Cytochrome P450 isoforms are differently up-regulated in aflatoxin B₁-exposed human lymphocytes and monocytes

The immunomodulatory effect of minocycline on gene expression of inflammation related cytokines in lipopolysaccharide-treated human peripheral blood mononuclear cells

To evaluate the immunomodulatory effect of minocycline, the present study was carried out on the gene expression of toll-like receptor type-4 (TLR4) and some pro-inflammatory (IL-1β, IL-6) and anti-inflammatory cytokines (IL-10) associated with lipopolysaccharide (LPS) -induced inflammation in human peripheral blood mononuclear cells (PBMCs). The PBMCs were collected and then 5.4 × 106 PBMCs/mL were used in eight groups as follows: control group (only media), LPS group (only LPS), methylprednisolone (Pred) group (LPS plus Pred), meloxicam (Melo) group (LPS plus Melo), three minocycline groups [M1, M5 and M25] (LPS plus 1, 5, and 25 µg/mL minocycline, respectively) and minocycline control (MC) group (5 µg/mL minocycline). After incubation for 24 h, the PBMCs were subjected to quantitative PCR assays. Gene expression levels of TLR4 were not changed in any groups. The IL-1β levels were increased in the LPS group but the increases were much more intense in the other groups except Pred group. Compared with control group, IL-6 levels increased significantly in Melo, M1 and M25 groups. Significant increases of IL-10 levels were also observed in Melo, M25 and MC groups. It can be concluded that minocycline had dual pro- and anti-inflammatory activities with potential clinical immunomodulatory effects.

The Novel Atypical Antipsychotic Lurasidone Affects Cytochrome P450 Expression in the Liver and Peripheral Blood Lymphocytes

Lurasidone is a novel atypical antipsychotic drug acting on dopaminergic, serotonergic and noradrenergic receptors; it is applied for the long-term treatment of schizophrenia and depression in patients with bipolar disorders. We aimed at performing a comparative study on the influence of chronic treatment with lurasidone on the expression of cytochrome P450 enzymes in the liver and in peripheral blood lymphocytes, and to evaluate the relationship between changes in the expression of CYP enzymes in the two experimental models. The obtained results show a fairly similar expression pattern of the main CYP enzymes in the rat livers and lymphocytes, and they indicate that in the liver, lurasidone exerts an inhibitory effect on the activity, protein and mRNA levels of CYP2B1/2 (not CYP2B2 mRNA), CYP2C11 and CYP2E1, while in the case of CYP3A1 and CYP3A2, it causes enzyme induction. At the same time, lurasidone decreases the expression of CYP2B, CYP2C11 (CYP2C11 protein only) and CYP2E1 but increases that of CYP3A2 (not CYP3A1) in lymphocyte cells. In conclusion, chronic treatment with lurasidone simultaneously and in the same way influences the expression and activity of CYP2B, CYP2C11, CYP2E1 and CYP3A2 in the liver and peripheral blood lymphocytes of rats. Thus, the lymphocyte cytochrome P450 profile may be utilized as an indicator of the hepatic cytochrome P450 profile in further clinical studies with lurasidone, and lymphocytes may serve as easily available surrogates for examining the impact of new drugs and chronic in vivo treatments on CYP enzyme expression, as well as to estimate drug-drug interactions and toxicity risk.

Response surface model to illustrate the benefits of tryptophan, melatonin, and N,N-dimethylglycine in quail chicks exposed to aflatoxin B1

A dose-response assay in a central composite design platform was conducted to investigate the responses (performance, immunity, and meat quality) of quail chicks to dietary tryptophan (Trp), melatonin (MEL), and N,N-dimethylglycine (DMG) exposed to aflatoxin B1 (AFB1). A total of 1,275 quail chicks were randomly allotted to 85-floor pens consisting of 17 treatments with 5 replicates and 15 birds per each pen. Dietary MEL and DMG had a different effect on growth rate and interacted with dietary Trp and AFB1 during the first 4 wk of age, while their effect disappeared at the last week of the experiment. Dietary Trp and AFB1 were only significant on the gain of quail chick after d 28 of the assay. During the second and third weeks of age, the reduction in feed intake caused by AFB1 attenuated by dietary MEL and DMG and dietary Trp profoundly affects feed intake in the last 2 wk of the experiment. Dietary MEL and DMG were effective on feed conversion ratio (FCR) during the second and third weeks of age. AFB1 decreased breast meat yield (BMY) and thigh meat yield (TMY), but the inclusion of either MEL or DMG removed the adverse effects of AFB1. Dietary Trp increased BMY, but it did not affect TMY. Increasing dietary Trp linearly increased the Lactobacillus bacteria (LAB) population, and AFB1 negatively impacts the LAB population. The inclusion of dietary DMG removed that negative effect on LAB. Although AFB1 decreased the antibody production against SRBC-antigen, increasing dietary Trp in intoxicated quails increased the plasma antibody in SRBC-challenged birds. At low levels of dietary Trp (0.15-0.19%), the addition of DMG increased malondialdehyde (MDA) production while increasing Trp reversed this adverse situation. In conclusion, these supplements may interact with AFB1 in younger chicks, and dietary Trp and AFB1 have a significant impact on the growth performance of quail chicks during the fifth and sixth week of age.

