Effect of reactive oxygen species on NH 4 + permeation in Xenopus laevis oocytes

2002 ◽  
Vol 282 (6) ◽  
pp. C1445-C1453 ◽  
Author(s):  
Marc Cougnon ◽  
Samia Benammou ◽  
Franck Brouillard ◽  
Philippe Hulin ◽  
Gabrielle Planelles
Keyword(s):  
Reactive Oxygen Species ◽  
Xenopus Laevis ◽  
Reactive Oxygen ◽  
Membrane Conductance ◽  
Xenopus Laevis Oocytes ◽  
Oxygen Species ◽  
Cation Conductance ◽  
Β Amyloid ◽  
Oocyte Membrane ◽  
Ros Scavengers

To investigate the effects of reactive oxygen species (ROS) on NH[Formula: see text]permeation in Xenopus laevis oocytes, we used intracellular double-barreled microelectrodes to monitor the changes in membrane potential ( V m) and intracellular pH (pHi) induced by a 20 mM NH4Cl-containing solution. Under control conditions, NH4Cl exposure induced a large membrane depolarization (to V m = 4.0 ± 1.5 mV; n = 21) and intracellular acidification [reaching a change in pHi(ΔpHi) of 0.59 ± 0.06 pH units in 12 min]; the initial rate of cell acidification (dpHi/d t) was 0.06 ± 0.01 pH units/min. Incubation of the oocytes in the presence of H2O2 or β-amyloid protein had no marked effect on the NH4Cl-induced ΔpHi. By contrast, in the presence of photoactivated rose bengal (RB), tert-butyl-hydroxyperoxide ( t-BHP), or xanthine/xanthine oxidase (X/XO), the same experimental maneuver induced significantly greater ΔpHi and dpHi/d t. These increases in ΔpHiand dpHi/d t were prevented by the ROS scavengers histidine and desferrioxamine, suggesting involvement of the reactive species 1ΔgO2 and ·OH. Using the voltage-clamp technique to identify the mechanism underlying the ROS-measured effects, we found that RB induced a large increase in the oocyte membrane conductance ( G m). This RB-induced G m increase was prevented by 1 mM diphenylamine-2-carboxylate (DPC) and by a low Na+concentration in the bath. We conclude that RB, t-BHP, and X/XO enhance NH[Formula: see text] influx into the oocyte via activation of a DPC-sensitive nonselective cation conductance pathway.

Amentoflavone: A Bifunctional Metal Chelator that Controls the Formation of Neurotoxic Soluble Aβ42 Oligomers

2020 ◽  
Author(s):  
Liang Sun ◽  
Anuj K. Sharma ◽  
Byung-Hee Han ◽  
Liviu M. Mirica
Keyword(s):  
Reactive Oxygen Species ◽  
Metal Ions ◽  
Antioxidant Properties ◽  
Reactive Oxygen ◽  
Amyloid Plaques ◽  
Transition Metal Ions ◽  
Oxygen Species ◽  
High Affinity ◽  
Amyloid Aβ ◽  
Β Amyloid

<p>Alzheimer's disease (AD) is the most common neurodegenerative disorder, yet the cause and progression of this disorder are not completely understood. While the main hallmark of AD is the deposition of amyloid plaques consisting of the β-amyloid (Aβ) peptide, transition metal ions are also known to play a significant role in disease pathology by expediting the formation of neurotoxic soluble β-amyloid (Aβ) oligomers, reactive oxygen species (ROS), and oxidative stress. Thus, bifunctional metal chelators that can control these deleterious properties are highly desirable. Herein, we show that amentoflavone (AMF) – a natural biflavonoid compound, exhibits good metal-chelating properties, especially for chelating Cu<sup>2+</sup> with very high affinity (pCu<sub>7.4</sub> = 10.44). In addition, AMF binds to Aβ fibrils with a high affinity (<i>K<sub>i</sub></i> = 287 ± 20 nM) – as revealed by a competition thioflavin T (ThT) assay, and specifically labels the amyloid plaques <i>ex vivo</i> in the brain sections of transgenic AD mice – as confirmed via immunostaining with an Ab antibody. The effect of AMF on Aβ<sub>42</sub> aggregation and disaggregation of Aβ<sub>42</sub> fibrils was also investigated, to reveal that AMF can control the formation of neurotoxic soluble Aβ<sub>42</sub> oligomers, both in absence and presence of metal ions, and as confirmed via cell toxicity studies. Furthermore, an ascorbate consumption assay shows that AMF exhibits potent antioxidant properties and can chelate Cu<sup>2+</sup> and significantly diminish the Cu<sup>2+</sup>-ascorbate redox cycling and reactive oxygen species (ROS) formation. Overall, these studies strongly suggest that AMF acts as a bifunctional chelator that can interact with various Aβ aggregates and reduce their neurotoxicity, can also bind Cu<sup>2+</sup> and mediate its deleterious redox properties, and thus AMF has the potential to be a lead compound for further therapeutic agent development for AD. </p>

scholarly journals Implication of the small GTPase Rac1 in the generation of reactive oxygen species in response to β-amyloid in C6 astroglioma cells

2002 ◽  
Vol 366 (3) ◽  
pp. 937-943 ◽  
Author(s):  
Mina LEE ◽  
Hye-Jin YOU ◽  
Sung-Hoon CHO ◽  
Chang-Hoon WOO ◽  
Min-Hyuk YOO ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Reactive Oxygen ◽  
Leukotriene B4 ◽  
Small Gtpase ◽  
Cell Surface Receptor ◽  
Oxygen Species ◽  
Exogenous Application ◽  
Essential Components ◽  
Β Amyloid ◽  
Astroglioma Cells

