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Canella R, Benedusi M, Vallese A, Pecorelli A, Guiotto A, Ferrara F, Rispoli G, Cervellati F, Valacchi G. The role of potassium current in the pulmonary response to environmental oxidative stress. Arch Biochem Biophys 2023; 737:109534. [PMID: 36740034 DOI: 10.1016/j.abb.2023.109534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 11/30/2022] [Accepted: 01/24/2023] [Indexed: 02/05/2023]
Abstract
Exposure of human lung epithelial cells (A549 cell line) to the oxidant pollutant ozone (O3) alters cell membrane currents inducing its decrease, when the cell undergoes to a voltage-clamp protocol ranging from -90 to +70mV. The membrane potential of these cells is mainly maintained by the interplay of potassium and chloride currents. Our previous studies indicated the ability of O3 to activate ORCC (Outward Rectifier Chloride Channel) and consequently increases the chloride current. In this paper our aim was to understand the response of potassium current to oxidative stress challenge and to identify the kind potassium channel involved in O3 induced current changes. After measuring the total membrane current using an intracellular solution with or without potassium ions, we obtained the contribution of potassium to the overall membrane current in control condition by a mathematical approach. Repeating these experiments after O3 treatment we observed a significant decrease of Ipotassium. Treatment of the cells with Iberiotoxin (IbTx), a specific inhibitor of BK channel, we were able to verify the presence and the functionality of BK channels. In addition, the administration of 4-Aminopyridine (an inhibitor of voltage dependent K channels but not BK channels) and Tetraethylammonium (TEA) before and after O3 treatment we observed the formation of BK oxidative post-translation modifications. Our data suggest that O3 is able to inhibit potassium current by targeting BK channel. Further studies are needed to better clarify the role of this BK channel and its interplay with the other membrane channels under oxidative stress conditions. These findings can contribute to identify the biomolecular pathway induced by O3 allowing a possible pharmacological intervention against oxidative stress damage in lung tissue.
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Affiliation(s)
- Rita Canella
- Department of Neuroscience and Rehabilitation, University of Ferrara, Via L. Borsari, 46, Ferrara, Italy.
| | - Mascia Benedusi
- Department of Neuroscience and Rehabilitation, University of Ferrara, Via L. Borsari, 46, Ferrara, Italy
| | - Andrea Vallese
- Department of Environmental Sciences and Prevention, University of Ferrara, Via L. Borsari, 46, Ferrara, Italy
| | - Alessandra Pecorelli
- Department of Environmental Sciences and Prevention, University of Ferrara, Via L. Borsari, 46, Ferrara, Italy
| | - Anna Guiotto
- Department of Environmental Sciences and Prevention, University of Ferrara, Via L. Borsari, 46, Ferrara, Italy
| | - Francesca Ferrara
- Department of Chemical, Pharmaceutical and Agricultural Sciences, University of Ferrara, Via L. Borsari, 46, Ferrara, Italy
| | - Giorgio Rispoli
- Department of Neuroscience and Rehabilitation, University of Ferrara, Via L. Borsari, 46, Ferrara, Italy
| | - Franco Cervellati
- Department of Neuroscience and Rehabilitation, University of Ferrara, Via L. Borsari, 46, Ferrara, Italy
| | - Giuseppe Valacchi
- Department of Environmental Sciences and Prevention, University of Ferrara, Via L. Borsari, 46, Ferrara, Italy; NC State University, Plants for Human Health Institute, Animal Science Dept. NC Research Campus 600 Laureate Way, Kannapolis, NC, 28081, USA; Department of Food and Nutrition, Kyung Hee University, Seoul, South Korea.
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2
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Hannemann J, Böger R. Dysregulation of the Nitric Oxide/Dimethylarginine Pathway in Hypoxic Pulmonary Vasoconstriction—Molecular Mechanisms and Clinical Significance. Front Med (Lausanne) 2022; 9:835481. [PMID: 35252268 PMCID: PMC8891573 DOI: 10.3389/fmed.2022.835481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 01/27/2022] [Indexed: 12/21/2022] Open
Abstract
The pulmonary circulation responds to hypoxia with vasoconstriction, a mechanism that helps to adapt to short-lived hypoxic episodes. When sustained, hypoxic pulmonary vasoconstriction (HPV) may become deleterious, causing right ventricular hypertrophy and failure, and contributing to morbidity and mortality in the late stages of several chronic pulmonary diseases. Nitric oxide (NO) is an important endothelial vasodilator. Its release is regulated, amongst other mechanisms, by the presence of endogenous inhibitors like asymmetric dimethylarginine (ADMA). Evidence has accumulated in recent years that elevated ADMA may be implicated in the pathogenesis of HPV and in its clinical sequelae, like pulmonary arterial hypertension (PAH). PAH is one phenotypic trait in experimental models with disrupted ADMA metabolism. In high altitude, elevation of ADMA occurs during long-term exposure to chronic or chronic intermittent hypobaric hypoxia; ADMA is significantly associated with high altitude pulmonary hypertension. High ADMA concentration was also reported in patients with chronic obstructive lung disease, obstructive sleep apnoea syndrome, and overlap syndrome, suggesting a pathophysiological role for ADMA-mediated impairment of endothelium-dependent, NO-mediated pulmonary vasodilation in these clinically relevant conditions. Improved understanding of the molecular (dys-)regulation of pathways controlling ADMA concentration may help to dissect the pathophysiology and find novel therapeutic options for these diseases.
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Affiliation(s)
- Juliane Hannemann
- Institute of Clinical Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Institute DECIPHER, German-Chilean Institute for Research on Pulmonary Hypoxia and its Health Sequelae, Hamburg, Germany
| | - Rainer Böger
- Institute of Clinical Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Institute DECIPHER, German-Chilean Institute for Research on Pulmonary Hypoxia and its Health Sequelae, Hamburg, Germany
- *Correspondence: Rainer Böger
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3
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Cui X, Chen W, Zhou H, Gong Y, Zhu B, Lv X, Guo H, Duan J, Zhou J, Marcon E, Ma H. Pulmonary Edema in COVID-19 Patients: Mechanisms and Treatment Potential. Front Pharmacol 2021; 12:664349. [PMID: 34163357 PMCID: PMC8215379 DOI: 10.3389/fphar.2021.664349] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 05/25/2021] [Indexed: 12/19/2022] Open
Abstract
COVID-19 mortality is primarily driven by abnormal alveolar fluid metabolism of the lung, leading to fluid accumulation in the alveolar airspace. This condition is generally referred to as pulmonary edema and is a direct consequence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. There are multiple potential mechanisms leading to pulmonary edema in severe Coronavirus Disease (COVID-19) patients and understanding of those mechanisms may enable proper management of this condition. Here, we provide a perspective on abnormal lung humoral metabolism of pulmonary edema in COVID-19 patients, review the mechanisms by which pulmonary edema may be induced in COVID-19 patients, and propose putative drug targets that may be of use in treating COVID-19. Among the currently pursued therapeutic strategies against COVID-19, little attention has been paid to abnormal lung humoral metabolism. Perplexingly, successful balance of lung humoral metabolism may lead to the reduction of the number of COVID-19 death limiting the possibility of healthcare services with insufficient capacity to provide ventilator-assisted respiration.
