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

A preliminary study on the pathology and molecular mechanism of fumonisin B1 nephrotoxicity in young quails

Fumonisin B1 (FB1) is a widely present mycotoxin that accumulates in biological systems and poses a health risk to animals. However, few studies have reported the molecular mechanism by which FB1 induces nephrotoxicity. The aim of this study was to assess the extent of nephrotoxicity during FB1 exposure and the possible molecular mechanisms behind it. Therefore, 180 young quails were equally divided into two groups. The control group was fed typical quail food, while the experimental group was fed quail food containing 30 mg·kg-1 FB1. Various parameters were assessed, which included histopathological, ultrastructural changes, levels of biochemical parameters, oxidative indicators, inflammatory factors, possible target organelles mitochondrial and endoplasmic reticulum (ER)-related factors, nuclear xenobiotic receptors (NXR) response, and cytochrome P450 system (CYP450s)-related factors in the kidneys on days 14, 28, and 42. The results showed that FB1 can induce oxidative stress through NXR response and disorder of the CYP450s system, leading to mitochondrial dysfunction and ER stress, promoting the expression of inflammatory factors (including IL-1β, IL-6, and IL-8) and causing kidney damage. This study elucidated the possible molecular mechanism by which FB1 induces nephrotoxicity in young quails.

Fumonisin B1 Induces Immunotoxicity and Apoptosis of Chicken Splenic Lymphocytes

Fumonisin B₁ (FB₁), produced by Fusarium, is among the most abundant and toxic mycotoxin contaminations in feed, causing damages to the health of livestock. However, the mechanisms of FB₁ toxicity in chickens are less understood. As splenic lymphocytes play important roles in the immune system, the aim of this study was to investigate the immunotoxic effects and mechanisms of FB₁ on chicken splenic lymphocytes. In the present study, the chicken primary splenic lymphocytes were harvested and treated with 0, 2.5, 5, 10, 20 and 40 μg/mL FB₁. Then, the cell proliferation, damage, ultrastructure, inflammation and apoptosis were evaluated. Results showed that the proliferation rate of splenic lymphocytes was decreased by FB₁ treatments. The activity of lactate dehydrogenase (LDH) was increased by FB₁ treatments in a dose-dependent manner, implying the induction of cell damage. Consistently, the ultrastructure of splenic lymphocytes showed that FB₁ at all the tested concentrations caused cell structure alterations, including nuclear vacuolation, mitochondrial swelling and mitochondrial crest fracture. Besides, immunosuppressive effects of FB₁ were observed by the decreased concentrations of interleukin-2 (IL-2), IL-4, IL-12 and interferon-γ (IFN-γ) in the cell culture supernatant. Furthermore, apoptosis was observed in FB₁-treated cells by flow cytometry. The mRNA expressions of apoptosis-related genes showed that the expression of Bcl-2 was decreased, while the expressions of the P53, Bax, Bak-1, and Caspase-3 were increased with FB₁ treatment. Similar results were found in the concentrations of apoptosis-related proteins in the cell supernatant by ELISA assay. Moreover, regression analysis indicated that increasing FB₁ concentration increased LDH activity, concentrations of Bax, Bak-1 and mRNA expression of Bak-1 linearly, increased M1 area percentage quadratically, decreased concentration of IFN-γ, mRNA expression of Bcl-2 linearly, and decreased concentrations of IL-2 and IL-4 quadratically. Besides, regression analysis also showed reciprocal relationships between IL-12 concentration, Caspase-3 mRNA expression and increasing FB₁ concentration. The increasing FB₁ concentration could decrease IL-12 concentration and increase Caspase-3 mRNA expression. Altogether, this study reported that FB₁ induced the immunotoxicity of chicken splenic lymphocytes and caused splenic lymphocytes apoptosis by the Bcl-2 family-mediated mitochondrial pathway of caspase activation.

Molecular and epigenetic modes of Fumonisin B1 mediated toxicity and carcinogenesis and detoxification strategies

Fumonisin B₁ (FB₁) is a natural contaminant of agricultural commodities that has displayed a myriad of toxicities in animals. Moreover, it is known to be a hepatorenal carcinogen in rodents and may be associated with oesophageal and hepatocellular carcinomas in humans. The most well elucidated mode of FB₁-mediated toxicity is its disruption of sphingolipid metabolism; however, enhanced oxidative stress, endoplasmic reticulum stress, autophagy, and alterations in immune response may also play a role in its toxicity and carcinogenicity. Alterations to the host epigenome may impact on the toxic and carcinogenic response to FB₁. Seeing that the contamination of FB₁ in food poses a considerable risk to human and animal health, a great deal of research has focused on new methods to prevent and attenuate FB₁-induced toxic consequences. The focus of the present review is on the molecular and epigenetic interactions of FB₁ as well as recent research involving FB₁ detoxification.

The low intestinal and hepatic toxicity of hydrolyzed fumonisin B₁ correlates with its inability to alter the metabolism of sphingolipids

