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Su BD, Li XM, Huang ZW, Wang Y, Shao J, Xu YY, Shu LX, Li YB. Development and application of the physiologically-based toxicokinetic (PBTK) model for ochratoxin A (OTA) in rats and humans. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2024; 276:116277. [PMID: 38604061 DOI: 10.1016/j.ecoenv.2024.116277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 03/15/2024] [Accepted: 03/29/2024] [Indexed: 04/13/2024]
Abstract
Ochratoxin A (OTA) is a common fungal toxin frequently detected in food and human plasma samples. Currently, the physiologically based toxicokinetic (PBTK) model plays an active role in dose translation and can improve and enhance the risk assessment of toxins. In this study, the PBTK model of OTA in rats and humans was established based on knowledge of OTA-specific absorption, distribution, metabolism, and excretion (ADME) in order to better explain the disposition of OTA in humans and the discrepancies with other species. The models were calibrated and optimized using the available kinetic and toxicokinetic (TK) data, and independent test datasets were used for model evaluation. Subsequently, sensitivity analyses and population simulations were performed to characterize the extent to which variations in physiological and specific chemical parameters affected the model output. Finally, the constructed models were used for dose extrapolation of OTA, including the rat-to-human dose adjustment factor (DAF) and the human exposure conversion factor (ECF). The results showed that the unbound fraction (Fup) of OTA in plasma of rat and human was 0.02-0.04% and 0.13-4.21%, respectively. In vitro experiments, the maximum enzyme velocity (Vmax) and Michaelis-Menten constant (Km) of OTA in rat and human liver microsomes were 3.86 and 78.17 μg/g min-1, 0.46 and 4.108 μg/mL, respectively. The predicted results of the model were in good agreement with the observed data, and the models in rats and humans were verified. The PBTK model derived a DAF of 0.1081 between rats and humans, whereas the ECF was 2.03. The established PBTK model can be used to estimate short- or long-term OTA exposure levels in rats and humans, with the capacity for dose translation of OTA to provide the underlying data for risk assessment of OTA.
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Affiliation(s)
- Bu-Da Su
- Tianjin State Key Laboratory of Modern Chinese Medicine, School of Chinese Materia Medica, Tianjin University of Traditional Chinese Medicine, Tianjin 301617, China
| | - Xiao-Meng Li
- Tianjin State Key Laboratory of Modern Chinese Medicine, School of Chinese Materia Medica, Tianjin University of Traditional Chinese Medicine, Tianjin 301617, China
| | - Zhi-Wei Huang
- Phase Ⅰ Clinical Research Center, Huashan Hospital, Fudan University, Shanghai 200040, China
| | - Yue Wang
- Tianjin State Key Laboratory of Modern Chinese Medicine, School of Chinese Materia Medica, Tianjin University of Traditional Chinese Medicine, Tianjin 301617, China
| | - Jia Shao
- Department of Pharmacy, Tianjin First Central Hospital, Tianjin 300192, China
| | - Yan-Yan Xu
- Tianjin State Key Laboratory of Modern Chinese Medicine, School of Chinese Materia Medica, Tianjin University of Traditional Chinese Medicine, Tianjin 301617, China.
| | - Le-Xin Shu
- Tianjin State Key Laboratory of Modern Chinese Medicine, School of Chinese Materia Medica, Tianjin University of Traditional Chinese Medicine, Tianjin 301617, China.
| | - Yu-Bo Li
- Tianjin State Key Laboratory of Modern Chinese Medicine, School of Chinese Materia Medica, Tianjin University of Traditional Chinese Medicine, Tianjin 301617, China.
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Więckowska M, Szelenberger R, Niemcewicz M, Harmata P, Poplawski T, Bijak M. Ochratoxin A-The Current Knowledge Concerning Hepatotoxicity, Mode of Action and Possible Prevention. Molecules 2023; 28:6617. [PMID: 37764392 PMCID: PMC10534339 DOI: 10.3390/molecules28186617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 09/10/2023] [Accepted: 09/12/2023] [Indexed: 09/29/2023] Open
Abstract
Ochratoxin A (OTA) is considered as the most toxic of the other ochratoxins synthesized by various fungal species belonging to the Aspergillus and Penicillium families. OTA commonly contaminates food and beverages, resulting in animal and human health issues. The toxicity of OTA is known to cause liver damage and is still being researched. However, current findings do not provide clear insights into the toxin mechanism of action. The current studies focusing on the use of potentially protective compounds against the effects of the toxin are insufficient as they are mainly conducted on animals. Further research is required to fill the existing gaps in both fields (namely the exact OTA molecular mechanism and the prevention of its toxicity in the human liver). This review article is a summary of the so far obtained results of studies focusing on the OTA hepatotoxicity, its mode of action, and the known approaches of liver cells protection, which may be the base for expanding other research in near future.
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Affiliation(s)
- Magdalena Więckowska
- Biohazard Prevention Centre, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz, Poland; (M.W.); (R.S.); (M.N.)
| | - Rafał Szelenberger
- Biohazard Prevention Centre, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz, Poland; (M.W.); (R.S.); (M.N.)
| | - Marcin Niemcewicz
- Biohazard Prevention Centre, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz, Poland; (M.W.); (R.S.); (M.N.)
| | - Piotr Harmata
- Faculty of Advanced Technologies and Chemistry, Military University of Technology, 2 gen. S. Kaliskiego St., 00-908 Warsaw, Poland;
| | - Tomasz Poplawski
- Department of Pharmaceutical Microbiology and Biochemistry, Medical University of Lodz, 92-215 Lodz, Poland;
| | - Michał Bijak
- Biohazard Prevention Centre, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz, Poland; (M.W.); (R.S.); (M.N.)
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Chen L, Li E, Wu W, Wang G, Zhang J, Guo X, Xing F. The Secondary Metabolites and Biosynthetic Diversity From Aspergillus ochraceus. Front Chem 2022; 10:938626. [PMID: 36092677 PMCID: PMC9452667 DOI: 10.3389/fchem.2022.938626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Accepted: 06/21/2022] [Indexed: 12/04/2022] Open
Abstract
Aspergillus ochraceus, generally known as a food spoilage fungus, is the representative species in Aspergillus section Circumdati. A. ochraceus strains are widely distributed in nature, and usually isolated from cereal, coffee, fruit, and beverage. Increasing cases suggest A. ochraceus acts as human and animal pathogens due to producing the mycotoxins. However, in terms of benefits to mankind, A. ochraceus is the potential source of industrial enzymes, and has excellent capability to produce diverse structural products, including polyketides, nonribosomal peptides, diketopiperazine alkaloids, benzodiazepine alkaloids, pyrazines, bis-indolyl benzenoids, nitrobenzoyl sesquiterpenoids, and steroids. This review outlines recent discovery, chemical structure, biosynthetic pathway, and bio-activity of the natural compounds from A. ochraceus.
