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 expression 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 stimuli, including IL-1 and TNF in the endothelial cell line ECV304 and in primary HUVECs. The induction of a NF-kappaB-dependent gene, IL-8, by TNF was also inhibited. The effect requires millimolar concentrations of vitamin C, which occur intracellularly in vivo, particularly during inflammation. Vitamin C was not toxic to cells, did not inhibit another inducible transcription factor, STAT1, and had no effect on the DNA binding of NF-kappaB. Inhibition by vitamin C was not simply an antioxidant effect, because redox-insensitive pathways to NF-kappaB were also blocked. Vitamin C was shown to block IL-1- and TNF-mediated degradation and phosphorylation of I-kappaBalpha (inhibitory 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 cells with vitamin C led to a rapid and sustained activation of p38, and the specific p38 inhibitor SB203580 reversed the inhibitory effect of vitamin C on IKK activity, I-kappaBalpha phosphorylation, and NF-kappaB activation. The results identify p38 as an intracellular target for high dose vitamin C.
Bowie
A G
AG
Department of Biochemistry, Trinity College, Dublin, Ireland. agbowie@tcd.ie
O'Neill
L A
LA
D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases
D000975:Antioxidants; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D001205:Ascorbic Acid