Role of mitogen activated protein kinases in skin tumorigenicity of Patulin

The mycobiome in human cancer: analytical challenges, molecular mechanisms, and therapeutic implications

The polymorphic microbiome is considered a new hallmark of cancer. Advances in High-Throughput Sequencing have fostered rapid developments in microbiome research. The interaction between cancer cells, immune cells, and microbiota is defined as the immuno-oncology microbiome (IOM) axis. Fungal microbes (the mycobiome), although representing only ∼ 0.1-1% of the microbiome, are a critical immunologically active component of the tumor microbiome. Accumulating evidence suggests a possible involvement of commensal and pathogenic fungi in cancer initiation, progression, and treatment responsiveness. The tumor-associated mycobiome mainly consists of the gut mycobiome, the oral mycobiome, and the intratumoral mycobiome. However, the role of fungi in cancer remains poorly understood, and the diversity and complexity of analytical methods make it challenging to access this field. This review aims to elucidate the causal and complicit roles of mycobiome in cancer development and progression while highlighting the issues that need to be addressed in executing such research. We systematically summarize the advantages and limitations of current fungal detection and analysis methods. We enumerate and integrate these recent findings into our current understanding of the tumor mycobiome, accompanied by the prospect of novel and exhilarating clinical implications.

Fungi, immunosenescence and cancer

Fungal microbes are a small but immunoreactive component of the human microbiome, which may influence cancer development, progression and therapeutic response. Immunosenescence is a process of immune dysfunction that occurs with aging, including lymphoid organ remodeling, contributing to alterations in the immune system in the elderly, which plays a critical role in many aspects of cancer. There is evidence for the interactions between fungi and immunosenescence in potentially regulating cancer progression and remodeling the tumor microenvironment (TME). In this review, we summarize potential roles of commensal and pathogenic fungi in modulating cancer-associated processes and provide more-detailed discussions on the mechanisms of which fungi affect tumor biology, including local and distant regulation of the TME, modulating antitumor immune responses and interactions with neighboring bacterial commensals. We also delineate the features of immunosenescence and its influence on cancer development and treatment, and highlight the interactions between fungi and immunosenescence in cancer. We discuss the prospects and challenges for harnessing fungi and immunosenescence in cancer diagnosis and/or treatment. Considering the limited understanding and techniques in conducting such research, we also provide our view on how to overcome challenges faced by the exploration of fungi, immunosenescence and their interactions on tumor biology.

Unveiling the hidden players: exploring the role of gut mycobiome in cancer development and treatment dynamics

The role of gut fungal species in tumor-related processes remains largely unexplored, with most studies still focusing on fungal infections. This review examines the accumulating evidence suggesting the involvement of commensal and pathogenic fungi in cancer biological process, including oncogenesis, progression, and treatment response. Mechanisms explored include fungal influence on host immunity, secretion of bioactive toxins/metabolites, interaction with bacterial commensals, and migration to other tissues in certain types of cancers. Attempts to utilize fungal molecular signatures for cancer diagnosis and fungal-derived products for treatment are discussed. A few studies highlight fungi's impact on the responsiveness and sensitivity to chemotherapy, radiotherapy, immunotherapy, and fecal microbiota transplant. Given the limited understanding and techniques in fungal research, the studies on gut fungi are still facing great challenges, despite having great potentials.

Fungi and cancer

The microbiome may impact cancer development, progression and treatment responsiveness, but its fungal components remain insufficiently studied in this context. In this review, we highlight accumulating evidence suggesting a possible involvement of commensal and pathogenic fungi in modulation of cancer-related processes. We discuss the mechanisms by which fungi can influence tumour biology, locally by activity exerted within the tumour microenvironment, or remotely through secretion of bioactive metabolites, modulation of host immunity and communications with neighbouring bacterial commensals. We examine prospects of utilising fungi-related molecular signatures in cancer diagnosis, patient stratification and assessment of treatment responsiveness, while highlighting challenges and limitations faced in performing such research. In all, we demonstrate that fungi likely constitute important members of mucosal and tumour-residing microbiomes. Exploration of fungal inter-kingdom interactions with the bacterial microbiome and the host and decoding of their causal impacts on tumour biology may enable their harnessing into cancer diagnosis and treatment.

