BioMetals (v.22, #2)
Tobacco smoke iron: an initiator/promoter of multiple diseases by E. D. Weinberg (207-210).
Tobacco smoking enhances risk for a diversity of acute and chronic diseases. Iron is a constant prominent component of mainstream tobacco smoke. The manifold toxic activities of inhaled iron could be responsible for a notable portion of the spectrum of smoking-related diseases.
Keywords: Impaired hearing; Infection; Iron; Neoplasm; Osteoporosis; Tobacco smoke; Vascular disease
Effects of marginal iron overload on iron homeostasis and immune function in alveolar macrophages isolated from pregnant and normal rats by Roberta J. Ward; Stephanie Wilmet; Rachida Legssyer; Daniel Leroy; Louise Toussaint; Robert R. Crichton; Christophe Pierreux; Louis Hue; Jacques Piette; Surjit Kaila Srai; Nita Solanky; Dominique Klein; Karl Summer (211-223).
The effects of changes in macrophage iron status, induced by single or multiple iron injections, iron depletion or pregnancy, on both immune function and mRNA expression of genes involved in iron influx and egress have been evaluated. Macrophages isolated from iron deficient rats, or pregnant rats at day 21 of gestation, either supplemented with a single dose of iron dextran, 10 mg, at the commencement of pregnancy, or not, showed significant increases of macrophage ferroportin mRNA expression, which was paralleled by significant decreases in hepatic Hamp mRNA expression. IRP activity in macrophages was not significantly altered by iron status or the inducement of pregnancy ± a single iron supplement. Macrophage immune function was significantly altered by iron supplementation and pregnancy. Iron supplementation, alone or combined with pregnancy, increased the activities of both NADPH oxidase and nuclear factor kappa B (NFκB). In contrast, the imposition of pregnancy reduced the ability of these parameters to respond to an inflammatory stimuli. Increasing iron status, if only marginally, will reduce the ability of macrophages to mount a sustained response to inflammation as well as altering iron homeostatic mechanisms.
Keywords: Iron homeostasis; Pregnancy; Macrophages; NFκB; Nitric oxide synthase
Arousing sleeping genes: shifts in secondary metabolism of metal tolerant actinobacteria under conditions of heavy metal stress by Götz Haferburg; Ingrid Groth; Ute Möllmann; Erika Kothe; Isabel Sattler (225-234).
Numerous microbial habitats are strongly influenced by elevated levels of heavy metals. This type of habitat has developed either due to ore mining and metal processing or by pedogenesis above metal-rich base rocks. Most actinobacteria are soil-borne microbes with a remarkable capability for the synthesis of a broad variety of biologically active secondary metabolites. One major obstacle in identifying secondary metabolites, however, is the known phenomenon of sleeping gene clusters which are present, but silent under standard screening conditions. Here, we proceed to show that sleeping gene clusters can be awakened by the induction in heavy metal stress. Both, a chemical and a biological screening with extracts of supernatant and biomass of 10 strains derived from metal contaminated and non-contaminated environments was carried out to assay the influence of heavy metals on secondary metabolite patterns of metal tolerant actinobacteria. Metabolite patterns of cultures grown in complex and minimal media were compared to nickel (or cadmium) spiked parallels. Extracts of some strains grown in the presence of a metal salt displayed intense antibiosis against Escherichia coli, Mycobacterium smegmatis, Staphylococcus aureus and Candida albicans. Contrarily to the widely held opinion of metals as hindrance in secondary metabolism, metals thus can induce or enhance synthesis of possibly potent and medically relevant metabolites in metal tolerant strains. Hence, re-screening of existing strain libraries as well as identification of new strains from contaminated areas are valid strategies for the detection of new antibiotics in the future.
Keywords: Actinobacteria ; Antibiosis; Heavy metal; Screening program; Secondary metabolism
Antifungal activity and mode of action of silver nano-particles on Candida albicans by Keuk-Jun Kim; Woo Sang Sung; Bo Kyoung Suh; Seok-Ki Moon; Jong-Soo Choi; Jong Guk Kim; Dong Gun Lee (235-242).
