells.

Effect of fumonisin-containing diet on the myenteric plexus of the jejunum in rats

Fumonisins are mycotoxins that naturally occur as contaminants in grains that are destined for animal and human consumption. These mycotoxins cause hepatotoxic, nephrotoxic, carcinogenic, teratogenic, immunotoxic, and neurotoxic effects in different intensities based on dose, time of exposure, and animal species. In the present study, male Wistar rats were fed between postnatal days 21 and 63 with diets that contained fumonisins B1+B2 at concentrations of 1 and 3mg/kg. The objective of the present study was to evaluate the effects of fumonisins on food intake, growth, weight gain, serum activity of the alanine aminotransferase and aspartate aminotransferase enzymes, and quantitative and morphometric parameters of myenteric neurons in the jejunum that are immunoreactive to HuC/D protein and neuronal nitric oxide synthase enzyme (nNOS). Diets that contained fumonisins did not significantly alter food intake or body and blood parameters. We did not observe significant differences in the neuronal density and proportion of nitrergic neurons but found a significant reduction of cell body areas in both neuronal populations. This study is the first to report the effects of fumonisins in the enteric nervous system. The possible mechanisms by which fumonisins impair neuronal development and the use of the enteric nervous system as a tool for the study of the neurotoxic effects of fumonisins are discussed. In conclusion, fumonisin-containing food negatively affected the growth of myenteric neurons.

Lipid metabolism disorders, lymphocytes cells death, and renal toxicity induced by very low levels of deoxynivalenol and fumonisin b1 alone or in combination following 7 days oral administration to mice

SCOPE

In our previous study focused on in vitro interactive effect of Fusarium mycotoxins deoxynivalenol (DON) and fumonisin B1 (FB1), we reported that these toxins tested at low level and in association could lead to additive or synergistic cytotoxic effect. The aim of the present study is to confirm those findings by in vivo study.

MATERIALS AND METHODS

Swiss mice were orally administered with low doses of DON (45 μg/kg bw/day), FB1 (110 μg/kg bw/day), and their mixture (DON + FB1) for 7 days.

RESULTS

As results, no death or abnormal symptoms were observed in all groups. The significant of loss of weight was observed in females group treated with FB1 and its association with DON. Serum chemistry examinations revealed that disorders in lipid metabolism, renal filtration perturb and a rhabdomyolysis. DON has been found as particular inducer of kidney cell deoxyribonucleic acid (DNA) methylation and blood lymphocytes cell death as measured by lymphocytes DNA fragmentation. Female mice were more sensitive and the mixture of DON and FB1 led to additive or more than additive effect particularly for their target kidney which showed different pattern of toxicity.

CONCLUSION

Based on the results of this study, the no-observed-adverse effect level (NOAEL) o both DON and FB1 should be low than 45 μg/kg bw/day and 110 μg/kg bw/day, respectively in mice.

Protective effects of silymarin on fumonisin B₁-induced hepatotoxicity in mice

The present study was conducted to investigate the effect of silymarin on experimental liver toxication induced by Fumonisin B₁ (FB₁) in BALB/c mice. The mice were divided into six groups (n = 15). Group 1 served as the control. Group 2 was the silymarin control (100 mg/kg by gavage). Groups 3 and 4 were treated with FB₁ (Group 3, 1.5 mg/kg FB₁, intraperitoneally; and Group 4, 4.5 mg/kg FB₁). Group 5 received FB₁ (1.5 mg/kg) and silymarin (100 mg/kg), and Group 6 was given a higher dose of FB₁ (4.5 mg/kg FB₁) with silymarin (100 mg/kg). Silymarin treatment significantly decreased (p < 0.0001) the apoptotic rate. FB₁ administration significantly increased (p < 0.0001) proliferating cell nuclear antigen and Ki-67 expression. Furthermore, FB₁ elevated the levels of caspase-8 and tumor necrosis factor-alpha mediators while silymarin significantly reduced (p < 0.0001) the expression of these factors. Vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2) expressions were significantly elevated in Group 4 (p < 0.0001). Silymarin administration alleviated increased VEGF and FGF-2 expression levels (p < 0.0001). In conclusion, silymarin ameliorated toxic liver damage caused by FB₁ in BALB/c mice.

Effects of combinations of Fusarium mycotoxins on the inhibition of macromolecular synthesis, malondialdehyde levels, DNA methylation and fragmentation, and viability in Caco-2 cells

We studied the interactive effects of either binary or tertiary mixtures of Fusarium mycotoxins, deoxynivalenol (DON), zearalenone (ZEA), and fumonisin B1 (FB1) on the human intestinal cell line, Caco-2, using the endpoints including malonedialdehyde (MDA) production, inhibition of protein and DNA syntheses, DNA methylation, DNA fragmentation, and cell viability as measured by the neutral red (NR) test. The mixtures of mycotoxins reduce cellular viability in increasing order: [FB1+ZEA]<[FB1+DON]<[ZEA+DON]<[FB1+DON+ZEA] in NR test. Because FB1 antagonizes the effects of estrogenic Zearalenone, FB1 was assayed against estradiol. In NR assay, mixture of FB1 and estradiol and/or ZEA improves Caco-2 cells viability in contrast to individual effects. Mixtures of ZEA or FB1 and DON, display synergistic effects in lipid peroxidation. The ability of the toxins to inhibit DNA synthesis is 45%, 70%, and 43% for 10 microM of ZEA, DON, and FBI, respectively. Their binary mixtures (at 10 microM each), inhibit DNA synthesis by 35%, 62%, and 65%, far less than additive effects. Surprisingly, the tertiary mixture (10 microM each) only inhibits DNA synthesis by 25%. ZEA, DON, and FB1 induce DNA fragmentation individually. However, mixtures of these mycotoxins always damage DNA to a greater extent. Each individual mycotoxin (10 microM) raises the percentage of 5-methylcytosine (m5dC) in DNA from 4.5% to 9%, while the combination does not increase this rate any further. Altogether, the data indicate that mixtures of Fusarium toxins are able to induce lipid peroxidation, DNA damage, DNA fragmentation, DNA methylation, and cytotoxicity in Caco-2 cells, and suggest a potential promoter effect in human intestinal cells.

