DNA damage by mycotoxins

The toxic effect of aflatoxin B1 on early porcine embryonic development

Aflatoxin B1 (AFB1) is a type of mycotoxin produced by the fungi Aspergillus flavus and Aspergillus parasiticus. AFB1 is considered as the most toxic mycotoxin owing to its toxic effect on health. In the present study, the toxic effect of AFB1 on early porcine embryonic development and its possible mechanism were investigated. Blastocyst formation was impaired with treatment of 1 nM AFB1 compared with control, 0.01, 0.1 group (40.13 ± 2.10%, 28.21 ± 1.62%, 32.34 ± 2.07% vs 19.01 ± 1.06%). Further study showed that the presence of AFB1 induced the generation of reactive oxygen species (ROS). And excessive ROS caused DNA damage which confirmed by the comet assay. Additionally, AFB1 also disrupted the DNA damage repair through the regulation of 53BP1. The AFB1 treatment significantly increased the γH2A foci and decreased the 53BP1 foci. TUNEL assay confirmed the generation of apoptosis, further resulting in the occurrence of autophagy. Moreover, AFB1 significantly increased the expression of pro-apoptosis genes Bax and Casp3 and reduced the expression of anti-apoptotic genes Bcl2 and Bcl-xl. In addition, the AFB1 also significantly increased the expression of autophagy related genes Lc3 and Beclin1. The presence of AFB1 significantly impaired the cell proliferation, a parameter of blastocyst quality for outgrowth. These results showed that the presence of AFB1 impaired porcine early embryonic development through oxidative stress, as well as DNA damage and repair, apoptosis, autophagy.

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

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

Structural Insight into the Discrimination between 8-Oxoguanine Glycosidic Conformers by DNA Repair Enzymes: A Molecular Dynamics Study of Human Oxoguanine Glycosylase 1 and Formamidopyrimidine-DNA Glycosylase

hOgg1 and FPG are the primary DNA repair enzymes responsible for removing the major guanine (G) oxidative product, namely, 7,8-dihydro-8-oxoguanine (OG), in humans and bacteria, respectively. While natural G adopts the anti conformation and forms a Watson-Crick pair with cytosine (C), OG can also adopt the syn conformation and form a Hoogsteen pair with adenine (A). hOgg1 removes OG paired with C but is inactive toward the OG:A pair. In contrast, FPG removes OG from OG:C pairs and also exhibits appreciable (although diminished) activity toward OG:A pairs. As a first step toward understanding this difference in activity, we have employed molecular dynamics simulations to examine how the anti and syn conformers of OG are accommodated in the hOgg1 and FPG active sites. When anti-OG is bound, hOgg1 active site residues are properly aligned to initiate catalytic base departure, while geometrical parameters required for the catalytic reaction are not conserved for syn-OG. On the other hand, the FPG catalytic residues are suitably aligned for both OG conformers, with anti-OG being more favorably bound. Thus, our data suggests that the differential ability of hOgg1 and FPG to accommodate the anti- and syn-OG glycosidic conformations is an important factor that contributes to the relative experimental excision rates. Nevertheless, the positions of the nucleophiles with respect to the lesion in the active sites suggest that the reactant complex is poised to initiate catalysis through a similar mechanism for both repair enzymes and supports a recently proposed mechanism in which sugar-ring opening precedes nucleoside deglycosylation.

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.

The molecular mechanism of cell cycle arrest in the Bursa of Fabricius in chick exposed to Aflatoxin B 1

Aflatoxin B₁ shows potent hepatotoxic, carcinogenic, genotoxic, immunotoxic potential in humans and many species of animals. The aim of this study was to clarify the underlying mechanism of G₀G₁ phase and G₂M phase arrest of cell cycle in the bursa of Fabricius in broilers exposed to dietary AFB₁. 144 one-day-old healthy Cobb broilers were randomly divided into two groups and fed on control diet and 0.6 mg·Kg⁻¹ AFB₁ diet for 3 weeks. Histological observation showed that AFB₁ induced the increase of nuclear debris and vacuoles in lymphoid follicle of BF. Results of flow cytometry studies showed that bursal cells arrested in G₂M phase at 7 days of age and blocked in G₀G₁ phase at 14 and 21 days of age following exposure to AFB₁. The qRT-PCR analysis indicated that cell cycle arrested in G₂M phase via ATM-Chk2-cdc25-cyclin B/cdc2 pathway, and blocked in G₀G₁ phase through ATM-Chk2-cdc25-cyclin D/CDK6 pathway and ATM-Chk2-p21-cyclin D/CDK6 route. In a word, our results provided new insights that AFB₁ diet induced G₂M and G₀G₁ phase blockage of BF cells in different periods, and different pathways were activated in different arrested cell cycle phase.

