1
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Palumbo JD, Sarreal SBL, Kim JH. Simultaneous detection of mycotoxigenic Aspergillus species of sections Circumdati and Flavi using multiplex digital PCR. Lett Appl Microbiol 2023; 76:ovad142. [PMID: 38111225 DOI: 10.1093/lambio/ovad142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 11/20/2023] [Accepted: 12/15/2023] [Indexed: 12/20/2023]
Abstract
Populations of ochratoxin-producing Aspergillus section Circumdati species and aflatoxin-producing Aspergillus section Flavi species frequently coexist in soil and are the main sources of mycotoxin contamination of tree nuts. Identification of mycotoxigenic Aspergillus species in these sections is difficult using traditional isolation and culture methods. We developed a multiplex digital PCR (dPCR) assay to detect and quantify Aspergillus ochraceus, Aspergillus westerdijkiae, and Aspergillus steynii (section Circumdati), as well as Aspergillus flavus and Aspergillus parasiticus (section Flavi), in environmental samples based on species-specific calmodulin gene sequences. Relative quantification of each species by dPCR of mixed-species templates correlated with corresponding DNA input ratios. Target species could be detected in soil inoculated with conidia from each species. Non-target species of sections Circumdati, Flavi, and Nigri were generally not detectable using this dPCR method. Detected non-target species (Aspergillus fresenii, Aspergillus melleus, Aspergillus sclerotiorum, and Aspergillus subramanianii) were discernible from A. ochraceus in dual-template dPCR reactions based on differential fluorescence intensity.
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Affiliation(s)
- Jeffrey D Palumbo
- Foodborne Toxin Detection and Prevention Research Unit, US Department of Agriculture, Agricultural Research Service, Albany, CA 94710, United States
| | - Siov Bouy L Sarreal
- Foodborne Toxin Detection and Prevention Research Unit, US Department of Agriculture, Agricultural Research Service, Albany, CA 94710, United States
| | - Jong H Kim
- Foodborne Toxin Detection and Prevention Research Unit, US Department of Agriculture, Agricultural Research Service, Albany, CA 94710, United States
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Aloisi CMN, Escher NA, Kim HS, Geisen SM, Fontana GA, Yeo JE, Schärer OD, Sturla SJ. A combination of direct reversion and nucleotide excision repair counters the mutagenic effects of DNA carboxymethylation. DNA Repair (Amst) 2022; 110:103262. [PMID: 35030424 PMCID: PMC9232693 DOI: 10.1016/j.dnarep.2021.103262] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 12/20/2021] [Accepted: 12/20/2021] [Indexed: 02/03/2023]
Abstract
Distinct cellular DNA damage repair pathways maintain the structural integrity of DNA and protect it from the mutagenic effects of genotoxic exposures and processes. The occurrence of O6-carboxymethylguanine (O6-CMG) has been linked to meat consumption and hypothesized to contribute to the development of colorectal cancer. However, the cellular fate of O6-CMG is poorly characterized and there is contradictory data in the literature as to how repair pathways may protect cells from O6-CMG mutagenicity. To better address how cells detect and remove O6-CMG, we evaluated the role of two DNA repair pathways in counteracting the accumulation and toxic effects of O6-CMG. We found that cells deficient in either the direct repair protein O6-methylguanine-DNA methyltransferase (MGMT), or key components of the nucleotide excision repair (NER) pathway, accumulate higher levels O6-CMG DNA adducts than wild type cells. Furthermore, repair-deficient cells were more sensitive to carboxymethylating agents and displayed an increased mutation rate. These findings suggest that a combination of direct repair and NER circumvent the effects O6-CMG DNA damage.
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Affiliation(s)
- Claudia M N Aloisi
- Department of Health Sciences and Technology, ETH Zurich, 8092 Zurich, Switzerland
| | - Nora A Escher
- Department of Health Sciences and Technology, ETH Zurich, 8092 Zurich, Switzerland
| | - Hyun Suk Kim
- Center for Genomic Integrity, Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea
| | - Susanne M Geisen
- Department of Health Sciences and Technology, ETH Zurich, 8092 Zurich, Switzerland
| | - Gabriele A Fontana
- Department of Health Sciences and Technology, ETH Zurich, 8092 Zurich, Switzerland
| | - Jung-Eun Yeo
- Center for Genomic Integrity, Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea; Department of Biological Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Orlando D Schärer
- Center for Genomic Integrity, Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea; Department of Biological Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
| | - Shana J Sturla
- Department of Health Sciences and Technology, ETH Zurich, 8092 Zurich, Switzerland.
