Role of Morphine in the Glutamate-Induced Oxidative Damage of C6 Glial Cells / 대한마취과학회지

BACKGROUND: Although many studies regarding several neurotransmitters and receptors have been conducted to define the mechanism involved in the development of dependence on opioids, definitive evidence has still not been presented. This study was designed to investigate the effect of morphine on glutamate-induced cytotoxicity of rat C6 glial cells. METHODS: The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay was used for cell viability. Morphology of nuclei was observed by fluorescent microscopy. Reduced glutathione (GSH) contents were measured in acid-soluble cell fractions. Generation of hydrogen peroxide (H2O2) was measured from the cultured supernatant of C6 glial cells using the scopoletin-horseradish peroxidase (HRP) assay. RESULTS: Glutamate induced the death of C6 glial cells in a time- and dose-dependent manner. Glutamate-induced cytotoxicity was protected by morphine and antioxidants, such as GSH and N-acetyl-L-cysteine (NAC). However, morphine antagonist, naloxone did not inhibit the protective effect of morphine on glutamate-induced cytotoxicity. In addition, the specific agonists, [D-Ala2, N-Me-Phe4, Gly5-ol]-Enkephalin acetate salt (DAMGO), [D-Pen2,5]-Enkephalin (DPDPE) and U69593 did not protect C6 glial cells from glutamate-induced cytotoxicity. Furthermore, morphine recovered the depletion of GSH by glutamate and inhibited the generation of H2O2 by glutamate in C6 glial cells. CONCLUSIONS: We suggest that morphine protects C6 glial cells from glutamate-induced cytotoxicity via the inhibition of GSH depletion and the generation of H2O2 by glutamate.

Protective Effect of Nitric Oxide Against Lipopolysaccharide-induced Cytotoxicity in C6-glial Cell / 대한해부학회지

Nitric oxide (NO) is mainly involved in brain ischemic damage to elucidate the protective mechanism of NO pretreatment on ischemic-induced cytotoxicity. This study was investigated whether NO pretreatment inhibits the increase of iNOS expression by lipopolysaccharide (LPS) combined phorbol 12-myristate 13-acetate (PMA) via regulating NF-kB activation in C6 glial cells. C6 glial cells with LPS and PMA for 72 hours markedly induced NO, but sodium nitroprusside (SNP) (100 nM) pretreatment before exposure of LPS and PMA significantly supressed NO production, iNOS expression and NF-kB activation by LPS and PMA. In addition, LPS and PMA treatment for 72 hours induced severely cell death and LDH release from cell into media in C6 glial cells. However SNP pretreatment before treatment of LPS and PMA significantly protected LPS and PMA induced cytotoxicity. Treatment with LPS and PMA induced caspase 3 activation follewed by chromosomal condensation, and fragmentation of nuclei in C6 glial cells. SNP pretreatment before exposure to LPS and PMA supressed caspase 3 activation and inhibited chromosomal condensation and fragmentation of nuclei. From these above results, it is suggest that the protective effects of SNP pretreatment against LPS and PMA induced cytotoxicity may be mediated by inhibiting the expression of iNOS via regulating NF-kB activation.