κ-Opioid receptor activation attenuates osteoarthritis synovitis by regulating macrophage polarization through the NF-κB pathway

Osteoarthritis (OA) is a prevalent and chronic joint disease that affects the aging population, causing pain and disability. Macrophages in synovium are important mediators of synovial inflammatory activity and pathological joint pain. Previous studies have demonstrated the significant involvement of κ-opioid receptor (KOR) in the regulation of pain and inflammation. Our study reveals a significant reduction in synovial KOR expression among patients and mice with OA. Here, we find that KOR activation effectively inhibits the expressions of the LPS-induced-inflammatory cytokines TNF-α and IL-6 by inhibiting macrophage M1 phenotype. Mechanistically, KOR activation effectively suppresses the proinflammatory factor secretion of macrophages by inhibiting the translocation of NF-κB into the nucleus. Our animal experiments reveal that activation of KOR effectively alleviates knee pain and prevents synovitis progression in OA mice. Consistently, KOR administration suppresses the expressions of M1 macrophage markers and the NF-κB pathway in the synovium of the knee. Collectively, our study suggests that targeting KOR may be a viable strategy for treating OA by inhibiting synovitis and improving joint pain in affected patients.

ALPK1 Expressed in IB4-Positive Neurons of Mice Trigeminal Ganglions Promotes MIA-Induced TMJ pain

Pain is one of the main reasons for patients with temporomandibular joint (TMJ) disorders seeking medical care. However, there is no effective treatment yet as its mechanism remains unclear. Herein, we found that the injection of monoiodoacetate (MIA) into mice TMJs can induce typical joint pain as early as 3 days, accompanied by an increased percentage of calcitonin gene-related peptide positive (CGRP+) neurons and isolectin B4 positive (IB4+) in the trigeminal ganglions (TGs). Our previous study has discovered that alpha-kinase 1 (ALPK1) may be involved in joint pain. Here, we detected the expression of ALPK1 in neurons of TGs in wild-type (WT) mice, and it was upregulated after intra-TMJ injection of MIA. Meanwhile, the increased percentage of neurons in TGs expressing ALPK1 and CGRP or ALPK1 and IB4 was also demonstrated by the immunofluorescent double staining. Furthermore, after the MIA injection, ALPK1-/- mice exhibited attenuated pain behavior, as well as a remarkably decreased percentage of IB4+ neurons and an unchanged percentage of CGRP+ neurons, as compared with WT mice. In vitro assay showed that the value of calcium intensity was weakened in Dil+ neurons from ALPK1-/- mice of TMJ pain induced by the MIA injection, in relation to those from WT mice, while it was significantly enhanced with the incubation of recombinant human ALPK1 (rhA). Taken together, these results suggest that ALPK1 promotes mice TMJ pain induced by MIA through upregulation of the sensitization of IB4+ neurons in TGs. This study will provide a new potential therapeutic target for the treatment of TMJ pain.

Identification of Lipid Biomarkers for Chronic Joint Pain Associated with Different Joint Diseases

Lipids, especially lysophosphatidylcholine LPC16:0, have been shown to be involved in chronic joint pain through the activation of acid-sensing ion channels (ASIC3). The aim of the present study was to investigate the lipid contents of the synovial fluids from controls and patients suffering from chronic joint pain in order to identify characteristic lipid signatures associated with specific joint diseases. For this purpose, lipids were extracted from the synovial fluids and analyzed by mass spectrometry. Lipidomic analyses identified certain choline-containing lipid classes and molecular species as biomarkers of chronic joint pain, regardless of the pathology, with significantly higher levels detected in the patient samples. Moreover, correlations were observed between certain lipid levels and the type of joint pathologies. Interestingly, LPC16:0 levels appeared to correlate with the metabolic status of patients while other choline-containing lipids were more specifically associated with the inflammatory state. Overall, these data point at selective lipid species in synovial fluid as being strong predictors of specific joint pathologies which could help in the selection of the most adapted treatment.

Expression of LINC00638 in rheumatoid arthritis patients with damp-heat obstruction syndrome and the regulatory mechanisms for inflammation and oxidative stress

OBJECTIVES

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation and joint destruction. Both inflammatory response and oxidative stress contribute to the pathogenesis of RA. Oxidative damage can induce and aggravate the imbalance of immune inflammation and promote cell and tissue damage. In this study, the expression of long non-coding RNA (lncRNA) LINC00638 in peripheral blood of patients with RA damp-heat arthralgia syndrome was observed, and the correlation between LINC00638 and disease activity, immune inflammation and oxidative stress indicator was investigated. Subsequently, the mechanisms for LINC00638 in regulating the inflammatory response and oxidative stress in RA fibroblast-like synoviocyte (FLS) under the condition of overexpression and interference were further explored.

METHODS

In this study, 48 RA patients with damp-heat arthralgia syndrome and 27 normal healthy subjects, who came from Department of Rheumatology, First Affiliated Hospital of Anhui University of Chinese Medicine, were included; and they were divided into a RA group and a control group. The expression of LINC00638 in peripheral blood mononuclear cells (PBMC) from the subjects was detected by real-time PCR. Enzyme linked immunosorbent assay (ELISA) was used to detect serum interleukin (IL)-10, IL-17, tumor necrosis factor-α (TNF-α), malondialdehyde (MDA), heme oxygenase 1 (HO-1) and superoxide dismutase 2 (SOD2) expression. Spearman method was used to study the relationship between LINC00638 and erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), rheumatoid factor (RF), anti-cyclic citrullinated peptide antibody (anti-CCP), and to observe the relation between LINC00638 and the Disease Activity Score of 28 Joint (DAS28), Quantitative Score of Damp Heat Syndrome, Visual Analogue Scale (VAS), Self-rating Anxiety Scale (SAS) and Self-rating Depression Scale (SDS). RA-FLS was induced by RA-PBMC, and the RA in vitro cell experimental model was established. LINC00638 overexpression plasmid and small interfering RNA (siRNA) were constructed and transfected into RA-FLS. The cell experiments were divided into 4 groups: a pcDNA3. 1- control group, a pcDNA3.1-LINC00638 group, a siRNA-control group, and a siRNA-LINC00638 group. The transfection efficiency of overexpression plasmid and siRNA was detected by real-time PCR, the expression of TNF-α and IL-10 was detected by ELISA, and the expression of antioxidant proteins HO-1 and SOD2 was detected by immunofluorescence.

RESULTS

Compared with the control group, the expression of LINC00638 in the RA group was lower (P<0.01). The area under the curve (AUC) of the receiver operating characteristic (ROC) curve of LINC00638 was 0.9271. The DAS28 in RA group was 5.70 (5.40-6.50), the Quantitative Score of Damp-heat Syndrome was 20.0 (17.0-23.0), and the VAS score was 7.0 (6.3-8.0). Compared with the control group, the ESR, CRP, RF, anti-CCP, SAS and SDS scores in the RA group were significantly increased (all P<0.01). Spearman correlation analysis showed that: LINC00638 was negatively correlated with ESR (r=-0.532, P<0.01), CRP (r=-0.367, P<0.05), TNF-α (r=-0.375, P<0.01), MDA (r= -0.295, P<0.05), DAS28 (r=-0.450, P<0.01), and which was positively correlated with SOD2 (r=0.370, P<0.05). After the induction of RA-FLS, the expression level of LINC00638 was significantly decreased (P<0.01), indicating that the stimulation of PBMC could effectively reduce the expression of LINC00638 in RA-FLS, so the experimental model of RA-FLS-induced by PBMC was utilized. Compared with the pcDNA3.1-control group, the expressions of LINC00638, IL-10, SOD2, and HO-1 in the pcDNA3.1-LINC00638 group were significantly increased (all P<0.01), and the expression of TNF-α was decreased (P<0.01). Compared with siRNA-control group, LINC00638, IL-10, SOD2 and HO-1 in the siRNA-LINC00638 group were significantly decreased (all P<0.01), and TNF-α was significantly increased (P<0.01).

CONCLUSIONS

LINC00638 is down-regulated in the peripheral blood of RA patients with damp-heat arthralgia syndrome, which is correlated with disease activity, immune inflammation and oxidative stress. Overexpression of LINC00638 can down-regulate pro-inflammatory factors, up-regulate anti-inflammatory factors, and increase antioxidant enzyme activity, thereby improving inflammation and oxidative stress in RA. LINC00638 is the differential lncRNA obtained by the research group's previous high-throughput sequencing of the whole transcriptome of peripheral blood PBMCs in RA patients and validation of clinical samples. In order to deepen the molecular biology research of this gene, the microRNA and mRNA targeted by LINC00638 can be further studied from the perspective of competing endogenous RNAs.

Semaphorin3B plays a central role in serum-induced arthritis model and is reduced in patients with rheumatoid arthritis

Objective

Semaphorin 3B (Sema3B) decreases the migratory and invasive capacities of fibroblast‐like synoviocytes (FLS) in rheumatoid arthritis (RA) and suppresses expression of matrix metalloproteinases. We undertook this study to examine the role of Sema3B in a mouse model of arthritis and its expression in RA patients.

Methods

Clinical responses, histologic features, and FLS function were examined in wild‐type (WT) and Sema3B^−/− mice in a K/BxN serum transfer model of arthritis. Protein and messenger RNA expression of Sema3B in mouse joints and murine FLS, as well as in serum and synovial tissue from patients with arthralgia and patients with RA, was determined using enzyme‐linked immunosorbent assay, immunoblotting, quantitative polymerase chain reaction, and RNA sequencing. FLS migration was determined using a wound closure assay.

Results

The clinical severity of serum‐induced arthritis was significantly higher in Sema3B^−/− mice compared to WT mice. This was associated with increased expression of inflammatory mediators and increased migratory capacity of murine FLS. Administration of recombinant mouse Sema3B reduced the clinical severity of serum‐induced arthritis and the expression of inflammatory mediators. Sema3B expression was significantly lower in the synovial tissue and serum of patients with established RA compared to patients with arthralgia. Serum Sema3B levels were elevated in patients with arthralgia that later progressed to RA, but not in those who did not develop RA; however, these levels drastically decreased 1 and 2 years after RA development.

Conclusion

Sema3B expression plays a protective role in a mouse model of arthritis. In RA patients, expression levels of Sema3B in the serum depend on the disease stage, suggesting different regulatory roles in disease onset and progression.

Quercetin decreases the antinociceptive effect of diclofenac in an arthritic gout-pain model in rats

OBJECTIVE

To analyse the antinociceptive interaction between quercetin (QUER) and diclofenac (DIC) in experimental arthritic gout-pain.

