Patulin: Mechanism of genotoxicity

The Microbiome and Metabolites in Fermented Pu-erh Tea as Revealed by High-Throughput Sequencing and Quantitative Multiplex Metabolite Analysis

Pu-erh is a tea produced in Yunnan, China by microbial fermentation of fresh Camellia sinensis leaves by two processes, the traditional raw fermentation and the faster, ripened fermentation. We characterized fungal and bacterial communities in leaves and both Pu-erhs by high-throughput, rDNA-amplicon sequencing and we characterized the profile of bioactive extrolite mycotoxins in Pu-erh teas by quantitative liquid chromatography-tandem mass spectrometry. We identified 390 fungal and 629 bacterial OTUs from leaves and both Pu-erhs. Major findings are: 1) fungal diversity drops and bacterial diversity rises due to raw or ripened fermentation, 2) fungal and bacterial community composition changes significantly between fresh leaves and both raw and ripened Pu-erh, 3) aging causes significant changes in the microbial community of raw, but not ripened, Pu-erh, and, 4) ripened and well-aged raw Pu-erh have similar microbial communities that are distinct from those of young, raw Ph-erh tea. Twenty-five toxic metabolites, mainly of fungal origin, were detected, with patulin and asperglaucide dominating and at levels supporting the Chinese custom of discarding the first preparation of Pu-erh and using the wet tea to then brew a pot for consumption.

Crocin protects the liver and kidney from patulin-induced apoptosis in vivo

Patulin (PAT) is a mycotoxin mainly produced by Aspergillus, Penicillium, and Bissochlamys. Given the high risk associated with this mycotoxin, its potential effects have been investigated by many studies. It is known to be teratogenic, mutagenic, and genotoxic, and it has been shown to induce damages in several organs in experimental animals. Our aim was to investigate the preventive effect against PAT-induced apoptosis in vivo using natural carotenoid, Crocin (CRO). Mice were divided into six groups: a control group, a "PAT alone" group, a "CRO alone" group, and a "PAT plus CRO" groups (pre-treatment conditions). Our results showed that CRO restored the normal levels of biochemical parameters in the liver and kidney. The analysis of the protein expression in these organs revealed that PAT-induced toxicity promotes the induction of apoptosis via the increase in P53, Bax, and cytochrome C and the decrease in Bcl2 expressions. We also found that PAT triggered caspase 3 activation and DNA fragmentation. However, pre-treatment with CRO demonstrated a reduction in the induction of apoptosis via the regulation of all tested biomarkers demonstrating that CRO is effective in the protection against PAT hazards. This could be relevant, particularly with the emergent demand for natural products which may counteract the detrimental toxic effects and therefore prevents multiple human diseases.

The effects of the mycotoxin austdiol on cell cycle progression, cytotoxicity and genotoxicity in Chinese hamster ovary (CHO-K1) cells

Austdiol is a mycotoxin mainly produced by Aspergillus ustus and Mycoleptodiscus indicus. These fungi are found in rye, oats, barley, corn and feed grains; thus, as a potential contaminant of human food and animal feed, this mycotoxin is of great concern. As such, the elucidation of the cytotoxicity and mutagenicity of austdiol is important. In this study, austdiol was purified from a rice-oat solid medium culture of M. indicus using chromatographic separation techniques. Chinese hamster ovary (CHO-K1) cells were then used to study the effect of austdiol on mammalian cell cycle, clonogenicity and DNA damage. Austdiol induced cell cycle arrest in G2/M phase, with a decreased S phase population and increased sub-G1 population. Austdiol also increased the polyploid population. These events resulted in cell death detected 7 days after treatment by clonogenic assay. DNA damage represents the main mechanism of action of austdiol, which induces DNA breaks and increases the frequency of micronuclei and nucleoplasmic bridges in binucleated cells in a CHO-K1 cell line. Moreover, cells exposed to austdiol and doxorubicin (DXR) combined treatments presented a reduced number of colonies and increased frequencies of micronuclei and nucleoplasmic bridges compared with negative control and cells treated with austdiol or DXR alone.

Transcriptomic responses of the basidiomycete yeast Sporobolomyces sp. to the mycotoxin patulin

BACKGROUND

Patulin is a mycotoxin produced by Penicillium expansum, the causal agent of blue mold of stored pome fruits, and several other species of filamentous fungi. This mycotoxin has genotoxic, teratogenic and immunotoxic effects in mammals, and its presence in pome fruits and derived products represents a serious health hazard. Biocontrol agents in the Pucciniomycotina, such as the yeasts Sporobolomyces sp. strain IAM 13481 and Rhodosporidium kratochvilovae strain LS11, are able to resist patulin and degrade it into the less toxic compounds desoxypatulinic acid and ascladiol.

