Localization, quantification, and activation of platelet-activating factor receptor in human endometrium during the menstrual cycle: PAF stimulates NO, VEGF, and FAKpp125.
Implantation is characterized by an inflammatory-like response with expansion of extracellular fluid volume, increased vascular permeability, and vasodilatation. These effects are believed to be mediated at the paracrine level by prostaglandin E2 and platelet-activating factor (PAF), but the cellular mechanism (or mechanisms) remains largely unknown. We demonstrate that PAF receptor (PAF-R) immunoreactivity and mRNA are detected in proliferative and secretory endometrial glands, however, the responsiveness of endometrium to physiological concentrations of PAF is confined predominantly to the secretory endometrium. Semiquantitative reverse transcription-polymerase chain reaction revealed that PAF-R transcript levels were highest in the mid-late proliferative and late secretory phases of the cycle. Interaction of PAF with its receptor resulted in the rapid release of nitric oxide (NO), increased expression of vascular endothelial growth factor (VEGF), and activation of FAKpp125, a focal adhesion kinase, demonstrating that the PAF-R is functionally active. Inhibition of NO synthesis by NG-monomethyl-L-arginine produced dose-dependent attenuation of PAF-evoked NO release, indicating NOS activation; the dependency of PAF-evoked NO release on PKC and extracellular Ca2+ was confirmed by PKC inhibitor Ro 31-8220 and by the removal of extracellular Ca2+. PAF up-regulated VEGF gene expression in a concentration- and time-dependent fashion in human endometrial epithelial cell lysates. Transcription of VEGF was rapidly followed by secretion of the protein. These data support our premise that this autocoid acts as an angiogenic mediator in the regeneration of the endometrium after menses and as a vasodilator to promote blastocyst attachment during the implantation process.
Ahmed
A
A
Department of Obstetrics and Gynaecology, Birmingham Women's Hospital, University of Birmingham, Edgbaston, UK. A.S.Ahmed@bham.ac.uk
Dearn
S
S
Shams
M
M
Li
X F
XF
Sangha
R K
RK
Rola-Pleszczynski
M
M
Jiang
J
J
D015815:Cell Adhesion Molecules / Q000187:drug effects / Q000378:metabolism*; D004717:Endometrium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016228:Endothelial Growth Factors / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D008222:Lymphokines / Q000378:metabolism* / Q000494:pharmacology; D008597:Menstrual Cycle / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D010766:Phosphorylation; D010972:Platelet Activating Factor / Q000494:pharmacology*; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D014443:Tyrosine / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D015815:Cell Adhesion Molecules; D016228:Endothelial Growth Factors; D008222:Lymphokines; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; C039351:platelet activating factor receptor; D009569:Nitric Oxide; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human