Vitamin C inhibits NF-kappa B activation by TNF via the activation of p38 mitogen-activated protein kinase

The transcription factor NF-kappaB is a central mediator of altered gene ex pression during inflammation, and is implicated in a number of pathologies, including cancer, atherosclerosis, and viral infection. We report in this study that vitamin C inhibits the activation of NF-kappaB by multiple stimu li, including IL-I and TNF in the endothelial cell line ECV304 and in prima ry HUVECs. The induction of a NF-kappaB-dependent gene, IL-8, by TNF was al so inhibited. The effect requires millimolar concentrations of vitamin C, w hich occur intracellularly in vivo, particularly during inflammation, Vitam in C was not toxic to cells, did not inhibit another inducible transcriptio n factor, STAT1, and had no effect on the DNA binding of NF-kappaB, Inhibit ion by vitamin C was not simply an antioxidant effect, because redox-insens itive pathways to NF-kappaB were also blocked, Vitamin C was shown to block IL-1-and TNF-mediated degradation and phosphorylation of I-kappaB alpha (i nhibitory protein that dissociates from NF-kappaB), due to inhibition of I- kappaB kinase (IKK) activation. Inhibition of TNF-driven IKK activation was mediated by p38 mitogen-activated protein kinase, because treatment of cel ls with vitamin C led to a rapid and sustained activation of p38, and the s pecific p38 inhibitor SB203580 reversed the inhibitory effect of vitamin C on IKK activity, I-kappaB alpha phosphorylation, and NF-kappaB activation. The results identify p38 as an intracellular target for high dose vitamin C .