Fumonisins are mycotoxins frequently found as natural contaminants in maize, where they are produced by the plant pathogen Fusarium verticillioides. They are toxic to animals and exert their effects through mechanisms involving disruption of sphingolipid metabolism. Fumonisin B₁ (FB₁) is the predominant fumonisin in this family. FB₁ is converted to its hydrolyzed analogs HFB₁, by alkaline cooking (nixtamalization) or through enzymatic degradation. The toxicity of HFB₁ is poorly documented especially at the intestinal level. The objectives of this study were to compare the toxicity of HFB₁ and FB₁ and to assess the ability of these toxins to disrupt sphingolipids biosynthesis. HFB₁ was obtained by a deesterification of FB₁ with a carboxylesterase. Piglets, animals highly sensitive to FB₁, were exposed by gavage for 2 weeks to 2.8 μmol FB₁ or HFB₁/kg body weight/day. FB₁ induced hepatotoxicity as indicated by the lesion score, the level of several biochemical analytes and the expression of inflammatory cytokines. Similarly, FB₁ impaired the morphology of the different segments of the small intestine, reduced villi height and modified intestinal cytokine expression. By contrast, HFB₁ did not trigger hepatotoxicity, did not impair intestinal morphology and slightly modified the intestinal immune response. This low toxicity of HFB₁ correlates with a weak alteration of the sphinganine/sphingosine ratio in the liver and in the plasma. Taken together, these data demonstrate that HFB₁ does not cause intestinal or hepatic toxicity in the sensitive pig model and only slightly disrupts sphingolipids metabolism. This finding suggests that conversion to HFB₁ could be a good strategy to reduce FB₁ exposure.

Chronic ingestion of deoxynivalenol and fumonisin, alone or in interaction, induces morphological and immunological changes in the intestine of piglets

Deoxynivalenol (DON) and fumonisins (FB) are mycotoxins produced by Fusarium species, which naturally co-occur in animal diets. The gastrointestinal tract represents the first barrier met by exogenous food/feed compounds. The purpose of the present study was to investigate the effects of DON and FB, alone and in combination, on some intestinal parameters, including morphology, histology, expression of cytokines and junction proteins. A total of twenty-four 5-week-old piglets were randomly assigned to four different groups, receiving separate diets for 5 weeks: a control diet; a diet contaminated with either DON (3 mg/kg) or FB (6 mg/kg); or both toxins. Chronic ingestion of these contaminated diets induced morphological and histological changes, as shown by the atrophy and fusion of villi, the decreased villi height and cell proliferation in the jejunum, and by the reduced number of goblet cells and lymphocytes. At the end of the experiment, the expression levels of several cytokines were measured by RT-PCR and some of them (TNF-α, IL-1β, IFN-γ, IL-6 and IL-10) were significantly up-regulated in the ileum or the jejunum. In addition, the ingestion of contaminated diets reduced the expression of the adherent junction protein E-cadherin and the tight junction protein occludin in the intestine. When animals were fed with a co-contaminated diet (DON+FB), several types of interactions were observed depending on the parameters and segments assessed: synergistic (immune cells); additive (cytokines and junction protein expression); less than additive (histological lesions and cytokine expression); antagonistic (immune cells and cytokine expression). Taken together, the present data provide strong evidence that chronic ingestion of low doses of mycotoxins alters the intestine, and thus may predispose animals to infections by enteric pathogens.

Differential cell sensitivity between OTA and LPS upon releasing TNF-α

The release of tumor necrosis factor α (TNF-α) by ochratoxin A (OTA) was studied in various macrophage and non-macrophage cell lines and compared with E. coli lipopolysaccharide (LPS) as a standard TNF-α release agent. Cells were exposed either to 0, 2.5 or 12.5 µmol/L OTA, or to 0.1 µg/mL LPS, for up to 24 h. OTA at 2.5 µmol/L and LPS at 0.1 µg/mL were not toxic to the tested cells as indicated by viability markers. TNF-α was detected in the incubated cell medium of rat Kupffer cells, peritoneal rat macrophages, and the mouse monocyte macrophage cell line J774A.1: TNF-α concentrations were 1,000 pg/mL, 1,560 pg/mL, and 650 pg/mL, respectively, for 2.5 µmol/L OTA exposure and 3,000 pg/mL, 2,600 pg/mL, and 2,115 pg/mL, respectively, for LPS exposure. Rat liver sinusoidal endothelial cells, rat hepatocytes, human HepG2 cells, and mouse L929 cells lacked any cytokine response to OTA, but showed a significant release of TNF-α after LPS exposure, with the exception of HepG2 cells. In non-responsive cell lines, OTA lacked both any activation of NF-κB or the translocation of activated NF-κB to the cell nucleus, i.e., in mouse L929 cells. In J774A.1 cells, OTA mediated TNF-α release via the pRaf/MEK 1/2-NF-κB and p38-NF-κB pathways, whereas LPS used pRaf/MEK 1/2–NF-κB, but not p38-NF-κB pathways. In contrast, in L929 cells, LPS used other pathways to activate NF-κB. Our data indicate that only macrophages and macrophage derived cells respond to OTA and are considered as sources for TNF-α release upon OTA exposure.

Some food-associated mycotoxins as potential risk factors in humans predisposed to chronic intestinal inflammatory diseases

Mycotoxins are fungal metabolites able to affect the functions of numerous tissues and organs in animals and humans, including intestinal and immune systems. However, the potential link between exposure to some mycotoxins and human chronic intestinal inflammatory diseases, such as celiac and Crohn's diseases or ulcerative colitis, has not been investigated. Instead, several theories based on bacterial, immunological or neurological events have been elaborated to explain the etiology of these pathologies. Here we reviewed the literature on mycotoxin-induced intestinal dysfunctions and compared these perturbations to the impairments of intestinal functions typically observed in human chronic intestinal inflammatory diseases. Converging evidence based on various cellular and animal studies show that several mycotoxins induce intestinal alterations that are similar to those observed at the onset and during the progression of inflammatory bowel diseases. Although epidemiologic evidence is still required, existing data are sufficient to suspect a role of some food-associated mycotoxins in the induction and/or persistence of human chronic intestinal inflammatory diseases in genetically predisposed patients.

