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Blixhavn CH, Haug FMŠ, Kleven H, Puchades MA, Bjaalie JG, Leergaard TB. A Timm-Nissl multiplane microscopic atlas of rat brain zincergic terminal fields and metal-containing glia. Sci Data 2023; 10:150. [PMID: 36944675 PMCID: PMC10030855 DOI: 10.1038/s41597-023-02012-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 02/09/2023] [Indexed: 03/23/2023] Open
Abstract
The ability of Timm's sulphide silver method to stain zincergic terminal fields has made it a useful neuromorphological marker. Beyond its roles in zinc-signalling and neuromodulation, zinc is involved in the pathophysiology of ischemic stroke, epilepsy, degenerative diseases and neuropsychiatric conditions. In addition to visualising zincergic terminal fields, the method also labels transition metals in neuronal perikarya and glial cells. To provide a benchmark reference for planning and interpretation of experimental investigations of zinc-related phenomena in rat brains, we have established a comprehensive repository of serial microscopic images from a historical collection of coronally, horizontally and sagittally oriented rat brain sections stained with Timm's method. Adjacent Nissl-stained sections showing cytoarchitecture, and customised atlas overlays from a three-dimensional rat brain reference atlas registered to each section image are included for spatial reference and guiding identification of anatomical boundaries. The Timm-Nissl atlas, available from EBRAINS, enables experimental researchers to navigate normal rat brain material in three planes and investigate the spatial distribution and density of zincergic terminal fields across the entire brain.
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Affiliation(s)
- Camilla H Blixhavn
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Finn-Mogens Š Haug
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Heidi Kleven
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Maja A Puchades
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Jan G Bjaalie
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Trygve B Leergaard
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
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2
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Kambe T, Taylor KM, Fu D. Zinc transporters and their functional integration in mammalian cells. J Biol Chem 2021; 296:100320. [PMID: 33485965 PMCID: PMC7949119 DOI: 10.1016/j.jbc.2021.100320] [Citation(s) in RCA: 99] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 01/15/2021] [Accepted: 01/20/2021] [Indexed: 12/14/2022] Open
Abstract
Zinc is a ubiquitous biological metal in all living organisms. The spatiotemporal zinc dynamics in cells provide crucial cellular signaling opportunities, but also challenges for intracellular zinc homeostasis with broad disease implications. Zinc transporters play a central role in regulating cellular zinc balance and subcellular zinc distributions. The discoveries of two complementary families of mammalian zinc transporters (ZnTs and ZIPs) in the mid-1990s spurred much speculation on their metal selectivity and cellular functions. After two decades of research, we have arrived at a biochemical description of zinc transport. However, in vitro functions are fundamentally different from those in living cells, where mammalian zinc transporters are directed to specific subcellular locations, engaged in dedicated macromolecular machineries, and connected with diverse cellular processes. Hence, the molecular functions of individual zinc transporters are reshaped and deeply integrated in cells to promote the utilization of zinc chemistry to perform enzymatic reactions, tune cellular responsiveness to pathophysiologic signals, and safeguard cellular homeostasis. At present, the underlying mechanisms driving the functional integration of mammalian zinc transporters are largely unknown. This knowledge gap has motivated a shift of the research focus from in vitro studies of purified zinc transporters to in cell studies of mammalian zinc transporters in the context of their subcellular locations and protein interactions. In this review, we will outline how knowledge of zinc transporters has been accumulated from in-test-tube to in-cell studies, highlighting new insights and paradigm shifts in our understanding of the molecular and cellular basis of mammalian zinc transporter functions.
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Affiliation(s)
- Taiho Kambe
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
| | - Kathryn M Taylor
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, United Kingdom
| | - Dax Fu
- Department of Physiology, Johns Hopkins School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA.
