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Ochratoxin A (OTA) is a mycotoxin occurring in foods consumed by humans. Recently, there has been growing global concern regarding OTA toxicity. The main target organ of OTA is the kidney, but the mechanism underlying renal toxicity is not well known. In this study, human-derived proximal tubular epithelial cells, HK-2 cells, were used for RNA-sequencing (RNA-seq) and transcriptome analysis. In total, 3193 differentially expressed genes were identified upon treatment with 200 nM OTA in HK-2 cells; of these, 2224 were upregulated and 969 were downregulated. Transcriptome analysis revealed that OTA significantly affects hypoxia, epithelial-mesenchymal transition (EMT), apoptosis, and xenobiotic metabolism pathways in kidney cells. Quantitative real-time PCR analysis showed gene expression patterns similar to RNA-seq analysis. Expression of EMT markers (E-cadherin and fibronectin), apoptosis markers (caspase-3 and Bax), and kidney injury molecule-1 (KIM-1) was suppressed by inhibiting AhR expression using siRNA, and the related transcription factors, Smad2/3, and HIF-1α were downregulated. Smad2/3 suppression with siRNA could inhibit fibronetcin, caspase-3, Bax, and KIM-1 expression. Fibronetcin, caspase-3, Bax, and KIM-1 expression could be increased with HIF-1α suppression with siRNA. Taken together, these findings suggest that OTA-mediated kidney toxicity via the AhR-Smad2/3-HIF-1α signaling pathways leads to induction of EMT, apoptosis, and kidney injury.

Ochratoxin A (OTA) is a toxin produced by fungi such as Aspergillus spp. and Penicillium spp. The key target organ of OTA toxicity is the kidney, and it is known that epithelial-to-mesenchymal transition (EMT) leading to fibrosis is enhanced after long-term exposure of the kidney to OTA. However, the mechanisms responsible for this onset are not precisely known. Therefore, the purpose of this study was to investigate the mechanism of OTA-induced EMT and fibrosis in human proximal tubule HK-2 cells and mouse kidneys. Cells were treated for 48 h with various concentrations of OTA (50, 100, and 200 nM) and mice underwent oral administration of various doses of OTA (200 and 1000 μg/kg body weight) for 12 weeks. Blood urea nitrogen and creatinine levels were increased in the serum of OTA-treated mice, and fibrosis was observed in kidney tissues. Furthermore, alpha-smooth muscle actin (α-SMA) and fibronectin levels were increased, and E-cadherin level was decreased by OTA in both HK-2 cells and kidney tissues. In addition, the expression levels of TGF-β, smad2/3, and β-catenin were increased after OTA treatment. α-SMA, E-cadherin, and fibronectin were shown to be regulated by the activation of transcription factors, smad2/3 and β-catenin. These results demonstrated that OTA induces EMT and renal fibrosis through Smad2/3 and β-catenin signaling pathways in vitro and in vivo.

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium, and it is found in many foods. Acrylamide (AA) can be produced in foods treated at high temperatures. In this study, we investigated the combined toxicity of OTA and AA against human renal and hepatic cells in vitro. The concentration at which the synergistic effect of OTA and AA occurs was determined using the combination index obtained from the cell viability results for OTA and AA individually or in combination. The synergistic toxicity of both substances was evaluated by cell viability and the production of reactive oxygen species. In addition, apoptosis-related markers were significantly upregulated by OTA and AA individually or in combination. To determine the combined toxic effects of OTA and AA on the cells, the levels of enzymes involved in the phase I reaction and apoptosis-related markers were determined using quantitative (q)PCR and Western blot. The expression levels of CYP enzymes CYP1A1 and CYP1A2 involved in the phase I reaction significantly increased when the cells were treated with OTA and AA in combination. The expression of apoptosis-related markers, Bcl2-associated X protein (Bax) and caspase 3, also increased when the cells were treated with OTA and AA in combination. Therefore, the synergistic toxicity of OTA and AA suggests that such effects may contribute to nephrotoxicity and hepatotoxicity.

