Effects of two metabolites of ochratoxin A, (4R)-4-hydroxyochratoxin A and ochratoxin alpha, on immune response in mice

Purification and characterization of the enzymes from Brevundimonas naejangsanensis that degrade ochratoxin A and B

Ochratoxin A (OTA) and Ochratoxin B (OTB) co-contaminate many types of agricultural products. Screening enzymes that degrade both OTA and OTB has significance in food safety. In this study, four novel OTA and OTB degrading enzymes, namely BnOTase1, BnOTase2, BnOTase3, and BnOTase4, were purified from the metabolites of the Brevundimonas naejangsanensis ML17 strain. These four enzymes hydrolyzed OTA into OTα and hydrolyzed OTB into OTβ. BnOTase1, BnOTase2, BnOTase3, and BnOTase4 have the apparent K_m values for hydrolyzing OTA of 19.38, 0.92, 12.11, 1.09 μmol/L and for hydrolyzing OTB of 0.76, 2.43, 0.60, 0.64 μmol/L respectively. OTα and OTβ showed no significant cytotoxicity to HEK293 cells, suggesting that these enzymes mitigate the toxicity of OTA and OTB. The discovery of the novel OTA and OTB degrading enzymes enriches the research on ochratoxin control and provides objects for protein rational design.

Molecular Docking and In Vitro Studies of Ochratoxin A (OTA) Biodetoxification Testing Three Endopeptidases

Ochratoxin A (OTA) is considered one of the main mycotoxins responsible for health problems and considerable economic losses in the feed industry. The aim was to study OTA's detoxifying potential of commercial protease enzymes: (i) Ananas comosus bromelain cysteine-protease, (ii) bovine trypsin serine-protease and (iii) Bacillus subtilis neutral metalloendopeptidase. In silico studies were performed with reference ligands and T-2 toxin as control, and in vitro experiments. In silico study results showed that tested toxins interacted near the catalytic triad, similar to how the reference ligands behave in all tested proteases. Likewise, based on the proximity of the amino acids in the most stable poses, the chemical reaction mechanisms for the transformation of OTA were proposed. In vitro experiments showed that while bromelain reduced OTA's concentration in 7.64% at pH 4.6; trypsin at 10.69% and the neutral metalloendopeptidase in 8.2%, 14.44%, 45.26% at pH 4.6, 5 and 7, respectively (p < 0.05). The less harmful α-ochratoxin was confirmed with trypsin and the metalloendopeptidase. This study is the first attempt to demonstrate that: (i) bromelain and trypsin can hydrolyse OTA in acidic pH conditions with low efficiency and (ii) the metalloendopeptidase was an effective OTA bio-detoxifier. This study confirmed α-ochratoxin as a final product of the enzymatic reactions in real-time practical information on OTA degradation rate, since in vitro experiments simulated the time that food spends in poultry intestines, as well as their natural pH and temperature conditions.

Enzymatic degradation of ochratoxin A in the gastrointestinal tract of piglets

Animal feeds are often contaminated with ochratoxin A (OTA), a potent natural mycotoxin hazardous to animal and human health that accumulates in blood and tissues. To the best of our knowledge, this study is the first to investigate the in vivo application of an enzyme (OTA amidohydrolase; OAH) that degrades OTA into the nontoxic molecules phenylalanine and ochratoxin α (OTα) in the gastrointestinal tract (GIT) of pigs. Piglets were fed six experimental diets over 14 days, varying in OTA contamination level (50 or 500 μg/kg; OTA50 and OTA500) and presence of OAH; a negative control diet (no OTA added) and a diet containing OTα at 318 µg/kg (OTα318). The absorption of OTA and OTα into the systemic circulation (plasma and dried blood spots, DBS), their accumulation in kidney, liver, and muscle tissues, and excretion through feces and urine were assessed. The efficiency of OTA degradation in the digesta content of the GIT was also estimated. At the end of the trial, accumulation of OTA in blood was significantly higher in OTA groups (OTA50 and OTA500) in comparison to enzyme groups (OAH50 and OAH500, respectively). The supplementation of OAH explicitly reduced the absorption of OTA (P < 0.005) into plasma by 54% and 59% (from 40.53 ± 3.53 to 18.66 ± 2.28 ng/mL in piglets fed the 50 μg OTA/kg diets and from 413.50 ± 71.88 to 168.35 ± 41.02 ng/mL in piglets fed the 500 μg OTA/kg diets, respectively) and in DBS by 50% and 53% (from 22.79 ± 2.63 to 10.67 ± 1.93 ng/mL in piglets fed the 50 μg OTA/kg diets and from 232.85 ± 35.16 to 105.71 ± 24.18 ng/mL in piglets fed the 500 μg OTA/kg diets, respectively). The OTA concentrations in plasma were positively associated with the OTA levels detected in all tissues analyzed; adding OAH reduced OTA levels in the kidney, liver, and muscle (P < 0.005) by 52%, 67%, and 59%, respectively. The analysis of GIT digesta content showed that OAH supplementation led to OTA degradation in the proximal GIT where natural hydrolysis is inefficient. Overall, the data of present in vivo study demonstrated that supplementation of swine feeds with OAH successfully reduced OTA levels in blood (plasma and DBS) as well as in kidney, liver, and muscle tissues. Therefore, an approach to use enzymes as feed additives might be most promising to mitigate the harmful effects of OTA on the productivity and welfare of pigs and at the same time improving the safety of pig-derived food products.

Genotoxic effects of the ochratoxin A (OTA), its main metabolite (OTα) per se and in combination with fumonisin B1 in HepG2 cells and human lymphocytes

Ochratoxin A (OTA) and fumonisin B₁ (FB₁) are mycotoxins distributed in a wide variety of foods for human or animal consumption and are classified as possible carcinogens for humans. This study aimed to evaluate the cytotoxic, cytostatic and genotoxic effects of OTA and its main metabolite, ochratoxin α (OTα), FB₁ and three combinations of OTA and FB₁ at moderate and environmental doses. Cell viability was evaluated through MTT assay and the trypan blue exclusion method. The cytostatic and genotoxic effects were evaluated through the cytokinesis-block micronucleus assay. The results showed synergistic time- and concentration-dependent cytotoxic effects of one of the combinations of OTA and FB₁. In contrast, significant differences were observed in the micronuclei (MN) frequency from OTA, OTα and coexposure of OTA + FB₁. Some of these combinations increased the frequency of nuclear buds, nucleoplasmic bridges, donut-shaped nuclei, necrotic and apoptotic cells and MN in mononucleated cells. In conclusion, OTA and its main metabolite OTα, as well as the co-exposure of OTA and FB₁, cause stable DNA damage at environmentally relevant concentrations, which was greater in metabolically competent cells. More studies are needed to understand the chemical interactions that occur due to the joint presence of mycotoxins, which occurs commonly.