Tumor necrosis factor alpha-mediated activation of c-Jun NH(2)-terminal kinase as a mechanism for fumonisin B(1) induced apoptosis in murine primary hepatocytes

Fumonisin B(1) is a mycotoxin produced by Fusarium verticillioides, frequently associated with corn. It produces species-specific and organ-specific toxicity, including equine leukoencephalomalacia, porcine pulmonary edema, and hepatic or renal damage in most animal species. Fumonisin B(1) perturbs sphingolipid metabolism by inhibiting ceramide synthase. Our previous studies indicated that fumonisin B(1) caused localized activation of cytokines in liver produced by macrophages and other cell types that modulate fumonisin B(1) induced hepatic apoptosis in mice. The role of tumor necrosis factor alpha (TNFalpha) in fumonisin B(1) mediated hepatocyte apoptosis has been established; not much is known about the downstream events leading to apoptosis. In the current study, fumonisin B(1) induced apoptosis in primary culture of liver cells. In consistence with previous reports, fumonisin B(1) caused accumulation of sphingoid bases and led to increase in TNFalpha expression. Phosphorylated and total c-Jun NH(2)-terminal kinase (JNK) activities were increased after 24 h fumonisin B(1) treatment. JNK inhibitor (SP600125) and anti-TNFalpha reduced the apoptosis induced by fumonisin B(1). The role of JNK signaling in fumonisin B(1) induced apoptosis is downstream of TNFalpha production, as fumonisin B(1)-mediated activation of JNK was reduced by the presence of anti-TNFalpha in the medium, whereas the presence of JNK inhibitor did not change the fumonisin B(1) induced TNFalpha expression. Results of this study imply that generation of fumonisin B(1) induced TNFalpha results in modulation of mitogen activated protein kinases, particularly of JNK, and provides a possible mechanism for apoptosis in murine hepatocytes.

Mechanism of action of sphingolipids and their metabolites in the toxicity of fumonisin B1

Fumonisins are a group of mycotoxins produced primarily by Fusarium moniliforme. Several fumonisins have been isolated through out the years but only fumonisin B1, B2 and B3 are the ones present in naturally contaminated foods, with B1 being the most toxic between them. The structural similarity between sphinganine and fumonisin B1 suggests that the mechanism of action of this mycotoxin is mainly via disruption of sphingolipid metabolism, this is an important step in the cascade of events leading to altered cell growth, differentiation and cell injury. Sphingolipids are a second type of lipid found in cell membranes, particularly nerve cells and brain tissues. Toxicity of fumonisin B1 is given via inhibition of ceramide synthase that catalyzes the formation of dihydroceramide from sphingosine. This mechanism of action may explain the wide variety of health effects observed when this mycotoxin is ingested like high rate of human oesophageal cancer and promotion of primary liver cancer.

Aromatic plants essential oils activity on Fusarium verticillioides Fumonisin B1 production in corn grain

The minimum inhibitory concentration (MIC) of Origanum vulgare, Aloysia triphylla, Aloysia polystachya and Mentha piperita essential oils (EOs) against Fusarium verticillioides M 7075 (F. moniliforme, Sheldon) were assessed, using the semisolid agar antifungal susceptibility (SAAS) technique. O. vulgare, A. triphylla, A. polystachya and M. piperita EOs were evaluated at final concentrations of 10, 20, 40, 50, 100, 200, 250, 500, 1000 and 1500 epsilonl per litre (epsilonl/l) of culture medium. A. triphylla and O. vulgare EOs showed the highest inhibitory effects on F. verticillioides mycelial development. This inhibition was observed at 250 and 500 epsilonl/l for EOs coming from Aloysia triphylla and O. vulgare, respectively. Thus, the effects of EOs on FB(1) production were evaluated using corn grain (Zea mays) as substrate. The EOs were inserted on the 5th, 10th, 15th and 20th day of maize postinoculation with a conidia suspension of F. verticillioides. O. vulgare and A. triphylla were applied to give final concentrations of 30 ppm and 45 ppm, respectively. Different effects were observed in the toxicogenicity at the 20th day treatment. The O. vulgare EO decreased the production level of FB(1) (P < 0.01) while A. triphyla EO increased it (P < 0.001) with respect to those obtained in the inoculated maize, not EOs treated. Results obtained in the present work indicate that fumonisin production could be inhibited or stimulated by some constituents of EOs coming from aromatic plants. Further studies should be performed to identify the components of EOs with modulatory activity on the growth and fumonisins production of Fusarium verticillioides.

Selective and transient activation of protein kinase C alpha by fumonisin B1, a ceramide synthase inhibitor mycotoxin, in cultured porcine renal cells

Fumonisin B(1) (FB(1)), a potent and naturally occurring mycotoxin produced by the fungus Fusarium verticillioides, has been implicated in fatal and debilitating diseases in animals and humans. FB(1) affects a variety of cell signaling proteins including protein kinase C (PKC); a serine/threonine kinase, involved in a number of signal transduction pathways that include cytokine induction, carcinogenesis and apoptosis. The aim of this study was to investigate the short-term temporal and concentration-dependent effects of FB(1) on PKC isoforms present in LLC-PK(1) cells in relation to the FB(1)-induced accumulation of sphinganine and sphingosine utilizing various inhibitors and activators. Our studies demonstrated that FB(1) (0.1-1 microM) selectively and transiently activated PKCalpha at 5 min, without affecting PKC-delta, -epsilon and -zeta isoforms. At higher FB(1) concentrations and later time points (15-120 min), PKCalpha membrane concentrations declined to untreated levels. The observed increase in cytosol PKCalpha protein expression at 15 min was not associated with an increase in its activity or protein biosynthesis. Calphostin C, a PKC inhibitor, abrogated the FB(1)-induced translocation of PKCalpha. Pre-incubation with the PKC activator, phorbol 12-myristate 13-acetate, resulted in an additive effect on membrane translocation of PKCalpha. Intracellular sphinganine and sphingosine concentrations were unaltered at the time points tested. Myriocin, a specific inhibitor of serine palmitoyltransferase, the first enzyme in de novo sphingolipid biosynthesis, did not prevent the FB(1)-induced PKCalpha cytosol to membrane redistribution. Altering PKCalpha and its signal transduction pathways may be of importance in the ability of FB(1) to exert its toxicity via apoptosis and/or carcinogenesis.

