Comparison of anorectic and emetic potencies of deoxynivalenol (vomitoxin) to the plant metabolite deoxynivalenol-3-glucoside and synthetic deoxynivalenol derivatives EN139528 and EN139544

Emesis to trichothecene deoxynivalenol and its congeners correspond to secretion of peptide YY and 5-HT

The type B trichothecenes pollute food crops and have been associated to alimentary toxicosis resulted in emetic reaction in human and animal. This group of mycotoxins consists deoxynivalenol (DON) and four structurally related congeners: 3-acetyl-deoxynivalenol (3-ADON), 15-acetyl deoxynivalenol (15-ADON), nivalenol (NIV) and 4-acetyl-nivalenol (fusarenon X, FX). While emesis induced by intraperitoneally dosed to DON in the mink has been related to plasma up-grading of 5-hydroxytryptamine (5-HT) and neurotransmitters peptide YY (PYY), the impact of oral dosing with DON or its four congeners on secretion of these chemical substances have not been established. The aim of this work was to contraste emetic influence to type B trichothecene mycotoxins by orally dosing and involve these influence to PYY and 5-HT. All five toxins attracted marked emetic reaction that are relevant to elevated PYY and 5-HT. The reduction in vomiting induced by the five toxins and PYY was due to blocking of the neuropeptide Y2 receptor. The inhibition of the induced vomiting response by 5-HT and all five toxins is regulated by the 5-HT3 receptor inhibitor granisetron. In a word, our results indicate that PYY and 5-HT take a key role in the emetic reaction evoked by type B trichothecenes.

Hazard characterisation for significant mycotoxins in food

This review updates the current status of activities related to hazard characterisation for mycotoxins, with special reference to regulatory work accomplished within the European Union. Because the relevant information on these topics is widely scattered in the scientific literature, this review intends to provide a condensed overview on the most pertinent aspects. Human health risk assessment is a procedure to estimate the nature and potential for harmful effects of mycotoxins on human health due to exposure to them via contaminated food. This assessment involves hazard identification, hazard characterisation, exposure assessment, and risk characterisation. Mycotoxins covered in this review are aflatoxins, ochratoxin A, cyclopiazonic acid, citrinin, trichothecenes (deoxynivalenol, nivalenol, T-2, and HT-2 toxins), fumonisins, zearalenone, patulin, and ergot alkaloids. For mycotoxins with clear genotoxic/carcinogenic properties, the focus is on the margin of exposure approach. One of its goals is to document predictive characterisation of the human hazard, based on studies in animals using conditions of low exposure. For the other, non-genotoxic toxins, individual 'no adverse effect levels' have been established, but structural analogues or modified forms may still complicate assessment. During the process of hazard characterisation, each identified effect is assessed for human relevance. The estimation of a 'safe dose' is the hazard characterisation endpoint. The final aim of all of these activities is to establish a system, which is able to minimise and control the risk for the consumer from mycotoxins in food. Ongoing research on mycotoxins constantly comes up with new findings, which may have to be implemented into this system.

Neither GLP-1 receptors nor GFRAL neurons are required for aversive or anorectic response to DON (vomitoxin)

Deoxynivalenol (DON), a type B trichothecene mycotoxin contaminating grains, promotes nausea, emesis and anorexia. With DON exposure, circulating levels of intestinally derived satiation hormones, including glucagon-like peptide 1 (GLP-1) are elevated. To directly test whether GLP-1 signaling mediates the effects of DON, we examined the response of GLP-1 or GLP-1R-deficient mice to DON injection. We found comparable anorectic and conditioned taste avoidance learning responses in GLP-1/GLP-1R deficient mice compared to control littermates, suggesting that GLP-1 is not necessary for the effects of DON on food intake and visceral illness. We then used our previously published data from translating ribosome affinity purification with RNA sequencing (TRAP-seq) analysis of area postrema neurons that express the receptor for the circulating cytokine growth differentiation factor (GDF15), growth differentiation factor a-like (GFRAL). Interestingly, this analysis showed that a cell surface receptor for DON, calcium sensing receptor (CaSR), is heavily enriched in GFRAL neurons. Given that GDF15 potently reduces food intake and can cause visceral illness by signaling through GFRAL neurons, we hypothesized that DON may also signal by activating CaSR on GFRAL neurons. Indeed, circulating GDF15 levels are elevated after DON administration but both GFRAL knockout and GFRAL neuron-ablated mice exhibited similar anorectic and conditioned taste avoidance responses compared to WT littermates. Thus, GLP-1 signaling and GFRAL signaling and neurons are not required for DON-induced visceral illness or anorexia.

