Human skin permeation of emerging mycotoxins (beauvericin and enniatins)

Computational Applications: Beauvericin from a Mycotoxin into a Humanized Drug

Drug discovery was initially attributed to coincidence or experimental research. Historically, the traditional approaches were complex, lengthy, and expensive, entailing costly random screening of synthesized compounds or natural products coupled with in vivo validation largely depending on the availability of appropriate animal models. Currently, in silico modeling has become a vital tool for drug discovery and repurposing. Molecular docking and dynamic simulations are being used to find the best match between a ligand and a molecule, an approach that could help predict the biomolecular interactions between the drug and the target host. Beauvericin (BEA) is an emerging mycotoxin produced by the entomopathogenic fungus Beauveria bassiana, being originally studied for its potential use as a pesticide. BEA is now considered a molecule of interest for its possible use in diverse biotechnological applications in the pharmaceutical industry and medicine. In this manuscript, we provide an overview of the repurposing of BEA as a potential therapeutic agent for multiple diseases. Furthermore, considerable emphasis is given to the fundamental role of in silico techniques to (i) further investigate the activity spectrum of BEA, a secondary metabolite, and (ii) elucidate its mode of action.

Impact of Enniatin B and Beauvericin on Lysosomal Cathepsin B Secretion and Apoptosis Induction

Enniatin B (ENN B) and Beauvericin (BEA) are cyclohexadepsipeptides that can be isolated from Fusarium and Beauveria bassiana, respectively. Both compounds are cytotoxic and ionophoric. In the present study, the mechanism of cell death induced by these compounds was investigated. Epidermal carcinoma-derived cell line KB-3-1 cells were treated with different concentrations of these compounds. The extracellular secretion of cathepsin B increased in a concentration-dependent manner, and the lysosomal staining by lysotracker red was reduced upon the treatment with any of the compounds. However, the extracellular secretion of cathepsin L and cathepsin D were not affected. Inhibition of cathepsin B with specific inhibitor CA074 significantly reduced the cytotoxic effect of both compounds, while inhibition of cathepsin D or cathepsin L did not influence the cytotoxic activities of both compounds. In vitro labelling of lysosomal cysteine cathepsins with Ethyl (2S, 3S)-epoxysuccinate-Leu-Tyr-Acp-Lys (Biotin)-NH2 (DCG04) was not affected in case of cathepsin L upon the treatment with both compounds, while it was significantly reduced in case of cathepsin B. In conclusion, ENN B and BEA increase lysosomal Ph, which inhibits delivery of cathepsin B from Golgi to lysosomes, thereby inducing cathepsin B release in cytosol, which activates caspases and hence the apoptotic pathway.

Depsipeptides Targeting Tumor Cells: Milestones from In Vitro to Clinical Trials

Cancer is currently considered one of the most threatening diseases worldwide. Diet could be one of the factors that can be enhanced to comprehensively address a cancer patient's condition. Unfortunately, most molecules capable of targeting cancer cells are found in uncommon food sources. Among them, depsipeptides have emerged as one of the most reliable choices for cancer treatment. These cyclic amino acid oligomers, with one or more subunits replaced by a hydroxylated carboxylic acid resulting in one lactone bond in a core ring, have broadly proven their cancer-targeting efficacy, some even reaching clinical trials and being commercialized as "anticancer" drugs. This review aimed to describe these depsipeptides, their reported amino acid sequences, determined structure, and the specific mechanism by which they target tumor cells including apoptosis, oncosis, and elastase inhibition, among others. Furthermore, we have delved into state-of-the-art in vivo and clinical trials, current methods for purification and synthesis, and the recognized disadvantages of these molecules. The information collated in this review can help researchers decide whether these molecules should be incorporated into functional foods in the near future.

Feedborne Mycotoxins Beauvericin and Enniatins and Livestock Animals

Mycotoxins are secondary metabolites produced by several species of fungi, including the Fusarium, Aspergillus, and Penicillium species. Currently, more than 300 structurally diverse mycotoxins are known, including a group called minor mycotoxins, namely enniatins, beauvericin, and fusaproliferin. Beauvericin and enniatins possess a variety of biological activities. Their antimicrobial, antibiotic, or ionoforic activities have been proven and according to various bioassays, they are believed to be toxic. They are mainly found in cereal grains and their products, but they have also been detected in forage feedstuff. Mycotoxins in feedstuffs of livestock animals are of dual concern. First one relates to the safety of animal-derived food. Based on the available data, the carry-over of minor mycotoxins from feed to edible animal tissues is possible. The second concern relates to detrimental effects of mycotoxins on animal health and performance. This review aims to summarize current knowledge on the relation of minor mycotoxins to livestock animals.

