ABSTRACT
Title
Studies on the toxic and neuroprotective effects of cannabinoids in models of cerebral ischemia
Authors
E. Landucci, E. Gerace, T. Scartabelli, F. Moroni and D.E. Pellegrini-Giampietro
Dept. of Preclinical Clinical Pharmacology, University of Florence, Florence.
Dept. of Preclinical Clinical Pharmacology, University of Florence, Florence.
Abstract
Cannabinoids (CBs) are implicated in a number of physiological and pathological mechanisms in the central nervous system, but their exact role in post-ischemic brain injury is unclear [1,2].The toxic and neuroprotective effects of synthetic and endogenous CBs were evaluated in rat organotypic hippocampal slices exposed to 20 min oxygen-glucose deprivation (OGD) and in gerbils subjected to bilateral carotid occlusion for 5 min [3].When present in the incubation medium, the synthetic CB agonists WIN 55212-2 and CP 55940 (1-30 µM)and the CB1 agonist ACEA exacerbated CA1 injury induced by OGD, whereas the CB1 receptor antagonists AM 251 and LY 320135 were neuroprotective with maximal activity at 1 µM. AM 251 (at 3 mg/kg, i.p.) also attenuated CA1 pyramidal cell death in gerbils in vivo. The endocannabinoid 2-arachidonoylglycerol (2-AG) reduced OGD injury in hippocampal slices at 0.1-1 µM, whereas anandamide (AEA) was neurotoxic at the same concentrations. The effects of WIN 55212-2, AEA and 2-AG in slices were all dependent on the activation of CB1 but not CB2 receptors, except for the toxic effects of AEA that were also dependent on vanilloid TRPV1 receptors. To evaluate the expression of CB1 receptors after OGD, we first carried out western blotting experiments using anti-CB1 antibodies. Our results show a reduction in CB1 receptor expression that was maximal 24 h after the insult, as compared to control hippocampal slices. Immunocytochemistry experiments revealed that OGD downregulated the expression of CB1 receptors in most interneurons, damaging the network of CB1-positive processes. We then determined the CA1 contents of AEA and 2-AG in control and OGD-treated hippocampal slices by LC-MS/MS. AEA, and to a lesser extent 2-AG, increased significantly immediately after OGD and returned to basal levels 3 h later. Our results suggest that exogenous administration of CB1 agonists and the production of endocannabinoids “on demand” may produce different, if not opposite, effects on the fate of neurons following cerebral ischemia.
[1] Pellegrini-Giampietro et al. (2009). The endocannabinoid system in the mechanisms of post-ischemic neuronal death. FEBS Journal 276, 2-12.
[2] van der Stelt and Di Marzo (2005). Cannabinoid receptors and their role in neuroprotection. Neuromolecular Medicine 7, 37-50
[3] Pellegrini-Giampietro et al. (1999). 1-Aminoindan-1,5-dicarboxylic acid and (S)-(+)-2-(3'-carboxybicyclo [1.1.1]pentyl)-glycine, two mGlu1 receptor-preferring antagonists, reduce neuronal death in in vitro and in vivo models of cerebral ischemia. European Journal of Neuroscience 11,3637-3647.
[1] Pellegrini-Giampietro et al. (2009). The endocannabinoid system in the mechanisms of post-ischemic neuronal death. FEBS Journal 276, 2-12.
[2] van der Stelt and Di Marzo (2005). Cannabinoid receptors and their role in neuroprotection. Neuromolecular Medicine 7, 37-50
[3] Pellegrini-Giampietro et al. (1999). 1-Aminoindan-1,5-dicarboxylic acid and (S)-(+)-2-(3'-carboxybicyclo [1.1.1]pentyl)-glycine, two mGlu1 receptor-preferring antagonists, reduce neuronal death in in vitro and in vivo models of cerebral ischemia. European Journal of Neuroscience 11,3637-3647.