Molecular Mechanisms of Cannabinoid Protection from Neuronal Excitotoxicity (original) (raw)
Related papers
Journal of Neurochemistry, 2002
The ability of cannabinoid CB 1 receptors to influence glutamatergic excitatory neurotransmission has fueled interest in how these receptors and their endogenous ligands may interact in conditions of excitotoxic insults. The present study characterized the impact of stimulated and inhibited CB 1 receptor function on NMDA-induced excitotoxicity. Neonatal (6-day-old) rat pups received a systemic injection of a mixed CB 1 /CB 2 receptor agonist (WIN55,212-2) or their respective antagonists (SR141716A for CB 1 and SR144528 for CB 2 ) prior to an unilateral intrastriatal microinjection of NMDA. The NMDA-induced excitotoxic damage in the ipsilateral forebrain was not influenced by agonist-stimulated CB 1 receptor function. In contrast, blockade of CB 1 , but not CB 2 , receptor activity evoked a robust neuroprotective response by reducing the infarct area and the number of cortical degenerating neurons. These results suggest a critical involvement of CB 1 receptor tonus on neuronal survival following NMDA receptorinduced excitotoxicity in vivo. Abbreviations used: CB 1 receptor, cannabinoid receptor subtype 1; CB 2 receptor, cannabinoid receptor subtype 2; GFAP, glial fibrilary acidic protein; KPBS, potassium phosphate-buffered saline; PBS, phosphate-buffered saline; D 9 -THC, D 9 -tetrahydrocannabinol; TdT, terminal deoxynucleotidyltransferase; TUNEL, terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling.
Δ9-Tetrahydrocannabinol protects hippocampal neurons from excitotoxicity
2007
Excitotoxic neuronal death underlies many neurodegenerative disorders. Because cannabinoid receptor agonists act presynaptically to inhibit glutamate release, we examined the effects of Win 55212-2, a full agonist at CB 1 receptors, and Δ 9-tetrahydrocannabinol (THC), a partial agonist, on the survival of neurons exposed to an excitotoxic pattern of synaptic activity. Reducing the extracellular Mg 2+ concentration ([Mg 2+ ] o) to 0.1 mM evoked an aberrant pattern of glutamatergic activity that produced synaptically mediated death of rat hippocampal neurons in culture. Neuronal viability was quantified with a multiwell fluorescence plate scanner equipped to detect propidium iodide fluorescence. Win 55212-2 (100 nM) and THC (100 nM) significantly reduced 0.1 mM [Mg 2+ ] o-induced cell death by 77 ± 11% and 84 ± 8%, respectively. Interestingly, the protection afforded by THC was not significantly different from that produced by Win 55212-2, suggesting that attenuation without a complete block of excitatory activity is sufficient for neuroprotection. The effect of prolonged drug exposure on the neuroprotection afforded by cannabinoid receptor agonists was also studied. When cultures were pretreated for 24 h with Win 55212-2 (100 nM) or THC (100 nM), inhibition of 0.1 mM [Mg 2+ ] o-induced toxicity was significantly reduced to 39 ± 19% and 45 ± 13%, respectively. Thus, desensitization of CB 1 receptors diminishes the neuroprotective effects of cannabinoids. This study demonstrates the importance of agonist efficacy and the duration of treatment on the neuroprotective effects of cannabinoids. It will be important to consider these effects on neuronal survival when evaluating pharmacologic treatments that modulate the endocannabinoid system.
