Involvement of caspases in 4-hydroxy-alkenal-induced apoptosis in human leukemic cells

4-Hydroxynonenal (HNE), a reactive and cytotoxic end-product of Lipid perox idation, has been suggested to be a key mediator of oxidative stress-induce d cell death and in various cell types has been shown to induce apoptosis. We have demonstrated that HNE, at micromolar concentrations, induces dose- and time-dependent apoptosis in a leukemic cell line (CEM-C7). Interestingl y, much higher concentrations of HNE (>15-fold) were required to induce apo ptosis in leukocytes obtained from normal individuals. We also demonstrate that HNE causes a decrease in clonogenicity of CEM-C7 cells. Furthermore, o ur data characterize the caspase cascade involved in HNE-induced apoptosis in CEM-C7 cells. Using specific fluorogenic substrates and irreversible pep tide inhibitors, we demonstrate that caspase 2, caspase 3, and caspase 8 ar e involved in NE-induced apoptosis, and that caspase 2 is the first initiat or caspase that activates the executioner caspase 3, either directly or via activation of caspase 8. Our studies also suggest the involvement of anoth er executioner caspase, which appears to be similar to caspase 8 but not ca spases 2 and 3, in its specificity. The demonstration of decreased clonogen icity by HNE in the leukemic cells, and their higher susceptibility to HNE- induced apoptosis as compared to the normal cells, suggests that such compo unds may have potential for leukemia chemotherapy. (C) 2001 Elsevier Scienc e Inc.