Detection, Contamination, Toxicity, and Prevention Methods of Ochratoxins: An Update Review

Ochratoxins (OTs) with nephrotoxic, immunosuppressive, teratogenic, and carcinogenic properties are thermostable fungal subordinate metabolites. OTs contamination can occur before or after harvesting, during the processing, packing, distribution, and storage of food. Mold development and mycotoxin contamination can occur in any crop or cereal that has not been stored properly for long periods of time and is subjected to high levels of humidity and temperature. Ochratoxin A (OTA) presents a significant health threat to creatures and individuals. There is also a concern of how human interaction with OTA will also express the remains of OTA from feedstuffs into animal-derived items. Numerous approaches have been studied for the reduction of the OTA content in agronomic products. These methods can be classified into two major classes: inhibition of OTA adulteration and decontamination or detoxification of food. A description of the various mycotoxins, the organism responsible for the development of mycotoxins, and their adverse effects are given. In the current paper, the incidence of OTA in various fodder and food materials is discussed, which is accompanied by a brief overview of the OTA mode of synthesis, physicochemical properties, toxic effects of various types of ochratoxins, and OTA decontamination adaptation methods. To our knowledge, we are the first to report on the structure of many naturally accessible OTAs and OTA metabolism. Finally, this paper seeks to be insightful and draw attention to dangerous OTA, which is too frequently neglected and overlooked in farm duplication from the list of discrepancy studies.

Removal of ochratoxin A by a carboxypeptidase and peptides present in liquid cultures of Bacillus subtilis CW14

Ochratoxin A (OTA) is an important mycotoxin that contaminates a variety of agricultural products. The cell-free supernatant of Bacillus subtilis CW14 liquid cultures were reported previously to be capable of removing OTA efficiently. In this work, we examined several substances that are probably involved in this removal of OTA using in vitro experiments. The strain CW14 culture supernatant that was separated by ultrafiltration showed that the fractions collected at >10 kDa and <3 kDa had a significant ability to reduce OTA (84.9 and 74.8%, respectively) when incubated with 6 μg/ml OTA at 37 °C for 24 h. A putative metalloenzyme was responsible for the activity of the >10-kDa fraction, which was confirmed by the detrimental effects of heat treatments or addition of SDS, proteinase K, or EDTA. Subsequently, a carboxypeptidase (CP) gene that was likely related to the enzymatic conversion of OTA by the >10-kDa fraction was cloned from the B. subtilis CW14 genome, and over-expressed in Escherichia coli. The recombinant CP degraded 71.3% of OTA at 37 °C for 24 h, and ochratoxin α (OTα) was confirmed as a degradation product. From the <3-kDa fraction, some small peptides (1.7 kDa >Mw >0.7 kDa) were purified and decreased OTA by 45.0% under the same conditions, but no product was detected. These peptides were presumed to be capable of binding OTA due to their affinity with the OTA molecule, and the OTA-peptide complexes escaped from the extraction procedures for OTA quantification. These results indicated there was a probable synergistic effect that was involved in removal of OTA by the strain CW14 culture supernatant, which included enzymatic degradation by a CP and physical adsorption by some small peptides.

Determination of 16 mycotoxins in vegetable oils using a QuEChERS method combined with high-performance liquid chromatography-tandem mass spectrometry

A simple and efficient method for determining multiple mycotoxins was developed using a QuEChERS (quick, easy, cheap, effective, rugged and safe)-based extraction procedure in vegetable oils. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used for the quantification and confirmation of 16 chemically diversified mycotoxins. Different extraction procedures were studied and optimised by spiking 16 analytes into blank matrix, and the extraction with 85% MeCN solution and C18 as cleaning sorbent allowed an efficient recovery of 72.8-105.8% with RSDs less than 7%. The limit of detection (LOD) ranged from 0.04 to 2.9 ng g^-1. The developed method was finally applied to screen mycotoxins in 62 vegetable oil samples. Zearalenone (ZEN), aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1) and α-zearalenol (α-ZOL) were detected, with maximum concentrations of 0.59 (AFG1)-42.5 (ZEN) ng g^-1. The method developed has the advantages of high sensitivity, accuracy and selectivity, and it can be applied to the target screening of mycotoxins in real samples.

Comparative Ochratoxin Toxicity: A Review of the Available Data

Ochratoxins are a group of mycotoxins produced by a variety of moulds. Ochratoxin A (OTA), the most prominent member of this toxin family, was first described by van der Merwe et al. in Nature in 1965. Dietary exposure to OTA represents a serious health issue and has been associated with several human and animal diseases including poultry ochratoxicosis, porcine nephropathy, human endemic nephropathies and urinary tract tumours in humans. More than 30 years ago, OTA was shown to be carcinogenic in rodents and since then extensive research has been performed in order to investigate its mode of action, however, this is still under debate. OTA is regarded as the most toxic family member, however, other ochratoxins or their metabolites and, in particular, ochratoxin mixtures or combinations with other mycotoxins may represent serious threats to human and animal health. This review summarises and evaluates current knowledge about the differential and comparative toxicity of the ochratoxin group.

Inhibition of CXCL12-mediated chemotaxis of Jurkat cells by direct immunotoxicants

Directional migration of cells to specific locations is required in tissue development, wound healing, and immune responses. Immune cell migration plays a crucial role in both innate and adaptive immunity. Chemokines are small pro-inflammatory chemoattractants that control the migration of leukocytes. In addition, they are also involved in other immune processes such as lymphocyte development and immune pathology. In a previous toxicogenomics study using the Jurkat T cell line, we have shown that the model immunotoxicant TBTO inhibited chemotaxis toward the chemokine CXCL12. In the present work, we aimed at assessing a novel approach to detecting chemicals that affect the process of cell migration. For this, we first evaluated the effects of 31 chemicals on mRNA expression of genes that are known to be related to cell migration. With this analysis, seven immunotoxicants were identified as potential chemotaxis modulators, of which five (CoCl2 80 µM, MeHg 1 µM, ochratoxin A 10 µM, S9-treated ochratoxin A 10 µM, and TBTO 100 nM) were confirmed as chemotaxis inhibitor in an in vitro trans-well chemotaxis assay using the chemokine CXCL12. The transcriptome data of the five compounds together with previously obtained protein phosphorylation profiles for two out of five compounds (i.e., ochratoxin A and TBTO) revealed that the mechanisms behind the chemotaxis inhibition are different for these immunotoxicants. Moreover, the mTOR inhibitor rapamycin had no effect on the chemotaxis of Jurkat cells, indicating that the mTOR pathway is not involved in CXCL12-mediated chemotaxis of Jurkat cells, which is opposite to the findings on human primary T cells (Munk et al. in PLoS One 6(9):e24667, 2011). Thus, the results obtained from the chemotaxis assay conducted with Jurkat cells might not fully represent the results obtained with human primary T cells. Despite this difference, the present study indicated that some compounds may exert their immunotoxic effects through inhibition of CXCL12-mediated chemotaxis.

