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 putat ive cannabinoid CB2-like receptor Ligand, palmitoylethanolamide. (R)-(+)-[2 ,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo-[ 1,2,3-de]-1,4-benzoxaz in-6-yl]-1-naphthalenylmethanone mesylate ((+)-WIN55212) and, to a lesser e xtent (-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxy -propyl)cyclohexan-1-ol (CP55940), significantly inhibited lipopolysacchari de stimulated nitric oxide production. The level of inhibition was found to be dependent on the concentration of lipopolysaccharide used to induce nit ric oxide production. Palmitoylethanolamide significantly inhibited nitric oxide production induced by lipopolysaccharide. The inhibition of nitric ox ide production by (+)-WIN55212 but not palmitoylethanolamide was significan tly 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-met hylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528). (+)-WIN552 12 produced a pertussis toxin-sensitive parallel rightward shift in the log concentration-response curve for lipopolysaccharide, causing a fivefold in crease 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 s hift in the lipopolysaccharide concentration-response curve. However, it di d produce a pertussis toxin-insensitive reduction in the E-max value. The r esults suggest that the inhibition of lipopolysaccharide mediated nitric ox ide release by(+)-WIN55212 in murine macrophages is mediated by cannabinoid CB2 receptors. In contrast, the inhibition by palmitoylethanolamide does n ot appear to be mediated by cannabinoid receptors. (C) 2000 Elsevier Scienc e B.V. All rights reserved.