Type B Trichothecenes in Cereal Grains and Their Products: Recent Advances on Occurrence, Toxicology, Analysis and Post-Harvest Decontamination Strategies

Type B trichothecenes (deoxynivalenol, nivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol) and deoxynivalenol-3-glucoside (DON-3G) are secondary toxic metabolites produced mainly by mycotoxigenic Fusarium fungi and have been recognized as natural contaminants in cereals and cereal-based foods. The latest studies have proven the various negative effects of type B trichothecenes on human health. Due to the widespread occurrence of Fusarium species, contamination by these mycotoxins has become an important aspect for public health and agro-food systems worldwide. Hence, their monitoring and surveillance in various foods have received a significant deal of attention in recent years. In this review, an up-to-date overview of the occurrence profile of major type B trichothecenes and DON-3G in cereal grains and their toxicological implications are outlined. Furthermore, current trends in analytical methodologies for their determination are overviewed. This review also covers the factors affecting the production of these mycotoxins, as well as the management strategies currently employed to mitigate their contamination in foods. Information presented in this review provides good insight into the progress that has been achieved in the last years for monitoring type B trichothecenes and DON-3G, and also would help the researchers in their further investigations on metabolic pathway analysis and toxicological studies of these Fusarium mycotoxins.

Substance P and Glucagon-like Peptide-17-36 Amide Mediate Anorexic Responses to Trichothecene Deoxynivalenol and Its Congeners

Type B trichothecenes commonly contaminate cereal grains and include five structurally related congeners: deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), fusarenon X (FX), and nivalenol (NIV). These toxins are known to have negative effects on human and animal health, particularly affecting food intake. However, the pathophysiological basis for anorexic effect is not fully clarified. The purpose of this study is to explore the potential roles of the brain-gut peptides substance P (SP) and glucagon-like peptide-1_7-36 amide (GLP-1) in anorexic responses induced by type B trichothecenes following both intraperitoneal (IP) and oral administration. SP and GLP-1 were elevated at 1 or 2 h and returned to basal levels at 6 h following exposure to DON and both ADONs. FX induced the production of both brain gut peptides with initial time at 1 or 2 h and duration > 6 h. Similar to FX, exposing IP to NIV caused elevations of SP and GLP-1 at 1 h and lasted more than 6 h, whereas oral exposure to NIV only increased both brain gut peptides at 2 h. The neurokinin-1 receptor (NK-1R) antagonist Emend^® dose-dependently attenuated both SP- and DON-induced anorexic responses. Pretreatment with the GLP-1 receptor (GLP-1R) antagonist Exending_9-39 induced a dose-dependent attenuation of both GLP-1- and DON-induced anorexic responses. To summarize, the results suggest that both SP and GLP-1 play important roles in anorexia induction by type B trichothecenes.

Glucose-Dependent Insulinotropic Polypeptide and Substance P Mediate Emetic Response Induction by Masked Trichothecene Deoxynivalenol-3-Glucoside through Ca2+ Signaling

Deoxynivalenol (DON), the most naturally-occurring trichothecenes, may affect animal and human health by causing vomiting as a hallmark of food poisoning. Deoxynivalenol-3-glucoside (D3G) usually co-occurs with DON as its glucosylated form and is another emerging food safety issue in recent years. However, the toxicity of D3G is not fully understood compared to DON, especially in emetic potency. The goals of this research were to (1) compare emetic effects to D3G by oral and intraperitoneal (IP) routes and relate emetic effects to brain-gut peptides glucose-dependent insulinotropic polypeptide (GIP) and substance P (SP) in mink; (2) determine the roles of calcium-sensing receptor (CaSR) and transient receptor potential (TRP) channel in D3G’s emetic effect. Both oral and IP exposure to D3G elicited marked emetic events. This emetic response corresponded to an elevation of GIP and SP. Blocking the GIP receptor (GIPR) diminished emetic response induction by GIP and D3G. The neurokinin 1 receptor (NK-1R) inhibitor Emend^® restrained the induction of emesis by SP and D3G. Importantly, CaSR antagonist NPS-2143 or TRP channel antagonist ruthenium red dose-dependently inhibited both D3G-induced emesis and brain-gut peptides GIP and SP release; cotreatment with both antagonists additively suppressed both emetic and brain-gut peptide responses to D3G. To summarize, our findings demonstrate that activation of CaSR and TRP channels contributes to D3G-induced emesis by mediating brain-gut peptide exocytosis in mink.

Structure-toxicity relationships, toxicity mechanisms and health risk assessment of food-borne modified deoxynivalenol and zearalenone: A comprehensive review

Mycotoxin, as one of the most common pollutants in foodstuffs, poses great threat to food security and human health. Specifically, deoxynivalenol (DON) and zearalenone (ZEN)-two mycotoxin contaminants with considerable toxicity widely existing in food products-have aroused broad public concerns. Adding to this picture, modified forms of DON and ZEN, have emerged as another potential environmental and health threat, owing to their higher re-transformation rate into parent mycotoxins inducing accumulation of mycotoxin in humans and animals. Given this, a better understanding of the toxicity of modified mycotoxins is urgently needed. Moreover, the lack of toxicity data means a proper risk assessment of modified mycotoxins remains challenging. To better evaluate the toxicity of modified DON and ZEN, we have reviewed the relationship between their structures and toxicities. The toxicity mechanisms behind modified DON and ZEN have also been discussed; briefly, these involve acute, subacute, chronic, and combined toxicities. In addition, this review also addresses the global occurrence of modified DON and ZEN, and summarizes novel methods-including in silico analysis and implementation of relative potency factors-for risk assessment of modified DON and ZEN. Finally, the health risk assessment of modified DON and ZEN has also been discussed comprehensively.

