CONCISE REPORTS Nuclear factor-êB activity in T cells from patients with rheumatic diseases: A preliminary report

Objective—The NF-êB/Rel family of transcription factors regulates the expression of many genes involved in the immune or inflammatory response at the transcriptional level. The aim of this study was to determine whether distinctive patterns of NF-kB activation are seen in diVerent forms of joint disease. Methods—The DNA binding activity of these nucleoproteins was examined in purified synovial and peripheral T cells from patients with various chronic rheumatic diseases (12: four with rheumatoid arthritis; five with spondyloarthropathies; and three with osteoarthritis). Results—Electrophoretic mobility shift assays disclosed two specific complexes bound to a NF-êB specific P-labelled oligonucleotide in nucleoproteins extracted from purified T cells isolated from synovial fluid and peripheral blood of patients with rheumatoid arthritis. The complexes consisted of p50/p50 homodimers and p50/ p65 heterodimers. Increased NF-kB binding to DNA in synovial T cells was observed relative to peripheral T cells. In non-rheumatoid arthritis, binding of NF-êB in synovial T cells was exclusively mediated by p50/p50 homodimers. Conclusion—Overall, the results suggest that NF-êB may play a central part in the activation of infiltrating T cells in chronic rheumatoid arthritis. The activation of this nuclear factor is qualitatively diVerent in rheumatoid synovial T cells to that in other forms of non-rheumatoid arthritis (for example, osteoarthritis, spondyloarthropathies). (Ann Rheum Dis 1998;57:738–741) Nuclear transcription factors are proteins that bind to promoters and enhancers to stimulate (or, occasionally, inhibit) gene transcription through direct interaction with DNA. Among those transcription factors, nuclear factor êB (NF-êB) is one of the most extensively studied. This factor, formerly described as a ê enhancer binding transcription factor constitutively present in the nuclei of mature B cells, regulates gene transcription by binding to decameric sequences (kB motifs) located in the promoter of many cellular and viral genes, particularly those encoding proteins involved in the immune and inflammatory response. 4 NF-êB is made of heteroor homodimeric combinations of several proteins belonging to the same family (Rel family). The five known mammalian Rel/NF-êB proteins, NF-êB1 (p50), NF-êB2 (p52), RelA (p65), RelB, and c-Rel, share a highly conserved Rel homology domain that contains sequences required for DNA binding, protein dimerisation, and nuclear localisation. The most common species are p50 subunit homodimers or heterodimers consisting of a p50 subunit and either a p65 (RelA) subunit or the product of the c-rel oncogen (c-Rel). In most cell types, NF-êB is found in an inactive cytosolic form, retained by association with inhibitory proteins called IkBs. Upon cell activation by a vast number of agents, IkB undergoes rapid phosphorylation in specific serine residues by the recently discovered IkB kinases, IKKá and IKKâ, (reviewed by Stancovski and Baltimore) ubiquitination and degradation by the 26S proteasome pathway, then releasing the active NF-êB to the nucleus. To determine whether the pattern of NF-êB activation is qualitatively diVerent in rheumatoid arthritis (RA) compared with other rheumatic diseases and hence establish whether this transcription factor plays some part in the pathogenesis of diVerent types of synovitis, we have examined the activation of NF-êB in T cells obtained from peripheral blood (PT) and synovial fluid (ST) from patients with diVerent types of arthritis, by studying the DNA binding of the NF-êB/Rel transcription factor family in these cells. We have found a diVerential pattern of NF-êB binding to DNA in T cells (ST and PT) from RA and non-RA patients, and the significance of this finding will be discussed.