Journal articles: 'Oxygen channels'

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Kemp, Paul J., and Chris Peers. "Oxygen sensing by ion channels." Essays in Biochemistry 43 (August 10, 2007): 77–90. http://dx.doi.org/10.1042/bse0430077.

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The ability to sense and react to changes in environmental oxygen levels is crucial to the survival of all aerobic life forms. In mammals, specialized tissues have evolved which can sense and rapidly respond to an acute reduction in oxygen and central to this ability in many is dynamic modulation of ion channels by hypoxia. The most widely studied oxygen-sensitive ion channels are potassium channels but oxygen sensing by members of both the calcium and sodium channel families has also been demonstrated. This chapter will focus on mechanisms of physiological oxygen sensing by ion channels, with particular emphasis on potassium channel function, and will highlight some of the consensuses and controversies within the field. Where data are available, this chapter will also make use of information gleaned from heterologous expression of recombinant proteins in an attempt to consolidate what we know currently about the molecular mechanisms of acute oxygen sensing by ion channels.

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Prentice, Howard M., Sarah L. Milton, Daniela Scheurle, and Peter L. Lutz. "Gene transcription of brain voltage-gated potassium channels is reversibly regulated by oxygen supply." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 285, no. 6 (December 2003): R1317—R1321. http://dx.doi.org/10.1152/ajpregu.00261.2003.

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Voltage-dependent potassium channels (Kv channels) are important determinants of brain electrical activity. Hypoxia may be an important modifier, because several voltage-gated K+ channels are reversibly blocked by acute hypoxia and are thought to act as oxygen sensors. Here we show, using the anoxia-tolerant turtle brain ( Trachemys scripta) as a model, that brain Kv1 channel transcription is reversibly regulated by oxygen supply. We found that in turtle brains exposed to 4-h anoxia Kv1 transcripts were reduced to 18.5% of normoxic levels. Kv1 channel mRNA levels were restored to normal within 4 h of subsequent reoxygenation. Our results provide clear evidence that brain Kv channel expression is sensitive to oxygen supply and indicate an important mechanism that matches brain activity to oxygen supply.

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Peers, C. "Oxygen-sensitive ion channels." Trends in Pharmacological Sciences 18, no. 11 (November 1, 1997): 405–8. http://dx.doi.org/10.1016/s0165-6147(97)01120-6.

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Peers, Chris. "Oxygen-sensitive ion channels." Trends in Pharmacological Sciences 18, no. 4 (July 1997): 405–8. http://dx.doi.org/10.1016/s0165-6147(97)90669-6.

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Ganfornina, M. D., and J. López-Barneo. "Potassium channel types in arterial chemoreceptor cells and their selective modulation by oxygen." Journal of General Physiology 100, no. 3 (September 1, 1992): 401–26. http://dx.doi.org/10.1085/jgp.100.3.401.

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Single K+ channel currents were recorded in excised membrane patches from dispersed chemoreceptor cells of the rabbit carotid body under conditions that abolish current flow through Na+ and Ca2+ channels. We have found three classes of voltage-gated K+ channels that differ in their single-channel conductance (gamma), dependence on internal Ca2+ (Ca2+i), and sensitivity to changes in O2 tension (PO2). Ca(2+)-activated K+ channels (KCa channels) with gamma approximately 210 pS in symmetrical K+ solutions were observed when [Ca2+]i was greater than 0.1 microM. Small conductance channels with gamma = 16 pS were not affected by [Ca2+]i and they exhibited slow activation and inactivation time courses. In these two channel types open probability (P(open)) was unaffected when exposed to normoxic (PO2 = 140 mmHg) or hypoxic (PO2 approximately 5-10 mmHg) external solutions. A third channel type (referred to as KO2 channel), having an intermediate gamma(approximately 40 pS), was the most frequently recorded. KO2 channels are steeply voltage dependent and not affected by [Ca2+]i, they inactivate almost completely in less than 500 ms, and their P(open) reversibly decreases upon exposure to low PO2. The effect of low PO2 is voltage dependent, being more pronounced at moderately depolarized voltages. At 0 mV, for example, P(open) diminishes to approximately 40% of the control value. The time course of ensemble current averages of KO2 channels is remarkably similar to that of the O2-sensitive K+ current. In addition, ensemble average and macroscopic K+ currents are affected similarly by low PO2. These observations strongly suggest that KO2 channels are the main contributors to the macroscopic K+ current of glomus cells. The reversible inhibition of KO2 channel activity by low PO2 does not desensitize and is not related to the presence of F-, ATP, and GTP-gamma-S at the internal face of the membrane. These results indicate that KO2 channels confer upon glomus cells their unique chemoreceptor properties and that the O2-K+ channel interaction occurs either directly or through an O2 sensor intrinsic to the plasma membrane closely associated with the channel molecule.

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Chung, Chin Ming, Ching Huei Lin, and Che Wei Lin. "COMSOL Simulations for Flow Channels of Low-Temperature Fuel Cell." Advanced Materials Research 343-344 (September 2011): 261–66. http://dx.doi.org/10.4028/www.scientific.net/amr.343-344.261.

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A multiple physical finite elements to analyze software (COMSOL Multiphysics) is employed to investigate serpentine flow channels of a small proton exchange membrane fuel cell with power 0.5W. Distributions of the oxygen flow, the liquid water, and the electric current density in three different designed flow channels are simulated and compared. Results show that increasing the channel width is conducive to increase the oxygen flow and reduce the production of liquid water. It thus enhances the electric current density. However, it will reduce the oxygen flow, produce more liquid water, and depress the current density if the channel width is decreased.

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Soto, Marco A., Carlos González, Eduardo Lissi, Cecilia Vergara, and Ramón Latorre. "Ca2+-activated K+ channel inhibition by reactive oxygen species." American Journal of Physiology-Cell Physiology 282, no. 3 (March 1, 2002): C461—C471. http://dx.doi.org/10.1152/ajpcell.00167.2001.

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We studied the effect of H2O2 on the gating behavior of large-conductance Ca2+-sensitive voltage-dependent K+ (KV,Ca) channels. We recorded potassium currents from single skeletal muscle channels incorporated into bilayers or using macropatches of Xenopus laevisoocytes membranes expressing the human Slowpoke(h Slo) α-subunit. Exposure of the intracellular side of KV,Ca channels to H2O2 (4–23 mM) leads to a time-dependent decrease of the open probability ( P o) without affecting the unitary conductance. H2O2 did not affect channel activity when added to the extracellular side. These results provide evidence for an intracellular site(s) of H2O2 action. Desferrioxamine (60 μM) and cysteine (1 mM) completely inhibited the effect of H2O2, indicating that the decrease in P o was mediated by hydroxyl radicals. The reducing agent dithiothreitol (DTT) could not fully reverse the effect of H2O2. However, DTT did completely reverse the decrease in P o induced by the oxidizing agent 5,5′-dithio-bis-(2-nitrobenzoic acid). The incomplete recovery of KV,Ca channel activity promoted by DTT suggests that H2O2 treatment must be modifying other amino acid residues, e.g., as methionine or tryptophan, besides cysteine. Noise analysis of macroscopic currents in Xenopus oocytes expressing h Slo channels showed that H2O2 induced a decrease in current mediated by a decrease both in the number of active channels and P o.

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8

Kim, Donghee. "Oxygen sensing with ion channels." Channels 8, no. 4 (July 2014): 290–91. http://dx.doi.org/10.4161/chan.29966.

