High-Performance Liquid Chromatography-Fluorescence Detection Method for Ochratoxin A Quantification in Small Mice Sample Volumes: Versatile Application across Diverse Matrices Relevant for Neurodegeneration Research

Ochratoxin A (OTA) is a mycotoxin commonly found in various food products, which poses potential health risks to humans and animals. Recently, more attention has been directed towards its potential neurodegenerative effects. However, there are currently no fully validated HPLC analytical methods established for its quantification in mice, the primary animal model in this field, that include pivotal tissues in this area of research, such as the intestine and brain. To address this gap, we developed and validated a highly sensitive, rapid, and simple method using HPLC-FLD for OTA determination in mice tissues (kidney, liver, brain, and intestine) as well as plasma samples. The method was rigorously validated for selectivity, linearity, accuracy, precision, recovery, dilution integrity, carry-over effect, stability, and robustness, meeting the validation criteria outlined by FDA and EMA guidelines. Furthermore, the described method enables the quantification of OTA in each individual sample using minimal tissue mass while maintaining excellent recovery values. The applicability of the method was demonstrated in a repeated low-dose OTA study in Balb/c mice, which, together with the inclusion of relevant and less common tissues in the validation process, underscore its suitability for neurodegeneration-related research.

Food-Borne Chemical Carcinogens and the Evidence for Human Cancer Risk

Commonly consumed foods and beverages can contain chemicals with reported carcinogenic activity in rodent models. Moreover, exposures to some of these substances have been associated with increased cancer risks in humans. Food-borne carcinogens span a range of chemical classes and can arise from natural or anthropogenic sources, as well as form endogenously. Important considerations include the mechanism(s) of action (MoA), their relevance to human biology, and the level of exposure in diet. The MoAs of carcinogens have been classified as either DNA-reactive (genotoxic), involving covalent reaction with nuclear DNA, or epigenetic, involving molecular and cellular effects other than DNA reactivity. Carcinogens are generally present in food at low levels, resulting in low daily intakes, although there are some exceptions. Carcinogens of the DNA-reactive type produce effects at lower dosages than epigenetic carcinogens. Several food-related DNA-reactive carcinogens, including aflatoxins, aristolochic acid, benzene, benzo[a]pyrene and ethylene oxide, are recognized by the International Agency for Research on Cancer (IARC) as causes of human cancer. Of the epigenetic type, the only carcinogen considered to be associated with increased cancer in humans, although not from low-level food exposure, is dioxin (TCDD). Thus, DNA-reactive carcinogens in food represent a much greater risk than epigenetic carcinogens.

New Evidences about the Carcinogenic Effects of Ochratoxin A and Possible Prevention by Target Feed Additives

A review of the carcinogenic effects of ochratoxin A (OTA) on various tissues and internal organs in laboratory and farm animals is made. Suggestions are made regarding how to recognize and differentiate the common spontaneous neoplastic changes characteristic for advanced age and the characteristic neoplasia in different tissues and organs in laboratory animals/poultry exposed to OTA. The synergistic effects of OTA together with its natural combination of penicillic acid are also investigated regarding possible carcinogenic effects. The malignancy and the target location of OTA-induced neoplasia is studied. The sex-differences of such neoplasia are investigated in the available literature. The time of appearance of the first neoplasia is investigated in long-term carcinogenic studies with OTA-treated animals. The possibility of target feed additives or herbs to counteract the toxic and carcinogenic effects of OTA is studied in the available literature. Some effective manners of prophylaxis and/or prevention against OTA contamination of feedstuffs/foods or animal production are suggested. The suitability of various laboratory animals to serve as experimental model for humans with regard to OTA-induced tumorigenesis is investigated.

A Computational Understanding of Inter-Individual Variability in CYP2D6 Activity to Investigate the Impact of Missense Mutations on Ochratoxin A Metabolism

Cytochrome P-450 (CYP) enzymes have a key role in the metabolism of xenobiotics of food origin, and their highly polymorphic nature concurs with the diverse inter-individual variability in the toxicokinetics (TK) and toxicodynamics (TD) of food chemicals. Ochratoxin A is a well-known mycotoxin which contaminates a large variety of food and is associated with food safety concerns. It is a minor substrate of CYP2D6, although the effects of CYP2D6 polymorphisms on its metabolism may be overlooked. Insights on this aspect would provide a useful mechanistic basis for a more science-based hazard assessment, particularly to integrate inter-individual differences in CYP2D6 metabolism. This work presents a molecular modelling approach for the analysis of mechanistic features with regard to the metabolic capacity of CYP2D6 variants to oxidise a number of substrates. The outcomes highlighted that a low-frequency CYP2D6 variant (CYP2D6*110) is likely to enhance ochratoxin A oxidation with possible consequences on TK and TD. It is therefore recommended to further analyse such TK and TD consequences. Generally speaking, we propose the identification of mechanistic features and parameters that could provide a semi-quantitative means to discriminate ligands based on the likelihood to undergo transformation by CYP2D6 variants. This would support the development of a fit-for-purpose pipeline which can be extended to a tool allowing for the bulk analysis of a large number of compounds. Such a tool would ultimately include inter-phenotypic differences of polymorphic xenobiotic-metabolising enzymes in the hazard assessment and risk characterisation of food chemicals.

