Mycotoxin Zearalenone Attenuates Innate Immune Responses and Suppresses NLRP3 Inflammasome Activation in LPS-Activated Macrophages

The Novel Role of the NLRP3 Inflammasome in Mycotoxin-Induced Toxicological Mechanisms

Mycotoxins are secondary metabolites produced by several fungi and moulds that exert toxicological effects on animals including immunotoxicity, genotoxicity, hepatotoxicity, teratogenicity, and neurotoxicity. However, the toxicological mechanisms of mycotoxins are complex and unclear. The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome is a multimeric cytosolic protein complex composed of the NLRP3 sensor, ASC adapter protein, and caspase-1 effector. Activation of the NLRP3 inflammasome plays a crucial role in innate immune defence and homeostatic maintenance. Recent studies have revealed that NLRP3 inflammasome activation is linked to tissue damage and inflammation induced by mycotoxin exposure. Thus, this review summarises the latest advancements in research on the roles of NLRP3 inflammasome activation in the pathogenesis of mycotoxin exposure. The effects of exposure to multiple mycotoxins, including deoxynivalenol, aflatoxin B1, zearalenone, T-2 toxin, ochratoxin A, and fumonisim B1, on pyroptosis-related factors and inflammation-related factors in vitro and in vivo and the pharmacological inhibition of specific and nonspecific NLRP3 inhibitors are summarized and examined. This comprehensive review contributes to a better understanding of the role of the NLRP3 inflammasome in toxicity induced by mycotoxin exposure and provides novel insights for pharmacologically targeting NLRP3 as a novel anti-inflammatory agent against mycotoxin exposure.

Toxicity, biodegradation, and nutritional intervention mechanism of zearalenone

Zearalenone (ZEA), a global mycotoxin commonly found in a variety of grain products and animal feed, causes damage to the gastrointestinal tract, immune organs, liver and reproductive system. Many treatments, including physical, chemical and biological methods, have been reported for the degradation of ZEA. Each degradation method has different degradation efficacies and distinct mechanisms. In this article, the global pollution status, hazard and toxicity of ZEA are summarized. We also review the biological detoxification methods and nutritional regulation strategies for alleviating the toxicity of ZEA. Moreover, we discuss the molecular detoxification mechanism of ZEA to help explore more efficient detoxification methods to better reduce the global pollution and hazard of ZEA.

Estrogen plays an important role by influencing the NLRP3 inflammasome

The nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome is an important part of the natural immune system that plays an important role in many diseases. Estrogen is a sex hormone that plays an important role in controlling reproduction and regulates many physiological and pathological processes. Recent studies have indicated that estrogen is associated with disease progression. Estrogen can ameliorate some diseases (e. g, sepsis, mood disturbances, cerebral ischemia, some hepatopathy, Parkinson's disease, amyotrophic lateral sclerosis, inflammatory bowel disease, spinal cord injury, multiple sclerosis, myocardial ischemia/reperfusion injury, osteoarthritis, and renal fibrosis) by inhibiting the NLRP3 inflammasome. Estrogen can also promote the development of diseases (e.g., ovarian endometriosis, dry eye disease, and systemic lupus erythematosus) by upregulating the NLRP3 inflammasome. In addition, estrogen has a dual effect on the development of cancers and asthma. However, the mechanism of these effects is not summarized. This article reviewed the progress in understanding the effects of estrogen on the NLRP3 inflammasome and its mechanisms in recent years to provide a theoretical basis for an in-depth study.

Detoxification of Selenium Yeast on Mycotoxins and Heavy Metals: a Review

Mycotoxins are secondary metabolites produced by specific fungi. More than 400 different mycotoxins are known in the world, and the concentration of these toxins in food and feed often exceeds the acceptable limit, thus causing serious harm to animals and human body. At the same time, modern industrial agriculture will also bring a lot of environmental pollution in the development process, including the increase of heavy metal content, and often the clinical symptoms of low/medium level chronic heavy metal poisoning are not obvious, thus delaying the best treatment opportunity. However, the traditional ways of detoxification cannot completely eliminate the adverse effects of these toxins on the body, and sometimes bring some side effects, so it is essential to find a new type of safe antidote. Trace element selenium is among the essential mineral nutrient elements of human and animal bodies, which can effectively remove excessive free radicals and reactive oxygen species in the body, and has the effects of antioxidant, resisting stress, and improving body immunity. Selenium is common in nature in inorganic selenium and organic selenium. In previous studies, it was found that the use of inorganic selenium (sodium selenite) can play a certain protective role against mycotoxins and heavy metal poisoning. However, while it plays the role of antioxidant, it will also have adverse effects on the body. Therefore, it was found in the latest study that selenium yeast could not only replace the protective effect of sodium selenite on mycotoxins and heavy metal poisoning, but also improve the immunity of the body. Selenium yeast is an organic selenium source with high activity and low toxicity, which is produced by selenium relying on the cell protein structure of growing yeast. It not only has high absorption rate, but also can be stored in the body after meeting the physiological needs of the body for selenium, so as to avoid selenium deficiency again in the short term. However, few of these studies can clearly reveal the protective mechanism of yeast selenium. In this paper, the detoxification mechanism of selenium yeast on mycotoxins and heavy metal poisoning was reviewed, which provided some theoretical support for further understanding of the biological function of selenium yeast and its replacement for inorganic selenium. The conclusions suggest that selenium yeast can effectively alleviate the oxidative damage by regulating different signaling pathways, improving the activity of antioxidant enzymes, reversing the content of inflammatory factors, regulating the protein expression of apoptosis-related genes, and reducing the accumulation of mycotoxins and heavy metals in the body.

