In vivo treatment with aflatoxin B1 increases DNA oxidation, base excision repair activity and 8-oxoguanine DNA glycosylase 1 levels in mouse lung

Biodetoxification of both AFB1 and ZEN by Bacillus subtilis ZJ-2019-1 in gastrointestinal environment and in mice

Aflatoxin B1 (AFB1) and zearalenone (ZEN) are the most prevalent mycotoxins in production, posing a serious threat to human and animal health. Therefore, it is very urgent to find a safe and efficient method for the biodegradation of these mycotoxins. Our previous study demonstrated that Bacillus subtilis ZJ-2019-1 moderately degrades both mycotoxins in vitro and ZEN in female gilts. In this study, we assessed the effect of B. subtilis ZJ-2019-1 on AFB1 and ZEN degradation in naturally moldy corn gluten meal in a gastrointestinal environment while also evaluating the cytotoxicity of degradation products using the Cell Counting Kit-8 (CCK-8) assay. The efficacy of B. subtilis in degrading mycotoxins was further evaluated by orally administering 5 mg/kg AFB1 and 50 mg/kg ZEN to mice, followed by treatment with B. subtilis ZJ-2019-1 for 15 d. The results showed that B. subtilis ZJ-2019-1 moderately degraded both AFB1 and ZEN present in naturally moldy corn gluten meal in simulated small intestinal fluids, with degradation rates reaching 14.71% for AFB1 and 19.53% for ZEN respectively. Following degradation by B. subtilis ZJ-2019-1, the toxicity of resulting products from both AFB1 and ZEN decreased by 11.68-46.41% and 42.62-59.25%, respectively. Moreover, oral administration of B. subtilis ZJ-2019-1 exhibited remarkable detoxification effects on AFB1 and ZEN in mice, as evidenced by significant restoration of abnormal serum biochemical indices (including aspartate aminotransferase/alanine transaminase, alkaline phosphatase, total cholesterol, etc.) and alleviation of liver, intestine, and uterine damage caused by mycotoxins in mice. These findings indicate that B. subtilis ZJ-2019-1 possesses the ability to moderately degrade both AFB1 and ZEN, making it a promising candidate for biodegrading multi-mycotoxin contaminants in food and feed.

Effect of aflatoxin B1 and sterigmatocystin on DNA repair genes in common carp

The present study aimed to investigate the short-time (24 h) effect of aflatoxin B1 (AFB1) and sterigmatocystin (STC) on the expression of hsp70, p53, gadd45, and ogg1 genes in common carp hepatopancreas. Our results showed that aflatoxin B1 and sterigmatocystin can stimulate the expression of DNA repair genes, mainly by hour 24. This significant finding contributes to our understanding of the short-term effects of these mycotoxins on ogg1 genes in common carp hepatopancreas. One-year-old common carp juveniles were randomly distributed into five groups (Control, AFB1 0.4 mg kg-1 feed, STC1 1 mg kg-1 feed, STC2 2 mg kg-1 feed, and STC3 3 mg kg-1 feed). Hepatopancreas samples were collected three times (8, 16, and 24 h) in each group. No significant ogg1 and p53 expression changes were observed at 8 and 16 h after exposure. All measured genes were upregulated by the 24th hour in aflatoxin and STC3 groups. An increase in hsp70 gene expression was detected in all groups and all sampling. A significant decrease in gadd45aa gene expression was observed in the aflatoxin B1 group at hour 8. At hour 16, there was no significant change, while at hour 24, all treated groups were significantly different from the control. In summary, our results suggest that aflatoxin B1 and sterigmatocystin can stimulate the expression of DNA repair genes, mainly by hour 24. Further investigations are needed to get information about DNA damage parallel to the DNA repair mechanisms.

Development of a targeted method for DNA adductome and its application as sensitive biomarkers of ambient air pollution exposure

DNA adducts are widely recognized as biomarkers of exposure to environmental carcinogens and associated health effects in toxicological and epidemiological studies. This study presents a targeted and sensitive method for comprehensive DNA adductome analysis using ultra-high-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS). The method was developed using calf thymus DNA, with careful optimization of mass spectrometric parameters, chromatographic separation conditions, and pretreatment methods. Ultimately, a targeted method was established for 41 DNA adducts, which showed good linearity (R2 ≥0.992), recovery (80.1-119.4 %), accuracy (81.3-117.8 %), and precision (relative standard deviation <14.2 %). The established method was employed to analyze DNA adducts in peripheral blood cells from pregnant women in Shanxi and Beijing. Up to 23 DNA adducts were successfully detected in samples of varying sizes. From 2 μg of maternal DNA samples, seven specific adducts were identified: 5-methyl-2'-deoxycytidine (5-MedC), 5-hydroxymethyl-2'-deoxycytidine (5-HmdC), N6-methyl-2'-deoxyadenosine (N6-MedA), 8-hydroxy-2'-deoxyguanosine (8-OHdG), 5-hydroxy-2'-deoxycytidine (5-OHdC), 1,N6-etheno-2'-deoxyadenosine (1,N6-εdA), and N2-methyl-2'-deoxyguanosine (N2-MedG). This study reveals that exposure to higher concentrations of ambient air pollutants may elevate the levels of DNA methylation and oxidative damage at different base sites, highlighting the application potential of DNA adducts as sensitive biomarkers of air pollution exposure.

