Endocannabinoid 2-arachidonoylglycerol protects neurons against β-amyloid insults

Exploring the diversity of cannabis cannabinoid and non-cannabinoid compounds and their roles in Alzheimer's disease: A review

Cannabis sativa is recognized for its chemical diversity and therapeutic potential, particularly in addressing neurodegenerative diseases such as Alzheimer's disease (AD). Given the complexity of AD, where single-target therapies often prove inadequate, a multi-target approach utilizing cannabis-derived compounds may offer promising alternatives. This review first highlights the chemical diversity of cannabis by categorizing its compounds into cannabinoids and non-cannabinoids. It then examines studies investigating the effects of these compounds on AD-related pathological features. By synthesizing existing knowledge, identifying research gaps, and facilitating comparative analysis, this review aims to advance future research and understanding. It underscores cannabis's potential as a multi-target therapeutic strategy for AD, contributing valuable insights to ongoing scientific discussions.

The role of cannabinoid-mediated signaling pathways and mechanisms in brain disorders

Cannabinoids play significant roles in the central nervous system (CNS), but cannabinoid-mediated physiopathological functions are not elaborated. Cannabinoid receptors (CBRs) mediate functions that include the regulation of neuroinflammation, oxidative stress, apoptosis, autophagy, and neurogenesis. Microglia are the primary immune cells responsible for mediating neuroinflammation in the CNS. Therefore, this article primarily focuses on microglia to summarize the inflammatory pathways mediated by cannabinoids in the CNS, including nuclear factor-κB (NF-κB), NOD-like receptor protein 3 (NLRP3) inflammasome, mitogen-activated protein kinase (MAPK), protein kinase B (Akt), and cAMP-dependent protein kinase (PKA) signaling pathways. Additionally, we provide a table summarizing the role of cannabinoids in various brain diseases. Medical use of cannabinoids has protective effects in preventing and treating brain diseases; however, excessive and repeated use can be detrimental to the CNS. We propose that cannabinoids hold significant potential for preventing and treating brain diseases, including ferroptosis, lactate metabolism, and mitophagy, providing new insights for further research on cannabinoids.

Cannabinoids: Role in Neurological Diseases and Psychiatric Disorders

An impact of legalization and decriminalization of marijuana is the gradual increase in the use of cannabis for recreational purposes, which poses a potential threat to society and healthcare systems worldwide. However, the discovery of receptor subtypes, endogenous endocannabinoids, and enzymes involved in synthesis and degradation, as well as pharmacological characterization of receptors, has led to exploration of the use of cannabis in multiple peripheral and central pathological conditions. The role of cannabis in the modulation of crucial events involving perturbed physiological functions and disease progression, including apoptosis, inflammation, oxidative stress, perturbed mitochondrial function, and the impaired immune system, indicates medicinal values. These events are involved in most neurological diseases and prompt the gradual progression of the disease. At present, several synthetic agonists and antagonists, in addition to more than 70 phytocannabinoids, are available with distinct efficacy as a therapeutic alternative in different pathological conditions. The present review aims to describe the use of cannabis in neurological diseases and psychiatric disorders.

Plasma Metabolomics Indicates Potential Biomarkers and Abnormal Metabolic Pathways in Female Melasma Patients

BACKGROUND

Melasma is a common and chronic pigmentary disorder with complex pathogenesis, and the relationship between melasma and metabolic syndrome remains elusive. Thus, metabolomics might contribute to the early detection of potential metabolic abnormalities in individuals with melasma.

OBJECTIVE

The present study aims to analyze changes in plasma metabolites of female melasma patients and identify disease markers as well as explore potential therapeutic targets.

METHODS

Plasma samples from 20 female patients with melasma and 21 healthy female controls that were comparable in terms of age and body mass index were collected for untargeted metabolomics investigations. Ultra-high performance liquid chromatography-mass spectrometry was used to analyze metabolites in the plasma. Metabolic pathway analyses were employed to identify significantly differentially expressed metabolites in melasma patients. Receiver operating characteristic curves were constructed, and correlation analyses were performed using the modified Melasma Area and Severity Index and oxidative stress levels.

RESULTS

In contrast to healthy subjects, melasma patients showed significant alterations in 125 plasma metabolites, including amino acids, lipids, and carbohydrate-related metabolites. KEGG pathway analysis suggested that primary pathways associated with the development of melasma include tryptophan metabolism, as well as the biosynthesis of phenylalanine, tyrosine, and tryptophan. Importantly, based on receiver operating characteristic curves and correlation analyses, several metabolites were identified as robust biomarkers for melasma.

CONCLUSION

Collectively, this study identified significant changes in plasma metabolites in melasma patients, providing new insights into the pathogenesis of melasma and opening novel therapeutic avenues.

Overabundant endocannabinoids in neurons are detrimental to cognitive function

2-Arachidonoylglycerol (2-AG) is the most prevalent endocannabinoid involved in maintaining brain homeostasis. Previous studies have demonstrated that inactivating monoacylglycerol lipase (MAGL), the primary enzyme responsible for degrading 2-AG in the brain, alleviates neuropathology and prevents synaptic and cognitive decline in animal models of neurodegenerative diseases. However, we show that selectively inhibiting 2-AG metabolism in neurons impairs cognitive function in mice. This cognitive impairment appears to result from decreased expression of synaptic proteins and synapse numbers, impaired long-term synaptic plasticity and cortical circuit functional connectivity, and diminished neurogenesis. Interestingly, the synaptic and cognitive deficits induced by neuronal MAGL inactivation can be counterbalanced by inhibiting astrocytic 2-AG metabolism. Transcriptomic analyses reveal that inhibiting neuronal 2-AG degradation leads to widespread changes in expression of genes associated with synaptic function. These findings suggest that crosstalk in 2-AG signaling between astrocytes and neurons is crucial for maintaining synaptic and cognitive functions and that excessive 2-AG in neurons alone is detrimental to cognitive function.

Dynamic endocannabinoid-mediated neuromodulation of retinal circadian circuitry

Circadian rhythms are biological rhythms that originate from the "master circadian clock," called the suprachiasmatic nucleus (SCN). SCN orchestrates the circadian rhythms using light as a chief zeitgeber, enabling humans to synchronize their daily physio-behavioral activities with the Earth's light-dark cycle. However, chronic/ irregular photic disturbances from the retina via the retinohypothalamic tract (RHT) can disrupt the amplitude and the expression of clock genes, such as the period circadian clock 2, causing circadian rhythm disruption (CRd) and associated neuropathologies. The present review discusses neuromodulation across the RHT originating from retinal photic inputs and modulation offered by endocannabinoids as a function of mitigation of the CRd and associated neuro-dysfunction. Literature indicates that cannabinoid agonists alleviate the SCN's ability to get entrained to light by modulating the activity of its chief neurotransmitter, i.e., γ-aminobutyric acid, thus preventing light-induced disruption of activity rhythms in laboratory animals. In the retina, endocannabinoid signaling modulates the overall gain of the retinal ganglion cells by regulating the membrane currents (Ca2+, K+, and Cl- channels) and glutamatergic neurotransmission of photoreceptors and bipolar cells. Additionally, endocannabinoids signalling also regulate the high-voltage-activated Ca2+ channels to mitigate the retinal ganglion cells and intrinsically photosensitive retinal ganglion cells-mediated glutamate release in the SCN, thus regulating the RHT-mediated light stimulation of SCN neurons to prevent excitotoxicity. As per the literature, cannabinoid receptors 1 and 2 are becoming newer targets in drug discovery paradigms, and the involvement of endocannabinoids in light-induced CRd through the RHT may possibly mitigate severe neuropathologies.

