Protease inhibitor-induced stabilization of p21(waf1/cip1) and cell-cycle arrest in chemical carcinogen-exposed mammary and lung cells

In previous studies, we have shown that human breast and lung carcinoma cells and mouse nontransformed type II lung cells fail to undergo cell-cycle arrest in G(1) phase in response to treatment with hydrocarbon carcinogens but rather accumulate in the S phase with damaged DNA. This situation may lead to replication of DNA on a damaged template and enhance frequency of mutations. The mechanism of this G(1) arrest failure was examined. Western immunoblot analyses of MCF7 human mammary cancer cells exposed to actinomycin D (used as a positive control for G(1) cell-cycle arrest) or hydrocarbon carcinogens revealed that while all of these chemicals caused an increase in p53, only trace levels of p21(waf1/cip1) protein were observed in the hydrocarbon carcinogen-treated samples. Similarly, in murine lung E10 type II cells, p53 but not p21(waf1/cip1) protein increased in response to benzo[a]pyrene dihydrodiol epoxide. Treatment of either MCF7 mammary or E10 lung cells with the protease inhibitor calpain I resulted in increased levels of p21(waf1/cip1) protein and enhancement of arrest of the cells in early phases of the cell cycle (G(1) and early S phase). The results suggest that failure of cell-cycle arrest in carcinogen-treated mammary and lung cells is related to increased protease-mediated degradation of p21(waf1/cip1) and/or related regulatory proteins.

Activation of estrogen receptor beta is a prerequisite for estrogen-dependent upregulation of nitric oxide synthases in neonatal rat cardiac myocytes

Physiological effects of estrogen on myocardium are mediated by two intracellular estrogen receptors, ERalpha and ERbeta, that regulate transcription of target genes through binding to specific DNA target sequences. To define the role of ERbeta in the transcriptional activation of both endothelial (eNOS) and inducible nitric oxide synthase (iNOS) in cardiac myocytes, we used the complete ER-specific antagonist R,R-tetrahydrochrysene (R,R-THC). R,R-THC inhibited activation of iNOS/eNOS promoter-luciferase reporter constructs (iNOS/eNOS-Luc) in a dose-dependent fashion in COS7 cells selectively transfected with ERbeta, but failed to influence ERalpha-mediated increase of iNOS/ eNOS-Luc. In neonatal rat cardiomyocytes transfected with eNOS-Luc or iNOS-Luc, incubation with 17betaestradiol (E2, 10(-8) M) for 24 h stimulated expression of eNOS and iNOS. R,R-THC (10(-5) M) completely inhibited this effect. Furthermore, eNOS and iNOS protein expression in cardiac myocytes induced by E2 was completely blocked by R,R-THC as shown by immunoblot analysis. Taken together, these results show that ERbeta mediates transcriptional activation of eNOS and iNOS by E2.

Synthesis and evaluation of hexahydrochrysene and tetrahydrobenzofluorene ligands for the estrogen receptor

To prepare novel estrogen receptor (ER) ligands, we have developed a facile approach to substituted hexahydrochrysene and tetrahydrobenzo[a]fluorene systems. Substituents, including basic side chains, were added to these systems, and their binding affinity to ERalpha and ERbeta, and in some cases their transcriptional activity were evaluated.

Polycyclic aromatic compounds as anticancer agents: structure-activity relationships of chrysene and pyrene derivatives

A large number of diamides and diamines were synthesized using 6-amino chrysene and 1-amino pyrene as starting materials. A structure activity study with cis-platinum as internal control against animal and human tumor lines was carried out in vitro. This study indicated that the in vitro cytotoxicity toward these lines depends on the functionality present in the molecules. The diamino compounds were found to be more potent than the diamides, and these were equally active irrespective of the end heterocyclic group, whereas the activity of the diamides was strongly dependent on the terminal unit. In general, the diamides containing chrysene as the chromophore were more active than those with a pyrene ring. The size of the end heterocyclic ring, along with the nature of the spacer connecting the polycyclic ring to the heterocyclic ring, seemed to affect the biological activity in certain cell lines. Hemolysis experiments on a lead compound established that it had activities similar to those described for membrane-stabilizing agents. This agent also demonstrated the capacity to produce differentiation in leukemia cell lines.

