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McGirr R, Sample C, Arwood L, Burch J, Alderman S. Validating Autoclave Cycles for Carcass Disposal in Animal Biosafety Level 2/3 Containment Laboratories. Appl Biosaf 2019; 24:134-140. [DOI: 10.1177/1535676019856799] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Introduction:Animal carcasses differ in composition from other types of solid waste, and through prior testing it was determined that cycle parameters applied to general, solid biohazardous waste did not ensure proper sterilization of ferret carcasses.Objectives:The goals of this study were to develop and validate an autoclave cycle that would ensure the decontamination of infectious animal carcasses before removal from an animal biosafety level 2/3 containment suite for downstream disposal and to test different ways to prepare and package animal carcasses for autoclaving.Methods:Intact ferret carcasses were implanted with biological indicators, and the carcasses were placed in biohazard bags, then into metal pans. To test the efficacy of the autoclave cycle on larger biomasses, 1, 2, or 4 ferret carcasses were placed in a biohazard bag. A total of 4 carcasses were placed in each pan. An autoclave cycle was created to begin the study. After initial tests, minor modifications to the initial test cycle parameters were made, and a new cycle was validated for ferret carcasses up to 2 kg each. Parameters for the validated cycle were as follows: sterilization time 240 minutes, temperature 125°C, 5 prevacuum pulses, and chamber pressure 15 psi.Results:The results of this study indicate that an extended sterilization time is required to successfully decontaminate animal carcasses compared with regular, solid, and biohazardous waste.Conclusions:This study demonstrates that it is possible to sterilize multiple intact ferret carcasses per load under validated autoclave cycle conditions.
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Affiliation(s)
| | | | - Leslee Arwood
- Duke University, Regional Biocontainment Laboratory, Durham, NC, USA
| | - James Burch
- Duke University, Regional Biocontainment Laboratory, Durham, NC, USA
| | - Scott Alderman
- Duke University, Regional Biocontainment Laboratory, Durham, NC, USA
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Liu L, Alizadeh K, Donnelly SC, Dassanayake P, Hou TT, McGirr R, Thompson RT, Prato FS, Gelman N, Hoffman L, Goldhawk DE. MagA expression attenuates iron export activity in undifferentiated multipotent P19 cells. PLoS One 2019; 14:e0217842. [PMID: 31170273 PMCID: PMC6553743 DOI: 10.1371/journal.pone.0217842] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 05/20/2019] [Indexed: 12/21/2022] Open
Abstract
Magnetic resonance imaging (MRI) is a non-invasive imaging modality used in longitudinal cell tracking. Previous studies suggest that MagA, a putative iron transport protein from magnetotactic bacteria, is a useful gene-based magnetic resonance contrast agent. Hemagglutinin-tagged MagA was stably expressed in undifferentiated embryonic mouse teratocarcinoma, multipotent P19 cells to provide a suitable model for tracking these cells during differentiation. Western blot and immunocytochemistry confirmed the expression and membrane localization of MagA in P19 cells. Surprisingly, elemental iron analysis using inductively-coupled plasma mass spectrometry revealed significant iron uptake in both parental and MagA-expressing P19 cells, cultured in the presence of iron-supplemented medium. Withdrawal of this extracellular iron supplement revealed unexpected iron export activity in P19 cells, which MagA expression attenuated. The influence of iron supplementation on parental and MagA-expressing cells was not reflected by longitudinal relaxation rates. Measurement of transverse relaxation rates (R2* and R2) reflected changes in total cellular iron content but did not clearly distinguish MagA-expressing cells from the parental cell type, despite significant differences in the uptake and retention of total cellular iron. Unlike other cell types, the reversible component R2′ (R2* ‒ R2) provided only a moderately strong correlation to amount of cellular iron, normalized to amount of protein. This is the first report to characterize MagA expression in a previously unrecognized iron exporting cell type. The interplay between contrast gene expression and systemic iron metabolism substantiates the potential for diverting cellular iron toward the formation of a novel iron compartment, however rudimentary when using a single magnetotactic bacterial gene expression system like magA. Since relatively few mammalian cells export iron, the P19 cell line provides a tractable model of ferroportin activity, suitable for magnetic resonance analysis of key iron-handling activities and their influence on gene-based MRI contrast.
