In vitro effects of very low levels of aflatoxin B1 on free radicals production and bactericidal activity of bovine blood neutrophils

Aflatoxin B1 exposure triggers inflammation and premature skin aging via ERMCS/Ca2+/ROS signaling cascade

Aflatoxin B1 (AFB1) is a recognized hazard environmental contaminant mainly found in cereal and fruits. The toxicity of AFB1 exposure to various organs has been revealed in some literature. In current study, we explored the effect of AFB1 exposure on premature aging/senescence of skin. In vivo, 8-week-old C57 mice were used as models to evaluate the effect of dietary AFB1 exposure on premature skin aging. The results showed that AFB1 exposure caused premature skin aging by testing aging markers. Additionally, AFB1 led to oxidative stress and inflammatory response. In vitro, AFB1 exposure triggered premature cellular senescence in mouse skin fibroblasts cells (L929 cells) by assessing a range of cellular senescence-related markers. Further, the potential molecular mechanism by which AFB1 induce the premature skin aging was studied. ROS and Ca2+ is proven to be the key molecules in AFB1-induced cellular senescence. Further, through eliminating Ca2+, AFB1-caused oxidative stress and cellular senescence were both attenuated, suggesting that Ca2+ overload in the mitochondria results in cellular senescence by increasing ROS production. Next, we analyzed the causes of Ca2+ overload, and results showed that AFB1 exposure induces Ca2+ overload through increasing the formation of mitoguardin (Miga) and vesicle-associated membrane protein (VAMP)-associated protein (Vap33)-mediated endoplasmic reticulum (ER)-mitochondria contact sites (ERMCS). AFB1 exposure also inhibited mitophagy, leading to accelerate L929 cell senescence. In short, combining in vivo and in vitro results, we demonstrate that exposure to AFB1 causes premature skin aging, which is dependent on ERMCS/Ca2+/ROS/ signaling axis. The current study suggests that prolonged exposure to AFB1 makes skin more vulnerable to damage.

Immunotoxicity and the mechanisms of aflatoxin B1-induced growth retardation in shrimp and alleviating effects of bile acids

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins prevalent in the environment and food chain, posing severe health risks to humans and animals. Bile acids are natural detergents synthesized from cholesterol and play a key role in the excretion of toxins in vertebrates. Here, pacific white shrimp (Litopenaeus vannamei) served as an animal model to examine the toxicity mechanisms of AFB1 and assess the potential alleviating effects of bile acids against AFB1. Our results revealed that AFB1 exposure significantly inhibited the growth performance and immune response of shrimp, accompanied by AFB1 accumulation and histological damage. Mechanistically, AFB1-induced DNA damage activated DNA repair mechanisms and induced the arrest of cell cycle via the ATR-cyclin B/cdc2 pathway. Additionally, AFB1 directly suppressed the immune response and growth performance of shrimp by inhibiting Toll and IMD pathways and the secretion of digestive enzymes. Notably, dietary bile acids significantly reduced AFB1 accumulation and alleviated AFB1-induced growth retardation and immunotoxicity in shrimp, and CCKAR, ATR, and Relish may be key mediators of the alleviating effects of bile acids. Our study provided new insights into the toxicity mechanisms of AFB1 in invertebrates and highlighted the potential of bile acids to alleviate AFB1 toxicity.

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.

Fungal Toxins and Host Immune Responses

Fungi are ubiquitous organisms that thrive in diverse natural environments including soils, plants, animals, and the human body. In response to warmth, humidity, and moisture, certain fungi which grow on crops and harvested foodstuffs can produce mycotoxins; secondary metabolites which when ingested have a deleterious impact on health. Ongoing research indicates that some mycotoxins and, more recently, peptide toxins are also produced during active fungal infection in humans and experimental models. A combination of innate and adaptive immune recognition allows the host to eliminate invading pathogens from the body. However, imbalances in immune homeostasis often facilitate microbial infection. Despite the wide-ranging effects of fungal toxins on health, our understanding of toxin-mediated modulation of immune responses is incomplete. This review will explore the current understanding of fungal toxins and how they contribute to the modulation of host immunity.

