Enhanced cytotoxicity in the rheumatoid joint

The interaction of transcription factors is critical in the regulation of gene expression. This study characterized the mechanism by which NF-κB family members interact to regulate the human TNF-α gene. A 120-bp TNF-α promoter-reporter, possessing binding sites for NF-κB (κB3), C/EBPβ (CCAAT/enhancer binding protein β), and c-Jun, was activated by cotransfection of plasmids expressing the wild-type version of each of these transcription factors. Employing adenoviral vectors, dominant-negative versions of NF-κB p65, and c-Jun, but not C/EBPβ, suppressed (p < 0.05–0.001) LPS-induced TNF-α secretion in primary human macrophages. Following LPS stimulation, NF-κB p50/p65 heterodimers bound to the κB3 site and c-Jun to the −103 AP-1 site of the TNF-α promoter. By transient transfection, NF-κB p65 and p50 synergistically activated the TNF-α promoter. In contrast, no synergy was observed between NF-κB p65, with or without NF-κB p50, and c-Jun or C/EBPβ, even in the presence of the coactivator p300. The contribution of the upstream κB binding sites was also examined. Following LPS stimulation, the κB1 site bound both NF-κB p50/p65 heterodimers and p50 homodimers. The binding by NF-κB p50 homodimers to the κB1, but not to the κB3, site contributed to the inability of macrophages to respond to a second LPS challenge. In summary, adjacent κB3 and AP-1 sites in the human TNF-α promoter contribute independently to LPS-induced activation. Although both the κB1 and κB3 sites bound transcriptionally active NF-κB p50/p65 heterodimers, only the κB1 site contributed to down-regulation by NF-κB p50 homodimers.

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“…Murine TNF-␣-mediated cytotoxicity was determined using TNF-sensitive L929 fibroblasts, as previously described (28).…”

Section: Tnf-␣ Secretion and Quantitationmentioning

confidence: 99%

TNF-α Gene Expression in Macrophages: Regulation by NF-κB Is Independent of c-Jun or C/EBPβ

Liu

Sidiropoulos

Song

et al. 2000

The Journal of Immunology

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199

150

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Elevated levels of TNF in the joints of adjuvant arthritic rats

et al. 1993

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Alteration in peripheral blood mononuclear cell function and serum cytokines in oral lichen planus

Karagouni

Dotsika

Sklavounou

1994

J Oral Pathology Medicine

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Different activation parameters of peripheral blood mononuclear cells (PBMC) from 31 patients with oral lichen planus (OLP) were examined and compared with 23 healthy donors. Impaired spontaneous (450 +/- 241 vs 1290 +/- 480 cpm) and mitogen-induced (39580 +/- 14470 vs 67000 +/- 11810 cpm) lymphocyte blastogenesis was observed in OLP patients. Furthermore, reduced cytokine production was found after phytohemagglutinin A (PHA) stimulation for all cytokines studied-tumour necrosis factor alpha (TNF alpha, 432.2 +/- 73.4 vs 979.8 +/- 46.3 units/ml), interleukin 2 (IL-2, 156.2 +/- 14.9 vs 572.6 +/- 12.9 pg/ml), interferon gamma (IFN gamma, 48.5 +/- 11.9 vs 82.6 +/- 12.4 pg/ml) and interleukin 6 (IL-6, 253.6 +/- 57.7 vs 1,419.0 +/- 279.6 units/ml)-except for interleukin 1 beta (IL-1 beta) and lymphotoxin (LT). In contrast, unstimulated culture supernatants showed increased TNF alpha (38.2 +/- 13.1 vs 8.0 +/- 0.2 units/ml), LT (10.2 +/- 2.2 units/ml vs < 0.4) and IL-6 (18.5 +/- 5.6 units/ml vs < 0.5) activity. Similarly, elevated concentrations of TNF alpha (19.6 +/- 6.3 units/ml) and IL-6 (22.9 +/- 4.7 units/ml) were detected in the sera of OLP patients. Combination of PHA and phorbol myristate acetate (PMA) could restore OLP proliferative T cell response and cytokine production to the level of healthy donors, whereas exogenous recombinant human IL-2 (rhuIL-2) plus PMA did not seem to be an effective stimulant for OLP T cells. These results indicate an alteration in the immune condition of OLP patients and an impairment in T lymphocyte function.

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Enhanced cytotoxicity in the rheumatoid joint

Cited by 4 publications

References 24 publications

TNF-α Gene Expression in Macrophages: Regulation by NF-κB Is Independent of c-Jun or C/EBPβ

TNF-α Gene Expression in Macrophages: Regulation by NF-κB Is Independent of c-Jun or C/EBPβ

Elevated levels of TNF in the joints of adjuvant arthritic rats

Alteration in peripheral blood mononuclear cell function and serum cytokines in oral lichen planus

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