Arthritis and cannabinoids: HU-210 and Win-55,212–2 prevent IL-1 α-induced matrix degradation in bovine articular chondrocytes in-vitro

Assessment of Clinical Outcomes in Patients With Osteoarthritis: Analysis From the UK Medical Cannabis Registry

Osteoarthritis accounts for 0.6% of disability-adjusted life years globally. There is a paucity of research focused on cannabis-based medicinal products (CBMPs) for osteoarthritic chronic pain management. This study aims to assess changes in validated patient-reported outcome measures (PROMs) and CBMP clinical safety in patients with osteoarthritis. A prospective case series from the UK Medical Cannabis Registry was analyzed. Primary outcomes were changes in the Brief Pain Inventory (BPI), McGill Pain Questionnaire (MPQ2), EQ-5D-5L, Generalized Anxiety Disorder-7 (GAD-7) questionnaire, and Single-Item Sleep Quality Scale (SQS) at 1-, 3-, 6-, and 12-month follow-ups from baseline. Common Terminology Criteria for Adverse Events v.4.0 was used for adverse event (AE) analysis. Statistical significance was defined as p < 0.050. Seventy-seven patients met inclusion criteria. CBMP initiation correlated with BPI pain severity (p = 0.004), pain interference (p = 0.005), and MPQ2 (p = 0.017) improvements at all follow-ups compared to baseline. There were improvements in the EQ-5D-5L index (p = 0.026), SQS (p < 0.001), and GAD-7 (p = 0.038) up to 6 and 3 months, respectively. Seventeen participants (22.08%) recorded 76 mild AEs (34.86%), 104 moderate AEs (47.71%), and 38 severe AEs (17.43%). Though causality cannot be assumed in this observational study, results support development of randomized control trials for osteoarthritis pain management with CBMPs.

Cannabinoids and endocannabinoids as therapeutics for nervous system disorders: preclinical models and clinical studies

Cannabinoids are lipophilic substances derived from Cannabis sativa that can exert a variety of effects in the human body. They have been studied in cellular and animal models as well as in human clinical trials for their therapeutic benefits in several human diseases. Some of these include central nervous system (CNS) diseases and dysfunctions such as forms of epilepsy, multiple sclerosis, Parkinson's disease, pain and neuropsychiatric disorders. In addition, the endogenously produced cannabinoid lipids, endocannabinoids, are critical for normal CNS function, and if controlled or modified, may represent an additional therapeutic avenue for CNS diseases. This review discusses in vitro cellular, ex vivo tissue and in vivo animal model studies on cannabinoids and their utility as therapeutics in multiple CNS pathologies. In addition, the review provides an overview on the use of cannabinoids in human clinical trials for a variety of CNS diseases. Cannabinoids and endocannabinoids hold promise for use as disease modifiers and therapeutic agents for the prevention or treatment of neurodegenerative diseases and neurological disorders.

Therapeutic Effects of Non-Euphorigenic Cannabis Extracts in Osteoarthritis

Introduction: Osteoarthritis (OA) is disabling and degenerative disease of the joints that is clinically characterized by pain and loss of function. With no disease-modifying treatment available, current therapies aim at pain management but are of limited efficacy. Cannabis products, specifically cannabinoids, are widely used to control pain and inflammation in many diseases with no scientific evidence demonstrating their efficacy in OA. Objective: We investigated the effects of non-euphorigenic cannabis extracts, CBD oil and cannabigerol oil (CBG oil), on pain and disease progression in OA mice. Methods and Results: Twelve-week-old male C57BL/6J mice received either sham or destabilization of the medial meniscus (DMM) surgery. DMM mice were treated with vehicle, CBD oil, or CBG oil. The gait of DMM mice was impaired as early as 2 weeks following surgery and continued deteriorating until week 8, which was restored by CBD oil and CBG oil treatments throughout the disease course. Mechanical allodynia developed in DMM mice, however, was not ameliorated by any of the treatments. On the other hand, both CBD oil and CBG oil ameliorated cold allodynia. In open field test, both oil treatments normalized changes in the locomotor activity of DMM mice. CBD oil and CBG oil treatments significantly reduced synovitis in DMM mice. Only CBG oil reduced cartilage degeneration, chondrocyte loss, and matrix metalloproteinase 13 expression, with a significant increase in the number of anabolic chondrocytes. Subchondral bone remodeling found in vehicle-treated DMM mice was not ameliorated by either CBD or CBG oil. Conclusions: Our results show evidence for the therapeutic efficacy of CBD oil and CBG oil, where both oils ameliorate pain and inflammation, and improve gait and locomotor activity in OA mice, representing clinical pain and function. Importantly, only CBG oil is chondroprotective, which may provide superior efficacy in future studies in OA patients.

Cannabis and Rheumatoid Arthritis: A Scoping Review Evaluating the Benefits, Risks, and Future Research Directions

Rheumatoid diseases, including rheumatoid arthritis, osteoarthritis, and fibromyalgia, are characterized by progressive inflammation in the musculoskeletal system, predominantly affecting the joints and leading to cartilage and bone damage. The resulting pain and ongoing degradation of the musculoskeletal system contribute to reduced physical activity, ultimately impacting quality of life and imposing a substantial socioeconomic burden. Unfortunately, current therapeutics have limited efficacy in slowing disease progression and managing pain. Thus, the development of novel and alternative therapies is imperative. Cannabinoids possess beneficial properties as potential treatments for rheumatoid diseases due to their anti-inflammatory and analgesic properties. Preclinical studies have demonstrated promising results in halting disease progression and relieving pain. However, there is a scarcity of patient clinical studies, and the available data show mixed results. Consequently, there are currently no established clinical recommendations regarding the utilization of cannabis for treating rheumatoid diseases. In this review, we aim to explore the concept of cannabis use for rheumatoid diseases, including potential adverse effects. We will provide an overview of the data obtained from preclinical and clinical trials and from retrospective studies on the efficacy and safety of cannabis in the treatment of rheumatoid diseases.

Influence of the Synthetic Cannabinoid Agonist on Normal and Inflamed Cartilage: An In Vitro Study

Medical marijuana (versus Marijuana derivatives) has been reported to possess analgesic, immunomodulatory, and anti-inflammatory properties. Recent studies in animal models of arthritis showed that cannabinoids, a group of compounds produced from marijuana, may attenuate joint damage. However, whether marijuana byproducts can suppress osteoarthritis (OA)-associated cartilage degradation has not been previously reported. In this study, human chondrocytes were isolated from healthy articular cartilage, expanded in vitro, and subjected to pellet culture in a chondrogenic medium to form cartilage tissues. We first examined the influence of marijuana byproducts on normal cartilage by treating chondrocyte-derived tissues with a synthetic cannabinoid agonist, Win-55,212-2 (Win), at different concentrations ranging from 0.01 to 10 µM. After treatment, the tissue phenotype was assessed using glycosaminoglycan (GAG) assay and real-time PCR. Next, cartilage tissues were pre-treated with interleukin-1β (IL-1β) to generate an inflamed phenotype and then cultured with Win to assess its therapeutic potential. The results showed that at concentrations lower than 1 µM, Win treatment did not significantly impair chondrocyte growth or cartilage formation capacity, but at a high level (>10 µM), it remarkably suppressed cell proliferation. Interestingly, under the condition of IL-1β pre-treatment, Win was able to partially preserve the cartilage matrix and decrease the production of interleukin-6, although the protective effect was mild. Taken together, our results indicated that the variable effects of Win on chondrocytes occur in a concentration-dependent manner. Whether cannabinoid derivatives can be used to treat cartilage degradation or can alter other structural changes in OA deserve further investigation.

