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Teixeira-Fonseca JL, Joviano-Santos JV, Beserra SS, de Lima Conceição MR, Leal-Silva P, Marques LP, Souza DS, Roman-Campos D. Exploring the involvement of TASK-1 in the control of isolated rat right atrium function from healthy animals and an experimental model of monocrotaline-induced pulmonary hypertension. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2023; 396:3775-3788. [PMID: 37338577 DOI: 10.1007/s00210-023-02569-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 06/02/2023] [Indexed: 06/21/2023]
Abstract
The TASK-1 channel belongs to the two-pore domain potassium channel family. It is expressed in several cells of the heart, including the right atrial (RA) cardiomyocytes and the sinus node, and TASK-1 channel has been implicated in the pathogenesis of atrial arrhythmias (AA). Thus, using the rat model of monocrotaline-induced pulmonary hypertension (MCT-PH), we explored the involvement of TASK-1 in AA. Four-week-old male Wistar rats were injected with 50 mg/kg of MCT to induce MCT-PH and isolated RA function was studied 14 days later. Additionally, isolated RA from six-week-old male Wistar rats were used to explore the ability of ML365, a selective blocker of TASK-1, to modulate RA function. The hearts developed right atrial and ventricular hypertrophy, inflammatory infiltrate and the surface ECG demonstrated increased P wave duration and QT interval, which are markers of MCT-PH. The isolated RA from the MCT animals showed enhanced chronotropism, faster contraction and relaxation kinetics, and a higher sensibility to extracellular acidification. However, the addition of ML365 to extracellular media was not able to restore the phenotype. Using a burst pacing protocol, the RA from MCT animals were more susceptible to develop AA, and simultaneous administration of carbachol and ML365 enhanced AA, suggesting the involvement of TASK-1 in AA induced by MCT. TASK-1 does not play a key role in the chronotropism and inotropism of healthy and diseased RA; however, it may play a role in AA in the MCT-PH model.
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Affiliation(s)
- Jorge Lucas Teixeira-Fonseca
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Botucatu Street, 862, Biological Science Building, 7th floor, São Paulo, São Paulo, Brazil
| | - Julliane V Joviano-Santos
- Post-Graduate Program in Health Sciences, Faculdade Ciências Médicas de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Samuel Santos Beserra
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Botucatu Street, 862, Biological Science Building, 7th floor, São Paulo, São Paulo, Brazil
| | - Michael Ramon de Lima Conceição
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Botucatu Street, 862, Biological Science Building, 7th floor, São Paulo, São Paulo, Brazil
| | - Polyana Leal-Silva
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Botucatu Street, 862, Biological Science Building, 7th floor, São Paulo, São Paulo, Brazil
| | - Leisiane Pereira Marques
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Botucatu Street, 862, Biological Science Building, 7th floor, São Paulo, São Paulo, Brazil
| | - Diego Santos Souza
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Botucatu Street, 862, Biological Science Building, 7th floor, São Paulo, São Paulo, Brazil
| | - Danilo Roman-Campos
- Laboratory of Cardiobiology, Department of Biophysics, Paulista School of Medicina, Federal University of Sao Paulo, Botucatu Street, 862, Biological Science Building, 7th floor, São Paulo, São Paulo, Brazil.
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TASK-1 regulates mitochondrial function under hypoxia. Biochem Biophys Res Commun 2021; 578:163-169. [PMID: 34571371 DOI: 10.1016/j.bbrc.2021.09.032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Accepted: 09/16/2021] [Indexed: 11/23/2022]
Abstract
TASK-1, TWIK-related acid-sensitive potassium channel 1, is a member of the two-pore- domain potassium channel family. It is constitutively active at resting potentials and strongly expressed in the heart. However, little is known about the role of TASK-1 channels in hypoxia. A cellular model of hypoxia and reoxygenation from rat heart-derived H9c2 cells or TASK-1 deficient HEK293T cells was employed to explore the role of TASK-1 channels in cytoprotection against hypoxia. The cell viability assay revealed that TASK-1 expression increased the number of viable cells subjected to 2 h of hypoxia followed by 2 h of reoxygenation (H/R). To dissect the protective role of TASK-1 on mitochondrial function, mitochondrial membrane potential (MMP) was assessed by tetramethylrhodamine fluorescence. It was demonstrated that MMP was significantly decreased by H/R, but it was maintained by TASK-1 expression or pretreatment with cyclosporin A, an inhibitor of mitochondrial permeability transition pore (mPTP). The effect of cyclosporin A on MMP was not further altered by TASK-1 expression. Moreover, TASK-1 expression significantly blocked cytochrome c release induced by H/R. While a small fraction of endogenous TASK-1 was found to colocalize with the mitochondrial marker MitoTracker in H9c2 cells, H/R did not alter the extent of colocalization of TASK-1 with MitoTracker. The total TASK-1 protein level was not significantly affected by H/R. In summary, we provided the evidence that TASK-1 channels confer cytoprotection against hypoxia-reoxygenation injury, possibly by their capacity of maintaining the mitochondrial membrane potential via inhibiting MPTP opening.
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Two-Pore-Domain Potassium (K 2P-) Channels: Cardiac Expression Patterns and Disease-Specific Remodelling Processes. Cells 2021; 10:cells10112914. [PMID: 34831137 PMCID: PMC8616229 DOI: 10.3390/cells10112914] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/18/2021] [Accepted: 10/22/2021] [Indexed: 12/23/2022] Open
Abstract
Two-pore-domain potassium (K2P-) channels conduct outward K+ currents that maintain the resting membrane potential and modulate action potential repolarization. Members of the K2P channel family are widely expressed among different human cell types and organs where they were shown to regulate important physiological processes. Their functional activity is controlled by a broad variety of different stimuli, like pH level, temperature, and mechanical stress but also by the presence of lipids or pharmacological agents. In patients suffering from cardiovascular diseases, alterations in K2P-channel expression and function have been observed, suggesting functional significance and a potential therapeutic role of these ion channels. For example, upregulation of atrial specific K2P3.1 (TASK-1) currents in atrial fibrillation (AF) patients was shown to contribute to atrial action potential duration shortening, a key feature of AF-associated atrial electrical remodelling. Therefore, targeting K2P3.1 (TASK-1) channels might constitute an intriguing strategy for AF treatment. Further, mechanoactive K2P2.1 (TREK-1) currents have been implicated in the development of cardiac hypertrophy, cardiac fibrosis and heart failure. Cardiovascular expression of other K2P channels has been described, functional evidence in cardiac tissue however remains sparse. In the present review, expression, function, and regulation of cardiovascular K2P channels are summarized and compared among different species. Remodelling patterns, observed in disease models are discussed and compared to findings from clinical patients to assess the therapeutic potential of K2P channels.