Celecoxib reduces Deoxynivalenol induced proliferation, inflammation and protein kinase C translocation via modulating downstream targets in mouse skin

Exposure to mycotoxins is mostly by ingestion but also occurs by the dermal and inhalation routes. The present study for the first time demonstrated that mycotoxin Deoxynivalenol (DON), permeates through Swiss albino mice skin, which demands awareness of health risks in people who are dermally exposed to mycotoxins especially agricultural farmers. Despite the widespread contamination of DON in food commodities studies to alleviate DON's toxicity are sparsely reported. Thus effective measures to combat mycotoxins associated toxicity remains an imperative aspect to be considered from the angle of dermal exposure. Topical application of Celecoxib (1-2 mg), followed by DON (100 μg) application on the dorsal side of mice, resulted in substantial decrease in DON-induced (i) edema, hyperplasia, cell proliferation (ii) inhibition of cytokine and prostaglandin-E2 levels (iii) phosphorylation of ERK1/2, JNK, p38, MAPKKs, CREB, P90-RSK (iv) downregulation of c-Jun, c- Fos, phospho-NF-kB and their downstream target proteins cyclin D1 and COX-2. Using Ro-31-8220 (Protein-Kinase-C inhibitor), it was observed PKC was responsible for DON induced upregulation of COX-2 and iNOS proteins. Treatment of Celecoxib decreased DON-induced translocation of Protein Kinase C isozymes (α,ε,γ), demonstrating the role of PKC in DON-mediated biochemical and molecular alterations responsible for its dermal toxicity. The present findings indicate that topical application of celecoxib is effective in the management of inflammatory skin disorders induced by foodborne fungal toxin DON. The skin permeation potential of Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor NSAID, was also assessed, and the results indicated that the permeation was relatively lower as compared to the oral mode of administration. Hence topical use of celecoxib may be preferred over oral dosing because of lower systemic absorption and to avoid the unwanted side effects. This study provides a prospect for exploring the clinical efficacy of topically applied COX-2 inhibitors for the management of inflammatory skin disorders induced by foodborne fungal toxins.

In Vitro Activity of Beauvericin against All Developmental Stages of Sarcoptes scabiei

Scabies is a frequent cutaneous infection caused by the mite Sarcoptes scabiei in a large number of mammals, including humans. As the resistance of S. scabiei against several chemical acaricides has been previously documented, the establishment of alternative and effective control molecules is required. In this study, the potential acaricidal activity of beauvericin was assessed against different life stages of S. scabiei var. suis and in comparison with dimpylate and ivermectin, two commercially available molecules used for the treatment of S. scabiei infection in animals and/or humans. The toxicity of beauvericin against cultured human fibroblast skin cells was evaluated using an MTT proliferation assay. In our in vitro model, developmental stages of S. scabiei were placed in petri dishes filled with Columbia agar supplemented with pig serum and different concentrations of the drugs. Cell sensitivity assays demonstrated low toxicity of beauvericin against primary human fibroblast skin cells. At 0.5 and 5 mM, beauvericin showed higher activity against adults and eggs of S. scabiei compared to dimpylate and ivermectin. These results revealed that the use of beauvericin is promising and might be considered for the treatment of S. scabiei infection.

Occupational Exposure to Mycotoxins: Current Knowledge and Prospects

Occupational exposure to mycotoxins is supposedly very frequent, but it is rarely reported in the scientific literature. Several recent studies described occupational exposure to the aflatoxin B1 (AFB1) mycotoxin in different occupational settings. Previously, exposure to other mycotoxins was shown in the animal husbandry and food processing sectors, confirming that occupational exposure cannot be negligible. However, no guidelines or standard methodologies are available for helping occupational hygienists to consider mycotoxin exposure in their interventions. This article reviews the literature on this problem and recommends some actions for the better management of this risk factor in occupational settings, especially where environmental conditions are favorable to fungal presence.

Effects of Subcutaneous Ochratoxin-A Exposure on Immune System of Broiler Chicks

Ochratoxin A (OTA), an immunosuppressive mycotoxin, can increase the risk of many infectious diseases and contribute to economic losses to the poultry industry. The immunosuppressive effect has mainly been investigated through oral exposure; however, birds may also be contaminated through skin absorption. The present study investigated the influence of OTA exposure on the defense system of broiler chicks through the subcutaneous route and including low doses. Groups of broiler chicks (Cobb), 05 days old, were exposed to subcutaneous inoculation of OTA at concentrations of 0.1; 0.5; 0.9; 1.3; and 1.7 mg OTA/kg body weight. The size of the lymphoid organs, circulating immune cells, and total IgY and IgA levels were evaluated 21 days post inoculation. Subcutaneous OTA exposure decreased the weight of the thymus, spleen, and bursa of Fabricius, and leukocytopenia (p < 0.05) was detected in chicks of the OTA treated groups. In a dose-dependent way, decreased levels of circulating lymphocytes and heterophils (p < 0.05), and increased levels of monocytes (p < 0.05) were detected. Decreased IgY and IgA serum concentrations were noted in the OTA treated groups (p < 0.05). In conclusion, subcutaneous OTA exposure induces immunosuppression even at low levels.