An aptasensor for ochratoxin A based on grafting of polyethylene glycol on a boron-doped diamond microcell

A novel strategy for the fabrication of an electrochemical label-free aptasensor for small-size molecules is proposed and demonstrated as an aptasensor for ochratoxin A (OTA). A long spacer chain of polyethylene glycol (PEG) was immobilized on a boron-doped diamond (BDD) microcell via electrochemical oxidation of its terminal amino groups. The amino-aptamer was then covalently linked to the carboxyl end of the immobilized PEG as a two-piece macromolecule, autoassembled at the BDD surface, forming a dense layer. Due to a change in conformation of the aptamer on the target analyte binding, a decrease of the electron transfer rate of the redox [Fe(CN)6](4-/3-) probe was observed. To quantify the amount of OTA, the decrease of the square wave voltammetry (SWV) peak maximum of this probe was monitored. The plot of the peak maximum against the logarithm of OTA concentration was linear along the range from 0.01 to 13.2 ng/L, with a detection limit of 0.01 ng/L. This concept was validated on spiked real samples of rice.

A new ochratoxin A biodegradation strategy using Cupriavidus basilensis Őr16 strain

Ochratoxin-A (OTA) is a mycotoxin with possibly carcinogenic and nephrotoxic effects in humans and animals. OTA is often found as a contaminant in agricultural commodities. The aim of the present work was to evaluate OTA-degrading and detoxifying potential of Cupriavidus basilensis ŐR16 strain. In vivo administration of OTA in CD1 male mice (1 or 10 mg/kg body weight for 72 hours or 0.5 mg/kg body weight for 21 days) resulted in significant elevation of OTA levels in the blood, histopathological alterations- and transcriptional changes in OTA-dependent genes (annexinA2, clusterin, sulphotransferase and gadd45 and gadd153) in the renal cortex. These OTA-induced changes were not seen in animals that have been treated with culture supernatants in which OTA was incubated with Cupriavidus basilensis ŐR16 strain for 5 days. HPLC and ELISA methods identified ochratoxin α as the major metabolite of OTA in Cupriavidus basilensis ŐR16 cultures, which is not toxic in vivo. This study has demonstrated that Cupriavidus basilensis ŐR16 efficiently degrade OTA without producing toxic adventitious metabolites.

Selection and characterization of a novel DNA aptamer for label-free fluorescence biosensing of ochratoxin A

Nucleic acid aptamers are emerging as useful molecular recognition tools for food safety monitoring. However, practical and technical challenges limit the number and diversity of available aptamer probes that can be incorporated into novel sensing schemes. This work describes the selection of novel DNA aptamers that bind to the important food contaminant ochratoxin A (OTA). Following 15 rounds of in vitro selection, sequences were analyzed for OTA binding. Two of the isolated aptamers demonstrated high affinity binding and selectivity to this mycotoxin compared to similar food adulterants. These sequences, as well as a truncated aptamer (minimal sequence required for binding), were incorporated into a SYBR® Green I fluorescence-based OTA biosensing scheme. This label-free detection platform is capable of rapid, selective, and sensitive OTA quantification with a limit of detection of 9 nM and linear quantification up to 100 nM.

Feeding a diet contaminated with ochratoxin A for broiler chickens at the maximum level recommended by the EU for poultry feeds (0.1 mg/kg). 2. Effects on meat quality, oxidative stress, residues and histological traits

The European Commission Recommendation 2006/576/EC indicates that the maximum tolerable level of ochratoxin A (OTA) in poultry feeds is 0.1 mg OTA/kg. Thirty-six 1-day-old male broiler chicks were divided into two groups, a control (basal diet) and an OTA (basal diet + 0.1 mg OTA/kg) group. The OTA concentration was quantified in serum, liver, kidney, breast and thigh samples. The thiobarbituric acid reactive substances (TBARS) content were evaluated in the liver, kidney, breast and thigh samples. The glutathione (GSH) content, and catalase (CAT) and superoxide dismutase (SOD) activity were measured in the liver and kidney samples. Histopathological traits were evaluated for the spleen, bursa of Fabricius and liver samples. Moreover, the chemical composition of the meat was analysed in breast and thigh samples. In the OTA diet-fed animals, a serum OTA concentration of 1.15 ± 0.35 ng/ml was found, and OTA was also detected in kidney and liver at 3.58 ± 0.85 ng OTA/g f.w. and 1.92 ± 0.21 ng OTA/g f.w., respectively. The TBARS content was higher in the kidney of the ochratoxin A group (1.53 ± 0.18 nmol/mg protein vs. 0.91 ± 0.25 nmol/mg protein). Feeding OTA at 0.1 mg OTA/kg also resulted in degenerative lesions in the spleen, bursa of Fabricius and liver. The maximum tolerable level of 0.1 mg OTA/kg, established for poultry feeds by the EU, represents a safe limit for the final consumer, because no OTA residues were found in breast and thigh meat. Even though no clinical signs were noticed in the birds fed the OTA-contaminated diet, moderate histological lesions were observed in the liver, spleen and bursa of Fabricius.

Biodegradation of ochratoxin a for food and feed decontamination

Ochratoxin A (OTA) is one of the most important mycotoxins that is found in food and feed products. It has proven toxic properties, being primarily known for its nephrotoxicity and carcinogenicity to certain animal species. OTA is produced by several species of Aspergillus and Penicillium that can be found in a wide variety of agricultural products, which makes the presence of OTA in these products common. Many countries have statutory limits for OTA, and concentrations need to be reduced to as low as technologically possible in food and feed. The most important measures to be taken to control OTA are preventive in order to avoid fungal growth and OTA production. However, these measures are difficult to implement in all cases with the consequence of OTA remaining in agricultural commodities. Remediation processes are often used to eliminate, reduce or avoid the toxic effects of OTA. Biological methods have been considered increasingly as an alternative to physical and chemical treatments. However, examples of practical applications are infrequent. This review will focus on the (i) known microorganisms and enzymes that are able to biodegrade OTA; (ii) mode of action of biodegradation and (iii) current applications. A critical discussion about the technical applicability of these strategies is presented.

