BQ-123 prevents LPS-induced preterm birth in mice via the induction of uterine and placental IL-10

Preterm birth (PTB), defined as any delivery occurring prior to the completion of 37weeks' gestation, currently accounts for 11-12% of all births in the United States. Maternal genito-urinary infections account for up to 40% of all PTBS and induce a pro-inflammatory state in the host. The potent vasoconstrictor Endothelin-1 (ET-1) is known to be upregulated in the setting of infection, and elicits its effect by binding to the ET_A receptor. We have previously shown that antagonism of the ET_A receptor with BQ-123 is capable of preventing LPS-induced PTB in mice. We hypothesize that the administration of BQ-123 post LPS exposure will dismantle a positive feedback loop observed with pro-inflammatory cytokines upstream of ET-1. On GD 15.5, pregnant C57BL/6 mice were injected with PBS, LPS, BQ-123, or LPS+BQ-123. Changes at both the level of transcription and translation were observed in uterus and placenta in the ET-1 axis and in pro- and anti-inflammatory cytokines over the course of 12h. We discovered that BQ-123, when administered 10h post LPS, is capable of increasing production of uterine and placental Interleukin-10, causing a shift away from the pro-inflammatory state. We also observed that antagonism of the ET_A receptor decreased IL-1β and TNFα in the placenta while also decreasing transcription of ET-1 in the uterus. Our results reinforce the role of ET-1 at the maternal fetal interface and highlight the potential benefit of ET_A receptor blockade via the suppression of ET-1, and induction of a Th2 cytokine dominant state.