METHODS

The antinociceptive effect of DIC and QUER alone and in combination were evaluated using an arthritic gout-pain model. Pain was induced through intra-articular administration of uric acid in the rats and the treatments were administered 2 h later. Additionally, the cyclooxygenase (COX) activity was determined in rats treated with DIC, QUER and their combination.

KEY FINDINGS

DIC induced a maximal effect of 69.7 ± 2.7% with 3.1 mg/kg; whereas QUER only produced 17.6 ± 2.6% with the maximal dose (316 mg/kg). Ten of twelve DIC + QUER combinations showed a lesser antinociceptive effect than DIC alone did (P < 0.05). Moreover, DIC reduced total-COX (70.4 ± 1.3 versus 52.4 ± 1.8 and 77.4 ± 9.0 versus 56.1 ± 1.3, P < 0.05) and COX-2 (60.1 ± 1.0 versus 42.4 ± 1.8 and 58.1 ± 2.4 versus 48.7 ± 1.3, P < 0.05) activity after 1 and 3 h, respectively. Nevertheless, only the COX-2 activity induced by DIC was prevented in the presence of QUER (63.2 ± 3.0 versus 60.1 ± 1.0 and 56.6 ± 1.3 versus 58.1 ± 2.4 at 1 and 3 h, respectively).

CONCLUSIONS

All these data demonstrated that the simultaneous administration of QUER + DIC produces an unfavorable interaction on the antinociceptive effect of DIC. Therefore, this combination might not be recommendable to relieve arthritic gout-pain.

CB2 agonism controls pain and subchondral bone degeneration induced by mono-iodoacetate: Implications GPCR functional bias and tolerance development

BACKGROUND AND PURPOSE

The endocannabinoid system became a promising target for osteoarthritis (OA) treatment. Functional selectivity of cannabinoids may increase their beneficial properties while reducing side effects. The aim of the present study was to evaluate the analgesic potential of two functionally biased CB2 agonists in different treatment regimens to propose the best pharmacological approach for OA management.

EXPERIMENTAL APPROACH

Two functionally selective CB2 agonists were administered i.p. - JWH133 (cAMP biased) and GW833972A (β-arrestin biased), in a chemically induced model of OA in rats. The drugs were tested in acute and chronic treatment regimens. Analgesic effects were assessed by pressure application measurement and kinetic weight bearing. X-ray microtomography was used for the morphometric analysis of the femur's subchondral bone tissue. Underlying biochemical changes were analysed via RT-qPCR.

KEY RESULTS

Dose-response studies established the effective dose for both JWH133 and GW833972A. In chronic treatment paradigms, JWH133 was able to elicit analgesia throughout the course of the experiment, whereas GW833972A lost its efficacy after 2 days of treatment. Later studies revealed improvement in subchondral bone architecture and decrement of matrix metalloproteinases and proinflammatory factors expression following JWH133 chronic treatment.

CONCLUSION AND IMPLICATIONS

Data presents analgesic and disease-modifying potential of CB2 agonists in OA treatment. Moreover, the study revealed more pronounced tolerance development for analgesic effects of the β-arrestin biased CB2 agonist GW833972A. These results provide a better understanding of the molecular underpinnings of the anti-nociceptive potential of CB2 agonists and may improve drug development processes for any cannabinoid-based chronic pain therapy.

Robust COX-2-mediated prostaglandin response may drive arthralgia and bone destruction in patients with chronic inflammation post-chikungunya

Patients following infection by chikungunya virus (CHIKV) can suffer for months to years from arthralgia and arthritis. Interestingly, methotrexate (MTX) a major immune-regulatory drug has proved to be of clinical benefit. We have previously shown that CHIKV can persist in the joint of one patient 18 months post-infection and plausibly driving chronic joint inflammation but through ill-characterized mechanisms. We have pursued our investigations and report novel histological and in vitro data arguing for a plausible role of a COX-2-mediated inflammatory response post-CHIKV. In the joint, we found a robust COX-2 staining on endothelial cells, synovial fibroblasts and more prominently on multinucleated giant cells identified as CD11c+ osteoclasts known to be involved in bone destruction. The joint tissue was also strongly stained for CD3, CD8, CD45, CD14, CD68, CD31, CD34, MMP2, and VEGF (but not for NO synthase and two B cell markers). Dendritic cells were rarely detected. Primary human synovial fibroblasts were infected with CHIKV or stimulated either by the synthetic molecule polyriboinosinic:polyribocytidylic acid (PIC) to mimic chronic viral infection or cytokines. First, we found that PIC and CHIKV enhanced mRNA expression of COX-2. We further found that PIC but not CHIKV increased the mRNA levels of cPLA2α and of mPGES-1, two other central enzymes in PGE2 production. IFNβ upregulated cPLA2α and COX-2 transcription levels but failed to modulated mPGES-1 mRNA expression. Moreover, PIC, CHIKV and IFNβ decreased mRNA expression of the PGE2 degrading enzyme 15-PGDH. Interestingly, MTX failed to control the expression of all these enzymes. In sharp contrast, dexamethasone was able to control the capacity of pro-inflammatory cytokines, IL-1β as well as TNFα, to stimulate mRNA levels of cPLA2α, COX-2 and mPGES-1. These original data argue for a concerted action of CHIKV (including viral RNA) and cytokines plausibly released from recruited leukocytes to drive a major COX-2-mediated PGE2 proinflammatory responses to induce viral arthritis.

It is important to have a better understanding of the immuno-pathogenesis of Chikungunya virus (CHIKV) and particularly focusing on the chronic phase associated to arthralgia and arthritis. Benefiting from our prospective cohort studies, we herein provide novel in vivo data identifying for the first time the implication of COX-2 and several other enzymes involved in prostaglandin biosynthesis and the persistence of the virus on the joint. Prostaglandin has major activities in inflammation and joint destruction. In vitro, we have used a model of human synovial fibroblasts to decipher the regulatory mechanisms of prostaglandin biosynthesis pathway. We have made important observations showing that the virus itself as well as major inflammatory cytokines can dramatically control the expression of all enzymes involved in the metabolism of prostaglandin. Interestingly, pharmacological investigations further revealed that dexamethasone, but not methotrexate (currently used to treat patients with chikungunya) may be of clinical values.

Fatty acid sensing GPCR (GPR84) signaling safeguards cartilage homeostasis and protects against osteoarthritis

It is well known that free fatty acids (FFAs) have beneficial effects on the skeletal system, however, which fatty acid sensing GPCR(s) and how the GPCR(s) regulating cartilage development and osteoarthritis (OA) pathogenesis is largely unknown. In this study, we found Gpr84, a receptor for medium-chain FFAs (MCFA), was the only FFA-sensing GPCR in human and mouse chondrocytes that exhibited elevated expression when stimulated by interleukin (IL)-1β. Gpr84-deficiency upregulated cartilage catabolic regulator expression and downregulated anabolic factor expression in the IL-1β-induced cell model and the destabilization of the medial meniscus (DMM)-induced OA mouse model. Gpr84-/- mice exhibited an aggravated OA phenotype characterized by severe cartilage degradation, osteophyte formation and subchondral bone sclerosis. Moreover, activating Gpr84 directly enhanced cartilage extracellular matrix (ECM) generation while knockout of Gpr84 suppressed ECM-related gene expression. Especially, the agonists of GPR84 protected human OA cartilage explants against degeneration by inducing cartilage anabolic factor expression. At the molecular level, GPR84 activation inhibited IL-1β-induced NF-κB signaling pathway. Furthermore, deletion of Gpr84 had little effect on articular and spine cartilaginous tissues during skeletal growth. Together, all of our results demonstrated that fatty acid sensing GPCR (Gpr84) signaling played a critical role in OA pathogenesis, and activation of GPR84 or MCFA supplementation has potential in preventing the pathogenesis and progression of OA without severe cartilaginous side effect.

Oral treatments with a flavonoid-enriched fraction from Cecropia hololeuca and with rutin reduce articular pain and inflammation in murine zymosan-induced arthritis

ETHNOPHARMACOLOGICAL RELEVANCE

Cecropia Loefl. species (Urticaceae) are widely spread across the rainforest in tropical and subtropical regions of Central and South America. Inhabitants of different regions of Brazil employ leaves, fruits and sprouts of Cecropia hololeuca Miq. mainly as anti-inflammatory, anti-asthmatic, expectorant, fever suppressant, and against cough.

AIM OF THE STUDY

To evaluate the antinociceptive and anti-inflammatory activities of an aqueous leaf extract of C. hololeuca in a murine model of zymosan-induced arthritis (ZIA) and characterize compounds contributing to these effects.

MATERIALS AND METHODS

The crude aqueous extract of C. hololeuca (CAE) was obtained by infusion, screened for antinociceptive and anti-inflammatory activities, and fractionated (solvent partition; RP-2 and Sephadex G-25 column chromatography), yielding fractions that were chemically and pharmacologically investigated. TLC, HPLC-DAD, HPLC-DAD-ESI-MS/MS and NMR analyses were peformed. The antinociceptive activity was assessed by means of acetic acid-induced writhing, hot-plate and rota-rod tests. ZIA was used to evaluate the anti-arthritic activity of oral treatment with CAE, butanolic (BF) and aqueous fraction (AF), as well as the fractions obtained from BF (F2, F2-A and F2-B). Rutin, a flavonoid found in C. hololeuca, was also tested. Mechanical hypernociception, joint edema, local neutrophil recruitment and articular TNF-α quantification were performed to measure the severity of arthritis and identify the anti-inflammatory potential of C. hololeuca.

RESULTS

CAE (0.03-1 g/kg, p.o.) showed a dose-related inhibitory effect on acetic acid-induced writhing test, but did not change the pain latency in the hotplate test, nor the first fall time on the rota-rod test. In addition, CAE (1 g/kg, p.o.) inhibited by 65% the mechanical hypernociception, 46% the joint edema, 54% the neutrophil recruitment and 53% the articular TNF-α concentration levels in ZIA. BF (0.4 g/kg, p.o.), AF (0.6 g/kg), F2 (0.1 g/kg) and F2-A (0.045 g/kg), but not F2-B (0.055 g/kg), inhibited the mechanical hypernociception, joint edema and neutrophil recruitment in ZIA. Rutin (0.001-0.03 g/kg, p.o.) produced dose-related inhibitory effects in the mechanical hypernociception, joint edema and neutrophil recruitment, and at 0.03 g/kg also inhibited articular TNF-α synthesis after intra-articular zymosan injection. Isoorientin, isovitexin, rutin and isoquercitrin were identified in the most active fraction (F2-A), along with luteolin and apigenin derivatives, tentatively identified as isoorientin-2″-O-glucoside and isovitexin-2″-O-glucoside.

