The Protective Effect Of Kallikrein Kinin System After Myocardial Infarction

Myocardial ischemia-induced inflammation andcardiomyocyte death lead to deleterious ventricular remodeling and heartfailure. We investigated the role and mechanisms of tissuekallikrein/kinin in protection against oxidative cardiac damage in ratsafter myocardial infarction (MI). In the first study, rats received purifiedtissue kallikrein immediately after permanent coronary artery ligation,with or without icatibant (a kinin B2 receptor antagonist) for 1 and 7 days.One day after MI, kallikrein delivery significantly reduced myocardialinfarct size and inhibited cardiomyocyte apoptosis in association withincreased nitric oxide (NO) levels, Akt and glycogen synthase kinase-3β(GSK-3β) phosphorylation and decreased caspase-3 activation. Kallikreininfusion for 7 days increased cardiac contractility reduced left ventricleend diastolic pressure and normalized left ventricular thickness, as well asdecreased monocyte/macrophage infiltration in the infarct region of theheart. Kallikrein treatment reduced oxidative stress as evidenced bydecreased NADH/NADPH oxidase expression and activity, superoxideformation and malondialdehyde levels in conjunction with reducedmonocyte chemoattractant protein-1 and vascular cell adhesion molecule-1 expression. Kallikrein also reduced MI-induced phosphorylation ofp38MAPK, JNK and Iκ-Bα, as well as NF-κB nuclear translocation andactivation. The effects of kallikrein on cardiac dysfunction, inflammationand signaling events were all abolished by icatibant. These resultsindicate that tissue kallikrein through kinin B2 receptor activation elicitscardioprotection by inhibiting apoptosis and inflammation andminimizing myocardial infarct size through increased NO formation and Akt-GSK-3βsignaling, and suppression of oxidative stress, MAPKsignaling pathways and NF-κB activation.In the second study, we investigated the effects of kallikrein andkinin infusion on ventricular remodeling in rats after chronic MI. At 1week after coronary artery ligation, rats were infused with tissuekallikrein or kinin via osmotic minipumps for 4 weeks. At 5 weeks afterMI, kallikrein and kinin infusion significantly improved cardiaccontractility and reduced diastolic dysfunction with no apparent effect oninfarct size or mean arterial pressure. Kallikrein and kinin significantlyincreased capillary and arteriole density, and immunostaining for vascularendothelial growth factor (VEGF) in the peri-infarct area. Kallikrein andkinin infusion also reduced heart weight/body weight ratio, leftventricular axis length, cardiomyocyte size, and ANP and BNPexpression in the non-infarcted region. Moreover, kallkrein and kinininfusion inhibited interstitial collagen deposition, collagen fractionvolume, and expression of collagen typesⅠandⅢin association withreduced TGF-β1 and PAI-1 expression and Smad2 phosphorylation. Theeffects of kallikrein and kinin on cardiac remodeling were associated withincreased cardiac nitric oxide (NO) levels and reduced NADPH oxidaseexpression and activity, superoxide formation and malondialdehydelevels. Moreover, kinin inhibited AngⅡ-induced TGF-β1 production incultured cardiac fibroblasts. These results indicate that a stable supply ofkallikrein or kinin at sub-depressor doses can restore impaired cardiacfunction post-infarction heart failure by inhibiting hypertrophy andfibrosis and promoting neovascularization through increased NOformation and suppression of oxidative stress and TGF-β1 and PAI-1 expression. In the third study, we investigate the role and signaling mechanismsof tissue kallikrein in arterigenesis and angiogenesis and cardiacremodeling in rats after MI. Adenovirus carrying human tissue kallikreinwith or without dorminant-negative Akt (Ad.DN-Akt), or catalyticallyactive GSK-3 S9A (Ad.GSK-3β) were locally injected into themyocardium at 1 hour after permanent coronary artery ligation.Expression of recombinant human tissue kallikrein in rats after genedelivery was identified by immunohistochemistry, ELISA and RT-PCR.At 10 days after MI, kallikrein gene delivery significantly improvedcardiac contractility, reduces diastolic dysfunction and infarct size, andkallikrein's effects were blocked by Ad.DN-Akt and Ad.GSK-3 S9A.Moreover, kallikrein increases capillary density and arteriole number asevidenced by increasedα-smooth muscle actin and CD-31immunostaining, and quantitative analysis at the infarct area of the heart.Kallikrein replacement reduced GSK-3βactivity and VEGF and VEGFreceptor expression, and Ad.DN-Akt or Ad.GSK-3βS9A abolished theseeffects. Furthermore, purified kallikrein or kinin dose-dependentlyincreases the proliferation of cultured human coronary endothelial cells.Tissue kallikrein also stimulates capillary tube formation and promotesmigration of cultured endothelial cells, and these effects were blocked byicatibant, tyrosine kinase inhibitor, tissue kallikrein antibody, VEGFantibody, Ad.DN-Akt and AdGSK-3βS9A. Furthermore, tissuekallikrein increases GSK-3βactivity, leading to increased VEGF andVEGF receptor expression in cultured endothelial cells. These findingsindicate that tissue kallikrein/kinin limits ventricular remodeling byenhancing angiogenesis and arteriogenesis through Akt-GSK-3β-VEGFsignaling pathway. Taken together, these results indicate that tissuekallikrein through kinin B2 receptor protects ischemic myocardium from heart failure by inhibiting apoptosis, inflammation and fibrosis, andpromoting arteriogenesis and angiogenesis.