Blood pressure changes and cardiovascular lesions found in rats given T-2 toxin, a trichothecene secondary metabolite of certain Fusarium microfungi

T-2 toxin induces cardiotoxicity by activating ferroptosis and inhibiting heme oxygenase-1

T-2 toxin, a natural secondary sesquiterpenoid metabolite produced by numerous strains of Fusarium fungi, is prevalent in both contaminated food and the environment. T-2 toxin is known to be highly toxic to the cardiovascular system, but the precise mechanisms that lead to T-2 toxin-induced cardiotoxicity are not yet fully understood. Recent findings indicate that ferroptosis is a pivotal factor in cardiovascular damage and exhibits a strong correlation with the detrimental impacts of T-2 toxin. The present study was designed to examine the involvement of ferroptosis in T-2 toxin-induced cardiac injury. Male mice and human cardiomyocytes were subjected to T-2 toxin for 24 h to induce acute cardiotoxicity for in vivo and in vitro studies, respectively. Our results demonstrated that T-2 toxin increased reactive oxygen species production, malondialdehyde, and decreased glutathione/oxidized glutathione and adenosine triphosphate levels. Furthermore, T-2 toxin was observed to activate ferroptosis, as evidenced by an increase in iron (Fe2+) concentration and upregulation of prostaglandin endoperoxide synthase 2, downregulation of glutathione peroxidase 4 and ferritin heavy chain 1, as well as ferroptotic morphological alterations. Inhibition of ferroptosis by Liproxstatin-1 reversed T-2 toxin-induced cardiac injury. Additionally, the downregulation of heme oxgenase-1 (HO-1) expression by T-2 toxin exacerbates ferroptosis and oxidative damage, which can be further aggravated by HO-1 inhibition with Sn-protoporphyrin. These findings provide novel insights into the mechanism of T-2 toxin-induced cardiotoxicity and suggest that targeting ferroptosis and HO-1 may represent a promising cardioprotective strategy against T-2 toxin.

PPAR-γ with its anti-fibrotic action could serve as an effective therapeutic target in T-2 toxin-induced cardiac fibrosis of rats

T-2 toxin, the most virulent toxin produced by the Fusarium genus, is thought to be the main cause of fatal cardiomyopathy known as Keshan disease. However, the mechanisms of T-2 toxin-induced cardiac toxicity and possible targets for its treatment remain unclear. In the present study, male Wistar rats were administered with 2 mg/kg b. w. T-2 toxin (i.g.) and sacrificed on day 7 after exposure. The hematological indices (CK, LDH) and electrocardiogram were significantly abnormal, the ultrastructure of mitochondria in the heart was changed, and the percentage of collagen area was significantly increased in the T-2 toxin-treated group. Meanwhile, T-2 toxin activated the TGF-β1/Smad2/3 signalling pathway, and also activated PPAR-γ expression in rats and H9C2 cells. Further application of PPAR-γ agonist (pioglitazone) and antagonist (GW9662) in H9C2 cells revealed that the up-regulation of PPAR-γ expression induced by T-2 toxin is a self-preservation phenomenon, and increasing exogenous PPAR-γ can alleviate the increase in TGF-β1 caused by T-2 toxin, thereby playing a role in relieving cardiac fibrosis. These findings for the first time demonstrate that T-2 toxin can regulate the expression of PPAR-γ and that PPAR-γ has the potential to serve as an effective therapeutic target in T-2 toxin-induced cardiac fibrosis of rats.

Subchronic dermal exposure to T-2 toxin produces cardiac toxicity in experimental Wistar rats

Our study aimed to determine the cardiac toxicities of T-2 toxin, a representative mycotoxin that frequently contaminates maize, cereals, and other agricultural products, harvested and stored under damp and cold conditions. Dermal exposure to T-2 toxin caused severe cardiotoxicity in experimental Wistar rats. Electrocardiography studies showed the conduction abnormalities including prolongation of the QT and corrected QT interval, shortening of the PR interval, and tachycardia. Biochemical studies also reported the toxicity of T-2 toxin. T-2 toxin induced acute cardiotoxicity in rats and characterized by significant ( p < 0.05) elevation of serum troponin I, creatine kinase (CK) isoenzyme MB, CK isoenzyme NAC, and lactate dehydrogenase as compared to control rats. It is concluded that cardiotoxicity effects of T-2 toxin are thought to be due to direct action on electrocardiac potentials and biochemical changes.

