Update on the role of cannabinoid receptors after ischemic stroke

Regulatory mechanisms of natural compounds from traditional Chinese herbal medicines on the microglial response in ischemic stroke

BACKGROUND

Development of clinically effective neuroprotective agents for stroke therapy is still a challenging task. Microglia play a critical role in brain injury and recovery after ischemic stroke. Traditional Chinese herbal medicines (TCHMs) are based on a unique therapeutic principle, have various formulas, and have long been widely used to treat stroke. Therefore, the active compounds in TCHMs and their underlying mechanisms of action are attracting increasing attention in the field of stroke drug development.

PURPOSE

To summarize the regulatory mechanisms of TCHM-derived natural compounds on the microglial response in animal models of ischemic stroke.

METHODS

We searched studies published until 10 April 2023 in the Web of Science, PubMed, and ScienceDirect using the following keywords: natural compounds, natural products or phytochemicals, traditional Chinese Medicine or Chinese herbal medicine, microglia, and ischemic stroke. This review was prepared according to PRISMA (Preferred Reporting Item for Systematic Reviews and Meta-Analysis) guidelines.

RESULTS

Natural compounds derived from TCHMs can attenuate the M1 phenotype of microglia, which is involved in the detrimental inflammatory response, via inhibition of NF-κB, MAPKs, JAK/STAT, Notch, TLR4, P2X7R, CX3CR1, IL-17RA, the NLRP3 inflammasome, and pro-oxidant enzymes. Additionally, the neuroprotective response of microglia with the M2 phenotype can be enhanced by activating Nrf2/HO-1, PI3K/AKT, AMPK, PPARγ, SIRT1, CB2R, TREM2, nAChR, and IL-33/ST2. Several clinical trials showed that TCHM-derived natural compounds that regulate microglial responses have significant and safe therapeutic effects, but further well-designed clinical studies are needed.

CONCLUSIONS

Further research regarding the direct targets and potential pleiotropic or synergistic effects of natural compounds would provide a more reasonable approach for regulation of the microglial response with the possibility of successful stroke drug development.

Cannabinoid Effect and Safety in Spasticity Following Stroke: A Double-Blind Randomized Placebo-Controlled Study

Background

Nabiximols is a cannabis-based drug to treat spasticity-associated symptoms currently approved for patients with multiple sclerosis only. Cannabinoids are useful in an increasing number of medical conditions but may bear an increased risk for cardiovascular events. SativexStroke is a double-blind randomized placebo-controlled crossover monocentric clinical trial investigating the efficacy and safety of nabiximols in patients with spasticity following stroke.

Methods

Patients were treated with nabiximols oromucosal spray or placebo and assessed before and after two phases of 1-month duration each. Cardiovascular safety was assessed before and during the trial. Primary endpoints were changes in spasticity numeric rating scale scores and electromyographic recording of the stretch reflex in affected wrist flexors. Secondary outcome measures were numeric rating scale scores for pain, sleep and bladder function, the number of daily spasms and clinical assessment of spasticity with the modified Ashworth scale. The study was registered with the EudraCT number 2016-001034-10.

Results

Between May 2, 2018, and February 20, 2020, 41 patients entered the study. Seven patients did not complete the study, so 34 were included in the analysis. Two serious adverse events occurred, but none related to cardiovascular function. Primary and secondary efficacy outcome measures did not change from baseline during nabiximols treatment relative to placebo.

Conclusion

This study suggests that nabiximols use is probably safe in stroke patients, therefore cannabinoid usefulness may be further investigated. The lack of nabiximols effect could be related to low pain levels in recruited patients or different spasticity mechanisms between post-stroke and multiple sclerosis patients. Similarly, a beneficial effect of nabiximols could have emerged if more patients with a higher level of spasticity at baseline were recruited.

Clinical Trial Registration

https://www.clinicaltrialsregister.eu/ctr-search/trial/2016-001034-10/IT.

The Endocannabinoid System: A Potential Target for the Treatment of Various Diseases

The Endocannabinoid System (ECS) is primarily responsible for maintaining homeostasis, a balance in internal environment (temperature, mood, and immune system) and energy input and output in living, biological systems. In addition to regulating physiological processes, the ECS directly influences anxiety, feeding behaviour/appetite, emotional behaviour, depression, nervous functions, neurogenesis, neuroprotection, reward, cognition, learning, memory, pain sensation, fertility, pregnancy, and pre-and post-natal development. The ECS is also involved in several pathophysiological diseases such as cancer, cardiovascular diseases, and neurodegenerative diseases. In recent years, genetic and pharmacological manipulation of the ECS has gained significant interest in medicine, research, and drug discovery and development. The distribution of the components of the ECS system throughout the body, and the physiological/pathophysiological role of the ECS-signalling pathways in many diseases, all offer promising opportunities for the development of novel cannabinergic, cannabimimetic, and cannabinoid-based therapeutic drugs that genetically or pharmacologically modulate the ECS via inhibition of metabolic pathways and/or agonism or antagonism of the receptors of the ECS. This modulation results in the differential expression/activity of the components of the ECS that may be beneficial in the treatment of a number of diseases. This manuscript in-depth review will investigate the potential of the ECS in the treatment of various diseases, and to put forth the suggestion that many of these secondary metabolites of Cannabis sativa L. (hereafter referred to as "C. sativa L." or "medical cannabis"), may also have potential as lead compounds in the development of cannabinoid-based pharmaceuticals for a variety of diseases.

