Mycotoxin ochratoxin A disrupts renal development via a miR-731/prolactin receptor axis in zebrafish

Membrane Receptor-Mediated Disruption of Cellular Homeostasis: Changes in Intracellular Signaling Pathways Increase the Toxicity of Ochratoxin A

Organisms maintain their cellular homeostatic balance by interacting with their environment through the use of their cell surface receptors. Membrane based receptors such as the transforming growth factor β receptor (TGFR), the prolactin receptor (PRLR), and hepatocyte growth factor receptor (HGFR), along with their associated signaling cascade, play significant roles in retaining cellular homeostasis. While these receptors and related signaling pathways are essential for health of cell and organism, their dysregulation can lead to imbalance in cell function with severe pathological conditions such as cell death or cancer. Ochratoxin A (OTA) can disrupt cellular homeostasis by altering expression levels of these receptors and/or receptor-associated intracellular downstream signaling modulators and/or pattern and levels of their phosphorylation/dephosphorylation. Recent studies have shown that the activity of the TGFR, the PRLR, and HGFR and their associated signaling cascades change upon OTA exposure. A critical evaluation of these findings suggests that while increased activity of the HGFR and TGFR signaling pathways leads to an increase in cell survival and fibrosis, decreased activity of the PRLR signaling pathway leads to tissue damage. This review explores the roles of these receptors in OTA-related pathologies and effects on cellular homeostasis.

MicroRNAs: exploring their role in farm animal disease and mycotoxin challenges

MicroRNAs (miRNAs) serve as key regulators in gene expression and play a crucial role in immune responses, holding a significant promise for diagnosing and managing diseases in farm animals. This review article summarizes current research on the role of miRNAs in various farm animal diseases and mycotoxicosis, highlighting their potential as biomarkers and using them for mitigation strategies. Through an extensive literature review, we focused on the impact of miRNAs in the pathogenesis of several farm animal diseases, including viral and bacterial infections and mycotoxicosis. They regulate gene expression by inducing mRNA deadenylation, decay, or translational inhibition, significantly impacting cellular processes and protein synthesis. The research revealed specific miRNAs associated with the diseases; for instance, gga-miR-M4 is crucial in Marek's disease, and gga-miR-375 tumor-suppressing function in Avian Leukosis. In swine disease such as Porcine Respiratory and Reproductive Syndrome (PRRS) and swine influenza, miRNAs like miR-155 and miR-21-3p emerged as key regulatory factors. Additionally, our review highlighted the interaction between miRNAs and mycotoxins, suggesting miRNAs can be used as a biomarker for mycotoxin exposure. For example, alterations in miRNA expression, such as the dysregulation observed in response to Aflatoxin B1 (AFB1) in chickens, may indicate potential mechanisms for toxin-induced changes in lipid metabolism leading to liver damage. Our findings highlight miRNAs potential for early disease detection and intervention in farm animal disease management, potentially reducing significant economic losses in agriculture. With only a fraction of miRNAs functionally characterized in farm animals, this review underlines more focused research on specific miRNAs altered in distinct diseases, using advanced technologies like CRISPR-Cas9 screening, single-cell sequencing, and integrated multi-omics approaches. Identifying specific miRNA targets offers a novel pathway for early disease detection and the development of mitigation strategies against mycotoxin exposure in farm animals.

Zebrafish as model organisms for toxicological evaluations in the field of food science

Food safety has long been an area of concern. The selection of stable and efficient model organisms is particularly important for food toxicology studies. Zebrafish (Danio rerio) are small model vertebrates, and 70% of human genes have at least one zebrafish ortholog. Zebrafish have advantages as model organisms due to their short life cycle, strong reproductive ability, easy rearing, and low cost. Zebrafish embryos have the advantage of being sensitive to the breeding environment and thus have been used as biosensors. Zebrafish and their embryos have been widely used for food toxicology assessments. This review provides a systematic and comprehensive summary of food toxicology studies using zebrafish as model organisms. First, we briefly introduce the multidimensional mechanisms and structure-activity relationship studies of food toxicological assessment. Second, we categorize these studies according to eight types of hazards in foods, including mycotoxins, pesticides, antibiotics, heavy metals, endocrine disruptors, food additives, nanoparticles, and other food-related ingredients. Finally, we list the applications of zebrafish in food toxicology studies in line with future research prospects, aiming to provide a valuable reference for researchers in the field of food science.

