Ochratoxin A Toxicity Research Articles

Ochratoxin A induces nephrotoxicity and immunotoxicity through different MAPK signaling pathways in PK15 cells and porcine primary splenocytes

Ochratoxin A (OTA) is reported to be a potent nephrotoxin and immunotoxin in animals and humans. However, the mechanisms underlying OTA toxicity have not been clearly determined until now. Toxicity of OTA and its mechanism was investigated in PK15 cells and in porcine primary splenocytes. The results showed that OTA at 2.0–8.0 μg/mL for 24 h induced cytotoxicity and apoptosis in a dose-dependent manner in PK 15 cells. OTA at 0.5–4.0 μg/mL for 24 h induced cytotoxicity and apoptosis in a dose-dependent manner in porcine primary splenocytes. In addition, OTA induced p38 and ERK1/2 phosphorylation both in PK15 cells and porcine primary splenocytes. Knock-down of p38 instead of ERK by their specific siRNA significantly eliminated the nephrotoxicity induced by OTA. Contrary, knock-down of ERK1/2 instead of p38 by their specific siRNA significantly eliminated the immunotoxicity induced by OTA. The observed effects indicate that OTA induced nephrotoxicity by p38 signaling pathway in PK15 cells and immunotoxicity by ERK signaling pathway in porcine primary splenocytes.

Ochratoxin A induced premature senescence in human renal proximal tubular cells.

Ochratoxin A (OTA) has many nephrotoxic effects and is a promising compound for the study of nephrotoxicity. Human renal proximal tubular cells (HKC) are an important model for the study of renal reabsorption, renal physiology and pathology. Since the induction of OTA in renal senescence is largely unknown, whether OTA can induce renal senescence, especially at a sublethal dose, and the mechanism of OTA toxicity remain unclear. In our study, a sublethal dose of OTA led to an enhanced senescent phenotype, β-galactosidase staining and senescence associated secretory phenotype (SASP). Cell cycle arrest and cell shape alternations also confirmed senescence. In addition, telomere analysis by RT-qPCR allowed us to classify OTA-induced senescence as a premature senescence. Western blot assays showed that the p53-p21 and the p16-pRB pathways and the ezrin-associated cell spreading changes were activated during the OTA-induced senescence of HKC. In conclusion, our results demonstrate that OTA promotes the senescence of HKC through the p53-p21 and p16-pRB pathways. The understanding of the mechanisms of OTA-induced senescence is critical in determining the role of OTA in cytotoxicity and its potential carcinogenicity.

Ochratoxin A cytotoxicity on Madin-Darby canine kidney cells in the presence of alpha-tocopherol: Effects on cell viability and tight junctions.

Ochratoxin A (OTA) is a potent nephrotoxic fungi metabolite that affects animal and human health. At the cellular level, OTA is able to alter functions and viability by several mechanisms of action. Several strategies to counteract its toxicity have been studied. We investigated the role of α-tocopherol in counteracting OTA oxidative damage in Madin-Darby canine kidney (MDCK) cells by pre-incubating the cells for 3hr with the antioxidant (1nm, 10μm) and then adding OTA (0-1.2μg/ml) for the following 24hr. Cell viability, lactate dehydrogenase (LDH) release, TUNEL staining and occludin and Zo1 localization by immunofluorescence were determined. Here, 1nm α-tocopherol was shown to significantly reduce (p<.05) the cytotoxicity, LDH release and apoptotic rate induced by OTA. The presence of the antioxidant at the same concentration maintained the localization of occludin and Zo1 in the rim of the MDCK cells after the 24-hr OTA exposure. These results indicate that a low concentration of α-tocopherol could block OTA toxicity, supporting its defensive role in the cellular membrane.

