Mechanisms of Mycotoxin-induced Dermal Toxicity and Tumorigenesis Through Oxidative Stress-related Pathways

Advances in Antitumor Effects Using Liposomal Citrinin in Induced Breast Cancer Model

The study aimed to evaluate the antitumor and toxicogenetic effects of liposomal nanoformulations containing citrinin in animal breast carcinoma induced by 7,12-dimethylbenzanthracene (DMBA). Mus musculus virgin females were divided into six groups treated with (1) olive oil (10 mL/kg); (2) 7,12-DMBA (6 mg/kg); (3) citrinin, CIT (2 mg/kg), (4) cyclophosphamide, CPA (25 mg/kg), (5) liposomal citrinin, LP-CIT (2 μg/kg), and (6) LP-CIT (6 µg/kg). Metabolic, behavioral, hematological, biochemical, histopathological, and toxicogenetic tests were performed. DMBA and cyclophosphamide induced behavioral changes, not observed for free and liposomal citrinin. No hematological or biochemical changes were observed for LP-CIT. However, free citrinin reduced monocytes and caused hepatotoxicity. During treatment, significant differences were observed regarding the weight of the right and left breasts treated with DMBA compared to negative controls. Treatment with CPA, CIT, and LP-CIT reduced the weight of both breasts, with better results for liposomal citrinin. Furthermore, CPA, CIT, and LP-CIT presented genotoxic effects for tumor, blood, bone marrow, and liver cells, although less DNA damage was observed for LP-CIT compared to CIT and CPA. Healthy cell damage induced by LP-CIT was repaired during treatment, unlike CPA, which caused clastogenic effects. Thus, LP-CIT showed advantages for its use as a model of nanosystems for antitumor studies.

An integrated approach for evaluating the interactive effects between azoxystrobin and ochratoxin A: Pathway-based in vivo analyses

Azoxystrobin (AZO) is a broad-spectrum strobilurin fungicide widely used in agriculture. However, its use increases the possibility of co-occurrence with mycotoxins such as ochratoxin A (OTA), which poses a significant risk to human health. Therefore, it is imperative to prioritize the evaluation of the combined toxicity of these two compounds. To assess the combined effects of AZO and OTA, the response genes and phenotypes for AZO or OTA exposure were obtained by utilizing Comparative Toxicogenomics Database, and Database for Annotation, Visualization and Integrated Discovery was used for GO and KEGG pathway enrichment analysis. In addition, we provided in-vivo evidence that AZO and OTA, in isolation and combination, could disrupt a variety of biological processes, such as oxidative stress, inflammatory response, apoptosis and thyroid hormone regulation under environmentally relevant concentrations. Notably, our findings suggest that the combined exposure group exhibited greater toxicity, as evidenced by the expression of various markers associated with the aforementioned biological processes, compared to the individual exposure group, which presents potential targets for the underlying mechanisms of induced toxicity. This study provides a novel methodological approach for exploring the mechanism of combined toxicity of a fungicide and a mycotoxin, which can shed light for conducting risk assessment of foodborne toxins.

Preventive role of cinnamaldehyde against tenuazonic acid- and Freund's adjuvant-induced histopathological and biochemical alterations in the mouse model

Introduction

This study was designed to assess the protective role of cinnamaldehyde (Cin) against the synergistic effect of tenuazonic acid (TeA) and Freund's adjuvant on different organs of Swiss albino mice.

Methods

TeA was administered singly and in combination with Freund's adjuvant intra-peritoneally. The mice were divided into control (vehicle treated), mycotoxicosis-induced (MI) groups, and treatment groups. The route of administration of TeA was intra-peritoneal. The treatment group (FAICT) received Cin orally as a protective agent against TeA-induced mycotoxicosis. The effects on performance, differential leukocyte counts (DLC), and pathological measurements in eight organs (liver, lungs, kidney, spleen, stomach, heart, brain, and testis) were taken into consideration.

Results

The body weight and feed consumption decreased significantly in the MI groups, which were reversed in the FAICT group. The necropsy observations revealed an increase in the relative organ-to-body weight percentage in the MI groups, which was restored to normal in the FAICT group. Freund's adjuvant enhanced the effects of TeA on DLC. The antioxidant enzymes SOD and CAT decreased, while MDA increased in the MI groups. Caspase-3 activity was reduced in all organs and remained stable in the treatment group. TeA elevated the ALT concentration in the liver and kidneys and the AST in the liver, kidney, heart, and brain tissues. The oxidative stress induced by TeA in the MI groups was ameliorated in the treatment group. Histopathological observations consisted of NASH, pulmonary oedema and fibrosis, renal crystals and inflammation, splenic hyperplasia, gastric ulceration and cyst, cerebral axonopathy, testicular hyperplasia, and vacuolation in the MI groups. However, no such pathology was recorded in the treatment group.