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3
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Zinc status is associated with inflammation, oxidative stress, lipid, and glucose metabolism. J Physiol Sci 2017; 68:19-31. [PMID: 28965330 PMCID: PMC5754376 DOI: 10.1007/s12576-017-0571-7] [Citation(s) in RCA: 282] [Impact Index Per Article: 40.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 09/18/2017] [Indexed: 12/14/2022]
Abstract
A number of studies have reported that zinc plays a substantial role in the development of metabolic syndrome, taking part in the regulation of cytokine expression, suppressing inflammation, and is also required to activate antioxidant enzymes that scavenge reactive oxygen species, reducing oxidative stress. Zinc also plays a role in the correct functioning of lipid and glucose metabolism, regulating and forming the expression of insulin. In numerous studies, zinc supplementation has been found to improve blood pressure, glucose, and LDL cholesterol serum level. Deeper knowledge of zinc’s properties may help in treating metabolic syndrome, thus protecting against stroke and angina pectoris, and ultimately against death.
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Lawson R, Maret W, Hogstrand C. Expression of the ZIP/SLC39A transporters in β-cells: a systematic review and integration of multiple datasets. BMC Genomics 2017; 18:719. [PMID: 28893192 PMCID: PMC5594519 DOI: 10.1186/s12864-017-4119-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 09/05/2017] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Pancreatic β-cells require a constant supply of zinc to maintain normal insulin secretory function. Following co-exocytosis with insulin, zinc is replenished via the Zrt- and Irt-like (ZIP; SLC39A) family of transporters. However the ZIP paralogues of particular importance for zinc uptake, and associations with β-cell function and Type 2 Diabetes remain largely unexplored. We retrieved and statistically analysed publically available microarray and RNA-seq datasets to perform a systematic review on the expression of β-cell SLC39A paralogues. We complemented results with experimental data on expression profiling of human islets and mouse β-cell derived MIN6 cells, and compared transcriptomic and proteomic sequence conservation between human, mouse and rat. RESULTS The 14 ZIP paralogues have 73-98% amino sequence conservation between human and rodents. We identified 18 datasets for β-cell SLC39A analysis, which compared relative expression to non-β-cells, and expression in response to PDX-1 activity, cytokines, glucose and type 2 diabetic status. Published expression data demonstrate enrichment of transcripts for ZIP7 and ZIP9 transporters within rodent β-cells and of ZIP6, ZIP7 and ZIP14 within human β-cells, with ZIP1 most differentially expressed in response to cytokines and PDX-1 within rodent, and ZIP6 in response to diabetic status in human and glucose in rat. Our qPCR expression profiling data indicate that SLC39A6, -9, -13, and - 14 are the highest expressed paralogues in human β-cells and Slc39a6 and -7 in MIN6 cells. CONCLUSIONS Our systematic review, expression profiling and sequence alignment reveal similarities and potentially important differences in ZIP complements between human and rodent β-cells. We identify ZIP6, ZIP7, ZIP9, ZIP13 and ZIP14 in human and rodent and ZIP1 in rodent as potentially biologically important for β-cell zinc trafficking. We propose ZIP6 and ZIP7 are key functional orthologues in human and rodent β-cells and highlight these zinc importers as important targets for exploring associations between zinc status and normal physiology of β-cells and their decline in Type 2 Diabetes.
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Affiliation(s)
- Rebecca Lawson
- King's College London, Faculty of Life Sciences and Medicine, Diabetes and Nutritional Sciences, Metal Metabolism Group, 150 Stamford St, London, SE1 9NH, UK
| | - Wolfgang Maret
- King's College London, Faculty of Life Sciences and Medicine, Diabetes and Nutritional Sciences, Metal Metabolism Group, 150 Stamford St, London, SE1 9NH, UK
| | - Christer Hogstrand
- King's College London, Faculty of Life Sciences and Medicine, Diabetes and Nutritional Sciences, Metal Metabolism Group, 150 Stamford St, London, SE1 9NH, UK.
