Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The intracellular metabolism of many carcinogenic polycyclic aryl hydrocarbons (PAHs, typified by the ubiquitous pollutant benzo[a]pyrene or B[a]P) generates electrophilic products that react covalently with genomic DNA. Cells that acquire PAH-induced DNA damage undergo growth arrest in a p53-independent manner (Vaziri, C., and Faller, D. V. (1997) J. Biol. Chem. 272, 2762-2769). In this report we have investigated the molecular basis of PAH-induced cell cycle arrest. Mitogenic signaling events involving cyclins D and E, Rb phosphorylation, and transcriptional activation of E2F-responsive genes (including cyclin E and cyclin A) were unaffected in cells containing PAH-damaged DNA. However, PAH-induced growth arrest was associated with post-transcriptional decreases in cyclin A expression. Mitogen-induced expression of cyclin B, an event that is temporally distal to cyclin A expression, was also inhibited in PAH-treated cells. The PAH-induced cell cycle block was transient, and arrested cells resumed DNA synthesis after a prolonged ( approximately 20 h) delay. Resumption of DNA synthesis in PAH-treated cells occurred concomitant with elevated expression of cyclins A and B. PAH-induced cell cycle arrest was overcome by ectopically expressed cyclin A (encoded by a recombinant adenovirus in transiently infected cells). Overall, our results suggest the existence of a DNA damage checkpoint pathway that arrests cell cycle progression via post-transcriptional control of cyclin A expression.
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PMID:A novel DNA damage checkpoint involving post-transcriptional regulation of cyclin A expression. 1063 67

Changes of gel temperature during single-strand conformation polymorphism (SSCP) electrophoresis increase the sensitivity of mutation detection in polymerase chain reaction (PCR) products and significantly reduce the overall time and costs of analysis. Based on these findings, a new method for single nucleotide polymorphism (SNP) and point mutation detection--multitemperature single-strand conformation polymorphism (MSSCP) was devised. In order to control the gel temperature with 0.1 degrees C accuracy during electrophoresis, new equipment was developed. We demonstrated that increasing the gel temperature by 8 degrees C or decreasing it by 10 degrees C from 23 degrees C led to the disappearance of all electrophoretic differences between five alleles of exon 8 of the human p53 gene during the SSCP analysis. The interesting result was the detection of two additional SNPs (out of seven analyzed) in exon 7 of the human PAH gene during a one hour MSSCP electrophoresis. This result is better than that obtained by three classical SSCP analyses of the same samples at different but constant gel temperatures. We advocate the MSSCP technology as a fast, reliable, and cost-effective tool for the screening and preselection stage of genomics surveys, especially when a high variability of the analyzed DNA fragment is expected.
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PMID:Multitemperature single-strand conformation polymorphism. 1166 39

Benzo[a]pyrene diol epoxide (BPDE)-DNA adducts are involved in the induction of p53 mutations and probably in the causation of human lung cancer associated with cigarette smoking. The ratio between CYP1A1 and GST enzyme activities is a critical determinant of the target dose of carcinogenic BPDE and other DNA-reactive PAH metabolites. In this review, we summarize the published data on modulation of (+)-anti-BPDE-DNA adduct levels in smokers' lungs by CYP1A1*2 genotypes alone or in combination with GSTM1 polymorphism and compare these results with those reported for aromatic/hydrophobic (bulky) DNA adducts. The data published so far show only a trend for a non-significant increase in bulky DNA adduct levels in subjects with GSTM1*0 or the CYP1A1*2-GSTM1*0 genotype combination. In contrast, a clear dependence of (+)-anti-BPDE-DNA adduct levels was found as a function of the CYP1A1 and GSTM1 genotypes: In lung parenchyma, this adduct was more pronounced in persons with the GSTM1*0 genotype, and CYP1A1*2-GSTM1*0 carriers had higher (+)-anti-BPDE-DNA adduct levels than those with CYP1A1*1/*1-GSTM1*0. The homozygous CYP1A1*2/*2 carriers in the GSTM1*0 group had the highest (+)-anti-BPDE-DNA adduct levels. Our analysis leads to the conclusion that the risk-modifying effects of metabolic genotypes and of gene interactions might be more easily identifiable if specific markers of structurally defined adducts were used, such as the (+)-anti-BPDE-DNA adduct. These results are also consistent with the hypothesis that BP (PAH) induce G:C to T:A transversion mutations in the hotspot codons of the p53 tumor suppressor gene and are thus involved in malignant transformation of the lung tissue of smokers.
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PMID:CYP1A1 and GSTM1 genotypes affect benzo[a]pyrene DNA adducts in smokers' lung: comparison with aromatic/hydrophobic adduct formation. 1250 20

