Exosome-delivered microRNAs promote IFN-α secretion by human plasmacytoid DCs via TLR7
Valentina Salvi, … , Silvano Sozzani, Daniela Bosisio
Valentina Salvi, … , Silvano Sozzani, Daniela Bosisio
Published May 17, 2018
Citation Information: JCI Insight. 2018;3(10):e98204. https://doi.org/10.1172/jci.insight.98204.
View: Text | PDF
Research Article Immunology

Exosome-delivered microRNAs promote IFN-α secretion by human plasmacytoid DCs via TLR7

Abstract

The excessive production of type I IFNs is a hallmark and a main pathogenic mechanism of many autoimmune diseases, including systemic lupus erythematosus (SLE). In these pathologies, the sustained secretion of type I IFNs is dependent on the improper activation of plasmacytoid DCs (pDCs) by self–nucleic acids. However, the nature and origin of pDC-activating self–nucleic acids is still incompletely characterized. Here, we report that exosomes isolated from the plasma of SLE patients can activate the secretion of IFN-α by human blood pDCs in vitro. This activation requires endosomal acidification and is recapitulated by microRNAs isolated from exosomes, suggesting that exosome-delivered microRNAs act as self-ligands of innate single-stranded endosomal RNA sensors. By using synthetic microRNAs, we identified an IFN induction motif that is responsible for the TLR7-dependent activation, maturation, and survival of human pDCs. These findings identify exosome-delivered microRNAs as potentially novel TLR7 endogenous ligands able to induce pDC activation in SLE patients. Therefore, microRNAs may represent novel pathogenic mediators in the onset of autoimmune reactions and potential therapeutic targets in the treatment of type I IFN–mediated diseases.

Authors

Valentina Salvi, Veronica Gianello, Sara Busatto, Paolo Bergese, Laura Andreoli, Ugo D’Oro, Alessandra Zingoni, Angela Tincani, Silvano Sozzani, Daniela Bosisio

×

Figure 5

Synthetic IIM microRNAs localize within early endosomes and antagonize the TLR7 ligand R848.

Options: View larger image (or click on image) Download as PowerPoint
Synthetic IIM microRNAs localize within early endosomes and antagonize t...
(A) pDCs were pretreated with increasing concentrations of CQ for 1 hour and then stimulated with miR574 (10 μg/ml) for 24 hours. The secretion of IFN-α was evaluated by ELISA (left y axis) and cell viability by propidium iodide staining (right y axis). Data are expressed as mean ± SEM of the percentage of IFN-α production or the percentage of live cells (n = 3); *P < 0.05 versus (0 µm CQ) by 1-way ANOVA with Dunnett’s post-hoc test. (B) pDCs were stimulated with 10 μg/ml miR574–Alexa 488 for 90 minutes. After fixation and permeabilization, pDCs were stained with an anti–early endosome antigen 1 (EEA1) mAb (red) or an anti–LAMP-1 Ab (red) and DAPI (blue). The image depicts results obtained with 1 representative donor out of 3; scale bars: 5 μm. (C) pDCs were pretreated (0h) with the indicated concentration of microRNAs or 1 μg/ml R848 for 24 hours, washed, and restimulated with 1 μg/ml R848 for an additional 5 hours. The production of IFN-α was evaluated by ELISA in cell-free supernatants. Data are expressed as the mean ± SEM of the percentage of IFN-α production (n = 4); *P < 0.05 versus (0 µm CQ) by 1-way ANOVA with Dunnett’s post-hoc test. (D) pDCs were pretreated (0h) with R848 (1 μg/ml) or miR574 (10 μg/ml) or left untreated for 24 hours, washed, and restimulated with miR574 for additional 24 hours. IFN-α was measured by ELISA in cell-free supernatants. Data are expressed as the mean ± SEM (n = 3); *P < 0.05 versus (–) by 1-way ANOVA with Dunnett’s post-hoc test.