Myeloid-derived suppressor cells (MDSC) expand during sepsis, suppress both innate and adaptive immunity, and promote chronic immunosuppression, which characterizes the late/chronic phase of sepsis. We previously reported that the transcription factors Stat3 and C/EBPb synergize to induces the expression of microRNA (miR)-21 and miR-181b to promote MDSC expansion in a mouse model of polymicrobial sepsis that progresses from an early/acute proinflammatory phase to a late/chronic immunosuppressive stage. We also showed that Gr1+CD11b+ cells, the precursors of MDSCs, from mice genetically deficient in the inflammatory protein S100A9 lack miR-21 or miR-181b in late sepsis, and are not immunosuppressive. In the present study, we show that S100A9 induces miR-21 and miR-181b during the late sepsis phase. We find that S100A9 associates with and stabilizes the Stat3-C/EBPb protein complex that activates the miRNA promoters. Reconstituting Gr1+CD11b+ cells from the S100A9 knockout mice with late sepsis with S100A9 protein restores the Stat3-C/EBPb protein complex and miRNA expressions, and switches the Gr1+CD11b+ cells into the immunosuppressive, MDSC phenotype. Importantly, we find that this process requires IL-10 mediated signaling, which induces S100A9 translocation from the cytosol to the nucleus. These results demonstrate that S100A9 promotes MDSC expansion and immunosuppression in late/chronic sepsis by inducing the expression of miR-21 and miR-181b.
| Identifer | oai:union.ndltd.org:ETSU/oai:dc.etsu.edu:asrf-1244 |
| Date | 12 April 2019 |
| Creators | Alkhateeb, Tuqa, PharmD, Kumbhare, Ajinkya, MD, Bah, Isatou, BS, Elgazzar, Mohamed, PhD |
| Publisher | Digital Commons @ East Tennessee State University |
| Source Sets | East Tennessee State University |
| Detected Language | English |
| Type | text |
| Source | Appalachian Student Research Forum |
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