Preeclampsia is associated with alterations in the p53-pathway in villous trophoblast.
BACKGROUND
Preeclampsia (PE) is characterized by exaggerated apoptosis of the villous trophoblast of placental villi. Since p53 is a critical regulator of apoptosis we hypothesized that excessive apoptosis in PE is mediated by abnormal expression of proteins participating in the p53 pathway and that modulation of the p53 pathway alters trophoblast apoptosis in vitro.


METHODS
Fresh placental villous tissue was collected from normal pregnancies and pregnancies complicated by PE; Western blotting and real-time PCR were performed on tissue lysate for protein and mRNA expression of p53 and downstream effector proteins, p21, Bax and caspases 3 and 8. To further assess the ability of p53 to modulate apoptosis within trophoblast, BeWo cells and placental villous tissue were exposed to the p53-activator, Nutlin-3, alone or in combination with the p53-inhibitor, Pifithrin-α (PFT-α). Equally, Mdm2 was knocked-down with siRNA.


RESULTS
Protein expression of p53, p21 and Bax was significantly increased in pregnancies complicated by PE. Conversely, Mdm2 protein levels were significantly depleted in PE; immunohistochemistry showed these changes to be confined to trophoblast. Reduction in the negative feedback of p53 by Mdm2, using siRNA and Nutlin-3, caused an imbalance between p53 and Mdm2 that triggered apoptosis in term villous explants. In the case of Nutlin, this was attenuated by Pifithrin-α.


CONCLUSIONS
These data illustrate the potential for an imbalance in p53 and Mdm2 expression to promote excessive apoptosis in villous trophoblast. The upstream regulation of p53 and Mdm2, with regard to exaggerated apoptosis and autophagy in PE, merits further investigation.
Maternal & Fetal Health Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom.
Andrew N
AN
Sharp
Maternal & Fetal Health Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom.
Alexander E P
AE
Heazell
Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada.
Dora
D
Baczyk
Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada.
Caroline E
CE
Dunk
Maternal & Fetal Health Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom.
Helen A
HA
Lacey
Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada.
Carolyn J P
CJ
Jones
Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada.
Jonathan E
JE
Perkins
Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada.
John C P
JC
Kingdom
Maternal & Fetal Health Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom ; Liggins Institute, University of Auckland, Auckland, New Zealand.
Philip N
PN
Baker
Maternal & Fetal Health Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, United Kingdom.
Ian P
IP
Crocker
D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism; D002824:Chorionic Villi / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D010920:Placenta / Q000378:metabolism / Q000473:pathology; D011225:Pre-Eclampsia / Q000235:genetics* / Q000378:metabolism*; D011247:Pregnancy; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism; D014327:Trophoblasts / Q000378:metabolism* / Q000473:pathology*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D053148:Caspase 3; D053181:Caspase 8