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

The role of cannabinoid receptor 2 in bone remodeling during orthodontic tooth movement

BACKGROUND

The purpose of this study is to explore the effects of CB2 on bone regulation during orthodontic tooth movement.

METHODS

Thirty male mice were allocated into 2 groups (n = 15 in each group): wild type (WT) group and CB2 knockout (CB2-/-) group. Orthodontic tooth movement (OTM) was induced by applying a nickel-titanium coil spring between the maxillary first molar and the central incisors. There are three subgroups within the WT groups (0, 7 and 14 days) and the CB2-/- groups (0, 7 and 14 days). 0-day groups without force application. Tooth displacement, alveolar bone mass and alveolar bone volume were assessed by micro-CT on 0, 7 and 14 days, and the number of osteoclasts was quantified by tartrate-resistant acid phosphatase (TRAP) staining. Moreover, the expression levels of RANKL and OPG in the compression area were measured histomorphometrically.

RESULTS

The WT group exhibited the typical pattern of OTM, characterized by narrowed periodontal space and bone resorption on the compression area. In contrast, the accelerated tooth displacement, increased osteoclast number (P < 0.0001) and bone resorption on the compression area in CB2-/- group. Additionally, the expression of RANKL was significantly upregulated, while OPG showed low levels in the compression area of the CB2 - / - group (P < 0.0001).

CONCLUSIONS

CB2 modulated OTM and bone remodeling through regulating osteoclast activity and RANKL/OPG balance.

Activation of cannabinoid receptors 2 alleviates myocardial damage in cecal ligation and puncture-induced sepsis by inhibiting pyroptosis

BACKGROUND

It has been reported that cannabinoid receptors 2 (CB2 receptors) play an important role in the pathophysiological process of sepsis, which may also be associated with the regulation of pyroptosis, an inflammatory programmed cell death. The present study aimed to investigate the protective effect of CB2 receptors on myocardial damage in a model of septic mice by inhibiting pyroptosis.

METHODS

The C57BL/6 mice underwent cecal ligation and puncture (CLP) to induce sepsis. All mice were randomly divided into the sham, CLP, or CLP+HU308 group. Blood and heart tissue samples were collected 12 h after surgery. Hematoxylin and eosin staining was used for analyzing histopathological results. Creatine kinase isoenzymes (CK-MB) and IL-1β were measured using ELISA, while lactate dehydrogenase (LDH) level was determined using photoelectric colorimetry. The expression levels of CB2 receptors and pyroptosis-associated proteins (NLRP3, caspase-1, and GSDMD) were measured using western blotting. The location and distribution of CB2 receptors and caspase-1 in myocardial tissues were assessed by immunofluorescence. TUNEL staining was used to quantify the number of dead cells in myocardial tissues.

RESULTS

The CLP procedure increased CB2 receptor expression in mice. CB2 receptors were located in myocardial macrophages. Activating CB2 receptors decreased the levels of myocardial damage mediator LDH, CK-MB, and inflammatory cytokine IL-1β. The results also showed that CLP increased the pyroptosis in myocardial tissues, while CB2 agonist HU308 inhibited pyroptosis by decreasing the level of NLRP3 and activating caspase-1 and GSDMD.

CONCLUSIONS

CB2 receptor activation has a protective effect on the myocardium of mice with sepsis by inhibiting pyroptosis.

Cannabidiol Mitigates Lipopolysaccharide-Induced Pancreatic Pathology: A Promising Therapeutic Strategy

Background: Lipopolysaccharides (LPSs) are a component of certain types of bacteria and can induce an inflammatory response in the body, including in the pancreas. Cannabidiol (CBD), a nonpsychoactive compound found in cannabis, has been shown to have anti-inflammatory effects and may offer potential therapeutic benefits for conditions involving inflammation and damage. The aim of this study was to investigate any potential preventative effects of CBD on experimental LPS-induced pancreatic pathology in rats. Materials and Methods: Thirty-two rats were randomly divided into four groups as control, LPS (5 mg/kg, intraperitoneally [i.p.]), LPS+CBD, and CBD (5 mg/kg, i.p.) groups. Six hours after administering LPS, the rats were euthanized, and blood and pancreatic tissue samples were taken for biochemical, polymerase chain reaction (PCR), histopathological, and immunohistochemical examinations. Results: The results indicated that LPS decreased serum glucose levels and increased lipase levels. It also caused severe hyperemia, increased vacuolization in endocrine cells, edema, and slight inflammatory cell infiltrations at the histopathological examination. Insulin and amylin expressions decreased during immunohistochemical analyses. At the PCR analysis, Silent Information Regulator 2 homolog 1 and peroxisome proliferator-activated receptor gamma coactivator-1 alpha expressions decreased and tumor protein p53 expressions increased in the LPS group. CBD improved the biochemical, PCR, histopathological, and immunohistochemical results. Conclusions: The findings of the current investigation demonstrated that LPS damages both the endocrine and exocrine pancreas. However, CBD demonstrated marked ameliorative effects in the pancreas in LPS induced rat model pancreatitis.

Cannabinoids Reduce Melanoma Cell Viability and Do Not Interfere with Commonly Used Targeted Therapy in Metastatic Melanoma In Vivo and In Vitro

Background: Cannabinoids are mainly used for recreational purposes, but also made their way into oncology, since these substances can be taken to increase appetite in tumour cachexia. Since there are some hints in the literature that cannabinoids might have some anti-cancerous effects, the aim of this study was to study if and how cannabinoids mediate pro-apoptotic effects in metastatic melanoma in vivo and in vitro and its value besides conventional targeted therapy in vivo. Methods: Several melanoma cell lines were treated with different concentrations of cannabinoids, and anti-cancerous efficacy was assessed by proliferation and apoptosis assays. Subsequent pathway analysis was performed using apoptosis, proliferation, flow cytometry and confocal microscopy data. The efficacy of cannabinoids in combination with trametinib was studied in NSG mice in vivo. Results: Cannabinoids reduced cell viability in multiple melanoma cell lines in a dose-dependent way. The effect was mediated by CB1, TRPV1 and PPARα receptors, whereby pharmacological blockade of all three receptors protected from cannabinoid-induced apoptosis. Cannabinoids initiated apoptosis by mitochondrial cytochrome c release with consecutive activation of different caspases. Essentially, cannabinoids significantly decreased tumour growth in vivo and were as potent as the MEK inhibitor trametinib. Conclusions: We could demonstrate that cannabinoids reduce cell viability in several melanoma cell lines, initiate apoptosis via the intrinsic apoptotic pathway by cytochrome c release and caspase activation and do not interfere with commonly used targeted therapy.

Distinct activation mechanisms regulate subtype selectivity of Cannabinoid receptors

Design of cannabinergic subtype selective ligands is challenging because of high sequence and structural similarities of cannabinoid receptors (CB₁ and CB₂). We hypothesize that the subtype selectivity of designed selective ligands can be explained by the ligand binding to the conformationally distinct states between cannabinoid receptors. Analysis of ~ 700 μs of unbiased simulations using Markov state models and VAMPnets identifies the similarities and distinctions between the activation mechanism of both receptors. Structural and dynamic comparisons of metastable intermediate states allow us to observe the distinction in the binding pocket volume change during CB₁ and CB₂ activation. Docking analysis reveals that only a few of the intermediate metastable states of CB₁ show high affinity towards CB₂ selective agonists. In contrast, all the CB₂ metastable states show a similar affinity for these agonists. These results mechanistically explain the subtype selectivity of these agonists by deciphering the activation mechanism of cannabinoid receptors.

Cannabinoid Receptor 1 Agonist ACEA and Cannabinoid Receptor 2 Agonist GW833972A Attenuates Cell-Mediated Immunity by Different Biological Mechanisms

Cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2) are components in the endocannabinoid system that play significant roles in regulating immune responses. There are many agonists for the cannabinoid receptors; however, their effects on T cell regulation have not been elucidated. In the present study, we determined the effects of the CB1 selective agonist ACEA and the CB2 selective agonist GW833972A on T cell responses. It was found that both agonists impaired anti-CD3 monoclonal antibody induced T cell proliferation. However, ACEA and GW833972A agonists down-regulated the expression of activation markers on CD4+ and CD8+ T cells and co-stimulatory molecules on B cells and monocytes in different manners. Moreover, only GW833972A suppressed the cytotoxic activities of CD8+ T cells without interfering in the cytotoxic activities of CD4+ T cells and NK cells. In addition, the CB2 agonist, but not CB1 agonist, caused the reduction of Th1 cytokine production. Our results demonstrated that the CB1 agonist ACEA and CB2 agonist GW833972A attenuated cell-mediated immunity in different mechanisms. These agonists may be able to be used as therapeutic agents for inducing T cell hypofunction in inflammatory and autoimmune diseases.

