Enhanced P53 and BAX gene expression and apoptosis in A549 cells by cis-Pt(II) complex of 3-aminoflavone in comparison with cis-DDP

Lung cancer remains one of the most common causes of cancer-related death worldwide. Approximately 80% is histologically non-small cell lung carcinoma (NSCLC) and in about 70% of patients it is an unresectable type. Clinical studies indicated that application of platinum derivatives caused good results and combinations of platinum with other agents could improve median survivals. In view of the central problem of sufficient efficiency of drugs in chemotherapy, efforts have focused on the development of alternative platinum-based analogues that can be more effective in cancer treatment. cis-bis(3-aminoflavone)dichloroplatinum(II) (cis-Pt(II) complex of 3-aminoflavone) represents a novel class of platinum-based potential antitumour agents. In order to evaluate the degree of apoptosis, acridine orange/ethidium bromide and Hoechst 33258/propidum iodide double staining as well as RT-PCR (P53 and BAX expression evaluation) were used in lung cancer cell line A549 after treatment with this compound in comparison with cis-diamminedichloroplatinum(II) (cis-DDP). Apoptotic cells at early and late stages and also necrotic ones were observed after usage of cis-Pt(II) complex of 3-aminoflavone and the percentage of these cells outnumbered the values obtained after cis-DDP application. The former compound induced a higher percentage of P53 and BAX expression in A549 cells in comparison with the latter one. Results indicate the beneficial properties of cis-Pt(II) complex of 3-aminoflavone as a potential antitumor drug.     

Genotoxicity assessment of chromium(III) propionate complex in the rat model using the comet assay

The aim of the study was to assess genotoxicity of a chromium(III) propionate complex in rat’s peripheral blood lymphocytes by the comet assay. The study was carried out on 18 12-weeks old female Wistar rats that were divided into three equal groups (six animals each): control (0), control-Cr(VI) and Cr(III)-tested rat fed ad libitum a basal diet and the diet supplemented either with 10 mg Cr(VI)/kg diet (given as K₂Cr₂O₇, equivalent of 1 mg/kg body mass/day) or 1000 mg Cr(III)/kg diet (given as [Cr₃O(O₂CCH₂CH₃)6(H₂O)₃]NO₃), equivalent of 100 mg Cr/kg body mass/day) for 4 weeks. High doses of supplementary Cr(III) were found to not affect body mass gain, feeding efficiency ratio and internal organ masses. Treatment of rats with the Cr(III) propionate complex, in contrast to Cr(VI), did not affect significantly the comet assay results in lymphocytes, which suggests that the compound does not exert genotoxic effects in rats.     

Synthesis and Characterization of a New Macrocyclic Ligand and Its Copper (II), Cadmium (II), and Lead (II) Complexes: Genotoxic Activity of These Complexes in Cultured Human Lymphocytes

A new macrocyclic ligand 1,1′-bis(bis-(6,6′-oxymethylenyl-2,2′-bipyridine) binaphthyl, (L), and its complexes CuL(ClO₄)₂, CuL(NO₃)₂·3H₂O, CdL(ClO₄)₂, and PbL(ClO₄)₂ have been synthesized and characterized on the basis of IR, ¹H NMR, ¹³C NMR, FAB mass, and elemental analyses. Genotoxicity of these metal complexes has also been investigated by cytokinesis-blocked micronucleus assay in cultured human lymphocytes. Blood cultures were set up from two healthy donors, and treatment was done with different test concentrations for 24 and 48 h. The current results indicate that all compounds caused cytotoxicity by decreasing the cell number at the 150 μg/mL doses for 48-h treatments. On the other hand, CuL(ClO₄)₂, CuL(NO₃)₂·3H₂O and PbL(ClO₄)₂ exhibited genotoxicity by inducing the number of micronucleated cells at doses of 150 μg/mL for 24-h treatments, but CdL(ClO₄)₂ did not significantly alter micronucleus induction. Hence, some test compounds may act as mutagens or produce clastogenic effects depending upon their chemical structures.     

