Growth inhibitory effects of 15-lipoxygenase-1 [13-(S)-HPODE and 13-(S)-HODE] and 15-lipoxygenase-2 [15-(S)-HPETE and 15-(S)-HETE] (15-LOX-1 and LOX-2) metabolites and the underlying mechanisms were studied on chronic myeloid leukemia cell line (K-562). The hydroperoxy metabolites, 15-(S)-HPETE and 13-(S)-HPODE rapidly inhibited the growth of K-562 cells by 3 h with IC50 values, 10 and 15 μM, respectively. In contrast, the hydroxy metabolite of 15-LOX-2, 15-(S)-HETE, showed 50% inhibition only at 40 μM by 6 h and 13-(S)-HODE, hydroxy metabolite of 15-LOX-1, showed no significant effect up to 160 μM. The cells exposed to 10 μM of 15-(S)-HPETE and 40 μM of 15-(S)-HETE showed typical apoptotic features like release of cytochrome c, caspase-3 activation and PARP-1 (poly(ADP) ribose polymerase-1) cleavage. A flow cytometry based DCFH-DA analysis and inhibitory studies with DPI, a pharmacological inhibitor of NADPH oxidase, NAC (N-acetyl cysteine) and GSH revealed that NADPH oxidase-mediated generation of ROS is responsible for caspase-3 activation and subsequent induction of apoptosis in the K-562 cell line.
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