Downregulation of c-FLIP, XIAP and Mcl-1 protein as well as depletion of reduced glutathione contribute to the apoptosis induction of glycyrrhetinic acid derivatives in leukemia cells.
The antiproliferative effects and apoptosis inducing abilities of four 18beta-glycyrrhetinic acid (GA) derivatives, methyl 2-cyano-3,11-dioxooleana-1,12-dien-30-oate (CDODO-Me-11), methyl 2-cyano-3,12-dioxooleana-1,12-dien-30-oate (CDODO-Me-12) and their non-esters were investigated in human leukemia cells. Methyl esterification and switching a keto group from position C(11) to C(12) significantly increased the antiproliferative effects. CDODO-Me-11 and CDODO-Me-12 were 10-fold more potent than their non-esters, respectively. CDODO-Me-12 was 10-fold more effective than CDODO-Me-11 in inducing apoptosis which was correlated with the activation of caspase-8 and caspase-9. Western blot analyses revealed that CDODO-Me-12 and CDODO-Me-11 downregulated the levels of anti-apoptosis proteins, c-FLIP, XIAP and Mcl-1, without altering the protein levels of Bcl-2 and the death receptors DR4 and DR5. Both agents decreased the levels of the mitochondrial membrane potential without altering the intracellular H(2)O(2) levels. Jurkat cells without expression of caspase-8 were not sensitive to CDODO-Me-12, but were somewhat responsive to CDODO-Me-11. K562 cells with higher intracellular reduced glutathione (GSH ) levels were less responsive to CDODO-Me-12 apoptosis induction than U937 cells even though both cell lines were equally sensitive to CDODO-Me-11 apoptosis induction. Both agents depleted intracellular GSH levels and exogenous GSH reversed apoptosis induction by either agent in HL-60 cells. N-acetylcysteine (NAC) significantly attenuated apoptosis induction by CDODO-Me-12, but only weakly, that by CDODO-Me-11. UV spectrophotometric analysis revealed that both agents interacted with GSH while only CDODO-Me-12 had high reactivity with NAC. These data suggest that both agents induce apoptosis requiring to bind to functional proteins with thiol groups and that GSH may play a protective role by forming inactive adducts with them.
Song
Dandan
D
Department of Pharmacology, Shenyang Pharmaceutical University, Shenyang, China.
Gao
Yuan
Y
Wang
Rui
R
Liu
Dan
D
Zhao
Linxiang
L
Jing
Yongkui
Y
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000235:genetics*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000096:biosynthesis* / Q000235:genetics; D015536:Down-Regulation; D004354:Drug Screening Assays, Antitumor; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects*; D005978:Glutathione / Q000378:metabolism*; D006034:Glycyrrhetinic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D018922:HL-60 Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells / Q000187:drug effects / Q000378:metabolism; D020014:K562 Cells / Q000187:drug effects / Q000378:metabolism; D015470:Leukemia, Myeloid, Acute / Q000473:pathology*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D010084:Oxidation-Reduction; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics; D020298:U937 Cells / Q000187:drug effects / Q000378:metabolism; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000096:biosynthesis* / Q000235:genetics
D000972:Antineoplastic Agents, Phytogenic; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C551463:methyl 2-cyano-3,11-dioxooleana-1,12-dien-30-oate; C551464:methyl 2-cyano-3,12-dioxooleana-1, 12-dien-30-oate; D005978:Glutathione; D006034:Glycyrrhetinic Acid