The Potential Therapeutic Effects of THC on Alzheimer's Disease

BACE1 inhibitors: Current status and future directions in treating Alzheimer's disease

Alzheimer's disease (AD) is an irreversible, progressive neurodegenerative brain disorder with no current cure. One of the important therapeutic approaches of AD is the inhibition of β-site APP cleaving enzyme-1 (BACE1), which is involved in the rate-limiting step of the cleavage process of the amyloid precursor protein (APP) leading to the generation of the neurotoxic amyloid β (Aβ) protein after the γ-secretase completes its function. The produced insoluble Aβ aggregates lead to plaques deposition and neurodegeneration. BACE1 is, therefore, one of the attractive targets for the treatment of AD. This approach led to the development of potent BACE1 inhibitors, many of which were advanced to late stages in clinical trials. Nonetheless, the high failure rate of lead drug candidates targeting BACE1 brought to the forefront the need for finding new targets to uncover the mystery behind AD. In this review, we aim to discuss the most promising classes of BACE1 inhibitors with a description and analysis of their pharmacodynamic and pharmacokinetic parameters, with more focus on the lead drug candidates that reached late stages of clinical trials, such as MK8931, AZD-3293, JNJ-54861911, E2609, and CNP520. In addition, the manuscript discusses the safety concerns and insignificant physiological effects, which were highlighted for the most successful BACE1 inhibitors. Furthermore, the review demonstrates with increasing evidence that despite tremendous efforts and promising results conceived with BACE1 inhibitors, the latest studies suggest that their clinical use for treating Alzheimer's disease should be reconsidered. Finally, the review sheds light on alternative therapeutic options for targeting AD.

Spontaneous, anecdotal, retrospective, open-label study on the efficacy, safety and tolerability of cannabis galenical preparation (Bedrocan)

OBJECTIVES

Our main aim was to investigate the short-term therapeutic effects, safety/tolerability and potential side effects of the cannabis galenical preparation (Bedrocan) in patients with a range of chronic conditions unresponsive to other treatments.

METHODS

In this retrospective, 'compassionate use', observational, open-label study, 20 patients (age 18-80 years) who had appealed to our 'Second Opinion Medical Consulting Network' (Modena, Italy), were instructed to take sublingually the galenical oil twice a day for 3 months of treatment. The usual starting dose was low (0.5 ml/day) and gradually titrated upward to the highest recommended dose (1 ml/day). Tolerability and adverse effects were assessed at baseline and monthly thereafter during the treatment period through direct contact (email or telephone) or visit if required. Patients' quality of life was evaluated at baseline and 3 months using the medical outcome short-form health survey questionnaire (SF-36).

KEY FINDINGS

From baseline to 6 months post-treatment, SF-36 scores showed: reductions in total pain (P < 0.03); improvements in the physical component (P < 0.02); vitality (P < 0.03); social role functioning (P < 0.02); and general health state (P < 0.02). No changes in role limitations (P = 0.02) due to emotional state (e.g. panic, depression, mood alteration) were reported. Monthly reports of psychoactive adverse effects showed significant insomnia reduction (P < 0.03) and improvement in mood (P < 0.03) and concentration (P < 0.01).

CONCLUSIONS

These data suggest that a cannabis galenical preparation may be therapeutically effective and safe for the symptomatic treatment of some chronic diseases. Further studies on the efficacy of cannabis as well as cannabinoid system involvement in the pathophysiology are warranted.

Theoretical Explanation for Reduced Body Mass Index and Obesity Rates in Cannabis Users

Introduction: Obesity is treatment-resistant, and is linked with a number of serious, chronic diseases. Adult obesity rates in the United States have tripled since the early 1960s. Recent reviews show that an increased ratio of omega-6 to omega-3 fatty acids contributes to obesity rates by increasing levels of the endocannabinoid signals AEA and 2-AG, overstimulating CB₁R and leading to increased caloric intake, reduced metabolic rates, and weight gain. Cannabis, or THC, also stimulates CB₁R and increases caloric intake during acute exposures. Goals: To establish the relationship between Cannabis use and body mass index, and to provide a theoretical explanation for this relationship. Results: The present meta-analysis reveals significantly reduced body mass index and rates of obesity in Cannabis users, in conjunction with increased caloric intake. Theoretical explanation: We provide for the first time a causative explanation for this paradox, in which rapid and long-lasting downregulation of CB₁R following acute Cannabis consumption reduces energy storage and increases metabolic rates, thus reversing the impact on body mass index of elevated dietary omega-6/omega-3 ratios.