CONCLUSION

This study corroborates the popular use by oral route of aqueous preparations of C. hololeuca against joint inflammatory disorders, such as rheumatoid arthritis. Our results demonstrated for the first time that oral administration of rutin shows antinociceptive and anti-inflammatory effects in ZIA, indicating that this flavonoid is one of the immunomodulatory compounds involved in the anti-arthritic activity of C. hololeuca.

The neurohypophysial oxytocin and arginine vasopressin system is activated in a knee osteoarthritis rat model

Osteoarthritis (OA) causes chronic joint pain and significantly impacts daily activities. Hence, developing novel treatment options for OA has become an increasingly important area of research. Recently, studies have reported that exogenous, as well as endogenous, hypothalamic-neurohypophysial hormones, oxytocin (OXT) and arginine-vasopressin (AVP), significantly contribute to nociception modulation. Moreover, the parvocellular OXT neurone (parvOXT) extends its projection to the superficial spinal dorsal horn, where it controls the transmission of nociceptive signals. Meanwhile, AVP produced in the magnocellular AVP neurone (magnAVP) is released into the systemic circulation where it contributes to pain management at peripheral sites. The parvocellular AVP neurone (parvAVP), as well as corticotrophin-releasing hormone (CRH), suppresses inflammation via activation of the hypothalamic-pituitary adrenal (HPA) axis. Previously, we confirmed that the OXT/AVP system is activated in rat models of pain. However, the roles of endogenous hypothalamic-neurohypophysial hormones in OA have not yet been characterised. In the present study, we investigated whether the OXT/AVP system is activated in a knee OA rat model. Our results show that putative parvOXT is activated and the amount of OXT-monomeric red fluorescent protein 1 positive granules in the ipsilateral superficial spinal dorsal horn increases in the knee OA rat. Furthermore, both magnAVP and parvAVP are activated, concurrent with HPA axis activation, predominantly modulated by AVP, and not CRH. The OXT/AVP system in OA rats was similar to that in systemic inflammation models, including adjuvant arthritis; however, magnocellular OXT neurones (magnOXT) were not activated in OA. Hence, localised chronic pain conditions, such as knee OA, activate the OXT/AVP system without impacting magnOXT.

Clinical Characteristics of Peripheral Neuropathy in Eosinophilic Granulomatosis with Polyangiitis: A Retrospective Single-Center Study in China

OBJECTIVE

To investigate clinical features, independent associated factors, treatment, and outcome of patients with peripheral neuropathy (PN) in eosinophilic granulomatosis with polyangiitis (EGPA).

METHODS

We retrospectively analyzed clinical data of 110 EGPA patients from 2007 to 2019 in Peking Union Medical College Hospital. The independent factors associated with PN in EGPA were analyzed with univariate and multivariate logistic regressions.

RESULTS

In EGPA with PN, paresthesia and muscle weakness were observed in 82% and 33% of patients, respectively. Both the upper and lower limbs were involved in 51% of patients. 30% of EGPA patients had symmetrical multiple peripheral neuropathy, whereas only 16.4% presented with mononeuritis multiplex. Compared to patients without PN, patients with PN had a higher erythrocyte sedimentation rate, C-reactive protein, rheumatoid factor, Birmingham vasculitis activity score (BVAS), and positivity of myeloperoxidase-antineutrophil cytoplasmic antibodies (MPO-ANCA). Regarding manifestations, patients with PN tended to develop weight loss and arthritis or joint pain. Notably, ANCA positivity, arthritis or joint pain, and higher BVAS were found to be independent associated factors for PN in EGPA. Patients with PN more frequently need glucocorticoid pulses and intravenous infusion of cyclophosphamide. With the longest follow-up of 11.0 years, we found that age and cardiac involvement were risk factors for survival, and female was the protective factor.

CONCLUSION

PN in EGPA frequently displays with symmetrical multiple peripheral neuropathy in China. Positive ANCA, arthritis or joint pain, and higher BVAS are the independent associated factors of PN in EGPA. Glucocorticoids with immunosuppressants are vital therapeutic strategy.

Effect and mechanism of the CACNA2D1-CGRP pathway in osteoarthritis-induced ongoing pain

This study built an OA model in rats by monosodium iodoacetate (MIA) injection to determine the effects and mechanism of the voltage-dependent calcium channel subunit alpha-2/delta-1 (CACNA2D1)-calcitonin gene-related protein (CGRP) pathway in osteoarthritis (OA)-induced ongoing pain. CACNA2D1 expression was measured by qPCR assay, western blotting assay, and immunofluorescence. Pain behaviors in rats were assessed with the measurement of thermal paw withdrawal latency (PWL) and mechanical paw withdrawal threshold (PWT). The expression of CACNA2D1, neuropeptide Y (NPY), activating transcription factor 3 (ATF3), CGRP, protein kinase A (PKA), phosphorylated (p)-PKA, adenylyl cyclase (AC), protein kinase C (PKC), p-PKC, phospholipase C (PLC), and mitogen-activated protein kinase (MAPK) signaling pathway proteins were measured, OA rats had higher CACNA2D1 expression than normal rats. Knockdown of CACNA2D1 led to the elevation of the pain threshold of OA rats, and CACNA2D1 over-expression decreased the pain threshold of normal rats. Moreover, CACNA2D1 over-expression inhibited the expression of CGRP, up-regulated the expressions of NPY, ATF3, p-PKA, AC, p-PKC, PLC, p-Jun N-terminal kinase (JNK), and p-p38, and had no significant effect on phosphorylated extracellular signal-regulated kinase (p-ERK) expression in vivo and in vitro. Using this model of MIA-induced OA, we demonstrated that CACNA2D1 might be involved in the process of pain by modulating the CGRP and AC-PKA/PKC/MAPK signaling pathways in the dorsal root ganglion.

Hesperidin methyl chalcone interacts with NFκB Ser276 and inhibits zymosan-induced joint pain and inflammation, and RAW 264.7 macrophage activation

Arthritis can be defined as a painful musculoskeletal disorder that affects the joints. Hesperidin methyl chalcone (HMC) is a flavonoid with analgesic, anti-inflammatory, and antioxidant effects. However, its effects on a specific cell type and in the zymosan-induced inflammation are unknown. We aimed at evaluating the effects of HMC in a zymosan-induced arthritis model. A dose-response curve of HMC (10, 30, or 100 mg/kg) was performed to determine the most effective analgesic dose after intra-articular zymosan stimuli. Knee joint oedema was determined using a calliper. Leukocyte recruitment was performed by cell counting on knee joint wash as well as histopathological analysis. Oxidative stress was measured by colorimetric assays (GSH, FRAP, ABTS and NBT) and RT-qPCR (gp91^phox and HO-1 mRNA expression) performed. In vitro, oxidative stress was assessed by DCFDA assay using RAW 264.7 macrophages. Cytokine production was evaluated in vivo and in vitro by ELISA. In vitro NF-κB activation was analysed by immunofluorescence. We observed HMC reduced mechanical hypersensitivity and knee joint oedema, leukocyte recruitment, and pro-inflammatory cytokine levels. We also observed a reduction in zymosan-induced oxidative stress as per increase in total antioxidant capacity and reduction in gp91^phox and increase in HO-1 mRNA expression. Accordingly, total ROS production and macrophage NFκB activation were diminished. HMC interaction with NFκB p65 at Ser276 was revealed using molecular docking analysis. Thus, data presented in this work suggest the usefulness of HMC as an analgesic and anti-inflammatory in a zymosan-induced arthritis model, possibly by targeting NFκB activation in macrophages.

Metabolic syndrome and osteoarthritis pain: common molecular mechanisms and potential therapeutic implications

There is no clear evidence from epidemiological and animal studies of a direct link between metabolic syndrome (MetS) and cartilage degeneration in osteoarthritis (OA) once body mass index (BMI) has been considered. However, recent epidemiological studies indicate a significant role for MetS in predicting increased knee pain after adjustment for BMI. This implies there are mechanisms that underlie both MetS and OA pain. In addition to the common systemic inflammatory and pro-inflammatory components of the two disorders, there are other molecular mechanisms that may link MetS and OA pain. These include regulation of the endocannabinoid system, activation of the transient receptor potential cation channel vanilloid subfamily member 1 (TRPV1) channel and gut dysbiosis. These three mechanisms are interlinked and are the target of therapeutic dietary or pharmacological interventions. Exploring and understanding these mechanisms may help improve outcomes for both pain and metabolic comorbidities affecting individuals with OA.

Emerging Targets for the Management of Osteoarthritis Pain

Worldwide, osteoarthritis (OA) is one of the leading causes of chronic pain, for which adequate relief is not available. Ongoing peripheral input from the affected joint is a major factor in OA-associated pain. Therefore, this review focuses predominantly on peripheral targets emerging in the preclinical and clinical arena. Nerve growth factor is the most advanced of these targets, and its blockade has shown tremendous promise in clinical trials in knee OA. A number of different types of ion channels, including voltage-gated sodium channels and calcium channels, transient receptor potential channels, and acid-sensing ion channels, are important for neuronal excitability and play a role in pain genesis. Few channel blockers have been tested in preclinical models of OA, with varying results. Finally, we discuss some examples of G-protein coupled receptors, which may offer attractive therapeutic strategies for OA pain, including receptors for bradykinin, calcitonin gene-related peptide, and chemokines. Since many of the pathways described above can be selectively and potently targeted, they offer an exciting opportunity for pain management in OA, either systemically or locally.

Involvement of the dynorphin/KOR system on the nociceptive, emotional and cognitive manifestations of joint pain in mice

Joint pain is a major clinical problem mainly associated to osteoarthritis, and characterized by articular cartilage degradation resulting in a complex chronic pain state that includes nociceptive, emotional and cognitive manifestations. Memory impairment, depressive- and anxiety-like symptoms have been reported to be associated with chronic pain, leading to a decrease of life quality. In this study, we evaluated the involvement of the endogenous dynorphin/kappa opioid receptor (KOR) system on the nociceptive, emotional, cognitive, neurochemical and epigenetic manifestations of joint pain. The murine model of monosodium iodoacetate (MIA) was used to induce joint pain in knockout mice for KOR (KOR-KO), prodynorphin (PDYN-KO) and their wild-type (WT) littermates. KOR-KO and PDYN-KO mice developed mechanical allodynia after intra-articular injection of MIA. This allodynia was significantly increased in both KOR-KO and PDYN-KO when compared to WT mice. Accordingly, both mutants showed increased microglial activation on the lumbar section of the spinal cord after MIA. The emotional responses were evaluated by measuring anxiety-like behaviour in the elevated plus maze and anhedonia as depressive-like behaviour, and cognitive alterations in the object recognition paradigm. Emotional and cognitive impairments after joint pain were differently modified in KOR-KO and PDYN-KO mice. Alterations of corticotropin-releasing factor (CRF) on the amygdala and hippocampus and down regulation of histone 3 acetylation on the amygdala suggest a possible mechanism to explain these emotional and cognitive manifestations. Our results reveal a specific involvement of the dynorphin/KOR system on joint pain manifestations that are usually associated to osteoarthritis.