Monoacylglycerol Lipase Inhibition Prevents Short-Term Mitochondrial Dysfunction and Oxidative Damage in Rat Brain Synaptosomal/Mitochondrial Fractions and Cortical Slices: Role of Cannabinoid Receptors

Inhibition of enzymes responsible for endocannabinoid hydrolysis represents an invaluable emerging tool for the potential treatment of neurodegenerative disorders. Monoacylglycerol lipase (MAGL) is the enzyme responsible for degrading 2-arachydonoylglycerol (2-AG), the most abundant endocannabinoid in the central nervous system (CNS). Here, we tested the effects of the selective MAGL inhibitor JZL184 on the 3-nitropropinic acid (3-NP)-induced short-term loss of mitochondrial reductive capacity/viability and oxidative damage in rat brain synaptosomal/mitochondrial fractions and cortical slices. In synaptosomes, while 3-NP decreased mitochondrial function and increased lipid peroxidation, JZL184 attenuated both markers. The protective effects evoked by JZL184 on the 3-NP-induced mitochondrial dysfunction were primarily mediated by activation of cannabinoid receptor 2 (CB2R), as evidenced by their inhibition by the selective CB2R inverse agonist JTE907. The cannabinoid receptor 1 (CB1R) also participated in this effect in a lesser extent, as evidenced by the CB1R antagonist/inverse agonist AM281. In contrast, activation of CB1R, but not CB2R, was responsible for the protective effects of JZL184 on the 3-NP-iduced lipid peroxidation. Protective effects of JZL184 were confirmed in other toxic models involving excitotoxicity and oxidative damage as internal controls. In cortical slices, JZL184 ameliorated the 3-NP-induced loss of mitochondrial function, the increase in lipid peroxidation, and the inhibition of succinate dehydrogenase (mitochondrial complex II) activity, and these effects were independent on CB1R and CB2R, as evidenced by the lack of effects of AM281 and JTE907, respectively. Our novel results provide experimental evidence that the differential protective effects exerted by JZL184 on the early toxic effects induced by 3-NP in brain synaptosomes and cortical slices involve MAGL inhibition, and possibly the subsequent accumulation of 2-AG. These effects involve pro-energetic and redox modulatory mechanisms that may be either dependent or independent of cannabinoid receptors' activation.

Astrocytes in Parkinson's Disease: From Role to Possible Intervention

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons. While neuronal dysfunction is central to PD, astrocytes also play important roles, both positive and negative, and such roles have not yet been fully explored. This literature review serves to highlight these roles and how the properties of astrocytes can be used to increase neuron survivability. Astrocytes normally have protective functions, such as releasing neurotrophic factors, metabolizing glutamate, transferring healthy mitochondria to neurons, or maintaining the blood-brain barrier. However, in PD, astrocytes can become dysfunctional and contribute to neurotoxicity, e.g., via impaired glutamate metabolism or the release of inflammatory cytokines. Therefore, astrocytes represent a double-edged sword. Restoring healthy astrocyte function and increasing the beneficial effects of astrocytes represents a promising therapeutic approach. Strategies such as promoting neurotrophin release, preventing harmful astrocyte reactivity, or utilizing regional astrocyte diversity may help restore neuroprotection.

G protein-coupled receptors in neurodegenerative diseases and psychiatric disorders

Neuropsychiatric disorders are multifactorial disorders with diverse aetiological factors. Identifying treatment targets is challenging because the diseases are resulting from heterogeneous biological, genetic, and environmental factors. Nevertheless, the increasing understanding of G protein-coupled receptor (GPCR) opens a new possibility in drug discovery. Harnessing our knowledge of molecular mechanisms and structural information of GPCRs will be advantageous for developing effective drugs. This review provides an overview of the role of GPCRs in various neurodegenerative and psychiatric diseases. Besides, we highlight the emerging opportunities of novel GPCR targets and address recent progress in GPCR drug development.

Inhibiting degradation of 2-arachidonoylglycerol as a therapeutic strategy for neurodegenerative diseases

Endocannabinoids are endogenous lipid signaling mediators that participate in a variety of physiological and pathological processes. 2-Arachidonoylglycerol (2-AG) is the most abundant endocannabinoid and is a full agonist of G-protein-coupled cannabinoid receptors (CB1R and CB2R), which are targets of Δ⁹-tetrahydrocannabinol (Δ⁹-THC), the main psychoactive ingredient in cannabis. While 2-AG has been well recognized as a retrograde messenger modulating synaptic transmission and plasticity at both inhibitory GABAergic and excitatory glutamatergic synapses in the brain, growing evidence suggests that 2-AG also functions as an endogenous terminator of neuroinflammation in response to harmful insults, thus maintaining brain homeostasis. Monoacylglycerol lipase (MAGL) is the key enzyme that degrades 2-AG in the brain. The immediate metabolite of 2-AG is arachidonic acid (AA), a precursor of prostaglandins (PGs) and leukotrienes. Several lines of evidence indicate that pharmacological or genetic inactivation of MAGL, which boosts 2-AG levels and reduces its hydrolytic metabolites, resolves neuroinflammation, mitigates neuropathology, and improves synaptic and cognitive functions in animal models of neurodegenerative diseases, including Alzheimer's disease (AD), multiple sclerosis (MS), Parkinson's disease (PD), and traumatic brain injury (TBI)-induced neurodegenerative disease. Thus, it has been proposed that MAGL is a potential therapeutic target for treatment of neurodegenerative diseases. As the main enzyme hydrolyzing 2-AG, several MAGL inhibitors have been identified and developed. However, our understanding of the mechanisms by which inactivation of MAGL produces neuroprotective effects in neurodegenerative diseases remains limited. A recent finding that inhibition of 2-AG metabolism in astrocytes, but not in neurons, protects the brain from TBI-induced neuropathology might shed some light on this unsolved issue. This review provides an overview of MAGL as a potential therapeutic target for neurodegenerative diseases and discusses possible mechanisms underlying the neuroprotective effects of restraining degradation of 2-AG in the brain.

Augmentation of 2-arachidonoylglycerol signaling in astrocytes maintains synaptic functionality by regulation of miRNA-30b

2-Arachidonoylglycerol (2-AG), the most abundant endocannabinoid, displays anti-inflammatory and neuroprotective properties. Inhibition of 2-AG degradation by inactivation of monoacylglycerol lipase (MAGL), a key enzyme degrading 2-AG in the brain, alleviates neuropathology and improves synaptic and cognitive functions in animal models of neurodegenerative diseases. In particular, global inactivation of MAGL by genetic deletion of mgll enhances hippocampal long-term potentiation (LTP) and hippocampus-dependent learning and memory. However, our understanding of the molecular mechanisms by which chronic inactivation of MAGL enhances synaptic activity is still limited. Here, we provide evidence that pharmacological inactivation of MAGL suppresses hippocampal expression of miR-30b, a small non-coding microRNA, and upregulates expression of its targets, including ephrin type-B receptor 2 (ephB2), sirtuin1 (sirt1), and glutamate ionotropic receptor AMPA type subunit 2 (GluA2). Importantly, suppression of miR-30b and increase of its targets by inactivation of MAGL result primarily from inhibition of 2-AG metabolism in astrocytes, rather than in neurons. Inactivation of MAGL in astrocytes prevents miR-30b overexpression-induced impairments in synaptic transmission and long-term potentiation (LTP) in the hippocampus. Suppression of miR-30b expression by inactivation of MAGL is apparently associated with augmentation of 2-AG signaling, as 2-AG induces a dose-dependent decrease in expression of miR-30b. 2-AG- or MAGL inactivation-suppressed expression of miR-30b is not mediated via CB1R, but by peroxisome proliferator-activated receptor γ (PPARγ). This is further supported by the results showing that MAGL inactivation-induced downregulation of miR-30b and upregulation of its targets are attenuated by antagonism of PPARγ, but mimicked by PPARγ agonists. In addition, we observed that 2-AG-induced reduction of miR-30b expression is mediated via NF-kB signaling. Our study provides evidence that 2-AG signaling in astrocytes plays an important role in maintaining the functional integrity of synapses in the hippocampus by regulation of miR-30b expression.

Chronic exposure to a synthetic cannabinoid alters cerebral brain metabolism and causes long-lasting behavioral deficits in adult mice

In recent years, there has been growing evidence that cannabinoids have promising medicinal and pharmacological effects. However, the growing interest in medical cannabis highlights the need to better understand brain alterations linking phytocannabinoids or synthetic cannabinoids to clinical and behavioral phenotypes. Therefore, the aim of this study was to investigate the effects of long-term WIN 55,212-2 treatment-with and without prolonged abstinence-on cerebral metabolism and memory function in healthy wildtype mice. Adult C57BI/6J mice were divided into two treatment groups to study the acute effects of WIN 55,212-2 treatment as well the effects of WIN 55,212-2 treatment after an extended washout phase. We could demonstrate that 3 mg/kg WIN 55,212-2 treatment in early adulthood leads to a hypometabolism in several brain regions including the hippocampus, cerebellum, amygdala and midbrain, even after prolonged abstinence. Furthermore, prolonged acute WIN 55,212-2 treatment in 6-months-old mice reduced the glucose metabolism in the hippocampus and midbrain. In addition, Win 55,212-2 treatment during adulthood lead to spatial memory and recognition memory deficits without affecting anxiety behavior. Overall we could demonstrate that treatment with the synthetic CB1/CB2 receptor aganist Win 55,212-2 during adulthood causes persistent memory deficits, especially when mice were treated in early adulthood. Our findings highlight the risks of prolonged WIN 55,212-2 use and provide new insights into the mechanisms underlying the effects of chronic cannabinoid exposure on the brain and behavior.

