title: Role of MMP2 and MMP9 in TRPV4-induced lung injury.
abstract: Ca(2+) entry through transient receptor potential vanilloid 4 (TRPV4) results in swelling, blebbing, and detachment of the epithelium and capillary endothelium in the intact lung. Subsequently, increased permeability of the septal barrier and alveolar flooding ensue. In this study, we tested the hypothesis that TRPV4 activation provides a Ca(2+) source necessary for proteolytic disruption of cell-cell or cell-matrix adhesion by matrix metalloproteinases (MMPs) 2 and 9, thus increasing septal barrier permeability. In our study, C57BL/6 or TRPV4(-/-) mouse lungs were perfused with varying doses of the TRPV4 agonist GSK-1016790A (Sigma) and then prepared for Western blot. Lung injury, assessed by increases in lung wet-to-dry weight ratios and total protein levels in the bronchoalveolar lavage fluid, was increased in a dose-dependent fashion in TRPV4(+/+) but not TRPV4(-/-) lungs. In concert with lung injury, we detected increased active MMP2 and MMP9 isoforms, suggesting that TRPV4 can provide the Ca(2+) source necessary for increased MMP2/9 activation. Furthermore, tissue inhibitor of metalloproteinases (TIMP) 2 levels in the TRPV4-injured lungs were decreased, suggesting that TRPV4 activation increases the availability of these active MMPs. We then determined whether MMP2 and MMP9 mediate TRPV4-induced lung injury. Pharmacological blockade (SB-3CT, 1 μM; Sigma) of MMP2 and MMP9 resulted in protection against TRPV4-induced lung injury. We conclude that TRPV4 activation and the subsequent Ca(2+) transient initiates a rapid cascade of events leading to release and activation of the gelatinase MMPs, which then contribute to lung injury.
authors.affiliation: Department of Physiology and Center for Lung Biology, University of South Alabama, Mobile, Alabama;
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Villalta
authors.affiliation: Department of Pharmacology, New York Medical College, Valhalla, New York.
authors.forename: Petra
authors.initials: P
authors.lastname: Rocic
authors.affiliation: Department of Physiology and Center for Lung Biology, University of South Alabama, Mobile, Alabama; Department of Medicine, University of South Alabama, Mobile, Alabama; and mtownsley@southalabama.edu.
authors.forename: Mary I
authors.initials: MI
authors.lastname: Townsley
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D021982:Cell-Matrix Junctions / Q000502:physiology*; D005260:Female; D055370:Lung Injury / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D050916:TRPV Cation Channels / Q000502:physiology*; D019714:Tissue Inhibitor of Metalloproteinases / Q000378:metabolism
chemical_list: D050916:TRPV Cation Channels; D019714:Tissue Inhibitor of Metalloproteinases; C486576:Trpv4 protein, mouse; D020778:Matrix Metalloproteinase 2; C522362:Mmp2 protein, mouse; D020780:Matrix Metalloproteinase 9; C501830:Mmp9 protein, mouse
keywords: lung permeability; matrix metalloproteinase 2; matrix metalloproteinase 9; transient receptor potential vanilloid 4