An improved method for the purification of the trichothecene deoxynivalenol (vomitoxin) from Fusarium graminearum culture

Biological Activity of trans-2-Hexenal Against the Storage Insect Pest Tribolium castaneum (Coleoptera: Tenebrionidae) and Mycotoxigenic Storage Fungi

Grain commodities in postharvest storage often deteriorate because of fungal and insect attacks. With the green consumption requirements of consumers, ecofriendly and safe pesticides are needed for grain storage. The current study investigated the efficacy of the plant volatile compound trans-2-hexenal against the storage insect pest Tribolium castaneum (Herbst) and three commonly occurring storage fungi, viz., Fusarium graminearum, Aspergillus flavus, and Aspergillus niger, to recommend its application as a botanical fumigant for grain commodities. trans-2-Hexenal weakly repels T. castaneum but has favorable insecticidal activity against multiple developmental stages of T. castaneum, ranging in sensitivity as follows: eggs (LC50 = 14.3 µl/l) > adults (31.6 µl/l) > young larvae (42.1 µl/l) > mature larvae (64.5 µl/l) > pupae (70.5 µl/l). Moreover, trans-2-hexenal caused a high malformation rate and high mortality in adults developed from fumigated pupae. In a 7-d grain, trans-2-hexenal at 0.8 µl/ml provided an appreciable efficacy (81.3%), and concentrations ≥ 0.1 µl/ml completely inhibited the offspring of T. castaneum. trans-2-Hexenal was nonphytotoxic to the seed germination and seedling growth of wheat seeds. Furthermore, trans-2-hexenal completely inhibited the growth of A. flavus, F. graminearum, and A. niger at 5, 10, and 10 µl/l, respectively. The favorable biological activity of trans-2-hexenal against T. castaneum and three frequently occurring mycotoxigenic storage fungi indicated the potential of trans-2-hexenal for simultaneously controlling pests and pathogens, which could reduce its application frequency in grains and decrease pesticide resistance risks.

In Vitro Assessment of Biocontrol Effects on Fusarium Head Blight and Deoxynivalenol (DON) Accumulation by DON-Degrading Bacteria

Fusarium head blight (FHB) of cereals is a severe disease caused by the Fusarium graminearum species complex. It leads to the accumulation of the mycotoxin deoxynivalenol (DON) in grains and other plant tissues and causes substantial economic losses throughout the world. DON is one of the most troublesome mycotoxins because it is a virulence factor to host plants, including wheat, and exhibits toxicity to plants and animals. To control both FHB and DON accumulation, a biological control approach using DON-degrading bacteria (DDBs) is promising. Here, we performed a disease control assay using an in vitro petri dish test composed of germinated wheat seeds inoculated with F. graminearum (Fg) and DDBs. Determination of both grown leaf lengths and hyphal lesion lengths as a measure of disease severity showed that the inoculation of seeds with the DDBs Devosia sp. strain NKJ1 and Nocardioides spp. strains SS3 or SS4 were protective against the leaf growth inhibition caused by Fg. Furthermore, it was as effective against DON accumulation. The inoculation with strains SS3 or SS4 also reduced the inhibitory effect on leaves treated with 10 µg mL^-1 DON solution (without Fg). These results indicate that the DDBs partially suppress the disease by degrading DON.

Paper-Based Microfluidic Device (DON-Chip) for Rapid and Low-Cost Deoxynivalenol Quantification in Food, Feed, and Feed Ingredients

Mycotoxin contamination causes over $5 billion of economic loss per year in the North American food and feed industry. A rapid, low-cost, portable, and reliable method for on-site detection of deoxynivalenol (DON), a representative mycotoxin predominantly occurring in grains, would be helpful to control mycotoxin contamination. In this study, a paper-based microfluidic chip capable of measuring DON (DON-Chip) in food, feed, and feed ingredients was developed. The DON-Chip incorporated a colorimetric competitive immunoassay into a paper microfluidic device and used gold nanoparticles as a signal indicator. Furthermore, a novel ratiometric analysis method was proposed to improve detection resolvability. Detection of DON in the aqueous extracts from solid food, feed, or feed ingredients was successfully validated with a detection range of 0.01-20 ppm (using dilution factors from 10 to 10⁴). Compared with conventional methods, the DON-Chip method could greatly reduce the cost and time of mycotoxin detection in the food and feed industry.

Aerobic De-Epoxydation of Trichothecene Mycotoxins by a Soil Bacterial Consortium Isolated Using In Situ Soil Enrichment

Globally, the trichothecene mycotoxins deoxynivalenol (DON) and nivalenol (NIV) are among the most widely distributed mycotoxins that contaminate small grain cereals. In this study, a bacterial consortium, PGC-3, with de-epoxydation activity was isolated from soil by an in situ soil enrichment method. Screening of 14 soil samples that were sprayed with DON revealed that 4 samples were able to biotransform DON into de-epoxydized DON (dE-DON). Among these, the PGC-3 consortium showed the highest and most stable activity to biotransform DON into dE-DON and NIV into dE-NIV. PGC-3 exhibited de-epoxydation activity at a wide range of pH (5–10) and temperatures (20–37 °C) values under aerobic conditions. Sequential subculturing with a continued exposure to DON substantially reduced the microbial population diversity of this consortium. Analyses of the 16S rDNA sequences indicated that PGC-3 comprised 10 bacterial genera. Among these, one species, Desulfitobacterium, showed a steady increase in relative abundance, from 0.03% to 1.55% (a 52-fold increase), as higher concentrations of DON were used in the subculture media, from 0 to 500 μg/mL. This study establishes the foundation to further develop bioactive agents that can detoxify trichothecene mycotoxins in cereals and enables for the characterization of detoxifying genes and their regulation.

Histopathological Effects of Dietary Fusarium Graminearum on Rat Duodenum

Microscopic pathology of duodenum in rats exposed to Fusarium graminearum, a fungus infecting small-grain cereals, was investigated. Intestinal haemorrhage was observed macroscopically in one of the rats. Light microscopy demonstrated detachments between the surface epithelium and the lamina propria and severe interstitial oedema in the lamina propria in the test group. Electron microscopy identified epithelial absorptive cells with highly expanded endoplasmic reticulum tubules, abundant cytoplasmic vesicles containing electron-lucent materials, swollen mitochondria with spongiform appearance, and prominent cellular swelling. Other observations included opening of junctional complexes between epithelial cells lining the duodenum, highly enlarged intercellular spaces in duodenal epithelium, and numerous eosinophilic granulocytes and mast cells in the lamina propria. These findings indicate that dietary F. graminearum causes epithelial cell and connective tissue damage in rat duodenum. This is the first histopathological study showing that F. graminearum ingestion is associated with duodenal damage.

An epimer of deoxynivalenol: purification and structure identification of 3-epi-deoxynivalenol

In an investigation of deoxynivalenol (DON)-transformation products by Devosia mutans 17-2-E-8, the major product was identified as 3-epi-DON. This DON-transformation product was analysed by liquid chromatography and identified by congruent retention time and UV/Vis spectrum, as well as mass spectrometric data. Nuclear magnetic resonance (NMR) experiments including correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC) and nuclear overhauser effect (NOE) were conducted for structural characterisation of 3-epi-DON. High-speed counter-current chromatography (HSCCC) was applied to scale up the separation of 3-epi-DON from DON in a D. mutans 17-2-E-8 culture. From the culture where 100 mg DON was applied, 56 mg of 3-epi-DON (purity of 96.8%) was obtained from the HSCCC. The purified 3-epi-DON will be used for toxicological characterisation studies of this chemical.

