Myometrial prostaglandin E2 synthetic enzyme mRNA expression: spatial and temporal variations with pregnancy and labour

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Abstract
We have investigated the hypothesis that the expression of the enzymes involved in PGE2 synthesis in the human uterus is co-ordinated. We have studied (i) the mRNA expression of the enzymes involved in PGE2 synthesis [phospholipases (cPLA2 and sPLA2), prostaglandin H synthase (PGHS)-2 and PG E synthases (PGES-1 and -2)] and their relationship to the expression of inflammatory cytokines in samples of myometrium obtained from pregnant women undergoing caesarean section (LSCS) either before or after the onset of labour at or before term; and (ii) the effect of IL-1β, IL-6, TNF-α, PGE2 and stretch on PGE2 enzyme mRNA expression. We found that cPLA2, sPLA2 and PGHS-2 mRNA expression were greater in labour samples; cPLA2, sPLA2, PGHS-2, PGES-1 and -2 mRNA expression were greater in lower- than upper-segment samples; and there was no effect of gestational age. PGHS-2 mRNA levels correlated with those of PGES-1, cPLA2, IL-1β and IL-8; PGES-1 mRNA levels correlated with those of IL-1β, IL-8 and cPLA2. In primary cultures of uterine myocytes, cPLA2 mRNA expression was increased by IL-1β and IL-6; PGHS-2 mRNA expression was increased by IL-1β, PGE2 and stretch; and PGES-1 mRNA expression was increased by IL‐1β only. These data show that labour is associated with increased expression of the enzymes involved in PGE2 synthesis and their expression is greater in the lower uterine segment. The presence of associations between the levels of PGE2 enzyme mRNA expression and the effects of IL-1β suggest that their expression is co-ordinated and that IL-1β is the responsible factor.

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