Inhibition of 2-arachidonoylglycerol degradation enhances glial immunity by single-cell transcriptomic analysis

BACKGROUND

2-Arachidonoylglycerol (2-AG) is the most abundant endogenous cannabinoid. Inhibition of 2-AG metabolism by inactivation of monoacylglycerol lipase (MAGL), the primary enzyme that degrades 2-AG in the brain, produces anti-inflammatory and neuroprotective effects in neurodegenerative diseases. However, the molecular mechanisms underlying these beneficial effects are largely unclear.

METHODS

Hippocampal and cortical cells were isolated from cell type-specific MAGL knockout (KO) mice. Single-cell RNA sequencing was performed by 10 × Genomics platform. Cell Ranger, Seurat (v3.2) and CellChat (1.1.3) packages were used to carry out data analysis.

RESULTS

Using single-cell RNA sequencing analysis, we show here that cell type-specific MAGL KO mice display distinct gene expression profiles in the brain. Inactivation of MAGL results in robust changes in expression of immune- and inflammation-related genes in microglia and astrocytes. Remarkably, upregulated expression of chemokines in microglia is more pronounced in mice lacking MAGL in astrocytes. In addition, expression of genes that regulate other cellular functions and Wnt signaling in astrocytes is altered in MAGL KO mice.

CONCLUSIONS

Our results provide transcriptomic evidence that cell type-specific inactivation of MAGL induces differential expression of immune-related genes and other fundamental cellular pathways in microglia and astrocytes. Upregulation of the immune/inflammatory genes suggests that tonic levels of immune/inflammatory vigilance are enhanced in microglia and astrocytes, particularly in microglia, by inhibition of 2-AG metabolism, which likely contribute to anti-inflammatory and neuroprotective effects produced by inactivation of MAGL in neurodegenerative diseases.

Cannabinoids in neuroinflammatory disorders: Focusing on multiple sclerosis, Parkinsons, and Alzheimers diseases

The medicinal properties of cannabis and cannabinoid-derivative are entirely investigated and known. In addition, the identification of psychotropic plant cannabinoids has led to more studies regarding the cannabinoid system and its therapeutic features in the treatment and management of clinical symptoms of neuroinflammatory disorders, such as multiple sclerosis (MS), Parkinsons disease (PD), and Alzheimers disease (AD). In fact, cannabinoid agonists are able to control and regulate inflammatory responses. In contrast to the cannabinoid receptor type 1 (CB1) and its unwanted adverse effects, the cannabinoid receptor type 2 (CB2) and its ligands hold promise for new and effective therapeutic approaches. So far, some successes have been achieved in this field. This review will discuss an outline of the endocannabinoid system's involvement in neuroinflammatory disorders. Moreover, the pharmacological efficacy of different natural and synthetic preparations of phytocannabinoids acting on cannabinoid receptors, particularly in MS, PD, and AD, will be updated. Also, the reasons for targeting CB2 for neurodegeneration will be explained.

Hippocampal Deletion of CB1 Receptor Impairs Social Memory and Leads to Age-Related Changes in the Hippocampus of Adult Mice

Endocannabinoid system activity declines with age in the hippocampus, along with the density of the cannabinoid receptor type-1 (CB1). This process might contribute to brain ageing, as previous studies showed that the constitutive deletion of the CB1 receptor in mice leads to early onset of memory deficits and histological signs of ageing in the hippocampus including enhanced pro-inflammatory glial activity and reduced neurogenesis. Here we asked whether the CB1 receptor exerts its activity locally, directly influencing hippocampal ageing or indirectly, accelerating systemic ageing. Thus, we deleted the CB1 receptor site-specifically in the hippocampus of 2-month-old CB1^flox/flox mice using stereotaxic injections of rAAV-Cre-Venus viruses and assessed their social recognition memory four months later. Mice with hippocampus-specific deletion of the CB1 receptor displayed a memory impairment, similarly as observed in constitutive knockouts at the same age. We next analysed neuroinflammatory changes in the hippocampus, neuronal density and cell proliferation. Site-specific mutant mice had enhanced glial cell activity, up-regulated levels of TNFα in the hippocampus and decreased cell proliferation, specifically in the subgranular zone of the dentate gyrus. Our data indicate that a local activity of the CB1 receptor in the hippocampus is required to maintain neurogenesis and to prevent neuroinflammation and cognitive decline.

The Therapeutic Potential of the Endocannabinoid System in Age-Related Diseases

The endocannabinoid system (ECS) dynamically regulates many aspects of mammalian physiology. ECS has gained substantial interest since growing evidence suggests that it also plays a major role in several pathophysiological conditions due to its ability to modulate various underlying mechanisms. Furthermore, cannabinoids, as components of the cannabinoid system (CS), have proven beneficial effects such as anti-inflammatory, immunomodulatory, neuromodulatory, antioxidative, and cardioprotective effects. In this comprehensive review, we aimed to describe the complex interaction between CS and most common age-related diseases such as neuro-degenerative, oncological, skeletal, and cardiovascular disorders, together with the potential of various cannabinoids to ameliorate the progression of these disorders. Since chronic inflammation is postulated as the pillar of all the above-mentioned medical conditions, we also discuss in this paper the potential of CS to ameliorate aging-associated immune system dysregulation.

Targeting the cannabinoid system to counteract the deleterious effects of stress in Alzheimer’s disease

Alzheimer’s disease is a progressive neurodegenerative disorder characterized histologically in postmortem human brains by the presence of dense protein accumulations known as amyloid plaques and tau tangles. Plaques and tangles develop over decades of aberrant protein processing, post-translational modification, and misfolding throughout an individual’s lifetime. We present a foundation of evidence from the literature that suggests chronic stress is associated with increased disease severity in Alzheimer’s patient populations. Taken together with preclinical evidence that chronic stress signaling can precipitate cellular distress, we argue that chronic psychological stress renders select circuits more vulnerable to amyloid- and tau- related abnormalities. We discuss the ongoing investigation of systemic and cellular processes that maintain the integrity of protein homeostasis in health and in degenerative conditions such as Alzheimer’s disease that have revealed multiple potential therapeutic avenues. For example, the endogenous cannabinoid system traverses the central and peripheral neural systems while simultaneously exerting anti-inflammatory influence over the immune response in the brain and throughout the body. Moreover, the cannabinoid system converges on several stress-integrative neuronal circuits and critical regions of the hypothalamic-pituitary-adrenal axis, with the capacity to dampen responses to psychological and cellular stress. Targeting the cannabinoid system by influencing endogenous processes or exogenously stimulating cannabinoid receptors with natural or synthetic cannabis compounds has been identified as a promising route for Alzheimer’s Disease intervention. We build on our foundational framework focusing on the significance of chronic psychological and cellular stress on the development of Alzheimer’s neuropathology by integrating literature on cannabinoid function and dysfunction within Alzheimer’s Disease and conclude with remarks on optimal strategies for treatment potential.

Phytocannabinoids and Cannabis-Based Products as Alternative Pharmacotherapy in Neurodegenerative Diseases: From Hypothesis to Clinical Practice

Historically, Cannabis is one of the first plants to be domesticated and used in medicine, though only in the last years the amount of Cannabis-based products or medicines has increased worldwide. Previous preclinical studies and few published clinical trials have demonstrated the efficacy and safety of Cannabis-based medicines in humans. Indeed, Cannabis-related medicines are used to treat multiple pathological conditions, including neurodegenerative disorders. In clinical practice, Cannabis products have already been introduced to treatment regimens of Alzheimer’s disease, Parkinson’s disease and Multiple Sclerosis’s patients, and the mechanisms of action behind the reported improvement in the clinical outcome and disease progression are associated with their anti-inflammatory, immunosuppressive, antioxidant, and neuroprotective properties, due to the modulation of the endocannabinoid system. In this review, we describe the role played by the endocannabinoid system in the physiopathology of Alzheimer, Parkinson, and Multiple Sclerosis, mainly at the neuroimmunological level. We also discuss the evidence for the correlation between phytocannabinoids and their therapeutic effects in these disorders, thus describing the main clinical studies carried out so far on the therapeutic performance of Cannabis-based medicines.

