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Biomedical subjects

Stephen S Hecht

Publications and source records attributed to Stephen S Hecht.

At least 37 records · Page 2Linked to original sources
PubMed2006

4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronides in the urine of infants exposed to environmental tobacco smoke.

Biomarkers of carcinogen uptake could provide important information pertinent to the question of exposure to environmental tobacco smoke (ETS) in childhood and cancer development later in life. Previous studies have focused on exposures before birth and during childhood, but carcinogen uptake from ETS in infants has not been reported. Exposures in infants could be higher than in children or adults because of their proximity to parents who smoke. Therefore, we quantified 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronides (total NNAL) in the urine of 144 infants, ages 3 to 12 months, who lived in homes with parents who smoked. Total NNAL is an accepted biomarker of uptake of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. Cotinine and its glucuronide (total cotinine) and nicotine and its glucuronide (total nicotine) were also quantified. Total NNAL was detectable in 67 of 144 infants (46.5%). Mean levels of total NNAL in the 144 infants were 0.083 +/- 0.200 pmol/mL, whereas those of total cotinine and total nicotine were 0.133 +/- 0.190 and 0.069 +/- 0.102 nmol/mL, respectively. The number of cigarettes smoked per week in the home or car by any family member when the infant was present was significantly higher (P < 0.0001) when NNAL was detected than when it was not (76.0 +/- 88.1 versus 27.1 +/- 38.2). The mean level of NNAL detected in the urine of these infants was higher than in most other field studies of ETS exposure. The results of this study show substantial uptake of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in infants exposed to ETS and support the concept that persistent ETS exposure in childhood could be related to cancer later in life.

Biomarkers↗
PubMed2006

Comparison of polymorphisms in genes involved in polycyclic aromatic hydrocarbon metabolism with urinary phenanthrene metabolite ratios in smokers.

The hypothesis that interindividual differences among smokers in the metabolism of polycyclic aromatic hydrocarbons (PAH) are related to lung cancer risk has been extensively investigated in the literature. These studies have compared lung cancer risk in groups of smokers with or without polymorphisms in genes involved in PAH metabolism. We believe that carcinogen metabolite phenotyping, involving the actual measurement of PAH metabolites, would be a better way to investigate differences in lung cancer risk. With this goal in mind, we have developed methods for quantifying phenanthrene metabolites in urine. Phenanthrene is the simplest PAH with a bay region, a feature closely associated with carcinogenicity. The urinary metabolite r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene (PheT) is a measure of metabolic activation, whereas phenanthrols (HOPhe) are a measure of detoxification. In this study, we quantified urinary PheT/HOPhe ratios in 346 smokers who were also genotyped for 11 polymorphisms in genes involved in PAH metabolism: CYP1A1MspI, CYP1A1I462V, CYP1B1R48G, CYP1B1A119S, CYP1B1L432V, CYP1B1N453S, EPHX1Y113H, EPHX1H139R, GSTP1I105V, GSTP1A114V, and GSTM1 null. The geometric mean molar PheT/3-HOPhe ratio was 4.08 (95% confidence interval, 3.79-4.39). Ten percent of the smokers had PheT/3-HOPhe ratios of > or =9.90. We found a significant association between the presence of the CYP1A1I462V polymorphism and high PheT/3-HOPhe ratios (P = 0.02). This effect was particularly strong in females and in combination with the GSTM1 null polymorphism. In contrast, the CYP1B1R48G and CYP1B1A119S polymorphisms were associated with significantly lower PheT/3-HOPhe ratios, particularly in Blacks. There were no consistent significant effects of any of the other polymorphisms on PheT/3-HOPhe ratios. The highest 10% of PheT/3-HOPhe ratios could not be predicted by the presence of any of the 11 polymorphisms individually or by certain combinations. The effects of the CYP1A1I462 polymorphism observed here, particularly in combination with GSTM1 null, are quite consistent with reports in the literature. However, the results of this study indicate that genotyping is not an effective way to predict PAH metabolism at least as represented by PheT/HOPhe ratios.

Adolescent↗
PubMed2006

Combined analysis of r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in smokers' plasma.

