Inhibitors of Tryptase as Mast Cell-Stabilizing Agents in the Human Airways: Effects of Tryptase and Other Agonists of Proteinase-Activated Receptor 2 on Histamine Release

Abstract

Tryptase, the major secretory product of human mast cells, is emerging as a new target for therapeutic intervention in allergic airways disease. We have investigated the ability of tryptase and inhibitors of tryptase to modulate histamine release from human lung mast cells and have examined the potential contribution of proteinase-activated receptor 2 (PAR2). The tryptase inhibitor APC366 [N-(1-hydroxy-2-naphthoyl)-L-arginyl-L-prolinamide hydrochloride] was highly effective at inhibiting histamine release stimulated by antiIgE antibody or calcium ionophore from enzymatically dispersed human lung cells. A concentration of APC366 as low as 10 M was able to inhibit anti-IgE-dependent histamine release by some 50%. Addition of leupeptin or the tryptic substrate N-benzoyl-D,L-arginine-p-nitroanilide also inhibited IgE-dependent histamine release. Purified tryptase in the presence of heparin stimulated a small but significant release of histamine from lung cells, suggesting that tryptase may provide an amplification signal from activated cells that may be susceptible to proteinase inhibitors. Trypsin was also able to induce histamine release apparently by a catalytic mechanism. Moreover, pretreatment of cells with metabolic inhibitors or with pertussis toxin reduced responses, indicating a noncytoxic pertussis toxin-sensitive G proteinmediated signaling process. Addition to cells of the PAR2 agonists SLIGKV-NH 2 or tc-LIGRLO-NH 2 or appropriate control peptides were without effect on histamine release, and PAR2 was not detected by immunohistochemistry in tissue mast cells. The potent actions of tryptase inhibitors as mast cell-stabilizing agents could be of value in the treatment of allergic inflammation of the respiratory tract, possibly by targeting the non-PAR2-mediated actions of tryptase.

Mast Cells Mediate Acute Kidney Injury through the Production of TNF

“…10,11 We measured kidney and serum tryptase levels, and tryptase is a major constituent of mast cells and is stored almost exclusively in mast cells. 34 In the kidney, mast cells are seen infrequently both before and after cisplatin treatment. However, we found a statistically significant increase in kidney mast-cell degranulation and TNF expression in mice treated with cisplatin.…”

The role of the mast cell in the pathophysiology of asthma

“…18 Tryptase-induced bronchoconstriction in animal models is likely to be mediated by mast cell activation because it may be blocked by pretreatment with antihistamines. Human tryptase can act as a stimulus for histamine release from mast cells from several tissues including those of the lung, 19 and consistent with this, inhibitors of this protease can be effective as mast cell stabilizing agents. In addition to its ability to stimulate cytokine release from ASM, tryptase can act as a potent mitogen in vitro.…”

Anti-IgE as a mast cell–stabilizing therapeutic agent

“…The inhibitors of tryptase and chymase can also function as mast cell-stabilizing agents; those for tryptase seem to act both extracellularly and intracellularly, whereas those for chymase act only intracellularly. 91,92 Thus although the significance of the mast cell-stabilizing effects of those inhibitors needs to be verified in vivo, the inhibitors of many mast cell mediators can not only counteract the actions of the mediators but also decrease their release from mast cells. 92 Signaling pathways are targets for intervention…”