LAM KID

[The pathogenic and clinical significance of the RANK-RANKL-osteoprotegerin system in rheumatoid arthritis]

SZENTPÉTERY Ágnes, VÁNCSA Andrea, SZABÓ Zoltán, SZEKANECZ Zoltán

DECEMBER 23, 2011

LAM KID - 2011;1(03)

[Rheumatoid arthritis (RA) is characterised by increased local and generalised bone resorption, which manifests in the develoment of marginal erosions and generalised osteoporosis, respectively. An increasing number of data suggest that lymphocytes, proinflammatory cytokines and other mediators involved in inflammation contribute to arthritic bone resorption. Therefore, the term ‘osteoimmunology’ has also become widely used. In RA, Receptor Activator of Nuclear Factor kappa B (RANK) and its ligand (RANKL) play a crucial role in bone resorption. These proteins, which belong to the tumor necrosis factor a (TNF-a) receptor and TNF ligand superfamilies, respectively, activate osteoclasts while interacting with T cells, synovial fibroblasts and other cytokines (e.g. IL-1, IL-17), which results in bone resorption. Osteoprotegerin (OPG) is a decoy receptor that also belongs to the TNF receptor family and inhibits RANK-RANKL interactions. There is increased RANKL production and decreased OPG production in RA. The interaction of RANKL with IL-17 is particularly important. Regarding therapy, sulfasalazine, methotrexate and biological agents, especially TNF inhibitors suppress RANKL-mediated bone resorption and thus the development of joint erosions. RANKL-RANK interaction can be directly inhibited by recombinant OPG or anti-RANKL antibody (denosumab). Among these agents, denosumab gave promising results in experiments performed in animal models of arthritis. These were followed by a phase II human RA trial, which proved that denosumab decreased MRI erosion scores in RA.]

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