Synthesis and characterization of deoxynivalenol glucuronide: its comparative immunotoxicity with deoxynivalenol

Vulnerability of polarised intestinal porcine epithelial cells to mycotoxin deoxynivalenol depends on the route of application

Background and Aims

Deoxynivalenol (DON) is a Fusarium derived mycotoxin, often occurring on cereals used for human and animal nutrition. The intestine, as prominent barrier for nutritional toxins, has to handle the mycotoxin from the mucosa protected luminal side (apical exposure), as well as already absorbed toxin, reaching the cells from basolateral side via the blood stream. In the present study, the impact of the direction of DON exposure on epithelial cell behaviour and intestinal barrier integrity was elucidated.

Methods

A non-transformed intestinal porcine epithelial cell line (IPEC-J2), cultured in membrane inserts, serving as a polarised in vitro model to determine the effects of deoxynivalenol (DON) on cellular viability and tight junction integrity.

Results

Application of DON in concentrations up to 4000 ng/mL for 24, 48 and 72 hours on the basolateral side of membrane cultured polarised IPEC-J2 cells resulted in a breakdown of the integrity of cell connections measured by transepithelial electrical resistance (TEER), as well as a reduced expression of the tight junction proteins ZO-1 and claudin 3. Epithelial cell number decreased and nuclei size was enlarged after 72 h incubation of 4000 ng/mL DON from basolateral. Although necrosis or caspase 3 mediated apoptosis was not detectable after basolateral DON application, cell cycle analysis revealed a significant increase in DNA fragmentation, decrease in G0/G1 phase and slight increase in G2/M phase after 72 hours incubation with DON 2000 ng/mL.

Conclusions

Severity of impact of the mycotoxin deoxynivalenol on the intestinal epithelial barrier is dependent on route of application. The epithelium appears to be rather resistant towards apical (luminal) DON application whereas the same toxin dose from basolateral severely undermines barrier integrity.

Cross-reactivity of antibodies in some commercial deoxynivalenol test kits against some fusariotoxins

Cross-reactivity of antibodies in AGRAQUANT, DON EIA, VERATOX, ROSA LF-DONQ, and MYCONTROLDON designed for deoxynivalenol (DON) determination in food and feedstuffs was evaluated against nivalenol, 3-acetylDON, 15-acetylDON, de-epoxy metabolite 1 of DON, DON-3β-glucoside, T2-toxin, HT2-toxin, fusarenone X, diacetoxyscirpenol, verrucarol, and zearalenone. Cross-reactivity measurements were run in water using the 50% reduction of absorbance of the blank for ELISA kits or through direct DON determination upon using the standards of mycotoxins via ROSA LF-DONQ or MYCONTROLDON. For the tested toxin concentrations, all DON kits have low cross-reactivity toward diacetoxyscirpenol, T2-toxin, HT2-toxin, verrucarol, and zearalenone and moderate cross-reactivity toward 15-AcetylDON and fusarenone X. AGRAQUANT, DON EIA, and VERATOX kits showed high cross-reactivity in various ranking orders against DON-3-Glc, DOM-1, and 3AcDON. DON EIA showed also high cross-reactivity against nivalenol and fusarenone X. These mycotoxins could coexist in food or feedstuffs, and analytical results can be wrongly interpreted. Cross-reactivity does not allow checking the compliance with the legal norms, but it does allow an overall risk assessment for the consumers. Updating regularly the cross-reactivity evaluation of the produced batches is recommended for 3-acetylDON, nivalenol, DON-3-Glc, de-epoxy metabolite 1, and fusarenone X.

Deoxynivalenol and nivalenol occurrence and exposure assessment

Deoxynivalenol (DON) and nivalenol (NIV) are common dietary contaminants in most temperate regions of the world. The frequency and levels of exposure will vary by geographic location, annual variations in rainfall patterns, national wealth and related agricultural and regulatory infrastructure, dietary diversity and food sufficiency. DON contamination is more frequent and at higher levels than NIV, though chronic exposure to both is predicted to occur in many parts of the world. In addition acute poisoning episodes are reported, particularly from China, and it is important to have the tools to assess both chronic and acute exposure. This review describes both traditional epidemiology and the development of biomarkers to assess exposure. The biomarker approaches are at an early stage, and it will be important to assess the applicability of these approaches in different settings and at different exposure levels. It is hoped that some of the developmental 'omics' technologies will support both 'exposure biomarker' and 'effect biomarker' development.