Polycyclic aromatic hydrocarbons (PAH) and tobacco-specific nitrosamines, such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), are widely accepted to be two important types of lung carcinogens in cigarette smoke. In this study, we have developed a method to estimate individual uptake of these compounds by quantifying r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene (PheT) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in 1 mL of smokers' plasma. PheT and NNAL are biomarkers of PAH and NNK uptake, respectively. [D10]PheT and [pyridine-D4]NNAL were added to plasma as internal standards. The plasma was treated with beta-glucuronidase to release any conjugated PheT and NNAL. The analytes were enriched by solid-phase extraction on a mixed mode cation exchange cartridge and the PheT fraction was further purified by high-performance liquid chromatography. The appropriate fractions were analyzed by gas chromatography-negative ion chemical ionization-mass spectrometry for PheT and liquid chromatography-electrospray ionization-mass spectrometry for NNAL. The method was sensitive (limits of quantitation: PheT, 13 fmol/mL; NNAL, 3 fmol/mL), accurate, and precise. Levels of PheT and NNAL in plasma from 16 smokers averaged 95 +/- 71 and 36 +/- 21 fmol/mL, respectively, which are approximately 1% to 2% of the amounts found in urine. This method should be useful in molecular epidemiology studies of carcinogen uptake and lung cancer in smokers.

Biomarkers↗
PubMed2006

Toxicant exposure in cigarette reducers versus light smokers.

BACKGROUND: The extent of exposure to tobacco toxicants in smokers who have reduced their cigarette intake compared with smokers who are light smokers is relatively unknown. The goal of this study is to investigate the occurrence of compensatory smoking in reducers compared with light smokers by measuring toxicant exposure. METHODS: Participants in two smoking reduction intervention studies (N = 64) were selected for comparison with a group of light smokers (N = 62) who smoked the same number of cigarettes as the reducers. A compensatory smoking score was defined (biomarker level for reducer/biomarker level for light smoker) and calculated for urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronides (total NNAL), metabolites of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-I-(3-pyridyl)-1-butanone, to measure the degree of smoking compensation in reducers when compared with the light smokers. RESULTS: The mean level of creatinine-adjusted total NNAL for reducers was over twice that of light smokers even when they smoked about the same number of cigarettes per day. The difference of the mean total NNAL concentrations between light smokers and reducers was highly significant (P < 0.0001). Wide variability in total NNAL concentrations was also observed in reducers, with the extent of this variability between light smokers and reducers being significantly different (P = 0.0005). The level of individual reduction was shown to be a consistent predictor of compensatory smoking (r = 0.50; adjusted Ps = 0.002), with greater cigarette reduction associated with more compensation. CONCLUSIONS: Compensatory smoking limits the harm reduction value of decreased smoking of cigarettes.

Administration, Cutaneous↗
PubMed2006

Mass spectrometric quantitation of nicotine, cotinine, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in human toenails.

Numerous studies have quantified total cotinine (the sum of cotinine and cotinine-N-glucuronide) and total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol [NNAL; the sum of NNAL and its O- and N-glucuronides (NNAL-Glucs)] in the urine and blood of smokers, smokeless tobacco users, and nonsmokers exposed to environmental tobacco smoke. Analysis of hair and nails has several advantages over blood and urine testing, such as accumulation of xenobiotics during long-term exposure, ease of collection, and indefinite stability of samples. We developed sensitive methods for quantitation of nicotine, cotinine, and NNAL in human toenails. Nicotine and cotinine were analyzed by gas chromatography-mass spectrometry-selected ion monitoring. NNAL was assayed using liquid chromatography-electrospray ionization-tandem mass spectrometry-selected reaction monitoring. The detection limits of the methods were 0.01 ng/mg toenail for nicotine, 0.012 ng/mg toenail for cotinine, and 0.02 pg/mg toenail for NNAL. In 35 smokers, the mean nicotine level was 5.9 +/- 5.6 ng/mg toenail, mean cotinine was 1.6 +/- 1.3 ng/mg toenail, and mean NNAL was 0.41 +/- 0.67 pg/mg toenail. Samples collected from six nonsmokers were negative for NNAL. In smokers, NNAL correlated with cotinine (r = 0.77; P < 0.0001). The results of this study for the first time show the presence of cotinine and NNAL in human toenails. These sensitive and quantitative methods should be useful in epidemiologic studies of the role of chronic tobacco smoke exposure, including environmental tobacco smoke exposure, in human cancer.

