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Boikov SI, Sibarov DA, Stepanenko YD, Karelina TV, Antonov SM. Calcium-Dependent Interplay of Lithium and Tricyclic Antidepressants, Amitriptyline and Desipramine, on N-methyl-D-aspartate Receptors. Int J Mol Sci 2022; 23:ijms232416177. [PMID: 36555818 PMCID: PMC9787943 DOI: 10.3390/ijms232416177] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 12/13/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
The facilitated activity of N-methyl-D-aspartate receptors (NMDARs) in the central and peripheral nervous systems promotes neuropathic pain. Amitriptyline (ATL) and desipramine (DES) are tricyclic antidepressants (TCAs) whose anti-NMDAR properties contribute to their analgetic effects. At therapeutic concentrations <1 µM, these medicines inhibit NMDARs by enhancing their calcium-dependent desensitization (CDD). Li+, which suppresses the sodium−calcium exchanger (NCX) and enhances NMDAR CDD, also exhibits analgesia. Here, the effects of different [Li+]s on TCA inhibition of currents through native NMDARs in rat cortical neurons recorded by the patch-clamp technique were investigated. We demonstrated that the therapeutic [Li+]s of 0.5−1 mM cause an increase in ATL and DES IC50s of ~10 folds and ~4 folds, respectively, for the Ca2+-dependent NMDAR inhibition. The Ca2+-resistant component of NMDAR inhibition by TCAs, the open-channel block, was not affected by Li+. In agreement, clomipramine providing exclusively the NMDAR open-channel block is not sensitive to Li+. This Ca2+-dependent interplay between Li+, ATL, and DES could be determined by their competition for the same molecular target. Thus, submillimolar [Li+]s may weaken ATL and DES effects during combined therapy. The data suggest that Li+, ATL, and DES can enhance NMDAR CDD through NCX inhibition. This ability implies a drug−drug or ion−drug interaction when these medicines are used together therapeutically.
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Kanzaki K, Watanabe D, Shi J, Wada M. Mechanisms of eccentric contraction-induced muscle damage and nutritional supplementations for mitigating it. J Muscle Res Cell Motil 2022; 43:147-156. [PMID: 35854160 DOI: 10.1007/s10974-022-09625-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 06/20/2022] [Indexed: 11/25/2022]
Abstract
Eccentric contraction (ECC) often results in large and long-lasting force deficits accompanied by muscle soreness, primarily due to muscle damage. In this sense, exercises that involve ECC are less desirable. Paradoxically, exercise training that includes a substantial eccentric phase leads to a more powerful activation of the genes responsible for skeletal muscle remodeling (e.g., hypertrophy) than other types of training that emphasize a concentric or isometric phase. Therefore, effective strategies that lessen ECC-induced muscle damage will be of interest and importance to many individuals. The purpose of this brief review is to highlight the published literature on the effects of ECC and/or nutritional supplementations on proteins, lipids, metabolic and ionic changes, and enzyme activities in skeletal muscles subjected to an acute bout of ECC. First, we discuss the potential mechanisms by which ECC causes muscle damage. Previous findings implicate a Ca2+ overload-oxidative modification pathway as one possible mechanism contributing to muscle damage. Thereafter, the efficacy of two nutritional supplementations, i.e., L-arginine and antioxidant, is discussed because L-arginine and antioxidant would be expected to ameliorate the adverse effects of Ca2+ overload and oxidative modification, respectively. Of these, L-arginine ingestion before ECC seems likely to be the effective strategy for mitigating ECC-related proteolysis. More studies are needed to establish the effectiveness of antioxidant ingestion. The application of effective strategies against muscle damage may contribute to improvements in health and fitness, muscle function, and sports performance.
