Potential effect of tobacco cigarettes smoking on global DNA methylation status and protamines transcripts in human spermatozoa

Abstract Background Epigenetics refers to an alteration in gene expression without alteration in the sequence of DNA and this process may be affected by environmental factors and lifestyle like cigarette smoking. This study was designed to evaluate the potential effect of cigarette smoking on the global DNA methylation status and the transcription level of protamine 1 and protamine 2 in human spermatozoa. A total of 188 semen samples were collected from men with a mean age of 34.9 ± 5.8 years old (98 heavy smokers and 90 non-smokers). The DNA and RNA were isolated from purified spermatozoa, then the status of global DNA methylation and the transcription level of protamine 1 and protamine 2 were evaluated using ELISA and qPCR, respectively. The chromatin non-condensation and DNA fragmentation in human spermatozoa were evaluated using chromomycin A3 staining and TUNEL assay, respectively. Results A significant increase has been found in the status of global DNA methylation in spermatozoa of heavy smokers compared to non-smokers (7.69 ± 0.69 ng/μl vs. 4.90 ± 0.40 ng/μl, P P P P r = 0.304, P r = 0.399, P r = 0.216, P = 0.003; r = 0.494, P Conclusion Tobacco cigarette smoking has a potential influence on the global DNA methylation and the transcription level of protamine genes in human spermatozoa, and consequently, affect negatively on the semen parameters.