Aflatoxin B1 Induced Compositional Changes in Gut Microbial Communities of Male F344 Rats

Aflatoxins are a group of potent foodborne toxicants naturally occurring in maize and groundnuts. Differential species-specific sensitivity to aflatoxins has been documented but cannot be fully explained by the differences in metabolism of these toxicants among animal species. Commensal microbial communities (microbiota) are critical to human and animal health, but few studies have assessed interactions between xenobiotic toxins and those microbiota, and its potential effects to humans and animals. Here, an exploratory dosing experiment was conducted to explore effects of Aflatoxin B1 (AFB1) on the gut microbiota in a commonly used rat model. Male F344 rats were randomly divided into groups and treated with different concentrations of AFB1. Microbial communities in fecal samples were assessed using 16S rRNA sequence analysis. We found that samples from the control group had a phylogenetically diverse community, and that increasing AFB1 doses decreased this diversity but increased evenness of community composition. In addition, the gut microbiota from different samples was clustered according to their dosing regimens. There is no community shift at the phylum level but some lactic acid bacteria were significantly depleted by AFB1. These findings suggested that AFB1 could modify the gut microbiota in a dose-dependent manner.

Effects of temperature, water activity and incubation time on fungal growth and aflatoxin B1 production by toxinogenic Aspergillus flavus isolates on sorghum seeds

Sorghum, which is consumed in Tunisia as human food, suffers from severe colonization by several toxigenic fungi and contamination by mycotoxins. The Tunisian climate is characterized by high temperature and humidity that stimulates mold proliferation and mycotoxin accumulation in foodstuffs. This study investigated the effects of temperature (15, 25 and 37°C), water activity (aw, between 0.85 and 0.99) and incubation time (7, 14, 21 and 28 d) on fungal growth and aflatoxin B1 (AFB1) production by three Aspergillus flavus isolates (8, 10 and 14) inoculated on sorghum grains. The Baranyi model was applied to identify the limits of growth and mycotoxin production. Maximum diameter growth rates were observed at 0.99 a(w) at 37°C for two of the isolates. The minimum aw needed for mycelial growth was 0.91 at 25 and 37°C. At 15°C, only isolate 8 grew at 0.99 a(w). Aflatoxin B1 accumulation could be avoided by storing sorghum at low water activity levels (≤0.91 a(w)). Aflatoxin production was not observed at 15°C. This is the first work on the effects of water activity and temperature on A. flavus growth and AFB1 production by A. flavus isolates on sorghum grains.

Ochratoxin A and T-2 Toxin Induce Clonogenicity and Cell Migration in Human Colon Carcinoma and Fetal Lung Fibroblast Cell Lines

T-2 toxin and Ochratoxin A (OTA) are toxic secondary metabolites produced by various fungi, and together they contaminate feedstuffs worldwide. T-2 toxin and OTA may exert carcinogenic action in rodent. Despite the various in vivo experiments, carcinogenicity of these two mycotoxins has not yet been proven for human. In this current study, we proposed to investigate, in Human colon carcinoma cells and fetal lung fibroblast-like cells transfected with MYC, the effect of T-2 toxin and OTA on cell clonogenicity and cell migration. Results of the present investigation showed that T2-toxin as well as OTA has an important clonogenic effect in all cell lines, suggesting that these mycotoxins could promote the transcription of c-myc gene. Furthermore, T-2 toxin and OTA enhanced the migration effect of HCT116 cells at very low concentrations, proposing that these mycotoxins may exhibit carcinogenesis-like properties in the studied cells.

Hetero-enzyme-based two-round signal amplification strategy for trace detection of aflatoxin B1 using an electrochemical aptasensor

An electrochemical aptasensor for trace detection of aflatoxin B1 (AFB1) was developed by using an aptamer as the recognition unit while adopting the telomerase and EXO III based two-round signal amplification strategy as the signal enhancement units. The telomerase amplification was used to elongate the ssDNA probes on the surface of gold nanoparticles, by which the signal response range of the signal-off model electrochemical aptasensor could be correspondingly enlarged. Then, the EXO III amplification was used to hydrolyze the 3'-end of the dsDNA after the recognition of target AFB1, which caused the release of bounded AFB1 into the sensing system, where it participated in the next recognition-sensing cycle. With this two-round signal amplified electrochemical aptasensor, target AFB1 was successfully measured at trace concentrations with excellent detection limit of 0.6*10(-4)ppt and satisfied specificity due to the excellent affinity of the aptamer against AFB1. Based on this designed two-round signal amplification strategy, both the sensing range and detection limit were greatly improved. This proposed ultrasensitive electrochemical aptasensor method was also validated by comparison with the classic instrumental methods. Importantly, this hetero-enzyme based two-round signal amplified electrochemical aptasensor offers a great promising protocol for ultrasensitive detection of AFB1 and other mycotoxins by replacing the core recognition sequence of the aptamer.

Coexistence of Aflatoxicosis with Protein Malnutrition Worsens Hepatic Oxidative Damage in Rats

To investigate the effects of the coexistence of aflatoxin B1 (AFB1) and protein malnutrition in rat liver, weanling rats were fed either normal protein diet (20% protein), low-protein (PEM) diet (5%), normal protein diet + 40 ppb AFB1, or low-protein diet + 40 ppb AFB1. After 8 weeks, biomarkers of hepatic functions and oxidative stress, caspase-3 activity, and tumor suppressor protein 53 (p53) were determined spectrophotometrically. Randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) was employed to determine genomic alterations among the groups. Coexistence of aflatoxicosis and PEM significantly decreased glutathione, glutathione-S-transferase, glutathione peroxidase, and superoxide dismutase, while it increased peroxidase and catalase. RAPD-PCR showed genomic alterations that were associated with significant increases in p53 level and caspase-3 activity in rats fed PEM diet + AFB1. In conclusion, the coexistence of aflatoxicosis and protein malnutrition induced oxidative stress with concomitant genomic alterations in the liver of weanling rats.

Changes in serum cytokine levels, hepatic and intestinal morphology in aflatoxin B1-induced injury: modulatory roles of melatonin and flavonoid-rich fractions from Chromolena odorata

Aflatoxins are known to produce chronic carcinogenic, mutagenic, and teratogenic effects, as well as acute inflammatory effects, especially in the gastrointestinal tract. The potentials of the flavonoid-rich extract from Chromolena odorata (FCO) and melatonin (a standard anti-oxidant and anti-inflammatory agent) against aflatoxin B1 (AFB1)-induced alterations in pro-inflammatory cytokine levels and morphology of liver and small intestines were evaluated in this study. We utilized Wistar albino rats (200-230 g) randomly divided into five groups made up of group A, control rats; group B, rats given AFB1 (2.5 mg/kg, intraperitoneal) twice on days 5 and 7; rats in groups C, D, and E were treated with melatonin (10 mg/kg, intraperitoneal) or oral doses of FCO1 (50 mg/kg) and FCO2 (100 mg/kg) for 7 days, respectively, along with AFB1 injection on days 5 and 7. Serum levels of interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) were determined using commercial ELISA kits and histopathological evaluation of the liver, duodenum, and ileum were also carried out. We observed significant elevation (p < 0.05) in serum IL-1β correlating with hemorrhages and leucocytic and lymphocytic infiltration in the liver and intestines as evidences of an acute inflammatory response to AFB1 administration. All treatments yielded significant reduction (p < 0.05) in IL-1β levels, although TNF-α levels were not significantly altered in all rats that received AFB1, irrespective of the treatments. Melatonin and FCO2 produced considerable protection of hepatic tissues, although melatonin was not quite effective in protecting the intestinal lesions. Our findings suggest a modulation of cytokine expression that may, in part, be responsible for the abilities of C. odorata or melatonin in amelioration of hepatic and intestinal lesions associated with aflatoxin B1 injury.

Exposure to aflatoxin B1 in Thailand by consumption of brown and color rice

This study assessed the aflatoxin B1 (AFB1) intake of the Thai population through consumption of contaminated brown and color rice. A total of 240 rice samples from two harvesting periods were collected in June/July 2012 (period I) and in December 2012/January 2013 (period II) and analyzed for AFB1 by HPLC with fluorescence detection (limit of detection (LOD) = 0.093 ng/g). Exposure assessment was based on AFB1 levels in rice and food intake data for rice according to Thai National Consumption. Frequency and levels of AFB1 were higher in period I (59%, <LOD = 26.61 μg kg(-1)) than in period II (10%, <LOD = 3.51 μg kg(-1)). Only one sample exceeded the Thai standard limit for total aflatoxin of 20 μg kg(-1), but 12 out of 240 rice samples exceeded the European Union maximum level for AFB1 of 2 μg kg(-1). The data showed that the quality and safety of Thai rice largely comply with the requirement for both exports and domestic consumption. According to the Thai National Consumption data, the estimated AFB1 intake via rice consumption in period I and period II was 0.80 and 0.12 μg kg(-1) bw day(-1), respectively. The potential risk for cancer, based on the recommendation of the JECFA, was estimated to be 0.011 person/year/100,000 people at a mean consumption. Although the risk via consumption of Thai rice seems to be low, the maximum levels of AFB1 in this staple food suggest that careful monitoring and surveillance of AFB1 contamination in rice is essential to ensure the safety of rice.

