Induction of ectopic inflammasome function in fetal lung mesenchyme (715.4)

Abstract

Bronchopulmonary Dysplasia (BPD) commonly affects preterm infants. Inflammation and the soluble inflammatory mediator interleukin‐1 beta (IL‐1beta) play major roles in BPD pathogenesis and inhibit normal lung airway formation. IL‐1beta release requires both NF‐kappaB dependent mRNA expression and post‐translational cleavage by caspase‐1 containing inflammasomes. Best characterized in immune cells, the inflammasome has not been investigated in the developing lung. Here we test the hypothesis that the endotoxin lipopolysaccharide (LPS) can induce ectopic inflammasome expression in fetal lung mesenchyme, leading to IL‐1beta release. In primary fetal mouse lung mesenchymal cells, LPS rapidly induced IL‐1beta mRNA expression, but neither LPS nor the inflammasome activator ATP stimulated the release of IL‐1beta peptide. However, treating mesenchymal cells with LPS for at least 6h and then stimulating with ATP did release IL‐1b peptide, suggesting LPS‐dependent priming. These results were consistent with immunoblots showing caspase‐1 cleavage when mesenchymal cells were primed with LPS and then activated with ATP. LPS priming also increased caspase‐1 mRNA expression. Mesenchymal cells expressing a constitutively active IKKbeta contained higher levels of IL‐1beta and inflammasome component mRNA, but did not release IL‐1beta peptide unless first primed with LPS and then activated with ATP. These data suggested that IKKbeta activity might not be sufficient to assemble a fully functional inflammasome. These data show that LPS can generate functional inflammasome expression and function in lung mesenchymal cells, potentially propagating the release of inflammatory cytokines within the lung.Grant Funding Source: Supported by 2R25GM059994‐14 and 5R01HL097195‐02