Browsing by Author "Costa, Judite"
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- Evaluation of the protective effect of MnTMPyP on the cytotoxicity induced by different oxidant agentsPublication . Fernandes, Ana Sofia; Gaspar, Jorge; Cabral, M. Fatima; Bettencourt, Ana F.; Caneiras, Catla; Rueff, Jose; Castro, Matilde; Costa, Judite; Oliveira, Nuno G.
- Fighting S. aureus catheter-related infections with sophorolipids: Electing an antiadhesive strategy or a release one?Publication . Mendes, Rita M.; Francisco, Ana Paula; Carvalho, Filomena A.; Dardouri, Maïssa; Costa, Bruna; Bettencourt, Ana; Costa, Judite; Gonçalves, Lídia; Costa, Fabíola; Ribeiro, Isabel A. C.Staphylococcus aureus medical devices related-infections, such as blood stream catheter are of major concern. Their prevention is compulsory and strategies, not prone to the development of resistance, to prevent S. aureus biofilms on catheter surfaces (e.g. silicone) are needed. In this work two different approaches using sophorolipids were studied to prevent S. aureus biofilm formation on medical grade silicone: i) an antiadhesive strategy through covalent bond of sophorolipids to the surface; ii) and a release strategy using isolated most active sophorolipids. Sophorolipids produced by Starmerella bombicola, were characterized by UHPLC-MS and RMN, purified by automatic flash chromatography and tested for their antimicrobial activity towards S. aureus. Highest antimicrobial activity was observed for C18:0 and C18:1 diacetylated lactonic sophorolipids showing a MIC of 50 μg mL−1. Surface modification with acidic or lactonic sophorolipids when evaluating the anti-adhesive or release strategy, respectively, was confirmed by contact angle, FTIR-ATR and AFM analysis. When using a mixture of acidic sophorolipids covalently bonded to silicone surface as antiadhesive strategy cytocompatible surfaces were obtained and a reduction of 90 % on biofilm formation was observed. Nevertheless, if a release strategy is adopted with purified lactonic sophorolipids a higher effect is achieved. Most promising compound was C18:1 diacateylated lactonic sophorolipid that showed no cellular viability reduction when a concentration of 1.5 mg mL−1 was selected and a reduction on biofilm around 5 log units. Results reinforce the applicability of these antimicrobial biosurfactants on preventing biofilms and disclose that their antimicrobial effect is imperative when comparing to their antiadhesive properties.
- Fighting S. aureus catheter-related infections with sophorolipids: electing an antiadhesive strategy or a release one?Publication . Mendes, Rita M.; Francisco, Ana P.; Carvalho, Filomena Almeida; Dardouri, Maissa; Costa, Bruna; Bettencourt, Ana F.; Costa, Judite; Gonçalves, Lidia; Costa, Fabíola; Ribeiro, Isabel A.C.Staphylococcus aureus medical devices related-infections, such as blood stream catheter are of major concern. Their prevention is compulsory and strategies, not prone to the development of resistance, to prevent S. aureus biofilms on catheter surfaces (e.g. silicone) are needed. In this work two different approaches using sophorolipids were studied to prevent S. aureus biofilm formation on medical grade silicone: i) an antiadhesive strategy through covalent bond of sophorolipids to the surface; ii) and a release strategy using isolated most active sophorolipids. Sophorolipids produced by Starmerella bombicola, were characterized by UHPLC-MS and RMN, purified by automatic flash chromatography and tested for their antimicrobial activity towards S. aureus. Highest antimicrobial activity was observed for C18:0 and C18:1 diacetylated lactonic sophorolipids showing a MIC of 50 μg mL-1. Surface modification with acidic or lactonic sophorolipids when evaluating the anti-adhesive or release strategy, respectively, was confirmed by contact angle, FTIR-ATR and AFM analysis. When using a mixture of acidic sophorolipids covalently bonded to silicone surface as antiadhesive strategy cytocompatible surfaces were obtained and a reduction of 90 % on biofilm formation was observed. Nevertheless, if a release strategy is adopted with purified lactonic sophorolipids a higher effect is achieved. Most promising compound was C18:1 diacateylated lactonic sophorolipid that showed no cellular viability reduction when a concentration of 1.5 mg mL-1 was selected and a reduction on biofilm around 5 log units. Results reinforce the applicability of these antimicrobial biosurfactants on preventing biofilms and disclose that their antimicrobial effect is imperative when comparing to their antiadhesive properties.
