Proapoptotic activity of aflatoxin B1 and sterigmatocystin in HepG2 cells

Investigating the individual and mixture cytotoxicity of co-occurring aflatoxin B1, enniatin B, and sterigmatocystin on gastric, intestinal, hepatic, and renal cellular models

This study investigates the individual and combined effects of the mycotoxins, Aflatoxin B1 (AFB1), Enniatin B (ENNB) and Sterigmatocystin (STG), on the cellular viability of gastric (NCI-N87), intestinal (Caco-2), hepatic (Hep-G2) and renal (Hek-293) cells, shedding light on synergistic or antagonistic effects using a constant ratio combination design proposed by Chou-Talalay. These toxins are prevalent in cereal-based foods, frequently consumed by children which raises concerns about their exposure to these mycotoxins. This population is particularly vulnerable to the effects of these toxins due to their underdeveloped organs and incompletely structured physiological processes. Results showed that ENB was the most toxic of the three mycotoxins across all cell lines, while STG and AFB1 showed lower toxicity. The combination of ENNB + STG was found to be the most potent in terms of binary mixtures. In regard to ternary combinations, Caco-2 cells are more sensitive to the tested mycotoxins, whereas NCI-N87 cells show lower levels of cell damage. Worrying dose reduction values (>10-fold) were found for ENNB in binary and ternary combinations at low exposure levels. These findings are significant for establishing initial reference values, which play a pivotal role in estimating reference doses that are subsequently incorporated into the broader risk assessment process.

The Biosynthesis, Structure Diversity and Bioactivity of Sterigmatocystins and Aflatoxins: A Review

Sterigmatocystins and aflatoxins are a group of mycotoxins mainly isolated from fungi of the genera Aspergillus. Since the discovery of sterigmatocystins in 1954 and aflatoxins in 1961, many scholars have conducted a series of studies on their structural identification, synthesis and biological activities. Studies have shown that sterigmatocystins and aflatoxins have a wide range of biological activities such as antitumour, antibacterial, anti-inflammatory, antiplasmodial, etc. The sterigmatocystins and aflatoxins had been shown to be hepatotoxic and nephrotoxic in animals. This review attempts to give a comprehensive summary of progress on the chemical structural features, synthesis, and bioactivity of sterigmatocystins and aflatoxins reported from 1954 to April 2024. A total of 72 sterigmatocystins and 20 aflatoxins are presented in this review. This paper reviews the chemical diversity and potential activity and toxicity of sterigmatocystins and aflatoxins, enhances the understanding of sterigmatocystins and aflatoxins that adversely affect humans and animals, and provides ideas for their prevention, research and development.

Toxicodynamic of combined mycotoxins: MicroRNAs and acute-phase proteins as diagnostic biomarkers

Mycotoxins, ubiquitous contaminants in food, present a global threat to human health and well-being. Mitigation efforts, such as the implementation of sound agricultural practices, thorough food processing, and the advancement of mycotoxin control technologies, have been instrumental in reducing mycotoxin exposure and associated toxicity. To comprehensively assess mycotoxins and their toxicodynamic implications, the deployment of effective and predictive strategies is imperative. Understanding the manner of action, transformation, and cumulative toxic effects of mycotoxins, moreover, their interactions with food matrices can be gleaned through gene expression and transcriptome analyses at cellular and molecular levels. MicroRNAs (miRNAs) govern the expression of target genes and enzymes that play pivotal roles in physiological, pathological, and toxicological responses, whereas acute phase proteins (APPs) exert regulatory control over the metabolism of therapeutic agents, both endogenously and posttranscriptionally. Consequently, this review aims to consolidate current knowledge concerning the regulatory role of miRNAs in the initiation of toxicological pathways by mycotoxins and explores the potential of APPs as biomarkers following mycotoxin exposure. The findings of this research highlight the potential utility of miRNAs and APPs as indicators for the detection and management of mycotoxins in food through biological processes. These markers offer promising avenues for enhancing the safety and quality of food products.

Allium sativum L. var. Voghiera Reduces Aflatoxin B1 Bioaccessibility and Cytotoxicity In Vitro

The present work focuses on the evaluation of AFB1's bioaccessibility and cytotoxicity in vitro using bread (naturally contaminated) enriched or not enriched with fresh Voghiera garlic (2%). Two different experiments were carried out: experiment 1 (E1), with low-AFB1-concentration breads (1.6-1.7 mg/kg); and experiment 2 (E2), with high-AFB1-concentration breads (96.4-102.7 mg/kg). Eight breads were prepared, four for E1 (experiment 1) and another four for E2 (experiment 2), with each experiment having a control group (C), a garlic-enriched group (2%) (G), an AFB1 group (A), and an AFB1 + garlic group (A + G). Simulated digestion was performed on each type of bread, and gastric and intestinal digests were obtained. AFB1 content in flours, baked bread, and gastric and intestinal digests was measured by High-Performance Liquid Chromatography coupled to Fluorescence Detection. The results demonstrate dose-dependent AFB1 bioaccessibility and that the presence of garlic contributed to its reduction in both doses (7-8%). Moreover, garlic's presence in AFB1-contaminated bread increased cell viability (9-18%) in differentiated Caco-2 cells and mitigated the arrest of S and G2/M phases provoked by AFB1 on Jurkat T cells and reduced apoptosis/necrosis, cellular reactive oxygen species (ROS), and mitochondrial ROS by 16%, 71%, and 24% respectively. The inclusion of garlic as a functional ingredient helped relieve the presence and effects of AFB1.

