2.6. Measurement of Intracellular ROS

To measure intracellular ROS production, the 2′, 7′,-dichlorofluorescein diacetate (DCFH-DA) assay was adopted in vitro according to the manufacturer instructions (20181219, Solarbio, Beijing, China). In the presence of ROS, DCFH reacts with ROS to form the fluorescent product DCF. After incubation and treatment, cells were washed three times with DMEM and then incubated with a DCFH-DA staining solution (10 μmol/L) 37°C for 30 min in the dark. A fluorescence microscope (EVOS M5000, Thermo Fisher Scientific, USA) was used to examine fluorescence values.