Structure-function relationships of 12,13-epoxytrichothecene mycotoxins in cell culture: comparison to whole animal lethality

Fhb7-GST catalyzed glutathionylation effectively detoxifies the trichothecene family

Trichothecene (TCN) contamination in food and feed is a serious challenge due to the negative health and economic impacts. Here, we confirmed that the glutathione S-transferase (GST) Fhb7-GST could broadly catalyze type A, type B and type D TCNs into glutathione epoxide adducts (TCN-13-GSHs). To evaluate the toxicity of TCN-13-GSH adducts, we performed cell proliferation assays in vitro, which demonstrated decreased cytotoxicity of the adducts. Moreover, in vivo assays (repeated-dose treatment in mice) confirmed that TCN-13-GSH adducts were dramatically less toxic than the corresponding TCNs. To establish whether TCN-13-GSH was metabolized back to free toxin during digestion, single-dose metabolic tests were performed in rats; DON-13-GSH was not hydrolyzed in vivo, but rather was quickly metabolized to another low-toxicity compound, DON-13-N-acetylcysteine. These results demonstrate the promise of Fhb7-GST as a candidate of detoxification enzyme potentially applied in TCN-contaminated agricultural samples, minimizing the detrimental effects of the mycotoxin.

A Chemically Defined Medium That Supports Mycotoxin Production by Stachybotrys chartarum Enabled Analysis of the Impact of Nitrogen and Carbon Sources on the Biosynthesis of Macrocyclic Trichothecenes and Stachybotrylactam

Stachybotrys chartarum (Hypocreales, Ascomycota) is a toxigenic fungus that is frequently isolated from water-damaged buildings or improperly stored feed. The secondary metabolites formed by this mold have been associated with health problems in humans and animals. Several authors have studied the influence of environmental conditions on the production of mycotoxins, but these studies focused on undefined or complex substrates, such as building materials and media that impeded investigations of the influence of specific nutrients. In this study, a chemically defined cultivation medium was used to investigate the impact of several nitrogen and carbon sources on growth of S. chartarum and its production of macrocyclic trichothecenes (MTs) and stachybotrylactam (STLAC). Increasing concentrations of sodium nitrate were found to positively affect mycelial growth, the level of sporulation, and MT production, while ammonium nitrate and ammonium chloride had an inhibitory effect. Potato starch was the superior and most reliable carbon source tested. Additionally, we observed that the level of sporulation was correlated with the production of MTs but not with that of STLAC. In this study, we provide a chemically well-defined cultivation medium suitable for standardized in vitro testing of the capacity of S. chartarum isolates to produce macrocyclic trichothecenes. IMPORTANCE Macrocyclic trichothecenes (MTs) are highly toxic secondary metabolites that are produced by certain Stachybotrys chartarum strains, which consequently pose a risk for animals and humans. To identify hazardous, toxin-producing strains by analytical means, it is important to grow them under conditions that support MT production. Nutrients determine growth and development and thus the synthesis of secondary metabolites. Complex rich media are commonly used for diagnostics, but batch differences of supplements pose a risk for inconsistent data. We have established a chemically defined medium for S. chartarum and used it to analyze the impact of nitrogen and carbon sources. A key finding is that nitrate stimulates MT production, whereas ammonium suppresses it. Defining nutrients that support MT production will enable a more reliable identification of hazardous S. chartarum isolates. The new medium will also be instrumental in analyzing the biosynthetic pathways and regulatory mechanisms that control mycotoxin production in S. chartarum.

Diacetoxyscirpenol, a Fusarium exometabolite, prevents efficiently the incidence of the parasitic weed Striga hermonthica

BACKGROUND

Certain Fusarium exometabolites have been reported to inhibit seed germination of the cereal-parasitizing witchweed, Striga hermonthica, in vitro. However, it is unknown if these exometabolites will consistently prevent S. hermonthica incidence in planta. The study screened a selection of known, highly phytotoxic Fusarium exometabolites, in identifying the most potent/efficient candidate (i.e., having the greatest effect at minimal concentration) to completely hinder S. hermonthica seed germination in vitro and incidence in planta, without affecting the host crop development and yield.

RESULTS

In vitro germination assays of the tested Fusarium exometabolites (i.e., 1,4-naphthoquinone, equisetin, fusaric acid, hymeglusin, neosolaniol (Neo), T-2 toxin (T-2) and diacetoxyscirpenol (DAS)) as pre-Striga seed conditioning treatments at 1, 5, 10, 20, 50 and 100 µM, revealed that only DAS, out of all tested exometabolites, completely inhibited S. hermonthica seed germination at each concentration. It was followed by T-2 and Neo, as from 10 to 20 µM respectively. The remaining exometabolites reduced S. hermonthica seed germination as from 20 µM (P < 0. 0001). In planta assessment (in a S. hermonthica-sorghum parasitic system) of the exometabolites at 20 µM showed that, although, none of the tested exometabolites affected sorghum aboveground dry biomass (P > 0.05), only DAS completely prevented S. hermonthica incidence. Following a 14-d incubation of DAS in the planting soil substrate, bacterial 16S ribosomal RNA (rRNA) and fungal 18S rRNA gene copy numbers of the soil microbial community were enhanced; which coincided with complete degradation of DAS in the substrate. Metabolic footprinting revealed that the S. hermonthica mycoherbicidal agent, Fusarium oxysporum f. sp. strigae (isolates Foxy-2, FK3), did not produce DAS; a discovery that corresponded with underexpression of key genes (Tri5, Tri4) necessary for Fusarium trichothecene biosynthesis (P < 0.0001).

CONCLUSIONS

Among the tested Fusarium exometabolites, DAS exhibited the most promising herbicidal potential against S. hermonthica. Thus, it could serve as a new biocontrol agent for efficient S. hermonthica management. Further examination of DAS specific mode of action against the target weed S. hermonthica at low concentrations (≤ 20 µM), as opposed to non-target soil organisms, is required.

4-O-Glucosylation of Trichothecenes by Fusarium Species: A Phase II Xenobiotic Metabolism for t-Type Trichothecene Producers

The t-type trichothecene producers Fusarium sporotrichioides and Fusarium graminearum protect themselves against their own mycotoxins by acetylating the C-3 hydroxy group with Tri101p acetylase. To understand the mechanism by which they deal with exogenously added d-type trichothecenes, the Δtri5 mutants expressing all but the first trichothecene pathway enzymes were fed with trichodermol (TDmol), trichothecolone (TCC), 8-deoxytrichothecin, and trichothecin. LC-MS/MS and NMR analyses showed that these C-3 unoxygenated trichothecenes were conjugated with glucose at C-4 by α-glucosidic linkage. As t-type trichothecenes are readily incorporated into the biosynthetic pathway following the C-3 acetylation, the mycotoxins were fed to the ΔFgtri5ΔFgtri101 mutant to examine their fate. LC-MS/MS and NMR analyses demonstrated that the mutant conjugated glucose at C-4 of HT-2 toxin (HT-2) by α-glucosidic linkage, while the ΔFgtri5 mutant metabolized HT-2 to 3-acetyl HT-2 toxin and T-2 toxin. The 4-O-glucosylation of exogenously added t-type trichothecenes appears to be a general response of the ΔFgtri5ΔFgtri101 mutant, as nivalenol and its acetylated derivatives appeared to be conjugated with hexose to some extent. The toxicities of 4-O-glucosides of TDmol, TCC, and HT-2 were much weaker than their corresponding aglycons, suggesting that 4-O-glucosylation serves as a phase II xenobiotic metabolism for t-type trichothecene producers.

