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Journal Cover Redox Biology
  [SJR: 2.382]   [H-I: 24]   [1 followers]  Follow
    
  This is an Open Access Journal Open Access journal
   ISSN (Online) 2213-2317
   Published by Elsevier Homepage  [3039 journals]
  • Hyperglycemia induced damage to mitochondrial respiration in renal
           mesangial and tubular cells: implications for diabetic nephropathy

    • Abstract: Publication date: Available online 17 September 2016
      Source:Redox Biology
      Author(s): Anna Czajka, Afshan N. Malik
      Damage to renal tubular and mesangial cells is central to the development of diabetic nephropathy (DN), a complication of diabetes which can lead renal failure. Mitochondria are the site of cellular respiration and produce energy in the form of ATP via oxidative phosphorylation, and mitochondrial dysfunction has been implicated in DN. Since the kidney is an organ with high bioenergetic needs, we postulated that hyperglycemia causes damage to renal mitochondria resulting in bioenergetic deficit. The bioenergetic profiles and the effect of hyperglycemia on cellular respiration of human primary mesangial (HMCs) and proximal tubular cells (HK-2) were compared in normoglycemic and hyperglycemic conditions using the seahorse bio-analyser. In normoglycemia, HK-2 had significantly lower basal, ATP-linked and maximal respiration rates, and lower reserve capacity compared to HMCs. Hyperglycemia caused a down-regulation of all respiratory parameters within 4 days in HK-2 but not in HMCs. After 8 days of hyperglycemia, down-regulation of respiratory parameters persisted in tubular cells with compensatory up-regulated glycolysis. HMCs had reduced maximal respiration and reserve capacity at 8 days, and by 12 days had compromised mitochondrial respiration despite which they did not enhance glycolysis. These data suggest that diabetes is likely to lead to a cellular deficit in ATP production in both cell types, although with different sensitivities, and this mechanism could significantly contribute to the cellular damage seen in the diabetic kidney. Prevention of diabetes induced damage to renal mitochondrial respiration may be a novel therapeutic approach for the prevention/treatment of DN.
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      PubDate: 2016-09-20T08:25:02Z
       
  • Advanced Oxidation Protein Products Sensitized the Transient Receptor
           Potential Vanilloid 1 via NADPH Oxidase 1 and 4 to Cause Mechanical
           Hyperalgesia

    • Abstract: Publication date: Available online 17 September 2016
      Source:Redox Biology
      Author(s): Ruoting Ding, Hui Jiang, Baihui Sun, Xiaoliang Wu, Wei Li, Siyuan Zhu, Congrui Liao, Zhaoming Zhong, Jianting Chen
      Oxidative stress is a possible pathogenesis of hyperalgesia. Advanced oxidation protein products (AOPPs), a new family of oxidized protein compounds, have been considered as a novel marker of oxidative stress. However, the role of AOPPs in the mechanism of hyperalgesia remains unknown. Our study aims to investigate whether AOPPs have an effect on hyperalgesia and the possible underlying mechanisms. To identify the AOPPs involved, we induced hyperalgesia in rats by injecting complete Freund’s adjuvant (CFA) in hindpaw. The level of plasma AOPPs in CFA-induced rats was 1.6-fold in comparison with what in normal rats (P<0.05). After intravenous injection of AOPPs-modified rat serum albumin (AOPPs-RSA) in Sprague-Dawley rats, the paw mechanical thresholds, measured by the electronic von Frey system, significantly declined. Immunofluorescence staining indicated that AOPPs increased expressions of NADPH oxidase 1 (Nox1), NADPH oxidase 4 (Nox4), transient receptor potential vanilloid 1 (TRPV1) and calcitonin gene-related peptide (CGRP) in the dorsal root ganglia (DRG) tissues. In-vitro studies were performed on primary DRG neurons which were obtained from both thoracic and lumbar DRG of rats. Results indicated that AOPPs triggered reactive oxygen species (ROS) production in DRG neurons, which were significantly abolished by ROS scavenger N-acetyl-l-cysteine (NAC) and small-interfering RNA (siRNA) silencing of Nox1 or Nox4. The expressions of Nox1, Nox4, TRPV1 and CGRP were significantly increased in AOPPs-induced DRG neurons. And relevant siRNA or inhibitors notably suppressed the expressions of these proteins and the calcium influxes in AOPPs-induced DRG neurons. In conclusion, AOPPs increased significantly in CFA-induced hyperalgesia rats and they activated Nox1/Nox4-ROS to sensitize TRPV1-dependent Ca2+ influx and CGRP release which led to inducing mechanical hyperalgesia.
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      PubDate: 2016-09-20T08:25:02Z
       
  • Autocrine IL-10 Functions as a Rheostat for M1 Macrophage Glycolytic
           Commitment by Tuning Nitric Oxide Production

    • Abstract: Publication date: Available online 16 September 2016
      Source:Redox Biology
      Author(s): Walter A. Baseler, Luke C. Davies, Laura Quigley, Lisa A. Ridnour, Jonathan M. Weiss, S. Perwez Hussain, David A. Wink, Daniel W. McVicar
      Inflammatory maturation of M1 macrophages by proinflammatory stimuli such as toll like receptor ligands results in profound metabolic reprogramming resulting in commitment to aerobic glycolysis as evidenced by repression of mitochondrial oxidative phosphorylation (OXPHOS) and enhanced glucose utilization. In contrast, “alternatively activated” macrophages adopt a metabolic program dominated by fatty acid-fueled OXPHOS. Despite the known importance of these developmental stages on the qualitative aspects of an inflammatory response, relatively little is know regarding the regulation of these metabolic adjustments. Here we provide evidence that the immunosuppressive cytokine IL-10 defines a metabolic regulatory loop. Our data show for the first time that lipopolysaccharide (LPS)-induced glycolytic flux controls IL-10-production via regulation of mammalian target of rapamycin (mTOR) and that autocrine IL-10 in turn regulates macrophage nitric oxide (NO) production. Genetic and pharmacological manipulation of IL-10 and nitric oxide (NO) establish that metabolically regulated autocrine IL-10 controls glycolytic commitment by limiting NO-mediated suppression of OXPHOS. Together these data support a model where autocine IL-10 production is controlled by glycolytic flux in turn regulating glycolytic commitment by preserving OXPHOS via suppression of NO. We propose that this IL-10-driven metabolic rheostat maintains metabolic equilibrium during M1 macrophage differentiation and that perturbation of this regulatory loop, either directly by exogenous cellular sources of IL-10 or indirectly via limitations in glucose availability, skews the cellular metabolic program altering the balance between inflammatory and immunosuppressive phenotypes.
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      PubDate: 2016-09-20T08:25:02Z
       
  • Changes in brain oxysterols at different stages of Alzheimer's disease:
           their involvement in neuroinflammation

    • Abstract: Publication date: Available online 16 September 2016
      Source:Redox Biology
      Author(s): Gabriella Testa, Erica Staurenghi, Chiara Zerbinati, Simona Gargiulo, Luigi Iuliano, Giorgio Giaccone, Fausto Fantò, Giuseppe Poli, Gabriella Leonarduzzi, Paola Gamba
      Alzheimer's disease (AD) is a gradually debilitating disease that leads to dementia. The molecular mechanisms underlying AD are still not clear, and at present no reliable biomarkers are available for the early diagnosis. In the last several years, together with oxidative stress and neuroinflammation, altered cholesterol metabolism in the brain has become increasingly implicated in AD progression. A significant body of evidence indicates that oxidized cholesterol, in the form of oxysterols, is one of the main triggers of AD. The oxysterols potentially most closely involved in the pathogenesis of AD are 24-hydroxycholesterol and 27-hydroxycholesterol, respectively deriving from cholesterol oxidation by the enzymes CYP46A1 and CYP27A1. However, the possible involvement of oxysterols resulting from cholesterol autooxidation, including 7-ketocholesterol and 7β-hydroxycholesterol, is now emerging. In a systematic analysis of oxysterols in post-mortem human AD brains, classified by the Braak staging system of neurofibrillary pathology, alongside the two oxysterols of enzymatic origin, a variety of oxysterols deriving from cholesterol autoxidation were identified; these included 7-ketocholesterol, 7α-hydroxycholesterol, 4β-hydroxycholesterol, 5α,6α-epoxycholesterol, and 5β,6β-epoxycholesterol. Their levels were quantified and compared across the disease stages. Some inflammatory mediators, and the proteolytic enzyme matrix metalloprotease-9, were also found to be enhanced in the brains, depending on disease progression. This highlights the pathogenic association between the trends of inflammatory molecules and oxysterol levels during the evolution of AD. Conversely, sirtuin 1, an enzyme that regulates several pathways involved in the anti-inflammatory response, was reduced markedly with the progression of AD, supporting the hypothesis that the loss of sirtuin 1 might play a key role in AD. Taken together, these results strongly support the association between changes in oxysterol levels and AD progression.