Inherited genetic traits co-determine the susceptibility of an individual to a toxic chemical. Special emphasis has been put on individual responses to environmental and industrial carcinogens, but other chronic diseases are of increasing interest. Polymorphisms of relevant xenobiotic metabolising enzymes may be used as toxicological susceptibility markers. A growing number of genes encoding enzymes involved in biotransformation of toxicants and in cellular defence against toxicant-induced damage to the cells has been identified and cloned, leading to increased knowledge of allelic variants of genes and genetic defects that may result in a differential susceptibility toward environmental toxicants. "Low penetrating" polymorphisms in metabolism genes tend to be much more common in the population than allelic variants of "high penetrating" cancer genes, and are therefore of considerable importance from a public health point of view. Positive associations between cancer and CYP1A1 alleles, in particular the *2C I462V allele, were found for tissues following the aerodigestive tract. Again, in most cases, the effect of the variant CYP1A1 allele becomes apparent or clearer in connection with the GSTM1 null allele. The CYP1B1 codon 432 polymorphism (CYP1B1*3) has been identified as a susceptibility factor in smoking-related head-and-neck squameous cell cancer. The impact of this polymorphic variant of CYP1B1 on cancer risk was also reflected by an association with the frequency of somatic mutations of the p53 gene. Combined genotype analysis of CYP1B1 and the glutathione transferases GSTM1 or GSTT1 has also pointed to interactive effects. Of particular interest for the industrial and environmental field is the isozyme CYP2E1. Several genotypes of this isozyme have been characterised which seem to be associated with different levels of expression of enzyme activity. The acetylator status for NAT2 can be determined by genotyping or by phenotyping. In the pathogenesis of human bladder cancer due to occupational exposure to "classical" aromatic amines (benzidine, 4-aminodiphenyl, 1-naphthylamine) acetylation by NAT2 is regarded as a detoxication step. Interestingly, the underlying European findings of a higher susceptibility of slow acetylators towards aromatic amines are in contrast to findings in Chinese workers occupationally exposed to aromatic amines which points to different mechanisms of susceptibility between European and Chinese populations. Regarding human bladder cancer, the hypothesis has been put forward that genetic polymorphism of GSTM1 might be linked with the occurrence of this tumour type. This supports the hypothesis that exposure to PAH might causally be involved in urothelial cancers. The human polymorphic GST catalysing conjugation of halomethanes, dihalomethanes, ethylene oxide and a number of other industrial compounds could be characterised as a class theta enzyme (GSTT1) by means of molecular biology. "Conjugator" and "non-conjugator" phenotypes are coincident with the presence and absence of the GSTT1 gene. There are wide variations in the frequencies of GSTT1 deletion (GSTT1*0/0) among different ethnicities. Human phenotyping is facilitated by the GST activity towards methyl bromide or ethylene oxide in erythrocytes which is representative of the metabolic GSTT1 competence of the entire organism. Inter-individual variations in xenobiotic metabolism capacities may be due to polymorphisms of the genes coding for the enzymes themselves or of the genes coding for the receptors or transcription factors which regulate the expression of the enzymes. Also, polymorphisms in several regions of genes may cause altered ligand affinity, transactivation activity or expression levels of the receptor subsequently influencing the expression of the downstream target genes. Studies of individual susceptibility to toxicants and gene-environment interaction are now emerging as an important component of molecular epidemiology.
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PMID:Markers of genetic susceptibility in human environmental hygiene and toxicology: the role of selected CYP, NAT and GST genes. 1287 24