The mitochondrial and death receptor pathways involved in the thymocytes apoptosis induced by aflatoxin B1

Aflatoxin B₁ (AFB₁) is a potent immunosuppressive agent in endotherms, which can be related to the up-regulated apoptosis of immune organs. In this study, we investigated the roles of the mitochondrial, death receptor, and endoplasmic reticulum pathways in Aflatoxin B₁ induced thymocytes apoptosis. Chickens were fed an aflatoxin B₁ containing diet (0.6 mg/kg AFB₁) for 3 weeks. Our results showed that (1) AFB₁ diet induced the decrease of T-cell subsets, morphological changes, and excessive apoptosis of thymus. (2) The excessive apoptosis involved the mitochondrial pathway (up-regulation of Bax, Bak, cytC and down-regulation of Bcl-2 and Bcl-xL) and death receptor pathway (up-regulation of FasL, Fas and FADD). (3) Oxidative stress, an apoptosis inducer, was confirmed in the thymus. In conclusion, this is the first study to demonstrate that mitochondrial and death receptor pathways involved in AFB₁ induced thymocytes apoptosis in broilers.

The effects of diosmin on aflatoxin-induced liver and kidney damage

Aflatoxin is among the natural toxins that cause serious side effects on living things. Diosmin is also one of the compounds with broad pharmacological effects. In this study, the effects on the oxidant/antioxidant system of 50 mg/kg body weight/day dose of diosmin, aflatoxin (500 μg/kg body weight/day), and combined aflatoxin (500 μg/kg body weight/day) plus diosmin (50 mg/kg body weight/day) given to the stomach via catheter female adult Wistar Albino rats is examined. Forty rats were used in the experiment, and these animals were randomly allocated to four equal groups. The test phase lasted 21 days, and blood samples and tissue (liver and kidney) samples were taken after this period was over. Some biochemical parameters (glucose, triglyceride, cholesterol, blood urea nitrogen, creatinine, uric acid, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total protein, albumin) and levels of malondialdehyde, nitric oxide, and 4-hydroxynonenal and activities of superoxide dismutase, catalase, and glutathione peroxidase were analyzed in the samples. The aflatoxin administered over the period indicated a significant increase in levels of malondialdehyde (MDA), nitric oxide (NO), and 4-hydroxynonenal (4-HNE) in all tissues and blood samples. Therewithal, the activity of antioxidant enzymes showed a change in the decreasing direction. Biochemical parameters of the group in which aflatoxin were administered alone changed unfavorably. Parallel effects were also observed in the histopathological findings of this group. The results showed that aflatoxin changed antioxidant/oxidant balance in favor of oxidant and eventually led to lipid peroxidation. Diosmin administration to aflatoxin-treated animals resulted in positive changes in antioxidant enzyme activities while the levels of MDA, NO, and 4-HNE were reduced in all tissues and blood samples examined. Diosmin alleviates the oxidative stress caused by aflatoxin. Similar improvement was observed in biochemical parameters of this group as well as in liver and kidney histopathology. No significant change was observed in the group treated with diosmin alone in terms of the parameters examined and histologic findings. As a result, diosmin may be included in compounds that can be used as a therapeutic and prophylactic agent in the event of the formation of aflatoxin exposure and poisoning in animals.

Combined cytotoxicity of aflatoxin B1 and deoxynivalenol to hepatoma HepG2/C3A cells

Co-occurrence of aflatoxin B1 (AFB1) and deoxynivalenol (DON) is one of the most common mycotoxin contaminations in cereal crops and food ingredients. However, the mechanism of their combined toxicity is poorly understood. In the current investigation, the hepatoma HepG2/C3A cell line was used to explore the combined cytotoxicity of AFB1 and DON. The values of IC50, based on a sulforhodamine B (SRB) assay, were 4.5 mM and 18.7 mM for DON and AFB1, respectively. The analysis of cytotoxicity endpoints using the combination index (CI) theory revealed that the changes of mitochondrial membrane permeability and ATP resulted from an additive cytotoxic effect (CI≈1) of AFB1 and DON. However, the endpoints of double strand DNA (ds-DNA), reactive oxygen species (ROS) and cell viability (SRB) were synergistically (CI<1) affected in a dose-dependent manner. RNA-seq analysis demonstrated a number of uniquely expressed genes in their combination (AFB1: 2.5 mM, DON: 0.56 mM), indicating a synergistic interaction between AFB1 and DON at a molecular level. Additional transcriptomics analysis showed that the endoplasmic reticulum stress-associated JNK/p38/MAPK pathway was induced by DON, whereas the p53 signalling pathway was activated by AFB1. The expression profiles of apoptosis-related genes caspase-3, Bax and Bcl-2 suggested a mitochondria-mediated apoptosis pathway that was shared between AFB1 and DON. Thus, different cytotoxicity pathways and their converging at the apoptotic process might be the mechanism of the additive/synergistic cytotoxicity of AFB1 and DON to HepG2/C3A cells.