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Affiliation(s)
- Keita Kanzaki
- Department of Clinical Nutrition, Faculty of Health Science and Technology, Kawasaki University of Medical Welfare, Okayama, Japan
| | - Daiki Watanabe
- Graduate School of Humanities and Social Sciences, Hiroshima University, 1-7-1 Kagamiyama, 739-8521, Higasihiroshima-shi, Hiroshima, Japan
| | - Jiayu Shi
- Graduate School of Integrated Arts and Sciences, Hiroshima University, Hiroshima, Japan
| | - Masanobu Wada
- Graduate School of Humanities and Social Sciences, Hiroshima University, 1-7-1 Kagamiyama, 739-8521, Higasihiroshima-shi, Hiroshima, Japan.
- Graduate School of Integrated Arts and Sciences, Hiroshima University, Hiroshima, Japan.
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Yi X, Sun X, Tian R, Li K, Ni M, Ying J, Xu L, Liu L, Wang Y. Genome-Wide Characterization of the Aquaporin Gene Family in Radish and Functional Analysis of RsPIP2-6 Involved in Salt Stress. FRONTIERS IN PLANT SCIENCE 2022; 13:860742. [PMID: 35909741 PMCID: PMC9337223 DOI: 10.3389/fpls.2022.860742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Accepted: 06/20/2022] [Indexed: 06/15/2023]
Abstract
Aquaporins (AQPs) constitute a highly diverse family of channel proteins that transport water and neutral solutes. AQPs play crucial roles in plant development and stress responses. However, the characterization and biological functions of RsAQPs in radish (Raphanus sativus L.) remain elusive. In this study, 61 non-redundant members of AQP-encoding genes were identified from the radish genome database and located on nine chromosomes. Radish AQPs (RsAQPs) were divided into four subfamilies, including 21 plasma membrane intrinsic proteins (PIPs), 19 tonoplast intrinsic proteins (TIPs), 16 NOD-like intrinsic proteins (NIPs), and 5 small basic intrinsic proteins (SIPs), through phylogenetic analysis. All RsAQPs contained highly conserved motifs (motifs 1 and 4) and transmembrane regions, indicating the potential transmembrane transport function of RsAQPs. Tissue- and stage-specific expression patterns of AQP gene analysis based on RNA-seq data revealed that the expression levels of PIPs were generally higher than TIPs, NIPs, and SIPs in radish. In addition, quantitative real-time polymerase chain reaction (qRT-PCR) revealed that seven selected RsPIPs, according to our previous transcriptome data (e.g., RsPIP1-3, 1-6, 2-1, 2-6, 2-10, 2-13, and 2-14), exhibited significant upregulation in roots of salt-tolerant radish genotype. In particular, the transcriptional levels of RsPIP2-6 dramatically increased after 6 h of 150 mM NaCl treatment during the taproot thickening stage. Additionally, overexpression of RsPIP2-6 could enhance salt tolerance by Agrobacterium rhizogenes-mediated transgenic radish hairy roots, which exhibited the mitigatory effects of plant growth reduction, leaf relative water content (RWC) reduction and alleviation of O2- in cells, as shown by nitro blue tetrazolium (NBT) staining, under salt stress. These findings are helpful for deeply dissecting the biological function of RsAQPs on the salt stress response, facilitating practical application and genetic improvement of abiotic stress resistance in radish.
