Epigallocatechin-3-gallate inhibits osteoclastogenesis by down-regulating c-Fos expression and suppressing the nuclear factor-kappaB signal.
Epigallocatechin-3-gallate (EGCG), the major anti-inflammatory compound in green tea, has been shown to suppress osteoclast differentiation. However, the precise molecular mechanisms underlying the inhibitory action of EGCG in osteoclastogenesis and the effect of EGCG on inflammation-mediated bone destruction remain unclear. In this study, we found that EGCG inhibited osteoclast formation induced by osteoclastogenic factors in bone marrow cell-osteoblast cocultures but did not affect the ratio of receptor activator of nuclear factor kappaB (NF-kappaB) ligand (RANKL) to osteoprotegerin induced by osteoclastogenic factors in osteoblasts. We also found that EGCG inhibited osteoclast formation from bone marrow macrophages (BMMs) induced by macrophage colony-stimulating factor plus RANKL in a dose-dependent manner without cytotoxicity. Pretreatment with EGCG significantly inhibited RANKL-induced the gene expression of c-Fos and nuclear factor of activated T-cells (NFATc1), essential transcription factors for osteoclast development. EGCG suppressed RANKL-induced activation of c-Jun N-terminal protein kinase (JNK) pathway, among the three well known mitogen-activated protein kinases and also inhibited RANKL-induced phosphorylation of the NF-kappaB p65 subunit at Ser276 and NF-kappaB transcriptional activity without affecting the degradation of IkappaBalpha and NF-kappaB DNA-binding in BMMs. The inhibitory effect of EGCG on osteoclast formation was somewhat reversed by retroviral c-Fos overexpression, suggesting that c-Fos is a downstream target for antiosteoclastogenic action of EGCG. In addition, EGCG treatment reduced interleukin-1-induced osteoclast formation and bone destruction in mouse calvarial bone in vivo. Taken together, our data suggest that EGCG has an antiosteoclastogenic effect by inhibiting RANKL-induced the activation of JNK/c-Jun and NF-kappaB pathways, thereby suppressing the gene expression of c-Fos and NFATc1 in osteoclast precursors.
Lee
Jong-Ho
JH
Department of Cell and Developmental Biology, School of Dentistry, Seoul National University, 28 Yeongon-Dong, Jongro-Gu, Seoul 110-749, Republic of Korea.
Jin
Hexiu
H
Shim
Hye-Eun
HE
Kim
Ha-Neui
HN
Ha
Hyunil
H
Lee
Zang Hee
ZH
D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects; D001862:Bone Resorption / Q000188:drug therapy* / Q000517:prevention & control; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002478:Cells, Cultured; D018920:Coculture Techniques; D015536:Down-Regulation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D050778:NFATC Transcription Factors; D010010:Osteoclasts / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D053244:Osteoprotegerin; D016760:Proto-Oncogene Proteins c-fos / Q000037:antagonists & inhibitors / Q000235:genetics*; D053245:RANK Ligand; D015398:Signal Transduction / Q000187:drug effects*
D016328:NF-kappa B; D050778:NFATC Transcription Factors; C494003:NFATC1 protein, human; D053244:Osteoprotegerin; D016760:Proto-Oncogene Proteins c-fos; D053245:RANK Ligand; C505688:TNFSF11 protein, human; D002392:Catechin; C045651:epigallocatechin gallate