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López-Barneo, Jóse, Patricia Ortega-Sáenz, Antonio Molina, Alfredo Franco-Obregón, Juan Ureña, and Antonio Castellano. "Oxygen sensing by ion channels." Kidney International 51, no. 2 (February 1997): 454–61. http://dx.doi.org/10.1038/ki.1997.61.

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Ivanov, I. I., A. V. Loktyushkin, R. A. Gus’kova, N. S. Vasil’ev, G. E. Fedorov, and A. B. Rubin. "Oxygen channels of erythrocyte membrane." Doklady Biochemistry and Biophysics 414, no. 1 (June 2007): 137–40. http://dx.doi.org/10.1134/s160767290703012x.

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11

Matalon, Sadis, Karin M. Hardiman, Lucky Jain, Douglas C. Eaton, Michael Kotlikoff, Jerry P. Eu, Junhui Sun, Gerhard Meissner, and Jonathan S. Stamler. "Regulation of ion channel structure and function by reactive oxygen-nitrogen species." American Journal of Physiology-Lung Cellular and Molecular Physiology 285, no. 6 (December 2003): L1184—L1189. http://dx.doi.org/10.1152/ajplung.00281.2003.

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Ion channels subserve diverse cellular functions. Reactive oxygen and nitrogen species modulate ion channel function by a number of mechanisms including 1) transcriptional regulation of gene expression, 2) posttranslational modifications of channel proteins, i.e. nitrosylation, nitration, and oxidation of key amino acid residues, 3) by altering the gain in other signaling pathways that may in turn lead to changes in channel activity or channel gene expression, and 4) by modulating trafficking or turnover of channel proteins, as typified by oxygen radical activation of NF-kB, with subsequent changes in proteasomal degradation of channel degradation. Regardless of the mechanism, as was discussed in a symposium at the 2003 Experimental Biology Meeting in San Diego, CA, changes in the cellular level of reactive oxygen and nitrogen species can have profound effects on the activity of ion channels and cellular function.

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Walewska, Agnieszka, Adam Szewczyk, and Piotr Koprowski. "Gas Signaling Molecules and Mitochondrial Potassium Channels." International Journal of Molecular Sciences 19, no. 10 (October 18, 2018): 3227. http://dx.doi.org/10.3390/ijms19103227.

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Recently, gaseous signaling molecules, such as carbon monoxide (CO), nitric oxide (NO), and hydrogen sulfide (H2S), which were previously considered to be highly toxic, have been of increasing interest due to their beneficial effects at low concentrations. These so-called gasotransmitters affect many cellular processes, such as apoptosis, proliferation, cytoprotection, oxygen sensing, ATP synthesis, and cellular respiration. It is thought that mitochondria, specifically their respiratory complexes, constitute an important target for these gases. On the other hand, increasing evidence of a cytoprotective role for mitochondrial potassium channels provides motivation for the analysis of the role of gasotransmitters in the regulation of channel function. A number of potassium channels have been shown to exhibit activity within the inner mitochondrial membrane, including ATP-sensitive potassium channels, Ca2+-activated potassium channels, voltage-gated Kv potassium channels, and TWIK-related acid-sensitive K+ channel 3 (TASK-3). The effects of these channels include the regulation of mitochondrial respiration and membrane potential. Additionally, they may modulate the synthesis of reactive oxygen species within mitochondria. The opening of mitochondrial potassium channels is believed to induce cytoprotection, while channel inhibition may facilitate cell death. The molecular mechanisms underlying the action of gasotransmitters are complex. In this review, we focus on the molecular mechanisms underlying the action of H2S, NO, and CO on potassium channels present within mitochondria.

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13

Gao, Weihua, Zhuocheng Su, Qinglian Liu, and Lei Zhou. "State-dependent and site-directed photodynamic transformation of HCN2 channel by singlet oxygen." Journal of General Physiology 143, no. 5 (April 14, 2014): 633–44. http://dx.doi.org/10.1085/jgp.201311112.

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Singlet oxygen (1O2), which is generated through metabolic reactions and oxidizes numerous biological molecules, has been a useful tool in basic research and clinical practice. However, its role as a signaling factor, as well as a mechanistic understanding of the oxidation process, remains poorly understood. Here, we show that hyperpolarization-activated, cAMP-gated (HCN) channels–which conduct the hyperpolarization-activated current (Ih) and the voltage-insensitive instantaneous current (Iinst), and contribute to diverse physiological functions including learning and memory, cardiac pacemaking, and the sensation of pain–are subject to modification by 1O2. To increase the site specificity of 1O2 generation, we used fluorescein-conjugated cAMP, which specifically binds to HCN channels, or a chimeric channel in which an in-frame 1O2 generator (SOG) protein was fused to the HCN C terminus. Millisecond laser pulses reduced Ih current amplitude, slowed channel deactivation, and enhanced Iinst current. The modification of HCN channel function is a photodynamic process that involves 1O2, as supported by the dependence on dissolved oxygen in solutions, the inhibitory effect by a 1O2 scavenger, and the results with the HCN2-SOG fusion protein. Intriguingly, 1O2 modification of the HCN2 channel is state dependent: laser pulses applied to open channels mainly slow down deactivation and increase Iinst, whereas for the closed channels, 1O2 modification mainly reduced Ih amplitude. We identified a histidine residue (H434 in S6) near the activation gate in the pore critical for 1O2 modulation of HCN function. Alanine replacement of H434 abolished the delay in channel deactivation and the generation of Iinst induced by photodynamic modification. Our study provides new insights into the instantaneous current conducted by HCN channels, showing that modifications to the region close to the intracellular gate underlie the expression of Iinst, and establishes a well-defined model for studying 1O2 modifications at the molecular level.

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Han, Bo, Tursonjan Tokay, Guangming Zhang, Peng Sun, and Shangwei Hou. "Eag1 K+Channel: Endogenous Regulation and Functions in Nervous System." Oxidative Medicine and Cellular Longevity 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/7371010.

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Ether-à-go-go1 (Eag1, Kv10.1, KCNH1) K+channel is a member of the voltage-gated K+channel family mainly distributed in the central nervous system and cancer cells. Like other types of voltage-gated K+channels, the EAG1 channels are regulated by a variety of endogenous signals including reactive oxygen species, rendering the EAG1 to be in the redox-regulated ion channel family. The role of EAG1 channels in tumor development and its therapeutic significance have been well established. Meanwhile, the importance of hEAG1 channels in the nervous system is now increasingly appreciated. The present review will focus on the recent progress on the channel regulation by endogenous signals and the potential functions of EAG1 channels in normal neuronal signaling as well as neurological diseases.

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15

Reeve, H. L., E. Michelakis, D. P. Nelson, E. K. Weir, and S. L. Archer. "Alterations in a redox oxygen sensing mechanism in chronic hypoxia." Journal of Applied Physiology 90, no. 6 (June 1, 2001): 2249–56. http://dx.doi.org/10.1152/jappl.2001.90.6.2249.

