Hyaluronan modulates TRPV1 channel opening, reducing peripheral nociceptor activity and pain.

Hyaluronan (HA) is present in the extracellular matrix of all body tissues, including synovial fluid in joints, in which it behaves as a filter that buffers transmission of mechanical forces to nociceptor nerve endings thereby reducing pain. Using recombinant systems, mouse-cultured dorsal root ganglia (DRG) neurons and in vivo experiments, we found that HA also modulates polymodal transient receptor potential vanilloid subtype 1 (TRPV1) channels. HA diminishes heat, pH and capsaicin (CAP) responses, thus reducing the opening probability of the channel by stabilizing its closed state. Accordingly, in DRG neurons, HA decreases TRPV1-mediated impulse firing and channel sensitization by bradykinin. Moreover, subcutaneous HA injection in mice reduces heat and capsaicin nocifensive responses, whereas the intra-articular injection of HA in rats decreases capsaicin joint nociceptor fibres discharge. Collectively, these results indicate that extracellular HA reduces the excitability of the ubiquitous TRPV1 channel, thereby lowering impulse activity in the peripheral nociceptor endings underlying pain.

[Reparative regeneration of connective tissue structures of mammals under antioxidant therapy conditions].

The influence of administration of the antioxidant complexes consisting of nonenzymatic antioxidants (alpha-tocopherol acetate preparation) and enzymatic antioxidants (ceruloplasmin) has been studied in rabbits with experimental arthritis. The introduction of alpha-tocopherol acetate (at a daily dose of 4 mg) improved metabolic processes in the organism (decreased in the rate of erythrocyte precipitation, total leukocytes and their stub and segmental forms; increased in erythrocyte count; reduced the glycosaminoglycan content as determined from uronic acid and hexose level; decreased ceruloplasmin activity and malonic dialdehyde level ion blood serum, all at p < 0.05), thus favoring reduction in the total activity of the inflammatory process as judged from hematological and biochemical data. Intra-articular introduction of ceruloplasmin (1.5 mg/kg, once per week) positively influenced the state of joint structures in damaged knee joints of the animals: decreased the activity of ceruloplasmin (from 5.28 ± 0.06 to 3.94 ± 0.01 AU), and malonic dialdehyde level (0.18 ± 0.02 to 0.08 ± 0.01 µM) in the articular fluid (all at p < 0.05). These effects are probably related to the elimination of inefficiency of the antioxidant system in the synovial medium, thus preventing inflammatory destruction of articular tissues, hindering the development of pannus, and assisting the activation of reparative regeneration of connective tissue structures.

Dietary fatty acid content regulates wound repair and the pathogenesis of osteoarthritis following joint injury.

OBJECTIVE: The mechanisms linking obesity and osteoarthritis (OA) are not fully understood and have been generally attributed to increased weight, rather than metabolic or inflammatory factors. Here, we examined the influence of fatty acids, adipokines, and body weight on OA following joint injury in an obese mouse model. METHODS: Mice were fed high-fat diets rich in various fatty acids (FA) including saturated FAs (SFAs), ω-6 polyunsaturated FAs (PUFAs), and ω-3 PUFAs. OA was induced by destabilising the medial meniscus. Wound healing was evaluated using an ear punch. OA, synovitis and wound healing were determined histologically, while bone changes were measured using microCT. Activity levels and serum cytokines were measured at various time-points. Multivariate models were performed to elucidate the associations of dietary, metabolic and mechanical factors with OA and wound healing. RESULTS: Using weight-matched mice and multivariate models, we found that OA was significantly associated with dietary fatty acid content and serum adipokine levels, but not with body weight. Furthermore, spontaneous activity of the mice was independent of OA development. Small amounts of ω-3 PUFAs (8% by kcal) in a high-fat diet were sufficient to mitigate injury-induced OA, decreasing leptin and resistin levels. ω-3 PUFAs significantly enhanced wound repair, SFAs or ω-6 PUFAs independently increased OA severity, heterotopic ossification and scar tissue formation. CONCLUSIONS: Our results indicate that with obesity, dietary FA content regulates wound healing and OA severity following joint injury, independent of body weight, supporting the need for further studies of dietary FA supplements as a potential therapeutic approach for OA.

