AMPA/kainate glutamate receptors contribute to inflammation, degeneration and pain related behaviour in inflammatory stages of arthritis

NBQX mediates ventricular fibrillation susceptibility in rat models of anxiety via the Nrf2/HO-1 pathway

Objective

Anxiety disorder (AD) is a common mental disorder related to cardiovascular disease morbidity. Oxidative stress plays a crucial role in the anxiety state and can lead to cardiac remodeling. Over-activation of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) in cardiomyocytes and neurons can cause oxidative stress. Additionally, the AMPAR inhibitor-2,3-dihydroxy-6-nitro-7-sulfamoyl-benzoquinoxaline-2,3-dione (NBQX) plays an important role in ameliorating oxidative stress. This study aimed to explore the anti-arrhythmic effects of NBQX in a rat model of anxiety.

Methods

The AD model was induced using empty bottle stimulation. Male Sprague Dawley rats were randomly divided into four groups: control + saline, control + NBQX, AD + saline, and AD + NBQX. Open field test was conducted to measure anxiety-like behavior. Electrophysiological experiments, histological analysis, biochemical detection and molecular biology were performed to verify the effects of NBQX on the amelioration of electrical remodeling and structural remodeling. Furthermore, the nuclear factor erythroid 2-related factor 2 (Nrf2) inhibitor (ML385) was used in vitro to demonstrate the signaling pathway.

Results

Oxidative stress levels increased with AMPAR over-activation in AD rats, leading to heightened vulnerability to ventricular fibrillation (VF). NBQX reverses anxiety and VF susceptibility. Our results showed that NBQX activated the Nrf2/heme oxygenase-1 (HO-1) pathway, leading to a decline in oxidative stress levels. Connexin 43 and ion channel expression was upregulated. NBQX treatment attenuated fibrosis and apoptosis. This effect was diminished by ML385 treatment in vitro.

Conclusion

NBQX can alleviate VF susceptibility in rat models of anxiety by alleviating electrical remodeling, structural remodeling via regulating the Nrf2/HO-1 pathway to some extent.

Neurotrophic factor Neuritin modulates T cell electrical and metabolic state for the balance of tolerance and immunity

The adaptive T cell response is accompanied by continuous rewiring of the T cell's electric and metabolic state. Ion channels and nutrient transporters integrate bioelectric and biochemical signals from the environment, setting cellular electric and metabolic states. Divergent electric and metabolic states contribute to T cell immunity or tolerance. Here, we report that neuritin (Nrn1) contributes to tolerance development by modulating regulatory and effector T cell function. Nrn1 expression in regulatory T cells promotes its expansion and suppression function, while expression in the T effector cell dampens its inflammatory response. Nrn1 deficiency causes dysregulation of ion channel and nutrient transporter expression in Treg and effector T cells, resulting in divergent metabolic outcomes and impacting autoimmune disease progression and recovery. These findings identify a novel immune function of the neurotrophic factor Nrn1 in regulating the T cell metabolic state in a cell context-dependent manner and modulating the outcome of an immune response.

Investigating mechanical and inflammatory pathological mechanisms in osteoarthritis using MSC-derived osteocyte-like cells in 3D

Introduction

Changes to bone physiology play a central role in the development of osteoarthritis with the mechanosensing osteocyte releasing factors that drive disease progression. This study developed a humanised in vitro model to detect osteocyte responses to either interleukin-6, a driver of degeneration and bone remodelling in animal and human joint injury, or mechanical loading, to mimic osteoarthritis stimuli in joints.

Methods

Human MSC cells (Y201) were differentiated in 3-dimensional type I collagen gels in osteogenic media and osteocyte phenotype assessed by RTqPCR and immunostaining. Gels were subjected to a single pathophysiological load or stimulated with interleukin-6 with unloaded or unstimulated cells as controls. RNA was extracted 1-hour post-load and assessed by RNAseq. Markers of pain, bone remodelling, and inflammation were quantified by RT-qPCR and ELISA.

Results

Y201 cells embedded within 3D collagen gels assumed dendritic morphology and expressed mature osteocytes markers. Mechanical loading of the osteocyte model regulated 7564 genes (Padj p<0.05, 3026 down, 4538 up). 93% of the osteocyte transcriptome signature was expressed in the model with 38% of these genes mechanically regulated. Mechanically loaded osteocytes regulated 26% of gene ontology pathways linked to OA pain, 40% reflecting bone remodelling and 27% representing inflammation. Load regulated genes associated with osteopetrosis, osteoporosis and osteoarthritis. 42% of effector genes in a genome-wide association study meta-analysis were mechanically regulated by osteocytes with 10 genes representing potential druggable targets. Interleukin-6 stimulation of osteocytes at concentrations reported in human synovial fluids from patients with OA or following knee injury, regulated similar readouts to mechanical loading including markers of pain, bone remodelling, and inflammation.

Discussion

We have developed a reproducible model of human osteocyte like cells that express >90% of the genes in the osteocyte transcriptome signature. Mechanical loading and inflammatory stimulation regulated genes and proteins implicated in osteoarthritis symptoms of pain as well as inflammation and degeneration underlying disease progression. Nearly half of the genes classified as 'effectors' in GWAS were mechanically regulated in this model. This model will be useful in identifying new mechanisms underlying bone and joint pathologies and testing drugs targeting those mechanisms.

Targeting dysregulated intracellular immunometabolism within synovial microenvironment in rheumatoid arthritis with natural products

Immunometabolism has been an emerging hotspot in the fields of tumors, obesity, and atherosclerosis in recent decades, yet few studies have investigated its connection with rheumatoid arthritis (RA). In principle, intracellular metabolic pathways upstream regulated by nutrients and growth factors control the effector functions of immune cells. Dynamic communication and hypermetabolic lesions of immune cells within the inflammatory synovial microenvironment contributes to the development and progression of RA. Hence, targeting metabolic pathways within immune subpopulations and pathological cells may represent novel therapeutic strategies for RA. Natural products constitute a great potential treasury for the research and development of novel drugs targeting RA. Here, we aimed to delineate an atlas of glycolysis, lipid metabolism, amino acid biosynthesis, and nucleotide metabolism in the synovial microenvironment of RA that affect the pathological processes of synovial cells. Meanwhile, therapeutic potentials and pharmacological mechanisms of natural products that are demonstrated to inhibit related key enzymes in the metabolic pathways or reverse the metabolic microenvironment and communication signals were discussed and highlighted.

The Effect of Depression on Disease Activity and Treatment Response in Patients with Inflammatory Arthritis: Results from a Narrative Literature Review

Background

Inflammatory arthritis refers to a group of diseases that have a common presentation of joint pain, stiffness, and inflammation. Meanwhile, major depressive disorder is a mental health disorder characterized by anhedonia and low mood. Inflammatory arthritis patients have high rates of major depressive disorder, estimated at being up to 38.8%. Depression leads to a significant reduction in patient's health-related quality of life, treatment adherence, and many other measures of health, both subjective and clinical.

Purpose

This literature review explores the effect that depression has on treatment response for the drugs used in inflammatory arthritis.

Methods

A systematic search using PubMed was conducted identifying articles which were each reviewed for relevance and eligibility.

Results

Depression was negatively associated with treatment response to all classes of drugs used to manage inflammatory arthritis, with an increased disease activity and/or number of swollen/tender joints, as well as a reduced rate of remission being recorded for patients with depression compared to those without. However, this effect on treatment response was less clear when conventional synthetic Disease Modifying Anti-rheumatic Drugs were studied, possibly because their anti-inflammatory effects have wide impacts on the whole immune system, whereas biologic Disease Modifying Anti-rheumatic Drugs have very specific targets.

