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PubMed1995

Excimer formation by hybridization using two pyrene-labeled oligonucleotide probes.

Pyrene excimer formation was achieved in an aqueous solution by nucleic acid hybridization. We used two different 16-mer oligonucleotide probes which had a combined continuous-sequence run complimentary to a target 32-mer. Prior to hybridization, the adjacent terminal ends (i.e., the 3'-terminal of one probe and the 5'-terminal of the other probe) were each labeled with one pyrene residue. The simultaneous hybridization of the probes to the target induced a 495-nm broad fluorescence band characteristic for pyrene excimer. Temperature and molecular configurations of the hybrid influenced the excimer formation.

Base Sequence↗

PubMed1996

Environmental and health monitoring in Lithuanian cities: exposure to heavy metals and benz(a)pyrene in Vilnius and Siauliai residents.

The Environmental and Health Monitoring program in the large cities of Lithuania is aimed at the evaluation of the population health status in terms of chemically induced diseases. During the 1991 to 1995 period, this program was carried out in two Lithuanian cities, Vilnius, the capital of the country, and Siauliai. Data on the chemical pollution of ambient air, soil, and drinking water and the morbidity were mapped. Risk zones of environmental pathology threat were defined within each city on the basis of the mapped data. Subsequently, chemical pollutants, namely, heavy metals and benz(a)pyrene, were determined in the biomedia of selected population groups in the risk zones. Exposure analysis of heavy metals (Pb, Cd, Ni, Cr, Cu, Zn) and benz(a)pyrene was carried out for standardized groups of children and pregnant women in the risk zones and in a relatively safe (control) zone. The evaluation of exposure to heavy metals was based on the levels found in blood, urine, and hair. Benz(a)pyrene was tested in urine samples. The obtained data are applied in the process of environmental health monitoring in the large cities of Lithuania.

Ambulatory Care Facilities↗

PubMed1997

Optimal configuration of pyrene excimer induced by the excimer-forming two-probe nucleic acid hybridization method.

Excimer-forming two-probe nucleic acid hybridization (ETPH) method with pyrene as a fluorophore enables homogeneous hybridization assays. We examined the effect of linker length between a pyrene residue and a terminal sugar moiety on Tm of hybrids in the presence of 20% dimethylformamide (DMF). The results including those of CD measurements indicated no interaction of pyrene residues with the duplex formed between a target 32-mer and a pyrenemethyliodoacetamide-introduced 16-mer probe (PMIA-P5)/a pyrenebutanoic acid-introduced 16-mer probe (PBuA-P3), which is the best pair of probes for intense excimer emission. This was also supported by a computer-assisted molecular modeling using Insight II and Discover software.

DNA↗

PubMed1987

Mutations and homologous recombination induced in mammalian cells by metabolites of benzo[a]pyrene and 1-nitropyrene.

Metabolites of two structurally related chemical carcinogens, benzo[a]pyrene and 1-nitropyrene, were compared for their ability to cause cytotoxicity and induce mutations in normally repairing or nucleotide excision repair-deficient diploid human fibroblasts; for their ability to induce mutations in a defined gene sequence, supF, when a plasmid containing adducts formed by these carcinogens replicates in human 293 cells; and for their ability to induce homologous recombination between duplicated genes in mouse L cells. Both of the metabolites tested, i.e., (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha, epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) and 1-nitrosopyrene (1-NOP), form adducts on guanine. BPDE binds principally at the N2 position of guanine; 1-NOP binds to guanine at the C8 position. Results of the studies in diploid human cells indicated that when compared on the basis of equal numbers of DNA adducts, BPDE is more effective than 1-NOP in inducing mutations in DNA repair-proficient cells, but when compared in repair-deficient xeroderma pigmentosum human cells that do not remove such adducts from their DNA, the frequency of mutants induced per adduct is equal. These results suggest that during the time available for repair of potentially mutagenic lesions, repair-proficient human cells excise 1-NOP adducts more rapidly than they excise BPDE adducts. Molecular analysis of the specific kinds of mutations induced when a plasmid containing BPDE residues was allowed to replicate in human cells showed that BPDE induces mainly base substitution mutations, predominantly G:C to T:A transversions.(ABSTRACT TRUNCATED AT 250 WORDS)

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed2004

Ultrafast proton-coupled electron-transfer dynamics in pyrene-modified pyrimidine nucleosides: model studies towards an understanding of reductive electron transport in DNA.

