Uhrf1-Mediated Tnf-α Gene Methylation Controls Pro-Inflammatory Macrophages in Experimental Colitis Resembling IBD

Abstract

Background & Aims: Macrophages drive the pathological process of inflammatory bowel diseases (IBD) mostly by secreting pro-inflammatory cytokines such as tumor necrosis factor α (Tnf-α). Recent studies have indicated the association between epigenetic modifications and macrophage functions. However, epigenetic mechanisms regulating macrophages' functional involvement in IBD remain unknown. We investigated whether the epigenetic regulator Uhrf1 plays a role in innate immunity by functionally regulating macrophages in intestines. Methods: We employed two transgenic strains of mice (one with Uhrf1 deficiency in macrophages (Uhrf1fl/flLyz2-Cre mice) and the other with the two mutations at Uhrf1's DNA methylation regulatory site (Uhrf1YP187/188AA mice)) to assess their susceptibility to dextran sodium sulfate (DSS)-induced colitis. We examined the cytokines derived from Uhrf1fl/flLyz2-Cre and Uhrf1YP187/188AA macrophages in response to lipopolysaccharide (LPS) stimulation. We also analyzed the effects of pro-inflammatory cytokines on Uhrf1 expression in macrophages. Findings: Uhrf1 deficiency and Uhrf1YP187/188AA mutation resulted in severe colitis in the DSS-treated mice. In vitro analysis revealed the hypomethylation of Tnf-α promoter and the increased Tnf-α expression in Uhrf1fl/flLyz2-Cre and Uhrf1YP187/188AA macrophages in response to LPS stimulation. Exogenous Tnf-α destabilized Uhrf1 protein through ubiquitination-mediated protein degradation, triggering macrophage activation. Interpretation: Uhrf1-mediated DNA methylation controls pro-inflammatory functions of macrophages in the experimental colitis resembling IBD. The epigenetic mechanisms that activate macrophages may provide new therapeutic targets for IBD treatment. Funding: This work is supported by the Major State Basic Research Development Program of China (973 Program, 2015CB554007), the National Natural Science Foundation of China Programs (81272559, 81572866, 81502572, 81773263 and 81773104), the International Science and Technology Corporation Program of Chinese Ministry of Science and Technology (2014DFA32920), the Science and Technology Program of Chinese Ministry of Education (113044A), the Frontier Exploration Program of Huazhong University of Science and Technology (2015TS153), the Natural Science Foundation Program of Hubei Province (2015CFA049), the Research Fund of Public Welfare in Health Industry (201402015) from the Health and Family Plan Committee of China, the Integrated Innovative Team for Major Human Diseases Program (2017) and the Academic Medical Doctor Program (2018) of Tongji Medical College, Huazhong University of Science and Technology. Declaration of Interest: The authors have declared that no conflict of interest exists. Ethical Approval: All the experiments with mice were performed according to the protocol approved by the Ethics Committee of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology on Care and Use of Laboratory Animals.