Abstract 552: Bradykinin Receptor B1/ Matrix Metalloprotease 3 Pathway is a Novel Target in Preventing Cardiac Ischemia-reperfusion Injury

Abstract

Introduction: Impaired endothelial function leads to the progression of heart failure after Ischemia-reperfusion (IR). Kinin activation of bradykinin receptor 1 (B1R), a G protein-coupled receptor that has been found to induce capillary leakage, may serve as a critical mediator in cardiac microvascular barrier dysfunction. However, the underlying mechanisms are not clear. We found that B1R inhibition abolished IR-induced endothelial matrix metalloprotease (MMP3) expression and improved endothelial barrier formation. Thus, we hypothesized that B1R antagonist protects against cardiac IR injury through an MMP3 pathway. Methods and Results: MMP3-/- mice and their littermate controls (WT) were subjected to either cardiac IR or sham control. The baseline characteristics of these mice showed minimal phenotypes. Cardiac function was determined at 3, 7 and 24 days post-IR by echocardiography. The MMP3-/- mice displayed improved cardiac function compared to the control mice, as determined by fractional shortening (26% ± 1.1 MMP3-/- vs. 21% ± 0.9 WT, p<0.05, n=5) and ejection fraction (48% ± 1.9 MMP3-/- vs. 42% ± 2.8.1 WT, p<0.05, n=5), and treating with B1R antagonist (300 μg/Kg) significantly reduced serum MMP3 levels (p<0.01). Compared to the control mice, MMP3-/- mice had significantly less infarction/area at risk 24 hours post-IR demonstrated through TTC staining. In vitro studies revealed that cellular hypoxia-reoxygenation (HR) injury significantly increased both B1R and MMP3 expression levels in primary isolated cardiac mice microvascular endothelial cells (mCMVEC). MMP3 levels were measured via ELISA. Moreover, B1R agonist treatment (1uM) increased MMP3 levels, while the use of the antagonist attenuated the increase of MMP3 in response to HR. Finally, the use of B1R antagonist improved MMP3 induced endothelial barrier dysfunction, which was measured by the electric cell-substrate impedance sensing (ECIS) system. Taken together, the results demonstrated that B1R antagonist abolished IR induced MMP3 induction and that the deletion of MMP3 is protective of cardiac function upon IR injury. Conclusions: MMP3 is a critical regulator of cardiac microvascular barrier function, and B1R/MMP3 could potentially serve as a novel therapeutic target for heart failure in response to IR injury.