Real and perceived risks for mycotoxin contamination in foods and feeds: challenges for food safety control

Mycotoxins are toxic compounds, produced by the secondary metabolism of toxigenic moulds in the Aspergillus, Alternaria, Claviceps, Fusarium, Penicillium and Stachybotrys genera occurring in food and feed commodities both pre- and post-harvest. Adverse human health effects from the consumption of mycotoxins have occurred for many centuries. When ingested, mycotoxins may cause a mycotoxicosis which can result in an acute or chronic disease episode. Chronic conditions have a much greater impact, numerically, on human health in general, and induce diverse and powerful toxic effects in test systems: some are carcinogenic, mutagenic, teratogenic, estrogenic, hemorrhagic, immunotoxic, nephrotoxic, hepatotoxic, dermotoxic and neurotoxic. Although mycotoxin contamination of agricultural products still occurs in the developed world, the application of modern agricultural practices and the presence of a legislatively regulated food processing and marketing system have greatly reduced mycotoxin exposure in these populations. However, in developing countries, where climatic and crop storage conditions are frequently conducive to fungal growth and mycotoxin production, much of the population relies on subsistence farming or on unregulated local markets. Therefore both producers and governmental control authorities are directing their efforts toward the implementation of a correct and reliable evaluation of the real status of contamination of a lot of food commodity and, consequently, of the impact of mycotoxins on human and animal health.

Impact of feed-borne mycotoxins on avian cell-mediated and humoral immune responses

Mycotoxins of economic importance in poultry production are mainly produced by Aspergillus, Penicillium and Fusarium fungi. The important mycotoxins in poultry production are aflatoxins, ochratoxins, trichothecenes, zearalenone and fumonisins. Mycotoxins exert their immunotoxic effects through various mechanisms which are manifested as reduced response of the immune system. Mycotoxin-induced immunosuppression in poultry may be manifested as decreased antibody production to antigens (e.g. sheep red blood cells) and impaired delayed hypersensitivity response (e.g. dinitrochlorobenzene), reduction in systemic bacterial clearance (e.g. Salmonella, Brucella, Listeria and Escherichia), lymphocyte proliferation (response to mitogens), macrophage phagocytotic ability, and alterations in CD4+/CD8+ ratio, immune organ weights (spleen, thymus and bursa of Fabricius), and histological changes (lymphocyte depletion, degeneration and necrosis). Mycotoxins, especially fumonisin B1 have been shown to down regulate proinflammatory cytokine levels including those of interferon (IFN)-γ, IFN-α, interleukin (IL)-1β, and IL-2 in broiler chickens. Fusarium mycotoxins exert part of their toxic effects by altering cytokine production in poultry. Mycotoxins adversely affect intestinal barrier functions by reducing the intestinal epithelial integrity and removing tight junction proteins. Apoptosis, increased colonisation of pathogenic microorganisms, cytotoxicity and oxidative stress, inhibition of protein synthesis and lipid peroxidation are characteristic of the toxic effects of mycotoxins on intestinal epithelium. These directly or indirectly affect host immune responses. Such immunotoxic effects of mycotoxins render poultry susceptible to many infectious diseases. The avian immune system is sensitive to most mycotoxins. Both cell-mediated and humoral immunity may be adversely affected after feeding mycotoxins to poultry. The avian immune system may be more sensitive to naturally contaminated feedstuffs because of the presence of multiple mycotoxins and the complex interactions between them which can cause severe adverse effects. Adverse effects of mycotoxins on the immune system reduce production and performance resulting in economic losses to poultry industries. Caution must be exercised while feeding grains contaminated with mycotoxins.

Inducible nitric oxide has protective effect on fumonisin B1 hepatotoxicity in mice via modulation of sphingosine kinase

Fumonisin B(1), a mycotoxin, is an inhibitor of ceramide synthase causing marked dysregulation of sphingolipid metabolism in cells. This mycotoxin causes accumulation of free sphingoid bases (sphingosine and dihydrosphingosine or sphinganine) and their metabolites, important messengers involved in signal transduction leading to either cell survival or death. Free sphingoid bases are known apoptotic molecules whereas sphingosine 1-phosphate is protective. We previously reported that fumonisin B(1) caused sphingosine kinase (SPHK) induction along with the increase of serine palmitoyltransferase (SPT). Fumonisin B(1) also increased inducible nitric oxide synthase (iNOS) expression. In the current study we employed a mouse strain with the targeted deletion of iNOS gene (Nos-KO) to evaluate the role of nitric oxide (NO) on fumonisin B(1)-induced hepatotoxicity. The Nos-KO mice exhibited increased hepatotoxicity after subacute fumonisin B(1) exposure compared to their wild type counterparts, the liver regeneration was lower in Nos-KO compared to that in the WT mice. Increased hepatotoxicity in Nos-KO was not related to the extent of free sphingoid base accumulation after fumonisin B(1) treatment; however, it was accompanied by a lack of fumonisin B(1)-induced SPHK induction. The fumonisin B(1)-induced SPT was unaffected by lack of iNOS gene. Deletion of iNOS gene did not prevent fumonisin B(1)-dependent induction of inflammatory cytokines, namely tumor necrosis factor alpha, interferon gamma and interleukin-12. The lack of fumonisin B(1)-induced SPHK induction in Nos-KO was supported by a similar effect on phosphorylated metabolites of sphingoid bases; the equilibrium between sphingoid bases and their phosphates is maintained by SPHK. We therefore conclude that iNOS induction produced by fumonisin B(1) modulates SPHK activity; the lack of iNOS prevents generation of sphingosine 1-phosphate and deprives cells from its protective effects.

