Experimental subchronic mycotoxicoses in mice: individual and combined effects of dietary exposure to fumonisins and aflatoxin B1

Toxicity mechanisms of aflatoxin M1 assisted with molecular docking and the toxicity-limiting role of trans-resveratrol

In this study, AFM₁ toxicity and the protective role of trans-resveratrol (t-rsv) against this toxicity were investigated with the help of multiple parameters in albino mice. As a result, AFM₁ (16 mg/kg b.w) administration caused a decrease in body, kidney and liver weights. This reduction was associated with a decrease in feed consumption. AFM₁ induced an increase in AST and ALT enzyme parameters and BUN, creatinine and MDA levels and a decrease in GSH levels. These increases have been associated with liver and kidney cell damage. AFM₁ decreased MI and encouraged increases in MN and CAs numbers. The decrease in MI was correlated with AFM1-tubulin and the increase in CAs was associated with the AFM₁-DNA interaction, which was demonstrated by molecular docking and spectral shifting. Besides, the decrease in DNA damage and amount was demonstrated by the comet assay technique. Administration of t-rsv (10 and 20 mg/kg b.w) reduced the toxic effects of AFM₁ and caused a dose-dependent improvement in all physiological, biochemical and cytogenetic parameter values studied. For this reason, foods containing t-rsv or food supplements should be consumed in the daily diet to reduce the effect of toxic agents.

Mycotoxin Contamination of Feeds and Raw Materials in China in Year 2021

In this research, we performed a large-scale survey of mycotoxin contamination in several feed commodities and assessed regional differences in mycotoxin occurrence in maize across China in 2021. Concentrations of aflatoxins, zearalenone (ZEN), fumonisins, and trichothecenes type B were analyzed in 2,643 raw material and compound feed samples collected from eight provinces. Generally, trichothecenes type B, fumonisins, and ZEN were most prevalent and detected in averages of positive concentrations at 1,167, 1,623, and 204 μg/kg, respectively. In the new season maize, samples were also seriously infested with trichothecenes type B, fumonisins, and ZEN, and their averages of positive concentrations were 1,302, 2,518, and 225 μg/kg, respectively. Wheat was commonly contaminated with trichothecenes type B and ZEN, and the highest concentration levels of trichothecenes type B, fumonisins, and ZEN were all detected in the samples from maize by-products. Among the different geographical regions, distinct trends were observed in new season maize. Samples from Shandong province were highly contaminated with trichothecenes type B, fumonisins, and ZEN, while special attention should be paid to aflatoxins and fumonisins in Anhui and Jiangsu provinces in East China. In addition, the present survey showed that compound feeds and raw materials are commonly contaminated by multiple mycotoxins. Trichothecenes type B and ZEN concentrations were correlated significantly in this survey.

Fumonisins B1 exposure triggers intestinal tract injury via activating nuclear xenobiotic receptors and attracting inflammation response

Fumonisins (FBs) are mycotoxins that are widely distributed in crops and feed, and ingestion of FBs -contaminated crops is harmful to animal health. Furthermore, it is unknown if Fumonisins B1 (FB1) can cause intestinal toxicity. To investigate FB1-induced intestinal toxicity, mice were treated with 0 or 5 mg/kg FB1 by gavage administration for 42 days. Histopathology indicated that FB1 exposure caused proliferation of intestinal epithelial cells, intestinal villi and epithelial layer shedding, intestinal gland atrophy, and necrosis. Notably, FB1 interfered with nuclear xenobiotic receptors (NXR) homeostasis by regulating the level of aryl hydrocarbon receptor (AHR), constitutive androstane receptor (CAR), pregnane X receptor (PXR) and downstream target genes (CYP450s). Moreover, abnormal expression of inflammatory cytokines (IL-1β, IL-2, IL-4, IL-10, and TNF-α) indicated the occurrence of inflammation. The present study provides new insights regarding the mechanism of FB1-induced intestinal toxicity through activating the NXR system and by triggering inflammatory responses in the intestinal tract in mice.

