Apoptosis signal-regulating kinase 1 promotes Ochratoxin A-induced renal cytotoxicity

Recent pharmacological insights on abating toxic protein species burden in neurological disorders: Emphasis on 26S proteasome activation

Protein homeostasis (proteostasis) refers to the plethora of mechanisms that safeguard the proper folding of the newly synthesized proteins. It entails various intricately regulated cues that demolish the toxic protein species to prevent their aggregation. The ubiquitin-proteasome system (UPS) is recognized as a salient protein degradation system, with a substantial role in maintaining proteostasis. However, under certain circumstances the protein degradation capacity of the UPS is overwhelmed, leading to the accumulation of misfolded proteins. Several neurodegenerative disorders, such as Alzheimer's disease, Parkinson's disease, Huntington disease, and amyotrophic lateral sclerosis are characterized with the presence of protein aggregates and proteinopathy. Accordingly, enhancing the 26S proteasome degradation activity might delineate a pioneering approach in targeting various proteotoxic disorders. Regrettably, the exact molecular approaches that enhance the proteasomal activity are still not fully understood. Therefore, this review aimed to underscore several signaling cascades that might restore the degradation capacity of this molecular machine. In this review, we discuss the different molecular components of the UPS and how 26S proteasomes are deleteriously affected in many neurodegenerative diseases. Moreover, we summarize different signaling pathways that can be utilized to renovate the 26S proteasome functional capacity, alongside currently known druggable targets in this circuit and various classes of proteasome activators.

Alterations in the proteomes of HepG2 and IHKE cells inflicted by six selected mycotoxins

Toxic fungal secondary metabolites, referred to as mycotoxins, emerge in moldy food and feed and constitute a potent but often underestimated health threat for humans and animals. They are structurally diverse and can cause diseases after dietary intake even in low concentrations. To elucidate cellular responses and identify cellular targets of mycotoxins, a bottom-up proteomics approach was used. We investigated the effects of the mycotoxins aflatoxin B1, ochratoxin A, citrinin, deoxynivalenol, nivalenol and penitrem A on the human hepatoblastoma cell line HepG2 and of ochratoxin A and citrinin on the human kidney epithelial cell line IHKE. Incubations were carried out at sub-cytotoxic concentrations to monitor molecular effects before acute cell death mechanisms predominate. Through these experiments, we were able to detect specific cellular responses that point towards the mycotoxins' mode of action. Besides very well-described mechanisms like the ribotoxicity of the trichothecenes, we observed not yet described effects on different cellular mechanisms. For instance, trichothecenes lowered the apolipoprotein abundance and aflatoxin B1 affected proteins related to inflammation, ribogenesis and mitosis. Ochratoxin A and citrinin upregulated the minichromosomal maintenance complex and nucleotide synthesis in HepG2 and downregulated histones in IHKE. Penitrem A reduced enzyme levels of the sterol biosynthesis. These results will aid in the elucidation of the toxicodynamic properties of this highly relevant class of toxins.

Ochratoxin A and Its Role in Cancer Development: A Comprehensive Review

Background: Ochratoxin A (OTA) is widely recognized for its broad spectrum of toxic effects and is classified as a potential human carcinogen, placed in group 2B by the International Agency for Research on Cancer (IARC). Its presence in food and beverages poses a significant health hazard. Extensive research has documented the efficient absorption and distribution of OTA throughout the body via the bloodstream and tissues, underscoring the associated health risk. Additionally, ongoing studies aim to clarify the link between OTA exposure and carcinogenesis. The obtained results indicate a strong correlation between OTA and renal cell carcinoma (RCC), with potential associations with other malignancies, including hepatocellular carcinoma (HCC), gallbladder cancer (GBC), and squamous cell carcinoma (SCC). OTA is implicated in oxidative stress, lipid peroxidation, apoptosis, DNA damage, adduct formation, miRNA deregulation, and distributions in the cell cycle, all of which may contribute to carcinogenesis. Conclusions: Despite significant research efforts, the topic remains inexhaustible and requires further investigation. The obtained results do not yield definitive conclusions, potentially due to species-specific differences in the animal models used and challenges in extrapolating these results to humans. In our review, we delve deeper into the potential mechanisms underlying OTA-induced carcinogenesis and discuss existing limitations, providing directions for future research.

Central role of Sigma-1 receptor in ochratoxin A-induced ferroptosis

Ochratoxin A (OTA), a secondary fungal metabolite known for its nephrotoxic effects, is prevalent in various feeds and food items. Our recent study suggests that OTA-induced nephrotoxicity is linked to the Sigma-1 receptor (Sig-1R)-mediated mitochondrial pathway apoptosis in human proximal tubule epithelial-originated kidney-2 (HK-2) cells. However, the contribution of Sig-1R to OTA-induced nephrotoxicity involving other forms of regulated cell death, such as ferroptosis, remains unexplored. In this investigation, cell viability, malondialdehyde (MDA) levels, glutathione (GSH) levels, and protein expressions in HK-2 cells treated with OTA and/or Ferrostatin-1/blarcamesine hydrochloride/BD1063 dihydrochloride were assessed. The results indicate that a 24 h-treatment with 1 μM OTA significantly induces ferroptosis by inhibiting Sig-1R, subsequently promoting nuclear receptor coactivator 4 (NCOA4), long-chain fatty acid-CoA ligase 4 (ACSL4), arachidonate 5-lipoxygenase (ALOX5), autophagy protein 5 (ATG5), and ATG7, inhibiting ferritin heavy chain (FTH1), solute carrier family 7 member 11 (SLC7A11/xCT), glutathione peroxidase 4 (GPX4), peroxiredoxin 6 (PRDX6), and ferroptosis suppressor protein 1 (FSP1), reducing GSH levels, and increasing MDA levels (P < 0.05). In conclusion, OTA induces ferroptosis by inhibiting Sig-1R, subsequently promoting ferritinophagy, inhibiting GPX4/FSP1 antioxidant systems, reducing GSH levels, and ultimately increasing lipid peroxidation levels in vitro.

