Abstract
The serine protease chymase has been reported to generate intracardiac angiotensin-II (Ang-II) from Ang-I as well as an intermediate precursor of endothelin-1 (ET-1), ET-1 (1–31) from Big-ET-1. Although humans possess only one chymase, several murine isoforms are documented, each with its own specific catalytic activity. Among these, mouse mast cell protease 4 (mMCP-4) is the isoform most similar to the human chymase for its activity. The aim of this study was to characterize the capacity of mMCP-4 to convert Big-ET-1 into its bioactive metabolite, ET-1, in vitro and in vivo in the mouse model. Basal mean arterial pressure did not differ between wild-type (WT) and mMCP-4(−/−) mice. Systemic administration of Big-ET-1 triggered pressor responses and increased blood levels of immunoreactive (IR) ET-1 (1–31) and ET-1 that were reduced by more than 50% in mMCP-4 knockout (−/−) mice compared with WT controls. Residual responses to Big-ET-1 in mMCP-4(−/−) mice were insensitive to the enkephalinase/neutral endopeptidase inhibitor thiorphan and the specific chymase inhibitor TY-51469 {2-[4-(5-fluoro-3-methylbenzo[b]thiophen-2-yl)sulfonamido-3-methanesulfonylphenyl]thiazole-4-carboxylic acid}. Soluble fractions from the lungs, left cardiac ventricle, aorta, and kidneys of WT but not mMCP-4(−/−) mice generated ET-1 (1–31) from exogenous Big-ET-1 in a TY-51469-sensitive fashion as detected by high-performance liquid chromatography/ matrix-assisted laser desorption/ionization-mass spectrometry. Finally, pulmonary endogenous levels of IR-ET-1 were reduced by more than 40% in tissues derived from mMCP-4(−/−) mice compared with WT mice. Our results show that mMCP-4 plays a pivotal role in the dynamic conversion of systemic Big-ET-1 to ET-1 in the mouse model.
Footnotes
- Received December 3, 2012.
- Accepted April 15, 2013.
This work was supported by the Canadian Institutes for Health Research [Grant MOP-57883 (to P.D.-J.)]; the National Institutes of Health [Grants R01-AI083516 (to M.G.) and GM 052585-15 (to M.G.)]; as well as by the Etienne Lebel Clinical Research Center of the Centre Hospitalier Universitaire de Sherbrooke. M.H. is in receipt of a Ph.D. scholarship from the Canadian Institutes for Health Research.
↵This article has supplemental material available at jpet.aspetjournals.org.
- Copyright © 2013 by The American Society for Pharmacology and Experimental Therapeutics
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