Discussions

Thus, it can be concluded that the toxicity of TeA was found to be enhanced when combined with Freund's adjuvant. However, Cin exhibited promising protective effects against TeA + Freund's adjuvant toxicity and reverted the pathological alterations caused by them. Additionally, this study emphasizes Freund's adjuvant's ability to increase mycotoxicity rather than just acting as an immunopotentiator.

Detoxication of Citrinin with Kojic Acid by the Formation of the Citrinin-Kojic Acid Adduct, and the Enhancement of Kojic Acid Production by Citrinin via Oxidative Stress in Aspergillus parasiticus

Our previous work showed that citrinin (CTN) produced bay Penicillium citrinum inhibited the production of aflatoxin by Aspergillus parasiticus. We also reported that CTN was non-enzymatically converted to a novel CTN-KA adduct with kojic acid (KA) in aqueous condition. We herein observed that unlike CTN, the CTN-KA adduct does not show antimicrobial activity against Escherichia coli or Bacillus subtilis or any cytotoxic effect on HeLa cells, suggesting that CTN was detoxified by KA by the formation of the CTN-KA adduct. To examine the function of KA production by fungi, we isolated A. parasiticus mutants with impaired KA production. When the mutants were incubated in either liquid or agar medium supplemented with CTN, they were more susceptible to CTN than the wild KA-producing strain. The same results were obtained when we used the A. oryzae KA-producing strain RIB40 and KA-non-producing strains. When KA was added to the CTN-containing agar medium, the inhibition of growth by CTN was remarkably mitigated, suggesting that the production of KA protected the fungal growth from CTN's toxicity. We also observed that CTN enhanced the production of KA by A. parasiticus as well as A. oryzae strains. Reverse transcription-PCR showed that CTN enhanced the expression of KA biosynthetic genes (kojA, kojR, and kojT) of A. parasiticus. However, the enhancement of KA production with CTN was repressed by the addition of α-tocopherol or butylated hydroxy anisole, suggesting that KA production is enhanced by oxidative stress via the formation of reactive oxygen species caused by CTN. In contrast, α-tocopherol did not affect inhibition of AF production as well as fungal growth by CTN, suggesting that the regulation of these inhibitions with CTN might be different from that of KA production. We propose a regulation scheme of CTN for each of KA production, AF production, and fungal growth in A. parasiticus.

Evaluation of the Role of Probiotics As a New Strategy to Eliminate Microbial Toxins: a Review

Probiotics are living microorganisms that have favorable effects on human and animal health. The most usual types of microorganisms recruited as probiotics are lactic acid bacteria (LAB) and bifidobacteria. To date, numerous utilizations of probiotics have been reported. In this paper, it is suggested that probiotic bacteria can be recruited to remove and degrade different types of toxins such as mycotoxins and algal toxins that damage host tissues and the immune system causing local and systemic infections. These microorganisms can remove toxins by disrupting, changing the permeability of the plasma membrane, producing metabolites, inhibiting the protein translation, hindering the binding to GTP binding proteins to GM1 receptors, or by preventing the interaction between toxins and adhesions. Here, we intend to review the mechanisms that probiotic bacteria use to eliminate and degrade microbial toxins.

T-2 Toxin Induces Ferroptosis by Increasing Lipid Reactive Oxygen Species (ROS) and Downregulating Solute Carrier Family 7 Member 11 (SLC7A11)

T-2 toxin is a trichothecene mycotoxin commonly found in animal feed and agricultural products. Evidence indicates that T-2 toxin induces apoptosis and autophagy. This study investigated the role of ferroptosis in T-2 toxin cytotoxicity. RAS-selective lethal compound 3 (RSL3) and Erastin were applied to initiate ferroptosis. RSL3- and Erastin-initiated cell death were enhanced by T-2 toxin. Treatment with the ferroptosis inhibitor ferrostatin-1 markedly restored the sensitizing effect of T-2 toxin to RSL3- or Erastin-initiated apoptosis, suggesting that ferroptosis plays a vital role in T-2 toxin-induced cytotoxicity. Mechanistically, T-2 toxin promoted ferroptosis by inducing lipid reactive oxygen species (ROS), as N-acetyl-l-cysteine significantly blocked T-2 toxin-induced ferroptosis. Moreover, T-2 toxin decreased the expression of solute carrier family 7 member 11 (SLC7A11) and failed to further enhance ferroptosis in SLC7A11-deficient cells. SLC7A11 overexpression significantly rescued the enhanced ferroptosis caused by T-2 toxin. T-2 toxin induces ferroptosis by downregulating SLC7A11 expression. Ferroptosis mediates T-2 toxin-induced cytotoxicity by increasing ROS and downregulating SLC7A11 expression.