Mycotoxins and the Enteric Nervous System

Mycotoxins are secondary metabolites produced by various fungal species. They are commonly found in a wide range of agricultural products. Mycotoxins contained in food enter living organisms and may have harmful effects on many internal organs and systems. The gastrointestinal tract, which first comes into contact with mycotoxins present in food, is particularly vulnerable to the harmful effects of these toxins. One of the lesser-known aspects of the impact of mycotoxins on the gastrointestinal tract is the influence of these substances on gastrointestinal innervation. Therefore, the present study is the first review of current knowledge concerning the influence of mycotoxins on the enteric nervous system, which plays an important role, not only in almost all regulatory processes within the gastrointestinal tract, but also in adaptive and protective reactions in response to pathological and toxic factors in food.

Fumonisins at Doses below EU Regulatory Limits Induce Histological Alterations in Piglets

Fumonisins (FBs) are mycotoxins produced by Fusarium species that can contaminate human food and animal feed. Due to the harmful effects of FBs on animals, the European Union (EU) defined a recommendation of a maximum of 5 mg FBs (B1 + B2)/kg for complete feed for swine and 1 µg FBs/kg body weight per day as the tolerable daily intake for humans. The aim of this study was to evaluate the toxicity of dietary exposure to low doses of FBs, including a dose below the EU regulatory limits. Four groups of 24 weaned castrated male piglets were exposed to feed containing 0, 3.7, 8.1, and 12.2 mg/kg of FBs for 28 days; the impact was measured by biochemical analysis and histopathological observations. Dietary exposure to FBs at a low dose (3.7 mg/kg of feed) significantly increased the plasma sphinganine-to-sphingosine ratio. FBs-contaminated diets led to histological modifications in the intestine, heart, lung, lymphoid organs, kidney, and liver. The histological alterations in the heart and the intestine appeared at the lowest dose of FBs-contaminated diet (3.7 mg/kg feed) and in the kidney at the intermediate dose (8.1 mg/kg feed). At the highest dose tested (12.2 mg/kg feed), all the organs displayed histological alterations. This dose also induced biochemical modifications indicative of kidney and liver alterations. In conclusion, our data indicate that FBs-contaminated diets at doses below the EU regulatory limit cause histological lesions in several organs. This study suggests that EU recommendations for the concentration of FBs in animal feed, especially for swine, are not sufficiently protective and that regulatory doses should be modified for better protection of animal health.

Global Mycotoxin Occurrence in Feed: A Ten-Year Survey

Mycotoxins contaminating animal feed can exert toxic effects in animals and be transferred into animal products. Therefore, mycotoxin occurrence in feed should be monitored. To this end, we performed a large-scale global survey of mycotoxin contamination in feed and assessed regional differences and year-to-year variation of mycotoxin occurrence. Concentrations of aflatoxin B1, zearalenone, fumonisins, ochratoxin A, deoxynivalenol, and T-2 toxin were analyzed in 74,821 samples of feed and feed raw materials (e.g., maize, wheat, soybean) collected from 100 countries from 2008 to 2017. In total, 88% of the samples were contaminated with at least one mycotoxin. Mycotoxin occurrence showed distinct regional trends and climate was a key determinant governing these trends. In most regions, the majority of samples complied with maximum levels and guidance values for mycotoxins in animal feed that are in effect in the European Union. However, 41.1%, 38.5%, and 20.9% of samples from South Asia, Sub-Saharan Africa, and Southeast Asia, respectively, exceeded the maximum level for aflatoxin B1 (20 µg/kg). In several regions, mycotoxin concentrations in maize showed a pronounced year-to-year variation that could be explained by rainfall or temperature during sensitive periods of grain development. A large fraction of samples (64%) was co-contaminated with ≥ 2 mycotoxins. Most frequently observed mycotoxin mixtures were combinations of deoxynivalenol, zearalenone, and fumonisins, as well as fumonisins and aflatoxin B1. Deoxynivalenol and zearalenone concentrations were correlated in maize and wheat. In conclusion, according to an extensive global survey, mycotoxin (co-)contamination of animal feed is common, shows regional trends, and is governed in part by climate and weather.

