Synovial fluid induced nuclear factor-kappaB DNA binding in a monocytic cell line.
OBJECTIVE
To determine the effects of synovial fluids (SF) on DNA binding activity of transcription factor nuclear factor-kappaB (NF-kappaB) in the Mono Mac 6 monocytic/macrophage cell line as a model for the interaction between SF and synovial tissue macrophages in arthritis.


METHODS
Mono Mac 6 cells were incubated with SF from the knee joints of human subjects with rheumatoid arthritis (RA), undifferentiated seronegative oligoarthritis, and osteoarthritis (OA). Nuclear extracts prepared from the Mono Mac 6 cells and RA synovial tissue were analyzed by electrophoretic mobility shift analysis (EMSA) for NF-kappaB DNA binding proteins.


RESULTS
Induction of NF-kappaB DNA binding by the p65(RelA)/p50 heterodimer was observed in response to incubation of Mono Mac 6 cells with SF (20% in culture medium) from 5 of 8 subjects with RA, 4 of 5 with OA, and none of 3 with undifferentiated seronegative oligoarthritis. Incubation of SF with neutralizing antibodies against tumor necrosis factor-alpha (TNF-alpha), but not antibodies against interleukin 6 (IL-6), significantly reduced the induction of p65/p50 binding activity in SF from subjects with RA and OA. Unexpectedly, a slowly migrating SF inducible NF-kappaB-binding complex was observed in EMSA of Mono Mac 6 cells after incubation with SF from 5 of 8 RA and 2 of 5 OA subjects. The induction of this complex by SF was not affected by neutralization of TNF-alpha or IL-6 in SF, and the complex was not inducible by TNF-alpha, IL-1beta, TNF-alpha/IL-1beta, IL-6, platelet derived growth factor, lipopolysaccharide, or tetradecanoyl phorbol acetate. The slowly migrating complex could not be supershifted with antibodies against NF-kappaB, Jun, or the transcriptional coactivators p300 or CBP. A NF-kappaB-binding complex with similar slow mobility was observed in nuclear extracts prepared from fresh human RA synovial tissue.


CONCLUSIONS
Biological activity of TNF-alpha in SF from RA and OA subjects is capable of inducing p65/p50 NF-kappaB DNA binding activity in macrophages. A property of SF that is independent of TNF-alpha and other cytokines is responsible for the induction of a novel slowly migrating NF-kappaB-binding complex. Soluble mediators in SF of subjects with RA and OA can therefore modulate binding of nuclear proteins to the NF-kappaB binding site in macrophages and may play a role in inflammatory gene expression in arthritis.
Lehmann
T
T
St. Vincent's Hospital Clinical School, University of New South Wales, and the Arthritis and Inflammation Research Program of the Garvan Institute of Medical Research, Sydney, Australia.
Nguyen
L Q
LQ
Handel
M L
ML
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000378:metabolism; D002135:Calcium-Binding Proteins; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D008875:Middle Aged; D009000:Monocytes / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I; D050863:Synaptotagmin I; D050857:Synaptotagmins; D013582:Synovial Fluid / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D015703:Antigens, CD; D002135:Calcium-Binding Proteins; D004268:DNA-Binding Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D050863:Synaptotagmin I; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D050857:Synaptotagmins; D004247:DNA