The African Fusarium/maize disease

There is a general but rather vague feeling that the use of maize (corn) as a staple foodstuff by black rural Africans is somehow a factor in, or is linked to, chronic disease found in these populations. An attempt is made in this review to consider the evidence for this connection and to identify what is actually the root of the problem. The main thrust of the argument to explain this perception is that maize is routinely contaminated with fungi and of these Fusarium verticillioides is found in maize throughout the world. Evidence is presented to this effect and, further, of the mycotoxins found in maize, the fumonisins are the most common and at the highest levels. Various animal chronic diseases arising from the consumption of contaminated maize are reviewed and possible human conditions listed, in some cases related to the known animal ones. A brief overview of the complicated cellular mechanisms of fumonisin B1 is given and it is concluded that the prime suspect in what might be called "the maize disease" can be attributed to the ingestion of this mycotoxin, sometimes in combination with other synergist mycotoxins and other disease factors, such as smoking and drinking.

Fusarium poae and Fusarium sporotrichioides in cereal grains of the Slovak Republic

The occurrence of Fusarium poae and F. sporotrichioides was examined in 37,172 cereal grains of 229 samples from the Slovak Republic. In an area where strains of Fusarium parasitized. 40% of grains on average, owing to unfavourable weather, 5 strains of F. poae were isolated (0.5% out of 1,015 strains of Fusarium). In an area where the situation was less unfavourable, Fusarium spp. contaminated on average 4.1% of grains, F. poae were present in 6.1% out of 82 strains of Fusarium. When cereal ripened and harvested under climatically favourable conditions. Fusarium spp. were isolated, on average, out of 3.0% of grains, but the strains of F. poae made an essential part of the mycoflora (25.5% out of 985 isolated Fusarium strains). In three samples there were ascertained 5%, 15% and 19.5% of grains contaminated by strains of F. poae, F. sporotrichioides was isolated only 5 times.

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.

Effects of T-2 toxin on saccharin aversion and food consumption in adult rats

The present experiment used a saccharin aversion paradigm to evaluate the potential aversive action of T-2 toxin, a trichothecene mycotoxin that induces emesis and weight loss. Adult male rats were fed either a control diet or a diet adulterated with 640 ppm lithium chloride (positive control) or with 2.5, 5.0 or 10.0 ppm T-2 toxin and given access to a 0.1% saccharin solution and to tap water during four training days. The rats were then shifted to the control diet during three extinction days. Moderate saccharin aversion induced by the positive control diet and the 5.0 and 10.0 ppm T-2 diets was apparent on the third day of exposure and the aversion to the saccharin solution abated during the extinction trials. Saccharin aversion was evident at levels of T-2 toxin that did not induce obvious tissue pathology.

Effects of radioprotective compounds and anti-inflammatory agents on the acute toxicity of trichothecenes

Antidotic effects of radioprotective and anti-inflammatory drugs against the acute toxicity of T-2 toxin and fusarenon-X, the trichothecene mycotoxins of Fusarium species, were examined in mice and rats with two toxicological parameters, the lethal toxicity and the increment of intestinal fluid volume. The s.c. and i.v. LD50 values of T-2 in male 6-week-old mice were 2.1 and 3.8 mg/kg, respectively, and the s.c. LD50 in 4-week-old mice was 1.6 mg/kg. Pretreatment of mice with steroidal anti-inflammatory agents such as prednisolone and hydrocortisone resulted in a marked reduction in the lethal toxicity of T-2 toxin. However, pretreatment of mice with several radioprotective agents exhibited neither a prolongation of survival time nor a decrease in lethal toxicity in the mice. Enteropooling assay revealed that the steroidal anti-inflammatory drugs also depressed the trichothecene-induced increment of intestinal fluid volume in rats, while no significant effects were observed with non-steroidal inhibitors of the arachidonate cascade. In rats given fusarenon-X, the content of cyclic AMP in the mucosa of ileum was dose- and time-dependently increased, but its maximal increment was only 1.5-fold of the control value. These findings indicate an involvement of the action site of steroidal anti-inflammatory drugs in the development of acute toxicity of trichothecenes in rodents.