Upregulation of miR-34a-5p antagonizes AFB1-induced genotoxicity in F344 rat liver

Aflatoxin B1 (AFB1) is a well-known human hepatotoxicant and genotoxicant. Recent studies demonstrated that aberrant miRNA expression patterns were correlated with the cellular and genetic lesions induced by chemicals. To explore the role of miRNAs in AFB1-induced hepatotoxicity and genotoxicity, we examined alterations in miRNA expression patterns in F334 rat livers after exposure to 100 μg/kg or 200 μg/kg AFB1 for 28 days. Using high-throughput sequencing, we discovered that rno-miR-34a-5p, rno-miR-200b-3p, and rno-miR-429 were up-regulated and that rno-miR-130a-3p was down-regulated in liver tissue from rats that received 200 μg/kg of AFB1; this finding was validated by real-time PCR. AFB1 treatment resulted in the upregulation of rno-miR-34a-5p and rno-miR-200b-3p in the rat H-4-II-E cell line similar to our in vivo observations. Moreover, rno-miR-34a-5p was transcriptionally elevated via p53 activation after AFB1 exposure. Upregulation of rno-miR-34a-5p suppressed the expression of the cell cycle-related genes CCND1, CCNE2 and MET and led to cell cycle arrest in the G0-G1 phase. The CBMN assay indicated that inhibition of rno-miR-34a-5p and p53 expression aggravated the DNA damage induced by AFB1, which might be associated with shortening of the DNA damage repair period. Circulating miR-34a-5p in rat sera preceded a significant increase in ALT activity and other miRNAs in the 100 μg/kg AFB1 group. These observations demonstrated that rno-miR-34a-5p responded sensitively to AFB1 exposure and facilitated p53 repair of DNA damage by impacting the cell cycle. Thus, circulating rno-miR-34a-5p may be a sensitive indicator for the induction of hepatic genotoxicity by AFB1 in rats.

Effect of Selenium Supplementation on Apoptosis and Cell Cycle Blockage of Renal Cells in Broilers Fed a Diet Containing Aflatoxin B1

The aim of the study was to investigate the competency of selenium (Se) in counteracting the adverse effects of aflatoxin B1 (AFB1) on apoptosis, cell cycle, and proliferation of nephritic cells. Two hundred forty 1-day-old healthy male avian broilers were randomly divided into four groups and fed basal diet (control group), 0.3 mg/kg AFB1 diet (AFB1 group), 0.4 mg/kg Se diet (+Se group), and 0.3 mg/kg AFB1 + 0.4 mg/kg Se diet (AFB1 + Se group), respectively. Compared to the control group, the number of apoptotic renal cells and expressions of Bax and caspase-3 messenger RNA (mRNA) were significantly increased, while the expression of Bcl-2 was significantly decreased in the AFB1 and the +Se groups (p < 0.01). A significantly decreased proliferating cell nuclear antigen (PCNA) expression and arrested G0/G1 phases of the cell cycle were also seen in the AFB1 and the +Se groups when compared with those of the control group. Moreover, these parameters were restored to the control group levels in the AFB1 + Se group. These results suggested that sodium selenite supplied in the diet could effectively inhibit AFB1-induced apoptosis and cell cycle blockage in renal cells of broiler.

Effect of aflatoxin B₁ on IgA⁺ cell number and immunoglobulin mRNA expression in the intestine of broilers

Aflatoxin B1 (AFB1) is the most toxic group of mycotoxins produced by two species of the Aspergillus, common contaminants of food and animal feed. The purpose of our study was to determine the effect of AFB1 on the number of IgA(+) cell and immunoglobulin mRNA expression in the intestine of broilers. One hundred and fifty six one-day-old healthy Cobb broilers were randomly divided into the control group (the dosage of 0 mg/kg AFB1) and AFB1 group (the dosage of 0.6 mg/kg AFB1) with three replicates per group and 26 birds per replicate for 21 days, respectively. After necropsy at 7, 14 and 21 days of age, duodenum, jejunum and ileum samples were taken for analyzing IgA(+) cell by immunohistochemistry and IgA, pIgR, IgM and IgG mRNA expression by qRT-PCR. IgA(+) cells were mainly distributed in the lamina propria of small intestinal mucosa in both groups at 14 and 21 days of age. A significant decrease in the number of IgA(+) cells in the duodenum, jejunum and ileum was revealed in the AFB1 group compared with that of the control group. The expression levels of IgA, pIgR, IgM and IgG mRNA in the intestinal mucosa were lower in the AFB1 group than those in the control group at 14 and 21 days of age. Our data demonstrated that the dosage of 0.6 mg/kg AFB1 in broiler diet reduced the number of IgA(+) cell and the expression of IgA, pIgR, IgM and IgG mRNA in the small intestine.

Highly Sensitive FRET-Based Fluorescence Immunoassay for Detecting of Aflatoxin B1 Using Magnetic/Silica Core-Shell as a Signal Intensifier

BACKGROUND

Recently, some new nanobiosensors using different nanoparticles or microarray systems for detection of mycotoxins have been designed . However, rapid, sensitive and early detection of aflatoxicosis would be very helpful to distinguish high-risk persons.

OBJECTIVES

We report a highly sensitive competitive immunoassay using magnetic/silica core shell as a signal intensifier for the determination of aflatoxin B1 using fluorescence resonance energy transfer (FRET) from Cd/Te quantum dots (antiaflatoxin B1 antibody immobilized on the surface of Cd/Te quantum dots) to Rhodamine 123 (Rho 123-labeled aflatoxin B1 bound to albumin). The specific immune-reaction between the anti-aflatoxin B1 antibody on the QDs and the labeledaflatoxin B1 brings the Rho 123 fluorophore (acting as the acceptor) and the QDs (acting as the donor) in close spatial proximity and causes FRET to occur upon photo-excitation of the QDs. Using magnetic/silica core shell to intensify the obtained signal is the novelty of this study.

MATERIALS AND METHODS

Cd/Te QDs were synthesized by the simultaneous reduction of cadmium chloride and tellurium in the presence of sodium borohydride under nitrogen atmosphere. Magnetic nanoparticles were synthesized using FeSO₄ and FeCl₃ (1:2 molar ratio) and ammonia as an oxidizing agent under nitrogen atmosphere. The prepared magnetic nanoparticles shelled by silica using tetraethoxysilane in the presence of ammonia. Nanoparticles synthesis and monodispersity confirmed by TEM. Immobilization of Cd/Te QDs to antibodies and labeling of aflatoxin B1-albumin by Rho 123 were performed by EDC/NHS reaction in reaction mixture buffer, pH 6, at room temperature.

RESULTS

By using the magnetic/silica core shell sensitivity of the system changed from 2×10^-11 in our previous study to 2×10^-12 in this work. The feasibility of the method established by the detection of aflatoxin B1 in spiked human serum. There is a linear relationship between the decreased fluorescence intensity of Rho 123 with increasing concentration of aflatoxin B1 in spiked samples, over the range of 0.01-0.06 μmol.mL^-1.

CONCLUSIONS

This homogeneous competitive detection scheme is simple, rapid and efficient, and does not require multiple separation steps and excessive washing.

Comparative study of in vitro prooxidative properties and genotoxicity induced by aflatoxin B1 and its laccase-mediated detoxification products

In this paper, the enzymatic detoxification of aflatoxin B1 (AFB1) by laccase was studied, and the prooxidant properties and mutagenicity of the detoxification products were compared with those of AFB1. The optimal enzymatic reaction occurred in 0.1M of citrate buffer containing 20% DMSO at 35 °C, a pH of 4.5, and a laccase activity of 30 U mL(-1). After 2 d, sixty-seven percent of the toxic substrate was removed. The prooxidative properties of the detoxified products (27% versus 86%) and the mutagenicity were significantly decreased in comparison with the parent toxin. Unlike AFB1, which promoted metabolism-dependent genetic mutations by base-pair substitution, the detoxified products did not induce genotoxicity. Comparison of the Km values for AFB1 and riboflavin, a valuable food nutrient, indicated that laccase showed greater affinity for the toxin than for riboflavin.

A structure-switchable aptasensor for aflatoxin B1 detection based on assembly of an aptamer/split DNAzyme

An ultrasensitive, colorimetric and homogeneous strategy for aflatoxin B1 (AFB1) detection, which uses a DNA aptamer and two split DNAzyme halves, has been developed. Split halves of a hemin-binding DNAzymes is combined with an AFB1 aptamer to generate a homogeneous colorimetric sensor that undergoes an AFB1 induced DNA structural change. In the absence of AFB1, the split probes have peroxidase mimicking DNAzyme activity associated with catalysis of a color change reaction. Specific recognition of AFB1 by the aptamer component leads to structural deformation of the aptamer-DNAzyme complex, which causes splitting of the DNAzyme halves and a reduction in peroxidase mimicking activity. Therefore, a decrease of colorimetric signal arising from the catalytic process takes place upon in the presence of AFB1 in a concentration dependent manner in the 0.1-1.0 × 10(4) ng/mL range and with a colorimetric detection limit of 0.1 ng/mL. The new assay system exhibits high selectivity for AFB1 over other mycotoxins and can be employed detect the presence of AFB1 in ground corn samples. Overall, the strategy should serve as the basis for the development of rapid, simple and low-cost methods for detection of mycotoxins.

