Cigarette smoking by the male partner adversely affects assisted reproductive techniques, suggesting that it may damage sperm chromatin/DNA and consequently embryo development. The effects of graded concentrations of research cigarettes smoke extract (CSE) on motility, mitochondrial membrane potential (MMP), chromatin integrity and apoptosis were evaluated in spermatozoa obtained from 13 healthy, non-smoking men with normal sperm parameters, by flow cytometry. CSE suppressed sperm motility in a concentration- and time-dependent manner and increased the number of spermatozoa with low MMP, the main source of energy for sperm motility. In addition, CSE had a detrimental effect on sperm chromatin condensation and apoptosis. Indeed, it increased the number of spermatozoa with phosphatidylserine externalization, an early apoptotic sign, and fragmented DNA, a late apoptotic sign, in a concentration- and time-dependent manner. These effects of CSE were of similar or even greater magnitude to those obtained following incubation with tumour necrosis factor-alpha, a cytokine known for its negative impact on sperm function, used as positive control. Since transmission of smoking-induced sperm DNA alterations has been found in pre-implantation embryos, and this may predispose offspring to a greater risk of malformations, cancer and genetic diseases, men seeking to father a child are recommended to give up smoking.

C. trachomatis causes sperm PS externalization and DNA fragmentation. These effects may explain the negative direct impact of C. trachomatis infection on sperm fertilizing ability.

The aim of this study was to evaluate the effects of tumour necrosis factor-alpha (TNF-alpha) on sperm motility, mitochondrial membrane potential (DeltaPsi), phosphatidylserine (PS) externalization, sperm chromatin packaging quality, and DNA fragmentation. Motile spermatozoa, obtained from 10 normozoospermic men, were incubated with increasing concentrations of TNF-alpha and analyzed 1, 3, 6, and 24 h after incubation by flow cytometry. TNF-alpha decreased total motility 24 h after incubation at 10 ng/mL and progressive motility 3 h after incubation. Accordingly, TNF-alpha reduced sperm DeltaPsi in a concentration- and time-dependent manner. TNF-alpha increased the percentage of spermatozoa with PS externalization from the concentration of 1 ng/mL 1 h after incubation. TNF-alpha produced sperm chromatin and DNA damage in a concentration- and time-dependent manner. In conclusion, these findings may explain the reduction of fertility, secondary to upregulated production of TNF-alpha, in men with urogenital infections.

The correct spelling of the last author's full name is Aldo E. Calogero.

This study showed that car exhaust exposure has a genotoxic effect on human spermatozoa. This may be of relevant importance not only for the reproductive performance of the men exposed, but also for the offspring health.