Endothelial ADRB3 protects the heart from myocardial infarction by suppressing endothelial-to-mesenchymal transition

AIMS: β3 adrenergic receptor (ADRB3) has recently emerged as an important regulator of cardiovascular homeostasis. However, the role of endothelial ADRB3 in cardiac repair after myocardial infarction (MI) remains unclear. As endothelial dysfunction critically drives post-MI remodeling, we hypothesized that ADRB3 preserves endothelial integrity and protects the heart from ischemic injury. METHODS AND RESULTS: Endothelial cell-specific ADRB3 knockout mice and adeno-associated virus serotype 9 (AAV9)-mediated endothelial ADRB3 overexpression mice were subjected to MI. Single-cell RNA sequencing (scRNA-seq) was performed to characterize cellular heterogeneity and endothelial phenotypic changes. scRNA-seq revealed enhanced EndoMT and activated TGFβ signaling in ADRB3-deficient hearts, accompanied by accelerated fibrotic remodeling and exacerbated ischemic injury. In contrast, endothelial ADRB3 overexpression suppressed EndoMT, reduced fibrosis, and improved cardiac function following MI. In vitro, ADRB3 knockdown induced EndoMT and endothelial dysfunction, whereas ADRB3 overexpression attenuated hypoxia-induced mesenchymal activation. Mechanistically, proximity ligation assay, co-immunoprecipitation, and mass spectrometry identified TGFβ receptor 2 (TGFβR2) as an endogenous binding partner of ADRB3. ADRB3 interaction with TGFβR2 prevented SMAD2 recruitment to TGFβR1 and inhibited downstream SMAD2 phosphorylation. Moreover, endothelial-specific TGFβR2 knockdown using AAV9 mitigated cardiac injury in ADRB3-deficient mice following MI. CONCLUSION: These findings demonstrate that endothelial ADRB3 protects against ischemic heart injury by limiting TGFβR2-SMAD2-dependent EndoMT, highlighting its role as a critical endothelial regulator and a potential therapeutic target for myocardial repair.