Central role of Nix in the autophagic response to ochratoxin A

Sinapic Acid Attenuates Chronic DSS-Induced Intestinal Fibrosis in C57BL/6J Mice by Modulating NLRP3 Inflammasome Activation and the Autophagy Pathway

Ulcerative colitis (UC) is a chronic gastrointestinal disease that results from repeated inflammation and serious complications. Sinapic acid (SA) is a hydroxycinnamic acid present in a variety of plants that has antioxidant, anti-inflammatory, anticancer, and other protective effects. This study investigated the antifibrotic effect of SA on chronic colitis induced by dextran sulfate sodium salt (DSS) in mice. We observed that SA could significantly reduce clinical symptoms (such as improved body weight loss, increased colon length, and decreased disease activity index score) and pathological changes in mice with chronic colitis. SA supplementation has been demonstrated to repair intestinal mucosal barrier function and maintain epithelial homeostasis by inhibiting activation of the NLRP3 inflammasome and decreasing the expression of IL-6, TNF-α, IL-17A, IL-18, and IL-1β. Furthermore, SA could induce the expression of antioxidant enzymes (Cat, Sod1, Sod2, Mgst1) by activating the Nrf2/keap1 pathway, thus improving antioxidant capacity. Additionally, SA could increase the protein expression of downstream LC3-II/LC3-I and Beclin1 and induce autophagy by regulating the AMPK-Akt/mTOR signaling pathway, thereby reducing the production of intestinal fibrosis-associated proteins Collagen-I and α-SMA. These findings suggest that SA can enhance intestinal antioxidant enzymes, reduce oxidative stress, expedite intestinal epithelial repair, and promote autophagy, thereby ameliorating DSS-induced colitis and intestinal fibrosis.

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.

Lonp1 and Sig-1R contribute to the counteraction of ursolic acid against ochratoxin A-induced mitochondrial apoptosis

Ochratoxin A (OTA), a secondary fungal metabolite with nephrotoxicity, is widespread in numerous kinds of feeds and foodstuffs. Ursolic acid (UA), a water-insoluble pentacyclic triterpene acid, exists in a wide range of food materials and medicinal plants. Our earlier researches provided preliminary evidence that mitochondria- and mitochondria-associated endoplasmic reticulum membranes (MAMs)-located stress-responsive Lon protease 1 (Lonp1) had a protective function in OTA-induced nephrotoxicity, and the renoprotective function of UA against OTA partially due to Lonp1. However, whether other MAMs-located protiens, such as endoplasmic reticulum stress (ERS)-responsive Sigma 1-type opioid receptor (Sig-1R), contribute to the protection of UA against OTA-induced nephrotoxicity together with Lonp1 needs further investigation. In this study, the cell viability, reactive oxygen species, and protein expressions of human proximal tubule epithelial-originated kidney-2 (HK-2) cells varied with OTA and/or UA/CDDO-me/AVex-73/Sig-1R siRNA treatments were determined. Results indicated that a 24 h-treatment of 5 μM OTA could significantly induce mitochondrial-mediated apoptosis via repressing Lonp1 and Sig-1R, thereby enhancing the protein expressions of GRP78, p-PERK, p-eIF2α, CHOP, IRE1α, and Bax, and inhibiting the protein expression of Bcl-2 in HK-2 cells, which could be remarkably relieved by a 2 h-pre-treatment of 4 μM UA (P < 0.05). In conclusion, through mutual promotion between Lonp1 and Sig-1R, UA could effectively relieve OTA-induced apoptosis in vitro and break the vicious cycle between oxidative stress and ERS, which activated the mitochondrial apoptosis pathway.

MicroRNA regulates the toxicological mechanism of four mycotoxins in vivo and in vitro

Mycotoxins can cause body poisoning and induce carcinogenesis, often with a high mortality rate. Therefore, it is of great significance to seek new targets that indicate mycotoxin activity and to diagnose and intervene in mycotoxin-induced diseases in their early stages. MicroRNAs (miRNAs) are physiological regulators whose dysregulation is closely related to the development of diseases. They are thus important markers for the occurrence and development of diseases. In this review, consideration is given to the toxicological mechanisms associated with four major mycotoxins (ochratoxin A, aflatoxin B1, deoxynivalenol, and zearalenone). The roles that miRNAs play in these mechanisms and the interactions between them and their target genes are explained, and summarize the important role of histone modifications in their toxicity. As a result, the ways that miRNAs are regulated in the pathogenicity signaling pathways are revealed which highlights the roles played by miRNAs in preventing and controlling the harmful effects of the mycotoxins. It is hoped that this review will provide a theoretical basis for the prevention and control of the damage caused by these mycotoxins.