A Review on the Synthesis and Bioactivity Aspects of Beauvericin, a Fusarium Mycotoxin

Beauvericin (BEA) is an emerging Fusarium mycotoxin that contaminates food and feeds globally. BEA biosynthesis is rapidly catalyzed by BEA synthetase through a nonribosomal, thiol-templated mechanism. This mycotoxin has cytotoxicity and is capable of increasing oxidative stress to induce cell apoptosis. Recently, large evidence further shows that this mycotoxin has a variety of biological activities and is being considered a potential candidate for medicinal and pesticide research. It is noteworthy that BEA is a potential anticancer agent since it can increase the intracellular Ca²⁺ levels and induce the cancer cell death through oxidative stress and apoptosis. BEA has exhibited effective antibacterial activities against both pathogenic Gram-positive and Gram-negative bacteria. Importantly, BEA exhibits an effective capacity to inhibit the human immunodeficiency virus type-1 integrase. Moreover, BEA can simultaneously target drug resistance and morphogenesis which provides a promising strategy to combat life-threatening fungal infections. Thus, in this review, the synthesis and the biological activities of BEA, as well as, the underlying mechanisms, are fully analyzed. The risk assessment of BEA in food and feed are also discussed. We hope this review will help to further understand the biological activities of BEA and cast some new light on drug discovery.

Transport of enniatin B and enniatin B1 across the blood-brain barrier and hints for neurotoxic effects in cerebral cells

Enniatins are common contaminants of food and feed and belong to the group of the "emerging" mycotoxins, which are produced by various Fusarium species. Although a wide range of toxic effects, like antibacterial, antifungal, insecticidal and cytotoxic properties, have been described in vitro, so far, no cases of mycotoxicosis connected to enniatins in vivo are reported. Among this group of mycotoxins, enniatin B and enniatin B1 are the most prevalent compounds and therefore are present in the human diet. Enniatins can reach systemic circulation, thus, the investigation of possible neurotoxic effects is of importance. Different cerebral cells were used to address effects on cell death having an impact on the blood-brain barrier. The influence of enniatin B and enniatin B1 on cellular viability was examined via Cell Counting kit-8 assay (CCK-8) in three different cell types of the blood-brain barrier: porcine brain capillary endothelial cells (PBCEC), human brain microvascular endothelial cells (HBMEC) and human astrocytoma cells (CCF-STTG1). CCF-STTG1 cells were more sensitive to enniatin B (IC50 = 8.9 μM) and enniatin B1 (IC50 = 4.4 μM) than both endothelial cell types. In CCF-STTG1 cells, caspase-3 activation and lactate dehydrogenase (LDH) release were evaluated. Both compounds did not induce any LDH release and only enniatin B increased caspase-3 activity as a marker for apoptosis. The transport kinetics of enniatin B and enniatin B1 across the blood-brain barrier in vitro were evaluated using PBCEC, cultivated on Transwell® filter inserts. Analysis of the apical and the basolateral compartment by high performance liquid chromatography-mass spectrometry revealed high influx rates for enniatin B and enniatin B1. Thus, both compounds can reach the brain parenchyma where neurotoxic effects cannot be ruled out.

Mouse tissue distribution and persistence of the food-born fusariotoxins Enniatin B and Beauvericin

The fusariotoxins Enniatin B (Enn B) and Beauvericin (Bea) have recently aroused interest as food contaminants and as potential anticancer drugs. However, limited data are available about their toxic profile. Aim of this study was to investigate their pharmacological behavior in vivo and their persistence in mice. Therefore, liquid chromatography tandem mass spectrometry (LC-MS/MS) was used to analyze the distribution of Enn B and Bea in selected tissue samples and biological fluids originating from mice treated intraperitoneally with these cyclohexadepsipeptides. Overall, no toxicological signs during life time or pathological changes were observed. Moreover, both fusariotoxins were found in all tissues and serum but not in urine. Highest amounts were measured in liver and fat demonstrating the moleculeś tendency to bioaccumulate in lipophilic tissues. While for Bea no metabolites could be detected, for Enn B three phase I metabolites (dioxygenated-Enn B, mono- and di-demethylated-Enn B) were found in liver and colon, with dioxygenated-Enn B being most prominent. Consequently, contribution of hepatic as well as intestinal metabolism seems to be involved in the overall metabolism of Enn B. Thus, despite their structural similarity, the metabolism of Enn B and Bea shows distinct discrepancies which might affect long-term effects and tolerability in humans.

The mycotoxin definition reconsidered towards fungal cyclic depsipeptides

Currently, next to the major classes, cyclic depsipeptides beauvericin and enniatins are also positioned as mycotoxins. However, as there are hundreds more fungal cyclic depsipeptides already identified, should these not be considered as mycotoxins as well? The current status of the mycotoxin definition revealed a lack of consistency, leading to confusion about what compounds should be called mycotoxins. Because this is of pivotal importance in risk assessment prioritization, a clear and quantitatively expressed mycotoxin definition is proposed, based on data of widely accepted mycotoxins. Finally, this definition is applied to a set of fungal cyclic depsipeptides, revealing that some of these should indeed be considered as mycotoxins.