      PubDate: 2016-09-20T08:25:02Z
       
  • EFFECTS OF DIETARY FATTY ACIDS AND CHOLESTEROL EXCESS ON LIVER INJURY: A
           LIPIDOMIC APPROACH

    • Abstract: Publication date: Available online 9 September 2016
      Source:Redox Biology
      Author(s): Gaetano Serviddio, Francesco Bellanti, Rosanna Villani, Rosanna Tamborra, Chiara Zerbinati, Maria Blonda, Marco Ciacciarelli, Giuseppe Poli, Gianluigi Vendemiale, Luigi Iuliano
      Lipid accumulation is the hallmark of Non-alcoholic Fatty Liver Disease (NAFLD) and has been suggested to play a role in promoting fatty liver inflammation. Previous findings indicate that during oxidative stress conditions excess cholesterol autoxidizes to oxysterols. To date, the role of oxysterols and their potential interaction with fatty acids accumulation in NASH pathogenesis remains little investigated. We used the nutritional model of high fatty acids (HFA), high cholesterol (HCh) or high fat and high cholesterol (HFA+FCh) diets and explored by a lipidomic approach, the blood and liver distribution of fatty acids and oxysterols in response to dietary manipulation. We observed that HFA or HCh diets induced fatty liver without inflammation, which was otherwise observed only after supplementation of HFA+HCh. Very interestingly, the combination model was associated with a specific oxysterol fingerprint. The present work provides a complete analysis of the change in lipids and oxysterols profile induced by different lipid dietary model and their association with histological alteration of the liver. This study allows the generation of interesting hypotheses on the role of interaction of lipid and cholesterol metabolites in the liver injury during NAFLD development and progression. Moreover, the changes in the concentration and quality of oxysterols induced by a combination diet suggest a novel potential pathogenic mechanism in the progression from simple steatosis to steatohepatitis.
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      PubDate: 2016-09-14T07:50:27Z
       
  • The Redox Mechanism for Vascular Barrier Dysfunction Associated with
           Metabolic Disorders: Glutathionylation of Rac1 in Endothelial Cells

    • Abstract: Publication date: Available online 11 September 2016
      Source:Redox Biology
      Author(s): Jingyan Han, Robert M. Weisbrod, Di Shao, Yosuke Watanabe, Xiaoyan Yin, Markus M. Bachschmid, Francesca Seta, Yvonne M.W. Janssen-Heininger, Reiko Matsui, Mengwei Zang, Naomi M. Hamburg, Richard A. Cohen
      Background Oxidative stress is implicated in increased vascular permeability associated with metabolic disorders, but the underlying redox mechanism is poorly defined. S-glutathionylation, a stable adduct of glutathione with protein sulfhydryl, is a reversible oxidative modification of protein and is emerging as an important redox signaling paradigm in cardiovascular physiopathology. The present study determines the role of protein S-glutathionylation in metabolic stress-induced endothelial cell permeability. Methods and Results In endothelial cells isolated from patients with type-2 diabetes mellitus, protein S-glutathionylation level was increased. This change was also observed in aortic endothelium in ApoE deficient (ApoE-/-) mice fed on Western diet. Metabolic stress-induced protein S-glutathionylation in human aortic endothelial cells (HAEC) was positively correlated with elevated endothelial cell permeability, as reflected by disassembly of cell-cell adherens junctions and cortical actin structures. These impairments were reversed by adenoviral overexpression of a specific de-glutathionylation enzyme, glutaredoxin-1 in cultured HAECs. Consistently, transgenic overexpression of human Glrx-1 in ApoE-/- mice fed the Western diet attenuated endothelial protein S-glutathionylation, actin cytoskeletal disorganization, and vascular permeability in the aorta. Mechanistically, glutathionylation and inactivation of Rac1, a small RhoGPase, were associated with endothelial hyperpermeability caused by metabolic stress. Glutathionylation of Rac1 on cysteine 81 and 157 located adjacent to guanine nucleotide binding site was required for the metabolic stress to inhibit Rac1 activity and promote endothelial hyperpermeability. Conclusions Glutathionylation and inactivation of Rac1 in endothelial cells represent a novel redox mechanism of vascular barrier dysfunction associated with metabolic disorders.
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      PubDate: 2016-09-14T07:50:27Z
       
  • Levels of inflammation and oxidative stress, and a role for taurine in
           dystropathology of the Golden Retriever Muscular Dystrophy dog model for
           Duchenne Muscular Dystrophy

    • Abstract: Publication date: Available online 30 August 2016
      Source:Redox Biology
      Author(s): Jessica R Terrill, Marisa N Duong, Rufus Turner, Caroline Le Guiner, Amber Boyatzis, Anthony J. Kettle, Miranda D Grounds, Peter G Arthur
      Duchenne Muscular Dystrophy (DMD) is a fatal skeletal muscle wasting disease presenting with excessive myofibre necrosis and increased inflammation and oxidative stress. In the mdx mouse model of DMD, homeostasis of the amino acid taurine is altered, and taurine administration drastically decreases muscle necrosis, dystropathology, inflammation and protein thiol oxidation. Since the severe pathology of the Golden Retriever Muscular Dystrophy (GRMD) dog model more closely resembles the human DMD condition, we aimed to assess the generation of oxidants by inflammatory cells and taurine metabolism in this species. In muscles of 8 month GRMD dogs there was an increase in the content of neutrophils and macrophages, and an associated increase in elevated myeloperoxidase, a protein secreted by neutrophils that catalyses production of the highly reactive hypochlorous acid (HOCl). There was also increased chlorination of tyrosines, a marker of HOCl generation, increased thiol oxidation of many proteins and irreversible oxidative protein damage. Taurine, which functions as an antioxidant by trapping HOCl, was reduced in GRMD plasma; however taurine was increased in GRMD muscle tissue, potentially due to increased muscle taurine transport and synthesis. These data indicate a role for HOCl generated by neutrophils in the severe dystropathology of GRMD dogs, which may be exacerbated by decreased availability of taurine in the blood. These novel data support continued research into the precise roles of oxidative stress and taurine in DMD and emphasise the value of the GRMD dogs as a suitable pre-clinical model for testing taurine as a therapeutic intervention for DMD boys.
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      PubDate: 2016-09-03T02:03:02Z
       
  • The deleterious effect of cholesterol and protection by quercetin on
           mitochondrial bioenergetics of pancreatic β-cells, glycemic control and
           inflammation: in vitro and in vivo studies

    • Abstract: Publication date: Available online 26 August 2016
      Source:Redox Biology
      Author(s): Catalina Carrasco-Pozo, Kah Ni Tan, Marjorie Reyes-Farias, Nicole De La Jara, Shyuan Thieu Ngo, Diego Fernando Garcia-Diaz, Paola Llanos, Maria Jose Cires, Karin Borges
      Studying rats fed high cholesterol diet and a pancreatic β-cell line (Min6), we aimed to determine the mechanisms by which quercetin protects against cholesterol-induced pancreatic β-cell dysfunction and impairments in glycemic control. Quercetin prevented the increase in total plasma cholesterol, but only partially prevented the high cholesterol diet-induced alterations in lipid profile. Quercetin prevented cholesterol-induced decreases in pancreatic ATP levels and mitochondrial bioenergetic dysfunction in Min6 cells, including decreases in mitochondrial membrane potentials and coupling efficiency in the mitochondrial respiration (basal and maximal oxygen consumption rate (OCR), ATP-linked OCR and reserve capacity). Quercetin protected against cholesterol-induced apoptosis of Min6 cells by inhibiting caspase-3 and −9 activation and cytochrome c release. Quercetin prevented the cholesterol-induced decrease in antioxidant defence enzymes from pancreas (cytosolic and mitochondrial homogenates) and Min6 cells and the cholesterol-induced increase of cellular and mitochondrial oxidative status and lipid peroxidation. Quercetin counteracted the cholesterol-induced activation of the NFκB pathway in the pancreas and Min6 cells, normalizing the expression of pro-inflammatory cytokines. Quercetin inhibited the cholesterol-induced decrease in sirtuin 1 expression in the pancreas and pancreatic β-cells. Taken together, the anti-apoptotic, antioxidant and anti-inflammatory properties of quercetin, and its ability to protect and improve mitochondrial bioenergetic function are likely to contribute to its protective action against cholesterol-induced pancreatic β-cell dysfunction, thereby preserving glucose-stimulated insulin secretion (GSIS) and glycemic control. Specifically, the improvement of ATP-linked OCR and the reserve capacity are important mechanisms for protection of quercetin. In addition, the inhibition of the NFκB pathway is an important mechanism for the protection of quercetin against cytokine mediated cholesterol-induced glycemic control impairment. In summary, our data highlight cellular, molecular and bioenergetic mechanisms underlying quercetin's protective effects on β-cells in vitro and in vivo, and provide a scientifically tested foundation upon which quercetin can be developed as a nutraceutical to preserve β-cell function.
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      PubDate: 2016-08-29T22:38:05Z
       
  • Redox signaling in cardiovascular pathophysiology: A focus on hydrogen
           peroxide and vascular smooth muscle cells

    • Abstract: Publication date: Available online 26 August 2016
      Source:Redox Biology
      Author(s): Chang Hyun Byon, Jack M Heath, Yabing Chen
      Oxidative stress represents excessive intracellular levels of reactive oxygen species (ROS), which plays a major role in the pathogenesis of cardiovascular disease. Besides having a critical impact on the development and progression of vascular pathologies including atherosclerosis and diabetic vasculopathy, oxidative stress also regulates physiological signaling processes. As a cell permeable ROS generated by cellular metabolism involved in intracellular signaling, hydrogen peroxide (H2O2) exerts tremendous impact on cardiovascular pathophysiology. Under pathological conditions, increased oxidase activities and/or impaired antioxidant systems results in uncontrolled production of ROS. In a pro-oxidant environment, vascular smooth muscle cells (VSMC) undergo phenotypic changes which can lead to the development of vascular dysfunction such as vascular inflammation and calcification. Investigations are ongoing to elucidate the mechanisms for cardiovascular disorders induced by oxidative stress. This review mainly focuses on the role of H2O2 in regulating physiological and pathological signals in VSMC.