Updated Review of the Toxicity of Selected Fusarium Toxins and Their Modified Forms

Mycotoxins are one of the most dangerous food and feed contaminants, hence they have significant influence on human and animal health. This study reviews the information reported over the last few years on the toxic effects of the most relevant and studied Fusarium toxins and their modified forms. Deoxynivalenol (DON) and its metabolites can induce intracellular oxidative stress, resulting in DNA damage. Recent studies have also revealed the capability of DON and its metabolites to disturb the cell cycle and alter amino acid expression. Several studies have attempted to explore the mechanism of action of T-2 and HT-2 toxins in anorexia induction. Among other findings, two neurotransmitters associated with this process have been identified, namely substance P and serotonin (5-hydroxytryptamine). For zearalenone (ZEN) and its metabolites, the literature points out that, in addition to their generally acknowledged estrogenic and oxidative potentials, they can also modify DNA by altering methylation patterns and histone acetylation. The ability of the compounds to induce alterations in the expression of major metabolic genes suggests that these compounds can contribute to the development of numerous metabolic diseases, including type 2 diabetes.

Deoxynivalenol: Mechanisms of action and its effects on various terrestrial and aquatic species

Deoxynivalenol, a type B trichothecene mycotoxin produced by Fusarium species of fungi, is a ubiquitious contaminant of cereal grains worldwide. Chronic, low dose consumption of feeds contaminated with DON is associated with a wide range of symptoms in terrestrial and aquatic species including decreased feed intake and feed refusal, reduced weight gain, and altered nutritional efficiency. Acute, high dose exposure to DON may be associated with more severe symptoms such as vomiting, diarrhea, intestinal inflammation and gastrointestinal hemorrhage. The toxicity of DON is partly related to its ability to disrupt eukaryotic protein synthesis via binding to the peptidyl transferase site of the ribosome. Moreover, DON exerts its effects at the cellular level by activating mitogen activated protein kinases (MAPK) through a process known as the ribotoxic stress response (RSR). The outcome of DON-associated MAPK activation is dose and duration dependent; acute low dose exposure results in immunostimulation characterized by the upregulation of cytokines, chemokines and other proinflammatory-related proteins, whereas longer term exposure to higher doses generally results in apoptosis, cell cycle arrest, and immunosuppression. The order of decreasing sensitivity to DON is considered to be: swine > rats > mice > poultry ≈ ruminants. However, studies conducted within the past 10 years have demonstrated that some species of fish, such as rainbow trout, are highly sensitive to DON. The aims of this review are to explore the effects of DON on terrestrial and aquatic species as well as its mechanisms of action, metabolism, and interaction with other Fusarium mycotoxins. Notably, a considerable emphasis is placed on reviewing the effects of DON on different species of fish.

In Vitro Assay of Translation Inhibition by Trichothecenes Using a Commercially Available System

Trichothecenes are a family of major secondary metabolites produced by some common filamentous fungi, including plant pathogenic and entomopathogenic fungi. It may be considered difficult to conduct a comparison between the toxicities of trichothecenes with consideration of different conditions and cell lines. In the current study, we developed an in vitro assay based on a commercially available system to estimate the translation inhibition, that is, the main toxicity, of trichothecenes. The assay was applied to estimate the inhibition of protein synthesis by trichothecenes. Initially, we examined the assay using trichothecene dissolved in water followed by an assessment of trichothecene solutions dissolved in acetonitrile. The obtained data showed that the assay tolerated the small amount of acetonitrile. The assay examined in this study has the advantages of a short operation time (one day), ease of use, and data stability, as it is a non-cell-based assay whose components are commercially available. It is expected that this assay will contribute to the evaluation of the toxicity of a vast number of trichothecenes.

Transcriptome Analysis of Caco-2 Cells upon the Exposure of Mycotoxin Deoxynivalenol and Its Acetylated Derivatives

Deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON) and 15-acetyldeoxynivalenol (15-ADON) are type B trichothecenes; one of the major pollutants in food and feed products. Although the toxicity of DON has been well documented, information on the toxicity of its acetylated derivative remains incomplete. To acquire more detailed insight into 3-ADON and 15-ADON, Caco-2 cells under 0.5 µM DON, 3-ADON and 15-ADON treatment for 24 h were subjected to RNA-seq analysis. In the present study, 2656, 3132 and 2425 differentially expressed genes (DEGs) were selected, respectively, and were enriched utilizing the Kyoto Encyclopedia of Genes and Genomes (KEGG) and the Gene Ontology (GO) database. The upregulation of ataxia-telangiectasia mutated kinase (ATM), WEE1 homolog 2 (WEE2) and downregulation of proliferating cell nuclear antigen (PCNA), minichromosome maintenance (MCMs), cyclin dependent kinase (CDKs), and E2Fs indicate that the three toxins induced DNA damage, inhibition of DNA replication and cell cycle arrest in Caco-2 cells. Additionally, the upregulation of sestrin (SENEs) and NEIL1 implied that the reason for DNA damage may be attributable to oxidative stress. Our study provides insight into the toxic mechanism of 3-ADON and 15-ADON.

The trichothecene neosolaniol stimulates an emetic response through neuropeptide Y2 and serotonin 3 receptors in mink

Type A trichothecene neosolaniol (NEO) is considered a potential risk to human and animal health by the European Food Safety Authority (EFSA). To date, available data do not allow making conclusions about the toxicological properties of this toxin. Trichothecenes have been previously demonstrated to induce emetic responses in mink, and this response has been associated with neurotransmitter peptide YY (PYY) and serotonin (5-hydroxytryptamine, 5-HT). The goal of this study was to compare emetic effects of NEO administered by intraperitoneal and oral routes and relate these effects to PYY and 5-HT. The effective doses resulting in emetic events in 50% of the animals following intraperitoneal and oral exposure to NEO were 0.4 and 0.09 mg/kg bw, respectively. This emetic response corresponded to elevated PYY and 5-HT levels. Blocking the neuropeptide Y2 receptor diminished emesis induction by PYY and NEO. The 5-HT3 receptor inhibitor granisetron completely restrained the induction of emesis by 5-HT and NEO. To summarize, our findings demonstrate that PYY and 5-HT play important roles in the NEO-induced emetic response.

The Ribosome-Binding Mode of Trichothecene Mycotoxins Rationalizes Their Structure-Activity Relationships

Trichothecenes are the most prevalent mycotoxins contaminating cereal grains. Some of them are also considered as the virulence factors of Fusarium head blight disease. However, the mechanism behind the structure-activity relationship for trichothecenes remains unexplained. Filling this information gap is a crucial step for developing strategies to manage this large family of mycotoxins in food and feed. Here, we perform an in-depth re-examination of the existing structures of Saccharomyces cerevisiae ribosome complexed with three different trichothecenes. Multiple binding interactions between trichothecenes and 25S rRNA, including hydrogen bonds, nonpolar pi stacking interactions and metal ion coordination interactions, are identified as important binding determinants. These interactions are mainly contributed by the key structural elements to the toxicity of trichothecenes, including the oxygen in the 12,13-epoxide ring and a double bond between C9 and C10. In addition, the C3-OH group also participates in binding. The comparison of three trichothecenes binding to the ribosome, along with their binding pocket architecture, suggests that the substitutions at different positions impact trichothecenes binding in two different patterns. Moreover, the binding of trichothecenes induced conformation changes of several nucleotide bases in 25S rRNA. This then provides a structural framework for understanding the structure-activity relationships apparent in trichothecenes. This study will facilitate the development of strategies aimed at detoxifying mycotoxins in food and feed and at improving the resistance of cereal crops to Fusarium fungal diseases.

