- freely available
Toxins 2013, 5(10), 1742-1766; doi:10.3390/toxins5101742
Published: 11 October 2013
Abstract: 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.
1. Overview of Mycotoxins
Mycotoxins are secondary metabolites of some fungi belonging to Aspergillus, Penicillium and Fusarium species and are common contaminants of human foodstuffs, such as wine, coffee beans, nuts and animal feed. Mycotoxins can enter the food chain through contaminated cereals and foodstuffs (e.g., milk, meat, eggs) obtained from animals fed mycotoxin-contaminated feedstuffs. Mycotoxins can cause serious health problems in animals and humans known as mycotoxicosis. The major problem associated with animal feed contaminated with mycotoxins is not acute disease episodes, but rather, the ingestion of low levels of toxins, which may cause an array of metabolic, physiologic and immunologic disturbances. The most extensively investigated mycotoxins are aflatoxins (AF), deoxynivalenol (DON), zearalenone (ZEN), fumonisin B1 (FB1) ochratoxin A (OTA) and T2 toxin [1,2,3,4,5].
Mycotoxins are challenging to classify, due to their diverse chemical structures and biosynthetic origins, their myriad of biological effects and their production by a wide number of different fungal species. Thus, mycotoxins can be classified as hepatotoxins, nephrotoxins, neurotoxins, immunotoxins, teratogens, mutagens, carcinogens, allergens, and so forth. Moreover, by their chemical structures, mycotoxins can be classified as lactones and coumarins, according to their biosynthetic origins, as polyketides, amino acid-derived, etc., and, finally, by the fungi that produce them (e.g., Aspergillus toxins, Penicillium toxins). Then, the same compound may get placed in different cognitive cubbyholes. Aflatoxin, for example, is a hepatotoxic, mutagenic, carcinogenic, difuran-containing, polyketide-derived Aspergillus toxin. Zearalenone is a Fusarium metabolite with potent estrogenic activity.
Some mycotoxins are specifically indicated or strongly suspected as the cause of severe human and animal diseases, such as Reye’s disease, caused by aflatoxin B1 (AFB1), equine leukoencephalomalacia and porcine pulmonary edema, caused by fuminisin B1 (FB1), human alimentary toxic aleukia, caused by T2 toxin, and Balkan endemic nephropathy, caused by ochratoxin A. The positive correlation between the consumption of AFB1-contaminated foods and the increased incidence of liver cancer in several Asian and African populations led to the classification of AFB1 as a group 1A carcinogens by the International Agency for Research on Cancer .
The first Joint Food and Agricultural Organization (FAO)/World Health Organization (WHO) Conference on Food Additives, was held in September, 1955 , and since then, there have been 76 meetings of the Committee. In 1991 the joint FAO/WHO Expert Committee on Food Additives (JECFA) first evaluated OTA and, based on the LOAEL (Lowest Observed Adverse Effect Level) in pig, allocated a Provisional Tolerable Weekly Intake (PTWI) of 112 ng/kg body weight (bw) . This value was rounded to 100 ng/kg bw/week and confirmed in several subsequent meetings [9,10].
In 1997, the Joint FAO/WHO Expert Committee on Food Additives provided qualitative and quantitative information on aflatoxins and concluded that aflatoxins should be treated as carcinogenic food contaminants, the intake of which should be reduced to levels as low as reasonably achievable . In 2002, the Joint FAO/WHO Expert Committee on Food additive evidenced that several mycotoxins may exist in many contaminated foodstuffs and foodstuff products. Moreover, contaminated feeds are frequently more toxic than the pure toxin in animals and humans, indicating possible interactions. The Committee, therefore, recommended further studies on mycotoxins occurring concomitantly in foods, their possible interactions and how the toxicological significance of such interactions could be assessed .
In 2007, the Joint FAO/WHO Expert Committee on Food Additives noted that the reduction of dietary AF exposure is an important public health goal, particularly in populations that consume high levels of any potentially AF-contaminated food. Moreover the Committee reported new data on estimates of dietary exposure to OTA, which causes various toxic effects, such as neurotoxicity, immunotoxicity, nephrotoxicity and genotoxicity . In 2008, JECFA applied a benchmark dose (BMD) modeling approach using carcinogenicity data .
Most studies were conducted in vitro and in vivo on mycotoxins, particularly on AFB1, OTA and FB1. This review focuses on ochratoxin A toxicity and the protective effects of antioxidants.
2. Ochratoxin A
OTA, or (R)-N-[(5-chloro-3,4-dihydro-8-hydroxy-3-methyl-1-oxo-1H-2-benzopyran-7-yl)carbonyl)-l-phenylalanine, is a naturally occurring mycotoxin soluble in organic solvents, in aqueous solution of sodium bicarbonate and slightly soluble in water. OTA is efficiently absorbed from the gastrointestinal tract, mainly in the small intestine. Information from a number of species shows that it is distributed via the blood, mainly to the kidneys, with lower concentrations found in liver, muscle and fat. Specific transporters may be involved in the cellular uptake of ochratoxin A into the kidney, where it accumulates . Transfer to milk has been demonstrated in rats, rabbits and humans, but little OTA is transferred to the milk of ruminants, owing to efficient hydrolysis of the amide bond by microflora in the rumen, to yield phenylalanine and ochratoxin alpha. Ochratoxin alpha, a chlorinated dihydroisocoumarin, is not the only metabolite of OTA. There are several papers dealing with biotransformation of OTA into several metabolites, such as Ochratoxin B (OTB), open-ring ochratoxin A (OP-OA), 4 hydroxylated OTA, 10 hydroxylated OTA, OTA without phenylalanine, OTB without phenylalanine, OTA hydroquinone (OTHQ) and a dechlorinated ochratoxin A derivative. Some of these, such as OTHQ and OP-OA, are much more toxic than OTA itself [15,16,17,18]. OTA is produced by several fungi of Aspergillus and Penicillium species, often found in a variety of food commodities, such as cereals, green coffee, cocoa, dried fruits and meat products, resulting in continuous exposure of the human population to OTA . OTA has been shown to be nephrotoxic, hepatotoxic, teratogenic and immunotoxic to several species of animals and is known to cause kidney and liver tumors in mice and rats [20,21,22]. In humans, it has been related to Balkan endemic nephropathy [23,24,25,26], although this hypothesis has not been completely demonstrated. Recently, other nephrotoxic agents have been put forward as the primary cause of Balkan endemic nephropathy (BEN) [27,28,29].
In farm animals, chronic exposure to OTA produces a well-described nephropathy . OTA is a mycotoxin, with important implications for animal and human health. Exposure to OTA is a worldwide phenomenon, as evidenced by its detection in sera from human individuals of many countries.
However, human epidemiology has been inconclusive. Epidemiological data were recently reviewed by several expert groups [31,32,33]. All concluded that the causality between the intake of OTA and human nephropathy could not be established. Therefore, the International Agency for Research on Cancer (IARC) statement that there is inadequate evidence for carcinogenicity in humans (group 2B) appears still valid .
In absence of adequate human data, risk assessments have relied on studies conducted in laboratory animals, where it causes various toxic effects, the most relevant being nephrotoxicity and nephrocarcinogenicity in rats . A number of mechanisms have been proposed to account for OTA toxicity and OTA-induced renal tumor formation: inhibition of protein synthesis, interference with metabolic systems involving phenylalanine, promotion of membrane lipid peroxidation, disruption of calcium homeostasis, inhibition of mitochondrial respiration and DNA damage [15,34,35,36,37,38]. Other research has focused on the ability of OTA to disturb cellular signaling and regulation, as well as to modulate physiological signals, known to influence cell viability and proliferation. Recent studies have specifically focused on (i) metabolism-mediated toxicity via oxidative stress, (ii) intracellular OTA accumulation as a function of organic anion transporters and (iii) inter- and intra-cellular signal transduction at nanomolar concentrations [39,40].
In a review by O’Brien and Dietrich  on its toxicological properties, OTA has justly been called “the continuing enigma”. According to the authors, it is not yet clear whether the predominant toxic mechanism of OTA is of a genotoxic or epigenetic nature, such as induced cytotoxicity, oxidative cell stress or increased cell proliferation, due to an imbalance between proliferative and antiproliferative intracellular signal pathways. However, both the carcinogenicity and cytotoxicity of OTA have been related to free radical-mediated oxidative cell damage [42,43,44,45,46,47,48,49,50,51]. Schaaf et al.  attributed proximal tubule cell damage caused by OTA to the formation of reactive oxygen species, such as the superoxide anion (O2∙), hydroxyl radical (∙OH) and peroxide (ROO∙), which induce a wide range of lesions in cell components. Other authors reported that the hydroxyl radical was not involved in the process, but a role for cytochrome P450 in this reaction was suggested: CYP450 is able to stimulate OTA-dependent lipid peroxidation and this action is mediated by OTA-Fe3+/2+ complexes [52,53,54]. It has been shown that oxidative damage contributes to the wide range of toxic effects of OTA [47,55,56].
Structure-activity studies have also suggested that the toxicity of OTA may be attributable to its isocoumarin moiety and that the lactone carbonyl group may be involved in its toxicity. Using a Bacillus brevis model, Hoehler’s et al. showed that OTA behaved as a cell pro-oxidant through mobilization of the Fe2+ and Ca2+ pathways, leading to uncoupling oxidative phosphorylation and increased production of hydroxyl radical via the Fenton reaction . However, in other studies using OTA and structural analogs, a direct correlation between toxicity and iron chelating capacity was only partially supported . The generation of an OTA hydroquinone/quinone couple from the oxidation of OTA (phenol oxidation) by electrochemical, photochemical and chemical processes was reported [17,18,44,58]. Quinone is thought to undergo reductions to form hydroquinone, postulated to be responsible for the formation of the glutathione conjugate of OTA. Such events are likely to result in redox cycling and in the generation of reactive oxygen species [16,44,59]. The formation of OTA-derived quinones has been observed in cell cultures in vitro  as well as in vivo [26,60].
Our previous study  was aimed at verifying whether OTA is related to free radical-mediated oxidative cell damage. Male Sprague-Dawley rats received the control diet supplemented with 200 parts per billion of OTA. After four weeks of treatment, animals were killed, and the liver, kidneys and brain of each rat were collected and homogenized to evaluate non-proteic thiol groups (RSH), lipid hydroperoxide (LOOH) levels and DNA fragmentation. We observed that OTA induced alterations in LOOH and RSH levels, confirming the involvement of the oxidative pathway in damage induced by OTA in all the examined tissues compared with the control group. Analysis of DNA fragmentation evidenced that, following chronic consumption of OTA, DNA damage occurred in all three tissues under examination. These results confirm that kidney is the target organ, but also demonstrate that OTA toxicity to other organs should not be underestimated. Moreover, Cavin et al.  reported an OTA-mediated increase of the inducible nitric oxide synthase (iNOS) expression in a normal rat kidney cell line and in rat hepatocyte cultures, suggesting the induction of both oxidative and nitrosative stress. Strong evidence suggests that nitric oxide (NO), produced by three isoforms of nitric oxide synthases (neuronal NOS, endothelial NOS and inducible NOS), mediates a variety of actions, such as vasodilatation, neurotransmission, host defense against bacteria and angiogenesis [62,63].
