Study Of Correlation Between Smoking And DNA Damage From Peasants Living In Mengjin County, Luoyang

Smoking can cause lung cancer, laryngeal cancer, pharyngeal cancer and other tumors. But so far the carcinogenic mechanism for cigarette smoking is still not clear. Considering that DNA is important genetic material, DNA damage might be one of the important carcinogenic mechanisms of smoking. Studies have shown that smoke contains large amounts of free radicals, which can directly cause DNA damage such as DNA strand breaks, and gene mutations.ObjectiveTo study the relationship of smoking and DNA damage by measuring the DNA and chromosomal damage indicators of smokers and nonsmokers, as well as accumulate data for further studies on carcinogenic mechanism of smoking.MethodsHealth non-smokers and smokers from Mengjin County, Luoyang were recruited as research objects by cluster sampling. ELISA method was used to detect the levels of serum cotinine, plasma 8-OHdG content and plasma PAH-DNA. Micro-whole blood specimen in alkaline single cell gel electrophoresis (SCGE) was used to detect tail moment and tail length of DNA damage. Two groups of the frequency of micronuclei in peripheral lymphocyte were detected by cytokinesis-block micronucleus assay in human lymphocyte test (CBMN). Then, the comparison and analysis of various indexes were conducted based on smoking frequency per day and smoking period.Results1. General status:The subject included 114 cases. There were 67 smokers and 47 non-smokers, and there was no significant difference (P>0.05) in ages between smoking group (53.406±7.061 years) and the non-smoking group (51.312±10.481 years). BMI were not significantly different between smoking group and non-smoking group in each age group (P>0.05). It showed that the smoking group and non-smoking group were comparable and balanced. 2.The results of cotinine:The cotinine levels of smokers group (327.011±1.293 ng/ml)was much higher than that of non-smokers group (4.661±1.802 ng/ml) (P <0.05). There was a positive linear correlation between the smoking period and the cotinine levels (r=0.815,P=0.021). Compared with<20 cig/day smokers group, cotinine levels in>20 cig/day smokers group was increased significantly (P<0.05), and a positive correlation between levels of cotinine and number of cigarette smoking per day was found. The cotinine levels of non-smokers were not linearly correlated to age (r=0.183,P=0.218).3. The results of genetic toxicity experiment:The rate of tailing cell and the tail length of non-smokers were not linearly correlated to age by using Pearson correlation analysis (the tail length:r=0.279, P=0.089; the rate of tailing cell:r=0.268, P=0.093). The rate of tailing cell and the tail length of smokers group (the tail length: 28.161±4.572μm; the rate of tailing cell:34.402±5.491%) was much higher than that of non-smokers group (the tail length:10.903±1.891μm; the rate of tailing cell: 18.5501.471%)(P<0.05). There was a positive linear relationship between the smoking period and the rate of tailing cell and the tail length of smokers (the tail length:r=0.772, P=0.001; the rate of tailing cell:r=0.811, P=0.001). Compared with <20 cig/day smokers group, the rate of tailing cell and the tail length in>20 cig/day smokers group was increased significantly (P<0.05), and a positive correlation between the rate of tailing cell and the tail length and number of cigarette smoking per day was found.The quartile of the frequency of micronuclei was from 5‰to 10‰and the median was 8%o. The frequency of micronuclei of smokers group (the median:10%o, P25=9‰, P75=11‰) was much higher than that of non-smokers group (the median: 5%o, P25= 3%o, P75= 6%o) (W=1128.500, P<0.05). The frequency of micronuclei of >20 cig/day smokers group had no significant difference compared with<20 cig/day smokers group (W=1204, P=0.491). However, the frequency of micronuclei among the three smoking period groups differed significantly (Chi-square statistic 30.701, P<0.05). With the increased in smoking period, the frequency of micronuclei was also significantly increased (P<0.05). 4. The results of DNA adducts:The 8-OHdG and PAH-DNA levels of non-smokers were not closely related to age (8-OHdG:r=0.232, P=0.107; PAH-DNA: r=0.124, P=0.115). The 8-OHdG and PAH-DNA levels of smokers group (8-OHdG: 3.912±0.461 ng/ml; PAH-DNA:96.811±4.882 ng/ml) was much higher than that of non-smokers group (8-OHdG:1.612±0.510 ng/ml; PAH-DNA:63.022±6.360 ng/ml) (P<0.05).There was a positive linear relationship between the smoking period and the PAH-DNA levels (r=0.702, P=0.001), but the 8-OHdG levels was not closely related to the smoking period (r=0.204, P=0.097). Compared with <20 cig/day smokers group, the 8-OHdG and PAH-DNA levels in(?)20 cig/day smokers group was increased significantly (P<0.05), and a positive correlation between levels of the 8-OHdG and PAH-DNA and number of cigarette smoking per day was found.ConclusionCigarettes Smoking leads to DNA single strand breaks and chromosomal damage in human peripheral lymphocyte. It shows a genotoxic effect. Cigarettes Smoking increased the level of DNA adducts such as 8-OHdG and PAH-DNA which showed DNA damage effect of smoking. The results suggest that cigarettes smoking might be an important factor inducing human genetic damage.