Prostacyclin post-treatment improves LPS-induced acute lung injury and endothelial barrier recovery via Rap1.

Abstract

Protective effects of prostacyclin (PC) or its stable analog beraprost against agonist-induced lung vascular inflammation have been associated with elevation of intracellular cAMP and Rac GTPase signaling which inhibited the RhoA GTPase-dependent pathway of endothelial barrier dysfunction. This study investigated a distinct mechanism of PC-stimulated lung vascular endothelial (EC) barrier recovery and resolution of LPS-induced inflammation mediated by small GTPase Rap1. Efficient barrier recovery was observed in LPS-challenged pulmonary EC after prostacyclin administration even after 15 h of initial inflammatory insult and was accompanied by the significant attenuation of p38 MAP kinase and NFκB signaling and decreased production of IL-8 and soluble ICAM1. These effects were reproduced in cells post-treated with 8CPT, a small molecule activator of Rap1-specific nucleotide exchange factor Epac. By contrast, pharmacologic Epac inhibitor, Rap1 knockdown, or knockdown of cell junction-associated Rap1 effector afadin attenuated EC recovery caused by PC or 8CPT post-treatment. The key role of Rap1 in lung barrier restoration was further confirmed in the murine model of LPS-induced acute lung injury. Lung injury was monitored by measurements of bronchoalveolar lavage protein content, cell count, and Evans blue extravasation and live imaging of vascular leak over 6 days using a fluorescent tracer. The data showed significant acceleration of lung recovery by PC and 8CPT post-treatment, which was abrogated in Rap1a(-/-) mice. These results suggest that post-treatment with PC triggers the Epac/Rap1/afadin-dependent mechanism of endothelial barrier restoration and downregulation of p38MAPK and NFκB inflammatory cascades, altogether leading to accelerated lung recovery.

• Authors: Anna A Birukova, Fanyong Meng, Yufeng Tian, Angelo Meliton, Nicolene Sarich, Lawrence A Quilliam, Konstantin G Birukov
• Journal: Biochimica et biophysica acta (Biochim Biophys Acta) Vol. 1852 Issue 5 Pg. 778-91 (May 2015) ISSN: 0006-3002 [Print] Netherlands
• PMID: 25545047 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)
• Copyright: Copyright © 2014 Elsevier B.V. All rights reserved.

Chemical References

• 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate
• Epac protein, mouse
• Guanine Nucleotide Exchange Factors
• Icam1 protein, mouse
• Interleukin-8
• Lipopolysaccharides
• Microfilament Proteins
• NF-kappa B
• Platelet Aggregation Inhibitors
• afadin
• Intercellular Adhesion Molecule-1
• beraprost
• Epoprostenol
• Cyclic AMP
• p38 Mitogen-Activated Protein Kinases
• rap1 GTP-Binding Proteins

Topics

• Acute Lung Injury (chemically induced, genetics, prevention & control)
• Animals
• Cell Membrane Permeability (drug effects)
• Cells, Cultured
• Cyclic AMP (analogs & derivatives, pharmacology)
• Endothelial Cells (drug effects, metabolism)
• Endothelium, Vascular (drug effects, metabolism)
• Epoprostenol (analogs & derivatives, pharmacology)
• Guanine Nucleotide Exchange Factors (metabolism)
• Humans
• Immunoblotting
• Intercellular Adhesion Molecule-1 (metabolism)
• Interleukin-8 (metabolism)
• Lipopolysaccharides
• Mice, Inbred C57BL
• Mice, Knockout
• Microfilament Proteins (genetics, metabolism)
• NF-kappa B (metabolism)
• Platelet Aggregation Inhibitors (pharmacology)
• RNA Interference
• Signal Transduction (drug effects)
• p38 Mitogen-Activated Protein Kinases (metabolism)
• rap1 GTP-Binding Proteins (genetics, metabolism)