Molecular characterization of hepatocarcinogenesis using mouse models

Hepatocellular carcinoma (HCC) is a deadly disease, often unnoticed until the late stages, when treatment options become limited. Thus, there is a crucial need to identify biomarkers for early detection of developing HCC, as well as molecular pathways that would be amenable to therapeutic intervention. Although analysis of human HCC tissues and serum components may serve these purposes, inability of early detection also precludes possibilities of identification of biomarkers or pathways that are sequentially perturbed at earlier phases of disease progression. We have therefore explored the option of utilizing mouse models to understand in a systematic and longitudinal manner the molecular pathways that are progressively deregulated by various etiological factors in contributing to HCC formation, and we report the initial findings in characterizing their validity. Hepatitis B surface antigen transgenic mice, which had been exposed to aflatoxin B1 at various stages in life, were used as a hepatitis model. Our findings confirm a synergistic effect of both these etiological factors, with a gender bias towards males for HCC predisposition. Time-based aflatoxin B1 treatment also demonstrated the requirement of non-quiescent liver for effective transformation. Tumors from these models with various etiologies resemble human HCCs histologically and at the molecular level. Extensive molecular characterization revealed the presence of an 11-gene HCC-expression signature that was able to discern transformed human hepatocytes from primary cells, regardless of etiology, and from other cancer types. Moreover, distinct molecular pathways appear to be deregulated by various etiological agents en route to formation of HCCs, in which common pathways converge, highlighting the existence of etiology-specific as well as common HCC-specific molecular perturbations. This study therefore highlights the utility of these mouse models, which provide a rich resource for the longitudinal analysis of molecular changes and biomarkers associated with HCC that could be exploited further for therapeutic targeting.

A major shift of viral and nutritional risk factors affects the hepatocellular carcinoma risk among Ivorian patients: a preliminary report

Hepatocellular carcinoma (HCC) is a major public health concern in Sub-Saharan Africa. Early research in Ivory Coast showed that chronic hepatitis B and aflatoxin B1 exposure were the two most important etiological agents of HCC in the country but, surprisingly, no survey analyzing HCC etiologies has been conducted since decades. In a preliminary report, we characterized for hepatitis B and C markers 30 consecutive cases of HCC recruited from Abidjan hospitals between June 2011 and December 2012. Nutritional and lifestyle features of patients were analyzed as well. The mean age of the patients was 53 ± 15 years with a sex ratio (M:F = 2.7). HBsAg was the most frequent viral marker in the series (63 %). All HBV isolates belonged to genotype E. With regards to regional standard, anti-HCV reached a very high level (47 %) in the present series. Hepatitis C was more frequent among patients living outside Abidjan (83 vs 23 %, P = 0.009). Patients living in Abidjan were significantly younger than individual living elsewhere in the country (48 ± 14 vs 60 ± 16 years old, P = 0.038) reflecting a possible role for local environmental pollution in tumor progression. Finally, we observed that patients born in Mandé/Gur-speaking regions (North) were younger (48 ± 14 vs 59 ± 15, P = 0.05) and consumed maize more frequently (80 vs 26 %, P = 0.009) than other patients. Interestingly, maize consumption was associated with a trend for aminotransferases elevation (mean = 1.7-1.8 fold, P = 0.06) suggesting a direct hepatic toxicity of this staple food in Ivory Coast. In conclusion, our work indicates that HCC epidemiology underwent recently major drifts in Ivory Coast.

Impact of aflatoxin B1 on hypothalamic neuropeptides regulating feeding behavior

The presence of mycotoxins in food is a major problem of public health as they produce immunosuppressive, hepatotoxic and neurotoxic effects. Mycotoxins also induce mutagenic and carcinogenic effects after long exposure. Among mycotoxins that contaminate food are aflatoxins (AF) such as AFB1, which is the most powerful natural carcinogen. The AF poisoning results in symptoms of depression, anorexia, diarrhea, jaundice or anemia that can lead to death, but very few studies have explored the impact of AF on neuroendocrine regulations. To better understand the neurotoxic effects of AF related to anorexia, we explored in rat the impact of AFB1 on the major hypothalamic neuropeptides regulating feeding behavior, either orexigenic (NPY, Orexin, AgRP, MCH) or anorexigenic (α-MSH, CART, TRH). We also studied the effect of AFB1 on a novel neuropeptide, the secretogranin II (SgII)-derived peptide EM66, which has recently been linked to the control of food intake. For this, adult male rats were orally treated twice a week for 5 weeks with a low dose (150 μg/kg) or a high dose (300 μg/kg) of AFB1 dissolved in corn oil. Repeated exposure to AFB1 resulted in reduced body weight gain, which was highly significant for the high dose of AF. Immunocytochemical and quantitative PCR experiments revealed a dose-related decrease in the expression of all the hypothalamic neuropeptides studied in response to AFB1. Such orexigenic and anorexigenic alterations may underlie appetite disorders as they are correlated to a dose-dependent decrease in body weight gain of treated rats as compared to controls. We also found a decrease in the number of EM66-containing neurons in the arcuate nucleus of AFB1-treated animals, which was associated with a lower expression of its precursor SgII. These findings show for the first time that repeated consumption of AFB1 disrupts the hypothalamic regulation of neuropeptides involved in feeding behavior, which may contribute to the lower body weight gain associated to AF exposure.

Aflatoxin B1 and aflatoxin M1 induced cytotoxicity and DNA damage in differentiated and undifferentiated Caco-2 cells

Aflatoxin B1 (AFB1) and aflatoxin M1 (AFM1) are natural mycotoxins that frequently present in food and feed and pose risks to human health. There are few data in the literature regarding the impairment of them in the intestine. Therefore, the present study investigated their cytotoxic effect on Caco-2 cells, especially the differentiated ones that resemble mature small intestinal enterocytes. Both undifferentiated (UC) and differentiated (DC) cells were treated with AFB1 and AFM1 at various concentrations for up to 72 h. Cell viability, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) production and DNA damage were determined. Data showed that AFB1 and AFM1 significantly inhibited UC and DC cell growth, increased LDH and caused genetic damage in a time- and dose-dependent manner (p < 0.05). In comparison, AFB1 was found to be more toxic than AFM1 on both UC and DC. All these cytotoxic outcomes might be associated with intracellular ROS generation, leading to membrane damage and DNA strand break. Additionally, DC was found to be more sensitive to aflatoxins, which might be due to the alteration of enzymes during cell differentiation. The present study provided the first in vitro evidence of DNA damage of DC induced by AFB1 and AFM1.

Aflatoxin B1 degradation during co-cultivation of Aspergillus flavus and Pleurotus ostreatus strains on rice straw

Aflatoxin B1 (AFB1) produced by Aspergillus flavus is known to have carcinogenic and teratogenic effects on animal health. Accidental feeding of AFB1-contaminated rice straw may be detrimental to dairy cattle. White-rot basidiomycetous fungus Pleurotus ostreatus can grow on different agronomic wastes by synthesizing different ligninolytic enzymes. These extracellular enzymes are capable of degrading many environmentally hazardous compounds including AFB1. The present study examines the ability of different strains of P. ostreatus to degrade AFB1 in contaminated rice straw. Different strains of A. flavus were inoculated on rice straw for AFB1 production. The moldy straw was then subjected to co-cultivation by different strains of P. ostreatus. The extent of AFB1 degradation was determined by high performance liquid chromatography. Results indicated the presence of AFB1 in the moldy straw samples at levels of 27.95 ± 0.23 and 21.26 ± 0.55 µg/g of dry substrate for A. flavus MTCC 2798 and A. flavus GHBF09, respectively. Co-cultivation of P. ostreatus strains on AFB1-contaminated rice straw revealed their ability to rapidly colonize the substrate by profuse hyphal ramification. Highest degradation of AFB1 (89.41 %) was recorded in the straw containing co-cultures of A. flavus MTCC 2798 and P. ostreatus GHBBF10. Natural isolate P. ostreatus GHBBF10 demonstrated higher AFB1-degradation potential than P.ostreatus MTCC 142. This basidiomycete strain can be further exploited to effectively degrade moderate concentrations of AFB1 in contaminated moldy rice straw.

Protective effect of curcumin against experimentally induced aflatoxicosis on the renal cortex of adult male albino rats: a histological and immunohisochemical study

BACKGROUND

Aflatoxin contamination of foods is a worldwide problem. Chronic aflatoxin exposure is associated with kidney damage. Curcumin is a herbal agent, used in medicine with a wide range of beneficial therapeutic effects.