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Alonso-Jauregui M, Font M, González-Peñas E, López de Cerain A, Vettorazzi A. Prioritization of Mycotoxins Based on Their Genotoxic Potential with an In Silico-In Vitro Strategy. Toxins (Basel) 2021; 13:734. [PMID: 34679027 PMCID: PMC8540412 DOI: 10.3390/toxins13100734] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 10/08/2021] [Accepted: 10/12/2021] [Indexed: 11/16/2022] Open
Abstract
Humans are widely exposed to a great variety of mycotoxins and their mixtures. Therefore, it is important to design strategies that allow prioritizing mycotoxins based on their toxic potential in a time and cost-effective manner. A strategy combining in silico tools (Phase 1), including an expert knowledge-based (DEREK Nexus®, Lhasa Limited, Leeds, UK) and a statistical-based platform (VEGA QSAR©, Mario Negri Institute, Milan, Italy), followed by the in vitro SOS/umu test (Phase 2), was applied to a set of 12 mycotoxins clustered according to their structure into three groups. Phase 1 allowed us to clearly classify group 1 (aflatoxin and sterigmatocystin) as mutagenic and group 3 (ochratoxin A, zearalenone and fumonisin B1) as non-mutagenic. For group 2 (trichothecenes), contradictory conclusions were obtained between the two in silico tools, being out of the applicability domain of many models. Phase 2 confirmed the results obtained in the previous phase for groups 1 and 3. It also provided extra information regarding the role of metabolic activation in aflatoxin B1 and sterigmatocystin mutagenicity. Regarding group 2, equivocal results were obtained in few experiments; however, the group was finally classified as non-mutagenic. The strategy used correlated with the published Ames tests, which detect point mutations. Few alerts for chromosome aberrations could be detected. The SOS/umu test appeared as a good screening test for mutagenicity that can be used in the absence and presence of metabolic activation and independently of Phase 1, although the in silico-in vitro combination gave more information for decision making.
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Affiliation(s)
- Maria Alonso-Jauregui
- Department of Pharmacology and Toxicology, Research Group MITOX, School of Pharmacy and Nutrition, Universidad de Navarra, 31008 Pamplona, Spain; (M.A.-J.); (A.L.d.C.)
| | - María Font
- Department of Pharmaceutical Technology and Chemistry, Research Group MITOX, School of Pharmacy and Nutrition, Universidad de Navarra, 31008 Pamplona, Spain; (M.F.); (E.G.-P.)
- IdiSNA, Navarra Institute for Health Research, 31008 Pamplona, Spain
| | - Elena González-Peñas
- Department of Pharmaceutical Technology and Chemistry, Research Group MITOX, School of Pharmacy and Nutrition, Universidad de Navarra, 31008 Pamplona, Spain; (M.F.); (E.G.-P.)
| | - Adela López de Cerain
- Department of Pharmacology and Toxicology, Research Group MITOX, School of Pharmacy and Nutrition, Universidad de Navarra, 31008 Pamplona, Spain; (M.A.-J.); (A.L.d.C.)
- IdiSNA, Navarra Institute for Health Research, 31008 Pamplona, Spain
| | - Ariane Vettorazzi
- Department of Pharmacology and Toxicology, Research Group MITOX, School of Pharmacy and Nutrition, Universidad de Navarra, 31008 Pamplona, Spain; (M.A.-J.); (A.L.d.C.)
- IdiSNA, Navarra Institute for Health Research, 31008 Pamplona, Spain
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Zhao J, Qi X, Dai Q, He X, Dweep H, Guo M, Luo Y, Gretz N, Luo H, Huang K, Xu W. Toxicity study of ochratoxin A using HEK293 and HepG2 cell lines based on microRNA profiling. Hum Exp Toxicol 2016; 36:8-22. [PMID: 26893291 DOI: 10.1177/0960327116632048] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Ochratoxin A (OTA) induced DNA damage, cytotoxicity, and apoptosis in mammalian cell lines. Micro RNAs (miRNAs) are involved in physiological and developmental processes and contribute to cancer development and progression. In our study, high-throughput miRNA profiling and Kyoto Encyclopedia of Genes and Genomes analysis were applied to comparatively study the toxicity of OTA in HEK293 cells and HepG2 cells treated with 25 μM OTA for 24 h. In these two cells, the same changing miRNAs were mostly related to signal transduction pathways, whereas the different changing miRNAs were mostly related to human cancer pathways. DGCR8, Dicer1, and Drosha were significantly suppressed in HEK293 cells, indicating an impairment of miRNA biogenesis. The damage seemed more extensive in HEK293 cells. Cell models and in vivo models were also compared. Many miRNAs in vitro were markedly different from those in vivo; however, OTA toxicity was observed both in vitro and in vivo. The classification of deregulated pathways is similar. The biogenesis of miRNA was impaired in both lines. In conclusion, deregulated miRNAs in vitro are mostly related to human cancer and signal transduction pathways. The deregulated pathways in vivo are similar to those in vitro.