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A lower X-gate in TASK channels traps inhibitors within the vestibule. Nature 2020; 582:443-447. [PMID: 32499642 DOI: 10.1038/s41586-020-2250-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 03/12/2020] [Indexed: 12/23/2022]
Abstract
TWIK-related acid-sensitive potassium (TASK) channels-members of the two pore domain potassium (K2P) channel family-are found in neurons1, cardiomyocytes2-4 and vascular smooth muscle cells5, where they are involved in the regulation of heart rate6, pulmonary artery tone5,7, sleep/wake cycles8 and responses to volatile anaesthetics8-11. K2P channels regulate the resting membrane potential, providing background K+ currents controlled by numerous physiological stimuli12-15. Unlike other K2P channels, TASK channels are able to bind inhibitors with high affinity, exceptional selectivity and very slow compound washout rates. As such, these channels are attractive drug targets, and TASK-1 inhibitors are currently in clinical trials for obstructive sleep apnoea and atrial fibrillation16. In general, potassium channels have an intramembrane vestibule with a selectivity filter situated above and a gate with four parallel helices located below; however, the K2P channels studied so far all lack a lower gate. Here we present the X-ray crystal structure of TASK-1, and show that it contains a lower gate-which we designate as an 'X-gate'-created by interaction of the two crossed C-terminal M4 transmembrane helices at the vestibule entrance. This structure is formed by six residues (243VLRFMT248) that are essential for responses to volatile anaesthetics10, neurotransmitters13 and G-protein-coupled receptors13. Mutations within the X-gate and the surrounding regions markedly affect both the channel-open probability and the activation of the channel by anaesthetics. Structures of TASK-1 bound to two high-affinity inhibitors show that both compounds bind below the selectivity filter and are trapped in the vestibule by the X-gate, which explains their exceptionally low washout rates. The presence of the X-gate in TASK channels explains many aspects of their physiological and pharmacological behaviour, which will be beneficial for the future development and optimization of TASK modulators for the treatment of heart, lung and sleep disorders.
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A fundamental evaluation of the electrical properties and function of cardiac transverse tubules. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1867:118502. [PMID: 31269418 DOI: 10.1016/j.bbamcr.2019.06.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 06/07/2019] [Accepted: 06/28/2019] [Indexed: 11/20/2022]
Abstract
This work discusses active and passive electrical properties of transverse (T-)tubules in ventricular cardiomyocytes to understand the physiological roles of T-tubules. T-tubules are invaginations of the lateral membrane that provide a large surface for calcium-handling proteins to facilitate sarcomere shortening. Higher heart rates correlate with higher T-tubular densities in mammalian ventricular cardiomyocytes. We assess ion dynamics in T-tubules and the effects of sodium current in T-tubules on the extracellular potential, which leads to a partial reduction of the sodium current in deep segments of a T-tubule. We moreover reflect on the impact of T-tubules on macroscopic conduction velocity, integrating fundamental principles of action potential propagation and conduction. We also theoretically assess how the conduction velocity is affected by different T-tubular sodium current densities. Lastly, we critically assess literature on ion channel expression to determine whether action potentials can be initiated in T-tubules.
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Li WY, Wang A, Jin H, Zou Y, Wang Z, Wang W, Kang J. Transient upregulation of TASK-1 expression in the hypoglossal nucleus during chronic intermittent hypoxia is reduced by serotonin 2A receptor antagonist. J Cell Physiol 2019; 234:17886-17895. [PMID: 30864194 DOI: 10.1002/jcp.28419] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 02/10/2019] [Accepted: 02/14/2019] [Indexed: 11/11/2022]
Abstract
Hypoglossal motoneurons innervate genioglossus muscle, the contraction of which is critical in the maintenance of upper airway patency in patients with obstructive sleep apnea. As a potassium channel distributed in hypoglossal motoneurons, TWIK-related acid-sensitive K+ channel-1 (TASK-1) could be inhibited by 5-HT. This study aimed to investigate if TASK-1 expression in hypoglossal nucleus could be influenced by chronic intermittent hypoxia (CIH) and 5-HT2A receptors antagonist. Two hundred twenty-eight rats were exposed to CIH or normoxia (NO) in the presence and absence of 5-HT 2A receptor antagonist (MDL-100907) microinjected into the hypoglossal nucleus. The expression of 5-HT and TASK-1 in the hypoglossal nucleus were detected by immunohistochemistry and reverse transcription quantitative polymerase chain reaction on the 1st, 3rd, 7th, 14th and 21st day of CIH exposure. The mean optical density (MOD) of 5-HT in the XII nucleus was significantly increased in the CIH and CIH + MDL group than the NO group on the 7th and 21st day ( p < 0.05). Compared with the NO group, the MOD and gene expression of TASK-1 in the CIH group was significantly increased on the 7th and 14th day ( p < 0.05), then normalized on the 21st day. The TASK-1 expression in the CIH + MDL group was significantly lower than the CIH + PBS and CIH group on the 7th and 14th day ( p < 0.05). The CIH-induced transiently upregulation of the TASK-1 expression in the hypoglossal nucleus could be reversed by 5-HT 2A receptor antagonist, indicating that the modulation of the TASK-1 expression in response to CIH involves 5-HT and 5-HT 2A receptors, and this CIH effect might be 5-HT 2A receptor-dependent.
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Affiliation(s)
- Wen-Yang Li
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Aidi Wang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Hongyu Jin
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Ying Zou
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Zanfeng Wang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Wei Wang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Jian Kang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
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Jones SA, Walton RD, Morton M, Lancaster MK. K 2p 3.1 protein is expressed as a transmural gradient across the rat left ventricular free wall. J Cardiovasc Electrophysiol 2018; 30:383-391. [PMID: 30516300 PMCID: PMC6446730 DOI: 10.1111/jce.13805] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 11/08/2018] [Accepted: 11/15/2018] [Indexed: 12/25/2022]
Abstract
Introduction K2p3.1, also known as TASK‐1, is a twin‐pore acid‐sensitive repolarizing K+ channel, responsible for a background potassium current that significantly contributes to setting the resting membrane potential of cardiac myocytes. Inhibition of IK2p3.1 alters cardiac repolarization and is proarrhythmogenic. In this study, we have examined the expression of K2p3.1 and function of this channel in tissue and myocytes from across the left ventricular free wall. Methods and Results Using fluorescence immunocytochemistry, the expression of K2p3.1 protein in myocytes from the subendocardial region was found to be twice (205% ± 13.5%) that found in myocytes from the subepicardial region of the left ventricle (100% ± 5.3%). The left ventricular free wall exhibited a marked transmural gradient of K2p3.1 protein expression. Western blot analysis confirmed significantly higher K2p3.1 protein expression in subendocardial tissue (156% ± 2.5%) than subepicardial tissue (100% ± 5.0%). However, there was no difference in K2p3.1 messenger RNA expression. Whole‐cell patch clamp identified IK2p3.1 current density to be significantly greater in myocytes isolated from the subendocardium (7.66 ± 0.53 pA/pF) compared with those from the subepicardium (3.47 ± 0.74 pA/pF). Conclusions This is the first study to identify a transmural gradient of K2p3.1 in the left ventricle. This gradient has implications for understanding ventricular arrhythmogenesis under conditions of ischemia but also in response to other modulatory factors, such as adrenergic stimulation and the presence of anesthetics that inhibits or activates this channel.
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Affiliation(s)
- Sandra A Jones
- Department of Biomedical Sciences, Department Faculty of Health Sciences, University of Hull, Hull, UK
| | - Richard D Walton
- Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Université de Bordeaux, Bordeaux, France.,Inserm, Centre de Recherche Cardio-Thoracique de Bordeaux, Bordeaux, France.,L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Fondation Bordeaux Université, Bordeaux, France
| | | | - Matthew K Lancaster
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK
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Ramirez JM, Severs LJ, Ramirez SC, Agosto‐Marlin IM. Advances in cellular and integrative control of oxygen homeostasis within the central nervous system. J Physiol 2018; 596:3043-3065. [PMID: 29742297 PMCID: PMC6068258 DOI: 10.1113/jp275890] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Accepted: 04/04/2018] [Indexed: 12/31/2022] Open
Abstract
Mammals must continuously regulate the levels of O2 and CO2 , which is particularly important for the brain. Failure to maintain adequate O2 /CO2 homeostasis has been associated with numerous disorders including sleep apnoea, Rett syndrome and sudden infant death syndrome. But, O2 /CO2 homeostasis poses major regulatory challenges, even in the healthy brain. Neuronal activities change in a differentiated, spatially and temporally complex manner, which is reflected in equally complex changes in O2 demand. This raises important questions: is oxygen sensing an emergent property, locally generated within all active neuronal networks, and/or the property of specialized O2 -sensitive CNS regions? Increasing evidence suggests that the regulation of the brain's redox state involves properties that are intrinsic to many networks, but that specialized regions in the brainstem orchestrate the integrated control of respiratory and cardiovascular functions. Although the levels of O2 in arterial blood and the CNS are very different, neuro-glial interactions and purinergic signalling are critical for both peripheral and CNS chemosensation. Indeed, the specificity of neuroglial interactions seems to determine the differential responses to O2 , CO2 and the changes in pH.
