title: Donepezil prevents RANK-induced bone loss via inhibition of osteoclast differentiation by downregulating acetylcholinesterase.
abstract: OBJECTIVE
  Donepezil, an inhibitor of acetylcholinesterase (AChE) targeting the brain, is a common medication for Alzheimer's disease. Interestingly, a recent clinical study found that administration of this agent is associated with lower risk of hip fracture independently of falling, suggesting its direct effect on bone tissues as well. AChE has been reported to be involved in osteoblast function, but the role of AChE on osteoclastogenesis still remains unclear. We analyzed the effect of AChE and donepezil on osteoclastogenesis in vivo and in vitro.
  
  
  METHODS
  Cell-based assays were conducted using osteoclasts generated in cultures of murine bone marrow macrophages (BMMs) with receptor activator of nuclear factor-kappa B ligand (RANKL). The effect of donepezil was also determined in vivo using a mouse model of RANKL-induced bone loss.
  
  
  RESULTS
  Recombinant AChE in BMMs cultured with RANKL further promoted RANKL-induced tartrate-resistant acid phosphatase (TRAP)-positive osteoclast differentiation. RANKL also upregulated AChE expression in BMMs. RNA interference-mediated knockdown of AChE significantly inhibited RANKL-induced osteoclast differentiation and suppressed gene expression specific for osteoclasts. AChE upregulated expression of RANK, the receptor of RANKL, in BMMs. Donepezil decreased cathepsin K expression in BMMs and the resorptive function of osteoclasts on dentine slices. Donepezil decreased RANK expression in BMMs, resulting in the inhibition of osteoclast differentiation with downregulation of c-Fos and upregulation of Id2. Moreover, administration of donepezil prevented RANKL-induced bone loss in vivo, which was associated with the inhibition of bone resorption by osteoclasts.
  
  
  CONCLUSIONS
  AChE promotes osteoclast differentiation in vitro. Donepezil inhibits osteoclast function in vitro and prevents bone loss by suppressing bone resorption in vivo, suggesting the possibility that donepezil reduces fracture risk in patients with Alzheimer's disease.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Saitama Medical University, Saitama, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Sato
authors.affiliation: Department of Oral and Maxillofacial Surgery, Saitama Medical University, Saitama, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Enoki
authors.affiliation: Department of Biomedical Research Center, Division of Analytical Science, Saitama Medical University, Saitama, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Sakamoto
authors.affiliation: Department of Rheumatology and Applied Immunology, Saitama Medical University, Saitama, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yokota
authors.affiliation: Department of Oral and Maxillofacial Surgery, Saitama Medical University, Saitama, Japan; Division of Functional Genomics and Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Okubo
authors.affiliation: Division of Functional Genomics and Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan.
authors.forename: Masahito
authors.initials: M
authors.lastname: Matsumoto
authors.affiliation: Department of Oral and Maxillofacial Surgery, Saitama Medical University, Saitama, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Hayashi
authors.affiliation: Department of Periodontology, Kyushu Dental University, Fukuoka, Japan.
authors.forename: Michihiko
authors.initials: M
authors.lastname: Usui
authors.affiliation: Division of Molecular Signaling and Biochemistry, Department of Health Promotion, Kyushu Dental University, Fukuoka, Japan.
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Kokabu
authors.affiliation: Department of Rheumatology and Applied Immunology, Saitama Medical University, Saitama, Japan.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Mimura
authors.affiliation: Department of Neurology, Saitama Medical University, Saitama, Japan.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Nakazato
authors.affiliation: Department of Neurology, Saitama Medical University, Saitama, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Araki
authors.affiliation: Department of Physiology and Cell Biology, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Fukuda
authors.affiliation: Division of Functional Genomics and Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Okazaki
authors.affiliation: Division of Functional Genomics and Systems Medicine, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Suda
authors.affiliation: Department of Physiology and Cell Biology, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Shu
authors.initials: S
authors.lastname: Takeda
authors.affiliation: Department of Oral and Maxillofacial Surgery, Saitama Medical University, Saitama, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yoda
keywords: Acetylcholinesterase; Alzheimer's disease; Differentiation; Donepezil; Osteoclast