Induction of cytochrome P450 1A1 in human hepatoma HepG2 cells by 6-nitrochrysene

The present study has determined the effects of 6-nitrochrysene (6-NC) on human cytochrome P450-dependent monooxygenases in human hepatoma HepG2 cells. Treatment of HepG2 cells with 6-NC increased the activities of microsomal benzo[a]pyrene hydroxylase, 7-ethoxycoumarin and 7-ethoxyresorufin O-deethylases, cytosolic glutathione S-transferase and N-acetyltransferase, and S9 metabolic activation of 6-NC in the Ames mutagenicity test. Immunoblot and RNA blot analyses revealed that 6-NC induced CYP1A1 protein and mRNA levels in the hepatoma cells. Nuclear transcription assay demonstrated that 6-NC increased the transcription rate of CYP1A1 gene in HepG2 cells. Treatment of human lung carcinoma NCI-H322 cells with 6-NC increased benzo[a]pyrene hydroxylase activity and CYP1A1 protein and mRNA levels. These results demonstrate that 6-NC is an inducer of human CYP1A1 and the induction occurs at a transcriptional level in HepG2 cells. The ability of 6-NC to induce liver and lung CYP1A1 may be an important factor to consider in assessing 6-NC metabolism and toxicity in humans.

Polycyclic aromatic compounds as anticancer agents: synthesis and biological evaluation of some chrysene derivatives

Synthesis and biological evaluation of new chrysene derivatives aimed at the development of anticancer agents were carried out.

Induction of cytochrome P450 1A in hamster liver and lung by 6-nitrochrysene

The present study has determined the effect of 6-nitrochrysene (6-NC) on hepatic and pulmonary cytochrome P450 (P450)-dependent monooxygenases using hamsters pretreated with the nitrated polycyclic aromatic hydrocarbon (nitro-PAH) at 5 mg/kg per day for 3 days. Pretreatment with 6-NC elevated serum gamma-glutamyltranspeptidase, lactate dehydrogenase, and bilirubin levels. Liver S9 fractions prepared from controls and hamsters pretreated with 6-NC markedly increased mutagenicity of the nitro-PAH in Salmonella typhimurium tester strains TA98, TA100, and TA102. The pretreatment selectively increased 1-nitropyrene reductase activities of lung cytosol and liver and lung microsomes. Pretreatment with 6-NC resulted in increases of microsomal 7-ethoxyresorufin and methoxyresorufin O-dealkylases activities in liver and lung without affecting the monooxygenase activities in kidney. Immunoblot analysis of microsomal proteins using mouse monoclonal antibody 1-12-3 to rat P450 1A1 revealed that 6-NC induced P450 1A-immunorelated proteins in liver and lung. RNA blot analysis using mouse P450 1A1 cDNA showed that 6-NC increased liver and lung P450 1A mRNA. 6-NC had no effect on the kidney P450 protein and mRNA. The present study demonstrates that the hamster enzymes can support 6-NC metabolic activation and the nitro-PAH induces liver and lung P4501A via a pretranslational mechanism.

