CB1 receptor selective activation inhibits β-amyloid-induced Inos protein expression in C6 cells and subsequently blunts tau protein hyperphosphorylation in co-cultured neurons

Among the wide range of neuro-inflammatory signalling molecules released by beta-amyloid-stimulated astroglial cells, nitric oxide (NO) plays a fundamental role in AD aethiopathogenesis since it directly promotes neuronal tau protein hyperphosphorylation leading to neurofibrillary tangle formation. Synthetic cannabinoids (CBs), via a selective CBI receptor activation, negatively modulates both iNOS protein expression and NO production induced by pro-inflammatory stimuli. In this study we investigated the role of both the non-selective WIN 55,212-2 and the selective CB I receptor agonist, ACEA, on: (i) NO production, (ii) iNOS protein expression in (1-42) beta-amyloid peptide (A beta)-stimulated C6 rat glioma cells and (iii) tau protein hyperphosphorylation in co-cultured differentiated PC 12 neurons. Our results demonstrated that synthetic CBs, by a selective CB 1 effect, down-regulate iNOS protein expression and NO production in A beta-stimulated C6 cells. This effect leads, in turn, to a significant and concentration-dependent inhibition of NO-dependent tau protein hyperphosphorylation in co-cultured PC 12 neurons. The results of the present study extend our knowledge about the neuroprotective actions of synthetic CBs on A beta-dependent neurotoxicity in vitro. Furthermore, our study allows us to identify, in the CB 1-mediated inhibition of astroglial-derived NO, a new potential target to blunt tau hyperphosphorylation and the consequent related tauopathy in AD. (c) 2006 Elsevier Ireland Ltd. All rights reserved.