RESULTS

In this investigation we applied a transcriptomic approach based on RNAseq to annotate the genome of Sporobolomyces sp. IAM 13481 and then study the changes of gene expression in Sporobolomyces sp. exposed to patulin. Patulin treatment leads to ROS production and oxidative stress that result in the activation of stress response mechanisms controlled by transcription factors. Upregulated Sporobolomyces genes were those involved in oxidation-reduction and transport processes, suggesting the activation of defense mechanisms to resist patulin toxicity and expel the mycotoxin out of the cells. Other upregulated genes encoded proteins involved in metabolic processes such as those of the glutathione and thioredoxin systems, which are essential to restore the cellular redox homeostasis. Conversely, patulin treatment decreased the expression of genes involved in the processes of protein synthesis and modification, such as transcription, RNA processing, translation, protein phosphorylation and biosynthesis of amino acids. Also, genes encoding proteins involved in transport of ions, cell division and cell cycle were downregulated. This indicates a reduction of metabolic activity, probably due to the high energy requirement by the cells or metabolic arrest while recovering from the insult caused by patulin toxicity.

CONCLUSIONS

Complex mechanisms are activated in a biocontrol yeast in response to patulin. The genes identified in this study can pave the way to develop i) a biodetoxification process of patulin in juices and ii) a biosensor for the rapid and cost-effective detection of this mycotoxin.

Sex-related variations in bone microstructure of rabbits intramuscularly exposed to patulin

BACKGROUND

Patulin, a toxic mold metabolite, has been found as natural contaminant of processed fruits, most notably apples, apple juices and other apple-based products. A number of adverse health effects in humans and animals are associated with patulin intoxication. The current study was performed to analyse possible toxic effects of patulin on femoral bone microstructure in adult rabbits in detail. Fourteen clinically healthy four-month-old rabbits of both sexes (6 males and 8 females) were included in the study. Animals from the experimental groups (group E♂, n = 3; group E♀, n = 4) were injected intramuscularly with patulin at dose 10 μg/kg body weight two times a week for 28 days. The dose of patulin was estimated based on the maximum permitted level of patulin for apple products intended for infants and young children. Three males and four females without patulin administration served as controls (groups C♂ and C♀). Cortical bone thickness and qualitative and quantitative histological characteristics of compact bone tissue were investigated.

RESULTS

Intramuscular applications of patulin significantly increased the thickness of cortical bone in both sexes of rabbits. In patulin-exposed males, an absence of primary vascular longitudinal bone tissue near the endosteal border was observed, which could be associated with intensive bone remodeling. Femoral diaphyses of females displayed a lower number of secondary osteons in the middle part of the substantia compacta, and occurrence of the osteons near the periosteum. This could indicate alterations in bone turnover. Histomorphometrical evaluations showed significantly increased sizes of the primary osteons' vascular canals (P < 0.05) in males exposed to patulin possibly due to mycotoxin-induced increased levels of testosterone.

CONCLUSIONS

This study demonstrates significant impact of intramuscular application of patulin on bone microstructure in adult rabbits. Moreover, we have found that the effects of patulin on qualitative and quantitative histological characteristics of compact bone are sex-dependent.

Risk analysis of main mycotoxins occurring in food for children: An overview

Mycotoxins are secondary metabolites produced by fungi contaminating the food chain that are toxic to animals and humans. Children up to 12 years old are recognized as a potentially vulnerable subgroup with respect to consumption of these contaminants. Apart from having a higher exposure per kg body weight, they have a different physiology from that of adults. Therefore they may be more sensitive to neurotoxic, endocrine and immunological effects. For these reasons, a specific and up-to-date risk analysis for this category is of great interest. In this review, an accurate analysis of the main mycotoxins occurring in food intended for children (deoxynivalenol, aflatoxins, ochratoxins, patulin and fumonisins) is presented. In particular, known mechanisms of toxicity and levels of exposure and bioaccessibility in children are shown. In addition, recent discoveries about the strategies of mycotoxins managing are discussed.

