Potential Therapeutic Targets to Modulate the Endocannabinoid System in Alzheimer’s Disease

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“Alzheimer’s disease (AD), the most common neurodegenerative disease (NDD), is characterized by chronic neuronal cell death through progressive loss of cognitive function. Amyloid beta (Aβ) deposition, neuroinflammation, oxidative stress, and hyperphosphorylated tau proteins are considered the hallmarks of AD pathology. Different therapeutic approaches approved by the Food and Drug Administration can only target a single altered pathway instead of various mechanisms that are involved in AD pathology, resulting in limited symptomatic relief and almost no effect in slowing down the disease progression.

Growing evidence on modulating the components of the endocannabinoid system (ECS) proclaimed their neuroprotective effects by reducing neurochemical alterations and preventing cellular dysfunction. Recent studies on AD mouse models have reported that the inhibitors of the fatty acid amide hydrolase (FAAH) and monoacylglycerol (MAGL), hydrolytic enzymes for N-arachidonoyl ethanolamine (AEA) and 2-arachidonoylglycerol (2-AG), respectively, might be promising candidates as therapeutical intervention.

The FAAH and MAGL inhibitors alone or in combination seem to produce neuroprotection by reversing cognitive deficits along with Aβ-induced neuroinflammation, oxidative responses, and neuronal death, delaying AD progression. Their exact signaling mechanisms need to be elucidated for understanding the brain intrinsic repair mechanism. The aim of this review was to shed light on physiology and pathophysiology of AD and to summarize the experimental data on neuroprotective roles of FAAH and MAGL inhibitors. In this review, we have also included CB1R and CB2R modulators with their diverse roles to modulate ECS mediated responses such as anti-nociceptive, anxiolytic, and anti-inflammatory actions in AD. Future research would provide the directions in understanding the molecular mechanisms and development of new therapeutic interventions for the treatment of AD.”

https://pubmed.ncbi.nlm.nih.gov/38612861/

https://www.mdpi.com/1422-0067/25/7/4050

A novel insight into the neuroprotective effects of cannabidiol: maintained apelin/dopamine synthesis, NRF2 signaling, and AKT/CREB/BDNF gene expressions

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“Neuroinflammation is a process associated with degeneration and loss of neurons in different parts of the brain. The most important damage mechanisms in its formation are oxidative stress and inflammation.

This study aimed to investigate the protective effects of cannabidiol (CBD) against neuroinflammation through various mechanisms.

Thirty‑two female rats were randomly divided into 4 groups as control, lipopolysaccharide (LPS), LPS + CBD and CBD groups. After six hours following LPS administration, rats were sacrificed, brain and cerebellum tissues were obtained. Tissues were stained with hematoxylin‑eosin for histopathological analysis. Apelin and tyrosine hydroxylase synthesis were determined immunohistochemically. Total oxidant status and total antioxidant status levels were measured, and an oxidative stress index was calculated. Protein kinase B (AKT), brain-derived neurotrophic factor (BDNF), cyclic‑AMP response element‑binding protein (CREB) and nuclear factor erythroid 2‑related factor 2 (NRF2) mRNA expression levels were also determined. In the LPS group, hyperemia, degeneration, loss of neurons and gliosis were seen in all three tissues. Additionally, Purkinje cell loss in the cerebellum, as well as neuronal loss in the cerebral cortex and hippocampus, were found throughout the LPS group. The expressions of AKT, BDNF, CREB and NRF2, apelin and tyrosine hydroxylase synthesis all decreased significantly.

CBD treatment reversed these changes and ameliorated oxidative stress parameters. CBD showed protective effects against neuroinflammation via regulating AKT, CREB, BDNF expressions, NRF2 signaling, apelin and tyrosine hydroxylase synthesis.”

https://pubmed.ncbi.nlm.nih.gov/38587319/

https://ane.pl/index.php/ane/article/view/2546

Cannabidiol improves the cognitive function of SAMP8 AD model mice involving the microbiota-gut-brain axis

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“Cannabidiol (CBD), a natural component extracted from Cannabis sativa L. exerts neuroprotective, antioxidant, and anti-inflammatory effects in Alzheimer’s disease (AD), a disease characterized by impaired cognition and accumulation of amyloid-B peptides (Aβ). Interactions between the gut and central nervous system (microbiota-gut-brain axis) play a critical role in the pathogenesis of neurodegenerative disorder AD. At present investigations into the mechanisms underlying the neuroprotective action of CBD in AD are not conclusive.