      PubDate: 2016-08-29T22:38:05Z
       
  • The pulmonary inflammatory response to multiwalled carbon nanotubes is
           influenced by gender and glutathione synthesis

    • Abstract: Publication date: Available online 21 August 2016
      Source:Redox Biology
      Author(s): Megan M. Cartwright, Stefanie C. Schmuck, Charlie Corredor, Bingbing Wang, David K. Scoville, Claire R. Chisholm, Hui-Wen Wilkerson, Zahra Afsharinejad, Theodor K. Bammler, Jonathan D. Posner, Vaithiyalingam Shutthanandan, Donald R. Baer, Somenath Mitra, William Altemeier, Terrance J. Kavanagh
      Inhalation of multiwalled carbon nanotubes (MWCNTs) during their manufacture or incorporation into various commercial products may cause lung inflammation, fibrosis, and oxidative stress in exposed workers. Some workers may be more susceptible to these effects because of differences in their ability to synthesize the major antioxidant and immune system modulator glutathione (GSH). Accordingly, in this study we examined the influence of GSH synthesis and gender on MWCNT-induced lung inflammation in C57BL/6 mice. GSH synthesis was impaired through genetic manipulation of Gclm, the modifier subunit of glutamate cysteine ligase, the rate-limiting enzyme in GSH synthesis. Twenty-four hours after aspirating 25µg of MWCNTs, all male mice developed neutrophilia in their lungs, regardless of Gclm genotype. However, female mice with moderate (Gclm heterozygous) and severe (Gclm null) GSH deficiencies developed significantly less neutrophilia. We found no indications of MWCNT-induced oxidative stress as reflected in the GSH content of lung tissue and epithelial lining fluid, 3-nitrotyrosine formation, or altered mRNA or protein expression of several redox-responsive enzymes. Our results indicate that GSH-deficient female mice are rendered uniquely susceptible to an attenuated neutrophil response. If the same effects occur in humans, GSH-deficient women manufacturing MWCNTs may be at greater risk for impaired neutrophil-dependent clearance of MWCNTs from the lung. In contrast, men may have effective neutrophil-dependent clearance, but may be at risk for lung neutrophilia regardless of their GSH levels.
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      PubDate: 2016-08-25T21:18:02Z
       
  • CRISPR/Cas9-mediated knockout of p22phox leads to loss of Nox1 and Nox4,
           but not Nox5 activity

    • Abstract: Publication date: Available online 24 August 2016
      Source:Redox Biology
      Author(s): Kim-Kristin Prior, Matthias S. Leisegang, Ivana Josipovic, Oliver Löwe, Ajay M. Shah, Norbert Weissmann, Katrin Schröder, Ralf P. Brandes
      The NADPH oxidases are important transmembrane proteins producing reactive oxygen species (ROS). Within the Nox family, different modes of activation can be discriminated. Nox1-3 are dependent on different cytosolic subunits, Nox4 seems to be constitutively active and Nox5 is directly activated by calcium. With the exception of Nox5, all Nox family members are thought to depend on the small transmembrane protein p22phox. With the discovery of the CRISPR/Cas9-system, a tool to alter genomic DNA sequences has become available. So far, this method has not been widely used in the redox community. On such basis, we decided to study the requirement of p22phox in the Nox complex using CRISPR/Cas9-mediated knockout. Knockout of the gene of p22phox, CYBA, led to an ablation of activity of Nox4 and Nox1 but not of Nox5. Production of hydrogen peroxide or superoxide after knockout could be rescued with either human or rat p22phox, but not with the DUOX-maturation factors DUOXA1/A2. Furthermore, different mutations of p22phox were studied regarding the influence on Nox4-dependent H2O2 production. P22phox Q130⁎ and Y121H affected maturation and activity of Nox4. Hence, Nox5-dependent O•- production is independent of p22phox, but native p22phox is needed for maturation of Nox4 and production of H2O2.
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      PubDate: 2016-08-25T21:18:02Z
       
  • The Anthocyanin Cyanidin-3-O-β-Glucoside Modulates Murine Glutathione
           Homeostasis in a Manner Dependent on Genetic Background

    • Abstract: Publication date: Available online 25 August 2016
      Source:Redox Biology
      Author(s): Katie M. Norris, Whitney Okie, Claire L. Yakaitis, Robert Pazdro
      Anthocyanins are a class of phytochemicals that have generated considerable interest due to their reported health benefits. It has been proposed that commonly consumed anthocyanins, such as cyandin-3-O-β-glucoside (C3G), confer cellular protection by stimulating biosynthesis of glutathione (GSH), an endogenous antioxidant. Currently, it is unknown whether the health effects of dietary anthocyanins are genetically determined. We therefore tested the hypothesis that anthocyanin-induced alterations in GSH homeostasis vary by genetic background. Mice representing five genetically diverse inbred strains (A/J, 129S1/SvImJ, CAST/EiJ, C57BL/6J, and NOD/ShiLtJ) were assigned to a control or 100mg/kg C3G diet (n=5/diet/strain) for six weeks. GSH and GSSG levels were quantified in liver, kidney, heart, pancreas, and brain samples using HPLC. The C3G diet promoted an increase in renal GSH concentrations, hepatic GSH/GSSG, and cardiac GSH/GSSG in CAST/EiJ mice. C3G treatment also induced an increase in pancreatic GSH/GSSG in C57BL/6J mice. In contrast, C3G did not affect GSH homeostasis in NOD/ShiLtJ mice. Surprisingly, the C3G-diet caused a decrease in hepatic GSH/GSSG in A/J and 129S1/SvImJ mice compared to controls; C3G-treated 129S1/SvImJ mice also exhibited lower total glutathione in the heart. Overall, we discovered that C3G modulates the GSH system in a strain- and tissue-specific manner. To our knowledge, this study is the first to show that the redox effects of anthocyanins are determined by genetic background.
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      PubDate: 2016-08-25T21:18:02Z
       
  • Lipid mediators involved in the oxidative stress and antioxidant defence
           of human lung cancer cells

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Agnieszka Gęgotek, Jacek Nikliński, Neven Žarković, Kamelija Žarković, Georg Waeg, Wojciech Łuczaj, Radosław Charkiewicz, Elżbieta Skrzydlewska
      Background The oxidative modifications of bioactive macromolecules have important roles in carcinogenesis. Of particular interest are lipid peroxidation products, which are involved in the activation of Nrf2 and endocannabinoids that affect cancer progression. Methods In lung cancer tissues (squamous cell lung carcinoma - SCC and adenocarcinoma - AC), the glutathione peroxidase and catalase activity and glutathione level, together with the expression of Nrf2 and its activators/inhibitors were estimated. The oxidative modifications of DNA (8-hydroxy-2′-deoxyguanosine and N7-methylguanine), endocannabinoids (anandamide and 2- arachidonylglyceriol), their receptors (CB1/2, TRV1, GPR55), phospholipid fatty acids (arachidonic, linoleic and docosahexaenoic), and reactive aldehydes (4-hydroxynonenal, 4-oxononenal and malondialdehyde) were determined. Results Tumour tissues showed lower antioxidant capacity than healthy tissues, which was accompanied by lower levels of fatty acids and higher levels of reactive aldehydes. Disturbances in antioxidant capacity and enhanced DNA oxidative modifications were observed in 88% of AC patients and 81% of SCC patients. The 4-hydroxynonenal-Histidine adducts were detected in the necrotic and stromal cells in all tumours. These findings were associated with the enhanced Nrf2 activity, especially in AC. The strong difference between the cancer subtypes was evident in the levels of endocannabinoids, with an increase in 89% of SCC and a decrease in 85% of AC patients being observed. Additionally, the increase in the expression of CB1/2 receptors was observed only in 82% of AC, while the expression of VR1 and GPR55 was enhanced in 79% of SCC and 82% of AC patients. Conclusions This study shows significant differences in the redox status, Nrf2 pathway and endocannabinoid system between SCC and AC tissues. Understanding the relation between the various lipid mediators and antioxidants in different lung cancer subtypes may be beginning for further research on the effective anticancer therapy.
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      PubDate: 2016-08-25T21:18:02Z
       
  • Connexin43 hemichannels contributes to the disassembly of cell junctions
           through modulation of intracellular oxidative status

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Yuan Chi, Xiling Zhang, Zhen zhang, Takahiko Mitsui, Manabu Kamiyama, Masayuki Takeda, Jian Yao
      Connexin (Cx) hemichannels regulate many cellular processes with little information available regarding their mechanisms. Given that many pathological factors that activate hemichannels also disrupts the integrity of cellular junctions, we speculated a potential participation of hemichannels in the regulation of cell junctions. Here we tested this hypothesis. Exposure of renal tubular epithelial cells to Ca2+-free medium led to disassembly of tight and adherens junctions, as indicated by the reduced level of ZO-1 and cadherin, disorganization of F-actin, and severe drop in transepithelial electric resistance. These changes were preceded by an activation of Cx43 hemichannels, as revealed by extracellular efflux of ATP and intracellular influx of Lucifer Yellow. Inhibition of hemichannels with chemical inhibitors or Cx43 siRNA greatly attenuated the disassembly of cell junctions. Further analysis using fetal fibroblasts derived from Cx43 wide-type (Cx43+/+), heterozygous (Cx43+/-) and knockout (Cx43-/-) littermates showed that Cx43-positive cells (Cx43+/+) exhibited more dramatic changes in cell shape, F-actin, and cadherin in response to Ca2+ depletion, as compared to Cx43-null cells (Cx43-/-). Consistently, these cells had higher level of protein carbonyl modification and phosphorylation, and much stronger activation of P38 and JNK. Hemichannel opening led to extracellular loss of the major antioxidant glutathione (GSH). Supplement of cells with exogenous GSH or inhibition of oxidative sensitive kinases largely prevented the above-mentioned changes. Taken together, our study indicates that Cx43 hemichannels promote the disassembly of cell junctions through regulation of intracellular oxidative status.
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      PubDate: 2016-08-25T21:18:02Z
       