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Affiliation(s)
- Linshan Liu
- Imaging, Lawson Health Research Institute, London, Ontario, Canada
- Medical Biophysics, Western University, London, Ontario, Canada
- Collaborative Graduate Program in Molecular Imaging, Western University, London, Ontario, Canada
| | - Kobra Alizadeh
- Imaging, Lawson Health Research Institute, London, Ontario, Canada
- Medical Biophysics, Western University, London, Ontario, Canada
- Collaborative Graduate Program in Molecular Imaging, Western University, London, Ontario, Canada
| | - Sarah C. Donnelly
- Imaging, Lawson Health Research Institute, London, Ontario, Canada
- Collaborative Graduate Program in Molecular Imaging, Western University, London, Ontario, Canada
- Microbiology and Immunology, Western University, London, Ontario, Canada
| | - Praveen Dassanayake
- Imaging, Lawson Health Research Institute, London, Ontario, Canada
- Medical Biophysics, Western University, London, Ontario, Canada
- Collaborative Graduate Program in Molecular Imaging, Western University, London, Ontario, Canada
| | - Tian Tian Hou
- Imaging, Lawson Health Research Institute, London, Ontario, Canada
| | - Rebecca McGirr
- Imaging, Lawson Health Research Institute, London, Ontario, Canada
| | - R. Terry Thompson
- Imaging, Lawson Health Research Institute, London, Ontario, Canada
- Medical Biophysics, Western University, London, Ontario, Canada
- Medical Imaging, Western University, London, Ontario, Canada
- Physics and Astronomy, Western University, London, Ontario, Canada
| | - Frank S. Prato
- Imaging, Lawson Health Research Institute, London, Ontario, Canada
- Medical Biophysics, Western University, London, Ontario, Canada
- Collaborative Graduate Program in Molecular Imaging, Western University, London, Ontario, Canada
- Medical Imaging, Western University, London, Ontario, Canada
- Physics and Astronomy, Western University, London, Ontario, Canada
| | - Neil Gelman
- Imaging, Lawson Health Research Institute, London, Ontario, Canada
- Medical Biophysics, Western University, London, Ontario, Canada
- Medical Imaging, Western University, London, Ontario, Canada
| | - Lisa Hoffman
- Imaging, Lawson Health Research Institute, London, Ontario, Canada
- Medical Biophysics, Western University, London, Ontario, Canada
- Collaborative Graduate Program in Molecular Imaging, Western University, London, Ontario, Canada
- Anatomy and Cell Biology, Western University, London, Ontario, Canada
| | - Donna E. Goldhawk
- Imaging, Lawson Health Research Institute, London, Ontario, Canada
- Medical Biophysics, Western University, London, Ontario, Canada
- Collaborative Graduate Program in Molecular Imaging, Western University, London, Ontario, Canada
- * E-mail:
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Sullivan R, McGirr R, Hu S, Tan A, Wu D, Charron C, Lalonde T, Arany E, Chakrabarti S, Luyt L, Dhanvantari S. Changes in the Cardiac GHSR1a-Ghrelin System Correlate With Myocardial Dysfunction in Diabetic Cardiomyopathy in Mice. J Endocr Soc 2017; 2:178-189. [PMID: 29450407 PMCID: PMC5799831 DOI: 10.1210/js.2017-00433] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 12/19/2017] [Indexed: 01/16/2023] Open
Abstract
Ghrelin and its receptor, the growth hormone secretagogue receptor 1a (GHSR1a), are present in cardiac tissue. Activation of GHSR1a by ghrelin promotes cardiomyocyte contractility and survival, and changes in myocardial GHSR1a and circulating ghrelin track with end-stage heart failure, leading to the hypothesis that GHSR1a is a biomarker for heart failure. We hypothesized that GHSR1a could also be a biomarker for diabetic cardiomyopathy (DCM). We used two models of streptozotocin (STZ)-induced DCM: group 1, adult mice treated with 35 mg/kg STZ for 3 days; and group 2, neonatal mice treated with 70 mg/kg STZ at days 2 and 5 after birth. In group 1, mild fasting hyperglycemia (11 mM) was first detected 8 weeks after the last injection, and in group 2, severe fasting hyperglycemia (20 mM) was first detected 1 to 3 weeks after the last injection. In group 1, left ventricular function was slightly impaired as measured by echocardiography, and Western blot analysis showed a significant decrease in myocardial GHSR1a. In group 2, GHSR1a levels were also decreased as assessed by Cy5-ghrelin(1–19) fluorescence microscopy, and there was a significant negative correlation between GHSR1a levels and glucose tolerance. There were significant positive correlations between GHSR1a and ghrelin and between GHSR1a and sarcoplasmic reticulum Ca2+-ATPase 2a (SERCA2a), a marker for contractility, but not between GHSR1a and B-type natriuretic peptide, a marker for heart failure. We conclude that the subclinical stage of DCM is accompanied by alterations in the myocardial ghrelin-GHSR1a system, suggesting the possibility of a biomarker for DCM.
