The putative cannabinoid receptor GPR55 affects osteoclast function in vitro and bone mass in vivo

Effects of Marijuana Use in Patients with Orthopaedic Trauma

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The use of cannabis and cannabis-related products has increased dramatically in the last 2 decades. As states continue to legalize cannabis products, it is important for surgeons to understand the effects they may have on patients who have sustained orthopaedic trauma.

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Cannabinoids have been shown to decrease the severity of certain symptoms related to traumatic brain injury as well as posttraumatic stress disorder.

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Cannabinoids can modulate the body's endocannabinoid system, which can play an important role in bone homeostasis. Activation of cannabinoid receptors has been shown to be bone-protective in adults.

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Venous thromboembolism is a major concern for trauma patients. Cannabis use has been linked to overall increased rates of venous thromboembolism events.

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Literature regarding human-based cannabis studies is sparse; however, the growing field is opening new opportunities for research of this topic.

Parkinson's disease related alterations in cannabinoid transmission

Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic (DAergic) neurons of the substantia nigra pars compacta (SNc) by neurodegeneration. Recent findings in animal models of PD propose tonic inhibition of the remaining DA neurons through GABA release from reactive glial cells. Movement dysfunctions could be ameliorated by promotion of activity in dormant DA cells. The endocannabinoid system (ECS) is extensively present in basal ganglia (BG) and is known as an indirect modulator of DAergic neurotransmission, thus drugs designed to target this system have shown promising therapeutic potential in PD patients. Interestingly, down/up-regulation of cannabinoid receptors (CBRs) varies across the different stages of PD, suggesting that some of the motor/ non-motor deficits may be related to changes in CBRs. Determination of the profile of changes of these receptors across the different stages of PD as well as their neural distribution within the BG could improve understanding of PD and identify pathways important in disease pathobiology. In this review, we focus on temporal and spatial alterations of CBRs during PD in the BG. At present, as inconclusive, but suggestive results have been obtained, future investigations should be conducted to extend preclinical studies examining CBRs changes within each stage in controlled clinical trials in order to determine the potential of targeting CBRs in management of PD.

Expression of the putative cannabinoid receptor GPR55 is increased in endometrial carcinoma

Although the expression of the putative cannabinoid receptor GPR55 has been shown to be involved in the growth of various tumours and is increased in a number of cancers, its expression has not been examined in patients with endometrial cancer (EC). Quantitative RT-PCR (for mRNA levels) and immunohistochemistry (for protein levels) were used to measure GPR55 expression in patients with Type 1 and Type 2 EC and correlated against cannabinoid receptor (CB1 and CB2) protein levels using non-cancerous endometrium as the control tissue. The data indicated that GPR55 transcript and GPR55 protein levels were significantly (p < 0.002 and p < 0.0001, respectively) higher in EC tissues than in control tissues. The levels of immunoreactive GPR55 protein were correlated with GPR55 transcript levels, but not with the expression of CB1 receptor protein, and were inversely correlated with CB2 protein expression, which was significantly decreased. It can be concluded that GPR55 expression is elevated in women with EC, and thus could provide a potential novel biomarker and therapeutic target for this disease.

Effect of Postoperative Analgesic Exposure to the Cannabinoid Receptor Agonist WIN55 on Osteogenic Differentiation and Spinal Fusion in Rats

BACKGROUND

After spinal surgery and other orthopaedic procedures, most patients receive opioids for pain, leading to potential complications such as pseudarthrosis and opioid abuse associated with long-term use. As an alternative, the endocannabinoid system has been shown to have antinociceptive activity, while contributing to bone homeostasis via the CB1 and CB2 cannabinoid receptors. This study evaluates the impact of the cannabinoid receptor agonist WIN55,212-2 (WIN55) on osteogenic differentiation in vitro as well as bone regeneration and spinal fusion in a preclinical rat model.

METHODS

Primary rat bone marrow stromal cells were cultured in standard or osteogenic media and exposed to vehicle alone or WIN55. Runx2 and Alkaline phosphatase (Alpl) were quantified via qPCR (quantitative real-time polymerase chain reaction), followed by assessment of ALP activity and matrix mineralization. For in vivo evaluation, 45 female Sprague Dawley rats (n = 15 per group) underwent L4-L5 posterolateral spinal fusion with bilateral placement of collagen scaffolds preloaded with low-dose rhBMP-2 (recombinant human bone morphogenetic protein-2; 0.5 μg/implant). Postoperatively, rats received the vehicle alone or 0.5 or 2.5 mg/kg WIN55 via daily intraperitoneal injections for 5 days. Bone regeneration and spinal fusion were assessed using radiography, manual palpation-based fusion scoring, microcomputed tomography imaging, and histology.

RESULTS

mRNA expression levels of Runx2 and Alp were similar among cells treated with vehicle alone and WIN55. Likewise, exposure to WIN55 did not inhibit ALP activity or bone matrix mineralization. In this animal model, no significant differences were found among groups with regard to mean fusion score, fusion rate, or new bone volume.

CONCLUSIONS

WIN55 showed no adverse impact on osteogenic differentiation, bone regeneration, and spinal fusion. This supports that cannabinoid receptor agonists should be further investigated as a potential alternative approach for postoperative analgesia following spinal fusion and other orthopaedic procedures requiring bone-healing.

CLINICAL RELEVANCE

The identification of alternative treatments for postoperative pain following orthopaedic surgical procedures is crucial in combating the ongoing opioid abuse crisis. The endocannabinoid system may represent a viable alternative target for addressing orthopaedic postoperative pain.

Modulation of Endocannabinoid Tone in Osteoblastic Differentiation of MC3T3-E1 Cells and in Mouse Bone Tissue over Time

Bone is a highly complex and metabolically active tissue undergoing a continuous remodeling process, which endures throughout life. A complex cell-signaling system that plays role in regulating different physiological processes, including bone remodeling, is the endocannabinoid system (ECS). Bone mass expresses CB1 and CB2 cannabinoid receptors and enzymatic machinery responsible for the metabolism of their endogenous ligands, endocannabinoids (AEA and 2-AG). Exogenous AEA is reported to increase the early phase of human osteoblast differentiation in vitro. However, regarding this cell context little is known about how endocannabinoids and endocannabinoid-related N-acylethanolamines like PEA and OEA are modulated, in vitro, during cell differentiation and, in vivo, over time up to adulthood. Here we characterized the endocannabinoid tone during the different phases of the osteoblast differentiation process in MC3T3-E1 cells, and we measured endocannabinoid levels in mouse femurs at life cycle stages characterized by highly active bone growth (i.e., of juvenile, young adult, and mature adult bone). Endocannabinoid tone was significantly altered during osteoblast differentiation, with substantial OEA increment, decline in 2-AG and AEA, and consistent modulation of their metabolic enzymes in maturing and mineralized MC3T3-E1 cells. Similarly, in femurs, we found substantial, age-related, decline in 2-AG, OEA, and PEA. These findings can expand existing knowledge underlying physiological bone cell function and contribute to therapeutic strategies for preventing bone-related metabolic changes accruing through lifespan.

The impact of E-cigarette vaping and vapour constituents on bone health

BACKGROUND

In contrast to cigarettes, electronic cigarette use (E-cigarettes) has grown substantially over the last decade. This is due to their promotion as both a safer alternative to cigarettes and as an aide to stop smoking. Critically, upon E-cigarette use, the user may be exposed to high doses of nicotine in addition to other compounds including flavouring chemicals, metal particulates and carbonyl compounds, particularly in highly vascularised tissues such as bone. However, there has been limited investigation into the impact of E-cigarette usage on bone physiology, particularly over extended time periods and there are no clinical recommendations regarding E-cigarette usage in relation to orthopaedic surgery. This literature review draws together data from studies that have investigated the impact of E-cigarette vapour and its major constituents on bone, detailing the models utilised and the relevant mechanistic and functional results.

MAIN BODY

Currently there is a lack of studies both in vivo and in vitro that have utilised E-cigarette vapour, necessary to account for changes in chemical composition of E-cigarette liquids upon vaping. There is however evidence that human bone and bone cells express nicotine receptors and exposure of both osteoblasts and osteoclasts to nicotine, in high concentrations may reduce their viability and impair function. Similarly, it appears that aldehydes and flavouring chemicals may also negatively impact osteoblast viability and their ability to form bone. However, such functional findings are predominantly the result of studies utilising bone cell lines such as MG-63 or Saos-2 cells, with limited use of human osteoblasts or osteoclasts. Additionally, there is limited consideration for a possible impact on mesenchymal stem cells, which can also play an import role in bone repair.

