Carcinogenic effects of aflatoxin B1 among wheat handlers

Aflatoxin Contamination: An Overview on Health Issues, Detection and Management Strategies

Aflatoxins (AFs) represent one of the main mycotoxins produced by Aspergillus flavus and Aspergillus parasiticus, with the most prevalent and lethal subtypes being AFB1, AFB2, AFG1, and AFG2. AFs are responsible for causing significant public health issues and economic concerns that affect consumers and farmers globally. Chronic exposure to AFs has been linked to liver cancer, oxidative stress, and fetal growth abnormalities among other health-related risks. Although there are various technologies, such as physical, chemical, and biological controls that have been employed to alleviate the toxic effects of AF, there is still no clearly elucidated universal method available to reduce AF levels in food and feed; the only mitigation is early detection of the toxin in the management of AF contamination. Numerous detection methods, including cultures, molecular techniques, immunochemical, electrochemical immunosensor, chromatographic, and spectroscopic means, are used to determine AF contamination in agricultural products. Recent research has shown that incorporating crops with higher resistance, such as sorghum, into animal feed can reduce the risk of AF contamination in milk and cheese. This review provides a current overview of the health-related risks of chronic dietary AF exposure, recent detection techniques, and management strategies to guide future researchers in developing better detection and management strategies for this toxin.

Route exposure and adverse effects monitoring of Aflatoxin B1 in the workers of wet waste management, the role of body redox system modulation

Exposure to dust, containing different fungi metabolites such as aflatoxins is a risk factor for developing liver and kidney health abnormalities. Occupational evaluation of the aflatoxin's exposure-induced health abnormalities should include the monitoring of bioaerosols in the workplace and personal air, and applying of appropriate blood biomarkers to assess Aflatoxin B₁ (AFB₁) detrimental effects on a worker's health. However, to the best of our knowledge, these appropriate methods, especially determining the associated-adverse effects on health, following exposure, haven't been well documented in the literature at the wet waste handling sites. In the current study, the AFB₁ quantity in the area, personal, and settled dust in wet household waste handling samples and AFB₁-Albumin levels in the serum of workers in comparison with the control group were determined using high-pressure liquid chromatography with a fluorescent detector (HPLC-FLD) methods. Moreover, the adverse effects of AFB₁ on the liver and kidney biochemical profiles of the exposed workers and its relation to antioxidant capacity in the household wet waste sorting were recorded in a consolidated investigation. The results demonstrated that the average airborne dust concentration and its associated AFB₁ content were significantly higher in wet waste management sections as compared to the control place, corresponding to the serum AFB₁-Albumin levels of workers. Furthermore, AFB₁-induced changes in the serum biochemicals evaluating liver and kidney function tests and antioxidant profiles of workers in wet waste handling sections were indicative of their function abnormalities. The results imply AFB₁-induced adverse effects on the liver and kidney functions may be mediated through the body redox system modulation.

Aflatoxin B1: metabolism, toxicology, and its involvement in oxidative stress and cancer development

Aflatoxins are a class of carcinogenic mycotoxins produced by Aspergillus fungi, which are widely distributed in nature. Aflatoxin B1 (AFB1) is the most toxic of these compounds and its metabolites have a variety of biological activities, including acute toxicity, teratogenicity, mutagenicity and carcinogenicity, which has been well-characterized to lead to the development of hepatocellular carcinoma (HCC) in humans and animals. This review focuses on the metabolism of AFB1, including epoxidation and DNA adduction, as it concerns the initiation of cancer and the underlying mechanisms. In addition to DNA adduction, inflammation and oxidative stress caused by AFB1 can also participate in the occurrence of cancer. Therefore, the main carcinogenic mechanism of AFB1 related ROS is summarized. This review also describes recent reports of AFB1 exposures in occupational settings. It is hoped that people will pay more attention to occupational health, in order to reduce the incidence of cancer caused by occupational exposure.

