Increased circulating LOX-1+ neutrophils activate T cells and demonstrate a pro-inflammatory role in allergic rhinitis.

Background: Low-density neutrophils are heterogeneous immune cells with immunosuppressive (such as polymorphonuclear myeloid-derived suppressor cells [PMN-MDSC]) or pro-inflammatory (such as low-density granulocytes [LDG]) properties that have been well described in multiple cancers and immune diseases. However, its role in allergic rhinitis (AR) is still unclear. Methods: In the present study, we defined low-density neutrophils as CD14-CD11B+CD15+LOX-1+ (LOX-1+ neutrophils), and their levels in the peripheral blood (PB) were evaluated and compared between patients with AR and healthy donors using flow cytometric analysis. LOX-1 expression on polymorphonuclear neutrophils was identified. Carboxyfluorescein succinimidyl ester (CFSE)-stained CD3+ T cells were cultured alone or with LOX-1+ neutrophils, T cell proliferation was assessed using flow cytometry, and pro-inflammatory cytokines in the supernatants were detected using enzyme-linked immunosorbent assay (ELISA). Clinicopathological analyses were performed to gain a thorough understanding of LOX-1+ neutrophils. Results: We determined that LOX-1+ neutrophils were significantly increased in the PB of patients with AR, and LOX-1 expression in neutrophils from patients with AR was elevated. Interestingly, LOX-1+ neutrophils derived from patients with AR, unlike PMN-MDSC, promoted T cell proliferation and pro-inflammatory cytokine production. Moreover, clinicopathological analysis revealed that there was no any relation between circulating LOX-1+ neutrophil levels and the levels of IgE, age and sex. Conclusion: These findings indicate that elevated circulating LOX-1+ neutrophils play a pro-inflammatory role in AR.

Small extracellular vesicles derived from human mesenchymal stem cells prevent Th17-dominant neutrophilic airway inflammation via immunoregulation on Th17 cells.

Type 17 helper T cells (Th17)-dominant neutrophilic airway inflammation is critical in the pathogenesis of steroid-resistant airway inflammation such as severe asthma. Small extracellular vesicles (sEV) derived from human mesenchymal stem cells (MSCs) display extensive therapeutic effects and advantages in many diseases. However, the role of MSC-sEV in Th17-dominant neutrophilic airway inflammation and the related mechanisms are still poorly studied. Here we found that MSC-sEV significantly alleviated the infiltration of inflammatory cells in peribronchial interstitial tissues and reduced levels of inflammatory cells, especially neutrophils, in bronchoalveolar lavage fluids (BALF) of mice with neutrophilic airway inflammation. Consistently, MSC-sEV significantly decreased levels of IL-17A in BALF and Th17 in lung tissues. Furthermore, we found that labelled MSC-sEV were taken up by human CD4+ T cells most obviously at 12 h after incubation, and distributed mostly in mouse lungs. More importantly, potential signaling pathways involved in the MSC-sEV mediated inhibition of Th17 polarization were found using RNA sequencing. Using Western blot, JAK2-STAT3 pathway was identified as an important role in the inhibition of Th17 polarization by MSC-sEV. We found that proteins in MSC-sEV were mostly involved in the therapeutic effects of MSC-sEV. In total, our study suggested that MSC-sEV could be a potential therapeutic strategy for the treatment of neutrophilic airway inflammation.

Dendritic cells mediated by small extracellular vesicles derived from MSCs attenuated the ILC2 activity via PGE2 in patients with allergic rhinitis.

BACKGROUND: Mesenchymal stromal cells-derived small extracellular vesicles (MSC-sEVs) have recently attracted considerable attention because of their therapeutic potential in various immune diseases. We previously reported that MSC-sEVs could exert immunomodulatory roles in allergic airway inflammation by regulating group 2 innate lymphoid cell (ILC2) and dendritic cell (DC) functions. Therefore, this study aimed to investigate the indirect effects of MSC-sEVs on ILC2s from patients with allergic rhinitis (AR) via DCs. METHODS: Here, we isolated sEVs from induced pluripotent stem cells-MSCs using anion-exchange chromatography and mature DCs (mDCs) were treated with MSC-sEVs. sEV-mDCs were co-cultured with peripheral blood mononuclear cells from patients with AR or purified ILC2s. The levels of IL-13 and GATA3 in ILC2s were examined by flow cytometry. Bulk RNA sequence for mDCs and sEV-mDCs was employed to further probe the potential mechanisms, which were then validated in the co-culture systems. RESULTS: sEV-mDCs showed impaired capacity in priming the levels of IL-13 and GATA3 in ILC2s when compared with mDCs. Furthermore, there was higher PGE2 and IL-10 production from sEV-mDCs, and the blockade of them especially the former one reversed the inhibitory effects of sEV-mDCs. CONCLUSIONS: We demonstrated that MSC-sEVs were able to dampen the activating effects of mDCs on ILC2s in patients with AR. Mechanismly, the PGE2-EP2/4 axis played an essential role in the immunomodulatory effects of sEV-mDCs on ILC2s. Herein, we provided new insights into the mechanism underlying the therapeutic effects of MSC-sEVs in allergic airway inflammation.