In this study, the antifungal effects of silver nano-particles (nano-Ag) and their mode of action were investigated. Nano-Ag showed antifungal effects on fungi tested with low hemolytic effects against human erythrocytes. To elucidate the antifungal mode of action of nano-Ag, flow cytometry analysis, a glucose-release test, transmission electron microscopy (TEM) and the change in membrane dynamics using 1,6-diphenyl-1,3,5-hexatriene (DPH), as a plasma membrane probe, were performed with Candida albicans. The results suggest nano-Ag may exert an antifungal activity by disrupting the structure of the cell membrane and inhibiting the normal budding process due to the destruction of the membrane integrity. The present study indicates nano-Ag has considerable antifungal activity, deserving further investigation for clinical applications.
Keywords: Silver nano-particles; Antifungal activity; Candida albicans ; Membrane disruption
Lap4, a vacuolar aminopeptidase I, is involved in cadmium-glutathione metabolism by Paula D. B. Adamis; Sergio C. Mannarino; Cristiano J. Riger; Giselle Duarte; Ana Cruz; Marcos D. Pereira; Elis C. A. Eleutherio (243-249).
In Saccharomyces cerevisiae, accumulation of cadmium-glutathione complex in cytoplasm inhibits cadmium absorption, glutathione transferase 2 is required for the formation of the complex and the vacuolar gamma-glutamyl transferase participates of the first step of glutathione degradation. Here, we proposed that Lap4, a vacuolar amino peptidase, is involved in glutathione catabolism under cadmium stress. Saccharomyces cerevisiae cells deficient in Lap4 absorbed almost 3-fold as much cadmium as the wild-type strain (wt), probably due to the lower rate of cadmium-glutathione complex synthesis in the cytoplasm. In wt, but not in lap4 strain, the oxidized/reduced GSH ratio and the Gtt activity increased in response to cadmium, confirming that the mutant is deficient in the synthesis of the complex probably because the degradation of vacuolar glutathione is impaired. Thus, under cadmium stress, Lap4 and gamma-glutamyl transferase seem to work together to assure an efficient glutathione turnover stored in the vacuole.
Keywords: Lap4; Cadmium; Glutathione; Mutagenesis; Saccharomyces cerevisiae
Hepatic distribution of iron, copper, zinc and cadmium-containing proteins in normal and iron overload mice by Yan Zhang; Bai Li; Chunying Chen; Zhonghong Gao (251-259).
Subcellular distribution of metal-containing proteins of Fe, Cu, Zn and Cd were determined in the liver samples of iron overload mice by size exclusion high performance liquid chromatography with on-line coupling to UV and inductively coupled plasma mass spectrometry. Collision cell techniques was used to remove polyatomic interferences for some elements, such as Fe. Comparative molecular weight (MW) information of the elemental fraction was obtained within a retention time of 40 min. Fe was present only in high-MW (HMW) protein; Cu, Zn and Cd were found in different MW proteins. It was also observed that these four elements studied showed predominant association with HMW fractions. Moreover, compared with the normal group, we found that the contents of these elements except Cu significantly increased and the distribution of some elements like Cd changed in iron overload mouse liver. It means that excessive iron accumulation in vivo may affect the metabolism of other element such as Zn and Cd.
Keywords: Iron overload; Metalloproteins; Hepatic distribution; SEC-HPLC-ICP-MS
Hg2+ and Cd2+ interact differently with biomimetic erythrocyte membranes by Mary Trang Le; Jürgen Gailer; Elmar J. Prenner (261-274).