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Affiliation(s)
- Xinyu Cui
- Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, and Jiangsu Key Laboratory for High Technology Research of TCM Formulae, College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Wuyue Chen
- Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, and Jiangsu Key Laboratory for High Technology Research of TCM Formulae, College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Haoyan Zhou
- Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, and Jiangsu Key Laboratory for High Technology Research of TCM Formulae, College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Yuan Gong
- Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, and Jiangsu Key Laboratory for High Technology Research of TCM Formulae, College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Bowen Zhu
- Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, and Jiangsu Key Laboratory for High Technology Research of TCM Formulae, College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Xiang Lv
- Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, and Jiangsu Key Laboratory for High Technology Research of TCM Formulae, College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Hongbo Guo
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, Canada
| | - Jinao Duan
- Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, and Jiangsu Key Laboratory for High Technology Research of TCM Formulae, College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Jing Zhou
- Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, and Jiangsu Key Laboratory for High Technology Research of TCM Formulae, College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
| | - Edyta Marcon
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON, Canada
| | - Hongyue Ma
- Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, and Jiangsu Key Laboratory for High Technology Research of TCM Formulae, College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, China
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4
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Scruggs AM, Grabauskas G, Huang SK. The Role of KCNMB1 and BK Channels in Myofibroblast Differentiation and Pulmonary Fibrosis. Am J Respir Cell Mol Biol 2020; 62:191-203. [PMID: 31486669 DOI: 10.1165/rcmb.2019-0163oc] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The differentiation of fibroblasts into myofibroblasts is critical for the development of fibrotic disorders, including idiopathic pulmonary fibrosis (IPF). Previously, we demonstrated that fibroblasts from patients with IPF exhibit changes in DNA methylation across the genome that contribute to a profibrotic phenotype. One of the top differentially methylated genes identified in our previous study was KCNMB1, which codes for the β subunit of the large-conductance potassium (BK, also known as MaxiK or KCa1.1) channel. Here, we examined how the expression of KCNMB1 differed between IPF fibroblasts and normal cells, and how BK channels affected myofibroblast differentiation. Fibroblasts from patients with IPF exhibited increased expression of KCNMB1, which corresponded to increased DNA methylation within the gene body. Patch-clamp experiments demonstrated that IPF fibroblasts had increased BK channel activity. Knockdown of KCNMB1 attenuated the ability of fibroblasts to contract collagen gels, and this was associated with a loss of α-smooth muscle actin (SMA) expression. Pharmacologic activation of BK channels stimulated α-SMA expression, whereas BK channel inhibitors blocked the upregulation of α-SMA. The ability of BK channels to enhance α-SMA expression was dependent on intracellular calcium, as activation of BK channels resulted in increased levels of intracellular calcium and the effects of BK agonists were abolished when calcium was removed. Together, our findings demonstrate that epigenetic upregulation of KCNMB1 contributes to increased BK channel activity in IPF fibroblasts, and identify a newfound role for BK channels in myofibroblast differentiation.
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Affiliation(s)
| | - Gintautas Grabauskas
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan
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5
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Canella R, Martini M, Cavicchio C, Cervellati F, Benedusi M, Valacchi G. Involvement of the TREK-1 channel in human alveolar cell membrane potential and its regulation by inhibitors of the chloride current. J Cell Physiol 2019; 234:17704-17713. [PMID: 30805940 DOI: 10.1002/jcp.28396] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2018] [Revised: 01/03/2019] [Accepted: 01/10/2019] [Indexed: 12/14/2022]
Abstract
K+ channels of the alveolar epithelium control the driving force acting on the ionic and solvent flow through the cell membrane contributing to the maintenance of cell volume and the constitution of epithelial lining fluid. In the present work, we analyze the effect of the Cl- channel inhibitors: (4-[(2-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-inden-5-yl)oxy] butanoic acid (DCPIB) and 9-anthracenecarboxylic acid (9-AC) on the total current in a type II pneumocytes (A549 cell line) model by patch clamp, immunocytochemical, and gene knockdown techniques. We noted that DCPIB and 9-AC promote the activation of K conductance. In fact, they significantly increase the intensity of the current and shift its reversal potential to values more negative than the control. By silencing outward rectifier channel in its anoctamin 6 portion, we excluded a direct involvement of Cl- ions in modulation of IK and, by means of functional tests with its specific inhibitor spadin, we identified the TREK-1 channel as the presumable target of both drugs. As the activity of TREK-1 has a key role for the correct functioning of the alveolar epithelium, the identification of DCPIB and 9-AC molecules as its activators suggests their possible use to build new pharmacological tools for the modulation of this channel.
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Affiliation(s)
- Rita Canella
- Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara, Italy
| | - Marta Martini
- Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara, Italy
| | - Carlotta Cavicchio
- Animal Science Department, Plants for Human Health Institute, NC State University, Kannapolis, North Carolina
| | - Franco Cervellati
- Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara, Italy
| | - Mascia Benedusi
- Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara, Italy
| | - Giuseppe Valacchi
- Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara, Italy.,Animal Science Department, Plants for Human Health Institute, NC State University, Kannapolis, North Carolina
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6
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Abstract
Mucociliary clearance is critically important in protecting the airways from infection and from the harmful effects of smoke and various inspired substances known to induce oxidative stress and persistent inflammation. An essential feature of the clearance mechanism involves regulation of the periciliary liquid layer on the surface of the airway epithelium, which is necessary for normal ciliary beating and maintenance of mucus hydration. The underlying ion transport processes associated with airway surface hydration include epithelial Na+ channel-dependent Na+ absorption occurring in parallel with CFTR and Ca2+-activated Cl- channel-dependent anion secretion, which are coordinately regulated to control the depth of the periciliary liquid layer. Oxidative stress is known to cause both acute and chronic effects on airway ion transport function, and an increasing number of studies in the past few years have identified an important role for autophagy as part of the physiological response to the damaging effects of oxidation. In this review, recent studies addressing the influence of oxidative stress and autophagy on airway ion transport pathways, along with results showing the potential of autophagy modulators in restoring the function of ion channels involved in transepithelial electrolyte transport necessary for effective mucociliary clearance, are presented.