Exposure to high levels of environmental air pollution is known to be associated with an increased carcinogenic risk. The individual contribution to this risk derived from specific carcinogenic chemicals within the complex mixture of air pollution is less certain, but may be explored by the use of molecular epidemiological techniques. Measurements of biomarkers of exposure, of effect and of susceptibility provide information of potential benefit for epidemiological and cancer risk assessment. The application of such techniques has been mostly concerned in the past with the carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) that are associated with particulate matter in air pollution, and has showed clear evidence of genotoxic effects, such as DNA adducts, chromosome aberrations (CA) and ras oncogene overexpression, in environmentally exposed Czech and Polish populations. We are currently extending these studies by an investigation of populations exposed to environmental pollution in three European countries, Czech Republic, Slovak Republic and Bulgaria. This pays particular attention to PAHs, but also investigates the extent of radically induced (oxidative) DNA damage in the exposed populations. Policemen, bus drivers and controls, who carried personal monitors to determine their exposures to PAHs have been studied, and blood and urine were collected. Antioxidant and dietary status were assessed in these populations. Stationary monitors were also used for ambient air monitoring. Amongst the parameters studied in the biological samples were: (a) exposure biomarkers, such as PAH adducts with DNA, p53 and p21(WAF1) protein levels, (b) oxidative DNA damage, (c) the biological effect of the exposure by measurement of chromosome damage by fluorescence in situ hybridisation (FISH) or conventional methods, and (d) polymorphisms in carcinogen metabolising and DNA repair enzymes. Repair ability was also measured by the Comet assay. In vitro systems are being evaluated to characterise the genotoxicity of the organic compounds adsorbed to air particles.
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PMID:Molecular epidemiology studies of carcinogenic environmental pollutants. Effects of polycyclic aromatic hydrocarbons (PAHs) in environmental pollution on exogenous and oxidative DNA damage. 1464 42

In this study we show that benzo[a]pyrene (B[a]P) and the cyclopenta polycyclic aromatic hydrocarbons (CP-PAH) cyclopenta[c,d]pyrene (CPP), benz[j]aceanthrylene (B[j]A) and benz[l]aceanthrylene (B[l]A) induce apoptosis in Hepa1c1c7 cells, as measured by fluorescence microscopy and flow cytometry. The compounds induced formation of the active form of caspase-3, cleavage of its intracellular substrate, poly(ADP-ribose)polymerase (PARP), and DNA fragmentation. B[j]A was found to be the most potent in inducing apoptosis, followed by B[a]P, CPP and B[l]A. All compounds increased expression of CYP1A1 with relative potencies B[j]A > B[a]P >> CPP > B[l]A, corresponding well with their relative apoptotic responses. alpha-Naphthoflavone (alphaNF), an inhibitor of CYP1A1, reduced the induced apoptosis. B[a]P and CP-PAH exposure also resulted in an accumulation of the tumour suppressor protein p53. No changes were observed in the protein levels of Bax and Bcl-2, whereas the anti-apoptotic Bcl-xl protein was down-regulated, as judged by western blot analysis. Fluorescence microscopic analysis revealed a translocation of p53 to the nucleus and of Bax to the mitochondria. Furthermore, caspase-8 was activated and Bid cleaved. Interestingly, the levels of anti-apoptotic phospho-Bad (Ser155 and Ser112) had a biphasic increase after B[a]P or CPP treatment. Whereas alphaNF markedly reduced the activation of B[a]P to reactive metabolites, as measured by covalent binding to macromolecules, it did not inhibit the up-regulation of phospho-Bad. Neither of the compounds triggered apoptosis in primary cultures of rat lung cells (Clara cells, type 2 cells and lung alveolar macrophages), possibly due to a lack of CYP1A1 induction. In conclusion, B[a]P and the CP-PAH induced apoptotic as well as anti-apoptotic signals in Hepa1c1c7 cells.
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PMID:Polycyclic aromatic hydrocarbons induce both apoptotic and anti-apoptotic signals in Hepa1c1c7 cells. 1472 87