Correlation between neuropeptide distribution, cancellous bone microstructure and joint pain in postmenopausal women with osteoarthritis and osteoporosis

OBJECTIVES

To explore the relationship between the distribution of neuropeptides, cancellous bone microstructure and joint pain in postmenopausal women with osteoarthritis (OA) and osteoporosis (OP).

METHODS

Cancellous bone of the femoral head was obtained at the time of hip arthroplasty from 20 postmenopausal women, 10 with OA and 10 with OP. Pain intensity was evaluated using the visual analog scale (VAS) before the operation. The microstructural parameters were measured with micro-CT and the neuropeptides of the cancellous bone were stained by an immunohistochemical method.

RESULTS

We observed that BV/TV, Tb.Th and Th.N values in the OP were significantly decreased compared to those in the OA. Immunohistochemical analysis revealed that the mean optical density (MOD) values for SP, CGRP, and VIP in the OA group were significantly higher than those in the OP, and the MOD value for NPY in the OA was significantly lower than that in the OP. We also observed that the MOD values for SP were positively correlated with AD, BV/TV, Tb.Th, Tb.N and Conn.D and negatively with MD, Tb.Sp and SMI in all patients. The MOD values for CGRP were positively correlated with AD, BV/TV and Tb.Th. MOD values for VIP were positively correlated with BV/TV and Tb.Th and negatively with SMI. The VAS score was correlated positively with the MOD values for SP, CGRP, VIP and negatively with NPY in all patients.

CONCLUSIONS

Neuropeptides play an important role in the pathogenesis of OA and OP, which may cause pain and influence the bone microstructure.

Joint production of IL-22 participates in the initial phase of antigen-induced arthritis through IL-1β production

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by neutrophil articular infiltration, joint pain and the progressive destruction of cartilage and bone. IL-22 is a key effector molecule that plays a critical role in autoimmune diseases. However, the function of IL-22 in the pathogenesis of RA remains controversial. In this study, we investigated the role of IL-22 in the early phase of antigen-induced arthritis (AIA) in mice.

METHODS

AIA was induced in C57BL/6, IL-22(-/-), ASC(-/-) and IL-1R1(-/-) immunized mice challenged intra-articularly with methylated bovine serum albumin (mBSA). Expression of IL-22 in synovial membranes was determined by RT-PCR. Articular hypernociception was evaluated using an electronic von Frey. Neutrophil recruitment and histopathological analyses were assessed in inflamed knee joint. Joint levels of inflammatory mediators and mBSA-specific IgG concentration in the serum were measured by ELISA.

RESULTS

The IL-22 mRNA expression and protein levels in synovial tissue were increased during the onset of AIA. In addition, pharmacological inhibition (anti-IL-22 antibody) and genetic deficiency (IL-22(-/-) mice) reduced articular pain and neutrophil migration in arthritic mice. Consistent with these findings, recombinant IL-22 joint administration promoted articular inflammation per se in WT mice, restoring joint nociception and neutrophil infiltration in IL-22(-/-) mice. Moreover, IL-22-deficient mice showed reduced synovitis (inflammatory cell influx) and lower joint IL-1β levels, whereas the production of IL-17, MCP-1/CCL2, and KC/CXCL1 and the humoral immune response were similar, compared with WT mice. Corroborating these results, the exogenous administration of IL-22 into the joints induced IL-1β production in WT mice and reestablished IL-1β production in IL-22(-/-) mice challenged with mBSA. Additionally, IL-1R1(-/-) mice showed attenuated inflammatory features induced by mBSA or IL-22 challenge. Articular nociception and neutrophil migration induced by IL-22 were also reduced in ASC(-/-) mice.

CONCLUSIONS

These results suggest that IL-22 plays a pro-inflammatory/pathogenic role in the onset of AIA through an ASC-dependent stimulation of IL-1β production.

Altered Central Sensitization and Pain Modulation in the CNS in Chronic Joint Pain

Musculoskeletal pain disorders are the second largest contributor to global disability underlining the significance of effective treatments. However, treating chronic musculoskeletal pain, and chronic joint pain (osteoarthritis (OA)) in particular, is challenging as the underlying peripheral and central pain mechanisms are not fully understood, and safe and efficient analgesic drugs are not available. The pain associated with joint pain is highly individual, and features from radiological imaging have not demonstrated robust associations with the pain manifestations. In recent years, a variety of human quantitative pain assessment tools (quantitative sensory testing (QST)) have been developed providing new opportunities for profiling patients and reaching a greater understanding of the mechanisms involved in chronic joint pain. As joint pain is a complex interaction between many different pain mechanisms, available tools are important for patent profiling and providing the basic knowledge for development of new drugs and for developing pain management regimes.

Expression of Prostaglandin E2 Enzymes in the Synovium of Arthralgia Patients at Risk of Developing Rheumatoid Arthritis and in Early Arthritis Patients

Objective

Arthralgia may precede the development of synovial inflammation in autoantibody-positive individuals at risk of developing rheumatoid arthritis (RA). A major pathway involved in pain is the prostaglandin (PG) E₂ pathway. We investigated this pathway in the synovium of individuals with RA-specific autoantibodies and in early arthritis patients.

Methods

Nineteen autoantibody-positive individuals (IgM-rheumatoid factor and/or anti-cyclic citrullinated peptide antibodies) with arthralgia (n=15) and/or a positive family history of RA (n=8), who had been prospectively followed for at least 2 years, were included. In addition, we included early arthritis patients (disease-modifying antirheumatic drug naïve) who after 2 years follow up fulfilled classification criteria for RA (n=63), spondyloarthritis (SpA; n=14), or had unclassified arthritis (UA; n=27). In all subjects we assessed pain and performed synovial biopsy sampling by mini-arthroscopy at baseline. Tissue sections were examined by immunohistochemistry to detect and quantify PGE₂ pathway enzymes expression levels (mPGES-1; COX-1 and -2; 15-PGDH).

Results

In both study groups synovial expression of PGE₂ enzymes was not clearly related to pain sensation. Expression levels at baseline were not associated with the development of arthritis after follow up (6 out of 19 autoantibody-positive individuals). However, in early SpA patients the expression levels of mPGES-1 and COX-1 were significantly increased compared to RA and UA patients.

Conclusion

Pain in autoantibody-positive individuals without synovial inflammation who are at risk of developing RA and in early arthritis patients may be regulated by pathways other than the PGE₂ pathway or originate at sites other than the synovium. In contrast, in SpA, the PGE2 pathway may be inherently linked to the pathophysiology/etiology of the disease.

Expression of Lectin-Like Transcript 1, the Ligand for CD161, in Rheumatoid Arthritis

Objectives

Precursor Th17 lineage cells expressing CD161 are implicated in Rheumatoid Arthritis (RA) pathogenesis. CD4+CD161+ T-cells accumulate in RA joints and may acquire a non classical Th1 phenotype. The endogenous ligand for CD161 is lectin-like transcript 1 (LLT1). CD161/LLT1 ligation may co-stimulate T-cell IFN-γ production. We investigated the presence and identity of LLT1-expressing cells in RA synovial fluid (SF) and synovial tissue (ST). We also assessed levels of soluble LLT1 (sLLT1) in different phases of RA development.

Methods

Paired samples of peripheral blood mononuclear cells (MC) and SFMC (n = 14), digested ST cells (n = 4) and ST paraffin sections (n = 6) from late-stage RA were analyzed for LLT1 expression by flow cytometry and immunohistochemistry. sLLT1 was measured using a sandwich ELISA. Sera and SF from late-stage RA (n = 26), recently diagnosed RA patients (n = 39), seropositive arthralgia patients (SAP, n = 31), spondyloarthropathy patients (SpA, n = 26) and healthy controls (HC, n = 31) were assayed.

Results

In RA SF, LLT1 was expressed by a small proportion of monocytes. In RA ST, LLT1-expressing cells were detected in the lining, sublining layer and in areas with infiltrates. The LLT1 staining pattern overlapped with the CD68 staining pattern. FACS analysis of digested ST confirmed LLT1 expression by CD68+ cells. Elevated systemic sLLT1 was found in all patient groups.

Conclusions

In RA joints, LLT1 is expressed by cells of the monocyte/macrophage lineage. Serum levels of sLLT1 were increased in all patient groups (patients with early- and late-stage RA, seropositive arthralgia and spondyloarthropathy) when compared to healthy subjects.

Calcitonin gene-related peptide-expressing sensory neurons and spinal microglial reactivity contribute to pain states in collagen-induced arthritis

OBJECTIVE

To evaluate the contribution of sensory neurons in ankle joints and adjacent tissue to the development of pain in collagen-induced arthritis (CIA), and to determine the relationship between pain and the appearance of clinical signs.

METHODS

Mechanical and heat hypersensitivity and hind paw swelling were assessed in Lewis rats before and until 18 days following collagen immunization. We examined the effect of intrathecal administration of a calcitonin gene-related peptide (CGRP) antagonist (CGRP(8-37) ) from day 11 to day 18 postimmunization on CIA-induced hypersensitivity. During CIA development, CGRP and p-ERK immunoreactivity was quantified in lumbar dorsal root ganglia in which sensory neurons innervating the ankle joint were identified by retrograde labeling with Fluoro-Gold. Microgliosis in the lumbar dorsal horn was assessed by immunohistochemistry, and release of CGRP evoked by activity of primary afferent fibers was measured using a preparation of isolated dorsal horn with dorsal roots attached.

RESULTS

CIA was associated with mechanical hypersensitivity that was evident before hind paw swelling and that was exacerbated with the development of swelling. Heat hyperalgesia developed along with swelling. Concomitant with the development of mechanical hypersensitivity, joint innervating neurons exhibited enhanced CGRP expression and an activated phenotype (increased p-ERK expression), and significant microgliosis became evident in the dorsal horn; these peripheral and central changes were augmented further with disease progression. CGRP release evoked by dorsal root stimulation was higher in the dorsal horn on day 18 in rats with CIA compared to control rats. Prolonged intrathecal administration of CGRP(8-37) attenuated established mechanical hypersensitivity and reduced spinal microgliosis.