CYP1A2, 2A13, and 3A4 network and interaction with aflatoxin B1

Aspergillus fungi are known to produce aflatoxins, among which aflatoxin B1 (AFB1) is the most potent carcinogen that is metabolised by cytochrome P450 (CYP450). In the liver, AFB1 is metabolised into exo-8,9-epoxide by the CYP1A2 enzymes. The resulting epoxide can react with guanine to cause DNA damage. Natural inhibitors are being identified. However, the modes of action are poorly understood. In the current study, we have investigated the mode of action of AFB1 with CYP1A2, CYP3A4 and CYP2A13 using molecular dynamic simulation (MD simulation) approaches. The interaction network and paths among CYP1A2, CYP3A4, and CYP2A13 have been investigated using the STRING database and PathLinker plugin of Cytoscape. CYP3A4 is the most active protein involved in interactions with AFB1 during its metabolism. Residues 362ARG, 445SER, 450LEU and 451PHE of CYP1A2 are important, interacting with AFB1 and converting it to toxic exo-AFB1-8,9-epoxide (AFBEX). The pathway shows that microsomal epoxide hydrolase (EPHX1) may acts as initiator in the signalling pathway where CYP1A2, CYP3A4 and CYP2A13 interact in a sequential order. The interaction network shows there to be a strong association in expression among CYP1A2, CYP3A4 and CYP2A13 along with other metabolising enzymes. The complex of AFB1 and CYP1A2 was found to be stable during the MD simulation. This study provides a better understanding of the mode of action between AFB1 and CYP1A2, CYP3A4 and CYP2A13 which relates to the effective management of AFB1 toxicity. EPHX1 in the protein network may be an ideal target when designing inhibitors to prevent the toxin’s activation. Peptide inhibitors may be designed to block the substrate site residues of CYP1A2 in order to prevent the conversion from AFB1 into AFBEX. This would either neutralise or reduce its toxicity.

Liver and kidney serum profile abnormalities in workers exposed to aflatoxin B1 in urban solid waste management centers

Many workers are exposed to health problems arising from molds, fungi, and their toxins during waste processing. Aflatoxin B₁ (AFB₁) level in airborne and settled dust, aflatoxin B₁-albumin (AFB₁-Alb) adduct in serum, liver and kidney biochemical tests, and body redox change of workers in municipal dry waste-processing sites were investigated. The surface, personal, and area air dust and the blood of workers' samples were collected from the plastic and bread waste-sorting sections in three recycling municipal dry waste sites. Digestion (only for serum samples), passed through SPE cartridge, elution, and collection with methanol, immune-affinity column clean-up, and HPLC system equipped with post-column derivatization method and fluorescence detection were performed for determination of AFB₁ and AFB₁-Alb levels in the samples. The mean level of dust and AFB₁ in the personal and area air, and in the settled dust and the AFB₁-Alb in the serum of workers in the bread waste sorting, was higher than plastic waste-sorting samples, in all of the sites. The differences in the biochemical profiles of subjects exposed to aflatoxin B₁ as compared to the control group especially in liver and kidney function parameters as well as antioxidant factors of the serum were significant. The workers in handling of municipal waste may be exposed to potentially hazardous levels of aflatoxin B₁. The adverse effects of AFB₁ on the kidney and liver may be caused by changes in the redox system.

Black tea and curcumin synergistically mitigate the hepatotoxicity and nephropathic changes induced by chronic exposure to aflatoxin-B1 in Sprague-Dawley rats