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Affiliation(s)
- Jan Marino Ramirez
- Center for Integrative Brain ResearchSeattle Children's Research InstituteDepartment of Neurological SurgeryUniversity of Washington School of MedicineSeattleWAUSA
- Department of Physiology and BiophysicsUniversity of WashingtonSeattleWAUSA
| | - Liza J. Severs
- Department of Physiology and BiophysicsUniversity of WashingtonSeattleWAUSA
| | - Sanja C. Ramirez
- Center for Integrative Brain ResearchSeattle Children's Research InstituteDepartment of Neurological SurgeryUniversity of Washington School of MedicineSeattleWAUSA
| | - Ibis M. Agosto‐Marlin
- Center for Integrative Brain ResearchSeattle Children's Research InstituteDepartment of Neurological SurgeryUniversity of Washington School of MedicineSeattleWAUSA
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Kang C, Hernandez VA, Hu K. Functional interaction of the two-pore domain potassium channel TASK-1 and caveolin-3. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017. [DOI: 10.1016/j.bbamcr.2017.06.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Abstract
Unique to striated muscle cells, transverse tubules (t-tubules) are membrane organelles that consist of sarcolemma penetrating into the myocyte interior, forming a highly branched and interconnected network. Mature t-tubule networks are found in mammalian ventricular cardiomyocytes, with the transverse components of t-tubules occurring near sarcomeric z-discs. Cardiac t-tubules contain membrane microdomains enriched with ion channels and signaling molecules. The microdomains serve as key signaling hubs in regulation of cardiomyocyte function. Dyad microdomains formed at the junctional contact between t-tubule membrane and neighboring sarcoplasmic reticulum are critical in calcium signaling and excitation-contraction coupling necessary for beat-to-beat heart contraction. In this review, we provide an overview of the current knowledge in gross morphology and structure, membrane and protein composition, and function of the cardiac t-tubule network. We also review in detail current knowledge on the formation of functional membrane subdomains within t-tubules, with a particular focus on the cardiac dyad microdomain. Lastly, we discuss the dynamic nature of t-tubules including membrane turnover, trafficking of transmembrane proteins, and the life cycles of membrane subdomains such as the cardiac BIN1-microdomain, as well as t-tubule remodeling and alteration in diseased hearts. Understanding cardiac t-tubule biology in normal and failing hearts is providing novel diagnostic and therapeutic opportunities to better treat patients with failing hearts.
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Affiliation(s)
- TingTing Hong
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California; and Department of Medicine, University of California Los Angeles, Los Angeles, California
| | - Robin M Shaw
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California; and Department of Medicine, University of California Los Angeles, Los Angeles, California
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Walton RD, Jones SA, Rostron KA, Kayani AC, Close GL, McArdle A, Lancaster MK. Interactions of Short-Term and Chronic Treadmill Training With Aging of the Left Ventricle of the Heart. J Gerontol A Biol Sci Med Sci 2015; 71:1005-13. [PMID: 26248561 PMCID: PMC4945880 DOI: 10.1093/gerona/glv093] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 05/22/2015] [Indexed: 02/06/2023] Open
Abstract
With aging, there is a decline in cardiac function accompanying increasing risk of arrhythmias. These effects are likely to be mechanistically associated with age-associated changes in calcium regulation within cardiac myocytes. Previous studies suggest that lifelong exercise can potentially reduce age-associated changes in the heart. Although exercise itself is associated with changes in cardiac function, little is known about the interactions of aging and exercise with respect to myocyte calcium regulation. To investigate this, adult (12 months) and old (24 months) C57/Bl6 mice were trained using moderate-intensity treadmill running. In response to 10 weeks’ training, comparable cardiac hypertrophic responses were observed, although aging independently associated with additional cardiac hypertrophy. Old animals also showed increased L- and T-type calcium channels, the sodium–calcium exchange, sarcoendoplasmic reticulum calcium ATPase, and collagen (by 50%, 92%, 66%, 88%, and 113% respectively). Short-term exercise training increased D-type and T-type calcium channels in old animals only, whereas an increase in sodium–calcium exchange was seen only in adult animals. Long-term (12 months) training generally opposed the effects of aging. Significant hypertrophy remained in long-term trained old animals, but levels of sarcoendoplasmic reticulum calcium ATPase, sodium–calcium exchange, and collagen were not significantly different from those found in the adult trained animals.
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Affiliation(s)
| | | | | | - Anna C Kayani
- Institute of Ageing & Chronic Disease, Faculty of Health and Life Sciences, University of Liverpool
| | - Graeme L Close
- Institute of Ageing & Chronic Disease, Faculty of Health and Life Sciences, University of Liverpool
| | - Anne McArdle
- Institute of Ageing & Chronic Disease, Faculty of Health and Life Sciences, University of Liverpool
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Jones SA, Lancaster MK. Progressive age-associated activation of JNK associates with conduction disruption in the aged atrium. Mech Ageing Dev 2015; 146-148:72-80. [PMID: 25956603 PMCID: PMC4461009 DOI: 10.1016/j.mad.2015.05.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 04/29/2015] [Accepted: 05/01/2015] [Indexed: 12/19/2022]
Abstract
Guinea pig atria from multiple ages ranging from neonate to old age were compared. Action potential conduction velocity showed a significant reduction in advanced age. Connexin43 protein reduced dramatically in the right atria with increasing age. An age-dependent rise in activated-JNK correlated with a rise in phosphorylated Cx43. JNK signalling is a mediator of gap junctional remodelling with increased age.
Connexin43 (Cx43) is critical for maintaining electrical conduction across atrial muscle. During progressive ageing atrial conduction slows associating with increasing susceptibility to arrhythmias. Changes in Cx43 protein expression, or its phosphorylation status, can instigate changes in the conduction of the cardiac action potential. This study investigated whether increased levels of activated c-jun N-terminal kinase (JNK) is responsible for the decline of Cx43 during ageing. Right atria from guinea pigs aged between 1 day and 38 months of age were examined. The area of the intercalated disc increased with age concurrent with a 75% decline in C43 protein expression. An age-dependent increase in activated-JNK correlated with a rise in phosphorylated Cx43, but also slowing of action potential conduction velocity across the atria from 0.38 ± 0.01 m/s at 1 month of age to 0.30 ± 0.01 m/s at 38 months. The JNK activator anisomycin increased activated JNK in myocytes and reduced Cx43 protein expression simulating ageing. The JNK inhibitor SP600125, was found to eradicate almost all trace of Cx43 protein. We conclude that in vivo activation of JNK increases with age leading to the loss of Cx43 protein resulting in impaired conduction and contributing to the increasing risk of atrial arrhythmias with advancing age.
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Affiliation(s)
- Sandra A Jones
- School of Biological, Biomedical and Environmental Sciences, University of Hull, Kingston-upon-Hull, HU6 7RX, UK.