Interactive effects of fumonisin B1 and α-zearalenol on proliferation and cytokine expression in Jurkat T cells

Mycotoxins are secondary metabolites of fungi that grow on various food and feed. These compounds elicit a wide spectrum of toxicological effects, including the capacity to alter normal immune function. Feed commodities are usually contaminated with more than one mycotoxin; however, extensive information on the interaction between concomitantly occurring mycotoxins and the consequence for their toxicity is lacking. In the present study, we examined the effects in vitro of fumonisin B1 (FB1) and alpha-zearalenol (alpha-ZEA), alone or in combination, on the immune function in the human lymphoblastoid Jurkat T cell line. Treatment of cells with increasing concentrations of FB1 resulted in a dose-dependent induction of proliferation. In contrast, alpha-ZEA showed a marked inhibitory effect on cell proliferation, even at very low doses, essentially mediated by apoptosis. In stimulated cells pre-incubated with FB1, the levels of IL-2 and IFN gamma mRNAs were similar to control whereas a reduction of cytokine transcripts was reported following alpha-ZEA treatment. Interestingly, co-administration of mycotoxins resulted in further inhibition of both proliferation and IFN gamma mRNA expression when compared with alpha-ZEA alone. In conclusion, FB1 and alpha-ZEA showed different immunomodulation abilities when individually administered. Combination of mycotoxins resulted instead in interactive effects.

Effect of fumonisins on macrophage immune functions and gene expression of cytokines in broilers

Fumonisin (FB1), a mycotoxin, is produced by Fusarium moniliforme and F. proliferatum. A prevalence survey in Taiwan by our laboratory showed that there was a contamination rate of 40% in domestic animal feeds, and the average contaminated level was 4.5 mg/kg. Ninety-six birds were allotted into four treatments fed with diets containing 0 (control), 5, 10, or 15 mg/kg of FB1 for three weeks. The results showed that the growth performance was not influenced by the FB1 challenge, but relative bursa weight was significantly decreased. The activity of serum aspartate aminotransferase, and the serum levels of albumin and cholesterol were significantly elevated by the FB1 challenges. When broilers were stimulated with injection of lipopolysaccharides, mRNA abundance (determined by semi-quantitative RT-PCR) interleukin-1beta (IL-1beta), IL-2, interferon-alpha (IFN-alpha), IFN-gamma, and inducible nitric oxide synthase (iNOS) reached a plateau at 3 h, and declined at 6 h. A FB1 challenge for three weeks increased cytokine mRNA abundance in broilers. The results also showed that 15 mg FB1 per kg feed significantly inhibited the expression of IL-1beta, IL-2, IFN-alpha, IFN-gamma, but had no effect on iNOS. The macrophage functional profile was significantly changed under an exposure of 15 mg FB1 per kg for three weeks. Taken together, our results suggest that FB1 up to 15 mg/kg does not affect growth performance, but impairs some parameters of blood biochemistry and the immunocompetence in broilers.

Sex-related differences in the immune response of weanling piglets exposed to low doses of fumonisin extract

Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium verticillioides, a fungus that commonly contaminates maize. Sex-related effects of FB1 have been observed with respect to carcinogenicity in rodents, to performances in pigs and immunosuppression in mice. In the present study the sex-related effect of FB1 on the pig immune response was determined. Female and castrated male piglets received for 28 d either control feed or feed contaminated with 8 mg FB1/kg feed in the form of F. verticillioides culture material. At day 7 and day 21, animals were immunised subcutaneously with a Mycoplasma agalactiae vaccine. Ingestion of FB1-contaminated feed significantly decreased weight gain in males but had no effect in females. No sex-related difference was observed in biochemical parameters, but a higher level of creatinine was noted in toxin-treated animals. FB1 also altered the pig immune response in a sex-specific manner. In males, ingestion of FB1-contaminated feed significantly decreased specific antibody levels after vaccination as well as the mRNA expression level of IL-10. In females, the toxin has no effect on specific antibodies or on cytokine mRNA levels. The results of the present study indicate that FB1 is immunosuppressive in pigs. The magnitude of this FB1-induced immunosuppression is highly dependent on sex, with males being more susceptible than females.

Amelioration of fumonisin B1 hepatotoxicity in mice by depletion of T cells with anti-Thy-1.2

Fumonisin B1 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 B1 perturbs sphingolipid metabolism by inhibiting ceramide synthase. Our previous studies in male mice indicated that fumonisin B1-induced hepatotoxicity is modulated by the localized activation of cytokines in liver macrophages and other cell types. In the current study, male athymic nude mice and their wild type counterparts (WT), the latter with or without depletion of T cells, were treated subcutaneously with fumonisin B1 at 2.25 mg/kg/day for 5 days and sampled 24 h after the last injection. Depletion of T cells in WT was achieved by a single intravenous injection of 50 microg monoclonal antibody against Thy-1.2 surface antigen of mature peripheral T lymphocytes 24 h before the first fumonisin B1 treatment. The depletion of T cells nearly abolished fumonisin B1-mediated liver toxicity as indicated by the near normal concentrations of circulating liver enzymes and by enumeration of apoptotic hepatocytes. There was no difference in the fumonisin B1-induced elevation in circulating liver enzymes between WT and nude mice. Fumonisin B1-induced mRNA expression of tumor necrosis factor alpha and interleukin-1alpha was observed in nude and WT mice but not in T cell-depleted mice. Hepatotoxic response to fumonisin B1 was unaltered in mice lacking natural killer cells. This study suggested that T cells and corresponding proinflammatory cytokines have a vital role in mediating fumonisin B1-induced hepatic toxicity.