Abdallah M, Chen X, Rajkovic A. Current Knowledge of Individual and Combined Toxicities of Aflatoxin B1 and Fumonisin B1 In Vitro

Mycotoxins are considered the most threating natural contaminants in food. Among these mycotoxins, aflatoxin B1 (AFB1) and fumonisin B1 (FB1) are the most prominent fungal metabolites that represent high food safety risks, due to their widespread co-occurrence in several food commodities, and their profound toxic effects on humans. Considering the ethical and more humane animal research, the 3Rs (replacement, reduction, and refinement) principle has been promoted in the last few years. Therefore, this review aims to summarize the research studies conducted up to date on the toxicological effects that AFB1 and FB1 can induce on human health, through the examination of a selected number of in vitro studies. Although the impact of both toxins, as well as their combination, were investigated in different cell lines, the majority of the work was carried out in hepatic cell lines, especially HepG2, owing to the contaminants' liver toxicity. In all the reviewed studies, AFB1 and FB1 could invoke, after short-term exposure, cell apoptosis, by inducing several pathways (oxidative stress, the mitochondrial pathway, ER stress, the Fas/FasL signaling pathway, and the TNF-α signal pathway). Among these pathways, mitochondria are the primary target of both toxins. The interaction of AFB1 and FB1, whether additive, synergistic, or antagonistic, depends to great extent on FB1/AFB1 ratio. However, it is generally manifested synergistically, via the induction of oxidative stress and mitochondria dysfunction, through the expression of the Bcl-2 family and p53 proteins. Therefore, AFB1 and FB1 mixture may enhance more in vitro toxic effects, and carry a higher significant risk factor, than the individual presence of each toxin.

In Vivo Genotoxicity and Toxicity Assessment of Sterigmatocystin Individually and in Mixture with Aflatoxin B1

Mycotoxins are natural food and feed contaminants produced by several molds. The primary mode of exposure in humans and animals is through mixtures. Aflatoxin B1 (AFB1) and sterigmatocystin (STER) are structurally related mycotoxins that share the same biosynthetic route. Few in vivo genotoxicity assays have been performed with STER. In the present genotoxicity study, Wistar rats were dosed orally with STER (20 mg/kg b.w.), AFB1 (0.25 mg/kg b.w.) or a mixture of both in an integrated micronucleus (bone marrow) and comet study (liver and kidney). STER was dosed at the highest feasible dose in corn oil. No increase in the percentage of micronuclei in bone marrow was observed at any condition. Slight DNA damage was detected in the livers of animals treated with AFB1 or the mixture (DNA strand breaks and Fpg (Formamidopyrimidine DNA glycosylase)-sensitive sites, respectively). Plasma, liver, and kidney samples were analyzed with LC-MS/MS demonstrating exposure to both mycotoxins. General toxicity parameters (organs absolute weight, biochemistry, and histopathology) were not altered either individually or in the mixture. The overall absence of individual genotoxicity did not allow us to set any type of interaction in the mixture. However, a possible toxicokinetic interaction was observed.

Aflatoxin B1 Exacerbates Genomic Instability and Apoptosis in the BTBR Autism Mouse Model via Dysregulating DNA Repair Pathway

The pathophysiology of autism is influenced by a combination of environmental and genetic factors. Furthermore, individuals with autism appear to be at a higher risk of developing cancer. However, this is not fully understood. Aflatoxin B1 (AFB1) is a potent food pollutant carcinogen. The effects of AFB1 on genomic instability in autism have not yet been investigated. Hence, we have aimed to investigate whether repeated exposure to AFB1 causes alterations in genomic stability, a hallmark of cancer and apoptosis in the BTBR autism mouse model. The data revealed increased micronuclei generation, oxidative DNA strand breaks, and apoptosis in BTBR animals exposed to AFB1 when compared to unexposed animals. Lipid peroxidation in BTBR mice increased with a reduction in glutathione following AFB1 exposure, demonstrating an exacerbated redox imbalance. Furthermore, the expressions of some of DNA damage/repair- and apoptosis-related genes were also significantly dysregulated. Increases in the redox disturbance and dysregulation in the DNA damage/repair pathway are thus important determinants of susceptibility to AFB1-exacerbated genomic instability and apoptosis in BTBR mice. This investigation shows that AFB1-related genomic instability can accelerate the risk of cancer development. Moreover, approaches that ameliorate the redox balance and DNA damage/repair dysregulation may mitigate AFB1-caused genomic instability.

Integrated Profiles of Transcriptome and mRNA m6A Modification Reveal the Intestinal Cytotoxicity of Aflatoxin B1 on HCT116 Cells

Aflatoxin B1 (AFB1) is widely prevalent in foods and animal feeds and is one of the most toxic and carcinogenic aflatoxin subtypes. Existing studies have proved that the intestine is targeted by AFB1, and adverse organic effects have been observed. This study aimed to investigate the relationship between AFB1-induced intestinal toxicity and N6-methyladenosine (m6A) RNA methylation, which involves the post-transcriptional regulation of mRNA expression. The transcriptome-wide m6A methylome and transcriptome profiles in human intestinal cells treated with AFB1 are presented. Methylated RNA immunoprecipitation sequencing and mRNA sequencing were carried out to determine the distinctions in m6A methylation and different genes expressed in AFB1-induced intestinal toxicity. The results showed that there were 2289 overlapping genes of the differentially expressed mRNAs and differentially m6A-methylation-modified mRNAs. After enrichment of the signaling pathways and biological processes, these genes participated in the terms of the cell cycle, endoplasmic reticulum, tight junction, and mitophagy. In conclusion, the study demonstrated that AFB1-induced HCT116 injury was related to the disruptions to the levels of m6A methylation modifications of target genes and the abnormal expression of m6A regulators.