Fumonisin B1-induced apoptosis is associated with delayed inhibition of protein kinase C, nuclear factor-kappaB and tumor necrosis factor alpha in LLC-PK1 cells

Fumonisin B1 (FB1), the most potent of the fumonisin mycotoxins, is a carcinogen and causes a wide range of species-specific toxicoses. FB1 modulates the activity of protein kinase C (PKC), a family of phospholipid-dependent serine/threonine kinases that play important role in modulating a variety of biologic responses ranging from regulation of cell growth to cell death. Although it has been demonstrated that FB1 induces apoptosis in many cell lines, the precise mechanism of apoptosis is not fully understood. In this study, we investigated the membrane localization of various PKC isoforms, PKC enzyme activity, and its downstream targets, namely nuclear factor-kappa B (NF-kappaB), tumor necrosis factor alpha (TNFalpha), and caspase 3, in porcine renal epithelial (LLC-PK1) cells. FB1 repressed cytosol to membrane translocation of PKC-alpha, -delta, -epsilon, and -zeta isoforms over 24-72 h. The FB1-induced membrane PKC repression was corroborated by a concentration-dependent decrease in total PKC activity. Exposure of cells to phorbol 12-myristate 13-acetate (PMA) for this duration also resulted in repressed PKC membrane localization and activity comparable to FB1. Exposure of cells to FB1 (10 microM) was associated with inhibition of cytosol to nuclear translocation of NF-kappaB and NF-kappaB-DNA binding at 72 h. The expression of TNFalpha was significantly inhibited at 24 and 48 h in response to 1 and 10 microM FB1. Increased caspase 3 activity was observed in LLC-PK1 cells exposed to > or =1 microM FB1 at 48 h. PMA also increased the caspase 3 activity at 24 and 48 h. Results suggest that FB1-induced apoptosis involves the activation of caspase 3, which is associated with the repression of PKC and possibly its down-stream effectors, NF-kappaB and TNFalpha.

Fusarial toxins and their role in animal diseases

Fusarial toxins are toxic metabolites produced mostly by toxigenic micromycetes of genus Fusarium. Dominant mycotoxins of this group include trichothecenes, moniliformin, zearalenone, and fumonisins. Recently, special attention has been paid to these toxins because of their harmful effects on both animals and humans. On the basis of the available literature, we review here the characteristics of major fusarial mycotoxins with an emphasis on their toxic effects on animals. The most important fusarial mycotoxins, their sources, and their pathology including clinical signs, necropsy findings, as well as changes in haematological, biochemical, and immunological indices, are addressed.

Paradoxical role of tumor necrosis factor alpha in fumonisin-induced hepatotoxicity in mice

Tumor necrosis factor alpha (TNFalpha) is involved in fumonisin-induced hepatotoxic effects in mice. The hepatic response to fumonisin B(1) (FB(1)) was reduced in transgenic animals lacking either of the two TNFalpha receptors. In the present study, we hypothesized that the effect of a similar fumonisin treatment in animals lacking either TNFalpha or both TNFalpha receptors would be considerably less than their wild type (WT) counterparts. The FB(1)-induced increase in circulating liver enzymes was enhanced by deletion of TNFalpha or unchanged in mice lacking both TNFalpha receptors. These findings corresponded with the degree of toxicity as established by microscopic examination of liver. FB(1) induced the expression of TNFalpha in the liver of all strains, except the animals with a deleted TNFalpha gene. The FB(1)-mediated increases in liver sphingosine or sphinganine paralleled the hepatotoxic responses. It is apparent that the presence of TNFalpha is not necessary for FB(1)-induced hepatotoxicity in mice and a lack of the function of this cytokine may aggravate the hepatotoxic responses to fumonisins, perhaps by preventing repair mechanisms or by expression of other signaling molecules. These observations were in accordance with our previous finding where over-expression of TNFalpha also protected against FB(1)-mediated hepatotoxicity, and with the reported beneficial functions of low-level TNFalpha in tissue regeneration.

Fumonisin B1-induced localized activation of cytokine network in mouse liver

Fumonisin B1 (FB1), a mycotoxin produced primarily by Fusarium veticillioides and related fungi, is a carcinogen and causative agent of various animal diseases. Our previous studies indicated the involvement of tumor necrosis factor-alpha (TNFalpha) in FB1-induced hepatotoxicity. Male B6,129 mice (five/group) were injected subcutaneously with vehicle or 2.25 mg/kg/day of FB1 for 5 days and sampled 1 day after the last treatment. FB1 treatment caused an increased expression of TNFalpha, interferon gamma (IFNgamma) and interleukin (IL)-12 p40 in liver without any changes in kidney or spleen, suggesting the localized site of their production. IL-1beta cytokine expression was increased in liver and kidney after FB1 exposure. Cells involved in TNFalpha production after FB1 treatment in liver were identified as Kupffer cells. FB1 increased alanine aminotransferase in plasma and increased apoptotic cells in liver. Selective increase in proinflammatory T helper (Th)1-cytokines (IL-12 and IFNgamma) and TNFalpha with no alteration in Th2-cytokines (IL-4, IL-6 and IL-10) suggest the involvement of IL-12, produced by Kupffer cells, in induction of IFNgamma production by natural killer (NK) cells and/or NK1+ T cells, which can undergo a positive amplification loop with TNFalpha produced by macrophages or other hepatic cells to elicit the toxic reaction.