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Affiliation(s)
- Lin Chen
- Comprehensive Utilization of Edible and Medicinal Plant Resources Engineering Technology Research Center, Zhengzhou Key Laboratory of Synthetic Biology of Natural Products, Zhengzhou Key Laboratory of Medicinal Resources Research, Huanghe Science and Technology College, Zhengzhou, China
| | - Erfeng Li
- Horticulture and Landscape College, Tianjin Agricultural University, Tianjin, China
| | - Wenqing Wu
- Horticulture and Landscape College, Tianjin Agricultural University, Tianjin, China
| | - Gang Wang
- Comprehensive Utilization of Edible and Medicinal Plant Resources Engineering Technology Research Center, Zhengzhou Key Laboratory of Synthetic Biology of Natural Products, Zhengzhou Key Laboratory of Medicinal Resources Research, Huanghe Science and Technology College, Zhengzhou, China
- Key Laboratory of Agro-Products Quality and Safety Control in Storage and Transport Process, Ministry of Agriculture and Rural Affairs, Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jiaqian Zhang
- Horticulture and Landscape College, Tianjin Agricultural University, Tianjin, China
| | - Xu Guo
- Horticulture and Landscape College, Tianjin Agricultural University, Tianjin, China
| | - Fuguo Xing
- Key Laboratory of Agro-Products Quality and Safety Control in Storage and Transport Process, Ministry of Agriculture and Rural Affairs, Institute of Food Science and Technology, Chinese Academy of Agricultural Sciences, Beijing, China
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Schrenk D, Bodin L, Chipman JK, del Mazo J, Grasl‐Kraupp B, Hogstrand C, Hoogenboom L(R, Leblanc J, Nebbia CS, Nielsen E, Ntzani E, Petersen A, Sand S, Schwerdtle T, Vleminckx C, Wallace H, Alexander J, Dall'Asta C, Mally A, Metzler M, Binaglia M, Horváth Z, Steinkellner H, Bignami M. Risk assessment of ochratoxin A in food. EFSA J 2020; 18:e06113. [PMID: 37649524 PMCID: PMC10464718 DOI: 10.2903/j.efsa.2020.6113] [Citation(s) in RCA: 92] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The European Commission asked EFSA to update their 2006 opinion on ochratoxin A (OTA) in food. OTA is produced by fungi of the genus Aspergillus and Penicillium and found as a contaminant in various foods. OTA causes kidney toxicity in different animal species and kidney tumours in rodents. OTA is genotoxic both in vitro and in vivo; however, the mechanisms of genotoxicity are unclear. Direct and indirect genotoxic and non-genotoxic modes of action might each contribute to tumour formation. Since recent studies have raised uncertainty regarding the mode of action for kidney carcinogenicity, it is inappropriate to establish a health-based guidance value (HBGV) and a margin of exposure (MOE) approach was applied. For the characterisation of non-neoplastic effects, a BMDL 10 of 4.73 μg/kg body weight (bw) per day was calculated from kidney lesions observed in pigs. For characterisation of neoplastic effects, a BMDL 10 of 14.5 μg/kg bw per day was calculated from kidney tumours seen in rats. The estimation of chronic dietary exposure resulted in mean and 95th percentile levels ranging from 0.6 to 17.8 and from 2.4 to 51.7 ng/kg bw per day, respectively. Median OTA exposures in breastfed infants ranged from 1.7 to 2.6 ng/kg bw per day, 95th percentile exposures from 5.6 to 8.5 ng/kg bw per day in average/high breast milk consuming infants, respectively. Comparison of exposures with the BMDL 10 based on the non-neoplastic endpoint resulted in MOEs of more than 200 in most consumer groups, indicating a low health concern with the exception of MOEs for high consumers in the younger age groups, indicating a possible health concern. When compared with the BMDL 10 based on the neoplastic endpoint, MOEs were lower than 10,000 for almost all exposure scenarios, including breastfed infants. This would indicate a possible health concern if genotoxicity is direct. Uncertainty in this assessment is high and risk may be overestimated.
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Tao Y, Xie S, Xu F, Liu A, Wang Y, Chen D, Pan Y, Huang L, Peng D, Wang X, Yuan Z. Ochratoxin A: Toxicity, oxidative stress and metabolism. Food Chem Toxicol 2018; 112:320-331. [DOI: 10.1016/j.fct.2018.01.002] [Citation(s) in RCA: 168] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 12/28/2017] [Accepted: 01/02/2018] [Indexed: 02/06/2023]
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Gayathri L, Karthikeyan BS, Rajalakshmi M, Dhanasekaran D, Li AP, Akbarsha MA. Metabolism-dependent cytotoxicity of citrinin and ochratoxin A alone and in combination as assessed adopting integrated discrete multiple organ co-culture (IdMOC). Toxicol In Vitro 2017; 46:166-177. [PMID: 28951292 DOI: 10.1016/j.tiv.2017.09.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 07/06/2017] [Accepted: 09/21/2017] [Indexed: 10/18/2022]
Abstract
Citrinin (CTN) and ochratoxin A (OTA) can be present as co-contaminants in cereals, foods and feed commodities, and can affect human health. Metabolism-dependent toxicity of these two mycotoxins, separately as well as in combination, is not yet understood. To fill this gap we adopted integrated discrete multiple organ co-culture (IdMOC) technique, which obviates animal experiments from the perspectives of species difference as well as animal welfare concerns. IdMOC facilitates co-culture of a metabolically competent cell (HepG2) and a metabolically incompetent cell (3T3) that are physically separated but provides for extracellular product(s) from one cell to interact with the other. After ascertaining that HepG2 is metabolically competent and 3T3 is not, adopting luciferin-IPA metabolism assay, CTN and OTA were tested separately and in combination in the co-culture set-up, when both proved to be metabolism-dependent cytotoxic agents. Hepatocytes metabolize CTN into a diffusible product that is cytotoxic to 3T3 cells but the cytotoxicity of OTA appears to be limited to the hepatocytes, i.e., local acting. As a combination at a concentration of 20% of IC50 of each, CTN forms a reactive metabolite that diffuses out of HepG2 to cause cytotoxicity to 3T3 cells synergistically with OTA parent molecule. The CYP isoenzymes involved in the metabolism OTA and CTN were identified adopting in silico methods which indicated that OTA and CTN can bind CYP proteins at specific sites.
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Affiliation(s)
- Loganathan Gayathri
- Department of Microbiology, Bharathidasan University, Tiruchirappalli 620024, India; Mahatma Gandhi-Doerenkamp Center, Bharathidasan University, Tiruchirappalli 620024, India
| | | | - Manikkam Rajalakshmi
- Department of Zoology, Holy Cross College (Autonomous), Tiruchirappalli 620024, India
| | | | - Albert P Li
- In Vitro ADMET Laboratories LLC, 9221 Rumsey Road, Columbia, MD 21045, USA
| | - Mohammad A Akbarsha
- Mahatma Gandhi-Doerenkamp Center, Bharathidasan University, Tiruchirappalli 620024, India; Nanobiotechnology and Molecular Biology Research Laboratory, Department of Food Science and Nutrition, College of Food Science and Agriculture, King Saud University, Riyadh 11451, Saudi Arabia.
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González-Arias CA, Marín S, Rojas-García AE, Sanchis V, Ramos AJ. UPLC-MS/MS analysis of ochratoxin A metabolites produced by Caco-2 and HepG2 cells in a co-culture system. Food Chem Toxicol 2017; 109:333-340. [PMID: 28888735 DOI: 10.1016/j.fct.2017.09.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 08/22/2017] [Accepted: 09/05/2017] [Indexed: 12/21/2022]
Abstract
Ochatoxin A (OTA) is one of the most important mycotoxins based on its toxicity. The oral route is the main gateway of entry of OTA into the human body, and specialized epithelial cells constitute the first barrier. The present study investigated the in vitro cytotoxic effect of OTA (5, 15 and 45 μM) and production of OTA metabolities in Caco-2 and HepG2 cells using a co-culture Transwell System to mimic the passage through the intestinal epithelium and hepatic metabolism. The results derived from MTS cell viability assays and transepithelial electrical resistance measurements showed that OTA was slightly cytotoxic at the lowest concentration at 3 h, but significant toxicity was observed at all concentrations at 24 h. OTA metabolites generated in this co-culture were ochratoxin B (OTB), OTA methyl ester, OTA ethyl ester and the OTA glutathione conjugate (OTA-GSH). OTA methyl ester was the major metabolite found in both Caco-2 and HepG2 cells after all treatments. Our results showed that OTA can cause cell damage through several mechanisms and that the OTA exposure time is more important that the dosage in in vitro studies. OTA methyl ester is proposed as an OTA exposure biomarker, although future studies should be conducted.
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Affiliation(s)
- Cyndia A González-Arias
- Food Technology Department, Lleida University, UTPV-XaRTA, Agrotecnio Center, Av. Rovira Roure 191, 25198 Lleida, Spain; Laboratorio de Contaminación y Toxicología Ambiental, Secretaría de Investigación y Posgrado, Universidad Autónoma de Nayarit, Ciudad de la Cultura S/N, Tepic, Nayarit C.P. 63155, Mexico
| | - Sonia Marín
- Food Technology Department, Lleida University, UTPV-XaRTA, Agrotecnio Center, Av. Rovira Roure 191, 25198 Lleida, Spain
| | - Aurora E Rojas-García
- Laboratorio de Contaminación y Toxicología Ambiental, Secretaría de Investigación y Posgrado, Universidad Autónoma de Nayarit, Ciudad de la Cultura S/N, Tepic, Nayarit C.P. 63155, Mexico
| | - Vicente Sanchis
- Food Technology Department, Lleida University, UTPV-XaRTA, Agrotecnio Center, Av. Rovira Roure 191, 25198 Lleida, Spain
| | - Antonio J Ramos
- Food Technology Department, Lleida University, UTPV-XaRTA, Agrotecnio Center, Av. Rovira Roure 191, 25198 Lleida, Spain.