An overview on plants cannabinoids endorsed with cardiovascular effects

Nowadays cardiovascular diseases (CVDs) are the major causes for the reduction of the quality of life. The endocannabinoid system is an attractive therapeutic target for the treatment of cardiovascular disorders due to its involvement in vasomotor control, cardiac contractility, blood pressure and vascular inflammation. Alteration in cannabinoid signalling can be often related to cardiotoxicity, circulatory shock, hypertension, and atherosclerosis. Plants have been the major sources of medicines until modern eras in which researchers are experiencing a rediscovery of natural compounds as novel therapeutics. One of the most versatile plant is Cannabis sativa L., containing phytocannabinoids that may play a role in the treatment of CVDs. The aim of this review is to collect and investigate several less studied plants rich in cannabinoid-like active compounds able to interact with cannabinoid system; these plants may play a pivotal role in the treatment of disorders related to the cardiovascular system.

β-Caryophyllene, A Natural Dietary CB2 Receptor Selective Cannabinoid can be a Candidate to Target the Trinity of Infection, Immunity, and Inflammation in COVID-19

Coronavirus disease (COVID-19), caused by novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is an ongoing pandemic and presents a public health emergency. It has affected millions of people and continues to affect more, despite tremendous social preventive measures. Identifying candidate drugs for the prevention and treatment of COVID-19 is crucial. The pathogenesis and the complications with advanced infection mainly involve an immune-inflammatory cascade. Therefore, therapeutic strategy relies on suppressing infectivity and inflammation, along with immune modulation. One of the most promising therapeutic targets for the modulation of immune-inflammatory responses is the endocannabinoid system, particularly the activation of cannabinoid type 2 receptors (CB2R), a G-protein coupled receptor which mediates the anti-inflammatory properties by modulating numerous signaling pathways. To pharmacologically activate the CB2 receptors, a naturally occurring cannabinoid ligand, beta-caryophyllene (BCP), received attention due to its potent anti-inflammatory, antiviral, and immunomodulatory properties. BCP is recognized as a full selective functional agonist on CB2 receptors and produces therapeutic effects by activating CB2 and the nuclear receptors, peroxisome proliferator-activated receptors (PPARs). BCP is regarded as the first dietary cannabinoid with abundant presence across cannabis and non-cannabis plants, including spices and other edible plants. BCP showed tissue protective properties and favorably modulates numerous signaling pathways and inhibits inflammatory mediators, including cytokines, chemokines, adhesion molecules, prostanoids, and eicosanoids. Based on its pharmacological properties, molecular mechanisms, and the therapeutic potential of BCP as an immunomodulator, anti-inflammatory, organ-protective, and antiviral, we hypothesize that BCP could be a promising therapeutic and/or preventive candidate to target the triad of infection, immunity, and inflammation in COVID-19. In line with numerous studies that proposed the potential of cannabinoids in COVID-19, BCP may be a novel candidate compound for pharmaceutical and nutraceutical development due to its unique functional receptor selectivity, wide availability and accessibility, dietary bioavailability, nonpsychoactivity, and negligible toxicity along with druggable properties, including favorable pharmacokinetic and physicochemical properties. Based on reasonable pharmacological mechanisms and therapeutic properties, we speculate that BCP has potential to be investigated against COVID-19 and will inspire further preclinical and clinical studies.

Cannabinoid CB1 receptor agonist ACEA alleviates brain ischemia/reperfusion injury via CB1-Drp1 pathway

Activation of the cannabinoid CB1 receptor induces neuroprotection against brain ischemia/reperfusion injury (IRI); however, the mechanism is still unknown. In this study, we used oxygen-glucose deprivation/reoxygenation (OGD/R)-induced injury in neuronal cells and middle cerebral artery occlusion (MCAO)-induced brain IRI in rats to mimic ischemic brain injury, and hypothesized that the CB1 receptor agonist arachidonyl-2-chloroethylamide (ACEA) would protect ischemic neurons by inhibiting mitochondrial fission via dynamin-related protein 1 (Drp1). We found that OGD/R injury reduced cell viability and mitochondrial function, increased lactate dehydrogenase (LDH) release, and increased cell apoptosis, and mitochondrial fission. Notably, ACEA significantly abolished the OGD/R-induced neuronal injuries described above. Similarly, ACEA significantly reversed MCAO-induced increases in brain infarct volume, neuronal apoptosis and mitochondrial fission, leading to the recovery of neurological functions. The neuroprotective effects of ACEA were obviously blocked by coadministration of the CB1 receptor antagonist AM251 or by the upregulation of Drp1 expression, indicating that ACEA alleviates brain IRI via the CB1-Drp1 pathway. Our findings suggest that the CB1 receptor links aberrant mitochondrial fission to brain IRI, providing a new therapeutic target for brain IRI treatment.

