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Summary Kisspeptin, the product of the KISS1 gene, plays an essential role in the regulation of spermatogenesis acting primarily at the hypothalamic level of the gonadotropic axis. However, the presence of kisspeptin and its canonical receptor, KISS1R, in spermatozoa has not been explored nor the direct effects of kisspeptin on sperm function have been studied so far. In the present study, we analysed the expression of kisspeptin and its receptor in sperm cells by western blot and immunocytochemistry assays and evaluated the effects of exposure to kisspeptin on sperm intracellular Ca2+ concentration, [Ca2+]i, sperm motility, sperm hyperactivation and the acrosome reaction. Changes in [Ca2+]i were monitored using Fura‐2, sperm kinematic parameters were measured using computer‐assisted sperm analysis (CASA), and the acrosome reaction was measured using fluorescein isothiocyanate‐coupled Pisum sativum agglutinin lectin (FITC–PSA method). We found that kisspeptin and its receptor are present in sperm cells, where both are mainly localized in the sperm head, around the neck and in the flagellum midpiece. Exposure to kisspeptin caused a slow, progressive increase in [Ca2+]i, which reached a plateau about 3–6 min after kisspeptin exposure. In addition, kisspeptin modulated sperm progressive motility causing a biphasic (stimulatory and inhibitory) response and also induced transient sperm hyperactivation. The effects of kisspeptin on sperm motility and hyperactivation were inhibited by the antagonist of KISS1R, peptide 234. Kisspeptin did not induce the acrosome reaction in human spermatozoa. These data show for the first time that kisspeptin and its receptor are present in human spermatozoa and modulate key parameters of sperm function. This may represent an additional mechanism for their crucial function in the control of male fertility.

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Tachykinins may be involved in reproduction. A reverse transcription-polymerase chain reaction assay was used to analyze the expression of tachykinins and tachykinin receptors in different types of reproductive cells from mice. The preprotachykinin (PPT) genes, PPT-A, PPT-B and PPT-C, that encode substance P/neurokinin A, neurokinin B, and hemokinin-1, respectively, and the genes that encode the tachykinin NK1, NK2, and NK3 receptors were all expressed, at different levels, in the uterus of superovulated, unfertilized mice. The mRNA of neprilysin (NEP), the main enzyme involved in tachykinin metabolism, was also expressed in the uterus. Isolated cumulus granulosa cells expressed PPT-A, PPT-B, PPT-C, and NEP and low levels of the tachykinin NK1 and NK2 receptors. Mouse oocytes expressed PPT-A and -B mRNA transcripts. A low expression of the three tachykinin receptors was observed but PPT-C and NEP were undetectable. Two- and 8- to 16-cell mouse embryos expressed only a low-abundance transcript corresponding to the NK1 receptor. However, the mRNAs of PPT-B, PPT-C and NEP appeared in blastocyst-stage embryos. A low-abundance transcript corresponding to the NK2 receptor was the only target gene detected in mice sperm. Female mice or rats treated neonatally with capsaicin showed a reduced fertility. A reduction in litter size was observed in female rats treated in vivo with the tachykinin NK3 receptor antagonist SR 142801. These data show that tachykinins of both neuronal and nonneuronal origin are differentially expressed in various types of reproductive cells and may play a role in female reproductive function.

Infertility has become a global health issue, with approximately 50% of infertility cases generated by disorders in male reproduction. Spermatozoa are conveyed towards female genital tracts in a safe surrounding provided by the seminal plasma. Interestingly, this dynamically changing medium is a rich source of proteins, essential not only for sperm transport, but also for its protection and maturation. Most of the seminal proteins are acquired by spermatozoa in transit through exosomes (epididymosomes and prostasomes). The high number of seminal proteins, the increasing knowledge of their origins and biological functions and their differential expression in the case of azoospermia, asthenozoospermia, oligozoospermia and teratozoospermia or other conditions of male infertility have allowed the identification of a wide variety of biomarker candidates and their involvement in biological pathways, thus to strongly suggest that the proteomic landscape of seminal plasma may be a potential indicator of sperm dysfunction. This review summarizes the current knowledge in seminal plasma proteomics and its potentiality as a diagnostic tool in different degrees of male infertility.

1 Studies were undertaken to determine the nature of the receptors mediating contractile effects of tachykinins in the uteri of nonpregnant women, and to analyse the expression of preprotachykinins (PPT), tachykinin receptors and the cell-surface peptidase, neprilysin (NEP), in the myometrium from pregnant and nonpregnant women. 2 The neurokinin B (NKB) precursor PPT-B was expressed in higher levels in the myometrium from nonpregnant than from pregnant women. Faint expression of PPT-A mRNA was detectable in the myometrium from nonpregnant but not pregnant women. PPT-C, the gene encoding the novel tachykinin peptide hemokinin-1 (HK-1), was present in trace amounts in the uteri from both pregnant and nonpregnant women. 3 Tachykinin NK 2 receptors were more strongly expressed in tissues from nonpregnant than from pregnant women. NK 1 receptor mRNA was present in low levels in tissues from both pregnant and nonpregnant women. A low abundance transcript corresponding to the NK 3 receptor was present only in tissues from nonpregnant women. 4 The mRNA expression of the tachykinin-degrading enzyme NEP was lower in tissues from nonpregnant than from pregnant women. 5 Substance P (SP), neurokinin A (NKA) and NKB, in the presence of the peptidase inhibitors thiorphan, captopril and bestatin, produced contractions of myometrium from nonpregnant women. The order of potency was NKAbSPXNKB. The potency of NKA was unchanged in the absence of peptidase inhibitors. Nle 10 ]NKA(4 -10). 8 These data are consistent with a role of tachykinins in the regulation of human uterine function, and reinforce the importance of NK 2 receptors in the regulation of myometrial contraction.

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Background: We have investigated the expression of voltage-gated sodium channels in human spermatozoa and characterized their role in sperm motility.