Effect of smoking on the functional aspects of sperm and seminal plasma protein profiles in patients with varicocele

Abstract

Study question: What are the effects of smoking on the functional aspects of the sperm, the levels of lipid peroxidation and the protein profile of seminal plasma in patients with varicocele?

Summary answer: In men with varicocele, smoking is associated with altered semen quality, decreased sperm functional integrity and seminal oxidative stress. Alterations in seminal plasma protein profiles are also present and may explain the altered semen phenotype.

What is known already: Varicocele is a major cause of male infertility. It reduces testicular blood renewal with a consequent accumulation of toxic substances. Thus, it can potentiate the toxic effects of environmental exposure to genotoxic substances such as those found in cigarette smoke.

Study design, size and duration: A cross-sectional study was performed in 110 patients presenting with variococele to the Human Reproduction Section of the Sao Paulo Federal University (2006-2010). The patients were divided into a control group of non-smokers, a moderate smokers group and a heavy smokers group.

Participants/materials, setting and methods: Semen parameters were analysed by standard methods. Sperm DNA integrity and mitochondrial activity were assessed by Comet assays and by 3,3'-diaminobenzidine deposition, respectively. The level of lipid peroxidation in semen was determined by malondialdehyde quantification. Proteomic studies were performed by 2D-electrophoresis and mass spectrometry.

Main results and the role of chance: Both groups of smokers showed reduced semen quality in comparison with the control group. In the groups of smokers, sperm DNA integrity and mitochondrial activity were also decreased and lipid peroxidation levels were increased. Proteomic analyses revealed 20 proteins differentially expressed between the study groups.

Limitations and reasons for caution: A study including smokers without varicocele is still warranted as these results apply only to smokers who present varicocele.

Wider implications of the findings: Patients with varicocele who are exposed to tobacco smoking present more important alterations to semen quality and sperm functional integrity and show changes in the seminal plasma proteome. This suggests testicular, and possibly systemic, adverse effects of smoking.

Study funding/competing interest(s): Funding for the study was provided by Fundação de Amparo à Pesquisa do Estado de São Paulo (Fapesp) (2007/59423-7) and by the Division of Urology, Human Reproduction Section at the São Paulo Federal University.