CONCLUSION

Sensory neuron-derived CGRP sustains mechanical hypersensitivity and spinal microglial reactivity in CIA, suggesting that central mechanisms play critical roles in chronic inflammatory pain. Blockade of these central events may provide pain relief in rheumatoid arthritis patients.

Association between metabolic syndrome, radiographic knee osteoarthritis, and intensity of knee pain: results of a national survey

CONTEXT

Although osteoarthritis (OA) has been suggested as another component of metabolic syndrome (MetS), weight-independent associations between MetS and knee OA or intensity of arthritic knee pain remain unclear.

OBJECTIVE

The objective of the study was to evaluate the above associations and suggest possible mechanisms.

DESIGN AND SETTING

This was a cross-sectional study using the fifth Korean National Health and Nutrition Examination Survey (2010).

PARTICIPANTS

A total of 2363 adults (≥50 y of age) who had completed both laboratory examinations and an evaluation for radiographic knee OA participated in the study.

MAIN OUTCOME AND MEASURES

Radiographic knee OA was defined as a Kellgren/Lawrence grade of 2 or greater, and the intensity of arthritic knee pain was assessed using a self-reported numeric rating scale. MetS was diagnosed based on National Cholesterol Education Program-Adult Treatment Panel III criteria, and insulin resistance was evaluated using the homeostasis model assessment-estimated insulin resistance index.

RESULTS

In a multivariable logistic regression analysis, MetS was associated with radiographic knee OA (adjusted odds ratio 1.49; 95% confidence interval 1.23-1.79; P < .001). This association was not changed significantly after further adjusting for homeostasis model assessment-estimated insulin resistance but became nonsignificant after adjusting for weight or body mass index. Age-, sex-, and weight (or body mass index)-adjusted mean score of knee pain was significantly higher in subjects with more components of MetS (P for trend = .010 or .035, respectively).

CONCLUSIONS

The association between MetS and radiographic knee OA can be largely explained by an excessive weight but not by insulin resistance, a key pathophysiology of MetS. Because accumulation of MetS components appears to be associated with a higher intensity of knee pain, independently of weight, appropriate treatment for MetS may be helpful for subjects with knee pain.

Osteopontin level in synovial fluid is associated with the severity of joint pain and cartilage degradation after anterior cruciate ligament rupture

Objective

To explore the molecular function of Osteopontin (OPN) in the pathogenesis of human OA, we compared the expression levels of OPN in synovial fluid with clinical parameters such as arthroscopic observation of cartilage damage and joint pain after joint injury.

Methods

Synovial fluid was obtained from patients who underwent anterior cruciate ligament (ACL) reconstruction surgery from 2009 through 2011 in our university hospital. The amounts of intact OPN (OPN Full) and it’s N-terminal fragment (OPN N-half) in synovial fluid from each patient were quantified by ELISA and compared with clinical parameters such as severity of articular cartilage damage (TMDU cartilage score) and severity of joint pain (Visual Analogue Scale and Lysholm score).

Results

Within a month after ACL rupture, both OPN Full and N-half levels in patient synovial fluid were positively correlated with the severity of joint pain. In contrast, patients with ACL injuries greater than one month ago felt less pain if they had higher amounts of OPN N-half in synovial fluid. OPN Full levels were positively correlated with articular cartilage damage in lateral tibial plateau.

Conclusion

Our data suggest that OPN Full and N-half have distinct functions in articular cartilage homeostasis and in human joint pain.

Increased BMP expression in arthrofibrosis after TKA

PURPOSE

Because of the multiple possible aetiologies of painful total knee arthroplasty (TKA), the diagnosis and treatment of such patients are challenging. In a considerable number of patients, an intraarticular pathology is present, although not verifiable with clinical and diagnostic imaging techniques as in cases of primary arthrofibrosis. In these patients, the differentiation between intra- and extraarticular causes of pain remains difficult. Until now, little attention has been paid to changes of the synovial fluid and tissue in these knees. The objective of this study was to analyse the changes of the synovial environment in patients suffering from arthrofibrosis after TKA in comparison with knees with referred pain suffering from hip arthritis. The changes of the synovial environment probably provide additional diagnostic information to verify an intraarticular pathology.

METHODS

The synovial fluid of 10 consecutive knees in 10 patients presenting with a primary arthrofibrosis after TKA without signs of infection, instability, malalignment, or loosening was analysed and compared to the synovial fluid of 10 knees with referred pain serving as controls. The BMP-2 concentration was measured in the synovial fluid, and the presence of cytokines leading to an overexpression of BMP-2 was detected by measuring the change of BMP-2 expression in a synoviocyte cell line following exposing to the synovial fluid of the patients.

RESULTS

The concentration of BMP-2 in the synovial fluid was significantly higher in arthrofibrotic TKA knees (24.3 ± 6.9 pg/mL), compared with the control group 5.9 ± 4.8 pg/mL (P < 0.001). Corresponding to this finding, BMP-2 expression in synoviocytes was upregulated 11.5-fold (P < 0.05) by synovial fluid of patients suffering from arthrofibrosis after TKA, compared with the control group with referred pain.

CONCLUSION

BMP-2 is overexpressed and its concentrations are consequently higher in patients suffering from arthrofibrosis after TKA. The synovial BMP-2 concentration may be a potential marker for differentiating between intra- and extraarticular causes of pain.

LEVEL OF EVIDENCE

II.

Analysis of the cytokine profiles of the synovial fluid in a normal temporomandibular joint: preliminary study

The purpose of this study was to compare the cytokine profiles of the synovial fluid from the temporomandibular joint (TMJ) spaces of normal individuals and temporomandibular disorder (TMD) patients. Thirty-four patients with planned orthognathic surgery did not present abnormalities of the TMJ on magnetic resonance images and radiographs and did not show the symptoms identified by the Research Diagnostic Criteria for TMD (RDC-TMD); as a result, they were assigned to the control group. Twenty-two patients who sought treatment for TMD during the same period were assigned to the TMD group. Synovial fluid was collected from superior TMJ spaces, and cytokine expression was analysed by an enzyme-linked immunosorbent assay (ELISA). Significant differences were tested using Fisher's exact test (p<0.05). Granulocyte Macrophage Colony stimulating Factor (GM-CSF), interferon (INF), interleukin (IL)-1β, IL-2, IL-6, IL-8, IL-10 and tumour necrosis factor (TNF)-α were detected in the TMD group, whereas no cytokines were detected in the control group. The most prevalent cytokines in the TMD group were IL-1β, IL-6 and GM-CSF. IL-4 and IL-5 were not detected in either the TMD group or in the control group. None of the cytokines that were detected in patients with TMD were found in the articular spaces of normal individuals.

[Comparative study of regulation of TLR/TRAF signaling pathway of classic prescriptions that deals with arthralgia syndrome based on relevent theory of prescription and syndrome]

OBJECTIVE

Based on relevent theory of prescription and syndrome, to compare the gene expression differences of TLR2, TRAF6, and Faslg with adjuvant arthritis in rat spleen among Wutou decoction, Guizhi Shaoyao Zhimu decoction and Baihu Guizhi decoction.

METHOD

The experiment animal model of adjuvant arthritis in rats was established. Relative expression amount of TLR2, TRAF6, and Faslg in rats spleen was detected by SYBR Green I dye methods and implementation of fluorescence quantitative PCR technology with 18sRNA as an internal gene. 2(delta delta CT) method was used for computing and data analysis.

RESULT

TLR2, TRAF6, and Faslg gene in adjuvant arthritis rat spleen was significantly higher than those in the blank group. The various doses of Wutou decoction, Guizhi Shaoyao Zhimu decoction and Baihu Guizhi decoction can significantly inhibit or reduce the abnormally high expression of TLR2, TRAF6, and Faslg genes. The gene expression level caused by three decoctions mentioned above was followed by strong to weak as Wutou decoction Guizhi Shaoyao Zhimu decoction and Baihu Guizhi decoction with the clinical equivalent dose, but the strength of the trend to reduce the role of TRAF6 is just the opposite with the TLR2 and Faslg genes.

CONCLUSION

Wutou decoction, Guizhi Shaoyao Zhimu decoction and Baihu Guizhi decoction can reduce the abnormally high expression of TLR2, TRAF6 and Faslg in rat spleen with adjuvant arthritis, but the differences of intensity exist and remain relatively consistent with that of pharmacodynamics and regulation trends of T cell subsets. Results suggest that the suppression of TLR2/TRAF6 signal pathway and apoptosis Faslg receptor gene may be the reasons that the pharmacodynamics of three decoctions on peripheral T cell subsets in regulating intensity was different.

The human pharmacokinetics of oral ingestion of glucosamine and chondroitin sulfate taken separately or in combination

OBJECTIVE

As part of the National Institutes of Health (NIH)-sponsored Glucosamine/Chondroitin sulfate Arthritis Intervention Trial (GAIT) our objective here was to examine (1) the pharmacokinetics (PK) of glucosamine (GlcN) and chondroitin sulfate (CS) when taken separately or in combination as a single dose in normal individuals (n=29) and (2) the PK of GlcN and CS when taken as a single dose after 3 months daily dosing with GlcN, CS or GlcN+CS, in patients with symptomatic knee pain (n=28).

METHODS

The concentration of GlcN in the circulation was determined by established fluorophore-assisted carbohydrate electrophoresis (FACE) methods. The hydrodynamic size and disaccharide composition of CS chains in the circulation and dosage samples was determined by Superose 6 chromatography and FACE.

RESULTS

We show that circulating levels of CS in human plasma are about 20 microg/ml. Most significantly, the endogenous concentration and CS disaccharide composition were not detectably altered by ingestion of CS, when the CS was taken alone or in combination with GlcN. On the other hand, the Cmax (single-dose study) and AUC values (multiple-dose study) for ingested GlcN were significantly reduced by combination dosing with CS, relative to GlcN dosing alone.

CONCLUSIONS

We conclude that pain relief perceived following ingestion of CS probably does not depend on simultaneous or prior intake of GlcN. Further, such effects on joint pain, if present, probably do not result from ingested CS reaching the joint space but may result from changes in cellular activities in the gut lining or in the liver, where concentrations of ingested CS, or its breakdown products, could be substantially elevated following oral ingestion. Moreover, since combined dosing of GlcN with CS was found to reduce the plasma levels seen with GlcN dosing alone, any improved pain relief by combination dosing cannot be explained by higher circulating concentrations of GlcN.

Arthrogenic lameness of the fetlock: synovial fluid markers of inflammation and cartilage turnover in relation to clinical joint pain

REASONS FOR PERFORMING THE STUDY

Joint pain is one of the most common causes of lameness in the horse but its pathogenesis is poorly understood.

