Recent studies indicate that
reactive oxygen species, such as H2O2, can be generated by anti-
cancer drugs, can damage cells, and then induce apoptotic cell death. In this study, we reported whether
polyamines were capable of affecting apoptotic cell death triggered by H2O2 in
leukemia cells or not.
Alpha-difluoromethylornithine treatment (DFMO, 3 mmol/L, 48 h), which depletes intracellular
putrescine by inhibiting
ornithine decarboxylase, reduced H2O2-induced cell death in the HL-60
leukemia cells. Cytotoxicity caused by H2O2 in
putrescine-depleted cells was 50% lower than that in the control cells, as determined by
propidium iodide, the
annexin V and DNA fragmentation assays. Following
putrescine (1 mmol/L) supplement, cell death induction caused by H2O2 was restored to a similar level as the DFMO-untreated control cells. It seems that this partly resulted from the intralysosomal
iron-dependent oxidation of the cells because DFMO did not significantly affect the increment of
enzymes related to oxidative-stress resistance.
Putrescine depletion by DFMO treatment reduced the cellular
iron uptake of the cells by about 70%. In parallel to the reduction of
iron uptake, lysosomal damage (assayed by
acridine orange relocalization or uptake test) in the DFMO-treated cells was far less than that in the control cells. Moreover,
putrescine supplement also restored the
iron uptake to the control cell levels. Pre-incubation with
desferrioxamine (DFO), which
chelates iron and forms a non-reactive Fe-DFO complex that is localized in the lysosomal compartment, inhibited H2O2-induced cell death. This work suggests that
polyamines may play a critical role in apoptotic cell death triggered by H2O2 via the regulation of the
iron-dependent instability of the lysosome.