Ochratoxin A induces locomotor impairment and oxidative imbalance in adult zebrafish

Ochratoxin A (OTA) is a mycotoxin produced by species of filamentous fungi widely found as a contaminant in food and with high toxic potential. Studies have shown that this toxin causes kidney and liver damage; however, data on the central nervous system effects of exposure to OTA are still scarce. Thus, this study aimed to investigate the effects of exposure to OTA on behavioral and neurochemical parameters in adult zebrafish. The animals were treated with different doses of OTA (1.38, 2.77, and 5.53 mg/kg) with intraperitoneal injections and submitted to behavioral evaluations in the open tank and social interaction tests. Subsequently, they were euthanized, and the brains were used to assess markers associated with oxidative status. In the open tank test, OTA altered distance traveled, absolute turn angle, mean speed, and freezing time. However, no significant effects were observed in the social interaction test. Moreover, OTA also increased glutathione peroxidase (GPx), glutathione-S-transferase (GST), and glutathione reductase (GR) levels and decreased non-protein thiols (NPSH) levels in the zebrafish brain. This study showed that OTA can affect behavior and neurochemical levels in zebrafish.

Prenatal diagnosis and mRNA profiles of fetal tetralogy of Fallot

Tetralogy of fallot (TOF) in the fetus is a typical congential heart disease that occurs during the early embryonic period, being characterized by the abnormal development of conus arteriosus. The early diagnosis and prevention of fetal TOF is very important and there is a great need for exploring the pathogenesis of it in clinic. In this study, there were three cases being detected with TOF by fetal echocardiogram and confirmed by autopsy. We characterize the difference of expression of lncRNAs and mRNAs through sequencing analysis of 3 pairs of myocardial tissues of fetal TOF and those of age-matched controls. Compared with normal group, there were 94 differentially expressed lncRNAs and 83 mRNA transcripts in TOF (P < 0.05). Correlation analysis between lncRNA and mRNA further showed that differentially expressed lncRNA can be linked to mRNAs, suggesting the potential regulator role of lncRNA in mRNA expression. Our data serve as a fundamental resource for understanding the disease etiology of TOF.

Zebrafish Embryos and Larvae as Alternative Animal Models for Toxicity Testing

Prerequisite to any biological laboratory assay employing living animals is consideration about its necessity, feasibility, ethics and the potential harm caused during an experiment. The imperative of these thoughts has led to the formulation of the 3R-principle, which today is a pivotal scientific standard of animal experimentation worldwide. The rising amount of laboratory investigations utilizing living animals throughout the last decades, either for regulatory concerns or for basic science, demands the development of alternative methods in accordance with 3R to help reduce experiments in mammals. This demand has resulted in investigation of additional vertebrate species displaying favourable biological properties. One prominent species among these is the zebrafish (Danio rerio), as these small laboratory ray-finned fish are well established in science today and feature outstanding biological characteristics. In this review, we highlight the advantages and general prerequisites of zebrafish embryos and larvae before free-feeding stages for toxicological testing, with a particular focus on cardio-, neuro, hepato- and nephrotoxicity. Furthermore, we discuss toxicokinetics, current advances in utilizing zebrafish for organ toxicity testing and highlight how advanced laboratory methods (such as automation, advanced imaging and genetic techniques) can refine future toxicological studies in this species.

The individual and combined effects of ochratoxin A with citrinin and their metabolites (ochratoxin B, ochratoxin C, and dihydrocitrinone) on 2D/3D cell cultures, and zebrafish embryo models