Journal of Pharmacology and Experimental Therapeutics, 2004
CB1 cannabinoid receptors (CB1Rs) are involved in protecting the brain from ischemia and related disorders. However, the underlying protective mechanisms are incompletely understood. We investigated the effect of CB1R activation on oxidative injury, which has been implicated in neuronal death after cerebral ischemia and neurodegenerative disorders, in mouse cortical neuron cultures. The CB1R agonist Win 55212-2 [R-(ϩ)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazin-yl]-(1-naphthalenyl)methanone mesylate] reduced neuronal death, measured by lactate dehydrogenase release, in cultures treated with 50 M FeCl 2 , and its protective effect was attenuated by the CB1R antagonist SR141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-cichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride]. The endocannabinoid anandamide reproduced the effect of Win 55212-2, as did the antioxidant 6-hydroxy-2,5,7,8tetramethylchroman-2-carboxylic acid (Trolox). Neuronal injury was more severe after in vitro or in vivo administration of FeCl 2 to CB1R-knockout compared with wild-type mice. Win 55212-2 reduced the formation of reactive oxidative species in cortical
Journal of neurochemistry, 2002
The ability of cannabinoid CB(1) receptors to influence glutamatergic excitatory neurotransmission has fueled interest in how these receptors and their endogenous ligands may interact in conditions of excitotoxic insults. The present study characterized the impact of stimulated and inhibited CB(1) receptor function on NMDA-induced excitotoxicity. Neonatal (6-day-old) rat pups received a systemic injection of a mixed CB(1) /CB(2) receptor agonist (WIN55,212-2) or their respective antagonists (SR141716A for CB(1) and SR144528 for CB(2) ) prior to an unilateral intrastriatal microinjection of NMDA. The NMDA-induced excitotoxic damage in the ipsilateral forebrain was not influenced by agonist-stimulated CB(1) receptor function. In contrast, blockade of CB(1), but not CB(2), receptor activity evoked a robust neuroprotective response by reducing the infarct area and the number of cortical degenerating neurons. These results suggest a critical involvement of CB(1) receptor tonus on neurona...
Modulation of the endocannabinoid system: Neuroprotection or neurotoxicity
Experimental Neurology, 2010
There is now a large volume of data indicating that compounds activating cannabinoid CB1 receptors, either directly or indirectly by preventing the breakdown of endogenous cannabinoids, can protect against neuronal damage produced by a variety of neuronal “insults”. Given that such neurodegenerative stimuli result in increased endocannabinoid levels and that animals with genetic deletions of CB1 receptors are more susceptible to the deleterious effects of such stimuli, a case can be made for an endogenous neuroprotective role of endocannabinoids. However, this is an oversimplification of the current literature, since (a) compounds released together with the endocannabinoids can contribute to the neuroprotective effect; (b) other proteins, such as TASK-1 and PPARα, are involved; (c) the CB1 receptor antagonist/inverse agonist rimonabant has also been reported to have neuroprotective properties in a number of animal models of neurodegenerative disorders. Furthermore, the CB2 receptor located on peripheral immune cells and activated microglia are potential targets for novel therapies. In terms of the clinical usefulness of targeting the endocannabinoid system for the treatment of neurodegenerative disorders, data are emerging, but important factors to be considered are windows of opportunity (for acute situations such as trauma and ischemia) and the functionality of the target receptors (for chronic neurodegenerative disorders such as Alzheimer's disease).
Journal of Pharmacology and Experimental Therapeutics, 2009
Although the activation of cannabinoid receptor-1 (CB1) receptors by cannabinoids is known to inhibit neuronal hyperexcitability and reduce excitotoxic cell death, the mechanistic links between these two actions remain elusive. We tested the hypothesis that activation of CB1 receptors inhibits N-methyl-Daspartic acid (NMDA)-mediated calcium influx and cell death via the inositol triphosphate (IP 3 ) signaling pathway in both primary dorsal root ganglia neurons and a cultured neuronal cell line (F-11 cells). These cells were pretreated with the cannabinoid agonist (R)-(ϩ)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de)-1,4-benzoxazin-6-yl]-1-napthalenylmethanone (R-(ϩ)-WIN 55,212-2; WIN) before exposure to NMDA. Concentrations of cytosolic calcium were measured with the ratiometric calcium indicator, Fura-2, and cell death was determined by a cell viability test. WIN dose-dependently attenuated both the calcium influx and cell death induced by NMDA. These effects were blocked by selective cannabinoid CB1 receptor antagonists N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carbox-
Neuroprotective Properties of Cannabinoids in Cellular and Animal Models: Hypotheses and Facts
2020
Progressive neuronal loss is a typical characteristic of neurodegenerative diseases. In Parkinson’s disease, the loss of dopaminergic neurons in the basal ganglia results in impaired mobility and flawed muscle control. The loss of cholinergic neurons largely in the basal forebrain contributes to memory and attention deficits and the overall cognitive impairment in Alzheimer’s disease. This being said, neuroprotective drugs should be expected to preserve and/or restore the functions affected by neuronal loss, and substantially prevent cell death. The endocannabinoid system, comprising lipid mediators able to bind to and activate cannabinoid receptors, has emerged as a therapeutic target of potential interest in a variety of central nervous system diseases. Palmitoylethanolamide (PEA) is one of the most important endocannabinoids, which has a key role in modulating oxidative stress and inflammatory response with neuroprotective potential in neurological disorders. Neurodegenerative di...