Bioenergetic Status of the Intestinal and Hepatic Cells after Short Term Exposure to Fumonisin B1 and Aflatoxin B1

Fumonisin B1 (FB1) and aflatoxin B1 (AFB1) are frequent contaminants of staple foods such as maize. Oral exposure to these toxins poses health hazards by disrupting cellular signaling. However, little is known regarding the multifaced mitochondrial dysfunction-linked toxicity of FB1 and AFB1. Here, we show that after exposure to FB1 and AFB1, mitochondrial respiration significantly decreased by measuring the oxygen consumption rate (OCR), mitochondrial membrane potential (MMP) and reactive oxygen species (ROS). The current work shows that the integrity of mitochondria (MMP and ROS), that is the central component of cell apoptosis, is disrupted by FB1 and AFB1 in undifferentiated Caco-2 and HepG2 cells as in vitro models for human intestine and liver, respectively. It hypothesizes that FB1 and AFB1 could disrupt the mitochondrial electron transport chain (ETC) to induce mitochondrial dysfunction and break the balance of transferring H⁺ between the mitochondrial inner membrane and mitochondrial matrix, however, the proton leak is not increasing and, as a result, ATP synthesis is blocked. At the sub-toxic exposure of 1.0 µg/mL for 24 h, i.e., a viability of 95% in Caco-2 and HepG2 cells, the mitochondrial respiration was, however, stimulated. This suggests that the treated cells could reserve energy for mitochondrial respiration with the exposure of FB1 and AFB1, which could be a survival advantage.

Hepatoprotective Role of Clay and Nano Clay for Alleviating Aflatoxin Toxicity in Male Rats

<b>Background and Objective:</b> Aflatoxin formed by <i>Aspergillus</i> sp. causes acute hepatotoxicity by DNA damage, gene expression disruption and induced liver carcinoma in humans and laboratory animals. The objectives of this research were to evaluate the protective role of both clay and nano clay as adsorbents to inhibit the side effect of Aflatoxin (AF) by measures the common biological assay of aflatoxicosis in rats along with hepatic gene expression and comet assay. <b>Materials and Methods:</b> Six weeks old male albino rats were distributed into 6 groups with 10 rats per group fed on, Group 1: Basal diet, Group 2: Basal diet with clay (5 g kg<sup></sup><sup>1</sup> diet), Group 3: Basal diet with nano clay (5 g kg<sup></sup><sup>1</sup> diet), Group 4: AF-contaminated diet (1 mg kg<sup></sup><sup>1</sup> diet), Group 5: AF with clay, Group 6: AF with nano clay. <b>Results:</b> AF induced a noticeable increase in the liver function parameters, accompanied by a significant decrease in antioxidant enzyme activities and significant histological alterations in liver tissues. The obtained qPCR results showed a significant up regulation in the expression of Cyp3A6, HO-1, TNFα and NFKB genes in the liver of rats treated with aflatoxin. In contrast, there is a significant down regulation in the expression levels of the Glut2 gene in liver rats treated with aflatoxin. Also, aflatoxin induced a significant increase in DNA damage. Clay and nano clay succeeded in ameliorating the toxic effects of aflatoxin. <b>Conclusion:</b> The results indicated the effective role of clay and nano clay in alleviating aflatoxin and reduce its harmful effects.

Development of an in vitro neuroblastoma 3D model and its application for sterigmatocystin-induced cytotoxicity testing

Given the increasing importance of establishing better risk assessments for mycotoxins, novel in vitro tools for the evaluation of their toxicity are mandatory. In this study, an in vitro 3D spheroid model from SH-SY5Y cells, a human neuroblastoma cell line, was developed, optimized and characterized to test the cytotoxic effects caused by the mycotoxin sterigmatocystin (STE). STE induced a concentration- and time-dependent cell viability decrease in spheroids. Spheroids displayed cell disaggregation after STE exposure, increasing in a dose-dependent manner and over time. STE also induced apoptosis as confirmed by immunofluorescence staining and Western blot. Following the decreased proliferation and increased apoptosis, STE cytostasis effects were observed by migration assays both in 2D and 3D cell culture. Increased ROS generation, as well as DNA damage were also observed. Taken together, these data highlight the cytotoxic properties of STE and suggest that cell culture models play a pivotal role in the toxicological risk assessment of mycotoxins. The evaluation of cytotoxicity in spheroids (3D) rather than monolayer cultures (2D) is expected to more accurately reflect in vivo-like cell behaviour.

Toxicogenicity and mechanistic pathways of aflatoxin B1 induced renal injury

The study investigated the toxicogenic effects, molecular mechanisms and proteomic assessment of aflatoxin B₁ (AFB₁ ) on human renal cells. Hek293 cells were exposed to AFB₁ (0-100 μM) for 24 h. The effect on cell viability was assessed using the methylthiazol tetrazolium (MTT) assay, which also produced the half maximal inhibitory concentration (IC₅₀ ) used in subsequent assays. Free radical production was evaluated by quantifying malondialdehyde (MDA) and nitrate concentration, while DNA fragmentation was determined using the single cell gel electrophoresis (SCGE) assay and DNA gel electrophoresis. Damage to cell membranes was ascertained using the lactate dehydrogenase (LDH) assay. The concentration of ATP, reduced glutathione (GSH), necrosis, annexin V and caspase activity was measured by luminometry. Western blotting and quantitative PCR was used to assess the expression of proteins and genes associated with apoptosis and oxidative stress. The MTT assay revealed a reduction in cell viability of Hek293 cells as the AFB₁ concentration was increased, with a half maximum inhibitory concentration (IC₅₀ ) of 32.60 μM. The decreased viability corresponded to decreased ATP concentration. The upregulation of Hsp70 indicated that oxidative stress was induced in the AFB₁ -treated cells. While this implies an increased production of free radicals, the accompanying upregulation of the antioxidant system indicates the activation of defense mechanisms to prevent cellular damage. Thus, membrane damage associated with increased radical formation was prevented as indicated by the reduced LDH release and necrosis. In addition, cytotoxic effects were evident as AFB₁ activated the intrinsic pathway of apoptosis with corresponding increased DNA fragmentation, p53 and Bax upregulation and increased caspase activity, but externalization of phosphatidylserine (PS), a major hallmark of apoptosis, did not occur in AFB₁ treated renal cells. The results suggest that AFB₁ induced oxidative stress leading to cell death by the intrinsic pathway of apoptosis in renal cells.

