Time Frame Analysis of Potassium Nitrate and Hydrogen Peroxide Diffusion into the Pulp Chamber.

OBJECTIVES: The primary objective of this study was to evaluate the effect of an innovative double-layer, single-application desensitizing/whitening technique of potassium nitrate (PN) and hydrogen peroxide (HP) diffusion at different time points. METHODS AND MATERIALS: Specimens were prepared from extracted caries-free human molars (n=90). Teeth were randomly assigned into four groups: Group A (HP CTRL) treated with 25% HP for 45 minutes, group B (PN CTRL) received a single-layer treatment of 5% PN for 45 minutes, group C received the double-layer treatment of 5% PN and 25% HP for 45 minutes, and group D received a 3% PN incorporated in a 40% HP gel for 45 minutes. PN and HP concentrations were measured at 5, 15, 30, and 45 minutes using standard chemical kits. Group comparisons were made using a repeated measures analysis of variance (ANOVA) test. Pairwise tests for differences in diffusion were done, using the Tukey adjustment of p values for multiple comparisons. A significance level of 5% was used. RESULTS: Group A showed no significant difference in HP diffusion rates between the 5- and 15-minute, 15- and 30-minute, or 30- and 45-minute time points; group D showed a similar trend; however, group C differed significantly at the 5-and 15-minute time points (p=0.0004), at the 15-and 30-minute time points (p=0.0026), and the 30- and 45-minute time points (p=0.0014). For PN diffusion, groups B and C had significantly different levels at the 15-, 30-, and 45-minute time points (p=0.0005, p=0.0002, and p<0.0001, respectively); and at the 15-, 30-, and 45-minute time points, groups D and C had significantly different PN diffusion (p=0.0327, p=0.0004, and p< 0.0001, respectively). Group C had significantly different PN diffusion at the 5- and 15-minute time points (p=0.0004), the 15- and 30-minute time points (p=0.0026), and at the 30- and 45-minute time points (p=0.0014). CONCLUSION: The double-layer technique showed superior diffusion of PN into the pulp chamber and did not affect the diffusion of HP when compared to other techniques. The double-layer technique may be suggested as an alternative tooth-whitening treatment to minimize tooth sensitivity.

The permeability of human red blood cell membranes to hydrogen peroxide is independent of aquaporins.

Hydrogen peroxide (H2O2) not only is an oxidant but also is an important signaling molecule in vascular biology, mediating several physiological functions. Red blood cells (RBCs) have been proposed to be the primary sink of H2O2 in the vasculature because they are the main cellular component of blood with a robust antioxidant defense and a high membrane permeability. However, the exact permeability of human RBC to H2O2 is neither known nor is it known if the mechanism of permeation involves the lipid fraction or protein channels. To gain insight into the permeability process, we measured the partition constant of H2O2 between water and octanol or hexadecane using a novel double-partition method. Our results indicated that there is a large thermodynamic barrier to H2O2 permeation. The permeability coefficient of H2O2 through phospholipid membranes containing cholesterol with saturated or unsaturated acyl chains was determined to be 4 × 10-4 and 5 × 10-3 cm s-1, respectively, at 37 °C. The permeability coefficient of human RBC membranes to H2O2 at 37 °C, on the other hand, was 1.6 × 10-3 cm s-1. Different aquaporin-1 and aquaporin-3 inhibitors proved to have no effect on the permeation of H2O2. Moreover, human RBCs devoid of either aquaporin-1 or aquaporin-3 were equally permeable to H2O2 as normal human RBCs. Therefore, these results indicate that H2O2 does not diffuse into RBCs through aquaporins but rather through the lipid fraction or a still unidentified membrane protein.

Systems Biology Approaches to Enzyme Kinetics.

Intracellular drug metabolism involves transport, bioactivation, conjugation, and other biochemical steps. The dynamics of these steps are each dependent on a number of other cellular factors that can ultimately lead to unexpected behavior. In this review, we discuss the confounding processes and coupled reactions within bioactivation networks that require a systems-level perspective in order to fully understand the time-varying behavior. When converting known in vitro characteristics of drug-enzyme interactions into descriptions of cellular systems, features such as substrate availability, cell-to-cell variability, and intracellular redox state, deserve special focus. Two examples are provided. First, a model of hydrogen peroxide clearance during chemotherapy treatment serves as a basis to discuss an example of sensitivity analysis. Second, an example of doxorubicin bioactivation is used for discussing points of consideration when constructing and analyzing network models of drug metabolism.