Time Course of Renal Transcriptomics after Subchronic Exposure to Ochratoxin A in Fisher Rats

The mycotoxin ochratoxin A (OTA) is a potent nephrocarcinogen, mainly in male rats. The aim of this study was to determine the time course of gene expression (GeneChip® Rat Gene 2.0 ST Array, Affymetrix) in kidney samples from male and female F344 rats, treated daily (p.o) with 0.50 mg/kg b.w. (body weight) of OTA for 7 or 21 days, and evaluate if there were differences between both sexes. After OTA treatment, there was an evolution of gene expression in the kidney over time, with more differentially expressed genes (DEG) at 21 days. The gene expression time course was different between sexes with respect to the number of DEG and the direction of expression (up or down): the female response was progressive and consistent over time, whereas males had a different early response with more DEG, most of them up-regulated. The statistically most significant DEG corresponded to metabolism enzymes (Akr1b7, Akr1c2, Adh6 down-regulated in females; Cyp2c11, Dhrs7, Cyp2d1, Cyp2d5 down-regulated in males) or transporters (Slc17a9 down-regulated in females; Slco1a1 (OATP-1) and Slc51b and Slc22a22 (OAT) down-regulated in males). Some of these genes had also a basal sex difference and were over-expressed in males or females with respect to the other sex.

Follow up long term preliminary studies on carcinogenic and toxic effects of ochratoxin A in rats and the putative protection of phenylalanine

Carcinogenic effects of ochratoxin A (OTA) on liver, kidneys, intestine, lung and eyes of Wistar rats exposed to 10 ppm or 5 ppm OTA in the diet and additionally supplemented or not with phenylalanine (PHE) were examined during 24-months experimental period. OTA was seen to provoke strong degenerative changes and slight pericapillary oedema in most internal organs, e.g. kidneys, liver, intestine, spleen and brain. Six of total nine neoplasms were identified as malignant and three as benign. Five of total six malignant neoplasms and two of total three benign neoplasms were seen in male rats. The pathological finding in rats after two weeks feeding with OTA-contaminated feed was dominated by degenerative changes in various internal organs, which were weaker in the group additionally supplemented with PHE. The protective effect of PHE was evident with respect to OTA-induced decrease of serum glucose and serum protein, but this protection was not singnificant with respect to serum enzymes activity. The number of neoplasms in PHE-supplemented group exposed to 10 ppm OTA was similar to that in the group exposed to twice lower feed levels of OTA alone, suggesting about a possible protective effect of PHE. The rats would not be able to serve as experimental model for humans with regard to OTA-induced tumorigenesis, because the target organ of OTA-toxicity in humans and pigs is mainly the kidney as opposed to the significant damages and carcinogenic effects seen in various organs in rats exposed to OTA.

Protective Effect of Hydroxytyrosol Against Oxidative Stress Induced by the Ochratoxin in Kidney Cells: in vitro and in vivo Study

Ochratoxin-A (OTA) is a mycotoxin that is a common contaminant of food products for both humans and animals. This mycotoxin has several toxic effects. In particular, ochratoxin has significant nephrotoxic potential. In fact, OTA has been described as being responsible for naturally occurring animal and human kidney disorders. The toxicity of this mycotoxin involves the induction of the oxidative stress pathways. Therefore, in the present study, we wanted to evaluate the potential protective effects of hydroxytyrosol (HT), a phenolic constituent with potent antioxidant activity, of extra virgin olive oil in three different renal cell lines, the Madin-Darby canine kidney cell line (MDCK), a pig kidney cell line (LLC-PK1), and a rabbit kidney cell line (RK 13), and in rats. Our results clearly showed that renal cells respond to OTA exposure by reducing cell proliferation and the induction of oxidative stress. Pre-incubation of the cells with HT prevented the cellular cytotoxicity and increased reactive oxygen species (ROS) levels induced by OTA. In addition, the antioxidative activity of HT was studied by measuring malondialdehyde (MDA) and lactate dehydrogenase (LDH) levels and nitrosative stress. Finally, we investigated the capability of HT (20 mg/kg, intraperitoneally) to act in vivo. In rats, HT reduced oxidative stress and collagen accumulation in the kidney and counteracted the augmentations in AST, ALT, and creatinine levels following OTA induction (250 μg/kg for 90 days orally). In conclusion, our findings demonstrate that HT is able to protect three renal cell lines from the damage induced by OTA and protect the kidneys of rats. Therefore, the use of this compound could be an important strategy for the treatment and prevention of this type of kidney dysfunction.

Lactic Acid Bacteria as Antifungal and Anti-Mycotoxigenic Agents: A Comprehensive Review

Fungal contamination of food and animal feed, especially by mycotoxigenic fungi, is not only a global food quality concern for food manufacturers, but it also poses serious health concerns because of the production of a variety of mycotoxins, some of which present considerable food safety challenges. In today's mega-scale food and feed productions, which involve a number of processing steps and the use of a variety of ingredients, fungal contamination is regarded as unavoidable, even good manufacturing practices are followed. Chemical preservatives, to some extent, are successful in retarding microbial growth and achieving considerably longer shelf-life. However, the increasing demand for clean label products requires manufacturers to find natural alternatives to replace chemically derived ingredients to guarantee the clean label. Lactic acid bacteria (LAB), with the status generally recognized as safe (GRAS), are apprehended as an apt choice to be used as natural preservatives in food and animal feed to control fungal growth and subsequent mycotoxin production. LAB species produce a vast spectrum of antifungal metabolites to inhibit fungal growth; and also have the capacity to adsorb, degrade, or detoxify fungal mycotoxins including ochratoxins, aflatoxins, and Fusarium toxins. The potential of many LAB species to circumvent spoilage associated with fungi has been exploited in a variety of human food and animal feed stuff. This review provides the most recent updates on the ability of LAB to serve as antifungal and anti-mycotoxigenic agents. In addition, some recent trends of the use of LAB as biopreservative agents against fungal growth and mycotoxin production are highlighted.

Antioxidant activities of Moringa oleifera leaf extract against pendimethalin-induced oxidative stress and genotoxicity in Nile tilapia, Oreochromis niloticus (L.)