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Lee HJ, Ryu D. Worldwide Occurrence of Mycotoxins in Cereals and Cereal-Derived Food Products: Public Health Perspectives of Their Co-occurrence. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2017; 65:7034-7051. [PMID: 27976878 DOI: 10.1021/acs.jafc.6b04847] [Citation(s) in RCA: 346] [Impact Index Per Article: 49.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Cereal grains and their processed food products are frequently contaminated with mycotoxins. Among many, five major mycotoxins of aflatoxins, ochratoxins, fumonisins, deoxynivalenol, and zearalenone are of significant public health concern as they can cause adverse effects in humans. Being airborne or soilborne, the cosmopolitan nature of mycotoxigenic fungi contribute to the worldwide occurrence of mycotoxins. On the basis of the global occurrence data reported during the past 10 years, the incidences and maximum levels in raw cereal grains were 55% and 1642 μg/kg for aflatoxins, 29% and 1164 μg/kg for ochratoxin A, 61% and 71,121 μg/kg for fumonisins, 58% and 41,157 μg/kg, for deoxynivalenol, and 46% and 3049 μg/kg for zearalenone. The concentrations of mycotoxins tend to be lower in processed food products; the incidences varied depending on the individual mycotoxins, possibly due to the varying stability during processing and distribution of mycotoxins. It should be noted that more than one mycotoxin, produced by a single or several fungal species, may occur in various combinations in a given sample or food. Most studies reported additive or synergistic effects, suggesting that these mixtures may pose a significant threat to public health, particularly to infants and young children. Therefore, information on the co-occurrence of mycotoxins and their interactive toxicity is summarized in this paper.
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Affiliation(s)
- Hyun Jung Lee
- School of Food Science, University of Idaho , 875 Perimeter Drive MS 2312, Moscow, Idaho 83844, United States
| | - Dojin Ryu
- School of Food Science, University of Idaho , 875 Perimeter Drive MS 2312, Moscow, Idaho 83844, United States
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Malir F, Ostry V, Pfohl-Leszkowicz A, Malir J, Toman J. Ochratoxin A: 50 Years of Research. Toxins (Basel) 2016; 8:E191. [PMID: 27384585 PMCID: PMC4963825 DOI: 10.3390/toxins8070191] [Citation(s) in RCA: 277] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 05/21/2016] [Accepted: 06/13/2016] [Indexed: 12/13/2022] Open
Abstract
Since ochratoxin A (OTA) was discovered, it has been ubiquitous as a natural contaminant of moldy food and feed. The multiple toxic effects of OTA are a real threat for human beings and animal health. For example, OTA can cause porcine nephropathy but can also damage poultries. Humans exposed to OTA can develop (notably by inhalation in the development of acute renal failure within 24 h) a range of chronic disorders such as upper urothelial carcinoma. OTA plays the main role in the pathogenesis of some renal diseases including Balkan endemic nephropathy, kidney tumors occurring in certain endemic regions of the Balkan Peninsula, and chronic interstitial nephropathy occurring in Northern African countries and likely in other parts of the world. OTA leads to DNA adduct formation, which is known for its genotoxicity and carcinogenicity. The present article discusses how renal carcinogenicity and nephrotoxicity cause both oxidative stress and direct genotoxicity. Careful analyses of the data show that OTA carcinogenic effects are due to combined direct and indirect mechanisms (e.g., genotoxicity, oxidative stress, epigenetic factors). Altogether this provides strong evidence that OTA carcinogenicity can also occur in humans.
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Affiliation(s)
- Frantisek Malir
- Department of Biology, Faculty of Science, University of Hradec Kralove, Hradec Kralove 50003, Czech Republic.
| | - Vladimir Ostry
- National Reference Center for Microfungi and Mycotoxins in Food Chains, Center of Health, Nutrition and Food in Brno, National Institute of Public Health in Prague, Brno 61242, Czech Republic.
| | - Annie Pfohl-Leszkowicz
- Department Bioprocess & Microbial Systems, Laboratory Chemical Engineering, INP/ENSA Toulouse, University of Toulouse, UMR 5503 CNRS/INPT/UPS, Auzeville-Tolosane 31320, France.
| | - Jan Malir
- Institute of State and Law, Czech Academy of Sciences, Narodni 18, Prague 11600, Czech Republic.
| | - Jakub Toman
- Department of Biology, Faculty of Science, University of Hradec Kralove, Hradec Kralove 50003, Czech Republic.
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Ochratoxin A: Molecular Interactions, Mechanisms of Toxicity and Prevention at the Molecular Level. Toxins (Basel) 2016; 8:111. [PMID: 27092524 PMCID: PMC4848637 DOI: 10.3390/toxins8040111] [Citation(s) in RCA: 171] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 03/31/2016] [Accepted: 04/06/2016] [Indexed: 01/28/2023] Open
Abstract
Ochratoxin A (OTA) is a widely-spread mycotoxin all over the world causing major health risks. The focus of the present review is on the molecular and cellular interactions of OTA. In order to get better insight into the mechanism of its toxicity and on the several attempts made for prevention or attenuation of its toxic action, a detailed description is given on chemistry and toxicokinetics of this mycotoxin. The mode of action of OTA is not clearly understood yet, and seems to be very complex. Inhibition of protein synthesis and energy production, induction of oxidative stress, DNA adduct formation, as well as apoptosis/necrosis and cell cycle arrest are possibly involved in its toxic action. Since OTA binds very strongly to human and animal albumin, a major emphasis is done regarding OTA-albumin interaction. Displacement of OTA from albumin by drugs and by natural flavonoids are discussed in detail, hypothesizing their potentially beneficial effect in order to prevent or attenuate the OTA-induced toxic consequences.
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Isocoumarins, miraculous natural products blessed with diverse pharmacological activities. Eur J Med Chem 2016; 116:290-317. [PMID: 27155563 DOI: 10.1016/j.ejmech.2016.03.025] [Citation(s) in RCA: 122] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Revised: 03/08/2016] [Accepted: 03/10/2016] [Indexed: 12/17/2022]
Abstract
Isocoumarins are lactonic natural products abundant in microbes and higher plants. These are considered an amazing scaffold consecrated with more or less all types of pharmacological applications. This review is complementary to the earlier reviews and aims to focus the overlooked aspects of their fascinating chemistry with special emphasis on their classification and diverse biological activities with some SAR conclusions. The most recent available literature on the structural diversity and biological activity of these natural products has been reviewed.
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Wen J, Mu P, Deng Y. Mycotoxins: cytotoxicity and biotransformation in animal cells. Toxicol Res (Camb) 2016; 5:377-387. [PMID: 30090353 PMCID: PMC6062401 DOI: 10.1039/c5tx00293a] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 01/06/2016] [Indexed: 12/12/2022] Open
Abstract
Mycotoxins are secondary metabolites produced by many microfungi. Hitherto, over 300 mycotoxins with diverse structures have been identified. They contaminate most cereals and feedstuffs, which threaten human and animal health by exerting acute, sub-acute and chronic toxicological effects, with some considered as carcinogens. Many mycotoxins at low concentrations are able to induce the expression of cytochrome P450 and other enzymes implicated in the biotransformation and metabolization of mycotoxins in vivo and in vitro. Mycotoxins and their metabolites elicit different cellular disorders and adverse effects such as oxidative stress, inhibition of translation, DNA damage and apoptosis in host cells, thus causing various kinds of cytotoxicities. In this review, we summarize the biotransformation of mycotoxins in animal cells by CYP450 isoforms and other enzymes, their altered expression under mycotoxin exposure, and recent progress in mycotoxin cytotoxicity in different cell lines. Furthermore, we try to generalize the molecular mechanisms of mycotoxin effects in human and animal cells.
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Affiliation(s)
- Jikai Wen
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms , College of Life Sciences , South China Agricultural University , Tianhe District , Guangzhou , Guangdong 510642 , P. R. China . ; ; Tel: +86 20 38604967
| | - Peiqiang Mu
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms , College of Life Sciences , South China Agricultural University , Tianhe District , Guangzhou , Guangdong 510642 , P. R. China . ; ; Tel: +86 20 38604967
| | - Yiqun Deng
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms , College of Life Sciences , South China Agricultural University , Tianhe District , Guangzhou , Guangdong 510642 , P. R. China . ; ; Tel: +86 20 38604967
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Heussner AH, Bingle LEH. Comparative Ochratoxin Toxicity: A Review of the Available Data. Toxins (Basel) 2015; 7:4253-82. [PMID: 26506387 PMCID: PMC4626733 DOI: 10.3390/toxins7104253] [Citation(s) in RCA: 203] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 09/27/2015] [Accepted: 10/15/2015] [Indexed: 11/19/2022] Open
Abstract
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.
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Affiliation(s)
- Alexandra H Heussner
- Human and Environmental Toxicology, University of Konstanz, Universitätsstrasse 10, 78457 Konstanz, Germany.
- Department of Pharmacy, Health and Well-Being, University of Sunderland, City Campus, Sunderland SR1 3SD, UK.
| | - Lewis E H Bingle
- Department of Pharmacy, Health and Well-Being, University of Sunderland, City Campus, Sunderland SR1 3SD, UK.