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Affiliation(s)
- J Zhao
- 1 Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - X Qi
- 1 Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - Q Dai
- 1 Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - X He
- 1 Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - H Dweep
- 2 Medical Research Center, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - M Guo
- 1 Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - Y Luo
- 1 Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - N Gretz
- 2 Medical Research Center, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - H Luo
- 3 State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China
| | - K Huang
- 1 Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - W Xu
- 1 Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China.,4 Beijing Laboratory for Food Quality and Safety, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
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Maternal-Fetal Cancer Risk Assessment of Ochratoxin A during Pregnancy. Toxins (Basel) 2016; 8:87. [PMID: 27023600 PMCID: PMC4848614 DOI: 10.3390/toxins8040087] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 03/16/2016] [Accepted: 03/17/2016] [Indexed: 12/16/2022] Open
Abstract
Increasing evidence has demonstrated that in utero exposure to environmental chemicals may interfere with fetal development and increase the risk of disease and cancer development later in life. Ochratoxin A (OTA) has been proven to induce diverse toxic effects including teratogenicity, carcinogenicity, immunotoxicity and potential endocrine disruption. Due to the continuous and widespread occurrence of OTA as a potential contaminant of staple foods, there is increasing concern of in utero exposure of fetus to this mycotoxin. In this study, maternal-fetal risk assessment of OTA during pregnancy was conducted using the benchmark dose approach for genotoxic carcinogens. The daily intake of OTA for Egyptian pregnant women was estimated based on their serum OTA level using the refined Klaassen equation for pregnancy. Fetal exposure level was also estimated based on the maternal data. Comparison between the estimated daily exposure and the negligible cancer risk intake (NCRI), and the calculation of margin of exposure (MOE) implicated that OTA exposure from dietary intake would be of low health concern for this general subpopulation of Egyptian women. This subpopulation of pregnant women was generally estimated not to be in high-risk for toxicity induced by OTA.
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Palumbo JD, O'Keeffe TL, Ho YS, Santillan CJ. Occurrence of ochratoxin a contamination and detection of ochratoxigenic Aspergillus species in retail samples of dried fruits and nuts. J Food Prot 2015; 78:836-42. [PMID: 25836414 DOI: 10.4315/0362-028x.jfp-14-471] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Ochratoxin A (OTA) is a mycotoxin produced by several species of Aspergillus and Penicillium and is a potential contaminant of a wide variety of food products. To determine the incidence of OTA contamination in dried fruits and tree nuts, retail packaged and bulk raisins, dates, figs, prunes, almonds, pistachios, and walnuts were collected from small and large supermarkets in seven areas of the United States between 2012 and 2014. Of the 665 samples analyzed, OTA was detected in 48 raisin samples, 4 fig samples, 4 pistachio samples, and 1 date sample. OTA contamination levels ranged from 0.28 to 15.34 ng/g in dried fruits and 1.87 to 890 ng/g in pistachios; two raisin samples and one pistachio sample exceeded the European Union regulatory limit of 10 ng/g. PCR detection of potential OTA-producing Aspergillus species revealed the presence of A. niger, A. welwitschiae, and A. carbonarius in 20, 7, and 7 of the 57 OTA-contaminated samples, respectively. However, OTA-producing A. carbonarius was isolated from only one raisin sample, and no other OTA-producing Aspergillus species were found. These results suggest that raisins are more frequently contaminated with low levels of OTA than are other dried fruits and nuts and that Aspergillus species are the likely source of that contamination.
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Affiliation(s)
- Jeffrey D Palumbo
- U.S. Department of Agriculture, Agricultural Research Service, Foodborne Toxin Detection and Prevention Research Unit, 800 Buchanan Street, Albany, California 94710, USA.
| | - Teresa L O'Keeffe
- U.S. Department of Agriculture, Agricultural Research Service, Foodborne Toxin Detection and Prevention Research Unit, 800 Buchanan Street, Albany, California 94710, USA
| | - Yvonne S Ho
- U.S. Department of Agriculture, Agricultural Research Service, Foodborne Toxin Detection and Prevention Research Unit, 800 Buchanan Street, Albany, California 94710, USA
| | - Carlo J Santillan
- U.S. Department of Agriculture, Agricultural Research Service, Foodborne Toxin Detection and Prevention Research Unit, 800 Buchanan Street, Albany, California 94710, USA
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Palumbo JD, O'Keeffe TL. Detection and discrimination of four Aspergillus section Nigri species by PCR. Lett Appl Microbiol 2014; 60:188-195. [PMID: 25384730 DOI: 10.1111/lam.12358] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 10/14/2014] [Accepted: 11/06/2014] [Indexed: 11/30/2022]
Abstract
Species of Aspergillus section Nigri are not easily distinguished by traditional morphological techniques, and typically are identified by DNA sequencing methods. We developed four PCR primers to distinguish between Aspergillus niger, Aspergillus welwitschiae, Aspergillus carbonarius and Aspergillus tubingensis, based on species-conserved differences in the calmodulin gene sequence. PCR amplification from total DNA using these primers was species specific; no amplification occurred from nontarget species DNA for each primer pair. Species-specific PCR could distinguish between species in mixed DNA templates, indicating a utility in determining culture uniformity of isolated Aspergillus strains. In addition, with these primer sets, each species could be detected in soil following mixed-species inoculation with Aspergillus spores. This indicates that PCR with these species-specific primers may be useful in determining the distribution of Aspergillus species in environmental samples without the need for species identification from isolated strains, as well as detecting species that may be infrequently isolated by culture-based methods.
