Responses to the proinflammatory cytokines interleukin‐1 and tumor necrosis factor α in cells derived from rheumatoid synovium and other joint tissues involve nuclear factor κB–mediated induction of the Ets transcription factor ESE‐1

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Abstract
Objective To investigate the expression of the novel Ets transcription factor ESE‐1 in rheumatoid synovium and in cells derived from joint tissues, and to analyze the role of nuclear factor κB (NF‐κB) as one of the central downstream targets in mediating the induction of ESE‐1 by proinflammatory cytokines. Methods ESE‐1 protein expression was analyzed by immunohistochemistry using antibodies in synovial tissues from patients with rheumatoid arthritis (RA) and osteoarthritis (OA). ESE‐1 messenger RNA (mRNA) levels were analyzed by reverse transcriptase–polymerase chain reaction or Northern blotting in human chondrocytes, synovial fibroblasts, osteoblasts, and macrophages, before and after exposure to interleukin‐1β (IL‐1β), tumor necrosis factor α (TNFα), or lipopolysaccharide (LPS) with or without prior infection with an adenovirus encoding the inhibitor of nuclear factor κB (IκB). The wild‐type ESE‐1 promoter and the ESE‐1 promoter mutated in the NF‐κB site were cloned into a luciferase reporter vector and analyzed in transient transfections. Electrophoretic mobility shift assays (EMSAs) and supershift assays with antibodies against members of the NF‐κB family were conducted using the NF‐κB site from the ESE‐1 promoter as a probe. Results Immunohistochemical analysis showed specific expression of ESE‐1 in cells of the synovial lining layer and in some mononuclear and endothelial cells in RA and OA synovial tissues. ESE‐1 mRNA expression could be induced by IL‐1β and TNFα in cells such as synovial fibroblasts, chondrocytes, osteoblasts, and monocytes. Transient transfection experiments and EMSAs showed that induction of ESE‐1 gene expression by IL‐1β requires activation of NF‐κB and binding of p50 and p65 family members to the NF‐κB site in the ESE‐1 promoter. Overexpression of IκB using an adenoviral vector blocked IL‐1β–induced ESE‐1 mRNA expression. Chromatin immunoprecipitation further confirmed that NF‐κB binds to the ESE‐1 promoter in vivo. Conclusion ESE‐1 is expressed in synovial tissues in RA and, to a variable extent, in OA, and is specifically induced in synovial fibroblasts, chondrocytes, osteoblasts, and monocyte/macrophages by IL‐1β, TNFα, or LPS. This induction relies on the translocation of the NF‐κB family members p50 and p65 to the nucleus and transactivation of the ESE‐1 promoter via a high‐affinity NF‐κB binding site. ESE‐1 may play a role in mediating some effects of proinflammatory stimuli in cells at sites of inflammation.