Interaction of 1-ethynylpyrene and hepatic CYPIA1 from rainbow trout

1-Ethynylpyrene (EP) inhibits microsomal 7-ethoxyresorufin O-deethylase (EROD) activities from the liver of both trout and rat. Trout hepatocytes treated with EP had increased microsomal EROD activity and a concomitant increase in CYPIA1 protein as measured by Western blot analysis. EP at 10(-9)-10(-6) M did not interfere with beta-naphthoflavone (BNF) induction of CYPIA1 in trout hepatocytes. In contrast, treatment with alpha-naphthoflavone (ANF), another inhibitor of CYPIA1, resulted in a significant inhibition of the basal (at 10(-6) M ANF) and BNF induced (at 10(-8) M and higher concentrations of ANF) level of EROD activity. ANF also did not significantly induce CYPIA1 protein but led to attenuation of the induction of CYPIA1 proteins by BNF in trout hepatocyte cultures. Thus, in trout hepatocytes, EP acts differently from ANF in the modulation of CYPIA1.

Transforming activity of selected polycyclic aromatic hydrocarbons and their nitro-derivatives in BALB/3T3 A31-1-1 cells

The transforming activities of four polycyclic aromatic hydrocarbons and six of their nitro-derivatives were studied using BALB/3T3 clone A31-1-1 cells in the absence of exogenous metabolic activation. Each compound was assayed two to four times to its maximal level of solubility. A transformation response was induced by 1-nitropyrene, 2-nitropyrene, 4-nitropyrene and benzo[a]pyrene in the BALB/3T3 mouse embryo cells. Pyrene and 7-nitrobenz[a]anthracene produced questionable responses, and benz[a]anthracene, chrysene, 6-nitrobenzo[a]pyrene and 6-nitrochrysene produced negative responses. The capacity of the assay system to indicate tumorigenicity of the test compounds is discussed.

The efficiency of solvent extraction of mutagenic compounds in particulates exhausted from a small diesel engine

Organic materials were extracted from particulates exhausted from a small diesel engine (displacement 269 ml) by the ultrasonic extraction method with three different solvent systems, methanol, dichloromethane and a 4:1 (v:v) mixture of benzene and ethanol. These solvent-extracted materials were tested for mutagenic activity by the Ames Salmonella/microsome assay system using Salmonella typhimurium strains TA98, TA100, TA98NR and TA98/1,8-DNP6. The concentrations of 1-nitropyrene (1-NP) and 1,6-dinitropyrene (1,6-diNP) in these extracted materials were also measured after nitroreduction by high pressure liquid chromatography. The methanol-extracted and benzene-ethanol-extracted materials showed the lowest and the highest mutagenic activity, respectively. The methanol-extracted, dichloromethane-extracted and benzene-ethanol-extracted materials induced 260, 1,570 and 3,240 His+ revertants per plate per mg of extracted materials, respectively, from strain TA98 in the absence of S9 mix. These materials showed decreased mutagenicity for strains TA98NR and TA98/1,8-DNP6, indicating that the particulates in the diesel engine exhaust contained 1-NP and diNPs. Actually, the amount of 1-NP and 1,6-diNP in the methanol-extracted, dichloromethane-extracted and benzene-ethanol-extracted materials were 17.0 and 0.03 ng, 37.5 and 0.97 ng, and 71.3 and 1.03 ng per mg of extracted materials, respectively, accounting for 11.9 and 3.2%, 4.4 and 17.3%, and 4.0 and 8.9%, respectively, of the total mutagenicity of the extracted materials. From these results it is concluded that a mixture of benzene-ethanol (4:1, v/v) is the most suitable solvent for extraction of organic matter containing nitrated polycyclic aromatic hydrocarbons such as NPs from particulates in diesel engine exhaust.

Reactivity of cysteinyl, arginyl, and lysyl residues of Escherichia coli phosphoenolpyruvate carboxykinase against group-specific chemical reagents

Calcium-activated phosphoenolpyruvate carboxykinase from Escherichia coli is not inactivated by a number of sulfhydryl-directed reagents [5,5'-dithiobis(2-nitrobenzoate), iodoacetate, N-ethylmaleimide, N-(1-pyrenyl)maleimide or N-(iodoacetyl)-N'-(5-sulfo-1-naphthylethylenediamine)], unlike phosphoenolpyruvate carboxykinase from other organisms. On the other hand, the enzyme is rapidly inactivated by the arginyl-directed reagents 2,3-butanedione and 1-pyrenylglyoxal. The substrates, ADP plus PEP in the presence of Mn2+, protect the enzyme against inactivation by the diones. Quantitation of pyrenylglyoxal incorporation indicates that complete inactivation correlates with the binding of one inactivator molecule per mole of enzyme. Chemical modification by pyridoxal 5'-phosphate also produces inactivation of the enzyme, and the labeled protein shows a difference spectrum with a peak at 325 nm, characteristic of a pyridoxyl derivative of lysine. The inactivation by this reagent is also prevented by the substrates. Binding stoichiometries of 1.25 and 0.30 mol of reagent incorporated per mole of enzyme were found in the absence and presence of substrates, respectively. The results suggest the presence of functional arginyl and lysyl residues in or near the active site of the enzyme, and indicate lack of reactive functional sulfhydryl groups.

