The accumulated data suggest that inflammation can increase the level of reactive oxygen species (ROS), which contribute to impaired sperm function and male infertility. Therefore, we propose that inflammation-mediated production of ROS in male and female reproductive tracts hinder sperm fertilisation. To test this hypothesis, phorbol myristate acetate (PMA) with polymorphonuclear leucocytes (PMNs) was applied to generate endogenous ROS. We evaluated the time-dependent effects of ROS on human sperm motility, viability and mitochondrial membrane potential (MMP). The results showed that after treatment with PMA and PMNs, the motility of human spermatozoa significantly decreased to 50% on Day 1 and 15% on Day 4 compared with that of the, respectively, negative controls (P = 0.012). The viability of human spermatozoa decreased on Day 4 of PMA + PMNs treatment (P = 0.028). The MMP of human spermatozoa significantly decreased from Day 2 to Day 4 in the PMA + PMN group compared with that of the controls (P = 0.019). Taken together, the 4-day cultivation approach provided an accurate evaluation of sperm quality, especially sperm motility and MMP. Our findings indicated that endogenous inflammation increased ROS levels, which might induce sperm oxidative damage. Additionally, sperm motility might be one of the earliest and most sensitive indicators of this damage.

Fertilization, the recognition and fusion between spermatozoa and oocyte, involves various molecules on the spermatozoa and oocyte membranes. Concanavalin A (ConA)-binding proteins may be one of the molecules involved in mammal spermatozoa fertilization; however, their structure and function remain largely unknown. Here, we initially identified a ConA-binding protein, Zn-α2-glycoprotein (ZAG), involved in regulating the acrosome reaction (AR) of human spermatozoa. ZAG is localized on the pre-equatorial region covering the acrosome, neck and tail (some parts of middle piece and principal piece respectively) regions of the acrosome intact human spermatozoa, and disappears in the acrosomal region of the acrosome-reacted spermatozoa. Polyclonal antibodies against human recombinant ZAG significantly reduced the AR and sperm capability binding to human zona pellucida or penetration into zona-free hamster oocytes. Furthermore, assessment of the signaling pathways regulated by ZAG revealed that ZAG affects sperm AR through both the cAMP/PKA and PKC pathways. These results indicate that ZAG, which is present on the human sperm membrane, plays a critical role in the AR and subsequently, may be involved in sperm fertility.

SUMMARYAdequate sperm motility is requisite for human fertilization, whereas the underlying causes or mechanisms of impaired sperm motility, asthenozoospermia, still remain largely unknown. RNASET2 (Ribonuclease T2) may be one of the effectors modulating human sperm motility. We determined if there is a correlation between RNASET2 expression levels in human semen from asthenozoospermia and fertile individuals. Thus, RNASET2 expression levels in spermatozoa and seminal plasma of healthy and asthenozoospermia individuals were evaluated using Western blot, laser scanning confocal microscope analysis, ELISA and flow cytometry. The results revealed that RNASET2 expression was identified in both human spermatozoa and seminal plasma. In spermatozoa from fertile individuals, it was localized to the acrosome, neck and the middle piece of tail regions. However, in spermatozoa from asthenozoospermia individuals (n = 67), RNASET2 staining was especially more frequent and evident in the neck and middle piece than that in fertile individuals (n = 59, p < 0.01). Similarly, higher RNASET2 expression was also apparent in seminal plasma from asthenozoospermia than in fertile individuals (p < 0.01). Moreover, purified RNASET2 had an inhibitory effect on sperm motility, especially on progressive motility (n = 23, p < 0.05). In conclusion, higher expression of RNASET2 in the semen of asthenozoospermia individuals may contribute to sperm motility impairment.