Cellular response to DNA damage from a potent carcinogen involves stabilization of p53 without induction of p21(waf1/cip1)

The effect of a potent mammary carcinogen, anti benzo[g]chrysene 11,12-dihydrodiol 13,14-epoxide, on the progress of human mammary carcinoma MCF-7 cells through the cell cycle was investigated. While these cells, which express wild-type p53, were arrested in G1 after treatment with actinomycin D (a positive control), treatment with the mammary carcinogen did not cause G1 arrest but instead delayed the cells in the DNA synthesis phase. In concert with the absence of a G1 arrest, it was found that though both chemical treatments led to increased levels of p53, only the p53 induced by actinomycin D was transcriptionally active and increased the levels of the cyclin dependent kinase inhibitor, p21(waf1/cip1). Since treatment of the cells with the mammary carcinogen did not abrogate the G1 arrest induced by actinomycin D, the lack of p21(waf1/cip1) and of G1 arrest, resulting from treatment with the mammary carcinogen alone, was not due to some general inhibition of transcription or translation. An analogous difference between these two chemicals was demonstrated also in other human cell systems. The stealth-like property of the mammary carcinogen that allows it to damage DNA without turning on the cells' 'guardian of the genome' defense mechanism presumably increases the likelihood of malignant change because DNA replication continues on a damaged template. It is suggested that this stealth characteristic may be a major contributor to the high carcinogenic potency of this mammary carcinogen and possibly to that of other highly potent carcinogens.

Regulation of c-jun by lung carcinogens in Clara cells of hamsters

In vitro differentiated hamster Clara cells were used to study the effects of lung carcinogens on the regulation of the c-jun oncogene. Northern blot analysis revealed a decrease in the expression of jun transcripts 24 h following the exposure of Clara cells to the direct acting forms of benzo[a]pyrene (BPDE*) or 5-methylchrysene (5MeCDE). To determine whether this decrease was mediated at the transcriptional level, we have used CAT reporter constructs driven by nested deletions of the 5' non-coding regulatory region of the c-jun oncogene. While BPDE was capable of activating certain regulatory domains of the c-jun promoter, this activation was not observed with either 5MeCDE or the less active lung carcinogens BADE or 6MeCDE. Analysis of enhancer elements identified the SP1 target site as a strong silencer after BPDE treatment. While positive regulatory element(s) mediating activation of c-jun by BPDE were localized within the promoter region up to -1639, further upstream sequences reduced this transcriptional activation. Thus, when the complete promoter region, up to -4500, was tested, no transcriptional activation was noted following BPDE treatment. These observations suggest that the regulation of c-jun in Clara cells exposed to potent lung carcinogens is mediated at the post-transcriptional level, possibly by reducing the stability and, in turn, the half life of c-jun mRNA. Overall, in contrast to the response of c-jun to numerous carcinogens and stress inducing agents noted in various other cell systems, our findings suggest the existence of a tissue-specific regulatory response for c-jun.

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.

Products formed from the in vitro reaction of metabolites of 3-aminochrysene with calf thymus DNA

3-Aminochrysene, a mutagenic geometric isomer of the mutagenic and carcinogenic aromatic amine 6-aminochrysene, has been synthesized and its metabolic activation studied by characterization of the products formed from the reaction of metabolites with calf thymus DNA. DNA adducts produced by 3-aminochrysene via N-oxidation were examined by preparing 3-nitrosochrysene and incubating the nitroso derivative with calf thymus DNA in the presence of ascorbic acid (to generate the N-hydroxy derivative) at pH 5. The major adduct, as determined by 1H-NMR and thermospray-mass spectrometry of the modified nucleoside obtained after enzymatic hydrolysis of the modified DNA, was N-(deoxyguanosin-8-yl)-3-aminochrysene. Thus, the reaction of N-hydroxy-3-aminochrysene with DNA differs from that of N-hydroxy-6-aminochrysene, which had previously been shown to generate N-(deoxyguanosin-8-yl)-6-aminochrysene, 5-(deoxyguanosin-N2-yl)-6-aminochrysene and N-(deoxyinosin-8-yl)-6- aminochrysene as major adducts. 32P-Postlabeling analysis of DNA treated with 3-aminochrysene in the presence of liver microsomes from rats pretreated with phenobarbital indicated an adduct pattern identical to that seen with DNA that had been treated with 3-nitrosochrysene and ascorbic acid. However, DNA treated with 3-aminochrysene (3-AC) in the presence of liver microsomes from rats pretreated with 3-methylcholanthrene contained a major adduct that was chromatographically distinct from N-(deoxyguanosin-8-yl)-3-aminochrysene.