Deoxynivalenol (Vomitoxin)-Induced Anorexia Is Induced by the Release of Intestinal Hormones in Mice

Deoxynivalenol (DON), also known as vomitoxin, is a mycotoxin that can cause antifeeding and vomiting in animals. However, the mechanism of DON inducing anorexia is complicated. Studies have shown that intestinal hormones play a significant part in the anorexia caused by DON. We adopted the “modeling of acute antifeeding in mice” as the basic experimental model, and used two methods of gavage and intraperitoneal injection to explore the effect of intestinal hormones on the antifeedant response induced by DON in mice. We found that 1 and 2.5 mg/kg·bw of DON can acutely induce anorexia and increase the plasma intestinal hormones CCK, PYY, GIP, and GLP-1 in mice within 3 h. Direct injection of exogenous intestinal hormones CCK, PYY, GIP, and GLP-1 can trigger anorexia behavior in mice. Furthermore, the PYY receptor antagonist JNJ-31020028, GLP-1 receptor antagonist Exendin(9-39), CCK receptor antagonist Proglumide, GIP receptor antagonist GIP(3-30)NH₂ attenuated both intestinal hormone and DON-induced anorectic responses. These results indicate that intestinal hormones play a critical role in the anorexia response induced by DON.

COVID-19, nausea, and vomiting

Exclusion of nausea (N) and vomiting (V) from detailed consideration as symptoms of COVID-19 is surprising as N can be an early presenting symptom. We examined the incidence of NV during infection before defining potential mechanisms. We estimate that the overall incidence of nausea (median 10.5%), although variable, is comparable with diarrhea. Poor definition of N, confusion with appetite loss, and reporting of N and/or V as a single entity may contribute to reporting variability and likely underestimation. We propose that emetic mechanisms are activated by mediators released from the intestinal epithelium by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) modulate vagal afferents projecting to the brainstem and after entry into the blood, activate the area postrema (AP) also implicated in anorexia. The receptor for spike protein of SARS-CoV-2, angiotensin 2 converting enzyme (ACE2), and transmembrane protease serine (for viral entry) is expressed in upper gastrointestinal (GI) enterocytes, ACE2 is expressed on enteroendocrine cells (EECs), and SARS-CoV-2 infects enterocytes but not EECs (studies needed with native EECs). The resultant virus-induced release of epithelial mediators due to exocytosis, inflammation, and apoptosis provides the peripheral and central emetic drives. Additionally, data from SARS-CoV-2 show an increase in plasma angiotensin II (consequent on SARS-CoV-2/ACE2 interaction), a centrally (AP) acting emetic, providing a further potential mechanism in COVID-19. Viral invasion of the dorsal brainstem is also a possibility but more likely in delayed onset symptoms. Overall, greater attention must be given to nausea as an early symptom of COVID-19 and for the insights provided into the GI effects of SARS-CoV-2.

The trichothecene neosolaniol stimulates an emetic response through neuropeptide Y2 and serotonin 3 receptors in mink

Type A trichothecene neosolaniol (NEO) is considered a potential risk to human and animal health by the European Food Safety Authority (EFSA). To date, available data do not allow making conclusions about the toxicological properties of this toxin. Trichothecenes have been previously demonstrated to induce emetic responses in mink, and this response has been associated with neurotransmitter peptide YY (PYY) and serotonin (5-hydroxytryptamine, 5-HT). The goal of this study was to compare emetic effects of NEO administered by intraperitoneal and oral routes and relate these effects to PYY and 5-HT. The effective doses resulting in emetic events in 50% of the animals following intraperitoneal and oral exposure to NEO were 0.4 and 0.09 mg/kg bw, respectively. This emetic response corresponded to elevated PYY and 5-HT levels. Blocking the neuropeptide Y2 receptor diminished emesis induction by PYY and NEO. The 5-HT3 receptor inhibitor granisetron completely restrained the induction of emesis by 5-HT and NEO. To summarize, our findings demonstrate that PYY and 5-HT play important roles in the NEO-induced emetic response.

