Signalling, inflammation and arthritis: NF-kappaB and its relevance to arthritis and inflammation

In the synovial cells of patients with RA, activation of thenuclear factor-B (NF-B) pathway results in the transactivationof a multitude of responsive genes that contribute to the inflammatoryphenotype, including TNF- from macrophages, matrix metalloproteinasesfrom synovial fibroblasts and chemokines that recruit immunecells to the inflamed pannus. This is largely a consequenceof activation of the ‘canonical’ NF-B pathway thatinvolves heterodimers of p50/p65. Whilst much information onthe role of NF-B in inflammation has been gleaned from geneticdeficiency of the respective genes in mice, important differencesexist in the signalling networks between human and murine immunecells and immortalized cell lines. Despite these differencesat the molecular level, the importance of NF-B in inflammationis undisputed and inhibition of the pathway is widely believedto have great potential as a therapeutic target in RA. Commercialeffort has gone into developing inhibitors of NF-B activation.However, inhibition of the NF-B activation can result in anexacerbation of inflammation if TNF- production by macrophagesis not controlled. It will be important that such inhibitorsare carefully monitored before their long-term use in chronicinflammatory conditions such as RA. KEY WORDS: NF-B, Signalling pathways, ReviewSubmitted 13 July 2007; revised version accepted 4 October 2007.