Effect of the MAGL/FAAH Dual Inhibitor JZL-195 on Streptozotocin-Induced Alzheimer's Disease-like Sporadic Dementia in Mice with an Emphasis on Aβ, HSP-70, Neuroinflammation, and Oxidative Stress

Alzheimer's disease is identified by pathological hallmarks such as intracellular neurofibrillary tangles (NFTs) and extracellular amyloid β plaques. Several hypotheses exist to define the neurodegeneration including microglial activation associated with neuroinflammatory processes. Recently, pharmacological inhibition of endocannabinoid (eCB)-degrading enzymes, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), is being investigated to modulate the pathology of Alzheimer's disease. While MAGL inhibitors upregulate 2-acyl glycerol (2-AG) levels and reduce neuroinflammation, FAAH inhibitors elevate anandamide (AEA) levels and prevent the degradation of HSP-70, thereby preventing the phosphorylation of tau protein and formation of NFTs in neural cells. We investigated the possible neuroprotective potential of the dual MAGL/FAAH inhibitor JZL-195 (20 mg/kg) against ICV-STZ-induced sporadic Alzheimer's disease (SAD) in Swiss albino mice using donepezil (5 mg/kg) as the standard. The protective effects of JZL-195 were observed by the reversal of altered levels of Aβ1-42, HSP-70, neuroinflammatory cytokines, and oxidative stress markers. However, JZL-195 expressed no cognitive improvement when assessed by spontaneous alternation behavior and Morris water maze tests and no effects on the AChE enzyme level in the hippocampal tissues of mice. Therefore, the findings of the present study indicate that although JZL-195 exhibited no improvement in cognitive deficits associated with sporadic Alzheimer's disease, it displayed significant reversal of the biochemical anomalies, thereby suggesting its therapeutic potential against the sporadic Alzheimer's disease model.

Molecular Signatures of Mitochondrial Complexes Involved in Alzheimer’s Disease via Oxidative Phosphorylation and Retrograde Endocannabinoid Signaling Pathways

Objective

The inability to intervene in Alzheimer's disease (AD) forces the search for promising gene-targeted therapies. This study was aimed at exploring molecular signatures and mechanistic pathways to improve the diagnosis and treatment of AD.

Methods

Microarray datasets were collected to filter differentially expressed genes (DEGs) between AD and nondementia controls. Weight gene correlation network analysis (WGCNA) was employed to analyze the correlation of coexpression modules with AD phenotype. A global regulatory network was established and then visualized using Cytoscape software to determine hub genes and their mechanistic pathways. Receiver operating characteristic (ROC) analysis was conducted to estimate the diagnostic performance of hub genes in AD prediction.

Results

A total of 2,163 DEGs from 13,049 background genes were screened in AD relative to nondementia controls. Among the six coexpression modules constructed by WGCNA, DEGs of the key modules with the strongest correlation with AD were extracted to build a global regulatory network. According to the Maximal Clique Centrality (MCC) method, five hub genes associated with mitochondrial complexes were chosen. Further pathway enrichment analysis of hub genes, such as oxidative phosphorylation and retrograde endocannabinoid signaling, was identified. According to the area under the curve (AUC) of about 70%, each hub gene exhibited a good diagnostic performance in predicting AD.

Conclusions

Our findings highlight the perturbation of mitochondrial complexes underlying AD onset, which is mediated by molecular signatures involved in oxidative phosphorylation (COX5A, NDUFAB1, SDHB, UQCRC2, and UQCRFS1) and retrograde endocannabinoid signaling (NDUFAB1) pathways.

Endocannabinoid Modulation in Neurodegenerative Diseases: In Pursuit of Certainty

Simple Summary

Neurodegenerative diseases represent an important cause of morbidity and mortality worldwide. Existing therapeutic options are limited and focus mostly on improving symptoms and reducing exacerbations. The endocannabinoid system is involved in the pathophysiology of such disorders, an idea which has been highlighted by recent scientific work. The current work focusses its attention on the importance and implications of this system and its synthetic and natural ligands in disorders such as Alzheimer’s, Parkinson’s, Huntington’s and multiple sclerosis.

Abstract

Neurodegenerative diseases are an increasing cause of global morbidity and mortality. They occur in the central nervous system (CNS) and lead to functional and mental impairment due to loss of neurons. Recent evidence highlights the link between neurodegenerative and inflammatory diseases of the CNS. These are typically associated with several neurological disorders. These diseases have fundamental differences regarding their underlying physiology and clinical manifestations, although there are aspects that overlap. The endocannabinoid system (ECS) is comprised of receptors (type-1 (CB1R) and type-2 (CB2R) cannabinoid-receptors, as well as transient receptor potential vanilloid 1 (TRPV1)), endogenous ligands and enzymes that synthesize and degrade endocannabinoids (ECBs). Recent studies revealed the involvement of the ECS in different pathological aspects of these neurodegenerative disorders. The present review will explore the roles of cannabinoid receptors (CBRs) and pharmacological agents that modulate CBRs or ECS activity with reference to Alzheimer’s Disease (AD), Parkinson’s Disease (PD), Huntington’s Disease (HD) and multiple sclerosis (MS).

Enhancing endocannabinoid signalling in astrocytes promotes recovery from traumatic brain injury

Traumatic brain injury is an important risk factor for development of Alzheimer's disease and dementia. Unfortunately, no effective therapies are currently available for prevention and treatment of the traumatic brain injury-induced Alzheimer's disease-like neurodegenerative disease. This is largely due to our limited understanding of the mechanisms underlying traumatic brain injury-induced neuropathology. Previous studies showed that pharmacological inhibition of monoacylglycerol lipase, a key enzyme degrading the endocannabinoid 2-arachidonoylglycerol, attenuates traumatic brain injury-induced neuropathology. However, the mechanism responsible for the neuroprotective effects produced by inhibition of monoacylglycerol lipase in traumatic brain injury remains unclear. Here we first show that genetic deletion of monoacylglycerol lipase reduces neuropathology and averts synaptic and cognitive declines in mice exposed to repeated mild closed head injury. Surprisingly, these neuroprotective effects result primarily from inhibition of 2-arachidonoylglycerol metabolism in astrocytes, rather than in neurons. Single-cell RNA-sequencing data reveal that astrocytic monoacylglycerol lipase knockout mice display greater resilience to traumatic brain injury-induced changes in expression of genes associated with inflammation or maintenance of brain homeostasis in astrocytes and microglia. The monoacylglycerol lipase inactivation-produced neuroprotection is abrogated by deletion of the cannabinoid receptor-1 or by adeno-associated virus vector-mediated silencing of astrocytic peroxisome proliferator-activated receptor-γ. This is further supported by the fact that overexpression of peroxisome proliferator-activated receptor-γ in astrocytes prevents traumatic brain injury-induced neuropathology and impairments in spatial learning and memory. Our results reveal a previously undefined cell type-specific role of 2-arachidonoylglycerol metabolism and signalling pathways in traumatic brain injury-induced neuropathology, suggesting that enhanced 2-arachidonoylglycerol signalling in astrocytes is responsible for the monoacylglycerol lipase inactivation-produced alleviation of neuropathology and deficits in synaptic and cognitive functions in traumatic brain injury.

Potentiation of microglial endocannabinoid signaling alleviates neuroinflammation in Alzheimer's disease

Alzheimer's disease (AD) isaprogressive neurodegenerative disorder characterized by chronic inflammation due to the presence of neurotoxic Aβ and tau proteins. Increased microglial activation and inflated immune response are the other factors to be considered in AD pathology. Microglial cells own biochemical machinery that synthesizes and release endocannabinoids. The exploitation of therapeutic actions of endocannabinoid system has newly emerged in the field of Alzheimer's disease. The activation of cannabinoid receptors/ cannabinoid system modulates inflammatory responses. This review assesses the association between the microglial endocannabinoid system and neuroinflammation in AD. The data supporting the anti-inflammatory role of pharmacological agents modulating cannabinoid system are also reviewed.