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The role of acid-sensitive two-pore domain potassium channels in cardiac electrophysiology: focus on arrhythmias. Pflugers Arch 2014; 467:1055-67. [PMID: 25404566 DOI: 10.1007/s00424-014-1637-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 10/14/2014] [Accepted: 10/21/2014] [Indexed: 10/24/2022]
Abstract
The current kinetics of two-pore domain potassium (K2P) channels resemble those of the steady-state K(+) currents being active during the plateau phase of cardiac action potentials. Recent studies support that K2P channels contribute to these cardiac currents and thereby influence action potential duration in the heart. Ten of the 15 K2P channels present in the human genome are sensitive to variations of the extracellular and/or intracellular pH value. This review focuses on a set of K2P channels which are inhibited by extracellular protons, including the subgroup of tandem of P domains in a weak inward-rectifying K(+) (TWIK)-related acid-sensitive potassium (TASK) and TWIK-related alkaline-activated K(+) (TALK) channels. The role of TWIK-1 in the heart is also discussed since, after successful expression, an extracellular pH dependence, similar to that of TASK-1, was described as a hallmark of TWIK-1. The expression profile in cardiac tissue of different species and the functional data in the heart are summarized. The distinct role of the different acid-sensitive K2P channels in cardiac electrophysiology, inherited forms of arrhythmias and pharmacology, and their role as drug targets is currently emerging and is the subject of this review.
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Bond RC, Choisy SCM, Bryant SM, Hancox JC, James AF. Inhibition of a TREK-like K+ channel current by noradrenaline requires both β1- and β2-adrenoceptors in rat atrial myocytes. Cardiovasc Res 2014; 104:206-15. [PMID: 25205295 PMCID: PMC4174890 DOI: 10.1093/cvr/cvu192] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
AIMS Noradrenaline plays an important role in the modulation of atrial electrophysiology. However, the identity of the modulated channels, their mechanisms of modulation, and their role in the action potential remain unclear. This study aimed to investigate the noradrenergic modulation of an atrial steady-state outward current (IKss). METHODS AND RESULTS Rat atrial myocyte whole-cell currents were recorded at 36°C. Noradrenaline potently inhibited IKss (IC50 = 0.90 nM, 42.1 ± 4.3% at 1 µM, n = 7) and potentiated the L-type Ca(2+) current (ICaL, EC50 = 136 nM, 205 ± 40% at 1 µM, n = 6). Noradrenaline-sensitive IKss was weakly voltage-dependent, time-independent, and potentiated by the arachidonic acid analogue, 5,8,11,14-eicosatetraynoic acid (EYTA; 10 µM), or by osmotically induced membrane stretch. Noise analysis revealed a unitary conductance of 8.4 ± 0.42 pS (n = 8). The biophysical/pharmacological properties of IKss indicate a TREK-like K(+) channel. The effect of noradrenaline on IKss was abolished by combined β1-/β2-adrenoceptor antagonism (1 µM propranolol or 10 µM β1-selective atenolol and 100 nM β2-selective ICI-118,551 in combination), but not by β1- or β2-antagonist alone. The action of noradrenaline could be mimicked by β2-agonists (zinterol and fenoterol) in the presence of β1-antagonist. The action of noradrenaline on IKss, but not on ICaL, was abolished by pertussis toxin (PTX) treatment. The action of noradrenaline on ICaL was mediated by β1-adrenoceptors via a PTX-insensitive pathway. Noradrenaline prolonged APD30 by 52 ± 19% (n = 5; P < 0.05), and this effect was abolished by combined β1-/β2-antagonism, but not by atenolol alone. CONCLUSION Noradrenaline inhibits a rat atrial TREK-like K(+) channel current via a PTX-sensitive mechanism involving co-operativity of β1-/β2-adrenoceptors that contributes to atrial APD prolongation.
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Affiliation(s)
- Richard C Bond
- Bristol Cardiovascular Research Laboratories, School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Stéphanie C M Choisy
- Bristol Cardiovascular Research Laboratories, School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Simon M Bryant
- Bristol Cardiovascular Research Laboratories, School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Jules C Hancox
- Bristol Cardiovascular Research Laboratories, School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Andrew F James
- Bristol Cardiovascular Research Laboratories, School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
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Inhibition of cardiac two-pore-domain K+ (K2P) channels – an emerging antiarrhythmic concept. Eur J Pharmacol 2014; 738:250-5. [DOI: 10.1016/j.ejphar.2014.05.056] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Accepted: 05/28/2014] [Indexed: 12/13/2022]
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17
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Doxapram hydrochloride aggravates adrenaline-induced arrhythmias accompanied by bidirectional ventricular tachycardia. ISRN CARDIOLOGY 2014; 2014:212045. [PMID: 24527224 PMCID: PMC3912761 DOI: 10.1155/2014/212045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 12/14/2013] [Indexed: 02/05/2023]
Abstract
Objectives. Doxapram hydrochloride is a respiratory stimulant that has an inhibitory effect on myocardial IK1 potassium channels and is thought to increase membrane instability and excitability in myocardial cells. We examined the arrhythmogenic effects of doxapram hydrochloride in a rat model of halothane adrenaline-induced arrhythmia. Methods. Thirteen female Wistar rats (12–14 weeks old) were used in the study. Animals were anesthetized with inhalation of halothane to permit observation of the effects of doxapram hydrochloride on halothane adrenaline-induced arrhythmia. Time-dependent changes in ECG repolarization characteristics (QT, QTc, JTp, JT, and Tp-e intervals) were studied. Results. Doxapram hydrochloride itself did not induce arrhythmia but did induce bidirectional ventricular tachycardia after addition of adrenaline. Conclusion. Drug-induced impairment of intracellular Ca2+ regulation caused BVT in the absence of genetic abnormalities in proteins in the sarcoplasmic reticulum.
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18
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Liang B, Soka M, Christensen AH, Olesen MS, Larsen AP, Knop FK, Wang F, Nielsen JB, Andersen MN, Humphreys D, Mann SA, Huttner IG, Vandenberg JI, Svendsen JH, Haunsø S, Preiss T, Seebohm G, Olesen SP, Schmitt N, Fatkin D. Genetic variation in the two-pore domain potassium channel, TASK-1, may contribute to an atrial substrate for arrhythmogenesis. J Mol Cell Cardiol 2013; 67:69-76. [PMID: 24374141 DOI: 10.1016/j.yjmcc.2013.12.014] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 12/09/2013] [Accepted: 12/17/2013] [Indexed: 12/22/2022]
Abstract
The two-pore domain potassium channel, K2P3.1 (TASK-1) modulates background conductance in isolated human atrial cardiomyocytes and has been proposed as a potential drug target for atrial fibrillation (AF). TASK-1 knockout mice have a predominantly ventricular phenotype however, and effects of TASK-1 inactivation on atrial structure and function have yet to be demonstrated in vivo. The extent to which genetic variation in KCNK3, that encodes TASK-1, might be a determinant of susceptibility to AF is also unknown. To address these questions, we first evaluated the effects of transient knockdown of the zebrafish kcnk3a and kcnk3b genes and cardiac phenotypes were evaluated using videomicroscopy. Combined kcnk3a and kcnk3b knockdown in 72 hour post fertilization embryos resulted in lower heart rate (p<0.001), marked increase in atrial diameter (p<0.001), and mild increase in end-diastolic ventricular diameter (p=0.01) when compared with control-injected embryos. We next performed genetic screening of KCNK3 in two independent AF cohorts (373 subjects) and identified three novel KCNK3 variants. Two of these variants, present in one proband with familial AF, were located at adjacent nucleotides in the Kozak sequence and reduced expression of an engineered reporter. A third missense variant, V123L, in a patient with lone AF, reduced resting membrane potential and altered pH sensitivity in patch-clamp experiments, with structural modeling predicting instability in the vicinity of the TASK-1 pore. These in vitro data suggest that the double Kozak variants and V123L will have loss-of-function effects on ITASK. Cardiac action potential modeling predicted that reduced ITASK prolongs atrial action potential duration, and that this is potentiated by reciprocal changes in activity of other ion channel currents. Our findings demonstrate the functional importance of ITASK in the atrium and suggest that inactivation of TASK-1 may have diverse effects on atrial size and electrophysiological properties that can contribute to an arrhythmogenic substrate.