Ochratoxin A (OTA) is a widespread mycotoxin produced by several species of the genera Aspergillus and Penicillium . OTA exists in a variety of foods, including rice, oats, and coffee and is hepatotoxic, with a similar mode of action as aflatoxin B1. The precise mechanism of cytotoxicity is not yet known, but oxidative damage is suspected to contribute to its cytotoxic effects. In this study, human hepatocyte HepG2 cells were treated with various concentrations of OTA (5-500 nM) for 48 h. OTA triggered oxidative stress as demonstrated by glutathione depletion and increased reactive oxygen species, malondialdehyde level, and nitric oxide production. Apoptosis was observed with 500 nM OTA treatment. OTA increased both the mRNA and protein expression of phase I and II enzymes. The same results were observed in an in vivo study using ICR mice. Furthermore, the relationship between phase I and II enzymes was demonstrated by the knockdown of the aryl hydrocarbon receptor (AhR) and NF-E2-related factor 2 (Nrf2) with siRNA. Taken together, our results show that OTA induces oxidative stress through the phase I reaction regulated by AhR and induces apoptosis, and that the phase II reaction is activated by Nrf2 in the presence of oxidative stress.

Because ochratoxin A (OTA) is widely found in foods, people are susceptible to OTA exposure. The mechanism leading to renal toxicity induced by OTA remains unclear. The aim of this study was to investigate OTA-induced toxicity in human proximal tubule HK-2 cells. OTA decreased cell viability, and the expression of kidney injury molecule-1 (KIM-1), a kidney damage marker, was increased when HK-2 cells were exposed to OTA. Additionally, OTA treatment of cells increased intracellular reactive oxygen species and malondialdehyde and decreased glutathione levels. OTA-treated cells induced the aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR) genes followed by induction of the cytochrome P450 1A1 (CYP1A1), CYP1A2, and CYP3A4 genes representing phase I enzyme. The mRNA expression of phase II enzymes such as heme oxygenase-1, nicotinamide adenine dinucleotide phosphate-quinone oxidoreductase 1, and glutamate cysteine ligase catalytic subunit were upregulated by activation of NF-E2-related factor 2 (Nrf2) translocation by treatment with OTA. The response of OTA-orally administered mice also showed marked increases in these enzymes as well as KIM-1. These results indicate that OTA induces phase I and II enzymes through the AhR, PXR, and Nrf2 signaling pathways in HK-2 cells, which may lead to modulation of proximal tubule injury., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Ochratoxin A (OTA) is a mycotoxin that induces fibrosis and epithelial-to-mesenchymal transitions (EMT) in kidneys and livers. It enters our bodies through food consumption, where it is absorbed in the intestines. However, the impact of OTA on the intestines is yet to be studied. MicroRNA (miRNAs) are small non-coding single-stranded RNAs that block the transcription of specific mRNAs and are, therefore, involved in many biochemical processes. Our findings indicate that OTA can induce EMT and intestinal fibrosis both in vivo and in vitro. This study examines the impact of OTA on intestinal toxicity and the role of miRNAs in this process. Following OTA treatment, miR-155-5p was the most elevated miRNA by next-generation sequencing. Our research showed that OTA increased miR-155-5p levels through transforming growth factor β (TGF-β), leading to the development of intestinal fibrosis and EMT. Additionally, the study identified that the modulation of TGF-β and miR-155-5p by OTA is linked to the inhibition of CCAAT/enhancer-binding protein β (C/EBPβ) and Smad2/3 accumulation in the progression of intestinal fibrosis. [ABSTRACT FROM AUTHOR]

Ochratoxin A (OTA) is a mycotoxin generated by Penicillium and Aspergillus species. It is often found in cereals. We hypothesized that OTA exposure induces epithelial–mesenchymal transition (EMT), leading to liver fibrosis. In this research, we explored whether the TGF‐β receptor I (TGF‐β RI)/Smad2/3 signaling pathway is related to EMT‐induced hepatic fibrosis. In vitro and in vivo experiments, mRNA and protein expression of liver fibrosis‐related markers such as fibronectin, α‐smooth muscle actin (α‐SMA) and E‐cadherin were assessed. The levels of alkaline phosphatase, alanine transaminase, aspartate aminotransferase, and total bilirubin, which are used to assess damage, increased. We also confirmed the increase in mRNA and protein expression of TGF‐β RI, Smad2, and Smad3. The expression of liver fibrosis‐related markers was decreased by siRNA‐mediated silencing of Smad2/3, as well as TGF‐RI suppression. Liver cells exposed to OTA showed enhanced TGF‐β RI expression on the cell membrane. These results demonstrated that OTA induces hepatic fibrosis through TGF‐β RI and Smad2/3 pathways in vitro and in vivo. [ABSTRACT FROM AUTHOR]