Oxidative DNA damage and multi-organ pathologies in male mice subchronically treated with aflatoxin B1

Aflatoxin B1 exposure induces Alzheimer's disease like pathology by disrupting redox homeostasis and activating ferroptotic signals in C57BL/6 J mice

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins with neurotoxicity. Human exposure to AFB1 via contaminated foodstuffs has been linked to the risk of cognitive impairment, which may contribute to the progression of Alzheimer's disease (AD). However, the mechanism underlying the pathogenesis of AD in relation to AFB1 exposure is not clear. Herein, C57BL/6 J mice were exposed to 1.5 mg/L AFB1 in drinking water for 8 weeks. It was found that AFB1 damaged blood-brain barrier function, accumulated in the brain, and led to cognitive impairments and AD-like pathology in the hippocampus. Impaired cognitive function was indicated by the significant alterations in Morris' water maze and Y-maze tests at 8 weeks after AFB1 exposure. Concurrently, AD-like pathology was evinced by a marked neuronal loss and the up-regulated AD related gene and protein expressions in the hippocampus. AFB1 exposure remarkably disrupted redox homeostasis and induced ferroptosis both in the hippocampus at 8 weeks after AFB1 exposure and in cultured hippocampal neuron in vitro as indicated by the suppressions on SOD and CAT activities, the down-regulation of Slc7a11/Gpx4 expressions, the decline in GSH content, the increase in MDA and the lipid peroxidation. AFB1 exposure also increased Fe2+ content significantly at 8 weeks after exposure. In addition, we demonstrated that ferroptosis inhibition by Fer-1 obviously alleviated AFB1 neurotoxicity in HT22 cells. These results revealed an unknown pivotal role of ferroptosis in AFB1 neurotoxicity in relation to AD pathogenesis and emphasized the importance to reduce the health risk of AFB1 exposure as an etiology of AD in humans.

Aflatoxin Exposure-Caused Male Reproductive Toxicity: Molecular Mechanisms, Detoxification, and Future Directions

Widespread endocrine disorders and infertility caused by environmental and food pollutants have drawn considerable global attention. Aflatoxins (AFTs), a prominent class of mycotoxins, are recognized as one of the key contributors to environmental and food contamination. Aflatoxin B1 (AFB1) is the most potent and toxic pollutant among them and is known to cause multiple toxic effects, including neuro-, nephro-, hepato-, immune-, and genotoxicity. Recently, concerns have been raised regarding AFB1-induced infertility in both animals and humans. Exposure to AFB1 can disrupt the structure and functionality of reproductive organs, leading to gametogenesis impairment in males, subsequently reducing fertility. The potential molecular mechanisms have been demonstrated to involve oxidative stress, cell cycle arrest, apoptosis, inflammatory responses, and autophagy. Furthermore, several signaling pathways, including nuclear factor erythroid 2-related factor 2; NOD-, LRR-, and pyrin domain-containing protein 3; nuclear factor kappa-B; p53; p21; phosphoinositide 3-kinase/protein kinase B; the mammalian target of rapamycin; adenosine 5'-monophosphate-activated protein kinase; and mitochondrial apoptotic pathways, are implicated in these processes. Various interventions, including the use of small molecules, Chinese herbal extracts, probiotic supplementation, and camel milk, have shown efficacy in ameliorating AFB1-induced male reproductive toxicity, by targeting these signaling pathways. This review provides a comprehensive summary of the harmful impacts of AFB1 exposure on male reproductive organs in mammals, highlighting the potential molecular mechanisms and protective agents.

The relationship between aflatoxin B1 with the induction of extrinsic/intrinsic pathways of apoptosis and the protective role of taraxasterol in TM3 leydig cell line

