Lung endothelial ADAM17 regulates the acute inflammatory response to lipopolysaccharide

Acute lung injury (ALI) is associated with increased vascular permeability, leukocyte recruitment, and pro-inflammatory mediator release. We investigated the role of the metalloproteinase ADAM17 in endotoxin-induced ALI with focus on endothelial ADAM17. In vitro, endotoxin-mediated induction of endothelial permeability and IL-8-induced transmigration of neutrophils through human microvascular endothelial cells required ADAM17 as shown by inhibition with GW280264X or shRNA-mediated knockdown. In vivo, ALI was induced by intranasal endotoxin-challenge combined with GW280264X treatment or endothelial adam17-knockout. Endotoxin-triggered upregulation of ADAM17 mRNA in the lung was abrogated in knockout mice and associated with reduced ectodomain shedding of the junctional adhesion molecule JAM-A and the transmembrane chemokine CX3CL1. Induced vascular permeability, oedema formation, release of TNF-α and IL-6 and pulmonary leukocyte recruitment were all markedly reduced by GW280264X or endothelial adam17-knockout. Intranasal application of TNF-α could not restore leukocyte recruitment and oedema formation in endothelial adam17-knockout animals. Thus, activation of endothelial ADAM17 promotes acute pulmonary inflammation in response to endotoxin by multiple endothelial shedding events most likely independently of endothelial TNF-α release leading to enhanced vascular permeability and leukocyte recruitment.