The utility of pathway selective estrogen receptor ligands that inhibit nuclear factor-κB transcriptional activity in models of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, debilitating condition affecting 0.5 to 1% of the world's population. The major goals of treatment of RA are to reduce pain and discomfort, to prevent deformities and loss of joint function, and to maintain a productive and active lifestyle. RA is characterized by chronic joint inflammation mediated by inflammatory cell infiltration into synovial tissues as well as joint destruction through the overexpression of matrix metalloproteinase (MMP) in articular synoviocytes and chondrocytes. The pathologic lesions of RA are driven, in part, by the production of inflammatory mediators in synoviocytes and macrophages, probably involving the transcription factor NF-κB. Because NF-κB is localized in the nuclei of synovial cells in patients with RA [1,2] and the inducers and targets of NF-κB almost perfectly match the list of pivotal mediators increased in RA [3], an important role for activated NF-κB in human RA is likely.NF-κB is a dimeric transcription factor composed of homodimeric and heterodimeric complexes of the Rel family of proteins, p65 (Rel A), p50/105, c-Rel, p52/100, and Rel B. Binding of cytoplasmic inhibitory protein-κB (IκB) to NF-κB masks the NF-κB nuclear localization signal and sequesters NF-κB in a non-activated form in the cytoplasm. Cell activation by a variety of extracellular signals such as oxidative stress, cytokines, and lipopolysaccharide induces a cascade of events that leads to the degradation of IκB; activated NF-κB then translocates to the nucleus, where it binds to DNA elements in the promoters of several proinflammatory gene families [4].Activation of NF-κB has been observed in synovial cells from patients with RA [5] and results in the induction of proinflammatory genes such as tumor necrosis factor-α (TNF-α), IL-1β, IL-6, MMP-1, and MMP-3 in ex vivo synovial membrane cultures [6]. Moreover, NF-κB activation might also be a pivotal factor protecting cells from apoptosis, thus contributing to synovial h