Deoxynivalenol-induced weight loss in the diet-induced obese mouse is reversible and PKR-independent

The trichothecene deoxynivalenol (DON), a potent ribotoxic mycotoxin produced by the cereal blight fungus Fusarium graminearum, commonly contaminates grain-based foods. Oral exposure to DON causes decreased food intake, reduced weight gain and body weight loss in experimental animals - effects that have been linked to dysregulation of hormones responsible for mediating satiety at the central nervous system level. When diet-induced obese (DIO) mice are fed DON, they consume less food, eventually achieving body weights of control diet-fed mice. Here, we extended these findings by characterizing: (1) reversibility of DON-induced body weight loss and anorexia in DIO mice and (2) the role of double-stranded RNA-activated protein kinase (PKR) which has been previously linked to initiation of the ribotoxic stress response. The results demonstrated that DON-induced weight loss was reversible in DIO mice and this effect corresponded to initiation of a robust hyperphagic response. When DIO mice deficient in PKR were exposed to DON, they exhibited weight suppression similar to DIO wild-type fed the toxin, suggesting the toxin's weight effects were not dependent on PKR. Taken together, DON's effects on food consumption and body weight are not permanent and, furthermore, PKR is not an essential signaling molecule for DON's anorectic and weight effects.

Thirteen novel deoxynivalenol-degrading bacteria are classified within two genera with distinct degradation mechanisms

The mycotoxin deoxynivalenol (DON), a secondary metabolite produced by species of the plant pathogen Fusarium, causes serious problems in cereal crop production because of its toxicity towards humans and livestock. A biological approach for the degradation of DON using a DON-degrading bacterium (DDB) appears to be promising, although information about DDBs is limited. We isolated 13 aerobic DDBs from a variety of environmental samples, including field soils and wheat leaves. Of these 13 strains, nine belonged to the Gram-positive genus Nocardioides and other four to the Gram-negative genus Devosia. The degradation phenotypes of the two Gram types were clearly different; all washed cells of the 13 strains degraded 100 μg mL(-1) DON to below the detection limit (0.5 μg mL(-1)), but the conditions inducing the DON-degrading activities differed between the two Gram types. The HPLC profiles of the DON metabolites were also distinct between the two genera, although all strains produced 3-epi-deoxynivalenol. The Gram-positive strains showed DON assimilation in media containing DON as a carbon source, whereas the Gram-negatives did not. Our results suggest that aerobic DDBs are distributed within at least two phylogenetically restricted genera, suggesting independent evolution of the DON-degradation mechanisms.

Efficacy of a mycotoxin binder against dietary fumonisin, deoxynivalenol, and zearalenone in rats

It was hypothesized that a mycotoxin binder, Grainsure E, would inhibit adverse effects of a mixture of fumonisin B1, deoxynivalenol, and zearalenone in rats. For 14 and 28 days, 8-10 Sprague-Dawley rats were fed control diet, Grainsure E (0.5%), toxins (7 μg fumonisin B1/g, 8 μg of deoxynivalenol/g and 0.2 μg of zearalenone/g), toxins (12 μg of fumonisin B1/g, 9 μg of deoxynivalenol/g, and 0.2 μg of zearalenone/g + Grainsure E), or pair-fed to control for food intake of toxin-fed rats. After 28 days, decreased body weight gain was prevented by Grainsure E in toxin-fed female rats, indicating partial protection against deoxynivalenol and fumonisin B1. Two effects of fumonisin B1 were partly prevented by Grainsure E in toxin-fed rats, increased plasma alanine transaminase (ALT) and urinary sphinganine/sphingosine, but sphinganine/sphingosine increase was not prevented in females at the latter time point. Grainsure E prevented some effects of fumonisin B1 and deoxynivalenol in rats.

Effects of deoxynivalenol consumption on body weight and adiposity in the diet-induced obese mouse

The potential for the obese state to alter sensitivity to toxic chemicals is poorly understood. In this study, dose-response effects of the trichothecene deoxynivalenol (DON), a common food-borne mycotoxin, were determined on body weight of diet-induced obese mice. In study 1, the effects of feeding adult female B6C3F1 mice a high-fat diet (HFD; 60% kcal from fat) containing 0, 2, 5, or 10 ppm DON for 10 wk on body weight and adiposity were compared. Mice consuming 5 or 10 ppm DON exhibited a 15 and 24% decrease in weight gain and a 50 and 83% reduction in periuterine fat, respectively. In study 2, mice were fed HFD for 8 wk to induce obesity and the effects of consuming HFD + 0, 2, 5, or 10 ppm DON for 8 wk were then determined. Mice fed 5 or 10 ppm DON exhibited a 16 and 23% weight reduction and a 0 and 40% periuterine fat reduction, respectively. In a follow-up experiment, food consumption was measured prior to and after the transition from HFD to HFD + 10 ppm DON. Exposure to DON was found to lower HFD consumption within 1 d, with significant weight loss in DON-fed mice evident after 6 d. In both studies 1 and 2, consumption of 5 or 10 ppm DON diminished circulating levels of insulin-like growth factor acid-labile subunit. Taken together, DON consumption lowered weight gain and produced weight loss in diet-induced obese mice at higher thresholds than that observed previously in normal B6C3F1 mice.

Suppression of insulin-like growth factor acid-labile subunit expression--a novel mechanism for deoxynivalenol-induced growth retardation

Consumption of deoxynivalenol (DON), a trichothecene mycotoxin commonly detected in cereal-based foods, causes impaired growth in many animal species. While growth retardation is used as a basis for regulating DON levels in human food, the underlying mechanisms remain poorly understood. Oral exposure of mice to DON rapidly induces multiorgan expression of proinflammatory cytokines, and this is followed by upregulation of several suppressors of cytokine signaling (SOCS), some of which are capable of impairing growth hormone (GH) signaling. The purpose of this study was to test the hypothesis that impairment of the GH axis precedes DON-induced growth retardation in the mouse. Subchronic dietary exposure of young (4-week old) mice to DON (20 ppm) over a period of 2-8 weeks was found to (1) impair weight gain, (2) result in a steady-state plasma DON concentration (40-60 ng/ml), (3) downregulate hepatic insulin-like growth factor acid-labile subunit (IGFALS) mRNA expression, and (4) reduce circulating insulin-like growth factor 1 (IGF1) and IGFALS levels. Acute oral exposure to DON at 0.5-12.5 mg/kg body weight (bw) markedly suppressed hepatic IGFALS mRNA levels within 2 h in a dose-dependent fashion, whereas 0.1 mg/kg bw was without effect. DON-induced IGFALS mRNA upregulation occurred both with and without exogenous GH treatment. These latter effects co-occurred with robust hepatic suppressors of cytokine signaling 3 upregulation. Taken together, these data suggest that oral DON exposure perturbs GH axis by suppressing two clinically relevant growth-related proteins, IGFALS and IGF1. Both have potential to serve as biomarkers of effect in populations exposed to this common foodborne mycotoxin.

Natural product isolation

Since the 1990s, interest in natural product research has increased considerably. Following several outstanding developments in the areas of separation methods, spectroscopic techniques, and sensitive bioassays, natural product research has gained new attention for providing novel chemical entities. This updated review deals with sample preparation and purification, recent extraction techniques used for natural product separation, liquid-solid and liquid-liquid isolation techniques, as well as multi-step chromatographic operations. It covers examples of papers published since the NPR review 'Modern separation methods' by Marston and Hostettmann,1 with major emphasis on methods developed and the research undertaken since 2000.

Immunochemical assessment of deoxynivalenol tissue distribution following oral exposure in the mouse

