Cannabinoid CB(2)-selective inverse agonist protects against antigen-induced bone loss

Inhibition of FAAH suppresses RANKL-induced osteoclastogenesis and attenuates ovariectomy-induced bone loss partially through repressing the IL17 pathway

Fatty amide hydrolase (FAAH) is a key degradation enzyme of the endocannabinoid system, mainly responsible for the hydrolysis of arachidonic acid ethanolamine (AEA). Previous investigations have shown that FAAH is involved in a series of biological processes, such as inflammation, immune regulation, and transmembrane signal transduction of neurons. Endogenous cannabinoids and cannabinoid receptors have been reported to participate in the regulation of bone homeostasis by regulating the differentiation of osteoblasts and osteoclasts. We hypothesized that FAAH may play an important role in osteoclastogenesis based on the above evidence. The present study found that the FAAH expression was increased at both mRNA and protein levels during RANKL-induced osteoclastogenesis. Pharmacological and genetic inhibition of FAAH in bone marrow-derived macrophages (BMMs) inhibited osteoclastogenesis, F-actin ring formation, bone resorption, and osteoclast-specific gene expression in vitro. Moreover, intragastric administration of the FAAH inhibitor PF-04457845(PF) ameliorated ovariectomy (OVX)-induced bone loss in mice. Further investigation revealed that nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways were inhibited by PF treatment and FAAH knockdown. RNAseq indicated that the IL17 pathway was blocked by PF, and administration of recombinant murine IL17 protein could partially restore osteoclastogenesis and activate NF-κB and MAPK pathways. To sum up, our findings demonstrate that targeting FAAH could be a promising candidate strategy for treating osteoclast-related diseases, especially osteoporosis.

N-[1,3-Dialkyl(aryl)-2-oxoimidazolidin-4-ylidene]-aryl(alkyl)sulphonamides as Novel Selective Human Cannabinoid Type 2 Receptor (hCB2R) Ligands; Insights into the Mechanism of Receptor Activation/Deactivation

Cannabinoid type 1 (hCB1) and type 2 (hCB2) receptors are pleiotropic and crucial targets whose signaling contributes to physiological homeostasis and its restoration after injury. Being predominantly expressed in peripheral tissues, hCB2R represents a safer therapeutic target than hCB1R, which is highly expressed in the brain, where it regulates processes related to cognition, memory, and motor control. The development of hCB2R ligands represents a therapeutic opportunity for treating diseases such as pain, inflammation and cancer. Identifying new selective scaffolds for cannabinoids and determining the structural determinants responsible for agonism and antagonism are priorities in drug design. In this work, a series of N-[1,3-dialkyl(aryl)-2-oxoimidazolidin-4-ylidene]-aryl(alkyl)sulfonamides is designed and synthesized and their affinity for human hCB1R and hCB2R is determined. Starting with a scaffold selected from the NIH Psychoactive Drug Screening Program Repository, through a combination of molecular modeling and structure-activity relationship studies, we were able to identify the chemical features leading to finely tuned hCB2R selectivity. In addition, an in silico model capable of predicting the functional activity of hCB2R ligands was proposed and validated. The proposed receptor activation/deactivation model enabled the identification of four pure hCB2R-selective agonists that can be used as a starting point for the development of more potent ligands.

Impact of Δ9-Tetrahydrocannabinol on Rheumatoid Arthritis Synovial Fibroblasts Alone and in Co-Culture with Peripheral Blood Mononuclear Cells

δ9-Tetrahydrocannabinol (THC) has demonstrated anti-inflammatory effects in animal models of arthritis, but its mechanism of action and cellular targets are still unclear. The purpose of this study is to elucidate the effects of THC (0.1-25 µM) on synovial fibroblasts from patients with rheumatoid arthritis (RASF) and peripheral blood mononuclear cells (PBMC) from healthy donors in respect to proliferation, calcium mobilization, drug uptake, cytokine and immunoglobulin production. Intracellular calcium and drug uptake were determined by fluorescent dyes Cal-520 and PoPo3, respectively. Cytokine and immunoglobulin production were evaluated by ELISA. Cannabinoid receptors 1 and 2 (CB1 and CB2) were detected by flow cytometry. RASF express CB1 and CB2 and the latter was increased by tumor necrosis factor (TNF). In RASF, THC (≥5 µM) increased intracellular calcium levels/PoPo3 uptake in a TRPA1-dependent manner and reduced interleukin-8 (IL-8) and matrix metalloprotease 3 (MMP-3) production at high concentrations (25 µM). Proliferation was slightly enhanced at intermediate THC concentrations (1-10 µM) but was completely abrogated at 25 µM. In PBMC alone, THC decreased interleukin-10 (IL-10) production and increased immunoglobulin G (IgG). In PBMC/RASF co-culture, THC decreased TNF production when cells were stimulated with interferon-γ (IFN-γ) or CpG. THC provides pro- and anti-inflammatory effects in RASF and PBMC. This is dependent on the activating stimulus and concentration of THC. Therefore, THC might be used to treat inflammation in RA but it might need titrating to determine the effective concentration.

