Tissue kallikrein and kinin infusion rescues failing myocardium after myocardial infarction

Abstract

Background: Tissue kallikrein is a serine proteinase that generates the vasoactive kinin peptide, which produces vasodilatory, angiogenic, and antiapoptotic effects. In this study, we investigated the effect of a stable supply of kallikrein and kinin on ventricular remodeling and blood vessel growth in rats after myocardial infarction.

Methods and results: At 1 week after coronary artery ligation, tissue kallikrein or kinin was infused through a minipump for 4 weeks. At 5 weeks after myocardial infarction, kallikrein and kinin infusion significantly improved cardiac contractility and reduced diastolic dysfunction without affecting systolic blood pressure. Kallikrein and kinin infusion significantly increased capillary density in the noninfarcted region. Kallikrein and kinin infusion also reduced heart weight/body weight ratio, cardiomyocyte size, and atrial natriuretic peptide and brain natriuretic peptide expression in the noninfarcted area. Moreover, kallikrein and kinin infusion inhibited interstitial collagen deposition, collagen fraction volume, and collagen I and collagen III mRNA levels, transforming growth factor (TGF)-beta1 and plasminogen activator inhibitor-1 expression, and Smad2 phosphorylation. The effects of kallikrein and kinin on cardiac remodeling were associated with increased nitric oxide levels and reduced NADPH oxidase expression and activity, superoxide formation, and malondialdehyde levels. Furthermore, in cultured cardiac fibroblasts, kinin inhibited angiotensin II-stimulated TGF-beta1 production, and the effect was blocked by icatibant.

Conclusion: These results indicate that a subdepressor dose of kallikrein or kinin can restore impaired cardiac function in rats with postinfarction heart failure by inhibiting hypertrophy and fibrosis and promoting angiogenesis through increased nitric oxide formation and suppression of oxidative stress and TGF-beta1 expression.

Fig. 1

Kallikrein and kinin promote neovascularization 5 weeks after MI. (A) Representative micrograph images of heart sections stained with antibodies against CD31 (400× magnification). (B) Capillary density in number of capillaries per mm². (C) Quantification of capillary-to-myocyte ratio. Data are expressed as mean ± SEM (n=6-8).

Fig. 2

Effect of kallikrein and kinin on cardiac hypertrophy in the non-infarcted region. (A) Representative histological left ventricular sections stained with Gordon and Sweet’s silver (400× magnification). (B) Quantification of cardiomyocyte area. Real-time PCR analysis of (C) ANP and (D) BNP mRNA levels. Data are expressed as mean ± SEM (n=6-8).

Fig. 3

Effect of kallikrein and kinin on cardiac fibrosis in the non-infarcted region. (A) Sirius Red staining and immunohistochemical staining of collagens I and III (200× magnification). (B) Collagen fraction volume was quantified from Sirius Red staining using Adobe Photoshop. Real-time PCR analysis of (C) collagen I and (D) collagen III mRNA levels. Data are expressed as mean ± SEM (n=6-8).

Fig. 4

Effect of kallikrein and kinin on (A) cardiac NO levels, (B) NADPH oxidase activity, (C) p22^phox mRNA levels, (D) MDA in the non-infarct myocardium and (E) superoxide formation. Data are expressed as mean ± SEM (n=6-7).

Fig. 5

Effect of kallikrein and kinin on the expression of pro-fibrotic molecules. (A) Representative Western blots of myocardial TGF-β1, PAI-1 and Smad2 levels. Real-time PCR analysis of (B) TGF-β1 and (C) PAI-1 mRNA levels. Data are expressed as mean ± SEM (n=6). (D) Effect of AngII and kinin on TGF-β1 levels in adult rat cardiac fibroblasts. Data are expressed as mean ± SEM (n=3). The data are representative of 3 independent experiments.