Role of neurotransmitters in immune-mediated inflammatory disorders: a crosstalk between the nervous and immune systems

Immune-mediated inflammatory diseases (IMIDs) are a group of common heterogeneous disorders, characterized by an alteration of cellular homeostasis. Primarily, it has been shown that the release and diffusion of neurotransmitters from nervous tissue could result in signaling through lymphocyte cell-surface receptors and the modulation of immune function. This finding led to the idea that the neurotransmitters could serve as immunomodulators. It is now manifested that neurotransmitters can also be released from leukocytes and act as autocrine or paracrine modulators. Increasing data indicate that there is a crosstalk between inflammation and alterations in neurotransmission. The primary goal of this review is to demonstrate how these two pathways may converge at the level of the neuron and glia to involve in IMID. We review the role of neurotransmitters in IMID. The different effects that these compounds exert on a variety of immune cells are also reviewed. Current and future developments in understanding the cross-talk between the immune and nervous systems will undoubtedly identify new ways for treating immune-mediated diseases utilizing agonists or antagonists of neurotransmitter receptors.

Endocannabinoid-Binding Receptors as Drug Targets

Cannabis plant has been used from ancient times with therapeutic purposes for treating human pathologies, but the identification of the cellular and molecular mechanisms underlying the therapeutic properties of the phytocannabinoids, the active compounds in this plant, occurred in the last years of the past century. In the late 1980s and early 1990s, seminal studies demonstrated the existence of cannabinoid receptors and other elements of the so-called endocannabinoid system. These G protein-coupled receptors (GPCRs) are a key element in the functions assigned to endocannabinoids and appear to serve as promising pharmacological targets. They include CB₁, CB₂, and GPR55, but also non-GPCRs can be activated by endocannabinoids, like ionotropic receptor TRPV₁ and even nuclear receptors of the PPAR family. Their activation, inhibition, or simply modulation have been associated with numerous physiological effects at both central and peripheral levels, which may have therapeutic value in different human pathologies, then providing a solid experimental explanation for both the ancient medicinal uses of Cannabis plant and the recent advances in the development of cannabinoid-based specific therapies. This chapter will review the scientific knowledge generated in the last years around the research on the different endocannabinoid-binding receptors and their signaling mechanisms. Our intention is that this knowledge may help readers to understand the relevance of these receptors in health and disease conditions, as well as it may serve as the theoretical basis for the different experimental protocols to investigate these receptors and their signaling mechanisms that will be described in the following chapters.

Cannabinoids as Immune System Modulators: Cannabidiol Potential Therapeutic Approaches and Limitations

Introduction: Cannabidiol (CBD) is the second most abundant Phytocannabinoid in Cannabis extracts. CBD has a binding affinity for several cannabinoid and cannabinoid-associated receptors. Epidiolex (oral CBD solution) has been lately licensed by the Food and Drug Administration (FDA) for the treatment of pediatric epileptic seizures. Methods: In this review, we discussed the most promising applications of CBD for chronic inflammatory conditions, namely CBD's anti-inflammatory effects during inflammatory bowel disease, coronavirus disease (antiviral effect), brain pathologies (neuroprotective and anti-inflammatory properties), as well as CBD immunomodulatory and antitumoral activities in the tumor microenvironment. Special focus was shed on the main therapeutic mechanisms of action of CBD, particularly in the control of the immune system and the endocannabinoid system. Results: Findings suggest that CBD is a potent immunomodulatory drug as it has manifested immunosuppressive properties in the context of sterile inflammation (e.g., inflammatory bowel disease, rheumatoid arthritis, and neurodegenerative diseases), and immunoprotective effects during viral infections (e.g. COVID-19) Similarly, CBD has exhibited a selective response toward cancer types by engaging different targets and signaling pathways. These results are in favor of the primary function of the endocannabinoid system which is homeostatic maintenance. Conclusion: The presented evidence suggests that the endocannabinoid system is a prominent target for the treatment of inflammatory and autoimmune diseases, rheumatoid diseases, viral infections, neurological and psychological pathologies, and cancer. Moreover, the antitumoral activities of CBD have been suggested to be potentially used in combination with chemo- or immunotherapy during cancer. However, clinical results are still lacking, which raises a challenge to apply translational cannabis research to the human immune system.

Potential Role of Cannabinoid Type 2 Receptors in Neuropsychiatric and Neurodegenerative Disorders

The endocannabinoid system (ECS) is composed of the two canonical receptor subtypes; type-1 cannabinoid (CB1R) and type 2 receptor (CB2R), endocannabinoids (eCBs) and enzymes responsible for the synthesis and degradation of eCBs. Recently, with the identification of additional lipid mediators, enzymes and receptors, the expanded ECS called the endocannabinoidome (eCBome) has been identified and recognized. Activation of CB1R is associated with a plethora of physiological effects and some central nervous system (CNS) side effects, whereas, CB2R activation is devoid of such effects and hence CB2Rs might be utilized as potential new targets for the treatment of different disorders including neuropsychiatric disorders. Previous studies suggested that CB2Rs were absent in the brain and they were considered as peripheral receptors, however, recent studies confirmed the presence of CB2Rs in different brain regions. Several studies have now focused on the characterization of its physiological and pathological roles. Studies done on the role of CB2Rs as a therapeutic target for treating different disorders revealed important putative role of CB2R in neuropsychiatric disorders that requires further clinical validation. Here we provide current insights and knowledge on the potential role of targeting CB2Rs in neuropsychiatric and neurodegenerative disorders. Its non-psychoactive effect makes the CB2R a potential target for treating CNS disorders; however, a better understanding of the fundamental pharmacology of CB2R activation is essential for the design of novel therapeutic strategies.

Activation of CD4+ T Cell-Derived Cannabinoid Receptor 2 Signaling Exacerbates Sepsis via Inhibiting IL-10

The cannabinoid receptor 2 (CB2) is a receptor mainly expressed in immune cells and believed to be immunosuppressive in infective or inflammatory models. However, its role in sepsis has not been fully elucidated. In this study, we delineate the function and mechanism of CB2 in the cecal ligation and puncture-induced septic model in mice. The activation of CB2 signaling with HU308 led to decreased survival rates and more severe lung injury in septic mice, and lower IL-10 levels in peritoneal lavage fluid were observed in the CB2 agonist group. The mice with conditional knockout of CB2-encoding gene CNR2 in CD4⁺ T cells (CD4 Cre CNR2^fl/fl) improved survival, enhanced IL-10 production, and ameliorated pulmonary damage in the sepsis model after CB2 activation. In addition, double-knockout of the CNR2 gene (Lyz2 Cre CD4 Cre CNR2^fl/fl) decreased the susceptibility to sepsis compared with Lyz2 Cre CNR2^fl/fl mice. Mechanistically, the blockade of IL-10 with the anti-IL-10 Ab abolished its protection in CD4 Cre CNR2^fl/fl mice. In accordance with the animal study, in vitro results revealed that the lack of CNR2 in CD4⁺ cells elevated IL-10 production, and CB2 activation inhibited CD4⁺ T cell-derived IL-10 production. Furthermore, in the clinical environment, septic patients expressed enhanced CB2 mRNA levels compared with healthy donors in PBMCs, and their CB2 expression was inversely correlated with IL-10. These results suggested that the activation of CD4⁺ T cell-derived CB2 increased susceptibility to sepsis through inhibiting IL-10 production.

