Metabolism and pharmacokinetics of T-2 toxin and related trichothecenes

Differential Role of Active Compounds in Mitophagy and Related Neurodegenerative Diseases

Neurodegenerative diseases, such as Alzheimer's disease or Parkinson's disease, significantly reduce the quality of life of patients and eventually result in complete maladjustment. Disruption of the synapses leads to a deterioration in the communication of nerve cells and decreased plasticity, which is associated with a loss of cognitive functions and neurodegeneration. Maintaining proper synaptic activity depends on the qualitative composition of mitochondria, because synaptic processes require sufficient energy supply and fine calcium regulation. The maintenance of the qualitative composition of mitochondria occurs due to mitophagy. The regulation of mitophagy is usually based on several internal mechanisms, as well as on signals and substances coming from outside the cell. These substances may directly or indirectly enhance or weaken mitophagy. In this review, we have considered the role of some compounds in process of mitophagy and neurodegeneration. Some of them have a beneficial effect on the functions of mitochondria and enhance mitophagy, showing promise as novel drugs for the treatment of neurodegenerative pathologies, while others contribute to a decrease in mitophagy.

Comparative toxicokinetics of Fusarium mycotoxins in pigs and humans

Mycotoxins frequently contaminate food and feed materials, posing a threat to human and animal health. Fusarium species produce important mycotoxins with regard to their occurrence and toxicity, especially deoxynivalenol (DON), fumonisin B1 (FB1), zearalenone (ZEN) and T-2 toxin (T-2). The susceptibility of an animal species towards the effects of these toxins in part depends on the absorption, distribution, metabolism and excretion (ADME processes) of these toxins from the body. For humans, in vivo information is scarce and often animal data is used for extrapolation to humans. From a kinetic and safety point of view, the pig seems to be a promising animal model to aid in the assessment of the toxicological risk of mycotoxins to humans. Qualitatively, the ADME processes seem to be quite similar between pigs and humans. In addition, similar metabolite and excretion patterns are observed, although some quantitative differences are noticed which are subject of this review. The high sensitivity of pigs towards mycotoxins and the similar kinetics are an advantage for the use of this animal species in the risk assessment of mycotoxins, and for the establishment of legal limits of mycotoxins.

T-2 mycotoxin treatment of newborn rat pups does not significantly affect nervous system functions in adulthood

T-2 toxin is primarily produced by Fusarium sp. abundant under temperate climatic conditions. Its main harmful effect is the inhibition of protein synthesis. Causing oxidative stress, it also promotes lipid peroxidation and changes plasma membrane phospholipid composition; this may lead to nervous system alterations. The aim of the present study was to examine whether a single dose of T-2 toxin administered at newborn age has any long-lasting effects on nervous system functions. Rat pups were treated on the first postnatal day with a single intraperitoneal dose of T-2 toxin (0.2 mg/bwkg). Body weight of treated pups was lower during the second and third week of life, compared to littermates; later, weight gain was recovered. At young adulthood, behavior was tested in the open field, and no difference was observed between treated and control rats. Field potential recordings from somatosensory cortex and hippocampus slices did not reveal any significant difference in neuronal network functions. In case of neocortical field EPSP, the shape was slightly different in treated pups. Long-term synaptic plasticity was also comparable in both groups. Seizure susceptibility of the slices was not different, either. In conclusion, T-2 toxin did not significantly affect basic nervous system functions at this dose.

T-2 toxin inhibits murine ES cells cardiac differentiation and mitochondrial biogenesis by ROS and p-38 MAPK-mediated pathway

OBJECTIVE

To investigate the effect of T-2 toxin on murine embryonic stem cells (ESCs) cardiac differentiation and mitochondrial biogenesis in vitro.