In order to characterize the potentially deleterious effects of toxic Hg2+ and Cd2+ on lipid membranes, we have studied their binding to liposomes whose composition mimicked erythrocyte membranes. Fluorescence spectroscopy utilizing the concentration dependent quenching of Phen Green™ SK by Hg2+ and Cd2+ was found to be a sensitive tool to probe these interactions at metal concentrations ≤1 μM. We have systematically developed a metal binding affinity assay to screen for the interactions of Hg2+ or Cd2+ with certain lipid classes. A biomimetic liposome system was developed that contained four major lipid classes of erythrocyte membranes (zwitterionic lipids: phosphatidylcholine and phosphatidylethanolamine; negatively charged: phosphatidylserine and neutral: cholesterol). In contrast to Hg2+, which preferentially bound to the negatively charged phosphatidylserine compared to the zwitterionic components, Cd2+ bound stronger to the two zwitterionic lipids. Thus, the observed distinct differences in the binding affinity of Hg2+ and Cd2+ for certain lipid classes together with their known effects on membrane properties represent an important first step toward a better understanding the role of these interactions in the chronic toxicity of these metals.
Keywords: Toxic metals; Hg2+ ; Cd2+ ; Liposomes; Model systems; Membranes; Lipids; Erythrocytes; Fluorescence spectroscopy
Correlation between organic acid exudation and metal uptake by ectomycorrhizal fungi grown on pond ash in vitro by Prasun Ray; Alok Adholeya (275-281).
Experiments were conducted to investigate the effect of coal ash on organic acid exudation and subsequent metal uptake by ectomycorrhizal fungi. Four isolates of ectomycorrhizal fungi namely, Pisolithus tinctorius (EM-1293 and EM-1299), Scleroderma verucosum (EM-1283) and Scleroderma cepa (EM-1233) were grown on pond ash moistened with Modified Melin-Norkans medium in vitro. Exudation of formic acid, malic acid and succinic acid by these fungi were detected by HPLC. Mycelial accumulation of Al, As, Cd, Cr, Ni and Pb by these fungi was assayed by atomic absorption spectrophotometer. Relationship between organic acid exudation and metal uptake was determined using classical multivariate linear regression model. Correlation between organic acid exudation and metal uptake could be substantiated when several metals are considered collectively. The finding supports the widespread role of low molecular weight organic acid as a function of tolerance, when exposed to metals in vitro.
Keywords: Fly ash; Mycorrhiza; Organic acid; Heavy metal
Interaction of DNA with a novel photoactive platinum diimine complex by Zhigang Zhang; Xindian Dong (283-288).
Interaction of DNA with a novel photoactive platinum diimine compound has been studied by electronic absorption spectra, fluorescence spectra and viscosity measurements. The red light-induced DNA cleavage activity of the platinum compound has also been studied by agarose gel electrophoresis. The results suggest that the platinum compound may interact with DNA by intercalation mode. When irradiated with red light, the platinum compound can generate singlet oxygen, resulting in cleavage of DNA.
Keywords: Platinum diimine complex; Photoactive; DNA binding
Absorption, excretion and retention of 51Cr from labelled Cr-(III)-picolinate in rats by Karin Kottwitz; Niels Laschinsky; Roland Fischer; Peter Nielsen (289-295).
The bioavailability of chromium from Cr-picolinate (CrPic3) and Cr-chloride (CrCl3) was studied in rats using 51Cr-labelled compounds and whole-body-counting. The intestinal absorption of Cr was twice as high from CrPic3 (1.16% vs 0.55%) than from CrCl3, however most of the absorbed 51Cr from CrPic3 was excreted into the urine within 24 h. After i.v. or i.p. injection, the whole-body retention curves fitted well to a multiexponential function, demonstrating that plasma chromium is in equilibrium with three pools. For CrPic3, a large pool exists with a very rapid exchange (T 1/2 = <0.5 days), suggesting that CrPic3 is absorbed as intact molecule, from which the main part is directly excreted by the kidney before degradation of the chromium complex in the liver can occur. CrCl3 is less well absorbed but the rapid exchange pool is much smaller, resulting in even higher Cr concentrations in tissue such as muscle and fat. However, 1–3 days after application, the relative distribution of 51Cr from both compounds was similar in all tissues studied, indicating that both compounds contribute to the same storage pool. In summary, the bioavailability of CrPic3 in rats is not superior compared to CrCl3.
Keywords: Chromium; Chromium picolinate; 51Cr; Absorption; Whole-body counting
DNA binding property, nuclease activity and cytotoxicity of Zn(II) complexes of terpyridine derivatives by Qin Jiang; Jianhui Zhu; Yangmiao Zhang; Nan Xiao; Zijian Guo (297-305).
