The Experts below are selected from a list of 1176 Experts worldwide ranked by ideXlab platform

Sabrina Le Bouter - One of the best experts on this subject based on the ideXlab platform.

  • Long-term amiodarone administration remodels expression of ion channel transcripts in the mouse heart
    Circulation, 2004
    Co-Authors: Sabrina Le Bouter, Arnaud Chambellan, Chloé Bellocq, Aziza El Harchi, Céline Marionneau, Toon A.b. Van Veen, Christophe Boixel, Bruno Gavillet, Hugues Abriel, Khai Le Quang
    Abstract:

    Background—The basis for the unique effectiveness of long-term amiodarone treatment on cardiac arrhythmias is incompletely understood. The present study investigated the pharmacogenomic profile of amiodarone on genes encoding ion-channel subunits. Methods and Results—Adult male mice were treated for 6 weeks with vehicle or oral amiodarone at 30, 90, or 180 mg ·k g 1 ·d 1 . Plasma and myocardial levels of amiodarone and N-desethylamiodarone increased dose-dependently, reaching therapeutic ranges observed in human. Plasma triiodothyronine levels decreased, whereas reverse triiodothyronine levels increased in amiodarone-treated animals. In ECG recordings, amiodarone dose-dependently prolonged the RR, PR, QRS, and corrected QT intervals. Specific microarrays containing probes for the complete ion-channel repertoire (IonChips) and real-time reverse transcription–polymerase chain reaction experiments demonstrated that amiodarone induced a dose-dependent remodeling in multiple ion-channel subunits. Genes encoding Na (SCN4A, SCN5A, SCN1B), connexin (GJA1), Ca 2 (CaCNA1C), and K channels (KCNA5, KCNB1, KCND2) were downregulated. In patch-clamp experiments, lower expression of K and Na channel genes was associated with decreased Ito,f ,I K,slow, and INa currents. Inversely, other K channel - and -subunits, such as KCNA4, KCNK1, KCNAB1, and KCNE3, were upregulated. Conclusions—Long-term amiodarone treatment induces a dose-dependent remodeling of ion-channel expression that is correlated with the cardiac electrophysiologic effects of the drug. This profile cannot be attributed solely to the amiodarone-induced cardiac hypothyroidism syndrome. Thus, in addition to the direct effect of the drug on membrane proteins, part of the therapeutic action of long-term amiodarone treatment is likely related to its effect on ion-channel transcripts. (Circulation. 2004;110:3028-3035.)

  • Microarray Analysis Reveals Complex Remodeling of Cardiac Ion Channel Expression With Altered Thyroid Status Relation to Cellular and Integrated Electrophysiology
    Circulation Research, 2003
    Co-Authors: Sabrina Le Bouter, Arnaud Chambellan, Franck Aimond, Gilles Toumaniantz, Gilles Lande, Sepideh Siavoshian, Isabelle Baró, Sophie Demolombe, Chloé Bellocq, Amber Pond
    Abstract:

    Although electrophysiological remodeling occurs in various myocardial diseases, the underlying molecular mechanisms are poorly understood. cDNA microarrays containing probes for a large population of mouse genes encoding ion channel subunits (“IonChips”) were developed and exploited to investigate remodeling of ion channel transcripts associated with altered thyroid status in adult mouse ventricle. Functional consequences of hypo- and hyperthyroidism were evaluated with patch-clamp and ECG recordings. Hypothyroidism decreased heart rate and prolonged QTc duration. Opposite changes were observed in hyperthyroidism. Microarray analysis revealed that hypothyroidism induces significant reductions in KCNA5, KCNB1, KCND2, and KCNK2 transcripts, whereas KCNQ1 and KCNE1 expression is increased. In hyperthyroidism, in contrast, KCNA5 and KCNB1 expression is increased and KCNQ1 and KCNE1 expression is decreased. Real-time RT-PCR validated these results. Consistent with microarray analysis, Western blot experiments ...

Jason X-j Yuan - One of the best experts on this subject based on the ideXlab platform.