Zearalenone and deoxynivalenol inhibited IL-4 receptor-mediated Th2 cell differentiation and aggravated bacterial infection in mice

The immunotoxicity of zearalenone (ZEA) and deoxynivalenol (DON), two of the most common environmental mycotoxins, has been well investigated. However, due to the complexity of the immune system, especially during bacterial infection, many types of immune cells are involved in invasion resistance and bacterial clearance. Of these, T helper 2 (Th2) cells, which are members of the helper T cell family, assist B cells to activate and differentiate into antibody-secreting cells, participate in humoral immune response, and, ultimately, eliminate pathogens. Thus, it is important to identify the stage at which these toxins affect the immune function, and to clarity the underlying mechanisms. In this study, mice infected with Listeria monocytogenes (Listeria) were used to study the effects of ZEA, DON, and ZEA + DON on Th2 differentiation, Interleukin-4 Receptor (IL-4R) expression, costimulatory molecules expression and cytokine secretion after Listeria infection. Naive CD4+ T cells, isolated from mice, were used to verify the in vivo effects and the associated mechanisms. In vivo experiments showed that these toxins aggravated spleen damage after Listeria infection and reduced the differentiation of Th2 cells by affecting the synthesis of IL-4R of CD4+ T cells. In addition, the level of the costimulatory molecule CD154 decreased. Consistent with this, in vitro studies showed that these toxins inhibited the differentiation of mouse naive CD4+ T cell into Th2 subtype and decreased IL-4R levels. In addition, the levels of costimulatory molecules CD154, CD278 and the Th2 cells secrete cytokines IL-4, IL-6, and IL-10 decreased. Based on our in vivo and in vitro experiments, we suggest that ZEA, DON, and ZEA + DON inhibit the expression of costimulatory molecules on CD4+ T cell, and inhibit the IL-4R-mediated Th2 cell differentiation. This may indicate that the body cannot normally resist or clear the pathogen after mycotoxin poisoning.

Carcinogenesis: Failure of resolution of inflammation?

Inflammation in the tumor microenvironment is a hallmark of cancer and is recognized as a key characteristic of carcinogens. However, the failure of resolution of inflammation in cancer is only recently being understood. Products of arachidonic acid and related fatty acid metabolism called eicosanoids, including prostaglandins, leukotrienes, lipoxins, and epoxyeicosanoids, critically regulate inflammation, as well as its resolution. The resolution of inflammation is now appreciated to be an active biochemical process regulated by endogenous specialized pro-resolving lipid autacoid mediators which combat infections and stimulate tissue repair/regeneration. Environmental and chemical human carcinogens, including aflatoxins, asbestos, nitrosamines, alcohol, and tobacco, induce tumor-promoting inflammation and can disrupt the resolution of inflammation contributing to a devastating global cancer burden. While mechanisms of carcinogenesis have focused on genotoxic activity to induce mutations, nongenotoxic mechanisms such as inflammation and oxidative stress promote genotoxicity, proliferation, and mutations. Moreover, carcinogens initiate oxidative stress to synergize with inflammation and DNA damage to fuel a vicious feedback loop of cell death, tissue damage, and carcinogenesis. In contrast, stimulation of resolution of inflammation may prevent carcinogenesis by clearance of cellular debris via macrophage phagocytosis and inhibition of an eicosanoid/cytokine storm of pro-inflammatory mediators. Controlling the host inflammatory response and its resolution in carcinogen-induced cancers will be critical to reducing carcinogen-induced morbidity and mortality. Here we review the recent evidence that stimulation of resolution of inflammation, including pro-resolution lipid mediators and soluble epoxide hydrolase inhibitors, may be a new chemopreventive approach to prevent carcinogen-induced cancer that should be evaluated in humans.

The effect of equine bone marrow-derived mesenchymal stem cells on the expression of apoptotic genes in neutrophils

BACKGROUND

Bone marrow mesenchymal stem cells (BM-MSCs), as multipotent cells with self-renewal and plastic-adherent properties, have immunomodulatory effects on immune cells, including neutrophils. These cells are in close proximity in bone marrow (BM) sinusoids with non-multiplicative immature neutrophils. BM-MSCs exert their immunomodulatory effects on adjacent cells both directly (cell-to-cell contact) and indirectly (secretion of soluble factors).

OBJECTIVES

The aim of this study was to evaluate the effect of equine bone marrow mesenchymal stem cells (BM-MSCs) on the expression of some pro- and anti-apoptotic genes (p53, survivin and Bcl₂ ) in neutrophils co-cultured with BM-MSCs.

METHODS

For this purpose, peripheral blood neutrophils were isolated and separately co-cultured for 12 hr with both BM-MSCs and the BM-MSCs΄ supernatant. Four groups were included: neutrophils with only culture media (as control), neutrophils co-cultured with BM-MScs, neutrophils cultured with BM-MSCs' supernatant and neutrophils cultured with lipopolysaccharide (LPS, as positive control). Then, the expression of mentioned genes (p53, survivin and Bcl₂ ) was evaluated by quantitative polymerase chain reaction (qPCR).

