Redox control of surface protein sulphhydryls in bovine spermatozoa reversibly modulates sperm adhesion to the oviductal epithelium and capacitation

Abstract

Oviductal fluid molecules, such as sulphated glycosaminoglycans and disulphide-reductants, may represent periovulatory signals for the release of spermatozoa from the oviductal reservoir in the bovine species. Disulphide-reductants release spermatozoa through the reduction of sperm-surface disulphides to sulphhydryls (SH). Herein, we studied sperm-surface protein SH through labelling with maleimidylpropionyl biocytin in the initial sperm suspension, in the subpopulations able and unable to adhere to the in vitro cultured oviductal epithelium, and in spermatozoa released either through the disulphide-reductant penicillamine (PEN) or the sulphated glycosaminoglycan heparin (HEP). Adhesion assays were performed to study the ability of released spermatozoa to readhere to the oviductal epithelium. Results showed that the level of SH in sperm-surface proteins was: 1) low in adhering spermatozoa; 2) high in spermatozoa unable to adhere; and 3) markedly increased in released spermatozoa. Adhesion assays showed that: 1) PEN-released spermatozoa promptly recovered adhesion after removal of the disulphide-reductant and could be released again in response to PEN; 2) conversely, a limited number of HEP-released spermatozoa was able to readhere to the oviductal epithelium and this ability was not affected by HEP removal. Recovery of adhesion was associated to reoxidation of sperm-surface protein SH and to the reversal of capacitation. In conclusion, redox modulation of sperm-surface protein SH is involved in the release of spermatozoa adhering to the oviduct in vitro; the reversible action of disulphide-reductants might be responsible for intermittent phases of adhesions and releases; and the irreversible action of HEP indicates that it may represent a terminal releasing signal.

Penicillamine prevents ram sperm agglutination in media that support capacitation

“…PEN, and other thiols (compounds with a sulfhydryl group), have been shown to initiate sperm release through the reduction of sperm surface disulfides to sulfhydryls (Talevi et al 2007, Gualtieri et al 2009. It is probable that PEN may prevent or revert sperm association by the reduction of disulphide bonds of a sperm protein, which are required for sperm binding, to free sulfhydryls.…”

Fertilization: a sperm’s journey to and interaction with the oocyte

“…Recently, BSP homologs were found in the human (BSPH1) and mouse (32). It has also been suggested that the reducing redox environment of the oviduct could promote the release of sperm by facilitating the reduction of cell surface thiols on sperm cell proteins important for sperm-oviduct binding (33).…”

Is there a role for endocannabinoids in sperm–oviduct interaction?

“…Both release inducers act on spermatozoa and trigger capacitation-related changes (Gualtieri et al 2005, Talevi et al 2007. Although both inducers trigger capacitation, we showed that only spermatozoa capacitated by penicillamine are able to revert this process (Gualtieri et al 2009). Interestingly, CB1 was not detectable in heparin-released spermatozoa by both immunocytochemistry and western blot analysis, whereas, in spermatozoa released by penicillamine, CB1 had the same immunolocalization observed in the initial sperm population.…”

“…At the end of coincubation, unbound spermatozoa were removed by extensive washings with TALP, and cocultures were fixed to quantify the number of adhering spermatozoa as previously described (Gualtieri et al 2009). To detect the effect of AEA on spermoviduct release, explants were inseminated in TALP as above, and after unbound sperm removal, cocultures were treated with AEA 2 nM, 5 mM, or TALP alone, and analyzed.…”