title: Protocatechuic acid inhibits osteoclast differentiation and stimulates apoptosis in mature osteoclasts.
abstract: BACKGROUND
  Imbalance in bone remodeling causes osteoporosis.
  
  
  OBJECTIVE
  In the present study, we identified that protocatechuic acid inhibits osteoclast differentiation and induces apoptosis in RAW264.7 murine macrophage cells.
  
  
  METHODS
  Tartrate-resistance acid phosphatase (TRAP) activity was used to determine osteoclast formation. Oxidative stress was analyzed through ROS, lipid peroxide and antioxidant enzyme activities. Osteoclast and inflammatory marker expressions were determined through western blot. Apoptosis induction was determined through membrane potential analysis, Cyt c release and caspase activation.
  
  
  RESULTS
  Protocatechuic acid dose dependently reduced RANKL-induced tartrate-resistance acid phosphatase (TRAP) activity and multinucleated osteoclasts formation. Protocatechuic acid inhibited oxidative stress by reducing ROS and lipid peroxide levels with concomitant increase in antioxidant status. Osteoclast specific marker expression (MMP, c-Src, TRAP, TRAF-6, Cathepsin) and transcription factor AP-1 and NFATc1 expression were significantly down regulated by protocatechuic acid. Further, MAPK activation and inflammatory proteins such as NF-kB and COX-2 expressions were significantly down regulated by protocatechuic acid treatment. Further, protocatechuic acid enhanced Nrf-2 translocation into the nucleus. In mature osteoclasts, protocatechuic acid induced apoptosis by inducing mitochondrial membrane potential, cytochrome c release and caspase activation.
  
  
  CONCLUSIONS
  The present findings shows evidence that, protocatechuic acid prevents osteoclast differentiation through regulating oxidative stress, inflammation and inducing apoptosis in RAW264.7 murine macrophage cells.
authors.affiliation: Department of Hip Injury, Luoyang Orthopedic Hospital of Henan Province, Orthopedic Institute of Henan Province, Henan 471000, China.
authors.forename: Yi-Xin
authors.initials: YX
authors.lastname: Wu
authors.affiliation: Medical Imaging, China Medicai University, Shenyang, Liaoning 110122, China.
authors.forename: Tong-Yu
authors.initials: TY
authors.lastname: Wu
authors.affiliation: Department of Orthopedics, Shenqiu People's Hospital, Henan 471000, China.
authors.forename: Bin-Bin
authors.initials: BB
authors.lastname: Xu
authors.affiliation: Department of Operating room, Luoyang Orthopedic Hospital of Henan Province, Orthopedic Institute of Henan Province, Henan 461000, China.
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Xu
authors.affiliation: Department of Hip Injury, Luoyang Orthopedic Hospital of Henan Province, Orthopedic Institute of Henan Province, Henan 471000, China.
authors.forename: Hong-Gan
authors.initials: HG
authors.lastname: Chen
authors.affiliation: Department of Ankle Injury, Luoyang Orthopedic Hospital Of Henan Province, Orthopedic Institute of Henan Province, Henan 471000, China. Electronic address: lixiyao381@hotmail.com.
authors.forename: Xi-Yao
authors.initials: XY
authors.lastname: Li
authors.affiliation: Department of Hand Microsurgery, Linyi People's Hospital, Linyi, Shandong 276003, China.
authors.forename: Guilong
authors.initials: G
authors.lastname: Wang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D051546:Cyclooxygenase 2 / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D062385:Hydroxybenzoates / Q000494:pharmacology*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D053245:RANK Ligand / Q000494:pharmacology; D000067996:RAW 264.7 Cells; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D015415:Biomarkers; D062385:Hydroxybenzoates; D051267:NF-E2-Related Factor 2; D016328:NF-kappa B; C495636:Nfe2l2 protein, mouse; D053245:RANK Ligand; D014157:Transcription Factors; C009091:protocatechuic acid; D051546:Cyclooxygenase 2; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases
keywords: Apoptosis; Inflammation; OC differentiation; Osteoclast; Oxidative stress; Protocatechuic acid