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Affiliation(s)
- Xiaofang Yi
- National Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Horticultural Crop Biology and Genetic Improvement (East China), Ministry of Agriculture and Rural Affairs, College of Horticulture, Nanjing Agricultural University, Nanjing, China
| | - Xiaochuan Sun
- College of Life Science and Food Engineering, Huaiyin Institute of Technology, Huai’an, China
| | - Rong Tian
- National Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Horticultural Crop Biology and Genetic Improvement (East China), Ministry of Agriculture and Rural Affairs, College of Horticulture, Nanjing Agricultural University, Nanjing, China
| | - Kexin Li
- National Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Horticultural Crop Biology and Genetic Improvement (East China), Ministry of Agriculture and Rural Affairs, College of Horticulture, Nanjing Agricultural University, Nanjing, China
| | - Meng Ni
- National Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Horticultural Crop Biology and Genetic Improvement (East China), Ministry of Agriculture and Rural Affairs, College of Horticulture, Nanjing Agricultural University, Nanjing, China
| | - Jiali Ying
- National Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Horticultural Crop Biology and Genetic Improvement (East China), Ministry of Agriculture and Rural Affairs, College of Horticulture, Nanjing Agricultural University, Nanjing, China
| | - Liang Xu
- National Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Horticultural Crop Biology and Genetic Improvement (East China), Ministry of Agriculture and Rural Affairs, College of Horticulture, Nanjing Agricultural University, Nanjing, China
| | - Liwang Liu
- National Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Horticultural Crop Biology and Genetic Improvement (East China), Ministry of Agriculture and Rural Affairs, College of Horticulture, Nanjing Agricultural University, Nanjing, China
| | - Yan Wang
- National Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Horticultural Crop Biology and Genetic Improvement (East China), Ministry of Agriculture and Rural Affairs, College of Horticulture, Nanjing Agricultural University, Nanjing, China
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Xiyuan Z, Fink RHA, Mosqueira M. NO-sGC Pathway Modulates Ca 2+ Release and Muscle Contraction in Zebrafish Skeletal Muscle. Front Physiol 2017; 8:607. [PMID: 28878687 PMCID: PMC5572320 DOI: 10.3389/fphys.2017.00607] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 08/07/2017] [Indexed: 11/26/2022] Open
Abstract
Vertebrate skeletal muscle contraction and relaxation is a complex process that depends on Ca2+ ions to promote the interaction of actin and myosin. This process can be modulated by nitric oxide (NO), a gas molecule synthesized endogenously by (nitric oxide synthase) NOS isoforms. At nanomolar concentrations NO activates soluble guanylate cyclase (sGC), which in turn activates protein kinase G via conversion of GTP into cyclic GMP. Alternatively, NO post-translationally modifies proteins via S-nitrosylation of the thiol group of cysteine. However, the mechanisms of action of NO on Ca2+ homeostasis during muscle contraction are not fully understood and we hypothesize that NO exerts its effects on Ca2+ homeostasis in skeletal muscles mainly through negative modulation of Ca2+ release and Ca2+ uptake via the NO-sGC-PKG pathway. To address this, we used 5–7 days-post fecundation-larvae of zebrafish, a well-established animal model for physiological and pathophysiological muscle activity. We evaluated the response of muscle contraction and Ca2+ transients in presence of SNAP, a NO-donor, or L-NAME, an unspecific NOS blocker in combination with specific blockers of key proteins of Ca2+ homeostasis. We also evaluate the expression of NOS in combination with dihydropteridine receptor, ryanodine receptor and sarco/endoplasmic reticulum Ca2+ ATPase. We concluded that endogenous NO reduced force production through negative modulation of Ca2+ transients via the NO-sGC pathway. This effect could be reversed using an unspecific NOS blocker or sGC blocker.
