Metabolic fate of T-2 toxin in a lactating cow

Integrated of multi-omics and molecular docking reveal PHGDH, PSAT1 and PSPH in the serine synthetic pathway as potential targets of T-2 toxin exposure in pig intestinal tract

T-2 toxin (T-2) with a molecular weight of 466.52 g/mol is an inevitable mycotoxin in food products and feeds, posing a significant threat to human and animal health. However, the underlying molecular mechanisms of the cytotoxic effects of T-2 exposure on porcine intestinal epithelial cells (IPEC-J2) remain unclear. Here, we investigated the cytotoxic effects of T-2 exposure on IPEC-J2 through the detection of cell viability, cell morphology, mitochondrial membrane potential, ROS, apoptosis and autophagy. Further transcriptomic and proteomic analyses of IPEC-J2 upon T-2 exposure were performed by using RNA-seq and TMT techniques. A total of 546 differential expressed genes (DEGs) and 269 differentially expressed proteins (DEPs) were detected. Among these, 24 common DEGs/DEPs were involved in IPEC-J2 upon T-2 exposure. Interestingly, molecular docking analysis revealed potential interactions between T-2 and three key enzymes (PHGDP, PSAT1, and PSPH) in the serine biosynthesis pathway. Besides, further experimental showed that PSAT1 knockdown exacerbated T-2-induced oxidative damage. Together, our findings indicated that the serine biosynthesis pathway including PHGDP, PSAT1, PSPH genes probably acts critical roles in the regulation of T-2-induced cell damage. This study provided new insights into the global molecular effects of T-2 exposure and identified the serine biosynthesis pathway as molecular targets and potential treatment strategies against T-2.

Regulated and Emerging Mycotoxins in Bulk Raw Milk: What Is the Human Risk?

Mycotoxins are abiotic hazards whose contamination occurs at the pre- and post-harvest stages of the maize value chain, with animal exposure through contaminated feed leading to their excretion into milk. Currently, only aflatoxin M1 is regulated in milk products. Since feed materials and complete feed present a multi-mycotoxin composition and are the main mycotoxin source into milk, it is important to recognize the occurrence of multiple toxins and their co-occurrence in this highly consumed food product. The aim of this study was to determine the content of regulated and emerging mycotoxins in milk samples, which allowed for evaluating the occurrence and co-occurrence patterns of different mycotoxins known to contaminate feed materials and complete animal feed. Human exposure considering the occurrence patterns obtained was also estimated. Aflatoxins, fumonisins, zearalenone, and emerging mycotoxins were among the mycotoxins found to be present in the 100 samples analyzed. Concentrations ranged from 0.006 to 16.3 μg L-1, with no sample exceeding the AFM1 maximum level. Though several mycotoxins were detected, no exceeding values were observed considering the TDI or PMTDI. It can be concluded that the observed exposure does not pose a health risk to milk consumers, though it is important to recognize vulnerable age groups.

Effects of maternal T-2 toxin exposure on microorganisms and intestinal barrier function in young mice

T-2 toxin belongs to the trichothecenes group A compound, mainly produced by Fusarium fungi. It has been shown that T-2 toxin could cross the placental barrier and breast milk, thus endangering the health of offspring. The present study aimed to explore the effects of maternal T-2 toxin exposure on the integrity of the intestinal barrier and the intestinal microflora of young mice. From late pregnancy (GD 14) to lactation (LD 21), pregnant mice were given T-2 toxin daily at 0, 0.005, or 0.05 mg T-2 toxin/kg BW. Postnatal day 21 (PND21), PND28, and PND56 young mice were chosen as objects to detect the influences of maternal T-2 toxin exposure to mice on the offspring. The results showed that maternal exposure to T-2 toxin disturbed the balance of the intestinal microbial flora of the young mice. Villous adhesions and fusion of ileum were observed in T-2-treated groups. In addition, supplementation of T-2 toxin significantly decreased the gene expressions of Claudin 1, Occludin, Tjp1, Il10, Il6, and Tnf in PND 21. However, in PND 28, the expressions of Tnf were significantly increased. The expressions of Claudin 1, Occludin, Tjp1, Il10, Il6 and Tnf were significantly increased after T-2 toxin treatment in PND 56. These results suggested that maternal exposure to T-2 toxin has negative influences on the intestine of young mice, which may be due to the alterations of microbial composition.

T-2 toxin and its cardiotoxicity: New insights on the molecular mechanisms and therapeutic implications

T-2 toxin is one of the most toxic and common trichothecene mycotoxins, and can cause various cardiovascular diseases. In this review, we summarized the current knowledge-base and challenges as it relates to T-2 toxin related cardiotoxicity. The molecular mechanisms and potential treatment approaches were also discussed. Pathologically, T-2 toxin-induced cardiac toxicity is characterized by cell injury and death in cardiomyocyte, increased capillary permeability, necrosis of cardiomyocyte, hemorrhage, and the infiltration of inflammatory cells in the heart. T-2 toxin exposure can cause cardiac fibrosis and finally lead to cardiac dysfunction. Mechanistically, T-2 toxin exposure-induced cardiac damage involves the production of ROS, mitochondrial dysfunction, peroxisome proliferator-activated receptor-gamma (PPAR-γ) signaling pathway, endoplasmic reticulum (ER stress), transforming growth factor beta 1 (TGF-β1)/smad family member 2/3 (Smad2/3) signaling pathway, and autophagy and inflammatory responses. Antioxidant supplementation (e.g., catalase, vitamin C, and selenium), induction of autophagy (e.g., rapamycin), blockade of inflammatory signaling (e.g., methylprednisolone) or treatment with PPAR-γ agonists (e.g., pioglitazone) may provide protective effects against these detrimental cardiac effects caused by T-2 toxin. We believe that our review provides new insights in understanding T-2 toxin exposure-induced cardiotoxicity and fuels effective prevention and treatment strategies against this important food-borne toxin-induced health problems.

