Molecular mechanism of tumor necrosis factor-alpha production in 1 -> 3-beta-glucan (Zymosan)-activated macrophages

The molecular details of 1 -->3-beta -glucans, a fungal cell wall component , induced inflammatory responses are not well understood. In the present st udy, we conducted a systematic analysis of the molecular events leading to tumor necrosis factor (TNF)-alpha production after glucan stimulation of ma crophages. We demonstrated that activation of nuclear factor kappaB (NF-kap paB) is essential in zymosan A (a source of 1 -->3-beta -glucans)-induced T NF-alpha production in macrophages (RAW264.7 cells). Zymosan A-induced TNF- alpha protein production was associated with an increase in the TNF-alpha g ene promoter activity. Activation of the TNF-alpha gene promoter was depend ent on activation of NF-kappaB. Time course studies indicated that DNA bind ing activity of NF-kappaB preceded TNF-alpha promoter activity. Inhibition of NF-kappaB activation led to a dramatic reduction in both TNF-alpha promo ter activity and TNF-alpha protein production in the response to zymosan A Mutation of a major NF-kappaB binding site (kappa3) in the gene promoter re sulted in a significant decrease in the induction of the gene promoter by z ymosan A, while mutation of Egr or CRE sites failed to inhibit the response to zymosan. Together, these results strongly suggest that NF-kappaB is inv olved in signal transduction of 1 -->3-beta -glucans-induced TNF-alpha expr ession.