Search results for "OXIDATION"

Dihydroquercetin (DHQ) induced HO-1 and NQO1 expression against oxidative stress through the Nrf2-dependent antioxidant pathway.

2013

Dihydroquercetin (DHQ) is a well-known antioxidant agent. In the present investigation, we reported for the first time that DHQ stimulates the expression of phase II detoxifying enzymes through the Nrf2-dependent signaling pathway. The IC50 values of DHQ for reduction of 2,2-diphenyl-1-picrylhydrazol (DPPH), reducing power assay, lipid peroxidation assay, and xanthine oxidase inhibition were 5.96, 4.31, 2.03, and 13.24 μM, respectively. DHQ possessed considerable protective activity from oxidative DNA damage. A luciferase reporter assay also demonstrated that DHQ-activated signaling resulted in the increased transcriptional activity of Nrf2 through binding to the ARE (antioxidant response e…

The repair of oxidized purines in the DNA of human lymphocytes requires an activation involving NF-YA-mediated upregulation of OGG1.

2014

8-Oxoguanine DNA glycosylase (OGG1), which initiates the repair of DNA purine modifications such as 8-oxo-7,8-dihydroguanine (8-oxoG), is often regarded as a house keeping protein ubiquitously active in mammalian cells. We have analysed the repair rates of oxidized purines generated by photosensitization in peripheral human lymphocytes and observed that the cells were virtually unable to remove these lesions (less than 10% removal within 24h). However, stimulation of the lymphocytes with phytohemagglutinin (PHA) strongly accelerated the repair so that ∼30% of the lesions were repaired within 4h. Within 24h following PHA stimulation and preceding the induction of cell proliferation, Western …

Peroxisome proliferators and peroxisome proliferator activated receptors (PPARs) as regulators of lipid metabolism.

1997

Peroxisome proliferation (PP) in mammalian cells, first described 30 years ago, represents a fascinating field of modern research. Major improvements made in its understanding were obtained through basic advances that have opened up new areas in cell biology, biochemistry and genetics. A decade after the first report on PP, a new metabolic pathway (peroxisomal beta-oxidation) and its inducibility by peroxisome proliferators were discovered. More recently, a new type of nuclear receptor, the peroxisome proliferator-activated receptor (PPAR), has been described. The first PPAR was discovered in 1990. Since then, many other PPARs have been characterized. This original class of nuclear receptor…

Role of reactive oxygen species in the regulation of HIF-1 by prolyl hydroxylase 2 under mild hypoxia

2012

The function and survival of eukaryotic cells depends on a constant and sufficient oxygen supply. Cells recognize and respond to hypoxia by accumulation of the transcription factor hypoxia-inducible factor 1 (HIF-1), composed of an oxygen-sensitive HIF-1α and a constitutive HIF-1β subunit. Besides physiology, HIF-1 induction is involved in major pathological processes such as cardiovascular disease, inflammation and cancer, which are associated with the formation of reactive oxygen species (ROS). ROS have been reported to affect HIF-1 activity but the role for ROS in regulating HIF-1 has not been definitely settled. In order to shed light on the redox-regulation of HIF-1 by ROS, we studied …

Catalytic CO oxidation over pumice supported Pd–Ag catalysts

2001

Abstract Results on the catalytic oxidation of CO at 523 K over bimetallic Pd–Ag catalysts supported on pumice are reported and compared with those obtained from the monometallic Pd and Ag catalysts. The catalysts were prepared by organometallic precursors and were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) after different treatments with air and with hydrogen. The activity of the catalysts decreases with increasing Ag/Pd atomic ratio, the monometallic palladium exhibiting the highest activity. Furthermore, the treatment with air and with hydrogen always results in a better catalytic performance. On the basis of the structural characterization by XRD…

The organic air pollutant cumene hydroperoxide interferes with NOantioxidant role in rehydrating lichen

2013

Organic pollutants effects on lichens have not been addressed. Rehydration is critical for lichens, a burst of free radicals involving NO occurs. Repeated dehydrations with organic pollutants could increase oxidative damage. Our aim is to learn the effects of cumene hydroperoxide (CP) during lichen rehydration using Ramalina farinacea (L.) Ach., its photobiont Trebouxia spp. and Asterochloris erici. Confocal imaging shows intracellular ROS and NO production within myco and phycobionts, being the chloroplast the main source of free radicals. CP increases ROS, NO and lipid peroxidation and reduces chlorophyll autofluorescence, although photosynthesis remains unaffected. Concomitant NO inhibit…

Chromatographic and mass spectrometric characteristics of 20-dihydroaldosterone.

1992

The 20 alpha-reduced derivative of aldosterone, 20 alpha-dihydroaldosterone, was needed as reference compound in order to continue the studies on 18-hydroxylation in the Y-1 adrenal cell line. It was obtained by reduction of aldosterone with sodium borohydride. Analysis of the products of the reaction as methoxime trimethylsilyl (MO-TMS) derivatives by gas chromatography (GC) and GC-mass spectrometry (GC-MS) showed three possible forms of the compound. Their identification was confirmed by comparison with the products obtained by stereospecific reduction of aldosterone using 3 alpha,20 beta-hydroxysteroid dehydrogenase. Chromatographic behavior and mass spectra are given for the three forms…

2017

A hybrid bioinspired material with manganese(II) complexes grafted on the surface of a mesostructured porous silica is investigated. The Mn sites mimic the manganese-dependent dioxygenase (MndD), which is an enzyme that catalyses the oxidation of catechol derivatives. The metal complexes were introduced in the silica using a dinuclear complex [Mn2L2(Cl)2(μ-Cl)2] as a precursor with a clickable ligand N,N′-bis[(pyridin-2-yl)methyl]prop-2-yn-1-amine (L). Azide moieties covalently grafted on MCM-41 type mesoporous silica were utilised to anchor the manganese complex through Huisgen cycloaddition using CuBr(PPh3)3 as a catalyst. A second functional group – trimethylsilyl or pyridine—was grafted…

Tris[oligo(1,4-phenylenevinylene)]methylium Dyes

2009

The tris[oligo(1,4-phenylenevinylene)]carbinols 2a–f (n =1–4) and the tris(4-styrylphenyl)methanes 7a,b have been prepared by Wittig–Horner (3 + 4a–f 2a–f) and Siegristreactions (5 + 6a,b 7a,b). The Wittig–Horner reactions in these examples are accompanied by an autoxidation, whereas a reduction occurs in the Siegrist reactions. Compound 2a, the lowest member (n = 1) of the series 2a–d with terminal dialkylamino groups, generates first, on treatment with acids, the methylium dye 2′a, which absorbs far into the NIR region (λmax = 1100 nm). The higher members 2b,c (n = 2,3) of the carbinol series yield by acidic treatment only N-protonated methylium dyes 2″′b,c. The different behavior is due …

Inhibitor-Induced Dimerization of an Essential Oxidoreductase from African Trypanosomes

2018

Trypanosomal and leishmanial infections claim tens of thousands of lives each year. The metabolism of these unicellular eukaryotic parasites differs from the human host and their enzymes thus constitute promising drug targets. Tryparedoxin (Tpx) from Trypanosoma brucei is the essential oxidoreductase in the parasite's hydroperoxide-clearance cascade. In vitro and in vivo functional assays show that a small, selective inhibitor efficiently inhibits Tpx. With X-ray crystallography, SAXS, analytical SEC, SEC-MALS, MD simulations, ITC, and NMR spectroscopy, we show how covalent binding of this monofunctional inhibitor leads to Tpx dimerization. Intra- and intermolecular inhibitor-inhibitor, pro…