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The mechanism of acute hypoxic pulmonary vasoconstriction (HPV) may involve the inhibition of several voltage-gated K+channels in pulmonary artery smooth muscle cells. Changes in Po 2 can either be sensed directly by the channel(s) or be transmitted to the channel via a redox-based effector mechanism. In control lungs, hypoxia and rotenone acutely decrease production of activated oxygen species, inhibit K+channels, and cause constriction. Two-day and 3-wk chronic hypoxia (CH) resulted in a decrease in basal activated oxygen species levels, an increase in reduced glutathione, and loss of HPV and rotenone-induced constriction. In contrast, 4-aminopyridine- and KCl-mediated constrictions were preserved. After 3-wk CH, pulmonary arterial smooth muscle cell membrane potential was depolarized, K+ channel density was reduced, and acute hypoxic inhibition of whole cell K+ current was lost. In addition, Kv1.5 and Kv2.1 channel protein was decreased. These data suggest that chronic reduction of the cytosol occurs before changes in K+ channel expression. HPV may be attenuated in CH because of an impaired redox sensor.

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Urrestarazu, Miguel, Pilar Carolina Mazuela, Abdelaziz Boukhalfa, Antonia Arán, and María del Carmen Salas. "Oxygen Content and its Diurnal Variation in a New Recirculanting Water Soilless Culture for Horticultural Crops." HortScience 40, no. 6 (October 2005): 1729–30. http://dx.doi.org/10.21273/hortsci.40.6.1729.

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Based on a new structure for plastic culture channels, a new system for soilless culture called New Growing Systems (NGS) has been developed. It is similar to the nutrient film technique (NFT) but with several potential advantages. Each NGS growing channel has five plastic layers and a large number of holes, there is a dripper every 0.5 m above the first layer of plastic, and each dripper supplies the nutrient solution which flows from the second layer over the others to the end. Three separate greenhouse experiments with tomato, cucumber, and sweet pepper using NGS channels were conducted in Almería (southeastern Spain). The oxygen content in the circulating nutrient solutions was determined at different points and different times along the channels of all crops. Depletion of oxygen content in the nutrient solution was lower than NFT channels. Oxygen content in NGS showed some advantages compared to NFT.

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Numaga-Tomita, Takuro, and Motohiro Nishida. "TRPC Channels in Cardiac Plasticity." Cells 9, no. 2 (February 17, 2020): 454. http://dx.doi.org/10.3390/cells9020454.

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The heart flexibly changes its structure in response to changing environments and oxygen/nutrition demands of the body. Increased and decreased mechanical loading induces hypertrophy and atrophy of cardiomyocytes, respectively. In physiological conditions, these structural changes of the heart are reversible. However, chronic stresses such as hypertension or cancer cachexia cause irreversible remodeling of the heart, leading to heart failure. Accumulating evidence indicates that calcium dyshomeostasis and aberrant reactive oxygen species production cause pathological heart remodeling. Canonical transient receptor potential (TRPC) is a nonselective cation channel subfamily whose multimodal activation or modulation of channel activity play important roles in a plethora of cellular physiology. Roles of TRPC channels in cardiac physiology have been reported in pathological cardiac remodeling. In this review, we summarize recent findings regarding the importance of TRPC channels in flexible cardiac remodeling (i.e., cardiac plasticity) in response to environmental stresses and discuss questions that should be addressed in the near future.

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Stephan, Huber. "Editorial: Ion Channels of Mature Human Erythrocytes." Open Biology Journal 4, no. 1 (January 31, 2011): 1–2. http://dx.doi.org/10.2174/18750362010040100001.

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Ion channels in the plasma membrane serve multiple functions such as setting the membrane potential, adjusting the cell volume and the intracellular electrolyte concentrations or eliciting versatile cytosolic Ca2+ signals. Channel activities regulate many basic cellular processes. Among those are cell proliferation, migration, differentiation and apoptotic cell death. Although devoid of nuclei and mitochondria, mature mammalian erythrocytes maintain a full set of functional ion channels in their plasma membrane. This special issue of The Open Biology Journal focuses on ion channels in the membrane of mature human erythrocytes, their regulation and their putative functions. Mature human erythrocytes travel about 100 miles and circulate more than 100.000 times through the body during their normal life span of 120 ± 4 days. The most obvious task thereby is the transport of blood oxygen and carbon dioxide as well as buffering of the pH in the blood. These functions depend on carboanhydrase, hemoglobin and band 3 anion exchanger. The latter two are the most abundant proteins in the erythrocyte cytosol and membrane, respectively. Because of this high abundance of hemoglobin which accounts for 98% of the cytosol protein content and because of the substantial absence of intracellular organelles, mature human erythrocytes are commonly simplified to hemoglobincontaining sacks. In sharp contrast to this view, increasing numbers of proteins are identified in mature human erythrocytes. Among those are proteins that build up signaling cascades. Outside-in signaling via membrane receptors such as purinergic receptors, as well as inside-out signaling via release of, e.g., ATP has been reported (see the article of Duranton et al. in this special issue). Moreover, intracellular signaling molecules such as protein kinases, have been unequivocally demonstrated to be functional suggesting that mature human erythrocytes are endowed with complex signaling similar to nucleated cells. As an example, circulating erythrocytes are cellular sensors of the oxygen tension and mechanical stress. Decline in oxygen partial pressure results in release of ATP regulated, presumably, through Gs protein, adenylcyclase and protein kinase Adependent activation of the ABC transporter CFTR. The released ATP, in turn, triggers vessel dilatation via formation of nitric oxide by the endothelium. Nitric oxide also negatively feeds back to the erythrocyte where it down-regulates ATP release. Hence, by releasing ATP at decreased oxygen pressure erythrocytes adapt the microcirculation to the oxygen consumption. In addition to ATP release, signaling via adenylcyclase and protein kinase A activates a CFTR-associated anion channel in mature erythrocytes (reviewed by Bouyer et al. in this special issue). Moreover, mature human erythrocytes activate organic osmolyte and anion channels via ATP release and autocrine purinergic signaling which is reminiscent of the activation of osmolyte channels in nucleated cells upon cell swelling (reviewed by Duranton et al. in this special issue). This indicates that mature human erythrocytes functionally express ion channel-regulating pathways similar if not identical to those implemented in nucleated cells. Erythrocyte ion channels are also involved in sensing cellular stress. Shumilina and Huber report in this special issue that cellular stress such as oxidative stress activates ClC-2, a further type of anion channel in the erythrocyte membrane which participates in the cellular stress response. Being largely silent under resting conditions, erythrocyte channels may build up membrane conductances in the nS range upon various signals (such as oxidative stress). A strong activator of erythrocyte ion channel activity is the intraerythrocytic amplification of the malaria parasite Plasmodium falciparum. Accordingly, most of what we know about the electrophysiology of ClC-2, the CFTR-associated anion channel, and the organic osmolyte and anion channel in human erythrocytes came from whole-cell and single-channel recording in Plasmodium-infected cells. The data on ClC-2, the CFTR-associated channel and the osmolyte channel are discussed in this special issue by the articles of Shumilina and Huber, Bouyer et al., and Duranton et al., respectively. The fourth article in this special issue, the article of Lars Kästner, summarizes our current knowledge about the cation channels in erythrocytes. Mature human erythrocytes express KCa3.1 (Gardos) K+ channels, different types of nonselective cation channels including TRPC6 and NMDA receptors. In addition circumstantial evidence hints to the expression of the voltage-gated Ca2+ channel CaV2.1 in human erythrocytes. Besides the comprehensive catalogue of the erythrocyte channel types, the article of Lars Käster gives a rewarding compendium about the history of channel research in human erythrocytes. Taken together, this special issue provides an overview of the unexpected diversity of erythrocyte ion channels that endows these small enucleated cells with a toolkit for electrosignaling. This toolkit enables erythrocytes to quickly respond to internal or external stimuli with changes in cytosolic free Ca2+, de- or hyperpolarization of the membrane, cell swelling or shrinkage, or release of channel-permeable solutes such as ATP. Moreover, the ion channels are integral modules of complex programs such as oxygen-regulated ATP release. Malaria is one example how such programs are exploited by the parasite, to adapt the erythrocyte cytosol to its needs.