Selenomethionine alleviated Ochratoxin A induced pyroptosis and renal fibrotic factors expressions in MDCK cells

Ochratoxin A (OTA) is universally known to induce nephrotoxicity via inducing oxidative stress and apoptosis, inhibiting protein synthesis and activating autophagy. Our previous studies have proved that OTA induces nephrotoxicity in vitro and in vivo by adjusting the NOD-like receptor protein 3 (NLRP3) inflammasome activation and caspase-1-dependent pyroptosis. Based on these findings, we further investigated the protective role of selenomethionine (SeMet) on OTA-caused nephrotoxicity using the Madin-Darby canine kidney (MDCK) epithelial cells as an in vitro model, proposing to offer a new way for remedying OTA-induced nephrotoxicity by nutritional manipulation. We measured the cell vitality, lactate dehydrogenase (LDH) activity and the expression of renal fibrotic genes, NLRP3 inflammasome and pyroptosis related genes. MTT and LDH results indicated that SeMet supplementation significantly mitigated 2.0 μg/ml OTA-induced cytotoxicity in MDCK cells (p < 0.05). Meanwhile, SeMet alleviated OTA induced increase of reactive oxygen species in MDCK cells. Then, the expressions of α-SMA, Vimentin, and TGF-β were detected both in mRNA and protein levels. The results indicated 8 μM SeMet supplementation could significantly downregulate the expression of OTA-induced renal fibrosis-related genes (p < 0.05). In addition, the upregulation of OTA-induced NLRP3 inflammasome and pyroptosis downstream genes was also significantly inhibited by 8 μM of SeMet (p < 0.05). In summary, SeMet could alleviate OTA-induced renal fibrotic genes expression and reduce NLRP3-caspase-1-dependent pyroptosis. Therefore, SeMet supplementation may become an effective approach for preserving animals from renal injury exposed to OTA.

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.

Degradation of ochratoxin A by supernatant and ochratoxinase of Aspergillus niger W-35 isolated from cereals

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus spp. and Penicillium spp. and poses a threat to food safety. Biodegradation may be a promising strategy for reducing the OTA contamination in the future. In this study, Aspergillus niger strain W-35 was isolated from cereals and studied for its ability to degrade OTA. Results showed that the supernatant of W-35 could degrade OTA both in vitro and in commercial feeds after incubation at 37 °C for 12 h by 78.0 and 37.0%, respectively. Ochratoxin α (OTα) was assayed as a degradation product by HPLC-FLD. Furthermore, an enzyme specific for OTA degradation (ochratoxinase, OTase) obtained from W-35 was successfully expressed in Escherichia coli BL21, and degraded OTA at a rate of 85.1% for 12 h. These results indicated that this OTA degradation is enzymatic and that the responsible enzyme is extracellular OTase. Reliable degradation of OTA has the potential for wide-ranging applications in the food and feed industries.

Nobiletin Triggers Reactive Oxygen Species-Mediated Pyroptosis through Regulating Autophagy in Ovarian Cancer Cells

Ovarian cancer is one of the most serious female malignancies worldwide. Despite intensive efforts being made to overcome ovarian cancer, there still remain limited optional treatments for this disease. Nobiletin, a prospective food-derived phytochemical extracted from citrus fruits, has recently been reported to suppress ovarian cancer cells, but the role of pyroptosis in ovarian carcinoma with nobiletin still remains unknown. In this study, we aim to explore the effect of nobiletin on ovarian carcinoma and further expound the underlying mechanisms of nobiletin-induced ovarian cancer cell death. Our results showed that nobiletin could significantly inhibit cell proliferation, induce DNA damage, and also lead to apoptosis by increasing the cleaved poly (ADP-ribose) polymerase (PARP) level of human ovarian cancer cells (HOCCs) in a dose-dependent manner. Moreover, we revealed that nobiletin decreased mitochondrial membrane potential and induced reactive oxygen species (ROS) generation and autophagy of HOCCs, contributing to gasdermin D-/gasdermin E-mediated pyroptosis. Taken together, nobiletin as a functional food ingredient represents a promising new anti-ovarian cancer candidate that could induce apoptosis and trigger ROS-mediated pyroptosis through regulating autophagy in ovarian cancer cells.

