EVALUATION OF DNA-DAMAGE IN LEUKOCYTES OF EX-SMOKERS BY SINGLE-CELL GEL-ELECTROPHORESIS

Single cell gel electrophoresis (SCGE), or comet assay, appears to be a promising tool to estimate DNA damage at the single cell level and i t provides information on the presence of damage among individual cell s, A follow-up study of 90 smokers who ceased smoking was undertaken t o determine the possible decrease of DNA damage in their leukocytes, B efore beginning the trial, volunteers smoked on average 26.1 +/- 8.4 c igarettes/day. Comet length did not correlate with the number of cigar ettes/day or with the condensate tar content, At the end of the study, 28 volunteers had abandoned the trial, 40 volunteers relapsed into sm oking at different times, but with a reduced number of cigarettes/day, whereas 22 fully succeeded in smoking cessation. Throughout the 5 sam pling times, a great variability of comet length at individual level w as found. However, after 1 year of follow-up, comet length means were found to be significantly shorter (p < 0.0001) in those volunteers who completely quit smoking compared to those who relapsed into smoking ( 27.2 +/- 1.6 vs. 31.9 +/- 5.1 mu m, respectively), irrespective of the amount of cigarettes previously smoked. No effect of age or sex was f ound. Six months later, these results were confirmed by a further stud y carried out on a reduced sample of volunteers. The present data stro ngly suggest that, in spite of the great variability observed, 1 year of smoking cessation is associated with a significant reduction of DNA damage in circulating leukocytes.