Predictive in silico modeling of emetic potency of liquid cleaning products using an historical in vivo database

The induction of vomiting by activation of mechanisms protecting the body against ingested toxins is not confined to natural products but can occur in response to manmade medicinal and non-medicinal products such as liquid cleaning products where it is a commonly reported adverse effect of accidental ingestion. The present study examined the utility of an historic database (>30 years old) reporting emetic effects of 98 orally administered liquid cleaning formulations studied in vivo (canine model) to objectively identify the main pro-emetic constituents and to derive a predictive model. Data were analysed by categorizing the formulation constituents into 10 main groups followed by using multivariate correlation, partial least squares and recursive partitioning analysis. Using the ED₅₀ we objectively identified high ionic strength, non-ionic surfactants (alcohol ethoxylate) and alkaline pH as the main pro-emetic factors. Additionally, a mathematical model was developed which allows prediction of the ED₅₀ based on formulation. The limitations of the use of historic data and the model are discussed. The results have practical applications in new product formulation and safety but additionally the principles underpinning this in silico study have wider applicability in demonstrating the potential utility of such archival data in current research contributing to animal replacement.

Type A Trichothecene Diacetoxyscirpenol-Induced Emesis Corresponds to Secretion of Peptide YY and Serotonin in Mink

The trichothecene mycotoxins contaminate cereal grains and have been related to alimentary toxicosis resulted in emetic response. This family of mycotoxins comprises type A to D groups of toxic sesquiterpene chemicals. Diacetoxyscirpenol (DAS), one of the most toxic type A trichothecenes, is considered to be a potential risk for human and animal health by the European Food Safety Authority. Other type A trichothecenes, T-2 toxin and HT-2 toxin, as well as type B trichothecene deoxynivalenol (DON), have been previously demonstrated to induce emetic response in the mink, and this response has been associated with the plasma elevation of neurotransmitters peptide YY (PYY) and serotonin (5-hydroxytryptamine, 5-HT). However, it is found that not all the type A and type B trichothecenes have the capacity to induce PYY and 5-HT. It is necessary to identify the roles of these two emetogenic mediators on DAS-induced emesis. The goal of this study was to determine the emetic effect of DAS and relate this effect to PYY and 5-HT, using a mink bioassay. Briefly, minks were fasted one day before experiment and given DAS by intraperitoneally and orally dosing on the experiment day. Then, emetic episodes were calculated and blood collection was employed for PYY and 5-HT test. DAS elicited robust emetic responses that corresponded to upraised PYY and 5-HT. Blocking the neuropeptide Y2 receptor (NPY2R) diminished emesis induction by PYY and DAS. The serotonin 3 receptor (5-HT3R) inhibitor granisetron totally restrained the induction of emesis by serotonin and DAS. In conclusion, our findings demonstrate that PYY and 5-HT have critical roles in DAS-induced emetic response.

The mycotoxin deoxynivalenol activates GABAergic neurons in the reward system and inhibits feeding and maternal behaviours

Deoxynivalenol (DON) or vomitoxin, is a trichothecene mycotoxin produced mainly by Fusarium graminearum and culmorum. Mycotoxins or secondary metabolic products of mold fungi are micro-pollutants, which may affect human and animal health. The neuronal and behavioural actions of DON were analysed in the present study. To address, which neurons can be affected by DON, the neuronal activation pattern following intraperitoneal injection of DON (1 mg/kg) was investigated in adult male rats and the results were confirmed in mice, too. DON-induced neuronal activation was assessed by c-Fos immunohistochemistry. DON injection resulted in profound c-Fos activation in only the elements of the reward system, such as the accumbens nucleus, the medial prefrontal cortex, and the ventral tegmental area. Further double labelling studies suggested that GABAergic neurons were activated by DON treatment. To study the behavioural relevance of this activation, we examined the effect of DON on feed intake as an example of reward-driven behaviours. Following DON injection, feed consumption was markedly reduced but returned to normal the following day suggesting an inhibitory action of DON on feed intake without forming taste-aversion. To further test how general the effect of DON on goal-directed behaviours is, its actions on maternal behaviour was also examined. Pup retrieval latencies were markedly increased by DON administration, and DON-treated mother rats spent less time with nursing suggesting reduced maternal motivation. In a supplementary control experiment, DON did not induce conditioned place preference arguing against its addictive or aversive actions. The results imply that acute uptake of the mycotoxin DON can influence the reward circuit of the brain and exert inhibitory actions on goal-directed, reward-driven behaviours. In addition, the results also suggest that DON exposure of mothers may have specific implications.

Microbiological quality of mink feed raw materials and feed production area

BACKGROUND

The quality of mink feed and raw ingredients affect health and growth. The objectives of this study were to examine the microbiological quality of ready-to-eat mink feed and its raw ingredients, screen the plant part of the feed for mycotoxins, and determine the hygiene of the production environment in the feed processing facilities. The results of the study are important for identification of critical steps in the feed production and for formulation of recommendations for improvements of production processes to obtain better quality feed. Feed and swab samples were taken at three Danish mink feed producers October 2016 and May 2017, respectively. Viable counts, detection of methicillin-resistant Staphylococcus aureus (MRSA), influenza virus and filamentous fungi were performed together with qualitative chemical analyses for bioactive fungal metabolites and mycotoxins. Swab samples were analyzed for total viable counts.