Association between recent cannabinoid use and acute ischemic stroke

Background

Studies that have analyzed the association between cannabis use and acute ischemic stroke (AIS) have provided conflicting results. In this study, we aim to determine the association of recent cannabis use detected through urine drug screen (UDS) among patients admitted with AIS.

Methods

A retrospective observational study was performed using the medical records database. All patients aged 18 years and older admitted from January 1, 2015, to December 31, 2017, who underwent urine toxicology testing on admission were included in the analysis. Multivariate logistic regression analysis was performed to analyze independent association between recent cannabis use and AIS.

Results

A total of 9,350 patients were determined to have undergone UDS during admission, and 18% (1,643) of this had a positive urine cannabis test. Unadjusted risk ratio showed a 50% decrease in risk of AIS among cannabis users (risk ratio = 0.505, 95% confidence interval [CI] 0.425-0.600). The effect was lost after adjusting for age, race, ethnicity, sickle cell disease, dyslipidemia, hypertension, obesity, diabetes mellitus, cigarette smoking, atrial fibrillation, and other cardiac conditions (odds ratio 1.038, 95% CI 0.773-1.394).

Conclusion

This is one of the few studies analyzing the association of recent cannabis use and AIS using admission urine toxicology test independent of polysubstance use. Although our study has limitations, we did not find an independent association between recent cannabis use and the incidence of AIS. Further studies using urine toxicology tests with larger sample size and including dosage of cannabis exposure should be conducted.

A Systematic Review of Essential Oils and the Endocannabinoid System: A Connection Worthy of Further Exploration

Aromatic compounds have a long history of use as medicines in most recorded cultures. An increasing interest in these therapeutic volatile molecules in both scientific and lay communities has led to the advancement of essential oils as phytomedicines. Recent discoveries suggest essential oils augment the endocannabinoid system in a positive manner to mitigate various pathologies. However, the exact mechanisms whereby essential oils influence endocannabinoid system activity are not fully known, these studies provide a glimpse into their involvement and warrant further evaluation. Additional study of the interaction between essential oils and the endocannabinoid system may lead to promising phytomedicines for the treatment of diseases and conditions involving dysregulation or activation of the endocannabinoid system.

Transient receptor potential ankyrin 1 (TRPA1)-mediated toxicity: friend or foe?

Transient receptor potential (TRP) channels have been widely studied during the last decade. New studies uncover new features and potential applications for these channels. TRPA1 has a huge distribution all over the human body and has been reported to be involved in different physiological and pathological conditions including cold, pain, and damage sensation. Considering its role, many studies have been devoted to evaluating the role of this channel in the initiation and progression of different toxicities. Accordingly, we reviewed the most recent studies and divided the role of TRPA1 in toxicology into the following sections: neurotoxicity, cardiotoxicity, dermatotoxicity, and pulmonary toxicity. Acetaminophen, heavy metals, tear gases, various chemotherapeutic agents, acrolein, wood smoke particulate materials, particulate air pollution materials, diesel exhaust particles, cigarette smoke extracts, air born irritants, sulfur mustard, and plasticizers are selected compounds and materials with toxic effects that are, at least in part, mediated by TRPA1. Considering the high safety of TRPA1 antagonists and their efficacy to resolve selected toxic or adverse drug reactions, the future of these drugs looks promising.

Modulation of the Endocannabinoid System Following Central Nervous System Injury

Central nervous system (CNS) injury, such as stroke or trauma, is known to increase susceptibility to various infections that adversely affect patient outcomes (CNS injury-induced immunodepression-CIDS). The endocannabinoid system (ECS) has been shown to have immunoregulatory properties. Therefore, the ECS might represent a druggable target to overcome CIDS. Evidence suggests that cannabinoid type 2 receptor (CB₂R) activation can be protective during the early pro-inflammatory phase after CNS injury, as it limits neuro-inflammation and, therefore, attenuates CIDS severity. In the later phase post CNS injury, CB₂R inhibition is suggested as a promising pharmacologic strategy to restore immune function in order to prevent infection.

Cannabinoids and Cardiovascular System

Cannabinoids influence cardiovascular variables in health and disease via multiple mechanisms. The chapter covers the impact of cannabinoids on cardiovascular function in physiology and pathology and presents a critical analysis of the proposed signalling pathways governing regulation of cardiovascular function by endogenously produced and exogenous cannabinoids. We know that endocannabinoid system is overactivated under pathological conditions and plays both a protective compensatory role, such as in some forms of hypertension, atherosclerosis and other inflammatory conditions, and a pathophysiological role, such as in disease states associated with excessive hypotension. This chapter focuses on the mechanisms affecting hemodynamics and vasomotor effects of cannabinoids in health and disease states, highlighting mismatches between some studies. The chapter will first review the effects of marijuana smoking on cardiovascular system and then describe the impact of exogenous cannabinoids on cardiovascular parameters in humans and experimental animals. This will be followed by analysis of the impact of cannabinoids on reactivity of isolated vessels. The article critically reviews current knowledge on cannabinoid induction of vascular relaxation by cannabinoid receptor-dependent and -independent mechanisms and dysregulation of vascular endocannabinoid signaling in disease states.