RESULTS

Compared with control neutrophils, in neutrophils co-cultured with both BM-MSCs and BM-MSCs' supernatant, the mRNA expression levels of p53, as pro-apoptotic gene, and survivin and Bcl₂ , as anti-apoptotic genes, were remarkably increased and decreased (p < .05), respectively.

CONCLUSIONS

These data revealed the notion that the direct contact of BM-MSCs is not obligatory for their effects on the apoptotic status of neutrophils and they affect neutrophils via soluble secreted factors, which is promising for clinical implications in equine medicine.

Resolution of eicosanoid/cytokine storm prevents carcinogen and inflammation-initiated hepatocellular cancer progression

Toxic environmental carcinogens promote cancer via genotoxic and nongenotoxic pathways, but nongenetic mechanisms remain poorly characterized. Carcinogen-induced apoptosis may trigger escape from dormancy of microtumors by interfering with inflammation resolution and triggering an endoplasmic reticulum (ER) stress response. While eicosanoid and cytokine storms are well-characterized in infection and inflammation, they are poorly characterized in cancer. Here, we demonstrate that carcinogens, such as aflatoxin B₁ (AFB₁), induce apoptotic cell death and the resulting cell debris stimulates hepatocellular carcinoma (HCC) tumor growth via an "eicosanoid and cytokine storm." AFB₁-generated debris up-regulates cyclooxygenase-2 (COX-2), soluble epoxide hydrolase (sEH), ER stress-response genes including BiP, CHOP, and PDI in macrophages. Thus, selective cytokine or eicosanoid blockade is unlikely to prevent carcinogen-induced cancer progression. Pharmacological abrogation of both the COX-2 and sEH pathways by PTUPB prevented the debris-stimulated eicosanoid and cytokine storm, down-regulated ER stress genes, and promoted macrophage phagocytosis of debris, resulting in suppression of HCC tumor growth. Thus, inflammation resolution via dual COX-2/sEH inhibition is an approach to prevent carcinogen-induced cancer.

Chronic and Acute Toxicities of Aflatoxins: Mechanisms of Action

There are presently more than 18 known aflatoxins most of which have been insufficiently studied for their incidence, health-risk, and mechanisms of toxicity to allow effective intervention and control means that would significantly and sustainably reduce their incidence and adverse effects on health and economy. Among these, aflatoxin B1 (AFB1) has been by far the most studied; yet, many aspects of the range and mechanisms of the diseases it causes remain to be elucidated. Its mutagenicity, tumorigenicity, and carcinogenicity-which are the best known-still suffer from limitations regarding the relative contribution of the oxidative stress and the reactive epoxide derivative (Aflatoxin-exo 8,9-epoxide) in the induction of the diseases, as well as its metabolic and synthesis pathways. Additionally, despite the well-established additive effects for carcinogenicity between AFB1 and other risk factors, e.g., hepatitis viruses B and C, and the hepatotoxic algal microcystins, the mechanisms of this synergy remain unclear. This study reviews the most recent advances in the field of the mechanisms of toxicity of aflatoxins and the adverse health effects that they cause in humans and animals.

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.

Aflatoxin compromises development of the preimplantation bovine embryo through mechanisms independent of reactive oxygen production

Aflatoxin is a potent carcinogen often found in animal feedstuffs. Although it reportedly impairs development of the preimplantation pig embryo, it is not known whether it adversely affects development of the preimplantation bovine embryo. We conducted 3 experiments to investigate this possibility and determine whether deleterious effects of aflatoxin were caused by increased production of reactive oxygen species (ROS). Experiments were conducted with embryos produced in vitro and cultured after fertilization with various concentrations of aflatoxin. For experiment 1, embryos were treated with 0 (control), 40, 400, or 4,000 µg/L of aflatoxin B₁ (AFB₁). Treatment at all concentrations of AFB₁ tended to reduce cleavage rate, with the 2 highest concentrations having significant effects. As compared with the control, 40 µg/L AFB₁ reduced the percentage of oocytes becoming blastocysts and the percentage of cleaved embryos becoming blastocysts (19.7 vs. 8.1% and 30.3 vs. 14.3%, respectively). Complete inhibition of blastocyst formation occurred at concentrations of 400 and 4,000 µg/L of AFB₁. Experiments 2 and 3 involved a 2 × 2 factorial design with effects of AFB₁ (0 and 40 µg/L), the antioxidant Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid, a water-soluble analog of vitamin E; 0 and 5 µM), and their interaction on production of ROS in putative zygotes (experiment 2) and development to the blastocyst stage (experiment 3). Production of ROS was increased by AFB₁, and this effect was reversed by Trolox. However, Trolox did not prevent the reduction in development to the blastocyst stage caused by AFB₁. Thus, the anti-developmental effects of AFB₁ are not caused solely by increased ROS production. Rather, other underlying mechanisms exist for the adverse effects of aflatoxin on embryonic development. Overall, results indicate the potential for feeding aflatoxin-contaminated feed to cause embryonic loss in cattle.