Conclusion

Inflammatory arthritis patients have a significantly lowered response to most drugs when they have depression. Screening and treating depression may attenuate this association. It is recommended that further research focuses on screening for and treating depression in inflammatory arthritis patients.

AMPA receptor inhibition alleviates inflammatory response and myocardial apoptosis after myocardial infarction by inhibiting TLR4/NF-κB signaling pathway

Myocardial infarction leads to myocardial inflammation and apoptosis, which are crucial factors leading to heart failure and cardiovascular dysfunction, eventually resulting in death. While the inhibition of AMPA receptors mitigates inflammation and tissue apoptosis, the effectiveness of this inhibition in the pathophysiological processes of myocardial infarction remains unclear. This study investigated the role of AMPA receptor inhibition in myocardial infarction and elucidated the underlying mechanisms. This study established a myocardial infarction model by ligating the left anterior descending branch of the coronary artery in Sprague-Dawley rats. The findings suggested that injecting the AMPA receptor antagonist NBQX into myocardial infarction rats effectively alleviated cardiac inflammation, myocardial necrosis, and apoptosis and improved their cardiac contractile function. Conversely, injecting the AMPA receptor agonist CX546 into infarcted rats exacerbated the symptoms and tissue damage, as reflected by histopathology. This agonist also stimulated the TLR4/NF-κB pathway, further deteriorating cardiac function. Furthermore, the investigations revealed that AMPA receptor inhibition hindered the nuclear translocation of P65, blocking its downstream signaling pathway and attenuating tissue inflammation. In summary, this study affirmed the potential of AMPA receptor inhibition in countering inflammation and tissue apoptosis after myocardial infarction, making it a promising therapeutic target for mitigating myocardial infarction.

A Dual-Targeted Metal-Organic Framework Based Nanoplatform for the Treatment of Rheumatoid Arthritis by Restoring the Macrophage Niche

Inflammatory infiltration and bone destruction are important pathological features of rheumatoid arthritis (RA), which originate from the disturbed niche of macrophages. Here, we identified a niche-disrupting process in RA: due to overactivation of complement, the barrier function of VSIg4⁺ lining macrophages is disrupted and mediates inflammatory infiltration within the joint, thereby activating excessive osteoclastogenesis and bone resorption. However, complement antagonists have poor biological applications due to superphysiologic dose requirements and inadequate effects on bone resorption. Therefore, we developed a dual-targeted therapeutic nanoplatform based on the MOF framework to achieve bone-targeted delivery of the complement inhibitor CRIg-CD59 and pH-responsive sustained release. The surface-mineralized zoledronic acid (ZA) of ZIF8@CRIg-CD59@HA@ZA targets the skeletal acidic microenvironment in RA, and the sustained release of CRIg-CD59 can recognize and prevent the complement membrane attack complex (MAC) from forming on the surface of healthy cells. Importantly, ZA can inhibit osteoclast-mediated bone resorption, and CRIg-CD59 can promote the repair of the VSIg4⁺ lining macrophage barrier to achieve sequential niche remodeling. This combination therapy is expected to treat RA by reversing the core pathological process, circumventing the pitfalls of traditional therapy.

Comprehensive dynamic and kinematic analysis of the rodent hindlimb during over ground walking

The rat hindlimb is a frequently utilized pre-clinical model system to evaluate injuries and pathologies impacting the hindlimbs. These studies have demonstrated the translational potential of this model but have typically focused on the force generating capacity of target muscles as the primary evaluative outcome. Historically, human studies investigating extremity injuries and pathologies have utilized biomechanical analysis to better understand the impact of injury and extent of recovery. In this study, we expand that full biomechanical workup to a rat model in order to characterize the spatiotemporal parameters, ground reaction forces, 3-D joint kinematics, 3-D joint kinetics, and energetics of gait in healthy rats. We report data on each of these metrics that meets or exceeds the standards set by the current literature and are the first to report on all these metrics in a single set of animals. The methodology and findings presented in this study have significant implications for the development and clinical application of the improved regenerative therapeutics and rehabilitative therapies required for durable and complete functional recovery from extremity traumas, as well as other musculoskeletal pathologies.

Phenylalanine-Based AMPA Receptor Antagonist as the Anticonvulsant Agent with Neuroprotective Activity-In Vitro and In Vivo Studies

Trying to meet the multitarget-directed ligands strategy, a series of previously described aryl-substituted phenylalanine derivatives, reported as competitive antagonists of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, were screened in vitro for their free-radical scavenging and antioxidant capacity in two different assays: ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity fluorescent (ORAC-FL) assays. The most active antioxidants 1 and 8 were further examined to evaluate their neuroprotective properties in vitro. In this study, compound 1 showed a significant neuroprotective effect against the neurotoxin 6-hydroxydopamine in neuroblastoma SH-SY5Y and IMR-32 cell lines. Both compounds also showed prevention from high levels of reactive oxygen species (ROS) in SH-SY5Y cells. Furthermore, the desired monoamine oxidase B (MAO-B) inhibition effect (IC₅₀ = 278 ± 29 nM) for 1 was determined. No toxic effects up to 100 µM of 1 and 8 against neuroblastoma cells were observed. Furthermore, in vivo studies showed that compound 1 demonstrated significant anticonvulsant potential in 6-Hz test, but in neuropathic pain models its antiallodynic and antihyperalgesic properties were not observed. Concluding, the compound 1 seems to be of higher importance as a new phenylalanine-based lead candidate due to its confirmed promise in in vitro and in vivo anticonvulsant activity.

Behavioral alterations in long-term Toxoplasma gondii infection of C57BL/6 mice are associated with neuroinflammation and disruption of the blood brain barrier

The Apicomplexa protozoan Toxoplasma gondii is a mandatory intracellular parasite and the causative agent of toxoplasmosis. This illness is of medical importance due to its high prevalence worldwide and may cause neurological alterations in immunocompromised persons. In chronically infected immunocompetent individuals, this parasite forms tissue cysts mainly in the brain. In addition, T. gondii infection has been related to mental illnesses such as schizophrenia, bipolar disorder, depression, obsessive-compulsive disorder, as well as mood, personality, and other behavioral changes. In the present study, we evaluated the kinetics of behavioral alterations in a model of chronic infection, assessing anxiety, depression and exploratory behavior, and their relationship with neuroinflammation and parasite cysts in brain tissue areas, blood-brain-barrier (BBB) integrity, and cytokine status in the brain and serum. Adult female C57BL/6 mice were infected by gavage with 5 cysts of the ME-49 type II T. gondii strain, and analyzed as independent groups at 30, 60 and 90 days postinfection (dpi). Anxiety, depressive-like behavior, and hyperactivity were detected in the early (30 dpi) and long-term (60 and 90 dpi) chronic T. gondii infection, in a direct association with the presence of parasite cysts and neuroinflammation, independently of the brain tissue areas, and linked to BBB disruption. These behavioral alterations paralleled the upregulation of expression of tumor necrosis factor (TNF) and CC-chemokines (CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1β and CCL5/RANTES) in the brain tissue. In addition, increased levels of interferon-gamma (IFNγ), TNF and CCL2/MCP-1 were detected in the peripheral blood, at 30 and 60 dpi. Our data suggest that the persistence of parasite cysts induces sustained neuroinflammation, and BBB disruption, thus allowing leakage of cytokines of circulating plasma into the brain tissue. Therefore, all these factors may contribute to behavioral changes (anxiety, depressive-like behavior, and hyperactivity) in chronic T. gondii infection.

Andrographolide attenuates synovial inflammation of osteoarthritis by interacting with tumor necrosis factor receptor 2 trafficking in a rat model

Background

Synovial inflammation plays a major role in the pathogenesis of osteoarthritis (OA). This study investigated the effect of andrographolide (Andro) on synovial inflammation mediated by tumor necrosis factor-alpha receptor 2 (TNFR2) trafficking and its utility in attenuating OA progression.

