erbstatin and Glioma

We have examined the neuroimmunoregulatory function of prolactin (PRL) on astrocytic inducible nitric oxide synthase (iNOS) expression in the C6 glioma cell line. After 24 h of PRL (5-100 nM) stimulation, a concentration-dependent increase of NO release, evaluated as nitrite, was observed in C6 culture medium. Moreover, both NO release and iNOS expression induced by interferon-gamma (250 U/ml) were enhanced by PRL (18-100 nM). PRL-induced NO release was inhibited by dexamethasone, an inhibitor of de novo iNOS synthesis. We used erbstatin (5 microg/ml), a potent inhibitor of protein tyrosine kinases, to test whether these proteins were required for signaling events evoked by PRL in these cells. This inhibitor was able to inhibit completely the PRL-induced NO production and iNOS expression. In conclusion, we provide evidence that NO production in glial cells can be regulated not only by cytokines but also by neuroimmunoregulatory hormones such as PRL, which is present in normal brain but may be elevated in several pathological states.

Topics: Animals; Blotting, Western; Dexamethasone; Enzyme Induction; Enzyme Inhibitors; Glioma; Hydroquinones; Immunoenzyme Techniques; Immunosuppressive Agents; Interferon-gamma; Neuroimmunomodulation; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Prolactin; Protein Kinase Inhibitors; Rats; Signal Transduction; Tumor Cells, Cultured

The effects of genistein and erbstatin analogue, inhibitors of tyrosine kinase, on Ca2+ mobilization evoked by thapsigargin (TG) were examined in rat glioma C6 cells. Genistein and erbstatin analogue inhibited the Ca2+ release from intracellular pools as well as Ca2+ entry from extracellular medium evoked by TG in a dose-dependent manner. However, they did not affect a Ca2+ entry due to leakage of Ca2+ from extracellular medium into cells. The present results suggest that tyrosine kinase inhibitors inhibit capacitative Ca2+ entry due to the inhibition of both Ca2+ entry itself and Ca2+ release in rat glioma C6 cells.

Topics: Animals; Calcium; Enzyme Inhibitors; Genistein; Glioma; Hydroquinones; Protein-Tyrosine Kinases; Rats; Thapsigargin; Tumor Cells, Cultured

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