Current Understanding of Innate Immune Cell Dysfunction in Childhood Undernutrition

Undernutrition affects millions of children in low- and middle-income countries (LMIC) and underlies almost half of all deaths among children under 5 years old. The growth deficits that characterize childhood undernutrition (stunting and wasting) result from simultaneous underlying defects in multiple physiological processes, and current treatment regimens do not completely normalize these pathways. Most deaths among undernourished children are due to infections, indicating that their anti-pathogen immune responses are impaired. Defects in the body's first-line-of-defense against pathogens, the innate immune system, is a plausible yet understudied pathway that could contribute to this increased infection risk. In this review, we discuss the evidence for innate immune cell dysfunction from cohort studies of childhood undernutrition in LMIC, highlighting knowledge gaps in almost all innate immune cell types. We supplement these gaps with insights from relevant experimental models and make recommendations for how human and animal studies could be improved. A better understanding of innate immune function could inform future tractable immune-targeted interventions for childhood undernutrition to reduce mortality and improve long-term health, growth and development.

Bioluminescence-based detection of astrocytes apoptosis and ATP depletion induced by biologically relevant level aflatoxin B1

Although brain accumulation of aflatoxin B1 (AFB1) suggests potential impact on brain cells, including astrocytes, there still exists a scarcity of research on this issue within the literature. This research investigates the apoptosis effect of AFB1 on primary mouse astrocytes. To this aim, a MTT colorimetric assay on astrocytes was performed to measure the toxicity/LC50 of various concentrations (0-320,000 nM) of AFB1 for 24 h. Further, the astrocytes were exposed to concentrations of 8, 16 and 32 nM of AFB1 for 24, 48 and 72 h. Concentration of intracellular ATP) and caspase-3/7 activity was then determined by luciferase-dependent bioluminescence. Furthermore, the percentage of apoptotic cells was obtained using flow cytometry (annexin V+/propidium iodide (PI)−; cytochrome c release from mitochondria, a hallmark of cell damage, was carried out by Western blot as well. MTT assay at post-exposure hours (PEH) 24 revealed that the LC50 of AFB1 was ~80,000 nM. Though at PEH 48 only 32 nM of AFB1 resulted in a significant diminished intracellular ATP content, at PEH 72 both 8 and 32 nM of AFB1 led to a significant ATP depletion in astrocytes. Similar patterns of changes were observed in bioluminescence intensity of AFB1-treated astrocytes. Flow cytometry-based annexin V and PI staining of astrocytes at PEH 24, 48 and 72 showed that 32 nM of AFB1 significantly and time dependently increased the percentage of apoptotic astrocytes (annexin V+/PI−). With 32 nM of AFB1, caspase-3/7 activity in astrocytes was increased ~4-fold at PEH 72. A remarkable release of cytochrome c was only detected in astrocytes exposed to 32 nM AFB1 for PEH 72. The results indicated that a biologically relevant level of AFB1 (32 nM) induces apoptosis in astrocytes through ATP depletion and caspases activation.

Changes of leukocyte counts and expression of pro- and anti-inflammatory cytokines in peripheral leukocytes in periparturient dairy cows with retained fetal membranes

In dairy cows, retained fetal membranes (RFM) affect reproductive performance. The aim of this study was to examine the leukocyte counts and the gene expression of tumour necrosis factor α (TNFα), interleukin 1β (IL-1β), IL-8, and IL-10 in polymorphonuclear leukocytes (PMNs) and peripheral blood mononuclear cells (PBMCs) in cows with (n = 5) or without (n = 5) RFM during the peripartum period. The lymphocyte counts in RFM cows were higher than those in control cows throughout the experiment (p < .05). The expression of IL-8 in PMNs of control cows was higher (p < .05) compared with that of RFM cows postpartum. In cows with RFM, IL-1β expression was higher (p < .05) in PMNs at 6 weeks postpartum whereas the expression of IL-1β was lower (p < .05) in PBMCs at 4 weeks postpartum. The expression of IL-10 in PBMCs of control cows was higher (p < .05) than that of RFM cows at 2 weeks prepartum and 4 weeks postpartum. Taken together, our data indicate that changes of gene expression of pro- and anti-inflammatory cytokines in RFM cows might be associated with the delayed placental separation and development of uterine inflammation in RFM cows.