Adaptation of the white shrimp Litopenaeus vannamei to gradual changes to a low-pH environment

pH variation could cause a stress response in euryhaline penaeids, we evaluated the mortality, growth performance, osmoregulation gene expression, digestive enzyme activity, histology, and resistance against Vibrio parahemolyticus of white shrimp Litopenaeus vannamei reared under conditions of gradual changes to a low-pH environment (gradual-low pH, 6.65-8.20) or a high-pH environment (gradual-high pH, 8.20-9.81) versus a normal pH environment (8.14-8.31) during a 28-d experiment. Consequently, under gradual-high pH, the cumulative mortality rate (CMR) rose with time until 39.9% on days 28; the weight gain percentage (WGP) and length gain percentage (LGP) decreased continuously. However, under gradual-low pH, the CMR of shrimp stabilized at 6.67% during 7-28 d; the WGP and LGP decreased first and then returned to normal. These results indicated that L. vannamei displayed a moderate tolerance to gradual-low pH, compared with gradual-high pH. Under gradual-low pH, the Na⁺/K⁺-ATPase, cytoplasmic carbonic anydrase (CAc), and glycosyl-phosphatidylinositol-linked carbonic anhydrase (CAg) transcripts of shrimp increased continuously or then back to normal; the amylase, lipase, and trypsin activities decreased first and then returned to normal or increased; the hepatopancreases and midguts showed histopathological lesions first and then got remission. Thus, the major adaptation mechanism of shrimp to gradual-low pH might be its high osmoregulation ability, which made shrimp achieve a new, balanced steady-state, then promoted longer intestinal villi and recuperative hepatopancreases of shrimp with enhanced digestive enzyme activities to increase nutrient absorption after long-term exposure. Meanwhile, the enhanced resistance against V. parahemolyticus under gradual-low pH would probably inhibit disease outbreak in the shrimp farming.

Worldwide Occurrence of Mycotoxins in Cereals and Cereal-Derived Food Products: Public Health Perspectives of Their Co-occurrence

Cereal grains and their processed food products are frequently contaminated with mycotoxins. Among many, five major mycotoxins of aflatoxins, ochratoxins, fumonisins, deoxynivalenol, and zearalenone are of significant public health concern as they can cause adverse effects in humans. Being airborne or soilborne, the cosmopolitan nature of mycotoxigenic fungi contribute to the worldwide occurrence of mycotoxins. On the basis of the global occurrence data reported during the past 10 years, the incidences and maximum levels in raw cereal grains were 55% and 1642 μg/kg for aflatoxins, 29% and 1164 μg/kg for ochratoxin A, 61% and 71,121 μg/kg for fumonisins, 58% and 41,157 μg/kg, for deoxynivalenol, and 46% and 3049 μg/kg for zearalenone. The concentrations of mycotoxins tend to be lower in processed food products; the incidences varied depending on the individual mycotoxins, possibly due to the varying stability during processing and distribution of mycotoxins. It should be noted that more than one mycotoxin, produced by a single or several fungal species, may occur in various combinations in a given sample or food. Most studies reported additive or synergistic effects, suggesting that these mixtures may pose a significant threat to public health, particularly to infants and young children. Therefore, information on the co-occurrence of mycotoxins and their interactive toxicity is summarized in this paper.

Sequential dietary exposure to aflatoxin B1 and fumonisin B1 in F344 rats increases liver preneoplastic changes indicative of a synergistic interaction

Dietary co-exposure to aflatoxin B1 (AFB1) and fumonisin B1 (FB1) and their interaction on hepatocellular carcinogenesis is of particular concern in toxicology and public health. In this study we evaluated the liver preneoplastic effects of single and sequential dietary exposure to AFB1 and FB1 in the F344 rat carcinogenesis model. Serum biochemical alterations, liver histopathological changes, and the formation of liver glutathione S transferase positive (GST-P+) foci were the major outcome parameters examined. Compared to the AFB1-only treatment, the FB1-only treatment induced less dysplasia, and more apoptosis and mitoses. Sequential AFB1 and FB1 treatment lead to increased numbers of dysplasia, apoptosis and foci of altered hepatocytes, as compared to either mycotoxin treatment alone. More importantly, sequential exposure to AFB1 and FB1 synergistically increased the numbers of liver GTP-P+ foci by approximately 7.3-and 12.9-fold and increased the mean sizes of GST-P+ foci by 6- and 7.5-fold, respectively, as compared to AFB1- or FB1-only treatment groups. In addition, liver ALT and AST levels were significantly increased after sequential treatment as compared to single treatment groups. The results demonstrate the interactive effect of dietary AFB1 and FB1 in inducing liver GST-P+ foci formation and provide information to model future intervention studies.

