Cytotoxicity induced by ochratoxin A, zearalenone, and α-zearalenol: effects of individual and combined treatment

Unexpected antagonism of deoxynivalenol and enniatins in intestinal toxicity through the Ras/PI3K/AKT signaling pathway

Deoxynivalenol (DON) is a kind of widespread traditional Fusarium mycotoxins in the environment, and its intestinal toxicity has received considerable attention. Recently, the emerging Fusarium mycotoxin enniatins (ENNs) have also been shown to frequently coexist with DON in animal feed and food with large consumption. However, the mechanism of intestinal damage caused by the two mycotoxins co-exposure remains unclear. In this study, Caco-2 cell line was used to investigate the combined toxicity and potential mechanisms of four representative ENNs (ENA, ENA1, ENB, and ENB1) and DON. The results showed that almost all mixed groups showed antagonistic effects, particularly ENB at 1/4 IC50 (CI = 6.488). Co-incubation of ENNs mitigated the levels of signaling molecule levels disrupted by DON, including reactive oxygen species (ROS), calcium mobilization (Ca2+), adenosine triphosphate (ATP). The differentially expressed genes (DEGs) between the mixed and ENB groups were significantly enriched in the Ras/PI3K/Akt signaling pathway, including 28 up-regulated genes and 40 down-regulated genes. Quantitative real-time PCR further confirmed the lower expression of apoptotic gene in the mixed group, thereby reducing the cytotoxic effects caused by DON exposure. This study emphasizes that co-exposure of ENNs and DON reduces cytotoxicity by regulating the Ras/PI3K/Akt signaling pathway. Our results provide the first comprehensive evidence about the antagonistic toxicity of ENNs and DON on Caco-2 cells, and new insights into mechanisms investigated by transcriptomics.

Cytotoxic effects induced by combined exposure to the mycotoxins sterigmatocystin, ochratoxin A and patulin on human tumour and healthy 3D spheroids

Humans are exposed to complex mixtures of mycotoxins through diet. Despite the serious threat they pose, mycotoxin risk assessment often overlooks co-exposure. With the aim of filling this gap, the present study investigates the combined cytotoxicity of sterigmatocystin (STE), ochratoxin A (OTA) and patulin (PAT) in human tumour Neuroblastoma and healthy Mesenchymal Stem Cells three-dimensional (3D) spheroids. The range of concentrations tested (1.56-50 μM for STE, 0.78-25 μM for OTA and 0.15-5 μM for PAT) was selected considering the IC50 values obtained in previous studies and the estimated dietary exposure of consumers. To ensure appropriate experimental conditions, assessments for single mycotoxins and their combinations were conducted simultaneously. The nature of the toxicological interactions among the mycotoxins was then defined using the isobologram analysis. Our results demonstrated increased cytotoxicity in mycotoxin mixtures compared to individual exposure, with abundance of synergistic interactions. These findings highlight that the co-occurrence of STE, OTA and PAT in food may increase their individual toxic effects and should not be underestimated. Moreover, the use of advanced culture models increased the reliability and physiological relevance of our results which can serve as a groundwork for formulating standardized regulatory approaches towards mycotoxin mixtures in food and feed.

Occurrence of the two major regulated mycotoxins, ochratoxin A and fumonisin B1, in cereal and cereal-based products in Europe and toxicological effects: A review

Among cereal contaminants, mycotoxins are of concern due to their importance in terms of food and feed safety. The difficulty in establishing a diagnosis for mycotoxicosis relies on the fact that the effects are most often subclinical for chronic exposure and the most common scenario is multi-contamination by various toxins. Mycotoxin co-occurrence is a major food safety concern as additive or even synergic toxic impacts may occur, but also regarding current regulations as they mainly concern individual mycotoxin levels in specific foods and feed in the food chain. However, due to the large number of possible mycotoxin combinations, there is still limited knowledge on co-exposure toxicity data, which depends on several parameters. In this context, this systematic review aims to provide an overview of the toxic effects of two regulated mycotoxins, namely ochratoxin A and fumonisin B1. This review focused on the 2012-2022 period and analysed the occurrence in Europe of the selected mycotoxins in different food matrices (cereals and cereal-derived products), and their toxic impact, alone or in combination, on in vitro intestinal and hepatic human cells. To better understand and evaluate the associated risks, further research is needed using new approach methodologies (NAM), such as in vitro 3D models. KEY CONTRIBUTION: Cereals and their derived products are the most important food source for humans and feed for animals worldwide. This manuscript is a state of the art review of the literature over the last ten years on ochratoxin A and fumonisin B1 mycotoxins in these products in Europe as well as their toxicological effects, alone and in combination, on human cells. Future perspectives and some challenges regarding the assessment of toxicological effects of mycotoxins are also discussed.

Efficacy of a multicomponent binding agent against combined exposure to zearalenone and ochratoxin A in weaned pigs

Introduction

The study aimed to evaluate the efficacy of a novel multicomponent substance against combined exposure to the mycotoxins zearalenone (ZEN) and ochratoxin A (OTA) in weaned piglets.

Methods

In total, 60 piglets at the age of 28 days were equally allocated to four experimental groups (A-D), consisting of eight female and seven male piglets each (15 animals per group, for a total trial duration of 42 days). Animals from group A received typical weaner feed without mycotoxins or the test product [multicomponent mycotoxin detoxifying agent (MMDA)]. Group B animals received the same weaner feed contaminated with 0.992 mg ZEN/kg feed and 0.531 mg OTA/kg feed without the addition of the MMDA. Animals in group C received the same contaminated feed as group B with the addition of 1.5 g MMDA/kg feed, whereas group D received the same feed as group B with the inclusion of 3 g MMDA/kg feed. Clinical signs and performance parameters [body weight (BW), average daily weight gain (ADWG), and feed conversion ratio (FCR)] were evaluated, while mycotoxin residues were also assessed in the liver and kidney tissues.