Selenium-chitosan alleviates the toxic effects of Zearalenone on antioxidant and immune function in mice

This study assessed the protective effects of selenium-chitosan (SC) against antioxidant and immune function-related damage induced by zearalenone (ZEN) in mice. In total, 150 female mice were allotted to five groups for a 30-day study. Control mice were fed a basal diet. Mice in the ZEN, ZEN-Se1, ZEN-Se2 and ZEN-Se3 groups were fed the basal diet supplemented with same dose of ZEN (2 mg/kg) and different doses of SC, 0.0, 0.2, 0.4 and 0.6 mg/kg, respectively (calculated by selenium). After 30 days, the total antioxidant capacity (T-AOC) level, glutathione peroxidase (GSH-Px) activity, total superoxide dismutase (T-SOD) activity and malondialdehyde (MDA) content in plasma and liver, as well as Con A-induced splenocyte proliferation, plasma interleukins concentrations and liver interleukin mRNA expression levels were determined. The plasma and liver GSH-Px activities, liver T-AOC levels, Con A-induced splenocyte proliferation, interleukin (IL) contents and mRNA expression levels in the ZEN group were significantly lower than in the control group (P < 0.01 or P < 0.05), whereas plasma and liver MDA contents in the ZEN group were significantly higher than in the control group (P < 0.01 or P < 0.05). Additionally, plasma and liver GSH-Px activities, liver T-AOC levels, Con A-induced splenocyte proliferation, IL-1β, IL-17A, IL-2 and IL-6 contents and mRNA expression levels in ZEN+Se2 and ZEN+Se3 groups were significantly higher than in the ZEN group (P < 0.01 or P < 0.05), whereas plasma and liver MDA contents in the ZEN+Se2 and ZEN+Se3 groups were significantly lower than in the ZEN group (P < 0.01 or P < 0.05). The plasma and liver GSH-Px activities, Con A-induced splenocyte proliferation, IL-1β and IL-6 contents, IL-2 and IL-17A mRNA expression levels in the ZEN+Se1 group were also significantly higher than in the ZEN group (P < 0.01 or P < 0.05), whereas the plasma MDA content in the ZEN+Se1 group was also significantly lower than in the ZEN group (P < 0.01). Thus, SC may alleviate antioxidant function-related damage and immunosuppression induced by ZEN in mice.

Roles of stress response-related signaling and its contribution to the toxicity of zearalenone in mammals

Zearalenone (ZEA) is a mycotoxin frequently found in cereal crops and cereal-derived foodstuffs worldwide. It affects plant productivity, and is also a serious hazard to humans and animals if being exposed to food/feed contaminated by ZEA. Studies over the last decade have shown that the toxicity of ZEA in animals is mainly mediated by the various stress responses, such as endoplasmic reticulum (ER) stress, oxidative stress, and others. Accumulating evidence shows that oxidative stress and ER stress signaling are actively implicated in and contributes to the pathophysiology of various diseases. Biochemically, the deleterious effects of ZEA are associated with apoptosis, DNA damage, and lipid peroxidation by regulating the expression of genes implicated in these biological processes. Despite these findings, the underlying mechanisms responsible for these alterations remain unclear. This review summarized the characteristics, metabolism, toxicity and the deleterious effects of ZEA exposure in various tissues of animals. Stress response signaling implicated in the toxicity as well as potential therapeutic options with the ability to reduce the deleterious effects of ZEA in animals were highlighted and discussed.

