Abstract
Smoking is strongly associated with abnormalities in histone-to-protamine transition and with alteration of protamine expression in human spermatozoa. A proper protamine to histone ratio is, however, essential for sperm chromatin maturity and DNA integrity. Alterations in these sperm nuclear proteins were observed in infertile men. The present prospective study is aimed at evaluating the possible relationship among smoking, semen quality and the histone-to-protamine transition ratio in mature spermatozoa. Histone H2B and protamine 1 (P1) and 2 (P2) were quantified using acid-urea polyacrylamide gel electrophoresis in the spermatozoa of 35 smokers and 19 non-smokers. Levels of lipid peroxidation marker malondialdehyde (MDA) were measured in seminal plasma by thiobarbituric acid assay. Cotinine concentrations were determined in seminal plasma using an enzyme-linked immunosorbent assay. Histone H2B levels in smokers (292.27 +/- 58.24 ng/10(6)) were significantly higher (p = 0.001) than that of non-smokers (109.1 +/- 43.70 ng/10(6)), besides, a significant difference (p > 0.0001) was found for the P1 and P2 ratio between smokers (1.71 +/- 0.071) and non-smokers (1.05 +/- 0.033). The H2B/(H2B+ P1 + P2) ratio (0.29 +/- 0.71) of smokers were significantly higher (p = <0.0001) than that of non-smokers (0.12 +/- 0.01). The concentrations of MDA (mu M) (7.13 +/- 1.15) and cotinine (ng/mL) (60.44 +/- 31.32) in seminal plasma of smokers were significantly higher (p = 0.001) than those in the samples of the non-smoker group (4.42 +/- 1.16 and 2.01 +/- 2.84 respectively). In addition, smokers showed significantly (p <= 0.002) lower sperm count, motility (p = 0.018), vitality (p = 0.009) and membrane integrity (p = 0.0001) than non-smokers. These results reveal that patients who smoke possess a higher proportion of spermatozoa with an alteration of the histone to protamine ratio than patients who do not smoke, and suggest that cigarette smoking may inversely affect male fertility.