STAT6/Arg1 promotes microglia/macrophage efferocytosis and inflammation resolution in stroke mice
Wei Cai, Xuejiao Dai, Jie Chen, Jingyan Zhao, Mingyue Xu, Lili Zhang, Boyu Yang, Wenting Zhang, Marcelo Rocha, Toshimasa Nakao, Julia Kofler, Yejie Shi, R. Anne Stetler, Xiaoming Hu, Jun Chen
Wei Cai, Xuejiao Dai, Jie Chen, Jingyan Zhao, Mingyue Xu, Lili Zhang, Boyu Yang, Wenting Zhang, Marcelo Rocha, Toshimasa Nakao, Julia Kofler, Yejie Shi, R. Anne Stetler, Xiaoming Hu, Jun Chen
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Research Article Inflammation Neuroscience

STAT6/Arg1 promotes microglia/macrophage efferocytosis and inflammation resolution in stroke mice

Abstract

Efferocytosis, or phagocytic clearance of dead/dying cells by brain-resident microglia and/or infiltrating macrophages, is instrumental for inflammation resolution and restoration of brain homeostasis after stroke. Here, we identify the signal transducer and activator of transcription 6/arginase1 (STAT6/Arg1) signaling axis as a potentially novel mechanism that orchestrates microglia/macrophage responses in the ischemic brain. Activation of STAT6 was observed in microglia/macrophages in the ischemic territory in a mouse model of stroke and in stroke patients. STAT6 deficiency resulted in reduced clearance of dead/dying neurons, increased inflammatory gene signature in microglia/macrophages, and enlarged infarct volume early after experimental stroke. All of these pathological changes culminated in an increased brain tissue loss and exacerbated long-term functional deficits. Combined in vivo analyses using BM chimeras and in vitro experiments using microglia/macrophage-neuron cocultures confirmed that STAT6 activation in both microglia and macrophages was essential for neuroprotection. Adoptive transfer of WT macrophages into STAT6-KO mice reduced accumulation of dead neurons in the ischemic territory and ameliorated brain infarction. Furthermore, decreased expression of Arg1 in STAT6–/– microglia/macrophages was responsible for impairments in efferocytosis and loss of antiinflammatory modality. Our study suggests that efferocytosis via STAT6/Arg1 modulates microglia/macrophage phenotype, accelerates inflammation resolution, and improves stroke outcomes.

Authors

Wei Cai, Xuejiao Dai, Jie Chen, Jingyan Zhao, Mingyue Xu, Lili Zhang, Boyu Yang, Wenting Zhang, Marcelo Rocha, Toshimasa Nakao, Julia Kofler, Yejie Shi, R. Anne Stetler, Xiaoming Hu, Jun Chen

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Figure 6

Both CNS microglia and peripheral macrophages contribute to STAT6-afforded protection against ischemic stroke.

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Both CNS microglia and peripheral macrophages contribute to STAT6-afford...
(A) Schematic illustration for the construction of WT/CX3CR1-GFP chimeric mice. (B–D) ImageStream analysis of pSTAT6 and Arg1 in CD45+CD11b+GFP– cells and CD45+CD11b+GFP+ macrophages in ipsilateral hemisphere of chimeric mice was performed 3d after tMCAO. (B) Representative images indicating pSTAT6 and Arg1 signal in both CD45+CD11b+GFP– cells and CD45+CD11b+GFP+ macrophages in ipsilateral brains. Scale bar: 7 μm. (C) Percentages of GFP– cells and GFP+ macrophages among CD45+CD11b+ cells were assessed in WT (left) and WT/CX3CR1-GFP chimeric mice (right). (D) Percentages of pSTAT6+ cells (left) and Arg1+ cells (right) observed among CD45+CD11b+GFP– cells and CD45+CD11b+GFP+ macrophages. n = 3 mice. (E) Chimeric mice were constructed by transplanting WT BM to WT recipients (WT/WT), STAT6-KO BM to WT recipients (WT/KO), or WT BM to STAT6-KO recipients (KO/WT) after irradiation of recipients. Chimeric mice were subjected to 60 minutes of tMCAO at 6 weeks after irradiation. (F and G) Infarct volume at 3d after tMCAO was quantified in MAP2-stained (green) coronal sections. Dashed lines outline the infarct area. n = 9–10 mice per group. Scale bar: 1 mm. (H and I) Neuronal death in chimeric mice was quantified by TUNEL (red) and NeuN (green) colabeling in infarct areas 3d after tMCAO. Scale bar: 10 μm. n = 3–5 mice per group. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001 vs. WT/WT, 1-way ANOVA.