N,N-dimethyl phytosphingosine induces caspase-8-dependent cytochrome c release and apoptosis through ROS generation in human leukemia cells

Journal Article · Sat Aug 15 04:00:00 EDT 2009 · Toxicology and Applied Pharmacology

DOI:https://doi.org/10.1016/j.taap.2009.05.020· OSTI ID:21272631

Kim, Byeong Mo; Choi, Yun Jung ^[1]; Han, Youngsoo ^[1]; Yun, Yeon-Sook ^[1]

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1. Division of Radiation Cancer Research, Korea Institute of Radiological and Medical Sciences, 215-4, Gongneung-Dong, Nowon-Gu, Seoul, 139-706 (Korea, Republic of)

N,N-dimethyl phytosphingosine (DMPS) blocks the conversion of sphingosine to sphingosine-1-phosphate (S1P) by the enzyme sphingosine kinase (SK). In this study, we elucidated the apoptotic mechanisms of DMPS action on a human leukemia cell line using functional pharmacologic and genetic approaches. First, we demonstrated that DMPS-induced apoptosis is evidenced by nuclear morphological change, distinct internucleosomal DNA fragmentation, and an increased sub-G1 cell population. DMPS treatment led to the activation of caspase-9 and caspase-3, accompanied by the cleavage of poly(ADP-ribose) polymerase (PARP) and led to cytochrome c release, depolarization of the mitochondrial membrane potential, and downregulation of the anti-apoptotic members of the bcl-2 family. Ectopic expression of bcl-2 and bcl-xL conferred resistance of HL-60 cells to DMPS-induced cell death, suggesting that DMPS-induced apoptosis occurs predominantly through the activation of the intrinsic mitochondrial pathway. We also observed that DMPS activated the caspase-8-Bid-Bax pathway and that the inhibition of caspase-8 by z-IETD-fmk or small interfering RNA suppressed the cleavage of Bid, cytochrome c release, caspase-3 activation, and apoptotic cell death. In addition, cells subjected to DMPS exhibited significantly increased reactive oxygen species (ROS) generation, and ROS scavengers, such as quercetin and Tiron, but not N-acetylcysteine (NAC), inhibited DMPS-induced activations of caspase-8, -3 and subsequent apoptotic cell death, indicating the role of ROS in caspase-8-mediated apoptosis. Taken together, these results indicate that caspase-8 acts upstream of caspase-3, and that the caspase-8-mediated mitochondrial pathway is important in DMPS-induced apoptosis. Our results also suggest that ROS are critical regulators of caspase-8-mediated apoptosis in DMPS-treated leukemia cells.

• OSTI ID: 21272631
• Journal Information: Toxicology and Applied Pharmacology, Journal Name: Toxicology and Applied Pharmacology Journal Issue: 1 Vol. 239; ISSN TXAPA9; ISSN 0041-008X
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
ADP
APOPTOSIS
DEPOLARIZATION
DNA
ENZYME INHIBITORS
ENZYMES
FRAGMENTATION
HUMAN POPULATIONS
LEUKEMIA
MITOCHONDRIA
MORPHOLOGICAL CHANGES
PHOSPHATES
QUERCETIN
RNA
TIRON
TOXICITY