Category Archives: Alzheimer’s Disease (AD)

Effects of cannabidiol interactions with Wnt/β-catenin pathway and PPARγ on oxidative stress and neuroinflammation in Alzheimer’s disease.

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“Alzheimer’s disease (AD) is a neurodegenerative disease, in which the primary etiology remains unknown. AD presents amyloid beta (Aβ) protein aggregation and neurofibrillary plaque deposits. AD shows oxidative stress and chronic inflammation.

In AD, canonical Wingless-Int (Wnt)/β-catenin pathway is downregulated, whereas peroxisome proliferator-activated receptor γ (PPARγ) is increased. Downregulation of Wnt/β-catenin, through activation of glycogen synthase kinase-3β (GSK-3β) by Aβ, and inactivation of phosphatidylinositol 3-kinase/Akt signaling involve oxidative stress in AD.

Cannabidiol (CBD) is a non-psychotomimetic phytocannabinoid from Cannabis sativa plant. In PC12 cells, Aβ-induced tau protein hyperphosphorylation is inhibited by CBD. This inhibition is associated with a downregulation of p-GSK-3β, an inhibitor of Wnt pathway. CBD may also increase Wnt/β-catenin by stimulation of PPARγ, inhibition of Aβ and ubiquitination of amyloid precursor protein.

CBD attenuates oxidative stress and diminishes mitochondrial dysfunction and reactive oxygen species generation. CBD suppresses, through activation of PPARγ, pro-inflammatory signaling and may be a potential new candidate for AD therapy.”

https://www.ncbi.nlm.nih.gov/pubmed/28981597

https://academic.oup.com/abbs/article-abstract/49/10/853/3978657/Effects-of-cannabidiol-interactions-with-Wnt?redirectedFrom=fulltext

Delta-9-Tetrahydrocannabinol (∆9-THC) Induce Neurogenesis and Improve Cognitive Performances of Male Sprague Dawley Rats.

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Neurotoxicity Research

“Neurogenesis is influenced by various external factors such as enriched environments. Some researchers had postulated that neurogenesis has contributed to the hippocampal learning and memory. This project was designed to observe the effect of Delta-9-tetrahydrocannabinol (∆9-THC) in cognitive performance that influenced by the neurogenesis.

Different doses of ∆9-THC were used for observing the neurogenesis mechanism occurs in the hippocampus of rats. The brains were stained with antibodies, namely BrdU, glial fibrillary acidic protein (GFAP), nestin, doublecortin (DCX) and class III β-tubulin (TuJ-1). The cognitive test was used novel-object discrimination test (NOD) while the proteins involved, DCX and brain-derived neurotrophic factor (BDNF), were measured.

Throughout this study, ∆9-THC enhanced the markers involved in all stages of neurogenesis mechanism. Simultaneously, the cognitive behaviour of rat also showed improvement in learning and memory functions observed in behavioural test and molecular perspective.

Administration of ∆9-THC was observed to enhance the neurogenesis in the brain, especially in hippocampus thus improved the cognitive function of rats.”

https://www.ncbi.nlm.nih.gov/pubmed/28933048

https://link.springer.com/article/10.1007%2Fs12640-017-9806-x

Receptor-heteromer mediated regulation of endocannabinoid signaling in activated microglia. Role of CB1 and CB2 receptors and relevance for Alzheimer’s disease and levodopa-induced dyskinesia.

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“Endocannabinoids are important regulators of neurotransmission and, acting on activated microglia, they are postulated as neuroprotective agents. Endocannabinoid action is mediated by CB1 and CB2 receptors, which may form heteromeric complexes (CB1-CB2Hets) with unknown function in microglia.

We aimed at establishing the expression and signaling properties of cannabinoidreceptors in resting and LPS/IFN-γ-activated microglia. Unlike CB1, CB2 receptors and CB1-CB2Hets were upregulated in activated microglia. Resting cell refractory CB2 receptors became robustly coupled to Gi in activated cells, in which CB1-CB2Hets mediated a positive cross-talk. Resting cells were refractory while activated cells were highly responsive to cannabinoids. Interestingly, similar results were obtained in cultures treated with ß-amyloid (Aß1-42). Activation microglial markers were detected in the striatum of a Parkinson’s disease (PD) model and, remarkably, in primary microglia cultures from the hippocampus of mutant β-amyloid precursor protein (APPSw,Ind) mice, a transgenic Alzheimer’s disease (AD) model. Also of note was the similar cannabinoid receptor signaling found in primary cultures of microglia from APPSw,Ind and in cells from control animals activated using LPS plus IFN- γ. Expression of CB1-CB2Hets was increased in the striatum from rats rendered dyskinetic by chronic levodopa treatment.