Results

Findings showed improved FCR in the group that received the greatest dose of the test product (3 g MMDA/kg feed) compared to the group that received the lower dose (1.5 g MMDA/kg feed). A few hematological and biochemical parameters were slightly altered, predominantly within normal limits. The residue analysis demonstrated a reduction of OTA in liver samples, a-ZEL in the liver and total tested samples, and a total of ZEN and metabolite contents in all samples of the group that received the greatest MMDA dose in comparison to the group that received the toxins without the addition of the test product.

Discussion

Therefore, a positive effect of the MMDA at the greatest dosage regime on reducing bioavailability and tissue deposition of ZEN and OTA, with a particularly positive effect on FCR in weaned pigs, is suggested under concurrent ZEN and OTA exposure in vivo.

Cytotoxic Effects of Major and Emerging Mycotoxins on HepaRG Cells and Transcriptomic Response after Exposure of Spheroids to Enniatins B and B1

Mycotoxins, produced by fungi, frequently occur at different stages in the food supply chain between pre- and postharvest. Globally produced cereal crops are known to be highly susceptible to contamination, thus constituting a major public health concern. Among the encountered mycotoxigenic fungi in cereals, Fusarium spp. are the most frequent and produce both regulated (i.e., T-2 toxin, deoxynivalenol -DON-, zearalenone -ZEA-) and emerging (i.e., enniatins -ENNs-, beauvericin -BEA-) mycotoxins. In this study, we investigated the in vitro cytotoxic effects of regulated and emerging fusariotoxins on HepaRG cells in 2D and 3D models using undifferentiated and differentiated cells. We also studied the impact of ENN B1 and ENN B exposure on gene expression of HepaRG spheroids. Gene expression profiling pinpointed the differentially expressed genes (DEGs) and overall similar pathways were involved in responses to mycotoxin exposure. Complement cascades, metabolism, steroid hormones, bile secretion, and cholesterol pathways were all negatively impacted by both ENNs. For cholesterol biosynthesis, 23/27 genes were significantly down-regulated and could be correlated to a 30% reduction in cholesterol levels. Our results show the impact of ENNs on the cholesterol biosynthesis pathway for the first time. This finding suggests a potential negative effect on human health due to the essential role this pathway plays.

Aflatoxin M1 decreases the expression of genes encoding tight junction proteins and influences the intestinal epithelial integrity

Aflatoxin M1 (AFM1) is a mycotoxin that is commonly found as a milk contaminant, and its presence in milk has been linked to cytotoxicity. The present study aimed to evaluate the acute cytotoxic effects of AFM1 on intestinal Caco-2 cells. Initially, we checked the morphology and viability of Caco-2 cells after treatment with different concentrations of AFM1 (5 ng/L, 50 ng/L, 250 ng/L, 500 ng/L, 1000 ng/L, and 2000 ng/L) for different time intervals (6 h, 12 h, and 24 h). It was found that AFM1 did not show any effect on cell morphology, but 10% decrease in viability above 1000 ng/L after 12 h. Furthermore, DCFDA assay showed increased ROS production after 6 h treatments. qPCR analysis showed an increased expression of epithelial-specific cytoskeleton marker genes, Cytokeratin, Villin, Vimentin, and JAM-1, and a decreased expression of tight junction protein genes, Claudin-1, Occludin, and ZO-1. Similarly, we found an increased expression of Cyp1a1 transcript with an increasing AFM1 concentration and incubation time. This gene expression analysis showed AFM1 can cause disruption of tight junctions between intestinal cells, which was further confirmed by a transwell experiment. In conclusion, consumption of AFM1-contaminated milk does not show any effect on cells morphology and viability but decreases the expression of intestinal barrier transcripts that may lead to the disruption of intestinal barrier function and leaky gut.

The Effect of Mycotoxins and Their Mixtures on Bovine Spermatozoa Characteristics

There is growing concern about the effects of mycotoxins on mammalian reproduction. Although the effects of single mycotoxins have been well documented, the impact of their mixtures on spermatozoon quality is less known. Here, frozen-thawed semen (n = 6 bulls) was in-vitro-cultured (2 h) without (control) or with (i) a single mycotoxin [zearalenone (ZEN), ochratoxin A (OTA), toxin 2 (T2), and diacetoxyscirpenol (DAS)] in a dose-response manner; (ii) binary mixtures (OTA + T2, OTA + ZEN, OTA + DAS, ZEN + T2, DAS + T2 and ZEN + DAS); or (iii) ternary mixtures (OTA + DAS + T2, OTA + ZEN + T2, and ZEN + DAS + T2). Then, the spermatozoa quality was characterized according to its plasma- and acrosome-membrane integrity, mitochondrial membrane potential, and oxidation status by a flow cytometer. Exposure to single mycotoxins or binary mixtures did not affect the spermatozoa characteristics. However, exposure to the ternary mixtures, OTA + DAS + T2 and OTA + ZEN + T2, reduced (p < 0.05) the mitochondrial membrane potential relative to the control. In addition, OTA + ZEN + T2 increased (p < 0.05) the proportion of spermatozoa with reactive oxygen species relative to the control. The most suggested interaction effect between the mycotoxins was found to be an additive one. A synergistic interaction, mainly regarding the oxidation status of the spermatozoa, was also found between the mycotoxins. The current study sheds light on the potential risk of exposing spermatozoa to a mycotoxin mixture.

Identification and Safety Evaluation of Ochratoxin A Transformation Product in Rapeseed Oil Refining Process

Ochratoxin A (OTA) is an important mycotoxin detected in edible oil, and it can be effectively removed by classical edible oil refining processes. However, the fate of OTA in the refining process has not been reported. In this study, we systematically tracked the OTA changes during the oil refining process by fortifying 100 μg/kg OTA in crude rapeseed oil. Results showed that about 10.57%, 88.85%, and 0.58% of OTA were removed during the degumming, deacidification, and decolorization processes. Among them, 16.25% OTA was transferred to the byproducts, including 9.85% in degumming wastewater, 5.68% in soap stock, 0.14% in deacidification wastewater, and 0.58% in the decolorizer; 83.75% OTA was found to transform into the lactone ring opened OTA (OP-OTA) during the deacidification stage, which is attributed to the hydrolysis of the lactone ring of OTA in the alkali refining. The OP-OTA was verified to distribute in the soap stock, and small amounts of OP-OTA could be transferred to deacidified wastewater when the OTA pollution level reached 500 μg/kg in crude rapeseed oil. The OP-OTA exhibited strong toxicity, especially nephrotoxicity, as reflected by the cell viability assay and in silico toxicity. Therefore, the safety of the soap stock processing products from OTA-contaminated rapeseed deserves attention.

