Pulmonary endothelium is a critical, semi-selective cellular barrier, which prevents the leakage of water, solutes, macromolecules and cells from the vasculature. Compromised pulmonary endothelial cell (EC) barrier integrity caused by mechanical ventilation at high tidal volumes is associated with altered patterns of cyclic stretch experienced by EC, and leads to increased permeability, alveolar flooding, leukocyte infiltration, hypoxemia, and increased morbidity and mortality. We have previously identified cytoskeletal mechanisms of EC permeability changes caused by barrier-protective (sphingosine 1-phosphate) and barrier-disruptive (thrombin) agents and described a critical involvement of small GTPases Rac and Rho in remodeling of cell focal adhesions and adherens junctions associated with EC barrier regulation. Our published results and preliminary data strongly suggest, that modulation of Rac and Rho activities by mechanical stimuli significantly impacts agonist-induced regulation of EC permeability. Our original hypothesis is that magnitude-dependent regulation of Rac and Rho GTPases by cyclic stretch (CS) may determine severity of the pulmonary EC barrier dysfunction and rates of barrier restoration during mechanical ventilation at high tidal volume. We also hypothesize that interactions of cytoskeletal (actin, cortactin), focal adhesion (paxillin, PKL/GIT2), and adherens junction (VE-cadherin, beta-catenin) effectors of small GTPases may be critically involved in the lung barrier regulation by mechanical forces.
Specific Aim #1 will determine physiological and pathologically relevant levels of CS experienced by pulmonary EC using combination of in vitro and in vivo approaches and will explore a link between magnitude-dependent Rac and Rho regulation and EC cytoskeletal changes.
Specific Aim #2 will investigate a role of physiological and pathological CS levels in the agonist-induced regulation of EC cytoskeleton, cell contacts, and monolayer integrity.
Specific Aim #3 will identify molecular mechanisms of mechanochemical regulation of small GTPase activities by Rac- and Rho-specific GEFs (Tiam1, Vav2, betaPIX, GEF-H1 and p115-RhoGEF). We speculate that the results obtained in this study will significantly impact our understanding of the role of small GTPases in the EC adaptation to alterations of mechanochemical environment via specific mechanisms involving cytoskeletal and cell adhesion remodeling (SA#1 and SA#2), discover novel mechanisms of GEF-mediated regulation of Rac and Rho by mechanochemical stimuli (SA#3), and allow us to develop new insights into cellular mechanisms underlying endothelial dysfunction in ventilator-induced lung injury.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Respiratory Integrative Biology and Translational Research Study Section (RIBT)
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Denholm, Elizabeth M
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University of Chicago
Internal Medicine/Medicine
Schools of Medicine
United States
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Sun, Xiaoguang; Shikata, Yasushi; Wang, Lichun et al. (2009) Enhanced interaction between focal adhesion and adherens junction proteins: involvement in sphingosine 1-phosphate-induced endothelial barrier enhancement. Microvasc Res 77:304-13
Birukova, Anna A; Cokic, Ivan; Moldobaeva, Nurgul et al. (2009) Paxillin is involved in the differential regulation of endothelial barrier by HGF and VEGF. Am J Respir Cell Mol Biol 40:99-107
Birukov, Konstantin G (2009) Cyclic stretch, reactive oxygen species, and vascular remodeling. Antioxid Redox Signal 11:1651-67
Birukov, Konstantin G (2009) Small GTPases in mechanosensitive regulation of endothelial barrier. Microvasc Res 77:46-52
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Birukova, Anna A; Arce, Fernando T; Moldobaeva, Nurgul et al. (2009) Endothelial permeability is controlled by spatially defined cytoskeletal mechanics: atomic force microscopy force mapping of pulmonary endothelial monolayer. Nanomedicine 5:30-41
Birukova, Anna A; Rios, Alexander; Birukov, Konstantin G (2008) Long-term cyclic stretch controls pulmonary endothelial permeability at translational and post-translational levels. Exp Cell Res 314:3466-77
Birukova, Anna A; Alekseeva, Elena; Cokic, Ivan et al. (2008) Cross talk between paxillin and Rac is critical for mediation of barrier-protective effects by oxidized phospholipids. Am J Physiol Lung Cell Mol Physiol 295:L593-602
Birukova, Anna A; Moldobaeva, Nurgul; Xing, Junjie et al. (2008) Magnitude-dependent effects of cyclic stretch on HGF- and VEGF-induced pulmonary endothelial remodeling and barrier regulation. Am J Physiol Lung Cell Mol Physiol 295:L612-23
Nonas, Stephanie; Birukova, Anna A; Fu, Panfeng et al. (2008) Oxidized phospholipids reduce ventilator-induced vascular leak and inflammation in vivo. Crit Care 12:R27

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