Browsing by Subject "Hydrogen peroxide"
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- PublicationOpen AccessBiological action of bleaching agents on tooth structure: A review(Universidad de Murcia. Departamento de Biología Celular e Histología, 2024) Bragança Aragão, Walessa Alana; Santos Chemelo, Victória; de Melo Alencar, Cristiane; Martins Silva, Cecy; Pessanha, Sofia; Reis, Alessandra; de Souza Rodrigues, Renata Duarte; Rodrigues Lima, RafaelThe use of bleaching agents to remove stains is one of the main dental procedures to improve the aesthetics of teeth. This review presents the main agents used for tooth whitening, existing clinical protocols, and the structural changes that may occur through their use. The main bleaching agents consist of hydrogen peroxide and carbamide peroxide, which are used in bleaching techniques for vital teeth. These techniques can be performed in the office by a professional or by the individual in a home environment under professional guidance. Bleaching agents come in a variety of concentrations and there are over-the-counter products available on the market with lower concentrations of hydrogen peroxide. Due to the chemical characteristics of the agents, changes in the organic and inorganic content of the tooth structure can be observed. These changes are related to morphological changes characterized by increased permeability and surface roughness, such changes compromise the mechanical resistance of the tooth. Furthermore, bleaching agents can promote molecular changes after reaching the dental pulp, resulting in oxidative stress of pulp cells and the release of proinflammatory mediators. Despite the bleaching effectiveness, tooth sensitivity is considered the main side effect of use. Therefore, among the heterogeneity of protocols, those that used the bleaching agent for a prolonged time and in lower concentrations presented more harmful effects on the tooth structure.
- PublicationOpen AccessEffect of highly concentrated bleaching gels on enamel microhardness and superficial morphology, and the recovery action of four remineralizing agents(BioMed Central, 2022-12-27) Melo, María; Fioresta, Rosella; Sanz, José Luis; Pecci Lloret, María Pilar; Llena, Carmen; Dermatología, Estomatología, Radiología y Medicina FísicaAbstract Background: Dental bleaching is a common clinical practice. The aim of this study is to investigate the efect of 35% hydrogen peroxide (HP) bleaching gel on the morphology and microhardness of enamel, and to analyze the efect of four remineralizing agents. Methods: One hundred blocks were prepared. The enamel surfaces were bleached with 35% HP in one session. The specimens were divided into four remineralization treatment groups (n=25). G1: Tooth Mousse, G2: Remin-Pro, G3: Colgate Pro-Relif, G4: Mirafuor. The remineralizing protocol was applied 3 min per day for one week. Vickers micro‑ hardness (HV) measurements and SEM observations were performed at baseline, after bleaching, and after remineral‑ izing treatment in all groups. Statistical analyses were performed using the paired t-test and ANOVA. Results: After bleaching, SEM showed an increase of irregularities on the surface of the samples. Enamel microhard‑ ness decreased a mean of 47.7 HV, equivalent to a mean decrease of 18.3% (p<0.05). After remineralization, the HV increased in all groups between 16 and 33% (p<0.01), recovering the initial microhardness of enamel samples. SEM images revealed a higher quantity of superfcial mineral deposits in groups 1 and 2 compared to the rest of the groups. Conclusions: The application of remineralizing products generates a signifcant increase in enamel microhardness. Tooth Mousse-treated samples showed a greater microhardness recovery, followed by Remin Pro. The superfcial morphology of the samples refects the results obtained in the HV tests. Keywords: Enamel microhardness, Enamel morphology, Remineralization, Hydrogen peroxide, Dental bleaching
- PublicationOpen AccessIdentification in Marinomonas mediterranea of a novel quinoprotein with glycine oxidase activity(WILEY, 2013) Campillo‐Brocal, Jonatan C.; Lucas‐Elio, Patricia; Sanchez‐Amat, Antonio; Genética y MicrobiologíaA novel enzyme with lysine-epsilon oxidase activity was previously described in the marine bacterium Marinomonas mediterranea. This enzyme differs from other l-amino acid oxidases in not being a flavoprotein but containing a quinone cofactor. It is encoded by an operon with two genes lodA and lodB. The first one codes for the oxidase, while the second one encodes a protein required for the expression of the former. Genome sequencing of M. mediterranea has revealed that it contains two additional operons encoding proteins with sequence similarity to LodA. In this study, it is shown that the product of one of such genes, Marme_1655, encodes a protein with glycine oxidase activity. This activity shows important differences in terms of substrate range and sensitivity to inhibitors to other glycine oxidases previously described which are flavoproteins synthesized by Bacillus. The results presented in this study indicate that the products of the genes with different degrees of similarity to lodA detected in bacterial genomes could constitute a reservoir of different oxidases.
- PublicationOpen AccessIn vitro effects of hormones and autacoids on the hydrogen peroxide production and the morphology of endotoxin-activated rat peritoneal macrophages(Murcia : F. Hernández, 2003) Kondomerkos, D.J.; Kalamidas, Stefanos; Kotoulas, Othon B.Peritoneal macrophages activated in vitro by endotoxin exhibit alterations of their capability to produce hydrogen peroxide after phorbol ester stimulation when certain hormones or autacoids are present in the culture medium. They also show morphological changes, mainly concerning cell size and nuclear appearance. Agents known to increase the intracellular levels of cyclic AMP, e.g. adrenalin and PGE2 reduce the hydrogen peroxide production. Insulin, which is known to decrease cyclic AMP levels, produces opposite results. Agents postulated to act via phospholipase C, e.g. serotonin, augment the production of hydrogen peroxide. We assume that this form of modulation may represent a regulatory mechanism of macrophage activation.