1H-NMR metabolomics response to a realistic diet contamination with the mycotoxin deoxynivalenol: Effect of probiotics supplementation

Low-level contamination of food and feed by deoxynivalenol (DON) is unavoidable. We investigated the effects of subclinical treatment with DON, and supplementation with probiotic yeast Saccharomyces cerevisiae boulardii I1079 as a preventive strategy in piglets. Thirty-six animals were randomly assigned to either a control diet, a diet contaminated with DON (3 mg/kg), a diet supplemented with yeast (4 × 10⁹ CFU/kg), or a DON-contaminated diet supplemented with yeast, for four weeks. Plasma and tissue samples were collected for biochemical analysis,¹H-NMR untargeted metabolomics, and histology. DON induced no significant modifications in biochemical parameters. However, lesion scores were higher and metabolomics highlighted alterations of amino acid and 2-oxocarboxylic acid metabolism. Administering yeast affected aminoacyl-tRNA synthesis and amino acid and glycerophospholipid metabolism. Yeast supplementation of piglets exposed to DON prevented histological alterations, and partial least square discriminant analysis emphasised similarity between the metabolic profiles of their plasma and that of the control group. The effect on liver metabolome remained marginal, indicating that the toxicity of the mycotoxin was not eliminated. These findings show that the ¹H-NMR metabolomics profile is a reliable biomarker to assess subclinical exposure to DON, and that supplementation with S. cerevisiae boulardii increases the resilience of piglets to this mycotoxin.

Reduced Toxicity of Trichothecenes, Isotrichodermol, and Deoxynivalenol, by Transgenic Expression of the Tri101 3-O-Acetyltransferase Gene in Cultured Mammalian FM3A Cells

In trichothecene-producing fusaria, isotrichodermol (ITDol) is the first intermediate with a trichothecene skeleton. In the biosynthetic pathway of trichothecene, a 3-O-acetyltransferase, encoded by Tri101, acetylates ITDol to a less-toxic intermediate, isotrichodermin (ITD). Although trichothecene resistance has been conferred to microbes and plants transformed with Tri101, there are no reports of resistance in cultured mammalian cells. In this study, we found that a 3-O-acetyl group of trichothecenes is liable to hydrolysis by esterases in fetal bovine serum and FM3A cells. We transfected the cells with Tri101 under the control of the MMTV-LTR promoter and obtained a cell line G3 with the highest level of C-3 acetylase activity. While the wild-type FM3A cells hardly grew in the medium containing 0.40 μM ITDol, many G3 cells survived at this concentration. The IC₅₀ values of ITDol and ITD in G3 cells were 1.0 and 9.6 μM, respectively, which were higher than the values of 0.23 and 3.0 μM in the wild-type FM3A cells. A similar, but more modest, tendency was observed in deoxynivalenol and 3-acetyldeoxynivalenol. Our findings indicate that the expression of Tri101 conferred trichothecene resistance in cultured mammalian cells.

Trichothecenes in Cereal Grains - An Update

Trichothecenes are sesquiterpenoid mycotoxins produced by fungi from the order Hypocreales, including members of the Fusarium genus that infect cereal grain crops. Different trichothecene-producing Fusarium species and strains have different trichothecene chemotypes belonging to the Type A and B class. These fungi cause a disease of small grain cereals, called Fusarium head blight, and their toxins contaminate host tissues. As potent inhibitors of eukaryotic protein synthesis, trichothecenes pose a health risk to human and animal consumers of infected cereal grains. In 2009, Foroud and Eudes published a review of trichothecenes in cereal grains for human consumption. As an update to this review, the work herein provides a comprehensive and multi-disciplinary review of the Fusarium trichothecenes covering topics in chemistry and biochemistry, pathogen biology, trichothecene toxicity, molecular mechanisms of resistance or detoxification, genetics of resistance and breeding strategies to reduce their contamination of wheat and barley.

The role of roughage provision on the absorption and disposition of the mycotoxin deoxynivalenol and its acetylated derivatives in calves: from field observations to toxicokinetics

A clinical case in Belgium demonstrated that feeding a feed concentrate containing considerable levels of deoxynivalenol (DON, 1.13 mg/kg feed) induced severe liver failure in 2- to 3-month-old beef calves. Symptoms disappeared by replacing the highly contaminated corn and by stimulating ruminal development via roughage administration. A multi-mycotoxin contamination was demonstrated in feed samples collected at 15 different veal farms in Belgium. DON was most prevalent, contaminating 80% of the roughage samples (mixed straw and maize silage; average concentration in positives: 637 ± 621 µg/kg, max. 1818 µg/kg), and all feed concentrate samples (411 ± 156 µg/kg, max. 693 µg/kg). In order to evaluate the impact of roughage provision and its associated ruminal development on the gastro-intestinal absorption and biodegradation of DON and its acetylated derivatives (3- and 15-ADON) in calves, a toxicokinetic study was performed with two ruminating and two non-ruminating male calves. Animals received in succession a bolus of DON (120 µg/kg bodyweight (BW)), 15-ADON (50 µg/kg BW), and 3-ADON (25 µg/kg) by intravenous (IV) injection or per os (PO) in a cross-over design. The absolute oral bioavailability of DON was much higher in non-ruminating calves (50.7 ± 33.0%) compared to ruminating calves (4.1 ± 4.5%). Immediately following exposure, 3- and 15-ADON were hydrolysed to DON in ruminating calves. DON and its acetylated metabolites were mainly metabolized to DON-3-glucuronide, however, also small amounts of DON-15-glucuronide were detected in urine. DON degradation to deepoxy-DON (DOM-1) was only observed to a relevant extent in ruminating calves. Consequently, toxicity of DON in calves is closely related to roughage provision and the associated stage of ruminal development.

Review article: Role of satiety hormones in anorexia induction by Trichothecene mycotoxins

The trichothecenes, produced by Fusarium, contaminate animal feed and human food in all stages of production and lead to a large spectrum of adverse effects for animal and human health. An hallmark of trichothecenes toxicity is the onset of emesis followed by anorexia and food intake reduction in different animal species (mink, mice and pig). The modulation of emesis and anorexia can result from a direct action of trichothecenes in the brain or from an indirect action in the gastrointestinal tract. The direct action of trichothecenes involved specific brain areas such as nucleate tractus solitarius in the brainstem and the arcuate nuclei in the hypothalamus. Activation of these areas in the brain leads to the activation of specific neuronal populations containing anorexigenic factors (POMC and CART). The indirect action of trichothecenes in the gastrointestinal tract involved, by enteroendocrine cells, the secretion of several gut hormones such as cholecystokinin (CCK) and peptide YY (PYY) but also glucagon-like peptide 1 (GLP-1), gastric inhibitory peptide (GIP) and 5-hydroxytryptamine (5-HT), which transmitted signals to the brain via the gut-brain axis. This review summarizes current knowledge on the effects of trichothecenes, especially deoxynivalenol, on emesis and anorexia and discusses the mechanisms underlying trichothecenes-induced food reduction.

