Substance P induces adverse myocardial remodelling via a mechanism involving cardiac mast cells

Abstract

Aims Substance P and neurokinin A (NKA) are sensory nerve neuropeptides encoded by the TAC1 gene. Substance P is a mast cell secretagogue and mast cells are known to play a role in adverse myocardial remodelling. Therefore, we wondered whether substance P and/or NKA modulates myocardial remodelling via a mast cell-mediated mechanism.Methods and resultsVolume overload was induced by aortocaval fistula in TAC1-/- mice and their respective wild types. Left ventricular internal diameter of wild-type (WT) fistulas increased by 31.9; this was prevented in TAC1-/- mice (4.2). Matrix metalloproteinase (MMP) activity was significantly increased in WT fistula mice and was prevented in TAC1-/- mice. Myocardial collagen volume fraction was decreased in WT fistula mice; this collagen degradation was not observed in the TAC1 -/- group. There were no significant differences between any groups in tumour necrosis factor (TNF)-α or cell death. Cardiac mast cells were isolated from rat hearts and stimulated with substance P or NKA. We found that these cells degranulated only to substance P, via the neurokinin-1 receptor. To determine the effect of substance P on mast cells in vivo, volume overload was created in Sprague-Dawley rats treated with the NK-1 receptor antagonist L732138 (5 mg/kg/day) for a period of 3 days. L732138 prevented: (i) increases in cardiac mast cell density; (ii) increased myocardial TNF-α; and (iii) collagen degradation.ConclusionsOur studies suggest that substance P may be important in mediating adverse myocardial remodelling secondary to volume overload by activating cardiac mast cells, leading to increased TNF-α and MMP activation with subsequent degradation of the extracellular matrix. © 2011 The Author.