Targeted drug development for arthritis

Negative Regulators of JAK/STAT Signaling in Rheumatoid Arthritis and Osteoarthritis

Elevated levels of pro-inflammatory cytokines are generally thought to be responsible for driving the progression of synovial joint inflammation in rheumatoid arthritis (RA) and osteoarthritis (OA). These cytokines activate several signal transduction pathways, including the Janus kinase/Signal Transducers and Activators of Transcription (JAK/STAT), Stress-Activated/Mitogen-Activated Protein Kinase (SAPK/MAPK) and phosphatidylinositol-3-kinase/Akt/mechanistic target of rapamycin (PI3K/Akt/mTOR) pathways which regulate numerous cellular responses. However, cytokine gene expression, matrix metalloproteinase gene expression and aberrant immune cell and synoviocyte survival via reduced apoptosis are most critical in the context of inflammation characteristic of RA and OA. Negative regulation of JAK/STAT signaling is controlled by Suppressor of Cytokine Signaling (SOCS) proteins. SOCS is produced at lower levels in RA and OA. In addition, gaining further insight into the role played in RA and OA pathology by the inhibitors of the apoptosis protein family, cellular inhibitor of apoptosis protein-1, -2 (c-IAP1, c-IAP2), X (cross)-linked inhibitor of apoptosis protein (XIAP), protein inhibitor of activated STAT (PIAS), and survivin (human) as well as SOCS appears to be a worthy endeavor going forward.

Anti-arthritic agents: progress and potential

Osteoarthritis and rheumatoid arthritis are the two most common types of arthritis. Cartilage breakdown is a key feature of both diseases which contributes to the pain and joint deformity experienced by patients. Therefore, anti-arthritis drugs are of great importance. The aim of this review is to present recent progress in studies of various agents against osteoarthritis and rheumatoid arthritis. The structures and activities of anti-arthritic agents, which used in medical practice or are in development, are presented and discussed. The effects and mechanisms of action of opioids, glucocorticoids, non-steroidal anti-inflammatory drugs, disease-modifying anti-rheumatic drugs, natural products derived from plants, nutraceuticals, and a number of new and perspective agents are considered. Various perspective targets for the treatment of osteoarthritis and rheumatoid arthritis are also discussed. Trials of good quality are needed to draw solid conclusions regarding efficacy of many of the studied agents. Unfortunately, to date, there is no pharmacologic agent proven to prevent the progression of both diseases, and there is an urgent need for further development of better anti-arthritic agents.

Intracellular Signaling Pathways in Rheumatoid Arthritis

Dysfunctional intracellular signaling involving deregulated activation of the Janus Kinase/Signal Transducers and Activators of Transcription (JAK/STAT) and "cross-talk" between JAK/STAT and the stress-activated protein kinase/mitogen-activated protein kinase (SAPK/MAPK) and Phosphatidylinositide-3-Kinase/AKT/mammalian Target of Rapamycin (PI-3K/AKT/mTOR) pathways play a critical role in rheumatoid arthritis. This is exemplified by immune-mediated chronic inflammation, up-regulated matrix metalloproteinase gene expression, induction of articular chondrocyte apoptosis and "apoptosis-resistance" in rheumatoid synovial tissue. An important consideration in the development of novel therapeutics for rheumatoid arthritis will be the extent to which inhibiting these signal transduction pathways will sufficiently suppress immune cell-mediated inflammation to produce a lasting clinical remission and halt the progression of rheumatoid arthritis pathology. In that regard, the majority of the evidence accumulated over the past decade indicated that merely suppressing pro-inflammatory cytokine-mediated JAK/ STAT, SAPK/MAPK or PI-3K/AKT/mTOR activation in RA patients may be necessary but not sufficient to result in clinical improvement. Thus, targeting aberrant enzyme activities of spleen tyrosine kinase, sphingosine kinases-1, -2, transforming growth factor β-activated kinase-1, bone marrow kinase, and nuclear factor-κB-inducing kinase for intervention may also have to be considered.