Production of platelet-activating factor by the pre-implantation sheep embryo

Battye, K. M.; Ammit, Alaina J.; O’Neill, Chris; Evans, G.

doi:10.1530/jrf.0.0930507

Cited by 42 publications

(19 citation statements)

References 14 publications

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“…2 Correspondence. FAX: 61 phocholine) that is released by the zygote of all mammalian species studied to date (e.g., mouse [1], human [6], rabbit [7], and sheep [8]). PAF is produced de novo from simple substrates by the zygote [9,10], and its release requires extracellular albumin [11,12].…”

Section: Introductionmentioning

confidence: 99%

Ligand-Activated Signal Transduction in the 2-Cell Embryo1

Bathgate

et al. 2003

Biology of Reproduction

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Platelet-activating factor (PAF) is an autocrine trophic/survival factor for the preimplantation embryo. PAF induced an increase in intracellular calcium concentration ([Ca2+]i) in the 2-cell embryo that had an absolute requirement for external calcium. L-type calcium channel blockers (diltiazem, verapamil, and nimodipine) significantly inhibited PAF-induced Ca2+ transients, but inhibitors of P/Q type (omega-agatoxin; omega-conotoxin MVIIC), N-type (omega-conotoxin GVIA), T-type (pimozide), and store-operated channels (SKF 96365 and econazole) did not block the transient. mRNA and protein for the alpha1-C subunit of L-type channels was expressed in the 2-cell embryo. The L-type calcium channel agonist (+/-) BAY K 8644 induced [Ca2+]i transients and, PAF and BAY K 8644 each caused mutual heterologous desensitization of each other's responses. Depolarization of the embryo (75 mM KCl) induced a [Ca2+]i transient that was inhibited by diltiazem and verapamil. Whole-cell patch-clamp measurements detected a voltage-gated channel (blocked by diltiazem, verapamil, and nifedipine) that was desensitized by prior responses of embryos to exogenous or embryo-derived PAF. Replacement of media Ca2+ with Mn2+ allowed Mn2+ influx to be observed directly; activation of a diltiazem-sensitive influx channel was an early response to PAF. The activation of a voltage-gated L-type calcium channel in the 2-cell embryo is required for normal signal transduction to an embryonic trophic factor.

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Section: Introductionmentioning

confidence: 99%

Ligand-Activated Signal Transduction in the 2-Cell Embryo1

Bathgate

et al. 2003

Biology of Reproduction

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“…In the presence of extracellular albumin, Paf is released into the embryo's environment (Ammit and O'Neill 1997a, b). The released Paf can be detected in embryo culture media for a range of species (mouse (O'Neill 1985); human (Collier et al 1988) sheep (Battye et al 1991(Battye et al ) 1991, rabbit (Minhas et al 1993), cow (Stock and Hansel 1992), and hamster (Velasquez et al 1995)). Paf exerts a range of paracrine actions within the reproductive tract (O'Neill 2005) and also acts upon receptors expressed by the embryo itself.…”

Section: Autocrine Ligandsmentioning

confidence: 99%

Survival Signalling in the Preimplantation Embryo

O’Neill

Jin

2015

Advances in Experimental Medicine and Biology

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The development of the preimplantation embryo (from fertilisation until the formation of the differentiated blastocyst) occurs without a requirement for exogenous mitogenic or survival signals. This distinguishes the behaviour of cells in the early embryo from all other normal cells. The discovery that fertilisation triggers the production and release of potent bioactive mediators by the embryo that act back on membrane receptors demonstrated the presence of closed autocrine embryotrophic loops. It is now clear that these ligands act in concert with paracrine mediators normally present within the reproductive tract to support the normal development of the embryo. These ligands act via receptors expressed by the embryo to activate signalling transduced by 1-o-phosphatidylinositol-3-kinase and the resultant formation of phosphatidylinositol-3,4,5-trisphosphate. This polyphosphorylated membrane phospholipid acts as a docking site for proteins possessing the PH domain. These include PDK1, AKT and phospholipase C. The activation of these proteins accounts for the initiation of new transcription from the embryonic genome to form a pro-survival, anti-apoptotic transcriptome and the post-transcriptional activation of pro-survival signalling within embryonic cells. This includes the attenuation of action of pro-apoptotic signals, such as P53. The production of embryotrophic ligands after fertilisation bootstraps development by the activation of transcription from the embryonic genome, followed by the activation of pro-survival settings within embryo cells.

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“…The binding of Paf to the platelet-activating factor receptor (PTAFR), a member of the G protein-coupled receptor family, accounts for many of the reported actions of Paf (Ishii et al 2002). Paf is produced and released by embryos during preimplantation development of all eutherian species studied to date: mouse (O'Neill 1985, Ryan et al 1989, Roudebush et al 2002, rabbit (Minhas et al 1993), sheep (Battye et al 1991), hamster (Velasquez et al 1995) and human (Collier et al 1990, Nakatsuka et al 1992. No embryos of marsupial species have yet been examined, although Paf appears to be produced by the endometrium of the tammar during the period of reactivation (Kojima et al 1993).…”

Section: Introductionmentioning

confidence: 99%

Paf receptor expression in the marsupial embryo and endometrium during embryonic diapause

et al. 2014

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The control of reactivation from embryonic diapause in the tammar wallaby (Macropus eugenii) involves sequential activation of the corpus luteum, secretion of progesterone that stimulates endometrial secretion and subsequent changes in the uterine environment that activate the embryo. However, the precise signals between the endometrium and the blastocyst are currently unknown. In eutherians, both the phospholipid Paf and its receptor, platelet-activating factor receptor (PTAFR), are present in the embryo and the endometrium. In the tammar, endometrial Paf release in vitro increases around the time of the early progesterone pulse that occurs around the time of reactivation, but whether Paf can reactivate the blastocyst is unknown. We cloned and characterised the expression of PTAFR in the tammar embryo and endometrium at entry into embryonic diapause, during its maintenance and after reactivation. Tammar PTAFR sequence and protein were highly conserved with mammalian orthologues. In the endometrium, PTAFR was expressed at a constant level in the glandular epithelium across all stages and in the luminal epithelium during both diapause and reactivation. Thus, the presence of the receptor appears not to be a limiting factor for Paf actions in the endometrium. However, the low levels of PTAFR in the embryo during diapause, together with its up-regulation and subsequent internalisation at reactivation, supports earlier results suggesting that endometrial Paf could be involved in reactivation of the tammar blastocyst from embryonic diapause.

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Production of platelet-activating factor by the pre-implantation sheep embryo

Cited by 42 publications

References 14 publications

Ligand-Activated Signal Transduction in the 2-Cell Embryo1

Ligand-Activated Signal Transduction in the 2-Cell Embryo1

Survival Signalling in the Preimplantation Embryo

Paf receptor expression in the marsupial embryo and endometrium during embryonic diapause

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