The adjuvant activity of pyrene in diesel exhaust on IgE antibody production in mice

In this communication, it is shown that pyrene has an adjuvant activity on IgE antibody production when mice are immunized by an intraperitoneal injection of ovalbumin (OA) or Japanese cedar pollen allergen (JCPA) with pyrene. The effects of pyrene on IgE antibody production in mice were investigated to clarify the relation between pollen allergy and the adjuvanticity of the chemical compounds contained in diesel-exhaust particulates (DEP). In the first experiment, three groups of mice were immunized intraperitoneally six times at 2-week intervals with 1 microgram of OA alone, 1 microgram of OA plus 1 mg of pyrene, and 1 microgram of OA plus 1 mg of DEP, respectively. The IgE antibody responses to OA in mice immunized with OA plus pyrene or OA plus DEP were extremely enhanced as compared with those in mice immunized with OA alone, and the highest responses were observed in mice immunized with OA plus DEP. In the second experiment, mice were immunized with 10 micrograms of JCPA alone or 10 micrograms of JCPA plus 5 mg of pyrene in the same way. The IgE antibody responses to JCPA in mice immunized with JCPA plus pyrene were higher than those in mice immunized with JCPA alone. The intraperitoneal macrophages of the mice also clearly stimulated in vitro by pyrene on chemiluminescence assay. These results suggest that pyrene contained in DEP acts as an adjuvant in IgE antibody production when mice are immunized with antigens.

Formation of DNA adducts and oxidative DNA damage in rats treated with 1,6-dinitropyrene

In vitro metabolism studies have indicated that the tumorigenic environmental pollutant 1,6-dinitropyrene has the potential to bind covalently to DNA and to induce oxidative DNA damage. We have determined if 1,6-dinitropyrene treatment will cause both types of DNA damage in vivo. Female Sprague-Dawley rats were given a single intraperitoneal injection of 1,6-dinitropyrene, and covalent DNA adduct formation, as indicated by the presence of N-(deoxyguanosin-8-yl)-1-amino-6-nitropyrene, and oxidative DNA damage, as indicated by increases in 5-hydroxymethyl-2'-deoxyuridine and 8-hydroxy-2'-deoxyguanosine, were assessed at 3, 12, 24 and 48 h after dosing. 32P-postlabeling analyses of DNA isolated from liver, mammary gland, bladder and nucleated blood cells indicated the formation of N-(deoxy-guanosin-8-yl)-1-amino-6-nitropyrene, with the levels being highest in the bladder. 5-hydroxymethyl-2'-deoxyuridine was detected in DNA from each of these tissues, and the levels of this oxidized nucleoside were higher in the mammary glands and livers of 1,6-dinitropyrene-treated rats. 1,6-Dinitropyrene dosing did not affect the levels of 8-hydroxy-2'-deoxyguanosine in these two tissues. These results indicate that exposure to 1,6-dinitropyrene can result in increased levels of 5-hydroxymethyl-2'-deoxyuridine in addition to covalent DNA adduct formation.

Determinants of protein modification versus heme alkylation: inactivation of cytochrome P450 1A1 by 1-ethynylpyrene and phenylacetylene

Reaction of cytochrome P450 enzymes with arylacetylenes results in heme N-alkylation [e.g., Komives, E. A., and Ortiz de Montellano, P. R., (1985) J. Biol. Chem. 260, 3330-3336] and/or protein modification [e.g., Gan, L.-S. L., Acebo, A. L. and Alworth, W. L. (1984) Biochemistry 23, 3827-3836]. To clarify the factors that determine whether heme or protein alkylation occurs, we have investigated the cytochrome P450 1A1-catalyzed oxidation of 1-ethynylpyrene (1-EP) and phenylacetylene (PA). Cytochrome P450 1A1 in microsomes from beta-naphthoflavone-induced rats is inactivated in a time- and NADPH-dependent manner by 1-EP and PA. Parallel loss of the heme chromophore is observed with PA but not with 1-EP, although partial heme chromophore loss is observed when the purified, reconstituted enzyme is inactivated by either agent. Product analysis shows that 1-EP and PA are oxidized to, respectively, (1'-pyrenyl)-acetic and phenylacetic acids. In contrast to the inactivation of cytochrome P450 2B1 by PA, no isotope effect is observed on enzyme inactivation or metabolite formation when the acetylenic hydrogen is replaced by deuterium in either 1-EP or PA. Inactivation of cytochrome P450 1A1 by 1-EP results in covalent binding of 0.8-0.9 equiv (relative to total cytochrome P450 content) of the inhibitor to the microsomal protein. The results demonstrate that a single isozyme can be inactivated, depending on the structure of the arylacetylene, by heme or protein alkylation. Spectroscopic binding constants (Ks) show that 1-EP binds to the enzyme with > 2000 times greater affinity that PA.(ABSTRACT TRUNCATED AT 250 WORDS)