Effect of heme oxygenase-1 on ochratoxin A-induced nephrotoxicity in mice

Heme oxygenase-1 (HO-1), a heme-degrading enzyme, is suggested to play an important role in kidney pathophysiology, mostly due to its anti-fibrotic, anti-apoptotic and anti-oxidant properties. One of the mycotoxin, ochratoxin A (OTA) was previously shown to affect HO-1 expression, however, the mechanisms of OTA-induced nephrotoxicity during HO-1 deficiency are unknown.We have shown that OTA regulates the number of pro-fibrotic, pro-inflammatory, anti-oxidative and pro-apoptotic factors in HO-1 dependent manner, as the lack of HO-1 accelerates whereas the induction of HO-1 expression by cobalt protoporphyrin (CoPP) attenuates nephrotoxic effect of OTA. The down-regulation of the nuclear factor-erythroid-2- related factor 2 (Nrf2) transcription factor by OTA, observed in HO-1 knock-out animals, might be another mechanism of OTA toxicity. Moreover, HO-1 level and OTA treatment influences the expression of microRNAs. Namely, p53-regulated miR-34a and pro-fibrotic miR-21 were already increased in HO-1−/− kidneys and were further induced by OTA administration, whereas anti-fibrotic miR-29c was down-regulated by this mycotoxin.Our study indicates that complex mechanisms of OTA nephrotoxicity may be partially overcome by HO-1 induction.

The effect of Ochratoxin A on antimicrobial polypeptide expression and resistance to water mold infection in channel catfish (Ictalurus punctatus)

Mycotoxin contamination of agricultural commodities poses a serious risk to animal health, including aquaculture species. Ochratoxin A (OA) is the most immunotoxic ochratoxin, yet little is known about its effect on immune function in fish. Antimicrobial polypeptides (AMPPs) are one of the most potent, innate, host defense factors, yet very little is known about what types of chronic stressors affect their expression. Among the most prevalent and potent AMPPs in fish are histone-like proteins (HLPs). In this study, fish were fed 2, 4, or 8 mg OA/kg diet. Skin antibacterial activity and HLP-1 levels were measured on Days 0, 28 and 56. Feeding 2, 4 or 8 mg OA/kg diet resulted in significant growth depression, but higher levels (4 or 8 mg OA/kg diet) resulted in lowering feed intake (FI) and impaired feed conversion ratio. In addition, feeding 8 mg OA/kg diet increased susceptibility to experimental water mold (Saprolegnia) challenge, suggesting that OA toxicity might contribute to some saprolegnosis outbreaks. However, there were no changes in AMPP expression in any treatment group. Our data suggests that the increased disease susceptibility of channel catfish due to OA is probably due to mechanisms other than a direct effect on antimicrobial polypeptide expression.

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

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

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.

EVALUATE THE ABILITY OF DIETARY ACTIVE YEAST TO ALLEVIATE NEGATIVE EFFECT OF OCHRATOXIN A (OTA) ON NILE TILAPIA (OREOCHROMIS NILOTICUS) FINGERLINGS

Ochratoxin A (OTA) is one of the most abundant mycotoxins in fish diets and cause a severe loss in fish body weight and suppression of immune responses. The present study was conducted to evaluate the ability of dietary active yeast (Saccharomyces cerevisiae) to alleviate the drastic effect of OTA on Nile tilapia (Oreochromis niloticus) fingerlings (23.39 ± 0.16 g). Six experimental treatments were applied in 18 circular fiberglass tanks (0.5 m3;three tanks per treatment). The treatments were: control, yeast supplementation (0.5 g kg-1 diets), low OTA dose (LOTA; 80 µg kg-1 bwt), high OTA dose (HOTA; 160 µg kg-1 bwt), LOTA plus yeast and HOTA plus yeast. The OTA doses applied as a single dose on the first day of the experiment by stomach intubation, then the experiment lasted for 8 weeks. All treatments were vaccinated with Aeromonas hydrophila bacterin after one month of OTA treatments. Results indicated that OTA caused a significant reduction in final bwt, weight gain, average daily gain and significant deterioration of feed conversion ratio (FCR) in a dose dependent manner compared to the control group. The survival rate decreased by 10 and 26.67% with low and high OTA doses, respectively than the control group. WBCs, lymphocytes, phagocytic activity, phagocytic index, total protein, albumin and globulin decreased significantly with both of OTA doses. Antibody titer was reduced significantly with OTA treatments in a dose dependent manner and the significant effect of OTA in high dose appeared after two weeks of vaccination compared to control. The histology of liver and posterior kidney revealed that there was an increase in the incidence and severity of histopathological lesions in a dose dependent manner. However, dietary yeast alone improved significantly growth performance, survival rate, FCR, and stimulated both innate and adaptive immune responses, also, didn’t show histological changes in tested organs. The yeast supplementation to OTA treated fish overcomes successfully the drastic effect of OTA on the all previous mentioned parameters. In conclusion, OTA causes interruption of Nile tilapia performance, suppression of innate and adaptive immune response, whereas, active yeast supplementation showed a protective effect of active yeast against the OTA toxicity.