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Affiliation(s)
- Bo Liang
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Magdalena Soka
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Alex Horby Christensen
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Morten S Olesen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Anders P Larsen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark; Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, USA
| | - Filip K Knop
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Fan Wang
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Jonas B Nielsen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Martin N Andersen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - David Humphreys
- Molecular Genetics Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Stefan A Mann
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Inken G Huttner
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia
| | - Jamie I Vandenberg
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia
| | - Jesper H Svendsen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Stig Haunsø
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Preiss
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Guiscard Seebohm
- Institute for Genetics of Heart Diseases (IfGH), Department of Cardiovascular Medicine, University Hospital Münster, Germany
| | - Søren-Peter Olesen
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark
| | - Nicole Schmitt
- Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark.
| | - Diane Fatkin
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, Australia; Faculty of Medicine, University of New South Wales, Kensington, New South Wales, Australia; Cardiology Department, St Vincent's Hospital, Darlinghurst, New South Wales, Australia
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Mant A, Williams S, O'Kelly I. Acid sensitive background potassium channels K2P3.1 and K2P9.1 undergo rapid dynamin-dependent endocytosis. Channels (Austin) 2013; 7:288-302. [PMID: 23807092 DOI: 10.4161/chan.25120] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Acid-sensitive, two-pore domain potassium channels, K(2P)3.1 and K(2P)9.1, are implicated in cardiac and nervous tissue responses to hormones, neurotransmitters and drugs. K(2P)3.1 and K(2P)9.1 leak potassium from the cell at rest and directly impact membrane potential. Hence altering channel number on the cell surface drives changes in cellular electrical properties. The rate of K(2P)3.1 and K(2P)9.1 delivery to and recovery from the plasma membrane determines both channel number at the cell surface and potassium leak from cells. This study examines the endocytosis of K(2P)3.1 and K(2P)9.1. Plasma membrane biotinylation was used to follow the fate of internalized GFP-tagged rat K(2P)3.1 and K(2P)9.1 transiently expressed in HeLa cells. Confocal fluorescence images were analyzed using Imaris software, which revealed that both channels are endocytosed by a dynamin-dependent mechanism and over the course of 60 min, move progressively toward the nucleus. Endogenous endocytosis of human K(2P)3.1 and K(2P)9.1 was examined in the lung carcinoma cell line, A549. Endogenous channels are endocytosed over a similar time-scale to the channels expressed transiently in HeLa cells. These findings both validate the use of recombinant systems and identify an endogenous model system in which K(2P)3.1 and K(2P)9.1 trafficking can be further studied.
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Affiliation(s)
- Alexandra Mant
- Human Development and Health; Centre for Human Development, Stem Cells and Regeneration; Faculty of Medicine; University of Southampton; Southampton, UK
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20
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Chan P, Liu IM, Li YX, Yu WJ, Cheng JT. Antihypertension Induced by Tanshinone IIA Isolated from the Roots of Salvia miltiorrhiza. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2011; 2011:392627. [PMID: 19542183 PMCID: PMC3135424 DOI: 10.1093/ecam/nep056] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Accepted: 05/07/2009] [Indexed: 12/15/2022]
Abstract
Tanshinone IIA is one of the active principles in danshen (Salvia miltiorrhiza Bge) widely used in treatment of cardiovascular disorders. We investigated the effect of danshen or tanshinone IIA on blood pressure and its possible mechanisms. An i.p. injection of danshen at 10 mg kg(-1) significantly lowered systolic blood pressure (SBP) of spontaneously hypertensive rats (SHRs) but failed to modify the SBP in normotensive Wistar-Kyoto rats (WKY). Oral administration of tanshinone IIA also decreased SBP in SHR but not in WKY. Tanshinone IIA produced a concentration-dependent relaxation in isolated SHR aortic rings precontracted with phenylephrine (10 nmol l(-1)) or potassium chloride (KCl) (40 mmol l(-1)). The relaxing effect of tanshinone IIA on tonic contraction of phenylephrine in isolated aortic rings without endothelium remained produced. Glibenclamide at concentration sufficient to block adenosine triphosphatase (ATP)-sensitive potassium (K(+)) channel attenuated this tanshinone IIA-induced relaxation that was not influenced by other inhibitors. We further investigated the effect of tanshinone IIA on the changes of intracellular calcium concentration ([Ca(2+)](i)) in cultured aortic smooth muscle (A7r5) cells using fura-2 as indicator. Tanshinone IIA decreased [Ca(2+)](i) elicited by phenylephrine (10 nmol l(-1)) or KCl (40 mmol l(-1)) in a concentration-dependent manner; glibenclamide, but not other inhibitors for K(+) channel, abated this effect. Our results suggest that tanshinone IIA acts as an active principle of danshen showing vasodilation through ATP-sensitive K(+) channel to lower [Ca(2+)](i).
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Affiliation(s)
- Paul Chan
- Division of Cardiovascular Medicine, Taipei Medical University-Wan Fang Hospital, Taipei City 11601, Taiwan
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21
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Goldoni D, Zhao Y, Green BD, McDermott BJ, Collins A. Inward rectifier potassium channels in the HL-1 cardiomyocyte-derived cell line. J Cell Physiol 2010; 225:751-6. [PMID: 20568224 DOI: 10.1002/jcp.22278] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
HL-1 is a line of immortalized cells of cardiomyocyte origin that are a useful complement to native cardiomyocytes in studies of cardiac gene regulation. Several types of ion channel have been identified in these cells, but not the physiologically important inward rectifier K(+) channels. Our aim was to identify and characterize inward rectifier K(+) channels in HL-1 cells. External Ba(2+) (100 µM) inhibited 44 ± 0.05% (mean ± s.e.m., n = 11) of inward current in whole-cell patch-clamp recordings. The reversal potential of the Ba(2+)-sensitive current shifted with external [K(+)] as expected for K(+)-selective channels. The slope conductance of the inward Ba(2+)-sensitive current increased with external [K(+)]. The apparent Kd for Ba(2+) was voltage dependent, ranging from 15 µM at -150 mV to 148 µM at -75 mV in 120 mM external K(+). This current was insensitive to 10 µM glybenclamide. A component of whole-cell current was sensitive to 150 µM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), although it did not correspond to the Ba(2+)-sensitive component. The effect of external 1 mM Cs(+) was similar to that of Ba(2+). Polymerase chain reaction using HL-1 cDNA as template and primers specific for the cardiac inward rectifier K(ir)2.1 produced a fragment of the expected size that was confirmed to be K(ir)2.1 by DNA sequencing. In conclusion, HL-1 cells express a current that is characteristic of cardiac inward rectifier K(+) channels, and express K(ir)2.1 mRNA. This cell line may have use as a system for studying inward rectifier gene regulation in a cardiomyocyte phenotype.
