Endotoxin induces endothelial barrier dysfunction through protein tyrosine phosphorylation

Area of Science:

• Cell biology
• Biochemistry
• Immunology

Background:

• Bacterial lipopolysaccharide (LPS) is known to disrupt endothelial cell (EC) barrier function.
• LPS induces actin reorganization, intercellular gap formation, and barrier dysfunction in vitro.
• The precise molecular mechanisms underlying LPS-induced endothelial barrier dysfunction require further elucidation.

Purpose of the Study:

• To investigate whether LPS-induced changes in endothelial barrier function and actin depolymerization are mediated by protein tyrosine phosphorylation.
• To identify specific signaling pathways involved in LPS-induced endothelial barrier disruption.

Main Methods:

• Exposure of bovine pulmonary artery endothelial cell (EC) monolayers to bacterial lipopolysaccharide (LPS).
• Assessment of 14C-labeled bovine serum albumin (BSA) flux across EC monolayers to measure barrier function.
• Analysis of actin depolymerization and tyrosine phosphorylation of cytoskeletal proteins, specifically paxillin.
• Pharmacological inhibition of protein tyrosine kinases (herbimycin A, genistein) and tyrosine phosphatases (sodium orthovanadate, phenylarsine oxide).

Main Results:

• LPS exposure increased tyrosine phosphorylation of the cytoskeletal protein paxillin in EC lysates.
• Inhibition of protein tyrosine kinases protected ECs against LPS-induced actin depolymerization, intercellular gap formation, and increased [14C]BSA flux.
• Inhibition of tyrosine phosphatases exacerbated LPS-induced actin depolymerization and transendothelial [14C]BSA flux.

Conclusions:

• LPS-induced endothelial barrier dysfunction and actin reorganization are significantly mediated by protein tyrosine phosphorylation.
• Tyrosine phosphorylation acts as a key signaling mechanism in the cellular response to LPS.
• Targeting tyrosine phosphorylation pathways may offer therapeutic strategies for managing LPS-induced endothelial barrier dysfunction.