Article

Polar head groups are important for barrier-protective effects of oxidized phospholipids on pulmonary endothelium.

Section of Pulmonary and Critical Medicine, Department of Medicine, Division of Biomedical Sciences, University of Chicago, 929 East 57th St., CIS Bldg., W410, Chicago, IL 60637, USA.
AJP Lung Cellular and Molecular Physiology (impact factor: 3.66). 05/2007; 292(4):L924-35. DOI:10.1152/ajplung.00395.2006 pp.L924-35
Source: PubMed

ABSTRACT We have previously described protective effects of oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (OxPAPC) on pulmonary endothelial cell (EC) barrier function and demonstrated the critical role of cyclopentenone-containing modifications of arachidonoyl moiety in OxPAPC protective effects. In this study we used oxidized phosphocholine (OxPAPC), phosphoserine (OxPAPS), and glycerophosphate (OxPAPA) to investigate the role of polar head groups in EC barrier-protective responses to oxidized phospholipids (OxPLs). OxPAPC and OxPAPS induced sustained barrier enhancement in pulmonary EC, whereas OxPAPA caused a transient protective response as judged by measurements of transendothelial electrical resistance (TER). Non-OxPLs showed no effects on TER levels. All three OxPLs caused enhancement of peripheral EC actin cytoskeleton. OxPAPC and OxPAPS completely abolished LPS-induced EC hyperpermeability in vitro, whereas OxPAPA showed only a partial protective effect. In vivo, intravenous injection of OxPAPS or OxPAPC (1.5 mg/kg) markedly attenuated increases in the protein content, cell counts, and myeloperoxidase activities detected in bronchoalveolar lavage fluid upon intratracheal LPS instillation in mice, although OxPAPC showed less potency. All three OxPLs partially attenuated EC barrier dysfunction induced by IL-6 and thrombin. Their protective effects against thrombin-induced EC barrier dysfunction were linked to the attenuation of the thrombin-induced Rho pathway of EC hyperpermeability and stimulation of Rac-mediated mechanisms of EC barrier recovery. These results demonstrate for the first time the essential role of polar OxPL groups in blunting the LPS-induced EC dysfunction in vitro and in vivo and suggest the mechanism of agonist-induced hyperpermeability attenuation by OxPLs via reduction of Rho and stimulation of Rac signaling.

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Keywords

agonist-induced hyperpermeability attenuation
 
bronchoalveolar lavage fluid
 
cell counts
 
critical role
 
EC barrier recovery
 
EC barrier-protective responses
 
EC hyperpermeability
 
intratracheal LPS instillation
 
LPS-induced EC hyperpermeability
 
myeloperoxidase activities
 
oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine
 
partial protective effect
 
peripheral EC actin cytoskeleton
 
polar head groups
 
polar OxPL groups
 
pulmonary EC
 
three OxPLs
 
thrombin-induced Rho pathway
 
transendothelial electrical resistance
 
transient protective response