Osteogenic growth peptide is a potent anti-inflammatory and bone preserving hormone via cannabinoid receptor type 2

The endocannabinoid system consists mainly of 2-arachidonoylglycerol and anandamide, as well as cannabinoid receptor type 1 (CB1) and type 2 (CB2). Based on previous studies, we hypothesized that a circulating peptide previously identified as Osteogenic Growth Peptide (OGP) maintains a bone-protective CB2 tone. We tested OGP activity in mouse models and cells, and in human osteoblasts. We show that the OGP effects on osteoblast proliferation, osteoclastogenesis, and macrophage inflammation in vitro, as well as rescue of ovariectomy-induced bone loss and prevention of ear edema in vivo are all abrogated by genetic or pharmacological ablation of CB2. We also demonstrate that OGP binds at CB2 and may act as both an agonist and positive allosteric modulator in the presence of other lipophilic agonists. In premenopausal women, OGP circulating levels significantly decline with age. In adult mice, exogenous administration of OGP completely prevented age-related bone loss. Our findings suggest that OGP attenuates age-related bone loss by maintaining a skeletal CB2 tone. Importantly, they also indicate the occurrence of an endogenous peptide that signals via CB2 receptor in health and disease.

Detection of cannabinoid receptor type 2 in native cells and zebrafish with a highly potent, cell-permeable fluorescent probe

Despite its essential role in the (patho)physiology of several diseases, CB₂R tissue expression profiles and signaling mechanisms are not yet fully understood. We report the development of a highly potent, fluorescent CB₂R agonist probe employing structure-based reverse design. It commences with a highly potent, preclinically validated ligand, which is conjugated to a silicon-rhodamine fluorophore, enabling cell permeability. The probe is the first to preserve interspecies affinity and selectivity for both mouse and human CB₂R. Extensive cross-validation (FACS, TR-FRET and confocal microscopy) set the stage for CB₂R detection in endogenously expressing living cells along with zebrafish larvae. Together, these findings will benefit clinical translatability of CB₂R based drugs.

Detection and visualization of the cannabinoid receptor type 2 by a cell-permeable high affinity fluorescent probe platform enables tracing receptor trafficking in live cells and in zebrafish.

Endocannabinoid system contributions to sex-specific adolescent neurodevelopment

With an increasing number of countries and states adopting legislation permitting the use of cannabis for medical purposes, there is a growing interest among health and research professionals into the system through which cannabinoids principally act, the endocannabinoid system (ECS). Much of the seminal research into the ECS dates back only 30 years and, although there has been tremendous development within the field during this time, many questions remain. More recently, investigations have emerged examining the contributions of the ECS to normative development and the effect of altering this system during important critical periods. One such period is adolescence, a unique period during which brain and behaviours are maturing and reorganizing in preparation for adulthood, including shifts in endocannabinoid biology. The purpose of this review is to discuss findings to date regarding the maturation of the ECS during adolescence and the consequences of manipulations of the ECS during this period to normative neurodevelopmental processes, as well as highlight sex differences in ECS function, important technical considerations, and future directions. Because most of what we know is derived from preclinical studies on rodents, we provide relevant background of this model and some commentary on the translational relevance of the research in this area.

New Insights and Potential Therapeutic Targeting of CB2 Cannabinoid Receptors in CNS Disorders

The endocannabinoid system (ECS) is ubiquitous in most human tissues, and involved in the regulation of mental health. Consequently, its dysregulation is associated with neuropsychiatric and neurodegenerative disorders. Together, the ECS and the expanded endocannabinoidome (eCBome) are composed of genes coding for CB1 and CB2 cannabinoid receptors (CB1R, CB2R), endocannabinoids (eCBs), and the metabolic enzyme machinery for their synthesis and catabolism. The activation of CB1R is associated with adverse effects on the central nervous system (CNS), which has limited the therapeutic use of drugs that bind this receptor. The discovery of the functional neuronal CB2R raised new possibilities for the potential and safe targeting of the ECS for the treatment of CNS disorders. Previous studies were not able to detect CB2R mRNA transcripts in brain tissue and suggested that CB2Rs were absent in the brain and were considered peripheral receptors. Studies done on the role of CB2Rs as a potential therapeutic target for treating different disorders revealed the important putative role of CB2Rs in certain CNS disorders, which requires further clinical validation. This review addresses recent advances on the role of CB2Rs in neuropsychiatric and neurodegenerative disorders, including, but not limited to, anxiety, depression, schizophrenia, Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's disease (HD) and addiction.

The Role of Cannabinoids in Bone Metabolism: A New Perspective for Bone Disorders

Novel interest has arisen in recent years regarding bone, which is a very complex and dynamic tissue deputed to several functions ranging from mechanical and protective support to hematopoiesis and calcium homeostasis maintenance. In order to address these tasks, a very refined, continuous remodeling process needs to occur involving the coordinated action of different types of bone cells: osteoblasts (OBs), which have the capacity to produce newly formed bone, and osteoclasts (OCs), which can remove old bone. Bone remodeling is a highly regulated process that requires many hormones and messenger molecules, both at the systemic and the local level. The whole picture is still not fully understood, and the role of novel actors, such as the components of the endocannabinoids system (ECS), including endogenous cannabinoid ligands (ECs), cannabinoid receptors (CBRs), and the enzymes responsible for endogenous ligand synthesis and breakdown, is extremely intriguing. This article reviews the connection between the ECS and skeletal health, supporting the potential use of cannabinoid receptor ligands for the treatment of bone diseases associated with accelerated osteoclastic bone resorption, including osteoporosis and bone metastasis.

On the Biomedical Properties of Endocannabinoid Degradation and Reuptake Inhibitors: Pre-clinical and Clinical Evidence

The endocannabinoid system (ECS) is composed of endogenous cannabinoids; components involved in their synthesis, transport, and degradation; and an expansive variety of cannabinoid receptors. Hypofunction or deregulation of the ECS is related to pathological conditions. Consequently, endogenous enhancement of endocannabinoid levels and/or regulation of their metabolism represent promising therapeutic approaches. Several major strategies have been suggested for the modulation of the ECS: (1) blocking endocannabinoids degradation, (2) inhibition of endocannabinoid cellular uptake, and (3) pharmacological modulation of cannabinoid receptors as potential therapeutic targets. Here, we focused in this review on degradation/reuptake inhibitors over cannabinoid receptor modulators in order to provide an updated synopsis of contemporary evidence advancing mechanisms of endocannabinoids as pharmacological tools with therapeutic properties for the treatment of several disorders. For this purpose, we revisited the available literature and reported the latest advances regarding the biomedical properties of fatty acid amide hydrolase and monoacylglycerol lipase inhibitors in pre-clinical and clinical studies. We also highlighted anandamide and 2-arachidonoylglycerol reuptake inhibitors with promising results in pre-clinical studies using in vitro and animal models as an outlook for future research in clinical trials.

Potential and Limits of Cannabinoids in Alzheimer's Disease Therapy

Simple Summary

This review was aimed at exploring the potentiality of drugging the endocannabinoid system as a therapeutic option for Alzheimer’s disease (AD). Recent discoveries have demonstrated how the modulation of cannabinoid receptor 1 (CB1) and receptor 2 (CB2) can exert neuroprotective effects without the recreational and pharmacological properties of Cannabis sativa. Thus, this review explores the potential of cannabinoids in AD, also highlighting their limitations in perspective to point out the need for further research on cannabinoids in AD therapy.

Abstract

Alzheimer’s disease (AD) is a detrimental brain disorder characterized by a gradual cognitive decline and neuronal deterioration. To date, the treatments available are effective only in the early stage of the disease. The AD etiology has not been completely revealed, and investigating new pathological mechanisms is essential for developing effective and safe drugs. The recreational and pharmacological properties of marijuana are known for centuries, but only recently the scientific community started to investigate the potential use of cannabinoids in AD therapy—sometimes with contradictory outcomes. Since the endocannabinoid system (ECS) is highly expressed in the hippocampus and cortex, cannabis use/abuse has often been associated with memory and learning dysfunction in vulnerable individuals. However, the latest findings in AD rodent models have shown promising effects of cannabinoids in reducing amyloid plaque deposition and stimulating hippocampal neurogenesis. Beneficial effects on several dementia-related symptoms have also been reported in clinical trials after cannabinoid treatments. Accordingly, future studies should address identifying the correct therapeutic dosage and timing of treatment from the perspective of using cannabinoids in AD therapy. The present paper aims to summarize the potential and limitations of cannabinoids as therapeutics for AD, focusing on recent pre-clinical and clinical evidence.

