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2‐Methoxystypandrone represses RANKL‐mediated osteoclastogenesis by down‐regulating formation of TRAF6–TAK1 signalling complexes
Author(s) -
Chiou WF,
Liao JF,
Huang CY,
Chen CC
Publication year - 2010
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.2010.00823.x
Subject(s) - rankl , osteoclast , chemistry , bone resorption , microbiology and biotechnology , activator (genetics) , cancer research , receptor , endocrinology , biology , biochemistry
BACKGROUND AND PURPOSE 2‐Methoxystypandrone (2‐MS) is a naphthoquinone isolated from Polygonum cuspidatum , a Chinese herb used to treat bone diseases. Here we have determined whether 2‐MS antagonised osteoclast development and bone resorption. EXPERIMENTAL APPROACH RAW264.7 cells were treated with receptor activator of nuclear factor κB (NF‐κB) ligand (RANKL) to induce differentiation into osteoclasts. RT‐PCR and Western blot were used to analyse osteoclast‐associated gene expression and signalling pathways. KEY RESULTS The number of multinuclear osteoclasts, actin rings and resorption pit formation were markedly inhibited by 2‐MS, targeting osteoclast differentiation at an early stage and without significant cytotoxicity. The anti‐resorption effect of 2‐MS was accompanied by decreasing dendritic cell‐specific transmembrane protein and matrix metalloproteinase‐9 (MMP‐9) mRNA expression. RANKL‐increased MMP‐9 gelatinolytic activity was also attenuated by concurrent, but not by subsequent addition of 2‐MS. 2‐MS markedly inhibited not only the RANKL‐triggered nuclear translocations of NF‐κB, c‐Fos and nuclear factor of activated T cells c1 (NFATc1), but also the subsequent NFATc1 induction. Degradation of IκB and phosphorylation of mitogen‐activated protein kinases were also suppressed. RANKL facilitated the formation of singaling complexes of tumour necrosis factor receptor‐associated factor 6 and transforming growth factor β‐activated kinase 1 (TRAF6–TAK1), important for osteoclastogenesis and formation of such signalling complexes was prevented by 2‐MS. CONCLUSIONS AND IMPLICATIONS The anti‐osteoclastogenic effects of 2‐MS could reflect the block of RANKL‐induced association of TRAF6–TAK1 complexes with consequent decrease of IκB‐mediated NF‐κB and mitogen‐activated protein kinases‐mediated c‐Fos activation pathways and suppression of NFATc1 and other gene expression, essential for bone resorption.