Engaging One Health for Non-Communicable Diseases in Africa: Perspective for Mycotoxins

The role of mycotoxins-e.g., aflatoxins, ochratoxins, trichothecenes, zearalenone, fumonisins, tremorgenic toxins, and ergot alkaloids-has been recognized in the etiology of a number of diseases. In many African countries, the public health impact of chronic (indoor) and/or repeated (dietary) mycotoxin exposure is largely ignored hitherto, with impact on human health, food security, and export of African agricultural food products. Notwithstanding, African scientific research reached milestones that, when linked to findings gained by the international scientific community, make the design and implementation of science-driven governance schemes feasible. Starting from Nigeria as leading African Country, this article (i) overviews available data on mycotoxins exposure in Africa; (ii) discusses new food safety issues, such as the environment-feed-food chain and toxic exposures of food producing animals in risk assessment and management; (iii) identifies milestones for mycotoxins risk management already reached in West Africa; and (iv) points out preliminary operationalization aspects for shielding communities from direct (on health) and indirect (on trade, economies, and livelihoods) effects of mycotoxins. An African science-driven engaging of scientific knowledge by development actors is expected therefore. In particular, One health/One prevention is suggested, as it proved to be a strategic and sustainable development framework.

Emerging Mycotoxins: Beyond Traditionally Determined Food Contaminants

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

Health Risks Associated with Exposure to Filamentous Fungi

Filamentous fungi occur widely in the environment, contaminating soil, air, food and other substrates. Due to their wide distribution, they have medical and economic implications. Regardless of their use as a source of antibiotics, vitamins and raw materials for various industrially important chemicals, most fungi and filamentous fungi produce metabolites associated with a range of health risks, both in humans and in animals. The association of filamentous fungi and their metabolites to different negative health conditions in humans and animals, has contributed to the importance of investigating different health risks induced by this family of heterotrophs. This review aims to discuss health risks associated with commonly occurring filamentous fungal species which belong to genera Aspergillus, Penicillium and Fusarium, as well as evaluating their pathogenicity and mycotoxic properties.

Protective effects of phenolics rich extract of ginger against Aflatoxin B1-induced oxidative stress and hepatotoxicity

Aflatoxin B1 (AFB1) is one of the predominant mycotoxin contaminant in food and feed, causing oxidative stress and hepatotoxicity. Ginger phenolics have been reported for its antioxidant potential and hepatoprotective activity. The present study investigated the protective effects of phenolics rich ginger extract (GE) against AFB1 induced oxidative stress and hepatotoxicity, in vitro and in vivo. The phenolic acid profiles of GE showed 6-gingerol and 6-shogaol as predominant components. Pretreatment of HepG2 cells with GE significantly inhibited the production of intracellular reactive oxygen species (ROS), DNA strand break, and cytotoxicity induced by AFB1. A comparable effect was observed in in vivo. Male Wistar rats were orally treated with GE (100 and 250mg/kg) daily, with the administration of AFB 1 (200μg/kg) every alternative day for 28days. Treatment with GE significantly reduced AFB1 induced toxicity on the serum markers of liver damage. In addition, GE also showed significant hepatoprotective effect by reducing the lipid peroxidation and by enhancing the antioxidant enzymes activities. These results combined with liver histopathological observations indicated that GE has potential protective effect against AFB1 induced hepatotoxicity. Additionally, administration of GE up-regulated Nrf2/HO-1 pathway, which further proved the efficiency of GE to inhibit AFB1 induced hepatotoxicity.