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Affiliation(s)
- Rebecca Sullivan
- Imaging Research, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada.,Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada
| | - Rebecca McGirr
- Imaging Research, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Shirley Hu
- Department of Physiology and Pharmacology, Western University, London, Ontario N6A 3K7, Canada
| | - Alice Tan
- Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada
| | - Derek Wu
- Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada
| | - Carlie Charron
- Department of Chemistry, Western University, London, Ontario N6A 5B7, Canada
| | - Tyler Lalonde
- Department of Chemistry, Western University, London, Ontario N6A 5B7, Canada
| | - Edith Arany
- Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada
| | - Subrata Chakrabarti
- Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada
| | - Leonard Luyt
- Department of Chemistry, Western University, London, Ontario N6A 5B7, Canada.,Departments of Oncology and Medical Imaging, Western University, London, Ontario N6A 4L6, Canada.,London Regional Cancer Program, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Savita Dhanvantari
- Imaging Research, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada.,Department of Pathology and Laboratory Medicine, Western University, London, Ontario N6A 4V2, Canada.,Department of Medical Biophysics, Western University, London, Ontario N6A 5C1, Canada
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Abbas A, Beamish C, McGirr R, Demarco J, Cockburn N, Krokowski D, Lee TY, Kovacs M, Hatzoglou M, Dhanvantari S. Characterization of 5-(2- 18F-fluoroethoxy)-L-tryptophan for PET imaging of the pancreas. F1000Res 2016; 5:1851. [PMID: 27909574 PMCID: PMC5112576 DOI: 10.12688/f1000research.9129.2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/04/2016] [Indexed: 12/23/2022] Open
Abstract
Purpose: In diabetes, pancreatic beta cell mass declines significantly prior to onset of fasting hyperglycemia. This decline may be due to endoplasmic reticulum (ER) stress, and the system L amino acid transporter LAT1 may be a biomarker of this process. In this study, we used 5-(2-
18F-fluoroethoxy)-L-tryptophan (
18F-L-FEHTP) to target LAT1 as a potential biomarker of beta cell function in diabetes. Procedures: Uptake of
18F-L-FEHTP was determined in wild-type C57BL/6 mice by
ex vivo biodistribution. Both dynamic and static positron emission tomography (PET) images were acquired in wild-type and Akita mice, a model of ER stress-induced diabetes, as well as in mice treated with streptozotocin (STZ). LAT1 expression in both groups of mice was evaluated by immunofluorescence microscopy. Results: Uptake of
18F-L-FEHTP was highest in the pancreas, and static PET images showed highly specific pancreatic signal. Time-activity curves showed significantly reduced
18F-L-FEHTP uptake in Akita mice, and LAT1 expression was also reduced. However, mice treated with STZ, in which beta cell mass was reduced by 62%, showed no differences in
18F-L-FEHTP uptake in the pancreas, and there was no significant correlation of
18F-L-FEHTP uptake with beta cell mass. Conclusions: 18F-L-FEHTP is highly specific for the pancreas with little background uptake in kidney or liver. We were able to detect changes in LAT1 in a mouse model of diabetes, but these changes did not correlate with beta cell function or mass. Therefore,
18F-L-FEHTP PET is not a suitable method for the noninvasive imaging of changes in beta cell function during the progression of diabetes.
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Affiliation(s)
- Ahmed Abbas
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada
| | - Christine Beamish
- Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Rebecca McGirr
- Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada; Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - John Demarco
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Neil Cockburn
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Dawid Krokowski
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Ting-Yim Lee
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada; Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Michael Kovacs
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada; Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Maria Hatzoglou
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Savita Dhanvantari
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada; Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada; Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada; Department of Pathology and Laboratory Medicine, Western University, London, ON, N6A 5C1, Canada
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5
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Abbas A, Beamish C, McGirr R, Demarco J, Cockburn N, Krokowski D, Lee TY, Kovacs M, Hatzoglou M, Dhanvantari S. Characterization of 5-(2- 18F-fluoroethoxy)-L-tryptophan for PET imaging of the pancreas. F1000Res 2016; 5:1851. [PMID: 27909574 PMCID: PMC5112576 DOI: 10.12688/f1000research.9129.1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/04/2016] [Indexed: 10/29/2023] Open
Abstract
Purpose: In diabetes, pancreatic beta cell mass declines significantly prior to onset of fasting hyperglycemia. This decline may be due to endoplasmic reticulum (ER) stress, and the system L amino acid transporter LAT1 may be a biomarker of this process. In this study, we used 5-(2- 18F-fluoroethoxy)-L-tryptophan ( 18F-L-FEHTP) to target LAT1 as a potential biomarker of beta cell function in diabetes. Procedures: Uptake of 18F-L-FEHTP was determined in wild-type C57BL/6 mice by ex vivo biodistribution. Both dynamic and static positron emission tomography (PET) images were acquired in wild-type and Akita mice, a model of ER stress-induced diabetes, as well as in mice treated with streptozotocin (STZ). LAT1 expression in both groups of mice was evaluated by immunofluorescence microscopy. Results: Uptake of 18F-L-FEHTP was highest in the pancreas, and static PET images showed highly specific pancreatic signal. Time-activity curves showed significantly reduced 18F-L-FEHTP uptake in Akita mice, and LAT1 expression was also reduced. However, mice treated with STZ, in which beta cell mass was reduced by 62%, showed no differences in 18F-L-FEHTP uptake in the pancreas, and there was no significant correlation of 18F-L-FEHTP uptake with beta cell mass. Conclusions:18F-L-FEHTP is highly specific for the pancreas with little background uptake in kidney or liver. We were able to detect changes in LAT1 in a mouse model of diabetes, but these changes did not correlate with beta cell function or mass. Therefore, 18F-L-FEHTP PET is not a suitable method for the noninvasive imaging of changes in beta cell function during the progression of diabetes.
