Generation of hydrogen peroxide precedes loss of mitochondrial membrane potential during DNA alkylation-induced apoptosis

Pulsed field gel electrophoresis showed that the initiation time of DIVA br eakage induced by the DNA alkylating agent duocarmycin A, which is not a re dox-cycling agent, mas almost the same in the human leukemia cell line HL-6 0 and its H2O2-resistant clone HP100. Catalase activity of HP100 cells was much higher than that of HL-60 cells. Duocarmycin A-mediated DIVA ladder fo rmation in HP100 cells nas delayed compared with that in HL-60 cells, sugge sting the involvement of H2O2 in duocarmycin A-induced apoptosis, Flow cyto metry demonstrated that peroxide formation preceded loss of mitochondrial m embrane potential (Delta Psi m) in cells treated with duocarmycin A. Then, caspase-3 was activated, followed by DNA ladder formation. These findings s uggest that DNA damage by duocarmycin A induces H2O2 generation, which caus es Delta Psi m loss and subsequently caspase-3 activation, resulting in apo ptosis, (C) 1999 Federation of European Biochemical Societies.