Ochratoxin A and citrinin are nephrotoxic mycotoxins produced by Aspergillus, Penicillium, and/or Monascus species. The combined effects of ochratoxin A and citrinin have been examined in more studies; however, only limited data are available regarding the co-exposure to their metabolites. In this investigation, the individual toxic effects of ochratoxin A, ochratoxin B, ochratoxin C, citrinin, and dihydrocitrinone were tested as well as the combinations of ochratoxin A with the latter mycotoxins were examined on 2D and 3D cell cultures, and on zebrafish embryos. Our results demonstrate that even subtoxic concentrations of certain mycotoxins can increase the toxic impact of ochratoxin A. In addition, typically additive effects or synergism were observed as the combined effects of mycotoxins tested. These observations highlight that different cell lines (e.g. MDBK vs. MDCK), cell cultures (e.g. 2D vs. 3D), and models (e.g. in vitro vs. in vivo) can show different (sometimes opposite) impacts. Mycotoxin combinations considerably increased miR-731 levels in zebrafish embryos, which is an early marker of the toxicity on kidney development. These results underline that the co-exposure to mycotoxins (and/or mycotoxin metabolites) should be seriously considered, since even the barely toxic mycotoxins (or metabolites) in combinations can cause significant toxicity.

Multidimensional analysis of the epigenetic alterations in toxicities induced by mycotoxins

Mycotoxins contaminate all types of food and feed, threatening human and animal health through food chain accumulation, producing various toxic effects. Increasing attention is being focused on the molecular mechanism of mycotoxin-induced toxicity in all kinds of in vivo and in vitro models. Epigenetic alterations, including DNA methylation, non-coding RNAs (ncRNAs), and protein post-translational modifications (PTMs), were identified as being involved in various types of mycotoxin-induced toxicity. In this review, the emphasis was on summarizing the epigenetic alterations induced by mycotoxin, including aflatoxin B1 (AFB1), ochratoxin A (OTA), zearalenone (ZEA), fumonisin B1 (FB1), and deoxynivalenol (DON). This review summarized and analyzed the roles of DNA methylation, ncRNAs, and protein PTMs after mycotoxin exposure based on recently published papers. Moreover, the main research methods and their deficiencies were determined, while some remedial suggestions are proposed. In summary, this review helps to understand better the epigenetic alterations induced by the non-genotoxic effects of mycotoxin.

Ochratoxin A-induced genotoxic and epigenetic mechanisms lead to Alzheimer disease: its modulation with strategies

Ochratoxin A (OTA) is a naturally occurring mycotoxin mostly found in food items including grains and coffee beans. It induces DNA single-strand breaks and has been considered to be carcinogenic. It is recognized as a serious threat to reproductive health both in males and females. OTA is highly nephrotoxic and carcinogenic, and its potency changes evidently between species and sexes. There is a close association between OTA, mutagenicity, carcinogenicity, and genotoxicity, but the underlying mechanisms are not clear. Reports regarding genotoxic effects in relation to OTA which leads to the induction of DNA adduct formation, protein synthesis inhibition, perturbation of cellular energy production, initiation of oxidative stress, induction of apoptosis, influences on mitosis, induction of cell cycle arrest, and interference with cytokine pathways. All these mechanisms are associated with nephrotoxicity, hepatotoxicity, teratotoxicity, immunological toxicity, and neurotoxicity. OTA administration activates various mechanisms such as p38 MAPK, JNKs, and ERKs dysfunctions, BDNF disruption, TH overexpression, caspase-3 and 9 activation, and ERK-1/2 phosphorylation which ultimately lead to Alzheimer disease (AD) progression. The current review will focus on OTA in terms of recent discoveries in the field of molecular biology. The main aim is to investigate the underlying mechanisms of OTA in regard to genotoxicity and epigenetic modulations that lead to AD. Also, we will highlight the strategies for the purpose of attenuating the hazards posed by OTA exposure.

The reproductive toxicity and potential mechanisms of combined exposure to dibutyl phthalate and diisobutyl phthalate in male zebrafish (Danio rerio)

Dibutyl phthalate (DBP) and diisobutyl phthalate (DiBP) are phthalate compounds frequently detected in the environment. Despite increasing awareness of their toxicity in human and animals, the male reproductive toxicity of their combined exposure remains elusive. The purposes of this study were to investigate whether combined exposure to DBP and DiBP could induce male reproductive toxicity, and to explore the potential toxicological mechanisms. Adult male zebrafish were exposed to DBP (11, 113 and 1133 μg L^-1), DiBP (10, 103 and 1038 μg L^-1) and their mixtures (Mix) (11 + 10, 113 + 103, 1133 + 1038 μg L^-1) for 30 days, and their effects on plasma hormone secretion, testis histology and transcriptomics were examined. Highest concentrations of Mix exposure caused greater imbalance ratio of T/E2 and more severe structural damage to testis than single exposure. These effects were consistent with the testis transcriptome analysis for which 4570 genes were differentially expressed in Mix exposure, while 2795 and 1613 genes were differentially expressed in DBP and DiBP, respectively. KEGG pathway analysis showed that both single and combined exposure of DBP and DiBP could affect cytokine-cytokine receptor interaction. The difference was that combined exposure could also affect steroid hormone synthesis, extracellular matrix receptor interaction, retinol metabolism, and PPAR signaling pathways. These results demonstrated that combined exposure to DBP and DiBP could disrupt spermatogenesis and elicit male reproductive toxicity in zebrafish.