Cannabinoid receptors are expressed in equine synovium and upregulated with synovitis

BACKGROUND

Osteoarthritis (OA) is a major cause of equine lameness. Cannabinoid receptors (CB) are now considered to be promising therapeutic targets in human rheumatology for pain and inflammation, however little is known about the equine endocannabinoid system.

OBJECTIVES

The primary goal was to assess the presence and expression pattern of CB1 and CB2 in the synovium of healthy joints. A secondary goal was to explore the relationship between the CB expression, degree of synovitis and OA pathology.

STUDY DESIGN

Ex vivo experimental study.

METHODS

Metacarpophalangeal joints (n=25) from a tissue bank were studied. The joints were dissected, and the articular cartilage lesions were scored. Synovial membrane specimens (n=45) were harvested, fixed and the degree of synovitis was graded on histological sections. Co-localised synovial sections were also immunostained with antibodies to CB1 and CB2. Five regions of interest (ROIs) were randomly selected from digital images of manually segmented synovial intima and scored blindly for positive cellular immunoreactive staining by 2 independent observers. Interobserver agreement was calculated with an intraclass correlation coefficient (ICC). Relationships between CB1 and CB2 immunoreactive scores and synovitis or joint OA grade were explored with mixed linear models.

RESULTS

CB1 was expressed in synovial intimal cells in all specimens studied whereas CB2 expression was identified in 94%. Both receptors were also expressed in the subintimal blood vessel walls. ICCs were 84.6% (CB1) and 92.9% (CB2) for the immunoreactivity scores. Both CB1 and CB2 expression were significantly upregulated (p=0.04 and p=0.03 respectively) with increasing degree of synovitis. Conversely, CB1 expression significantly decreased (p=0.03) with increasing severity of OA.

MAIN LIMITATIONS

The type of synovial cell expressing CB1 or CB2 was not investigated.

CONCLUSIONS

Equine synovial intimal cells constitutively express both CB1 and CB2 receptors that are upregulated with synovitis and may have a role in joint pain. They are potential targets for therapy with cannabinoid molecules or their derivatives. This article is protected by copyright. All rights reserved.

Components of the Endocannabinoid System and Effects of Cannabinoids Against Bone Diseases: A Mini-Review

Background: The endocannabinoid system (ECS) is involved in multiple physiological processes, including appetite regulation, pain perception, motor function development, and immune response regulation. Cannabinoids have been approved for the clinical treatment of nausea and vomiting caused by cytostatic therapy or cancer chemotherapy, loss of appetite in HIV/AIDS-associated cachexia, refractory spasms induced by multiple sclerosis, chronic pain, and urinary incontinence.

Methods: Check out the research on ECS and bone diseases in the past 20 years.

Results: Many studies have demonstrated that endocannabinoids (eCBs) and cannabinoid receptors (CBRs) are expressed in bone and synovial tissues, playing important roles in bone metabolism. Preclinical studies using cannabis-based therapies in animal models have shown that cannabinoids (CBs) can alleviate the development of osteoarthritis (OA), prevent osteoporosis (OP), reduce cancer-induced osteolytic destruction, and improve fracture healing, highlighting the therapeutic potential of CBs for human bone diseases.

Conclusions: The present review summarizes various components of the ECS in bone diseases and their potential as a therapeutic target.

Therapeutic Prospects of Cannabinoids in the Immunomodulation of Prevalent Autoimmune Diseases

Introduction: Cannabinoids such as ▵-9-THC and CBD can downregulate the immune response by modulating the endocannabinoid system. This modulation is relevant for the treatment of prevalent autoimmune diseases (ADs), such as multiple sclerosis (MS), systemic lupus erythematosus (SLE), diabetes mellitus type 1 (DMT1), and rheumatoid arthritis (RA). These conditions require new therapeutic options with fewer side effects for the control of the autoimmune response. Objective: to conduct a literature review of preclinical scientific evidence that supports further clinical investigations for the use of cannabinoids (natural or synthetic) as potential immunomodulators of the immune response in ADs. Methodology: A systematic search was carried out in different databases using different MeSH terms, such as Cannabis sativa L., cannabinoids, immunomodulation, and ADs. Initially, 677 journal articles were found. After filtering by publication date (from 2000 to 2020 for SLE, DMT1, and RA; and 2010 to 2020 for MS) and removing the duplicate items, 200 articles were selected and analyzed by title and summary associated with the use of cannabinoids as immunomodulatory treatment for those diseases. Results: Evidence of the immunomodulatory effect of cannabinoids in the diseases previously mentioned, but SLE that did not meet the search criteria, was summarized from 24 journal articles. CBD was found to be one of the main modulators of the immune response. This molecule decreased the number of Th1 and Th17 proinflammatory cells and the production of the proinflammatory cytokines, interleukin (IL)-1, IL-12, IL-17, interferon (IFN)-γ, and tumor necrosis factor alpha, in mouse models of MS and DMT1. Additionally, new synthetic cannabinoid-like molecules, with agonist or antagonist activity on CB1, CB2, TRPV1, PPAR-α, and PPAR-γ receptors, have shown anti-inflammatory properties in MS, DMT1, and RA. Conclusion: Data from experimental animal models of AD showed that natural and synthetic cannabinoids downregulate inflammatory responses mediated by immune cells responsible for AD chronicity and progression. Although synthetic cannabinoid-like molecules were evaluated in just two clinical trials, they corroborated the potential use of cannabinoids to treat some ADs. Notwithstanding, new cannabinoid-based approaches are required to provide alternative treatments to patients affected by the large group of ADs.

Cannabinoid-based therapy as a future for joint degeneration. Focus on the role of CB2 receptor in the arthritis progression and pain: an updated review

Over the last several decades, the percentage of patients suffering from different forms of arthritis has increased due to the ageing population and the increasing risk of civilization diseases, e.g. obesity, which contributes to arthritis development. Osteoarthritis and rheumatoid arthritis are estimated to affect 50-60% of people over 65 years old and cause serious health and economic problems. Currently, therapeutic strategies are limited and focus mainly on pain attenuation and maintaining joint functionality. First-line therapies are nonsteroidal anti-inflammatory drugs; in more advanced stages, stronger analgesics, such as opioids, are required, and in the most severe cases, joint arthroplasty is the only option to ensure joint mobility. Cannabinoids, both endocannabinoids and synthetic cannabinoid receptor (CB) agonists, are novel therapeutic options for the treatment of arthritis-associated pain. CB₁ receptors are mainly located in the nervous system; thus, CB₁ agonists induce many side effects, which limit their therapeutic efficacy. On the other hand, CB₂ receptors are mainly located in the periphery on immune cells, and CB₂ modulators exert analgesic and anti-inflammatory effects in vitro and in vivo. In the current review, novel research on the cannabinoid-mediated analgesic effect on arthritis is presented, with particular emphasis on the role of the CB₂ receptor in arthritis-related pain and the suppression of inflammation.

