“Inhibition of monoacylglycerol lipase (MAGL), the primary enzyme that hydrolyzes the endocannabinoid 2-arachidonoylglycerol (2-AG) in the brain, produces profound anti-inflammatory and neuroprotective effects and improves synaptic and cognitive functions in animal models of Alzheimer’s disease (AD). However, the molecular mechanisms underlying the beneficial effects produced by inhibition of 2-AG metabolism are still not clear.
The cannabinoid receptor type 2 (CB2R) has been thought to be a therapeutic target for AD. Here, we provide evidence, however, that CB2R does not play a role in ameliorating AD neuropathology produced by inactivation of MAGL in 5XFAD APP transgenic mice, an animal model of AD.
Our results suggest that CB2R is not required in ameliorating neuropathology and preventing cognitive decline by inhibition of 2-AG metabolism in AD model animals.”
“The main pathological feature of Parkinson’s disease (PD) is the loss of dopaminergic neurons in the substantia nigra. In this study, we investigated the role of cannabinoid receptor 2 (CB2R) agonist AM1241 on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity in a mouse model of PD. Upon treatment with AM1241, the decreased CB2R level in the PD mouse brain was reversed and the behavior score markedly elevated, accompanied with a dose-dependent increase of dopamine and serotonin. In addition, western blot assay and immunostaining results suggested that AM1241 significantly activated PI3K/Akt/MEK phosphorylation and increased the expression of Parkin and PINK1, both in the substantia nigra and hippocampus. The mRNA expression analysis further demonstrated that AM1241 increased expression of the CB2R and activated Parkin/PINK1 signaling pathways. Furthermore, the increased number of TH-positive cells in the substantia nigra indicated that AM1241 regenerated DA neurons in PD mice, and could therefore be a potential candidate for PD treatment. The clear co-localization of CB2R and DA neurons suggested that AM1241 targeted CB2R, thus also identifying a novel target for PD treatment. In conclusion, the selective CB2 agonist AM1241 has a significant therapeutic effect on PD mice and resulted in regeneration of DA neurons following MPTP-induced neurotoxicity. The possible mechanisms underlying the neurogenesis effect of AM1241 might be the induction of CB2R expression and an increase in phosphorylation of the PI3K/AKT signaling pathway.”
“In the era of combined antiretroviral therapy (cART), human immunodeficiency virus type 1 (HIV-1) is considered a chronic disease that specifically targets the brain and causes HIV-1-associated neurocognitive disorders (HAND). Endocannabinoids (eCBs) elicit neuroprotective and anti-inflammatory actions in several central nervous system (CNS) disease models, but their effects in HAND remain unknown. HIV-1 does not infect neurons, but produces viral toxins, such as transactivator of transcription (Tat), that disrupt neuronal calcium equilibrium and give rise to synaptodendritic injuries and cell death, the former being highly correlated with HAND. Consequently, we tested whether the eCBs N-arachidonoyl ethanolamine (anandamide/AEA) and 2-arachidonoyl-glycerol (2-AG) offer neuroprotective actions in a neuronal culture model. Specifically, we examined the neuroprotective actions of these eCBs on Tat excitotoxicity in primary cultures of prefrontal cortex neurons (PFC), and whether cannabinoid receptors mediate this neuroprotection. Tat-induced excitotoxicity was reflected by increased intracellular calcium levels, synaptodendritic damage, neuronal excitability, and neuronal death. Further, upregulation of cannabinoid 1 receptor (CB1R) protein levels was noted in the presence of HIV-1 Tat. The direct application of AEA and 2-AG reduced excitotoxic levels of intracellular calcium and promoted neuronal survival following Tat exposure, which was prevented by the CB1R antagonist rimonabant, but not by the CB2R antagonist AM630. Overall, our findings indicate that eCBs protect PFC neurons from Tat excitotoxicity in vitro via a CB1R-related mechanism. Thus, the eCB system possesses promising targets for treatment of neurodegenerative disorders associated with HIV-1 infection.”
