Cellular ATP generation was measured to reflect mitochondrial function. Firstly, A549 cells were washed three times with cold PBS at room temperature. Subsequently, a luciferase-based ATP assay kit (CellTiter-Glo® Luminescent Cell Viability Assay; cat. no. G7570; Promega Corporation, Madison, WI, USA) was used to analyze ATP content, according to the manufacturer's protocols (10 (link)). ATP production was measured using a microplate reader at a wavelength of 570 nm (Epoch 2; BioTek Instruments, Inc., Winooski, VT, USA) (26 (link)). To observe the mitochondrial potential, JC-1 staining (cat no. M34152; Thermo Fisher Scientific Inc.) was used. Briefly, 10 mg/ml JC-1 was added to the medium for 10 min at 37°C in the dark, in order to label mitochondria. Images were captured under an Olympus IX81 microscope (Olympus Corporation). Normal mitochondrial potential was indicated by red fluorescence, whereas damaged mitochondrial potential was indicated by green fluorescence (27 (link)).