Ochratoxin A Sequentially Activates Autophagy and the Ubiquitin-Proteasome System

Ochratoxin A (OTA) is a carcinogenic mycotoxin, which is produced by Aspergillus and Penicillium genera of fungi and commonly contaminates food and feed. We and others have previously shown that OTA causes sustained activation of PI3K/AKT and MAPK/ERK1-2 signaling pathways in different cell types and animal models. Given the close relationship between cellular signaling activity and protein stability, we were curious whether increased PI3K/AKT and MAPK/ERK1-2 signaling may be the result of OTA-stimulated alterations in proteolytic activity. We show that both of the major proteolytic systems, autophagy, and the ubiquitin-proteasome system (UPS), are activated upon OTA exposure in human kidney proximal tubule HK-2 and mouse embryonic fibroblast (MEF) cells. OTA stimulates transient autophagic activity at early time points of treatment but autophagic activity subsides after 6 h even in the sustained presence of OTA. Interestingly, OTA exposure also results in increased cell death in wild-type MEF cells but not in autophagy-halted Atg5-deficient cells, suggesting that autophagy exerts a pro-death effect on OTA-induced cytotoxicity. In addition, prolonged OTA exposure decreased ubiquitinated protein levels by increasing proteasomal activity. Using purified and cellular proteasomes, we observed enhanced chymotrypsin-, caspase-, and trypsin-like activities of the 26S but not the 20S proteasome in the presence of OTA. However, in the cellular context, increased proteasomal activity depended on prior induction of autophagy. Our results suggest that autophagy and subsequent UPS activation are responsible for sustained activation of PI3K/AKT and MAPK/ERK1-2 pathways through regulating the levels of critical phosphatases VHR/DUSP3, DUSP4, and PHLPP, which are known to be involved in OTA toxicity and carcinogenicity.

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.

Ochratoxin A causes mitochondrial dysfunction, apoptotic and autophagic cell death and also induces mitochondrial biogenesis in human gastric epithelium cells

Ochratoxin A (OTA) is a common natural contaminant found in human and animal food worldwide. Our previous work has shown that OTA can cause oxidative DNA damage, G₂ arrest and malignant transformation of human gastric epithelium (GES-1) cells. Mitochondria are considered to be target for the action of many cytotoxic agents. However, the role of mitochondria in the cytotoxicity of OTA remains unknown. The aim of this study is to explore the putative role of mitochondria on OTA cytotoxicity by analyzing mitochondrial changes in GES-1 cells. The results showed that OTA treatment (5, 10, 20 µM) for different times caused increases in the production of reactive oxygen species, and induced mitochondrial damage, shown by loss of mitochondrial membrane potential (ΔΨM), and decrease in cellular ATP concentration. Subsequently, the mitochondrial apoptotic pathway was activated, presented by increase of apoptotic rate and activation of apoptotic proteins. Autophagic cell death was also triggered, demonstrated by the conversion of light chain 3B (LC3B)-I to LC3B-II and elevated levels of green fluorescent protein-LC3 (GFP-LC3) puncta. Moreover, Parkin-dependent mitophagy was also activated presented by the colocalization of MitoTracker with LysoTracker or GFP-LC3 puncta. The inhibition of autophagy and mitophagy by inhibitors or siRNA attenuated the toxic effect of OTA on cell growth. Interestingly, OTA treatment also enhanced mitochondrial biogenesis confirmed by activation of AMPK/PGC-1α/TFAM pathway and promoted cell survival. Collectively, the effects of OTA on mitochondria of GES-1 cells are complex. OTA could cause mitochondrial function disturbance, apoptotic and autophagic cell death and also induce mitochondrial biogenesis.

PCV2 replication promoted by oxidative stress is dependent on the regulation of autophagy on apoptosis

Porcine circovirus type 2 (PCV2) is an economically important swine pathogen but some extra trigger factors are required for the development of PCV2-associated diseases. By evaluating cap protein expression, viral DNA copies and the number of infected cells, the present study further confirmed that oxidative stress can promote PCV2 replication. The results showed that oxidative stress induced autophagy in PCV2-infected PK15 cells. Blocking autophagy with inhibitor 3-methyladenine or ATG5-specific siRNA significantly inhibited oxidative stress-promoted PCV2 replication. Importantly, autophagy inhibition significantly increased apoptosis in oxidative stress-treated PK15 cells. Suppression of apoptosis by benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone in conditions of autophagy inhibition restored PCV2 replication. Taken together, autophagy protected host cells against potential apoptosis and then contributed to PCV2 replication promotion caused by oxidative stress. Our findings can partly explain the pathogenic mechanism of PCV2 related to the oxidative stress-induced autophagy.

Endoplasmic reticulum stress contributes to the pathogenesis of stress urinary incontinence in postmenopausal women

Objective

To investigate the relationship between endoplasmic reticulum stress (ERS) and the pathogenesis of stress urinary incontinence (SUI) in postmenopausal women.

