Associations between dietary mycotoxins exposures and risk of hepatocellular carcinoma in a European cohort

Mycotoxins have been hypothesized to contribute to a diversity of adverse health effects in humans, even at low concentrations. Certain mycotoxins are established human carcinogens, whereas for others research suggests potential carcinogenic effects. The aim of this study was to determine the association between dietary exposure to mycotoxins and hepatobiliary cancers in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. EPIC questionnaire data were matched to mycotoxin food occurrence data compiled by the European Food Safety Authority to assess long-term dietary mycotoxin exposure (expressed as μg/kg body weight/day) and then relate them to the risk of hepatocellular carcinoma (HCC) (n = 255) and biliary tract cancers (n = 273). Analyses were conducted using multivariable Cox proportional hazards regression models to compute hazard ratios (HR) and 95% confidence intervals (95% CI). Key food groups contributing to mycotoxin exposure were cereals and cereal-based products, vegetables, non-alcoholic beverages (including fruit juices) and fruits. Estimated intake of deoxynivalenol (DON) and its derivatives was positively associated with HCC risk (HRT3vsT1: 1.90, 95% CI: 1.18-3.05, p-trend <0.01). No statistically significant associations were found for the other mycotoxins. Further research to confirm our observations and investigate potential underlying mechanisms of these compounds is warranted. These data may provide evidence of HCC risks associated with higher dietary intake levels of DON, which has not yet been classified as a human carcinogen.

Effects of Increasing Oral Deoxynivalenol Gavage on Growth Performance, Blood Biochemistry, Metabolism, Histology, and Microbiome in Rats

Mycotoxin-contaminated feed or food can affect physiological responses and cause illnesses in humans and animals. In this study, we evaluated the effects of deoxynivalenol (DON) toxicity on the growth performance, blood biochemistry, histology, microbiome, and metabolism of rats fed with different toxin concentrations. After 1 week of acclimatization, seven-week-old male rats received 0.9% saline as a control, 0.02 mg/kg DON as T1, and 0.2 mg/kg DON as T2 via oral gavage for 4 weeks. The final body weight of the T2 group was significantly lower than that of the control and T1; however, the average daily gain, feed intake, and feed conversion ratio did not differ. Fibrosis and apoptosis were observed in various tissues as DON concentration increased. Creatinine and alkaline phosphatase levels were significantly lower in the DON-treated group than in the control. Firmicutes and Desulfobacterota phyla dominated the cecum, whereas those in the feces were Proteobacteria and Bacteroidetes. Metabolomic profiling showed phenylalanine, tyrosine, and tryptophan biosynthesis as the most prominent pathways. Overall, our results suggest that low-dose and short-term DON exposure can trigger several adverse effects in rats. Dietary toxicants in rats may explain the physiological effects associated with the metabolism commonly reported in animals.

Effects of deoxynivalenol on the histomorphology of the liver and kidneys and the expression of MAPKs in weaned rabbits

Deoxynivalenol (DON) is widely present in grain-based feeds and food. It has attracted great attention due to its high contamination rate and strong toxicity. The objective of this study was to analyse the toxic effects of DON on the liver and kidneys of weaned rabbits. 45 weaned male rabbits were allocated into control, low DON dose (0.5 mg/kg body weight), and high DON dose (1.5 mg/kg body weight) groups. Saline or DON was administrated intragastrically in the empty stomach of rabbits every morning. After 24 days of treatment, liver and kidney samples were collected for histological, reverse transcription-quantitative polymerase chain reaction (qRT-PCR), and immunohistochemistry analyses. Haematoxylin eosin staining showed that 0.5 mg/kg BW DON caused mild damage to the liver and kidney morphology, while 1.5 mg/kg body weight DON resulted in hepatic vacuolation and necrosis, as well as tubular stenosis and lesions. Data from qRT-PCR, Western blot, and immunohistochemistry revealed that the mRNA and protein expression and the distribution range of extracellular signal-regulated kinase, p38, and c-Jun NH2-terminal kinase were increased in the liver and kidneys. In conclusion, DON at the tested concentrations damaged the liver and kidneys of rabbits by affecting the expression of key proteins from the mitogen-activated protein kinase signalling pathway. The damage extent was proportional to the amount of DON ingested.

