[Effect of chrysotile and cigarette smoking solution on DNA damage and repair in human alveolar epithelial cells]

To study the effect of chrysotile and solution of cigarette smoke separately or combined on DNA damage and repair.

Single-cells gel electrophoresis assay was used to detect break in DNA strand and to analyze its repair function in human alveolar epithelial cell line A549, which were exposed to chrysotile or cigarette smoke solution separately or combined for one hour and then immediately cultured for different time.

Break in DNA strands was induced obviously in A549 cells after exposure to 40 microg/ml of chrysotile or 2.5 x 10(-4) cig/ml of cigarettes smoke solution for one hour. Repair for DNA break could be seen clearly in chrysotile-treated cells after continuing culture for three hours, and 30.6% had been repaired after culture for four hours. Repair could also be seen clearly in cigarette smoke solution-treated cells after continuing culture for two hours, and 65.2% had been repaired after culture for four hours. Repair of DNA in cells exposed to both chrysotile and cigarette smoke solution combined was similar to that exposed to cigarette smoke solution only.

Damage to DNA caused by chrysotile is more difficult to repair than that induced by cigarette smoking solution.