Sterigmatocystin-induced DNA damage triggers cell-cycle arrest via MAPK in human neuroblastoma cells

Sterigmatocystin (STE) is a common mycotoxin found in food and feed. Many studies showed that STE is genotoxic. However, up to now, the potential genotoxicity of STE on human neuronal system remains unknown. In this study, we explored the effect of STE on DNA damage and cell-cycle progression on human neuroblastoma SH-SY5Y cells exposed to various concentrations of STE (0.78, 1.56 and 3.12 µM) for 24 h. The results indicated that STE exposure induced DNA damage, as evidenced by DNA comet tails formation and increased γH2AX foci. Additionally, genotoxicity was confirmed by micronuclei (MN) analysis. Furthermore, we found that STE exposure led to cell-cycle arrest at the S and the G₂/M phase. Considering the important role played by MAPK and p53 signaling pathways in cell-cycle arrest, we explored their potential involvement in STE-induced cell-cycle arrest by using specific inhibitors. The inhibition of JNK and ERK resulted to attenuate S and G₂/M arrest, whereas the inhibition of p38 and p53 attenuated only STE-induced S phase arrest. In conclusion, the present study demonstrates that STE induced DNA damage and triggered MAPK and p53 pathways activation, resulting in cell-cycle arrest at the S and the G₂/M phase.

Aflatoxin B1 inhibited autophagy flux by inducing lysosomal alkalinization in HepG2 cells

Aflatoxin B1 (AFB1) is a hazard food pollutant and the most toxic one of all the aflatoxins. It is mainly metabolized in the liver and exerts strong hepatotoxicity and carcinogenesis. Autophagy is an important biological process to maintain the homeostasis of intracellular environment. But the role of autophagy in AFB1-exposured hepatotoxicity remains unclear. The objective of this study was to explore the effect of AFB1 on autophagy flux and its potential mechanisms in HepG2 cells. The data showed AFB1 with no-observed adverse effect level (NOAEL) induced the accumulation of autophagosomes by detecting the level of LC3 and MDC staining. Subsequent findings revealed that autophagosome accumulation was caused by the inhibition of autophagy flux by transfection mRFP-GFP-LC3 adenovirus in the presence of autophagy inhibitor 3-MA and CQ. Further, we investigated lysosomal pH by Acridine orange (AO) and Lysotracker Red (LTR) staining and found that AFB1 exposure caused lysosomal alkalinization. These results indicated AFB1 with NOAEL could inhibit autophagy flux by inducing lysosomal alkalinization. Our study was helpful to further explain early hepatotoxicity mechanism of AFB1.

Settled dust assessment in clinical environment: useful for the evaluation of a wider bioburden spectrum

The collection and analysis of settled dust samples from indoor environments has become one of several environmental sampling methods used to assess bioburden indoors. The aim of the study was to characterize the bioburden in vacuumed settled dust from 10 Primary Health Care Centers by culture based and molecular methods. Results for bacterial load ranged from 1 to 12 CFU.g^-1 of dust and Gram-negative bacteria ranged between 1 to 344 CFU.g^-1 of dust. Fungal load ranged from 0 CFU.g^-1 of dust to uncountable. Aspergillus section Fumigati was detected in 4 sampling sites where culture base-methods could not identify this section. Mucorales (Rhizopus sp.) was observed on 1 mg/L voriconazole. Three out of 10 settled dust samples were contaminated by mycotoxins. Settled dust sampling coupled with air sampling in a routine way might provide useful information about bioburden exposure.

Cytotoxicity assessment of Aflatoxin B1 after high voltage atmospheric cold plasma treatment

Aflatoxin B1 (AFB1) is a secondary metabolite produced by Aspergillus flavus and A. parasiticus, and is a known carcinogen in humans and animals. High voltage atmospheric cold plasma (HVACP) technology has already shown promise to decontaminate AFB1 in food and feed. This study aimed to investigate the cytotoxicity of AFB1 after HVACP treatment. AFB1 (100 μM) was treated at 85 kV with HVACP for 0, 2, 5, 10, and 20 min. HepG2 cells were exposed to HVACP-treated AFB1 for 72 h and assessed for cell viability, caspase-3 activity, DNA fragmentation, and protein carbonyls for each treatment time. Cell viability, caspase-3 activity, DNA fragmentation levels, and protein carbonyls contents of HepG2 cells exposed to HVACP-treated AFB1 after 20 min was not significantly different compared to non-exposed HepG2 cells (P > 0.05). However, their contents were significantly higher in non-exposed cells compared to the other HVACP treatment times (P < 0.01). Twenty minutes of HVACP treatment for AFB1 significantly reduced AFB1 cytotoxicity and oxidative damage and showed potential as a safe aflatoxin decontamination technology.

Performance of a UV-A LED system for degradation of aflatoxins B1 and M1 in pure water: kinetics and cytotoxicity study

The efficacy of a UV-A light emitting diode system (LED) to reduce the concentrations of aflatoxin B₁, aflatoxin M₁ (AFB₁, AFM₁) in pure water was studied. This work investigates and reveals the kinetics and main mechanism(s) responsible for the destruction of aflatoxins in pure water and assesses the cytotoxicity in liver hepatocellular cells. Irradiation experiments were conducted using an LED system operating at 365 nm (monochromatic wave-length). Known concentrations of aflatoxins were spiked in water and irradiated at UV-A doses ranging from 0 to 1,200 mJ/cm². The concentration of AFB₁ and AFM₁ was determined by HPLC with fluorescence detection. LC–MS/MS product ion scans were used to identify and semi-quantify degraded products of AFB₁ and AFM₁. It was observed that UV-A irradiation significantly reduced aflatoxins in pure water. In comparison to control, at dose of 1,200 mJ/cm² UV-A irradiation reduced AFB₁ and AFM₁ concentrations by 70 ± 0.27 and 84 ± 1.95%, respectively. We hypothesize that the formation of reactive species initiated by UV-A light may have caused photolysis of AFB₁ and AFM₁ molecules in water. In cell culture studies, our results demonstrated that the increase of UV-A dosage decreased the aflatoxins-induced cytotoxicity in HepG2 cells, and no significant aflatoxin-induced cytotoxicity was observed at UV-A dose of 1,200 mJ/cm². Further results from this study will be used to compare aflatoxins detoxification kinetics and mechanisms involved in liquid foods such as milk and vegetable oils.

