Abstract 524: Activated Fms-like Tyrosine Kinase 3 Receptor Prevents Ventricular Remodeling Induced by Ang Ii Through the Attenuation of Autophagy

Abstract

Aim: FMS-like tyrosine kinase 3 (Flt3) is a receptor tyrosine kinase. This study was to determine whether activation Flt3 could regulate autophagy ameliorate AngII-induced heart cardiac remodeling and to elucidate the mechanisms of action. Methods: In vivo cardiac remodeling was induced in male C57BL/6 mice by implanting subcutaneously osmotic minipumps releasing Angiotensin II (Ang II) for 28 days (1100ng/kg/min). Flt3 ligand (FL) was administered intraperitoneally (5μg/mouse/2days). Heart hypertrophy, fibrosis and function were evaluated based on echocardiography, histological and biochemical measurements. In vitro, hypertrophy was induced by Ang II on adenovirus vector-mediated overexpression Flt3 receptor in H9c2 cells, and NRCMs. Crystal violet staining, flow cytometry and TUNEL were used for in vitro experiments. The levels of signaling proteins were measured using western blotting, while the expression of the relevant genes was analyzed using real-time qRT-PCR. Results: Echocardiography demonstrated that Ang II induced marked damaged heart function, while cardiac Flt3 receptor activation significantly decrease left ventricular internal dimension at end-diastole (LVIDd), left ventricular posterior wall thickness at end-diastole (LVPWd), and increase ejection fraction (EF%) and fractional shortening (FS%). FL-treated mice showed a significant attenuation of cardiac hypertrophy, ratios of heart weight/body weight (HW/BW) and heart weight/tibia length (HW/TL), as well as cardiac fibrosis and apoptosis. Additionally, the autophagic levels in cardiomyocytes of FL-treated mice were distinctly decreased as evidenced by expression of LC3 in immunohistochemical staining and western blotting. In H9c2 cells with adenovirus vector-mediated overexpression of Flt3 and neonatal rat cardiomyocytes, FL treatment significantly decrease the cell size, apoptosis and autophagy induced by Ang II. Additionally, using rapamycin or metformin, respectively canceled FL protective effects. Conclusion: Flt3 activation suppresses Ang II-induced cardiac hypertrophy and apoptosis via AMPK /mTOR/ FOXO3a autophagy signaling pathway. These results provide evidence supporting Flt3 as a novel therapeutic target in cardiac remodeling.