Two zinc(II) terpyridine complexes Zn(atpy)2(PF6)2 (1) (atpy = 4′-p-N9′-adeninylmethylphenyl-2,2′:6,2′′-terpyridine) and Zn(ttpy)2(PF6)2 (2) (ttpy = 4′-p-tolyl-2,2′:6,2′′-terpyridine) have been synthesized and characterized by elemental analysis, 1H NMR and electrospray mass spectroscopy. The structure of complex 2 was also determined by X-ray crystallography, which revealed a ZnN6 coordination in an octahedral geometry with two terpyridine acting as equatorial ligands. The circular dichroism data showed that complex 1 exhibited an ICD signal at around 300 nm and induced more evident disturbances on DNA base stacking than complex 2, reflecting the impact of the adenine moiety on DNA binding modes. Complex 1 exhibited higher cleavage activity to supercoiled pUC 19 DNA than complex 2 under aerobic conditions, suggesting a promotional effect of adenine moiety in DNA nuclease ability. Interestingly, both complexes demonstrated potent in vitro cytotoxicity against a series human tumor cell lines such as human cervix carcinoma cell line (HeLa), human liver carcinoma cell line (HepG2), human galactophore carcinoma cell line (MCF-7) and human prostate carcinoma cell line (pc-3). The cytotoxicity is averagely 10 times more active than the anticancer drug cisplatin.
Keywords: Adenine; DNA binding; DNA cleavage; Terpyridine; Zinc
Nickel and copper ion-induced stress signaling in human hepatoma cells: analysis of phosphoinositide 3′-kinase/Akt signaling by Anna Eckers; Kerstin Reimann; Lars-Oliver Klotz (307-316).
Nickel compounds may act as carcinogens, affecting both initiation and promotion stages of carcinogenesis due, in large parts, to their capability of inducing DNA damage and of modulating cellular signaling cascades known to affect cellular proliferation, respectively. We have previously demonstrated that the phosphoinositide 3-kinase (PI3K)/Akt signaling cascade is stimulated in cells exposed to copper ions, resulting in phosphorylation and nuclear exclusion of FoxO transcription factors. Here, human hepatoma cells were exposed to nickel or copper ions, followed by comparative analysis of PI3K/Akt-dependent signaling. Exposure of hepatoma cells to copper ions resulted in extensive oxidation of cellular glutathione, while no such effect was detected with nickel ions. Similarly, copper ions were more than 100-fold more toxic to cells than nickel, as deduced from analyses of colony forming abilities. Despite this lack of oxidative and cytotoxic action, exposure of hepatoma cells to Ni2+ resulted in a significant activation of Akt that was abrogated by inhibitors of PI3K. Interestingly, activation of Akt—although coincident with a phosphorylation of Akt substrates, such as glycogen synthase kinase-3—did not result in significant nuclear exclusion of FoxO1a. In line with this finding, no significant modulation of the activity of a FoxO-responsive promoter construct was observed in cells exposed to nickel ions. In summary, exposure of HepG2 human hepatoma cells to nickel ions results in stimulation of the Ser/Thr kinase Akt in a PI3K-dependent fashion, activation most likely being independent of oxidative processes. In sharp contrast to copper ions, nickel-induced Akt activation is not propagated further downstream to FoxO-dependent signaling beyond the phosphorylation of FoxO1a and 3a.
Keywords: Nickel; Copper; Heavy metal signaling; Insulin signaling; PI3-kinase; FoxO transcription factors
Lanthanum chloride suppresses hydrogen peroxide-enhanced calcification in rat calcifying vascular cells by Yu Shi; Bao-Di Gou; Yan-Ling Shi; Tian-Lan Zhang; Kui Wang (317-327).