Fumonisin B1 Production by Fusarium Species and Mycotoxigenic Effect on Larval Zebrafish

Fumonisin B₁ (FB₁) is a common mycotoxin produced by Fusarium species particularly F. proliferatum and F. verticillioides. The toxin produced can cause adverse effects on humans and animals. The objectives of this study were to detect the production of FB₁ based on the amplification of FUM1 gene, to quantify FB₁ produced by the isolates using Ultra-fast Liquid Chromatography (UFLC) analysis, to examine the embryotoxicity effect of FB₁ and to determine EC₅₀ toward the larvae of zebrafish (Danio rerio). Fifty isolates of Fusarium species were isolated from different hosts throughout Malaysia. Successful amplification of the FUM1 gene showed the presence of this gene (800 bp) in the genome of 48 out of 50 isolates. The highest level of FB₁ produced by F. proliferatum isolate B2433 was 6677.32 ppm meanwhile F. verticillioides isolate J1363 was 954.01 ppm. From the assessment of embryotoxicity test of FB₁ on larvae of zebrafish, five concentrations of FB₁ (0.43 ppm, 0.58 ppm, 0.72 ppm, 0.87 ppm and 1.00 ppm) were tested. Morphological changes of the FB₁ exposed-larvae were observed at 24 to 168 hpf. The mortality rate and abnormality of zebrafish larvae were significantly increased at 144 hpf exposure. Meanwhile, the spontaneous tail coiling showed a significant difference. There were no significant differences in the heartbeat rate. As a conclusion, the presence of FUM1 in every isolate can be detected by FUM1 gene analysis and both of the species produced different concentrations of FB₁. This is the first report of FB₁ produced by Fusarium species gave a significant effect on zebrafish development.

Larval zebrafish as an in vitro model for evaluating toxicological effects of mycotoxins

The presence of mycotoxins in food has created concern. Mycotoxin prevalence in our environment has changed in the last few years maybe due to climatic and other environmental changes. Evidence has emerged from in vitro and in vivo models: some mycotoxins have been found to be potentially carcinogenic, embryogenically harmful, teratogenic, and to generate nephrotoxicity. The risk assessment of exposures to mycotoxins at early life stages became mandatory. In this regard, the effects of toxic compounds on zebrafish have been widely studied, and more recently, mycotoxins have been tested with respect to their effects on developmental and teratogenic effects in this model system, which offers several advantages as it is an inexpensive and an accessible vertebrate model to study developmental toxicity. External post-fertilization and quick maturation make it sensitive to environmental effects and facilitate the detection of endpoints such as morphological deformities, time of hatching, and behavioral responses. Therefore, there is a potential for larval zebrafish to provide new insights into the toxicological effects of mycotoxins. We provide an overview of recent mycotoxin toxicological research in zebrafish embryos and larvae, highlighting its usefulness to toxicology and discuss the strengths and limitations of this model system.

Zebrafish as an integrative vertebrate model to identify miRNA mechanisms regulating toxicity

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Zebrafish are an established vertebrate model for toxicity studies.

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Zebrafish have a fully sequenced genome and the capability to create genetic models.

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Zebrafish have over 80 % homology for genes related to human disease.

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Functions of miRNAs in the zebrafish genome are being characterized.

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Zebrafish are ideal for mechanistic studies on how miRNAs regulate toxicity.