Strains of Aureobasidium pullulans can lower ochratoxin A contamination in wine grapes

Wine contamination with ochratoxin A (OTA) is due to the attack of wine grapes by ochratoxigenic Aspergillus carbonarius and Aspergillus spp. section Nigri. Four A. pullulans strains, AU14-3-1, AU18-3B, AU34-2, and LS30, are resistant to and actively degrade ochratoxin A in vitro. The less toxic ochratoxin alpha and the aminoacid L-beta-phenylalanine were the major degradation products, deriving from the cleavage of the amide bond linking these two moieties of OTA. The same strains were studied further as biocontrol agents of A. carbonarius on wine grapes in laboratory experiments. Three of the four strains significantly prevented infections by A. carbonarius. Berries pretreated with the biocontrol agents and infected with A. carbonarius contained lower amounts of OTA as compared to the untreated infected control berries. Two of these strains were shown to degrade OTA to ochratoxin alpha in fresh grape must, but the mechanisms of the decrease of OTA accumulation in infected berries pretreated with the biocontrol agents remain to be elucidated. Assessment of one strain carried out in the vineyard during the growing season of 2006 showed that the tested strain was an effective biocontrol agent, reducing both severity of Aspergillus rots and OTA accumulation in wine grapes. To our knowledge this is the first report describing the positive influence of biocontrol agents on OTA accumulation in this crop species.

Ochratoxin A: The Continuing Enigma

The mycotoxin ochratoxin A (OTA) has been linked to the genesis of several disease states in both animals and humans. It has been described as nephrotoxic, carcinogenic, teratogenic, immunotoxic, and hepatotoxic in laboratory and domestic animals, as well as being thought to be the probable causal agent in the development of nephropathies (Balkan Endemic Nephropathy, BEN and Chronic Interstitial Nephropathy, CIN) and urothelial tumors in humans. As a result, several international agencies are currently attempting to define safe legal limits for OTA concentration in foodstuffs (e.g., grain, meat, wine, and coffee), in processed foods, and in animal fodder. In order to achieve this goal, an accurate risk assessment of OTA toxicity including mechanistic and epidemiological studies must be carried out. Ochratoxin has been suggested by various researchers to mediate its toxic effects via induction of apoptosis, disruption of mitochondrial respiration and/or the cytoskeleton, or, indeed, via the generation of DNA adducts. Thus, it is still unclear if the predominant mechanism is of a genotoxic or an epigenetic nature. One aspect that is clear, however, is that the toxicity of OTA is subject to and characterized by large species- and sex-specific differences, as well as an apparently strict structure-activity relationship. These considerations could be crucial in the investigation of OTA-mediated toxicity. Furthermore, the use of appropriate in vivo and in vitro model systems appears to be vital in the generation of relevant experimental data. The intention of this review is to collate and discuss the currently available data on OTA-mediated toxicity with particular focus on their relevance for the in vivo situation, and also to suggest possible future strategies for unlocking the secrets of ochratoxin A.

Isolation and purification of an enzyme hydrolyzing ochratoxin A from Aspergillus niger

Ochratoxin A is a mycotoxin produced by several Aspergillus and some Penicillium species which may be present in food and feed products. It can be enzymatically hydrolyzed into ochratoxin alpha and L: -beta-phenylalanine, thereby decreasing its toxicity. The ochratoxin A degradation capacity of Aspergillus niger is well known and here we report the isolation and purification of a novel enzyme from A. niger that hydrolyzes this mycotoxin. A wheat germ medium supplemented with ochratoxin A was used to produce the enzyme, which was purified from culture filtrate by acetone precipitation and anion exchange chromatography. An overall purification of 2.5-fold with a recovery of 68% and a final specific activity of 36 U/mg was obtained. The enzyme is a metalloenzyme as it was inhibited at 10 mM EDTA, whereas PMSF had no effect. The ochratoxin A hydrolytic enzyme presented a V (max) of 0.44 microM/min and a K (m) of 0.5 mM when the reaction was carried out at pH 7.5 and 37 degrees C.

Occurrence of pathogenic fungal species in Tunisian vineyards

Mycotoxins are secondary metabolites produced by filamentous fungi detected in food, such are grapes. OTA was evaluated in ten handle musts from different Tunisian vineyard. This mycotoxin was found at levels 1.1 mug/L to 4.3 mug/L. A survey was conducted to assess the contamination of the Tunisian vineyard with pathogenic fungal species, in particular those responsible of the OTA production. The results were evaluated for the first time in parcels cultivated in the North, in the Centre and in the South of the country. Italia Muscate and Superior Seedless varieties were concerned at three developmental stages of the berry, setting, veraison and maturity. Carigon variety was used as positive control for musts contaminating by OTA. The main fungal species isolated were Aspergillus spp. (33.32%), Botrytis cinerea (23.32%), Alternaria spp. (12.80%), Cladosporium spp. (10.59%) and Penicillium spp. (8.3%). The isolates of the Aspergillus genus were identified as Aspergillus niger aggregate (77%), Aspergillus carbonarius (15%) and Aspergillus flavus (8%). Their presence was characterized by a significant decrease in the Centre during the veraison and a slight increase in the North and the South during the maturity stage. Furthermore, when comparing Superior Seedless and Italia Muscate cultivated in the same area, the aspergilli were particularly less abundant at the setting stage in the case of Superior Seedless. There is no correlation between the OTA amount in musts and the contamination by Aspergillus species in different vineyards and for grape varieties studied.

Black aspergilli and ochratoxin A production in French vineyards

A survey on the occurrence on grape of black Aspergillus species and their capability to produce ochratoxin A (OTA) was conducted in France over three years (2001-2003) in 10 vineyards from four winemaking regions with different geographical locations and climatic conditions. During 2001 and 2002, from setting to harvest, the total numbers of fungal isolates were respectively 721 and 711 increasing in 2003 to reach 1035. The Aspergillus genus was essentially represented by Section Nigri (99%) and it was predominant (80%+/-4.6) when compared to Penicillium (20%+/-4.6). Regardless of sampling year, 32.5% (+/-sigma=1.26) of the fungal isolates were OTA producers and 93% (+/-sigma=2.65) belonging to black aspergilli. The ochratoxigenic potential of the isolates and their occurrence on grapes revealed that Aspergillus carbonarius was the main OTA producer (up to 37.5 mug/g). At harvest time, the fungal population was maximal and this was the most critical period influencing OTA contamination. Grapes from Languedoc-Roussillon region were most infested with ochratoxigenic fungi and had the highest concentrations of OTA (up to 2.8 ng/g).