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.

Biphasic effects of THC in memory and cognition

A generally undesired effect of cannabis smoking is a reversible disruption of short-term memory induced by delta-9-tetrahydrocannabinol (THC), the primary psychoactive component of cannabis. However, this paradigm has been recently challenged by a group of scientists who have shown that THC is also able to improve neurological function in old animals when chronically administered at low concentrations. Moreover, recent studies demonstrated that THC paradoxically promotes hippocampal neurogenesis, prevents neurodegenerative processes occurring in animal models of Alzheimer's disease, protects from inflammation-induced cognitive damage and restores memory and cognitive function in old mice. With the aim to reconcile these seemingly contradictory facts, this work will show that such paradox can be explained within the framework of hormesis, defined as a biphasic dose-response.

Combinatorial Treatment Effects in a Cell Culture Model of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is the leading cause of dementia, and as its prevalence increases, so does its detrimental impact on society. The currently available therapies have limited efficacy, leaving AD patients on an irrevocably fatal path of this disease.

OBJECTIVE

The purpose of this study was to test efficacy of a novel combinatorial treatment approach to alleviate AD-like pathology.

METHODS

We selected four naturally occurring compounds and used them in different combinations to test their effect on AD-like pathology. Employing a well-established cell culture AD model system, we evaluated levels of several diverse biomarkers associated with a number of cellular pathways associated with AD. The readouts included: amyloid-β peptides, anti-inflammatory and anti-apoptotic proteins, oxidative enzymes, and reactive oxygen species.

RESULTS

Using this approach, we demonstrated that the compounds delivered in combination had higher efficacy than individual treatments. Specifically, we observed significant reduction in levels of the amyloid-β peptides, as well as pro-inflammatory proteins and reactive oxygen species. Similarly, delivery of compounds in combination resulted in an increased expression of anti-apoptotic proteins and anti-oxidative enzymes. Collectively, these modifications in AD pathology biomarkers reflect a promising therapeutic and preventive strategy to combat this disease.

CONCLUSION

The above findings support a novel therapeutic approach to address a currently unmet medical need, which would benefit not only AD patients and their caregivers, but also society as a whole.

Commentary: Navigating the complexities of marijuana

Science needs to drive our thinking as we navigate a new legislative environment in which many Americans have access to marijuana for therapeutic or recreational use. With the responsibility to fund, conduct, and make use of the research on marijuana, and understand the impacts of new policies, comes the obligation of not thinking in simplistic, black-and-white terms about this substance. The drug's unique harms include neurodevelopmental impacts that may be long lasting or permanent, yet some evidence suggests the drug may benefit people with certain medical conditions (e.g., chronic pain). Marijuana use is also entangled with other substance use and should not be considered in isolation. Finally, policy options are not limited to the extremes of prohibition vs. full commercialization; a spectrum of intermediate options can and should be considered and evaluated as states create new policies around this drug.

Endocannabinoid system in neurodegenerative disorders

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 system in NDDs and converse the therapeutic efficacy of targeting the endocannabinoid system to rescue NDDs.

Emerging treatments for Alzheimer's disease for non-amyloid and non-tau targets

INTRODUCTION

The number of people with dementia, including Alzheimer's disease, is growing as a result of an ageing global population. Treatments available for AD only alleviate the symptoms of the disease, and are effective in some people with AD for a limited time. There is no disease-modifying treatment available, and despite research efforts, the underlying mechanisms of AD and optimal treatment targets have not been fully elucidated. Amyloid and tau are key pathological markers of AD with ongoing trials targeting both. However, there are also many trials at various stages of development that primarily target other markers and processes implicated in the disease, which are now being investigated. Areas covered: This review summarizes current treatment approaches for AD and explores both repositioned and novel therapies that target non amyloid and non tau mechanisms that are in the clinical trials pipeline. This includes treatments for cognitive and neuropsychiatric symptoms and potentially disease modifying therapies. The studies included in this review have been obtained from searches of PubMed and clinical trials databases. Expert commentary: There is a renewed energy in identifying better treatments for behavioural symptoms of AD using both novel drugs and repositioning existing drugs. Lack of success in clinical trials of drugs targeting amyloid and tau have led to a surge in targeting alternative mechanisms. Progress in the development of biomarkers will provide further tools for clinical trials of potential therapeutics for both symptomatic treatment and disease modification in AD.

