Roles of mast cell tryptase and chymase in airway function

Mast cells are abundant and are widely distributed in airway tissues. They release their secretory products into microenvironments as diverse as epithelium, smooth muscle, and glands. The major secretory granule proteins of mast cells are proteases that are released outside of the cell with heparin, histamine, and other preformed mediators. In the past few years, investigations in a number of laboratories have rapidly increased our knowledge of the chemical and biological properties of the two major mast cell secretory proteases, tryptase and chymase. Recent experimental evidence suggests the possibility of biologically important roles for tryptase and chymase in the airways, particularly in the regulation of neuropeptide activity, bronchomotor tone, and submucosal gland secretion. The purpose of this commentary is to examine critically the evidence of participation of these mast cell proteases in molecular and physiological events in the airways.