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Affiliation(s)
- J D Palumbo
- Foodborne Toxin Detection and Prevention Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Albany, CA, USA
| | - T L O'Keeffe
- Foodborne Toxin Detection and Prevention Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Albany, CA, USA
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Safety evaluation of multiple strains of Lactobacillus plantarum and Pediococcus pentosaceus in Wistar rats based on the Ames test and a 28-day feeding study. ScientificWorldJournal 2014; 2014:928652. [PMID: 25379552 PMCID: PMC4212542 DOI: 10.1155/2014/928652] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 09/04/2014] [Indexed: 11/29/2022] Open
Abstract
Three lactic acid bacterial strains, Lactobacillus plantarum, HK006, and HK109, and Pediococcus pentosaceus PP31 exhibit probiotic potential as antiallergy agents, both in vitro and in vivo. However, the safety of these new strains requires evaluation when isolated from infant faeces or pickled cabbage. Multiple strains (HK006, HK109, and PP31) were subject to a bacterial reverse mutation assay and a short-term oral toxicity study. The powder product exhibited mutagenic potential in Salmonella Typhimurium strains TA98 and TA1535 (with or without metabolic activation). In the short-term oral toxicity study, rats received a normal dosage of 390 mg/kg/d (approximately 9 × 109 CFU/kg/d) or a high dosage of 1950 mg/kg/d (approximately 4.5 × 1010 CFU/kg/d) for 28 d. No adverse effects were observed regarding the general condition, behaviour, growth, feed and water consumption, haematology, clinical chemistry indices, organ weights, or histopathologic analysis of the rats. These studies have demonstrated that the consumption of multiple bacterial strains is not associated with any signs of mutagenicity of S. Typhimurium or toxicity in Wistar rats, even after consuming large quantities of bacteria.
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Piotrowska M, Roszak J, Stańczyk M, Palus J, Dziubałtowska E, Stępnik M. Effects of lactic acid bacteria and Saccharomyces cerevisiae on growth of Aspergillus westerdijkiae and ochratoxin A production and toxicity. WORLD MYCOTOXIN J 2014. [DOI: 10.3920/wmj2013.1588] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The aim of this study was to examine three strains of the yeast Saccharomyces cerevisiae and three strains of lactic acid bacteria belonging to the genus Lactobacillus for their antifungal activity against the ochratoxin A producer Aspergillus westerdijkiae, as well as for their effect on OTA genotoxicity and cytotoxicity. When inoculated simultaneously, fungal growth was completely inhibited by S. cerevisiae. In the case of lactic acid bacteria, growth inhibition also occurred but to a less extent. A significant decrease in toxin production in co-culture with the yeast strains and LAB was observed. The supernatant of 24-h-old cultures of yeast strains in medium with OTA did not influence significantly the viability of porcine kidney epithelial LLC-PK1 cell line, whereas the supernatant from the LAB increased the viability compared to the control. Regarding genotoxicity, a decreased fragmentation of DNA was observed in the presence of the supernatant from wine and brewing yeasts, and Lactobacillus brevis strains. Based on the results obtained, it might be concluded that S. cerevisiae yeasts and lactic acid bacteria could be used to minimise the negative effect of OTA on humans and animals.
