Cytotoxic and cytostatic activity of copper(II) complexes. Importance of the speciation for the correct interpretation of the in vitro biological results

Exploiting Co(III)-Cyclopentadienyl Complexes To Develop Anticancer Agents

In recent years, organometallic complexes have attracted much attention as anticancer therapeutics aiming at overcoming the limitations of platinum drugs that are currently marketed. Still, the development of half-sandwich organometallic cobalt complexes remains scarcely explored. Four new cobalt(III)-cyclopentadienyl complexes containing N,N-heteroaromatic bidentate, and phosphane ligands were synthesized and fully characterized by elemental analysis, spectroscopic techniques, and DFT methods. The cytotoxicity of all complexes was determined in vitro by the MTS assay in colorectal (HCT116), ovarian (A2780), and breast (MDA-MB-231 and MCF-7) human cancer cell lines and in a healthy human cell line (fibroblasts). The complexes showed high cytotoxicity in cancer cell lines, mostly due to ROS production, apoptosis, autophagy induction, and disruption of the mitochondrial membrane. Also, these complexes were shown to be nontoxic in vivo in an ex ovo chick embryo yolk sac membrane (YSM) assay.

Zn2+ Interaction with Amyloid-Β: Affinity and Speciation

Conflicting values, obtained by different techniques and often under different experimental conditions have been reported on the affinity of Zn²⁺ for amyloid-β, that is recognized as the major interaction responsible for Alzheimer’s disease. Here, we compare the approaches employed so far, i.e., the evaluation of K_d and the determination of the stability constants to quantitatively express the affinity of Zn²⁺ for the amyloid-β peptide, evidencing the pros and cons of the two approaches. We also comment on the different techniques and conditions employed that may lead to divergent data. Through the analysis of the species distribution obtained for two selected examples, we show the implications that the speciation, based on stoichiometric constants rather than on K_d, may have on data interpretation. The paper also demonstrates that the problem is further complicated by the occurrence of multiple equilibria over a relatively narrow pH range.

Main targets of tetraaza macrocyclic copper complex on L1210 murine leukemia cells

Several metal complex agents have already been introduced into clinical tumor therapy and others are subject of antitumor studies. In this study we focused on the tetraaza macrocyclic copper complex (Cu(TAAB)Cl(2)). We studied the influence of the substance on cell growth, cell cycle, membrane integrity, necrosis, apotosis and glutathione level on the leukemic cell line L1210 in 1-day (22 h) and 3-day (72 h) experiments. The metal complex shows a dose-dependent antiproliferative effect, without affecting cell cycle phases. The present results confirm that copper complex can damage plasmatic membranes and trigger apoptosis, and that after treatment of leukemic cells with the copper complex, glutathione levels were increased.

Synthesis, structure, and antitumor activity of a novel tetranuclear titanium complex

The coordination complex cyclo-tetrakis[bis(1-phenyl-3-methyl-4-benzoylpyrazolon-5-ato++ +)mu-o xotitanium(IV)] has been synthesized and characterized with IR and NMR spectroscopies and X-ray diffraction. The core of this species consists of an eight-membered Ti-mu-oxo ring with alternate short-long Ti-O bond lengths. Besides these two O ligands, each metal is bound octahedrally to four O atoms from two chelating 1-phenyl-3-methyl-4-benzoylpyrazolon-5-ato anions. Several sets of Ti-O bond lengths are present: the shortest are the two Ti-O(oxo) (which are cis to each other), the longest are the two Ti-O(acyl) (cis to each other), and the two Ti-O(pyrazolonato) (trans to each other) are intermediate. The beta-diketonate ligand asymmetry, a feature considered essential in other antitumor Ti compounds, induces the short-long Ti-O(oxo) sequence of bond lengths. The antitumor activity of this compound, encapsulated in a dipalmitoylphosphatidylcholine liposome, has been studied in vitro using TA-3 (mouse mammary adenocarcinoma), HEP-2 (human epithelial larynx carcinoma), and VERO (African green monkey kidney) cell lines and in vivo in CF-1 and AJ female mice ip inoculated with TA-3. In vitro cytotoxicity is greater for TA-3 than for HEP-2 and null for VERO cell lines. In vivo results show a marked increase in survival time (T/C = 293% for AJ and 208% for CF-1), whereas tumor weight decrease was observed for CF-1-treated mice. These results suggest the Ti complex-liposome system may be promising as an antitumor drug.

Bis(acetato)bis(1-methyl-4,5-diphenylimidazole)copper(II): preparation, characterization, crystal structure, DNA strand breakage and cytogenetic effect

The preparation, characterization and antitumour properties of the complex [Cu(O2CMe)2L2] (1), where L = 1-methyl-4,5-diphenylimidazole, are described. The crystal structure of 1 (triclinic, space group P1, a = 6.743(1), b = 8.006(1), c = 15.898(1) A, alpha = 102.87(1), beta = 101.10(1), gamma = 76.76(1) degree, Z = 1) has been determined (R = 0.0254, Rw = 0.0275). In the centrosymmetric complex the copper ion is in an essentially square planar environment consisting of two pyridine-type imidazole nitrogen atoms and an oxygen atom from each acetate ligand; the second oxygen atoms of the carboxylate functionalities are involved in weak interactions with the metal completing the coordination to a very distorted tetragonal bipyramid. Complex 1 has been also characterized by elemental analyses, thermal methods, variable-temperature magnetic susceptibility and spectroscopic (IR and far-IR, FT-Raman, UV/VIS, EPR) techniques. The effect of the complex on the in vitro DNA strand breakage was examined. It was found that 1 causes degradation on the linearized pKS DNA, ds and ss DNA. High concentrations of this Cu(II) complex cause scissions on the relaxed and the supercoiled DNA. Furthermore, the in vivo cytogenic effect of 1 was examined on human lymphocyte cells. This study presents indications that 1 could have some relevance in the treatment of tumour cell lines. An orbital interpretation of the interaction of 1 with the DNA bases is proposed.

Copper(II) complexes encapsulated in human red blood cells

Copper(II) complexes were encapsulated in human red blood cells in order to test their possible use as antioxidant drugs by virtue of their labile character. ESR spectroscopy was used to verify whether encapsulation in red blood cells leads to the modification of such complexes. With copper(II) complexes bound to dipeptides or tripeptides, an interaction with hemoglobin was found to be present, the hemoglobin having a strong coordinative site formed by four nitrogen donor atoms. Instead, with copper(II) complexes with TAD or PheANN3, which have the greatest stability. ESR spectra always showed the original species. Only the copper(II) complex with GHL gave rise to a complicated behavior, which contained signals from iron(III) species probably coming from oxidative processes. Encapsulation of all copper(II) complexes in erythrocytes caused a slight oxidative stress, compared to the unloaded and to the native cells. However, no significant differences were observed in the major metabolic properties (GSH, glycolytic rate, hexose monophosphate shunt, Ca(2+)-ATPase) of erythrocytes loaded with different copper(II) complexes, with the exception of methemoglobin levels, which were markedly increased in the case of [Cu(GHL)H-1] compared to [Cu(TAD)]. This latter finding suggests that methemoglobin formation can be affected by the type of complex used for encapsulation, depending on the direct interaction of the copper(II) complex with hemoglobin.