Toxicokinetics of HT-2 Toxin in Rats and Its Metabolic Profile in Livestock and Human Liver Microsomes

The lack of information on HT-2 toxin leads to inaccurate hazard evaluations. In the present study, toxicokinetic studies of HT-2 toxin were investigated following intravenous (iv) and oral administration to rats at dosages of 1.0 mg per kilogram of body weight. After oral administration, HT-2 toxin was not detected in plasma, whereas its hydroxylated metabolite, 3'-OH HT-2 was identified. Following iv administration, HT-2 toxin; its 3'-hydroxylated product; and its glucuronide derivative, 3-GlcA HT-2, were observed in plasma, and the glucuronide conjugate was the predominant metabolite. To explore the missing HT-2 toxin in plasma, metabolic studies of HT-2 toxin in liver microsomes were conducted. Consequently, eight phase I and three phase II metabolites were identified. Hydroxylation, hydrolysis, and glucuronidation were the main metabolic pathways, among which hydroxylation was the predominant one, mediated by 3A4, a cytochrome P450 enzyme. Additionally, significant interspecies metabolic differences were observed.

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.

Revisión: Implicaciones toxicológicas y nutricionales de la toxina T-2 / Review: Toxicological and nutritional implications of T-2 toxin

Trichothecenes are mycotoxins produced by species of the genus Fusarium. These toxins are associated with health problems in humans and animals. The most common trichothecenes in cereals are deoxynivalenol, HT-2 toxin, diacetoxyscirpenol, nivalenol, neosolaniol and T-2 toxin; the latter is the most widely studied because it is easy to produce in the laboratory. The effects of T-2 toxicosis include dermatonecrosis, reduced body weight and efficiency of food utilization, severe diarrhoea, haemorrhage, necrosis of the upper alimentary tract, anaemia, immuno suppression ; and in birds, poor feathering. This paper reviews the latest information about the occurrence, chemical characteristics, toxicity, metabolic alterations, biotransformation and detoxifi cation methods of the T-2 toxin.

Chemical, physical and technological properties of milk as affected by the mycotoxin load of dairy herds

Abstract. The aim of the study was to determine the impacts of different levels of mycotoxin load of Czech dairy herds on the larger scale of the milk indicators including milk physical and technological properties. During three subsequent years individual milk samples (IMSs) were collected from four herds of Czech Fleckvieh (C) and from four herds of Holstein cows (H). The IMSs were collected regularly twice in summer and twice in winter, resulting in a total of 936 IMSs. The feeding rations consisted mainly of conserved roughage and supplemental mixtures according to milk yield and standard demands. Samples of feedstuffs were collected at the same time as IMSs and were analysed for content of deoxynivalenol (DON), fumonisins (FUM), zearalenone (ZEA), aflatoxin (AFL), and T-2 toxin using enzyme-linked immunosorbent assay (ELISA) methods. Based on the mycotoxin load, herds were divided into three groups – Load 1 (negligible, n =  36), Load 2 (low, n =  192), and Load 3 (medium, n =  708). All feedstuff samples were positive for at least one mycotoxin. The most frequently occurring mycotoxins were FUM, DON, and ZEA. Relatively high incidence of AFL (56 % positive samples) was observed. The following milk indicators were influenced by the mycotoxin load of herds: fat, acetone (Ac), log Ac, pH, electric conductivity, alcohol stability, curds quality, curd firmness, whey volume, whey protein, non-protein nitrogen (NPN), urea N in NPN, fat ∕ crude protein ratio, and casein numbers on crude and true protein basis, respectively (P < 0.05). The overall level of mycotoxin load was relatively low, with no clear effect on milk characteristics.

Review on Mycotoxin Issues in Ruminants: Occurrence in Forages, Effects of Mycotoxin Ingestion on Health Status and Animal Performance and Practical Strategies to Counteract Their Negative Effects

Ruminant diets include cereals, protein feeds, their by-products as well as hay and grass, grass/legume, whole-crop maize, small grain or sorghum silages. Furthermore, ruminants are annually or seasonally fed with grazed forage in many parts of the World. All these forages could be contaminated by several exometabolites of mycotoxigenic fungi that increase and diversify the risk of mycotoxin exposure in ruminants compared to swine and poultry that have less varied diets. Evidence suggests the greatest exposure for ruminants to some regulated mycotoxins (aflatoxins, trichothecenes, ochratoxin A, fumonisins and zearalenone) and to many other secondary metabolites produced by different species of Alternaria spp. (e.g., AAL toxins, alternariols, tenuazonic acid or 4Z-infectopyrone), Aspergillus flavus (e.g., kojic acid, cyclopiazonic acid or β-nitropropionic acid), Aspergillus fuminatus (e.g., gliotoxin, agroclavine, festuclavines or fumagillin), Penicillium roqueforti and P. paneum (e.g., mycophenolic acid, roquefortines, PR toxin or marcfortines) or Monascus ruber (citrinin and monacolins) could be mainly related to forage contamination. This review includes the knowledge of mycotoxin occurrence reported in the last 15 years, with special emphasis on mycotoxins detected in forages, and animal toxicological issues due to their ingestion. Strategies for preventing the problem of mycotoxin feed contamination under farm conditions are discussed.

