Ultraviolet light-emitting diode irradiation induces reactive oxygen species production and mitochondrial membrane potential reduction in HL-60 cells

OBJECTIVE: Ultraviolet light-emitting diode (UV LED) irradiation at 280 nm has been confirmed to induce apoptosis in cultured HL-60 cells, but the underlying mechanisms remain unclear. This study aimed to investigate the effects of 280 nm UV LED irradiation on reactive oxygen species (ROS) production and mitochondrial membrane potential (MMP) in HL-60 cells. METHODS: HL-60 cells were irradiated with 0, 8, 15, or 30 J/m(2) of 280 nm UV LED and incubated for 2 hours. The intracellular ROS levels were assessed using the fluorescent probe 2ʹ-7ʹ-dichlorodihydrofluorescein diacetate (DCFH-DA) and a fluorescence plate reader. MMP was determined by flow cytometry using 5,5ʹ,6,6ʹ-tetrachloro-1,1ʹ,3,3ʹ-tetraethylbenzimidazol-carbocyanine iodide (JC-1) staining. The apoptosis-related proteins Bax and Bcl-2 were evaluated by western blot. RESULTS: UV LED irradiation at 280 nm induced a dose-dependent increase in ROS production and loss of MMP, and it activated apoptosis at irradiation doses of 8 to 30 J/m(2). These results were consistent with a previous apoptosis study from the authors’ group. CONCLUSION: Enhanced ROS production and mitochondrial depolarization are two distinct but interacting events, and both are involved in UV LED-induced apoptosis in HL-60 cells.