On the Biomedical Properties of Endocannabinoid Degradation and Reuptake Inhibitors: Pre-clinical and Clinical Evidence

The endocannabinoid system (ECS) is composed of endogenous cannabinoids; components involved in their synthesis, transport, and degradation; and an expansive variety of cannabinoid receptors. Hypofunction or deregulation of the ECS is related to pathological conditions. Consequently, endogenous enhancement of endocannabinoid levels and/or regulation of their metabolism represent promising therapeutic approaches. Several major strategies have been suggested for the modulation of the ECS: (1) blocking endocannabinoids degradation, (2) inhibition of endocannabinoid cellular uptake, and (3) pharmacological modulation of cannabinoid receptors as potential therapeutic targets. Here, we focused in this review on degradation/reuptake inhibitors over cannabinoid receptor modulators in order to provide an updated synopsis of contemporary evidence advancing mechanisms of endocannabinoids as pharmacological tools with therapeutic properties for the treatment of several disorders. For this purpose, we revisited the available literature and reported the latest advances regarding the biomedical properties of fatty acid amide hydrolase and monoacylglycerol lipase inhibitors in pre-clinical and clinical studies. We also highlighted anandamide and 2-arachidonoylglycerol reuptake inhibitors with promising results in pre-clinical studies using in vitro and animal models as an outlook for future research in clinical trials.

Endocannabinoid Metabolism and Traumatic Brain Injury

Traumatic brain injury (TBI) represents a major cause of morbidity and disability and is a risk factor for developing neurodegenerative diseases, including Alzheimer’s disease (AD). However, no effective therapies are currently available for TBI-induced AD-like disease. Endocannabinoids are endogenous lipid mediators involved in a variety of physiological and pathological processes. The compound 2-arachidonoylglycerol (2-AG) is the most abundant endocannabinoid with profound anti-inflammatory and neuroprotective properties. This molecule is predominantly metabolized by monoacylglycerol lipase (MAGL), a key enzyme degrading about 85% of 2-AG in the brain. Studies using animal models of inflammation, AD, and TBI provide evidence that inactivation of MAGL, which augments 2-AG signaling and reduces its metabolites, exerts neuroprotective effects, suggesting that MAGL is a promising therapeutic target for neurodegenerative diseases. In this short review, we provide an overview of the inhibition of 2-AG metabolism for the alleviation of neuropathology and the improvement of synaptic and cognitive functions after TBI.

Cannabinoids for the treatment of dementia

BACKGROUND

Dementia is a common chronic condition, mainly affecting older adults, characterised by a progressive decline in cognitive and functional abilities. Medical treatments for dementia are limited. Cannabinoids are being investigated for the treatment of dementia.

OBJECTIVES

To determine the efficacy and safety of cannabinoids for the treatment of dementia.

SEARCH METHODS

We searched ALOIS - the Cochrane Dementia and Cognitive Improvement Group's Specialised Register - on 8 July 2021, using the terms cannabis or cannabinoid or endocannabinoid or cannabidiol or THC or CBD or dronabinol or delta-9-tetrahydrocannabinol or marijuana or marihuana or hashish. The register contains records from all major healthcare databases (the Cochrane Library, MEDLINE, Embase, PsycINFO, CINAHL, LILACS), as well as from many clinical trials registries and grey literature sources.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) of cannabinoids for the treatment of dementia. We included participants of any age and of either sex with diagnosed dementia of any subtype, or with unspecified dementia of any severity, from any setting. We considered studies of cannabinoids administered by any route, at any dose, for any duration, compared with placebo, no treatment, or any active control intervention.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened and selected studies for inclusion, extracted data, and assessed the risk of bias in included studies. When necessary, other review authors were involved in reaching consensus decisions. We conducted meta-analyses using a generic inverse variance fixed-effect model to derive estimates of effect size. We used GRADE methods to assess our confidence in the effect estimates.

MAIN RESULTS

We included four studies (126 participants) in this review. Most participants had Alzheimer's disease; a few had vascular dementia or mixed dementia. Three studies had low risk of bias across all domains; one study had unclear risk of bias for the majority of domains.  The included studies tested natural delta-9-tetrahydrocannabinol (THC) (Namisol) and two types of synthetic THC analogue (dronabinol and nabilone). Three trials had a cross-over design. Interventions were applied over 3 to 14 weeks; one study reported adverse events over 70 weeks of follow-up. One trial was undertaken in the USA, one in Canada, and two in The Netherlands. Two studies reported non-commercial funding, and two studies were conducted with the support of both commercial and non-commercial funding. Primary outcomes in this review were changes in global and specific cognitive function, overall behavioural and psychological symptoms of dementia (BPSD), and adverse events. We found very low-certainty evidence suggesting there may be little or no clinically important effect of a synthetic THC analogue on cognition assessed with the standardised Mini-Mental State Examination (sMMSE) (mean difference (MD) 1.1 points, 95% confidence interval (CI) 0.1 to 2.1; 1 cross-over trial, 28 participants).  We found low-certainty evidence suggesting there may be little or no clinically important effect of cannabinoids on overall behavioural and psychological symptoms of dementia assessed with the Neuropsychiatric Inventory (or its modified nursing home version) (MD -1.97, 95% CI -3.87 to -0.07; 1 parallel group and 2 cross-over studies, 110 participants). All included studies reported data on adverse events. However, the total number of adverse events, the total numbers of mild and moderate adverse events, and the total number of serious adverse events (SAEs) were not reported in a way that permitted meta-analysis.  There were no clear differences between groups in numbers of adverse events, with the exception of sedation (including lethargy), which was more frequent among participants taking nabilone (N = 17) than placebo (N = 6) (odds ratio (OR) 2.83, 95% CI 1.07 to 7.48; 1 cross-over study, 38 participants). We judged the certainty of evidence for adverse event outcomes to be low or very low due to serious concerns regarding imprecision and indirectness.

AUTHORS' CONCLUSIONS

Based on data from four small, short, and heterogeneous placebo-controlled trials, we cannot be certain whether cannabinoids have any beneficial or harmful effects on dementia. If there are benefits of cannabinoids for people with dementia, the effects may be too small to be clinically meaningful. Adequately powered, methodologically robust trials with longer follow-up are needed to properly assess the effects of cannabinoids in dementia.

The role of endocannabinoid pathway in the neuropathology of Alzheimer's disease: Can the inhibitors of MAGL and FAAH prove to be potential therapeutic targets against the cognitive impairment associated with Alzheimer's disease?

Alzheimer's disease is a neurodegenerative disease characterized by progressive decline of cognitive function in combination with neuronal death. Current approved treatment target single dysregulated pathway instead of multiple mechanism, resulting in lack of efficacy in slowing down disease progression. The proclivity of endocannabinoid system to exert neuroprotective action and mitigate symptoms of neurodegeneration condition has received substantial interest. Growing evidence suggest the endocannabinoids (eCB) system, viz. anadamide (AEA) and arachidonoyl glycerol (2-AG), as potential therapeutic targets with the ability to modify Alzheimer's pathology by targeting the inflammatory, neurodegenerative and cognitive aspects of the disease. In order to modulate endocannabinoid system, number of agents have been reported amongst which are inhibitors of the monoacylglycerol (MAGL) and fatty acid amide hydrolase (FAAH), the enzymes that hydrolyses 2-AG and AEA respectively. However, little is known regarding the exact mechanistic signalling and their effects on pathophysiology and cognitive decline associated with Alzheimer's disease. Both MAGL and FAAH inhibitors possess fascinating properties that may offer a multi-faceted approach for the treatment of Alzheimer's disease such as potential to protect neurons from deleterious effect of amyloid-β, reducing phosphorylation of tau, reducing amyloid-β induced oxidative stress, stimulating neurotrophin to support brain intrinsic repair mechanism etc. Based on empirical evidence, MAGL and FAAH inhibitors might have potential for therapeutic efficacy against cognitive impairment associated with Alzheimer's disease. The aim of this review is to summarize the experimental studies demonstrating the polyvalent properties of MAGL or FAAH inhibitor compounds for the treatment of Alzheimer's disease, and also effect of these on learning and types of memories, which together encourage to study these compounds over other therapeutics targets. Further research in this direction would enhance the molecular mechanisms and development of applicable interventions for the treatment of Alzheimer's disease, which nevertheless stay as the primary unmet need.