Ochratoxin A triggers endoplasmic reticulum stress through PERK/NRF2 signaling and DNA damage during early embryonic developmental competence in pigs

Ochratoxin A (OTA), a mycotoxin found in foods, has a deleterious effect on female reproduction owing to its endocrine-disrupting activity mediated through endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) production. However, the mechanisms of OTA-induced ER stress in pig embryos during in vitro culture (IVC) are not yet fully understood. In the present study, porcine embryos were cultured for two days in an IVC medium supplemented with 0.5, 1.0, and 5.0 μM OTA, which led to an OTA-induced reduction in the developmental rate of blastocysts. The mRNA-seq transcriptome analysis revealed that the reduced blastocyst development ability of OTA-exposed porcine embryos was caused by ER stress, ultimately resulting in the accumulation of ROS and the occurrence of apoptosis. The expression levels of some UPR/PERK signaling-related genes (DDIT3, EIF2AK3, EIF2S1, NFE2L2, ATF4, EIF2A, and KEAP1) were found to differ in OTA-exposed pig embryos. OTA induces DNA damage by triggering an increase in RAD51/γ-H2AX levels and suppressing p-NRF2 activity. This effect is mediated through intracellular ROS and superoxide accumulation in the nuclei of porcine embryos. The cytotoxicity of OTA increased the activation of the PERK signal pathways (p-PERK, PERK, p-eIF2α, eIF2α, ATF4, and CHOP) in porcine embryos, with abnormal distribution of the ER observed around the nucleus. Collectively, our findings indicate that ER stress is a major cause of decline in the development of porcine embryos exposed to OTA. Therefore, OTA exposure induces ER stress and DNA damage via oxidative stress by disrupting PERK/NRF2 signaling activity in the developmental competence of porcine embryos during IVC.

Excessive ER-phagy contributes to ochratoxin A-induced apoptosis

The nephrotoxic secondary fungal metabolite ochratoxin A (OTA) is ubiquitously existed in foodstuffs and feeds. Although our earlier research provided preliminary evidence that endoplasmic reticulum (ER) was crucial in OTA-induced nephrotoxicity, more research is necessary to understand the fine-tune mechanisms involving ER stress (ERS), ER-phagy, and apoptosis. In the present study, the cell viability and protein expressions of human proximal tubule epithelial (HK-2) cells in response to OTA and/or chloroquine/rapamycin/sodium phenylbutyrate/tunicamycin were determined via cell viability assay, apoptosis analysis, and Western blot analysis. The findings showed that a 24 h-treatment of 0.25-4 μM OTA could significantly reduced the cell viability (P < 0.05), which notably increased with the addition of chloroquine and sodium phenylbutyrate, while decreased with the addition of rapamycin and tunicamycin as compared to group OTA (P < 0.05). A 24 h-treatment of 1-4 μM OTA could markedly induce apoptosis via increasing the protein expressions of GRP78, p-eIF2α, Chop, LC3B-II, Bak, and Bax, and inhibiting the protein expressions of DDRGK1, UBA5, Lonp1, Tex264, FAM134B, p-mTOR, p62, and Bcl-2 in HK-2 cells (P < 0.05). In conclusion, OTA activated ERS, unfolded protein response, and subsequent excessive ER-phagy, thus inducing apoptosis, and the vicious cycle between excessive ER-phagy and ERS could further promote apoptosis in vitro.

Protective effect of selenomethionine on kidney injury induced by ochratoxin A in rabbits

The purpose of this study was to investigate the protective effect and mechanism of selenomethionine (SeMet) on ochratoxin A (OTA)-induced nephrotoxicity in rabbits. In total, sixty Ira rabbits were randomly divided into 5 groups (the control group, OTA group, 0. 2 mg/kg SeMet + OTA group, 0. 4 mg/kg SeMet + OTA group, and 0. 6 mg/kg SeMet + OTA group). The rabbits were fed diets supplemented with different doses of SeMet for 21 days and given 0. 2 mg/kg OTA starting on day 15 for a week. The results showed that the SeMet supplementation could improve the changes in blood physiological indices and renal function decline caused by OTA poisoning, and alleviate pathological kidney injury in the rabbits. SeMet also increased the activities of total antioxidant capacity, superoxide dismutase, and glutathione peroxidase, and decreased the contents of malondialdehyde and reactive oxygen species and the expression of interleukin-1β, interleukin-6, and tumor necrosis factor-α in the damaged kidneys of the rabbits. In addition, the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream gene heme oxygenase 1 (HO-1) was also inhibited after OTA poisoning, while SeMet activated the Nrf2 signaling pathway and enhanced the expression of Nrf2 and the downstream gene HO-1. In conclusion, SeMet protected against kidney injury caused by OTA in rabbits, and the mechanism may be the activation of the Nrf2 signaling pathway.

