An intrauterine injection of lipopolysaccharide (LPS) was administered to CD1 mice at embryonic day 16, ± CRTH2 agonist/vehicle controls. Mice were killed at 4.5 hr to assess fetal wellbeing and to harvest myometrium and pup brain for analysis of NF-κB, and T helper type 1/2 interleukins. To examine the effects of the CRTH2 agonist on LPS-induced preterm labour, mice were allowed to labour spontaneously. Direct effects of the CRTH2 agonist on uterine U0126 ic50 contractility were examined ex vivo on contracting myometrial strips. The CRTH2 agonist increased fetal survival from 20 to 100% in LPS-treated mice,
and inhibited circular muscle contractility ex vivo. However, it augmented LPS-induced labour and significantly increased myometrial NF-κB, IL-1β, KC-GRO, interferon-γ and tumour necrosis factor-α. This suggests that the action of 15dPGJ2 is not via CRTH2 and therefore small molecule CRTH2 agonists are not likely to be beneficial for the prevention of inflammation-induced preterm labour. Preterm labour is one of the most challenging complications of human pregnancy. Its incidence in the western world remains between 6 and 15% depending on the geography and demographics of the population. It
is a heterogeneous condition, with the only firm causal link being that of infection. Despite the increased awareness of the association between infection and inflammation and preterm labour, there have been limited advances in the treatment and prevention of preterm labour. Currently, there is a drive to develop anti-inflammatory therapies to not only delay preterm labour, AZD2014 in vivo but to prevent the long-term neurological damage thought to be a
result of the impact of pro-inflammatory factors on fetal inflammatory response syndrome. The transcription factor nuclear factor-κB (NF-κB), which is classically associated with inflammation, is central to regulating the biochemical pathways involved in both term labour and preterm labour. The oxytocin receptor and cyclo-oxygenase-2 (COX-2) genes contain NF-κB response elements in their promoter regions.[6, 7] The oxytocin receptor mediates oxytocin-induced myometrial contractions through activation of phospholipase C and downstream calcium release from intracellular Leukocyte receptor tyrosine kinase stores. The COX-2 enzyme is the rate-limiting step for prostaglandin synthesis, which is responsible for uterine contractions and cervical dilatation. NF-κB is also involved in the transcriptional regulation of matrix metalloproteinases, including matrix metalloproteinase-9, which are required for remodelling of the extracellular matrix, leading to cervical ripening and fetal membrane rupture. A positive feed-forward loop also exists from activation of NF-κB by the pro-inflammatory cytokines and subsequently their transcriptional activation, including tumour necrosis factor-α (TNF-α) and interleukin-1β (IL-1β).