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Affiliation(s)
- Ahmed Abbas
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada
| | - Christine Beamish
- Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Rebecca McGirr
- Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - John Demarco
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Neil Cockburn
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Dawid Krokowski
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Ting-Yim Lee
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Michael Kovacs
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
| | - Maria Hatzoglou
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Savita Dhanvantari
- Department of Medical Biophysics, Western University, London, ON, N6A 5C1, Canada
- Metabolism and Diabetes Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
- Imaging Program, Lawson Health Research Institute, London, ON, N6A 4V2, Canada
- Department of Pathology and Laboratory Medicine, Western University, London, ON, N6A 5C1, Canada
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Behnam Azad B, Rota V, Yu L, McGirr R, St Amant AH, Lee TY, Dhanvantari S, Luyt LG. Synthesis and evaluation of optical and PET GLP-1 peptide analogues for GLP-1R imaging. Mol Imaging 2016; 14. [PMID: 25762192 DOI: 0.2310/7290.2014.00057] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/29/2022] Open
Abstract
A fluorescein-GLP-1 (7-37) analog was generated to determine GLP-1R distribution in various cell types of the pancreas in both strains of mice and receptor-specific uptake was confirmed by blocking with exendin-4. Biodistribution studies were carried out using 68Ga-labeled GLP-1(7-37) peptides in CD1 and C57BL/6 mice. In addition, immunocompromised mice bearing GLP-1R-expressing insulinomas were evaluated by positron emission tomography (PET) imaging and ex vivo biodistribution studies. The optical GLP-1 probe strongly colocalized with immunofluorescence for insulin and glucagon, and more weakly with amylase (exocrine pancreas) and cytokeratin 19 (ductal cells), confirming its application for in situ GLP-1R imaging in various pancreatic cell types. Insulinomas were clearly visualized by in vivo PET. Reducing the peptide positive charge decreased renal retention as well as tumor uptake. Results demonstrate the application of the developed GLP-1 peptide analogues for in situ (optical) and in vivo (PET) imaging of GLP-1R expression.
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Bondoc AB, Detombe S, Dunmore-Buyze J, Gutpell KM, Liu L, Kaszuba A, Han S, McGirr R, Hadway J, Drangova M, Hoffman LM. Application of 3-d echocardiography and gated micro-computed tomography to assess cardiomyopathy in a mouse model of duchenne muscular dystrophy. Ultrasound Med Biol 2014; 40:2857-2867. [PMID: 25308942 DOI: 10.1016/j.ultrasmedbio.2014.07.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 04/15/2014] [Accepted: 07/27/2014] [Indexed: 06/04/2023]
Abstract
The purpose of this study was to measure changes in cardiac function as cardiomyopathy progresses in a mouse model of Duchenne muscular dystrophy using 3-D ECG-gated echocardiography. This study is the first to correlate cardiac volumes acquired using 3-D echocardiography with those acquired using retrospectively gated micro-computed tomography (CT). Both were further compared with standard M-mode echocardiography and histologic analyses. We found that although each modality measures a decrease in cardiac function as disease progresses in mdx/utrn(-/-) mice (n = 5) compared with healthy C57BL/6 mice (n = 8), 3-D echocardiography has higher agreement with gold-standard measurements acquired by gated micro-CT, with little standard deviation between measurements. M-Mode echocardiography measurements, in comparison, exhibit considerably greater variability and user bias. Given the radiation dose associated with micro-CT and the geometric assumptions made in M-mode echocardiography to calculate ventricular volume, we suggest that use of 3-D echocardiography has important advantages that may allow for the measurement of early disease changes that occur before overt cardiomyopathy.
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Affiliation(s)
- Andrew B Bondoc
- Imaging Program, Lawson Health Research Institute, London, Ontario, Canada; Department of Medical Biophysics, Western University, London, Ontario, Canada
| | - Sarah Detombe
- Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada
| | - Joy Dunmore-Buyze
- Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada
| | - Kelly M Gutpell
- Imaging Program, Lawson Health Research Institute, London, Ontario, Canada; Department of Anatomy & Cell Biology, Western University, London, Ontario, Canada
| | - Linshan Liu
- Imaging Program, Lawson Health Research Institute, London, Ontario, Canada; Department of Medical Biophysics, Western University, London, Ontario, Canada
| | - Amanda Kaszuba
- Imaging Program, Lawson Health Research Institute, London, Ontario, Canada
| | - Seongryoung Han
- Imaging Program, Lawson Health Research Institute, London, Ontario, Canada
| | - Rebecca McGirr
- Imaging Program, Lawson Health Research Institute, London, Ontario, Canada
| | - Jennifer Hadway
- Imaging Program, Lawson Health Research Institute, London, Ontario, Canada; Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada
| | - Maria Drangova
- Department of Medical Biophysics, Western University, London, Ontario, Canada; Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada
| | - Lisa M Hoffman
- Imaging Program, Lawson Health Research Institute, London, Ontario, Canada; Department of Medical Biophysics, Western University, London, Ontario, Canada; Department of Anatomy & Cell Biology, Western University, London, Ontario, Canada.