Vegetable biocholine as a hepatoprotectant in laying hens fed with diet contaminated with aflatoxin B1

The aim of the study was to determine whether the addition of vegetable biocholine (VB) in laying hens feed minimises the effects of daily intake of aflatoxin B1 (AFB1). We allocated Hy-line Brown line laying hens into four groups with four replications/group and four birds/repetition. The treatments were as follows: Afla0Bio0: basal feed without aflatoxin and VB (natural contamination: 0.026 mg AFB1/kg), Afla0Bio800, basal feed supplementation of 800 mg VB/kg (natural contamination: 0.024 mg AFB1/kg); Afla2.5Bio0, basal feed contaminated experimentally with aflatoxin (2.51 mg/kg); Afla2.5Bio800, basal feed contaminated with aflatoxin (2.50 mg/kg) and supplemented with 800 mg VB/kg. The experiment took place over a period of 42 days, divided into two cycles of 21 days each. Significance was indicated by P≤0.05. The inclusion of aflatoxin reduced egg production after 42 days of consumption of contaminated feed. VB supplementation in the tested dose was insufficient to minimise the negative effects of the toxin on the laying rate. There was a lower percentage of yolk in Afla2Bio0 than in Afla0Bio0, and a higher percentage of albumen and specific gravity in Afla2.5Bio0 than in Afla0Bio0. Ingestion of aflatoxin in the feed increased lipoperoxidation (LPO) and decreased antioxidant capacity in the egg yolk; however, when VB was added, LPO was similar to the control. Lower total bacterial count (TBC) in the eggshell was observed when the birds consumed VB, as well as higher TBC in the eggshell of the birds was challenged with aflatoxin. In the blood of birds that consumed aflatoxin (Afla2.5Bio0) there was an increase in the activity of alkaline phosphatase and a reduction in the activities of glutathione S-transferase and glutathione peroxidase (GPx). In the birds that consumed VB without aflatoxin challenge, we observed that there was a stimulation of GPx activity. We conclude that the consumption of VB had positive effects on the health of the laying hens and improved the quality of the eggs.

N-Acetylcysteine Inhibits Patulin-Induced Apoptosis by Affecting ROS-Mediated Oxidative Damage Pathway

Patulin (PAT) belongs to the family of food-borne mycotoxins. Our previous studies revealed that PAT caused cytotoxicity in human embryonic kidney cells (HEK293). In the present research, we systematically explored the detailed mechanism of ROS production and ROS clearance in PAT-induced HEK293 cell apoptosis. Results showed that PAT treatment (2.5, 5, 7.5, 10 μM) for 10 h could regulate the expression of genes and proteins involved in the mitochondrial respiratory chain complex, resulting in dysfunction of mitochondrial oxidative phosphorylation and induction of ROS overproduction. We further investigated the role of N-acetylcysteine (NAC), an ROS scavenger, in promoting the survival of PAT-treated HEK293 cells. NAC improves PAT-induced apoptosis of HEK293 cells by clearing excess ROS, modulating the expression of mitochondrial respiratory chain complex genes and proteins, and maintaining normal mitochondrial function. In addition, NAC protects the activity of antioxidant enzymes, maintains normal GSH content, and relieves oxidative damage. Additionally, 4 mM NAC alleviated 7.5 μM PAT-mediated apoptosis through the caspase pathway in HEK293 cells. In summary, our study demonstrated that ROS is significant in PAT-mediated cytotoxicity, which provides valuable insight into the management of PAT-associated health issues.

Aflatoxin Biosynthesis, Genetic Regulation, Toxicity, and Control Strategies: A Review

Aflatoxins (AFs) are highly toxic and cancer-causing compounds, predominantly synthesized by the Aspergillus species. AFs biosynthesis is a lengthy process that requires as minimum as 30 genes grouped inside 75 kilobytes (kB) of gene clusters, which are regulated by specific transcription factors, including aflR, aflS, and some general transcription factors. This paper summarizes the status of research on characterizing structural and regulatory genes associated with AF production and their roles in aflatoxigenic fungi, particularly Aspergillus flavus and A. parasiticus, and enhances the current understanding of AFs that adversely affect humans and animals with a great emphasis on toxicity and preventive methods.

