Abstract Body (Do not enter title and authors here): Carvedilol (CAR) is an FDA-approved adrenergic blocker commonly given to cardiovascular disease patients. Interestingly, CAR also shows anti-cancer potential in reducing cancer-specific mortality in breast cancer patients. To advance CAR usage in cardio-oncology, we hypothesize that elucidating the molecular mechanism of the energy sensing and homeostasis pathways underlying CAR’s cardioprotective capabilities can enhance its clinical translation.

Canine cardiac slices were generated from 3 euthanized pet dogs free of cardiovascular disease. CAR pretreatment (1μM, 4 hrs) with or without a 24-hr exposure to 5μM of cardiotoxic doxorubicin (DOX) was performed. Murine slices from 5 C57Bl6 mice with the same treatments as above was also performed. Direct tissue imaging on IVIS Spectrum was carried out to assess apoptosis by Annexin V staining, autophagy with autophagy detecting nanoparticle (ADN) developed in-house, and DOX retention in tissue by the inherent DOX fluorescence. Tissue was analyzed by histological staining of apoptosis and Western blot of autophagy and energy sensing pathways. Energetics quantified by Seahorse assay was performed in isolated mitochondria from cardiac slices in rat cardiomyoblasts (H9C2 cells) and human iPSC-induced cardiomyocytes (iCells).

In both canine and murine cardiac slices, autophagy was significantly reduced (p<0.05) by DOX while apoptosis was significantly increased (p<0.05), both of which were reversed by CAR. CAR did not change DOX fluorescence in tissue. Western blot of autophagy biomarkers LC3, p62 and Beclin-1 confirmed that autophagy impaired by DOX was restored by CAR. The beneficial autophagy restoration by CAR was modulated by a significantly increased phosphorylation of AMP kinase (AMPK), a key energy sensing pathway that activates autophagy via significantly reducing mTOR (p<0.0001). In mitochondria isolated from cardiac slices, basal respiration and ATP production that were significantly impaired by DOX were rescued (p<0.0001) by CAR. Similar rescue of basal respiration and ATP production by CAR was seen in murine and human cardiomyocytes, suggesting that CAR exerts a direct protective effect on the at-risk cardiomyocytes during DOX stress.

We demonstrated for the first time in human, canine, and murine that CAR targets the AMPK pathway to activate autophagy, reduce cardiomyocyte apoptosis, and restore mitochondrial energetics, thus with immense translational potential in cardioprotection.