CONCLUSION

Understanding the function and mechanism of action of the various components of E-cigarette vapour in mediating human bone cell function, in addition to long term studies to determine the potential harm of chronic E-cigarette use on human bone will be important to inform users of potential risks, particularly regarding bone healing following orthopaedic surgery and injury.

Peptide targeting of lysophosphatidylinositol-sensing GPR55 for osteoclastogenesis tuning

BACKGROUND

The G-protein-coupled receptor GPR55 has been implicated in multiple biological activities, which has fuelled interest in its functional targeting. Its controversial pharmacology and often species-dependent regulation have impacted upon the potential translation of preclinical data involving GPR55.

RESULTS

With the aim to identify novel GPR55 regulators, we have investigated lysophosphatidylinositol (LPI)-induced GPR55-mediated signal transduction. The expression system for wild-type and mutated GPR55 was HeLa cells silenced for their endogenous receptor by stable expression of a short-hairpin RNA specific for GPR55 5'-UTR, which allowed definition of the requirement of GPR55 Lys⁸⁰ for LPI-induced MAPK activation and receptor internalisation. In RAW264.7 macrophages, GPR55 pathways were investigated by Gpr55 silencing using small-interfering RNAs, which demonstrated that LPI increased intracellular Ca²⁺ levels and induced actin filopodium formation through GPR55 activation. Furthermore, the LPI/GPR55 axis was shown to have an active role in osteoclastogenesis of precursor RAW264.7 cells induced by 'receptor-activator of nuclear factor kappa-β ligand' (RANKL). Indeed, this differentiation into mature osteoclasts was associated with a 14-fold increase in Gpr55 mRNA levels. Moreover, GPR55 silencing and antagonism impaired RANKL-induced transcription of the osteoclastogenesis markers: 'nuclear factor of activated T-cells, cytoplasmic 1', matrix metalloproteinase-9, cathepsin-K, tartrate-resistant acid phosphatase, and the calcitonin receptor, as evaluated by real-time PCR. Phage display was previously used to identify peptides that bind to GPR55. Here, the GPR55-specific peptide-P1 strongly inhibited osteoclast maturation of RAW264.7 macrophages, confirming its activity as a blocker of GPR55-mediated functions. Although osteoclast syncytium formation was not affected by pharmacological regulation of GPR55, osteoclast activity was dependent on GPR55 signalling, as shown with resorption assays on bone slices, where LPI stimulated and GPR55 antagonists inhibited bone erosion.

CONCLUSIONS

Our data indicate that GPR55 represents a target for development of novel therapeutic approaches for treatment of pathological conditions caused by osteoclast-exacerbated bone degradation, such as in osteoporosis or during establishment of bone metastases. Video abstract.

Repurposing Cannabidiol as a Potential Drug Candidate for Anti-Tumor Therapies

In recent years, evidence has accumulated that cannabinoids-especially the non-psychoactive compound, cannabidiol (CBD)-possess promising medical and pharmacological activities that might qualify them as potential anti-tumor drugs. This review is based on multiple studies summarizing different mechanisms for how CBD can target tumor cells including cannabinoid receptors or other constituents of the endocannabinoid system, and their complex activation of biological systems that results in the inhibition of tumor growth. CBD also participates in anti-inflammatory activities which are related to tumor progression, as demonstrated in preclinical models. Although the numbers of clinical trials and tested tumor entities are limited, there is clear evidence that CBD has anti-tumor efficacy and is well tolerated in human cancer patients. In summary, it appears that CBD has potential as a neoadjuvant and/or adjuvant drug in therapy for cancer.

The cannabinoid system and microglia in health and disease

Recent years have yielded significant advances in our understanding of microglia, the immune cells of the central nervous system (CNS). Microglia are key players in CNS development, immune surveillance, and the maintenance of proper neuronal function throughout life. In the healthy brain, homeostatic microglia have a unique molecular signature. In neurological diseases, microglia become activated and adopt distinct transcriptomic signatures, including disease-associated microglia (DAM) implicated in neurodegenerative disorders. Homeostatic microglia synthesise the endogenous cannabinoids 2-arachidonoylglycerol and anandamide and express the cannabinoid receptors CB1 and CB2 at constitutively low levels. Upon activation, microglia significantly increase their synthesis of endocannabinoids and upregulate their expression of CB2 receptors, which promote a protective microglial phenotype by enhancing their production of neuroprotective factors and reducing their production of pro-inflammatory factors. Here, we summarise the effects of the microglial cannabinoid system in the CNS demyelinating disease multiple sclerosis, the neurodegenerative diseases Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis, chronic inflammatory and neuropathic pain, and psychiatric disorders including depression, anxiety and schizophrenia. We discuss the therapeutic potential of cannabinoids in regulating microglial activity and highlight the need to further investigate their specific microglia-dependent immunomodulatory effects.

Effects of a Novel GPR55 Antagonist on the Arachidonic Acid Cascade in LPS-Activated Primary Microglial Cells

Neuroinflammation is a crucial process to maintain homeostasis in the central nervous system (CNS). However, chronic neuroinflammation is detrimental, and it is described in the pathogenesis of CNS disorders, including Alzheimer’s disease (AD) and depression. This process is characterized by the activation of immune cells, mainly microglia. The role of the orphan G-protein-coupled receptor 55 (GPR55) in inflammation has been reported in different models. However, its role in neuroinflammation in respect to the arachidonic acid (AA) cascade in activated microglia is still lacking of comprehension. Therefore, we synthesized a novel GPR55 antagonist (KIT 10, 0.1–25 µM) and tested its effects on the AA cascade in lipopolysaccharide (LPS, 10 ng / mL)-treated primary rat microglia using Western blot and EIAs. We show here that KIT 10 potently prevented the release of prostaglandin E₂ (PGE₂), reduced microsomal PGE₂ synthase (mPGES-1) and cyclooxygenase-2 (COX-2) synthesis, and inhibited the phosphorylation of Ikappa B-alpha (IκB-α), a crucial upstream step of the inflammation-related nuclear factor-kappaB (NF-κB) signaling pathway. However, no effects were observed on COX-1 and -2 activities and mitogen-activated kinases (MAPK). In summary, the novel GPR55 receptor antagonist KIT 10 reduces neuroinflammatory parameters in microglia by inhibiting the COX-2/PGE₂ pathway. Further experiments are necessary to better elucidate its effects and mechanisms. Nevertheless, the modulation of inflammation by GPR55 might be a new therapeutic option to treat CNS disorders with a neuroinflammatory background such as AD or depression.

The Immunopathology of COVID-19 and the Cannabis Paradigm

Coronavirus disease-19 caused by the novel RNA betacoronavirus SARS-CoV2 has first emerged in Wuhan, China in December 2019, and since then developed into a worldwide pandemic with >99 million people afflicted and >2.1 million fatal outcomes as of 24th January 2021. SARS-CoV2 targets the lower respiratory tract system leading to pneumonia with fever, cough, and dyspnea. Most patients develop only mild symptoms. However, a certain percentage develop severe symptoms with dyspnea, hypoxia, and lung involvement which can further progress to a critical stage where respiratory support due to respiratory failure is required. Most of the COVID-19 symptoms are related to hyperinflammation as seen in cytokine release syndrome and it is believed that fatalities are due to a COVID-19 related cytokine storm. Treatments with anti-inflammatory or anti-viral drugs are still in clinical trials or could not reduce mortality. This makes it necessary to develop novel anti-inflammatory therapies. Recently, the therapeutic potential of phytocannabinoids, the unique active compounds of the cannabis plant, has been discovered in the area of immunology. Phytocannabinoids are a group of terpenophenolic compounds which biological functions are conveyed by their interactions with the endocannabinoid system in humans. Here, we explore the anti-inflammatory function of cannabinoids in relation to inflammatory events that happen during severe COVID-19 disease, and how cannabinoids might help to prevent the progression from mild to severe disease.