Toxicopathological alterations induced by high dose dietary T-2 mycotoxin and its residue detection in Wistar rats

T-2 toxin is one of the most potent cytotoxic and food-borne mycotoxins. Most experimental studies on the T-2 toxin have been performed at extremely low doses (ppb level). However, several field reports of contaminated feed have shown concentration of T-2 toxin to be as high as ≥20 ppm. Therefore, the impact of high dose T-2 toxin (20 ppm) after subacute exposure was investigated in an experimental setup with respect to growth performance, oxidative stress, and detailed pathomorphology in young male Wistar rats. Furthermore, to see the effect of such a high dose on the accumulation of T-2 toxin, its residues in various organs were quantified by high-performance thin-layer chromatography (HPTLC). Apart from obvious clinical toxicosis, rats in the toxin-fed group showed significant hemato-biochemical alterations and increased levels of biological markers of oxidative stress with concomitant decrease in levels of serum and tissue catalase and superoxide dismutase. These alterations were strongly supported by histopathological changes, such as hyperkeratosis and hyperplasia of the squamous gastric mucosa, oxidative damage to hepatocytes, atrophy of the thymus and spleen, and overall decrease in the spermatogenic activity of testes. An economical, simple, reliable, and quick method for the detection and quantification of T-2 toxin residues by HPTLC is also reported here. No residual T-2 toxin was detected in any of the organs tested, suggesting that T-2 toxin does not accumulate in tissues even at such a high exposure level.

Metabolic pathways of T-2 toxin in in vivo and in vitro systems of Wistar rats

In the present study, metabolites of T-2 toxin in in vivo and in vitro systems of Wistar rats were identified and elucidated by ultraperformance liquid chromatography-quadrupole/time-of-flight tandem mass spectrometry (UPLC-Q/TOF-MS). Expected and unexpected metabolites were detected by Metabolynx(XS) software, which could automatically compare MS(E) data from the sample and control. A total of 19 metabolites of T-2 toxin were identified in this research, 9 of them being novel, which were 15-deacetyl-T-2, 3'-OH-15-deacetyl-T-2, 3',7-dihydroxy-T-2, isomer of 3',7-dihydroxy-T-2, 7-OH-HT-2, isomer of 7-OH-HT-2, de-epoxy-3',7-dihydroxy-HT-2, 9-OH-T-2, and 3',9-dihydroxy-T-2. The results showed that the main metabolic pathways of T-2 toxin were hydrolysis, hydroxylation, and de-epoxidation. In addition, the results also revealed one novel metabolic pathway of T-2 toxin, hydroxylation at C-9 position, which was demonstrated by the metabolites 9-OH-T-2 and 3',9-dihydroxy-T-2. In addition, hydroxylation at C-9 of T-2 toxin was also generated in in vitro of liver systems. Interestingly, several metabolites of hydroxylation at C-7 of T-2 toxin were also detected in in vivo male Wistar rats, but they were not found in in vivo female rats and in in vitro systems of Wistar rats.

Identification and apoptotic potential of T-2 toxin metabolites in human cells

The mycotoxin T-2 toxin, produced by various Fusarium species, is a widespread contaminant of grain and grain products. Knowledge about its toxicity and metabolism in the human body is crucial for any risk assessment as T-2 toxin can be detected in processed and unprocessed food samples. Cell culture studies using cells of human origin represent a potent model system to study the metabolic fate of T-2 toxin as well as the cytotoxicity in vitro. In this study the metabolism of T-2 toxin was analyzed in a cell line derived from human colon carcinoma cells (HT-29) and primary human renal proximal tubule epithelial cells (RPTEC) using high-performance liquid chromatography coupled with Fourier transformation mass spectrometry (HPLC-FTMS). Both cell types metabolized T-2 toxin to a variety of compounds. Furthermore, cell cycle analysis in RPTEC proved the apoptotic effect of T-2 toxin and its metabolites HT-2 toxin and neosolaniol in micromolar concentrations.

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.

T-2 toxin, a trichothecene mycotoxin: review of toxicity, metabolism, and analytical methods

This review focuses on the toxicity and metabolism of T-2 toxin and analytical methods used for the determination of T-2 toxin. Among the naturally occurring trichothecenes in food and feed, T-2 toxin is a cytotoxic fungal secondary metabolite produced by various species of Fusarium. Following ingestion, T-2 toxin causes acute and chronic toxicity and induces apoptosis in the immune system and fetal tissues. T-2 toxin is usually metabolized and eliminated after ingestion, yielding more than 20 metabolites. Consequently, there is a possibility of human consumption of animal products contaminated with T-2 toxin and its metabolites. Several methods for the determination of T-2 toxin based on traditional chromatographic, immunoassay, or mass spectroscopy techniques are described. This review will contribute to a better understanding of T-2 toxin exposure in animals and humans and T-2 toxin metabolism, toxicity, and analytical methods, which may be useful in risk assessment and control of T-2 toxin exposure.

