Theophylline inhibits NF-kappaB activation in human peripheral blood mononuclear cells.

Background: Theophylline not only dilates the bronchi, but also modulates the production of proinflammatory cytokines and inhibits inflammation. Theophylline exerts an antiinflammatory effect on allergic inflammation through inhibition of NF-kappaB activation in mast cells. However, the action of theophylline on monocytes/macrophages and T cells is unknown.

Methods: We examined whether or not theophylline inhibits tumor necrosis factor (TNF)-alpha-induced activation of the nuclear transcription factor NF-kappaB, a factor that is essential for the expression of proinflammatory cytokines, in human monocytic U-937 cells, a T cell line (Jurkat) and peripheral blood mononuclear cells (PBMC). The inhibitory effect of theophylline on TNF-alpha-induced NF-kappaB activation was evaluated by Western blotting, flow cytometry and chloramphenicol acetyltransferase (CAT) assaying. Expression of the IkappaBalpha protein was evaluated by Western blotting.

Results: Western blotting demonstrated that theophylline inhibits NF-kappaB activation in U-937 and Jurkat cells and PBMC. Flow cytometry demonstrated that theophylline inhibits NF-kappaB activation in U-937 and Jurkat cells in a dose-related manner. CAT assaying indicated that NF-kappaB-dependent reporter gene expression is inhibited in U-937 cells pretreated with theophylline. Western blotting of cytoplasmic extracts of U-937 cells revealed that this inhibition was linked to theophylline-induced preservation of expression of the IkappaBalpha protein.

Conclusions: These findings are consistent with the idea that theophylline suppresses the production of proinflammatory cytokines via inhibition of NF-kappaB activation through preservation of the IkappaBalpha protein in monocytes/macrophages and T cells.