Onosma L. as a source of anticancer agents: phytochemistry to mechanistic insight

Onosma (O.) is a genus of perennial flowering plants in the family Boraginaceae with approximately 250 species widely dispersed in temperate, tropical, and subtropical areas. It is traditionally used to treat rheumatism, fever, asthma, stomach irritation, and inflammatory ailments. The bioactive constituents present in the genus O. include benzoquinones, naphthazarins, alkaloids, phenolic, naphthoquinones, and flavonoids whereas shikonins and onosmins are the most significant. The review compiled contemporary research on O. L., including its distribution, morphology, traditional applications, phytochemistry, ethnopharmacology, and toxicology. This review also highlights a few critical challenges and possible future directions for O. L. research. Modern research has demonstrated a wide range of pharmacological effects of different species of O. L., including anti-diabetic, anticancer, anti-inflammatory, and cardiovascular protective. However, the studies on the O. genus are still not fully explored, therefore, researchers need to discover novel products with their toxicity studies, molecular mechanism, and associated side effects. Future exploration of potent constituents from this genus and clinical trials are required to explore its pharmacological importance.

Current Review of Mycotoxin Biodegradation and Bioadsorption: Microorganisms, Mechanisms, and Main Important Applications

Mycotoxins are secondary metabolites produced by fungi. Food/feed contamination by mycotoxins is a great threat to food safety. The contamination can occur along the food chain and can cause many diseases in humans and animals, and it also can cause economic losses. Many detoxification methods, including physical, chemical, and biological techniques, have been established to eliminate mycotoxins in food/feed. The biological method, with mycotoxin detoxification by microorganisms, is reliable, efficient, less costly, and easy to use compared with physical and chemical ones. However, it is important to discover the metabolite's toxicity resulting from mycotoxin biodegradation. These compounds can be less or more toxic than the parent. On the other hand, mechanisms involved in a mycotoxin's biological control remain still unclear. Mostly, there is little information about the method used by microorganisms to control mycotoxins. Therefore, this article presents an overview of the most toxic mycotoxins and the different microorganisms that have a mycotoxin detoxification ability. At the same time, different screening methods for degradation compound elucidation are given. In addition, the review summarizes mechanisms of mycotoxin biodegradation and gives some applications.

A perspective review on medicinal plant resources for their antimutagenic potentials

Mutagens present in the environment manifest toxic effects and are considered as serious threat for human health and healthcare. Recent reports reveal that medicinal plant resources are being explored for identifying potent antimutagenic as well as cancer preventing agents. There is mounting evidence that cancer and other mutation-related diseases can be prevented with the use of medicinal pant resources including crude extracts, active fractions, phytochemicals, and pure phytomolecules. These medicinal plant resources possessing antimutagenic potentials have been shown to target molecular mechanisms underlying the mutagenic impacts. Technological advents and high-throughput screening/activity methods have revolutionized this field, though several potent plants and their active principles have been reported as effective antimutagens. The translational success rate needs to be improved, but the trends are encouraging. In this review, we present the current understandings and updates on various mutagens in the environment, toxicities related/attributed to them, the resultant mutations (and cancer), and how medicinal plants come to the rescue. A perspective review has been presented on whether and how medicinal plant resources can be an effective approach for addressing mutagens in the environment. An account of medicinal plant resources used as antimutagenic agents has been given along with the underlying mechanism of action and their therapeutic potential in various models of cancer. Recent success stories, current challenges, and future prospects are discussed.