The regulatory role of PGC1α-related coactivator in response to drug-induced liver injury

PGC1α-Related Coactivator (PRC) is a transcriptional coactivator promoting cytokine expression in vitro in response to mitochondrial injury and oxidative stress, however, its physiological role has remained elusive. Herein we investigate aspects of the immune response function of PRC, first in an in vivo thioacetamide (TAA)-induced mouse model of drug-induced liver injury (DILI), and subsequently in vitro in human monocytes, HepG2, and dendritic (DC) cells. TAA treatment resulted in the dose-dependent induction of PRC mRNA and protein, both of which were shown to correlate with liver injury markers. Conversely, an adenovirus-mediated knockdown of PRC attenuated this response, thereby reducing hepatic cytokine mRNA expression and monocyte infiltration. Subsequent in vitro studies with conditioned media from HepG2 cells overexpressing PRC, activated human monocytes and monocyte-derived DC, demonstrated up to 20% elevated expression of CD86, CD40, and HLA-DR. Similarly, siRNA-mediated knockdown of PRC abolished this response in oligomycin stressed HepG2 cells. A putative mechanism was suggested by the co-immunoprecipitation of Signal Transducer and Activator of Transcription 1 (STAT1) with PRC, and induction of a STAT-dependent reporter. Furthermore, PRC co-activated an NF-κB-dependent reporter, indicating interaction with known major inflammatory factors. In summary, our study indicates PRC as a novel factor modulating inflammation in DILI.

Proteomics reveals the alleviation of zinc towards aflatoxin B1-induced cytotoxicity in human hepatocyes (HepG2 cells)

Aflatoxin B1 (AFB1) is a known carcinogen found in contaminated food and designated by the World Health Organization as a class I carcinogenic substance. AFB1 presents with carcinogenicity, teratogenicity, and mutagenicity, and the liver is the human organ most susceptible to AFB1. Zinc (Zn), which is one of the essential nutrient elements that could protect the cells from biological toxins, heavy metals, hydrogen peroxide, metal chelators and radiation, is assessed in this study for its potential to alleviate AFB1-induced cytotoxicity. Samples were divided into three groups, namely CK, AFB1, and AFB1+Zn. Protein expressions were analyzed by two-way electrophoresis combined with flight mass spectrometry, with 41 differentially expressed proteins identified in the results, mainly related to oxidative stress, cell apoptosis, DNA damage, and energy metabolism. Zn was found to regulate the expression of peroxidases (peroxiredoxin-1, peroxiredoxin-5, peroxiredoxin-6) to relieve AFB1-induced oxidative stress. Moreover, Zn could decrease the expression of pro-apoptotic genes (cleaved-caspase-3, caspase-9, and Bax) and increase the expression of anti-apoptotic genes (Bcl-2 and Bcl-xl) to alleviate the cell apoptosis induced by AFB1. In addition, AFB1 reduced intracellular ATP levels, whereas Zn supplementation boosted ATP levels and maintained homeostasis and a steady state of cellular energy metabolism by modulating AMPK-ACC phosphorylation levels, while many zinc finger proteins changed after AFB1 treatment. These results, therefore, indicate that Zn could alleviate AFB1-induced cytotoxicity by changing the expressions of zinc finger proteins in liver hepatocellular carcinoma (HepG2 cells).

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.

The role of mitochondria in sterigmatocystin-induced apoptosis on SH-SY5Y cells

Mitochondria are cellular organelles involved in many crucial functions, such as generation of energy (ATP) and initiation of apoptosis. The aim of the present study was to evaluate the role of mitochondria in the toxicity induced by sterigmatocystin (STE), a mycotoxin produced by fungi of the genus Aspergillus, on SH-SY5Y cells. Our results showed that STE exposure decreased cell viability in a time- and concentration-dependent manner by MTT assay and caused mitochondrial dysfunction, as highlighted by the increase of STE cytotoxicity in cells forced to rely on mitochondrial oxidative phosphorylation. Furthermore, intracellular ATP depletion and increased mitochondrial reactive oxygen species were also observed. Since mitochondria play a pivotal role in apoptosis, the induction of this process in response to STE exposure was decided to study. Our results showed an increase in apoptotic cell population by flow cytometry, further confirmed by the up-regulation of the expression levels of the pro-apoptotic genes Bax and Casp-3 and the down-regulation of the anti-apoptotic gene Bcl-2 by qPCR technique. Taken together, our results provide novel insights in the signalling pathways of the cell death process induced by STE in SH-SY5Y cells, highlighting the key role played by mitochondria in STE toxicity.

Mitigation of aflatoxin B1- and sodium arsenite-induced cytotoxicities in HUC-PC urinary bladder cells by curcumin and Khaya senegalensis