5-(Pyren-1-yl)-2'-deoxyuridine (PydU) and 5-(Pyren-1-yl)-2'-deoxycytidine (PydC) were used as model nucleosides for DNA-mediated reductive electron transport (ET) in steady-state fluorescence and femtosecond time-resolved transient absorption spectroscopy studies. Excitation of the pyrene moiety in PydU and PydC leads to an intramolecular electron transfer that yields the pyrenyl radical cation and the corresponding pyrimidine radical anion (dU.- and dC.-. By comparing the excited state dynamics of PydC and PydU, we derived information about the energy difference between the two pyrimidine radical anion states. To determine the influence of protonation on the rates of photoinduced intramolecular ET, the spectroscopic investigations were performed in acetonitrile, MeCN, and in water at different pH values. The results show a significant difference in the basicity of the generated pyrimidine radical anions and imply an involvement of proton transfer during electron hopping in DNA. Our studies revealed that the radical anion dC.- is being protonated even in basic aqueous solution on a picosecond time scale (or faster). These results suggest that protonation of dC.- may also occur in DNA. In contrast, efficient ET in PydU could only be observed at low pH values (< 5). In conclusion, we propose--based on the free energy differences and the different basicities--that only dT.- but not dC.- can participate as an intermediate charge carrier for excess electron migration in DNA.

Anions↗

PubMed1976

Independent regulation of two types of aryl hydrocarbon (benzo(a)pyrene) hydroxylase in mammalian cells.

Aryl hydrocarbon (benzo(a)pyrene) hydroxylase induced by dibutyryl cyclic AMP (dcAMP), plus aminophylline (AHH I) can be ditsinguished from the hydroxylase induced by benz (a) anthracene (AHH II) by its lower Km for benzo (a) pyrene. Treatment with the combination of benzo (a) anthracene and dcAMP plus aminophylline induced both AHH I and AHH II activities. After optimal induction of AHH II activity by benz (a) anthracene, the addition of dcAMP plus aminophylline gave an induction of AHH I. Although AHH I activity declined to an almost basal level 24 h after treatment with dcAMP plus aminophylline, the addition of benz (a) anthracene prevented this decline. Inducibility by dcAMP plus aminophylline or by benz (a) anthracene varied in different cell lines. Some cell lines were induced by both substances, with a higher induction by benz (a) anthracene, while other lines were inducible only by benz (a) anthracene, and a third cell type was not inducible by either. Selection for resistance to benzo (a) pyrene of a cell line inducible by both compounds resulted in a fourth cell type which was more inducible by dcAMP plus aminophylline than by benz (a) anthracene. The results suggest that there is an independent regulation of hydroxylase AHH I and AHH II and that the induction of these two enzyme activities is determined by different genetic controls.

Aminophylline↗

PubMed1977

Metabolism of the carcinogenic hydrocarbon benzo(a)pyrene in human fibroblast and epithelial cells. II. Differences in metabolism to water-soluble products and aryl hydrocarbon hydroxylase activity.

Aryl hydrocarbon (benzo(a)pyrene) hydroxylase (AHH) activity and metabolism of benzo(a)pyrene to water-soluble products were measured in cultures of body fibroblasts and kidney epithelial cells from different human embryos. AHH activity at 24 h after treatment with or without benz(a)anthracene was determined in cultures from 23 embryos, and 3 days' accumulated metabolism of benzo(a)pyrene to water soluble products was measured in cultures from 18 embryos. The body fibroblasts from the different embryos could be divided into three groups according to the amount of water-soluble products, but not according to the AHH activity. These three groups were not found by either assay in the cultures of kidney epithelial cells. In both fibroblast and epithelial cells, high metabolism to water-soluble products was not necessarily associated with high AHH activity. The results extend our previous finding (Huberman and Sachs, 1973) of three presumably genetic groups for BP metabolism to water-soluble products in human fibroblast but not in epithelial cells and indicate that this grouping was not found in these cells by measuring AHH activity.

