According to the study of mitochondrial membrane potential (MMP) was carried out with minor modifications. Briefly, the treatment of the cells with rotenone was taken place for indicating periods after pretreated with Celastrol for almost 90 min. After the treatment of cells for 24 h, Rhodamine 123 was added and was incubated for 30 min at 37°C and 5% CO2 in the dark. Excess dye was washed using PBS and fluorescence intensity was measured using a BMG Fluostar Optima fluorescence microplate reader set at excitation wavelengths of 492 nm and 520 nm, and emission wavelengths of 544 nm and 590 nm. The ratio of the fluorescence intensities at 590 nm/520 nm were used as an indication of MMP and the results were expressed as fluorescence/mg of protein.