Teratogenicity of Ochratoxin A and the Degradation Product, Ochratoxin α, in the Zebrafish (Danio rerio) Embryo Model of Vertebrate Development

Ochratoxins, and particularly ochratoxin A (OTA), are toxic fungal-derived contaminants of food and other agricultural products. Growing evidence supports the degradation of OTA by chemical, enzymatic and/or microbial means as a potential approach to remove this mycotoxin from food products. In particular, hydrolysis of OTA to ochratoxin α (OTα) and phenylalanine is the presumptive product of degradation in most cases. In the current study, we employed the zebrafish (Danio rerio) embryo, as a model of vertebrate development to evaluate, the teratogenicity of OTA and OTα. These studies show that OTA is potently active in the zebrafish embryo toxicity assay (ZETA), and that toxicity is both concentration- and time-dependent with discernible and quantifiable developmental toxicity observed at nanomolar concentrations. On the other hand, OTα had no significant effect on embryo development at all concentrations tested supporting a decreased toxicity of this degradation product. Taken together, these results suggest that ZETA is a useful, and highly sensitive, tool for evaluating OTA toxicity, as well as its degradation products, toward development of effective detoxification strategies. Specifically, the results obtained with ZETA, in the present study, further demonstrate the toxicity of OTA, and support its degradation via hydrolysis to OTα as an effective means of detoxification.

Nephropathy and hepatopathy in weaned piglets provoked by natural ochratoxin A and involved mechanisms

Ochratoxin A (OTA) contamination is a worldwide problem in pig industry. The objectives of the present study were to investigate the toxicity of natural OTA in weaned piglets and to further explore the underlying mechanisms. Totally, 36 crossbred ([Landrace×Yorkshire]×Duroc) piglets were randomly divided into 3 groups (three replicates per group, 4 piglets per replicate), and fed a basal diet (Con group) and basal diets added with 0.4mg (OTA-L group) or 0.8mg OTA/kg (OTA-H group), respectively for 42 days. The results showed that growth performance was significantly decreased (P<0.05) in OTA added groups compared with Con group. OTA concentration was relatively high in serum and OTA concentration in kidney was higher than in liver, respectively. AST, creatinine and urea in serum of OTA added groups were significantly increased (P<0.05), while glucose, total protein, albumin and globulin in serum of OTA added groups were significantly decreased (P<0.05) compared with Con group. Degenerative changes were observed in the epithelial cells of proximal tubules and in hepatocytes of OTA added groups. Antioxidant capacities in blood of OTA added groups and in kidney of OTA-H group were significantly decreased (P<0.05) compared with Con group. The mRNA expressions of bcl-2 were up-regulated, mRNA expressions of bax were down-regulated and the ratio of bcl-2 and bax was increased in kidney and liver of OTA added groups compared with Con group. In conclusion, OTA could reduce antioxidant capacity and suppress apoptosis in tissues and cause degenerative changes in the epithelial cells in proximal tubules and hepatic cells, which may have a negative effect on the growth performance of piglets.

Ochratoxin A-induced cytotoxicity, genotoxicity and reactive oxygen species in kidney cells: An integrative approach of complementary endpoints

Ochratoxin A (OTA) is a well-known nephrotoxic and potential carcinogenic agent but no consensus about the molecular mechanisms underlying its deleterious effects has been reached yet. The aim of this study is to integrate several endpoints concerning OTA-induced toxicological effects in Vero kidney cells in order to obtain additional mechanistic data, especially regarding the influence of reactive oxygen species (ROS). One innovative aspect of this work is the use of the superoxide dismutase mimic (SODm) MnTnHex-2-PyP as a mechanistic tool to clarify the involvement of oxidative stress in OTA toxicity. The results showed concentration and time-dependent cytotoxic effects of OTA (crystal violet, neutral red and LDH leakage assays). While the SODm mildly increased cell viability, trolox and ascorbic acid had no effect with regards to this endpoint. OTA induced micronuclei formation. Using the FPG modified comet assay, OTA modestly increased the % of DNA in tail, revealing the presence of oxidative DNA lesions. This mycotoxin increased apoptosis, which was attenuated by SODm. In addition, the SODm decreased the ROS accumulation observed in DHE assay. Taken together, our data suggest that ROS partially contribute to the cytotoxicity and genotoxicity of OTA, although other mechanisms may be relevant in OTA-induced deleterious effects.