“Parkinson’s disease (PD) is one of the most common neurodegenerative disorders and is characterized by the loss of dopaminergic neurons in the substantia nigra (SN). Although the causes of PD are not understood, evidence suggests that its pathogenesis is associated with oxidative stress and inflammation. Recent studies have suggested a protective role of the cannabinoid signalling system in PD. β-caryophyllene (BCP) is a natural bicyclic sesquiterpene that is an agonist of the cannabinoid type 2 receptor (CB2R). Previous studies have suggested that BCP exerts prophylactic and/or curative effects against inflammatory bowel disease through its antioxidative and/or anti-inflammatory action. The present study describes the neuroprotective effects of BCP in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced murine model of PD, and we report the results of our investigation of its neuroprotective mechanism in neurons and glial cells. In the murine model, BCP pretreatment ameliorated motor dysfunction, protected against dopaminergic neuronal losses in the SN and striatum, and alleviated MPTP-induced glia activation. Additionally, BCP inhibited the levels of inflammatory cytokines in the nigrostriatal system. The observed neuroprotection and inhibited glia activation were reversed upon treatment with the CB2R selective antagonist AM630, confirming the involvement of the CB2R. These results indicate that BCP acts via multiple neuroprotective mechanisms in our murine model and suggest that BCP may be viewed as a potential treatment and/or preventative agent for PD.” https://www.ncbi.nlm.nih.gov/pubmed/28684694
“Most neurodegenerative disorders (NDDs) are characterized by cognitive impairment and other neurological defects. The definite cause of and pathways underlying the progression of these NDDs are not well defined. Several mechanisms have been proposed to contribute to the development of NDDs. These mechanisms may proceed concurrently or successively, and they differ among cell types at different developmental stages in distinct brain regions. The endocannabinoid system, which involves cannabinoid receptors type 1 (CB1R) and type 2 (CB2R), endogenous cannabinoids and the enzymes that catabolize these compounds, has been shown to contribute to the development of NDDs in several animal models and human studies. In this review, we discuss the functions of the endocannabinoid (EC) system in NDDs and converse the therapeutic efficacy of targeting the endocannabinoid system to rescue NDDs.”
“Glioblastoma (GBM) is the most common primary malignant brain tumor in adults. The challenging problem in cancer treatment is to find a way to upregulate radiosensitivity of GBM while protecting neurons and neural stem/progenitor cells in the brain. The goal of the present study was upregulation of the cytotoxic effect of γ-irradiation in GBM by non-psychotropic and non-toxic cannabinoid, cannabidiol (CBD).
We emphasized three main aspects of signaling mechanisms induced by CBD treatment (alone or in combination with γ-irradiation) in human GBM that govern cell death: 1) CBD significantly upregulated the active (phosphorylated) JNK1/2 and MAPK p38 levels with the subsequent downregulation of the active phospho-ERK1/2 and phospho-AKT1 levels. MAPK p38 was one of the main drivers of CBD-induced cell death, while death levels after combined treatment of CBD and radiation were dependent on both MAPK p38 and JNK. Both MAPK p38 and JNK regulate the endogenous TRAIL expression. 2) NF-κB p65-P(Ser536) was not the main target of CBD treatment and this transcription factor was found at high levels in CBD-treated GBM cells. Additional suppression of p65-P(Ser536) levels using specific small molecule inhibitors significantly increased CBD-induced apoptosis. 3) CBD treatment substantially upregulated TNF/TNFR1 and TRAIL/TRAIL-R2 signaling by modulation of both ligand and receptor levels followed by apoptosis.
Our results demonstrate that radiation-induced death in GBM could be enhanced by CBD-mediated signaling in concert with its marginal effects for neural stem/progenitor cells and astrocytes. It will allow selecting efficient targets for sensitization of GBM and overcoming cancer therapy-induced severe adverse sequelae.”
