Quantification of Hemoglobin and White Blood Cell DNA Adducts of the Tobacco Carcinogens 2-Amino-9H-pyrido[2,3-b]indole and 4-Aminobiphenyl Formed in Humans by Nanoflow Liquid Chromatography/Ion Trap Multistage Mass Spectrometry

Aromatic amines covalently bound to hemoglobin (Hb) as sulfinamide adducts at the cysteine 93 residue of the Hb β chain have served as biomarkers to assess exposure to this class of human carcinogens for the past 30 years. In this study, we report that 2-amino-9H-pyrido[2,3-b]indole (AαC), an abundant carcinogenic heterocyclic aromatic amine formed in tobacco smoke and charred cooked meats, also reacts with Hb to form a sulfinamide adduct. A novel nanoflow liquid chromatography/ion trap multistage mass spectrometry (nanoLC-IT/MS3) method was established to assess exposure to AαC and the tobacco-associated bladder carcinogen 4-aminobiphenyl (4-ABP) through their Hb sulfinamide adducts. Following mild acid hydrolysis of Hb in vitro, the liberated AαC and 4-ABP were derivatized with acetic anhydride to form the N-acetylated amines, which were measured by nanoLC-IT/MS3. The limits of quantification (LOQ) for AαC- and 4-ABP-Hb sulfinamide adducts were ≤7.1 pg/g Hb. In a pilot study, the mean level of Hb sulfinamide adducts of AαC and 4-ABP were, respectively, 3.4-fold and 4.8-fold higher in smokers (>20 cigarettes/day) than nonsmokers. In contrast, the major DNA adducts of 4-ABP, N-(2'-deoxyguanosin-8-yl)-4-aminobiphenyl, and AαC, N-(2'-deoxyguanosin-8-yl)-2-amino-9H-pyrido[2,3-b]indole, were below the LOQ (3 adducts per 109 bases) in white blood cell (WBC) DNA of smokers and nonsmokers. These findings reaffirm that tobacco smoke is a major source of exposure to AαC. Hb sulfinamide adducts are suitable biomarkers to biomonitor 4-ABP and AαC; however, neither carcinogen binds to DNA in WBC, even in heavy smokers, at levels sufficient for biomonitoring.

Expression of N-acetyltransferases in periodontal granulation tissue

Smoking is a major risk of periodontal diseases. At the site of first contact, the gingiva is exposed to aromatic amines and polycyclic hydrocarbons. These are metabolized by the N-acetyltransferases (NAT), leading to local detoxification and/or activation reactions contributing to the risk of periodontal destruction in smokers. The purpose of this study was to detect the expression of N-acetyltransferase isoenzymes NAT1 and NAT2 in periodontal granulation tissue. In 24 specimens obtained from periodontitis patients or control subjects, mRNA encoding for NAT1 and NAT2 was detected by RT-PCR, and proteins were identified by immunohistochemistry. In periodontal granulation tissues, immunoreactivity for NAT1 and NAT2 was detected in infiltrating leukocytes and fibroblasts. In normal gingiva, both enzymes were found in epithelial cells, whereas NAT1 was also detected in endothelial cells. The results suggest that these enzymes may play a role in the defense against xenobiotics and the accelerated progression of periodontal disease in smokers.