Metal catalyzed oxidation of tyrosine residues by different oxidation systems of copper/hydrogen peroxide

Metal-catalysed oxidation (MCO) reactions result in the formation of reactive oxygen species (ROS) in biological systems. These ROS cause oxidative stress that contributes to a number of pathological processes leading to a variety of diseases. Tyrosine is one residue that is very susceptible to oxidative modification and the formation of dityrosine (DT) and 3,4-dihydroxyphenylalanine (DOPA) have been widely reported in a number of diseases. However, the mechanisms of MCO of tyrosine in biological systems are poorly understood and require further investigation. In this study we investigated the mechanism of DT and DOPA formation by MCO using N-acetyl tyrosine ethyl ester as a model for tyrosine in proteins and peptides. The results showed that DT formation could be observed upon Cu²⁺/H₂O₂ oxidation at pH 7.4. Our results indicate that it is unlikely to be via Fenton chemistry since Cu⁺/H₂O₂ oxidative conditions did not lead to the formation of DT.

Methionine regulates copper/hydrogen peroxide oxidation products of Aβ

Metal-catalysed oxidation (MCO) may play a causative role in the pathogenesis of Alzheimer's disease (AD). Amyloid peptide (A), the major biomarker of AD, in the presence of copper ions reduces Cu2+ to Cu+ and catalyses the formation of H2O2 that subsequently induces radicals through Fenton chemistry. A is also subject to attack by free radicals, where the presence of Cu2+ in conjunction with H2O2 catalyses oxygenation, primarily at the methionine sulfur atom. This work investigates MCO of A, to gain further insight into the role of oxidative stress in AD. By combining a fluorescence assay with gel electrophoresis to monitor MCO reactions of A (1-28) in the presence and absence of methionine it was determined that methionine can both protect some residues against MCO and promote the oxidation of Tyr(10) specifically. Electrospray ionization mass spectrometric analysis of methionine MCO products indicated the formation of methionine sulfoxide, methionine sulfone and related hydroxylated products. Similar products could be formed from the oxidation of Met(35) of A and may relate to changes in properties of the peptide following MCO.

Pulse-lavage brushing followed by hydrogen peroxide-gauze packing for bone-bed preparation in cemented total hip arthroplasty : a bovine model

To compare the effectiveness of pulse-lavage brushing followed by hydrogen peroxide-gauze packing with either technique alone or normal-saline irrigation in bone-bed preparation for cemented total hip arthroplasty. 44 fresh-frozen ox femoral canals were prepared for cemented total hip arthroplasty using 4 techniques: normal-saline irrigation, pulse-lavage brushing, hydrogen peroxide-soaked gauze packing, and a combination of the latter 2 techniques. The maximum tensile pull-out force required to separate the prosthesis from the femoral canal was measured as an indicator of the strength of the cement-bone interface. The mean pull-out force to separate the prosthesis from the femoral canal was significantly higher in specimens prepared with pulse-lavage brushing followed by hydrogen peroxide-soaked gauze packing or pulse-lavage brushing alone than those prepared with normal-saline irrigation or hydrogen peroxide-soaked gauze packing alone 300(p<0.001). Pulse-lavage brushing is more effective at cleansing the femoral canal and increasing mechanical strength at the cement-bone interface than preparation with normal-saline irrigation or hydrogen peroxide-soaked gauze packing.

Surface evolution of a gradient structured Ti in hydrogen peroxide solution

In this work, the interaction between hydrogen peroxide (H₂O₂) and a gradient structured Ti was investigated extensively. The gradient structured Ti (SMAT Ti) was produced by surface mechanical attrition treatment (SMAT), and then it was immersed in H₂O₂ solution for different time until 48 h at room temperature (25 °C). The structure and surface morphology evolution were examined by Raman spectra and scanning electron microscopy (SEM). The formation mechanism of nanoporous titania was discussed based on above results.

Influence of hydrogen peroxide in the preparation of nanocrystalline ceria

The influence of H2O2 in the preparation of nanocrystalline CeO2 has been investigated by treating solutions of Ce(III) with NaOH in the presence of different concentrations of H2O2. The resulting precipitated material was then examined by a range of techniques, including transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). A decrease in CeO2 crystallite size with increasing H2O2 concentration was observed. This was found to be associated with the formation of an amorphous material containing an η2-peroxide (O22-) species.