Visualisation of H2O2 penetration through skin indicates importance to develop pathway-specific epidermal sensing.

Elevated amounts of reactive oxygen species (ROS) including hydrogen peroxide (H2O2) are observed in the epidermis in different skin disorders. Thus, epidermal sensing of H2O2 should be useful to monitor the progression of skin pathologies. We have evaluated epidermal sensing of H2O2 in vitro, by visualising H2O2 permeation through the skin. Skin membranes were mounted in Franz cells, and a suspension of Prussian white microparticles was deposited on the stratum corneum face of the skin. Upon H2O2 permeation, Prussian white was oxidised to Prussian blue, resulting in a pattern of blue dots. Comparison of skin surface images with the dot patterns revealed that about 74% of the blue dots were associated with hair shafts. The degree of the Prussian white to Prussian blue conversion strongly correlated with the reciprocal resistance of the skin membranes. Together, the results demonstrate that hair follicles are the major pathways of H2O2 transdermal penetration. The study recommends that the development of H2O2 monitoring on skin should aim for pathway-specific epidermal sensing, allowing micrometre resolution to detect and quantify this ROS biomarker at hair follicles.Graphical abstract.

The effect of Yang Yan Qing E Wan on senescent phenotypes and the expression of ß-catenin and p16INK4a in human skin fibroblasts.

This aim of this study was to observe the effect of Yang Yan Qing E Wan (YYQEW) on senescent phenotypes and the expression of ß-catenin and p16INK4a in the hydrogen peroxide (H2O2)-induced premature senescence of normal human skin fibroblasts (NHSFs). Primary normal human skin fibroblasts were randomly divided into a normal group, a blank group, a model group, and a YYQEW group. The cells of the model group and the YYQEW group were exposed to 150 µmol/L H2O2 for 2 h. The morphological changes of the cells were analyzed by microscopy and by kits used to estimate the activities of the senescence-associated ß-galactosidase (SA-ß-gal), reactive oxygen species (ROS), and superoxide dismutase (SOD). The outcomes revealed that dyeing rate proportion of SA-ß-gal was 2.78% ± 0.22% in the normal group, 2.83% ± 0.29% in the blank group, 37.58% ± 2.56% in the model group, and 28.39% ± 0.93% in the YYQEW group. The number of SA-ß-gal positive cells was thus significantly higher in the model group than in the normal or blank group. There were also fewer SA-ß-gal positive cells in the YYQEW group compared with the model group. The expression of ROS and p16INK4a in the model group increased significantly compared with that in the normal or blank groups, while the expression of ROS and p16INK4a in the YYQEW group decreased significantly compared with that in the model group. The expression of SOD and ß-catenin in the model group decreased significantly compared with that in the normal or blank group, and the expression of SOD and ß-catenin in the YYQEW group increased significantly compared with that in the model group. Overall, it was found that YYQEW was able to delay the senescence of NHSFs induced by H2O2 treatment by alleviating oxidative stress and regulating a number of senescence-related molecules, such as ß-catenin and p16INK4a.

Identification of caffeic acid and rutin by UHPLC MS/MS and antioxidant activity of Commelina erecta Lineu. in cell culture.

The Commelina erecta L. (C. erecta) also known as erva-de-santa-luzia is reported by local population to have medical properties against some pathological conditions. In this study, two extracts of C. erecta leaves (aqueous and ethanolic) were phytochemically analysed and evaluated for their in-vitro antioxidant activities by DPPH, TBARS, NO assays and cell viability assays. The ultra-high performance liquid chromatography followed by tandem mass spectrometry analysis showed the presence of rutin and caffeic acid in aqueous and ethanolic extract. The total polyphenols in aqueous and ethanolic extracts found were 142.7 ± 3.0 and 123.1 ± 5.8 µg/mL of GAE, respectively. The ethanolic extract (5 mg/mL) inhibits TBARS by 33.8%, and the aqueous extract (5 mg/mL) exhibited scavenger property against nitric oxide derivatives to an extent of 77.8%. In cell culture, both extracts improved cell survivability under H2O2 induced oxidative stress. Thus, C. erecta extract is a good candidate to become a phytotherapic medicine.