Estimating the transfer of contaminants in animal feedstuffs to livestock tissues, milk and eggs: a review

Literature studies on the transfer from livestock feed of residues of organic contaminants, metals and mycotoxins to edible livestock commodities have been reviewed. This review focuses on contaminants relevant to risks assessment of livestock feeds, especially those contaminants for which regulatory standards have been established. Those involved in the supply of livestock feed need to be aware of maximum levels for various contaminants in food and develop strategies to ensure food derived from livestock complies. An impediment to profiling feed ingredients has been the lack of accessible information on the transfer of residues from feed to tissues, milk and eggs derived from exposed livestock. Transfer factors are summarised for 72 contaminants for cattle, sheep, goats, pigs and poultry and can be used in the first tiers of risk assessment to identify contaminant and feed ingredient combinations that require management.

Biomonitoring of Fusarium spp. Mycotoxins: Perspectives for an Individual Exposure Assessment Tool

Fusarium species are probably the most prevalent toxin-producing fungi of the northern temperate regions and are commonly found on cereals grown in the temperate regions of America, Europe and Asia. Among the toxins formed by Fusarium we find trichothecenes of the A-type or B-type, zearalenone, fumonisins or nivalenol. The current exposure assessment consists of the qualitative and/or quantitative evaluation based on the knowledge of the mycotoxin occurrence in the food and the dietary habits of the population. This process permits quantifying the mycotoxin dietary intake through deterministic or probabilistic methods. Although these methods are suitable to assess the exposure of populations to contaminants and to identify risk groups, they are not recommended to evaluate the individual exposition, due to a low accuracy and sensitivity. On the contrary, the use of biochemical indicators has been proposed as a suitable method to assess individual exposure to contaminants. In this work, several techniques to biomonitor the exposure to fumonisins, deoxynivalenol, zearalenone or T-2 toxin have been reviewed.

Placental and milk transmission of trichothecene mycotoxins, nivalenol and fusarenon-X, in mice

In order to investigate the transfer of nivalenol (NIV) and fusarenon-X (FX) from pregnant to fetal mice and from lactating to suckling mice, (3)H-NIV or (3)H-FX was given p.o. to pregnant or lactating mice. Radioactivity was detected in the whole fetal tissues as well as the fetal liver and kidney, the levels being comparable to those of the maternal tissues. Radioactivity was also detected in the milk, and liver and kidney tissues taken from suckling mice of both (3)H-NIV or (3)H-FX administered dams. HPLC analysis of fetal tissue homogenates from non-labeled FX- or NIV-administered pregnant mice revealed transmission of NIV to fetuses after administration of either toxin. In mice given the non-labeled FX, major and minor peaks of NIV and FX on HPLC were noted in suckling pup tissue homogenates. The results demonstrate that NIV transfers in unchanged form to fetal or suckling mice via placenta or milk, respectively, and that FX does so mainly after being metabolized to NIV in maternal body.

Absence of detectable levels of the cyanobacterial toxin (microcystin-LR) carry-over into milk

The potential for the carry-over of the cyanobacterial toxin, microcystin-LR, from feed to milk was assessed using four Holstein-Friesian cows in a 4 week feeding trial. Two cows were used as control and the other two dosed daily at increasing weekly concentrations of microcystins from zero to a maximum dosage of 13 microg toxin kg x (-1) d x (-1) (or 7.4 mg toxin day(-1)). The absence of any deviation from the control in terms of physiological response and plasma indicators (total bilirubin, gamma-glutamyl transpeptidase and alkaline phosphatase) suggests that the microcystin-LR dosage did not have a detrimental effect on cattle liver function or milk yield during the course of the study. While the milk production did decrease over the period of the trial, no difference was observed between control and dosed cattle. Protein phosphatase inhibition assays were successfully used to determine the presence of microcystin-LR in prepared milk samples with an average recovery of 88% for samples spiked with 0.6 microg x l(-1) microcystin-LR. The level of microcystin-LR in all milk samples during the trial was less than 0.2 microg x l(-1). This suggests that after digestion, microcystin--LR is either not present in milk or sufficiently modified to render it non-toxic.

Identification of mycotoxins in keratomycosis-derived Fusarium isolates by gas chromatography-mass spectrometry

The production of mycotoxins from Fusarium species has been demonstrated in isolates cultured from patients suffering from keratomycosis. The method employed a combination of thin-layer chromatography directly performed on gel plugs taken from the growth medium, cartridge column chromatography, silylation and gas chromatography on a non-polar stationary phase capillary column linked to mass spectrometry. The sensitivities of detection obtained for a signal-to-noise ratio of 33:1, were 200 pg for single stage GC-MS and 20 pg using tandem GC-MS-MS. Two mycotoxins, diacetoxyscirpenol and T-2 toxin were identified in three cultures.

