MicroRNA Cargo of Extracellular Vesicles from Alcohol-exposed Monocytes Signals Naive Monocytes to Differentiate into M2 Macrophages

Abstract

Membrane-coated extracellular vesicles (EVs) released by cells can serve as vehicles for delivery of biological materials and signals.Recently, we demonstrated that alcohol-treated hepatocytes cross-talk with immune cells via exosomes containing microRNA (miRNAs). Here, we hypothesized that alcohol-exposed monocytes can communicate with naive monocytes via EVs. We observed increased numbers of EVs, mostly exosomes, secreted by primary human monocytes and THP-1 monocytic cells in the presence of alcohol in a concentration-and time-dependent manner. EVs derived from alcohol-treated monocytes stimulated naive monocytes to polarize into M2 macrophages as indicated by increased surface expression of CD68 (macrophage marker), M2 markers (CD206 (mannose receptor) and CD163 (scavenger receptor)), secretion of IL-10, and TGF␤ and increased phagocytic activity. miRNA profiling of the EVs derived from alcohol-treated THP-1 monocytes revealed high expression of the M2-polarizing miRNA, miR-27a. Treatment of naive monocytes with control EVs overexpressing miR-27a reproduced the effect of EVs from alcohol-treated monocytes on naive monocytes and induced M2 polarization, suggesting that the effect of alcohol EVs was mediated by miR-27a. We found that miR27a modulated the process of phagocytosis by targeting CD206 expression on monocytes. Importantly, analysis of circulating EVs from plasma of alcoholic hepatitis patients revealed increased numbers of EVs that contained high levels of miR-27a as compared with healthy controls. Our results demonstrate the following: first, alcohol increases EV production in monocytes; second, alcoholexposed monocytes communicate with naive monocytes via EVs; and third, miR-27a cargo in monocyte-derived EVs can program naive monocytes to polarize into M2 macrophages.

Mitochondrial DNA–enriched microparticles promote acute-on-chronic alcoholic neutrophilia and hepatotoxicity

“…Blockage of the CXCL1 receptor CXCR1/2 ameliorated alcoholic steatohepatitis in mice (14). In addition to chemokines, extracellular vesicles (EVs) are new players in cellto-cell communication and play an important role in promoting inflammation and neutrophil infiltration in a variety of diseases (15,16), including liver diseases (17)(18)(19)(20)(21)(22)(23)(24)(25). EVs are nanometer-sized, membrane-bound extracellular milieu vesicles derived from cells (17).…”

“…The functions of EVs are mediated by delivering their contents from one cell to another. For example, stressed hepatocytes can activate macrophages via the release of EVs that contain lipids, proteins, chemokines, and nucleic acids (e.g., mitochondrial DNA [mtDNA]) (17)(18)(19)(20)(21)(22)(23)(24)(25). However, whether EVs also contribute to the elevation of circulating and hepatic neutrophils induced by acute-on-chronic alcoholic liver injury in human and mice remains unknown.…”

Therapeutic opportunities for alcoholic steatohepatitis and nonalcoholic steatohepatitis: exploiting similarities and differences in pathogenesis

“…Sphingolipid cargoes, specifically C16:0 ceramide and sphingosine 1-phosphate (S1P), on EVs are implicated in the recruitment of macrophages to the steatotic liver in NASH (103). Macrophages themselves communicate through EVs, and EV-trafficked miRs such as miR-27a enable communication between alcohol-exposed monocytes and naive monocytes, which further promotes sterile inflammation (104). Thus, inhibition of EV release and interruption of signaling pathways activated by EV cargoes represent attractive therapeutic targets.…”

Exosome: An Emerging Participant in the Development of Liver Disease

“…In various liver injury models induced by alcohol, drug, inflammation, or diet, the changes in the protein contents as well as mRNA levels/types in the exosomes have been proven to be satisfactory indicators for evaluating inflammation and promising biomarkers for detecting liver injury (46)(47)(48)(49)(50)(51)(52)(53).…”

“…In the AH patients, the remarkably increased number of exosomes in their circulation system is comprised mostly of exosomes derived from alcohol-exposed monocytes, which contain a significantly elevated level of miR27a. The exosomal miR-27a can stimulate naïve monocytes to differentiate into M2 macrophages, increase the secretion of IL-10, and transforming growth factor β, thus enhancing the phagocytic capacity (49). Recently, Vikas et al…”