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.

Individual and combined effects of Aflatoxin B1, Deoxynivalenol and Zearalenone on HepG2 and RAW 264.7 cell lines

To understand the combinatorial toxicity of mycotoxins, we measured the effects of individual, binary and tertiary combinations of Aflatoxin B₁ (AFB₁), Deoxynivalenol (DON) and Zearalenone (ZEN) on the cell viability and cellular perturbations of HepG2 and RAW 264.7 cells. The nature of mycotoxins interactions was assessed using mathematical modeling (Chou-Talalay). Mechanisms of cytotoxicity were studied using high content screening (HCS) that probed cytotoxicity responses, such as changes in intracellular reactive oxygen species (ROS), mitochondrial membrane potential (MMP), intracellular calcium ([Ca²⁺]_i) flux, and cell membrane damage. Our results showed that individual cytotoxicity of mycotoxins in a decreasing order was DON>AFB₁>ZEN. Varying combinations of mycotoxins at differing concentrations showed different types of interactions. Most of the mixtures showed increasing toxic effects-synergism and/or addition while antagonistic effects were observed with combination of AFB₁+ZEN. Generally, combination of mycotoxins showed significantly increased intracellular ROS production and [Ca²⁺]_i flux, and decreased MMP in both cell lines, showing that the synergistic and additive effects of mycotoxin combination originate from perturbations of multiple cellular functions. Additionally, this study demonstrated the applicability of HCS for gaining mechanistic understanding on the toxicity of individual as well as combinatorial mycotoxins, and also provided scientific bases for formulating regulatory policies.

Seasonally Feed-Related Aflatoxins B 1 and M 1 Spread in Semiarid Industrial Dairy Herd and Its Deteriorating Impacts on Food and Immunity

To comparatively determine the levels of aflatoxin (AF) B1 in feedstuffs and of AFM1 in milk from semiarid industrial cattle farms in northeastern Iran during four seasons and to elucidate the effects of mixed AFB1 and AFM1 on bovine granulocytes, 72 feedstuffs (concentrate, silage, and totally mixed ration (TMR)) and 200 bulk milk samples were simultaneously collected for ELISA-based AFs detection. Isolated blood and milk neutrophils (n=8/treatment) were also preincubated with mix of 10 ng/ml AFB1 and 10 ng/ml AFM1 for 12 h; the impact was assessed on neutrophils functions. AFB1 levels in feedstuffs averaged 28 μg/kg (4–127 μg/kg), with TMR maximal (38±6.3 μg/kg), concentrate (32±6.5 μg/kg), and silage (16±1.5 μg/kg). The levels of AFB1 and AFM1 in feedstuffs and milk averaged 42±9.3, 27±2.8, 26±4.1, and 18.5±2.8 μg/kg and 85±7.3, 62±6.1, 46±6.2, and 41±6.5 ppb μg/kg in winter (maximal), autumn, spring, and summer, respectively. Mix of AFB1 and AFM1 weakened various functions of granulocytes. It adds new reason why during winter semiarid raised food-producing animals show more immune-incompetence.

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

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

Inorganic arsenic can be potent granulotoxin in mammalian neutrophils in vitro

An important outcome arising out of occupational/environmental exposure to arsenic (As) is immunotoxicity. To determine the impact of inorganic As on innate immune cells, effects of a low dose of NaAsO2 (i.e. 20 ng As/ml) on select parameters associated with human and bovine neutrophils (PMN) were evaluated in vitro. PMN isolated from the blood of healthy individuals and cows (n = 8/treatment) were pre-incubated with NaAsO2 for 12 h before effects on PMN phagocytosis, transcription of TLR2, TLR4 and CD64 in human PMN - as well as on phagocytosis-dependent/-independent cell chemiluminescence (CL), phagocytosis and killing of Staphylococcus aureus and Escherichia coli, PMN H2O2 production and necrosis and TLR4 transcription in bovine PMN - were assessed. Relative to control (no As) PMN, treatment with As significantly decreased phagocytic capacity and CD64 mRNA, but increased TLR2 and TLR4 mRNA, in human PMN. In bovine PMN, while As also led to increased TLR4 mRNA abundance, it resulted in decreases in phagocytosis-dependent and -independent CL, PMN H2O2 production, PMN phagocytosis and killing of both E. coli and S. aureus by PMN. Considering the broad roles of PMN in immunology, the results of these studies increase our understanding of functional consequences of As exposure in inducing immunotoxicity and increasing susceptibility to (infectious) diseases in mammals.