Production of [14C]fumonisin B1 by Fusarium moniliforme MRC 826 in corn cultures

Kinetics of growth and fumonisin production by Fusarium moniliforme MRC 826 in corn "patty" cultures were investigated, and a technique was developed for the production of [14C]fumonisin B1 ([14C]FB1) by using L-[methyl-14C]methionine as the precursor. A significant (P < 0.01) correlation exists between fungal growth and FB1 (r = 0.89) and FB2 (r = 0.87) production in corn patties, beginning after 2 days and reaching the stationary phase after 14 days of incubation. [14C]FB1 was produced by adding L-[methyl-14C]methionine daily to cultures during the logarithmic phase of production. Incorporation of the isotope occurred at C-21 and C-22 of the fumonism molecule and was enhanced in the presence of unlabeled L-methionine. Although the concentration of exogenous unlabeled methionine is critical for incorporation of the 14C label, optimum incorporation was achieved by adding 50 mg of unlabeled L-methionine and 200 mu Ci of L-[methyl-14C]methionine to a corn patty (30 g) over a period of 9 days, yielding [14C]FB1 with a specific activity of 36 mu Ci/mmol.

Chromatographic methods as tools in the field of mycotoxins

Achievements in the applications of chromatographic techniques in mycotoxicology are reviewed. Historically, column chromatography (CC) and paper chromatography (PC) were applied first, followed by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC) and gas chromatography (GC). Although PC techniques are no longer used in the analysis of mycotoxins, selected applications of PC are included to underline historical continuity. The most important achievements published from 1980 onwards are described. They include clean-up methods, TLC, CC, HPLC and GC of mycotoxins in environmental samples, foods, feeds, body fluids and in studies on biosynthesis and biotransformations of mycotoxins. Advantages and disadvantages of chromatographic techniques used in mycotoxicology are also evaluated.

Drug and chemical residues in livestock

The problem of drug and chemical residues in foods of animal origin has become increasingly important to the entire livestock industry as growing consumer health concerns continue to erode the demand for these products. Although nearly 90 per cent of all drugs approved for use in livestock are available for over-the-counter sales, in the public's view, it is only the veterinarian who administers drugs to animals and who, therefore, is responsible for all drug residues in food. Congress has responded to these consumer concerns by applying increased pressure on the FDA to restrict the extra-label use of drugs by veterinarians. The veterinary profession now finds itself in a position in which it must reexamine its current drug-use policies and strive to develop policies that are more responsible to the consumer, both in appearance and substance.

Effects of T-2 mycotoxin on gastrointestinal tissues: a review of in vivo and in vitro models

T-2 mycotoxin, a trichothecene, is the principal toxic component of Fusarium sp. Agricultural products and food are frequently contaminated with this toxin. Various animal models have been used to determine its metabolic fate, rate of excretion, and distribution. A modulation effect on cell-mediated immunity and alterations in gastrointestinal propulsion have been demonstrated. The toxin has been shown to produce some similar pathologic alterations in various animal species studied. The consistent alteration appears to mainly affect mitotic cells of the gastrointestinal tract and the lymphoid system. A host of bioassay systems are now being used as alternative methods to the use of animals for testing of the mycotoxin. These tests may accurately assess and define the role of the subject-toxin interactions following consumption of T-2 mycotoxin contaminated food sources. T-2 mycotoxin, as observed above with in vivo and in vitro models, promotes a chemically-induced change in structure and function of affected gastrointestinal cells from a transient and reversible aberration in a single enzymatic reaction to cell death. Regardless of the end point measured, the toxic response brought about in cells appears to involve the interactions of virtually all subcellular processes--membrane transport and permeability, chemical metabolism, DNA function, and energy production/expenditure--as cells attempt to maintain their functional integrity while disposing of the toxicant. The variation in the quality of the toxic response with dose suggests that more cellular processes are perturbed as the chemical dose is increased.

The role of intestinal microflora in the metabolism of trichothecene mycotoxins

The role of faecal and intestinal microflora on the metabolism of trichothecene mycotoxins was examined in this study. Suspensions of microflora obtained from the faeces of horses, cattle, dogs, rats, swine and chickens were incubated anaerobically with the trichothecene mycotoxin, diacetoxyscirpenol (DAS). Micro-organisms from rats, cattle and swine completely biotransformed DAS, primarily to the deacylated deepoxidation products, deepoxy monoacetoxyscirpenol (DE MAS) and deepoxy scirpentriol (DE SCP). By contrast, faecal microflora from chickens, horses and dogs failed to reduce the epoxide group in DAS and yielded only the deacylation products, monoacetoxyscirpenol (MAS) and scirpentriol (SCP), in addition to unmetabolized parent compound. Intestinal microflora obtained from rats completely biotransformed DAS to DE MAS, DE SCP and SCP; and T-2 toxin to the deepoxy products, deepoxy HT-2 (DE HT-2) and deepoxy T-2 triol (DE TRIOL). Rat intestinal microflora also biotransformed the polar trichothecenes, T-2 tetraol and scirpentriol, to their corresponding deepoxy analogues. Deepoxy T-2 toxin (DE T-2) was synthesized from T-2 toxin and demonstrated to be 400 times less toxic than T-2 toxin in the rat skin irritation bioassay and non-toxic to mice given 60 mg/kg ip, demonstrating that epoxide reduction is a significant single step detoxification reaction for trichothecene mycotoxins.

