title: Effects of light-emitting diode irradiation on RANKL-induced osteoclastogenesis.
abstract: OBJECTIVE
  Bone homeostasis is maintained by a balance between osteoblastic bone formation and osteoclastic bone resorption, where intracellular reactive oxygen species (ROS) are crucial mediators of osteoclastogenesis. Recently, low-level light therapy (LLLT), a form of laser medicine used in various clinical fields, was shown to alleviate oxidative stress by scavenging intracellular ROS. The present study aimed to investigate the impact of 635 nm irradiation from a light-emitting diode (LED) on osteoclastogenesis from receptor activator of nuclear factor kappa-B (NF-κB) ligand (RANKL)-stimulated mouse bone marrow-derived macrophages (BMMs).
  
  
  METHODS
  The effects of LED irradiation on osteoclastogenesis were assessed in tartrate-resistant acid phosphatase (TRAP), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), cell viability, and resorption pit formation, respectively. Quantitative real-time polymerase chain reaction (qPCR) and Western blot analyses were also performed to assess mRNA expression of osteoclastogenesis-related genes and phosphorylation of extracellular signal-regulated kinase 1/2 (ERK 1/2), p38, and c-Jun-N-terminal kinase (JNK). NF-κB activity was assayed by luciferase reporter assay and Intracellular ROS generation was investigated by the 2',7'-dichlorodihydrofluorescein diacetate (H2 DCF-DA) detection method.
  
  
  RESULTS
  LED irradiation significantly inhibited RANKL-mediated osteoclast differentiation from BMMs and mRNA expression of TRAP, osteoclast-associated immunoglobulin-like receptor (OSCAR), and dendrocyte-expressed seven-transmembrane protein (DC-STAMP). Exposure to LED light likewise significantly decreased RANKL-facilitated NF-κB activity, p38 and ERK phosphorylation and intracellular ROS generation, and increased gene expression of nuclear factor E2-related factor 2 (Nrf2).
  
  
  CONCLUSIONS
  Taken together, the results presented herein show that LED irradiation downregulates osteoclastogenesis by reducing ROS production. Therefore, LED irradiation/LLLT might be useful as an alternative, conservative approach to osteoporosis management.
authors.affiliation: Department of Orthopaedic Surgery, Chosun University Hospital, Dong-Gu, Gwangju, Korea.
authors.forename: HongMoon
authors.initials: H
authors.lastname: Sohn
authors.affiliation: Department of Orthopaedic Surgery, Chosun University Hospital, Dong-Gu, Gwangju, Korea.
authors.forename: Youngjong
authors.initials: Y
authors.lastname: Ko
authors.affiliation: Department of Orthopaedic Surgery, Chosun University Hospital, Dong-Gu, Gwangju, Korea.
authors.forename: Mineon
authors.initials: M
authors.lastname: Park
authors.affiliation: Department of Orthopaedic Surgery, Chosun University Hospital, Dong-Gu, Gwangju, Korea.
authors.forename: Donghwi
authors.initials: D
authors.lastname: Kim
authors.affiliation: Department of Orthopaedic Surgery, Chosun University Hospital, Dong-Gu, Gwangju, Korea.
authors.forename: Young Lae
authors.initials: YL
authors.lastname: Moon
authors.affiliation: Department of Orthopaedic Surgery, Chosun University Hospital, Dong-Gu, Gwangju, Korea.
authors.forename: Yeon Joo
authors.initials: YJ
authors.lastname: Jeong
authors.affiliation: Department of Orthopaedic Surgery, Chosun University Hospital, Dong-Gu, Gwangju, Korea.
authors.forename: Hyeonjun
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Dental Hygiene, Chodang University, Jeollanam-do, South Korea.
authors.forename: Yeonhee
authors.initials: Y
authors.lastname: Moon
authors.affiliation: Medical Research Center for Biomineralization Disorders, School of Dentistry, Chonnam National University, Gwangju, Korea.
authors.forename: Byung-Chul
authors.initials: BC
authors.lastname: Jeong
authors.affiliation: Department of Oral Pathology, School of Dentistry, Chonnam National University, Bug-Gu, Gwangju, Korea.
authors.forename: Okjoon
authors.initials: O
authors.lastname: Kim
authors.affiliation: Department of Orthopaedic Surgery, Chosun University Hospital, Dong-Gu, Gwangju, Korea.|Department of Premedical Program, School of Medicine, Chosun University, Dong-Gu, Gwangju, Korea.
authors.forename: Wonbong
authors.initials: W
authors.lastname: Lim
mesh_terms: D000818:Animals; D001862:Bone Resorption / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000528:radiation effects; D028022:Low-Level Light Therapy / Q000295:instrumentation*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010010:Osteoclasts / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D053245:RANK Ligand / Q000502:physiology*
chemical_list: D053245:RANK Ligand
keywords: low-level light therapy; osteoclastogenesis; osteoporosis; reactive oxygen species