Pharmacological antagonism of fumonisin B1 cytotoxicity in porcine renal epithelial cells (LLC-PK1): a model for reducing fumonisin-induced nephrotoxicity in vivo

Fumonisin B1 is a mycotoxin commonly found on corn. It is hepatotoxic and nephrotoxic in domestic and experimental animals, and causes equine leukoencephalomalacia and porcine pulmonary oedema. It is a potent inhibitor of ceramide synthase. Inhibition leads to accumulation of free sphingoid bases in cells and tissues. In pig kidney epithelial cells (LLC-PK1), fumonisin B1 induces increased tumour necrosis factor alpha (TNFalpha) expression independent of the accumulation of sphingoid bases. The objective of this study was to investigate pharmacological approaches for intervening in fumonisin B1 toxicity using the LLC-PK1 cell model. The toxicity of fumonisin B1 was assayed using cell viability and lactate dehydrogenase (lactate dehydrogenase) release. Pretreatment of cells with myriocin, preventing sphinganine accumulates, prevented the fumonisin B1-induced decrease in cell viability and increased lactate dehydrogenase release. Modulation of adenosine receptor activity did not reduce the fumonisin B1 cytotoxicity. As with myriocin, silymarin pretreatment prevented the fumonisin B1-induced effects on cell viability and lactate dehydrogenase release. When added 6 or 24 hr after treatment of cells with fumonisin B1, both myriocin and silymarin reversed the decreased cell viability and suppressed the increased lactate dehydrogenase release. Myriocin, but not silymarin, blocked the accumulation of sphinganine in fumonisin B1-treated cells. Silymarin, unlike myriocin, induced expression of TNFalpha to an extent similar to fumonisin B1, but pretreatment with silymarin decreased the fumonisin B1-induced TNFalpha expression in LLC-PK1 cells. Results suggest that the mechanisms by which myriocin and silymarin protect renal cells are different, and silymarin potentially prevents fumonisin B1-induced toxicity by modulating TNFalpha expression or signals downstream of the inhibition of ceramide synthase.

In vitro and in vivo studies to assess the effectiveness of cholestyramine as a binding agent for fumonisins

Several adsorbent materials were tested at I mg/ml for their in vitro capacity to adsorb fumonisin B1(FB1) from aqueous solutions. Cholestyramine showed the best adsorption capacity (85% from a solution containing 200 microg/ml FB1) followed by activated carbon (62% FB1). Bentonite adsorbed only 12% of the toxin from a solution containing 13 microg/ml FB1, while celite was not effective even at the lowest tested FB1 concentration (3.2 microg/ml). Cholestyramine was tested in vivo to evaluate its capacity to reduce the bioavailability of fumonisins (FBs) in rats fed diet contaminated with toxigenic Fusarium verticillioides culture material. Rats were exposed for one week to FBs-free diet, FBs-contaminated diet containing 6 or 20 microg/g FB1 + FB2 and the same FBs-contaminated diet added of 20 mg/g cholestyramine. The increase of sphinganine/sphingosine (SA/SO) ratio in urine and kidney of treated rats was used as specific and sensitive biomarker of fumonisin exposure. The addition of cholestyramine to the FBs-contaminated diets consistently reduced the effect of FBs by reducing significantly (P < 0.05) both urinary and renal SA/SO ratios.

Temporal expression of fumonisin B(1)-induced tumor necrosis factor-alpha and interferon gamma in mice

Fumonisin B(1) (FB(1)), a toxic metabolite of Fusarium verticillioides, is a carcinogen and causative agent of various animal diseases. Our previous studies indicated the involvement of tumor necrosis factor-alpha (TNF alpha) in FB(1)-induced toxic responses. To further investigate the time-course of TNF alpha production and signaling, mice (four/group) were treated subcutaneously (s.c.) or per os (p.o.) with either vehicle or 25 mg/kg of FB(1) as a single dose and sacrificed at 0, 2, 4, 8, 12 and 24 h after treatment. The TNF alpha expression was increased in liver and kidney after both routes of FB(1) exposure without any alterations in spleen. The p.o.-route FB(1) treatment caused greater hepatotoxicity compared to the s.c. route, as depicted by increased alanine aminotransferase and aspartate aminotransferase level in plasma, observed only after p.o. FB(1) treatment. The increase in enzymes at 8 h after p.o. treatment correlated with the highest TNF alpha expression, also noted at 8 h after p.o. treatment, thus further confirming the involvement of TNF alpha in FB(1) toxicity. The interferon (IFN)-gamma expression was increased in liver at 4 h after p.o. FB(1) treatment, suggesting a possible combined role of TNF alpha and IFN gamma in their induction and hepatotoxicity.

Immunobiological effects of fumonisin B1 in experimental subchronic mycotoxicoses in rats

Fumonisin B1 (FB1), the principal secondary metabolite produced by the fungus Fusarium verticillioides (Gibberella fujikuroi mating population A), is a potent toxin that can be found in fungus-contaminated corn and corn-based food products. We have investigated the immunobiological effects of subchronic dietary exposure to FB1 in male Wistar rats. Animals were fed with diets containing 0 (control) or 100 ppm of FB1 for 12 weeks. The total FB1 intake on day 90 was 810 mg/kg of body weight. Food consumption, body weight, and body weight gain on day 90 were reduced in animals exposed to FB1. Histopathologic changes consisted of histiocytic perivascular infiltrate and an increased number of Kupffer cells in the liver, necrosis and apoptosis of tubular epithelial cells in the kidney, and increased mitotic figures and lymphocytic infiltrate in the small intestine. Serum enzyme alkaline phosphatase was significantly elevated in rats fed FB1, while triglyceride levels decreased compared to controls. Treatment with FB1 in vivo or in vitro did not have a significant effect on mitogen-induced proliferation of spleen mononuclear cells. However, increased levels of interleukin-4 (IL-4) and decreased levels of IL-10 were released by these cells in culture compared to controls. FB1 in vivo or in vitro decreased the hydrogen peroxide (H(2)O(2)) released by peritoneal macrophages, while no changes in levels of superoxide anion produced by total peritoneal cells were detected. The results from the present work demonstrate that subchronic FB1 intake could affect the small intestine and alter the interleukin profile and some main functions of macrophages in antitumor activity.