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Affiliation(s)
- M. Piotrowska
- Institute of Fermentation Technology and Microbiology, Lodz University of Technology, Wolczanska 171/173, 90-924 Lodz, Poland
| | - J. Roszak
- Nofer Institute of Occupational Medicine, sw. Teresy 8, 91-348 Lodz, Poland
| | - M. Stańczyk
- Nofer Institute of Occupational Medicine, sw. Teresy 8, 91-348 Lodz, Poland
| | - J. Palus
- Nofer Institute of Occupational Medicine, sw. Teresy 8, 91-348 Lodz, Poland
| | - E. Dziubałtowska
- Nofer Institute of Occupational Medicine, sw. Teresy 8, 91-348 Lodz, Poland
| | - M. Stępnik
- Nofer Institute of Occupational Medicine, sw. Teresy 8, 91-348 Lodz, Poland
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Ali R, Guo X, Lin H, Khan QM, Ismail M, Waheed U, Ali T, Bhalli JA. Mutant frequency in comparison to oxidative DNA damage induced by ochratoxin A in L5178Ytk+/−(3.7.2C) mouse lymphoma cells. Drug Chem Toxicol 2013; 37:227-32. [DOI: 10.3109/01480545.2013.838775] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Palumbo JD, O'Keeffe TL. Distribution and mycotoxigenic potential of Aspergillus section Nigri species in naturally contaminated almonds. J Food Prot 2013; 76:702-6. [PMID: 23575138 DOI: 10.4315/0362-028x.jfp-12-431] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In a previous study, inedible almond pick-out samples were assayed for aflatoxin and aflatoxigenic Aspergillus species. These samples contained high populations of black-spored Aspergillus section Nigri species. To investigate whether these species may contribute to the total potential mycotoxin content of almonds, Aspergillus section Nigri strains were isolated from these samples and assayed for ochratoxin A (OTA) and fumonisin B2 (FB2). The majority of isolates (117 strains, 68%) were identified as Aspergillus tubingensis, which do not produce either mycotoxin. Of the 47 Aspergillus niger and Aspergillus awamori isolates, 34 strains (72%) produced FB2 on CY20S agar, and representative strains produced lower but measurable amounts of FB2 on almond meal agar. No OTA-producing strains of Aspergillus section Nigri were detected. Almond pick-out samples contained no measurable FB2, suggesting that properly dried and stored almonds are not conducive for FB2 production by resident A. niger and A. awamori populations. However, 3 of 21 samples contained low levels (<1.5 ng/g) of OTA, indicating that sporadic OTA contamination may occur but may be caused by OTA-producing strains of other Aspergillus species.
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Affiliation(s)
- Jeffrey D Palumbo
- U.S. Department of Agriculture, Agricultural Research Service, Plant Mycotoxin Research Unit, Albany, California 94710, USA.
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Mally A. Ochratoxin a and mitotic disruption: mode of action analysis of renal tumor formation by ochratoxin A. Toxicol Sci 2012; 127:315-30. [PMID: 22403158 DOI: 10.1093/toxsci/kfs105] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The mycotoxin and food contaminant ochratoxin A (OTA) is a potent renal carcinogen in rodents, but its mode of action (MoA) is still poorly defined. In 2006, the European Food Safety Authority concluded that there is a "lack of evidence for the existence of OTA-DNA adducts" and thus insufficient evidence to establish DNA reactivity as a MoA for tumor formation by OTA. In reviewing the available database on OTA toxicity, a MoA for renal carcinogenicity of OTA is developed that involves a combination of genetic instability and increased proliferative drive as consequences of OTA-mediated disruption of mitosis, whereby the organ- and site-specificity of tumor formation by OTA is determined by selective renal uptake of OTA into the proximal tubule epithelium. The proposed MoA is critically assessed with respect to concordance of dose-response of the suggested key events and tumor formation, their temporal association, consistency, and biological plausibility. Uncertainties, data gaps and needs for further research are highlighted.
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Affiliation(s)
- Angela Mally
- Department of Toxicology, University of Würzburg, 97078 Würzburg, Germany.
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Kumar S, Kunwar A, Gautam S, Sharma A. Inactivation of A. ochraceus Spores and Detoxification of Ochratoxin A in Coffee Beans by Gamma Irradiation. J Food Sci 2012; 77:T44-51. [DOI: 10.1111/j.1750-3841.2011.02572.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Haighton LA, Lynch BS, Magnuson BA, Nestmann ER. A reassessment of risk associated with dietary intake of ochratoxin A based on a lifetime exposure model. Crit Rev Toxicol 2012; 42:147-68. [PMID: 22276591 PMCID: PMC3310481 DOI: 10.3109/10408444.2011.636342] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 10/25/2011] [Accepted: 10/26/2011] [Indexed: 12/23/2022]
Abstract
Mycotoxins, such as ochratoxin A (OTA), can occur from fungal growth on foods. OTA is considered a possible risk factor for adverse renal effects in humans based on renal tumors in male rats. For risk mitigation, Health Canada proposed maximum limits (MLs) for OTA based largely on a comparative risk assessment conducted by Health Canada (Kuiper-Goodman et al., 2010), in which analytical data of OTA in foods were used to determine the possible impact adopting MLs may have on OTA risks. The EU MLs were used for comparison and resultant risk was determined based on age-sex strata groups. These data were reevaluated here to determine comparative risk on a lifetime basis instead of age strata. Also, as there is scientific disagreement over the mechanism of OTA-induced renal tumors, mechanistic data were revisited. On a lifetime basis, risks associated with dietary exposure were found to be negligible, even without MLs, with dietary exposures to OTA three to four orders of magnitude below the pivotal animal LOAEL and the TD(05). Our review of the mechanistic data supported a threshold-based mechanism as the most plausible. In particular, OTA was negative in genotoxicity assays with the highest specificity and levels of DNA adducts were very low and not typical of genotoxic carcinogens. In conclusion, OTA exposures from Canadian foods do not present a significant cancer risk.
