Impact of smoking on the frequencies of micronuclei and other nuclear abnormalities in exfoliated oral cells: a comparative study with different cigarette types.

The primary aim of the study was to investigate the impact of tar and nicotine contents of cigarettes on chromosomal damage in oral mucosa cells of smokers. We monitored the effect of smoking different cigarette types (i.e., of ultralight filter, light filter, medium filter and unfiltered cigarettes) on induction of nuclear anomalies including micronuclei (MN), broken eggs (BE), binucleates (BN), condensed chromatin (CC), karyorrhexis (KR), karyolysis (KL) and pyknosis (P) in exfoliated buccal cells. The cells were collected from 83 healthy heavy smokers (n=15-25/group) consuming a similar number of cigarettes (26-33) per day and from never smokers as controls (n=20). The frequencies of KR, CC, KL, BE and BN were increased significantly only in smokers of medium (MF) and non-filtered (NF) types of cigarettes while MN levels were only elevated (p < 0.0001) in the group that smoked NF cigarettes. Since BN and BE were increased (p < 00001) as a consequence of exposure to lower levels of toxic constituents in tobacco, it suggests that these endpoints, which both reflect DNA damage, are more sensitive than MN, which is the only parameter scored in most earlier studies. The induction of MN, BN, KR and KL increased significantly with daily tar exposure and decreased simultaneously with daily nicotine uptake (in all cases, P was < 0.0001). These findings also suggest that nicotine potentially protects cells against DNA reactive carcinogens contained in tobacco smoke although earlier in vitro and animal studies showed that the alkaloid induces DNA damage per se. A significant inverse correlation between the frequencies of endpoints such as cells with MN (- 1.56), MN (-1.69), BN (-1.36), KR (-1.10) and KL (-1.87) with the nicotine levels in cigarettes was found. However, this observation requires further verification by a controlled intervention study. In case it can be substantiated it will have an impact on the ongoing discussion of the health risks associated with nicotine replacement therapy.