3-keto-DON, but Not 3-epi-DON, Retains the in Planta Toxicological Potential after the Enzymatic Biotransformation of Deoxynivalenol

Deoxynivalenol (DON) is a secondary fungal metabolite that is associated with many adverse toxicological effects in agriculture as well as human/animal nutrition. Bioremediation efforts in recent years have led to the discovery of numerous bacterial isolates that can transform DON to less toxic derivatives. Both 3-keto-DON and 3-epi-DON were recently shown to exhibit reduced toxicity, compared to DON, when tested using different cell lines and mammalian models. In the current study, the toxicological assessment of 3-keto-DON and 3-epi-DON using in planta models surprisingly revealed that 3-keto-DON, but not 3-epi-DON, retained its toxicity to a large extent in both duckweeds (Lemna minor L.) and common wheat (Triticum aestivum L.) model systems. RNA-Seq analysis revealed that the exposure of L. minor to 3-keto-DON and DON resulted in substantial transcriptomic changes and similar gene expression profiles, whereas 3-epi-DON did not. These novel findings are pivotal for understanding the environmental burden of the above metabolites as well as informing the development of future transgenic plant applications. Collectively, they emphasize the fundamental need to assess both plant and animal models when evaluating metabolites/host interactions.

Structure-Function Analysis of a Quinone-Dependent Dehydrogenase Capable of Deoxynivalenol Detoxification

The pyrroloquinoline quinone (PQQ)-dependent dehydrogenase DepA detoxifies deoxynivalenol (DON) by converting the C3-OH into a keto group. Herein, two crystal structures of DepA and its complex with PQQ were determined, together with biochemical evidence confirming the interactions of DepA with PQQ and DON and revealing a unique tyrosine residue important for substrate selection. Furthermore, four loops over the active site essential for DepA activity were identified, of which three loops were stabilized by PQQ, and the fourth loop invisible in both structures was considered important for binding DON, together constituting a lid for the active site. Preliminary engineering of the loop showed its potential for enzyme improvement. This study provides structural insights into how a PQQ-dependent dehydrogenase is equipped with the function of DON conversion and for the first time shows the necessity of a lid structure for PQQ-dependent dehydrogenase activity, laying foundation for structure-based design to enhance catalysis efficiency.

4-Phenylbutyric acid alleviated 3-acetyldeoxynivalenol-induced immune cells response by inhibiting endoplasmic reticulum stress in mouse spleen

3-Acetyldeoxynivalenol (3-Ac-DON), an acetylated derivative of deoxynivalenol (DON), has contaminated grains and grain-based products in general and been harmful to human and animal health. However, the damage effects and regulatory mechanisms to the host immune system have not been well explored. In the present study, our results revealed that 3-Ac-DON significantly decreased spleen index, elevated MPO activity, upregulated mRNA and protein levels of IL-1α, IL-1β, IL-6, IL-17A, TNF-α, M-CSF, G-CSF, CCL2, IFN-β, and IL-10 in the spleen and serum. Interestingly, 4-phenylbutyric acid (4-PBA), an inhibitor of endoplasmic reticulum (ER) stress, largely abolished the above adverse effects. Importantly, 3-Ac-DON enhanced the mRNA abundances of ER stress-related indicators, such as BIP, IRE1A, ATF6, XBP-1, EIF2A, ATF4, and CHOP, which were abolished by 4-PBA, indicating the inhibiting effects of ER stress by 4-PBA in the spleen. Furthermore, 3-Ac-DON reshaped the populations of innate immune cells (neutrophils, macrophages, dendritic cells, natural killer cells) and adaptive immune cells (T lymphocytes, helper T cells, suppressor T cells, and B lymphocytes) in the peripheral blood and spleen lymphocytes. In conclusion, our studies demonstrated that the adverse effects of 3-Ac-DON on immune cells response could be implemented by ER stress and the ameliorative effect of 4-PBA.