- Kinetic study of dissociation of a copper(II) complex of a 14-membered tetraaza-macrocyclic ligand containing pyridine and pendant N-carboxymethyl armsPublication . Lubal, Premysl; Albrecht-Gary, Anne-Marie; Blanc, Sylvie; Costa, Judite; Delgado, RitaThe kinetics of acid-catalyzed dissociation of the copper(II) complex with 7-methyl-3,7,11,17-tetraazabicyclo[11.3.1] heptadeca-1(17), 13,15-triene-3,11-diacetic acid (ac(2)Me[14] pyN(4)) at [H+] = 0.05-0.25 mol l(-1), I = 0.25 mol l(-1) (Na, H) ClO4, and T = 298.16 K was studied with conventional and stopped-flow UV/VIS spectroscopy. Three steps of consecutive complex reaction were observed. The very fast first and second steps characterized by k(1) = 70 +/- 10 and k(2) = 0.23 +/- 0.01 l mol(-1) s(-1) depend on the H+ concentration. The third step is very slow, k(3) = (1.08 +/- 0.03) x 10(-3) s(-1), and does not depend on the H+ concentration. Latter rate-determining step involves an isomerisation process forcing the copper(II) ion to leave rapidly the macrocyclic cavity. The reaction mechanism of the complex dissociation has been proposed, taking into account the results obtained for related systems by independent methods: potentiometry, UV/VIS and EPR spectroscopies, X-ray diffraction analysis, and molecular mechanics calculations.
- Macrocyclic copper(II) complexesPublication . Fernandes, Ana S.; Gaspar, Jorge; Cabral, M. Fatima; Caneiras, Catia; Guedes, Rita; Rueff, Jose; Castro, Matilde; Costa, Judite; Oliveira, Nuno G.Synthetic superoxide dismutase mimetics have emerged as a potential novel class of drugs for the treatment of oxidative stress related diseases. Among these agents, metal complexes with macrocyclic ligands constitute an important group. In this work we synthesized five macrocyclic copper(II) complexes and evaluated their ability to scavenge the superoxide anions generated by the xanthine-xanthine oxidase system. Two different endpoints were used, the nitro blue tetrazolium (NBT) reduction assay (colorimetric method) and the dihydroethidium (DHE) oxidation assay (fluorimetric method). IC50 values in the low micromolar range were found in four out of five macrocyclic complexes studied, demonstrating their effective ability to scavenge the superoxide anion. The IC50 values obtained with the NBT assay for the macrocyclic copper(II) complexes, were consistently higher, approximately threefold, than those obtained with the DHE assay. Spectroscopic and electrochemical studies were performed in order to correlate the structural features of the complexes with their superoxide scavenger activity. Cytotoxicity assays were also performed using the MTT method in V79 mammalian cells and we found that the complexes, in the range of concentrations tested in the superoxide scavenging assays were not considerably toxic. In summary, some of the presented macrocyclic copper(II) complexes, specially those with a high stability constant and low IC50 appear to be promising superoxide scavenger agents, and should be considered for further biological assays. (c) 2007 Elsevier Inc. All rights reserved.
- Novel copper(II) macrocyclic complexes with superoxide scavenging activityPublication . Fernandes, Ana Sofia; Cabral, M. Fatima; Rueff, Jose; Caneiras, Catia; Gaspar, Jorge; Castro, Matilde; Costa, Judite; Oliveira, Nuno G.
