The kinin B1 receptor contributes to the cardioprotective effect of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in mice

Recent studies have shown that inhibition of angiotensin-converting enzyme (ACE) or angiotensin II receptor causes up-regulation of the B1 receptor (B1R). Here we tested the hypothesis that activation of B1R partially contributes to the cardiac beneficial effect of ACE inhibitor (ACEi) and angiotensin II receptor blockers (ARB). B1R knockout mice (B1R-/-) and C57Bl/6J (wild-type controls, WT) were subjected to myocardial infarction (MI) by ligating the left anterior descending coronary artery. Three weeks after MI, each strain of mice was treated with vehicle, ACEi (ramipril, 2.5 mg/kg/day in drinking water) or ARB (valsartan, 40 mg/kg/day in drinking water) for 5 weeks. We found that 1) compared to WT mice, B1R-/- that underwent sham surgery had slightly but significantly increased LV diastolic dimension, LV mass and myocyte size, whereas SBP, cardiac function and collagen deposition did not differ between strains; 2) MI leads to LV hypertrophy, chamber dilatation and dysfunction similarly in both WT and B1R-/-; and 3) ACEi and ARB improved cardiac function and remodeling in both strains; however, these benefits were significantly diminished in B1R-/- mice. Our data suggest that kinins acting via the B1R participate in the cardioprotective effects of ACEi and ARB

Role of the B1 kinin receptor in the regulation of cardiac function and remodeling after myocardial infarction

Kinins exert cardioprotective effects via 2 G-protein-coupled receptors, B1 and B2. Using B1 kinin receptor gene knockout mice (B1 -/-), we tested the hypotheses that the B1 receptor plays an important role in preservation of cardiac function, whereas lack of B1 may accelerate cardiac remodeling and dysfunction after myocardial infarction, and that B2 receptors may compensate for lack of B1, whereas blockade of B2 receptors in B1 -/- mice may cause further deterioration of cardiac function and remodeling. Female B1 -/- mice and wild-type controls (C57BL/6J, B1 -/+) underwent sham surgery or myocardial infarction and were treated with either vehicle or B 2-antagonist (icatibant, 500 μg/kg per day, subcutaneous) for 8 weeks. We found that in sham myocardial infarction, B1 -/- mice had a larger left ventricular diastolic chamber dimension both initially and at 4 to 8 weeks compared with B1 +/+. Left ventricular mass and myocyte size were also larger in B1 -/- with sham operation than in B1 +/+, although cardiac function did not differ between strains. After myocardial infarction, cardiac remodeling and function were similar in both strains, although B1 -/- mice tended to have lower blood pressure. Blockade of B2 receptors tended to worsen cardiac remodeling and dysfunction in B1 -/- but not in B1 -/-. These results may suggest that B 2 receptors play an important role in compensating for lack of B 1 receptors in mice with myocardial infarction. Dual blockade of both B1 and B2 eliminates this compensation, leading to further deterioration of cardiac dysfunction and remodeling after myocardial infarction