Role of ADAM17 in endotoxin-induced pulmonary inflammation

Acute lung inflammation is associated with enhanced vascular permeability and leukocyte recruitment. Several proinflammatory, soluble and surface-expressed mediators, including TNFα, TNFR1/2, amphiregulin, IL-6R, IL-1R, L-selectin, CX3CL1, and JAMs may become released by the activity of the metalloproteinases ADAM10 and ADAM17. We examined the role of these proteases in vascular permeability and leukocyte transmigration in vitro by pharmacological inhibition and lentiviral-mediated siRNA knockdown of ADAM10 and ADAM17. The in vivo role of these proteases was studied in a murine model of LPS-induced lung injury by pharmacological inhibition. The relevance of ADAM17 was further analyzed by knockout of ADAM17 in endothelial or smooth muscle cells. The BAL protein levels and the wet/dry-ratio served as markers of vascular permeability and edema formation. Cell recruitment to the alveolar space and lung tissue was analyzed by flow cytometry; cytokines were determined by ELISA. In vitro, transmigration of neutrophils to IL-8 through pulmonary endothelial cells was reduced by pharmacological inhibition as well as knockdown of ADAM10 or ADAM17. LPS-mediated induction of permeability was reduced by pharmacological inhibition, but not by ADAM10 knockdown, indicating a predominant role of ADAM17 in the regulation of endothelial permeability. In vivo, LPS challenge increased the wet/dry-ratio as well as the BAL levels of protein, TNFα, IL-6 and leukocytes. All these effects were largely prevented by inhibitor application or by knockout of ADAM17 in smooth muscle or endothelial cells. These results indicate that local ADAM17 is involved in the onset of inflammation and tissue injury during endotoxin-induced lung inflammation.