Protective role of fermented whey and pumpkin extract against aflatoxin B1 and ochratoxin A toxicity in Jurkat T-cells

The beneficial effect of fermented whey and pumpkin extract rich in carotenoids was evaluated in Jurkat cells against aflatoxin B1 (AFB1) and ochratoxin A (OTA) cytotoxicity through a proteomic approach. The functional ingredients were added into mycotoxin contaminated bread formulation, which were digested in vitro in order to simulate human intestinal absorption. Cell cultures were exposed during 7 days to these mycotoxins dissolved in: (a) 0.1% organic solvent (DMSO), (b) an intestinal digest of bread with pumpkin individually (PID) and (c) an intestinal digest of bread with pumpkin mixed with fermented whey (PID+WF). Extracted proteins were subjected to reduction and alkylation and subsequently a tryptic digestion in order to be analysed by liquid chromatography coupled with quadrupole time of flight (LC/MS-Q-TOF). Results obtained highlighted the beneficial role of functional ingredients employed through the identification of proteins involved in several biological processes and metabolic pathways, mainly antioxidant activity, nucleosome assembly and secretory senescence phenotype. Among proteins involved in antioxidant activity, peroxiredoxin 1 and 2 stand out. Comparing the different conditions investigated, a remarkable change was observed in their expression, ranging from a repression using the standard (DMSO 0.1%), to an overexpression when treated with the functional ingredients. Similarly, after PID and PID+WF treatment, histones’ expression implicated in the metabolic pathway of nucleosome assembly, such as H2A, H2B, H2C, H3 and H4, was increased. Furthermore, the expression of protein cyclin A2, which downregulation is involved in limiting carcinogenic cells growth, was lower in presence of both functional ingredients. Based on these findings, functional ingredients can act as protectors against genomic stress caused by mycotoxins, preventing the loss of vital cell functions and paralysing the growth of carcinogenic cells.

Protective and detoxifying effects conferred by selenium against mycotoxins and livestock viruses: A review

Animal feed can easily be infected with molds during production and storage processes, and this can lead to the production of secondary metabolites, such as mycotoxins, which eventually threaten human and animal health. Furthermore, livestock production is also not free from viral infections. Under these conditions, the essential trace element, selenium (Se), can confer various biological benefits to humans and animals, especially due to its anticancer, antiviral, and antioxidant properties, as well as its ability to regulate immune responses. This article reviews the latest literature on the antagonistic effects of Se on mycotoxin toxicity and viral infections in animals. We outlined the systemic toxicity of mycotoxins and the primary mechanisms of mycotoxin-induced toxicity in this analysis. In addition, we pay close attention to how mycotoxins and viral infections in livestock interact. The use of Se supplementation against mycotoxin-induced toxicity and cattle viral infection was the topic of our final discussion. The coronavirus disease 2019 (COVID-19) pandemic, which is currently causing a health catastrophe, has altered our perspective on health concerns to one that is more holistic and increasingly embraces the One Health Concept, which acknowledges the interdependence of humans, animals, and the environment. In light of this, we have made an effort to present a thorough and wide-ranging background on the protective functions of selenium in successfully reducing mycotoxin toxicity and livestock viral infection. It concluded that mycotoxins could be systemically harmful and pose a severe risk to human and animal health. On the contrary, animal mycotoxins and viral illnesses have a close connection. Last but not least, these findings show that the interaction between Se status and host response to mycotoxins and cattle virus infection is crucial.

Underestimation of Heritability across the Molecular Layers of the Gene Expression Process

We investigated the extent of the heritability underestimation for molecules from an infinitesimal model in mixed model analysis. To this end, we estimated the heritability of transcription, ribosome occupancy, and translation in lymphoblastoid cell lines from Yoruba individuals. Upon considering all genome-wide nucleotide variants, a considerable underestimation in heritability was observed for mRNA transcription (−0.52), ribosome occupancy (−0.48), and protein abundance (−0.47). We employed a mixed model with an optimal number of nucleotide variants, which maximized heritability, and identified two novel expression quantitative trait loci (eQTLs; p < 1.0 × 10−5): rs11016815 on chromosome 10 that influences the transcription of SCP2, a trans-eGene on chromosome 1—whose expression increases in response to MGMT downregulation-induced apoptosis, the cis-eGene of rs11016815—and rs1041872 on chromosome 11 that influences the ribosome occupancy of CCDC25 on chromosome 8 and whose cis-eGene encodes ZNF215, a transcription factor that potentially regulates the translation speed of CCDC25. Our results suggest that an optimal number of nucleotide variants should be used in a mixed model analysis to accurately estimate heritability and identify eQTLs. Moreover, a heterogeneous covariance structure based on gene identity and the molecular layers of the gene expression process should be constructed to better explain polygenic effects and reduce errors in identifying eQTLs.