Gender-dependent immunosuppression following subacute exposure to fumonisin B1

The effects of fumonisin B1 (FB1), a mycotoxin produced by Fusarium lertcillioides, on the immune system are controversial; FB1 exposure causing immunosuppression in poultry, swine, bovine and rodents species and immunostimulation in rodent species. The current study was conducted to examine the effects of FB1 on the immune system of BALB/c mice and to determine if there is sex specificity. Female and male mice (five per group) received five daily subcutaneous (s.c.) injections of 2.25 mg/kg/day of FB1, on the following day tissues were collected for immunological examinations. FB1 treatment dramatically reduced relative spleen and thymus weights in females, whereas there was no effect on organ weights in males. Exposure to FB1 reduced splenic cellularity and the basal rate of lymphocyte proliferation in females only. In addition, phytohemagglutinin (PHA-P)-induced T-lymphocyte and LPS-induced B-lymphocyte proliferation were reduced in female mice. Splenocytes from female mice exposed to FB1 showed a reduced expression of interleukin-2 mRNA. These changes occurred in the absence of alterations in tumor necrosis factor alpha or interleukin-1beta mRNA expression. Phenotypic analysis indicated that FB treatment caused a relative increase in the T-lymphocyte population in the spleen of female mice only. In contrast, FB1 dramatically reduced the immature CD4+/CD8+ double positive cell population in the thymus of females. No changes were evident in the thymocyte populations of male mice treated with FB1. The results of this study indicate that FB1 is immunosuppressive in mice; the magnitude of FB1-induced immunosuppression is highly dependent on sex, females being more susceptible than males.

Gender-related differences in subacute fumonisin B1 hepatotoxicity in BALB/c mice

Fumonisin B1 (FB1), a potent mycotoxin prevalent in corn, is a carcinogen and causative agent of various animal diseases. Species and sex variations to chronic FB1 toxicity have been reported. Free sphingoid bases and cytokine levels are the two major biochemical alterations of FB1 in vivo and may explain any sex differences in FB1 toxicity. Male and female BALB/c mice (5/group) were injected subcutaneously with either saline vehicle or 2.25 mg/kg/day of FB1 for 5 days. One day after the last injection females showed a greater increase in circulating alanine aminotransferase and greater number of apoptotic cells in liver after FB1 treatment than males, indicating greater hepatotoxicity. Peripheral leukocytic counts, including neutrophils, were increased in females only after FB1 treatment. The increased toxicity in females correlated with a greater increase of sphinganine and sphingosine levels in liver after FB1 treatment compared to males. No sex differences in kidney sphinganine or sphingosine levels were observed after FB1 treatment. Previously we have shown the induction of tumor necrosis factor alpha (TNFalpha) in FB1-induced hepatotoxicity. While in males FB1 treatment caused increased expression of TNFalpha, interleukin (IL)-12 p40, interferon gamma (IFNgamma), IL-1beta, IL-6 and IL-10, females showed an increased expression of IL-6 only, and a downward modulation of IFNgamma, indicating gender differences in cytokine pathways in liver activated by FB1. The basal expression of TNFalpha, IL-12 p40, IL-1beta and IFNgamma in liver of females was higher compared to males. Gender differences in alterations of free sphingoid bases and cytokine modulation after FB1 treatment suggest their possible involvement in sex-dependent differential hepatotoxicity in mice.

Fumonisin B1 promotes aflatoxin B1 and N-methyl-N'-nitro-nitrosoguanidine-initiated liver tumors in rainbow trout

Laboratory studies have described the carcinogenicity of fumonisin B1 (FB1) in rodents and epidemiological evidence suggests an association between FB1 (a mycotoxin produced by Fusarium moniliforme) and cancer in humans. This study was designed to reveal in rainbow trout, a species with very low spontaneous tumor incidence, if FB1 was (i) a complete carcinogen, in the absence of an initiator; (ii) a promoter of liver tumors in fish initiated as fry with aflatoxin B1 (AFB1); and (iii) a promoter of liver, kidney, stomach, or swim bladder tumors in fish initiated as fry with N-methyl-N'-nitro-nitrosoguanidine (MNNG). FB1 was not a complete carcinogen in trout. No tumors were observed in any tissue of fish fed diets containing 0, 3.2, 23, or 104 ppm FB1 for a total of 34 weeks (4 weeks FB1 exposure, 2 weeks outgrowth on control diet, followed by 30 weeks FB1 diet) in the absence of a known initiator. FB1 promoted AFB1 initiated liver tumors in fish fed > or = 23 ppm FB1 for 42 weeks. A 1-week pretreatment of FB1 did not alter the amount of liver [3H]AFB1 DNA adducts, which suggests that short-term exposure to FB1 will not alter phase I or phase II metabolism of AFB1. In MNNG-initiated fish, liver tumors were promoted in the 104 ppm FB1 treatment (42 weeks), but FB1 did not promote tumors in any other tissue. Tumor incidence decreased in kidney and stomach in the 104 ppm FB1 treatment of MNNG-initiated trout. The FB1 promotional activity in AFB1-initiated fish was correlated with disruption of sphingolipid metabolism, suggesting that alterations in associated sphingolipid signaling pathways are potentially responsible for the promotional activity of FB1 in AFB1-initiated fish.

