Brahma-related gene 1 bridges epigenetic regulation of proinflammatory cytokine production to steatohepatitis in mice

Authors

  • Wenfang Tian,

    1. State Key Laboratory of Reproductive Medicine, Department of Pathophysiology, Key Laboratory of Cardiovascular Disease and Molecular Intervention, Nanjing Medical University, Nanjing, China
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    • These authors contributed equally to this work.

  • Huihui Xu,

    1. State Key Laboratory of Reproductive Medicine, Department of Pathophysiology, Key Laboratory of Cardiovascular Disease and Molecular Intervention, Nanjing Medical University, Nanjing, China
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    • Potential conflict of interest: Nothing to report.

  • Fei Fang,

    1. State Key Laboratory of Reproductive Medicine, Department of Pathophysiology, Key Laboratory of Cardiovascular Disease and Molecular Intervention, Nanjing Medical University, Nanjing, China
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  • Qi Chen,

    1. State Key Laboratory of Reproductive Medicine, Department of Pathophysiology, Key Laboratory of Cardiovascular Disease and Molecular Intervention, Nanjing Medical University, Nanjing, China
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  • Yong Xu,

    Corresponding author
    1. State Key Laboratory of Reproductive Medicine, Department of Pathophysiology, Key Laboratory of Cardiovascular Disease and Molecular Intervention, Nanjing Medical University, Nanjing, China
    • Address reprint requests to: Yong Xu, Nanjing Medical University, 140 Hanzhong Road, Nanjing, Jiangsu 210029, ChinaNantong University, 19 Qixiu Road, Nantong, Jiangsu 226001, China. E-mail: yxu2005@gmail.com shen_aiguo@yahoo.com fax: (86)-25-86862888 fax: (86)-513-85051999

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  • Aiguo Shen

    Corresponding author
    1. Department of Immunology, Medical College, Nantong University, Nantong, China
    • Address reprint requests to: Yong Xu, Nanjing Medical University, 140 Hanzhong Road, Nanjing, Jiangsu 210029, ChinaNantong University, 19 Qixiu Road, Nantong, Jiangsu 226001, China. E-mail: yxu2005@gmail.com shen_aiguo@yahoo.com fax: (86)-25-86862888 fax: (86)-513-85051999

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  • Supported in part by grants from the National Basic Research “973” Program of China (2012CB517503, 2012CB822104, 2011CB910604), the National Natural Science Foundation of China (31270802, 31070723), the Natural Science Foundation of Jiangsu Province (BK2012043), the Program for New Century Excellent Talents in University of China (NCET-11-0991), the Ministry of Education (212059), and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

  • See Editorial on Page 486

Abstract

Chronic inflammation, inflicted by the spillover of proinflammatory mediators, links metabolic dysfunction to nonalcoholic steatohepatitis (NASH). The epigenetic maneuverings that underscore accelerated synthesis of proinflammatory mediators in response to nutritional inputs are not clearly defined. Here we report that the ATP-dependent chromatin remodeling proteins Brahma-related gene 1 (Brg1) and Brahma (Brm) were up-regulated in vitro in cultured hepatocytes treated with free fatty acid or glucose and in vivo in animal models of NASH. Occupancy of Brg1 and Brm on the promoter regions of proinflammatory genes was increased in vitro in cells and ex vivo in liver tissues. Estradiol suppressed the induction and recruitment of Brg1/Brm by palmitate. Recruitment of Brg1 and Brm relied on nuclear factor kappa B/p65; reciprocally, Brg1 and Brm contributed to the stabilization of p65 binding. Importantly, overexpression of Brg1/Brm enhanced, whereas knockdown of Brg1/Brm attenuated, the induction of proinflammatory mediators in hepatocytes challenged with excessive nutrient. Mechanistically, Brg1 and Brm were involved in the maintenance of a chromatin microenvironment marked by active histone modifications and friendly to the access of the general transcriptional machinery. Finally, depletion of Brg1/Brm by short hairpin RNA attenuated the release of proinflammatory mediators in the liver and significantly ameliorated hepatic pathology in NASH mice. Conclusion: Our data illustrate a Brg1-dependent pathway that connects the epigenetic regulation of proinflammatory genes to the pathogenesis of NASH and point to a potential druggable target in the therapeutic intervention of NASH. (HEPATOLOGY 2013;58:576–588)

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