Background Concomitant exposure to environmental/occupational toxicants such as aflatoxin B1 (AFB1) and arsenic in some regions of the world has been well reported. Therefore, this calls for the assessment of the efficacy of agents such as phytochemicals, which are already known for their ethno-medicinal uses in prophylaxis/remediation. We investigated the possible cytotoxic bio-interactions between AFB1 and sodium arsenite (SA) in urinary bladder cells. We also assessed the cytoprotective effects of curcumin and the ethanol stem bark extract of Khaya senegalensis (K2S). Methods The cells were exposed to graded levels of AFB1, SA, curcumin, and K2S for 24, 48, and 72 h. Subsequently, using optimum toxic concentrations of AFB1 and SA, respectively, the influence of non-toxic levels of curcumin and/or K2S was tested on exposure of the cells to AFB1 and/or SA. Hoechst 33342/propidium iodide staining technique was used to determine the end-points due to cytotoxicity with changes in adenosine triphosphate (ATP) levels determined using Promega's CellTiter-Glo luminescent assay. Results Co-treatment of the cells with AFB1 and SA resulted in synergy in cytotoxic effects. Cytotoxicity was reduced by 3.5- and 2.9-fold by pre-treatment of the cells with curcumin and K2S before treatment with AFB1, while post-treatment resulted in 1.1- and 2.6-fold reduction, respectively. Pre-exposure of the cells with curcumin and K2S before treatment with SA ameliorated cytotoxicity by 3.8- and 3.0-fold, but post-treatment caused a 1.2- and 1.3-fold reduction, respectively. Conclusions Pre-treatment of the cells with either curcumin or K2S exhibited cytoprotective effects by ameliorating AFB1- and SA-induced cytotoxicity with inferred tendencies to prevent carcinogenesis.

Quercetin protects the buffalo rat liver (BRL-3A) cells from aflatoxin B1-induced cytotoxicity via activation of Nrf2-ARE pathway

Aflatoxin B1 (AFB1) is the most toxic mycotoxin widely presented in agricultural products, and the protective effect of quercetin (QUE), a natural antioxidant, against AFB1-induced cytotoxicity to the buffalo rat liver (BRL-3A) cells was investigated. With an IC50 of 23 μM, AFB1 induced a significant oxidative stress to BRL-3A cells evidenced by a dose-dependent reduction of mitochondria membrane potential (MMP), ATP content, and activities of endogenous antioxidant enzymes along with increased levels of reactive oxygen species (ROS) and lipid peroxidation biomarker of malondialdehyde (MDA). The activity of CYP1A2, the key enzyme to convert AFB1 to reactive AFB1 exo-8,9- epoxide, was also increased, which, probably in together with ROS, led to cell apoptosis with DNA fragmentation, chromatin condensation and increased lactate dehydrogenase release. After the BRL cells were pre-treated by low level QUE (2.5 and/or 5 μM) for 24 h and then exposed to AFB1, the activities of antioxidant enzymes including haeme oxygenase-1, glutathione S-transferase, superoxide dismutase, and the ratio of reduced to oxidised glutathione were significantly increased whereas the levels of intracellular ROS and MDA were reduced. The QUE pre-treatment also increased the levels of MMP, ATP and DNA integrity, and reduced the expression of apoptosis related genes of Bax and Caspase-3. The Western blotting study revealed increased content of phosphorylated Akt and nuclear NF-E2-related factor 2 (Nrf2), indicating an activation of Nrf2-ARE pathway in counteracting oxidative stress and cytotoxicity of AFB1. Thus, the QUE pre-treatment enhanced the anti-stress capacity of the cells through the activation of the Nrf2-ARE pathway, and QUE-based measures could be developed to ameliorate the toxicity caused by AFB1.

Anticancer effect of fucoidan on cell proliferation, cell cycle progression, genetic damage and apoptotic cell death in HepG2 cancer cells

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The centre of the attraction of this article is inevitably associated with fucoidan polymers in terms of brown seaweed such as Turbinaria conoides.

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Fucoidan in various cancer types exhibited by targeting apoptotic molecules and mitigate the toxicity of chemotherapeutic agents and radiation.

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To treat deadly liver cancer by identifying bioactive compounds available in the dietary supplement that rekindles the direction of research against cancer diseases.

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Fucoidan in a HepG2 cell line was studied with typical techniques such as cell viability, colony formation, cell migration, cell cycle progression, genetic damage and apoptosis along with their nuclear morphology and mitochondrial membrane potential.

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This study concluded that the fucoidan contain brown seaweeds consumed as dietary supplement not predispose to liver cancer.

The centre of the attraction of this article is inevitably associated with fucoidan polymers in terms of brown seaweed such as Turbinaria conoides. Fucoidan is a sulphated polysaccharide constitutes fucose as a major principle sugar along with other monosugars such as glucuronic acid, xylose and galactose. The core value of fucoidan in terms of various cancer types were substantially exhibited through targeting the key apoptotic molecules and subsequently mitigate the toxicity that are essentially included in the chemotherapeutic agents and radiation. The pragmatic investigation about the anti-cancer effect of fucoidan in a hepatoblastoma-derived (HepG2) cell line was thoroughly analyzed by the typical techniques such as cell viability, colony formation, cell migration, cell cycle progression, genetic damage and apoptosis along with their nuclear morphology and mitochondrial membrane potential. Following the analyzes, the cell viability was precisely evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. And hence, cell cycle arrest and apoptosis was appropriately examined staining with propidium iodide (PI) and annexin V-fluorescein isothiocyante (FITC) by flowcytometer, respectively. Primarily, genetic damage by fucoidan in HepG2 cell line was evaluated by following Trevigen’s comet assay kit. In addition, alteration of nuclear content and mitochondrial membrane potential were also detected with Hoechst and mitochondrial membrane potential dye (JC-1: 5,5′6,6′-tetrachloro-1,1′3,3′tetraethylbenzimi-dazolycarbocyanine iodide) by fluorescence microscopy, respectively. The results of the present study showed that cells constituted with fucoidan/quercetin standard at 50, 100 and 200 μg/ml exhibited cell viability about 71, 60 & 40/80, 65 & 45%, respectively. The above recorded effect of fucoidan was a concentration-dependant inhibition on the basis of decline in colony forming and cell migration potential of HepG2 cancer cells. Compared with untreated control, fucoidan consituted cells were significantly (p ≤  0.05) accumulated proliferative cells in the G₀/G₁ phase of the cell cycle in a concentration dependent manner. Increasing concentration of fucoidan (50,100 and 200 μg/ml) was remarkably enhanced the DNA damage which reflected through tail moment value of 3.8, 7.1 & 12.8 folds with respect to the untreated control. Fucoidan induced total apoptotic cells were observed ∼20–40% at 50–200 μg/ml concentrations. The apoptotic cell formation effected by change in the nuclear content and mitochondrial membrane potential was confirmed in HepG2 cancer cells under fluorescence microscopy. It was eventually concluded that the fucoidan display promising anti-cancer activity against HepG2 cancer cells by promoting the inhibition of cell proliferation, migration and cell arrest on concentration dependent-manner that was well correlated with genetic damage and apoptosis.