Effects of chronic Δ9-tetrahydrocannabinol treatment on Rho/Rho-kinase signalization pathway in mouse brain

Δ⁹-Tetrahydrocannabinol (Δ⁹-THC) shows its effects by activating cannabinoid receptors which are on some tissues and neurons. Cannabinoid systems have role on cell proliferation and development of neurons. Furthermore, it is interesting that cannabinoid system and rho/rho-kinase signalization pathway, which have important role on cell development and proliferation, may have role on neuron proliferation and development together. Thus, a study is planned to investigate rhoA and rho-kinase enzyme expressions and their activities in the brain of chronic Δ⁹-THC treated mice. One group of mice are treated with Δ⁹-THC once to see effects of acute treatment. Another group of mice are treated with Δ⁹-THC three times per day for one month. After this period, rhoA and rho-kinase enzyme expressions and their activities in mice brains are analyzed by ELISA method. Chronic administration of Δ⁹-THC decreased the expression of rhoA while acute treatment has no meaningful effect on it. Administration of Δ⁹-THC did not affect expression of rho-kinase on both chronic and acute treatment. Administration of Δ⁹-THC increased rho-kinase activity on both chronic and acute treatment, however, chronic treatment decreased its activity with respect to acute treatment. This study showed that chronic Δ⁹-THC treatment down-regulated rhoA expression and did not change the expression level of rho-kinase which is downstream effector of rhoA. However, it elevated the rho-kinase activity. Δ⁹-THC induced down-regulation of rhoA may cause elevation of cypin expression and may have benefit on cypin related diseases. Furthermore, use of rho-kinase inhibitors and Δ⁹-THC together can be useful on rho-kinase related diseases.

Cannabinoids therapeutic use: what is our current understanding following the introduction of THC, THC:CBD oromucosal spray and others?

INTRODUCTION

The complexity of the endocannabinoid (eCB) system is becoming better understood and new drivers of eCB signaling are emerging. Modulation of the activities of the eCB system can be therapeutic in a number of diseases. Research into the eCB system has been paralleled by the development of agents that interact with cannabinoid receptors. In this regard it should be remembered that herbal cannabis contains a myriad of active ingredients, and the individual cannabinoids have quite distinct biological activities requiring independent studies. Areas covered: This article reviews the most important current data involving the eCB system in relation to human diseases, to reflect the present (based mainly on the most used prescription cannabinoid medicine, THC/CBD oromucosal spray) and potential future uses of cannabinoid-based therapy. Expert commentary: From the different therapeutic possibilities, THC/CBD oromucosal spray has been in clinical use for approximately five years in numerous countries world-wide for the management of multiple sclerosis (MS)-related moderate to severe resistant spasticity. Clinical trials have confirmed its efficacy and tolerability. Other diseases in which different cannabinoids are currently being investigated include various pain states, Alzheimer's disease, Parkinson's disease, Huntington's disease and epilepsy. The continued characterization of individual cannabinoids in different diseases remains important.

Dissecting the Signaling Pathways Involved in the Crosstalk between Metabotropic Glutamate 5 and Cannabinoid Type 1 Receptors

The metabotropic glutamate 5 receptor and the cannabinoid type 1 receptor are G protein-coupled receptors that are widely expressed in the central nervous system. Metabotropic glutamate 5 receptors, present at the postsynaptic site, are coupled to Gαq/11 proteins and display an excitatory response upon activation, whereas the cannabinoid type 1 receptor, mainly present at presynaptic terminals, is coupled to the Gi/o protein and triggers an inhibitory response. Recent studies suggest that the glutamatergic and endocannabinoid systems exhibit a functional interaction to modulate several neural processes. In this review, we discuss possible mechanisms involved in this crosstalk and its relationship with physiologic and pathologic conditions, including nociception, addiction, and fragile X syndrome.