Calvatia Lilacina Extracts Exert Anti-Breast-Cancer Bioactivity through the Apoptosis Induction Dependent on Mitochondrial Reactive Oxygen Species and Caspase Activation

Puffballs are a class of fungi widely distributed worldwide and associated with various bioactivities. This research mainly showed the antitumor bioactivity of extracts from Calvatia lilacina (CL), which is a common variety of puffballs. NMR and high-performance liquid chromatography methods are used to characterize the extracts. Results showed that CL extracts obtained with petroleum ether, ethyl acetate, ethanol, and water elicited obvious inhibitory effects on the proliferation of A549, Caco-2, and MDA-MB-231. Among these extracts, petroleum ether extract demonstrated the highest performance. This extract was then separated into seven sub-fractions (SFs). Three of these SFs (3#, 6#, and 7#) induces a decrease in the viability of MDA-MB-231 cells in which 7# SF exhibited the highest cytotoxicity, where the major component was found to be ergosta-7,22-dien-3-one. Further tests revealed that 7# SF from petroleum ether extract could trigger severe cell death in human breast cancer cells (MDA-MB-231) by activating the apoptotic pathway dependent on mitochondrial reactive oxygen species and caspase activation. All these results in combination indicate that the mechanism of extract-potentiated apoptosis associates closely with ROS-dependent mitochondrial dysfunction events which further induces mitochondria-mediated intrinsic cytochrome C-caspase-related pathway of apoptosis.Supplemental data for this article is available online at https://doi.org/10.1080/01635581.2021.1936576.

Exploring the dermotoxicity of the mycotoxin deoxynivalenol: combined morphologic and proteomic profiling of human epidermal cells reveals alteration of lipid biosynthesis machinery and membrane structural integrity relevant for skin barrier function

Deoxynivalenol (vomitoxin, DON) is a secondary metabolite produced by Fusarium spp. fungi and it is one of the most prevalent mycotoxins worldwide. Crop infestation results not only in food and feed contamination, but also in direct dermal exposure, especially during harvest and food processing. To investigate the potential dermotoxicity of DON, epidermoid squamous cell carcinoma cells A431 were compared to primary human neonatal keratinocytes (HEKn) cells via proteome/phosphoproteome profiling. In A431 cells, 10 µM DON significantly down-regulated ribosomal proteins, as well as mitochondrial respiratory chain elements (OXPHOS regulation) and transport proteins (TOMM22; TOMM40; TOMM70A). Mitochondrial impairment was reflected in altered metabolic competence, apparently combined with interference of the lipid biosynthesis machinery. Functional effects on the cell membrane were confirmed by live cell imaging and membrane fluidity assays (0.1–10 µM DON). Moreover, a common denominator for both A431 and HEKn cells was a significant downregulation of the squalene synthase (FDFT1). In sum, proteome alterations could be traced back to the transcription factor Klf4, a crucial regulator of skin barrier function. Overall, these results describe decisive molecular events sustaining the capability of DON to impair skin barrier function. Proteome data generated in the study are fully accessible via ProteomeXchange with the accession numbers PXD011474 and PXD013613.

Involvement of NADPH oxidase in patulin-induced oxidative damage and cytotoxicity in HEK293 cells

Patulin (PAT) is a kind of mycotoxins that commonly found in decayed fruits and their products. Our previous studies have shown that PAT induced cell apoptosis and the overproduction of reactive oxygen species (ROS) in human embryonic kidney (HEK293) cells. The present study aimed to further investigate the functional role of NADPH oxidase, one of the main cellular sources of ROS, in PAT-induced apoptosis and oxidative damage in HEK293 cells. We demonstrated that the protein and mRNA expression levels of NADPH oxidase catalytic subunit NOX2 and regulatory subunit p47phox were up-regulated under PAT stress. Inhibiting of NADPH oxidase with the specific antagonist diphenyleneiodonium (DPI) suppressed cytotoxicity and apoptosis induced by PAT as evidenced by the increase of cell viability, the decrease of LDH release and the inhibition of caspase activities. Furthermore, DPI re-established mitochondrial membrane potential (MMP) and enhanced cellular ATP content. Importantly, DPI supplementation elevated endogenous GSH contents as well as the ratio of GSH/GSSG. Meanwhile, the antioxidant-enzyme activities of GPx, GR, CAT and SOD were significantly promoted. Collectively, our results suggested that NADPH oxidase played a critical role in PAT-induced nephrotoxicity, and inhibition of NADPH oxidase by DPI attenuated cell injury and apoptosis via regulation of oxidative damage.

Post-Flood Impacts on Occurrence and Distribution of Mycotoxin-Producing Aspergilli from the Sections Circumdati, Flavi, and Nigri in Indoor Environment

