A Novel Function for Transforming Growth Factor-β1: Upregulation of the Expression and the IgE-Independent Extracellular Release of a Mucosal Mast Cell Granule-Specific β-Chymase, Mouse Mast Cell Protease-1

Abstract

Intestinal mucosal mast cells (IMMC) express granule neutral proteases that are regulated by T-cell–derived cytokines, including interleukin-3 (IL-3) and IL-9, and by stem cell factor (SCF). The IMMC-specific chymase, mouse mast cell protease-1 (mMCP-1), is released in substantial quantities into the blood stream during gastrointestinal allergic responses. We used cultured bone marrow-derived mast cells (mBMMC) to identify cytokines that regulate the expression and extracellular release of mMCP-1. When grown in IL-3–rich WEHI (15% vol/vol) and 50 ng/mL recombinant rat SCF (rrSCF) bone marrow cells supplemented with IL-9 (5 ng/mL) differentiated into mBMMC that expressed a maximum of less than 250 ng mMCP-1/106 cells and 189 ng mMCP-1/mL of culture supernatant. Supplementation of the same three cytokines with transforming growth factor-β1(TGF-β1; 1 ng/mL) resulted in substantially enhanced expression (6 μg/106 mBMMC) and extracellular release (2 μg/mL of culture supernatant) of mMCP-1. The response to TGF-β1 was dose-dependent, with maximal effect at 1 ng/mL, and was associated with immunohistochemical and ultrastructural changes in the secretory granules. IL-9–induced expression of mMCP-1 may be due to endogenously expressed TGF-β1, because it was blocked by anti–TGF-β antibodies. In conclusion, the expression and extracellular release of the IMMC-specific chymase, mMCP-1, is strictly regulated by TGF-β1.