Sustained induction of IP-10 by MRP8/14 via the IFNβ–IRF7 axis in macrophages exaggerates lung injury in endotoxemic mice

Abstract

Background As a damage-associated molecular pattern, the myeloid-related protein 8/14 (MRP8/14) heterodimer mediates various inflammatory diseases, such as sepsis. However, how MRP8/14 promotes lung injury by regulating the inflammatory response during endotoxemia remains largely unknown. This study aims at illuminating the pathological functions of MRP8/14 in endotoxemia. Methods An endotoxemic model was prepared with wild-type and myeloid cell-specific Mrp8 deletion (Mrp8ΔMC) mice for evaluating plasma cytokine levels. Lung injury was evaluated by hematoxylin and eosin (H&E) staining, injury scoring and wet-to-dry weight (W/D) ratio. The dynamic profile of interferon γ (IFNγ)-inducible protein 10 (IP-10) mRNA expression induced by macrophage MRP8/14 was determined by quantitative real-time polymerase chain reaction (qPCR). Immunoblotting was used to evaluate the increase in IP-10 level induced by activation of the JAK–STAT signaling pathway. Luciferase reporter assay was performed to detect the involvement of IRF7 in Ip-10 gene transcription. In vivo air pouch experiments were performed to determine the biological function of IP-10 induced by MRP8/14. Results Experiments with Mrp8ΔMC mice showed that MRP8/14 promoted the production of cytokines, including IP-10, in the bronchoalveolar lavage fluid (BALF) and lung injury in endotoxic mice. The result of qPCR showed sustained expression of Ip-10 mRNA in macrophages after treatment with MRP8/14 for 12 h. Neutralization experiments showed that the MRP8/14-induced Ip-10 expression in RAW264.7 cells was mediated by extracellular IFNβ. Western blotting with phosphorylation-specific antibodies showed that the JAK1/TYK2-STAT1 signaling pathway was activated in MRP8/14-treated RAW264.7 cells, leading to the upregulation of Ip-10 gene expression. IRF7 was further identified as a downstream regulator of the JAK–STAT pathway that mediated Ip-10 gene expression in macrophages treated with MRP8/14. In vivo air pouch experiments confirmed that the IFNβ-JAK1/TYK2-STAT1-IRF7 pathway was required for chemokine (C-X-C motif) receptor 3 (CXCR3)+ T lymphocyte migration, which promoted lung injury in the context of endotoxemia. Conclusions In summary, our study demonstrates that MRP8/14 induces sustained production of IP-10 via the IFNβ-JAK1/TYK2-STAT1-IRF7 pathway to attract CXCR3+ T lymphocytes into lung tissues and ultimately results in lung injury by an excessive inflammatory response in the context of endotoxemia.

Pathoimmunological analyses of fatal E11 infection in premature infants

“…Therefore, inhibiting IP10 may serve as one of the therapeutic targets for treating E11-induced liver injury. Animal experiments have revealed that, during sepsis, myeloid-related protein 8/14 (MRP8/14) induces sustained IP10 production through the IFN-β-JAK1/TYK2-STAT1-IRF7 pathway ( Wang et al., 2023a ). Our findings were consistent with the results of these animal experiments, suggesting that IRF7 might also be one of the targets implicated in severe E11 infection leading to liver injury.…”

Macrophage plasticity: signaling pathways, tissue repair, and regeneration

“… 338 , 339 IL‐10 inhibits the production of proinflammatory cytokines, such as TNF‐α, IL‐1β, and IL‐6, by M1 macrophages and other immune cells and downregulates the expression of MHC class II molecules and costimulatory molecules on antigen‐presenting cells, thereby suppressing the activation and proliferation of T cells. 340 , 341 , 342 In addition to IL‐10, M2 macrophages produce TGF‐β, which has anti‐inflammatory and immunosuppressive effects. 343 TGF‐β inhibits the activation and proliferation of T cells, suppresses the production of proinflammatory cytokines, and promotes the differentiation of regulatory T cells, which play a crucial role in maintaining immune homeostasis and resolving inflammation.…”