Human aquaporin-11 guarantees efficient transport of H2O2 across the endoplasmic reticulum membrane.

Hydrogen peroxide (H2O2) is an essential second intracellular messenger. To reach its targets in the cytosol, H2O2 must cross a membrane, a feat that requires aquaporins (AQP) endowed with 'peroxiporin' activity (AQP3, AQP8, AQP9). Here, we exploit different organelle-targeted H2O2-sensitive probes to show that also AQP11 efficiently conduits H2O2. Unlike other peroxiporins, AQP11 is localized in the endoplasmic reticulum (ER), accumulating partly in mitochondrial-associated ER membranes (MAM). Its downregulation severely perturbs the flux of H2O2 through the ER, but not through the mitochondrial or plasma membranes. These properties make AQP11 a potential regulator of ER redox homeostasis and signaling.

Oncolytic Nanoreactors Producing Hydrogen Peroxide for Oxidative Cancer Therapy.

In situ generation of anticancer agents at the place of the disease is a new paradigm for cancer therapy. The production of highly potent drugs by nanoreactors through a facile synthesis pathway is demanded. We report an oncolytic nanoreactor platform loaded with the enzyme glucose oxidase (GOX) to produce hydrogen peroxide. For the first time, we realized a core-shell structure with encapsulated GOX under mild synthetic conditions, which ensured high remaining activity of GOX inside of the nanoreactor. Moreover, the nanoreactor protected the loaded GOX from proteolysis and contributed to increased thermal stability of the enzyme. The nanoreactors were effectively taken up into different cancer cells, in which they produced hydrogen peroxide by consuming intracellular glucose and oxygen, thereby leading to effective death of the cancer cells. In summary, our robust nanoreactors are a promising platform for effective anticancer therapy and sustained enzyme utilization.

Lipid peroxidation increases hydrogen peroxide permeability leading to cell death in cancer cell lines that lack mtDNA.

4-Hydroxynonenal (HNE) is an important product of plasma membrane lipid peroxidation, which is a cause of cell and tissue injury. Mitochondrial DNA (mtDNA)-depleted ρ0 cells were established using human cervical cancer and oral squamous cell carcinoma cell lines. We investigated the effect of reactive oxygen species in ρ0 cells, especially the mechanism of hydrogen peroxide (H2 O2 )-mediated cell death. These cell were subjected to high oxidative stress and, compared with their parental cells, showed greater sensitivity to H2 O2 and high lipid peroxidation. Upregulation of HNE in the plasma membrane was observed prior to the increase in intracellular H2 O2 . The amount of oxidized lipid present changed H2 O2 permeability and administration of oxidized lipid led to further cell death after treatment with H2 O2 . Expression levels of lipoxygenase ALOX genes (ie ALOX5, ALOX12, and ALOX15) were upregulated in ρ0 cells, as were expression levels of ALOX12 and ALOX15 proteins. ALOX5 protein was mainly distributed in the nucleus, while ALOX12 and ALOX15 proteins were distributed in the nucleus and the cytoplasm. Although expression of COX2 gene was upregulated, its protein expression did not increase. ALOX (especially ALOX15) may be involved in the sensitivity of cancer cells to treatment. These data offer promise for the development of novel anticancer agents by altering the oxidation state of the plasma membrane. Our results showed that lipid peroxidation status is important for H2 O2 sensitivity and that ALOX15 is involved in lipid peroxidation status.

Photo-Fenton reaction at mildly acidic conditions: assessing the effect of bio-organic substances of different origin and characteristics through experimental design.