Deoxynivalenol: Toxicology, Degradation by Bacteria, and Phylogenetic Analysis

Deoxynivalenol (DON) is a toxic secondary metabolite produced by fungi that contaminates many crops, mainly wheat, maize, and barley. It affects animal health, causing intestinal barrier impairment and immunostimulatory effect in low doses and emesis, reduction in feed conversion rate, and immunosuppression in high doses. As it is very hard to completely avoid DON’s production in the field, mitigatory methods have been developed. Biodegradation has become a promising method as new microorganisms are studied and new enzymatic routes are described. Understanding the common root of bacteria with DON degradation capability and the relationship with their place of isolation may bring insights for more effective ways to find DON-degrading microorganisms. The purpose of this review is to bring an overview of the occurrence, regulation, metabolism, and toxicology of DON as addressed in recent publications focusing on animal production, as well as to explore the enzymatic routes described for DON’s degradation by microorganisms and the phylogenetic relationship among them.

3-Acetyldeoxynivalenol induces cell death through endoplasmic reticulum stress in mouse liver

Ingestion of food or cereal products contaminated by deoxynivalenol (DON) and related derivatives poses a threat to the health of humans and animals. However, the toxicity and underlying mechanisms of 3-acetyldeoxynivalenol (3-Ac-DON), an acetylated form of deoxynivalenol, have not been fully elucidated. In the present study, we showed that 3-Ac-DON caused significant oxidative damage, as shown by elevated aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactic dehydrogenase (LDH) in serum, increased lipid peroxidation products, such as hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), decreased activities of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). In addition, 3-Ac-DON exposure led to elevated infiltrations of immune cell, increased apoptosis and autophagy in the liver. Interestingly, 3-Ac-DON-resulted apoptosis and liver injury were partially reduced by autophagy inhibitors. Further study showed that 3-Ac-DON-treated mice had altered ultrastructural changes of endoplasmic reticulum (ER), as well as enhanced protein levels of p-IRE1α, p-PERK, and downstream targets, indicating activation of unfolded protein response (UPR) in the liver. Importantly, 3-Ac-DON induced ER stress, oxidative damage, cell death, infiltration of immune cells, and increased mRNA levels of inflammatory cytokines were significantly abolished by 4-phenylbutyric acid (4-PBA), an ER stress inhibitor, indicating a critical role of UPR signaling for the cellular damage of the liver in response to 3-Ac-DON exposure. In conclusion, using mice as an animal model, we showed that 3-Ac-DON exposure impaired the function of liver, as shown by oxidative damage, cell death, and infiltration of immune cell, in which ER stress played an important role. Restoration of the ER function might be a preventive strategy to reduce the deleterious effect of 3-Ac-DON on the liver of animals.

Effects of deoxynivalenol exposure at peripuberty over testicles of rats: structural and functional alterations

Deoxynivalenol (DON) is related to reduced reproductive performance in males and females in several species. Children and adolescents showed a high risk of exposure to DON, however, no study has evaluated reproductive effects of DON at puberty. The present study aimed to evaluate the effects of DON at peripuberty on the testicles of pubertal rats. To achieve this, 10 Wistar rats (28 days old) were fed for 28 days with a DON-contaminated diet (9.4 mg/kg) or a control diet. After the experimental period, rats (56 days old) were euthanised and the following evaluations were performed in the testicles: dynamics of spermatogenesis, tubular morphometry, number of Sertoli cells and Leydig cells, analysis of caspase-3 expression, and the index of cell proliferation using the nucleolus organising regions (NOR) method. Ingestion of DON-contaminated diet induced a significant reduction in the number of Sertoli and Leydig cells and the number of seminiferous tubules in stage XIV. A significant increase in the number of NORs in seminiferous tubules in stage I-VI was observed in animals receiving the DON diet. No significant difference was noted in tubular morphometry or caspase-3 expression. Taken together, our results unravelled that the peripubertal exposure to DON compromised the testicular structure of pubertal rats, changing the dynamics of spermatogenesis.