“Beneficial effects of cannabidiol (CBD) have been described for a wide range of psychiatric disorders, including anxiety, psychosis, and depression. The mechanisms responsible for these effects, however, are still poorly understood. Similar to clinical antidepressant or atypical antipsychotic drugs, recent findings clearly indicate that CBD, either acutely or repeatedly administered, induces plastic changes. For example, CBD attenuates the decrease in hippocampal neurogenesis and dendrite spines density induced by chronic stress and prevents microglia activation and the decrease in the number of parvalbumin-positive GABA neurons in a pharmacological model of schizophrenia. More recently, it was found that CBD modulates cell fate regulatory pathways such as autophagy and others critical pathways for neuronal survival in neurodegenerative experimental models, suggesting the potential benefit of CBD treatment for psychiatric/cognitive symptoms associated with neurodegeneration. These changes and their possible association with CBD beneficial effects in psychiatric disorders are reviewed here.”
“Redox imbalance may lead to overproduction of reactive oxygen and nitrogen species (ROS/RNS) and subsequent oxidative tissue damage which is a critical event in the course of neurodegenerative diseases. It is still not fully elucidated, however, whether oxidative stress is the primary trigger or a consequence in process of neurodegeneration.
Recent Advances: Increasing evidence suggests that oxidative stress is involved in the propagation of neuronal injury and consequent inflammatory response, which in concert promote development of pathological alterations characteristic of most common neurodegenerative diseases.
Critical Issue: Accumulating recent evidence also suggests that there is an important interplay between the lipid endocannabinoid system (ECS; comprising of the main cannabinoid 1 and 2 receptors (CB1 and CB2), endocannabinoids and their synthetic and metabolizing enzymes) and various key inflammatory and redox-dependent processes.
Targeting the ECS in order to modulate redox state-dependent cell death, and to decrease consequent or preceding inflammatory response holds therapeutic potential in multitude of oxidative stress-related acute or chronic neurodegenerative disorders from stroke and traumatic brain injury to Alzheimer`s and Parkinson`s diseases, and multiple sclerosis, just to name a few, which will be discussed in this overview.”
“It has been suggested that the endocannabinoid system elicits neuroprotection against excitotoxic brain damage.
In the present study the therapeutic potential of AM 404 on ischaemia-induced neuronal injury was investigated in vivo and compared with that of the classical cannabinoid receptor type 1 (CB1) agonist, Δ9-tetraydrocannabinol (THC), using a model of transient global cerebral ischaemia in the gerbil.
Our findings demonstrate that AM 404 and THC reduce neuronal damage caused by bilateral carotid occlusion in gerbils and that this protection is mediated through an interaction with CB1 and opioid receptors.
Endocannabinoids might form the basis for the development of new neuroprotective drugs useful for the treatment of stroke and other neurodegenerative pathologies.
There is some evidence from experiments with mice that increasing anandamide or 2-arachidonoyl glycerol content may lead to neuroprotection.
Collectively, our data demonstrate that AM 404 and THC protect against neuronal ischaemia-induced injury through a mechanism involving cannabinoid and opioid receptors but not vanilloid receptors.”
“The cannabinoid receptors subtype 2 (CB2R) are emerging as novel targets for the development of new therapeutic approaches and PET probes useful to early diagnose neuroinflammation as first step in several neurodegenerative disorders such as Alzheimer’s disease (AD) and Parkinson disease (PD).
This Research Topic is mainly focused on the involvment of CB2R in neurodegenerative disorders and on the usefulness of CB2R ligands in the therapy and early diagnosis of neuroinflammation as onset of neurodegeneration.
In the reviews of Aso and Ferrer and Cassano et al. an interesting and exaustive overview of the endogenous cannabinoid signaling and its role in neuroinflammation and neurogenesis is reported. The potential of CB2R as therapeutic target in AD is argued by several evidences derived by robust experimental models and the effects modulated by CB2R agonists on different pathways involved in the pathogenesis of AD are discussed; indeed, these ligands are able to reduce inflammation, Aβ production and deposition, tau protein hyper-phosphorylation and oxidative stress damage caused by Aβ peptides. CB2R agonists are also able to induce Aβ clearance leading to cognitive improvement in AD models.
In conclusion, considering that neuroinflammation has been widely reported as indicator and modulator of neurodegeneration, the reduction of the neuroinflammatory responses could be considered as a new therapeutic strategy in these diseases. Moreover, the selective CB2R overexpression on the activated-microglial cells provides also a highly specialized target useful to an early diagnosis of the neurodegenerative diseases.”