Human CYP1A1-activated aneugenicity of aflatoxin B1 in mammalian cells and its combined effect with benzo(a)pyrene

Aflatoxin B1 (AFB1) is the most toxic mycotoxin and a proven human carcinogen that requires metabolic activation, known by cytochrome P450 (CYP) 1A2 and 3A4. Previous evidence showed that AFB1 is activated by human recombinant CYP1A1 expressed in budding yeast. Yet, the toxicity, in particular the genotoxicity of the reactive metabolites formed from AFB1 remains unclear. Humans could be exposed to both AFB1 and benzo(a)pyrene (BaP) simultaneously, thus we were interested in their combined genotoxic effects subsequent to metabolic activation by CYP1A1. In this study, molecular docking of AFB1 to human CYP1A1 indicated that AFB1 is valid as a substrate. In the incubations with AFB1 in human CYP1A1-expressed microsomes, AFM1 as a marking metabolite of AFB1 was detected. Moreover, AFB1 induced micronucleus formation in a Chinese hamster V79-derived cell line and in a human lung epithelial BEAS-2B cell line, both expressing recombinant human CYP1A1, V79-hCYP1A1 and 2B-hCYP1A1 cells, respectively. Immunofluorescence of centromere protein B stained micronuclei was dominant in AFB1-treated BEAS-2B cells exposed to AFB1, suggesting an aneugenic effect. Moreover, AFB1 elevated the levels of ROS, 8-OHdG, AFB1-DNA adduct, and DNA breaks in 2B-hCYP1A1 cells, compared with those in the parental BEAS-2B cells. Meanwhile, AFB1 increased CYP1A1, RAD51, and γ-H2AX protein levels in 2B-hCYP1A1 cells, which were attenuated by the CYP1A1 inhibitor bergamottin. Co-exposure of AFB1 with BaP increased 8-OHdG, RAD51, and γ-H2AX levels (indicating DNA damage). In conclusion, AFB1 could be activated by human CYP1A1 for potent aneugenicity, which may be further enhanced by co-exposure to BaP.

A Bacillus subtilis Strain ZJ20 with AFB1 Detoxification Ability: A Comprehensive Analysis

As a class I carcinogen, aflatoxin can cause serious damage to various tissues and organs through oxidative stress injuries. The liver, as the target organ of AFB1, is the most seriously damaged. Biological methods are commonly used to degrade AFB1. In our study, the aflatoxin B1-degrading strain ZJ20 was screened from AFB1-contaminated feed and soil, and the degradation of AFB1 by ZJ20 was investigated. The whole genome of strain ZJ20 was analyzed, revealing the genomic complexity of strain ZJ20. The 16S rRNA analysis of strain ZJ20 showed 100% identity to Bacillus subtilis IAM 12118. Through whole gene functional annotation, it was determined that ZJ20 has high antioxidant activity and enzymatic activity; more than 100 CAZymes and 11 gene clusters are involved in the production of secondary metabolites with antimicrobial properties. In addition, B. subtilis ZJ20 was predicted to contain a cluster of genes encoding AFB1-degrading enzymes, including chitinase, laccase, lactonase, and manganese oxidase. The comprehensive analysis of B. subtilis provides a theoretical basis for the subsequent development of the biological functions of ZJ20 and the combinatorial enzyme degradation of AFB1.

Research update on aflatoxins toxicity, metabolism, distribution, and detection: A concise overview

Serious health risks associated with the consumption of food products contaminated with aflatoxins (AFs) are worldwide recognized and depend predominantly on consumed AF concentration by diet. A low concentration of aflatoxins in cereals and related food commodities is unavoidable, especially in subtropic and tropic regions. Accordingly, risk assessment guidelines established by regulatory bodies in different countries help in the prevention of aflatoxin intoxication and the protection of public health. By assessing the maximal levels of aflatoxins in food products which are a potential risk to human health, it's possible to establish appropriate risk management strategies. Regarding, a few factors are crucial for making a rational risk management decision, such as toxicological profile, adequate information concerning the exposure duration, availability of routine and some novel analytical techniques, socioeconomic factors, food intake patterns, and maximal allowed levels of each aflatoxin in different food products which may be varied between countries.

A new toxicity mechanism of N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone: Formation of DNA adducts in mammalian cells and aqueous organisms

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPDQ), one of the oxidation products of rubber antioxidant 6PPD, has been identified as a novel toxicant to many organisms. However, an understanding of its underlying toxicity mechanisms remained elusive. In this study, we reported that 6PPDQ could react with deoxyguanosine to form one isomer of 3-hydroxy-1, N²-6PPD-etheno-2'-deoxyguanosine (6PPDQ-dG). Next, by employing an ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) method, we found that 6PPDQ-dG could be detected in genomic DNA from 6PPDQ-treated mammalian cells and Chlamydomonas reinhardtii. We observed positive correlations between concentrations of exogenous 6PPDQ and the amounts of 6PPDQ-dG, and a recovery period after removal of 6PPDQ also led to decreased levels of the adduct in both organisms, which suggested potential repair pathways for this adduct in mammalian cells and unicellular algae. Additionally, we extracted the genomic DNA from tissues of frozen capelin and observed substantial amounts of the adduct in roe and gills, as well as livers at a relatively lower level. These results provided insights into the target organs and tissues that 6PPDQ might accumulate or harm fish. Overall, our study provides a new understanding of the mechanisms of toxicity of 6PPDQ in mammalian cells and aqueous organisms.