Oral Ingestion of Cannabis sativa: Risks, Benefits, and Effects on Malaria-Infected Hosts

Background: The emergence of a multidrug-resistant strain of Plasmodium falciparum (Pf Pailin) raises concern about malaria control strategies. Unfortunately, the role(s) of natural plants/remedies in curtailing malaria catastrophe remains uncertain. The claims of potential antimalarial activity of Cannabis sativa in vivo have not been well established nor the consequences defined. This study was, therefore, designed to evaluate the effects of whole cannabis consumption on malaria-infected host.

Methods: Thirty mice were inoculated with dose of 1×10⁷ chloroquine-resistant Plasmodium berghei ANKA-infected erythrocyte and divided into six treatment groups. Cannabis diet formulations were prepared based on weighted percentages of dried cannabis and standard mice diet and the study animals were fed ad libitum. Chemosuppression of parasitemia, survival rates, parasite clearance, and recrudescence time were evaluated. Histopathological studies were performed on the prefrontal cortex (PFC) and hippocampus of the animals after 14 days' consumption of cannabis diet formulation by naive mice.

Results: There was a significant difference (p<0.05) in the day-4 chemosuppression of parasitemia between the animals that were fed C. sativa and chloroquine relative to the untreated controls. There was also a significant difference in the survival rate (p<0.05) of animals fed C. sativa diet (40%, 20%, 10%, and 1%) in contrast to control animals on standard mice diet. A parasite clearance time of 2.18±0.4 was recorded in the chloroquine treatment group, whereas recrudescence in chloroquine group occurred on day 7. There were slight histomorphological changes in the PFC and cell densities of the dentate gyrus of the hippocampus of animals that were fed C. sativa.

Conclusions:C. sativa displayed mild antimalarial activity in vivo. There was evident reduction in symptomatic manifestation of malaria disease, though unrelated to levels of parasitemia. This disease tolerance status may be beneficial, but may also constitute a transmission burden through asymptomatic carriage of parasites by habitual cannabis users.

Bidirectional Microglia-Neuron Communication in Health and Disease

Microglia are ramified cells that exhibit highly motile processes, which continuously survey the brain parenchyma and react to any insult to the CNS homeostasis. Although microglia have long been recognized as a crucial player in generating and maintaining inflammatory responses in the CNS, now it has become clear, that their function are much more diverse, particularly in the healthy brain. The innate immune response and phagocytosis represent only a little segment of microglia functional repertoire that also includes maintenance of biochemical homeostasis, neuronal circuit maturation during development and experience-dependent remodeling of neuronal circuits in the adult brain. Being equipped by numerous receptors and cell surface molecules microglia can perform bidirectional interactions with other cell types in the CNS. There is accumulating evidence showing that neurons inform microglia about their status and thus are capable of controlling microglial activation and motility while microglia also modulate neuronal activities. This review addresses the topic: how microglia communicate with other cell types in the brain, including fractalkine signaling, secreted soluble factors and extracellular vesicles. We summarize the current state of knowledge of physiological role and function of microglia during brain development and in the mature brain and further highlight microglial contribution to brain pathologies such as Alzheimer’s and Parkinson’s disease, brain ischemia, traumatic brain injury, brain tumor as well as neuropsychiatric diseases (depression, bipolar disorder, and schizophrenia).

Ca2+-dependent potassium channels and cannabinoid signaling in the endothelium of apolipoprotein E knockout mice before plaque formation

Endothelial Ca2+-dependent K+ channels (KCa) regulate endothelial function. We also know that stimulation of type 2 cannabinoid (CB2) receptors ameliorates atherosclerosis. However, whether atherosclerosis is accompanied by altered endothelial KCa- and CB2 receptor-dependent signaling is unknown. By utilizing an in situ patch-clamp approach, we directly evaluated the KCa channel function and the CB2 receptor-dependent electrical responses in the endothelium of aortic strips from young ApoE-/- and C57Bl/6 mice. In the ApoE-/- group, the resting membrane potential (-30.1±1.1mV) was less negative (p<0.05) compared to WT (-38.9±1.4mV) and voltage ramps generated an overall KCa current of reduced amplitude. The peak hyperpolarization to 2μM Ach was not different between the groups. However, the sustained component was significantly reduced in ApoE-/- strips. In contrast, the peak hyperpolarization to 0.2μM Ach was increased in the ApoE-/- group, and SKA-31, a direct IKCa/SKCa channel opener, produced a hyperpolarization and whole-cell current of greater amplitude. The BKCa opener NS1619 produced hyperpolarization that was enhanced in ApoE-/- group. N-arachidonoyl glycine, a BKCa opener, produced a hyperpolarization of enhanced amplitude in ApoE-/- arteries. Selective CB2 receptor agonist AM1241 (5μM) had no effect on endothelial membrane potential in WT group; however, in ApoE-/- group, it elicited hyperpolarization that was inhibited by a selective CB2 receptor antagonist AM630. Conclusively, our data point to functional down-regulation of basal IKCa activity in unstimulated endothelium of ApoE-/- mice. Direct and indirect IKCa stimulation resulted in increased recruitment of the channels. In addition, our data point to up-regulation of endothelial BKCa channels and CB2 receptors in ApoE-/- arteries.