The Mycobiome: Cancer Pathogenesis, Diagnosis, and Therapy

Cancer is among the leading causes of death globally. Despite advances in cancer research, a full understanding of the exact cause has not been established. Recent data have shown that the microbiome has an important relationship with cancer on various levels, including cancer pathogenesis, diagnosis and prognosis, and treatment. Since most studies have focused only on the role of bacteria in this process, in this article we review the role of fungi-another important group of the microbiome, the totality of which is referred to as the "mycobiome"-in the development of cancer and how it can impact responses to anticancer medications. Furthermore, we provide recent evidence that shows how the different microbial communities interact and affect each other at gastrointestinal and non-gastrointestinal sites, including the skin, thereby emphasizing the importance of investigating the microbiome beyond bacteria.

miR-27b inhibition contributes to cytotoxicity in patulin-exposed HEK293 cells

Patulin (PAT) is a mycotoxin produced by Penicillium and other fungi that contaminate fruit. PAT targets the kidney and is associated with nephrotoxicity. Micro-RNAs (miRNA) may offer new insights into PAT-induced nephrotoxicity. Cytochrome P₄₅₀ family 1, subfamily B, polypeptide 1 (CYP1B1), involved in metabolism of dietary toxins is negatively regulated by miR-27b and linked with the nuclear factor kappa B (NF-κB) pathway and peroxisome proliferator activated receptor gamma (PPARɣ) in renal fibrosis. This study investigated the effects of PAT on miR-27b, CYP1B1, PPARɣ and cytotoxicity in human kidney (HEK293) cells. HEK293 cells were exposed to PAT (2.5 μM, 24h). Protein expression of CYP1B1, PPARɣ, NF-κB (p65), pNF-κB (p65) (phospho-Ser563) and cleaved PARP-1 was quantified using western blotting. QPCR evaluated mRNA levels of CYP1B1, IL-6, miR-27b, OGG1, mtDNA, TFAM and UCP2. Mitochondrial membrane potential and phosphatidylserine (PS) externalization was evaluated by flow cytometry while levels of ATP and caspase -9, -8, -3/7 activity was measured using luminometry. PAT significantly decreased miR-27b levels (p = 0.0014) and increased CYP1B1 mRNA (p = 0.0015) and protein (p = 0.0013) levels. PPARɣ protein expression was significantly increased (p = 0.0002) and associated with decreased NF-κB activation (p = 0.0273) and IL-6 mRNA levels (p = 0.0265). Finally, PAT significantly compromised mitochondrial repair mechanisms and increased apoptotic biomarkers. PAT altered miR-27b levels and PPARɣ, with associated changes to NF-κB activation, downstream IL-6 and CYP1B1 expression. These results show that PAT impairs detoxification mechanisms leading to mitochondrial damage and apoptosis. In conclusion, PAT altered the epigenetic environment and impaired detoxification processes, supporting a mechanism for nephrotoxic outcomes.

Transcriptomic and proteomic insights into patulin mycotoxin-induced cancer-like phenotypes in normal intestinal epithelial cells

Patulin (PAT) is a natural contaminant of fruits (primarily apples) and their products. Significantly, high levels of contamination have been found in fruit juices all over the world. Several in vitro studies have demonstrated PAT's ability to alter intestinal structure and function. However, in real life, the probability of low dose long-term exposure to PAT to humans is significantly higher through contaminated food items. Thus, in the present study, we have exposed normal intestinal cells to non-toxic levels of PAT for 16 weeks and observed that PAT had the ability to cause cancer-like properties in normal intestinal epithelial cells after chronic exposure. Here, our results showed that chronic exposure to low doses of PAT caused enhanced proliferation, migration and invasion ability, and the capability to grow in soft agar (anchorage independence). Moreover, an in vivo study showed the appearance of colonic aberrant crypt foci (ACFs) in PAT-exposed Wistar rats, which are well, establish markers for early colon cancer. Furthermore, as these neoplastic changes are consequences of alterations at the molecular level, here, we combined next-generation RNA sequencing with liquid chromatography mass spectrometry-based proteomic analysis to investigate the possible underlying mechanisms involved in PAT-induced neoplastic changes.

