The role of reactive oxygen species in the modulation of the contraction induced by angiotensin II in carotid artery from diabetic rat

The modulation played by reactive oxygen species on the angiotensin II-induced contraction in type I-diabetic rat carotid was investigated. Concentration-response curves for angiotensin II were obtained in endothelium-intact or endothelium-denuded carotid from control or streptozotocin-induced diabetic rats, pre-treated with tiron (superoxide scavenger), PEG-catalase (hydrogen peroxide scavenger), dimethylthiourea (hydroxyl scavenger), apocynin [NAD(P) H oxidase inhibitor], SC560 (cyclooxygenase-1 inhibitor), SC236 (cyclooxygenase-2 inhibitor) or Y-27632 (Rho-kinase inhibitor). Reactive oxygen species were measured by flow cytometry in dihydroethidium (DHE)-loaded endothelial cells. Cyclooxygenase and AT1-receptor expression was assessed by immunohistochemistry. Diabetes increased the angiotensin II-induced contraction but reduced the agonist potency in rat carotid. Endothelium removal, tiron or apocynin restored the angiotensin II-induced contraction in diabetic rat carotid to control levels. PEG-catalase, DMTU or SC560 reduced the angiotensin II-induced contraction in diabetic rat carotid at the same extent. SC236 restored the angiotensin II potency in diabetic rat carotid. Y-27632 reduced the angiotensin II-induced contraction in endothelium-intact or -denuded diabetic rat carotid. Diabetes increased the DHE-fluorescence of carotid endothelial cells. Apocynin reduced the DHE-fluorescence of endothelial cells from diabetic rat carotid to control levels. Diabetes increased the muscular cyclooxygenase-2 expression but reduced the muscular AT1-receptor expression in rat carotid. In summary, hydroxyl radical, hydrogen peroxide and superoxide anion-derived from endothelial NAD(P) H oxidase mediate the hyperreactivity to angiotensin II in type I-diabetic rat carotid, involving the participation of cyclooxygenase-1 and Rho-kinase. Moreover, increased muscular cyclooxygenase-2 expression in type I-diabetic rat carotid seems to be related to the local reduced AT1-receptor expression and the reduced angiotensin II potency. (C) 2011 Elsevier B. V. All rights reserved.

The lectin-like domain of tumor necrosis factor improves lung function after rat lung transplantation--potential role for a reduction in reactive oxygen species generation

To test the hypothesis that the lectin-like domain of tumor necrosis factor, mimicked by the TIP peptide, can improve lung function after unilateral orthotopic lung isotransplantation. Because of a lack of a specific treatment for ischemia reperfusion-mediated lung injury, accompanied by a disrupted barrier integrity and a dysfunctional alveolar liquid clearance, alternative therapies restoring these parameters after lung transplantation are required.

Loss of sphingosine kinase-1 in carcinoma cells increases formation of reactive oxygen species and sensitivity to doxorubicin-induced DNA damage

Sphingosine kinases (SK) catalyse the formation of sphingosine 1-phosphate, which is a key lipid mediator regulating cell responses such as proliferation, survival and migration. Here we have investigated the effect of targeted inhibition of SK-1 on cell damage and elucidated the mechanisms involved.

Arginase II Promotes Macrophage Inflammatory Responses Through Mitochondrial Reactive Oxygen Species, Contributing to Insulin Resistance and Atherogenesis

Macrophage-mediated chronic inflammation is mechanistically linked to insulin resistance and atherosclerosis. Although arginase I is considered antiinflammatory, the role of arginase II (Arg-II) in macrophage function remains elusive. This study characterizes the role of Arg-II in macrophage inflammatory responses and its impact on obesity-linked type II diabetes mellitus and atherosclerosis.

The Yeast Saccharomyces cerevisiae Contains Two Glutaredoxin Genes That Are Required for Protection against Reactive Oxygen Species

