Regulatory role of the endocannabinoid system on glial cells toward cognitive function in Alzheimer’s disease: A systematic review and meta-analysis of animal studies

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“Objective: Over the last decade, researchers have sought to develop novel medications against dementia. One potential agent under investigation is cannabinoids. This review systematically appraised and meta-analyzed published pre-clinical research on the mechanism of endocannabinoid system modulation in glial cells and their effects on cognitive function in animal models of Alzheimer’s disease (AD). 

Methods: A systematic review complying with PRISMA guidelines was conducted. Six databases were searched: EBSCOHost, Scopus, PubMed, CINAHL, Cochrane, and Web of Science, using the keywords AD, cannabinoid, glial cells, and cognition. The methodological quality of each selected pre-clinical study was evaluated using the SYRCLE risk of bias tool. A random-effects model was applied to analyze the data and calculate the effect size, while I2 and p-values were used to assess heterogeneity. 

Results: The analysis included 26 original articles describing (1050 rodents) with AD-like symptoms. Rodents treated with cannabinoid agonists showed significant reductions in escape latency (standard mean difference [SMD] = -1.26; 95% confidence interval [CI]: -1.77 to -0.76, p < 0.00001) and ability to discriminate novel objects (SMD = 1.40; 95% CI: 1.04 to 1.76, p < 0.00001) compared to the control group. Furthermore, a significant decrease in Aβ plaques (SMD = -0.91; 95% CI: -1.55 to -0.27, p = 0.006) was observed in the endocannabinoid-treated group compared to the control group. Trends were observed toward neuroprotection, as represented by decreased levels of glial cell markers including glial fibrillary acid protein (SMD = -1.47; 95% CI: -2.56 to -0.38, p = 0.008) and Iba1 (SMD = -1.67; 95% CI: -2.56 to -0.79, p = 0.0002). Studies on the wild-type mice demonstrated significantly decreased levels of pro-inflammatory markers TNF-α, IL-1, and IL-6 (SMD = -2.28; 95% CI: -3.15 to -1.41, p = 0.00001). Despite the non-significant decrease in pro-inflammatory marker levels in transgenic mice (SMD = -0.47; 95% CI: -1.03 to 0.08, p = 0.09), the result favored the endocannabinoid-treated group over the control group. 

Conclusion: The revised data suggested that endocannabinoid stimulation promotes cognitive function via modulation of glial cells by decreasing pro-inflammatory markers in AD-like rodent models. Thus, cannabinoid agents may be required to modulate the downstream chain of effect to enhance cognitive stability against concurrent neuroinflammation in AD. Population-based studies and well-designed clinical trials are required to characterize the acceptability and real-world effectiveness of cannabinoid agents.”

https://pubmed.ncbi.nlm.nih.gov/36959856/

“Numerous traditional medical applications of cannabis have already been established and are now accepted practices in medicine.”

https://www.frontiersin.org/articles/10.3389/fphar.2023.1053680/full

Investigation of Cannabis sativa Phytochemicals as Anti-Alzheimer’s Agents: An In Silico Study

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“Cannabis sativa is a medicinal plant that has been known for years and is used as an Ayurvedic medicine. This plant has great potential in treating various types of brain diseases. Phytochemicals present in this plant act as antioxidants by maintaining synaptic plasticity and preventing neuronal loss.

Cannabidiol (CBD) and Tetrahydrocannabinol (THC) are both beneficial in treating Alzheimer’s disease by increasing the solubility of Aβ42 amyloid and Tau aggregation. Apart from these therapeutic effects, there are certain unknown functions of these phytochemicals in Alzheimer’s disease that we want to elucidate through this study.

In this research, our approach is to analyze the effect of phytochemicals in Cannabis sativa on multiple culprit enzymes in Alzheimer’s disease, such as AChE (Acetylcholinesterase), BChE (Butyrylcholinesterase), γ-secretase, and BACE-1. In this study, the compounds were selected by Lipinski’s rule, ADMET, and ProTox based on toxicity. Molecular docking between the selected compounds (THCV, Cannabinol C2, and Cannabidiorcol) and enzymes mentioned above was obtained by various software programs including AutoDock Vina 4.2, AutoDock, and iGEMDOCK.

In comparison to Donepezil (BA = -8.4 kcal/mol, Ki = 1.46 mM), Rivastigmine (BA = -7.0 kcal/mol, Ki = 0.02 mM), and Galantamine (BA = -7.1, Ki = 2.1 mM), Cannabidiorcol (BA = -9.4 kcal/mol, Ki = 4.61 mM) shows significant inhibition of AChE. On the other hand, Cannabinol C2 (BA = -9.2 kcal/mol, Ki = 4.32 mM) significantly inhibits Butyrylcholinesterase (BuChE) in comparison to Memantine (BA = -6.8 kcal/mol, Ki = 0.54 mM).

