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https://www.readbyqxmd.com/read/28408648/azithromycin-causes-a-novel-proarrhythmic-syndrome
#1
Zhenjiang Yang, Joseph K Prinsen, Kevin R Bersell, Wangzhen Shen, Liudmila Yermalitskaya, Tatiana Sidorova, Paula B Luis, Lynn Hall, Wei Zhang, Liping Du, Ginger Milne, Patrick Tucker, Alfred L George, Courtney M Campbell, Robert A Pickett, Christian M Shaffer, Nagesh Chopra, Tao Yang, Bjorn C Knollmann, Dan M Roden, Katherine T Murray
BACKGROUND: The widely used macrolide antibiotic azithromycin increases risk of cardiovascular and sudden cardiac death, although the underlying mechanisms are unclear. Case reports, including the one we document here, demonstrate that azithromycin can cause rapid, polymorphic ventricular tachycardia in the absence of QT prolongation, indicating a novel proarrhythmic syndrome. We investigated the electrophysiological effects of azithromycin in vivo and in vitro using mice, cardiomyocytes, and human ion channels heterologously expressed in human embryonic kidney (HEK 293) and Chinese hamster ovary (CHO) cells...
April 2017: Circulation. Arrhythmia and Electrophysiology
https://www.readbyqxmd.com/read/28389584/control-of-kir-channel-gating-by-cytoplasmic-domain-interface-interactions
#2
William F Borschel, Shizhen Wang, Sunjoo Lee, Colin G Nichols
Inward rectifier potassium (Kir) channels are expressed in almost all mammalian tissues and play critical roles in the control of excitability. Pancreatic ATP-sensitive K (KATP) channels are key regulators of insulin secretion and comprise Kir6.2 subunits coupled to sulfonylurea receptors. Because these channels are reversibly inhibited by cytoplasmic ATP, they link cellular metabolism with membrane excitability. Loss-of-function mutations in the pore-forming Kir6.2 subunit cause congenital hyperinsulinism as a result of diminished channel activity...
April 7, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/28383527/activation-of-the-hypoglossal-to-tongue-musculature-motor-pathway-by-remote-control
#3
Garret A Horton, Jimmy J Fraigne, Zoltan A Torontali, Matthew B Snow, Jennifer L Lapierre, Hattie Liu, Gaspard Montandon, John H Peever, Richard L Horner
Reduced tongue muscle tone precipitates obstructive sleep apnea (OSA), and activation of the tongue musculature can lessen OSA. The hypoglossal motor nucleus (HMN) innervates the tongue muscles but there is no pharmacological agent currently able to selectively manipulate a channel (e.g., Kir2.4) that is highly restricted in its expression to cranial motor pools such as the HMN. To model the effect of manipulating such a restricted target, we introduced a "designer" receptor into the HMN and selectively modulated it with a "designer" drug...
April 6, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28365825/inhibition-of-inwardly-rectifying-kir2-x-channels-by-the-novel-anti-cancer-agent-gambogic-acid-depends-on-both-pore-block-and-pip2-interference
#4
Daniel Scherer, Benedikt Schworm, Claudia Seyler, Panagiotis Xynogalos, Eberhard P Scholz, Dierk Thomas, Hugo A Katus, Edgar Zitron
The caged xanthone gambogic acid (GA) is a novel anti-cancer agent which exhibits anti-proliferative, anti-inflammatory and cytotoxic effects in many types of cancer tissues. In a recent phase IIa study, GA exhibits a favourable safety profile. However, limited data are available concerning its interaction with cardiac ion channels. Heteromeric assembly of Kir2.x channels underlies the cardiac inwardly rectifying IK1 current which is responsible for the stabilization of the diastolic resting membrane potential...
April 2, 2017: Naunyn-Schmiedeberg's Archives of Pharmacology
https://www.readbyqxmd.com/read/28345117/inwardly-rectifying-k-currents-in-cultured-oligodendrocytes-from-rat-optic-nerve-are-insensitive-to-ph
#5
Alberto Pérez-Samartín, Edith Garay, Juan Pablo H Moctezuma, Abraham Cisneros-Mejorado, María Victoria Sánchez-Gómez, Guadalupe Martel-Gallegos, Leticia Robles-Martínez, Manuel Canedo-Antelo, Carlos Matute, Rogelio O Arellano
Inwardly rectifying K(+) (Kir) channel expression signals at an advanced stage of maturation during oligodendroglial differentiation. Knocking down their expression halts the generation of myelin and produces severe abnormalities in the central nervous system. Kir4.1 is the main subunit involved in the tetrameric structure of Kir channels in glial cells; however, the precise composition of Kir channels expressed in oligodendrocytes (OLs) remains partially unknown, as participation of other subunits has been proposed...