Comparison between the genotoxicity of cis-Pt(ll) complex of 3-aminoflavone and cis-DDP in lymphocytes evaluated by the comet assay

cis-bis(3-aminoflavone)dichloroplatinum(II) [cis-Pt(II) complex of 3-aminoflavone] is an analog of cis-DDP characterized by low cytotoxicity and anticancer properties in vivo. In order to evaluate genotoxic properties of this chemical compound, the comet assay in human lymphocytes was used. The analysis of DNA damage after 1-h cell incubation with cis-Pt(II) complex of 3-aminoflavone and cis-DDP was carried out, and DNA repair kinetics were evaluated after 0.5-h, 1-h, and 1.5-h postexposure incubation. It has been shown that cis-Pt(II) complex of 3-aminoflavone causes the increase in tail moments in comparison with cis-DDP. On the other hand, the decrease in these values caused by cis-DDP was connected mainly with the presence of DNA and DNA-protein crosslinks. The decrease in tail moments after cis-Pt(II) complex of 3-aminoflavone lymphocyte treatment was already observed after 0.5-h postexposure incubation, whereas in the variant with hydrogen peroxide application these values after cis-Pt(II) complex of 3-aminoflavone addition were higher in comparison with cis-DDP. Results obtained on the basis of the comet assay could confirm the occurrence of DNA breaks and cross-links induced by cis-Pt(II) complex of 3-aminoflavone.     

Genotoxicity of marine sediments in the fish hepatoma cell line PLHC-1 as assessed by the Comet assay

The main goal of this study was to test the usefulness of the Comet assay in the PLHC-1 hepatoma fish cell line as a tool for detecting the presence of genotoxic compounds in contaminated marine sediments. The system has been tested using both model chemicals (benzo[a]pyrene (B[a]P) and ethyl methanesulfonate (EMS)) and extracts of sediment samples obtained with solvent dichloromethane/methanol. For all of the analysed sediment extracts as well as for the model chemicals a concentration dependent genotoxic effect was observed. The sediment with the highest observed genotoxic potential was additionally extracted using various solvents in order to test which class of compounds, according to their polarity, is most responsible for the observed genotoxic effect. Non-polar solvents (cyclohexane and dichloromethane) yielded stronger genotoxic effect but the highest level of DNA damage was determined after exposure to sediment extract obtained with the solvent mixture dichloromethane/methanol which extracts a wide range of contaminants. Our results indicate that the PLHC-1 cell line is a suitable in vitro model in sediment genotoxicity assessment and encourage the use of fish cell lines as versatile tools in ecogenotoxicology.     

The Comet Assay with Multiple Mouse Organs: Comparison of Comet Assay Results and Carcinogenicity with 208 Chemicals Selected from the IARC Monographs and U.S. NTP Carcinogenicity Database

ABSTRACT

The comet assay is a microgel electrophoresis technique for detecting DNA damage at the level of the single cell. When this technique is applied to detect genotoxicity in experimental animals, the most important advantage is that DNA lesions can be measured in any organ, regardless of the extent of mitotic activity. The purpose of this article is to summarize the in vivo genotoxicity in eight organs of the mouse of 208 chemicals selected from International Agency for Research on Cancer (IARC) Groups 1, 2A, 2B, 3, and 4, and from the U.S. National Toxicology Program (NTP) Carcinogenicity Database, and to discuss the utility of the comet assay in genetic toxicology.