Probing the Characterization of the Interaction of Aflatoxins B1 and G1 with Calf Thymus DNA In Vitro

The binding characterization of aflatoxins with calf thymus DNA (ctDNA) under physiological conditions was investigated. Multispectroscopic techniques, ctDNA melting, viscosity measurements, and molecular docking techniques were employed to elucidate the binding mechanism of the aflatoxins with DNA. The fluorescence results indicated that both aflatoxin B1 (AFB1) and aflatoxin G1 (AFG1) bound to the ctDNA, forming complexes through hydrogen bonding. The binding constants of AFB1 and AFG1 with ctDNA reached up to 10³ L·mol-1 and 10⁴ L·mol-1, respectively, and AFG1 exhibited a higher binding propensity than that of AFB1. Furthermore, both AFB1 and AFG1 bound to the ctDNA through groove binding, as evidenced by the results of the spectroscopic, iodide quenching effect, viscosity, and ctDNA melting measurements. Changes in the circular dichroism signal manifested that both AFB1 and AFG1 induced an increase in the right-handed helicity, but only minimally influenced the base stacking of the DNA. A molecular docking study of the aflatoxin's binding with the DNA revealed a groove binding mode, which was driven mainly by hydrogen bonding. This study of aflatoxin-ctDNA interaction may provide novel insights into the toxicological effect of the mycotoxins.

The Molecular Basis of Toxins' Interactions with Intracellular Signaling via Discrete Portals

An understanding of the molecular mechanisms by which microbial, plant or animal-secreted toxins exert their action provides the most important element for assessment of human health risks and opens new insights into therapies addressing a plethora of pathologies, ranging from neurological disorders to cancer, using toxinomimetic agents. Recently, molecular and cellular biology dissecting tools have provided a wealth of information on the action of these diverse toxins, yet, an integrated framework to explain their selective toxicity is still lacking. In this review, specific examples of different toxins are emphasized to illustrate the fundamental mechanisms of toxicity at different biochemical, molecular and cellular- levels with particular consideration for the nervous system. The target of primary action has been highlighted and operationally classified into 13 sub-categories. Selected examples of toxins were assigned to each target category, denominated as portal, and the modulation of the different portal’s signaling was featured. The first portal encompasses the plasma membrane lipid domains, which give rise to pores when challenged for example with pardaxin, a fish toxin, or is subject to degradation when enzymes of lipid metabolism such as phospholipases A₂ (PLA₂) or phospholipase C (PLC) act upon it. Several major portals consist of ion channels, pumps, transporters and ligand gated ionotropic receptors which many toxins act on, disturbing the intracellular ion homeostasis. Another group of portals consists of G-protein-coupled and tyrosine kinase receptors that, upon interaction with discrete toxins, alter second messengers towards pathological levels. Lastly, subcellular organelles such as mitochondria, nucleus, protein- and RNA-synthesis machineries, cytoskeletal networks and exocytic vesicles are also portals targeted and deregulated by other diverse group of toxins. A fundamental concept can be drawn from these seemingly different toxins with respect to the site of action and the secondary messengers and signaling cascades they trigger in the host. While the interaction with the initial portal is largely determined by the chemical nature of the toxin, once inside the cell, several ubiquitous second messengers and protein kinases/ phosphatases pathways are impaired, to attain toxicity. Therefore, toxins represent one of the most promising natural molecules for developing novel therapeutics that selectively target the major cellular portals involved in human physiology and diseases.

Involvement of ROS in nanosilver-caused suppression of aflatoxin production from Aspergillus flavus

A possible mechanism involving transmembrane release of O₂⁻was revealed to explain nanosilver-caused suppression of aflatoxin production fromAspergillus flavus.

Aflatoxin B₁-Induced Developmental and DNA Damage in Caenorhabditis elegans

Aflatoxin B₁ (AFB₁) is a ubiquitous mycotoxin produced by toxicogenic Aspergillus species. AFB₁ has been reported to cause serious adverse health effects, such as cancers and abnormal development and reproduction, in animals and humans. AFB₁ is also a potent genotoxic mutagen that causes DNA damage in vitro and in vivo. However, the link between DNA damage and abnormal development and reproduction is unclear. To address this issue, we examined the DNA damage, germline apoptosis, growth, and reproductive toxicity following exposure to AFB₁, using Caenorhabditis elegans as a study model. Results found that AFB₁ induced DNA damage and germline apoptosis, and significantly inhibited growth and reproduction of the nematodes in a concentration-dependent manner. Exposure to AFB₁ inhibited growth or reproduction more potently in the DNA repair-deficient xpa-1 nematodes than the wild-type N2 strain. According to the relative expression level of pathway-related genes measured by real-time PCR, the DNA damage response (DDR) pathway was found to be associated with AFB₁-induced germline apoptosis, which further played an essential role in the dysfunction of growth and reproduction in C. elegans.