Risk to human and animal health related to the presence of 4,15-diacetoxyscirpenol in food and feed

4,15‐Diacetoxyscirpenol (DAS) is a mycotoxin primarily produced by Fusarium fungi and occurring predominantly in cereal grains. As requested by the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM) assessed the risk of DAS to human and animal health related to its presence in food and feed. Very limited information was available on toxicity and on toxicokinetics in experimental and farm animals. Due to the limitations in the available data set, human acute and chronic health‐based guidance values (HBGV) were established based on data obtained in clinical trials of DAS as an anticancer agent (anguidine) after intravenous administration to cancer patients. The CONTAM Panel considered these data as informative for the hazard characterisation of DAS after oral exposure. The main adverse effects after acute and repeated exposure were emesis, with a no‐observed‐adverse‐effect level (NOAEL) of 32 μg DAS/kg body weight (bw), and haematotoxicity, with a NOAEL of 65 μg DAS/kg bw, respectively. An acute reference dose (ARfD) of 3.2 μg DAS/kg bw and a tolerable daily intake (TDI) of 0.65 μg DAS/kg bw were established. Based on over 15,000 occurrence data, the highest acute and chronic dietary exposures were estimated to be 0.8 and 0.49 μg DAS/kg bw per day, respectively, and were not of health concern for humans. The limited information for poultry, pigs and dogs indicated a low risk for these animals at the estimated DAS exposure levels under current feeding practices, with the possible exception of fattening chicken. Assuming similar or lower sensitivity than for poultry, the risk was considered overall low for other farm and companion animal species for which no toxicity data were available. In consideration of the similarities of several trichothecenes and the likelihood of co‐exposure via food and feed, it could be appropriate to perform a cumulative risk assessment for this group of substances.

Mycotoxins co-contamination: Methodological aspects and biological relevance of combined toxicity studies

Mycotoxins are secondary fungal metabolites produced mainly by Aspergillus, Penicillium, and Fusarium. As evidenced by large-scale surveys, humans and animals are simultaneously exposed to several mycotoxins. Simultaneous exposure could result in synergistic, additive or antagonistic effects. However, most toxicity studies addressed the effects of mycotoxins separately. We present the experimental designs and we discuss the conclusions drawn from in vitro experiments exploring toxicological interactions of mycotoxins. We report more than 80 publications related to mycotoxin interactions. The studies explored combinations involving the regulated groups of mycotoxins, especially aflatoxins, ochratoxins, fumonisins, zearalenone and trichothecenes, but also the "emerging" mycotoxins beauvericin and enniatins. Over 50 publications are based on the arithmetic model of additivity. Few studies used the factorial designs or the theoretical biology-based models of additivity. The latter approaches are gaining increased attention. These analyses allow determination of the type of interaction and, optionally, its magnitude. The type of interaction reported for mycotoxin combinations depended on several factors, in particular cell models and the tested dose ranges. However, synergy among Fusarium toxins was highlighted in several studies. This review indicates that well-addressed in vitro studies remain valuable tools for the screening of interactive potential in mycotoxin mixtures.

Risks to human and animal health related to the presence of deoxynivalenol and its acetylated and modified forms in food and feed

Deoxynivalenol (DON) is a mycotoxin primarily produced by Fusarium fungi, occurring predominantly in cereal grains. Following the request of the European Commission, the CONTAM Panel assessed the risk to animal and human health related to DON, 3-acetyl-DON (3-Ac-DON), 15-acetyl-DON (15-Ac-DON) and DON-3-glucoside in food and feed. A total of 27,537, 13,892, 7,270 and 2,266 analytical data for DON, 3-Ac-DON, 15-Ac-DON and DON-3-glucoside, respectively, in food, feed and unprocessed grains collected from 2007 to 2014 were used. For human exposure, grains and grain-based products were main sources, whereas in farm and companion animals, cereal grains, cereal by-products and forage maize contributed most. DON is rapidly absorbed, distributed, and excreted. Since 3-Ac-DON and 15-Ac-DON are largely deacetylated and DON-3-glucoside cleaved in the intestines the same toxic effects as DON can be expected. The TDI of 1 μg/kg bw per day, that was established for DON based on reduced body weight gain in mice, was therefore used as a group-TDI for the sum of DON, 3-Ac-DON, 15-Ac-DON and DON-3-glucoside. In order to assess acute human health risk, epidemiological data from mycotoxicoses were assessed and a group-ARfD of 8 μg/kg bw per eating occasion was calculated. Estimates of acute dietary exposures were below this dose and did not raise a health concern in humans. The estimated mean chronic dietary exposure was above the group-TDI in infants, toddlers and other children, and at high exposure also in adolescents and adults, indicating a potential health concern. Based on estimated mean dietary concentrations in ruminants, poultry, rabbits, dogs and cats, most farmed fish species and horses, adverse effects are not expected. At the high dietary concentrations, there is a potential risk for chronic adverse effects in pigs and fish and for acute adverse effects in cats and farmed mink.

Mycotoxin Biotransformation by Native and Commercial Enzymes: Present and Future Perspectives

Worldwide mycotoxins contamination has a significant impact on animal and human health, and leads to economic losses accounted for billions of dollars annually. Since the application of pre- and post- harvest strategies, including chemical or physical removal, are not sufficiently effective, biological transformation is considered the most promising yet challenging approach to reduce mycotoxins accumulation. Although several microorganisms were reported to degrade mycotoxins, only a few enzymes have been identified, purified and characterized for this activity. This review focuses on the biotransformation of mycotoxins performed with purified enzymes isolated from bacteria, fungi and plants, whose activity was validated in in vitro and in vivo assays, including patented ones and commercial preparations. Furthermore, we will present some applications for detoxifying enzymes in food, feed, biogas and biofuel industries, describing their limitation and potentialities.

Microbial Detoxification of Deoxynivalenol (DON), Assessed via a Lemna minor L. Bioassay, through Biotransformation to 3-epi-DON and 3-epi-DOM-1

Mycotoxins are toxic metabolites produced by fungi. To mitigate mycotoxins in food or feed, biotransformation is an emerging technology in which microorganisms degrade toxins into non-toxic metabolites. To monitor deoxynivalenol (DON) biotransformation, analytical tools such as ELISA and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) are typically used. However, these techniques do not give a decisive answer about the remaining toxicity of possible biotransformation products. Hence, a bioassay using Lemna minor L. was developed. A dose-response analysis revealed significant inhibition in the growth of L. minor exposed to DON concentrations of 0.25 mg/L and higher. Concentrations above 1 mg/L were lethal for the plant. This bioassay is far more sensitive than previously described systems. The bioassay was implemented to screen microbial enrichment cultures, originating from rumen fluid, soil, digestate and activated sludge, on their biotransformation and detoxification capability of DON. The enrichment cultures originating from soil and activated sludge were capable of detoxifying and degrading 5 and 50 mg/L DON. In addition, the metabolites 3-epi-DON and the epimer of de-epoxy-DON (3-epi-DOM-1) were found as biotransformation products of both consortia. Our work provides a new valuable tool to screen microbial cultures for their detoxification capacity.