Effect of anesthetizing individual compartments of the stifle joint in horses with experimentally induced stifle joint lameness.

OBJECTIVE: To evaluate the effects of sequential anesthesia of the individual compartments of the equine stifle joint on lameness induced by intra-articular deposition of interleukin (IL)-1ß. ANIMALS: 6 horses. PROCEDURES: For each horse, baseline hind limb lameness was first evaluated. A randomly selected compartment of 1 stifle joint was then injected with IL-1ß to induce synovitis and lameness; subsequently, the same compartment was anesthetized with 2% mepivacaine hydrochloride, and lameness was reevaluated. Two weeks later, baseline lameness was evaluated, and lameness was similarly induced; thereafter, the 2 synovial compartments of the stifle joint not injected with IL-1ß were anesthetized sequentially in random order (ie, first and second blocks); lameness was evaluated after each block. Finally, the IL-1ß-treated compartment was anesthetized (third block); lameness was again evaluated. This second experiment was repeated for the contralateral stifle joint 2 weeks later. Throughout the study, lameness was quantified objectively by assessing vertical pelvic movement asymmetry with a wireless, inertial sensor-based system. RESULTS: Intra-articular deposition of IL-1ß induced lameness in all injected limbs. In the first experiment, anesthesia of the compartment injected with IL-1ß resulted in a significant decrease in lameness, with vertical pelvic movement asymmetry approaching baseline. In the second experiment, lameness improved significantly after the second and third blocks and was almost completely abolished after all 3 synovial compartments were anesthetized. CONCLUSIONS AND CLINICAL RELEVANCE: In horses, lameness caused by a lesion in 1 compartment of a stifle joint can be improved more by instillation of local anesthetic solution into that compartment than by anesthesia of the other compartments.

Analgesic effect of the neuropeptide cortistatin in murine models of arthritic inflammatory pain.

OBJECTIVE: To investigate the role of the antiinflammatory neuropeptide cortistatin in chronic pain evoked by joint inflammation. METHODS: Thermal and mechanical hyperalgesia was evoked in mouse knee joints by intraplantar injection of tumor necrosis factor α and intraarticular infusion of Freund's complete adjuvant, and the analgesic effects of cortistatin, administered centrally, peripherally, and systemically, were assessed. In addition, the effects of cortistatin on the production of nociceptive peptides and the activation of pain signaling were assayed in dorsal root ganglion cultures and in inflammatory pain models. The role of endogenous cortistatin in pain sensitization and perpetuation of chronic inflammatory states was evaluated in cortistatin-deficient mice. Finally, the effect of noxious/inflammatory stimuli in the production of cortistatin by the peripheral nociceptive system was assayed in vitro and in vivo. RESULTS: Expression of cortistatin was observed in peptidergic nociceptors of the peripheral nociceptive system, and endogenous cortistatin was found to participate in the tuning of pain sensitization, especially in pathologic inflammatory conditions. Results showed that cortistatin acted both peripherally and centrally to reduce the tactile allodynia and heat hyperalgesia evoked by arthritis and peripheral tissue inflammation in mice, via mechanisms that were independent of its antiinflammatory action. These mechanisms involved direct action on nociceptive neurons and regulation of central sensitization. The analgesic effects of cortistatin in murine arthritic pain were linked to binding of the neuropeptide to somatostatin and ghrelin receptors, activation of the G protein subunit Gαi , impairment of ERK signaling, and decreased production of calcitonin gene-related peptide in primary nociceptors. CONCLUSION: These findings indicate that cortistatin is an antiinflammatory factor with potent analgesic effects that may offer a new approach to pain therapy in pathologic inflammatory states, including osteoarthritis and rheumatoid arthritis.

The effectiveness of Echinacea extract or composite glucosamine, chondroitin and methyl sulfonyl methane supplements on acute and chronic rheumatoid arthritis rat model.

