Tobacco smoking and its impact on the expression level of sperm nuclear protein genes: H2BFWT, TNP1, TNP2, PRM1 and PRM2

The aim of this current study was to investigate the influence of tobacco smoke on sperm quality determined by standard parameters, on sperm DNA maturity tested by chromomycin A3 (CMA3) staining, on sperm DNA fragmentation tested by TUNEL assay and on the transcript level of sperm nuclear proteins H2BFWT, PRM1, PRM2, TNP1 and TNP2 genes quantified by RT-PCR. One hundred forty-one (141) sperm samples (43 nonsmokers (G.1) and 98 heavy smokers (G.2)) of couples undergoing ICSI were enrolled in this study. In G2, a significant decrease in standard semen parameters in comparison with nonsmokers was shown (p < .01). In contrast, protamine deficiency (CMA3 positivity) and sperm DNA fragmentation (sDF) were significantly higher in G2 than in G1 (p < .01). Furthermore, the studied genes were differentially expressed (p < .01), down-regulated in the spermatozoa of G.2 compared to that of G.1 (fold change <0.5) and were significantly correlated between each other (p < .01). Moreover, in comparison with G1, the protamine mRNA ratio in G2 was significantly higher (p < .01). It can therefore be concluded that smoking alters mRNA expression levels of H2BFWT, TNP1, TNP2, PRM1 and PRM2 genes and the protamine mRNA ratio and consequently alters normal sperm function.