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Fedorova, Irina, Roman Zdorovennov, Galina Zdorovennova, and Aleksei Aksenov. "Ice-covering hydrological and hydrochemical investigations on the Lena River delta." E3S Web of Conferences 163 (2020): 05003. http://dx.doi.org/10.1051/e3sconf/202016305003.

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The study reported here was conducted on the channels of the Lena River delta in April 2019. The water temperature, specific conductivity, dissolved oxygen, PAR fluxes, and currents were measured on the cross-sections in the Olenekskaya and Bykovskaya channels, as well as in the main channel of the Lena River near Samoilov Island using the multiparameter probes CTD-48M, CTD-90M and RBR-Concerto. An analysis of the data showed that the water in the channels of the Lena River delta in winter is well saturated with oxygen (4.9-6.3 ml/l), has a very low temperature (from -0.1°C to +0.8°C). The specific conductivity of water Lena River delta channels changed from 460 to 530 )S/cm. A thick layer of snow 0.1-0.5 m with an ice thickness of more than 1.5 m prevents the penetration of solar radiation into the subglacial layer, where the PAR fluxes does not exceed 10 µmol/m2s. Current velocities reached 20–25 cm/s in the Bykovskaya channel, in Olenekskaya channel – 5-11 cm/s, and in the main channel – 12-18 cm/s. The currents data obtained made it possible to calculate the discharge in the channels during the ice-period.

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Mori, Yasuo, Nobuaki Takahashi, Nozomi Ogawa, and Thomas Gudermann. "Oxygen physiology: sensors and ion channels." Pflügers Archiv - European Journal of Physiology 468, no. 1 (November 21, 2015): 1–2. http://dx.doi.org/10.1007/s00424-015-1762-9.

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Detweiler, Neil D., Li Song, Samantha J. McClenahan, Rachel J. Versluis, Sujay V. Kharade, Richard C. Kurten, Sung W. Rhee, and Nancy J. Rusch. "BK Channels in Rat and Human Pulmonary Smooth Muscle Cells are BKα-β1 Functional Complexes Lacking the Oxygen-Sensitive Stress Axis Regulated Exon Insert." Pulmonary Circulation 6, no. 4 (December 2016): 563–75. http://dx.doi.org/10.1086/688838.

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A loss of K+ efflux in pulmonary arterial smooth muscle cells (PASMCs) contributes to abnormal vasoconstriction and PASMC proliferation during pulmonary hypertension (PH). Activation of high-conductance Ca2+-activated (BK) channels represents a therapeutic strategy to restore K+ efflux to the affected PASMCs. However, the properties of BK channels in PASMCs—including sensitivity to BK channel openers (BKCOs)—are poorly defined. The goal of this study was to compare the properties of BK channels between PASMCs of normoxic (N) and chronic hypoxic (CH) rats and then explore key findings in human PASMCs. Polymerase chain reaction results revealed that 94.3% of transcripts encoding BKα pore proteins in PASMCs from N rats represent splice variants lacking the stress axis regulated exon insert, which confers oxygen sensitivity. Subsequent patch-clamp recordings from inside-out (I-O) patches confirmed a dense population of BK channels insensitive to hypoxia. The BK channels were highly activated by intracellular Ca2+ and the BKCO lithocholate; these responses require BK α-β1 subunit coupling. PASMCs of CH rats with established PH exhibited a profound overabundance of the dominant oxygen-insensitive BKα variant. Importantly, human BK (hBK) channels in PASMCs from human donor lungs also represented the oxygen-insensitive BKα variant activated by BKCOs. The hBK channels showed significantly enhanced Ca2+ sensitivity compared with rat BK channels. We conclude that rat BK and hBK channels in PASMCs are oxygen-insensitive BK α-β1 complexes highly sensitive to Ca2+ and the BKCO lithocholate. BK channels are overexpressed in PASMCs of a rat model of PH and may provide an abundant target for BKCOs designed to restore K+ efflux.

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Chu, Qi, Jingmeng Li, Sila Jin, Shuang Guo, Eungyeong Park, Jiku Wang, Lei Chen, and Young Mee Jung. "Charge-Transfer Induced by the Oxygen Vacancy Defects in the Ag/MoO3 Composite System." Nanomaterials 11, no. 5 (May 14, 2021): 1292. http://dx.doi.org/10.3390/nano11051292.

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In this paper, an Ag/MoO3 composite system was cosputtered by Ar plasma bombardment on a polystyrene (PS) colloidal microsphere array. The MoO3 formed by this method contained abundant oxygen vacancy defects, which provided a channel for charge transfer in the system and compensated for the wide band gap of MoO3. Various characterization methods strongly demonstrated the existence of oxygen vacancy defects and detected the properties of oxygen vacancies. 4-Aminothiophenol (p-aminothiophenol, PATP) was used as a candidate surface-enhanced Raman scattering (SERS) probe molecule to evaluate the contribution of the oxygen vacancy defects in the Ag/MoO3 composite system. Interestingly, oxygen vacancy defects are a kind of charge channel, and their powerful effect is fully reflected in their SERS spectra. Increasing the number of charge channels and increasing the utilization rate of the channels caused the frequency of SERS characteristic peaks to shift. This interesting phenomenon opens up a new horizon for the study of SERS in oxygen-containing semiconductors and provides a powerful reference for the study of PATP.

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Reiss, Krystle, Uriel Morzan, Alex Grigas, and Victor Batista. "Water Network Dynamics Next to the Oxygen-Evolving Complex of Photosystem II." Inorganics 7, no. 3 (March 11, 2019): 39. http://dx.doi.org/10.3390/inorganics7030039.

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The influence of the environment on the functionality of the oxygen-evolving complex (OEC) of photosystem II has long been a subject of great interest. In particular, various water channels, which could serve as pathways for substrate water diffusion, or proton translocation, are thought to be critical to catalytic performance of the OEC. Here, we address the dynamical nature of hydrogen bonding along the water channels by performing molecular dynamics (MD) simulations of the OEC and its surrounding protein environment in the S1 and S2 states. Through the eigenvector centrality (EC) analysis, we are able to determine the characteristics of the water network and assign potential functions to the major channels, namely that the narrow and broad channels are likely candidates for proton/water transport, while the large channel may serve as a path for larger ions such as chloride and manganese thought to be essential during PSII assembly.

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Idikuda, Vinay, Weihua Gao, Khade Grant, Zhuocheng Su, Qinglian Liu, and Lei Zhou. "Singlet oxygen modification abolishes voltage-dependent inactivation of the sea urchin spHCN channel." Journal of General Physiology 150, no. 9 (July 24, 2018): 1273–86. http://dx.doi.org/10.1085/jgp.201711961.

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Photochemically or metabolically generated singlet oxygen (1O2) reacts broadly with macromolecules in the cell. Because of its short lifetime and working distance, 1O2 holds potential as an effective and precise nanoscale tool for basic research and clinical practice. Here we investigate the modification of the spHCN channel that results from photochemically and chemically generated 1O2. The spHCN channel shows strong voltage-dependent inactivation in the absence of cAMP. In the presence of photosensitizers, short laser pulses transform the gating properties of spHCN by abolishing inactivation and increasing the macroscopic current amplitude. Alanine replacement of a histidine residue near the activation gate within the channel’s pore abolishes key modification effects. Application of a variety of chemicals including 1O2 scavengers and 1O2 generators supports the involvement of 1O2 and excludes other reactive oxygen species. This study provides new understanding about the photodynamic modification of ion channels by 1O2 at the molecular level.

