Quantitative and morphological aspects of cutaneous irritation by trichothecene mycotoxins

The Effect of T-2 Toxin on the Acute Phase Reaction in Mice

The effects of T-2 toxin on a murine model of the acute phase response were studied. Two murine acute phase reactants, serum amyloid P component and plasma fibronectin, were measured after subcutaneous and intraperitoneal administration of T-2 toxin in varying doses. No acute phase response was observed. Furthermore, T-2 toxin also blocked the acute phase reaction to subcutaneous AgNO3 in a dose-dependent fashion. These observations were not explained by damage to liver, the site of synthesis of acute phase proteins. Since the acute phase response is an immediate physiological reaction to tissue injury and may be a nonspecific participant in the repair phenomenon, its abrogation by T-2 toxin may contribute to the toxicity of this trichothecene mycotoxin.

Comparison of the inhibition of deoxynivalenol and T-2 toxin on bovine and porcine platelet function

A platelet model system has been used to investigate the inhibitory effects of deoxynivalenol (DON, vomitoxin) and T-2 toxin, alone and in combination. In both bovine and porcine systems, the most dramatic effect observed was the instability in the platelet aggregates formed in the presence of the mycotoxins. Bovine platelets were more sensitive to the inhibitory effects of both of the mycotoxins than porcine platelets and in both species T-2 toxin was a more effective platelet inhibitor than DON. The mycotoxins may inhibit platelet function by a similar mechanism since an additive inhibitory response was observed when DON and T-2 toxin were added together to platelet suspensions.

Alteration of major cytokines produced by mitogen-activated peritoneal macrophages and splenocytes in T-2 toxin-treated male CD-1 mice

Fusarium T-2 toxin has immunotoxic properties that may be related to the modulation of cytokine expression by cells of the immune system. Male CD-1 mice were used to study the effect of in vivo exposure to T-2 toxin on the alteration of interleukin (IL)-1α, tumor necrosis factor α (TNF), and IL-6 in lipopolysaccharide-stimulated peritoneal macrophages, and IL-2, IL-3, and interferon γ (IFNγ) in concanavalin A (Con A)-stimulated splenocytes. Mice were orally dosed with 0, 0.1, 0.5, and 2.5 mg T-2 toxin/kg body weight for 2 weeks on alternate days. Northern blot analysis of IL-1α, TNF, and IL-6 mRNA from activated peritoneal macrophages showed no significant differences between control and treated groups. Measurements of secreted protein by immunoassay demonstrated suppression of these cytokines in all treated groups, suggesting that T-2 toxin affects the translational or post-translational regulation of these cytokines from peritoneal macrophages. Levels of IL-2, IL-3, and IFNγ mRNA from Con A-activated splenocytes were higher in all treated groups. The increases were significant for IL-2 and IFNγ in the groups receiving low (0.1 mg/kg) and high (2.5 mg/kg) doses of T-2 toxin, and for IL-3 in the group receiving a medium (0.5 mg/kg) dose of this toxin (P ≤ 0.05). Results indicated that T-2 toxin given orally at low or medium doses induces transcription or increases mRNA stability of IL-2, IFNγ, and IL-3. Protein levels of all three cytokines were also increased, indicating that T-2 toxin also increases translational/post-translational efficiency of IFNγ, IL-2, and IL-3. Possible mechanisms in the immunosuppressive effects of T-2 toxin may involve endotoxemia resulting after the toxin administration, alteration of the stability of mRNA, or previously described effects of T-2 toxin on protein synthesis.

Survey of natural occurrence of trichothecene mycotoxins and zearalenone in Korean cereals harvested in 1992 using gas chromatography/mass spectrometry

For the survey of the natural occurrence of trichothecene mycotoxins, produced by species of fungi imperfecti such as Fusarium and Trichothecium, a sensitive analytical method was developed for the simultaneous detection and quantitation of the major trichothecene mycotoxins, viz. T-2 toxin (T-2), HT-2 toxin (HT-2), nivalenol (NIV), fusarenon-X (F-X), deoxynivalenol (DON), 3-acetyl deoxynivalenol (3-Ac DON), and zearalenone (ZEN), using gas chromatography/mass spectrometry-selected ion monitoring (GC/MS-SIM) mode after trimethyl silyl derivatization. The incidence of NIV and DON in 30 barley samples were 93% and 67%, respectively; the average contents of NIV and DON in positive samples were 390 ng/g (range 40-2038) and 106 ng/g (range 5-361) respectively. In 15 maize samples, the incidences of NIV and DON were 53% and 93% respectively and the average contents were 168 ng/g and 145 ng/g, respectively. These results suggest that NIV and DON were the major contaminating trichothecene mycotoxins in Korean barley and maize samples harvested in 1992.