Synthesis and receptor dependent 4D-QSAR studies of 4,5-dihydro-1,3,4-oxadiazole derivatives targeting cannabinoid receptor

Cannabinoid receptor has been shown to be overexpressed in various types of cancers, especially non-small cell lung cancer. As a result, it could be used as novel target for anticancer treatments. Because receptor-dependent 4D-QSAR generates conformational ensemble profiles of compounds by molecular dynamics simulations at the binding site of the enzyme, this work describes the synthesis, biological activity evaluation and 4D-QSAR studies of 4,5-dihydro-1,3,4-oxadiazole derivatives targeting cannabinoid receptor. Compared with WIN55,212-2, compound 5 f showed the best antiproliferative activity. The receptor-dependent 4D-QSAR model was generated by multiple linear regression method using QSARINS. Leave-n-out cross-validation and chemical applicability domain were performed to analyse the independent test set and to verify the robustness of the model. The best 4D-QSAR model showed the following statistics: r² = 0.8487, Q²_LOO = 0.7667, Q²_LNO = 0.7524, and r²_Pred = 0.8358.

Low-dose cannabinoid receptor 2 agonist induces microglial activation in a cancer pain-morphine tolerance rat model

AIMS

Cancer pain seriously affects the life quality of patients. Morphine is commonly used for cancer pain, but tolerance development limits its clinical administration. Central immune signaling is important in the development of cancer pain and morphine tolerance. Cannabinoid receptor 2 (CB2) inhibits cancer pain and morphine tolerance by regulating central immune signaling. In the present study, we investigated the mechanisms of central immune signaling involved in morphine tolerance inhibition by the CB2 agonist AM1241 in cancer pain treatment.

MAIN METHODS

Rats were implanted with tumor cells and divided into 4 groups: Vehicle (PBS), 0.07 μg AM1241, 0.03 μg AM1241, and AM630 (10 μg) + AM1241 (0.07 μg). All groups received morphine (20 μg/day, i.t.) for 8 days. AM630 (CB2 antagonist) was intrathecally injected 30 min before AM1241, and AM1241 was intrathecally injected 30 min before morphine. The spinal cord (SC) and dorsal root ganglion (DRG) were collected to determine the expression of Toll-like receptor 4 (TLR4), the p38 mitogen-activated protein kinase (MAPK), microglial markers, interleukin (IL)-1β, and tumor necrosis factor (TNF)-α.

KEY FINDINGS

The expression of TLR4, p38 MAPK, microglial markers, IL-1β, and TNF-α was significantly higher in AM1241-pretreated groups than in the vehicle group (P < 0.05). No difference in microglial markers, IL-1β, and TNF-α expression was detected in the AM630 + AM1241 group compared with the vehicle group.

SIGNIFICANCE

Our results suggest that in a cancer pain-morphine tolerance model, an i.t. non-analgesic dose of AM1241 induces microglial activation and IL-1β TNF-α upregulation in SC and DRG via the CB2 receptor pathway.

Phytocannabinoids: General Aspects and Pharmacological Potential in Neurodegenerative Diseases

In the last few years research into Cannabis and its constituent phytocannabinoids has burgeoned, particularly in the potential application of novel cannabis phytochemicals for the treatment of diverse illnesses related to neurodegeneration and dementia, including Alzheimer's (AD), Parkinson's (PD) and Huntington's disease (HD). To date, these neurological diseases have mostly relied on symptomatological management. However, with an aging population globally, the search for more efficient and disease-modifying treatments that could delay or mitigate disease progression is imperative. In this context, this review aims to present state of the art in the research with cannabinoids and novel cannabinoid-based drug candidates that have been emerged as novel promising alternatives for drug development and innovation in the therapeutics of a number of diseases, especially those related to CNS-disturbance and impairment.

A cannabinoid type 2 (CB2) receptor agonist augments NOS-dependent responses of cerebral arterioles during type 1 diabetes

While activation of cannabinoid (CB2) receptors has been shown to be neuroprotective, no studies have examined whether this neuroprotection is directed at cerebral arterioles and no studies have examined whether activation of CB2 receptors can rescue cerebrovascular dysfunction during a chronic disease state such as type 1 diabetes (T1D). Our goal was to test the hypothesis that administration of a CB2 agonist (JWH-133) would improve impaired endothelial (eNOS)- and neuronal (nNOS)-dependent dilation of cerebral arterioles during T1D. In vivo diameter of cerebral arterioles in nondiabetic and T1D rats was measured in response to an eNOS-dependent agonist (adenosine 5'-diphosphate; ADP), an nNOS-dependent agonist (N-methyl-d-aspartate; NMDA), and an NOS-independent agonist (nitroglycerin) before and 1 h following JWH-133 (1 mg/kg IP). Dilation of cerebral arterioles to ADP and NMDA was greater in nondiabetic than in T1D rats. Treatment with JWH-133 increased responses of cerebral arterioles to ADP and NMDA in both nondiabetic and T1D rats. Responses of cerebral arterioles to nitroglycerin were similar between nondiabetic and T1D rats, and JWH-133 did not influence responses to nitroglycerin in either group. The restoration in responses to the agonists by JWH-133 could be inhibited by treatment with a specific inhibitor of CB2 receptors (AM-630; 3 mg/kg IP). Thus, activation of CB2 receptors can potentiate reactivity of cerebral arterioles during physiologic and pathophysiologic states. We speculate that treatment with CB2 receptor agonists may have potential therapeutic benefits for the treatment of cerebral vascular diseases via a mechanism that can increase cerebral blood flow.

(Endo)Cannabinoids and Gynaecological Cancers

Simple Summary

Cancers of the female reproductive system are common and are responsible for a large number of deaths in women. The exact reasons why some of these cancers occur are unknown. It is, however, known that for most of these cancers, several factors interact for them to happen. These interactions involve factors external and internal to the woman. An understanding of some of the internal factors involved in how these cancers arise will not only help drive preventive strategies, but will speed the development of new treatment approaches. The endocannabinoid system is a family including chemicals (known as endocannabinoids) produced in the body that are similar to those derived from the cannabis plant. This system, which is widely distributed in the body, has been shown to be involved in various functions. Its disruption has been shown to lead to various diseases, one of which is cancer. In this review, we summarise current knowledge of this system, its various constituents, and how they are involved in reproductive events and their pathologies, especially cancers. Furthermore, we discuss the role of the endocannabinoid system in these cancers and how targeting it could lead to new approaches to diagnosis and treatment of cancers of the female reproductive system.

Abstract

Gynaecological cancers can be primary neoplasms, originating either from the reproductive tract or the products of conception, or secondary neoplasms, representative of metastatic disease. For some of these cancers, the exact causes are unknown; however, it is recognised that the precise aetiopathogeneses for most are multifactorial and include exogenous (such as diet) and endogenous factors (such as genetic predisposition), which mutually interact in a complex manner. One factor that has been recognised to be involved in the pathogenesis and progression of gynaecological cancers is the endocannabinoid system (ECS). The ECS consists of endocannabinoids (bioactive lipids), their receptors, and metabolic enzymes responsible for their synthesis and degradation. In this review, the impact of plant-derived (Cannabis species) cannabinoids and endocannabinoids on gynaecological cancers will be discussed within the context of the complexity of the proteins that bind, transport, and metabolise these compounds in reproductive and other tissues. In particular, the potential of endocannabinoids, their receptors, and metabolic enzymes as biomarkers of specific cancers, such as those of the endometrium, will be addressed. Additionally, the therapeutic potential of targeting selected elements of the ECS as new action points for the development of innovative drugs will be presented.

Bench to bedside: Multiple facets of cannabinoid control in epilepsy

Epilepsy is a neurological disease recognized as the consequence of excessive neuronal excitability. Endocannabinoid system, the critical regulator of synaptic inhibition in brain, was supposed to be closely involved in epilepsy. Cannabinoid receptors mostly locate on presynaptic terminals of both excitatory and inhibitory neurons, but with characteristic distribution varying in different brain areas and synapses. Endocannabinoids are synthesized in postsynaptic neurons and retrogradely act on presynaptic cannabinoid receptors. Accumulating evidence suggest that the expression of cannabinoid receptors and synthesis or breakdown of endocannabinoids were cell-type specifically altered and spatiotemporally regulated in seizures, and intervention of the expression of cannabinoid receptors or the level of endocannabinoids could affect seizure actions. Further in clinic, cannabidiol as an add-on treatment could reduce seizures in patients with treatment-resistant epilepsy, but the underlying mechanisms are still unclear and independent of the endocannabinoid system. Therefore, we review recent advances from bench to bedside, to address the cannabinoid control on seizures, discuss the existing confusion in current studies and provide directions for further research, which may be clinically important for the design of cannabinoid-based precise therapeutic interventions for epilepsy.