Methods

Anterior vaginal wall tissue was collected from postmenopausal women with SUI and control subjects. Western blotting was performed for glucose-regulated protein (GRP78), inositol-requiring enzyme 1(IRE1), protein kinase-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), C/EBP-homologous protein (CHOP), and B-cell lymphoma 2 (Bcl-2). Additionally, mRNA expression levels of PERK, activating transcription factor 4 (ATF4), and CHOP were examined by real-time polymerase chain reaction.

Results

GRP78 protein and mRNA expression levels were significantly lower in women with SUI, compared with control subjects. PERK and p-PERK expression levels were higher in women with SUI than in control subjects. However, no differences in IRE1 or ATF6 expression levels were observed in either group. Notably, higher CHOP and lower Bcl-2 protein expression levels were detected in women with SUI, compared with control subjects. Furthermore, PERK, ATF4, and CHOP mRNA expression levels were significantly higher in women with SUI than in control subjects.

Conclusions

Alterations of ERS markers in SUI suggest that ERS may be involved in the development of SUI in postmenopausal women.

Ochratoxin A induces cytoprotective autophagy via blocking AKT/mTOR signaling pathway in PK-15 cells

Ochratoxin A (OTA) could cause a variety of toxicological effects especially nephrotoxicity in animals and humans. Autophagy is a highly conserved metabolic process that plays an important role in the maintenance of cellular homeostasis under stress. However, the role of autophagy in OTA-induced nephrotoxicity is unknown. In the present study, we demonstrated that OTA treatment at 2.0-8.0 μM could increase cytotoxicity of PK-15 cells by inducing apoptosis as shown by the increased Annexin V/PI staining, increased caspase-3 and PARP cleavage and increased apoptotic nuclei. Meantime, autophagy was triggered when OTA was administrated, as indicated by markedly increased expressions of LC3-II, ATG5 and Beclin-1, accumulation of GFP-LC3 dots and increased double- or single-membrane vesicles. OTA treatment decreased p-AKT and p-mTOR activities, and OTA-induced autophagy was inhibited when insulin was applied. Furthermore, OTA treatments with autophagy inhibitors (3-methyladenine or chloroquine) or knockdown of autophagy-related genes (ATG5 or Beclin-1) resulted in significantly reduced autophagy level and enhanced cytotoxicity. In conclusion, OTA induces cytoprotective autophagy against its cytotoxicity and inactivation of AKT/mTOR axis plays a critical role in autophagy induction.

Advances in Biodetoxification of Ochratoxin A-A Review of the Past Five Decades

Ochratoxin A (OTA) is a toxic secondary fungal metabolite that widely takes place in various kinds of foodstuffs and feeds. Human beings and animals are inevitably threatened by OTA as a result. Therefore, it is necessary to adopt various measures to detoxify OTA-contaminated foods and feeds. Biological detoxification methods, with better safety, flavor, nutritional quality, organoleptic properties, availability, and cost-effectiveness, are more promising than physical and chemical detoxification methods. The state-of-the-art research advances of OTA biodetoxification by degradation, adsorption, or enzymes are reviewed in the present paper. Researchers have discovered a good deal of microorganisms that could degrade and/or adsorb OTA, including actinobacteria, bacteria, filamentous fungi, and yeast. The degradation of OTA to non-toxic or less toxic OTα via the hydrolysis of the amide bond is the most important OTA biodegradation mechanism. The most important influence factor of OTA adsorption capacity of microorganisms is cell wall components. A large number of microorganisms with good OTA degradation and/or adsorption ability, as well as some OTA degradation enzymes isolated or cloned from microorganisms and animal pancreas, have great application prospects in food and feed industries.

Protective mechanisms involving enhanced mitochondrial functions and mitophagy against T-2 toxin-induced toxicities in GH3 cells