Suicide inhibitors of cytochrome P450 1A1 and P450 2B1

The inhibition of the P450 1A1 dependent de-ethylation of 7-ethoxyphenoxazone (7EPO) and the P450 2B1 dependent de-pentylation of 7-pentoxyphenoxazone (7PPO) by 1-ethynylnaphthalene (1EN), 2-ethynylnaphthalene (2EN), 1-ethynylanthracene (1EA), 2-ethynylanthracene (2EA), 9-ethynylanthracene (9EA), 2-ethynylphenathrene (2EPh), 3-ethynylphenanthrene (3EPh), 9-ethynylphenanthrene (9EPh), 1-ethynylpyrene (1EP) and 2-ethynylpyrene (2EP) was studied in hepatic microsomal preparations from rats. Although all of the polycyclic aromatic acetylenes studied inhibited the dealkylation of 7EPO or 7PPO, only some of the acetylenes produced a mechanism-based irreversible inactivation (suicide inhibition) of the P450 dependent dealkylation of 7EPO or 7PPO. Of the molecules tested, only 1EP, 1EN, 2EN, 2EPh and 3EPh were effective suicide inhibitors of the P450 1A1 dependent de-ethylation of 7EPO and only 1EN, 2EN, 1EA and 9EPh were effective suicide inhibitors of the P450 2B1 dependent de-pentylation of 7PPO. In addition to the size and shape of the polycyclic aromatic ring system, placement of the carbon--carbon triple bond on the ring system was critical for suicide inhibition. In contrast to 1EP, 2EP was not a mechanism-based inhibitor of P450 1A1; 9EPh, but not 2EPh or 3EPh, was a suicide inhibitor of P450 2B1. None of the aryl acetylenes tested produced heme destruction under assay conditions that produced the suicide inhibition of the P450 dependent 7EPO or 7PPO dealkylation activities. Because a precise orientation of the terminal acetylene is required to produce suicide inhibition without heme destruction, acetylenic suicide inhibitors can potentially be used to differentiate between P450 isozymes and to establish some distinguishing geometric features of the active site of these isozymes.

Potent inhibitory effects of suicide inhibitors of P450 isozymes on 7,12-dimethylbenz[a]anthracene and benzo[a]pyrene initiated skin tumors

A single dose of 1-ethynylpyrene (EP), 1-vinylpyrene (VP) or 2-ethynylnaphthalene (EN) was applied to the skin of SENCAR mice 5 min before an initiating dose of 7,12-dimethylbenz[a]anthracene (DMBA) or benzo[a]pyrene (B[a]P) and the development of skin tumors then promoted with biweekly topical applications of 12-O-tetradecanoylphorbol-13-acetate (TPA). The application of EP strongly inhibited the formation of skin tumors initiated by either DMBA or B[a]P in a dose-dependent manner. Application of 44 pmol of EP inhibited tumor initiation by 10 nmol of DMBA approximately 25%; application of 440 nmol of EP inhibited tumor initiation by 200 nmol of B[a]P approximately 51%. A high single dose of EP (4.4-44 mumol) nearly eliminated skin tumor initiation by either 10 nmol of DMBA or 200 nmol of B[a]P. Application of VP also inhibited the formation of skin tumors initiated by either DMBA or B[a]P in a dose-dependent manner, but higher doses of VP than of EP were required to produce comparable inhibitions. Application of 44 nmol of VP inhibited tumor initiation by 10 nmol of DMBA approximately 30%; application of 4.4 mumol of VP inhibited tumor initiation by 200 nmol of B[a]P approximately 56%. Application of EN yielded contrasting results. EN inhibited the formation of skin tumors initiated by 10 nmol of DMBA, but the observed dose-dependence was minimal; tumors were decreased about 40% by 3.3 mumol of EN and only about 65% by 132 mumol of EN. A high single dose of EN (132 mumol) increased both the mean number of tumors per mouse and the percentage of mice that developed tumors after initiation by 200 nmol of B[a]P. Topical application of 4.4 mumol of EP, 22 mumol of VP or 33 mumol of EN to the skin of SENCAR mice 5 min before a single initiation dose of 2.5 mumol of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) had a minimal inhibitory effect (14-28%) on the development of skin tumors produced by subsequent biweekly promotion with TPA. A single dose of 44 mumol of EP or 132 mumol of EN followed by biweekly applications of TPA did not produce skin tumors; however, a dose of 44 mumol of VP followed by promotion with TPA produced a low but significant number of skin tumors.(ABSTRACT TRUNCATED AT 400 WORDS)