  • Quercetin affects glutathione levels and redox ratio in human aortic
           endothelial cells not through oxidation but formation and cellular export
           of quercetin-glutathione conjugates and upregulation of glutamate-cysteine
           ligase

    • Abstract: Publication date: Available online 21 August 2016
      Source:Redox Biology
      Author(s): Chuan Li, Wei-Jian Zhang, Jaewoo Choi, Balz Frei
      Endothelial dysfunction due to vascular inflammation and oxidative stress critically contributes to the etiology of atherosclerosis. The intracellular redox environment plays a key role in regulating endothelial cell function and is intimately linked to cellular thiol status, including and foremost glutathione (GSH). In the present study we investigated whether and how the dietary flavonoid, quercetin, affects GSH status of human aortic endothelial cells (HAEC) and their response to oxidative stress. We found that treating cells with buthionine sulfoximine to deplete cellular GSH levels significantly reduced the capacity of quercetin to inhibit lipopolysaccharide (LPS)-induced oxidant production. Furthermore, incubation of HAEC with quercetin caused a transient decrease and then full recovery of cellular GSH concentrations. The initial decline in GSH was not accompanied by a corresponding increase in glutathione disulfide (GSSG). To the contrary, GSSG levels, which were less than 0.5% of GSH levels at baseline (0.26 ± 0.01 vs. 64.7 ± 1.9 nmol/mg protein, respectively), decreased by about 25% during incubation with quercetin. As a result, the GSH:GSSG ratio increased by about 70%, from 253 ± 7 to 372 ± 23. These quercetin-induced changes in GSH and GSSG levels were not affected by treating HAEC with 500µM ascorbic acid phosphate for 24h to increase intracellular ascorbate levels. Incubation of HAEC with quercetin also led to the appearance of extracellular quercetin-glutathione conjugates, which was paralleled by upregulation of the multidrug resistance protein 1 (MRP1). Furthermore, quercetin slightly but significantly increased mRNA and protein levels of glutamate-cysteine ligase (GCL) catalytic and modifier subunits. Taken together, our results suggest that quercetin causes loss of GSH in HAEC, not because of oxidation but due to formation and cellular export of quercetin-glutathione conjugates. Induction by quercetin of GCL subsequently restores GSH levels, thereby suppressing LPS-induced oxidant production.
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      PubDate: 2016-08-25T21:18:02Z
       
  • The Methyl Donor S-Adenosylmethionine Prevents Liver Hypoxia and
           Dysregulation of Mitochondrial Bioenergetic Function in a Rat Model of
           Alcohol-Induced Fatty Liver Disease

    • Abstract: Publication date: Available online 17 August 2016
      Source:Redox Biology
      Author(s): Adrienne L. Kinga, Sudheer K. Mantena, Kelly K. Andringa, Telisha Millender-Swain, Kimberly J. Dunham-Snary, Claudia R. Oliva, Corinne E. Griguer, Shannon M. Bailey
      Background Mitochondrial dysfunction and bioenergetic stress play an important role in the etiology of alcoholic liver disease. Previous studies from our laboratory show that the primary methyl donor S-adenosylmethionine (SAM) minimizes alcohol-induced disruptions in several mitochondrial functions in the liver. Herein, we expand on these earlier observations to determine whether the beneficial actions of SAM against alcohol toxicity extend to changes in the responsiveness of mitochondrial respiration to inhibition by nitric oxide (NO), induction of the mitochondrial permeability transition (MPT) pore, and the hypoxic state of the liver. Methods For this, male Sprague-Dawley rats were pair-fed control and alcohol-containing liquid diets with and without SAM for 5 weeks and liver hypoxia, mitochondrial respiration, MPT pore induction, and NO−dependent control of respiration were examined. Results Chronic alcohol feeding significantly enhanced liver hypoxia, whereas SAM supplementation attenuated hypoxia in livers of alcohol-fed rats. SAM supplementation prevented alcohol-mediated decreases in mitochondrial state 3 respiration and cytochrome c oxidase activity. Mitochondria isolated from livers of alcohol-fed rats were more sensitive to calcium-mediated MPT pore induction (i.e., mitochondrial swelling) than mitochondria from pair-fed controls, whereas SAM treatment normalized sensitivity for calcium-induced swelling in mitochondria from alcohol-fed rats. Liver mitochondria from alcohol-fed rats showed increased sensitivity to NO−dependent inhibition of respiration compared with pair-fed controls. In contrast, mitochondria isolated from the livers of SAM treated alcohol-fed rats showed no change in the sensitivity to NO-mediated inhibition of respiration. Conclusion Collectively, these findings indicate that the hepato-protective effects of SAM against alcohol toxicity are mediated, in part, through a mitochondrial mechanism involving preservation of key mitochondrial bioenergetic parameters and the attenuation of hypoxic stress.
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      PubDate: 2016-08-19T20:08:17Z
       
  • Uncouplingprotein 2 modulation of the NLRP3 inflammasome in astrocytes and
           its implications in depression

    • Abstract: Publication date: Available online 18 August 2016
      Source:Redox Biology
      Author(s): Ren-Hong Du, Fang-Fang Wu, Ming Lu, Xiao-dong Shu, Jian-Hua Ding, Guangyu Wu, Gang Hu
      Mitochondrial uncoupling protein 2 (UCP2) has been well characterized to control the production of reactive oxygen species (ROS) and astrocytes are the major cells responsible for the ROS production and the inflammatory responses in the brain. However, the function of UCP2 in astrocytes and the contribution of astrocytic UCP2 to depression remain undefined. Herein, we demonstrated that UCP2 knockout (KO) mice displayed aggravated depressive-like behaviors, impaired neurogenesis, and enhanced loss of astrocytes in the chronic mild stress (CMS)-induced anhedonia model of depression. We further found that UCP2 ablation significantly enhanced the activation of the nod-like receptor protein 3 (NLRP3) inflammasome in the hippocampus and in astrocytes. Furthermore, UCP2 deficiency promoted the injury of mitochondria, the generation of ROS and the physical association between thioredoxin-interacting protein (TXNIP) and NLRP3 in astrocytes. Moreover, transiently expressing exogenous UCP2 partially rescued the deleterious effects of UCP2 ablation on the astrocytes. These data indicate that UCP2 negatively regulates the activation of NLRP3 inflammasome and inhibited the ROS-TXNIP-NLRP3 pathway in astrocytes. Collectively, our findings reveal that UCP2 regulates inflammation responses in astrocytes and plays an important role in the pathogenesis of depression and that UCP2 may be a promising therapeutic target for depression.
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      PubDate: 2016-08-19T20:08:17Z
       
  • Absorbance and redox based approaches for measuring free heme and free
           hemoglobin in biological matrices

    • Abstract: Publication date: Available online 10 August 2016
      Source:Redox Biology
      Author(s): Joo-Yeun Oh, Jennifer Hamm, Xin Xu, Kristopher Genschmer, Ming Zhong, Jeffrey Lebensburger, Marisa B. Marques, Jeffrey D. Kerby, Jean-Francois Pittet, Amit Gaggar, Rakesh P. Patel
      Cell-free heme (CFH) and hemoglobin (Hb) have emerged as distinct mediators of acute injury characterized by inflammation and microcirculatory dysfunction in hemolytic conditions and critical illness. Several reports have shown changes in Hb and CFH in specific pathophysiological settings. Using PBS, plasma from patients with sickle cell disease, acute respiratory distress syndrome (ARDS) patients and supernatants from red cells units, we found that commonly used assays and commercially available kits do not distinguish between CFH and Hb. Furthermore, they suffer from a variety of false-positive interferences and limitations (including from bilirubin) that lead to either over- or underestimation of CFH and/ or Hb. Moreover, commonly used protocols to separate CFH and Hb based on molecular weight (MWt) are inefficient due to CFH hydrophobicity. In this study, we developed and validated a new approach based on absorbance spectrum deconvolution with least square fitting analyses that overcomes these limitations and simultaneously measures CFH and Hb in simple aqueous buffers, plasma or when associated with red cell derived microvesicles. We show how incorporating other plasma factors that absorb light over the visible wavelength range (specifically bilirubin), coupled with truncating the wavelength range analyzed, or addition of mild detergent significantly improves fits allowing measurement of oxyHb, CFH and metHb with >90% accuracy. When this approach was applied to samples from SCD patients, we observed that CFH levels are higher than previously reported and of similar magnitude to Hb.
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      PubDate: 2016-08-14T19:35:18Z
       
  • The Impact of High and Low Dose Ionising Radiation on the Central Nervous
           System

