Volume 43, Issue 11 pp. 2501-2512
Basic Science

Activation, differential localization, and regulation of the stress-activated protein kinases, extracellular signal–regulated kinase, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase, in synovial tissue and cells in rheumatoid arthritis

Georg Schett

Georg Schett

University of Vienna, Vienna, Austria

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Makiyeh Tohidast-Akrad

Makiyeh Tohidast-Akrad

Ludwig Boltzmann Institute for Rheumatology and Balneology, Vienna, Austria

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Josef S. Smolen

Corresponding Author

Josef S. Smolen

University of Vienna, and Ludwig Boltzmann Institute for Rheumatology and Balneology, Vienna, Austria

Division of Rheumatology, Department of Internal Medicine III, University of Vienna, Währinger Gürtel 18-20, A-1180 Vienna, AustriaSearch for more papers by this author
Beatrice Jahn Schmid

Beatrice Jahn Schmid

University of Vienna, Vienna, Austria

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Carl-Walter Steiner

Carl-Walter Steiner

University of Vienna, Vienna, Austria

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Peter Bitzan

Peter Bitzan

University of Vienna, Vienna, Austria

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Peter Zenz

Peter Zenz

Hospital Baumgartner Höhe, Vienna, Austria

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Kurt Redlich

Kurt Redlich

University of Vienna, Vienna, Austria

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Qingbo Xu

Qingbo Xu

Austrian Academy of Sciences, Innsbruck, Austria

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Günter Steiner

Günter Steiner

University of Vienna, and Ludwig Boltzmann Institute for Rheumatology and Balneology, Vienna, Austria

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Abstract

Objective

To investigate whether stress- and mitogen-activated protein kinases (SAPK/MAPK), such as extracellular signal–regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK, are significantly activated in rheumatoid arthritis (RA) synovial tissue compared with their activation in degenerative joint disease; to assess the localization of SAPK/MAPK activation in rheumatoid synovial tissue; and to search for the factors leading to stress kinase activation in human synovial cells.

Methods

Immunoblotting and immunohistology by antibodies specific for the activated forms of SAPK/MAPK were performed on synovial tissue samples from patients with RA and osteoarthritis (OA). In addition, untreated and cytokine-treated human synovial cells were assessed for SAPK/MAPK activation and downstream signaling by various techniques.

Results

ERK, JNK, and p38 MAPK activation were almost exclusively found in synovial tissue from RA, but not OA, patients. ERK activation was localized around synovial microvessels, JNK activation was localized around and within mononuclear cell infiltrates, and p38 MAPK activation was observed in the synovial lining layer and in synovial endothelial cells. Tumor necrosis factor α, interleukin-1 (IL-1), and IL-6 were the major inducers of ERK, JNK, and p38 MAPK activation in cultured human synovial cells.

Conclusion

Signaling through SAPK/MAPK pathways is a typical feature of chronic synovitis in RA, but not in degenerative joint disease. SAPK/MAPK signaling is found at distinct sites in the synovial tissue, is induced by proinflammatory cytokines, and could lead to the design of highly targeted therapies.

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