ABSTRACT
BACKGROUND: Besides its proinflammatory properties, prostaglandin E(2) (PGE(2)) acts as a regulator of the expression of inducible genes. Inhibition of PGE(2) synthesis might thus result in a paradoxical deleterious effect on inflammation. OBJECTIVE: To examine the effect of PGE(2) on monocyte chemoattractant protein-1 (MCP-1) expression in cultured synovial fibroblasts (SF) stimulated with interleukin (IL)1beta. METHODS: MCP-1 expression was assessed in SF stimulated with IL1beta in the presence of PGE(2) or different NSAIDs by RT-PCR or northern blot and immunocytochemistry. Expression of cyclo-oxygenase (COX) isoforms was studied by western blot techniques. The role of PGE(2) receptors (EP) in PGE(2) action was assessed employing EP receptor subtype-specific agonists. RESULTS: PGE(2) significantly inhibited IL1beta induced MCP-1 expression in SF in a dose dependent manner. IL1beta increased COX-2 and did not alter COX-1 synthesis in SF. 11-Deoxy-PGE(1), an EP(2)/EP(4) agonist, reproduced PGE(2) action on MCP-1 expression. Butaprost, a selective EP(2) agonist, was less potent than PGE(2). Sulprostone, an EP(1)/EP(3) agonist, had no effect on IL1beta induced MCP-1 expression. Inhibition of endogenous PGE(2) synthesis by NSAIDs further enhanced MCP-1 mRNA expression in IL1beta stimulated SF, an effect prevented by addition of exogenous PGE(2). CONCLUSION: Activation of EP(2)/EP(4) receptors down regulates the expression of MCP-1 in IL1beta stimulated SF, while PGE(2) pharmacological inhibition cuts off this signalling pathway and results in a superinduction of MCP-1 expression. The data suggest that NSAIDs may intercept a natural regulatory circuit controlling the magnitude of inflammation, which questions their continuous administration in inflammatory joint diseases.
Subject(s)
Chemokine CCL2/biosynthesis , Interleukin-1/pharmacology , Receptors, Prostaglandin E/physiology , Synovial Membrane/metabolism , Animals , Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Cells, Cultured , Chemokine CCL2/genetics , Dinoprostone/biosynthesis , Dinoprostone/pharmacology , Dose-Response Relationship, Drug , Fibroblasts/drug effects , Fibroblasts/metabolism , Gene Expression Regulation/drug effects , Humans , NF-kappa B/physiology , RNA, Messenger/genetics , Rabbits , Receptors, Prostaglandin E/agonists , Receptors, Prostaglandin E, EP2 Subtype , Receptors, Prostaglandin E, EP4 Subtype , Recombinant Proteins/pharmacology , Signal Transduction , Synovial Membrane/cytology , Synovial Membrane/drug effectsABSTRACT
OBJECTIVE: Glucosamine sulfate (GS) is a commonly used drug for the treatment of osteoarthritis. The mechanism of the action of this drug does, however, remain to be elucidated. In human osteoarthritic chondrocytes (HOC) stimulated with a proinflammatory cytokine, we studied whether GS could modify the NFkappaB activity and the expression of COX-2, a NFkappaB-dependent gene. METHODS: Using HOC in culture stimulated with interleukin-1 beta (IL-1beta), the effects of GS on NFkappaB activation, nuclear translocation of NFkappaB/Rel family members, COX-1 and COX-2 expressions and syntheses and prostaglandin E2 (PGE2) concentration were studied. RESULTS: GS significantly inhibited NFkappaB activity in a dose-dependent manner, as well as the nuclear translocation of p50 and p65 proteins. Furthermore, GS-preincubated IL-1beta-stimulated HOC showed an increase in IkappaBalpha in the cell cytoplasm in comparison with HOC incubated with IL-1beta alone. GS also inhibited the gene expression and the protein synthesis of COX-2 induced by IL-1beta, while no effect on COX-1 synthesis was seen. GS also inhibited the release of PGE2 to conditioned media of HOC stimulated with IL-1beta. CONCLUSIONS: GS inhibits the synthesis of proinflammatory mediators in HOC stimulated with IL-1beta through a NFkappaB-dependent mechanism. Our study further supports the role of GS as a symptom- and structure-modifying drug in the treatment of OA.