Aflatoxins B1 (AFB1) a dangerous type of aflatoxin, poses a serious threat to human health. Meanwhile, Taraxasterol, a bioactive compound in dandelion, exhibits strong anti-inflammatory and antioxidant activity. Therefore, the aim of this study was to investigate the impact of AFB1 on the intrinsic and extrinsic pathways of apoptosis, as well as evaluate the protective role of taraxasterol in the TM3 Leydig cell line. Cell viability was evaluated using an MTT assay, measuring the effects of 3.6 µM AFB1 and varying concentrations of taraxasterol. Expression levels of Caspase 3,8, and 9 were analyzed with RT-qPCR, and flow cytometry was used to assess cell cycle progression and apoptotic alterations. The findings of this study demonstrated that exposure to 3.6 µM of AFB1 resulted in an upregulation of Caspase 3 and Caspase 9 expression, indicating an activation of apoptotic pathways in TM3 cells. Additionally, the analysis of apoptosis revealed a significant increase in cellular apoptosis at this AFB1 concentration. However, when TM3 cells were exposed to 5 µM of taraxasterol, a downregulation of Caspase 3 and Caspase 9 expression was observed, suggesting a protective effect against apoptosis. Moreover, the apoptotic rate in TM3 cells was reduced in the presence of 5 µM of taraxasterol. Consequently, this study highlights the potential of taraxasterol as a protective agent against AFB1-induced apoptosis and suggest its potential application in regulating cell survival and apoptosis-related processes. Further investigations are necessary to elucidate the underlying mechanisms and evaluate the clinical implications of taraxasterol in the context of fertility disorders and other conditions associated with AFB1 exposure.

Transgenerational toxicity induced by maternal AFB1 exposure in Caenorhabditis elegans associated with underlying epigenetic regulations

Aflatoxin B1 (AFB1), usually seriously contaminates in grain and oil foods or feed, displayed significant acute and chronic toxic effects in human and animal populations. However, little is known about the transgenerational toxic effects induced by a maternal AFB1 intake at a lower dose on offspring. In our study, only parental wild-type Caenorhabditis elegans was exposed to AFB1 (0-8 μg/ml) and the following three filial generations were grown on AFB1-free NGM. Results showed that the toxic effects of AFB1 on the growth (body length) and reproduction (brood size, generation time and morphology of gonad arm) can be transmitted through generations. Moreover, the levels of MMP and ATP were irreversibly inhibited in the filial generations. By using RNomics and molecular biology techniques, we found that steroid biosynthesis, phagosome, valine/leucine/isoleucine biosynthesis and oxidative phosphorylation (p < 0.05) were the core signaling pathways to exert the transgenerational toxic effects on nematodes. Also, notably increased histone methylation level at H3K36me3 was observed in the first generation. Taken together, our study demonstrated that AFB1 has notable transgenerational toxic effects, which were resulted from the complex regulatory network of various miRNAs, mRNAs and epigenetic modification in C. elegans.

Effects of aflatoxin B1 exposure on sperm in rodents: a systematic review and meta-analysis

Exposure to aflatoxin B1 can be associated with reproductive toxicity, accompanied by decreased sperm concentration in animal models. The aim of this meta-analysis was to determine the correlation between aflatoxin B1 exposure and sperm concentrations of male rodents (both mice and rats). According to inclusion and exclusion criteria, 8 articles were selected to assess in the current meta-analysis. The random effects and pooled analysis indicated that sperm concentration was decreased in mice [MD sperm = -20.79×106/sperm/g testis (95%CI =-1.3 to -50.5)] and in rats [-24.34×106/sperm/g testis (95%CI: -7.60 to -44.35)] after exposure to aflatoxin B1 compared with control groups. A significant heterogeneity was found among studies (for mice I2=99.7%, %, P<0.000 and rats =I2=98.8, P<0.000). The findings of present meta-analysis showed the association between aflatoxin B1 exposure and a decrease in sperm concentration in rodents.

Effects of antimony exposure on DNA damage and genome-wide variation in zebrafish (Danio rerio) liver

Antimony (Sb) is a potentially toxic and carcinogenic cumulative contaminant that poses a serious threat to aquatic ecosystems. To better clarify the genotoxicity of Sb and its mechanism of action. In this study, we investigated DNA damage and genome-wide variation in the liver of a model organism, zebrafish (Danio rerio), under subacute Sb exposure and explored its potential toxicological mechanisms. The results showed that medium and high concentrations of Sb significantly reduced the total antioxidant capacity and increased the content of reactive oxygen species in zebrafish liver, and further studies revealed that it increased oxidative DNA damage and DNA-DNA cross-link (DDC), but had little effect on DNA-protein cross-link (DPC). The result of resequencing showed that the mutation sites of the genes with high concentrations of Sb were higher than those with medium concentrations, and the mutation was mainly a single nucleotide. The pathways significantly enriched for nonsynonymous single nucleotide polymorphisms (SNPs) and insertion/deletion mutations (InDels) variant genes in the coding regions of both the medium and high Sb-treated groups were ECM-receptor interactions, and the high Sb-treated group also included lysine degradation, hematopoietic cell lineage, and cytokine-cytokine receptor interactions. This suggests that ECM-receptor interactions play an important role in the mechanism of antimony toxicity to the liver of zebrafish.

