Regulation of RANKL-Induced Osteoclastogenesis by 635-nm Light-Emitting Diode Irradiation Via HSP27 in Bone Marrow-Derived Macrophages

• Published in: Photomedicine and laser surgery Vol. 35; no. 2; p. 78
• Main Authors: Lee, Gwangchul, Kim, Bora, Ko, Youngjong, Park, Mineon, Kim, Donghwi, Ryu, Kang Hyeon, Jun, Yong Cheol, Sohn, Hong Moon, Lim, Wonbong
• Format: Journal Article
• Language: English
• Published: United States 01.02.2017
• Subjects: Animals; Blotting, Western; Bone Resorption - genetics; Cells, Cultured; Disease Models, Animal; Gene Expression Regulation; Low-Level Light Therapy; Macrophages - cytology; Macrophages - radiation effects; Male; Mice; Mice, Inbred BALB C; Osteoclasts - pathology; Osteoclasts - radiation effects; Osteogenesis - radiation effects; Random Allocation; RANK Ligand - genetics; Real-Time Polymerase Chain Reaction - methods; RNA, Small Interfering - metabolism; Sensitivity and Specificity; RANKL; heat shock protein 27; osteoclastogenesis; 635-nm irradiation; reactive oxygen species
• DOI: 10.1089/pho.2016.4134

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. 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. In control or HSP27-siRNA-treated BMMs, the effects of LED irradiation with 635 nm and 5 mW/cm on 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 (H DCF-DA) detection method. 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. 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.