Mechanism of deoxynivalenol mediated gastrointestinal toxicity: Insights from mitochondrial dysfunction

Deoxynivalenol (DON) is a mycotoxin predominantly produced by Fusarium genus, and widely contaminates cereals and associated products all over the world. The intestinal toxicity of DON is well established. However, intestinal homeostasis involves mitochondria, which has rarely been considered in the context of DON exposure. We summarize the recent knowledge on mitochondria as a key player in maintaining intestinal homeostasis based on their functions in cellular energy metabolism, redox homeostasis, apoptosis, intestinal immune responses, and orchestrated bidirectional cross-talk with gut microbe. In addition, we discuss the pivotal roles of mitochondrial dysfunction in the intestinal toxicity of DON and highlight promising mitochondrial-targeted therapeutics for DON-induced intestinal injury. Recent studies support that the intestinal toxicity of DON is attributed to mitochondrial dysfunction as a critical factor. Mitochondrial dysfunction characterized by failure in respiratory capacities and ROS overproduction has been demonstrated in intestinal cells exposed to DON. Perturbation of mitochondrial respiration leading to ROS accumulation is implicated in the early initiation of apoptosis. DON-induced intestinal inflammatory response is tightly linked to the mitochondrial ROS, whereas immunosuppression is intimately associated with mitophagy inhibition. DON perturbs the orchestrated bidirectional cross-talk between gut microbe and host mitochondria, which may be involved in DON-induced intestinal toxicity.

Deoxynivalenol downregulates NRF2-induced cytoprotective response in human hepatocellular carcinoma (HepG2) cells

Deoxynivalenol (DON) commonly infects agricultural foods; it exhibits toxicity by inducing oxidative stress and inhibiting protein synthesis. Nuclear factor erythroid 2-related factor 2 (NRF2) regulates the cellular antioxidant response. We investigated the cytotoxicity of DON and its effect on the NRF2 antioxidant response in HepG2 cells. The Methyl Thiazol Tetrazolium (MTT), glutathione (GSH) and ATP assays evaluated toxicity, whilst lipid peroxidation and membrane damage were assessed using the Thiobarbituric acid reactive substance (TBARS) and lactate dehydrogenase (LDH) assays. Protein expression of NRF2, phosphorylated (p-ser40) NRF2, catalase (CAT), superoxide dismutase 2 (SOD2), and Sirtuin 3 (Sirt3) were quantified by Western Blotting. Gene expression of glutathione peroxidase (GPx), CAT and SOD2 was determined using qPCR. DON decreased cell viability, GSH concentrations and ATP levels and increased lipid peroxidation and membrane damage. DON significantly decreased total NRF2 and increased p-NRF2 and downregulated the transcription and translation of NRF2 target antioxidant enzymes. Further, expression of the mitochondrial stress response protein, Sirt3 was significantly decreased. In conclusion, DON induced oxidative stress and downregulated NRF2-induced cytoprotection by suppressing the antioxidant signalling mechanism in HepG2 cells.

Deoxynivalenol: toxicological profiles and perspective views for future research

Deoxynivalenol (DON) is a secondary metabolite mainly produced by the fungi Fusarium in agricultural crops, widely existing in feeds and cereal-based foodstuffs. Because of the high occurrence and potentials to induce a variety of toxic effects on animals and humans, DON has been a very harmful exogenous dietary toxicant threating public health. The focus of this review is to summarise the DON-induced broad spectrum of adverse health effects, to probe the current state of knowledge of combined toxicity of DON with other mycotoxins and its derivatives, and to put forward prospective ideas that multi-generational toxicity of DON and its overall impacts on intestinal-immuno-neuroendocrine system could receive more attention in future investigations. The general aim is to provide a scientific basis for the necessity to re-consider risk-assessment and regulations.

