Seminal tumor necrosis factor-alpha level and sperm nuclear DNA integrity in normozoospermic men

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DNA damage in the male germ line is associated with poor semen quality, low fertilization rates or impaired preimplantation development. The causes of this DNA damage are still uncertain but the major candidates are oxidative stress and aberrant apoptosis. Tumor necrosis factor-alpha (TNF-a), a proinflammatory cytokine, is able to induce apoptosis and act as a proapoptotic factor. In vitro study demonstrated that co-incubation of TNF-a with sperms decreases total motility and produces chromatin and DNA fragmentation in a concentration- and time-dependent manner. To date, seminal concentration of TNF-a in relevant to sperm nuclear DNA integrity has not been studied. The present study aimed to evaluate seminal concentration of TNF-a in correlation with sperm parameters and nuclear DNA integrity in normozoospermic men. Prospective study. Forty-five ejaculated semen samples were obtained from healthy donors (n = 41) or male partners undergoing infertility investigation (n = 4) with age ranged from 25 to 50 years. All of subjects had no signs of genital inflammation and had normal sperm concentration (mean ± SD, 648.2 ± 273.5×106/mL). Sperm motilities were ranged between 22.7% and 86.3%. Routine sperm quality was assessed by computer-assisted semen analysis (CASA) and nuclear DNA integrity was measured by the TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick-end labelling (TUNEL) assay in raw semen. After centrifugation without washing, seminal plasmas were separated and then immediately frozen. TNF-a concentrations were measured by enzyme-linked immunosorbent assay (ELISA) in thawed seminal plasmas. Statistical analysis was performed using MedCalc. Sperm DNA fragmentation rates were ranged between 1.9% and 53.0% (mean ± SD, 12.4 ± 9.6%). Univariate analysis revealed that DNA fragmentation rate was not associated with sperm concentration and motility but had a negative correlation with linearity (r = −0.3247, P=0.0295). Seminal TNF-a was not detectable in 12 subjects (<1.0 pg/mL). The mean seminal concentration of TNF-a was 4.9 pg/mL with a range from 1.1 to 22.6 pg/mL. The TNF-a concentration had no correlation with clinically relevant parameters of sperm quality or nuclear DNA fragmentation rate. Our results indicate that sperm nuclear DNA fragmentation is not associated with seminal TNF-a level or sperm quality in asymptomatic normozoospermic men. Sperm nuclear DNA fragmentation in asymptomatic normozoospermic men may be not caused by seminal TNF-a.