Highly efficient synthetic iron-dependent nucleases activate both intrinsic and extrinsic apoptotic death pathways in leukemia cancer cells

• Published in: Journal of inorganic biochemistry Vol. 128; pp. 38 - 47
• Main Authors: Horn, Adolfo, Fernandes, Christiane, Parrilha, Gabrieli L., Kanashiro, Milton M., Borges, Franz V., de Melo, Edésio J.T., Schenk, Gerhard, Terenzi, Hernán, Pich, Claus T.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-11-2013
• Subjects: Apoptosis - drug effects; Caspases - metabolism; Cell Line, Tumor; Cell Survival - drug effects; Coordination Complexes - chemical synthesis; Coordination Complexes - metabolism; Coordination Complexes - pharmacology; Cytochrome C; Cytochromes c - secretion; Deoxyribonucleases - chemical synthesis; Deoxyribonucleases - metabolism; Deoxyribonucleases - pharmacology; Dinuclear μ-oxo iron complex; DNA - chemistry; DNA - genetics; DNA - metabolism; DNA, Superhelical - chemistry; DNA, Superhelical - drug effects; Enzyme Activation - drug effects; Extrinsic apoptosis pathway; HL-60 Cells; Humans; Hydrogen-Ion Concentration; Hydrolysis - drug effects; Intrinsic apoptosis pathway; Iron Compounds - chemical synthesis; Iron Compounds - metabolism; Iron Compounds - pharmacology; Jurkat Cells; Kinetics; Leukemia - metabolism; Leukemia - pathology; Leukemia cancer cell; Leukocytes, Mononuclear - cytology; Leukocytes, Mononuclear - drug effects; Membrane Potential, Mitochondrial - drug effects; Microscopy, Electron, Transmission; Mitochondria - metabolism; Mitochondria - physiology; Mitochondria - ultrastructure; Nuclease; Signal Transduction - drug effects; U937 Cells; Cytochrome C; Dinuclear μ-oxo iron complex; Leukemia cancer cell; Intrinsic apoptosis pathway; Nuclease; Extrinsic apoptosis pathway
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2013.07.019

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 339million-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.
The iron complexes increase the velocity of DNA cleavage by ~eight orders of magnitude. They induce cell death through apoptosis employing both the intrinsic and extrinsic pathways, since caspases 8 and 9 are activated. [Display omitted]
•The complexes increase the velocity of DNA cleavage by eight orders of magnitude.•The high nuclease activity of the complexes does not translate into high cytotoxicity.•The complexes induce apoptosis in leukemia cancer cells.•The complexes induce mitochondrial damages.•Intrinsic and extrinsic apoptosis pathways are involved in the cell death mechanism.