Zebrafish (Danio rerio) are an integrative vertebrate model ideal for toxicity studies. The zebrafish genome is sequenced with detailed characterization of all life stages. With their genetic similarity to humans, zebrafish models are established to study biological processes including development and disease mechanisms for translation to human health. The zebrafish genome, similar to other eukaryotic organisms, contains microRNAs (miRNAs) which function along with other epigenetic mechanisms to regulate gene expression. Studies have now established that exposure to toxins and xenobiotics can change miRNA expression profiles resulting in various physiological and behavioral alterations. In this review, we cover the intersection of miRNA alterations from toxin or xenobiotic exposure with a focus on studies using the zebrafish model system to identify miRNA mechanisms regulating toxicity. Studies to date have addressed exposures to toxins, particulate matter and nanoparticles, various environmental contaminants including pesticides, ethanol, and pharmaceuticals. Current limitations of the completed studies and future directions for this research area are discussed.

Ochratoxin A triggered intracerebral hemorrhage in embryonic zebrafish: Involvement of microRNA-731 and prolactin receptor

Ochratoxin A (OTA), a mycotoxin widely found in foodstuffs, reportedly damages multiple brain regions in developing rodents, but the corresponding mechanisms have not been elucidated. In this study, zebrafish embryos at 6 h post fertilization (hpf) were exposed to various concentrations of OTA and the phenomenon associated with intracerebral hemorrhage was observed at 72 hpf. Exposure of embryos to OTA significantly increased their hemorrhagic rate in a dose-dependent manner. Large numbers of extravagated erythrocytes were observed in the midbrain/hindbrain areas of Tg(fli-1a:EGFP; gata1:DsRed) embryos following exposure to OTA. OTA also disrupted the vascular patterning, especially the arch-shaped central arteries (CtAs), in treated embryos. Histological analysis revealed a cavity-like pattern in their hindbrain ventricles, implying the possibility of cerebral edema. OTA-induced intracerebral hemorrhage and CtA vessel defects were partially reversed by the presence of miR-731 antagomir or the overexpression of prolactin receptor a (prlra); prlra is a downstream target of miR-731. These results suggest that exposure to OTA has a negative effect on cerebral vasculature development by interfering with the miR-731/PRLR axis in zebrafish.

Involvement of the miR-462/731 cluster in hypoxia response in Megalobrama amblycephala

MicroRNAs (miRNAs) are non-coding small RNAs showing both evolutionarily conserved and unique features and are involved in nearly all biological processes. In the present study, the role played by miR-462/731 cluster miRNAs in hypoxia response in Megalobrama amblycephala, an important freshwater fish, was investigated. The M. amblycephala miR-462/731 cluster locus and their 5' flanking sequences were sequenced and analyzed. In M. amblycephala and other teleost fish species, the mature sequences of miR-462 and miR-731 were identical and hypoxia-responsive elements (HREs) were identified upstream of the miR-462/731 loci. The two miRNAs were significantly induced in the liver, spleen, gill, muscle, and brain after hypoxia treatment. The expression of both miRNAs was also upregulated in cells that received treatment which mimicked hypoxia. Furthermore, reporter assay revealed that M. amblycephala HREs can be activated by hypoxia. Taken together, the 462/731 cluster may play a role in the regulation of the hypoxia response in M. amblycephala.

Mycotoxins as human carcinogens-the IARC Monographs classification

Humans are constantly exposed to mycotoxins (e.g. aflatoxins, ochratoxins), mainly via food intake of plant and animal origin. The health risks stemming from mycotoxins may result from their toxicity, in particular their carcinogenicity. In order to prevent these risks, the International Agency for Research on Cancer (IARC) in Lyon (France)-through its IARC Monographs programme-has performed the carcinogenic hazard assessment of some mycotoxins in humans, on the basis of epidemiological data, studies of cancer in experimental animals and mechanistic studies. The present article summarizes the carcinogenic hazard assessments of those mycotoxins, especially aflatoxins (aflatoxin B1, B2, G1, G2 and M1), fumonisins (fumonisin B1 and B2) and ochratoxin A (OTA). New information regarding the genotoxicity of OTA (formation of OTA-DNA adducts), the role of OTA in oxidative stress and the identification of epigenetic factors involved in OTA carcinogenesis-should they indeed provide strong evidence that OTA carcinogenicity is mediated by a mechanism that also operates in humans-could lead to the reclassification of OTA.