Electrochemical method for analyzing intracellular redox activity changes of the etoposide-induced apoptosis in HL-60 cells Original Research Article

An electrochemical method for analyzing HL-60 cell apoptosis (programmed cell death) induced by etoposide was examined. The cyclic voltammetric response of HL-60 cells was observed over the life-cycle of apoptotic cells. It showed that the oxidation peak current of cells decreased with etoposide treatment. The decrease of peak current of HL-60 cells appeared at 2 μg ml−1 etoposide treatment after 24 h and became significant at 20 μg ml−1, which occurred before the typical changes of cell morphology and DNA contents caused by apoptosis. Flow cytometric-DNA (FCM-DNA) analysis revealed that 10.5–20% of the cells were apoptotic while the peak current decreased from 1.8 to 0.4 μA after 2–4 h of treatment with 200 μg ml−1 etoposide. Changes of cyclic voltammetric response during the early stages of apoptosis are attributed to changes in the intracellular redox reactivity of HL-60 cells. The electrochemical responses of living cells can be used for probing intracellular redox activity of initiation of apoptosis and analyzing the whole process of apoptosis.