Large Extracellular Vesicles Derived from LPS-preconditioned Cardiomyocytes Alleviate Myocarditis via Mediating Macrophage Polarization and Modulating p38 MAPK Pathway

Myocarditis is an inflammatory injury to the myocardium characterized by disrupted intercellular communication, involving macrophages and cardiomyocytes as key players. However, the interactions between macrophages and cardiomyocytes during myocarditis remain inadequately explored. Emerging evidence indicated that extracellular vesicles (EVs) play a crucial role in intercellular communication. Here, we demonstrated that large EVs derived from lipopolysaccharide (LPS)-preconditioned cardiomyocytes (C-lEVLPS) exhibited anti-inflammatory effects on macrophages and alleviated cardiac inflammation and dysfunction in a mouse model of CVB3-induced myocarditis. Additionally, C-lEVLPS facilitated macrophage polarization toward the M2-like phenotype and inhibits M1 polarization, both in vitro and in vivo. label-free proteomics analysis showed, compared to phosphate-buffered saline (PBS)-preconditioned cardiomyocytes (C-lEVPBS), C-lEVLPS was enriched in the phosphatase 2 scaffold subunit alpha protein (PP2AA), which can recruit other subunits to form the PP2A complex, ultimately leading to the dephosphorylates of p38. This study highlights the effect of C-lEVLPS in myocarditis and uncovers the potential mechanism that modulates macrophage polarization by delivering PP2AA from cardiomyocytes to macrophages and regulating the p38 MAPK pathway. These findings provide a promising therapeutic strategy for myocarditis.