Subject(s)
Cartilage, Articular/drug effects , Chondrocytes/drug effects , Glucosamine/pharmacology , Interleukin-1/metabolism , NF-kappa B/metabolism , Osteoarthritis, Knee/metabolism , Acetylglucosamine/pharmacology , Blotting, Western/methods , Cartilage, Articular/metabolism , Cells, Cultured , Chondrocytes/metabolism , Cyclooxygenase 1 , Cyclooxygenase 2 , Dinoprostone/biosynthesis , Electrophoretic Mobility Shift Assay/methods , Fluorescent Antibody Technique/methods , Galactosamine/pharmacology , Gene Expression Regulation, Enzymologic , Humans , Isoenzymes/biosynthesis , Membrane Proteins , Prostaglandin-Endoperoxide Synthases/biosynthesisABSTRACT
OBJECTIVE: Fibrin deposits adhered to the synovial surface are typical of rheumatoid joints. Since fibrin appears to have a role in arthritis perpetuation our aim was to investigate how these deposits are formed and the consequences of their adhesion to the tissue. METHODS: The appearance of fibrin aggregates either free in the synovial fluid or attached to the membrane was studied in rabbits with antigen-induced arthritis by histological techniques at different time points from challenge. In the fixed synovial membranes areas of fibrin-bound synovium were evaluated by qualitative variables to obtain a sequential profile of morphological changes. RESULTS: Fibrin aggregates appeared from the initial stages of the disease in the synovial effusion. Later on, they were localized on the synovial surface and progressive changes were noted at the fibrin-tissue interface, ending with the invasion of the aggregates by synovial cells and their incorporation into the tissue. CONCLUSION: Fibrin aggregates generated inside the joint cavity may constitute a source of activation and acquisition of invasiveness of the synovial fibroblasts, a process to explore within the perpetuating mechanisms of rheumatoid arthritis.
Subject(s)
Arthritis, Rheumatoid/metabolism , Fibrin/analysis , Synovial Fluid/metabolism , Synovial Membrane/metabolism , Synovitis/metabolism , Animals , Arthritis, Rheumatoid/pathology , Fibrinogen/analysis , Fibroblasts/pathology , Fibronectins/analysis , Hindlimb , Immunohistochemistry , Models, Animal , Ovalbumin , Rabbits , Synovial Membrane/pathology , Time Factors , Tissue AdhesionsABSTRACT
OBJECTIVE: To study the effect of meloxicam (MXC) and diclofenac (DCF) on the recruitment of leucocytes during acute experimental arthritis. METHODS: Rabbits with antigen-induced arthritis were treated with MXC, DCF, or not treated. After 48 hours, synovial fluid (SF) leucocyte influx and prostaglandin E(2) (PGE(2)) levels were evaluated. Interleukin 8 (IL8) and monocyte chemotactic peptide-1 (MCP-1) expression and synthesis were studied in the inflamed tissues. RESULTS: Arthritic knees showed synovial effusion with a high leucocyte count and PGE(2) concentration, and an increased expression of IL8 and MCP-1. Both non-steroidal anti-inflammatory drugs (NSAIDs) reduced PGE(2) levels and the polymorphonuclear cell (PMN) concentration in SF, while the mononuclear cell (MN) concentration was unchanged in the treated groups in comparison with controls. A definite reduction of IL8 levels was obtained with the treatments, but the drugs did not prevent the up regulation of MCP-1. CONCLUSION: The effect of these NSAIDs in acute arthritis may be related to the down regulation of IL8 production. The results suggest a differential effect of anti-inflammatory drugs on PMN and MN recruitment to the joint.