Deoxynivalenol (DON or vomitoxin) is a trichothecene mycotoxin commonly found in cereal grains that adversely affects growth and immune function in experimental animals. A competitive enzyme-linked immunosorbent assay (ELISA) was used to monitor the kinetics of distribution and clearance of DON in tissues of young adult B6C3F1 male mice that were orally administered 25mg/kg bw of the toxin. DON was detectable from 5 min to 24h in plasma, liver, spleen and brain and from 5 min to 8h in heart and kidney. The highest DON plasma concentrations were observed within 5-15 min (12 microg/mL) after dosing. There was rapid clearance following two-compartment kinetics (t(1/2)alpha=20.4 min, t 1/2 beta=11.8h) with 5% and 2% maximum plasma DON concentrations remaining after 8 and 24h, respectively. DON distribution and clearance kinetics in other tissues were similar to that of plasma. At 5 min, DON concentrations in mug/g were 19.5+/-1.9 in liver, 7.6+/-0.5 in kidney, 7.3+/-0.8 in spleen, 6.8+/-0.9 in heart and 0.8+/-0.1 in the brain. DON recoveries in tissues by ELISA were comparable to a previous study that employed (3)H-DON and 25mg/kg bw DON dose. The ELISA was further applicable to the detection of DON in plasma of mice exposed to the toxin via diet. This approach provides a simple strategy that can be used to answer relevant questions in rodents of how dose, species, age, gender, genetic background and route/duration of exposure impact DON uptake and clearance.

Purification of deoxynivalenol from Fusarium graminearum rice culture and mouldy corn by high-speed counter-current chromatography

Deoxynivalenol (DON) is a mycotoxin produced by several Fusarium species and is toxic to a wide range of organisms, including human beings and livestock. To produce large amounts of pure DON for research purposes, a novel method using high-speed counter-current chromatography (HSCCC) was developed. Rice cultured with Fusarium graminearum and field mouldy corn infected by F. graminearum were extracted with methanol and found to contain 1.16 and 1.30 mg DON/g, respectively. The extracts were concentrated and then separated using a biphasic solvent system consisting of ethyl acetate-water (1:1, v/v). Collected fractions were analyzed by high-performance liquid chromatography (HPLC) and identified by congruent retention time and UV/vis spectrum and mass spectrometric data. Fractions containing DON were combined and freeze-dried. This method produced 116 mg and 65 mg DON with a purity of greater than 94.9% from 200 g of the rice culture and the mouldy corn, respectively. The HSCCC method had a recovery rate of DON at 88% from the crude extracts of both samples. This one-step purification method provided a simple and effective tool for obtaining a large amount of DON, an essential material for studies related to toxicology and detoxification of this mycotoxin.

Toxic Alterations in Chick Embryonic Liver and Spleen by Acute Exposure to Fusarium-Producing Mycotoxin Deoxynivalenol

Food mycotoxin deoxynivalenol (vomitoxin, DON) produced by Fusarium graminearum and F. culmorum can induce rapid diminution of lymphoid tissues and lymphopenia in the growing chickens and mammals. We first investigated the direct acute effects of DON on the chick immune-related embryo tissues such as embryonic liver and spleen. Direct DON administration into the embryonic eggs caused toxin accumulation in liver in a time-dependent manner. Electron microscopic observation showed a notable accumulation of fat droplet in the liver tissue and the re-exposed hatched chicken showed more distinguishing enlarged fat globules, so-called fatty cysts like human steatosis. Regarding effects of deoxynivalenol on the chick embryonic spleen, fatty change was also observed in splenocytes. Functionally, mitogen-stimulated cellular and humoral lympho-proliferations were suppressed in the DON-treated embryo. Conclusively, acute direct exposure to deoxynivalenol in the chick embryo caused toxic histological alterations in the liver and spleen and suppressed in vitro lymphoblastogenesis.

LPS priming potentiates and prolongs proinflammatory cytokine response to the trichothecene deoxynivalenol in the mouse