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Affiliation(s)
- Lois A Haighton
- Cantox Health Sciences International, An Intertek Company, Mississauga, Ontario, Canada.
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Palumbo J, O’Keeffe T, Vasquez S, Mahoney N. Isolation and identification of ochratoxin A-producing Aspergillus section Nigri strains from California raisins. Lett Appl Microbiol 2011; 52:330-6. [DOI: 10.1111/j.1472-765x.2011.03004.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Characterization of ochratoxin A-induced apoptosis in primary rat hepatocytes. Cell Biol Toxicol 2009; 26:239-54. [DOI: 10.1007/s10565-009-9131-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Accepted: 06/18/2009] [Indexed: 10/20/2022]
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Behm C, Degen GH, Föllmann W. The Fusarium
toxin enniatin B exerts no genotoxic activity, but pronounced cytotoxicity in vitro. Mol Nutr Food Res 2009; 53:423-30. [DOI: 10.1002/mnfr.200800183] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Föllmann W, Behm C, Degen GH. The emerging Fusarium toxin enniatin B: in-vitro studies on its genotoxic potential and cytotoxicity in V79 cells in relation to other mycotoxins. Mycotoxin Res 2008; 25:11-9. [DOI: 10.1007/s12550-008-0002-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Revised: 10/10/2008] [Accepted: 10/13/2008] [Indexed: 11/29/2022]
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20
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Mally A, Dekant W. Mycotoxins and the kidney: Modes of action for renal tumor formation by ochratoxin A in rodents. Mol Nutr Food Res 2008; 53:467-78. [DOI: 10.1002/mnfr.200800149] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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21
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Abstract
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.
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Affiliation(s)
- Evelyn O'Brien
- Environmental Toxicology, University of Konstanz, Germany.
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Delatour T, Mally A, Richoz J, Ozden S, Dekant W, Ihmels H, Otto D, Gasparutto D, Marin-Kuan M, Schilter B, Cavin C. 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; 52:472-82. [PMID: 18381679 DOI: 10.1002/mnfr.200700276] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The contribution of DNA adduct formation in the carcinogenic action of the mycotoxin ochratoxin A (OTA) has been subject to much debate. Recently, a carbon-bonded ochratoxin A-2'-deoxyguanosine adduct (dGuoOTA) formed by photochemical reaction in vitro has been shown by 32P-postlabeling/TLC to comigrate with a spot detected in DNA isolated from rat and pig kidney following exposure to OTA. Considering the large body of evidence arguing against covalent DNA binding of OTA and the poor resolution and specificity of postlabeling analysis, we developed a stable isotope dilution LC-MS/MS method to analyze dGuoOTA in kidney DNA isolated from rats treated with OTA. dGuoOTA and nitrogen-15-labeled dGuoOTA (15N(5)-dGuoOTA) were prepared by photoirradiation of OTA in the presence of dGuo or nitrogen-15-labeled dGuo. Conditions for DNA hydrolysis were optimized using a synthetic oligonucleotide containing dGuoOTA to ensure complete release of dGuoOTA. The LOD of the method (S/N > 3) was 10 fmol dGuoOTA on-column. However, dGuoOTA was not detected in DNA samples isolated from male F344 rats treated with OTA for up to 90 days at doses known to cause renal tumor formation. Detection limits, calculated for each individual sample based on the absolute LOD and the amount of DNA injected, were as low as 3.5 dGuoOTA/10(9) nucleotides. These data are consistent with previous results showing lack of DNA adduct formation by OTA and demonstrate that dGuoOTA is not formed in biologically relevant amounts under physiological conditions in vivo.
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Affiliation(s)
- Thierry Delatour
- Institut für Toxikologie, Universität Würzburg, Würzburg, Germany.
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23
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Mosesso P, Cinelli S, Bellacima R, Pepe G. In Vitro Cytogenetic Results Supporting a DNA Nonreactive Mechanism for Ochratoxin A, Potentially Relevant for Its Carcinogenicity. Chem Res Toxicol 2008; 21:1235-43. [DOI: 10.1021/tx800029f] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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24
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Palumbo JD, O'Keeffe TL, Mahoney NE. Inhibition of ochratoxin A production and growth of Aspergillus species by phenolic antioxidant compounds. Mycopathologia 2007; 164:241-8. [PMID: 17874203 DOI: 10.1007/s11046-007-9057-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Accepted: 08/29/2007] [Indexed: 11/27/2022]
Abstract
The phenolic antioxidants, gallic acid, vanillic acid, protocatechuic acid, 4-hydroxybenzoic acid, catechin, caffeic acid, and chlorogenic acid were studied for their effects on ochratoxin A (OTA) production and fungal growth of ochratoxigenic Aspergilli. Of the 12 strains tested, which included A. alliaceus, A. lanosus, A. ochraceus, A. albertensis, A. melleus, A. sulphureus, A. carbonarius, A. elegans, and A. sclerotiorum, the greatest inhibition of OTA production was seen in A. sulphureus, A. elegans, and A. lanosus. Vanillic acid and 4-hydroxybenzoic acid were the most inhibitory to both OTA production and growth of most of the strains tested. However, A. ochraceus was not inhibited by either compound, and A. carbonarius was not inhibited by vanillic acid. The effect of each compound on OTA production and growth differed among strains and generally was variable, suggesting that species-specific OTA production and response to phenolic compounds may be influenced by different ecological and developmental factors. In addition, inhibition of OTA production by antioxidant compounds may be useful in determining biosynthetic and regulatory genes involved in both OTA production and stress response in ochratoxigenic Aspergilli.