Purified NAD(P)H-quinone oxidoreductase enhances the mutagenicity of dinitropyrenes in vitro

The effect of highly purified rat liver cytosolic NAD(P)H-quinone oxidoreductase [EC 1.6.99.2] on the mutagenicity of 1,3- 1,6- and 1,8-dinitropyrene (DNP) was studied in the Ames Salmonella typhimurium mutagenicity assay. NAD(P)H-quinone oxidoreductase over the range of 0.02-0.8 micrograms/plate (38-1500) units increased up to threefold the mutagenicity of all three DNPs in S. typhimurium TA 98. In TA98NR, a strain deficient in "classical" nitro-reductase, the mutagenicity of 1,6- and 1,8-DNP was essentially unchanged, whereas that of 1,3-DNP was markedly reduced. NAD(P)H-quinone oxidoreductase enhanced the mutagenicity of 1,6- and 1,8-DNP to approximately equivalent extents in TA98NR and TA98. The mutagenicity of 1,3-DNP in TA98NR was potently enhanced by the addition of NAD(P)H-quinone oxidoreductase in a dose-responsive manner. In the presence of 0.8 micrograms NAD(P)H-quinone oxidoreductase, 1,3-DNP displayed a mutagenic response in TA98NR that was comparable to that obtained in TA98. NAD(P)H-quinone oxidoreductase was found to increase the mutagenicity of 1,6- but not 1,3- or 1,8-DNP to mutagenic intermediates in TA98/1,8-DNP6, a strain deficient in O-acetyltransferase activity. The results suggest that NAD(P)H-quinone oxidoreductase not only catalyzes reduction of the parent DNP but also that of partially reduced metabolites generated from that DNP. Such reductive metabolism may lead to increased formation of the penultimate mutagenic species.

Photosensitization of cultured cells and viruses by pyrene lipids

Administration of pyrene-linked fatty acids and lipids to cultured cells or an enveloped (vesicular stomatitis) virus induced photosensitization which, following irradiation with a long ultra-violet light (LUV), resulted in killing of the cells and loss of the infectivity of the virus with the following specific effects. (i) LUV illumination of the pyrene-sphingomyelin administered cultured skin fibroblasts derived from normal individuals and patients with Niemann-Pick disease permitted selective killing of the latter. (ii) Similarly LUV illumination of pyrenedodecanoic acid (P12) incubates of leukemic cell lines mixed with human bone marrow cells permitted selective killing of the former. (iii) LUV illumination of P12 incubates of vesicular stomatitis virus decreased the infectivity of the virus by up to 12 logs.

Inhibitors directed to binding domains in neutrophil elastase

Human neutrophil elastase (HNE) can be inhibited by unsaturated fatty acids, including oleic acid [Ashe, B. M., & Zimmerman, M. (1977) Biochem. Biophys. Res. Commun. 75, 194-199; Cook, L., & Ternai, B. (1988) Biol. Chem. Hoppe-Seyler 369, 627-631], but is not affected by saturated fatty acids. We have shown that the interaction of oleic acid with HNE can be characterized by two apparent inhibitory modes: a high-affinity mode (Ki = 48 +/- 3 nM), resulting in partial noncompetitive inhibition (87% residual activity), and a competitive inhibitory mode of lower affinity (Ki = 16 +/- 1 microM). Binding of oleate in the high-affinity mode induces a blue shift in the endogenous fluorescence arising from the tryptophan residues in HNE. This shift is maximal in the presence of 1 microM oleate; higher concentrations of fatty acid have no further effect on the fluorescence spectrum. The negatively charged fluorescent ester of oleic acid and hydroxypyrenetrisulfonate (HPTSoleate) interacts with HNE at an apparent single site (Ki = 44 +/- 3 nM), resulting in competitive inhibition. A blue shift in the emission maximum of the pyrene fluorescence at 410 nm and a decrease in the ratio of the intensities of the maximum at 388 and 410 nm indicate that upon binding to HNE the environment of the pyrene ring in HPTSoleate becomes more hydrophobic.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of nucleotide excision repair in human cells on intrachromosomal homologous recombination induced by UV and 1-nitrosopyrene