TGF-β/Smad signaling pathway plays a crucial role in patulin-induced pro-fibrotic changes in rat kidney via modulation of slug and snail expression

Patulin (PAT) is a mycotoxin that contaminates a variety of food and foodstuffs. Earlier in vitro and in vivo findings have indicated that kidney is one of the target organs for PAT-induced toxicity. However, no study has evaluated the chronic effects of PAT exposure at environmentally relevant doses or elucidated the detailed mechanism(s) involved. Here, using in vitro and in vivo experimental approaches, we delineated the mechanism/s involved in pro-fibrotic changes in the kidney after low-dose chronic exposure to PAT. We found that non-toxic concentrations (50 nM and 100 nM) of PAT to normal rat kidney cells (NRK52E) caused a higher generation of reactive oxygen species (ROS) (mainly hydroxyl (•OH), peroxynitrite (ONOO^-), and hypochlorite radical (ClO-). PAT exposure caused the activation of mitogen-activated protein kinases (MAPKs) and its downstream c-Jun/Fos signaling pathways. Moreover, our chromatin immunoprecipitation (ChIP) analysis suggested that c-Jun/Fos binds to the promoter region of Transforming growth factor beta (TGF-β₁) and possibly induces its expression. Results showed that PAT-induced TGF-β₁ further activates the TGF-β₁/smad signaling pathways. Higher activation of slug and snail transcription factors further modulates the regulation of pro-fibrotic molecules. Similarly, in vivo results showed that PAT exposure to rats through gavage at 25 and 100 μg/kg b. wt had higher levels of kidney injury/toxicity markers namely vascular endothelial growth factor (VEGF), kidney Injury Molecule-1 (Kim-1), tissue inhibitor of metalloproteinase-1 (Timp-1), and clusterin (CLU). Additionally, histopathological analysis indicated significant alterations in renal tubules and glomeruli along with collagen deposition in PAT-treated rat kidneys. Overall, our data provide evidence of the involvement of ROS mediated MAPKs and TGF-β₁/smad pathways in PAT-induced pro-fibrotic changes in the kidney via modulation of slug and snail expression.

Cardiotoxicity of patulin was found in H9c2 cells

Patulin (PAT) is a kind of mycotoxins that is universally found at rotten fruits, especially apples and apple products. Previous studies have shown that PAT has hepatotoxicity and nephrotoxicity. However, cardiotoxicity of PAT is rarely reported. Present study aimed at investigate the cardiotoxicity and relevant mechanisms of PAT on H9c2 cells. Cytotoxicity of PAT were evaluated by MTT assay and LDH. Hoechst 33258 staining was used to examine the nuclear morphology and AV/PI double staining was employed for apoptosis on H9c2 cells. Expression level of Caspase-3, Caspase-9, Bax, Bcl-2 were quantified to verify the potential mechanism of mitochondrial apoptosis pathway. The tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and interleukin 6 (IL-6) were quantified to determine the inflammatory response by using ELISA assay. ROS, SOD, MDA, GSH levels were measured to determine the oxidative stress status. Results demonstrated that PAT significantly induced cell injury, as evidenced by the down-regulated of cell viability, and the increase of LDH release. Hoesst33258 staining and flow cytometry showed that apoptosis rate was elevated by PAT. PAT treatment up-regulated the expression of Caspase-3, Caspase-9, Bax level and down-regulated the expression of Bcl-2 level. TNF-α, IL-1β, IL-6 levels showed that PAT increased the pro-inflammatory response. As PAT concentration increased, intracellular MDA, ROS content were elevated, while GSH content and the activity of SOD were significantly decreased. Thus, it is concluded that PAT may induce apoptosis of H9c2 cells through oxidative stress.

