Protective effects of high-molecular weight polyethylene glycol (PEG) in human lung endothelial cell barrier regulation: role of actin cytoskeletal rearrangement.

Acute lung injury represents the result of multiple pathways initiated by local or systemic insults and is characterized by profound vascular permeability, pulmonary edema, and life-threatening respiratory failure. Permeability-reducing therapies are of potential clinical utility but are currently unavailable. We hypothesized that polyethylene glycol (PEG) compounds, inert and non-toxic polymers that serve as a surrogate mucin lining in intestinal epithelium, may attenuate agonist-mediated lung endothelial cell (EC) barrier dysfunction. High molecular weight PEG (PEG15-20) produced rapid, dose-dependent increases in transendothelial electrical resistance (TER) in human lung endothelium cultured on gold microelectrodes, reflecting increased paracellular integrity. The maximal effective concentration of 8% PEG induced a sustained 125% increase in TER (40 h), results similar to barrier-enhancing agonists such as sphingosine 1-phosphate (40% increase in TER). Maximal PEG barrier enhancement was achieved at 45-60 min and PEG effectively reversed both thrombin- and LPS-induced EC barrier dysfunction. Consistent with the increase in TER, immunofluorescent studies demonstrated that PEG produced significant cytoskeletal rearrangement with formation of well-defined cortical actin rings and lamellipodia containing the actin-binding proteins, cortactin and MLCK, known participants in cell-matrix and cell-cell junctional adhesion. Finally, PEG challenge induced rapid alterations in levels of MAP kinase and MLC phosphorylation. In summary, PEG joins a number of EC barrier-regulatory agents which rapidly activate barrier-enhancing signal transduction pathways which target the cytoskeleton and provides a potential therapeutic strategy in inflammatory lung injury.