Effects of aflatoxin B1 and T-2 toxin on the granulocyte-macrophage progenitor cells in mouse bone marrow cultures

Myelotoxic effects of aflatoxin B1 (AFB1) and T-2 toxin on the proliferation of the granulocyte-macrophage progenitor cells to granulocyte, macrophage and granulocyte-macrophage (GM) colonies were investigated in male CD-1 mice by a semisolid in vitro culture technique. Mice received 0, 0.03, 0.145 and 0.7 mg/kg or 0, 0.1, 0.5, and 2.5 mg/kg body weight of AFB1 and T-2 toxin, respectively, for 2 weeks on alternate days. Granulocyte, macrophage, and GM-colonies were suppressed in the group that received the highest dose of AFB1 (0.7 mg/kg body weight). Treatment with T-2 toxin activated granulocyte colonies at 0.5 mg/kg and macrophage colonies at 0.1 and 2.5 mg/kg but suppressed GM-colonies at 0.5 and 2.5 mg/kg body weight. Bone marrow cells from normal CD-1 mice were cultured with different concentrations of AFB1 (1-50 microM) or T-2 toxin (1-10 nM) in vitro. Significant activation of granulocyte colonies with 1 microM AFB1 and suppression of all three types of colonies with the highest concentration of AFB1 (50 microM) were observed. The suppression of granulocyte and GM-colonies associated with T-2 toxin was concentration-dependent. The greatest suppression occurred in macrophage colonies with three highest concentrations of T-2 toxin (3, 6, and 10 nM). Results suggest that AFB1 is myelotoxic both in vivo and in vitro, whereas T-2 toxin is more toxic in vitro.

Mesenteric mast cell degranulation in acute T-2 toxin poisoning

T-2 toxin-induced alterations in rat mesenteric mast cell granulation were measured by cytophotometric analyses of the metachromatic reaction of mast cell granules with azure B. Hypogranulation (diminution of metachromatic material) was observed 8 h following injections of T-2 toxin (0.5-1.5 LD50, i.p.). These data suggest that mast cell activation occurs during acute T-2 intoxication and raise the possibility that mast cell mediators may contribute to toxin-induced cardiovascular collapse.

Penetration of [3H]T-2 mycotoxin through abraded and intact skin and methods to decontaminate [3H]T-2 mycotoxin from abrasions

Penetration of 50 muCi of [3H]T-2 mycotoxin through abraded and intact skin was studied in anesthetized rats sacrificed at 5, 15, 30, 45, 60 and 90 min post-exposure. The greatest penetration was through abraded skin (49 +/- 7%) at 90 min post-exposure, whereas penetration through intact skin (2 +/- 3%) was substantially less (P less than 0.0015). Methods to decontaminate [3H]T-2 mycotoxin from abraded skin over time were studied. Treatment of [3H]T-2 contaminated abrasions by applying Trau + Medic dressing, applying Charcoal Cloth-Anti-bacterial Field Dressing (Charcoal Dressing), or swabbing with povidone-iodine 30 min post-exposure removed 17-32% of the applied [3H]T-2. Immediate blotting with immediate removal of the dressings absorbed 103 +/- 4% (Trau + Medic) and 87 +/- 4% (Charcoal Dressing) of the applied [3H]T-2, while immediate blotting and leaving the dressing in place for 30 min removed 91 +/- 5% (Trau + Medic) and 76 +/- 3% (Charcoal Dressing). It appears that immediate blotting with either dressing followed by immediate removal before application of a clean dressing is an effective method for decontaminating [3H]T-2 from abrasions.