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In vitro and in vivo metabolism of ochratoxin A: a comparative study using ultra-performance liquid chromatography-quadrupole/time-of-flight hybrid mass spectrometry. Anal Bioanal Chem 2015; 407:3579-89. [DOI: 10.1007/s00216-015-8570-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2014] [Revised: 02/04/2015] [Accepted: 02/17/2015] [Indexed: 11/26/2022]
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Goyary D, Chattopadhyay P, Giri S, Aher V, Upadhyay A, Veer V. Ochratoxin A induces cytotoxicity, DNA damage and apoptosis in rat hepatocyte primary cell culture at nanomolar concentration. WORLD MYCOTOXIN J 2014. [DOI: 10.3920/wmj2013.1627] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ochratoxin A (OTA), a mycotoxin produced by several species of Aspergillus and Penicillum, is widely found as a contaminant of food. OTA exhibits a wide range of toxic activities, including nephro- and hepatotoxicity. Although the mechanisms of its genotoxicity and carcinogenicity have been studied before, many controversial results have been published. In addition, the studies were mostly conducted with kidney cells. Therefore, the present study used a primary culture of Wistar rat hepatocytes incubated with increasing concentrations of OTA (2.0-6.0 nanomolar). OTA treatment showed dose-dependent cytotoxicity and DNA damage. Further, flow cytometric analysis of hepatocytes showed dose-dependent apoptosis, suggesting that OTA-induced hepatotoxicity is, may be partly, mediated by apoptosis. Vascular endothelial growth factor gene, a potent pro-angiogenic in hepatocellular carcinoma and responsible for hepatocyte regeneration, did not show any change with OTA treatment, as analysed by reverse transcription polymerase chain reaction. Thus, the present data indicated OTA-induced rat hepatotoxicity in vitro at nanomolar concentration, which inferred a major possible target other than kidney cells.
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Affiliation(s)
- D. Goyary
- Division of Pharmaceutical Technology, Defence Research Laboratory, Post Bag No.2, Tezpur 784 001, Assam, India
| | - P. Chattopadhyay
- Division of Pharmaceutical Technology, Defence Research Laboratory, Post Bag No.2, Tezpur 784 001, Assam, India
| | - S. Giri
- Department of Pharmaceutics, Gupta College of Technological Science, Ashram more, G.T. Road, Asansol 713 301, West Bengal, India
| | - V. Aher
- Division of Pharmaceutical Technology, Defence Research Laboratory, Post Bag No.2, Tezpur 784 001, Assam, India
| | - A. Upadhyay
- Division of Pharmaceutical Technology, Defence Research Laboratory, Post Bag No.2, Tezpur 784 001, Assam, India
| | - V. Veer
- Division of Pharmaceutical Technology, Defence Research Laboratory, Post Bag No.2, Tezpur 784 001, Assam, India
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Case report evidence of relationships between hepatocellular carcinoma and ochratoxicosis. PLoS One 2013; 8:e71423. [PMID: 23977041 PMCID: PMC3748048 DOI: 10.1371/journal.pone.0071423] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 07/02/2013] [Indexed: 12/22/2022] Open
Abstract
Purpose The incidence of Hepatocellular carcinoma (HCC) is on the rise, but what is causing that trend has remained a mystery. Mycotoxins are almost entirely ignored health problems, and sometimes actually naively belittled in advanced medical care. Ochratoxin A (OTA) is one of the most abundant food contaminating mycotoxins worldwide that is carcinogenic, but no studies have evaluated its levels in HCC patients. Therefore, this study was designed to monitor the presence of OTA in the serum of HCC patients and to quantify the strength of the association between OTA and HCC. Methods We conducted a case control-based study on 61 participants. Thirty-nine were HCC cases identified between 2010 and 2012 and individually matched by age, sex, residence and date of recruitment to 22 healthy controls. Serum OTA and alpha-fetoprotein levels were measured by using high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay, respectively. Results HPLC analysis of 61 serum samples indicated that the highest incidence of elevated OTA was found in the HCC group and was 5-fold higher than in the control group. The concentration of OTA in the HCC group ranged between 0.129 and 10.93 ng/mL with a mean value±SD of 1.1±0.3 ng/mL, while in the normal group it ranged between 0.005 and 0.50 ng/mL with a mean value±SD of 0.201±0.02 ng/mL. The odds ratio for HCC patients presenting OTA levels above the cut-off of 0.207 (calculated by the receiver operating characteristic curve) was 9.78 (95% confidence interval = 2.9095–32.9816, P = 0.0002) with respect to normal controls, suggesting that HCC is 9.8 times as frequent in the exposed group to OTA. Conclusion Our results reveal a strong association between the presence of OTA and HCC, which may offer a coherent explanation for much of the descriptive epidemiology of HCC and suggest new avenues for analytical research.
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Han Z, Zhao Z, Shi J, Liao Y, Zhao Z, Zhang D, Wu Y, De Saeger S, Wu A. Combinatorial approach of LC–MS/MS and LC–TOF-MS for uncovering in vivo kinetics and biotransformation of ochratoxin A in rat. J Chromatogr B Analyt Technol Biomed Life Sci 2013; 925:46-53. [DOI: 10.1016/j.jchromb.2013.02.028] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 02/18/2013] [Accepted: 02/25/2013] [Indexed: 10/27/2022]
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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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Ayed-Boussema I, Pascussi JM, Zaied C, Maurel P, Bacha H, Hassen W. Ochratoxin A induces CYP3A4, 2B6, 3A5, 2C9, 1A1, and CYP1A2 gene expression in primary cultured human hepatocytes: a possible activation of nuclear receptors. Drug Chem Toxicol 2011; 35:71-80. [PMID: 21834667 DOI: 10.3109/01480545.2011.589438] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ochratoxin A (OTA) is a mycotoxin produced by fungi of two genera: Penicillium and Aspergillus. OTA has been shown to be nephrotoxic, hepatotoxic, teratogenic, and immunotoxic to several species of animals and to cause kidney and liver tumors in mice and rats. Biotransformation of OTA has not been entirely elucidated. Several metabolites have been characterized in vitro and/or in vivo, whereas other metabolites remain to be characterized. At present, data available regarding OTA metabolism and cytochrome inductions concern only rodents or in vitro systems. The aim of the present study was to explore the effect of OTA on mRNA expression of some cytochromes known to be regulated by pregnane X receptor (PXR), constitutive androstane receptor (CAR), and aryl hydrocarbon receptor (AhR), using primary cultures of human hepatocytes. Our results showed that OTA reduced hepatocyte viability in a dose-dependent manner. Using quantitative real-time reverse-transcription polymerase chain reaction, our study showed that treatment of primary cultured human hepatocytes with noncytotoxic increasing concentrations of OTA for 24 hours caused a significant upregulation of CYP3A4, CYP2B6, and, to a lesser extent, CYP3A5 and CYP2C9. PXR mRNA expression increased in only 1 treated liver, whereas CAR mRNA expression was not affected. OTA was found also to induce an overexpression of CYP1A1 and CYP1A2 genes accompanied by an increase in AhR mRNA expression. These findings suggest that OTA could activate PXR and AhR; however, further investigations are needed to confirm nuclear-receptor activation by OTA.
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Affiliation(s)
- Imen Ayed-Boussema
- Laboratory of Research on Biologically Compatible Compounds, Faculty of Dentistry, Monastir, Tunisia
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Saeed A. Synthesis of 5-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin. JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH 2011; 13:505-511. [PMID: 21623513 DOI: 10.1080/10286020.2011.572552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The synthesis of title isocoumarin, the 5-chloro analog of naturally occurring 7-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin, isolated from Tessmannia densiflora is described. Chlorination of ethyl 2-(2-ethoxy-2-oxoethyl)-4,6-dimethoxybenzoate (2) afforded 3-chloro ester (3) followed by hydrolysis to furnish the 2-(carboxymethyl)-3-chloro-4,6-dimethoxybenzoic acid (4) that was converted to corresponding anhydride (5). Condensation of the latter with hexanoyl chloride in the presence of tetramethylguanidine and triethyl amine afforded 5-chloro-6,8-dimethoxy-3-pentylisocoumarin (6) which upon regioselective demethylation yielded the title isocoumarin (1).
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Affiliation(s)
- Aamer Saeed
- Department of Chemistry, Quaid-I-Azam University, Islamabad, Pakistan.