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Affiliation(s)
- Scott M O'Grady
- Departments of Animal Science, Integrative Biology and Physiology, University of Minnesota , St. Paul, Minnesota
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7
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Bartoszewski R, Matalon S, Collawn JF. Ion channels of the lung and their role in disease pathogenesis. Am J Physiol Lung Cell Mol Physiol 2017; 313:L859-L872. [PMID: 29025712 PMCID: PMC5792182 DOI: 10.1152/ajplung.00285.2017] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 10/03/2017] [Accepted: 10/03/2017] [Indexed: 12/16/2022] Open
Abstract
Maintenance of normal epithelial ion and water transport in the lungs includes providing a thin layer of surface liquid that coats the conducting airways. This airway surface liquid is critical for normal lung function in a number of ways but, perhaps most importantly, is required for normal mucociliary clearance and bacterial removal. Preservation of the appropriate level of hydration, pH, and viscosity for the airway surface liquid requires the proper regulation and function of a battery of different types of ion channels and transporters. Here we discuss how alterations in ion channel/transporter function often lead to lung pathologies.
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Affiliation(s)
- Rafal Bartoszewski
- Department of Biology and Pharmaceutical Botany, Medical University of Gdansk, Gdansk, Poland
| | - Sadis Matalon
- Department of Anesthesiology and Perioperative Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
- Department of Cell, Developmental, and Integrative Biology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
- Pulmonary Injury and Repair Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and
- Gregory Fleming James Cystic Fibrosis Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - James F Collawn
- Department of Cell, Developmental, and Integrative Biology, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama;
- Pulmonary Injury and Repair Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and
- Gregory Fleming James Cystic Fibrosis Center, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
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8
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Canella R, Martini M, Borriello R, Cavicchio C, Muresan XM, Benedusi M, Cervellati F, Valacchi G. Modulation of Chloride Currents in Human Lung Epithelial Cells Exposed to Exogenous Oxidative Stress. J Cell Physiol 2017; 232:1817-1825. [DOI: 10.1002/jcp.25705] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 11/22/2016] [Indexed: 11/07/2022]
Affiliation(s)
- Rita Canella
- Department of Life Sciences and Biotechnology; University of Ferrara; Ferrara Italy
| | - Marta Martini
- Department of Life Sciences and Biotechnology; University of Ferrara; Ferrara Italy
| | - Roberta Borriello
- Department of Life Sciences and Biotechnology; University of Ferrara; Ferrara Italy
| | - Carlotta Cavicchio
- Department of Life Sciences and Biotechnology; University of Ferrara; Ferrara Italy
| | - Ximena M. Muresan
- Department of Life Sciences and Biotechnology; University of Ferrara; Ferrara Italy
| | - Mascia Benedusi
- Department of Life Sciences and Biotechnology; University of Ferrara; Ferrara Italy
| | - Franco Cervellati
- Department of Life Sciences and Biotechnology; University of Ferrara; Ferrara Italy
| | - Giuseppe Valacchi
- Department of Life Sciences and Biotechnology; University of Ferrara; Ferrara Italy
- Department of Animal Science; North Carolina State University; PHHI NC Research Campus; Kannapolis North Carolina
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9
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Hermann A, Sitdikova GF, Weiger TM. Oxidative Stress and Maxi Calcium-Activated Potassium (BK) Channels. Biomolecules 2015; 5:1870-911. [PMID: 26287261 PMCID: PMC4598779 DOI: 10.3390/biom5031870] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 07/17/2015] [Accepted: 07/20/2015] [Indexed: 01/13/2023] Open
Abstract
All cells contain ion channels in their outer (plasma) and inner (organelle) membranes. Ion channels, similar to other proteins, are targets of oxidative impact, which modulates ion fluxes across membranes. Subsequently, these ion currents affect electrical excitability, such as action potential discharge (in neurons, muscle, and receptor cells), alteration of the membrane resting potential, synaptic transmission, hormone secretion, muscle contraction or coordination of the cell cycle. In this chapter we summarize effects of oxidative stress and redox mechanisms on some ion channels, in particular on maxi calcium-activated potassium (BK) channels which play an outstanding role in a plethora of physiological and pathophysiological functions in almost all cells and tissues. We first elaborate on some general features of ion channel structure and function and then summarize effects of oxidative alterations of ion channels and their functional consequences.
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Affiliation(s)
- Anton Hermann
- Department of Cell Biology, Division of Cellular and Molecular Neurobiology, University of Salzburg, Salzburg 5020, Austria.
| | - Guzel F Sitdikova
- Department of Physiology of Man and Animals, Kazan Federal University, Kazan 420008, Russia.
| | - Thomas M Weiger
- Department of Cell Biology, Division of Cellular and Molecular Neurobiology, University of Salzburg, Salzburg 5020, Austria.
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10
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Brune K, Frank J, Schwingshackl A, Finigan J, Sidhaye VK. Pulmonary epithelial barrier function: some new players and mechanisms. Am J Physiol Lung Cell Mol Physiol 2015; 308:L731-45. [PMID: 25637609 DOI: 10.1152/ajplung.00309.2014] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 01/27/2015] [Indexed: 12/20/2022] Open
Abstract
The pulmonary epithelium serves as a barrier to prevent access of the inspired luminal contents to the subepithelium. In addition, the epithelium dictates the initial responses of the lung to both infectious and noninfectious stimuli. One mechanism by which the epithelium does this is by coordinating transport of diffusible molecules across the epithelial barrier, both through the cell and between cells. In this review, we will discuss a few emerging paradigms of permeability changes through altered ion transport and paracellular regulation by which the epithelium gates its response to potentially detrimental luminal stimuli. This review is a summary of talks presented during a symposium in Experimental Biology geared toward novel and less recognized methods of epithelial barrier regulation. First, we will discuss mechanisms of dynamic regulation of cell-cell contacts in the context of repetitive exposure to inhaled infectious and noninfectious insults. In the second section, we will briefly discuss mechanisms of transcellular ion homeostasis specifically focused on the role of claudins and paracellular ion-channel regulation in chronic barrier dysfunction. In the next section, we will address transcellular ion transport and highlight the role of Trek-1 in epithelial responses to lung injury. In the final section, we will outline the role of epithelial growth receptor in barrier regulation in baseline, acute lung injury, and airway disease. We will then end with a summary of mechanisms of epithelial control as well as discuss emerging paradigms of the epithelium role in shifting between a structural element that maintains tight cell-cell adhesion to a cell that initiates and participates in immune responses.