Cotinine↗
PubMed2005

Comparative analysis of tobacco-specific nitrosamines and total N-nitroso compounds in moldovan cigarette tobacco.

While previous studies have evaluated levels of tobacco-specific nitrosamines (TSNA) and total N-nitroso compounds (NOC) in tobacco, there are no reports in the literature on TSNA and total NOC in the same tobacco products. We compared levels of TSNA, total NOC, and NOC precursors (NOCP) in tobacco of cigarettes purchased in Moldova and in some tobacco types commonly used for the manufacturing of Moldovan cigarettes. Cigarette tobaccos included those from non-Moldovan, traditional Moldovan, and blended Moldovan cigarettes. The results demonstrate that tobacco of non-Moldovan cigarettes contains higher TSNA and NOC levels (mean, 16 and 63 nmol/g tobacco, n = 6) than that of Moldovan cigarettes (mean, 5 and 23 nmol/g tobacco, n = 25). TSNA and NOC levels were also generally higher in tobacco of blended than in traditional Moldovan cigarettes. NOCP levels in Moldovan and non-Moldovan cigarette tobacco were similar as follows: 29000 +/- 30000 and 33000 +/- 28000 nmol/g tobacco (mean +/- SD). Total NOC were strongly correlated with total TSNA levels (r = 0.66; P < 0.0001). These findings demonstrate that current technologies involved in the manufacture of some blended cigarettes create conditions that favor N-nitrosation of alkaloids and other tobacco constituents.

Moldova↗
PubMed2005

Phenethyl isothiocyanate and sulforaphane and their N-acetylcysteine conjugates inhibit malignant progression of lung adenomas induced by tobacco carcinogens in A/J mice.

We have shown previously that naturally occurring isothiocyanates derived from cruciferous vegetables and their N-acetylcysteine conjugates inhibit lung adenoma formation induced by tobacco carcinogens in A/J mice at the post-initiation stage. The tumor-inhibitory activity by these compounds is linked with activation of activator protein and induction of apoptosis in lung tissues, suggesting that these compounds may also inhibit the development of adenomas to adenocarcinomas in lung. In this study, the chemopreventive activity of phenethyl isothiocyanate and sulforaphane and their N-acetylcysteine conjugates during progression of lung adenomas to malignant tumors was investigated in A/J mice. Mice were divided into 14 groups and treated with a mixture of 3 micromol benzo(a)pyrene [B(a)P] and 3 micromol 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) given by gavage once weekly for 8 weeks. Twenty weeks after the beginning of carcinogen administration, a total of 20 mice in the treatment groups were sacrificed with an average yield of 7.3 +/- 4.5 lung adenomas per mouse. The remaining mice in each group were fed diets containing phenethyl isothiocyanate (3 and 1.5 mmol/kg diet), sulforaphane (3 and 1.5 mmol/kg diet), phenethyl isothiocyanate-N-acetylcysteine (8 and 4 mmol/kg diet), sulforaphane-N-acetylcysteine (8 and 4 mmol/kg diet) during weeks 21 to 42. Four mice in each of the high-dose treatment groups were sacrificed during weeks 28 and 36 and the bioassay was terminated during week 42; lung tissues were harvested for histopathologic examination of tumors and for cell proliferation (proliferating cell nuclear antigen) and apoptosis (caspase-3) assays using immunohistochemical staining. At termination, the incidence of adenocarcinoma in the 3 mmol/kg diet phenethyl isothiocyanate group and 8 mmol/kg diet phenethyl isothiocyanate-N-acetylcysteine group was reduced to 19% and 13%, respectively, compared with 42% in the carcinogen-treated control group. At the lower doses, phenethyl isothiocyanate and its N-acetylcysteine conjugate also inhibited the incidences of lung adenocarcinoma, however, the decreases were not statistically significant. The lung tumor incidences in groups treated with sulforaphane-N-acetylcysteine in the diet were also significantly reduced to 11% or 16%. Furthermore, the malignant lung tumor multiplicity was significantly reduced from 1.0 tumor/mouse in the carcinogen-treated control group to 0.3 in the sulforaphane low-dose group, 0.3 and 0.4 in the two sulforaphane-N-acetylcysteine groups, and 0.4 in the phenethyl isothiocyanate high-dose group. The malignant tumor multiplicities in other treatment groups were also reduced (0.5-0.8 tumors/mouse), but not significantly. Unlike lung adenocarcinomas, both incidences and multiplicities of lung adenomas were not much affected by treatment with isothiocyanates or their conjugates. Immunohistochemical examination of the lung tumors from all time points indicated that significant reduction in proliferating cell nuclear antigen and induction of apoptosis (terminal nucleotidyl transferase-mediated nick end labeling and caspase-3) were observed in the isothiocyanate and isothiocyanate-N-acetylcysteine-treated groups that showed inhibition of the development of lung adenocarcinomas. The results of the study provide a basis for future evaluation of the potential of phenethyl isothiocyanate and sulforaphane and their conjugates as chemopreventive agents in smokers and ex-smokers with early lung lesions.