Although conflicting data has been reported, an overwhelming amount of clinical and experimental evidence suggests a positive association between iNOS/endothelial NOS (eNOS) overexpression, NO production and tumor progression [64,65,66,67]. In particular, NO produced by eNOS may be involved in tumor angiogenesis . Modulation of NO production may therefore play an important role in the regulation of angiogenesis and, consequently, in tumor progression. Kostorou et al. reported the involvement of dimethylarginine dimethylaminohydrolase (DDAH) in cerebral tumor growth and the development of tumor vasculature ; this enzyme metabolizes the endogenous NOS inhibitor, asymmetric dimethylarginine (ADMA). Two isoforms of DDAH with distinct tissue distribution have been identified: DDAH-1 and DDAH-2 . Both isoforms have been identified in the kidney and liver tissues, but the expression of the DDAH-1 isoform appears more abundant [71,72]. In consideration of OTA nephrotoxicity and its possible involvement in the development of urinary tract tumors and, also, in view of the involvement of DDAH and NOS in tumor growth and the development of tumor vasculature, the aim of our subsequent study was to evaluate the effect of chronic OTA-exposure on the DDAH/NOS pathway in rats . The experiments were performed in male Sprague-Dawley albino rats treated under the same experimental conditions of our previous study . After four weeks of daily treatment, liver and kidneys were processed for eNOS, iNOS and DDAH-1 Western blotting, nitrite level evaluation and DDAH activity determination. It has been reported that the kidney is the target organ of OTA toxicity, probably because OTA is actively accumulated in kidney cells . Nevertheless, OTA has been shown to affect other organs, as well, including the liver. OTA has been shown to be hepatotoxic in rats . Recently, OTA renal and hepatic carcinogenicity was also observed in chicks .
Although the liver is not the main target organ for OTA, hepatocytes are exposed to OTA, since it has to pass through the liver after intestinal absorption . Results obtained in our study, in line with in vitro studies by Cavin  and Ferrante , allow us to suggest that, through iNOS induction, OTA is able to induce overproduction of NO, both in kidney and liver, resulting in increased nitrite and nitrate levels. Under normal conditions, NO presents a broad range of biological activities; conversely, in excess, it may behave as a toxic radical. In fact, NO is known to react with O2∙ to form the pro-oxidant peroxynitrite, ONOO− , with consequent nitrosative stress. As reported in our previous research , four-week OTA exposure is able to induce oxidative damage, both in kidney and in liver; then, overproduction of OTA-induced NO, in the same experimental conditions, may form the pro-oxidant ONOO−, both in kidney and liver. However, our data demonstrate that, only in kidney, OTA is also able to induce eNOS and DDAH-1 overexpression and DDAH activation with a further increase of NO levels. These data allowed us to speculate that, even if four weeks of exposure to OTA were much too low to induce renal tumors, one of the many possible mechanisms by which long-term OTA exposure may cause nephrocarcinogenity might consist in eNOS-DDAH involvement. Therefore, modulation of NO production may play an important role in regulation of angiogenesis and, consequently, in tumor progression.
2.1. Is OTA a Genotoxic or Non-Genotoxic Carcinogen?
Over the last few decades, studies aimed at elucidating the modes of action implicated in OTA toxicity and carcinogenicity have been published . There has been considerable debate for many years over the genotoxicity of OTA and its actual role in carcinogenicity [8,9,10,13,31,32,33,81,82,83]. Several authors and expert groups have concluded that OTA is genotoxic [35,37,38]. However, other authors indicate that OTA is unlikely to act through a direct genotoxic mechanism [12,32] and that its carcinogenicity is due to an indirect mechanism, such as induction of oxidative stress [36,87].
The genotoxic and mutagenic activity of OTA has been assessed in a variety of standard tests, in order to evidence direct DNA damage that could be the origin of the mechanism involved in chemical carcinogenesis, but the results that have been published are controversial. OTA was originally regarded as a non-mutagenic compound, because most bacterial assays gave negative results [85,86,87,88,89]. Positive results using Salmonella typhimurium Ames strains have only been reported using OTA-exposed hepatocyte culture medium  or in the presence of kidney microsomal fractions, instead of hepatic ones, as the metabolic activation system . These results suggested an important role on the part of metabolism in the genotoxicity of OTA and/or a selective toxicity in target kidney cells. In assays that detect unscheduled DNA synthesis due to repair processes, contradictory results have also been found. Bendele et al.  did not detect DNA repair synthesis induction in primary rat hepatocyte cultures; Mori et al.  found a weak DNA repair synthesis induction in mice and rat hepatocytes; a more pronounced effect was found in porcine urinary bladder epithelial cells by Dörrenhaus and Föllmann . These results pointed to a selective toxic effect of OTA in target cells.
The potential of OTA to form covalent DNA adducts has been subjected to debate, due to conflicting data in the literature. Using 32P-postlabelling analysis, large numbers of OTA-derived DNA adducts have been reported to be present in a wide range of tissues from OTA-treated rats, mice, as well as pigs [15,59,82,94,95,96]. However, according to some authors, these adducts have never been observed by any other highly-specific techniques, such as radioactivity measurements using 3H-labelled OTA (3H-OTA) accelerator mass spectrometry (AMS) or liquid chromatography-tandem mass spectrometry (LCMS/MS) [97,98], while for others, the formation of DNA adducts has been proven by isotope dilution LC-MS/MS . While results reported by Schlatter et al. and by Delatour et al. [97,98] indicate that covalent binding of OTA or some of its metabolites to DNA is not produced, therefore excluding the possibility of a genotoxic mechanism in the carcinogenicity of OTA, results reported by Mantle et al.  would not exclude it.
As reported by Pfohl-Leszkowicz A. , the 32P-postlabelling method evidences both adducts that contain the OTA itself and adducts that contain OTA metabolites, such as quinone (OTQ), derived as the products of oxidative stress. Nevertheless, other data suggest the idea that the phenoxyl radical of OTA can have a role in DNA adduction in vivo .
In the different assays that measure DNA fragmentation and chromosome aberrations, OTA has always given positive results. It has been shown to cause single-strand DNA breaks in rat and mice kidney and liver [100,101,102] and also in target and non-target cell lines of different species [35,56,103,104]. Many studies have been performed with the comet assay, and a few have evaluated oxidative DNA damage [56,100]. It has also been found that OTA induces micronuclei in cell lines of different origins, Hep G2, SHE (Syrian Hamster embryo) and OSV (ovine seminal vesicle) [103,105,106]. With the aim to study the ability of OTA to cause DNA damage in human kidney cells derived from proximal tubular cells, which are the toxic target, Arbillaga et al.  assayed the ability of OTA to induce DNA strand breaks and oxidative DNA damage using the alkaline comet assay in the human renal proximal tubular epithelial cell line (HK-2). Obtained data suggest that OTA is not acting as a direct genotoxic carcinogen and that oxidative stress is implicated in the genotoxicity and cytotoxicity observed in these human renal cells. In the same cell line (HK2), as well as in rat liver and kidney, covalent DNA adducts have been observed and related to OTA biotransformation [17,108]. Although, oral exposure to mycotoxins is the common route, it has been suggested by WHO that because of the employment of manual labor during the pre- and post-harvest stages of agriculture, dermal exposure to these chemicals may also occur . Therefore, Abel et al.  employed a two-stage mouse skin tumorigenesis model to study the tumorigenic property of OTA and related molecular events. Recently, Kumar et al. reported that topical application of OTA causes DNA damage and tumor initiation in mouse skin . It has been well established that DNA damage is an important event in the initiation of chemical carcinogenesis . Although conflicting data are reported regarding evidence of OTA-DNA adduct formation [16,17,51,60,113,114,115,116], the DNA damaging potential of OTA has been reported by various investigators, both in vivo and in vitro [32,41,56,83,100]. Therefore, it has been suggested that ROS and oxidative DNA damage could be one of the causative factors for OTA-induced toxicity and tumorigenicity . Kumar et al.  revealed that OTA has a skin tumor initiating property under in vivo conditions, which may be related to oxidative stress, Mitogen-activated protein kinases (MAPKs) signaling and DNA damage in mouse skin, and antioxidants may have a role in the prevention of OTA-induced tumorigenesis, which needs to be investigated.
OTA has been found to induce an increase in ROS levels and oxidative damage in some immortalized renal cell and cancer cell lines, such as human renal proximal tubular epithelial cells (HK-2), primary rat proximal tubular cells, proximal tubular cells (LLC-PK1), human hepatoma-derived cells (HepG2) and human colonic adenocarcinoma cells (CaCo-2) [43,107,118,119]. Cui et al. showed that OTA could induce G2 phase arrest and apoptosis in immortalized human gastric epithelial cells (GES-1) . Though most of the studies on OTA have been focused on renal toxicity or carcinogenicity [15,121], the immunosuppressive effects of OTA caused more and more attentions in the biomedical field. It is worth noting that OTA is frequently found in human blood, due to its widespread contamination in food and grains [24,122,123]. More importantly, OTA is a persistent toxin, which, following a single oral dose, remains in human circulation for a long time, due to the unfavorable kinetics of renal elimination [97,124]. As reported by Castegnaro et al. , with an average weekly intake of OTA that varies from 1.9 to 206 ng/kg body weight (twice the tolerable weekly intake recommended by JECFA), OTA blood concentrations are in a range reaching 10 µg/L.
Thus, it is quite reasonable for the objective evaluation of the hazardous bioeffects of OTA exposure on human to explore the possible effects of OTA on the immune cells in human peripheral blood. Assaf et al. showed that OTA could induce immunosuppression via marked apoptosis in human lymphocytes . It has been generally accepted that the induction of cell cycle arrest and apoptosis was an important bioeffect of many carcinogenic mycotoxins.
Liu et al. hypothesized that OTA exposure in blood might induce cell cycle arrest and apoptosis also in human peripheral blood mononuclear cells (hPBMC). The authors reported that in hPBMC, oxidative stress is involved in OTA-induced human immunotoxicity, and they conclude that OTA-induced DNA damage and G1 arrest may play roles in the carcinogenesis of OTA .
Moreover, studies have shown that OTA is produced by phytopathogenic Aspergillus ochraceus and Aspergillus carbonarius strains, suggesting that this toxin may play a role in the etiology of plant diseases . The plant response to attempted infection by microbial pathogens is often accompanied by rapid cell death in and around the initial infection site, a reaction known as the hypersensitive response (HR). Xenobiotics could also induce HR-like lesions. In the presence of OTA, the growth of Arabidopsis thaliana on media was significantly inhibited; in addition, cell death was observed with features resembling the HR-type lesions in excised leaves that were infiltrated with this toxin. There was also evidence that cell death was induced by OTA, such as the occurrence of an oxidative burst and the deposition of callose and phenolic compounds (autofluorescence) .
3. Ochratoxin A Toxicity: The Effect of Antioxidant Substances and Food Components
Due to its widespread threat to human health, the detoxification of OTA has been of major interest to researchers. Physical, chemical and biological methods have been developed to reduce and/or eliminate the toxic effects of contaminated products, improve food safety and minimize economic losses . However, the process of detoxification is often accompanied with a loss of palatability and nutritional values. The addition of nutrients or additives with protective properties to contaminated foodstuffs is one approach that reduces the toxicity of mycotoxins.
A growing number of in vitro and in vivo studies has been collected and described evidence compatible with a role for oxidative stress in OTA toxicity and carcinogenicity. For these reasons, several studies have been performed using antioxidants to try to counteract the adverse effects of oxygen radicals generated under OTA-treatment. Some of these studies are elaborately discussed below.
