Bacterial lipopolysaccharide disrupts endothelial monolayer integrity and survival signaling events through caspase cleavage of adherens junction proteins

Bacterial lipopolysaccharide or endotoxin induces actin reorganization, inc reased paracellular permeability, and endothelial cell detachment from the underlying extracellular matrix in vitro. We studied the effect of endotoxi n on transendothelial albumin flux and detachment of endothelial cells cult ured on gelatin-impregnated filters. The endotoxin-induced changes in endot helial barrier function and detachment occurred at doses and times that wer e compatible with endotoxin-induced apoptosis. Since the actin cytoskeleton and cell-cell and cell-matrix adhesion all participate in the regulation o f the paracellular pathway and cell-matrix interactions, we studied whether protein components of the actin-linked adherens junctions were modified in response to endotoxin. Components of cell-cell (beta- and gamma-catenin) a nd cell-matrix (focal adhesion kinase and p130(Cas)) adherens junctions wer e cleaved by caspases activated during apoptosis with dose and time require ments that paralleled those seen for barrier dysfunction and detachment. Cl eavage of focal adhesion kinase led to its dissociation from the focal adhe sion-associated signaling protein, paxillin, resulting in reduced paxillin tyrosine phosphorylation. Inhibition of caspase-mediated cleavage of these proteins protected against detachment but not opening of the paracellular p athway. Therefore, endotoxin-induced disruption of endothelial monolayer in tegrity and survival signaling events is mediated, in part, through caspase cleavage of adherens junction proteins.