Methods

Knee joints were harvested from rats subjected to radial transection of the medial collateral ligament (MCLT) and medial meniscus (MMT) to examine the effect of Andro on synovial inflammation and OA progression. Quantitative real-time polymerase chain reaction was used to evaluate the expression of inflammatory factors in primary fibroblast-like synoviocytes (FLSs) after Andro treatment in vitro. The mechanism underlying Andro-mediated regulation of TNFR2 distribution and nuclear factor-κB (NF-κB) expression was verified using endosome maturation inhibitor hydroxychloroquine (HCQ) through flow cytometry, immunofluorescence, and western blot analysis.

Results

Andro treatment was found to reduce synovial inflammation and OA progression in vivo. Furthermore, a decrease in pain hypersensitivity and dorsal horn neuron activation was observed after treatment. Andro also downregulated the expression of inflammatory mediators and TNFR2 in FLSs. TNFR2 is crucial for the activation of the NF-κB signaling pathway, and Andro-induced degradation of TNFR2 was associated with lysosomal function, which in turn, reduced the downstream phosphorylation of p65 in the NF-κB signaling pathway.

Conclusions

Andro could suppress synovial inflammation via regulation of TNFR2 trafficking and degradation. This also suggests it could be a potential treatment for the prevention of synovial inflammation and OA progression.

The translational potential of this article

This study provides strong evidence that Andro reduces NF-κB activation and inflammatory responses in OA FLSs via regulation of TNFR2 trafficking. The inhibition of TNFR2 and Andro could be a novel therapeutic approach for OA and pain management.

Novel thienopyrimidine analogues as potential metabotropic glutamate receptors inhibitors and anticancer activity: Synthesis, In-vitro, In-silico, and SAR approaches

There is a continuous need in drug development approach for synthetic anticancer analogues with new therapeutic targets to diminish chemotherapeutic resistance of cancer cells. This study presents new group of synthetic thienopyrimidine analogues (1-9) aims as mGluR-1 inhibitors with anticancer activity. In-vitro antiproliferative assessment was carried out using viability assay against cancer cell lines (MCF-7, A-549 and PC-3) compared to WI-38 normal cell line. Analogues showed variable anticancer activity with IC₅₀ ranging from 6.60 to 121 µg/mL with compound 7b is the most potent analogue against the three cancer cell lines (MCF-7; 6.57 ± 0.200, A-549; 6.31 ± 0.400, PC-3;7.39 ± 0.500 µg/mL) compared to Doxorubicin, 5-Flurouracil and Riluzole controls. Selected compounds were tested as mGluR-1 inhibitors in MCF-7 cell line and results revealed compound 7b induced significant reduction in extracellular glutamate release (IC₅₀; 4.96 ± 0.700 µM) compared to other analogues and next to Riluzole (IC₅₀; 2.80 ± 0.500 µM) of the same suggested mode of action. Furthermore, both cell cycle and apoptosis assays confirmed the potency of compound 7b for early apoptosis of MCF-7 at G₂/M phase and apoptotic positive cell shift to (91.4%) compared to untreated control (19.6%) and Raptinal positive control (51.4%). On gene expression level, compound 7b induced over-expression of extrinsic (FasL, TNF-α and Casp-8), intrinsic (Cyt-C, Casp-3, Bax) apoptotic genes with down-regulation of anti-apoptotic Bcl-2 gene with boosted Bax/Bcl-2 ratio to 2.6-fold increase. Molecular docking and dynamic studies confirmed the biological potency through strong binding and stability modes of 7b where it was faster in reaching the equilibrium point and achieving the stability than Riluzole over 20 ns MD. These results suggest compound 7b as a promising mGluR inhibitory scaffold with anticancer activity that deserves further optimization and in-depth In-vivo and clinical investigations.

AMPA/kainate glutamate receptor antagonists prevent posttraumatic osteoarthritis

Musculoskeletal disorders represent the third greatest burden in terms of death and disability in the developed world. Osteoarthritis is the single greatest cause of chronic pain, has no cure, and affects 8.5 and 27 million people in the UK and US, respectively. Osteoarthritis is most prevalent in older people, but as it commonly occurs after joint injury, young people with such injuries are also susceptible. Painful joints are often treated with steroid or hyaluronic acid (HA) injections, but treatments to prevent subsequent joint degeneration remain elusive. In animals, joint injury increases glutamate release into the joint, acting on nerves to cause pain, and joint tissues to cause inflammation and degeneration. This study investigated synovial fluid glutamate concentrations and glutamate receptor (GluR) expression in injured human joints and compared the efficacy of GluR antagonists with current treatments in a mouse model of injury-induced osteoarthritis (ACL rupture). GluRs were expressed in the ligaments and meniscus after knee injury, and synovial fluid glutamate concentrations ranged from 19 to 129 μM. Intra-articular injection of NBQX (GluR antagonist) at the time of injury substantially reduced swelling and degeneration in the mouse ACL rupture model. HA had no effect, and Depo-Medrone reduced swelling for 1 day but increased degeneration by 50%. Intra-articular administration of NBQX modified both symptoms and disease to a greater extent than current treatments. There is an opportunity for repurposing related drugs, developed for CNS disorders and with proven safety in humans, to prevent injury-induced osteoarthritis. This could quickly reduce the substantial burden associated with osteoarthritis.

Anti‑chondrocyte apoptosis effect of genistein in treating inflammation‑induced osteoarthritis

Osteoarthritis (OA) is a chronic disease that is mainly characterized by chondrocyte degeneration. Inflammatory mediators participate in the development of OA, leading to chondrocyte apoptosis and destruction of the cartilage. Genistein is the major active component of isoflavone, with a chemical composition and a biological effect that is similar to that of estrogens, which prevents the degradation of cartilage; however, its underlying mechanisms of action remain unknown. The aim of the present study was to investigate the anti-apoptotic effects of genistein on chondrocytes for the treatment of inflammation-induced OA. Interleukin (IL)-1β was used to establish a chondrocyte OA model. After treatment with different concentrations of genistein, western blotting identified that expression levels of collagen II and aggrecan were increased in a concentration-dependent manner, while caspase 3 expression gradually decreased after genistein application. Moreover, flow cytometry and ELISA results demonstrated that genistein could decrease chondrocyte apoptosis and reduce the levels of tumor necrosis factor (TNF)-α in a dose-dependent manner. Furthermore, the in vitro data were evaluated in an OA rat model. Genistein increased the collagen and acid glycosaminoglycan content, as well as decreased the levels of TNF-α and IL-1β. Genistein also promoted the expression levels of collagen II and aggrecan in the articular cartilage, and decreased the expression of caspase 3, thus alleviating cartilage degradation. In conclusion, the results indicated that genistein mediated inflammation and had an anti-apoptotic role in treating OA. Therefore, genistein may serve as an alternative treatment for OA.

A kainate receptor-selective RNA aptamer

Kainate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are two major, closely related receptor subtypes in the glutamate ion channel family. Excessive activities of these receptors have been implicated in a number of central nervous system diseases. Designing potent and selective antagonists of these receptors, especially of kainate receptors, is useful for developing potential treatment strategies for these neurological diseases. Here, we report on two RNA aptamers designed to individually inhibit kainate and AMPA receptors. To improve the biostability of these aptamers, we also chemically modified these aptamers by substituting their 2'-OH group with 2'-fluorine. These 2'-fluoro aptamers, FB9s-b and FB9s-r, were markedly resistant to RNase-catalyzed degradation, with a half-life of ∼5 days in rat cerebrospinal fluid or serum-containing medium. Furthermore, FB9s-r blocked AMPA receptor activity. Aptamer FB9s-b selectively inhibited GluK1 and GluK2 kainate receptor subunits, and also GluK1/GluK5 and GluK2/GluK5 heteromeric kainate receptors with equal potency. This inhibitory profile makes FB9s-b a powerful template for developing tool molecules and drug candidates for treatment of neurological diseases involving excessive activities of the GluK1 and GluK2 subunits.