Alimentary Risk of Mycotoxins for Humans and Animals

Mycotoxins can be found in many foods consumed by humans and animals. These substances are secondary metabolites of some fungi species and are resistant to technological processes (cooking, frying, baking, distillation, fermentation). They most often contaminate products of animal (beef, pork, poultry, lamb, fish, game meat, milk) and plant origin (cereals, processed cereals, vegetables, nuts). It is estimated that about 25% of the world's harvest may be contaminated with mycotoxins. These substances damage crops and may cause mycotoxicosis. Many mycotoxins can be present in food, together with mold fungi, increasing the exposure of humans and animals to them. In this review we characterized the health risks caused by mycotoxins found in food, pet food and feed. The most important groups of mycotoxins are presented in terms of their toxicity and occurrence.

Human Proximal Tubule Epithelial Cells (HK-2) as a Sensitive In Vitro System for Ochratoxin A Induced Oxidative Stress

Ochratoxin A (OTA) is a mycotoxin that is potentially carcinogenic to humans. Although its mechanism remains unclear, oxidative stress has been recognized as a plausible cause for the potent renal carcinogenicity observed in experimental animals. The effect of OTA on oxidative stress parameters in two cell lines of LLC-PK1 and HK-2 derived from the kidneys of pig and human, respectively, were investigated and compared. We found that the cytotoxicity of OTA on LLC-PK1 and HK-2 cells was dose- and time-dependent in both cell lines. Furthermore, increased intracellular reactive oxygen species (ROS) induced by OTA in both cell lines were observed in a time-dependent manner. Glutathione (GSH) was depleted by OTA at >48 h in HK-2 but not in LLC-PK1 cells. While the mRNA levels of glucose-6-phosphate dehydrogenase (G6PD) and glutathione peroxidase 1 (GPX1) in LLC-PK1 were down-regulated by 0.67- and 0.66-fold, respectively, those of catalase (CAT), glutathione reductase (GSR), and superoxide dismutase 1 (SOD) in HK-2 were up-regulated by 2.20-, 2.24-, and 2.75-fold, respectively, after 72 h exposure to OTA. Based on these results, we conclude that HK-2 cells are more sensitive to OTA-mediated toxicity than LLC-PK1, and OTA can cause a significant oxidative stress in HK-2 as indicated by changes in the parameter evaluated.

Ochratoxin A-Induced Nephrotoxicity: Up-to-Date Evidence

Ochratoxin A (OTA) is a mycotoxin widely found in various foods and feeds that have a deleterious effect on humans and animals. It has been shown that OTA causes multiorgan toxicity, and the kidney is the main target of OTA among them. This present article aims to review recent and latest intracellular molecular interactions and signaling pathways of OTA-induced nephrotoxicity. Pyroptosis, lipotoxicity, organic anionic membrane transporter, autophagy, the ubiquitin-proteasome system, and histone acetyltransferase have been involved in the renal toxicity caused by OTA. Meanwhile, the literature reviewed the alternative or method against OTA toxicity by reducing ROS production, oxidative stress, activating the Nrf2 pathway, through using nanoparticles, a natural flavonoid, and metal supplement. The present review discloses the molecular mechanism of OTA-induced nephrotoxicity, providing opinions and strategies against OTA toxicity.

Exosomes mediated the delivery of ochratoxin A-induced cytotoxicity in HEK293 cells

Ochratoxin A (OTA) is one of the mycotoxins, which widely pollutes food systems and seriously threatens human health. OTA's target organ is the kidney. Exosome, as one of the extracellular vesicles, could be secreted by all kinds of cells. It contains different proteins, nucleic acid, and lipid, which are decided by their donor cells and could be uptake by the recipient cells, release their contents, and affect the recipient cell's life activity. In this study, a 24 h-treatment with 5 μM OTA was found to significantly reduce the cell viability of HEK293 cells and meanwhile to provide a sufficient quantity of exosomes, thus this concentration and time were selected for subsequent experiments. In addition, exosomes extracted by ultracentrifugation had higher purity, fewer impurities, and uniform morphology than that by the ExoQuick-TC kit. Furthermore, these exosomes increased ROS levels and decreased mitochondrial membrane potential in HEK293 cells. By RNA-seq, the cytotoxicity mechanisms induced by OTA-treated HEK293 cell-derived exosomes (EXO-OTA) and OTA were mainly the metabolism of proteins and the cell cycle respectively. Also, it proved that exosomes deliver partial OTA-induced cytotoxicity.

Biological Mechanisms Induced by Soybean Agglutinin Using an Intestinal Cell Model of Monogastric Animals

Soybean agglutinin (SBA) has a toxic effect on most animals. The anti-nutritional mechanisms of SBA are not fully understood, in terms of cell survival activity and metabolism of intestinal cells. This study aims to investigate the effects of SBA on the cell cycle, apoptosis, and to verify the mechanism of SBA anti-nutritional characters based on proteomic-based analysis. The IPEC-J2 cell line was cultured with medium containing 0.0, 0.5, or 2.0 mg/mL SBA. With increasing SBA levels, the percentage of the cells at G0/G1 phase, cell apoptosis rates, expressions of Bax and p21, and the activities of Casp-3 and Casp-9 were increased, while cyclin D1 and Bcl-2 expressions were declined (p < 0.05). The proteomic analysis showed that the numbers of differentially expressed proteins, induced by SBA, were mainly enriched in different pathways including DNA replication, base excision repair, nucleus excision repair, mismatch repair, amide and peptide biosynthesis, ubiquitin-mediated proteolysis, as well as structures and functions of mitochondria and ribosome. In conclusion, the anti-nutritional mechanism of SBA is a complex cellular process. Such process including DNA related activities; protein synthesis and metabolism; signal-conducting relation; as well as subcellular structure and function. This study provides comprehensive information to understand the toxic mechanism of SBA in monogastrics.

