n-(3-n-(benzyloxycarbonyl)amino-1-carboxypropyl)leucyl-o-methyltyrosine-n-methylamide and erbstatin

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

Topics: Animals; Astrocytes; DNA; DNA-Binding Proteins; Enzyme Inhibitors; Glioma; Humans; Hydroquinones; I-kappa B Proteins; NF-kappa B; NF-kappa B p50 Subunit; Oligopeptides; Phosphorylation; Rats; Rats, Sprague-Dawley; Receptor Protein-Tyrosine Kinases; Time Factors; Transcription Factors; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha