Reduction of tumor necrosis factor induced nuclear factor-kappaB nuclear translocation and DNA binding by dexamethasone in human osteoarthritic synovial tissue explants.
OBJECTIVE
The antiinflammatory effects of glucocorticoids are mediated by several mechanisms, including inhibition of nuclear factor-kappaB (NF-kappaB) nuclear translocation and DNA binding. This mechanism is not evident in some cell types, including endothelial cells and rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS). We determined the effect of glucocorticoids and tumor necrosis factor (TNF) on nuclear localization and DNA binding of the transcription factor NF-kappaB in osteoarthritic (OA) synovial tissue.


METHODS
Explants of synovial tissue from patients undergoing joint replacement surgery for arthritis were placed in culture and treated with dexamethasone 10(-6) M for 18 h and again at 30 min prior to stimulation with TNF for a further 30 min. NF-kappaB and AP-1 DNA binding activities were determined by electrophoretic mobility shift analysis of nuclear extracts prepared from 6 whole tissue explants. Nuclear localization of NF-kappaB was determined by quantitative immunohistochemistry for Rel-A(p65) in thin sections of 5 synovial tissue explants.


RESULTS
TNF induced NF-kappaB nuclear translocation and DNA binding in all OA synovial tissue explants, although there were no consistent effects on AP-1 DNA binding. Dexamethasone reduced TNF stimulated nuclear translocation of RelA(p65) in all 5 OA synovial explants analyzed by immunohistochemistry. Dexamethasone partially decreased NF-kappaB DNA binding in 5 of 6 TNF stimulated explants and 4 of 6 unstimulated explants. In cultured rheumatoid arthritis and OA fibroblast-like synoviocytes and Mono Mac 6 cells the effects of dexamethasone on NF-kappaB DNA binding were not evident.


CONCLUSIONS
Dexamethasone partially inhibits TNF induced NF-kappaB DNA binding in human synovial tissue. It is feasible to use explants of intact fresh human synovium as a substrate for the action of antirheumatic drugs targeting a transcription factor.
Lehmann
Thomas
T
St Vincent's Hospital Clinical School, University of New South Wales, Sydney, Australia.
Murphy
Christian
C
Zahra
David G
DG
Handel
Malcolm L
ML
D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D004338:Drug Combinations; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology; D011994:Recombinant Proteins; D013583:Synovial Membrane / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D000893:Anti-Inflammatory Agents; D004268:DNA-Binding Proteins; D004338:Drug Combinations; D016328:NF-kappa B; D011994:Recombinant Proteins; D018808:Transcription Factor AP-1; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone; D004247:DNA