The interleukin-1 system in gestational tissues at term: Effect of labour

Abstract

Previous studies suggest that the interleukin-1 (IL-1) system is involved in preterm labour, at least in cases associated with intrauterine infection. To investigate the effect of term labour without infection on the IL-1 system, the messenger ribonucleic acid (mRNA) expression of IL-1β, IL-1 receptor type I (IL-1R tI), IL-1 receptor antagonist (IL-1ra), and IL-1β converting enzyme (ICE) were examined by Northern blot analysis and by reverse transcriptase-polymerase chain reaction (RT-PCR) in paired samples of decidua and placenta obtained from women having spontaneous vaginal delivery (group 1) or elective caesarean section (group 2) at term. In additon, concentrations of IL-1β and IL-1ra proteins were measured by ELISA in paired decidual and placental cytosols. In all decidual samples, IL-1β mRNA was expressed strongly, and the IL-1β concentration was 40- to 50-fold higher than in paired placental samples, in which the signal for IL-1β mRNA could be detected by RT-PCR only, and the amount of IL-1β protein was undetectable or very low. A comparison between the study groups reveald that the decidual IL-1β mRNA level tended to be higher in group I, and the median IL-1β concentration in decidual cytosols was significantly higher in group 1 than in group 2 ( P<0.05). The IL-1R tI mRNA transcript was stronger in decidual than in paired placental samples in both groups. The mRNAs encoding ICE and IL-1ra were detected by RT-PCR in decidual and placental samples from both groups. The IL-1ra concentration tended to be higher in decidual cytosols than in paired placental cytosols, but there was no difference between the study groups. The IL-1ra/IL-1β ratio was significantly lower in decidual samples in women with spontaneous labour than in women without labour ( P<0.05). The results of this study confirm that decidua is the major site of IL-1β production and action in term gestational tissues. Furthermore, the results show that the major change in decidual/placental IL-1 system during parturition is the increase in decidual IL-1β production. Whether the increased IL-1β production precedes or is a consequence of labour, remains still unclear.