The anti-inflammatory effects of minocycline on lipopolysaccharide-induced paw oedema in rats: a histopathological and molecular study

Minocycline is a semi-synthetic antimicrobial agent with claimed anti-inflammatory properties reported from different experimental models. This study was aimed to evaluate the anti-inflammatory effects of minocycline, compared to the actions of two common anti-inflammatory agents, on lipopolysaccharide (LPS)-induced paw oedema through some clinical, histopathological, haematological and molecular analyses. Forty-eight rats were divided into eight groups (n = 6). In control group (Ctrl), each animal was injected with normal saline into its sub-plantar region of hind paw. In groups 2-7, hind paw oedema was induced by injection of LPS. One hour before injections, groups 1 (Ctrl) and 2 (LPS) were treated orally with distilled water, 3 and 4 with methylprednisolone (Pred) and meloxicam (Melo) and 5-7 with minocycline in doses of 50, 150 and 450 mg/kg (M50, M150 and M450, respectively). The 8th group (MC) was given minocycline (150 mg/kg) orally and normal saline was injected into sub-plantar region. Paw swelling and body temperature were assessed at 0, 2, 4, 6 and 24 h post-injections. At 24 h, samples of blood and liver, kidney, spleen and hind paw tissues were taken for haematological and histopathological examinations. Some samples of the paw were also obtained for molecular analysis of some inflammatory-related cytokines at mRNA level. Paw swelling and body temperature increased in all LPS-injected groups 2 h post-injection. In LPS group, they remained significantly increased up to 24 h; however, these parameters decreased to normal in Pred, Melo and all minocycline groups. The histological findings showed mild-to-moderate signs of inflammation in tissue samples of groups 2-6, but not in group M450. Additionally, gene expression of pro-inflammatory cytokines (IL-1β and IL-6) increased significantly in LPS group compared to other groups. In conclusion, this study supports the role of minocycline as an anti-inflammatory agent with effects comparable to those of meloxicam and methylprednisolone.

Immunotoxicity of Three Environmental Mycotoxins and Their Risks of Increasing Pathogen Infections

Aflatoxin B1 (AFB1), ochratoxin A (OTA), and deoxynivalenol (DON) are the three mycotoxins that have received the most scholarly attention and have been tested most routinely in clinics. These mycotoxins not only suppress immune responses but also induce inflammation and even increase susceptibility to pathogens. Here, we comprehensively reviewed the determining factors for the bidirectional immunotoxicity of the three mycotoxins, their effects on pathogens, and their action mechanisms. The determining factors include mycotoxin exposure doses and times, as well as species, sex, and some immunologic stimulants. Moreover, mycotoxin exposure can affect the infection severity of some pathogens, including bacteria, viruses, and parasites. Their specific action mechanisms include three aspects: (1) mycotoxin exposure directly promotes the proliferation of pathogenic microorganisms; (2) mycotoxins produce toxicity, destroy the integrity of the mucosal barrier, and promote inflammatory response, thereby improving the susceptibility of the host; (3) mycotoxins reduce the activity of some specific immune cells and induce immune suppression, resulting in reduced host resistance. The present review will provide a scientific basis for the control of these three mycotoxins and also provide a reference for research on the causes of increased subclinical infections.

Human CYP1B1 enzyme-mediated, AhR enhanced activation of aflatoxin B1 for its genotoxicity in human cells

Aflatoxin B1 (AFB1) is a human procarcinogen known to be activated by cytochrome P450 (CYP) 1A2 and 3A4. In a previous study AFB1 caused chromosomal rearrangement in a yeast strain genetically engineered for stably expressing human CYP1B1. Yet, further verification of the effect of AFB1 in human cells, a potential role of the aryl hydrocarbon receptor (AhR), and CYP1B1-catalyzed AFB1 metabolism remain unidentified. In this study, a human hepatocyte (L-02) line and a human lymphoblastoid (TK6) cell line were genetically engineered for the expression of human CYP1B1, producing L-02-hCYP1B1 and TK6-hCYP1B1, respectively. They were exposed to AFB1 and analyzed for the formation of micronucleus and elevation of γ-H2AX (indicating double-strand DNA breaks); the metabolites formed by CYP1B1 from AFB1 after incubation of AFB1 with human CYP1B1 isoenzyme microsomes were determined by LC-MS. The results showed significantly more potent induction of micronucleus by AFB1 in L-02-hCYP1B1 and TK6-hCYP1B1 than in the parental (L-02 and TK6) cells, and the effects were reduced by (E)- 2,3',4,5'-tetramethoxystilbene, a specific CYP1B1 inhibitor. In the AFB1- CYP1B1 microsomes incubations AFM1, a known stable metabolite of AFB1, was detected. Moreover, in L-02 and TK6 cells, AFB1 apparently increased the protein levels of AhR, ANRT and CYP1B1, and caused the nuclear translocation of AhR and ARNT, the latter effect being blocked by BAY-218 (an inhibitor of AhR). In conclusion, this study indicates that human CYP1B1 is capable of metabolically activating AFB1 through the AhR signaling pathway.

Alveolar Macrophages Participate in the Promotion of Influenza Virus Infection by Aflatoxin B1 at an Early Stage

Aflatoxin B1 (AFB1), one of the most common environmental mycotoxin contaminations in food and feed, poses significant threats to human and animal health. Our previous study indicated that even non-toxic AFB1 concentrations could promote influenza virus replication and induce influenza virus-infected alveolar macrophages polarizing from M1 (immunostimulatory phenotype) to M2 (immunosuppressive phenotype) over time. However, whether AFB1 promotes influenza replication via modulating the polarization of alveolar macrophages is unknown. Here, we specifically depleted alveolar macrophages using clodronate-containing liposomes in swine influenza virus (SIV)-infected mice to explore the mechanism the promotion of SIV replication by AFB1. The results show that the depletion of alveolar macrophages significantly alleviated the AFB1-induced weight loss, inflammatory responses, and lung and immune organ damage of the SIV-infected mice after 14 days and greatly diminished the AFB1-promoted SIV replication. In contrast, the depletion of alveolar macrophages did not alleviate the AFB1-induced weight loss, and lung and immune organ damage of the SIV-infected mice after 28 days and slightly diminished the AFB1-promoted SIV replication. Collectively, the data indicate that alveolar macrophages play a crucial role the promotion of SIV infection by AFB1 in the early rather than late stage, and AFB1 can promote SIV replication by inducing alveolar macrophages to polarize towards M1 macrophages. This research provides novel targets for reducing the risk of AFB1-promoted influenza virus infection.