Mice lacking both TNFα receptors show increased constitutive expression of IFNγ: A possible reason for lack of protection from fumonisin B1 hepatotoxicity☆

Fumonisin B1 is a mycotoxin prevalent in corn that produces species-, gender-, and organ-specific diseases. Mice lacking TNFalpha receptor (TNFR) 1 or 2 exhibited a diminished hepatotoxic response to fumonisin B1; however, the protection was lost when both TNFRs were deleted. We therefore investigated the constitutive expression of selected apoptotic factors and their response to fumonisin B1 in the liver from mice lacking both TNFRs (DRKO). Compared to their wild-type (WT) counterparts the DRKO strain had a higher constitutive mRNA expression of interferon (IFN)gamma, Fas, and interleukin (IL)-18. The mRNA expression of Bcl-2 was also higher in DRKO than in WT mice. The mRNA expression of IL-1 receptor antagonist (IL-1Ra) was decreased; that of TNF-related apoptosis-inducing ligand (TRAIL) was dramatically reduced. Induction of most apoptotic genes in response to fumonisin B1 was similar in both WT and DRKO strains; except in DRKO mice it was greater for Max and lesser for IL-1Ra than that in WT strain. Fumonisin B1 hepatotoxicity in DRKO mice was reduced by pretreatment with anti-IFNgamma antibody. It appears that in the absence of TNFalpha signaling other apoptotic pathways become operative; particularly the increase of IFNgamma, Fas and IL-18 may compensate for the loss of TNFalpha effects. Fumonisin B1 toxicity therefore appears to be a complex phenomenon that may utilize more than one cytotoxic pathway consequent to sphingoid deregulation; a higher expression of IFNgamma and other apoptotic factors in DRKO may be responsible for the observed fumonisin hepatotoxicity.

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.

Effect of sodium acetate on cell proliferation and induction of proinflammatory cytokines: a preliminary evaluation

We have studied the effect of sodium acetate exposure on the viability and proliferative activity of cultured human gastric adenocarcinoma epithelial (AGS) cells and changes in the release of proinflammatory cytokines. We evaluated the levels of IL-6, TNF-alpha, IL-8, and IL-1beta in cell culture supernatants using enzyme-linked immunosorbent assays, and cytokine mRNA levels were measured in whole cells using reverse transcriptase-polymerase chain reaction. We also measured cytokine levels in mice using immunohistochemistry. In vitro studies demonstrated that incubation with sodium acetate (up to 12.5 mM) for 72 h stimulated AGS cell viability and proliferation in a dose-dependent manner; however, incubation with >12.5 mM sodium acetate inhibited cell growth, also in a dose-dependent manner (the largest decrease in viability was >50%). Incubation with sodium acetate for 24 h increased the levels of IL-1beta, IL-8, and TNF-alpha protein and mRNAs (IL-6 was detected but its mRNA was not). The effect of sodium acetate on the expression of these cytokines in cell culture was verified in mice. Our data suggest that ingestion of high concentrations of sodium acetate in food has cytotoxic effects.

Fumonisin B1 Induces Necrotic Cell Death in BV-2 Cells and Murine Cultured Astrocytes and is Antiproliferative in BV-2 Cells While N2A Cells and Primary Cortical Neurons are Resistant

Fumonisin B1 (FB1), a mycotoxin produced by Fusarium verticillioides, causes equine leukoencephalomalacia, impairs myelination, and inhibits neuronal growth in vitro. Intact mice do not show brain damage after systemic administration of FB1. We recently reported that intracerebroventricular administration of FB1 in mice caused neurodegeneration in the cortex and activation of astrocytes in the hippocampal area; results suggested that the neuronal damage may be secondary to activation of immunocompetent non-neuronal cells. Current study investigated effects of FB1 upon murine microglial (BV-2) and neuroblastoma (N2A) cell lines, and primary astrocytes and cortical neurons. BV-2 and N2A cultures and cells prepared from neonatal and postnatal brains of BALB/c mice were exposed to various concentrations of FB1 for 4 (BV-2 and N2A) or 4 and 8 (astrocytes and cortical neurons) days. FB1 at 25 microM decreased viability in BV-2 cells, whereas at 50 microM caused necrotic but not apoptotic cell death in both BV-2 and primary astrocytes (at day 8 only), assessed by lactic dehydrogenase release, and pripidium iodide and annexin V staining. Thymidine incorporation indicated that 2.5 microM FB1 decreased proliferation in BV-2 cells. DNA analysis by flow cytometry showed that the inhibition was not caused by cell cycle arrest. The mitochondrial activity decreased dose-dependently in BV-2 cells and was significantly elevated at 25 microM FB1, but not at 50 microM at days 4 or 8 in astrocytes. In BV-2 cells and primary astrocytes, the expression of TNFalpha and IL-1beta analyzed by real-time polymerase chain reaction was downregulated at 6 or 24 h. In all cell types tested the FB1 treatment caused accumulation of free sphinganine and decrease in free sphingosine levels at selected time points. Results indicated that primary and established murine brain immunocompetent cells are vulnerable to the FB1-dependent cytotoxicity in vitro whereas neuronal cells are not. The toxic effects on the neuronal tissue may therefore be secondary to modulation of astrocyte or glial cell function.