T-2 toxin and diacetoxyscirpenol metabolism by Baccharis spp

Hybrids resulting from crosses between Baccharis sarothroides and B. pilularis (FS1), B. sarothroides (FS2) and B. megapotamica (FS3) were tested for their tolerance to trichothecenes as well as their ability to metabolize the toxins. B. sarothroides (desert broom) was placed in an aqueous solution containing 500 ppm of T-2 toxin and showed visible signs of toxicity on the twigs at 21 h after exposure but not at 6 h, indicating some resistance. Samples of the twigs harvested 6 and 21 h after treatment contained, respectively, T-2 (0.03 and 2.2 micrograms/g), HT-2 (0.09 and 7.6 micrograms/g), and T-2-tetraol (2.1 and 2.6 micrograms/g). The hybrid FS1 showed no signs of toxicity 6 h after treatment, and its twigs contained T-2 (0.8 micrograms/g), HT-2 (10.2 micrograms/g), and T-2-tetraol (10.8 micrograms/g). The leaves at 6 h contained 0.5 micrograms of T-2, 1.7 micrograms of HT-2, 0.01 microgram of 3'-hydroxy-HT-2, and 41 micrograms of T-2-tetraol per g. At 21 h, toxic signs were apparent and the twigs contained T-2 (39 micrograms/g), HT-2 (62 micrograms/g), 3'-hydroxy-HT-2 (0.8 microgram/g), and T-2-tetraol (22 micrograms/g).(ABSTRACT TRUNCATED AT 250 WORDS)

Uptake and metabolism of T-2 toxin in relation to its cytotoxicity in lymphoid cells

The sensitivity of lymphoid cells to the cytotoxic effects of T-2 toxin (T-2) varies according to their degree of differentiation. To understand the mechanisms of these variations, the uptake and the metabolism of T-2 in susceptible (human lymphoma Daudi and phytohaemagglutinin-stimulated murine lymphocytes) and resistant (human leukaemia KE37 and REH) cells were studied in culture. When cells were incubated with [3H]T-2 a significant increase in the quantity of T-2 associated with the cell occurred during the first 30 min, this increased further from 10-16 hr, and decreased after 24 hr. Daudi and REH cells took up 20 and 3% of the T-2 present in the medium, respectively. Metabolites, extracted from the culture medium and from cells, were analysed by the thin-layer chromatography. The products were identified by comparison with standards for T-2 tetraol, T-2 triol, HT-2 toxin, neosolaniol and T-2. Qualitatively, similar metabolic pathways were found in all cells examined. The presence of these metabolites demonstrated that T-2 was taken up by these cells. A correlation existed between the relative sensitivities of the cells toward T-2 and the amount of intracellular T-2 and/or metabolites. It is thought that differences in the kinetics of uptake and processing of T-2 account for the known differences in cellular sensitivities to the toxin.

Metabolism of T-2 toxin in vascularly autoperfused jejunal loops of rats

The intestinal metabolism of T-2 toxin, a major trichothecene mycotoxin, was investigated in rats using the method of the vascularly autoperfused jejunal loop in situ. Tritium-labeled T-2 toxin was injected into the tied-off intestinal segments at a dose of 5 or 500 nmol, respectively. T-2 toxin and its metabolites in the blood draining from the jejunal loops, in the intestinal lumen, and in the intestinal tissue were determined by HPLC and GLC-MS. There was an extensive metabolic degradation of T-2 toxin, the metabolite pattern being similar for the two dosage levels. During the experimental period of 50 min only some 2% of the total dose appeared in the effluent plasma as unchanged T-2 toxin. Likewise at the end of the experiments unchanged T-2 toxin in the intestinal lumen and tissue was present in minute amounts only (less than 1% of the dose). HT-2 toxin was the main metabolite. About 25% of the total radioactivity administered appeared in the effluent plasma as HT-2 toxin, 18% in the lumen and 10% in the tissue. 3'-OH-HT-2 toxin accounted for 4-7% (effluent plasma), 5% (lumen), and 2% (tissue) of the total dose. Furthermore small amounts (less than 2% of the dose) of 3'-OH-T-2 toxin, T-2 tetraol, and 4-deacetylneosolaniol were found. No glucuronide or sulfate conjugates could be detected. In the jejunal segments which had been exposed to the 5-nmol dose only minimal morphological alterations were observed. On the other hand, in jejunal segments exposed to the high dose marked tissue damage was present. Nevertheless the gut tissue retained its ability to metabolize T-2 toxin. From the present results it is concluded that T-2 toxin is subject to a marked presystemic first pass effect after oral ingestion in vivo.

Pharmacokinetics and protein binding of trichothecene mycotoxins, T-2 toxin and HT-2 toxin, in dogs

The pharmacokinetics of T-2 toxin, following i.m. and i.v. administration (0.4 mg/kg), were investigated in five dogs. Following i.m. administration, the mean pharmacokinetic parameters for T-2 and HT-2 toxins were, respectively: apparent half-life 21 +/- 5 and 73 +/- 7 min; peak plasma concentration 182 +/- 42 and 74 +/- 16 ng/ml; time to reach peak plasma concentration 9.4 +/- 6.4 and 49 +/- 11 min. Mean residence time calculation, using moment analysis, showed that the terminal slope of T-2 toxin plasma levels following i.m. administration corresponds to the absorption rate constant of the toxin due to the flip-flop phenomenon. T-2 toxin was completely absorbed following i.m. administration and its absolute bioavailability was 1.17 +/- 0.25. A plasma protein binding study showed that in a concentration range of 70-500 ng/ml, T-2 and HT-2 toxins have a mean free fraction of 30.6 +/- 3.1% and 32.6 +/- 3.6% with no concentration dependency. At physiological conditions (temperature and pH), both T-2 and HT-2 toxins were unstable in whole blood and their in vitro stability half-lives were 6.9 and 0.84 hr, respectively. However, under similar conditions, these toxins were stable in plasma for 7 hr. Their instability in whole blood, therefore, may be related to enzymes present in the blood cells.

