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Gyamfi OA, Bortey-Sam N, Donkor AB, White CW, Logue BA. Analysis of TRPA1 antagonist, A-967079, in plasma using high-performance liquid chromatography tandem mass-spectrometry. J Pharm Anal 2020; 10:157-163. [PMID: 32373387 PMCID: PMC7192962 DOI: 10.1016/j.jpha.2019.12.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 12/11/2019] [Accepted: 12/12/2019] [Indexed: 02/06/2023] Open
Abstract
The noxious effects from exposure to toxic inhalation hazards (TIHs, such as isocyanates, chlorine, etc.) are known to be triggered by the activation of transient receptor potential ankyrin 1 (TRPA1) ion channel. Antagonists of TRPA1 have shown near complete attenuation of the noxious effects from TIH exposure. One of the TRPA1 antagonists, (1E,3E)-1-(4-fluorophenyl)-2-methyl-1-pentene-3-one oxime (A-967079), has shown impressive efficacy, high selectivity, high potency, and oral bioavailability. Although a validated method to quantify A-967079 in biological matrices is vital for the further development of A-967079 as a therapeutic agent, no method for its analysis from any matrix is currently available. Hence, a rapid and simple HPLC-MS/MS method was developed and validated to quantify A-967079 in rabbit plasma. The method presented here features an excellent LOD of 25 nM and a wide linear range (0.05-200 μM), with good accuracy and precision (100 ± 10.5% and <14.2% relative standard deviation, respectively). The stability of A-967079 in plasma was excellent for most of the storage conditions evaluated. The method was successfully applied to determine A-967079 from treated animals and it may facilitate the development of this TRPA1 antagonist as a therapeutic agent against the noxious effects of TIH exposure.
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Affiliation(s)
- Obed A. Gyamfi
- Department of Chemistry and Biochemistry, South Dakota State University, Box 2202, Brookings, SD, 57007, USA
| | - Nesta Bortey-Sam
- Department of Chemistry and Biochemistry, South Dakota State University, Box 2202, Brookings, SD, 57007, USA
| | - Abigail B. Donkor
- Department of Chemistry and Biochemistry, South Dakota State University, Box 2202, Brookings, SD, 57007, USA
| | - Carl W. White
- Pediatrics-Pulmonary Medicine, University of Colorado-Denver, Denver, CO, 80045, USA
| | - Brian A. Logue
- Department of Chemistry and Biochemistry, South Dakota State University, Box 2202, Brookings, SD, 57007, USA
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Ganguly BB, Mandal S, Banerjee N, Kadam NN, Abbi R. Effect of age at exposure on chromosome abnormalities in MIC-exposed Bhopal population detected 30 years post-disaster. Mutat Res 2018; 809:32-50. [PMID: 29684722 DOI: 10.1016/j.mrfmmm.2018.03.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 03/23/2018] [Accepted: 03/28/2018] [Indexed: 10/17/2022]
Abstract
Follow-up cytogenetic study was carried out on 145 individuals from areas stratified by Indian Council of Medical Research, for evaluation of the effect of age-at-exposure and its interaction with exposure status on chromosomal aberrations (CA) in blood-lymphocytes. CA was presented as abnormal cell (Abc), aberrations (Abn) and number of aberration/abnormal cell (Abn/Abc), and correlated with age-at-exposure (childhood: <1-10 years; young: 11-26 years; adult: >27 years). Age related increase in abnormalities (Abc, Abn, Abn/Abc) was observed in all exposure strata, except moderately exposed adult-group, which has exhibited lower Abn/Abc than similarly exposed childhood and young age-groups. Elevation of CA was also related to exposure status. Abn/Abc frequency was significantly higher in the severely exposed young and adult groups compared to the controls of the same age. Two-way ANOVA revealed significant abnormalities between the exposed groups; however, interaction of age and exposure was not statistically significant. Significant difference in group-means of Abc and Abn was also observed between adult and childhood in Tukey HSD test. Altogether, a significant interaction of age and MIC-exposure on CA could not be established due to inter-individual variation and lack of baseline information on CA. Significantly higher Abn was observed in people consuming tobacco; however, interaction of lifestyle with additional environmental/occupational exposures during last 30 years against a background exposure to MIC remained un-elucidated. Nevertheless, the study was important for demonstration of the correlation of the current status of CA in circulating lymphocytes with age and exposure status of the MIC-exposed survivors.
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Affiliation(s)
- Bani Bandana Ganguly
- MGM Center for Genetic Research & Diagnosis, MGM New Bombay Hospital, Navi Mumbai, India.
| | - Shouvik Mandal
- MGM Center for Genetic Research & Diagnosis, MGM New Bombay Hospital, Navi Mumbai, India
| | - Nalok Banerjee
- National Institute for Research in Environmental Health (NIREH/ICMR), Bhopal, India
| | - Nitin N Kadam
- Department of Pediatrics, MGM Medical College, Navi Mumbai, India
| | - Rita Abbi
- School of Biomedical Sciences, MGM Institute of Health Sciences, Navi Mumbai, India
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Ganguly BB, Mandal S. Cytogenetic changes in the Bhopal population exposed to methyl isocyanate (MIC) in 1984: Then and 30 years later. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2017; 824:9-19. [PMID: 29150050 DOI: 10.1016/j.mrgentox.2017.10.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 10/09/2017] [Accepted: 10/11/2017] [Indexed: 12/15/2022]
Abstract
Following the 1984 Bhopal methyl isocyanate (MIC) gas disaster, genetic alterations were sporadically reported on small cohorts. However, the outcome of the multi-center cytogenetic screening conducted at that time remains unknown and no follow-up studies on the long-term effects of MIC exposure have been published. The present work examines genetic changes in the exposed population,with the aim of identifying any long-term effects of MIC. G-Banded metaphases were studied in lymphocytes of 130 individuals. Chromosomal aberrations (CA) were broadly grouped as abnormal cells (Abc), aberrations (Abn), and aberration/abnormal cell (Abn/Abc). From the previous multi-center screening, 946 records were retrieved, from which CA, sister chromatid exchanges (SCE), and cell-cycle kinetics (RI) were computed. In our analysis of the previous study, Abc and Abn were higher in the moderately and severely exposed groups than in the unexposed population. Abc appeared uniform in all groups of the present study, although Abn and Abn/Abc were higher in the exposed groups. Aberrations were now significantly higher in the unexposed and moderately exposed groups than in the previous screening. Although Abn and Abc now appeared lower in severely exposed subjects, the Abn/Abc ratio was higher, perhaps due to more rearrangements and damage in a smaller number of Abc. This result may be attributed to differences between the methods used in the studies, then and now. Elevated SCEs and reduced RI were seen in the severely exposed population shortly after exposure, and stable/clonal rearrangements were seen 30 y later. Follow-up of index cases and their progenies is needed.
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Affiliation(s)
- Bani Bandana Ganguly
- MGM Center for Genetic Research & Diagnosis, MGM New Bombay Hospital, Navi Mumbai, India.
| | - Shouvik Mandal
- MGM Center for Genetic Research & Diagnosis, MGM New Bombay Hospital, Navi Mumbai, India
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Dietz MC, Gerber A, Groneberg DA, Bendels MHK. Die Katastrophe von Bhopal. ZENTRALBLATT FÜR ARBEITSMEDIZIN, ARBEITSSCHUTZ UND ERGONOMIE 2017. [DOI: 10.1007/s40664-017-0216-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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A retrospective review of cytogenetic studies on methyl isocyanate with special reference to the Bhopal gas tragedy: is the next generation also at risk? Int J Occup Med Environ Health 2013; 26:324-36. [PMID: 23857370 DOI: 10.2478/s13382-013-0110-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 04/25/2013] [Indexed: 11/20/2022] Open
Abstract
The world's worst industrial disaster, at Union Carbide, Bhopal, India, took place on 2-3 December 1984, leading to the leakage of poisonous methyl-isocyanate into the environment, causing thousands of deaths, pregnancy loss and for some, incapacitation for life. More than a quarter of a century later, the Indian Council of Medical Research undertook to redefine the abysmal consequences of the toxic gas exposure on the exposed population. This invigorated the interest of scientific community in the evaluation of the long-term effects, with reference to cytogenetic parameters. The thrust area was identified in terms of genetic disorders, low birth weight, developmental/growth disorders and congenital malformations. Also the impact on epigenetic factors, which may have contributed to variations in the functional expression of genes, was not negated, stimulating intense scientific research on in utero exposure and the progeny of the exposed population. To accomplish this mammoth task, molecular cytogenetic investigations must be undertaken in conjunction with conventional cytogenetics, using techniques such as FISH, Immuno-FISH, SKY and SNP analysis, to build up a cytogenetic database of the surviving population.
