Search results for "Benzopyrenes"

Marine Actinomycetes-Derived Secondary Metabolites Overcome TRAIL-Resistance via the Intrinsic Pathway through Downregulation of Survivin and XIAP

2020

Resistance of cancer cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis represents the major hurdle to the clinical use of TRAIL or its derivatives. The discovery and development of lead compounds able to sensitize tumor cells to TRAIL-induced cell death is thus likely to overcome this limitation. We recently reported that marine actinomycetes&rsquo

Studies on the importance of microsomal epoxide hydrolase in the detoxification of arene oxides using the heterologous expression of the enzyme in ma…

1994

In order to investigate the role of the microsomal epoxide hydrolase (mEH) in the detoxification of arene oxides in the presence of a high endogenous glutathione S-transferase (GST) activity-a situation found in several organs--we expressed the rat mEH cDNA in BHK21 Syrian hamster cells. These cells have high GST activities but contain an extremely low endogenous mEH enzyme activity. We obtained several cell clones which expressed the mEH heterologously, as determined by immunoblotting. The cell clone BHK21-mEH/Mz1 had the highest level of mEH protein. Immunofluorescence showed that the level of expression was almost homogeneous throughout the cell population. Total protein isolated from th…

Effects of the modulation of epoxide hydrolase activity on the binding of benzo[a]pyrene metabolites to DNA in the intact nuclei.

1983

Microsomal activation of dibenzo[def,mno]chrysene (anthanthrene), a hexacyclic aromatic hydrocarbon without a bay-region, to mutagenic metabolites.

2002

Metabolically formed dihydrodiol epoxides in the bay-region of polycyclic aromatic hydrocarbons are thought to be responsible for the genotoxic properties of these environmental pollutants. The hexacyclic aromatic hydrocarbon dibenzo[def,mno]chrysene (anthanthrene), although lacking this structural feature, was found to exhibit considerable bacterial mutagenicity in histidine-dependent strains TA97, TA98, TA100, and TA104 of S. typhimurium in the range of 18-40 his(+)-revertant colonies/nmol after metabolic activation with the hepatic postmitochondrial fraction of Sprague-Dawley rats treated with Aroclor 1254. This mutagenic effect amounted to 44-84% of the values determined with benzo[a]py…

Synthesis and mutagenicity of the diastereomeric fjord-region 11,12-dihydrodiol 13,14-epoxides of dibenzo[a,l]pyrene.

1994

Extensive tumorigenicity studies in rodents revealed that dibenzo[a,l]pyrene (DB[a,l]P) is the most potent carcinogen among all polycyclic aromatic hydrocarbons (PAHs) tested so far. The structure of the genotoxic metabolite(s) responsible for this exceptional carcinogenicity is unknown. The fjord-region syn- and anti-DB[a,l]P-11,12-dihydrodiol 13,14-epoxides (syn- and anti-DB[a,l]PDE) were synthesized to clarify their role as possible ultimate mutagenic and carcinogenic metabolites of DB[a,l]P.9-Formyl-11,12-dimethoxybenzo[g] chrysene was prepared from 9-phenanthrylacetic acid by a photochemical route. After reaction of the aldehyde with trimethylsulfonium iodide to generate an oxiranyl si…

Tumor formation in the neonatal mouse bioassay indicates that the potent carcinogen dibenzo[def,p]chrysene (dibenzo[a,l]pyrene) is activated in vivo …

2004

The hexacyclic aromatic hydrocarbon dibenzo[def,p]chrysene, better known as dibenzo[a,l]pyrene (DBP) in the field of chemical carcinogenesis, is present in the environment as a combustion product of organic matter. This compound is probably the strongest chemical carcinogen ever tested. As ultimate genotoxic metabolites of DBP two electrophilically reactive species are discussed: (i) radical cations generated by one-electron oxidation, and (ii) fjord region dihydrodiol epoxides formed via the trans-11,12-dihydroxy 11,12-dihydro derivative of DBP (11,12-dihydrodiol). In order to delineate the metabolic pathway(s) involved in tumor formation by DBP, newborn Crl:CD-1(ICR)BR mice were intraperi…

Applications of stable V79-derived cell lines expressing rat cytochromes P4501A1, 1A2, and 2B1.

1992

1. Chinese hamster V79-derived cell lines, stably expressing cytochromes P4501A1, 1A2, and 2B1 activities, were constructed by genetic engineering in continuation of our work to establish a battery of V79 derived cell lines designed to study the metabolism of xenobiotics. 2. Cell lines XEM1 and XEM2, expressing cytochrome P4501A1, were capable of the O-dealkylation of 7-ethoxycoumarin and the hydroxylation of benzo[a]pyrene. 3. Cell lines XEMd.MZ and XEMd.NH, expressing P4501A2, were shown to hydroxylate 17 beta-estradiol and 2-aminofluorene. 4. Cell line SD1, expressing cytochrome P4502B1, was able to hydroxylate testosterone stereo- and regio-specifically at the 16 alpha and 16 beta posit…

NADPH-cytochrome P-450 reductase: Preferential inhibition by ellipticine and other type II compounds having little effect on NADPH-cytochrome c reduc…

1980

Abstract Ellipticine (5,11-dimethyl-[6H]-pyrido[4,3b]carbazole) binds with an affinity greater than most other compounds known to interact with P-450. Control and 3-methylcholanthrene-induced aryl hydrocarbon (benzo[ a ]pyrene) hydroxylase (EC 1.14.14.2) and acetanilide 4-hydroxylase and control and phenobarbital-induced ethylmorphine N -demethylase activities are all markedly inhibited by ellipticine to about the same extent. Ellipticine and other Type II compounds (metyrapone, octylamine-1, pyridine and aniline) preferentially inhibit NADPH-cytochrome P-450 reductase activity, while affecting NADPH-cytochrome c reductase activity very little. Butanol-1, a compound having pure Reverse Type…

Antibodies against homogeneous epoxide hydratase provide evidence for a single enzyme hydrating styrene oxide and benz(a)pyrene 4,5-oxide

1976

THE microsomal enzyme epoxide hydratase (EC 4.2.1.63) is potentially important in the inactivation of metabolically produced epoxides which may be responsible for the mutagenic and/or carcinogenic properties of polycyclic hydrocarbons (for reviews see refs 1–3). Reports4,5 suggest that the enzyme plays a dual role in (a) producing proximate carcinogens which, after biotransformation to carcinogens by microsomal mono-oxygenase(s) are (b) inactivated by epoxide hydratase. As this enzyme can be induced6–8, activated9–10 and inhibited9–13 it should be useful in studies of the mechanism of chemical carcinogenesis: some inverse correlations have been reported between susceptibility to carcinogene…

The catalytic activity of the endoplasmic reticulum-resident protein microsomal epoxide hydrolase towards carcinogens is retained on inversion of its…

1996

Diol epoxides formed by the sequential action of cytochrome P-450 and the microsomal epoxide hydrolase (mEH) in the endoplasmic reticulum (ER) represent an important class of ultimate carcinogenic metabolites of polycyclic aromatic hydrocarbons. The role of the membrane orientation of cytochrome P-450 and mEH relative to each other in this catalytic cascade is not known. Cytochrome P-450 is known to have a type I topology. According to the algorithm of Hartman, Rapoport and Lodish [(1989) Proc. Natl. Acad. Sci. U.S.A. 86, 5786–5790], which allows the prediction of the membrane topology of proteins, mEH should adopt a type II membrane topology. Experimentally, mEH membrane topology has been …