Toxic Effects of Fumonisin in Mouse Liver Are Independent of the Peroxisome Proliferator-Activated Receptor α

Fumonisin mycotoxins occur worldwide in corn and corn-based foods. Fumonisin B1 (FB1) is a rodent liver carcinogen and suspected human carcinogen. It inhibits ceramide synthase and increases tissue sphinganine (Sa) and sphingosine (So) concentrations. Events linking disruption of sphingolipid metabolism and fumonisin toxicity are not fully understood; however, Sa and So were shown to bind mouse recombinant peroxisome proliferator-activated receptor alpha (PPARalpha) in vitro. To investigate the role of PPARalpha in fumonisin hepatotoxicity in vivo, wild-type (WT) and PPARalpha-null mice were fed control diets or diets containing 300 ppm FB1, Fusarium verticillioides culture material (CM) providing 300 ppm FB1, or 500 ppm of the peroxisome proliferator WY-14,643 (WY) for 1 week. WY-fed WT mice exhibited hepatomegaly, an effect not found in WY-fed PPARalpha-null mice, and WY did not change liver sphingoid base concentrations in either strain. Hepatotoxicity found in FB1- and CM-fed WT and PPARalpha-null mice was similar, qualitatively different from that found in WY-treated animals, and characterized by increased Sa concentration, apoptosis, and cell proliferation. Transcript profiling using oligonucleotide arrays showed that CM and FB1 elicited similar expression patterns of genes involved in cell proliferation, signal transduction, and glutathione metabolism that were different from that altered by WY. Real-time RT-PCR analysis of gene expression demonstrated PPARalpha-dependence of lipid metabolism gene expression in WY-treated mice, whereas PPARalpha-independent alterations of genes in lipid metabolism, and other categories, were found in CM- and FB1-fed mice. Together, these findings demonstrate that FB1- and CM-induced hepatotoxicity in mice does not require PPARalpha.

Endotoxin exposure alters brain and liver effects of fumonisin B1 in BALB/c mice: implication of blood brain barrier

Fumonisin B(1) (FB(1)), a mycotoxin produced by Fusarium verticillioides, causes equine leukoencephalomalacia and hepatotoxicity. We studied the modulation of FB(1) toxicity in brain and liver of female BALB/c mice after endotoxin administration to compromise the blood-brain barrier (BBB) integrity. Mice were injected intraperitoneally with saline or 3 mg/kg of lipopolysaccharide (LPS) followed 2 h later by either a single or three daily subcutaneous doses of 2.25 mg/kg of FB(1). After 4h of a single FB(1) injection the inhibition of sphingolipid biosynthesis occurred in liver. Circulating alanine aminotransferase increased by LPS alone at this time. In brain LPS triggered inflammation increasing the expression of tumor necrosis factor (TNF) alpha, interferon (IFN) gamma, interleukin (IL)-1beta, IL-6, and IL-12; no effect of FB(1) was observed. In liver LPS+FB(1) attenuated the expression TNFalpha and IFNgamma compared to LPS alone. One day after the 3-day FB(1) treatment the biosynthesis of sphingolipids was markedly reduced in brain and liver and it was further inhibited when LPS was given before FB(1). FB(1) induced hepatotoxicity, as measured by circulating liver enzymes, was reduced after the combined treatment with LPS+FB(1) compared to FB(1) alone. FB(1) decreased the LPS-induced brain expression of IFNgamma and IL-1beta, whereas the expression of IL-6 and IL-12 was augmented. In liver FB(1) also reduced the expression of IL-1beta and IFNgamma compared to LPS alone. Results indicated that endotoxemia concurrent with FB(1) intoxication facilitated the permeability of fumonisin in brain indicated by increased accumulation of sphinganine and endotoxin modified the effects of FB(1) in both brain and liver.

Oral exposure to culture material extract containing fumonisins predisposes swine to the development of pneumonitis caused by Pasteurella multocida

Fumonisin B(1) (FB(1)) is a mycotoxin produced by Fusarium verticillioides and F. proliferatum that commonly occurs in maize. In swine, consumption of contaminated feed induces liver damage and pulmonary edema. Pasteurella multocida is a secondary pathogen, which can generate a respiratory disorder in predisposed pigs. In this study, we examined the effect of oral exposure to fumonisin-containing culture material on lung inflammation caused by P. multocida. Piglets received by gavage a crude extract of fumonisin, 0.5mg FB(1)/kg body weight/day, for 7 days. One day later, the animals were instilled intratracheally with a non toxin producing type A strain of P. multocida and followed up for 13 additional days. Pig weight and cough frequency were measured throughout the experiment. Lung lesions, bronchoalveolar lavage fluid (BALF) cell composition and the expression of inflammatory cytokines were evaluated at the autopsy. Ingestion of fumonisin culture material or infection with P. multocida did not affect weight gain, induced no clinical sign or lung lesion, and only had minimal effect on BALF cell composition. Ingestion of mycotoxin extract increased the expression of IL-8, IL-18 and IFN-gamma mRNA compared with P. multocida infection that increased the expression of TNF-alpha. The combined treatment with fumonisin culture material and P. multocida delayed growth, induced cough, and increased BALF total cells, macrophages and lymphocytes. Lung lesions were significantly enhanced in these animals and consisted of subacute interstitial pneumonia. TNF-alpha, IFN-gamma and IL-18 mRNA expression was also increased. Taken together, our data showed that fumonisin culture material is a predisposing factor to lung inflammation. These results may have implications for humans and animals consuming FB(1) contaminated food or feed.

Comparative pathologic changes in broiler chicks on feed amendedwith Fusarium proliferatum culture material or purified fumonisinB1 and moniliformin*