The study aimed to clarify the characteristics of black tea (BTE) and/or curcumin (CMN) against aflatoxin-B1 (AFB1). Forty eight adult male Sprague-Dawley rats were divided into eight groups. G1 was non-treated control. G2, G3, and G4 were olive oil, BTE, and CMN, respectively. G5 was olive oil-dissolved AFB1 (25 µg/kg b.w). G6, G7, and G8 were AFB1 along with BTE (2%), CMN (200 mg/kg b.w.), and BTE plus CMN, respectively. All treatments were orally given for consecutive 90 days. After treatment period, rats were sacrificed. Serobiochemical analysis and histopathology showed hepatorenal dysfunction in response to AFB1. Glutathione-antioxidants were significantly decreased versus increased lipid peroxides (p < .05-.001). AFB1 significantly increased the expression of the antitumor p53, but decreased that of antiapoptotic Bcl2 in liver or kidney tissue, either (p < .05). BTE or CMN ameliorated those changes induced by AFB1 in both liver and kidney with highly pronounced improvement when combined BTE/CMN was used. PRACTICAL APPLICATIONS: Black tea (BTE) and curcumin (CMN) were known for their antioxidant effects, and several studies reported their independent effects against different toxicities including aflatoxicosis. The current study clarifies the ameliorative characteristics of both agents; BTE and/or CMN, against the toxicity resulted from the chronic exposure to aflatoxin-B1 (AFB1) (25 µg/kg b.w. for consecutive 90 days). The dose of either agents, BTE or CMN, was 200 mg/kg b.w. along with AFB1. The pathologic changes, serobiochemical parameters, oxidative stress, histological changes, and the molecular disruption, induced by AFB1 in both liver and kidney were obviously and significantly ameliorated after BTE and/or CMN treatments in variable potencies where both agents showed the most effective antitoxic capacities.

Optimization and validation of a LC-HRMS method for aflatoxins determination in urine samples

Mycotoxins' exposure by inhalation and/or dermal contact can occur in different branches of industry especially where heavily dusty settings are present and the handling of dusty commodities is performed. This study aims to explore the possible contribution of the occupational exposure to aflatoxins by analysing urine samples for the presence of aflatoxins B₁ and M₁ and aflatoxin B₁-N⁷-guanine adduct. The study was conducted in 2017 on two groups of volunteers, the workers group, composed by personnel employed in an Italian feed plant (n = 32), and a control group (n = 29), composed by the administrative employees of the same feed plant; a total of 120 urine samples were collected and analysed. A screening method and a quantitative method with high-resolution mass spectrometry determination were developed and fully validated. Limits of detections were 0.8 and 1.5 pg/mL_urine for aflatoxin B₁ and M₁, respectively. No quantitative determination was possible for the adduct aflatoxin B₁-N⁷-guanine. Aflatoxin B₁ and its adduct were not detected in the analysed samples, and aflatoxin M₁, instead, was found in 14 samples (12%) within the range 1.9-10.5 pg/mL_urine. Only one sample showed a value above the limit of quantification (10.5 pg/mL_urine). The absence of a statistical difference between the mean values for workers and the control group which were compared suggests that in this specific setting, no professional exposure occurs. Furthermore, considering the very low level of aflatoxin M₁ in the collected urine samples, the contribution from the diet to the overall exposure is to be considered negligible.

Environmental Health Research in Africa: Important Progress and Promising Opportunities

The World Health Organization in 2016 estimated that over 20% of the global disease burden and deaths were attributed to modifiable environmental factors. However, data clearly characterizing the impact of environmental exposures and health endpoints in African populations is limited. To describe recent progress and identify important research gaps, we reviewed literature on environmental health research in African populations over the last decade, as well as research incorporating both genomic and environmental factors. We queried PubMed for peer-reviewed research articles, reviews, or books examining environmental exposures and health outcomes in human populations in Africa. Searches utilized medical subheading (MeSH) terms for environmental exposure categories listed in the March 2018 US National Report on Human Exposure to Environmental Chemicals, which includes chemicals with worldwide distributions. Our search strategy retrieved 540 relevant publications, with studies evaluating health impacts of ambient air pollution (n=105), indoor air pollution (n = 166), heavy metals (n = 130), pesticides (n = 95), dietary mold (n = 61), indoor mold (n = 9), per- and polyfluoroalkyl substances (PFASs, n = 0), electronic waste (n = 9), environmental phenols (n = 4), flame retardants (n = 8), and phthalates (n = 3), where publications could belong to more than one exposure category. Only 23 publications characterized both environmental and genomic risk factors. Cardiovascular and respiratory health endpoints impacted by air pollution were comparable to observations in other countries. Air pollution exposures unique to Africa and some other resource limited settings were dust and specific occupational exposures. Literature describing harmful health effects of metals, pesticides, and dietary mold represented a context unique to Africa. Studies of exposures to phthalates, PFASs, phenols, and flame retardants were very limited. These results underscore the need for further focus on current and emerging environmental and chemical health risks as well as better integration of genomic and environmental factors in African research studies. Environmental exposures with distinct routes of exposure, unique co-exposures and co-morbidities, combined with the extensive genomic diversity in Africa may lead to the identification of novel mechanisms underlying complex disease and promising potential for translation to global public health.