Aryl Hydrocarbon Hydroxylases↗

PubMed1977

Transformation of normal hamster cells by benzo(a)pyrene diol-epoxide.

The frequency of cell transformation was determined after treatment of normal hamster embryo cells with benzo(a)pyrene (BP) and six of its metabolites. These metabolites included the trans 4,5-, 7,8- and 9,10-dihydrodiols; the 4,5-epoxide; and two stereoisomers of the non-K-region diol epoxides r-7, t-8-dihydroxy t-9, 10-oxy-7,8,9,10-tetrahydrobenzo(a)pyrene (diol-epoxide 1) and r-7, t-8, dihydroxy c-9, 10-oxy-7,8,9,10-tetrahydrobenzo(a)pyrene (diol-epoxide 11). The trans 7,8-dihydrodiol was more active than the other two dihydrodiols tested and was also more active than the parent hydrocrabon BP. Of the three epoxides tested, the diol-epoxide 1 was more active than the 4,5-epoxide and diol-epoxide 11. The results suggest that diol-epoxide 1 is a major cell-transforming metabolite of BP.

Animals↗

PubMed1979

Large interindividual variations in metabolism of benzo(alpha)pyrene by peripheral lung tissue from lung cancer patients.

A very large variation (44-fold) was observed in the ability of short-term organ cultures of peripheral lung tissue from lung-cancer patients to metabolize the environmental carcinogen benzo(alpha)pyrene to organic solvent-soluble metabolites. The amounts of benzo(alpha)pyrene (2 microM) metabolized ranged from little (1%) to almost total (96.2%) metabolism within 24 h of culture. Previous work by Kellerman et al. (1973) has suggested a relationship between susceptibility to lung cancer and the indicibility of aryl hydrocarbon hydroxylase activity in cultured human lymphocytes. The metabolic fate of carcinogenic polycyclic aromatic hydrocarbons in the respiratory tract in vivo is undoubtedly more closely mimicked by short-term organ culture of human lung than by cultured lymphocytes. Thus the very wide interindividual variation observed in pulmonary metabolism of benzo(alpha)pyrene in this study and the large variations in covalent binding to human bronchial DNA observed by Harris et al. (1976) strongly suggest that there may be little basis for screening humans for variations in lymphocyte aryl hydrocarbon hydroxylase activity as a means of assessing their susceptibility to lung cancer.

Aged↗

PubMed1993

Benzo(a)pyrene hydroxylase activity in yeast is mediated by P450 other than sterol 14 alpha-demethylase.

Benzo(a)pyrene hydroxylation has been observed in Saccharomyces cerevisiae and the role of sterol 14 alpha-demethylase (CYP51A1) in this activity has been examined by using a strain which contains a gene disruption of CYP51A1. This strain still contained P450 protein(s) with a Soret absorption maximum at 448nm in reduced carbon monoxide difference spectra of the microsomal fraction. On addition of benzo(a)pyrene to this microsomal extract a typical Type I substrate-binding spectrum was obtained and was also observed for the isogenic sister strain containing no CYP51A1 gene disruption. Microsomal extracts of both strains had equivalent activity in the aryl hydrocarbon hydroxylase assay. These results indicate a yeast benzo(a)pyrene hydroxylase activity distinct from sterol 14 alpha-demethylase P450.

Aryl Hydrocarbon Hydroxylases↗

PubMed1998

Influence of Polarity and Viscosity of the Micellar Interface on the Fluorescence Quenching of Pyrenic Compounds by Indole Derivatives in AOT Reverse Micelles Solutions.

