Activation of human tonsil and skin mast cells by agonists of proteinase activated receptor‐2

Aim: To investigate the effects of the agonists of proteinase activated receptor (PAR)‐2, and histamine on degranulation of human mast cells. Methods: Human mast cells were enzymatically dispersed from tonsil and skin tissues. The dispersed cells were then cultured with various stimuli, and tryptase and histamine levels in cell supernatants collected from challenge tubes were measured. Results: PAR‐2 agonist peptide SLIGKV provoked a dose‐dependent release of histamine from skin mast cells. It also induced tryptase release from tonsil mast cells. tc‐LIGRLO appeared less potent than SLIGKV in induction of release of histamine and tryptase. Trypsin was able to induce a “bell” shape increase in tryptase release from tonsil mast cells. It was also able to induce a dose‐dependent release of histamine from both tonsil and skin mast cells. The actions of trypsin on mast cells were inhibited by soy bean trypsin inhibitor (SBTI) or α(1)‐antitrypsin (α(1)‐AT). Time course study revealed that both stimulated tryptase or histamine release initiated within 10 s and reached their peak release between 4 and 6 min. Pretreatment of cells with metabolic inhibitors or pertussis toxin reduced the ability of mast cells to release tryptase or histamine. Conclusion: It was demonstrated that the in vitro tryptase release properties of human tonsil and skin mast cells suggested a novel type of mast cell heterogeneity. The activation of mast cells by PAR‐2 agonists indicated a self‐amplification mechanism of mast cell degranulation.