Septic Murine Pulmonary Microvascular Endothelial Cell Barrier Dysfunction is Regulated by Tissue Inhibitor of Metalloproteinases 3

Sepsis causes dysfunction of pulmonary microvascular endothelial cells (PMVEC) leading to severe pulmonary edema. Metalloproteinases regulate endothelial function through processing of cell surface proteins, which can be associated with increased permeability. Tissue inhibitor of metalloproteinases 3 (TIMP3) regulates metalloproteinase activity in the lung following injury. Thus, we hypothesize TIMP3 promotes PMVEC barrier function through inhibition of metalloproteinase activity. PMVEC were isolated from WT and Timp3-/- mice. TIMP3 levels (mRNA and protein) were decreased in WT PMVEC under septic conditions. Analysis of leak (transendothelial electrical resistance, dextran, and albumin flux) revealed Timp3-/-PMVEC had significantly higher permeability under resting conditions vs. WT PMVEC. Increased basal Timp3-/- PMVEC permeability was associated with disrupted surface vascular endothelial-cadherin localization, both of which were rescued by treatment with GM6001, a synthetic metalloproteinase inhibitor. Our data suggest TIMP3 supports normal PMVEC barrier function, and septic downregulation of TIMP3 may be an important contributor to septic PMVEC barrier dysfunction