prostaglandin-d2 and Osteoarthritis--Knee

Aiming to delineate novel neuro-immune mechanisms for NGF/TrkA signalling in osteoarthritis (OA) pain, we evaluated inflammatory changes in the knee joints following injection of monoiodoacetate (MIA) in mice carrying a TrkA receptor mutation (P782S; TrkA KI mice).. In behavioural studies we monitored mechanical hypersensitivity following intra-articular MIA and oral prostaglandin D. In TrkA KI mice we observed rapid development of mechanical hypersensitivity and amplification of dorsal horn neurons and microglia activation 7 days after MIA. In TrkA KI knee joints we detected significant leukocyte infiltration and mast cells located in the vicinity of synovial nociceptive fibres. We demonstrated that mast cells exposure to NGF results in up-regulation of COX-2 and increase of PGD. Using the TrkA KI mouse model, we delineated a novel neuro-immune pathway and suggest that NGF-induced production of PGD

Topics: Animals; Arthritis, Experimental; Cartilage Diseases; Cartilage, Articular; Cyclooxygenase 2; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Enzyme Inhibitors; Female; Injections, Intra-Articular; Intramolecular Oxidoreductases; Iodoacetic Acid; Lipocalins; Macrophages; Male; Mast Cells; Mice, Inbred C57BL; Osteoarthritis, Knee; Prostaglandin D2; Receptor, trkA; Stifle; T-Lymphocytes; Up-Regulation

Blunt trauma of articular cartilage, often resulting from accidents or sports injuries, is associated with local inflammatory reactions and represents a major risk factor for development of post-traumatic osteoarthritis. TNF-α is increased in synovial fluid early after trauma, potentiates injury-induced proteoglycan degradation and may act proapoptotic under permissive conditions. We asked whether TNF-α also influences chondrocyte death, gene expression of catabolic and anabolic markers and the release of proinflammatory mediators in the early post-traumatic phase. Interactive effects of a defined single impact trauma (0.59 J) and TNF-α (100 ng/ml) on human early-stage osteoarthritic cartilage were investigated in vitro over 24 h. Exposure of traumatized cartilage to TNF-α did not increase chondrocyte death. IL-6-synthesis was augmented by trauma, TNF-α and combined treatment. The impact increased the release of PGE2 and PGD2 in the presence and absence of TNF-α to a similar extent while TNF-α alone showed no effect. In contrast, NOS2A-expression and nitric oxide (NO)-release were not affected by trauma but significantly increased by TNF-α. Expression of OPG and RANKL was not affected by TNF-α but modulated by trauma. TNF-α with and without trauma significantly induced MMP1 gene expression. These results indicate that TNF-α does not potentiate early cell death in early-stage osteoarthritic cartilage after blunt injury. However, trauma and TNF-α showed independent and interactive effects concerning prostaglandin and NO release. TNF-α probably contributes to cartilage degradation after trauma by an early induction of MMP1 gene expression. Our study confirms that an anti-TNF-α therapy may have inhibitory effects on catabolic and, partly, on inflammatory processes after a single impact trauma. As TNF-α does not contribute to the loss of chondrocytes in the initial post-traumatic phase, a combination with pharmaco-therapeutic strategies reducing early cell death could be reasonable.

Topics: Aged; Apoptosis; Cartilage, Articular; Cell Survival; Chondrocytes; Cyclooxygenase 2; Dinoprostone; Gene Expression; Humans; Interleukin-6; Intramolecular Oxidoreductases; Lipocalins; Matrix Metalloproteinase 1; Middle Aged; Nitrates; Nitric Oxide Synthase Type II; Osteoarthritis, Knee; Osteoprotegerin; Prostaglandin D2; Prostaglandin-E Synthases; RANK Ligand; Tissue Culture Techniques; Tumor Necrosis Factor-alpha

Elevated production of prostaglandin E2 (PGE2) plays an important role in the pathogenesis of arthritis. Recently, an inducible microsomal prostaglandin E synthase-1 (mPGES-1) was identified. This enzyme is functionally coupled with cyclooxygenase-2 (COX-2) and converts the COX product PGH2 to PGE2. We analyzed expression of mPGES-1 in human normal and osteoarthritic (OA) cartilage and determined the effect of different inflammatory agonists on the expression of mPGES-1 in OA chondrocytes.. Expression of mPGES-1 mRNA and protein in cartilage was determined by quantitative real-time reverse transcriptase-polymerase chain reaction and immunohistochemistry, respectively. OA chondrocytes were treated with different inflammatory agents, and mPGES-1 protein expression was evaluated by Western blot. Activation of the mPGES-1 promoter was assessed in transient transfection experiments.. Levels of mPGES-1 mRNA and protein were markedly elevated in OA versus normal cartilage. Treatment of chondrocytes with interleukin 1beta (IL-1beta) induced expression of mPGES-1 protein in a dose- and time-dependent manner. This appears to occur at the transcriptional level, as IL-1beta induced expression of mPGES-1 mRNA and the activity of this gene promoter. Tumor necrosis factor-alpha (TNF-alpha) and IL-17 also upregulated expression of mPGES-1 protein and displayed a synergistic effect with IL-1beta. Peroxisome proliferator-activated receptor-gamma ligands, 15-deoxy-delta(12,14)-prostaglandin J2 and troglitazone, inhibited IL-1beta-induced mPGES-1 protein expression, an effect that was reversed by exogenous PGE2.. Our study shows that mPGES-1 expression is upregulated in OA versus normal cartilage and that proinflammatory cytokines increased mPGES-1 expression in chondrocytes. These data suggest that mPGES-1 may prove to be an interesting therapeutic target for controlling PGE2 synthesis.

Topics: Aged; Cartilage, Articular; Cells, Cultured; Chondrocytes; Dinoprostone; Gene Expression Regulation, Enzymologic; Humans; Interleukin-1; Interleukin-17; Intramolecular Oxidoreductases; Microsomes; Middle Aged; Osteoarthritis, Knee; PPAR gamma; Prostaglandin D2; Prostaglandin-E Synthases; RNA, Messenger; Transcription, Genetic; Tumor Necrosis Factor-alpha

The PGD(2) metabolite 15-deoxy-delta12,14 PGJ(2) (15d-PGJ(2)), a potent peroxisome proliferator-activated receptor gamma (PPARgamma) activator, has recently received attention for its potential antiinflammatory effects, but its effect on the cyclooxygenase-2 (COX-2) production is still under debate. We investigated the effect of 15d-PGJ(2) on COX-2 and prostaglandin E(2) (PGE(2)) production in the absence or the presence of interleukin-1beta (IL-1beta) in human osteoarthritic chondrocytes.Data showed that, as expected, IL-1beta induced both COX-2 and PGE(2) production. The addition of 15d-PGJ(2) completely blocked (by 93%) the IL-1beta-induced PGE(2) synthesis, whereas COX-2 level was only partially reduced (by 72%). Interestingly in the absence of any COX-2 inducer, 15d-PGJ(2) up-regulated COX-2 expression without concomitant elevation of PGE(2) synthesis. This study showed that the PPARgamma agonist, 15d-PGJ(2), exerts a dual effect on COX-2 production. The mechanisms by which 15d-PGJ(2) favors COX-2 production will be discussed.

Topics: Chondrocytes; Cyclooxygenase 2; Dinoprostone; Humans; Immunologic Factors; Interleukin-1; Isoenzymes; Membrane Proteins; Osteoarthritis, Knee; Peroxidases; Prostaglandin D2; Prostaglandin-Endoperoxide Synthases; Up-Regulation