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Affiliation(s)
- Zhou Xiyuan
- Medical Biophysics Unit, Institute of Physiology and Pathophysiology, Heidelberg University HospitalHeidelberg, Germany.,Department of Traumatic Surgery, TongJi Hospital affiliated to TongJi Medical College, Huazhong University of Science and TechnologyWuhan, China
| | - Rainer H A Fink
- Medical Biophysics Unit, Institute of Physiology and Pathophysiology, Heidelberg University HospitalHeidelberg, Germany
| | - Matias Mosqueira
- Medical Biophysics Unit, Institute of Physiology and Pathophysiology, Heidelberg University HospitalHeidelberg, Germany
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Han YE, Ryu SY, Park SH, Lee KH, Lee SH, Ho WK. Ca(2+) clearance by plasmalemmal NCLX, Li(+)-permeable Na(+)/Ca(2+) exchanger, is required for the sustained exocytosis in rat insulinoma INS-1 cells. Pflugers Arch 2015; 467:2461-72. [PMID: 26100674 DOI: 10.1007/s00424-015-1715-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 06/03/2015] [Accepted: 06/11/2015] [Indexed: 11/29/2022]
Abstract
Na(+)/Ca(2+) exchangers are key players for Ca(2+) clearance in pancreatic β-cells, but their molecular determinants and roles in insulin secretion are not fully understood. In the present study, we newly discovered that the Li(+)-permeable Na(+)/Ca(2+) exchangers (NCLX), which were known as mitochondrial Na(+)/Ca(2+) exchangers, contributed to the Na(+)-dependent Ca(2+) movement across the plasma membrane in rat INS-1 insulinoma cells. Na(+)/Ca(2+) exchange activity by NCLX was comparable to that by the Na(+)/Ca(2+) exchanger, NCX. We also confirmed the presence of NCLX proteins on the plasma membrane using immunocytochemistry and cell surface biotinylation experiments. We further investigated the role of NCLX on exocytosis function by measuring the capacitance increase in response to repetitive depolarization. Small interfering (si)RNA-mediated downregulation of NCLX did not affect the initial exocytosis, but significantly suppressed sustained exocytosis and recovery of exocytosis. XIP (NCX inhibitory peptide) or Na(+) replacement for inhibiting Na(+)-dependent Ca(2+) clearance also selectively suppressed sustained exocytosis. Consistent with the idea that sustained exocytosis requires ATP-dependent vesicle recruitment, mitochondrial function, assessed by mitochondrial membrane potential (ΔΨ), was impaired by siNCLX or XIP. However, depolarization-induced exocytosis was hardly affected by changes in intracellular Na(+) concentration, suggesting a negligible contribution of mitochondrial Na(+)/Ca(2+) exchanger. Taken together, our data indicate that Na(+)/Ca(2+) exchanger-mediated Ca(2+) clearance mediated by NCLX and NCX is crucial for optimizing mitochondrial function, which in turn contributes to vesicle recruitment for sustained exocytosis in pancreatic β-cells.
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Affiliation(s)
- Young-Eun Han
- Department of Physiology and Biomembrane Plasticity Research Center, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Shin-Young Ryu
- Department of Physiology and Biomembrane Plasticity Research Center, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Sun-Hyun Park
- Department of Physiology and Biomembrane Plasticity Research Center, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Kyu-Hee Lee
- Department of Physiology and Biomembrane Plasticity Research Center, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Suk-Ho Lee
- Department of Physiology and Biomembrane Plasticity Research Center, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea
| | - Won-Kyung Ho
- Department of Physiology and Biomembrane Plasticity Research Center, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 110-799, Republic of Korea.
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Tu J, Lu L, Cai W, Ballard HJ. cAMP/protein kinase A activates cystic fibrosis transmembrane conductance regulator for ATP release from rat skeletal muscle during low pH or contractions. PLoS One 2012; 7:e50157. [PMID: 23226244 PMCID: PMC3511434 DOI: 10.1371/journal.pone.0050157] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 10/22/2012] [Indexed: 11/18/2022] Open
Abstract
We have shown that cystic fibrosis transmembrane conductance regulator (CFTR) is involved in ATP release from skeletal muscle at low pH. These experiments investigate the signal transduction mechanism linking pH depression to CFTR activation and ATP release, and evaluate whether CFTR is involved in ATP release from contracting muscle. Lactic acid treatment elevated interstitial ATP of buffer-perfused muscle and extracellular ATP of L6 myocytes: this ATP release was abolished by the non-specific CFTR inhibitor, glibenclamide, or the specific CFTR inhibitor, CFTRinh-172, suggesting that CFTR was involved, and by inhibition of lactic acid entry to cells, indicating that intracellular pH depression was required. Muscle contractions significantly elevated interstitial ATP, but CFTRinh-172 abolished the increase. The cAMP/PKA pathway was involved in the signal transduction pathway for CFTR-regulated ATP release from muscle: forskolin increased CFTR phosphorylation and stimulated ATP release from muscle or myocytes; lactic acid increased intracellular cAMP, pCREB and PKA activity, whereas IBMX enhanced ATP release from myocytes. Inhibition of PKA with KT5720 abolished lactic-acid- or contraction-induced ATP release from muscle. Inhibition of either the Na+/H+-exchanger (NHE) with amiloride or the Na+/Ca2+-exchanger (NCX) with SN6 or KB-R7943 abolished lactic-acid- or contraction-induced release of ATP from muscle, suggesting that these exchange proteins may be involved in the activation of CFTR. Our data suggest that CFTR-regulated release contributes to ATP release from contracting muscle in vivo, and that cAMP and PKA are involved in the activation of CFTR during muscle contractions or acidosis; NHE and NCX may be involved in the signal transduction pathway.