Understanding the Molecular Mechanisms Underlying the Pathogenesis of Arthritis Pain Using Animal Models

Arthritis, including osteoarthritis (OA) and rheumatoid arthritis (RA), is the leading cause of years lived with disability (YLD) worldwide. Although pain is the cardinal symptom of arthritis, which is directly related to function and quality of life, the elucidation of the mechanism underlying the pathogenesis of pain in arthritis has lagged behind other areas, such as inflammation control and regulation of autoimmunity. The lack of therapeutics for optimal pain management is partially responsible for the current epidemic of opioid and narcotic abuse. Recent advances in animal experimentation and molecular biology have led to significant progress in our understanding of arthritis pain. Despite the inherent problems in the extrapolation of data gained from animal pain studies to arthritis in human patients, the critical assessment of molecular mediators and translational studies would help to define the relevance of novel therapeutic targets for the treatment of arthritis pain. This review discusses biological and molecular mechanisms underlying the pathogenesis of arthritis pain determined in animal models of OA and RA, along with the methodologies used.

Serotonin-evoked cytosolic Ca2+ release and opioid receptor expression are upregulated in articular cartilage chondrocytes from osteoarthritic joints in horses

Osteoarthritis is a pain-associated progressive disease and pain mediators, such as opioid receptors, expressed in articular cartilage could represent novel therapeutic targets. Acute and chronic stages of OA indicate different metabolic abilities of the chondrocytes depending on inflammatory state. This study aimed to investigate the response of healthy and osteoarthritic chondrocytes and their expression and release of pain mediators in response to acute inflammation. Interleukin-1 beta (IL-1β) and lipopolysaccharide (LPS) were used to induce an acute inflammatory response in cultured equine chondrocytes harvested from healthy joints (HC) and osteoarthritic joints (OAC), the latter representing acute exacerbation of a chronic inflammatory state. Intracellular Ca2+ release was determined after exposure to serotonin (5-hydroxytryptamine (5-HT), glutamate or ATP. Protein expression levels of F- and G-actin, representing actin rearrangement, and opioid receptors were investigated. Glutamate concentrations in culture media were measured. Cartilage was immunohistochemically stained for µ (MOR), κ (KOR), and δ (DOR) opioid receptors. Upon exposure to acute inflammatory stimuli, OAC showed increased intracellular Ca2+ release after 5-HT stimulation and increased expression of MOR and KOR. When cells were stimulated by inflammatory mediators, glutamate release was increased in both HC and OAC. Immunostaining for MOR was strong in OA cartilage, whereas KOR was less strongly expressed. DOR was not expressed by cultured HC and OAC and immunostaining of OA cartilage equivocal. We show that chondrocytes in different inflammatory stages react differently to the neurotransmitter 5-HT with respect to intracellular Ca2+ release and expression of peripheral pain mediators. Our findings suggest that opioids and neurotransmitters are important in the progression of equine OA. The inflammatory stage of OA (acute versus chronic) should be taken into consideration when therapeutic strategies are being developed.

Extracellular Vesicles in the Synovial Joint: Is there a Role in the Pathophysiology of Osteoarthritis?

The role of extracellular vesicles (EV) in osteoarthritis has become the focus of much research. These vesicles were isolated from several cell types found in synovial joint including chondrocytes and synovium. As articular cartilage is an avascular tissue surrounded by synovial fluid, it is believed that EV might play a crucial role in the homeostasis of cartilage and also could hold key information in the pathogenesis of osteoarthritis. This is thought to be due to activation of pro-inflammatory factors leading to a catabolic state and degradation of cartilage. In addition, due to the nature of articular cartilage lacking neuronal innervation, knowledge of EV can contribute to identification of novel biomarkers in this debilitating condition. This can be either directly isolated from aspirate of synovial fluid or from peripheral blood. Finally, EVs are known to shuttle important signalling molecules which can be utilised as unique modality in transferring therapeutic compounds in a cell free manner.

Towards prevention of post-traumatic osteoarthritis: report from an international expert working group on considerations for the design and conduct of interventional studies following acute knee injury

OBJECTIVE

There are few guidelines for clinical trials of interventions for prevention of post-traumatic osteoarthritis (PTOA), reflecting challenges in this area. An international multi-disciplinary expert group including patients was convened to generate points to consider for the design and conduct of interventional studies following acute knee injury.

DESIGN

An evidence review on acute knee injury interventional studies to prevent PTOA was presented to the group, alongside overviews of challenges in this area, including potential targets, biomarkers and imaging. Working groups considered pre-identified key areas: eligibility criteria and outcomes, biomarkers, injury definition and intervention timing including multi-modality interventions. Consensus agreement within the group on points to consider was generated and is reported here after iterative review by all contributors.

RESULTS

The evidence review identified 37 studies. Study duration and outcomes varied widely and 70% examined surgical interventions. Considerations were grouped into three areas: justification of inclusion criteria including the classification of injury and participant age (as people over 35 may have pre-existing OA); careful consideration in the selection and timing of outcomes or biomarkers; definition of the intervention(s)/comparator(s) and the appropriate time-window for intervention (considerations may be particular to intervention type). Areas for further research included demonstrating the utility of patient-reported outcomes, biomarkers and imaging outcomes from ancillary/cohort studies in this area, and development of surrogate clinical trial endpoints that shorten the duration of clinical trials and are acceptable to regulatory agencies.

CONCLUSIONS

These considerations represent the first international consensus on the conduct of interventional studies following acute knee joint trauma.

Therapeutic benefits of Indole-3-Carbinol in adjuvant-induced arthritis and its protective effect against methotrexate induced-hepatic toxicity

BACKGROUND

Rheumatoid arthritis (RA) being an incapacitating disease requires early effective intervention. Considering Methotrexate (MTX)- the first line of treatment for RA- intoxicates the liver; therefore, alternative therapies with similar efficacy yet lower cytotoxicity are desired. Indole-3-Carbinol (I3C) which is found in cruciferous vegetables was examined for its possible therapeutic potentials in comparison with MTX by investigating its anti-inflammatory, anti-arthritic, anti-oxidant, and hepatoprotective potentials in adjuvant-induced arthritis (AIA) rat model.

METHODS

Arthritis was induced in Sprague Dawley rats by injection of Complete Freund's Adjuvant (CFA). Arthritic rats were treated with I3C and/or MTX. To examine the anti-inflammatory and anti-arthritic effect, the following parameters were assessed: body weight, macroscopic scoring of the hind paw, the level of the pivotal cytokines (TNF-α, IL-6) heavily involved in the pathogenesis, spleen index, and erythrocyte sedimentation rate. At a histological level, the tibiotarsal joint was stained with several specific stains. To assess the hepatoprotective and anti-oxidant effects, several oxidative stress parameters were monitored, and the liver histology was examined.

RESULTS

Both I3C and MTX attenuated the inflammation that was aggravated by arthritis by downregulating the inflammatory markers and mediators and alleviating the histopathological changes affecting the tibiotarsal joint. I3C attenuated the liver impairment that was initiated by arthritis and MTX treatment. It did so by downregulating the pro-oxidants and up-regulating the anti-oxidant defenses and by reducing the pathological changes affecting the liver.

CONCLUSION

Our results suggest that I3C is as potent as MTX as an anti-inflammatory and anti-arthritic agent. In addition, I3C does so while protecting the liver from damage as opposed to MTX.