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5
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Ranasinghe P, Pigera S, Galappatthy P, Katulanda P, Constantine GR. Zinc and diabetes mellitus: understanding molecular mechanisms and clinical implications. ACTA ACUST UNITED AC 2015; 23:44. [PMID: 26381880 PMCID: PMC4573932 DOI: 10.1186/s40199-015-0127-4] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 08/20/2015] [Indexed: 01/08/2023]
Abstract
Background Diabetes mellitus is a leading cause of morbidity and mortality worldwide. Studies have shown that Zinc has numerous beneficial effects in both type-1 and type-2 diabetes. We aim to evaluate the literature on the mechanisms and molecular level effects of Zinc on glycaemic control, β-cell function, pathogenesis of diabetes and its complications. Methods A review of published studies reporting mechanisms of action of Zinc in diabetes was undertaken in PubMed and SciVerse Scopus medical databases using the following search terms in article title, abstract or keywords; (“Zinc” or “Zn”) and (“mechanism” or “mechanism of action” or “action” or “effect” or “pathogenesis” or “pathology” or “physiology” or “metabolism”) and (“diabetes” or “prediabetes” or “sugar” or “glucose” or “insulin”). Results The literature search identified the following number of articles in the two databases; PubMed (n = 1799) and SciVerse Scopus (n = 1879). After removing duplicates the total number of articles included in the present review is 111. Our results show that Zinc plays an important role in β-cell function, insulin action, glucose homeostasis and the pathogenesis of diabetes and its complications. Conclusion Numerous in-vitro and in-vivo studies have shown that Zinc has beneficial effects in both type-1 and type-2 diabetes. However further randomized double-blinded placebo-controlled clinical trials conducted for an adequate duration, are required to establish therapeutic safety in humans. Electronic supplementary material The online version of this article (doi:10.1186/s40199-015-0127-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Priyanga Ranasinghe
- Department of Pharmacology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka.
| | - Shehani Pigera
- Department of Pharmacology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka
| | | | - Prasad Katulanda
- Diabetes Research Unit, Department of Clinical Medicine, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka
| | - Godwin R Constantine
- Diabetes Research Unit, Department of Clinical Medicine, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka
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6
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Slepchenko KG, Daniels NA, Guo A, Li YV. Autocrine effect of Zn²⁺ on the glucose-stimulated insulin secretion. Endocrine 2015; 50:110-22. [PMID: 25771886 DOI: 10.1007/s12020-015-0568-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 03/02/2015] [Indexed: 12/30/2022]
Abstract
It is well known that zinc (Zn(2+)) is required for the process of insulin biosynthesis and the maturation of insulin secretory granules in pancreatic beta (β)-cells, and that changes in Zn(2+) levels in the pancreas have been found to be associated with diabetes. Glucose-stimulation causes a rapid co-secretion of Zn(2+) and insulin with similar kinetics. However, we do not know whether Zn(2+) regulates insulin availability and secretion. Here we investigated the effect of Zn(2+) on glucose-stimulated insulin secretion (GSIS) in isolated mouse pancreatic islets. Whereas Zn(2+) alone (control) had no effect on the basal secretion of insulin, it significantly inhibited GSIS. The application of CaEDTA, by removing the secreted Zn(2+) from the extracellular milieu of the islets, resulted in significantly increased GSIS, suggesting an overall inhibitory role of secreted Zn(2+) on GSIS. The inhibitory action of Zn(2+) was mostly mediated through the activities of KATP/Ca(2+) channels. Furthermore, during brief paired-pulse glucose-stimulated Zn(2+) secretion (GSZS), Zn(2+) secretion following the second pulse was significantly attenuated, probably by the secreted endogenous Zn(2+) after the first pulse. Such an inhibition on Zn(2+) secretion following the second pulse was completely reversed by Zn(2+) chelation, suggesting a negative feedback mechanism, in which the initial glucose-stimulated Zn(2+) release inhibits subsequent Zn(2+) secretion, subsequently inhibiting insulin co-secretion as well. Taken together, these data suggest a negative feedback mechanism on GSZS and GSIS by Zn(2+) secreted from β-cells, and the co-secreted Zn(2+) may act as an autocrine inhibitory modulator.