March 27, 2017: Neurochemical Research
https://www.readbyqxmd.com/read/28301408/k-cl-cotransporter-2-mediated-cl-extrusion-determines-developmental-stage-dependent-impact-of-propofol-anesthesia-on-dendritic-spines
#6
Martin Puskarjov, Hubert Fiumelli, Adrian Briner, Timea Bodogan, Kornel Demeter, Claudia-Marvine Lacoh, Martina Mavrovic, Peter Blaesse, Kai Kaila, Laszlo Vutskits
BACKGROUND: General anesthetics potentiating γ-aminobutyric acid (GABA)-mediated signaling are known to induce a persistent decrement in excitatory synapse number in the cerebral cortex when applied during early postnatal development, while an opposite action is produced at later stages. Here, the authors test the hypothesis that the effect of general anesthetics on synaptogenesis depends upon the efficacy of GABA receptor type A (GABAA)-mediated inhibition controlled by the developmental up-regulation of the potassium-chloride (K-Cl) cotransporter 2 (KCC2)...
May 2017: Anesthesiology
https://www.readbyqxmd.com/read/28289282/the-schizophrenia-and-autism-associated-gene-transcription-factor-4-regulates-the-columnar-distribution-of-layer-2-3-prefrontal-pyramidal-neurons-in-an-activity-dependent-manner
#7
S C Page, G R Hamersky, R A Gallo, M D Rannals, N E Calcaterra, M N Campbell, B Mayfield, A Briley, B N Phan, A E Jaffe, B J Maher
Disruption of the laminar and columnar organization of the brain is implicated in several psychiatric disorders. Here, we show in utero gain-of-function of the psychiatric risk gene transcription factor 4 (TCF4) severely disrupts the columnar organization of medial prefrontal cortex (mPFC) in a transcription- and activity-dependent manner. This morphological phenotype was rescued by co-expression of TCF4 plus calmodulin in a calcium-dependent manner and by dampening neuronal excitability through co-expression of an inwardly rectifying potassium channel (Kir2...
March 14, 2017: Molecular Psychiatry
https://www.readbyqxmd.com/read/28284503/renal-denervation-regulates-the-atrial-arrhythmogenic-substrates-through-reverse-structural-remodeling-in-heart-failure-rabbit-model
#8
Shinya Yamada, Li-Wei Lo, Yu-Hui Chou, Wei-Lun Lin, Shih-Lin Chang, Yenn-Jiang Lin, Shih-Ann Chen
BACKGROUND: Heart failure (HF) causes atrial remodeling and increases the incidence of atrial fibrillation (AF). Renal denervation (RDN) has been shown to decrease the development of AF. This study aimed to identify the effects of RDN on the atrial arrhythmogenic substrates in HF. METHODS: Rabbits were classified into four groups: control (n=9), RDN (n=10), HF (n=6) and HF-RDN (n=9). Surgical and chemical RDN was approached through bilateral retroperitoneal flank incisions in RDN and HF-RDN...
May 15, 2017: International Journal of Cardiology
https://www.readbyqxmd.com/read/28148533/inhibition-of-vascular-smooth-muscle-inward-rectifier-k-channels-restores-myogenic-tone-in-mouse-urinary-bladder-arterioles
#9
Nathan R Tykocki, Adrian D Bonev, Thomas Andrew Longden, Thomas J Heppner, Mark T Nelson
Prolonged decreases in urinary bladder blood flow are linked to overactive and underactive bladder pathologies. However, the mechanisms regulating bladder vascular reactivity are largely unknown. To investigate these mechanisms, we examined myogenic and vasoactive properties of mouse bladder feed arterioles (BFAs). Unlike similar-sized arterioles from other vascular beds, BFAs failed to constrict in response to increases in intraluminal pressure (5-80 mmHg). Consistent with this lack of myogenic tone, arteriolar smooth muscle cell membrane potential was hyperpolarized (-72...
February 1, 2017: American Journal of Physiology. Renal Physiology
https://www.readbyqxmd.com/read/28112313/soluble-epoxide-hydrolase-inhibitors-might-prevent-ischemic-arrhythmias-via-microrna-1-repression-in-primary-neonatal-mouse-ventricular-myocytes
#10
Qiong Liu, Xuan Zhao, Ran Peng, Mi Wang, Wang Zhao, Ya-Jun Gui, Cai-Xiu Liao, Dan-Yan Xu
Ischemic arrhythmias are the main causes of sudden cardiac death. It has been reported that soluble epoxide hydrolase inhibitors (sEHis) could prevent arrhythmias; however, the underlying molecular mechanisms remain unclear. In recent years, the proarrhythmic role of microRNA-1 (miR-1) has been investigated. This study aimed to elucidate whether sEHis prevented ischemic arrhythmias by suppressing miR-1. The primary neonatal mouse ventricular myocyte model of miR-1 overexpression was established by incubating with agonist microONTM mmu-miR-1a-3p agomir (DAEDstain(TM) Dye) (agomiR-1)...
