Abstract 17570: Therapeutic Impact of Autophagy-inducing Peptide on Pressure Overload-induced Heart Failure
Tat-Beclin1 (TB1), which binds human immunodeficiency virus-1 Nef, is a potent inducer of autophagy. We investigated the therapeutic potential of TB1 in the heart during pressure overload (PO). At baseline, treatment of cardiomyocytes (CMs) with 25 μM TB1 significantly increased both GFP/RFP double positive (Yellow) LC3 puncta (8.3±1.1 vs 1.4±0.2, P<0.05) and RFP LC3 puncta (4.2±1.1 vs 1.5±0.3, p<0.05) compared to treatment with Tat-scrambled (TS). After treatment for 2 weeks with TB1 or TS at 20 mg/kg daily, GFP-LC3 puncta were significantly increased in mouse hearts with TB1 compared to those with TS, with (31.6±5.0 and 20.3±5.9, p<0.05) or without chloroquine (21.7±4.3 and 8.1±2.2, p<0.05), indicating that TB1 stimulates autophagy in the heart. We investigated whether lysosomal clearance of mitochondria, reflecting mitochondrial autophagy, is stimulated by TB1, using Mito-Keima. Puncta with a high ratio of excitation at 560/440 nm co-localized with Alexa 488 Dextran, reflecting lysosomal localization of Mito-Keima, were significantly increased after TB1 compared to after TS treatment (5.68±1.18 vs 1.37±0.76, p<0.05). In order to evaluate the effect of TB1 upon the heart during PO, C57BL/6J mice were subjected to i.p. injections of TB1 or TS for 2 weeks, and the mice were sacrificed after 1 week. Ejection fraction (EF) was maintained (78.3±1.2 vs 63.3±3.0, p<0.05), lung weight/tibial length was lower (7.9±0.3 vs 8.2±0.2, p<0.05), the pressure gradient was greater (89.3±4.4 vs 71.8±4.3, p<0.05), and the end diastolic pressure (EDP) was lower (8.2±0.9 vs 11.5±1.5, p<0.05) in TB1- than in TS-treated mice. Mitochondrial ATP production was better preserved in TB1- than in TS-treated mice (1.72±0.16 vs 1.00±0.16, p<0.05). Mitochondrial DNA content (0.54±0.05 vs 1.00±0.11, p<0.05) and the Cox1 level in mitochondria (0.47±0.11 vs 1.00±0.18, p<0.05) were lower in TB1- than in TS-treated mice, consistent with increased degradation of mitochondria. In EM analyses of the mouse heart, autophagosomes containing mitochondria were observed after TB1 treatment, but not TS treatment. These results suggest that TB1 induces general autophagy and mitophagy in the heart and acts protectively against cardiac dysfunction after PO.
Author Disclosures: A. Shirakabe: None. Y. Ikeda: None. P. Zai: None. T. Saito: None. J. Sadoshima: None.
- © 2015 by American Heart Association, Inc.