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This Article Full Text Full Text (PDF) All Versions of this Article: 294/2/L266    most recent 00107.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Troyanovsky, B. Articles by Schaphorst, K. L. Search for Related Content PubMed PubMed Citation Articles by Troyanovsky, B. Articles by Schaphorst, K. L.

Thrombin enhances the barrier function of rat microvascular endothelium in a PAR-1-dependent manner

University of South Alabama Center for Lung Biology, Mobile, Alabama

Submitted 19 March 2007 ; accepted in final form 25 November 2007

Thrombin is a multifunctional coagulation protease with pro- and anti-inflammatory vascular effects. We questioned whether thrombin may have segmentally differentiated effects on pulmonary endothelium. In cultured rat endothelial cells, rat thrombin (10 U/ml) recapitulated the previously reported decrease in transmonolayer electrical resistance (TER), F-actin stress fiber formation, paracellular gap formation, and increased permeability. In contrast, in rat pulmonary microvascular endothelial cells (PMVEC), isolated on the basis of Griffonia simplicifolia lectin recognition, thrombin increased TER, induced fewer stress fibers, and decreased permeability. To assess for differential proteinase-activated receptor (PAR) expression as a basis for the different responses, PAR family expression was analyzed. Both pulmonary artery endothelial cells and PMVEC expressed PAR-1 and PAR-2; however, only PMVEC expressed PAR-3, as shown by both RT-PCR and Western analysis. PAR-1 activating peptides (PAR-APs: SFLLRN-NH₂ and TFLLRN-NH₂) were used to confirm a role for the PAR-1 receptor. PAR-APs (25–250 µM) also increased TER, formed fewer stress fibers, and did not induce paracellular gaps in PMVEC in contrast to that shown in pulmonary artery endothelial cells. These results were confirmed in isolated perfused rat lung preparations. PAR-APs (100 µg/ml) induced a 60% increase in the filtration coefficient over baseline. However, by transmission electron microscopy, perivascular fluid cuffs were seen only along conduit veins and arteries without evidence of intra-alveolar edema. We conclude that thrombin exerts a segmentally differentiated effect on endothelial barrier function in vitro, which corresponds to a pattern of predominant perivascular fluid cuff formation in situ. This may indicate a distinct role for thrombin in the microcirculation.

proteinase-activated receptor; permeability