Harmine, a β-carboline alkaloid, inhibits osteoclast differentiation and bone resorption in vitro and in vivo.
Bone homeostasis is controlled by the balance between osteoblastic bone formation and osteoclastic bone resorption. Excessive bone resorption is involved in the pathogenesis of bone-related disorders such as osteoporosis, arthritis and periodontitis. To obtain new antiresorptive agents, we searched for natural compounds that can inhibit osteoclast differentiation and function. We found that harmine, a β-carboline alkaloid, inhibited multinucleated osteoclast formation induced by receptor activator of nuclear factor-κB ligand (RANKL) in RAW264.7 cells. Similar results were obtained in cultures of bone marrow macrophages supplemented with macrophage colony-stimulating factor and RANKL, as well as in cocultures of bone marrow cells and osteoblastic UAMS-32 cells in the presence of vitamin D(3) and prostaglandin E(2). Furthermore, harmine prevented RANKL-induced bone resorption in both cell and bone tissue cultures. Treatment with harmine (10 mg/kg/day) also prevented bone loss in ovariectomized osteoporosis model mice. Structure-activity relationship studies showed that the C3-C4 double bond and 7-methoxy group of harmine are important for its inhibitory activity on osteoclast differentiation. In mechanistic studies, we found that harmine inhibited the RANKL-induced expression of c-Fos and subsequent expression of nuclear factor of activated T cells (NFAT) c1, which is a master regulator of osteoclastogenesis. However, harmine did not affect early signaling molecules such as ERK, p38 MAPK and IκBα. These results indicate that harmine inhibits osteoclast formation via downregulation of c-Fos and NFATc1 induced by RANKL and represses bone resorption. These novel findings may be useful for the treatment of bone-destructive diseases.
Department of Nutriproteomics, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan.
Takayuki
T
Yonezawa
Shin-ichi
S
Hasegawa
Midori
M
Asai
Tadashi
T
Ninomiya
Toshinori
T
Sasaki
Byung-Yoon
BY
Cha
Toshiaki
T
Teruya
Hidehiro
H
Ozawa
Kazumi
K
Yagasaki
Kazuo
K
Nagai
Je-Tae
JT
Woo
D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism; D001862:Bone Resorption / Q000188:drug therapy / Q000473:pathology*; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D018920:Coculture Techniques; D015536:Down-Regulation; D005260:Female; D006247:Harmine / Q000737:chemistry / Q000494:pharmacology*; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism; D051379:Mice; D008813:Mice, Inbred ICR; D050778:NFATC Transcription Factors / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism; D010010:Osteoclasts / Q000187:drug effects* / Q000502:physiology; D010052:Ovariectomy; D053245:RANK Ligand / Q000378:metabolism; D015398:Signal Transduction; D013329:Structure-Activity Relationship
D050778:NFATC Transcription Factors; D053245:RANK Ligand; D006247:Harmine; D016173:Macrophage Colony-Stimulating Factor