OBJECTIVE

to evaluate the effect of curcumin against experimentally induced aflatoxicosis on the renal cortex of adult male albino rats.

MATERIALS AND METHODS

Forty adult male rats were included and they were divided equally into 4 groups (10 rats each): Group I (control group), group II (Curcumin group): The rats received curcumin (200 mg/kg b.w.) orally by gastric tube for 5 days/week, group III (Aflatoxin B1 group): The rats received aflatoxin B1 (250 μg/kg b.w./day) orally by gastric tube 5 days/week for 4 weeks, group IV (Aflatoxin B1 and Curcumin group): The rats received aflatoxin and curcumin orally by gastric tube 5 days/week for 4 weeks. Kidney specimens were prepared and sections were stained with hematoxylin and eosin, Masson's trichrome, Periodic acid Schiff, immunohistochemical detection of desmin and Bcl2.

RESULTS

The tubules of group III showed degenerative and necrotic changes with disruption of basal lamina. There was a significant decrease Bcl2 expression in the tubules, but the glomeruli showed an enlargement with dilation of their capillaries lumina in some areas, while the other areas showed glomerular atrophy with obliteration of their capillaries lumina. There was a significant increase in desmin expression in the glomerular cells. The interstitium showed hemorrhage and cellular infiltration. Group IV showed improvement of the histological and immunohistochemical changes described before.

CONCLUSION

Aflatoxin B1 has deleterious effects of on the histological structure of the rat's renal cortex and curcumin minimized these effects as it has antioxidant, anti-inflammatory and antiapoptotic activities. We advise eating nutritious diets that contain sufficient amounts of curcumin and regulation must implement to avoid the presence of aflatoxins in high concentrations in human food.

Aflatoxin B1 augments the synthesis of corticotropin releasing hormone in JEG-3 placental cells

Aflatoxins pose a major threat to food safety. These toxins are classified as hepatocarcinogens; however, their effect on the other tissues is unclear. During pregnancy, the fetus and placental tissues are especially sensitive to toxin exposure. In the present study aflatoxin B1 was found to induce the mRNA expression of corticotrophin-releasing hormone (CRH) in placental cells. A corresponding increase in CRH peptide in the culture medium was also observed. Since signal transduction pathways have been described previously in the control of CRH transcription, the status of protein kinase Cs (PKCs) and mitogen-activated protein kinases (MAPKs) were determined by Western analysis. In the aflatoxin B1-treated cultures, PKC α/βII/δ and ERK-1/2 were activated. As the PKC inhibitor bisindolylmaleimide I and the ERK inhibitor PD98059 could revert the induced CRH expression, the pathways dictated by PKC and ERK were likely involved in the transcriptional regulation. Electrophoretic mobility shift assay showed that C/EBP could be the ultimate activated transcription factor. Taken together, this study demonstrated that aflatoxin B1 could increase the parturition-related placental hormone in vitro. These findings might have significant implications for public health.

Chitosan nanoparticles and quercetin modulate gene expression and prevent the genotoxicity of aflatoxin B1 in rat liver

The aims of the current study were to prepare chitosan nanoparticles (CNPs) and to evaluate its protective role alone or in combination with quercetin (Q) against AFB₁-induce cytotoxicity in rats. Male Sprague-Dawley rats were divided into 12 groups and treated orally for 4 weeks as follow: the control group, the group treated with AFB₁ (80 μg/kg b.w.) in corn oil, the groups treated with low (140 mg/kg b.w.) or high (280 mg/kg b.w.) dose of CNPs, the group treated with Q (50 mg/kg b.w.), the groups treated with Q plus the low or the high dose of CNPs and the groups treated with AFB₁ plus Q and/or CNPs at the two tested doses. The results also revealed that administration of AFB₁ resulted in a significant increase in serum cytokines, Procollagen III, Nitric Oxide, lipid peroxidation and DNA fragmentation accompanied with a significant decrease in GPx I and Cu–Zn SOD-mRNA gene expression. Q and/or CNPs at the two tested doses overcome these effects especially in the group treated with the high dose of CNPs plus Q. It could be concluded that CNPs is a promise candidate as drug delivery enhances the protective effect of Q against the cytogenetic effects of AFB₁ in high endemic areas.

Quality evaluation of five commercial enzyme linked immunosorbent assay kits for detecting aflatoxin b1 in feedstuffs

The objective of this study was to evaluate the quality of five commercial enzyme linked immunosorbent assay (ELISA) kits (A, B, C, D, and E) from different suppliers for detecting aflatoxin B₁ (AFB₁). AFB₁-free corn samples supplemented with different levels of AFB₁ (5, 10, and 20 μg/kg) were used as positive controls and 6 replicates of each control sample were tested to evaluate the accuracy and precision of these kits. In addition, we also evaluated the performance of these ELISA kits for AFB₁ in 30 feed samples, including corn, distillers dried grains with soluble, wheat samples, soybean meal, and poultry feed, which were verified by high performance liquid chromatography. Results showed that the coefficients of variation ranged from 1.18% to 16.22% in intra-plate and 2.85% to 18.04% in inter-plate for the determination of AFB₁. The half maximal inhibitory concentration for five kits ranged from 3.72 to 7.22 μg/kg. The quantitation limits of AFB₁ were all under the legal limit in China but somewhat inconsistent with kit instructions. Although the recovery rate of four of the five kits were either less than 90% or more than 110%, all these values were acceptable in practice. Two kits had high false positive rates (C and E). In conclusion, our results revealed that the qualities of five tested ELISA kits were significantly different.

Influence of aflatoxin B1 on copy number variants in human leukocytes in vitro

BACKGROUND

Aflatoxin B1 (AFB1) is a mycotoxin produced by Aspergillus spec. The latter are worldwide contaminants of food with mutagenic and carcinogenic activities in animals and humans. AFB1 was shown to have deleterious effects on metabolism of eukaryotes in many model systems, including the ability to inhibit DNA replication. An agent that disturbs DNA replication may also have the potential to induce de novo DNA copy number variations (CNVs).

RESULTS

Blood samples of three clinically healthy carriers were treated in vitro with AFB1 and chromosome preparations were subjected to parental origin determination fluorescence in situ hybridization (pod-FISH). Probes able to visualize CNVs in 8p21.2 and 15q11.2 were applied. In this setting here for the first time an influence of AFB1 on molecular-cytogenetically detectable CNVs could be shown.

CONCLUSIONS

The obtained results indicate that: (i) pod-FISH is a single cell directed, sensitive and suitable method for the analysis of mutagen induced CNVs, (ii) AFB1 has the potential to induce in vitro instability of known CNVs in human leukocytes.

Challenging Role of Dietary Aflatoxin B1 Exposure and Hepatitis B Infection on Risk of Hepatocellular Carcinoma

Aflatoxins (AFT) are poisonous substances which are classified in Group 1 carcinogenic agents to humans by International Agency for Research on Cancer (IARC). AFT can occur naturally in food commodities (maize, corn, rice) as a result of fungal contamination in hot and humid environments. In the food, toxin contamination can remain during manufacturing and long after fungi have stopped being biologically active. Aflatoxin B1 (AFB1) is the most dominant and potent agent from all AFT. In developing countries, high exposure to AFB1 can cause chronic toxicity and usually increases the incidence of Hepatocellular Carcinoma (HCC). However, in these regions hepatitis B is the most common risk factor for HCC cases. Many researches were aimed to enlighten the mechanism and the role of two etiological agents on risk of HCC, but the obtained data was conflicting with each other. It was uncertain that the indicators/biomarkers might be the contribution of the carcinogenic status of the patient; and, the biomarker samples from the subject may only reflect the recent effects of the toxin exposure after consumption of AFB1 contaminated commodities. The studies were facing with the errors of methods which were un-fit to enlighten the possible interaction between Hepatitis B and AFB1 on contribution to HCC. It was pivotal to understand the effect of each risk factor in order to prevent and improve public health in poor and undeveloped regions. Although some of the studies evaluate AFB1 alone as a considerable factor on HCC risk, according to this review it was concluded vice versa. This study was aimed to clarify the main etiological agent of HCC where AFB1 and HBV are endangering public health. In additionally, the purpose was to enlighten the possible synergistic effect between these two factors among HCC pathogenesis. Hence forth, appropriate and right applications could be conducted in undeveloped countries in order to protect public health.

