Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: DrugBank:APRD00249 (Mutagen)
 5,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is important to determine sensitive biomarkers for both exposure and susceptibility since differences in individual susceptibility to potentially hazardous chemicals may represent a major variable in the assessment of risk. Induction of cytochrome P450IA1 (CYP1A1) may be a measure of environmental exposure to aromatic hydrocarbons in cigarette smoke. This study investigated the use of reverse transcriptase-polymerase chain reaction (RT-PCR) to detect constitutive levels of CYP1A1 mRNA in the peripheral lymphocytes of a population of smokers and non-smokers as a potential marker of exposure. In addition, the presence of an Msp 1 restriction fragment length polymorphism was analyzed using a simple PCR method as a biomarker for susceptibility. DNA and RNA were isolated from the peripheral lymphocytes of 20 smokers and a matched group of non-smokers. RT-PCR was used to detect the endogenous levels of CYP1A1 mRNA with glyceraldehyde-3-phosphate dehydrogenase as a control gene. The 3'-region of CYP1A1 gene was amplified by PCR and underwent restriction digestion with Msp 1 to detect the polymorphism. The endogenous CYP1A1 expression as detected by RT-PCR was very low and variable and there was a slight but not significant increase in the smokers by comparison with non-smokers. Thirty-two of the volunteers were homozygous for the normal allele while 8 were heterozygous for the uncommon Msp 1 allele and none was homozygous for the polymorphism. The allele frequency (0.1) was found to be in Hardy-Weinberg equilibrium. Since only a slight increase was seen in endogenous CYP1A1 mRNA levels in the peripheral lymphocytes of smokers by comparison with non-smokers, the effect may have been diluted by variation in sensitivity to dose, a threshold of exposure effect, or the return of mRNA to baseline between exposures. The wide variation in mRNA levels may reflect the influence and exposure of different environmental factors. The sensitivity of PCR-based methods suggests that they may have an important role in future overall biomonitoring of exposure and susceptibility to environmental chemicals.
Teratog Carcinog Mutagen 1996
PMID:Detection of CYP1A1 mRNA levels and CYP1A1 Msp polymorphisms as possible biomarkers of exposure and susceptibility in smokers and non-smokers. 879 34

In the human glutathione S-transferase (GST) mu gene family, homozygous deletion of GSTM1 is the null phenotype (frequency of approximately 50% in Caucasians). In the current study, GSTM1 status was determined in human cell lines using reverse transcriptase, polymerase chain reaction, and immunochemistry. Cell lines were challenged with a range of doses of styrene-7,8-oxide (SO) and then toxicity and genotoxicity were monitored. Toxicity was determined by growth in flasks and genotoxicity by cloning in microplates in the presence/absence of 6-thioguanine, to detect mutations at the hypoxanthine phosphoribosyltransferase (hprt) locus. A SO concentration-dependent decrease in survival was observed for all cell lines, with GSTM1-deficient lines being more sensitive. The IC(50)s of deficient and proficient cell lines were 0.45 and 0.55 mM SO, respectively. The difference between survival of GSTM1-deficient and -proficient cell lines approached statistical significance. The background mutation frequency of GSTM1-deficient cell lines was 2 x 10(-5), and that of GSTM1-proficient cell lines was 3 x 10(-6). GSTM1-deficient cell lines were significantly more sensitive than GSTM1-proficient cell lines to mutation induction for concentrations up to 2.5 mM SO (P < 0.001, regression analysis). These results suggest that cell lines containing metabolically competent GSTM1 are able to efficiently use GSTM1 to conjugate SO and reduce its hazard. This supports the epidemiological evidence that GSTM1 influences sensitivity to chemical carcinogenesis and subsequent risk of cancer induction.
Environ Mol Mutagen 2001
PMID:Role of glutathione S-transferase mu (GSTM1) in styrene-7,8-oxide toxicity and mutagenicity. 1142 77

