Abstract 13538: Impact of Autophagy Modulation on Apoptosis in Chemotherapy-Induced Cardiac Toxicity

Abstract

Background: Cardiotoxicity due to chemotherapy remains a challenge. Cardioprotective interventions have not slowed the progression to heart failure. Cardiomyocyte (CM) death can be attributed to autophagy impairment during chemotherapy-induced toxicity. We hypothesize that autophagy activation can be a viable cardioprotective strategy. Methods: H9C2 rat cardiac myoblasts and cardiac slices generated from euthanized dog hearts were treated with 5-50μM doxorubicin (Dox) +/- autophagy activators for 24 hours. Annexin V (Anx) and TUNEL detection of apoptosis, MTT assay of cell viability, and western blots were performed. C57Bl6 mice were challenged with either single Dox (15 mg/kg i.p.), or repeated doses (4 mg/kg i.p., weekly, 5x) +/- 24-hour pre-starvation. Cardiac function was assessed by echo. Results: Dox significantly increased H9C2 apoptosis, rescued by rapamycin (Fig. A). Autophagy induction by phosphatidylinositol-3-phosphate (Pi3P) restored autophagic flux via downregulating autophagy-inhibitory Rubicon (Fig. B). Autophagy stimulation by Pi3P, statins, or starvation significantly reduced H9C2 apoptosis and improved viability (Fig. C-E), but not in human cancer cells. Single high Dox dose in mice markedly increased CM apoptosis by 24 hours, attenuated by pre-starvation without perturbing Dox retention in the heart (Fig. F). In chronically treated Dox mice, starvation before each Dox dose improved cardiac function and survival (Fig. G-H). Viable dog cardiac slices generated (Fig. I-J) exhibited preserved autophagic flux (Fig. K). Dox (5μM, 30-min exposure) induces autophagy blockade at 24 hours leading to apoptosis (Fig. L). Autophagy restoration by rapamycin reduced apoptosis in cardiac slices but not primary canine cancer cells (Fig. M). Conclusions: Autophagy restoration via modulating Rubicon exerts anti-apoptotic effects in murine and canine CMs, but not in cancer cells, potentially translatable to impact cardio-oncology treatment.