How do stupendous cannabinoids modulate memory processing via affecting neurotransmitter systems?

In the present study, we wanted to review the role of cannabinoids in learning and memory in animal models, with respect to their interaction effects with six principal neurotransmitters involved in learning and memory including dopamine, glutamate, GABA (γ-aminobutyric acid), serotonin, acetylcholine, and noradrenaline. Cannabinoids induce a wide-range of unpredictable effects on cognitive functions, while their mechanisms are not fully understood. Cannabinoids in different brain regions and in interaction with different neurotransmitters, show diverse responses. Previous findings have shown that cannabinoids agonists and antagonists induce various unpredictable effects such as similar effect, paradoxical effect, or dualistic effect. It should not be forgotten that brain neurotransmitter systems can also play unpredictable roles in mediating cognitive functions. Thus, we aimed to review and discuss the effect of cannabinoids in interaction with neurotransmitters on learning and memory. In addition, we mentioned to the type of interactions between cannabinoids and neurotransmitter systems. We suggested that investigating the type of interactions is a critical neuropharmacological issue that should be considered in future studies.

The synthetic cannabinoids phenomenon: from structure to toxicological properties. A review

The word "cannabinoid" refers to every chemical substance, regardless of structure or origin, that joins the cannabinoid receptors of the body and brain and that have similar effects to those produced by the Cannabis plant and based on their source of production, cannabinoids can be classified into endocannabinoids, phytocannabinoids and synthetic cannabinoids. Synthetic cannabinoids represent the largest class of drugs detected through the EU Early Warning System with a total of 190 substances notified from 2008 to 2018 and about 280 have been reported worldwide to the United Nations Office on Drugs and Crime. Sprayed on natural herb mixtures with the aim to mimic the euphoria effect of cannabis and sold as "herbal smoking blends" or "herbal incense" under brand names like "Spice" or "K2", synthetic cannabinoids are available from websites for the combination with herbal materials or more recently, for the use in e-cigarettes. Currently labeled as "not for human consumption" to circumvent legislation, their legal status varies by country with many government institutions currently pushing for their control. However, due to the emergence of new substances, it requires a constant update of the list of controlled drugs. Little is known about how these substances work and their toxic effects in humans and the same product could vary not only in the amount and in the type of substance added. In the last years, synthetic cannabinoids have been associated with deaths and acute intoxications in Europe and, despite a range of new measures introduced in this area, continue to represent a challenge to current drug policy models. These synthetic substances are much more potent than natural cannabis, as well as displayed greater efficacy, acting as full agonists at the cannabinoid receptors. It is possible that, along with being highly potent, some may also have long half-lives, potentially leading to a prolonged psychoactive effect. The present work provides a review on existing literature about the development of synthetic cannabinoids as substances of abuse, current patterns of abuse and their legal status, chemical classification, and some pharmacological and toxicological properties.

Endocannabinoid Modulation of Microglial Phenotypes in Neuropathology

Microglia, the resident immune cells of the central nervous system, mediate brain homeostasis by controlling neuronal proliferation/differentiation and synaptic activity. In response to external signals from neuropathological conditions, homeostatic (M0) microglia can adopt one of two activation states: the classical (M1) activation state, which secretes mediators of the proinflammatory response, and the alternative (M2) activation state, which presumably mediates the resolution of neuroinflammation and tissue repair/remodeling. Since chronic inflammatory activation of microglia is correlated with several neurodegenerative diseases, functional modulation of microglial phenotypes has been considered as a potential therapeutic strategy. The endocannabinoid (eCB) system, composed of cannabinoid receptors and ligands and their metabolic/biosynthetic enzymes, has been shown to activate anti-inflammatory signaling pathways that modulate immune cell functions. Growing evidence has demonstrated that endogenous, synthetic, and plant-derived eCB agonists possess therapeutic effects on several neuropathologies; however, the molecular mechanisms that mediate the anti-inflammatory effects have not yet been identified. Over the last decade, it has been revealed that the eCB system modulates microglial activation and population. In this review, we thoroughly examine recent studies on microglial phenotype modulation by eCB in neuroinflammatory and neurodegenerative disease conditions. We hypothesize that cannabinoid 2 receptor (CB2R) signaling shifts the balance of expression between neuroinflammatory (M1-type) genes, neuroprotective (M2-type) genes, and homeostatic (M0-type) genes toward the latter two gene expressions, by which microglia acquire therapeutic functionality.

Design and synthesis of fluorescent ligands for the detection of cannabinoid type 2 receptor (CB2R)

The Cannabinoid 2 receptor, CB2R, belonging to the endocannabinoid system, ECS, is involved in the first steps of neurodegeneration and cancer evolution and progression and thus its modulation may be exploited in the therapeutic and diagnostic fields. However, CB2Rs distribution and signaling pathways in physiological and pathological conditions are still controversial mainly because of the lack of reliable diagnostic tools. With the aim to produce green and safe systems to detect CB2R, we designed a series of fluorescent ligands with three different green fluorescent moieties (4-dimethylaminophthalimide, 4-DMAP, 7-nitro-4-yl-aminobenzoxadiazole, NBD, and Fluorescein-thiourea, FTU) linked to the N1-position of the CB2R pharmacophore N-adamantyl-4-oxo-1,4-dihydroquinoline-3-carboxamide through polymethylene chains. Compound 28 emerged for its compromise between good pharmacodynamic properties (CB2R K_i = 130 nM and no affinity vs the other subtype CB1R) and optimal fluorescent spectroscopic properties. Therefore, compound 28 was studied through FACS (saturation and competitive binding studies) and fluorescence microscopy (visualization and competitive binding) in engineered cells (CB2R-HEK293 cells) and in diverse tumour cells. The fluoligand binding assays were successfully set up, and affinity values for the two reference compounds GW405833 and WIN55,212-2, comparable to the values obtained by radioligand binding assays, were obtained. Fluoligand 28 also allowed the detection of the presence and quantification of the CB2R in the same cell lines. The interactions of compound 28 within the CB2R binding site were also investigated by molecular docking simulations, and indications for the improvement of the CB2R affinity of this class of compounds were provided. Overall, the results obtained through these studies propose compound 28 as a safe and green alternative to the commonly used radioligands for in vitro investigations.

Cannabinoids CB2 Receptors, One New Promising Drug Target for Chronic and Degenerative Pain Conditions in Equine Veterinary Patients

Osteoarticular equine disease is a common cause of malady; in general, its therapy is supported on steroids and nonsteroidal anti-inflammatories. Nevertheless, many side effects may develop when these drugs are administered. Nowadays, the use of new alternatives for this pathology attention is demanded; in that sense, cannabinoid CB2 agonists may represent a novel alternative. Cannabinoid belongs to a group of molecules known by their psychoactive properties; they are synthetized by the Cannabis sativa plant, better known as marijuana. The aim of this study was to contribute to understand the pharmacology of cannabinoid CB2 receptors and its potential utilization on equine veterinary patients with a chronic degenerative painful condition. In animals, two main receptors for cannabinoids are recognized, the cannabinoid receptor type 1 and the cannabinoid receptor type 2. Once they are activated, both receptors exert a wide range of physiological responses, as nociception modulation. Recently, it has been proposed the use of synthetic cannabinoid type 2 receptor agonists; those receptors looks to confer antinociceptive properties but without the undesired psychoactive side effects; for that reason, veterinary patients, whit chronical degenerative diseases as osteoarthritis may alleviate one of the most common symptom, the pain, which in some cases for several reasons, as patient individualities, or side effects produced for more conventional treatments cannot be attended in the best way.

Reduced cannabinoid 2 receptor activity increases susceptibility to induced seizures in mice

OBJECTIVE

The endocannabinoid system (ECS) is comprised of cannabinoid receptors 1 and 2 (CB1R and CB2R), endogenous ligands, and regulatory enzymes, and serves to regulate several important physiological functions throughout the brain and body. Recent evidence suggests that the ECS may be a promising target for the treatment of epilepsy, including epilepsy subtypes that arise from mutations in the voltage-gated sodium channel SCN1A. The objective of this study was to explore the effects of modulating CB2R activity on seizure susceptibility.

