Endothelium-derived contraction in a model of rheumatoid arthritis is mediated via angiotensin II type 1 receptors

A role for endothelium-derived constricting factors (EDCF), and the angiotensin II type 1 receptor (AT1R) pathway, in the vascular impairment found in the rat Freund's complete adjuvant (FCA)-model of rheumatoid arthritis (RA) was examined. FCA arthritis was induced in rats±losartan. Vehicle-treated rats served as controls. Knee-joint swelling and red blood cell (RBC) aggregation were measured as indicators of inflammation and endothelium reactivity assessed by response to acetylcholine (ACh) on aortic rings. Results show that knee-joint swelling and RBC aggregation were elevated in the FCA+vehicle group and restored to control levels in the FCA+losartan-treated animals. ACh-induced relaxation of aortic rings taken from FCA+vehicle animals was significantly impaired compared to vehicle-controls and this vasoreactivity was restored to control levels in the FCA+losartan-treated group. Further examination of aorta from the FCA+vehicle animals revealed an EDCF that was reliant on cyclooxygenase-2 (but not cyclooxygenase-1), generation of superoxide anion generation (but not hydrogen peroxide) and activation of thromboxane-prostanoid receptor. Losartan administration in vivo or ex vivo (to aortic rings) prevented the generation of the EDCF. In summary, this is the first evidence of an EDCF in a model of RA and identifies this mechanism as potentially significant in the cardiovascular disorder associated with the disease

Proteinase-activated receptor 2 modulates OA-related pain, cartilage and bone pathology

Objective Proteinase-activated receptor 2 (PAR2) deficiency protects against cartilage degradation in experimental osteoarthritis (OA). The wider impact of this pathway upon OA-associated pathologies such as osteophyte formation and pain is unknown. Herein, we investigated early temporal bone and cartilage changes in experimental OA in order to further elucidate the role of PAR2 in OA pathogenesis. Methods OA was induced in wild-type (WT) and PAR2-deficient (PAR2−/−) mice by destabilisation of the medial meniscus (DMM). Inflammation, cartilage degradation and bone changes were monitored using histology and microCT. In gene rescue experiments, PAR2−/− mice were intra-articularly injected with human PAR2 (hPAR2)-expressing adenovirus. Dynamic weight bearing was used as a surrogate of OA-related pain. Results Osteophytes formed within 7 days post-DMM in WT mice but osteosclerosis was only evident from 14 days post induction. Importantly, PAR2 was expressed in the proliferative/hypertrophic chondrocytes present within osteophytes. In PAR2−/− mice, osteophytes developed significantly less frequently but, when present, were smaller and of greater density; no osteosclerosis was observed in these mice up to day 28. The pattern of weight bearing was altered in PAR2−/− mice, suggesting reduced pain perception. The expression of hPAR2 in PAR2−/− mice recapitulated osteophyte formation and cartilage damage similar to that observed in WT mice. However, osteosclerosis was absent, consistent with lack of hPAR2 expression in subchondral bone. Conclusions This study clearly demonstrates PAR2 plays a critical role, via chondrocytes, in osteophyte development and subchondral bone changes, which occur prior to PAR2-mediated cartilage damage. The latter likely occurs independently of OA-related bone changes

Essential role for proteinase-activated receptor-2 in arthritis

Using physiological, pharmacological, and gene disruption approaches, we demonstrate that proteinase-activated receptor-2 (PAR-2) plays a pivotal role in mediating chronic inflammation. Using an adjuvant monoarthritis model of chronic inflammation, joint swelling was substantially inhibited in PAR-2-deficient mice, being reduced by more than fourfold compared with wild-type mice, with virtually no histological evidence of joint damage. Mice heterozygous for PAR-2 gene disruption showed an intermediate phenotype. PAR-2 expression, normally limited to endothelial cells in small arterioles, was substantially upregulated 2 weeks after induction of inflammation, both in synovium and in other periarticular tissues. PAR-2 agonists showed potent proinflammatory effects as intra-articular injection of ASKH95, a novel synthetic PAR-2 agonist, induced prolonged joint swelling and synovial hyperemia. Given the absence of the chronic inflammatory response in the PAR-2-deficient mice, our findings demonstrate a key role for PAR-2 in mediating chronic inflammation, thereby identifying a novel and important therapeutic target for the management of chronic inflammatory diseases such as rheumatoid arthritis

The IĸB protein BCL3 controls osteogenesis and bone health

Objective: IĸB protein B-cell lymphoma 3-encoded protein (BCL3) is a regulator of the NF-κB family of transcription factors. NF-κB signalling fundamentally influences the fate of bone-forming osteoblasts and bone-resorbing osteoclasts, but the role of BCL3 in bone biology has not been investigated. The objective of this study was to evaluate BCL3 in skeletal development, maintenance and osteoarthritic pathology. Methods: To assess the contribution of BCL3 to skeletal homeostasis, neonatal mice (n = 6-14) lacking BCL3 (Bcl3−/−) and WT controls were characterised for bone phenotype and density. To reveal the contribution to bone phenotype by the osteoblast compartment in Bcl3−/− mice, transcriptomic analysis of early osteogenic differentiation and cellular function (n = 3-7) were assessed. Osteoclast differentiation and function in Bcl3−/− mice (n = 3-5) was assessed. Adult 20-week Bcl3−/− and WT mice bone phenotype, strength and turnover were assessed. A destabilisation of the medial meniscus (DMM) model of osteoarthritic ostephytogenesis was utilised to understand adult bone formation in Bcl3−/− mice (n = 11-13). Results: Evaluation of Bcl3−/− mice revealed congenitally increased bone density, long bone dwarfism, increased bone biomechanical strength and altered bone turnover. Molecular and cellular characterisation of mesenchymal precursors showed that Bcl3−/− cells display an accelerated osteogenic transcriptional profile that leads to enhanced differentiation into osteoblasts with increased functional activity; which could be reversed with a mimetic peptide. In a model of osteoarthritis-induced osteophytogenesis, Bcl3−/− mice exhibit decreased pathological osteophyte formation (P < 0.05). Conclusion: Cumulatively, these findings demonstrate that BCL3 controls developmental mineralisation to enable appropriate bone formation, whilst in a pathological setting it contributes to skeletal pathology

How serious is diabetes? : perceptions of patients and health professionals

The study set out to test the hypothesis that both people with diabetes, and health professionals, perceive diabetes to be less serious if treated with diet than if tablets or insulin injections are used. A triangulation of methods was used. Results supported this hypothesis but the relationship is far from simple and linear