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.

Photoimmunological properties of borage in bovine neutrophil in vitro model

Borage (Echium amoenum fisch) is one of the most commonly used medicinal plants, and has long been used as a traditional herbal medicine for many (non)infectious diseases in Iran. Study on photoredox and photoimmunology of borage is little. Natural immunomodulatory plants with minimal adverse/toxic effects could help boost animal health and, ultimately, public health. To determine the effect of borage on the functions of key circulating innate immune cells, effects of borage extract (BE) on bovine neutrophils (PMN) photoredox and phagocytosis events were evaluated using an in vitro model system. Blood PMN isolated from healthy high yielding dairy cows (n = 8/treatment) were pre-incubated with BE and the impact on phagocytosis-dependent-and-independent cellular chemiluminescence (CL), phagocytosis, killing of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), fluorescence-based PMN H2O2 production and necrosis were assessed. Relative to control (no BE) PMN, treatment with BE significantly increased phagocytosis-dependent-and-independent PMN CL (>10-15% increase). While BE also led to increased PMN H2O2 production, necrosis was also surprisingly higher in these cells. Phagocytosis and killing of both E. coli and S. aureus by PMN treated with BE was substantially higher than that by control PMN. The increased photoimmunobiological events especially intracellular CL, intracellular H2O2 formation, and phagocytic capacity of BE-treated PMN support the potential immunotherapeutic implications of borage and its components for particularly immunocompromised animals and humans.

Cytoprotective and genoprotective effects of β-glucans against aflatoxin B₁-induced DNA damage in broiler chicken lymphocytes

The polysaccharide β-glucan presents beneficial effects on the immune system, although the mechanisms of the immunomodulatory effect remain poorly understood. The potential cytoprotective and genoprotective effects of β-glucans were evaluated in broiler chicken lymphocytes exposed to increasing concentrations of aflatoxin B₁ (AFB₁) and/or β-glucans. AFB₁ significantly decreased cell viability at the concentrations of 10 and 20 μg/ml at 72 h of incubation (p<0.01 and p<0.001, respectively). Moreover, the AFB₁ concentrations of 1, 10 and 20 μg/ml increased DNA fragmentation levels at 24 h (p<0.001). Conversely, lymphocyte death was prevented by β-glucans at the concentrations of 1% and 10%, indicating a cytoprotective effect. Reactive oxygen species levels were increased in the cells treated with 20 μg/ml AFB₁ at 24 h (p<0.05) and 10% β-glucans with or without AFB₁ at 24, 48 and 72 h of incubation (p<0.001). DNA damage increased by more than 100% in AFB₁-treated lymphocytes when compared to control group. β-glucans at 1% was able to fully revert the AFB₁-induced lymphocyte DNA damage, indicating a genoprotective effect and maintaining DNA integrity. In conclusion, β-glucans showed in vitro dose-dependent cytoprotective and genoprotective effects in broiler chicken lymphocytes exposed to AFB₁.

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.

The effect of single nucleotide polymorphisms in the tumor necrosis factor-α gene on reproductive performance and immune function in dairy cattle

The present study aimed to assess the effect of polymorphisms in the tumor necrosis factor α (TNF-α) promoter (A/A, A/G and G/G) and exons (T/T, T/C and C/C) on immune function and reproductive performance in dairy cows. The occurrence of the first postpartum ovulation within 3 weeks in the cows with the TNF-α promoter A/G and G/G genotypes was higher than in the A/A group. Among the different TNF-α exon genotypes, the occurrence of early first postpartum ovulation was higher in the T/C and C/C genotype groups than in the T/T group. Single nucleotide polymorphisms (SNPs) in the TNF-α gene did not affect the rate of artificial insemination (AI) or duration from parturition to next conception (days open). The apoptosis rate of polymorphonuclear leukocytes (PMNs) did not differ among the TNF-α promoter genotypes, but the PMN transmigration rate was significantly higher for the A/A and A/G genotypes than for the G/G genotype. Interleukin 8 (IL-8) mRNA expression in PMNs and peripheral blood mononuclear cells (PBMCs) before culture was significantly higher for the A/A genotype compared with the G/G genotype. There were no significant differences between the genotypes in the mRNA expression of TNF-α, IL-6, IL-1β, and toll-like receptor 4 (TLR4) in PMNs and PBMCs before and 4 h after culture. IL-8 and IL-1β production by PBMCs cultured for 4 h was significantly higher for the animals with the A/A genotype than for those with the G/G genotype. On the other hand, no significant difference was observed in IL-8 and IL-1β production by PMNs among different TNF-α genotypes. Taken together, these results suggest that SNP in the TNF-α gene affects immune function and reproductive performance in dairy cows.