    • Abstract: Publication date: Available online 10 August 2016
      Source:Redox Biology
      Author(s): Calina Betlazar, Ryan J. Middleton, Richard B. Banati, Guo-Jun Liu
      Responses of the central nervous system (CNS) to stressors and injuries, such as ionising radiation, are modulated by the concomitant responses of the brains innate immune effector cells, microglia. Exposure to high doses of ionising radiation in brain tissue leads to the expression and release of biochemical mediators of ‘neuroinflammation’, such as pro-inflammatory cytokines and reactive oxygen species (ROS), leading to tissue destruction. Contrastingly, low dose ionising radiation may reduce vulnerability to subsequent exposure of ionising radiation, largely through the stimulation of adaptive responses, such as antioxidant defences. These disparate responses may be reflective of non-linear differential microglial activation at low and high doses, manifesting as an anti-inflammatory or pro-inflammatory functional state. Biomarkers of pathology in the brain, such as the mitochondrial Translocator Protein 18kDa (TSPO), have facilitated in vivo characterisation of microglial activation and ‘neuroinflammation’ in many pathological states of the CNS, though the exact function of TSPO in these responses remains elusive. Based on the known responsiveness of TSPO expression to a wide range of noxious stimuli, we discuss TSPO as a potential biomarker of radiation-induced effects.
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      PubDate: 2016-08-14T19:35:18Z
       
  • Hydrogen sulfide metabolism regulates endothelial solute barrier function

    • Abstract: Publication date: Available online 11 August 2016
      Source:Redox Biology
      Author(s): Shuai Yuan, Sibile Pardue, Xinggui Shen, J. Steven Alexander, A. Wayne Orr, Christopher G. Kevil
      Hydrogen sulfide (H2S) is an important gaseous signaling molecule in the cardiovascular system. In addition to free H2S, H2S can be oxidized to polysulfide which can be biologically active. Since the impact of H2S on endothelial solute barrier function is not known, we sought to determine whether H2S and its various metabolites affect endothelial permeability. In vitro permeability was evaluated using albumin flux and transendothelial electrical resistance. Different H2S donors were used to examine the effects of exogenous H2S. To evaluate the role of endogenous H2S, mouse aortic endothelial cells (MAECs) were isolated from wild type mice and mice lacking cystathionine γ-lyase (CSE), a predominant source of H2S in endothelial cells. In vivo permeability was evaluated using the Miles assay. We observed that polysulfide donors induced rapid albumin flux across endothelium. Comparatively, free sulfide donors increased permeability only with higher concentrations and at later time points. Increased solute permeability was associated with disruption of endothelial junction proteins claudin 5 and VE-cadherin, along with enhanced actin stress fiber formation. Importantly, sulfide donors that increase permeability elicited a preferential increase in polysulfide levels within endothelium. Similarly, CSE deficient MAECs showed enhanced solute barrier function along with reduced endogenous bound sulfane sulfur. CSE siRNA knockdown also enhanced endothelial junction structures with increased claudin 5 protein expression. In vivo, CSE genetic deficiency significantly blunted VEGF induced hyperpermeability revealing an important role of the enzyme for barrier function. In summary, endothelial solute permeability is critically regulated via exogenous and endogenous sulfide bioavailability with a prominent role of polysulfides.
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      PubDate: 2016-08-14T19:35:18Z
       
  • Omeprazole impairs vascular redox biology and causes xanthine
           oxidoreductase-mediated endothelial dysfunction

    • Abstract: Publication date: Available online 4 August 2016
      Source:Redox Biology
      Author(s): Lucas C. Pinheiro, Gustavo Oliveira-Paula, Rafael L. Portella, Daniele A. Guimarães, Celio D. de Angelis, Jose E. Tanus-Santos
      Proton pump inhibitors (PPIs) are widely used drugs that may increase the cardiovascular risk by mechanisms not entirely known. While PPIs increase asymmetric dimethylarginine (ADMA) levels and inhibit nitric oxide production, it is unknown whether impaired vascular redox biology resulting of increased xanthine oxidoreductase (XOR) activity mediates PPIs-induced endothelial dysfunction (ED). We examined whether increased XOR activity impairs vascular redox biology and causes ED in rats treated with omeprazole. We also examined whether omeprazole aggravates the ED found in hypertension. Treatment with omeprazole reduced endothelium-dependent aortic responses to acetylcholine without causing hypertension. However, omeprazole did not aggravate two-kidney, one-clip (2K1C) hypertension, nor hypertension-induced ED. Omeprazole and 2K1C increased vascular oxidative stress as assessed with dihydroethidium (DHE), which reacts with superoxide, and by the lucigenin chemiluminescence assay. The selective XOR inhibitor febuxostat blunted both effects induced by omeprazole. Treatment with omeprazole increased plasma ADMA concentrations, XOR activity and systemic markers of oxidative stress. Incubation of aortic rings with ADMA increased XOR activity, DHE fluorescence and lucigenin chemiluminescence signals, and febuxostat blunted these effects. Providing functional evidence that omeprazole causes ED by XOR-mediated mechanisms, we found that febuxostat blunted the ED caused by omeprazole treatment. This study shows that treatment with omeprazole impairs the vascular redox biology by XOR-mediated mechanisms leading to ED. While omeprazole did not further impair hypertension-induced ED, further studies in less severe animal models are warranted. Our findings may have major relevance, particularly to patients with cardiovascular diseases taking PPIs.
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      PubDate: 2016-08-09T18:59:02Z
       
  • Distinctive adaptive response to repeated exposure to hydrogen peroxide
           associated with upregulation of DNA repair genes and cell cycle arrest

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Gloria A. Santa-Gonzalez, Andrea Gomez-Molina, Mauricio Arcos-Burgos, Joel N. Meyer, Mauricio Camargo
      Many environmental and physiological stresses are chronic. Thus, cells are constantly exposed to diverse types of genotoxic insults that challenge genome stability, including those that induce oxidative DNA damage. However, most in vitro studies that model cellular response to oxidative stressors employ short exposures and/or acute stress models. In this study, we tested the hypothesis that chronic and repeated exposure to a micromolar concentration of hydrogen peroxide (H2O2) could activate DNA damage responses, resulting in cellular adaptations. For this purpose, we developed an in vitro model in which we incubated mouse myoblast cells with a steady concentration of ~50μM H2O2 for one hour daily for seven days, followed by a final challenge of a 10 or 20X higher dose of H2O2 (0.5 or 1mM). We report that intermittent long-term exposure to this oxidative stimulus nearly eliminated cell toxicity and significantly decreased genotoxicity (in particular, a >5-fold decreased in double-strand breaks) resulting from subsequent acute exposure to oxidative stress. This protection was associated with cell cycle arrest in G2/M and induction of expression of nine DNA repair genes. Together, this evidence supports an adaptive response to chronic, low-level oxidative stress that results in genomic protection and up-regulated maintenance of cellular homeostasis.
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      PubDate: 2016-07-30T16:58:21Z
       
  • Dual NRF2 paralogs in Coho salmon and their antioxidant response element
           targets

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Richard Ramsden, Evan P. Gallagher
      The transcription factor NFE2L2 (Nuclear Factor, Erythroid 2-Like 2, or NRF2) plays a key role in maintaining the redox state within cells. Characterization of this pathway has extended to fish, most notably zebrafish (Danio rerio), in which two paralogs of the transcription factor exist: Nrf2a, an activator, and Nrf2b, a negative regulator during embryogenesis. Only one ARE target has been thoroughly delineated in zebrafish, and this deviated from the canonical sequence derived from studies in mammals. In general, the mechanistic pathway has not been characterized in non-model aquatic organisms that are commonly exposed to environmental pollutants. The current study compares the zebrafish paralogs to those found in a non-model teleost, the ecologically important salmonid, Oncorhnychus kisutch (coho salmon). Two salmon paralogs, Nrf2A and -2B, described here were found to possess only slightly greater identity between one another (84% of amino acids) than to the singleton ortholog of the esocid Esox lucius (80–82%), the nearest non-salmonid outgroup. Unlike one of the zebrafish forms, each is a strong activating factor based on sequence homology and in vitro testing. To uncover functional target AREs in coho, promoter flanking sequences were isolated for five genes that protect cells against oxidative stress: heme oxygenase 1, peroxiredoxin 1, glutamate-cysteine ligase, and the glutathione S-transferases pi and rho (hmox1, prdx1, gclc, gstp, and gstr). All except gstr had functional elements and all fit the standard mammalian-derived canonical sequence, unlike the motif found in zebrafish gstp. Expression studies demonstrate the presence of both Nrf2 paralogs in multiple organs, although in differing ratios. Collectively, our findings extend the conservation of Nrf2 and the ARE to salmonids, and should help inform future work in teleosts on mechanisms of redox control, as well as responsiveness of this pathway and its downstream antioxidant gene targets to chemical exposures in the environment.
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      PubDate: 2016-07-30T16:58:21Z
       
  • Quercetin inhibits LPS-induced adhesion molecule expression and oxidant
           production in human aortic endothelial cells by p38-mediated Nrf2
           activation and antioxidant enzyme induction