Highly sensitive SERS-based immunoassay of aflatoxin B1 using silica-encapsulated hollow gold nanoparticles

Aflatoxin B1 (AFB1) is a well-known carcinogenic contaminant in foods. It is classified as an extremely hazardous compound because of its potential toxicity to the human nervous system. AFB1 has also been extensively used as a biochemical marker to evaluate the degree of food spoilage. In this study, a novel surface-enhanced Raman scattering (SERS)-based immunoassay platform using silica-encapsulated hollow gold nanoparticles (SEHGNs) and magnetic beads was developed for highly sensitive detection of AFB1. SEHGNs were used as highly stable SERS-encoding nano tags, and magnetic beads were used as supporting substrates for the high-density loading of immunocomplexes. Quantitative analysis of AFB1 was performed by monitoring the intensity change of the characteristic peaks of Raman reporter molecules. The limit of detection (LOD) of AFB1, determined by this SERS-based immunoassay, was determined to be 0.1 ng/mL. This method has some advantages over other analytical methods with respect to rapid analysis (less than 30 min), good selectivity, and reproducibility. The proposed method is expected to be a new analytical tool for the trace analysis of various mycotoxins.

Aflatoxin B1 Degradation by Metabolites of Phoma glomerata PG41 Isolated From Natural Substrate Colonized by Aflatoxigenic Aspergillus flavus

Background:

Aflatoxin B1 (AFB1), produced by Aspergillus flavus, is one of the most life threatening food contaminants causing significant economic losses worldwide. Biological AFB1 degradation by microorganisms, or preferably microbial enzymes, is considered as one of the most promising approaches.

Objectives:

The current work aimed to study the AFB1-degrading metabolites, produced by Phoma glomerata PG41, sharing a natural substrate with aflatoxigenic A. flavus, and the preliminary determination of the nature of these metabolites.

Materials and Methods:

The AFB1-degrading potential of PG41 metabolites was determined by a quantitative high performance liquid chromatography (HPLC) of residual AFB1 after 72 hours incubation at 27ºC. The effects of pH, heat, and protease treatment on the AFB1-destroying activity of extracellular metabolites were examined.

Results:

The AFB1-degrading activity of protein-enriched fractions, isolated from culture liquid filtrate and cell-free extract, is associated with high-molecular-weight components, is time- and pH-dependent, thermolabile, and is significantly reduced by proteinase K treatment. The AFB1 degradation efficiency of these fractions reaches 78% and 66%, respectively.

Conclusions:

Phomaglomerata PG41 strain sharing natural substrate with toxigenic A. flavus secretes metabolites possessing a significant aflatoxin-degrading activity. The activity is associated mainly with a protein-enriched high-molecular-weight fraction of extracellular metabolites and appears to be of enzymatic origin.

Genotoxicity of Aflatoxin B1 and Ochratoxin A after simultaneous application of the in vivo micronucleus and comet assay

Aflatoxin B1 (AFB1) and Ochratoxin A (OTA) are genotoxic mycotoxins that can contaminate a variety of foodstuffs, the liver and the kidney being their target organs, respectively. The micronucleus (MN) assay (bone marrow) and the comet assay (liver and kidney) were performed simultaneously in F344 rats, treated with AFB1 (0.25 mg/kg b.w.), OTA (0.5 mg/kg b.w.) or both mycotoxins. After AFB1 treatment, histopathology and biochemistry analysis showed liver necrosis, focal inflammation and an increase in Alanine Aminotransferase and Aspartate Aminotransferase. OTA alone did not cause any alteration. The acute hepatotoxic effects caused by AFB1 were less pronounced in animals treated with both mycotoxins. With regard to the MN assay, after 24 h, positive results were obtained for AFB1 and negative results were obtained for OTA, although both toxins caused bone marrow toxicity. In the combined treatment, OTA reduced the toxicity and the number of MN produced by AFB1. In the comet assay, after 3 h, positive results were obtained for AFB1 in the liver and for OTA in the kidney. The combined treatment reduced DNA damage in the liver and had no influence in the kidney. Altogether, these results may be indicative of an antagonistic relationship regarding the genotoxicity of both mycotoxins.

Toxicity of aflatoxin B1 towards the vitamin D receptor (VDR)

This research describes an unexpected toxicity of the aflatoxin B1 towards the vitamin D receptors. Rickets is a childhood disease, and calcium deficiency is the aetiological cause in Africa, being primarily associated with nutritional problems; in this research the contribution of aflatoxin B1 exposure during the early months of life is an interesting factor to deepen in order to prevent liver damages or the development of rickets. The results show that the expression of vitamin D receptor in osteosarcoma cell line SAOS-2 is significantly down-modulated by exposure to aflatoxin B1. This seems to suggest that Aflatoxin B1, toxic towards the vitamin D receptor, interferes with the actions of the vitamin D on calcium binding gene expression in the kidney and intestine. Experimental data indicate a 58% and 86% decrease if the cells are exposed to 5 ng/mL and 50 ng/mL of aflatoxin B1, respectively. These results seem to indicate that natural occurrence of the aflatoxin B1 and allelic variant of vitamin D receptor on (F allele) increase the risk of developing rickets of African children.

Ability of Lactobacillus plantarum MON03 to mitigate aflatoxins (B1 and M1) immunotoxicities in mice

Aflatoxin B1 (AFB1) and M1 (AFM1) are mycotoxins produced by numerous Aspergillus species in pre- or post-harvest cereals and milk. AFB1 and AFM1 display a potent economic loss in livestock and also cause severe immunological problems. The aims of this study were to: evaluate a new AFB1 and AFM1-binding/degrading micro-organism for biological detoxification; examine its ability to degrade AFB1 and AFM1 in liquid medium; and evaluate its potential for in vivo preventative effects against AFB1- and AFM1-induced immunomodulation in mice. Lactobacillus plantarum MON03 (LP) isolated from Tunisian artisanal butter was found to display significant binding ability to AFB1 and AFM1 in PBS (i.e. 82% and 89%, respectively) within 24 h of incubation and able to tolerate gastric acidity, have strongly hydrophilic cells surface properties, and adhere efficacy to Caco-3 cells in vitro. The in vivo study was conducted using Balb/c mice that received by oral gavage vehicle (control), LP only (2 × 10(9) CFU/L, ~2 g/kg BW), AFB1 or AFM1 alone (0.25 and 0.27 mg/kg, respectively), or AFB1 + LP or AFM1 + LP daily for 15 days. Compared to in control mice, treatments with AFB1 and AFM1 led to significantly decreased body weight gains, histopathological changes, and decrements in all hematologic and immune parameters assessed. Co-treatment with LP strongly reduced the adverse effects of each mycotoxin. In fact, the mice receiving AFB1 + LP or AFM1 + LP co-treatment displayed no significant differences in the assayed parameters as compared to the control mice. By itself, the bacteria alone had no adverse effects in the mice. From these data, it is concluded that the tested bacteria could be beneficial in biotechnology detoxification of contaminated food and feed for humans and animals.

Proapoptotic activity of aflatoxin B1 and sterigmatocystin in HepG2 cells

Aflatoxin B1 (AFB1) and sterigmatocystin (ST) are two hepatocarcinogenic mycotoxins that are commonly coexisted in cereal grains, and their co-proapoptotic activity in HepG2 cells was studied. The values of IC50, which is the dosage of mycotoxin resulting in a 50% cell growth inhibition measured by a sulforhodamine B (SRB) colorimetric assay, were 16.9 μM and 7.3 μM for AFB1 and ST, respectively. Additively and dose-dependently, cell apoptosis-related toxicity endpoints of double strand DNA and ATP content were decreased while the intracellular ROS and mitochondria membrane permeability (MMP) were increased. Consistently, when cell cycle is arrest at G0/G1 or S phase by AFB1 and/or ST, the experimental results from flow cytometry assay demonstrated that the rate of cell apoptosis and mitochondrial membrane potential were also additively increased and decreased, respectively, in a dose-dependent manner. Thus, the integrity of mitochondria (MMP and membrane potential) that is the central component of cell apoptosis is disrupted by AFB1 and ST in an additive manner. With the immunocytochemistry analysis showing increased expression of apoptosis-related proteins of Bax, Caspase-3 and p53 and decreased expression of Bcl-2 protein, an additive nature of the co-proapoptotic activity of AFB1 and ST was revealed.

Prenatal exposure of mice to the human liver carcinogen aflatoxin B1 reveals a critical window of susceptibility to genetic change

It has become axiomatic that critical windows of susceptibility to genotoxins exist and that genetic damage in utero may be a trigger for later life cancers. Data supporting this critical window hypothesis are remarkably few. This study provides a quantitative bridge between DNA damage by the liver carcinogen aflatoxin B1 (AFB1 ) during prenatal development and the risk of later life genetic disease. AFB1 was given to pregnant C57BL/6J mice, carrying F1 gestation day 14 (GD14) embryos of the B6C3F1 genotype. Ultra-high performance liquid chromatography and mass spectrometry (UPLC-MS) using aflatoxin-(15) N5 -guanine adduct standards afforded measurement of the AFB1 -N(7) -Gua and AFB1 -FAPY adducts 6-hr post dosing in liver DNA of mothers and embryos. A parallel cohort gave birth and the livers of the F1 were analyzed for mutations in the gpt gene at 3 and 10 weeks of age. The data revealed mutational spectra dominated by G:C to T:A mutations in both the mother and offspring that are characteristic of AFB1 and distinct from background. It was shown that adducts in GD14 embryos were 20-fold more potent inducers of mutagenesis than adducts in parallel-dosed adults. This sensitivity enhancement correlated with Ki67 staining of the liver, reflecting the proliferative potential of the tissue. Taken together, these data provide insight into the relative genetic risks of prenatal and adult exposures to AFB1 . Early life exposure, especially during the embryonic period, is strikingly more mutagenic than treatment later in life. Moreover the data provide a baseline against which risk prevention strategies can be evaluated.