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

CONTEXT

Aflatoxins (AFs) are highly hazardous mycotoxins with potent carcinogenic, mutagenic and immune disregulatory properties. Cytochrome P450 (CYP) isoforms are central for enhanced AFB₁ toxicity in situ. It remains to be seen whether and how these AFB₁ activators work in human leukocytes.

OBJECTIVE

To investigate the involvement of CYP isoforms in AFB₁ toxicity of circulating mononuclear cells, we examined the impact of environmentally relevant levels of AFB1 on lymphocytes and monocytes.

MATERIALS AND METHODS

Very low and moderate doses of AFB₁ with/without CYP inducers on transcription of key CYP isoforms and toll-like receptor 4 (TLR4) were examined in human lymphocytes, monocytes and HepG2 cells; cell cycle distribution and viability were also analyzed in AFB₁-exposed lymphocytes and monocytes.

RESULTS

Only CYP1A1, CYP1B1, CYP3A4, CYP3A5 and CYP3A7 expressed in lymphocytes and monocytes. TLR4 much more expressed in monocytes than in lymphocytes, but HepG2 showed little TLR4 transcription. While CYP1A1, CYP1B1 and CYP3A4 were highly induced by AFB₁ in monocytes, in lymphocytes only CYP1A1 was induced. Among CYP1A1, CYP1B1 and CYP3A4 only CYP1A1 responded to low and moderate levels of AFB₁. Enhanced transcripts of CYPs by AFB₁ yielded little synergies on TLR4 transcription in lymphocytes and monocytes. Cell cycle arrest and necrosis were also detected in AFB₁-exposed lymphocytes and monocytes.

CONCLUSIONS

Our novel findings indicate that AFB₁ more intensively stimulates CYP genes expression in monocytes than in lymphocytes. Mechanistically, this could explain a more pronounced immunotoxicity of AFB₁ in myeloid than in lymphoid lineage cells in vitro/situ/vivo.

Biologically relevant doses of mixed aflatoxins B and G up-regulate MyD88, TLR2, TLR4 and CD14 transcripts in human PBMCs

CONTEXT

Aflatoxins (AFs) are highly hazardous carcinogenic mycotoxins originated from very common fungi present in the environment. Their effect on key immune-surveillance molecules is unclear.

OBJECTIVE

We aimed to examine the effect of mixed AFs on immunologically relevant molecules and on viability in human peripheral blood mononuclear cells (PBMCs), in conditions similar to those occurring naturally, i.e. using a mixture of environmentally relevant levels of AFB₁, AFB₂, AFG₁ and AFG₂.

MATERIALS AND METHODS

We evaluated the mRNA expression of MyD88, toll-like receptor (TLR)-2, TLR4 and CD14, in human PBMCs treated with a mixture of AFB₁, AFB₂, AFG₁ and AFG₂ at different doses for 2, 12 and 24 h. We used qRT-PCR to assess changes in transcripts of MyD88, TLR2, TLR4 and CD14 in PBMCs. We also evaluated the viability of PBMCs exposed to AFs.

RESULTS

Biologically relevant levels of mixed AFs elicited early immune modulation in human PBMCs. qRT-PCR results showed several folds increase of MyD88, TLR2, TLR4 and CD14 transcripts in PBMCs as early as 2 h post-exposure to mixed AFs. Kinetics and dose-response of the up-regulation differed for mentioned gene transcripts. Further, prolonged exposure to mixed AFs decreased PBMCs viability.

CONCLUSION

Immunotoxicity of AFs on PBMCs may be mediated by up-regulation of key immune-surveillance molecule transcripts. The description of these effects induced by AFs on PBMCs are novel and should be taken into account when considering AF-related infectious and noninfectious diseases in areas highly exposed to AFs.