OBJECTIVES

To investigate which synovial fluid markers may be related to the presence of clinically detectable joint pain in the horse.

METHODS

Concentrations of structural (CPII, C2C, GAG) and inflammatory markers (PGE2, LTB4, CysLTs, bradykinin and substance P) were measured in fetlock joint fluid from 22 horses in which lameness was localised to the fetlock region by perineural anaesthesia. Levels of these markers were then compared in horses that responded (n = 15) to those that did not (n = 7) to subsequent intra-articular anaesthesia (IAA).

RESULTS

Of all markers analysed, only substance P levels were significantly higher (P = 0.0358) in synovial fluid of horses that showed a positive response to IAA compared to those with a negative response to IAA. Notably, while PGE2 levels were found to be elevated in all 22 lame horses compared to sound controls (P = 0.0025), they were not related to the response to IAA.

CONCLUSIONS

While levels of PGE2 are elevated in synovial fluid of lame horses that respond to perineural anaesthesia, only substance P is related to joint pain as detected by the response to intra-articular anaesthesia.

POTENTIAL RELEVANCE

Substance P is associated with clinically detectable joint pain in the horse. Elevated levels of PGE2 in fetlock-lame horses, regardless of their response to IAA, indicate that either this mediator does not reflect intra-articular pain or that IAA might have limitations in differentiating between intra- and peri-articular sources of pain. Either way, a negative response to IAA may not exclude intra-articular pathology.

Increased interleukin 6 and tumour necrosis factor α expression in the infrapatellar fat pad of the knee joint with the anterior knee pain syndrome: a preliminary report

The pathway of pain in the anterior knee pain syndrome remains unclear. It has been hypothesized that some biochemical mediators of inflammation, such as cytokines contribute to the process. The objective of this work was to evaluate the synovial membrane and the infrapatellar fat pad expression of the inflammatory mediators and potentially chondrodestructive cytokines interleukin 6 (IL-6) and tumour necrosis factor α (TNF-α) in the anterior knee pain syndrome, and to determine whether the cytokine expression counterpart with/corresponds to the amount of chondral damage in this syndrome. Ten consecutive patients with the anterior knee pain syndrome (group I) participated in the study. Patients with a history of trauma were excluded from this group. For comparison we used 10 patients with anterior cruciate ligament rupture or meniscal lesion with no history of pain in the anterior compartment (group II). Immunohistochemical techniques using a polyclonal rabbit anti-human antibody to IL-6 and a monoclonal mouse anti-human antibody to TNF-α were employed. The results show a statistically significant higher expression of IL-6 in infrapatellar fat pad (p < 0.05) as well as TNF-α in the infrapatellar fad pad and the synovium (p < 0.03, and p < 0.02, respectively) in group I as compared to control subjects. There is no any difference in the amount of chondral damage present in group I as compared to group II. The results of this study provide the immunohistochemical evidence suggesting that the anterior knee pain syndrome could be characterized by infrapatellar fat pad and synovial inflammation variations without the articular cartilage loss.

[Effect of body mass index on bone mass of lumbar spine of male patients with ostealgia and arthralgia but without osteoporosis]

For the purpose of identifying the effect of body mass index on bone mineral density, an investigation was made in regard to the relationship between body mass index (BMI), bone mineral density (BMD) and bone mineral content (BMC) of lumbar vertebrals of men without osteoporosis. 838 male patients were diagnosed and treated in West China Hospital of Sichuan University because of ostealgia and arthralgia from Aug. 2003 to Dec. 2005. They were examined by dual-energy X-ray absorptiometry, their L2-L4 bone mineral density being < -2.5SD. Then they were graded by body mass index (Kg/m2) [1st group BMI > or =23, 454 cases (Group A BMI > or = 29, 46 cases; Group B 25 < or = BMI < 28.9, 201 cases; Group C 23 < or = BMI < 24, 9193 cases); 2nd group 18.5 < BMI < 22.9, 311 cases; 3rd group BMI < or = 18.5, 68 cases]. The relationships between BMI and BMD of lumbar spine were analyzed using SPSS 13.0. The results revealed their positions in series: (1) Among Groups 1-3, BMD, average BMD and aBMC of L2-L4 being 3rd group > 2nd group > 1st group, the differencs are statistically significant (P < 0.05 or P < 0.01); BMC, aBMC of L3 and L4 and aBMC of L2 being 3rd group > 2nd group > 2nd group, the differences are significant (P < 0.01); besides BMC of L2 and T-score,the differencs among three groups are not statistically significant (P > 0.05); (2) Among the 1st group, BMD and average BMD of L2-L4 being Group C > Group B > Group A,the differencs are significant (P < 0.05 or P < 0.01); BMC, aBMC of L and I being Group C > Group B > Group A,the differences among the three groups are significant (P < 0.05 or P < 0.01); BMC, aBMC of L3 and L4 and aBMC of L2 being Group C > Group B > Group A, the differences are significant, besides BMC of L2 and T-score,the differences among three groups are not significant (P > 0.05), (3) BMI correlated negatively (P < 0.01, r = -0.189) to the average BMD of lumbar spine. The average BMD of lumbar spine decreases when BMI increases in males without osteoporosis. When obesity is more obvious, the decrease in average BMD of lumbar spine bone is more evidently decreased. The decrease of BMD, BMC and total BMC in L3 and L may be greater than that in L2.

Presence of NGF and its receptor TrkA in degenerative lumbar facet joint specimens

In a preliminary study, the recurrent presence of nervous terminations was demonstrated with optical microscopy in several slides of degenerative lumbar facet joints and surrounding soft tissues. The purpose of this study was to prove the presence of NGF (nerve growth factor) and its receptor TrkA (tyrosine kinase receptor) with immunofluorescence. The peri/articular tissues were harvested from the lumbar facet joints of ten patients surgically treated for degenerative diseases. There were seven females (one bilateral) and two males whose mean age at surgery was 72 years (range, 67-80 years). The affected levels were L3-L4 in two cases and L4-L5 in seven cases (one bilateral). All specimens were fixed in formalin, dehydrated and enclosed in paraffin. From each specimen, four slides were obtained. Two slides were employed for the search of NGF: one was treated with specific antibodies and marked with FITC (fluorescein isothiocyanate conjugated), and the second slide was for control purposes. It was exposed to FITC, but without prior exposure to the specific antibody. The same procedure was repeated to obtain on two more slides, to repeat the search for Trka with specific antibodies. All the slides were finally studied on a fluoromicroscope. The analysis of these specimens revealed the presence of the neurotrophin (NGF) and its own receptor (TrkA) in all cases: the immunohistochemical reaction between the specimens and the specific antibodies marked with FITC was seen under fluoromicroscopy, but in none of the control cases treated with FITC only. NGF is released by mastocytes, fibroblasts and other cell types involved in the inflammatory processes. The level of peripheral NGF is increased in inflammatory processes, while the administration of exogenous NGF has a hyperalgesic effect on rats and produces muscular pain in humans. Furthermore, NGF produces hypersensitization to heat stimulation in humans and mammals in general. There is considerable evidence showing that the system constituted by the NGF and its high-affinity receptor TrkA plays a fundamental role in the molecular processes underlying the main forms of "persistent" pain. This indicates a possible therapeutic area for the antibodies that could block the NGF/TrkA system, in order to modulate the frequency and the duration of the action potential of nociceptive neurons during chronic inflammation. This study demonstrated the presence of NGF and TrkA in specimens collected from degenerative facet joints, suggesting that specific molecules could be used in order to modulate chronic pain in patients with degenerative lumbar spine.

Different effects of spinally applied prostaglandin D2 on responses of dorsal horn neurons with knee input in normal rats and in rats with acute knee inflammation

Prostaglandin D2(PGD2) is the most produced prostanoid in the CNS of mammals, and in behavioral experiments it has been implicated in the modulation of spinal nociception. In the present study we addressed the effects of spinal PGD2 on the discharge properties of nociceptive spinal cord neurons with input from the knee joint using extracellular recordings in vivo, both in normal rats and in rats with acute inflammation in the knee joint. Topical application of PGD2 to the spinal cord of normal rats did not influence responses to mechanical stimulation of the knee and ankle joint except at a high dose. Specific agonists at either the prostaglandin D2 receptor 1 (DP1) or the prostaglandin D2 receptor 2 (DP2) receptor had no effect on responses to mechanical stimulation of the normal knee. By contrast, in rats with inflamed knee joints either PGD2 or a DP1 receptor agonist decreased responses to mechanical stimulation of the inflamed knee and the non-inflamed ankle thus reducing established inflammation-evoked spinal hyperexcitability. Vice versa, spinal application of an antagonist at DP1 receptors increased responses to mechanical stimulation of the inflamed knee joint and the non-inflamed ankle joint suggesting that endogenous PGD2 attenuated central sensitization under inflammatory conditions, through activation of DP1 receptors. Spinal application of a DP2 receptor antagonist had no effect. The conclusion that spinal PGD2 attenuates spinal hyperexcitability under inflammatory conditions is further supported by the finding that spinal coapplication of PGD2 with prostaglandin E2 (PGE2) attenuated the PGE2-induced facilitation of responses to mechanical stimulation of the normal joint.

Oral and Maxillofacial Pathology: Interleukin-1 β, interleukin-6, and tissue inhibitor of metalloproteinase-1 in the synovial fluid of the temporomandibular joint with respect to cartilage destruction

OBJECTIVE

The distribution and biological roles of interleukin (IL)-1 beta, IL-6, and tissue inhibitor of metalloproteinase-1 (TIMP-1) in the synovial fluid of patients with non-inflammatory chronic temporomandibular joint (TMJ) disorders were evaluated in relation to pain upon joint movements and X-ray and magnetic resonance imaging (MRI) findings.

MATERIALS AND METHODS

TMJ aspirates were obtained from 48 patients (48 joints) with chronic TMJ disorders and from 18 controls (18 joints). The IL-1 beta and IL-6 levels in the aspirates were determined by using an enzyme-linked immunosorbent assay and the TIMP-1 level was measured by an enzyme immunoassay. Following examinations for pain upon joint movements and X-ray and MRI observations, the IL-1 beta, IL-6, and TIMP-1 levels and frequencies of their detection were compared.

RESULTS

The IL-1 beta level and frequency of detection showed no correlation with pain upon joint movements or with the X-ray and MRI findings. In the frequency of detection of IL-6, there were significant differences between control (no detection) and all chronic TMJ disorder groups that were classified by imaging diagnosis (P < 0.001). A correlation was also noted between the presence of IL-6 and pain upon joint movements. The IL-6 level was correlated with the TIMP-1 level and with pain upon joint movements. TIMP-1 level was correlated with pain upon joint movements. The TIMP-1 was present in higher level from patients with chronic TMJ disorders who exhibited osseous changes on the X-ray images.

