Selective cannabinoid CB1 receptor-mediated inhibition of inducible nitric oxide synthase protein expression in C6 rat glioma cells

We have studied the effects of two cannabinoid receptor agonists, WIN 55,212-2 and cannabinol, on nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression in the C6 glioma cell line. After 24 h of lipopolysaccharide (LPS) (1 mug/mL) and interferon-gamma (IFN-gamma) (300 U/mL) stimulation, a significant increase in NO production, evaluated as nitrite, was observed in the culture medium. WIN 55,212-2 (0.1 -10000 nm) and cannabinol (0.3-30000 nm), dose-dependently inhibited nitrite production showing a different potency (WIN 55,212-2 EC50: 4.2 nm; cannabinol EC50: 700 nm). WIN 55,212-2 (100 nm), given concomitantly to the stimulus also inhibited NOS expression but had no effect when added to the cells 2 h after LPS/IFN-gamma, indicating a possible interference at the protein synthesis level or at an earlier step, as gene transcription. The cannabinoid CB1 receptor antagonist, SR141716A (0.1-100 nm), but not the cannabinoid CB2 receptor antagonist, SR144528 (0.1-100 nm), reduced in a dose-related manner WIN 55,212-2-and cannabinol-induced inhibition of nitrite production. SR141161A also reversed the WIN 55,212-2-induced inhibition of NOS expression. These data suggest that selective cannabinoid CB1 receptor activation, by inhibiting NOS expression and NO overproduction in glial cells, might be helpful in NO-mediated inflammation leading to neurodegeneration.