Urban-waste bio-organic substances (UW-BOS) have been shown to be capable of extending the photo-Fenton reaction to mildly acidic conditions. In this study, the effects of pH (3-7), UW-BOS, H2O2 and iron concentrations on the photo-Fenton process were systematically assessed using a Doehlert experimental design and response surface methodology for two UW-BOS (CVT230 and FORSUD). Solutions of the model antibiotic sulfadiazine (SDZ) were irradiated in a solar simulator equipped with a 550 W Xenon lamp. The results showed that for UW-BOS contents below 30 mg L-1, SDZ removal proceeds at pH 5 with similar rates for both CVT230 and FORSUD, regardless of Fe(III) concentration. For 50 mg L-1 of UW-BOS or higher, CVT230 performs better than FORSUD, even for low Fe(III) content (1-3 mg L-1). In contrast, half-life times of 35-40 min can only be achieved under mildly acidic conditions with FORSUD for iron concentrations higher than 10 mg L-1. The better performance of CVT230 can be associated with its high hydrophilic/hydrophobic ratio, low E2:E3, higher iron content and possibly higher yields of triplet reactive species generation upon solar irradiation. The most appropriate conditions for each UW-BOS studied are discussed for the first time, which are advantageous for possible engineered applications.

Fe-N-C Artificial Enzyme: Activation of Oxygen for Dehydrogenation and Monoxygenation of Organic Substrates under Mild Condition and Cancer Therapeutic Application.

Developing highly efficient biomimetic catalysts that directly use O2 as the terminal oxidant to dehydrogenate and monoxygenate substrates with high selectivity under mild conditions has long been pursued but rarely achieved yet. Herein, we report that heterogeneous Fe-N-C, which is commonly used as an electrocatalyst for oxygen reduction reaction, had unusual biomimetic catalytic activity in both dehydrogenation and monoxygenation of a series of organic molecules (∼100% selectivity) by directly using O2. The Fe-N x center was verified to be the active site that reductively activated O2 by spontaneously generating specific reactive oxygen species (ROS) (1O2, O2•-, and H2O2). Aided by these ROS, under physiological conditions, the Fe-N-C was further successfully exampled to kill proliferative lung cancer cells. Fe-N-C had several striking superior features with respect to natural enzymes, classical heterogeneous nanozymes, and homogeneous artificial enzymes incapable of working under harsh conditions (extreme pH and high temperature), ease of separation and recycling, and direct use of O2. It would open up a new vista of Fe-N-C as an artificial enzyme in biomimetic catalysis, ranging from fundamental simulation of oxidase/oxygenase metabolism to industrial oxidation processes and to disease treatment.

ROS-Responsive Chalcogen-Containing Polycarbonates for Photodynamic Therapy.

Reactive oxygen species (ROS)-responsive polymers have attracted attention for their potential in photodynamic therapy. Herein, we report the ROS-responsive aliphatic polycarbonates prepared by the ring-opening polymerization (ROP) of three six-membered cyclic carbonate monomers with ethyl selenide, phenyl selenide or ethyl telluride groups. Under catalysis of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), all three monomers underwent the controlled anionic ROP, showing a feature of equilibrium polymerization due to the bulky effect of 5,5-disubstituents. With PEG macroinitiator, three series amphiphilic block copolymers were prepared. They could form spherical nanoparticles of ∼100 nm, which were stable in neutral phosphate buffer but dissociated rapidly under triggering of H2O2. We studied the H2O2-induced oxidation profiles of selenide- or telluride-containing small molecules by 1H NMR and revealed the factors that affect the oxidation kinetics and products. On this basis, the oxidative degradation mechanism of the copolymer nanoparticles has been clarified. Under the same oxidative condition, the telluride-containing nanoparticle degraded with the fastest rate while the phenyl selenide-based one degraded most slowly. These ROS-responsive nanoparticles could load photosensitizer chlorin e6 (Ce6) and anticancer drug doxorubicin (DOX). Under red light irradiation, Ce6-sensitized production of 1O2 that triggered the degradation of nanoparticles, resulting in an accelerated payload release. In vitro cytotoxicity assays demonstrate that the nanoparticles coloaded with DOX and Ce6 exhibited a synergistic cell-killing effect to MCF-7 cells, representing a novel responsive nanoplatform for PDT and/or chemotherapy.

Effect of Bleaching Gel Viscosity on Tooth Whitening Efficacy and Pulp Chamber Penetration: An In Vitro Study.