Mycotoxin-producing Aspergilli (Circumdati, Flavi, and Nigri), usually associated with contaminated food, may also cause respiratory disorders and are insufficiently studied in water-damaged indoor environments. Airborne (N = 71) and dust borne (N = 76) Aspergilli collected at post-flood and control locations in Croatia resulted in eleven different species based on their calmodulin marker: A. ochraceus, A. ostianus, A. pallidofulvus, A. sclerotiorum, and A. westerdijkiae (Circumdati); A. flavus (Flavi); and A. tubingensis, A. welwitschiae, A. niger, A. piperis, and A. uvarum (Nigri). Most of the airborne (73%) and dust borne (54%) isolates were found at post-flood locations, and the highest concentrations measured in indoor air (5720 colony-forming units (CFU)/m³) and dust (2.5 × 10⁵ CFU/g) were up to twenty times higher than in the control locations. A. flavus dominated among airborne isolates (25%) at the unrepaired locations, while 56% of the dust borne Aspergilli were identified as A. tubingensis and A. welwitschiae. The ability of identified isolates to produce mycotoxins aflatoxin B₁ (AFB₁), fumonisin B₂ (FB₂), and ochratoxin A were assessed by LC-MS analysis. All ochratoxin A (OTA)-producing Circumdati belonged to A. westerdijkiae (13.7 ± 15.81 µg/mL); in the section, FlaviA. flavus produced AFB₁ (2.51 ± 5.31 µg/mL), while A. welwitschiae and A. niger (section Nigri) produced FB₂ (6.76 ± 13.51 µg/mL and 11.24 ± 18.30 µg/mL, respectively). Water damage dominantly supported the occurrence of aflatoxigenic A. flavus in indoor environments. Yet unresolved, the causal relationship of exposure to indoor Aspergilli and adverse health effects may support the significance of this research.

An update on T-2 toxin and its modified forms: metabolism, immunotoxicity mechanism, and human exposure assessment

T-2 toxin is the most toxic trichothecene mycotoxin, and it exerts potent toxic effects, including immunotoxicity, neurotoxicity, and reproductive toxicity. Recently, several novel metabolites, including 3',4'-dihydroxy-T-2 toxin and 4',4'-dihydroxy-T-2 toxin, have been uncovered. The enzymes CYP3A4 and carboxylesterase contribute to T-2 toxin metabolism, with 3'-hydroxy-T-2 toxin and HT-2 toxin as the corresponding primary products. Modified forms of T-2 toxin, including T-2-3-glucoside, exert their immunotoxic effects by signaling through JAK/STAT but not MAPK. T-2-3-glucoside results from hydrolyzation of the corresponding parent mycotoxin and other metabolites by the intestinal microbiota, which leads to enhanced toxicity. Increasing evidence has shown that autophagy, hypoxia-inducible factors, and exosomes are involved in T-2 toxin-induced immunotoxicity. Autophagy promotes the immunosuppression induced by T-2 toxin, and a complex crosstalk between apoptosis and autophagy exists. Very recently, "immune evasion" activity was reported to be associated with this toxin; this activity is initiated inside cells and allows pathogens to escape the host immune response. Moreover, T-2 toxin has the potential to trigger hypoxia in cells, which is related to activation of hypoxia-inducible factor and the release of exosomes, leading to immunotoxicity. Based on the data from a series of human exposure studies, free T-2 toxin, HT-2 toxin, and HT-2-4-glucuronide should be considered human T-2 toxin biomarkers in the urine. The present review focuses on novel findings related to the metabolism, immunotoxicity, and human exposure assessment of T-2 toxin and its modified forms. In particular, the immunotoxicity mechanisms of T-2 toxin and the toxicity mechanism of its modified form, as well as human T-2 toxin biomarkers, are discussed. This work will contribute to an improved understanding of the immunotoxicity mechanism of T-2 toxin and its modified forms.

N-acetyl-cysteine in combination with celecoxib inhibits Deoxynivalenol induced skin tumor initiation via induction of autophagic pathways in swiss mice

Deoxynivalenol is a trichothecene mycotoxin which naturally contaminates small grain, cereals intended for human and animal consumption. Investigations for dermal toxicity of DON has been needed and highlighted by WHO. Previous studies on dermal toxicity suggest that DON has DNA damaging potential leading to skin tumor initiation in mice skin. However, considering its toxicological manifestations arising after dermal exposure, strategies for its prevention/protection are barely available in literatute. Collectively, our study demonstrated that N-acetylcysteine (NAC), precursor of glutathione, significantly alters the genotoxic potential of DON. Further NAC in combination with Celecoxib (CXB) inhibits tumor growth by altering antioxidant status and increasing autophagy in DON initiated Swiss mice. Despite the broad spectrum use of CXB, its use is limited by the concerns about its adverse effects on the cardiovascular system. Serum parameters and histology analysis revealed that CXB (2 mg) when applied topically for 24 weeks did not impart any cardiovascular toxicity which could be because skin permeation potential of CXB was quite low when analyzed through HPLC analysis. Although the anticancer effects of CXB and NAC have been studied, however, the combination of NAC and CXB has yet not been explored for any cancer treatment. Therefore our observations provide additional insights into the therapeutic effects of combinatorial treatment of CXB and NAC against skin tumor prevention. This approach might form a novel alternative strategy for skin cancer treatment as well as skin associated toxicities caused by mycotoxins such as DON. This combinatorial approach can overcome the limitations associated with the use of CXB for long term as topical application of the same seems to be safe in comparison to the oral mode of administration.