Protective effects of green tea and its main constituents against natural and chemical toxins: A comprehensive review

Toxins are natural or chemical poisonous substances with severe side effects on health. Humans are generally exposed by widespread toxic contaminations via air, soil, water, food, fruits and vegetables. Determining a critical antidote agent with extensive effects on different toxins is an ultimate goal for all toxicologists. Traditional medicine is currently perceived as a safe and natural approach against toxins. In this regard, we focused on the protective effects of green tea (Camellia sinensis) and its main components such as catechin, epicatechin, epicatechin gallate, gallocatechin, epigallocatechin and epigallocatechin gallate as a principal source of antioxidants against both natural and chemical toxins. This literate review demonstrates that protective effects of green tea and its constituents were mainly attributed to their anti-oxidative, radical scavenging, chelating, anti-apoptotic properties and modulating inflammatory responses. Although, some studies reveal they have protective effects by increasing toxin metabolism and neutralizing PLA₂, proteases, hyaluronidase and l-amino acid oxidase enzymes.

Individual and combined effects of feed artificially contaminated with with fumonisin B1 and T-2 toxin in weaned rabbits

Co-contamination of feed and feed raw materials with two or more mycotoxins is frequently reported, however, only a few studies have investigated the combined effects of low doses of multiple mycotoxins. In the present study the individual and combined effects of 10 mg/kg fumonisin B1 and 2 mg/kg T-2 toxin (n=12/group) were investigated in weaned rabbits. Mycotoxin contaminated feed was produced by adding fungal cultures of Fusarium verticillioides and Fusarium sporotrichioides, and fed to 40 days old rabbits during 28 days. Feed intake and body weight were measured weekly, serum biochemistry and antioxidant parameters on day 0, 14 and 28, while histopathological examination and comet assay were performed at the end of the experiment. T-2 exposure both alone and in combination resulted in 15-18% less final body weight compared to the control and FB1 treatment. There was a significant increase in the concentration of plasma total protein, albumin, fructosamine and creatinine in the group treated with FB1 compared to the control. The liver and the kidney of most animals treated with T-2 toxin, FB1 and their combination showed pathological changes, occurring more frequent in animals exposed to both toxins. T-2 resulted in depletion of lymphocytes in the spleen. FB1 and T-2 exerted synergistic effect on the antioxidant/oxidative parameters after 2 weeks of exposure, manifesting in less glutathione and glutathione peroxidase, while more malondialdehyde was produced. Both toxins caused DNA damage in the lymphocytes, which was more pronounced in the group fed T-2 toxin and T-2 combined with FB1, without additive or synergistic effects.

Diet-related DNA adduct formation in relation to carcinogenesis

The human diet contributes significantly to the initiation and promotion of carcinogenesis. It has become clear that the human diet contains several groups of natural foodborne chemicals that are at least in part responsible for the genotoxic, mutagenic, and carcinogenic potential of certain foodstuffs. Electrophilic chemicals are prone to attack nucleophilic sites in DNA, resulting in the formation of altered nucleobases, also known as DNA adducts. Since DNA adduct formation is believed to signal the onset of chemically induced carcinogenesis, the DNA adduct-inducing potential of certain foodstuffs has been investigated to gain more insight into diet-related pathways of carcinogenesis. Many studies have investigated diet-related DNA adduct formation. This review summarizes work on known or suspected dietary carcinogens and the role of DNA adduct formation in hypothesized carcinogenesis pathways.

Fungal allelochemicals in insect pest management

Interactions between insects and fungi are widespread, and important mediators of these interactions are fungal chemicals that can therefore be considered as allelochemicals. Numerous studies suggest that fungal chemicals can affect insects in many different ways. Here, we apply the terminology established by insect-plant ecologists for categorizing the effect of fungal allelochemicals on insects and for evaluating the application potential of these chemicals in insect pest management. Our literature survey shows that fungal volatile and non-volatile chemicals have an enormous potential to influence insect behavior and fitness. Many of them still remain to be discovered, but some recent examples of repellents and toxins could open up new ways for developing safe insect control strategies. However, we also identified shortcomings in our understanding of the chemical ecology of insect-fungus interactions and the way they have been investigated. In particular, the mode-of-action of fungal allelochemicals has often not been appropriately designated or examined, and the way in which induction by insects affects fungal chemical diversity is poorly understood. This review should raise awareness that in-depth ecological studies of insect-fungus interactions can reveal novel allelochemicals of particular benefit for the development of innovative insect pest management strategies.