Ochratoxin A in human blood in Abidjan, Côte d'Ivoire

Ochratoxin A (OTA) produced by Aspergillus and Penicillium genera contaminates a diversity of foods including cereals; cereals-derived foods; dry fruits; beans; cocoa; coffee; beer; wine; and foodstuffs of animal origin mainly poultry, eggs, pork and milk, including human breast milk. OTA is nephrotoxic to all animal species studied so far and most likely to humans, who show the longest half-life for elimination of this toxin among all species examined. Among other toxic effects, OTA is teratogenic, immunotoxic, genotoxic, mutagenic and carcinogenic, all of which lead to life-threatening pathologies through several molecular pathways. In Côte d'Ivoire, preliminary surveys conducted by us have proven from 1998 to 2004 the reality of ochratoxin A-contamination of foodstuffs. To assess OTA in human blood, the immunoaffinity columns were used along with HPLC for separation and fluorimetric quantification of blood samples collected in Abidjan from two categories of people: apparently healthy donors (n=63) and nephropathy patients undergoing dialysis (n=39). Among healthy donors, 34.9% show OTA concentrations ranging from 0.01 - 5.81 microg/l with a mean value of 0.83 microg/l, whereas, among nephropathy patients undergoing dialysis 20.5% are OTA positive in a range of 0.167-2.42 microg/l and a mean value of 1.05. Although the sex ratio is 0.82 (46 females for 56 males) ochratoxin A contamination is equally distributed in both sexes. Nephropathy patients undergoing dialysis appear, however, less frequently contaminated than healthy donors (20.5 versus 34.9%) and show higher OTA concentrations (higher mean value, p=0.01). Ochratoxin A concentrations found in human blood reflect concentrations previously detected in cereals and peanuts according to the eating habits and diets of people in Côte d'Ivoire. But, the prevalence of ochratoxin A in blood of nephropathy people undergoing dialysis appears lower than expected from the frequency of OTA contamination in cereals and peanuts. Pearson chi(2)-test indicates that among OTA-positive individuals renal dialysis and age are important modalities for consideration.

Immunotoxic activity of ochratoxin A

Ochratoxin A (OTA) is an immunosuppressant fungal compound, produced by toxigenic species of Aspergillus and Penicillium fungi in a wide variety of climates and geographical regions. The contamination of food by this mycotoxin takes place primarily during preharvest periods. Almost all types of food can be contaminated. In addition, its chemical stability against heat and during industrial food processing makes OTA one of the most abundant food contaminating mycotoxins. Due in part to its long serum half-life in man, almost 100% of all human blood samples from some geographic regions may be positive for OTA. The immunosuppressant activity of OTA is characterized by size reduction of vital immune organs, such as thymus, spleen, and lymph nodes, depression of antibody responses, alterations in the number and functions of immune cells, and modulation of cytokine production. The immunotoxic activity of OTA probably results from degenerative changes and cell death following necrosis and apoptosis, in combination with slow replacement of affected immune cells, due to inhibition of protein synthesis.

Alterations induced in vitro by ochratoxin A in rat lymphoid cells

Ochratoxin A (OTA) is a nephrotoxic mycotoxin produced by species of the genus Penicillium and Aspergillus that is present in food and feed as a natural contaminant. It modifies the immune function in animals and inhibits the proliferative response of lymphocytes in vitro. The toxic effect of OTA (0.5, 2, 20 microM) in lympho-proliferative response, natural killer (NK) cell activity, cytotoxic T lymphocytes (CTL) activity and macrophages' bacteriolytic capability was studied in vitro after 1 hour of treatment. The proliferative response of lymphocytes to concanavalin A and lipopolysaccharide was not affected by OTA; the cytotoxic activity of NK cells was dose-dependent decreased; the CTL activity was significantly decreased at the lowest concentration; the bacteriolytic activity of macrophages varied only slightly. These in vitro results reproduced, at least in part, some effects detected previously in vivo. The protein synthesis inhibition and the oxidative metabolism of OTA coupled to the prostaglandin synthesis are probably implicated in NK cells' toxicity, because the effects were reverted by the addition of phenylalanine or piroxicam to the culture medium. The induction of apoptosis seems to be the principal mechanism of action in the CTL effect. The intracellular concentration of OTA after 1 hour was analysed by HPLC and was found to be proportional to the quantity of OTA added to the culture medium for the three cell types; the presence of phenylalanine and piroxicam on the culture medium did not change the intracellular OTA concentration.

Synergistic effects of fumonisin B1 and ochratoxin A: are in vitro cytotoxicity data predictive of in vivo acute toxicity?

Contamination of food and feeds by mycotoxins is a major problem of human and animals health concern which is also extremely detrimental to economy. Mycotoxins producing moulds may produce a diversity of toxins such as aflatoxins, ochratoxins, trichothecenes, zearalenone, fumonisins, tremorgenic toxins and ergot alkaloids. Although toxicological, environmental and epidemiological studies have addressed the problem of these toxins one by one, more than one mycotoxin are found usually in the same contaminated commodities. That rises the incommensurable problem of multi-toxicosis in which the respective metabolites are also involved. These mycotoxins bear potential toxicity leading to acute and chronic effects in humans and animals, depending on species. The mechanisms that lead to toxic effects, such as immune toxicity, and carcinogenicity are complexe. The risk assessment for humans potentially exposed to multi-mycotoxins suffers very much from the lack of adequate food consumption data. Furthermore, for a given mycotoxin synergism and antagonism with other mycotoxins found in the same food commodities are not taken into account. The case of combination of ochratoxin A (OTA) and fumonisin B1 (FB1) has been addressed in the present paper with the purpose of predicting the in vivo toxicity using a simple in vitro test, i.e. neutral red uptake, in three different cell-lines, C6 glioma cells, Caco-2 cells and Vero cells. Using the equation of [ATLA 27 (1999) 957], in vivo toxicity (LD50) is in adequation with the in vitro data, (IC50 values) for both toxins as well as for the combination of 10 microM OTA and variable concentrations of FB1 (10-50 microM). A synergistic effect is prouved in vitro that is in line with some in vivo data from the literature. Such simple in vitro test may thus help predicting in vivo toxicity of combinations of mycotoxins naturally occurring in foodstuffs.

Ochratoxin A and β2-microglobulinuria in healthy individuals and in chronic interstitial nephropathy patients in the Centre of Tunisia: a hot spot of Ochratoxin A exposure

Ochratoxin A (OTA) is a nephrotoxic mycotoxin considered to be the causal agent of the Balkan endemic nephropathy (BEN). In Tunisia, a chronic interstitial nephropathy (CIN) of unknown aetiology, resembling BEN, has been characterised wherein OTA seems to be implicated too. However, despite the considerable number of investigations conducted so far, the role of OTA in the outcome of this human nephropathy is still uncertain. In this study, an attempt is being made to consolidate the link between OTA and the Tunisian CIN of unknown aetiology. Blood OTA and beta(2)-microglobulinuria levels were measured in several groups of healthy individuals and patients having different renal diseases of known and unknown aetiologies (100 nephropathy patients and 40 healthy subjects). The high blood OTA and beta(2)-microglobulinuria levels seem to be strongly associated to the CIN of unknown aetiology. Our results support the involvement of this nephrotoxic agent in the outcome of this particular human nephropathy and underline furthermore the importance of beta(2)-microglobulinuria in the characterization of this disease.

