IL-27-Ucp2-FoxO3 axis mediating the polarization of alternatively activated macrophages and ameliorating inflammatory pain.

BACKGROUND: The signaling pathways of inflammatory pain are widely explored, but practical clinical approaches to ameliorate pain remain inadequate. METHODS: Quantitative PCR (qPCR) and ELISA methods were applied to measure the concentration of interleukin (IL)-27 in the inflammatory pain mouse model. Flow cytometry was conducted to identify the source of IL-27. Bone marrow-derived macrophages were stimulated by IL-27, IL-4, lipopolysaccharide, and/or interferon-gamma, followed by qPCR to assess pro-inflammatory and pro-resolving markers' dynamic expression. Then, the molecule profiling of IL-27-primed macrophages was determined using transcriptomic and proteomic sequencing. The Agilent Seahorse XF analyzer calculated energy metabolism indicators. The adoptive cell transfer method was used to verify that forkhead box class O3 (FoxO3) mediates alternatively activated macrophage differentiation induced by IL-27-Ucp2, contributing to alleviating pain sensation in mice. RESULTS: IL-27 is highly expressed centrally and peripherally in rodent pain models. Selective downregulation of IL-27 intensifies pain sensitivity in mice. In macrophages, IL-27 promotes the secretion of anti-inflammatory molecules, such as Arginase-1. Further, transcriptome, energy metabolic examination, and proteome analyses identified that IL-27 restructures the metabolism in macrophages, which is mediated by uncoupling protein 2 (Ucp2) and subsequently activates transcription factor FoxO3. Conditional knockdown of FoxO3 (si-FoxO3) in macrophages refrains the production of anti-inflammatory genes in vitro; meanwhile, adoptive transfer of macrophages with si-FoxO3 but no wild-type macrophages (or IL-27 primed macrophages) prolongs mechanical hyperalgesia in mice. CONCLUSIONS: These findings reveal that the IL-27-Ucp2-FoxO3 axis regulates macrophage plasticity distinct from the canonical IL-4-mediated pathway through metabolic rewiring and facilitates alleviating Inflammatory pain.