Objective. To determine whether steroids inhibit the production of inflammatory cytokines by the inhibition of nuclear factor κB (NF-κB) activation in fibroblast-like rheumatoid synoviocytes (FLSs) under inflammatory conditions, and to determine whether steroids stimulate the induction of synthesis of the inhibitory protein IκB-α in the anti-inflammatory immune response of these cells. Methods. Expression of the interleukin-6 (IL-6) and interleukin-1 β (IL-1β) genes was measured by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR), and the secreted IL-6 was measured with the enzyme-linked immunosorbent assay. Inhibition of the NF-κB activation was examined with the electrophoretic mobility shift assay (EMSA). In order to study dexamethasone (DEX)-dependent regulation of IκB-α expression, we performed Western blotting before and after stimulation with tumour necrosis factor α (TNF-α). Results. The inflammatory cytokine study showed that DEX suppressed gene expression and the production of protein in FLSs. EMSA demonstrated that identical amounts of NF-κB were present in the nucleus of the FLSs stimulated by TNF-α, with or without pretreatment with DEX. Treatment of FLSs with DEX did not induce an increase in IκB-α sufficient to prevent nuclear translocation of NF-κB on stimulation with TNF-α. Conclusion. DEX may suppress the production of inflammatory cytokines, such as IL-6 and IL-1β, but it neither prevents the translocation of NF-κB to the nucleus nor induces the synthesis of IκB-α protein in FLSs stimulated by TNF-α.
Bibliographical noteFunding Information:
The authors wish to thank Hae-Kyung Cho and Sun-Hee Kim for assistance with cell culture and Philip McElroy and Michelle Van Balkom for revision of the English. This work was supported by the Molecular Medicine Research Group Program (98-J03-01–01-A-05) of the Ministry of Science and Technology.
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- Rheumatoid arthritis