Glucocorticoid-mediated repression of inflammatory cytokine production in fibroblast-like rheumatoid synoviocytes is independent of nuclear factor-kappaB activation induced by tumour necrosis factor alpha.
OBJECTIVE
To determine whether steroids inhibit the production of inflammatory cytokines by the inhibition of nuclear factor kappaB (NF-kappaB) activation in fibroblast-like rheumatoid synoviocytes (FLSs) under inflammatory conditions, and to determine whether steroids stimulate the induction of synthesis of the inhibitory protein IkappaB-alpha in the anti-inflammatory immune response of these cells.


METHODS
Expression of the interleukin-6 (IL-6) and interleukin-1beta (IL-1beta) 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-kappaB activation was examined with the electrophoretic mobility shift assay (EMSA). In order to study dexamethasone (DEX)-dependent regulation of IkappaB-alpha expression, we performed Western blotting before and after stimulation with tumour necrosis factor alpha (TNF-alpha).


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-kappaB were present in the nucleus of the FLSs stimulated by TNF-alpha, with or without pretreatment with DEX. Treatment of FLSs with DEX did not induce an increase in IkappaB-alpha sufficient to prevent nuclear translocation of NF-kappaB on stimulation with TNF-alpha.


CONCLUSIONS
DEX may suppress the production of inflammatory cytokines, such as IL-6 and IL-1beta, but it neither prevents the translocation of NF-kappaB to the nucleus nor induces the synthesis of IkappaB-alpha protein in FLSs stimulated by TNF-alpha.
Han
C W
CW
Department of Orthopaedic Surgery, College of Medicine, The Catholic University of Korea, Seoul.
Choi
J H
JH
Kim
J M
JM
Kim
W Y
WY
Lee
K Y
KY
Oh
G T
GT
D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D016207:Cytokines / Q000096:biosynthesis* / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation / Q000502:physiology; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D020672:I-kappa B Proteins; D007249:Inflammation / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology; D007375:Interleukin-1 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*
D016207:Cytokines; D004268:DNA-Binding Proteins; D005938:Glucocorticoids; D020672:I-kappa B Proteins; D007375:Interleukin-1; D015850:Interleukin-6; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D003907:Dexamethasone