2-Arachidonoylglycerol elicits neuroprotective effects on excitotoxically lesioned dentate gyrus granule cells via abnormal-cannabidiol-sensitive receptors on microglial cells.
Endocannabinoids like 2-arachidonoylglycerol (2-AG) exert neuroprotective effects after brain injuries. According to current concepts, these neuroprotective effects are due to interactions between 2-AG and cannabinoid (CB)1 receptors on neurons. Moreover, 2-AG modulates migration and proliferation of microglial cells which are rapidly activated after brain lesion. This effect is mediated via CB2- and abnormal-cannabidiol (abn-CBD)-sensitive receptors. In the present study, we investigated whether the abn-CBD-sensitive receptor on microglial cells contributes to 2-AG-mediated neuroprotection in organotypic hippocampal slice cultures (OHSCs) after excitotoxic lesion induced by NMDA (50 microM) application for 4 h. This lesion caused neuronal damage and accumulation of microglial cells within the granule cell layer. To analyze the role of abn-CBD-sensitive receptors for neuroprotection and microglial cell accumulation, two agonists of the abn-CBD-sensitive receptor, abn-CBD or 2-AG, two antagonists, 1,3-dimethoxy-5-methyl-2-[(1R,6R)-3-methyl-6-(1-methylethenyl)-2-cyclohexen1-yl]-benzene (O-1918) or cannabidiol (CBD), and the CB1 receptor antagonist AM251, were applied to NMDA-lesioned OHSC. Propidium iodide (PI) labeling was used as a marker of degenerating neurons and isolectin B(4) (IB(4)) as a marker of microglial cells. Application of both, abn-CBD or 2-AG to lesioned OHSC significantly decreased the number of IB(4)(+) microglial cells and PI(+) neurons in the dentate gyrus. In contrast to AM251, application of O-1918 or CBD antagonized these effects. When microglial cells were depleted by preincubation of OHSC with the bisphosphonate clodronate (100 microg/mL) for 5 days before excitotoxic lesion, 2-AG and abn-CBD lost their neuroprotective effects. We therefore propose that the endocannabinoid 2-AG exerts its neuroprotective effects via activation of abn-CBD-sensitive receptors on microglial cells.
Dr. Senckenbergische Anatomie, Institut für Anatomie II, J. W. Goethe-Universität, Frankfurt am Main, Germany.
Susanne
S
Kreutz
Marco
M
Koch
Charlotte
C
Böttger
Chalid
C
Ghadban
Horst-Werner
HW
Korf
Faramarz
F
Dehghani
D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology*; D063386:Cannabinoid Receptor Agonists; D063387:Cannabinoid Receptor Antagonists; D016923:Cell Death / Q000187:drug effects; D018891:Dentate Gyrus / Q000166:cytology*; D004305:Dose-Response Relationship, Drug; D063388:Endocannabinoids; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity*; D005989:Glycerides / Q000494:pharmacology*; D037102:Lectins / Q000378:metabolism; D017628:Microglia / Q000378:metabolism*; D018613:Microscopy, Confocal / Q000379:methods; D016202:N-Methylaspartate / Q000633:toxicity*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D043882:Receptors, Cannabinoid / Q000502:physiology*
D001095:Arachidonic Acids; D063386:Cannabinoid Receptor Agonists; D063387:Cannabinoid Receptor Antagonists; D063388:Endocannabinoids; D018690:Excitatory Amino Acid Agonists; D005989:Glycerides; D037102:Lectins; D018696:Neuroprotective Agents; D043882:Receptors, Cannabinoid; D016202:N-Methylaspartate; C094503:glyceryl 2-arachidonate