Effects of smoking cessation on eight urinary tobacco carcinogen and toxicant biomarkers

Abstract

We determined the persistence at various times (3, 7, 14, 21, 28, 42, and 56 days) of eight tobacco smoke carcinogen and toxicant biomarkers in the urine of 17 smokers who stopped smoking. The biomarkers were 1-hydroxy-2-(N-acetylcysteinyl)-3-butene (1) and 1-(N-acetylcysteinyl)-2-hydroxy-3-butene (2) [collectively called MHBMA for monohydroxybutyl mercapturic acid] and 1,2-dihydroxy-4-(N-acetylcysteinyl)butane (3) [DHBMA for dihydroxybutyl mercapturic acid], metabolites of 1,3-butadiene; 1-(N-acetylcysteinyl)-propan-3-ol (4, HPMA for 3-hydroxypropyl mercapturic acid), a metabolite of acrolein; 2-(N-acetylcysteinyl)butan-4-ol (5, HBMA for 4-hydroxybut-2-yl mercapturic acid), a metabolite of crotonaldehyde; (N-acetylcysteinyl)benzene (6, SPMA for S-phenyl mercapturic acid), a metabolite of benzene; (N-acetylcysteinyl)ethanol (7, HEMA for 2-hydroxyethyl mercapturic acid), a metabolite of ethylene oxide; 1-hydroxypyrene (8) and its glucuronides (1-HOP), metabolites of pyrene; and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (9) and its glucuronides (total NNAL), a biomarker of exposure to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). These biomarkers represent some of the major carcinogens and toxicants in cigarette smoke: 1,3-butadiene, acrolein, crotonaldehyde, benzene, ethylene oxide, polycyclic aromatic hydrocarbons (PAH), and NNK. With the exception of DHBMA, levels of which did not change after cessation of smoking, all other biomarkers decreased significantly after 3 days of cessation (P < 0.001). The decreases in MHBMA, HPMA, HBMA, SPMA, and HEMA were rapid, nearly reaching their ultimate levels (81-91% reduction) after 3 days. The decrease in total NNAL was gradual, reaching 92% after 42 days, while reduction in 1-HOP was variable among subjects to about 50% of baseline. Since DHBMA did not change upon smoking cessation, there appear to be sources of this metabolite other than 1,3-butadiene. The results of this study demonstrate that the tobacco smoke carcinogen/toxicant biomarkers MHBMA, HPMA, HBMA, SPMA, HEMA, 1-HOP, and NNAL are related to smoking and are good indicators of the impact of smoking on human exposure to 1,3-butadiene, acrolein, crotonaldehyde, benzene, ethylene oxide, PAH, and NNK.

Figure 1

Chromatograms obtained upon LC-ESI-MS/MS-SRM analysis of MHBMA, DHBMA, HPMA, HBMA, SPMA, and HEMA in the urine of a smoker at baseline (denoted by “smoking” and in that subject’s urine after 4 weeks of cessation. Each pair of chromatograms was obtained by SRM for the analyte (upper) and internal standard (lower), represented by the shaded peaks. For MHBMA, the peak eluting at 14.14 min in the top chromatogram is one diastereomer of 1 while the peak eluting at 15.51 min is the other diastereomer of 1 and both diastereomers of 2, as determined by HPLC analysis (21). The same distribution applies to the other MHBMA chromatograms. The two peaks in the HBMA chromatograms are presumed to be diastereomers.

Figure 2

Percent reduction from baseline of eight tobacco carcinogen and toxicant biomarkers at various intervals after cessation. Values are means ± S.D. (N = 17), except for 1-HOP (N = 15) for which 2 subjects with highly variable data were omitted.

Scheme 1

Metabolism of 1,3-butadiene (10) to MHBMA (1 and 2) and DHBMA (3) a. GSH, GSTs; b. γ-glutamyltranspeptidase; c. cysteinylglycine dipeptidase; d. cysteine S-conjugate N-acetyltransferase; EH, epoxide hydrolase; ADH, alcohol dehydrogenase; CR, carbonyl reductase

Chart 1

Structures of urinary biomarkers (8 and 9 also occur as glucuronides)