  • Tetramerization domain mutations in KCNA5 affect channel kinetics and cause abnormal trafficking patterns
    American journal of physiology. Cell physiology, 2009
    Co-Authors: Elyssa D Burg, Oleksandr Platoshyn, Igor F. Tsigelny, Beatriz Lozano-ruiz, Brinda K. Rana, Jason X-j Yuan
    Abstract:

    The activity of voltage-gated K+ (KV) channels plays an important role in regulating pulmonary artery smooth muscle cell (PASMC) contraction, proliferation, and apoptosis. The highly conserved NH2-terminal tetramerization domain (T1) of KV channels is important for proper channel assembly, association with regulatory KV β-subunits, and localization of the channel to the plasma membrane. We recently reported two nonsynonymous mutations (G182R and E211D) in the KCNA5 gene of patients with idiopathic pulmonary arterial hypertension, which localize to the T1 domain of KCNA5. To study the electrophysiological properties and expression patterns of the mutants compared with the wild-type (WT) channel in vitro, we transfected HEK-293 cells with WT KCNA5, G182R, E211D, or the double mutant G182R/E211D channel. The mutants form functional channels; however, whole cell current kinetic differences between WT and mutant channels exist. Steady-state inactivation curves of the G182R and G182R/E211D channels reveal accelerated inactivation; the mutant channels inactivated at more hyperpolarized potentials compared with the WT channel. Channel protein expression was also decreased by the mutations. Compared with the WT channel, which was present in its mature glycosylated form, the mutant channels are present in greater proportion in their immature form in HEK-293 cells. Furthermore, G182R protein level is greatly reduced in COS-1 cells compared with WT. Immunostaining data support the hypothesis that, while WT protein localizes to the plasma membrane, mutant protein is mainly retained in intracellular packets. Overall, these data support a role for the T1 domain in channel kinetics as well as in KCNA5 channel subcellular localization.

  • Hypoxia selectively inhibits KCNA5 channels in pulmonary artery smooth muscle cells.
    Annals of the New York Academy of Sciences, 2009
    Co-Authors: Amy L. Firth, Oleksandr Platoshyn, Elena E Brevnova, Elyssa D Burg, Frank L. Powell, Gabriel H. Haddad, Jason X-j Yuan
    Abstract:

    Abstract Acute hypoxia induces pulmonary vasoconstriction and chronic hypoxia causes pulmonary vascular remodeling characterized by significant vascular medial hypertrophy. Electromechanical and pharmacomechanical mechanisms are involved in regulating pulmonary vasomotor tone, while changes in cytosolic Ca2+ concentration ([Ca2+](cyt)) are an important signal in regulating contraction and proliferation of pulmonary artery smooth muscle cells (PASMC). Hypoxia-induced increases in [Ca2+](cyt) are, in part, mediated by selective inhibition of voltage-gated K+ (Kv) channels in PASMC. Kv1.5, encoded by the KCNA5 gene, is a Kv channel alpha subunit that forms functional homotetrameric and heterotetrameric Kv channels in PASMC. Activity of Kv channels contributes to the regulation of resting membrane potential. Overexpression of the human KCNA5 gene in rat PASMC and other cell types increases whole-cell Kv currents and causes membrane hyperpolarization. However, acute hypoxia only reduced Kv currents in KCNA5-transfected PASMC. These results provide compelling evidence that Kv1.5 is an important hypoxia-sensitive Kv channel in PASMC, contributing to regulation of membrane potential and intracellular Ca2+ homeostasis during hypoxia. This hypoxia-sensitive mechanism essential for inhibiting Kv1.5 channel activity is exclusively present in PASMC.