Synthetic and Natural Derivatives of Cannabidiol

The non-psychoactive component of Cannabis Sativa, cannabidiol (CBD), has centered the attention of a large body of research in the last years. Recent clinical trials have led to the FDA approval of CBD for the treatment of children with drug-resistant epilepsy. Even though it is not yet in clinical phases, its use in sleep-wake pathological alterations has been widely demonstrated.Despite the outstanding current knowledge on CBD therapeutic effects in numerous in vitro and in vivo disease models, diverse questions still arise from its molecular pharmacology. CBD has been shown to modulate a wide variety of targets including the cannabinoid receptors, orphan GPCRs such as GPR55 and GPR18, serotonin, adenosine, and opioid receptors as well as ligand-gated ion channels among others. Its pharmacology is rather puzzling and needs to be further explored in the disease context.Also, the metabolism and interactions of this phytocannabinoid with other commercialized drugs need to be further considered to elucidate its clinical potential for the treatment of specific pathologies.Besides CBD, natural and synthetic derivatives of this chemotype have also been reported exhibiting diverse functional profiles and providing a deeper understanding of the potential of this scaffold.In this chapter, we analyze the knowledge gained so far on CBD and its analogs specially focusing on its molecular targets and metabolic implications. Phytogenic and synthetic CBD derivatives may provide novel approaches to improve the therapeutic prospects offered by this promising chemotype.

Diversity of molecular targets and signaling pathways for CBD

Cannabidiol (CBD) is the second most abundant component of the Cannabis plant and is known to have effects distinct from Δ9 -tetrahydrocannabinol (THC). Many studies that examined the behavioral effects of CBD concluded that it lacks the psychotomimetic effects attributed to THC. However, CBD was shown to have a broad spectrum of effects on several conditions such as anxiety, inflammation, neuropathic pain, and epilepsy. It is currently thought that CBD engages different targets and hence CBD's effects are thought to be due to multiple molecular mechanisms of action. A well-accepted set of targets include GPCRs and ion channels, with the serotonin 5-HT1A receptor and the transient receptor potential cation channel TRPV1 channel being the two main targets. CBD has also been thought to target G protein-coupled receptors (GPCRs) such as cannabinoid and opioid receptors. Other studies have suggested a role for additional GPCRs and ion channels as targets of CBD. Currently, the clinical efficacy of CBD is not completely understood. Evidence derived from randomized clinical trials, in vitro and in vivo models and real-world observations support the use of CBD as a drug treatment option for anxiety, neuropathy, and many other conditions. Hence an understanding of the current status of the field as it relates to the targets for CBD is of great interest so, in this review, we include findings from recent studies that highlight these main targets.

Role of Metabolism in Bone Development and Homeostasis

Carbohydrates, fats, and proteins are the underlying energy sources for animals and are catabolized through specific biochemical cascades involving numerous enzymes. The catabolites and metabolites in these metabolic pathways are crucial for many cellular functions; therefore, an imbalance and/or dysregulation of these pathways causes cellular dysfunction, resulting in various metabolic diseases. Bone, a highly mineralized organ that serves as a skeleton of the body, undergoes continuous active turnover, which is required for the maintenance of healthy bony components through the deposition and resorption of bone matrix and minerals. This highly coordinated event is regulated throughout life by bone cells such as osteoblasts, osteoclasts, and osteocytes, and requires synchronized activities from different metabolic pathways. Here, we aim to provide a comprehensive review of the cellular metabolism involved in bone development and homeostasis, as revealed by mouse genetic studies.

In vitro and in vivo pharmacological activity of minor cannabinoids isolated from Cannabis sativa

The Cannabis sativa plant contains more than 120 cannabinoids. With the exceptions of ∆⁹-tetrahydrocannabinol (∆⁹-THC) and cannabidiol (CBD), comparatively little is known about the pharmacology of the less-abundant plant-derived (phyto) cannabinoids. The best-studied transducers of cannabinoid-dependent effects are type 1 and type 2 cannabinoid receptors (CB1R, CB2R). Partial agonism of CB1R by ∆⁹-THC is known to bring about the 'high' associated with Cannabis use, as well as the pain-, appetite-, and anxiety-modulating effects that are potentially therapeutic. CB2R activation by certain cannabinoids has been associated with anti-inflammatory activities. We assessed the activity of 8 phytocannabinoids at human CB1R, and CB2R in Chinese hamster ovary (CHO) cells stably expressing these receptors and in C57BL/6 mice in an attempt to better understand their pharmacodynamics. Specifically, ∆⁹-THC, ∆⁹-tetrahydrocannabinolic acid (∆⁹-THCa), ∆⁹-tetrahydrocannabivarin (THCV), CBD, cannabidiolic acid (CBDa), cannabidivarin (CBDV), cannabigerol (CBG), and cannabichromene (CBC) were evaluated. Compounds were assessed for their affinity to receptors, ability to inhibit cAMP accumulation, βarrestin2 recruitment, receptor selectivity, and ligand bias in cell culture; and cataleptic, hypothermic, anti-nociceptive, hypolocomotive, and anxiolytic effects in mice. Our data reveal partial agonist activity for many phytocannabinoids tested at CB1R and/or CB2R, as well as in vivo responses often associated with activation of CB1R. These data build on the growing body of literature showing cannabinoid receptor-dependent pharmacology for these less-abundant phytocannabinoids and are critical in understanding the complex and interactive pharmacology of Cannabis-derived molecules.

Cannabidiol: A Potential New Alternative for the Treatment of Anxiety, Depression, and Psychotic Disorders

The potential therapeutic use of some Cannabis sativa plant compounds has been attracting great interest, especially for managing neuropsychiatric disorders due to the relative lack of efficacy of the current treatments. Numerous studies have been carried out using the main phytocannabinoids, tetrahydrocannabinol (THC) and cannabidiol (CBD). CBD displays an interesting pharmacological profile without the potential for becoming a drug of abuse, unlike THC. In this review, we focused on the anxiolytic, antidepressant, and antipsychotic effects of CBD found in animal and human studies. In rodents, results suggest that the effects of CBD depend on the dose, the strain, the administration time course (acute vs. chronic), and the route of administration. In addition, certain key targets have been related with these CBD pharmacological actions, including cannabinoid receptors (CB₁r and CB₂r), 5-HT_1A receptor and neurogenesis factors. Preliminary clinical trials also support the efficacy of CBD as an anxiolytic, antipsychotic, and antidepressant, and more importantly, a positive risk-benefit profile. These promising results support the development of large-scale studies to further evaluate CBD as a potential new drug for the treatment of these psychiatric disorders.

High fat-fed GPR55 null mice display impaired glucose tolerance without concomitant changes in energy balance or insulin sensitivity but are less responsive to the effects of the cannabinoids rimonabant or Δ(9)-tetrahydrocannabivarin on weight gain

Background

The insulin-sensitizing phytocannabinoid, Δ(9)-tetrahydrocannabivarin (THCV) can signal partly via G-protein coupled receptor-55 (GPR55 behaving as either an agonist or an antagonist depending on the assay). The cannabinoid receptor type 1 (CB1R) inverse agonist rimonabant is also a GPR55 agonist under some conditions. Previous studies have shown varied effects of deletion of GPR55 on energy balance and glucose homeostasis in mice. The contribution of signalling via GPR55 to the metabolic effects of THCV and rimonabant has been little studied.

Methods

In a preliminary experiment, energy balance and glucose homeostasis were studied in GPR55 knockout and wild-type mice fed on both standard chow (to 20 weeks of age) and high fat diets (from 6 to 15 weeks of age). In the main experiment, all mice were fed on the high fat diet (from 6 to 14 weeks of age). In addition to replicating the preliminary experiment, the effects of once daily administration of THCV (15 mg kg⁻¹ po) and rimonabant (10 mg kg⁻¹ po) were compared in the two genotypes.

Results

There was no effect of genotype on absolute body weight or weight gain, body composition measured by either dual-energy X-ray absorptiometry or Nuclear Magnetic Resonance (NMR), fat pad weights, food intake, energy expenditure, locomotor activity, glucose tolerance or insulin tolerance in mice fed on chow. When the mice were fed a high fat diet, there was again no effect of genotype on these various aspects of energy balance. However, in both experiments, glucose tolerance was worse in the knockout than the wild-type mice. Genotype did not affect insulin tolerance in either experiment. Weight loss in rimonabant- and THCV-treated mice was lower in knockout than in wild-type mice, but surprisingly there was no detectable effect of genotype on the effects of the drugs on any aspect of glucose homeostasis after taking into account the effect of genotype in vehicle-treated mice.

