Session Title: Rheumatoid Arthritis - Human Etiology and Pathogenesis
Session Type: Abstract Submissions (ACR)
Background/Purpose: , Rheumatoid arthritis (RA) is a disease of unknown origin, which develops continuous inflammation and progressive joint destruction resulting from an autoimmune response mainly occurred in the joints. Although genetic factors in RA have been reported, another factors might be important for RA because of low concordance rate of monozygotic twins. Additionally, it is well known that environmental factors, for example smoking and infections, are involved in the pathogenesis of RA. Recently, epigenetic abnormalities in acquired chronic disorders including RA have been reported. DNA methylations, microRNAs, and histone modifications are major epigenetic abnormalities. DNA methylations and microRNAs in RA have been well characterized, however, evidences of histone modifications in RA are limited. Histone modifications are associated with gene transcriptions. In promoter regions of target genes, high-level histone acetylation and histone H3 lysine 4 trimethylation (H3K4me3) exist. One of the major pathological conditions in RA may be overproduction of interleukin (IL)-6 from RA synovial fibroblasts (SFs) stimulated by tumor necrosis factor (TNF)-alpha derived from activated macrophages. The purpose of this study is to clarify the relation of histone modifications in the IL-6 gene promoter region and IL-6 gene transcription in RASFs.
Methods: , Synovial fibroblasts from the patients with RA and osteoarthritis (OA) as a control were harvested on the occasion of total knee arthroplasty in our hospital and were used for passages 4 through 8. Histone modifications (histone H3 acetylation (H3ac), H3K4me3) in the IL-6 gene promoter region were compared between RASFs and OASFs by chromatin immunoprecipitation (ChIP) assay. IL-6 mRNA and protein levels after stimulation with 10 ng/ml of TNF-alpha were detected using reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. Furthermore, we investigated how a treatment of histone acetyltransferase inhibitor (HATi) before stimulation with TNF-alpha had an influence on H3ac in the IL-6 gene promoter region and IL-6 mRNA in RASFs.
Results: IL-6 mRNA of RASFs were significantly increased compared with OASFs. In ChIP assay, both H3ac and H3K4me3 in the IL-6 gene promoter region of RASFs were significantly higher than those of OASFs. IL-6 mRNA and protein levels of RASFs were significantly increased more than those of OASFs after stimulation with TNF-alpha. Taken together, it is suggested that high levels of H3ac and H3K4me3 in the IL-6 gene promoter region of RASFs lead to be accessible for transcription factors to bind the region. In order to obtain more confirmed evidence of H3ac in the IL-6 gene promoter region in RASFs, we examined H3ac in the IL-6 gene promoter region and IL-6 mRNA of RASFs treated by HATi, curcumin. Both H3ac in the IL-6 promoter region and IL-6 mRNA of RASFs treated by curcumin were significantly reduced compared with those of untreated RASFs.
Conclusion: Histone modifications, especially high levels of H3ac and H3K4me3 in the IL-6 gene promoter region of RASFs, could be involved in a part of the pathogenesis in RA.
T. T. Wada,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/histone-modifications-in-the-interluekin-6-gene-promoter-region-of-rheumatoid-arthritis-synovial-fibroblasts/