Acetylcysteine↗
PubMed2005

Tobacco-specific nitrosamines in smokeless tobacco products marketed in India.

Smokeless tobacco products are a known cause of oral cancer in India. Carcinogenic tobacco-specific nitrosamines in these products are believed to be at least partially responsible for cancer induction, but there have been no recent analyses of their amounts. We quantified levels of 4 tobacco-specific nitrosamines, N'-nitrosonornicotine (NNN), N'-nitrosoanatabine (NAT), N'-nitrosoanabasine (NAB) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in 32 products marketed currently in India. Levels of nitrate, nitrite and nicotine were also determined. The highest levels of tobacco-specific nitrosamines were found in certain brands of khaini, zarda and other smokeless tobacco products. Concentrations of NNN and NNK in these products ranged from 1.74-76.9 and 0.08-28.4 microg/g, respectively. Levels of tobacco-specific nitrosamines in gutka were generally somewhat lower than in these products, but still considerably higher than nitrosamine levels in food. Tobacco-specific nitrosamines were rarely detected in supari, which does not contain tobacco, or in tooth powders. The results of our study demonstrate that exposure to substantial amounts of carcinogenic tobacco-specific nitrosamines through use of smokeless tobacco products remains a major problem in India.

Carcinogens↗
PubMed2005

Carcinogenicity studies of inhaled cigarette smoke in laboratory animals: old and new.

A new study demonstrates that lifetime whole-body exposure of B6C3F1 mice to high doses of cigarette smoke robustly increases lung cancer incidence compared with sham exposed animals. This is the first study to demonstrate a strong effect of inhaled cigarette smoke on lung cancer in an animal model. This commentary attempts to put the new results in perspective with the existing literature on cigarette smoke inhalation studies in animals and discusses strengths, limitations and possible applications of available models.

Animals↗
PubMed2005

Synthesis and properties of an acetaldehyde-derived oligonucleotide interstrand cross-link.

Acetaldehyde (AA), occurring widely in the human environment, is a mutagen and carcinogen. AA can react with DNA to form AA-DNA adducts. Several types of adducts, including an interstrand cross-link 3-(2-deoxyribos-1-yl)-5,6,7,8-tetrahydro-8-(N2-deoxyguanosyl)-6-methylpyrimido[1,2-a]purine-10(3H)one (7), have been previously characterized by our laboratory. We hypothesize that cross-link 7 may be involved in determining the mutagenic and carcinogenic properties of AA. To address this question, the double-stranded oligonucleotide 13, bearing cross-link 7, was synthesized in a sequence appropriate for mutagenicity studies in human cells. Oligonucleotide 9, containing 2-fluoro-O6-(trimethylsilylethyl)deoxyinosine (dIno), was reacted with 4-amino-1,2-pentanediol, followed by treatment with NaIO4. The resulting oligonucleotide 11 containing the 1,N2-propano-deoxyguanosine (dGuo) 5 was incubated with the complementary oligonucleotide 12 to give the desired cross-link 13, which was characterized by negative-ion electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS) and enzymatic hydrolysis to cross-link 7. The formation of cross-link 13 at 5'-CpG-3' was confirmed by incubation of 11 with [15N5]12 containing a 5'-Cp[15N5]G-3' sequence. The formation of cross-link 13 was reversible. Therefore, oligonucleotide 24 containing the irreversible analogue of cross-link 7, 1,3-bis(2'-deoxyguanos-N2-yl)butane, was synthesized for use as a control in the mutagenicity studies. Oligonucleotide 21 was reacted with 1,3-diaminobutane dihydrochloride, followed by incubation with the complementary oligonucleotide 23, to give 24. To determine the optimum distance and orientation for cross-link formation, six oligonucleotides, containing 5 at the i + 1, i + 2, and i + 3 or the i - 1, i - 2, and i - 3 positions relative to dGuo in the complementary strand, were 5'-end labeled with [gamma-32P]ATP, followed by incubation of each labeled oligonulceotide with its complementary strand and then analysis by denaturing polyacrylamide gel electrophoresis. Only the oligonucleotide containing 5'-Cp5-3' formed the cross-link with the complementary 5'-CpG-3' sequence. The results of this study confirm the structure of an AA-derived DNA cross-link, supply characterized cross-link-containing oligonucleotides for mutagenicity studies, and provide information on the optimum distance and orientation for cross-link formation.

