title: Haplophytin-A induces caspase-8-mediated apoptosis via the formation of death-inducing signaling complex in human promyelocytic leukemia HL-60 cells.
abstract: Haplophytin-A (10-methoxy-2,2-dimethyl-2,6-dihydro-pyrano[3,2-c]quinolin-5-one), a novel quinoline alkaloid, was isolated from the Haplophyllum acutifolium. In this study, we investigated the effect of haplophytin-A on the apoptotic activity and the molecular mechanism of action in human promyelocytic leukemia HL-60 cells. Treatment with haplophytin-A (50μM) induced classical features of apoptosis, such as, DNA fragmentation, DNA ladder formation, and the externalization of annexin-V-targeted phosphatidylserine residues in HL-60 cells. In addition, haplophytin-A triggered the activations of caspase-8, -9, and -3, and the cleavage of poly (ADP-ribose) polymerase (PARP) in HL-60 cells. In addition, haplophytin-A caused the loss of mitochondrial membrane potential (ΔΨ(m)) and the release of cytochrome c and Smac/DIABLO to the cytosol, and modulated the expression levels of Bcl-2 family proteins. We further demonstrated that knockdown of caspase-8 using its siRNA inhibited the mitochondrial translocation of tBid, the activations of caspase-9 and caspase-3, and subsequent DNA fragmentation by haplophytin-A. Furthermore, haplophytin-A-induced the formation of death-inducing signaling complex (DISC) and then activated caspase-8 in HL-60 cells. During haplophytin-A-induced apoptosis, caspase-8-stimulated tBid provide a link between the death receptor-mediated extrinsic pathway and the mitochondria- mediated intrinsic pathway. Taken together, these results suggest that the novel compound haplophytin-A play therapeutical role for leukemia via the potent apoptotic activity through the extrinsic pathway, involving the intrinsic pathway.
authors.affiliation: Department of Pharmaceutical Biochemistry, Kyung Hee University, Dongdaemun-gu, Seoul 130-701, Republic of Korea.
authors.forename: Kyung-Jae
authors.initials: KJ
authors.lastname: Won
authors.forename: Kyung-Sook
authors.initials: KS
authors.lastname: Chung
authors.forename: Yong Sup
authors.initials: YS
authors.lastname: Lee
authors.forename: Muhammad Shaiq
authors.initials: MS
authors.lastname: Alia
authors.forename: Muhammad Kashif
authors.initials: MK
authors.lastname: Pervez
authors.forename: Samreen
authors.initials: S
authors.lastname: Fatima
authors.forename: Jung-Hye
authors.initials: JH
authors.lastname: Choi
authors.forename: Kyung-Tae
authors.initials: KT
authors.lastname: Lee
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D053181:Caspase 8 / Q000378:metabolism*; D053418:Death Domain Receptor Signaling Adaptor Proteins / Q000096:biosynthesis*; D053222:Fas Ligand Protein / Q000378:metabolism; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000473:pathology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011714:Pyrans / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology*; D015363:Quinolones / Q000494:pharmacology*; D019014:fas Receptor / Q000378:metabolism
chemical_list: C554291:10-methoxy-2,2-dimethyl-2,6-dihydropyrano(3,2-c)quinolin-5-one; D053418:Death Domain Receptor Signaling Adaptor Proteins; C491901:FAS protein, human; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D011714:Pyrans; D011804:Quinolines; D015363:Quinolones; D019014:fas Receptor; D053181:Caspase 8