Prevalence of aflatoxin and fumonisins (B1 + B2) in maize consumed in rural Malawi

A study was carried out to assess levels of contamination of aflatoxins and fumonisins (B₁ + B₂) in maize produced, stored and consumed in rural households in Malawi. A total of 9 districts were selected across the country representing 3 districts from each of the Northern, Central and Southern regions respectively. Households were selected at random in each district where 10 maize samples were collected for laboratory analysis. Aflatoxins and fumonisins were analyzed using a single step lateral flow immunochromatographic assay based on a competitive immunoassay format. The detection limit for aflatoxins was 2 μg/kg with a quantitation range of 2–150 μg/kg and that for fumonisins was 1 mg/kg with a quantitation range of 1–7 mg/kg. It was found that samples in the Southern region were highly contaminated, with the Chikhwawa district having high levels of both aflatoxins and fumonisins in maize. The Northern region had the least contamination. The maximum detected amount of aflatoxins was 140 μg/kg. The maximum detected amounts of fumonisins was 7 mg/kg. About 20% of maize samples exceeded the tolerable maximum limit for aflatoxins in Malawi. Aflatoxins and fumonisins were found to co-occur with contamination levels exceeding 100 μg/kg for both aflatoxins and fumonisins.

Hepatotoxic effects of mycotoxin combinations in mice

This study was performed to assess the individual and combined toxic effects of aflatoxin B1 (AFB1), zearalenone (ZEA) and deoxynivalenol (DON) within the liver of mice. A total of 56 4-week-old weanling female mice were divided into seven groups (n = 8). For 2 weeks, each group received an oral administration of either solvent (control), AFB1, ZEA, DON, AFB1 + ZEA, AFB1 + DON or ZEA + DON per day. The results showed that AFB1, ZEA and DON induced liver injury, indicated by elevated relative liver weight, activities of alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST), as well as decreased albumin (ALB) and/or total protein (TP) concentration in the serum. These mycotoxins also decreased hepatic total antioxidant capacity (T-AOC), and/or increased the concentration of malondialdehyde (MDA). Moreover, AFB1 + DON displayed synergistic effects, while AFB1 + ZEA displayed antagonistic effects on those parameters previously described. Furthermore, the apoptotic potential was demonstrated associated with an upregulation of the apoptotic genes Caspase-3 and Bax, along with a downregulation of the antiapoptotic gene Bcl-2 in liver. In conclusion, this study provides a better understanding of the toxic effects of AFB1, ZEA, DON, alone or in combinations on the liver of mice, which could contribute to the risk assessment of these mycotoxins in food and feed.

Human health implications from co-exposure to aflatoxins and fumonisins in maize-based foods in Latin America: Guatemala as a case study

Co-occurrence of fumonisin B1 (FB1) and aflatoxin B1 (AFB1) in maize has been demonstrated in many surveys. Combined-exposure to FB1 and AFB1 was of concern to the Joint FAO/WHO Expert Committee on Food Additives because of the known genotoxicity of AFB1 and the ability of FB1 to induce regenerative proliferation in target tissues. Humans living where maize is a dietary staple are at high risk for exposure to both mycotoxins. Our work has focused on Guatemala, a country in Central America where maize is consumed in large amounts every day and where intake of FB1 has been shown to be potentially quite high using biomarker-based studies. In 2012 a survey was conducted which analysed maize samples for FB1 and AFB1 from all 22 departments of Guatemala. The results show that the levels of AFB1 exposure are also potentially quite high in Guatemala, and likely throughout Central America and Mexico. The implications of co-exposure for human health are numerous, but one area of particular concern is the potential of FB1 to modulate AFB1 hepatoxicity and/or hepatocarcinogenicity. Both the mechanism of action of FB1 and its ability to promote liver carcinogenicity in rats and rainbow trout is consistent with this concern. In farm and laboratory animals FB1 inhibits ceramide synthases, key enzymes in de novo ceramide biosynthesis. The inhibition of sphingolipid signalling pathways mediating programmed cell death and activation of pathways stimulating cell proliferation in livers of individuals exposed to AFB1 could contribute to the tumorigenicity of AFB1. Studies investigating the health effects of either toxin should consider the potential for co-exposure to both toxins. Also, in countries where maize-based food are prepared by alkaline treatment of the maize kernels, the effect of traditional processing on AFB1 levels and toxicity needs to be determined, especially for maize highly contaminated with AFB1.