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Guizzetti L, McGirr R, Dhanvantari S. Two dipolar α-helices within hormone-encoding regions of proglucagon are sorting signals to the regulated secretory pathway. J Biol Chem 2014; 289:14968-80. [PMID: 24727476 DOI: 10.1074/jbc.m114.563684] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Proglucagon is expressed in pancreatic α cells, intestinal L cells, and some hypothalamic and brainstem neurons. Tissue-specific processing of proglucagon yields three major peptide hormones as follows: glucagon in the α cells and glucagon-like peptides (GLP)-1 and -2 in the L cells and neurons. Efficient sorting and packaging into the secretory granules of the regulated secretory pathway in each cell type are required for nutrient-regulated secretion of these proglucagon-derived peptides. Our previous work suggested that proglucagon is directed into granules by intrinsic sorting signals after initial processing to glicentin and major proglucagon fragment (McGirr, R., Guizzetti, L., and Dhanvantari, S. (2013) J. Endocrinol. 217, 229-240), leading to the hypothesis that sorting signals may be present in multiple domains. In the present study, we show that the α-helices within glucagon and GLP-1, but not GLP-2, act as sorting signals by efficiently directing a heterologous secretory protein to the regulated secretory pathway. Biophysical characterization of these peptides revealed that glucagon and GLP-1 each encode a nonamphipathic, dipolar α-helix, whereas the helix in GLP-2 is not dipolar. Surprisingly, glicentin and major proglucagon fragment were sorted with different efficiencies, thus providing evidence that proglucagon is first sorted to granules prior to processing. In contrast to many other prohormones in which sorting is directed by ordered prodomains, the sorting determinants of proglucagon lie within the ordered hormone domains of glucagon and GLP-1, illustrating that each prohormone has its own sorting "signature."
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Affiliation(s)
| | - Rebecca McGirr
- the Metabolism/Diabetes and Imaging Programs, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada
| | - Savita Dhanvantari
- From the Departments of Medical Biophysics, the Metabolism/Diabetes and Imaging Programs, Lawson Health Research Institute, London, Ontario N6A 4V2, Canada Pathology, and Medicine, University of Western Ontario, London, Ontario N6A 3K7 and
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Douglas GAF, McGirr R, Charlton CL, Kagan DB, Hoffman LM, Luyt LG, Dhanvantari S. Characterization of a far-red analog of ghrelin for imaging GHS-R in P19-derived cardiomyocytes. Peptides 2014; 54:81-8. [PMID: 24468548 DOI: 10.1016/j.peptides.2014.01.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 01/16/2014] [Accepted: 01/16/2014] [Indexed: 11/29/2022]
Abstract
Ghrelin and its receptor, the growth hormone secretagogue receptor (GHS-R), are expressed in the heart, and may function to promote cardiomyocyte survival, differentiation and contractility. Previously, we had generated a truncated analog of ghrelin conjugated to fluorescein isothiocyanate for the purposes of determining GHS-R expression in situ. We now report the generation and characterization of a far-red ghrelin analog, [Dpr(3)(octanoyl), Lys(19)(Cy5)]ghrelin (1-19), and show that it can be used to image changes in GHS-R in developing cardiomyocytes. We also generated the des-acyl analog, des-acyl [Lys(19)(Cy5)]ghrelin (1-19) and characterized its binding to mouse heart sections. Receptor binding affinity of Cy5-ghrelin as measured in HEK293 cells overexpressing GHS-R1a was within an order of magnitude of that of fluorescein-ghrelin and native human ghrelin, while the des-acyl Cy5-ghrelin did not bind GHS-R1a. Live cell imaging in HEK293/GHS-R1a cells showed cell surface labeling that was displaced by excess ghrelin. Interestingly, Cy5-ghrelin, but not the des-acyl analog, showed concentration-dependent binding in mouse heart tissue sections. We then used Cy5-ghrelin to track GHS-R expression in P19-derived cardiomyocytes. Live cell imaging at different time points after DMSO-induced differentiation showed that GHS-R expression preceded that of the differentiation marker aMHC and tracked with the contractility marker SERCA 2a. Our far-red analog of ghrelin adds to the tools we are developing to map GHS-R in developing and diseased cardiac tissues.
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Affiliation(s)
- Gregory A F Douglas
- Departments of Pathology, Chemistry, Medical Imaging, Medical Biophysics, and Oncology, Western University, Richmond Street, London, Ontario, Canada; Imaging Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario N6A 4V2, Canada
| | - Rebecca McGirr
- Departments of Pathology, Chemistry, Medical Imaging, Medical Biophysics, and Oncology, Western University, Richmond Street, London, Ontario, Canada; Imaging Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario N6A 4V2, Canada
| | - Carlie L Charlton
- Departments of Pathology, Chemistry, Medical Imaging, Medical Biophysics, and Oncology, Western University, Richmond Street, London, Ontario, Canada; Imaging Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario N6A 4V2, Canada
| | - Dov B Kagan
- Departments of Pathology, Chemistry, Medical Imaging, Medical Biophysics, and Oncology, Western University, Richmond Street, London, Ontario, Canada; Imaging Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario N6A 4V2, Canada
| | - Lisa M Hoffman
- Departments of Pathology, Chemistry, Medical Imaging, Medical Biophysics, and Oncology, Western University, Richmond Street, London, Ontario, Canada; Imaging Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario N6A 4V2, Canada
| | - Leonard G Luyt
- Departments of Pathology, Chemistry, Medical Imaging, Medical Biophysics, and Oncology, Western University, Richmond Street, London, Ontario, Canada; Imaging Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario N6A 4V2, Canada
| | - Savita Dhanvantari
- Departments of Pathology, Chemistry, Medical Imaging, Medical Biophysics, and Oncology, Western University, Richmond Street, London, Ontario, Canada; Imaging Program, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario N6A 4V2, Canada.