Inhibition of 2-Arachidonoylglycerol Metabolism Alleviates Neuropathology and Improves Cognitive Function in a Tau Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia, which affects more than 5 million individuals in the USA. Unfortunately, no effective therapies are currently available to prevent development of AD or to halt progression of the disease. It has been proposed that monoacylglycerol lipase (MAGL), the key enzyme degrading the endocannabinoid 2-arachidonoylglycerol (2-AG) in the brain, is a therapeutic target for AD based on the studies using the APP transgenic models of AD. While inhibition of 2-AG metabolism mitigates β-amyloid (Aβ) neuropathology, it is still not clear whether inactivation of MAGL alleviates tauopathies as accumulation and deposition of intracellular hyperphosphorylated tau protein are the neuropathological hallmark of AD. Here we show that JZL184, a potent MAGL inhibitor, significantly reduced proinflammatory cytokines, astrogliosis, phosphorylated GSK3β and tau, cleaved caspase-3, and phosphorylated NF-kB while it elevated PPARγ in P301S/PS19 mice, a tau mouse model of AD. Importantly, tau transgenic mice treated with JZL184 displayed improvements in spatial learning and memory retention. In addition, inactivation of MAGL ameliorates deteriorations in expression of synaptic proteins in P301S/PS19 mice. Our results provide further evidence that MAGL is a promising therapeutic target for AD.

GPR18 drives FAAH inhibition-induced neuroprotection against HIV-1 Tat-induced neurodegeneration

Human immunodeficiency virus type 1 (HIV-1) is known to provoke microglial immune responses which likely play a paramount role in the development of chronic neuroinflammatory conditions and neuronal damage related to HIV-1 associated neurocognitive disorders (HAND). In particular, HIV-1 Tat protein is a proinflammatory neurotoxin which predisposes neurons to synaptodendritic injury. Drugs targeting the degradative enzymes of endogenous cannabinoids have shown promise in reducing inflammation with minimal side effects in rodent models. Considering that markers of neuroinflammation can predict the extent of neuronal injury in HAND patients, we evaluated the neurotoxic effect of HIV-1 Tat-exposed microglia following blockade of fatty acid amid hydrolyze (FAAH), a catabolic enzyme responsible for degradation of endocannabinoids, e.g. anandamide (AEA). In the present study, cultured murine microglia were incubated with Tat and/or a FAAH inhibitor (PF3845). After 24 h, cells were imaged for morphological analysis and microglial conditioned media (MCM) was collected. Frontal cortex neuron cultures (DIV 7–11) were then exposed to MCM, and neurotoxicity was assessed via live cell calcium imaging and staining of actin positive dendritic structures. Results demonstrate a strong attenuation of microglial responses to Tat by PF3845 pretreatment, which is indicated by 1) microglial changes in morphology to a less proinflammatory phenotype using fractal analysis, 2) a decrease in release of neurotoxic cytokines/chemokines (MCP-1/CCL2) and matrix metalloproteinases (MMPs; MMP-9) using ELISA/multiplex assays, and 3) enhanced production of endocannabinoids (AEA) using LC/MS/MS. Additionally, PF3845’s effects on Tat-induced microglial-mediated neurotoxicity, decreased dysregulation of neuronal intracellular calcium and prevented the loss of actin-positive staining and punctate structure in frontal cortex neuron cultures. Interestingly, these observed neuroprotective effects appeared to be independent of cannabinoid receptor activity (CB₁R & CB₂R). We found that a purported GPR18 antagonist, CID-85469571, blocked the neuroprotective effects of PF3845 in all experiments. Collectively, these experiments increase understanding of the role of FAAH inhibition and Tat in mediating microglial neurotoxicity in the HAND condition.

The rise and fall of anandamide: processes that control synthesis, degradation, and storage

Anandamide is an endocannabinoid derived from arachidonic acid-containing membrane lipids and has numerous biological functions. Its effects are primarily mediated by the cannabinoid receptors CB1 and CB2, and the vanilloid TRPV1 receptor. Anandamide is known to be involved in sleeping and eating patterns as well as pleasure enhancement and pain relief. This manuscript provides a review of anandamide synthesis, degradation, and storage and hence the homeostasis of the anandamide signaling system.

Mini-review: The therapeutic role of cannabinoids in neuroHIV

In the era of combined antiretroviral therapy (cART), human immunodeficiency virus type 1 (HIV-1) is considered a chronic disease with an inflammatory component that specifically targets the brain and causes a high prevalence of HIV-1-associated neurocognitive disorders (HAND). The endocannabinoid (eCB) system has attracted interest as a target for treatment of neurodegenerative disorders, due to the potential anti-inflammatory and neuroprotective properties of cannabinoids, including its potential therapeutic use in HIV-1 neuropathogenesis. In this review, we summarize what is currently known about the structural and functional changes of the eCB system under conditions of HAND. This will be followed by summarizing the current clinical and preclinical findings on the effects of cannabis use and cannabinoids in the context of HIV-1 infection, with specifically focusing on viral load, cognition, inflammation, and neuroprotection. Lastly, we present some potential future directions to better understand the involvement of the eCB system and the role that cannabis use and cannabinoids play in neuroHIV.

Design and synthesis of new carbamates as inhibitors for fatty acid amide hydrolase and cholinesterases: Molecular dynamic, in vitro and in vivo studies

As anandamide (N-arachidonoylethanolamine, AEA) shows neuroprotective effects, the inhibition of its degradative enzyme, fatty acid amide hydrolase (FAAH) has been considered as a hopeful avenue for the treatment of neurodegenerative diseases, like Alzheimer's disease (AD). Memory loss, cognitive impairment and diminution of the cholinergic tone, due to the dying cholinergic neurons in the basal forebrain, are common hallmarks in patients with AD. By taking advantage of cholinesterase inhibitors (ChEIs), the degradation of acetylcholine (ACh) is decreased leading to enhanced cholinergic neurotransmission in the aforementioned region and ultimately improves the clinical condition of AD patients. In this work, new carbamates were designed as inhibitors of FAAH and cholinestrases (ChEs) (acetylcholinestrase (AChE), butyrylcholinestrase (BuChE)) inspired by the structure of the native substrates, structure of active sites and the SARs of the well-known inhibitors of these enzymes. All the designed compounds were synthesized using different reactions. All the target compounds were tested for their inhibitory activity against FAAH and ChEs by employing the Cayman assay kit and Elman method respectively. Generally, compounds possessing aminomethyl phenyl linker was more potent compared to their corresponding compounds possessing piperazinyl ethyl linker. The inhibitory potential of the compounds 3a-q extended from 0.83 ± 0.03 μM (3i) to ˃100 μM (3a) for FAAH, 0.39 ± 0.02 μM (3i) to 24% inhibition in 113 ± 4.8 μM (3b) for AChE, and 1.8 ± 3.2 μM (3i) to 23.2 ± 0.2 μM (3b) for BuChE. Compound 3i a heptyl carbamate analog possessing 2-oxo-1,2-dihydroquinolin ring and aminomethyl phenyl linker showed the most inhibitory activity against three enzymes. Also, compound 3i was investigated for memory improvement using the Morris water maze test in which the compound showed better memory improvement at 10 mg/kg compared to reference drug rivastigmine at 2.5 mg/kg. Molecular docking and molecular dynamic studies of compound 3i into the enzymes displayed the possible interactions of key residues of the active sites with compound 3i. Finally, kinetic study indicated that 3i inhibits AChE through the mixed- mode mechanism and non-competitive inhibition mechanism was revealed for BuChE.

Conformational gating, dynamics and allostery in human monoacylglycerol lipase

Inhibition of human Monoacylglycerol Lipase (hMGL) offers a novel approach for treating neurological diseases. The design of inhibitors, targeting active-inactive conformational transitions of the enzyme, can be aided by understanding the interplay between structure and dynamics. Here, we report the effects of mutations within the catalytic triad on structure, conformational gating and dynamics of hMGL by combining kinetics, NMR, and HDX-MS data with metadynamics simulations. We found that point mutations alter delicate conformational equilibria between active and inactive states. HDX-MS reveals regions of the hMGL that become substantially more dynamic upon substitution of catalytic acid Asp-239 by alanine. These regions, located far from the catalytic triad, include not only loops but also rigid α-helixes and β-strands, suggesting their involvement in allosteric regulation as channels for long-range signal transmission. The results identify the existence of a preorganized global communication network comprising of tertiary (residue-residue contacts) and quaternary (rigid-body contacts) networks that mediate robust, rapid intraprotein signal transmission. Catalytic Asp-239 controls hMGL allosteric communications and may be considered as an essential residue for the integration and transmission of information to enzymes' remote regions, in addition to its well-known role to facilitate Ser-122 activation. Our findings may assist in the identification of new druggable sites in hMGL.

