title: Regulation of protease-activated receptor-1 in mononuclear cells by neutrophil proteases.
abstract: Neutrophils and mononuclear cells are implicated in the pathogenesis of several inflammatory conditions including chronic obstructive pulmonary disease (COPD). Neutrophil-derived serine proteases, such as cathepsin G (CG) and neutrophil elastase (NE), may interact with mononuclear cells via protease-activated receptors (PARs) which are seven-transmembrane G protein-coupled receptors activated by proteolytic cleavage of the extracellular N-terminus, and which, on activation, induce the release of several mediators and cytokines. We determined whether CG and NE could affect PAR-1 expression and function in mononuclear cells. Human blood mononuclear cells were isolated from 20 healthy donors. Surface and intracellular receptor expression and calcium mobilisation (using the calcium chelator, FLUO3-AM) were studied by fluorescence-assisted cell sorting (FACS analysis). Positive controls, i.e. thrombin (0.1-100 mU/ml) and the PAR-1-activating peptide SFLLRN (100 microM) induced a rapid and transient intemalisation of PAR-1 in monocytes and lymphocytes. CG but not NE had a similar effect. By contrast, in monocytes intracellular calcium mobilisation was induced by thrombin and SFLLRN but not by CG and NE. Thus, CG can induce intracellular PAR-1 sequestration without activation of the receptor, and may act as an antagonist and prevent subsequent activation of PAR-1 in mononuclear cells. These findings may be of relevance to the pathogenesis of COPD.
authors.affiliation: Department of Thoracic Medicine, Imperial College School of Medicine at National Heart & Lung Institute, London, UK.
authors.forename: N
authors.initials: N
authors.lastname: Roche
authors.forename: R G
authors.initials: RG
authors.lastname: Stirling
authors.forename: S
authors.initials: S
authors.lastname: Lim
authors.forename: B G
authors.initials: BG
authors.lastname: Oliver
authors.forename: K F
authors.initials: KF
authors.lastname: Chung
mesh_terms: D002118:Calcium / Q000378:metabolism; D056649:Cathepsin G; D002403:Cathepsins / Q000494:pharmacology*; D002478:Cells, Cultured; D006801:Humans; D019272:Leukocyte Elastase / Q000494:pharmacology*; D009000:Monocytes / Q000201:enzymology*; D009504:Neutrophils / Q000201:enzymology*; D044463:Receptor, PAR-1; D018179:Receptors, Thrombin / Q000378:metabolism*; D012697:Serine Endopeptidases
chemical_list: D044463:Receptor, PAR-1; D018179:Receptors, Thrombin; D002403:Cathepsins; D012697:Serine Endopeptidases; C534094:CTSG protein, human; D056649:Cathepsin G; D019272:Leukocyte Elastase; D002118:Calcium