Cytophotometric assessment of granulosa cell protein and nucleic acid levels during the estrous cycle in rats treated with T-2 toxin

Female Sprague-Dawley rats (160-180g.) with normal estrous cyclicity established by vaginal smears, were injected intraperitoneally with 0.45 mg/kg (low dose) or 0.68 mg/kg (high dose) of T-2 toxin, a trichothecene with potent protein inhibitory abilities. Control animals were injected with only the 100% ethanol vehicle. All animals were decapitated at 8 hours post-exposure, and their ovaries removed and processed for paraffin sectioning. Coomassie, Feulgen, and azure B/DNase staining procedures were used to show granulosa cell protein levels, F-DNA stainability, and basophilia/RNA levels, respectively. Quantification of these parameters was accomplished using scanning-integrating microdensitometry. T-2 toxin treatment groups had granulosa cell protein levels significantly lower than those of the control animals. However, rats exposed to the lower dose of T-2 toxin generally showed a more marked suppression of protein levels than the high dose group, regardless of the stage of the estrous cycle. In addition, rats that received lower doses of T-2 toxin had impaired translation and template activity in response to injury, when compared with the rats in the high dose group. These results are attributed to the lesser degree of circulatory impairment in the low T-2 toxin dosage group, which allows a higher amount of T-2 toxin to interact with the cells.

T-2 toxin effect on rat aorta: cellular changes in vivo and growth of smooth muscle cells in vitro

Rats were injected intraperitoneally with T-2 toxin and their aortas were studied by light and electron microscopy. The growth of smooth muscle cell explants taken from the tunica media of aortas of similarly treated animals was observed. A single large dose (2 mg/kg) or four injections of 0.3 mg/kg T-2 toxin caused damage and occasional necrosis of endothelial cells, accumulation of basement membrane-like material in the intima, and swelling and activation of smooth muscle cells in the tunica media. Three or more weeks after the last injection of 0.3 mg/kg T-2 toxin the endothelial cells were normal but an excess of fragmented intimal basement membrane-like material persisted and smooth muscle cells were still activated. Outgrowths from explants of aortic tunica media taken within 1 week of the last dose of T-2 toxin showed marked inhibition of smooth muscle cell growth. Three or more weeks after the toxin, the explants showed significantly increased outgrowths. These findings suggest that T-2 toxin causes early endothelial and smooth muscle cell injury accompanied by inhibition of smooth muscle cell growth in culture. This is followed by stimulation of the proliferative capacity of smooth muscle cells in vitro. If a similar mechanism is operative in vivo, it could explain the chronic vascular changes observed after limited exposure to T-2 toxin.

Effects of low-level long-term oral exposure to T-2 toxin in CD-1 mice

In a 16-month feeding study male and female CD-1 mice received semi-synthetic diets containing 0, 1.5 or 3.0 ppm T-2 toxin. Feed consumption, body-weight gains, clinical findings (including haematological examinations at 16 months) and the development of external lesions were recorded. At 3, 6, 12 and 16 months, animals were killed for assessment of their immune function. Disease-related deaths did not differ among groups. Histological examination of all organs revealed statistically significant differences from controls in the incidence of pulmonary adenomas and hepatic adenomas in the 3.0-ppm group. Other treatment-related findings were an increased prevalence of epithelial hyperplasia in the forestomach of animals treated with T-2 toxin, and increased heart weights in treated male mice. T-lymphocyte-dependent humoral immunity tests did not reveal treatment effects and haematology revealed no particular trends. It is concluded that chronic feeding of T-2 toxin at low levels is not immunosuppressive but has a carcinogenic or tumour-promoting effect in mice.

Cardiovascular pathology induced by passive transfer of splenic cells from syngeneic rats treated with T-2 toxin

Mononuclear cells were separated from spleens and lymph nodes of Lewis rats treated 5 weeks previously with repeated small doses of T-2 toxin or solvent only. The cells from each site were then injected intraperitoneally into 4 groups of syngeneic Lewis rats. The animals injected with spleen cells from T-2 toxin-treated donors developed marked cardiovascular changes which were similar to those due to T-2 toxin itself. Rats injected with lymph node cells as well as those given each kind of cell from solvent-treated donors showed only occasional mild vascular changes. The changes seen after splenic cell transfer may be due to superinduction of interleukin 2 by T-2 toxin.

