Lipopolysaccharide/Interferon-gamma Induced Nitric Oxide Production in C6 Glioma Cells: Modulation by Dexamethasone

ABSTRACT

BACKGROUND: Glial cell-derived nitric oxide (NO), and its regulation has significant implications for central nervous system pathophysiology. The aim of the present study was to see the production of NO in lipopolysaccharide (LPS)/interferon-gamma (IFN-)-treated C6 glioma cells and the effect of dexamethasone on NO production and apoptosis of LPS/IFN--treated C6 glioma cells. METHODS: The apoptosis of LPS/IFN- treated C6 glioma cell was examined with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) method and the production of NO in culture medium was measured. The expression of iNOS mRNA was examined by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). The effect of the N-monomethyl L-arginine (NMMA) and dexamethasone on the apoptosis and NO production was also examined. RESULTS: Inducible nitric oxide synthase (iNOS) mRNA and NO production were markedly increased in LPS/IFN--treated C6 glioma cells. The expression of iNOS mRNA arose at 3 hours, peaked at 12 hours, and declined 24 hours after LPS/IFN--treatment. Accumulation of NO derivatives in the culture media was increased at least upto 48 hours after LPS/IFN-. The induction of iNOS expression and NO production in LPS/IFN--treated C6 cells was correlated with apoptotic cell death judged by TUNEL staining. After treatment of NMMA, one of the NOS inhibitors, NO production and apoptosis were markedly decreased. Dexamehasone treatment suppressed the NO production by concentration depenedent manner. CONCLUSIONS: From the above results it is concluded that the LPS/IFN- induced apoptosis of C6 cells is mediated by iNOS-derived NO and NO production and apoptosis was suppressed by dexamethasone.