Alkylating agents, amides, aromatic amines, azo compounds, cyclic nitro compounds, hydrazines, halides having reactive halogens, and polycyclic aromatic hydrocarbons were chemicals showing high positive effects in this assay. The responses detected reflected the ability of this assay to detect the fragmentation of DNA molecules produced by DNA single strand breaks induced chemically and those derived from alkali-labile sites developed from alkylated bases and bulky base adducts. The mouse or rat organs exhibiting increased levels of DNA damage were not necessarily the target organs for carcinogenicity. It was rare, in contrast, for the target organs not to show DNA damage. Therefore, organspecific genotoxicity was necessary but not sufficient for the prediction of organ-specific carcinogenicity. It would be expected that DNA crosslinkers would be difficult to detect by this assay, because of the resulting inhibition of DNA unwinding. The proportion of 10 DNA crosslinkers that was positive, however, was high in the gastrointestinal mucosa, stomach, and colon, but less than 50% in the liver and lung. It was interesting that the genotoxicity of DNA crosslinkers could be detected in the gastrointestinal organs even though the agents were administered intraperitoneally.

Chemical carcinogens can be classified as genotoxic (Ames test-positive) and putative nongenotoxic (Ames test-negative) carcinogens. The Ames test is generally used as a first screening method to assess chemical genotoxicity and has provided extensive information on DNA reactivity. Out of 208 chemicals studied, 117 are Ames test-positive rodent carcinogens, 43 are Ames test-negative rodent carcinogens, and 30 are rodent noncarcinogens (which include both Ames test-positive and negative noncarcinogens). High positive response ratio (110/117) for rodent genotoxic carcinogens and a high negative response ratio (6/30) for rodent noncarcinogens were shown in the comet assay. For Ames test-negative rodent carcinogens, less than 50% were positive in the comet assay, suggesting that the assay, which detects DNA lesions, is not suitable for identifying nongenotoxic carcinogens. In the safety evaluation of chemicals, it is important to demonstrate that Ames test-positive agents are not genotoxic in vivo. This assay had a high positive response ratio for rodent genotoxic carcinogens and a high negative response ratio for rodent genotoxic noncarcinogens, suggesting that the comet assay can be used to evaluate the in vivo genotoxicity of in vitro genotoxic chemicals. For chemicals whose in vivo genotoxicity has been tested in multiple organs by the comet assay, published data are summarized with unpublished data and compared with relevant genotoxicity and carcinogenicity data.

Because it is clear that no single test is capable of detecting all relevant genotoxic agents, the usual approach should be to carry out a battery of in vitro and in vivo tests for genotoxicity. The conventional micronucleus test in the hematopoietic system is a simple method to assess in vivo clastogenicity of chemicals. Its performance is related to whether a chemical reaches the hematopoietic system. Among 208 chemicals studied (including 165 rodent carcinogens), 54 rodents carcinogens do not induce micronuclei in mouse hematopoietic system despite the positive finding with one or two in vitro tests. Forty-nine of 54 rodent carcinogens that do not induce micronuclei were positive in the comet assay, suggesting that the comet assay can be used as a further in vivo test apart from the cytogenetic assays in hematopoietic cells. In this review, we provide one recommendation for the in vivo comet assay protocol based on our own data.     

Interactions Between Anticancer Pt(Ⅱ) complexes and Human Erythrocyte Spectrin

用荧光及园二色谱对人红细胞收缩蛋白（ＳＰ）与不同组成和构型的Ｐｔ（Ｉ）络合物的作用进行了研究。结果表明，ＳＰ有４７×１０２个顺铂（ＣＤＤＰ）结合部位。其中，最高亲和性部位７０个，Ｋ１＞３４７×１０６；较高亲和性的１８×１０２个，其Ｋ２＝３４７×１０６；其余２２×１０２个为低亲和性的，其Ｋ３＝８７７×１０５。Ｐｔ（Ｉ）络合物与ＳＰ的结合导致ＳＰ构象变化，这种变化与Ｐｔ（Ｉ）络合物浓度及络合物与ＳＰ的浓度比有关。ＣＤＤＰ及顺式二水二氨合铂（Ｉ）与ＳＰ的作用在初始１ｈ内遵从双阶段一级动力学，动力学常数也已测定。反应１ｈ后，为络合物与ＳＰ作用的后续变化阶段，这一阶段可能涉及ＳＰ的构象改变、聚合及解聚。值得注意的是，ＳＰ与１，２环己二胺不同异构体作为载体配体的Ｐｔ（Ｉ）络合物作用时，空间匹配性比Ｐｔ（Ｉ）与ＳＰ的巯基的亲和性显得更为重要。     