In summary, our results showed sensitivity of activated microglial cells to cannabinoids, increased CB1-CB2Het expression in activated microglia and in microglia from the hippocampus of an AD model, and a correlation between levodopa-induced dyskinesia and striatal microglial activation in a PD model. Cannabinoid receptors and the CB1-CB2 heteroreceptor complex in activated microglia have potential as targets in the treatment of neurodegenerative diseases.”

https://www.ncbi.nlm.nih.gov/pubmed/28843453

http://www.sciencedirect.com/science/article/pii/S0889159117304038

Modulation of Astrocyte Activity by Cannabidiol, a Nonpsychoactive Cannabinoid.

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“The astrocytes have gained in recent decades an enormous interest as a potential target for neurotherapies, due to their essential and pleiotropic roles in brain physiology and pathology. Their precise regulation is still far from understood, although several candidate molecules/systems arise as promising targets for astrocyte-mediated neuroregulation and/or neuroprotection.

The cannabinoid system and its ligands have been shown to interact and affect activities of astrocytes. Cannabidiol (CBD) is the main non-psychotomimetic cannabinoid derived from Cannabis. CBD is devoid of direct CB1 and CB2 receptor activity, but exerts a number of important effects in the brain. Here, we attempt to sum up the current findings on the effects of CBD on astrocyte activity, and in this way on central nervous system (CNS) functions, across various tested models and neuropathologies.

The collected data shows that increased astrocyte activity is suppressed in the presence of CBD in models of ischemia, Alzheimer-like and Multiple-Sclerosis-like neurodegenerations, sciatic nerve injury, epilepsy, and schizophrenia. Moreover, CBD has been shown to decrease proinflammatory functions and signaling in astrocytes.”

https://www.ncbi.nlm.nih.gov/pubmed/28788104

http://www.mdpi.com/1422-0067/18/8/1669

Modeling Neurodegenerative Disorders for Developing Cannabinoid-Based Neuroprotective Therapies.

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Methods in Enzymology

“The increase in lifespan during the last 50 years, mainly in developed countries, has originated a progressive elevation in the incidence of chronic neurodegenerative disorders, for which aging is the key risk factor. This fact will definitively become the major biomedical challenge during the present century, in part because the expectation of a persisting elevation in the population older than 65 years over the whole population and, on the other hand, because the current lack of efficacious therapies to control these disorders despite years of intense research.

This chapter will address this question and will stress the urgency of developing better neuroprotective and neurorepair strategies that may delay/arrest the progression of these disorders, reviewing the major needs to solve the causes proposed for the permanent failures experienced in recent years, e.g., to develop multitarget strategies, to use more predictive experimental models, and to identify early disease biomarkers.

This chapter will propose the cannabinoids and their classic (e.g., endocannabinoid receptors and enzymes) and nonclassic (e.g., peroxisome proliferator-activated receptors, transcription factors) targets as a useful strategy for developing novel therapies for these disorders, based on their broad-spectrum neuroprotective profile, their activity as an endogenous protective system, the location of the endocannabinoid targets in cell substrates critical for neuronal survival, and their ability to serve for preservation and rescue, but also for repair and/or replacement, of neurons and glial cells against cytotoxic insults.”

https://www.ncbi.nlm.nih.gov/pubmed/28750802

http://www.sciencedirect.com/science/article/pii/S0076687917301787?via%3Dihub

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

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Molecular Neurobiology

“Inhibition of monoacylglycerol lipase (MAGL), the primary enzyme that hydrolyzes the endocannabinoid 2-arachidonoylglycerol (2-AG) in the brain, produces profound anti-inflammatory and neuroprotective effects and improves synaptic and cognitive functions in animal models of Alzheimer’s disease (AD). However, the molecular mechanisms underlying the beneficial effects produced by inhibition of 2-AG metabolism are still not clear.

The cannabinoid receptor type 2 (CB2R) has been thought to be a therapeutic target for AD. Here, we provide evidence, however, that CB2R does not play a role in ameliorating AD neuropathology produced by inactivation of MAGL in 5XFAD APP transgenic mice, an animal model of AD.

