The effect of oxygen tension on intracellular survival signalling in primary villous trophoblasts.
Villous trophoblasts undergo increased apoptosis and experience a wider gradient of oxygen tensions (pO(2)) in pregnancies complicated by intrauterine growth restriction. We hypothesize that pO(2)affects trophoblast apoptosis by altering survival signalling through the phosphatidylinositol-3 (PI-3)-kinase and mitogen activated protein kinase (MAPK) pathways. Cytotrophoblasts were cultured at pO(2)from <10 to approximately 140 mmHg with Epidermal Growth Factor (EGF), Vascular Endothelial Growth Factor (VEGF) and basic Fibroblast Growth Factor (bFGF) at concentrations of 0.1 to 10 ng/ml for 1 to 12 h, then assessed for apoptosis (TUNEL) and specific protein expressions (Western blot analysis). Spontaneous apoptosis was highest at <10 mmHg and lowest approximately 15 mmHg. Only EGF activated either signalling pathway at any pO(2). Inhibition of both pathways was required to inhibit EGF-stimulated survival. Maximal EGF activation of either pathway was insensitive to pO(2). At lower oxygen tensions, MAPK phosphorylation was maximal at 1 ng/ml EGF compared with 10 ng/ml for the PI-3-kinase path. The EGF receptor was spontaneously phosphorylated with increasing culture times at lower oxygen levels, an effect reflected down-stream by PI-3-kinase and Akt phosphorylation. We conclude that strong survival signalling in trophoblasts requires both PI-3- and MAP-kinase pathways, is rather insensitive to pO(2)changes and is spontaneously activated with increasing hypoxic exposure.
Mackova
M
M
Department of Obstetrics and Gynecology and Physiology, Perinatal Research Centre, University of Alberta, AB, Edmonton, Canada.
Kilani
R T
RT
Davidge
S T
ST
Guilbert
L J
LJ
D000328:Adult; D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D002824:Chorionic Villi / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006801:Humans; D020287:In Situ Nick-End Labeling; D020928:Mitogen-Activated Protein Kinases / Q000096:biosynthesis*; D010100:Oxygen / Q000378:metabolism* / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000096:biosynthesis*; D011247:Pregnancy; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014327:Trophoblasts / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology
D004338:Drug Combinations; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; D004815:Epidermal Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; D010100:Oxygen