AFG1-induced TNF-α-mediated inflammation enhances gastric epithelial cell injury via CYP2E1

Aflatoxin G₁ (AFG₁), a member of the aflatoxin family with cytotoxic and carcinogenic properties, is one of the most common mycotoxins occurring in various agricultural products, animal feed, and human foods and drinks worldwide. Epithelial cells in the gastrointestinal tract are the first line of defense against ingested mycotoxins. However, the toxicity of AFG₁ to gastric epithelial cells (GECs) remains unclear. In this study, we explored whether and how AFG₁-induced gastric inflammation regulates cytochrome P450 to contribute to DNA damage in GECs. Oral administration of AFG₁ induced gastric inflammation and DNA damage in mouse GECs associated with P450 2E1 (CYP2E1) upregulation. Treatment with the soluble TNF-α receptor sTNFR:Fc inhibited AFG₁-induced gastric inflammation, and reversed CYP2E1 upregulation and DNA damage in mouse GECs. TNF-α-mediated inflammation plays an important role in AFG₁-induced gastric cell damage. Using the human gastric cell line GES-1, AFG₁ upregulated CYP2E1 through NF-κB, causing oxidative DNA damage in vitro. The cells were also treated with TNF-α and AFG₁ to mimic AFG₁-induced TNF-α-mediated inflammation. TNF-α activated the NF-κB/CYP2E1 pathway to promote AFG₁ activation, which enhanced DNA cellular damage in vitro. In conclusion, AFG₁ ingestion induces TNF-α-mediated gastric inflammation, which upregulates CYP2E1 to promote AFG₁-induced DNA damage in GECs.

Development of QM/MM (ABEEM polarizable force field) method to simulate the excision reaction mechanism of damaged cytosine

DNA damages are regarded as having harmful effects on cell. The base excision repair mechanism combats these effects by removing damaged bases. The deglycosylation mechanism of excising damaged bases by DNA glycosylase and the state of the leaving base have been controversial. The enzymatic reaction of DNA glycosylase to remove the damaged bases involves not only the formation and breaking of chemical bonds, but also complex polarization effect and charge transfer, which cannot be accurately simulated by the QM/MM method combined with the fixed charge force field. This work has developed the ABEEM fluctuating polarizable force field combining with the QM method, that is (QM/MM[ABEEM]), to accurately simulate the proton transfer, charge transfer and the charge distribution. The piecewise function is used as the valence-state electronegativity in the QM/MM (ABEEM) to realize the accurate fitting of the charge distribution in reaction. And the charge transfer is accurately simulated by the local charge conservation conditions. Four deglycosylation mechanisms including the monofunctional and difunctional mechanisms of four neutral and protonated cytosine derivatives are explored. It is confirmed that the monofunctional mechanism of Asp-activated nucleophile water is a better deglycosylation mechanism and the base is protonated before the reaction occurs. Protonization of the base reduced the activation energy by 10.00-17.00 kcal/mol. Asp provides the necessary charge for the reaction, and DNA glycosylase preferentially cleaves ɛC. This work provides a theoretical basis for the research of excising damaged bases by DNA glycosylase.

8-oxoguanine and 8-oxodeoxyguanosine Biomarkers of Oxidative DNA Damage: A Review on HPLC-ECD Determination

Reactive oxygen species (ROS) are continuously produced in living cells due to metabolic and biochemical reactions and due to exposure to physical, chemical and biological agents. Excessive ROS cause oxidative stress and lead to oxidative DNA damage. Within ROS-mediated DNA lesions, 8-oxoguanine (8-oxoG) and its nucleotide 8-oxo-2'-deoxyguanosine (8-oxodG)-the guanine and deoxyguanosine oxidation products, respectively, are regarded as the most significant biomarkers for oxidative DNA damage. The quantification of 8-oxoG and 8-oxodG in urine, blood, tissue and saliva is essential, being employed to determine the overall effects of oxidative stress and to assess the risk, diagnose, and evaluate the treatment of autoimmune, inflammatory, neurodegenerative and cardiovascular diseases, diabetes, cancer and other age-related diseases. High-performance liquid chromatography with electrochemical detection (HPLC-ECD) is largely employed for 8-oxoG and 8-oxodG determination in biological samples due to its high selectivity and sensitivity, down to the femtomolar range. This review seeks to provide an exhaustive analysis of the most recent reports on the HPLC-ECD determination of 8-oxoG and 8-oxodG in cellular DNA and body fluids, which is relevant for health research.

Pharmacological Applications and Action Mechanisms of Phytochemicals as Alternatives to Antibiotics in Pig Production

Antibiotics are widely used for infectious diseases and feed additives for animal health and growth. Antibiotic resistant caused by overuse of antibiotics poses a global health threat. It is urgent to choose safe and environment-friendly alternatives to antibiotics to promote the ecological sustainable development of the pig industry. Phytochemicals are characterized by little residue, no resistance, and minimal side effects and have been reported to improve animal health and growth performance in pigs, which may become a promising additive in pig production. This paper summarizes the biological functions of recent studies of phytochemicals on growth performance, metabolism, antioxidative capacity, gut microbiota, intestinal mucosa barrier, antiviral, antimicrobial, immunomodulatory, detoxification of mycotoxins, as well as their action mechanisms in pig production. The review may provide the theoretical basis for the application of phytochemicals functioning as alternative antibiotic additives in the pig industry.