METHODS

Cardiac differentiation of the mouse ESCs was initiated by embryoid bodies (EBs) formation in hanging drops. EBs were exposed to 0.5ng/ml T-2 toxin for 24, 72 and 120h. Cultures were observed daily for the appearance of contracting clusters, and cardiac-specific protein (α-actiniin) were measured by Western blot and immunocytochemistry. Mitochondrial ultrastructure was observed by confocal laser scanning microscopy and transmission EM photography. Reactive oxygen species (ROS) was monitored by H2-dichlorofluorescein-diacetate (H2DCF-DA). The phosphorylation of the p38 (p-p38) and p38 mitogen-activated protein kinase (MAPK) and the expression of mitochondrial biogenesis proteins, including peroxisome proliferator activated receptor coactivator-1 alpha (PGC-1α), nuclear respiratory factor 1 (NRF-1), mitochondrial transcription factor A (mtTFA), and mitochondrial respiratory chain complex IV (COXIV) were analyzed using Western blot. In some experiments, mESCs were pre-treated with the antioxidant Trolox (200μM) for 30min, then exposed to Trolox (200μM) and T-2 toxin (0.5ng/ml) for 72h.

RESULTS

Contracting clusters were observed under the microscope light and cardiac-specific protein (α-actinin) expressed positively indicated mESCs directly differentiated in cardiomyocytes. However, the cardiac differentiation was inhibited by T-2 toxin treatment 72 and 120h. ROS accumulated in murine ES cells in a time-dependent manner. The expression of p-p38 significantly increased in 24h group and decrease in 72 and 120h groups. The decrease of mitochondrial number and the mitochondrial biogenesis-related proteins expression, including PGC-1α, NRF-1, mtTFA, and COXIV decreased in a time-dependent manner with T-2 toxin treatment. However, the inhibition of mitochondrial biogenesis by T-2 toxin in differentiated mESCs was recovered significantly in the presence of the antioxidant Trolox.

CONCLUSION

Taken together, T-2 toxin decreased the expression of PGC-1α, NRF-1, and mtTFA, inhibited mitochondrial biogenesis, and then inhibited the cardiac differentiation of murine ES cells, and the effect was partly responsible for the p38 MAPK mediated by ROS.

The roles of carboxylesterase and CYP isozymes on the in vitro metabolism of T-2 toxin

BACKGROUND

T-2 toxin poses a great threat to human health because it has the highest toxicity of the currently known trichothecene mycotoxins. To understand the in vivo toxicity and transformation mechanism of T-2 toxin, we investigated the role of one kind of principal phase I drug-metabolizing enzymes (cytochrome P450 [CYP450] enzymes) on the metabolism of T-2 toxin, which are crucial to the metabolism of endogenous substances and xenobiotics. We also investigated carboxylesterase, which also plays an important role in the metabolism of toxic substances.

METHODS

A chemical inhibition method and a recombinant method were employed to investigate the metabolism of the T-2 toxin by the CYP450 enzymes, and a chemical inhibition method was used to study carboxylesterase metabolism. Samples incubated with human liver microsomes were analyzed by high performance liquid chromatography-triple quadrupole mass spectrometry (HPLC- QqQ MS) after a simple pretreatment.

RESULTS

In the presence of a carboxylesterase inhibitor, only 20 % T-2 toxin was metabolized. When CYP enzyme inhibitors and a carboxylesterase inhibitor were both present, only 3 % of the T-2 toxin was metabolized. The contributions of the CYP450 enzyme family to T-2 toxin metabolism followed the descending order CYP3A4, CYP2E1, CYP1A2, CYP2B6 or CYP2D6 or CYP2C19.

CONCLUSION

Carboxylesterase and CYP450 enzymes are of great importance in T-2 toxin metabolism, in which carboxylesterase is predominant and CYP450 has a subordinate role. CYP3A4 is the principal member of the CYP450 enzyme family responsible for T-2 toxin metabolism. The primary metabolite produced by carboxylesterase is HT-2, and the main metabolite produced by CYP 3A4 is 3'-OH T-2. The different metabolites show different toxicities. Our results will provide useful data concerning the toxic mechanism, the safety evaluation, and the health risk assessment of T-2 toxin.