Detrimental effects of 2-arachidonoylglycerol on whole blood platelet aggregation and on cerebral blood flow after a focal ischemic insult in rats

2-Arachidonoylglycerol (2-AG) is a major modulator of blood flow and platelet aggregation and a potential neuroprotectant. The present study investigated, for the first time, the effects of 2-AG on cerebral blood flow (CBF) in the first critical hours during middle cerebral artery occlusion (MCAO) and on platelet aggregation in rats. Adult male Sprague-Dawley rats ( n = 30) underwent permanent MCAO under isoflurane anesthesia and were randomly assigned to receive either 2-AG (6 mg/kg iv), monoacylglycerol lipase inhibitor JZL-184 (10 mg/kg iv), or vehicle ( n = 6 rats/group) treatment. CBF and cardiovascular responses were measured, by a blinded investigator, for up to 4 h. In separate experiments, platelet aggregation by 2-AG (19-300 µM) was assessed by whole blood aggregometry ( n = 40). 2-AG and JZL-184 significantly increased the severity of the CBF deficit versus vehicle (20.2 ± 8.8% and 22.7 ± 6.4% vs. 56.4 ± 12.1% of pre-MCAO baseline, respectively, P < 0.05) but had no effect on blood pressure or heart rate. While JZL-184 significantly increased the number of thrombi after MCAO, this did not reach significance by 2-AG. 2-AG induced platelet aggregation in rat whole blood in a similar manner to arachidonic acid and was significantly reduced by the cyclooxygenase inhibitors indomethacin and flurbiprofen and the thromboxane receptor antagonist ICI 192,605 ( P < 0.05). This is the first study showing that 2-AG increases the severity of the CBF deficit during MCAO, and further interrogation confirmed 2-AG-induced platelet aggregation in rats. These findings are important because 2-AG had previously been shown to exert neuroprotective actions and therefore force us to reevaluate the circumstances under which 2-AG is beneficial. NEW & NOTEWORTHY 2-Arachidonoylglycerol (2-AG) has neuroprotective properties; however, the present study revealed that 2-AG increases the severity of the cerebral blood flow deficit during middle cerebral artery occlusion in rats. Further interrogation showed that 2-AG induces platelet aggregation in rats. These findings force us to reevaluate the circumstances under which 2-AG is beneficial.

A randomised controlled cross-over double-blind pilot study protocol on THC:CBD oromucosal spray efficacy as an add-on therapy for post-stroke spasticity

INTRODUCTION

Stroke is the most disabling neurological disorder and often causes spasticity. Transmucosal cannabinoids (tetrahydrocannabinol and cannabidiol (THC:CBD), Sativex) is currently available to treat spasticity-associated symptoms in patients with multiple sclerosis. Cannabinoids are being considered useful also in the treatment of pain, nausea and epilepsy, but may bear and increased risk for cardiovascular events. Spasticity is often assessed with subjective and clinical rating scales, which are unable to measure the increased excitability of the monosynaptic reflex, considered the hallmark of spasticity. The neurophysiological assessment of the stretch reflex provides a precise and objective method to measure spasticity. We propose a novel study to understand if Sativex could be useful in reducing spasticity in stroke survivors and investigating tolerability and safety by accurate cardiovascular monitoring.

METHODS AND ANALYSIS

We will recruit 50 patients with spasticity following stroke to take THC:CBD in a double-blind placebo-controlled cross-over study. Spasticity will be assessed with a numeric rating scale for spasticity, the modified Ashworth scale and with the electromyographical recording of the stretch reflex. The cardiovascular risk will be assessed prior to inclusion. Blood pressure, heart rate, number of daily spasms, bladder function, sleep disruption and adverse events will be monitored throughout the study. A mixed-model analysis of variance will be used to compare the stretch reflex amplitude between the time points; semiquantitative measures will be compared using the Mann-Whitney test (THC:CBD vs placebo) and Wilcoxon test (baseline vs treatment).

ETHICS AND DISSEMINATION

The study was registered on the EudraCT database with number 2016-001034-10 and approved by both the Italian Medicines Agency (Agenzia Italiana del Farmaco) and local Ethics Committee 'Comitato Etico Regionale della Liguria'. Data will be made anonymous and uploaded to a open access repository. Results will be disseminated by presentations at national and international conferences and by publication in journals of clinical neuroscience and neurology.