Mold, Mycotoxins and a Dysregulated Immune System: A Combination of Concern?

Fungi represent one of the most diverse and abundant eukaryotes on earth. The interplay between mold exposure and the host immune system is still not fully elucidated. Literature research focusing on up-to-date publications is providing a heterogenous picture of evidence and opinions regarding the role of mold and mycotoxins in the development of immune diseases. While the induction of allergic immune responses by molds is generally acknowledged, other direct health effects like the toxic mold syndrome are controversially discussed. However, recent observations indicate a particular importance of mold/mycotoxin exposure in individuals with pre-existing dysregulation of the immune system, due to exacerbation of underlying pathophysiology including allergic and non-allergic chronic inflammatory diseases, autoimmune disorders, and even human immunodeficiency virus (HIV) disease progression. In this review, we focus on the impact of mycotoxins regarding their impact on disease progression in pre-existing immune dysregulation. This is complemented by experimental in vivo and in vitro findings to present cellular and molecular modes of action. Furthermore, we discuss hypothetical mechanisms of action, where evidence is missing since much remains to be discovered.

Dietary Se deficiency dysregulates metabolic and cell death signaling in aggravating the AFB1 hepatotoxicity of chicks

The objective of this study was to use isobaric tags for relative and absolute quantitation (iTRAQ) proteomic technology to systematically analyze the hepatotoxic mechanism of aflatoxin B₁ (AFB₁) and its prevention by Se in broilers. Four groups of day-old broilers were allocated into a 2 × 2 factorial design trial that fed a Se-deficient based diet (BD) or the BD + 1.0 mg AFB₁/kg, 0.3 mg Se/kg, or 1.0 mg AFB₁/kg plus 0.3 mg Se/kg for 3 wk. Dietary AFB₁ increased serum ALT and decreased total protein and albumin concentrations, and induced hepatic histopathological lesions in Se adequate groups. Notably, Se deficiency exacerbated these AFB₁-induced changes. Furthermore, Se deficiency reduced hepatic glutathione peroxidase but increased thioredoxin reductase and glutathione S-transferase activities and 8-hydroxydeoxyguanosine concentration in AFB₁ administrated groups. Moreover, AFB₁ dysregulated 261 co-differentially expressed proteins (DEPs) in both Se adequate and deficiency diets, and Se deficiency dysregulated 64 DEPs in AFB₁ administrated diets. These DEPs are mainly related to phase I and II metabolizing enzymes, heat shock proteins, DNA repair, fatty acid metabolism and apoptosis. The in vitro study has verified that aldo-keto reductase family1, member10 plays an important role in AFB₁-induced hepatotoxicity and Se-mediated detoxification of AFB₁ in a chicken leghorn male hepatoma cells. Conclusively, this study has analyzed the hepatic proteome response to dietary AFB₁ and Se, and thus shed new light on the mechanisms of hepatotoxicity of AFB₁ and its detoxification by Se in broilers.

Diet containing grape seed meal by-product counteracts AFB1 toxicity in liver of pig after weaning

Liver is the earliest target for AFB1 toxicity in both human and animals. In the last decade, plant derived by-products have been used in animal feed to reduce AFB1 induced toxicity. In the present study we investigated whether the presence of 8% grape seed meal by-product is able to counteract the hepatotoxic effects produced by AFB1 in liver of pig after weaning exposed to the toxin through the contaminated feed for 28 days. Twenty four weaned cross-bred TOPIGS-40 piglets with an average body weight of 9.13±0.03 were allocated to the following experimentally treatments: control diet without AFB1 (normal compound feed for weaned pigs); contaminated diet with 320 mg kg^-1 AFB1; GSM diet (compound feed plus 8% grape seed meal) and AFB1+GSM diet (320 mg kg^-1 AFB1 contaminated feed plus 8% grape seed meal). Pigs fed AFB1 diet had altered performance, body weight decreasing with 25.1% (b.w.: 17.17 kg for AFB1 vs 22.92 kg for control). Exposure of piglets to AFB1 contaminated diet caused liver oxidative stress as well as liver histological damage, manly characterized by inflammatory infiltrate, fibrosis and parenchyma cells vacuolation when compared to control and GSM meal group. 94.12% of the total analysed genes (34) related to inflammation and immune response was up-regulated. The addition of GSM into the AFB1 diet diminished the gene overexpression and ameliorate histological liver injuries and oxidative stress. The protective effect of GSM diet in diminishing the AFB1 harmful effect was mediated through the decreasing of gene and protein expression of MAPKs and NF-κB signalling overexpressed by AFB1 diet. The inclusion of grape seed by-products in the diet of pigs after weaning might be used as a novel nutritional intervention to reduce aflatoxin toxicity.