Exogenous application of β-amyloid (Aβ25—35, a fragment of Aβ1—42) significantly elevated levels of reactive oxygen species (ROS) in C6 astroglioma cells, as measured by confocal microscopic analysis of H2O2-sensitive 2′,7′-dichlorofluorescin fluorescence. Subsequent characterization of the signalling pathway revealed that expression of RacN17, a dominant-negative Rac1 mutant, completely blocked Aβ25—35-induced generation of ROS, which is indicative of the crucial role played by Rac GTPase in this process. To better understand the downstream mediators affected by Rac, we assessed the degree to which inhibition of cytosolic phospholipase A2 (cPLA2) and 5-lipoxygenase (5-LO) contributed to the response and found that inhibition of either enzyme completely blocked Aβ25—35-induced ROS generation, indicating its dependence on arachidonic acid synthesis and metabolism to leukotrienes (e.g. leukotriene B4). Consistent with those findings, Aβ25—35 Rac-dependently stimulated translocation of 5-LO to the nuclear envelope and increased intracellular levels of leukotriene B4, while exogenous application of leukotriene B4 increased intracellular H2O2 via BLT, its cell-surface receptor. In addition to the aforementioned downstream mediators, inhibition of phosphoinositide 3-kinase (PI 3-kinase), an enzyme situated upstream of Rac, also completely blocked Aβ25—35-induced H2O2 generation. Our findings thus demonstrate that PI 3-kinase, Rac, cPLA2 and 5-LO are all essential components of the β-amyloid signaling cascade leading to generation of ROS.

Activation of a Ca 2+ -dependent cation conductance with properties of TRPM2 by reactive oxygen species in lens epithelial cells

2017 ◽  
Vol 161 ◽  
pp. 61-70 ◽  
Author(s):  
Susanne Keckeis ◽  
Laura Wernecke ◽  
Daniel J. Salchow ◽  
Nadine Reichhart ◽  
Olaf Strauß
Keyword(s):  
Reactive Oxygen Species ◽  
Epithelial Cells ◽  
Reactive Oxygen ◽  
Lens Epithelial Cells ◽  
Oxygen Species ◽  
Cation Conductance

scholarly journals Manganoporphyrin-Polyphenol Multilayer Capsules as Radical and Reactive Oxygen Species (ROS) Scavengers

2018 ◽  
Vol 30 (2) ◽  
pp. 344-357 ◽  
Author(s):  
Aaron Alford ◽  
Veronika Kozlovskaya ◽  
Bing Xue ◽  
Nirzari Gupta ◽  
William Higgins ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Ros Scavengers

scholarly journals Reactive Oxygen Species-Mediated Pancreatic β-Cell Death Is Regulated by Interactions between Stress-Activated Protein Kinases, p38 and c-Jun N-Terminal Kinase, and Mitogen-Activated Protein Kinase Phosphatases

Endocrinology ◽  
2008 ◽  
Vol 149 (4) ◽  
pp. 1654-1665 ◽  
Author(s):  
Ni Hou ◽  
Seiji Torii ◽  
Naoya Saito ◽  
Masahiro Hosaka ◽  
Toshiyuki Takeuchi
Keyword(s):  
Reactive Oxygen Species ◽  
Cell Death ◽  
Protein Kinases ◽  
Reactive Oxygen ◽  
Mitogen Activated Protein Kinase ◽  
Oxygen Species ◽  
Β Cell ◽  
Min6 Cell ◽  
Jnk Activation ◽  
Ros Scavengers

Pancreatic β-cells are susceptible to reactive oxygen species (ROS), which are known to be generated by high or low glucose (LG), hypoxic, or cytokine-producing conditions. When we cultured mouse β-cell-derived MIN6 cells in a LG condition, we detected a significant generation of ROS, including hydrogen peroxide, which was comparable to the ROS production in hypoxic or cytokine-treated conditions. ROS accumulation induced by the LG culture led to cell death, which was prevented by the ROS scavengers N-acetylcysteine and manganese(III)tetrakis(4-benzoic acid) porphyrin. We next investigated the mechanism of stress-activated protein kinases (SAPKs), c-jun N-terminal kinase (JNK) and p38, in ROS-induced MIN6 cell death. Activation of p38 occurred immediately after the LG culture, whereas JNK activation increased slowly 8 h later. Adenoviral p38 expression decreased MIN6 cell death, whereas the JNK expression increased it. Consistently, blocking p38 activation by inhibitors increased β-cell death, whereas JNK inhibitors decreased it. We then examined the role of MAPK phosphatases (MKPs) specific for stress-activated protein kinases in β-cell death. We found that MKP-1 presented an increase in its oxidized product after the LG culture. ROS scavengers prevented the appearance of this oxidized product and JNK activation. Thus, ROS-induced MKP inactivation causes sustained activation of JNK, which contributes to β-cell death. Adenoviral overexpression of MKP-1 and MKP-7 prevented the phosphorylation of JNK at 36 h after the LG culture, and decreased MIN6 β-cell death. We suggest that β-cell death is regulated by interactions between JNK and its specific MKPs.

scholarly journals β-Amyloid Fibrils in Alzheimer Disease Are Not Inert When Bound to Copper Ions but Can Degrade Hydrogen Peroxide and Generate Reactive Oxygen Species

2014 ◽  
Vol 289 (17) ◽  
pp. 12052-12062 ◽  
Author(s):  
Jennifer Mayes ◽  
Claire Tinker-Mill ◽  
Oleg Kolosov ◽  
Hao Zhang ◽  
Brian J. Tabner ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Hydrogen Peroxide ◽  
Alzheimer Disease ◽  
Amyloid Fibrils ◽  
Copper Ions ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Β Amyloid
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