Metabolic Disruption by Naturally Occurring Mycotoxins in Circulation: A Focus on Vascular and Bone Homeostasis Dysfunction

Naturally occurring food/feed contaminants have become a significant global issue due to animal and human health implications. Despite risk assessments and legislation setpoints on the mycotoxins' levels, exposure to lower amounts occurs, and it might affect cell homeostasis. However, the inflammatory consequences of this possible everyday exposure to toxins on the vascular microenvironment and arterial dysfunction are unexplored in detail. Circulation is the most accessible path for food-borne toxins, and the consequent metabolic and immune shifts affect systemic health, both on vascular apparatus and bone homeostasis. Their oxidative nature makes mycotoxins a plausible underlying source of low-level toxicity in the bone marrow microenvironment and arterial dysfunction. Mycotoxins could also influence the function of cardiomyocytes with possible injury to the heart. Co-occurrence of mycotoxins can modulate the metabolic pathways favoring osteoblast dysfunction and bone health losses. This review provides a novel insight into understanding the complex events of coexposure to mixed (low levels) mycotoxicosis and subsequent metabolic/immune disruptions contributing to chronic alterations in circulation.

Colostrum fails to prevent bovine/camelid neonatal neutrophil damage from AFB1

Exposure to environmental toxicants that affect the immune system and overall health of many mammals is mostly unavoidable. One of the more common substances is the mycotoxins, especially carcinogenic aflatoxin (AF)B₁ which also causes immune suppression/dysregulation in exposed hosts. The present study analyzed the effects of naturally occurring levels of AFB₁ on apoptosis of healthy bovine and camelid neonatal neutrophils (PMN) that were isolated both before and after host consumption of colostrum. Cells from bovine and camel neonates (n = 12 sets of PMN/mammal/timepoint) were exposed for 24 h to a low level of AFB₁ (i.e. 10 ng AFB₁/ml) and then intracellular ATP content and caspase-3, -7, and -9 activities (determined by bioluminescence) were assessed. The results indicated a significant lessening of intracellular ATP content and equivalents of luminescence intensity in AFB₁-treated PMN in all studied samples, i.e. isolated pre-and post-colostrum consumption. In contrast, caspase-3, -7, and -9 activities in both pre- and post-colostrum consumption bovine and camelid PMN were noticeably increased (∼>2-fold). The damaging effects of AFB₁ were more pronounced in bovine neonate PMN than in camelid ones. These results showed that camelid or bovine neonatal PMN collected pre- and post-colostrum are sensitive (moreso after consumption) to naturally occurring levels of AFB₁. While merits of colostrum are well known, its failure to mitigate toxic effects of AFB₁ in what would translate into a critical period in the development of immune competence (i.e. during the first few days of life in bovine and camelid calves) is surprising. The observed in vitro toxicities can help clarify underlying mechanisms of immune disorders caused by AFs in animals/humans.

Neuroimmune disruptions from naturally occurring levels of mycotoxins

Substantial pieces of evidence support the potential of exogenous toxins in disrupting neuroimmune homeostasis. It appears that mycotoxins are one of the noticeable sources of naturally occurring substances dysregulating the immune system, which involves the physiology of many organs, such as the central nervous system (CNS). The induction of inflammatory responses in microglial cells and astrocytes, the CNS resident cells with immunological characteristics, could interrupt the hemostasis upon even with low-level exposure to mycotoxins. The inevitable widespread occurrence of a low level of mycotoxins in foods and feed is likely increasing worldwide, predisposing individuals to potential neuroimmunological dysregulations. This paper reviews the current understanding of mycotoxins' neuro-immunotoxic features under low-dose exposure and the possible ways for detoxification and clearance as a perspective.

Human Family 1-4 cytochrome P450 enzymes involved in the metabolic activation of xenobiotic and physiological chemicals: an update

This is an overview of the metabolic activation of drugs, natural products, physiological compounds, and general chemicals by the catalytic activity of cytochrome P450 enzymes belonging to Families 1-4. The data were collected from > 5152 references. The total number of data entries of reactions catalyzed by P450s Families 1-4 was 7696 of which 1121 (~ 15%) were defined as bioactivation reactions of different degrees. The data were divided into groups of General Chemicals, Drugs, Natural Products, and Physiological Compounds, presented in tabular form. The metabolism and bioactivation of selected examples of each group are discussed. In most of the cases, the metabolites are directly toxic chemicals reacting with cell macromolecules, but in some cases the metabolites formed are not direct toxicants but participate as substrates in succeeding metabolic reactions (e.g., conjugation reactions), the products of which are final toxicants. We identified a high level of activation for three groups of compounds (General Chemicals, Drugs, and Natural Products) yielding activated metabolites and the generally low participation of Physiological Compounds in bioactivation reactions. In the group of General Chemicals, P450 enzymes 1A1, 1A2, and 1B1 dominate in the formation of activated metabolites. Drugs are mostly activated by the enzyme P450 3A4, and Natural Products by P450s 1A2, 2E1, and 3A4. Physiological Compounds showed no clearly dominant enzyme, but the highest numbers of activations are attributed to P450 1A, 1B1, and 3A enzymes. The results thus show, perhaps not surprisingly, that Physiological Compounds are infrequent substrates in bioactivation reactions catalyzed by P450 enzyme Families 1-4, with the exception of estrogens and arachidonic acid. The results thus provide information on the enzymes that activate specific groups of chemicals to toxic metabolites.