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10
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Abstract
Proglucagon is expressed in pancreatic alpha cells, intestinal L cells and brainstem neurons. Tissue-specific processing of proglucagon yields the peptide hormones glucagon in the alpha cell and glucagon-like peptide (GLP)-1 and GLP-2 in L cells. Both glucagon and GLP-1 are secreted in response to nutritional status and are critical for regulating glycaemia. The sorting of proglucagon to the dense-core secretory granules of the regulated secretory pathway is essential for the appropriate secretion of glucagon and GLP-1. We examined the roles of carboxypeptidase E (CPE), a prohormone sorting receptor, the processing enzymes PC1/3 and PC2 and putative intrinsic sorting signals in proglucagon sorting. In Neuro 2a cells that lacked CPE, PC1/3 and PC2, proglucagon co-localised with the Golgi marker p115 as determined by quantitative immunofluorescence microscopy. Expression of CPE, but not of PC1/3 or PC2, enhanced proglucagon sorting to granules. siRNA-mediated knockdown of CPE disrupted regulated secretion of glucagon from pancreatic-derived alphaTC1-6 cells, but not of GLP-1 from intestinal cell-derived GLUTag cells. Mutation of the PC cleavage site K70R71, the dibasic R17R18 site within glucagon or the alpha-helix of glucagon, all significantly affected the sub-cellular localisation of proglucagon. Protein modelling revealed that alpha helices corresponding to glucagon, GLP-1 and GLP-2, are arranged within a disordered structure, suggesting some flexibility in the sorting mechanism. We conclude that there are multiple mechanisms for sorting proglucagon to the regulated secretory pathway, including a role for CPE in pancreatic alpha cells, initial cleavage at K70R71 and multiple sorting signals.
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Affiliation(s)
- Rebecca McGirr
- Metabolism and Diabetes and Imaging Programs, Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario, Canada
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11
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Abstract
Duchenne muscular dystrophy (DMD) is a severe genetic neuromuscular disorder that affects 1 in 3,500 boys, and is characterized by progressive muscle degeneration. In patients, the ability of resident muscle satellite cells (SCs) to regenerate damaged myofibers becomes increasingly inefficient. Therefore, transplantation of muscle progenitor cells (MPCs)/myoblasts from healthy subjects is a promising therapeutic approach to DMD. A major limitation to the use of stem cell therapy, however, is a lack of reliable imaging technologies for long-term monitoring of implanted cells, and for evaluating its effectiveness. Here, we describe a non-invasive, real-time approach to evaluate the success of myoblast transplantation. This method takes advantage of a unified fusion reporter gene composed of genes (firefly luciferase [fluc], monomeric red fluorescent protein [mrfp] and sr39 thymidine kinase [sr39tk]) whose expression can be imaged with different imaging modalities. A variety of imaging modalities, including positron emission tomography (PET), single-photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), optical imaging, and high frequency 3D-ultrasound are now available, each with unique advantages and limitations. Bioluminescence imaging (BLI) studies, for example, have the advantage of being relatively low cost and high-throughput. It is for this reason that, in this study, we make use of the firefly luciferase (fluc) reporter gene sequence contained within the fusion gene and bioluminescence imaging (BLI) for the short-term localization of viable C2C12 myoblasts following implantation into a mouse model of DMD (muscular dystrophy on the X chromosome [mdx] mouse). Importantly, BLI provides us with a means to examine the kinetics of labeled MPCs post-implantation, and will be useful to track cells repeatedly over time and following migration. Our reporter gene approach further allows us to merge multiple imaging modalities in a single living subject; given the tomographic nature, fine spatial resolution and ability to scale up to larger animals and humans, PET will form the basis of future work that we suggest may facilitate rapid translation of methods developed in cells to preclinical models and to clinical applications.