In vitro exposure of Penicillium mycotoxins with or without a modified yeast cell wall extract (mYCW) on bovine macrophages (BoMacs).

Penicillium mycotoxins (PMs) are contaminants that are frequently found in grain or crop-based silage for animal feed. Previously, we have characterized the potential immunotoxicity of the following PMs: citrinin (CIT), ochratoxin A (OTA), patulin (PAT), mycophenolic acid (MPA), and penicillic acid (PA) by using a bovine macrophage cell line (BoMacs). In the present study, cell proliferation was used as a bioassay endpoint to evaluate the efficacy of a modified yeast cell wall extract (mYCW), for preventing PM toxicity under various in vitro conditions such as the following: pH (3, 5, 7), incubation time (1, 2, 4, 6 h), percentage of mYCW (0.05, 0.1, 0.2, 0.5, 1.0 %), and PM concentration. mYCW was most effective in preventing the toxicity of 12.88 and 25.8 μM OTA at pH 3.0 (p < 0.0001), regardless of incubation time (p < 0.0001) and the percentage of mYCW (p < 0.0001). An incubation time of 6 h (p < 0.05) or 0.5 and 1.0 % mYCW (p < 0.0001) significantly improved the efficacy of mYCW for preventing CIT toxicity. In contrast, 0.5 and 1.0 % of mYCW appeared to exacerbate the PAT toxicity (p < 0. 0001). This effect on PAT toxicity was constantly observed with higher PAT concentrations, and it reached significance at a concentration of 0.70 μM (p < 0.0001). mYCW had no effect on PA toxicity. These results suggest that mYCW may reduce OTA toxicity and, to some extent, CIT toxicity at pH 3.0. Although PAT toxicity was increased by mYCW treatment, PAT is readily degraded during heat treatment and may therefore be dealt with using other preventative measures.

Lipid Rafts Disruption Increases Ochratoxin A Cytotoxicity to Hepatocytes.

Lipid rafts are microdomains in plasma membrane and can mediate cytotoxicity. In this study, the role of lipid rafts in ochratoxin A-induced toxicity was investigated using Hepatoblastoma Cell Line HepG-2 cells. Disruption of cholesterol-containing lipid rafts enhanced Ochratoxin A (OTA) toxicity, as shown by increased lactate dehydrogenase leakage, increased reactive oxygen species level and reduction of superoxide dismutase activity in a time-dependent manner. Isobaric tags for relative and absolute quantitation-based proteomics of the cell membranes showed that nearly 85.5% proteins were downregulated by OTA, indicating that OTA inhibited the membrane protein synthesis. Most of altered proteins were involved in Gene Ontology "transport", "cell adhesion" and "vesicle-mediated transport". In conclusion, lipid rafts play a key role in OTA-induced cytotoxicity. This study provides insight into how OTA toxicity is regulated by the plasma membrane, especially the lipid rafts.

Effect of ochratoxin A on the intestinal mucosa and mucosa-associated lymphoid tissues in broiler chickens.

The immunotoxic effect of ochratoxin A (OTA) on the intestinal mucosa-associated lymphoid tissue and its cytotoxic action on the intestinal epithelium were studied in broiler chickens experimentally treated with the toxin. From the 7th day of life, 80 male broiler chickens (Ross 308) were randomly divided into four groups of 20 birds each. The three experimental groups (E1-3) were treated with OTA for 28 days (E1: 50 μg/kg body weight [bw]/day; E2: 20 μg/kg bw/day; E3: 1 μg/kg bw/day) and the fourth group served as control. Histological examination of the intestinal mucosa and immunohistochemical staining for identification of CD4+, CD8+, TCR1 and TCR2 lymphocytes in the duodenum, jejunum and ileocaecal junction were performed, and CD4+/CD8+ and TCR1/TCR2 ratios were calculated. OTA toxicity resulted in decreased body weight gain, poorer feed conversion ratio, lower leukocyte and lymphocyte count, and altered intestinal mucosa architecture. After 14 days of exposure to OTA, immunohistochemistry showed a significant reduction of the lymphocyte population in the intestinal epithelium and the lamina propria. After 28 days of exposure, an increase in the CD4+ and CD8+ values in both the duodenum and jejunum of chickens in Groups E1 and E2 was observed, but the TCR1 and TCR2 lymphocyte counts showed a significant reduction. No significant changes were observed in Group E3. The results indicate that OTA induced a decrease in leukocyte and lymphocyte counts and was cytotoxic to the intestinal epithelium and the mucosa-associated lymphoid tissue, altering the intestinal barrier and increasing susceptibility to various associated diseases.