To assess the ameliorative effects of Moringa oleifera (MO) leaf extract on haematological and biochemical changes, liver DNA damage and oxidative stress biomarkers in Nile tilapia (Oreochromis niloticus) exposed to a sublethal concentration (0.52 mg/l) of pendimethalin (PM). Tilapia fish were allocated into four equal groups in tri-replicates as follows: first group was the control group, second group was treated with MO (20 ml/30 l water), third group was exposed to 0.52 mg PM/l and fourth group was exposed to 0.52 mg PM/l and treated with MO leaf extract (20 ml/30 l water) for 28 days. At the end of this period, blood and liver tissue samples were collected and haematological and biochemical changes, hepatic DNA fragmentation and oxidative stress biomarkers were analysed. Pendimethalin caused significant reduction in haematological profile [White blood cells (WBCs) and red blood cells (RBCs) counts, haemoglobin (Hb) concentration and haematocrit (Ht) level]; meanwhile, serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), creatinine, uric acid, glucose, cortisol, cholesterol and lactate dehydrogenase (LDH) were significantly increased. On the other hand, serum total protein, albumin, globulin and acetylcholinesterase (AChE) were decreased. Significant reduction in hepatic superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (TAC) and glutathione peroxidase (GSH-Px) levels and marked increments of hepatic malondialdehyde (MDA) and DNA fragmentation were observed in PM-exposed fish compared to the control group. The addition of Moringa oleifera leaf extract into the water could overcome the negative impacts of pendimethalin and normalise the examined parameters nearly to the control values. Moringa oleifera was used for the first time to protect tilapia fish against PM-induced toxicity. The present study revealed that Moringa oleifera has potent antioxidant and antigenotoxic actions against pendimethalin toxicity.

Sex-dependent gene expression after ochratoxin A insult in F344 rat kidney

Ochratoxin A (OTA) is a potent rodent nephrocarcinogen; being males more sensitive than females. The objective was to study the response between sexes at gene expression level (whole genome transcriptomics) in kidneys of F344 rats treated with 0.21 or 0.50 mg/kg bw OTA for 21 days. DNA methylation analysis of selected genes was also studied (MALDI-TOF mass spectrometry). OTA-induced response was dose-dependent in males and females, although clearer in males. Females showed a higher number of altered genes than males but functional analysis revealed a higher number of significantly enriched toxicity lists in 0.21 mg/kg treated males. OTA modulated damage, signaling and metabolism related lists, as well as inflammation, proliferation and oxidative stress in both sexes. Eleven toxicity lists (damage, fibrosis, cell signaling and metabolism) were exclusively altered in males while renal safety biomarker and biogenesis of mitochondria lists were exclusively enriched in females. A high number of lists (39) were significantly enriched in both sexes. However, they contained many sex-biased OTA-modulated genes, mainly phase I and II, transporters and nuclear receptors, but also others related to cell proliferation/apoptosis. No biologically relevant changes were observed in the methylation of selected genes.

Toxicity reduction of ochratoxin A by lactic acid bacteria

Ochratoxin A (OTA) is a mycotoxin produced by the metabolism of fungus belonging to the genus Aspergillus and Penicillium. In this paper we report, the capacity of different cultures of lactic acid bacteria (LAB) to degrade OTA present in MRS broth at both pH 3.5 and 6.5. A study of OTA reduction during gastrointestinal digestion carried out with the LAB was also performed. Taking into account the two reduction mechanisms of OTA studied in this work as the enzymatic one and the adsorption on the cell wall, as well as at pH 3.5 and 6.5 the reduction values of OTA were in a range of 30-99%, being the strains with greater reduction (97% and 95%) Lb. rhamnosus CECT 278T and Lb. plantarum CECT 749 respectively. In the experiments carried out digesting the OTA in MRS medium with LAB, the highest bioaccessibility reduction was observed by the strain of Lb. johnsonii CECT 289, showing a mean reduction around all the gastrointestinal digestion process of 97.4%. The mass spectrometry associated to the linear ion trap method identified ochratoxin alpha (OTα) m/z = 256.1 and phenylalanine (Phe) m/z = 166.1 as the major metabolites of OTA degradation in LAB cultures.

Mycotoxins as human carcinogens-the IARC Monographs classification

Humans are constantly exposed to mycotoxins (e.g. aflatoxins, ochratoxins), mainly via food intake of plant and animal origin. The health risks stemming from mycotoxins may result from their toxicity, in particular their carcinogenicity. In order to prevent these risks, the International Agency for Research on Cancer (IARC) in Lyon (France)-through its IARC Monographs programme-has performed the carcinogenic hazard assessment of some mycotoxins in humans, on the basis of epidemiological data, studies of cancer in experimental animals and mechanistic studies. The present article summarizes the carcinogenic hazard assessments of those mycotoxins, especially aflatoxins (aflatoxin B1, B2, G1, G2 and M1), fumonisins (fumonisin B1 and B2) and ochratoxin A (OTA). New information regarding the genotoxicity of OTA (formation of OTA-DNA adducts), the role of OTA in oxidative stress and the identification of epigenetic factors involved in OTA carcinogenesis-should they indeed provide strong evidence that OTA carcinogenicity is mediated by a mechanism that also operates in humans-could lead to the reclassification of OTA.

Gene expression kinetics of renal transporters induced by ochratoxin A in male and female F344 rats

Ochratoxin A (OTA) is a mycotoxin that contaminates foodstuffs. The most relevant concern is its high kidney carcinogenicity in male rats and its unclear mechanism of action. It has been hypothesized that variations in transport mechanisms in kidney cells may be the reason of different sex-dependent sensitivities towards OTA. The aim of this study was to analyze, by RT- qPCR, renal transporters expression in 15-week-old male (M) and female (F) F344 rats at basal level and after single oral OTA administration (0.50 mg/kg bw). Temporal profiles (24h, 48h, 72h, 96h, 1 and 2 months) were studied per sex and transporter. The reference gene for all comparisons was Ppia. At basal level, sex differences were confirmed for Oatp1, Bcrp (M>F) and Oat2 (F>M). OTA tended to inhibit the expression of almost all transporters in both sexes, but clearly induced the expression of Oat2 in males. Regarding time profiles, the highest sex differences involved Oat (Slc22) transporters: Oat2, Oat3 and Oat5 expression showed a significant increase in males (24h) while Oat1, Oat2 and Oat5 level decreased in females (48h). Overall, basal sex differences in F344 rats and the specific sex-dependent response to OTA of Oat2 might contribute to high kidney damage in male rats.

