Dihydroethidium (DHE) staining

Cells were digested and collected by centrifugation at 800 rpm for 3 min. Cells were then resuspended in warm PBS and centrifuged at 800 rpm for 3 min before being incubated with DHE solution (7.5 μM) for 30 min in the dark. Cells were centrifuged at 800 rpm for 3 min, resuspended, and washed with PBS three times. Then cells were resuspended with PBS, transferred to a flow tube, and measured on the flow cytometer (BD Biosciences) in the FITC channel. Data acquisition and analysis were performed using FACSDiva and FlowJo software (BD Biosciences).