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Affiliation(s)
- Jie Tu
- Department of Physiology, The University of Hong Kong, Pokfulam, Hong Kong, Special Administrative Region, People's Republic of China
- Shenzhen Key Laboratory for Neuropsychiatric Modulation, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, People's Republic of China
| | - Lin Lu
- Department of Physiology, The University of Hong Kong, Pokfulam, Hong Kong, Special Administrative Region, People's Republic of China
- Institute of Cardiovascular Science and Medicine, The University of Hong Kong, Pokfulam, Hong Kong, Special Administrative Region, People's Republic of China
| | - Weisong Cai
- Department of Physiology, The University of Hong Kong, Pokfulam, Hong Kong, Special Administrative Region, People's Republic of China
- Institute of Cardiovascular Science and Medicine, The University of Hong Kong, Pokfulam, Hong Kong, Special Administrative Region, People's Republic of China
| | - Heather J. Ballard
- Department of Physiology, The University of Hong Kong, Pokfulam, Hong Kong, Special Administrative Region, People's Republic of China
- Institute of Cardiovascular Science and Medicine, The University of Hong Kong, Pokfulam, Hong Kong, Special Administrative Region, People's Republic of China
- * E-mail:
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Sacchi O, Rossi ML, Canella R, Fesce R. Regulation of the subthreshold chloride conductance in the rat sympathetic neuron. Eur J Neurosci 2007; 25:1112-26. [PMID: 17331207 DOI: 10.1111/j.1460-9568.2007.05357.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The mechanisms that control chloride conductance (gCl) in the rat sympathetic neuron have been studied by the two-electrode voltage-clamp technique in mature, intact superior cervical ganglia in vitro. In addition to voltage dependence in the membrane potential range -120/-50 mV, gCl displays time- and activity-dependent regulation (sensitization). The resting membrane potential is governed by voltage-dependent gK and gCl, which determine values of cell input conductance ranging from 7 to 18 nS (full deactivation) to an upper value of about 130 nS (full activation and maximal gCl sensitization). The quiescent neuron, held at constant membrane potential, spontaneously and gradually moved from a low- to a high-conductance status. An increase (about 40 nS) in gCl accounted for this phenomenon, which could be prevented by imposing intermittent hyperpolarizing episodes. Following spike firing, gCl increased by 20-33 nS, independent of the cell conductance value preceding tetanization, and thereafter decayed to the pre-stimulus level within 5 min. Intracellular sodium depletion and its successive ionophoretic restoration moved the neuron from a stable low-conductance state to maximum gCl sensitization, pointing to a link between gCl sensitization and [Na+]i. The dependence of gCl build-up on [Na+]i and the time-course of such Na+-related modulation have been examined: gCl sensitization was absent at 0 [Na+]i, was well developed (20 nS) at 15 mM and tended towards a saturating value of 60 nS for higher [Na+]i. Sensitization was transient in response to neuron activity. In the silent neuron, sensitization of gCl shifted membrane potential over a range of about 15 mV.
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Affiliation(s)
- Oscar Sacchi
- Department of Biology, Section of Physiology and Biophysics and Center of Neuroscience, Ferrara University, Via Borsari, 46, I-44100 Ferrara, Italy.
