Anti-inflammatory drugs and tumor necrosis factor-alpha production from monocytes: role of transcription factor NF-kappaB and implication for rheumatoid arthritis therapy

Inhibition of tumor necrosis factor-alpha (TNF-alpha) represents a relevant target in rheumatoid arthritis therapy. Besides inhibiting cyclooxygenase, anti-inflammatory drugs can affect the activation of transcription factors. We investigated the ability of dexamethasone, indomethacin, and rofecoxib to modulate nuclear factor-kappaB (NF-kappaB) activation and TNF-alpha release from human monocytes challenged with lipopolysaccharide (LPS) or phorbol 12-myristate 13-acetate (PMA). Both stimuli induced NF-kappaB nuclear translocation and TNF-a secretion. Dexamethasone potently inhibited TNF-alpha release, indomethacin inhibited only PMA-evoked release, while rofecoxib had no effect. In the electrophoretic mobility shift assay, dexamethasone and rofecoxib dose-dependently inhibited the DNA binding activity of NF-kappaB in stimulated monocytes, whereas indomethacin failed to inhibit the LPS-evoked one. These results were further confirmed by evaluating the drugs' ability to reduce nuclear NF-kappaB subunits, as well as the amount of phosphorylated IkappaBalpha in cytosolic fractions. In conclusion, these results indicate that anti-inflammatory drugs differ largely in their ability to inhibit NF-kappaB activity and/or TNF-alpha release from human monocytes. These effects can be relevant to rheumatoid arthritis therapy.