Combinations of antiretroviral drugs that include nucleoside reverse transcriptase inhibitors (NRTIs) are superior to single-agent regimens in treating or preventing HIV infection, but the potential long-term health hazards of these treatments in humans are uncertain. In earlier studies, our group found that coexposure of TK6 human lymphoblastoid cells to 3'-azido-2',3'-dideoxythymidine (AZT) and 2',3'-dideoxyinosine (ddI), the first two NRTIs approved by the FDA as antiretroviral drugs, produced multiplicative synergistic enhancement of DNA incorporation of AZT and mutagenic responses in both the HPRT and TK reporter genes, as compared with single-drug exposures (Meng Q et al. [2000a]: Proc Natl Acad Sci USA 97:12667-12671). The purpose of the current study was to characterize the mutational specificity of equimolar mixtures of 100 microM or 300 microM AZT + ddI at the HPRT and TK loci of exposed cells vs. unexposed control cells, and to compare the resulting mutational spectra data to those previously found in cells exposed to AZT alone (Sussman H et al. [1999]: Mutat Res 429:249-259; Meng Q et al. [2000b]: Toxicol Sci 54:322-329). Molecular analyses of HPRT mutant clones were performed by reverse transcription-mediated production of cDNA, PCR amplification, and cDNA sequencing to define small DNA alterations, followed by multiplex PCR amplification of genomic DNA to define the fractions of deletion events. TK mutants with complete gene deletions were distinguished by Southern blot analysis. The observed HPRT mutational categories included point mutations, microinsertions/microdeletions, splicing-error mutations, and macrodeletions including partial and complete gene deletions. The only significant difference or shift in the mutational spectra for NRTI-treated cells vs. control cells was the increase in the frequency of complete TK gene deletions following exposures (for 3 days) to 300 microM AZT-ddI (P = 0.034, chi-square test of homogeneity); however, statistical analyses comparing the observed mutant fraction values (measured mutant frequency x percent of a class of mutation) between control and NRTI-treated cells for each class of mutation showed that the occurrences of complete gene deletions of both HPRT and TK were significantly elevated over background values (0.34 x 10(-6) in HPRT and 6.0 x 10(-6) in TK) at exposure levels of 100 microM AZT-ddI (i.e., 1.94 x 10(-6) in HPRT and 18.6 x 10(-6) in TK) and 300 microM AZT-ddI (i.e., 5.6 x 10(-6) in HPRT and 34.6 x 10(-6) in TK) (P < 0.05, Mann-Whitney U-statistic). These treatment-related increases in complete gene deletions were consistent with the spectra data for AZT alone (ibid.) and with the known mode of action of AZT and ddI as DNA chain terminators. In addition, cotreatments of ddI with AZT led to substantial absolute increases in the mutant fraction of other classes of mutations, unlike cells exposed solely to AZT [e.g., the frequency of point mutations among HPRT mutants was significantly increased by 130 and 323% over the background value (4.25 x 10(-6)) in cells exposed to 100 and 300 microM AZT-ddI, respectively]. These results indicate that, at the same time that AZT-ddI potentiates therapeutic or prophylactic efficacy, the use of a second NRTI with AZT may confer a greater cancer risk, characterized by a spectrum of mutations that deviates from that produced solely by AZT.
Environ Mol Mutagen 2002
PMID:Molecular analysis of mutations at the HPRT and TK loci of human lymphoblastoid cells after combined treatments with 3'-azido-3'-deoxythymidine and 2',3'-dideoxyinosinedagger. 1211 80