Polydatin reduces aflatoxin-B1 induced oxidative stress, DNA damage, and inflammatory cytokine levels in mice

This study showed the protective effect of polydatin (PD), which has an antioxidant activity against oxidative stress in mice caused by aflatoxin B1 (AFB1). In this study, 36 male Swiss albino mice were divided equally into 6 groups: 0.2 mL of FTS was administered to the control group, 0.2 mL of olive oil to the second group, and 0.75 mg/kg AFB1 to the third group by intragastric gavage every day for 28 days. The fourth, fifth, and sixth groups were administered 50, 100, and 200 mg/kg PD and 0.75 mg/kg AFB1 intragastrically for 28 days, respectively. AFB1 administration increased plasma aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, blood urea nitrogen, creatinine, and malondialdehyde levels in blood and tissue samples but decreased the level of glutathione and the activities of superoxide dismutase and catalase. On the other hand, it was determined that PD applications depending on the increasing doses brought these levels closer to normal. In addition, AFB1 administration increased the amount of ssDNA and liver COX-2, TNF-α, IL-6, NFκB, and Cyp3a11 mRNA expression levels; on the other hand, it decreased the IL-2 mRNA expression level. In contrast, increasing doses of PD application regulated the amount of ssDNA and these mRNA expression levels. Additionally, histopathological damage was observed in the liver and kidney tissues of the AFB1 group, while PD applications in a dose-dependent manner improved these damages. As a result, it was determined that PD reduced AFB1-induced oxidative stress, DNA damage, and inflammation and exhibited a protective effect on tissues in mice.

Variation of Aflatoxin Levels in Stored Edible Seed and Oil Samples and Risk Assessment in the Local Population

Five hundred and twenty samples of edible seeds and oilseeds (sunflower, palm, peanut, sesame, cotton, and grapeseed) were purchased from markets, farmers, and superstores in the central cities of Punjab, Pakistan. A total of 125 (48.1%) edible seed samples from a 6 ≤ months storage period, and 127 (48.8%) from a 2 ≥ years storage period were found to be infested with AFs. The average elevated amount of AFB1 and total AFs was observed in a 2 ≥ years storage period, i.e., 28.6 ± 4.5 and 51.3 ± 10.4 µg/kg, respectively, in sesame seeds. The minimum amount of AFB1 and total AFs was observed in palm seed samples with a storage period of 6 ≤ months, i.e., 9.96 ± 2.4, and 11.7 ± 1.90 µg/kg, respectively. The maximum amount of AFB1 and total AFs were observed in peanut oil samples, i.e., 21.43 ± 2.60 and 25.96 ± 4.30 µg/kg, respectively, with a storage period of 2 ≥ years. Therefore, the maximum dietary intake of 59.60 ng/kg/day was observed in oil samples stored at a ≥ 2 years storage period. The results of the present study concluded that a significant difference was found in the amounts of total AFs in edible seed samples stored at 6 ≤ months and 2 ≥ years storage periods (p < 0.05).

Apigeninidin-enriched Sorghum bicolor (L. Moench) extracts alleviate Aflatoxin B1-induced dysregulation of male rat hypothalamic-reproductive axis