The aim of this study was thus to examine the influence of CBD on cognition and involvement of the microbiota-gut-brain axis using a senescence-accelerated mouse prone 8 (SAMP8) model.

Data demonstrated that administration of CBD to SAMP8 mice improved cognitive function as evidenced from the Morris water maze test and increased hippocampal activated microglia shift from M1 to M2. In addition, CBD elevated levels of Bacteriodetes associated with a fall in Firmicutes providing morphologically a protective intestinal barrier which subsequently reduced leakage of intestinal toxic metabolites. Further, CBD was found to reduce the levels of hippocampal and colon epithelial cells lipopolysaccharide (LPS), known to be increased in AD leading to impaired gastrointestinal motility, thereby promoting neuroinflammation and subsequent neuronal death.

Our findings demonstrated that CBD may be considered a beneficial therapeutic drug to counteract AD-mediated cognitive impairment and restore gut microbial functions associated with the observed neuroprotective mechanisms.”

https://pubmed.ncbi.nlm.nih.gov/38590254/

https://www.tandfonline.com/doi/full/10.1080/15287394.2024.2338914

Involvement of CB1 and CB2 receptors in neuroprotective effects of cannabinoids in experimental TDP-43 related frontotemporal dementia using male mice

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“Background: The elevation of endocannabinoid levels through inhibiting their degradation afforded neuroprotection in CaMKIIα-TDP-43 mice, a conditional transgenic model of frontotemporal dementia. However, which cannabinoid receptors are mediating these benefits is still pending to be elucidated.

Methods: We have investigated the involvement of the CB1 and the CB2 receptor using chronic treatments with selective ligands in CaMKIIα-TDP-43 mice, analysis of their cognitive deterioration with the Novel Object Recognition test, and immunostaining for neuronal and glial markers in two areas of interest in frontotemporal dementia.

Results: Our results confirmed the therapeutic value of activating either the CB1 or the CB2 receptor, with improvements in the animal performance in the Novel Object Recognition test, preservation of pyramidal neurons, in particular in the medial prefrontal cortex, and attenuation of glial reactivity, in particular in the hippocampus. In addition, the activation of both CB1 and CB2 receptors reduced the elevated levels of TDP-43 in the medial prefrontal cortex of CaMKIIα-TDP-43 mice, an effect exerted by mechanisms that are currently under investigation.

Conclusions: These data reinforce the notion that the activation of CB1 and CB2 receptors may represent a promising therapy against TDP-43-induced neuropathology in frontotemporal dementia. Future studies will have to confirm these benefits, in particular with one of the selective CB2 agonists used here, which has been thoroughly characterized for clinical development.”

https://pubmed.ncbi.nlm.nih.gov/38522237/

https://www.sciencedirect.com/science/article/pii/S0753332224003573?via%3Dihub

Cannabidiol improves memory and decreases IL-1β serum levels in rats with lipopolysaccharide-induced inflammation

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“Memory improving and anti-inflammatory properties of cannabidiol (CBD) were investigated in an experimental model of lipopolysaccharide (LPS)-induced inflammation.”

https://pubmed.ncbi.nlm.nih.gov/38351784/

“Cannabis sativa is a plant that has been cultivated by humans and utilized in medicine since ancient times.”

“Cannabidiol (CBD) is one of the most important Cannabis-derived molecules,”

“CBD improved spatial working and recognition memory in rats with LPS-induced inflammation. Suppression of IL-1β production could be attributed to the observed effect.”

https://foliamedica.bg/article/107259/

Alzheimer’s disease, aging, and cannabidiol treatment: a promising path to promote brain health and delay aging

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“Alzheimer’s disease (AD) is the most common neurodegenerative disease characterized by progressive memory loss, neurodegeneration, and cognitive decline. Aging is one of the risk factors for AD. Although the mechanisms underlying aging and the incidence rate of AD are unclear, aging and AD share some hallmarks, such as oxidative stress and chronic inflammation.

Cannabidiol (CBD), the major non-psychoactive phytocannabinoid extracted from Cannabis sativa, has recently emerged as a potential candidate for delaying aging and a valuable therapeutic tool for the treatment of aging-related neurodegenerative diseases due to its antioxidant and anti-inflammation properties.

