ag-490 and Osteoarthritis

Osteoarthritis (OA) is a complex chronic inflammatory disease characterized by articular degeneration and pain. Recent studies have identified interleukin 6 (IL-6) as a potential mediator leading to OA, but the therapeutic effects of inhibiting IL-6 signaling in intreating OA need to be further clarified. Here, we identified the intracellular signal transduction induced by recombinant IL-6 and focused on the impact of tyrphostin AG490 (a JAK2 inhibitor) on cartilage degeneration and OA pain. We found that IL-6 increased the inflammatory cytokines production and hypertrophic markers expression of primary mouse chondrocytes by activating JAK2/STAT3. Meanwhile, tyrphostin AG490 significantly attenuated articular degeneration and osteophyte formation in experimental mice with anterior cruciate ligament transection (ACLT) surgery. In vivo electrophysiological experiments showed that articular stimulation of IL-6 induced spinal hyperexcitability, which was prevented by coinjection of tyrphostin AG490. Specifically, compared with DMSO-treated ACLT mice, tyrphostin AG490 improved ambulate activity of mice and abolished the enhancement of serum bradykinin induced by IL-6. Together, we suggest that tyrphostin AG490 protected against progression of OA and improved OA prognosis by reducing cartilage degeneration and arthritis pain. Our findings provide further evidence for targeting IL-6 signaling in the treatment of OA.

Topics: Animals; Cartilage, Articular; Chondrocytes; Disease Models, Animal; Interleukin-6; Osteoarthritis; Pain; Tyrphostins

Emerging data has suggested a high prevalence of osteoarthritis (OA) among obese people. As an important adipokine secreted by white adipose tissue, leptin may be a key mediator in the progression of OA. Leptin exerts a catabolic effect on OA cartilage by increasing the production of metalloproteinase (MMP) enzymes, and contributes to apoptosis in chondrocytes. The current study aimed to explore the role of leptin on the apoptosis of chondrocytes in OA, and its underlying mechanisms. In the in vitro model of OA used in the present study, administration of exogenous leptin induced the generation of reactive oxygen species (ROS) and apoptosis in chondrocytes. It has been demonstrated that leptin is associated with the pathogenesis of OA via the Janus kinase 2 (JAK2)‑signal transducer and activator of transcription 3 (STAT3) signaling pathway, and data gathered in the present study demonstrated that suppression of this signaling pathway using a JAK2 inhibitor, AG490, significantly ameliorated leptin‑induced apoptosis in damaged chondrocytes in vitro, and reduced the generation of ROS. Furthermore, the protein expression levels of MMP‑13 and B‑cell lymphoma 2‑associated X protein were downregulated in the AG490‑treated group. The results of the present study may provide insight into the underlying molecular mechanism by which leptin induces apoptosis in chondrocytes. These findings indicated the importance of leptin as a therapeutic target for the treatment of OA in the overweight population.

Topics: Animals; Anterior Cruciate Ligament; Apoptosis; bcl-2-Associated X Protein; Blotting, Western; Cells, Cultured; Chondrocytes; Disease Models, Animal; Down-Regulation; Janus Kinase 2; Leptin; Male; Matrix Metalloproteinase 13; Osteoarthritis; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Signal Transduction; STAT3 Transcription Factor; Tyrphostins

Interleukin (IL)-23 stimulates T lymphocytes to produce inflammatory molecules, which can cause inflammatory arthritis. This study was undertaken to explore the role of IL-23 in stimulating the expression of the receptor activator of the nuclear factor kappa B (NF-kappaB) ligand (RANKL) and osteoclastogenic activity in human fibroblast-like synoviocytes (FLS). These cells were separated from the synovium of patients with rheumatoid arthritis (RA-FLS) and osteoarthritis (OA-FLS) and stimulated with IL-23. RANKL expression was measured by real-time polymerase chain reaction (PCR) amplification and immunostaining. Osteoclast precursor cells were cocultured with IL-23-stimulated RA-FLS and OA-FLS and subsequently stained for tartrate-resistant acid phosphatase (TRAP) activity. IL-23 upregulated RANKL expression in RA-FLS. The expression of RANKL mRNA and protein was blocked completely by inhibitors of NF-kappaB (parthenolide) or of the JAK II-STAT3 pathway (AG490), showing that the RANKL expression pathway is mediated by NF-kappaB and STAT3. TRAP-positive osteoclastogenesis was enhanced in IL-23-stimulated FLS. RA-FLS were more responsive to IL-23 in terms of their RANKL expression than OA-FLS or normal FLS. Thus, IL-23 appears to induce joint inflammation and bone destruction by stimulating RANKL expression in RA-FLS. These interactions between IL-23 and FLS indicate possible new therapeutic approaches for treating bone destruction in patients with inflammatory diseases.

Topics: Adult; Aged; Arthritis, Rheumatoid; Cell Differentiation; Female; Fibroblasts; Gene Expression Regulation; Humans; Interleukin-23; Male; Middle Aged; NF-kappa B; Osteoarthritis; Osteoclasts; RANK Ligand; Sesquiterpenes; Signal Transduction; STAT3 Transcription Factor; Synovial Membrane; Tyrphostins