Mast Cell Degranulation Increases Mouse Mast Cell Protease 4-Dependent Vasopressor Responses to Big Endothelin-1 But Not Angiotensin I.

Mouse mast cell protease 4 (mMCP-4), the murine functional analog to the human chymase, is a serine protease synthesized and stored in mast cell secretory granules. Our previous studies reported physiologic and pathologic roles for mMCP-4 in the maturation and synthesis of the vasoactive peptide endothelin-1 (ET-1) from its precursor, big ET-1. The aim of this study was to investigate the impact of mast cell degranulation or stabilization on mMCP-4-dependent pressor responses after the administration of big ET-1 or angiotensin I (Ang I). In anesthetized mice, mast cell degranulation induced by compound 48/80 (C48/80) or stabilization by cromolyn enhanced or repressed, respectively, the dose-dependent vasopressor responses to big ET-1 in wild-type (WT) mice but not in mMCP-4 knockout mice in a chymase inhibitor (TY-51469)-sensitive fashion. In addition, mMCP-4-dependent hydrolysis of the fluorogenic substrate Suc-Leu-Leu-Val-Tyr-7-amino-4-methylcoumarin was depleted or enhanced in peritoneal mast cells isolated from mice pretreated with C48/80 or cromolyn, respectively. Furthermore, C48/80 or cromolyn markedly increased or abolished, respectively, ET-1 (1-31) conversion from exogenous big ET-1 in WT mice peritoneal fluid-isolated mast cells, in vitro Finally, the vasopressor responses to Ang I were unaffected by mast cell activation or stabilization, whereas those induced by the angiotensin-converting enzyme-resistant Ang I analog, [Pro, D-Ala] Ang I, were potentiated by C48/80. Altogether, the present study shows that mast cell activation enhances the mMCP-4-dependent vasoactive properties of big ET-1 but not Ang I in the mouse model. SIGNIFICANCE STATEMENT: The current work demonstrates a significant role for mast cell stability in the cardiovascular pharmacology of big endothelin-1 but not angiotensin I in the murine systemic circulation.