Optimization and validation of a LC-HRMS method for aflatoxins determination in urine samples

Mycotoxins' exposure by inhalation and/or dermal contact can occur in different branches of industry especially where heavily dusty settings are present and the handling of dusty commodities is performed. This study aims to explore the possible contribution of the occupational exposure to aflatoxins by analysing urine samples for the presence of aflatoxins B₁ and M₁ and aflatoxin B₁-N⁷-guanine adduct. The study was conducted in 2017 on two groups of volunteers, the workers group, composed by personnel employed in an Italian feed plant (n = 32), and a control group (n = 29), composed by the administrative employees of the same feed plant; a total of 120 urine samples were collected and analysed. A screening method and a quantitative method with high-resolution mass spectrometry determination were developed and fully validated. Limits of detections were 0.8 and 1.5 pg/mL_urine for aflatoxin B₁ and M₁, respectively. No quantitative determination was possible for the adduct aflatoxin B₁-N⁷-guanine. Aflatoxin B₁ and its adduct were not detected in the analysed samples, and aflatoxin M₁, instead, was found in 14 samples (12%) within the range 1.9-10.5 pg/mL_urine. Only one sample showed a value above the limit of quantification (10.5 pg/mL_urine). The absence of a statistical difference between the mean values for workers and the control group which were compared suggests that in this specific setting, no professional exposure occurs. Furthermore, considering the very low level of aflatoxin M₁ in the collected urine samples, the contribution from the diet to the overall exposure is to be considered negligible.

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.

Inadequacy of nutrients and contaminants found in porridge-type complementary foods in Rwanda

Child malnutrition remains persistently high in Rwanda. Complementary foods play a key role in young child nutrition. This study explores the quality and safety of complementary food products available in the Rwandan market. Ten of the most consumed porridge-type complementary food products in Rwanda have been analysed. Mean values of macronutrient and micronutrient contents were compared against three international standards and evaluated against label claims. Mean mycotoxin, microbiological, and pesticide contamination were compared with maximum tolerable limits. Mean energy density (385 kcal/100 g) and total fat content (7.9 g/100 g) were lower than all three international benchmarks. The mean fibre content of 8.5 g/100 g was above the maximum recommended amount of Codex Alimentarius and more than double the amount claimed on labels. Mean levels of vitamin A (retinyl palmitate, 0.54 mg/100 g) and vitamin E (α-tocopherol, 3.7 mg/100 g) fell significantly short of all three standards, whereas calcium and zinc requirements were only partially met. Average iron content was 12.1 mg/100 g. The analysis revealed a mean aflatoxin contamination of 61 μg/kg, and high mold and yeast infestation. Escherichia coli and pesticide residues were found, whereas no heavy metals could be quantitated. Overall, complementary food products in Rwanda show inadequate nutrient contents and high aflatoxin and microbial contamination levels. Improved regulation and monitoring of both local and imported products are needed to improve the quality and safety of complementary foods in Rwanda.

Immunoliposome-based fluorometric patulin assay by using immunomagnetic nanoparticles

A fluorometric immunoassay is described for the determination of patulin, a highly toxic fungal metabolite. A rabbit anti-patulin-bovine serum albumin (BSA) IgG conjugate was prepared and used to compose immunoliposomes and immunomagnetic nanoparticles. The immunomagnetic nanoparticles are then added to the sample to form the patulin-antibody composites which can be magnetically separated. The immunoliposomes are then added to form a sandwich. After magnetic separation of the composites and adding n-octyl-β-D-glucopyranoside, the fluorophore sulforhodamine B (SRB) is released. Its fluorescence intensity was then measured at excitation/emission wavelengths of 550/585 nm. The immunoliposome-based immunomagnetic nanoparticle assay can detect 8 μg L⁻¹ of patulin in apple juice without the need for extraction, separation, and purification. The detection limit falls within the European regulatory limit for infants and children’s products (10 μg L⁻¹). The method is rapid, enviroment-friendly, and reliable.

Graphical abstract

Alternariol induced proliferation in primary mouse keratinocytes and inflammation in mouse skin is regulated via PGE2/EP2/cAMP/p-CREB signaling pathway

Alternariol (AOH) is a mycotoxin that contaminates various food stuffs as well as animal feed and may cause toxicity after consumption. However, a dermal toxic potential of AOH has not been explored so far. In the present study, skin toxicity after topical exposure of AOH and the involved mechanism/s are revealed. Single topical application of different AOH doses (12.5, 25, 50 μg/animal) caused increased bi-fold thickness as well as hyperplasia and higher production of prostaglandin E2 (PGE₂) along with cAMP in the skin demonstrating its inflammatory potential. Western blot analysis showed that exposure of AOH lead to phosphorylation of CREB and increased the expression of COX-2, cyclin D1 as well as prostanoid EP2 receptor. Further studies on primary mouse keratinocytes (PMK) revealed that very low concentrations of AOH (50-500 nM) resulted in significant PMK proliferation. Additionally, using specific antagonist or agonist of prostanoid receptors, we delineated that EP2 receptor play a key role in AOH-induced PMKs proliferation. Collectively, our findings show that AOH can lead to dermal toxicity in mice by activating the EP2/cAMP/p-CREB signaling cascade.

