title: Photobiomodulation with 670 nm light increased phagocytosis in human retinal pigment epithelial cells.
abstract: OBJECTIVE
  Photobiomodulation is the treatment with light in the far-red to near-infrared region of the spectrum and has been reported to have beneficial effects in various animal models of disease, including an age-related macular degeneration (AMD) mouse model. Previous reports have suggested that phagocytosis is reduced by age-related increased oxidative stress in AMD. Therefore, we investigated whether photobiomodulation improves phagocytosis caused by oxidative stress in the human retinal pigment epithelial (ARPE-19) cell line.
  
  
  METHODS
  ARPE-19 cells and human primary retinal pigment epithelium (hRPE) cells were incubated and irradiated with near-infrared light (670 nm LED light, 2,500 lx, twice a day, 250 s/per time) for 4 d. Next, hydrogen peroxide (H2O2) and photoreceptor outer segments (POS) labeled using a pH-sensitive fluorescent dye were added to the cell culture, and phagocytosis was evaluated by measuring the fluorescence intensity. Furthermore, cell death was observed by double staining with Hoechst33342 and propidium iodide after photobiomodulation. CM-H2DCFDA, JC-1 dye, and CCK-8 were added to the cell culture to investigate the reactive oxygen species (ROS) production, mitochondrial membrane potential, and cell viability, respectively. We also investigated the expression of phagocytosis-related proteins, such as focal adhesion kinase (FAK) and Mer tyrosine kinase (MerTK).
  
  
  RESULTS
  Oxidative stress inhibited phagocytosis, and photobiomodulation increased the oxidative stress-induced hypoactivity of phagocytosis in ARPE-19 cells and hRPE cells. Furthermore, H2O2 and photobiomodulation did not affect cell death in this experimental condition. Photobiomodulation reduced ROS production but did not affect cell viability or mitochondrial membrane potential. The expression of phosphorylated MerTK increased, but phosphorylated FAK was not affected by photobiomodulation.
  
  
  CONCLUSIONS
  These findings indicate that near-infrared light photobiomodulation (670 nm) may be a noninvasive, inexpensive, and easy adjunctive therapy to help inhibit the development of ocular diseases induced by the activation of phagocytosis.
authors: Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, Gifu, Japan.
authors: Shinichiro
authors: S
authors: Fuma
authors: Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, Gifu, Japan.
authors: Hiromi
authors: H
authors: Murase
authors: Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, Gifu, Japan.
authors: Yoshiki
authors: Y
authors: Kuse
authors: Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, Gifu, Japan.
authors: Kazuhiro
authors: K
authors: Tsuruma
authors: Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, Gifu, Japan.
authors: Masamitsu
authors: M
authors: Shimazawa
authors: Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, Gifu, Japan.
authors: Hideaki
authors: H
authors: Hara
mesh_terms: D000818:Animals; D002460:Cell Line; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D006801:Humans; D007259:Infrared Rays / Q000627:therapeutic use; D008268:Macular Degeneration / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control; D053078:Membrane Potential, Mitochondrial / Q000528:radiation effects; D051379:Mice; D018384:Oxidative Stress / Q000528:radiation effects; D010587:Phagocytosis / Q000528:radiation effects*; D010789:Phototherapy / Q000379:methods; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects*; D013552:Swine; D000076202:c-Mer Tyrosine Kinase
chemical_list: D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; C097072:MERTK protein, human; D020794:Receptor Protein-Tyrosine Kinases; D000076202:c-Mer Tyrosine Kinase; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human