Bradykinin B2 receptor agonism: a novel therapeutic strategy for myocardial infarction?

Comparative effect of angiotensin converting enzyme inhibitor versus angiotensin ii type i receptor blocker in acute myocardial infarction with non-obstructive coronary arteries; from the Korea Acute Myocardial Infarction Registry - National Institute of Health

BACKGROUND

Selecting angiotensin converting enzyme inhibitor (ACEI) or angiotensin II type I receptor blocker (ARB) in patients diagnosed as acute myocardial infarction (AMI) with non-obstructive coronary arteries (MINOCA) is not established. The purpose of this study is to compare the clinical effect of ACEI vs. ARB in MINOCA patients.

METHODS AND RESULTS

A total of 273 patients between November 2011 to June 2015, diagnosed with MINOCA who were registered in the Korea Acute Myocardial Infarction Registry - National Institute of Health were enrolled. Patients were divided into ACEI (n = 112) and ARB groups (n = 161). The primary endpoint was cumulative incidence of major adverse cardiac events (MACE) defined as cardiac death, recurrent MI, any new revascularization during 2 years clinical follow-up. Secondary endpoint was heart failure requiring re-hospitalization. Propensity score matching analysis was done. The incidence of primary endpoint was similar (10.4% vs. 15.6%, HR: 0.65; 95% CI: 0.29-1.47; p = 0.301) among both groups. However, the incidence of recurrent MI was significantly lower in ACEI group compared to ARB group (2.1% vs. 10.4%, HR: 0.18, 95% CI: 0.04-0.86; p = 0.031).

CONCLUSIONS

In the present study, the risk and incidence of MACE was similar between ACEI and ARB therapy in MINOCA patients. However, ACEI significantly reduced the risk of recurrent MI. Further larger scale multi-center randomized clinical trials are needed to clarify the proper use of renin-angiotensin-aldosterone system blocker in these patients.

Pharmacological evidence of bradykinin regeneration from extended sequences that behave as peptidase-activated B2 receptor agonists

While bradykinin (BK) is known to be degraded by angiotensin converting enzyme (ACE), we have recently discovered that Met-Lys-BK-Ser-Ser is paradoxically activated by ACE. We designed and evaluated additional "prodrug" peptides extended around the BK sequence as potential ligands that could be locally activated by vascular or blood plasma peptidases. BK regeneration was estimated using the contractility of the human umbilical vein as model of vascular functions mediated by endogenous B2 receptors (B2Rs) and the endocytosis of the fusion protein B2R-green fluorescent protein (B2R-GFP) expressed in Human Embryonic Kidney 293 cells. Of three BK sequences extended by a C-terminal dipeptide, BK-His-Leu had the most desirable profile, exhibiting little direct affinity for the receptor but a significant one for ACE (as shown by competition of [(3)H]BK binding to B2R-GFP or of [(3)H]enalaprilat to recombinant ACE, respectively). The potency of the contractile effect of this analog on the vein was reduced 18-fold by the ACE inhibitor enalaprilat, pharmacologically evidencing BK regeneration in situ. BK-Arg, a potential substrate of arginine carboxypeptidases, had a low affinity for B2Rs and its potency as a contractile agent was reduced 15-fold by tissue treatment with an inhibitor of these enzymes, Plummer's inhibitor. B2R-GFP internalization in response to 100 nM of the extended peptides recapitulated these findings, as enalaprilat selectively inhibited the effect of BK-His-Leu and Plummer's inhibitor, that of BK-Arg. The two peptidase inhibitors did not affect BK-induced effects in either assay. The novel C-terminally extended BKs had no or very little affinity for the kinin B1 receptor (competition of [(3)H]Lys-des-Arg(9)-BK binding). The feasibility of peptidase-activated B2R agonists is illustrated by C-terminal extensions of the BK sequence.