Ochratoxin A: 50 Years of Research

Since ochratoxin A (OTA) was discovered, it has been ubiquitous as a natural contaminant of moldy food and feed. The multiple toxic effects of OTA are a real threat for human beings and animal health. For example, OTA can cause porcine nephropathy but can also damage poultries. Humans exposed to OTA can develop (notably by inhalation in the development of acute renal failure within 24 h) a range of chronic disorders such as upper urothelial carcinoma. OTA plays the main role in the pathogenesis of some renal diseases including Balkan endemic nephropathy, kidney tumors occurring in certain endemic regions of the Balkan Peninsula, and chronic interstitial nephropathy occurring in Northern African countries and likely in other parts of the world. OTA leads to DNA adduct formation, which is known for its genotoxicity and carcinogenicity. The present article discusses how renal carcinogenicity and nephrotoxicity cause both oxidative stress and direct genotoxicity. Careful analyses of the data show that OTA carcinogenic effects are due to combined direct and indirect mechanisms (e.g., genotoxicity, oxidative stress, epigenetic factors). Altogether this provides strong evidence that OTA carcinogenicity can also occur in humans.

Evaluation of renal in vitro models used in ochratoxin research

Ochratoxin A (OTA) induces renal carcinomas in rodents with a specific localisation in the S3 segment of proximal tubules and distinct early severe tissue alterations, which have been observed also in other species. Pronounced species- and sex-specific differences in toxicity occur and similar effects cannot be excluded in humans, however precise mechanism(s) remain elusive until today. In such cases, the use of in vitro models for mechanistic investigations can be very useful; in particular if a non-genotoxic mechanism of cancer formation is assumed which include cytotoxic effects. However, potential genotoxic mechanisms can also be investigated in vitro. A crucial issue of in vitro research is the choice of the appropriate cell model. Apparently, the cellular target of OTA is the renal proximal tubular cell; therefore cells from this tissue area are the most reasonable model. Furthermore, cells from affected species should be used and can be compared to cells of human origin. Another important parameter is whether to use primary cultures or to choose a cell line from the huge variety of cell lines available. In any case, important characteristics and quality controls need to be verified beforehand. Therefore, this review discusses the renal in vitro models that have been used for the investigation of renal ochratoxin toxicity. In particular, we discuss the choice of the models and the essential parameters making them suitable models for ochratoxin research together with exemplary results from this research. Furthermore, new promising models such as hTERT-immortalised cells and 3D-cultures are briefly discussed.

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.

Ochratoxin A Producing Fungi, Biosynthetic Pathway and Regulatory Mechanisms

Ochratoxin A (OTA), mainly produced by Aspergillus and Penicillum species, is one of the most important mycotoxin contaminants in agricultural products. It is detrimental to human health because of its nephrotoxicity, hepatotoxicity, carcinogenicity, teratogenicity, and immunosuppression. OTA structurally consists of adihydrocoumarin moiety linked with l-phenylalanine via an amide bond. OTA biosynthesis has been putatively hypothesized, although several contradictions exist on some processes of the biosynthetic pathway. We discuss recent information on molecular studies of OTA biosynthesis despite insufficient genetic background in detail. Accordingly, genetic regulation has also been explored with regard to the interaction between the regulators and the environmental factors. In this review, we focus on three aspects of OTA: OTA-producing strains, OTA biosynthetic pathway and the regulation mechanisms of OTA production. This can pave the way to assist in protecting food and feed from OTA contamination by understanding OTA biosynthetic pathway and regulatory mechanisms.

Grafting of gallic acid onto chitosan nano particles enhances antioxidant activities in vitro and protects against ochratoxin A toxicity in catfish (Clarias gariepinus)

This study aimed to prepare and characterize enzymatic modified chitosan nanoparticles (CSNPs) with gallic acid (GA) or octyl gallate (OG) to optimize its potential in human application and to evaluate their protective role against ochrtoxin A (OTA) toxicity in catfish. The modified CSNPs have average size around 90 nm with positive charge and high scavenging activity especially GA-CSNPs. In the in vivo study, catfish were divided into 8 groups and treated for 3 weeks as follow: the control group, OTA-treated group (1 mg/kg b.w.), the groups treated with CSNPs, GA-CSNPs or OG-CSNPs (280 mg/kg b.w.) anole or in combination with OTA. Blood, liver and kidney samples were collected for different analyses. OTA induced a significant biochemical disturbances accompanied with oxidative stress in liver and kidney, histological changes and increase DNA fragmentation in the kidney. Co-treatment with OTA plus the different CSNPs resulted in a significant improvement in all tested parameters and histological picture of the kidney. This improvement was more pronounced in the group treated with GA-CSNPs. It could be concluded that grafting of GA or its ester improved the properties of CSNPs. Moreover, GA-CSNPs showed strong scavenging properties than OG-CSNPs due to the blocking of carboxyl groups responsible of the scavenging activity in OG.