Mycotoxin co-contamination of food and feed: meta-analysis of publications describing toxicological interactions

Most fungi are able to produce several mycotoxins simultaneously; moreover food and feed can be contaminated by several fungi species at the same time. Thus, humans and animals are generally not exposed to one mycotoxin but to several toxins at the same time. Most of the studies concerning the toxicological effect of mycotoxins have been carried out taking into account only one mycotoxin. In the present review, we analysed 112 reports where laboratory or farm animals were exposed to a combination of mycotoxins, and we determined for each parameter measured the type of interaction that was observed. Most of the published papers concern interactions with aflatoxins and other mycotoxins, especially fumonisins, ochratoxin A and trichothecenes. A few papers also investigated the interaction between ochratoxin A and citrinin, or between different toxins from Fusarium species. Only experiments with a 2×2 factorial design with individual and combined effects of the mycotoxins were selected. Based on the raw published data, we classified the interactions in four different categories: synergistic, additive, less than additive or antagonistic effects. This review highlights the complexity of mycotoxins interactions which varies according to the animal species, the dose of toxins, the length of exposure, but also the parameters measured.

Subchronic mycotoxicoses in rats. Histopathological changes and modulation of the sphinganine to sphingosine (Sa/So) ratio imbalance induced by Fusarium verticillioides culture material, due to the coexistence of aflatoxin B1 in the diet

Mycotoxicoses are diseases caused by consumption of diets contaminated with mycotoxins, a special class of fungal secondary metabolites. Fumonisin B1 (FB1) and aflatoxin B1 (AFB1), the main toxins synthesized by toxicogenic stocks of Fusarium spp. and Aspergillus spp., respectively, can coexist in grains and in its by-products. We investigated a probable synergism of a fumonisins-containing Fusarium verticillioides culture material and AFB1 in the induction of hepatocyte apoptosis in rats subchronically fed on a mixture of them. Furthermore, the possibility of modifications in the fumonisins-induced Sa/So ratio imbalance in tissues and urine from rats poisoned with this mycotoxin, due to the presence of AFB1 in the diet, was evaluated. The co-exposure to fumonisins and AFB1 produced a higher liver toxicity, with respect to their individual administration, inducing apoptosis and mitotic hepatocytes. There was an inversion of the typical Sa/So ratio in rats fed on the culture material as well as in those subjected to a diet co-contamined with fumonisins and AFB1. Moreover, the later had a synergistic effect in the induction of Sa/So variations in kidneys. Therefore, the mixture of fumonisins and AFB1 induced toxic responses which could not be considered a sum of the effects caused individually by these mycotoxins.

Effects of oral administration of aflatoxin B1 and fumonisin B1 in rabbits (Oryctolagus cuniculus)

The effects of prolonged oral administration (21 days) of fumonisin B(1) (FB(1)) and aflatoxin B(1) (AFB(1)) were studied in male New Zealand rabbits by clinical, pathological, biochemical and sphingolipid analyses. Twenty-four animals were randomly divided into the following four experimental groups: (A) 0 mg FB(1)+0 microg AFB(1)/(kg body weight(bw)day) (control); (B) 0 mg FB(1)+30 microg AFB(1)/(kg bw day); (C) 1.5 mg FB(1)/(kg bw day)+30 microg AFB(1)/(kg bw day); (D) 1.5 mg FB(1)/(kg bw day)+0 microg AFB(1). Animals from group B and principally from group C presented clinical signs of intoxication. Rabbits from group C presented a lower body weight gain than controls. Differences were observed between intoxicated rabbits and controls with respect to absolute and relative liver and kidney weight, hepatic function, serum urea and creatinine levels and Sa/So ratio. The most frequent hepatic and renal injuries were vacuolar degeneration of the liver and kidney as shown by the histopathological and serum biochemical results. Combined administration of AFB(1) and FB(1) resulted in synergistic toxic effects both in the liver and in the kidney, but hepatic injuries were more marked.