January 23, 2017: Molecular BioSystems
https://www.readbyqxmd.com/read/28007664/effects-of-seasonal-acclimatization-on-action-potentials-and-sarcolemmal-k-currents-in-roach-rutilus-rutilus-cardiac-myocytes
#11
Ahmed Badr, Minna Hassinen, Mohamed F El-Sayed, Matti Vornanen
Temperature sensitivity of electrical excitability is a potential limiting factor for high temperature tolerance of ectotherms. The present study examines whether heat resistance of electrical excitability of cardiac myocytes is modified by seasonal thermal acclimatization in roach (Rutilus rutilus), a eurythermal teleost species. To this end, temperature dependencies of ventricular action potentials (APs), and atrial and ventricular K(+) currents were measured from winter-acclimatized (WiR) and summer-acclimatized (SuR) roach...
March 2017: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
https://www.readbyqxmd.com/read/27882143/expression-of-connexin-43-ion-channels-and-ca-2-handling-proteins-in-rat-pulmonary-vein-cardiomyocytes
#12
Yaqiong Xiao, Xue Cai, Andrew Atkinson, Sunil Jit Logantha, Mark Boyett, Halina Dobrzynski
Atrial fibrillation (AF) is the most common cardiac arrhythmia. AF is thought to be triggered by ectopic beats, originating primarily in the myocardial sleeves surrounding the pulmonary veins (PVs). The mechanisms underlying these cardiac arrhythmias remain unclear. To investigate this, frozen sections of heart and lung tissue from adult rats without arrhythmia were obtained in different planes, stained with Masson's trichrome, and immunolabeled for connexin 43 (Cx43), caveolin-3 (Cav3), hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4), Nav1...
November 2016: Experimental and Therapeutic Medicine
https://www.readbyqxmd.com/read/27872214/effects-of-prolonged-anoxia-on-electrical-activity-of-the-heart-in-crucian-carp-carassius-carassius
#13
Elisa Tikkanen, Jaakko Haverinen, Stuart Egginton, Minna Hassinen, Matti Vornanen
The effects of sustained anoxia on cardiac electrical excitability were examined in the anoxia-tolerant crucian carp (Carassius carassius). The electrocardiogram (ECG) and expression of excitation-contraction coupling genes were studied in fish acclimatised to normoxia in summer (+18°C) or winter (+2°C), and in winter fish after 1, 3 and 6 weeks of anoxia. Anoxia induced a sustained bradycardia from a heart rate of 10.3±0.77 beats min(-1) to 4.1±0.29 beats min(-1) (P<0.05) after 5 weeks, and heart rate slowly recovered to control levels when oxygen was restored...
February 1, 2017: Journal of Experimental Biology
https://www.readbyqxmd.com/read/27696527/differential-kv1-3-kca3-1-and-kir2-1-expression-in-classically-and-alternatively-activated-microglia
#14
Hai M Nguyen, Eva M Grössinger, Makoto Horiuchi, Kyle W Davis, Lee-Way Jin, Izumi Maezawa, Heike Wulff
Microglia are highly plastic cells that can assume different phenotypes in response to microenvironmental signals. Lipopolysaccharide (LPS) and interferon-γ (IFN-γ) promote differentiation into classically activated M1-like microglia, which produce high levels of pro-inflammatory cytokines and nitric oxide and are thought to contribute to neurological damage in ischemic stroke and Alzheimer's disease. IL-4 in contrast induces a phenotype associated with anti-inflammatory effects and tissue repair. We here investigated whether these microglia subsets vary in their K(+) channel expression by differentiating neonatal mouse microglia into M(LPS) and M(IL-4) microglia and studying their K(+) channel expression by whole-cell patch-clamp, quantitative PCR and immunohistochemistry...
January 2017: Glia
https://www.readbyqxmd.com/read/27527100/structural-basis-of-control-of-inward-rectifier-kir2-channel-gating-by-bulk-anionic-phospholipids
#15
Sun-Joo Lee, Feifei Ren, Eva-Maria Zangerl-Plessl, Sarah Heyman, Anna Stary-Weinzinger, Peng Yuan, Colin G Nichols
Inward rectifier potassium (Kir) channel activity is controlled by plasma membrane lipids. Phosphatidylinositol-4,5-bisphosphate (PIP2) binding to a primary site is required for opening of classic inward rectifier Kir2.1 and Kir2.2 channels, but interaction of bulk anionic phospholipid (PL(-)) with a distinct second site is required for high PIP2 sensitivity. Here we show that introduction of a lipid-partitioning tryptophan at the second site (K62W) generates high PIP2 sensitivity, even in the absence of PL(-) Furthermore, high-resolution x-ray crystal structures of Kir2...