Conclusions

Our two experiments differ from those reported by others in finding impaired glucose tolerance in GPR55 knockout mice in the absence of any effect on body weight, body composition, locomotor activity or energy expenditure. Nor could we detect any effect of genotype on insulin tolerance, so the possibility that GPR55 regulates glucose-stimulated insulin secretion merits further investigation. By contrast with the genotype effect in untreated mice, we found that THCV and rimonabant reduced weight gain, and this effect was in part mediated by GPR55.

Recent advances in roles of G-protein coupled receptors in intestinal intraepithelial lymphocytes

Intestinal intraepithelial lymphocytes (IELs) potentially provide the first line of immune defense against enteric pathogens. In addition, there is growing evidence supporting the involvement of IELs in the pathogenesis of gut disorders such as inflammatory bowel diseases. Various kinds of molecules are involved in the dynamics of IELs, such as homing to the intestinal epithelium and retention in the intestinal mucosa. G protein-coupled receptors (GPCRs) comprise the largest family of cell surface receptors and regulate many biological responses. Although some GPCRs, like CCR9, have been implicated to have roles in IEL homing, little is still known regarding the functional roles of GPCRs in IEL biology. In this review, we provide a concise overview of recent advances in the roles of novel GPCRs like GPR55 and GPR18 in the dynamics of IELs.

Cannabinoid Use in Musculoskeletal Illness: a Review of the Current Evidence

PURPOSE OF REVIEW

The use of cannabinoids has increased since legalization of recreational and medical use in the USA. It is likely that many orthopaedic patients consume cannabinoid products during the traumatic or perioperative period. The purpose of this study was to investigate the pre-clinical data evaluating the mechanism of action of cannabidiol (CBD) and Δ9-Tetrahydrocannabinol (Δ9-THC) and to evaluate the current clinical data on the use of cannabinoids in musculoskeletal illness.

RECENT FINDINGS

Recent pre-clinical studies have demonstrated that cannabinoid use and the endocannabinoid system (ECS) has an important role in bone healing and bone homeostasis. There is data that suggests that the use of cannabidiol (CBD) may increase bone healing, whereas the use of Δ9-Tetrahydrocannabinol (Δ9-THC), the major psychoactive ingredient in marijuana, likely inhibits bone metabolism and repair. The clinical implications and consumption of marijuana by orthopaedic patients have not been thoroughly evaluated. Studies have demonstrated concern for negative cardiovascular and psychiatric effects caused by marijuana use, but have not yet elucidated outcomes in the orthopaedic literature. With the recent increase in advertising of CBD products and legalization of marijuana, it is likely that many orthopaedic patients are consuming cannabinoid products. The clinical implications and consumption of these products are unclear. We need more robust and well-designed clinical studies prior to making further recommendations to our patients on the consumption of these products.

Identification of human glycerophosphodiesterase 3 as an ecto phospholipase C that converts the G protein-coupled receptor 55 agonist lysophosphatidylinositol to bioactive monoacylglycerols in cultured mammalian cells

A family of glycerol-based lysolipid mediators comprises lysophosphatidic acid as a representative phospholipidic member but also a monoacylglycerol as a non-phosphorus-containing member. These critical lysolipid mediators are known to be produced from different lysophospholipids by actions of lysophospholipases C and D in mammals. Some members of the glycerophosphodiesterase (GDE) family have attracted recent attention due to their phospholipid-metabolizing activity. In this study, we found selective depletion of lysophosphatidylinositol among lysophospholipids in the culture medium of COS-7 cells transfected with a vector containing glycerophosphodiester phosphodiesterase 2 (GDPD2, GDE3). Thin-layer chromatography and liquid chromatography-tandem mass spectrometry of lipids extracted from GDE3-transfected COS-7 cells exposed to fluorescent analogs of phosphatidylinositol (PI) revealed that GDE3 acted as an ecto-type lysophospholipase C preferring endogenous lysophosphatidylinositol and PI having a long-chain acyl and a short-chain acyl group rather than endogenous PI and its fluorescent analog having two long chain acyl groups. In MC3T3-E1 cells cultured with an osteogenic or mitogenic medium, mRNA expression of GDE3 was increased by culturing in 10% fetal bovine serum for several days, concomitant with increased activity of ecto-lysophospholipase C, converting arachidonoyl-lysophosphatidylinositol, a physiological agonist of G protein-coupled receptor 55, to arachidonoylglycerol, a physiological agonist of cannabinoid receptors 1 and 2. We suggest that GDE3 acts as an ecto-lysophospholipase C, by switching signaling from lysophosphatidylinositol to that from arachidonoylglycerol in an opposite direction in mouse bone remodeling.

The effect of O-1602, a GPR55 agonist, on the cyclophosphamide-induced rat hemorrhagic cystitis

The goal of our study was to determine whether GPR55 agonists, O-1602, could reverse the cyclophosphamide (CYP)-induced changes in cystometric and inflammatory parameters, indicative of the development of bladder inflammation and overactivity. If confirmed, the stimulation of novel cannabinoid receptor - GPR55, could be a reasonable strategy as a treatment of CYP-induced haemorrhagic cystitis. The experiments were conducted in female Wistar rats. Based on the methodology of our published studies on CYP-induced heamorrhagic cystitis we performed experiments after administration of CYP, O-1602 or CYP plus O-1602. These included surgical procedures, conscious cystometry, measurements of bladder oedema and urothelium thickness using the Evans Blue dye leakage technique, as well as biochemical analyses with particular ELISA kits. O-1602 ameliorated the symptoms of CYP-induced detrusor overactivity leading to an increase in voided volume (0.59 vs. 0.93 ml), and lowering the detrusor overactivity index (703 vs. 115 cm H2O/ml). Intravenous administration of the GPR55 agonist to animals that received CYP significantly decreased Evans Blue extravasation and increased urothelium thickness. O-1602 also reversed the pro-inflammatory activity of CYP by restoring concentrations of brain-derived neurotrophic factor, nerve growth factor, calcitonin gene related peptide, interleukin 1-beta, interleukin-6, tumour necrosis factor alpha, malondialdehyde, nitrotyrosine, occludin, and organic cation transporter 3. GPR55 agonist, O-1602, represents a novel class of uroprotective agents, targeting the inflammatory basis of cystitis. To our knowledge, this is the first paper proposing O-1602 agent, as a candidate for future studies in the treatment of CYP-induced cystitis.

Oleoylethanolamide Exhibits GPR119-Dependent Inhibition of Osteoclast Function and GPR119-Independent Promotion of Osteoclast Apoptosis

Oleoylethanolamide (OEA), a bioactive lipid in bone, is known as an endogenous ligand for G protein-coupled receptor 119 (GPR119). Here, we explored the effects of OEA on osteoclast differentiation, function, and survival. While OEA inhibits osteoclast resorptive function by disrupting actin cytoskeleton, it does not affect receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation. OEA attenuates osteoclast spreading, blocks actin ring formation, and eventually impairs bone resorption. Mechanistically, OEA inhibits Rac activation in response to macrophage colony-stimulating factor (M-CSF), but not RANKL. Furthermore, the OEA-mediated cytoskeletal disorganization is abrogated by GPR119 knockdown using small hairpin RNA (shRNA), indicating that GPR119 is pivotal for osteoclast cytoskeletal organization. In addition, OEA induces apoptosis in both control and GPR119 shRNAtransduced osteoclasts, suggesting that GPR119 is not required for osteoclast apoptosis. Collectively, our findings reveal that OEA has inhibitory effects on osteoclast function and survival of mature osteoclasts via GPR119-dependent and GPR119-independent pathways, respectively.