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Affiliation(s)
- Jeffrey D Palumbo
- Plant Mycotoxin Research Unit, U.S. Department of Agriculture, Agricultural Research Service, 800 Buchanan St., Albany, CA 94710, USA.
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25
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Palma N, Cinelli S, Sapora O, Wilson SH, Dogliotti E. Ochratoxin A-induced mutagenesis in mammalian cells is consistent with the production of oxidative stress. Chem Res Toxicol 2007; 20:1031-7. [PMID: 17567156 PMCID: PMC2367102 DOI: 10.1021/tx700027j] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Ochratoxin A (OTA) is a widespread mycotoxin in food and a powerful nephrocarcinogen in rats. The mutagenicity of OTA has been extensively investigated but with conflicting results, thus leaving open the mechanistic question for OTA carcinogenicity. Here, we examined the mutagenicity of OTA by using well-standardized mutation assays such as the hypoxanthine-guanine phosphoribosyltransferase (HPRT) assay in Chinese hamster V79 cells and the thymidine kinase assay in mouse lymphoma LY5178 cells. OTA-induced HPRT mutations were characterized at the molecular level. In V79 cells, OTA produced a dose- and time-related decrease in cell number as a consequence of the transitory cytostatic effect mediated by G2/M cell cycle arrest. In both mutation assays, OTA was weakly mutagenic and this effect was independent of biotransformation. OTA-induced mutations were characterized by point mutations (48%) and a lack of a detectable reverse-transcription polymerase chain reaction product (52%). The pattern of OTA-induced point mutations was similar to that of spontaneous mutants, suggesting that OTA induced an increase of the endogenous oxidative metabolism but not covalent DNA adducts. Our data support a model where OTA is mutagenic via oxidative DNA damage induction.
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Affiliation(s)
- Nieves Palma
- Department of Environment and Primary Prevention, Istituto Superiore di Sanita', Viale Regina Elena 299, 00161 Rome, Italy
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26
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Induction of micronuclei by ochratoxin A is a sensitive parameter of its genotoxicity in cultured cells. Mycotoxin Res 2007; 23:101-9. [DOI: 10.1007/bf02946034] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2006] [Accepted: 03/28/2007] [Indexed: 11/30/2022]
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27
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Opinion of the Scientific Panel on contaminants in the food chain [CONTAM] related to ochratoxin A in food. EFSA J 2006. [DOI: 10.2903/j.efsa.2006.365] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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28
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Clark HA, Snedeker SM. Ochratoxin a: its cancer risk and potential for exposure. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2006; 9:265-96. [PMID: 16621780 DOI: 10.1080/15287390500195570] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Ochratoxin A (OA) is a naturally occurring mycotoxin known to contaminate a variety of foods and beverages. The cancer risk posed by OA was reviewed as relevant to human exposure, regulatory activities, and risk management efforts occurring worldwide, particularly in Europe. OA moves through the food chain and has been found in the tissues and organs of animals, including human blood and breast milk. Results from the National Toxicology Program's rodent bioassays show significantly increased incidence of mammary gland tumors in female rats and kidney tumors in male and female rats given OA orally. Liver tumors in female mice fed OA in the diet have also been observed. In humans, OA exposure has been most often associated with the kidney disease Balkan endemic nephropathy (BEN), symptoms of which include tumors of the kidney and urinary tract. No epidemiological studies have yet adequately evaluated the cancer risk of OA in human populations. Studies have shown OA to be genotoxic as well as immunotoxic, although its mode of action is not fully understood. Organizations and agencies in many countries are currently promulgating standards for OA in foods and beverages. Increased efforts in farm management and food safety are being made to mitigate the risks to public health posed by OA. The U.S. Food and Drug Administration (FDA) is currently evaluating data on OA levels in domestic and imported commodities but has not established official regulations or guidelines for OA in the U.S. food supply.
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Affiliation(s)
- Heather A Clark
- Program on Breast Cancer and Environmental Risk Factors (BCERF), Sprecher Institute for Comparative Cancer Research, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401, USA.