OBJECTIVES: Whitening efficacy has been related to hydrogen peroxide (HP) diffusion into tooth structure. However, little information is available relating rheological properties to whitening efficacy. The purpose was to evaluate the whitening efficacy and HP penetration level of a 10% HP gel at three different viscosities and to compare them to a strip delivery system. METHODS AND MATERIALS: Extracted molars (n=120) were randomly assigned into five groups (n=24/ group): NC_MED (negative control; median): medium viscosity gel without HP; LOW: 10% HP gel (low viscosity experimental gel, Ultradent Products Inc); MED: 10% HP gel (medium viscosity experimental gel, Ultradent); HIGH: 10% HP gel (high viscosity gel, Ultradent); and CWS: Crest 3D Whitestrips 1-Hour Express (Procter & Gamble). All teeth were subjected to five 60-minute whitening sessions. Instrumental color measurements were performed at baseline (T0), and 1-day after each application (T1-T5), and 1-month after whitening (T6). HP penetration was estimated with leucocrystal violet and horseradish peroxidase. A Kruskal-Wallis test and post hoc Bonferroni test were performed to assess the difference in tooth color change and HP penetration among the groups (α=0.05). RESULTS: Hydrogen peroxide penetration levels and overall color changes at T6 were 0.24 µg/mL / 2.80; 0.48 µg/mL / 8.48; 0.44 µg/mL / 7.72; 0.35 µg/mL / 8.49; 0.36 µg/mL / 7.30 for groups NC, LOW, MED, HIGH, and CWS, respectively. There was a significant difference for HP penetration, while there was no significant difference among the four experimental groups for tooth color change. CONCLUSION: Rheological properties should be considered when developing new whitening formulations.

N-acetylcysteine improves the quality of red blood cells stored for transfusion.

Storage inflicts a series of changes on red blood cells (RBC) that compromise the cell survival and functionality; largely these alterations (storage lesions) are due to oxidative modifications. The possibility of improving the quality of packed RBC stored for transfusion including N-acetylcysteine (NAC) in the preservation solution was explored. Relatively high concentrations of NAC (20-25 mM) were necessary to prevent the progressive leakage of hemoglobin, while lower concentrations (≥2.5 mM) were enough to prevent the loss of reduced glutathione during the first 21 days of storage. Peroxiredoxin-2 was also affected during storage, with a progressive accumulation of disulfide-linked dimers and hetero-protein complexes in the cytosol and also in the membrane of stored RBC. Although the presence of NAC in the storage solution was unable to avoid the formation of thiol-mediated protein complexes, it partially restored the capacity of the cell to metabolize H2O2, indicating the potential use of NAC as an additive in the preservation solution to improve RBC performance after transfusion.

Effect of Dental Pigmentation Intensity on the Transenamel and Transdentinal Penetration of Hydrogen Peroxide.

Abastract This study aimed to evaluate the transenamel and transdentinal penetration of hydrogen peroxide (H202) applied to bovine teeth pigmented with black tea at different intensities. The following groups were formed DW: immersion in distilled water; BT100: immersion in an infusion of 1.6 g of black tea per 100 mL distilled water; BT10: immersion in an infusion of 1.6 g black tea per 10 mL distilled water. All groups were immersed for 6 days. To quantify the penetration of H202, the specimens were placed in artificial pulp chambers (APCs) and subjected to bleaching treatment with 38% H2O2 once per week for 3 weeks. After bleaching treatment, the acetate buffer solution of APCs with peroxidase enzyme was evaluated in a reflection spectrophotometer. The transenamel and transdentinal penetration of H2O2 and the L* values obtained at T1, T2 and T3 were subjected to Kruskal-Wallis and Friedman statistical tests. At T1, the H2O2 diffusion in DW was higher than that in BT100 and BT10. At the other evaluation times, the penetration values in BT100 and BT10 increased and remained similar. The L* values increased significantly in all groups at T1. At T2, the L* values were higher in DW, while the values in BT100 and BT10 were similar to each other. At the end of the experiment, BT10 showed the lowest L* values. The pigmentation level did not affect the penetration of H2O2 through the enamel and dentin and the bleaching agent effectively changed the color of the teeth.

