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Early onset of joint inflammation in the MIA model of OA. a Knee joint diameter was significantly increased on days 1, 3 and 10 compared with saline control. b Joint blood flow increased on day 1, but subsequently was not significantly different from control joints. c Leukocyte rolling was augmented on day 1 and then returned to control levels thereafter. d Leukocyte adherence within synovial post-capillary venules was significantly increased on day 1, but gradually returned to control over the succeeding days. ****P < 0.0001, *P < 0.05 two-way ANOVA with Bonferroni post-hoc test; n = 4–28. Data presented as mean ± SEM. i.artic. intra-articular, MIA monoiodoacetate
Source publication
Abstract Background The endocannabinoid system has been shown to reduce inflammatory flares and pain in rodent models of arthritis. A limitation of endocannabinoids is that they are rapidly denatured by hydrolysing enzymes such as fatty acid amide hydrolase (FAAH) which renders them physiologically inert. Osteoarthritis (OA) is primarily a degenera...
Citations
... It has become more evident that also inflammation contributes to pain in OA 33,34 . We therefore evaluated the efficacy of CXB-PEAMs in the PGPS rat model, a model characterized by severe flares of inflammation. ...
Objective
Drug delivery platforms that allow for gradual drug release after intra-articular administration have become of much interest as a treatment strategy for OA. The aim of this study was to investigate the safety and efficacy of an intra-articular sustained release formulation containing celecoxib (CXB), a COX-2 selective inhibitor.
Methods
Amino acid-based polyesteramide microspheres (PEAMs), a biodegradable and non-toxic platform, were loaded with CXB and employed in two in vivo models of arthritis: an acute inflammatory arthritis model in rats (n=12), and a randomized controlled study in chronic OA dog patients (n=30). In parallel, the bioactivity of sustained release of CXB was evaluated in monolayer cultures of primary dog chondrocytes under inflammatory conditions.
Results
Sustained release of CXB did not alleviate acute arthritis signs in the rat arthritis model, based on pain measurements and synovitis severity. However, in OA dog patients, sustained release of CXB improved limb function as objective parameter of pain and quality of life based on gait analysis and owner questionnaires. It also decreased pain medication dependency over a 2-month period and caused no adverse effects. Prostaglandin E2 levels, a marker for inflammation, were lower in the synovial fluid of CXB-treated dog OA patients and in CXB-treated cultured dog chondrocytes.
Conclusion
These results show that local sustained release of CXB is less suitable to treat acute inflammation in arthritic joints, while safe and effective in treating pain in chronic OA in dogs.
... Growing attention has focused on the development of FAAH inhibitors as potential therapeutic agents for inflammation, and hypertension [23][24][25][26][27]. Notably, the renal cortex possesses a higher level of FAAH expression than renal medulla [28]. ...
... For example, inhibition of FAAH has been shown to activate Nrf2/ antioxidant signaling [57], reduce the activity of reactive oxygen species (ROS)-generating enzymes [58], and prevent the increase of lipid peroxidation in the membranes of erythrocytes from hypertensive rats [59]. The above evidence suggests that anti-inflammatory properties of enhanced AEA by FAAH inhibition [24][25][26] may be closely related to the antioxidant effects. ...
Although cannabinoid receptors (CB) are recognized as targets for renal fibrosis, the role of endogenous cannabinoid anandamide (AEA) and its primary hydrolytic enzyme, fatty acid amide hydrolase (FAAH), in renal fibrogenesis remains unclear. The present study used a mouse model of post-ischemia-reperfusion renal injury (PIR) to test the hypothesis that FAAH participates in the renal fibrogenesis. Our results demonstrated that PIR showed upregulated expression of FAAH in renal proximal tubules, accompanied with decreased AEA levels in kidneys. Faah knockout mice recovered the reduced AEA levels and ameliorated PIR-triggered increases in blood urea nitrogen, plasma creatinine as well as renal profibrogenic markers and injuries. Correspondingly, a selective FAAH inhibitor, PF-04457845, inhibited the transforming growth factor-beta 1 (TGF-β1)–induced profibrogenic markers in human proximal tubular cell line (HK-2 cells) and mouse primary cultured tubular cells. Knockdown of FAAH by siRNA in HK-2 cells had similar effects as PF-04457845. Tubular cells isolated from Faah−/− mice further validated the protection against TGF-β1–induced damages. The CB 1 or CB2 receptor antagonist and exogenous FAAH metabolite arachidonic acid failed to reverse the protective effects of FAAH inactivation in HK-2 cells. However, a substrate-selective inhibitor of AEA-cyclooxygenase-2 (COX-2) pathway significantly suppressed the anti-profibrogenic actions of FAAH inhibition. Further, AEA-COX-2 metabolite, prostamide E2 exerted anti-fibrogenesis effect. These findings suggest that FAAH activation and the consequent reduction of AEA contribute to the renal fibrogenesis, and that FAAH inhibition protects against fibrogenesis in renal cells independently of CB receptors via the AEA-COX-2 pathway by the recovery of reduced AEA.