Study on the apoptosis mechanism induced by T-2 toxin

T-2 toxin is known to induce apoptosis in mammalian cells. The mechanism of apoptosis induced by T-2 toxin has been proposed to be linked with oxidative stress and mitochondrial pathway. In the current study, the toxic effect of T-2 on Hela, Bel-7402, and Chang liver cells was examined in dose-dependent and time-dependent manner by MTT assay. Caspase-3 was found to be up-regulated under T-2 toxin stress, which suggested that T-2 toxin induced cell apoptosis. Endogenous GSH and MDA levels in all three cell lines were found down- and up-regulated respectively, which indicated the link between toxic effect of T-2 toxin and intracellular oxidative stress. It was also found by MTT assay that NAC, which maintained the level of GSH in cells, could protect cells from death. Western-blot result showed that the level of both activated Caspase-8 and Caspase-9 increased when cells were treated by T-2 toxin. Caspase-9 was found to be activated earlier than Caspase-8. It was also found that p53 was up-regulated under T-2 toxin stress in the study. These results implied that the effect of T-2 toxin on cells was apoptosis rather than necrosis, and it was probably induced through mitochondrial pathway. To the best of our knowledge, the present study is the first to show that JunD is down-regulated in T-2 toxin induced apoptosis. By construction of an over-expression vector for the JunD gene, we observed that the survival ratio of JunD over-expressed cells obviously increased under T-2 toxin stress. These results suggested that the mechanism of T-2 induced cell death was closely connected with oxidative stress, and that JunD plays an important role in the defensive process against T-2 toxin stress.

A direct assessment of mycotoxin biomarkers in human urine samples by liquid chromatography tandem mass spectrometry

Detection of mycotoxin biomarkers in urine of humans and animals provides a direct approach for assessing exposure to these mycotoxins as opposed to the indirect approach of food analysis, which in most cases is affected by the heterogeneity of the toxin in the food samples. Seven (7) mycotoxins and their metabolites (total 18 analytes) were selected and an LC-MS/MS method for their determination in human urine was developed and validated. The method consisted of direct analysis of two mycotoxin conjugates, deoxynivalenol-glucuronide and zearalenone-glucuronide without beta glucuronidase digestion of the urine samples. Since high method sensitivity is of utmost importance in such study, critical factors which could improve the analyte recovery and method sensitivity were investigated by a D-optimal experimental design. Urine samples (10 mL) were first extracted with 15 mL ethyl acetate/formic acid (99/1, v/v) followed by SAX SPE clean-up of the acidified aqueous fraction. Both extracts were combined and analyzed using an LC-MS/MS system operated in the positive ionization mode. A total run time of 28 min was adopted with all the 18 analytes eluting within 15 min. The method was validated by taking into consideration the guidelines specified in Commission Decision 2002/657/EC and 401/2006/EC. Forty samples obtained from volunteers within the laboratory research group were analyzed as part of a pilot study. All results were expressed per mg creatinine. A total of 9 samples were found contaminated with one or more of the following analytes: DON, OTA, OTα, 4-OH OTA, ZEN, CIT and β-ZOL. One-eighth (5/40) of the samples were contaminated with DON in the range of 3.7-67 ng mg(-1) creatinine. Samples with detectable levels of DON did not show any co-occurrence of DON-3Glu. One sample was found to be contaminated with 4-OH OTA (<LOQ), co-occurring with only OTA (0.2 ng mg(-1) creatinine). OTα (up to 4.4 ng mg(-1) creatinine) was detected in three other samples co-occurring with low levels of OTA (up to 0.3 ng mg(-1) creatinine) and no 4-OH OTA detected. ZEN was detected in 10% (4/40) of the samples analyzed. Three samples were contaminated with β-ZOL (3.3-20 ng mg(-1) creatinine), co-occurring with ZEN (<LOQ-10.8 ng mg(-1) creatinine). The ratio of ZEN/β-ZOL varied for all the three samples. α-ZOL was not detected in any of the 40 samples. CIT was detected in one sample at 4.5 ng mg(-1) creatinine. This is the first study carried out with a small group of the Belgian population to assess exposure to mycotoxins using biomarkers.

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.