The effect of patulin on femoral bone structure in male rabbits

A lot of kinds of crops are susceptible to fungal attack, leading to considerable financial losses and damage the health of humans and animals. Patulin, a toxic fungal metabolite, can be found mainly in apple and apple products, with much less frequent contamination in other food products. Because of its high incidence and harmful health effects, patulin belongs to a class of mycotoxins, which are strictly monitored. However, its effect on bone structure is still unknown. This study was designed to investigate the impact of patulin on femoral bone structure in adult male rabbits. Four month-old male rabbits were randomly divided into two groups of three animals each. Rabbits from the experimental group (group A, n=3) were intramuscularly administered with patulin at dose 10 μg.kg-1 body weight (b.w.) twice a week for 4 weeks. The second group without patulin administration served as a control (group B, n=3). At the end of the experiment, body weight, femoral weight and length, cortical bone thickness and histological structure of femoral bones from all rabbits were determined. The results did not show any significant differences in body weight, femoral weight and length between experimental and control groups of rabbits. On the other hand, intramuscular application of patulin induced a significant increase in cortical bone thickness (p <0.05) and considerable changes in qualitative histological characteristics of compact bone in adult male rabbits. In patulin-intoxicated males, the primary vascular longitudinal bone tissue was absent near endosteal border. On the other hand, this tissue occurred near periosteum and also in the middle part of the femoral bone in these rabbits. The values for the primary osteons' vascular canals were significantly lower (p <0.05) in males exposed to patulin as compared to the control group. Based on these findings we can conclude that intramuscular patulin administration demonstrably influences cortical bone thickness and histological structure of femoral bone in adult male rabbits.

The formation of biofilms by Pseudomonas aeruginosa: a review of the natural and synthetic compounds interfering with control mechanisms

P. aeruginosa is an opportunistic pathogenic bacterium responsible for both acute and chronic infections. Beyond its natural resistance to many drugs, its ability to form biofilm, a complex biological system, renders ineffective the clearance by immune defense systems and antibiotherapy. The objective of this report is to provide an overview (i) on P. aeruginosa biofilm lifestyle cycle, (ii) on the main key actors relevant in the regulation of biofilm formation by P. aeruginosa including QS systems, GacS/GacA and RetS/LadS two-component systems and C-di-GMP-dependent polysaccharides biosynthesis, and (iii) finally on reported natural and synthetic products that interfere with control mechanisms of biofilm formation by P. aeruginosa without affecting directly bacterial viability. Concluding remarks focus on perspectives to consider biofilm lifestyle as a target for eradication of resistant infections caused by P. aeruginosa.

The mycotoxin patulin reacts with DNA bases with and without previous conjugation to GSH: implication for related α,β-unsaturated carbonyl compounds?

The α,β-unsaturated carbonyl group is recognized as alert for mutagenicity, attributed to (1) its direct reaction with DNA, counteractable by glutathione (GSH), and (2) oxidative stress caused indirectly by GSH depletion. Accordingly, the α,β,γ,δ-unsaturated lactone patulin (PAT), a mycotoxin detected in fruits and products derived thereof, is known to induce gene, chromosome, and genome mutations in vitro, its mutagenicity correlating inversely with intracellular GSH levels. Thus, the reactivity of PAT against DNA bases and nucleosides in the absence and presence of GSH and glutathione S-transferases (GSTs) was investigated under cell-free conditions using HPLC mass spectrometry techniques for identification of reaction products. Adduct formation with all four nucleobases as well as with purine base nucleosides occurred even in the presence of GSH, revealing several adducts of PAT, mono- and disubstituted with nucleobases/nucleosides as well as novel GSH-PAT adducts. In addition, novel mixed GSH-PAT-nucleobase adducts were observed. These adducts exhibited a ketohexanoic acid-type structure of the PAT molecule, C6 substituted with GSH and linking C1 of PAT with nitrogens of nucleobases/nucleosides via an amide bond. Formation of GSH-PAT-adenine adducts was not prevented by GSTs, and excess of GSH needed to reduce their formation was higher than for PAT-adenine adducts. The formation of mixed GSH-DNA base adducts has not been described for PAT or any other α,β-unsaturated carbonyl before, although the reaction mechanism seems to be applicable to a variety of α,β-unsaturated carbonyls occurring in food and in the environment.

