Apoptosis of myelocytic leukemia HL-60 cells by polyphenol compound cyaniding-3-rutinoside is mediated by redox stress.

A90

Anthocyanins are a group of naturally occurring phenolic compounds presented in both fruits and vegetables of human diets. One of the anthocyanin class, cyanidin-3-rutinoside (C-3-R), induced human leukemia and lymphoma cells (HL-60, MOLT-4 and Daudi) apoptotic death in dose- and time-dependent manners. The present study focused on the effect of C-3-R on HL-60 cells as indicated by cytochrome c/smac release, caspase activation, Bax/Bcl-2 ratio increase, and nuclear fragmentation. Over-expression of Bcl-2 or Bcl-_XL blocked cell death and caspase activation. C-3-R treatment resulted in the activation of p38 kinase (prolonged) and JNKs (transient), as well as down-regulation of ERKs. Furthermore, C-3-R treatment led to Bim-EL phosphorylation and modification, Bax conformational change as well as Bak upregulation. Treatment of cells with specific inhibitors of p38 or JNKs, as well as N-acetyl-cysteine or catalase but not NADPH oxidase inhibitor DPI, blunted C-3-R-induced apoptotic events, whereas ERKs inhibitor augmented the cell death. Measurement of reactive oxygen species (ROS) indicated that C-3-R could scavenge ROS in test tube system; however, it perturbed intracellular peroxide levels with a two-phase manner and resulted in the accumulation of hydrogen peroxide in HL-60 cells. Importantly, C-3-R treatment showed minor affect on normal human peripheral blood mononuclear cells with or without stimulation of PHA, accompanying with less influence on intracellular ROS. These compatible results suggest that redox stress plays a crucial role in C-3-R-induced MAPK activation, Bim phosphorylation and cell death via intrinsic pathway.