Co-occurrence of mycotoxins: A review on bioanalytical methods for simultaneous analysis in human biological samples, mixture toxicity and risk assessment strategies

Mycotoxins are the toxic chemical substances that are produced by various fungal species and some of these are harmful to humans. Mycotoxins are ubiquitous in nature and humans could be exposed to multiple mycotoxins simultaneously. Unfortunately, exposure to mixed mycotoxins is not very well studied. Various studies have demonstrated the capacity of mycotoxins to show synergistic effect in the presence of other mycotoxins, thus, increasing the risk of toxicity. Hence, it is important to monitor mixed mycotoxins in human biological samples which would serve as a crucial information for risk assessment. Through this review paper, we aim to summarize the mixture toxicity of mycotoxins and the various bio-analytical techniques that are being used for the simultaneous analysis of mixed mycotoxins in human biological samples. Different sample preparation and clean-up techniques employed till date for eliminating the interferences from human biological samples without affecting the analyses of the mycotoxins are also discussed. Further, a brief introduction of risk assessment strategies that have been or could be adopted for multiple mycotoxin risk assessments is also mentioned. To the best of our knowledge, this is the first review that focuses solely on the occurrence of multiple mycotoxins in human biological samples as well as their risk assessment strategies.

Cytotoxicity of Mycotoxins and Their Combinations on Different Cell Lines: A Review

Mycotoxins are secondary metabolites of molds and mainly produced by species of the genera Aspergillus, Penicillium and Fusarium. They can be synthesized on the field, during harvest as well as during storage. They are fairly stable compounds and difficult to remove. Among several hundreds of mycotoxins, according to the WHO, ochratoxin A, aflatoxins, zearalenone, deoxynivalenol, patulin, fumonisins as well as T-2 and HT-2 toxins deserve special attention. Cytotoxicity is one of the most important adverse properties of mycotoxins and is generally assessed via the MTT assay, the neutral red assay, the LDH assay, the CCK-8 assay and the ATP test in different cell lines. The apoptotic cell ratio is mainly assessed via flow cytometry. Aside from the assessment of the toxicity of individual mycotoxins, it is important to determine the cytotoxicity of mycotoxin combinations. Such combinations often exhibit stronger cytotoxicity than individual mycotoxins. The cytotoxicity of different mycotoxins often depends on the cell line used in the experiment and is frequently time- and dose-dependent. A major drawback of assessing mycotoxin cytotoxicity in cell lines is the lack of interaction typical for complex organisms (for example, immune responses).

Proteomic analysis of zearalenone toxicity on mouse thymic epithelial cells

Zearalenone (ZEA) is one of the most major food contaminants in cereal crops worldwide, risking health of both livestock and humans. This study aimed to assess the cytotoxicity and the underlying mechanism of ZEA on thymic epithelial cells. By using proteomics analysis, we identified 596 differentially expressed proteins in MTEC1 cells upon zearalenone exposure, of which 245 were upregulated and 351 were downregulated. Gene ontology (GO) analysis suggested that differentially expressed proteins were participated in protein synthesis, oxidative phosphorylation, and ATP binding. KEGG pathway enrichment analysis showed that differentially expressed proteins were mainly related to mitochndrial metabolism, such as citrate cycle (TCA cycle) and oxidative phosphorylation. We demonstrated that ZEA treatment was able to increase the intracellular reactive oxygen species (ROS) level, to decrease ΔΨm, ATP level, and the copy number of mtDNA, leading to necrotic cell death. Moreover, we showed that ZEA treatment inhibited cell proliferation and induced G2/M phase arrest by downregulation of proliferation-associated proteins ERK, p-ERK, CDK1, and p-CHK1. Taken together, we found that the toxicity of ZEA on thymic epithelial cells is mainly caused by the inhibition of mitochondrial dysfunction and cell proliferation. Our study might open new avenues for treatment strategies.

Protective Effects of the Hydroethanolic Extract of Fridericia chica on Undifferentiated Human Neuroblastoma Cells Exposed to α-Zearalenol (α-ZEL) and β-Zearalenol (β-ZEL)

Fridericia chica (Bignoniaceae) is a traditional medicinal plant. The aim of this research was to determine the protective effects of the hydroethanolic extract from the F. chica leaves (HEFc) against the cytotoxicity of zearalenone (α-ZEL) and β-ZEL on SH-SY5Y cells. Free radical scavenging activity of HEFc was evaluated using the DPPH method. The cytotoxicity of both zearalenone metabolites and HEFc was examined using MTT test, as was the cytoprotective effects of the HEFc on cells treated with these mycotoxins. The chemical composition of HEFc was determined using UPLC-QTOF-MS/MS. HEFc elicited good DPPH radical scavenging activity following a concentration-dependent relationship. Cells exposed to α-ZEL exhibited a viability ˂50% after 48 h of treatment (25 and 50 µM), while those exposed to β-ZEL showed viability ˂50% (100 µM) and ˂25% (25-100 µM) after 24 and 48 h of exposure, respectively. HEFc showed a significant increase in cell viability after exposure to α-ZEL (25 and 50 µM) and β-ZEL (6-100 µM) (p < 0.05). UPLC-QTOF-MS/MS analyses allowed the identification of 10 phytochemical components in the HEFc. In short, the hydroethanolic extract of F. chica grown in Colombian Caribbean can protect against the effects of mycotoxins and it is a valuable source of compounds with antioxidant properties.