Lanthanum chloride (LaCl3) has been shown to retard the progression of established atherosclerotic lesions in animal models, and used as a calcium channel blocker in various cellular experiments. In this study, we assessed the role of lanthanum chloride (LaCl3) in H2O2-enhanced calcification in rat calcifying vascular cells (CVCs) and examined the involvement of MAPK signaling pathways. H2O2 induced growth inhibition of CVCs, as well as increases in intracellular levels of calcium and reactive oxygen species, ALP activity, apoptosis and calcium deposition. These effects of H2O2 were suppressed by pretreatment of the cells with 1 μM of LaCl3 for 2 h. In addition, H2O2 activated the phosphorylation of ERK1/2, JNK and p38 MAPK, but only the last two were associated with the ALP activity. Our findings demonstrate that H2O2-enhanced osteoblastic differentiation and apoptosis are responsible for the increased calcification in rat CVCs, and LaCl3 can counteract these effects by suppressing the activation of JNK (JNK2, but not JNK1) and p38 MAPK signaling pathway.
Keywords: Lanthanum; Hydrogen peroxide; Calcifying vascular cells; Calcification; MAPK signaling
The neuroprotective role of l-cysteine towards the effects of short-term exposure to lanthanum on the adult rat brain antioxidant status and the activities of acetylcholinesterase, (Na+,K+)- and Mg2+-ATPase by Charis Liapi; Apostolos Zarros; Stamatios Theocharis; Hussam Al-Humadi; Foteini Anifantaki; Elena Gkrouzman; Zois Mellios; Nikolina Skandali; Stylianos Tsakiris (329-335).
Lanthanum (La) is a rare earth element that is widely used for industrial, medical and agricultural purposes. Its neurotoxic effects are linked to its physical and chemical properties and its interaction with certain trace elements and membrane-bound enzymes. The aim of this study was to investigate the effects of short-term La-administration (as LaCl3, 53 mg/kg) on the adult rat whole brain total antioxidant status (TAS) and the activities of acetylcholinesterase (AChE), Na+,K+-ATPase and Mg2+-ATPase, as well as the potential effect of the co-administration of the antioxidant l-cysteine (Cys, 7 mg/kg) on the above parameters. Twenty-eight male Wistar rats were divided into four groups: A (saline-treated control), B (La), C (Cys),and D (La and Cys). All rats were treated once daily with intraperitoneal injections of the tested compounds, for 1-week. Rats were sacrificed by decapitation and the above mentioned parameters were measured spectrophotometrically. Rats treated with La exhibited a significant reduction in brain TAS (−36%, P < 0.001, BvsA), that was partially limited by the co-administration of Cys (−13%, P < 0.01, DvsA), while Cys (group C) had no effect on TAS. The rat brain AChE activity was found significantly increased by both La (+23%, P < 0.001, BvsA) and Cys (+59%, P < 0.001, CvsA), while it was adjusted to control levels by the co-administration of La and Cys. The activity of rat brain Na+,K+-ATPase was significantly decreased by La-administration (−28%, P < 0.001, BvsA), while Cys supplementation could not reverse this decrease. The activity of Mg2+-ATPase exhibited a slight but statistically significant reduction due to La (−8%, P < 0.01, BvsA), that was further reduced by Cys co-administration (−25%, P < 0.001, DvsA). The above findings suggest that La short-term in vivo administration causes a statistically significant decrease in the rat brain TAS and an increase in AChE activity. Both effects can be, partially or totally, reversed into control levels by Cys co-administration, which could thus be considered for future applications as a neuroprotective agent against chronic exposure to La. The activities of Na+,K+- and Mg2+-ATPase that were inhibited by La, could not be reversed by Cys co-administration. A role for the already reported concentration-dependent interaction of La with Ca-binding sites (such as Ca2+-ATPase) might be considered for certain of the above phenomena.
Keywords: Lanthanum chloride; Rat brain; Antioxidant status; Acetylcholinesterase; Na+,K+-ATPase; Mg2+-ATPase; l-Cysteine
Iron transport in Francisella in the absence of a recognizable TonB protein still requires energy generated by the proton motive force by Lidia M. Crosa; Jorge H. Crosa; Fred Heffron (337-344).
