Vitamin C suppresses TNF alpha-induced NF kappa B activation by inhibiting I kappa B alpha phosphorylation

Biochemistry. 2002 Oct 29;41(43):12995-3002. doi: 10.1021/bi0263210.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Active Transport, Cell Nucleus / drug effects
  • Active Transport, Cell Nucleus / physiology
  • Anti-Inflammatory Agents, Non-Steroidal / pharmacology
  • Antioxidants / pharmacology
  • Ascorbic Acid / pharmacology*
  • Cell Line
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism
  • Enzyme Activation / drug effects
  • Enzyme Activation / physiology
  • HL-60 Cells
  • HeLa Cells
  • Humans
  • I-kappa B Kinase
  • I-kappa B Proteins / antagonists & inhibitors*
  • I-kappa B Proteins / metabolism*
  • Mitogen-Activated Protein Kinases / metabolism
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / antagonists & inhibitors*
  • NF-kappa B / metabolism*
  • Phosphorylation / drug effects
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Serine-Threonine Kinases / metabolism
  • Transcriptional Activation / drug effects
  • Tumor Necrosis Factor-alpha / antagonists & inhibitors*
  • Tumor Necrosis Factor-alpha / physiology*
  • U937 Cells
  • p38 Mitogen-Activated Protein Kinases

Substances

  • Anti-Inflammatory Agents, Non-Steroidal
  • Antioxidants
  • I-kappa B Proteins
  • NF-kappa B
  • NFKBIA protein, human
  • Tumor Necrosis Factor-alpha
  • NF-KappaB Inhibitor alpha
  • Protein-Serine-Threonine Kinases
  • CHUK protein, human
  • I-kappa B Kinase
  • IKBKB protein, human
  • IKBKE protein, human
  • Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • NF-kappa B kinase
  • Ascorbic Acid