Fbxw7 increases CCL2/7 in CX3CR1hi macrophages to promote intestinal inflammation
Jia He, Yinjing Song, Gaopeng Li, Peng Xiao, Yang Liu, Yue Xue, Qian Cao, Xintao Tu, Ting Pan, Zhinong Jiang, Xuetao Cao, Lihua Lai, Qingqing Wang
Jia He, Yinjing Song, Gaopeng Li, Peng Xiao, Yang Liu, Yue Xue, Qian Cao, Xintao Tu, Ting Pan, Zhinong Jiang, Xuetao Cao, Lihua Lai, Qingqing Wang
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Research Article Immunology Inflammation

Fbxw7 increases CCL2/7 in CX3CR1hi macrophages to promote intestinal inflammation

Abstract

Resident and inflammatory mononuclear phagocytes (MPhs) with functional plasticity in the intestine are critically involved in the pathology of inflammatory bowel diseases (IBDs), the mechanism of which remains incompletely understood. In the present study, we found that increased expression of the E3 ligase F-box and WD repeat domain–containing 7 (FBXW) in the inflamed intestine was significantly correlated with IBD severity in both human diseases and in mouse models. Myeloid Fbxw7 deficiency protected mice from colitis induced by dextran sodium sulfate (DSS) or 2,6,4-trinitrobenzene sulfonic acid (TNBS). Fbxw7 deficiency resulted in decreased production of the chemokines CCL2 and CCL7 by colonic CX3CR1hi resident macrophages and reduced the accumulation of CX3CR1int proinflammatory MPhs in colitis-affected colon tissue. Mice that received adeno-associated virus–shFbxw7 (AAV-shFbxw7) showed significantly improved survival rates and alleviation of colitis. Mechanism screening demonstrated that FBXW7 suppressed H3K27me3 modification and promoted Ccl2 and Ccl7 expression via degradation of the histone-lysine N-methyltransferase enhancer of zeste homolog 2 (EZH2) in macrophages. Taken together, our results indicate that FBXW7 degrades EZH2 and increases Ccl2 and Ccl7 in CX3CR1hi macrophages, thereby promoting the recruitment of CX3CR1int proinflammatory MPhs into local colon tissues with colitis. Targeting FBXW7 might represent a potential therapeutic approach for the treatment of intestinal inflammation.

Authors

Jia He, Yinjing Song, Gaopeng Li, Peng Xiao, Yang Liu, Yue Xue, Qian Cao, Xintao Tu, Ting Pan, Zhinong Jiang, Xuetao Cao, Lihua Lai, Qingqing Wang

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Figure 5

Fbxw7 deficiency downregulates CCL2 and CCL7 in resident macrophages.

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Fbxw7 deficiency downregulates CCL2 and CCL7 in resident macrophages. (...
(A) Colon tissue was cultured overnight, and cytokines in the supernatant were measured by ELISA (n = 5). (B) Heatmap showing expression changes of inflammation-related genes in BMDMs from LysM+ Fbxw7fl/fl mice and Fbxw7fl/fl littermates. The expression profile is accompanied by a colored bar indicating the standardized log2 intensities. BMDMs were isolated from LysM+ Fbxw7fl/fl mice and Fbxw7fl/fl littermates and stimulated with LPS (100 ng/mL) for the transcriptomic assay. (C) CD11b+CX3CR1hi resident macrophages and CD11b+CX3CR1int proinflammatory MPhs were sorted from CLP of Fbxw7fl/fl (WT) and LysM+ Fbxw7fl/fl (KO) mice (n = 5) after 5 days of DSS or H2O administration, and gene expression levels were quantified by gene-specific amplification and qRT-PCR. The ratio of Ccl2 and Ccl7 expression in CX3CR1hi resident macrophages to Ccl2 and Ccl7 expression in CX3CR1int MPhs is shown. (D) Colonic tissues of WT and KO mice treated with DSS were cultured overnight, CCL2 and CCL7 expression in the supernatant was measured by ELISA (n = 5). (E) In a Transwell assay, the number of monocytes in the lower chamber recruited by supernatant of CLP-derived CX3CR1hi resident macrophages and CX3CR1int proinflammatory MPhs was counted by flow cytometry (n = 5). (F) Concentration of CCL2 and CCL7 in the culture medium of CX3CR1hi macrophages and CX3CR1int MPhs (n = 5). (G) Number of monocytes in the lower chamber recruited by the supernatant of CX3CR1hi resident macrophages from WT mice, with or without anti-CCL2 and anti-CCL7 Ab treatment (n = 5). (H) Gross morphology of colons from Fbxw7fl/fl and LysM+ Fbxw7fl/fl mice, with or without anti-CCL2 and anti-CCL7 Ab treatment and colon length measurements on day 9 (n = 5). (I) Body weight changes were assessed daily (n = 5). (J) The percentages of labeled WT and KO monocytes gated on CD45+Ly6Chi living cells from DSS-challenged recipient mice (n = 5) were analyzed by flow cytometry. Graph shows a summary of the percentages of labeled WT monocytes recruited to the CLP of WT and KO recipient mice on day 5 or 9 after DSS treatment. Data are presented as the mean ± SD and are representative of 3 independent experiments. *P < 0.05, **P < 0.01, and ***P < 0.001, by unpaired, 2-tailed Student’s t test.