Citrinin exposure affects oocyte maturation and embryo development by inducing oxidative stress-mediated apoptosis

Citrinin is one of the mycotoxins and has been shown to have various toxic effects in animals and humans. Although previous study showed the toxic effects of citrinin on the female reproductive system, especially on oocyte maturation, however, the causes or mechanism of citrinin on oocyte quality is unclear. In present study we deeply investigated this topic. We found thatcitrinin toxin exposure inhibited mouse oocyte maturation and early embryo development. Further investigation showed that the actin distribution in oocytes and embryos was disrupted, and the reduced expression of actin nucleator ARP2 expression in the oocyte cortex further confirmed this. We also found that meiotic spindle morphology was abnormal after citrinin treatment. These results indicated that citrinin toxin exposure could disrupt cytoskeleton dynamics to affect oocyte maturation and early embryo development. We also examined the ROS level and early apoptosis marker Annexin signals, and the results showed that both levels increased, indicating that citrinin induced oxidative stress and further resulted in oocyte early apoptosis. Taken together, our results indicated that citrinin toxin exposure could reduce mouse oocyte maturation and early embryo development capability by affecting cytoskeletal dynamics, which may be due to the oxidative stress induced early apoptosis.

Different Toxicity Mechanisms for Citrinin and Ochratoxin A Revealed by Transcriptomic Analysis in Yeast

Citrinin (CIT) and ochratoxin A (OTA) are important mycotoxins, which frequently co-contaminate foodstuff. In order to assess the toxicologic threat posed by the two mycotoxins separately or in combination, their biological effects were studied here using genomic transcription profiling and specific live cell gene expression reporters in yeast cells. Both CIT and OTA cause highly transient transcriptional activation of different stress genes, which is greatly enhanced by the disruption of the multidrug exporter Pdr5. Therefore, we performed genome-wide transcription profiling experiments with the pdr5 mutant in response to acute CIT, OTA, or combined CIT/OTA exposure. We found that CIT and OTA activate divergent and largely nonoverlapping gene sets in yeast. CIT mainly caused the rapid induction of antioxidant and drug extrusion-related gene functions, while OTA mainly deregulated developmental genes related with yeast sporulation and sexual reproduction, having only a minor effect on the antioxidant response. The simultaneous exposure to CIT and OTA gave rise to a genomic response, which combined the specific features of the separated mycotoxin treatments. The application of stress-specific mutants and reporter gene fusions further confirmed that both mycotoxins have divergent biological effects in cells. Our results indicate that CIT exposure causes a strong oxidative stress, which triggers a massive transcriptional antioxidant and drug extrusion response, while OTA mainly deregulates developmental genes and only marginally induces the antioxidant defense.

Cytotoxic Effects of Ochratoxin A in Neuro-2a Cells: Role of Oxidative Stress Evidenced by N-acetylcysteine

Ochratoxin-A (OTA), is toxic secondary metabolite and is found to be a source of vast range of toxic effects like hepatotoxicity, nephrotoxicity. However, the information available currently regarding neurotoxic effects exerted by OTA is scanty. Hence, the present study was aimed to evaluate the neurotoxic effects of OTA and the possible mechanisms of toxicity as well as the role of cytotoxic oxidative stress on neuronal (Neuro-2a) cell line was evaluated in vitro. Results of the MTT and LDH assay showed that, OTA induced dose-dependent cell death in Neuro-2a cells and EC50 value was determined as 500 nM. OTA induced high levels of reactive oxygen species (ROS) and elevated levels of malondialdehyde, also loss of mitochondrial membrane potential was observed in a dose depended manner. Effects of OTA on ROS induced chromosomal DNA damage was assessed by Comet assay and plasmid DNA damage assay in which increase in DNA damage was observed in Neuro-2a cells by increasing the OTA concentration. Further western blotting analysis of OTA treated Neuro-2a cells indicated elevated expression levels of c-Jun, JNK3 and cleaved caspase-3 leading to apoptotic cell death. Other hand realtime-Q-PCR analysis clearly indicates the suppressed expression of neuronal biomarker genes including AChE, BDNF, TH and NOS2. Further N-acetylcysteine (NAC) pretreatment to Neuro-2a cells followed by OTA treatment clearly evidenced that, the significant reversal of toxic effects exerted by OTA on Neuro-2a cells. In the present study, results illustrate that ROS a principle event in oxidative stress was elevated by OTA toxicity in Neuro-2a cells. However, further in vivo, animal studies are in need to conclude the present study reports and the use of NAC as a remedy for OTA induced neuronal stress.