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Affiliation(s)
- Kelly Gutpell
- Imaging Program, Lawson Health Research Institute, USA
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12
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McGirr R, McFarland MS, McTavish J, Luyt LG, Dhanvantari S. Design and characterization of a fluorescent ghrelin analog for imaging the growth hormone secretagogue receptor 1a. ACTA ACUST UNITED AC 2011; 172:69-76. [DOI: 10.1016/j.regpep.2011.08.011] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 08/17/2011] [Accepted: 08/23/2011] [Indexed: 01/11/2023]
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13
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Goldhawk DE, Lemaire C, McCreary CR, McGirr R, Dhanvantari S, Thompson RT, Figueredo R, Koropatnick J, Foster P, Prato FS. Magnetic Resonance Imaging of Cells Overexpressing MagA, an Endogenous Contrast Agent for Live Cell Imaging. Mol Imaging 2009. [DOI: 10.2310/7290.2009.00006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Molecular imaging with magnetic resonance imaging (MRI) may benefit from the ferrimagnetic properties of magnetosomes, membrane-enclosed iron biominerals whose formation in magnetotactic bacteria is encoded by multiple genes. One such gene is MagA, a putative iron transporter. We have examined expression of MagA in mouse neuroblastoma N2A cells and characterized their response to iron loading and cellular imaging by MRI. MagA expression augmented both Prussian blue staining and the elemental iron content of N2A cells, without altering cell proliferation, in cultures grown in the presence of iron supplements. Despite evidence for iron incorporation in both MagA and a variant, MagAE137V, only MagA expression produced intracellular contrast detectable by MRI at 11 Tesla. We used this stable expression system to model a new sequence for cellular imaging with MRI, using the difference between gradient and spin echo images to distinguish cells from artifacts in the field of view. Our results show that MagA activity in mammalian cells responds to iron supplementation and functions as a contrast agent that can be deactivated by a single point mutation. We conclude that MagA is a candidate MRI reporter gene that can exploit more fully the superior resolution of MRI in noninvasive medical imaging.
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Affiliation(s)
- Donna E. Goldhawk
- From the Imaging and Diabetes and Metabolism Programs, Lawson Health Research Institute, St. Joseph's Health Care, London, ON; Department of Physics and Astronomy, University of Waterloo, Waterloo, ON; Hotchkiss Brain Institute, University of Calgary, Calgary, AB; Departments of Medical Biophysics, Pathology and Medicine, and Medical Imaging, University of Western Ontario, London, ON; London Regional Cancer Program, London, ON; and Robarts Research Institute, University of Western Ontario, London, ON
| | - Claude Lemaire
- From the Imaging and Diabetes and Metabolism Programs, Lawson Health Research Institute, St. Joseph's Health Care, London, ON; Department of Physics and Astronomy, University of Waterloo, Waterloo, ON; Hotchkiss Brain Institute, University of Calgary, Calgary, AB; Departments of Medical Biophysics, Pathology and Medicine, and Medical Imaging, University of Western Ontario, London, ON; London Regional Cancer Program, London, ON; and Robarts Research Institute, University of Western Ontario, London, ON
| | - Cheryl R. McCreary
- From the Imaging and Diabetes and Metabolism Programs, Lawson Health Research Institute, St. Joseph's Health Care, London, ON; Department of Physics and Astronomy, University of Waterloo, Waterloo, ON; Hotchkiss Brain Institute, University of Calgary, Calgary, AB; Departments of Medical Biophysics, Pathology and Medicine, and Medical Imaging, University of Western Ontario, London, ON; London Regional Cancer Program, London, ON; and Robarts Research Institute, University of Western Ontario, London, ON
| | - Rebecca McGirr
- From the Imaging and Diabetes and Metabolism Programs, Lawson Health Research Institute, St. Joseph's Health Care, London, ON; Department of Physics and Astronomy, University of Waterloo, Waterloo, ON; Hotchkiss Brain Institute, University of Calgary, Calgary, AB; Departments of Medical Biophysics, Pathology and Medicine, and Medical Imaging, University of Western Ontario, London, ON; London Regional Cancer Program, London, ON; and Robarts Research Institute, University of Western Ontario, London, ON
| | - Savita Dhanvantari
- From the Imaging and Diabetes and Metabolism Programs, Lawson Health Research Institute, St. Joseph's Health Care, London, ON; Department of Physics and Astronomy, University of Waterloo, Waterloo, ON; Hotchkiss Brain Institute, University of Calgary, Calgary, AB; Departments of Medical Biophysics, Pathology and Medicine, and Medical Imaging, University of Western Ontario, London, ON; London Regional Cancer Program, London, ON; and Robarts Research Institute, University of Western Ontario, London, ON
| | - R. Terry Thompson
- From the Imaging and Diabetes and Metabolism Programs, Lawson Health Research Institute, St. Joseph's Health Care, London, ON; Department of Physics and Astronomy, University of Waterloo, Waterloo, ON; Hotchkiss Brain Institute, University of Calgary, Calgary, AB; Departments of Medical Biophysics, Pathology and Medicine, and Medical Imaging, University of Western Ontario, London, ON; London Regional Cancer Program, London, ON; and Robarts Research Institute, University of Western Ontario, London, ON
| | - Rene Figueredo