Simultaneous exposure to lipopolysaccharide (LPS) markedly amplifies induction of proinflammatory cytokine expression as well as IL-1-driven lymphocyte apoptosis by trichothecene deoxynivalenol (DON) in the mouse. The purpose of this research was to test the hypothesis that LPS priming will sensitize a host to DON-induced proinflammatory cytokine induction and apoptosis. In mice primed with LPS (1 mg/kg bw) ip. and treated 8 h later with DON po., the minimum DON doses for inducing IL-1alpha, IL-1beta, IL-6 and TNF-alpha serum proteins and splenic mRNAs were significantly lower than the DON doses required for vehicle-primed mice. LPS priming also decreased onset time and dramatically increased magnitude and duration of cytokine responses. LPS-primed mice maintained heightened sensitivity to DON for up to 24 h. LPS priming doses as low as 50 microg/kg bw evoked sensitization. DNA fragmentation analysis and flow cytometry also revealed that mice primed with LPS (1 mg/kg) for 8 h and exposed to DON (12.5 mg/kg) exhibited massive thymocyte loss by apoptosis 12 h later compared to mice exposed to DON or LPS alone. LPS priming decreased DON-induced p38 and ERK 1/2 phosphorylation suggesting that enhanced mitogen-activated protein kinase activation was not involved in increased cytokine responses. Taken together, exposure to LPS rendered mice highly susceptible to DON induction of cytokine expression and this correlated with increased apoptosis in the thymus.

Truncated deoxynivalenol-induced splenic immediate early gene response in mice consuming (n-3) polyunsaturated fatty acids

Expression profiling has previously revealed that acute exposure to the common foodborne mycotoxin deoxynivalenol (DON) induces a large number of immediate early genes in murine lymphoid tissues that potentially affect immune function. The purpose of this study was to test the hypothesis that consumption of (n-3) polyunsaturated fatty acids (PUFAs) found in fish oil interferes with DON-induced immediate early gene expression. Mice were fed AIN-93G diet containing 1% corn oil (CO) plus 6% oleic acid (control) or a diet containing 1% CO, 2% fish oil enriched in the (n-3)-PUFAs docosahexaenoic and eicosapentaenoic acid and 4% oleic acid. After 12 weeks, the mice were gavaged orally with 25 mg/kg DON and the kinetics of immediate early gene expression in spleen monitored over 8 h by real-time polymerase chain reaction (PCR). Deoxynivalenol was found to readily induce expression of cytokines (IL-1alpha, IL-1beta, and IL-6 and IL-11), chemokines (MCP-1, MCP-3, CINC-1 and MIP-2), components of the activator protein-1 (AP-1) transcription factor complex (c-Fos, Fra-2, c-Jun and JunB), as well as two hydrolases (MKP1, CnAbeta). Expression of these genes was transient, peaking within 2-4 h and declining thereafter, with the single exception being IL-11 that was elevated at 8 h. (n-3)-PUFA consumption significantly suppressed DON-induced expression of IL-1alpha, IL-6, IL-11, MCP-1, MCP-3, MIP-2 and Fra-2 at 8 h. In contrast, mice fed (n-3)-PUFA exhibited significant increases in MKP1 and CnAbeta expression. Taken together, these data suggest that dietary supplementation with (n-3)-PUFAs prematurely truncated cytokine, chemokine and transcription factor expression responses to DON that may impact its previously described capacity to disrupt immune function including immunoglobulin A (IgA) production. Since expression of many of these genes has been linked to mitogen-activated protein kinase (MAPK) activation, enhanced expression of MKP1, a negative MAPK regulator in (n-3)-PUFA-fed mice might contribute to this suppression.

Modulation of Murine Host Response to Enteric Reovirus Infection by the Trichothecene Deoxynivalenol