To study the role of nucleotide excision repair in the induction of intrachromosomal homologous recombination in mammalian cells, we introduced a plasmid containing a substrate for recombination into three human cell lines that differ in their repair capacity and compared the frequency of recombination induced by UV radiation and by 1-nitrosopyrene. One strain had a normal capacity for nucleotide excision repair, the second exhibited an intermediate rate of repair, and the third, derived from a patient with xeroderma pigmentosum, had no ability to repair UV- or 1-nitrosopyrene-induced DNA damage. The endogenous thymidine kinase genes in these cell strains had been inactivated, and the cells contained an integrated copy of a plasmid carrying duplicated copies of the herpes simplex virus type 1 thymidine kinase (Htk) gene, each inactivated by an 8-base-pair XhoI site inserted at a unique site. A functional tk gene can only be generated by a productive recombination event between the two Htk genes. In all three stains, UV and 1-nitrosopyrene induced dose-dependent increases in the frequency of recombinants. However, the doses required to cause a specific increase in recombination in the repair-deficient strains were 10 to 30 times lower than the dose required for the cell strain with a normal capacity for repair. These results strongly suggest that unexcised DNA lesions, rather than excision repair per se, stimulate intrachromosomal homologous recombination. Southern blot analysis of DNA from representative recombinants indicated that in all cases one of the two Htk genes had become wild type (XhoI resistant). The majority (90%) retained the Htk duplication, consistent with nonreciprocal transfer of genetic information (gene conversion).

Inhibition of the binding of 7,12-dimethylbenz[a]anthracene and benzo[a]pyrene to DNA in mouse skin epidermis by 1-ethynylpyrene

The effects of 1-ethynylpyrene (EP), 1-vinylpyrene (VP) and 2-ethynlnaphthalene (EN) on the covalent binding of 7,12-dimethylbenz[a]anthracene (DMBA) and of benzo[a]-pyrene (B[a]P) to the epidermal DNA in mouse skin were investigated. When applied topically, 5 min before an initiating dose of 10 nmol DMBA or of 200 nmol B[a]P, EP was an effective inhibitor of the formation of the covalent complexes of these procarcinogenic polycyclic aromatic hydrocarbons (PAHs) with the epidermal DNA. VP, applied under the same conditions, was a significantly less effective inhibitor of the binding of DMBA to DNA and showed even weaker inhibition of the binding of B[a]P. EN was ineffective as an inhibitor of the binding of either DMBA or B[a]P. These results establish that both the pyrene nucleus and the ethynyl substituent of EP contribute to the effective inhibition of the binding of DMBA and B[a]P to the epidermal DNA of mouse skin. No significant changes in the ratios of the anti- to the syndiol epoxide-DNA adducts of DMBA or of B[a]P were produced by doses of EP that produced inhibitions of the binding to DNA. At doses of VP that inhibited covalent binding of both DMBA and B[a]P, no changes in DMBA-DNA adduct distributions were observed but changes in the relative proportions of several B[a]P-DNA adducts were noted. These data are discussed in terms of the potential of aryl acetylenes to act as suicide inhibitors (mechanism-based inactivators) of cytochrome P450-dependent monooxygenase isozymes.

Effects of 1-ethynylpyrene and related inhibitors of P450 isozymes upon benzo[a]pyrene metabolism by liver microsomes

The effects of three aryl acetylenes, 1-ethynylpyrene (EP), 2-ethynylnaphthalene (EN) and 3-ethynylperylene (EPE), upon the metabolism of benzo[a]pyrene (BaP) by microsomes isolated from rat liver were investigated. These aryl acetylenes all inhibited the total metabolism of BaP. Formation of BaP 7,8-dihydrodiol and BaP tetrol products by microsomal preparations from rats that had been pretreated with 3-methylcholanthrene (3MC) were preferentially inhibited. The effects of EP upon the metabolism of BaP 7,8-dihydrodiol by microsomes from rat liver were also studied. This aryl acetylene strongly inhibited the formation of BaP tetrols from BaP 7,8-dihydrodiol by liver microsomes both from untreated rats and from rats pretreated with 3MC, but enhanced the conversion of the BaP dihydrodiol into other metabolites.

Cytotoxic and transformation responses of rat tracheal epithelial cells exposed to nitrated polycyclic aromatic hydrocarbons in culture