Acetaldehyde↗
PubMed2005

Cytochrome P450 2A-catalyzed metabolic activation of structurally similar carcinogenic nitrosamines: N'-nitrosonornicotine enantiomers, N-nitrosopiperidine, and N-nitrosopyrrolidine.

N'-Nitrosonornicotine (NNN) and N-nitrosopiperidine (NPIP) are potent esophageal and nasal cavity carcinogens in rats and pulmonary carcinogens in mice. N-Nitrosopyrrolidine (NPYR) induces mainly liver tumors in rats and is a weak pulmonary carcinogen in mice. These nitrosamines may be causative agents in human cancer. alpha-Hydroxylation is believed to be the key activation pathway in their carcinogenesis. P450 2As are important enzymes of nitrosamine alpha-hydroxylation. Therefore, a structure-activity relationship study of rat P450 2A3, mouse P450 2A4 and 2A5, and human P450 2A6 and 2A13 was undertaken to compare the catalytic activities of these enzymes for alpha-hydroxylation of (R)-NNN, (S)-NNN, NPIP, and NPYR. Kinetic parameters differed significantly among the P450 2As although their amino acid sequence identities were 83% or greater. For NNN, alpha-hydroxylation can occur at the 2'- or 5'-carbon. P450 2As catalyzed 5'-hydroxylation of (R)- or (S)-NNN with Km values of 0.74-69 microM. All of the P450 2As except P450 2A6 catalyzed (R)-NNN 2'-hydroxylation with Km values of 0.73-66 microM. (S)-NNN 2'-hydroxylation was not observed. Although P450 2A4 and 2A5 differ by only 11 amino acids, they were the least and most efficient catalysts of NNN 5'-hydroxylation, respectively. The catalytic efficiencies (kcat/Km) for (R)-NNN differed by 170-fold whereas there was a 46-fold difference for (S)-NNN. In general, P450 2As catalyzed (R)- and (S)-NNN 5'-hydroxylation with significantly lower Km and higher kcat/Km values than NPIP or NPYR alpha-hydroxylation (p <0.05). Furthermore, P450 2As were better catalysts of NPIP alpha-hydroxylation than NPYR. P450 2A4, 2A5, 2A6, and 2A13 exhibited significantly lower Km and higher kcat/Km values for NPIP than NPYR alpha-hydroxylation (p <0.05), similar to previous reports with P450 2A3. Taken together, these data indicate that critical P450 2A residues determine the catalytic activities of NNN, NPIP, and NPYR alpha-hydroxylation.

Animals↗
PubMed2005

Mass spectrometric analysis of relative levels of pyridyloxobutylation adducts formed in the reaction of DNA with a chemically activated form of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