Appropriateness to set a group health based guidance value for T2 and HT2 toxin and its modified forms

The EFSA Panel on Contaminants in the Food Chain (CONTAM) established a tolerable daily intake (TDI) for T2 and HT2 of 0.02 μg/kg body weight (bw) per day based on a new in vivo subchronic toxicity study in rats that confirmed that immune‐ and haematotoxicity are the critical effects of T2 and using a reduction in total leucocyte count as the critical endpoint. An acute reference dose (ARfD) of 0.3 μg for T2 and HT2/kg bw was established based on acute emetic events in mink. Modified forms of T2 and HT2 identified are phase I metabolites mainly formed through hydrolytic cleavage of one or more of the three ester groups of T2. Less prominent hydroxylation reactions occur predominantly at the side chain. Phase II metabolism involves conjugation with glucose, modified glucose, sulfate, feruloyl and acetyl groups. The few data on occurrence of modified forms indicate that grain products are their main source. The CONTAM Panel found it appropriate to establish a group TDI and a group ARfD for T2 and HT2 and its modified forms. Potency factors relative to T2 for the modified forms were used to account for differences in acute and chronic toxic potencies. It was assumed that conjugates (phase II metabolites of T2, HT2 and their phase I metabolites), which are not toxic per se, would be cleaved releasing their aglycones. These metabolites were assigned the relative potency factors (RPFs) of their respective aglycones. The RPFs assigned to the modified forms were all either 1 or less than 1. The uncertainties associated with the present assessment are considered as high. Using the established group, ARfD and TDI would overestimate any risk of modified T2 and HT2.

The Impact of Deoxynivalenol on Pigeon Health: Occurrence in Feed, Toxicokinetics and Interaction with Salmonellosis

Seed-based pigeon diets could be expected to result in exposure of pigeons to mycotoxins such as deoxynivalenol (DON). Ingestion of low to moderate contamination levels of DON may impair intestinal health, immune function and/or pathogen fitness, resulting in altered host-pathogen interactions and thus different outcome of infections. Here we demonstrate that DON was one of the most frequently detected mycotoxins in seed-based racing pigeons feed, contaminating 5 out of 10 samples (range 177–1,466 μg/kg). Subsequently, a toxicokinetic analysis revealed a low absolute oral bioavailability (F) of DON in pigeons (30.4%), which is comparable to other avian species. Furthermore, semi-quantitative analysis using high-resolution mass spectrometry revealed that DON-3α-sulphate is the major metabolite of DON in pigeons after intravenous as well as oral administration. Following ingestion of DON contaminated feed, the intestinal epithelial cells are exposed to significant DON concentrations which eventually may affect intestinal translocation and colonization of bacteria. Feeding pigeons a DON contaminated diet resulted in an increased percentage of pigeons shedding Salmonella compared to birds fed control diet, 87 ± 17% versus 74 ± 13%, respectively. However, no impact of DON was observed on the Salmonella induced disease signs, organ lesions, faecal and organ Salmonella counts. The presented risk assessment indicates that pigeons are frequently exposed to mycotoxins such as DON, which can affect the outcome of a Salmonella infection. The increasing number of pigeons shedding Salmonella suggests that DON can promote the spread of the bacterium within pigeon populations.

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.

Natural Co-Occurrence of Mycotoxins in Foods and Feeds and Their in vitro Combined Toxicological Effects

Some foods and feeds are often contaminated by numerous mycotoxins, but most studies have focused on the occurrence and toxicology of a single mycotoxin. Regulations throughout the world do not consider the combined effects of mycotoxins. However, several surveys have reported the natural co-occurrence of mycotoxins from all over the world. Most of the published data has concerned the major mycotoxins aflatoxins (AFs), ochratoxin A (OTA), zearalenone (ZEA), fumonisins (FUM) and trichothecenes (TCTs), especially deoxynivalenol (DON). Concerning cereals and derived cereal product samples, among the 127 mycotoxin combinations described in the literature, AFs+FUM, DON+ZEA, AFs+OTA, and FUM+ZEA are the most observed. However, only a few studies specified the number of co-occurring mycotoxins with the percentage of the co-contaminated samples, as well as the main combinations found. Studies of mycotoxin combination toxicity showed antagonist, additive or synergic effects depending on the tested species, cell model or mixture, and were not necessarily time- or dose-dependent. This review summarizes the findings on mycotoxins and their co-occurrence in various foods and feeds from all over the world as well as in vitro experimental data on their combined toxicity.

Assessment of a potential preventive ability of amygdalin in mycotoxin-induced ovarian toxicity

The possible effects of a natural substance amygdalin and its combination with the mycotoxin deoxynivalenol (DON) on the steroid hormone secretion (progesterone and 17-β-estradiol) by porcine ovarian granulosa cells (GCs) were examined in this in vitro study. Ovarian GCs were incubated without (control group) and with amygdalin (1, 10, 100, 1,000 and 10,000 μg mL(1)), or its combination with DON (1 μg mL(1)) for 24 h. The release of steroid hormones was determined by ELISA. The progesterone secretion by porcine ovarian GCs was not affected by amygdalin in comparison to the control. However, the highest amygdalin dose (10,000 μg mL(1)) caused a significant stimulation of the 17-β-estradiol release. A combination of amygdalin with DON significantly (P < 0.05) increased the progesterone release at all concentrations. Similarly, a stimulatory effect of amygdalin co-administered with DON was detected with respect to the 17-β-estradiol secretion at the highest dose (10,000 μg mL(1)) of amygdalin and 1 μg mL(1) of DON. Noticeable differences between the effects of amygdalin alone and its combination with DON on the progesterone release were detected. In contrast, no differences between the stimulatory effects of amygdalin and its combination with DON on the 17-β-estradiol synthesis by porcine GCs were observed. Findings from this in vitro study did not confirm the expected protective effect of amygdalin on mycotoxin induced reprotoxicity. Our results indicate that the stimulatory effect of amygdalin combined with DON on the progesterone release was clearly caused by the DON addition, not by the presence amygdalin per se. On the other hand, the stimulation of 17-β-estradiol production was solely caused by the presence of amygdalin addition. These findings suggest a possible involvement of both natural substances into the processes of steroidogenesis and appear to be endocrine modulators of porcine ovaries.

Structure-function analysis of porcine cytochrome P450 3A29 in the hydroxylation of T-2 toxin as revealed by docking and mutagenesis studies

T-2 toxin, one of the type A trichothecenes, presents a potential hazard to human and animal health. Our previous work demonstrated that porcine cytochrome P450 3A29 (CYP3A29) played an important role in the hydroxylation of T-2 toxin. To identify amino acids involved in this metabolic process, T-2 toxin was docked into a homology model of CYP3A29 based on a crystal structure of CYP3A4 using AutoDock 4.0. Nine residues of CYP3A29, Arg105, Arg106, Phe108, Ser119, Lys212, Phe213, Phe215, Arg372 and Glu374, which were found within 5 Å around T-2 toxin were subjected to site-directed mutagenesis. In the oxidation of nifedipine, the CL_int value of R106A was increased by nearly two-folds compared with the wild-type CYP3A29, while the substrate affinities and CL_int values of S119A and K212A were significantly reduced. In the hydroxylation of T-2 toxin, the generation of 3′-OH-T-2 by R105A, S119A and K212A was significantly less than that by the wild-type, whereas R106A slightly increased the generation of 3′-OH-T-2. These results were further confirmed by isothermal titration calorimetry analysis, suggesting that these four residues are important in the hydroxylation of T-2 toxin and Arg105 may be a specific recognition site for the toxin. Our study suggests a possible structure-function relationship of CYP3A29 in the hydroxylation of T-2 toxin, providing with new insights into the mechanism of CYP3A enzymes in the biotransformation of T-2 toxin.