In Vitro Evaluation of the Individual and Combined Cytotoxic and Estrogenic Effects of Zearalenone, Its Reduced Metabolites, Alternariol, and Genistein

Mycotoxins are toxic metabolites of filamentous fungi. Previous studies demonstrated the co-occurrence of Fusarium and Alternaria toxins, including zearalenone (ZEN), ZEN metabolites, and alternariol (AOH). These xenoestrogenic mycotoxins appear in soy-based meals and dietary supplements, resulting in the co-exposure to ZEN and AOH with the phytoestrogen genistein (GEN). In this study, the cytotoxic and estrogenic effects of ZEN, reduced ZEN metabolites, AOH, and GEN are examined to evaluate their individual and combined impacts. Our results demonstrate that reduced ZEN metabolites, AOH, and GEN can aggravate ZEN-induced toxicity; in addition, the compounds tested exerted mostly synergism or additive combined effects regarding cytotoxicity and/or estrogenicity. Therefore, these observations underline the importance and the considerable risk of mycotoxin co-exposure and the combined effects of mycoestrogens with phytoestrogens.

Transcriptomic alterations induced by aflatoxin B1 and ochratoxin A in LMH cell line

Aflatoxin B1 (AFB1) and ochratoxin A (OTA), which are toxic metabolites of ubiquitously occurring molds, show diverse toxicological effects such as hepatotoxicity, genotoxicity, and immunotoxicity in human and animals. Despite poultry show sensitivity to AFB1 and OTA, the mechanism of these mycotoxins in chickens has not been fully investigated. Here, we aimed to elucidate the molecular mechanism induced by AFB1 and/or OTA in chicken hepatic cells using transcriptomic analysis. Aflatoxin B1 and OTA induced cytotoxic effects in a dose-dependent manner at 48 h after exposure. Furthermore, correlation effect indicated an antagonism between the 2 toxins. The mRNA sequencing of AFB1-treated or OTA-treated chicken hepatocarcinoma and functional analysis revealed the pathways that were commonly regulated by both mycotoxins, especially PPAR signaling, focal adhesion, and MAPK signaling. Based on these findings, a possible hypothesis is that AFB1 and OTA have similar toxic mechanisms and compete for some steps in the chicken liver, and it is expected that the mycotoxins would have antagonistic effects. In addition, genes identified through transcriptome analysis provide candidates for further study of AFB1 and OTA toxicity and targets for efforts to improve the health of chickens exposed to mycotoxins.

Mycotoxins: Biotransformation and Bioavailability Assessment Using Caco-2 Cell Monolayer

The determination of mycotoxins content in food is not sufficient for the prediction of their potential in vivo cytotoxicity because it does not reflect their bioavailability and mutual interactions within complex matrices, which may significantly alter the toxic effects. Moreover, many mycotoxins undergo biotransformation and metabolization during the intestinal absorption process. Biotransformation is predominantly the conversion of mycotoxins meditated by cytochrome P450 and other enzymes. This should transform the toxins to nontoxic metabolites but it may possibly result in unexpectedly high toxicity. Therefore, the verification of biotransformation and bioavailability provides valuable information to correctly interpret occurrence data and biomonitoring results. Among all of the methods available, the in vitro models using monolayer formed by epithelial cells from the human colon (Caco-2 cell) have been extensively used for evaluating the permeability, bioavailability, intestinal transport, and metabolism of toxic and biologically active compounds. Here, the strengths and limitations of both in vivo and in vitro techniques used to determine bioavailability are reviewed, along with current detailed data about biotransformation of mycotoxins. Furthermore, the molecular mechanism of mycotoxin effects is also discussed regarding the disorder of intestinal barrier integrity induced by mycotoxins.

In Silico and In Vitro Studies of Mycotoxins and Their Cocktails; Their Toxicity and Its Mitigation by Silibinin Pre-Treatment

Mycotoxins found in randomly selected commercial milk thistle dietary supplement were evaluated for their toxicity in silico and in vitro. Using in silico methods, the basic physicochemical, pharmacological, and toxicological properties of the mycotoxins were predicted using ACD/Percepta. The in vitro cytotoxicity of individual mycotoxins was determined in mouse macrophage (RAW 264.7), human hepatoblastoma (HepG2), and human embryonic kidney (HEK 293T) cells. In addition, we studied the bioavailability potential of mycotoxins and silibinin utilizing an in vitro transwell system with differentiated human colon adenocarcinoma cells (Caco-2) simulating mycotoxin transfer through the intestinal epithelial barrier. The IC50 values for individual mycotoxins in studied cells were in the biologically relevant ranges as follows: 3.57-13.37 nM (T-2 toxin), 5.07-47.44 nM (HT-2 toxin), 3.66-17.74 nM (diacetoxyscirpenol). Furthermore, no acute toxicity was obtained for deoxynivalenol, beauvericin, zearalenone, enniatinENN-A, enniatin-A1, enniatin-B, enniatin-B1, alternariol, alternariol-9-methyl ether, tentoxin, and mycophenolic acid up to the 50 nM concentration. The acute toxicity of these mycotoxins in binary combinations exhibited antagonistic effects in the combinations of T-2 with DON, ENN-A1, or ENN-B, while the rest showed synergistic or additive effects. Silibinin had a significant protective effect against both the cytotoxicity of three mycotoxins (T-2 toxin, HT-2 toxin, DAS) and genotoxicity of AME, AOH, DON, and ENNs on HEK 293T. The bioavailability results confirmed that AME, DAS, ENN-B, TEN, T-2, and silibinin are transported through the epithelial cell layer and further metabolized. The bioavailability of silibinin is very similar to mycotoxins poor penetration.