Exposure to the tobacco-related nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine is carcinogenic to humans. Metabolic activation of NNK leads to the formation of DNA adducts, which play a critical role in NNK carcinogenesis. Adducts specific to NNK result from covalent linkage of a pyridyloxobutyl (POB-1-yl) group to DNA. Furthermore, some such adducts are unstable, releasing the degradation product 4-hydroxy-1-(3-pyridyl)-1-butanone (4-HPB). Previous qualitative reports from our laboratory have established the chemical structures of the major POB-1-yl-DNA adducts. In this study, we have quantitated the levels of each of these adducts in vitro, as well as their contribution to the biomarker of DNA pyridyloxobutylation, 4-HPB. Standards for the POB-DNA adducts O(6)-(POB-1-yl)dGuo, 7-(POB-1-yl)Gua, O(2)-(POB-1-yl)dThd, and O(2)-(POB-1-yl)Cyt were synthesized and used to determine standard responses by reverse phase HPLC-electrospray ionization-tandem mass spectrometry (ESI-MS/MS). DNA was incubated with varying amounts of 4-(acetoxymethylnitrosamino)-1-(3-pyridyl)-1-butanone in the presence of an esterase, conditions favorable to the formation of an active pyridyloxobutylating agent. After sequential enzymatic and neutral thermal hydrolysis, isolation, and purification, the pyridyloxobutylated mixture was analyzed by HPLC-ESI-MS/MS to quantify the relative level of each of these four adducts as well as the released 4-HPB. The most abundant product was 4-HPB, which accounted for two-thirds of the analyzed mixture. The highest adduct levels measured were those of bases that result from loss of deoxyribose upon neutral thermal hydrolysis. These adducts, 7-(POB-1-yl)Gua and O(2)-(POB-1-yl)Cyt, comprised an average of 23 and 6% of the analyzed mixture, respectively. O(2)-(POB-1-yl)dThd and the mutagenic adduct O(6)-(POB-1-yl)dGuo were detected at the lowest levels, 4 and 2%, respectively. The relative levels of adducts determined in this study provide further insight regarding the chemical reactivity of the activated form of NNK with respect to DNA bases. Furthermore, the analytical standards and mass spectrometric methods used lay the groundwork for establishing a representative array of pyridyloxobutylation adducts as biomarkers of tobacco exposure in further biochemical and in vivo studies.

Animals↗
PubMed2005

Metabolic activation of the tobacco carcinogen 4-(methylnitrosamino)-(3-pyridyl)-1-butanone by cytochrome P450 2A13 in human fetal nasal microsomes.

Among human P450s studied to date, P450 2A13 is the most efficient catalyst of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) alpha-hydroxylation. This reaction is a key bioactivation pathway in NNK-induced carcinogenesis. P450 2A13 mRNA has been detected in human tissues, but it is unknown whether the enzyme is functional in vivo. Therefore, we studied NNK alpha-hydroxylation in human fetal nasal mucosal microsomes, which have been shown to contain high levels of P450 2A protein, presumed to be a mixture of P450 2A6 and 2A13. The microsomes efficiently catalyzed NNK alpha-hydroxylation at the methylene and methyl carbons, as well as carbonyl reduction. Antibodies against mouse P450 2A5 inhibited alpha-hydroxylation by these microsomes greater than 90%. K(m) and V(max) values for alpha-methylene hydroxylation were 6.5 +/- 1.1 muM and 3.0 +/- 0.1 pmol/min/mg; for alpha-methyl hydroxylation, they were 6.7 +/- 0.8 microM and 0.85 +/- 0.03 pmol/min/mg. The K(m) values agree closely with those for NNK metabolism by P450 2A13. Using a new technique, we separated P450 2A13 from P450 2A6 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Quantitative immunoblot analysis indicated that the level of P450 2A13 in the pooled fetal nasal microsome sample used for kinetic analysis was approximately 1.6 pmol/mg protein. In the same sample, P450 2A6 was not detected (detection limit, 67 fmol/mg protein). These kinetic, immunoinhibition, and immunoblot data confirm that P450 2A13 is a functional enzyme and the catalyst of NNK alpha-hydroxylation in human fetal nasal mucosa. The results are also the first to demonstrate high efficiency NNK alpha-hydroxylation in a human tissue.

Adult↗
PubMed2005

Smokeless tobacco topography and toxin exposure.

This study examined the relationship between oral smokeless tobacco (ST) topographical measures and biomarkers of tobacco and carcinogen exposure. During 2 weeks of baseline ad libitum ST use, 54 male participants (mean age=32.1+/-7.5 years) were required to record the time each dip was placed in and removed from their mouths. Urine samples were collected twice during baseline and analyzed for nicotine, cotinine, and their glucuronides (total nicotine and total cotinine) and for metabolites of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronides (total NNAL). The results suggest that frequency and duration measures of ST use (p<.01 to p<.001), particularly total dip duration, are significantly correlated with total cotinine, total nicotine, and total NNAL. These results suggest that how long a ST user has tobacco in his mouth is most predictive of tobacco toxin exposure.