Effect of Dental Pigmentation Intensity on the Transenamel and Transdentinal Penetration of Hydrogen Peroxide

Abastract This study aimed to evaluate the transenamel and transdentinal penetration of hydrogen peroxide (H202) applied to bovine teeth pigmented with black tea at different intensities. The following groups were formed DW: immersion in distilled water; BT100: immersion in an infusion of 1.6 g of black tea per 100 mL distilled water; BT10: immersion in an infusion of 1.6 g black tea per 10 mL distilled water. All groups were immersed for 6 days. To quantify the penetration of H202, the specimens were placed in artificial pulp chambers (APCs) and subjected to bleaching treatment with 38% H2O2 once per week for 3 weeks. After bleaching treatment, the acetate buffer solution of APCs with peroxidase enzyme was evaluated in a reflection spectrophotometer. The transenamel and transdentinal penetration of H2O2 and the L* values obtained at T1, T2 and T3 were subjected to Kruskal-Wallis and Friedman statistical tests. At T1, the H2O2 diffusion in DW was higher than that in BT100 and BT10. At the other evaluation times, the penetration values in BT100 and BT10 increased and remained similar. The L* values increased significantly in all groups at T1. At T2, the L* values were higher in DW, while the values in BT100 and BT10 were similar to each other. At the end of the experiment, BT10 showed the lowest L* values. The pigmentation level did not affect the penetration of H2O2 through the enamel and dentin and the bleaching agent effectively changed the color of the teeth.

Resumo Este estudo teve como objetivo avaliar a penetração trans-amelodentinária do peróxido de hidrogênio (H2O2) aplicados em dentes bovinos pigmentados com chá preto em diferentes intensidades. Divisão dos grupos: AD em água destilada; CP100 em uma infusão de 1,6 g de chá preto para 100 mL de água destilada; CP10 em uma infusão de 1,6 g de chá preto para 10 mL de água destilada. Todos os grupos foram imersos por 6 dias. Para quantificar a penetração de H2O2, as amostras foram colocadas em câmaras pulpares artificiais (CPAs) e submetidas a um tratamento clareador com PH a 38%, uma vez por semana durante 3 semanas. Após o tratamento clareador, a solução tampão de acetato das CPAs com a enzima da peroxidase, foi avaliada num espectrofotômetro de reflexão. A penetração trans-amelodentinária de PH e os valores de L* obtidos em T1, T2 e T3 foram submetidos ao teste estatístico de Kruskal-Wallis e Friedman. Em T1, a difusão de H2O2 no AD foi mais elevada do que em CP100 e CP10. Nos outros tempos de avaliação, os valores de penetração no CP100 e CP10 aumentaram e permaneceram semelhantes. Os valores L* aumentaram significativamente em todos os grupos no T1. No T2, os valores L* foram maiores no AD e os valores em CP100 e CP10 foram semelhantes entre si. No último tempo, o CP10 apresentou os menores valores de L*. Diferentes níveis de pigmentação não afetaram a penetração de H2O2 através do esmalte e dentina e o agente de clareador foi eficaz na alteração cromática.

Clinical, Radiographic and Microbiological Evaluation of High Level Laser Therapy, a New Photodynamic Therapy Protocol, in Peri-Implantitis Treatment; a Pilot Experience.

Aim. Endosseous implants are widely used to replace missing teeth but mucositis and peri-implantitis are the most frequent long-term complications related with dental implants. Removing all bacterial deposits on contaminated implant surface is very difficult due to implant surface morphology. The aim of this study was to evaluate the bactericidal potential of photodynamic therapy by using a new high level laser irradiation protocol associated with hydrogen peroxide in peri-implantitis. Materials and Methods. 10 patients affected by peri-implantitis were selected for this study. Medical history, photographic documentation, periodontal examination, and periapical radiographs were collected at baseline and 6 months after surgery. Microbiological analysis was performed with PCR Real Time. Each patient underwent nonsurgical periodontal therapy and surgery combined with photodynamic therapy according to High Level Laser Therapy protocol. Results. All peri-implant pockets were treated successfully, without having any complication and not showing significant differences in results. All clinical parameters showed an improvement, with a decrease of Plaque Index (average decrease of 65%, range 23-86%), bleeding on probing (average decrease of 66%, range 26-80%), and probing depth (average decrease of 1,6 mm, range 0,46-2,6 mm). Periapical radiographs at 6 months after surgery showed a complete radiographic filling of peri-implant defect around implants treated. Results showed a decrease of total bacterial count and of all bacterial species, except for Eikenella corrodens, 6 months after surgery. Conclusion. Photodynamic therapy using HLLT appears to be a good adjunct to surgical treatment of peri-implantitis.

