title: A dual role for poly(ADP-ribose) polymerase-1 during caspase-dependent apoptosis.
abstract: 2,3,5-Tris(glutathion-S-yl)hydroquinone (TGHQ), a metabolite of benzene, catalyzes the generation of reactive oxygen species (ROS) and caspase-dependent apoptosis in human promyelocytic leukemia (HL-60) cells. We now report that TGHQ induces severe DNA damage, as evidenced by DNA ladder formation and H2AX phosphorylation. The subsequent activation of the DNA nick sensor enzyme, poly(ADP-ribose) polymerase-1 (PARP-1), leads to the rapid depletion of ATP and NAD and the concomitant formation of poly(ADP-ribosylated) proteins (PARs). PJ-34 (a PARP-1 inhibitor) completely prevented the formation of PARs, partially attenuated TGHQ-mediated ATP depletion, but had little effect on NAD depletion. Intriguingly, although z-vad-fmk (a pan-caspase inhibitor) attenuated TGHQ-induced apoptosis, cotreatment with PJ-34 led to a further decrease in apoptosis, suggesting that PARP-1 participates in caspase-dependent apoptosis. Indeed, PARP-1 inhibition reduced TGHQ-induced caspase-3, -7, and -9 activation, at least partially by attenuating cytochrome c translocation from mitochondria to the cytoplasm. In contrast, PJ-34 potentiated TGHQ-induced caspase-8 activation, suggesting that PARP-1 plays a dual role in regulating TGHQ-induced apoptosis via opposing effects on the intrinsic (mitochondrial) and extrinsic (death-receptor) pathways. PARP-1 knockdown in HL-60 cells confirmed that PARP-1 participates in effector caspase activation. Finally, PJ-34 also inhibited TGHQ-induced apoptosis-inducing factor (AIF) nuclear translocation, but neither c-jun NH(2)-terminal kinase nor p38 MAPK (p38 mitogen-activated protein kinase) activation was required for AIF translocation. In summary, TGHQ-induced apoptosis of HL-60 cells is accompanied by PARP-1, caspase activation, and AIF nuclear translocation. TGHQ-induced apoptosis appears to primarily occur via engagement of the mitochondrial-mediated pathway in a process amenable to PARP inhibition. Residual cell death in the presence of PJ-34 is likely mediated via the extrinsic apoptotic pathway.
authors.affiliation: Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona Health Sciences Center, Tucson, Arizona 85721, USA.
authors.forename: Fengjiao
authors.initials: F
authors.lastname: Zhang
authors.forename: Serrine S
authors.initials: SS
authors.lastname: Lau
authors.forename: Terrence J
authors.initials: TJ
authors.lastname: Monks
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D020169:Caspases / Q000378:metabolism*; D003474:Curcumin / Q000494:pharmacology; D004249:DNA Damage; D004789:Enzyme Activation; D005978:Glutathione / Q000031:analogs & derivatives / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology; D009243:NAD / Q000378:metabolism; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*
chemical_list: D006873:Hydroquinones; D009243:NAD; C078765:2,3,5-(triglutathion-S-yl)hydroquinone; D000255:Adenosine Triphosphate; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases; D005978:Glutathione; D003474:Curcumin