Comparative in vitro metabolism of T-2 toxin by hepatic microsomes prepared from phenobarbital-induced or control rats, mice, rabbits and chickens

Hepatic microsomes were prepared from phenobarbital (PB)-treated and control rats, mice, rabbits and chickens and were incubated with T-2 toxin (100 micrograms/mg microsomal protein). Additional microsomes from PB-induced animals were incubated with T-2 toxin and the esterase inhibitor paraoxon (PA) at 2.5 nmol/mg microsomal protein. The major metabolite in microsomal preparations from both control and PB-induced rats, rabbits and mice was HT-2. In microsomes isolated from PB-treated chickens, 3'-hydroxy T-2 was the major metabolite, but 30 and 79% of the added T-2 toxin remained unmetabolized at 60 min in incubations from PB-induced and control birds, respectively. The percentage of hydroxylated metabolites formed in the microsomal preparations of the four species studied was significantly increased following PB treatment compared with the non-treated controls. The addition of PA to the incubation system effectively inhibited the hydrolysis of the ester groups in T-2 toxin, resulting in 1.4- and 1.25-fold increases in the percentage of 3'-hydroxy T-2 in the mouse and rat microsomal samples, respectively. In the rabbit microsomal preparations, 3'-hydroxy T-2, which was not detected in the absence of PA, represented 11% of the added substrate in the PB/PA incubation samples. Addition of PA did not cause a significant change in the amount of 3'-hydroxy T-2 formed in chicken microsomal samples, since competition between hydrolysis and hydroxylation pathways for the T-2 toxin substrate was not an important factor in this species. Two new metabolites, designated RLM-2 and RLM-3 were detected in chicken, rat and mouse microsomal preparations. On the basis of gas chromatography/mass spectrometry data, the compounds were tentatively identified as isomers of 3'-hydroxy T-2.

Pharmacokinetics of T-2 tetraol, a urinary metabolite of the trichothecene mycotoxin, T-2 toxin, in dog

1. The urinary metabolites of T-2 toxin were identified and analysed quantitatively after i.v. administration to dogs. 2. A new routine assay for T-2 tetraol was developed and a pharmacokinetic study was carried out on this final hydrolytic metabolite of T-2 toxin. T-2 tetraol was excreted in urine for 2-3 days. Its 'sigma minus' plot demonstrated a significantly longer apparent half-life than its precursors (T-2 toxin and HT-2 toxin). This fact was explained by extraplasma binding causing prolongation of the metabolism and excretion of T-2 toxin metabolites. 3. The urinary metabolites of T-2 toxin were: HT-2 toxin, T-2 triol and T-2 tetraol. The metabolites were excreted in free and conjugated forms. In two dogs T-2 toxin was found in the urine in an amount which accounts for 3.2 and 16% of the administered dose respectively. The cumulative amount of the identified metabolites and toxins formed in the urine ranged from 9.7 to 17.3% in four dogs and 44.7% in one dog.

The cytochrome P-450-dependent hydroxylation of T-2 toxin in various animal species

Gas-liquid chromatography was used to investigate the hepatic and intestinal metabolism of T-2 toxin, a cytotoxic and immunodepressive trichothecene produced by species of Fusarium. The hepatic S-9 and microsomal fractions of various species hydroxylated T-2 toxin to form 3'-hydroxy-T-2. HT-2 toxin, a deacetylated metabolite of T-2 toxin formed by reactions involving microsomal esterases, was also hydroxylated, to 3'-hydroxy HT-2 toxin. Experiments with inhibitors and inducers of the cytochrome P-450-dependent system revealed that these two hydroxylation reactions were catalysed by the cytochrome P-450-dependent monooxygenase system. Species comparisons using rats, mice, guinea-pigs, rabbits, pigs, cows and chickens showed that the rate of the hydroxylation reaction was highest in the hepatic microsomes of guinea-pigs, followed by mice. Chickens possessed a low activity both in the hydrolysis and hydroxylation reactions. No hydroxylated metabolites were produced by the intestinal microsomes of rabbits. These two hydroxylated metabolites were far less cytotoxic to Reuber hepatoma cells than the parent compound, T-2 toxin.