High mobility group box-1 protects against Aflatoxin G1-induced pulmonary epithelial cell damage in the lung inflammatory environment

Aflatoxin G₁ (AFG₁) is a member of the carcinogenic aflatoxin family. Our previous studies indicated that oral administration of AFG₁ caused tumor necrosis factor (TNF)-α-dependent inflammation that enhanced oxidative DNA damage in alveolar epithelial cells, which may be related to AFG₁-induced lung carcinogenesis. High mobility group box-1 (HMGB1) is a nuclear DNA-binding protein; the intracellular and extracellular roles of HMGB1 have been shown to contribute to DNA repair and sterile inflammation. The role of HMGB1 in DNA damage in an aflatoxin-induced lung inflammatory environment was investigated in this study. Upregulation of HMGB1, TLR2, and RAGE was observed in AFG₁-induced lung inflamed tissues and adenocarcinoma. Blocking AFG₁-induced inflammation by neutralization of TNF-α inhibited the upregulation of HMGB1 in mouse lung tissues, suggesting that AFG₁-induced TNF-α-dependent inflammation regulated HMGB1 expression. In the in vitro human pulmonary epithelial cell line model, Beas-2b, AFG₁ directly enhanced the cytosolic translocation of HMGB1 and its extracellular secretion. The addition of extracellular soluble HMGB1 protected AFG₁-induced DNA damage through the TLR2/NF-κB pathway in Beas-2b cells. In addition, blockade of endogenous HMGB1 by siRNA significantly enhanced AFG₁-induced damage. Thus, our findings showed that both extracellularly-released and nuclear and cytosolic HMGB1 could protect the cell from AFG₁-induced cell damage in a TNF-α-dependent lung inflammatory environment.

EFSA Panel on Contaminants in the Food Chain (CONTAM), Schrenk D, Bignami M, Bodin L, Chipman JK, del Mazo J, Grasl‐Kraupp B, Hogstrand C, Hoogenboom L(R, Leblanc J, Nebbia CS, Nielsen E, Ntzani E, Petersen A, Sand S, Schwerdtle T, Vleminckx C, Marko D, Oswald IP, Piersma A, Routledge M, Schlatter J, Baert K, Gergelova P, Wallace H. Risk assessment of aflatoxins in food

EFSA was asked to deliver a scientific opinion on the risks to public health related to the presence of aflatoxins in food. The risk assessment was confined to aflatoxin B1 (AFB1), AFB2, AFG1, AFG2 and AFM1. More than 200,000 analytical results on the occurrence of aflatoxins were used in the evaluation. Grains and grain-based products made the largest contribution to the mean chronic dietary exposure to AFB1 in all age classes, while 'liquid milk' and 'fermented milk products' were the main contributors to the AFM1 mean exposure. Aflatoxins are genotoxic and AFB1 can cause hepatocellular carcinomas (HCCs) in humans. The CONTAM Panel selected a benchmark dose lower confidence limit (BMDL) for a benchmark response of 10% of 0.4 μg/kg body weight (bw) per day for the incidence of HCC in male rats following AFB1 exposure to be used in a margin of exposure (MOE) approach. The calculation of a BMDL from the human data was not appropriate; instead, the cancer potencies estimated by the Joint FAO/WHO Expert Committee on Food Additives in 2016 were used. For AFM1, a potency factor of 0.1 relative to AFB1 was used. For AFG1, AFB2 and AFG2, the in vivo data are not sufficient to derive potency factors and equal potency to AFB1 was assumed as in previous assessments. MOE values for AFB1 exposure ranged from 5,000 to 29 and for AFM1 from 100,000 to 508. The calculated MOEs are below 10,000 for AFB1 and also for AFM1 where some surveys, particularly for the younger age groups, have an MOE below 10,000. This raises a health concern. The estimated cancer risks in humans following exposure to AFB1 and AFM1 are in-line with the conclusion drawn from the MOEs. The conclusions also apply to the combined exposure to all five aflatoxins.

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.

tRNA modification and cancer: potential for therapeutic prevention and intervention

Transfer RNAs (tRNAs) undergo extensive chemical modification within cells through the activity of tRNA methyltransferase enzymes (TRMs). Although tRNA modifications are dynamic, how they impact cell behavior after stress and during tumorigenesis is not well understood. This review discusses how tRNA modifications influence the translation of codon-biased transcripts involved in responses to oxidative stress. We further discuss emerging mechanistic details about how aberrant TRM activity in cancer cells can direct programs of codon-biased translation that drive cancer cell phenotypes. The studies reviewed here predict future preventative therapies aimed at augmenting TRM activity in individuals at risk for cancer due to exposure. They further predict that attenuating TRM-dependent translation in cancer cells may limit disease progression while leaving noncancerous cells unharmed.

DNA Repair Protein OGG1 in Pulmonary Infection and Other Inflammatory Lung Diseases

In the last decades, extensive research has uncovered functional roles and underlying mechanisms of DNA repair enzyme 8-oxoguanine DNA glycosylase (OGG1) in the pathogenesis of inflammatory response in infection and other diseases in the lung. OGG1 excises 8-oxo-7,8-dihydroguanine (8-oxo-dG) lesion on DNA that is often induced by generation of reactive oxygen species (ROS) and has been linked to mutations, cancer development, and tissue damage. Most, if not all, environmental toxic agents and mammalian cellular metabolites elicit the generation of ROS, either directly, indirectly, or both, which is among the first cellular responses. ROS in combination with other oxidative molecules/moieties are recognized as a major factor for killing invading pathogens but meanwhile can cause tissue damage. ROS potentially modify proteins, lipids, and DNA due to the strong molecular reactivity. While oxidative stress causes increased levels of all types of oxidatively modified DNA bases, accumulation of 8-oxo-dG in the DNA has been singled out to be a main culprit linking to various inflammatory disease processes. Oxidatively damaged DNA bases such as 8-oxo-dG are primarily repaired by the base excision repair (BER) mechanism, in which OGG1, as the lesion recognition enzyme, plays a fundamental role in fixing this DNA damage. In this chapter, we summarize the roles and potential mechanistic analyses of OGG1 in lung infection and other inflammatory diseases.

