Regulation of RANKL-Induced Osteoclastogenesis by 635-nm Light-Emitting Diode Irradiation Via HSP27 in Bone Marrow-Derived Macrophages.
OBJECTIVE
This study was designed to investigate the effect of 635-nm irradiation from a light-emitting diode (LED) on osteoclastogenesis in receptor activator of nuclear factor kappa-B (NF-κB) ligand (RANKL)-stimulated mouse bone marrow-derived macrophages (BMMs). We determined whether 635-nm irradiation modulated the RANKL-induced osteoclastic signaling pathway in heat shock protein-27 (HSP27)-silenced cells and analyzed the functional cross talk between these factors in osteoclastic differentiation and activation.


BACKGROUND
HSP27, a member of the small HSP family, regulates oxidative stress. Clinical reports suggest that low-level laser therapy or LED therapy (LEDT) could be an effective alternative treatment for osteolytic bone disease.


METHODS
In control or HSP27-siRNA-treated BMMs, the effects of LED irradiation with 635 nm and 5 mW/cm2on RANKL-induced osteoclastic differentiation and activity were assessed by measuring tartrate-resistant acid phosphatase (TRAP) and resorption pit formation. Quantitative real-time polymerase chain reaction and western blot assays were carried out to assess the mRNA expression of osteoclastogenesis-related genes and phosphorylation of c-Jun-N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2 (ERK1/2), AKT, and p38, respectively. Intracellular reactive oxygen species (ROS) generation was measured using the 2',7'-dichlorodihydrofluorescein diacetate (H2DCF-DA) detection method.


RESULTS
The 635-nm irradiation treatment significantly increased HSP27 expression and decreased intracellular ROS generation, as well as p38 and AKT phosphorylation, leading to reductions in the expression of c-fos, NFATc1, and DC-STAMP and TRAP activation and osteoclastic bone resorption in RANKL-induced BMMs. However, in HSP27-silenced BMMs, no change was observed.


CONCLUSIONS
Thus, 635-nm irradiation modulates RANKL-induced osteoclastogenesis via HSP27 in BMMs. Thus, HSP27 may play a role in regulating the osteoclastic response to LEDT.
1 Department of Orthopedic Surgery, Chosun University Hospital , Gwangju, Korea.
Gwangchul
G
Lee
2 Department of Premedical Science, College of Medicine, Chosun University , Gwangju, Korea.
Bora
B
Kim
2 Department of Premedical Science, College of Medicine, Chosun University , Gwangju, Korea.
Youngjong
Y
Ko
2 Department of Premedical Science, College of Medicine, Chosun University , Gwangju, Korea.
Mineon
M
Park
1 Department of Orthopedic Surgery, Chosun University Hospital , Gwangju, Korea.
Donghwi
D
Kim
1 Department of Orthopedic Surgery, Chosun University Hospital , Gwangju, Korea.
Kang Hyeon
KH
Ryu
1 Department of Orthopedic Surgery, Chosun University Hospital , Gwangju, Korea.
Yong Cheol
YC
Jun
1 Department of Orthopedic Surgery, Chosun University Hospital , Gwangju, Korea.
Hong Moon
HM
Sohn
1 Department of Orthopedic Surgery, Chosun University Hospital , Gwangju, Korea.|2 Department of Premedical Science, College of Medicine, Chosun University , Gwangju, Korea.
Wonbong
W
Lim
D000818:Animals; D015153:Blotting, Western; D001862:Bone Resorption / Q000235:genetics; D002478:Cells, Cultured; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D028022:Low-Level Light Therapy; D008264:Macrophages / Q000166:cytology / Q000528:radiation effects*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010010:Osteoclasts / Q000473:pathology / Q000528:radiation effects; D010012:Osteogenesis / Q000528:radiation effects*; D053245:RANK Ligand / Q000235:genetics*; D034741:RNA, Small Interfering / Q000378:metabolism; D011897:Random Allocation; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity
D053245:RANK Ligand; D034741:RNA, Small Interfering; C505689:Tnfsf11 protein, mouse
635-nm irradiation; RANKL; heat shock protein 27; osteoclastogenesis; reactive oxygen species