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Background: Reperfusion may cause injuries to the myocardium in ischemia situation. Emerging studies suggest that exosomes may serve as key mediators in myocardial ischemia/reperfusion (MI/R) injury.

Objective: The study was conducted to figure out the mechanism of M2 macrophage-derived exosomes (M2-exos) in MI/R injury with the involvement of microRNA-148a (miR-148a).

Methods And Results: M2 macrophages were prepared and M2-exos were collected and identified. Neonatal rat cardiomyocytes (NCMs) were extracted for in vitro hypoxia/reoxygenation (H/R) model establishment, while rat cardiac tissues were separated for in vivo MI/R model establishment. Differentially expressed miRNAs in NCMs and H/R-treated NCMs after M2-exos treatment were evaluated using microarray analysis. The target relation between miR-148a and thioredoxin-interacting protein (TXNIP) was identified using dual luciferase reporter gene assay. Gain- and loss- of function studies of miR-148a and TXNIP were performed to figure out their roles in MI/R injury. Meanwhile, the activation of the TLR4/NF-κB/NLRP3 inflammasome signaling pathway and pyroptosis of NCMs were evaluated. M2 macrophages carried miR-148a into NCMs. Over-expression of miR-148a enhanced viability of H/R-treated NCMs, reduced infarct size in vivo, and alleviated dysregulation of cardiac enzymes and Ca overload in both models. miR-148a directly bound to the 3'-untranslated region (3'UTR) of TXNIP. Over-expressed TXNIP triggered the TLR4/NF-κB/NLRP3 signaling pathway activation and induced cell pyroptosis of NCMs, and the results were reproduced in in vivo studies.

Conclusion: This study demonstrated that M2-exos could carry miR-148a to mitigate MI/R injury via down-regulating TXNIP and inactivating the TLR4/NF-κB/NLRP3 inflammasome signaling pathway. This study may offer new insights into MI/R injury treatment.