α-Tocopherol is a member of the vitamin E compound group that has several biological roles [131,132]. Vitamin E is a potent antioxidant; its function as a peroxyl radical scavenger that terminates chain reactions is well documented [133,134]. In one human and four animal cell lines, Baldi et al.  determined the half lethal concentration (LC50) of OTA, its effect on ROS production, and its ability to induce cytochrome P450 activity. They also examined the protective effect of α-tocopherol in the most sensitive cell lines (bovine mammary epithelial cells (BME-UV1) and Madin Darby canine kidney cells (MDCK)). Pre-incubation for 3 h with α-tocopherol significantly ameliorated the OTA-induced reduction in cell viability and significantly decreased ROS production. These findings indicate that oxidative stress is an important factor in OTA cytotoxicity, and supplementation with α-tocopherol may counteract OTA cytotoxicity. Fusi et al.  studied the role of α-tocopherol in counteracting several types of damage induced by OTA in primary porcine fibroblast cultures. OTA cytotoxicity developed through several mechanisms of action, such as Lactate dehydrogenase (LDH) release and DNA fragmentation. α-Tocopherol treatments reduce the damage induced by OTA at different cellular levels. The authors concluded that the use of α-tocopherol could offer new strategies to reduce OTA cytotoxicity, supporting its defensive role in the cell membrane and its multiple functions in cellular metabolism. Grosse et al.  reported the effects of some vitamins, such as retinol (A), ascorbic acid (C) and α-tocopherol (E), which are known to act as superoxide anion scavengers, on OTA genotoxicity. Pretreatment of mice by vitamin E decreased DNA adducts by 80% in kidney. Vitamin A decreased DNA adduct levels by 70% and vitamin C, by 90% in kidney. The decrease of the genotoxicity of OTA by vitamin A is due to the antioxidant properties of vitamin A. The decrease of the genotoxicity of OTA by vitamin E is due to the scavenging of lipid hydroperoxyl radicals by vitamin E. This is due to the increase of glutathione peroxidase, which utilizes glutathione (GSH) to catalyze the reduction of hydroperoxides. Vitamin E also induced Nicotinamide adenine dinucleotide phosphate reduced (NADPH):quinone reductase and glutathione S-transferase, which are detoxifying enzymes that reduce quinones. Ascorbic acid is the most efficient vitamin for inhibiting OTA genotoxicity. Vitamin C is an important antioxidant and a free radical scavenger, thereby preventing the production of electrophilic metabolites. Moreover, it is indispensable for the regeneration of vitamin E in lipid membranes and acts synergistically with other biological antioxidants, such as glutathione. This vitamin also decreased the activities of several cytochrome P450 isoenzymes.
3.2. Phenolic Compounds
Catechins are a class of phenolic compounds presents in green tea leaves, chocolate and some plants. They have been shown to have several healthy properties. Among them are anticancer properties [136,137] and protective capacity against oxidative stress-related diseases [138,139,140,141]. Costa et al. investigated the protective effect of two catechins (epigallocatechin gallate (EGCG) and epicatechin gallate (ECG)) against OTA-induced cytotoxicity in a pig kidney cell line (LLC-PK1) . The ability of the catechins to reduce ROS production and DNA fragmentation induced by OTA was also investigated. Costa et al. reported the cytoprotective effects of catechins in vitro from OTA-induced cell damage and a good scavenging power based on the inhibition of ROS production. In particular, a 24-h pre-treatment with EGCG or ECG restored cell viability with respect to OTA alone. Pretreatment with EGCG at low concentration for eight days protected cells from OTA-induced cell death. Moreover, both catechins reduced OTA-induced ROS production. A reduction of OTA-induced DNA fragmentation was found for LLC-PK1 cells pre-treated with EGCG and ECG. The free-radical scavenging capacity of both catechins was tested with the Briggs-Rauscher oscillating method and the Trolox equivalent antioxidant capacity (TEAC) assay. The results show a good scavenging power in accordance with the inhibition of ROS production. The authors concluded that catechins could be useful for developing alimentary strategies for both humans and animals to prevent OTA-induced cytotoxicity. Corcuera et al. prepared a polyphenol-enriched cocoa extract (PECE) and evaluated its ability to reduce OTA cytotoxicity and ROS induction in a cell-free system and in Hep G2 cells. Results reported by Corcuera et al. evidenced that polyphenols extracted from cocoa have a good antioxidant activity and may be efficient at reducing the generation of ROS produced by mycotoxins or other oxidant agents . The aim of our previous study  was to verify whether the oral administration of cyanidin 3-O-β-D-glucoside (C3G), an anthocyanin largely present in the human diet through beans, fruits, vegetables and red wine, might counteract damage induced by chronic exposure to OTA in rats and if its effect may be mediated by heme oxygenase-1 (HO-1). Male Sprague-Dawley rats were divided into four groups of ten animals. A control group received a commercial diet. Group C3G received the control diet supplemented with C3G (1 g/kg feed). Group OTA received the control diet supplemented with 200 parts per billion of OTA, and group OTA plus C3G received the OTA group diet supplemented with C3G. After four weeks of treatment, animals were killed, and the liver, kidneys and brain of each rat were processed as described above. In the OTA plus C3G group, both RSH content and LOOH levels were similar to those observed in the control group, demonstrating that C3G was able to counteract the effects of OTA. A significant induction of HO-1 was evident in kidney and liver of both OTA and C3G groups. DNA damage occurred in all the examined tissues of the OTA group, whereas C3G was able to prevent it. Results obtained in this study confirmed that the effects of OTA are mediated by oxidative stress and demonstrated that C3G efficiently counteracted the deleterious effects of OTA because of its antioxidant and HO-1-inducing properties. Since it has been reported that naturally occurring antioxidants that potently induce HO-1 expression lead to an increased resistance to oxidative stress-mediated damage, the beneficial actions attributed to several natural substances, such as C3G, could be due to their intrinsic ability to activate the HO-1 pathway [144,145,146].
Moreover, another of our previous studies  demonstrates that C3G, besides its well-known antioxidant activity, may also act with different molecular mechanisms. For this study, male Sprague-Dawley rats were treated and liver and kidneys were processed as described above. eNOS, iNOS and DDAH-1 Western blotting were performed. Nitrite levels were evaluated, and DDAH activity was determined. It has been reported that in tumor growth and tumor angiogenesis are involved different enzymes, such as iNOS, eNOS and DDAH-1. We reported that in kidney of rats treated with OTA plus C3G, iNOS, eNOS and DDAH-1 expression levels were less pronounced compared with those observed in the OTA group. Coherent with decreased iNOS, eNOS and DDAH-1 expression, a decrease of nitrite and nitrate levels and of DDAH activity was observed in the OTA plus C3G group. These results allow us to speculate that long-term consumption of C3G might contribute toward reducing OTA-induced tumor growth and tumor angiogenesis in kidney.
Liquorice extract from the dried roots of Glycyrrhiza glabra L. (Fabaceae) is one of the herbal medicines that is used widely in various countries . Extracted liquorice containing glycyrrhizin has been used as an additive for flavoring and sweetening tobacco, candies and beverages in many countries [148,149]. Vaya et al. demonstrated that liquorice plant extract (LPE) exerts a potent antioxidant capacity, as it possesses compounds, such as flavonoids . Malekinejad et al. showed a protective effect of LPE on OTA-induced nephrotoxicity in rats . Moreover, the authors in another study reported that histopathological analyses demonstrated that in OTA-exposed rats, testicular degeneration, seminiferous tubule atrophy, dissociation of germinative epithelium, vasodilatation with vascular thrombosis, perivascular immune cell infiltration, hypertrophied leydic cells, giant cell formation and a negative tubular differentiation index (TDI) were observed. They tested the effect of Glycyrrhiza glabra extract (GgE), as a natural antioxidant, and melatonin (MEL). Both the biochemical and histopathological examinations showed that MEL and GgE, albeit with some differences, exerted a protective effect on OTA-induced damages. The authors suggest that OTA contamination in animal feeds and human foods could cause reproductive abnormalities. Their data indicate that OTA, at least partly by interfering in the oxidative stress system, exerts its toxic effects on testes, whereas MEL and GgE, with antioxidant properties, could fairly protect rats against OTA toxic effects .
Oral administration of OTA to young weanling mice (Mus musculus) caused several hematological changes and induced hepatoma and renal carcinoma. Concurrent administration of berry and leaf juice of the common grape (Vitis vinifera) to mice together with OTA significantly reduced the hepatic and renal damage caused by ingestion of this mycotoxin. None of the animals receiving berry/leaf juice of Vitis vinifera showed the formation of hepatorenal carcinoma, whereas 25% of animals receiving only OTA developed well-differentiated renal carcinoma and hepatic lesions .
Lycopene, the most prevalent carotenoid in the Western diet, is majorly present in tomatoes. The consumption of tomatoes and/or tomato products is associated with increased lycopene blood levels and reduced oxidative damage of lipids, proteins and DNA . Lycopene has been suggested to have strong antioxidant potency in vitro, almost being 100 times more efficient in quenching singlet oxygen (1O2) than vitamin E . Lycopene may act as a chemopreventive agent against certain types of cancers (i.e., cancers of prostate, stomach, breast and lung) and was found to be protective against chemotherapeutic-induced renal damage in several studies [155,156,157,158]. Palabiyik et al.  investigated the possible protective effect of lycopene against the renal toxic effects of OTA. Male Sprague-Dawley rats were treated with OTA (0.5 mg/kg/day) and/or lycopene (5 mg/kg/day) by gavage for 14 days. Histopathological examinations were performed, and apoptotic cell death in both cortex and medulla was evaluated by Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. OTA treatment was found to induce oxidative stress in rat kidney, as evidenced by marked decreases in catalase (CAT) activity and total glutathione (GSH) levels, as well as an increase in superoxide dismutase (SOD) activity. Furthermore, TUNEL analysis revealed a significant increase in the number of TUNEL-positive cells in cortex and medulla in the OTA-administered group compared to the control. Lycopene supplementation with OTA increased glutathione peroxidase (GPx) activity and GSH levels and decreased apoptotic cell death in both cortex and medulla vs. control. The results of this study showed that lycopene might be partially protective against OTA-induced nephrotoxicity and oxidative stress in rat, as evidenced by partial recovery in histopathology, apoptosis and antioxidant parameters. These data are in line with those of Baudrimont et al. .
GSH is a biological antioxidant and the major non-protein sulfhydryl present in cells; while its conjugation with strong electrophiles is considered a mechanism of cellular protection, certain conjugates act as toxicants in tissues rich in γ-glutamyl transpeptidase (γ-GT) . A dual activity of glutathione with OTA has been reported: in liver, glutathione protects against genotoxicity, but increases the toxic effect in kidney. In fact, as reported by El Adlouni et al. , OTA is genotoxic and can be metabolized not only by different cytochrome P450 (CYP), but also by peroxidases involved in the arachidonic cascade. In kidney microsomes from rabbit, OTA biotransformation increased DNA-adduct formation through pathways involving microsomal glutathione-S-transferase and CYP2C9. Moreover, Faucet-Marquis et al.  reported that pretreatment of opossum kidney cells (OK) by modulators of glutathione pathways, such as 2-mercaptoethane sulfonate (MESNA) or N-acetylcysteine (another agent that, like MESNA, reduces oxidative stress by increasing free thiols in kidney), buthionine sulfoximine (BSO) (an inhibitor of glutathione-synthase) and alpha amino-3-chloro-4,5-dihydro-5-isoxazole acetic acid (ACIVICIN) (an inhibitor of gamma glutamyl transpeptidase), did not diminish OTA cytotoxicity significantly; indeed, ACIVICIN increased OTA cytotoxicity.
