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S100A8/A9 as a biomarker for synovial inflammation and joint damage in patients with rheumatoid arthritis

The Korean Journal of Internal Medicine 2014년 29권 1호 p.12 ~ p.19

강귀영(Kang Kwi-Young) - Catholic University College of Medicine Department of Internal Medicine
우정원(Woo Jung-Won) - Catholic University College of Medicine Seoul St. Mary’s Hospital Department of Convergent Research Consortium for Immunologic Disease
박성환(Park Sung-Hwan) - Catholic University College of Medicine Department of Internal Medicine

Abstract

S100A8 and S100A9 are major leukocyte proteins, known as damage-associated molecular patterns, found at high concentrations in the synovial fluid of patients with rheumatoid arthritis (RA). A heterodimeric complex of S100A8/A9 is secreted by activated leukocytes and binds to Toll-like receptor 4, which mediates downstream signaling and promotes inflammation and autoimmunity. Serum and synovial fluid levels of S100A8/A9 are markedly higher in patients with RA than in patients with osteoarthritis or miscellaneous inflammatory arthritis. Serum levels of S100A8/A9 are significantly correlated with clinical and laboratory markers of inflammation, such as C-reactive protein, erythrocyte sedimentation rate, rheumatoid factor, and the Disease Activity Score for 28 joints. Significant correlations have also been found between S100A8/A9 and radiographic and clinical assessments of joint damage, such as hand radiographs and the Rheumatoid Arthritis Articular Damage score. In addition, among known inflammatory markers, S100A8/A9 has the strongest correlation with total sum scores of ultrasonography assessment. Furthermore, baseline levels of S100A8/A9 are independently associated with progression of joint destruction in longitudinal studies and are responsive to change during conventional and biologic treatments. These findings suggest S100A8/A9 to be a valuable diagnostic and prognostic biomarker for RA.