The study aimed to investigate the effect of the oral administration for 15 days of either Echinacea (E) or genuphil (a composite of chondroitin sulphate, glucosamine and methyl sulfonyl methane [GCM]) nutraceutical supplements on female rat model of acute or chronic arthritis induced by bacterial outer membrane protein (OMP) from faecal flora of healthy and rheumatic humans. Anti-cyclic citrullinated peptide (anti-CCP2), C-reactive protein (CRP) and rheumatoid factor (RF) values increased (p < 0.05) in both arthritic groups as compared to normal values. The rheumatic markers anti-CCP2, CRP and RF values decreased significantly in E- and GCM-treated groups compared to arthritic none-treated acute or chronic groups. The results of RF values of GCM-treated groups in acute and chronic models decreased exhibiting no statistical difference compared with the normal value. Histological examinations of the hind paw sections revealed moderate inflammation, oedema and mild proliferation of synovial cells in acute arthritic rats and more damage to cartilage and bone with severe inflammation in chronic ones. Echinacea acute treated group showed edema with proliferated synovial membrane and partial damage in cartilage and bone. While in the E-chronic treated group, rough edge with destructed cartilage and bone existed. However, the acute GCM group revealed mild cartilage damage. But the chronic GCM group showed mild synovial cells proliferation and revealed no inflammation with mild cartilage damage edge. Results demonstrated the OMP arthropathic property and through promising light on arthritis treatment using E- or GCM, with the advantage of GMC results over that of E-. The composite GCM is needed for further studies over the dose and duration to assess its preventive effects against the bacterial OMP arthrogenicity.

Double blind investigation of the effects of oral supplementation of combined glucosamine hydrochloride (GHCL) and chondroitin sulphate (CS) on stride characteristics of veteran horses.

REASONS FOR PERFORMING STUDY: Oral chondroprotective supplements are commercially popular for veteran (and other athletic or arthritic) horses prone to joint degeneration, yet lack conclusive scientific support. OBJECTIVES: To quantify the effects of an oral joint supplement (combination glucosamine hydrochloride (GHCL), chondroitin sulphate (CS) and N-acetyl-D-glucosamine) in vivo on stride parameters of veteran horses. METHODS: Twenty veteran horses were randomly assigned to a treatment (n = 15) or placebo group (n = 5). Pre-treatment gait characteristics were recorded at trot using digital video footage (50 Hz). The range of joint motion, stride length, and swing and stance duration were assessed using 2-dimensional motion analysis. Treatment (or placebo) was administered daily for 12 weeks at the manufacturer's recommended dosage. Gait was reassessed every 4 weeks using the pre-treatment protocol. Double blind procedure was implemented throughout. Relationships between variables were analysed using General Linear Model. RESULTS: Differences occurred in the treated horses by week 8. Range of joint motion increased significantly in the elbow (P<0.05), stifle and hind fetlock (P<0.01). Stride length increased significantly (P<0.05) with treatment. Swing duration was significantly increased at week 12 (P<0.05), whilst stance duration remained constant. CONCLUSION: The oral chondroprotective offered symptomatic relief to veteran horses, evidenced by improved stride characteristics. POTENTIAL RELEVANCE: Oral GHCL and CS supplementation may improve welfare by alleviating symptoms of degenerative joint disease.

Inactivation of xanthine oxidoreductase is associated with increased joint swelling and nitrotyrosine formation in acute antigen-induced arthritis.