Kefiran ameliorates malfunctions in primary and functional immune cells caused by lipopolysaccharides

Kefiran is a water-soluble polysaccharide well recognized as a bioactive ingredient to enhance nutritional and health-promoting features. Also, some therapeutic properties have made this macromolecule an active ingredient in ointments and oral anti-inflammatory drugs. However, the details of the molecular and cellular aspects of these effects have not been addressed. In this study, lipopolysaccharides (LPS)-induced monocytes, lymphocytes, and monocyte-derived dendritic cells (MDDCs) as representative cells for both innate and adaptive immunity were treated with kefiran for 2 h. Kefiran had an anti-inflammatory effect on monocytes to reduce pro-inflammatory cytokines, interleukin 1 β (IL-1β) & tumor necrosis factor α (TNF-α), as well as nuclear factor kappa b (NF-kb). However, it did not affect lymphocytes. Overexpression of Toll-like receptor 4 (TLR4) in LPS-induced cells was not reduced after kefiran treatment. Kefiran balanced MDDCs secretion of pro/anti-inflammatory cytokines by reducing and enhancing the expression of IL-1β and interleukin 10 (IL-10), respectively. Also, kefiran decreased the number of apoptotic immature MDDCs and promoted dose-dependent phagocytosis capacity of MDDCs. According to the results of the current study, it may be concluded that the immunomodulatory effects of kefiran are due to antagonist against innate immune receptors especially TLR4. The results of this study can be used as a guide to developing kefiran-based non-aggressive anti-inflammatory drugs. Furthermore, understanding the immunobiological effects of kefiran on monocytes and lymphocytes was another outcome of this study.

Expression of xenobiotic metabolising enzymes in lungs of horses with or without histological evidence of lower airway inflammation

Mild, moderate and severe equine asthma is a problem for equine welfare. The aetiology of the disease is not known in detail but is likely multi‐factorial. One important factor may be inhaled dust which carries harmful substances which may be bioactivated and thus can lead to local inflammation in the airways. The aim of this study was to investigate gene expression and protein localisation of cytochrome P450 (CYP) enzymes, superoxide dismutase and glutathione‐S‐transferases (GST) involved in bioactivation and detoxification of harmful substances in lungs of horses with or without histological evidence of lower airway inflammation. Significantly lower gene expression of CYP2A13 and GSTM1 was observed in lungs from horses with histological evidence of lower airway inflammation compared with horses without. A higher expression, although not significant, was found for CYP1A1 in horses with histological evidence of lower airway inflammation. There were no differences in gene expression of GSTP1 and SOD3. The proteins were localised in the respiratory epithelium which is of relevance as a defence to local exposure of inhaled harmful substances. In conclusion, our study reports differential gene expression of enzymes involved in bioactivation and detoxification of foreign substances in the lungs of horses with histological evidence of lower airway inflammation compared with horses without.

Insights into Aflatoxin B1 Toxicity in Cattle: An In Vitro Whole-Transcriptomic Approach

Aflatoxins, and particularly aflatoxin B1 (AFB1), are toxic mycotoxins to humans and farm animal species, resulting in acute and chronic toxicities. At present, AFB1 is still considered a global concern with negative impacts on health, the economy, and social life. In farm animals, exposure to AFB1-contaminated feed may cause several untoward effects, liver damage being one of the most devastating ones. In the present study, we assessed in vitro the transcriptional changes caused by AFB1 in a bovine fetal hepatocyte-derived cell line (BFH12). To boost the cellular response to AFB1, cells were pre-treated with the co-planar PCB 3,3′,4,4′,5-pentachlorobiphenyl (PCB126), a known aryl hydrocarbon receptor agonist. Three experimental groups were considered: cells exposed to the vehicle only, to PCB126, and to PCB126 and AFB1. A total of nine RNA-seq libraries (three replicates/group) were constructed and sequenced. The differential expression analysis showed that PCB126 induced only small transcriptional changes. On the contrary, AFB1 deeply affected the cell transcriptome, the majority of significant genes being associated with cancer, cellular damage and apoptosis, inflammation, bioactivation, and detoxification pathways. Investigating mRNA perturbations induced by AFB1 in cattle BFH12 cells will help us to better understand AFB1 toxicodynamics in this susceptible and economically important food-producing species.

Low-dose microcystin-LR antagonizes aflatoxin B1 induced hepatocarcinogenesis through decreasing cytochrome P450 1A2 expression and aflatoxin B1-DNA adduct generation

Aflatoxin B1 (AFB1) and microcystin-LR (MC-LR) co-existed in food and water, and were associated with hepatocellular carcinoma (HCC). AFB1 induced HCC by activating oxidative stress and generating AFB1-DNA adducts, while MC-LR could promote HCC progression. However, whether they have co-effects in HCC progression remains uncertain. In this study, we found the antagonistic effects of MC-LR on AFB1 induced HCC when they were exposed simultaneously. Compared with single exposure to AFB1, co-exposed to MC-LR significantly repressed the AFB1 induced malignant transformation of human hepatic cells and the glutathione S-transferase Pi positive foci formation in rat livers. MC-LR inhibited AFB1 induced upregulation of cytochrome P450 family 1 subfamily A member 2 (CYP1A2) and reduced the AFB1-DNA adducts generation in both human hepatic cells and rat livers. These results suggest that when co-exposure with AFB1, MC-LR might repress hepatocarcinogenicity of AFB1, which might be associated with its repression on AFB1 induced CYP1A2 upregulation and activation.