Transcriptome analysis revealed that aflatoxin M1 could cause cell cycle arrest in differentiated Caco-2 cells

Being a hydroxylated metabolite of aflatoxin B1 (AFB1) and the most threatening aspect of AFB1 contamination, aflatoxin M1 (AFM1) can lead to hepatotoxicity and hepato-carcinogenicity, and possess intestinal cytotoxicity. However, little is known about the potential mechanisms of the extrahepatic effect. The aim of this study was to investigate intestinal dysfunction induced by AFM1 via transcriptome analysis. Gene expression profiling was analyzed to comparatively characterize the differentially expressed genes (DEGs) after differentiated Caco-2 cells were exposed to different concentrations of AFM1 for 48 h. A total of 165 DEGs were significantly clustered into two down-regulated patterns. Protein-protein interaction (PPI) network analysis based on Search Tool for Retrieval of Interacting Genes (STRING)suggested that 23 key enzymes mainly participated in the regulation of the cell cycle. Q-PCR analysis was performed to validate that key 12 genes (BUB1, BUB1B, MAD2L1, CCNA2, RB1, CDK1, ANAPC4, ATM, KITLG, PRKAA2, SIRT1, and SOS1) were involved. This study firstly revealed that the toxicity of AFM1 to intestinal functions may be partly due to the occurrence of cell cycle arrest, which is linked to changes in CDK1, SOS1/Akt, and AMPK signaling molecules.

Cytotoxic and inflammatory effects of individual and combined exposure of HepG2 cells to zearalenone and its metabolites

Zearalenone (ZEA), a mycotoxin produced by several Fusarium spp., is most commonly found as a contaminant in stored grain. ZEA derivatives (α-zearalenol (α-ZOL), β-zearalenol (β-ZOL)) can also be produced by Fusarium spp. in corn stems infected by fungi in the field. Also, following oral exposure, zearalenone is metabolized in various tissues, particularly in the liver, the major metabolites being α-ZOL and β-ZOL. The co-exposure of cells to mixture of a combination of mycotoxins may cause an increase of toxicity produced by these mycotoxins. In this in vitro study, we investigated the combined effects of ZEA, α-ZOL, β-ZOL in binary mixtures on the viability and inflammatory response of human liver cancer cell line (HepG2). Cell viability was assessed after 72 h using a neutral red assay. Effect of the toxins and their binary combinations on the expression of genes involved in inflammation (IL-1β, TNF-α, and IL-8) were assessed through qPCR. Our viability data showed that irrespective of the toxin combinations, the toxins have synergistic effect. ZEA + α-ZOL and ZEA + β-ZOL mixtures have induced a slight to high antagonistic response on inflammatory cytokines at low concentrations that have turned into strong synergism for high concentrations. α-ZOL + β-ZOL showed antagonistic effects on inflammation for IL-1β and TNF-α, but act synergic for IL-8 at high toxin concentrations. This study clearly shows that co-contamination of food and feed with ZEA metabolites should be taken into consideration, as the co-exposure to mycotoxins might result in stronger adverse effect than resulted from the exposure to individual toxin.

A critical evaluation of health risk assessment of modified mycotoxins with a special focus on zearalenone

A comprehensive definition introducing the term "modified mycotoxins" to encompass all possible forms in which mycotoxins and their modifications can occur was recently proposed and has rapidly gained wide acceptance within the scientific community. It is becoming increasingly evident that exposure to such modified mycotoxins due to their presence in food and feed has the potential to pose a substantial additional risk to human and animal health. Zearalenone (ZEN) is a well-characterized Fusarium toxin. Considering the diversity of modified forms of ZEN occurring in food and feed, the toxicologically relevant endocrine activity of many of these metabolites, and the fact that modified forms add to a dietary exposure which approaches the tolerable daily intake by free ZEN alone, modified forms of ZEN present an ideal case study for critical evaluation of modified mycotoxins in food safety. Following a summary of recent scientific opinions of EFSA dealing with health risk assessment of ZEN alone or in combination with its modified forms, uncertainties and data gaps are highlighted. Issues essential for evaluation and prioritization of modified mycotoxins in health risk assessment are identified and discussed, including opportunities to improve exposure assessment using biomonitoring data. Further issues such as future consideration of combinatory effects of the parent toxin with its modified forms and also other compounds co-occurring in food and feed are addressed. With a particular focus on ZEN, the most pressing challenges associated with health risk assessment of modified mycotoxins are identified and recommendations for further research to fill data gaps and reduce uncertainties are made.

Combination of Selenomethionine and N-Acetylcysteine Alleviates the Joint Toxicities of Aflatoxin B1 and Ochratoxin A by ERK MAPK Signal Pathway in Porcine Alveolar Macrophages

Our previous studies showed that aflatoxin B1 (AFB1) and ochratoxin A (OTA) could trigger joint immune toxicity. Little is known about the combined effects of selenomethionine (SeMet) and N-acetylcysteine (NAC) on the joint toxicities of the two toxins. In this study, results showed that SeMet or NAC alone or in combination significantly alleviated the downswing of cell viability, glutathione production, and phagorytosis induced by AFB1 and OTA in porcine alveolar macrophages. The uptrend of lactate dehydrogenase activities, apoptosis, reactive oxygen species levels, and the relative mRNA of inflammatory cytokines triggered by the two toxins was decreased. Combination of them was more effective than single application. Knockdown of p38, c-JUN N-terminal kinase (JNK), or extracellular signal-regulated kinase (ERK) via use of the corresponding specific siRNA could alleviate the joint toxicities of AFB1 and OTA. However, the ERK but not p38 or JNK pathway was involved in the protection of SeMet and NAC against the immunotoxicity. In conclusion, combination of SeMet and NAC might be a new therapeutic orientation for preventing the joint toxicities induced by AFB1 and OTA.

Immunotoxicity of ochratoxin A and aflatoxin B1 in combination is associated with the nuclear factor kappa B signaling pathway in 3D4/21 cells

The co-contamination of cereals, grains, crops, and animal feeds by mycotoxins is a universal problem. Humans and animals are exposed to several mycotoxins simultaneously as evidenced by extensive studies on this topic. Yet, most studies have addressed the effects of mycotoxins individually. Aflatoxin B1 and ochratoxin A can induce immunotoxicity. However, it remains unclear whether a combination of these mycotoxins aggravates immunotoxicity and the potential mechanism underlying this effect. In this study, we used the cell line 3D4/21, swine alveolus macrophages and innate immune cell. The results showed that the percentage of cell inhibition, annexin V/PI-positive rates, and the expression of pro-inflammatory cytokines (tumor necrosis factor alpha and interleukin-6) significantly increased and the release of lactate dehydrogenase and phagocytotic index were significantly decreased at different concentrations of aflatoxin B1 and ochratoxin A combination when compared with control. The combination of aflatoxin B1 and ochratoxin A significantly decreased the production of GSH and increased reactive oxygen species level. However, N-acetylcysteine suppressed the oxidative stress and alleviated the immunotoxicity induced by the combination. The combination of aflatoxin B1 and ochratoxin A markedly enhanced the degradation of IκBa, the phosphorylation of nuclear factor kappa B (p65), and the translocation of activated nuclear factor kappa B (NF-κB) into the nuclei as demonstrated by western blotting and confocal laser scanning microscopy. These effects could be reversed by BAY 11-7082, a specific inhibitor of NF-κB. Taken together, a combination of aflatoxin B1 and ochratoxin A could aggravate immunotoxicity by activating the NF-κB signaling pathway.