Four nitropolycyclic aromatic hydrocarbons (NPAHs) were investigated for their cytotoxic effects on rat tracheal epithelial (RTE) cells. 6-Nitrochrysene (6-NC), 1,6-dinitropyrene (1,6-DNP), 1-nitropyrene (1-NP) and 4-nitropyrene (4-NP) induced dose-dependent decreases in the relative colony-forming efficiency (RCFE) of RTE cells. The compounds could be separated into two groups based on their cytotoxic potencies, a group that displayed high cytotoxic effects (6-NC and 1,6-DNP), and a group that displayed low cytotoxic effects (1-NP and 4-NP). The most cytotoxic compound was 6-NC, with an ED50 of 0.13 microM, followed by 1,6-DNP, 4-NP and 1-NP with ED50s of 1.25, 8.9 and 9.1 microM, respectively. The most cytotoxic compound (6-NC) and one of the components with low cytotoxicity (1-NP) were assayed for their ability to induce preneoplastic transformation of RTE cells using equally toxic doses of both compounds. The frequencies of transformation induced by 6-NC in cells isolated from control animals or from animals pretreated with 3-methylcholanthrene (3-MC) were 8.4 X 10(-3) and 21.4 X 10(-3), respectively. 1-NP did not induce cell transformation. Equally toxic doses of the direct acting carcinogen N-methyl-N'-nitro-N-nitrosoguanidine, used as a positive control, induced transformation frequencies of 8.7 X 10(-3) and 6.4 X 10(-3) in cells isolated from control animals or from animals pretreated with 3-MC, respectively. These studies show that RTE cells have the metabolic capacity to activate NPAHs to toxic metabolites; thus, the RTE system should be very useful for evaluating the potential toxic effects of this ubiquitous class of airborne pollutants. In addition, the observed differences in cellular toxicity and transformation capabilities of 6-NC and 1-NP were consistent with the results of other studies that demonstrated the greater potency for induction of tumors in animals of 6-NC relative to 1-NP.

DNA binding by 1-nitropyrene and dinitropyrenes in vitro and in vivo: effects of nitroreductase induction

1-Nitropyrene, the predominant nitropolycyclic aromatic hydrocarbon found in diesel exhaust, is both a mutagen and a tumorigen. 1,6-Dinitropyrene is present in diesel exhaust in much smaller quantities than is 1-nitropyrene, but is much more mutagenic and carcinogenic. In an attempt to understand this difference in biological potencies, we have compared the extents to which these two nitropyrenes bind DNA in vivo. We have also determined the effect of 1-nitropyrene pretreatment upon the induction of nitroreductases and the subsequent DNA binding by both 1-nitropyrene and 1,6-dinitropyrene. In subsequent experiments, we have examined the importance of acetylation phenotype in the formation of DNA adducts from dinitropyrene in vivo. After a single intraperitoneal injection of 1-nitropyrene, covalent DNA binding could not be detected in vivo; however, 1,6-dinitropyrene formed N-(deoxyguanosin-8-yl)-1-amino-6-nitropyrene as the major DNA adduct in rat liver, kidney, urinary bladder, and mammary gland, with the highest levels being found in the bladder. The capability of liver microsomes to catalyze the oxidative metabolism of 1-nitropyrene was unchanged after treating rats with a single dose of 8 mg of 1-nitropyrene per kilogram of body weight. Cytochrome P-450, reduced nicotinamide adenine dinucleotide phosphate (NADPH2)-cytochrome P-450 reductase, and cytochrome b5 levels were also unchanged, while slight increases were detected in reduced nicotinamide adenine dinucleotide (NADH)-cytochrome b5 reductase and epoxide hydrase activities. Liver cytosolic and microsomal nitroreductase activities toward both 1-nitropyrene and 1,6-dinitropyrene were increased twofold, and cytosolic nitrosoreductase activity toward 1-nitrosopyrene and 1-nitro-6-nitrosopyrene was elevated by about 20 percent. DNA binding of both 1-nitropyrene and 1,6-dinitropyrene in vitro was twofold higher when cytosol from rats pretreated with 1-nitropyrene was used. However, pretreatment of rats with 1-nitropyrene only slightly increased the amount of in vivo DNA binding by 1,6-dinitropyrene except in the kidney, where there was a 60 percent increase. In the presence of S-acetylcoenzyme A, liver cytosol from slow-acetylator phenotype hamster strains Bio. 1.5 and 82.73 catalyzed the binding of two-to-three times more 1,8-dinitropyrene to DNA than was observed with the fast-acetylator phenotype strain Bio. 87.20. Similarly, when 1,8-dinitropyrene was administered in vivo and the extent of binding was assayed in liver, bladder, and intestinal DNA, there was more binding in strain Bio. 1.5 than in strain Bio. 87.20.(ABSTRACT TRUNCATED AT 400 WORDS)

Oxygen diffusion-concentration in erythrocyte plasma membranes studied by the fluorescence quenching of anionic and cationic pyrene derivatives

Fluorescence quenching by oxygen of cationic [pyrene-(CH2)nN(CH3)3+; n = 1, 4, and 11] and anionic [pyrene-(CH2)nCO2-, n = 3, 8, 11, and 15] probes was investigated in erythrocyte plasma membranes (leaky) in order to assess the ability of oxygen molecules to interact with solutes located at different positions in the membrane. The pseudounimolecular quenching rate constants measured increase, both for cationic and anionic probes, when n increases. These results are interpreted in terms of an increased oxygen solubility toward the center of the membrane interior, and imply that lateral diffusion contributes more than transverse diffusion to total oxygen mobility. For all of the probes considered, quenching rates increase when n-alkanols are added. The effect observed increases when n decreases and when the size of the n-alkanol alkyl chain increases. Arrhenius-type plots for the quenching rate constants show noticeable downward curvatures. Average (0-40 degrees C) activation energies are approximately 6 kcal/mol.