Aflatoxin-Guanine DNA Adducts and Oxidatively Induced DNA Damage in Aflatoxin-Treated Mice in Vivo as Measured by Liquid Chromatography-Tandem Mass Spectrometry with Isotope Dilution

Dietary exposure to aflatoxin B₁ (AFB₁) is a significant contributor to the incidence of hepatocellular carcinomas globally. AFB₁ exposure leads to the formation of AFB₁-N⁷-guanine (AFB₁-N⁷-Gua) and two diastereomers of the imidazole ring-opened 8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxyaflatoxin B₁ (AFB₁-FapyGua) in DNA. These adducts lead to G → T transversion mutations with the ring-opened adduct being more mutagenic than the cationic species. Accurate measurement of these three adducts as biomarkers in DNA and urine will help identify dietary exposure to AFB₁ as a risk factor in the development of hepatocellular carcinoma worldwide. Herein, we report an improved methodology for the measurement of AFB₁-N⁷-Gua and the two diastereomers of AFB₁-FapyGua using liquid chromatography-tandem mass spectrometry with isotope dilution. We measured the levels of these compounds in liver DNA of six control mice and six AFB₁-treated mice. Levels varying from 1.5 to 45 lesions/10⁶ DNA bases in AFB₁-treated mice were detected depending on the compound and animal. No background levels of these adducts were detected in control mice. We also tested whether the AFB₁ treatment caused oxidatively induced DNA base damage using gas chromatography-tandem mass spectrometry with isotope dilution. Although background levels of several pyrimidine- and purine-derived lesions were detected, no increases in these levels were found upon AFB₁ treatment of mice. On the other hand, significantly increased levels of (5' R)- and (5' S)-8,5'-cyclo-2'-deoxyadenosines were observed in liver DNA of AFB₁-treated mice. The impact of this work is expected to achieve the accurate measurement of three AFB₁-DNA adducts and oxidatively induced DNA lesions as biomarkers of AFB₁ exposure as germane to investigations designed for the prevention of aflatoxin-related hepatocellular carcinomas and for determining the effects of genetic deficiencies in human populations.

The effects of low levels of aflatoxin B1 on health, growth performance and reproductivity in male rabbits

This study investigated the chronic effects of relatively low exposure to aflatoxin B1 (AFB1) on the growth performance, immune situation and reproduction in male rabbits. Bucks (n=32, 4.82±0.22 kg) were individually assigned to 4 treatments (8 replicates each) using a randomised complete block design. Four diets containing 0, 0.02, 0.05, and 0.1 mg AFB1/kg, were provided to bucks for 8 wk. Growth performance and semen quality were measured. Blood, organ and tissue samples were collected to measure haematological indices, liver function, organ weights and immune parameters. Compared to control, AFB1-contaminated diets reduced body weight and average daily gain (<em>P</em>&lt;0.05), altered certain haematological indices and liver function with decreased monocytes percentage and mean corpuscular haemoglobin concentration, and increased plateletcrit and albumin (<em>P</em>&lt;0.05), slightly impaired reproductive parameters with enhanced ratio of morphologically abnormal sperm cells at early stage and reduced post-stage acrosome integrity, testis weight and serum testosterone concentration (<em>P</em>&lt;0.05), decreased immune function with reduced relative liver weight (%) and tumour necrosis factor-α levels in serum and liver tissue, and increased serum 8-hydroxy-2’-deoxyguanosine levels (<em>P</em>&lt;0.05). Furthermore, bucks fed diets with relatively high AFB1 (0.05 and 0.1 mg AFB1/kg) had reduced red blood cell and haematocrit (<em>P</em>&lt;0.05) in contrast with the low AFB1 group (0.02 mg AFB1/kg). In conclusion, diets containing 0.05 and 0.1 mg AFB1/kg had negative effects on bucks’ growth performance, haematology, reproductivity and immune function, whereas diet containing 0.02 mg AFB1/kg had only minor effects on the parameters measured.

Microcystin-LR increases genotoxicity induced by aflatoxin B1 through oxidative stress and DNA base excision repair genes in human hepatic cell lines

Aflatoxin B1 (AFB1) and microcystin-LR (MC-LR) simultaneously exist in polluted food and water in humid and warm areas, and each has been reported to be genotoxic to liver and associated with hepatocellular carcinoma (HCC). However, the genotoxic effects of the two biotoxins in combination and potential mechanism remain unknown. We treated the human hepatic cell line HL7702 with AFB1 and MC-LR together at different ratios, examined their genotoxic effects using micronuclei and comet assays, and evaluated the possible mechanism by measuring oxidative stress markers and DNA base excision repair (BER) genes. Our data show that co-exposure to AFB1 and MC-LR significantly increased DNA damage compared with AFB1 or MC-LR alone as measured by the levels of both micronuclei and tail DNA. Meanwhile, AFB1 and MC-LR co-exposure showed biphasic effects on ROS production, and a gradual trend towards increased Glutathione (GSH) levels and activity of Catalase (CAT) and Superoxide Dismutase (SOD). Furthermore, MC-LR, with or without AFB1, significantly down-regulated the expression of the base excision repair (BER) genes 8-oxoguanine glycosylase-1 (OGG1) and X-ray repair cross complementing group 1 (XRCC1). AFB1 and MC-LR in combination upregulated the expression of the BER gene apurinic/apyrimidinic endonuclease 1 (APE1), whereas either agent alone had no effect. In conclusion, our studies show that MC-LR exacerbates AFB1-induced genotoxicity and we report for the first time that this occurs through effects on oxidative stress and the deregulation of DNA base excision repair genes.

