Item – Theses Canada

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OCLC number
1007094819
Link(s) to full text
LAC copy
LAC copy
Author
Payne, Shawn,1966-
Title
The role of sphingolipids in the control of apoptosis in human placental primary trophoblasts.
Degree
Ph. D. -- University of Alberta, 2001
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, [2002]
Description
2 microfiches
Notes
Includes bibliographical references.
Abstract
Apoptosis in placental trophoblasts appears to be a normal, regulated event that can be induced by TNF/IFN[gamma] (Tumour necrosis factor/interferon-gamma) and inhibited by EGF (epidermal growth factor). A higher than normal incidence of apoptosis in the placenta has been linked to some complications during pregnancy. In this study I investigated the role of sphingolipids in determining the fate of trophoblasts in response to TNF/IFN[gamma] and EGF. In addition, I investigated whether trophoblasts express the death receptor Fas. Cultured primary human cytotrophoblasts express Fas antigen on the cell surface. Western blot and RT-PCR analysis indicate that the Fas protein is full length. However, cross-linking anti-Fas antibody and Fas ligand expressing cells did not induce apoptosis. Pretreatment with IFN[gamma] and treatment with protein synthesis inhibitors did not sensitize trophoblasts to Fas-mediated apoptosis. The role of Fas in trophoblast biology is still unclear. Sphingolipids have been shown to play a role in both cytokine-induced cell death and survival. Activation of sphingomyelinase (SMase), and the resulting increase in cellular ceramide has been implicated in TNF[alpha]-induction of apoptosis while the activation of sphingosine kinase, and the increase in sphingosine 1-phosphate (SPP), have has been shown to be anti-apoptotic. Exogenous ceramide and acid SMase induce apoptosis in trophoblasts, which can be completely abrogated by cotreatment with EGF. EGF lowered endogenous basal ceramide levels and reduced the level of acid SMase-induced ceramide formation. An acidic ceramidase inhibitor increased cellular ceramide levels and induced apoptosis that could not be blocked by cotreatment with EGF. Exogenous bacterial (neutral) SMase increased ceramide levels but did not induce apoptosis. In addition, an inhibitor of alkaline ceramidase increased ceramide levels but did not induce apoptosis nor inhibit EGF protection from apoptosis. These data would suggest a role for acid SMase and acid ceramidase in the control of apoptosis in trophoblasts. The addition of SPP to trophoblast cultures inhibited TNF/IFN[gamma] and ceramide induced apoptosis. Inhibitors of sphingosine kinase induced apoptosis, which could not be blocked by EGF. Moreover, EGF activated sphingosine kinase activity, suggesting a role for sphingosine kinase activity, and therefore SPP, in EGF induced protection from apoptosis as well as presents a novel, EGF-regulated mechanism for the activation of sphingosine kinase.
ISBN
0612603326
9780612603325