This study sheds new light and opens new avenues for elucidating the role of bioactive compounds present in Cannabis sativa in treating Alzheimer’s disease.”

https://pubmed.ncbi.nlm.nih.gov/36771595/

“In comparison to known drugs, THCV, Cannabinol C2 and Cannabidiorcol dominated cannabinoids’ inhibitory activities on AChE and BuChE. Computational approaches suggest that THCV, Cannabinol C2, and Cannabidiorcol are more appropriate for the inhibition of the enzymes AChE and BuChE, which act as the culprits of Alzheimer’s disease. Cell and animal studies are needed to improve the efficacy of these cannabinoids and to learn more about the effecting pathways.”

https://www.mdpi.com/2223-7747/12/3/510

Parkin Mediates Cannabidiol Prevention of Amyloid-Beta-Induced Senescence in Human Astrocytes

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“Introduction: As aging is the leading risk factor for Alzheimer’s disease (AD), ablation of senescent cells is a promising therapeutic approach to prevent AD. It is known that astrocytes lose their ability to maintain a healthy brain environment when aging. Studies have recently shown that cannabidiol (CBD) provides a promising therapeutic avenue for AD; however, if or how CBD prevents astrocyte aging is not known. 

Materials and Methods: In this study, human astrocytes were employed to measure amyloid-beta (Aβ)-induced senescence features, including senescence-associated β-galactosidase (SA-β-gal), p16INK4Ap21WAF1, and p53. The effects of CBD on the production of mitochondrial dysfunction and mitophagy pathway were measured by Western blot and fluorescence assay. Caenorhabditis elegans was used as in vivo AD model to investigate the effects of CBD on life span and health span. All experimental procedures were approved by the Human Research Ethics Committee, University of Wollongong, Australia. 

Results: In human astrocytes, we show that treatment with Aβ, an endogenous pathogenic agent of AD, results in an increase in the percentage of SA-β-gal-positive cells and induces mitochondrial reactive oxygen species (ROS). However, CBD treatment protects from Aβ-induced senescence. Furthermore, the anti-senescence and anti-apoptotic activities of CBD were observed to be mediated through the protective effect of Parkin-dependent mitophagy. In C. elegans, we used the transgenic GRU102 strain, which expresses the human Aβ peptide, and found that CBD treatment extended life span, improved pumping rate, and decreased mitochondrial ROS. 

Conclusion and Significance: Our results demonstrate that CBD prevents the human astrocyte senescence induced by Aβ by a mechanism involving the Parkin-mediated mitophagy pathway. Our findings support the new therapeutic avenues of CBD for the treatment of AD patients.”

https://pubmed.ncbi.nlm.nih.gov/36695672/

Hemp Protein Hydrolysates Modulate Inflammasome-Related Genes in Microglial Cells

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“A prolonged inflammatory response can lead to the development of neurodegenerative diseases such as Alzheimer’s disease. Enzymatic hydrolysis is a sustainable way to increase the value of protein sources by obtaining peptides that can exert bioactivity.

Hemp (Cannabis sativa L.) protein hydrolysates have been proven to exert anti-inflammatory activity.

In this study, two hemp protein hydrolysate (HPHs), obtained with Alcalase as sole catalyst, or with Alcalase followed by Flavourzyme, were evaluated as inflammatory mediators (TNFα, IL-1β, IL-6, and IL-10), microglial polarization markers (Ccr7iNosArg1, and Ym1), and genes related to inflammasome activation (Nlrp3AscCasp1, and Il18), employing the lipopolysaccharide (LPS)-induced neuroinflammation model in murine BV-2 microglial cells.

A significant decrease of the expression of proinflammatory genes (e.g., TnfαCcr7inos, and Nlrp3, among others) and increase of the expression anti-inflammatory cytokines in microglial cells was observed after treatment with the test HPHs. This result in the cell model suggests a polarization toward an anti-inflammatory M2 phenotype. Our results show that the evaluated HPHs show potential neuroprotective activity in microglial cells via the inflammasome.”

https://pubmed.ncbi.nlm.nih.gov/36671742/

“Neuroinflammation can lead to the development of neurodegenerative diseases. Food-derived peptides released by the action of enzymes have been proven to modulate several physiological processes. In this study, peptides obtained from hemp protein were evaluated as anti-inflammatory agents employing a cell model, measuring the responses of inflammatory mediators, microglial polarization markers, and genes related to inflammasome activation, as markers of inflammation and the potential counteraction exerted by the peptides, related to neurodegenerative processes. Results showed a neuroprotective effect based on anti-inflammatory activity of the peptides, via the inflammasome. The use of these peptides in the diet could help to prevent inflammation and promote a healthy aging of humans.”

