Endothelial cells as early sensors of pulmonary interstitial edema.
We studied responses of endothelial and epithelial cells in the thin portion of the air-blood barrier to a rise in interstitial pressure caused by an increase in extravascular water (interstitial edema) obtained in anesthetized rabbits receiving saline infusion (0.5 ml.kg(-1).min(-1) for 3 h). We obtained morphometric analyses of the cells and of their microenvironment (electron microscopy); furthermore, we also studied in lung tissue extracts the biochemical alterations of proteins responsible for signal transduction (PKC, caveolin-1) and cell-cell adhesion (CD31) and of proteins involved in membrane-to-cytoskeleton linkage (alpha-tubulin and beta-tubulin). In endothelial cells, we observed a folding of the plasma membrane with an increase in cell surface area, a doubling of plasmalemma vesicular density, and an increase in cell volume. Minor morphological changes were observed in epithelial cells. Edema did not affect the total plasmalemma amount of PKC, beta-tubulin, and caveolin-1, but alpha-tubulin and CD-31 increased. In edema, the distribution of these proteins changed between the detergent-resistant fraction of the plasma membrane (DRF, lipid microdomains) and the rest of the plasma membrane [high-density fractions (HDFs)]. PKC and tubulin isoforms shifted from the DRF to HDFs in edema, whereas caveolin-1 increased in DRF at the expense of a decrease in phosphorylated caveolin-1. The changes in cellular morphology and in plasma membrane composition suggest an early endothelial response to mechanical stimuli arising at the interstitial level subsequently to a modest (approximately 5%) increase in extravascular water.
Daffara
Rossella
R
Department of Experimental, Environmental Medicine and Biotechnology, University of Milano-Bicocca, Monza 20052, Italy.
Botto
Laura
L
Beretta
Egidio
E
Conforti
Elena
E
Faini
Andrea
A
Palestini
Paola
P
Miserocchi
Giuseppe
G
D000818:Animals; D051242:Caveolin 1; D022461:Caveolins / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism* / Q000648:ultrastructure*; D040542:Mechanotransduction, Cellular; D008565:Membrane Proteins / Q000378:metabolism; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D011654:Pulmonary Edema / Q000378:metabolism* / Q000473:pathology*; D011817:Rabbits; D015398:Signal Transduction; D014404:Tubulin / Q000378:metabolism*
D051242:Caveolin 1; D022461:Caveolins; D008565:Membrane Proteins; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D014404:Tubulin; D011493:Protein Kinase C