Synovial membrane receptors as therapeutic targets: A review of receptor localization, structure, and function

Joint pathology and degeneration is a significant cause of pain. The synovial membrane plays an important role in maintenance of the joint, contributes to the pathology of many arthropathies and may be adversely affected in joint disease. Improving knowledge of the receptors present within the synovium will aid in a better understanding of joint pathology and the development of new treatments for diseases such as osteoarthritis and rheumatoid arthritis. Knowledge of the location and function of synovial membrane receptors (both in healthy and diseased synovium) may provide important targets in the treatment of various arthropathies. Classic pain receptors such as opioid receptors in the synovium are a mainstay in local and systemic management of chronic pain in many species. In addition to these, many other receptors such as bradykinin, neurokinin, transient receptor potential vanilloid, and inflammatory receptors, such as prostanoid and interleukin receptors have been discovered within the synovial membrane. These receptors are important in pain, inflammation, and in maintenance of normal joint function and may serve as targets for pharmacologic intervention in pathologic states. The goal of this review is to outline synovial membrane receptor localization and local therapeutic modulation of these receptors, in order to stimulate further research into pharmacological management of arthropathies at the local level. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1589-1605, 2017.

Metabolic signatures of T-cells and macrophages in rheumatoid arthritis

In most autoimmune diseases, a decade-long defect in self-tolerance eventually leads to clinically relevant, tissue-destructive inflammatory disease. The pathogenic potential of chronic persistent immune responses during the pre-clinical and clinical phase is ultimately linked to the bioenergetic fitness of innate and adaptive immune cells. Chronic immune cell stimulation, high cellular turn-over, structural damage to the host tissue and maladaptive wound healing, all require a reliable supply of nutrients, oxygen, and biosynthetic precursors. Here, we use the model system of rheumatoid arthritis (RA) to discuss immunometabolism from the vantage point of T-cells and macrophages that encounter fundamentally different metabolic stress scenarios in the RA host. We outline the general principle that both insufficient nutrient supply, as well as nutrient excess generate cellular stress responses and guide immune function. ATP^low, NADPH^high, ROS^low T-cells hyperproliferate and are forced into premature senescence. ATP^high, ROS^high macrophages dimerize the glycolytic enzyme pyruvate kinase to amplify STAT3-dependent inflammatory effector functions. A corollary of this model is that simple nutraceutical interventions will be insufficient to re-educate the immune system in RA. Instead, interference with cell-type-exclusive and differentiation-stage-dependent metabolic setpoints will be needed to reprogram arthritogenic pathways.

Nociceptive neuronal Fc-gamma receptor I is involved in IgG immune complex induced pain in the rat

Antigen-specific immune diseases such as rheumatoid arthritis are often accompanied by pain and hyperalgesia. Our previous studies have demonstrated that Fc-gamma-receptor type I (FcγRI) is expressed in a subpopulation of rat dorsal root ganglion (DRG) neurons and can be directly activated by IgG immune complex (IgG-IC). In this study we investigated whether neuronal FcγRI contributes to antigen-specific pain in the naïve and rheumatoid arthritis model rats. In vitro calcium imaging and whole-cell patch clamp recordings in dissociated DRG neurons revealed that only the small-, but not medium- or large-sized DRG neurons responded to IgG-IC. Accordingly, in vivo electrophysiological recordings showed that intradermal injection of IgG-IC into the peripheral receptive field could sensitize only the C- (but not A-) type sensory neurons and evoke action potential discharges. Pain-related behavioral tests showed that intradermal injection of IgG-IC dose-dependently produced mechanical and thermal hyperalgesia in the hindpaw of rats. These behavioral effects could be alleviated by localized administration of non-specific IgG or an FcγRI antibody, but not by mast cell stabilizer or histamine antagonist. In a rat model of antigen-induced arthritis (AIA) produced by methylated bovine serum albumin, FcγRI were found upregulated exclusively in the small-sized DRG neurons. In vitro calcium imaging revealed that significantly more small-sized DRG neurons responded to IgG-IC in the AIA rats, although there was no significant difference between the AIA and control rats in the magnitude of calcium changes in the DRG neurons. Moreover, in vivo electrophysiological recordings showed that C-nociceptive neurons in the AIA rats exhibited a greater incidence of action potential discharges and stronger responses to mechanical stimuli after IgG-IC was injected to the receptive fields. These results suggest that FcγRI expressed in the peripheral nociceptors might be directly activated by IgG-IC and contribute to antigen-specific pain in pathological conditions.

Immunometabolism in early and late stages of rheumatoid arthritis

One of the fundamental traits of immune cells in rheumatoid arthritis (RA) is their ability to proliferate, a property shared with the joint-resident cells that form the synovial pannus. The building of biomass imposes high demands for energy and biosynthetic precursors, implicating metabolic control as a basic disease mechanism. During preclinical RA, when autoreactive T cells expand and immunological tolerance is broken, the main sites of disease are the secondary lymphoid tissues. Naive CD4⁺ T cells from patients with RA have a distinct metabolic signature, characterized by dampened glycolysis, low ATP levels and enhanced shunting of glucose into the pentose phosphate pathway. Equipped with high levels of NADPH and depleted of intracellular reactive oxygen species, such T cells hyperproliferate and acquire proinflammatory effector functions. During clinical RA, immune cells coexist with stromal cells in the acidic milieu of the inflamed joint. This microenvironment is rich in metabolic intermediates that are released into the extracellular space to shape cell-cell communication and the functional activity of tissue-resident cells. Increasing awareness of how metabolites regulate signalling pathways, guide post-translational modifications and condition the tissue microenvironment will help to connect environmental factors with the pathogenic behaviour of T cells in RA.

Increased Expression of Glutaminase in Osteoblasts Promotes Macrophage Recruitment in Periapical Lesions

INTRODUCTION

Recently, we have shown that tissue hypoxia stimulates the progression of periapical lesions by up-regulating glycolysis-dependent apoptosis of osteoblasts. Other facets of hypoxia-induced metabolic reprogramming in disease pathogenesis require further investigation. In this study, we examined the connection between hypoxia-augmented glutamine catabolism in osteoblasts and the development of periapical lesions.

METHODS

Primary human osteoblasts were cultured under hypoxia. The expression of glutaminase 1 (GLS1) was examined using Western blot analysis. The production of glutamate was measured by colorimetric assay. Knockdown of GLS1 was performed with small interfering RNA technology. C-C motif chemokine ligand 2 (CCL2) secretion and chemotaxis of J774 macrophages were examined by enzyme-linked immunosorbent assay and transwell migration assay, respectively. In a rat model of induced periapical lesions, the relations between disease progression and osteoblastic expression of GLS1 or macrophage recruitment were studied.

RESULTS

Hypoxia enhanced GLS1 expression and subsequent glutamate production in osteoblasts. Glutamate induced chemoattraction of macrophages by osteoblasts through up-regulation of CCL2 synthesis. Hypoxia promoted CCL2 secretion and macrophage recruitment through augmentation of glutaminolysis. Knockdown of GLS1 abolished hypoxia-induced effects. In rat periapical lesions, progressive bone resorption was significantly related to elevated GLS1 expression in osteoblasts and increased macrophage recruitment.

CONCLUSIONS

In addition to the rise in glycolytic activity, the progression of periapical lesions is also associated with enhanced glutamine catabolism in osteoblasts. GLS1 may be a potential therapeutic target in the management of periapical lesions.

