Intraamniotic LPS modulates expression of antimicrobial peptides in the fetal sheep lung

BACKGROUND: Damage-associated molecular patterns (DAMPs) and antimicrobial peptides (AMPs) are components of pulmonary innate immunity and tissue repair. We hypothesized that DAMPs and AMPs would increase in response to fetal pulmonary inflammation caused by chorioamnionitis in a time-dependent manner. METHODS: Fetal sheep were exposed to intra-amniotic saline or LPS (10mg) between 5 hours and 15 days prior to preterm delivery at 125±2 days. Lung tissue mRNAs for pro-inflammatory cytokines; AMPs: myeloid antimicrobial peptide-29 (MAP29), dodecapeptide, sheep beta-defensin-1 (SBD1), sheep beta-defensin-2 (SBD2); DAMPs: IL-1α, lactoferrin, heat-shock protein-70 (HSP70), high-mobility group box protein-B1 (HMGB1), receptor for advanced glycation endproducts (RAGE) were measured by RT-qPCR. Immunohistochemistry of DAMPs and in situ hybridization of AMPs was performed. RESULTS: IL-1α, IL-1β, IL-6, IL-8, IL-10, MCP-1, and TNF-α mRNA increased after LPS exposure. MAP29, dodecapeptide, SBD1 and SBD2 mRNA were suppressed at 24 hours. MAP29 and dodecapeptide mRNA then increased at 8 days. Lactoferrin increased at 24 hours. There were no changes for HMGB1, HSP70 or RAGE. MAP29 and dodecapeptide localized to alveolar cells, increased 8 days after exposure to LPS. CONCLUSION: AMPs are initially suppressed in the fetal lung by LPS-induced chorioamnionitis. The late induction of MAP29 and Dodecapeptide may be related to lung repair.