Occupational Exposure to Mycotoxins: Current Knowledge and Prospects

Occupational exposure to mycotoxins is supposedly very frequent, but it is rarely reported in the scientific literature. Several recent studies described occupational exposure to the aflatoxin B1 (AFB1) mycotoxin in different occupational settings. Previously, exposure to other mycotoxins was shown in the animal husbandry and food processing sectors, confirming that occupational exposure cannot be negligible. However, no guidelines or standard methodologies are available for helping occupational hygienists to consider mycotoxin exposure in their interventions. This article reviews the literature on this problem and recommends some actions for the better management of this risk factor in occupational settings, especially where environmental conditions are favorable to fungal presence.

Non‑infective occupational risk factors for hepatocellular carcinoma: A review (Review)

Liver cancer is the second leading worldwide cause of cancer‑associated mortalities. Hepatocellular carcinoma, which accounts for the majority of liver tumors, ranks fifth among types of human cancer. Well‑established risk factors for liver cancer include the hepatitis B and C viruses, aflatoxins, alcohol consumption, and oral contraceptives. Tobacco smoking, androgenic steroids, and diabetes mellitus are suspected risk factors. Current knowledge regarding non‑infective occupational risk factors for liver cancer is inconclusive. The relevance of liver disorders to occupational medicine lies in the fact that the majority of chemicals are metabolized in the liver, and toxic metabolites generated via metabolism are the predominant cause of liver damage. However, their non‑specific clinical manifestations that are similar in a number of liver diseases make diagnosis difficult. Furthermore, concomitant conditions, such as viral hepatitis and alcohol or drug abuse, may mask liver disorders that result from occupational hepatotoxic agents and block the demonstration of an occupational cause. The identification of environmental agents that result in human cancer is a long and often difficult process. The purpose of the present review is to summarize current knowledge regarding the association of non‑infective occupational risk exposure and HCC, to encourage further research and draw attention to this global occupational public health problem.

Comparative Hepatotoxicity of Aflatoxin B1 among Workers Exposed to Different Organic Dust with Emphasis on Polymorphism Role of Glutathione S-Transferase Gene

AIM:

The study aimed to investigate effects of organic dust exposure from different sources on aflatoxin B1-albumin adducts (AFB1/Alb), and role of glutathione S-transferase (GST) gene polymorphism in hepatotoxicity of (AFB1) among exposed workers.

MATERIAL AND METHODS:

Liver enzymes, AFB1/Alb, and GST polymorphism were estimated in 132 wheat flour dust and 87 woods sawmill workers, and 156 controls.

RESULTS:

Results revealed that AFB1/Alb and liver enzymes were significantly elevated in exposed workers compared to controls, and were significantly higher in sawmill workers compared to flour workers. AFB1/Alb in flour and sawmill workers with GSTT1 and GSTM1&GSTT1 null genotypes were significantly higher than controls, and in sawmill workers with GSTM1&GSTT1 null than flour workers. Liver enzymes (ALT and AST) in sawmill workers were significantly higher than flour workers and controls in all GST polymorphism; except in GSTT1 polymorphism, where these enzymes were significantly higher in the two exposed groups than controls.

CONCLUSIONS:

In conclusion, organic dust exposure may cause elevation in AFB1/Alb and liver enzymes of exposed workers, and GST gene polymorphism plays an important role in susceptibility to hepatic parenchymal cell injury; except in workers with GSTT1&GSTM1 null genotype, gene susceptibility seemed to have little role and the main role was for environmental exposures.