Porous Silicon Optical Devices: Recent Advances in Biosensing Applications

This review summarizes the leading advancements in porous silicon (PSi) optical-biosensors, achieved over the past five years. The cost-effective fabrication process, the high internal surface area, the tunable pore size, and the photonic properties made the PSi an appealing transducing substrate for biosensing purposes, with applications in different research fields. Different optical PSi biosensors are reviewed and classified into four classes, based on the different biorecognition elements immobilized on the surface of the transducing material. The PL signal modulation and the effective refractive index changes of the porous matrix are the main optical transduction mechanisms discussed herein. The approaches that are commonly employed to chemically stabilize and functionalize the PSi surface are described.

Ochratoxin A induces nephrotoxicity in vitro and in vivo via pyroptosis

Ochratoxin A (OTA), a prevalent nephrotoxic mycotoxin contaminant in food and feedstuff, has been reported to induce renal injury. To disclose the nephrotoxicity of continuous administration of OTA and to investigate potential mechanisms related to pyroptosis, male C57BL/6 mice were intraperitoneally injected with 1.0 and 2.0 mg/kg B.W. OTA every other day for 14 days. At 2.0 mg/kg B.W. OTA administration significantly increased histological injury and renal fibrosis molecules (α-SMA, Vimentin, TGF-β) and activated the NOD-like receptor protein 3 (NLRP3) inflammasome and induced pyroptosis compared with control. In the in vitro tests, Madin-Darby canine kidney (MDCK) epithelial cells were exposed to 0-4.0 μg/ml OTA for 24 h in serum-free medium. Data showed that OTA dose-dependently affected cell viability and significantly up-regulated renal fibrosis genes (α-SMA, Vimentin, TGF-β). 2.0 μg/ml OTA significantly induced NLRP3 inflammasome activation and caspase-1-dependent pyroptosis, increasing the expression and secretion of pro-inflammatory cytokines (IL-6, TNF-α) and pyroptosis-related genes (GSDMD, IL-1β, IL-18) in MDCK cells. These outcomes were significantly abrogated after inhibiting NLRP3 activation with inhibitor MCC950 and silencing NLRP3 with small interfering RNA (siRNA). Furthermore, knockdown of caspase-1 also ameliorated OTA-induced renal fibrosis via the inhibition of pyroptosis. Collectively, the chosen doses of OTA-triggered nephrotoxicity through NLRP3 inflammasome activation and caspase-1-dependent pyroptosis both in vitro and in vivo.

Central role of TRAP1 in the ameliorative effect of oleanolic acid on the mitochondrial-mediated and endoplasmic reticulum stress-excitated apoptosis induced by ochratoxin A

Ochratoxin A (OTA) is a nephrotoxic mycotoxin that is widely distributed in foodstuffs and feeds, meanwhile oleanolic acid (OA) is ubiquitous in various fruit skins, food materials, and medicinal herbs. Due to that OA has a nephroprotective effect, it has the poteintial to counteract OTA-induced nephrotoxicity by nutritional intervention of OA. Furthermore, tumor necrosis factor receptor-associated protein 1 (TRAP1) acts as the core of endoplasmic reticulum (ER)-mitochondria crosstalk, becoming our focus in the mechanism investigation. In this study, the cell viability, apoptosis rate, and protein expressions of human proximal tubule epithelial-originated kidney-2 (HK-2) cells in response to OTA and/or OA were determined. Results indicated that a 24 h-treatment of 1-5 μM OTA could notably induce mitochondrial-mediated and ER stress (ERS)-excitated apoptosis via inhibiting TRAP1, thereby activating CypD, Bax, Cyt-C, Cleaved Caspase-9, Cleaved Caspase-3, GRP78, p-PERK, p-eIF2α, ATF4, and CHOP and inhibiting Bcl-2 (P < 0.05). Results of the RNA interference of TRAP1 further ascertained its anti-apoptotic function via inhibiting CypD, Bax, GRP78, and CHOP and enhancing Bcl-2 (P < 0.05). The pre-treatment of 2 μM OA for 2 h could remarkably relieve OTA-induced suppression of TRAP1 (P < 0.05). In conclusion, TRAP1 played a central role in the ameliorative effect of OA on the mitochondrial-mediated and ERS-excitated apoptosis induced by OTA.