We examined the protective effect of the apigeninidin (API)-enriched fraction from Sorghum bicolor sheaths extracts (SBE-05, SBE-06, and SBE-07) against aflatoxin B₁ (AFB₁)-induced dysregulation of male rat's reproductive system that may trigger infertility. Male rats (160 ± 12 g) were treated with AFB₁ (50 µg/kg) along with 5 or 10 mg/kg of SBE-05, SBE-06, and SBE-07 for 28 days. Subsequently, we assessed the reproductive hormone-prolactin, FSH, LH, testosterone levels, and testicular function enzymes. Moreover, we examined rats' testes, epididymis, and hypothalamus for oxidative and inflammatory stress biomarkers, caspase-9 activity and tissues pathology. We observed that comparative to AFB₁ alone treated rats, API co-treatment significantly (p < 0.05) abated the AFB₁-mediated decrease in prolactin and antioxidant defenses and lessened lipid peroxidation (LPO) and reactive oxygen and nitrogen species levels in the examined organs-testes, epididymis, and hypothalamus. API abated AFB₁-induced hormone decreases-testosterone, FSH, and LH; and caused improvement in sperm quantity and quality. API lessened AFB₁-mediated increase in pro-inflammatory cytokine, increased interleukin-10 level, an anti-inflammatory cytokine and reduced caspase-9 activities. In addition, API reduced alterations in the examined tissue histology. Our findings suggest that S. bicolor API-enrich extracts have active antioxidative, antiapoptotic, and anti-inflammatory activities, which can protect against AFB₁-induced dysfunction of the hypothalamic-pituitary-gonadal axis.

The metabolism and biotransformation of AFB1: Key enzymes and pathways

Aflatoxins B₁ (AFB₁) is a hepatoxic compound produced by Aspergillus flavus and Aspergillus parasiticus, seriously threatening food safety and the health of humans and animals. Understanding the metabolism of AFB₁ is important for developing detoxification and intervention strategies. In this review, we summarize the AFB₁ metabolic fates in humans and animals and the key enzymes that metabolize AFB₁, including cytochrome P450s (CYP450s) for AFB₁ bioactivation, glutathione-S-transferases (GSTs) and aflatoxin-aldehyde reductases (AFARs) in detoxification. Furthermore, AFB₁ metabolism in microbes is also summarized. Microorganisms specifically and efficiently transform AFB₁ into less or non-toxic products in an environmental-friendly approach which could be the most desirable detoxification strategy in the future. This review provides a wholistic insight into the metabolism and biotransformation of AFB₁ in various organisms, which also benefits the development of protective strategies in humans and animals.

Aflatoxins: History, Significant Milestones, Recent Data on Their Toxicity and Ways to Mitigation

In the early 1960s the discovery of aflatoxins began when a total of 100,000 turkey poults died by hitherto unknown turkey "X" disease in England. The disease was associated with Brazilian groundnut meal affected by Aspergillus flavus. The toxin was named Aspergillus flavus toxin-aflatoxin. From the point of view of agriculture, aflatoxins show the utmost importance. Until now, a total of 20 aflatoxins have been described, with B1, B2, G1, and G2 aflatoxins being the most significant. Contamination by aflatoxins is a global health problem. Aflatoxins pose acutely toxic, teratogenic, immunosuppressive, carcinogenic, and teratogenic effects. Besides food insecurity and human health, aflatoxins affect humanity at different levels, such as social, economical, and political. Great emphasis is placed on aflatoxin mitigation using biocontrol methods. Thus, this review is focused on aflatoxins in terms of historical development, the principal milestones of aflatoxin research, and recent data on their toxicity and different ways of mitigation.

AFB1-induced mice liver injury involves mitochondrial dysfunction mediated by mitochondrial biogenesis inhibition

Aflatoxin B1 (AFB1) pollutes foodstuffs and feeds, causing a food safety problem and seriously endangering human and animal health. Liver is the principal organ for AFB1 accumulation and biotransformation, during which AFB1 can cause acute and chronic liver damage, however, the specific mechanism is not completely clear. Mitochondria are the primary organelle of cellular bio-oxidation, providing 95% energy for liver to execute its multiple functions. Therefore, we speculated that mitochondrial dysfunction is involved in AFB1-induced liver injury. To verify the hypothesis, a total of eighty healthy male mice were randomly divided into four groups on average, and exposed with 0, 0.375, 0.75 and 1.5 mg/kg body weight AFB1 by intragastric administration for 30 d. The results displayed that AFB1 triggered liver injury accompanied by oxidative stress. AFB1 exposure also damaged mitochondria structure, decreased mitochondrial membrane potential (MMP), as well as increased cytoplasmic cytochrome c (Cyt-c) protein expression, Bax, p53, Caspase-3/9 protein and/or mRNA expression levels and terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine-5'-triphosphate (dUTP) nick end labeling (TUNEL) staining positive cells in mice liver. Meanwhile, AFB1 exposure elevated pyruvate content, inhibited tricarboxylic acid (TCA) cycle rate-limiting enzymes and electron transport chain (ETC) complexes I-V activities, disturbed ETC complexes I-V subunits mRNA expression levels and reduced adenosine triphosphate (ATP) level in mice liver. These results indicated that AFB1 destroyed mitochondrial structure, activated mitochondrion-dependent apoptosis and induced mitochondrial dysfunction. In addition, AFB1 disrupted mitochondrial biogenesis, presented as the abnormalities of protein and/or gene expression levels of voltage dependent anion channel protein 1 (VDAC1), peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), nuclear respiratory factor 1 (Nrf1) and mitochondrial transcription factor A (Tfam). This may contribute to hepatic and mitochondrial lesions induced by AFB1. These results provide a new perspective for elucidating the mechanisms of AFB1 hepatotoxicity.

