The mycotoxin ochratoxin A (OTA) is found widely in agricultural commodities. OTA can induce various toxicities. In this study, rats were gavaged with OTA for different weeks. Then, the expression of microRNAs, mRNAs and proteins were measured in the rat livers treated with OTA for 13 weeks. Our sequencing data suggests that the medial and the high doses of OTA exert different effects on livers. Five distinctive pathways were induced after OTA treatment as collectively demonstrated at miRNA, mRNA and protein levels. Two (primary bile acid biosynthesis, and metabolism of xenobiotics by cytochrome P450) are directly associated with liver damage, whereas the remaining pathways (arginine and proline metabolism, cysteine and methionine metabolism, and PPAR signaling pathway) cause metabolic disease. This study reveals OTA-induced early hepatotoxicity for the first time by combining multi-omics methods. The novel metabolic pathways may contribute to the pathogenesis of metabolic diseases later in life.O chratoxin A (OTA) is a low molecular weight mycotoxin produced by certain strains of filamentous fungi of the Aspergillus and Penicillium genera and has been detected in a large variety of agricultural commodities. OTA carries potential health-associated risks and has been classified as a possible human carcinogen (group 2B) by the International Agency for Research on Cancer 1 . OTA has previously been found to induce various toxic effects including nephrotoxicity, hepatotoxicity, immunotoxicity, genotoxicity, carcinogenicity, teratogenicity, neurotoxicity and mutagenicity.The liver is one of the major target organs of OTA biotransformation. Although, some early hepatotoxicity studies employed relative high concentrations of OTA and found remarkable liver lesion 2,3 , lower doses of OTA did not provoke significant pathological changes 4-6 . Most of the previous studies have been extensively focused on OTA-induced kidney damage, less on liver. However, it is still unknown how OTA affects the liver which is the largest detoxification organ of body. Therefore, the identification of early hepatotoxicity can be helpful to understand the mechanism of some diseases that may be developed and progressed by OTA in later stage, and to prevent these diseases in early stage to improve human health.Omics approaches, such as transcriptome and proteome, are promising to detect the pathological changes of liver at a molecular level. Till date, omics technology has been employed only in a few studies to understand the mechanism of OTA hepatotoxicity. Moreover, a high-throughput microarray profiling study on HepG2 liver cell transcriptome demonstrated that multiple hepatic metabolism genes are modulated by OTA exposure 7 . In addition, proteomic approaches have helped identify key proteins in the livers of pigs treated with OTA 8 . These omics approaches have widened our view about OTA hepatotoxicity, however the mechanism of OTA actions remains largely unknown.Recently, microRNAs (miRNAs) in animals and plants are shown to play an impor...

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.

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 (1)H-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.

Ochratoxin A (OTA), which is found in a variety of food products, is associated with the development of nephrotoxicity and carcinogenicity in rats and has raised public health concerns. A previous study in our laboratory indicated that OTA exposure induced cytotoxicity by decreasing global DNA methylation in vitro. However, the relationship between OTA-induced nephrotoxicity and DNA methylation changes in vivo remains unclear. The object of this study was to investigate whether OTA can change global DNA methylation or alter the expression of several critical tumour-related genes by inducing methylation modifications before carcinogenesis. We focused on the mechanism of action of OTA in regard to DNA methylation, including the expression of DNA methyltransferases and the regulation of specific cell signalling pathways. Dynamic and dose-dependent changes of global DNA methylation were observed during OTA-induced nephrotoxicity and probably associated with the expression of DNA methyltransferase 1. 13-week exposure of OTA caused hypermethylation in the promoters of critical cell adhesion-related genes, E-cadherin and N-cadherin, leading to reduction of the corresponding mRNA expression, accompanied by transcriptional activation of the Wnt and PI3K/AKT pathways. These findings suggested that long-term OTA exposure could disrupt DNA methylation profile, which might be one of the possible mechanisms of OTA-induced nephrotoxicity.

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.