Timed use of digoxin prevents heart ischemia–reperfusion injury through a REV-ERBα–UPS signaling pathway

Myocardial ischemia–reperfusion injury (MIRI) induces life-threatening damages to the cardiac tissue, and pharmacological means to achieve cardioprotection are sorely needed. MIRI severity varies along the day–night cycle and is molecularly linked to components of the cellular clock, including the nuclear receptor REV-ERBα, a transcriptional repressor. Here we show that digoxin administration in mice is cardioprotective when timed to trigger REV-ERBα protein degradation. In cardiomyocytes, digoxin increases REV-ERBα ubiquitinylation and proteasomal degradation, which depend on REV-ERBα’s ability to bind its natural ligand, heme. Inhibition of the membrane-bound Src tyrosine-kinase partially alleviated digoxin-induced REV-ERBα degradation. In untreated cardiomyocytes, REV-ERBα proteolysis is controlled by several E3 ubiquitin ligases and the proteasome subunit PSMB5. Among these, only SIAH2 and PSMB5 contributed to digoxin-induced degradation of REV-ERBα. Thus, controlling REV-ERBα proteostasis through the ubiquitin–proteasome system is an appealing cardioprotective strategy. Our data support the timed use of clinically approved cardiotonic steroids in prophylactic cardioprotection.