T-2 toxin is the most toxic member of trichothecene mycotoxin. So far, the mechanism of mitochondrial toxicity and protective mechanism in mammalian cells against T-2 toxin are not fully understood. In this study, we aimed to investigate the cellular and mitochondrial toxicity of T-2 toxin, and the cellular protective mechanisms in rat pituitary GH3 cells. We showed that T-2 toxin significantly increased reactive oxygen species (ROS) and DNA damage and caused apoptosis in GH3 cells. T-2 toxin induced abnormal cell morphology, cytoplasm and nuclear shrinkage, nuclear fragmentation and formation of apoptotic bodies and autophagosomes. The mitochondrial degradative morphologies included local or total cristae collapse and small condensed mitochondria. T-2 toxin decreased the mitochondrial membrane potential. However, T-2 toxin significantly increased the superoxide dismutase (SOD) activity and expression of antioxidant genes glutathione peroxidase 1 (GPx-1), catalase (CAT), mitochondria-specific SOD-2 and mitochondrial uncoupling protein-1, -2 and -3 (UCP-1, 2 and 3). Interestingly, T-2 toxin increased adenosine triphosphate (ATP) levels and mitochondrial complex I activity, and increased the expression of most of mitochondrial electron transport chain subunits tested and critical transcription factors controlling mitochondrial biogenesis and mitochondrial DNA transcription and replication. T-2 toxin increased mitophagic activity by increasing the expression of mitophagy-specific proteins NIP-like protein X (NIX), PTEN-induced putative kinase protein 1 (PINK1) and E3 ubiquitin ligase Parkin. T-2 toxin activated the protective protein kinase A (PKA) signaling pathway, which activated the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/PINK1/Parkin pathway to mediate mitophagy. Taken together, our results suggested that the mammalian cells could increase their resistance against T-2 toxin by increasing the antioxidant activity, mitophagy and mitochondrial function.

Ochratoxin A-induced autophagy in vitro and in vivo promotes porcine circovirus type 2 replication

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium. Porcine circovirus type 2 (PCV2) is recognized as the causative agent of porcine circovirus-associated diseases. Recently, we reported that low doses of OTA promoted PCV2 replication in vitro and in vivo, but the underlying mechanism needed further investigation. The present studies further confirmed OTA-induced PCV2 replication promotion as measured by cap protein expression, viral titer, viral DNA copies and the number of infected cells. Our studies also showed that OTA induced autophagy in PK-15 cells, as assessed by the markedly increased expression of microtubule-associated protein 1 light chain 3 (LC3)-II, autophagy-related protein 5 (ATG5), and Beclin-1 and the accumulation of green fluorescent protein (GFP)-LC3 dots. OTA induced complete autophagic flux, which was detected by monitoring p62 degradation and LC3-II turnover using immunoblotting. Inhibition of autophagy by 3-methylademine (3-MA) and chloroquine (CQ) significantly attenuated OTA-induced PCV2 replication promotion. The observed phenomenon was further confirmed by the knock-down of ATG5 or Beclin-1 by specific siRNA. Further studies showed that N-acetyl-L-cysteine (NAC), an ROS scavenger could block autophagy induced by OTA, indicating that ROS may be involved in the regulation of OTA-induced autophagy. Furthermore, we observed significant increases in OTA concentrations in lung, spleen, kidney, liver and inguinal lymph nodes (ILN) and bronchial lymph nodes (BLN) of pigs fed 75 and 150 μg/kg OTA compared with controls in vivo. Administration of 75 μg/kg OTA significantly increased PCV2 replication and autophagy in the lung, spleen, kidney and BLN of pigs. Taken together, it could be concluded that OTA-induced autophagy in vitro and in vivo promotes PCV2 replication.

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.

miR-122 plays an important role in ochratoxin A-induced hepatocyte apoptosis in vitro and in vivo

OTA can induce hepatotoxicity. Our previous research has shown that miRNAs play important roles in the OTA-induced hepatotoxicity. And miR-122 is the most abundant miRNA in the liver and is involved in diverse biological processes. This study was performed to clarify the role of miR-122 in OTA-induced hepatotoxicity. The expression levels of miR-122 and the target genes were quantified by real-time PCR. The OTA-induced apoptosis of hepatocyte and HepG2 cells was evaluated using a TUNEL kit, a CCK-8 kit, a flow cytometer and Hoechst 33342. miR-122 was inhibited in HepG2 cells. The results revealed that OTA affected rat hepatocyte apoptosis. miR-122 decreased at 4 weeks but increased at 13 weeks in the OTA-treated livers, and increased in the OTA-treated HepG2 cells; and the mRNA levels of CCNG1 and Bcl-w increased at 4 weeks and decreased at 13 weeks in the high-dose OTA-treatment groups and decreased in HepG2 cells. The apoptosis of HepG2 cells displayed a dose-related increase with OTA. However, the inhibition of miR-122 greatly reduced OTA-induced apoptosis. p53 decreased in vivo and in vitro. miR-122 is a primary effector of OTA-induced hepatocyte apoptosis through the CCNG1/p53 pathway and Bcl-w/caspase-3 pathway in vivo and in vitro. And miR-122 plays an important role in OTA-induced hepatotoxicity.