Marijuana in Orthopaedics: Effects on Bone Health, Wound-Healing, Surgical Complications, and Pain Management

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Marijuana use is on the rise in the United States, and there is a paucity of information on the effects of cannabis and its chemical constituents on bone health, wound-healing, surgical complications, and pain management.

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Current evidence suggests that cannabidiol (CBD) may enhance bone health and metabolism, while Δ9-tetrahydrocannabinol (Δ9-THC), the major psychoactive component in marijuana, has an inhibitory effect.

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Marijuana users are at higher risk for delayed bone-healing, demonstrate lower bone mineral density, are at increased risk for fracture, and may experience postoperative complications such as increased opioid use and hyperemesis.

Involvement of the endocannabinoid system in osteoarthritis pain

Osteoarthritis is a degenerative joint disease associated with articular cartilage degradation. The major clinical outcome of osteoarthritis is a complex pain state that includes both nociceptive and neuropathic mechanisms. Currently, the therapeutic approaches for osteoarthritis are limited as no drugs are available to control the disease progression and the analgesic treatment has restricted efficacy. Increasing evidence from preclinical studies supports the interest of the endocannabinoid system as an emerging therapeutic target for osteoarthritis pain. Indeed, pharmacological studies have shown the anti-nociceptive effects of cannabinoids in different rodent models of osteoarthritis, and compelling evidence suggests an active participation of the endocannabinoid system in the pathophysiology of this disease. The ubiquitous distribution of cannabinoid receptors, together with the physiological role of the endocannabinoid system in the regulation of pain, inflammation and even joint function further support the therapeutic interest of cannabinoids for osteoarthritis. However, limited clinical evidence has been provided to support this therapeutic use of cannabinoids, despite the promising preclinical data. This review summarizes the promising results that have been recently obtained in support of the therapeutic value of cannabinoids for osteoarthritis management.

Disease modification of breast cancer-induced bone remodeling by cannabinoid 2 receptor agonists

Most commonly originating from breast malignancies, metastatic bone cancer causes bone destruction and severe pain. Although novel chemotherapeutic agents have increased life expectancy, patients are experiencing higher incidences of fracture, pain, and drug-induced side effects; furthermore, recent findings suggest that patients are severely undertreated for their cancer pain. Strong analgesics, namely opiates, are first-line therapy in alleviating cancer-related pain despite the severe side effects, including enhanced bone destruction with sustained administration. Bone resorption is primarily treated with bisphosphonates, which are associated with highly undesirable side effects, including nephrotoxicity and osteonecrosis of the jaw. In contrast, cannabinoid receptor 2 (CB(2) ) receptor-specific agonists have been shown to reduce bone loss and stimulate bone formation in a model of osteoporosis. CB(2) agonists produce analgesia in both inflammatory and neuropathic pain models. Notably, mixed CB(1) /CB(2) agonists also demonstrate a reduction in ErbB2-driven breast cancer progression. Here we demonstrate for the first time that CB(2) agonists reduce breast cancer-induced bone pain, bone loss, and breast cancer proliferation via cytokine/chemokine suppression. Studies used the spontaneously-occurring murine mammary cell line (66.1) implanted into the femur intramedullary space; measurements of spontaneous pain, bone loss, and cancer proliferation were made. The systemic administration of a CB(2) agonist, JWH015, for 7 days significantly attenuated bone remodeling, assuaged spontaneous pain, and decreased primary tumor burden. CB(2) -mediated effects in vivo were reversed by concurrent treatment with a CB(2) antagonist/inverse agonist but not with a CB(1) antagonist/inverse agonist. In vitro, JWH015 reduced cancer cell proliferation and inflammatory mediators that have been shown to promote pain, bone loss, and proliferation. Taken together, these results suggest CB(2) agonists as a novel treatment for breast cancer-induced bone pain, in which disease modifications include a reduction in bone loss, suppression of cancer growth, attenuation of severe bone pain, and increased survival without the major side effects of current therapeutic options.