Ochratoxin A and some of its derivatives modulate radical formation of porcine blood monocytes and granulocytes

Modulating effects of ochratoxin A (OTA) and some of its derivatives on viability and oxidative burst activity of porcine monocytes and granulocytes have been studied. The formation of free oxygen radicals by monocytes was suppressed by OTA and ochratoxin C (OTC) at concentrations between 10 and 1000 ng/ml. Intracellular radical formation of granulocytes was in part already significantly reduced at 1 ng/ml of these mycotoxins. Conversely, the intracellular formation of radicals in monocytes of individual pigs was stimulated by the toxins at 1-100 ng/ml. A biologically active fraction of the crude toxin (RE2) which had been identified as OTC had a stronger effect than all other derivatives of ochratoxin A. Whether these modulating effects of OTA and OTC on phagocyte functions are of significance in the pathogenesis of infectious diseases, needs to be studied in more detail. In this context, the occurrence of OTC in food and feeds should be examined more closely.

Metabolism-mediated cytotoxicity of ochratoxin A

Ochratoxin A (OTA) is produced by various strains of Aspergillus and Penicillium and is a common contaminant of food commodities. OTA is metabolised by cytochrome P450 (CYP450) enzymes resulting in hydroxylated metabolites, 4R-OH-OTA and 4S-OH-OTA, and possibly in other minor metabolites including OTA-quinones. However, until now conflicting data have been presented regarding the role of biotransformation products in the adverse effects of OTA. Hence, the aim of this study was to further assess the metabolism-mediated cytotoxicity of OTA in an in vitro model encompassing NIH/3T3 cells, stably expressing the human CYP450 enzymes CYP2C9 and CYP3A4, respectively. In addition, modulation of the cellular glutathione (GSH) content was used to identify a role of GSH in OTA-induced cytotoxicity. Following exposure to OTA, cells expressing CYP2C9 showed a significant reduction in neutral red (NR) uptake but not in Alamar blue (AB) reduction, as compared to the control LNCX cells which do not express CYP450 enzymes. CYP3A4-expressing cells showed no difference in viability from control LNCX cells. When pre-treated with l-buthionine S,R-sulphoximine (BSO) to deplete GSH, CYP2C9-expressing cells showed also a loss of cell viability as compared to LNCX cells, although to a lesser extent as compared to non-depleted CYP2C9-expressing cells. Data presented in this study support previous findings, indicating that different biotransformation pathways contribute to the cytotoxicity induced by OTA.

Ochratoxin A Induces Apoptosis in Human Lymphocytes through Down Regulation of Bcl-xL

Ochratoxin A (OTA) is a widespread mycotoxin contaminating feed and food. Besides its potent nephrotoxicity, OTA also affects the immune system. We demonstrate here a role for Bcl-x(L) in OTA-induced apoptosis in human lymphocytes. In particular, human peripheral blood lymphocytes and the human lymphoid T cell line, Kit 225 cells, underwent apoptosis in a time- and dose-dependent manner. This apoptosis was inhibited by z-VAD.fmk, suggesting that caspases were responsible for the induction of apoptosis. Moreover, OTA triggered mitochondrial transmembrane potential (Deltachim) loss and caspase-9 and caspase-3 activation. Interestingly, Bcl-x(L) protein expression was decreased by OTA treatment, whereas Bcl-2 protein level was not affected. Down-regulation of bcl-x(L) mRNA was not observed in cells treated with OTA. Overexpression of Bcl-x(L) in Kit 225 cells protected them against mitochondrial perturbation and retarded the appearance of apoptotic cells. Taken together, our data indicate that mitochondria are a central component in OTA-induced apoptosis and that the loss of Bcl-x(L) may participate in OTA-induced cell death.

Immunotoxic effects of Ochratoxin A in wistar rats after oral administration

Ochratoxin A (OTA) is a mycotoxin produced by species of the genus Aspergillus and Penicillium. Human exposure has been demonstrated worldwide and its origin seems to be the intake of contaminated foods. The kidneys are the target organ of this mycotoxin. Immunotoxic and genotoxic effects of OTA were investigated in Wistar male rats (aged 12 weeks), treated by gavage with 50, 150 or 450 microg OTA/kg body weight for 28 days, in the context of a general toxicity study, which was designed following the recommendations of OECD guideline 407. At the end of the study, the mean plasma concentration of the mycotoxin was determined, several immune function assays were performed and bone marrow smears were obtained and stained in order to analyse micronuclei in polychromatic erytrocytes. Mean plasma concentration was found to be 187, 600 and 807 microg/L, respectively. At the highest dose, a decrease in body weight gain was observed. Histopathological investigations revealed tubulonephrosis and acute tubular necrosis in the kidneys of the animals treated with OTA. The frequency and severity of the lesions increased with the dose. The response of splenocytes to sheep red blood cells was decreased in a dose-dependent manner; however, nonstatistically significant differences were obtained. The natural killer cell activity was strongly affected by OTA treatment. Cytotoxic T lymphocyte activity was lower in the animals exposed to 50 microg OTA/kg b.w. but was not modified in the groups exposed to 150 and 450 microg OTA/ kg b.w. The bacteriolytic capability of macrophages was significantly reduced in groups exposed to 50 and 450 microg OTA/ kg b.w. The number of micronuclei in bone marrow polychromatic erytrocytes did not vary significantly with respect to the control at any dose, but a false negative result can not be ruled out because the exposure doses were much lower than those recommended in OECD guideline 474.

Apoptosis and oxidative stress induced by ochratoxin A in rat kidney

Ochratoxin A (OTA) is a widespread mycotoxin produced by several species of fungi. OTA induces a tubular-interstitial nephropathy in humans and in animals. It has been implicated as one of the aetiological agents involved in the development of endemic nephropathy. OTA-induced oxidative stress and apoptosis may play key roles in the development of chronic tubulointerstitial nephritis connected to the long-term exposure to this food contaminant. We studied the effects of low doses of OTA on kidney cells. Wistar rats were treated with 120 microg OTA/kg bodyweight daily, for 10, 30 or 60 days. Toxin concentration in kidney was proportional to the time of exposure, and amounted to 547.2, 752.5 and 930.3 ng OTA/g kidney tissue after 10, 30 and 60 days, respectively. OTA treatment caused an increased number of cells undergoing apoptosis in both proximal and distal epithelial kidney cells. The apoptotic cells were visualised using the TUNEL assay and staining with haematoxylin and eosin in situ. The number of apoptotic cells in rats treated for 10, 30 and 60 days increased by 5-, 6.4- and 12.7-fold, respectively, compared with the control cells. However, DNA electrophoresis did not show characteristic fragmentation (DNA laddering). The oxidative stress was evident via increased malondialdehyde formation. The concentration of lipid peroxides showed an increase (36%), but the activity of superoxide dismutase decreased (26%) in 60-day treated rats. In spite of the observed biochemical and morphological changes in the kidney cells, renal functional status was preserved to the end of experiment. This study demonstrates that a combination of morphologic and biochemical markers can be used to monitor early cell death in OTA-induced renal injury. We have shown that the exposure to the relatively low OTA concentrations has activated apoptotic processes and oxidative damage in kidney cells.