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Svendsen ER, Whittle NC, Sanders L, McKeown RE, Sprayberry K, Heim M, Caldwell R, Gibson JJ, Vena JE. GRACE: public health recovery methods following an environmental disaster. ARCHIVES OF ENVIRONMENTAL & OCCUPATIONAL HEALTH 2010; 65:77-85. [PMID: 20439226 PMCID: PMC4090107 DOI: 10.1080/19338240903390222] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Different approaches are necessary when community-based participatory research (CBPR) of environmental illness is initiated after an environmental disaster within a community. Often such events are viewed as golden scientific opportunities to do epidemiological studies. However, the authors believe that in such circumstances, community engagement and empowerment needs to be integrated into the public health service efforts in order for both those and any science to be successful, with special care being taken to address the immediate health needs of the community first, rather than the pressing needs to answer important scientific questions. The authors will demonstrate how they have simultaneously provided valuable public health service, embedded generalizable scientific knowledge, and built a successful foundation for supplemental CBPR through their on-going recovery work after the chlorine gas disaster in Graniteville, South Carolina.
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Affiliation(s)
- Erik R Svendsen
- Arnold School of Public Health and the Department of Epidemiology and Biostatistics, University of South Carolina, Columbia, SC South Carolina Department of Health and Environmental Control, Columbia, SC, USA.
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8
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Zhong BZ, Depree GJ, Siegel PD. Differentiation of the mechanism of micronuclei induced by cysteine and glutathione conjugates of methylenedi-p-phenyl diisocyanate from that of 4,4'-methylenedianiline. Mutat Res 2001; 497:29-37. [PMID: 11525905 DOI: 10.1016/s1383-5718(01)00246-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Methylenedi-p-phenyl diisocyanate (MDI) is widely used in the production of polyurethane products. Diisocyanates are reactive compounds, MDI can react under physiological conditions with various functional groups found on biological molecules resulting in conjugate formation or undergo non-enzymatic hydrolysis to form 4,4'-methylenedianiline (MDA). We have previously reported that addition of MDI directly to Chinese hamster lung fibroblasts (V79) cultures did not induce micronuclei (MN), but MDA, and the glutathione and cysteine conjugates of MDI (BisGS-MDI and BisCYS-MDI), induced a concentration-dependent increase in the frequency of MN. The conventional MN assay does not discriminate between MN produced by acentric chromosome fragments from those arising due to whole lagging chromosomes that were not incorporated into daughter nuclei at the time of cell division. The mechanism of MN induction from these potential MDI metabolites/reaction products was explored in the present study using immunofluorescent staining of kinetochore in MN of cytokinesis-blocked V79 cells. This assay discerns the presence of centromere within the MN to distinguish the MN containing centric chromosomes from those containing acentric fragments. Eighty five percent of MDA-induced MN were negative with respect to anti-kinetochore antibody binding (KC(-)). This is consistent with an interaction between MDA and DNA resulting in chromosome breakage. However, BisGS-MDI and BisCYS-MDI induced a higher percentage of MN that were positively stained by the anti-kinetochore antibody (KC(+)). These results suggest that the mechanism of MN formation induced by BisGS-MDI and BisCYS-MDI is mediated through disruption and/or by affecting the function of the mitotic spindle. This mechanism is distinctly different from the mechanism of MN induction by MDA.