Synthesis, characterization and cytotoxicity of diam(m)-ineplatinum(II) complexes containing beta-phenylisosuccinate ligand

Four diam(m)ineplatinum(II) complexes containing beta-phenylisosuccinate as the leaving groups were prepared, characterized, and evaluated for their cytotoxicity against A549/ATCC human lung cancer cell line and SGC-7901 human gastric cancer cell line. One of the complexes, (trans-1R,2R-diaminocyclohexane)-beta-phenylisosuccinatoplatinum(II) 4, was much more active than cisplatin and carboplatin.     

LC-MS/MS and density functional theory study of copper(II) and nickel(II) chelating complexes of elesclomol (a novel anticancer agent)

Elesclomol (N-malonyl-bis(N'-methyl-N'-thiobenzoylhydrazide)), which is a novel anticancer agent, can form chelating complexes with Fe(II), Co(II), Ni(II), Cu(II), and Zn(II) in the gas phase during electrospray ionization (ESI) mass spectrometry. In the solution phase with acidic medium during chromatographic separation, however, only Cu(II) and Ni(II) to a lesser degree favor the formation of chelating complexes with elesclomol. The Cu(II)-chelating complex [Cu(II)+elesclomol-H]+· exhibits more complicated MS/MS fragmentation pathways than the Ni(II)-chelating complex [Ni(II)+elesclomol-H]+. One significant difference is the ready occurrence of the electron transfer upon collision-induced dissociation (CID) of [Cu(II)+elesclomol-H]+·. This leads to the reduction of Cu(II) to Cu(I). However, such phenomenon was not observed upon CID of [Ni(II)+elesclomol-H]+. On the basis of the density functional theory (DFT) calculations at the B3LYP/6-31+G(d)/LANL2DZ level, the Cu(II)- and Ni(II)-chelating complexes of elesclomol exist in the keto-form with tetra-coordinated trapezoid geometry in the gas phase but at different levels of distortion. As compared to the Ni(II)-elesclomol complex, the Cu(II)-elesclomol complex is more stable (by -55.25 kcal/mol). This relative stability of the chelating complexes of elesclomol is consistent with the Irving-Williams series of bindings to ligands.     

Synthesis,characterization, and determination of genotoxic effect of a novel dimeric 8-hydroxyquinoline Cd(II) SCN complex

In this study, a Cd(II) complex was synthesized using 8-hydroxyquinoline and thiocyanate as the ligands and structurally characterized with the combination of FTIR, ¹H-NMR, ¹³C-NMR, UV–vis, and MS spectral data. Then, genotoxic effects of the prepared complex were investigated. Genotoxic properties of the dimeric 8-hydroxyquinolinthiocyanatoCd(II) [Cd₂(8Q)₂(SCN)₂] complex synthesized as drug raw material were analyzed in human peripheral blood lymphocytes. Concentrations of 1, 2, 4, 6, and 8?μg/mL [Cd₂(8Q)₂(SCN)₂] were used for 24 and 48 h durations. [Cd₂(8Q)₂(SCN)₂] significantly increased chromosomal aberrations (CAs) at 4, 6, and 8?μg/mL concentrations after a 24-?h period and 2 and 4?μg/mL after a 48-h period. [Cd₂(8Q)₂(SCN)₂] significantly decreased the mitotic index (MI) at all concentrations, both at 24 and 48?h. Micronuclei frequency (MN) was not affected by [Cd₂(8Q)₂(SCN)₂] treatment compared with the control. After application for a 48?h period, 6 and 8?μg/mL concentrations showed toxic effects both in chromosomal abnormality and in micronucleus tests. It also decreased the cytokinesis-block proliferation index (CBPI), but this result was statistically significant only at 6 and 8?μg/mL concentrations. In the comet assay (single-cell gel electrophoresis (SCGE)), significant increases in comet tail length, tail moment, and tail intensity were observed at all concentrations. [Cd₂(8Q)₂(SCN)₂] displays clastogenic effect in the concentrations used in human peripheral lymphocytes at chromosomal abnormality, micronucleus tests, and cytokinesis-block proliferation index parameters. Further studies should be conducted in other test systems to evaluate the complete genotoxic potential of [Cd₂(8Q)₂(SCN)₂].     

