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Oxidative Stress Conditions (oxidative + stress_condition)
Selected AbstractsIscR acts as an activator in response to oxidative stress for the suf operon encoding Fe-S assembly proteinsMOLECULAR MICROBIOLOGY, Issue 1 2006Won-Sik Yeo Summary In Escherichia coli, Fe-S clusters are assembled by gene products encoded from the isc and suf operons. Both the iscRSUA and sufABCDSE operons are induced highly by oxidants, reflecting an increased need for providing and maintaining Fe-S clusters under oxidative stress conditions. Three cis -acting oxidant-responsive elements (ORE-I, II, III) in the upstream of the sufA promoter serve as the binding sites for OxyR, IHF and an uncharacterized factor respectively. Using DNA affinity fractionation, we isolated an ORE-III-binding factor that positively regulates the suf operon in response to various oxidants. MALDI-TOF mass analysis identified it with IscR, known to serve as a repressor of the iscRSUA gene expression under anaerobic condition as a [2Fe-2S]-bound form. The iscR null mutation abolished ORE-III-binding activity in cell extracts, and caused a significant decrease in the oxidant induction of sufA in vivo. OxyR and IscR contributed almost equally to activate the sufA operon in response to oxidants. Purified IscR that lacked Fe-S cluster bound to the ORE-III site and activated transcription from the sufA promoter in vitro. Mutations in Fe-S-binding sites of IscR enabled sufA activation in vivo and in vitro. These results support a model that IscR in its demetallated form directly activates sufA transcription, while it de-represses isc operon, under oxidative stress condition. [source] Tyrosine nitration in the human leucocyte antigen-G-binding domain of the Ig-like transcript 2 proteinFEBS JOURNAL, Issue 15 2009Angel Díaz-Lagares Ig-like transcript 2 (ILT2) is a suppressive receptor that participates in the control of the autoimmune reactivity. This action is usually carried out in a proinflammatory microenvironment where there is a high production of free radicals and NO. However, little is known regarding whether these conditions modify the protein or affect its suppressive functions. The present study aimed to investigate the suppressive response of the ILT2 receptor under oxidative stress. To address this topic, we treated the ILT2-expressing natural killer cell line, NKL, with the NO donor N -(4-[1-(3-aminopropyl)-2-hydroxy-2-nitrosohydrazino]butyl)propane-1,3-diamine (DETA-NO). We observed that DETA-NO caused ILT2 protein nitration. MS analysis of the chimeric recombinant human ILT2-Fc protein after treatment with the peroxynitrite donor 3-(morpholinosydnonimine hydrochloride) (SIN-1) showed the nitration of Tyr35, Tyr76 and Tyr99, which are involved in human leucocyte antigen-G binding. This modification is selective because other Tyr residues were not modified by SIN-1. Recombinant human ILT2-Fc treated with SIN-1 bound a significantly higher quantity of human leucocyte antigen-G than untreated recombinant human ILT2-Fc. DETA-NO did not modify ILT2 mRNA expression or protein expression at the cell surface. Preincubation of NKL cells with DETA-NO decreased the cytotoxic lysis of K562-human leucocyte antigen-G1 cells compared to untreated NKL cells (P < 0.05) but increased cytotoxicity against K562-pcDNA cells (P < 0.05). Intracellular tyrosine phosphorylation produced after human leucocyte antigen-G binding was not affected by DETA-NO cell pretreatment. These results support the hypothesis that the ILT2,human leucocyte antigen-G interaction should have a central role in tolerance under oxidative stress conditions when other tolerogenic mechanisms are inhibited. Structured digital abstract ,,MINT-7144982: ILT2 (uniprotkb:Q8NHL6) binds (MI:0407) to HLA-G (uniprotkb:P17693) by affinity technologies (MI:0400) [source] Modifications of the iron,neuromelanin system in Parkinson's diseaseJOURNAL OF NEUROCHEMISTRY, Issue 4 2006Mauro Fasano Abstract Parkinson's disease is a common neurodegenerative disorder with a mainly sporadic aetiology, although a number of monogenic familiar forms are known. Most of the motor symptoms are due to selective depletion of dopaminergic, neuromelanin-containing neurones of the substantia nigra pars compacta. Neuromelanin is the dark insoluble macromolecule that confers the black (substantia nigra) or grey (locus coeruleus) colour to monoaminergic basal ganglia. In particular, nigral neurones are pigmented because of the accumulation of by-products of oxidative metabolism of the neurotransmitter dopamine. The occurrence of dopamine (and all the enzymatic machinery required for dopamine synthesis, re-uptake and disposal) and neuromelanin, and a large amount of iron ions that interact with them, makes dopaminergic nigral neurones peculiarly susceptible to oxidative stress conditions that, in turn, may become amplified by the iron,neuromelanin system itself. In this mini-review we describe biophysical evidence for iron,neuromelanin modifications that support this hypothesis. Furthermore, we discuss the formation of the covalent linkage between ,-synuclein and neuromelanin from the early stages of the disease. [source] Activation of phosphoinositide-3 kinase/Akt pathway by FeSO4 in rat cerebral cortex synaptic endingsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 13 2007Romina M. Uranga Abstract The aim of this work was to study the involvement of the phosphoinositide-3-kinase (PI3K)/Akt pathway in synaptic endings incubated under oxidative stress conditions. Synaptosomes purified from rat cerebral cortex were exposed to FeSO4 (50 ,M) for different periods of time. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction and lactate dehydrogenate (LDH) leakage were significantly affected after 5 min of incubation in the presence of FeSO4, with respect to control conditions. In whole synaptosomes incubated in the presence of [,- 32P]ATP, phosphoinositide (PPI) labeling was increased after 5 min of Fe2+ exposure. This effect was prevented by the specific PI3K inhibitor LY294002. Anti-p85 immunoprecipitates (IPs) obtained from synaptosomes preincubated with Fe2+ (5 min) showed a PI3K activity two-fold higher than the activity recovered under control conditions. Additionally, Akt activation was temporally coincident with PI3K activation. LY294002 was not able to prevent the LDH leakage and diminution of MTT reduction induced by Fe2+. Our results demonstrate that free iron provokes the early activation of PI3K/Akt pathway, but this activation is not sufficient for protecting synaptic endings from oxidative damage. © 2007 Wiley-Liss, Inc. [source] IscR acts as an activator in response to oxidative stress for the suf operon encoding Fe-S assembly proteinsMOLECULAR MICROBIOLOGY, Issue 1 2006Won-Sik Yeo Summary In Escherichia coli, Fe-S clusters are assembled by gene products encoded from the isc and suf operons. Both the iscRSUA and sufABCDSE operons are induced highly by oxidants, reflecting an increased need for providing and maintaining Fe-S clusters under oxidative stress conditions. Three cis -acting oxidant-responsive elements (ORE-I, II, III) in the upstream of the sufA promoter serve as the binding sites for OxyR, IHF and an uncharacterized factor respectively. Using DNA affinity fractionation, we isolated an ORE-III-binding factor that positively regulates the suf operon in response to various oxidants. MALDI-TOF mass analysis identified it with IscR, known to serve as a repressor of the iscRSUA gene expression under anaerobic condition as a [2Fe-2S]-bound form. The iscR null mutation abolished ORE-III-binding activity in cell extracts, and caused a significant decrease in the oxidant induction of sufA in vivo. OxyR and IscR contributed almost equally to activate the sufA operon in response to oxidants. Purified IscR that lacked Fe-S cluster bound to the ORE-III site and activated transcription from the sufA promoter in vitro. Mutations in Fe-S-binding sites of IscR enabled sufA activation in vivo and in vitro. These results support a model that IscR in its demetallated form directly activates sufA transcription, while it de-represses isc operon, under oxidative stress condition. [source] Changes in zinc uptake in response to ascorbic acid and folic acid in rat liver slices under normal and oxidative stress conditionsBIOFACTORS, Issue 1 2007R.S. Tupe Abstract Zinc plays a dual role, as an integral part of metabolic machinery and in defense against reactive oxygen species. Hepatocytes are important sites for zinc metabolism for synthesis of zinc metalloproteins and maintaining its homeostasis. However, the factors influencing post absorptive zinc metabolism under normal and oxidative stress (OS) conditions are not well understood. Using rat liver slices, we conducted a series of four in vitro zinc uptake experiments to study influence of ascorbic acid and folic acid in normal and oxidative stress conditions with Zn concentrations representing deficient to excess states (7.7,30.7 millimole/L). Zinc uptakes under OS at these four zinc levels were lower than the normal conditions. Folic acid showed significant inhibitory effect on zinc uptake under both normal and OS conditions in a dose response manner. Nevertheless, dose response of ascorbic acid at four zinc levels indicated its marked enhancing effect under OS condition. Differences in zinc uptake trend lines between the normal and OS conditions for interaction of both the vitamins narrowed down as the zinc levels increased. Our results suggest that folic acid causes inhibitory effect, while ascorbic acid may be protective in OS with reference to zinc uptake. [source] Identification of 1-palmitoyl-2-linoleoyl-phosphatidylethanolamine modifications under oxidative stress conditions by LC-MS/MSBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009M. Rosário M. Domingues Abstract Phosphatidylethanolamines are a major class of phospholipids found in cellular membranes. Identification of the alterations in these phospholipids, induced by free radicals, could provide new tools for in vivo diagnosis of oxidative stress. In this study, 1-palmitoyl-2-linoleoyl-phosphatidylethanolamine oxidation products, induced by the hydroxyl radical, were studied using LC-MS and LC-MS/MS. Data obtained allowed the identification and separation of isomeric oxidative products with modifications in the sn -2 acyl chain, attributed to long- and short-chain products. Among long-chain products keto, keto-hydroxy, hydroxy, poly-hydroxy, peroxy and hydroxy,peroxy derivatives were identified. Product ions formed by loss of two H2O molecules vs loss of HOOH, allowed the identification of, respectively, di- (or poli-) hydroxy vs peroxy derivatives. Location of functional groups was determined by the product ions formed by cleavage of C,C bonds, in the vicinity of the oxidation positions, allowing the identification of C9, C12 and C13 as the predominant substituted positions. Short-chain products identified comprised aldehydes, hydroxy-aldehydes and carboxylic derivatives, with modified sn -2 acyl lengths of C7,C9 and C11, C12. Among the short-chain products identified, C9 products showed higher relative abundance. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||