The mechanism of iron transport in Francisella is still a puzzle since none of the sequenced Francisella strains appears to encode a TonB protein, the energy transducer of the proton motive force necessary to act on the bacterial outer membrane siderophore receptor to allow the internalization of iron. In this work we demonstrate using kinetic experiments of radioactive Fe3+ utilization, that iron uptake in Francisella novicida, although with no recognizable TonB protein, is indeed dependent on energy generated by the proton motive force. Moreover, mutants of a predicted outer membrane receptor still transport iron and are sensitive to the iron dependent antimicrobial compound streptonigrin. Our studies suggest that alternative pathways to internalize iron might exist in Francisella.
Keywords: Francisella ; Iron transport; Proton motive force
Absolute requirement for iron in the development of chemically induced uroporphyria in mice treated with 3-methylcholanthrene and 5-aminolevulinate by Kenzi Nakano; Mayumi Ishizuka; Kentaro Q. Sakamoto; Shoichi Fujita (345-351).
Accumulating evidence, including experiments using cytochrome P450 1a2 (Cyp1a2) gene knock-out mice (Cyp1a2(−/−)), indicates that the development of chemically induced porphyria requires the expression of CYP1A2. It has also been demonstrated that iron enhances and expedites the development of experimental uroporphyria, but that iron alone without CYP1A2 expression, as in Cyp1a2(−/−) mice, does not cause uroporphyria. The role of iron in the development of porphyria has not been elucidated. We examined the in vivo effect of iron deficiency on hepatic URO accumulation in experimental porphyria. Mice were fed diets containing low (iron-deficient diet (IDD), 8.5 mg iron/kg) or normal (normal diet (ND), 213.7 mg iron/kg) levels of iron. They were treated with 3-methylcholanthrene (MC), an archetypal inducer of CYP1A, and 5-aminolevulinate (ALA), precursors of porphyrin and heme. We found that uroporphyrin (URO) levels and uroporphyrinogen oxidation (UROX) activity were markedly increased in ND mice treated with MC and ALA, while the levels were not raised in IDD mice with the same treatments. CYP1A2 levels and methoxyresorufin O-demethylase (MROD) activities, the CYP1A2-mediated reaction, were markedly induced in the livers of both ND and IDD mice treated with MC and ALA. UROX activity, supposedly a CYP1A2-dependent activity, was not enhanced in iron-deficient mice in spite of the fact of induction of CYP1A2. We showed that a sufficient level of iron is essential for the development of porphyria and UROX activity.
Keywords: Porphyria; Uroporphyrin; CYP1A2; Uroporphyrinogen oxidation; Iron
The effects of lactoferrin in a rat model of catecholamine cardiotoxicity by Přemysl Mladěnka; Vladimír Semecký; Zuzana Bobrovová; Petr Nachtigal; Jaroslava Vávrová; Magdaléna Holečková; Vladimir Palicka; Yvona Mazurová; Radomír Hrdina (353-361).
Lactoferrin is recently under intense investigation because of its proposed several pharmacologically positive effects. Based on its iron-binding properties and its physiological presence in the human body, it may have a significant impact on pathological conditions associated with iron-catalysed reactive oxygen species (ROS). Its effect on a catecholamine model of myocardial injury, which shares several pathophysiological features with acute myocardial infarction (AMI) in humans, was examined. Male Wistar rats were randomly divided into four groups according to the received medication: control (saline), isoprenaline (ISO, 100 mg kg−1 s.c.), bovine lactoferrin (La, 50 mg kg−1 i.v.) or a combination of La + ISO in the above-mentioned doses. After 24 h, haemodynamic functional parameters were measured, a sample of blood was withdrawn and the heart was removed for analysis of various parameters. Lactoferrin premedication reduced some impairment caused by ISO (e.g. a stroke volume decrease, an increase in peripheral resistance and calcium overload). These positive effects were likely to have been mediated by the positive inotropic effect of lactoferrin and by inhibition of ROS formation due to chelation of free iron. The failure of lactoferrin to provide higher protection seems to be associated with the complexity of catecholamine cardiotoxicity and with its hydrophilic character.