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Mally A, Dekant W. DNA adduct formation by ochratoxin A: review of the available evidence. ACTA ACUST UNITED AC 2006; 22 Suppl 1:65-74. [PMID: 16332624 DOI: 10.1080/02652030500317544] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The mycotoxin ochratoxin A (OTA) is a potent nephrotoxin and renal carcinogen in rodents. However, the mechanism of OTA-induced tumour formation is unknown and conflicting results regarding the potential of OTA to react with DNA have been obtained. While experiments using radiolabelled ((3)H or (14)C) OTA and liquid scintillation counting or accelerator mass spectrometry indicate lack of formation of covalent DNA-adducts, spots detected by (32)P-postlabelling have been attributed to treatment with OTA. However, these putative DNA-adducts have not been shown to contain OTA or part of the OTA molecule and so far no structural information has been provided. Consistent with the absence of DNA-binding of radiolabelled OTA, studies on biotransformation in vivo and in vitro indicate that OTA is poorly metabolized and does not form reactive intermediates capable of interacting with DNA. Recently however, the structures of a carbon- and an oxygen-bonded OTA-deoxyguanosine adduct which is formed by photoirradiation of OTA in the presence of deoxyguanosine have been reported and suggested to be involved in OTA carcinogenicity. The aim of this manuscript is to provide an overview of the available literature regarding DNA adduct formation by OTA.
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Affiliation(s)
- Angela Mally
- Department of Toxicology, University of Würzburg, Germany
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Mally A, Keim-Heusler H, Amberg A, Kurz M, Zepnik H, Mantle P, Völkel W, Hard GC, Dekant W. Biotransformation and nephrotoxicity of ochratoxin B in rats. Toxicol Appl Pharmacol 2005; 206:43-53. [PMID: 15963343 DOI: 10.1016/j.taap.2004.11.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2004] [Revised: 11/04/2004] [Accepted: 11/04/2004] [Indexed: 01/31/2023]
Abstract
Ochratoxin B (OTB), a secondary metabolite of Aspergillus ochraceus, is the nonchlorinated analogue of the mycotoxin ochratoxin A (OTA), which is one of the most potent renal carcinogens in rodents. Despite the closely related structure, OTB is considered to be of much lower toxicity. OTA is poorly metabolized and slowly eliminated, and this may play an important role in OTA toxicity, carcinogenicity, and organ specificity. Since little is known regarding biotransformation and renal toxicity of OTB, the aim of this study was to investigate biotransformation of OTB in rats and to characterize the nephrotoxicity and cytotoxicity of OTB. Male F344 rats were administered either a single dose of OTB (10 mg/kg bw) or repeated doses (2 mg/kg bw, 5 days/week for 2 weeks) and euthanized 72 h after the last dosing. In proximal tubule cells of animals treated with a single high dose of OTB, a slight increase in mitotic figures was observed, but no treatment-related changes were evident in clinical chemistry, in renal function, and histopathology after repeated administration. Excretion of OTB and metabolites in urine and feces was analyzed using both HPLC with fluorescence detection and LC-MS/MS. Ochratoxin beta, which results from cleavage of the peptide bond, was the major metabolite excreted in urine in addition to small amounts of 4-hydroxy-OTB. In total, 19% of the administered dose was recovered as OTB and ochratoxin beta in urine and feces within 72 h after a single dose. In contrast to OTA, no tissue-specific retention of OTB was evident after single and repeated administration. In LLC-PK1 cells, a renal cell culture system that retains much of the specific features of the proximal tubule, only minor differences in the extent of cytotoxicity of OTA and OTB were observed. At low concentrations (< 25 microM), treatment with OTA was slightly more toxic, whereas reduction in cell viability was similar at concentrations up to 100 microM. In summary, these data suggest that OTA and OTB have a similar potential to induce cytotoxicity in vitro, but large differences in their potential to induce nephrotoxicity in rodents. OTB is more extensively metabolized and more rapidly eliminated than OTA. The lack of specific retention of OTB in the kidneys and the differences in toxicokinetics may therefore provide an explanation for the lower toxicity of OTB.
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Affiliation(s)
- Angela Mally
- Institut für Toxikologie, Universität Würzburg, 97078 Würzburg, Germany
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31
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Abstract
In vitro assays are increasingly being used in drug metabolism studies to screen novel chemicals. Their advantages are twofold: first, they allow testing early in the drug discovery phase, providing important information on chemical characteristics; second, human cells or cell constituents can be utilized, increasing the relevance to man. However, the process of isolation, transformation or storage of these cell systems may alter their phenotype (and, in the case of tumour-derived cell lines, genotype as well). A review of the systems currently employed shows that, whereas all systems have their own caveats, it is possible to find an appropriate system for any particular question that is asked.
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Affiliation(s)
- Nick Plant
- School of Biomedical and Molecular Sciences, University of Surrey, Guildford, UK.
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