Practical Application of Urinary Zearalenone Monitoring System for Feed Hygiene Management of a Japanese Black Cattle Breeding Herd—The Relationship between Monthly Anti-Müllerian Hormone and Serum Amyloid A Concentrations

This study addresses an advantageous application of a urinary zearalenone (ZEN) monitoring system not only for surveillance of ZEN exposure at the production site of breeding cows but also for follow-up monitoring after improvement of feeds provided to the herd. As biomarkers of effect, serum levels of the anti-Müllerian hormone (AMH) and serum amyloid A (SAA) concentrations were used. Based on the results of urinary ZEN measurement, two cows from one herd had urinary ZEN concentrations which were two orders of magnitude higher (ZEN: 1.34 mg/kg, sterigmatocystin (STC): 0.08 mg/kg in roughages) than the levels of all cows from three other herds (ZEN: not detected, STC: not detected in roughages). For the follow-up monitoring of the herd with positive ZEN and STC exposure, urine, blood, and roughage samples were collected from five cows monthly for one year. A monitoring series in the breeding cattle herd indicated that feed concentrations were not necessarily reflected in urinary concentrations; urinary monitoring assay by ELISA may be a simple and accurate method that reflects the exposure/absorption of ZEN. Additionally, although the ZEN exposure level appeared not to be critical compared with the Japanese ZEN limitation in dietary feeds, a negative regression trend between the ZEN and AMH concentrations was observed, indicating that only at extremely universal mycotoxin exposure levels, ZEN exposure may affect the number of antral follicles in cattle. A negative regression trend between the ZEN and SAA concentrations could also be demonstrated, possibly indicating the innate immune suppression caused by low-level chronic ZEN exposure. Finally, significant differences (p = 0.0487) in calving intervals between pre-ZEN monitoring (mean ± SEM: 439.0 ± 41.2) and post-ZEN monitoring (349.9 ± 6.9) periods were observed in the monitored five cows. These preliminary results indicate that the urinary ZEN monitoring system may be a useful practical tool not only for detecting contaminated herds under field conditions but also provides an initial look at the effects of long-term chronic ZEN/STC (or other co-existing mycotoxins) exposure on herd productivity and fertility.

Modulatory Properties of Food and Nutraceutical Components Targeting NLRP3 Inflammasome Activation

Inflammasomes are key intracellular multimeric proteins able to initiate the cellular inflammatory signaling pathway. NLRP3 inflammasome represents one of the main protein complexes involved in the development of inflammatory events, and its activity has been largely demonstrated to be connected with inflammatory or autoinflammatory disorders, including diabetes, gouty arthritis, liver fibrosis, Alzheimer’s disease, respiratory syndromes, atherosclerosis, and cancer initiation. In recent years, it has been demonstrated how dietary intake and nutritional status represent important environmental elements that can modulate metabolic inflammation, since food matrices are an important source of several bioactive compounds. In this review, an updated status of knowledge regarding food bioactive compounds as NLRP3 inflammasome modulators is discussed. Several chemical classes, namely polyphenols, organosulfurs, terpenes, fatty acids, proteins, amino acids, saponins, sterols, polysaccharides, carotenoids, vitamins, and probiotics, have been shown to possess NLRP3 inflammasome-modulating activity through in vitro and in vivo assays, mainly demonstrating an anti-NLRP3 inflammasome activity. Plant foods are particularly rich in important bioactive compounds, each of them can have different effects on the pathway of inflammatory response, confirming the importance of the nutritional pattern (food model) as a whole rather than any single nutrient or functional compound.

Staphylococcal Enterotoxin A Induces Intestinal Barrier Dysfunction and Activates NLRP3 Inflammasome via NF-κB/MAPK Signaling Pathways in Mice

Staphylococcal enterotoxin A (SEA), the toxin protein secreted by Staphylococcus aureus, can cause staphylococcal food poisoning outbreaks and seriously threaten global public health. However, little is known about the pathogenesis of SEA in staphylococcal foodborne diseases. In this study, the effect of SEA on intestinal barrier injury and NLRP3 inflammasome activation was investigated by exposing BALB/c mice to SEA with increasing doses and a potential toxic mechanism was elucidated. Our findings suggested that SEA exposure provoked villi injury and suppressed the expression of ZO-1 and occludin proteins, thereby inducing intestinal barrier dysfunction and small intestinal injury in mice. Concurrently, SEA significantly up-regulated the expression of NLRP3 inflammasome-associated proteins and triggered the mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signaling pathways in jejunum tissues. Notably, selective inhibitors of MAPKs and NF-κB p65 ameliorated the activation of NLRP3 inflammasome stimulated by SEA, which further indicated that SEA could activate NLRP3 inflammasome through NF-κB/MAPK pathways. In summary, SEA was first confirmed to induce intestinal barrier dysfunction and activate NLRP3 inflammasome via NF-κB/MAPK signaling pathways. These findings will contribute to a more comprehensive understanding of the pathogenesis of SEA and related drug-screening for the treatment and prevention of bacteriotoxin-caused foodborne diseases via targeting specific pathways.