Antiretroviral therapies based on nucleoside reverse transcriptase inhibitors (NRTIs), like zidovudine (3'-azido-3'-deoxythymidine; AZT) and lamivudine ((-)2',3'-dideoxy-3'-thiacytidine; 3TC), markedly reduce mother-to-child transmission of the human immunodeficiency virus (HIV). However, AZT induces damage in nuclear DNA of mice exposed in utero and postnatally, and mitochondrial DNA (mtDNA) damage has been observed in both human and mouse neonates following perinatal exposure to AZT and AZT/3TC in combination. To provide animal data modeling the NRTI-induced heart damage reported in human infants, we treated pregnant CD-1 mice throughout gestation and treated their pups by direct gavage from postnatal day (PND) 4 through PND 28 with daily doses of 150 mg/kg body weight (bw)/day AZT, 75 mg/kg bw/day 3TC, 125/62.5 mg/kg bw/day AZT/3TC, or the vehicle control. Half the pups were euthanized on PND 28; the remainder received no further dosing, and were euthanized at week 10. Heart tissue was collected, total DNA was extracted, and mtDNA copy number relative to nuclear DNA copy number, mtDNA damage, and mtDNA mutation assays were performed using PCR-based methods. Analyses revealed increases in mtDNA lesions in 4-week-old males and females treated with AZT or 3TC, but not in 10-week-old mice, suggesting that the damage resolved after treatment ceased. Interestingly, 10-week-old females treated with AZT/3TC had significant increases in mtDNA damage. Point mutations were elevated in 10-week-old females treated with AZT or AZT/3TC, but not 3TC; no increases in mutations were seen in either gender at 4 weeks of age. Our data suggest that AZT/3TC combination treatment produces greater mtDNA damage than either agent individually, and that female mice are more sensitive than males to AZT/3TC-induced mtDNA damage.
Environ Mol Mutagen
PMID:Mitochondrial toxicity in hearts of CD-1 mice following perinatal exposure to AZT, 3TC, or AZT/3TC in combination. 1639 92

Nucleoside analogs were first approved by the U.S. Food and Drug Administration for use against HIV-AIDS in 1987. Since then, these agents, now commonly referred to as nucleoside reverse transcriptase inhibitors (NRTIs), have become essential components of the Highly Active Antiretroviral Therapy (HAART) drug combinations used for treatment of Human Immunodeficiency Virus-1 (HIV-1) infections. Their antiretroviral activity is likely two-fold: incorporation of the drug into viral DNA and inhibition of the viral reverse transcriptase. However, incorporation of the drug into host nuclear and mitochondrial DNA may be largely responsible for dose-limiting toxicities. Azidothymidine (AZT, 3'-azido-3'-deoxythymidine, zidovudine), the first NRTI approved for the therapy of HIV-1, is incorporated into DNA, causes mutations in the hypoxanthine-guanine phosphoribosyl-transferase (HPRT) and thymidine kinase (TK) genes, and induces micronuclei, chromosomal aberrations, sister chromatid exchange, shortened telomeres, and other genotoxic effects in cultured cells. Genomic instability would be predicted as a consequence of these events. Metabolic pathways that result in the phosphorylation of AZT play a crucial role in AZT-DNA incorporation, and may be altered after prolonged treatment. For example, thymidine kinase 1, the enzyme responsible for AZT mono-phosphorylation, is down-regulated during long-term exposure and appears to be associated with AZT-induced replication inhibition and the accumulation of cells in S-phase. Detailed information on the mechanisms underlying NRTI-associated antiretroviral efficacy, toxicity, and metabolic resistance were not available when AZT was first approved for use as an antiretroviral agent. Current insights, based on 15 years of research, may lead to intervention strategies to attenuate toxicity without altering drug efficacy.
Environ Mol Mutagen
PMID:Mechanisms of genotoxicity of nucleoside reverse transcriptase inhibitors. 1639 95