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Affiliation(s)
- Dana Goldoni
- Cardiovascular Remodelling Group, Centre for Vision and Vascular Science, School of Medicine, Dentistry and Biomedical Sciences, Queen's University, Belfast, UK
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22
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Enyedi P, Czirják G. Molecular background of leak K+ currents: two-pore domain potassium channels. Physiol Rev 2010; 90:559-605. [PMID: 20393194 DOI: 10.1152/physrev.00029.2009] [Citation(s) in RCA: 620] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Two-pore domain K(+) (K(2P)) channels give rise to leak (also called background) K(+) currents. The well-known role of background K(+) currents is to stabilize the negative resting membrane potential and counterbalance depolarization. However, it has become apparent in the past decade (during the detailed examination of the cloned and corresponding native K(2P) channel types) that this primary hyperpolarizing action is not performed passively. The K(2P) channels are regulated by a wide variety of voltage-independent factors. Basic physicochemical parameters (e.g., pH, temperature, membrane stretch) and also several intracellular signaling pathways substantially and specifically modulate the different members of the six K(2P) channel subfamilies (TWIK, TREK, TASK, TALK, THIK, and TRESK). The deep implication in diverse physiological processes, the circumscribed expression pattern of the different channels, and the interesting pharmacological profile brought the K(2P) channel family into the spotlight. In this review, we focus on the physiological roles of K(2P) channels in the most extensively investigated cell types, with special emphasis on the molecular mechanisms of channel regulation.
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Affiliation(s)
- Péter Enyedi
- Department of Physiology, Semmelweis University, Budapest, Hungary.
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23
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Zhang M, Leung FP, Huang Y, Bian ZX. Increased colonic motility in a rat model of irritable bowel syndrome is associated with up-regulation of L-type calcium channels in colonic smooth muscle cells. Neurogastroenterol Motil 2010; 22:e162-70. [PMID: 20122129 DOI: 10.1111/j.1365-2982.2009.01467.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
OBJECTIVE This paper aimed to investigate the relationship between up-regulation of L-type calcium channels and altered motility disorder in a rat model of irritable bowel syndrome (IBS). METHODS Male Sprague-Dawley rats were subjected to neonatal maternal separation (NMS) from postnatal day 2-14 or normal handling (NH), and used when weighted 250-300 g. Colonic smooth muscle contractions was studied in an organ bath system. L-type Ca(2+) channel alpha(1c) subunit expression in smooth muscles from rat colon were studied by immunofluorescence and Western blotting analysis. The intracellular calcium concentration ([Ca(2+)](i)) of enzymatically isolated single colonic smooth muscle cell was studied with laser confocal fluorescent microscopy. RESULTS The fecal pellets during 1 h water avoidance stress (WAS) were significantly increased; the amplitude of spontaneous contractions and contractions induced by Bay K 8644 (10 nM-1 microM), KCl (10-60 mM) and ACh (100 nM-10 microM) were significantly increased in NMS rats, when comparing with that of NH rats. [Ca(2+)]i induced by Bay K 8644 (1 microM), KCl (40 mM), and ACh (10 microM) significantly increased in muscle cells of NMS rats than NH rats. Further, alpha(1c) protein expression was significantly up-regulated in colonic smooth muscle of NMS rats than NH rats. CONCLUSION These results suggest that NMS lead to up-regulation of L-type Ca(2+) channels expression in the colon, which contributes to the colonic motility disorder. Our findings provide direct evidence to help understanding the underlying mechanism of chronic stress-induced colonic motility disorder in IBS.
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Affiliation(s)
- M Zhang
- School of Chinese Medicine, Hong Kong Baptist University, Hong Kong SAR, China
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24
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Developmental expression of a functional TASK-1 2P domain K+ channel in embryonic chick heart. J Biomed Sci 2009; 16:104. [PMID: 19930646 PMCID: PMC2788539 DOI: 10.1186/1423-0127-16-104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Accepted: 11/23/2009] [Indexed: 11/30/2022] Open
Abstract
Background Background K+ channels are the principal determinants of the resting membrane potential (RMP) in cardiac myocytes and thus, influence the magnitude and time course of the action potential (AP). Methods RT-PCR and in situ hybridization are used to study the distribution of TASK-1 and whole-cell patch clamp technique is employed to determine the functional expression of TASK-1 in embryonic chick heart. Results Chicken TASK-1 was expressed in the early tubular heart, then substantially decreased in the ventricles by embryonic day 5 (ED5), but remained relatively high in ED5 and ED11 atria. Unlike TASK-1, TASK-3 was uniformly expressed in heart at all developmental stages. In situ hybridization studies further revealed that TASK-1 was expressed throughout myocardium at Hamilton-Hamburger stages 11 and 18 (S11 & S18) heart. In ED11 heart, TASK-1 expression was more restricted to atria. Consistent with TASK-1 expression data, patch clamp studies indicated that there was little TASK-1 current, as measured by the difference currents between pH 8.4 and pH 7.4, in ED5 and ED11 ventricular myocytes. However, TASK-1 current was present in the early embryonic heart and ED11 atrial myocytes. TASK-1 currents were also identified as 3 μM anandamide-sensitive currents. 3 μM anandamide reduced TASK-1 currents by about 58% in ED11 atrial myocytes. Zn2+ (100 μM) which selectively inhibits TASK-3 channel at this concentration had no effect on TASK currents. In ED11 ventricle where TASK-1 expression was down-regulated, IK1 was about 5 times greater than in ED11 atrial myocytes. Conclusion Functional TASK-1 channels are differentially expressed in the developing chick heart and TASK-1 channels contribute to background K+ conductance in the early tubular embryonic heart and in atria. TASK-1 channels act as a contributor to background K+ current to modulate the cardiac excitability in the embryonic heart that expresses little IK1.
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Gurney A, Manoury B. Two-pore potassium channels in the cardiovascular system. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2008; 38:305-18. [DOI: 10.1007/s00249-008-0326-8] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 03/31/2008] [Accepted: 04/02/2008] [Indexed: 12/24/2022]
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Lee PY, Chen W, Liu IM, Cheng JT. VASODILATATION INDUCED BY SINOMENINE LOWERS BLOOD PRESSURE IN SPONTANEOUSLY HYPERTENSIVE RATS. Clin Exp Pharmacol Physiol 2007; 34:979-84. [PMID: 17714082 DOI: 10.1111/j.1440-1681.2007.04668.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
1. Sinomenine is an alkaloid with a wide range of pharmacological actions. In the present study, we investigated the effect of sinomenine on blood pressure and its possible mechanisms of action. 2. Spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were given intraperitoneal injections of sinomenine. At 30 min, 2.5-10 mg/kg sinomenine decreased systolic blood pressure (SBP) in a dose-dependent manner in SHR, but had no effect on the SBP in WKY rats. 3. The vascular effect of sinomenine was then examined in aortic rings isolated from Wistar rats. Sinomenine (0.1-10 micromol/L) produced concentration-dependent relaxation in aortic rings precontracted with phenylephrine (10 nmol/L) or KCl (40 mmol/L). Glibenclamide (1-100 micromol/L), a specific inhibitor of ATP-sensitive K(+) channels attenuated the sinomenine-induced relaxation, but this effect was not observed when inhibitors of other types of K(+) channels were used. 4. We further investigated the effects of sinomenine on changes in intracellular Ca(2+) concentrations ([Ca(2+)](i)) in cultured aortic smooth muscle (A7r5) cells by using the Ca(2+)-sensitive dye fura-2 as an indicator. Sinomenine, over the concentration range 0.1-10 micromol/L, decreased the increases in [Ca(2+)](i) elicited by phenylephrine (1 micromol/L) or KCl (40 mmol/L) in a concentration-dependent manner. Glibenclamide (1-100 micromol/L) abolished the effects of sinomenine. 5. In conclusion, sinomenine causes vascular relaxation by opening ATP-sensitive K(+) channels, thus decreasing [Ca(2+)](i).