METHODS

We examined susceptibility to induced seizures using a number of paradigms in CB2R knockout mice (Cnr2^-/- ), and determined the effects of the CB2R agonist, JWH-133, and the CB2R antagonist, SR144528, on seizure susceptibility in wild-type mice. We also examined seizure susceptibility in Cnr2 mutants harboring the human SCN1A R1648H (RH) epilepsy mutation and performed Electroencephalography (EEG) analysis to determine whether the loss of CB2Rs would increase spontaneous seizure frequency in Scn1a RH mutant mice.

RESULTS

Both heterozygous (Cnr2^+/- ) and homozygous (Cnr2^-/- ) knockout mice exhibited increased susceptibility to pentylenetetrazole (PTZ)-induced seizures. The CB2R agonist JWH-133 did not significantly alter seizure susceptibility in wild-type mice; however, administration of the CB2R antagonist SR144528 resulted in increased susceptibility to PTZ-induced seizures. In offspring from a cross between the Cnr2 × RH lines, both Cnr2 and RH mutants were susceptible to PTZ-induced seizures; however, seizure susceptibility was not significantly increased in mutants expressing both mutations. No spontaneous seizures were observed in either RH or Cnr2/RH mutants during 336-504 hours of continuous EEG recordings.

SIGNIFICANCE

Our results demonstrate that reduced CB2R activity is associated with increased seizure susceptibility. CB2Rs might therefore provide a therapeutic target for the treatment of some forms of epilepsy.

A functional variant of CB2 receptor gene interacts with childhood trauma and FAAH gene on anxious and depressive phenotypes

BACKGROUND

Accumulating data suggest that CB2 receptor plays a crucial role in development of anxiety via regulatory function of stress response and neuroimmune crosstalk. Although animal experiments confirm this relationship, relevant human genetic studies on CB2 receptor gene (CNR2) in association with affective phenotype are absent.

METHODS

CNR2 R63Q and FAAH C385A functional polymorphisms were genotyped of 921 volunteers from the general population. Phenotypic variables were measured by the Zung Self-related Depression Scale (ZSDS), The State-Trait Anxiety Inventory (Trait subscale, STAI-T) and the depressive and anxious subscales of the Brief Symptom Inventory (BSI-DEP and BSI-ANX). Early life trauma was assesssed by the Childhood Trauma Questionnaire (CHQ). Using general linear models we tested possible associations between phenotypic variance and genotype distribution.

RESULTS

There was a significant main effect of RR genotype of R63Q on ZSDS score (p = 0.007) and a remarkble interacting effect of CHQ and R63Q on scores of ZSDS, STAI-T and BSI-ANX scales (p = 0.009; p = 0.003; p = 0.001; respectively). R allele of R63Q and A allele of FAAH C385A were associated with significantly higher ZSDS, STAI-T and BSI-ANX scores compared to non-risk allele carriers (p = 0.009; p = 0.007; p = 0.007, respectively). The highest phenotypic scores were observed in GxGxE model (p_ZSDS = 0.04; p_BSI-DEP = 0.006; p_STAI-T = 0.001; p_BSI-ANX = 3.8 × 10^-5).

CONCLUSIONS

In this first human genetic study on CNR2 and childhood trauma we revealed that dysfunctional CB2 receptor and FAAH can contribute to greater sensitivity for childhood trauma possibly via weaker inhibiton of inflammatory and overactivated HPA axis.

Cannabinoids for the treatment of rheumatic diseases - where do we stand?

As medical use of cannabis is increasingly legalized worldwide, a better understanding of the medical and hazardous effects of this drug is imperative. The pain associated with rheumatic diseases is considered a prevalent indication for medicinal cannabis in various countries. Thus far, preliminary clinical trials have explored the effects of cannabis on rheumatoid arthritis, osteoarthritis and fibromyalgia; preliminary evidence has also found an association between the cannabinoid system and other rheumatic conditions, including systemic sclerosis and juvenile idiopathic arthritis. The potential medicinal effects of cannabis could be attributable to its influence on the immune system, as it exerts an immunomodulatory effect on various immune cells, including T cells, B cells and macrophages. However, the available evidence is not yet sufficient to support the recommendation of cannabinoid treatment for rheumatic diseases.

Bipolar disorder and the endocannabinoid system

OBJECTIVE

Bipolar disorder (BD) is a debilitating, lifelong neuropsychiatric illness characterised by unsteady mood states which vacillate from (hypo)mania to depression. Despite the availability of pharmaceutical agents which can be effective in ameliorating the acute affective symptoms and prevent episodic relapse, BD is inadequately treated in a subset of patients. The endocannabinoid system (ECS) is known to exert neuromodulatory effects on other neurotransmitter systems critical in governing emotions. Several studies ranging from clinical to molecular, as well as anecdotal evidence, have placed a spotlight on the potential role of the ECS in the pathophysiology of BD. In this perspective, we present advantages and disadvantages of cannabis use in the management of illness course of BD and provide mechanistic insights into how this system might contribute to the pathophysiology of BD.

RESULTS

We highlight the putative role of selective cannabinoid receptor 2 (CB2) agonists in BD and briefly discuss findings which provide a rationale for targeting the ECS to assuage the symptoms of BD. Further, data encourage basic and clinical studies to determine how cannabis and cannabinoids (CBs) can affect mood and to investigate emerging CB-based options as probable treatment approaches.

CONCLUSION

The probable role of the ECS has been almost neglected in BD; however, from data available which suggest a role of ECS in mood control, it is justified to support conducting comprehensive studies to determine whether ECS manipulation could positively affect BD. Based on the limited available data, we suggest that activation of CB2 may stabilise mood in this disorder.

Should Oncologists Recommend Cannabis?

OPINION STATEMENT

Cannabis is a useful botanical with a wide range of therapeutic potential. Global prohibition over the past century has impeded the ability to study the plant as medicine. However, delta-9-tetrahydrocannabinol (THC) has been developed as a stand-alone pharmaceutical initially approved for the treatment of chemotherapy-related nausea and vomiting in 1986. The indication was expanded in 1992 to include treatment of anorexia in patients with the AIDS wasting syndrome. Hence, if the dominant cannabinoid is available as a schedule III prescription medication, it would seem logical that the parent botanical would likely have similar therapeutic benefits. The system of cannabinoid receptors and endogenous cannabinoids (endocannabinoids) has likely developed to help us modulate our response to noxious stimuli. Phytocannabinoids also complex with these receptors, and the analgesic effects of cannabis are perhaps the best supported by clinical evidence. Cannabis and its constituents have also been reported to be useful in assisting with sleep, mood, and anxiety. Despite significant in vitro and animal model evidence supporting the anti-cancer activity of individual cannabinoids-particularly THC and cannabidiol (CBD)-clinical evidence is absent. A single intervention that can assist with nausea, appetite, pain, mood, and sleep is certainly a valuable addition to the palliative care armamentarium. Although many healthcare providers advise against the inhalation of a botanical as a twenty-first century drug-delivery system, evidence for serious harmful effects of cannabis inhalation is scant and a variety of other methods of ingestion are currently available from dispensaries in locales where patients have access to medicinal cannabis. Oncologists and palliative care providers should recommend this botanical remedy to their patients to gain first-hand evidence of its therapeutic potential despite the paucity of results from randomized placebo-controlled clinical trials to appreciate that it is both safe and effective and really does not require a package insert.

A structure-function approach identifies L-PGDS as a mediator responsible for glucocorticoid-induced leptin expression in adipocytes

Leptin is an adipokine predominantly secreted by adipocytes and has many physiological roles, including in energy homeostasis. We identified that AM630, a cannabinoid receptor 2 (CB2) antagonist, down-regulated leptin expression in mature adipocytes differentiated from either stromal vascular fractions isolated from inguinal fat pads of C57BL/6J mice or 3T3-L1 preadipocytes. However, the leptin-suppressive effects of AM630 preserved in CB2-deficient adipocytes indicated the off-target activity of AM630 in leptin expression. Pharmacological and genetic studies, cheminformatics, and docking simulation were applied to identify the potential protein target of AM630 that modulates leptin expression in differentiated primary preadipocytes. Screening of the reported off-targets of AM630 identified a synthetic cannabinoid WIN55212-2 exerting the same function. Target deconvolution and docking simulation suggested that AM630 and WIN55212-2 were both inhibitors of lipocalin-type prostaglandin D2 synthase (L-PGDS). Further studies showed that L-PGDS positively regulates leptin expression. Although glucocorticoid and aldosterone were previously reported to induce expression of both L-PGDS and leptin, our data demonstrated that L-PGDS mediates only glucocorticoid-induced leptin expression in differentiated primary preadipocytes. No effect was observed after aldosterone treatment. This newly discovered glucocorticoid - L-PGDS - leptin pathway may provide insights into current clinical use of glucocorticoid and management of their undesired effects such as obesity.