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23
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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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Röschenthaler R, Creppy EE, Dirheimer G. Ochratoxin A: On the Mode of Action of a Ubiquitous Mycotoxin. ACTA ACUST UNITED AC 2008. [DOI: 10.3109/15569548409012701] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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25
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Molecular and cellular effects of food contaminants and secondary plant components and their plausible interactions at the intestinal level. Food Chem Toxicol 2008; 46:813-41. [DOI: 10.1016/j.fct.2007.12.006] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2007] [Revised: 10/25/2007] [Accepted: 12/03/2007] [Indexed: 01/16/2023]
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26
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Pfohl-Leszkowicz A, Manderville RA. Ochratoxin A: An overview on toxicity and carcinogenicity in animals and humans. Mol Nutr Food Res 2007; 51:61-99. [PMID: 17195275 DOI: 10.1002/mnfr.200600137] [Citation(s) in RCA: 697] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Ochratoxin A (OTA) is a ubiquitous mycotoxin produced by fungi of improperly stored food products. OTA is nephrotoxic and is suspected of being the main etiological agent responsible for human Balkan endemic nephropathy (BEN) and associated urinary tract tumours. Striking similarities between OTA-induced porcine nephropathy in pigs and BEN in humans are observed. International Agency for Research on Cancer (IARC) has classified OTA as a possible human carcinogen (group 2B). Currently, the mode of carcinogenic action by OTA is unknown. OTA is genotoxic following oxidative metabolism. This activity is thought to play a central role in OTA-mediated carcinogenesis and may be divided into direct (covalent DNA adduction) and indirect (oxidative DNA damage) mechanisms of action. Evidence for a direct mode of genotoxicity has been derived from the sensitive 32P-postlabelling assay. OTA facilitates guanine-specific DNA adducts in vitro and in rat and pig kidney orally dosed, one adduct comigrates with a synthetic carbon (C)-bonded C8-dG OTA adduct standard. In this paper, our current understanding of OTA toxicity and carcinogenicity are reviewed. The available evidence suggests that OTA is a genotoxic carcinogen by induction of oxidative DNA lesions coupled with direct DNA adducts via quinone formation. This mechanism of action should be used to establish acceptable intake levels of OTA from human food sources.
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Affiliation(s)
- Annie Pfohl-Leszkowicz
- Laboratoire de Génie Chimique, UMR CNRS/INPT/UPS 5503, INP/ENSA Toulouse, Auzeville-Tolosane, France
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Faucet-Marquis V, Pont F, Størmer FC, Rizk T, Castegnaro M, Pfohl-Leszkowicz A. Evidence of a new dechlorinated ochratoxin A derivative formed in opossum kidney cell cultures after pretreatment by modulators of glutathione pathways: correlation with DNA-adduct formation. Mol Nutr Food Res 2006; 50:530-42. [PMID: 16671059 DOI: 10.1002/mnfr.200500219] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Ochratoxin A (OTA), a nephrotoxic mycotoxin probably implicated in human Balkan endemic nephropathy and associated urothelial tumors, induces renal carcinomas in rodents and nephrotoxicity in pigs. OTA induces DNA-adduct formation, but the structure of the adducts and their role in nephrotoxicity and carcinogenicity have only partly been elucidated. In vivo, 2-mercaptoethane sulfonate (MESNA) protects rats against OTA-induced nephrotoxicity but not against carcinogenicity, indicating two different mechanisms leading to nephrotoxicity or carcinogenicity. To better understand how DNA-adduct could be generated, opossum kidney cells (OK) have been treated by OTA alone or in presence of several compounds such as MESNA or N-acetylcysteine (another agent that, like MESNA, reduces oxidative stress by increasing of free thiols in kidney), buthionine sulfoximine (BSO) (an inhibitor of glutathione-synthase), and alpha amino-3-chloro-4,5-dihydro-5-isoxazole acetic acid (ACIVICIN) (an inhibitor of gamma glutamyl transpeptidase). Cytotoxicity of OTA on OK cells was evaluated by applying the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. None of the listed agents diminished OTA cytotoxicity significantly; ACIVICIN even increases OTA cytotoxicity. In contrast, analysis of the HPLC profiles of OTA metabolites produced during these incubations indicated that the pattern, the quantity of metabolites, and the nature of the derivatives were modulated by these agents. Ochratoxin B (OTB), open-ring ochratoxin A (OP-OA), 4 hydroxylated OTA, 10 hydroxylated OTA, OTA without phenylalanine, OTB without phenylalanine, and a dechlorinated OTA metabolite could be identified by nano-ESI-IT-MS.
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Affiliation(s)
- Virginie Faucet-Marquis
- Department BioSyM, Laboratoire de Génie Chimique, UMR CNRS/INPT/UPS5503, Auzeville-Tolosane, France
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Dietrich DR, Heussner AH, O'Brien E. Ochratoxin A: comparative pharmacokinetics and toxicological implications (experimental and domestic animals and humans). ACTA ACUST UNITED AC 2006; 22 Suppl 1:45-52. [PMID: 16332621 DOI: 10.1080/02652030500309327] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The causal factors for the species- and sex-differences associated with ochratoxin-mediated toxicity remain unclear. Variations in kinetic parameters may play a major role in explaining these differences, however, discrepancies and inaccuracies in the toxicokinetics reported in the literature for various species, make comparison and hence the extrapolation to the human situation impossible. The one- and two-compartment open models currently proposed may be insufficient to enable an accurate representation of the actual situation in vivo. It is likely that at least three if not four compartments must be assumed to account for the reported effects. The application of such models to existing raw data would most likely provide for a more accurate base set of toxicokinetic data and contribute to a more accurate human risk assessment. Possible explanations for the reported inconsistencies and their impact on the proposed mechanism(s) of action of OTA and risk assessment are discussed.
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Affiliation(s)
- Daniel R Dietrich
- Department of Environmental and Human Toxicology, University of Konstanz, Germany.
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Ringot D, Chango A, Schneider YJ, Larondelle Y. Toxicokinetics and toxicodynamics of ochratoxin A, an update. Chem Biol Interact 2006; 159:18-46. [PMID: 16293235 DOI: 10.1016/j.cbi.2005.10.106] [Citation(s) in RCA: 298] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Revised: 10/14/2005] [Accepted: 10/14/2005] [Indexed: 11/16/2022]
Abstract
Ochratoxin A (OTA) is a mycotoxin produced by fungi of two genera: Penicillium and Aspergillus. OTA has been shown to be nephrotoxic, hepatotoxic, teratogenic and immunotoxic to several species of animals and to cause kidney and liver tumours in mice and rats. Because of differences in the physiology of animal species, wide variations are seen in the toxicokinetic patterns of absorption, distribution and elimination of the toxin. Biotransformation of OTA has not been entirely elucidated. At present, data regarding OTA metabolism are controversial. Several metabolites have been characterized in vitro and/or in vivo, whereas other metabolites remain to be characterized. Several major mechanisms have been shown as involved in the toxicity of OTA: inhibition of protein synthesis, promotion of membrane peroxidation, disruption of calcium homeostasis, inhibition of mitochondrial respiration and DNA damage. The contribution of metabolites in OTA genotoxicity and carcinogenicity is still unclear. The genotoxic status of OTA is still controversial because contradictory results were obtained in various microbial and mammalian tests, notably regarding the formation of DNA adducts. More recent studies are focused on the OTA ability to disturb cellular signalling and regulation, to modulate physiological signals and thereby to influence cells viability and proliferation. The present paper offers an update on these different issues. In addition since humans and animals are likely to be simultaneously exposed to several mycotoxins, especially through their diet, the little information available on the combined effects of OTA and other mycotoxins has also been reviewed.
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Affiliation(s)
- Diana Ringot
- Institut Supérieur d'Agriculture de Beauvais, Rue Pierre Waguet, BP 30313, Beauvais, Cedex 60026, France.
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Gross-Steinmeyer K, Weymann J, Hege HG, Metzler M. Metabolism and lack of DNA reactivity of the mycotoxin ochratoxin a in cultured rat and human primary hepatocytes. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2002; 50:938-945. [PMID: 11829671 DOI: 10.1021/jf0111817] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
It is still unclear whether the carcinogenic mycotoxin ochratoxin A (OTA) is bioactivated to DNA-binding metabolites in rodents and humans. Therefore, we have incubated cultured rat and human primary hepatocytes with noncytotoxic concentrations of (3)H-OTA ranging from 10(-7) to 10(-5) M for 8 h and determined its metabolism and covalent DNA binding. In rat hepatocytes, OTA was metabolized to small amounts of three products, which were further studied by electrospray ionization (ESI)-MS/MS techniques. In addition to 4-hydroxy-OTA, which is a known product of OTA biotransformation, two novel metabolites were detected and tentatively identified as hexose and pentose conjugates of OTA. The in vitro induction with 3-methylcholanthrene (3MC) increased the formation of 4-hydroxy-OTA but did not alter the formation of the conjugated metabolites. No covalent binding of (3)H-OTA or its metabolites to DNA was observed in rat hepatocytes with or without 3MC induction with a limit of detection of 2 adducts per 10(9) nucleotides. However, the cellular ratio of reduced glutathione to oxidized glutathione was significantly decreased by treatment with OTA. In cultured human hepatocytes, (3)H-OTA was only very poorly metabolized, and no covalent DNA binding was observed. In conclusion, the results of this in vitro study do not support the notion that OTA has the potential to undergo metabolic activation and form covalent DNA adducts in rodents and humans.
