The Local and Systemic Immune Response to Intrauterine LPS in the Prepartum Mouse

Abstract

Inflammation plays a key role in human term and preterm labor (PTL). Intrauterine LPS has been widely used to model inflammation-induced complications of pregnancy, including PTL. It has been shown to induce an intense myometrial inflammatory cell infiltration, but the role of LPS-induced inflammatory cell activation in labor onset and fetal demise is unclear. We investigated this using a mouse model of PTL, where an intrauterine injection of 10 μg of LPS (serotype 0111:B4) was given at E16 of CD1 mouse pregnancy. This dose induced PTL at an average of 12.7 h postinjection in association with 85% fetal demise. Flow cytometry showed that LPS induced a dramatic systemic inflammatory response provoking a rapid and marked leucocyte infiltration into the maternal lung and liver in association with increased cytokine levels. Although there was acute placental inflammatory gene expression, there was no corresponding increase in fetal brain inflammatory gene expression until after fetal demise. There was marked myometrial activation of NFκB and MAPK/AP-1 systems in association with increased chemokine and cytokine levels, both of which peaked with the onset of parturition. Myometrial macrophage and neutrophil numbers were greater in the LPS-injected mice with labor onset only; prior to labor, myometrial neutrophils and monocytes numbers were greater in PBS-injected mice, but this was not associated with an earlier onset of labor. These data suggest that intrauterine LPS induces parturition directly, independent of myometrial inflammatory cell infiltration, and that fetal demise occurs without fetal inflammation. Intrauterine LPS provokes a marked local and systemic inflammatory response but with limited inflammatory cell infiltration into the myometrium or placenta.

The response of the innate immune and cardiovascular systems to LPS in pregnant and nonpregnant mice†

“…However, as our earliest time point was 6 h after LPS, any transcription factor may have been missed. After intrauterine LPS administration, we observed NFκB and MAPK/AP-1 activation in the myometrium at 3 h and this continued for NFκB at 7 h after LPS [28], this suggests that the failure to detect activation in the heart is unlikely to be due to timing, and is more likely to be due to a limitation of the method or variation in the timing of response between mice.…”

“…Tissues were weighed and single-cell suspensions were prepared in 1 mL of Intracellular (IC) Fixation Buffer (eBioscience) using a gentleMACs dissociator (Miltenyi Biotec Ltd) and M tubes as described previously [28]. Cell suspension and whole blood were incubated with the following fluorophore-conjugated rat anti-mouse mAbs antibodies used: Ly6C (HK1.4) (BioLegend), Gr1 (RB6-8C5) (BioLegend), NK1.…”

Ascending Vaginal Infection Using Bioluminescent Bacteria Evokes Intrauterine Inflammation, Preterm Birth, and Neonatal Brain Injury in Pregnant Mice

“…Intravaginal E. coli K1 leads to an up-regulation of several inflammatory genes in the uteroplacental tissues commonly associated with preterm parturition. 6 , 7 , 44 , 45 IL-1β appears to be an important mediator of labor in all of the uteroplacental tissues infected by E. coli K1 and this was supported by studies using IL-1β to induce premature delivery in mice. 46 , 47 The different concentrations of E. coli strains used in the pregnant dams in this study may have had differing effects on the inflammatory response.…”

Aminophylline and progesterone prevent inflammation-induced preterm parturition in the mouse†

“…The mouse model of inflammation-induced PTL is well established in our group [15,16]. On day 16 of gestation (E16), dams were pre-treated with either an intra-peritoneal injection of vehicle (DMSO; dimethyl sulfoxide, Thermo Fisher Scientific, UK) or 10mg/kg Am (Sigma Aldrich, UK).…”