Resveratrol inhibits aflatoxin B1-induced oxidative stress and apoptosis in bovine mammary epithelial cells and is involved the Nrf2 signaling pathway

Aflatoxins are widely occurring food contaminants that are particularly harmful to dairy products and cows. The plant polyphenol resveratrol has been reported to have a good effect on increasing the resistance of cells toward toxins. Therefore, we measured the effects of aflatoxin B1 and resveratrol on the viability of the MAC-T cow mammary epithelial cell line. The appropriate treatment concentrations were assayed (12.81 μM aflatoxin B1 and 43.81 μM resveratrol) to verify the protective effect of resveratrol toward mammary epithelial cells. The results showed that resveratrol alleviates aflatoxin B1-induced cytotoxicity, including the increase in ROS and the decrease in mitochondrial membrane potential (MMP) and apoptosis in MAC-T cells. The expression of mRNA transcripts (including Nrf2, Keap1, NQO1, HO-1, SOD2 and HSP70) for components of the Nrf2 signaling pathway was evaluated by real-time fluorescent quantitative PCR, with resveratrol also exhibiting a good regulatory effect. Thus, resveratrol was shown to have an ameliorating effect on aflatoxin toxicity in MAC-T cells.

Variation of Fungal Metabolites in Sorghum Malts Used to Prepare Namibian Traditional Fermented Beverages Omalodu and Otombo

Sorghum malts, which are important ingredients in traditional fermented beverages, are commonly infected by mycotoxigenic fungi and mycotoxins may transfer into the beverages, risking consumers’ health. Liquid chromatography–tandem mass spectrometry was used to determine variation of fungal metabolites in 81 sorghum malts processed for brewing of Namibian beverages, otombo (n = 45) and omalodu (n = 36). Co-occurrence of European Union (EU)-regulated mycotoxins, such as patulin, aflatoxins (B₁, B₂, and G₂), and fumonisins (B₁, B₂, and B₃) was detected in both malts with a prevalence range of 2–84%. Aflatoxin B₁ was quantified in omalodu (44%) and otombo malts (14%), with 20% of omalodu malts and 40% of otombo malts having levels above the EU allowable limit. Fumonisin B₁ was quantified in both omalodu (84%) and otombo (42%) malts. Emerging mycotoxins, aflatoxin precursors, and ergot alkaloids were quantified in both malts. Notably, 102 metabolites were quantified in both malts, with 96% in omalodu malts and 93% in otombo malts. An average of 48 metabolites were quantified in otombo malts while an average of 67 metabolites were quantified in omalodu malts. The study accentuates the need to monitor mycotoxins in sorghum malts intended for brewing and to determine their fate in the beverages.

Cytotoxicity of gamma irradiated aflatoxin B1 and ochratoxin A

Toxicity of gamma irradiated mycotoxins aflatoxin B₁ (AFB₁) and ochratoxin A (OTA) was investigated in vitro. AFB₁ and OTA stock solutions (50 mM, in methanol) were gamma irradiated (5 and 10 kGy) and non-irradiated and irradiated mycotoxins solutions were tested for cytotoxicity on Pk15, HepG2 and SH-SY5Y cell lines (MTT assay, 1-500 μM concentration range; 24 h exposure). Degradation of mycotoxin molecules was examined by liquid chromatography tandem mass spectrometry (HPLC-MS/MS). AFB₁ and OTA radiolytic products were less toxic than the parent mycotoxins to all of the tested cell lines. Gamma irradiation even at 5 kGy had effect on AFB₁ and OTA molecules however, this effect was dependent on chemical structure of mycotoxin. Since gamma irradiation at low dose reduced initial level of both mycotoxins, and gamma irradiated mycotoxins had lower toxicity in comparison to non-irradiated mycotoxins, it can be concluded that gamma irradiation could be used as decontamination method.

Sterigmatocystin in foodstuffs and feed: aspects to consider

Sterigmatocystin (STC) is a possible human carcinogen (2B) according to International Agency for Research on Cancer classification and has been associated with immunotoxic and immunomodulatory activity, together with mutagenic effects. It might be found in numerous substrates, from foods and feeds to chronically damp building materials and indoor dust. Although European Food Safety Authority concluded that the exposure to STC to be of low concern for public health, reinforces the need of data concerning exposure of European citizens. Climate change can represent an increased risk of exposure to STC since it is a crucial factor for agro-ecosystem powering fungal colonisation and mycotoxin production This aspect can represent an increased risk for European countries with temperate climates and it was already reported by the scientific community.

Multi-parameter analysis of combined hepatotoxicity induced by mycotoxin mixtures in HepG2 cells

Evaluation of combined toxicity and exploring the corresponding mechanism is of great significance in characterising the interactions of mixed mycotoxins. This study used high content analysis and multiple evaluation models to estimate combined toxic hepatotoxicity in HepG2 cells, due to aflatoxin B1, zearalenone and deoxynivalenol, which are often detected simultaneously in the same grain sample. All mycotoxins induced cell loss in HepG2 cells in a concentration dependent manner. The combined toxic effects observed by multiple evaluation models (CA, IA and CI) suggested a similar mechanism and dominant synergistic effects for binary and ternary combinations. Based on reactive oxygen species, intracellular glutathione (GSH), and mitochondrial transmembrane potential (MMP) assessment, the synergistic mechanisms may be associated with mitochondrial damage by reducing GSH and MMP.