Molecular and Cellular Neuroscience, 2005
Cannabinoids (CBs) are neuroprotective in vivo and in vitro, but the mechanisms of their actions are unknown. The aim of this study was to elucidate the signaling pathways that mediate the protective effect of CBs on primary cultured neurons. The neurotoxin S-AMPA induced significant death of rat primary cortical neurons, which was inhibited by the CB agonist HU-210. Antagonists selective for CB 1 or CB 2 receptors (AM 281 or AM 630, respectively) reversed the neuroprotective effect of HU-210 on S-AMPA-induced cell death. HU-210 triggered activation of AKT, but not activation of the ERK1/2, JNK or p38 signaling pathways. The phosphatidylinositol 3-kinase (PI 3-K) inhibitors LY294002 and wortmannin prevented phosphorylation of AKT in response to HU-210, and reversed the neuroprotective effect of HU-210 on S-AMPA-induced excitotoxicity. Thus the PI 3-K/AKT signaling pathway mediates the neuroprotective effect of exogenous cannabinoids such as HU-210 in primary CNS neurons.
A restricted population of CB1 cannabinoid receptors with neuroprotective activity
Proceedings of the National Academy of Sciences, 2014
The CB 1 cannabinoid receptor, the main molecular target of endocannabinoids and cannabis active components, is the most abundant G protein-coupled receptor in the mammalian brain. Of note, CB 1 receptors are expressed at the synapses of two opposing (i.e., GABAergic/inhibitory and glutamatergic/excitatory) neuronal populations, so the activation of one and/or another receptor population may conceivably evoke different effects. Despite the widely reported neuroprotective activity of the CB 1 receptor in animal models, the precise pathophysiological relevance of those two CB 1 receptor pools in neurodegenerative processes is unknown. Here, we first induced excitotoxic damage in the mouse brain by (i) administering quinolinic acid to conditional mutant animals lacking CB 1 receptors selectively in GABAergic or glutamatergic neurons, and (ii) manipulating corticostriatal glutamatergic projections remotely with a designer receptor exclusively activated by designer drug pharmacogenetic approach. We next examined the alterations that occur in the R6/2 mouse, a well-established model of Huntington disease, upon (i) fully knocking out CB 1 receptors, and (ii) deleting CB 1 receptors selectively in corticostriatal glutamatergic or striatal GABAergic neurons. The data unequivocally identify the restricted population of CB 1 receptors located on glutamatergic terminals as an indispensable player in the neuroprotective activity of (endo)cannabinoids, therefore suggesting that this precise receptor pool constitutes a promising target for neuroprotective therapeutic strategies. neuroprotection | neuromodulation | excitotoxicity E ndocannabinoids are a family of neuron-communication messengers that act by engaging CB 1 cannabinoid receptors, which are also targeted by Δ 9 -tetrahydrocannabinol (THC), the main bioactive component of cannabis. Endocannabinoid signaling serves as a pivotal feedback mechanism to prevent excessive presynaptic activity, thereby tuning the functionality and plasticity of many synapses (1, 2). The CB 1 receptor is the most abundant G protein-coupled receptor in the brain, and is highly expressed in GABAergic terminals of the forebrain (particularly in cholecystokinin-positive and parvalbumin-negative interneurons) (3), where it inhibits GABA release. Functional CB 1 receptors reside as well on terminals of glutamatergic neurons in several brain regions, where they inhibit glutamate release (4). In concert with this well-established neuromodulatory function, the CB 1 receptor protects neurons in many different animal models of acute brain damage and chronic neurodegeneration, which, during recent years, has raised hope about the possible clinical use of cannabinoids as neuroprotective drugs, especially in still unexplored conditions such as Alzheimer's disease, Huntington disease (HD), amyotrophic lateral sclerosis, and stroke (5-7). However, the assessment of the physiological relevance and therapeutic potential of the CB 1 receptor in neurological diseases is hampered, at least in part, by the lack of knowledge of the neuron-population specificity of CB 1 receptor action. Here, by using various genetic models of CB 1 receptor loss of function, together with pharmacological and pharmacogenetic tools, we show that a unique population of CB 1 receptors, namely that located on glutamatergic terminals, plays an indispensable role in the neuroprotective activity of the endocannabinoid system in the mouse brain. This finding opens a new conceptual view on how the CB 1 receptor evokes neuroprotection, and provides preclinical support for improving the development of cannabinoidbased neuroprotective therapies.