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 µg/mL) and interferon-γ (IFN-γ) (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 EC[sub 50]: 4.2 nm; cannabinol EC[sub 50]: 700 nm). WIN 55,212–2 (100 nm), given concomitantly to the stimulus also inhibited iNOS expression but had no effect when added to the cells 2 h after LPS/IFN-γ, indicating a possible interference at the protein synthesis level or at an earlier step, as gene transcription. The cannabinoid CB[sub 1] receptor antagonist, SR141716A (0.1–100 nm), but not the cannabinoid CB[sub 2] 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 iNOS expression. These data suggest that selective cannabinoid CB[sub 1] receptor activation, by inhibiting iNOS expression and NO overproduction in glial cells, might be helpful in NO-mediated inflammation leading to neurodegeneration. [ABSTRACT FROM AUTHOR]