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Chuan Li, Wei-Jian Zhang, Balz Frei
      Atherosclerosis, the underlying cause of ischemic heart disease and stroke, is an inflammatory disease of arteries in a hyperlipidemic milieu. Endothelial expression of cellular adhesion molecules, such as endothelial-leukocyte adhesion molecule-1 (E-selectin) and intercellular adhesion molecule-1 (ICAM-1), plays a critical role in the initiation and progression of atherosclerosis. The dietary flavonoid, quercetin, has been reported to inhibit expression of cellular adhesion molecules, but the underlying mechanisms are incompletely understood. In this study, we found that quercetin dose-dependently (5–20µM) inhibits lipopolysaccharide (LPS)-induced mRNA and protein expression of E-selectin and ICAM-1 in human aortic endothelial cells (HAEC). Incubation of HAEC with quercetin also significantly reduced LPS-induced oxidant production, but did not inhibit activation of the nuclear factor-kappaB (NF-κB). Furthermore, quercetin induced activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) and subsequent mRNA and protein expression of the antioxidant enzymes, heme oxygenase-1 (HO-1), NAD(P)H dehydrogenase, quinone 1, and glutamate-cysteine ligase. The induction of Nrf2 and antioxidant enzymes was partly inhibited by the p38 mitogen-activated protein kinase (p38) inhibitor, SB203580. Our results suggest that quercetin suppresses LPS-induced oxidant production and adhesion molecule expression by inducing Nrf2 activation and antioxidant enzyme expression, which is partially mediated by p38; and the inhibitory effect of quercetin on adhesion molecule expression is not due to inhibition of NF-κB activation, but instead due to antioxidant-independent effects of HO-1.
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      PubDate: 2016-07-25T16:54:31Z
       
  • Diabetes-induced oxidative stress in the vitreous humor

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Zsuzsanna Géhl, Edina Bakondi, Miklós D. Resch, Csaba Hegedűs, Katalin Kovács, Petra Lakatos, Antal Szabó, Zoltán Nagy, László Virág
      Purpose Diabetes is accompanied by fundamental rearrangements in redox homeostasis. Hyperglycemia triggers the production of reactive oxygen and nitrogen species which contributes to tissue damage in various target organs. Proliferative diabetic retinopathy (PDR) is a common manifestation of diabetic complications but information on the possible role of reactive intermediates in this condition with special regard to the involvement of the vitreous in PDR-associated redox alterations is scarce. The aim of the study was to determine key parameters of redox homeostasis [advanced glycation endproducts (AGE); protein carbonyl and glutathione (GSH)] content in the vitreous in PDR patients. Methods The study population involved 10 diabetic patients undergoing surgery for complications of proliferative diabetic retinopathy and 8 control (non-diabetic) patients who were undergoing surgery for epiretinal membranes. Vitreal fluids were assayed for the above biochemical parameters. Results We found elevated levels of AGE in the vitreous of PDR patients (812.10 vs 491.69ng AGE/mg protein). Extent of protein carbonylation was also higher in the samples of diabetic patients (2.08 vs 0.67A/100μg protein). The GSH content also increased in the vitreous of PDR patients as compared to the control group (4.54 vs 2.35μmol/μg protein), respectively. Conclusion The study demonstrates that diabetes-associated redox alterations also reach the vitreous with the most prominent changes being increased protein carbonylation and increased antioxidant levels.
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      PubDate: 2016-07-25T16:54:31Z
       
  • The hydroxypyridinone iron chelator CP94 increases
           methyl-aminolevulinate-based photodynamic cell killing by increasing the
           generation of reactive oxygen species

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Yuktee Dogra, Daniel C.J. Ferguson, Nicholas J.F. Dodd, Gary R. Smerdon, Alison Curnow, Paul G. Winyard
      Methyl-aminolevulinate-based photodynamic therapy (MAL-PDT) is utilised clinically for the treatment of non-melanoma skin cancers and pre-cancers and the hydroxypyridinone iron chelator, CP94, has successfully been demonstrated to increase MAL-PDT efficacy in an initial clinical pilot study. However, the biochemical and photochemical processes leading to CP94-enhanced photodynamic cell death, beyond the well-documented increases in accumulation of the photosensitiser protoporphyrin IX (PpIX), have not yet been fully elucidated. This investigation demonstrated that MAL-based photodynamic cell killing of cultured human squamous carcinoma cells (A431) occurred in a predominantly necrotic manner following the generation of singlet oxygen and ROS. Augmenting MAL-based photodynamic cell killing with CP94 co-treatment resulted in increased PpIX accumulation, MitoSOX-detectable ROS generation (probably of mitochondrial origin) and necrotic cell death, but did not affect singlet oxygen generation. We also report (to our knowledge, for the first time) the detection of intracellular PpIX-generated singlet oxygen in whole cells via electron paramagnetic resonance spectroscopy in conjunction with a spin trap.


      PubDate: 2016-07-25T16:54:31Z
       
  • A biphasic effect of TNF-α in regulation of the Keap1/Nrf2 pathway in
           cardiomyocytes

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Gobinath Shanmugam, Madhusudhanan Narasimhan, Ramasamy Sakthivel, Rajesh Kumar R, Christopher Davidson, Sethu Palaniappan, William W. Claycomb, John R. Hoidal, Victor M. Darley-Usmar, Namakkal Soorappan Rajasekaran
      Antagonizing TNF-α signaling attenuates chronic inflammatory disease, but is associated with adverse effects on the cardiovascular system. Therefore the impact of TNF-α on basal control of redox signaling events needs to be understand in more depth. This is particularly important for the Keap1/Nrf2 pathway in the heart and in the present study we hypothesized that inhibition of a low level of TNF-α signaling attenuates the TNF-α dependent activation of this cytoprotective pathway. HL-1 cardiomyocytes and TNF receptor1/2 (TNFR1/2) double knockout mice (DKO) were used as experimental models. TNF-α (2–5ng/ml, for 2h) evoked significant nuclear translocation of Nrf2 with increased DNA/promoter binding and transactivation of Nrf2 targets. Additionally, this was associated with a 1.5 fold increase in intracellular glutathione (GSH). Higher concentrations of TNF-α (>10–50ng/ml) were markedly suppressive of the Keap1/Nrf2 response and associated with cardiomyocyte death marked by an increase in cleavage of caspase-3 and PARP. In vivo experiments with TNFR1/2-DKO demonstrates that the expression of Nrf2-regulated proteins (NQO1, HO-1, G6PD) were significantly downregulated in hearts of the DKO when compared to WT mice indicating a weakened antioxidant system under basal conditions. Overall, these results indicate that TNF-α exposure has a bimodal effect on the Keap1/Nrf2 system and while an intense inflammatory activation suppresses expression of antioxidant proteins a low level appears to be protective.
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      PubDate: 2016-07-19T16:24:15Z
       
  • Redox mechanisms in age-related lung fibrosis

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Ashish Kurundkar, Victor J. Thannickal
      Redox signaling and oxidative stress are associated with tissue fibrosis and aging. Aging is recognized as a major risk factor for fibrotic diseases involving multiple organ systems, including that of the lung. A number of oxidant generating enzymes are upregulated while antioxidant defenses are deficient with aging and cellular senescence, leading to redox imbalance and oxidative stress. However, the precise mechanisms by which redox signaling and oxidative stress contribute to the pathogenesis of lung fibrosis are not well understood. Tissue repair is a highly regulated process that involves the interactions of several cell types, including epithelial cells, fibroblasts and inflammatory cells. Fibrosis may develop when these interactions are dysregulated with the acquisition of pro-fibrotic cellular phenotypes. In this review, we explore the roles of redox mechanisms that promote and perpetuate fibrosis in the context of cellular senescence and aging.
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      PubDate: 2016-07-09T14:19:36Z
       
  • Pleiotropic effects of 4-hydroxynonenal on oxidative burst and
           phagocytosis in neutrophils

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Balu K. Chacko, Stephanie B. Wall, Philip A. Kramer, Saranya Ravi, Tanecia Mitchell, Michelle S. Johnson, Landon Wilson, Stephen Barnes, Aimee Landar, Victor M. Darley-Usmar
      Metabolic control of cellular function is significant in the context of inflammation-induced metabolic dysregulation in immune cells. Generation of reactive oxygen species (ROS) such as hydrogen peroxide and superoxide are one of the critical events that modulate the immune response in neutrophils. When activated, neutrophil NADPH oxidases consume large quantities of oxygen to rapidly generate ROS, a process that is referred to as the oxidative burst. These ROS are required for the efficient removal of phagocytized cellular debris and pathogens. In chronic inflammatory diseases, neutrophils are exposed to increased levels of oxidants and pro-inflammatory cytokines that can further prime oxidative burst responses and generate lipid oxidation products such as 4-hydroxynonenal (4-HNE). In this study we hypothesized that since 4-HNE can target glycolysis then this could modify the oxidative burst. To address this the oxidative burst was determined in freshly isolated healthy subject neutrophils using 13-phorbol myristate acetate (PMA) and the extracellular flux analyzer. Neutrophils pretreated with 4-HNE exhibited a significant decrease in the oxidative burst response and phagocytosis. Mass spectrometric analysis of alkyne-HNE treated neutrophils followed by click chemistry detected modification of a number of cytoskeletal, metabolic, redox and signaling proteins that are critical for the NADPH oxidase mediated oxidative burst. These modifications were confirmed using a candidate immunoblot approach for critical proteins of the active NADPH oxidase enzyme complex (Nox2 gp91phox subunit and Rac1 of the NADPH oxidase) and glyceraldehyde phosphate dehydrogenase, a critical enzyme in the metabolic regulation of oxidative burst. Taken together, these data suggest that 4-HNE-induces a pleiotropic mechanism to inhibit neutrophil function. These mechanisms may contribute to the immune dysregulation associated with chronic pathological conditions where 4-HNE is generated.
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      PubDate: 2016-07-09T14:19:36Z
       
  • Artemisinin protects human retinal pigment epithelial cells from hydrogen
           peroxide-induced oxidative damage through activation of ERK/CREB signaling
           

