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Ye Li, Haifeng Hu, Jingchen Liu, Qingsan Zhu, Rui Gu
PURPOSE: To investigate the effects of aquaporin 4 (AQP4) and inward rectifier potassium channel 4.1 (Kir4.1) on medullospinal edema after treatment with methylprednisolone (MP) to suppress acute spinal cord injury (ASCI) in rats. METHODS: Sprague Dawley rats were randomly divided into control, sham, ASCI, and MP-treated ASCI groups. After the induction of ASCI, we injected 30 mg/kg MP via the tail vein at various time points. The Tarlov scoring method was applied to evaluate neurological symptoms, and the wet-dry weights method was applied to measure the water content of the spinal cord...
February 2018: Acta Cirúrgica Brasileira
Meagan Milton, Patrice D Smith
An acute ischemic stroke is characterized by the presence of a blood clot that limits blood flow to the brain resulting in subsequent neuronal loss. Acute stroke threatens neuronal survival, which relies heavily upon proper function of astrocytes. Neurons are more susceptible to cell death when an astrocyte is unable to carry out its normal functions in supporting the neuron in the area affected by the stroke (Rossi et al., 2007; Takano et al., 2009). For example, under normal conditions, astrocytes initially swell in response to changes in extracellular osmotic pressure and then reduce their regulatory volume in response to volume-activated potassium (K+ ) and chloride channels (Vella et al...
2018: Frontiers in Cellular Neuroscience
Peng Wu, Zhong-Xiuzi Gao, Xin-Peng Duan, Xiao-Tong Su, Ming-Xiao Wang, Dao-Hong Lin, Ruimin Gu, Wen-Hui Wang
AT2R (AngII [angiotensin II] type 2 receptor) is expressed in the distal nephrons. The aim of the present study is to examine whether AT2R regulates NCC (Na-Cl cotransporter) and Kir4.1 of the distal convoluted tubule. AngII inhibited the basolateral 40 pS K channel (a Kir4.1/5.1 heterotetramer) in the distal convoluted tubule treated with losartan but not with PD123319. AT2R agonist also inhibits the K channel, indicating that AT2R was involved in tonic regulation of Kir4.1. The infusion of PD123319 stimulated the expression of tNCC (total NCC) and pNCC (phosphorylated NCC; Thr53 ) by a time-dependent way with the peak at 4 days...
February 26, 2018: Hypertension
Francesco Nicita, Giorgio Tasca, Marta Nardella, Emanuele Bellacchio, Ilaria Camponeschi, Gessica Vasco, Tommaso Schirinzi, Enrico Bertini, Ginevra Zanni
Mutations in KCNJ10, which encodes the inwardly rectifying potassium channel Kir4.1, a primary regulator of membrane excitability and potassium homeostasis, cause a complex syndrome characterized by seizures, sensorineural deafness, ataxia, intellectual disability, and electrolyte imbalance called SeSAME/EAST syndrome. We describe a 41-year-old patient with non-syndromic, slowly progressive, early-onset ataxia. Targeted next-generation sequencing identified a novel c.180 T > G (p.Ile60Met) missense homozygous mutation...
February 23, 2018: Cerebellum
Kayla Thompson, Jonathan Chen, Qianyi Luo, Yucheng Xiao, Theodore R Cummins, Ashay D Bhatwadekar
Diabetic retinopathy (DR) is a major cause of adult blindness. Retinal Müller cells maintain water homeostasis and potassium concentration via inwardly rectifying Kir4.1 channels. Accumulation of advanced glycation end products (AGEs) is a major pathologic event in DR. While diabetes leads to a decrease in the Kir4.1 channels, it remains unknown whether AGEs-linked to the basement membrane (BM) affect normal Kir4.1 channels. For this study, we hypothesized that AGE-modification of laminin is detrimental to Kir4...