Toznolovanu et al.  reported that OTA, as well as electrophiles generated from its metabolism react with reduced glutathione (GSH) to produce GSH-conjugates. In kidney, OTB-GSH is the major metabolite. This was not the case in liver, where appreciable quantities of OTAα and OTHQ-GSH in addition to OTB-GSH were generated. These results provide insight to the susceptibility of rat kidney to OTA carcinogenesis. In kidney, higher levels of GSH conjugates, suggest a greater level of OTA bioactivation, which is required for DNA adduction. Moreover, in kidney, GSH conjugates may be involved in the nephrotoxicity, genotoxicity and carcinogenicity of OTA, as a consequence of the relatively high activity of γ-GT and dipeptidases within the brush border membrane of renal proximal tubular epithelial cells, whereas much higher levels of OTAα are detected in liver compared to kidney, and the formation of OTAα is a detoxification pathway for OTA, suggesting greater sensitivity of the kidney to OTA.
Zinc is widely considered as a potential antioxidant in vitro. Zinc protects protein sulfhydryl groups against oxidation and decreases the formation of hydroxyl radical through the antagonism of redox-active transition metals, such as iron and copper . Moreover, zinc is an essential component of Cu/Zn superoxide dismutase (SOD1). Zinc also regulates the expression of many genes that are involved in antioxidant processes, such as metallothionein (MT), GPx and glutamylcysteine synthetase (GCS), through the activation of metal response transcription factor-1 (MTF-1) . Zheng et al. investigated whether zinc supplement could inhibit OTA-induced oxidative damage and DNA damage in HepG2 cells and the mechanism of inhibition . They demonstrated that OTA toxicity is associated with the inhibition of cell proliferation, a decrease in the intracellular zinc concentration, the induction of ROS production, decreases in SOD activity and mitochondrial membrane potential (Δψm), DNA strand breaks, DNA oxidation and hypomethylation and 8-hydroxy-2′-deoxyguanosine (8-OHdG) formation. Moreover, zinc depletion by the zinc chelator, N,N,N′,N′-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN), aggravates OTA-induced oxidative damage. Zinc supplement significantly reduced the OTA-induced production of ROS and a decrease in superoxide dismutase (SOD) activity; the protective effects of zinc against OTA toxicity may be related to its antioxidant properties and its involvement in redox signaling through regulating the expression of antioxidant proteins, such as MT, through the activation of MTF-1. Zinc also helps maintain the stability and integrity of DNA in OTA-treated cells by reducing DNA strand breaks and the formation of 8-OHdG and by reinstating DNA methylation. In the paper of Zheng et al., it was proven for the first time that zinc is able to reduce the cytotoxicity of OTA through inhibition of oxidative damage and DNA damage and regulation of the expression of zinc-associated genes. Thus, the addition of zinc can potentially be used to reduce the OTA toxicity of contaminated feeds.
3.7. Antioxidant Mixture
Melatonin (Mel) and coenzyme Q10 (CoQ10) are well-known antioxidants and free radical scavengers. Mel, N-acetyl-5- methoxytryptamine, is a hormonal product of the pineal gland that plays many roles within the body, including control of reproductive functions, modulation of immune system activity, limitation of tumorigenesis and effective inhibition of oxidative stress . CoQ10 is an integral component of the mitochondrial oxidative phosphorylation system and is a lipid-soluble redox carrier between particular respiratory enzyme complexes in the electron transport chain in the mitochondrial inner membrane . Yenilmez et al. investigated the effects of a relatively high single-dose of OTA and the antioxidant effects of Mel and CoQ10 on OTA-induced oxidative damage in rats . Male Sprague-Dawley rats were divided into four groups of seven rats each: control, OTA, Mel + OTA and CoQ10 + OTA groups. Malondialdehyde (MDA) levels in the plasma and GSH levels in whole blood were measured; kidneys (for histological inspection and for apoptosis detection by TUNEL method) and bone marrow samples (for chromosome aberration and mitotic index) were taken. The rats in the OTA group showed limited degeneration of tubular cells. In some tubules, karyomegaly, desquamated cells and vacuolization were observed by light microscopy. Mel and CoQ10 treatment significantly reduced the severity of the lesions. The MDA levels of the OTA group were significantly higher than the control, OTA + Mel and OTA + CoQ10 groups, while GSH levels were significantly lower than the control, OTA + Mel and OTA + CoQ10 groups. Higher incidences of apoptotic bodies were observed in the kidneys of the OTA group, although OTA administration did not significantly change the incidence of apoptotic bodies when compared to the control and antioxidant-administered groups. Although the percentage of the mitotic index was lowest in the OTA group, no statistical difference was found among the groups. Additionally, OTA had no numerical and structurally significant effects on chromosomes. It was observed that single-dose OTA administration caused oxidative damage in rat kidney, and Mel or CoQ10 treatment appeared to ameliorate the OTA-induced tissue injuries. Atroshi et al. performed a study of the appearance of liver apoptosis after OTA administration in male mice . They demonstrated that the administration of OTA twice a week for one- or two-week periods resulted in the occurrence of apoptosis in mice liver. The presence of intracellular apoptosis bodies was detected at two weeks after toxin treatment. Light microscopic examination demonstrated the presence of eosinophilic globules, often containing apoptotic bodies. Moreover, the ability of selenium combined with other antioxidants, such as CoQ10, L-carnitine, Zn, Mg, N-acetyl cysteine, vitamin C, vitamin E or tamoxifen, to intervene in apoptosis induced by OTA in livers of mice was also investigated. The authors demonstrated that the antioxidants have inhibitory effects on OTA-induced apoptosis. The cellular redox state and/or the equilibrium between ROS generated by OTA and ROS detoxification by the antioxidants could influence the early stage of apoptosis.
In conclusion, several mechanisms have been proposed for OTA toxicity and OTA renal tumor formation: inhibition of protein synthesis, interference with metabolic systems, promotion of membrane lipid peroxidation, disruption of calcium homeostasis, inhibition of mitochondrial respiration and DNA damage. A growing number of in vitro and in vivo studies has been collected and describe evidence compatible with a role for oxidative stress in OTA toxicity and carcinogenicity. For these reasons, several studies have been performed using antioxidants to try to counteract the adverse effects of oxygen radicals generated under OTA-treatment.
These studies demonstrated that antioxidants are able to counteract the deleterious effects of chronic consumption of OTA and confirmed the potential effectiveness of dietary strategies to counteract OTA toxicity.
Conflicts of Interest
The authors declare no conflict of interest.
- Binder, E.M. Managing the risk of mycotoxins in modern feed production. Anim. Feed Sci. Technol. 2007, 133, 149–166, doi:10.1016/j.anifeedsci.2006.08.008.
- Sweeney, M.J.; Dobson, A.D.W. Mycotoxin production by Aspergillus, Fusarium and Penicillium species. Int. J. Food Microbiol. 1998, 43, 141–158, doi:10.1016/S0168-1605(98)00112-3.
- Bryden, W.L. Mycotoxins and Animal Production: Insidious Problems Associated with Contaminated Feedstuffs. In Proceedings of the International Symposium on Recent Advances in Animal Nutrition, Kuala Lumpur, Malaysia, 2004.
- Bryden, W.L. Mycotoxin contamination of the feed supply chain: Implications for animal productivity and feed security. Anim. Feed Sci. Technol. 2012, 173, 134–158, doi:10.1016/j.anifeedsci.2011.12.014.
- Oswald, I.P.; Marin, D.E.; Bouhet, S.; Pinton, P.; Taranu, I.; Accensi, F. Immunotoxicological risk of mycotoxins for domestic animals. Food Addit. Contam. 2005, 22, 354–360, doi:10.1080/02652030500058320.
- International Agency for Research on Cancer (IARC). Some Naturally Occurring Substances: Food Items and Constituents, Heterocyclic Aromatic Amines and Mycotoxins. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans; IARC: Lyon, France, 1993; Volume 56.
- FAO/WHO. Joint FAO/WHO Conference on Food Additives.
- JECFA. Evaluation of Certain Food Additives and Contaminants: Ochratoxin A; WHO Technical Report Series 806; WHO: Geneva, Switzerland, 1991.
- JECFA. Evaluation of Certain Food Additives and Contaminants: Ochratoxin A; WHO Technical Report Series 859; WHO: Geneva, Switzerland, 1995.
- JECFA. Evaluation of Certain Mycotoxins in Food: Ochratoxin A; WHO Technical Report Series 906; WHO: Geneva, Switzerland, 2002.
- JFAO/WHO Expert Committee on Food Additives. Toxicological Evaluation of Certain Food Additives; WHO Feed Additives Series; JFAO/WHO Expert Committee on Food Additives: Geneva, Switzerland, 1997.
- JECFA. Evaluation of Certain Food Additives and Contaminants; WHO Technical Report Series, 947; Geneva, Switzerland, 2007.
- JECFA. Ochratoxin A (addendum). In WHO Food Additive Series 59: Safety Evaluations of Certain Food Additives and Contaminants; IPCS, WHO: Geneva, Switzerland, 2008.
- Ringot, D.; Chango, A.; Schneider, Y.; Larondelle, Y. Toxicokinetics and toxicodynamics of ochratoxin A, an update. Chem. Biol. Interact. 2006, 159, 18–46, doi:10.1016/j.cbi.2005.10.106.
- Pfohl-Leszkowicz, A.; Manderville, R.A. Ochratoxin A: An overview on toxicity and carcinogenicity in animals and humans. Mol. Nutr. Food Res. 2007, 51, 61–99, doi:10.1002/mnfr.200600137.
- Faucet-Marquis, V.; Pont, F.; Størmer, F.C.; Rizk, T.; Castegnaro, M.; Pfohl-Leszkowicz, A. Evidence of a new dechlorinated ochratoxin A derivative formed in opossum kidney cell cultures after pretreatment by modulators of glutathione pathways: Correlation with DNA-adduct formation. Mol. Nutr. Food Res. 2006, 50, 530–542, doi:10.1002/mnfr.200500219.
- Tozlovanu, M.; Faucet-Marquis, V.; Pfohl-Leszkowicz, A.; Manderville, R.A. Genotoxicity of the hydroquinone metabolite of ochratoxin a: Structure-activity relationships for covalent DNA adduction. Chem. Res. Toxicol. 2006, 19, 1241–1247, doi:10.1021/tx060138g.
- Hadjeba-Medjdoub, K.; Tozlovanu, M.; Pfohl-Leszkowicz, A.; Frenette, C.; Paugh, R.J.; Manderville, R.A. Structure-activity relationships imply different mechanisms of action for Ochratoxin A-mediated cytotoxicity and genotoxicity. Chem. Res. Toxicol. 2012, 25, 181–190, doi:10.1021/tx200406c.
- Duarte, S.C.; Pena, A.; Lino, C.M. A review on ochratoxin A occurrence and effects of processing of cereal and cereal derived food products. Food Microbiol. 2010, 27, 187–198, doi:10.1016/j.fm.2009.11.016.
