Highly efficient synthetic iron-dependent nucleases activate both intrinsic and extrinsic apoptotic death pathways in leukemia cancer cells.
The nuclease activity and the cytotoxicity toward human leukemia cancer cells of iron complexes, [Fe(HPClNOL)Cl2]NO3 (1), [Cl(HPClNOL)Fe(μ-O)Fe(HPClNOL)Cl]Cl2·2H2O (2), and [(SO4)(HPClNOL)Fe(μ-O)Fe(HPClNOL)(SO4)]·6H2O (3) (HPClNOL=1-(bis-pyridin-2-ylmethyl-amino)-3-chloropropan-2-ol), were investigated. Each complex was able to promote plasmid DNA cleavage and change the supercoiled form of the plasmid to circular and linear ones. Kinetic data revealed that (1), (2) and (3) increase the rate of DNA hydrolysis about 278, 192 and 339 million-fold, respectively. The activity of the complexes was inhibited by distamycin, indicating that they interact with the minor groove of the DNA. The cytotoxic activity of the complexes toward U937, HL-60, Jukart and THP-1 leukemia cancer cells was studied employing 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), fluorescence and electronic transmission microscopies, flow cytometry and a cytochrome C release assay. Compound (2) has the highest activity toward cancer cells and is the least toxic for normal ones (i.e. peripheral blood mononuclear cells (PBMCs)). In contrast, compound (1) is the least active toward cancer cells but displays the highest toxicity toward normal cells. Transmission electronic microscopy indicates that cell death shows features typical of apoptotic cells, which was confirmed using the annexin V-FITC/PI (fluorescein isothiocyanate/propidium iodide) assay. Furthermore, our data demonstrate that at an early stage during the treatment with complex (2) mitochondria lose their transmembrane potential, resulting in cytochrome C release. A quantification of caspases 3, 9 (intrinsic apoptosis pathway) and caspase 8 (extrinsic apoptosis pathway) indicated that both the intrinsic (via mitochondria) and extrinsic (via death receptors) pathways are involved in the apoptotic stimuli.
Laboratório de Ciências Químicas, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, 28013-602 RJ, Brazil. Electronic address: adolfo@uenf.br.
Adolfo
A
Horn
Christiane
C
Fernandes
Gabrieli L
GL
Parrilha
Milton M
MM
Kanashiro
Franz V
FV
Borges
Edésio J T
EJ
de Melo
Gerhard
G
Schenk
Hernán
H
Terenzi
Claus T
CT
Pich
D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D045304:Cytochromes c / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004278:DNA, Superhelical / Q000737:chemistry / Q000187:drug effects; D003851:Deoxyribonucleases / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis / Q000187:drug effects; D058085:Iron Compounds / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D019169:Jurkat Cells; D007700:Kinetics; D007938:Leukemia / Q000378:metabolism / Q000473:pathology; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D015398:Signal Transduction / Q000187:drug effects*; D020298:U937 Cells
D056831:Coordination Complexes; D004278:DNA, Superhelical; D058085:Iron Compounds; D045304:Cytochromes c; D004247:DNA; D003851:Deoxyribonucleases; D020169:Caspases
Cytochrome C; Dinuclear μ-oxo iron complex; Extrinsic apoptosis pathway; Intrinsic apoptosis pathway; Leukemia cancer cell; Nuclease