The fluorescence quenching of the pyrene derivatives (4-(1-pyrenyl)butyl) trimethylammonium bromide (PBTMA), (1-(1-pyrenyl)methyl) trimethylammonium iodide (PMTMA), and 1-pyrene sulfonic acid (PSA) by indole methyl substituted in positions 1 and 2, tryptophan and tryptamine, was studied in AOT/heptane reverse micelles as a function of R = [water]/[AOT]. In these systems the pyrenic probes are associated to the micellar interface. Bulk and intramicellar quenching rate constants were determined for neutral indoles. The quenching rate constants of PBTMA by indole or 1,2-dimethylindole increase with R, whereas for those for PMTMA or PSA by indole the increment is much smaller. For the quenchers, tryptophan and tryptamine, that are bound to the interface of the reverse micelle, the bimolecular intramicellar quenching rate constant is much lower than in water. The results can be explained by a high microviscosity of the interface, and a micropolarity similar to that sensed by other probes. Moreover, the observed trend in the rate constants when R is varied is in line with the reported changes in micropolarity and microviscosity. Laser flash photolysis experiments show that in these systems the main result of the quenching process is the formation of the excited triplet of the probe. Copyright 1998 Academic Press.

Journal Article↗

PubMed1981

Investigation of the tumorigenic response to benzo(a)pyrene in aqueous caffeine solution applied orally to Sprague-Dawley rats.

In a lifetime experiment benzo(a)pyrene (B(a)P) was administered to Sprague-Dawley rats either as an admixture to the diet or by gavage in an aqueous 1.5% caffeine solution. Dissolved benzo(a)pyrene induced more tumors of the forestomach than undissolved benzo(a)pyrene. The 1.5% caffeine solution (annual dose 27 g/kg) did not exert any carcinogenic activity under the conditions of this bioassay.

Administration, Oral↗

PubMed1977

The Environmental fate of three carcinogens: benzo-(alpha)-pyrene, benzidine, and vinyl chloride evaluated in laboratory model ecosystems.

Radiolabeled benzo-((alpha)-pyrene, benzidine, and vinyl chloride were evaluated in laboratory model ecosystems for environmental fate, degradation pathways, bioconcentration, and food chain accumulation. The comparative effects of microsomal detoxications were evaluated using the inhibitor piperonyl butoxide. The accumulation and bioconcentration of benzo-(alpha)-pyrene and benzidine were closely correlated with their octanol/water partition coefficients and water solubility. Benzo-(alpha)-pyrene as predicted by these parameters was bioaccumulated to substantial levels in several organisms. Vinyl chloride was not accumulated because of its high volatility.

Animals↗

PubMed1986

3-Hydroxybenzo[a]pyrene glucuronidation by cells: a direct fluorometric assay in culture medium.

A direct fluorometric assay for measuring the glucuronidation by cultured cells using 3-hydroxybenzo[a]pyrene (less than 1 microM) as substrate is described. The method is based on the different characteristics in the fluorescence spectra of 3-hydroxybenzo[a]pyrene and benzo[a]pyrene-3-glucuronide. The analytical procedure operates directly on the culture medium without extraction steps. The sensitivity of detection is 1 nmol glucuronide/1 mumol substrate.

Animals↗

PubMed1984

Induction of lipid storage in cultured leukemic myeloid cells by pyrene-dodecanoic acid.

When incubated for 1-3 days in the presence of the fatty acid analog, 12-(1-pyrene)dodecanoic acid, the neutral lipid content of cultured human leukemic myeloid cells increased considerably, while that of the phospholipids increased to a much lesser extent. Among the neutral lipids, di- and monoacylglycerols predominated and a considerable portion of the fatty acyl residues of these newly synthesized neutral lipids consisted of pyrene-dodecanoic acid. Light microscopy showed evidence for the presence of highly fluorescent lipid droplets within the cells. Electron microscopy showed lipid globules, mostly devoid of a unit membrane, multivesicular inclusion bodies and some multilamellar membranous structures. In comparison, cells incubated with palmitic acid show neither these cellular structures, nor the increase of the neutral lipid content. The lipid storage, induced by pyrene-dodecanoic acid, is probably related to ineffective degradation of this fatty acid analog and might serve as an experimental model of cellular lipidosis.