Hydrogen peroxide diffusion with and without light activation.

OBJECTIVE: The aim of this study was to assess the dental bleaching efficacy of 37.5% hydrogen peroxide (HP), with and without light activation, in HP-exposed and unexposed areas. METHOD: 28 bovine teeth were selected and divided into two groups (n = 14). Crowns were detached and stained with tea. The gingival half was covered with a gingival barrier. In the incisal half, 37.5% HP (Pola Office+, SDI) was applied three times, with a 1-week interval between applications. In HP-A group, the bleaching agent was activated for 3 min with a LED lamp. No light activation was applied in HP-N group. Dental color variation was determined through a spectrophotometer in both halves. Statistical analysis between groups was performed with an ANOVA test, and intragroup differences were evaluated, with an ANOVA test for paired data, with a significance level of P < 0.05. RESULTS: An increase in lightness and a decrease in chroma were found in both groups and halves. No significant differences in ΔE between groups (P > 0.5) were detected in the incisal half. After treatment, a significantly higher ΔE was found in the gingival half for HP-A group (P < 0.05). For the same group, a significantly higher bleaching effect was found in the gingival half, compared with the incisal half (P < 0.05). CONCLUSIONS: LED activation did not have a significant effect in terms of bleaching in the incisal half, but increased clearance in the gingival half. CLINICAL RELEVANCE: HP light activation does not significantly increase the whitening effect, but it can improve the bleaching diffusion to areas where it has not been directly applied.

Heme oxygenase­1 protects H2O2­insulted glomerular mesangial cells from excessive autophagy.

Increasing evidence has demonstrated that the activation of heme oxygenase (HO)­1 reduces autophagy stimulated by oxidative stress injury, in which the supraphysiological production of reactive oxygen species (ROS) is detected. However, the potential mechanism underlying this effect remains unclear. The present study aimed to investigate the function of HO­1 activation in the regulation of autophagy in glomerular mesangial cells subjected to H2O2­induced oxidative stress injury. The results demonstrated that the HO­1 agonist, hemin, reduces the LC3 protein level, which was enhanced by H2O2 treatment. Furthermore, hemin­activated HO­1 may function as a regulator of oxidative stress­induced autophagy in a dose­dependent manner. Pharmacological activation of c­Jun N­terminal kinase (JNK) inhibited the effect of hemin, indicating that the JNK signaling pathway is associated with the mechanism of HO­1 in impeding excessive autophagy. In addition to successfully alleviating H2O2­induced oxidative stress and cellular apoptosis, hemin­activated HO­1 may provide cytoprotection against rapamycin, a specific autophagy agonist. The present result suggested the inhibitory action of HO­1 in the avoidance of a potentially enhanced linkage between autophagy and apoptosis, particularly in the setting of excessive ROS. Therefore, enhancing the intracellular activity of HO­1 may assist the crosstalk between oxidative stress, autophagy and apoptosis, and represent a novel therapeutic strategy for renal ischemic disease.

Aquaporin-9 facilitates membrane transport of hydrogen peroxide in mammalian cells.

Aquaporin (AQP) 9, a member of the transmembrane water channel family, is defined as a water/glycerol transporting protein. Some AQPs including AQP3 and AQP8 have been recently found to transport hydrogen peroxide (H2O2). Here we show that AQP9 facilitates the membrane transport of H2O2 in human and mice cells. Enforced expression of human AQP9 in Chinese hamster ovary-K1 potentiated the increase in cellular H2O2 after adding exogenous H2O2. In contrast, AQP9 knockdown by siRNA in human hepatoma HepG2 cells reduced the import of extracellular H2O2. In addition, the uptake of extracellular H2O2 was suppressed in erythrocytes and bone marrow-derived mast cells from AQP9 knockout mice compared with wild-type cells. Coincidentally, H2O2-induced cytotoxicity was attenuated by AQP9 deficiency in human and mice cells. Our findings implicate the involvement of AQP9 in H2O2 transport in human and mice cells.