Expression of the pro-inflammatory protein S100A12 (EN-RAGE) in rheumatoid and psoriatic arthritis.

OBJECTIVES Infiltration of synovial tissue by neutrophils is crucial in rheumatoid arthritis (RA), psoriatic arthritis (PsA) and seronegative arthritis (SA). Altered vascular function and endothelial activation are important in PsA. S100A12 (EN-RAGE) is secreted by activated granulocytes and binds to the receptor for advanced glycation end products, which induces nuclear factor (NF)-kappaB-dependent activation of endothelium. METHODS Immunohistochemical studies were performed to detect synovial S100A12 expression. We analysed serum and synovial fluid of 42 patients for S100A12 levels. RESULTS S100A12 was strongly expressed in inflamed synovial tissue whereas it was nearly undetectable in synovia of controls or patients after successful treatment. Serum levels of S100A12 correlated with disease activity. CONCLUSIONS Local expression of S100A12 in inflamed tissue suggests a role in synovitis, especially in PsA. High serum concentrations of S100A12 in patients with active arthritis compared with healthy controls or patients in remission point to its usefulness as a serum marker.