The intestine as a possible target for fumonisin toxicity

Fumonisins constitute a family of toxic and carcinogenic mycotoxins produced by Fusarium verticillioides (formerly F. moniliforme), a common fungal contaminant of corn. Contamination with fumonisin B(1) (FB(1)) is of concern as this mycotoxin causes various animal diseases. The gastrointestinal tract represents the first barrier against ingested chemicals, food contaminants, and natural toxins. Following ingestion of fumonisin-contaminated food or feed, intestinal epithelial cells could be exposed to a high concentration of toxin. In this review, we have summarized the data dealing with the impact of FB(1) on the intestine. Although FB(1 )is poorly absorbed and metabolized in the intestine, it induces intestinal disturbances (abdominal pain or diarrhea) and causes extra-intestinal organ pathologies (pulmonary edema, leukoencephalomalacia, or neural tube defects). The main toxicological effect of FB(1) reported in vivo and in vitro is the accumulation of sphingoid bases associated with the depletion of complex sphingolipids. This disturbance of the sphingolipid biosynthesis pathway could explain the other observed toxicological effects such as an alteration in intestinal epithelial cell viability and proliferation, a modification of cytokine production, and a modulation of intestinal physical barrier function.

Immunobiological effects of AFB1 and AFB1-FB1 mixture in experimental subchronic mycotoxicoses in rats

Maize co-contamination with aflatoxin B1 (AFB1) and fumonisin B1 (FB1) is frequently found in several countries. Although the alterations on nutritional and immunologic parameters induced by these mycotoxins, when administered individually, are partially characterised, little is known about the effects induced in animals by a subchronic administration of both toxins mixtures. We have studied the nutritional and immunological alterations induced in rats fed during 90 days with a diet without mycotoxins, containing 40 ppb AFB1, and with a diet containing a mixture of 40 ppb AFB1 and 100 ppm FB1. Animals fed with the mixture of toxins obtained lower body weight than the control ones. The mitogenic response of spleen mononuclear cells (SMC) in vivo was higher in animals fed with AFB1. In in vitro studies, lower proliferations of SMC pre-exposed to AFB1 and to the mixture of toxins were detected. The SMC of animals fed with AFB1 produced lower levels of IL-2, higher of IL-4 and equal levels of IL-10. The SMC of animals fed with both toxins produced higher levels of IL-4, lower of IL-10 and equal levels of IL-2. The SMC preincubated with an AFB1-FB1 mixture produced higher concentrations of IL-4, lower of IL-10 and equal levels of IL-2. The peritoneal macrophages of animals that consumed AFB1 released less H(2)O(2), while animals fed with the mixture of toxins produced higher levels. In in vitro studies, macrophages pre-exposed to the mixture of toxins released less H(2)O(2). These results show different immunobiological effects produced by a mixture of mycotoxins in comparison to the individual action of the same toxins.

Immunobiological effects of fumonisin B1 in experimental subchronic mycotoxicoses in rats

Fumonisin B1 (FB1), the principal secondary metabolite produced by the fungus Fusarium verticillioides (Gibberella fujikuroi mating population A), is a potent toxin that can be found in fungus-contaminated corn and corn-based food products. We have investigated the immunobiological effects of subchronic dietary exposure to FB1 in male Wistar rats. Animals were fed with diets containing 0 (control) or 100 ppm of FB1 for 12 weeks. The total FB1 intake on day 90 was 810 mg/kg of body weight. Food consumption, body weight, and body weight gain on day 90 were reduced in animals exposed to FB1. Histopathologic changes consisted of histiocytic perivascular infiltrate and an increased number of Kupffer cells in the liver, necrosis and apoptosis of tubular epithelial cells in the kidney, and increased mitotic figures and lymphocytic infiltrate in the small intestine. Serum enzyme alkaline phosphatase was significantly elevated in rats fed FB1, while triglyceride levels decreased compared to controls. Treatment with FB1 in vivo or in vitro did not have a significant effect on mitogen-induced proliferation of spleen mononuclear cells. However, increased levels of interleukin-4 (IL-4) and decreased levels of IL-10 were released by these cells in culture compared to controls. FB1 in vivo or in vitro decreased the hydrogen peroxide (H(2)O(2)) released by peritoneal macrophages, while no changes in levels of superoxide anion produced by total peritoneal cells were detected. The results from the present work demonstrate that subchronic FB1 intake could affect the small intestine and alter the interleukin profile and some main functions of macrophages in antitumor activity.