WF11605, an antagonist of leukotriene B4 produced by a fungus. I. Producing strain, fermentation, isolation and biological activity

WF11605, a new antagonist of leukotriene B4 (LTB4) was isolated as a product of fungal strain F11605. The molecular formula of WF11605 was determined to be C38H60O11. WF11605 inhibited LTB4-induced chemotaxis of rabbit polymorphonuclear leukocytes (PMNLs) with an IC50 value of 1.7 x 10(-7) M and blocked 3H-LTB4 binding to PMNL membranes at 5.6 x 10(-6) M (IC50). WF11605 also inhibited LTB4-induced degranulation of rabbit PMNLs at 3.0 x 10(-6) M (IC50). However, WF11605 did not show any inhibitory effect on platelet activating factor (PAF)- and N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP)-induced degranulation at concentrations up to 10(-4) M. These results suggest that WF11605 is a specific antagonist of LTB4.

WF11605, an antagonist of leukotriene B4 produced by a fungus. II. Structure determination

The structure of WF11605, a novel tetracyclic triterpene glucoside, was determined to be 1. The plane structure of deacetyl-WF11605 aglycone was elucidated as 2 through the concerted application of a series of 2D NMR techniques. The relative configurations were established by X-ray crystallographic analysis of bis(p-bromobenzoyl) derivative 3 and absolute stereochemistry by CD exciton chirality method.

An efficient multiple-exposure analysis of the toxicity of crisnatol, a DNA intercalator in phase II clinical trials

To investigate the toxicity and mechanism of action of crisnatol (CRS), a new DNA intercalator currently in phase II clinical trials, we analyzed cellular and nuclear flow cytometric (FCM) parameters of murine erythroleukemic cells (MELC) exposed to a range of CRS concentrations over three exposure conditions: short-term (4 h), long-term (24 h), and short-term with recovery (4 h+/19 h-). At 0.5-1.0 microM CRS, 4 h exposure results in a reversible G2-phase block, while 24 h exposure results in greater than G2 polyploidy. At 5-10 microM CRS concentrations, cells exhibit persistent retardation of S-phase progression or irreversible G2 and/or greater than G2 blocks, depending on duration of exposure. Cells terminally blocked in G2 exhibit increased nuclear/cellular volumes and increased nuclear fluorescein isothiocyanate (protein) staining, suggestive of unbalanced growth. At 25-50 microM CRS concentrations, MELC exhibit severe membrane perturbation (loss of viability) regardless of exposure. In contrast, following similar exposures to an inactive isomer of CRS, MELC exhibit minimal cell cycle effects, suggesting that cell cycle kinetics may be a useful criterion for assessing potential efficacy. Similar analyses with different classes of chemotherapeutic agents reveal that the range of induced cellular/nuclear perturbations varies with the class of compound used. Taken together, these results suggest that drug toxicity can vary with both concentration and duration of exposure and, as such, a selective multiple-exposure FCM analysis may better represent the spectrum of drug action for drug development and pharmacodynamic studies.

Evaluation of arylmethylaminopropanediols by a novel in vitro pharmacodynamic assay: correlation with antitumor activity in vivo

