Essential Role for IL-10 in Resistance to Lipopolysaccharide-Induced Preterm Labor in Mice

Abstract

IL-10 is highly expressed in the uterus and placenta and is implicated in controlling inflammation-induced pathologies of pregnancy. To investigate the role of IL-10 in regulating preterm labor, the response of IL-10 null mutant mice to low-dose LPS in late gestation was evaluated. When IL-10 null mutant C57BL/6 (IL-10^−/−) and control (IL-10^+/+) mice were administered LPS on day 17 of pregnancy, the dose of LPS required to elicit 50% preterm fetal loss was 10-fold lower in IL-10^−/− mice than in IL-10^+/+ mice. Surviving fetuses in IL-10^−/− mice exhibited fetal growth restriction at lower doses of LPS than IL-10^+/+ mice. Marked elevation of LPS-induced immunoactive TNF-α and IL-6 was evident in the serum, uterus, and placenta of IL-10^−/− mice, and TNF-α and IL-6 mRNA expression was elevated in the uterus and placenta, but not the fetus. Serum IL-1α, IFN-γ, and IL-12p40 were increased and soluble TNFRII was diminished in the absence of IL-10, with these changes also reflected in the gestational tissues. Administration of rIL-10 to IL-10^−/− mice attenuated proinflammatory cytokine synthesis and alleviated their increased susceptibility to preterm loss. Exogenous IL-10 also protected IL-10^+/+ mice from fetal loss. These data show that IL-10 modulates resistance to inflammatory stimuli by down-regulating proinflammatory cytokines in the uterus and placenta. Abundance of endogenous IL-10 in gestational tissues is therefore identified as a critical determinant of resistance to preterm labor, and IL-10 may provide a useful therapeutic agent in this common condition.