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López-Barneo, José, Raquel del Toro, Konstantin L. Levitsky, María D. Chiara, and Patricia Ortega-Sáenz. "Regulation of oxygen sensing by ion channels." Journal of Applied Physiology 96, no. 3 (March 2004): 1187–95. http://dx.doi.org/10.1152/japplphysiol.00929.2003.

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O2 sensing is of critical importance for cell survival and adaptation of living organisms to changing environments or physiological conditions. O2-sensitive ion channels are major effectors of the cellular responses to hypoxia. These channels are preferentially found in excitable neurosecretory cells (glomus cells of the carotid body, cells in the neuroepithelial bodies of the lung, and neonatal adrenal chromaffin cells), which mediate fast cardiorespiratory adjustments to hypoxia. O2-sensitive channels are also expressed in the pulmonary and systemic arterial smooth muscle cells where they participate in the vasomotor responses to low O2 tension (particularly in hypoxic pulmonary vasoconstriction). The mechanisms underlying O2 sensing and how the O2 sensors interact with the ion channels remain unknown. Recent advances in the field give different support to the various current hypotheses. Besides the participation of ion channels in acute O2 sensing, they also contribute to the gene program developed under chronic hypoxia. Gene expression of T-type calcium channels is upregulated by hypoxia through the same hypoxiainducible factor-dependent signaling pathway utilized by the classical O2-regulated genes. Alteration of acute or chronic O2 sensing by ion channels could participate in the pathophysiology of human diseases, such as sudden infant death syndrome or primary pulmonary hypertension.

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Ortega-Sáenz, Patricia, Alberto Pascual, Raquel Gómez-Díaz, and José López-Barneo. "Acute Oxygen Sensing in Heme Oxygenase-2 Null Mice." Journal of General Physiology 128, no. 4 (September 11, 2006): 405–11. http://dx.doi.org/10.1085/jgp.200609591.

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Hemeoxygenase-2 (HO-2) is an antioxidant enzyme that can modulate recombinant maxi-K+ channels and has been proposed to be the acute O2 sensor in the carotid body (CB). We have tested the physiological contribution of this enzyme to O2 sensing using HO-2 null mice. HO-2 deficiency leads to a CB phenotype characterized by organ growth and alteration in the expression of stress-dependent genes, including the maxi-K+ channel α-subunit. However, sensitivity to hypoxia of CB is remarkably similar in HO-2 null animals and their control littermates. Moreover, the response to hypoxia in mouse and rat CB cells was maintained after blockade of maxi-K+ channels with iberiotoxin. Hypoxia responsiveness of the adrenal medulla (AM) (another acutely responding O2-sensitive organ) was also unaltered by HO-2 deficiency. Our data suggest that redox disregulation resulting from HO-2 deficiency affects maxi-K+ channel gene expression but it does not alter the intrinsic O2 sensitivity of CB or AM cells. Therefore, HO-2 is not a universally used acute O2 sensor.

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Gu, Yao Xin, and Hong Chao Qiao. "Study on the Manufacturing Process of Polymer Microfluidic Chip with Integrated Cu Micro Array Electrode." Applied Mechanics and Materials 723 (January 2015): 884–87. http://dx.doi.org/10.4028/www.scientific.net/amm.723.884.

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To produce perfect polymer microfluidic chip with integrated metal micro array electrode, an oxygen-plasma assisted manufacturing process was developed. The Cu micro array electrodes on the poly substrate was formed by photolithography, sputtering and wet etching; the micro channels on the polymer plate were hot-embossed using metal master; the bonding of cover plate and substrate using thermal bonding. The surface of the polymer plate with micro channels was treated by oxygen-plasma before thermal bonding. The oxygen-plasma treatment could decrease thermal bonding temperature from 100 °C to 85 °C. The bonding of this chip is complete, the micro electrode array keeps its integrity, and the micro channel is not distorted obviously.

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Patel, A. J., and E. Honoré. "Molecular physiology of oxygen-sensitive potassium channels." European Respiratory Journal 18, no. 1 (July 1, 2001): 221–27. http://dx.doi.org/10.1183/09031936.01.00204001.

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Kemp, Paul J., Vsevolod Telezhkin, William J. Wilkinson, Ruth Mears, Stuart B. Hanmer, Hanne C. Gadeberg, Carsten T. Müller, Daniela Riccardi, and Stephen P. Brazier. "Enzyme-Linked Oxygen Sensing by Potassium Channels." Annals of the New York Academy of Sciences 1177, no. 1 (October 2009): 112–18. http://dx.doi.org/10.1111/j.1749-6632.2009.05025.x.

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Malinska, Dominika, Sandra R. Mirandola, and Wolfram S. Kunz. "Mitochondrial potassium channels and reactive oxygen species." FEBS Letters 584, no. 10 (January 16, 2010): 2043–48. http://dx.doi.org/10.1016/j.febslet.2010.01.013.

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Numata, Tomohiro, Nozomi Ogawa, Nobuaki Takahashi, and Yasuo Mori. "TRP channels as sensors of oxygen availability." Pflügers Archiv - European Journal of Physiology 465, no. 8 (February 17, 2013): 1075–85. http://dx.doi.org/10.1007/s00424-013-1237-9.

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Pramana, Stevin S., Wim T. Klooster, and T. J. White. "Framework `interstitial' oxygen in La10(GeO4)5(GeO5)O2 apatite electrolyte." Acta Crystallographica Section B Structural Science 63, no. 4 (July 17, 2007): 597–602. http://dx.doi.org/10.1107/s0108768107024317.

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Oxygen conduction at low temperatures in apatites make these materials potentially useful as electrolytes in solid-oxide fuel cells, but our understanding of the defect structures enabling ion migration is incomplete. While conduction along [001] channels is dominant, considerable inter-tunnel mobility has been recognized. Using neutron powder diffraction of stoichiometric `La10(GeO4)6O3', it has been shown that this compound is more correctly described as an La10(GeO4)5(GeO5)O2 apatite, in which high concentrations of interstitial oxygen reside within the channel walls. It is suggested that these framework interstitial O atoms provide a reservoir of ions that can migrate into the conducting channels of apatite, via a mechanism of inter-tunnel oxygen diffusion that transiently converts GeO4 tetrahedra to GeO5 distorted trigonal bipyramids. This structural modification is consistent with known crystal chemistry and may occur generally in oxide apatites.

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33

Kourie, Joseph I. "Interaction of reactive oxygen species with ion transport mechanisms." American Journal of Physiology-Cell Physiology 275, no. 1 (July 1, 1998): C1—C24. http://dx.doi.org/10.1152/ajpcell.1998.275.1.c1.