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Affiliation(s)
- Kieran Brune
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland
| | - James Frank
- The Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, San Francisco VA Medical Center, and NCIRE/Veterans Health Research Institute, San Francisco, California
| | - Andreas Schwingshackl
- Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee
| | - James Finigan
- Division of Oncology, Cancer Center, National Jewish Health, Denver, Colorado
| | - Venkataramana K Sidhaye
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland;
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11
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Sforna L, Cenciarini M, Belia S, D'Adamo MC, Pessia M, Franciolini F, Catacuzzeno L. The role of ion channels in the hypoxia-induced aggressiveness of glioblastoma. Front Cell Neurosci 2015; 8:467. [PMID: 25642170 PMCID: PMC4295544 DOI: 10.3389/fncel.2014.00467] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 12/24/2014] [Indexed: 12/16/2022] Open
Abstract
The malignancy of glioblastoma multiform (GBM), the most common and aggressive form of human brain tumors, strongly correlates with the presence of hypoxic areas, but the mechanisms controlling the hypoxia-induced aggressiveness are still unclear. GBM cells express a number of ion channels whose activity supports cell volume changes and increases in the cytosolic Ca2+ concentration, ultimately leading to cell proliferation, migration or death. In several cell types it has previously been shown that low oxygen levels regulate the expression and activity of these channels, and more recent data indicate that this also occurs in GBM cells. Based on these findings, it may be hypothesized that the modulation of ion channel activity or expression by the hypoxic environment may participate in the acquisition of the aggressive phenotype observed in GBM cells residing in a hypoxic environment. If this hypothesis will be confirmed, the use of available ion channels modulators may be considered for implementing novel therapeutic strategies against these tumors.
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Affiliation(s)
- Luigi Sforna
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Marta Cenciarini
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Silvia Belia
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Maria Cristina D'Adamo
- Faculty of Medicine, Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Mauro Pessia
- Faculty of Medicine, Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Fabio Franciolini
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Luigi Catacuzzeno
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
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12
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Purkey MT, Li J, Mentch F, Grant SFA, Desrosiers M, Hakonarson H, Toskala E. Genetic variation in genes encoding airway epithelial potassium channels is associated with chronic rhinosinusitis in a pediatric population. PLoS One 2014; 9:e89329. [PMID: 24595210 PMCID: PMC3940609 DOI: 10.1371/journal.pone.0089329] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 01/18/2014] [Indexed: 11/19/2022] Open
Abstract
Background Apical potassium channels regulate ion transport in airway epithelial cells and influence air surface liquid (ASL) hydration and mucociliary clearance (MCC). We sought to identify whether genetic variation within genes encoding airway potassium channels is associated with chronic rhinosinusitis (CRS). Methods Single nucleotide polymorphism (SNP) genotypes for selected potassium channels were derived from data generated on the Illumnia HumanHap550 BeadChip or Illumina Human610-Quad BeadChip for 828 unrelated individuals diagnosed with CRS and 5,083 unrelated healthy controls from the Children's Hospital of Philadelphia (CHOP). Statistical analysis was performed with set-based tests using PLINK, and corrected for multiple testing. Results Set-based case control analysis revealed the gene KCNMA1 was associated with CRS in our Caucasian subset of the cohort (598 CRS cases and 3,489 controls; p = 0.022, based on 10,000 permutations). In addition there was borderline evidence that the gene KCNQ5 (p = 0.0704) was associated with the trait in our African American subset of the cohort (230 CRS cases and 1,594 controls). In addition to the top significant SNPs rs2917454 and rs6907229, imputation analysis uncovered additional genetic variants in KCNMA1 and in KCNQ5 that were associated with CRS. Conclusions We have implicated two airway epithelial potassium channels as novel susceptibility loci in contributing to the pathogenesis of CRS.
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Affiliation(s)
- Michael T. Purkey
- Department of Otorhinolaryngology, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Jin Li
- Center for Applied Genomics, the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Frank Mentch
- Center for Applied Genomics, the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Struan F. A. Grant
- Division of Human Genetics, the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
| | - Martin Desrosiers
- Department of Otolaryngology, Montreal General Hospital, McGill University, Montreal, Québec Canada
| | - Hakon Hakonarson
- Center for Applied Genomics, the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
- Division of Human Genetics, the Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States of America
- Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail: (HH); (ET)
| | - Elina Toskala
- Department of Otolaryngology, Temple University, Philadelphia, Pennsylvania, United States of America
- * E-mail: (HH); (ET)
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13
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Gu XQ, Pamenter ME, Siemen D, Sun X, Haddad GG. Mitochondrial but not plasmalemmal BK channels are hypoxia-sensitive in human glioma. Glia 2014; 62:504-13. [PMID: 24446243 DOI: 10.1002/glia.22620] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 12/09/2013] [Accepted: 12/10/2013] [Indexed: 11/05/2022]
Abstract
Tumor cells are resistant to hypoxia but the underlying mechanism(s) of this tolerance remain poorly understood. In healthy brain cells, plasmalemmal Ca(2+)-activated K(+) channels ((plasma)BK) function as oxygen sensors and close under hypoxic conditions. Similarly, BK channels in the mitochondrial inner membrane ((mito)BK) are also hypoxia sensitive and regulate reactive oxygen species production and also permeability transition pore formation. Both channel populations are therefore well situated to mediate cellular responses to hypoxia. In tumors, BK channel expression increases with malignancy, suggesting these channels contribute to tumor growth; therefore, we hypothesized that the sensitivity of (plasma)BK and/or (mito)BK to hypoxia differs between glioma and healthy brain cells. To test this, we examined the electrophysiological properties of (plasma)BK and (mito)BK from a human glioma cell line during normoxia and hypoxia. We observed single channel activities in whole cells and isolated mitoplasts with slope conductance of 199 ± 8 and 278 ± 10 pA, respectively. These currents were Ca(2+)- and voltage-dependent, and were inhibited by the BK channel antagonist charybdotoxin (0.1 μM). (plasma)BK could only be activated at membrane potentials >+40 mV and had a low open probability (NPo) that was unchanged by hypoxia. Conversely, (mito)BK were active across a range of membrane potentials (-40 to +40 mV) and their NPo increased during hypoxia. Activating (plasma)BK, but not (mito)BK induced cell death and this effect was enhanced during hypoxia. We conclude that unlike in healthy brain cells, glioma (mito)BK channels, but not (plasma)BK channels are oxygen sensitive.