Cannabinoid Receptors: An Update on Cell Signaling, Pathophysiological Roles and Therapeutic Opportunities in Neurological, Cardiovascular, and Inflammatory Diseases

The identification of the human cannabinoid receptors and their roles in health and disease, has been one of the most significant biochemical and pharmacological advancements to have occurred in the past few decades. In spite of the major strides made in furthering endocannabinoid research, therapeutic exploitation of the endocannabinoid system has often been a challenging task. An impaired endocannabinoid tone often manifests as changes in expression and/or functions of type 1 and/or type 2 cannabinoid receptors. It becomes important to understand how alterations in cannabinoid receptor cellular signaling can lead to disruptions in major physiological and biological functions, as they are often associated with the pathogenesis of several neurological, cardiovascular, metabolic, and inflammatory diseases. This review focusses mostly on the pathophysiological roles of type 1 and type 2 cannabinoid receptors, and it attempts to integrate both cellular and physiological functions of the cannabinoid receptors. Apart from an updated review of pre-clinical and clinical studies, the adequacy/inadequacy of cannabinoid-based therapeutics in various pathological conditions is also highlighted. Finally, alternative strategies to modulate endocannabinoid tone, and future directions are also emphasized.

The endocannabinoid signaling pathway as an emerging target in pharmacotherapy, earmarking mitigation of destructive events in rheumatoid arthritis

Rheumatoid arthritis is an inflammatory autoimmune disease, characterized by synovial proliferation, destruction to articular cartilage and severe pain. The cannabinoids obtained from Cannabis sativa exhibited their actions via cannabinoid-1 and -2 receptors, which also provides a platform for endocannabinoids to act. The endocannabinoid system comprises endocannabinoid molecules involved in signaling processes, along with G-protein coupled receptors and enzymes associated with ligand biosynthesis, activation and degradation. The action of endocannabinoid system in immune system regulation, via primary CB2 activation, followed by inhibition of production of pro-inflammatory cytokines, auto-antibodies and MMPs, FLSs proliferation and T-cell mediated immune response, are elaborated as potential therapeutic regimes in rheumatoid arthritis. The involvement of endocannabinoid system in immune cells like, B cells, T cells and macrophages, as well as regulatory actions on sensory noniceptors to ameliorate pain is significantly highlighted in the review, elaborating the actions of endocannabinoid signaling in mitigating the disease events. The review also focuses on enhancement of endocannabinoid tone, either by inhibiting the degradation enzymes, like FAAH, MAGL, COX, CytP450, LOX, etc. or by retarding cellular uptake processes. Moreover, the review portrays the optimizing role of endocannabinoid system, in abbreviating the symptoms and complications of rheumatoid arthritis in patients and mitigating inflammation, pain and immune mediated effects significantly.

Targeting the endocannabinoid system: a predictive, preventive, and personalized medicine-directed approach to the management of brain pathologies

Cannabis-inspired medical products are garnering increasing attention from the scientific community, general public, and health policy makers. A plethora of scientific literature demonstrates intricate engagement of the endocannabinoid system with human immunology, psychology, developmental processes, neuronal plasticity, signal transduction, and metabolic regulation. Despite the therapeutic potential, the adverse psychoactive effects and historical stigma, cannabinoids have limited widespread clinical application. Therefore, it is plausible to weigh carefully the beneficial effects of cannabinoids against the potential adverse impacts for every individual. This is where the concept of "personalized medicine" as a promising approach for disease prediction and prevention may take into the account. The goal of this review is to provide an outline of the endocannabinoid system, including endocannabinoid metabolizing pathways, and will progress to a more in-depth discussion of the therapeutic interventions by endocannabinoids in various neurological disorders.

Dose-Dependent Cannabidiol-Induced Elevation of Intracellular Calcium and Apoptosis in Human Articular Chondrocytes

Cannabidiol (CBD) is the most abundant non-psychoactive compound of Cannabis sativa extracts. Cannabinoids have been shown to exhibit anti-inflammatory, analgesic, antioxidant, neuroprotective, and anti-tumorigenic effects. In the present study, we investigated the effects of CBD on human articular chondrocytes. Cell viability was determined by Resazurin assays. Apoptosis was analyzed by annexin-V/7-actinomycin D (7-AAD) staining followed by flow cytometry. Caspase 3/7 activity was measured with caspase assays. Intracellular Ca²⁺ ([Ca²⁺ ]_i ) was monitored by time-lapse fluorescence imaging. The perforated whole-cell patch-clamp technique was used for measuring the cell membrane potential. Erk1/2 phosphorylation was assessed by western blot analysis. The chondrocyte cell line C28/I2 and primary chondrocytes showed a reduced viability after treatment with concentrations of CBD greater than 4 µM. This apoptotic effect was accompanied by an increase of caspase 3/7 activity and an increase in the early apoptotic cell population. CBD elevated [Ca²⁺ ]_i , which was accompanied by depolarization of the cell membrane potential. The increase of [Ca²⁺ ]_i was abrogated, when Ca²⁺ was omitted from the bath solution, indicating an influx of extracellular Ca²⁺ . The cannabinoid receptor 1 (CB1) antagonist AM251 inhibited the Ca²⁺ influx triggered by CBD. Preincubation with AM251 reduced the toxic effects of CBD. By looking for mediators of the apoptotic CBD effect downstream of the CB1 receptor, enhanced Erk1/2 phosphorylation could be detected after CBD treatment. However, this Erk1/2 activation proved to be unaffected by CB1 receptor blockage. The present study demonstrates that CBD promotes apoptosis and [Ca²⁺ ]_i elevation in human articular chondrocytes via a CB1-receptor-mediated mechanism. © 2019 The Authors. Journal of Orthopaedic Research^® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society J Orthop Res 37:2540-2549, 2019.

A selective CB2 agonist protects against the inflammatory response and joint destruction in collagen-induced arthritis mice

Rheumatoid arthritis (RA) is a chronic, inflammatory, synovitis-dominated systemic disease with unknown etiology. RA is characterized by the involvement of multiple affected joints, symmetry, and invasive arthritis of the limbs, which can lead to joint deformity, cartilage destruction, and loss of function. Cannabinoid receptor 2 (CB₂) has potent immunomodulatory and anti-inflammatory effects and is predominantly expressed in non-neuronal tissues. In the current study, the role of CB₂ in the process of inflammatory bone erosion in RA was examined. The selective agonist or high-affinity ligand of CB₂ (4-quinolone-3-carboxamides CB2 agonist, 4Q3C CB₂ agonist, 4Q3C) significantly reduced the severity of arthritis, decreased histopathological findings, and markedly reduced bone erosion in collagen-induced arthritis (CIA) mice. In addition, 4Q3C prevented an increase in the nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG) ratio and inhibited the formation of osteoclasts in CIA mice. Furthermore, the expression of tumor necrosis factor-alpha, interleukin-1β, cyclooxygenase-2, and inducible nitric oxide synthase was lower in 4Q3C-treated CIA mice than in control CIA mice. Micro-computed tomography corroborated the finding that 4Q3C reduced joint destruction. These data clearly indicate that the CB₂-selective agonist, 4Q3C, may have anti-inflammatory and anti-osteoclastogenesis effects in RA and may be considered to be a novel treatment for RA.

Electroacupuncture potentiates peripheral CB2 receptor-inhibited chronic pain in a mouse model of knee osteoarthritis

Purpose

Knee osteoarthritis (KOA) is a highly prevalent, chronic joint disorder, with chronic pain as its typical symptom. Although studies have shown that an activated peripheral CB2 receptor can reduce acute pain, whether the CB2 receptor is involved in electroacupuncture (EA) inhibiting chronic pain and the involved mechanism remains unclear. The aim of this study was to investigate whether EA may strengthen peripheral CB2 receptor-inhibited chronic pain in a mouse model of KOA.