Applications of flow cytometry to toxicological mycotoxin effects in cultured mammalian cells: a review

This review gives an overview of flow cytometry applications to toxicological studies of several physiological target sites of mycotoxins on different mammalian cell lines. Mycotoxins are secondary metabolites of fungi that may be present in food, feed, air and water. The increasing presence of mycotoxins in crops, their wide distribution in the food chain, and their potential for toxicity demonstrate the need for further knowledge. Flow cytometry has become a valuable tool in mycotoxin studies in recent years for the rapid analysis of single cells in a mixture. In toxicology, the power of these methods lies in the possibility of determining a wide range of cell parameters, providing valuable information to elucidate cell growth and viability, metabolic activity, mitochondrial membrane potential and membrane integrity mechanisms. There are studies using flow cytometry technique on Alternaria, Aspergillus, Fusarium and Penicillium mycotoxins including information about cell type, assay conditions and functional parameters. Most of the studies collected in the literature are on deoxynivalenol and zearalenone mycotoxins. Cell cycle analysis and apoptosis are the processes more widely investigated.

Neutrophil priming by hypoxic preconditioning protects against epithelial barrier damage and enteric bacterial translocation in intestinal ischemia/reperfusion

Intestinal ischemia/reperfusion (I/R) induces mucosal barrier dysfunction and bacterial translocation (BT). Neutrophil-derived oxidative free radicals have been incriminated in the pathogenesis of ischemic injury in various organs, but their role in the bacteria-containing intestinal tract is debatable. Primed neutrophils are characterized by a faster and higher respiratory burst activity associated with more robust bactericidal effects on exposure to a second stimulus. Hypoxic preconditioning (HPC) attenuates ischemic injury in brain, heart, lung and kidney; no reports were found in the gut. Our aim is to investigate whether neutrophil priming by HPC protects against intestinal I/R-induced barrier damage and bacterial influx. Rats were raised in normoxia (NM) or kept in a hypobaric hypoxic chamber (380 Torr) 17 h/day for 3 weeks for HPC, followed by sham operation or intestinal I/R. Gut permeability was determined by using an ex vivo macromolecular flux assay and an in vivo magnetic resonance imaging-based method. Liver and spleen homogenates were plated for bacterial culturing. Rats raised in HPC showed diminished levels of BT, and partially improved mucosal histopathology and epithelial barrier function compared with the NM groups after intestinal I/R. Augmented cytokine-induced neutrophil chemoattractant (CINC)-1 and -3 levels and myeloperoxidase activity correlated with enhanced infiltration of neutrophils in intestines of HPC-I/R compared with NM-I/R rats. HPC alone caused blood neutrophil priming, as shown by elevated production of superoxide and hydrogen peroxide on stimulation, increased membrane translocation of cytosolic p47(phox) and p67(phox), as well as augmented bacterial-killing and phagocytotic activities. Neutrophil depletion reversed the mucosal protection by HPC, and aggravated intestinal leakiness and BT following I/R. In conclusion, neutrophil priming by HPC protects against I/R-induced BT via direct antimicrobial activity by oxidative respiratory bursts and through promotion of epithelial barrier integrity for luminal confinement of enteric bacteria.

Evidence that polymorphonuclear neutrophils infiltrate into the developing corpus luteum and promote angiogenesis with interleukin-8 in the cow

BACKGROUND

After ovulation in the cow, the corpus luteum (CL) rapidly develops within a few days with angiogenesis and progesterone production. CL formation resembles an inflammatory response due to the influx of immune cells. Neutrophils play a role in host defense and inflammation, and secrete chemoattractants to stimulate angiogenesis. We therefore hypothesized that neutrophils infiltrate in the developing CL from just after ovulation and may play a role in angiogenesis of the CL.

METHODS AND RESULTS

Polymorphonuclear neutrophils (PMN) were detected in CL tissue by Pas-staining, and interleukin-8 (IL-8, a neutrophil-specific chemoattractant) was measured in supernatant of the CL tissue culture: considerable amounts of PMNs and the high level of IL-8 were observed during the early luteal phase (days 1-4 of the estrous cycle). PMNs and IL-8 were low levels in the mid and late luteal phases, but IL-8 was increased during luteal regression. The PMN migration in vitro was stimulated by the supernatant from the early CL but not from the mid CL, and this activity was inhibited by neutralizing with an anti-IL-8 antibody, indicating the major role of IL-8 in inducing active PMN migration in the early CL. Moreover, IL-8 stimulated proliferation of CL-derived endothelial cells (LECs), and both the supernatant of activated PMNs and IL-8 stimulated formation of capillary-like structures of LECs.

CONCLUSION

PMNs migrate into the early CL partially due to its major chemoattractant IL-8 produced at high levels in the CL, and PMNs is a potential regulator of angiogenesis together with IL-8 in developing CL in the cow.