Evaluation of rapid test kits for quantification of deoxynivalenol in naturally contaminated oats and wheat

The aim of this study was to evaluate the performance of rapid test kits for analysis of deoxynivalenol (DON), a mycotoxin commonly found in small-grain cereals. Concentrations of DON and its acetylated derivative 3-acetyldeoxynivalenol (3-ADON) were analysed in naturally contaminated wheat (n=56) and oats (n=81) using two enzyme-linked immunosorbent assays, i.e. Ridascreen® DON (‘Standard ELISA’) and Ridascreen® FAST DON (‘Fast ELISA’), and two lateral flow devices, i.e. Rida® QUICK DON (‘Quick LFD’) and Rosa® DON (‘Rosa LFD’). Analysis by the LC-MS/MS reference method showed a median DON + 3-ADON concentration of 1,168 μg/kg (90th percentile 3,264 μg/kg) in wheat and 2,250 μg/kg (90th percentile of 9,008 μg/kg) in oats. Rosa LFD offered the best reliability, achieving detection that was stable across toxin levels in both matrices. In addition, Rosa LFD had the highest accuracy (i.e. proportion of correct results) at a DON level of 1,250 μg/kg in wheat (0.83) and 8,000 μg/kg in oats (0.96). Standard ELISA achieved the highest accuracy at a DON level of 1,750 μg/kg in oats (0.85). Detection by Quick LFD in wheat and Fast ELISA in both wheat and oats differed significantly among toxin levels (P≤0.05), with recoveries outside European Union requirements (70-120%) in some cases. The correlation with results from LC-MS/MS analysis in oats was best for Rosa LFD (R2=0.79). In wheat, however the correlation was best for Fast ELISA (R2=0.81). Rosa LFD was regarded as well-suited for on-site detection. Standard ELISA allowed simultaneous testing of several samples and achieved detection that was stable across toxin levels in both matrices, making it a useful alternative in laboratories. To our knowledge, this is the first report describing the performance of rapid test kits for detection of DON in naturally contaminated oats.

The phytotoxicity ofFusarium metabolites: An update since 1989

The present article summarises the published phytotoxic effects of severalFusarium metabolites (mycotoxins, phytotoxins, antibiotics and pigments) since 1989. The phytotoxicity of many of the commonly isolated metabolites cannot be disputed, but their role in pathogenesis ofFusarium-induced plant diseases is uncertain. Plant species/varieties differ in their susceptibililty resistance to these toxinsin vitro, as well as toFusarium pathogens under field conditions. Such variations in plant response may reflect resistance mechanisms that operate at several levels, including an initial ability to prevent fungal invasion; prevention of fungal spread and toxin tolerance or degradation. Little is known about the mode of action of most of these metabolites on either animal or plant cells. Several novelFusarium metabolites have been isolated in the past few years. Many are toxic to animals and cell lines, but assessment of their phytotoxicity has largely been neglected. Since many plant pathogenic Fusaria produce a plethora of metabolites, the additive or synergistic actions of toxins in combination must be considered in plant pathology.

Verrucarin A sensitizes TRAIL-induced apoptosis via the upregulation of DR5 in an eIF2α/CHOP-dependent manner

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is one of the most promising candidates for new cancer therapeutics. However, resistance to TRAIL in some cancers remains a current problem in recent. The protein-folding compartment of the endoplasmic reticulum (ER) is particularly sensitive to disturbances, which, if severe, may trigger apoptosis. Therefore, we examined whether verrucarin A (VA) sensitize TRAIL-induced apoptosis in cancer cells by induction of ER stress. We first found that VA induces a major molecule of ER stress, CCAAT/enhancer binding protein homologous protein (CHOP)-dependent DR5 induction and subsequently increases TRAIL-induced cleavage of caspases and PARP in TRAIL-resistant Hep3B cells. Importantly, the transient knockdown using siRNA for CHOP abrogated VA-induced DR5 expression and attenuated TRAIL-induced apoptosis. Treatment with VA also increased the levels of phosphorylation of eukaryotic translation initiation factor-2α (eIF2α), which is a common cellular response of ER stress. Furthermore, salubrinal, a specific eIF2α phosphorylation-inducing agent, increased CHOP and DR5 expression in the presence of VA. In contrast, transfection of mutant-eIF2α significantly reversed VA-induced apoptosis with downregulation of CHOP-dependent DR5 expression. Therefore, VA-induced eIF2α phosphorylation seemed to be important for CHOP and DR5 upregulation and TRAIL-induced apoptosis. In addition, generation of reactive oxygen species (ROS) is an effector molecular in sensitization of VA-induced ER stress. We concluded that VA triggers TRAIL-induced apoptosis by eIF2α/CHOP-dependent DR5 induction via ROS generation.

Potent Toxic Macrocyclic Trichothecenes from the Marine-Derived Fungus Myrothecium verrucaria Hmp-F73

Activity-guided fractionation of a methanol extract from the culture broth of Myrothecium verrucaria Hmp-F73, a fungus associated with the sponge Hymeniacidon perleve, afforded six macrocyclic trichothecenes, verrucarin J (1), 8-hydroxyverrucarin J (2), verrucarin A (3), 8-acetoxyroridin H (4), isororidin E (5), and roridin E (6), along with trichoverrin B (7). All seven metabolites displayed potent toxicity to the brine shrimp ( Artemia salina). In addition, compounds 2, 3, and 6 showed weak phytotoxic activities against lettuce seeds. A preliminary structure-activity relationship of the metabolites is also discussed.

Conversion of deoxynivalenol to 3-acetyldeoxynivalenol in barley-derived fuel ethanol co-products with yeast expressing trichothecene 3-O-acetyltransferases

BACKGROUND

The trichothecene mycotoxin deoxynivalenol (DON) may be concentrated in distillers dried grains with solubles (DDGS; a co-product of fuel ethanol fermentation) when grain containing DON is used to produce fuel ethanol. Even low levels of DON (≤ 5 ppm) in DDGS sold as feed pose a significant threat to the health of monogastric animals. New and improved strategies to reduce DON in DDGS need to be developed and implemented to address this problem. Enzymes known as trichothecene 3-O-acetyltransferases convert DON to 3-acetyldeoxynivalenol (3ADON), and may reduce its toxicity in plants and animals.

RESULTS

Two Fusarium trichothecene 3-O-acetyltransferases (FgTRI101 and FfTRI201) were cloned and expressed in yeast (Saccharomyces cerevisiae) during a series of small-scale ethanol fermentations using barley (Hordeum vulgare). DON was concentrated 1.6 to 8.2 times in DDGS compared with the starting ground grain. During the fermentation process, FgTRI101 converted 9.2% to 55.3% of the DON to 3ADON, resulting in DDGS with reductions in DON and increases in 3ADON in the Virginia winter barley cultivars Eve, Thoroughbred and Price, and the experimental line VA06H-25. Analysis of barley mashes prepared from the barley line VA04B-125 showed that yeast expressing FfTRI201 were more effective at acetylating DON than those expressing FgTRI101; DON conversion for FfTRI201 ranged from 26.1% to 28.3%, whereas DON conversion for FgTRI101 ranged from 18.3% to 21.8% in VA04B-125 mashes. Ethanol yields were highest with the industrial yeast strain Ethanol Red®, which also consumed galactose when present in the mash.