RESULTS

Viable counts varied between 7.2 × 102 and 9.3 × 107 cfu/g in raw ingredients and between 107 and 109 cfu/cm2 on different surfaces at the feed production facilities. A pork meat product, pork haemoglobin, pork liver and a poultry mix was found positive for MRSA, while monophasic Salmonella [4,5,12:i:-] was detected in a pork meat product. Neither MRSA nor Salmonella was detected in any ready-to-eat feed. Influenza A virus was not detected in any sample. Filamentous fungi were detected in all analysed samples of ready-to-eat feed while dihydro-demethyl-sterigmatocystin was found in almost 50% of all ready-to-eat feed samples and in 80% of the sugar beet pulp. Fumonisins and other Fusarium toxins were found especially in corn gluten meal and extruded barley and wheat.

CONCLUSIONS

Mink feed contained a cocktail of mycotoxins and bacteria, which may not per se cause clinical disease, but may affect organ function and animal performance and well-being.

Review article: Role of satiety hormones in anorexia induction by Trichothecene mycotoxins

The trichothecenes, produced by Fusarium, contaminate animal feed and human food in all stages of production and lead to a large spectrum of adverse effects for animal and human health. An hallmark of trichothecenes toxicity is the onset of emesis followed by anorexia and food intake reduction in different animal species (mink, mice and pig). The modulation of emesis and anorexia can result from a direct action of trichothecenes in the brain or from an indirect action in the gastrointestinal tract. The direct action of trichothecenes involved specific brain areas such as nucleate tractus solitarius in the brainstem and the arcuate nuclei in the hypothalamus. Activation of these areas in the brain leads to the activation of specific neuronal populations containing anorexigenic factors (POMC and CART). The indirect action of trichothecenes in the gastrointestinal tract involved, by enteroendocrine cells, the secretion of several gut hormones such as cholecystokinin (CCK) and peptide YY (PYY) but also glucagon-like peptide 1 (GLP-1), gastric inhibitory peptide (GIP) and 5-hydroxytryptamine (5-HT), which transmitted signals to the brain via the gut-brain axis. This review summarizes current knowledge on the effects of trichothecenes, especially deoxynivalenol, on emesis and anorexia and discusses the mechanisms underlying trichothecenes-induced food reduction.

Role of Glucagon-Like Peptide-1 and Gastric Inhibitory Peptide in Anorexia Induction Following Oral Exposure to the Trichothecene Mycotoxin Deoxynivalenol (Vomitoxin)

Deoxynivalenol (DON), which is a Type B trichothecene mycotoxin produced by Fusarium, frequently contaminates cereal staples, such as wheat, barley and corn. DON threatens animal and human health by suppressing food intake and impairing growth. While anorexia induction in mice exposed to DON has been linked to the elevation of the satiety hormones cholecystokinin and peptide YY3-36 in plasma, the effects of DON on the release of other satiety hormones, such as glucagon-like peptide-1 (GLP-1) and gastric inhibitory peptide (GIP), have not been established. The purpose of this study was to determine the roles of GLP-1 and GIP in DON-induced anorexia. In a nocturnal mouse food consumption model, the elevation of plasma GLP-1 and GIP concentrations markedly corresponded to anorexia induction by DON. Pretreatment with the GLP-1 receptor antagonist Exendin9-39 induced a dose-dependent attenuation of both GLP-1- and DON-induced anorexia. In contrast, the GIP receptor antagonist Pro3GIP induced a dose-dependent attenuation of both GIP- and DON-induced anorexia. Taken together, these results suggest that GLP-1 and GIP play instrumental roles in anorexia induction following oral exposure to DON, and the effect of GLP-1 is more potent and long-acting than that of GIP.

Risks to human and animal health related to the presence of deoxynivalenol and its acetylated and modified forms in food and feed

Deoxynivalenol (DON) is a mycotoxin primarily produced by Fusarium fungi, occurring predominantly in cereal grains. Following the request of the European Commission, the CONTAM Panel assessed the risk to animal and human health related to DON, 3-acetyl-DON (3-Ac-DON), 15-acetyl-DON (15-Ac-DON) and DON-3-glucoside in food and feed. A total of 27,537, 13,892, 7,270 and 2,266 analytical data for DON, 3-Ac-DON, 15-Ac-DON and DON-3-glucoside, respectively, in food, feed and unprocessed grains collected from 2007 to 2014 were used. For human exposure, grains and grain-based products were main sources, whereas in farm and companion animals, cereal grains, cereal by-products and forage maize contributed most. DON is rapidly absorbed, distributed, and excreted. Since 3-Ac-DON and 15-Ac-DON are largely deacetylated and DON-3-glucoside cleaved in the intestines the same toxic effects as DON can be expected. The TDI of 1 μg/kg bw per day, that was established for DON based on reduced body weight gain in mice, was therefore used as a group-TDI for the sum of DON, 3-Ac-DON, 15-Ac-DON and DON-3-glucoside. In order to assess acute human health risk, epidemiological data from mycotoxicoses were assessed and a group-ARfD of 8 μg/kg bw per eating occasion was calculated. Estimates of acute dietary exposures were below this dose and did not raise a health concern in humans. The estimated mean chronic dietary exposure was above the group-TDI in infants, toddlers and other children, and at high exposure also in adolescents and adults, indicating a potential health concern. Based on estimated mean dietary concentrations in ruminants, poultry, rabbits, dogs and cats, most farmed fish species and horses, adverse effects are not expected. At the high dietary concentrations, there is a potential risk for chronic adverse effects in pigs and fish and for acute adverse effects in cats and farmed mink.