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Affiliation(s)
- Xiang Q Gu
- Section of Respiratory Medicine, Department of Pediatrics, University of California San Diego, La Jolla, California
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14
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K+ channels regulate ENaC expression via changes in promoter activity and control fluid clearance in alveolar epithelial cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1818:1682-90. [PMID: 22406554 DOI: 10.1016/j.bbamem.2012.02.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 02/16/2012] [Accepted: 02/22/2012] [Indexed: 12/21/2022]
Abstract
Active Na+ absorption by alveolar ENaC is the main driving force of liquid clearance at birth and lung edema resorption in adulthood. We have demonstrated previously that long-term modulation of KvLQT1 and KATP K+ channel activities exerts sustained control in Na+ transport through the regulation of ENaC expression in primary alveolar type II (ATII) cells. The goal of the present study was: 1) to investigate the role of the alpha-ENaC promoter, transfected in the A549 alveolar cell line, in the regulation of ENaC expression by K+ channels, and 2) to determine the physiological impact of K+ channels and ENaC modulation on fluid clearance in ATII cells. KvLQT1 and KATP channels were first identified in A549 cells by PCR and Western blotting. We showed, for the first time, that KvLQT1 activation by R-L3 (applied for 24 h) increased alpha-ENaC expression, similarly to KATP activation by pinacidil. Conversely, pharmacological KvLQT1 and KATP inhibition or silencing with siRNAs down-regulated alpha-ENaC expression. Furthermore, K+ channel blockers significantly decreased alpha-ENaC promoter activity. Our results indicated that this decrease in promoter activity could be mediated, at least in part, by the repressor activity of ERK1/2. Conversely, KvLQT1 and KATP activation dose-dependently enhanced alpha-ENaC promoter activity. Finally, we noted a physiological impact of changes in K+ channel functions on ERK activity, alpha-, beta-, gamma-ENaC subunit expression and fluid absorption through polarized ATII cells. In summary, our results disclose that K+ channels regulate alpha-ENaC expression by controlling its promoter activity and thus affect the alveolar function of fluid clearance.
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15
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Hollenhorst MI, Lips KS, Wolff M, Wess J, Gerbig S, Takats Z, Kummer W, Fronius M. Luminal cholinergic signalling in airway lining fluid: a novel mechanism for activating chloride secretion via Ca²⁺-dependent Cl⁻ and K⁺ channels. Br J Pharmacol 2012; 166:1388-402. [PMID: 22300281 DOI: 10.1111/j.1476-5381.2012.01883.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND AND PURPOSE Recent studies detected the expression of proteins involved in cholinergic metabolism in airway epithelial cells, although the function of this non-neuronal cholinergic system is not known in detail. Thus, this study focused on the effect of luminal ACh as a regulator of transepithelial ion transport in epithelial cells. EXPERIMENTAL APPROACH RT-PCR experiments were performed using mouse tracheal epithelial cells for ChAT and organic cation transporter (OCT) transcripts. Components of tracheal airway lining fluid were analysed with desorption electrospray ionization (DESI) MS. Effects of nicotine on mouse tracheal epithelial ion transport were examined with Ussing-chamber experiments. KEY RESULTS Transcripts encoding ChAT and OCT1-3 were detected in mouse tracheal epithelial cells. The DESI experiments identified ACh in the airway lining fluid. Luminal ACh induced an immediate, dose-dependent increase in the transepithelial ion current (EC₅₀: 23.3 µM), characterized by a transient peak and sustained plateau current. This response was not affected by the Na⁺-channel inhibitor amiloride. The Cl⁻-channel inhibitor niflumic acid or the K⁺-channel blocker Ba²⁺ attenuated the ACh effect. The calcium ionophore A23187 mimicked the ACh effect. Luminal nicotine or muscarine increased the ion current. Experiments with receptor gene-deficient animals revealed the participation of muscarinic receptor subtypes M₁ and M₃. CONCLUSIONS AND IMPLICATIONS The presence of luminal ACh and activation of transepithelial ion currents by luminal ACh receptors identifies a novel non-neuronal cholinergic pathway in the airway lining fluid. This pathway could represent a novel drug target in the airways.
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Affiliation(s)
- Monika I Hollenhorst
- Institute of Animal Physiology, Justus-Liebig-University Giessen, Giessen, Germany
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16
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Ion transport by pulmonary epithelia. J Biomed Biotechnol 2011; 2011:174306. [PMID: 22131798 PMCID: PMC3205707 DOI: 10.1155/2011/174306] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Accepted: 08/16/2011] [Indexed: 12/13/2022] Open
Abstract
The lung surface of air-breathing vertebrates is formed by a continuous epithelium that is covered by a fluid layer. In the airways, this epithelium is largely pseudostratified consisting of diverse cell types such as ciliated cells, goblet cells, and undifferentiated basal cells, whereas the alveolar epithelium consists of alveolar type I and alveolar type II cells. Regulation and maintenance of the volume and viscosity of the fluid layer covering the epithelium is one of the most important functions of the epithelial barrier that forms the outer surface area of the lungs. Therefore, the epithelial cells are equipped with a wide variety of ion transport proteins, among which Na+, Cl−, and K+ channels have been identified to play a role in the regulation of the fluid layer. Malfunctions of pulmonary epithelial ion transport processes and, thus, impairment of the liquid balance in our lungs is associated with severe diseases, such as cystic fibrosis and pulmonary oedema. Due to the important role of pulmonary epithelial ion transport processes for proper lung function, the present paper summarizes the recent findings about composition, function, and ion transport properties of the airway epithelium as well as of the alveolar epithelium.
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Du Q, Jovanović S, Sukhodub A, Barratt E, Drew E, Whalley KM, Kay V, McLaughlin M, Telfer EE, Barratt CLR, Jovanović A. Human oocytes express ATP-sensitive K(+) channels. Hum Reprod 2010; 25:2774-82. [PMID: 20847183 DOI: 10.1093/humrep/deq245] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND ATP-sensitive K(+) (K(ATP)) channels link intracellular metabolism with membrane excitability and play crucial roles in cellular physiology and protection. The K(ATP) channel protein complex is composed of pore forming, Kir6.x (Kir6.1 or Kir6.2) and regulatory, SURx (SUR2A, SUR2B or SUR1), subunits that associate in different combinations. The objective of this study was to determine whether mammalian oocytes (human, bovine, porcine) express K(ATP) channels. METHODS Supernumerary human oocytes at different stages of maturation were obtained from patients undergoing assisted conception treatments. Bovine and porcine oocytes in the germinal vesicle (GV) stage were obtained by aspirating antral follicles from abattoir-derived ovaries. The presence of mRNA for K(ATP) channel subunits was determined using real-time RT-PCR with primers specific for Kir6.2, Kir6.1, SUR1, SUR2A and SUR2B. To assess whether functional K(ATP) channels are present in human oocytes, traditional and perforated patch whole cell electrophysiology and immunoprecipitation/western blotting were used. RESULTS Real-time PCR revealed that mRNA for Kir6.1, Kir6.2, SUR2A and SUR2B, but not SUR1, were present in human oocytes of different stages. Only SUR2B and Kir6.2 mRNAs were detected in GV stage bovine and porcine oocytes. Immunoprecipitation with SUR2 antibody and western blotting with Kir6.1 antibody identified bands corresponding to these subunits in human oocytes. In human oocytes, 2,4-dinitrophenol (400 µM), a metabolic inhibitor known to decrease intracellular ATP and activate K(ATP) channels, increased whole cell K(+) current. On the other hand, K(+) current induced by low intracellular ATP was inhibited by extracellular glibenclamide (30 µM), an oral antidiabetic known to block the opening of K(ATP) channels. CONCLUSIONS In conclusion, mammalian oocytes express K(ATP) channels. This opens a new avenue of research into the complex relationship between metabolism and membrane excitability in oocytes under different conditions, including conception.