Effects of the mycotoxin ochratoxin A and some of its metabolites on the human cell line THP-1

The immunomodulatory effects of ochratoxin A (OTA) and some of its metabolites on the human monocyte/macrophage line THP-1 are described. Metabolic activity, cell proliferation, cell membrane integrity, cell differentiation, phagocytic behaviour, nitrogen oxide synthesis and cell surface markers were largely suppressed by these mycotoxins at concentrations between 10 and 1000 ng/ml, in individual cases already at 1 ng/ml. After analysis of a crude toxin, a substance designated RE2 could be isolated besides OTA, which was identified as ochratoxin C (OTC). The latter showed a stronger suppressive effect on most functions studied than all other metabolites of OTA. Because of the immunomodulatory effects of OTA and OTC, more attention should be paid to their immunopathogenic importance in addition to their known cytotoxic and genotoxic effects. The occurrence and importance of the mycotoxin OTC should be more closely examined in this context.

Fungal flora and ochratoxin a production in grapes and musts from france

Eleven samples of grapes and musts used in red table wines were investigated for the occurrence of potential ochratoxin A (OTA)-producing molds. From these samples, 59 filamentous fungi and 2 yeasts were isolated. Among the 30 genera isolated, Deuteromycetes were the most frequent (70%) followed by Ascomycetes (10%). Six of the eleven grapes samples were contaminated by potentially ochratoxinogenic strains (Penicillium chrysogenum and Aspergillus carbonarius). When cultivated in vitro on solid complex media, the 14 strains of A. carbonarius produced OTA. No other species produced OTA under the same conditions. Among must samples, eight of eleven were found to be contaminated by OTA (concentrations from <10 to 461 ng/L). There is a strong correlation between the presence of ochratoxin-producing strains on grapes and OTA in musts. These findings should be connected with the OTA contamination of human blood in these areas and in France.

Subchronic effects of ochratoxin A on young adult rat brain and partial prevention by aspartame, a sweetener

1. Ochratoxin A (OTA) is a mycotoxin produced by several fungi, especially Aspergillus and Penicillium species. Many food and foodstuffs can be contaminated by ochratoxin A, which is consequently found in blood of animals and humans. 2. The distribution into the brain of young adult rats fed OTA for 1 to 6 weeks and some consequences have been investigated in the present study. 3. Our results on rats given OTA (289 microg/kg/48 h) indicated that OTA accumulated in the whole brain as function of time according to a regression curve, Y=-8.723 a+16.72 with a correlation coefficient of r=0.989, where Y-axis is the OTA concentration in ng/g of brain and X-axis is the duration of the treatment in weeks. The brain OTA contents was 11.95 +/- 2.2, 23.89 +/- 4.4, 39.9 +/- 4.5, 50.3 +/- 7.3, 78.8 +/- 6.3, 94 +/- 16 ng/g of brain in the mycotoxin-treated animals for respectively 1, 2, 3, 4, 5 and 6-weeks treatment. OTA induced modifications of free amino-acid concentrations in the brain, mainly, Tyrosine (Tyr) and phenylalanine (Phe). Tyr decreased significantly as compared to control (p < 0.05). Phe increased significantly as compared to control (p < 0.05). 4. Aspartame, (25 mg/kg/48 h) a structural analogue of OTA largely modified the distribution and prevented the accumulation of OTA in the brain since the respective brain OTA contents decreased respectively to 9.6 +/- 7.9, 19.2 +/- 3.0, 26.8 +/- 4.2, 19.7 +/- 1.9, 13.7 /- 5.6 and 11.0 +/- 6.0 ng/g of tissue, for the same duration of treatment. It also prevented the modifications of Tyr and Phe levels. 5. The histological investigations showed several necrotic cells with pyknotic nucleus, detected in OTA treated animals with higher frequency as compared to the controls and Aspartame treated ones. Aspartame appeared to significantly prevent this nuclear effect as well, the meaning of which is discussed.

Prevention of lipid peroxidation induced by ochratoxin A in Vero cells in culture by several agents

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus ochraceus as well as other moulds. This mycotoxin contaminates animal feed and food and is nephrotoxic for all animal species studied so far. OTA is immunosuppressive, genotoxic, teratogenic and carcinogenic. It is a structural analogue of phenylalanine and contains a chlorinated dihydroisocoumarinic moiety. Ochratoxin A inhibits protein synthesis by competition with phenylalanine in the phenylalanine-tRNA aminoacylation reaction. Recently lipid peroxidation induced by OTA has been reported, indicating that the lesions induced by this toxin could also be related to oxidative damage. An attempt to prevent its toxic effect, mainly the lipid peroxidation, has been made using aspartame (L-aspartyl-L-phenylalanine methyl ester) a structural analogue of both OTA and phenylalanine, piroxicam, a non steroidal anti-inflammatory drug and superoxide dismutase+catalase (endogenous oxygen radical scavengers). Lipid peroxidation was assayed in monkey kidney cells (Vero cells) treated by increasing concentrations of OTA (5-50 microM). After 24 h incubation OTA induced lipid peroxidation in Vero cells in a concentration dependent manner, as measured by malonaldehyde (MDA) production. The MDA production, in Vero cells, was significantly increased by 50.5% from 694.1 +/- 21.0 to 1041.5 +/- 23.5 pmol/mg of protein. In the presence of superoxide dismutase (SOD)+catalase (25 micrograms/ml each) the MDA production induced by OTA was significantly decreased. At 50 microM of OTA concentration (optimal production of MDA) the MDA production decreased from 1041.5 +/- 23.5 to 827.5 +/- 21.3 pmol/mg of protein. SOD and catalase, when applied prior to the toxin, seemed to prevent lipid peroxidation more efficiently than piroxicam (at a ten-fold higher concentration than OTA) and aspartame (at equimolar concentration). These molecules also partially prevented the OTA-induced leakage of MDA in the culture medium.

Influence of perinatal ochratoxin A exposure on the immune system in mice

The mycotoxin ochratoxin A (OA) is a well-documented immunotoxic agent which affects both cellular and humoral immunity. In the present study, the effects of maternal exposure to single doses of OA during gestation or lactation were studied in Balb/c offspring. A single dose exposure of the dams to OA (500 micrograms/kg body weight) on day 16 of gestation resulted in decreased proliferation of splenic and thymic lymphocytes in response to mitogens in the pups at 15 days of age. Flow cytometry analysis of thymocyte subpopulations revealed lower percentages of mature CD4+ cells and higher percentages of immature, double-positive (CD4+CD8+) cells in the exposed pups. In contrast, a single exposure of the dams of OA on day 10 postpartum significantly increased the proliferative responsiveness of lymphocytes in the offspring when stimulated with B or T cell mitogens 3 days after the exposure. This effect was most prominent in the highest dose group (500 micrograms/kg body weight). The present results are in accordance with previous observations in rats, and show that the time of exposure significantly influences the immunotoxic effects of OA on the developing immune system in rodents.