Integrated transcriptional and proteomic analysis with in vitro biochemical assay reveal the important role of CYP3A46 in T-2 toxin hydroxylation in porcine primary hepatocytes

Both T-2 toxin and its metabolites are highly potent mycotoxins that can cause severe human and animal diseases upon exposure. Understanding the toxic mechanism and biotransformation process of T-2 toxin at a cellular level is essential for the development of counter-measures. We investigated the effect of T-2 toxin in porcine primary hepatocytes using porcine genome array and two-dimensional difference gel electrophoresis with matrix-assisted laser desorption/ionization tandem time of flight mass spectrometry. Integrated transcriptional and proteomic analysis demonstrated that T-2 toxin adversely affected porcine hepatocytes by initiating lipid metabolism disorder, oxidative stress response, and apoptosis. In addition, xenobiotic metabolism genes, including cytochrome P450 3As (CYP3A46 and CYP3A39), carboxylesterase 1Cs (CES1C4 and CES1C5), and epoxide hydrolase (EPHX1), increased in T-2 toxin treatment cells. Using HepG2 cells to over-express the recombinant xenobiotic metabolism genes above and rapid resolution liquid chromatography/tandem mass spectrometry to detect metabolites of T-2 toxin, we determined that porcine CYP3A46 mainly catalyzed T-2 to form 3'-hydroxy-T-2, which was further confirmed by purified CYP3A46 protein. However, recombinant porcine CES1C5 and EPHX1 did not enhance hydrolysis and de-epoxidation of T-2 implying that other esterases and epoxide hydrolases may play dominant roles in those reactions.

Biotransformation of terpenoids by mammals, microorganisms, and plant-cultured cells

This review article summarizes our knowledge of the metabolism of mono- and sesquiterpenoids in mammals, microorganisms, cloned-insect enzymes, and plant-cultured cells. A number of unusual enzymatic reactions and products are reported such as the stereoselective formation of primary alcohols from sterically congested Me2C groups. Such enzymatic processes, including unknown chemical transformations under abiotic conditions, could lead to the discovery of new chemical reactions and might be helpful in the design of new drugs. The transformations of the following mono- and sesquiterpenoids (in alphabetical order) are discussed: (+)-(1R)-aromadendrene (61), (-)-allo-aromadendrene (62), (+/-)-camphene (21), (-)-cis-carane (20), (+)-3-carene (17), (+/-)-carvone (27), (-)-beta-caryophyllene (43), (+)-cedrol (35), cuminaldehyde (25), (+)-curdione (69), (-)-cyclocolorenone (60), (-)-elemol (51), (2E,6E)-farnesol (31), germacrone (67), ginsenol (40), (-)-globulol (63), isoprobotryan-9alpha-ol (82a), juvenile hormone III (33), (+)-ledol (65), (+)-longifolene (46), myrcene (3), (-)-myrtenal (23), (+)-nootkatone (48), patchouli alcohol (37), (-)-perillaldehyde (24), (-)-alpha- and beta-pinene (8 and 9), alpha-santalol (28), (-)-6beta-santonin (83a), 6beta-tetrahydrosantonin (83b), beta-selinene (57), alpha-thujone (26a), beta-thujone (26b), T-2 toxin (87), and valerianol (53).

Nivalenol--induced apoptosis in thymus, spleen and Peyer's patches of mice

ICR:CD-1 male mice were orally administered with Nivalenol(NIV) at the dose levels of 5, 10 and 15 mg/kg body weight, and examined at 12, 24 and 48 hours after inoculation (HAI), respectively, to elucidate the process of development of apoptosis in the thymus, spleen and Peyer's patch. There were no signs of clinical disorders and no changes in body and organ weights until 48 HAI except for that the thymus weight significantly decreased at 48 HAI. Immunohistochemically, the number of apoptotic lymphocytes evaluated by in situ detection for fragmented DNA showed a dose-dependent increase at 12 HAI in both the thymus and the Peyer's patch, while it became to increase at 24 HAI in the spleen. Dead lymphocytes in the thymus, spleen and Peyer's patch showed ultrastructural characteristics of apoptosis. Moreover, the DNA ladder was first detected by agarose gel electrophoresis at 12 HAI in the thymus of 15 mg/kg-group. The results clearly indicate that NIV is able to induce apoptosis in the lymphoid tissues of mice.