Assessment of deoxynivalenol metabolite profiles in UK adults

Deoxynivalenol (DON) requires no activation for toxicity, though susceptibility may reflect individual variations in detoxification. This study reports the measurement of un-metabolised urinary DON (free DON) and DOM-1 in samples previously analysed for the combined measure of free DON+DON-glucuronide (fD+DG), with a concentration >5 ng/ml, for 34 UK adults. Four consecutive daily urine samples were analysed from twenty-two individuals, whilst from 12 individuals only a single sample was analysed. The mean (median) concentration of urinary fD+DG in this sub-set was 17.8 ng/ml (13.8 ng/ml), range 5.0-78.2 ng/ml. In 23/34 (68%) individuals, free DON was detected, mean 2.4 ng/ml; range 0.5-9.3 ng/ml. Urinary DOM-1 was detected in 1/34 (3%) of individuals; present at ∼1% of urinary fD+DG concentration for that individual. The concentration of fD+DG combined was significantly correlated with urinary free DON (p<0.001, R(2)=0.65), but not with the percentage of free DON to fD+DG (p=0.615, R(2)=0.01), suggesting that the level of DON exposure did not affect the metabolism to DG within the range observed. In this survey most individuals had no detectable urinary DOM-1 and 68% did not detoxify all of the ingested DON to DON-glucuronide. This study needs to be extended to understand whether the fD / DG ratio provides a phenotypic measure of DON susceptibility.

Effects of milling and cooking processes on the deoxynivalenol content in wheat

Deoxynivalenol (DON, vomitoxin) is a natural-occuring mycotoxin mainly produced by Fusarium graminearum, a food-borne fungi widely distributed in crops and it is one of the most important mycotoxins in wheat and wheat-based foods and feeds. DON affects animal and human health causing diarrhea, vomiting, gastro-intestinal inflammation, and immunomodulation. Since the rate of the occurrence of DON in wheat is high, effective procedures to remove or eliminate DON from food products is essential to minimize exposures in those who consume large amounts of wheat. Cleaning prior to milling reduced to some extent the concentration of DON in final products. Since DON is distributed throughout the kernels, with higher content in the outer skin, milling is also effective in reducing the DON levels of wheat-based foods if bran and shorts are removed before thermal cooking. DON is water-soluble and cooking with larger amounts of water lowers DON content in products such as spaghetti and noodles. During baking or heating, DON is partially degraded to DON-related chemicals, whose toxicological effects are not studied well. This paper reviews the researches on the effects of milling and cooking on the DON level and discusses the perspectives of further studies.

Immunochemical methods in health risk assessment: cross reactivity of antibodies against mycotoxin deoxynivalenol with deoxynivalenol-3-glucoside

Co-occurrence of deoxynivalenol (DON) with other DON derivatives/metabolites and other Fusarium toxins, including zearalenone, nivalenol and as well as other mycotoxins (e.g. fumonisins) is frequently observed in food and feed. DON-3beta-glucopyranoside (DON-3-glucoside) was described as detoxification product of DON in wheat. This mycotoxin conjugate was observed in maize, barley, malt, beer and wort. Digestion of this conjugate in intestine is still unclear but due to possibility to release DON after hydrolysis is considered as potential masked mycotoxin. DON is analytically quantified by various methods and also with immunochemical methods. There is no available information about specificity of anti-DON antibodies used in commercial ELISA kits with DON-3-glucoside. Preliminary testing of anti-DON monoclonal antibodies used in ELISA kits RIDASCREEN DON (R-BiopharmAG, Germany) approved a hypothesis that these antibodies have high relative cross reactivity with DON-3-glucoside. In two repeated tests cross reaction 82 and 98% were observed. Analytical results produced by these ELISA kits can be interpreted as an approximate sum of both mycotoxins. Described cross reactivity can lead to overestimating of DON concentration. Over these cross reactions immunochemical methods are mentioned still valuable for quantitative screening and even for an initial exposure assessment in situations when there are practical or economical reasons not to use another analytical method with a reasonable low limit of quantification (< 50 ppb).

Tissue distribution and proinflammatory cytokine gene expression following acute oral exposure to deoxynivalenol: comparison of weanling and adult mice

The frequent presence of deoxynivalenol (DON) in cereal-based foods and the high intake of these foods by children raises particular concerns about the relative susceptibility of this subpopulation to adverse effects evoked by this mycotoxin. We tested the hypothesis that both toxicokinetics and proinflammatory cytokine gene expression following a oral DON exposure at 5mg/kg bw differ between weanling (3-4 wk) and young adult (8-10 wk) female mice. DON was rapidly taken up with maximum plasma concentrations reaching 1.0 microg/ml in adult mice at 15 min, whereas DON levels were approximately twice as much in weanling mice at these times. DON was rapidly cleared in both weanling and adult mice with concentrations being reduced by 78% and 81% of the peak levels, respectively, after 2h. DON accumulation and clearance in spleen, liver, lung and kidney followed similar kinetics to that of plasma with tissue burdens also reaching twice that of adult mice. When TNF-alpha, IL-1beta and IL-6 mRNAs in spleens (a primary source of systemic proinflammatory cytokines) were used as biomarkers of the DON's effects, expression of these mRNAs was two to three times greater in weanling than adult mouse. However, differences in proinflammatory cytokine expression were less robust or not apparent in the liver or lung. Taken together, these data suggest that young mice are modestly more susceptible than adult mice to the adverse effects of DON and that this might result from a greater toxin tissue burden.