Comparison of the radiorecovery activity of copper(II)2(3,5-diisopropylsalicylate)4 and copper(II) (chloride)2

Copper(II)₂(3,5-diisopropylsalicylate)₄ [Cu(II)₂(3,5-DIPS)₄] and copper(II)(chloride)₂ [Cu(II)Cl₂ were used to treat γ-irradiated female C57BL/6 mice after irradiation at levels LD50/30 to compare their efficacy in facilitating recovery from radiation-induced systemic inflammatory disease accompanied by loss of body mass and in increasing survival of irradiated mice. Doses of 5, 10 or 20 μmol Cu(II)Cl₂ or 5, 10 or 20 μmol [Cu(II)₂(3,5-DIPS)₄]/kg were administered subcutaneously 3 h after LD_50/30 irradiation and body mass and survival determined throughout the 30-day post-irradiation period compared with controls. Treatment with Cu(II)₂(3,5-DIPS)₄ or Cu(II)Cl₂ facilitated recovery of radiation-induced systemic inflammatory disease, recovery of body mass, and increased survival. Treatment with 5, 10 or 20 (μmol [Cu(II)₂(3,5-DIPS)₄]/kg produced a 44%, 67% or 44% increase in survival, respectively, compared with the vehicle-treated control group. Treatment with 5,10 or 20 μmol Cu(II)Cl₂/kg produced a 7%, 21% or 29% increase in survival, respectively, compared with the vehicle-treated control group. The recovery of radiation-induced loss in body mass and an increase in survival document that both Cu(II)₂(3,5-DIPS)₄ and Cu(II)Cl₂ are effective radiorecovery agents. In addition, Cu(II)₂(3,5-DIPS)₄ is a more effective radiorecovery agent than Cu(II)Cl₂.     

Application of novel Ni(II) complex and ZrO2 nanoparticle as mediators for electrocatalytic determination of N-acetylcysteine in drug samples

The electrooxidation of N-acetylcysteine (N-AC) was studied by a novel Ni(II) complex modified ZrO₂ nanoparticle carbon paste electrode [Ni(II)/ZrO₂/NPs/CPE] using voltammetric methods. The results showed that Ni(II)/ZrO₂/NPs/CPE had high electrocatalytic activity for the electrooxidation of N-AC in aqueous buffer solution (pH = 7.0). The electrocatalytic oxidation peak currents increase linearly with N-AC concentrations over the concentration ranges of 0.05–600μM using square wave voltammetric methods. The detection limit for N-AC was equal to 0.009μM. The catalytic reaction rate constant, k_h, was calculated (7.01 × 10² M⁻¹ s⁻¹) using the chronoamperometry method. Finally, Ni(II)/ZrO₂/NPs/CPE was also examined as an ultrasensitive electrochemical sensor for the determination of N-AC in real samples such as tablet and urine.     

Role of the Copper(II) Complex Cu[15]pyN5 in Intracellular ROS and Breast Cancer Cell Motility and Invasion