Materials and methods:

KOA was induced by intra-articular injection of monosodium iodoacetate (MIA) into the left knee joint of mice. Thermal hyperalgesia was tested with the hot plate test, and mechanical allodynia was quantified using von Frey filaments. The expression of CB2 receptor and IL-1β were quantified by using immunofluorescence labeling.

Results

EA treatment at 2 Hz+1 mA significantly increased the expression of CB2 receptor in fibroblasts and decreased the expression of IL-1β in the menisci compared with that in the KOA group. However, EA had no effect on the expression of IL-1β in CB2^−/− mice. At 2 Hz+1 mA, EA significantly increased mechanical threshold, thermal latency, and weight borne after KOA modeling. However, knockout of the CB2 receptor blocked these effects of EA. After 2 Hz+1 mA treatment, EA significantly reduced the Osteoarthritis Research Society International (OARSI) score after KOA modeling. However, EA had no significant effect on the OARSI score in CB2^−/− mice.

Conclusion

EA reduced the expression of IL-1β by activating the CB2 receptor, thus inhibiting the chronic pain in the mouse model of KOA.

Cannabinoid WIN-55,212-2 mesylate inhibits tumor necrosis factor-α-induced expression of nitric oxide synthase in dorsal root ganglion neurons

Tumor necrosis factor-α (TNF-α) is an established pain modulator in the peripheral nervous system. Elevated levels of TNF-α in dorsal root ganglion (DRG) neurons reportedly is critical for neuropathic pain processing. It has been shown that the production of nitric oxide, a key player in the development and maintenance of nociception, depends on the expression of nitric oxide synthases (NOSs) and their activities. Accumulating evidence also supports an important role of cannabinoids in modulating neuropathic pain. In this study, we explored the effects and the underlying mechanisms of crosstalk between TNF-α and cannabinoid on the expression/activity of NOS in DRG neurons. With or without knockdown of p38 mitogen-activated protein kinase (MAPK), DRG neurons were treated with TNF-α in the presence or absence of synthetic cannabinoid WIN-55,212-2 mesylate (WIN-55) and selective cannabinoid receptor (CB) antagonists. TNF-α significantly increased the NOS activity as well as the mRNA stability and expression of neuronal NOS (nNOS) in DRG neurons; this was abolished by inhibiting p38 MAPK signaling. WIN-55 inhibited TNF-α-induced p38 MAPK activity as well as TNF-α-induced increase of mRNA stability and expression/activity of nNOS; the inhibitory effect of WIN-55 was blocked by a selective CB2 antagonist. Our findings suggest that TNF-α induces the expression/activity of nNOS in DRG neurons by increasing its mRNA stability by a p38 MAPK-dependent mechanism; WIN-55 inhibits this effect of TNF-α by inhibiting p38 MAPK via CB2. By linking the functions of TNF-α, NOS and cannabinoid in DRG neurons, this study adds new insights into the molecular mechanisms underlying the pharmacologic effects of cannabinoids on neuropathic pain as well as into the pathophysiology of neuropathic pain.

Joint problems arising from lack of repair mechanisms: can cannabinoids help?

Osteoarthritis (OA) is the most common disease of joints, which are complex organs where cartilage, bone and synovium cooperate to allow a range of movements. During progression of the disease, the function of all three main components is jeopardized. Nevertheless, the involvement of each tissue in OA development is still not established and is the topic of the present review. The OA therapies available are symptomatic, largely targeting pain management rather than disease progression. The strong need to develop a treatment for cartilage degeneration, bone deformation and synovial inflammation has led to research on the involvement of the endocannabinoid system in the development of OA. The current review discusses the research on this topic to date and notes the advantages of exploiting endocannabinoid system modulation for cartilage, bone and synovium homeostasis, which could prevent the further progression of OA. LINKED ARTICLES: This article is part of a themed section on 8^th European Workshop on Cannabinoid Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.10/issuetoc.

Activation of the cannabinoid receptor 1 by ACEA suppresses senescence in human primary chondrocytes through sirt1 activation

Senescence of chondrocytes and cartilage degeneration induced by the proinflammatory cytokine interleukin-1β is associated with the pathogenesis of osteoarthritis. The cannabinoid receptor 1 has been involved in the pathological development of various diseases. Here, we evaluated whether activation of cannabinoid receptor 1 using its selective agonist arachidonyl-2-chloroethylamide had an influence on cellular senescence induced by interleukin-1βin human chondrocytes. Our findings demonstrate that agonist arachidonyl-2-chloroethylamidedecreased senescence-associated β-galactosidase activity and cell cycle arrest in the G0/G1 phase induced by interleukin-1β. Importantly, our results display interleukin-1βtreatment significantly increased the expressions of senescence genes (caveolin-1, PAI-1 and p21), which were prevented by agonist arachidonyl-2-chloroethylamide treatment. However, it was noticed that these functions of agonist arachidonyl-2-chloroethylamide were abolished by the cannabinoid receptor 1 selective antagonist AM251, suggesting the involvement of cannabinoid receptor 1. Also, our results indicate that agonist arachidonyl-2-chloroethylamide enhanced the expression of sirt1. These findings suggest that activation of cannabinoid receptor 1 by agonist arachidonyl-2-chloroethylamide might have a protective effect against pro-inflammatory cytokines such as interleukin-1β-induced chondrocytes senescence in osteoarthritis patients. Impact statement Senescence of chondrocytes and cartilage degeneration induced by the proinflammatory cytokine interleukin-1β (IL-1β) are associated with the pathogenesis of osteoarthritis (OA). Here we found that: (a) the CB1 agonist ACEA abolished IL-1β-induced senescence and cell arrest in chondrocytes; (b) the CB1 agonist ACEA also abolished IL-1β-induced expression of caveolin-1, PAI-1, and p21;

Inhibition of interleukin-1β-induced endothelial tissue factor expression by the synthetic cannabinoid WIN 55,212-2

The role of cannabinoids in thrombosis remains controversial. In view of the primary importance of tissue factor (TF) in blood coagulation and its involvement in the pathology of several cardiovascular, inflammatory and neoplastic diseases, a regulation of this initial procoagulant signal seems to be of particular interest. Using human umbilical vein endothelial cells (HUVEC) the present study investigated the impact of the synthetic cannabinoid WIN 55,212-2 on interleukin (IL)-1β-induced TF expression and activity. WIN 55,212-2 caused a time- and concentration-dependent suppression of IL-1β-induced TF protein accompanied by decreases in TF mRNA and activity. Inhibition of TF protein expression by WIN 55,212-2 was mimicked by its cannabinoid receptor-inactive enantiomer WIN 55,212-3 but not by structurally unrelated phyto-, endo- and synthetic cannabinoids. In addition, the inhibitory effect of WIN 55,212-2 was not reversed by antagonists to cannabinoid receptors (CB₁, CB₂) or transient receptor potential vanilloid 1. Mechanistic approaches revealed WIN 55,212-2 to suppress IL-1β-induced TF expression via inhibition of ceramide formation and via decreased phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinases. Further inhibitor experiments demonstrated neutral sphingomyelinase (nSMase) to confer ceramide generation upon IL-1β treatment with the parallel IL-1β-mediated activation of MAPKs occurring via an nSMase-independent pathway. Finally, a receptor-independent inhibition of IL-1β-induced TF protein by WIN 55,212-2 was confirmed in human blood monocytes. Collectively, this data provide a hitherto unknown receptor-independent anticoagulatory action of the cannabinoid WIN 55,212-2.