Based on the known capacity of deoxynivalenol (DON) to target gut lymphoid tissue and IgA production, it was hypothesized that this mycotoxin interferes with the immune response to enteric reovirus infection. When mice were orally gavaged, first with 25 mg/kg bw DON, and then with reovirus serotype 1, strain Lang (T1/L) 2 or 12 h later, viral titers in the GI tract were 10-fold higher than control mice after 5 days. Virus was almost completely cleared in both treatment and control groups from intestinal tissue after 10 days. Real-time PCR indicated that, in infected control mice, reovirus lambda2 core spike (L2 gene) RNA per g feces in infected mice that were pretreated with DON was significantly higher at 1, 3, and 5 days than in infected mice only. In reovirus-infected mice, DON at doses of 10 and 25 mg/kg bw but not 2 and 5 mg/kg bw increased fecal L2 RNA, whereas DON doses as low as 2 mg/kg potentiated L2 RNA levels in Peyer's patches (PP). Reovirus-specific IgA levels in feces of mice treated with DON were significantly elevated, as were specific IgA responses in lamina propria and PP fragment cultures. Similar effects were observed for serum IgA and IgG. DON suppressed IFN-gamma responses in PP to reovirus at 3 and 5 days as compared to infected controls, while IL-2 mRNA concentrations were unaffected. Although reovirus alone did not induce Th2 cytokine mRNAs in PP, DON exposure significantly elevated IL-4, IL-6, and IL-10 mRNA expression at various times during the infection. ELISPOT revealed that mRNA expression data corresponded to suppression of IFN-gamma- and enhancement of IL-4-producing cell responses in PP cultures from DON-treated mice. Taken together, these data suggest that DON transiently increased both severity of the reovirus infection and shedding in feces as well as elevated reovirus IgA responses. These effects corresponded to suppressed Th1 and enhanced Th2 cytokine expression.

Threat assessment of mycotoxins as weapons: molecular mechanisms of acute toxicity

Mycotoxins are impractical as tactical weapons, butthey can be used by small poor terrorist organizations to poison food and water sources or can be released in crowded, confined areas. Crude concentrated or dried extracts of readily grown fungal cultures can be used as weapons. The production of fungal weapons does not require elaborate facilities for the growth of fungi, sophisticated equipment for the purification of the toxins, or highly trained personnel. Aflatoxin B1, fumonisin B1, ochratoxin A, and the trichothecenes T-2 toxin and deoxynivalenol could be weaponized for bioterrorism. Knowledge of the symptoms of intoxication and the biochemical mechanisms of action of mycotoxins is necessary for the rapid identification of the toxins, the development of prophylactic antidotes, and the design of effective treatments of affected persons. All of these mycotoxins except deoxynivalenol are carcinogens (Stark, A. A., Annu. Rev. Microbiol. 34:235-262, 1980; Stark, A. A., p. 435-445, in P. S. Steyn and R. Vleggaar, ed., Mycotoxins and phycotoxins, 1986; Stark, A. A., p. 47-60, in C. L. Wilson and S. Droby, ed., Microbial food contamination, 2000; Stark, A. A., and N. Paster, p. 60-64, in M. L. Wahlqvist, A. S. Truswell, R. Smith, and P. L. Nestel, ed., Nutrition in a sustainable environment, 1994). Because immediate and widespread death, illness, or panic is the goal of bioterrorists, the mechanisms by which mycotoxins exert acute toxicity are the focus of this article.

Role of cyclooxygenase-2 in deoxynivalenol-induced immunoglobulin a nephropathy

Ingestion of the trichothecene mycotoxin deoxynivalenol (DON) induces serum IgA elevation and kidney mesangial IgA deposition in a manner that mimics the early stages of IgA nephropathy (IgAN), the most common human glomerulonephritis. Previous studies indicate that elevated interleukin-6 (IL-6) expression is crucial for this model and that DON induction of cyclooxygenase-2 (COX-2) might drive IL-6 upregulation. We hypothesized that COX-2 and its metabolites are essential for DON-induced IgAN and thus might be a suitable target for prophylaxis against aberrant IgA upregulation. DON feeding studies using COX-2 knockout mice or the COX-2 specific inhibitor, rofecoxib (Vioxx), were employed to test the hypothesis. Study 1 results demonstrated that DON consumption induced serum IgA and IgA-immune complex (IC) accumulation, IgA kidney deposition and splenic IgA secretion in wild-type mice. COX-2 deficiency did not affect upregulation of these parameters but rather, promoted DON-induced serum IgA elevation. Study 2 demonstrated that rofecoxib could not block DON-induced serum IgA, serum IgA-IC and mesangial IgA accumulation but instead increased enhanced serum IgA upregulation. These corroborating results suggest that COX-2 is not a requisite for DON-induced IgAN and furthermore, that COX-2 inhibitors such as rofecoxib would be contraindicated for the prevention of early stages of IgAN.

