Inhibition of macrophage nitric oxide production by tetrahydrocannabinol in vivo and in vitro

Delta(9)-Tetrahydrocannabinol (THC, 10 mu g) was administered intraperitoneally to thioglycollate-treated mice. After 18 h, peritoneal macrophages were harvested and nitric oxide (NO .) production was induced by lipopolysaccharide (LPS, 1 mu g/ml) and interferon-gamma (IFN-gamma, 0.1-10 U/ml). Macrophages from THC-treated mice produced about half as much NO . as controls. THC (1 mu g/ml) added in vitro caused further inhibition. Greater inhibition was observed at the lower (0.1-0.3 U/ml) IFN-gamma concentrations. The results suggest that the use of THC can reduce NO . production and thereby affect host defense mechanisms, inflammation and autoimmune responses. (C) 1997 International Society for Immunopharmacology.