Decreased fumonisin hepatotoxicity in mice with a targeted deletion of tumor necrosis factor receptor 1

Fumonisin B1 (FB1), a mycotoxin produced by Fusarium verticillioides and related fungi infests corn and other cereals, and causes a variety of toxic effects in different mammalian species. Hepatotoxicity is a common toxic response in most species. The cellular responses of FB1 involve inhibition of ceramide synthase leading to accumulation of free sphingoid bases and a corresponding induction of tumor necrosis factor alpha (TNFalpha). We recently reported that FB1 hepatotoxicity was considerably reduced in a mouse strain lacking tumor necrosis factor receptor 2 (TNFR2 or TNFR1b). To further investigate the relative contribution of the two TNFalpha receptors (TNFR1 and TNFR2 or P55 and P75 receptors) we evaluated the hepatotoxicity of FB1 in male C57BL/6J mice (WT) and a corresponding TNFR1 knockout (TNFRKO) strain, genetically modified by a targeted deletion of this receptor. The hepatotoxic effects of five daily injections of 2.25 mg/kg per day of FB1 were observed in WT but were reduced in TNFRKO, evidenced by the microscopic evaluation of the liver and increased concentrations of circulating alanine aminotransferase and aspartate aminotransferase. FB1 induced the expression of TNFalpha, and similar increases in free sphinganine and sphingosine in livers of both WT and TNFRKO mice. Results indicated that both P55 and P75 receptors are required for FB1-induced hepatotoxicity and TNFalpha plays an important role in such response in mouse liver.

Disruption of sphingolipid metabolism in small intestines, liver and kidney of mice dosed subcutaneously with fumonisin B(1)

Fumonisin B(1) is a fungal inhibitor of ceramide synthase, a key enzyme in the de novo biosynthesis of sphingolipids. The resulting increase in tissue free sphinganine (and sometimes sphingosine) is used as a biomarker for fumonisin exposure. This study determined whether a single subcutaneous injection of fumonisin B(1) could cause an increase in free sphingoid bases in the intestinal epithelial cells of mice over 24 hr. It was hypothesized that fumonisin administered subcutaneously would be excreted into the small intestine via biliary excretion, and this should be detectable by increased sphingoid bases in the intestine. A significant time-dependent increase in sphingoid bases occurred in the intestine and liver peaking at 4-8 hr and declining to control levels by 24 hr. In the kidney the increase in free sphinganine was persistent. The parallel time course of the change in sphinganine in the intestine and liver suggested fumonisin B(1) was rapidly excreted into the small intestine. Rapid cell turnover in the intestine could account for the reversal of the sphinganine increase. The rapid return to the control level in liver was unexpected since ceramide synthase inhibition in cultured cells is persistent suggesting that liver handles fumonisin B(1) or sphingoid bases quite differently than kidney.

Fumonisin toxicity in a transgenic mouse model lacking the mdr1a/1b P-glycoprotein genes

The toxicity of fumonisin B(1) (FB(1)) was investigated in male mdr1a/1b double knockout (MDRK) mice, lacking the drug-transporting P-glycoproteins. These transgenic animals are deficient in their blood:brain barrier and accumulate different drugs in brain and other tissues. The MDRK and their wild-type counterparts, FVB mice, were injected subcutaneously with 2.25 mg/kg per day of FB(1) for 5 days and sampled one day after the last treatment in a protocol that has resulted in marked hepatic and renal damage in other strains. FB(1) caused liver enlargement in both FVB and MDRK. Hematological parameters were not affected in either strain. Plasma levels of alanine aminotransferase and aspartate aminotransferase, measures of liver damage, were increased by FB(1) in both FVB and MDRK mice. Histopathological evaluation of liver corroborated this finding. Kidney lesions were induced by FB(1) in both types of mice. Concentrations of free sphingosine and sphinganine increased in liver and kidney of both strains after the FB(1) treatment, although the increase in liver sphingoid bases was half as much in MDRK as compared to FVB. The levels of sphinganine-containing complex sphingolipids were increased in kidney. The levels of sphingosine-containing complex sphingolipids in kidney were unaffected by FB(1) treatment but were significantly lower in control MDRK than in FVB mice. The levels of neurotransmitters and their metabolites were similarly affected in both strains by FB(1), suggesting no influence of disrupted blood:brain barrier on FB(1)-induced neurotoxicity. In both strains, the liver mRNA for tumor necrosis factor alpha was increased; however, the increase was statistically significant only in FVB. It was apparent that mice deficient in P-glycoprotein do not exhibit greater sensitivity to FB(1), the cellular or brain transport of FB(1) appears to be independent of this multidrug transporting system.

Tolerance to fumonisin toxicity in a mouse strain lacking the P75 tumor necrosis factor receptor

Fumonisin B1 (FB1), a potent mycotoxin prevalent in corn and cereals, causes a variety of toxic effects in different mammalian species. The biochemical responses of FB1 involve inhibition of ceramide synthase leading to accumulation of free sphingoid bases and a possible involvement of tumor necrosis factor alpha (TNFalpha). To further characterize the role of TNFalpha, toxic response to FB1 was investigated in male C57BL/6J mice (WT) and a corresponding TNFalpha receptor knockout (TRK) strain, genetically modified to lack the TNFalpha1b receptor. The hepatotoxic effects of 5 daily injections of 2.25 mg/kg per day of FB1 were observed in WT but were reduced in TRK, evidenced by circulating alanine aminotransferase and aspartate aminotransferase levels and histopathological evaluation of the tissue. FB1 induced TNFalpha expression in the livers of both WT and TRK mice to a similar extent (3-4 fold over control); however, a corresponding increase of cellular NFkappaB, expected after the downstream cellular signaling of TNFalpha, was noted only in the WT. Accumulation of liver sphingosine after FB1 treatment was similar in both WT and TRK, but the FB1-induced increases in liver sphinganine and kidney sphingosine and sphinganine were lower in TRK than in WT. Results emphasized the role of TNFalpha in FB1-induced hepatotoxicity in mice and the possible relationship of sphingoid base accumulation and TNFalpha induction. Moreover, the presence of TNFalpha receptor 1b appears to be important in mediating the hepatotoxic responses of TNFalpha and FB1 in mice.

The regulation of apoptosis by microbial pathogens

In the past few years, there has been remarkable progress unraveling the mechanism and significance of eukaryotic programmed cell death (PCD), or apoptosis. Not surprisingly, it has been discovered that numerous, unrelated microbial pathogens engage or circumvent the host's apoptotic program. In this chapter, we briefly summarize apoptosis, emphasizing those studies which assist the reader in understanding the subsequent discussion on PCD and pathogens. We then examine the relationship between virulent bacteria and apoptosis. This section is organized to reflect both common and diverse mechanisms employed by bacteria to induce PCD. A short discussion of parasites and fungi is followed by a detailed description of the interaction of viral pathogens with the apoptotic machinery. Throughout the review, apoptosis is considered within the broader contexts of pathogenesis, virulence, and host defense. Our goals are to update the reader on this rapidly expanding field and identify topics in the current literature which demand further investigation.