Docosahexaenoic acid attenuates mycotoxin-induced immunoglobulin a nephropathy, interleukin-6 transcription, and mitogen-activated protein kinase phosphorylation in mice

The purpose of this investigation was to evaluate the dose-dependent effects of docosahexaenoic acid (DHA) on deoxynivalenol (DON)-induced IgA nephropathy in mice and their relation to proinflammatory gene expression and mitogen-activated protein kinase (MAPK) activation. Consumption of a modified AIN-93G diet containing 1, 5, and 30 g/kg DHA resulted in dose-dependent increases of DHA in liver phospholipids with concomitant decreases in arachidonic acid compared with control diets. DHA dose dependently inhibited increases in serum IgA and IgA immune complexes (IC) as well as IgA deposition in the kidney in DON-fed mice; the 30 g/kg DHA diet had the earliest detectable effects and maximal efficacy. Both splenic interleukin-6 (IL-6) mRNA and heterogeneous nuclear RNA (hnRNA), an indicator of IL-6 transcription, were significantly reduced in DON-fed mice that consumed 5 and 30 g/kg DHA; a similar reduction was observed for cyclooxygenase (COX-2) mRNA. In a subsequent study, acute DON exposure (25 mg/kg body weight) induced splenic IL-6 mRNA and hnRNA as well as COX-2 mRNA in mice fed the control diet, whereas induction of both RNA species was significantly inhibited in mice fed 30 g/kg DHA. These latter inhibitory effects corresponded to a reduction in DON-induced phosphorylation of p38, extracellular-signal related kinase 1/2, and c-Jun N-terminal kinase 1/2 MAPKs in the spleen. Taken together, the results indicate that DHA dose-dependently inhibited DON-induced IgA dysregulation and nephropathy, and that impairment of MAPK activation and expression of COX-2 and IL-6 are potential critical upstream mechanisms.

Kidney damage by dietary Fusarium graminearum in rats: a microscopic study

Fusarium graminearum is a fungus frequently isolated from cereal grants. In this study, the histopathological effects of dietary F. graminearum on rat kidneys were examined. Treated rats and controls were fed F. graminearum-inoculated and non-inoculated rice, respectively. After 14 days, all the rats were killed and their kidneys were removed and examined using light microscopy. The kidneys of the rats in the treatment group were characterized by the following histopathological findings: patch-like mononuclear cell infiltrations in the cortex; prominent necrosis of proximal tubules; debris areas containing mononuclear cells and degraded renal tubules; shrunken and densely eosinophilic apoptotic cells in the proximal tubule epithelium; karyorrhexis and mitotic figures in the epithelium of both proximal and distal tubules; and many apoptotic bodies in the areas between the renal tubules. It was concluded that dietary F. graminearum caused inflammation and tubular damage in the rat kidney. This is the first microscopic study showing that F. graminearum ingestion is associated with renal damage.

Microscopic pathology of the liver in rats fed a Fusarium graminearum-inoculated diet

Fusarium graminearum is a fungus frequently isolated from cereal grains. This study investigates the histopathological effects of dietary F. graminearum on rat liver. Treatment and control group rats were fed F. graminearum-inoculated and non-inoculated rice, respectively. After 14 days, all rats were sacrificed, and their livers analysed by electron and light microscopy. Electron microscopy of treatment group livers identified hepatocytes with well-developed smooth endoplasmic reticulum, swollen mitochondria, lipid accumulation, numerous vesicles containing electron-lucent materials and increased lysosomes. Many Kupffer's cells containing apoptotic bodies were also seen. Light microscopy identified hepatocytes from the treatment group with: cytoplasmic and nuclear pleomorphism; foci of necrosis; mononuclear cell infiltration; and presence of apoptotic bodies. These changes were absent in control rat livers indicating that dietary F. graminearum causes inflammation and parenchymal damage in the rat liver. This is the first histopathological study showing the association between F. graminearum and liver damage.