Identifying SARS-CoV-2 antiviral compounds by screening for small molecule inhibitors of nsp14/nsp10 exoribonuclease

SARS-CoV-2 is a coronavirus that emerged in 2019 and rapidly spread across the world causing a deadly pandemic with tremendous social and economic costs. Healthcare systems worldwide are under great pressure, and there is an urgent need for effective antiviral treatments. The only currently approved antiviral treatment for COVID-19 is remdesivir, an inhibitor of viral genome replication. SARS-CoV-2 proliferation relies on the enzymatic activities of the non-structural proteins (nsp), which makes them interesting targets for the development of new antiviral treatments. With the aim to identify novel SARS-CoV-2 antivirals, we have purified the exoribonuclease/methyltransferase (nsp14) and its cofactor (nsp10) and developed biochemical assays compatible with high-throughput approaches to screen for exoribonuclease inhibitors. We have screened a library of over 5000 commercial compounds and identified patulin and aurintricarboxylic acid (ATA) as inhibitors of nsp14 exoribonuclease in vitro. We found that patulin and ATA inhibit replication of SARS-CoV-2 in a VERO E6 cell-culture model. These two new antiviral compounds will be valuable tools for further coronavirus research as well as potentially contributing to new therapeutic opportunities for COVID-19.

Patulin activates the NRF2 pathway by modulation of miR-144 expression in HEK293 cells

Patulin (PAT) is a mycotoxin produced by various fungal species that commonly contaminate apples and other fruit products. PAT is associated with glutathione (GSH) depletion and oxidative stress. Cytoprotective and antioxidant (AO) enzymes limit toxic outcomes and confer resistance to oxidative stress by influencing the expression of cytoprotective genes. The induction of these genes is tightly regulated by transcription factor nuclear factor erythroid 2 p45-related factor 2 (NRF2), a potential target of microRNA (miR)-144. This study aims to determine a possible role for miR-144 in NRF2 pathway activation following PAT exposure in human embryonic kidney (HEK293) cells. HEK293 cells were exposed to varying PAT concentrations (0, 0.2, 0.5, 1 μmol/L; 24 h). Protein expression of Keap1, NRF2, and phosphorylated (p) NRF2 (ser40) was quantified using western blotting. Gene expression of NRF2, SOD2, CAT, GPx, NQO1, GSTA1, HMOX, and miR-144 were evaluated by qPCR. PAT significantly decreased miR-144 (p = 0.0249) and concomitantly increased NRF2 protein expression, stability, and activation as evidenced by increased pNRF2 (p = 0.0216) expression and decreased total NRF2 (p = 0.0237). This was consistent with qPCR data which showed increased transcript levels of NRF2 (p = 0.0378) as well as the target genes CAT (p = 0.0273), NQO1 (p = 0.0156), HMOX (p = 0.0249), and GSTA1 (p = 0.0237). No changes were observed in Keap1 expression (p = 0.6444). This study implicates microRNAs in a mechanistic role in PAT-induced toxicity. PAT decreased miR-144 expression leading to NRF2 pathway activation and elevated AO gene expression.

Prevention and detoxification of patulin in apple and its products: A review

Patulin-producing fungi pose an unavoidable problem for apple and its product quality, thereby threatening human and/or animal health. Studies on controlling the patulin-producing fungal growth and patulin contamination in apple and its products by physical methods, chemical fungicides, and biological methods have been performed for decades, but patulin contamination has not been addressed. Here, the important of studying regulation mechanism of patulin production in apple at the protein expression and metabolism levels is proposed, which will facilitate the development of controlling patulin production by using physical, chemical, and biological methods. Furthermore, the advantages or disadvantages and effects or mechanisms of using physical, chemical, biological methods to control the decay caused by Penicillium expansum and to remove patulin in food was discussed. The development of physical methods to remove patulin depends on the development of special equipment. Chemical methods are economical and efficient, if we have ensured that there are no unknown reactions or toxic by-products by using these chemicals. The biological method not only effectively controls the decay caused by Penicillium espansum, but also removes the toxins that already exist in the food. Degradation of patulin by microorganisms or biodegradation enzymes is an efficient and promising method to remove patulin in food if the microorganisms used and the degradation products are completely non-toxic.