  • Acute hypoxia selectively inhibits KCNA5 channels in pulmonary artery smooth muscle cells.
    American journal of physiology. Cell physiology, 2005
    Co-Authors: Oleksandr Platoshyn, Elena E Brevnova, Elyssa D Burg, Carmelle V Remillard, Jason X-j Yuan
    Abstract:

    Acute hypoxia causes pulmonary vasoconstriction in part by inhibiting voltage-gated K(+) (Kv) channel activity in pulmonary artery smooth muscle cells (PASMC). The hypoxia-mediated decrease in Kv currents [I(K(V))] is selective to PASMC; hypoxia has little effect on I(K(V)) in mesenteric artery smooth muscle cells (MASMC). Functional Kv channels are homo- and/or heterotetramers of pore-forming alpha-subunits and regulatory beta-subunits. KCNA5 is a Kv channel alpha-subunit that forms functional Kv channels in PASMC and regulates resting membrane potential. We have shown that acute hypoxia selectively inhibits I(K(V)) through KCNA5 channels in PASMC. Overexpression of the human KCNA5 gene increased I(K(V)) and caused membrane hyperpolarization in HEK-293, COS-7, and rat MASMC and PASMC. Acute hypoxia did not affect I(K(V)) in KCNA5-transfected HEK-293 and COS-7 cells. However, overexpression of KCNA5 in PASMC conferred its sensitivity to hypoxia. Reduction of Po(2) from 145 to 35 mmHg reduced I(K(V)) by approximately 40% in rat PASMC transfected with human KCNA5 but had no effect on I(K(V)) in KCNA5-transfected rat MASMC (or HEK and COS cells). These results indicate that KCNA5 is an important Kv channel that regulates resting membrane potential and that acute hypoxia selectively reduces KCNA5 channel activity in PASMC relative to MASMC and other cell types. Because Kv channels (including KCNA5) are ubiquitously expressed in PASMC and MASMC, the observation from this study indicates that a hypoxia-sensitive mechanism essential for inhibiting KCNA5 channel activity is exclusively present in PASMC. The divergent effect of hypoxia on I(K(V)) in PASMC and MASMC also may be due to different expression levels of KCNA5 channels.

Khai Le Quang - One of the best experts on this subject based on the ideXlab platform.

  • Long-term amiodarone administration remodels expression of ion channel transcripts in the mouse heart
    Circulation, 2004
    Co-Authors: Sabrina Le Bouter, Arnaud Chambellan, Chloé Bellocq, Aziza El Harchi, Céline Marionneau, Toon A.b. Van Veen, Christophe Boixel, Bruno Gavillet, Hugues Abriel, Khai Le Quang
    Abstract:

    Background—The basis for the unique effectiveness of long-term amiodarone treatment on cardiac arrhythmias is incompletely understood. The present study investigated the pharmacogenomic profile of amiodarone on genes encoding ion-channel subunits. Methods and Results—Adult male mice were treated for 6 weeks with vehicle or oral amiodarone at 30, 90, or 180 mg ·k g 1 ·d 1 . Plasma and myocardial levels of amiodarone and N-desethylamiodarone increased dose-dependently, reaching therapeutic ranges observed in human. Plasma triiodothyronine levels decreased, whereas reverse triiodothyronine levels increased in amiodarone-treated animals. In ECG recordings, amiodarone dose-dependently prolonged the RR, PR, QRS, and corrected QT intervals. Specific microarrays containing probes for the complete ion-channel repertoire (IonChips) and real-time reverse transcription–polymerase chain reaction experiments demonstrated that amiodarone induced a dose-dependent remodeling in multiple ion-channel subunits. Genes encoding Na (SCN4A, SCN5A, SCN1B), connexin (GJA1), Ca 2 (CaCNA1C), and K channels (KCNA5, KCNB1, KCND2) were downregulated. In patch-clamp experiments, lower expression of K and Na channel genes was associated with decreased Ito,f ,I K,slow, and INa currents. Inversely, other K channel - and -subunits, such as KCNA4, KCNK1, KCNAB1, and KCNE3, were upregulated. Conclusions—Long-term amiodarone treatment induces a dose-dependent remodeling of ion-channel expression that is correlated with the cardiac electrophysiologic effects of the drug. This profile cannot be attributed solely to the amiodarone-induced cardiac hypothyroidism syndrome. Thus, in addition to the direct effect of the drug on membrane proteins, part of the therapeutic action of long-term amiodarone treatment is likely related to its effect on ion-channel transcripts. (Circulation. 2004;110:3028-3035.)