An aptamer-based dipstick assay for the rapid and simple detection of aflatoxin B1

A rapid and simple dipstick assay based on an aptamer has been developed for the determination of aflatoxin B1 (AFB1). The dipstick assay format was based on a competitive reaction of the biotin-modified aptamer specific to AFB1 between target and cy5-modified DNA probes. Streptavidin and anti-cy5 antibody as capture reagents were immobilized at test and control lines on a membrane of the dipstick assay. After optimization, the limit of detection for the dipstick assay was 0.1 ng/ml AFB1 in buffer. The method was confirmed to be specific to AFB1, and the entire process of the assay can be completed within 30 min. Aqueous methanol (20%) provided a good extraction efficiency, and the matrix influence from corn extracts was successfully reduced through 2-fold dilution. The results of AFB1 analysis for corn samples spiked with known concentration of AFB1 by the dipstick assay and ELISA showed good agreement. The cut-off value of the dipstick assay for corn samples was 0.3 ng/g AFB1. Therefore, the dipstick assay is first reported and considered as a rapid, simple, on-site and inexpensive screening tool for AFB1 determination in grains as well as a corn.

Efficacy of Angelica archangelica essential oil, phenyl ethyl alcohol and α- terpineol against isolated molds from walnut and their antiaflatoxigenic and antioxidant activity

Mold association, aflatoxin B1 contamination as well as oxidative deterioration of agri-food items during storage and processing are some global task for food industries. In view of the adverse effects of some synthetic preservatives on treated food items and subsequently on consumers health, recently plant based chemicals are encouraged by food industries as better alternatives of synthetics. The present study recommends the combination (1:1:1) of Angelica archangelica essential oil: Phenyl ethyl alcohol (PEA): α- terpineol as botanical preservative against molds, aflatoxin contamination and oxidative deterioration of walnut samples. Eight mold species were procured from stored walnut samples, including some aflatoxigenic Aspergillus flavus strains. The combination inhibited growth of aflatoxigenic strain Aspergillus flavus NKDW-7 and aflatoxin B1 production at 2.25 and 2.0 μL mL(-1) respectively. The IC50 value of the combination was recorded as 3.89 μL mL(-1), showing strong antioxidant potential. The antifungal action of the combination showed > 90 % decrease in ergosterol content in plasma membrane of A. flavus at 2.0 μL mL(-1). The LD50 of the combination, through oral administration on mice, was 9562.9 μL kg(-1) body weight, indication favourable safety profile as a plant based preservative. The combination may be recommended as safe preservative against molds, aflatoxin contamination and oxidative deterioration of walnut samples.

The cytotoxicity of aflatoxin b1 in human lymphocytes

OBJECTIVES

Aflatoxin B1 (AFB1) is a naturally occurring carcinogenic and immunosuppressive compound. This study was designed to measure its toxic effects on human peripheral blood mononuclear cells (PBMC).

METHODS

The study recruited 7 healthy volunteers. PBMC were isolated and cellular respiration was monitored using a phosphorescence oxygen analyser. The intracellular caspase activity was measured by the caspase-3 substrate N-acetyl-asp-glu-val-asp-7-amino-4-methylcoumarin. Phosphatidylserine exposure and membrane permeability to propidium iodide (PI) were measured by flow cytometry.

RESULTS

Cellular oxygen consumption was inhibited by 2.5 μM and 25 μM of AFB1. Intracellular caspase activity was noted after two hours of incubation with 100 μM of AFB1. The number of Annexin V-positive cells increased as a function of AFB1 concentration and incubation time. At 50 μM, a significant number of cells became necrotic after 24 hours (Annexin V-positive and PI-positive).

CONCLUSION

The results show AFB1 is toxic to human lymphocytes and that its cytotoxicity is mediated by apoptosis and necrosis.

Genome-wide miRNA-profiling of aflatoxin B1-induced hepatic injury using deep sequencing

Aflatoxin B1 is a potent carcinogen which can induce** hepatocellular carcinoma (HCC) in mammals. Though microRNAs are known to play important roles in tumorigenesis, the functional complexity of microRNAs in AFB1-induced hepatocellular tumorigenesis has not yet been elucidated. Here, we applied Illumina deep sequencing technology for high-throughput profiling of microRNA in rat liver tissue before and after treatment with aflatoxin B1. Analysis of mature miRNAs from different arms of pre-miRNAs allowed us to identify the predominant form of miRNA. We studied the differential expression profile of miRNAs in two libraries, identifying several cancer-related microRNAs which exhibit abnormal expression. KEGG analysis indicated that predicted target genes of differentially expressed miRNAs are involved in cancer-related pathways. Bioinformatic analysis predicted 16 potential novel miRNAs. Our work provides new insights at the miRNA level into AFB1-induced hepatic injury which may lead to HCC.

Evaluation of STAT5A Gene Expression in Aflatoxin B1 Treated Bovine Mammary Epithelial Cells

PURPOSE

Aflatoxin B1 (AFB1) is a potent mycotoxin which has been produced by fungi such as Aspergillus flavus and Aspergillus parasiticus as secondary metabolites due to their growth on food stuffs and induces hepatocellular carcinoma in many animal species, including humans. In the present study, the effect of AFB1 on STAT5A gene expression was investigated in bovine mammary epithelial cells using real time RT-PCR.

METHODS

Bovine mammary epithelial cells were seeded in a 24-well culture plate for three-dimensional (3D) culture in Matrigel matrix. After 21 days of 3D culture and reaching the required number of cells, cells were treated with AFB1 and incubated for 8 h. For real time PCR reaction, total RNA from the cultured and treated cells was extracted and used for complementary DNA synthesis.

RESULTS

The expression of STAT5A gene was significantly down regulated by AFB1 in dose- dependent manner and led to the reduction of proliferation and differentiation of epithelial cells, which has direct effect in milk protein quantity and quality.

CONCLUSION

According to the results, it seems that down regulation of STAT5A gene in AFB1-treated cells maybe due to DNA damage induced by AFB1 in bovine mammary epithelial cells.

Production of Group Specific Monoclonal Antibody to Aflatoxins and its Application to Enzyme-linked Immunosorbent Assay

Through the present study, we produced a monoclonal antibody against aflatoxin B1 (AFB1) using AFB1- carboxymethoxylamine BSA conjugates. One clone showing high binding ability was selected and it was applied to develop a direct competitive ELISA system. The epitope densities of AFB1-CMO against BSA and KLH were about 1 : 6 and 1 : 545, respectively. The monoclonal antibody (mAb) from cloned hybridoma cell was the IgG1 subclass with λ-type light chains. The IC50s of the monoclonal antibody developed for AFB1, AFB2, AFG1 and AFG2 were 4.36, 7.22, 6.61 and 29.41 ng/ml, respectively, based on the AFB1-KLH coated ELISA system and 15.28, 26.62, 32.75 and 56.67 ng/ml, respectively, based on the mAb coated ELISA. Cross-relativities of mAb to AFB1 for AFB2, AFG1 and AFG2 were 60.47, 65.97 and 14.83% in the AFB1-KLH coated ELISA, and 59.41, 46.66 and 26.97% in the mAb coated ELISA, respectively. Quantitative calculations for AFB1 from the AFB1-Ab ELISA and AFB1-Ag ELISA ranged from 0.25 to 25 ng/ml (R(2) > 0.99) and from 1 to 100 ng/ml (R(2) > 0.99), respectively. The intra- and inter-assay precision CVs were < 10% in both ELISA assay, representing good reproducibility of developed assay. Recoveries ranged from 79.18 to 91.27%, CVs ranged from 3.21 to 7.97% after spiking AFB1 at concentrations ranging from 5 to 50 ng/ml and following by extraction with 70% methanol solution in the Ab-coated ELISA. In conclusion, we produced a group specific mAb against aflatoxins and developed two direct competitive ELISAs for the detection of AFB1 in feeds based on a monoclonal antibody developed.

Effects of aflatoxin B1 on oxidative stress markers and apoptosis of spleens in broilers

The purpose of the present study was to investigate the oxidative damage and apoptosis induced by aflatoxin B1 (AFB1) in spleen of broilers. A total of 200 one-day-old avian male broilers were randomly divided into 4 equal groups of 50 each and were fed for 21 days as follows: a control diet and three AFB1 diets containing 0.15, 0.3, and 0.6 mg AFB1/kg diet. Consumption of AFB1 diets induced oxidative stress in the spleen of chicken as evidenced by reduced glutathione peroxidase, glutathione reductase, and catalase activities, decreased glutathione contents, and increased malondialdehyde contents in explaining the pathogenesis. Flow cytometer method and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling assay revealed that the apoptotic splenocytes were increased in AFB1 groups. The results suggest that AFB1 induced excessive apoptosis of splenic lymphocytes, which is correlated with increased oxidative stress. The present results may be helpful for explaining the pathogenesis of AFB1-induced immunosuppression.