... 64 A similar reduction in leukocyte adherence following treatment with URB597 was also demonstrated in the model of MIA-induced knee inflammation. 65 Diabetes Type 1 diabetes (T1D) is an autoimmune disease that involves a loss of insulin-producing b-cells in the pancreas, leading to an inability to maintain glucose regu-lation. Histopathologically, T1D is characterized by immune cell infiltration of pancreatic tissue and associated destruction of pancreatic b cells. ...
Introduction: The endocannabinoid system (ECS) is an endogenous regulatory system involved in a wide range of physiologic and disease processes. Study of ECS regulation provides novel drug targets for disease treatment. Intravital microscopy (IVM), a microscopy-based imaging method that allows the observation of cells and cell-cell interactions within various tissues and organs in vivo, has been utilized to study tissues and cells in their physiologic microenvironment. This article reviews the current state of the IVM techniques used in ECS-related inflammation research. Methodological Aspects of IVM: IVM with focus on conventional fluorescent microscope has been introduced in investigation of microcirculatory function and the behavior of individual circulating cells in an in vivo environment. Experimental setting, tissue protection under physiologic condition, and microscopical observation are described. Application of IVM in Experimental Inflammatory Disorders: Using IVM to investigate the effects of immune modulation by cannabinoids is extensively reviewed. The inflammatory disorders include sepsis, arthritis, diabetes, interstitial cystitis, and inflammatory conditions in the central nervous system and eyes. Conclusion: IVM is a critical tool in cannabinoid and immunology research. It has been applied to investigate the role of the ECS in physiologic and disease processes. This review demonstrates that the IVM technique provides a unique means in understanding ECS regulation on immune responses in diseases under their physical conditions, which could not be achieved by other methods.
... Certain, but not all, echinacea extracts inhibit the Fatty acid amide hydrolase (FAAH) in in vitro assays (Chicca et al., 2009), with both CAD and AKA contributing to activity (Liu et al., 2020). FAAH inhibitors have been reported to effectively reduce pain in rodent models of osteoarthritis by reducing inflammatory flares (McDougall et al., 2017). Furthermore, alkylamides are known to be metabolized by hepatic CYP450 enzymes following oral administration. ...
Historical ethnobotanies of indigenous peoples of the North American prairies reveal treatment of many painful conditions by Echinacea spp. Recent evidence suggests a pharmacological basis for such use as the bioactivity of E. angustifolia and E. purpurea is mediated, in part, through activation of the endocannabinoid system (ECS). Whereas the cannabimimetic effects of individual echinacea products and alkylamides have been described, the activity of crude extracts has not been compared between cannabinoid (CB) receptors or across species or genotypes. Moreover, few studies have explored echinacea’s engagement of the ECS for historic treatments or new therapeutic applications in peripheral inflammatory pain. We hypothesized that 1) the in vitro effects of root extracts on CB receptor internalization would vary with species and phytochemistry, and that echinacea root extracts would reduce inflammatory pain in vivo through activation of the ECS. Root extracts of different E. angustifolia and E. purpurea accessions were prepared, analyzed by HPLC-DAD to quantify caffeic acid derivatives and alkylamides (AKA), and tested for agonist and antagonist activities using receptor redistribution assays. Linear regression of activity relative to phytochemistry identified predictive compounds that were assessed individually in redistribution assays. Extracts were evaluated in the Hargreaves model of chronic inflammatory pain in rats with co-administration of selective CB1/2 antagonists to gauge involvement of the ECS. CB receptor agonist activity varied among accessions of both species with linear regression revealing a significant relationship between CB1 activity and AKA2 for E angustifolia, and AKA 9 + 10 for E purpurea. CB2 activity was positively related with AKA 9 + 10 and total AKAs in E. angustifolia. Four isolated AKA demonstrated agonist activity in the CB2, but not CB1, assay. In the inflammatory pain model, oral administration of either E angustifolia or E. purpurea root extract produced dose-dependent analgesic effects that were partially reversed by co-administration of CB receptor antagonists. This study demonstrates that in vitro effects of crude echinacea root extracts on CB receptors is predicted by phytochemistry. In vivo, echinacea has potential applications for peripheral inflammatory pain such as arthritis and burns, reflecting the traditional uses of Indigenous North Americans.