Synthesis, molecular modeling and SAR study of novel pyrazolo[5,1-f][1,6]naphthyridines as CB2 receptor antagonists/inverse agonists

Pyrazolo[5,1-f][1,6]naphthyridine-carboxamide derivatives were synthesized and evaluated for the affinity at CB₁ and CB₂ receptors. Based on the AgOTf and proline-cocatalyzed multicomponent methodology, the ethyl 5-(p-tolyl)pyrazolo[5,1-f][1,6]naphthyridine-2-carboxylate (12) and ethyl 5-(2,4-dichlorophenyl)pyrazolo[5,1-f][1,6]naphthyridine-2-carboxylate (13) intermediates were synthesized from the appropriate o-alkynylaldehydes, p-toluenesulfonyl hydrazide and ethyl pyruvate. Most of the novel compounds feature a p-tolyl (8a-i) or a 2,4-dichlorophenyl (8j) motif at the C₅-position of the tricyclic pyrazolo[5,1-f][1,6]naphthyridine scaffold. Structural variation on the carboxamide moiety at the C₂-position includes basic monocyclic, terpenoid and adamantine-based amines. Among these derivatives, compound 8h (N-adamant-1-yl-5-(p-tolyl)pyrazolo[5,1-f][1,6]naphthyridine-2-carboxamide) exhibited the highest CB₂ receptor affinity (K_i=33nM) and a high degree of selectivity (K_iCB₁/K_iCB₂=173:1), whereas a similar trend in the near nM range was seen for the bornyl analogue (compound 8f, K_i=53nM) and the myrtanyl derivative 8j (K_i=67nM). Effects of 8h, 8f and 8j on forskolin-stimulated cAMP levels were determined, showing antagonist/inverse agonist properties for such compounds. Docking studies conducted for these derivatives and the reference antagonist/inverse agonist compound 4 (SR144528) disclosed the specific pattern of interactions probably related to the pyrazolo[5,1-f][1,6]naphthyridine scaffold as CB₂ inverse agonists.

CB2 Cannabinoid Receptor As Potential Target against Alzheimer's Disease

The CB2 receptor is one of the components of the endogenous cannabinoid system, a complex network of signaling molecules and receptors involved in the homeostatic control of several physiological functions. Accumulated evidence suggests a role for CB2 receptors in Alzheimer's disease (AD) and indicates their potential as a therapeutic target against this neurodegenerative disease. Levels of CB2 receptors are significantly increased in post-mortem AD brains, mainly in microglia surrounding senile plaques, and their expression levels correlate with the amounts of Aβ42 and β-amyloid plaque deposition. Moreover, several studies on animal models of AD have demonstrated that specific CB2 receptor agonists, which are devoid of psychoactive effects, reduce AD-like pathology, resulting in attenuation of the inflammation associated with the disease but also modulating Aβ and tau aberrant processing, among other effects. CB2 receptor activation also improves cognitive impairment in animal models of AD. This review discusses available data regarding the role of CB2 receptors in AD and the potential usefulness of specific agonists of these receptors against AD.

Synthesis and biological evaluation of (3',5'-dichloro-2,6-dihydroxy-biphenyl-4-yl)-aryl/alkyl-methanone selective CB2 inverse agonist

Cannabinoid receptor 2 (CB2) selective agonists and inverse agonists possess significant potential as therapeutic agents for regulating inflammation and immune function. Although CB2 agonists have received the greatest attention, it is emerging that inverse agonists also manifest anti-inflammatory activity. In process of designing new cannabinoid ligands we discovered that the 2,6-dihydroxy-biphenyl-aryl methanone scaffold imparts inverse agonist activity at CB2 receptor without functional activity at CB1. To further explore the scaffold we synthesized a series of (3',5'-dichloro-2,6-dihydroxy-biphenyl-4-yl)-aryl/alkyl-methanone analogs and evaluated the CB1 and CB2 affinity, potency, and efficacy. The studies reveal that an aromatic C ring is required for inverse agonist activity and that substitution at the 4 position is optimum. The resorcinol moiety is required for optimum CB2 inverse agonist activity and selectivity. Antagonist studies against CP 55,940 demonstrate that the compounds 41 and 45 are noncompetitive antagonists at CB2.