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Cheong-Meng Chong, Wenhua Zheng
      The pathological increase in the levels of reactive oxygen species (ROS) in the retinal pigment epithelium (RPE), is implicated in the development of age-related macular degeneration (AMD). The discovery of drug candidates to effectively protect RPE cells from oxidative damage is required to resolve the pathological aspects and modify the process of AMD. In this study, a FDA-approved anti-malaria drug, Artemisinin was found to suppress hydrogen peroxide (H2O2)-induced cell death in human RPE cell-D407 cells. Further study showed that Artemisinin significantly suppressed H2O2 − induced D407 cell death by restoring abnormal changes in nuclear morphology, intracellular ROS, mitochondrial membrane potential and apoptotic biomarkers. Western blotting analysis showed that Artemisinin was able to activate extracellular regulated ERK/CREB survival signaling. Furthermore, Artemisinin failed to suppress H2O2-induced cytotoxicity and the increase of caspase 3/7 activity in the presence of the ERK inhibitor PD98059. Taken together, these results suggest that Artemisinin is a potential protectant with the pro-survival effects against H2O2 insult through activation of the ERK/CREB pathway.
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      PubDate: 2016-07-04T13:28:49Z
       
  • Plasma cysteine/cystine redox couple disruption in animal models of
           temporal lobe epilepsy

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Li-Ping Liang, Manisha Patel
      Currently the field of epilepsy lacks peripheral blood-based biomarkers that could predict the onset or progression of chronic seizures following an epileptogenic injury. Thiol/disulfide ratios have been shown to provide a sensitive means of assessing the systemic redox potential in tissue and plasma. In this study, we utilized a rapid, simple and reliable method for simultaneous determination of several thiol-containing amino acids in plasma using HPLC with electrochemical detection in kainic acid (KA) and pilocarpine rat models of epilepsy. In contrast to GSH and GSSG levels, the levels of cysteine (Cys) were decreased by 42% and 62% and cystine (Cyss) were increased by 46% and 23% in the plasma of KA- and pilocarpine-injected rats, respectively after 48h. In chronically epileptic rats, plasma cysteine was decreased by 40.4% and 37.7%, and plasma GSSG increased by 33.8% and 35.0% following KA and pilocarpine, respectively. Treatment of rats with a catalytic antioxidant, 60min after KA or pilocarpine significant attenuated the decrease of plasma Cys/Cyss ratios at the 48h time point in both models. These observations suggest that the decreased cysteine and ratio of Cys/Cyss in plasma could potentially serve as redox biomarkers in temporal lobe epilepsy.
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      PubDate: 2016-06-14T19:55:24Z
       
  • Imaging free radicals in organelles, cells, tissue, and in vivo with
           immuno-spin trapping

    • Abstract: Publication date: August 2016
      Source:Redox Biology, Volume 8
      Author(s): Ronald Paul Mason
      The accurate and sensitive detection of biological free radicals in a reliable manner is required to define the mechanistic roles of such species in biochemistry, medicine and toxicology. Most of the techniques currently available are either not appropriate to detect free radicals in cells and tissues due to sensitivity limitations (electron spin resonance, ESR) or subject to artifacts that make the validity of the results questionable (fluorescent probe-based analysis). The development of the immuno-spin trapping technique overcomes all these difficulties. This technique is based on the reaction of amino acid- and DNA base-derived radicals with the spin trap 5, 5-dimethyl-1-pyrroline N-oxide (DMPO) to form protein- and DNA-DMPO nitroxide radical adducts, respectively. These adducts have limited stability and decay to produce the very stable macromolecule-DMPO-nitrone product. This stable product can be detected by mass spectrometry, NMR or immunochemistry by the use of anti-DMPO nitrone antibodies. The formation of macromolecule-DMPO-nitrone adducts is based on the selective reaction of free radical addition to the spin trap and is thus not subject to artifacts frequently encountered with other methods for free radical detection. The selectivity of spin trapping for free radicals in biological systems has been proven by ESR. Immuno-spin trapping is proving to be a potent, sensitive (a million times higher sensitivity than ESR), and easy (not quantum mechanical) method to detect low levels of macromolecule-derived radicals produced in vitro and in vivo. Anti-DMPO antibodies have been used to determine the distribution of free radicals in cells and tissues and even in living animals. In summary, the invention of the immuno-spin trapping technique has had a major impact on the ability to accurately and sensitively detect biological free radicals and, subsequently, on our understanding of the role of free radicals in biochemistry, medicine and toxicology.
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      PubDate: 2016-06-14T19:55:24Z
       
  • N-acetylcysteine inhibits lipid accumulation in mouse embryonic adipocytes

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): A. Pieralisi, C. Martini, D. Soto, M.C. Vila, J.C. Calvo, L.N. Guerra
      Oxidative stress plays critical roles in the pathogenesis of diabetes, hypertension, and atherosclerosis; some authors reported that fat accumulation correlates to systemic oxidative stress in human and mice, but cellular redox environment effect on lipid accumulation is still unclear. In our laboratory we used mouse embryonic fibroblasts (undifferentiated cells: CC), which are capable of differentiating into mature adipocytes (differentiated cells: DC) and accumulate lipids, as obesity model. Here we analyzed the role of the well-known antioxidant and glutathione precursor N-acetylcysteine (NAC) in cellular MAPK modulation and lipid accumulation. We evaluated the effect of NAC on the adipogenic differentiation pathway using different doses: 0.01, 0.1, 1 and 5mM; no toxic doses in these cells. A dose of 5mM NAC [DCN-5] provoked a significant decrease in triglyceride accumulation (72±10 [DCN-5] vs 169±15 [DC], p<0.01), as well in Oil Red O stained neutral lipid content (120±2 [DCN-5] vs 139±12 [DC], p<0.01). Molecular mechanisms responsible for adipogenic differentiation involve increase of the expression of phosphoERK½ and phosphoJNK, 5mM NAC treatment inhibited both pERK½ and pJNK protein levels. We also evaluated the mitotic clonal expansion (MCE) which takes place during adipogenesis and observed an increase in DC at a rate of 1.5 cells number compared to CC at day 2, whereas the highest doses of NAC significantly inhibited MCE. Our results suggest that NAC inhibits lipid accumulation and the MAPK phosphorylation in mouse embryonic fibroblasts during adipogenic differentiation and further contribute to probe the importance of cellular redox environment in adipogenesis.
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      PubDate: 2016-06-14T19:55:24Z
       
  • Simvastatin and oxidative stress in humans: A randomized, double-blinded,
           placebo-controlled clinical trial

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Sanne Tofte Rasmussen, Jon Trærup Andersen, Torben Kjær Nielsen, Vanja Cejvanovic, Kasper Meidahl Petersen, Trine Henriksen, Allan Weimann, Jens Lykkesfeldt, Henrik Enghusen Poulsen
      Simvastatin reduces the blood concentration of cholesterol by inhibiting hydroxymethylglutaryl-coenzyme A reductase, the rate-limiting enzyme in cholesterol synthesis, and thereby reduces the risk of cardiovascular disease. In addition, simvastatin treatment leads to a reduction in fluxes in mitochondrial respiratory complexes I and II and might thereby reduce the formation of reactive oxygen species, which have been implicated in the pathogenesis of arteriosclerosis. Therefore, we hypothesized that simvastatin may reduce oxidative stress in humans in vivo. We conducted a randomized, double-blinded, placebo-controlled study in which subjects were treated with either 40mg of simvastatin or placebo for 14 days. The endpoints were six biomarkers for oxidative stress, which represent intracellular oxidative stress to nucleic acids, lipid peroxidation and plasma antioxidants, that were measured in urine and plasma samples. A total of 40 participants were included, of which 39 completed the trial. The observed differences between simvastatin and placebo groups in the primary outcomes, DNA and RNA oxidation, were small and nonsignificant (p=0.68), specifically, 3% in the simvastatin group compared to 7.1% in the placebo group for DNA oxidation and 7.3% in the simvastatin group compared to 3.4% in the placebo group. The differences in biomarkers related to plasma were not statistically significant between the treatments groups, with the exception of total vitamin E levels, which, as expected, were reduced in parallel with the reduction in plasma cholesterol. In healthy young male volunteers, short-term simvastatin treatment, which considerably reduces cholesterol, does not lead to a clinically relevant reduction in a panel of measures of oxidative stress. Whether simvastatin has effects on oxidative stress in diseased populations, such as diabetes or hemochromatosis, where oxidative stress is prominent, is unknown but seems unlikely.
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      PubDate: 2016-06-14T19:55:24Z
       
  • Direct measurement of actual levels of nitric oxide (NO) in cell culture
           conditions using soluble NO donors

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Weilue He, Megan C. Frost
      Applying soluble nitric oxide (NO) donors is the most widely used method to expose cells of interest to exogenous NO. Because of the complex equilibria that exist between components in culture media, the donor compound and NO itself, it is very challenging to predict the dose and duration of NO cells actually experience. To determine the actual level of NO experienced by cells exposed to soluble NO donors, we developed the CellNO Trap, a device that allows continuous, real-time monitoring of the level of NO adherent cells produce and/or experience in culture without the need to alter cell culturing procedures. Herein, we directly measured the level of NO that cells grown in the CellNO Trap experienced when soluble NO donors were added to solutions in culture wells and we characterized environmental conditions that effected the level of NO in in vitro culture conditions. Specifically, the dose and duration of NO generated by the soluble donors S-nitroso-N-acetylpenicillamine (SNAP), S-nitrosoglutathione (GSNO), S-nitrosocysteine (CysNO) and the diazeniumdiolate diethyltriamine (DETA/NO) were investigated in both phosphate buffered saline (PBS) and cell culture media. Other factors that were studied that potentially affect the ultimate NO level achieved with these donors included pH, presence of transition metals (ion species), redox level, presence of free thiol and relative volume of media. Then murine smooth muscle cell (MOVAS) with different NO donors but with the same effective concentration of available NO were examined and it was demonstrated that the cell proliferation ratio observed does not correlate with the half-lives of NO donors characterized in PBS, but does correlate well with the real-time NO profiles measured under the actual culture conditions. This data demonstrates the dynamic characteristic of the NO and NO donor in different biological systems and clearly illustrates the importance of tracking individual NO profiles under the actual biological conditions.
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      PubDate: 2016-06-14T19:55:24Z
       