Effective reduction in maternal-fetal human immunodeficiency virus-1 (HIV-1) transmission has been achieved by administration of nucleoside reverse transcriptase inhibitors (NRTIs) during pregnancy, and although most exposed children are clinically normal at birth, mitochondrial dysfunction has been reported. To examine mitochondrial integrity on a molecular level, we evaluated mitochondrial morphology by electron microscopy (EM) and mitochondrial DNA (mtDNA) quantity in umbilical cords and cord blood from NRTI-exposed and unexposed human and monkey newborns. Human subjects included infants born to HIV-1-infected mothers who received Combivir (Zidovudine [AZT] plus Lamivudine [3TC]) (n = 9) or AZT plus Didanosine [ddI] (n = 2) during pregnancy, and infants born to HIV-1-uninfected mothers (n = 7). NRTI-exposed Erythrocebus patas monkey dams (n = 3 per treatment group) were given human-equivalent dosing regimens containing 3TC, AZT/3TC, AZT/ddI, or Stavudine (d4T)/3TC during gestation. Four infants born to unexposed patas dams served as controls. Mitochondria in umbilical cord endothelial cells from NRTI-exposed monkey and human infants showed substantial abnormal pathology by EM, the extent of which was quantified from coded photomicrographs and shown to be different (P < 0.05) from the unexposed monkey and human newborns. Significant (P < 0.05) mtDNA depletion was found in umbilical cords from both human and monkey NRTI-exposed infants and in human, but not in monkey, cord blood leukocytes. For umbilical cords, an increase in mitochondrial morphological damage correlated with reduction in mtDNA quantity in fetal monkeys (r = 0.94). The treatment-induced mitochondrial compromise in infant monkeys ranked as follows: d4T/3TC > AZT/ddI > AZT/3TC > 3TC. The study demonstrates that transplacental NRTI exposures induce similar mitochondrial damage in cord blood and umbilical cords taken from retroviral-uninfected monkey infants and from human infants born to HIV-1-infected women.
Environ Mol Mutagen
PMID:Transplacentally exposed human and monkey newborn infants show similar evidence of nucleoside reverse transcriptase inhibitor-induced mitochondrial toxicity. 1653 87

Nucleoside reverse transcriptase inhibitors (NRTIs) in combinations with other antiretrovirals (highly active antiretroviral therapy, HAART) are the cornerstones of AIDS therapy, turning HIV infection into a manageable clinical entity. Despite the initial positive impact of NRTIs, therapeutic experience revealed serious side effects that appeared to originate in the mitochondria and which ultimately manifested as dysfunction of that organelle. It may be reasonable to consider that as the AIDS epidemic continues and as survival with HIV infection is prolonged by treatment with HAART, long-term side effects of NRTIs may become increasingly common. This consideration may be underscored in children who are born to HIV-infected mothers who received NRTI therapy in utero during gestation. The long-term effect of that NRTI exposure in utero is not clear yet. This review examines some proposed mechanisms of NRTI mitochondrial toxicity, including genetic predisposition, defects in mitochondria DNA replication, the encompassing "DNA pol-gamma hypothesis," the relationship between mitochondrial nucleotide and NRTI pools, mitochondrial DNA mutation and dysfunction, and oxidative stresses related to HIV infection and NRTIs. Mechanisms of mitochondrial toxicity are reviewed with respect to key cell biological, pathological, and pharmacological events.
Environ Mol Mutagen
PMID:A brief overview of mechanisms of mitochondrial toxicity from NRTIs. 1675 72

Long-term use of antiretroviral nucleoside reverse transcriptase inhibitors (NRTIs) as therapy for human immunodeficiency virus-1 (HIV-1) infection is limited by mitochondrial toxicity. Here we document mitochondrial pathology during the long-term culture of human HeLa cells in the presence or absence of the NRTI Zidovudine(R) (AZT, 800 muM) for up to 77-passages (p), with samples taken at early (p5-p11), middle (p36 and p37), and late (p70-p77) passages. Samples were analyzed for changes in mitochondrial morphology, mitochondrial (mt)DNA quantity, nuclear and mitochondrial gene expression, and mitochondrial membrane potential. Mitochondria showed abnormal proliferation at p5 and abnormal morphology >/=p36. mtDNA quantity was increased at p5 and p11, and 65% depleted at p71. Hierarchical clustering of nuclear gene expression, examined at p37 by the NCI cDNA microarray in AZT-exposed cells, showed down-regulation of 13 out of 16 lipid-metabolizing genes, and up-regulation of most oxidative phosphorylation (OXPHOS) genes. OXPHOS genes encoded by mtDNA, examined at p5, p36, and p75 using the Mitochondrial Gene Mini Array, revealed up-regulation of genes coding for polypeptides of NADH dehydrogenase, ATP synthase, and cytochrome c oxidase. Mitochondrial membrane potential, monitored by JC1 staining, was elevated at p10 and p32, and essentially completely absent at p71. The data show that during chronic exposure of HeLa cells to AZT, a compensatory response was induced at the earlier passages (p5-p37), and by p71 there was widespread mitochondrial morphological damage, severe mtDNA depletion, and a substantial loss of mitochondrial membrane potential.
Environ Mol Mutagen
PMID:Morphological and molecular course of mitochondrial pathology in cultured human cells exposed long-term to Zidovudine. 1689 29