Neurological Regulation of the Bone Marrow Niche

The bone marrow (BM) hematopoietic niche is the microenvironment where in the adult hematopoietic stem and progenitor cells (HSPCs) are maintained and regulated. This regulation is tightly controlled through direct cell-cell interactions with mesenchymal stromal stem (MSCs) and reticular cells, adipocytes, osteoblasts and endothelial cells, through binding to extracellular matrix molecules and through signaling by cytokines and hematopoietic growth factors. These interactions provide a healthy environment and secure the maintenance of the HSPC pool, their proliferation, differentiation and migration. Recent studies have shown that innervation of the BM and interactions with the peripheral sympathetic neural system are important for maintenance of the hematopoietic niche, through direct interactions with HSCPs or via interactions with other cells of the HSPC microenvironment. Signaling through adrenergic receptors (ARs), opioid receptors (ORs), endocannabinoid receptors (CRs) on HSPCs and MSCs has been shown to play an important role in HSPC homeostasis and mobilization. In addition, a wide range of neuropeptides and neurotransmitters, such as Neuropeptide Y (NPY), Substance P (SP) and Tachykinins, as well as neurotrophins and neuropoietic growth factors have been shown to be involved in regulation of the hematopoietic niche. Here, a comprehensive overview is given of their role and interactions with important cells in the hematopoietic niche, including HSPCs and MSCs, and their effect on HSPC maintenance, regulation and mobilization.

A Novel, Tumor-Induced Osteoclastogenesis Pathway Insensitive to Denosumab but Interfered by Cannabidiol

Bone metabolism is strictly regulated, and impaired regulation caused by hormonal imbalances induces systemic bone loss. Local bone loss caused by tumor invasion into bone is suggested to be induced by the generation of cytokines, which affect bone metabolism, by tumor cells. The major cause of systemic and local bone losses is excess bone resorption by osteoclasts, which differentiate from macrophages by receptor activator of nuclear factor kappa-B ligand (RANKL) or tumor necrosis factor-alpha (TNF-α). We previously found a novel pathway for tumor-induced osteoclastogenesis targeting osteoclast precursor cells (OPCs). Tumor-induced osteoclastogenesis was resistant to RANKL and TNF-α inhibitors. In the present study, we confirmed that exosomes derived from oral squamous cell carcinoma (OSCC) cells induced osteoclasts from OPCs. We also showed that the depletion of exosomes from culture supernatants of OSCC cells partially interfered with osteoclastogenesis, and cannabidiol, an innoxious cannabinoid without psychotropic effects, almost completely suppressed tumor-induced osteoclastogenesis. Osteoclastogenesis and its interference by cannabidiol were independent of the expression of nuclear factor of T cell c1 (NFATc1). These results show that osteoclastogenesis induced by OSCC cells targeting OPCs is a novel osteoclastogenic pathway independent of NFATc1 expression that is partially caused by tumor-derived exosomes and suppressed by cannabidiol.

The effects of neurectomy and hibernation on bone properties and the endocannabinoid system in marmots (Marmota flaviventris)

Hibernators have adapted a physiological mechanism allowing them to undergo long periods of inactivity without experiencing bone loss. However, the biological mechanisms that prevent bone loss are unknown. Previous studies found meaningful changes, between active and hibernating marmots, in the endocannabinoid system of many tissues, including bone. Cannabinoid receptors (CB1 and CB2) have divergent localization in bone. CB1 is predominately found on sympathetic nerve terminals, while CB2 is more abundant on bone cells and their progenitors. This study aimed to determine the contribution of innervation on endocannabinoid regulation of bone properties in hibernating (during torpor) and non-hibernating yellow-bellied marmots. Neurectomy, a model for disuse osteoporosis, was performed unilaterally in both hibernating and active marmots. Endocannabinoid concentrations were measured in bone marrow, cortical, and trabecular regions from fourth metatarsals of both hindlimbs using microflow chromatography-tandem quadrupole mass spectrometry. Trabecular bone architectural properties of fifth metatarsals were evaluated using micro-computed tomography. There were ligand-specific increases with neurectomy in active, but not hibernating, marmots. Trabecular bone architectural properties were not affected by neurectomy during hibernation, but did show some minor negative changes in active marmots. These findings suggest protection from bone loss in hibernating rodents is peripherally rather than centrally regulated. Furthermore, findings suggest even active marmots with normal metabolism are partially protected from disuse induced bone loss compared to laboratory rodents. Understanding the mechanism hibernators use to maintain bone density may guide development for novel bone loss prevention therapies.

Cannabidiol-from Plant to Human Body: A Promising Bioactive Molecule with Multi-Target Effects in Cancer

Cannabis sativa L. is a plant long used for its textile fibers, seed oil, and oleoresin with medicinal and psychoactive properties. It is the main source of phytocannabinoids, with over 100 compounds detected so far. In recent years, a lot of attention has been given to the main phytochemicals present in Cannabis sativa L., namely, cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC). Compared to THC, CBD has non-psychoactive effects, an advantage for clinical applications of anti-tumor benefits. The review is designed to provide an update regarding the multi-target effects of CBD in different types of cancer. The main focus is on the latest in vitro and in vivo studies that present data regarding the anti-proliferative, pro-apoptotic, cytotoxic, anti-invasive, anti-antiangiogenic, anti-inflammatory, and immunomodulatory properties of CBD together with their mechanisms of action. The latest clinical evidence of the anticancer effects of CBD is also outlined. Moreover, the main aspects of the pharmacological and toxicological profiles are given.

A role for G protein-coupled receptor 137b in bone remodeling in mouse and zebrafish

G protein-coupled receptor 137b (GPR137b) is an orphan seven-pass transmembrane receptor of unknown function. In mouse, Gpr137b is highly expressed in osteoclasts in vivo and is upregulated during in vitro differentiation. To elucidate the role that GPR137b plays in osteoclasts, we tested the effect of GPR137b deficiency on osteoclast maturation and resorbing activity. We used CRISPR/Cas9 gene editing in mouse-derived ER-Hoxb8 immortalized myeloid progenitors to generate GPR137b-deficient osteoclast precursors. Decreasing Gpr137b in these precursors led to increased osteoclast differentiation and bone resorption activity. To explore the role of GPR137b during skeletal development, we generated zebrafish deficient for the ortholog gpr137ba. Gpr137ba-deficient zebrafish are viable and fertile and do not display overt morphological defects as adults. However, analysis of osteoclast function in gpr137ba^-/- mutants demonstrated increased bone resorption. Micro-computed tomography evaluation of vertebral bone mass and morphology demonstrated that gpr137ba-deficiency altered the angle of the neural arch, a skeletal site with high osteoclast activity. Vital staining of gpr137ba^-/- fish with calcein and alizarin red indicated that bone formation in the mutants is also increased, suggesting high bone turnover. These results identify GPR137b as a conserved negative regulator of osteoclast activity essential for normal resorption and patterning of the skeleton. Further, these data suggest that coordination of osteoclast and osteoblast activity is a conserved process among vertebrates and may have similar regulation.

Bones and Joints: The Effects of Cannabinoids on the Skeleton

CONTEXT

The endocannabinoid system uses tissue-specific lipid ligands and G protein‒coupled transmembrane receptors to regulate neurologic, metabolic, and immune responses. Recent studies demonstrate that the endocannabinoid system influences bone metabolism. With the increasing use of endocannabinoid mimetics (e.g., tetrahydrocannabinol and cannabidiol), the involvement of endocannabinoids in bone growth and remodeling has become clinically relevant.

EVIDENCE ACQUISITION

This literature review is based on a search of PubMed and Google Scholar databases as of June 2019 for all English-language publications relating to cannabinoids and bone. We evaluated retrieved articles for relevance, experimental design, data acquisition, statistical analysis, and conclusions.

EVIDENCE SYNTHESIS

Preclinical studies establish a role for endocannabinoids in bone metabolism. These studies yield complex and often contradictory results attributed to differences in the specific experimental model examined. Studies using human cells or subjects are limited.

CONCLUSIONS

In vitro and animal models document that endocannabinoids are involved in bone biology. The relevance of these observations to humans is not clear. The increasing long-term use of medical and recreational cannabis underscores the need to better understand the role of endocannabinoids in human bone metabolism. Moreover, it is important to evaluate the role of endocannabinoids as a therapeutic target to prevent and treat disorders associated with bone loss.

Development and Genome Sequencing of a Laboratory-Inbred Miniature Pig Facilitates Study of Human Diabetic Disease

Pig has been proved to be a valuable large animal model used for research on diabetic disease. However, their translational value is limited given their distinct anatomy and physiology. For the last 30 years, we have been developing a laboratory Asian miniature pig inbred line (Bama miniature pig [BM]) from the primitive Bama xiang pig via long-term selective inbreeding. Here, we assembled a BM reference genome at full chromosome-scale resolution with a total length of 2.49 Gb. Comparative and evolutionary genomic analyses identified numerous variations between the BM and commercial pig (Duroc), particularly those in the genetic loci associated with the features advantageous to diabetes studies. Resequencing analyses revealed many differentiated gene loci associated with inbreeding and other selective forces. These together with transcriptome analyses of diabetic pig models provide a comprehensive genetic basis for resistance to diabetogenic environment, especially related to energy metabolism.

