Human semen contains spermatozoa as well as populations of round nonspermatozoal cells primarily consisting of leukocytes. Activation of white blood cells present in the seminal plasma during genital tract inflammation and cellular reactions against microbial agents may provoke a release of a variety of products such as cytokines and reactive oxygen species. The aim of this study was to evaluate whether a panel of selected cytokines (interleukin [IL]‐1β, IL‐6, IL‐8, and tumor necrosis factor‐α [TNFα]) detectable in seminal plasma during male genital tract inflammation could be considered as mediators between altered semen parameters and changed levels of pro‐oxidant and antioxidant substances. Studies using chemiluminometric, spectrophotometric, and enzyme‐linked immunosorbent assay methods indicate that proinflammatory cytokines such as IL‐1β, IL‐6, IL‐8, and TNFα may modulate pro‐oxidant and antioxidant activities in the male genital tract. The data also suggest that the function of pro‐oxidant and antioxidant systems in semen may directly influence basic semen parameters. The elevated numbers of leukocytes present in semen during male genital tract inflammation without an associated contribution of cytokines and semen antioxidant capacity appear to be of little prognostic value in evaluating male fertilization potential.

The invasion of the male reproductive tract by microorganisms, and its subsequent consequences for sperm fertilizing potential, has been intensely discussed. The role of the bacteria that are responsible for the colonization and contamination of the male urogenital tract, rather than its infection, in diminished sperm parameters raises the most controversy. There are numerous premises suggesting that bacterial semen infection is associated with male infertility. However, the molecular mechanism by which the fertility is affected is complex and multifactorial, and still presents a puzzle. Some authors have suggested that direct interactions between bacteria and human spermatozoa facilitate sperm immobilization, affect sperm morphology, and thus weaken the ability of sperm to fertilize. On the other hand, the massive infiltration of activated leukocytes into the inflammatory site may be associated with impairment of sperm fertilizing potential, due to oxidative, apoptotic, and immune processes. This review presents current research trends and aims to summarize the present knowledge of semen inflammation and causative bacterial agents in the male urogenital tract, with its consequence on seminological parameters, and male fertility status.

We have examined the effect of white blood cells (WBCs), various proinflammatory cytokines, or a combination of the two on the peroxidation of human sperm membrane lipids in in vitro conditions. Six recombinant cytokines, such as interleukin‐1β (IL‐1β), IL‐6, IL‐8, IL‐12, IL‐18, and tumor necrosis factor alpha (TNF‐α), used singly or in combinations, were analyzed. WBCs were isolated from the whole heparinized blood using a density gradient technique (Histopaque 1.077). Spermatozoa were isolated from semen samples with normal sperm parameters by both the swim‐up technique (swim‐up fraction) and by a discontinuous Percoll gradient centrifugation (90% and 47% Percoll fractions). Peroxidative damage to sperm membrane lipids was assessed by determining the concentration of malondialdehyde (MDA) in lysates of spermatozoa using high‐performance liquid chromatography (HPLC). There were no statistically significant differences in MDA concentrations between sperm fractions incubated with cytokines and respective controls (spermatozoa alone). In spermatozoa isolated by the swim‐up technique, the MDA level was significantly higher only after incubation with IL‐6 and IL‐8 plus WBCs when compared to sperm incubated with leukocytes alone (0.62 ± 0.21 μmol/L and 0.42 ± 0.22 μmol/L, respectively; P < .05). In spermatozoa recovered from the 47% Percoll, only a combination of IL‐12 and IL‐18 used together with WBCs was linked with a significant increase in MDA concentration (from 0.41 ± 0.13 μmol/L to 0.65 ± 0.19 μmol/L; P < .05). The results obtained suggest that cytokines produced during the inflammatory process intensify the level of oxidative stress caused by leukocytes, which may have serious consequences for sperm membrane integrity.

Abnormal standard semen characteristics and reduced sperm chromatin maturity can appear with increasing male age. However, the influence of paternal age on semen parameters is still controversial. Therefore, this study was designed to estimate the influence of paternal age not only on conventional semen characteristics but also on sperm DNA integrity. This research was carried out on ejaculated sperm cells obtained from men (n = 1124) aged ≥40 y and 10% DFI, low fertility potential) in the groups of men aged ≥40 y than in the groups of men aged <40 y. Older men had over twice the odds ratio for high sperm DNA damage as younger men. Our findings suggest a detrimental effect of advanced paternal age on sperm chromatin integrity. The data show that the evaluation of sperm DNA has greater clinical utility than standard semen analysis in case of male fertility potential assessment.