Modulation of the xenobiotic transformation system and inflammatory response by ochratoxin A exposure using a co-culture system of Caco-2 and HepG2 cells

Cytotoxicity of ochratoxin A (OTA) was evaluated using the MTS assay, and membrane integrity was measured using transepithelial electrical resistance (TEER). A transwell system was used to investigate the effect of OTA on the expression of the CYP450 (1A1, 2A6, 2B6, 3A4 and 3A5), NAT2, COX-2, LOX-5, and MRP2 genes in Caco-2 and HepG2 cells. TEER decreased by a mean of 63.2% after 24 h in Caco-2 differentiated cells without inducing cell detachment; revealing damage to the intestinal epithelial cell tight junction proteins and an increase in cell permeability. Gene expression analysis showed that modulation of gene expression by OTA was higher in Caco-2 cells than in HepG2 cells, and generally, the duration of exposure to OTA had a more significant effect than the OTA dose. A general OTA down-regulation effect was observed in Caco-2 cells, in contrast with the down- and up-regulation observed in HepG2 cells. In Caco-2 cells, CYP1A1 was the gene with the highest regulation, followed by CYP3A4 and CYP3A5. Conversely, in HepG2 cells, CYP2B6 was highly regulated at 3 and 12 h compared to the other cytochromes; CYP1A1 was slightly modulated during the first 12 h, but an overexpression was observed at 24 h. Our data support the involvement of the COX-2 and 5-LOX genes in liver metabolism of OTA. On the basis of the gene expression analysis, the results suggest a possible impairment in OTA secretion at the intestinal and hepatic level due to MRP2 repression. In addition, we provide evidence of the effect of OTA on NAT2 gene expression, which had not been reported before.

Aspirin and probenecid inhibit organic anion transporter 3-mediated renal uptake of cilostazol and probenecid induces metabolism of cilostazol in the rat

This study aimed to evaluate the transporter-mediated renal excretion mechanism for cilostazol and to characterize the mechanism of drug-drug interaction (DDI) between cilostazol and aspirin or probenecid. Concentrations of cilostazol and its metabolites OPC-13015 [6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy]-2(1H)-quinolinone] and OPC-13213 [3,4-dihydro-6-[4-[1-(trans-4-hydroxycyclohexyl)-1H-tetrazol-5-yl]butoxy]-2-(1H)-quinolinone] in rat biologic or cell samples were measured by liquid chromatography-tandem mass spectrometry. Coadministration with probenecid, benzylpenicillin, or aspirin decreased the cumulative urinary excretion of cilostazol and renal clearance. Concentrations of cilostazol and OPC-13213 in plasma decreased, and the concentration of OPC-13015 increased in the presence of probenecid. By contrast, rat plasma cilostazol, in combination with benzylpenicillin or aspirin, sharply increased, and concentrations of OPC-13015 and OPC-13213 did not change. In urine, OPC-13015 was below the level of detection. The cumulative urinary excretion of OPC-13213 decreased in the presence of probenecid, benzylpenicillin, or aspirin. Cilostazol was distributed in the kidney and liver, with tissue to plasma partition coefficient (Kp) values of 8.4 ml/g and 16.3 ml/g, respectively. Probenecid and aspirin reduced cilostazol distribution in the kidney. Probenecid did not affect cilostazol metabolism in the kidney but increased cilostazol metabolism in the liver, and aspirin had no effect on cilostazol metabolism. Benzylpenicillin, aspirin, and cyclo-trans-4-l-hydroxyprolyl-l-serine (JBP485) reduced cilostazol uptake in kidney slices and human organic anion transporter 3 (hOAT3)-human embryonic kidney 293 (HEK293) cells, whereas p-aminohippuric acid did not. Compared with the vector, hOAT3-HEK293 cells accumulated more cilostazol, whereas hOAT1-HEK293 cells did not. OAT3 and Oat3 play a major role in cilostazol renal excretion, whereas OAT1 and Oat1 do not. Oat3 and Cyp3a are both targets of the DDI between cilostazol and probenecid. Aspirin inhibits OAT3-mediated uptake of cilostazol and does not influence cilostazol metabolism.

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 200 g) were fed with OTA-contaminated feed (initially approximately 300 μg kg(-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 12.5 μg ml(-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.

Ochratoxin A: developmental and reproductive toxicity-an overview

Ochratoxin A (OTA) is nephrotoxic, hepatotoxic, reprotoxic, embryotoxic, teratogenic, neurotoxic, immunotoxic, and carcinogenic for laboratory and farm animals. Male and female reproductive health has deteriorated in many countries during the last few decades. A number of toxins in environment are suspected to affect reproductive system in male and female. OTA is one of them. OTA has been found to be teratogenic in several animal models including rat, mouse, hamster, quail, and chick, with reduced birth weight and craniofacial abnormalities being the most common signs. The presence of OTA also results in congenital defects in the fetus. Neither the potential of OTA to cause malformations in human nor its teratogenic mode of action is known. Exposure to OTA leads to increased embryo lethality manifested as resorptions or dead fetuses. The mechanism of OTA transfer across human placenta (e.g., which transporters are involved in the transfer mechanism) is not fully understood. Some of the toxic effects of OTA are potentiated by other mycotoxins or other contaminants. Therefore, OTA exposure of pregnant women should be minimized. OTA has been shown to be an endocrine disruptor and a reproductive toxicant, with abilities of altering sperm quality. Other studies have shown that OTA is a testicular toxin in animals. Thus, OTA is a biologically plausible cause of testicular cancer in man.

Toxicity of ochratoxin a and its modulation by antioxidants: a review

Ochratoxin A (OTA) is a mycotoxin involved in the development of different types of cancers in rats, mice and humans. A growing number of in vitro and in vivo studies has been collected and has described evidence compatible with a role for oxidative stress in OTA toxicity and carcinogenicity. Because the contribution of the oxidative stress response in the development of cancers is well established, a role in OTA carcinogenicity is plausible. Several studies have been performed to try to counteract the adverse effects of oxygen radicals generated under OTA-exposure. A number of molecules with various antioxidant properties were tested, using in vivo or in vitro models. Protection against OTA-induced DNA damage, lipid peroxidation, as well as cytotoxicity were observed, further confirming the link between OTA toxicity and oxidative damage. These studies demonstrated that antioxidants are able to counteract the deleterious effects of chronic consumption or exposure to OTA and confirmed the potential effectiveness of dietary strategies to counteract OTA toxicity.

