A mechanistic study on the mu-opioid receptor in human spermatozoa

Van Niekerk, Nadia (2021-12)

Thesis (MSc)--Stellenbosch University, 2021.

Thesis

Background: Infertility remains a complex and often unexplained phenomenon. The effect of opioids on male reproductive parameters is best understood by the suppression of the hypothalamic- pituitary-gonadal (HPG) axis. However, since the discovery of all three opioid receptor types on human spermatozoa, it has been hypothesized that the opioid system plays a regulatory role on sperm functional parameters. Literature regarding the possible mechanisms involved in these regulatory processes remain contradictory and scarce. Therefore, this study aimed to clarify the role of the mu- opioid receptor in human spermatozoa. Methods: 30 semen samples were collected from healthy, human donors of reproductive age. Each sample was divided into 4 equal groups and treated accordingly. The study consisted of a control group, a codeine (opioid agonist) treated group, a naloxone (opioid antagonist) treated group, and a combination (codeine and naloxone) treated group. After a 3 hour incubation period, sperm functional parameters were assessed: Total motility, progressive motility and sperm kinematics were assessed using the Computer-Aided Sperm Analysis (CASA) system. Furthermore, viability, acrosome reaction and DNA fragmentation were investigated. By performing western blot analyses the total expression of A-kinase anchoring protein 3 (AKAP3) and protein kinase C𝛼 (PKC𝛼) were evaluated. Results: No differences in sperm functional parameters were detected. It was observed that codeine influenced the acrosome reaction and DNA fragmentation negatively, and that naloxone seemed to alleviate these effects, but the results were not significant. Interestingly, the study found that naloxone significantly decreased the total protein expression of AKAP3 (1 ± 0.016 vs. 0.766 ± 0.025). Conclusion: In order to clarify the role of opioid receptors on spermatozoa membranes, more research is necessary. The study results suggest that opioids may utilize sperm-specific signalling mechanisms downstream of the opioid receptors located on human spermatozoa. Understanding these mechanisms could prove to be invaluable in enhancing our understanding of infertility.

Agtergrond: Onvrugbaarheid bly 'n komplekse en dikwels onverklaarbare verskynsel. Tans word die effek van opioïede op manlike voortplantings parameters verklaar in terme van die onderdrukking van die hipotalamus-pituïtêre-gonadale (HPG)-as, maar sedert die ontdekking van al drie opioïedredeptor tipes op die menslike spermatozoa word daar gehipotiseer dat die opioïedstelsel moontlik ‘n direkte regulerende rol op spermfunksionele parameters speel. Literatuur rakende die moontlike meganismes betrokke by hierdie reguleringsprosesse bly teenstrydig en skaars. Daarom was die doel van hierdie studie om die rol van die mu-opioïedreseptor in menslike spermatosoa uit te klaar. Metodes: Semenmonsters van 30 gesonde, menslike skenkers van reproduktiewe ouderdom was versamel. Elke monster was in 4 gelyke groepe verdeel en dienooreenkomstig behandel. Die studie het bestaan uit 'n kontrolegroep, 'n kodeïenbehandelde groep (opioeïd agonis), 'n naloksoonbehandelde groep (opioeïd antagonis) en 'n kombinasie (kodeïen en naloksoon) behandelde groep. Na 'n 3 uur inkubasieperiode is sperm funksionele parameters geassesseer: Totale beweeglikheid, progressiewe beweeglikheid en sperm kinematika was geassesseer deur gebruik te maak van die Rekenaargesteunde Sperm Analise (CASA) sisteem. Lewensvatbaarheid, akrosoomreaksie en DNA-fragmentasie was ondersoek. Die proteïen uitdrukking van AKAP3 en PKCα was geëvalueer met behulp van die Western klad tegniek. Resultate: Daar was geen beduidende verskille tussen sperm funksionele parameters nie. Daar is waargeneem dat kodeïen die akrosoomreaksie en DNA-fragmentasie negatief beïnvloed het, en dat naloksoon blykbaar hierdie effekte verminder het, maar die resultate was nie betekenisvol nie. Interessant genoeg het die studie bevind dat naloksoon die totale uitdrukking van AKAP3 verminder het. Gevolgtrekking: Om die rol van opioïedreseptore op spermatozoa membrane te verduidelik, is meer navorsing nodig. Die studieresultate dui daarop dat opioïede spermspesifieke seinmeganismes stroomaf van die opioïedreseptore, wat op menslike spermatosoa geleë is, kan gebruik. Om hierdie meganismes te verstaan, kan van onskatbare waarde wees om ons begrip van onvrugbaarheid te verbeter

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/124570
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