Production and characterization of antibodies against HT-2 toxin and T-2 tetraol tetraacetate

Three new immunogens which were prepared by conjugation of the carboxymethyl oxime (CMO) derivatives of HT-2 toxin, T-2 tetraol (T-2 4ol), and T-2 tetraol tetraacetate (T-2 4Ac) to bovine serum albumin (BSA) were tested for the production of antibodies against the major metabolites of T-2 toxin. Antibodies against HT-2 toxin and T-2 4Ac were obtained from rabbits 5 to 10 weeks after immunizing the animals with CMO-HT-2-BSA and CMO-T-2 4Ac-BSA conjugates. Immunization with CMO-T-2 4ol-BSA resulted in no antibody against T-2 4ol. The antibody produced against HT-2 toxin had great affinity for HT-2 toxin as well as good cross-reactivity with T-2 toxin. The relative cross-reactivities of anti-HT-2 toxin antibody with HT-2 toxin, T-2 toxin, iso-T-2 toxin, acetyl-T-2 toxin, 3'-OH HT-2, 3'-OH T-2, T-2 triol, and 3'-OH acetyl-T-2, were 100, 25, 10, 3.3, 0.25, 0.15, 0.12 and 0.08%, respectively. Antibody against CMO-T-2 4Ac was very specific for T-2 4Ac and had less than 0.1% cross-reactivity with T-2 toxin, HT-2 toxin, acetyl-T-2 toxin, diacetoxyscirpenol, deoxynivalenol, and deoxynivalenol triacetate as compared with T-2 4Ac. The detection limits for HT-2 toxin and T-2 4ol by radioimmunoassay were approximately 0.1 and 0.5 ng per assay, respectively.

Identification of glucuronide metabolites of T-2 toxin and diacetoxyscirpenol in the bile of isolated perfused rat liver

Isolated rat livers were perfused with either 2 mg T-2 toxin or diacetoxyscirpenol (DAS) in a recirculating perfusion system. To identify glucuronide conjugates, equal amounts of bile samples were incubated with and without (control) a beta-glucuronidase preparation and analyzed by capillary gas liquid chromatography-chemical ionization mass spectrometry. Enzyme treatment of bile obtained from liver perfused with T-2 toxin resulted in the detection of a total of 954 micrograms HT-2 toxin (control 6 micrograms), demonstrating that excretion into the bile was mainly as glucuronide conjugates. Minor metabolites of T-2 toxin in bile were identified as 3'-hydroxy HT-2 toxin (TC-3), 3'-hydroxy-7-hydroxy HT-2 toxin (TC-6), and the glucuronide form of T-2 triol (trace amount). The glucuronide conjugates of monoacetoxyscirpenol (340 micrograms) and scirpenetriol (10 micrograms) were found in bile obtained from liver perfused with DAS, while nonconjugated metabolites were not detected. It is assumed that considerable amounts of T-2 toxin and DAS were metabolized biphasically. In phase I both trichothecenes were deacetylated, in phase II the metabolites were conjugated giving rise to the glucuronic acid adducts.

Rapid screening procedure for the detection of trichothecenes in plasma and urine

A rapid and easy procedure to screen for trichothecenes in plasma and urine is presented. The toxins are extracted using a Clin-Elut column, hydrolyzed to their corresponding parent alcohols and cleaned up with a silica cartridge followed by derivatization for gas chromatographic analysis. The detection of any of the parent alcohols in plasma or urine would indicate an exposure to trichothecenes. Recoveries in urine are between 78 and 119% at levels of 50-1000 ng/ml and recoveries in plasma are between 80 and 116% at levels of 50-500 ng/ml. The limit of detection is better than 25 ppb.

Metabolism of T-2 toxin by rat liver carboxylesterase

The trichothecene T-2 toxin was rapidly hydrolyzed by rat liver microsomal fraction into HT-2 toxin which was the main metabolite. The metabolism was completely blocked by paraoxon, a serine esterase inhibitor, but not affected by EDTA or 4-hydroxy mercury benzoate, inhibitors of arylesterase and esterases containing SH-group in active site, respectively. Among the serine esterases carboxylesterase (EC 3.1.1.1), but not cholinesterase (EC 3.1.1.8) hydrolysed T-2 toxin to HT-2 toxin. Carboxylesterase activity from liver microsomes was separated into at least five different isoenzymes by isoelectric focusing, and only the isoenzyme of pI 5.4 was able to hydrolyse T-2 toxin to HT-2 toxin. The toxicity of T-2 toxin in mice was enhanced by pre-treatment with tri-o-cresyl phosphate (TOCP), a specific carboxylesterase inhibitor. This confirms the importance of carboxylesterase in detoxification of trichothecenes.

Pharmacokinetics of the trichothecene mycotoxin, T-2 toxin, in swine and cattle

The pharmacokinetics of the trichothecene mycotoxin, T-2 toxin, were determined in growing gilts and heifers. Following intra-aortal administration in swine and intravenous administration in calves, the disappearance of the parent T-2 toxin followed a 2-compartment open model. Mean elimination phase half-lives were 13.8 and 17.4 min and mean apparent specific volumes of distribution were 0.366 and 0.376 l/kg in swine and calves, respectively. The fraction of T-2 toxin eliminated as parent compound in the urine was negligible. In spite of administration of a lethal oral dose in swine (2.4 mg/kg) and toxic oral doses (up to 3.6 mg/kg) in calves, no parent T-2 toxin was detected in plasma or urine. After intra-aortal administration in swine, tissue concentrations of T-2 toxin were consistently highest in lymphoid organs. Tissue residues of T-2 toxin were rapidly depleted such that, in spite of administration of a potentially lethal intra-aortal dose, no quantifiable T-2 toxin was present in any of the tissues collected at 4 hr after dosing. No T-2 toxin could be detected in liver, even at 1 hr after dosing.