Murat Oz - One of the best experts on this subject based on the ideXlab platform.

  • The Pattern of mRNA Expression Is Changed in Sinoatrial Node from Goto-Kakizaki Type 2 Diabetic Rat Heart
    Experimental Diabetes Research, 2018
    Co-Authors: F. C. Howarth, K. Parekh, Pychadathil Jayaprakash, M. A. Qureshi, Murat Oz, Halina Dobrzynski, T. E. Adrian
    Abstract:

    Background. In vivo experiments in Goto-Kakizaki (GK) type 2 diabetic rats have demonstrated reductions in heart rate from a young age. The expression of genes encoding more than 70 proteins that are associated with the generation and conduction of electrical activity in the GK sinoatrial node (SAN) have been evaluated to further clarify the molecular basis of the low heart rate. Materials and Methods. Heart rate and expression of genes were evaluated with an extracellular electrode and real-time RT-PCR, respectively. Rats aged 12-13 months were employed in these experiments. Results. Isolated spontaneous heart rate was reduced in GK heart (161 ± 12 bpm) compared to controls (229 ± 11 bpm). There were many differences in expression of mRNA, and some of these differences were of particular interest. Compared to control SAN, expression of some genes were downregulated in GK-SAN: gap junction, Gja1 (Cx43), Gja5 (Cx40), Gjc1 (Cx45), and Gjd3 (Cx31.9); cell membrane transport, Trpc1 (TRPC1) and Trpc6 (TRPC6); hyperpolarization-activated cyclic nucleotide-gated channels, Hcn1 (HCN1) and Hcn4 (HCN4); calcium channels, Cacna1d (Cav1.3), Cacna1g (Cav3.1), Cacna1h (Cav3.2), Cacna2d1 (Cavα2δ1), Cacna2d3 (Cavα2δ3), and Cacng4 (Cavγ4); and potassium channels, Kcna2 (Kv1.2), Kcna4 (Kv1.4), KCNA5 (Kv1.5), Kcnb1 (Kv2.1), Kcnd3 (Kv4.3), Kcnj2 (Kir2.1), Kcnk1 (TWIK1), Kcnk5 (K2P5.1), Kcnk6 (TWIK2), and Kcnn2 (SK2) whilst others were upregulated in GK-SAN: Ryr2 (RYR2) and Nppb (BNP). Conclusions. This study provides new insight into the changing expression of genes in the sinoatrial node of diabetic heart.

  • Shortening and intracellular Ca2+ in ventricular myocytes and expression of genes encoding cardiac muscle proteins in early onset type 2 diabetic Goto–Kakizaki rats
    Experimental Physiology, 2012
    Co-Authors: K. A. Salem, K. Parekh, M. A. Qureshi, Murat Oz
    Abstract:

    Abstract There has been a spectacular rise in the global prevalence of type 2 diabetes mellitus. Cardiovascular complications are the major cause of morbidity and mortality in diabetic patients. Contractile dysfunction, associated with disturbances in excitation-contraction coupling, has been widely demonstrated in the diabetic heart. The aim of this study was to investigate the pattern of cardiac muscle genes that are involved in the process of excitation-contraction coupling in the hearts of early onset (8-10 weeks of age) type 2 diabetic Goto-Kakizaki (GK) rats. Gene expression was assessed in ventricular muscle with real-time RT-PCR; shortening and intracellular Ca(2+) were measured in ventricular myocytes with video edge detection and fluorescence photometry, respectively. The general characteristics of the GK rats included elevated fasting and non-fasting blood glucose and blood glucose at 120 min following a glucose challenge. Expression of genes encoding cardiac muscle proteins (Myh6/7, Mybpc3, Myl1/3, Actc1, Tnni3, Tnn2, Tpm1/2/4 and Dbi) and intercellular proteins (Gja1/4/5/7, Dsp and Cav1/3) were unaltered in GK ventricle compared with control ventricle. The expression of genes encoding some membrane pumps and exchange proteins was unaltered (Atp1a1/2, Atp1b1 and Slc8a1), whilst others were either upregulated (Atp1a3, relative expression 2.61 ± 0.69 versus 0.84 ± 0.23) or downregulated (Slc9a1, 0.62 ± 0.07 versus 1.08 ± 0.08) in GK ventricle compared with control ventricle. The expression of genes encoding some calcium (Cacna1c/1g, Cacna2d1/2d2 and Cacnb1/b2), sodium (Scn5a) and potassium channels (Kcna3/5, Kcnj3/5/8/11/12, Kchip2, Kcnab1, Kcnb1, Kcnd1/2/3, Kcne1/4, Kcnq1, Kcng2, Kcnh2, Kcnk3 and Kcnn2) were unaltered, whilst others were either upregulated (Cacna1h, 0.95 ± 0.16 versus 0.47 ± 0.09; Scn1b, 1.84 ± 0.16 versus 1.11 ± 0.11; and Hcn2, 1.55 ± 0.15 versus 1.03 ± 0.08) or downregulated (Hcn4, 0.16 ± 0.03 versus 0.37 ± 0.08; Kcna2, 0.35 ± 0.03 versus 0.80 ± 0.11; Kcna4, 0.79 ± 0.25 versus 1.90 ± 0.26; and Kcnj2, 0.52 ± 0.07 versus 0.78 ± 0.08) in GK ventricle compared with control ventricle. The amplitude of ventricular myocyte shortening and the intracellular Ca(2+) transient were unaltered; however, the time-to-peak shortening was prolonged and time-to-half decay of the Ca(2+) transient was shortened in GK myocytes compared with control myocytes. The results of this study demonstrate changes in expression of genes encoding various excitation-contraction coupling proteins that are associated with disturbances in myocyte shortening and intracellular Ca(2+) transport.

Elizabeth R. Lawlor - One of the best experts on this subject based on the ideXlab platform.

  • Abstract 3288: The KCNA5 promoter is hypermethylated in Ewing sarcoma and silencing contributes to cell proliferation
    Tumor Biology, 2015
    Co-Authors: Katherine E. Ryland, Allegra G. Hawkins, Daniel J. Weisenberger, Scott C. Borinstein, Peter W. Laird, Jeffrey R. Martens, Elizabeth R. Lawlor
    Abstract:

    Potassium channels regulate a variety of biological processes and dysfunction of these channels contributes to cancer initiation and progression. We recently showed that the KCNA5-encoded channel, Kv1.5, is a target of polycomb-group (PcG)-dependent repression in aggressive pediatric solid tumors and that this epigenetic silencing of the Kv1.5 channel contributes to cell survival under hypoxic stress. In human cancer, the promoters of PcG target genes are often subject to aberrant DNA hypermethylation. Therefore, in the current study we investigated whether the KCNA5 locus is hypermethylated in Ewing sarcoma. The methylation status of KCNA5 was determined in tumor samples, non-transformed cells and a panel of cancer cell lines using a custom Illumina GoldenGate® methylation array and by MethyLight. Promoter methylation and expression of KCNA5 were measured by MethyLight and qRT-PCR, respectively, before and after exposure to decitabine. Proliferation was assessed in untreated and decitabine treated cells in the presence or absence of the Kv1.5 channel blocker diphenyl phosphine oxide-1 (DPO-1). Methylation array studies of normal tissues and Ewing sarcoma tumors and cell lines showed that the KCNA5 promoter is hypermethylated in Ewing sarcoma compared to normal tissues. This hypermethylation was confirmed by MethyLight analysis in an independent set of primary tumors and cell lines. These studies also showed that methylation was relatively higher in cell lines than primary tumors. Exposure of Ewing sarcoma cells to decitabine led to demethylation of the KCNA5 promoter and directly correlated with increased expression of the KCNA5 transcript. Decitabine treatment did not affect the viability of Ewing sarcoma cell lines; however it led to a decreased proliferation. Significantly, pharmacologic inhibition of the Kv1.5 channel by DPO-1 partially reversed the decitabine-induced reduction in cell proliferation in three different cell lines (TC-71, A673 and A4573). Together these studies show that the KCNA5 promoter is hypermethylated in Ewing sarcoma and that inactivation of the Kv1.5 channel promotes cell proliferation. This work identifies DNA methylation as another epigenetic mechanism that regulates KCNA5 expression in cancer and further implicates epigenetic repression of the Kv1.5 potassium ion channel in tumor pathogenesis. Citation Format: Katherine Ryland, Allegra Hawkins, Daniel J. Weisenberger, Scott Borinstein, Peter W. Laird, Jeffrey R. Martens, Elizabeth R. Lawlor. The KCNA5 promoter is hypermethylated in Ewing sarcoma and silencing contributes to cell proliferation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3288. doi:10.1158/1538-7445.AM2015-3288