Cannabidiol Treatment Might Promote Resilience to Cocaine and Methamphetamine Use Disorders: A Review of Possible Mechanisms

Currently, there are no approved pharmacotherapies for addiction to cocaine and other psychostimulant drugs. Several studies have proposed that cannabidiol (CBD) could be a promising treatment for substance use disorders. In the present work, the authors describe the scarce preclinical and human research about the actions of CBD on the effects of stimulant drugs, mainly cocaine and methamphetamine (METH). Additionally, the possible mechanisms underlying the therapeutic potential of CBD on stimulant use disorders are reviewed. CBD has reversed toxicity and seizures induced by cocaine, behavioural sensitization induced by amphetamines, motivation to self-administer cocaine and METH, context- and stress-induced reinstatement of cocaine and priming-induced reinstatement of METH seeking behaviours. CBD also potentiated the extinction of cocaine- and amphetamine-induced conditioned place preference (CPP), impaired the reconsolidation of cocaine CPP and prevented priming-induced reinstatement of METH CPP. Observational studies suggest that CBD may reduce problems related with crack-cocaine addiction, such as withdrawal symptoms, craving, impulsivity and paranoia (Fischer et al., 2015). The potential mechanisms involved in the protective effects of CBD on addiction to psychostimulant drugs include the prevention of drug-induced neuroadaptations (neurotransmitter and intracellular signalling pathways changes), the erasure of aberrant drug-memories, the reversion of cognitive deficits induced by psychostimulant drugs and the alleviation of mental disorders comorbid with psychostimulant abuse. Further, preclinical studies and future clinical trials are necessary to fully evaluate the potential of CBD as an intervention for cocaine and methamphetamine addictive disorders.

The role of GPCRs in bone diseases and dysfunctions

The superfamily of G protein-coupled receptors (GPCRs) contains immense structural and functional diversity and mediates a myriad of biological processes upon activation by various extracellular signals. Critical roles of GPCRs have been established in bone development, remodeling, and disease. Multiple human GPCR mutations impair bone development or metabolism, resulting in osteopathologies. Here we summarize the disease phenotypes and dysfunctions caused by GPCR gene mutations in humans as well as by deletion in animals. To date, 92 receptors (5 glutamate family, 67 rhodopsin family, 5 adhesion, 4 frizzled/taste2 family, 5 secretin family, and 6 other 7TM receptors) have been associated with bone diseases and dysfunctions (36 in humans and 72 in animals). By analyzing data from these 92 GPCRs, we found that mutation or deletion of different individual GPCRs could induce similar bone diseases or dysfunctions, and the same individual GPCR mutation or deletion could induce different bone diseases or dysfunctions in different populations or animal models. Data from human diseases or dysfunctions identified 19 genes whose mutation was associated with human BMD: 9 genes each for human height and osteoporosis; 4 genes each for human osteoarthritis (OA) and fracture risk; and 2 genes each for adolescent idiopathic scoliosis (AIS), periodontitis, osteosarcoma growth, and tooth development. Reports from gene knockout animals found 40 GPCRs whose deficiency reduced bone mass, while deficiency of 22 GPCRs increased bone mass and BMD; deficiency of 8 GPCRs reduced body length, while 5 mice had reduced femur size upon GPCR deletion. Furthermore, deficiency in 6 GPCRs induced osteoporosis; 4 induced osteoarthritis; 3 delayed fracture healing; 3 reduced arthritis severity; and reduced bone strength, increased bone strength, and increased cortical thickness were each observed in 2 GPCR-deficiency models. The ever-expanding number of GPCR mutation-associated diseases warrants accelerated molecular analysis, population studies, and investigation of phenotype correlation with SNPs to elucidate GPCR function in human diseases.

l-α-Lysophosphatidylinositol (LPI) aggravates myocardial ischemia/reperfusion injury via a GPR55/ROCK-dependent pathway

The phospholipid l-α-lysophosphatidylinositol (LPI), an endogenous ligand for GPR55, is elevated in patients with acute coronary syndrome, and a GPR55 antagonist cannabidiol (CBD) reduces experimental ischemia/reperfusion (I/R) injury. While LPI activates multiple signaling pathways, little is known about which ones are important in cardiomyocytes. In this study we explored whether activation of the Rho kinase/ROCK/p38 MAPK pathway is responsible for LPI-induced extension of I/R injury. Using a high-throughput screening method (dynamic mass redistribution; DMR), mouse- and human-induced pluripotent stem cell (iPSC) cardiomyocytes exposed to LPI were shown to exhibit a rapid, sustained, and concentration-dependent (1 nmol L-1-30 μmol L-1) cellular response. Y-27632 (ROCK inhibitor; 10 & 50 μmol L-1) and CBD (1 μmol L-1) both abolished the DMR response to LPI (10 μmol L-1). In murine iPSC cardiomyocytes, LPI-induced ROCK and p38 MAPK phosphorylation, both of which were prevented by Y-27632 and CBD, but did not induce JNK activation or cleavage of caspase-3. In hearts isolated from wild type (WT) mice subjected to 30 minutes global I/R, LPI (10 μmol L-1) administered via the coronary circulation increased infarct size when applied prior to ischemia onset, but not when given at the time of reperfusion. The exacerbation of tissue injury by LPI was not seen in hearts from GPR55-/- mice or in the presence of Y-27632, confirming that injury is mediated via the GPR55/ROCK/p38 MAPK pathway. These findings suggest that raised levels of LPI in the vicinity of a developing infarct may worsen the outcome of AMI.

Hexadecane biodegradation of high efficiency by bacterial isolates from Santos Basin sediments

The aim of the study was the investigation of bacterial diversity from sediments collected at Santos Estuarine System, regarding to their abilities for hexadecane biotransformation. Hexadecane is a medium-chain linear alkane, considered as a model molecule for hydrocarbon biodegradation studies. It is a component from aliphatic fraction of crude petroleum, commonly related to environmental contamination by diesel oil. Santos Basin is an area with historical petroleum contamination. In the present work, sediment samples from this area were inoculated in artificial seawater (ASW), containing hexadecane as carbon source. Six bacterial isolates were selected as resistant to hexadecane. Chromatographic results showed biodegradation indexes above 97%. After 48 h of culture, five of them could degrade >80% of the initial hexadecane added. These isolates were characterized by 16S rDNA gene sequencing analysis. The following species were found: Bacillus amyloliquefaciens, Staphylococcus epidermidis, Micrococcus luteus, Nitratireductor aquimarinus, and Bacillus pumilus.

Cannabinoids and bone regeneration

Bone is a complex tissue with unique properties such as high strength and regeneration capabilities while carrying out multiple functions. Bone regeneration occurs both in physiological situations (bone turnover) and in pathological situations (e.g. fractures), being performed by osteoblasts and osteoclasts. If this process is inadequate, fracture nonunion or aseptic loosening of implants occurs and requires a complex treatment. Exogenous factors are currently used to increase bone regeneration process when needed, such as bisphosphonates and vitamin D, but limitations do exist. Cannabinoid system has been shown to have positive effects on bone metabolism. Cannabinoids at bone level mainly act on two receptors called CB-1 and CB-2, but GPR55, GPR119, TPRV1, TPRV4 receptors may also be involved. The CB-2 receptors are found in bone cells at higher levels compared to other receptors. Endocannabinods represented by anandamide and 2-arachidonoylglycerol, can stimulate osteoblast formation, bone formation and osteoclast activity. CB-2 agonists including HU-308, HU-433, JWH133, and JWH015 can stimulate osteoblast proliferation and activity, while CB-2 antagonists such as AM630 and SR144528 can inhibit osteoclast differentiation and function. CB-1 antagonist AM251 has been shown to inhibit osteoclast differentiation and activity, while GPR55 antagonist cannabidiol increases osteoblast activity and decreases osteoclast function. An optimal correlation of dose, duration, moment of action, and affinity can lead to an increased bone regeneration capacity, with important benefits in many pathological situations which involve bone tissue. As adverse reactions of cannabinoids have not been described in patients under controlled medication, cannabinoids can represent future treatment for bone regeneration.

