Mononuclear leukocyte DNA damage and oxidative stress: The association with smoking of hand-rolled and filter-cigarettes

Abstract

Cigarette smoking is a major cause of human cancer at various sites, although its carcinogenic mechanisms still remain unestablished. Based on the use of a filter, cigarette smoke can be divided into a gas phase and a tar phase. Both contain different concentrations of oxidants, free radicals and tobacco-specific carcinogens. To explore the effects of both filtered and non-filtered cigarette smoke on DNA damage and oxidative status, we measured the level of mononuclear leukocyte DNA damage by use of the single-cell gel electrophoresis (Comet) assay. We also determined malondialdehyde (MDA), protein carbonyl content (PC) and total antioxidative capacity (TAC) levels in blood plasma of smokers of manufactured filter-cigarettes and of hand-rolled cigarettes. Cotinine levels were also measured in plasma to estimate the degree of smoking. Mononuclear leukocyte DNA damage, plasma MDA, plasma PC and plasma cotinine levels were found significantly higher, while plasma TAC levels were found significantly lower in smokers of filter-cigarettes and smokers of hand-rolled cigarettes, compared with control subjects. TAC levels in hand-rolled and manufactured filter-cigarette smokers were not significantly different from each other. However, the levels of DNA damage, plasma MDA, plasma cotinine, and plasma protein oxidation were significantly higher in hand-rolled cigarette smokers than in filter-cigarette smokers. There was a significant positive correlation between MDA and DNA damage in both hand-rolled cigarette smokers and manufactured filter-cigarette smokers. This study indicates that smoking of hand-rolled cigarettes has stronger genotoxic and oxidative effects on the metabolism than smoking of manufactured filter-cigarettes. We propose that these harmful effects could be attributed to the higher level of oxidants.