The aim of this study was to investigate the genotoxic effect of single carcinogenic polycyclic aromatic hydrocarbons (c-PAHs), as well as their binary and artificial mixtures containing c-PAHs in the same relative proportions as real complex mixtures, and to investigate the genotoxic effect of environmental mixtures such as EOM (extractable organic matter adsorbed to respirable air particles). We used normal human diploid lung fibroblasts (HEL) in a confluent ("quiescent") state as being closer to in vivo conditions. We determined DNA adducts by (32)P -postlabelling and the expression of p53 and p21(WAF1) proteins by Western blotting. Our results showed that the DNA binding potencies of c-PAHs in quiescent HEL cells were as follows: DB[al]P>>B[a]P>>B[b]F approximately CHRY approximately B[k]F approximately B[a]A approximately DB[ah]A approximately I[cd]P > B[ghi]P. Both DB[al]P and B[a]P were chosen to assess the genotoxic effect of other c-PAHs when present in binary mixtures. In all cases, co-treatment resulted in significantly lower DNA adduct levels as compared with adduct levels resulting from single compounds. The highest inhibitory effect was found in the presence of DB[ah]A followed by B[k]F. In both artificial and EOM mixtures a strong inhibitory effect of other compounds was observed. BPDE-adduct levels were up to five-fold lower in an artificial c-PAH mixture and up to 10-fold lower in an EOM sample than expected from applying B[a]P alone at the same concentration. These results suggest a competition for the metabolic activation enzymes, their saturation and/or inactivation by PAH metabolites. We did not observe the decrease of DNA adducts and induced levels of both p53 and p21(WAF1) proteins during the post-treatment period up to 6 days following exposure. We suggest that parent c-PAHs accumulate inside cells and that they are further activated by newly synthesised enzymes during the post-treatment period. Therefore, unaltered c-PAHs may act as a reservoir inside the cells for the long-term production of active metabolites. The total DNA adduct levels induced in HEL cells after exposure to EOM were generally low as compared with exposure to B[a]P alone under the same conditions. Human diploid lung fibroblasts possess low metabolic capacity than other human target cells. Therefore, it may be easier to competitively inhibit the metabolising enzymes in this cell system. We hypothesise that this finding might explain the generally low PAH-DNA adduct levels detected in human studies using surrogate cells such as blood WBC or lymphocytes that also possess low metabolic capacity.
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PMID:The genotoxic effect of carcinogenic PAHs, their artificial and environmental mixtures (EOM) on human diploid lung fibroblasts. 1501 5

This report reviews the literature on the genotoxicity of mainstream tobacco smoke and cigarette smoke condensate (CSC) published since 1985. CSC is genotoxic in nearly all systems in which it has been tested, with the base/neutral fractions being the most mutagenic. In rodents, cigarette smoke induces sister chromatid exchanges (SCEs) and micronuclei in bone marrow and lung cells. In humans, newborns of smoking mothers have elevated frequencies of HPRT mutants, translocations, and DNA strand breaks. Sperm of smokers have elevated frequencies of aneuploidy, DNA adducts, strand breaks, and oxidative damage. Smoking also produces mutagenic cervical mucus, micronuclei in cervical epithelial cells, and genotoxic amniotic fluid. These data suggest that tobacco smoke may be a human germ-cell mutagen. Tobacco smoke produces mutagenic urine, and it is a human somatic-cell mutagen, producing HPRT mutations, SCEs, microsatellite instability, and DNA damage in a variety of tissues. Of the 11 organ sites at which smoking causes cancer in humans, smoking-associated genotoxic effects have been found in all eight that have been examined thus far: oral/nasal, esophagus, pharynx/larynx, lung, pancreas, myeoloid organs, bladder/ureter, uterine cervix. Lung tumors of smokers contain a high frequency and unique spectrum of TP53 and KRAS mutations, reflective of the PAH (and possibly other) compounds in the smoke. Further studies are needed to clarify the modulation of the genotoxicity of tobacco smoke by various genetic polymorphisms. These data support a model of tobacco smoke carcinogenesis in which the components of tobacco smoke induce mutations that accumulate in a field of tissue that, through selection, drive the carcinogenic process. Most of the data reviewed here are from studies of human smokers. Thus, their relevance to humans cannot be denied, and their explanatory powers not easily dismissed. Tobacco smoke is now the most extreme example of a systemic human mutagen.
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PMID:Genotoxicity of tobacco smoke and tobacco smoke condensate: a review. 1557 90