Occurrence of T-2 toxin in processed cereals and pulses in Turkey determined by HPLC and TLC

The purpose of this study was to investigate the T-2 toxin level of contaminated cereal and pulse products in Turkey. T-2 toxin was detected using high performance liquid chromatography (HPLC) with UV detection at 208 nm and thin layer chromatography (TLC) was used for confirmation of the T-2 toxin-contaminated samples (> or = 1 ppm). The recovery was 93 +/- 3.3% (SD 3.29, n = 5) for chickpea spiked with a known amount of T-2 toxin (1 ppm). The detection limits for T-2 toxin for HPLC and TLC were 25 ng per injection and 50 ng per spot, respectively. A total of 50 commercially available cereal and pulse product samples, collected from markets and street bazaars, were analysed. Incidences of T-2 toxin detected in cereal and pulse products were 23.5% and 31.2%, respectively and the maximum detected amount was 1.9 ppm in a sample of dried beans. The incidence of toxin-contaminated specimens is not so low relative to the volume of specimens produced.

Apoptosis in mouse fetuses from dams exposed to T-2 toxin at different days of gestation

T-2 toxin (2 mg/kg b.w.) was orally inoculated to pregnant mice at gestational day (GD) 8.5, 9.5, 10.5, 11.5, 12.5, 13.5, 14.5, 15.5 and GD 16.5, respectively, and the fetuses were examined 24 hours later. The number and region of pyknotic or karyorrhectic cells varied according to inoculation date. In the GD 13.5-subgroup, a moderate to high number of pyknotic or karyorrhectic neuronal cells were observed in the central nervous system, peri-ventricular zone to subventricular zone, and pyknosis or karyorrhexis were also observed in a small number of chondroblasts and chondrocytes. In the GD 16.5-subgroup, a moderate to high number of pyknotic or karyorrhectic cells were observed in the thymus and renal subcapsular parenchyma. The nuclei of these pyknotic or karyorrhectic cells were strongly stained by the terminal deoxy nucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end labeling method widely used for the in situ detection of apoptotic nuclei. In addition, a few fetuses from dams which were given T-2 toxin at GD 13.5 or GD 14.5 and killed at GD 17.5 showed skeletal abnormalities such as wavy ribs and short scapula. From the present findings and the well known fact that T-2 toxin readily crosses the rat placenta, it seems that T-2 toxin-induced apoptosis in the developing mouse fetuses might be a direct effect of T-2 toxin on fetuses.

Brazilian Baccharis toxins: livestock poisoning and the isolation of macrocyclic trichothecene glucosides

Samples of the toxic Brazilian plant, Baccharis coridifolia, which is responsible for numerous cases of livestock poisoning in southern Brazil and Argentina, were collected during the growing season, and the toxicities in calves of the plant materials were correlated with the levels of macrocyclic trichothecenes present. Female plants in flower were considerably more toxic than male plants or plants not in flower. Plants not in flower were of intermediate toxicity. The female plants in flower typically contained 5-10 times the levels of toxins as were found in the male plants. In addition, six new glucosides of the macrocyclic trichothecenes were isolated and characterized. The most prominent glucosides, those of roridins A and E, were found in high levels in the female plants.

Pharmacokinetic profile of conjugated verrucarol urinary metabolites in dogs

The pharmacokinetics and renal excretion of a trichothecene mycotoxin, verrucarol, were studied in six mongrel dogs following IV administration (0.4 mg kg-1). The fraction of verrucarol excreted intact in the urine ranged from 0.9% to 2.7% of the administered dose. The fraction of verrucarol metabolites excreted in the urine was 32-60% for verrucaryl glucuronides and 32-47% for verrucaryl sulphates. These urinary conjugated metabolites were analysed quantitatively following their enzymatic hydrolysis. The half-life of verrucarol calculated from the urinary data of its conjugated metabolites was not significantly different from the half-life calculated from the plasma data of the parent compound.