... Consistent with that, MIA injection in the knee is associated with an increased release of peptides from primary afferent fibres and intrathecal CGRP antagonists can reverse established MIA-induced referred allodynia [31,32]. Neuronal injury secondary to peripheral inflammation in the MIA model is suggested to play a role in pain phenotype [33]. In keeping, with a neuropathic component to human OA pain [34], we show an increased expression of nerve injury marker ATF3, the neuropeptide galanin and CSF1. ...
... ATF3 was chosen as a marker of neuronal injury, as described in MIA-treated rats [35], confirms a neuropathic involvement in the pain [22,36]. Blocking joint inflammation in the early stage of the model prevents joint nerve damage in the latter stage of the disease [33], thus we hypothesise that exacerbation of inflammation in TRPC5 KO mice leads to a more pronounced expression of nerve injury markers. ...
Introduction
Osteo-arthritis (OA) involves joint degradation and usually pain; with mechanisms poorly understood and few treatment options. There is evidence that the transient receptor potential canonical 5 (TRPC5) mRNA expression is reduced in OA patients’ synovia. Here we examine the profile of TRPC5 in DRG and involvement in murine models of OA.
Design
TRPC5 KO mice were subjected to partial meniscectomy (PMNX) or injected with monoiodoacetate (MIA) and pain-related behaviours were determined. Knee joint pathological scores were analysed and gene expression changes in ipsilateral synovium and dorsal root ganglia (DRG) determined. c-Fos protein expression in the ipsilateral dorsal horn of the spinal cord was quantified.
Results
TRPC5 KO mice developed a discrete enhanced pain-related phenotype. In the MIA model, the pain-related phenotype correlated with c-Fos expression in the dorsal horn and increased expression of nerve injury markers ATF3, CSF1 and galanin in the ipsilateral DRG. There were negligible differences in the joint pathology between WT and TRPC5 KO mice, however detailed gene expression analysis determined increased expression of the mast cell marker CD117 as well as extracellular matrix remodelling proteinases MMP2, MMP13 and ADAMTS4 in MIA-treated TRPC5 KO mice. TRPC5 expression was defined to sensory subpopulations in DRG.
Conclusions
Deletion of TRPC5 receptor signalling is associated with exacerbation of pain-like behaviour in OA which correlates with increased expression of enzymes involved in extracellular remodelling, inflammatory cells in the synovium and increased neuronal activation and injury in DRG. Together, these results identify a modulating role for TRPC5 in OA-induced pain-like behaviours.
... Changes of the endocannabinoid system-which is a well-described feature of human and canine OA [21,65]-do not only occur at the joint level, but also at the spinal level [48,66]. Inhibition of endocannabinoid degradative enzymes and endocannabinoid receptor agonism are two strategies found to reduce joint inflammation and pain in different arthritis and osteoarthritis animal models [48,[67][68][69]. The issue has been extensively reviewed in [70]. ...
Chronic mixed pain and orthopedic dysfunction are the most frequently associated consequences of canine osteoarthritis (OA). An unmet need remains for safe and effective therapies for OA. Palmitoyl-glucosamine (PGA) and curcumin are safe and naturally occurring compounds whose use is limited by poor bioavailability. Micronization is an established technique to increase bioavailability. The aim of this study was to investigate if the dietary supplementation with PGA co-micronized with curcumin (PGA-Cur, 2:1 ratio by mass) could limit pathologic process in two well-established rat models of inflammation and OA pain, i.e., subplantar carrageenan (CAR) and knee injection of sodium monoiodoacetate (MIA), respectively. In CAR-injected animals, a single dose of PGA-cur significantly reduced paw edema and hyperalgesia, as well as tissue damage and neutrophil infiltration. The repeated administration of PGA-Cur three times per week for 21 days, starting the third day after MIA injection resulted in a significant anti-allodynic effect. Protection against cartilage damage and recovery of locomotor function by 45% were also recorded. Finally, PGA-cur significantly counteracted MIA-induced increase in serum levels of TNF-α, IL-1β, NGF, as well as metalloproteases 1, 3, and 9. All the effects of PGA-Cur were superior compared to the compounds used singly. PGA-Cur emerged as a useful dietary intervention for OA.