Relationship of the hypothalamic-pituitary-adrenal axis with chemically induced immunomodulation. I. Stress-like response after exposure to T-2 toxin

T-2 toxin (T-2), a trichothecene mycotoxin, produced by several members of the genus Fusarium is a cytotoxic feed contaminant and has been shown to by immunomodulatory. It is suspected that T-2 associated immunomodulation is mediated partly through the hypothalamic-pituitary-adrenal (HPA) axis. T-2, prepared in 4% ethanol/corn oil, was administered orally to male CD-1 mice. Endotoxemia was evident 24 h after a single, oral exposure to T-2. Blood levels of corticosterone, indicative of the stress-response, increased 24 h after T-2 exposure. Hypothalamic norepinephrine and serum corticosterone levels increased in a dose-related manner after 2 weeks of T-2 exposure. Endotoxin, detected in the serum of animals exposed to 2.5 mg/kg T-2 for 1 week, was not associated with bacteremia. Neither endotoxin nor bacteremia were detectable after 2 or 4 weeks of T-2 exposure. Exposure to 2.5 mg/kg T-2 also affected several organs. The forestomach was ulcerated, with lymphocytic infiltration, epithelial proliferation, and hyperkeratinization. Increased spleen weight was associated with a proliferative red pulp. No histological changes were observed in the enlarged liver. Gastritis has been associated with increased corticosteroid production; cortical depletion and reduced mass of the thymus are phenomena attributable to increased corticosteroid levels. An increased corticosteroid level has been associated with thymic involution leading potentially to decreased T-dependent antibody response, a known effect of T-2.

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.

Dermal toxicity of Fusarium toxins in combinations

T 2 toxin (T 2), diacetoxyscirpenol (DAS), fusarenon X (FX) and butenolide (Bd) at concentrations of 0.2, 0.3, 5 and 10 micrograms/site, respectively, were applied individually and in combinations on shaved skin of guinea pigs. Erythema and induration were observed on skin patches treated with the toxins. Increase in the thickness of stratum malpighii was the major histological change observed. Mild to moderate degeneration of fibrocytes and cellular infiltration were found in the corium of skin treated with FX, Bd, DAS and T 2. The order of toxicity of individual toxins was T 2 greater than DAS greater than FX greater than Bd. Combinations of T 2 + FX and T 2 + Bd resulted in antagonism, while DAS + FX and DAS + Bd caused synergism.

Skin effects of trichothecenes and their amelioration by decontamination

The ability of trichothecenes, in particular T2 toxin (T2), to cause irritant effects on the skin has been investigated in laboratory rodents and rabbits. Quantitatively, T2 was found to be highly potent in this respect, causing irritant reactions on rat skin at contamination densities of less than 1 microgram.cm-2. The first appearance of skin effects was delayed for approximately 6 h after application, irrespective of the dose applied. Similarly, variation in solvent or injection into or beneath the skin failed to accelerate the onset of the irritant reaction. An aqueous soap solution was largely effective in removing low doses of T2 from the skin, but was ineffective in removing larger doses. However, washing the contaminated skin with polyethylene glycol 300 was very effective at removing even large doses of T2 from the skin. The macrocyclic trichothecene verrucarin A was of comparable irritancy to T2 on rat skin. Diacetoxyscirpenol and nivalenol were less potent.

Comparison of penetration and metabolism of [3H]diacetoxyscirpenol, [3H]verrucarin A and [3H]T-2 toxin in skin

The purpose of this research was to determine the rate of cutaneous penetration and metabolism of [3H]diacetoxyscirpenol (DAS) and [3H]verrucarin A (VCA) and compare these values to previously determined values for [3H]T-2 toxin (T-2), to compare the cutaneous penetration and metabolism of DAS in human and guinea-pig skin, and to compare the effects of dose and of two vehicles, methanol and dimethylsulphoxide (DMSO), on penetration rates. DAS or VCA was applied to the epidermal surface of excised skin, and the receptor fluid bathing the dermal surface was sampled periodically for 48 hr. Whether the applied dose (581 ng/cm2) was dissolved in methanol or DMSO, the rate of penetration through human skin was lower for VCA than for DAS or T-2, the rates for the two latter compounds being similar at this dose. Metabolism of DAS occurred during penetration through excised human skin and did not occur in the receptor fluid as a result of enzymes leaching out of the skin. VCA appeared to be metabolized by human skin, but this conclusion is tentative because of the relative instability of this compound. DAS penetrated significantly (P less than 0.05) faster through excised guinea-pig skin than through human skin. Metabolism of DAS was greater in human skin than in guinea-pig skin. When compared with methanol, DMSO increased the penetration of DAS and VCA by factors of between 7 and 52. At the low dose (79 ng/cm2) DAS penetrated human and guinea-pig skin significantly (P less than 0.05) faster than T-2 using either vehicle.