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Affiliation(s)
- B Z Zhong
- Analytical Services Branch, M/S L4218, Health Effect Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505-2888, USA
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9
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Lee MS. Enzyme induction and comparative oxidative desulfuration of isothiocyanates to isocyanates. Chem Res Toxicol 1996; 9:1072-8. [PMID: 8902261 DOI: 10.1021/tx950213f] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Enzyme induction of oxidative metabolism of isothiocyanates to isocyanates by rat liver microsomes and comparative metabolic conversion of some isothiocyanates were investigated. Metabolic activity was assayed by trapping the isocyanate metabolites from isothiocyanates with the inclusion of 2-aminofluorene to form the respective mixed ureas as previously described for the 2-naphthyl isothiocyanate. Male F344 rats were fed either a conventional grain diet for induction with Aroclor 1254 or AIN 76A diet without antioxidant beginning 2 weeks before treatment with Aroclor 1254, beta-naphthoflavone, isosafrole, or phenobarbital. Enzymes responsible for the metabolism of 1- and 2-naphthyl isothiocyanate were inducible by all four agents, Aroclor being the best under the current induction protocol and metabolic conversion assay procedure. On the other hand, enzymes responsible for the metabolism of benzyl isothiocyanate were induced only by Aroclor and, to a lesser extent, by phenobarbital. For the comparative metabolic conversion studies, using the microsomes from Aroclor-treated rats fed a conventional grain diet, the rates of metabolic conversion followed the order of 1-naphthyl > > phenyl > benzyl and phenethyl > > propyl, ethyl, and methyl isothiocyanates.
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Affiliation(s)
- M S Lee
- Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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Varma DR, Guest I. The Bhopal accident and methyl isocyanate toxicity. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1993; 40:513-29. [PMID: 8277516 DOI: 10.1080/15287399309531816] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The Bhopal accident, the world's worst industrial disaster, in which nearly 40 metric tons of methyl isocyanate (MIC) was released from the Union Carbide pesticide plant, occurred nearly 10 yr ago during the night of December 2 and 3, 1984. Over 3000 people residing in areas adjacent to the plant died of pulmonary edema within 3 d of the accident. Follow-up studies revealed pulmonary, ophthalmic, reproductive, immunologic, neurological, and hematologic toxicity among the survivors. Despite high reactivity, MIC can traverse cell membranes and reach distant organs, perhaps as a reversible conjugate with glutathione, which may explain some of the systemic effects of MIC. MIC can be degraded as a result of pyrolysis and interaction with water, but none of the breakdown products can duplicate the toxicity observed in Bhopal and in animal models. MIC may be the most toxic of all isocyanates because of its very high vapor pressure relative to other isocyanates and because of its ability to exert toxic effects on numerous organ systems.
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Affiliation(s)
- D R Varma
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
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Varma DR, Guest I. The Bhopal accident and methyl isocyanate toxicity. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1993; 40:513-529. [PMID: 8277516 DOI: 10.1016/b978-012088523-7/50008-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The Bhopal accident, the world's worst industrial disaster, in which nearly 40 metric tons of methyl isocyanate (MIC) was released from the Union Carbide pesticide plant, occurred nearly 10 yr ago during the night of December 2 and 3, 1984. Over 3000 people residing in areas adjacent to the plant died of pulmonary edema within 3 d of the accident. Follow-up studies revealed pulmonary, ophthalmic, reproductive, immunologic, neurological, and hematologic toxicity among the survivors. Despite high reactivity, MIC can traverse cell membranes and reach distant organs, perhaps as a reversible conjugate with glutathione, which may explain some of the systemic effects of MIC. MIC can be degraded as a result of pyrolysis and interaction with water, but none of the breakdown products can duplicate the toxicity observed in Bhopal and in animal models. MIC may be the most toxic of all isocyanates because of its very high vapor pressure relative to other isocyanates and because of its ability to exert toxic effects on numerous organ systems.
