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Title: In vitro hypoxia-reoxygenation as a model for placental oxidative stress in preeclampsia
Author: Hung, T. H.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2003
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Oxidative stress of the placenta is considered a key intermediary step in the pathogenesis of preeclampsia, but the cause for the stress remains unknown. Ischaemia-reperfusion injury, as a result of intermittent placental perfusion secondary to deficient trophoblast invasion of the endometrial arteries, is a possible mechanism. This thesis therefore tests whether hypoxia-reoxygenation (H/R) in vitro can induce placental oxidative stress, and cause increased apoptosis and production of tumour necrosis factor-α as seen in the preeclamptic placenta. The first aim was to examine the oxidative status of human placental tissues during periods of hypoxia and reoxygenation in vitro. Rapid generation of reactive oxygen species (ROS) was detected using a fluorescent marker when hypoxic villous samples were reoxygenated. The expression of oxidative stress markers including nitrotyrosine residues, 4-hydroxy-2-nonenal adducts, and inducible heat shock protein 72 was greatly increased in villous samples subjected to H/R compared to the controls maintained under constant hypoxia. Furthermore, preloading villous samples with ROS scavengers such as desferrioxamine and α-phenyl-N-tert-butylnitrone significantly reduced the levels of oxidative stress in H/R. Having demonstrated that in vitro H/R is capable of inducing oxidative stress in a reproducible and manipulable manner, investigations were next carried out to study the effects of resultant oxidative stress on apoptosis within the trophoblast. Compared to hypoxic and normoxic controls, there was a significant increase in the release of cytochrome c from mitochondria, activation of caspase , and cleavage of poly (ADP-ribose) polymerase in villous samples subjected to H/R. These events were associated with an increased number of syncytiotrophoblastic nuclei displaying apoptotic changes and increased lactate dehydrogenase release into the medium. The causal relationship between the generation of ROS and these apoptotic changes was revealed by the fact that pre-administration of desferrioxamine attenuated the insult.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available