Exosomal miR-409-3p secreted from activated mast cells promotes microglial migration, activation and neuroinflammation by targeting Nr4a2 to activate the NF-κB pathway

Abstract

Objective Neuroinflammation plays a critical role in central nervous system diseases. Exosomal miRNAs released from various cells are implicated in cell-to-cell communication. Prior studies have placed substantial emphasis on the role of cytokines in mast cell-microglia interactions during neuroinflammation. However, it has never been clearly determined whether exosomal miRNAs participate in the interaction between mast cells and microglia and thus mediate neuroinflammation. Methods The characteristics of exosomes isolated from cell culture supernatants were confirmed by transmission electron microscopy (TEM), nanoparticle-tracking analysis (NTA) and Western blot. The transfer of PKH67-labelled exosomes and Cy3-labelled miR-409-3p was observed by fluorescence microscopy. Migration and activation of murine BV-2 microglial cells were evaluated through Transwell assays and immunofluorescence staining for Iba1 and CD68. CD86, IL-1β, IL-6 and TNF-α were assessed via qRT-PCR and ELISA. MiR-409-3p was detected by qRT-PCR. Nr4a2 and NF-κB levels were measured by western blot. Regulatory effects were identified by luciferase reporter assays. Results Lipopolysaccharide (LPS)-stimulated murine P815 mast cells secreted exosomes that were efficiently taken up by murine BV-2 cells, which promoted murine BV-2 cell migration and activation. LPS-P815 exosomes increased the CD86, IL-1β, IL-6 and TNF-α levels in murine BV-2 microglia. Furthermore, activated mast cells delivered exosomal miR-409-3p to murine BV-2 microglia. Upregulated miR-409-3p promoted murine BV-2 microglial migration, activation and neuroinflammation by targeting Nr4a2 to activate the NF-κB pathway. Conclusion Exosomal miR-409-3p secreted from activated mast cells promotes microglial migration, activation and neuroinflammation by targeting Nr4a2 to activate the NF-κB pathway, which provides evidence that not only cytokines but also exosomal miRNAs participate in neuroinflammation. In the future, targeting exosomal miRNAs may provide new insights into neuroinflammation.

Construction of Exosomes that Overexpress CD47 and Evaluation of Their Immune Escape

“…Previous studies found that CD47, a transmembrane glycoprotein, is present in a variety of cells, that its expression is significantly increased in tumor cells ( Hu et al, 2021 ), and there is also some increased expression in normal ADMSCs. Other studies showed that the EXOs secreted by some tumor cells have roles in the onset and development of tumors ( Whiteside, 2016 ).…”

“…A recent study reported that the CD47 level in EXOs from the plasma of breast cancer patients was higher than in healthy controls ( Hu et al, 2021 ). Another study reported that the retention of EXOs derived from fibroblasts of mice with CD47 knockout was reduced in vivo ( Kamerkar et al, 2017 ).…”

Research Progress in the Application of Exosomes in Immunotherapy

“…It is evident that MC exosomes can transmit signals in endosomes by delivering bioactive surface ligands to intracellular compartments. In addition, the exosomal miR-409-3p secreted by activated MCs promotes microglia relocation and activation and neuroinflammation by targeting Nr4a2 to stimulate the NF-κB pathway ( 41 ), suggesting that exosomes and cytokines are involved in the interaction between MCs and microglia to cause neuroinflammation.…”

Extracellular Vesicles as Emerging Players in Intercellular Communication: Relevance in Mast Cell-Mediated Pathophysiology

“…Several studies have reported the central and peripheral MC critical roles in neuroinflammation by interacting with microglial cells to increase their migration and release of proinflammatory cytokines. An example of this interaction was found to occur via EVs released from LPS-activated MCs, which could transfer miR-409-3p to microglia, causing the downregulation of nuclear receptor subfamily 4 group A member (2Nr4a2) expression and activation of the NF-κB pathway, thereby promoting microglial migration, activation, and neuroinflammation [39].…”