A review on ochratoxin A transcriptomic studies

The mycotoxin Ochratoxin A (OTA) is a potent renal carcinogen in male rats. Transcriptomic studies on OTA (4 in vitro, 6 in vivo, 2 in vitro/in vivo) have been reviewed. The aim of 6 of them was mainly mechanistic whereas the rest had mostly predictive (1) or evaluation (5) purposes. An overall tendency towards gene expression downregulation was observed, probably as a result of protein synthesis inhibition. DNA damage response genes were not deregulated in most of the studies. Genes involved in acute renal injury, cell survival and cell proliferation were upregulated in several in vivo studies. Apoptosis genes were deregulated in vitro but less affected in vivo; activation of several MAPKs has been observed. Many genes related to oxidative stress or involved in cell-to-cell interaction pathways (Wnt) or cytoskeleton structure appeared to be deregulated either in vitro or in vivo. Regucalcin was highly downregulated in vivo and other calcium homeostasis genes were significantly deregulated in vitro. Genes related to OTA transport (OATs) and metabolism (CYPs) appeared downregulated in vivo. Overall, the mechanism of action of OTA remains unclear, however transcriptomic data have contributed to new mechanistic hypothesis generation and to in vitro-in vivo comparison.

A review of the diagnosis and treatment of Ochratoxin A inhalational exposure associated with human illness and kidney disease including focal segmental glomerulosclerosis

Ochratoxin A (OTA) exposure via ingestion and inhalation has been described in the literature to cause kidney disease in both animals and humans. This paper reviews Ochratoxin A and its relationship to human health and kidney disease with a focus on a possible association with focal segmental glomerulosclerosis (FSGS) in humans. Prevention and treatment strategies for OTA-induced illness are also discussed, including cholestyramine, a bile-acid-binding resin used as a sequestrant to reduce the enterohepatic recirculation of OTA.

Structure-activity relationships imply different mechanisms of action for ochratoxin A-mediated cytotoxicity and genotoxicity

Ochratoxin A (OTA) is a fungal toxin that is classified as a possible human carcinogen based on sufficient evidence for carcinogenicity in animal studies. The toxin is known to promote oxidative DNA damage through production of reactive oxygen species (ROS). The toxin also generates covalent DNA adducts, and it has been difficult to separate the biological effects caused by DNA adduction from that of ROS generation. In the current study, we have derived structure-activity relationships (SAR) for the role of the C5 substituent of OTA (C5-X = Cl) by first comparing the ability of OTA, OTBr (C5-X = Br), OTB (C5-X = H), and OTHQ (C5-X = OH) to photochemically react with GSH and 2'-deoxyguanosine (dG). OTA, OTBr, and OTHQ react covalently with GSH and dG following photoirradiation, while the nonchlorinated OTB does not react photochemically with GSH and dG. These findings correlate with their ability to generate covalent DNA adducts (direct genotoxicity) in human bronchial epithelial cells (WI26) and human kidney (HK2) cells, as evidenced by the (32)P-postlabeling technique. OTB lacks direct genotoxicity, while OTA, OTBr, and OTHQ act as direct genotoxins. In contrast, their cytotoxicity in opossum kidney epithelial cells (OK) and WI26 cells did not show a correlation with photoreactivity. In OK and WI26 cells, OTA, OTBr, and OTB are cytotoxic, while the hydroquinone OTHQ failed to exhibit cytotoxicity. Overall, our data show that the C5-Cl atom of OTA is critical for direct genotoxicity but plays a lesser role in OTA-mediated cytotoxicity. These SARs suggest different mechanisms of action (MOA) for OTA genotoxicity and cytotoxicity and are consistent with recent findings showing OTA mutagenicity to stem from direct genotoxicity, while cytotoxicity is derived from oxidative DNA damage.

An update on direct genotoxicity as a molecular mechanism of ochratoxin a carcinogenicity

Ochratoxin A (OTA) is a naturally occurring chlorophenolic fungal toxin that contaminates a wide range of food products and poses a cancer threat to humans. The mechanism of action (MOA) for OTA renal carcinogenicity is a controversial issue. In 2005, direct genotoxicity (covalent DNA adduct formation) was proposed as a MOA for OTA-mediated carcinogenicity [ Manderville , R. A. ( 2005 ) Chem. Res. Toxicol. 18 , 1091 - 1097 ]. At that time, inconsistent results had been published on OTA genotoxicity/mutagenicity, and conclusive evidence for OTA-mediated DNA adduction had been lacking. In this update, published data from the past 6-7 years are presented that provide new hypotheses for the MOA of OTA-mediated carcinogenicity. While direct genotoxicity remains a controversial issue for OTA, new findings from the Umemura and Nohmi laboratories provide definitive results for the mutagenicity of OTA in the target tissue (outer medulla) of male rat kidney that rules out oxidative DNA damage. These findings, coupled with our own efforts that provide new structural evidence for DNA adduction by OTA, has strengthened the argument for involvement of direct genotoxicity in OTA-mediated renal carcinogenesis. This MOA should be taken into consideration for OTA human risk assessment.