Patulin induces pyroptosis through the autophagic-inflammasomal pathway in liver

Patulin (PAT), a kind of mycotoxin, is produced by many common fungi in fruit and vegetable-based products. It has been shown to cause hepatotoxicity. However, the possible mechanisms are not completely elucidated. The present study aimed to characterize the role of autophagic-inflammasomal pathway on pyroptosis induced by PAT. In mouse livers, PAT induced pyroptosis, and increased inflammation through the activation of NLRP3 inflammasome. In liver cells, we noticed that PAT induced pyroptotic cell death, which was confirmed by the activation of GSDMD, caspase-1, the release of LDH, and the result of PI/Hoechst assay. In addition, PAT-induced pyroptosis was dependent upon the activation of NLRP3 inflammasome and the release of cathepsin B. Cells had less expression of caspase-1 and IL-1β protein levels after treated by NLRP3 inhibitor MCC950 or cathepsin B inhibitor CA-074Me. The expression of GSDMD and IL-1β protein levels were also decrease after treated by caspase-1 inhibitor Ac-YVAD-cmk. Moreover, autophagy inhibitor 3-methyladenine (3-MA) attenuated PAT-induced increase in cytoplasmic cathepsin B expression, and subsequent LDH release, the activation of NLRP3 inflamosomes, pyroptotic cell death, and inflammation. These findings suggested that PAT-induced pyroptosis maybe through autophagy-cathepsin B-inflammasomal pathway in the liver. These results provide new mechanistic insights into PAT-induced hepatotoxicity.

The characteristics, occurrence, and toxicological effects of patulin

Mycotoxins are the secondary metabolites secreted by different types of fungi to which humans can get exposed mainly via ingestion. Patulin (C₇H₆O₄) is a polyketide lactone produced by various fungal specifies, including Penicillium expansum as the main producer. P. expansum can infect different fruits and vegetables yet it has preference to apples in which they cause blue rot. Therefore, apples and apple-based food products are the main source of Patulin exposure for humans. Patulin was first identified in 1943 under the name of tercinin as a possible antimicrobial agent. Although it is categorized as a non-carcinogen, Patulin has been linked, in the last decades, to neurological, gastrointestinal, and immunological adverse effects, mainly causing liver and kidney damages. In this review, the characteristics of and possible human exposure pathways to Patulin are discussed. Various surveillance and toxicity studies on the levels of Patulin in various food products and effects of Patulin on cells and animal models have been documented as well. Importance of epidemiological studies and a summary of the possible toxicity mechanisms are highlighted with a case study. The commonly used control methods as described in the literature are also discussed to guide future researchers to focus on mitigating mycotoxins contamination in the food industry.

The signaling involved in autophagy machinery in keratinocytes and therapeutic approaches for skin diseases

Autophagy is responsible for the lysosomal degradation of proteins, organelles, microorganisms and exogenous particles. Epidermis primarily consists of keratinocytes which functions as an extremely important barrier. Investigation on autophagy in keratinocytes has been continuously renewing, but is not so systematic due to the complexity of the autophagy machinery. Here we reviewed recent studies on the autophagy in keratinocyte with a focus on interplay between autophagy machinery and keratinocytes biology, and novel autophagy regulators identified in keratinocytes. In this review, we discussed the roles of autophagy in apoptosis, differentiation, immune response, survival and melanin metabolism, trying to reveal the possible involvement of autophagy in skin aging, skin disorders and skin color formation. Since autophagy routinely plays a double-edged sword role in various conditions, its functions in skin homeostasis and potential application as a therapeutic target for skin diseases remains to be clarified. Furthermore, more investigations are needed on optimizing designed strategies to inhibit or enhance autophagy for clinical efficacy.