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Affiliation(s)
- Ping-Ying Lee
- Division of Cardiology, Department of Internal Medicine, Mackay Memorial Hospital, Mackay Medicine, Nursing and Management College, Taipei, Taiwan
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27
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Putzke C, Hanley PJ, Schlichthörl G, Preisig-Müller R, Rinné S, Anetseder M, Eckenhoff R, Berkowitz C, Vassiliou T, Wulf H, Eberhart L. Differential effects of volatile and intravenous anesthetics on the activity of human TASK-1. Am J Physiol Cell Physiol 2007; 293:C1319-26. [PMID: 17699638 DOI: 10.1152/ajpcell.00100.2007] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Volatile anesthetics have been shown to activate various two-pore (2P) domain K(+) (K(2P)) channels such as TASK-1 and TREK-1 (TWIK-related acid-sensitive K(+) channel), and mice deficient in these channels are resistant to halothane-induced anesthesia. Here, we investigated whether K(2P) channels were also potentially important targets of intravenous anesthetics. Whole cell patch-clamp techniques were used to determine the effects of the commonly used intravenous anesthetics etomidate and propofol on the acid-sensitive K(+) current in rat ventricular myocytes (which strongly express TASK-1) and selected human K(2P) channels expressed in Xenopus laevis oocytes. In myocytes, etomidate decreased both inward rectifier K(+) (K(ir)) current (I(K1)) and acid-sensitive outward K(+) current at positive potentials, suggesting that this drug may inhibit TASK channels. Indeed, in addition to inhibiting guinea pig Kir2.1 expressed in oocytes, etomidate inhibited human TASK-1 (and TASK-3) in a concentration-dependent fashion. Propofol had no effect on human TASK-1 (or TASK-3) expressed in oocytes. Moreover, we showed that, similar to the known effect of halothane, sevoflurane and the purified R-(-)- and S-(+)-enantiomers of isoflurane, without stereoselectivity, activated human TASK-1. We conclude that intravenous and volatile anesthetics have dissimilar effects on K(2P) channels. Human TASK-1 (and TASK-3) are insensitive to propofol but are inhibited by supraclinical concentrations of etomidate. In contrast, stimulatory effects of sevoflurane and enantiomeric isoflurane on human TASK-1 can be observed at clinically relevant concentrations.
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MESH Headings
- Anesthetics, Inhalation/pharmacology
- Anesthetics, Intravenous/pharmacology
- Animals
- Arachidonic Acids/pharmacology
- Cells, Cultured
- Dose-Response Relationship, Drug
- Etomidate/pharmacology
- Halothane/pharmacology
- Humans
- Hydrogen-Ion Concentration
- Isoflurane/pharmacology
- Membrane Potentials/drug effects
- Methyl Ethers/pharmacology
- Myocytes, Cardiac/cytology
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/physiology
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/physiology
- Oocytes/drug effects
- Oocytes/metabolism
- Oocytes/physiology
- Patch-Clamp Techniques
- Potassium/metabolism
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Tandem Pore Domain/genetics
- Potassium Channels, Tandem Pore Domain/physiology
- Propofol/pharmacology
- RNA, Complementary/genetics
- Rats
- Sevoflurane
- Xenopus laevis
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Affiliation(s)
- C Putzke
- Department of Anesthesiology and Critical Care Medicine, Philipps-University Marburg, Baldingerstrasse 1, 35043, Marburg, Germany.
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Abstract
The regulation of ion channels involves more than just modulation of their synthesis and kinetics, as controls on their trafficking and localization are also important. Although the body of knowledge is fairly large, the entire trafficking pathway is not known for any one channel. This review summarizes current knowledge on the trafficking of potassium channels that are expressed in the heart. Our knowledge of channel assembly, trafficking through the Golgi apparatus and on to the surface is covered, as are controls on channel surface retention and endocytosis.
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Affiliation(s)
- David F Steele
- Department of Physiology, University of British Columbia, 2146 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3
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Musset B, Meuth SG, Liu GX, Derst C, Wegner S, Pape HC, Budde T, Preisig-Müller R, Daut J. Effects of divalent cations and spermine on the K+ channel TASK-3 and on the outward current in thalamic neurons. J Physiol 2006; 572:639-57. [PMID: 16513667 PMCID: PMC1780017 DOI: 10.1113/jphysiol.2006.106898] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The potassium channels TASK-1 and TASK-3 show high sequence homology but differ in their sensitivity to extracellular divalent cations. Heterologous expression in HEK293 cells showed that the single-channel conductance of TASK-3 increased approximately four-fold after removal of external divalent cations, whereas the conductance of TASK-1 was unaffected. Replacing the glutamate at position 70 of TASK-3 by a lysine or arginine residue abolished the sensitivity to divalent cations. The reverse mutation in TASK-1 (K70E) induced sensitivity to divalent cations. The organic polycations spermine and ruthenium red modulated the conductance of TASK-3 in a similar way as Ca2+ or Mg2+. Our data suggest that these effects were mediated by shielding of the negative charges in the extracellular loops of TASK-3. Whole-cell currents carried by TASK-3 channels were inhibited by spermine and ruthenium red even in the presence of external divalent cations. These data suggest that, in addition to their effect on single-channel conductance, spermine and ruthenium red decreased the open probability of TASK-3 channels, probably by binding to residue E70. The standing outward current in thalamocortical relay neurons, which is largely carried by TASK channels, was also inhibited by divalent cations and spermine. Using the differential sensitivity of TASK-1 and TASK-3 to divalent cations and spermine we found that about 20% of the standing outward current in thalamocortical relay neurons flows through TASK-3 channels. We conclude from our results that inhibition of TASK-3 channels may contribute to the neuromodulatory effect of spermine released from neurons during repetitive activity or during hypoxia.
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Affiliation(s)
- Boris Musset
- Institut für Physiologie, Universität Marburg, Deutschhausstrasse 2, 35037 Marburg, Germany
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Jones SA, Lancaster MK, Boyett MR. Ageing-related changes of connexins and conduction within the sinoatrial node. J Physiol 2004; 560:429-37. [PMID: 15308686 PMCID: PMC1665255 DOI: 10.1113/jphysiol.2004.072108] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Clinical studies have shown that sinoatrial node dysfunction occurs at the highest incidence in the elderly population. Guinea-pigs were studied throughout their lifespan (i.e. birth to 38 months) to investigate the possible mechanism leading to nodal dysfunction. Using immunofluorescence with confocal microscopy, Cx43 protein expression was shown at birth to be present throughout the sinoatrial node and atrial muscle, however, at one month Cx43 protein was not expressed in the centre of the sinoatrial node. Throughout the remainder of the animal's lifespan the area of tissue lacking Cx43 protein progressively increased. Western blot provided verification by quantitative analysis that Cx43 protein expression within the sinoatrial node decreased with age; however, the expression of other cardiac connexins, Cx40 and Cx45, did not differ with age. Analysis of conduction maps showing propagation of the action potential across the sinoatrial node, from the initiation point to the crista terminalis, found that the action potential conduction time taken and conduction distance increased proportionally with age; conversely the conduction velocity decreased with age. We have shown ageing induces degenerative changes in action potential conduction, contributed to by the observed loss of Cx43 protein. Our data identify Cx43 as a potential therapeutic target for quashing the age-related deterioration of the cardiac pacemaker.
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Affiliation(s)
- Sandra A Jones
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK.