Our results suggest that CB2R is not required in ameliorating neuropathology and preventing cognitive decline by inhibition of 2-AG metabolism in AD model animals.”

 https://www.ncbi.nlm.nih.gov/pubmed/28733897
https://link.springer.com/article/10.1007%2Fs12035-017-0689-x

Amyloid proteotoxicity initiates an inflammatory response blocked by cannabinoids.

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“The beta amyloid (Aβ) and other aggregating proteins in the brain increase with age and are frequently found within neurons. The mechanistic relationship between intracellular amyloid, aging and neurodegeneration is not, however, well understood.

We use a proteotoxicity model based upon the inducible expression of Aβ in a human central nervous system nerve cell line to characterize a distinct form of nerve cell death caused by intracellular Aβ. It is shown that intracellular Aβ initiates a toxic inflammatory response leading to the cell’s demise. Aβ induces the expression of multiple proinflammatory genes and an increase in both arachidonic acid and eicosanoids, including prostaglandins that are neuroprotective and leukotrienes that potentiate death.

Cannabinoids such as tetrahydrocannabinol stimulate the removal of intraneuronal Aβ, block the inflammatory response, and are protective.

Altogether these data show that there is a complex and likely autocatalytic inflammatory response within nerve cells caused by the accumulation of intracellular Aβ, and that this early form of proteotoxicity can be blocked by the activation of cannabinoid receptors.”

 https://www.ncbi.nlm.nih.gov/pubmed/28721267
https://www.nature.com/articles/npjamd201612

Deletion of Type-2 Cannabinoid Receptor Induces Alzheimer’s Disease-Like Tau Pathology and Memory Impairment Through AMPK/GSK3β Pathway.

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Molecular Neurobiology

“Although several studies have shown that type-2 cannabinoid receptor (CB2R) is involved in Alzheimer’s disease (AD) pathology, the effects of CB2R on AD-like tau abnormal phosphorylation and its underlying mechanism remain unclear.

Herein, we employed the CB2R-/- mice as the animal model to explore roles of CB2R in regulating tau phosphorylation and brain function.

Taken together, our study indicated that deletion of CB2R induces behavior damage and AD-like pathological alternation via AMPK/GSK3β pathway. These findings proved that CB2R/AMPK/GSK3β pathway can be a promising new drug target for AD.”

 https://www.ncbi.nlm.nih.gov/pubmed/28717968
https://link.springer.com/article/10.1007%2Fs12035-017-0676-2

Endocannabinoid System in Neurodegenerative Disorders.

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Journal of Neurochemistry

“Most neurodegenerative disorders (NDDs) are characterized by cognitive impairment and other neurological defects. The definite cause of and pathways underlying the progression of these NDDs are not well defined. Several mechanisms have been proposed to contribute to the development of NDDs. These mechanisms may proceed concurrently or successively, and they differ among cell types at different developmental stages in distinct brain regions. The endocannabinoid system, which involves cannabinoid receptors type 1 (CB1R) and type 2 (CB2R), endogenous cannabinoids and the enzymes that catabolize these compounds, has been shown to contribute to the development of NDDs in several animal models and human studies. In this review, we discuss the functions of the endocannabinoid (EC) system in NDDs and converse the therapeutic efficacy of targeting the endocannabinoid system to rescue NDDs.”

https://www.ncbi.nlm.nih.gov/pubmed/28608560

http://onlinelibrary.wiley.com/doi/10.1111/jnc.14098/abstract

Plastic and Neuroprotective Mechanisms Involved in the Therapeutic Effects of Cannabidiol in Psychiatric Disorders.

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“Beneficial effects of cannabidiol (CBD) have been described for a wide range of psychiatric disorders, including anxiety, psychosis, and depression. The mechanisms responsible for these effects, however, are still poorly understood. Similar to clinical antidepressant or atypical antipsychotic drugs, recent findings clearly indicate that CBD, either acutely or repeatedly administered, induces plastic changes. For example, CBD attenuates the decrease in hippocampal neurogenesis and dendrite spines density induced by chronic stress and prevents microglia activation and the decrease in the number of parvalbumin-positive GABA neurons in a pharmacological model of schizophrenia. More recently, it was found that CBD modulates cell fate regulatory pathways such as autophagy and others critical pathways for neuronal survival in neurodegenerative experimental models, suggesting the potential benefit of CBD treatment for psychiatric/cognitive symptoms associated with neurodegeneration. These changes and their possible association with CBD beneficial effects in psychiatric disorders are reviewed here.”

https://www.ncbi.nlm.nih.gov/pubmed/28588483

http://journal.frontiersin.org/article/10.3389/fphar.2017.00269/full