Abstract

Mouse mast cell protease 4 (mMCP-4), the murine functional analogue to the human chymase, is a serine protease synthesized and stored in mast cell secretory granules. Our previous studies reported physiological and pathological roles for mMCP-4 in the maturation and synthesis of the vasoactive peptide endothelin-1 (ET-1) from its precursor, big endothelin-1 (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 following 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 pre-treated 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 analogue, [Pro¹¹, D-Ala¹²] 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 ET-1 but not Ang I in the murine systemic circulation. This study also demonstrate for the first time that an ACE-resistant Ang I analogue is susceptible to chymase-dependent activation in the mouse model.