Toxicological effects of patulin mycotoxin on the mammalian system: an overview

The mycotoxin PAT (4-hydroxy-4H-furo[3,2c]pyran-2[6H]-one) is a secondary metabolic product of molds such as Penicillium, Aspergillus, and Byssochlamys species. PAT is a common contaminant of fruit and vegetable based products, most notably apples. Despite PAT's original discovery as an antibiotic, it has come under heavy scrutiny for its potential to impart negative health effects. Studies investigating these health effects have proved its toxic potential. PAT occurrence in the food commodities poses a serious threat and necessitates novel and cost-effective mitigation methods to remove it from food products. It also creates a demand to improve handling and food processing techniques. With this being the case, several studies have been devoted to understanding the key biological and chemical attributes of PAT. While past research has elucidated a great deal, PAT contamination continues to be a challenge for the food industry. Here, we review its influence within the mammalian system, including its regulation, incidences of experimental evidence of PAT toxicity, its interaction with intracellular components, and the effects of PAT induced systemic toxicity on vital organs. Finally, key areas where future PAT research should focus to best control the PAT contamination problem within the food industry have been addressed.

Deoxynivalenol induced mouse skin tumor initiation: Elucidation of molecular mechanisms in human HaCaT keratinocytes

Among food contaminants, mycotoxins are toxic to both human and animal health. Our prior studies suggest that Deoxynivalenol (DON), a mycotoxin, behaves as a tumor promoter by inducing edema, hyperplasia, ODC activity and activation of MAPK's in mouse skin. In this study, topical application of DON, 336 and 672 nmol significantly enhanced ROS levels, DNA damage and apoptosis with concomitant downregulation of Ki-67, cyclin D, cyclin E, cyclin A and cyclin-dependent kinases (CDK4 and CDK2) thereby resulting in tumor initiation in mouse skin. Further, the elucidation of molecular mechanisms of tumor initiation by DON (0.42-3.37 nmol/ml) in HaCaT keratinocytes, revealed (i) enhanced ROS generation with cell cycle phase arrest in G0/G1 phase, (ii) increase in levels of 8-OxoG (6-24 hr) and γH2AX protein, (iii) significant enhancement in oxidative stress marker enzymes LPO, GSH, GR with concomitant decrease in antioxidant enzymes catalase, GPx, GST, SOD and mitochondrial membrane potential after DON (1.68 nmol) treatment, (iv) suppression of Nrf2 translocation to nucleus, enhanced phosphorylation with subsequent activation ERK1/2, p38 and JNK MAPK's following DON (1.68 nmol) treatment, (v) overexpression of c-jun, c-fos proteins, upregulation of Bax along with downregulation of Bcl-2 proteins, (vi) increase in cytochrome-c, caspase-9, caspase-3 and poly ADP ribose polymerase levels leads to apoptosis. Pretreatment of superoxide dismutase, mannitol and ethanol to HaCaT cells resulted in significant reduction in ROS levels and apoptosis indicating the role of superoxide and hydroxyl radicals in DON induced apoptosis as an early event and skin tumor initiation as a late event.

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.

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

Among the many mycotoxins, T-2 toxin, citrinin (CTN), patulin (PAT), aflatoxin B1 (AFB1) and ochratoxin A (OTA) are known to have the potential to induce dermal toxicity and/or tumorigenesis in rodent models. T-2 toxin, CTN, PAT and OTA induce apoptosis in mouse or rat skin. PAT, AFB1 and OTA have tumor initiating properties, and OTA is also a tumor promoter in mouse skin. This paper reviews the molecular mechanisms of dermal toxicity and tumorigenesis induced in rodent models by these mycotoxins especially from the viewpoint of oxidative stress-mediated pathways.

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.

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.