Neurotoxic effects of aflatoxin B1 on human astrocytes in vitro and on glial cell development in zebrafish in vivo

Aflatoxin B1 is one of the well-known mycotoxins and mainly found in contaminated animal feed and various agricultural products inducing acute and chronic toxicology, tumor, and abnormal neural development. However, the effects of aflatoxin B1 on the human brain, especially on astrocytes, have not been studied in depth. In the present study, we studied the neurotoxic effects of aflatoxin B1, in vitro and in vivo. Aflatoxin B1 decreased the proliferation and stopped cell cycle progression at the sub G0/G1 stage with an increase in BAX, BAK, and cytochrome c proteins in human astrocytes. In addition, it increased the mitochondrial depolarization, oxidative stress, and calcium influx in both the cytosol and mitochondria. Surprisingly, inhibition of calcium overload in the cytosol and mitochondria, using calcium chelators and an inhibitor, partially rescued the proliferation of aflatoxin B1-treated astrocytes. Based on the toxicity assays using zebrafish models, aflatoxin B1 decreased the embryo survival rate with physiological changes and an increase in the caspase and tp53 genes. It also decreased the expression of gfap, mbp, and olig2 in the transgenic zebrafish embryo's brain and axon. Our results revealed the specific mechanism of the neurotoxic effects of aflatoxin B1 on human astrocytes and zebrafish glial cells.

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.

Naturally Occurring Level of Aflatoxin B1 Injures Human, Canine and Bovine Leukocytes Through ATP Depletion and Caspase Activation

Aflatoxin (AF) B₁ is a potent hepatotoxic, mutagenic, teratogenic mycotoxin and may cause immune suppression/dysregulation in humans and animals. Toxic effects of AFB₁ on key mammalian immune cells (ie, leukocytes) needs to be mechanistically elucidated. In this study, along with the determination of AFB₁'s LC₅₀ for certain leukocytes, we analyzed the effect of naturally occurring levels of AFB₁ on apoptosis/necrosis of neutrophils, lymphocytes, and monocytes from healthy young humans (20- to 25-year-old male), dogs (1- to 2-year-old Persian/herd breed), and cattle (1- to 2-year-old cattle). Leukocytes were incubated for approximately 24 hours with naturally occurring levels of AFB₁ (10 ng/mL). Intracellular adenosine triphosphate (ATP) depletion and caspase-3/7 activity were then determined by luciferase-dependent bioluminescence (BL). Furthermore, the necrotic leukocytes were measured using propidium iodide (PI)-related flow cytometry. A significant decrease (24%-45%, 33.2% ± 2.7%) in intracellular ATP content was observed in AFB₁-treated neutrophils, lymphocytes, and monocytes in all studied mammals. Also, with such a low level (10 ng/mL) of AFB₁, BL-based caspase-3/7 activity (BL intensity) in all 3 tested mammalian leukocyte lineages was noticeably increased (∼>2-fold). Flow cytometry-based PI staining (for viability assay) of the AFB₁-treated leukocytes showed slightly/insignificantly more increase of necrotic (PI⁺) neutrophils, lymphocytes, and monocytes in human, dogs, and cattle. Even though in vitro LC₅₀s for AFB_1' (∼20,000-40,000 ng/mL) were approximately 2,000 to 4,000 times higher than background, these studies demonstrate leukocytes from human and farm/companion animals are sensitive to naturally occurring levels of AFB₁. The observed in vitro ATP depletion and caspase activation in AFB₁-exposed leukocytes can partially explain the underlying mechanisms of AFB₁-induced immune disorders in mammals.

Neonatal cytochrome P450 CYP3A7: A comprehensive review of its role in development, disease, and xenobiotic metabolism

The human cytochrome P450 CYP3A7, once thought to be an enzyme exclusive to fetal livers, has more recently been identified in neonates and developing infants as old as 24 months post-gestational age. CYP3A7 has been demonstrated to metabolize two endogenous compounds that are known to be important in the growth and development of the fetus and neonate, namely dehydroepiandrosterone sulfate (DHEA-S) and all-trans retinoic acid (atRA). In addition, it is also known to metabolize a variety of drugs and xenobiotics, albeit generally to a lesser extent relative to CYP3A4/5. CYP3A7 is an important component in the development and protection of the fetal liver and additionally plays a role in certain disease states, such as cancer and adrenal hyperplasia. Ultimately, a full understanding of the expression, regulation, and metabolic properties of CYP3A7 is needed to provide neonates with appropriate individualized pharmacotherapy. This article summarizes the current state of knowledge of CYP3A7, including its discovery, distribution, alleles, RNA splicing, expression and regulation, metabolic properties, substrates, and inhibitors.

The Molecular Mechanisms of Protective Role of Se on the G0/G1 Phase Arrest Caused by AFB1 in Broiler's Thymocytes

This research was designed to explore the protective effects of sodium selenite on G₀/G₁ phase arrest induced by AFB₁ in thymocytes of broilers. Two hundred eighty-eight Cobb broilers were divided into control group, + Se group (0.4 mg/kg Se), AFB₁ group (0.6 mg/kg AFB₁), and AFB₁ + Se group (0.6 mg/kg AFB₁ + 0.4 mg/kg Se). The results revealed that 0.4 mg/kg Se supplement in diets could improve the AFB₁-induced histological lesions in the thymus consisting of the more vacuoles and nuclear debris in thymic cortical area. The results of flow cytometric detect showed that 0.4 mg/kg Se relieved the G₀/G₁ phase arrest caused by AFB₁ in thymocytes. The results of transcription levels of ATM, p53, p21, p27, p15, p16, CyclinD₁, CyclinE, Cdk6, Cdk2, and PCNA genes by qRT-PC, and protein expression level of PCNA by immunohistochemistry demonstrated that 0.4 mg/kg Se could reduce the adverse effects of AFB₁ on these parameters. In conclusion, Se could relieve AFB₁-induced G₀/G₁ phase arrest by p15 (or p16)-CyclinD₁/Cdk6, ATM-p53-p21-CyclinE/Cdk2, p27-CyclinE/Cdk2 pathways.