Glutaredoxins are small heat-stable proteins that act as glutathione-dependent disulfide oxidoreductases. Two genes, designated GRX1 and GRX2, which share 40–52% identity and 61–76% similarity with glutaredoxins from bacterial and mammalian species, were identified in the yeast Saccharomyces cerevisiae. Strains deleted for both GRX1 and GRX2 were viable but lacked heat-stable oxidoreductase activity using β-hydroxyethylene disulfide as a substrate. Surprisingly, despite the high degree of homology between Grx1 and Grx2 (64% identity), the grx1 mutant was unaffected in oxidoreductase activity, whereas the grx2 mutant displayed only 20% of the wild-type activity, indicating that Grx2 accounted for the majority of this activity in vivo. Expression analysis indicated that this difference in activity did not arise as a result of differential expression of GRX1 and GRX2. In addition, a grx1 mutant was sensitive to oxidative stress induced by the superoxide anion, whereas a strain that lacked GRX2 was sensitive to hydrogen peroxide. Sensitivity to oxidative stress was not attributable to altered glutathione metabolism or cellular redox state, which did not vary between these strains. The expression of both genes was similarly elevated under various stress conditions, including oxidative, osmotic, heat, and stationary phase growth. Thus, Grx1 and Grx2 function differently in the cell, and we suggest that glutaredoxins may act as one of the primary defenses against mixed disulfides formed following oxidative damage to proteins.

Susceptibility of cloned K+ channels to reactive oxygen species.

Free radical-induced oxidant stress has been implicated in a number of physiological and pathophysiological states including ischemia and reperfusion-induced dysrhythmia in the heart, apoptosis of T lymphocytes, phagocytosis, and neurodegeneration. We have studied the effects of oxidant stress on the native K+ channel from T lymphocytes and on K+ channels cloned from cardiac, brain, and T-lymphocyte cells and expressed in Xenopus oocytes. The activity of three Shaker K+ channels (Kv1.3, Kv1.4, and Kv1.5), one Shaw channel (Kv3.4), and one inward rectifier K+ channel (IRK3) was drastically inhibited by photoactivation of rose bengal, a classical generator of reactive oxygen species. Other channel types (such as Shaker K+ channel Kv1.2, Shab channels Kv2.1 and Kv2.2, Shal channel Kv4.1, inward rectifiers IRK1 and ROMK1, and hIsK) were completely resistant to this treatment. On the other hand tert-butyl hydroperoxide, another generator of reactive oxygen species, removed the fast inactivation processes of Kv1.4 and Kv3.4 but did not alter other channels. Xanthine/xanthine oxidase system had no effect on all channels studied. Thus, we show that different types of K+ channels are differently modified by reactive oxygen species, an observation that might be of importance in disease states.

Probing molecular changes induced in DNA by reactive oxygen species with monoclonal antibodies

Antibodies reactive with native double stranded DNA are characteristic of the chronic inflammatory disease systemic lupus erythematosus. Native DNA is however, a poor immunogen and the mechanism of anti-DNA antibody production is incompletely understood. Modification of DNA can increase its immunogenicity and in inflammatory disease states reactive oxygen species produced from phagocytic cells have been shown to thus modify DNA. In this study, monoclonal antibodies produced spontaneously by two mice strains with lupus-like disease were used in a competition ELISA to monitor changes to DNA induced by reactive oxygen species. Different procedures for reactive oxygen species generation were found to cause distinct and characteristic changes to DNA involving modifications of base residues, the sugar-phosphate backbone and the gross conformational structure of double-stranded DNA. In view of this, it may be possible to use these antibodies further to probe DNA and infer the source and nature of the reactive oxygen species it has been exposed to, particularly in vivo.

Antioxidants, reactive oxygen and nitrogen species, gene induction and mitochondrial function

Redox-sensitive cell signalling Thiol groups and the regulation of gene expression Redox-sensitive signal transduction pathways Protein kinases Protein phosphatases Lipids and phospholipases Antioxidant (electrophile) response element Intracellular calcium signalling Transcription factors NF-?B AP-1 p53 Cellular responses to oxidative stress Cellular responses to change in redox state Proliferation Cell death Immune cell function Reactive oxygen and nitrogen species – good or bad? Reactive oxygen species and cell death Reactive oxygen species and inflammation Are specific reactive oxygen species and antioxidants involved in modulating cellular responses? Specific effects of dietary antioxidants in cell regulation Carotenoids Vitamin E Flavonoids Inducers of phase II enzymes Disease states affected Oxidants, antioxidants and mitochondria Introduction Mitochondrial generation of reactive oxygen and nitrogen species Mitochondria and apoptosis Mitochondria and antioxidant defences Key role of mitochondrial GSH in the defence against oxidative damage Mitochondrial oxidative damage Direct oxidative damage to the mitochondrial electron transport chain Nitric oxide and damage to mitochondria Effects of nutrients on mitochondria Caloric restriction and antioxidants Lipids Antioxidants Techniques and approaches Mitochondrial techniques cDNA microarray approaches Proteomics approaches Transgenic mice as tools in antioxidant research Gene knockout and over expression Transgenic reporter mice Conclusions Future research needs