Acute toxicity of T2 toxin in rats, mice, guinea pigs, and pigeons

The acute intravenous, intragastric, subcutaneous, intraperitoneal and intratracheal toxicity of T2 toxin has been studied in rats, mice, guinea-pigs, and pigeons. The acute LD50 values obtained varied between 1.0 and 14 mg X kg-1, there being little difference between the various routes in any given species. T2 caused vomiting in pigeons at doses of one fifth or less the LD50. In rats doses of 3.0 and 5.0 mg X kg-1 T2 produced lymphopenia, reticulocytosis, and in the highest dose groups normoblastaemia. Additionally, changes in plasma alkaline phosphatase and aspartate aminotransferase activities were seen. Histological changes were observed in lymphoid organs and were most severe in the thymus, lymph nodes, and Peyer's patches. The spleen was less severely affected. Gastrointestinal changes consisting of dead and dying lymphoid cells throughout the lamina propria were seen together with, in some cases, mucosal ulceration. The time course of the development and of the reversal of the changes was followed.

Cutaneous injury by topical T-2 toxin: involvement of microvessels and mast cells

Topical applications of various doses of T-2 toxin to rats led to delayed skin reactions. Following a dose-dependent latent period of 12-24 hr, there appeared vascular dilation, stasis, edema and mononuclear cell infiltration, with many degranulating mast cells. These signs were earliest and strongest in the subcutis. Epidermal necrosis occurred 1-2 days later and was probably caused secondarily by ischemia, due to microcirculatory failure. Ultrastructurally, endothelial cells of small vessels were the earliest sites of change. While intercellular junctions remained closed and pinocytosis decreased, the cytoplasm contained many ribosomes, vacuoles, and abnormal mitochondria. Another early effect of topical T-2 toxin was an increase in number and degranulation of mast cells, especially in the subcutis. The resemblance of the skin injury to that produced by irradiation is noted.

Assessment of potential therapies for acute T-2 toxicosis in the rat

The efficacy of a variety of approaches for the treatment of animals with acute T-2 toxicosis was assessed utilizing young female rats. A single large dose of the water soluble salt of methylprednisolone significantly prolonged survival times in T-2 toxin treated animals. The use of diltiazem hydrochloride, dazemgrel, N-acetylcysteine, dimethyl sulfoxide, adenosine triphosphate (ATP), ATP combined with magnesium chloride, ascorbic acid, and aprotinin did not prolong survival times at the dosages administered. Trichodermin, a trichothecene similar in structure and biochemical activity to T-2 toxin but much less acutely toxic, had a detrimental effect on survival times whether given 1 hr prior to or after T-2 toxin.

Myocardial and pancreatic lesions induced by T-2 toxin, a trichothecene mycotoxin, in swine

Myocardial and pancreatic lesions induced by sublethal doses of T-2 toxin in swine were characterized by light and electron microscopy. Toxin was given intravenously to six 17- to 18-week-old pigs. Pigs were killed 24 or 48 hours after treatment. Grossly, subendocardial hemorrhages, multifocal pinpoint white foci in myocardium, and pancreatic edema occurred in one treated pig. Histologic changes in myocardium of treated pigs consisted of multifocal edema, mononuclear cell infiltration, myofiber hyalinization, vacuolation, and contraction bands with nuclear pyknosis. Ultrastructurally, there were areas of edema, myofibrillar disorganization, dilation of sarcoplasmic reticulum, and formation of hypercontraction bands. Myocardial mineralization was seen in the pig with gross lesions. Pancreatic changes in treated pigs consisted of multifocal acinar degeneration and necrosis. Ultrastructural changes included irregular dilation of rough endoplasmic reticulum and abnormal zymogen granules. Thus, in addition to radiomimetic lesions of the gastrointestinal tract and lymphoid organs, heart and pancreas are target organs of T-2 toxin in swine.

