Drs. Hou and Lin contributed equally to this work.
Lipopolysaccharide Increases the Incidence of Collagen-Induced Arthritis in Mice Through Induction of Protease HTRA-1 Expression
Article first published online: 28 OCT 2013
Copyright © 2013 by the American College of Rheumatology
Arthritis & Rheumatism
Volume 65, Issue 11, pages 2835–2846, November 2013
How to Cite
Hou, Y., Lin, H., Zhu, L., Liu, Z., Hu, F., Shi, J., Yang, T., Shi, X., Zhu, M., Godley, B. F., Wang, Q., Li, Z. and Zhao, Y. (2013), Lipopolysaccharide Increases the Incidence of Collagen-Induced Arthritis in Mice Through Induction of Protease HTRA-1 Expression. Arthritis & Rheumatism, 65: 2835–2846. doi: 10.1002/art.38124
- Issue published online: 28 OCT 2013
- Article first published online: 28 OCT 2013
- Accepted manuscript online: 27 AUG 2013 03:29PM EST
- Manuscript Accepted: 1 AUG 2013
- Manuscript Received: 25 NOV 2012
- National Basic Research Program of China. Grant Numbers: 2010CB945301, 2011CB710900, 2010CB529100
- National Natural Science Foundation for General and Key Programs. Grant Numbers: C81130055, U0832003
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.
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.
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).
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.