BMAL1-HIF2A heterodimer modulates circadian variations of myocardial injury.

Abstract

Acute myocardial infarction is a leading cause of morbidity and mortality worldwide¹. Clinical studies have shown that the severity of cardiac injury after myocardial infarction exhibits a circadian pattern, with larger infarcts and poorer outcomes in patients experiencing morning-onset events^2-7. However, the molecular mechanisms underlying these diurnal variations remain unclear. Here we show that the core circadian transcription factor BMAL1^7-11 regulates circadian-dependent myocardial injury by forming a transcriptionally active heterodimer with a non-canonical partner-hypoxia-inducible factor 2 alpha (HIF2A)^12-16-in a diurnal manner. To substantiate this finding, we determined the cryo-EM structure of the BMAL1-HIF2A-DNA complex, revealing structural rearrangements within BMAL1 that enable cross-talk between circadian rhythms and hypoxia signalling. BMAL1 modulates the circadian hypoxic response by enhancing the transcriptional activity of HIF2A and stabilizing the HIF2A protein. We further identified amphiregulin (AREG)^16,17 as a rhythmic target of the BMAL1-HIF2A complex, critical for regulating daytime variations of myocardial injury. Pharmacologically targeting the BMAL1-HIF2A-AREG pathway provides cardioprotection, with maximum efficacy when aligned with the pathway's circadian phase. These findings identify a mechanism governing circadian variations of myocardial injury and highlight the therapeutic potential of clock-based pharmacological interventions for treating ischaemic heart disease.