Inhibition of nitric oxide production in RAW264.7 macrophages by cannabinoids and palmitoylethanolamide

We have investigated the inhibition of lipopolysaccharide stimulated nitric oxide production in RAW264.7 macrophages by the cannabinoids and the putative cannabinoid CB2-like receptor Ligand, palmitoylethanolamide. (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo-[ 1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone mesylate ((+)-WIN55212) and, to a lesser extent (-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxy-propyl)cyclohexan-1-ol (CP55940), significantly inhibited lipopolysaccharide stimulated nitric oxide production. The level of inhibition was found to be dependent on the concentration of lipopolysaccharide used to induce nitric oxide production. Palmitoylethanolamide significantly inhibited nitric oxide production induced by lipopolysaccharide. The inhibition of nitric oxide production by (+)-WIN55212 but not palmitoylethanolamide was significantly attenuated in the presence of the cannabinoid CB2 receptor antagonist, N-[(1S)-endo-1,3,3-trimethyl bicycle [2.2.1] heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528). (+)-WIN55212 produced a pertussis toxin-sensitive parallel rightward shift in the log concentration-response curve for lipopolysaccharide, causing a fivefold increase in the EC50 value for lipopolysaccharide with no change in the E-max value. (-)-WIN55212 had no effect on the log concentration-response curve for lipopolysaccharide. Palmitoylethanolamide did not produce a rightward shift in the lipopolysaccharide concentration-response curve. However, it did produce a pertussis toxin-insensitive reduction in the E-max value. The results suggest that the inhibition of lipopolysaccharide mediated nitric oxide release by(+)-WIN55212 in murine macrophages is mediated by cannabinoid CB2 receptors. In contrast, the inhibition by palmitoylethanolamide does not appear to be mediated by cannabinoid receptors. (C) 2000 Elsevier Science B.V. All rights reserved.