The pharmacodynamics of a new series of antitumor DNA intercalators, known as arylmethylaminopropanediols (AMAPs), has been evaluated in vitro against adherent (MCF-7 human breast cancer) and nonadherent (P388 murine leukemia) cell lines. Previous work had shown that the in vitro antitumor activity of the model AMAP crisnatol was a function of exposure (Cn x T), rather than concentration alone. A unique exposure parameter, the minimum C x T, was proposed as an end point for antitumor activity in cell culture. Comparison of crisnatol to several established agents by the minimum C x T versus the standard concentration producing 10% survival indicated that these end points were not equivalent. The current work examined the validity of the pharmacodynamic approach using AMAP isomers from three different ring systems that were known to exhibit a spectrum of activity against the P388 tumor in vivo. The results indicated that antiproliferative, but not cytotoxic, activity of AMAPs in the pharmacodynamic assay correlated with their differential activity in vivo, expressed as percentage of increase in life span. In contrast, the concentration producing 10% survival either at 1 h or after continuous exposure did not show a similar correlation. The pharmacodynamic assay also revealed that certain AMAPs, while equipotent by concentration alone, required significantly less time and therefore less overall exposure for efficacy. Finally, the activity of AMAP isomers in P388 cells differed from that in MCF-7 cells, which may indicate AMAP selectivity for certain tumor types. Since AMAP action was a function of exposure, drug effects on cellular targets could likewise depend on exposure rather than concentration. These findings emphasize the importance of relating drug mechanisms to the pharmacodynamics of anticancer agents.

Induction of the P-450 I family of proteins by polycyclic aromatic hydrocarbons: possible relationship to their carcinogenicity

The hypothesis has been put forward that mutagenic polycyclic aromatic hydrocarbons which induce the P-450 I family of cytochromes, the major enzyme system responsible for their activation, are likely to be carcinogenic. In order to test this hypothesis, rats have been pretreated with a number of polycyclic aromatic hydrocarbons of different mutagenic and carcinogenic potency and hepatic P-450 I activity was monitored using chemical probes such as the O-deethylation of ethoxyresorufin and metabolic activation of Glu-P-1 to mutagens, and immunologically employing polyclonal antibodies against purified rat P-450 I A1. All compounds studied enhanced P-450 I activity and induced P-450 I apoproteins but the extent of induction was very markedly different. The results are discussed with reference to the mutagenicity of these chemicals in the Ames test and their carcinogenicity in the classical mouse skin model. A relationship appears to exist between carcinogenicity of polycyclic aromatic hydrocarbons and their ability to induce hepatic P-450 I activity.

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.

In vitro pharmacodynamic assay for cancer drug development: application to crisnatol, a new DNA intercalator

A microtiter pharmacodynamic assay is described that evaluates antitumor activity in vitro within a matrix of extracellular drug concentrations (C) and exposure times (T). The results were analyzed according to the pharmacodynamic principle: Cn x T = k, where n is the concentration coefficient and k is the drug exposure constant. This assay was used to characterize the antitumor activity of crisnatol (BW A770U), a member of the new arylmethylaminopropanediol class of DNA intercalators, in MCF-7 human breast cancer cells. The assay showed that drug action was a function of k, the extracellular drug exposure. Crisnatol had no effect at k less than 30 (n less than or equal to 1); was growth inhibitory at k = 30-1000 (n = 1), cytostatic at 1500, and cytotoxic at k greater than 2000 microMn-h (n = 2). These effects were directly related to increasing cellular retention of crisnatol. The threshold for growth inhibition was 0.02 fmol/cell, while cytoreduction required over 1 fmol/cell. The assay also yielded concentration-time curves of the form C = (k/T)1/n at specific surviving fractions, which were useful in selecting exposure conditions for further studies and emphasized the impact of exposure time on crisnatol activity. The hyperbolic nature of these curves suggested a unique parameter for comparing antitumor agents: the minimum C x T. This parameter represents the minimum exposure conditions required for a specified level of antitumor activity and accounts for differences in concentration coefficients among agents. The pharmacodynamic assay for crisnatol illustrates the importance of both concentration and exposure time in drug action and suggests a pharmacodynamic basis for comparing antitumor agents that conform to the Cn x T = k principle. Such agents include doxorubicin, 5-fluorouracil, cisplatin, etoposide, and tamoxifen. Analysis of these agents in the MCF-7 model shows that the minimum C x T parameter gives a relative cytotoxicity profile distinct from that found with the standard IC90 end point. This disparity was also seen in another, less differentiated breast cancer cell line (MDA-MB-231), and in normal human skin fibroblasts. Regardless of the end point, the in vitro cytotoxicity of crisnatol compares favorably with that of some clinically useful antitumor agents.