- Oxidative injury in V79 Chinese hamster cells: protectivePublication . Fernandes, Ana S.; Serejo, João; Gaspar, Jorge; Cabral, Fátima; Bettencourt, Ana F.; Rueff, José; Castro, Matilde; Costa, Judite; Oliveira, Nuno G.Oxidative cell injury could be induced by different reactive oxygen species (ROS) operating in multiple pathways. The present work is focused on three different models of oxidative stress: the xanthine/xanthine oxidase system (XXO), an extracellular superoxide anion generator; tert-butylhydroperoxide (TBHP), an analogue of lipid hydroperoxides; and doxorubicin (Dox), an anticancer drug. Superoxide and peroxyl radicals, among other ROS, could be effectively scavenged by MnTM-4-PyP, a polyfunctional catalytic antioxidant. In this report, we have addressed the role of MnTM-4-PyP on the protection against the cytotoxicity induced by the three aforementioned oxidants. The effect of MnTM-4-PyP (0.1–100 μM) was evaluated in V79 fibroblasts using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide reduction and the crystal violet assays, as well as the mitotic index. Also, the generation of intracellular ROS was studied by the fluorescent probe dihydroethidium. MnTM-4-PyP has shown significant protective effects against the cytotoxicity of XXO and TBHP, increasing the cell viability in approximately 40% and reducing the intracellular level of ROS. However, no considerable protection occurred against Dox. The three oxidants caused a mitotic index reduction that was not altered by MnTM-4-PyP. In summary, MnTM-4-PyP appears to be a promising agent for the protection against oxidative injury. However, it has shown differential responses, reinforcing the need to study different experimental models for the adequate evaluation of its potentialities as a catalytic antioxidant.
- Properties of a new 4-imidazolyl derivative of a 14-membered tetraazamacrocyclic chelating agentPublication . Nunes, Rute M.; Delgado, Rita; Cabral, M. Fatima; Costa, Judite; Brandao, Paula; Felix, Vitor; Goodfellow, Brian J.A new bis-N,N'-(5-methylimidazol-4-ylmethyl) derivative of a 14-membered tetraazamacrocycle, L-1, has been synthesized. The protonation constants of this compound and the stability constants of its complexes with divalent first-row transition metal ions and Fe3+ were determined at 298.2 K in aqueous 0.10 mol dm(-3) KNO3. Compound L-1 exhibits high overall basicity, which is mainly conferred by theimidazolyl groups. The complexes of the divalent first row-transition metal ions of L-1 follow the Irving-Williams order of stability with the maximum for Cu2+ as expected, but a steep fall of constants is verified for the Mn2+, Fe2+ and Co2+, in one side, and for the Zn2+ complexes, in the other side. Additionally, L-1 shows a large affinity for Fe3+, and the relative stability constants for its Cd2+ and Pb2+ complexes indicate that L-1 may be useful for the complexometric determination of these two toxic metal ions in solutions containing both metal ions. These studies together with NMR, UV-vis and EPR spectroscopic data indicated the presence of mononuclear complexes, which adopt distorted pyramidal or octahedral geometries depending on the metal centre. The X-ray crystal structure of [ Cu(HL1)](PF6)(2)(NO3) center dot H2O showed that the coordination sphere of the copper centre can be described as a distorted square pyramid with the basal plane defined by three nitrogen donors of the macrocycle backbone and one nitrogen atom from one imidazolyl pendant arm. The apical position is occupied by the nitrogen atom of the macrocycle trans to the pyridine ring. To achieve this coordination environment, the macrocycle is folded along the axis defined by the two N atoms contiguous to the pyridine ring. The free methylimidazolyl arm points away from the metal centre leading to an intramolecular Cu center dot center dot center dot N distance of 5.155( 1) angstrom.
- Pyridine-containing macrocyclic copper(II) complexesPublication . Fernandes, Ana S.; Oliveira, Nuno G.; Gaspar, Jorge; Cabral, M. Fatima; Caneiras, Catia; Rueff, Jose; Castro, Matilde; Costa, Judite
- Shielding of actin by the endoplasmic reticulum impacts nuclear positioningPublication . Janota, Cátia; Pinto, Andreia; Pezzarossa, Anna; Machado, Pedro; Costa, Judite; Campinho, Pedro; Franco, Claudio; Gomes, EdgarNuclear position is central to cell polarization, and its disruption is associated with various pathologies. The nucleus is moved away from the leading edge of migrating cells through its connection to moving dorsal actin cables, and the absence of connections to immobile ventral stress fibers. It is unclear how these asymmetric nucleo-cytoskeleton connections are established. Here, using an in vitro wound assay, we find that remodeling of endoplasmic reticulum (ER) impacts nuclear positioning through the formation of a barrier that shields immobile ventral stress fibers. The remodeling of ER and perinuclear ER accumulation is mediated by the ER shaping protein Climp-63. Furthermore, ectopic recruitment of the ER to stress fibers restores nuclear positioning in the absence of Climp-63. Our findings suggest that the ER mediates asymmetric nucleo-cytoskeleton connections to position the nucleus.