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Gardener MJ, Johnson IT, Burnham MP, Edwards G, Heagerty AM, Weston AH. Functional evidence of a role for two-pore domain potassium channels in rat mesenteric and pulmonary arteries. Br J Pharmacol 2004; 142:192-202. [PMID: 15066906 PMCID: PMC1574915 DOI: 10.1038/sj.bjp.0705691] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Experiments were performed to elucidate the mechanism by which alterations of extracellular pH (pH(o)) change membrane potential (E(M)) in rat mesenteric and pulmonary arteries. 2. Changing pH(o) from 7.4 to 6.4 or 8.4 produced a depolarisation or hyperpolarisation, respectively, in mesenteric and pulmonary arteries. Anandamide (10 microm) or bupivacaine (100 microm) reversed the hyperpolarisation associated with alkaline pH(o), shifting the E(M) of both vessels to levels comparable to that at pH 6.4. In pulmonary arteries, clofilium (100 microm) caused a significant reversal of hyperpolarisation seen at pH 8.4 but was without effect at pH 7.4. 3. K(+) channel blockade by 4-aminopyridine (4-AP) (5 mm), tetraethylammonium (TEA) (10 mm), Ba(2+) (30 microm) and glibenclamide (10 microm) depolarised the pulmonary artery. However, shifts in E(M) with changes in pH(o) remained and were sensitive to anandamide (10 microm), bupivacaine (100 microm) or Zn(2+) (200 microm). 4. Anandamide (0.3-60 microm) or bupivacaine (0.3-300 microm) caused a concentration-dependent increase in basal tone in pulmonary arteries. 5. RT-PCR demonstrated the expression of TASK-1, TASK-2, THIK-1, TRAAK, TREK-1, TWIK-1 and TWIK-2 in mesenteric arteries and TASK-1, TASK-2, THIK-1, TREK-2 and TWIK-2 in pulmonary arteries. TASK-1, TASK-2, TREK-1 and TWIK-2 protein was demonstrated in both arteries by immunostaining. 6. These experiments provide evidence for the presence of two-pore domain K(+) channels in rat mesenteric and pulmonary arteries. Collectively, they strongly suggest that modulation of TASK-1 channels is most likely to have mediated the pH-induced changes in membrane potential observed in these vessels, and that blockade of these channels by anandamide or bupivacaine generates a small increase in pulmonary artery tone.
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Affiliation(s)
- M J Gardener
- School of Biological Sciences, Stopford Building, University of Manchester, Manchester M13 9PT
| | - I T Johnson
- School of Biological Sciences, Stopford Building, University of Manchester, Manchester M13 9PT
| | - M P Burnham
- School of Biological Sciences, Stopford Building, University of Manchester, Manchester M13 9PT
| | - G Edwards
- School of Biological Sciences, Stopford Building, University of Manchester, Manchester M13 9PT
| | - A M Heagerty
- Department of Medicine, Manchester Royal Infirmary, Oxford Road, Manchester M13 9WL
| | - A H Weston
- School of Biological Sciences, Stopford Building, University of Manchester, Manchester M13 9PT
- Author for correspondence:
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Rasmussen HB, Møller M, Knaus HG, Jensen BS, Olesen SP, Jørgensen NK. Subcellular localization of the delayed rectifier K+channels KCNQ1 and ERG1 in the rat heart. Am J Physiol Heart Circ Physiol 2004; 286:H1300-9. [PMID: 14670813 DOI: 10.1152/ajpheart.00344.2003] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the heart, several K+channels are responsible for the repolarization of the cardiac action potential, including transient outward and delayed rectifier K+currents. In the present study, the cellular and subcellular localization of the two delayed rectifier K+channels, KCNQ1 and ether- a- go- go-related gene-1 (ERG1), was investigated in the adult rat heart. Confocal immunofluorescence microscopy of atrial and ventricular cells revealed that whereas KCNQ1 labeling was detected in both the peripheral sarcolemma and a structure transversing the myocytes, ERG1 immunoreactivity was confined to the latter. Immunoelectron microscopy of atrial and ventricular myocytes showed that the ERG1 channel was primarily expressed in the transverse tubular system and its entrance, whereas KCNQ1 was detected in both the peripheral sarcolemma and in the T tubules. Thus, whereas ERG1 displays a very restricted subcellular localization pattern, KCNQ1 is more widely distributed within the cardiac cells. The localization of these K+channels to the transverse tubular system close to the Ca2+channels renders them with maximal repolarizing effect.
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Affiliation(s)
- Hanne Borger Rasmussen
- Department of Medical Physiology and Copenhagen Heart Research, University of Copenhagen, The Panum Institute, DK-2200 Copenhagen N, Denmark.
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Wong KL, Chan P, Huang WC, Yang TL, Liu IM, Lai TY, Tsai CC, Cheng JT. Effect of tetramethylpyrazine on potassium channels to lower calcium concentration in cultured aortic smooth muscle cells. Clin Exp Pharmacol Physiol 2003; 30:793-8. [PMID: 14516420 DOI: 10.1046/j.1440-1681.2003.03913.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. Tetramethylpyrazine (TMP) is one of the active principles contained in Ligusticum chuanxiong Hort. (Umbelliferae), a herb that has been used widely in China to treat vascular disorders. 2. In an attempt to elucidate the possible mechanisms of action of TMP, the effect of TMP on intracellular calcium concentrations ([Ca2+]i) was investigated in cultured vascular smooth muscle (A7r5) cells using the Ca(2+)-sensitive dye Fura-2 as an indicator. 3. The increase in [Ca2+]i in A7r5 cells produced by vasopressin (1 micromol/L) or phenylephrine (1 micromol/L) was attenuated by TMP in a concentration-dependent manner. Only inhibitors specific to ATP-sensitive potassium (KATP) channels or small conductance calcium-activated potassium (SKCa) channels attenuated the action of TMP (10 micromol/L) on [Ca2+]i. However, blockers of other K+ channels failed to modify the inhibitory action of TMP (10 micromol/L) on [Ca2+]i. 4. The action of TMP on membrane potential in A7r5 cells was monitored by the fluorescence of bisoxonol. Tetramethylpyrazine caused a concentration-dependent inhibition of changes in membrane potential elicited by KCl (20 mmol/L) or phenylephrine (1 micro mol/L), an effect that was totally reversed by glibenclamide (100 micromol/L) and apamin (100 nmol/L) in combination. 5. The results obtained indicate that the decrease in [Ca2+]i in A7r5 cells produced by TMP is mediated mainly by opening of KATP and/or SKCa channels.
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Affiliation(s)
- Kar-Lok Wong
- Divison of Cardiovascular Medicine, Graduate Institute of Medical Sciences, Taipei Medical University and affiliated Taipei Wan-Fang Hospital, Taipei City, Taiwan
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Dobrzynski H, Janvier NC, Leach R, Findlay JBC, Boyett MR. Effects of ACh and adenosine mediated by Kir3.1 and Kir3.4 on ferret ventricular cells. Am J Physiol Heart Circ Physiol 2002; 283:H615-30. [PMID: 12124209 DOI: 10.1152/ajpheart.00130.2002] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The inotropic effects of ACh and adenosine on ferret ventricular cells were investigated with the action potential-clamp technique. Under current clamp, both agonists resulted in action potential shortening and a decrease in contraction. Under action potential clamp, both agonists failed to decrease contraction substantially. In the absence of agonist, application of the short action potential waveform (recorded previously in the presence of agonist) also resulted in a decrease in contraction. Under action potential clamp, application of ACh resulted in a Ba(2+)-sensitive outward current with the characteristics of muscarinic K+ current (I(K,ACh)); the presence of the muscarinic K+ channel was confirmed by PCR and immunocytochemistry. In the absence of agonist, on application of the short ACh action potential waveform, the decrease in contraction was accompanied by loss of the inward Na(+)/Ca(2+) exchange current (I(NaCa)). ACh also inhibited the background inward K+ current (I(K,1)). It is concluded that ACh activates I(K,ACh), inhibits I(K,1), and indirectly inhibits I(NaCa); this results in action potential shortening, decrease in contraction, and, as a result of the inhibition of I(K,1), minimum decrease in excitability.
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Affiliation(s)
- H Dobrzynski
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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