IkappaBalpha degradation is not a requirement for the X-ray-induced activation of nuclear factor kappaB in normal rat astrocytes and human brain tumour cells

Int J Radiat Biol. 1998 Nov;74(5):617-24. doi: 10.1080/095530098141195.


Purpose: To investigate the mechanism of NFkappaB activation by X-rays in normal primary rat astrocytes.

Materials and methods: Primary cultures of type I astrocytes generated from the cortex of neonatal rats were exposed to X-rays with and without various kinase inhibitors and a protease inhibitor. The nuclear or cytoplasmic protein extracts were collected at specified times after treatment and analysed for NFkappaB-DNA binding activity and IkappaB protein levels.

Results: The NFkappaB-DNA binding activity was induced by X-rays in a dose- and time-dependent manner in the absence of IkappaB protein degradation in astrocytes as well as in the human glioma cell line U-373MG. Whereas a protease inhibitor (calpain inhibitor 1) and a protein kinase C inhibitor (CGP-41251) did not affect X-ray-induced NFkappaB-DNA binding, treatment of astrocytes with the tyrosine kinase inhibitor (erbstatin) completely prevented the increase in NFkappaB activity after irradiation. Erbstatin also reduced the phosphorylation of IkappaBalpha after X-ray exposure.

Conclusions: These results indicate that, in contrast with the more frequently investigated activators of NFkappaB, radiation-induced activation of this transcription factor proceeds in the absence of IkappaBalpha degradation and requires tyrosine phosphorylation.

Publication types

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

MeSH terms

  • Animals
  • Astrocytes / drug effects
  • Astrocytes / metabolism
  • Astrocytes / radiation effects*
  • DNA / metabolism*
  • DNA-Binding Proteins / drug effects
  • DNA-Binding Proteins / metabolism
  • DNA-Binding Proteins / radiation effects*
  • Enzyme Inhibitors / pharmacology
  • Glioma / metabolism
  • Glioma / pathology
  • Humans
  • Hydroquinones / pharmacology
  • I-kappa B Proteins*
  • NF-kappa B / drug effects
  • NF-kappa B / metabolism
  • NF-kappa B / radiation effects*
  • NF-kappa B p50 Subunit
  • Oligopeptides / pharmacology
  • Phosphorylation
  • Rats
  • Rats, Sprague-Dawley
  • Receptor Protein-Tyrosine Kinases / antagonists & inhibitors
  • Time Factors
  • Transcription Factors / drug effects
  • Transcription Factors / metabolism
  • Transcription Factors / radiation effects*
  • Tumor Cells, Cultured / drug effects
  • Tumor Cells, Cultured / radiation effects
  • Tumor Necrosis Factor-alpha / pharmacology


  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • Hydroquinones
  • I kappa B beta protein
  • I-kappa B Proteins
  • NF-kappa B
  • NF-kappa B p50 Subunit
  • NFKB1 protein, human
  • Oligopeptides
  • Transcription Factors
  • Tumor Necrosis Factor-alpha
  • N-(3-N-(benzyloxycarbonyl)amino-1-carboxypropyl)leucyl-O-methyltyrosine N-methylamide
  • DNA
  • Receptor Protein-Tyrosine Kinases
  • erbstatin