- Boorman, G.A.; McDonald, M.R.; Imoto, S.; Persing, R. Renal lesions induced by ochratoxin A exposure in the F344 rat. Toxicol. Pathol. 1992, 20, 236–245, doi:10.1177/019262339202000210.
- Castegnaro, M.; Mohr, U.; Pfohl-Leszkowicz, A.; Esteve, J.; Steinmann, J.; Tillmann, T.; Michelon, J.; Bartsch, H. Sex- and strain-specific induction of renal tumors by ochratoxin A in rats correlates with DNA adduction. Int. J. Cancer 1998, 77, 70–75, doi:10.1002/(SICI)1097-0215(19980703)77:1<70::AID-IJC12>3.0.CO;2-D.
- Bendele, A.M.; Carlton, W.W.; Krogh, P.; Lillehoj, E.B. Ochratoxin A carcinogenesis in the (C57BL/6J X C3H) F1 mouse. J. Natl. Cancer Inst. 1985, 75, 733–742.
- Bozic, Z.; Duancic, V.; Belicza, M.; Kraus, O.; Skljarov, I. Balkan endemic nephropathy: Still a mysterious disease. Eur. J. Epidemiol. 1995, 11, 235–238, doi:10.1007/BF01719495.
- Pfohl-Leszkowicz, A.; Petkova-Bocharova, T.; Chernozemsky, I.N.; Castegnaro, M. Balkan endemic nephropathy and associated urinary tract tumors: A review on aetiological causes and the potential role of mycotoxins. Food Addit. Contam. 2002, 19, 282–302, doi:10.1080/02652030110079815.
- Pfohl-Leszkowicz, A.; Tozlovanu, M.; Manderville, R.; Peraica, M.; Castegnaro, M.; Stefanovic, V. New molecular and field evidences for the implication of mycotoxins but not aristolochic acid in Human Nephropathy and Urinary tract tumor. Mol. Nutr. Food Res. 2007, 51, 131–146.
- Pfohl-Leszkowicz, A. Ochratoxin A and aristolochic acid involvement in nephropathies and associated urothelial tract tumors. Arh. Hig. Rada Toksikol. 2009, 60, 465–483, doi:10.2478/10004-1254-60-2009-2000.
- Miletic’-Mednev, M. Prevalence of endemic nephropathy and utothelial cancer in Croatia. In Symposium on Recent Advances in Endemic Nephropathy: The Role of Toxins in an Environmental Disease, Zagreb, Croatia, 20–22 October 2006.
- Grollman, A.P.; Jelaković, B. Role of environmental toxins in endemic (Balkan) nephropathy. J. Am. Soc. Nephrol. 2007, 18, 2817–2823, doi:10.1681/ASN.2007050537.
- Grollman, A.P.; Shibutani, S.; Moriya, M.; Miller, F.; Wu, L.; Moll, U.; Suzuki, N.; Fernandes, A.; Rosenquist, T.; Medverec, Z.; et al. Aristolochic acid and the etiology of endemic (Balkan) nephropathy. Proc. Natl. Acad. Sci. USA 2007, 104, 12129–12134, doi:10.1073/pnas.0701248104.
- Krogh, P. Epidemiology of mycotoxic porcine nephropathy. Nord. Vet. Med. 1976, 28, 452–458.
- Fink-Gremmels, J. Conclusions from the workshops on Ochratoxin A in Food: Recent developments and significance, organized by ILSI Europe in Baden (Austria), 29 June–1 July 2005. Food Addit. Contam. 2005, 22 (Suppl. 1), 1–5, doi:10.1080/02652030500358415.
- EFSA. Opinion of the Scientific Panel on Contaminants in the food chain on a request from the commission related to Ochratoxin A in Food. EFSA J. 2006, 365, 1–56.
- JECFA. Ochratoxin A; WHO Technical Report Series 947; IPCS, WHO: Geneva, Switzerland, 2007; pp. 169–180.
- Cavin, C.; Delatour, T.; Marin-Kuan, M.; Fenaille, F.; Holzhauser, D.; Guignard, G.; Bezencxon, C.; Piguet, D.; Parisod, V.; Richoz-Payot, J.; et al. Ochratoxin A-Mediated DNA and protein damage: Roles of nitrosative and oxidative stresses. Toxicol. Sci. 2009, 11, 84–94.
- Russo, A.; la Fauci, L.; Acquaviva, R.; Campisi, A.; Raciti, G.; Scifo, C.; Renis, M.; Galvano, G.; Vanella, A.; Galvano, F. Ochratoxin A-induced DNA damage in human fibroblast: Protectiveeffect of cyanidin 3-O-β-D-glucoside. J. Nutr. Biochem. 2005, 16, 31–37, doi:10.1016/j.jnutbio.2004.05.005.
- Arbillaga, L.; Azqueta, A.; van Delft, J.H.; Lopez de Cerain, A. In vitro gene expression data supporting a DNA non-reactive genotoxic mechanism for ochratoxin A. Toxicol. Appl. Pharmacol. 2007, 220, 216–224, doi:10.1016/j.taap.2007.01.008.
- Pfohl-Leszkowicz, A.; Manderville, R.A. An update on direct genotoxicity as a molecular mechanism of ochratoxin a carcinogenicity. Chem. Res. Toxicol. 2012, 25, 252–262, doi:10.1021/tx200430f.
- Fusi, E.; Rebucci, R.; Pecorini, C.; Campagnoli, A.; Pinotti, L.; Saccone, F.; Cheli, F.; Purup, S.; Sejrsen, K.; Baldi, A. Alpha-tocopherol counteracts the cytotoxicity induced by ochratoxin a in primary porcine fibroblasts. Toxins 2010, 2, 1265–1278, doi:10.3390/toxins2061265.
- Boesch-Saadatmandi, C.; Loboda, A.; Jozkowicz, A.; Huebbe, P.; Blank, R.; Wolffram, S.; Dulak, J.; Rimbach, G. Effect of ochratoxin A on redox-regulated transcription factors, antioxidant enzymes and glutathione-S-transferase in cultured kidney tubulus cells. Food Chem. Toxicol. 2008, 46, 2665–2671, doi:10.1016/j.fct.2008.04.023.
- Malekinejad, H.; Farshid, A.A.; Mirzakhani, N. Liquorice plant extract reduces ochratoxin A-induced nephrotoxicity in rats. Exp. Toxicol. Pathol. 2011, 63, 125–130, doi:10.1016/j.etp.2009.10.006.
- O’Brien, E.; Dietrich, D.R. Ochratoxin A: The continuing enigma. Crit. Rev. Toxicol. 2005, 35, 33–60.
- Gautier, J.C.; Holzhaeuser, D.; Markovoc, J.; Gremaud, E.; Schilter, B.; Turesky, R.J. Oxidative damage and stress response from ochratoxin A exposure in rats. Free Radic. Biol. Med. 2001, 30, 1089–1098, doi:10.1016/S0891-5849(01)00507-X.
- Schaaf, G.J.; Nijmeijer, S.M.; Maas, R.F.; Roestenberg, P.; de Groene, E.M.; Fink-Gremmel, J. The role of oxidative stress in the ochratoxin A-mediated toxicity in proximal tubular cells. Biochim. Biophys. Acta 2002, 1588, 149–158, doi:10.1016/S0925-4439(02)00159-X.
- Gillman, I.G.; Clark, T.N.; Manderville, R.A. Oxidation by ochratoxin A by an Fe-porphyrin system: Model for enzymatic activation and DNA cleavage. Chem. Res. Toxicol. 1999, 12, 1066–1076, doi:10.1021/tx9901074.
- Hoehler, D.; Marquardt, R.R.; McIntosh, A.R.; Xiao, H. Free radical generation as induced by ochratoxin A and its analogs in bacteria (Bacillus brevis). J. Biol. Chem. 1996, 271, 27388–27394.
- Hoehler, D.; Marquardt, R.R.; McIntosh, A.R.; Hatch, G.M. Induction of free radicals in hepatocytes, mitochondria and microsomes of rats by ochratoxin A and its analogs. Biochim. Biophys. Acta 1997, 1357, 225–233, doi:10.1016/S0167-4889(97)00026-8.
- Rahimtula, A.D.; Bereziat, J.C.; Bussacchini-Griot, V.; Bartsch, H. Lipid peroxidation as a possible cause of ochratoxin A toxicity. Biochem. Pharmacol. 1988, 37, 4469–4477, doi:10.1016/0006-2952(88)90662-4.
- Pfohl-Leszkowicz, A.; Grosse, Y.; Kane, A.; Gharbi, A.; Baudrimont, I.; Obrecht, S.; Creppy, E.E.; Dirheimer, G. Is the Oxydative Pathway Implicated in the Genotoxicity of Ochratoxin A? In Human Ochratoxicosis and Related Pathologies; Creppy, E., Castegnaro, M., Dirheimer, G., Eds.; John Lib-bey Eurotex, Colloque INSERM: Montrouge, France, 1993; Volume 231, pp. 177–187.
- Baudrimont, I.; Betbeder, A.M.; Gharbi, A.; Pfohl-Leszkowicz, A.; Dirheimer, G.; Creppy, E.E. Effect of superoxide dismutase and catalase on the nephrotoxicity induced by subchronical administration of ochratoxin A in rats. Toxicology 1994, 89, 101–111, doi:10.1016/0300-483X(94)90218-6.
- Grosse, Y.; Chekir-Ghedira, L.; Huc, A.; Obrecht-Pflumio, S.; Dirheimer, G.; Bacha, H.; Pfohl-Leszkowicz, A. Retinol, ascorbic acid and α-tocopherol prevent DNA adduct formation in mice treated with the mycotoxins ochratoxin A and zearalenone. Cancer Lett. 1997, 114, 225–229, doi:10.1016/S0304-3835(97)04669-7.
- Pfohl-Leszkowicz, A.; Bartsch, H.; Azémar, B.; Mohr, U.; Estève, J.; Castegnaro, M. MESNA protects rats against nephrotoxicity but not carcinogenity induced by Ochratoxin A, implicating two separate pathways. Facta Univ. Ser.: Med. Biol. 2002, 9, 57–63.
- De Groene, E.M.; Hassing, I.G.; Blom, M.J.; Seinen, W.; Fink-Gremmels, J.; Horback, G.J. Development of human cytochrome P450-expressing cell lines, application in mutagenicity testing of ochratoxin A. Cancer Res. 1996, 56, 299–304.
- Omar, R.F.; Hasimoff, B.B.; Mejilla, F.; Rahimtula, A.D. Mechanism of ochratoxin A stimulated lipid peroxidation. Biochem. Pharmacol. 1990, 40, 1183–1191, doi:10.1016/0006-2952(90)90382-U.
- Baudrimont, I.; Betbeder, A.M.; Creppy, E.E. Reduction of the ochratoxin A-induced cytotoxicity in Vero-cells by aspartame. Arch. Toxicol. 1997, 71, 290–298, doi:10.1007/s002040050389.
- Belmadani, A.; Steyn, P.S.; Tramu, G.; Betbeder, A.M.; Baudrimont, I.; Creppi, E.E. Selective toxicity of ochratoxin A in primary culture from different brain regions. Arch. Toxicol. 1999, 73, 108–114, doi:10.1007/s002040050594.