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Affiliation(s)
- Kerstin Gross-Steinmeyer
- Drug Metabolism and Pharmacokinetics, Knoll GmbH, P.O. Box 210805, D-67008 Ludwigshafen, Germany
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Rásonyi T, Schlatter J, Dietrich DR. The role of alpha2u-globulin in ochratoxin A induced renal toxicity and tumors in F344 rats. Toxicol Lett 1999; 104:83-92. [PMID: 10048753 DOI: 10.1016/s0378-4274(98)00347-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
The mycotoxin ochratoxin A (OTA) was shown to be a potent kidney carcinogen in rats demonstrating a marked sex difference in the response. Compared to female rats, male rats had a 10-fold higher incidence of kidney carcinomas. The objective of this study was to investigate whether this sex difference in tumor response is due to an exacerbation of effect resulting from the interaction of the male rat specific urinary protein alpha2u-globulin (alpha2u) with OTA. Male and female rats were treated by oral gavage with OTA (1 mg/kg per day), D-limonene (dL; 1650 mg/kg per day) as a positive control or corn oil for 7 consecutive days. OTA induced severe renal lesions predominantly in the P3 region of the proximal tubules. The lesions consisted of necrotic cells and cell exfoliations. No hyaline droplets were found in the P2 segment following OTA treatment, whereas dL induced the expected accumulation of droplets. The results suggest that OTA induced kidney lesions are in all characteristic points different from the known alpha2u-nephropathy induced by dL. Based on these experiments the male rat specific protein alpha2u does not seem to be involved in the mechanism(s) leading to the high tumor incidence observed in OTA exposed male rats.
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Affiliation(s)
- T Rásonyi
- Institute of Toxicology, Swiss Federal Institute of Technology (ETH) and University of Zurich, Schwerzenbach
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Hoehler D, Marquardt RR, McIntosh AR, Hatch GM. Induction of free radicals in hepatocytes, mitochondria and microsomes of rats by ochratoxin A and its analogs. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1357:225-33. [PMID: 9223626 DOI: 10.1016/s0167-4889(97)00026-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Oxidative damage may be one of the manifestations of cellular damage in the toxicity of ochratoxin A (OA). OA; its three natural analogs, OB, OC and O alpha; and three synthetic analogs, the ethyl amide of OA (OE-OA), O-methylated OA (OM-OA), and the lactone-opened OA (OP-OA) were used to study free radical generation in hepatocytes, mitochondria and microsomes from rats. Electron paramagnetic resonance spectroscopy (EPR) using alpha-(4-pyridyl-1-oxide)-N-tert-butyl nitrone (4-POBN) as a spin trapping agent showed an enhanced free radical generation due to the addition of NADPH to the microsomes. An EPR signal was not observed in the mitochondria and hepatocyte samples when they were treated with a variety of agents. Addition of OM-OA together with NADPH and Fe3+ to the microsomes resulted in a strong EPR signal compared with the other analogs, whereas the signal could be quenched by the addition of catalase. OM-OA does not have a dissociable phenolate group and does not chelate Fe3+. The spin adduct hyperfine splitting constants indicated the presence of alpha-hydroxyethyl radicals resulting from generated hydroxyl radicals, which were trapped by 4-POBN. The results also suggested that the production of hydroxyl radicals by OA does not require a dissociable phenolate group or the prior formation of an OA-Fe complex.
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Affiliation(s)
- D Hoehler
- Department of Animal Science, University of Manitoba, Winnipeg, Canada.
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Omar RF, Gelboin HV, Rahimtula AD. Effect of cytochrome P450 induction on the metabolism and toxicity of ochratoxin A. Biochem Pharmacol 1996; 51:207-16. [PMID: 8573185 DOI: 10.1016/0006-2952(95)02194-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Liver microsomes from rats treated with various P450 inducers were examined for their ability to metabolize the mycotoxin ochratoxin A (OTA) to 4(R)-4-hydroxyochratoxin A (4R), the major metabolite, and 4(S)-4-hydroxyochratoxin A (4S), the minor metabolite. Pretreatment of rats with phenobarbital (PB), dexamethasone (DXM), 3-methylcolcanthrene (3MC) and isosafrole (ISF) greatly induced 4R formation. PB, DXM, 3MC, clofibrate (CLF) and ISF treatments also induced 4S formation. Isoniazid (INH) pretreatment primarily induced 4S formation. The pH optimum for 4R formation was found to be 6.0 with 3MC microsomes, and 6.5 with PB and DXM microsomes. For 4S formation, the pH optimum was 7.0. At the optimum pH (compared with pH 7.4), 4R formation increased 40-50% with PB and DXM microsomes but 8.0-fold with 3MC microsomes. Studies using the inhibitors metyrapone and alpha-naphthoflavone as well as monoclonal antibodies against various P450s suggested that at least the P450 isoforms IA1/IA2, IIB1 and IIIA1/IIIA2 are involved in 4R formation. Using urinary excretion of the enzymes alkaline phosphatase and gamma-glutamyl transferase as an index of renal damage, we observed that pretreatment of rats with PB, which induced hepatic P450 (P450II2B1), protected against OTA nephrotoxicity, whereas cobalt-protoporphyrin IX pretreatment, which decreased P450 levels, exacerbated OTA nephrotoxicity. Our results suggest that at least P450IIB1-dependent metabolism of OTA leads to its detoxication and that OTA itself may be toxic in some circumstances or that other pathways are responsible for its activation.
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Affiliation(s)
- R F Omar
- Biochemistry Department, Memorial University of Newfoundland, St. John's, Canada
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Xiao H, Marquardt RR, Abramson D, Frohlich AA. Metabolites of ochratoxins in rat urine and in a culture of Aspergillus ochraceus. Appl Environ Microbiol 1996; 62:648-55. [PMID: 8593066 PMCID: PMC167831 DOI: 10.1128/aem.62.2.648-655.1996] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
We studied the metabolic profile of ochratoxin A (OA) in rats and in a culture of OA-producing Aspergillus ochraceus. Ochratoxin alpha (O alpha), ochratoxin beta (O beta), 4-R-hydroxyochratoxin A (4-R-OH OA), 4-R-hydroxyochratoxin B (4-R-OH OB), and 10-hydroxyochratoxin A (10-OH OA) were isolated from a culture of A. ochraceus and structurally characterized by 1H nuclear magnetic resonance spectroscopy, mass spectrometry and high-pressure liquid chromatography. 4-R-OH OA and O alpha were consistently produced and were the dominant biotransformed metabolites in the fungal culture and in rats treated with OA and ochratoxin C (OC), while the formation of 10-OH OA was conditional in the fungal system. Green fluorescent biomacromolecules were isolated by detergent extraction of the fungal culture followed by cold-acetone precipitation and gel filtration. Acid hydrolysis of the fluorescent macromolecules resulted in the release of several ochratoxins, including O alpha (80%), OA (2%), and OC (5%), and other unidentified fluorescent compounds but not OB and O beta. Cross-reactivity studies of the natural macromolecule conjugates of OA with anti-OA polyclonal antibodies indicated that they were covalently linked to the macromolecules via a group other than the carboxyl group. These studies demonstrated that a fungus can produce some of the same metabolites of OA as the rat and that O alpha, OA, and OC may be covalently linked to fungal macromolecules.
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Affiliation(s)
- H Xiao
- Department of Animal Science, University of Manitoba, Winnipeg, Canada
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Ruhland M, Engelhardt G, Wallnöfer PR. Transformation of the mycotoxin ochratoxin A in plants. 2. Time course and rates of degradation and metabolite production in cell-suspension cultures of different crop plants. Mycopathologia 1996; 134:97-102. [PMID: 9011828 DOI: 10.1007/bf00436871] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Ochratoxin A, one of the most toxic mycotoxins, can be metabolized nearly completely by suspension cultures of various plant cells. The transformation products identified in this study were almost the same in the cell-suspension cultures of maize, carrot, tomato, potato, soybean, wheat and barley, but the quantitative distribution differed strongly depending on incubation time and species of plant-cell culture. The compounds were extracted with ethyl acetate and detected by reversed-phase HPLC with gradient elution. From the result it is supposed that besides ochratoxin A also ochratoxin derivatives may occur in food and feedstuff of plant origin.
