Stimulation of platelet-activating factor synthesis by progesterone and A23187 in human spermatozoa

The presence of platelet-activating factor (PAF) has been demonstrated recently in mammalian spermatozoa, together with evidence for a role of this phospholipid in enhancing sperm motility and fertilizing ability. To investigate whether PAF synthesis and release occurs in human spermatozoa following incubation with stimuli that induce acrosome reaction, spermatozoa were incubated with progesterone and A23187, two known inducers of the exocytotic event. PAF synthesis (remodelling pathway) was assessed by [3H]acetate incorporation into PAF. Treatment of spermatozoa with progesterone and A23187 resulted in an increase of [3H]acetate incorporation into PAF. Most of the newly synthesized [3H]PAF formed in response to acrosome reaction was found in the supernatant, suggesting a release of the phospholipid from spermatozoa. PAF-like material extracted from human spermatozoa was able to induce aggregation of rabbit platelets and showed identical retention time and the same ion m/e values as authentic PAF when analysed with g.c.-m.s. Lyso-PAF:acetyl-CoA acetyltransferase (EC 2.3.1.67) activity in human spermatozoa was also studied and showed similar kinetic parameters to those described for other cell systems. Stimulation of spermatozoa with progesterone and A23187 induced an increase of [3H]arachidonic acid release, suggesting an activation of phospholipase A. In conclusion, our results demonstrated increased production and release of PAF in human sperm following stimulation with progesterone and A23187 and suggest a role for this phospholipid in the activation of spermatozoa.

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Role of Angiotensin-(1–7) via MAS receptor in human sperm motility and acrosome reaction

Reproduction ◽

10.1530/rep-19-0274 ◽

2020 ◽

Vol 159 (3) ◽

pp. 241-249 ◽

Cited By ~ 9

Author(s):

Asier Valdivia ◽

Lorea Cortés ◽

Maider Beitia ◽

Lide Totorikaguena ◽

Naiara Agirregoitia ◽

...

Keyword(s):

Sperm Motility ◽

Acrosome Reaction ◽

Mrna Level ◽

Human Sperm ◽

Human Spermatozoa ◽

Dependent Manner ◽

Mas Receptor ◽

Sperm Mobility ◽

Specific Antagonist

Rennin-angiotensin system (RAS) has been involved in sperm function, even so, little is known about the implication of one of the RAS axis formed by Ang-(1–7) (angiotensin-(1–7)) and MAS receptor. Hence, in the present work, we focused on elucidating the function of the MAS receptor in human spermatozoa. We analyzed the expression and localization of MAS receptor in human spermatozoa and we observed if its activation is able to modulate the sperm motility of normal motility and/or asthenozoospermic patients, as well as, the acrosome reaction of the spermatozoa. MAS receptor is present in human mature spermatozoa, not only at the mRNA level but also at protein level. MAS is localized at the acrosome region, as well as, in the tail of spermatozoa. The sperm incubation with MAS agonist Ang-(1–7) activates at dose-dependent manner the PI3K/AKT pathway (P < 0.01 vs control) and improves the motility of asthenozoospermic patients (P < 0.01 vs control), which is blocked by the specific antagonist (A779) (P < 0.01), but it do not modulate the acrosome reaction. These findings suggest that the ACE2/Ang-(1–7)/Mas axis may be a useful biochemical tool for the treatment of male infertility related to sperm mobility.

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436. Investigation of the role of SRC in capacitation associated tyrosine phosphorylation of human spermatozoa

Reproduction Fertility and Development ◽

10.1071/srb08abs436 ◽

2008 ◽

Vol 20 (9) ◽

pp. 116

Author(s):

L. A. Mitchell ◽

B. Nixon ◽

M. A. Baker ◽

R. J. Aitken

Keyword(s):

Tyrosine Kinase ◽

Tyrosine Phosphorylation ◽

Signal Transduction Pathway ◽

Human Sperm ◽

Complex Signal ◽

Phosphorylation Cascade ◽

A Site ◽

Signalling Cascade ◽

Mammalian Spermatozoa

Capacitation is a pre-requisite for mammalian spermatozoa allowing them to gain the ability to fertilise an oocyte. A fundamental part of this mechanism is a dramatic increase in tyrosine phosphorylation. Implicated in this process in the mouse is a unique cAMP/PKA-mediated pathway involving a PKA-activated tyrosine kinase suggested to be pp60c-src (SRC). The Src kinases examined were predominantly expressed in the human sperm tail, a site compatible with a role in mediating the capacitation-associated tyrosine phosphorylation cascade. Co-immunoprecipitation revealed that PKA-c could be isolated from sperm and this interaction was restricted to capacitated cells, suggesting PKA-mediated activation of SRC forms an integral part of the signalling cascade assembled during capacitation. Upon activation, SRC undergoes autophosphorylation of Y416 and thus phosphorylation of this residue indicates the presence of active SRC kinase. The phosphorylation status of SRC was compared using both 2D-immunoblotting and immunocytochemical studies, both revealing a significant increase in SRC activation during capacitation. Furthermore, suppression of PKA and SRC through application of SU6656, or H89, a PKA inhibitor, led to a dramatic decrease in tyrosine phosphorylation and SRC activity. In conclusion, this study has provided evidence for the involvement of non-receptor tyrosine kinase, SRC, in regulating tyrosine phosphorylation associated with capacitation. Inhibition of SRC did not completely suppress tyrosine phosphorylation suggesting this complex signal transduction pathway exhibits a degree of functional redundancy.

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Stimulation of calcium influx by platelet activating factor in Dictyostelium

Journal of Cell Science ◽

10.1242/jcs.108.4.1597 ◽

1995 ◽

Vol 108 (4) ◽

pp. 1597-1603

Author(s):

R. Schaloske ◽

C. Sordano ◽

S. Bozzaro ◽

D. Malchow

Keyword(s):

Plasma Membrane ◽

G Protein ◽

Dictyostelium Discoideum ◽

Calcium Influx ◽

Platelet Activating Factor ◽

Inactive Compound ◽

Time Period ◽

Dependent Pathway ◽

Stimulation Of

Platelet activating factor (PAF) induces Ca2+ influx in Dictyostelium discoideum. In this investigation we used this activity to analyze the mechanism of PAF action. We found that PAF activity was confined to the period of spike-shaped oscillations and suggest that the role of PAF is to augment cAMP relay. PAF seems to act only a few times during this time period of two hours, since Ca2+ entry adapted to a subsequent stimulus for about 30 minutes. PAF showed a reduced response in the G protein beta- strain LW14 and was unable to induce Ca2+ influx in the G alpha 2- strains HC85 and JM1. The latter expresses the cAMP receptors cAR1 constitutively, and exhibits cAMP-induced Ca2+ influx, albeit at a reduced level. In order to decide whether the inability of PAF to elicit a Ca2+ response in JM1 cells was due to the lack of differentiation and/or the lack of G alpha 2, we inhibited the IP3-dependent pathway with compound U73122 and found that Ca2+ entry was blocked, whereas a closely related inactive compound, U73343, did not alter the response. In agreement with this, NBD-Cl, an inhibitor of Ca2+ uptake into the IP3-sensitive store in Dictyostelium, also abolished PAF activity. The latter was not inhibited by the plasma membrane antagonists BN-52021 or WEB 2170. Therefore PAF seems to operate intracellularly via the IP3-signalling pathway at or upstream of the IP3-sensitive store.

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