Vitamin C suppresses TNF alpha-induced NF kappa B activation by inhibiting I kappa B alpha phosphorylation.
Extracellular stimuli signal for activation of the transcription factor NFkappaB, leading to gene expression regulating processes involved in immune responses, inflammation, and cell survival. Tumor necrosis factor-alpha (TNFalpha) activates NFkappaB via a well-defined kinase pathways involving NFkappaB-inducing kinase (NIK), which activates downstream multisubunit IkappaB kinases (IKK). IKK in turn phosphorylates IkappaB, the central regulator of NFkappaB function. We found that intracellular vitamin C inhibits TNFalpha-induced activation of NFkappaB in human cell lines (HeLa, monocytic U937, myeloid leukemia HL-60, and breast MCF7) and primary endothelial cells (HUVEC) in a dose-dependent manner. Vitamin C is an important antioxidant, and most cells accumulate ascorbic acid (AA) intracellularly by transporting the oxidized form of the vitamin, dehydroascorbic acid (DHA). Because ascorbic acid is a strong pro-oxidant in the presence of transition metals in vitro, we loaded cells with vitamin C by incubating them with DHA. Vitamin C-loaded cells showed significantly decreased TNFalpha-induced nuclear translocation of NFkappaB, NFkappaB-dependent reporter transcription, and IkappaBalpha phosphorylation. Our data point to a mechanism of vitamin C suppression of NFkappaB activation by inhibiting TNFalpha-induced activation of NIK and IKKbeta kinases independent of p38 MAP kinase. These results suggest that intracellular vitamin C can influence inflammatory, neoplastic, and apoptotic processes via inhibition of NFkappaB activation.
Cárcamo
Juan M
JM
Program in Molecular Pharmacology and Chemistry and Department of Clinical Chemistry, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Box 451, New York, New York 10021, USA.
Pedraza
Alicia
A
Bórquez-Ojeda
Oriana
O
Golde
David W
DW
D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology*; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D018922:HL-60 Cells; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; 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; D015533:Transcriptional Activation / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000502:physiology*; D020298:U937 Cells; D048051:p38 Mitogen-Activated Protein Kinases; D000097782:NF-kappaB-Inducing Kinase
D000894:Anti-Inflammatory Agents, Non-Steroidal; D000975:Antioxidants; D001205:Ascorbic Acid; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins; D020928:Mitogen-Activated Protein Kinases; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B; D017346:Protein Serine-Threonine Kinases; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D000097782:NF-kappaB-Inducing Kinase; C000606204:NFKBIA protein, human; C496559:CHUK protein, human; C496560:IKBKB protein, human; C496565:IKBKE protein, human