The mycotoxin zearalenone enhances cell proliferation, colony formation and promotes cell migration in the human colon carcinoma cell line HCT116

Zearalenone (ZEN) and Aflatoxin B1 (AFB1) are fungal secondary metabolites produced by Fusarium and Aspergillus genera, respectively. These mycotoxins are found world-wide as corn and wheat contaminants. AFB1 is probably the most toxic and carcinogenic mycotoxin. It has been demonstrated to be mutagenic, genotoxic, and hepatocarcinogenic. ZEN is a non-steroidal estrogenic mycotoxin that displays hepatotoxicity, immunotoxicity and genotoxicity. Its mutagenic and carcinogenic properties have so far remained controversial and questionable. Using the colon carcinoma cell line HCT116, we will show here that ZEN, at low concentrations, enhances cell proliferation, increases colony formation and fastens cell migration after wound healing. The highest effect of ZEN was observed at a concentration 10 times lower as compared to AFB1. Our findings suggest thus that this mycotoxin exhibits carcinogenesis-like properties in HCT116 cells.

Experimental Studies on Some Immunotoxicological Aspects of Aflatoxins Containing Diet and Protective Effect of Bee Pollen Dietary Supplement

Aflatoxins (AFs), widely distributed food-borne mycotoxins, affect quality and safety of food and cause economic losses in livestock. In this study, the protective effect of Bee Pollen (BP) against some immunotoxic hazards elucidated from eating of AFs-containing diet was investigated in Wistar rats. Rats were randomly classified intofour groups and treated for 30 days, Group 1; control negative, Group 2; Total AFs (3 mg kg(-1) basal diet), Group 3; BP (20 g kg(-1) basal diet) and Group 4; AFs+BP in basal diet. The immunoprotective effect of BP was revealed in terms of increasing (relative to levels seen in Group 2 rats that consumed the AFs diet) serum total protein and globulin levels, restored normal neutrophil (PMN)/lymphocyte ratio, increased PMN phagocytic activity and increased lymphocyte proliferative capacity. Also, the use of the BP reduced spleen H2O2 levels and increased GSH content while maintaining normal levels of NO formation. Histopathologic analysis showed thatthe AFs caused lymphocytic depletion in the spleen; however, BP induced lymphocytic hyperplasia and reduced the levels of AFs-inducible cellular exhaustion or depletion. These results provide evidence of a protective effect of BP against some immunotoxic actions induced in situ by consumption of AFs.

The Genomes of Three Uneven Siblings: Footprints of the Lifestyles of Three Trichoderma Species

The genus Trichoderma contains fungi with high relevance for humans, with applications in enzyme production for plant cell wall degradation and use in biocontrol. Here, we provide a broad, comprehensive overview of the genomic content of these species for "hot topic" research aspects, including CAZymes, transport, transcription factors, and development, along with a detailed analysis and annotation of less-studied topics, such as signal transduction, genome integrity, chromatin, photobiology, or lipid, sulfur, and nitrogen metabolism in T. reesei, T. atroviride, and T. virens, and we open up new perspectives to those topics discussed previously. In total, we covered more than 2,000 of the predicted 9,000 to 11,000 genes of each Trichoderma species discussed, which is >20% of the respective gene content. Additionally, we considered available transcriptome data for the annotated genes. Highlights of our analyses include overall carbohydrate cleavage preferences due to the different genomic contents and regulation of the respective genes. We found light regulation of many sulfur metabolic genes. Additionally, a new Golgi 1,2-mannosidase likely involved in N-linked glycosylation was detected, as were indications for the ability of Trichoderma spp. to generate hybrid galactose-containing N-linked glycans. The genomic inventory of effector proteins revealed numerous compounds unique to Trichoderma, and these warrant further investigation. We found interesting expansions in the Trichoderma genus in several signaling pathways, such as G-protein-coupled receptors, RAS GTPases, and casein kinases. A particularly interesting feature absolutely unique to T. atroviride is the duplication of the alternative sulfur amino acid synthesis pathway.

Panax ginseng extract modulates oxidative stress, DNA fragmentation and up-regulate gene expression in rats sub chronically treated with aflatoxin B1 and fumonisin B 1

