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The objective of this study is to examine the differential expression of mast cell tryptase and its receptor, protease-activated receptor-2 (PAR-2), in the synovium and synovial fluid of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). Biochemical and immunohistochemical analyses were performed to determine whether the trypsin-like protease in the synovium is identical to mast cell tryptase. The effects of mast cell tryptase on the proliferation of synovial fibroblast-like cells (SFCs) and the release of IL-8 thereof were evaluated by the [3H]-thymidine incorporation and ELISA, respectively. The trypsin-like protease in the synovium of RA patients was identical to human mast cell tryptase, which was composed of two subunits: 33 and 34 kDa. The 33- and 34-kDa proteins are different glycosylated forms of the 31-kDa protein, which was unglycosylated. Mast cell tryptase activity in RA synovial fluid was significantly higher than that in OA synovial fluid, while their activities and expression in the synovium were similar. Expression of PAR-2 mRNA in the synovium was higher in RA than in OA. Mast cell tryptase containing the unglycosylated 31-kDa subunit was the predominant form in synovial fluid. RA patients had higher amounts of this subunit in their synovial fluid than OA patients. Mast cell tryptase and PAR-2 activating peptide stimulated the proliferation of SFCs and release of IL-8 from these cells. Mast cell tryptase secretion into RA synovial fluid is higher than OA synovial fluid. Mast cell tryptase in synovial fluid stimulates the proliferation of SFCs and the release of pro-inflammatory cytokines via PAR-2, which may contribute to exacerbation of synovitis in RA. [ABSTRACT FROM AUTHOR]

The human airway trypsin-like protease (HAT) is a respiratory epithelium-associated, type II transmembrane serine protease, which is also detected as an extracellular enzyme in lung fluids during airway inflammatory disorders. We have evaluated its capacity to affect the urokinase-type plasminogen activator receptor (uPAR), a membrane glycolipid-anchored, three- domain (D1D2D3) glycoprotein that plays a crucial role in innate immunity and inflammation by supporting cell migration and matrix degradation, with structure and biological properties that can be regulated via limited endoproteolysis. With the use of immunoblot- ting, flow immunocytometry, and ELISA analyses applied to a re- combinant uPAR protein and to uPAR-expressing monocytic and human bronchial epithelial cells, it was shown that exposure of uPAR to soluble HAT in the range of 10-500 nM resulted in the proteolytic processing of the full-length (D1D2D3) into the truncated (D2D3) species, with cleavage occurring in the D1 to D2 linker sequence after arginine residues at position 83 and 89. Using immunohistochemistry, we found that both HAT and uPAR were expressed in the human bronchial epithelium. Moreover, transient cotransfection in epithelial cells showed that membrane coexpression of the two partners produced a constitutive and extensive shedding of the D1 domain, occurring for membrane-associated HAT concentrations in the nanomolar range. Because the truncated receptor was found to be unable to bind two of the major uPAR ligands, the adhesive matrix protein vitronectin and the serine protease urokinase, it thus appears that proteolytic regulation of uPAR by HAT is likely to modulate cell adherence and motility, as well as tissue remodeling during the inflammatory response in the airways. [ABSTRACT FROM AUTHOR]

Human airway trypsin-like protease (HAT) was isolated from airway secretions and localized to bronchial epithelial cells by immunohistochemistry. In the present study, we examined whether HAT could stimulate DNA synthesis and proliferation of primary human bronchial fibroblasts (HBF). HAT significantly stimulated the proliferation of HBF by 20-55%, a level similar to that of the mitogenic activity of lung mast cell tryptase (MCT). HAT also stimulated the incorporation of [3H]thymidine in HBF, and this HAT-induced DNA synthesis was abolished by leupeptin. Protease-activated receptor-2 (PAR-2) mRNA was expressed and localized to the cell surface in HBF. PAR-2 activating peptide (AP) also enhanced DNA synthesis, and both HAT and PAR-2 AP induced receptor internalization, similar to the response to trypsin. Pretreatment of HBF with anti-PAR-2 antibody significantly suppressed both HAT and PAR-2 AP-induced DNA synthesis. In addition, HAT and PAR-2 AP induced intracellular Ca2+ mobilization in HBF. The HAT-induced increase in Ca2+ was desensitized by pretreatment with trypsin or PAR-2 AP. U0126, a specific MAPK inhibitor, completely inhibited HAT-induced DNA synthesis as well as HAT-induced phosphorylation of MAPK. The effect of HAT and MCT together was additive, whereas the effect of HAT and insulin together on HBF DNA synthesis was synergistic. These results indicate that HAT stimulates fibroblast proliferation in bronchial airways through a PAR-2-dependent MEK-MAPK mediated pathway and that HAT is linked to airway processes involving fibroblasts. [ABSTRACT FROM AUTHOR]

Human airway trypsin-like protease (HAT) has been isolated from mucoid sputum of patients with chronic airway diseases. In order to clarify the cellular source of this novel protease in the human airway, we examined the localization of immunoreactive HAT in bronchial tissues obtained at surgery and fixed in 4% paraformaldehyde using an extremely sensitive immunohistochemical technique called a catalyzed signal amplification method and a monoclonal antibody against recombinant HAT. HAT immunoreactivity was demonstrated in cytoplasm of ciliated cells of bronchial epithelium and/or at the basal part of cilia. No positive reaction was found in submucosal glands or mast cells. The heterogeneous distribution of HAT immunoreactivity within the bronchial epithelium indicates that its expression might be changeable and that it might be closely related to the physiological status of the airway epithelium. Non-specific but intense reaction caused by endogenous avidin-binding activity (EABA) was selectively detected in submucosal glands, but was effectively blocked by successive treatments with avidin and biotin. These results indicate that HAT may be synthesized in the ciliated cells and that it may play some physiological roles within the epithelial layer and on the airway surface. It is necessary to keep in mind that some cells show strong EABA, especially when a highly sensitive immunohistochemical technique is applied. [ABSTRACT FROM AUTHOR]

Changes with age in the lecithin (especially saturated lecithin) content of human and rat lung and in lecithin synthetic activities in rat lung were examined to obtain information on lecithin metabolism in the lung in old age. In lung tissues of humans and rats, the content of saturated lecithin as a percentage of total lecithin was fairly constant (about 35%) throughout adult and old age. The percentage content in bronchial wash was 55-60% in both young and old rats. The radioactivities incorporated into lung tissue per milligram total and saturated lecithin after intravenous administration of palmitic acid-H were similar in young and old rats. These results suggest that lung tissue contains a rather constant amount of saturated lecithin throughout adult and old age and that lecithin synthesis in the lung is still active in old age. [ABSTRACT FROM PUBLISHER]