Do Plant-Bound Masked Mycotoxins Contribute to Toxicity?

Masked mycotoxins are plant metabolites of mycotoxins which co-contaminate common cereal crops. Since their discovery, the question has arisen if they contribute to toxicity either directly or indirectly through the release of the parent mycotoxins. Research in this field is rapidly emerging and the aim of this review is to summarize the latest knowledge on the fate of masked mycotoxins upon ingestion. Fusarium mycotoxins are the most prevalent masked mycotoxins and evidence is mounting that DON3Glc and possibly other masked trichothecenes are stable in conditions prevailing in the upper gut and are not absorbed intact. DON3Glc is also not toxic per se, but is hydrolyzed by colonic microbes and further metabolized to DOM-1 in some individuals. Masked zearalenone is rather more bio-reactive with some evidence on gastric and small intestinal hydrolysis as well as hydrolysis by intestinal epithelium and components of blood. Microbial hydrolysis of ZEN14Glc is almost instantaneous and further metabolism also occurs. Identification of zearalenone metabolites and their fate in the colon are still missing as is further clarification on whether or not masked zearalenone is hydrolyzed by mammalian cells. New masked mycotoxins continuously emerge and it is crucial that we gain detailed understanding of their individual metabolic fate in the body before we can assess synergistic effects and extrapolate the additive risk of all mycotoxins present in food.

In silico analysis sheds light on the structural basis underlying the ribotoxicity of trichothecenes-A tool for supporting the hazard identification process

Deoxynivalenol is a food borne mycotoxin belonging to the trichothecenes family that may cause severe injuries in human and animals. The inhibition of protein synthesis via the interaction with the ribosome has been identified as a crucial mechanism underlying toxic action. However, it is not still fully understood how and to what extent compounds belonging to trichothecenes family affect human and animal health. In turn, this scenario causes delay in managing the related health risk. Aimed at supporting the hazard identification process, the in silico analysis may be a straightforward tool to investigate the structure-activity relationship of trichothecenes, finding out molecules of possible concern to carry forth in the risk assessment process. In this framework, this work investigated through a molecular modeling approach the structural basis underlying the interaction with the ribosome under a structure-activity relationship perspective. To identify further forms possibly involved in the total trichothecenes-dependent ribotoxic load, the model was challenged with a set of 16 trichothecene modified forms found in plants, fungi and animals, including also compounds never tested before for the capability to bind and inhibit the ribosome. Among them, only the regiospecific glycosylation in the position 3 of the sesquiterpenoid scaffold (i.e. T-2 toxin-3-glucuronide, α and β isomers of T-2 toxin-3-glucoside and deoxynivalenol-3-glucuronide) was found impairing the interaction with the ribosome, while the other compounds tested (i.e. neosolaniol, nivalenol, fusarenon-X, diacetoxyscirpenol, NT-1 toxin, HT-2 toxin, 19- and 20-hydroxy-T-2 toxin, T-2 toxin triol and tetraol, and 15-deacetyl-T-2 toxin), were found potentially able to inhibit the ribosome. Accordingly, they should be included with high priority in further risk assessment studies in order to better characterize the trichothecenes-related hazard.

Masked trichothecene and zearalenone mycotoxins withstand digestion and absorption in the upper GI tract but are efficiently hydrolyzed by human gut microbiota in vitro

SCOPE

Cereal grains are commonly contaminated with Fusarium mycotoxins and their plant-derived masked metabolites. The fate of masked mycotoxins in the human gut is poorly understood. Here we assess the metabolism and transport of glucoside metabolites of common trichothecenes (deoxynivalenol, nivalenol, T-2 toxin) and zearalenone compounds (zearalenone, α- and β-zearalenol) in the human gut in vitro.

METHODS AND RESULTS

Masked mycotoxins were incubated with artificial digestive juices and absorption was assessed in differentiated Caco-2/TC7 cells. Colonic metabolism was studied using fecal batch cultures from five donors and mycotoxins were detected using LC-MS/MS. All masked mycotoxins were stable under upper GI tract conditions and no absorption was observed. Free trichothecenes were absorbed intact whereas free zearalenone compounds were absorbed and metabolized to undetected compounds by Caco-2/TC7 cells. Human gut microbiota efficiently hydrolyzed all masked mycotoxins. Trichothecenes were fully recovered as parent mycotoxins whereas 40-70% of zearalenone compounds were further metabolized to unknown metabolites.