The Endocannabinoid System as a Target in Cancer Diseases: Are We There Yet?

The endocannabinoid system (ECS) has been placed in the anti-cancer spotlight in the last decade. The immense data load published on its dual role in both tumorigenesis and inhibition of tumor growth and metastatic spread has transformed the cannabinoid receptors CB1 (CB1R) and CB2 (CB2R), and other members of the endocannabinoid-like system, into attractive new targets for the treatment of various cancer subtypes. Although the clinical use of cannabinoids has been extensively documented in the palliative setting, clinical trials on their application as anti-cancer drugs are still ongoing. As drug repurposing is significantly faster and more economical than de novo introduction of a new drug into the clinic, there is hope that the existing pharmacokinetic and safety data on the ECS ligands will contribute to their successful translation into oncological healthcare. CB1R and CB2R are members of a large family of membrane proteins called G protein-coupled receptors (GPCR). GPCRs can form homodimers, heterodimers and higher order oligomers with other GPCRs or non-GPCRs. Currently, several CB1R and CB2R-containing heteromers have been reported and, in cancer cells, CB2R form heteromers with the G protein-coupled chemokine receptor CXCR4, the G protein-coupled receptor 55 (GPR55) and the tyrosine kinase receptor (TKR) human V-Erb-B2 Avian Erythroblastic Leukemia Viral Oncogene Homolog 2 (HER2). These protein complexes possess unique pharmacological and signaling properties, and their modulation might affect the antitumoral activity of the ECS. This review will explore the potential of the endocannabinoid network in the anti-cancer setting as well as the clinical and ethical pitfalls behind it, and will develop on the value of cannabinoid receptor heteromers as potential new targets for anti-cancer therapies and as prognostic biomarkers.

G-protein Gα13 functions as a cytoskeletal and mitochondrial regulator to restrain osteoclast function

Excessive osteoclastic bone erosion disrupts normal bone remodeling and leads to bone loss in many skeletal diseases, including inflammatory arthritis, such as rheumatoid arthritis (RA) and psoriatic arthritis, periodontitis and peri-prosthetic loosening. Functional control of osteoclasts is critical for the maintenance of bone homeostasis. However, the mechanisms that restrain osteoclast resorptive function are not fully understood. In this study, we identify a previously unrecognized role for G-protein Gα13 in inhibition of osteoclast adhesion, fusion and bone resorptive function. Gα13 is highly expressed in mature multinucleated osteoclasts, but not during early differentiation. Deficiency of Gα13 in myeloid osteoclast lineage (Gα13ΔM/ΔM mice) leads to super spread morphology of multinucleated giant osteoclasts with elevated bone resorptive capacity, corroborated with an osteoporotic bone phenotype in the Gα13ΔM/ΔM mice. Mechanistically, Gα13 functions as a brake that restrains the c-Src, Pyk2, RhoA-Rock2 mediated signaling pathways and related gene expressions to control the ability of osteoclasts in fusion, adhesion, actin cytoskeletal remodeling and resorption. Genome wide analysis reveals cytoskeleton related genes that are suppressed by Gα13, identifying Gα13 as a critical cytoskeletal regulator in osteoclasts. We also identify a genome wide regulation of genes responsible for mitochondrial biogenesis and function by Gα13 in osteoclasts. Furthermore, the significant correlation between Gα13 expression levels, TNF activity and RA disease activity in RA patients suggests that the Gα13 mediated mechanisms represent attractive therapeutic targets for diseases associated with excessive bone resorption.

Computational systems pharmacology analysis of cannabidiol: a combination of chemogenomics-knowledgebase network analysis and integrated in silico modeling and simulation

With treatment benefits in both the central nervous system and the peripheral system, the medical use of cannabidiol (CBD) has gained increasing popularity. Given that the therapeutic mechanisms of CBD are still vague, the systematic identification of its potential targets, signaling pathways, and their associations with corresponding diseases is of great interest for researchers. In the present work, chemogenomics-knowledgebase systems pharmacology analysis was applied for systematic network studies to generate CBD-target, target-pathway, and target-disease networks by combining both the results from the in silico analysis and the reported experimental validations. Based on the network analysis, three human neuro-related rhodopsin-like GPCRs, i.e., 5-hydroxytryptamine receptor 1 A (5HT_1A), delta-type opioid receptor (OPRD) and G protein-coupled receptor 55 (GPR55), were selected for close evaluation. Integrated computational methodologies, including homology modeling, molecular docking, and molecular dynamics simulation, were used to evaluate the protein-CBD binding modes. A CBD-preferred pocket consisting of a hydrophobic cavity and backbone hinges was proposed and tested for CBD-class A GPCR binding. Finally, the neurophysiological effects of CBD were illustrated at the molecular level, and dopamine receptor 3 (DRD3) was further predicted to be an active target for CBD.

Atypical cannabinoid ligands O-1602 and O-1918 administered chronically in diet-induced obesity

Atypical cannabinoid compounds O-1602 and O-1918 are ligands for the putative cannabinoid receptors G protein-coupled receptor 55 and G protein-coupled receptor 18. The role of O-1602 and O-1918 in attenuating obesity and obesity-related pathologies is unknown. Therefore, we aimed to determine the role that either compound had on body weight and body composition, renal and hepatic function in diet-induced obesity. Male Sprague-Dawley rats were fed a high-fat diet (40% digestible energy from lipids) or a standard chow diet for 10 weeks. In a separate cohort, male Sprague-Dawley rats were fed a high-fat diet for 9 weeks and then injected daily with 5 mg/kg O-1602, 1 mg/kg O-1918 or vehicle (0.9% saline/0.75% Tween 80) for a further 6 weeks. Our data demonstrated that high-fat feeding upregulates whole kidney G protein receptor 55 expression. In diet-induced obesity, we also demonstrated O-1602 reduces body weight, body fat and improves albuminuria. Despite this, treatment with O-1602 resulted in gross morphological changes in the liver and kidney. Treatment with O-1918 improved albuminuria, but did not alter body weight or fat composition. In addition, treatment with O-1918 also upregulated circulation of pro-inflammatory cytokines including IL-1α, IL-2, IL-17α, IL-18 and RANTES as well as plasma AST. Thus O-1602 and O-1918 appear not to be suitable treatments for obesity and related comorbidities, due to their effects on organ morphology and pro-inflammatory signaling in obesity.

GPR55 controls functional differentiation of self-renewing epithelial progenitors for salivation

GPR55, a lipid-sensing receptor, is implicated in cell cycle control, malignant cell mobilization, and tissue invasion in cancer. However, a physiological role for GPR55 is virtually unknown for any tissue type. Here, we localize GPR55 to self-renewing ductal epithelial cells and their terminally differentiated progeny in both human and mouse salivary glands. Moreover, we find GPR55 expression downregulated in salivary gland mucoepidermoid carcinomas and GPR55 reinstatement by antitumor irradiation, suggesting that GPR55 controls renegade proliferation. Indeed, GPR55 antagonism increases cell proliferation and function determination in quasiphysiological systems. In addition, Gpr55-/- mice present ~50% enlarged submandibular glands with many more granulated ducts, as well as disordered endoplasmic reticuli and with glycoprotein content. Next, we hypothesized that GPR55 could also modulate salivation and glycoprotein content by entraining differentiated excretory progeny. Accordingly, GPR55 activation facilitated glycoprotein release by itself, inducing low-amplitude Ca2+ oscillations, as well as enhancing acetylcholine-induced Ca2+ responses. Topical application of GPR55 agonists, which are ineffective in Gpr55-/- mice, into adult rodent submandibular glands increased salivation and saliva glycoprotein content. Overall, we propose that GPR55 signaling in epithelial cells ensures both the life-long renewal of ductal cells and the continuous availability of saliva and glycoproteins for oral health and food intake.