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Affiliation(s)
- D R Varma
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
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12
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Tamura N, Aoki K, Lee MS. Selective reactivities of isocyanates towards DNA bases and genotoxicity of methylcarbamoylation of DNA. Mutat Res 1992; 283:97-106. [PMID: 1381495 DOI: 10.1016/0165-7992(92)90140-d] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The reactivities of methyl isocyanate (MIC) and phenyl isocyanate (PIC) with DNA, and the genotoxicity of MIC were investigated. MIC and PIC reacted with the exocyclic amino group of deoxycytidine, deoxyadenosine and deoxyguanosine to produce carbamoylated products. The reactions of both isocyanates with deoxycytidine were 2 and 4 orders of magnitude higher than with deoxyadenosine and deoxyguanosine, respectively. To explore the genotoxicity of MIC, M13mp9 RF DNA was modified with MIC and then introduced into E. coli. The plaque-forming efficiencies of DNA decreased with increasing dose levels, and the decreases were more pronounced in Uvr endonuclease-deficient strains (uvrA, uvrB and uvrC) than in the Uvr endonuclease-proficient strain, JM103. The differences in survival in JM103 and uvr- strains suggest that the methylcarbonyl adducts can be removed by the uvr excision-repair system. Modification of M13mp9 RF DNA with MIC induced MIC-dose-related, SOS-dependent mutations in the beta-galactosidase locus. These results demonstrate the genotoxic response of MIC-modified DNA in E. coli.
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Affiliation(s)
- N Tamura
- Department of Chemical Carcinogenesis, Michigan Cancer Foundation, Detroit 48201
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Goswami HK, Rangnekar GV, Varshney S, Gandhi P, Jain B, Joshi A. Crossed renal ectopia with pelvic lipomatosis: a new syndrome involving chromosome 1. Hum Genet 1992; 89:666-70. [PMID: 1511984 DOI: 10.1007/bf00221959] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
An 18-year-old male patient is described who possesses both kidneys on one side (crossed renal ectopia), together with pelvic lipomatosis. In general, lipomatosis is benign, but here the tissue shows the rare feature of malignancy. Chromosomally, the patient is typically characterised by somatic translocations involving chromosome 1 (37% metaphases); these almost always exhibit a whole chromosome translocation with chromosome 6 (35%), although involvement of chromosome 1 with chromosome 8 is present in 2% of metaphases. Other chromosomal features encountered in Giemsa-stained and G-banded preparations from lymphocyte cultures include the prevalence of a small Y chromosome in 25% of metaphases, the presence of marker dots in 20%, and acrocentric associations in 8%-10% of metaphases. However, more than 50% of metaphases have a normal 46XY karyotype with a normal-sized Y-chromosome. Crossed renal ectopia with pelvic lipomatosis can therefore be assigned to a new syndrome characterised by a whole-chromosome translocation involving chromosomes 1 and 6.
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Affiliation(s)
- H K Goswami
- Department of Genetics, University Campus, Bhopal, India
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14
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Dalton A, Curtis D, Harrington CI. Synergistic effects of azathioprine and ultraviolet light detected by sister chromatid exchange analysis. CANCER GENETICS AND CYTOGENETICS 1990; 45:93-9. [PMID: 2302691 DOI: 10.1016/0165-4608(90)90072-i] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The immunosuppressant azathioprine and longwave ultraviolet (UV) light have been postulated to have a synergistic effect on DNA resulting in carcinogenic change. This study investigated the in vitro effect of UV light on renal transplant recipients (RTRs) immunosuppressed with azathioprine and prednisolone to prevent rejection and patients on azathioprine for skin conditions and normal controls on no drug therapy. The results show clearly that there is an increase in sister chromatid exchanges (SCEs) in both patient groups in response to UV light with the greatest increase shown by the RTRs. Both patient groups without exposure to UV also showed a significant increase, as compared with normal controls, with the RTRs again showing the highest level. Both patient groups also showed disruption of the cell cycle in response to UV light as measured by the proliferative rate index (PRI) but the controls did not. These findings support the hypothesis of a synergistic effect between azathioprine and UV light and correlate well with the clinical pattern of carcinogenesis observed in these patients, with RTRs having a well-documented increased risk of neoplasia, particularly skin carcinomas in light-exposed areas.