The promise and dilemma of cannabinoid therapy: lessons from animal studies of bone disease

The endocannabinoid system plays an important role in numerous physiological processes and represents a potential drug target for diseases ranging from brain disorders to cancer. Recent preclinical studies implicated endocannabinoids and their receptors in the regulation of bone cell activity and in the pathogenesis of bone loss. Cells and intervening nerves in the skeleton express cannabinoid receptors and the machinery for the synthesis and breakdown of endocannabinoids. In healthy adult mice, pharmacological and genetic inactivation of the cannabinoid type 1 receptor (CB1) and putative cannabinoid receptor GPR55 (G protein-coupled receptor 55) inhibit osteoclastic bone resorption and increase bone mass, suggesting that both receptors have a negative role in early bone development. Although no distinct abnormalities in bone development were observed in healthy adult mice deficient in cannabinoid type 2 receptors (CB2), pharmacological blockage of this receptor was effective in suppressing bone loss associated with increased bone turnover, particularly in mouse models of osteoporosis, arthritis and osteolytic bone disease. In the aging skeleton, CB1 deficiency causes accelerated osteoporosis characterized mainly by a significant reduction in bone formation coupled to enhanced adipocyte accumulation in the bone marrow. A similar acceleration of bone loss was also reported in aging CB2-deficient mice but found to be associated with enhanced bone turnover. This perspective describes the role of cannabinoid ligands and their receptors in bone metabolism and highlights the promise and dilemma of therapeutic exploitation of the endocannabinoid system for treatment of bone disorders.

Role of cannabinoids in the regulation of bone remodeling

The endocannabinoid system plays a key role in regulating a variety of physiological processes such as appetite control and energy balance, pain perception, and immune responses. Recent studies have implicated the endocannabinoid system in the regulation of bone cell activity and bone remodeling. These studies showed that endogenous cannabinoid ligands, cannabinoid receptors, and the enzymes responsible for ligand synthesis and breakdown all play important roles in bone mass and in the regulation of bone disease. These findings suggest that the endocannabinoid pathway could be of value as a therapeutic target for the prevention and treatment of bone diseases. Here, we review the role of the skeletal endocannabinoid system in the regulation of bone remodeling in health and disease.

Mechanisms of osteoclastogenesis inhibition by a novel class of biphenyl-type cannabinoid CB(2) receptor inverse agonists

The cannabinoid CB(2) receptor is known to modulate osteoclast function by poorly understood mechanisms. Here, we report that the natural biphenyl neolignan 4'-O-methylhonokiol (MH) is a CB(2) receptor-selective antiosteoclastogenic lead structure (K(i) < 50 nM). Intriguingly, MH triggers a simultaneous G(i) inverse agonist response and a strong CB(2) receptor-dependent increase in intracellular calcium. The most active inverse agonists from a library of MH derivatives inhibited osteoclastogenesis in RANK ligand-stimulated RAW264.7 cells and primary human macrophages. Moreover, these ligands potently inhibited the osteoclastogenic action of endocannabinoids. Our data show that CB(2) receptor-mediated cAMP formation, but not intracellular calcium, is crucially involved in the regulation of osteoclastogenesis, primarily by inhibiting macrophage chemotaxis and TNF-α expression. MH is an easily accessible CB(2) receptor-selective scaffold that exhibits a novel type of functional heterogeneity.