Reproductive toxicity is one of the potential side effects of anticancer alkylating agents, with potential effects on vimentin intermediate filaments, one of the main components of the Sertoli cytoskeleton. Research suggests (Aumuller et al, 1988; Aumuller et al, 1992) that the highly organized and active Sertoli cytoskeleton is important in spermatogenesis. The aim of the current study was to investigate the effects of alkylating agents on vimentin filament expression in vitro. Sertoli cells, isolated from 20-day-old mice testes, were cultured for 5 days and then incubated with 0, 50, 100, and 200 micromol/L nitrogen mustard (HN2). Morphologic changes in Sertoli cells were observed per 30-minute interval at 12-hour exposure time points to 100 micromol/L HN2. Vimentin expression was investigated by immunocytochemistry at 6 hours and 24 hours posttreatment and reverse transcriptase polymerase chain reaction and Western blot at 12 hours posttreatment with 50, 100, and 200 micromol/L HN2. Exposure to HN2 resulted in a comparatively small Sertoli cell body with diminished cytoplasm. Sertoli cells were shrunk or detached. Cytoskeletal disruption increased with increasing HN2 concentration. The optical density values of vimentin antibody and expression of vimentin mRNA and protein were significantly decreased with increasing concentration of HN2. Significant treatment dose-dependent and time-dependent differences of vimentin mRNA and protein expression levels were also noted. Our data suggest that the change in the biochemical properties of vimentin may indicate that one of the mechanisms of reproductive toxicity resulting from HN2 is disruption of Sertoli cell vimentin filament structure, accompanied by a down-regulation of vimentin expression.
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PMID:Cytoskeleton vimentin disruption of mouse sertoli cells injured by nitrogen mustard in vitro. 1719

The prophylactic use of zidovudine (3'-azido-3'-deoxythymidine, AZT) during pregnancy greatly reduces transmission of HIV-1 from infected mothers to their infants; however, the affinity of host cell DNA polymerases for AZT also allows for its incorporation into host cell DNA, predisposing to cancer development. To expand upon previous transplacental carcinogenesis assays performed in CD-1 mice, the transplacental carcinogenicity of AZT was evaluated in a second mouse strain and a second rodent species. Date-mated female mice and rats were gavaged daily with 0, 80, 240, or 480 mg AZT/kg bw during the last 7 days of gestation. At 2 years postpartum, male and female B6C3F1 mouse and F344 rat offspring (n = 44-46 of each sex and species/treatment group) were necropsied for gross and microscopic tissue examinations. Under the conditions of these two-year studies, there was clear evidence of carcinogenic activity based upon significant dose-related trends and increases in the incidences of hemangiosarcoma in male mice and mononuclear cell leukemia in female rats. There was some evidence of carcinogenic activity in the livers of male mice based upon a positive trend and an increased incidence of hepatic carcinoma in the high-dose AZT group. The incidence of gliomas in female rats exceeded the historical background rates for gliomas in F344 rats. P53 overexpression was detected in some AZT-treated mouse neoplasms. These and other cancer-related findings confirm and extend those of previous transplacental carcinogenicity studies of AZT in mice, support the need for long-term follow-up of nucleoside reverse transcriptase inhibitor (NRTI)-exposed children, and indicate the necessity for effective protective strategies against NRTI-induced side effects.
Environ Mol Mutagen
PMID:Transplacental carcinogenicity of 3'-azido-3'-deoxythymidine in B6C3F1 mice and F344 rats. 1735 26


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