title: Effects of low-intensity ultrasound on oxidative damage in retinal pigment epithelial cells in vitro.
abstract: Oxidative stress in retinal pigment epithelium (RPE) is one of the key causative factors of RPE injury in age-related macular degeneration (AMD). Low-intensity ultrasound (LIUS) less than 1 W/cm(2) in intensity has been found to have cytoprotective and anti-inflammatory effects in many cell types and diseases. In this study, we investigated for the first time the feasibility of using LIUS to protect RPE cells from oxidative damage. ARPE-19 cells were treated with H2O2 (an exogenous source of reactive oxygen species) or L-buthionine-(S,R)-sulfoximine (BSO), a glutathione synthase inhibitor, and exposed immediately to LIUS at intensities of 50, 100 and 200 mW/cm(2) and a frequency of 1 MHz for 20 min. Both H2O2 and BSO increased the percentage of cells positive for mitochondrial reactive oxygen species at 1 h, but not at 24 h. Co-treatment with LIUS clearly repressed these cells similarly at all intensities by approximately 34%-43% for H2O2 and 24%-25% for BSO (p < 0.05). The percentage of cells with mitochondrial membrane depolarization also increased with H2O2 and BSO treatment, particularly at 1 h, and decreased by approximately 60% with LIUS at 100 mW/cm(2) (p < 0.05). The amount of intracellular calcium ion ([Ca(2+)]i) was elevated only by BSO at 24 h and was also significantly diminished, by approximately 45%, by LIUS at 100 mW/cm(2) (p < 0.05). Both H2O2 and BSO significantly hampered cell viability at 24 h, but LIUS at 100 mW/cm(2) restored only BSO-induced cell viability by approximately 2.7-fold (p < 0.05). This study illustrated that LIUS has a protective effect on RPE cells against oxidative damage caused by BSO, an endogenous mitochondrial reactive oxygen species generator. We speculate that LIUS has the potential to treat oxidative damage and related pathologic changes in RPE.
authors.affiliation: Department of Physiology, Inha University College of Medicine, Incheon, Republic of Korea.
authors.forename: Na Kyeong
authors.initials: NK
authors.lastname: Kim
authors.affiliation: Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Chan Yun
authors.initials: CY
authors.lastname: Kim
authors.affiliation: Department of Medicine, College of Medicine, Cheju National University, Cheju, Republic of Korea.
authors.forename: Min Joo
authors.initials: MJ
authors.lastname: Choi
authors.affiliation: Department of Physiology, Inha University College of Medicine, Incheon, Republic of Korea. Electronic address: srpark@inha.ac.kr.
authors.forename: So Ra
authors.initials: SR
authors.lastname: Park
authors.affiliation: Department of Biomedical Sciences, Inha University College of Medicine, Incheon, Republic of Korea. Electronic address: bryan@inha.ac.kr.
authors.forename: Byung Hyune
authors.initials: BH
authors.lastname: Choi
mesh_terms: D002460:Cell Line; D004307:Dose-Response Relationship, Radiation; D004847:Epithelial Cells / Q000166:cytology* / Q000502:physiology* / Q000528:radiation effects; D006801:Humans; D018384:Oxidative Stress / Q000502:physiology* / Q000528:radiation effects; D011829:Radiation Dosage; D017382:Reactive Oxygen Species / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000166:cytology* / Q000502:physiology* / Q000528:radiation effects; D000069453:Ultrasonic Waves
chemical_list: D017382:Reactive Oxygen Species
keywords: Cytoprotection; Low-intensity ultrasound; Mitochondria; Oxidative stress; Retinal pigment epithelium