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Changes in amniotic arachidonic acid metabolism associated with increased cyclo-oxygenase gene expression
P R Bennett1, D Slater, M Sullivan
1Action Research Laboratory for the Molecular Biology of Fetal Development, University of London, Royal Postgraduate Medical School, Queen Charlottes and Chelsea Hospital, UK.
Objectives:
To study the differences in the metabolism of arachidonic acid, to prostaglandins and other eicosanoids, between amnion cells before and after labour. To study the changes in the expression of the type 1 cyclo-oxygenase gene associated with the changes in arachidonic acid metabolism.
Design:
Amnion cells collected before labour, at elective caesarean section, and following spontaneous labour and delivery were established in mono-layer culture. Intracellular arachidonic acid pools were radio-labelled and the metabolic fate of endogenous archidonic acid was then studied using high performance liquid chromatography. RNA was extracted from the cell cultures and expression of the cyclooxygenase gene was studied using northern hybridisation to a sheep cyclo-oxygenase cDNA.
Results:
Metabolism of endogenous arachidonic acid in amnion cells established in culture prior to labour is principally via lipoxygenase and epoxygenase enzyme pathways to di- and mono-HETEs and EET with little cyclo-oxygenase metabolism to prostaglandins. Following labour there is a large increase in arachidonic acid metabolism with a change in the cyclo-oxygenase: lipoxygenase enzyme pathway ratio in favour synthesis of prostaglandin E2. Whilst synthesis of lipoxygenase metabolites doubles, the increase in prostaglandin E2 synthesis is ten fold. Expression of the cyclo-oxygenase gene is significantly greater in cell cultures established following spontaneous labour and delivery than in those established following elective caesarean section prior to labour.
Conclusions:
In association with labour there is an increase in arachidonic acid metabolism in amnion cells and a change in the ratio of metabolism via cyclo-oxygenase and lipoxygenase enzyme pathways to increase synthesis of prostaglandin E2. This change is associated with increased expression of the cyclooxygenase gene.