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Affiliation(s)
- Qingyou Du
- Division of Medical Sciences/MACHS, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
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18
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Bardou O, Trinh NTN, Brochiero E. Molecular diversity and function of K+ channels in airway and alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 2008; 296:L145-55. [PMID: 19060226 DOI: 10.1152/ajplung.90525.2008] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Multiple K(+) channels are expressed in the respiratory epithelium lining airways and alveoli. Of the three main classes [1) voltage-dependent or Ca(2+)-activated, 6-transmembrane domains (TMD), 2) 2-pores 4-TMD, and 3) inward-rectified 2-TMD K(+) channels], almost 40 different transcripts have already been detected in the lung. The physiological and functional significance of this high molecular diversity of lung epithelial K(+) channels is intriguing. As detailed in the present review, K(+) channels are located at both the apical and basolateral membranes in the respiratory epithelium, where they mediate K(+) currents of diverse electrophysiological and regulatory properties. The main recognized function of K(+) channels is to control membrane potential and to maintain the driving force for transepithelial ion and liquid transport. In this manner, KvLQT1, KCa and K(ATP) channels, for example, contribute to the control of airway and alveolar surface liquid composition and volume. Thus, K(+) channel activation has been identified as a potential therapeutic strategy for the resolution of pathologies characterized by ion transport dysfunction. K(+) channels are also involved in other key functions in lung physiology, such as oxygen-sensing, inflammatory responses and respiratory epithelia repair after injury. The purpose of this review is to summarize and discuss what is presently known about the molecular identity of lung K(+) channels with emphasis on their role in lung epithelial physiology.
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Affiliation(s)
- Olivier Bardou
- Centre de recherche du CHUM, Hôtel-Dieu, 3840, Saint-Urbain, Montréal, Québec H2W 1T8, Canada
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19
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Testosterone deprivation by castration impairs expression of voltage-dependent potassium channels in rat aorta. Eur J Pharmacol 2008; 593:87-91. [DOI: 10.1016/j.ejphar.2008.07.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Revised: 06/26/2008] [Accepted: 07/09/2008] [Indexed: 11/21/2022]
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Gu XQ, Siemen D, Parvez S, Cheng Y, Xue J, Zhou D, Sun X, Jonas EA, Haddad GG. Hypoxia increases BK channel activity in the inner mitochondrial membrane. Biochem Biophys Res Commun 2007; 358:311-6. [PMID: 17481584 DOI: 10.1016/j.bbrc.2007.04.110] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Accepted: 04/19/2007] [Indexed: 10/23/2022]
Abstract
To explore the potential function of the BK channel in the inner mitochondrial membrane under physiological and hypoxic conditions, we used on-mitoplast and whole-mitoplast patches. Single BK channels had a conductance of 276+/-9 pS under symmetrical K(+) solutions, were Ca(2+)- and voltage-dependent and were inhibited by 0.1 microM charybdotoxin. In response to hypoxia, BK increased open probability, shifted its reversal potential (9.3+/-2.4 mV) in the positive direction and did not change its conductance. We conclude that (1) the properties at rest of this mitoplast K(+) channel are similar to those of BK channels in the plasma membrane; (2) hypoxia induces an increase, rather than a decrease (as in the plasmalemma), in the open probability of this K(+) channel, leading to K(+) efflux from the mitochondrial matrix to the outside. We speculate that this increase in K(+) efflux from mitochondria into the cytosol is important during hypoxia in maintaining cytosolic K(+).
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Affiliation(s)
- Xiang Q Gu
- Department of Pediatrics (Section of Respiratory Medicine), University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0735, USA
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21
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Kim EY, Zou S, Ridgway LD, Dryer SE. Beta1-subunits increase surface expression of a large-conductance Ca2+-activated K+ channel isoform. J Neurophysiol 2007; 97:3508-16. [PMID: 17329633 DOI: 10.1152/jn.00009.2007] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Auxiliary (beta) subunits of large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels regulate the gating properties of the functional channel complex. Here we show that an avian beta1-subunit also stimulates the trafficking of BK(Ca) channels to the plasma membrane in HEK293T cells and in a native population of developing vertebrate neurons. One C-terminal variant of BK(Ca) alpha-subunits, called the VEDEC isoform after its five last residues, is largely retained in intracellular compartments when it is heterologously expressed in HEK293T cells. A closely related splice variant, called QEERL, shows high levels of constitutive trafficking to the plasma membrane. Co-expression of beta1-subunits with the VEDEC isoform resulted in a large increase in surface BK(Ca) channels as assessed by cell-surface biotinylation assays, whole cell recordings of membrane current, and confocal microscopy in HEK293T cells. Co-expression of beta1-subunits slowed the gating kinetics of BK(Ca) channels, as reported previously. Consistent with this, overexpression of beta1-subunits in a native cell type that expresses intracellular VEDEC channels, embryonic day 9 chick ciliary ganglion neurons, resulted in a significant increase in macroscopic Ca(2+)-activated K(+) current. Both the cytoplasmic N- and C-terminal domains of avian beta1 are able to bind directly to VEDEC and QEERL channels. However, overexpression of the N-terminal domain by itself is sufficient to stimulate trafficking of VEDEC channels to the plasma membrane, whereas overexpression of either the cytoplasmic C-terminal domain or the extracellular loop domain did not affect surface expression of VEDEC.