The Endogenous Cannabinoid System: A Budding Source of Targets for Treating Inflammatory and Neuropathic Pain

A great need exists for the development of new medications to treat pain resulting from various disease states and types of injury. Given that the endogenous cannabinoid (that is, endocannabinoid) system modulates neuronal and immune cell function, both of which play key roles in pain, therapeutics targeting this system hold promise as novel analgesics. Potential therapeutic targets include the cannabinoid receptors, type 1 and 2, as well as biosynthetic and catabolic enzymes of the endocannabinoids N-arachidonoylethanolamine and 2-arachidonoylglycerol. Notably, cannabinoid receptor agonists as well as inhibitors of endocannabinoid-regulating enzymes fatty acid amide hydrolase and monoacylglycerol lipase produce reliable antinociceptive effects, and offer opioid-sparing antinociceptive effects in myriad preclinical inflammatory and neuropathic pain models. Emerging clinical studies show that 'medicinal' cannabis or cannabinoid-based medications relieve pain in human diseases such as cancer, multiple sclerosis, and fibromyalgia. However, clinical data have yet to demonstrate the analgesic efficacy of inhibitors of endocannabinoid-regulating enzymes. Likewise, the question of whether pharmacotherapies aimed at the endocannabinoid system promote opioid-sparing effects in the treatment of pain reflects an important area of research. Here we examine the preclinical and clinical evidence of various endocannabinoid system targets as potential therapeutic strategies for inflammatory and neuropathic pain conditions.

Characterization of endocannabinoids and related acylethanolamides in the synovial fluid of dogs with osteoarthritis: a pilot study

Background

Cannabis-based drugs have been shown to be effective in inflammatory diseases. A number of endocannabinoids including N- arachidonoylethanolamide (anandamide, AEA) and 2-arachidonyl glycerol (2-AG) with activity at the cannabinoid receptors (CBR) CBR1 and CBR2, have been identified. Other structurally related endogenous fatty acid compounds such as oleoylethanolamide (OEA) and palmitoyl ethanolamide (PEA) have been identified in biological tissues. These compounds do not bind to CBR but might be involved in facilitating the actions of directly acting endocannabinoids and thus are commonly termed “entourage” compounds due to their ability to modulate the endocannabinoid system. The aim of this study was to evaluate the presence of endocannabinoids and entourage compounds in the synovial fluid of dogs with osteoarthritis subjected to arthrotomy of the knee joint. Cytokines and cytology were studied as well.

Results

AEA, 2-AG, OEA and PEA were all present in the synovial fluid of arthritic knees and in the contralateral joints; in addition, a significant increase of OEA and 2AG levels were noted in SF from OA knees when compared to the contralateral joints.

Conclusion

The identification and quantification of endocannabinoids and entourage compounds levels in synovial fluids from dogs with OA of the knee is reported for the first time. Our data are instrumental for future studies involving a greater number of dogs. Cannabinoids represent an emerging and innovative pharmacological tool for the treatment of OA and further studies are warranted to evaluate the effectiveness of cannabinoids in veterinary medicine.

Expression of matrix metalloproteinases and components of the endocannabinoid system in the knee joint are associated with biphasic pain progression in a rat model of osteoarthritis

Matrix metalloproteinases (MMPs) are considered important in articular cartilage breakdown during osteoarthritis (OA). Similarly, the endocannabinoid system (ECS) is implicated in joint function and modulation of nociceptive processing. Functional interplay between ECS and MMPs has been recently indicated. Here, we tested if changes in the expression of selected MMPs and major ECS elements temporally correlate with the intensity of OA-related pain. Knee OA was induced in male Wistar rats by intra-articular sodium monoiodoacetate injection. OA-like pain behavior was tested using the dynamic weight bearing. Joint tissue samples at different time points after OA induction were subjected to gene (quantitative polymerase chain reaction) and protein (Western blot) expression analyses. Monoiodoacetate-induced nocifensive responses in rats showed a biphasic progression pattern. The alterations in expression of selected MMPs elegantly corresponded to the two-stage development of OA pain. The most substantial changes in the expression of the ECS system were revealed at a later stage of OA progression. Alterations within ECS are involved in the process of adaptation to persistent painful stimuli. The accumulation of MMPs in osteoarthritic cartilage may have a role in the biphasic progression of OA-related pain. Temporal association of changes in ECS and MMPs expression shows a potential therapeutic approach that utilizes the concept of combining indirect ECS-mediated MMP inhibition and ECS modulation of pain transduction.

Immunohistochemistry detected and localized cannabinoid receptor type 2 in bovine fetal pancreas at late gestation

At present, data on the endocannabinoid system expression and distribution in the pancreatic gland appear scarce and controversial as descriptions are limited to humans and laboratory animals. Since the bovine pancreas is very similar to the human in endocrine portion development and control, studies on the fetal gland could prove to be very interesting, as an abnormal maternal condition during late pregnancy may be a predisposing trigger for adult metabolic disorders. The present investigation studied cannabinoid receptor type 2 presence and distribution in the bovine fetal pancreas towards the end of gestation. Histological analyses revealed numerous endocrinal cell clusters or islets which were distributed among exocrine adenomeri in connectival tissue. Immunohistochemistry showed that endocrine-islets contained some CB2-positive cells with a very peculiar localization that is a few primarily localized at the edges of islets and some of them also scattered in the center of the cluster. Characteristically, also the epithelium of the excretory ducts and the smooth muscle layers of the smaller arteries, in the interlobular glandular septa, tested positive for the CB2 endocannabinoid receptor. Consequently, the endocannabinoid system, via the cannabinoid receptor type 2, was hypothesized to play a major role in controlling pancreas function from normal fetal development to correct metabolic functioning in adulthood.

Cannabinoid WIN‑55,212‑2 mesylate inhibits ADAMTS‑4 activity in human osteoarthritic articular chondrocytes by inhibiting expression of syndecan‑1

A central feature of osteoarthritis (OA) is the loss of articular cartilage, which is primarily attributed to cartilage breakdown. A group of metalloproteinases termed the A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) family are reported to be important in cartilage breakdown. Recent studies have suggested that ADAMTS-4 is a major contributor to the pathogenesis of OA and that syndecan-1 is closely associated with activation of ADAMTS-4 in human chondrocytes. Accumulating evidence also suggests that cannabinoids have chondroprotective effects. The current study explored the effects of synthetic cannabinoid WIN-55,212-2 mesylate (WIN-55) on the expression of syndecan-1 and ADAMTS-4, as well as ADAMTS-4 activity, in unstimulated and interleukin (IL)-1β-stimulated OA chondrocytes. Primary human OA articular chondrocytes were treated with WIN-55 in the presence or absence of IL-1β and cannabinoid receptor antagonists. The results of the present study demonstrated that WIN-55 inhibited ADAMTS-4 activity in unstimulated and IL-1β-stimulated primary human OA articular chondrocytes in a concentration-dependent manner. Cannabinoid receptor type 1 (CB1) and 2 (CB2) were constitutively expressed in human OA articular chondrocytes. Furthermore, selective CB2 antagonist, JTE907, but not selective CB1 antagonist, MJ15, abolished the inhibitory effect of WIN-55 on ADAMTS-4 activity. WIN55 inhibited the expression of syndecan-1 but not ADAMTS-4, and overexpression of syndecan-1 reversed the inhibitory effect of WIN-55 on the ADAMTS-4 activity in unstimulated and IL-1β-stimulated human OA articular chondrocytes. Despite having no significant effect on syndecan-1 gene promoter activity, WIN-55 markedly decreased the stability of syndecan-1 mRNA via CB2. In conclusion, to the best of our knowledge, the present study provides the first in vitro evidence supporting that the synthetic cannabinoid WIN-55 inhibits ADAMTS-4 activity in unstimulated and IL-1β-stimulated human OA articular chondrocytes by decreasing the mRNA stability/expression of syndecan-1 via CB2. This suggests a novel mechanism by which cannabinoids may prevent cartilage breakdown in OA. In addition, it also provides novel insights into the pharmacological effects of synthetic cannabinoids on OA.