Ochratoxin A induces DNA damage and G2 phase arrest in human esophageal epithelium Het-1A cells in vitro.

Ochratoxin A (OTA), a toxin produced by several species of Aspergillus and Penicillium, is one of the most abundant food-contaminating mycotoxins. The International Agency for Research on Cancer (IARC) has classified OTA as a possible human carcinogen. Our previous study showed that there were high levels of OTA contaminations in wheat in the areas with high incidence of esophageal cancer in north China. This finding suggests that exposure to low levels of OTA may be a critical etiological factor for esophageal cancer in these areas. However, up to now, the potential biological effects of OTA on human esophageal epithelial cells have not been fully elucidated. In the present study, we explored the cytotoxicity of OTA in human esophageal epithelium immortalized cells (Het-1A). We found that OTA could induce DNA strand breaks and chromosome aberrations in Het-1A cells. OTA-induced DNA damage was followed by G2 cell cycle arrest, and down-regulation of Cdc2 and cyclinB1 contributed to the OTA-induced G2 arrest in Het-1A cells. Additionally, OTA induced apoptosis in Het-1A cells by activating caspase-3. In conclusion, our results indicated that OTA could induce DNA damage, G2 arrest and apoptosis in Het-1A cells, which may be involved in the esophageal toxicity of OTA.

Discovery of systematic responses and potential biomarkers induced by ochratoxin A using metabolomics

Ochratoxin A (OTA) is known to be nephrotoxic and hepatotoxic in rodents when exposed orally. To understand the systematic responses to OTA exposure, GC-MS- and 1H-NMR-based metabolomic techniques together with histopathological assessments were applied to analyse the urine and plasma of OTA-exposed rats. It was found that OTA exposure caused significant elevation of amino acids (alanine, glycine, leucine etc.), pentose (ribose, glucitol, xylitol etc.) and nucleic acid metabolites (pseudouridine, adenosine, uridine). Moreover, myo-inositol, trimethylamine-oxide (TMAO), pseudouridine and leucine were identified as potential biomarkers for OTA toxicity. The primary pathways included the pentose phosphate pathway (PPP), the Krebs cycle (TCA), the creatine pathway and gluconeogenesis. The activated PPP was attributed to the high requirements for nicotinamide adenine dinucleotide phosphate (NADPH), which is involved in OTA metabolism through cytochrome P450. The elevated gluconeogenesis and TCA suggest that energy metabolism was involved. The up-regulated synthesis of creatinine reveals the elevated catabolism of proteins. These findings provide an overview of systematic responses to OTA exposure and metabolomic insight into the toxicological mechanism of OTA.

The effects of orchidectomy on toxicological responses to dietary ochratoxin A in Wistar rats

Ochratoxin A (OTA) causes pathological lesions in the organs of animals. Males are more sensitive to OTA exposure than females but the reasons for this are unknown.The objective of this study was to explore the role of testosterone in male rats with OTA-related pathogenesis. To test the effect of testosterone on OTA toxicity, the testes of a group of rats were surgically removed. Male and female rats (approximately 300 and 200g) were fed with OTA-contaminated feed (initially approximately 300μgkg−1 b.w. per day) for 24 weeks. The organs of all the animals were collected and their organ lesion pathology, caspase-3 expression, OTA plasma and organ concentrations and total plasma testosterone concentrations were evaluated. OTA treatment created serious lesions in the kidney, liver and testes of rats. The major histopathological changes in the kidney and liver were karyomegaly, hemorrhages and vacuolization. In the testes, there was a marked decrease in the amount of spermatozoon. The degrees of organ lesion were evaluated and the castrated males had the lowest kidney and liver lesion scores, indicating that testosterone reduction in males dramatically reduces OTA-related organ damage. The plasma OTA levels for the intact males, the castrated and the females were 6.34, 8.42 and 12.5μgml−1, respectively.In conclusion, despite the similar plasma OTA levels of the intact and castrated males, OTA is less toxic in the castrated males. Therefore, the well-known gender specific toxicity of OTA seems to be related to the testosterone levels of rats.