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Affiliation(s)
- A Dalton
- Department of Biochemistry, University of Sheffield, Western Bank, England
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15
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Segal A, Solomon JJ, Li FJ. Isolation of methylcarbamoyl-adducts of adenine and cytosine following in vitro reaction of methyl isocyanate with calf thymus DNA. Chem Biol Interact 1989; 69:359-72. [PMID: 2731306 DOI: 10.1016/0009-2797(89)90122-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Methylisocyanate (MIC) is the direct-acting acylating compound involved in the Bhopal, India disaster which occurred on December 3rd, 1984. The accidental release of MIC resulted in at least 2000 deaths, thousands of injuries and exposure of at least 200,000 people to varying amounts of MIC. We have studied how MIC reacts with 2'-deoxyribonucleosides at pH 7.0 and 37 degrees C for 1 h. MIC acylates exocyclic amino groups resulting in the following methylcarbamoyl (MC) adducts: N6-MC-Ade (0.5% yield) and N4-MC-dCyd (6%). No adducts were detected with dThd and dGuo. UV, NMR and mass spectrometry were employed to spectroscopically characterize these adducts. MIC was reacted with calf thymus DNA (pH 7.0, 37 degrees C, 1 h) and yielded N6-MC-Ade (0.3 nmol/mg DNA) and N4-MC-dCyd (2.0 nmol/mg DNA). The inability of others to observe genetic mutations by MIC in Salmonella and Drosophila is consistent with the exocyclic adducts at N4 of Cyt and N6 of Ade where normal hydrogen bonding can occur after rotation of the methylcarbamoyl group anti to the Watson-Crick side of the molecule assuming that MIC binds to DNA within the intact cell.
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Affiliation(s)
- A Segal
- Department of Environmental Medicine, New York University School of Medicine, NY
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16
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Das BC. Factors that influence formation of sister chromatid exchanges in human blood lymphocytes. Crit Rev Toxicol 1988; 19:43-86. [PMID: 3056658 DOI: 10.3109/10408448809040817] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Sister chromatid exchange (SCE) reflects an interchange of DNA sequences between helices in a replicating chromosome. This was initially accomplished by Taylor and colleagues (1957) using tritiated thymidine incorporation followed by autoradiography. The development of an elegant technique for differential staining of sister chromatids by incorporating a thymidine analog, 5-bromodeoxyuridine (BrdU) has greatly simplified the detection of SCEs in metaphase chromosomes. In recent years, the analysis of SCE has been considered to be a highly sensitive and additional (i.e., with chromosome aberrations) end point for measuring mutagenic/carcinogenic potential of various environmental agents and is increasingly being used to detect and differentiate among chromosome fragility human diseases that predispose to neoplasia. Attention has been focused to see if the induction of SCEs in lymphocyte cultures can be used as a reliable "biological dosimeter" for genetic risk assessment and to monitor the exposed populations. Several physical or preparatory as well as biological factors that modify the response and formation of SCEs make the monitoring difficult. The purpose of this article is to review and analyze these factors to facilitate an effective development of a standard protocol for SCE testing and for appropriate evaluation of test results. This may also provide clues to understand the yet unknown molecular mechanism(s) and biological significance of SCE formation.
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Affiliation(s)
- B C Das
- Molecular Oncology Division, Indian Council of Medical Research, New Delhi
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Abstract
Carbamoylation of macromolecules occurs by the displacement of hydrogen on several groups, but the most stable addition at neutral pH is on amino groups. This reaction occurs predominantly with proteins and results from the administration in vivo of inorganic cyanate or organic isocyanates. The latter act more rapidly, but also are more rapidly hydrolyzed in aqueous solution. This instability has been a factor limiting study of the pharmacological properties of organic isocyanates. However, organic isocyanates are released from some nitrosoureas of value in cancer therapy such as 1,3-bis(2-chlorethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU). The carbamoylating activities of BCNU and CCNU are generally considered less significant than their alkylating activity in the action of these drugs on tumors, but carbamoylation may serve to inhibit DNA repair. There is evidence that carbamoylating agents can exert selective inhibitory effects on metabolite uptake and macromolecular synthesis in neoplastic tissues. Such selectivity is much more notable in vivo than in vitro. In the case of cyanate, the selectivity in vivo has been variously attributed to a requirement for metabolic activation, to selective effects on circulation in solid tumors, and to diminished pH in tumors. It is the distinction between such factors and the identification of critical cellular targets which provide major challenges in present studies on the effects of carbamoylating agents on tumor metabolism.
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Affiliation(s)
- M A Lea
- Department of Biochemistry, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark
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