Individual and combined cytotoxicity assessment of zearalenone with ochratoxin A or α-zearalenol by full factorial design

The combined mycotoxins zearalenone (ZEA) with ochratoxin A (OTA) or α-zearalenol (α-ZOL) are frequently found together in milk. Toxicological data concerning the combined effects of these mycotoxins are sparse. In present study, individual and combined ZEA, OTA and α-ZOL caused cytotoxicity and oxidative damage, including reductions in intracellular superoxide dismutase and glutathione peroxidase activities and glutathione content, along with increases in malonaldehyde content on human Hep G2 cells after 48 h of exposure. Among individual mycotoxins, OTA had the greatest cytotoxic effect followed by α-ZOL. Compared with individual mycotoxins, combinations produced more serious negative effects, more importantly, ZEA + OTA was antagonistic for these effects, whereas ZEA + α-ZOL was antagonistic at low concentrations, but synergistic at high concentrations of ZEA, which were evaluated by 3 × 3 full factorial analysis and estimated marginal means plots. Our results also demonstrated a significant correlation between cytotoxicity and oxidative damage in response to these combinations.

Mycotoxins co-contamination: Methodological aspects and biological relevance of combined toxicity studies

Mycotoxins are secondary fungal metabolites produced mainly by Aspergillus, Penicillium, and Fusarium. As evidenced by large-scale surveys, humans and animals are simultaneously exposed to several mycotoxins. Simultaneous exposure could result in synergistic, additive or antagonistic effects. However, most toxicity studies addressed the effects of mycotoxins separately. We present the experimental designs and we discuss the conclusions drawn from in vitro experiments exploring toxicological interactions of mycotoxins. We report more than 80 publications related to mycotoxin interactions. The studies explored combinations involving the regulated groups of mycotoxins, especially aflatoxins, ochratoxins, fumonisins, zearalenone and trichothecenes, but also the "emerging" mycotoxins beauvericin and enniatins. Over 50 publications are based on the arithmetic model of additivity. Few studies used the factorial designs or the theoretical biology-based models of additivity. The latter approaches are gaining increased attention. These analyses allow determination of the type of interaction and, optionally, its magnitude. The type of interaction reported for mycotoxin combinations depended on several factors, in particular cell models and the tested dose ranges. However, synergy among Fusarium toxins was highlighted in several studies. This review indicates that well-addressed in vitro studies remain valuable tools for the screening of interactive potential in mycotoxin mixtures.

Modulations of DNMT1 and HDAC1 are involved in the OTA-induced cytotoxicity and apoptosis in vitro

Ochratoxin A (OTA) as a fungal metabolite is reported to induce cytotoxicity and apoptosis through the mechanism of oxidative stress. Oxidative stress could induce the epigenetic enzymes modifications. However, whether epigenetic enzymes modifications are involved in OTA-induced cytotoxicity and apoptosis has not been reported until now. Therefore, the objectives of this study were to verify OTA-induced cytotoxicity and apoptosis and to investigate the potential role of epigenetic enzymes in OTA-induced cytotoxicity and apoptosis in PK15 cells. The results demonstrated that OTA at 4 μg/ml treatment for 12 h and 24 h induced cytotoxicity and apoptosis as demonstrated by decreasing cell viability, increasing LDH release, Annexin V/PI staining, Bcl-2/Bax mRNA ratio and apoptotic nuclei in PK15 cells. OTA treatment up-regulated ROS production and down-regulated GSH levels. In addition, OTA treatment activated the epigenetics related enzymes DNA methyltransferase 1 (DNMT1) and Histone deacetylase 1 (HDAC1). Adding DNMT1 inhibitor (5-Aza-2dc) or HDAC1 inhibitor (LBH589) depressed the up-regulation of DNMT1 or HDAC1 expression, the decreases of GSH levels and increases of ROS production induced by OTA, respectively. Furthermore, inhibition of DNMT1 or HDAC1 by their inhibitor reversed the decreases of cell viability and increases of LDH activity and apoptosis induced by OTA, respectively. In conclusion, the observed effects indicate that the critical modulation of DNMT1 and HDAC1 is related to OTA-induced cytotoxicity and apoptosis.

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.

Zearalenone as an endocrine disruptor in humans

Zearalenone (ZEA), a fungal mycotoxin, is present in a wide range of human foods. Many animal studies have found ZEA to possess a disruptive effect on the hormonal balance, mainly due to its similarity to naturally-occurring estrogens. With increasing consciousness of the adverse effects of endocrine disruptors on human health, it is becoming more important to monitor ZEA concentrations in food and identify its potential effects on human health. Based on a review of recent studies on animal models and molecular pathways in which ZEA is reported to have an influence on humans, we postulate that ZEA might act as an endocrine disruptor in humans in a similar way to animals. Moreover, its endocrine-disrupting effect might be also a causative factor in carcinogenesis. This review article summarizes the latest knowledge about the influence of ZEA on the human hormonal balance.