CONCLUSION

The results indicated that the IL-6 and TIMP-1 levels in the TMJ aspirates of patients with chronic TMJ disorders have been raised. The former was not detected in the TMJ aspirates of the control. These findings suggest that IL-6 and TIMP-1 might play a role in the etiology of chronic TMJ disorders, but further studies are needed to validate this.

Symptoms associated with menopausal transition and reproductive hormones in midlife women

OBJECTIVE

To test the hypothesis that prevalence of women with menopausal symptoms of hot flushes; aches, joint pain, and stiffness; depressed mood; poor sleep; decreased libido; or vaginal dryness increases with progression through the menopausal transition.

METHODS

Women in the Penn Ovarian Aging Study were assessed longitudinally for 9 years. Data were obtained from structured interviews, a validated symptom questionnaire, menstrual bleeding dates and early follicular hormone measures (estradiol [E2], follicle-stimulating hormone [FSH], and inhibin b). Menopausal stages were based on menstrual bleeding patterns. Other risk factors included age, race, history of depression, current smoking, body mass index, and perceived stress. Generalized linear regression models for repeated measures were used to estimate associations among the variables with each symptom.

RESULTS

The prevalence of hot flushes; aches, joint pain, and stiffness; and depressed mood increased in the menopausal transition. Menopausal stage was associated with hot flushes (P<.001); aches joint pain, and stiffness (P<.001); and depressed mood (P=.002). Within-woman fluctuations of E2 were associated with hot flushes and aches. Poor sleep, decreased libido, and vaginal dryness were not associated with menopausal stages. There was 80% power to detect an absolute difference of 11% for libido and vaginal dryness and 17% for poor sleep in the prevalence of these symptoms in the late menopausal transition compared with premenopausal status.

CONCLUSION

The study highlights the role of menopausal stages for some symptoms of midlife women and indicates that stages in the transition to menopause are associated with hot flushes; aches, joint pain, and stiffness; and depressed mood. Fluctuations of E2, decreased levels of inhibin b, and increased FSH levels were associated with these symptoms.

LEVEL OF EVIDENCE

II.

[Intra-articular pain during gonarthrosis: a case report about an extremely increased cathepsin expression in chondrocytes]

AIM AND BACKGROUND

Cysteine proteases as cathepsins K and L as well as matrix metalloproteases are considered to be basically involved in collagen turnover. Degenerative joint diseases such as gonarthrosis are characterised by massive cartilage degradation mediated by increased activities of these proteases. These enzymes are, therefore, interesting targets for the treatment of painful arthritic joint diseases. The aim of these studies was to reconsider the hypothesis that cathepsin activities are enhanced in patients suffering from osteoarthritis.

METHOD AND RESULTS

We report on a 69-year-old female suffering from severe pain due to predominant retropatellar arthrosis. The clinical symptoms of this patient did not significantly differ from that of 30 other patients who were involved in this study. All patients undergone an endoprosthetic knee joint replacement. During the operation we harvested cartilage probes and isolated the chondrocytes from the joint cartilage for determination of the mRNA and the activities of cathepsins B, H, K and L. Compared to chondrocytes isolated from the control patients we found the activity of cysteine proteases to be extremely enhanced in chondrocytes of this patient. Moreover, the concentration of cystatin c, an endogenous inhibitor of cathepsins, was not detectable.

CONCLUSION

The results raise doubts on the predominant role of cysteine proteases in severe cartilage destruction.

TRPV1 receptors in the CNS play a key role in broad-spectrum analgesia of TRPV1 antagonists

Vanilloid receptor type 1 (TRPV1) is a ligand-gated nonselective cation channel that is considered to be an important integrator of various pain stimuli such as endogenous lipids, capsaicin, heat, and low pH. In addition to expression in primary afferents, TRPV1 is also expressed in the CNS. To test the hypothesis that the CNS plays a differential role in the effect of TRPV1 antagonists in various types of pain, the analgesic effects of two TRPV1 antagonists with similar in vitro potency but different CNS penetration were compared in vivo. Oral administration of either A-784168 (1-[3-(trifluoromethyl)pyridin-2-yl]-N-[4-(trifluoromethylsulfonyl)phenyl]-1,2,3,6-tetrahydropyridine-4-carboxamide) (good CNS penetration) or A-795614 (N-1H-indazol-4-yl-N'-[(1R)-5-piperidin-1-yl-2,3-dihydro-1H-inden-1-yl]urea) (poor CNS penetration) blocked capsaicin-induced acute pain with the same potency. In complete Freund's adjuvant (CFA)-induced chronic inflammatory pain, oral administration of either compound blocked thermal hyperalgesia with similar potency. Furthermore, intraplantar or intrathecal administration of A-784168 blocked CFA-induced thermal hyperalgesia, suggesting that both peripheral and CNS TRPV1 receptors may play a role in inflammatory thermal hyperalgesia. The effects of the two TRPV1 antagonists were further assessed in models presumably mediated by central sensitization, including CFA- and capsaicin-induced mechanical allodynia and osteoarthritic pain. In these models, the potency of the two compounds was similar after intrathecal administration. However, when administered orally, A-784168, with good CNS penetration, was much more potent than A-795614. Together, these results demonstrate that TRPV1 receptors in the CNS play an important role in pain mediated by central sensitization. In addition, these results demonstrate that significant CNS penetration is necessary for a TRPV1 antagonist to produce broad-spectrum analgesia.

GABA(B2) receptor subunit mRNA decreases in the thalamus of monoarthritic animals

Many studies have implicated GABA(B) receptors in pain transmission mechanisms, especially in the spinal cord. In the thalamus, mRNA expression of the GABA(B(1b)) isoform was shown to be regulated in relay nuclei in response to chronic noxious input arising from experimental monoarthritis. GABA(B(1a)) and GABA(B2) mRNA expression was here determined by in situ hybridisation in the brain of control, 2, 4, 7 and 14 days monoarthritic rats, to evaluate whether this expression was regulated by chronic noxious input in thalamic nuclei. mRNA labelling was analysed quantitatively in the ventrobasal complex, posterior, central medial/central lateral and reticular thalamic nuclei; the thalamic visual relay and dentate gyrus were examined for control. No mRNA expression was detected for GABA(B(1a)) in control and monoarthritic animals. Similarly, GABA(B2) mRNA was not found in the reticular nucleus. However, GABA(B2) mRNA expression was observed in the ventrobasal complex, posterior and central medial/central lateral nuclei of control animals. A significant decrease of 42% at 2 days and 27% at 4 days of monoarthritis was observed in the ventrobasal complex contralaterally, when compared with controls, returning to basal levels at 7 days of monoarthritis. In the ipsilateral posterior nucleus, there was a significant decrease of 38% at 2 days of monoarthritis. No significant changes were observed in central medial/central lateral nuclei. The data suggest that GABA(B2) mRNA expression in the ventrobasal complex and posterior nucleus is regulated by noxious input and that GABA(B) receptors might play a role in the plasticity of these relay nuclei during chronic inflammatory pain.

Omega-3 fatty acids (fish oil) as an anti-inflammatory: an alternative to nonsteroidal anti-inflammatory drugs for discogenic pain

BACKGROUND

The use of NSAID medications is a well-established effective therapy for both acute and chronic nonspecific neck and back pain. Extreme complications, including gastric ulcers, bleeding, myocardial infarction, and even deaths, are associated with their use. An alternative treatment with fewer side effects that also reduces the inflammatory response and thereby reduces pain is believed to be omega-3 EFAs found in fish oil. We report our experience in a neurosurgical practice using fish oil supplements for pain relief.

METHODS

From March to June 2004, 250 patients who had been seen by a neurosurgeon and were found to have nonsurgical neck or back pain were asked to take a total of 1200 mg per day of omega-3 EFAs (eicosapentaenoic acid and decosahexaenoic acid) found in fish oil supplements. A questionnaire was sent approximately 1 month after starting the supplement.

RESULTS

Of the 250 patients, 125 returned the questionnaire at an average of 75 days on fish oil. Seventy-eight percent were taking 1200 mg and 22% were taking 2400 mg of EFAs. Fifty-nine percent discontinued to take their prescription NSAID medications for pain. Sixty percent stated that their overall pain was improved, and 60% stated that their joint pain had improved. Eighty percent stated they were satisfied with their improvement, and 88% stated they would continue to take the fish oil. There were no significant side effects reported.

CONCLUSIONS

Our results mirror other controlled studies that compared ibuprofen and omega-3 EFAs demonstrating equivalent effect in reducing arthritic pain. omega-3 EFA fish oil supplements appear to be a safer alternative to NSAIDs for treatment of nonsurgical neck or back pain in this selective group.

Comparison of two delivery methods of local anesthetic distribution after intra-articular knee injection

We studied the intra-articular distribution of radiopaque dye to compare the efficacy of a continuous low-volume infusion with an intermittent high-volume bolus infusion. Knee arthroscopy patients were randomized with 10 cc of dye infused over 2.5 hours versus 10 cc bolus of dye. Radiographs were independently evaluated. Eleven knees (low-volume infusion) filled an average of 3 of 7 compartments, while 10 knees (bolus group) had complete filling of all seven compartments (P < .001). This study supports high-volume bolus injections of local anesthetics to achieve consistent distribution to all knee compartments while enhancing pain control.

Expression of capsaicin receptor TRPV-1 in synovial tissues of patients with symptomatic internal derangement of the temporomandibular joint and joint pain

OBJECTIVE

To elucidate expression of capsaicin receptor TRPV-1 in synovial tissues of the human temporomandibular joint (TMJ) with internal derangement and discuss its relationship with joint pain.

STUDY DESIGN

Fifty-four TMJs in 54 patients were examined using an immunohistochemical technique. As controls, 10 TMJs with habitual dislocation without pain were also examined.

RESULTS

TRPV-1 was expressed mainly in the blood vessels beneath the lining cells in synovial tissues from 31 of the 54 joints with internal derangement and from 8 of the 10 control joints. The extent score of TRPV-1-stained cells with internal derangement was not significantly higher than that of controls. The extent score of TRPV-1 showed no correlation with joint pain.

CONCLUSIONS

TRPV-1 was detected in the region of the posterior disk attachment of synovial tissues from the TMJ in patients with internal derangement and controls. TRPV-1 may play a role in maintenance of the physiologic condition of the TMJ.

Temporomandibular joint internal derangement: relationship between joint pain and MR grading of effusion and total protein concentration in the joint fluid

OBJECTIVES

The objective of this study was to determine whether there is any association between the protein concentration in the synovial fluid and (i) the amount of articular hydrops, as graded in magnetic resonance (MR) images, and (ii) joint pain in temporomandibular joints (TMJs) with and without displacement of the disc.