Hepatitis B virus X antigen and aflatoxin B1 synergistically cause hepatitis, steatosis and liver hyperplasia in transgenic zebrafish

Aflatoxin B1 (AFB1) and the hepatitis B virus X antigen (HBx) are linked to the formation of liver diseases and hepatocellular carcinoma (HCC). The aim of this study was to investigate the synergistic effects between HBx and AFB1 in causing liver disorders using a transgenic zebrafish animal model. Histopathology, Periodic acid-Schiff (PAS) staining, Sirius red staining, TdT-mediated dUTP Nick End Labeling (TUNEL) assay, immunohistochemistry, and quantitative reverse transcriptase-polymerase chain reaction (Q-RT-PCR) were used to examine the livers of the HBx transgenic fish injected with AFB1. We found that HBx and AFB1 synergistically promoted steatosis as indicated by histopathological examinations and the increased expression of lipogenic factors, enzymes, and genes related to lipid metabolism. Moreover, treatment of AFB1 in HBx transgenic fish accelerated the development of liver hyperplasia and enhanced the expression of cell cycle related genes. PCNA was co-localized with active caspase 3 protein expression in HBx zebrafish liver samples and human HBV positive HCC samples by double fluorescence immunostaining. Finally, we found that in human patients with liver disease, significant glycogen accumulated in the inflammation, cirrhosis stage, and all cases of hepatocellular and cholangiocellular carcinoma showed a moderate cytoplasmic accumulation of glycogen. Our data demonstrated a synergistic effect of AFB1 and HBx on the regulation of lipid metabolism related genes and cell cycle/division-related genes which might contribute to enhanced steatosis and hyperplasia at 5.75months.

Analysis of the contrast between natural occurrence of toxigenic Aspergilli of the Flavi section and aflatoxin B1 in cassava

Aflatoxin B1 (AFB1) is a carcinogenic mycotoxin produced by Aspergilli of the section Flavi that may contaminate food, in the field or during storage. Cassava represents an important staple food in sub-Saharan Africa. The analysis of aflatoxigenic fungi in 36 cassava samples obtained from producers in Benin indicated that 40% were contaminated by Aspergilli of the section Flavi. Upon morphological and molecular characterization of the 20 isolates, 16 belonged to Aspergillus flavus, 2 to Aspergillus parvisclerotigenus and 2 to Aspergillus novoparasiticus. This is the first time that this latter species is isolated from food. Although most of these isolates were toxigenic on synthetic media, no AFB1 contamination was observed in these cassava samples. In order to determine the action of cassava on AFB1 synthesis, a highly toxigenic strain of A. flavus, was inoculated onto fresh cassava and despite a rapid development, no AFB1 was produced. The anti-aflatoxin property was observed with cassava from different geographical origins and on other aflatoxigenic strains of the section Flavi, but it was lost after heating, sun drying and freezing. Our data suggest that fresh cassava is safe regarding AFB1 contamination, however, processing may alter its ability to block toxinogenesis leading to secondary contamination.

In vitro investigation of individual and combined cytotoxic effects of aflatoxin B1 and other selected mycotoxins on the cell line porcine kidney 15

In the present study, we evaluated the nephrotoxicity of individual mycotoxins and combinations of aflatoxin B1 (AFB1), zearalenone (ZEA), deoxynivalenol (DON), and fumonisin B1 (FB1) to livestock using porcine kidney 15 cells (PK-15) as a disease model via biochemical approaches. The toxicity of individual mycotoxins on cell viability and cell membrane damage was determined using the MTT and lactate dehydrogenase (LDH) assays, respectively. Individual cytotoxicity of mycotoxins in increasing order were FB1<ZEA<AFB1<DON. The MTT results of central composite design (CCD) showed synergetic effects after co-exposure of AFB1+ZEA or AFB1+DON; however, AFB1 and ZEA showed antagonistic effects in the ternary mixtures. AFB1 and DON significantly induced ROS production and apoptosis in a concentration-dependent manner, but ZEA (10-40μM) had no effect on cell apoptosis and only slightly induced ROS production. ZEA ameliorated the ROS production caused by 1μM AFB1; however, ZEA and DON displayed synergistic effects in combination with AFB1 at 5 and 10μM. The existence of 10μM ZEA attenuated AFB1-induced apoptosis. In conclusion, AFB1+ZEA or DON showed synergetic effects on cytotoxicity. Low levels of AFB1 were antagonistic to ZEA, but high doses of AFB1 displayed synergistic effects with ZEA or DON on oxidative damage. ZEA also ameliorated AFB1-induced apoptosis. Generally, the combined effects of mycotoxins acted in a concentration-dependent manner.

Synergistic effect of black tea and curcumin in improving the hepatotoxicity induced by aflatoxin B1 in rats

Aflatoxin B1 (AFB1) is a toxic compound commonly found as a contaminant in human food. It is carcinogenic due its potential in inducing the oxidative stress and distortion of the most antioxidant enzymes. Since black tea possesses strong antioxidant activity, it protects cells and tissues against oxidative stress. Curcumin (CMN), a naturally occurring agent, has a combination of biological and pharmacological properties that include antioxidant activity. Therefore, the present study was carried out to investigate the possible role of separate and mixed supplementation of black tea extract and CMN in the hepatotoxicity induced by AFB1 in rats. A total of 48: adult male Sprague Dawley rats were randomly divided into eight groups with six rats in each group. Group 1 (normal control) includes rats that received no treatment. Groups 2, 3, and 4 (positive control) include rats that received olive oil, black tea extract, and CMN, respectively. Group 5 includes rats that received AFB1 at a dose of 750 μg/kg body weight (b.w.) dissolved in olive oil. Groups 6, 7, and 8 include rats that received AFB1 along with 2% black tea extract, CMN at a dose of 200 mg/kg b.w., and both black tea extract and CMN at the same previous doses, respectively. After 90 days, biochemical and histopathological examination was carried out for the blood samples and liver tissues. A significant decrease in the antioxidant enzymes and a significant increase in the lipid peroxidation and hydrogen peroxide in the rats treated with AFB1 were observed. Moreover, there were dramatic changes in the liver function biomarkers, lipid profile, and liver architecture. Supplementation of black tea extract or CMN showed an efficient role in repairing the distortion of the biochemical and histological changes induced by AFB1 in liver. This improvement was more pronounced when both CMN and black tea were used together.

Effect of Aflatoxin B1 on Growth of Bovine Mammary Epithelial Cells in 3D and Monolayer Culture System

PURPOSE

Many studies have been showed transfer of aflatoxins, toxins produced by Aspergillus flvaus and Aspergillus parasiticus fungi, into milk. These toxins are transferred into the milk through digestive system by eating contaminated food. Due to the toxicity of these materials, it seems that it has side effects on the growth of mammary cells. Therefore, the present work aimed to investigate possible toxic effects of aflatoxin B1 (AFB1) on bovine mammary epithelial cells in monolayer and three-dimensional cultures.

METHODS

Specimens of the mammary tissue of bovine were sized out in size 2×2 cm in slaughterhouse. After disinfection and washing in sterile PBS, primary cell culture was performed by enzymatic digestion of tissue with collagenase. When proper numbers of cells were achieved in monolayer culture, cells were seeded in a 24-well culture plate for three-dimensional (3D) culture in Matrigel matrix. After 21 days of 3D culture and reaching the required number of cells, the concentrations of 15, 25 and 35 µL of AFB1 were added to the culture in quadruplicate and incubated for 8 hours. Cellular cytotoxicity was examined using standard colorimetric assay and finally, any change in the morphology of the cells was studied by microscopic technique.

RESULTS

Microscopic investigations showed necrosis of the AFB1-exposed cells compared to the control cells. Also, bovine mammary epithelial cells were significantly affected by AFB1 in dose and time dependent manner in cell viability assays.

CONCLUSION

According to the results, it seems that AFB1 can induce cytotoxicity and necrosis in bovine mammary epithelial cells.

Analysis of aflatoxin b1 in Iranian foods using HPLC and a monolithic column and estimation of its dietary intake

A high performance liquid chromatographic method was developed for determination of aflatoxin B1 (AFB1) in foods using a monolithic column with sample clean up on an immunoaffinity column. The method was validated for analysis of AFB1 in rice, bread, puffed corn snack, wheat flour and peanut samples. The average recoveries for AFB1 in different foods ranged from 94.4 to 102.5% with the coefficient of variation lower than 10% for all foods. Limit of detection was 0.01 ng/g. A survey of AFB1 was performed on 90 samples collected from Tehran retail market in June 2005. The results showed that none of the bread and wheat flour samples were contaminated with AFB1. The mean AFB1 levels in rice, puffed corn snack and peanut samples were 4.17, 0.11, and 1.97 ng/g, respectively. The level of contamination of 3 samples (one rice sample and two peanuts samples) to AFB1 was found to be higher than 5 ng/g. Although all food samples had mean concentration of AFB1 below the maximum tolerated level in Iran, the mean intake of AFB1 from rice was estimated 3.49 times higher than the guidance value of 1 ng AFB1/Kg body weight/day. Therefore, it is strongly recommended to monitor AFB1 in foods, especially in rice, in Iran. This is the first study on exposure assessment of Iranian population to AFB1.

