Macrophage-derived extracellular vesicles regulate concanavalin A-induced hepatitis by suppressing macrophage cytokine production.

Acute liver failure is a clinical syndrome of severe hepatic dysfunction. Immune cells play an important role in the failure. In recent years, the immunoregulatory function of extracellular vesicles (EVs) has been reported; therefore, it is inferred that EVs have some role in an immune mediated liver injury. In this study, we investigated the immunoregulatory function of EVs in a concanavalin A (Con A)-induced liver injury. The mouse model was prepared by a single intravenous administration of 15 mg/kg Con A, in which there was a significant increase in serum EVs number. In in vitro study, the secreted EVs number was also significantly increased in Con A-treated RAW264.7, a mouse macrophage cell line, but not Hepa1-6, a mouse hepatoma cell line. In in vitro EVs treatment study, the EVs from Con A-treated mice serum and Con A-treated RAW264.7 suppressed the inflammatory cytokines production in Con A-stimulated RAW264.7. miRNA sequencing analysis showed that mmu-miR-122-5p and mmu-miR-148a-3p were commonly increased in these EVs and the EVs-treated cells. The enriched pathways in the miRNAs predicted target genes included the inflammatory response pathways. mRNA levels of the target genes in the pathways (mitogen-activated protein kinase, Phosphoinositide 3-kinase/Akt and Rho/Rho associated coiled-coil containing protein kinase pathways) were decreased in the EVs-treated cells. In in vivo RNA interference study, knock down of liver RAB27A, an EVs secretion regulator, significantly exacerbated the Con A-induced liver injury. These data suggest that macrophage-derived EVs play an important role in a Con A-induced liver injury through the immunoregulation. miRNA profiles in RAW264.7 cells and extracellular vesicles from mouse serum or RAW264.7 culture supernatant were analyzed with MiSeq system (Illumina).