Pneumonia is a life-threatening disease often caused by infection with Streptococcus pneumo niae and Pseudomonas aeruginosa. Many of the mediators (e.g., TNF, IL-6R) and junction molecules
(e.g., E-cadherin) orchestrating inflammatory cell recruitment and loss of barrier integrity are prote olytically cleaved through a disintegrin and metalloproteinases (ADAMs). We could show by Western
blot, surface expression analysis and measurement of proteolytic activity in cell-based assays, that
ADAM10 in epithelial cells is upregulated and activated upon infection with Pseudomonas aeruginosa
and Exotoxin A (ExoA), but not upon infection with Streptococcus pneumoniae. Targeting ADAM10
by pharmacological inhibition or gene silencing, we demonstrated that this activation was critical
for cleavage of E-cadherin and modulated permeability and epithelial integrity. Stimulation with
heat-inactivated bacteria revealed that the activation was based on the toxin repertoire rather than
the interaction with the bacterial particle itself. Furthermore, calcium imaging experiments showed
that the ExoA action was based on the induction of calcium influx. Investigating the extracellular
vesicles and their proteolytic activity, we could show that Pseudomonas aeruginosa triggered exosomal
release of ADAM10 and proteolytic cleavage in trans. This newly described mechanism could consti tute an essential mechanism causing systemic inflammation in patients suffering from Pseudomonas
aeruginosa-induced pneumonia stimulating future translational studies