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The use of electrophysiological and molecular biology techniques has shed light on reactive oxygen species (ROS)-induced impairment of surface and internal membranes that control cellular signaling. These deleterious effects of ROS are due to their interaction with various ion transport proteins underlying the transmembrane signal transduction, namely, 1) ion channels, such as Ca2+ channels (including voltage-sensitive L-type Ca2+currents, dihydropyridine receptor voltage sensors, ryanodine receptor Ca2+-release channels, andd- myo-inositol 1,4,5-trisphosphate receptor Ca2+-release channels), K+ channels (such as Ca2+-activated K+ channels, inward and outward K+ currents, and ATP-sensitive K+ channels), Na+ channels, and Cl− channels; 2) ion pumps, such as sarcoplasmic reticulum and sarcolemmal Ca2+pumps, Na+-K+-ATPase (Na+ pump), and H+-ATPase (H+ pump); 3) ion exchangers such as the Na+/Ca2+exchanger and Na+/H+exchanger; and 4) ion cotransporters such as K+-Cl−, Na+-K+-Cl−, and Pi-Na+cotransporters. The mechanism of ROS-induced modifications in ion transport pathways involves 1) oxidation of sulfhydryl groups located on the ion transport proteins, 2) peroxidation of membrane phospholipids, and 3) inhibition of membrane-bound regulatory enzymes and modification of the oxidative phosphorylation and ATP levels. Alterations in the ion transport mechanisms lead to changes in a second messenger system, primarily Ca2+ homeostasis, which further augment the abnormal electrical activity and distortion of signal transduction, causing cell dysfunction, which underlies pathological conditions.

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DeCoursey, Thomas E. "Voltage-Gated Proton Channels Find Their Dream Job Managing the Respiratory Burst in Phagocytes." Physiology 25, no. 1 (February 2010): 27–40. http://dx.doi.org/10.1152/physiol.00039.2009.

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The voltage-gated proton channel bears surprising resemblance to the voltage-sensing domain (S1–S4) of other voltage-gated ion channels but is a dimer with two conduction pathways. The proton channel seems designed for efficient proton extrusion from cells. In phagocytes, it facilitates the production of reactive oxygen species by NADPH oxidase.

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Kicinska, Anna, Bartlomiej Augustynek, Bogusz Kulawiak, Wieslawa Jarmuszkiewicz, Adam Szewczyk, and Piotr Bednarczyk. "A large-conductance calcium-regulated K+ channel in human dermal fibroblast mitochondria." Biochemical Journal 473, no. 23 (November 25, 2016): 4457–71. http://dx.doi.org/10.1042/bcj20160732.

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Potassium channels have been found in the inner mitochondrial membrane of various cells. These channels regulate the mitochondrial membrane potential, respiration and production of reactive oxygen species. In the present study, we identified the activity of a mitochondrial large-conductance Ca2+-regulated potassium channel (mitoBKCa channel) in mitoplasts isolated from a primary human dermal fibroblast cell line. A potassium selective current was recorded with a mean conductance of 280 ± 2 pS in a symmetrical 150 mM KCl solution. The mitoBKCa channel was activated by the Ca2+ and by potassium channel opener NS1619. The channel activity was irreversibly inhibited by paxilline, a selective inhibitor of the BKCa channels. In isolated fibroblast mitochondria NS1619 depolarized the mitochondrial membrane potential, stimulated nonphosphorylating respiration and decreased superoxide formation. Additionally, the α- and β-subunits (predominantly the β3-form) of the BKCa channels were identified in fibroblast mitochondria. Our findings indicate, for the first time, the presence of a large-conductance Ca2+-regulated potassium channel in the inner mitochondrial membrane of human dermal fibroblasts.

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Bao, Hui-Fang, John Z. Song, Billie J. Duke, He-Ping Ma, Donald D. Denson, and Douglas C. Eaton. "Ethanol stimulates epithelial sodium channels by elevating reactive oxygen species." American Journal of Physiology-Cell Physiology 303, no. 11 (December 1, 2012): C1129—C1138. http://dx.doi.org/10.1152/ajpcell.00139.2012.

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Alcohol affects total body sodium balance, but the molecular mechanism of its effect remains unclear. We used single-channel methods to examine how ethanol affects epithelial sodium channels (ENaC) in A6 distal nephron cells. The data showed that ethanol significantly increased both ENaC open probability ( Po) and the number of active ENaC in patches ( N). 1-Propanol and 1-butanol also increased ENaC activity, but iso-alcohols did not. The effects of ethanol were mimicked by acetaldehyde, the first metabolic product of ethanol, but not by acetone, the metabolic product of 2-propanol. Besides increasing open probability and apparent density of active channels, confocal microscopy and surface biotinylation showed that ethanol significantly increased α-ENaC protein in the apical membrane. The effects of ethanol on ENaC Po and N were abolished by a superoxide scavenger, 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy (TEMPOL) and blocked by the phosphatidylinositol 3-kinase inhibitor LY294002. Consistent with an effect of ethanol-induced reactive oxygen species (ROS) on ENaC, primary alcohols and acetaldehyde elevated intracellular ROS, but secondary alcohols did not. Taken together with our previous finding that ROS stimulate ENaC, the current results suggest that ethanol stimulates ENaC by elevating intracellular ROS probably via its metabolic product acetaldehyde.

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Demidchik, Vadim, and Sergey Shabala. "Mechanisms of cytosolic calcium elevation in plants: the role of ion channels, calcium extrusion systems and NADPH oxidase-mediated 'ROS-Ca2+ Hub'." Functional Plant Biology 45, no. 2 (2018): 9. http://dx.doi.org/10.1071/fp16420.

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Elevation in the cytosolic free calcium is crucial for plant growth, development and adaptation. Calcium influx into plant cells is mediated by Ca2+ depolarisation-activated, hyperpolarisation-activated and voltage-independent Ca2+-permeable channels (DACCs, HACCs and VICCs respectively). These channels are encoded by the following gene families: (1) cyclic nucleotide-gated channels (CNGCs), (2) ionotropic glutamate receptors (GLRs), (3) annexins, (4) ‘mechanosensitive channels of small (MscS) conductance’-like channels (MSLs), (5) ‘mid1-complementing activity’ channels (MCAs), Piezo channels, and hyperosmolality-induced [Ca2+]cyt. channel 1 (OSCA1). Also, a ‘tandem-pore channel1’ (TPC1) catalyses Ca2+ efflux from the vacuole in response to the plasma membrane-mediated Ca2+ elevation. Recent experimental data demonstrated that Arabidopsis thaliana (L.) Heynh. CNGCs 2, 5–10, 14, 16 and 18, GLRs 1.2, 3.3, 3.4, 3.6 and 3.7, TPC1, ANNEXIN1, MSL9 and MSL10,MCA1 and MCA2, OSCA1, and some their homologues counterparts in other species, are responsible for Ca2+ currents and/or cytosolic Ca2+ elevation. Extrusion of Ca2+ from the cytosol is mediated by Ca2+-ATPases and Ca2+/H+ exchangers which were recently examined at the level of high resolution crystal structure. Calcium-activated NADPH oxidases and reactive oxygen species (ROS)-activated Ca2+ conductances form a self-amplifying ‘ROS-Ca2+hub’, enhancing and transducing Ca2+ and redox signals. The ROS-Ca2+ hub contributes to physiological reactions controlled by ROS and Ca2+, demonstrating synergism and unity of Ca2+ and ROS signalling mechanisms.

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Williams, Beatrice A., and Keith J. Buckler. "Biophysical properties and metabolic regulation of a TASK-like potassium channel in rat carotid body type 1 cells." American Journal of Physiology-Lung Cellular and Molecular Physiology 286, no. 1 (January 2004): L221—L230. http://dx.doi.org/10.1152/ajplung.00010.2003.