Sub-lethal UV-C radiation induces callose, hydrogen peroxide and defence-related gene expression in Arabidopsis thaliana

Exposure of plants to UV-C irradiation induces gene expression and cellular responses that are commonly associated with wounding and pathogen defence, and in some cases can lead to increased resistance against pathogen infection. We examined, at a physiological, molecular and biochemical level, the effects of and responses to, sub-lethal UV-C exposure on Arabidopsis plants when irradiated with increasing dosages of UV-C radiation. Following UV-C exposure plants had reduced leaf areas over time, with the severity of reduction increasing with dosage. Severe morphological changes that included leaf glazing, bronzing and curling were found to occur in plants treated with the 1000 J·m(-2) dosage. Extensive damage to the mesophyll was observed, and cell death occurred in both a dosage- and time-dependent manner. Analysis of H2 O2 activity and the pathogen defence marker genes PR1 and PDF1.2 demonstrated induction of these defence-related responses at each UV-C dosage tested. Interestingly, in response to UV-C irradiation the production of callose (β-1,3-glucan) was identified at all dosages examined. Together, these results show plant responses to UV-C irradiation at much lower doses than have previously been reported, and that there is potential for the use of UV-C as an inducer of plant defence.

NDRG2 promotes myoblast proliferation and caspase 3/7 activities during differentiation, and attenuates hydrogen peroxide - but not palmitate-induced toxicity

The function of the stress-responsive N-myc downstream-regulated gene 2 (NDRG2) in the control of myoblast growth, and the amino acids contributing to its function, are not well characterized. Here, we investigated the effect of increased NDRG2 levels on the proliferation, differentiation and apoptosis in skeletal muscle cells under basal and stress conditions. NDRG2 overexpression increased C2C12 myoblast proliferation and the expression of positive cell cycle regulators, cdk2, cyclin B and cyclin D, and phosphorylation of Rb, while the serine/threonine-deficient NDRG2, 3A-NDRG2, had less effect. The onset of differentiation was enhanced by NDRG2 as determined through the myogenic regulatory factor expression profiles and myocyte fusion index. However, the overall level of differentiation in myotubes was not different. While NDRG2 up-regulated caspase 3/7 activities during differentiation, no increase in apoptosis was measured by TUNEL assay or through cleavage of caspase 3 and PARP proteins. During H2O2 treatment to induce oxidative stress, NDRG2 helped protect against the loss of proliferation and ER stress as measured by GRP78 expression with 3A-NDRG2 displaying less protection. NDRG2 also attenuated apoptosis by reducing cleavage of PARP and caspase 3 and expression of pro-apoptotic Bax while enhancing the pro-survival Bcl-2 and Bcl-xL levels. In contrast, Mcl-1 was not altered, and NDRG2 did not protect against palmitate-induced lipotoxicity. Our findings show that NDRG2 overexpression increases myoblast proliferation and caspase 3/7 activities without increasing overall differentiation. Furthermore, NDRG2 attenuates H2O2-induced oxidative stress and specific serine and threonine amino acid residues appear to contribute to its function in muscle cells.

Isolation and polyphasic characterization of a novel hyper catalase producing thermophilic bacterium for the degradation of hydrogen peroxide.

A newly isolated microbial strain of thermophilic genus Geobacillus has been described with emphasis on polyphasic characterization and its application for degradation of hydrogen peroxide. The validation of this thermophilic strain of genus Geobacillus designated as BSS-7 has been demonstrated by polyphasic taxonomy approaches through its morphological, biochemical, fatty acid methyl ester profile and 16S rDNA sequencing. This thermophilic species of Geobacillus exhibited growth at broad pH and temperature ranges coupled with production of extraordinarily high quantities of intracellular catalase, the latter of which as yet not been reported in any member of this genus. The isolated thermophilic bacterial culture BSS-7 exhibited resistance against a variety of organic solvents. The immobilized whole cells of the bacterium successfully demonstrated the degradation of hydrogen peroxide (H2O2) in a packed bed reactor. This strain has potential application in various analytical and diagnostic methods in the form of biosensors and biomarkers in addition to applications in the textile, paper, food and pharmaceutical industries.

Effect of arsenic on transcription factor AP-1 and NF-kB DNA binding activity and related gene expression

Both acute (24 h) and chronic (10–20 week) exposure of human fibroblast cells to low dose sodium arsenite (As(III)) significantly affects activating protein-1 (AP-1) and nuclear factor kappa B (NF-κB) DNA binding activity. Short-term treatment with 0.1–5 μM As(III) up-regulates expression of c-Fos and c-Jun and the redox regulators, thioredoxin (Trx) and Redox factor-1 (Ref-1) and activates both AP-1 and NF-κB binding. Chronic exposure to 0.1 or 0.5 μM As(III) decreased c-Jun, c-Fos and Ref-1 protein levels and AP-1 and NF-κB binding activity, but increased Trx expression. Short term exposure to phorbol 12-myristate 13-acetate (TPA), a phorbol ester tumour promoter, or hydrogen peroxide (H₂O₂) also activates AP-1 and NF-κB binding. However, pre-treatment with As(III) prevents this increase. These results suggest that As(III) may alter AP-1 and NF-κB activity, in part, by up-regulating Trx and Ref-1. The different effects of short- versus long-term As(III) treatment on acute-phase response to oxidative stress reflect changes in the expression of Ref-1, c-Fos and c-Jun, but not Trx.