2018: PloS One
Uri Kahanovitch, Vishnu A Cuddapah, Natasha L Pacheco, Leanne M Holt, Daniel K Mulkey, Alan K Percy, Michelle L Olsen
Rett syndrome (RTT) is an X-linked neurodevelopmental disorder usually caused by mutations in methyl-CpG-binding protein 2 (MeCP2). RTT is typified by apparently normal development until 6-18 mo of age, when motor and communicative skills regress and hand stereotypies, autonomic symptoms, and seizures present. Restoration of MeCP2 function selectively to astrocytes reversed several deficits in a murine model of RTT, but the mechanism of this rescue is unknown. Astrocytes carry out many essential functions required for normal brain functioning, including extracellular K+ buffering...
January 2018: ENeuro
Yihui Cui, Yan Yang, Zheyi Ni, Yiyan Dong, Guohong Cai, Alexandre Foncelle, Shuangshuang Ma, Kangning Sang, Siyang Tang, Yuezhou Li, Ying Shen, Hugues Berry, Shengxi Wu, Hailan Hu
Enhanced bursting activity of neurons in the lateral habenula (LHb) is essential in driving depression-like behaviours, but the cause of this increase has been unknown. Here, using a high-throughput quantitative proteomic screen, we show that an astroglial potassium channel (Kir4.1) is upregulated in the LHb in rat models of depression. Kir4.1 in the LHb shows a distinct pattern of expression on astrocytic membrane processes that wrap tightly around the neuronal soma. Electrophysiology and modelling data show that the level of Kir4...
February 14, 2018: Nature
Wei Wu, Hang Yao, Helen W Zhao, Juan Wang, Gabriel G Haddad
Chronic mountain sickness (CMS) or Monge's disease is a disease in highlanders. These patients have a variety of neurologic symptoms such as migraine, mental fatigue, confusion, dizziness, loss of appetite, memory loss and neuronal degeneration. The cellular and molecular mechanisms underlying CMS neuropathology is not understood. In the previous study, we demonstrated that neurons derived from CMS patients' fibroblasts have a decreased expression and altered gating properties of voltage-gated sodium channel...
January 17, 2018: Neuroscience
Heng Li, Shiren Sun, Jianghua Chen, Goushuang Xu, Hanmin Wang, Qi Qian
Background: Magnesium (Mg2+), the second most abundant cation in the cell, is woven into a multitude of cellular functions. Dysmagnesemia is associated with multiple diseases and, when severe, can be life-threatening. Summary: This review discusses Mg2+ homeostasis and function with specific focus on renal Mg2+ handling. Intrarenal channels and transporters related to Mg2+ absorption are discussed. Unraveling the rare genetic diseases with manifestations of dysmagnesemia has greatly increased our understanding of the complex and intricate regulatory network in the kidney, specifically, functions of tight junction proteins including claudin-14, -16, -19, and -10; apical ion channels including: TRPM6, Kv1...
December 2017: Kidney Diseases
Ming-Xiao Wang, Catherina A Cuevas, Xiao-Tong Su, Peng Wu, Zhong-Xiuzi Gao, Dao-Hong Lin, James A McCormick, Chao-Ling Yang, Wen-Hui Wang, David H Ellison
Kir4.1 in the distal convoluted tubule plays a key role in sensing plasma potassium and in modulating the thiazide-sensitive sodium-chloride cotransporter (NCC). Here we tested whether dietary potassium intake modulates Kir4.1 and whether this is essential for mediating the effect of potassium diet on NCC. High potassium intake inhibited the basolateral 40 pS potassium channel (a Kir4.1/5.1 heterotetramer) in the distal convoluted tubule, decreased basolateral potassium conductance, and depolarized the distal convoluted tubule membrane in Kcnj10flox/flox mice, herein referred to as control mice...
