Homocysteine thiolactone induces apoptotic DNA damage mediated by increased intracellular hydrogen peroxide and caspase 3 activation in HL-60 cells

The cytotoxicity of homocysteine derivatives an chromosomal damage in somat ic cells is not well established. The present study used reactive homocyste ine derivative of homocysteine thiolactone (Hcy) to investigate its causal effect on apoptotic DNA injury in human promyeloid HL-60 cells. Our results demonstrated that Hey induced cell death and features of apoptosis includi ng increased phosphotidylserine exposure on the membrane surface, increased apoptotic cells with hypoploid DNA contents, and internucleosomal DNA frag mentation, all of which occurred in a time- and concentration-dependent man ner. Hey treatment also significantly increased intracellular reactive oxyg en species H2H2, which coincided with the elimination of caspase 3 proenzym e levels and increased caspase 3 activity at the time of the appearance of apoptotic DNA fragmentation. Preincubation of Hey-treated HL-60 cells with catalase completely scavenged intracellular H2O2, thus inhibiting caspase 3 activity and protecting cells from apoptotic DNA damage. In contrast, supe roxide dismutase failed to inhibit Hey-induced DNA damage. Taken together, these results demonstrate that Hey exerted its genotoxic effects on HL-60 c ells through an apoptotic pathway, which is mediated by the activation of c aspase 3 activity induced by an increase in intracellular hydrogen peroxide , (C) 2001 Elsevier Science Inc. All rights reserved.