Expression of Cannabinoid Receptors in Human Osteoarthritic Cartilage: Implications for Future Therapies

Introduction: Cannabinoids have shown to reduce joint damage in animal models of arthritis and reduce matrix metalloproteinase expression in primary human osteoarthritic (OA) chondrocytes. The actions of cannabinoids are mediated by a number of receptors, including cannabinoid receptors 1 and 2 (CB1 and CB2), G-protein-coupled receptors 55 and 18 (GPR55 and GPR18), transient receptor potential vanilloid-1 (TRPV1), and peroxisome proliferator-activated receptors alpha and gamma (PPARα and PPARγ). However, to date very few studies have investigated the expression and localization of these receptors in human chondrocytes, and expression during degeneration, and thus their potential in clinical applications is unknown. Methods: Human articular cartilage from patients with symptomatic OA was graded histologically and the expression and localization of cannabinoid receptors within OA cartilage and underlying bone were determined immunohistochemically. Expression levels across regions of cartilage and changes with degeneration were investigated. Results: Expression of all the cannabinoid receptors investigated was observed with no change with grade of degeneration seen in the expression of CB1, CB2, GPR55, PPARα, and PPARγ. Conversely, the number of chondrocytes within the deep zone of cartilage displaying immunopositivity for GPR18 and TRPV1 was significantly decreased in degenerate cartilage. Receptor expression was higher in chondrocytes than in osteocytes in the underlying bone. Conclusions: Chondrocytes from OA joints were shown to express a wide range of cannabinoid receptors even in degenerate tissues, demonstrating that these cells could respond to cannabinoids. Cannabinoids designed to bind to receptors inhibiting the catabolic and pain pathways within the arthritic joint, while avoiding psychoactive effects, could provide potential arthritis therapies.

The type 2 cannabinoid receptor regulates susceptibility to osteoarthritis in mice

OBJECTIVE

Cannabinoid receptors and their ligands have been implicated in the regulation of various physiological processes but their role in osteoarthritis has not been investigated. The aim of this study was to evaluate the role of the type 2 cannabinoid receptor (Cnr2) in regulating susceptibility to osteoarthritis in mice.

METHODS

We analysed the severity of knee osteoarthritis as assessed by the Osteoarthritis Research Society International (OARSI) scoring system in mice with targeted deletion of Cnr2 (Cnr2(-/-)) and wild type (WT) littermates. Studies were conducted in mice subjected to surgical destabilisation of the medial meniscus (DMM) and in those with spontaneous age-related osteoarthritis (OA).

RESULTS

Osteoarthritis was more severe following DMM in the medial compartment of the knee in Cnr2(-/-) compared with WT mice (mean ± sem score = 4.9 ± 0.5 vs 3.6 ± 0.3; P = 0.017). Treatment of WT mice with the CB2-selective agonist HU308 following DMM reduced the severity of OA in the whole joint (HU308 = 8.4 ± 0.2 vs vehicle = 10.4 ± 0.6; P = 0.007). Spontaneous age related osteoarthritis was also more severe in the medial compartment of the knee in 12-month old Cnr2(-/-) mice compared with WT (5.6 ± 0.5 vs 3.5 ± 0.3, P = 0.008). Cultured articular chondrocytes from Cnr2(-/-) mice produced less proteoglycans in vitro than wild type chondrocytes.

CONCLUSION

These studies demonstrate that the Cnr2 pathway plays a role in the pathophysiology of osteoarthritis in mice and shows that pharmacological activation of CB2 has a protective effect. Further studies of the role of cannabinoid receptors in the pathogenesis of osteoarthritis in man are warranted.

The endocannabinoid system and its therapeutic implications in rheumatoid arthritis

Since the discovery of the endogenous receptor for Δ(9)-tetrahydrocannabinol, a main constituent of marijuana, the endocannabinoid system (comprising cannabinoid receptors and their endogenous ligands, as well as the enzymes involved in their metabolic processes) has been implicated as having multiple regulatory functions in many central and peripheral conditions, including rheumatoid arthritis (RA). RA is an immune-mediated inflammatory disease that is associated with the involvement of many kinds of cells (such as fibroblastlike synoviocytes [FLSs], osteoclasts, T cells, B cells, and macrophages) and molecules (such as interleukin-1β, tumor necrosis factor-α, interleukin-6, matrix metalloproteinases [MMPs], and chemokines). Increasing evidence suggests that the endocannabinoid system, especially cannabinoid receptor 2 (CB2), has an important role in the pathophysiology of RA. Many members of the endocannabinoid system are reported to inhibit synovial inflammation, hyperplasia, and cartilage destruction in RA. In particular, specific activation of CB2 may relieve RA by inhibiting not only the production of autoantibodies, proinflammatory cytokines, and MMPs, but also bone erosion, immune response mediated by T cells, and the proliferation of FLSs. In this review, we will discuss the possible functions of the endocannabinoid system in the modulation of RA, which may be a potential target for treatment.

Activation of cannabinoid receptor 2 attenuates synovitis and joint distruction in collagen-induced arthritis

OBJECTIVES

Recent studies have suggested immunomodulatory and anti-inflammatory effects of cannabinoid receptor 2 (CB2R) activation, which is devoid of psychoactivity. We have demonstrated the expression of CB2R in synovial tissue from patients with rheumatoid arthritis (RA), and its specific activation shows inhibitory effects on fibroblast-like synoviocytes. However, it is still unclear whether selective activation of CB2R inhibits joint inflammation or protects joint damage in RA.

METHODS

A murine model of collagen-induced arthritis (CIA) was used to evaluate the therapeutic efficacy of HU-308, a selective CB2R agonist. The disease severity was evaluated by semi-quantitative scoring of joint swelling, histological assessment of joint inflammation and structure, and radiographic assessment of joint destruction by using digital plain radiographs and micro-CT scans. The concentrations of various isotypes of anti-collagen II antibodies in sera and the levels of cytokines in culture supernatants were determined by ELISA.

RESULTS

Compared with vehicle treatment, protective treatment with intraperitoneal injection of HU-308 (0.3-1.0 mg/kg) failed to decrease the incidence of the development of CIA, but it effectively suppressed the severity of the disease. In CIA mice, treatment with HU-308 significantly decreased joint swelling, synovial inflammation, and joint destruction, as well as serum levels of anti-collagen II antibodies. In vitro, HU-308 (1-10 μM) significantly suppressed the production of proinflammatory cytokines IL-6 and TNF-α from lipopolysaccharide-stimulated murine peritoneal macrophages with intact CB2R in dose-dependent manners. HU-308 failed to elicit any inhibitory effect of on lipopolysaccharide-stimulated macrophages from CB2R-knockout mice.