OBJECTIVE: Arthritis is associated with increased articular formation of nitrotyrosine, which may contribute to injury. Nitrotyrosine is formed by nitration of tyrosine by reactive nitrogen species such as peroxynitrite, the formation of which may be enhanced by xanthine oxidoreductase (XOR), since it can generate nitric oxide from nitrite/nitrate, and superoxide during xanthine metabolism. We hypothesized that inactivation of XOR would protect against antigen-induced arthritis (AIA) and decrease nitrotyrosine formation. METHODS: AIA was induced with methylated bovine serum albumin (mBSA) in three groups of Wistar rats: animals fed on (1) tungsten-enriched chow (0.7 g/kg) (TG), which inactivates XOR, (2) standard chow (SG), and (3) rats treated with allopurinol (50 mg/kg/day; p.o.) (AG). Nitrotyrosine in patella-synovium was quantified by mass spectrometry three weeks after intra-articular (i.a.) antigen injection. RESULTS: Treatment with tungsten, but not allopurinol, suppressed plasma and articular XOR activity at < or = 0.9% of normal levels. XOR inactivation was associated with increased knee swelling 24-48 hrs post i.a. mBSA, compared with controls (mean increase +/- SEM of knee diameter from baseline of 3.3 +/- 0.5, 2.0 +/- 0.3 and 1.9 +/- 0.2 mm in TG, SG and AG (n = 14 each group), respectively; p < 0.05, TG vs SG, ANOVA). Mean ratio of articular nitrotyrosine-tyrosine (+/- SEM) was increased in the XOR-inactivated group, compared with controls: 12.3 +/- 0.7, 9.6 +/- 0.8 and 10.4 +/- 0.5 pg/microg in TG, SG and AG, respectively; p < 0.05, TG vs SG. CONCLUSION: Contrary to expectation, XOR inactivation was associated with increased joint swelling and articular tyrosine nitration in acute AIA, suggesting a novel, protective role for XOR in inflammatory arthritis.

Effect of low-level laser therapy on osteoarthropathy in rabbit.

The aim of this study was to determine whether low-level laser therapy (LLLT) aided the recovery of damaged articular cartilage in joints with artificially induced osteoarthropathy (OA). OA was induced by injecting hydrogen peroxide (H2O2) into the articular spaces of both knees in rabbits, twice a week for 4 weeks. The induction of OA and the effect of LLLT were evaluated by biochemical, radiological and histopathological analysis. Superoxide dismutase (SOD) activity increased about 40% in the OA group, as compared to the controls. Although SOD activity in the OA group was not significantly different from the 2-week groups, it was significantly different from the 4-week control and treatment groups. There was also a significant difference between the 4-week control and treatment groups. Simple radiographs and three-dimensional computed tomographs (3D CT) did not show detectable arthropathy in the OA group, nor any particular changes in the 2-week groups. In contrast, distinct erosions were seen in the distal articular cartilage of the femur, with irregularity of the articular surface, in the 4-week control group, while the erosions were reduced and arthropathy improved slightly in the 4-week treatment group. Grossly, erosions formed on the articular surface in the OA group. In comparison, severe erosions damaged the articular cartilage in the 4-week control group, but not in the 2-week control and treatment groups. Regeneration of articular cartilage was seen in gross observations in the 4-week treatment group. Histopathologically, there was slight irregularity of the articular surface and necrosis in the OA group, and serious cartilage damage, despite slight chondrocyte regeneration, in the 4-week control group. Conversely, the 4-week treatment group showed chondrocyte replacement, with sometimes close to normal articular cartilage on the articular surface. These results suggest that LLLT was effective in the treatment of chemically-induced OA.

Differential function of nitric oxide in murine antigen-induced arthritis.

BACKGROUND: The aim of our study was to investigate the role of inducible nitric oxide synthase (iNOS)-derived nitric oxide (NO) production in different stages of murine antigen-induced arthritis (AiA). METHODS: Clinical, histological and microcirculatory parameters (measured by intravital fluorescence microscopy) were assessed in the knee joint during acute and chronic AiA after inhibition of iNOS with L-N(6)-(1-iminoethyl)lysine (L-NIL). Plasma concentrations of and were evaluated by the Griess reaction and the expression of iNOS, P- and E-selectin, intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) by immunohistochemistry. RESULTS: In both stages of the disease, plasma concentrations of and were increased and iNOS was expressed. In the acute phase, swelling, leucocyte adhesion, leucocyte infiltration and expression of adhesion molecules were increased in arthritic animals treated with L-NIL in comparison with untreated arthritic animals. In the chronic phase, no change in the disease parameters could be detected after L-NIL treatment. CONCLUSION: Increased NO production induced by iNOS during the acute phase of AiA can be regarded as a protective response in the prevention of further leucocytic infiltration and joint destruction, whereas it seems to play a subordinate role in chronic AiA.