Keywords: Lactoferrin; Isoprenaline; Iron chelators; Reactive-oxygen species; Iron; Catecholamines
Structural model of the CopA copper ATPase of Enterococcus hirae based on chemical cross-linking by Mathias Lübben; Reto Portmann; Gerd Kock; Raphael Stoll; Malin M. Young; Marc Solioz (363-375).
The CopA copper ATPase of Enterococcus hirae belongs to the family of heavy metal pumping CPx-type ATPases and shares 43% sequence similarity with the human Menkes and Wilson copper ATPases. Due to a lack of suitable protein crystals, only partial three-dimensional structures have so far been obtained for this family of ion pumps. We present a structural model of CopA derived by combining topological information obtained by intramolecular cross-linking with molecular modeling. Purified CopA was cross-linked with different bivalent reagents, followed by tryptic digestion and identification of cross-linked peptides by mass spectrometry. The structural proximity of tryptic fragments provided information about the structural arrangement of the hydrophilic protein domains, which was integrated into a three-dimensional model of CopA. Comparative modeling of CopA was guided by the sequence similarity to the calcium ATPase of the sarcoplasmic reticulum, Serca1, for which detailed structures are available. In addition, known partial structures of CPx-ATPase homologous to CopA were used as modeling templates. A docking approach was used to predict the orientation of the heavy metal binding domain of CopA relative to the core structure, which was verified by distance constraints derived from cross-links. The overall structural model of CopA resembles the Serca1 structure, but reveals distinctive features of CPx-type ATPases. A prominent feature is the positioning of the heavy metal binding domain. It features an orientation of the Cu binding ligands which is appropriate for the interaction with Cu-loaded metallochaperones in solution. Moreover, a novel model of the architecture of the intramembranous Cu binding sites could be derived.
Keywords: Copper ATPase; Structure model; Cross-linking; Mass spectrometry; Serca1
The role of copper in drug-resistant murine and human tumors by S. Majumder; S. Chatterjee; Smarajit Pal; J. Biswas; T. Efferth; Soumitra Kumar Choudhuri (377-384).
Multidrug resistance (MDR) is still a major threat to successful clinical application of cancer chemotherapy. Copper plays an important role in biological systems, and copper is also involved in carcinogenesis. In the present investigation, we addressed the question whether metal copper might be involved in drug resistance of murine and human tumors. By means of atomic absorption spectroscopy, we determined serum copper concentrations. We found that the blood serum of tumor-bearing mice contained higher amounts of copper than healthy mice with tumors. Secondly, mice bearing doxorubicin-resistant Ehrlich ascites carcinoma- or cyclophosphamide-resistant Lewis lung carcinoma contained more copper in their serum than mice bearing the corresponding drug-sensitive parental tumors. Furthermore, the analysis of patients with breast cancer, colon carcinoma or lung cancer showed that the serum copper contents were higher in patients not responding to chemotherapy when compared to patients whose tumors responded to treatment. The copper levels in serum of healthy volunteers were lower than in cancer patients irrespective of their response to chemotherapy. Our results imply that the level of serum copper may be considered as a biomarker for treatment response.
Keywords: Biomarker; Copper; Multidrug resistance; Serum copper
Electrochemical and spectroscopic evidences of the interaction between DNA and Pt(II)(dppf)-complex by Lucilene D. Mello; Emerson S. Ribeiro; Lauro T. Kubota; Sofi K. C. Elmroth; Regina M. S. Pereira (385-392).
The interaction of Pt(II)(dppf)-complex, namely [Pt(dppf)(H2O)2]2+ with DNA was investigated by DPV and 1H-NMR techniques. The results showed that the interaction process has been characterized by changes in the electrochemical parameters of both compounds and the formation of a new anodic current peak close to the anodic current peak of the [Pt(dppf)(H2O)2]2+. In addition, the 1H-NMR spectra show that the coordination of Pt(II)(dppf)-complex to dsDNA occurs via N(7) of guanine. Others parameters like pH and ionic strength that affect the interaction process were also investigated.
Keywords: DNA; Platinum; Transition metal complexes; DNA–metal complex interaction