Effects of aflatoxin B1 on the cell cycle distribution of splenocytes in chickens

The purpose of the present study was to evaluate effects of aflatoxin B1 (AFB1) on the cell cycle and proliferation of splenic cells in chickens. A total of 144 one-day-old Cobb male chickens were randomly divided into 2 equal groups of 72 each and were fed on diets as follows: a control diet and a 0.6 mg/kg AFB1 diet for 21 days. The AFB1 diet reduced body weight, absolute weight and relative weight of the spleen in broilers. Histopathological lesions in AFB1 groups were characterized as slight congestion in red pulp and lymphocytic depletion in white pulp. Compared with the control group, the expression levels of ataxia-telangiectasia mutated (ATM), cyclin E1, cyclin-dependent kinases 6 (CDK6), CDK2, p53, p21 and cyclin B3 mRNA were significantly increased, while the mRNA expression levels of cyclin D1, cdc2 (CDK1), p16, p15 were significantly decreased in the AFB1 groups. Significantly decreased proliferating cell nuclear antigen (PCNA) expression and arrested G0G1 phases of the cell cycle were also seen in the AFB1 groups. In conclusion, dietary AFB1 could induce cell cycle blockage at G0G1 phase and impair the immune function of the spleen. Cyclin D1/CDK6 complex, which inhibits the activin/nodal signaling pathway, might play a significant role in the cell cycle arrest induced by AFB1.

Data on environmentally relevant level of aflatoxin B1-induced human dendritic cells' functional alteration

We assessed the effects of naturally occurring levels of AFB₁ on the expression of key immune molecules and function of human monocyte-derived dendritic cells (MDDCs) by cell culture, RT-qPCR, and flow cytometry. Data here revealed that an environmentally relevant level of AFB₁ led to remarkably weakened key functional capacity of DCs, up-regulation of key transcripts and DCs apoptosis, down-regulation of key phagocytic element, CD64, and creation of pseudolicensing direction of DCs. Flow cytometry data confirmed a damage towards DCs, i.e., increased apoptosis. The detailed data and their mechanistic effects and the outcome are available in this research article (Mehrzad et al., 2018) [1]. The impaired phagocytosis capacity with triggered pseudolicensing direction of MDDCs caused by AFB₁ and dysregulation of the key functional genes could provide a mechanistic explanation for the observed in vivo immunotoxicity associated with this mycotoxin.

Aryl hydrocarbon receptor is activated in patients and mice with chronic kidney disease

Patients with chronic kidney disease (CKD) are exposed to uremic toxins and have an increased risk of cardiovascular disease. Some uremic toxins, like indoxyl sulfate, are agonists of the transcription factor aryl hydrocarbon receptor (AHR). These toxins induce a vascular procoagulant phenotype. Here we investigated AHR activation in patients with CKD and in a murine model of CKD. We performed a prospective study in 116 patients with CKD stage 3 to 5D and measured the AHR-Activating Potential of serum by bioassay. Compared to sera from healthy controls, sera from CKD patients displayed a strong AHR-Activating Potential; strongly correlated with eGFR and with the indoxyl sulfate concentration. The expression of the AHR target genes Cyp1A1 and AHRR was up-regulated in whole blood from patients with CKD. Survival analyses revealed that cardiovascular events were more frequent in CKD patients with an AHR-Activating Potential above the median. In mice with 5/6 nephrectomy, there was an increased serum AHR-Activating Potential, and an induction of Cyp1a1 mRNA in the aorta and heart, absent in AhR^-/- CKD mice. After serial indoxyl sulfate injections, we observed an increase in serum AHR-AP and in expression of Cyp1a1 mRNA in aorta and heart in WT mice, but not in AhR^-/- mice. Thus, the AHR pathway is activated both in patients and mice with CKD. Hence, AHR activation could be a key mechanism involved in the deleterious cardiovascular effects observed in CKD.

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.

Human Microglial Cells Undergo Proapoptotic Induction and Inflammatory Activation upon in vitro Exposure to a Naturally Occurring Level of Aflatoxin B1

OBJECTIVE

Knowledge regarding interactions of AFB1 with the human nervous system and how a naturally occurring level of AFB1 could potentially induce neuroimmune dysregulation is very limited. To assess the cellular effects of AFB1 on the human brain, we used the human microglia cell line CHME5 as a model to pinpoint its potential in vivo translation.

METHODS

We used the CHME5 cell line culture system, multiplex qPCR, (chemi)bioluminescence, Luminex ELISA, and flow cytometry assays to evaluate the toxic effects of a naturally occurring level of AFB1 on human microglia.

RESULTS

A low concentration of AFB1 upregulates the mRNA expression of many proinflammatory molecules, such as TLRs, MyD88, NFκB, and CxCr4, induces intracellular ATP depletion, and increases caspase-3/7 activity at different time points following exposure to the toxin. Furthermore, AFB1-exposed microglia secreted significantly higher levels of IFN-γ and GM-CSF after treatment. We also observed a slight increase in the percentage of apoptotic microglia (annexin V+/PI-) at 48 h posttreatment.

CONCLUSION

Our work confirmed that the environmentally relevant level of AFB1 could cause an inflammatory reaction in human microglial cells that is potentially harmful or toxic to the homeostasis of the human central nervous system and might increase susceptibility to neurodegenerative diseases.