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Affiliation(s)
- M Ruhland
- Bayerische Landesantalt für Ernährung, Abteilung Ernährung, München, Germany
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37
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Creppy EE, Baudrimont I, Betbeder AM. Prevention of nephrotoxicity of ochratoxin A, a food contaminant. Toxicol Lett 1995; 82-83:869-77. [PMID: 8597155 DOI: 10.1016/0378-4274(95)03601-6] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
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.
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Affiliation(s)
- E E Creppy
- Toxicology Department, University of Bordeaux, France
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38
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Omar RF, Rahimtula AD. Possible role of an iron-oxygen complex in 4(S)-4-hydroxyochratoxin a formation by rat liver microsomes. Biochem Pharmacol 1993; 46:2073-81. [PMID: 8267656 DOI: 10.1016/0006-2952(93)90650-l] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Rat liver microsomes were examined for their ability to oxidize the mycotoxin ochratoxin A (OTA) to 4(R)-4-hydroxyochratoxin A [(R)-4-OH-OTA] and 4(S)-4-hydroxyochratoxin A [(S)-4-OH-OTA] and to induce OTA-dependent lipid peroxidation. Microsomes isolated from rats pretreated with pregnenolone-16 alpha-carbonitrile greatly induced both (R)-4-OH-OTA and (S)-4-OH-OTA formation whereas isoniazid pretreatment primarily induced (S)-4-OH-OTA. (R)-4-OH-OTA and (S)-4-OH-OTA formation showed significant differences with respect to pH optima, effect of antioxidants, and iron chelators. (R)-4-OH-OTA showed a pH optimum of 6.5 and was not inhibited by the antioxidants butylated hydroxyanisole or N,N-diphenyl-1,4-phenylenediamine or the iron chelators. Desferal or bathophenanthrolinedisulfonic acid. In contrast, both (S)-4-OH-OTA and lipid peroxidation showed a pH optimum of 7.0 and both activities were sensitive to inhibition by the above antioxidants and iron chelators. Lipid peroxidation was not involved in (S)-4-OH-OTA formation since addition of linoleic acid hydroperoxide to microsomes did not give rise to (S)-4-OH-OTA. Cytochrome P450 appeared to be essential since other hemoproteins like horseradish peroxidase and hemoglobin were ineffective in metabolizing OTA in the presence of hydroperoxides. The results suggest that (R)-4-OH-OTA is formed by normal mixed-function oxidation but that (S)-4-OH-OTA formation may involve free iron. It is likely that an active Fe2(+)-oxygen complex, formed via NADPH-cytochrome P450 reductase and cytochrome P450-dependent reduction of free Fe3+ followed by oxygen binding, serves as the species inducing lipid peroxidation and at least part of (S)-4-OH-OTA formation.
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Affiliation(s)
- R F Omar
- Department of Biochemistry, Memorial University, St. John's, Newfoundland, Canada
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39
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Abstract
Relationships between structural features and biological effects of mycotoxins are reviewed. Structure-activity relationships are characterized at the molecular, subcellular, cellular, or supracellular level. Major chemical and physicochemical factors responsible for bioactivity of mycotoxins are stressed. A variety of chemical families of mycotoxins are then discussed from the point of view of structure-activity relationships. The structurally related families comprise small lactones, macrocyclic lactones, isocoumarin derivatives, aflatoxins and related compounds trichothecenes, anthraquinones, indole-derived tremorgens and selected amino acid-derived mycotoxins such as sporidesmins and cyclosporines. Biological effects of mycotoxins include acute and chronic toxicity, antimicrobial activity, mutagenicity and genotoxicity, carcinogenicity and biochemical modes of action.
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Affiliation(s)
- V Betina
- Department of Environmental Chemistry and Technology, Faculty of Chemistry, Slovak Polytechnical University, Bratislava
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Khan S, Martin M, Bartsch H, Rahimtula AD. Perturbation of liver microsomal calcium homeostasis by ochratoxin A. Biochem Pharmacol 1989; 38:67-72. [PMID: 2910308 DOI: 10.1016/0006-2952(89)90150-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effect of ochratoxin A on hepatic microsomal calcium sequestration was studied both in vivo and in vitro. The rate of ATP-dependent calcium uptake was inhibited by 42-45% in ochratoxin A intoxicated rats as compared to controls. In the presence of NADPH, addition of ochratoxin A (2.5 to 100 microM) caused a concentration-dependent inhibition of calcium uptake (28-94%) by untreated rat liver microsomes. The rate of NADPH-dependent lipid peroxidation, measured as malondialdehyde formed, was also greatly enhanced by ochratoxin A. Various agents that inhibited ochratoxin A enhanced lipid peroxidation were also able to block the destruction of calcium uptake activity. Lipid peroxidation enhanced by ochratoxin A was also accompanied by leakage of calcium from calcium-loaded microsomes. These results suggest that ochratoxin A disrupts microsomal calcium homeostasis by an impairment of the endoplasmic reticulum membrane probably via enhanced lipid peroxidation.
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Affiliation(s)
- S Khan
- Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada
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Rahimtula AD, Béréziat JC, Bussacchini-Griot V, Bartsch H. Lipid peroxidation as a possible cause of ochratoxin A toxicity. Biochem Pharmacol 1988; 37:4469-77. [PMID: 3202889 DOI: 10.1016/0006-2952(88)90662-4] [Citation(s) in RCA: 117] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Addition of the mycotoxin ochratoxin A (OA), a nephrotoxic carcinogen, to rat liver microsomes greatly enhanced the rate of NADPH or ascorbate-dependent lipid peroxidation as measured by malondialdehyde formation. NADPH-dependent lipid peroxidation in kidney microsomes was similarly enhanced by OA. The process required the presence of trace amounts of iron but cytochrome P-450 and free active oxygen species appeared not to be involved. The efficiency of several ochratoxins (ochratoxins A, B, C, alpha and O-methyl-ochratoxin C) to enhance lipid peroxidation was related to the presence and reactivity of the phenolic hydroxyl group. Furthermore, the ability of these ochratoxins to enhance lipid peroxidation in microsomes correlated precisely with their known toxicities in chicks. Administration of ochratoxin A to rats also resulted in enhanced lipid peroxidation in vivo as evidenced by a seven-fold increase in the rate of ethane exhalation. These results suggest that lipid peroxidation may play a role in the observed toxicity of ochratoxin A in animals; a mechanism is proposed. (Formula: see text). Ochratoxin A: X = Cl; R1 = R2 = R3 = R4 = H Ochratoxin B: X = H; R1 = R2 = R3 = R4 = H Ochratoxin C: X = Cl; R1 = R2 = R3 = H; = R4 = CH3 O-Methyl-ochratoxin C: X = Cl; R2 = R3 = H; R1 = R4 = CH3 (4R)-4-hydroxyochratoxin A: X = Cl; R1 = R3 = R4 = H; R2 = OH (4S)-4-hydroxyochratoxin A: X = Cl; R1 = R2 = R4 = H; R3 = OH Fig. 1. Chemical structures of the various ochratoxins.
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Affiliation(s)
- A D Rahimtula
- International Agency for Research on Cancer, Lyon, France
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Hornish RE, Gosline RE, Nappier JM. Comparative metabolism of lincomycin in the swine, chicken, and rat. Drug Metab Rev 1987; 18:177-214. [PMID: 3330515 DOI: 10.3109/03602538708998305] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- R E Hornish
- Upjohn Company, Agricultural Division, Kalamazoo, Michigan 49001
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43
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Størmer FC, Kolsaker P, Holm H, Rogstad S, Elling F. Metabolism of ochratoxin B and its possible effects upon the metabolism and toxicity of ochratoxin A in rats. Appl Environ Microbiol 1985; 49:1108-12. [PMID: 4004232 PMCID: PMC238514 DOI: 10.1128/aem.49.5.1108-1112.1985] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
A metabolic product was formed from ochratoxin B by rat liver microsomal fractions in the presence of NADPH. It was isolated from the incubation mixture by extraction, thin-layer chromatography, high-pressure liquid chromatography, and crystallization. On the basis of mass and nuclear magnetic resonance spectroscopy, the structure is suggested to be 4-hydroxyochratoxin B. The Km for the formation of 4-hydroxyochratoxin B was determined, and the hydroxylation of ochratoxin A was not altered by the presence of ochratoxin B. Rats were given ochratoxin A or B, or a mixture of both intraperitoneally. The ratios of the three metabolites, ochratoxin A, (4R)-4-hydroxyochratoxin A, and ochratoxin alpha, excreted in the urine did not change in the presence of ochratoxin B. Ochratoxin B was metabolized to 4-hydroxyochratoxin B and ochratoxin beta, but in a different ratio than for the ochratoxin A metabolites. When given intraperitoneally, ochratoxin beta was excreted within 24 h. In rats treated with ochratoxin A alone, the food intake was reduced by 50%, and histologically severe lesions, degeneration, and necrosis were observed in the proximal tubules. When ochratoxin A and B given in combination, the animals were clinically unaffected and histologically there was only slight damage of proximal tubules. These observations indicate that ochratoxin B considerably reduces the toxic effects of ochratoxin A.