We developed a real-time PCR assay for measuring relative quantities (RQ) of p53 tumor suppressor mRNA in the whitefish (Coregonus lavaretus, Salmonidae, Teleostei). Real-time PCR primers for the p53 gene were designed from a region that was found to be conserved among salmonid p53 genes. To test for the usefulness of the assay we performed a treatment study, using benzo[a]pyrene (B[a]P) a putative p53-inducer. Two groups of hatchery raised whitefish, with an average body mass of 15 g and total length of 12 cm were either given an intraperitoneal injection (10 mg x kg(-1)) of B[a]P in corn oil (2 mg B[a]P ml(-1) corn oil) or corn oil alone (Control). After treatment (48 h, 7 degrees C), two random fish from each group were anesthetized and the liver, head kidney and brain were collected for mRNA isolation and analysis. In the control fish, relative quantification analysis based on the p53 mRNA levels in liver (RQ=1.00) showed higher basal levels of p53 mRNA in the head kidney (RQ= 1.69), and lower in the brain (RQ=0.41). In all three tissues sampled, p53 mRNA was affected by treatment with B[a]P. Liver tissue showed the greatest induction (RQ=1.53) from base levels (RQ=1.00), followed by brain (RQ=1.36), and head kidney (RQ=1.23). These results confirm that p53 mRNA is generally present at lower levels in differentiated tissues (liver and brain) than in those tissues with cell lines (head kidney), and demonstrate that p53 is moderately inducible by B[a]P in the whitefish. The approach presented here has the advantage of providing rapid and accurate measures of p53 induction in various tissues of fish responding to PAH contaminant exposure.
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PMID:Real-time PCR analysis of p53 mRNA levels in tissues of whitefish (Coregonus lavaretus) exposed to benzo[a]pyrene. 1678 Jan 82

The effect of exposure to organic compounds adsorbed onto respirable air particles (<2.5microm) on DNA adducts in lymphocytes was studied in a group of non-smoking policemen (N=109, aged 35+/-0.9 years) working in the downtown area of Prague and spending >8h daily outdoors. Personal exposure to carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) adsorbed on respirable particles was monitored in each subject for 48h before biological sampling. DNA adducts were analyzed by a (32)P-postlabelling assay, and total DNA adduct levels and B[a]P-like spots were determined. Further biomarkers included cotinine levels in urine to control for exposure to tobacco smoke, plasma levels of vitamins A, E and C and polymorphisms of metabolic genotypes (GSTM1, GSTP1, GSTT1, CYP 1A1-Msp I and Ile/Val, MTHFR, MS), DNA repair genotypes (XRCC1, hOGG1 and XPD exons 6 and 23) and the p53 gene (p53 Msp I and BstU I). All the biomarkers of exposure and effect were analyzed repeatedly during a period of one year at 2-3 month intervals (January, March, June, September 2004) to cover periods with high (winter) and low (summer) levels of air pollution. The highest personal exposure to c-PAHs was found in January (8.1+/-8.8ng/m(3)), while the other three sampling periods exhibited 3-4-fold lower c-PAH exposure. The total DNA adducts were only slightly elevated in January (2.08+/-1.60) compared to March (1.66+/-0.65), June (1.96+/-1.73) and September (1.77+/-1.77). B[a]P-like DNA adducts, however, were significantly higher in January than in the March and June sampling periods (0.26+/-0.14 vs. 0.19+/-0.12 and 0.22+/-0.13, respectively; p<0.0001 and p=0.017) indicating that c-PAH exposure probably plays a crucial role in DNA adduct formation in lymphocytes. No effect of individual metabololic or DNA repair genotypes on DNA adduct levels was observed. However, the combination of two genotypes encoding enzymes metabolizing c-PAHs - CYP 1A1 and GSTM1 - was associated with the levels of total and B[a]P-like DNA adducts under conditions of increased exposure to c-PAHs. Our study suggests that DNA adducts in the lymphocytes of subjects exposed to increased c-PAH levels are an appropriate biomarker of a biologically effective dose, directly indicating whether or not the extent of exposure to these compounds is related to an increased mutagenic and carcinogenic risk.
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PMID:Biomarkers of air pollution exposure--a study of policemen in Prague. 1749 40


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