title: Trifolin acetate-induced cell death in human leukemia cells is dependent on caspase-6 and activates the MAPK pathway.
abstract: In the present study we demonstrated that the flavonoid derivative trifolin acetate (TA), obtained by acetylation of naturally occurring trifolin, induces apoptosis. Associated downstream signaling events were also investigated. TA-induced cell death was prevented by the non-specific caspase inhibitor z-VAD-fmk and reduced by the presence of the selective caspase inhibitors z-LEHD-fmk (caspase-9), z-DEVD-fmk (caspase-3) and z-VEID-fmk (caspase-6). The apoptotic effect of TA was associated with (i) the release of cytochrome c from mitochondria which was not accompanied by dissipation of the mitochondrial membrane potential (DeltaPsi(m)), (ii) the activation of the mitogen-activated protein kinases (MAPKs) pathway and (iii) abrogated by the over-expression of Bcl-2 or Bcl-x(L). TA-induced cell death was attenuated by inhibition of extracellular signal-regulated kinases (ERK) 1/2 with U0126 and inhibition of p38(MAPK) with SB203580. In contrast, inhibition of c-Jun NH(2)-terminal kinase (JNK) by SP600125 significantly enhanced apoptosis. Although reactive oxygen species (ROS) increased in response to TA, this did not seem to play a pivotal role in the apoptotic process since different anti-oxidants were unable to provide cell protection. The present study demonstrates that TA-induced cell death is mediated by an intrinsic-dependent apoptotic event involving mitochondria and MAPK, and through a mechanism independent of ROS generation.
authors.affiliation: Department of Biochemistry, Instituto Canario de Investigación del Cáncer (I.C.I.C.), University of Las Palmas de Gran Canaria, Plaza Dr. Pasteur s/n, 35016, Las Palmas de Gran Canaria, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Torres
authors.forename: José
authors.initials: J
authors.lastname: Quintana
authors.forename: Jesús G
authors.initials: JG
authors.lastname: Díaz
authors.forename: Armando J
authors.initials: AJ
authors.lastname: Carmona
authors.forename: Francisco
authors.initials: F
authors.lastname: Estévez
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D053178:Caspase 6 / Q000502:physiology*; D005697:Galactosides / Q000494:pharmacology*; D018922:HL-60 Cells; D006801:Humans; D044949:Kaempferols / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D020298:U937 Cells
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D005697:Galactosides; D044949:Kaempferols; D017382:Reactive Oxygen Species; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C530019:trifolin acetate; C066407:kaempferol-3-O-galactoside; D053178:Caspase 6