Abstract 15546: Loss of Mitochondrial UCP3-Cytochrome c Oxidase Complexes Underlies Maladaptive Autophagy and Cardiac Failure in Anthracycline Cardiotoxicity

Abstract

Doxorubicin is known for its cardiotoxic effects and inducing cardiac failure. Herein we demonstrate a novel signaling pathway that functionally links activation and preferential mitochondrial targeting of Bnip3 to doxorubicin cardiotoxicity. Perturbations to mitochondria including increased calcium, ROS, loss of αΨm and mPTP opening were observed in cardiac myocytes treated with doxorubicin. This coincided with a decline in maximal respiratory capacity, loss of respiratory chain complexes of uncoupling protein 3 (UCP3) and cytochrome c oxidase complex IV subunit 1, (COX) and cell viability. Impaired mitochondrial function was accompanied by an accumulated increase in autophagosomes and necrosis demonstrated by increase release of LDH, cTnT and loss of nuclear High Mobility Group Protein 1 (HMGB-1) immunoreactivity. Interestingly, pharmacological or genetic inhibition of autophagy with 3-methyl adenine (3-MA), or Atg7 knock-down suppressed necrotic cell death induced by doxorubicin. Conversely, loss of function of Bnip3 or mutations of Bnip3 defective for mitochondrial targeting restored UCP3-COX complexes, mitochondrial respiratory integrity and suppressed necrotic cell death induced by doxorubicin. Finally, mice germ-line deficient for Bnip3 were resistant to the cytotoxic effects of doxorubicin displaying mitochondrial morphology, cardiac function and survival rates comparable to vehicle treated control mice. To our knowledge the findings of the present study provide the first direct evidence that doxorubicin triggers maladaptive autophagy and necrotic cell death of ventricular myocytes by a mechanism mutually dependent and obligatorily linked to Bnip3. Hence, therapeutic interventions to selectively inhibit Bnip3 may prove beneficial in suppressing mitochondrial injury and heart failure in cancer patients undergoing doxorubicin treatment.