Cannabinoids in the Cardiovascular System

Cannabinoids are known to modulate cardiovascular functions including heart rate, vascular tone, and blood pressure in humans and animal models. Essential components of the endocannabinoid system, namely, the production, degradation, and signaling pathways of endocannabinoids have been described not only in the central and peripheral nervous system but also in myocardium, vasculature, platelets, and immune cells. The mechanisms of cardiovascular responses to endocannabinoids are often complex and may involve cannabinoid CB₁ and CB₂ receptors or non-CB_1/2 receptor targets. Preclinical and some clinical studies have suggested that targeting the endocannabinoid system can improve cardiovascular functions in a number of pathophysiological conditions, including hypertension, metabolic syndrome, sepsis, and atherosclerosis. In this chapter, we summarize the local and systemic cardiovascular effects of cannabinoids and highlight our current knowledge regarding the therapeutic potential of endocannabinoid signaling and modulation.

The endocannabinoid system, a novel and key participant in acupuncture's multiple beneficial effects

Acupuncture and its modified forms have been used to treat multiple medical conditions, but whether the diverse effects of acupuncture are intrinsically linked at the cellular and molecular level and how they might be connected have yet to be determined. Recently, an emerging role for the endocannabinoid system (ECS) in the regulation of a variety of physiological/pathological conditions has been identified. Overlap between the biological and therapeutic effects induced by ECS activation and acupuncture has facilitated investigations into the participation of ECS in the acupuncture-induced beneficial effects, which have shed light on the idea that the ECS may be a primary mediator and regulatory factor of acupuncture's beneficial effects. This review seeks to provide a comprehensive summary of the existing literature concerning the role of endocannabinoid signaling in the various effects of acupuncture, and suggests a novel notion that acupuncture may restore homeostasis under different pathological conditions by regulating similar networks of signaling pathways, resulting in the activation of different reaction cascades in specific tissues in response to pathological insults.

Brain cannabinoid receptor 2: expression, function and modulation

Cannabis sativa (marijuana) is a fibrous flowering plant that produces an abundant variety of molecules, some with psychoactive effects. At least 4% of the world's adult population uses cannabis annually, making it one of the most frequently used illicit drugs in the world. The psychoactive effects of cannabis are mediated primarily through cannabinoid receptor (CBR) subtypes. The prevailing view is that CB1Rs are mainly expressed in the central neurons, whereas CB₂Rs are predominantly expressed in peripheral immune cells. However, this traditional view has been challenged by emerging strong evidence that shows CB₂Rs are moderately expressed and function in specific brain areas. New evidence has demonstrated that brain CB₂Rs modulate animal drug-seeking behaviors, suggesting that these receptors may exist in brain regions that regulate drug addiction. Recently, we further confirmed that functional CB₂Rs are expressed in mouse ventral tegmental area (VTA) dopamine (DA) neurons and that the activation of VTA CB₂Rs reduces neuronal excitability and cocaine-seeking behavior. In addition, CB₂R-mediated modulation of hippocampal CA3 neuronal excitability and network synchronization has been reported. Here, we briefly summarize recent lines of evidence showing how CB₂Rs modulate function and pathophysiology in the CNS.

Concise review of the management of iatrogenic emesis using cannabinoids: emphasis on nabilone for chemotherapy-induced nausea and vomiting

Chemotherapy-induced nausea and vomiting (CINV) is a prevalent, distressing, and burdensome side effect of cancer chemotherapy. It is estimated to affect the majority of patients receiving certain anti-cancer drug regimens and can be treatment-limiting, even for life-saving medications. Despite seemingly numerous options, such as antimuscarinic anticholinergics, antihistamines, 5-HT₃ receptor antagonists, dopamine receptor antagonists, and neurokinin-1 receptor antagonists, preventative therapies are often inadequately effective, particularly for "delayed CINV"-leaving an important unmet clinical need. Cannabinoid receptor agonists, by virtue of their unique mechanism of action and efficacy and safety data reported in clinical trials, appear to offer a useful additional option. The mechanistic value of cannabinoids has been well known for many years, but these agents may have been underutilized in the past because of the notoriety and legal status of marijuana. While botanical marijuana contains nearly 500 components, including the psychoactive tetrahydrocannabinol (THC), nabilone is an established, single-entity synthetic cannabinoid receptor agonist that has become the focus of renewed interest. We review the basic pharmacology and clinical trial data of nabilone for use in prophylaxis and treatment of CINV.