Adult↗
PubMed2005

A urinary metabolite of phenanthrene as a biomarker of polycyclic aromatic hydrocarbon metabolic activation in workers exposed to residual oil fly ash.

Residual oil fly ash is a chemically complex combustion product containing a significant component of potentially carcinogenic transition metals and polycyclic aromatic hydrocarbons (PAH). Various biomarkers of PAH exposure have been investigated previously, most notably 1-hydroxypyrene (1-OHP), in urine. In this study, we assessed the utility of r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene (trans, anti-PheT), a metabolite of phenanthrene, to detect occupational PAH exposure. Urine samples collected across the workweek were analyzed for 1-OHP and trans, anti-PheT in boilermakers (n = 20) exposed to residual oil fly ash. Median baseline urinary trans, anti-PheT concentrations were 0.50 microg/g creatinine in current tobacco smokers and 0.39 microg/g creatinine in nonsmokers. Median baseline urinary 1-OHP concentrations in smokers and nonsmokers were 0.31 and 0.13 microg/g creatinine, respectively. To study further the effect of smoking exposure on the urinary PAH markers, urinary cotinine was used. Although urinary trans, anti-PheT and 1-OHP concentrations were correlated (Spearman r = 0.63; P < 0.001) for all subjects, the regression coefficient between log-transformed trans, anti-PheT and log 1-OHP was statistically significant only for subjects with low levels of urinary cotinine or for nonsmokers. Each 1-unit increase in log 1-OHP was associated with a 0.77-unit increase (95% confidence interval, 0.45-1.09) in log trans, anti-PheT in subjects with low levels of urinary cotinine (P < 0.001). In these subjects, dichotomized occupational exposure status was a significant predictor of log trans, anti-PheT (P = 0.02) but not of log 1-OHP (P = 0.2). In conclusion, we found that urinary trans, anti-PheT was detected in levels comparable with 1-OHP in occupationally exposed workers, particularly nonsmokers. This study shows that urinary trans, anti-PheT may be an effective biomarker of uptake and metabolic activation of PAHs.

Adult↗
PubMed2005

Similar uptake of lung carcinogens by smokers of regular, light, and ultralight cigarettes.

Cigarette design has changed markedly over the past 60 years and sales-weighed levels of tar and nicotine have decreased. Currently, cigarettes are classified as regular (>14.5 mg tar), light (>6.5-14.5 mg tar), and ultralight (< or =6.5 mg tar), based on a Federal Trade Commission-specified machine-smoking protocol. Epidemiologic studies suggest that there is no difference in lung cancer risk among people who smoke light or ultralight cigarettes compared with regular cigarettes, but the uptake of lung carcinogens in smokers of these types of cigarettes has never been reported. We recruited 175 smokers, who filled out a tobacco use questionnaire in which their current brand was identified as regular, light, or ultralight. Urine samples were collected and analyzed for 1-hydroxypyrene (1-HOP), total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL plus its glucuronides) and total cotinine (cotinine plus its glucuronides). 1-HOP and total NNAL are biomarkers of uptake of polycyclic aromatic hydrocarbons and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, lung carcinogens in cigarette smoke. Total cotinine is a biomarker of nicotine uptake. There were no statistically significant differences in urinary levels of 1-HOP, total NNAL, and total cotinine in smokers of regular, light, and ultralight cigarettes, whether the results were expressed per mg urinary creatinine, per mL of urine, or per mg creatinine divided by cigarettes per day. Levels of machine measured tar were available for the cigarettes smoked by 149 of the subjects. There was no correlation between levels of tar and any of the biomarkers. These results indicate that lung carcinogen and nicotine uptake, as measured by urinary 1-HOP, total NNAL, and total cotinine is the same in smokers of regular, light, and ultralight cigarettes. The results are consistent with epidemiologic studies that show no difference in lung cancer risk in smokers of these cigarettes.

Adult↗