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Abstract
Skeletal muscle is the largest single organ of the body. Skeletal muscle damage may lead to loss of muscle function, and widespread muscle damage may have serious systemic implications due to leakage of intracellular constituents to the circulation. Ca2+ acts as a second messenger in all muscle and may activate a whole range of processes ranging from activation of contraction to degradation of the muscle cell. It is therefore of vital importance for the muscle cell to control [Ca2+] in the cytoplasm ([Ca2+]c). If the permeability of the sarcolemma for Ca2+ is increased, the muscle cell may suffer Ca2+ overload, defined as an inability to control [Ca2+]c. This could lead to the activation of calpains, resulting in proteolysis of cellular constituents, activation of phospholipase A2 (PLA2), affecting membrane integrity, an increased production of reactive oxygen species (ROS), causing lipid peroxidation, and possibly mitochondrial Ca2+ overload, all of which may further worsen the damage in a self-reinforcing process. An increased influx of Ca2+ leading to Ca2+ overload in muscle may occur in a range of situations such as exercise, mechanical and electrical trauma, prolonged ischemia, Duchenne muscular dystrophy, and cachexia. Counteractions include membrane stabilizing agents, Ca2+ channel blockers, calpain inhibitors, PLA2 inhibitors, and ROS scavengers.
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Affiliation(s)
- Hanne Gissel
- Institute of Physiology and Biophysics, University of Aarhus, Ole Worms Alle 1160, DK-8000 Arhus C, Denmark.
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Fonseca CP, Montezinho LP, Nabais C, Tomé AR, Freitas H, Geraldes CFGC, Castro MMCA. Effects of Li+ transport and intracellular binding on Li+/Mg2+ competition in bovine chromaffin cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2004; 1691:79-90. [PMID: 15110989 DOI: 10.1016/j.bbamcr.2003.12.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2003] [Revised: 12/16/2003] [Accepted: 12/17/2003] [Indexed: 11/18/2022]
Abstract
Li(+) transport, intracellular immobilisation and Li(+)/Mg(2+) competition were studied in Li(+)-loaded bovine chromaffin cells. Li(+) influx rate constants, k(i), obtained by atomic absorption (AA) spectrophotometry, in control (without and with ouabain) and depolarising (without and with nitrendipine) conditions, showed that L-type voltage-sensitive Ca(2+) channels have an important role in Li(+) uptake under depolarising conditions. The Li(+) influx apparent rate constant, k(iapp), determined under control conditions by (7)Li NMR spectroscopy with the cells immobilised and perfused, was much lower than the AA-determined value for the cells in suspension. Loading of cell suspensions with 15 mmol l(-1) LiCl led, within 90 min, to a AA-measured total intracellular Li(+) concentration, [Li(+)](iT)=11.39+/-0.56 mmol (l cells)(-1), very close to the steady state value. The intracellular Li(+) T(1)/T(2) ratio of (7)Li NMR relaxation times of the Li(+)-loaded cells reflected a high degree of Li(+) immobilisation in bovine chromaffin cells, similar to neuroblastoma, but larger than for lymphoblastoma and erythrocyte cells. A 52% increase in the intracellular free Mg(2+) concentration, Delta[Mg(2+)](f)=0.27+/-0.05 mmol (l cells)(-1) was measured for chromaffin cells loaded with the Mg(2+)-specific fluorescent probe furaptra, after 90-min loading with 15 mmol l(-1) LiCl, using fluorescence spectroscopy, indicating significant displacement of Mg(2+) by Li(+) from its intracellular binding sites. Comparison with other cell types showed that the extent of intracellular Li(+)/Mg(2+) competition at the same Li(+) loading level depends on intracellular Li(+) transport and immobilisation in a cell-specific manner, being maximal for neuroblastoma cells.