CONCLUSION

Our results demonstrate that masked trichothecenes will reach the colon intact to be released as parent mycotoxins by gut microbiota, hence contributing to mycotoxin exposure. Masked zearalenone compounds are metabolized by gut microbiota and epithelial cells and the identity and toxicity of metabolites remain to be determined.

Calcium-Sensing Receptor and Transient Receptor Ankyrin-1 Mediate Emesis Induction by Deoxynivalenol (Vomitoxin)

The common foodborne mycotoxin deoxynivalenol (DON, vomitoxin) can negatively impact animal and human health by causing food refusal and vomiting. Gut enteroendocrine cells (EECs) secrete hormones that mediate DON's anorectic and emetic effects. In prior work utilizing a cloned EEC model, our laboratory discovered that DON-induced activation of calcium-sensing receptor (CaSR), a G-coupled protein receptor (GPCR), and transient receptor ankyrin-1 (TRPA1), a transient receptor potential (TRP) channel, drives Ca2+-mediated hormone secretion. Consistent with these in vitro findings, CaSR and TRPA1 mediate DON-induced satiety hormone release and food refusal in the mouse, an animal model incapable of vomiting. However, the roles of this GPCR and TRP in DON's emetic effects remain to be determined. To address this, we tested the hypothesis that DON triggers emesis in mink by activating CaSR and TRPA1. Oral gavage with selective agonists for CaSR (R-568) or TRPA1 (allyl isothiocyanate; AITC) rapidly elicited emesis in the mink in dose-dependent fashion. Oral pretreatment of the animals with the CaSR antagonist NPS-2143 or the TRP antagonist ruthenium red (RR), respectively, inhibited these responses. Importantly, DON-induced emesis in mink was similarly inhibited by oral pretreatment with NPS-2143 or RR. In addition, these antagonists suppressed concurrent DON-induced elevations in plasma peptide YY3-36 and 5-hydroxytryptamine-hormones previously demonstrated to mediate the toxin's emetic effects in mink. Furthermore, antagonist co-treatment additively suppressed DON-induced emesis and peptide YY 3-36 release. To summarize, the observations here strongly suggest that activation of CaSR and TRPA1 might have critical roles in DON-induced emesis.

Modeling the emetic potencies of food-borne trichothecenes by benchmark dose methodology

Trichothecene mycotoxins commonly co-contaminate cereal products. They cause immunosuppression, anorexia, and emesis in multiple species. Dietary exposure to such toxins often occurs in mixtures. Hence, if it were possible to determine their relative toxicities and assign toxic equivalency factors (TEFs) to each trichothecene, risk management and regulation of these mycotoxins could become more comprehensive and simple. We used a mink emesis model to compare the toxicities of deoxynivalenol, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, nivalenol, fusarenon-X, HT-2 toxin, and T-2 toxin. These toxins were administered to mink via gavage and intraperitoneal injection. The United States Environmental Protection Agency (EPA) benchmark dose software was used to determine benchmark doses for each trichothecene. The relative potencies of each of these toxins were calculated as the ratios of their benchmark doses to that of DON. Our results showed that mink were more sensitive to orally administered toxins than to toxins administered by IP. T-2 and HT-2 toxins caused the greatest emetic responses, followed by FX, and then by DON, its acetylated derivatives, and NIV. Although these results provide key information on comparative toxicities, there is still a need for more animal based studies focusing on various endpoints and combined effects of trichothecenes before TEFs can be established.

Potential roles for calcium-sensing receptor (CaSR) and transient receptor potential ankyrin-1 (TRPA1) in murine anorectic response to deoxynivalenol (vomitoxin)

Food contamination by the trichothecene mycotoxin deoxynivalenol (DON, vomitoxin) has the potential to adversely affect animal and human health by suppressing food intake and impairing growth. In mice, the DON-induced anorectic response results from aberrant satiety hormone secretion by enteroendocrine cells (EECs) of the gastrointestinal tract. Recent in vitro studies in the murine STC-1 EEC model have linked DON-induced satiety hormone secretion to activation of calcium-sensing receptor (CaSR), a G-coupled protein receptor, and transient receptor potential ankyrin-1 (TRPA1), a TRP channel. However, it is unknown whether similar mechanisms mediate DON's anorectic effects in vivo. Here, we tested the hypothesis that DON-induced food refusal and satiety hormone release in the mouse are linked to activation of CaSR and TRPA1. Oral treatment with selective agonists for CaSR (R-568) or TRPA1 (allyl isothiocyanate (AITC)) suppressed food intake in mice, and the agonist's effects were suppressed by pretreatment with corresponding antagonists NPS-2143 or ruthenium red (RR), respectively. Importantly, NPS-2143 or RR inhibited both DON-induced food refusal and plasma elevations of the satiety hormones cholecystokinin (CCK) and peptide YY_3-36 (PYY_3-36); cotreatment with both antagonists additively suppressed both anorectic and hormone responses to DON. Taken together, these in vivo data along with prior in vitro findings support the contention that activation of CaSR and TRPA1 contributes to DON-induced food refusal by mediating satiety hormone exocytosis from EEC.