CONCLUSIONS

Activation of CB2R by HU-308 has therapeutic potential for RA to suppress synovitis and alleviate joint destruction by inhibiting the production of autoantibodies and proinflammatory cytokines.

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.

Expression of cannabinoid receptor 2 and its inhibitory effects on synovial fibroblasts in rheumatoid arthritis

OBJECTIVE

Recent studies have suggested immunomodulatory and anti-inflammatory effects of cannabinoid receptor 2 (CB2R) activation, which shows no psychoactivity. However, it is still unclear whether CB2R is expressed in fibroblast-like synoviocytes (FLS) of RA. In this study we investigated whether CB2R is expressed in FLS of RA, and whether CB2R activation modulates the function of RA-FLS.

METHODS

Expression of CB2R in synovial tissue and FLS was studied by immunohistochemistry, western blotting and RT-PCR. mRNA expression levels of CB2R, IL-6 and MMPs were analysed by quantitative real-time RT-PCR. The protein concentrations of IL-6 and MMPs in culture supernatants were determined by ELISA. The protein levels of signal transducing molecules were assayed by western blotting.

RESULTS

Both mRNA and protein expression of CB2R were found in synovial tissue and cultured FLS with slightly higher levels in RA patients than in OA patients. In cultured RA-FLS, the expression level of CB2R was up-regulated by stimulation with IL-1β, TNF-α or lipopolysaccharide. In vitro, HU-308, a selective CB2R agonist, inhibited IL-1β-induced proliferation of RA-FLS as well as IL-1β-induced production of MMP-3, MMP-13 and IL-6 in RA-FLS in a dose-dependent manner. HU-308 also suppressed IL-1β-induced activation of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase in FLS.

CONCLUSION

In RA-FLS, proinflammatory mediators up-regulate the expression of CB2R, which negatively regulates the production of proinflammatory cytokines and MMPs. These data suggest that CB2R may be a potential therapeutic target of RA.

Cannabinoid WIN-55,212-2 mesylate inhibits interleukin-1β induced matrix metalloproteinase and tissue inhibitor of matrix metalloproteinase expression in human chondrocytes

OBJECTIVE

Interleukin-1β (IL-1β) is involved in the up-regulation of matrix metalloproteinases (MMPs) leading to cartilage degradation. Cannabinoids are anti-inflammatory and reduce joint damage in animal models of arthritis. This study aimed to determine a mechanism whereby the synthetic cannabinoid WIN-55,212-2 mesylate (WIN-55) may inhibit cartilage degradation.

METHODS

Effects of WIN-55 were studied on IL-1β stimulated production of MMP-3 and -13 and their inhibitors TIMP-1 and -2 in human chondrocytes. Chondrocytes were obtained from articular cartilage of patients undergoing total knee replacement. Chondrocytes were grown in monolayer and 3D alginate bead cultures. Real-time polymerase chain reaction (PCR) was used to determine the gene expression of MMP-3, -13, TIMP-1 and -2 and Enzyme Linked Immunosorbent Assay (ELISA) to measure the amount of MMP-3 and MMP-13 protein released into media. Immunocytochemistry was used to investigate the expression of cannabinoid receptors in chondrocyte cultures.

RESULTS

Treatment with WIN-55 alone or in combination with IL-1β, decreased or abolished MMP-3, -13, TIMP-1 and -2 gene expression in human chondrocyte monolayer and alginate bead cultures in both a concentration and time dependent manner. WIN-55 treatment alone, and in combination with IL-1β, reduced MMP-3 and -13 protein production by chondrocytes cultured in alginate beads. Immunocytochemistry demonstrated the expression of cannabinoid receptors in chondrocyte cultures.

CONCLUSION

Cannabinoid WIN-55 can reduce both basal and IL-1β stimulated gene and protein expression of MMP-3 and -13. However WIN-55 also decreased basal levels of TIMP-1 and -2 mRNA. These actions of WIN-55 suggest a mechanism by which cannabinoids may act to prevent cartilage breakdown in arthritis.

Cannabinoid receptor 2 activation: a means to prevent monocyte-endothelium engagement

This Commentary highlights the article by Rom et al which shows that selective cannabinoid receptor 2 activation in leukocytes decreases key steps in monocyte-blood brain barrier engagement suppressing inflammatory leukocyte responses and preventing neuroinflammation.

Cannabinoids: novel therapies for arthritis?

A key feature of osteoarthritis and rheumatoid arthritis is the loss of articular cartilage. Cartilage breakdown is mediated by complex interactions of proinflammatory cytokines, such as IL-1, inflammatory mediators, including nitric oxide and prostaglandin E2, and proteases, including matrix metalloproteinases and aggrecanases, such as ADAMTS-4 and -5. Cannabinoids have been shown to reduce joint damage in animal models of arthritis. They have also been shown to prevent IL-1-induced matrix breakdown of collagen and proteoglycan, indicating that cannabinoids may mediate chondroprotective effects. Cannabinoids produce their effects via several cannabinoid receptors and it is important to identify the key cannabinoids and their receptors that are involved in chondroprotection. This review aims to outline the current and future prospects of cannabinoids as anti-arthritic therapeutics, in terms of their ability to prevent cartilage breakdown.

Tissue Engineering of Cartilage; Can Cannabinoids Help?

This review discusses the role of the cannabinoid system in cartilage tissue and endeavors to establish if targeting the cannabinoid system has potential in mesenchymal stem cell based tissue-engineered cartilage repair strategies. The review discusses the potential of cannabinoids to protect against the degradation of cartilage in inflamed arthritic joints and the influence of cannabinoids on the chondrocyte precursors, mesenchymal stem cells (MSCs). We provide experimental evidence to show that activation of the cannabinoid system enhances the survival, migration and chondrogenic differentiation of MSCs, which are three major tenets behind the success of a cell-based tissue-engineered cartilage repair strategy. These findings highlight the potential for cannabinoids to provide a dual function by acting as anti-inflammatory agents as well as regulators of MSC biology in order to enhance tissue engineering strategies aimed at cartilage repair.

Inhibition of cyclooxygenase 2 expression by diallyl sulfide on joint inflammation induced by urate crystal and IL-1beta

OBJECTIVE

Investigation of the effects of diallyl sulfide (DAS), a garlic sulfur compound, on joint tissue inflammatory responses induced by monosodium urate (MSU) crystals and interleukin-1beta (IL-1beta).

DESIGN

The HIG-82 synovial cell line was used to establish the experimental model and DAS regime. Primary cultures of articular chondrocytes and synovial fibroblasts obtained from patients undergoing joint replacement for osteoarthritis were used in experimental studies. Cyclooxygenase (COX) expression following MSU crystal and IL-1beta stimulation with/without DAS co-incubation was assessed by reverse transcription-polymerase chain reaction (RT-PCR), western blotting, and immunocytochemistry and nuclear factor-kappa B (NF-kappaB) activation determined by electrophoretic mobility shift assay. Prostaglandin E2 (PGE(2)) production was measured by enzyme-linked immunosorbent assay (ELISA). DAS effects on COX gene expression in an MSU crystal-induced acute arthritis in rats were assessed by RT-PCR.

