Objective: To determine matrix metalloproteinase-3 (MMP-3) serum levels in patients with rheumatic diseases and to study the relation between MMP-3 and C reactive protein (CRP) levels. Methods: MMP-3 serum levels were determined by enzyme linked immunosorbent assay (ELISA) in (a) patients with active inflammatory rheumatic diseases: rheumatoid arthritis (RA), psoriatic arthritis, polymyalgia rheumatica, acute crystal arthritis, and ankylosing spondylitis; (b) patients with active inflammatory systemic diseases: cutaneo-articular or renal systemic lupus erythematosus (SLE), systemic sclerosis, and vasculitides; (c) patients with non-inflammatory rheumatic diseases: osteoarthritis and fibromyalgia; (d) critically ill patients without rheumatic diseases, representing an acute inflammatory control group; (e) healthy controls. Results: MMP-3 serum levels were significantly increased in patients with active RA, psoriatic arthritis, and polymyalgia rheumatica, whether treated or not by corticosteroids, and in female patients with acute crystal arthritis. MMP-3 serum levels were normal in steroid-free patients with active cutaneo-articular or renal SLE, systemic sclerosis, and vasculitides but were significantly increased in steroid treated patients. MMP-3 levels were normal in fibromyalgia, osteoarthritis, ankylosing spondylitis, and acute inflammatory controls. MMP-3 was significantly correlated with CRP in RA (r=0.5, p=0.0004) but not in any of the other disease groups. Conclusions: MMP-3 serum levels are increased in inflammatory rheumatic diseases characterised by joint synovitis, such as RA, polymyalgia rheumatica, psoriatic arthritis, and acute crystal arthritis-that is, whether the diseases are acute or chronic, erosive or not. They are normal in SLE, systemic sclerosis, and vasculitides as well as in non-rheumatic inflammatory controls, but are significantly increased by steroids. These data strongly suggest that serum MMP-3 reflects synovial inflammation.

(18)F-FDG PET is a unique imaging technique for assessing the metabolic activity of synovitis. The PET findings are correlated with MRI and US assessments of the pannus in RA, as well as with the classical serum parameter of inflammation, CRP, and the synovium-derived parameter, serum MMP-3. Further studies are warranted to establish the place of metabolic imaging of synovitis in RA.

We have previously shown that nuclear factor-B inhibition by adenovirus expressing mutated IB-␣ or by proteasome inhibitor increases human articular chondrocytes sensibility to apoptosis. Moreover, the nuclear factor-B inhibitor BAY11-7085, a potent anti-inflammatory drug in rat adjuvant arthritis, is itself a proapoptotic agent for chondrocytes. In this work, we show that BAY 11-7085 but not the proteasome inhibitor MG-132 induced a rapid and sustained phosphorylation of extracellular signal-regulated kinases (ERK1/2) in human articular chondrocytes. The level of ERK1/2 phosphorylation correlated with BAY 11-7085 concentration and chondrocyte apoptosis. 15-Deoxy-⌬ 12,14 -prostaglandin J2 (15d-PGJ2) and its precursor prostaglandin (PG) D2 but not PGE2 and PGF2␣ rescued chondrocytes from BAY 11-7085-induced apoptosis. 15d-PGJ2 markedly inhibited BAY 11-7085-induced phosphorylation of ERK1/2. BAY 11-7085 also induced ERK1/2 phosphorylation and apoptosis in human synovial fibroblasts, and these reactions were down-regulated by 15d-PGJ2. Further analysis in synovial fibroblasts showed that only molecules that suppressed BAY 11-7085-induced phosphorylation of ERK1/2 (i.e. 15d-PGJ2, PGD2, and to a lesser extent, MEK1/2 inhibitor UO126, but not prostaglandins E2 and F2␣ or peroxisome proliferator-activated receptor-␥ agonist ciglitazone) were able protect cells from apoptosis. These results suggested that the antiapoptotic effect of 15d-PGJ2 on chondrocytes and synovial fibroblasts might involve inhibition of ERK1/2 phosphorylation.

Increased MMP-3 levels in SF are found in inflammatory arthropathies and are not specific for erosive joint diseases. MMP-3 in SF is therefore a potential candidate for the assessment of the inflammatory process in joints. However, the exclusive determination of the active form could indicate the degree of joint destruction.

2D-nano-UPLC-ESI-Q-Orbitrap 2 Dimensional-nano-ultra performance liquid chromatography-electrospay ionization-Q-Orbitrap CALR Calreticulin CPPA Chronic pyrophosphate arthropathy CRP C-reactive protein DAMPS Damage-associated molecular patterns ER Endoplasmic reticulum ERAD ER-associated degradation FLS Fibroblast-like synoviocytes GRP78 Glucose-regulated protein 78 kDa LC-MS/MS Liquid chromatography-tandem mass spectrometry LFQ Label free quantification MRI Magnetic resonance imaging OA Osteoarthritis PMN Polymorphonuclear cells PSM Peptide spectrum match RA Rheumatoid arthritis TLR Toll-like receptors TXNDC5 Thioredoxin domain-containing protein 5 UPR Unfolded protein response US Ultrasonography Osteoarthritis (OA) was for long considered as a degenerative cartilage disease for which synovitis was only visualized in the late stages and considered as secondary to mechanic aggression of bone and cartilage degradation. However, several observations demonstrated that synovitis could appear even in the early stages of OA. Synovium can also acquire an "inflammatory" phenotype in OA with similar characteristics than those observed in rheumatoid arthritis (RA) for which synovitis is the hallmark: [i.e. synovial lining and villous hyperplasia, infiltration by macrophages and lymphocytes, neo-angiogenesis and fibrosis] 1,2. Using magnetic resonance imaging (MRI), Roemer et al. noted a synovitis in 96.3% of knee joints with effusion and in 70% of knee joint without effusion 3. We previously published by using ultrasonography (US) examination that 53.7% (322/600) of patients with painful knee OA had no sign of inflammation whereas 2.7% (16/600) had synovitis alone, 14.2% (85/600) had both synovitis and effusion and 29.5% (177/600) had joint effusion alone 4. US knee synovitis and US joint effusion were significantly associated with a more severe radiological grade (Kellgren-Lawrence grade ≥ 3) and a moderate-important joint effusion at clinical examination 4. Further, several other studies have confirmed the correlation between synovitis area observed by MRI and specific histologic features of synovitis 5. Two major pathways at least can explain the development of synovitis: activation of toll-like receptors (TLR) and activation of the complement cascade 1. Endogenous "damage-associated molecular patterns" (DAMPS) can activate the innate immune response through TLRs recognition promoting pro-inflammatory mediators secretion 6,7. Activation of the complement cascade induces complement deposits sparsely found in the synovium of OA patients. Deposits of synovial complement components were only observed during acute OA flare but not during chronic OA 8. More recently, proteomic analyses of OA synovial fluids 9,10 and transcriptomic studies of OA synovial membranes 10 confirmed the expression and activation of complement in joints 11. Proteomic analysis of synovial tissue was rarely performed 12,13 and none was compared to the histological pattern of synovium. In this work, we compared protein profiles generated by a proteomic s...