Ochratoxin A-induced genotoxic and epigenetic mechanisms lead to Alzheimer disease: its modulation with strategies

Ochratoxin A (OTA) is a naturally occurring mycotoxin mostly found in food items including grains and coffee beans. It induces DNA single-strand breaks and has been considered to be carcinogenic. It is recognized as a serious threat to reproductive health both in males and females. OTA is highly nephrotoxic and carcinogenic, and its potency changes evidently between species and sexes. There is a close association between OTA, mutagenicity, carcinogenicity, and genotoxicity, but the underlying mechanisms are not clear. Reports regarding genotoxic effects in relation to OTA which leads to the induction of DNA adduct formation, protein synthesis inhibition, perturbation of cellular energy production, initiation of oxidative stress, induction of apoptosis, influences on mitosis, induction of cell cycle arrest, and interference with cytokine pathways. All these mechanisms are associated with nephrotoxicity, hepatotoxicity, teratotoxicity, immunological toxicity, and neurotoxicity. OTA administration activates various mechanisms such as p38 MAPK, JNKs, and ERKs dysfunctions, BDNF disruption, TH overexpression, caspase-3 and 9 activation, and ERK-1/2 phosphorylation which ultimately lead to Alzheimer disease (AD) progression. The current review will focus on OTA in terms of recent discoveries in the field of molecular biology. The main aim is to investigate the underlying mechanisms of OTA in regard to genotoxicity and epigenetic modulations that lead to AD. Also, we will highlight the strategies for the purpose of attenuating the hazards posed by OTA exposure.

Risk assessment of ochratoxin A in food

The European Commission asked EFSA to update their 2006 opinion on ochratoxin A (OTA) in food. OTA is produced by fungi of the genus Aspergillus and Penicillium and found as a contaminant in various foods. OTA causes kidney toxicity in different animal species and kidney tumours in rodents. OTA is genotoxic both in vitro and in vivo; however, the mechanisms of genotoxicity are unclear. Direct and indirect genotoxic and non-genotoxic modes of action might each contribute to tumour formation. Since recent studies have raised uncertainty regarding the mode of action for kidney carcinogenicity, it is inappropriate to establish a health-based guidance value (HBGV) and a margin of exposure (MOE) approach was applied. For the characterisation of non-neoplastic effects, a BMDL 10 of 4.73 μg/kg body weight (bw) per day was calculated from kidney lesions observed in pigs. For characterisation of neoplastic effects, a BMDL 10 of 14.5 μg/kg bw per day was calculated from kidney tumours seen in rats. The estimation of chronic dietary exposure resulted in mean and 95th percentile levels ranging from 0.6 to 17.8 and from 2.4 to 51.7 ng/kg bw per day, respectively. Median OTA exposures in breastfed infants ranged from 1.7 to 2.6 ng/kg bw per day, 95th percentile exposures from 5.6 to 8.5 ng/kg bw per day in average/high breast milk consuming infants, respectively. Comparison of exposures with the BMDL 10 based on the non-neoplastic endpoint resulted in MOEs of more than 200 in most consumer groups, indicating a low health concern with the exception of MOEs for high consumers in the younger age groups, indicating a possible health concern. When compared with the BMDL 10 based on the neoplastic endpoint, MOEs were lower than 10,000 for almost all exposure scenarios, including breastfed infants. This would indicate a possible health concern if genotoxicity is direct. Uncertainty in this assessment is high and risk may be overestimated.

Transcriptome Analysis of Ochratoxin A-Induced Apoptosis in Differentiated Caco-2 Cells

Ochratoxin A (OTA), an important mycotoxin that occurs in food and animal feed, has aroused widespread concern in recent years. Previous studies have indicated that OTA causes nephrotoxicity, hepatotoxicity, genotoxicity, immunotoxicity, cytotoxicity, and neurotoxicity. The intestinal toxicity of OTA has gradually become a focus of research, but the mechanisms underlying this toxicity have not been described. Here, differentiated Caco-2 cells were incubated for 48 h with different concentrations of OTA and transcriptome analysis was used to estimate damage to the intestinal barrier. Gene expression profiling was used to compare the characteristics of differentially expressed genes (DEGs). There were altogether 10,090 DEGs, mainly clustered into two downregulation patterns. The Search Tool for Retrieval of Interacting Genes (STRING), which was used to analyze the protein-protein interaction network, indicated that 24 key enzymes were mostly responsible for regulating cell apoptosis. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis was used to validate eight genes, three of which were key genes (CASP3, CDC25B, and EGR1). The results indicated that OTA dose-dependently induces apoptosis in differentiated Caco-2 cells. Transcriptome analysis showed that the impairment of intestinal function caused by OTA might be partly attributed to apoptosis, which is probably associated with downregulation of murine double minute 2 (MDM2) expression and upregulation of Noxa and caspase 3 (CASP3) expression. This study has highlighted the intestinal toxicity of OTA and provided a genome-wide view of biological responses, which provides a theoretical basis for enterotoxicity and should be useful in establishing a maximum residue limit for OTA.