- Kamp, H.G.; Eisenbrand, G.; Schlatter, J.; Wurth, K.; Janzowski, C. Ochratoxin A: Induction of (oxidative) DNA damage, cytotoxicity and apoptosis in mammalian cell lines and primary cells. Toxicology 2005, 206, 413–425, doi:10.1016/j.tox.2004.08.004.
- Xiao, H.; Madhyastha, S.; Marquardt, R.R.; Li, S.; Vodela, J.K.; Frohlich, A.A.; Kemppainen, B.W. Toxicity of ochratoxin A, its opened lactone form and several of its analogs: Structure-activity relationships. Toxicol. Appl. Pharmacol. 1996, 137, 182–192, doi:10.1006/taap.1996.0071.
- Dai, J.; Park, G.; Wright, M.W.; Adams, M.; Akman, S.A.; Manderville, R.A. Detection and characterization of a glutathione conjugate of ochratoxin A. Chem. Res. Toxicol. 2002, 15, 1581–1588, doi:10.1021/tx0255929.
- Manderville, R.A.; Pfohl-Leszkowicz, A. Chapter 4 genotoxicity of chlorophenols and ochratoxin A. Adv. Mol. Toxicol. 2006, 1, 85–138, doi:10.1016/S1872-0854(06)01004-6.
- Manderville, R.A.; Pfohl-Leszkowicz, A. Bioactivation and DNA adduction as a rationale for ochratoxin A carcinogenesis. World Mycotoxin J. 2008, 1, 357–367, doi:10.3920/WMJ2008.x039.
- Di Giacomo, C.; Acquaviva, R.; Piva, A.; Sorrenti, V.; Vanella, L.; Piva, G.; Casadei, G.; la Fauci, L.; Ritieni, A.; Bognanno, M.; et al. Protective effect of cyanidin 3-O-β-d-glucoside on ochratoxin A-mediated damage in the rat. Br. J. Nutr. 2007, 98, 937–943.
- Chinje, E.C.; Stratford, I.J. Role of nitric oxide in growth of solid tumors: A balancing act. Essays Biochem. 1997, 32, 61–72.
- Griffioen, A.W.; Molema, G. Angiogenesis: Potentials or pharmacologic intervention in the treatment of cancer; cardiovascular diseas and crhonic inflammation. Pharm. Rev. 2000, 52, 237–268.
- Chen, G.G.; Lee, T.W.; Xu, H.; Yip, J.H.; Li, M.; Mok, T.S.; Yim, A.P. Increased inducible nitric oxide synthase in lung carcinoma of smokers. Cancer 2008, 112, 372–381, doi:10.1002/cncr.23166.
- Lukes, P.; Pàcovà, H.; Kucera, T.; Vesely, D.; Martinek, J.; Asti, J. Expression of endothelial and inducible nitric oxide synthase and caspase-3 in tonsillar cancer; chronic tonsillitis and healthy tonsils. Folia Biol. 2008, 5, 141–145.
- Brennan, P.A.; Palacios-Callender, M.; Zaki, G.A.; Spedding, A.V.; Langdon, J.D. Type II nitric oxide synthase (NOS2) expression correlates with lynphnode status in oral squamous carcinoma. J. Oral Pathol. Med. 2001, 30, 129–134.
- Lim, K.H.; Ancrile, B.B.; Kashatus, D.F.; Counter, C.M. Tumour maintenance is mediated by eNOS. Nature 2008, 452, 646–649, doi:10.1038/nature06778.
- Shang, Z.J.; Li, J.R. Expression of endothelial nitric oxide synthase and vascular endothelial growth factor in oral squamous cell carcinoma: Its correlation with angiogenesis and disease progression. J. Oral Pathol. Med. 2005, 34, 134–139, doi:10.1111/j.1600-0714.2004.00259.x.
- Kostourou, V.; Robinson, S.P.; Cartwright, J.E.; Whitley, G.S. Dimethylarginine dimethylaminohydrolase I enhances tumour growth and angiogenesis. Br. J. Cancer 2002, 87, 673–680, doi:10.1038/sj.bjc.6600518.
- Leiper, J.; Santa Maria, J.; Chubb, A.; MacAllister, R.J.; Charles, I.G.; Whithley, G.S.J.; Vallance, P. Identification of two human dimethylarginine dimethylaminohydrolases with distinct tissue distributions and homology to microbial arginine deiminases. Biochem. J. 1999, 343, 209–214, doi:10.1042/0264-6021:3430209.
- Nijveldt, R.J.; Teerlink, T.; van Guldener, C.; Prins, H.A.; van Lambalgen, A.A.; Stehouwer, C.D.; Rauwerda, J.A.; van Leeuwen, P.A. Handling of asymmetrical dimethylarginine and symmetrical dimethylarginine by the rat kidney under basal conditions and during endotoxaemia. Nephrol. Dial. Transplant. 2003, 18, 2542–2550, doi:10.1093/ndt/gfg452.
- Tran, C.T.; Fox, M.F.; Vallance, P.; Leiper, J.M. Chromosomal localization; gene structure; and expression pattern of DDAH1: Comparison with DDAH2 and implications for evolutionary origins. Genomics 2000, 68, 101–105, doi:10.1006/geno.2000.6262.
- Sorrenti, V.; di Giacomo, C.; Acquaviva, R.; Bognanno, M.; Grilli, E.; D’Orazio, N.; Galvano, F. Dimethylarginine dimethylaminohydrolase/nitric oxidesynthase pathway in liver and kidney: Protective effect of cyanidin 3-O-β-D-glucoside on ochratoxin-A toxicity. Toxins 2012, 4, 353–363, doi:10.3390/toxins4050353.
- Gekle, M.; Sauvant, C.; Schwerdt, G. Ochratoxin A at nanomolar concentrations: A signal modulator in renal cells. Mol. Nutr. Food Res. 2005, 49, 118–130, doi:10.1002/mnfr.200400062.
- Gagliano, N.; Doone, I.D.; Torri, C.; Migliori, M.; Grizzi, F.; Milzani, A.; Filippi, C.; Annoni, G.; Colombo, P.; Costa, F.; et al. Early cytotoxic effects of ochratoxin A in rat liver: A morphological, biochemical and molecular study. Toxicology 2006, 225, 214–224, doi:10.1016/j.tox.2006.06.004.
- Stoev, S.D. Studies on carcinogenic and toxic effects of ochratoxin A in chicks. Toxins 2010, 2, 649–664, doi:10.3390/toxins2040649.
- Vettorazzi, A.; de Trocóniz, I.F.; González-Peñas, E.; Arbillaga, L.; Corcuera, L.A.; Gil, A.G.; de Cerain, A.L. Kidney and liver distribution of ochratoxin A in male and female F344 rats. Food Chem. Toxicol. 2011, 49, 1935–1942, doi:10.1016/j.fct.2011.04.021.
- Ferrante, M.C.; Mattace Raso, G.; Bilancione, M.; Esposito, E.; Iacono, A.; Meli, R. Differential modification of inflammatory enzymes in J774A.1 macrophages by ochratoxin A alone or in combination with lipopolysaccharide. Toxicol. Lett. 2008, 181, 40–46, doi:10.1016/j.toxlet.2008.06.866.
- Radi, R. Nitric oxide, oxidants, and protein tyrosine nitration. Proc. Natl. Acad. Sci. USA 2004, 101, 4003–4008, doi:10.1073/pnas.0307446101.
- Schilter, B.; Marin-Kuan, M.; Delatour, T.; Nestler, S.; Mantle, P.; Cavin, C. Ochratoxin A: Potential epigeneticmechanisms of toxicity and carcinogenicity. Food Addit. Contam. 2005, 22, 88–93, doi:10.1080/02652030500309319.
- Kuiper-Goodman, T.; Hilts, C.; Billiard, S.M.; Kiparissis, Y.; Richard, I.D.K.; Hayward, S. Health risk assessment of ochratoxin a for all age-sex strata in a market economy. Food Addit. Contam. 2010, 27, 212–240, doi:10.1080/02652030903013278.
- Manderville, R.A. A case for the genotoxicity of ochratoxin a by bioactivation and covalent DNA adduction. Chem. Res. Toxicol. 2005, 18, 1091–1097, doi:10.1021/tx050070p.
- Turesky, R.J. Perspective: Ochratoxin A is not a genotoxic carcinogen. Chem. Res. Toxicol. 2005, 18, 1082–1090, doi:10.1021/tx050076e.
- Petrik, J.; Zanic-Grubisic, T.; Barisic, K.; Pepeljnjak, S.; Radic, B.; Ferencic, Z.; Cepelak, I. Apoptosis and oxidative stress induced by ochratoxin-A in rat kidney. Arch. Toxicol. 2003, 77, 685–693, doi:10.1007/s00204-003-0501-8.
- Kuczuk, M.H.; Benson, P.M.; Heath, H.; Hayes, A.W. Evaluation of the mutagenic potential of mycotoxins using Salmonella typhimurium and Saccharomyces cerevisiae. Mutat. Res. 1978, 53, 11–20, doi:10.1016/0165-1161(78)90375-8.
- Wehner, F.C.; Thiel, P.G.; van Reusburg, S.J.; Demasius, P.C. Mutagenicity to Salmonella typhimurium of some Aspergillus and Penicillium mycotoxins. Mutat. Res. 1978, 58, 193–203, doi:10.1016/0165-1218(78)90009-5.
- Bendele, A.M.; Neal, S.B.; Oberly, T.J.; Thompson, C.Z.; Bewsey, B.; Hill, L.E.; Rexroat, M.A.; Carlton, W.W.; Probst, G.S. Evaluation of ochratoxin A for mutagenicity in a battery of bacterial and mammalian cell assay. Food Chem. Toxicol. 1985, 23, 911–918, doi:10.1016/0278-6915(85)90107-3.
- Würgler, F.E.; Friederich, U.; Schlatter, J. Lack of mutagenicity of ochratoxin A and B, citrinin, patulin and cnestine in Salmonella typhimurium TA102. Mutat. Res. 1991, 261, 209–216, doi:10.1016/0165-1218(91)90069-X.
- Sakai, M.; Abe, K.I.; Okumura, H.; Kawamura, O.; Sugiura, Y.; Horie, Y.; Ueno, Y. Genotoxicity of fungi evaluated by SOS microplate assay. Nat. Toxins 1992, 1, 27–34, doi:10.1002/nt.2620010107.
- Henning, A.; Fink-Gremmels, J.; Leistner, L. Mutagenicity and Effects of Ochratoxin A on the Frecuency of Sister Chromatid Exchange after Metabolic Activation. IARC Sci. Publ. 1991, 115, 255–260.
- Obrecht-Pflumio, S.; Chassat, T.; Dirheimer, G.; Marzin, D. Genotoxicity of ochratoxin A by Salmonella mutagenicity test after bioactivation by mouse kidney microsomas. Mutat. Res. 1999, 446, 95–102, doi:10.1016/S1383-5718(99)00152-7.
- Mori, H.; Kawai, K.; Ohbayashi, F.; Kuniyasu, T.; Yamazaki, M.; Hamasaki, T.; Williams, G.M. Genotoxicity of a variety of mycotoxins in the hepatocyte primary culture/DNA repair test using rat and mouse hepatocytes. Cancer Res. 1984, 44, 2918–2923.
