Chymase Inhibition Reduces Infarction and Matrix Metalloproteinase-9 Activation and Attenuates Inflammation and Fibrosis after Acute Myocardial Ischemia/Reperfusion

Abstract

Chymase is activated after acute myocardial ischemia/reperfusion (AMI-R) and is associated with an early activation of matrix metalloproteinase-9 (MMP-9), which increases infarct size after experimental AMI, and late fibrosis. We assessed the effect of chymase inhibition on myocardial protection and early signs of fibrosis after AMI-R. Fourteen pigs underwent AMI-R and received intravenously either vehicle (V; n ϭ 7) or chymase inhibitor (CM; n ϭ 7). Separately, rat myocardial fibroblast was incubated with vehicle (n ϭ 4), low-dose chymase (n ϭ 4), high-dose chymase (n ϭ 4), or high-dose chymase plus chymase inhibitor (n ϭ 4). Infarct size (V, 41 Ϯ 5; CM, 24 Ϯ 5; P Ͻ 0.01) and serum troponin T (P ϭ 0.03) at the end of reperfusion were significantly reduced in CM. Chymase activity in both the area at risk (AAR) (P ϭ 0.01) and nonischemic area (P ϭ 0.02) was significantly lower in CM. Myocardial levels of pro, cleaved, and cleaved/pro-MMP-9 in the AAR were significantly lower in CM than V (P Ͻ 0.01, Ͻ 0.01, and ϭ 0.02, respectively), whereas phospho-endothelial nitric-oxide synthase (eNOS) (P Ͻ 0.01) and total eNOS (P ϭ 0.03) were significantly higher in CM. Apoptotic cells (P ϭ 0.05), neutrophils (P Ͻ 0.05), and MMP-9-colocalizing mast cells (P Ͻ 0.05) in the AAR were significantly reduced in CM. Interleukin-18 (P Ͻ 0.05) and intercellular adhesion molecule-1 (P Ͻ 0.05) mRNA levels were significantly lower in CM. In cultured cardiac fibrosis, Ki-67-positive cells were significantly higher in the high-dose chymase groups (P Ͻ 0.03). This study demonstrates that chymase inhibition plays crucial roles in myocardial protection related to MMP-9, inflammatory markers, and the eNOS pathway. It may also attenuate fibrosis induced by activated chymase after AMI-R.

Chymase-mediated intestinal epithelial permeability is regulated by a protease-activating receptor/matrix metalloproteinase-2-dependent mechanism

“…We demonstrate chymase-mediated MMP-2 activation in the absence of cofactors including TIMP-2, MT1-MMP, or proteoglycan (PG)-GAG, indicating that chymase is sufficient to promote proteolytic MMP-2 activation. A role for chymase in MMP-9 processing and activation in animal models and Mcpt4 Ϫ/Ϫ mice has also been reported (25,27,47). We did not observe chymase-induced MMP-9 activation in our in vitro analyses.…”

Multiple Mechanisms for the Action of Chymase Inhibitors

“…The elevated chymase activity has been found to augment angiotensin II formation and MMP-9 activity, while chymase inhibitors attenuated angiotensin II formation and MMP-9 activity (3,14). Chymase inhibitors attenuated the cardiac dysfunction and extended survival (3,14,15).…”

“…Chymase is activated in the ischemic myocardium after ligation of the coronary artery in animal models (3,14). The elevated chymase activity has been found to augment angiotensin II formation and MMP-9 activity, while chymase inhibitors attenuated angiotensin II formation and MMP-9 activity (3,14).…”

IGF-1 degradation by mouse mast cell protease 4 promotes cell death and adverse cardiac remodeling days after a myocardial infarction

“…Postischemic cardiac dysfunction and remodeling are intimately linked to infarct size (16). In pig hearts subjected to ischemia, and then perfused for approximately 2 h, chymase inhibitor treatment reduced infarct size as assessed by serum troponin levels or infarct size relative to the area at risk (17). We investigated whether MMCP-4 deficiency influences post-I/R infarct development.…”