Feed amended with autoclaved culture material (CM) of Fusarium proliferatum containing fumonisin B1 (FB1) (61-546 ppm), fumonisin B2 (FB2) (14-98 ppm) and moniliformin (66-367 ppm) was given to 228 male chicks in three separate feeding trials. In a fourth feeding trial, purified FB1 (125 and 274 ppm) and moniliformin (27 and 154 ppm) were given separately and in combination (137 and 77 ppm, respectively). Chicks that died during the trial periods, survivors and controls were subjected to postmortem examination. Specimens (liver, kidney, pancreas, lung, brain, intestine, testis, bursa of Fabricius, heart and skeletal muscle) were examined grossly and preserved for subsequent histopathologic and ultrastructural examination. Prominent gross lesions in affected birds fed diets amended with CM or purified FB1 and moniliformin included ascites, hydropericardium, hepatopathy, nephropathy, cardiomyopathy, pneumonitis, gizzard ulceration, and enlarged bursa of Fabricius filled with caseous material. The various concentrations of FB1 and moniliformin in the amended rations produced well-defined dose-response lesions in all groups in all four trials. Histopathologic changes included hemorrhage, leucocytic infiltration, fatty change or infiltration, individual cell necrosis and fibrosis in liver, kidneys, lungs, heart, intestines, gizzard, bursa of Fabricius and pancreas. Edema and hemorrhage were prominent in brains of treated birds. Ultrastructural changes included cytoplasmic and nuclear enlargement of cells in affected liver, lungs, kidneys, heart and pancreas. There were thickened membranes of the smooth endoplasmic reticulum, dilation of the rough endoplasmic reticulum with loss of ribosomes and vacuolated or deformed mitochondria.

Fumonisin B1-Induced Neurodegeneration in Mice after Intracerebroventricular Infusion is Concurrent with Disruption of Sphingolipid Metabolism and Activation of Proinflammatory Signaling

Fumonisin B1 (FB1), a mycotoxin produced by Fusarium verticillioides, causes equine leukoencephalomalacia, a condition not reproduced in any other species. We hypothesized that direct exposure of murine brain to FB1 will result in neurotoxicity, characterized by biochemical and pathological alterations. The present study compared the toxicity of FB1 in mouse brain after an intracerebroventricular (icv) or subcutaneous (sc) infusion. Female BALB/c mice (5/group) were infused (0.5 microl/h) with total doses of 0, 10 or 100 microg FB1 in saline over 7 days via osmotic pumps implanted either via icv cannulation of the ventricle or via the sc route. One day after the last day of treatment, brains were dissected either fresh or after intracardiac paraformaldehyde fixation. In mice given 100 microg of FB1 icv, FluoroJade B staining revealed neurodegeneration in the cortex, and anti-glial fibrillary acidic protein staining detected activated astrocytes in the hippocampus. High performance liquid chromatography indicated accumulation of free sphinganine in animals given FB1 icv in all brain regions and increased free sphingosine after the 100 microg FB1 in the cortex. The concentration of cortical sphingomyelin and complex sphingolipids remained unchanged. The icv administration of FB1 induced expression of tumor necrosis factor alpha, interleukin-1beta, interleukin-6 and interferon gamma after both doses, assayed by the real-time polymerase chain reaction. The sc administration of 100 microg FB1 caused slight sphinganine accumulation and increased IL-1beta expression in cortex only. Results indicated that icv injection of FB1 caused neurodegeneration with simultaneous inhibition of de novo ceramide synthesis, stimulation of astrocytes, and upregulation of pro-inflammatory cytokines in the murine brain. A relative lack of FB1 availability into the brain could be responsible for the absence of its neurotoxicity in mouse.

Fumonisin B1 hepatotoxicity in mice is attenuated by depletion of Kupffer cells by gadolinium chloride

Fumonisin B1 (FB1) is a toxic and carcinogenic mycotoxin produced by Fusarium verticillioides found on corn worldwide. The biological effects of FB1 are attributed to sphingolipid metabolism disruption as a result of ceramide synthase inhibition. Tumor necrosis factor alpha (TNFalpha) is an important modulator of FB1 hepatotoxicity. Kupffer cells are major source of cytokine production in liver. In the present study we investigated the effects of Kupffer cell depletion by gadolinium on FB1 hepatotoxicity in female BALB/c mice. Mice were given saline or 50 mg/kg of gadolinium chloride once via the tail vein; 16 h later they were treated with subcutaneous injections of vehicle or 2.25 mg/kg/day FB1 in saline for three successive days. Gadolinium significantly attenuated FB1-induced increases in the activities of circulating alanine aminotransferase and aspartate aminotransferase and reduced the FB1-induced hepatocyte apoptosis and free sphinganine accumulation in liver. Both gadolinium and FB1 treatments individually increased the expression of selected cell signal factors; e.g., TNFalpha, TNF receptor 1, TNF-related apoptosis-inducing ligand, lymphotoxin beta, interferon gamma, and transforming growth factor beta1; gadolinium chloride did not alter FB1-induced expression of the above genes. Results indicated that Kupffer cells play a role in FB1 hepatotoxicity. Decreased FB1-induced sphinganine accumulation and increased protective TNFalpha signaling by gadolinium chloride may in part account for its ameliorating effect on FB1 liver damage.

Augmented fumonisin B1 toxicity in co-cultures: evidence for crosstalk between macrophages and non-parenchymatous liver epithelial cells involving proinflammatory cytokines

Fumonisin B1, a common mycotoxin produced by Fusarium verticillioides found in corn, causes several fatal animal diseases. Liver and kidney are target organs of fumonisin B1 in laboratory animals, but primary rodent hepatocytes and liver slices were resistant to fumonisin B1-induced cytotoxic effects. We have shown that fumonisin B1 induces expression of tumor necrosis factor (TNF)alpha, interferon (IFN)gamma, and interleukine (IL) 12, in mouse liver. In various models of acute liver injury, a positive amplification loop involving TNFalpha, IFNgamma, and IL-12 has been implied that involves Kupffer cells (macrophages), hepatic lymphocytes and non-parenchymatous liver epithelial cells (NPECs). In the current study, cellular interactions in fumonisin B1-induced toxicity were investigated, using co-cultures of murine macrophages (J774A.1) and NPECs (NMuLi). Treatment of the co-cultures with fumonisin B1-produced cytotoxicity, whereas either J774A.1 or NMuLi cultures alone showed no response to the mycotoxin. Accumulation of sphinganine occurred to the similar extent in individual cultures as well as co-cultures. Expression of TNFalpha and IL-12 was increased in co-cultures but not in individual cultures. Transfer of conditioned medium from fumonisin B1-treated J774A.1 cells to NMuLi cultures produced an increase in IFNgamma expression in NMuLi cells. Results indicated that macrophages and liver epithelial cells interact in response to fumonisin B1 and potentiate the cytokines expression, which may have implications in making hepatocytes responsive to cytotoxicity of fumonisin B1.