In vitro and in vivo effects of a mycotoxin, deoxynivalenol, and a trace metal, cadmium, alone or in a mixture on the intestinal barrier

Deoxynivalenol (DON), one of the most widespread mycotoxins in Europe, and cadmium (Cd), a widespread environmental pollutant, are common food contaminants. They exert adverse effects on different organs including kidney, liver, and intestine. The intestine is a common target of DON and Cd when they are ingested. Most studies have focused on their individual effects whereas their combined toxicity has rarely been studied. The aim of this study was thus to evaluate their individual and combined effects on the intestinal barrier function in vitro and in vivo. In vitro, Caco-2 cells were treated with increasing concentrations of DON and Cd (1-30 μM). In vivo, Wistar rats were used as controls or exposed to DON contaminated feed (8.2 mg/kg feed), Cd-contaminated water (5 mg/l) or both for four weeks. In Caco-2 cells, DON, Cd and the DON+Cd mixture reduced transepithelial electrical resistance (TEER) and increased paracellular permeability in a dose-dependent manner. Impairment of the barrier function was associated with a decrease in the amount of E-cadherin and occludin after exposure to the two contaminants alone or combined. A decrease in E-cadherin expression was observed in rats exposed to the two contaminants alone or combined, whereas occludin expression only decreased in animals exposed to DON and DON+Cd. Jejunal crypt depth was reduced in rats exposed to DON or Cd, whereas villi height was not affected. In vitro and in vivo results showed that the effects of exposure to combined DON and Cd on the intestinal barrier function in the jejunum of Wistar rats and in the colorectal cancer cell line (Caco-2) was similar to the effects of each individual contaminant. This suggests that regulations for each individual contaminant are sufficiently protective for consumers.

Individual and combined mycotoxins deoxynivalenol, nivalenol, and fusarenon-X induced apoptosis in lymphoid tissues of mice after oral exposure

Lymphocytes are involved in the adaptive immune response and are highly sensitive to type B trichothecenes. In grains and their products, deoxynivalenol (DON) is the most widely distributed trichothecene. It usually co-occurs with other type B members, such as nivalenol (NIV) and fusarenon-X (FX), because they are all produced by the same Fusarium fungi. However, the combined effects of mycotoxins are complex and cannot be predicted based on individual toxicity. Thus, the adverse effects of combined toxins are of increasing concern. The aim of this study was to compare the toxicity to lymphoid tissues of mice of DON alone or mixed with NIV or FX. Forty, 3-week-old male ICR mice were given a single oral administration of a vehicle control, one toxin, binary, or ternary mixtures and then sacrificed at 12 h after exposure. Mice treated with FX alone showed marked nuclear condensation and fragmentation of lymphocytes in the cortical thymus and germinal center of Peyer's patches and spleen. Similarly, these animals clearly displayed TUNEL- and Caspase-3-positive cells in the regions. In contrast, minimal changes were noticed in the lymphoid tissues of mice receiving combined toxins when compared to this toxin alone. In addition, oral exposure to FX alone significantly up-regulated the relative expression of Bax, Caspase-3, Caspase-9, and Trp53. These data increase our understanding of the toxic actions of DON, NIV, and FX alone or in combination to lymphocytes and can be used to assess the possible risk associated with their co-occurrences in foodstuffs to human and animal health.

Interaction between the three frequently co-occurring Fusarium mycotoxins in rats

To test the complex, acute biochemical effects of combined, naturally co-occurring fusariotoxins, a 5-day rat study was performed. Mycotoxin treatment was invented by intraperitoneal injection: FB₁ (F): 9 µg/animal/day (approx. 30 µg/kg bw/day), DON (D): 16.5 µg/animal/day (approx. 55 µg/kg bw/day) and ZEN (Z): 12.75 µg/animal/day (approx. 42.5 µg/kg bw/day). The binary groups (FB₁ and DON [FD], FB₁ and ZEN [FZ] and DON and ZEN [DZ]) as well as the ternary (FB₁ , DON and ZEN [FDZ]) group were dosed at the same combined level as the individual mycotoxins. Body weight, feed intake and mortality were not affected by any of the treatments. FB₁ and DON in combination (FD) increased the plasma aspartate aminotransferase activity synergistically (compared to the individual FB₁ and DON). In the liver, both the total glutathione (GSH) and the glutathione peroxidase (GPx) activity were increased (p < 0.05) by the binary FB₁ and ZEN (FZ) and the DON and ZEN (DZ) groups as well as the ternary FB₁ , DON and ZEA group (FDZ) compared to the control. The GSH level of the ternary group was significantly increased compared to the FB₁ group, whereas the GPx activity of the ternary group was significantly increased compared to all three the individual mycotoxin groups. The Bliss independence method revealed synergism between DON and ZEN (DZ), as well as FB₁ and DON (FD) on liver GPx activity. None of the toxins alone or in combination exerted strong genotoxicity on lymphocytes, neither on the gross histopathological characteristics. However, even at these low levels acute exposure of more than one of these mycotoxins (FB₁ , DON and ZEN) affected metabolic and detoxification changes.