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Affiliation(s)
- C P Fonseca
- Department of Biochemistry and Centre for Neuroscience of Coimbra, University of Coimbra, P.O. Box 3126, 3001-401 Coimbra, Portugal
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Palty R, Ohana E, Hershfinkel M, Volokita M, Elgazar V, Beharier O, Silverman WF, Argaman M, Sekler I. Lithium-calcium exchange is mediated by a distinct potassium-independent sodium-calcium exchanger. J Biol Chem 2004; 279:25234-40. [PMID: 15060069 DOI: 10.1074/jbc.m401229200] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Sodium-calcium exchangers have long been considered inert with respect to monovalent cations such as lithium, choline, and N-methyl-d-glucamine. A key question that has remained unsolved is how despite this, Li(+) catalyzes calcium exchange in mammalian tissues. Here we report that a Na(+)/Ca(2+) exchanger, NCLX cloned from human cells (known as FLJ22233), is distinct from both known forms of the exchanger, NCX and NCKX in structure and kinetics. Surprisingly, NCLX catalyzes active Li(+)/Ca(2+) exchange, thereby explaining the exchange of these ions in mammalian tissues. The NCLX protein, detected as both 70- and 55-KDa polypeptides, is highly expressed in rat pancreas, skeletal muscle, and stomach. We demonstrate, moreover, that NCLX is a K(+)-independent exchanger that catalyzes Ca(2+) flux at a rate comparable with NCX1 but without promoting Na(+)/Ba(2+) exchange. The activity of NCLX is strongly inhibited by zinc, although it does not transport this cation. NCLX activity is only partially inhibited by the NCX inhibitor, KB-R7943. Our results provide a cogent explanation for a fundamental question. How can Li(+) promote Ca(2+) exchange whereas the known exchangers are inert to Li(+) ions? Identification of this novel member of the Na(+)/Ca(2+) superfamily, with distinct characteristics, including the ability to transport Li(+), may provide an explanation for this phenomenon.
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Affiliation(s)
- Raz Palty
- Department of Physiology, Faculty of Health Sciences, The National Institute for Molecular Biology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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Deval E, Levitsky DO, Marchand E, Cantereau A, Raymond G, Cognard C. Na(+)/Ca(2+) exchange in human myotubes: intracellular calcium rises in response to external sodium depletion are enhanced in DMD. Neuromuscul Disord 2002; 12:665-73. [PMID: 12207936 DOI: 10.1016/s0960-8966(02)00022-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This study aims to investigate the sodium/calcium exchanger expression in human co-cultured skeletal muscle cells and to compare the effects of Na(+)/Ca(2+) exchange activity in normal and dystrophic (Duchenne's muscular dystrophy) human co-cultured myotubes. For this purpose, variations of intracellular calcium concentration ([Ca(2+)](int)) were monitored, as the variations of the fluorescence ratio of indo-1 probe, in response to external sodium depletion. External sodium withdrawal induced [Ca(2+)](int) rises within several seconds in both normal and Duchenne's muscular dystrophy myotubes. These Na(+)-free-induced [Ca(2+)](int) elevations were attributed to the reverse mode of the Na(+)/Ca(2+) exchange mechanism since the phenomenon was dependent on extracellular calcium concentration ([Ca(2+)](ext)), and since it was sensitive to external Ni(2+) ions. Amplitudes of Na(+)-free-induced [Ca(2+)](int) rises were significantly greater in Duchenne's muscular dystrophy cells than in normal ones. Such a difference disappeared when the sarcoplasmic reticulum was pharmacologically blocked, suggesting that the reverse mode of the Na(+)/Ca(2+) exchange mechanism was able to generate enhanced calcium-induced calcium-release in Duchenne's muscular dystrophy myotubes. Immunostaining images of Na(+)/Ca(2+) exchanger (NCX) isoforms, obtained by confocal microscopy, revealed the presence of NCX1 and NCX3 at the sarcolemmal level of both normal and Duchenne's muscular dystrophy myotubes. No differences were observed in the location of NCX isoforms expression between normal and Duchenne's muscular dystrophy co-cultured myotubes.
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Affiliation(s)
- Emmanuel Deval
- Laboratoire des Biomembranes et Signalisation Cellulaire, UMR CNRS 6558, Université de Poitiers, 40 avenue du Recteur Pineau, 86022 Cedex, Poitiers, France
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