This article reviews the relevant literature on AD, CBD treatment for AD, cellular senescence, aging, and CBD treatment for aging in recent years. By analyzing these published data, we attempt to explore the complex correlation between cellular senescence, aging, and Alzheimer’s disease, clarify the positive feedback effect between the senescence of neurocytes and Alzheimer’s disease, and summarize the role and possible molecular mechanisms of CBD in preventing aging and treating AD.

These data may provide new ideas on how to effectively prevent and delay aging, and develop effective treatment strategies for age-related diseases such as Alzheimer’s disease.”

https://pubmed.ncbi.nlm.nih.gov/38227160/

https://link.springer.com/article/10.1007/s11033-023-09162-1

Identification of Anti-Neuroinflammatory Bioactive Compounds in Essential Oils and Aqueous Distillation Residues Obtained from Commercial Varieties of Cannabis sativa L

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“Neuroinflammation, which is mainly triggered by microglia, is a key contributor to multiple neurodegenerative diseases.

Natural products, and in particular Cannabis sativa L., due to its richness in phytochemical components, represent ideal candidates to counteract neuroinflammation.

We previously characterized different C. sativa commercial varieties which showed significantly different chemical profiles. On these bases, the aim of this study was to evaluate essential oils and aqueous distillation residues from the inflorescences of three different hemp varieties for their anti-neuroinflammatory activity in BV-2 microglial cells. Cells were pretreated with aqueous residues or essential oils and then activated with LPS. Unlike essential oils, aqueous residues showed negligible effects in terms of anti-inflammatory activity. Among the essential oils, the one obtained from ‘Gorilla Glue’ was the most effective in inhibiting pro-inflammatory mediators and in upregulating anti-inflammatory ones through the modulation of the p38 MAPK/NF-κB pathway. Moreover, the sesquiterpenes (E)-caryophyllene, α-humulene, and caryophyllene oxide were identified as the main contributors to the essential oils’ anti-inflammatory activity. To our knowledge, the anti-neuroinflammatory activity of α-humulene has not been previously described.

In conclusion, our work shows that C. sativa essential oils characterized by high levels of sesquiterpenes can be promising candidates in the prevention/counteraction of neuroinflammation.”

https://pubmed.ncbi.nlm.nih.gov/38068924/

https://www.mdpi.com/1422-0067/24/23/16601

Characterizing cannabis-prevalent terpenes for neuroprotection reveal a role for α and β-pinenes in mitigating amyloid β-evoked neurotoxicity and aggregation in vitro

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Background: Cannabis Sativa L. (C. sativa) can efficiently synthesize of over 200 terpenes, including monoterpenes, sesquiterpenes and triterpenes that may contribute to the known biological activities of phytocannabinoids of relevance for the burgeoning access to medicinal cannabis formulations globally; however, to date have been uncharacterized. We assessed twelve predominant terpenes in C. sativa for neuroprotective and anti-aggregative properties in semi-differentiated PC12 neuronal cell line that is robust and validated as a cell model responsive to amyloid β (Aβ1-42) protein exposure and oxidative stress.

Methods: Cell viability was assessed biochemically using the MTT assay in the presence of myrcene, β-caryophyllene, terpinolene, limonene, linalool, humulene, α-pinene, nerolidol, β-pinene, terpineol, citronellol and friedelin (1-200μM) for 24hr. Sub-toxic threshold test concentrations of each terpene were then applied to cells, alone or with concomitant incubation with the lipid peroxidant tert-butyl hyrdroperoxide (t-BHP; 0-250μM) or amyloid β (Aβ1-42; 0-1μM) to assess neuroprotective effects. Direct effects of each terpene on Aβ fibril formation and aggregation were also evaluated using the Thioflavin T (ThT) fluorometric kinetic assay and transmission electron microscopy (TEM) to visualize fibril and aggregate morphology

Results: Terpenes were intrinsically benign to PC12 cells up to 50μM, with higher concentrations of β-caryophyllene, humulene and nerolidol inducing some loss of PC12 cell viability. No significant protective effects of terpenes were observed following t-BHP (0-200µM) administration, with some enhanced toxicity instead demonstrated from both β-caryophyllene and humulene treatment (each at 50µM). α-pinene and β-pinene demonstrated a significant neuroprotective effect against amyloid β exposure. α-pinene, β-pinene, terpineol, terpinolene and friedelin were associated with a variable inhibition of Aβ1-42 fibril and aggregate density.