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Affiliation(s)
- Kira G Slepchenko
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, 45701, USA
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7
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Liu Y, Batchuluun B, Ho L, Zhu D, Prentice KJ, Bhattacharjee A, Zhang M, Pourasgari F, Hardy AB, Taylor KM, Gaisano H, Dai FF, Wheeler MB. Characterization of Zinc Influx Transporters (ZIPs) in Pancreatic β Cells: ROLES IN REGULATING CYTOSOLIC ZINC HOMEOSTASIS AND INSULIN SECRETION. J Biol Chem 2015; 290:18757-69. [PMID: 25969539 PMCID: PMC4513131 DOI: 10.1074/jbc.m115.640524] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Indexed: 12/12/2022] Open
Abstract
Zinc plays an essential role in the regulation of pancreatic β cell function, affecting important processes including insulin biosynthesis, glucose-stimulated insulin secretion, and cell viability. Mutations in the zinc efflux transport protein ZnT8 have been linked with both type 1 and type 2 diabetes, further supporting an important role for zinc in glucose homeostasis. However, very little is known about how cytosolic zinc is controlled by zinc influx transporters (ZIPs). In this study, we examined the β cell and islet ZIP transcriptome and show consistent high expression of ZIP6 (Slc39a6) and ZIP7 (Slc39a7) genes across human and mouse islets and MIN6 β cells. Modulation of ZIP6 and ZIP7 expression significantly altered cytosolic zinc influx in pancreatic β cells, indicating an important role for ZIP6 and ZIP7 in regulating cellular zinc homeostasis. Functionally, this dysregulated cytosolic zinc homeostasis led to impaired insulin secretion. In parallel studies, we identified both ZIP6 and ZIP7 as potential interacting proteins with GLP-1R by a membrane yeast two-hybrid assay. Knock-down of ZIP6 but not ZIP7 in MIN6 β cells impaired the protective effects of GLP-1 on fatty acid-induced cell apoptosis, possibly via reduced activation of the p-ERK pathway. Therefore, our data suggest that ZIP6 and ZIP7 function as two important zinc influx transporters to regulate cytosolic zinc concentrations and insulin secretion in β cells. In particular, ZIP6 is also capable of directly interacting with GLP-1R to facilitate the protective effect of GLP-1 on β cell survival.
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Affiliation(s)
- Ying Liu
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Battsetseg Batchuluun
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Louisa Ho
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Dan Zhu
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Kacey J Prentice
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Alpana Bhattacharjee
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Ming Zhang
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Farzaneh Pourasgari
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Alexandre B Hardy
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Kathryn M Taylor
- the Breast Cancer Molecular Pharmacology Unit, School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Redwood Building, King Edward VIIth Avenue, Cardiff CF10 3NB United Kingdom
| | - Herbert Gaisano
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Feihan F Dai
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
| | - Michael B Wheeler
- From the Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada and
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8
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Davidson HW, Wenzlau JM, O'Brien RM. Zinc transporter 8 (ZnT8) and β cell function. Trends Endocrinol Metab 2014; 25:415-24. [PMID: 24751356 PMCID: PMC4112161 DOI: 10.1016/j.tem.2014.03.008] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 03/17/2014] [Accepted: 03/19/2014] [Indexed: 02/07/2023]
Abstract
Human pancreatic β cells have exceptionally high zinc content. In β cells the highest zinc concentration is in insulin secretory granules, from which it is cosecreted with the hormone. Uptake of zinc into secretory granules is mainly mediated by zinc transporter 8 (ZnT8), the product of the SLC30A8 [solute carrier family 30 (zinc transporter), member 8] gene. The minor alleles of several single-nucleotide polymorphisms (SNPs) in SLC30A8 are associated with decreased risk of type 2 diabetes (T2D), but the precise mechanisms underlying the protective effects remain uncertain. In this article we review current knowledge of the role of ZnT8 in maintaining zinc homeostasis in β cells, its role in glucose metabolism based on knockout mouse studies, and current theories regarding the link between ZnT8 function and T2D.
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Affiliation(s)
- Howard W Davidson
- Barbara Davis Center for Diabetes, University of Colorado Denver Anschutz Medical Campus, Aurora, CO 80045, USA; Integrated Department of Immunology, University of Colorado Denver Anschutz Medical Campus, Aurora, CO 80045, USA.
