Pre-eclampsia and intrauterine growth restriction (IUGR) are common complications of pregnancy with significant implications for mother and fetus. The exact cause is unknown, but current theories suggest that abnormal trophoblast invasion leads to placental under perfusion and hypoxia with the generation of reactive oxygen species (ROS). A result of this insult is increased trophoblast apoptosis. The cell cycle regulator p53 has been identified in increased amounts in the trophoblast in pre-eclampsia and IUGR. It is possible that modulation of this potent apoptotic signal could improve placental function, potentially offering a therapy for these presently untreatable conditions.In these studies, trophoblast apoptosis was induced with Nutlin-3, a synthetic compound which inhibits the binding of p53 to its inhibitor, Mdm2, therefore acting as a p53 activator. Treatment with Nutlin-3 induced apoptotic cell death in BeWo choriocarcinoma cells, primary trophoblast cells and placental villous explants, suggesting that p53 is intrinsic to trophoblast survival. This increase in apoptosis was associated with an increase in p53, Mdm2, p21 and Puma protein expression in BeWo cells and p21 and Puma mRNA in placental villous explants. No effect was observed in Bax expression. Co-treatment with Nutlin-3 and the p53 inhibitor Pifithrin-α reduced apoptosis to the level of control tissue in BeWo cells, primary trophoblast cells and villous explants, suggesting that reducing p53 activity improves trophoblast function.The use of hypoxia and ROS was associated with an increase in apoptosis and p21 and Puma in placental villous explants. Furthermore, the extent of apoptosis and p21 and Puma expression was reduced by co-treatment with Pifithrin-α, suggesting that the ameliorating effects of Pifithrin-α on trophoblast apoptosis are maintained following an insult from a less specific p53 activating mechanism, further supporting the continued investigation of p53 modulation as a therapeutic manipulation of placental function.Pregnant mice were exposed to Nutlin-3 to ascertain the effect of p53 over-activity on pregnancy outcome. The establishment of a model of placental dysfunction in the mouse would have allowed investigation into the effect of p53 inhibition with Pifithrin-α. Despite clear evidence of p53 modulation in maternal tissues, the decidua, no effect was observed upon pregnancy outcome or upon fetal or placental tissue. These findings suggest that the mouse placenta may not be a good model of p53 over-activity, although the exact mechanism of resistance remains unclear.In conclusion, p53 exaggeration is inducible in trophoblast with Nutlin-3, hypoxia and ROS. Furthermore, Pifithrin-α is able to reduce this effect, suggesting that the p53 pathway may be a realistic target for modulation in the placenta.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:548686 |
| Date | January 2011 |
| Creators | Sharp, Andrew |
| Contributors | Crocker, Ian ; Aplin, John ; Heazell, Alexander |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/the-role-of-p53-modulation-in-correcting-aberrant-placental-apoptosis-in-preeclampsia-and-iugr(5234cc67-e56a-48c5-b474-1e5ae6232e5c).html |
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