Mechanism of miR-378a-3p enriched in M2 macrophage-derived extracellular vesicles in cardiomyocyte pyroptosis after MI

The development of novel therapies targeting cardiomyocyte pyroptosis is needed for myocardial infarction (MI). The current study sought to analyze the role and mechanism of M2 macrophage-derived extracellular vesicles (M2-EVs) in cardiomyocyte pyroptosis after MI. M2 macrophages were induced, and M2-EVs were separated and characterized. A mouse model of MI was successfully established, followed by an assessment of myocardial injury and cardiomyocyte pyroptosis. An in vitro cell model was established, followed by a comprehensive evaluation of cell viability and pyroptosis. The binding relationships of miR-378a-3p and ELAVL1 [human antigen R (HuR)], HuR, and NLR family pyrin domain containing 3 (NLRP3) were analyzed. A functional rescue experiment was designed to validate the role of HuR. After M2-EV treatment, the cardiac functions of mice with MI were restored, the myocardial injury was attenuated and cardiomyocyte pyroptosis was reduced. In vitro, M2-EVs suppressed hypoxic cell injury and pyroptosis. Mechanistically, M2-EVs delivered miR-378a-3p into cardiomyocytes to upregulate miR-378a-3p expression and inhibit ELAVL1 (HuR) expression and transport of HuR to the cytoplasm, thus destabilizing NLRP3 and inhibiting activation of the NLRP3/Caspase-1/GSDMD pathways. Overexpression of HuR inhibited the protective effect of M2-EVs in cardiomyocytes. Overall, our findings showed that M2-EV-enveloped miR-378a-3p inhibited HuR expression and HuR translocation to the cytoplasm to destabilize NLRP3 and block activation of the NLRP3/Caspase-1/GSDMD pathways, thereby attenuating cardiomyocyte pyroptosis.