  • The impact of partial hepatectomy on oxidative state in the liver remnant
           – An in vivo swine model

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Åse Florholmen-Kjær, Rasmus Goll, Ole-Martin Fuskevåg, Ingvild Engdal Nygård, Ruth H. Paulssen, Arthur Revhaug, Kim Erlend Mortensen
      Background Previous studies on oxidative state after partial hepatectomy (PHx) report conflicting data on levels of glutathione (GSH) and are mainly presented in rodent models by methodology less sensitive than the present technologies. The current swine model presents GSH levels and the following genetic response post-PHx, utilizing an analytical platform more sensitive and precise than earlier available. Method Twelve pigs were randomized to a PHx- and a control group (n=6 in each). The PHx group had a 60% hepatectomy. Serial in vivo liver biopsies during 12h of anaesthesia post-PHx were analyzed for GSH by liquid chromatography mass spectrometry (LC-MS/MS). Transcriptional alterations of genes (GS, GCLM, GCLC, GR, HGF, NFE2L2, TGFβ1) regulating GSH synthesis were measured by real-time PCR. Results No difference was detected between the GSH levels in the PHx- and the control group during the experiment (P=0.247). Still, decreased gene expression of GS (P=0.026) and NFE2L2 (P=0.014) the first nine hours, and a decrease of TGFβ1 (P=0.029) the first seven hours post-PHx was seen in the liver remnant. Conclusion The results show that the liver has an extended capacity to maintain GSH homeostasis during major stress and parenchymal loss, even at the early onset of such trauma. This observation was not explained by increased expression of key genes in GSH pathways. Consequently, the results indicate an inherent compensatory capacity to maintain GSH homeostasis in the reduced organ.
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      PubDate: 2016-06-14T19:55:24Z
       
  • Glutathione peroxidase 4 and vitamin E cooperatively prevent
           hepatocellular degeneration

    • Abstract: Publication date: October 2016
      Source:Redox Biology, Volume 9
      Author(s): Bradley A. Carlson, Ryuta Tobe, Elena Yefremova, Petra A. Tsuji, Victoria J. Hoffmann, Ulrich Schweizer, Vadim N. Gladyshev, Dolph L. Hatfield, Marcus Conrad
      The selenoenzyme glutathione peroxidase 4 (Gpx4) is an essential mammalian glutathione peroxidase, which protects cells against detrimental lipid peroxidation and governs a novel form of regulated necrotic cell death, called ferroptosis. To study the relevance of Gpx4 and of another vitally important selenoprotein, cytosolic thioredoxin reductase (Txnrd1), for liver function, mice with conditional deletion of Gpx4 in hepatocytes were studied, along with those lacking Txnrd1 and selenocysteine (Sec) tRNA (Trsp) in hepatocytes. Unlike Txnrd1- and Trsp-deficient mice, Gpx4 −/− mice died shortly after birth and presented extensive hepatocyte degeneration. Similar to Txnrd1-deficient livers, Gpx4 −/− livers manifested upregulation of nuclear factor (erythroid-derived)-like 2 (Nrf2) response genes. Remarkably, Gpx4 −/− pups born from mothers fed a vitamin E-enriched diet survived, yet this protection was reversible as subsequent vitamin E deprivation caused death of Gpx4-deficient mice ~4 weeks thereafter. Abrogation of selenoprotein expression in Gpx4 −/− mice did not result in viable mice, indicating that the combined deficiency aggravated the loss of Gpx4 in liver. By contrast, combined Trsp/Txnrd1-deficient mice were born, but had significantly shorter lifespans than either single knockout, suggesting that Txnrd1 plays an important role in supporting liver function of mice lacking Trsp. In sum our study demonstrates that the ferroptosis regulator Gpx4 is critical for hepatocyte survival and proper liver function, and that vitamin E can compensate for its loss by protecting cells against deleterious lipid peroxidation.
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      PubDate: 2016-06-14T19:55:24Z
       
  • Cellular and subcellular oxidative stress parameters following severe
           spinal cord injury

    • Abstract: Publication date: Available online 30 December 2015
      Source:Redox Biology
      Author(s): Nishant P. Visavadiya, Samir P. Patel, Jenna L. VanRooyen, Patrick G. Sullivan, Alexander G. Rabchevsky
      The present study undertook a comprehensive assessment of the acute biochemical oxidative stress parameters in both cellular and, notably, mitochondrial isolates following severe upper lumbar contusion spinal cord injury (SCI) in adult female Sprague Dawley rats. At 24h post-injury, spinal cord tissue homogenate and mitochondrial fractions were isolated concurrently and assessed for glutathione (GSH) content and production of nitric oxide (NO•), in addition to the presence of oxidative stress markers 3-nitrotyrosine (3-NT), protein carbonyl (PC), 4-hydroxynonenal (4-HNE) and lipid peroxidation (LPO). Moreover, we assessed production of superoxide (O2 •¯) and hydrogen peroxide (H2O2) in mitochondrial fractions. Quantitative biochemical analyses showed that compared to sham, SCI significantly lowered GSH content accompanied by increased NO• production in both cellular and mitochondrial fractions. SCI also resulted in increased O2 •¯ and H2O2 levels in mitochondrial fractions. Western blot analysis further showed that reactive oxygen/nitrogen species (ROS/RNS) mediated PC and 3-NT production were significantly higher in both fractions after SCI. Conversely, neither 4-HNE levels nor LPO formation were increased at 24h after injury in either tissue homogenate or mitochondrial fractions. These results indicate that by 24h post-injury ROS-induced protein oxidation is more prominent compared to lipid oxidation, indicating a critical temporal distinction in secondary pathophysiology that is critical in designing therapeutic approaches to mitigate consequences of oxidative stress.
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      PubDate: 2016-01-03T17:47:57Z
       
  • Interplay between oxidant species and energy metabolism

    • Abstract: Publication date: August 2016
      Source:Redox Biology, Volume 8
      Author(s): Celia Quijano, Madia Trujillo, Laura Castro, Andrés Trostchansky
      It has long been recognized that energy metabolism is linked to the production of reactive oxygen species (ROS) and critical enzymes allied to metabolic pathways can be affected by redox reactions. This interplay between energy metabolism and ROS becomes most apparent during the aging process and in the onset and progression of many age-related diseases (i.e. diabetes, metabolic syndrome, atherosclerosis, neurodegenerative diseases). As such, the capacity to identify metabolic pathways involved in ROS formation, as well as specific targets and oxidative modifications is crucial to our understanding of the molecular basis of age-related diseases and for the design of novel therapeutic strategies. Herein we review oxidant formation associated with the cell's energetic metabolism, key antioxidants involved in ROS detoxification, and the principal targets of oxidant species in metabolic routes and discuss their relevance in cell signaling and age-related diseases.
      Graphical abstract image

      PubDate: 2016-01-03T17:47:57Z
       
  • Protein S-glutathionlyation links energy metabolism to redox signaling in
           mitochondria

    • Abstract: Publication date: Available online 31 December 2015
      Source:Redox Biology
      Author(s): Ryan J. Mailloux, Jason R. Treberg
      At its core mitochondrial function relies on redox reactions. Electrons stripped from nutrients are used to form NADH and NADPH, electron carriers that are similar in structure but support different functions. NADH supports ATP production but also generates reactive oxygen species (ROS) superoxide (O2 ●-) and hydrogen peroxide (H2O2). NADH-driven ROS production is counterbalanced by NADPH which maintains antioxidants in an active state. Mitochondria rely on a redox buffering network composed of reduced glutathione (GSH) and peroxiredoxins (Prx) to quench ROS generated by nutrient metabolism. As H2O2 is quenched, NADPH is expended to reactivate antioxidant networks and reset the redox environment. Thus, the mitochondrial redox environment is in a constant state of flux reflecting changes in nutrient and ROS metabolism. Changes in redox environment can modulate protein function through oxidation of protein cysteine thiols. Typically cysteine oxidation is considered to be mediated by H2O2 which oxidizes protein thiols (SH) forming sulfenic acid (SOH). However, problems begin to emerge when one critically evaluates the regulatory function of SOH. Indeed SOH formation is slow, non-specific, and once formed SOH reacts rapidly with a variety of molecules. By contrast, protein S-glutathionylation (PGlu) reactions involve the conjugation and removal of glutathione moieties from modifiable cysteine residues. PGlu reactions are driven by fluctuations in the availability of GSH and oxidized glutathione (GSSG) and thus should be exquisitely sensitive to changes ROS flux due to shifts in the glutathione pool in response to varying H2O2 availability. Here, we propose that energy metabolism-linked redox signals originating from mitochondria are mediated indirectly by H2O2 through the GSH redox buffering network in and outside mitochondria. This proposal is based on several observations that have shown that unlike other redox modifications PGlu reactions fulfill the requisite criteria to serve as an effective posttranslational modification that controls protein function.
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      PubDate: 2016-01-03T17:47:57Z
       
 
 
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