Pollution of mycological surfaces in hospital emergency departments correlates positively with blood NKT CD3(+) 16(+) 56(+) and negatively with CD4(+) cell levels of their staff

The aim of the present study was the assessment of the putative influence of yeast and filamentous fungi in healthcare and control (office) workplaces (10 of each kind) on immune system competence measured by NK (natural killer), CD4⁺, and NKT (natural killer T lymphocyte) cell levels in the blood of the personnel employed at these workplaces.

Imprints from floors and walls were collected in winter. The blood was taken in spring the following year, from 40 men, 26 to 53 years old, healthcare workers of hospital emergency departments (HED), who had been working for at least five years in their current positions, and from 36 corresponding controls, working in control offices. Evaluation of blood leukocyte subpopulations was done by flow cytometry. The qualitative analysis of the surface samples revealed a prevalence of strains belonging to Aspergillus spp. and Penicillium spp. genus. There was no statistically significant difference between the level of NKT; however, the percentage of NK cells was lower in the blood of HED workers than in the blood of offices personnel. Spearman analysis revealed the existence of positive correlation (r = 0.4677, p = 0.002) between the total CFU/25 cm² obtained by imprinting method from walls and floors of HED and the percentage of NKT (CD3⁺16⁺56⁺) lymphocytes collected from the blood of their personnel, and negative correlation (r = –0. 3688, p = 0.019) between this parameter of fungal pollution and the percentage of CD4⁺ lymphocytes in the blood of HED staff. No other correlations were found.

Identification of AFB1-interacting proteins and interactions between RPSA and AFB1

A method using immobilized affinity chromatography (IAC) was developed to screen for aflatoxin B1 (AFB1)-binding proteins. AFB1 and bovine serum albumin (BSA) coupled protein (BSA-AFB1) was prepared using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. The resulting coupled compound was immobilized onto PVDF transfer membranes, which were then incubated with total protein from mouse liver. AFB1-binding proteins were eluted, after non-specific washing, by specific elution, and the eluted proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Two candidate AFB1-binding proteins were identified by liquid chromatography-tandem mass spectrometry as the 40S ribosomal protein SA (RPSA) and a putative uncharacterized protein. RPSA and AFB1 interactions were further analyzed by ELISA in vitro and laser confocal immunofluorescence analysis in vivo. The results from ELISA and immunofluorescence showed that RPSA efficiently bound AFB1 in vitro and in vivo. This study's conclusion laid the foundation for further exploration of the role of AFB1-binding proteins in AFB1 toxicology towards hepatocytes and the entry pathway of AFB1 into hepatocytes.

Negative correlation between mycological surfaces pollution in hospital emergency departments and blood monocytes phagocytosis of healthcare workers

The aim of the present study was to find a possible relationship between the presence of yeast and filamentous fungi in hospital emergency departments and the activity levels of blood granulocytes and monocytes in emergency personnel. The study of mycological pollution was conducted in winter; the samples were collected from 10 Warsaw hospitals emergency departments (HE D) and in 10 control locations (office spaces) and included air samples and swabbing of floor and walls. The blood for immunological investigation was taken in spring, from 40 men, 26 to 53 years old, healthcare workers of these departments, who have been working for at least 5 years in their current positions, and from 36 corresponding controls, working in control offices. Evaluation of blood leukocyte subpopulations was done by hematological analyzer and cytometry analysis and monocyte and granulocyte phagocytosis by Phagotest. There were no significant differences in the level of mycological contamination between the test and control places. The qualitative analysis of the surfaces and air samples revealed a prevalence of strains belonging to Aspergillus spp. and Penicillium spp. genus. Statistical analysis revealed the existence of negative correlation between the number of phagocytizing blood monocytes and fungi spores content on floor and wall surfaces in hospital emergency departments (r = -0.3282, p < 0.05 and positive correlation between the number of phagocytizing monocytes in the blood of office workers and fungi pollution of control offices (r = 0.4421, p < 0.01).