September 2016: Journal of General Physiology
https://www.readbyqxmd.com/read/27511995/effect-of-ethanol-and-acetaldehyde-at-clinically-relevant-concentrations-on-atrial-inward-rectifier-potassium-current-ik1-separate-and-combined-effect
#16
Z Horakova, P Matejovic, M Pasek, J Hosek, M Simurdova, J Simurda, M Bebarova
Atrial fibrillation is the most common arrhythmia at alcohol consumption. Its pathogenesis is complex, at least partly related to changes of cardiac inward rectifier potassium currents including IK1. Both ethanol and acetaldehyde have been demonstrated to considerably modify IK1 in rat ventricular myocytes. However, analogical data on the atrial IK1 are lacking. The present study aimed to analyse IK1 changes induced by ethanol and acetyldehyde in atrial myocytes. The experiments were performed by the whole cell patch-clamp technique at 23 ± 1°C on enzymatically isolated rat and guinea-pig atrial myocytes as well as on expressed human Kir2...
June 2016: Journal of Physiology and Pharmacology: An Official Journal of the Polish Physiological Society
https://www.readbyqxmd.com/read/27235552/hypoxic-stress-up-regulates-kir2-1-expression-and-facilitates-cell-proliferation-in-brain-capillary-endothelial-cells
#17
Hideto Yamamura, Yoshiaki Suzuki, Hisao Yamamura, Kiyofumi Asai, Yuji Imaizumi
The blood-brain barrier (BBB) is mainly composed of brain capillary endothelial cells (BCECs), astrocytes and pericytes. Brain ischemia causes hypoxic encephalopathy and damages BBB. However, it remains still unclear how hypoxia affects BCECs. In the present study, t-BBEC117 cells, an immortalized bovine brain endothelial cell line, were cultured under hypoxic conditions at 4-5% oxygen for 72 h. This hypoxic stress caused hyperpolarization of resting membrane potential. Patch-clamp recordings revealed a marked increase in Ba(2+)-sensitive inward rectifier K(+) current in t-BBEC117 cells after hypoxic culture...
August 5, 2016: Biochemical and Biophysical Research Communications
https://www.readbyqxmd.com/read/27117805/pharmacological-inhibition-of-ik1-by-pa-6-in-isolated-rat-hearts-affects-ventricular-repolarization-and-refractoriness
#18
Mark A Skarsfeldt, Helena Carstensen, Lasse Skibsbye, Chuyi Tang, Rikke Buhl, Bo H Bentzen, Thomas Jespersen
The inwardly rectifying potassium current (IK 1) conducted through Kir2.X channels contribute to repolarization of the cardiac action potential and to stabilization of the resting membrane potential in cardiomyocytes. Our aim was to investigate the effect of the recently discovered IK 1 inhibitor PA-6 on action potential repolarization and refractoriness in isolated rat hearts. Transiently transfected HEK-293 cells expressing IK 1 were voltage-clamped with ramp protocols. Langendorff-perfused heart experiments were performed on male Sprague-Dawley rats, effective refractory period, Wenckebach cycle length, and ventricular effective refractory period were determined following 200 nmol/L PA-6 perfusion...
April 2016: Physiological Reports
https://www.readbyqxmd.com/read/27078635/optical-control-of-a-neuronal-protein-using-a-genetically-encoded-unnatural-amino-acid-in-neurons
#19
Ji-Yong Kang, Daichi Kawaguchi, Lei Wang
Photostimulation is a noninvasive way to control biological events with excellent spatial and temporal resolution. New methods are desired to photo-regulate endogenous proteins expressed in their native environment. Here, we present an approach to optically control the function of a neuronal protein directly in neurons using a genetically encoded unnatural amino acid (Uaa). By using an orthogonal tRNA/aminoacyl-tRNA synthetase pair to suppress the amber codon, a photo-reactive Uaa 4,5-dimethoxy-2-nitrobenzyl-cysteine (Cmn) is site-specifically incorporated in the pore of a neuronal protein Kir2...
March 28, 2016: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/27009332/complex-molecular-and-functional-outcomes-of-single-versus-sequential-cytokine-stimulation-of-rat-microglia
#20
Tamjeed A Siddiqui, Starlee Lively, Lyanne C Schlichter
BACKGROUND: Microglia are the "professional" phagocytes of the CNS. Phagocytosis is crucial for normal CNS development and maintenance, but it can be either beneficial or detrimental after injury or disease. For instance, white matter damage releases myelin debris that must be cleared by microglia in order for re-myelination to occur. However, phagocytosis can also produce damaging reactive oxygen species (ROS). Furthermore, microglia can acquire pro-inflammatory (M1) or anti-inflammatory (M2) activation states that affect cell functions...
March 24, 2016: Journal of Neuroinflammation
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