  • Abstract 3968: Polycomb-mediated suppression of the voltage-gated potassium channel KCNA5 promotes Ewing sarcoma cell survival
    Tumor Biology, 2014
    Co-Authors: Katherine E. Ryland, Jeffrey R. Martens, Laurie K. Svoboda, Elizabeth R. Lawlor
    Abstract:

    Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA In Ewing sarcoma (ES) relapse is prevalent indicating that some cancer cells are resistant to treatment; however, the mechanism(s) governing treatment resistance and relapse are unknown. Voltage-gated potassium (Kv) channels play an essential role in maintaining a balance between cell survival and apoptosis. In particular, the Kv1.5 channel is a key sensor of oxygen tension and regulator of apoptosis, controlling potassium efflux and caspase activation. It was recently discovered that brain tissue can be tolerized to conditions of hypoxia and nutrient deprivation and that this ischemic tolerance is mediated by upregulation of the polycomb (PcG) protein BMI-1 and epigenetic repression of the Kv1.5-encoding locus KCNA5. Given that Kv1.5 expression is often downregulated in human cancers and that ES cells upregulate the PcG proteins BMI-1 and EZH2, we hypothesized that polycomb-dependent suppression of KCNA5 contributes to ES cell survival under conditions of stress. To test this hypothesis, we exposed ES and non-transformed cells to conditions of hypoxia (1% O2) and growth factor deprivation and measured cell viability in the presence and absence of potassium channel blockers 4′-aminopyridine (4′AP) and diphenyl phosphine oxide-1 (DPO-1). These studies were repeated in ES cells following BMI-1 knockdown, treatment with the EZH2 inhibitor GSK-126 and in ES cells that were genetically altered to ectopically express active wild-type (WT) or inactive (Pore-Dead (PD)) Kv1.5 channel. Chromatin immunoprecipitation (ChIP) was used to determine PcG protein binding at the KCNA5 locus. Exposure of non-transformed cells to hypoxia and growth factor deprivation resulted in significant cell death. In contrast, ES cell viability was unaffected. Significantly, however, knockdown of BMI-1 and inhibition of EZH2 resulted in diminished ES cell viability in conditions of stress and this cell death was blocked by 4′AP and DPO-1. Likewise, pharmacologic inhibition of Kv1.5 also inhibited stress-induced death of non-transformed cells. ES cells transduced to ectopically express WT- but not PD-Kv1.5 were sensitized to stress-induced cell death and this reduction in cell viability was again reversed by 4′AP and DPO-1. Caspase activation assays confirmed that cell death was mediated by apoptosis. Finally, ChIP studies revealed the presence of BMI-1 and the EZH2-dependent histone modification, H3K27me3, at the KCNA5 promoter in ES cells. Together these data show that ES cells are resistant to hypoxia and growth factor induced cell death and that this resistance is mechanistically linked to downregulation of Kv1.5 channel activity. Further, we have determined that suppression of the Kv1.5 channel is mediated epigenetically, by polycomb-dependent repression of the KCNA5 locus. Together these studies reveal a novel mechanism of ES cell survival under conditions of physiologic stress. Citation Format: Katherine Ryland, Laurie Svoboda, Jeffrey R. Martens, Elizabeth R. Lawlor. Polycomb-mediated suppression of the voltage-gated potassium channel KCNA5 promotes Ewing sarcoma cell survival. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3968. doi:10.1158/1538-7445.AM2014-3968