Degradation of Monocyte Chemoattractant Protein-1 by Tryptase Co-Released in Immunoglobulin E-Dependent Activation of Primary Human Cultured Mast Cells.

BACKGROUND: Mast cells are key immune effector cells which release chemokines, proteases, and other inflammatory mediators upon activation by immunological stimuli. The aim of this study was to investigate the effects of co-releasing proteases on the kinetics of release of the chemokine monocyte chemoattractant protein-1 (MCP-1) in immunoglobulin E (IgE)-mediated activation of human mast cells.

METHODS: Homogenous populations of mature and functional primary human mast cells were generated from CD34+ progenitors originated from buffy coats of healthy adult donors. The releases of MCP-1 from human mast cells in basal conditions and in response to FcεRI cross-linking were assessed at different time points. The effects of different types of protease inhibitors on MCP-1 release from these mast cells under stimulated or unstimulated conditions were also investigated.

RESULTS: Cultured human mast cells released MCP-1 in basal conditions and its levels increased in a time-dependent manner. When stimulated by FcεRI cross-linking, the levels of MCP-1 detected in the medium gradually decreased over time after the initial peak induction. Such a decline in MCP-1 levels after IgE-dependent activation was completely prevented by pretreatment with a cocktail of protease inhibitors or the specific tryptase inhibitor APC366.

CONCLUSIONS: Direct regulation of MCP-1 expression by co-release of tryptase in cultured human mast cells upon IgE-dependent activation demonstrates a role of the serglycin:serine protease axis in modulation of inflammatory reactions through proteolytic degradation of mediators such as chemokines.