Cannabinoid Receptor 2 Agonist JWH-015 Inhibits Interleukin-1β-Induced Inflammation in Rheumatoid Arthritis Synovial Fibroblasts and in Adjuvant Induced Arthritis Rat via Glucocorticoid Receptor

Management of pain in the treatment of rheumatoid arthritis (RA) is a priority that is not fully addressed by the conventional therapies. In the present study, we evaluated the efficacy of cannabinoid receptor 2 (CB2) agonist JWH-015 using RA synovial fibroblasts (RASFs) obtained from patients diagnosed with RA and in a rat adjuvant-induced arthritis (AIA) model of RA. Pretreatment of human RASFs with JWH-015 (10–20 μM) markedly inhibited the ability of pro-inflammatory cytokine interleukin-1β (IL-1β) to induce production of IL-6 and IL-8 and cellular expression of inflammatory cyclooxygenase-2 (COX-2). JWH-015 was effective in reducing IL-1β-induced phosphorylation of TAK1 (Thr^184/187) and JNK/SAPK in human RASFs. While the knockdown of CB2 in RASFs using siRNA method reduced IL-1β-induced inflammation, JWH-015 was still effective in eliciting its anti-inflammatory effects despite the absence of CB2, suggesting the role of non-canonical or an off-target receptor. Computational studies using molecular docking and molecular dynamics simulations showed that JWH-105 favorably binds to glucocorticoid receptor (GR) with the binding pose and interactions similar to its well-known ligand dexamethasone. Furthermore, knockdown of GR using siRNA abrogated JWH-015's ability to reduce IL-1β-induced IL-6 and IL-8 production. In vivo, administration of JWH-015 (5 mg/kg, daily i.p. for 7 days at the onset of arthritis) significantly ameliorated AIA in rats. Pain assessment studies using von Frey method showed a marked antinociception in AIA rats treated with JWH-015. In addition, JWH-015 treatment inhibited bone destruction as evident from micro-CT scanning and bone analysis on the harvested joints and modulated serum RANKL and OPG levels. Overall, our findings suggest that CB2 agonist JWH-015 elicits anti-inflammatory effects partly through GR. This compound could further be tested as an adjunct therapy for the management of pain and tissue destruction as a non-opioid for RA.

Interaction of neurotransmitters and neurochemicals with lymphocytes

Neurotransmitters and neurochemicals can act on lymphocytes by binding to receptors expressed by lymphocytes. This review describes lymphocyte expression of receptors for a selection of neurotransmitters and neurochemicals, the anatomical locations where lymphocytes can interact with neurotransmitters, and the effects of the neurotransmitters on lymphocyte function. Implications for health and disease are also discussed.

Cannabinoid receptor 2: a potential novel therapeutic target for sepsis?

OBJECTIVE

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection. It is the most common cause of death among critically ill patients in non-coronary intensive care units and the incidence continues to rise. Although advanced management was applied, the prognosis of sepsis patients remains poor. As a G-protein coupled receptor, cannabinoid receptor 2 (CB2R) was implicated in a wide variety of diseases. In this study, we aimed to investigate the role of CB2R in sepsis.

METHODS

Literature search was performed using "sepsis" and "Cannabinoid Receptor" as search terms in PubMed, EMbase, and the Cochrane Library.

RESULTS AND DISCUSSION

Briefly, 97 records were identified by the search strategy, of which 76 were duplicate or irrelevant publications. With the anti-inflammatory and immunomodulatory effects, CB2R is a novel and promising therapeutic target in the management of sepsis. Indeed, specific CB2R agonists have been reported to attenuate leukocyte recruitment, oxidative burst, systemic inflammatory mediator release, bacteremia, and lung tissue damage, while improving survival in different sepsis models. In addition, autophagy has also been implicated in the protective role of CB2R activation in sepsis. However, almost all of the current outcomes result from animal studies or in vitro cultured cells. Due to the lack of clinical evidence and the ambiguous mechanisms underlying, the clinical application of CB2R stimulation in sepsis is limited. Further studies are needed to delineate the therapeutic effect and the related-pathways of CB2R agonists in sepsis.

Cannabinoid-sensitive receptors in cardiac physiology and ischaemia

The classical cannabinoid receptors CB1 and CB2 as well as the cannabinoid-sensitive receptor GPR55 are widely distributed throughout the mammalian body. In the cardiovascular field, CB1 and CB2 crucially impact on diseases characterized by inflammatory processes, such as atherosclerosis and acute myocardial infarction. Both receptors and their endogenous ligands anandamide and 2-arachidonoylglycerol are up-regulated in the ischaemic heart in humans and animal models. Pharmacological and genetic interventions with CB1 and CB2 vitally affect acute ischaemia-induced cardiac inflammation. Herein, CB1 rather aggravates the inflammatory response whereas CB2 mitigates inflammation via directly affecting immune cell attraction, macrophage polarization and lymphocyte clusters in the pericardial adipose tissue. Furthermore, cannabinoids and their receptors affect numerous cardiac risk factors. In this context, cannabis consumption is debated to trigger arrhythmias and even myocardial infarction. Moreover, CB1 activation is linked to impaired lipid and glucose metabolism and therefore obesity and diabetes, while its antagonism leads to the reduction of plasma triglycerides, low-density lipoprotein cholesterol, leptin, insulin and glucose. On the other hand, activation of cannabinoid-sensitive receptors can also counteract unfavourable predictors for cardiovascular diseases. In particular, hypertension can be mitigated via CB1 agonism and impaired adrenoceptor responsiveness prevented by functional GPR55. Taken together, current insights identify the cannabinoid system as promising target not only to therapeutically interfere with the vasculature, but also to affect the heart as target organ. This review discusses current knowledge regarding a direct cardiac role of the cannabinoid system and points out its feasible therapeutic manipulation in the ischaemic myocardium.

Protective Effect of N-Arachidonoyl Glycine-GPR18 Signaling after Excitotoxical Lesion in Murine Organotypic Hippocampal Slice Cultures

N-arachidonoyl glycine (NAGly) is an endocannabinoid involved in the regulation of different immune cells. It was shown to activate the GPR18 receptor, which was postulated to switch macrophages from cytotoxic to reparative. To study GPR18 expression and neuroprotection after NAGly treatment we used excitotoxically lesioned organotypic hippocampal slice cultures (OHSC). The effect of NAGly was also tested in isolated microglia and astrocytes as these cells play a crucial role during neuronal injury. In the present study, the GPR18 receptor was found in OHSC at mRNA level and was downregulated after N-Methyl-D-aspartate (NMDA) treatment at a single time point. Furthermore, treatment with NAGly reduced neuronal damage and this effect was abolished by GPR18 and cannabinoid receptor (CB)₂ receptor antagonists. The activation but not motility of primary microglia and astrocytes was influenced when incubated with NAGly. However, NAGly alone reduced the phosphorylation of Akt but no changes in activation of the p44/42 and p38 MAPK and CREB pathways in BV2 cells could be observed. Given NAGly mediated actions we speculate that GPR18 and its ligand NAGly are modulators of glial and neuronal cells during neuronal damage.