Cell Division↗

PubMed1992

Vanadium redox cycling, lipid peroxidation and co-oxygenation of benzo(a)pyrene-7,8-dihydrodiol.

Mechanism of lipid peroxidation triggered by vanadium in human term placental microsomes was reinvestigated in vitro. Production of lipid peroxyl radicals was estimated from co-oxygenation of benzo(a)pyrene and benzo(a)pyrene-7,8-dihydrodiol. Vanadyl(IV), but not vanadate(V) caused a dose-dependent co-oxygenation. Vanadate(V) required the presence of reduced nicotinamide adenine dinucleotide phosphate to trigger co-oxygenation of benzo(a)pyrene-7,8-dihydrodiol. To determine the role of pre-formed lipid hydroperoxides, the results obtained with partially peroxidized linoleic acid were compared with those of fresh linoleate. Superoxide dismutase inhibited the co-oxygenation of reaction when fresh linoleic acid was used. To further characterize the role of superoxide anion-radical in the vanadium redox cycling, the increase of optical density of vanadate(V) dissolved in Tris buffer was measured at 328 nm during the addition of KO2. The rate of this reaction producing peroxy-vanadyl complex was decreased by superoxide dismutase, especially, in the presence of catalase. It is suggested that vanadium catalyzes two separate processes, both leading to enhanced lipid peroxidation: (i) initiation, dependent on superoxide and triggered by peroxy-vanadyl; (ii) propagation, dependent on pre-formed lipid hydroperoxide not sensitive to superoxide dismutase. It is postulated that the vanadium-triggered initiation of lipid peroxidation may be crucial for toxicity in organs with limited endogenous lipid peroxidation.

Chromatography, High Pressure Liquid↗

PubMed1980

Benzo[a]pyrene 4,5-oxide. Discrepancy between induction of sister chromatid exchange and binding to DNA in cultured human fibroblasts.

Benzo[a]pyrene 4,5-oxide was covalently bound to DNA of cultured human fibroblasts and caused sister chromatid exchange. The monooxygenase inhibitor alpha-napthoflavone suppressed this induction of sister chromatic exchange, but did not affect binding to DNA. Control experiments with 4-nitroquinoline 1-oxide showed that alpha-naphthoflavone does not inhibit sister chromatid exchange in general. A more likely explanation for the discrepancy between induction of sister chromatid exchange and binding to DNA is that benzo[a]pyrene 4,5-oxide itself can bind to DNA, but this binding does not lead to a significant increase in sister chromatid exchange. However benzo[a]pyrene 4,5-oxide can be oxidized by monooxygenase to yet unknown products which are potent inducers of sister chromatid exchange. An important conclusion from this is that a biological effect such as the induction of sister chromatid exchange may correlate with the exact nature of DNA binding rather than with total binding, to the point where just measuring total binding may be completely misleading if intended to detect the causes of the biological effect.

Alkylating Agents↗

PubMed1983

Endogenous induction of epoxide hydrolase, benzo(a)pyrene hydroxylase and glutathione-S-transferase in "responsive" C57Bl/6 mice and in "nonresponsive" DBA/2 mice during pregnancy.

Gestational changes in activity for three enzymes associated with different hepatic and pulmonary drug metabolizing systems were investigated in C57Bl/6 and DBA/2 mice: benzo(a)pyrene hydroxylase, epoxide hydrolase and glutathione-S-transferase. The gestational profiles of hepatic and pulmonary benzo(a)pyrene hydrolase, and epoxide hydrolase were similar in both strains. In addition, we demonstrated higher endogenous stimulation of the three studied enzymic activities in C57Bl/6 mice. During the second moiety of pregnancy, temporal variations were observed: a peak of activity occurred between days 17 and 18 for lung and liver benzo(a)pyrene hydroxylase and at day 20 for epoxide hydrolase in both strains. Hepatic glutathione-S-transferase variations were similar in both strains. However, pulmonary glutathione-S-transferase increased gradually throughout pregnancy in C57Bl/6 mice, while a peak of glutathione-S-transferase activity occurred on day 18 of gestation in DBA/2 mice.

Animals↗