Pulmonary and systemic inflammatory responses to intra-amniotic IL-1α in fetal sheep

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Clinical and epidemiological studies implicate IL-1 as an important mediator of perinatal inflammation. We tested the hypothesis that intra-amniotic IL-1α would induce pulmonary and systemic fetal inflammatory responses. Sheep with singleton fetuses were given an intra-amniotic injection of recombinant sheep IL-1α (100 μg) and were delivered 1, 3, or 7 days later, at 124 ± 1 days gestation ( n=5–8/group). A separate group of sheep were given two intra-amniotic IL-1α injections (100 μg dose each): 7 days and again 1 day prior to delivery. IL-1α induced a robust increase in monocytes, neutrophils, lymphocytes, and IL-8 protein in bronchoalveolar lavage fluid. H2O2secretion was increased in inflammatory cells isolated from lungs of IL-1α-exposed lambs upon LPS challenge in vitro compared with control monocytes. T lymphocytes were recruited to the lung. IL-1β, cyclooxygenase-1, and cyclooxygenase-2 mRNA expression increased in the lung 1 day after intra-amniotic IL-1α exposure. Lung volumes increased 7 days after intra-amniotic IL-1α exposure, with minimal anatomic changes in air space morphology. The weight of the posterior mediastinal lymph node draining the lung and the gastrointestinal tract doubled, inducible nitric oxide synthase (NOSII)-positive cells increased, and Foxp3-positive T-regulatory lymphocytes decreased in the lymph node after IL-1α exposure. In the blood, neutrophil counts and plasma haptoglobin increased after IL-1α exposure. Compared with a single exposure, exposure to intra-amniotic IL-1α 7 days and again 1 day before delivery had a variable effect (increases in some inflammatory markers, but not pulmonary cytokines). IL-1α is a potent mediator of the fetal inflammatory response syndrome.