| | - Janet M Wenzlau
- Barbara Davis Center for Diabetes, University of Colorado Denver Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Richard M O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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9
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Abstract
Zinc (Zn2+) is an essential element crucial for growth and development, and also plays a role in cell signaling for cellular processes like cell division and apoptosis. In the mammalian pancreas, Zn2+ is essential for the correct processing, storage, secretion, and action of insulin in beta (β)-cells. Insulin is stored inside secretory vesicles or granules, where two Zn2+ ions coordinate six insulin monomers to form the hexameric-structure on which maturated insulin crystals are based. The total Zn2+ content of the mammalian pancreas is among the highest in the body, and Zn2+ concentration reach millimolar levels in the interior of the dense-core granule. Changes in Zn2+ levels in the pancreas have been found to be associated with diabetes. Hence, the relationship between co-stored Zn2+ and insulin undoubtedly is critical to normal β-cell function. The advances in the field of Zn2+ biology over the last decade have facilitated our understanding of Zn2+ trafficking, its intracellular distribution and its storage. When exocytosis of insulin occurs, insulin granules fuse with the β-cell plasma membrane and release their contents, i.e., insulin as well as substantial amount of free Zn2+, into the extracellular space and the local circulation. Studies increasingly indicate that secreted Zn2+ has autocrine or paracrine signaling in β-cells or the neighboring cells. This review discusses the Zn2+ homeostasis in β-cells with emphasis on the potential signaling role of Zn2+ to islet biology.
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Affiliation(s)
- Yang V Li
- Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, 346 Irvine Hall, Athens, OH, 45701, USA,
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10
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Pae EK, Kim G. Insulin production hampered by intermittent hypoxia via impaired zinc homeostasis. PLoS One 2014; 9:e90192. [PMID: 24587273 PMCID: PMC3934988 DOI: 10.1371/journal.pone.0090192] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 01/31/2014] [Indexed: 12/18/2022] Open
Abstract
Without zinc, pancreatic beta cells cannot either assemble insulin molecules or precipitate insulin crystals; thus, a lack of zinc concentration in the beta cells would result in a decreased insulin production. ZIP8 is one of the zinc uptake transporters involved in zinc influx into the cytosol of beta cells. Thus, if ZIP8 is down-regulated, a decreased insulin production would result. We assumed that intermittent hypoxic exposure to the beta cells may result in a decreased production of insulin due to a lack of zinc. To test this hypothesis we harvested pancreatic islets from the rats conditioned under intermittent hypoxia (IH) (fluctuating between 20.5% and 10% every 4 min for 1 h) and compared the results with those from control animals and islets. We also compared their insulin and glucose homeostasis using glucose tolerance tests (GTT) after 3 weeks. GTT results show a significant delay (P<0.05) in recovery of the blood glucose level in IH treated pups. ZIP8 expression in the beta cell membrane was down-regulated. The zinc concentration in the cell as well as insulin production was significantly decreased in the islets harvested from IH animals. However, mRNA for insulin and C-peptide/insulin protein levels in the total cell lysates remained the same as those of controls. When we treated the beta cells using siRNA mediated ZIP8, we observed the commensurate results from the IH-treated islets. We conclude that a transient IH exposure could knockdown ZIP8 transporters at mRNA as well as protein levels in the beta cells, which would decrease the level of blood insulin. However, the transcriptional activity of insulin remains the same. We conclude that the precipitation process of insulin crystal may be disturbed by a lack of zinc in the cytosol that is modulated by mainly ZIP8 after IH exposure.
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Affiliation(s)
- Eung-Kwon Pae
- Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Maryland, Baltimore, Maryland, United States of America
- * E-mail:
| | - Gyuyoup Kim
- Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Maryland, Baltimore, Maryland, United States of America
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11
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Slepchenko KG, James CBL, Li YV. Inhibitory effect of zinc on glucose-stimulated zinc/insulin secretion in an insulin-secreting β-cell line. Exp Physiol 2013; 98:1301-11. [PMID: 23603373 DOI: 10.1113/expphysiol.2013.072348] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Diminished or inappropriate secretion of insulin is associated with type II diabetes. The cellular/molecular mechanism coupled with the regulation of insulin secretion is still under intense investigation. Divalent ion zinc (Zn(2+)) is co-packaged and co-secreted with insulin and is intimately involved in the process of insulin biosynthesis and the maturation of insulin secretory granules. The study reported here investigated glucose-stimulated zinc secretion (GSZS) and the effect of zinc on glucose-stimulated insulin secretion (GSIS) in the HIT-T15 pancreatic β-cell line. Zinc secretion was measured using a newly developed fluorescent zinc imaging approach, and the insulin secretion was measured using an enzyme-linked immunosorbent assay. There was apparent granular-like zinc staining in β-cells. The application of glucose induced detectable zinc secretion or GSZS. Like GSIS, GSZS was dependent on the glucose concentration (5-20 mm) and the presence of extracellular calcium. The application of a zinc chelator enhanced GSZS. When brief paired-pulse glucose stimulations, which involve the initial glucose stimulation followed by a second round of glucose stimulation, were applied, zinc secretion or GSZS that followed the first pulse was inhibited. This inhibition was reversed by zinc chelation, suggesting a feedback mechanism on GSZS by zinc secreted from β-cells. Finally, the application of zinc (50 μm) strongly inhibited GSIS as measured by enzyme-linked immunosorbent assay. The present study suggests that insulin secretion is regulated by co-secreted zinc that may act as an autocrine inhibitory modulator.
