Extracellular vesicles induce STING-mediated proinflammatory cytokines in Dermatomyositis

Summary: Dermatomyositis (DM) is an acquired inflammatory myopathy characterized by chronic skin inflammation. The pathogenesis of DM is still unclear. Extracellular vesicles (EVs) are lipid bilayer membrane vesicles existing in various bodily fluids and implicated in the pathogenesis of autoimmune diseases. As type I interferons, specifically IFN-b, are uniquely elevated in DM, and Stimulator of interferon genes (STING) works as a critical sensor and adaptor in type I IFN signaling, we hypothesized that EVs derived from DM patients’ plasma might trigger STING-mediated proinflammatory effects. DM patients were recruited in the dermatology clinic at U Penn. Peripheral blood mononuclear cells (PBMCs) were isolated by Ficoll gradient. EVs derived from plasma were isolated via ultracentrifugation. The supernatant was harvested for ELISA and the lysed cells were collected for Western blot after HC derived PBMCs were stimulated by EVs. We found that DM patients’ plasma derived EVs triggered cytokines release (IFNb: (30.24±0.65) vs control (2.683±0.35); TNFα: (1451±98.40) vs control (16.75±1.407)pg/mL; n=6) with STING phosphorylation. Inhibition of STING significantly attenuated DM patients’ plasma derived EVs-triggered cytokines production (IFNb: (21.58±2.22) vs (28.34±1.73); TNFα: (434.8±94.50) vs (919.1±133.0)pg/mL; n=6) via suppressing STING and its down-stream signal TBK1, IRF3, and NFκB phosphorylation. To further explore whether STING phosphorylation and the proinflammatory effects were caused by EVs-captured DNA, EVs were pretreated with Triton X-100 and DNase to digest DNA. Triton X-100 and DNase pretreatment decreased EVs-triggered cytokines release (IFNb: (4.113±2.08) vs (28.94±5.47); TNFα: (290.3±57.03) vs (1361±293.6) pg/mL; n=3-6) and STING activation. Thus we found EVs derived from plasma could trigger STING-mediated proinflammatory effects in DM. The STING phosphorylation during EVs triggering of proinflammatory effects was at least partially mediated by DNA captured by EVs. Targeting STING might provide insight into a potential therapeutic approach for DM.