Topical application of ochratoxin A causes DNA damage and tumor initiation in mouse skin

Skin cancer is one of the most common forms of cancer and 2-3 million new cases are being diagnosed globally each year. Along with UV rays, environmental pollutants/chemicals including mycotoxins, contaminants of various foods and feed stuffs, could be one of the aetiological factors of skin cancer. In the present study, we evaluated the DNA damaging potential and dermal carcinogenicity of a mycotoxin, ochratoxin A (OTA), with the rationale that dermal exposure to OTA in workers may occur during their involvement in pre and post harvest stages of agriculture. A single topical application of OTA (20-80 µg/mouse) resulted in significant DNA damage along with elevated γ-H2AX level in skin. Alteration in oxidative stress markers such as lipid peroxidation, protein carbonyl, glutathione content and antioxidant enzymes was observed in a dose (20-80 µg/mouse) and time-dependent (12-72 h) manner. The oxidative stress was further emphasized by the suppression of Nrf2 translocation to nucleus following a single topical application of OTA (80 µg/mouse) after 24 h. OTA (80 µg/mouse) application for 12-72 h caused significant enhancement in- (a) reactive oxygen species generation, (b) activation of ERK1/2, p38 and JNK MAPKs, (c) cell cycle arrest at G0/G1 phase (37-67%), (d) induction of apoptosis (2.0-11.0 fold), (e) expression of p53, p21/waf1, (f) Bax/Bcl-2 ratio, (g) cytochrome c level, (h) activities of caspase 9 (1.2-1.8 fold) and 3 (1.7-2.2 fold) as well as poly ADP ribose polymerase cleavage. In a two-stage mouse skin tumorigenesis protocol, it was observed that a single topical application of OTA (80 µg/mouse) followed by twice weekly application of 12-O-tetradecanoylphorbol-13-acetate for 24 week leads to tumor formation. These results suggest that OTA has skin tumor initiating property which may be related to oxidative stress, MAPKs signaling and DNA damage.

Regulation of patulin-induced oxidative stress processes in the fission yeast Schizosaccharomyces pombe

Patulin (PAT), is one of the most widely disseminated mycotoxins found in agricultural products. In this study the PAT-induced accumulation of reactive oxygen species (ROS) and the regulation of the specific activities of antioxidant enzymes were investigated in the single cell eukaryotic organism Schizosaccharomyces pombe. In comparison with the untreated cells, 500 μM PAT treatment caused a 43% decrease in the concentration of the main intracellular antioxidant, glutathione (GSH); this depletion of GSH initiated a 2.44- and a 2.6-fold accumulation of superoxide anion and hydrogen peroxide, respectively, but did not increase the concentration of hydroxyl radicals; the reduction of ROS-induced adaptation processes via the activation of Pap1 transcription factor resulted in significantly increased specific activities of Cu/Zn superoxide dismutase, catalase and glutathione S-transferase to protect the cells against the ROS-induced unbalanced redox state. However, no change was measured in the activities of glutathione reductase, glutathione peroxidase and glucose-6-phosphate dehydrogenase. It seems reasonable to assume that the temporary PAT-induced ROS accumulation plays a crucial role in adaptation processes. The adverse effects of PAT may be exerted mainly through the destruction of cellular membranes and protein/enzyme functions.

ERK and p38 MAPK signaling pathways are involved in ochratoxin A-induced G2 phase arrest in human gastric epithelium cells

Ochratoxin A (OTA) is a ubiquitous mycotoxin with potential nephrotoxic, hepatotoxic, and immunotoxic effects. Recent work from our laboratory found that OTA evoked G2 phase arrest in GES-1 cells in vitro by modulating the key factors Cdc25C, Cdc2 and cyclinB1, which were critical to the G2/M phase transmission, suggested that OTA-induced G2 arrest mediate at least in part OTA toxicity effect. However, the molecular mechanism of this effect is currently unclear. In the present study, we showed that treatment of GES-1 cells with OTA could induce the activation of MAPK family members ERK and p38. ERK inhibitor PD98059 and p38 inhibitor SB203580 significantly reversed the depression of Cdc25C/p-Cdc25C, Cdc2/p-Cdc2, cyclinB1 as well as the cyclinB1-Cdc2 complex, thereby, abolished the delay in G2 phase. In addition, silencing ERK and p38 expression with siRNA significantly inhibited OTA-induced G2 arrest in GES-1 cells as well. Collectively, these data suggest that the ERK and p38 MAPK signaling pathways play important roles in the regulation of OTA-induced G2 arrest in GES-1 cells.