Asbestos upregulates expression of the urokinase-type plasminogen activator receptor on mesothelial cells.
Inhalation of asbestos is associated with pathologic changes in the pleural space, including pleural thickening, pleural plaques, and mesothelioma. These processes are characterized by altered local proteolysis, cellular proliferation, and cell migration, suggesting that the urokinase-type plasminogen activator receptor (uPAR) could be involved in the pathogenesis of asbestos-induced pleural disease. We hypothesized that mesothelial cell uPAR expression is induced by exposure to asbestos. To test this hypothesis, we used complementary techniques in rabbit and human mesothelial cells to determine whether uPAR expression is altered by exposure to asbestos. uPAR expression was induced by chrysotile and crocidolite asbestos, but not by wollastonite, as indicated by binding of radiolabeled urokinase-type plasminogen activator (uPA) to rabbit or human mesothelial cells. uPA was not induced by fiber exposure. Exposure to exogenous uPA increased uPA activity of cells exposed to wollastonite but not asbestos-treated MeT5A cells. uPAR expression increased further when asbestos was preincubated with vitronectin (VN) or serum. Increases in uPAR expression were confirmed by binding of uPA to uPAR in cell membrane preparations and immunofluorescent staining of uPAR at the cell surface, and were associated with increases in steady-state uPAR messenger RNA. Mesothelial cell uPAR expression was also induced by media from monocytes cultured with asbestos incubated with VN and serum. By antibody neutralization, the latter effect appeared to be in part mediated by transforming growth factor-beta. We found that asbestos increases uPAR at the surface of rabbit and human mesothelial cells, suggesting that altered expression of this receptor could be involved in asbestos-induced remodeling of the pleural mesothelium.
Perkins
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RC
Department of Specialty Care, The University of Texas Health Center at Tyler, Tyler, Texas 75710, USA. perkins@uthct.edu
Broaddus
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VC
Shetty
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Hamilton
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Idell
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D000818:Animals; D017638:Asbestos, Crocidolite / Q000494:pharmacology*; D017632:Asbestos, Serpentine / Q000494:pharmacology*; D017610:Calcium Compounds / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007457:Iodine Radioisotopes; D009000:Monocytes / Q000187:drug effects; D010960:Plasminogen Activators / Q000096:biosynthesis; D010994:Pleura / Q000166:cytology; D012333:RNA, Messenger / Q000096:biosynthesis; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000096:biosynthesis* / Q000235:genetics; D055293:Receptors, Urokinase Plasminogen Activator; D017640:Silicates / Q000494:pharmacology; D013047:Specific Pathogen-Free Organisms; D015854:Up-Regulation / Q000187:drug effects; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism
D017632:Asbestos, Serpentine; D017610:Calcium Compounds; D017077:Culture Media, Conditioned; D007457:Iodine Radioisotopes; C524898:PLAUR protein, human; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D017640:Silicates; D017638:Asbestos, Crocidolite; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator; C031293:calcium silicate