Immunomodulation by Yersinia enterocolitica: comparison of live and heat-killed bacteria

This study compared the immunomodulating properties of viable and killed Yersinia enterocolitica O9 in BALB/c mice. At 10 days after infection by the intragastric route, ex vivo assays showed a suppression of spleen cell proliferation in response to Salmonella lipopolysaccharide, concanavalin A and heat-killed yersiniae. Mice infected with Y. enterocolitica O9 for 10 days resisted the challenge with a lethal dose of Listeria monocytogenes. In contrast, intravenous administration of heat-killed yersiniae did not modify the ability of spleen cells to proliferate in response to lipopolysaccharide or concanavalin A, and proliferation in response to killed yersiniae was significantly increased. By 3 days after administration of a single dose of heat-killed yersiniae, the resistance of mice to L. monocytogenes challenge was significantly increased. Our findings show profound differences in immunomodulation by viable and heat-killed yersiniae, but suggest that killed yersiniae retain interesting immunomodulating properties.

Increased expression of CD95-ligand and other apoptotic signaling factors by fumonisin B1, a hepatotoxic mycotoxin, in livers of mice lacking tumor necrosis factor α

Fumonisin B1 (FB1), a mycotoxin, is a potent inhibitor of ceramide synthase, and produces organ-, species-, and even gender-specific toxic responses in animals. The hepatotoxic response of FB1 in mice involves accumulation of free sphingoid bases and induction of inflammatory cytokines including tumor necrosis factor alpha (TNFalpha). The FB1-induced hepatotoxic responses were reduced in mice lacking TNFalpha receptor (TNFR) 1 or TNFR2. However, the hepatotoxicity was exacerbated in mice lacking TNFalpha. We therefore investigated the modulation of various other apoptotic signaling factors in TNFalpha-knockout (TKO) mice compared to wild-type (WT) strain after repeated daily subcutaneous injections of 2.25 mg/kg FB1 treatment for 5 days. Expression of various signaling genes in liver was evaluated by ribonuclease protection assay. Expression of CD95-ligand (FasL) was more than doubled in TKO animals after FB1 whereas it was unaltered in the WT group. FB1 did not alter CD95 expression in either strain; however, expressions of TRAIL, and downstream signaling factors FADD, TRADD, and caspase 8 were higher in FB1-treated TKO mice than in the corresponding WT animals. The TKO strain had a higher constitutive expression of apoptotic factors except CD95L. In addition to the CD95 and TNFalpha systems, the expression of apoptotic molecules bcl-2, b-myc, c-myc, bax, max, mad and IL1alpha was induced by FB1 in TKO mice to a greater extent than in WT animals; many of these factors also had a higher constitutive expression in TKO animals than WT mice. Results indicated that FB1 can induce CD95 modulated signaling when TNFalpha is absent. Differential constitutive expression of apoptotic genes in TKO mice may explain their increased sensitivity to FB1. These results are important in characterizing the modulating effect of TNFalpha on apoptotic signaling and in explaining the unexpected sensitivity of mice lacking this cytokine in response to hepatotoxic xenobiotics.

Deletion of IFN-gamma reduces fumonisin-induced hepatotoxicity in mice via alterations in inflammatory cytokines and apoptotic factors

Fumonisin B(1) (FB(1)) produces species-specific and organ-specific toxicity, including equine leukoencephalomalacia, porcine pulmonary edema, and hepatic or renal damage in other animals. FB(1) causes inhibition of ceramide synthase, leading to accumulation of free sphingoid bases. We previously reported that such cytokines as tumor necrosis factor-alpha (TNF-alpha) modify FB(1)-induced hepatic apoptosis in male mice. FB(1) also caused induction of interferon-gamma (IFN-gamma) in mouse liver, and, therefore, it was worthwhile to determine the role IFN-gamma plays in FB(1) toxicity. In the current study, male IFN-gamma-knockout (GKO) mice and their wild-type (WT) counterparts, C57BL/6J, were treated subcutaneously (s.c.) with 2.25 mg/kg/day of FB(1) for 5 days and sampled 1 day after the last injection. The levels of circulating liver enzymes were increased in WT animals but considerably less in GKO mice. Reduced hepatotoxicity in GKO mice was evident by histologic evaluation and enumeration of apoptotic cells. The induction of TNF-alpha and interleukin-12 (IL-12) p40 by FB(1) in liver was less in GKO mice compared with WT animals. The GKO mice also had a reduced accumulation of liver sphinganine than did WT mice after FB(1) treatment. Results suggested the implication of IFN-gamma in FB(1)-induced hepatotoxicity, which can be explained by a lack of TNF-alpha and IL-12 amplification in the liver of the GKO mice. In addition, the GKO mice had altered expression of various apoptotic and antiapoptotic factors in liver. These changes were accompanied by a greater number of proliferating cells in the liver of GKO mice after FB(1) treatment, which may also contribute to the reduced hepatotoxicity of FB(1) in GKO mice. Whereas the GKO mice show reduced sensitivity to FB(1) and FB(1) treatment elevates IFN-gamma expression, decreased hepatotoxicity to FB(1) could result from alterations in sphingolipid metabolism in the GKO strain.