January 6, 2018: Kidney International
Kuihao Chen, Dongchuan Zuo, Zheng Liu, Haijun Chen
Strong inward rectifier K+ channels (Kir2.1) mediate background K+ currents primarily responsible for maintenance of resting membrane potential. Multiple types of cells exhibit two levels of resting membrane potential. Kir2.1 and K2P1 currents counterbalance, partially accounting for the phenomenon of human cardiomyocytes in subphysiological extracellular K+ concentrations or pathological hypokalemic conditions. The mechanism of how Kir2.1 channels contribute to the two levels of resting membrane potential in different types of cells is not well understood...
December 27, 2017: Pflügers Archiv: European Journal of Physiology
Saeed Fadal Alrashdi, Devy Deliyanti, Dean Michael Talia, Jennifer Louise Wilkinson-Berka
Although increasing evidence indicates that endothelin-2 (Edn2) has distinct roles in tissue pathology including inflammation, glial cell dysfunction, and angiogenesis, its role in the retina and the factors that regulate its actions are not fully understood. We hypothesized that Edn2 damages the blood-retinal barrier (BRB) and this is mediated by interactions with the renin-angiotensin aldosterone system and reactive oxygen species derived from NADPH oxidase (Nox). C57BL/6J mice received an intravitreal injection of Edn2 or control vehicle to examine the blood pressure-independent effects of Edn2...
December 14, 2017: American Journal of Pathology
Viktor N Tomilin, Oleg Zaika, Arohan R Subramanya, Oleh Pochynyuk
The renal collecting duct contains two distinct cell types, principal and intercalated cells, expressing potassium Kir4.1/5.1 (KCNJ10/16) and chloride ClC-K2 (ClC-Kb in humans) channels on their basolateral membrane, respectively. Both channels are thought to play important roles in controlling systemic water-electrolyte balance and blood pressure. However, little is known about mechanisms regulating activity of Kir4.1/5.1 and ClC-K2/b. Here, we employed patch clamp analysis at the single channel and whole cell levels in freshly isolated mouse collecting ducts to investigate regulation of Kir4...
November 13, 2017: Pflügers Archiv: European Journal of Physiology
Shao-Ping Zhang, Man Zhang, Hong Tao, Yan Luo, Tao He, Chun-Hui Wang, Xiao-Cheng Li, Ling Chen, Lin-Na Zhang, Tao Sun, Qi-Kuan Hu
Potassium channels can be affected by epileptic seizures and serve a crucial role in the pathophysiology of epilepsy. Dimethylation of histone 3 lysine 9 (H3K9me2) and its enzyme euchromatic histone‑lysine N‑methyltransferase 2 (G9a) are the major epigenetic modulators and are associated with gene silencing. Insight into whether H3K9me2 and G9a can respond to epileptic seizures and regulate expression of genes encoding potassium channels is the main purpose of the present study. A total of 16 subtypes of potassium channel genes in pilocarpine‑modelled epileptic rats were screened by reverse transcription‑quantitative polymerase chain reaction, and it was determined that the expression ATP‑sensitive inward rectifier potassium channel 10 (Kcnj10) increased in hippocampus and insular cortex, while the expression of most of the other subtypes decreased...
January 2018: Molecular Medicine Reports
Iván A Aréchiga-Figueroa, Leticia G Marmolejo-Murillo, Meng Cui, Mayra Delgado-Ramírez, Marcel A G van der Heyden, José A Sánchez-Chapula, Aldo A Rodríguez-Menchaca
Inward rectifier potassium (Kir) channels are expressed in almost all mammalian tissues and contribute to a wide range of physiological processes. Kir4.1 channel expression is found in the brain, inner ear, eye, and kidney. Loss-of-function mutations in the pore-forming Kir4.1 subunit cause an autosomal recessive disorder characterized by epilepsy, ataxia, sensorineural deafness and tubulopathy (SeSAME/EST syndrome). Despite its importance in physiological and pathological conditions, pharmacological research of Kir4...
