ABSTRACT
The new complex formed by Cd(II) and the 1:2 Schiff-base-type ligand 2,6-bis[1-(4-amino-1,2,3,6-tetrahydro-1,3-dimethyl-2,6-dioxopyrimidin-5-yl)imino]ethylpyridine (DAPDAAU) has been chemically and structurally characterized by X-ray diffraction: the ion Cd(II) is surrounded by six nitrogen atoms from two DAPDAAU ligands which coordinates each one in a tridentate fashion through the pyridine ring (N1) and both azomethine nitrogen atoms (N5). The interaction of the Cd(II) complex (compound I) with calf-thymus DNA as observed by circular dichroism spectroscopy suggests the initial unwinding of the DNA double helix strongly depends on increasing incubation times and metal-to-nucleic acid molar ratios. Electrophoretic experiments indicate that the cadmium complex induces cleavage of the plasmid pBR322 DNA to give ulterior nicking and shortening of this molecule, as a result of the complex binding to DNA, resulting in the conclusion that compound I behaves as a chemical nuclease. Cytotoxic activity of the Cd(II) complex against selected different human cancer cell lines is specific and increases with increasing concentration of the metal compound; this fact indicates the potential antitumor character of the complex. When the culture medium is supplemented with compound I, a remarkable inhibition of the growing cell is observed, important cell degeneration appears before 48 h and abundant precipitates are formed that correspond to cell residues and denatured proteins.
Subject(s)
Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , DNA/drug effects , Animals , Antineoplastic Agents/chemical synthesis , Cadmium/chemistry , Cattle , Cell Proliferation/drug effects , Circular Dichroism , Crystallography, X-Ray , DNA/metabolism , DNA Damage , Electrophoresis , Humans , Molecular Structure , Organometallic Compounds , Plasmids/drug effects , Tumor Cells, Cultured , Uracil/chemistryABSTRACT
The new potential antitumour soluble drug K[Ru(eddp)Cl(2)].3H(2)O, (eddp=ethylenediamine-N,N'-di-3-propionate) has been isolated and characterized. The analysis of the interaction of this complex with pBR322 plasmid DNA by circular dichroism spectroscopy shows that the ruthenium complex initially induces alteration of both CD positive and negative features resembling those previously observed for monofunctional platinum complexes. Further addition of drug at r(i) higher than 0.50 suggests appreciable conformational alterations of typical secondary structure of B-type DNA, implying loss of DNA helicity and unwinding of the double helix. The results reported herein about the binding of K[Ru(eddp)Cl(2)] to the named plasmid performed by electrophoresis indicate that the Ru(III) center preferentially forms initial monofunctional adducts with this plasmid. In addition, the DNA binding data suggest that the plasmid is cleaved by K[Ru(eddp)Cl(2)] in the presence of physiological concentrations of ascorbate. These results support the hypothesis that reactive Ru(II) species may be formed from Ru(III) upon incubation with a reductant agent such as ascorbate. The testing of the cytotoxic activity of this complex against several human cancer cell lines evidenced that K[Ru(eddp)Cl(2)] complex had a remarkable and selective antiproliferative effect against the cervix carcinoma HeLa and colon adenocarcinoma HT-29, behaving in these two cases as an antineoplastic drug.
Subject(s)
Antineoplastic Agents/chemistry , DNA/chemistry , Organometallic Compounds/chemistry , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/pharmacology , Ascorbic Acid/chemistry , Cell Division/drug effects , Cell Line, Tumor , Chromatography, Agarose , Circular Dichroism , Dose-Response Relationship, Drug , HT29 Cells , HeLa Cells , Humans , Hydrolysis , Intercalating Agents/chemical synthesis , Intercalating Agents/chemistry , Intercalating Agents/pharmacology , Nucleic Acid Conformation/drug effects , Organometallic Compounds/chemical synthesis , Organometallic Compounds/pharmacology , Oxidation-Reduction , Plasmids/chemistry , Ruthenium/chemistry , Spectrophotometry, Infrared , Spectrophotometry, UltravioletABSTRACT
We have reported, previously, some effect of allogenic hepatic cells for islet tolerance when they are injected mixed (hepatic cells and islets) in different proportions via portal vein, in diabetic Wistar rats. Now we have studied the role of allogenic hepatic cells injected sequentially 15 min before islets, comparing via the portal vein (A and B groups) and via the cava vein (C and D groups) with a control group of islets alone. The allogenic islets were always injected via portal vein, in similar conditions, while the ratio of hepatic cells/islets was 100:1 (A, C groups) or 200:1 (B, D groups). Islets and hepatic cells were obtained from several different rats. The transplanted rats were observed during 30 days and results compared among the different rat groups: porta-porta (P/P), cava-porta (C/P), and control group. Statistically, a significant interaction between type of transplant and proportion of hepatic cells was observed. Also, C plus D groups showed statistical difference with the control group (p < 0.017) and also all the groups together (p < 0.047). These results suggest that hepatic cells can induce, in some cases, islet graft prolongation in Wistar rats. Better results were obtained when hepatic cells were injected via the cava vein than via the portal vein. Because we used a liver cell suspension integrated for several kinds of cells, the study does not clarify if this effect can be related to some specific hepatic cell subpopulation. To confirm the results and to determine if the hypothetical mechanism can be attributed to a block of the immune system or to some factor secreted by hepatic cells, more studies must be performed.