Investigation of the interaction between patulin and human serum albumin by a spectroscopic method, atomic force microscopy, and molecular modeling

The interaction of patulin with human serum albumin (HSA) was studied in vitro under normal physiological conditions. The study was performed using fluorescence, ultraviolet-visible spectroscopy (UV-Vis), circular dichroism (CD), atomic force microscopy (AFM), and molecular modeling techniques. The quenching mechanism was investigated using the association constants, the number of binding sites, and basic thermodynamic parameters. A dynamic quenching mechanism occurred between HSA and patulin, and the binding constants (K) were 2.60 × 10(4), 4.59 × 10(4), and 7.01 × 10(4) M(-1) at 288, 300, and 310 K, respectively. Based on fluorescence resonance energy transfer, the distance between the HSA and patulin was determined to be 2.847 nm. The ΔG (0), ΔH (0), and ΔS (0) values across various temperatures indicated that hydrophobic interaction was the predominant binding force. The UV-Vis and CD results confirmed that the secondary structure of HSA was altered in the presence of patulin. The AFM results revealed that the individual HSA molecule dimensions were larger after interaction with patulin. In addition, molecular modeling showed that the patulin-HSA complex was stabilized by hydrophobic and hydrogen bond forces. The study results suggested that a weak intermolecular interaction occurred between patulin and HSA. Overall, the results are potentially useful for elucidating the toxigenicity of patulin when it is combined with the biomolecular function effect, transmembrane transport, toxicological, testing and other experiments.

Cytokinesis-block micronucleus assay adapted for analyzing genomic instability of human mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) are multipotent cells used in cell therapy research. One of the problems involving hMSCs is the possibility of genetic instability during in vitro expansion required to obtain a suitable number of cells for clinical applications. The cytokinesis-block micronucleus (CBMN) assay measures genetic instability by analyzing the presence of micronucleus (MN), nucleoplasmic bridges (NPBs), and nuclear buds (NBUDs) in binucleated cells. The present study describes modifications in the CBMN assay methodology to analyze genetic instability in hMSCs isolated from the umbilical vein and in vitro expanded. The best protocol to achieve binucleated hMSCs with preserved cytoplasm was as follows: cytochalasin B concentration (4.0 μg/mL), use of hypotonic treatment (3 min), and the fixative solution (9 methanol:1 acetic acid). These adaptations were reproduced in three hMSC primary cell cultures and also in XP4PA and A549 cell lines. The frequency of hMSCs treated with mitomycin-C presenting MN was lower than that with other nuclear alterations, indicating that the hMSCs contain mechanisms to avoid a high level of chromosomal breaks. However, a high frequency of cells with NPBs was detected and spontaneous anaphase bridges under normal hMSC in vitro culture were observed. Considering that anaphase bridges are characteristic alterations in tumor cells, the CBMN assay is indicated as an important tool associated with other genetic analyses in order to ensure the safe clinical use of hMSCs in cell therapy.

Patulin induces pro-survival functions via autophagy inhibition and p62 accumulation

Patulin (PAT) is one of the most common mycotoxins found in moldy fruits. Skin contact is one of the most likely exposure routes of PAT. Investigation of dermal toxicity of PAT is clearly needed and has been highlighted by WHO. In the present study, using human keratinocyte HaCaT cells as a model, we found that treatment with PAT caused an increased autophagosome accumulation. Measurements of autophagic flux demonstrated that the accumulation of autophagosomes by PAT was not directly due to enhanced autophagosome formation but due to inhibition of autophagosome degradation. Reductions in the activities of the lysosomal enzymes cathepsin B and cathepsin D by PAT might contribute to this inhibitory effect. Consistent with this, inhibition of autophagosome degradation by PAT resulted in accumulation of p62 that functioned as a pro-survival signal. The pro-survival function of p62 was found to be attributed to reactive oxygen species-mediated cytoprotective endoplasmic reticulum (ER) stress response. ER stress exerted cytoprotective effect via extracellular signal-regulated kinase1/2-dependent B-cell CLL/lymphoma 2-associated agonist of cell death inhibitory phosphorylation. Given the critical role of autophagy and its substrate p62 in carcinogenesis, our findings may have important implications in PAT-induced skin carcinogenesis.

Occurrence of patulin in organic and conventional apple-based food marketed in Catalonia and exposure assessment

In the last years, consumption of organic foods has become increasingly popular. Nevertheless, safety of organic foods is still unclear, and needs to be thoroughly evaluated. Patulin is a mycotoxin mainly present in rotten apples and apple-based products. The aim of this study is to analyse the content of patulin in apple juices and purees derived from organic and conventional production systems, in order to assess the risk to consumers, particularly in children. A total of 93 apple-based products marketed in Catalonia were analysed, 49 of which were derived from conventional and 44 from organic farming. The results showed higher incidence of positive samples and higher concentration of patulin in organic apple purees when comparing with conventional ones. In the case of juices, significant differences were found between conventional and organic samples, but applying a multivariate analysis the type of agriculture did not seem to have a relevant contribution to patulin occurrence, being cloudiness the main factor involved. The estimated daily intake of patulin for infants and young children (0-3 years old), children (4-18 years old) and adults (19-66 years old), were below the provisional maximum tolerable daily intake (PMTDI) of 0.4 μg/kg bw in all scenarios considered.

