Mast cell chymase as a mediator of inflammation in the human airways

Abstract

Sequentially cut thin sections of bronchial tissues from patients with cystic fibrosis (CF) or chronic obstructive pulmonary disease (COPD), or from control tissues, were stained immunohistochemically for mast cell chymase and tryptase, as well as for neutrophil and eosinophil markers.  The numbers of chymase- and tryptase-containing cells, as well as those of neutrophils were increased in tissues from CF patients compared with the two other groups of patients, whereas eosinophil counts were little different between groups.  Chymase-containing cells were identified throughout the tissues, with large number present in the vicinity of glands in all three groups.  The proportion of mast cells that contained chymase was increased in airways from CF patients, and particularly in the epithelial layer.

Recombinant human prochymase was produced using a baculovirus expression system, isolated to high purity using heparin-agarose column chromatography and gel filtration, and activated with dipeptidyl peptidase I (DPPI).  In addition, chymase was purified by similar methods from high salt extracts of human skin tissue.  Addition of either form of chymase to 16HBE 14o- epithelial cells stimulated within 3h marked increases in expression of mRNA for IL-6, IL-8 and GM-CSF, as detected by reverse transcription-polymerase chain reaction (RT-PCR).  This was followed by increased secretion of IL-6 (maximal at 6h), IL-8 and to some extent GM-CSF (both maximal at 24h).  This was not reflected in increased cell numbers, and the rate of proliferation of epithelial cells was actually reduced at the higher concentrations.  Chymase appeared to degrade IL-8 to a small extent, though no Il-6 or GM-CSF.  The concentrations of chymase employed in this study (10 to 40mU/ml) did not induce cytotoxicity.  The actions of chymase were in all cases inhibited by heat inactivation or by addition of the selective chymase inhibitor Y-40018, or chymostatin.

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