The effects of bay-region methyl substitution on 6-nitrochrysene mutagenicity in Salmonella typhimurium and tumorigenicity in newborn mice

The mutagenic activities in Salmonella typhimurium and tumorigenic activities in newborn mice of 6-nitrochrysene (6-NC), 5-methyl-6-nitrochrysene (5-Me-6-NC), 11-methyl-6-nitrochrysene (11-Me-6-NC) and 5-methylchrysene (5-MeC) were compared. In S. typhimurium TA100 in the absence of rat liver 9000 g supernatant, 11-Me-6-NC was the most active compound followed by 6-NC; 5-Me-6-NC and 5-MeC were inactive. In the assays conducted in the presence of rat liver 9000 g supernatant, the order of activity was 11-Me-6-NC greater than 6-NC greater than 5-Me-6-NC approximately 5-MeC. In S. typhimurium TA98 a similar trend was observed. For the tumorigenicity studies, groups of mice were treated with the appropriate compounds in DMSO by i.p. injections on the 1st, 8th and 15th day of life. At a dose of 100 nmol/mouse 6-NC induced significantly more lung tumors than 5-MeC, which in turn was more active than 11-Me-6-NC and 5-Me-6-NC. All compounds induced significant numbers of liver tumors in treated males compared to controls; the order of activity was the same as that observed for lung tumor induction. The results of this study clearly indicate that bay region methyl substitution can either inhibit (5-position) or enhance (11-position) the mutagenic activity of 6-NC. In contrast, bay region methyl substitution (5- and 11-positions) inhibited the tumorigenic activity of 6-NC in newborn mice. Since ring oxidation and nitroreduction are involved in the metabolic activation of 6-NC in newborn mice, bay region methyl substitution may either inhibit the nitroreduction pathway or hinder the formation of the appropriate bay region diol epoxide. Steric factors may be important in determining the tumorigenicity of methylated nitrochrysenes.

6-Amino-chrysene, a potent inhibitor of transferase activity in single living RTG2 cells

Previous reports on the inhibitory effect of 6-amino-chrysene (6AC) on benzo(a)pyrene (BP) metabolism using single living cells have suggested that aryl hydrocarbon hydroxylase (AHH) is not the only pathway for 6AC metabolism. We present here results demonstrating that direct glucuronidation may constitute an alternative pathway for 6AC elimination. First, we describe the conjugate of 6AC to UDP-glucuronic acid (UDPGA) in solution. We performed competition experiments between 6AC and monohydroxy BP, which are known to be good substrates for glucuronic transferase (GT), in RTG2 cells, using microspectrofluorimetry. Because of intracellular accumulation of fluorescent metabolites during BP metabolism, RTG2 cells can be used as a tool for simultaneous study of AHH and GT activities. When RTG2 cells have been simultaneously treated with BP and 6AC, GT appeared to be a more specific target for 6AC than AHH in these cells. Therefore, 6AC can be expected to act as a more specific inhibitor for GT than for AHH activity.

Resolution of complex fluorescence spectra recorded on single unpigmented living cells using a computerised method

The identification and quantification of fluorescent compounds in a complex fluorescence spectra are always difficult, especially in the case of low signal:noise ratio. We propose a computerised method that allows the resolution of low light level complex fluorescence spectra into its components. Based on a linear combination of N possible characteristic fluorescence spectra, and using N weighting functions, this method allows the integration of fluorescence intensities over the entire fluorescence spectra and the generation of n equations with N unknowns. The compounds that participate in complex fluorescence spectra are identified and quantified. Because fluorescence intensities can be integrated we can resolve complex fluorescence spectra presenting a low signal:noise ratio. The reliability and sensitivity of our method are shown through examples of resolution of complex intracellular fluorescence of single living cells pretreated with benzo(a)pyrene. Depending on the cell type and treatment, two, four, or five components can be identified in the complex fluorescence spectra.