β-Caryophyllene/Hydroxypropyl-β-Cyclodextrin Inclusion Complex Improves Cognitive Deficits in Rats with Vascular Dementia through the Cannabinoid Receptor Type 2 -Mediated Pathway

This work was conducted to prepare β-caryophyllene-hydroxypropyl-β-cyclodextrin inclusion complex (HPβCD/BCP) and investigate its effects and mechanisms on cognitive deficits in vascular dementia (VD) rats. First, HPβCD/BCP was prepared, optimized, characterized, and evaluated. HPβCD/BCP and AM630 were then administered to VD rats to upregulate and downregulate the cannabinoid receptor type 2 (CB2). Results showed that HPβCD/BCP can significantly increase the bioavailability of BCP. Through the Morris water maze test, HPβCD/BCP can attenuate learning and memory deficits in rats. Cerebral blood flow (CBF) monitoring results indicated that HPβCD/BCP can promote the recovery of CBF. Moreover, molecular biology experiments showed that HPβCD/BCP can increase the expression levels of CB2 in brain tissues, particularly the hippocampus and white matter tissues, as well as the expression levels of PI3K and Akt. Overall, the findings demonstrated the protective effects of HPβCD/BCP against cognitive deficits induced by chronic cerebral ischemia and suggested the potential of HPβCD/BCP in the therapy of vascular dementia in the future.

Cannabis, Cannabinoids, and Cerebral Metabolism: Potential Applications in Stroke and Disorders of the Central Nervous System

No compound has generated more attention in both the scientific and recently in the political arena as much as cannabinoids. These diverse groups of compounds referred collectively as cannabinoids have both been vilified due to its dramatic and potentially harmful psychotropic effects and glorified due to its equally dramatic and potential application in a number of acute and chronic neurological conditions. Previously illegal to possess, cannabis, the plant where natural form of cannabinoids are derived, is now accepted in a growing number of states for medicinal purpose, and some even for recreational use, increasing opportunities for more scientific experimentation. The purpose of this review is to summarize the growing body of literature on cannabinoids and to present an overview of our current state of knowledge of the human endocannabinoid system in the hope of defining the future of cannabinoids and its potential applications in disorders of the central nervous system, focusing on stroke.

Expression of the Endocannabinoid Receptor 1 in Human Stroke: An Autoptic Study

OBJECTIVE

Stroke is one of the leading causes of disability and death in the world. The endocannabinoid (eCB) system is upregulated in several neurological diseases including stroke. A previous animal study demonstrated an increased expression of the endocannabinoid receptor 1 (CB1R) in the penumbra area surrounding the ischemic core, suggesting a crucial role in inflammation/reperfusion after stroke. Regarding the localization of CB1/CB2 receptors, animal studies showed that cortical neurons, activated microglia, and astroglia are involved. Our aim was to evaluate the cerebral expression of CB1R in the ischemic brain areas of 9 patients who died due to acute cerebral infarction in the middle cerebral artery territory.

METHODS

The cerebral autoptic tissue was collected within 48 hours since death. Ischemic and contralateral normal-appearing areas were identified. After tissue preprocessing, 4-µm-thick cerebral sections were incubated with the primary CB1R antibodies (Cayman Chemical Company, Ann Arbor, MI). Thereafter, all cerebral sections were hematoxylin treated. In each section, the total cell number and CB1R-positive cells were counted and the CB1R-positive cell count ratio was calculated. For statistical analysis, Student's t-test was used.

RESULTS

In normal tissue, CB1R-positive neurons were the majority; a few non-neuronal cells expressed CB1R. In the ischemic areas, a few neurons were detectable. A significant increase in total CB1R staining was found in the ischemic regions compared to contralateral areas.

CONCLUSIONS

We found an increase in CB1R expression in the ischemic region (neuronal and non-neuronal cell staining), suggesting the inflammatory reaction to the ischemic insult. Whether such response might mediate neuroprotective actions or excitotoxicity-related detrimental effects is still unclear.

Non-Selective Cannabinoid Receptor Antagonists, Hinokiresinols Reduce Infiltration of Microglia/Macrophages into Ischemic Brain Lesions in Rat via Modulating 2-Arachidonolyglycerol-Induced Migration and Mitochondrial Activity

Growing evidence suggests that therapeutic strategies to modulate the post-ischemic inflammatory responses are promising approaches to improve stroke outcome. Although the endocannabinoid system has been emerged as an endogenous therapeutic target to regulate inflammation after stroke insult, the downstream mechanisms and their potentials for therapeutic intervention remain controversial. Here we identified trans- and cis-hinokiresinols as novel non-selective antagonists for two G-protein-coupled cannabinoid receptors, cannabinoid receptor type 1 and type 2. The Electric Cell-substrate Impedance Sensing and Boyden chamber migration assays using primary microglial cultures revealed that both hinokiresinols significantly inhibited an endocannabinoid, 2-arachidonoylglycerol-induced migration. Hinokiresinols modulated 2-arachidonoylglycerol-induced mitochondrial bioenergetics in microglia as evidenced by inhibition of ATP turnover and reduction in respiratory capacity, thereby resulting in impaired migration activity. In rats subjected to transient middle cerebral artery occlusion (1.5-h) followed by 24-h reperfusion, post-ischemic treatment with hinokiresinols (2 and 7-h after the onset of ischemia, 10 mg/kg) significantly reduced cerebral infarct and infiltration of ED1-positive microglial/macrophage cells into cerebral ischemic lesions in vivo. Co-administration of exogenous 2-AG (1 mg/kg, i.v., single dose at 2 h after starting MCAO) abolished the protective effect of trans-hinokiresionol. These results suggest that hinokiresinols may serve as stroke treatment by targeting the endocannabinoid system. Alteration of mitochondrial bioenergetics and consequent inhibition of inflammatory cells migration may be a novel mechanism underlying anti-ischemic effects conferred by cannabinoid receptor antagonists.