... A total of 75 male C57BL/6 J mice (8 weeks, 20 ± 2 g) were purchased from JOINN Laboratories (Suzhou), Inc. (License No. SCXK(Su) 2018-0006, Suzhou, China). Following arrival at the facility, mice were allowed at least 1 week to acclimatize [26]. Experimental animals (3-5 mice/cage) were housed in a room at 23 ± 2°C, with 55 ± 10 % humidity and lighting was maintained at a 12 -hs-on-12 -hs-off schedule (light on from 7:00 a.m. to 7:00 p.m.). ...
Etoricoxib, a selective Cyclooxygenase-2 (COX-2) inhibitor, is commonly used in osteoarthritis (OA) for pain relief, however, little is known about the effects on subchondral bone. In the current study, OA was induced via destabilization of the medial meniscus (DMM) in C57BL/6 mice. Two days after surgery, mice were treated with different concentrations of Etoricoxib. Four weeks after treatment, micro computed tomography (Micro-CT) analysis, histological analysis, atomic force microscopy (AFM) analysis, and scanning electron microscopy (SEM) were performed to evaluate OA progression. We demonstrated that Etoricoxib inhibited osteophyte formation in the subchondral bone. However, it also reduced the bone volume fraction (BV/TV), lowered trabecular thickness (Tb.Th), and more microfractures and pores were observed in the subchondral bone. Moreover, Etoricoxib reduced the elastic modulus of subchondral bone. Exposure to Etoricoxib further increased the empty/total osteocyte ratio of the subchondral bone. Etoricoxib did not show significant improvement in articular cartilage destruction and synovial inflammation in early OA. Together, our observations suggested that although Etoricoxib can relieve OA-induced pain and inhibit osteophyte formation in the subchondral bone, it can also change the microstructures and biomechanical properties of subchondral bone, promote subchondral bone loss, and reduce subchondral bone quality in early OA mice.
... Another interesting approach is elevating endocannabinoid levels by inhibition of their degrading enzymes. Lowin et al. and McDougll et al. demonstrated beneficial effects for treatments that include FAAH inhibitors in murine models for osteoarthritis (OA) and RA [94,95]. In patients with OA and RA increased FAAH activity was detected in the synovia and the endocannabinoids AEA and 2-AG were identified in the synovial fluid [96]. ...
The Cannabis plant contains numerous components, including cannabinoids and other active molecules. The phyto-cannabinoid activity is mediated by the endocannabinoid system. Cannabinoids affect the nervous system and play significant roles in the regulation of the immune system. While Cannabis is not yet registered as a drug, the potential of cannabinoid-based medicines for the treatment of various conditions has led many countries to authorize their clinical use. However, the data from basic and medical research dedicated to medical Cannabis is currently limited. A variety of pathological conditions involve dysregulation of the immune system. For example, in cancer, immune surveillance and cancer immuno-editing result in immune tolerance. On the other hand, in autoimmune diseases increased immune activity causes tissue damage. Immuno-modulating therapies can regulate the immune system and therefore the immune-regulatory properties of cannabinoids, suggest their use in the therapy of immune related disorders. In this contemporary review, we discuss the roles of the endocannabinoid system in immunity and explore the emerging data about the effects of cannabinoids on the immune response in different pathologies. In addition, we discuss the complexities of using cannabinoid-based treatments in each of these conditions.
... The endocannabinoid system is showing increasing promise as an effective target for the control of joint inflammation and pain [13]. Enhancing anandamide accumulation in joint tissues by inhibiting FAAH bioactivity has already been shown to ameliorate OA pain in rodent models [14,15]. The main limitation of some of these FAAH inhibitors is that they can have off-target effects, and high levels of AEA can activate pro-algesic targets such as TRPV1 [15,16]. ...