Prenatal exposure of Balb/c mice to ochratoxin A: effects on the immune system in the offspring

Effects of prenatal exposure to the mycotoxin ochratoxin A (OA) on the immune system were evaluated in Balb/c mice. Dams were exposed to OA in their diet at doses of 0.18 (control), 30 or 200 micrograms/kg before and during gestation. At birth, pups were cross-fostered to non-exposed dams. OA exposure of the dams did not influence reproductive outcome, that is, the numbers of litters, litter sizes and body weight of the pups. Flow cytomety analysis of T-lymphocyte subpopulations on days 14 and 28 postpartum revealed a decrease in the percentages of splenic CD4+ and CD8+ cells in offspring from the high-dose group (200 micrograms/kg diet), but no significant alterations in absolute numbers of these cell populations nor in the total numbers of splenocytes were observed. In the thymus, a relative as well as an absolute increase in the CD4+ subpopulation was seen in exposed pups on day 14. On day 28, the absolute numbers of CD4+, CD8+ and CD4+CD8+ (double positive) cells were increased, reflecting an elevated number of thymocytes in the high-dose group. No significant differences were found in the proliferative responses of splenic or thymic lymphocytes to mitogens, or in the production of interleukin-2 in concanavalin A-stimulated cell cultures. Further, the plaque-forming cell response to sheep red blood cells and the humoral antibody response to the viral antigen PR8 were not affected by prenatal exposure to OA. No significant differences in natural killer cell activity were observed. The results indicate that exposure of dams to relatively low levels of dietary OA alters absolute and relative numbers of lymphocyte subpopulations in lymphoid organs, but does not suppress immune functions in the offspring.

Effects of ochratoxin A on the rat immune system after perinatal exposure

Effects on the immune system after perinatal exposure to ochratoxin A (OA) were studied in Sprague-Dawley rats after single or repeated exposure of the dams. In a short-term study, dams with litters were given a single dose of OA (0, 10, 50 or 250 micrograms/kg body weight) on day 11 of lactation. The effects on cell numbers in spleen and thymus añd on the mitogen responses of lymphocytes were evaluated in the suckling pups on day 14 of lactation. The proliferative response of splenocytes to the T-cell mitogen Concanavalin A (Con A) was significantly stimulated in pups from dams given 10 or 50 micrograms OA/kg body weight as compared to control pups. In addition, proliferation of thymocytes in response to Con A was stimulated in pups from dams exposed to 50 micrograms OA/kg body weight. In a long-term, cross-fostering study comparing pre- and postnatal exposure, half of the dams received 50 micrograms OA/kg body weight 5 days a week by gastric intubation 2 weeks before mating, during gestation and then 7 days a week until weaning. Effects on immune parameters were studied in the pups on day 14 of lactation and at 13 weeks of age. Suppressed mitogenic responses were seen to both lipopolysaccharide (LPS) and Con A in prenatally exposed pups sampled on day 14 of lactation. At 13 weeks the response of splenocytes to LPS was still impaired. The primary antibody response to a viral antigen was also lower in the prenatally exposed pups than in the control pups. These effects on the immune response were not seen in the groups of pups exposed postnatally or both pre- and postnatally, although blood concentrations of OA were higher in these groups at the time of the first sampling. This indicates that the decrease in proliferation and antibody production resulted from prenatal modulation of the immune system. The results show that prenatal exposure to relatively low doses of OA may induce immunosuppression. In contrast, short-term exposure of suckling pups to OA via the milk stimulates the proliferative responses of lymphocytes to polyclonal activation.

Prevention of nephrotoxicity of ochratoxin A, a food contaminant

Ochratoxin A (OTA) is a mycotoxin produced by ubiquitous Aspergilli, mainly by Aspergillus ochraceus and also by Penicilium verrucosum. It was found all over the world in feed and human food and blood as well as in animal blood and tissues. The most threatening effects of OTA are its nephrotoxicity and carcinogenicity, since this mycotoxin is nephrotoxic to all animal species studied so far and is increasingly involved in the Balkan endemic nephropathy (BEN), a human chronic interstitial nephropathy which is most of the time associated to urinary tract tumours. Since it seems impossible to avoid contamination of foodstuffs by toxigenic fungi, detoxification and detoxication for OTA are needed. To reduce or abolish the OTA-induced toxic effects, several mechanisms were investigated. The results of these investigations showed that some of the potential antidotes were efficient in preventing the main OTA toxic effects whereas some others were not. Promising compounds are structural analogues of OTA, and/or compounds having a high binding affinity for plasma proteins such as piroxicam, a non-steroidal anti-inflammatory drug (NSAID). Some enzymes such as superoxide dismutase (SOD) and catalase, radical scavengers, vitamins, prostaglandin (PG) synthesis inhibitors, (such as piroxicam), pH modificators, adsorbant resin such as cholestyramine etc. are efficient in vivo. Some of the results obtained in vivo were already confirmed in vitro and gave useful information on how to safely use these antidotes. The most generally acting compound seems to be A19 (Aspartame), a structural analogue of OTA and phenylalanine. When given to rats A19 (25 mg/kg/48 h) combined to OTA (289 micrograms/kg/48 h) for several weeks largely prevented OTA nephrotoxicity and genotoxicity. When given after intoxication of animals with OTA it washes out the toxin efficiently from the body. In vitro, A19 (10 micrograms/ml) prevents OTA (20-500 micrograms/ml) binding to plasma proteins. Its general action without any known side effect in humans and in animals, points at A19 to be the best candidate for preventing the OTA-induced subchronic effects.

Effects of ochratoxin A on the mouse immune system after subchronic exposure

The effects on the immune system of oral, subchronic exposure to ochratoxin A (OA) at 6, 250 or 2600 micrograms/kg diet were studied in female Balb/c mice. After 28 days of exposure, antibody production plague-forming cells/spleen, was suppressed in a dose-dependent manner which was significant in the two highest exposure groups. In addition, a decrease in thymocyte cell counts was seen in the 250-micrograms/kg group. After 90 days exposure, flow cytometry analysis of thymic lymphocyte subpopulations revealed a decreased proportion of mature (CD4+ or CD8+) cells. Furthermore, the mitogenic responsiveness of thymocytes and splenocytes to concanavalin A (Con A) was significantly decreased. This effect was observed in all three treatment groups. Interleukin-2 production of Con A-stimulated lymphocytes, natural killer cell activity, and humoral antibody titres to a viral antigen were not affected by OA treatment. The present results indicate that subchronic, oral exposure to OA affects certain immune functions in mice at exposure levels that may be found in contaminated food products.