Time-Dependent Protection of CB2 Receptor Agonist in Stroke

Recent studies have indicated that type 2 cannabinoid receptor (CB2R) agonists reduce neurodegeneration after brain injury through anti-inflammatory activity. The purpose of this study was to examine the time-dependent interaction of CB2R and inflammation in stroke brain. Adult male rats were subjected to right middle cerebral artery occlusion (MCAo). CB2R mRNA expression was significantly elevated >20 fold on day 2, peaked >40-fold on day 5, and normalized on day 10 post-stroke. Inflammatory markers IBA1 and TLR4 were significantly upregulated 15 fold until day 5 after MCAo. Because of the delayed upregulation of CB2R and IBA1, we next treated animals daily with CB2R agonist AM1241 or anti-inflammatory PPAR-γ agonist pioglitazone from 2 to 5 days after MCAo. Delayed treatment with pioglitazone significantly reduced abnormal neurological scores and body asymmetry as well as brain infarction in stroke animals. No behavioral improvement or reduction in brain infarction was found in animals receiving AM1241. Pioglitazone, but not AM1241, significantly reduced IBA1 expression in the stroke cortex, suggesting that delayed treatment with AM1241 failed to alter ischemia-mediated IBA-1 upregulation. In contrast, pretreatment with AM1241 significantly reduced brain infarction and neurological deficits. In conclusion, our data support a time-dependent neuroprotection of CB2 agonist in an animal model of stroke. Delayed post- treatment with PPAR-γ agonist induced behavioral recovery and microglial suppression; early treatment with CB2R agonist suppressed neurodegeneration in stroke animals.

Promising cannabinoid-based therapies for Parkinson's disease: motor symptoms to neuroprotection

Parkinson’s disease (PD) is a slow insidious neurological disorder characterized by a loss of dopaminergic neurons in the midbrain. Although several recent preclinical advances have proposed to treat PD, there is hardly any clinically proved new therapeutic for its cure. Increasing evidence suggests a prominent modulatory function of the cannabinoid signaling system in the basal ganglia. Hence, use of cannabinoids as a new therapeutic target has been recommended as a promising therapy for PD. The elements of the endocannabinoid system are highly expressed in the neural circuit of basal ganglia wherein they bidirectionally interact with dopaminergic, glutamatergic, and GABAergic signaling systems. As the cannabinoid signaling system undergoes a biphasic pattern of change during progression of PD, it explains the motor inhibition typically observed in patients with PD. Cannabinoid agonists such as WIN-55,212-2 have been demonstrated experimentally as neuroprotective agents in PD, with respect to their ability to suppress excitotoxicity, glial activation, and oxidative injury that causes degeneration of dopaminergic neurons. Additional benefits provided by cannabinoid related compounds including CE-178253, oleoylethanolamide, nabilone and HU-210 have been reported to possess efficacy against bradykinesia and levodopa-induced dyskinesia in PD. Despite promising preclinical studies for PD, use of cannabinoids has not been studied extensively at the clinical level. In this review, we reassess the existing evidence suggesting involvement of the endocannabinoid system in the cause, symptomatology, and treatment of PD. We will try to identify future threads of research that will help in the understanding of the potential therapeutic benefits of the cannabinoid system for treating PD.

What we know and do not know about the cannabinoid receptor 2 (CB2)

It has been well appreciated that the endocannabinoid system can regulate immune responses via the cannabinoid receptor 2 (CB2), which is primarily expressed by cells of the hematopoietic system. The endocannabinoid system is composed of receptors, ligands and enzymes controlling the synthesis and degradation of endocannabinoids. Along with endocannabinoids, both plant-derived and synthetic cannabinoids have been shown to bind to and signal through CB2 via G proteins leading to both inhibitory and stimulatory signals depending on the biological process. Because no cannabinoid ligand has been identified that only binds to CB2, the generation of mice deficient in CB2 has greatly expanded our knowledge of how CB2 contributes to immune cell development and function in health and disease. In regards to humans, genetic studies have associated CB2 with a variety of human diseases. Here, we review the endocannabinoid system with an emphasis on CB2 and its role in the immune system.

Neuroprotection in stroke: past, present, and future

Stroke is a devastating medical condition, killing millions of people each year and causing serious injury to many more. Despite advances in treatment, there is still little that can be done to prevent stroke-related brain damage. The concept of neuroprotection is a source of considerable interest in the search for novel therapies that have the potential to preserve brain tissue and improve overall outcome. Key points of intervention have been identified in many of the processes that are the source of damage to the brain after stroke, and numerous treatment strategies designed to exploit them have been developed. In this review, potential targets of neuroprotection in stroke are discussed, as well as the various treatments that have been targeted against them. In addition, a summary of recent progress in clinical trials of neuroprotective agents in stroke is provided.