Ameliorative effect of ursolic acid on ochratoxin A-induced renal cytotoxicity mediated by Lonp1/Aco2/Hsp75

Ochratoxin A (OTA) is a mycotoxin ubiquitous in feeds and foodstuffs. The water-insoluble pentacyclic triterpene bioactive compound, ursolic acid (UA), is widespread in various cuticular waxes of edible fruits, food materials, and medicinal plants. Although studies have reported that oxidative stress was involved in both the nephrotoxicity of OTA and the renoprotective function of UA, the role of stress-responsive Lon protease 1 (Lonp1) in the renoprotection of UA against OTA is still unknown. In this study, cell viability, reactive oxygen species (ROS) production, and several proteins' expressions of human embryonic kidney 293T (HEK293T) cells in response to UA, OTA, and/or Lonp1 inhibitor CDDO-me treatment were detected to reveal the protective mechanism of UA against OTA-induced renal cytotoxicity. Results indicated that a 2 h-treatment of 1 μM UA could significantly alleviate the ROS production and cell death induced by a 24 h-treatment of 8 μM OTA in HEK293T cells (P < 0.05). Compared with the control, the protein expressions of Lonp1, Aco2 and Hsp75 were significantly inhibited after 8 μM OTA treating for 24 h (P < 0.05), which could be notably reversed by the pre-treatment and post-treatment of 1 μM UA (P < 0.05). The protein expressions of Lonp1, Aco2 and Hsp75 were inhibited by the addition of CDDO-me. The three protein expression trends were similar before and after the addition of CDDO-me. In conclusion, OTA could inhibit the expression of Lonp1, suppressing Aco2 and Hsp75 as a result, thereby activating ROS and inducing cell death in HEK293T cells, which could be alleviated by UA pre-treatment.

An in vitro attempt at precision toxicology reveals the involvement of DNA methylation alteration in ochratoxin A-induced G0/G1 phase arrest

Precision toxicology evaluates the toxicity of certain substances by isolating a small group of cells with a typical phenotype of interest followed by a single cell sequencing-based analysis. In this in vitro attempt, ochratoxin A (OTA), a typical mycotoxin and food contaminant, is found to induce G0/G1 phase cell cycle arrest in human renal proximal tubular HKC cells at a concentration of 20 μM after a 24h-treatment. A small number of G0/G1 phase HKC cells are evaluated in both the presence and absence of OTA. These cells are sorted with a flow cytometer and subjected to mRNA and DNA methylation sequencing using Smart-Seq2 and single-cell reduced-representation bisulfite sequencing (scRRBS) technology, respectively. Integrated analysis of the transcriptome and methylome profiles reveals that OTA causes abnormal expression of the essential genes that regulate G1/S phase transition, act as signal transductors in G1 DNA damage checkpoints, and associate with the anaphase-promoting complex/cyclosome. The alteration of their DNA methylation status is a significant underlying epigenetic mechanism. Furthermore, Notch signaling and Ras/MAPK/CREB pathways are found to be suppressed by OTA. This attempt at precision toxicology paves the way for a deeper understanding of OTA toxicity and provides an innovative strategy to researchers in the toxicology and pharmacology field.

MAP3K kinases and kidney injury

Mitogen-activated protein kinases (MAP kinases) are functionally connected kinases that regulate key cellular process involved in kidney disease such as all survival, death, differentiation and proliferation. The typical MAP kinase module is composed by a cascade of three kinases: a MAP kinase kinase kinase (MAP3K) that phosphorylates and activates a MAP kinase kinase (MAP2K) which phosphorylates a MAP kinase (MAPK). While the role of MAPKs such as ERK, p38 and JNK has been well characterized in experimental kidney injury, much less is known about the apical kinases in the cascade, the MAP3Ks. There are 24 characterized MAP3K (MAP3K1 to MAP3K21 plus RAF1, BRAF and ARAF). We now review current knowledge on the involvement of MAP3K in non-malignant kidney disease and the therapeutic tools available. There is in vivo interventional evidence clearly supporting a role for MAP3K5 (ASK1) and MAP3K14 (NIK) in the pathogenesis of experimental kidney disease. Indeed, the ASK1 inhibitor Selonsertib has undergone clinical trials for diabetic kidney disease. Additionally, although MAP3K7 (MEKK7, TAK1) is required for kidney development, acutely targeting MAP3K7 protected from acute and chronic kidney injury; and targeting MAP3K8 (TPL2/Cot) protected from acute kidney injury. By contrast MAP3K15 (ASK3) may protect from hypertension and BRAF inhibitors in clinical use may induced acute kidney injury and nephrotic syndrome. Given their role as upstream regulators of intracellular signaling, MAP3K are potential therapeutic targets in kidney injury, as demonstrated for some of them. However, the role of most MAP3K in kidney disease remains unexplored.

S, Abeer EKM, Ali GI, El-Habashi N. Experimental ochratoxicosis A in Nile tilapia and its amelioration by some feed additives

Ochratoxin A (OTA) formation prevention is not usually available so counteracting strategies are urgent. This study investigated the toxic effects of OTA on Nile tilapia with trials to neutralize these effects by using some feed additives. Supplements used as one percent (Garlen Extra4, Nigella sativa, Garlen Extra4 plus Nigella sativa and a commercial mycotoxins binder, Fero Bind Pro) were added to 500 ppb/kg OTA-contaminated diet. Fish were fed at 3% body weight per day for 10 weeks. The clinical signs recorded in OTA - intoxicated positive control group were sluggish swimming and off food before death with reduction in survivability (53%) and growth performance. Several post-mortem lesions were in liver, kidneys and spleen. Serum levels of ALT, AST, creatinine and urea were significantly increased with reduction in total protein, albumin and globulin in ochratoxicated fish group compared to the negative control group. Concerning the pathological changes that have been noticed in ochratoxin treated fish were almost completely alleviated in examined tissues of fish that were fed on diet with Garlen Extra4 plus Nigella sativa or Nigella sativa and partially in fish that were fed on diet with Garlen Extra4 or Fero Bind Pro, respectively. Best detoxifying results were obtained by using 30 g/kg Nigella sativa plus 0.1 g/kg Garlen Extra4 followed by Nigella sativa, Garlen Extra4 then Fero Bind Pro as a commercial Mycotoxins binder. It could be concluded that inclusions of 30 g/kg Nigella sativa plus 0.1 g/kg Garlen Extra4 in Oreochromis niloticus (O. niloticus) diets could partially reduce OTA toxic effects.

