Abstract 10979: Impairment of Autophagic Flux in Doxorubicin Cardiotoxicity and Its Restoration and Improvement of Cardiac Function by Prior Starvation
Active autophagy has recently been reported in doxorubicin-induced cardiotoxicity, of which pathophysiological role we here investigated. Acute cardiotoxicity was induced in green fluorescent protein-microtubule-associated protein 1 light chain 3 (GFP-LC3) transgenic mice by injection of 10 mg/kg doxorubicin twice per week. A starvation group was deprived of food for 48 h before each injection to induce autophagy in advance. Doxorubicin treatment caused left ventricular dilatation and dysfunction within 6 days (the left ventricular diameter [LVDd] = 3.94±0.25 mm and ejection fraction [EF] = 46.7±4.4%), which were significantly mitigated by the preceding starvation (LEDd = 3.41±0.31 mm and EF = 63.9±6.4%, both p < 0.05 compared with the control). Cardiomyocyte autophagy looked to be activated in the doxorubicin group, based on LC3, p62 and cathepsin D expression while it seemed somewhat diminished by starvation prior to doxorubicin treatment. Unexpectedly, however, myocardial ATP levels were reduced in the doxorubicin group, and this reduction was prevented by earlier starvation. Electron microscopy revealed that the autophagic process was indeed initiated in the doxorubicin group as shown by the increased lysosomes, but was not completed; i.e., autophagolysosome formation was rare. Starvation prior to doxorubicin treatment partially restored autophagosome formation toward control levels. An autophagic flux assays at both in vivo and in vitro models confirmed that doxorubicin impairs completion of autophagic process in cardiomyocytes. Both AMP-activated protein kinase (AMPK) and ULK1 (a homolog of yeast Atg1) activities were decreased by doxorubicin, which were restored by prior starvation. In conclusion, myocardial autophagic flux is impaired in acute doxorubicin cardiotoxicity probably through inactivation of AMPK and ULK1, which could be mitigated by prior starvation to improve cardiac function.
- © 2012 by American Heart Association, Inc.