The psychoactive compound of Cannabis sativa, Δ(9)-tetrahydrocannabinol (THC) inhibits the human trophoblast cell turnover

The noxious effects of cannabis consumption for fertility and pregnancy outcome are recognized for years. Its consumption during gestation is associated with alterations in foetal growth, low birth weight and preterm labor. The main psychoactive molecule of cannabis, Δ(9)-tetrahydrocannabinol (THC) impairs the production of reproductive hormones and is also able to cross the placenta barrier. However, its effect on the main placental cells, the trophoblasts, are unknown. Actually, the role of THC in cell survival/death of primary human cytotrophoblasts (CTs) and syncytiotrophoblasts (STs) and in the syncytialization process remains to be explored. Here, we show that THC has a dual effect, enhancing MTT metabolism at low concentrations, whereas higher doses decreased cell viability, on both trophoblast phenotypes, though the effects on STs were more evident. THC also diminished the generation of oxidative and nitrative stress and the oxidized form of glutathione, whereas the reduced form of this tripeptide was increased, suggesting that THC prevents ST cell death due to an antioxidant effect. Moreover, this compound enhanced the mitochondrial function of STs, as observed by the increased MTT metabolism and intracellular ATP levels. These effects were independent of cannabinoid receptors activation. Besides, THC impaired CT differentiation into STs, since it decreased the expression of biochemical and morphological biomarkers of syncytialization, through a cannabinoid receptor-dependent mechanism. Together, these results suggest that THC interferes with trophoblast turnover, preventing trophoblast cell death and differentiation, and contribute to disclose the cellular mechanisms that lead to pregnancy complications in women that consume cannabis-derived drugs during gestation.

CSF lactate levels, τ proteins, cognitive decline: a dynamic relationship in Alzheimer's disease

OBJECTIVES

To investigate, in patients with Alzheimer's Disease (AD), the possible interplay linking alteration of neuronal energy metabolism, as measured via cerebrospinal fluid (CSF) lactate concentration, to severity of AD neurodegenerative processes and impairment of cognitive abilities.

METHODS

In this study we measured and correlated CSF lactate concentrations, AD biomarker levels (τ-proteins and β-amyloid) and Mini-Mental State Examination (MMSE) score in a population of drug-naïve patients with AD ranging from mild (MMSE≥21/30) to moderate-severe (MMSE<21/30) cognitive decline. They were compared to healthy controls and patients with vascular dementia (VaD).

RESULTS

Patients with AD (n=145) showed a significant increase of CSF lactate concentration compared to controls (n=80) and patients with VaD (n=44), which was higher in mild (n=67) than in patients with moderate-severe AD (n=78). Moreover, we found, in either the whole AD population or both subgroups, a CSF profile in which higher CSF levels of t-τ and p-τ proteins corresponded to lower concentrations of lactate.

CONCLUSIONS

We verified the occurrence of high CSF lactate levels in patients with AD, which may be ascribed to mitochondria impairment. Hypothesising that τ proteins may exert a detrimental effect on the entire cellular energy metabolism, the negative correlation found between lactate and τ-protein levels may allow speculation that τ toxicity, already demonstrated to have affected mitochondria, could also impair glycolytic metabolism with a less evident increase of lactate levels in more severe AD. Thus, we suggest a dynamic relationship between neuronal energy metabolism, τ proteins and cognitive decline in AD and propose the clinical potential of assessing CSF lactate levels in patients with AD to better define the neuronal brain metabolism damage.

Interactions between misfolded protein oligomers and membranes: A central topic in neurodegenerative diseases?

The deposition of amyloid material has been associated with many different diseases. Although these diseases are very diverse the amyloid material share many common features such as cross-β-sheet structure of the backbone of the proteins deposited. Another common feature of the aggregation process for a wide variety of proteins is the presence of prefibrillar oligomers. These oligomers are linked to the cytotoxicity occurring during the aggregation of proteins. These prefibrillar oligomers interact extensively with lipid membranes and in some cases leads to destabilization of lipid membranes. This interaction is however highly dependent on the nature of both the oligomer and the lipids. Anionic lipids are often required for interaction with the lipid membrane while increased exposure of hydrophobic patches from highly dynamic protein oligomers are structural determinants of cytotoxicity of the oligomers. To explore the oligomer lipid interaction in detail the interaction between oligomers of α-synuclein and the 4th fasciclin-1 domain of TGFBIp with lipid membranes will be examined here. For both proteins the dynamic species are the ones causing membrane destabilization and the membrane interaction is primarily seen when the lipid membranes contain anionic lipids. Hence the dynamic nature of oligomers with exposed hydrophobic patches alongside the presence of anionic lipids could be essential for the cytotoxicity observed for prefibrillar oligomers in general. This article is part of a Special Issue entitled: Lipid-protein interactions.