Effects of skin storage conditions and concentration of applied dose on [3H]T-2 toxin penetration through excised human and monkey skin

Penetration of [3H]T-2 toxin through excised human and monkey skin stored at -60 degrees C was faster than through human and monkey skin stored at 4 degrees C, respectively. The permeability of refrigerated human skin was 34% of the permeability of refrigerated monkey skin. Increasing the concentration of [3H]T-2 toxin applied to the refrigerated monkey skin increased the amount of [3H]T-2 toxin penetrating the skin and enhanced the efficiency of penetration. Metabolites of [3H]T-2 toxin were identified in the receptor fluid bathing the dermal side of the excised human and monkey skin.

Toxic fungal metabolites in food

About 100 fungal metabolites may cause cancer, embryological defects, or other histopathological effects in mammals. They are produced by a wide variety of fungi. Few of these metabolites have significant acute toxicity. With the exception of aflatoxin B1 and sterigmatocystin, there is no conclusive evidence that any of them is carcinogenic. However, several of the compounds are mutagenic. Cytochalasin D and T-2 toxin are probably teratogenic. A wide variety of other histopathological effects have been shown. Liver damage has been most frequently reported. In almost all cases the molecular bases of these effects have not been extensively investigated. Although much is known about the routes by which some of the compounds are synthesized in vivo, nothing is known about control at the molecular level of these biosynthetic routes. Little is known about the biological degradation of these compounds or about the levels and incidences of them in food and animal feed. Future work in all these areas will depend on the further development of sensitive assay methods that are applicable to their measurement in food, in animal feed, and in animal tissues and body fluids and on the application of these methods to define exposure to these compounds in the diet.

Systemic effects of topical application of T-2 toxin in mice

Topical application of T-2 toxin in dimethyl sulfoxide (DMSO) resulted in the death of 20/20 mice in the 20-, 30-, and 40-mg/kg body weight (BW) dose groups within 4 to 6 days after application, whereas 17/20 and 5/20 animals died in the 10- and 5 mg/kg BW groups, respectively, within 7 days. Histological examination of thymus, spleen, and duodenum at 6, 12, 18, and 24 hr after topical application of 5 or 40 mg/kg BW to mice revealed that the characteristic radiomimetic effects of this trichothecene mycotoxin are easily recognizable at 6 hr after topical application, with the severity of damage being dependent on the organ and time. The lesions are quantitatively and qualitatively identical with those seen after intragastrical application of T-2 toxin. Both the postmortem and, to some extent, the general histological findings were not specific enough to arrive at an etiological diagnosis without prior knowledge of the fact that a mycotoxin was applied to the skin, unless one had the opportunity to look for the characteristic intestinal lesions prior to 24 hr after application, or for necrosis in spleen an thymus after 24 hr.

Penetration of [3H]T-2 toxin through excised human and guinea-pig skin during exposure to [3H]T-2 toxin adsorbed to corn dust

An in vitro test system was used to measure the penetration of [3H]T-2 toxin through human epidermis, human whole skin (isolated dermis and epidermis), and through guinea-pig whole skin. To simulate the conditions which occur when agricultural workers are exposed to corn dust contaminated with T-2 toxin, the epidermal surface of each skin preparation was dosed with [3H]T-2 toxin adsorbed onto corn dust. The applied dose was 3.27 to 4.75 mg of corn dust containing 18.2 ppm [3H]T-2 toxin. The rate of percutaneous penetration was determined by measuring the accumulation of radioactivity in the receptor fluid bathing the dermal side of the excised skin. The total penetrations (expressed as percentage dose) through isolated human epidermis, human whole skin and through isolated guinea-pig whole skin were 1.12 +/- 0.26% (mean +/- standard deviation), 0.33 +/- 0.07%, and 0.13 +/- 0.07% respectively. The radioactive compounds in the receptor fluid bathing the human whole skin corresponded to T-2 toxin (69%) and HT-2 toxin (25%), as determined by thin-layer chromatography. Thus T-2 toxin adsorbed onto corn dust can partition into and penetrate through excised human and guinea-pig skin.