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Affiliation(s)
- Eun Young Kim
- Dept. of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA
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22
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Peth S, Karle C, Dehnert C, Bärtsch P, Mairbäurl H. K+ channel activation with minoxidil stimulates nasal-epithelial ion transport and blunts exaggerated hypoxic pulmonary hypertension. High Alt Med Biol 2006; 7:54-63. [PMID: 16544967 DOI: 10.1089/ham.2006.7.54] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Increased pulmonary capillary pressure and inhibition of alveolar Na+ transport putatively contribute to the formation of pulmonary edema in alveolar hypoxia such as at high altitude. Since both events might be linked to the inhibition of K+ channels, we studied whether in vivo application of minoxidil, a stimulator of ATP-gated K channels (K+ ATP channel activator) prevents both effects. In a double- blind, placebo-controlled crossover study on 17 volunteers with no known susceptibility to high altitude pulmonary edema, we tested whether a single dose of minoxidil (5 mg) prevents pulmonary hypertension and inhibition of nasal-epithelial Na+ transport in normobaric hypoxia (12% O2, 2 h). In hypoxia, arterial SO2 was decreased to about 80%, and systolic pulmonary artery pressure (PAP) measured by Doppler echocardiography increased significantly from approximately 25 mmHg (normoxia) to approximately 38 mmHg (hypoxia; range 22 to 61 mmHg). Minoxidil decreased PAP in hypoxia in those individuals who had the highest increase in PAP in hypoxia when taking placebo. Nasal potentials decreased by about 10% in hypoxia. Although minoxidil had no effect on nasal potentials in normoxia, it increased nasal potentials significantly above normoxic control values after 2-h hypoxia. These results show that the K+ ATP activator minoxidil prevents the decrease in nasal-epithelial potential by hypoxia and seems to blunt an exaggerated increase in PAP in acute hypoxia.
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Affiliation(s)
- Simon Peth
- Medical Clinic VII, Sports Medicine, University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany
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23
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Femling JK, Cherny VV, Morgan D, Rada B, Davis AP, Czirják G, Enyedi P, England SK, Moreland JG, Ligeti E, Nauseef WM, DeCoursey TE. The antibacterial activity of human neutrophils and eosinophils requires proton channels but not BK channels. J Gen Physiol 2006; 127:659-72. [PMID: 16702353 PMCID: PMC2151543 DOI: 10.1085/jgp.200609504] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Accepted: 04/25/2006] [Indexed: 02/01/2023] Open
Abstract
Electrophysiological events are of central importance during the phagocyte respiratory burst, because NADPH oxidase is electrogenic and voltage sensitive. We investigated the recent suggestion that large-conductance, calcium-activated K(+) (BK) channels, rather than proton channels, play an essential role in innate immunity (Ahluwalia, J., A. Tinker, L.H. Clapp, M.R. Duchen, A.Y. Abramov, S. Page, M. Nobles, and A.W. Segal. 2004. Nature. 427:853-858). In PMA-stimulated human neutrophils or eosinophils, we did not detect BK currents, and neither of the BK channel inhibitors iberiotoxin or paxilline nor DPI inhibited any component of outward current. BK inhibitors did not inhibit the killing of bacteria, nor did they affect NADPH oxidase-dependent degradation of bacterial phospholipids by extracellular gIIA-PLA(2) or the production of superoxide anion (O(2*)(-)). Moreover, an antibody against the BK channel did not detect immunoreactive protein in human neutrophils. A required role for voltage-gated proton channels is demonstrated by Zn(2+) inhibition of NADPH oxidase activity assessed by H(2)O(2) production, thus validating previous studies showing that Zn(2+) inhibited O(2*)(-) production when assessed by cytochrome c reduction. In conclusion, BK channels were not detected in human neutrophils or eosinophils, and BK inhibitors did not impair antimicrobial activity. In contrast, we present additional evidence that voltage-gated proton channels serve the essential role of charge compensation during the respiratory burst.
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Affiliation(s)
- Jon K Femling
- Inflammation Program, Roy J. and Luille A. Carver College of Medicine, University of Iowa, Coralville, 52241, USA
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Murray F, Insel PA, Yuan JXJ. Role of O2-sensitive K+ and Ca2+ channels in the regulation of the pulmonary circulation: Potential role of caveolae and implications for high altitude pulmonary edema. Respir Physiol Neurobiol 2006; 151:192-208. [PMID: 16364695 DOI: 10.1016/j.resp.2005.10.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 09/30/2005] [Accepted: 10/01/2005] [Indexed: 11/25/2022]
Abstract
High altitude pulmonary edema (HAPE) is a potentially fatal complication in response to exposure to low O(2) at high altitudes. Hypoxia, by causing pulmonary vasoconstriction, increases pulmonary vascular resistance and pulmonary arterial pressure, both of which are features in the pathogenesis of HAPE. Uneven hypoxic pulmonary vasoconstriction is thought to be responsible for increased capillary pressure and leakage, resulting in edema. O(2)-sensitive ion channels are known to play pivotal roles in determining vascular tone in response to hypoxia. K(+), Ca(2+) and Na(+) channels are ubiquitously expressed in both endothelial and smooth muscle cells of the pulmonary microvasculature, subfamilies of which are regulated by local changes in P(O(2)). Hypoxia reduces activity of voltage-gated K(+) channels and down-regulates their expression leading to membrane depolarization, Ca(2+) influx in pulmonary artery smooth muscle cells (by activating voltage-dependent Ca(2+) channels) and vasoconstriction. Hypoxia up-regulates transient receptor potential channels (TRPC) leading to enhanced Ca(2+) entry through receptor- and store-operated Ca(2+) channels. Altered enrichment of ion channels in membrane microdomains, in particular in caveolae, may play a role in excitation-contraction coupling and perhaps in O(2)-sensing in the pulmonary circulation and thereby may contribute to the development of HAPE. We review the role of ion channels, in particular those outlined above, in response to low O(2) on vascular tone and pulmonary edema. Advances in the understanding of ion channels involved in the physiological response to hypoxia should lead to a greater understanding of the pathogenesis of HAPE and perhaps in the identification of new therapies.
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Affiliation(s)
- Fiona Murray
- Department of Pharmacology, School of Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0725, USA
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25
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McCartney CE, McClafferty H, Huibant JM, Rowan EG, Shipston MJ, Rowe ICM. A cysteine-rich motif confers hypoxia sensitivity to mammalian large conductance voltage- and Ca-activated K (BK) channel alpha-subunits. Proc Natl Acad Sci U S A 2005; 102:17870-6. [PMID: 16306267 PMCID: PMC1308893 DOI: 10.1073/pnas.0505270102] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Cellular responses to hypoxia are tissue-specific and dynamic. However, the mechanisms that underlie this differential sensitivity to hypoxia are unknown. Large conductance voltage- and Ca-activated K (BK) channels are important mediators of hypoxia responses in many systems. Although BK channels are ubiquitously expressed, alternative pre-mRNA splicing of the single gene encoding their pore-forming alpha-subunits provides a powerful mechanism for generating functional diversity. Here, we demonstrate that the hypoxia sensitivity of BK channel alpha-subunits is splice-variant-specific. Sensitivity to hypoxia is conferred by a highly conserved motif within an alternatively spliced cysteine-rich insert, the stress-regulated exon (STREX), within the intracellular C terminus of the channel. Hypoxic inhibition of the STREX variant is Ca-sensitive and reversible, and it rapidly follows the change in oxygen tension by means of a mechanism that is independent of redox or CO regulation. Hypoxia sensitivity was abolished by mutation of the serine (S24) residue within the STREX insert. Because STREX splice-variant expression is tissue-specific and dynamically controlled, alternative splicing of BK channels provides a mechanism to control the plasticity of cellular responses to hypoxia.