Ochratoxin A induces CYP3A4, 2B6, 3A5, 2C9, 1A1, and CYP1A2 gene expression in primary cultured human hepatocytes: a possible activation of nuclear receptors

Ochratoxin A (OTA) is a mycotoxin produced by fungi of two genera: Penicillium and Aspergillus. OTA has been shown to be nephrotoxic, hepatotoxic, teratogenic, and immunotoxic to several species of animals and to cause kidney and liver tumors in mice and rats. Biotransformation of OTA has not been entirely elucidated. Several metabolites have been characterized in vitro and/or in vivo, whereas other metabolites remain to be characterized. At present, data available regarding OTA metabolism and cytochrome inductions concern only rodents or in vitro systems. The aim of the present study was to explore the effect of OTA on mRNA expression of some cytochromes known to be regulated by pregnane X receptor (PXR), constitutive androstane receptor (CAR), and aryl hydrocarbon receptor (AhR), using primary cultures of human hepatocytes. Our results showed that OTA reduced hepatocyte viability in a dose-dependent manner. Using quantitative real-time reverse-transcription polymerase chain reaction, our study showed that treatment of primary cultured human hepatocytes with noncytotoxic increasing concentrations of OTA for 24 hours caused a significant upregulation of CYP3A4, CYP2B6, and, to a lesser extent, CYP3A5 and CYP2C9. PXR mRNA expression increased in only 1 treated liver, whereas CAR mRNA expression was not affected. OTA was found also to induce an overexpression of CYP1A1 and CYP1A2 genes accompanied by an increase in AhR mRNA expression. These findings suggest that OTA could activate PXR and AhR; however, further investigations are needed to confirm nuclear-receptor activation by OTA.

Human ochratoxin a biomarkers--from exposure to effect

Ochratoxin A (OTA) is a nephrotoxic mycotoxin that has received particular attention because of the toxic effects, widespread occurrence in contaminated food and feed chain, suspected causal effect on nephropathies, and, more recently, possibility of exposure by inhalation in domicile and occupational settings. Biomarkers have been used not only to ascertain the role of OTA in inducing chronic renal failure diseases, but also as a means to portray general populations' risk to the mycotoxin. Biomonitoring can thus be used to assess internal OTA exposure, with no need to recognize the main source of exposure. And so it presents undeniable advantages over the monitoring of external dose. With a just right understanding of biomarkers, it is possible to follow the trail from exposure right to effect, and so contribute both to surveillance plans and etiological studies. In recognition of the long serum half-life and the renal elimination of OTA, most of the studies present serum/plasma and/or urine analyses as markers of exposure. In this review and for each of these main matrices, a comparison over the advantages and disadvantages is offered. Although currently limited, an overview of the current knowledge on OTA biomarkers and the influential role of the individual characteristics, namely gender and age, along with season and geographical location is given. Attention is also given to the ongoing debate over the existence of OTA-DNA adducts, a biomarker of effective dose regarded as an alternative to biomarkers of internal dose. Although unspecific, OTA effect biomarkers are also reviewed.

«Suspects» in etiology of endemic nephropathy: aristolochic acid versus mycotoxins

Despite many hypotheses that have been challenged, the etiology of endemic nephropathy (EN) is still unknown. At present, the implications of aristolochic acid (AA) and mycotoxins (ochratoxin A-OTA and citrinin-CIT) are under debate. AA-theory is based on renal pathohistological similarities between Chinese herbs nephropathy (CHN) and EN, findings of AA-DNA adducts in EN and in patients with urinary tract tumors (UTT), as well as the domination of A:T®T:A transversions in the p53 mutational spectrum of UTT patients, which corresponds with findings of such mutations in AA-treated rats. However, exposure pathways of EN residents to AA are unclear. Experimental studies attempting to deduce whether nephrotoxins OTA and CIT appear at higher frequencies or levels (or both) in the food and blood or urine of EN residents support the mycotoxin theory. Also, some molecular studies revealed the presence of OTA-DNA adducts in the renal tissue of EN and UTT patients. In this review, data supporting or arguing against AA and mycotoxin theory are presented and discussed.

Ochratoxin A: in utero exposure in mice induces adducts in testicular DNA

Ochratoxin A (OTA) is a nephrotoxin and carcinogen that is associated with Balkan endemic nephropathy and urinary tract tumors. OTA crosses the placenta and causes adducts in the liver and kidney DNA of newborns. Because the testis and kidney develop from the same embryonic tissue, we reasoned that OTA also may cause adducts transplacentally in the testis. We tested the hypothesis that acute exposure to OTA, via food and via exposure in utero , causes adducts in testicular DNA and that these lesions are identical to those that can be produced in the kidney and testis by the consumption of OTA. Adult mice received a single dose of OTA (from 0–1,056 µg/kg) by gavage. Pregnant mice received a single i.p. injection of OTA (2.5 mg/kg) at gestation day 17. DNA adducts were determined by 32P-postlabeling. Gavage-fed animals sacrificed after 48 hours accumulated OTA in kidney and testis and showed DNA adducts in kidney and testis. Some OTA metabolites isolated from the tissues were similar in both organs (kidney and testis). The litters of mice exposed prenatally to OTA showed no signs of overt toxicity. However, newborn and 1-month old males had DNA adducts in kidney and testis that were chromatographically similar to DNA adducts observed in the kidney and testis of gavage-fed adults. One adduct was identified previously as C8-dG-OTA adduct by LC MS/MS. No adducts were observed in males from dams not exposed to OTA. Our findings that in utero exposure to OTA causes adducts in the testicular DNA of male offspring support a possible role for OTA in testicular cancer.

Ochratoxin a: general overview and actual molecular status

Ochratoxin A (OTA) is a mycotoxin produced by several species of Aspergillus and Penicillium fungi that structurally consists of a para-chlorophenolic group containing a dihydroisocoumarin moiety that is amide-linked to L-phenylalanine. OTA is detected worldwide in various food and feed sources. Studies show that this molecule can have several toxicological effects such as nephrotoxic, hepatotoxic, neurotoxic, teratogenic and immunotoxic. A role in the etiology of Balkan endemic nephropathy and its association to urinary tract tumors has been also proved. In this review, we will explore the general aspect of OTA: physico-chemical properties, toxicological profile, OTA producing fungi, contaminated food, regulation, legislation and analytical methods. Due to lack of sufficient information related to the molecular background, this paper will discuss in detail the recent advances in molecular biology of OTA biosynthesis, based on information and on new data about identification and characterization of ochratoxin biosynthetic genes in both Penicillium and Aspergillus species. This review will also cover the development of the molecular methods for the detection and quantification of OTA producing fungi in various foodstuffs.