The Molecular Mechanisms of Protective Role of Se on the G2/M Phase Arrest of Jejunum Caused by AFB1

Aflatoxin B₁ (AFB₁) is the most toxic among the mycotoxins and causes detrimental health effects on human and animals. Selenium (Se) plays an important role in chemopreventive, antioxidant, anticarcinogen, and detoxification and involved in cell cycle regulation. The aim of this study was to explore the molecular mechanisms of selenium involved in inhibition of G₂/M cell cycle arrest of broiler's jejunum. A total of 240 one-day-old healthy Cobb broilers were randomly divided into four groups and fed with basal diet (control group), 0.6 mg/kg AFB₁ (AFB₁ group), 0.4 mg/kg Se (+Se group), and 0.6 mg/kg AFB₁ + 0.4 mg/kg Se (AFB₁ + Se group) for 21 days, respectively. The histological observation and morphological analysis revealed that 0.4 mg/kg Se prevented the AFB₁-associated lesions of jejunum including the shedding of the apical region of villi, the decreased villus height, and villus height/crypt ratio. The cell cycle analysis by flow cytometry showed that 0.4 mg/kg Se ameliorated the AFB₁-induced G₂/M phase arrest in jejunal cells. Moreover, the expressions of ATM, Chk2, p53, Mdm2, p21, PCNA, Cdc25, cyclin B, and Cdc2 analyzed by immunohistochemistry and qRT-PCR demonstrated that 0.4 mg/kg Se restored these parameters to be close to those in the control group. In conclusion, Se promoted cell cycle recovery from the AFB₁-induced G₂/M phase arrest by the molecular regulation of ATM pathway in the jejunum of broilers. The outcomes from the present study may lead to a better understanding of the nature of selenium's essentiality and its protective roles against AFB₁.

Interaction Effects of AFB1 and MC-LR Co-exposure with Polymorphism of Metabolic Genes on Liver Damage: focusing on SLCO1B1 and GSTP1

AFB1 and MC-LR are two major environmental risk factors for liver damage worldwide, especially in warm and humid areas, but there are individual differences in health response of the toxin-exposed populations. Therefore, we intended to identify the susceptible genes in transport and metabolic process of AFB1 and MC-LR and find their effects on liver damage. We selected eight related SNPs that may affect liver damage outcomes in AFB1 and MC-LR exposed persons, and enrolled 475 cases with liver damage and 475 controls of healthy people in rural areas of China. The eight SNPs were genotyped by PCR and restriction fragment length polymorphism. We found that SLCO1B1 (T521C) is a risk factor for liver damage among people exposed to high AFB1 levels alone or combined with MC-LR, and that GSTP1 (A1578G) could indicate the risk of liver damage among those exposed to high MC-LR levels alone or combined with high AFB1 levels. However, GSTP1 (A1578G) could reduce the risk of liver damage in populations exposed to low MC-LR levels alone or combined with high AFB1 levels. In conclusion, SLCO1B1 (T521C) and GSTP1 (A1578G) are susceptible genes for liver damage in humans exposed to AFB1 and/or MC-LR in rural areas of China.

Cytochrome P450 1A1 and 1B1 promoter CpG island methylation regulates rat liver injury induced by isoniazid

DNA methylation is an important component of epigenetics that is involved in the occurrence and development of a variety of diseases. The present study aimed to clarify the relationship between cytochrome P450 (CYP)1A1 and CYP1B1 promoter CpG island methylation and isoniazid-induced liver injury in rats, and to explore the possible mechanism, rats were given an intragastric dose of isoniazid (55 mg·kg⁻¹·d⁻¹). High performance liquid chromatography was used to analyze the DNA methylation level of the whole genome in liver tissue. Methylation-specific polymerase chain reaction (PCR) was used to detect the methylation level of CpG islands in the promoter region of CYP1A1 and CYP1B1. Reverse transcription-quantitative PCR was used to determine the mRNA expression levels of CYP1A1, CYP1B1, toll-like receptor 4 (TLR4), extracellular signal-regulated kinase (ERK) 2, peroxisome proliferator-activated receptor (PPAR) -γ, interleukin (IL)-6 and tumor necrosis factor (TNF)-α. The expression levels of CYP1A1 and CYP1B1 proteins were measured by ELISA, and malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were analyzed by colorimetric method. Liver tissue pathology, an indicator of liver function, indicated rat liver injury at 10 days following isoniazid treatment. Whole-genome methylation levels were gradually reduced, and methylation at day 7 post-treatment was significantly lower than the control group. CYP1A1 and CYP1B1 promoter CpG island methylation level was significantly increased at 3 days post-treatment. CYP1A1 and CYP1B1 mRNA expression levels were significantly reduced from day 7 and 10, respectively. These results suggested that CpG island hypermethylation of the CYP1A1 and CYP1B1 promoters regulate the low expression of genes involved in the occurrence of isoniazid-induced liver injury. With the alterations of CYP1A1 and CYP1B1 expression, the mRNA expression levels of TLR4, ERK, MDA, IL-6 and TNF-α were upregulated, and the expression of SOD and PPAR-γ were downregulated. These data demonstrated that alterations in methylation patterns may involve changes in the TLR4-ERK signaling pathway and PPAR-γ, which may alter the expression of MDA, SOD, IL-6 and TNF-α, leading to liver injury.

Tobacco smoking differently influences cell types of the innate and adaptive immune system-indications from CpG site methylation

Background

Tobacco smoke is worldwide one of the main preventable lifestyle inhalative pollutants causing severe adverse health effects. Epidemiological studies revealed association of tobacco smoking with epigenetic changes at single CpGs in blood. However, the biological relevance of the often only marginal methylation changes remains unclear.