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Affiliation(s)
- Claire E McCartney
- Department of Physiology and Pharmacology, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow G4 0NR, United Kingdom
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Affiliation(s)
- E Kenneth Weir
- Department of Medicine, Minneapolis Veterans Affairs Medical Center and University of Minnesota, Minneapolis 55417, USA.
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Budas GR, Jovanovic S, Crawford RM, Jovanovic A. Hypoxia-induced preconditioning in adult stimulated cardiomyocytes is mediated by the opening and trafficking of sarcolemmal KATP channels. FASEB J 2004; 18:1046-8. [PMID: 15084521 PMCID: PMC2128706 DOI: 10.1096/fj.04-1602fje] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The opening of sarcolemmal and mitochondrial ATP-sensitive K(+) (KATP) channels in the heart is believed to mediate ischemic preconditioning, a phenomenon whereby brief periods of ischemia/reperfusion protect the heart against myocardial infarction. Here, we have applied digital epifluorescent microscopy, immunoprecipitation and Western blotting, perforated patch clamp electrophysiology, and immunofluorescence/laser confocal microscopy to examine the involvement of KATP channels in cardioprotection afforded by preconditioning. We have shown that adult, stimulated-to-beat, guinea-pig cardiomyocytes survived in sustained hypoxia for approximately 17 min. An episode of 5-min-long hypoxia/5-min-long reoxygenation before sustained hypoxia dramatically increased the duration of cellular survival. Experiments with different antagonists of KATP channels, applied at different times during the experimental protocol, suggested that the opening of sarcolemmal KATP channels at the beginning of sustained hypoxia mediate preconditioning. This conclusion was supported by perforated patch clamp experiments that revealed activation of sarcolemmal KATP channels by preconditioning. Immunoprecipitation and Western blotting as well as immunofluorescence and laser confocal microscopy showed that the preconditioning is associated with the increase in KATP channel proteins in sarcolemma. Inhibition of trafficking of KATP channel subunits prevented preconditioning without affecting sensitivity of cardiomyocytes to hypoxia in the absence of preconditioning. We conclude that the preconditioning is mediated by the activation and trafficking of sarcolemmal KATP channels.
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Affiliation(s)
- Grant R Budas
- Maternal and Child Health Sciences, Tayside Institute of Child Health, Ninewells Hospital & Medical School, University of Dundee, Dundee, Scotland, UK
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Crawford RM, Jovanović S, Budas GR, Davies AM, Lad H, Wenger RH, Robertson KA, Roy DJ, Ranki HJ, Jovanović A. Chronic mild hypoxia protects heart-derived H9c2 cells against acute hypoxia/reoxygenation by regulating expression of the SUR2A subunit of the ATP-sensitive K+ channel. J Biol Chem 2003; 278:31444-55. [PMID: 12791696 PMCID: PMC2134977 DOI: 10.1074/jbc.m303051200] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chronic exposure to lower oxygen tension may increase cellular resistance to different types of acute metabolic stress. Here, we show that 24-h-long exposure to slightly decreased oxygen tension (partial pressure of oxygen (PO2) of 100 mm Hg instead of normal 144 mm Hg) confers resistance against acute hypoxia/reoxygenation-induced Ca2+ loading in heart-derived H9c2 cells. The number of ATP-sensitive K+ (K(ATP)) channels were increased in cells exposed to PO2 = 100 mm Hg relative to cells exposed to PO2 = 144 mm Hg. This was due to an increase in transcription of SUR2A, a K(ATP) channel regulatory subunit, but not Kir6.2, a K(ATP) channel pore-forming subunit. PO2 = 100 mm Hg also increased the SUR2 gene promoter activity. Experiments with cells overexpressing wild type of hypoxia-inducible factor (HIF)-1alpha and dominant negative HIF-1beta suggested that the HIF-1-signaling pathway did not participate in observed PO2-mediated regulation of SUR2A expression. On the other hand, NADH inhibited the effect of PO2 = 100 mm Hg but not the effect of PO2 = 20 mm Hg. LY 294002 and PD 184 352 prevented PO2-mediated regulation of K(ATP) channels, whereas rapamycin was without any effect. HMR 1098 inhibited the cytoprotective effect of PO2 = 100 mm Hg, and a decrease of PO2 from 144 to 100 mm Hg did not change the expression of any other gene, including those involved in stress and hypoxic response, as revealed by Affymetrix high density oligonucleotide arrays. We conclude that slight hypoxia activates HIF-1alpha-independent signaling cascade leading to an increase in SUR2A protein, a higher density of K(ATP) channels, and a cellular phenotype more resistant to acute metabolic stress.
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Affiliation(s)
- Russell M. Crawford
- Maternal and Child Health Sciences, Tayside Institute of Child Health, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Sofija Jovanović
- Maternal and Child Health Sciences, Tayside Institute of Child Health, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Grant R. Budas
- Maternal and Child Health Sciences, Tayside Institute of Child Health, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Anthony M. Davies
- Maternal and Child Health Sciences, Tayside Institute of Child Health, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Harish Lad
- Maternal and Child Health Sciences, Tayside Institute of Child Health, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Roland H. Wenger
- Carl-Ludwig-Institute of Physiology, University of Leipzig, D-04103 Leipzig, Germany
| | - Kevin A. Robertson
- Scottish Centre for Genomic Technology and Informatics, The University of Edinburgh, Summerhall EH9 1QH, United Kingdom
| | - Douglas J. Roy
- Scottish Centre for Genomic Technology and Informatics, The University of Edinburgh, Summerhall EH9 1QH, United Kingdom
| | - Harri J. Ranki
- Maternal and Child Health Sciences, Tayside Institute of Child Health, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom
| | - Aleksandar Jovanović
- Maternal and Child Health Sciences, Tayside Institute of Child Health, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom
- To whom correspondence should be addressed: Tayside Inst. of Child Health, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK. Tel.: 44-0-1382-496-269; Fax: 44-0-1382-632-597; E-mail:
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