Treatment of animals with Pyl A

alone increased NF-κB activity in the myometrium, which was enhanced with co-administration of LPS (Fig. 6a). The inability Alpelisib of Pyl A to inhibit NF-κB implies that CRTH2 is not involved in the mechanism of 15dPGJ2-mediated inhibition. In support of this, we demonstrated that CRTH2 is not required for 15dPGJ2-mediated inhibition of NF-κB in human amniocytes, myocytes and lymphocytes.[41] Surprisingly, myometrial COX-2 protein levels remained unchanged 4·5 hr post treatment in all groups. As preterm labour was typically induced following LPS/Pyl A treatment at 5·8 hr (SEM ± 0·7) it was expected that any COX-2 up-regulation in the myometrium should have already been apparent by 4·5 hr post treatment. It is possible that COX-2 was already up-regulated before intrauterine injection in preparation for term labour, which is one limitation of using a model at E16. Progesterone withdrawal in the mouse occurs late E16 and so downstream activation of pro-labour genes is not likely to have been initiated in our model.[44] Consistent

with this the majority of labour-associated find more proteins such as PGE2, PGF2α, the oxytocin receptor and Connexin-43 are not significantly up-regulated until E18.[45, 46] We have shown, however, that COX-2 is suppressed in pregnancy and is up-regulated from E16, which was not increased further in term labour.[47] We further explored the possibility that, despite seeing no change at the protein level, COX-2 was still activated by LPS and LPS plus Pyl A. Messenger RNA was indeed increased

in LPS-treated mice, and was further increased with co-injection of Pyl A (Fig. 6e). COX-2 requires peroxidases for activation and the endogenous peroxide tone of smooth muscle cells can be mimicked by nitration.[48] Previous studies have shown that peroxynitrite increases the activity of COX-2 with no alteration of COX-2 protein expression.[49, Protirelin 50] Consistent with our results, Aisemberg et al.[51] demonstrated an increase in LPS-induced mRNA COX-2 with no effect at the protein level. It is plausible that this is a result of LPS-induced NO leading to the formation of peroxynitrite, which in turn, activates COX-2 without alteration of protein expression. Alternatively, it is also plausible that the nitrated form of COX-2 is not recognized by the COX-2 antibody. Analysis of pup brain extracts collected from LPS-treated dams revealed a decrease in levels of phosphorylated p65 (ser 536). It is thought that this may reflect protein degradation induced by the pre-terminal state of the live pups (Fig. 6b). A significant increase in in utero fetal viability was achieved with Pyl A treatment (Fig. 5a) but this was not associated with altered NF-κB activity. This also highlights the contrasting effects of Pyl A compared with the 15dPGJ2 because we have previously shown that 15dPGJ2 inhibits NF-κB in the pup brain of dams treated with LPS.