https://www.mdpi.com/2079-7737/12/1/49

Oral THC: CBD cannabis extract in main symptoms of Alzheimer disease: agitation and weight loss

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“Objectives: Ten million new cases of dementia are recorded annually worldwide, with agitation and idiopathic weight loss being the most common symptoms. Several pharmacological therapies have emerged in recent years, but the clinical use of cannabis extracts in older patients with AD is constantly growing. This retrospective, analytical, observational, spontaneous trial aimed to enhance the clinical action of THC: CBD cannabis extract administration in AD patients with severe symptoms such as agitation, weight loss, cognitive impairment, and sleep disturbance.

Methods: Thirty patients (9 men and 21 women) diagnosed with mild, moderate, or severe AD, aged 65-90 years, appealing to our Second Opinion Medical Consultation (Modena, Italy), were enrolled and required to use oil-diluted cannabis extract, Bedrocan® (22% THC, 0.5% CBD, Olive Oil 50 ml), twice a day for 12 weeks. The efficacy of cannabinoid therapy was evaluated at baseline and 12 weeks after therapy, employing three self-administered questionnaires completed by the parents of the enrolled patients: NPI-Q, CMAI, and MMSE.

Key findings: The NPI-Q demonstrated a reduction (p<0.0001) in agitation, apathy, irritability, sleep disturbances, and eating disturbances, consequently improving caregiver distress. Levels of physically and verbally aggressive behaviours, measured using the CMAI questionnaire, were lower (p<0.0001) in all patients. The MMSSE questionnaire confirmed a significant decrease (p<0.0001) in cognitive impairment in 45% of the patients.

Conclusion: Our anecdotical, spontaneous, and observational study demonstrated the efficacy and safety of oil-diluted cannabis extract in patients with AD. The limitations of our study are: 1) small patient cohort, 2) absence of control group, 3) self-administered questionnaires that are the most practical but not objective instruments to assess the neurologic functions of AD patients.”

https://pubmed.ncbi.nlm.nih.gov/36655645/

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.”

https://pubmed.ncbi.nlm.nih.gov/36637897/

https://iubmb.onlinelibrary.wiley.com/doi/10.1002/biof.1936

Cannabinoids in Late Life Parkinson’s Disease and Dementia: Biological Pathways and Clinical Challenges

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“The use of cannabinoids as therapeutic drugs has increased among aging populations recently. Age-related changes in the endogenous cannabinoid system could influence the effects of therapies that target the cannabinoid system. At the preclinical level, cannabidiol (CBD) induces anti-amyloidogenic, antioxidative, anti-apoptotic, anti-inflammatory, and neuroprotective effects. These findings suggest a potential therapeutic role of cannabinoids to neurodegenerative disorders such as Parkinson’s disease (PD) and Alzheimer.

Emerging evidence suggests that CBD and tetrahydrocannabinol have neuroprotective therapeutic-like effects on dementias. In clinical practice, cannabinoids are being used off-label to relieve symptoms of PD and AD. In fact, patients are using cannabis compounds for the treatment of tremor, non-motor symptoms, anxiety, and sleep assistance in PD, and managing responsive behaviors of dementia such as agitation. However, strong evidence from clinical trials is scarce for most indications.

Some clinicians consider cannabinoids an alternative for older adults bearing Parkinson’s disease and Alzheimer’s dementia with a poor response to first-line treatments. In our concept and experience, cannabinoids should never be considered a first-line treatment but could be regarded as an adjuvant therapy in specific situations commonly seen in clinical practice. To mitigate the risk of adverse events, the traditional dogma of geriatric medicine, starting with a low dose and proceeding with a slow titration regime, should also be employed with cannabinoids. In this review, we aimed to address preclinical evidence of cannabinoids in neurodegenerative disorders such as PD and AD and discuss potential off-label use of cannabinoids in clinical practice of these disorders.”

https://pubmed.ncbi.nlm.nih.gov/36552056/

“Cannabinoids constitute a promising pharmacological approach to treatment of neuropsychiatric disorders in late life.

Overall, cannabinoids compounds are well tolerated and appear to be safer than most psychotropic medication, but given the vulnerability of patients with dementia, they require appropriate monitoring by the clinician.”

https://www.mdpi.com/2076-3425/12/12/1596

The gut microbiota in neurodegenerative diseases: revisiting possible therapeutic targets for cannabidiol

Heliyon | Journal | ScienceDirect.com by Elsevier

“Understanding the pathophysiology of Alzheimer’s disease (AD) is essential to improve the efficacy of treatments and, consequently, patients’ lives. Unfortunately, traditional therapeutic strategies have not been effective. There is therefore an urgent need to discover or develop alternative treatment strategies.