- From the Imaging and Diabetes and Metabolism Programs, Lawson Health Research Institute, St. Joseph's Health Care, London, ON; Department of Physics and Astronomy, University of Waterloo, Waterloo, ON; Hotchkiss Brain Institute, University of Calgary, Calgary, AB; Departments of Medical Biophysics, Pathology and Medicine, and Medical Imaging, University of Western Ontario, London, ON; London Regional Cancer Program, London, ON; and Robarts Research Institute, University of Western Ontario, London, ON
| | - Jim Koropatnick
- From the Imaging and Diabetes and Metabolism Programs, Lawson Health Research Institute, St. Joseph's Health Care, London, ON; Department of Physics and Astronomy, University of Waterloo, Waterloo, ON; Hotchkiss Brain Institute, University of Calgary, Calgary, AB; Departments of Medical Biophysics, Pathology and Medicine, and Medical Imaging, University of Western Ontario, London, ON; London Regional Cancer Program, London, ON; and Robarts Research Institute, University of Western Ontario, London, ON
| | - Paula Foster
- From the Imaging and Diabetes and Metabolism Programs, Lawson Health Research Institute, St. Joseph's Health Care, London, ON; Department of Physics and Astronomy, University of Waterloo, Waterloo, ON; Hotchkiss Brain Institute, University of Calgary, Calgary, AB; Departments of Medical Biophysics, Pathology and Medicine, and Medical Imaging, University of Western Ontario, London, ON; London Regional Cancer Program, London, ON; and Robarts Research Institute, University of Western Ontario, London, ON
| | - Frank S. Prato
- From the Imaging and Diabetes and Metabolism Programs, Lawson Health Research Institute, St. Joseph's Health Care, London, ON; Department of Physics and Astronomy, University of Waterloo, Waterloo, ON; Hotchkiss Brain Institute, University of Calgary, Calgary, AB; Departments of Medical Biophysics, Pathology and Medicine, and Medical Imaging, University of Western Ontario, London, ON; London Regional Cancer Program, London, ON; and Robarts Research Institute, University of Western Ontario, London, ON
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14
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Goldhawk DE, Lemaire C, McCreary CR, McGirr R, Dhanvantari S, Thompson RT, Figueredo R, Koropatnick J, Foster P, Prato FS. Magnetic resonance imaging of cells overexpressing MagA, an endogenous contrast agent for live cell imaging. Mol Imaging 2009; 8:129-139. [PMID: 19723470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023] Open
Abstract
Molecular imaging with magnetic resonance imaging (MRI) may benefit from the ferrimagnetic properties of magnetosomes, membrane-enclosed iron biominerals whose formation in magnetotactic bacteria is encoded by multiple genes. One such gene is MagA, a putative iron transporter. We have examined expression of MagA in mouse neuroblastoma N2A cells and characterized their response to iron loading and cellular imaging by MRI. MagA expression augmented both Prussian blue staining and the elemental iron content of N2A cells, without altering cell proliferation, in cultures grown in the presence of iron supplements. Despite evidence for iron incorporation in both MagA and a variant, MagAE137V, only MagA expression produced intracellular contrast detectable by MRI at 11 Tesla. We used this stable expression system to model a new sequence for cellular imaging with MRI, using the difference between gradient and spin echo images to distinguish cells from artifacts in the field of view. Our results show that MagA activity in mammalian cells responds to iron supplementation and functions as a contrast agent that can be deactivated by a single point mutation. We conclude that MagA is a candidate MRI reporter gene that can exploit more fully the superior resolution of MRI in noninvasive medical imaging.
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Affiliation(s)
- Donna E Goldhawk
- Imaging Program, Lawson Health Research Institute, St. Joseph's Health Care, London, ON.
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15
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Tai JH, Nguyen B, Wells RG, Kovacs MS, McGirr R, Prato FS, Morgan TG, Dhanvantari S. Imaging of Gene Expression in Live Pancreatic Islet Cell Lines Using Dual-Isotope SPECT. J Nucl Med 2007; 49:94-102. [DOI: 10.2967/jnumed.107.043430] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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16
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Abstract
We have investigated the effects of chronically elevated glucose concentrations on the pancreatic alpha-cell line alphaTC1-6. We show that basal glucagon secretion and proglucagon gene expression were increased in response to high glucose levels. The extent of acute stimulated secretion of glucagon was also increased in response to high glucose, as was the transcription of the prohormone processing enzymes PC1/3 and PC2. The secretion of GLP-1, a proglucagon-derived peptide produced by cleavage of proglucagon by PC1/3, was also increased in response to high glucose. Gene expression profiling experiments showed that a number of components of the regulated secretory pathway were up-regulated at high glucose concentrations, including processing enzymes and exocytotic proteins. Immunoblot analysis showed that the expression of the exocytotic SNARE proteins, as well as that of PC1/3, chromogranin A, and 7B2, were all increased after chronic exposure to high glucose levels. Immunocytochemistry showed no changes in the expression of the mature alpha-cell markers glucagon and brn-4 and no induction of the immature alpha-cell marker pdx-1. We conclude that chronically elevated glucose concentrations up-regulate the regulated secretory response of the alpha-cell.
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Affiliation(s)
- Rebecca McGirr
- Lawson Health Research Institute, 268 Grosvenor Street, London, Ontario, Canada N6A 4V2
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