Serine palmitoyltransferase inhibition reverses anti-proliferative effects of ceramide synthase inhibition in cultured renal cells and suppresses free sphingoid base accumulation in kidney of BALBc mice

The purpose of this study was to determine the ability of the fungal serine palmitoyltransferase (SPT) inhibitor, myriocin, to prevent the anti-proliferative and cytotoxic effects of fumonisin B(1) in cultured pig kidney epithelial cells, LLC-PK(1). In an earlier study with LLC-PK(1) cells, β-chloroalanine (a nonspecific SPT inhibitor) was found to inhibit the fumonisin-induced accumulation of free sphinganine by >90% but only partially reversed (50-60%) fumonisin's antiproliferative and cytotoxic effects. β-Chloroalanine is not the ideal SPT inhibitor for this type of study because it also inhibits other pyridoxal 5'-phosphate-dependent enzymes. A potent and selective fungal SPT inhibitor (myriocin) was partially purified from liquid cultures of Isaria (=Cordyceps) sinclairii by a combination of organic extraction and column chromatography. The various fractions were bioassayed for their ability to inhibit fumonisin-induced sphinganine accumulation in LLC-PK(1) cells. The activity in partially purified material was compared to the activity of highly purified myriocin and the results expressed as myriocin equivalents. The estimated IC(50) and IC(95) for inhibition of fumonisin-induced sphinganine accumulation were approximately 1.8 and 22 nM, respectively. The IC(95) concentration of the fungal SPT inhibitor reversed the antiproliferative effects and prevented fumonisin-induced apoptosis after 48 h exposure to 50 μM fumonisin B(1). The SPT inhibitor was also effective at reducing free sphinganine in vivo. Free sphinganine concentration was reduced 60% in kidney of mice injected i.p. with SPT inhibitor plus fumonisin B(1) when compared to fumonisin B(1) alone. The ability of SPT inhibition to reduce fumonisin B(1)-induced sphinganine accumulation in vivo may be useful in the development of therapeutic agents for treatment of animals suspected to have been exposed to toxic levels of fumonisin in feeds.

In vivo effects of fumonisin B1-producing and fumonisin B1-nonproducing Fusarium moniliforme isolates are similar: fumonisins B2 and B3 cause hepato- and nephrotoxicity in rats

Fumonisins are mycotoxins produced by Fusarium moniliforme, F. proliferatum, and related Fusarium species found on corn. They occur naturally in corn-based feeds and foods and are suspected human esophageal carcinogens. Fumonisin B1 (FB1), the most common homologue, causes the animal diseases associated with F. moniliforme. Hepato- and nephrotoxicities, disrupted sphingolipid metabolism, and liver cancer have been found in rats fed FB1. To determine the in vivo effects of diets containing fumonisins B2 (FB2) or B3 or (FB3), male rats were fed culture materials (CM) of FB1 non-producing F. moniliforme isolates to provide low (4.6-6.7 ppm), mid (32-49 ppm) or high (219-295 ppm) dietary levels of either FB2 (FB2CM) or FB3 (FB3CM). Other groups were fed culture material of an FB1 producing isolate (FB1CM) providing 6.9, 53 or 303 ppm total fumonisins (FB1: FB2: FB3 = 1.0: 0.38: 0.15) and a tenth group was fed a control diet having no detectable fumonisins. One-half (n = 5/group) the animals were killed after three weeks, at which time the toxicological and histopathological effects of the three culture materials were similar, mimicked the effects of FB1, and included decreased body weight gains, serum chemical indicators of hepatotoxicity, decreased kidney weights, and apoptosis of hepatocytes and kidney tubular epithelium. FB1CM, FB2CM, and FB3CM affected sphingolipids, causing increased sphinganine to sphingosine ratios (Sa/So) in both liver and kidneys. The remaining animals (n = 5/group0 were fed a control diet for three additional weeks. All body weight and tissue specific effects, including increased Sa/So, induced by the FB2Cm, FB3CM and low level FB1CM diets were absent following the recovery period. Except for mild biliary lesions found in the high dose of FB1CM group and a few apoptotic hepatocytes present in one mid- and two high-dose FB1CM rats, no evidence of toxicity remained in these groups, following the recovery period.

Effects of fumonisin B1 in pregnant rats. Part 2

The developmental toxicity of purified fumonisin B1 (FB1), a mycotoxin from the common corn fungus Fusarium moniliforme, was examined in Charles River rats. Pregnant rats were dosed orally on gestation days 3-16 at 0, 6.25, 12.5, 25 or 50 mg FB1/kg body weight/day. FB1 was not teratogenic at the doses tested. At 50 mg/kg, maternal toxicity (inappetence, emaciation, lethargy, death, resorption of entire litters) and foetal toxicity (increased number of late deaths, decreased foetal body weight, decreased crown rump length, increased incidence of hydrocephalus, increased incidence of skeletal anomalies) were seen. The foetal toxicity observed at 50 mg/kg may be related to maternal toxicity. Histopathological evaluation of tissues from dams of control and all treated groups revealed dose-related toxic changes in kidney and liver tissues. Acute toxic tubular nephrosis was seen in kidneys from all treated groups. Hepatocellular cytoplasmic alteration and individual cellular necrosis of the liver was seen in the two high-dose groups. Sphinganine (Sa) and sphingosine (So) were measured in day-17 adult and foetal tissues. Dose related increases in Sa/So ratios were seen in maternal liver, kidney, serum and brain, but there was no effect on foetal liver, kidney and brain. These data suggest that FB1 does not cross the placenta and further suggest that the observed foetal toxicity is a secondary response to maternal toxicity.