Induction of rat hepatic cytochromes P-450 by environmental nitropolycyclic aromatic hydrocarbons

Nitrated polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants that result from various incomplete combustion processes. We have examined the activity of hepatic microsomal enzymes in rats pretreated with a series of environmentally occurring nitrated PAHs including: 1- and 4-nitropyrene, 1,3-, 1,6- and 1,8-dinitropyrene, 6-nitrochrysene, 7-nitrobenz[a]anthracene, 3-nitrofluoranthene, and 1-, 3-, and 6-nitrobenzo[a]pyrene. None of the compounds increased the cytochrome P-450 content more than 2-fold. 1,8-Dinitropyrene, 6-nitrochrysene, and 1- and 3-nitrobenzo[a]pyrene significantly increased arylhydrocarbon hydroxylase activity 2- to 8-fold higher than solvent-treated controls. The induction of 7-ethoxycoumarin O-deethylase activity paralleled that found with arylhydrocarbon hydroxylase. The maximum induction of aminopyrine N-demethylase was only 1.5-fold, and none of the nitrated PAHs caused significant increases in epoxide hydrase or NADPH-cytochrome c reductase. 1-Nitropyrene reductase activity was induced by each of the compounds with the exception of 6-nitrobenzo[a]pyrene. The greatest increase was caused by 1-nitrobenzo[a]pyrene followed by 1,3-dinitropyrene, 3-nitrobenzo[a]pyrene and 6-nitrochrysene. These data suggest that nitrated PAHs may potentiate the effects of subsequent exposures to various chemical carcinogens.

Formation of DNA adducts in mouse skin treated with metabolites of chrysene

Analysis by 32P-postlabelling of DNA isolated from mouse skin that had been treated in vivo with the polycyclic hydrocarbon chrysene revealed the presence of 7 adducts. All 7 adducts were also present in DNA from mice treated with trans-1,2-dihydro-1,2-dihydroxychrysene (chrysene-1,2-diol), and one of them, adduct 2, was formed from the triol derivative 9-hydroxy-trans-1,2- dihydro-1,2-dihydroxychrysene (9-hydroxychrysene-1,2-diol) and from 3-hydroxychrysene. Adducts were not detected in DNA from mice treated with trans-3,4-dihydro-3,4-dihydroxychrysene (chrysine-3,4-diol) or with 1-, 2-, 4-, 5- or 6-hydroxychrysene. In vitro modification of DNA by the anti-isomer of the bay-region diol-epoxide yielded adducts 3-7, while the corresponding triol-epoxide yielded adducts 2. It is concluded that chrysene activation in mouse skin proceeds principally via the bay-region diol-epoxide and to a lesser extent via the related bay-region triol-epoxide.

Mutation in mammalian cells by isomers of 5-methylchrysene diolepoxide

The two pairs of diastereomeric anti- and syn-diolepoxide derivatives of 5-methylchrysene in both bay regions were tested for cytotoxicity and for mutagenicity at the hprt locus of chinese hamster V79 cells as determined by the ability of the cells to form colonies in medium containing 6-thioguanine. The concentration of compound in the cell media required to achieve 37% survival ranged from 0.3 to 4.5 micrograms/ml. Although the mutagenic effectiveness, i.e. the induced mutation frequency per unit concentration of compounds, varied over a 30-fold range, the mutagenic efficiency, i.e. the induced mutation frequency at an equivalent level of cell survival, showed only a 3-fold variation. The anti-1,2-diol-3,4-epoxide isomer (anti-5MCDE-I) was found to be the most mutagenic of the 5-methylchrysene diolepoxide isomers. This finding is consistent with previous observations on the tumorigenicity of these diolepoxides.