... Having established an anti-inflammatory and analgesic effect of MAGL and COX-2 inhibition acutely, experiments were undertaken to test the effect of early treatment with KML29 and CXB on OA progression in the MIA model. Previously, it has been demonstrated that prophylactic administration of the phytocannabinoid CBD [11] or the FAAH inhibitor URB597 [14] have the ability to reduce pain development at later stages of the MIA model of OA. Prophylactic treatment of MIA-injected animals in the early inflammatory phase of the model (days 1-3) with the combination of KML29 and CXB prevented MIA-induced mechanical allodynia at day 14 compared to vehicle or either treatment alone. ...
Background:
Endocannabinoids are showing great promise as effective mediators for controlling joint inflammation and pain. One strategy that could be harnessed to promote endogenous cannabinoid function is to inhibit the enzymatic break down of endocannabinoids locally in the joint. KML29 is an inhibitor of monoacylglycerol lipase (MAGL) activity which has been shown to promote increased 2-arachodonylglycerol (2-AG) levels in the circulation and in peripheral tissues. It is also known that 2-AG can be metabolised via the cyclo-oxygenase-2 (COX-2) pathway leading to the production of pro-inflammatory prostaglandins, which may counteract the effects of 2-AG. Therefore, this study examined the effect of KML29 alone as well as in combination with low-dose celecoxib (CXB) on joint pain and inflammation in the monoiodoacetate (MIA) model of osteoarthritis (OA) pain.
Methods:
Injection of MIA (3 mg) into the knee joints of male Wistar rats was used to model OA pain, inflammation, and nerve damage. Pain behaviour was assessed by von Frey hair algesiometry, and inflammation was evaluated using intravital microscopy to measure leukocyte trafficking in the synovial microvasculature.
Results:
Intra-articular injection of MIA produced mechanical hypersensitivity as measured by von Frey hair algesiometry. Local injection of KML29 (700 μg) reduced joint pain at day 14 post-MIA induction, and this analgesic effect was blocked by the cannabinoid receptor antagonists AM281 and AM630 (P < 0.0001; n = 6). During the acute inflammatory phase of the MIA model (day 1), a significant reduction in withdrawal threshold (P < 0.0001; n = 6-8) and leukocyte trafficking was seen after treatment with KML29 + CXB (P < 0.0001; n = 6-8). Early treatment of MIA-injected knees (days 1-3) with KML29 + CXB ameliorated the development of mechanical secondary allodynia (P < 0.0001; n = 8) in the later stages of the MIA model.
Conclusions:
Combination therapy of KML29 plus CXB reduced joint pain and inflammation. Thus, dual inhibition of MAGL and cyclooxygenase-2 pathways could be a useful approach to alleviate joint inflammation and pain in OA joints.
... Targeting the EC system could address these needs, also taking into account the presence in RA synovial fluid of CB receptors together with AEA, 2-AG, and the enzyme FAAH [53]. In particular, several authors have reported that the inhibition of FAAH with selective drugs reduces joint inflammation in many kinds of arthritis, including RA [53,54]. In 2018, Falconer et al. observed that JWH-133, a CB2 selective agonist, causes a switch in macrophage phenotype from the pro-inflammatory M1 to the anti-inflammatory M2, counteracting the inflammation in collagen-induced arthritis (CIA) mice [55]. ...
Endocannabinoid system consists of cannabinoid type 1 (CB1) and cannabinoid type 2 (CB2) receptors, their endogenous ligands, and the enzymes responsible for their synthesis and degradation. CB2, to a great extent, and CB1, to a lesser extent, are involved in regulating the immune response. They also regulate the inflammatory processes by inhibiting pro-inflammatory mediator release and immune cell proliferation. This review provides an overview on the role of the endocannabinoid system with a major focus on cannabinoid receptors in the pathogenesis and onset of inflammatory and autoimmune pediatric diseases, such as immune thrombocytopenia, juvenile idiopathic arthritis, inflammatory bowel disease, celiac disease, obesity, neuroinflammatory diseases, and type 1 diabetes mellitus. These disorders have a high social impact and represent a burden for the healthcare system, hence the importance of individuating more innovative and effective treatments. The endocannabinoid system could address this need, representing a possible new diagnostic marker and therapeutic target.