Ability of structurally related polycyclic aromatic carcinogens to induce homologous recombination between duplicated chromosomal sequences in mouse L cells

To investigate the role of DNA damage in the induction of homologous recombination in mammalian cells, a series of structurally related, polycyclic aromatic carcinogens, i.e., 1-nitrosopyrene (1-NOP), N-acetoxy-2-acetylaminofluorene (N-AcO-AAF), and 4-nitroquinoline 1-oxide (4-NQO), were compared for their ability to cause intrachromosomal homologous recombination between two herpes simplex virus thymidine kinase (Htk) genes stably integrated in the genome of a tk- mouse L cell strain 333 M. Each Htk gene contains an 8-bp XhoI linker inserted at a unique site so that expression of a functional Htk enzyme requires a productive recombinational event between the two nonfunctional genes. Each carcinogen caused a dose-dependent increase in the frequency of recombination. The results were compared to what had been found previously for a structurally related carcinogen, (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE). As a function of concentration, BPDE was the most active agent, followed by 4-NQO, and 1-NOP, and then N-AcO-AAF. When compared on the basis of equal cell killing, the most efficient carcinogen was 1-NOP, followed by N-AcO-AAF and BPDE, and then 4-NQO. Use of tritium-labeled compounds to determine the frequency of recombination as a function of the number of adducts initially bound to DNA showed that the most effective agent was BPDE, followed by 1-NOP and 4-NQO, and then N-AcO-AAF (ratio, 6.6:2.5:1.8:1.0). To determine if these differences in recombinagenic effectiveness reflected different rates of removal of the adducts from DNA, we measured the percentage of DNA adducts removed during the 24-h period post treatment and found that 1-NOP, 4-NQO and N-AcO-AAF residues were removed at approximately the same rate, i.e., 25%-30% off. Cellular analysis of a series of independent recombinants indicated that approximately 82% of the recombinational events induced by each agent were consistent with gene conversion. DNA-DNA hybridization analysis confirmed this, and showed that each recombinant tested contained an XhoI-resistant (wild-type) Htk gene; with the majority retaining the Htk gene duplication, consistent with nonreciprocal transfer of wild-type genetic information. In the rest, only a single copy of the Htk gene remained, reflecting a single reciprocal exchange within a chromatid or a single unequal exchange between sister chromatids.

[The spatial interrelationships between influenza virus hemagglutinin and the lipid phase in the liposomal membrane]

A scheme has been proposed demonstrating the location of tryptophan residues of hemagglutinin molecule in relation to the middle of the lipid layer 1.2 nm thick with a fluorescent probe pyrene. In the immediate proximity to it, one tryptophanyl of protein molecule is located in a hydrophobic "pocket". At a distance of 2.85 nm from the middle of the lipid zone 3 tryptophanyls are located and the remaining five at a distance over 3.6 nm. After treatment with proteolytic enzyme bromelin of the liposomes with hemagglutinin incorporated into their bilayer, the hydrophobic "anchor" of protein molecule contains one tryptophanyl which is raised by 0.3 nm and its hydrophobic environment is changed.

Activation of two environmental mixtures by plant S9

Nitrated and ozonized pyrene mixtures were assayed for their mutagenic activity in the presence or absence of pea S9 using Salmonella typhimurium TA98 as the indicator organism. The plant enzymes increased the mutagenic response of these mixtures above that obtained in the absence of S9. The optimum S9 protein concentration for the activation of the nitrated pyrene mixture at 0.1 microgram was 3.9 mg/plate whereas that for the ozonized pyrene mixture at 33.3 micrograms was 3.2 mg protein/plate. BSA could not replace S9, and NADPH was a required co-factor in the activation of both mixtures by pea S9. Although the nitrated pyrene mixture was determined to consist of approximately 90% 1-nitropyrene, the mutagenic response due to this compound ranged from 30 to 50% of that of the mixture.

The clastogenic activity of 1,6-dinitropyrene in peripheral human lymphocytes

The ability of 1,6-dinitropyrene to induce chromosome damage in peripheral human lymphocyte cultures has been demonstrated. Low levels of clastogenic activity were detected following 3-h treatments with 1,6-dinitropyrene in the presence of a rat-liver cytosol fraction. The clastogenic activity reached a peak at a concentration of 1.25 micrograms/ml of 1,6-dinitropyrene after which the frequency of aberrations decreased. This unusual genotoxic dose response is similar to that found previously in yeast and rat-liver cells. The fact that a positive result was obtained using human lymphocytes shows that, in the presence of the appropriate activation system, dinitropyrene is genotoxic in human cells.