GPR55 deficiency is associated with increased adiposity and impaired insulin signaling in peripheral metabolic tissues

Emerging evidence indicates that G-protein coupled receptor 55 (GPR55), a nonclassic receptor of the endocannabinoid system that is activated by L-α-lysophosphatidylinositol and various cannabinoid ligands, may regulate endocrine function and energy metabolism. We examined how GPR55 deficiency and modulation affects insulin signaling in skeletal muscle, adipose tissue, and liver alongside expression analysis of proteins implicated in insulin action and energy metabolism. We show that GPR55-null mice display decreased insulin sensitivity in these tissues, as evidenced by reduced phosphorylation of PKB/Akt and its downstream targets, concomitant with increased adiposity and reduced physical activity relative to wild-type counterparts. Impaired tissue insulin sensitivity coincided with reduced insulin receptor substrate-1 abundance in skeletal muscle, whereas in liver and epididymal fat it was associated with increased expression of the 3-phosphoinoistide lipid phosphatase, phosphatase and tensin homolog. In contrast, GPR55 activation enhanced insulin signaling in cultured skeletal muscle cells, adipocytes, and hepatocytes; this response was negated by receptor antagonists and GPR55 gene silencing in L6 myotubes. Sustained GPR55 antagonism in 3T3-L1 adipocytes enhanced expression of proteins implicated in lipogenesis and promoted triglyceride accumulation. Our findings identify GPR55 as a positive regulator of insulin action and adipogenesis and as a potential therapeutic target for countering obesity-induced metabolic dysfunction and insulin resistance.-Lipina, C., Walsh, S. K., Mitchell, S. E., Speakman, J. R., Wainwright, C. L., Hundal, H. S. GPR55 deficiency is associated with increased adiposity and impaired insulin signaling in peripheral metabolic tissues.

Modulation of the Oxidative Stress and Lipid Peroxidation by Endocannabinoids and Their Lipid Analogues

Growing evidence supports the pivotal role played by oxidative stress in tissue injury development, thus resulting in several pathologies including cardiovascular, renal, neuropsychiatric, and neurodegenerative disorders, all characterized by an altered oxidative status. Reactive oxygen and nitrogen species and lipid peroxidation-derived reactive aldehydes including acrolein, malondialdehyde, and 4-hydroxy-2-nonenal, among others, are the main responsible for cellular and tissue damages occurring in redox-dependent processes. In this scenario, a link between the endocannabinoid system (ECS) and redox homeostasis impairment appears to be crucial. Anandamide and 2-arachidonoylglycerol, the best characterized endocannabinoids, are able to modulate the activity of several antioxidant enzymes through targeting the cannabinoid receptors type 1 and 2 as well as additional receptors such as the transient receptor potential vanilloid 1, the peroxisome proliferator-activated receptor alpha, and the orphan G protein-coupled receptors 18 and 55. Moreover, the endocannabinoids lipid analogues N-acylethanolamines showed to protect cell damage and death from reactive aldehydes-induced oxidative stress by restoring the intracellular oxidants-antioxidants balance. In this review, we will provide a better understanding of the main mechanisms triggered by the cross-talk between the oxidative stress and the ECS, focusing also on the enzymatic and non-enzymatic antioxidants as scavengers of reactive aldehydes and their toxic bioactive adducts.

Activation of GPR55 increases neural stem cell proliferation and promotes early adult hippocampal neurogenesis

BACKGROUND AND PURPOSE

The cannabinoid system exerts functional regulation of neural stem cell (NSC) proliferation and adult neurogenesis, yet not all effects of cannabinoid-like compounds seen can be attributed to the cannabinoid 1 (CB₁ ) or CB₂ receptor. The recently de-orphaned GPR55 has been shown to be activated by numerous cannabinoid ligands suggesting that GPR55 is a third cannabinoid receptor. Here, we examined the role of GPR55 activation in NSC proliferation and early adult neurogenesis.

EXPERIMENTAL APPROACH

The effects of GPR55 agonists (LPI, O-1602, ML184) on human (h) NSC proliferation in vitro were assessed by flow cytometry. Human NSC differentiation was determined by flow cytometry, qPCR and immunohistochemistry. Immature neuron formation in the hippocampus of C57BL/6 and GPR55^-/- mice was evaluated by immunohistochemistry.

KEY RESULTS

Activation of GPR55 significantly increased proliferation rates of hNSCs in vitro. These effects were attenuated by ML193, a selective GPR55 antagonist. ML184 significantly promoted neuronal differentiation in vitro while ML193 reduced differentiation rates as compared to vehicle treatment. Continuous administration of O-1602 into the hippocampus via a cannula connected to an osmotic pump resulted in increased Ki67+ cells within the dentate gyrus. O-1602 increased immature neuron generation, as assessed by DCX+ and BrdU+ cells, as compared to vehicle-treated animals. GPR55^-/- animals displayed reduced rates of proliferation and neurogenesis within the hippocampus while O-1602 had no effect as compared to vehicle controls.

CONCLUSIONS AND IMPLICATIONS

Together, these findings suggest GPR55 activation as a novel target and strategy to regulate NSC proliferation and adult neurogenesis.

LH-21 and abnormal cannabidiol improve β-cell function in isolated human and mouse islets through GPR55-dependent and -independent signalling

AIMS

To examine the effects of Abn-CBD (GPR55 agonist) and LH-21 (CB1 antagonist) on human and mouse islet function, and to determine signalling via GPR55 using islets from GPR55^-/- mice.

MATERIALS AND METHODS

Islets isolated from human organ donors and mice were incubated in the absence or presence of Abn-CBD or LH-21, and insulin secretion, [Ca²⁺ ]_i, cAMP_, apoptosis, β-cell proliferation and CREB and AKT phosphorylation were examined using standard techniques.

RESULTS

Abn-CBD potentiated glucose-stimulated insulin secretion and elevated [Ca²⁺ ]_i in human islets and islets from both GPR55^+/+ and GPR55^-/- mice. LH-21 also increased insulin secretion and [Ca²⁺ ]_i in human islets and GPR55^+/+ mouse islets, but concentrations of LH-21 up to 0.1 μM were ineffective in islets from GPR55^-/- mice. Neither ligand affected basal insulin secretion or islet cAMP levels. Abn-CBD and LH-21 reduced cytokine-induced apoptosis in human islets and GPR55^+/+ mouse islets, and these effects were suppressed after GPR55 deletion. They also increased β-cell proliferation: the effects of Abn-CBD were preserved in islets from GPR55^-/- mice, while those of LH-21 were abolished. Abn-CBD and LH-21 increased AKT phosphorylation in mouse and human islets.

CONCLUSIONS

This study showed that Abn-CBD and LH-21 improve human and mouse islet β-cell function and viability. Use of islets from GPR55^-/- mice suggests that designation of Abn-CBD and LH-21 as a GPR55 agonist and a CB1 antagonist, should be revised.

Lysophosphatidylinositols, from Cell Membrane Constituents to GPR55 Ligands

Lysophosphatidylinositols (LPIs) are membrane constituents that alter the properties of said membranes. However, recent data showing that the once orphan receptor, GPR55, can act as a receptor for LPIs has sparked a renewed interest in LPIs as bioactive lipids. As evidence supporting the importance of LPIs and/or GPR55 is continuously accumulating and because LPI levels are altered in a number of pathologies such as obesity and cancer, the coming years should bring new, exciting discoveries to this field. In this review, we discuss the recent work on LPIs and on their molecular target, the GPR55 receptor. First, we summarize the metabolism of LPIs before outlining the cellular pathways activated by GPR55. Then, we review the actions of LPIs and GPR55 that could have potential pharmacological or therapeutic applications in several pathophysiological settings, such as cancer, obesity, pain, and inflammation.

Advances in the Physiology of GPR55 in the Central Nervous System

Background:

The G protein-coupled receptor 55 (GPR55) is a mammalian orphan receptor that awaits a formal classification. There are an increasing number of reports directed to know the physiology and pathophysiology of this receptor. Lamentably, its functions in the central nervous system (CNS) have been scarcely elucidated.

Methods:

A bibliographic search in PubMed database about GPR55 actions in the CNS was made. The information was grouped for brain structures to facilitate the interpretation. Finally, we constructed a schematic representation of the current knowledge about the potential participation of GPR55 in some physiological and pathophysiological events.

Results:

Seventy nine papers were included in the review. Only few of them showed data about GPR55 (mRNA/protein) expression in multiple brain areas. The rest showed findings in different preparations both in vitro and in vivo conditions that allowed us to speculate a potential activity of GPR55 in the different brain areas.

Conclusion:

GPR55 mRNA is expressed in several brain areas as the hippocampus, hypothalamus, frontal cortex and cerebellum; but due to the lack of information, only some speculative information about its function in these regions has been suggested. Therefore, this review provide relevant information to motivate further research about GPR55 physiology/pathophysiology in the CNS.