Small-molecule mediated MuRF1 inhibition protects from doxorubicin-induced cardiac atrophy and contractile...

Cancer chemotherapy induces cell stress in rapidly dividing cancer cells to trigger their growth arrest and apoptosis. However, adverse effects related to cardiotoxicity underpinned by a limited regenerative potential of the heart limits clinical application: In particular, chemotherapy with doxorubicin (DOXO) causes acute heart injury that can transition to persisting cardiomyopathy (DOXO-CM). Here, we tested if MuRF1 inhibition ("MuRFi") was able to attenuate DOXO-CM. To mimic DOXO chemotherapy, we treated mice over four weeks with five DOXO injections, resulting in a cumulative dosage of 25 mg/kg. At day 28, mice had lower body and heart weights, reduced cardiac cross-sectional myofibrillar areas (CSAs), and disturbed functional ejection fractions (EFs) and fractional shortenings (FS) as indicated by echocardiography (ECHO). In contrast, mice with a 1 g/kg Myomed#205 spiked diet, a previously described experimental MuRFi therapy, showed lower DOXO-CM at day 28, and also reduced acute DOXO cardiac injury at day 7 (single DOXO dose; 15 mg/kg). Underlying molecular signatures using Western blot (WB) assays showed at day 28 reduced phospho-AKT (AKTp) and phospo-4EBP1 (4 EBP1p) levels following DOXO that were normalized following MuRFi treatment. Taken together, our data suggest that MuRFi treatment is suitable to attenuate DOXO-CM by preserving AKTp and 4 EBP1p levels in DOXO stressed cardiomyocytes, thereby supporting de novo protein translation and cardiomyocyte survival under translational arrest stress.