CONCLUSIONS

This study demonstrates the potential of using yeast expressing a trichothecene 3-O-acetyltransferase to modify DON during commercial fuel ethanol fermentation.

A comparison of hepatic in vitro metabolism of T-2 toxin in rats, pigs, chickens, and carp

T-2 toxin, a highly toxic member of the type-A trichothecenes, is produced by various Fusarium moulds that can potentially affect human health. It is strongly cytotoxic for human hematopoietic progenitors. Alimentary toxic aleukia (ATA), a disease typically associated with human, is primarily induced by T-2 toxin. A comparison of the metabolism of T-2 toxin incubated with hepatocytes of rats, piglets, chickens, and the hepatic subcellular fractions (microsomes and cytosol) of piglets, chickens, rats, and carp (common carp and grass carp) was carried out. The activities of the recombinant pig CYP3A29 on the transformation of T-2 and HT-2 toxins were preliminary studied. Metabolites were identified by novel LC/MS-IT-TOF. Qualitative similarities and differences across the species were observed. In liver microsomes, HT-2 toxin, neosolaniol (NEO), 3'-OH-T-2, and 3'-OH-HT-2 were detected in rats, chickens, and pigs. 3'-OH-HT-2 and HT-2 toxin was not detectable in common carp and grass crap, respectively. Moreover, in liver microsomes, the hydroxyl metabolites accounted for the largest percentage in carp, whereas the hydrolysis product, HT-2 toxin, was the major one for the land animals. Only hydrolysis products such as NEO and HT-2 toxin were detected in hepatocytes. Recombinant pig CYP3A29 was able to convert T-2 and HT-2 toxins to high rates of 3'-OH-T-2 and 3'-OH-HT-2, respectively. Both CYP450 and carboxylesterase enzymes have been found to play a role in the metabolism of T-2 toxin. Metabolism of T-2 toxin across species produces a similar spectrum of metabolites. Preliminary metabolic studies of carp reveal that ester hydrolysis of T-2 toxin in carp may not play as important a role as is the case with land animals.

Accumulation kinetics of three scirpentriol-based toxins in oats inoculated in Vitro with isolates of Fusarium sporotrichioides and Fusarium poae

Autoclaved oats were inoculated with a strain of Fusarium sporotrichioides or Fusarium poae. Moisture content of oats after inoculation was at 38%, incubation took place in standing culture at 28 °C. The A-type trichothecenes, 4,15-diacetoxyscirpenol (4,15-DAS), 15-monoacetoxyscirpenol (15-MAS), and scirpentriol (SCIRP) were analyzed by GC/MS. For each strain, three culture flasks were harvested at 2-3 day intervals starting immediately after inoculation. Total incubation time was 42 days (F. poae) and 56 days (F. sporotrichioides). Following peak accumulation, 4,15-DAS decreased below the detection limit for both strains, 15-MAS decreased below this limit for the isolate of F. sporotrichioides, for the isolate of F. poae it decreased to a level markedly below the peak value. SCIRP, after having peaked, decreased to some extent for the strain F. sporotrichioides, with a significant (P = 0.0029) negative linear regression of toxin content against culture age during this period. The content of 15-MAS, and in part also of 4,15-DAS, decreased along with an increase of SCIRP. This sequential accumulation pattern suggests the successive induction of esterases deacetylating 4,15-DAS and 15-MAS, as well as of enzymes involved in the metabolization of the parent alcohol, SCIRP. The results may explain, at least in part, the somewhat higher incidence in naturally contaminated compounds reported in the literature for SCIRP compared to 4,15-DAS and 15-MAS.

Kinetics of satratoxin g tissue distribution and excretion following intranasal exposure in the mouse

Intranasal exposure of mice to satratoxin G (SG), a macrocyclic trichothecene produced by the indoor air mold Stachybotrys chartarum, selectively induces apoptosis in olfactory sensory neurons (OSNs) of the nose and brain. The purpose of this study was to measure the kinetics of distribution and clearance of SG in the mouse. Following intranasal instillation of female C57B16 mice with SG (500 microg/kg bw), the toxin was detectable from 5 to 60 min in blood and plasma, with the highest concentrations, 30 and 19 ng/ml, respectively, being observed at 5 min. SG clearance from plasma was rapid and followed single-compartment kinetics (t(1/2) = 20 min) and differed markedly from that of other tissues. SG concentrations were maximal at 15-30 min in nasal turbinates (480 ng/g), kidney (280 ng/g), lung (250 ng/g), spleen (200 ng/g), liver (140 ng/g), thymus (90 ng/g), heart (70 ng/g), olfactory bulb (14 ng/g), and brain (3 ng/g). The half-lives of SG in the nasal turbinate and thymus were 7.6 and 10.1 h, respectively, whereas in other organs, these ranged from 2.3 to 4.4 h. SG was detectable in feces and urine, but cumulative excretion over 5 days via these routes accounted for less than 0.3% of the total dose administered. Taken together, SG was rapidly taken up from the nose, distributed to tissues involved in respiratory, immune, and neuronal function, and subsequently cleared. However, a significant amount of the toxin was retained in the nasal turbinate, which might contribute to SG's capacity to evoke OSN death.

Structural elucidation of T-2 toxin thermal degradation products and investigations toward their occurrence in retail food

The stability of T-2 toxin under the conditions of baking or cooking was investigated using heating experiments with the model substances alpha-d-glucose, alpha-d-methyl-glucopyranosid, N-alpha-acetyl-l-lysine methyl ester, and N-alpha-acetyl-cysteine methyl ester. The reaction residue was screened for degradation products using gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography with evaporative light-scattering detection (HPLC-ELSD). Although T-2 toxin was degraded under all conditions, only heating of T-2 toxin with alpha-d-glucose produced a mixture of three degradation products, which were isolated and identified by MS and nuclear magnetic resonance (NMR) experiments. The reaction mechanism for the formation of the T-2 degradation products was elucidated by quantum chemical calculations. The relevance of these degradation products was investigated by baking experiments as well as the analysis of retail food samples. In cell-culture studies using immortalized human kidney epithelial (IHKE) cells, the T-2 degradation products were less cytotoxic (formazan dye cytotoxicity assay) compared to T-2 toxin.

Large-scale production of selected type A trichothecenes: the use of HT-2 toxin and T-2 triol as precursors for the synthesis of d 3-T-2 and d 3-HT-2 toxin

The type A trichothecenes T-2 and HT-2 toxins are toxic secondary metabolites produced by fungi of the Fusarium genus. Their occurrence in cereals, especially in oats, implies health risks for the consumer. Therefore, it is an important task to develop selective and sensitive methods for the analysis of T-2 and HT-2 toxins, and to undertake further studies on their stability and toxicity. Although most toxins are commercially available, their high prices are the limiting factor on the realization of these experiments. Thus, we developed a method for large-scale production of T-2 and HT-2 toxin as well as T-2 triol and T-2 tetraol. T-2 toxin was obtained in gram quantities by biosynthetic production with cultures of F. sporotrichioides. As HT-2 toxin was only formed as a by-product, and T-2 triol and T-2 tetraol were not generated, these compounds were produced by alkaline hydrolysis of T-2 toxin. Separation and isolation of crude toxins was achieved by fast centrifugal partition chromatography (FCPC), which is an efficient tool for the large-scale purification of natural products. Using this fast and yield effective technique, several hundred milligrams of HT-2 toxin, T-2 triol, and T-2 tetraol were obtained. Subsequent, HT-2 toxin and T-2 triol were used for the large-scale synthesis of isotope-labeled T-2 and HT-2 toxin, respectively. Using these standards, an isotope dilution-(ID)-HPLC-MS/MS method for the quantification of T-2 and HT-2 toxin in different matrices was developed.

