Global DNA Methylation and DNA Methyltransferase Status Among Cigarette Smokers in Saudi

Smoking is a serious public health concern worldwide. It is a common environmental factor causing epigenetic alterations. This study aimed to explore the effect of smoking on DNA methylation by quantifying global DNA methylation, measuring the concentrations of plasma DNA methyltransferases (DNMT1, DNMT3A, and DNMT3B) among cigarette smokers in Saudi, and comparing these results with those of nonsmokers. Whole blood specimens were collected from Saudi cigarette smokers (n = 36) and non-smokers as controls (n = 36). Global DNA alteration was determined by a 5-methylation Cytosine (5-mC) colorimetric assay, and the concentration of DNMT proteins was measured by enzyme-linked immunosorbent assay (ELISA). DNA hypomethylation was found in smokers compared with controls (p < 0.001). Cigarette smokers showed significantly increased DNMT concentrations (DNM-1, DNMT-3A, and DNMT-3B) (p < 0.005). Global DNA hypomethylation correlated significantly with smoking duration (r = -0.854, p = 0.040) but not with other clinical parameters. In addition, DNMTs also were significantly correlated with smoking duration DNMT1 (r = 0.033, p = 0.002), DNMT3A (r = 0.431, p < 0.001), and DNMT3B (r = 0.553, p = 0.015). Our findings suggest that cigarette smoke induces epigenetic dysregulation, a principal player in cancer and various diseases through global DNA hypomethylation and high concentrations of DNMTs among cigarette smokers compared with nonsmokers.