EGFR-mediated Akt and MAPKs signal pathways play a crucial role in patulin-induced cell proliferation in primary murine keratinocytes via modulation of Cyclin D1 and COX-2 expression

Patulin (PAT), a present day major contaminant of commercial apple and apple products is reported to be carcinogenic, embryotoxic, and immunotoxic. While oral and inhalation are considered to be the most prevalent routes of exposure to this toxin, exposure through skin is now being extensively investigated. Our previous study showed that short-term dermal exposure to PAT resulted in toxicological injury to the skin, while long-term exposure induced skin tumorigenesis. In this study, we explore the mechanism involve in proliferation of mouse keratinocytes by PAT. Our study revealed that PAT rapidly induces phosphorylation of EGFR, activation of the Ras/MAPKs, and Akt pathways. This in-turn leads to the activation of NF-κB/AP-1 transcription factors which then binds to the promoter region of the cell growth regulatory genes Cyclin D1 and COX-2 inducing their expression leading ultimately to PMKs proliferation. Inhibition of EGFR or the Ras/MAPKs, PI3/Akt pathways with different pharmacological inhibitors or knockdown of NF-κB, c-jun, c-fos, Cyclin D1, and COX-2 with siRNA inhibited PAT-induced PMKs proliferation.

Evaluation of genotoxicity, cytotoxicity and cytostasis in human lymphocytes exposed to patulin by using the cytokinesis-block micronucleus cytome (CBMN cyt) assay

Patulin (PAT) is a fungal secondary metabolite commonly present in apples and apple products. In the present study, PAT was evaluated for its genotoxic, cytotoxic and cytostatic effects to human peripheral blood lymphocytes by using the cytokinesis-block micronucleus cytome (CBMN Cyt) assay. Lymphocyte cultures were treated with PAT at the following concentrations, 0.1, 0.3, 0.5, 1.0, 2.5, 5.0, and 7.5 μM, as well as 0.5 μM mitomycin c (MMC) as a positive control and dimethyl sulfoxide (DMSO) as a vehicle control. PAT was found to induce nucleoplasmic bridges (NPBs) at 5.0 and 7.5 μM concentrations (P < 0.05), apoptotic cells at 0.1, 1.0, 5.0 μM (P < 0.05), 7.5 μM concentrations (P < 0.01) and necrotic cells at 0.3 and 2.5 μM (P < 0.05), 5.0 and 7.5 μM (P < 0.01) concentrations in human lymphocytes. The 2.5, 5.0, and 7.5 μM PAT concentrations also led to a clear decrease in the nuclear division index (NDI) (P < 0.05). PAT caused a significant dose-dependent increase in the number cells of NPBs, in the frequency of apoptotic and necrotic cells, and a significant dose-dependent decrease in the NDI values in lymphocytes. These results indicate that PAT at high concentrations is genotoxic, cytotoxic and cytostatic in cultured human lymphocytes.

The mycotoxin patulin increases colonic epithelial permeability in vitro

The gastrointestinal lumen is directly exposed to dietary contaminants, including patulin, a mycotoxin produced by moulds. Patulin is known to increase permeability across intestinal Caco-2 monolayers. This study aimed to determine the effect of patulin on permeability, ion transport and morphology in isolated rat colonic mucosae. Mucosal sheets were mounted in Ussing chambers and voltage clamped. Apical addition of patulin (100-500 μM) rapidly reduced transepithelial electrical resistance (TEER) and increased permeability to [(14)C] mannitol (2.9-fold). Patulin also inhibited carbachol-induced electrogenic chloride secretion and histological evidence of mucosal damage was observed. To examine potential mechanisms of action of patulin on colonic epithelial cells, high-content analysis of Caco-2 cells was performed and this novel, quantitative fluorescence-based approach confirmed its cytotoxic effects. With regard to time course, the cytotoxicity determined by high content analysis took longer than the almost immediate reduction of electrical resistance in isolated mucosal sheets. These data indicate patulin is not only cytotoxic to enterocytes but also has the capacity to directly alter permeability and ion transport in intact intestinal mucosae. These data corroborate and extend findings in intestinal cell culture monolayers, and further suggest that safety limits on consumption of patulin may be warranted.