Pretreatment with toll-like receptor 4 antagonist inhibits lipopolysaccharide-induced preterm uterine contractility, cytokines, and prostaglandins in rhesus monkeys

Abstract

Intrauterine infection, which occurs in most early preterm births, triggers an immune response culminating in preterm labor. The authors hypothesize that blockade of lipopolysaccharide (LPS)-induced immune responses by a toll-like receptor 4 antagonist (TLR4A) would prevent elevations in amniotic fluid (AF) cytokines, prostaglandins, and uterine contractility. Chronically catheterized rhesus monkeys at 128 to 147 days' gestation received intra-amniotic infusions of either (1) saline (n = 6), (2) LPS (0.15-10 microg; n = 4), or (3) TLR4A pretreatment with LPS (10 microg) 1 hour later (n = 4). AF cytokines, prostaglandins, and uterine contractility were compared using 1-way ANOVA with Bonferroni-adjusted pairwise comparisons. Compared with saline controls, LPS induced significant elevations in AF interleukin-8 (IL-8), tumor necrosis factor (TNF)- alpha, PGE(2), PGF(2)(alpha), and uterine contractility (P < .05). In contrast, TLR4A pretreatment inhibited LPS-induced uterine activity and was associated with significantly lower AF IL-8, TNF-alpha, PGE(2), and PGF(2)( alpha) versus LPS alone (P < .05). Toll-like receptor antagonists, together with antibiotics, may delay or prevent infection-associated preterm birth.

Figure 1

Temporal relationships among LPS inoculation, uterine activity, and amniotic fluid (AF) cytokines and prostaglandins are shown in representative animals from each experimental group. The x-axis represents gestational age in days ranging from the vascular implantation surgery until cesarean section. The y-axis is hourly contraction area (HCA), or the level of amniotic fluid TNF-alpha (orange line) or prostaglandin E2 (blue line). A: A representative animal receiving intra-amniotic LPS (red arrow head). B: A representative animal receiving intra-amniotic TLR4A (green arrow head) one hour prior to intra-amniotic LPS (red arrow head). In this animal, the intraamniotic LPS administration was repeated at the same dose 7 days later in the absence of TLR4A and again at a higher dose 5 days later, demonstrating moderate recovery of LPS responsiveness.

Figure 2

Bar height is mean and error bars indicate standard error of the mean. A: Uterine activity as measured by the peak HCA following saline, LPS, or LPS + TLR4A infusion. The peak HCA is chosen after averaging HCA over each 24 hour period in the first 7 days following infusion. Peak amniotic fluid prostaglandins (B) and cytokines (C) in control and experimental groups are also shown.