Multiple mechanisms related to metastases undergo redox regulation. Cu[15]pyN₅ is a redox‐active copper(II) complex previously studied as a chemotherapy sensitizer in mammary cells. The effects of a cotreatment with Cu[15]pyN₅ and doxorubicin (dox) were evaluated in two human breast cancer cell lines: MCF7 (low aggressiveness) and MDA‐MB‐231 (highly aggressive). Cu[15]pyN₅ decreased MCF7‐directed cell migration. In addition, a cotreatment with dox and Cu[15]pyN₅ reduced the proteolytic invasion of MDA‐MB‐231 cells. Cell detachment was not affected by exposure to these agents. Cu[15]pyN₅ and dox significantly increased intracellular ROS in both cell lines. This increase could be at least partially due to H₂O₂ accumulation. The combination of Cu[15]pyN₅ with dox may be beneficial in breast cancer treatment as it could help reduce cancer cell migration and invasion. Moreover, the ligand [15]pyN₅ has a high affinity for copper(II) and displays potential anti‐angiogenic properties. Overall, we present a potential drug that might arrest the progression of breast cancer by different and complementary mechanisms.     

Formation, properties and antimicrobial activities of cotton xanthate-Cu(II)-homosulfamine complex

To develop a cotton derivatives with prolonged antimicrobial activities, homosulfamine (Hs) was coupled to cotton xanthate (CX) via chelate bond in the presence of Cu(II) ion by one-and two-bath processes. In one-bath process, CX was treated with Cu(II)-Hs solution. In two-bath process, CX was treated with Cu(II) ion solution to produce CX-Cu(II) complex, which was isolated and treated in turn with Hs solution. Effects of concentration, Cu(II)/Hs ratio, and pH on the binding of Hs were investigated at 10°C. In one-bath process, binding of Hs took place readily with optimum pH around 5∼6. The amount of binding increased to give a maximum within 5 min and decreased slowly to establish an equilibrium within an hour. In two-bath process, binding of Hs was much lower than that of one-bath process. Release of Hs from CX-Cu(II)-Hs was investigated by batch and flow method. Antimicrobial activities of CX-Cu(II)-Hs were tested againstStaphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa andEscherichia coli and it showed prolonged activity compared to that of free Hs.     

Anti-tumour activity in non-small cell lung cancer models and toxicity profiles for novel ruthenium(II) based organo-metallic compounds

Novel ruthenium(II) organo-metallic compounds are active in ovarian cancer models [Aird RE, Cummings J, Ritchie AA, Muir M, Morris RE, Chen H, et al. In vitro and in vivo activity and cross resistance profiles of novel ruthenium(II) organometallic arene complexes in human ovarian cancer. Br J Cancer 2002;86(10):1652-7]. [(eta6-C6H5C6H5)Ru(en)Cl]+ (as a PF6 salt, where en=ethylenediamine (RM175)) has been evaluated in a 13-cell line panel. Particular sensitivity (approximately 10-fold lower than mean IC50) was noted in breast cancer and non-small cell lung cancer cell lines. In addition, IC50 in the A549 was 2 microM and RM175 (25 mg kg-1, days 1 and 5, i.p.) caused a significant (p=0.004) growth delay in a xenograft model. HC11 [(eta6-tetrahydroanthracene)Ru(en)Cl]PF6 was more potent in the A549 cell line (IC50 0.5 microM). HC11 (25 mg kg-1, days 1, 8 and 15, i.p.) was also active in vivo. Following RM175 25 mg kg-1, days 1 and 5, and 15 mg kg-1, days 1-5, HC11 25 and 40 mg kg-1, day 1, elevated alanine transaminase levels were detected, suggesting hepatotoxicity. No changes were observed in kidney or haematological parameters. In liver sections, multi-focal hepatic necrosis was seen, becoming confluent at high doses of HC11. In vitro studies confirmed that HC11 was more toxic than RM175 to fresh human hepatocytes and equitoxic to mithramycin. Liver toxicity may be related to the arene ligand and modification may reduce the potential for hepatic toxicity, while maintaining the anti-tumour activity seen.     