Aflatoxins and fumonisins are important food-borne mycotoxins implicated in human health and have cytotoxic effects. The aims of the current study were to evaluate the protective role of Panax ginseng extract (PGE) against the synergistic effect of subchronic administration of aflatoxin B1 (AFB1) and fumonisin B1 (FB1) on DNA and gene expression in rat. Female Sprague-Dawley rats were divided into eight groups (ten rats/group) and treated for 12 weeks including the control group, the group having received AFB1 (80 µg/kg bw), the group having received FB1 (100 µg/kg bw), the group having received AFB1 plus FB1 and the groups having received PGE (20 mg/kg bw) alone or with AFB1 and/or FB1. At the end of experiment, liver and kidney were collected for the determination of DNA fragmentation, lipid peroxidation (LP), glutathione (GSH) contents and alterations in gene expression. The results indicated that these mycotoxins increased DNA fragmentation, LP and decreased GSH content in liver and kidney and down-regulated gene expression of antioxidants enzymes. The combined treatments with AFB1 and/or FB1 plus PGE suppressed DNA fragmentation only in the liver, normalized LP and increased GSH in the liver and kidney as well as up-regulated the expression of GPx, SOD1 and CAT mRNA. It could be concluded that AFB1 and FB1 have synergistic genotoxic effects. PGE induced protective effects against their oxidative stress and genotoxicity through its antioxidant properties.

Longitudinal evaluation of aflatoxin exposure in two cohorts in south-western Uganda

Aflatoxins (AF) are a group of mycotoxins. AF exposure causes acute and chronic adverse health effects such as aflatoxicosis and hepatocellular carcinoma in human populations, especially in the developing world. In this study, AF exposure was evaluated using archived serum samples from human immunodeficiency virus (HIV)-seronegative participants from two cohort studies in south-western Uganda. AFB1-lysine (AFB-Lys) adduct levels were determined via HPLC fluorescence in a total of 713 serum samples from the General Population Cohort (GPC), covering eight time periods between 1989 and 2010. Overall, 90% (642/713) of the samples were positive for AFB-Lys and the median level was 1.58 pg mg(-1) albumin (range = 0.40-168 pg mg(-1) albumin). AFB-Lys adduct levels were also measured in a total of 374 serum samples from the Rakai Community Cohort Study (RCCS), across four time periods between 1999 and 2003. The averaged detection rate was 92.5% (346/374) and the median level was 1.18 pg mg(-1) albumin (range = 0.40-122.5 pg mg(-1) albumin). In the GPC study there were no statistically significant differences between demographic parameters, such as age, sex and level of education, and levels of serum AFB-Lys adduct. In the RCCS study, longitudinal analysis using generalised estimating equations revealed significant differences between the adduct levels and residential areas (p = 0.05) and occupations (p = 0.02). This study indicates that AF exposure in people in two populations in south-western Uganda is persistent and has not significantly changed over time. Data from one study, but not the other, indicated that agriculture workers and rural area residents had more AF exposure than those non-agricultural workers and non-rural area residents. These results suggest the need for further study of AF-induced human adverse health effects, especially the predominant diseases in the region.

Polymorphisms in the precursor microRNAs and aflatoxin B1-related hepatocellular carcinoma

The altered expression of some microRNAs (miRNAs) is observed in hepatocellular carcinoma (HCC); however, the genetic polymorphisms in the precursor miRNAs (pre-miRNAs) in aflatoxin B1 (AFB1)-related HCC have not yet been investigated. A hospital-based case-control study, including 1,706 HCC cases and 2,270 controls without any liver diseases or tumors, was conducted in a high AFB1 exposure area of China to assess the relationship between 48 polymorphisms in the pre-miRNAs and AFB1-related HCC risk and prognosis. Among 48 polymorphisms, only rs28599926 (in the miRNA 1268a) affected HCC risk. Compared with the homozygote of rs28599926C alleles (rs28599926-CC), the genotypes of rs28599926 T alleles (namely rs28599926-CT or -TT) increased HCC risk (odds ratio [OR]: 1.63 and 5.52, 95% confidence interval [CI]: 1.40-1.90 and 4.27-7.14, respectively). Significant interactive effects between risk genotypes and AFB1 exposure status were also observed in the joint effects analysis. This polymorphism was associated not only with larger tumor size, higher portal vein tumor risk, and tumor dedifferentiation, but also with higher AFB1 adducts levels and increasing the mutation risk of TP53 gene. Furthermore, rs28599926 modified the tumor recurrence-free survival (hazard ratio [HR]: 2.86, 95% CI: 2.36-3.43) and overall survival (HR: 2.12, 95% CI: 1.86-2.41) of cases. Additionally, one target of miR-1268a was show to be the ADAMTS4 mRNA and rs28599926 polymorphism might modify ADAMTS4 expression. These findings indicate that polymorphisms in the pre-miRNAs may be risk and prognostic biomarkers of AFB1-related HCC, and rs28599926 in miR-1268a is such a potential candidate. © 2015 Wiley Periodicals, Inc.

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.

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.