Kinds and spectrum of mutations induced by 1-nitrosopyrene adducts during plasmid replication in human cells

1-Nitropyrene has been shown in bacterial assays to be the principal mutagenic agent in diesel emission particulates. It has also been shown to be mutagenic in human fibroblasts and carcinogenic in animals. To investigate the kinds of mutations induced by this carcinogen and compare them with those induced by a structurally related carcinogen, (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetra-hydrobenzo [a]pyrene (BPDE) (J.-L. Yang, V. M. Maher, and J. J. McCormick, Proc. Natl. Acad. Sci. USA 84:3787-3791, 1987), we treated a shuttle vector with tritiated 1-nitrosopyrene (1-NOP), a carcinogenic mutagenic intermediate metabolite of 1-nitropyrene which forms the same DNA adduct as the parent compound, and introduced the plasmids into a human embryonic kidney cell line, 293, for DNA replication to take place. The treated plasmid, pZ189, carrying a bacterial suppressor tRNA target gene, supF, was allowed 48 h to replicate in the human cells. Progeny plasmids were then rescued, purified, and introduced into bacteria carrying an amber mutation in the beta-galactosidase gene in order to detect those carrying mutations in the supF gene. The frequency of mutants increased in direct proportion to the number of DNA-1-NOP adducts formed per plasmid. At the highest level of adduct formation tested, the frequency of supF mutants was 26 times higher than the background frequency of 1.4 X 10(-4). DNA sequencing of 60 unequivocally independent mutant derived from 1-NOP-treated plasmids indicated that 80% contained a single base substitution, 5% had two base substitutions, 4% had small insertions or deletions (1 or 2 base pairs), and 11% showed a deletion or insertion of 4 or more base pairs. Sequence data from 25 supF mutants derived from untreated plasmids showed that 64% contained deletions of 4 or more base pairs. The majority (83%) of the base substitution in mutants from 1-NOP-treated plasmids were transversions, with 73% of these being G . C --> T . A. This is very similar to what we found previously in this system, using BPDE, but each carcinogen produced its own spectrum of mutations. Of the five hot spots for base substitution mutations produced in the supF gene with 1-NOP, two were the same as seen with BPDE-treated plasmids. However, the three other hot spots were cold spots for BPDE-treated plasmids. Conversely, four of the other five hot spots seen with BPDE-treated plasmids were cold spots for 1-NOP-treated plasmids. Comparison of the two carcinogens for the frequency of supF mutants induced per DNA adduct showed that 1-NOP-induced adducts were 3.8 times less than BPDE adducts. However, the 293 cell excised 1-NOP-induced adducts faster than BPDE adducts.

[Reversible inhibition of cholinesterases by salts of pyrilium, thiopyrilium and selenopyrilium derivatives]

Salts of pyrilium, thiopyrilium and selenopyrilium derivatives at pH 7.5 and temperature of 25 degrees C are studied for their effect on the catalytic activity of acetyl cholinesterase (EC 3.1.1.7) of human blood erythrocytes and butyryl cholinesterase (EC 3.1.1.8) of horse blood serum which is measured by the method of potentiometric titration. All enumerated salts are established to be strong reversible inhibitors of mixed-type cholinesterases, that is testified by small values of the inhibitory constants: competitive Ki, noncompetitive K'i and generalized K epsilon. Pyrilium and selenopyrilium salts inhibit acetyl cholinesterase of human blood erythrocytes to a higher extent than butyryl cholinesterase of horse blood serum, and thiopyrilium salts inhibit the latter to the highest extent. By the value of the inhibitory effect on acetyl cholinesterase of human blood erythrocytes thiopyrilium salts exceed the analogous pyrilium salts, whereas in experiments with butyl cholinesterase of horse blood serum there is an opposite dependence.

Adsorption of mutagens by refined corn bran

Refined corn bran (RCB), a dietary fiber derived from the mechanical refining of corn hulls, effectively adsorbed various environmental mutagens. When RCB was added at a concentration of 10 mg/ml to an aqueous solution of dinitropyrene (DNP), 91.6% of the mutagenicity towards Salmonella tester strain TA98 disappeared. Under similar conditions decreases in mutagenicity of DNP using wheat bran and cellulose powder were 58.4% and 43.0%, respectively. The adsorption of DNP to the fibers appeared irreversible since little mutagenicity was recovered by washing the treated fibers with aqueous buffer solutions of various pHs. Even with an organic solvent (methanol: ammonium hydroxide 50:1), only 2/3 of the mutagenicity of DNP was recovered. RCB could similarly adsorb mutagenic heterocyclic amines such as IQ, Trp-P-1, Trp-P-2, Glu-P-1, and Glu-P-2.