Reaction of zearalenone and α-zearalenol with allyl isothiocyanate, characterization of reaction products, their bioaccessibility and bioavailability in vitro

This study investigates the reduction of zearalenone (ZEA) and α-zearalenol (α-ZOL) on a solution model using allyl isothiocyanate (AITC) and also determines the bioaccessibility and bioavailability of the reaction products isolated and identified by MS-LIT. Mycotoxin reductions were dose-dependent, and ZEA levels decreased more than α-ZOL, ranging from 0.2 to 96.9% and 0 to 89.5% respectively, with no difference (p⩽0.05) between pH 4 and 7. Overall, simulated gastric bioaccessibility was higher than duodenal bioaccessibility for both mycotoxins and mycotoxin-AITC conjugates, with duodenal fractions representing ⩾63.5% of the original concentration. Simulated bioavailability of reaction products (α-ZOL/ZEA-AITC) were lower than 42.13%, but significantly higher than the original mycotoxins. The cytotoxicity of α-ZOL and ZEA in Caco-2/TC7 cells was also evaluated, with toxic effects observed at higher levels than 75μM. Further studies should be performed to evaluate the toxicity and estrogenic effect of α-ZOL/ZEA-AITC.

Aflatoxin M1 cytotoxicity against human intestinal Caco-2 cells is enhanced in the presence of other mycotoxins

Aflatoxin M1 (AFM1), a class 2B human carcinogen, is the only mycotoxin with established maximum residue limits (MRLs) in milk. Toxicological data for other mycotoxins in baby food, containing cereals and milk, either in isolation or in combination with AFM1, are sparse. The aim of this study was to investigate the cytotoxicity of AFM1, ochratoxin A (OTA), zearalenone (ZEA), and α-zearalenol (α-ZOL), individually and in combinations, in human Caco-2 cells. The tetrazolium salt (MTT) assay demonstrated that (i) OTA and AFM1 had similar cytotoxicity, which was higher than that of ZEA and α-ZOL, after a 72 h exposure; and (ii) the quaternary combination had the highest cytotoxicity, followed by tertiary and binary combinations and individual mycotoxins. Isobologram analysis indicated that the presence of OTA, ZEA, and/or α-ZOL with AFM1 led to additive and synergistic cytotoxicity in most combinations. The cytotoxicity of OTA was similar to that of AFM1, suggesting that OTA in food poses a health risk to consumers. Furthermore, AFM1 cytotoxicity increased dramatically in the presence of OTA, ZEA, and/or α-ZOL (p < 0.01), indicating that the established MRLs for AFM1 should be re-evaluated considering its frequent co-occurrence with other mycotoxins in baby food which contains milk and cereals.

Binary and tertiary combination of alternariol, 3-acetyl-deoxynivalenol and 15-acetyl-deoxynivalenol on HepG2 cells: Toxic effects and evaluation of degradation products

Fungi producers of mycotoxins are able to synthesize more than one toxin. Alternariol (AOH) is one of the mycotoxins produced by several Alternaria species, the most common one being Alternaria alternata. The toxins 3-Acetyl-deoxynivalenol (3-ADON) and 15-Acetyl-deoxynivalenol (15-ADON) are acetylated forms of deoxynivalenol (DON) produced by Fusarium graminearum. In the present work it is determined and evaluated the toxic effects of binary and tertiary combination treatment of HepG2 cells with AOH, 3-ADON and 15-ADON, by using the MTT assay (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide), to subsequently apply the isobologram method and elucidate if the mixtures of these mycotoxins produced synergism, antagonism or additive effect; and lastly, to analyze mycotoxins conversion into metabolites produced and released by HepG2 cells after applying the treatment conditions by liquid chromatography tandem mass spectrometry (LC-MS/MS) equipment and extracted from culture media. HepG2 cells were treated at different concentrations over 24, 48 and 72h. IC50 values detected at all times assayed, ranged from 0.8 to >25μM in binary combinations; while in tertiary it ranged from 7.5 to 12μM. Synergistic, antagonism or additive effect detected in the mixtures of these mycotoxins was different depending on low or high concentration. Among all four mycotoxins combinations assayed, 15-ADON+3-ADON presented the highest toxic potential. At all assayed times, recoveries values oscillated depending on the time and combination studied.

Biodegradation of zearalenone by Saccharomyces cerevisiae: Possible involvement of ZEN responsive proteins of the yeast

The mycotoxin zearalenone, also known as F-2 mycotoxin or RAL is a potent estrogenic metabolite produced by some Gibberella and Fusarium species. It is a common contaminant of cereal crops, livestock and poultry products. However, detoxification of zearalenone (ZEN) remains a challenge. Recently, biological approach for ZEN detoxification is being explored. In this study, we investigated the biodegradation of ZEN by using Saccharomyces cerevisiae and the possible mechanisms involved. The findings revealed that, after 48h of incubation of S. cerevisiae in combination with ZEN, the ZEN was completely degraded by S. cerevisiae. On the contrary, heat-killed cells and cell-free culture filtrates of S. cerevisiae could not degrade ZEN. Furthermore, addition of cycloheximide to S. cerevisiae combined with ZEN at time 0h prevented ZEN degradation, while addition of cycloheximide at 12h significantly slowed down degradation. The results also indicated cellular proteomics of S. cerevisiae. Several differential proteins were identified, most of which were related to basic metabolism.

BIOLOGICAL SIGNIFICANCE

The findings revealed that, after 48h of incubating ZEN together with S. cerevisiae, ZEN was completely degraded by S. cerevisiae. The mechanisms involved in the degradation of ZEN by S. cerevisiae may be the production of associated intracellular and extracellular enzymes, which have the ability to degrade ZEN. In addition, there were some functional proteins produced by S. cerevisiae, indicating that the basic metabolism of S. cerevisiae was improved when ZEN was added. This novel discovery by the authors, will greatly contribute to the field of biodegradation of mycotoxin by antagonists. The authors also believed this innovation will open the grounds for further research and improvement of S. cerevisiae in the field of biodegradation.