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Abstract
Twenty-one pigs weighing approximately 18 kg were placed in 7 groups of 3 and given diets containing respectively aflatoxin B1 alone at 0.375 and 0.0750 mg/kg, ochratoxin A alone at 1 and 2 mg/kg, 0.375 mg/kg of aflatoxin B1 plus 1 mg/kg of ochratoxin A and 0.750 mg/kg aflatoxin B1 and 2 mg/kg of ochratoxin A. The remaining group served as untreated control. At the respective dose levels, pigs receiving similar doses of ochratoxin A alone or in combination with aflatoxin B1, were similarly affected, the clinical effects of aflatoxin having been mostly obscured by those due to ochratoxin A. Mild degenerative hepatic changes typical of aflatoxicosis were observed in pigs fed this toxin alone or in combination with ochratoxin A. In kidneys of pigs fed diet containing 1 and 2 mg of ochratoxin A alone changes included interstitial fibrosis of the vortex and dystrophy and degeneration of the tubular epithelium. Similar lesions but less pronounced fibrosis were found in kidneys of pigs receiving both toxins. The respective lower dose levels of mycotoxins selected were judged to be about the no-effect levels for each dosed separately under the conditions of the trial. Such levels have been found not infrequently on mould affected grain and stock foods. The result highlights the difficulties that may be experienced in the recognition of such multimycotoxicoses as they are likely to occur in the field and indicate the need for toxicological analysis as well as pathological investigation in establishing a diagnosis.
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Abstract
Mycotoxin problems are one of great concern to health scientists. Toxic fungal metabolites such as aflatoxins, trichothecenes, zearalenone and others are contaminated in our environments and induce various diseases. In this manuscript, the author will summarize the recent advances on toxicology of mycotoxins in special references to toxicological characters, cytotoxicity, genotoxicity (mutagenicity and carcinogenicity), metabolism, and biochemical mode of action. Interaction of mycotoxins with cellular components will be reviewed in order to clarify the toxicological characteristics of mycotoxins such as aflatoxins, trichothecenes, zearalenone, toxic peptides, and anthraquinoid mycotoxins.
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46
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Stein AF, Phillips TD, Kubena LF, Harvey RB. Renal tubular secretion and reabsorption as factors in ochratoxicosis: effects of probenecid on nephrotoxicity. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1985; 16:593-605. [PMID: 4087321 DOI: 10.1080/15287398509530766] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Ochratoxin A (OA) is a food-borne fungal metabolite capable of producing nephrotoxicity. Renal clearance of [3H]OA and the effects of probenecid on clearance were compared in sham-operated and partially nephrectomized (surgical removal of 70% of the total renal mass), impaired renal function rats. Sham-operated and partially nephrectomized rats cleared OA at 0.109 and 0.078 ml/min, respectively. These values were significantly lower than glomerular filtration rate (GFR) determined by inulin clearance, indicating net tubular reabsorption. Clearance of a single dose of OA in both sham-operated and partially nephrectomized rats pretreated with probenecid was significantly diminished and provided evidence for the involvement of secretory processes in the elimination of OA. Probenecid (administered before OA or simultaneously with OA) failed to prevent nephrotoxicity in rats exposed to five daily doses of mycotoxin. On the contrary, enhanced nephrotoxicity was exhibited. Decreases in urine osmolality, Na+ and K+ concentrations, and body weight were prominent and, interestingly, renal levels of parent OA were increased (over OA treatment alone) in the presence of probenecid. These data suggest that renal tubular secretion and reabsorption are important factors in modulating the nephrotoxicity of OA and may facilitate the residual persistence of this mycotoxin in the kidneys (via renal recycling). Renal metabolism may contribute to the detoxification of OA.
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47
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Elling F, Nielsen JP, Lillehøj EB, Thomassen MS, Størmer FC. Ochratoxin A-induced porcine nephropathy: enzyme and ultrastructure changes after short-term exposure. Toxicon 1985; 23:247-54. [PMID: 4024134 DOI: 10.1016/0041-0101(85)90147-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Four pigs were treated with ochratoxin A (800 micrograms/kg) for five consecutive days. Subsequently, urine and bile were collected and kidneys were perfusion fixed unilaterally. Liver and kidney samples were examined for the distribution of ochratoxin A and metabolites in subcellular fractions and the effects of the toxin on protein synthesis and enzyme activities. Ochratoxin A and the hydrolytic product, ochratoxin alpha, were found in urine. Elevated levels of toxin accumulation in kidney (283 ng/g) compared with liver (189 ng/g) and toxin-mediated reductions in protein synthesis and enzyme activities in kidney identified it as a target organ of ochratoxin toxicity. Ultrastructural investigations of kidney in toxin-exposed animals identified a process of condensation of cellular material with disappearance of membranes and continuous desquamation in the lower part of the proximal convoluted tubules. In target cells peroxisomes appeared to have lost membrane integrity and the organelles were leaking materials into the cytosol. Reduction of structural integrity was associated with an increase in the presence of catalase and cyanide insensitive fatty acid oxidase activity in the soluble kidney fractions.
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48
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Cooray R. Effects of some mycotoxins on mitogen-induced blastogenesis and SCE frequency in human lymphocytes. Food Chem Toxicol 1984; 22:529-34. [PMID: 6235161 DOI: 10.1016/0278-6915(84)90222-9] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The effects of T-2 toxin, diacetoxyscirpenol, ochratoxin A and zearalenone on DNA synthesis in phytohaemagglutinin-stimulated human peripheral blood lymphocytes were studied by assaying the incorporation of [3H]thymidine. Total inhibition was obtained with 8 ng T-2 toxin/ml, 8 ng diacetoxyscirpenol/ml or 30 micrograms zearalenone/ml, and with 20 micrograms ochratoxin A/ml inhibition was almost complete; 50% inhibition was produced by 1.5 ng T-2 toxin/ml, 2.7 ng diacetoxyscirpenol/ml, 14 micrograms zearalenone/ml or 14 micrograms ochratoxin A/ml. The toxicity of the trichothecenes to the lymphocytes was slightly reduced when rat liver cells were present whereas the toxicity of ochratoxin A and zearalenone was unaltered. Low concentrations of trichothecenes did not produce any inhibition of DNA synthesis when the cultures were washed and placed in fresh media containing only phytohaemagglutinin 4 hr after the addition of the test compounds. Sister chromatid exchange frequency was not elevated by T-2 toxin, diacetoxyscirpenol or ochratoxin A. Zearalenone had a weak enhancing effect on the frequency of sister chromatid exchanges.
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Creppy EE, Størmer FC, Kern D, Röschenthaler R, Dirheimer G. Effects of ochratoxin A metabolites on yeast phenylalanyl-tRNA synthetase and on the growth and in vivo protein synthesis of hepatoma cells. Chem Biol Interact 1983; 47:239-47. [PMID: 6652810 DOI: 10.1016/0009-2797(83)90160-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The ochratoxin A (OTA) metabolite (4R)-4-hydroxyochratoxin A [4R)-OTA) inhibits the aminoacylation of phenylalanine tRNA catalyzed by phenylalanyl-tRNA synthetase (PheRS) with a Ki-value of 0.9 mM as compared to 1.3 mM for OTA. It also inhibits protein synthesis and cell growth in the same manner as OTA. Ochratoxin alpha (OT alpha) does not affect either protein synthesis or cell growth.
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Syvertsen C, Størmer FC. Oxidation of two hydroxylated ochratoxin A metabolites by alcohol dehydrogenase. Appl Environ Microbiol 1983; 45:1701-3. [PMID: 6347065 PMCID: PMC242520 DOI: 10.1128/aem.45.5.1701-1703.1983] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
(4R)-4-hydroxyochratoxin A, (4S)-4-hydroxyochratoxin A, and 10-hydroxyochratoxin A, all formed from ochratoxin A, were incubated with alcohol dehydrogenase in the presence of NAD. Only (4R)-4-hydroxyochratoxin A and 10-hydroxyochratoxin A acted as substrates for the enzyme. K(m) and turnover number for 10-hydroxyochratoxin A were 110 muM and 0.1 s(-1), respectively.
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