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The single channel properties of TASK-like oxygen-sensitive potassium channels were studied in rat carotid body type 1 cells. We observed channels with rapid bursting kinetics, active at resting membrane potentials. These channels were highly potassium selective with a slope conductance of 14–16 pS, values similar to those reported for TASK-1. In the absence of extracellular divalent cations, however, single channel conductance increased to 28 pS in a manner similar to that reported for TASK-3. After patch excision, channel activity ran down rapidly. Channel activity in inside-out patches was markedly increased by 2 and 5 mM ATP and by 2 mM ADP but not by 100 μM ADP or 1 mM AMP. In cell-attached patches, both cyanide and 2,4-dinitrophenol strongly inhibited channel activity. We conclude that 1) whilst the properties of this channel are consistent with it being a TASK-like potassium channel they do not precisely conform to those of either TASK-1 or TASK-3, 2) channel activity is highly dependent on cytosolic factors including ATP, and 3) changes in energy metabolism may play a role in regulating the activity of these background K+ channels.

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39

López-Pozos, Roberto, Gabino Alberto Martínez-Gutiérrez, Rafael Pérez-Pacheco, and Miguel Urrestarazu. "The Effects of Slope and Channel Nutrient Solution Gap Number on the Yield of Tomato Crops by a Nutrient Film Technique System under a Warm Climate." HortScience 46, no. 5 (May 2011): 727–29. http://dx.doi.org/10.21273/hortsci.46.5.727.

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Inadequate oxygenation of the nutrient solution (NS) in recirculating hydroponic systems leads to root hypoxia in several plants as a result of low oxygen solubility, and this is most notable in warm climates. Hypoxia affects crop nutrient and water absorption and results in reduced crop yield. However, increased air supply to the NS serves as a source of oxygen for the roots. To evaluate the incorporation of oxygen into the system, we varied the slope of 14-m long containers from 2% to 4% and applied zero, one, two, or three gaps of NS. The channel width measured 10 cm and was equidistant from the end points. The effect of the dissolved oxygen in the NS was measured by the production of a tomato cultivar. The oxygen dissolved in the NS was 5% greater in the channels with a 4% slope compared with those with a 2% slope. The channels that included the gaps incorporated a higher quantity of dissolved oxygen during cultivation. In the middle of the day, the available oxygen was the limiting factor for the yield. The best results were obtained with a steeper slope, and gaps also improved the tomato yield. More rapid changes in NS were associated with a higher quantity of dissolved oxygen.

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40

Sasaki, Mari, Akihiro Tojo, Yoshifumi Okochi, Nana Miyawaki, Daisuke Kamimura, Akihito Yamaguchi, Masaaki Murakami, and Yasushi Okamura. "Autoimmune disorder phenotypes in Hvcn1-deficient mice." Biochemical Journal 450, no. 2 (February 15, 2013): 295–301. http://dx.doi.org/10.1042/bj20121188.

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Hv channels (voltage-gated proton channels) are expressed in blood cells, microglia and some types of epithelial cells. In neutrophils Hv channels regulate the production of reactive oxygen species through regulation of membrane potential and intracellular pH. Hv channels have also been suggested to play a role in sperm physiology in the human. However, the functions of the Hv channel at the whole-body level are not fully understood. In the present paper we show that Hvcn1 (voltage-gated hydrogen channel 1)-knockout mice show splenomegaly, autoantibodies and nephritis, that are reminiscent of human autoimmune diseases phenotypes. The number of activated T-cells was larger in Hvcn1-deficient mice than in the wild-type mice. Upon viral infection this was remarkably enhanced in Hvcn1-deficient mice. The production of superoxide anion in T-cells upon stimulation with PMA was significantly attenuated in the Hvcn1-deficient mice. These results suggest that Hv channels regulate T-cell homoeostasis in vivo.

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41

Adebiyi, Adebowale, Elizabeth M. McNally, and Jonathan H. Jaggar. "Vasodilation induced by oxygen/glucose deprivation is attenuated in cerebral arteries of SUR2 null mice." American Journal of Physiology-Heart and Circulatory Physiology 301, no. 4 (October 2011): H1360—H1368. http://dx.doi.org/10.1152/ajpheart.00406.2011.

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Physiological functions of arterial smooth muscle cell ATP-sensitive K+ (KATP) channels, which are composed of inwardly rectifying K+ channel 6.1 and sulfonylurea receptor (SUR)-2 subunits, during metabolic inhibition are unresolved. In the present study, we used a genetic model to investigate the physiological functions of SUR2-containing KATP channels in mediating vasodilation to hypoxia, oxygen and glucose deprivation (OGD) or metabolic inhibition, and functional recovery following these insults. Data indicate that SUR2B is the only SUR isoform expressed in murine cerebral artery smooth muscle cells. Pressurized SUR2 wild-type (SUR2wt) and SUR2 null (SUR2nl) mouse cerebral arteries developed similar levels of myogenic tone and dilated similarly to hypoxia (<10 mmHg Po2). In contrast, vasodilation induced by pinacidil, a KATP channel opener, was ∼71% smaller in SUR2nl arteries. Human cerebral arteries also expressed SUR2B, developed myogenic tone, and dilated in response to hypoxia and pinacidil. OGD, oligomycin B (a mitochondrial ATP synthase blocker), and CCCP (a mitochondrial uncoupler) all induced vasodilations that were ∼39–61% smaller in SUR2nl than in SUR2wt arteries. The restoration of oxygen and glucose following OGD or removal of oligomycin B and CCCP resulted in partial recovery of tone in both SUR2wt and SUR2nl cerebral arteries. However, SURnl arteries regained ∼60–82% more tone than did SUR2wt arteries. These data indicate that SUR2-containing KATP channels are functional molecular targets for OGD, but not hypoxic, vasodilation in cerebral arteries. In addition, OGD activation of SUR2-containing KATP channels may contribute to postischemic loss of myogenic tone.

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42

Zhang, Qiang, and Zhenhai Yao. "Flumazenil preconditions cardiomyocytes via oxygen radicals and KATP channels." American Journal of Physiology-Heart and Circulatory Physiology 279, no. 4 (October 1, 2000): H1858—H1863. http://dx.doi.org/10.1152/ajpheart.2000.279.4.h1858.

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We determined whether flumazenil mimics ischemic preconditioning in chick cardiomyocytes and examined the role of intracellular reactive oxygen species (ROS) and ATP-dependent potassium (KATP) channels in mediating the effect. Chick ventricular myocytes were perfused with a balanced salt solution in a flow-through chamber. Cell viability was quantified using propidium iodide, and ROS generation was assessed using the reduced form of 2′,7′-dichlorofluorescin (DCFH). Cells were exposed to 1 h of simulated ischemia and 3 h of reoxygenation. Preconditioning was initiated with 10 min of ischemia followed by 10 min of reoxygenation. Alternatively, flumazenil was added to the perfusate for 10 min and removed 10 min before the start of ischemia. Flumazenil (1 and 10 μM) and preconditioning reduced cell death [54 ± 5%, n = 3; 26 ± 4%, n = 6 ( P < 0.05); and 20 ± 2%, n = 6 (P < 0.05), respectively, vs. 57 ± 7%, n = 10, in controls] and increased DCFH oxidation (an index of ROS production) [0.35 ± 0.11, n = 3; 2.64 ± 0.69, n = 8 ( P < 0.05); and 2.46 ± 0.52, n = 6 ( P< 0.05), respectively, vs. 0.26 ± 0.05, n = 9, in controls]. Protection and increased ROS signals with flumazenil (10 μM) were abolished with the thiol reductant N-(2-mercaptopropionyl)-glycine (2-MPG, 800 μM), an antioxidant (cell death: 2-MPG + flumazenil, 55 ± 12%, n = 6; ROS signals: 2-MPG + flumazenil, 0.11 ± 0.19, n = 6). Treatment with 5-hydroxydecanoate (1 mM), a selective mitochondrial KATP channel antagonist, abolished its protection. These results demonstrate that flumazenil mimics preconditioning to reduce cell death in myocytes. ROS signals with the resultant mitochondrial KATP channel activation are important components of the intracellular signaling pathway of flumazenil.

