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Neutrophilia, gelatinase release and microvascular leakage induced by human mast cell tryptase in a mouse model: Lack of a role of protease‐activated receptor 2 ( PAR 2)
Author(s) -
Khedr M. E. M. S.,
Abdelmotelb A. M.,
Pender S. L. F.,
Zhou X.,
Walls A. F.
Publication year - 2018
Publication title -
clinical and experimental allergy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 154
eISSN - 1365-2222
pISSN - 0954-7894
DOI - 10.1111/cea.13108
Subject(s) - tryptase , mast cell , neutrophilia , protease activated receptor 2 , gelatinase , peritoneum , immunology , leupeptin , chemistry , pharmacology , receptor , protease , matrix metalloproteinase , biology , medicine , biochemistry , pathology , enzyme , enzyme linked receptor
Summary Background Tryptase, the most abundant protease of the human mast cell, has been implicated as a key mediator of allergic inflammation that acts through activation of PAR 2. Objectives To investigate the contribution of PAR 2 in the pro‐inflammatory actions mediated by tryptase in a mice model. Methods We have injected recombinant human β II ‐tryptase into the peritoneum of PAR 2‐deficient and wild‐type C57 BL /6 mice. After 6, 12 and 24 hours, mice were killed, peritoneal lavage performed and inflammatory changes investigated. Results Tryptase stimulated an increase in neutrophil numbers in the peritoneum, but responses did not differ between PAR 2‐deficient and wild‐type mice. Heat inactivation of tryptase or pre‐incubation with a selective tryptase inhibitor reduced neutrophilia, but neutrophil accumulation was not elicited with a peptide agonist of PAR 2 ( SLIGRL ‐ NH 2 ). Zymography indicated that tryptase stimulated the release of matrix metalloproteinases ( MMP ) 2 and 9 in the peritoneum of both mouse strains. Studies involving immunomagnetic isolation of neutrophils suggested that neutrophils represent the major cellular source of tryptase‐induced MMP 2 and MMP 9. At 24 hours after tryptase injection, there was increased microvascular leakage as indicated by high levels of albumin in peritoneal lavage fluid, and this appeared to be partially abolished by heat‐inactivating tryptase or addition of a protease inhibitor. There was no corresponding increase in levels of histamine or total protein. The extent of tryptase‐induced microvascular leakage or gelatinase release into the peritoneum did not differ between PAR 2‐deficient and wild‐type mice. Conclusions Our findings indicate that tryptase is a potent stimulus for neutrophil accumulation, MMP release and microvascular leakage. Although these actions required an intact catalytic site, the primary mechanism of tryptase in vivo would appear to involve processes independent of PAR 2.