Toxicity and sphinganine levels are correlated in rats fed fumonisin B(1) (FB(1)) or hydrolyzed FB(1)

Nixtamalization of Fusarium moniliforme culture material reduced, but did not eliminate, its toxicity to rats. Liver and kidney sphinganine concentration and sphinganine to sphingosine ratio of the animals fed diets containing water extracted (8 ppm fumonisin B(1) (FB(1))), nixtamalized (58 ppm hydrolyzed FB(1)), or unprocessed culture material (71 ppm FB(1)) were increased compared to those fed a diet lacking detectable fumonisins. Increases were generally correlated with the severity of hepatic and renal lesions and were highly correlated (P<0.0001) with body weight effects and serum chemical indications of hepatotoxicity. The findings are further evidence that inhibition of the enzyme ceramide synthase may be a key event in fumonisin toxigenesis.

Demonstration of in-situ apoptosis in mouse liver and kidney after short-term repeated exposure to fumonisin B1

Fumonisin B1, a mycotoxin produced by Fusarium moniliforme, inhibits the activity of ceramide synthetase, the key enzyme in sphingolipid biosynthesis, leading to accumulation ofsphinganine and sphingosine. Ceramide and other sphingolipid pathways have been implicated in signal-induced apoptosis in cells. Groups of male BALB/c mice received subcutaneous injections (0, 0.25, 0.75, 2.25 or 6.25 mg/kg) of fumonisin B1 daily for 5 days and the liver and kidneys were sampled 1 day after the last injection. A decrease in kidney weight was observed after fumonisin treatment. A "blind" random evaluation of stained sections revealed dose-dependent fumonisin B1-associated hepatic and renal lesions in all groups. Terminal uridine triphosphate (UTP) nick-end labelling (TUNEL) in liver and kidney sections confirmed the presence of dose-related apoptotic cells at all treatment levels. Thus fumonisin B1 produced apoptosis after a brief exposure to relatively low doses. The toxicity of fumonisin B1 was greater than that previously found in studies on oral toxicity.

Disruption of sphingolipid metabolism and induction of equine leukoencephalomalacia by Fusarium proliferatum culture material containing fumonisin B(2) or B(3)

Fumonisin B(1), B(2), and B(3) are inhibitors of ceramide synthase, a key enzyme in the pathway for de novo sphingolipid biosynthesis. Corn, naturally contaminated with either predominantly fumonisin B(1) or pure fumonisin B(1), has been shown to cause equine leukoencephalomalacia (ELEM). It has been hypothesized that fumonisin-induced disruption of sphingolipid metabolism is an early event in the development of ELEM. Recently, it was shown that Fusarium proliferatum corn culture diets containing predominantly fumonisin B(2), but not diets which were predominantly fumonisin B(3), at 75 ppm (0.75 mg/kg BW/day) caused hepatotoxicity and ELEM. Analysis of free sphingoid bases and complex sphingolipids in serum, liver, and kidney, revealed that both the fumonisin B(2) and B(3) diets caused significant disruption of sphingolipid metabolism, however, the fumonisin B(2) culture material diet was significantly more effective than the fumonisin B(3) culture material diet at disrupting sphingolipid metabolism and in causing hepatotoxicity and clinical signs indicative of the onset of ELEM. A significant increase in the ratio of free sphinganine to free sphingosine in serum was first evident at day 4 and 11 with the fumonisin B(2) and B(3) diets, respectively. Increase in serum enzymes indicative of liver toxicity was first evident at day 34 in ponies fed the fumonisin B(2) diet and clinical signs (head shaking, gait problems, and muscle tremors) were first observed at day 48. Ponies fed the fumonisin B(3) diets showed no increase in serum enzymes or clinical signs for as long as 65 days when the study with fumonisin B(3) was stopped. The results support the conclusion fumonisin B(2) is more effective than fumonisin B(3) in disrupting sphingolipid metabolism and induction of ELEM and liver injury in ponies.

Evidence for disruption of sphingolipid metabolism as a contributing factor in the toxicity and carcinogenicity of fumonisins

Fumonisins are inhibitors of the biosynthesis of sphingosine and more complex sphingolipids. In eucaryotic cells, fumonisin inhibition of sphingolipid biosynthesis is a result of inhibition of the enzyme ceramide synthase. Large increase in free sphinganine concentration in plant and animal cells are observed within a few hours after exposure to fumonisins and/or Alternaria toxins (AAL-toxins). Some of the sphinganine is metabolized to other bioactive intermediates, and some is released from cells. In animals, free sphinganine accumulates in tissues and quickly appears in blood and urine. Free sphingoid bases are toxic to most cells, and complex sphingolipids are essential for normal cell growth. Fumonisin B1 stimulates sphinganine-dependent DNA synthesis in Swiss 3T3 cells, but is mitoinhibitory in other cell types. In cultured cells the accumulation of bioactive long-chain sphingoid bases and depletion of complex sphingolipids are clearly contributing factors in growth inhibition, increased cell death, and (in Swiss 3T3 cells) mitogenicity of fumonisins. While disruption of sphingolipid metabolism directly affects cells, it may indirectly affect some tissues. For example, fumonisin B1 impairs the barrier function of endothelial cells in vitro. Adverse effects on endothelial cells could indirectly contribute to the neurotoxicity and pulmonary edema caused by fumonisins. It is hypothesized that fumonisin-induced changes in the sphingolipid composition of target tissues could directly or indirectly contribute to all Fusarium moniliforme-associated diseases.

Fumonisin toxicity and metabolism studies at the USDA. Fumonisin toxicity and metabolism

Fumonisins are responsible for many of the toxic effects of the common corn fungus, Fusarium moniliforme. They are acute renal and liver toxins in rats, and have tumor promoting activity. Fumonisin B1 is poorly absorbed, rapidly excreted, and persists in small amounts in the liver and kidney. Fumonisins are specific inhibitors of ceramide synthase, and the toxic effects they produce may be related to their ability to disrupt sphingolipid metabolism, resulting in a myriad of problems in cell regulation and communication. In this paper, research that has been conducted on F. monilforme and the fumonisins at the USDA's Russell Research Center is reviewed.