Ochratoxins-food contaminants: impact on human health

Ochratoxins are secondary metabolites of Aspergillus and Penicillium, that are hazardous to health through contamination of dietary foods. Ochratoxin A (OTA) remains the single most potent member of this group of mycotoxins. OTA has a long half-life in humans and is thus easily detected in serum. Dietary intake studies have confirmed link between endemic nephrotoxicity in humans to their daily household intake of OTA. OTA has been reported to contribute to endemic nephrotoxicity and carcinogenicity in humans and animals. OTA produces renal tumours, DNA adducts and chromosomal aberrations in kidneys. OTA may be embryotoxic, teratogenic, and immunotoxic only at doses higher than those causing nephrotoxicity. The incidence of endemic nephrotoxicity has been mostly reported in northeast Europe since the early fifties. Recent studies however have warned that OTA and other toxins, such as aristolochic acid, show very similar renal pathology. There is thus the need for thorough co-occurrence studies on toxin incidence.

Studies on carcinogenic and toxic effects of ochratoxin A in chicks

Carcinogenic/toxic effects of ochratoxin A (OTA) in various internal organs of Plymouth Rock chicks were determined. The number of OTA-induced neoplasms was similar in chicks given 25 ppm L-β-phenylalanine (PHE) in addition to 5 ppm OTA compared to chicks given only 5 ppm OTA, which showed that PHE cannot be used as a real protector against the carcinogenic or toxic effects of OTA in chicks. OTA was found to provoke strong degenerative changes in liver and kidneys, degenerative changes and depletion of cells in lymphoid organs, oedematous and degenerative changes in the brain, muscular haemorrhages and fatty changes in the bone marrow. The target organs for carcinogenic effect of OTA in chicks were found to be kidneys and liver.

Oncological outcomes in rats given nephrocarcinogenic exposure to dietary ochratoxin a, followed by the tumour promoter sodium barbital for life: a pilot study

The potent experimental renal carcinogenesis of ochratoxin A (OTA) in male rats makes the dietary contaminant a potential factor in human oncology. We explored whether the tumour promoter sodium barbitate could shorten the otherwise long latency between exposure to toxin and tumourigenesis. Young rats, of a hybrid in which mononuclear leukaemia was rare, were given feed contaminated (5 ppm) with OTA for 36 weeks to initiate renal tumourigenesis. Some individuals were thereafter given sodium barbitate (500 ppm in drinking water) for life. Pathological outcomes were studied at or near the end of natural life. Renal tumours in males given barbitate became evident after latency of one year, but only slightly before those without barbitate. In contrast, female mammary tumourigenesis was advanced by at least 6 months synchronously in all rats given the OTA-barbitate regimen compared to tumourigenesis in controls. Diagnosis of malignant mammary angiosarcoma in a female given the OTA-barbitate regimen is a new finding in the rat. The long latency of OTA-induced renal tumourigenesis was not notably susceptible to accelerated promotion by barbitate, contrasting with an apparently marked effect of barbitate on development of mammary tumours.

Ochratoxin A and aristolochic acid involvement in nephropathies and associated urothelial tract tumours

This review addresses the unresolved aetiology of several nephropathies and associated upper tract tumours diagnosed all over the world, but especially in the Balkan regions. Studies conducted over the last 35 years point to mycotoxins, mainly ochratoxin A (OTA) as the main culprit. Recent theories however have implicated aristolochic acids (AA). The aim of this review is to put forward arguments in favour of the mycotoxin theory and to show the incoherence of the AA theory. It discusses the differences between the epidemiology of Balkan endemic nephropathy (BEN) and aristolochic acid nephropathy (AAN); OTA and AA carcinogenicity; clinical and pathological effects induced by OTA and AA; sources of OTA contamination (food, air, drinking water); OTA- and AA-DNA adduct formation; the role of genetic polymorphisms; and the risk for young children.

Enzymatic hemisynthesis of metabolites and conjugates of anthocyanins

This work aims to study the phase II metabolization of anthocyanins that is likely to occur in vivo. Anthocyanins (delphinidin, cyanidin, and malvidin-3-glucosides) were incubated with phase II enzymes in the presence of activated cofactors in order to obtain glutathionyl conjugates, methylated and glucuronydated compounds. Overall, the three anthocyanins tested were metabolized in vitro. Two compounds were detected by HPLC after incubation of human liver cytosolic fraction with cyanidin-3-glucoside and one compound with delphinidin-3-glucoside. These compounds were identified as monomethylated products. LC-MS analysis yielded mass data that fit with the anthocyanin structures bearing an additional methyl group in ring B. Several compounds were detected by HPLC after incubation of human liver microsomes with malvidin, cyanidin, and delphinidin-3-glucosides. These compounds were identified as monoglucuronides products after HPLC analysis. Conjugation with glutathione also occurred as proved by the mass data obtained. However, in this case, two anthocyanin equilibrium forms (flavylium and chalcone or water adducts) conjugated with glutathione were detected. Overall, the data of the present work shows the feasibility of the in vitro enzymatic hemisynthesis of metabolites and glutathione conjugates of anthocyanins. This first experimental approach may further allow the achievement of new purified forms of anthocyanins, some of which do not occur in nature, and also the determination of whether these compounds are the bioactive forms responsible for some of the biological activities reported for anthocyanins.