The Food Contaminant Deoxynivalenol Exacerbates the Genotoxicity of Gut Microbiota

An increasing number of human beings from developed countries are colonized by Escherichia coli strains producing colibactin, a genotoxin suspected to be associated with the development of colorectal cancers. Deoxynivalenol (DON) is the most prevalent mycotoxin that contaminates staple food-especially cereal products-in Europe and North America. This study investigates the effect of the food contaminant DON on the genotoxicity of the E. coli strains producing colibactin. In vitro, intestinal epithelial cells were coexposed to DON and E. coli producing colibactin. In vivo, newborn rats colonized at birth with E. coli producing colibactin were fed a DON-contaminated diet. Intestinal DNA damage was estimated by the phosphorylation of histone H2AX. DON exacerbates the genotoxicity of the E. coli producing colibactin in a time- and dose-dependent manner in vitro Although DON had no effect on the composition of the gut microbiota, and especially on the number of E. coli, a significant increase in DNA damage was observed in intestinal epithelial cells of animals colonized by E. coli strains producing colibactin and coexposed to DON compared to animals colonized with E. coli strains unable to produce colibactin or animals exposed only to DON. In conclusion, our data demonstrate that the genotoxicity of E. coli strains producing colibactin, increasingly present in the microbiota of asymptomatic human beings, is modulated by the presence of DON in the diet. This raises questions about the synergism between food contaminants and gut microbiota with regard to intestinal carcinogenesis.IMPORTANCE An increasing number of human beings from developed countries are colonized by Escherichia coli strains producing colibactin, a genotoxin suspected to be associated with the development of colorectal cancers. Deoxynivalenol (DON) is the most prevalent mycotoxin that contaminates staple food-especially cereal products-in Europe and North America. Our in vitro and in vivo results demonstrate that the intestinal DNA damage induced by colibactin-producing E. coli strains was exacerbated by the presence of DON in the diet. This raises questions about the synergism between food contaminants and gut microbiota with regard to intestinal carcinogenesis.

Toxicology of deoxynivalenol and its acetylated and modified forms

Mycotoxins are the most frequently occurring natural contaminants in human and animal diet. Among them, deoxynivalenol (DON), produced by Fusarium, is one of the most prevalent and thus represents an important health risk. Recent detection methods revealed new mycotoxins and new molecules derivated from the "native" mycotoxins. The main derivates of DON are the acetylated forms produced by the fungi (3- and 15-acetyl-DON), the biologically "modified" forms produced by the plant (deoxynivalenol-3-β-D-glucopyranoside), or after bacteria transformation (de-epoxy DON, 3-epi-DON and 3-keto-DON) as well as the chemically "modified" forms (norDON A-C and DON-sulfonates). High proportions of acetylated and modified forms of DON co-occur with DON, increasing the exposure and the health risk. DON and its acetylated and modified forms are rapidly absorbed following ingestion. At the molecular level, DON binds to the ribosome, induces a ribotoxic stress leading to the activation of MAP kinases, cellular cell-cycle arrest and apoptosis. The toxic effects of DON include emesis and anorexia, alteration of intestinal and immune functions, reduced absorption of the nutrients as well as increased susceptibility to infection and chronic diseases. In contrast to DON, very little information exists concerning the acetylated and modified forms; some can be converted back to DON, their ability to bind to the ribosome and to induce cellular effects varies according to the toxin. Except for the acetylated forms, their toxicity and impact on human and animal health are poorly documented.