Natural Co-Occurrence of Mycotoxins in Foods and Feeds and Their in vitro Combined Toxicological Effects

Some foods and feeds are often contaminated by numerous mycotoxins, but most studies have focused on the occurrence and toxicology of a single mycotoxin. Regulations throughout the world do not consider the combined effects of mycotoxins. However, several surveys have reported the natural co-occurrence of mycotoxins from all over the world. Most of the published data has concerned the major mycotoxins aflatoxins (AFs), ochratoxin A (OTA), zearalenone (ZEA), fumonisins (FUM) and trichothecenes (TCTs), especially deoxynivalenol (DON). Concerning cereals and derived cereal product samples, among the 127 mycotoxin combinations described in the literature, AFs+FUM, DON+ZEA, AFs+OTA, and FUM+ZEA are the most observed. However, only a few studies specified the number of co-occurring mycotoxins with the percentage of the co-contaminated samples, as well as the main combinations found. Studies of mycotoxin combination toxicity showed antagonist, additive or synergic effects depending on the tested species, cell model or mixture, and were not necessarily time- or dose-dependent. This review summarizes the findings on mycotoxins and their co-occurrence in various foods and feeds from all over the world as well as in vitro experimental data on their combined toxicity.

The Effect of Low Monotonic Doses of Zearalenone on Selected Reproductive Tissues in Pre-Pubertal Female Dogs--A Review

The growing interest in toxic substances combined with advancements in biological sciences has shed a new light on the problem of mycotoxins contaminating feeds and foods. An interdisciplinary approach was developed by identifying dose-response relationships in key research concepts, including the low dose theory of estrogen-like compounds, hormesis, NOAEL dose, compensatory response and/or food tolerance, and effects of exposure to undesirable substances. The above considerations increased the researchers’ interest in risk evaluation, namely: (i) clinical symptoms associated with long-term, daily exposure to low doses of a toxic compound; and (ii) dysfunctions at cellular or tissue level that do not produce clinical symptoms. Research advancements facilitate the extrapolation of results and promote the use of novel tools for evaluating the risk of exposure, for example exposure to zearalenone in pre-pubertal female dogs. The arguments presented in this paper suggest that low doses of zearalenone in commercial feeds stimulate metabolic processes and increase weight gains. Those processes are accompanied by lower proliferation rates in the ovaries, neoangiogenesis and vasodilation in the ovaries and the uterus, changes in the steroid hormone profile, and changes in the activity of hydroxysteroid dehydrogenases. All of the above changes result from exogenous hyperestrogenizm.

Enantioselective and Synergetic Toxicity of Axial Chiral Herbicide Propisochlor to SP2/0 Myeloma Cells

The axial chiral herbicide propisochlor is used to control weeds. Different enantiomers of a compound usually have different biological activities. It is unclear how the toxicities of the propisochlor enantiomers differ. Propisochlor enantiomers, separated by high-performance liquid chromatography, were tested on SP2/0 myeloma cells. Cytotoxicity and apoptosis were measured, and interactions between the enantiomers were evaluated. The rac-propisochlor, pure R-(+) isomer, and pure S-(-) isomer inhibited cell proliferation and induced apoptosis. The rac-propisochlor, R-(+) isomer, and S-(-) isomer half maximal effective concentration values after 24 h of incubation were 111 ± 0.15, 68 ± 0.09, and 99 ± 0.21 μM, respectively. R-(+) isomer induced the most apoptosis. R-(+) isomer was ∼1.63 times more cytotoxic than rac-propisochlor and ∼1.46 times more cytotoxic than S-(-) isomer. Antagonistic cytotoxic interactions were found between R-(+) and S-(-) isomers. This is the first time the toxicities of these enantiomers and antagonism between the enantiomers have been reported. The antagonism indicates that the ecotoxicological effects of the enantiomers should be investigated.

Taxonomic Characterization and Secondary Metabolite Profiling of Aspergillus Section Aspergillus Contaminating Feeds and Feedstuffs

Xerophilic fungal species of the genus Aspergillus are economically highly relevant due to their ability to grow on low water activity substrates causing spoilage of stored goods and animal feeds. These fungi can synthesize a variety of secondary metabolites, many of which show animal toxicity, creating a health risk for food production animals and to humans as final consumers, respectively. Animal feeds used for rabbit, chinchilla and rainbow trout production in Argentina were analysed for the presence of xerophilic Aspergillus section Aspergillus species. High isolation frequencies (>60%) were detected in all the studied rabbit and chinchilla feeds, while the rainbow trout feeds showed lower fungal charge (25%). These section Aspergillus contaminations comprised predominantly five taxa. Twenty isolates were subjected to taxonomic characterization using both ascospore SEM micromorphology and two independent DNA loci sequencing. The secondary metabolite profiles of the isolates were determined qualitatively by HPLC-MS. All the isolates produced neoechinulin A, 17 isolates were positive for cladosporin and echinulin, and 18 were positive for neoechinulin B. Physcion and preechinulin were detected in a minor proportion of the isolates. This is the first report describing the detailed species composition and the secondary metabolite profiles of Aspergillus section Aspergillus contaminating animal feeds.

Individual and combined cytotoxic effects of aflatoxin B1, zearalenone, deoxynivalenol and fumonisin B1 on BRL 3A rat liver cells

This study was performed to determine the individual and combined cytotoxic effects of Aflatoxin B1 (AFB1), zearalenone (ZEA), deoxynivalenol (DON) and fumonisin B1 (FB1) on BRL 3A rat liver cells. After the mycotoxins treated the BRL 3A cells for 12, 24 and 48 h, cell viability was determined using the MTT assay. The cytotoxicity of individual mycotoxins on BRL 3A cell viability in decreasing order were DON > AFB1 > ZEA > FB1. The central composite design (CCD) was used to assess the toxicity of binary and ternary mixtures of these mycotoxins. The mixtures of AFB1+ZEA and AFB1+DON showed the synergetic toxic effects on BRL 3A cells. These toxins decreased the viability of cells by inducing intracellular reactive oxygen species (ROS) production and promoting apoptosis in the BRL 3A cells. This effect was mediated by an upregulation of the stress and apoptotic genes Hsp70, p53, Bax, Caspase-3 and Caspase-8, along with a downregulation of the antiapoptotic gene Bcl-2. In conclusion, our results suggested that the coexistence of AFB1 and ZEA or DON in agricultural products could be more hepatotoxic than individually, suggests that the toxicological interactions of these toxins need to be better understood to assess health risks.