Recently, some pieces of the puzzle appear to emerge: on a hand, the gut microbiota (GM) has gained attention since intestinal dysbiosis aggravates and generates some of the pathological processes of AD; on the other hand, cannabidiol (CBD), a phytocannabinoid, attenuates intestinal inflammation and possesses neuroprotective properties.

Intestinal dysbiosis (increased population of proinflammatory bacteria) in AD increases plasma lipopolysaccharide and Aβ peptide levels, both responsible for increasing the permeability of the blood-brain barrier (BBB). A leaky BBB may facilitate the entry of peripheral inflammatory mediators into the central nervous system and ultimately aggravate neuroinflammation and neuronal death due to chronic activation of glial cells. Studies investigating the GM reported a strong relationship between intestinal dysbiosis and AD. In this review we conjecture that the GM is a promising therapeutic target for CBD in the context of AD.”

https://pubmed.ncbi.nlm.nih.gov/36544841/

https://www.cell.com/heliyon/fulltext/S2405-8440(22)03460-0?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2405844022034600%3Fshowall%3Dtrue

Cannabidiol Protects Striatal Neurons by Attenuating Endoplasmic Reticulum Stress

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“Introduction: The aggregation of misfolded proteins in the endoplasmic reticulum (ER) is a pathological trait shared by many neurodegenerative disorders. This aggregation leads to the persistent activation of the unfolded protein response (UPR) and ultimately apoptosis as a result of ER stress. Cannabidiol (CBD) has been demonstrated to be neuroprotective in various cellular and animal models of neurodegeneration, which has been attributed to its antioxidant and anti-inflammatory properties. However, little is known about the role of CBD in the context of protein folding and ER stress. The purpose of this study was to investigate whether CBD is neuroprotective against an in vitro model of ER stress. 

Materials and Methods: Using different exposure models, mouse striatal STHdhQ7/Q7 cells were exposed to either the ER stress inducer thapsigargin (TG) and/or CBD. Cell viabilities assays were used to investigate the effect of CBD pre-treatment, co-treatment, and post-treatment on TG-induced cell death. Real-time quantitative polymerase chain reaction was used to measure changes in ER stress regulators and UPR genes such as glucose-regulated protein-78 (GRP78), mesencephalic astrocyte-derived neurotrophic factor (MANF), B cell lymphoma 2 (BCL-2), BCL-2 interacting mediator of cell death (BIM), and caspase-12. 

Results: Cell viability increased significantly when cells were pre-treated with CBD before TG exposure. An increase in the gene expression of pro-survival ER chaperone GRP78 and ER-resident neurotrophic factor MANF coincided with this effect and decreased ER-mediated pro-apoptotic markers such as BIM, and caspase-12 was observed. 

Conclusions: These data suggest that CBD pre-treatment is neuroprotective against TG-induced cell death. Understanding the role of ER stress in CBD-driven neuroprotection provides insight into the therapeutic potential of CBD and the role of ER dysfunction in neurodegenerative disorders.”

https://pubmed.ncbi.nlm.nih.gov/36454179/

https://www.liebertpub.com/doi/10.1089/can.2022.0090

Cannabidiol for neurodegenerative disorders: A comprehensive review

Frontiers - Crunchbase Company Profile & Funding

“Despite the significant advances in neurology, the cure for neurodegenerative conditions remains a formidable task to date. Among various factors arising from the complex etiology of neurodegenerative diseases, neuroinflammation and oxidative stress play a major role in pathogenesis. To this end, some phytocannabinoids isolated from Cannabis sativa (widely known as marijuana) have attracted significant attention as potential neurotherapeutics. The profound effect of ∆9-tetrahydrocannabinol (THC), the major psychoactive component of cannabis, has led to the discovery of the endocannabinoid system as a molecular target in the central nervous system (CNS). Cannabidiol (CBD), the major non-psychoactive component of cannabis, has recently emerged as a potential prototype for neuroprotective drug development due to its antioxidant and anti-inflammatory properties and its well-tolerated pharmacological behavior. This review briefly discusses the role of inflammation and oxidative stress in neurodegeneration and demonstrates the neuroprotective effect of cannabidiol, highlighting its general mechanism of action and disease-specific pathways in Parkinson’s disease (PD) and Alzheimer’s disease (AD). Furthermore, we have summarized the preclinical and clinical findings on the therapeutic promise of CBD in PD and AD, shed light on the importance of determining its therapeutic window, and provide insights into identifying promising new research directions.”

https://pubmed.ncbi.nlm.nih.gov/36386183/

https://www.frontiersin.org/articles/10.3389/fphar.2022.989717/full