Global hypomethylation in hepatocellular carcinoma and its relationship to aflatoxin B(1) exposure

AIM

To determine global DNA methylation in paired hepatocellular carcinoma (HCC) samples using several different assays and explore the correlations between hypomethylation and clinical parameters and biomarkers, including that of aflatoxin B(1) exposure.

METHODS

Using the radio labeled methyl acceptance assay as a measure of global hypomethylation, as well as two repetitive elements, including satellite 2 (Sat2) by MethyLight and long interspersed nucleotide elements (LINE1), by pyrosequencing.

RESULTS

By all three assays, mean methylation levels in tumor tissues were significantly lower than that in adjacent tissues. Methyl acceptance assay log (mean ± SD) disintegrations/min/ng DNA are 70.0 ± 54.8 and 32.4 ± 15.6, respectively, P = 0.040; percent methylation of Sat2 42.2 ± 55.1 and 117.9 ± 88.8, respectively, P < 0.0001 and percent methylation LINE1 48.6 ± 14.8 and 71.7 ± 1.4, respectively, P < 0.0001. Aflatoxin B(1)-albumin (AFB(1)-Alb) adducts, a measure of exposure to this dietary carcinogen, were inversely correlated with LINE1 methylation (r = -0.36, P = 0.034).

CONCLUSION

Consistent hypomethylation in tumor compared to adjacent tissue was found by the three different methods. AFB(1) exposure is associated with DNA global hypomethylation, suggesting that chemical carcinogens may influence epigenetic changes in humans.

Efficacy of aqueous garlic extract on growth, aflatoxin B1 production, and cyto-morphological aberrations of Aspergillus flavus, causing human ophthalmic infection: topical treatment of A. flavus keratitis

By using agar well diffusion assay, antifungal activity of aqueous extract prepared from Egyptian garlic (Allium sativum L.) was evaluated in vitro against two strains of Aspergillus flavus (OC1 and OC10) causing human ocular infection. The recorded minimum inhibitory concentration (MIC) for growth inhibition of both strains was 3.60 mg/ml. Aqueous garlic extract (AGE) was used in successive in vivo tests as an attempt to cure rabbit's fungal keratitis caused by A. flavus OC1. Findings showed that diluted preparation of AGE was effective topical antifungal agent and succeeded to cure severe A. flavus keratitis in a time course less than 10 days without any observable side effects. Microscopic examination showed that AGE induced deleterious cyto-morphological aberrations in A. flavus target cells. AGE applied to Czapek's broth via contact method was more effective on growth, spores and aflatoxin B1 production than AGE applied to the same broth at the same concentration via fumigation method.

Candida parapsilosis as a Potent Biocontrol Agent against Growth and Aflatoxin Production by Aspergillus Species

BACKGROUND

Aflatoxin contamination of food and feed stuff is a serious health problem and significant economic concerns. In the present study, the inhibitory effect of Candida parapsilosis IP1698 on mycelial growth and aflatoxin production in aflatoxigenic strains of Aspergillus species was investigated.

METHODS

Mycelial growth inhibitions of nine strains of aflatoxigenic and non-aflatoxigenic Aspergillus species in the presence of C. parapsilosis investigated by pour plate technique at different pH, temperature and time of incubation. Reduction of aflatoxin was evaluated in co-cultured fungi in yeast extract sucrose broth after seven days of incubation using HPLC method. The data were analyzed by SPSS 11.5.

RESULTS

The presence of the C. parapsilosis at different pH did not affect significantly the growth rate of Aspergillus isolates. On the other hand, temperature and time of incubation showed to be significantly effective when compared to controls without C. parapsilosis (P≤0.05). In aflatoxigenic strains, minimum percentage of reductions in total aflatoxin and B1, B2, G1, G2 fractions were 92.98, 92.54, 77.48, 54.54 and 72.22 and maximum percentage of reductions were 99.59, not detectable, 94.42, and not detectable in both G1 and G2, respectively.

CONCLUSION

C. parapsilosis might employ as a good biocontrol agent against growth and aflatoxin production by aflatoxigenic Aspergillus species.

Global hypomethylation in hepatocellular carcinoma and its relationship to aflatoxin B(1) exposure

AIM

To determine global DNA methylation in paired hepatocellular carcinoma (HCC) samples using several different assays and explore the correlations between hypomethylation and clinical parameters and biomarkers, including that of aflatoxin B(1) exposure.

METHODS

Using the radio labeled methyl acceptance assay as a measure of global hypomethylation, as well as two repetitive elements, including satellite 2 (Sat2) by MethyLight and long interspersed nucleotide elements (LINE1), by pyrosequencing.

RESULTS

By all three assays, mean methylation levels in tumor tissues were significantly lower than that in adjacent tissues. Methyl acceptance assay log (mean ± SD) disintegrations/min/ng DNA are 70.0 ± 54.8 and 32.4 ± 15.6, respectively, P = 0.040; percent methylation of Sat2 42.2 ± 55.1 and 117.9 ± 88.8, respectively, P < 0.0001 and percent methylation LINE1 48.6 ± 14.8 and 71.7 ± 1.4, respectively, P < 0.0001. Aflatoxin B(1)-albumin (AFB(1)-Alb) adducts, a measure of exposure to this dietary carcinogen, were inversely correlated with LINE1 methylation (r = -0.36, P = 0.034).

CONCLUSION

Consistent hypomethylation in tumor compared to adjacent tissue was found by the three different methods. AFB(1) exposure is associated with DNA global hypomethylation, suggesting that chemical carcinogens may influence epigenetic changes in humans.

Hepatocellular carcinoma in developing countries: Prevention, diagnosis and treatment

Hepatocellular carcinoma (HCC) occurs commonly and with increasing frequency in developing countries, where it also carries an especially grave prognosis. The major risk factor for HCC in these regions is chronic hepatitis B virus (HBV) infection, although dietary exposure to aflatoxin B1 also plays an important etiological role. Prevention of HCC in developing regions is unlikely in the foreseeable future. Although an effective vaccine against HBV is available, the percentage of babies born in developing countries that receive the full course of immunization remains low. Moreover, the usually long interval between infection with HBV and the development of HCC means that 30 to 50 years will elapse before the full effect of the vaccine will be realized. Practical measures to prevent aflatoxin B1 exposure are not in place. Serum α-fetoprotein levels are a useful pointer to the diagnosis of HCC in low-income countries, but definitive diagnosis is hampered both by the lack of the sophisticated imaging equipment now available in developed countries and by obstacles to obtaining histological proof. In the majority of patients in low-income regions, the tumor is inoperable by the time the patient presents. Hepatic resection is seldom possible in sub-Saharan Africa, although the tumor is successfully resected in a larger number of patients in China. Liver transplantation for HCC is rarely performed in either region. Sophisticated new radiotherapy techniques are not available in developing countries. The beneficial effects of the multikinase inhibitor, sorafenib, are encouraging, although financial considerations may restrict its use in low-income countries.

Protective Effect of Korean Red Ginseng against Aflatoxin B1-Induced Hepatotoxicity in Rat

Korean red ginseng (KRG), the steamed root of Panax ginseng Meyer, has a variety of biological properties, including anti-inflammatory, antioxidant and anticancer effects. Aflatoxin B1 (AFB1) produced by the Aspergillus spp. causes acute hepatotoxicity by lipid peroxidation and oxidative DNA damage, and induces liver carcinoma in humans and laboratory animals. This study was performed to examine the protective effects of KRG against hepatotoxicity induced by AFB1 using liver-specific serum marker analysis, histopathology, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling. In addition, to elucidate the possible mechanism of hepatoprotective effects, superoxide dismutase, catalase, glutathione peroxidase, and malondialdehyde were analyzed. Rats were treated with 250 mg/kg of KRG (KRG group) or saline (AFB1 group) for 4 weeks and then received 150 μg/kg of AFB1 intraperitoneally for 3 days. Rats were sacrificed at 12 h, 24 h, 48 h, 72 h, or 1 wk after AFB1 treatment. In the KRG pre-treatment group, serum alanine aminotransferase, aspartate aminotransferase, and malondialdehyde levels were low, but superoxide dismutase, catalase, and glutathione peroxidase activities were high as compared to the AFB1 alone group. Histopathologically, AFB1 treatment induced necrosis and apoptosis in hepatocytes, and led to inflammatory cells infiltration in the liver. KRG pre-treatment ameliorated these changes. These results indicate that KRG may have protective effects against hepatotoxicity induced by AFB1 that involve the antioxidant properties of KRG.