Ochratoxin A induces ER stress and apoptosis in mesangial cells via a NADPH oxidase-derived reactive oxygen species-mediated calpain activation pathway

Ochratoxin A (OTA) contaminated food increases reactive oxygen species (ROS) production in glomerulus and causes glomerulopathy. The molecular mechanisms still remain uncertain. In this study, we used mouse and rat glomerular mesangial cells and delineate the signaling pathway behind the OTA-triggered cell apoptosis. OTA dose-dependently induced expression of ER stress markers including phospho-PERK, phospho-eIF2α, GRP78, GRP94, and CHOP. Apoptosis events including cleavage of caspase-12, caspase-7, and PARP are also observed. OTA activated oxidative stress and increased NADPH oxidase activity. NADPH oxidase inhibitor, apocynin, significantly attenuated OTA-induced cell apoptosis. Moreover, OTA markedly increased the calpain activity which significantly inhibited by apocynin. Transfection of calpain-siRNA effectively inhibited the OTA-increased ER stress-related protein expression. These findings suggest that OTA activated NADPH oxidase and calpain, induced ER stress and ROS production, and caused glomerular mesangial cells apoptosis which leads to glomerulopathy.

A Review: Epigenetic Mechanism in Ochratoxin A Toxicity Studies

Ochratoxin A (OTA) is a natural contaminant that has displayed nephrotoxicity and hepatotoxicity in mammals. It contaminates a great variety of foodstuffs and threatens people's lives. The molecular mechanism of OTA-induced toxicity has been studied since 1965. Moreover, epigenetic mechanisms are also studied in OTA-induced toxicity. Additionally, the mode of OTA epigenetic research has been advanced in research hotspots. However, there is still no epigenetic study of OTA-induced toxicity. In this review, we discuss the relationship between these epigenetic mechanisms and OTA-induced toxicity. We found that studies on the epigenetic mechanisms of OTA-induced toxicity all chose the whole kidney or liver as the model, which cannot reveal the real change in DNA methylation or miRNAs or histone in the target sites of OTA. Our recommendations are as follows: (1) the specific target site of OTA should be detected by advanced technologies; and (2) competing endogenous RNAs (ceRNA) should be explored with OTA.

Toxicity study of ochratoxin A using HEK293 and HepG2 cell lines based on microRNA profiling

Ochratoxin A (OTA) induced DNA damage, cytotoxicity, and apoptosis in mammalian cell lines. Micro RNAs (miRNAs) are involved in physiological and developmental processes and contribute to cancer development and progression. In our study, high-throughput miRNA profiling and Kyoto Encyclopedia of Genes and Genomes analysis were applied to comparatively study the toxicity of OTA in HEK293 cells and HepG2 cells treated with 25 μM OTA for 24 h. In these two cells, the same changing miRNAs were mostly related to signal transduction pathways, whereas the different changing miRNAs were mostly related to human cancer pathways. DGCR8, Dicer1, and Drosha were significantly suppressed in HEK293 cells, indicating an impairment of miRNA biogenesis. The damage seemed more extensive in HEK293 cells. Cell models and in vivo models were also compared. Many miRNAs in vitro were markedly different from those in vivo; however, OTA toxicity was observed both in vitro and in vivo. The classification of deregulated pathways is similar. The biogenesis of miRNA was impaired in both lines. In conclusion, deregulated miRNAs in vitro are mostly related to human cancer and signal transduction pathways. The deregulated pathways in vivo are similar to those in vitro.

Ochratoxin A: Molecular Interactions, Mechanisms of Toxicity and Prevention at the Molecular Level

Ochratoxin A (OTA) is a widely-spread mycotoxin all over the world causing major health risks. The focus of the present review is on the molecular and cellular interactions of OTA. In order to get better insight into the mechanism of its toxicity and on the several attempts made for prevention or attenuation of its toxic action, a detailed description is given on chemistry and toxicokinetics of this mycotoxin. The mode of action of OTA is not clearly understood yet, and seems to be very complex. Inhibition of protein synthesis and energy production, induction of oxidative stress, DNA adduct formation, as well as apoptosis/necrosis and cell cycle arrest are possibly involved in its toxic action. Since OTA binds very strongly to human and animal albumin, a major emphasis is done regarding OTA-albumin interaction. Displacement of OTA from albumin by drugs and by natural flavonoids are discussed in detail, hypothesizing their potentially beneficial effect in order to prevent or attenuate the OTA-induced toxic consequences.