Structural properties and role of the endocannabinoid lipases ABHD6 and ABHD12 in lipid signalling and disease

The endocannabinoid (eCB) system is an important part of both the human central nervous system (CNS) and peripheral tissues. It is involved in the regulation of various physiological and neuronal processes and has been associated with various diseases. The eCB system is a complex network composed of receptor molecules, their cannabinoid ligands, and enzymes regulating the synthesis, release, uptake, and degradation of the signalling molecules. Although the eCB system and the molecular processes of eCB signalling have been studied extensively over the past decades, the involved molecules and underlying signalling mechanisms have not been described in full detail. An example pose the two poorly characterised eCB-degrading enzymes α/β-hydrolase domain protein six (ABHD6) and ABHD12, which have been shown to hydrolyse 2-arachidonoyl glycerol-the main eCB in the CNS. We review the current knowledge about the eCB system and the role of ABHD6 and ABHD12 within this important signalling system and associated diseases. Homology modelling and multiple sequence alignments highlight the structural features of the studied enzymes and their similarities, as well as the structural basis of disease-related ABHD12 mutations. However, homologies within the ABHD family are very low, and even the closest homologues have widely varying substrate preferences. Detailed experimental analyses at the molecular level will be necessary to understand these important enzymes in full detail.

Presynaptic cannabinoid CB2 receptors modulate [3 H]-Glutamate release at subthalamo-nigral terminals of the rat

Recent studies suggested the expression of CB2 receptors in neurons of the CNS, however, most of these studies have only explored one aspect of the receptors, i.e., expression of protein, messenger RNA, or functional response, and more complete studies appear to be needed to establish adequately their role in the neuronal function. Electron microscopy studies showed the presence of CB2r in asymmetric terminals of the substantia nigra pars reticulata (SNr), and its mRNA appeared is expressed in the subthalamic nucleus. Here, we explore the expression, source, and functional effects of such receptors by different experimental approaches. Through PCR and immunochemistry, we showed mRNA and protein for CB2rs in slices and primary neuronal cultures from subthalamus. GW833972A, GW405833, and JHW 133, three CB2r agonists dose-dependent inhibited K⁺ -induced [³ H]-Glutamate release in slices of SNr, and the two antagonist/inverse agonists, JTE-907 and AM630, but not AM281, a CB1r antagonist, prevented GW833972A effect. Subthalamus lesions with kainic acid prevented GW833972A inhibition on release and decreased CB2r protein in nigral synaptosomes, thus nigral CB2rs originate in subthalamus. Inhibition of [³ H]-Glutamate release was PTX- and gallein-sensitive, suggesting a Gi_βγ -mediated effect. P/Q Ca²⁺ -type channel blocker, ω-Agatoxin-TK, also inhibited the [³ H]-Glutamate release, this effect was occluded with GW833972A inhibition, indicating that the βγ subunit effect is exerted on Ca²⁺ channel activity. Finally, microinjections of GW833972A in SNr induced contralateral turning. Our data showed that presynaptic CB2rs inhibit [³ H]-Glutamate release in subthalamo-nigral terminals by P/Q-channels modulation through the Gi_βγ subunit and suggested their participation in motor behavior.

Effects of Cocaine Self-Administration and Its Extinction on the Rat Brain Cannabinoid CB1 and CB2 Receptors

The aim of this study was to evaluate changes in the expression of cannabinoid type 1 (CB1) and 2 (CB2) receptor proteins in several brain regions in rats undergoing cocaine self-administration and extinction training. We used a triad-yoked procedure to distinguish between the motivational and pharmacological effects of cocaine. Using immunohistochemistry, we observed a significant decrease in CB1 receptor expression in the prefrontal cortex, dorsal striatum, and the basolateral and basomedial amygdala following cocaine (0.5 mg/kg/infusion) self-administration. Increased CB1 receptor expression in the ventral tegmental area in rats with previous cocaine exposure was also found. Following cocaine abstinence after 10 days of extinction training, we detected increases in the expression of CB1 receptors in the substantia nigra in both cocaine groups and in the subregions of the amygdala for only the yoked cocaine controls, while any method of cocaine exposure resulted in a decrease in CB2 receptor expression in the prefrontal cortex (p < 0.01), nucleus accumbens (p < 0.01), and medial globus pallidus (p < 0.01). Our findings further support the idea that the eCB system and CB1 receptors are involved in cocaine-reinforced behaviors. Moreover, we detected a cocaine-evoked adaptation in CB2 receptors in the amygdala, prefrontal cortex, and globus pallidus.

Effect of maternal high-fat diet on key components of the placental and hepatic endocannabinoid system

Maternal obesity in pregnancy has been linked to a spectrum of adverse developmental changes. Involvement of eCBs in obesity is well characterized. However, information regarding eCB physiology in obesity associated with pregnancy is sparse. This study evaluated fetomaternal hepatic, systemic, and placental eCB molecular changes in response to maternal consumption of a HFD. From ≥9 mo before conception, nonpregnant baboons ( Papio spp.) were fed a diet of either 45 (HFD; n = 11) or 12% fat or a control diet (CTR; n = 11), and dietary intervention continued through pregnancy. Maternal and fetal venous plasma samples were evaluated using liquid chromatography-mass spectrometry to quantify AEA and 2-AG. Placental, maternal and fetal hepatic tissues were analyzed using RT-PCR, Western blot, and immunohistochemistry. mRNA and protein expression of endocannabinoid receptors (CB1R and CB2R), FAAH, DAGL, MAGL, and COX-2 were determined. Statistical analyses were performed with the nonparametric Scheirer-Ray-Hare extension of the Kruskal-Wallis test to analyze the effects of diet (HFD vs. CTR), fetal sex (male vs. female), and the diet × sex interaction. Fetal weight was influenced by fetal sex but not by maternal diet. The increase in maternal weight in animals fed the HFD vs. the CTR diet approached significance ( P = 0.055). Maternal circulating 2-AG concentrations increased, and fetal circulating concentrations decreased in the HFD group, independently of fetal sex. CB1R receptor expression was detected in syncytiotrophoblasts (HFD) and the fetal endothelium (CTR and HFD). Placental CB2R protein expression was higher in males and lower in female fetuses in the HFD group. Fetal hepatic CB2R, FAAH, COX-2 (for both fetal sexes), and DAGLα (in male fetuses) protein expression decreased in the HFD group compared with the CTR group. We conclude that consumption of a HFD during pregnancy results in fetal systemic 2-AG and hepatic eCB deficiency.

The role of monocytosis and neutrophilia in atherosclerosis

Monocytosis and neutrophilia are frequent events in atherosclerosis. These phenomena arise from the increased proliferation of hematopoietic stem and multipotential progenitor cells (HSPCs) and HSPC mobilization from the bone marrow to other immune organs and circulation. High cholesterol and inflammatory signals promote HSPC proliferation and preferential differentiation to the myeloid precursors (i.e., myelopoiesis) that than give rise to pro-inflammatory immune cells. These cells accumulate in the plaques thereby enhancing vascular inflammation and contributing to further lesion progression. Studies in animal models of atherosclerosis showed that manipulation with HSPC proliferation and differentiation through the activation of LXR-dependent mechanisms and restoration of cholesterol efflux may have a significant therapeutic potential.

A Fluorescent Probe to Unravel Functional Features of Cannabinoid Receptor CB1 in Human Blood and Tonsil Immune System Cells

The human endogenous cannabinoid system (ECS) regulates key physiological processes and alterations in its signaling pathways, and endocannabinoid levels are associated with diseases such as neurological and neuropsychiatric conditions, cancer, pain and inflammation, obesity, and metabolic and different immune related disorders. Immune system cells express the G-protein coupled cannabinoid receptor 1 (CB₁), but its functional role has not been fully understood, likely due to the lack of appropriate tools. The availability of novel tools to investigate the role of CB₁ in immune regulation might contribute to identify CB₁ as a potential novel therapeutic target or biomarker for many diseases. Herein, we report the development and validation of the first fluorescent small molecule probe to directly visualize and quantify CB₁ in blood and tonsil immune cells by flow cytometry and confocal microscopy. We coupled the cannabinoid agonist HU210 to the fluorescent tag Alexa Fluor 488, generating a fluorescent probe with high affinity for CB₁ and selectivity over CB₂. We validate HU210-Alexa488 for the rapid, simultaneous, and reproducible identification of CB₁ in human monocytes, T cells, and B cells by multiplexed flow cytometry. This probe is also suitable for the direct visualization of CB₁ in tonsil tissues, allowing the in vivo identification of tonsil CB₁-expressing T and B cells. This study provides the first fluorescent chemical tool to investigate CB₁ expression and function in human blood and tonsil immune cells, which might well pave the way to unravel essential features of CB₁ in different immune and ECS-related diseases.