Potential application of endocannabinoid system agents in neuropsychiatric and neurodegenerative diseases-focusing on FAAH/MAGL inhibitors

The endocannabinoid system (ECS) has received extensive attention for its neuroprotective effect on the brain. This system comprises endocannabinoids, endocannabinoid receptors, and the corresponding ligands and proteins. The molecular players involved in their regulation and metabolism are potential therapeutic targets for neuropsychiatric diseases including anxiety, depression and neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). The inhibitors of two endocannabinoid hydrolases, i.e., fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), have the capacity to increase the level of endocannabinoids indirectly, causing fewer side effects than those associated with direct supplementation of cannabinoids. Their antidepressant and anxiolytic mechanisms are considered to modulate the hypothalamic-pituitary-adrenal axis and regulate synaptic and neural plasticity. In terms of AD/PD, treatment with FAAH/MAGL inhibitors leads to reduction in amyloid β-protein deposition and inhibition of the death of dopamine neurons, which are commonly accepted to underlie the pathogenesis of AD and PD, respectively. Inflammation as the cause of depression/anxiety and PD/AD is also the target of FAAH/MAGL inhibitors. In this review, we summarize the application and involvement of FAAH/MAGL inhibitors in related neurological diseases. Focus on the latest research progress using FAAH/MAGL inhibitors is expected to facilitate the development of novel approaches with therapeutic potential.

Potential Astrocytic Receptors and Transporters in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia and is characterized by the progressive loss of memory and cognition in the aging population. However, the etiology of and therapies for AD remain far from understood. Astrocytes, the most abundant neuroglia in the brain, have recently aroused substantial concern due to their involvement in synaptotoxicity, amyloidosis, neuroinflammation, and oxidative stress. In this review, we summarize the candidate molecules of astrocytes, especially receptors and transporters, that may be involved in AD pathogenesis. These molecules include excitatory amino acid transporters (EAATs), metabotropic glutamate receptor 5 (mGluR5), the adenosine 2A receptor (A2AR), the α7-nicotinic acetylcholine receptor (α7-nAChR), the calcium-sensing receptor (CaSR), S100β, and cannabinoid receptors. We describe the characteristics of these molecules and the neurological and pharmacological underpinnings of these molecules in AD. Among these molecules, EAATs, A2AR, and mGluR5 are strongly related to glutamate-mediated synaptotoxicity and are involved in glutamate transmission or the clearance of extrasynaptic glutamate in the AD brain. The α7-nAChR, CaSR, and mGluR5 are receptors of Aβ and can induce a plethora of toxic effects, such as the production of excess Aβ, synaptotoxicity, and NO production triggered by changes in intracellular calcium signaling. Antagonists or positive allosteric modulators of these receptors can repair cognitive ability and modify neurobiological changes. Moreover, blocking S100β or activating cannabinoid receptors reduces neuroinflammation, oxidative stress, and reactive astrogliosis. Thus, targeting these molecules might provide alternative approaches for treating AD.

Inflammation and tissue homeostasis: the NF-κB system in physiology and malignant progression

Disruption of tissue function activates cellular stress which triggers a number of mechanisms that protect the tissue from further damage. These mechanisms involve a number of homeostatic modules, which are regulated at the level of gene expression by the transactivator NF-κB. This transcription factor shifts between activation and repression of discrete, cell-dependent gene expression clusters. Some of its target genes provide feedback to NF-κB itself, thereby strengthening the inflammatory response of the tissue and later terminating inflammation to facilitate restoration of tissue homeostasis. Disruption of key feedback modules for NF-κB in certain cell types facilitates the survival of clones with genomic aberrations, and protects them from being recognized and eliminated by the immune system, to enable thereby carcinogenesis.

Benzisothiazolinone Derivatives as Potent Allosteric Monoacylglycerol Lipase Inhibitors That Functionally Mimic Sulfenylation of Regulatory Cysteines

We describe a set of benzisothiazolinone (BTZ) derivatives that are potent inhibitors of monoacylglycerol lipase (MGL), the primary degrading enzyme for the endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG). Structure-activity relationship studies evaluated various substitutions on the nitrogen atom and the benzene ring of the BTZ nucleus. Optimized derivatives with nanomolar potency allowed us to investigate the mechanism of MGL inhibition. Site-directed mutagenesis and mass spectrometry experiments showed that BTZs interact in a covalent reversible manner with regulatory cysteines, Cys201 and Cys208, causing a reversible sulfenylation known to modulate MGL activity. Metadynamics simulations revealed that BTZ adducts favor a closed conformation of MGL that occludes substrate recruitment. The BTZ derivative 13 protected neuronal cells from oxidative stimuli and increased 2-AG levels in the mouse brain. The results identify Cys201 and Cys208 as key regulators of MGL function and point to the BTZ scaffold as a useful starting point for the discovery of allosteric MGL inhibitors.

Cannabinoid Actions on Neural Stem Cells: Implications for Pathophysiology

With the increase of life expectancy, neurodegenerative disorders are becoming not only a health but also a social burden worldwide. However, due to the multitude of pathophysiological disease states, current treatments fail to meet the desired outcomes. Therefore, there is a need for new therapeutic strategies focusing on more integrated, personalized and effective approaches. The prospect of using neural stem cells (NSC) as regenerative therapies is very promising, however several issues still need to be addressed. In particular, the potential actions of pharmacological agents used to modulate NSC activity are highly relevant. With the ongoing discussion of cannabinoid usage for medical purposes and reports drawing attention to the effects of cannabinoids on NSC regulation, there is an enormous, and yet, uncovered potential for cannabinoids as treatment options for several neurological disorders, specifically when combined with stem cell therapy. In this manuscript, we review in detail how cannabinoids act as potent regulators of NSC biology and their potential to modulate several neurogenic features in the context of pathophysiology.

A novel mechanism of synaptic and cognitive impairments mediated via microRNA-30b in Alzheimer's disease

BACKGROUND

It is widely accepted that cognitive and memory deficits in Alzheimer's disease (AD) primarily result from synaptic failure. However, the mechanisms that underlie synaptic and cognitive dysfunction remain unclear.

METHODS

We utilized molecular biology techniques, electrophysiological recordings, fluorescence in situ hybridization (FISH), immuno- and Golgi-staining, chromatin immunoprecipitation (CHIP); lentivirus (LV)-based microRNA overexpression and 'sponging', and behavioral tests to assess upregulated miR-30b causing synaptic and cognitive declines in APP transgenic (TG) mice.

FINDINGS

We provide evidence that expression of miR-30b, which targets molecules important for maintaining synaptic integrity, including ephrin type-B receptor 2 (ephB2), sirtuin1 (sirt1), and glutamate ionotropic receptor AMPA type subunit 2 (GluA2), is robustly upregulated in the brains of both AD patients and APP transgenic (TG) mice, an animal model of AD, while expression of its targets is significantly downregulated. Overexpression of miR-30b in the hippocampus of normal wild-type (WT) mice impairs synaptic and cognitive functions, mimicking those seen in TG mice. Conversely, knockdown of endogenous miR-30b in TG mice prevents synaptic and cognitive decline. We further observed that expression of miR-30b is upregulated by proinflammatory cytokines and Aβ42 through NF-κB signaling.

INTERPRETATION

Our results provide a previously undefined mechanism by which unregulated miR-30b causes synaptic and cognitive dysfunction in AD, suggesting that reversal of dysregulated miR-30b in the brain may prevent or slow cognitive declines in AD. FUND: This work was supported by National Institutes of Health grants R01NS076815, R01MH113535, R01AG058621, P30GM103340 Pilot Project, and by the LSUHSC School of Medicine Research Enhancement Program grant (to C.C.).