Protein synthesis inhibition and cardiac lesions associated with deoxynivalenol ingestion in mice

Deoxynivalenol (DON), an occasional contaminant of foodstuffs, has been implicated in outbreaks of mycotoxicosis. Balb-c mice that had ingested 0.35 mg/kg of DON showed a drastic decrease in food intake and concomitant loss of weight. Severe depletion of the lymphoid organs and liver were also observed. Cardiac lesions, appeared as calcified pericarditis foci in young animals fed a diet contaminated by 10 to 20 ppm of DON for a period of a few weeks. DON inhibited protein synthesis. This inhibition occurred at lower doses for the heart than for the other organs. This preferential effect on cardiac tissue correlated with the cardiotoxicity observed.

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.

T-2 toxin effect on cultured myocardial cells

Beat rate, contractility and viability of cultured myocardial cells perfused with solutions containing various concentrations of T-2 toxin were studied. While doses below 50 micrograms/ml had no immediate effect, those above 250 micrograms/ml decreased beat rate and amplitude. After 10-30 min of perfusion most cells stopped beating and did not restart after withdrawal of toxin. Nevertheless, most cells remained viable as judged by morphology and trypan blue exclusion. A 24-h exposure to doses of 5 or 2.5 micrograms/ml of toxin decreased the beat rate and inotropic responses of the myocytes. After 48 h cell death ensued. Thus T-2 toxin has some direct toxicity to myocardial cells but the lethal dose seems too high to make this the cause of cardiovascular failure.

T-2 toxemia and brain prostaglandins

T-2 toxin is a trichothecene mycotoxin which is a member of a family of closely related sesquiterpenoids. It was recently shown that T-2 toxemia is associated with elevated plasma levels of eicosanoids. To study further the effect of T-2 on the cyclooxygenase pathway of arachidonate we examined the release of PGE2, TXB2 and 6-keto-FGF1 alpha from brain tissue exposed to T-2 toxin in vivo or in vitro. Administration of T-2 toxin (0.75 or 2 mg/kg) to conscious rats caused a transient increase in the rate of the release of 6-keto-PGF1 alpha and TXB2 from brain slices taken from the cortex (C); no effect was found in the hypothalamus (HT) or the nucleus tractus solitarius (NTS) region of the medulla oblogata. PGE2 showed time and dose related increments (over 5 folds) in both the C and HT but not in the NTS. Incubation of cortical or hypothalamic slices in oxygenated Krebs buffer with a wide range of T-2 toxin concentrations (10(-9)-10(-3) M) demonstrated a complex response: stimulation of PGE2 and TXB2 release from C slices at 10(-7) M (greater than 40%, p less than 0.01 and 20%, p less than 0.05, respectively) and inhibition at high concentrations (greater than 10(-4) M) of all PGs studied. Hypothalamic slices showed decrease in all PGs released by very low (10(-9)-10(-8)) or very high (10(-4) M) concentrations of T-2. These studies are consistent with the possibility that the arachidonate cascade in the central nervous system might have a role in the pathophysiology of trichothecene mycotoxicosis.

Quantitative cytophotometric analysis of brain neuronal RNA and protein changes in acute T-2 mycotoxin poisoned rats