Cannabinoid receptors as target for treatment of osteoporosis: a tale of two therapies

The central nervous system plays an important role in regulating bone metabolism in health and in disease with a number of neurotransmitters been reported to influence bone cell activity through a central relay. In keeping with this, recent studies demonstrated that endocannabinoids and their receptors are involved in the pathogenesis of osteoporosis. The endocannabinoids anandamide and 2-arachidonylglycerol are found in the skeleton and numerous studies also showed that bone cells express the cannabinoid receptors CB1 and CB2 and the orphan receptor GPR55. Pharmacological and genetic inactivation of CB1, CB2 and GPR55 in adult mice suppress bone resorption, increase bone mass and protect against bone loss, suggesting that inverse agonists/antagonists of these receptors may serve as anti-resorptive agents. In the ageing skeleton however CB1 and CB2 receptors have a protective effect against age-dependent bone loss in both male and female mice. CB1 receptor deficiency in aged mice results in accelerated age-dependent osteoporosis due to marked increase in bone resorption and significant reduction in bone formation coupled to enhanced adipocyte accumulation in the bone marrow compartment. Similar acceleration of bone loss was also reported in CB2 deficient mice of similar age but found to be associated with enhanced bone turnover. This review summarises in vitro and in vivo findings relating to the influence of cannabinoid ligands on bone metabolism and argues in favour of the exploitation of cannabinoid receptors as targets for both anabolic and anti-resorptive therapy for treatment of complex multifaceted bone diseases such as osteoporosis.

Label-free screening assays: a strategy for finding better drug candidates

The last 10 years have seen advances in automation and high-throughput biochemistry in the drug-discovery arena. However, these advances have not led to improvements in drug-discovery success. Drug programs must find new ways to identify superior compounds. Advances in label-free assay technologies may provide advantages needed for improved drug discovery. In this article, we will discuss high-throughput MS, a technology that allows screening with native substrates and with targets inaccessible to standard assay formats. We will then discuss cell-based label-free biosensors, focusing on the increased information content available when using these platforms. We will conclude with speculation on the future and ways to obtain relevant biological information early in development to ensure the best compounds are promoted to medicinal chemistry campaigns.

Cannabinoids and bone: friend or foe?

The endocannabinoid system is recognized to play an important role in regulating a variety of physiological processes, including appetite control and energy balance, pain perception, and immune responses. The endocannabinoid system has also recently been implicated in the regulation of bone metabolism. Endogenously produced cannabinoids are hydrophobic molecules derived from hydrolysis of membrane phospholipids. These substances, along with plant-derived and synthetic cannabinoids, interact with the type 1 (CB(1)) and 2 (CB(2)) cannabinoid receptors and the GPR55 receptor to regulate cellular function through a variety of signaling pathways. Endocannabinoids are produced in bone, but the mechanisms that regulate their production are unclear. Skeletal phenotyping of mice with targeted inactivation of cannabinoid receptors and pharmacological studies have shown that cannabinoids play a key role in the regulation of bone metabolism. Mice with CB(1) deficiency have high peak bone mass as a result of an osteoclast defect but develop age-related osteoporosis as a result of impaired bone formation and accumulation of bone marrow fat. Mice with CB(2) deficiency have relatively normal peak bone mass but develop age-related osteoporosis as a result of increased bone turnover with uncoupling of bone resorption from bone formation. Mice with GPR55 deficiency have increased bone mass as a result of a defect in the resorptive activity of osteoclasts, but bone formation is unaffected. Cannabinoids are also produced within synovial tissues, and preclinical studies have shown that cannabinoid receptor ligands are effective in the treatment of inflammatory arthritis. These data indicate that cannabinoid receptors and the enzymes responsible for ligand synthesis and breakdown play important roles in bone remodeling and in the pathogenesis of joint disease.

Characterizing cannabinoid CB2 receptor ligands using DiscoveRx PathHunter beta-arrestin assay

The authors have characterized a set of cannabinoid CB(2) receptor ligands, including triaryl bis sulfone inverse agonists, in a cell-based receptor/beta-arrestin interaction assay (DiscoveRx PathHunter). The results were compared with results using a competitive ligand binding assay, and with effects on forskolin-stimulated cAMP levels (PerkinElmer LANCE). The authors show good correlation between the 3 assay systems tested, with the beta-arrestin protein complementation assay exhibiting a more robust signal than the cAMP assay for cannabinoid CB(2) agonists. Further assay validation shows that DiscoveRx PathHunter HEK293 CB(2) beta-arrestin assay can be carried out from cryopreserved cell suspensions, eliminating variations caused by the need for multiple cell pools during live cell screening campaigns. These results, and the authors' results evaluating a test set of random library compounds, validate the use of ligand-induced interaction between the human cannabinoid CB(2) receptor and beta-arrestin as an appropriate and valuable screening platform for compounds specific for the cannabinoid CB(2) receptor.