Mycotoxin Patulin Suppresses Innate Immune Responses by Mitochondrial Dysfunction and p62/Sequestosome-1-dependent Mitophagy

Innate immune responses are important for pathogen elimination and adaptive immune response activation. However, excess inflammation may contribute to immunopathology and disease progression (e.g. inflammation-associated hepatocellular carcinoma). Immune modulation resulting from pattern recognition receptor-induced responses is a potential strategy for controlling immunopathology and related diseases. This study demonstrates that the mycotoxin patulin suppresses Toll-like receptor- and RIG-I/MAVS-dependent cytokine production through GSH depletion, mitochondrial dysfunction, the activation of p62-associated mitophagy, and p62-TRAF6 interaction. Blockade of autophagy restored the immunosuppressive activity of patulin, and pharmacological activation of p62-dependent mitophagy directly reduced RIG-I-like receptor-dependent inflammatory cytokine production. These results demonstrated that p62-dependent mitophagy has an immunosuppressive role to innate immune response and might serve as a potential immunomodulatory target for inflammation-associated diseases.

p53 activation contributes to patulin-induced nephrotoxicity via modulation of reactive oxygen species generation

Patulin is a major mycotoxin found in fungal contaminated fruits and their derivative products. Previous studies showed that patulin was able to induce increase of reactive oxygen species (ROS) generation and oxidative stress was suggested to play a pivotal role in patulin-induced multiple toxic signaling. The objective of the present study was to investigate the functional role of p53 in patulin-induced oxidative stress. Our study demonstrated that higher levels of ROS generation and DNA damage were induced in wild-type p53 cell lines than that found in either knockdown or knockout p53 cell lines in response to patulin exposure, suggesting p53 activation contributed to patulin-induced ROS generation. Mechanistically, we revealed that the pro-oxidant role of p53 in response to patulin was attributed to its ability to suppress catalase activity through up-regulation of PIG3. Moreover, these in vitro findings were further validated in the p53 wild-type/knockout mouse model. To the best of our knowledge, this is the first report addressing the functional role of p53 in patulin-induced oxidative stress. The findings of the present study provided novel insights into understanding mechanisms behind oxidative stress in response to patulin exposure.

Comparative Ochratoxin Toxicity: A Review of the Available Data

Ochratoxins are a group of mycotoxins produced by a variety of moulds. Ochratoxin A (OTA), the most prominent member of this toxin family, was first described by van der Merwe et al. in Nature in 1965. Dietary exposure to OTA represents a serious health issue and has been associated with several human and animal diseases including poultry ochratoxicosis, porcine nephropathy, human endemic nephropathies and urinary tract tumours in humans. More than 30 years ago, OTA was shown to be carcinogenic in rodents and since then extensive research has been performed in order to investigate its mode of action, however, this is still under debate. OTA is regarded as the most toxic family member, however, other ochratoxins or their metabolites and, in particular, ochratoxin mixtures or combinations with other mycotoxins may represent serious threats to human and animal health. This review summarises and evaluates current knowledge about the differential and comparative toxicity of the ochratoxin group.

Molecular characterization of patulin producing and non-producing Penicillium species in apples from Morocco

The isolation of patulin-producing Penicillia in apples collected in different markets in four localities in Morocco is reported. Fungi were identified by β-tubulin sequencing and further characterized using a specific PCR-based method targeting the isoepoxydon dehydrogenase (IDH) gene to discriminate between patulin-producing and non-producing strains. Production of patulin was also evaluated using standard cultural and biochemical methods. Results showed that 79.5% of contaminant fungi belonged to the genus Penicillium and that Penicillium expansum was the most isolated species (83.9%) followed by Penicillium chrysogenum (~9.7%) and Penicillium crustosum (~6.4%). Molecular analysis revealed that 64.5% of the Penicillium species produced the expected IDH-amplicon denoting patulin production in these strains. However, patulin production was not chemically confirmed in all P. expansum strains. The isolation of IDH(-)/patulin(+) strains poses the hypothesis that gentisylaldehyde is not a direct patulin precursor, supporting previous observations that highlighted the importance of the gentisyl alcohol in the production of this mycotoxin. Total agreement between IDH-gene detection and cultural/chemical methods employed was observed in 58% of P. expansum strains and for 100% of the other species isolated. Overall the data reported here showed a substantial genetic variability within P. expansum population from Morocco.