MicroRNA profiling of rats with ochratoxin A nephrotoxicity.

BackgroundNephrotoxicity is the most prominent one among the various toxicities of ochratoxin A (OTA). MicroRNAs (miRNAs) are small non-coding RNAs that have an impact on a wide range of biological processes by regulating gene expression at post-transcriptional level or protein systhesis level. The objective of this study is to analyze miRNA profiling in the kidneys of rats gavaged with OTA.ResultsTo profile miRNAs in the kidneys of rats with OTA nephrotoxicity, high-throughput sequencing and bioinformatics approaches were applied to analyze the miRNAs in the kidney of rats following OTA treatment. A total of 409 known miRNAs and 8 novel miRNAs were identified in the kidney and the levels of the novel miRNAs were varied in response to different doses of OTA. Expression of miR-129, miR-130a, miR-130b, miR-141, miR-218b and miR-3588 were uniquely suppressed in mid dose but then elevated in high dose, with opposite expression to their target genes. The expression pattern was closely related with the “MAPK signaling pathway”. Dicer1 and Drosha were significantly suppressed, indicating an impairment of miRNA biogenesis in response to OTA.ConclusionsThe abrogation of miRNA maturation process suggests a new target of OTA toxicity. Moreover, the identification of the differentially expressed miRNAs provides us a molecular insight into the nephrtoxicity of OTA.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-333) contains supplementary material, which is available to authorized users.

Protective effect of N-acetylcysteine against DNA damage and S-phase arrest induced by ochratoxin A in human embryonic kidney cells (HEK-293)

N-acetylcysteine (NAC) has recently gained particular interest as a beneficial antioxidant. This study investigated the protective effects of NAC against ochratoxin A (OTA)-induced DNA damage and S-phase arrest in human embryonic kidney cells (HEK-293). OTA exposure results in nephrotoxicity, hepatotoxicity as well as immunotoxicity; and, in the present study, the toxicity of OTA toward HEK-293 cells was explored by analyzing the involvement of the oxidative pathway. It was found that OTA treatment led to oxidative damage; meanwhile, OTA treatment induced significant DNA damage and S-phase arrest by down-regulating cyclin A2, cyclin E1, and CDK2 expression. However, NAC pretreatment alleviated OTA-induced ROS overproduction, the loss of mitochondrial membrane potential (ΔΨm), and the decrease in superoxide dismutase (SOD) activity. NAC pretreatment was also discovered to attenuate OTA-induced DNA damage using the comet assay and by determining the expression of γ-H2AX. In addition, NAC pretreatment partly ameliorated OTA-induced S-phase arrest by preventing the down-regulation of cyclin A2, cyclin E1 and CDK2 expression in HEK-293 cells. All of these results demonstrated that oxidative damage was involved in OTA-induced DNA damage and cell cycle arrest in HEK-293 cells. Therefore, NAC has the potential to reverse the DNA damage and S-phase arrest induced by OTA.

Central role of Nix in the autophagic response to ochratoxin A

Nephrotoxicity is the most prominent toxicological effects of ochratoxin A (OTA). We have previously shown that autophagy might be involved in OTA-induced early renal cytotoxicity, but the mechanisms of action are unknown. Since OTA is known to induce mitochondrial damage and Nix is a selective autophagy receptor for mitochondrial clearance, the objective of this study was to investigate whether Nix mediates autophagic response to OTA-induced renal cytotoxicity. Our results showed that OTA induced autophagic and mitophagic activitits. Nix shRNA HEK 293 cells were more sensitive than scrambled shRNA cells to OTA-induced cell death, and differentially affect the mRNA expression of SDHA, AIFM1, and Bad and protein expression of AIF, VDAC, SDHA and LONP1 after OTA treatment. In particular, up-regulation of the pro-apoptotic Bad and AIF after OTA treatment was prominent only in Nix shRNA cells, which might explain the higher ratio of cell death. These results might indicate that Nix plays a critical role in the cellular protection against OTA toxicity through autophagy and mitochondria.