- Dörrenhaus, A.; Föllmann, W. Effects of ochratoxin A on DNA repair in cultures of rat hepatocytes and porcine urinary bladder epithelial cells. Arch. Toxicol. 1997, 71, 709–713, doi:10.1007/s002040050449.
- Faucet, V.; Pfohl-Leszkowicz, A.; Dai, J.; Castegnaro, M.; Manderville, R.A. Evidence for covalent DNA adduction by ochratoxin A following chronic exposure to rat and subacute exposure to pig. Chem. Res. Toxicol. 2004, 17, 1289–1296, doi:10.1021/tx049877s.
- Mantle, P.G.; Faucet-Marquis, V.; Manderville, R.A.; Squillaci, B.; Pfohl-Leszkowicz, A. Structures of covalent adducts between DNA and ochratoxin A: A new factor in debate about genotoxicity and human risk assessment. Chem. Res. Toxicol. 2010, 23, 89–98, doi:10.1021/tx900295a.
- Pfohl-Leszkowicz, A.; Castegnaro, M. Further arguments in favour of direct covalent binding of Ochratoxin A (OTA) after metabolic biotransformation. Food Addit. Contam. 2005, 22, 75–87, doi:10.1080/02652030500309400.
- Schlatter, C.; Studer-Rohr, C.J.; R´asonyi, T. Carcinogenicity and kinetic aspects of ochratoxin A. Food Addit. Contam. 1996, 13, 43–44.
- Delatour, T.; Mally, A.; Richoz, J.; Ozden, S.; Dekant, W.; Ihmels, H.; Otto, D.; Gasparutto, D.; Marin-Kuan, M.; Schilter, B.; et al. Absence of 2’-deoxyguanosine-carbon 8-bound ochratoxin A adduct in rat kidney DNA monitored by isotope dilution LC-MS/MS. Mol. Nutr. Food Res. 2008, 52, 472–482, doi:10.1002/mnfr.200700276.
- Pfohl-Leszkowicz, A.; Gabryelski, W.; Manderville, R.A. Formation of 2'-deoxyguanosine-carbon 8-bound ochratoxin A adduct in rat kidney DNA. Mol. Nutr. Food Res. 2009, 53, 154–155, doi:10.1002/mnfr.200890049.
- Mally, A.; Pepe, G.; Ravoori, S.; Fiore, M.; Gupta, R.C.; Dekant, W.; Mosesso, P. Ochratoxin A causes DNA damage and cytogenetic effects but no DNA adducts in rats. Chem. Res. Toxicol. 2005, 18, 1253–1261, doi:10.1021/tx049650x.
- Creppy, E.E.; Kane, A.; Dirheimer, G.; Lafarge-Frayssinet, C.; Mousset, S.; Frayssinet, C. Genotoxicity of ochratoxin A in mice: DNA single-strand break evaluation in spleen, liver and kidney. Toxicol. Lett. 1985, 28, 29–35, doi:10.1016/0378-4274(85)90006-2.
- Kane, A.; Creppy, E.E.; Roth, A.; Roschenthaler, R.; Dirheimer, G. Distribution of the (3H)-label from low doses of radioactive ochratoxin A ingested by rats, and evidence for DNA single-strand breaks caused in liver and kidneys. Arch. Toxicol. 1986, 58, 219–224, doi:10.1007/BF00297109.
- Ehrlich, V.; Darroudi, F.; Uhl, M.; Steinkellner, H.; Gann, M.; Majer, B.J.; Eisenbauer, M.; Knasmüller, S. Genotoxic effects of ochratoxin A in human-derived hepatoma (HepG2) cells. Food Chem. Toxicol. 2002, 40, 1085–1090, doi:10.1016/S0278-6915(02)00045-5.
- Lebrun, S.; Follmann, W. Detection of ochratoxin A-induced DNA damage in MDCK cells by alcaline single-cell gel electrophoresis (comet assay). Arch. Toxicol. 2002, 75, 734–741, doi:10.1007/s00204-001-0291-9.
- Degen, G.H.; Gerber, M.M.; Obrecht-Pflumio, S.; Dirheimer, G. Induction of micronuclei with ochratoxin A in ovine seminal vesicle cell cultures. Arch. Toxicol. 1997, 71, 365–371, doi:10.1007/s002040050400.
- Dopp, E.; Muller, J.; Hahnel, C.; Schiffmann, D. Induction of genotoxic effects and modulation of the intracellular calcium level in syrian hamster embryo (SHE) fibroblast caused by ochratoxin A. Food Chem. Toxicol. 1999, 37, 713–721, doi:10.1016/S0278-6915(99)00057-5.
- Arbillaga, L.; Azqueta, A.; Ezpeleta, O.; Lopez de Cerain, A. Oxidative DNA damage induced by Ochratoxin A in the HK-2 human kidney cell line: Evidence of the relationship with cytotoxicity. Mutagenesis 2007, 22, 35–42.
- Tozlovanu, M.; Canadas, D.; Pfohl-Leszkowicz, A.; Frenette, C.; Paugh, R.J.; Manderville, R.A. Glutathione conjugates of ochratoxin A as biomarkers of exposure. Arh. Hig. Rada Toksikol. 2012, 63, 417–427.
- WHO. Safety evaluation of certain mycotoxins in food. Prepared by 49th meeting of JECFA; WHO: Geneva, Switzerland, 1998.
- Abel, E.L.; Angel, J.M.; Kiguchi, K.; Digiovanni, J. Multi-stage chemical carcinogenesis in mouse skin: Fundamentals and applications. Nat. Protoc. 2009, 4, 1350–1362, doi:10.1038/nprot.2009.120.
- Kumar, R.; Ansari, K.M.; Chaudhari, B.P.; Dhawan, A.; Dwivedi, P.D.; Jain, S.K.; Das, M. Topicalapplication of ochratoxin A causesDNAdamage and tumor initiation in mouse skin. PLoS One 2012, 7, e47280.
- Poirier, M.C. Chemical-induced DNA damage and human cancer risk. Nat. Rev. Cancer 2004, 4, 630–637, doi:10.1038/nrc1410.
- Grosse, Y.; Baudrimont, I.; Castegnaro, M.; Betbeder, A.M.; Creppy, E.E.; Dirheimer, G.; Pfohl-Leszkowicz, A. Ochratoxin A metabolites and DNA-adducts formation in Monkey kidney cell. Chem. Biol. Interact. 1995, 95, 175–187, doi:10.1016/0009-2797(94)03359-5.
- Grosse, Y.; Monje, M.C.; Mace, K.; Pfeifer, A.M.; Pfohl-leszkowicz, A. Use of bronchial epithelial cells expressing human cytochrome P450 for study on metabolism and genotoxicity of ochratoxin A. In Vitro Toxicol. 1997, 10, 93–102.
- Pfohl-Leszkowicz, A.; Pinelli, E.; Bartsch, H.; Mohr, U.; Castegnaro, M. Sex and Strain differences in ochratoxin A metabolism and DNA adduction in two strains of rats. Mol. Carcinog. 1998, 23, 76–83, doi:10.1002/(SICI)1098-2744(199810)23:2<76::AID-MC4>3.0.CO;2-B.
- Jennings Gee, J.E.; Tozlovanu, M.; Manderville, R.; Miller, M.S.; Pfohl-Leszkowicz, A.; Schwartz, G.G. Ochratoxin A: In utero exposure in mice induces adducts in testicular DNA. Toxins 2010, 2, 1428–1444, doi:10.3390/toxins2061428.
- Marin-Kuan, M.; Ehrlich, V.; Delatour, T.; Cavin, C.; Schilter, B. Evidence for a role of oxidative stress in the carcinogenicity of Ochratoxin A. J. Toxicol. 2011, 2011, 645361.
- Guerra, M.C.; Galvano, F.; Bonsi, L.; Speroni, E.; Costa, S.; Renzulli, C.; Cervellati, R. Cyanidin-3-O-beta-glucopyranoside, a natural free-radical scavenger against aflatoxin B1- and ochratoxin A-induced cell damage in a human hepatoma cell line (Hep G2) and a human colonic adenocarcinoma cell line (CaCo-2). Br. J. Nutr. 2005, 94, 211–220, doi:10.1079/BJN20051425.
- Kamp, H.G.; Eisenbrand, G.; Janzowski, C.; Kiossev, J.; Latendresse, J.R.; Schlatter, J.; Turesky, R.J. Ochratoxin A induces oxidative DNA damage in liver and kidney after oral dosing to rats. Mol. Nutr. Food Res. 2005, 49, 160–1167.
- Cui, J.; Xing, L.; Li, Z.; Wu, S.; Wang, J.; Liu, J.; Wang, J.; Yan, X.; Zhang, X. Ochratoxin A induces G2 phase arrest in human gastric epithelium GES-1 cells in vitro. Toxicol. Lett. 2010, 193, 152–158, doi:10.1016/j.toxlet.2009.12.019.
- National Toxicology Program. Toxicology and carcinogenesis studies of ochratoxin A (CAS No. 303-47-9) in F344/N rats (gavage studies). Natl. Toxicol. Program Tech. Rep. Ser. 1989, 358, 1–142.
- Petkova-Bocharova, T.; Castegnaro, M.; Pfohl-Leszkowicz, A.; Garren, L.; Grosso, F.; Nikolov, I.; Vrabcheva, T.; Dragacci, S.; Chernozemsky, I.N. Analysis of ochratoxin A in serum and urine of inhabitants from an area with Balkan Endemic Nephropathy: A one month follow up study. Facta Univ. Ser. Med. Biol. 2003, 10, 62–68.
- Malir, F.; Ostry, V.; Pfohl-Leszkowicz, A.; Roubal, T. Ochratoxin A exposure biomarkers in the Czech Republic and comparison with other countries. Biomarkers 2012, 17, 577–589, doi:10.3109/1354750X.2012.692392.
- Petzinger, E.; Ziegler, K. Ochratoxin A from a toxicological perspective. J. Vet. Pharmacol. Ther. 2000, 23, 91–98, doi:10.1046/j.1365-2885.2000.00244.x.
- Castegnaro, M.; Canadas, D.; Vrabcheva, T.; Petkova-Bocharova, T.; Chernozemsky, I.N.; Pfohl-Leszkowicz, A. Balkan endemic nephropathy: Role of ochratoxins A through biomarkers. Mol. Nutr. Food Res. 2006, 50, 519–529, doi:10.1002/mnfr.200500182.
- Assaf, H.; Azouri, H.; Pallardy, M. Ochratoxin A induces apoptosis in human lymphocytes through down regulation of Bcl-xL. Toxicol. Sci. 2004, 79, 35–344.
- Liu, J.; Wang, Y.; Cui, J.; Xing, L.; Shen, H.; Wu, S.; Lian, H.; Wang, J.; Yan, X.; Zhang, X. Ochratoxin A induces oxidative DNA damage and G1 phase arrest in human peripheral blood mononuclear cells in vitro. Toxicol. Lett. 2012, 211, 164–171, doi:10.1016/j.toxlet.2012.03.800.
- Xu, W.T.; Peng, X.L.; Luo, Y.B.; Wang, J.A.; Guo, X.; Huang, K.L. Physiological and biochemical responses of grapefruit seed extract dip on ‘Redglobe’ grape. LWT-Food Sci. Technol. 2009, 42, 471–476, doi:10.1016/j.lwt.2008.09.002.