Insights into Aflatoxin B1 Toxicity in Cattle: An In Vitro Whole-Transcriptomic Approach

Aflatoxins, and particularly aflatoxin B1 (AFB1), are toxic mycotoxins to humans and farm animal species, resulting in acute and chronic toxicities. At present, AFB1 is still considered a global concern with negative impacts on health, the economy, and social life. In farm animals, exposure to AFB1-contaminated feed may cause several untoward effects, liver damage being one of the most devastating ones. In the present study, we assessed in vitro the transcriptional changes caused by AFB1 in a bovine fetal hepatocyte-derived cell line (BFH12). To boost the cellular response to AFB1, cells were pre-treated with the co-planar PCB 3,3′,4,4′,5-pentachlorobiphenyl (PCB126), a known aryl hydrocarbon receptor agonist. Three experimental groups were considered: cells exposed to the vehicle only, to PCB126, and to PCB126 and AFB1. A total of nine RNA-seq libraries (three replicates/group) were constructed and sequenced. The differential expression analysis showed that PCB126 induced only small transcriptional changes. On the contrary, AFB1 deeply affected the cell transcriptome, the majority of significant genes being associated with cancer, cellular damage and apoptosis, inflammation, bioactivation, and detoxification pathways. Investigating mRNA perturbations induced by AFB1 in cattle BFH12 cells will help us to better understand AFB1 toxicodynamics in this susceptible and economically important food-producing species.

Aflatoxins as a risk factor for liver cirrhosis: a systematic review and meta-analysis

Background

Liver cirrhosis is characterized by fibrosis and nodule formation in the liver, due to a chronic injury, and subsequent alteration of the normal architecture of the liver. Even though there is a huge effort to elucidate the possible etiologic factors of liver cirrhosis, a significant number of cases are cryptogenic, especially in Sub Saharan Africa, where there is a high burden of aflatoxin exposure. Aflatoxins are known to cause hepatocellular carcinoma, which share similar etiologic factors with liver cirrhosis. This study aimed to assess the association between aflatoxin exposure and the risk of liver cirrhosis.

Methods

Relevant studies were identified through systematic searches conducted in Ovid MEDLINE, PubMed and Google Scholar. Also, by searching the references of retrieved articles. The abstracts and full text were screened for eligibility and the risk of bias was assessed for each study using Joanna Briggs Institute (JBI) critical appraisal checklist for observational studies. The extracted data from included studies using Microsoft Excel were exported to Stata software version 15.0 for analyses. The overall pooled estimation of outcomes was calculated using a random-effects model of DerSimonian–Laird method at a 95% confidence level. The heterogeneity of studies was determined using I2 statistics. The presence of publication bias between studies was evaluated using the Begg’s and Egger’s tests and funnel plot. The protocol of this systematic review and meta-analysis was registered in the Prospero database with reference number ID: CRD42019148481.

Results

A total of 5 studies published between the years 2005 and 2018 that met the pre-defined inclusion and exclusion criteria were included. The meta-analysis showed that a significant increase in the risk of liver cirrhosis is associated with aflatoxin exposure (unadjusted pooled odds ratio (OR) = 3.35, 95% CI: 2.74–4.10, p = 0.000; I² = 88.3%, p = 0.000; adjusted OR = 2.5, 95% CI: 1.84–3.39, p = 0.000; I² = 0%, p = 0.429).

Conclusions

The present meta-analysis suggests that aflatoxin exposure is associated with a higher risk of liver cirrhosis.