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Affiliation(s)
- Kira G Slepchenko
- Department of Biomedical Sciences, Ohio University Heritage College of Osteopathic Medicine, Athens, OH 45701, USA
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12
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Palacios-Prado N, Hoge G, Marandykina A, Rimkute L, Chapuis S, Paulauskas N, Skeberdis VA, O'Brien J, Pereda AE, Bennett MVL, Bukauskas FF. Intracellular magnesium-dependent modulation of gap junction channels formed by neuronal connexin36. J Neurosci 2013; 33:4741-53. [PMID: 23486946 PMCID: PMC3635812 DOI: 10.1523/jneurosci.2825-12.2013] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 01/07/2013] [Accepted: 01/08/2013] [Indexed: 11/21/2022] Open
Abstract
Gap junction (GJ) channels composed of Connexin36 (Cx36) are widely expressed in the mammalian CNS and form electrical synapses between neurons. Here we describe a novel modulatory mechanism of Cx36 GJ channels dependent on intracellular free magnesium ([Mg(2+)]i). We examined junctional conductance (gj) and its dependence on transjunctional voltage (Vj) at different [Mg(2+)]i in cultures of HeLa or N2A cells expressing Cx36. We found that Cx36 GJs are partially inhibited at resting [Mg(2+)]i. Thus, gj can be augmented or reduced by lowering or increasing [Mg(2+)]i, respectively. Similar changes in gj and Vj-gating were observed using MgATP or K2ATP in pipette solutions, which increases or decreases [Mg(2+)]i, respectively. Changes in phosphorylation of Cx36 or in intracellular free calcium concentration were not involved in the observed Mg(2+)-dependent modulation of gj. Magnesium ions permeate the channel and transjunctional asymmetry in [Mg(2+)]i resulted in asymmetric Vj-gating. The gj of GJs formed of Cx26, Cx32, Cx43, Cx45, and Cx47 was also reduced by increasing [Mg(2+)]i, but was not increased by lowering [Mg(2+)]i; single-channel conductance did not change. We showed that [Mg(2+)]i affects both open probability and the number of functional channels, likely through binding in the channel lumen. Finally, we showed that Cx36-containing electrical synapses between neurons of the trigeminal mesencephalic nucleus in rat brain slices are similarly affected by changes in [Mg(2+)]i. Thus, this novel modulatory mechanism could underlie changes in neuronal synchronization under conditions in which ATP levels, and consequently [Mg(2+)]i, are modified.
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Affiliation(s)
- Nicolás Palacios-Prado
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Gregory Hoge
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Alina Marandykina
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
- Institute of Cardiology, Lithuanian University of Health Sciences, LT-50009 Kaunas, Lithuania, and
| | - Lina Rimkute
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
- Institute of Cardiology, Lithuanian University of Health Sciences, LT-50009 Kaunas, Lithuania, and
| | - Sandrine Chapuis
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Nerijus Paulauskas
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
- Institute of Cardiology, Lithuanian University of Health Sciences, LT-50009 Kaunas, Lithuania, and
| | - Vytenis A. Skeberdis
- Institute of Cardiology, Lithuanian University of Health Sciences, LT-50009 Kaunas, Lithuania, and
| | - John O'Brien
- Department of Ophthalmology and Visual Science, University of Texas Medical School at Houston, Houston, Texas 77030
| | - Alberto E. Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Michael V. L. Bennett
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
| | - Feliksas F. Bukauskas
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461
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