Purification and comparative neurotoxicity of the trichothecenes satratoxin G and roridin L2 from Stachybotrys chartarum

Satratoxin G (SG), a macrocyclic trichothecene produced by Stachybotrys chartarum, induces apoptosis in cultured neuronal cells as well as nasal olfactory sensory neurons (OSN) in the nose and brain of mice exposed intranasally to this toxin. The purposes of this study were to (1) develop a facile method for production and purification of both SG and its putative biosynthetic precursor, roridin L2 (RL2), from S. chartarum cultures and (2) compare their relative neurotoxicity in vitro and in vivo. Stachybotrys chartarum 29-58-17 was cultured in Fernbach flasks on rice (5 x 10(5) spores/250 g rice) for 4 to 6 wk. Following extraction with acetonitrile, the extract was dried, dissolved in dichloromethane, and subjected to Michel-Miller silica-gel chromatography using a stepwise acetonitrile-dichloromethane gradient with SG and RL2 eluting in the 30 and 40% acetonitrile fractions, respectively. Purification of the two compounds was completed by C18 semipreparative reverse-phase liquid chromatography using an acetonitrile-water gradient, and purity was confirmed by electrospray ionization/collision-induced dissociation (ESI-CID) tandem mass spectroscopy. Although viability significantly decreased in PC-12 neuronal cells treated with 10 to 25 ng/ml of SG, RL2 at concentrations up to 1000 ng/ml was not toxic. Flow cytometry and agarose DNA fragmentation assays revealed that SG at 10 to 25 ng/ml induced apoptotic death in the PC-12 cells, while RL2 at concentrations up to 1000 ng/ml was without effect. In a similar fashion, intranasal exposure of mice (female B6C3F1) to SG at 100 microg/kg body weight (bw) induced marked OSN apoptosis and atrophy of the olfactory epithelium, whereas RL2 at the equivalent dose did not exhibit toxicity. Taken together, an optimized protocol for production and isolation of trichothecenes from S. chartarum cultures is described and further demonstrates that while the macrocyclic SG was neurotoxic in vitro and in vivo, its biosynthetic precursor, RL2, was nontoxic.

Trichothecenes in cereal grains

Trichothecenes are sesquiterpenoid mycotoxins associated with fusarium head blight (FHB) of cereals, with worldwide economic and health impacts. While various management strategies have been proposed to reduce the mycotoxin risk, breeding towards FHB-resistance appears to be the most effective means to manage the disease, and reduce trichothecene contamination of cereal-based food products. This review provides a brief summary of the trichothecene synthesis in Fusarium species, their toxicity in plants and humans, followed by the current methods of screening and breeding for resistance to FHB and trichothecene accumulation.

Plasma haptoglobin and immunoglobulins as diagnostic indicators of deoxynivalenol intoxication

This study aimed to discover potential biomarkers for dioxynivalenol (DON) intoxication. B6C3F1 male mice were orally exposed to 0.83, 2.5 and 7.5 mg/kg body weight (bw) DON for 8 days and the differential protein expressions in their blood plasma were determined by SELDI - Time-of-Flight/Mass Spectrometry (TOF/MS) and the immunoglobulins (Igs) G, A, M and E in the serum were investigated. 11.7 kDa protein was significantly highly expressed according to DON administration and this protein was purified by employing a methyl ceramic HyperD F column with using optimization buffer for adsorption and desorption. The purified protein was identified as a haptoglobin precursor by peptide mapping with using LC/Q-TOF/MS and MALDI-TOF/MS and this was confirmed by western blotting and ELISA. IgG and IgM in serum were decreased in a dose-dependent manner and IgA was decreased at 7.5 mg/kg bw DON administration, but the IgE level was not changed. To compare the expressions of haptoglobin and the Igs patterns between aflatoxin B1 (AFB1), zearalenone (ZEA) and DON intoxications, rats were orally administered with AFB1 1.0, ZEA 240 and DON 7.5 mg/kg bw for 8 days. Haptoglobin was increased only at DON 7.5 mg/kg bw, while it was slightly decreased at ZEA 240 mg/kg bw and it was not detected at all at AFB1 1.0 mg/kg bw. IgG and IgA were decreased by DON, but IgG, IgA, IgM and IgE were all increased by AFB1. No changes were observed by ZEA administration. These results show that plasma haptoglobin could be a diagnostic biomarker for DON intoxication when this is combined with examining the serum Igs.

Changes in the spleen and liver of pregnant sows and full-term piglets after feeding diets naturally contaminated with deoxynivalenol and zearalenone

Wheat contaminated naturally with the Fusarium toxins deoxynivalenol (DON) and zearalenone (ZON) was fed to pregnant Landrace sows for 35days. On day 110, caesarean section was carried out, the offspring were killed immediately after birth, and their livers and spleens examined. At necropsy there were no macroscopic lesions observed in any organ of either sows or piglets. Histopathological evaluation of tissues from sows of the treated group revealed changes in liver and spleen tissues, whereas no significant changes were observed in these tissues in their piglets. Liver damage, as measured by prominent elevated transaminase activities, was not detected in the serum of the sows. In pregnant sows there were individual variations in sensitivity to the Fusarium toxins. In conclusion, it can be assumed that there are no adverse effects on the liver and spleen of full-term piglets when their mothers consumed diets containing up to 9570 and 358mug DON/ZON per kg diet.

Stachybotrys chartarum, trichothecene mycotoxins, and damp building-related illness: new insights into a public health enigma

Damp building-related illnesses (DBRI) include a myriad of respiratory, immunologic, and neurologic symptoms that are sometimes etiologically linked to aberrant indoor growth of the toxic black mold, Stachybotrys chartarum. Although supportive evidence for such linkages is limited, there are exciting new findings about this enigmatic organism relative to its environmental dissemination, novel bioactive components, unique cellular targets, and molecular mechanisms of action which provide insight into the S. chartarum's potential to evoke allergic sensitization, inflammation, and cytotoxicity in the upper and lower respiratory tracts. Macrocyclic trichothecene mycotoxins, produced by one chemotype of this fungus, are potent translational inhibitors and stress kinase activators that appear to be a critical underlying cause for a number of adverse effects. Notably, these toxins form covalent protein adducts in vitro and in vivo and, furthermore, cause neurotoxicity and inflammation in the nose and brain of the mouse. A second S. chartarum chemotype has recently been shown to produce atranones-mycotoxins that can induce pulmonary inflammation. Other biologically active products of this fungus that might contribute to pathophysiologic effects include proteinases, hemolysins, beta-glucan, and spirocyclic drimanes. Solving the enigma of whether Stachybotrys inhalation indeed contributes to DBRI will require studies of the pathophysiologic effects of low dose chronic exposure to well-characterized, standardized preparations of S. chartarum spores and mycelial fragments, and, coexposures with other environmental cofactors. Such studies must be linked to improved assessments of human exposure to this fungus and its bioactive constituents in indoor air using both state-of-the-art sampling/analytical methods and relevant biomarkers.