Lipopolysaccharide Increases the Incidence of Collagen-Induced Arthritis in Mice Through Induction of Protease HTRA-1 Expression

Authors

  • Yuzhu Hou,

    1. State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, and Chinese Academy of Sciences, Beijing, China
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    • Drs. Hou and Lin contributed equally to this work.

  • Haijiang Lin,

    1. University of Texas Medical Branch, Galveston
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    • Drs. Hou and Lin contributed equally to this work.

  • Linnan Zhu,

    1. State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, and Chinese Academy of Sciences, Beijing, China
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    • Ms L. Zhu and Drs. Liu and Hu contributed equally to this work.

  • Zhaoting Liu,

    1. State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, and Chinese Academy of Sciences, Beijing, China
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    • Ms L. Zhu and Drs. Liu and Hu contributed equally to this work.

  • Fanlei Hu,

    1. Clinical Immunology Center and Peking University People's Hospital, Beijing, China
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    • Ms L. Zhu and Drs. Liu and Hu contributed equally to this work.

  • Jianfeng Shi,

    1. State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, and Chinese Academy of Sciences, Beijing, China
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  • Tao Yang,

    1. State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, and Chinese Academy of Sciences, Beijing, China
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  • Xiaoyun Shi,

    1. State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, and General Hospital of Chinese People's Armed Police Forces, Beijing, China
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  • Mingzhao Zhu,

    1. Institute of Biophysics and Chinese Academy of Sciences, Beijing, China
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  • Bernard F. Godley,

    1. University of Texas Medical Branch, Galveston
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  • Qiang Wang,

    Corresponding author
    1. State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, and Chinese Academy of Sciences, Beijing, China
    • State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beichen West Road 1-5, Chaoyang District, Beijing, China 100101Department of Rheumatology and Immunology, Clinical Immunology Center, Peking University People's Hospital, 11 Xizhimen South Street, Beijing, China 100044. E-mail: qiangwang@ioz.ac.cn zgli@yahoo.cn zhaoy@ioz.ac.cn

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  • Zhanguo Li,

    Corresponding author
    1. Clinical Immunology Center and Peking University People's Hospital, Beijing, China
    • State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beichen West Road 1-5, Chaoyang District, Beijing, China 100101Department of Rheumatology and Immunology, Clinical Immunology Center, Peking University People's Hospital, 11 Xizhimen South Street, Beijing, China 100044. E-mail: qiangwang@ioz.ac.cn zgli@yahoo.cn zhaoy@ioz.ac.cn

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  • Yong Zhao

    Corresponding author
    1. State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, and Chinese Academy of Sciences, Beijing, China
    • State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beichen West Road 1-5, Chaoyang District, Beijing, China 100101Department of Rheumatology and Immunology, Clinical Immunology Center, Peking University People's Hospital, 11 Xizhimen South Street, Beijing, China 100044. E-mail: qiangwang@ioz.ac.cn zgli@yahoo.cn zhaoy@ioz.ac.cn

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Abstract

Objective

The protease HTRA-1 is closely associated with rheumatoid arthritis (RA). The molecular mechanisms that control HTRA-1 expression are currently unknown. This study was undertaken to determine the regulatory role of Toll-like receptors (TLRs) on HTRA-1 expression in mice with collagen-induced arthritis (CIA) and in synovial cells from RA patients.

Methods

HTRA-1 messenger RNA and protein production in mouse fibroblasts, mouse macrophages, and freshly isolated RA patient synovial cells treated with TLR ligands were detected by real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Arthritis incidence and severity were determined using clinical scores and histopathologic analysis. Involvement of HTRA-1 in lipopolysaccharide (LPS)–increased arthritis incidence and severity in mice was determined using anti–HTRA-1 monoclonal antibody. The signal pathways involved in HTRA-1 expression were accessed by specific inhibitors, RNA interference, dual-luciferase reporter, and chromatin immunoprecipitation methods.

Results

LPS and tenascin-C, but not the other TLR ligands tested, strongly induced HTRA-1 expression. LPS significantly increased HTRA-1 expression in the joint tissue as well as arthritis incidence and severity in mice with CIA. Blocking HTRA-1 by antibody significantly decreased LPS-promoted CIA severity. Inhibiting NF-κB significantly decreased LPS-induced HTRA-1 expression in mouse and human cells. Dual-luciferase reporter assay and ChIP analysis showed that p65 directly binds to HTRA-1 promoter (amino acid 347).

Conclusion

Our findings indicate that TLR-4 activation increases HTRA-1 expression through the NF-κB pathway in fibroblasts and macrophages. HTRA-1 expression is involved in the enhancing effects of LPS on CIA. This study offers new insights into the regulation of HTRA-1 expression via LPS/TLR-4 and the role of HTRA-1 in RA pathogenesis.

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