Seasonal, age and sex fluctuations in aflatoxin B1 content in the liver and kidney of brown hares (Lepus europaeus Pall)

The goal of this study was to monitor the accumulation of aflatoxin B₁ in the liver and kidney of brown hares (Lepus europaeus Pall) in the region of south-western Slovakia. A total of 65 samples were involved for analysis by RIA method. Brown hares were divided into the groups according to age, sex and season (month). The sex was determined visually after shooting, and the age was assigned from dried eye lens. The average concentration of AFB₁ in the liver of hares was 0.54 ± 0.053 µg/kg, and lower values were measured in the kidney (0.41 ± 0.038 µg/kg). The significantly (P < 0.05) higher values were found in winter months when compared to summer months. According to the age, juvenile animals showed significant higher accumulation of B₁ in both organs than adults (P < 0.05). Wild animals can serve as a good model of real environmental contamination. Thus, monitoring of risk factors such as mycotoxins in the environment is important with regard to public health, as game animals constitute an important part of food chain for humans.

Protective Effects of Sporoderm-Broken Spores of Ganderma lucidum on Growth Performance, Antioxidant Capacity and Immune Function of Broiler Chickens Exposed to Low Level of Aflatoxin B₁

This study was conducted to investigate the toxic effects of aflatoxin B₁ (AFB₁) and evaluate the effects of sporoderm-broken spores of Ganoderma lucidum (SSGL) in relieving aflatoxicosis in broilers. A total of 300 one-day-old male Arbor Acre broiler chickens were randomly divided into four dietary treatments; the treatment diets were: Control (a basal diet containing normal peanut meal); AFB₁ (the basal diet containing AFB₁-contaminated peanut meal); SSGL (basal diet with 200 mg/kg of SSGL); AFB₁+SSGL (supplementation of 200 mg/kg of SSGL in AFB₁ diet). The contents of AFB₁ in AFB₁ and AFB₁+SSGL diets were 25.0 μg/kg in the starter period and 22.5 μg/kg in the finisher period. The results showed that diet contaminated with a low level of AFB₁ significantly decreased (p < 0.05) the average daily feed intake and average daily gain during the entire experiment and reduced (p < 0.05) serum contents of total protein IgA and IgG. Furthermore, a dietary low level of AFB₁ not only increased (p < 0.05) levels of hydrogen peroxide and lipid peroxidation, but also decreased (p < 0.05) total antioxidant capability, catalase, glutathione peroxidase, and hydroxyl radical scavenger activity in the liver and spleen of broilers. Moreover, the addition of SSGL to AFB₁-contaminated diet counteracted these negative effects, indicating that SSGL has a protective effect against aflatoxicosis.

Lung inflammation caused by inhaled toxicants: a review

Exposure of the lungs to airborne toxicants from different sources in the environment may lead to acute and chronic pulmonary or even systemic inflammation. Cigarette smoke is the leading cause of chronic obstructive pulmonary disease, although wood smoke in urban areas of underdeveloped countries is now recognized as a leading cause of respiratory disease. Mycotoxins from fungal spores pose an occupational risk for respiratory illness and also present a health hazard to those living in damp buildings. Microscopic airborne particulates of asbestos and silica (from building materials) and those of heavy metals (from paint) are additional sources of indoor air pollution that contributes to respiratory illness and is known to cause respiratory illness in experimental animals. Ricin in aerosolized form is a potential bioweapon that is extremely toxic yet relatively easy to produce. Although the aforementioned agents belong to different classes of toxic chemicals, their pathogenicity is similar. They induce the recruitment and activation of macrophages, activation of mitogen-activated protein kinases, inhibition of protein synthesis, and production of interleukin-1 beta. Targeting either macrophages (using nanoparticles) or the production of interleukin-1 beta (using inhibitors against protein kinases, NOD-like receptor protein-3, or P2X7) may potentially be employed to treat these types of lung inflammation without affecting the natural immune response to bacterial infections.

Mycotoxins: cytotoxicity and biotransformation in animal cells

Mycotoxins are secondary metabolites produced by many microfungi. Hitherto, over 300 mycotoxins with diverse structures have been identified. They contaminate most cereals and feedstuffs, which threaten human and animal health by exerting acute, sub-acute and chronic toxicological effects, with some considered as carcinogens. Many mycotoxins at low concentrations are able to induce the expression of cytochrome P450 and other enzymes implicated in the biotransformation and metabolization of mycotoxins in vivo and in vitro. Mycotoxins and their metabolites elicit different cellular disorders and adverse effects such as oxidative stress, inhibition of translation, DNA damage and apoptosis in host cells, thus causing various kinds of cytotoxicities. In this review, we summarize the biotransformation of mycotoxins in animal cells by CYP450 isoforms and other enzymes, their altered expression under mycotoxin exposure, and recent progress in mycotoxin cytotoxicity in different cell lines. Furthermore, we try to generalize the molecular mechanisms of mycotoxin effects in human and animal cells.