Results

Comparing genome-wide changes in CpG methylation of three recently reported epidemiological datasets, two obtained on whole blood and one on peripheral blood mononuclear cells (PBMCs), it becomes evident that the majority of methylation changes (86.7 and 93.3 %) in whole blood account for changes in granulocytes. Analyzing, in more detail, seven highly significant reported smoking-induced methylation changes at single CpGs in different blood cell types of healthy volunteers (n = 32), we confirmatively found a strong cell-type specificity. Two CpGs in GFI1 and F2RL3 were significantly hypomethylated in granulocytes (−11.3 %, p = 0.001; −8.7 %, p = 0.001, respectively) but not in PBMCs of smokers while two CpGs in CPOX and GPR15 were found to be hypomethylated in PBMC (−4.3 %, p = 0.003; −4.2 %, P = 0.009, respectively) and their subtypes of GPR15 non-expressing (−3.2 %, p = 0.027; −2.5 %, p = 0.032, respectively) and smoking-evoked GPR15 expressing T cells (−15.8 %, p < 0.001; −13.8 %, p = 0.018, respectively) but not in granulocytes. In contrast, cg05575921 within AHRR was hypomethylated in every analyzed cell type of smokers, but with a different degree. Both, hypomethylation at cg05575921 in granulocytes (−55.2 % methylation change in smokers, p < 0.001) and the frequency of GPR15+ T cells (9.8–37.1 % in smokers), possessing a specific hypomethylation at cg19859270, were strongly associated with smoking behavior at individual level and could therefore serve as valuable biomarkers indicating a disturbed homeostasis in smokers.

In contrast to the reported long-term persistent methylation changes in adult smokers after cessation, the hypomethylation at cg05575921 in prenatally tobacco smoke-exposed children (n = 13) from our LINA cohort was less stable and disappeared already within 2 years after birth.

Conclusions

Studying cell type-specific methylation changes provides helpful information regarding the biological relevance of epigenetic modifications. Here, we could show that smoking differently affects both cells of the innate and adaptive immune systems.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0249-7) contains supplementary material, which is available to authorized users.

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.

Impact of physiological, pathological and environmental factors on the expression and activity of human cytochrome P450 2D6 and implications in precision medicine

With only 1.3-4.3% in total hepatic CYP content, human CYP2D6 can metabolize more than 160 drugs. It is a highly polymorphic enzyme and subject to marked inhibition by a number of drugs, causing a large interindividual variability in drug clearance and drug response and drug-drug interactions. The expression and activity of CYP2D6 are regulated by a number of physiological, pathological and environmental factors at transcriptional, post-transcriptional, translational and epigenetic levels. DNA hypermethylation and histone modifications can repress the expression of CYP2D6. Hepatocyte nuclear factor-4α binds to a directly repeated element in the promoter of CYP2D6 and thus regulates the expression of CYP2D6. Small heterodimer partner represses hepatocyte nuclear factor-4α-mediated transactivation of CYP2D6. GW4064, a farnesoid X receptor agonist, decreases hepatic CYP2D6 expression and activity while increasing small heterodimer partner expression and its recruitment to the CYP2D6 promoter. The genotypes are key determinants of interindividual variability in CYP2D6 expression and activity. Recent genome-wide association studies have identified a large number of genes that can regulate CYP2D6. Pregnancy induces CYP2D6 via unknown mechanisms. Renal or liver diseases, smoking and alcohol use have minor to moderate effects only on CYP2D6 activity. Unlike CYP1 and 3 and other CYP2 members, CYP2D6 is resistant to typical inducers such as rifampin, phenobarbital and dexamethasone. Post-translational modifications such as phosphorylation of CYP2D6 Ser135 have been observed, but the functional impact is unknown. Further functional and validation studies are needed to clarify the role of nuclear receptors, epigenetic factors and other factors in the regulation of CYP2D6.

The mycotoxin aflatoxin B1 stimulates Epstein-Barr virus-induced B-cell transformation in in vitro and in vivo experimental models

Although Epstein-Barr virus (EBV) infection is widely distributed, certain EBV-driven malignancies are geographically restricted. EBV-associated Burkitt's lymphoma (eBL) is endemic in children living in sub-Saharan Africa. This population is heavily exposed to food contaminated with the mycotoxin aflatoxin B1 (AFB1). Here, we show that exposure to AFB1 in in vitro and in vivo models induces activation of the EBV lytic cycle and increases EBV load, two events that are associated with an increased risk of eBL in vivo. AFB1 treatment leads to the alteration of cellular gene expression, with consequent activations of signaling pathways, e.g. PI3K, that in turn mediate reactivation of the EBV life cycle. Finally, we show that AFB1 triggers EBV-driven cellular transformation both in primary human B cells and in a humanized animal model. In summary, our data provide evidence for a role of AFB1 as a cofactor in EBV-mediated carcinogenesis.

Environmentally Relevant Level of Aflatoxin B1 Dysregulates Human Dendritic Cells Through Signaling on Key Toll-Like Receptors

Aflatoxins (AFs) are highly hazardous fungal biometabolites usually present in feeds and foods. Aflatoxin B1 (AFB1) is the most toxic and a known carcinogen. Toll-like receptors (TLRs), highly expressed by myeloid dendritic cells (DC), are key innate immune-surveillance molecules. Toll-like receptors not only sense pathogen-associated molecular patterns but also contribute to infections and cancer. To assess AFB1–TLR interactions on human myeloid DC, pure CD11c+ DC were generated from monocytes isolated from healthy individuals and then exposed to relevant level of AFB1 for 2 hours. Both quantitative polymerase chain reaction and flow cytometric assays were used to quantify, respectively, expression of TLR2 and TLR4 at the messenger RNA (mRNA) and protein levels in these DC. Levels of interleukin (IL) 1β, IL-6, and IL-10 were also analyzed in AFB1- and mock-treated DC. Compared to nontreated CD11c+ DC, expression levels of both TLR2 and TLR4 mRNA and proteins were significantly upregulated in AFB1-treated cells. Further, although IL-10 levels in AFB1-treated DC were similar to those in the mock-treated DC, the AFB1-exposed DC secreted higher amounts of IL-1β and IL-6. Dendritic cells are sensitive to environmentally relevant level of AFB1, and TLR2 and TLR4 are involved in sensing AFB1. Considering the broad roles of TLR2, TLR4, and DC in immunity and infections, our novel findings open a new door to understanding the molecular mechanisms and functional consequences of AFB1 in inducing immunodysregulation, immunotoxicity, and thus (non)infectious diseases in humans.