Male Sprague-Dawley rats (200 g) injected intraperitoneally with T-2 toxin, a trichothecene mycotoxin protein synthesis inhibitor, at dosages of 0.75, 1.0, 1.5 and 6.0 mg/kg (1 LD50 = 0.9 mg/kg) were decapitated at 8 hr post-exposure. Data were obtained on changes in neuronal (perikaryal) RNA levels, protein contents and nucleolar volumes in cerebrocortical (layer III) and striatal (caudate-putamen) brain regions using quantitative azure B-RNA and Coomassie-protein cytophotometry and ocular filar micrometry. Correlative observations were made on changes in brain cytomorphology. Reductions in neuronal RNA/protein contents and nucleolar volume were used as indices of impaired perikaryal functioning. At 8 hr after T-2 toxin poisoning the following results were obtained in cerebrocortical and striatal brain compartments: neuronal RNA contents were generally maintained at control values in both brain regions, however, moderate RNA depletion was evidenced in the cerebral cortex with 1.5 mg/kg T-2 and in the striatum with a 6.0 mg/kg dose; neuronal protein levels were suppressed in a dose-dependent fashion within the cerebrocortex, while in the striatum there was no direct correspondence between protein loss and T-2 dosage; neuronal nucleolar volumes were typically maintained at control levels in both neuronal compartments. Microscopic observations revealed no gross evidence of T-2-induced brain cytopathology. These data indicate that T-2 toxin does not elicit direct cytopathic actions in these two brain regions, thus indicating that cerebrocortical and striatal compartments do not represent primary target sites of T-2 toxicant action.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal antibodies to T-2 toxin. In vitro neutralization of protein synthesis inhibition and protection of rats against lethal toxemia

A murine monoclonal antibody (15H6) against the trichothecene mycotoxin T-2 was capable of neutralizing the in vitro protein synthesis inhibitory effect of T-2 toxin in human B lymphoblastoid cultures. It was further shown that 15H6 given to rats (250 mg/kg) 30 min before or 15 min after a lethal dose (1 mg/kg) of T-2 toxin conferred 100% survival. A lower dose of 15H6 (125 mg/kg), given 15 min after the lethal dose of T-2 toxin, protected 25% of the rats. An increased time to death and 45% survival was seen in rats given the full dose of 15H6 antibody 60 min after lethal toxin. These data are the first demonstration of effective prophylaxis and therapy for T-2 toxemia.

T-2 toxin can cause vasoconstriction in an in vitro bovine ear perfusion system

An in vitro bovine ear perfusion system was used to examine the effect of T-2 toxin on peripheral vasculature. T-2 toxin caused a dose-related increase in the perfusion pressure, with an apparent threshold concentration of 1 X 10(-5) M. The effect of the toxin was observed irrespective of the presence of either histamine or norepinephrine in the system. The presence of known histaminic or noradrenergic antagonists did not affect the response to the toxin. Once the vessel was exposed to T-2 toxin, the response to histamine or norepinephrine was decreased.

Immunoperoxidase localization of T-2 toxin

Antibody against T-2 toxin was used for monitoring the fate of T-2 toxin in mice given a single po dose of 11 mg/kg by the peroxidase-antiperoxidase (PAP) method. T-2 toxin was demonstrable in the esophagus from 5 min to about 24 hr postdosing. In the stomach, T-2 toxin was detected within the cytoplasm of intact and injured epithelial cells. In the duodenum, T-2 toxin was primarily localized within the surface epithelium and phagocytic elements (macrophages and neutrophils) of the duodenal lamina propria, especially toward the tips of the villi. Following sloughing of duodenal villous tips, the recovering villous tip epithelial cells frequently showed both cytoplasmic and nuclear T-2 toxin. The jejunum showed weak T-2 toxin within the cytoplasm of villous tip epithelial cells only. The ileum never demonstrated T-2 toxin. Tissue response in the gastrointestinal (GI) tract was characterized by transient edema, marked cytolysis and sloughing, and a subsequent leukocytic invasion of the stomach and proximal small intestine. Evidence of severe gastric and less severe duodenal bleeding was apparent and associated with a marked loss of gastric epithelium and intestinal villous tips. The kidney medulla contained the majority of T-2 toxin stain. T-2 toxin was noted within the distal tubular cells, the cells of the collecting tubules, and the epithelium covering the papilla. T-2 toxin was never demonstrated in any of the hepatic tissue examined.

T-2 toxin effect on isolated perfused rat hearts

T-2 toxin is the major lethal component of several Fusarium fungi implicated in the disease of man and animals. We used isolated rats hearts to test the T-2 toxin cardiotoxicity. Electrodynamics and ultrastructural parameters were studied. The main changes consisted of decreased contractility and electrocardiographic abnormalities without much effect on heart rate or QRS and QT intervals. Ultrastructurally, swelling of myofibers and their mitochondria occurred and damage to the plasma membrane was seen. It is possible that the T-2 effect is mediated through soluble thiol to cause cytoplasmic calcium decrease and loss of plasma membrane integrity.