Antioxidant Activity and Neuroprotective Activity of Stilbenoids in Rat Primary Cortex Neurons via the PI3K/Akt Signalling Pathway

Antioxidant activity and neuroprotective activity of three stilbenoids, namely, trans-4-hydroxystilbene (THS), trans-3,5,4′-trihydroxy-stilbene (resveratrol, RES), and trans-3′,4′,3,5-tetrahydroxy-stilbene (piceatannol, PIC), against β-amyloid (Aβ)-induced neurotoxicity in rat primary cortex neurons were evaluated. THS, RES, and PIC significantly scavenged DPPH• and •OH radicals. All three stilbenoids were able to inhibit Aβ neurotoxicity by decreasing intracellular reactive oxygen species (ROS) via the PI3K/Akt signalling pathway. Specifically, stilbenoids significantly promoted Akt phosphorylation; suppressed Bcl-2/Bax expression; and inhibited caspase-9, caspase-3, and PARP cleavage. Molecular docking between stilbenoids with Akt indicated that stilbenoids could form hydrogen bond interactions with the COOH-terminal region of Akt. Additionally, the neuroprotective activity of stilbenoids correlated with the number and position of hydroxyl groups. The lack of meta-dihydroxyl groups on THS did not affect its neuroprotective activity in comparison with RES, whereas the ortho-dihydroxyl moiety on PIC significantly enhanced neuroprotective activity. These results provide new insights into the correlation between the biological activity and chemical structure of stilbenoids.

Cannabinoid pharmacology/therapeutics in chronic degenerative disorders affecting the central nervous system

The endocannabinoid system (ECS) exerts a modulatory effect of important functions such as neurotransmission, glial activation, oxidative stress, or protein homeostasis. Dysregulation of these cellular processes is a common neuropathological hallmark in aging and in neurodegenerative diseases of the central nervous system (CNS). The broad spectrum of actions of cannabinoids allows targeting different aspects of these multifactorial diseases. In this review, we examine the therapeutic potential of the ECS for the treatment of chronic neurodegenerative diseases of the CNS focusing on Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. First, we describe the localization of the molecular components of the ECS and how they are altered under neurodegenerative conditions, either contributing to or protecting cells from degeneration. Second, we address recent advances in the modulation of the ECS using experimental models through different strategies including the direct targeting of cannabinoid receptors with agonists or antagonists, increasing the endocannabinoid tone by the inhibition of endocannabinoid hydrolysis, and activation of cannabinoid receptor-independent effects. Preclinical evidence indicates that cannabinoid pharmacology is complex but supports the therapeutic potential of targeting the ECS. Third, we review the clinical evidence and discuss the future perspectives on how to bridge human and animal studies to develop cannabinoid-based therapies for each neurodegenerative disorder. Finally, we summarize the most relevant opportunities of cannabinoid pharmacology related to each disease and the multiple unexplored pathways in cannabinoid pharmacology that could be useful for the treatment of neurodegenerative diseases.

2-arachidonyl glycerol modulates astrocytic glutamine synthetase via p38 and ERK1/2 pathways

Background

The glutamine synthetase (GS), an astrocyte-specific enzyme, is involved in lipopolysaccharide (LPS)-induced inflammation which activates the mitogen-activated protein kinase (MAPK) signaling. Endocannabinoid 2-arachidonyl glycerol (2-AG) has been described to serve as an endogenous mediator of analgesia and neuroprotection. However, whether 2-AG can directly influence astrocytic GS and MAPK expressions remains unknown.

Methods

In the present study, the effects of 2-AG on astrocytic GS expression, p38 and ERK1/2 expression, cell viability, and apoptosis following LPS exposure were investigated.

Results

The results revealed that LPS exposure increased GS expression with p38 activation in the early phase and decreased GS expression with activation of ERK1/2, decrease of cell viability, and increase of apoptosis in the late phase. Inhibition of p38 reversed GS increase in the early phase while inhibition of ERK1/2 reversed GS decrease in the late phase induced by LPS exposure. 2-AG protected astrocytes from increase of apoptosis and decrease of cell viability induced by the late phase of LPS exposure. In the early phase of LPS exposure, 2-AG could suppress the increase of GS expression and activation of p38 signaling. In the late phase of LPS exposure, 2-AG could reverse the decrease of GS expression and activation of ERK1/2 induced by LPS.

Conclusion

These findings suggest that 2-AG could maintain the GS expression in astrocytes to a relatively stable level through modulating MAPK signaling and protect astrocytes from LPS exposure.

Alleviation of Neuropathology by Inhibition of Monoacylglycerol Lipase in APP Transgenic Mice Lacking CB2 Receptors

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. We observed that expression of APP and β-secretase as well as production of total Aβ and Aβ42 were significantly reduced in APP transgenic mice lacking CB2R (TG-CB2-KO) treated with JZL184, a selective and potent inhibitor for MAGL. Inactivation of MAGL also alleviated neuroinflammation and neurodegeneration in TG-CB2-KO mice. Importantly, TG-CB2-KO mice treated with JZL184 still exhibited improvements in spatial learning and memory. In addition, MAGL inhibition prevented deterioration in expression of important synaptic proteins in TG-CB2-KO mice. 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.

Potential of Endocannabinoids to Control Bladder Pain

Bladder-related pain is one of the most common forms of visceral pain, and visceral pain is among the most common complaints for which patients seek physician consultation. Despite extensive studies of visceral innervation and treatment of visceral pain, opioids remain a mainstay for management of bladder pain. Side effects associated with opioid therapy can profoundly diminish quality of life, and improved options for treatment of bladder pain remain a high priority. Endocannabinoids, primarily anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are endogenously-produced fatty acid ethanolamides with that induce analgesia. Animal experiments have demonstrated that inhibition of enzymes that degrade AEA or 2-AG have the potential to prevent development of visceral and somatic pain. Although experimental results in animal models have been promising, clinical application of this approach has proven difficult. In addition to fatty acid amide hydrolase (FAAH; degrades AEA) and monacylglycerol lipase (MAGL; degrades 2-AG), cyclooxygenase (COX) acts to metabolize endocannabinoids. Another potential limitation of this strategy is that AEA activates pro-nociceptive transient receptor potential vanilloid 1 (TRPV1) channels. Dual inhibitors of FAAH and TRPV1 or FAAH and COX have been synthesized and are currently undergoing preclinical testing for efficacy in providing analgesia. Local inhibition of FAAH or MAGL within the bladder may be viable options to reduce pain associated with cystitis with fewer systemic side effects, but this has not been explored. Further investigation is required before manipulation of the endocannabinoid system can be proven as an efficacious alternative for management of bladder pain.

Enhanced endocannabinoid tone as a potential target of pharmacotherapy

The endocannabinoid system is up-regulated in numerous pathophysiological states such as inflammatory, neurodegenerative, gastrointestinal, metabolic and cardiovascular diseases, pain, and cancer. It has been suggested that this phenomenon primarily serves an autoprotective role in inhibiting disease progression and/or diminishing signs and symptoms. Accordingly, enhancement of endogenous endocannabinoid tone by inhibition of endocannabinoid degradation represents a promising therapeutic approach for the treatment of many diseases. Importantly, this allows for the avoidance of unwanted psychotropic side effects that accompany exogenously administered cannabinoids. The effects of endocannabinoid metabolic pathway modulation are complex, as endocannabinoids can exert their actions directly or via numerous metabolites. The two main strategies for blocking endocannabinoid degradation are inhibition of endocannabinoid-degrading enzymes and inhibition of endocannabinoid cellular uptake. To date, the most investigated compounds are inhibitors of fatty acid amide hydrolase (FAAH), an enzyme that degrades the endocannabinoid anandamide. However, application of FAAH inhibitors (and consequently other endocannabinoid degradation inhibitors) in medicine became questionable due to a lack of therapeutic efficacy in clinical trials and serious adverse effects evoked by one specific compound. In this paper, we discuss multiple pathways of endocannabinoid metabolism, changes in endocannabinoid levels across numerous human diseases and corresponding experimental models, pharmacological strategies for enhancing endocannabinoid tone and potential therapeutic applications including multi-target drugs with additional targets outside of the endocannabinoid system (cyclooxygenase-2, cholinesterase, TRPV1, and PGF_2α-EA receptors), and currently used medicines or medicinal herbs that additionally enhance endocannabinoid levels. Ultimately, further clinical and preclinical studies are warranted to develop medicines for enhancing endocannabinoid tone.

Endocannabinoids exert CB1 receptor-mediated neuroprotective effects in models of neuronal damage induced by HIV-1 Tat protein

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-arachidonoylethanolamine (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.