RESULTS

MSU crystals upregulated COX-2 expression in HIG-82 cells and this was inhibited by co-incubation with DAS. DAS inhibited MSU crystal and IL-1beta induced elevation of COX-2 expression in primary synovial cells and chondrocytes. Production of PGE(2) induced by crystals was suppressed by DAS and celecoxib. MSU crystals had no effect on expression of COX-1 in synovial cells. NF-kappaB was activated by MSU crystals and this was blocked by DAS. Increased expression of COX-2 in synovium following intraarticular injection of MSU crystals in a rat model was inhibited by co-administration of DAS.

CONCLUSIONS

DAS prevents IL-1beta and MSU crystal induced COX-2 upregulation in synovial cells and chondrocytes and ameliorates crystal induced synovitis potentially through a mechanism involving NF-kappaB. Anti-inflammatory actions of DAS may be of value in treatment of joint inflammation.

Local administration of WIN 55,212-2 reduces chronic granuloma-associated angiogenesis in rat by inhibiting NF-κB activation

Chronic inflammation is often associated with granuloma formation that is a hallmark of many human diseases. The transcription factor nuclear factor-kappa B (NF-kappaB) plays a central role in this process by regulating the expression of several pro-inflammatory genes. Cannabinoids (CBs) from Cannabis sativa L. exert a large number of biological effects including anti-inflammatory and anti-angiogenic effects. In this study, we investigated the role of CBs on granuloma formation induced by lambda-carrageenin-soaked sponge implant in rat. Our results show that local administration of WIN 55,212-2, a CB(1)/CB(2) agonist, given daily or at time of implantation significantly decreased weight and neo-angiogenesis in granuloma tissue and inhibited nuclear factor-kappa B (NF-kappaB)/DNA binding that was associated with a reduced inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2), tumor necrosis factor alpha (TNF-alpha), and vascular endothelial growth factor (VEGF) messenger RNA (mRNA) and protein expression. Also, arachidonyl-2-chloroethylamide (ACEA), a CB(1) selective agonist, and JWH-015, a CB(2) selective agonist, exhibited the same effects that were reversed by SR141716-A and SR144528, respectively, CB(1) and CB(2) selective antagonists. These results indicate that CBs given locally may represent a potential therapeutic tool in controlling chronic inflammation avoiding psychotropic effects.

Metalloproteinase and inhibitor expression profiling of resorbing cartilage reveals pro-collagenase activation as a critical step for collagenolysis

Excess proteolysis of the extracellular matrix (ECM) of articular cartilage is a key characteristic of arthritis. The main enzymes involved belong to the metalloproteinase family, specifically the matrix metalloproteinases (MMPs) and a group of proteinases with a disintegrin and metalloproteinase domain with thrombospondin motifs (ADAMTS). Chondrocytes are the only cell type embedded in the cartilage ECM, and cell-matrix interactions can influence gene expression and cell behaviour. Thus, although the use of monolayer cultures can be informative, it is essential to study chondrocytes encapsulated within their native environment, cartilage, to fully assess cellular responses. The aim of this study was to profile the temporal gene expression of metalloproteinases and their endogenous inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), reversion-inducing cysteine-rich protein with Kazal motifs (RECK), and α₂-macroglobulin (α₂M), in actively resorbing cartilage. The addition of the pro-inflammatory cytokine combination of interleukin-1 (IL-1) + oncostatin M (OSM) to bovine nasal cartilage induces the synthesis and subsequent activation of pro-metalloproteinases, leading to cartilage resorption. We show that IL-1+OSM upregulated the expression of MMP-1, -2, -3, -9, 12, -13, -14, TIMP-1, and ADAMTS-4, -5, and -9. Differences in basal expression and the magnitude of induction were observed, whilst there was no significant modulation of TIMP-2, -3, RECK, or ADAMTS-15 gene expression. IL-1+OSM downregulated MMP-16,TIMP-4, and α₂M expression. All IL-1+OSM-induced metalloproteinases showed marked upregulation early in the culture period, whilst inhibitor expression was reduced throughout the stimulation period such that metalloproteinase production would be in excess of inhibitors. Moreover, although pro-collagenases were upregulated and synthesized early (by day 5), collagenolysis became apparent later with the presence of active collagenases (day 10) when inhibitor levels were low. These findings indicate that the activation cascades for pro-collagenases are delayed relative to collagenase expression, further confirm the coordinated regulation of metalloproteinases in actively resorbing cartilage, and support the use of bovine nasal cartilage as a model system to study the mechanisms that promote cartilage degradation.

Arthritis and pain. Future targets to control osteoarthritis pain

Clinical presentation of osteoarthritis (OA) is dominated by pain during joint use and at rest. OA pain is caused by aberrant functioning of a pathologically altered nervous system with key mechanistic drivers from peripheral nerves and central pain pathways. This review focuses on symptomatic pain therapy exemplified by molecular targets that alter sensitization and hyperexcitability of the nervous system, for example, opioids and cannabinoids. We highlight opportunities for targeting inflammatory mediators and their key receptors (for example, prostanoids, kinins, cytokines and chemokines), ion channels (for example, NaV1.8, NaV1.7 and CaV2.2) and neurotrophins (for example, nerve growth factor), noting evidence that relates to their participation in OA etiology and treatment. Future neurological treatments of pain appear optimistic but will require the systematic evaluation of emerging opportunities.

The endocannabinoid system as an emerging target of pharmacotherapy

The recent identification of cannabinoid receptors and their endogenous lipid ligands has triggered an exponential growth of studies exploring the endocannabinoid system and its regulatory functions in health and disease. Such studies have been greatly facilitated by the introduction of selective cannabinoid receptor antagonists and inhibitors of endocannabinoid metabolism and transport, as well as mice deficient in cannabinoid receptors or the endocannabinoid-degrading enzyme fatty acid amidohydrolase. In the past decade, the endocannabinoid system has been implicated in a growing number of physiological functions, both in the central and peripheral nervous systems and in peripheral organs. More importantly, modulating the activity of the endocannabinoid system turned out to hold therapeutic promise in a wide range of disparate diseases and pathological conditions, ranging from mood and anxiety disorders, movement disorders such as Parkinson's and Huntington's disease, neuropathic pain, multiple sclerosis and spinal cord injury, to cancer, atherosclerosis, myocardial infarction, stroke, hypertension, glaucoma, obesity/metabolic syndrome, and osteoporosis, to name just a few. An impediment to the development of cannabinoid medications has been the socially unacceptable psychoactive properties of plant-derived or synthetic agonists, mediated by CB(1) receptors. However, this problem does not arise when the therapeutic aim is achieved by treatment with a CB(1) receptor antagonist, such as in obesity, and may also be absent when the action of endocannabinoids is enhanced indirectly through blocking their metabolism or transport. The use of selective CB(2) receptor agonists, which lack psychoactive properties, could represent another promising avenue for certain conditions. The abuse potential of plant-derived cannabinoids may also be limited through the use of preparations with controlled composition and the careful selection of dose and route of administration. The growing number of preclinical studies and clinical trials with compounds that modulate the endocannabinoid system will probably result in novel therapeutic approaches in a number of diseases for which current treatments do not fully address the patients' need. Here, we provide a comprehensive overview on the current state of knowledge of the endocannabinoid system as a target of pharmacotherapy.