One aptamer, two functions: the full-length aptamer inhibits AMPA receptors, while the short one inhibits both AMPA and kainate receptors

AMPA and kainate receptors, along with NMDA receptors, are distinct subtypes of glutamate ion channels. Excessive activity of AMPA and kainate receptors has been implicated in neurological diseases, such as epilepsy and neuropathic pain. Antagonists that block their activities are therefore potential drug candidates. In a recent article in the Journal of Biological Chemistry by Jaremko et al. 2017, we have reported on the discovery and molecular characterization of an RNA aptamer of a dual functionality: the full-length RNA (101 nucleotide) inhibits AMPA receptors while the truncated or the short (55 nucleotide) RNA inhibits both the AMPA and kainate receptors. The full-length RNA aptamer was isolated through a specially designed, systematic evolution of ligands by exponential enrichment (SELEX) using only a single type of AMPA receptors expressed in HEK-293 cells. The design feature and the results of our recent article are highlighted here, as they demonstrate the utility of the SELEX approach and the potential of using a single AMPA receptor type to develop potent, novel RNA aptamers targeting multiple subunits and AMPA/kainate receptor subtypes with length-dependent functionalities.

Gait analysis methods for rodent models of arthritic disorders: reviews and recommendations

Gait analysis is a useful tool to understand behavioral changes in preclinical arthritis models. While observational scoring and spatiotemporal gait parameters are the most widely performed gait analyses in rodents, commercially available systems can now provide quantitative assessments of spatiotemporal patterns. However, inconsistencies remain between testing platforms, and laboratories often select different gait pattern descriptors to report in the literature. Rodent gait can also be described through kinetic and kinematic analyses, but systems to analyze rodent kinetics and kinematics are typically custom made and often require sensitive, custom equipment. While the use of rodent gait analysis rapidly expands, it is important to remember that, while rodent gait analysis is a relatively modern behavioral assay, the study of quadrupedal gait is not new. Nearly all gait parameters are correlated, and a collection of gait parameters is needed to understand a compensatory gait pattern used by the animal. As such, a change in a single gait parameter is unlikely to tell the full biomechanical story; and to effectively use gait analysis, one must consider how multiple different parameters contribute to an altered gait pattern. The goal of this article is to review rodent gait analysis techniques and provide recommendations on how to use these technologies in rodent arthritis models, including discussions on the strengths and limitations of observational scoring, spatiotemporal, kinetic, and kinematic measures. Recognizing rodent gait analysis is an evolving tool, we also provide technical recommendations we hope will improve the utility of these analyses in the future.

Transmission pathways and mediators as the basis for clinical pharmacology of pain

INTRODUCTION

Mediators in pain transmission are the targets of a multitude of different analgesic pharmaceuticals. This review explores the most significant mediators of pain transmission as well as the pharmaceuticals that act on them. Areas covered: The review explores many of the key mediators of pain transmission. In doing so, this review uncovers important areas for further research. It also highlights agents with potential for producing novel analgesics, probes important interactions between pain transmission pathways that could contribute to synergistic analgesia, and emphasizes transmission factors that participate in transforming acute injury into chronic pain. Expert commentary: This review examines current pain research, particularly in the context of identifying novel analgesics, highlighting interactions between analgesic transmission pathways, and discussing factors that may contribute to the development of chronic pain after an acute injury.

Novel Application of Behavioral Assays Allows Dissociation of Joint Pathology from Systemic Extra-Articular Alterations Induced by Inflammatory Arthritis

Introduction

Although rheumatoid arthritis (RA) is a disease of articular joints, patients often suffer from co-morbid neuropsychiatric changes, such as anxiety, that may reflect links between heightened systemic inflammation and abnormal regulation of the hypothalamic-pituitary-adrenal (HPA) axis. Here, we apply behavioral neuroscience methods to assess the impact of antigen-induced arthritis (AIA) on behavioral performance in wild type (WT) and interleukin-10 deficient (Il10-/-) mice. Our aim was to identify limb-specific motor impairments, as well as neuropsychological responses to inflammatory arthritis.

Methods

Behavioral testing was performed longitudinally in WT and Il10-/- mice before and after the induction of arthritic joint pathology. Footprint analysis, beam walking and open field assessment determined a range of motor, exploratory and anxiety-related parameters. Specific gene changes in HPA axis tissues were analyzed using qPCR.

Results

Behavioral assessment revealed transient motor and exploratory impairments in mice receiving AIA, coinciding with joint swelling. Hind limb coordination deficits were independent of joint pathology. Behavioral impairments returned to baseline by 10 days post-AIA in WT mice. Il10-/- mice demonstrated comparable levels of swelling and joint pathology as WT mice up to 15 days post-AIA, but systemic differences were evident in mRNA expression in HPA axis tissues from Il10-/- mice post-AIA. Interestingly, the behavioral profile of Il10-/- mice revealed a significantly longer time post-AIA for activity and anxiety-related behaviors to recover.

Conclusions

The novel application of sensitive behavioral tasks has enabled dissociation between behaviors that occur due to transient joint-specific pathology and those generated by more subtle systemic alterations that manifest post-AIA.

The Influence of Na(+), K(+)-ATPase on Glutamate Signaling in Neurodegenerative Diseases and Senescence

Decreased Na(+), K(+)-ATPase (NKA) activity causes energy deficiency, which is commonly observed in neurodegenerative diseases. The NKA is constituted of three subunits: α, β, and γ, with four distinct isoforms of the catalytic α subunit (α1-4). Genetic mutations in the ATP1A2 gene and ATP1A3 gene, encoding the α2 and α3 subunit isoforms, respectively can cause distinct neurological disorders, concurrent to impaired NKA activity. Within the central nervous system (CNS), the α2 isoform is expressed mostly in glial cells and the α3 isoform is neuron-specific. Mutations in ATP1A2 gene can result in familial hemiplegic migraine (FHM2), while mutations in the ATP1A3 gene can cause Rapid-onset dystonia-Parkinsonism (RDP) and alternating hemiplegia of childhood (AHC), as well as the cerebellar ataxia, areflexia, pescavus, optic atrophy and sensorineural hearing loss (CAPOS) syndrome. Data indicates that the central glutamatergic system is affected by mutations in the α2 isoform, however further investigations are required to establish a connection to mutations in the α3 isoform, especially given the diagnostic confusion and overlap with glutamate transporter disease. The age-related decline in brain α2∕3 activity may arise from changes in the cyclic guanosine monophosphate (cGMP) and cGMP-dependent protein kinase (PKG) pathway. Glutamate, through nitric oxide synthase (NOS), cGMP and PKG, stimulates brain α2∕3 activity, with the glutamatergic N-methyl-D-aspartate (NMDA) receptor cascade able to drive an adaptive, neuroprotective response to inflammatory and challenging stimuli, including amyloid-β. Here we review the NKA, both as an ion pump as well as a receptor that interacts with NMDA, including the role of NKA subunits mutations. Failure of the NKA-associated adaptive response mechanisms may render neurons more susceptible to degeneration over the course of aging.

Understanding autoimmunity: The ion channel perspective

Ion channels are integral membrane proteins that orchestrate the passage of ions across the cell membrane and thus regulate various key physiological processes of the living system. The stringently regulated expression and function of these channels hold a pivotal role in the development and execution of various cellular functions. Malfunction of these channels results in debilitating diseases collectively termed channelopathies. In this review, we highlight the role of these proteins in the immune system with special emphasis on the development of autoimmunity. The role of ion channels in various autoimmune diseases is also listed out. This comprehensive review summarizes the ion channels that could be used as molecular targets in the development of new therapeutics against autoimmune disorders.