Intestinal toxicity of the masked mycotoxin deoxynivalenol-3-β-D-glucoside

Natural food contaminants such as mycotoxins are an important problem for human health. Deoxynivalenol (DON) is one of the most common mycotoxins detected in cereals and grains. Its toxicological effects mainly concern the immune system and the gastrointestinal tract. This toxin is a potent ribotoxic stressor leading to MAP kinase activation and inflammatory response. DON frequently co-occurs with its glucosylated form, the masked mycotoxin deoxynivalenol-3-β-D-glucoside (D3G). The toxicity of this later compound remains unknown in mammals. This study aimed to assess the ability of D3G to elicit a ribotoxic stress and to induce intestinal toxicity. The toxicity of D3G and DON (0-10 µM) was studied in vitro, on the human intestinal Caco-2 cell line, and ex vivo, on porcine jejunal explants. First, an in silico analysis revealed that D3G, contrary to DON, was unable to bind to the A-site of the ribosome peptidyl transferase center, the main targets for DON toxicity. Accordingly, D3G did not activate JNK and P38 MAPKs in treated Caco-2 cells and did not alter viability and barrier function on cells, as measured by the trans-epithelial electrical resistance. Treatment of intestinal explants for 4 h with 10 µM DON induced morphological lesions and up-regulated the expression of pro-inflammatory cytokines as measured by qPCR and pan-genomic microarray analysis. By contrast, expression profile of D3G-treated explants was similar to that of controls, and these explants did not show histomorphology alteration. In conclusion, our data demonstrated that glucosylation of DON suppresses its ability to bind to the ribosome and decreases its intestinal toxicity.

Dysregulation of energy balance by trichothecene mycotoxins: Mechanisms and prospects

Trichothecenes are toxic metabolites produced by fungi that constitute a worldwide hazard for agricultural production and both animal and human health. More than 40 countries have introduced regulations or guidelines for food and feed contamination levels of the most prevalent trichothecene, deoxynivalenol (DON), on the basis of its ability to cause growth suppression. With the development of analytical tools, evaluation of food contamination and exposure revealed that a significant proportion of the human population is chronically exposed to DON doses exceeding the provisional maximum tolerable daily dose. Accordingly, a better understanding of trichothecene impact on health is needed. Upon exposure to low or moderate doses, DON and other trichothecenes induce anorexia, vomiting and reduced weight gain. Several recent studies have addressed the mechanisms by which trichothecenes induce these symptoms and revealed a multifaceted action targeting gut, liver and brain and causing dysregulation in neuroendocrine signaling, immune responses, growth hormone axis, and central neurocircuitries involved in energy homeostasis. Newly identified trichothecene toxicosis biomarkers are just beginning to be exploited and already open up new questions on the potential harmful effects of chronic exposure to DON at apparently asymptomatic very low levels. This review summarizes our current understanding of the effects of DON and other trichothecenes on food intake and weight growth.

The Food-Associated Ribotoxin Deoxynivalenol Modulates Inducible NO Synthase in Human Intestinal Cell Model

The intestinal epithelium possesses active immune functions including the production of proinflammatory cytokines and antimicrobial molecules such as nitric oxide (NO). As observed with immune cells, the production of NO by the intestinal epithelium is mainly due to the expression of the inducible NO synthase (iNOS or NOS2). Epithelial immune functions could be affected by many factors including pathogenic microorganisms and food-associated toxins (bacterial and fungal). Among the various mycotoxins, deoxynivalenol (DON) is known to alter the systemic and intestinal immunity. However, little is known about the effect of DON on the production of NO by the intestinal epithelium. We studied the impact of DON on the intestinal expression of iNOS using the Caco-2 cell model. In line with its proinflammatory activity, we observed that DON dose-dependently up-regulates the expression of iNOS mRNA. Surprisingly, DON failed to increase the expression of iNOS protein. When testing the effects of DON on cytokine-mediated induction of iNOS, we found that very low concentrations of DON (ie, 1 µM) decrease the amount of iNOS protein but not of iNOS mRNA. We demonstrated that DON's effect on iNOS protein relies on its ability to activate signal pathways and to increase iNOS ubiquitinylation and degradation through the proteasome pathway. Taken together, our results demonstrate that although DON causes intestinal inflammation, it suppresses the ability of the gut epithelium to express iNOS and to produce NO, potentially explaining the increased susceptibility of animals to intestinal infection following exposure to low doses of DON.