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Firth, Amy L., Kathryn H. Yuill, and Sergey V. Smirnov. "Mitochondria-dependent regulation of Kv currents in rat pulmonary artery smooth muscle cells." American Journal of Physiology-Lung Cellular and Molecular Physiology 295, no. 1 (July 2008): L61—L70. http://dx.doi.org/10.1152/ajplung.90243.2008.

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Voltage-gated K+ (Kv) channels are important in the regulation of pulmonary vascular function having both physiological and pathophysiological implications. The pulmonary vasculature is essential for reoxygenation of the blood, supplying oxygen for cellular respiration. Mitochondria have been proposed as the major oxygen-sensing organelles in the pulmonary vasculature. Using electrophysiological techniques and immunofluorescence, an interaction of the mitochondria with Kv channels was investigated. Inhibitors, blocking the mitochondrial electron transport chain at different complexes, were shown to have a dual effect on Kv currents in freshly isolated rat pulmonary arterial smooth muscle cells (PASMCs). These dual effects comprised an enhancement of Kv current in a negative potential range (manifested as a 5- to 14-mV shift in the Kv activation to more negative membrane voltages) with a decrease in current amplitude at positive potentials. Such effects were most prominent as a result of inhibition of Complex III by antimycin A. Investigation of the mechanism of antimycin A-mediated effects on Kv channel currents ( IKv) revealed the presence of a mitochondria-mediated Mg2+ and ATP-dependent regulation of Kv channels in PASMCs, which exists in addition to that currently proposed to be caused by changes in intracellular reactive oxygen species.

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Wareing, Mark, Xilian Bai, Fella Seghier, Claire M. Turner, Susan L. Greenwood, Philip N. Baker, Michael J. Taggart, and Gregor K. Fyfe. "Expression and function of potassium channels in the human placental vasculature." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 291, no. 2 (August 2006): R437—R446. http://dx.doi.org/10.1152/ajpregu.00040.2006.

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In the placental vasculature, where oxygenation may be an important regulator of vascular reactivity, there is a paucity of data on the expression of potassium (K) channels, which are important mediators of vascular smooth muscle tone. We therefore addressed the expression and function of several K channel subtypes in human placentas. The expression of voltage-gated (Kv)2.1, KV9.3, large-conductance Ca2+-activated K channel (BKCa), inward-rectified K+ channel (KIR)6.1, and two-pore domain inwardly rectifying potassium channel-related acid-sensitive K channels (TASK)1 in chorionic plate arteries, veins, and placental homogenate was assessed by RT-PCR and Western blot analysis. Functional activity of K channels was assessed pharmacologically in small chorionic plate arteries and veins by wire myography using 4-aminopyridine, iberiotoxin, pinacidil, and anandamide. Experiments were performed at 20, 7, and 2% oxygen to assess the effect of oxygenation on the efficacy of K channel modulators. KV2.1, KV9.3, BKCa, KIR6.1, and TASK1 channels were all demonstrated to be expressed at the message level. KV2.1, BKCa, KIR6.1, and TASK1 were all demonstrated at the protein level. Pharmacological manipulation of voltage-gated and ATP-sensitive channels produced the most marked modifications in vascular tone, in both arteries and veins. We conclude that K channels play an important role in controlling placental vascular function.

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Chen, Yingjie, Jay H. Traverse, Jianyi Zhang, and Robert J. Bache. "Selective blockade of mitochondrial KATPchannels does not impair myocardial oxygen consumption." American Journal of Physiology-Heart and Circulatory Physiology 281, no. 2 (August 1, 2001): H738—H744. http://dx.doi.org/10.1152/ajpheart.2001.281.2.h738.

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Opening of mitochondrial ATP-sensitive potassium (KATP) channels has been postulated to prevent inhibition of respiration resulting from matrix contraction during high rates of ATP synthesis. Glibenclamide, which blocks KATP channels on the sarcolemma of vascular smooth muscle cells and myocardial myocytes as well as on the inner mitochondrial membrane, results in a decrease of myocardial oxygen consumption (MV˙o 2) both at rest and during exercise. This study examined whether this represents a primary effect of blockade of mitochondrial KATP channels or occurs secondary to coronary resistance vessel constriction with a decrease of coronary blood flow (CBF) and myocardial oxygen availability. MV˙o 2 was measured at rest and during treadmill exercise in 10 dogs during control conditions, after selective mitochondrial KATP channel blockade with 5-hydroxydecanoate (5-HD), and after nonselective KATPchannel blockade with glibenclamide. During control conditions, exercise resulted in progressive increases of CBF and MV˙o 2. Glibenclamide (50 μg · kg−1 · min−1 ic) resulted in a 17 ± 6% decrease of resting CBF with a downward shift of CBF during exercise and a decrease of coronary venous Po 2, indicating increased myocardial oxygen extraction. In contrast with the effects of glibenclamide, 5-HD (0.7 mg · kg−1 · min−1 ic) had no effect on CBF, MV˙o 2, or myocardial oxygen extraction. These findings suggest that glibenclamide decreased MV˙o 2 by causing resistance vessel constriction with a decrease of CBF and oxygen available to the myocardium rather than to a primary reduction of mitochondrial respiration.

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López-López, José Ramón, and M. Teresa Pérez-García. "Oxygen sensitive Kv channels in the carotid body." Respiratory Physiology & Neurobiology 157, no. 1 (July 2007): 65–74. http://dx.doi.org/10.1016/j.resp.2007.01.022.

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Yang, Shih-Hsien, Che-Yi Lin, Yuan-Ming Chang, Mengjiao Li, Ko-Chun Lee, Ciao-Fen Chen, Feng-Shou Yang, et al. "Oxygen-Sensitive Layered MoTe2 Channels for Environmental Detection." ACS Applied Materials & Interfaces 11, no. 50 (November 20, 2019): 47047–53. http://dx.doi.org/10.1021/acsami.9b15036.

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48

Valenzeno, Dennis P. "OXYGEN REGULATION OF ION CHANNELS AND GENE EXPRESSION." Shock 11, no. 1 (January 1999): 76. http://dx.doi.org/10.1097/00024382-199901000-00017.

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49

Gonzalez, Constancio, Luis M. Vaquero, José Ramón López-López, and M. Teresa Pérez-García. "Oxygen-Sensitive Potassium Channels in Chemoreceptor Cell Physiology." Annals of the New York Academy of Sciences 1177, no. 1 (October 2009): 82–88. http://dx.doi.org/10.1111/j.1749-6632.2009.05037.x.

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50

Abman, S. H. "Oxygen sensing, potassium channels, and the ductus arteriosus." Journal of Clinical Investigation 98, no. 9 (November 1, 1996): 1945–46. http://dx.doi.org/10.1172/jci118995.

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Journal articles on the topic 'Oxygen channels'

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