Honokiol for the Treatment of Neonatal Pain and Prevention of Consequent Neurobehavioral Disorders

This study examined the short- and long-term neuroprotective and analgesic activity of honokiol (a naturally occurring lignan isolated from Magnolia) on developing brains in neonates exposed to inflammatory pain, known to cause neuronal cell death. Postnatal day 4 (P4) neonatal rat pups were subjected to intraplantar formalin injection to four paws as a model of severe neonatal pain. Intraperitoneal honokiol (10 mg/kg) or corn oil vehicle control was administered 1 h prior to formalin insult, and animals were maintained on honokiol through postnatal day 21 (P21). Behavioral tests for stress and pain were performed after the painful insult, followed by morphological examinations of the brain sections at P7 and P21. Honokiol significantly attenuated acute pain responses 30 min following formalin insult and decreased chronic thermal hyperalgesia later in life. Honokiol-treated rats performed better on tests of exploratory behavior and performed significantly better in tests of memory. Honokiol treatment normalized hippocampal and thalamic c-Fos and hippocampal alveus substance P receptor expression relative to controls at P21. Together, these findings support that (1) neonatal pain experiences predispose rats to the development of chronic behavioral changes and (2) honokiol prevents and reduces both acute and chronic pathological pain-induced deteriorations in neonatal rats.

Excitatory amino acid glutamate: role in peripheral nociceptive transduction and inflammation in experimental and clinical osteoarthritis

Although a large proportion of patients with osteoarthritis (OA) show inflammation in their affected joints, the pathological role of inflammation in the development and progression of OA has yet to be clarified. Glutamate is considered an excitatory amino acid (EAA) neurotransmitter in the mammalian central nervous system (CNS). There are cellular membrane glutamate receptors and transporters for signal input modulation and termination as well as vesicular glutamate transporters (VGLUTs) for signal output through exocytotic release. Glutamate been shown to mediate intercellular communications in bone cells in a manner similar to synaptic transmission within the CNS. Glutamate-mediated events may also contribute to the pathogenesis and ongoing processes of peripheral nociceptive transduction and inflammation of experimental arthritis models as well as human arthritic conditions. This review will discuss the differential roles of glutamate signaling and blockade in peripheral neuronal and non-neuronal joint tissues, including bone remodeling systems and their potentials to impact OA-related inflammation and progression. This will serve to identify several potential targets to direct novel therapies for OA. Future studies will further elucidate the role of glutamate in the development and progression of OA, as well as its association with the clinical features of the disease.

In vitro effects of glutamate and N-methyl-D-aspartate receptor (NMDAR) antagonism on human tendon derived cells

It is known that extracellular glutamate concentrations are increased in tendinopathy but the effects of glutamate upon human tendon derived cells are unknown. The primary purpose was to investigate the effect of glutamate exposure on human tendon-derived cells in terms of viability, protein, and gene expression. The second purpose was to assess whether NMDAR antagonism would affect the response of tendon-derived cells to glutamate exposure. Human tendon-derived cells were obtained from supraspinatus tendon tissue obtained during rotator cuff repair (tendon tear derived cells) and from healthy hamstring tendon tissue (control cells). The in vitro impact of glutamate exposure and NMDAR antagonism (MK-801) was measured using the Alamar blue cell viability assay, immunocytochemistry, and quantitative real-time PCR. Glutamate reduced cell viability at 24 h in tendon tear derived cells but not in control cells at concentrations of 7.5 mM and above. Cell viability was significantly reduced after 72 h of 1.875 mM glutamate in both cell groups; this deleterious effect was attenuated by NMDAR antagonism with 10 µM MK-801. Both 24 and 72 h of 1.875 mM glutamate exposure reduced Type 1 alpha 1 collagen (COL1A1) and Type 3 alpha 1 collagen (COL3A1) gene expression, but increased Aggrecan gene expression. We propose that these effects of glutamate on tendon derived cells including reduced cell viability and altered matrix gene expression contribute to the pathogenesis of tendinopathy.

Coupled cell networks are target cells of inflammation, which can spread between different body organs and develop into systemic chronic inflammation

Several organs in the body comprise cells coupled into networks. These cells have in common that they are excitable but do not express action potentials. Furthermore, they are equipped with Ca²⁺ signaling systems, which can be intercellular and/or extracellular. The transport of small molecules between the cells occurs through gap junctions comprising connexin 43. Examples of cells coupled into networks include astrocytes, keratinocytes, chondrocytes, synovial fibroblasts, osteoblasts, connective tissue cells, cardiac and corneal fibroblasts, myofibroblasts, hepatocytes, and different types of glandular cells. These cells are targets for inflammation, which can be initiated after injury or in disease. If the inflammation reaches the CNS, it develops into neuroinflammation and can be of importance in the development of systemic chronic inflammation, which can manifest as pain and result in changes in the expression and structure of cellular components. Biochemical parameters of importance for cellular functions are described in this review.

Differences in glutamate receptors and inflammatory cell numbers are associated with the resolution of pain in human rotator cuff tendinopathy

INTRODUCTION

The relationship between peripheral tissue characteristics and pain symptoms in soft tissue inflammation is poorly understood. The primary aim of this study was to determine immunohistochemical differences in tissue obtained from patients with persistent pain and patients who had become pain-free after surgical treatment for rotator cuff tendinopathy. The secondary aim was to investigate whether there would be differences in glutaminergic and inflammatory gene expression between disease-derived and healthy control cells in vitro.

METHODS

Supraspinatus tendon biopsies were obtained from nine patients with tendon pain before shoulder surgery and from nine further patients whose pain had resolved completely following shoulder surgery. Histological markers relating to the basic tendon characteristics, inflammation and glutaminergic signalling were quantified by immunohistochemical analysis. Gene expression of glutaminergic and inflammatory markers was determined in tenocyte explants derived from painful rotator cuff tendon tears in a separate cohort of patients and compared to that of explants from healthy control tendons. Dual labelling was performed to identify cell types expressing nociceptive neuromodulators.

RESULTS

Tendon samples from patients with persistent pain demonstrated increased levels of metabotropic glutamate receptor 2 (mGluR2), kainate receptor 1 (KA1), protein gene product 9.5 (PGP9.5), CD206 (macrophage marker) and CD45 (pan-leucocyte marker) versus pain-free controls (p <0.05). NMDAR1 co-localised with CD206-positive cells, whereas PGP9.5 and glutamate were predominantly expressed by resident tendon cells. These results were validated by in vitro increases in the expression of mGluR2, N-methyl-D-aspartate receptor (NMDAR1), KA1, CD45, CD206 and tumour necrosis factor alpha (TNF-α) genes (p <0.05) in disease-derived versus control cells.

CONCLUSIONS

We conclude that differences in glutamate receptors and inflammatory cell numbers are associated with the resolution of shoulder pain in rotator cuff tendinopathy, and that disease-derived cells exhibit a distinctly different neuro-inflammatory gene expression profile to healthy control cells.

Emerging regulators of the inflammatory process in osteoarthritis

Chronic, low-grade inflammation in osteoarthritis (OA) contributes to symptoms and disease progression. Effective disease-modifying OA therapies are lacking, but better understanding inflammatory pathophysiology in OA could lead to transformative therapy. Networks of diverse innate inflammatory danger signals, including complement and alarmins, are activated in OA. Through inflammatory mediators, biomechanical injury and oxidative stress compromise the viability of chondrocytes, reprogramming them to hypertrophic differentiation and proinflammatory and pro-catabolic responses. Integral to this reprogramming are 'switching' pathways in transcriptional networks, other than the well-characterized effects of NFκB and mitogen-activated protein kinase signalling; HIF-2α transcriptional signalling and ZIP8-mediated Zn(2+) uptake, with downstream MTF1 transcriptional signalling, have been implicated but further validation is required. Permissive factors, including impaired bioenergetics via altered mitochondrial function and decreased activity of bioenergy sensors, interact with molecular inflammatory responses and proteostasis mechanisms such as the unfolded protein response and autophagy. Bioenergy-sensing by AMPK and SIRT1 provides 'stop signals' for oxidative stress, inflammatory, and matrix catabolic processes in chondrocytes. The complexity of molecular inflammatory processes in OA and the involvement of multiple inflammatory mediators in tissue repair responses, raises daunting questions about how to therapeutically target inflammatory processes and macroscopic inflammation in OA. Bioenergy sensing might provide a pragmatic 'entry point'.