PATIENTS AND METHODS

This study involved 16 joints in 16 patients referred to our clinic with the complaint of pain and limited mouth opening. The control group consisted of 15 joints in 15 patients with unilaterally normal disc and condyle relationship and no pain while the opposite side had a non-painful joint with disc displacement without reduction (DDwoR). The subjects and controls were different individuals and only a single joint was used for each. Pain and dysfunction were evaluated by visual analogue scale. Bilateral proton density and T2 weighted images of the TMJs of the 31 subjects were analysed for fluid and condyle bony changes as well as disc position. The amount of fluid, identified as an area of high signal intensity in the region of the upper and lower joint spaces, was characterized as none, minimal, moderate or marked. Arthrocentesis was performed both for synovial fluid analysis of total protein concentration and the treatment of the joints with DDwoR. Total protein concentration was measured by using protein dye binding on spectrophotometry.

RESULTS

All patients experienced a significant (P<0.01) increase in maximal mouth opening immediately post-arthrocentesis. In the study group, the disc was displaced most frequently in an anteriormedial direction (75%) and deformation of disc form was seen in 13 joints. Condylar bony changes were seen in 27% of joints in the control group and in 81% of joints in the study group. A statistically significant association was found between joints with disc displacement, disc form and condylar bony changes (P<0.05). In the control group, only one joint, which had an osteophyte, showed joint effusion (JE) with moderate fluid. In the study group, only four joints had no fluid (25%). JE was found in 10 (63%) joints with disc displacement on anteromedial direction, in 10 (63%) joints with disc deformation and in 10 (63%) joints with osteophytes and erosion. Mean total protein concentration was 16.87+/-7.9 (range 7.4-34.1 mg dl-1) in control joints, 55.08+/-35.16 (range 21.5-153.9 mg dl-1) in study joints. There were significant differences in the mean total protein concentration between the control and study groups (P<0.01). Significant positive correlation was found between the total protein concentration and JE (r=0.65, P<0.01). No significant correlation was found between the level of pain and dysfunction and JE and total protein concentration in either control or study groups (P>0.05).

CONCLUSION

Pain in the TMJ was not related to MR findings of effusion in internal derangement and synovial fluid aspirate findings of total protein concentration. However, total protein concentration was related to the amount of JE in DDwoR joints and painful joints were more likely to demonstrate the JE.

The role of peripheral 5HT2A and 5HT1A receptors on the orofacial formalin test in rats with persistent temporomandibular joint inflammation

The role of peripheral serotonin (5HT) 2A and 5HT1A receptors on the orofacial nocifensive behavioral activities evoked by the injection of formalin into the masseter muscle was evaluated in the rats with persistent temporomandibular joint (TMJ) inflammation evoked by Complete Freund's Adjuvant (CFA). The orofacial nocifensive behavioral activities evoked by the injection of formalin into masseter muscle were significantly enhanced at 1 day (CFA day 1 group) or 7 days (CFA day 7 group) during TMJ inflammation. Pretreatment with local administration of 5HT2A receptor antagonist, ketanserin (0.01, 0.1 mg/rat) into the masseter muscle or systemic administration of ketanserin via i.p. injection (1 mg/kg) reduced the orofacial nocifensive behavioral activities of the late phase evoked by formalin injection into masseter muscle on the side of TMJ inflammation (CFA day 7 group). However, local (0.001-0.1 mg/rat) or systemic (1 mg/kg) administration of 5HT1A receptor antagonist, propranolol, into masseter muscle did not produce the antinociceptive effect in CFA day 7 group. Moreover, local administration of ketanserin (0.1 mg) or propranolol (0.1 mg) into masseter muscle did not inhibit nocifensive orofacial behavior in rats without TMJ inflammation. These data suggest that persistent TMJ inflammation causes the elevation of the orofacial nocifensive behavior, and peripheral 5HT2A receptors play an important role in mediating the deep craniofacial tissue nociception in rats with TMJ inflammation.

Evidence for the involvement of endogenous ATP and P2X receptors in TMJ pain

Evidence is accumulating which supports a role for ATP in the initiation of pain by acting on P2X receptors expressed on nociceptive afferent nerve terminals. To investigate whether these receptors play a role in temporomandibular (TMJ) pain, we studied the presence of functional P2X receptors in rat TMJ by examining the nociceptive behavioral response to the application of the selective P2X receptor agonist alpha,beta-methylene ATP (alpha,beta-meATP) into the TMJ region of rat. The involvement of endogenous ATP in the development of TMJ inflammatory hyperalgesia was also determined by evaluating the effect of the general P2 receptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) on carrageenan-induced TMJ inflammatory hyperalgesia. Application of alpha,beta-meATP into the TMJ region of rats produced significant nociceptive responses that were significantly reduced by the co-application of lidocaine N-ethyl bromide quaternary salt, QX-314, (2%) or of the P2 receptor antagonist PPADS. Co-application of PPADS with carrageenan into the TMJ significantly reduced inflammatory hyperalgesia. The results indicate that functional P2X receptors are present in the TMJ and suggest that endogenous ATP may play a role in TMJ inflammatory pain mechanisms possibly by acting primarily in these receptors.

Levels of soluble cytokine factors in temporomandibular joint effusions seen on magnetic resonance images

OBJECTIVE

To elucidate the correlations between joint effusion (JE) on T2-weighted magnetic resonance images (MRI) of the temporomandibular joint (TMJ) and the levels of various cytokine receptors, cytokine antagonists, and protein in the synovial fluid of patients with temporomandibular joint disorders (TMD).

STUDY DESIGN

Fifty-five TMJs of 55 patients with TMD were scanned by MRI, and synovial fluid samples were obtained on the same day. The grade of JE was evaluated on a scale of 0 to 3: Grades 0 and 1 indicated absence, and grades 2 and 3 indicated the presence of JE. Correlations were evaluated between JE and the concentrations of soluble tumor necrosis factor receptors I and II (sTNFR-I and sTNFR-II, respectively), IL-6 soluble receptor (IL-6sR), IL-1 soluble receptor type II, and IL-1 receptor antagonist and protein in the synovial fluid of patients with TMD.

RESULTS

The concentrations of sTNFR-I and protein in the group with JE (18 joints) were significantly higher than in the group without JE (37 joints). In addition, there were significant positive correlations between the grade of JE and the levels of sTNFR-I, sTNFR-II, and protein.

CONCLUSIONS

sTNFRs and protein may play important roles in the pathogenesis of TMD. These mediators seem to influence the expression of JE, which may reflect synovial inflammation of the TMJ.

The expression and localization of somatostatin receptors in dorsal root ganglion neurons of normal and monoarthritic rats

Somatostatin has antinociceptive effects by acting on somatostatin (sst) receptors in primary afferent neurons. Five sst receptor subtypes (sst(1-5)) have been identified. In the present study we assessed the expression and localization of the sst receptor subtypes in lumbar dorsal root ganglia of normal rats and of rats with unilateral antigen-induced arthritis (AIA) in the knee joint. We used polymerase chain reaction (PCR) of material from dorsal root ganglia and immunohistochemistry in dorsal root ganglion paraffin sections. PCR data show that sst(1), sst(2(a)), sst(2(b)), sst(3), and sst(4) receptors are expressed in lumbar dorsal root ganglia of the rat. The sst(5) receptor was expressed in a few samples. Available antibodies revealed sst(2(a)) and sst(2(b)) receptor-like immunoreactivity in the vast majority of neurons, and sst(4) receptor-like immunoreactivity in about 40% of the dorsal root ganglion neurons and in some satellite cells. Real time PCR at 3, 10 and 21 days after induction of AIA did not reveal changes in receptor expression. Immunohistochemistry showed that a similar high proportion of neuronal profiles expressed sst(2(b)) receptor-like IR in control and AIA rats, but the proportion of neuronal profiles with sst(2(a)) receptor-like IR was significantly lower in acute and chronic AIA rats than in control rats. Although the proportion of neuronal profiles with sst(4) receptor-like IR was significantly higher at 21 days than at 3 days values at 3 or at 21 days were not significantly different from control. These data show that the majority of dorsal root ganglion neurons exhibit somatostatin receptor-like IR thus suggesting a high potential for inhibition by somatostatin. The reduction in the proportion of neuronal profiles with sst(2(a)) immunoreactivity suggests that inhibition of neuronal activity by somatostatin is reduced during painful arthritis.

Modulation of the gait deficit in arthritic rats by infusions of muscimol and bicuculline

Gait analysis in the adjuvant-induced arthritic rat model of chronic pain was used to examine the role of GABA(A) receptors in the development of pain. Drug solutions were administered continuously at 5+/-0.75 microl/h for 14 days via Alzet osmotic pumps (2ML2) placed under the skin of the back. The GABA(A) receptor agonist, muscimol, produces a dose-dependent reversal of the gait deficits seen in arthritic rats without reducing the tibiotarsal joints inflammatory edema or the histological picture of joint erosion and inflammation. The higher infusion rate for muscimol, 20 microg/h, caused the gait for the arthritic rats to be indistinguishable from that of normal non-arthritic rats. In normal, non-arthritic rats, muscimol did not show any effect on gait. The GABA(A) receptor antagonist bicuculline showed small but significant exacerbation of stride length (P < 0.05) single and double stance time (P < 0.05) and swing time deficits (P < 0.05) in the arthritic rats, but no changes in measures of gait in the normal control rat. The results suggest that the development of arthritic pain is increased in the absence of GABA(A) receptor tone and that increasing GABA(A) receptor tone can reduce arthritic pain but does not affect the disease process.

The proportion of TRPV1 protein-positive lumbar DRG neurones does not increase in the course of acute and chronic antigen-induced arthritis in the knee joint of the rat

The TRPV1 receptor, previously called VR1 receptor, is a non-selective cation channel gated by capsaicin, noxious heat, protons and anandamide. The TRPV1 receptor is essential for the development of thermal hyperalgesia. The present study investigated whether the proportion of neurones with TRPV1 receptor increases in lumbar DRG neurones in the course of an antigen-induced arthritis (AIA) of one knee joint in the rat. In control rats 38.1+/-2.3% of the neurones from sections of the L1-L5 ganglia showed TRPV1-like immunoreactivity. Neither in the acute (3 days) nor chronic phase (21 days) of AIA in the knee joint the proportion of TRPV1-like immunoreactive profiles showed significant changes. Thus AIA in the knee joint is not associated with an up-regulation of the TRPV1 receptor in the lumbar DRG neurones.