- PublicationOpen AccessMechanism of Dihydrofolate Reductase Downregulation in Melanoma by 3-O-(3,4,5-Trimethoxybenzoyl)-(-)-Epicatechin(WILEY, 2010-06-01) Chazarra Parres, Soledad; Cabezas Herrera, Juan; Montenegro Arce, María Fernanda; Rodríguez López, José Neptuno; Sánchez del Campo Ferrer, Luis; Bioquímica y Biología Molecular AIn our search to improve the stability and cellular absorption of tea polyphenols, we synthesized 3-O-(3,4,5-trimethoxybenzoyl)-(-)-epicatechin (TMECG), which showed high antiproliferative activity against melanoma. TMECG downregulates dihydrofolate reductase (DHFR) expression in melanoma cells and we detail the sequential mechanisms that result from this even. TMECG is specifically activated in melanoma cells to form a stable quinone methide (TMECG-QM). TMECG-QM has a dual action on these cells. First, it acts as a potent antifolate compound, disrupting folate metabolism and increasing intracellular oxidized folate coenzymes, such as dihydrofolate, which is a noncompetitive inhibitor of dihydropterine reductase, an enzyme essential for tetrahydrobiopterin (H4B) recycling. Such inhibition results in H4B deficiency, endothelial nitric oxide synthase (eNOS) uncoupling and superoxide production. Second, TMECG-QM acts as an efficient superoxide scavenger and promotes intra-cellular H2O2 accumulation. Here, we present evidence that TMECG markedly reduces melanoma H4B and NO bioavailability and that TMECG action is abolished by the eNOS inhibitor N-omega-nitro-L-arginine methyl ester or the H2O2 scavenger catalase, which strongly suggests H2O2-dependent DHFR downregulation. In addition, the data presented here indicate that the simultaneous targeting of important pathways for melanoma survival, such as the folate cycle, H4B recycling, and the eNOS reaction, could represent an attractive strategy for fighting this malignant skin pathology
- PublicationEmbargoNon-enzymatic screen-printed sensor based on PtNPs@polyazure A for the real-time tracking of the H2O2 secreted from living plant cells(Elsevier, 2020-08) Jiménez Pérez, Rebeca; González Sánchez, María Isabel; Valero, Edelmira; Almagro Romero, Lorena; Pedreño García, María Ángeles; Biología VegetalMonitoring of hydrogen peroxide (H2O2) in living cells has high significance for understanding its functions. We herein report an enzymeless H2O2 sensor consisting of a previously activated screen-printed carbon electrode modified with Pt nanoparticles electrogenerated on a supporting conductive layer of polyazure A-dodecyl sulfate. This electrode was used to investigate the dynamic process of H2O2 release from living grapevine cells under different (a)biotic stresses. The modified surfaces were characterized by FESEM/EDX, EIS and cyclic voltammetry. Sensor analytical performance was studied in a cell culture medium under aerobic conditions, as required for cell survival. In relation to the synergistic effect between the metal nanoparticles and the conjugated polymer, this electrode showed good stability, excellent analytical performance combined with a rapid response (<2s) and limit of detection of 24.9 nM in the culture medium. The modified electrodes could fulfill the real-time measurement requirement of H2O2 release from living plant cells to the extracellular medium operating continuously, even in experiments lasting more than 12 h. Methyl jasmonate, L-methionine, clopyralid and the fungus Botrytis cinerea were the eliciting agents chosen to induce oxidative stress in the plant cells. This work demonstrates the huge potential of this sensor for the real-time tracking of the H2O2 released from living cells under different physiological conditions.
- PublicationEmbargoProduction and localization of hydrogen peroxide and nitric oxide in grapevine cells elicited with cyclodextrins and methyl jasmonate(Elsevier, 2019-06) Abellán Rubio, Marina; Almagro Romero, Lorena; Belchí Navarro, Sarai; Pedreño García, María Ángeles; Biología VegetalThe use of methyl jasmonate, alone or in combination with cyclic oligosaccharides such as cyclodextrins, has proved to be a successful strategy for increasing the production of trans-resveratrol in Vitis vinifera cell cultures. However, understanding the intracellular signalling pathways involved in its production would improve the management of grapevine cells as biofactories of this high-value natural product. The results obtained herein confirm the involvement of hydrogen peroxide and nitric oxide in cyclodextrins and methyl jasmonate-induced trans-resveratrol production in grapevine cell cultures. In fact, methyl jasmonate led to maximal intracellular levels of hydrogen peroxide and nitric oxide after 24 h of treatment, but extracellular hydrogen peroxide was only detected in the culture medium when grapevine cells were treated with cyclodextrins. The results derived from the cytochemical detection of H2O2 in elicited grapevine cell cultures also suggested that the combined treatment with cyclodextrins and methyl jasmonate not only increased the production of H2O2 but also released cell wall fragments with electron-dense deposits. Moreover, nitric oxide was localized in all the cellular compartments, particularly in the nucleus and cyto-plasmic organelles, whereas hydrogen peroxide was mainly found in cytoplasmic areas close to the cell wall, and in the nucleoplasm.