Conclusions: The outcomes of this study underline a neuroprotective role of α-pinene and β-pinene against Aβ-mediated neurotoxicity associated with an inhibition of Aβ1-42 fibrilization and density. This demonstrates the bioactive potential of selected terpenes for consideration in the development of medicinal cannabis formulations targeting neurodegenerative diseases.”

https://pubmed.ncbi.nlm.nih.gov/38070653/

“In summary, the outcomes from this study reveal a novel and efficacious neuroprotective and anti-aggregatory effect of α-pinene and β-pinene against β amyloid-mediated toxicity. The modest inhibition of lipid peroxidation from α-pinene, β-pinene, and terpinolene may also contribute to the multifaceted neuroprotection of C. sativa-prevalent terpenes. In addition, limited anti-aggregatory effects were observed from terpineol, terpinolene, α-pinene, β-pinene and friedelin. The outcomes of this study contribute to an emerging body of knowledge towards the potential synergistic bioactivities of selected terpenes for consideration in the development of medicinal cannabis formulations targeting neurodegenerative diseases.”

https://www.sciencedirect.com/science/article/pii/S0161813X23001699?via%3Dihub

Assessing Cannabidiol as a Therapeutic Agent for Preventing and Alleviating Alzheimer’s Disease Neurodegeneration

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“Alzheimer’s disease (AD) is a leading neurodegenerative condition causing cognitive and memory decline. With small-molecule drugs targeting Aβ proving ineffective, alternative targets are urgently needed. Neuroinflammation, which is central to AD’s pathology, results in synaptic and neuronal damage, highlighting the importance of addressing inflammation and conserving neuronal integrity. Cannabidiol (CBD), derived from cannabis, is noted for its neuroprotective and anti-inflammatory properties, having shown efficacy in neuropathic pain management for epilepsy. To investigate the therapeutic efficacy of CBD in AD and to elucidate its underlying mechanisms, we aimed to contribute valuable insights for incorporating AD prevention recommendations into future CBD nutritional guidelines. Aβ1-42 was employed for in vivo or in vitro model establishment, CBD treatment was utilized to assess the therapeutic efficacy of CBD, and RNA-seq analysis was conducted to elucidate the underlying therapeutic mechanism. CBD mitigates Aβ-induced cognitive deficits by modulating microglial activity, promoting neurotrophic factor release, and regulating inflammatory genes. The administration of CBD demonstrated a protective effect against Aβ toxicity both in vitro and in vivo, along with an amelioration of cognitive impairment in mice. These findings support the potential inclusion of CBD in future nutritional guidelines for Alzheimer’s disease prevention.”

https://pubmed.ncbi.nlm.nih.gov/38067101/

https://www.mdpi.com/2073-4409/12/23/2672

The Interplay between Cannabinoid Receptors and Microglia in the Pathophysiology of Alzheimer’s Disease

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“Alzheimer’s disease (AD) is characterized by massive neuronal death, brain atrophy, and loss of neurons and synapses, which all lead to a progressive cognitive decline. Neuroinflammation has been recently identified as one of the main causes of AD progression, and microglia cells are considered to have a central role in this process.

Growing evidence suggests that cannabinoids may be used as preventive treatment for AD.

An altered expression of the endocannabinoids (eCBs) and their receptors (CBRs) is reported in several neurodegenerative disorders, including AD. Moreover, the modulation of CBRs demonstrated neuroprotective effects in reducing aggregated protein deposition, suggesting the therapeutic potential of natural and synthetic CBR ligands in the treatment of neurodegenerative proteinopathies. Here, we review the current knowledge regarding the involvement of CBRs in the modulation of microglia activation phenotypes, highlighting the role of neuroinflammation in the pathogenesis of neurodegenerative diseases, like AD. We also provide an overview of recently developed candidate drugs targeting CBRs that may afford a new innovative strategy for the treatment and management of AD.”

https://pubmed.ncbi.nlm.nih.gov/38068253/

https://www.mdpi.com/2077-0383/12/23/7201