October 6, 2017: European Journal of Pharmacology
Oleg Palygin, Vladislav Levchenko, Daria V Ilatovskaya, Tengis S Pavlov, Oleh M Pochynyuk, Howard J Jacob, Aron M Geurts, Matthew R Hodges, Alexander Staruschenko
Supplementing diets with high potassium helps reduce hypertension in humans. Inwardly rectifying K+ channels Kir4.1 (Kcnj10) and Kir5.1 (Kcnj16) are highly expressed in the basolateral membrane of distal renal tubules and contribute to Na+ reabsorption and K+ secretion through the direct control of transepithelial voltage. To define the importance of Kir5.1 in blood pressure control under conditions of salt-induced hypertension, we generated a Kcnj16 knockout in Dahl salt-sensitive (SS) rats (SSKcnj16-/-). SSKcnj16-/- rats exhibited hypokalemia and reduced blood pressure, and when fed a high-salt diet (4% NaCl), experienced 100% mortality within a few days triggered by salt wasting and severe hypokalemia...
September 21, 2017: JCI Insight
Marcos Emilio Frizzo
Sertraline (Zoloft) and fluoxetine (Prozac) are selective serotonin reuptake inhibitors whose antidepressant mechanism of action is classically attributed to an elevation of the extracellular levels of serotonin in the synaptic cleft. However, the biological effects of these drugs seem to be more complex than their traditionally described mechanism of action. Among their actions is the inhibition of different types of Na(+) and K(+) channels, as well as of glutamate uptake activity. The clearance of extracellular glutamate is essential to maintain the central nervous system within physiological conditions, and this excitatory neurotransmitter is removed from the synaptic cleft by astrocyte transporters...
2017: Current Therapeutic Research, Clinical and Experimental
Antigone Papavasiliou, Katerina Foska, John Ioannou, Mato Nagel
BACKGROUND: Epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome is a multi-organ disorder that links to autosomal recessive mutations in the KCNJ10 gene, which encodes for the Kir4.1 potassium channel. It is mostly described in consanguineous, non-European families. CASE REPORT: A European male of non-consanguineous birth, with early-onset, static ataxic motor disorder, intellectual disability and epilepsy, imitating cerebral palsy, presented with additional findings of renal tubulopathy, sensorineural deafness and normal neuroimaging leading to the diagnosis of epilepsy, ataxia, sensorineural deafness, tubulopathy syndrome...
2017: SAGE Open Medical Case Reports
Sonia Hasan, Ameera Balobaid, Alessandro Grottesi, Omar Dabbagh, Marta Cenciarini, Rifaat Rawashdeh, Afaf Al-Sagheir, Cecilia Bove, Lara Macchioni, Mauro Pessia, Mohammed Al-Owain, Maria Cristina D'Adamo
A 2-yr-old boy presented profound developmental delay, failure to thrive, ataxia, hypotonia, and tonic-clonic seizures that caused the death of the patient. Targeted and whole exome sequencing revealed two heterozygous missense variants: a novel mutation in the KCNJ10 gene that encodes for the inward-rectifying K + channel Kir4.1 and another previously characterized mutation in KCNT1 that encodes for the Na + -activated K + channel known as Slo2.2 or SLACK. The objectives of this study were to perform the clinical and genetic characterization of the proband and his family and to examine the functional consequence of the Kir4...
October 1, 2017: Journal of Neurophysiology
Brian Roland Larsen, Nanna MacAulay
During neuronal activity in the mammalian brain, the K(+) released into the synaptic space is initially buffered by the astrocytic compartment. In parallel, the extracellular space (ECS) shrinks, presumably due to astrocytic cell swelling. With the Na(+) /K(+) /2Cl(-) cotransporter and the Kir4.1/AQP4 complex not required for the astrocytic cell swelling in the hippocampus, the molecular mechanisms underlying the activity-dependent ECS shrinkage have remained unresolved. To identify these molecular mechanisms, we employed ion-sensitive microelectrodes to measure changes in ECS, [K(+) ]o and [H(+) ]o /pHo during electrical stimulation of rat hippocampal slices...
July 26, 2017: Glia
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