- Peng, X.L.; Xu, W.T.; Wang, Y.; Huang, K.L.; Liang, Z.H.; Zhao, W.W.; Luo, Y.B. Mycotoxin ochratoxin A-induced cell death and changes in oxidative metabolism of Arabidopsis thaliana. Plant Cell Rep. 2010, 29, 153–161, doi:10.1007/s00299-009-0808-x.
- Gholampour Azizi, I.; Rahimi, K.; Shateri, S. Ochratoxin: Contamination and Toxicity (A Review). Glob. Veterinaria 2012, 8, 519–524.
- Azzi, A.; Breyer, I.; Feher, M.; Pastori, M.; Ricciarelli, R.; Spycher, S.; Staffieri, M.; Stocker, A.; Zimmer, S.; Zingg, J.M. Specific cellular responses to alpha-tocopherol. J. Nutr. 2000, 130, 1649–1652.
- Baldi, A. Vitamin E in dairy cows. Livest. Prod. Sci. 2005, 98, 117–122, doi:10.1016/j.livprodsci.2005.10.004.
- Azzi, A. Molecular mechanism of α-tocopherol action. Free Radic. Biol. Med. 2007, 43, 16–21, doi:10.1016/j.freeradbiomed.2007.03.013.
- Wang, X.; Quinn, P.J. Vitamin E and its function in membranes. Prog. Lipid Res. 1999, 38, 309–336, doi:10.1016/S0163-7827(99)00008-9.
- Baldi, A.; Losio, M.N.; Cheli, F.; Rebucci, R.; Sangalli, L.; Fusi, E.; Bertasi, B.; Pavoni, E.; Carli, S.; Politis, I. Evaluation of the protective effects of α-tocopherol and retinol against ochratoxin A cytotoxicity. Br. J. Nutr. 2004, 91, 507–512, doi:10.1079/BJN20041092.
- Cooper, R.; Morre, D.J.; Morre, D.M. Medicinal benefits of green tea: Part I. Review of non cancer health benefits. J. Altern. Complement. Med. 2005, 11, 521–528, doi:10.1089/acm.2005.11.521.
- Yang, C.S.; Liao, J.; Yang, G.Y.; Lu, G. Inhibitions of lung tumorigenesis by tea. Exp. Lung Res. 2005, 31, 135–144, doi:10.1080/01902140490495525.
- Takabayashi, F.; Tahara, S.; Kaneko, T.; Harada, N. Effect of green tea catechins on oxidative DNA damage of hamster pancreas and liver induced by N-nitrosobis(2-oxopropyl) amine and/or oxidized soybean oil. Biofactors 2004, 21, 335–337, doi:10.1002/biof.552210165.
- Rizvi, S.I.; Zaid, M.A.; Anis, R.; Mishra, N. Protective role of tea catechins against oxidation-induced damage of type 2 diabetic erythrocytes. Clin. Exp. Pharmacol. Physiol. 2005, 32, 70–75, doi:10.1111/j.1440-1681.2005.04160.x.
- Erba, D.; Riso, P.; Bordoni, A.; Foti, P.; Biagi, P.L.; Testolin, G. Effectiveness of moderate green tea consumption on antioxidative status and plasma lipid profile in humans. J. Nutr. Biochem. 2005, 16, 144–149, doi:10.1016/j.jnutbio.2004.11.006.
- Hsu, S. Green tea and the skin. J. Am. Acad. Dermatol. 2005, 52, 1049–1059, doi:10.1016/j.jaad.2004.12.044.
- Costa, S.; Utan, A.; Cervellati, R.; Speroni, E.; Guerra, M.C. Catechins: Natural free-radical scavengers against ochratoxin A-induced cell damage in a pig kidney cell line (LLC-PK1). Food Chem. Toxicol. 2007, 45, 1910–1917, doi:10.1016/j.fct.2007.04.008.
- Corcuera, L.A.; Amézqueta, S.; Arbillaga, L.; Vettorazzi, A.; Touriño, S.; Torres, J.L.; López de Cerain, A. A polyphenol-enriched cocoa extract reduces free radicals produced by mycotoxins. Food Chem. Toxicol. 2012, 50, 989–995, doi:10.1016/j.fct.2011.11.052.
- Scapagnini, G.; Foresti, R.; Calabrese, V.; Giuffrida Stella, A.M.; Green, C.J.; Motterlini, R. Caffeic acid phenethyl ester and curcumin: A novel class of heme oxygenase-1 inducers. Mol. Pharmacol. 2002, 3, 554–561.
- Balogun, E.; Hoque, M.; Gong, P.; Kileen, E.; Green, C.J.; Foresti, R.; Alam, J.; Motterlini, R. Curcumin activates the haem oxygenase-1 gene via regulation of Nrf2 and the antioxidant responsive element. Biochem. J. 2003, 371, 887–895, doi:10.1042/BJ20021619.
- Motterlini, R.; Foresti, R.; Bassi, R.; Green, C.J. Curcumin, an antioxidant and anti-inflammatory agent, induces heme oxygenase- 1 and protects endothelial cells against oxidative stress. Free Radic. Biol. Med. 2000, 28, 1303–1312, doi:10.1016/S0891-5849(00)00294-X.
- Wang, Z.Y.; Nixon, D.W. Licorice and cancer. Nutr. Cancer 2001, 39, 1–11, doi:10.1207/S15327914nc391_1.
- Baltina, L.A.; Flekhter, O.B.; Nigmatullina, L.R.; Boreko, E.I.; Pavlova, N.I.; Nikolaeva, S.N.; Savinova, O.V.; Tolstikov, G.A. Lupane triterpenes and derivatives with antiviral activity. Bioorg. Med. Chem. Lett. 2003, 13, 3549–3552, doi:10.1016/S0960-894X(03)00714-5.
- Rauchensteiner, F.; Matsumura, Y.; Yamamoto, Y.; Yamaji, S.; Tani, T. Analysis and comparison of Radix Glycyrrhizae (licorice) from Europe and China by capillary- zone electrophoresis (CZE). J. Pharm. Biomed. Anal. 2005, 38, 594–600, doi:10.1016/j.jpba.2005.01.038.
- Vaya, J.; Belinky, P.A.; Aviram, M. Antioxidant constituents from licorice roots: Isolation, structure elucidation and antioxidative capacity toward LDL oxidation. Free Radic. Biol. Med. 1997, 23, 302–313, doi:10.1016/S0891-5849(97)00089-0.
- Malekinejad, H.; Mirzakhani, N.; Razi, M.; Cheraghi, H.; Alizadeh, A.; Dardmeh, F. Protective effects of melatonin and Glycyrrhiza glabra extract on ochratoxin A--induced damages on testes in mature rats. Hum. Exp. Toxicol. 2011, 30, 110–123, doi:10.1177/0960327110368416.
- Jeswal, P. Antidotal effect of grape juice (Vitis vinifera) on ochratoxin A caused hepatorenal carcinogenesis in mice (Mus musculus). Cytobios 1998, 93, 123–128.
- Rao, A.V.; Agarwal, S. Effect of diet and smoking on serum lycopene and lipid peroxidation. Nutr. Res. 1998, 18, 713–721, doi:10.1016/S0271-5317(98)00057-8.
- Mordente, A.; Guantario, B.; Meucci, E.; Silvestrini, A.; Lombardi, E.; Martorana, G.E.; Giardina, B.; Böhm, V. Lycopene and cardiovascular diseases: An update. Curr. Med. Chem. 2011, 18, 1146–1163, doi:10.2174/092986711795029717.
- Atessahin, A.; Yilmaz, S.; Karahan, I.; Ceribasi, A.O.; Karaoglu, A. Effects of lycopene against cisplatin-induced nephrotoxicity and oxidative stress in rats. Toxicology 2005, 212, 116–123, doi:10.1016/j.tox.2005.04.016.
- Dogukan, A.; Tuzcu, M.; Agca, C.A.; Gencoglu, H.; Sahin, N.; Onderci, M.; Ozercan, I.H.; Ilhan, N.; Kucuk, O.; Sahin, K. A tomato lycopene complex protects the kidney from cisplatin-induced injury via affecting oxidative stress as well as Bax, Bcl-2, and HSPs expression. Nutr. Cancer 2011, 63, 427–434, doi:10.1080/01635581.2011.535958.
- Mein, J.R.; Lian, F.; Wang, X.D. Biological activity of lycopene metabolites: Implications for cancer prevention. Nutr. Rev. 2008, 66, 667–683, doi:10.1111/j.1753-4887.2008.00120.x.
- Wang, Y.; Ausman, L.M.; Greenberg, A.S.; Russell, R.M.; Wang, X.D. Dietary lycopene and tomato extract supplementations inhibit non alcoholic steatohepatitis promoted hepatocarcinogenesis in rats. Int. J. Cancer 2010, 126, 1788–1796.
- Palabiyik, S.S.; Erkekoglu, P.; Zeybek, N.D.; Kizilgun, M.; Baydar, D.E.; Sahin, G.; Giray, B.K. Protective effect of lycopene against ochratoxin A induced renal oxidative stress and apoptosis in rats. Exp. Toxicol. Pathol. 2013, 65, 853–861, doi:10.1016/j.etp.2012.12.004.
- El Adlouni, C.; Pinelli, E.; Azémar, B.; Zaoui, D.; Beaune, P.; Pfohl-Leszkowicz, A. Phenobarbital increases DNA adduct and metabolites formed by ochratoxin A: Role of CYP 2C9 and microsomal glutathione-S-transferase. Environ. Mol. Mutagen. 2000, 35, 123–131, doi:10.1002/(SICI)1098-2280(2000)35:2<123::AID-EM7>3.0.CO;2-L.
- Powell, S.R. The antioxidant properties of zinc. J. Nutr. 2000, 130, 1447S–1454S.
- Hogstrand, C.; Zinc. Homeostasis and Toxicology of Essential Metals-Fish Physiology; Wood, C.M., Farrell, A.P., Brauner, C.A., Eds.; Elsevier: San Diego, CA, USA, 2012; pp. 135–200.
- Zheng, J.; Zhang, Y.; Xu, W.; Luo, Y.; Hao, J.; Shen, X.L.; Yang, X.; Li, X.; Huang, K. Zinc protects HepG2 cells against the oxidative damage and DNA damage induced by ochratoxin A. Toxicol. Appl. Pharmacol. 2013, 268, 123–131, doi:10.1016/j.taap.2013.01.021.
- Reiter, R.J. Antioxidant actions of melatonin. Adv. Pharmacol. 1997, 38, 103–117, doi:10.1016/S1054-3589(08)60981-3.
- Linnane, A.W.; Marzuki, S.; Ozawa, T.; Tanaka, M. Mitochondrial DNA mutations as an important contributor to ageing and degenerative diseases. Lancet 1989, 1, 642–645.
- Yenilmez, A.; Isikli, B.; Aral, E.; Degirmenci, I.; Sutken, E.; Baycu, C. Antioxidant effects of melatonin and coenzyme Q10 on oxidative damage caused by single-dose ochratoxin A in rat kidney. Chin. J. Physiol. 2010, 53, 310–317, doi:10.4077/CJP.2010.AMK073.
- Atroshi, F.; Biese, I.; Saloniemi, H.; Ali-Vehmas, T.; Saari, S.; Rizzo, A.; Veijalainen, P. Significance of apoptosis and its relationship to antioxidants after ochratoxin A administration in mice. J. Pharm. Pharm. Sci. 2000, 3, 281–291.
© 2013 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).