Aflatoxin B1 impairs sperm quality and fertilization competence

Aflatoxins are poisonous byproducts of the soilborne fungus Aspergillus, involved in the decomposition of plant materials. Aflatoxins can be found in various food products, such as maize, sorghum, millet, rice and wheat. AFB1 is the most toxic of these, classified as a carcinogen and mutagen for both humans and animals. AFB1 has been detected in human cord blood and placenta; however, its toxic effect on sperm is less known. The current study examines sperm responses associated with AFB1 exposure. These included acrosome integrity and function, mitochondrial polarity, DNA fragmentation, fertilization competence and early embryonic development. Spermatozoa were obtained from bull ejaculate and epididymis and capacitated in vitro for 4h with 0, 0.1, 1, 10 and 100μM AFB1. Following capacitation, acrosome reaction (AR) was induced by Ca²⁺ ionophore. The integrity and functionality of sperm were examined simultaneously by florescent staining. A Halosperm DNA fragmentation kit was used to evaluate DNA integrity. An in-vitro culture system was used to evaluate fertilization competence and blastocyst formation rate, using bovine oocytes. Findings indicate dose-responsive variation among compartments to AFB1 exposure. Sperm viability, expressed by integrity of the plasma membrane, was lower in sperm isolated from ejaculate or epididymis after culturing with AFB1. Exposure to AFB1 reduced the proportion of sperm from the epididymis tail undergoing acrosome reaction induced by Ca²⁺ ionophore. AFB1 impaired mitochondrial membrane potential (ΔYm) in sperm isolated from ejaculate and the epididymis tail. Exposing ejaculated sperm to AFB1 increased the proportion of sperm with fragmented DNA and reduced the proportion of embryos that cleaved to the 2- to 4-cell stage, 42h postfertilization, however, the proportion of embryos that developed to blastocysts, 7days postfertilization, did not differ among groups. The findings explore the harmful effects of AFB1 on sperm viability, ΔΨm and DNA integrity associated with fertility competence. We postulate that AFB1-induced fragmentation in paternal DNA might have a carryover effect on the quality of developing embryos. Further evaluation for the quality of blastocysts derived from sperm exposed to AFB1 is warranted.

Emerging Mycotoxins: Beyond Traditionally Determined Food Contaminants

Modern analytical techniques can determine a multitude of fungal metabolites contaminating food and feed. In addition to known mycotoxins, for which maximum levels in food are enforced, also currently unregulated, so-called "emerging mycotoxins" were shown to occur frequently in agricultural products. The aim of this review is to critically discuss the relevance of selected emerging mycotoxins to food and feed safety. Acute and chronic toxicity as well as occurrence data are presented for enniatins, beauvericin, moniliformin, fusaproliferin, fusaric acid, culmorin, butenolide, sterigmatocystin, emodin, mycophenolic acid, alternariol, alternariol monomethyl ether, and tenuazonic acid. By far not all of the detected compounds are toxicologically relevant at their naturally occurring levels and are therefore of little or no health concern to consumers. Still, gaps in knowledge have been identified for several compounds. These gaps should be closed by the scientific community in the coming years to allow a proper risk assessment.

Acute aflatoxin B1 - Induced hepatotoxicity alters gene expression and disrupts lipid and lipoprotein metabolism in rats

In this study, alterations in lipid metabolism associated with acute aflatoxin B1 (AFB1) induced hepatotoxicity and gene expression changes underlying these effects were investigated. Rats were orally administered three doses (0.25 mg/kg, 0.5 mg/kg and 1.0 mg/kg) of AFB1 for seven days; after which blood was collected and liver excised. Lipid profiles of plasma and liver were determined spectrophotometrically while the expression of genes associated with lipid and lipoprotein metabolism was assayed by reverse transcriptase polymerase chain reaction. Acute exposure to AFB1 increased the levels of plasma and liver cholesterol, triglycerides and phospholipids. AFB1 at 0.5 mg/kg and 1.0 mg/kg resulted in a dose-dependent (1.2 and 1.5 fold, respectively) downregulation of hepatic Cpt1a with a concomitant 1.2 and 1.5 fold increase in the level of plasma FFA, respectively. A similar observation of 1.2 and 1.3 fold increase was also observed in plasma triglyceride concentration, at both respective doses. AFB1 also decreased the relative expression of Ahr, Lipc and Lcat whereas, it upregulated Scarb1 in a dose dependent manner. AFB1-induced dysregulation of the expression of lipid and lipoprotein metabolizing genes may be one mechanism linking AFB1 to altered lipid metabolism and ultimately risk for coronary heart disease.

Acute aflatoxin B1 - Induced hepatotoxicity alters gene expression and disrupts lipid and lipoprotein metabolism in rats

In this study, alterations in lipid metabolism associated with acute aflatoxin B1 (AFB1) induced hepatotoxicity and gene expression changes underlying these effects were investigated. Rats were orally administered three doses (0.25 mg/kg, 0.5 mg/kg and 1.0 mg/kg) of AFB1 for seven days; after which blood was collected and liver excised. Lipid profiles of plasma and liver were determined spectrophotometrically while the expression of genes associated with lipid and lipoprotein metabolism was assayed by reverse transcriptase polymerase chain reaction. Acute exposure to AFB1 increased the levels of plasma and liver cholesterol, triglycerides and phospholipids. AFB1 at 0.5 mg/kg and 1.0 mg/kg resulted in a dose-dependent (1.2 and 1.5 fold, respectively) downregulation of hepatic Cpt1a with a concomitant 1.2 and 1.5 fold increase in the level of plasma FFA, respectively. A similar observation of 1.2 and 1.3 fold increase was also observed in plasma triglyceride concentration, at both respective doses. AFB1 also decreased the relative expression of Ahr, Lipc and Lcat whereas, it upregulated Scarb1 in a dose dependent manner. AFB1-induced dysregulation of the expression of lipid and lipoprotein metabolizing genes may be one mechanism linking AFB1 to altered lipid metabolism and ultimately risk for coronary heart disease.