Response of the hepatic transcriptome to aflatoxin B1 in ducklings

This study was conducted to determine the effects of aflatoxin B1 (AFB1) on the hepatic transcriptome in ducklings through RNA-sequencing (RNA-Seq). Twenty four, 1-day-old ducklings were divided into 4 treatment groups. Each group received an oral dose of AFB1 at 0, 10, 20, 40 μg/kg BW per day for 2 weeks. Administration of 20 and 40 μg/kg BW of AFB1 significantly decreased body weight, feed intake, serum total protein and albumin, while increasing serum aspartate aminotransferase and alanine aminotransferase activities, and hepatic histopathological lesions. Furthermore, RNA was extracted from the liver of ducklings administrated 0 and 40 μg/kg BW of AFB1. Two RNA-Seq libraries were created from pooled samples and produced over 149 M reads, totaling 14.9 Gb of sequence. Approximately 96,953 predicted transcripts were assembled, 749 of which had significant differential expressions (≥ 2-fold) between the control and AFB1 treatment. GO and KEGG pathway analysis results showed that many genes involved in phase I metabolism, phase II detoxification, oxidation-reduction process, carcinogenesis, apoptosis and cell cycle, and fatty acid metabolism were affected by AFB1 exposure. Conclusion, this study determined the hepatic transcriptome responded to AFB1 exposure, and provide candidate genes can be targeted to prevent and/or reduce aflatoxicosis in ducklings.

The impact of chronic Aflatoxin B1 exposure and p53 genotype on base excision repair in mouse lung and liver

Aflatoxin B1 (AFB1) is produced by species of Aspergillus, and is a known human carcinogen. AFB1-induced oxidative DNA damage, specifically 8-hydroxy-2-deoxyguanosine (8-OHdG) lesions, has been demonstrated in both animal models and in humans, and is repaired by base excision repair (BER). The tumour suppressor gene p53 is implicated in the regulation of DNA repair, and heterozygous p53 knockouts have an attenuated nucleotide excision repair response to AFB1. Male heterozygous p53 knockout mice and their wild-type controls were exposed to 0, 0.2 or 1.0ppm AFB1 for 26 weeks in their diet. BER activity of lung and liver was assessed with an in vitro assay, using 8-OHdG-damaged plasmid DNA as a substrate. BER activity did not differ between livers or lungs from untreated wild-type versus heterozygous p53 knockout mice. In wild-type mice, repair was 65% lower in liver extracts from mice exposed to 1.0ppm AFB1 than in liver extracts from mice exposed to 0.2ppm AFB1 (p<0.05), but not significantly lower than that in liver extracts from control mice. AFB1 did not affect BER in lung extracts from wild-type mice, or in lung and liver extracts from heterozygous p53 knockout mice. In liver and lung, AFB1 exposure did not alter levels of 8-oxoguanine glycosylase protein, a key enzyme in the repair of 8-OHdG, and did not cause hepatotoxicity, as indicated by plasma alanine aminotransferase levels. In conclusion, chronic exposure to AFB1 did not affect BER in lungs or livers of heterozygous p53 knockout mice. BER activity was lower in livers from p53 wild type mice exposed to 1.0ppm AFB1 versus those exposed to 0.2ppm AFB1, an effect that was not attributable to liver cell death or altered levels of 8-oxoguanine glycosylase.

Effect of 8-oxoguanine glycosylase deficiency on aflatoxin B1 tumourigenicity in mice

The mycotoxin aflatoxin B1 (AFB1) may initiate cancer by causing oxidatively damaged DNA, specifically by causing 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) lesions. Base excision repair removes these lesions, with 8-oxoguanine glycosylase (OGG1) being the rate-limiting enzyme. The aim of this study was to determine the effect of ogg1 deficiency on AFB1-induced oxidatively damaged DNA and tumourigenesis. Female wild-type, heterozygous and homozygous ogg1 null mice were given a single dose of 50mg/kg AFB1 or 40 µl dimethyl sulfoxide (DMSO) ip. Neither ogg1 genotype nor AFB1 treatment affected levels of oxidised guanine in lung or liver 2h post-treatment. AFB1-treated ogg1 null mice showed exacerbated weight loss and mortality relative to DMSO-treated ogg1 null mice, but AFB1 treatment did not significantly increase lung or liver tumour incidence compared with controls, regardless of ogg1 genotype. Suspect lung masses from three of the AFB1-treated mice were adenomas, and masses from two of the mice were osteosarcomas. No osteosarcomas were observed in DMSO-treated mice. All liver masses from AFB1-treated mice were adenomas, and one also contained a hepatocellular carcinoma. In DNA from the lung tumours, the K-ras mutation pattern was inconsistent with initiation by AFB1. In conclusion, ogg1 status did not have a significant effect on AFB1-induced oxidatively damaged DNA or tumourigenesis, but deletion of one or both alleles of ogg1 did increase susceptibility to other aspects of AFB1 toxicity.