title: Mast cell beta-tryptase selectively cleaves eotaxin and RANTES and abrogates their eosinophil chemotactic activities.
abstract: Recent studies have shown that a lack of eosinophils in asthmatic airway smooth muscle (ASM) bundles in contrast to the large number of mast cells is a key feature of asthma. We hypothesized that this is caused by beta-tryptase, the predominant mast cell-specific protease, abrogating the eosinophil chemotactic activities of ASM cell-derived eosinophil chemoattractants such as eotaxin and RANTES. We studied the effect of beta-tryptase on the immunoreactivities of human ASM cell-derived and recombinant eotaxin and other recombinant chemokines that are known to be produced by human ASM cells. We report in this study that purified beta-tryptase markedly reduced the immunoreactivity of human ASM cell-derived and recombinant eotaxin, but had no effect on eotaxin mRNA expression. The effect was mimicked by recombinant human beta-tryptase in the presence of heparin and was reversed by heat inactivation and the protease inhibitor leupeptin, suggesting that the proteolytic activity of tryptase is required. beta-Tryptase also exerted similar effects on recombinant RANTES, but not on the other chemokines and cytokines that were screened. Furthermore, a chemotaxis assay revealed that recombinant eotaxin and RANTES induced eosinophil migration concentration-dependently, which was abrogated by pretreatment of these chemokines with beta-tryptase. Another mast cell protease chymase also markedly reduced the immunoreactivity of eotaxin, but had no effect on RANTES and other chemokines and did not affect the influence of beta-tryptase on RANTES. These findings suggest that mast cell beta-tryptase selectively cleaves ASM-derived eotaxin and RANTES and abrogates their chemotactic activities, thus providing an explanation for the eosinophil paucity in asthmatic ASM bundles.
authors.affiliation: Division of Respiratory Medicine, City Hospital, University of Nottingham, Hucknall Road, Nottingham NG5 1PB, United Kingdom. linhua.pang@nottingham.ac.uk
authors.forename: Linhua
authors.initials: L
authors.lastname: Pang
authors.forename: Mei
authors.initials: M
authors.lastname: Nie
authors.forename: Lisa
authors.initials: L
authors.lastname: Corbett
authors.forename: Amy
authors.initials: A
authors.lastname: Sutcliffe
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Knox
mesh_terms: D001249:Asthma / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D054413:Chemokine CCL11; D018946:Chemokine CCL5 / Q000276:immunology / Q000378:metabolism*; D019742:Chemokines, CC / Q000235:genetics / Q000378:metabolism*; D002633:Chemotaxis; D004804:Eosinophils / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007976:Leupeptins / Q000378:metabolism; D008407:Mast Cells / Q000201:enzymology*; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D053802:Tryptases
chemical_list: C515456:CCL11 protein, human; D054413:Chemokine CCL11; D018946:Chemokine CCL5; D019742:Chemokines, CC; D007976:Leupeptins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D012697:Serine Endopeptidases; D053802:Tryptases; C032854:leupeptin