Inflammatory cytokines and cellular metabolites as synovial fluid biomarkers of posttraumatic ankle arthritis

BACKGROUND

There is a paucity of research on posttraumatic ankle arthritis (PTAA). We aimed to identify synovial fluid PTAA biomarkers using cytokine analysis and metabolic profiling.

METHODS

Ankle joint synovial fluid was obtained from 20 patients with PTAA and 20 patients with no ankle pain and no radiographic evidence of ankle arthritis (control group). Synovial fluid samples were analyzed for IFN-γ, TNF-α, MIP-1β, MCP-1, IL-1β, IL-1Ra, IL-4, IL-6, IL-8, IL-10, IL-13, and IL-15 using ELISA and for more than 3000 metabolites using liquid and gas chromatography with mass spectroscopy. To compare presence of cytokines and metabolites between groups, t tests were used. Random forest analysis was performed on metabolites to determine whether control and PTAA samples could be differentiated based on metabolic profile.

RESULTS

IL-1Ra, IL-6, IL-8, IL-10, IL-15, and MCP-1 were significantly elevated in the PTAA group. In addition, 107 metabolites in the PTAA group were significantly altered, including derangement in amino acid, carbohydrate, lipid, and energy metabolism, extracellular matrix turnover, and collagen degradation. Random forest analysis yielded a predictive accuracy of 90% when using the metabolic profiles to distinguish between control and PTAA samples.

CONCLUSION

This study identified inflammatory cytokines and metabolites present in the synovial fluid of PTAA.

CLINICAL RELEVANCE

Several of these entities have previously been implicated in rheumatoid arthritis and osteoarthritis of the knee, but many could potentially be used as novel biomarkers of PTAA. Most importantly, the findings suggest that metabolites could be used to distinguish synovial fluid from patients with PTAA.

High plasma glutamate levels are associated with poor functional outcome in acute ischemic stroke

The aim of the present study was to investigate the relationship between acute ischemic stroke and glutamate levels and to determine the prognosis value of plasma glutamate levels to predict the functional outcome. Two hundred and forty-two patients with acute ischemic stroke and 100 sex- and age-matched controls were included in the study. Plasma glutamate levels were determined by HPLC at admission in both groups. Stroke severity was assessed using the National Institutes of Health Stroke Scale (NIHSS). The modified Rankin Scale (mRS) scores at 3 months was determined to outcomes, and unfavorable outcomes were defined as mRS at 3-6. The prognostic value analyzed by logistic regression analysis, after adjusting for the possible confounders. In the 94 patients with an unfavorable functional outcome, plasma glutamate levels were higher compared with those in patients with a favorable outcome [221(IQR, 152-321) μM; 176(IQR, 112-226) μM, respectively; P < 0.0001). In multivariate logistic regression analysis, glutamate was an independent predictor of functional outcome, with an adjusted OR of 6.99 (95 % confidence interval [CI] 2.21-21.23). Receiver operating characteristics to predict functional outcome demonstrated areas under the curve of glutamate of 0.821 (95 % CI 0.733-0.878; P < 0.0001) and combined model (glutamate and NIHSS) improved the NIHSS score alone. Plasma glutamate levels can be seen as an independent short-term prognostic marker of functional outcome in Chinese patients with acute ischemic stroke even after correcting for possible confounding factors.

Analgesic, anti-inflammatory, and chondroprotective activities of Cryptolepis buchanani extract: in vitro and in vivo studies

Cryptolepis buchanani Roem. & Schult. is widely used in folk medicine in Southeast Asia for treating muscle tension and arthritis. This study aimed to investigate an analgesic activity of the methanol extract of C. buchanani (CBE) in acetic acid-induced writhing response in mice, and to examine its anti-inflammatory activity in ethyl phenylpropiolate- (EPP-) induced ear edema and carrageenan-induced paw edema in rats. Its effects on cartilage degradation induced by interleukin-1β (IL-1β) in porcine cartilage explant culture were also determined. This study demonstrated that CBE significantly reduced acetic acid-induced writhing response. It also inhibited edema formation in both EPP-induced ear edema and carrageenan-induced paw edema models. In cartilage explant culture, CBE significantly reduced the sulfated glycosaminoglycan and hyaluronan released into culture media while it reserved the uronic acid and collagen within the cartilage tissues. It also suppressed the matrix metalloproteinase-2 activity with no effect on cell viability. In conclusion, CBE shows analgesic, anti-inflammatory, and chondroprotective effects in this preliminary study. Therefore, CBE may be useful as an alternative treatment for osteoarthritis.

Osteoarthritis joint pain: the cytokine connection

Osteoarthritis is a chronic and painful disease of synovial joints. Chondrocytes, synovial cells and other cells in the joint can express and respond to cytokines and chemokines, and all of these molecules can also be detected in synovial fluid of patients with osteoarthritis. The presence of inflammatory cytokines in the osteoarthritic joint raises the question whether they may directly participate in pain generation by acting on innervating joint nociceptors. Here, we first provide a systematic discussion of the known proalgesic effects of cytokines and chemokines that have been detected in osteoarthritic joints, including TNF-α, IL-1, IL-6, IL-15, IL-10, and the chemokines, MCP-1 and fractalkine. Subsequently, we discuss what is known about their contribution to joint pain based on studies in animal models. Finally, we briefly discuss limited data available from clinical studies in human osteoarthritis.

Deletion of P58(IPK), the Cellular Inhibitor of the Protein Kinases PKR and PERK, Causes Bone Changes and Joint Degeneration in Mice

OBJECTIVE

Protein kinase-like endoplasmic reticulum kinase (PERK) and protein kinase R (PKR) are implicated in endoplasmic reticulum stress-induced arthritis and pro-inflammatory cytokine-mediated cartilage degradation in vitro, respectively. We determined whether knockout of the cellular inhibitor of PERK and PKR, P58(IPK) causes joint degeneration in vivo and whether these molecules are activated in human osteoarthritis (OA).

MATERIALS AND METHODS

Sections of knee joints from P58(IPK)-null and wild-type mice aged 12-13 and 23-25 months were stained with toluidine blue and scored for degeneration using the osteoarthritis research society international (OARSI) system. Bone changes were assessed by radiology and high-resolution micro-computed tomography of hind limbs. Sections from the medial tibial plateaus of two human knees, removed in total knee replacement surgery for OA, were immunolabelled for phosphorylated PERK and PKR and P58(IPK).

RESULTS

Knockout mice exhibited narrower tibiae (p = 0.0031) and smaller epiphyses in tibiae (p = 0.0004) and femora (p = 0.0214). Older knockout mice had reduced total volume inside the femoral periosteal envelope (p = 0.023), reduced tibial (p = 0.03), and femoral (p = 0.0012) bone volumes (BV) and reduced femoral BV fraction (p = 0.025). Compared with wild-types, younger P58(IPK)-null mice had increased OARSI scores in medial femoral condyles (p = 0.035). Thirty four percent of null mice displayed severe joint degeneration with complete articular cartilage loss from the medial compartment and heterotopic chondro-osseous tissue in the medial joint capsule. Phosphorylated PERK and PKR were localized throughout human osteoarthritic tibial plateaus but, in particular, in areas exhibiting the most degeneration. There was limited expression of P58(IPK).

CONCLUSION

This study is the first to reveal a critical role for P58(IPK) in maintaining joint integrity in vivo, implicating the PKR and PERK stress signaling pathways in bony changes underlying the pathogenesis of joint degeneration.