Preparation and properties of selected Zn(II)-peptide complexes in suspension

The preparation and properties of low soluble, suspended Zn(II) complexes containing the selected peptides: tyroliberin (TRH), gonadorelin (GnRH), dalarelin and corticothropin (ACTH) were studied. The amount of Zn(II) bound by 1 muM of the selected peptide (n) was defined, as well as affinity of Zn(II) to the peptide (Ka) and the durability of the created complex Zn(II)-peptide (Kd). ACTH associated the highest amount of Zn(II), and GnRH the lowest one: 1 microM of ACTH complexed 0.81 microM +/- 0.03 Zn(II), the same quantity of GnRH-0.52 microM +/- 0.07 and TRH and dalarelin associated 0.75+/-0.03 and 0.79+/-0.02 microM of Zn(II), respectively. The closest affinity was stated between Zn(II) and GnRH (Ka=157.692+/-21.300 microM(-1)), the smallest-towards ACTH (Ka=1.136+/-0.042 microM(-1)). The lower amount of Zn(II) associated by the studied peptide, the higher was its affinity versus this metal (r=-0.942). The analysis of the kinetics of the Zn(II)-peptide linkage revealed that the most stable complexes with this metal were formed by GnRH (Kd=0.006+/-0.001 microM(-1)) and by dalarelin (Kd=0.020+/-0.001 microM(-1)). Zn(II) with GnRH complexes are about 147 times more durable than ACTH (Kd=0.880+/-0.033 microM(-1)) ones. It was established that the Zn(II)-peptide complexes were more stable in the case of lower molecular weight of the peptide (r=0.963), and the inferior number of the amino acid residues accessible in the peptide (r=0.967).     

Antileukemic action of novel diamine Pt(II) halogenido complexes: Comparison of the representative novel Pt(II) with corresponding Pt(IV) complex

This study presents the synthesis, characterization, and antitumor action of five new Pt(II ) halogenido, chlorido, and iodido complexes with edda type of ligands. (S,S)‐ Ethylenediamine‐N,N′‐di‐2‐(3‐cyclohexyl)propanoic acid dihydrochloride and its methyl, ethyl, and n‐propyl esters were prepared according to the previously reported procedure. All investigated complexes were characterized by IR , ESI ‐MS (¹H, ¹³C, and HMBC ) NMR spectroscopy, and elemental analysis. Their cytotoxic action was investigated in four human tumor cell lines: promyelocytic (HL ‐60) and lymphocytic (REH ) leukemia, glioma (U251), and lung carcinoma (H460). Cell viability was assessed by acid phosphatase and LDH assay, while oxidative stress and cell death parameters were analyzed by flow cytometry. The results showed that novel Pt(II ) complexes exhibited antitumor action superior to precursor ligands, with iodido complexes being more efficient than corresponding chlorido complexes. Human promyelocytic cell line (HL ‐60) was the most sensitive to antitumor action of all investigated substances and was used for investigation of the underlying mode of antileukemic action. The investigated Pt(II ) complexes showed more potent antileukemic action than corresponding Pt(IV ) complex, through induction of oxidative stress and apoptosis, evidenced by caspase (8, 9, and 3) activation and phosphatidylserine externalization.     

Effect of calcium (II) and magnesium (II) ions on the 18–23 γ-carboxyglutamic acid containing cyclic peptide loop of bovine prothrombin An AMBER molecular mechanics study

The effect of calcium (II) and magnesium (II) ions on the conformation of the 18–23 cyclic peptide loop of bovine prothrombin are investigated by the molecular mechanics program AMBER (Assisted Model Building with Energy Refinement). The work is an extension of an earlier paper (Eastman et al, Int. J. Peptide Protein Res. 27, 1986, 530–553) that employed the program ECEPP (Empirical Conformational Energy Program for Peptides). In the absence of either metal ion, or in the presence of either one Ca(II) or one Mg(II) ion, the lowest-energy forms found by AMBER have the Gla21-Pro22 peptide bond in a trans conformation. In the presence of two Ca(II) or Mg(II) ions, the loop form of lowest energy is decidedly cis. The coordination about the Ca(II) and Mg(II) ions is different in both the single and double metal cases. In addition, the peptide chains that emerge from the loop are oriented parallel to each other in the lowest-energy complex with two Ca(II) ions, but are not parallel in the lowest-energy complex with two Mg(II) ions.