Novel aspects of the liver microenvironment in hepatocellular carcinoma pathogenesis and development

Hepatocellular carcinoma (HCC) is a prevalent primary liver cancer that is derived from hepatocytes and is characterised by high mortality rate and poor prognosis. While HCC is driven by cumulative changes in the hepatocyte genome, it is increasingly recognised that the liver microenvironment plays a pivotal role in HCC propensity, progression and treatment response. The microenvironmental stimuli that have been recognised as being involved in HCC pathogenesis are diverse and include intrahepatic cell subpopulations, such as immune and stellate cells, pathogens, such as hepatitis viruses, and non-cellular factors, such as abnormal extracellular matrix (ECM) and tissue hypoxia. Recently, a number of novel environmental influences have been shown to have an equally dramatic, but previously unrecognized, role in HCC progression. Novel aspects, including diet, gastrointestinal tract (GIT) microflora and circulating microvesicles, are now being recognized as increasingly important in HCC pathogenesis. This review will outline aspects of the HCC microenvironment, including the potential role of GIT microflora and microvesicles, in providing new insights into tumourigenesis and identifying potential novel targets in the treatment of HCC.

Involvement of DNA damage response pathways in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has been known as one of the most lethal human malignancies, due to the difficulty of early detection, chemoresistance, and radioresistance, and is characterized by active angiogenesis and metastasis, which account for rapid recurrence and poor survival. Its development has been closely associated with multiple risk factors, including hepatitis B and C virus infection, alcohol consumption, obesity, and diet contamination. Genetic alterations and genomic instability, probably resulted from unrepaired DNA lesions, are increasingly recognized as a common feature of human HCC. Dysregulation of DNA damage repair and signaling to cell cycle checkpoints, known as the DNA damage response (DDR), is associated with a predisposition to cancer and affects responses to DNA-damaging anticancer therapy. It has been demonstrated that various HCC-associated risk factors are able to promote DNA damages, formation of DNA adducts, and chromosomal aberrations. Hence, alterations in the DDR pathways may accumulate these lesions to trigger hepatocarcinogenesis and also to facilitate advanced HCC progression. This review collects some of the most known information about the link between HCC-associated risk factors and DDR pathways in HCC. Hopefully, the review will remind the researchers and clinicians of further characterizing and validating the roles of these DDR pathways in HCC.

Deficient glutathione in the pathophysiology of mycotoxin-related illness

Evidence for the role of oxidative stress in the pathophysiology of mycotoxin-related illness is increasing. The glutathione antioxidant and detoxification systems play a major role in the antioxidant function of cells. Exposure to mycotoxins in humans requires the production of glutathione on an “as needed” basis. Research suggests that mycotoxins can decrease the formation of glutathione due to decreased gene expression of the enzymes needed to form glutathione. Mycotoxin-related compromise of glutathione production can result in an excess of oxidative stress that leads to tissue damage and systemic illness. The review discusses the mechanisms by which mycotoxin-related deficiency of glutathione may lead to both acute and chronic illnesses.

Mycotoxins' activity at toxic and sub-toxic concentrations: differential cytotoxic and genotoxic effects of single and combined administration of sterigmatocystin, ochratoxin A and citrinin on the hepatocellular cancer cell line Hep3B

Food safety organizations indicate the likelihood of constant human and animal exposure to mycotoxin mixtures as a possible negative public health impact. Risk assessment demonstrates that certain mycotoxins of Aspergillus and Penicillium spp. are toxic and hold a significant genotoxic efficacy at nanomolar concentrations. The aim of the current study was to investigate the potential cytogenetic effects of sterigmatocystin (STER), ochratoxin A (OTA) and citrinin (CTN) alone or in combination, at pM to μΜ concentrations, on the human hepatocellular cancer cell line Hep3B. MTT reduction, mitotic divisions, cell cycle delays and sister chromatid exchange rates (SCE) were determined as endpoints of metabolic activity, cytotoxicity, cytostaticity, and genotoxicity, respectively. All mycotoxin treatments induce SCE rates from 10-12 M, while their cytotoxic and cytostatic potential varies. In PRI and MI assays, but not at MTT, STER alone or in combination with OTA + CTN appeared cytostatic and cytotoxic, even at 10-12 M, while CTN alone and all other combinations displayed substantial cellular survival inhibition in doses ≥ 10-8 M. Co-administration of STER + OTA or STER + CTN in concentrations ≤ 10-1 M, increased the MI and MTT activity, while it did not affect the PRI. Mycotoxin co-treatments revealed in general similar-to-additive or antagonistic genotoxic and cytotoxic effects. Our results for the first time describe that STER alone or in combination with OTA and/or CTN share a cytotoxic and cytogenetic potential even at picoMolar concentrations on human hepatoma cells in vitro.