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Lall R, Mohammed R, Ojha U. What are the links between hypoxia and Alzheimer's disease? Neuropsychiatr Dis Treat 2019; 15:1343-1354. [PMID: 31190838 PMCID: PMC6535079 DOI: 10.2147/ndt.s203103] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 03/01/2019] [Indexed: 01/30/2023] Open
Abstract
Alzheimer's disease (AD) is the most common neurodegenerative disease. Histological characterization of amyloid plaques and neurofibrillary tangles in the brains of AD patients, alongside genetic studies in individuals suffering the familial form of the disease, has fueled the accumulation of the amyloid-β protein as the initial pathological trigger of disease. Association studies have recently showed that cerebral hypoxia, via both genetic and epigenetic mechanisms, increase amyloid-β deposition by altering expression levels of enzymes involved in the production/degradation of the protein. Furthermore, hypoxia has also been linked to neuronal and glial-cell calcium dysregulation through formation of calcium-permeable pores, dysregulated glutamate signaling, and intracellular calcium-store dysfunction. Hypoxia has also been strongly linked to neuroinflammation; however, this relationship to AD has not been thoroughly discussed in the literature. Here, we highlight and organize critical research evidence showing that in both hypoxic and AD brains, there are similarities in terms of 1) the substances mediating/modulating the neuroinflammatory environment and 2) the immune cells that drive the formation of these substances.
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Affiliation(s)
- Rahul Lall
- Department of Medicine, University of Cambridge, Cambridge, UK
| | - Raihan Mohammed
- Department of Medicine, University of Cambridge, Cambridge, UK
| | - Utkarsh Ojha
- Faculty of Medicine, Imperial College London, London, UK
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2
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Smith NA, Kress BT, Lu Y, Chandler-Militello D, Benraiss A, Nedergaard M. Fluorescent Ca 2+ indicators directly inhibit the Na,K-ATPase and disrupt cellular functions. Sci Signal 2018; 11:11/515/eaal2039. [PMID: 29382785 DOI: 10.1126/scisignal.aal2039] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Fluorescent Ca2+ indicators have been essential for the analysis of Ca2+ signaling events in various cell types. We showed that chemical Ca2+ indicators, but not a genetically encoded Ca2+ indicator, potently suppressed the activity of Na+- and K+-dependent adenosine triphosphatase (Na,K-ATPase), independently of their Ca2+ chelating activity. Loading of commonly used Ca2+ indicators, including Fluo-4 acetoxymethyl (AM), Rhod-2 AM, and Fura-2 AM, and of the Ca2+ chelator BAPTA AM into cultured mouse or human neurons, astrocytes, cardiomyocytes, or kidney proximal tubule epithelial cells suppressed Na,K-ATPase activity by 30 to 80%. Ca2+ indicators also suppressed the agonist-induced activation of the Na,K-ATPase, altered metabolic status, and caused a dose-dependent loss of cell viability. Loading of Ca2+ indicators into mice, which is carried out for two-photon imaging, markedly altered brain extracellular concentrations of K+ and ATP. These results suggest that a critical review of data obtained with chemical Ca2+ indicators may be necessary.
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Affiliation(s)
- Nathan A Smith
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA.,Center for Neuroscience Research, Children's Research Institute, Children's National Health System, Washington, DC 20010, USA
| | - Benjamin T Kress
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Yuan Lu
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Devin Chandler-Militello
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Abdellatif Benraiss
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Departments of Neurosurgery and Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA.
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3
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Hettiarachchi NT, Boyle JP, Dallas ML, Al-Owais MM, Scragg JL, Peers C. Heme oxygenase-1 derived carbon monoxide suppresses Aβ 1-42 toxicity in astrocytes. Cell Death Dis 2017; 8:e2884. [PMID: 28617444 PMCID: PMC5520931 DOI: 10.1038/cddis.2017.276] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 04/19/2017] [Accepted: 05/12/2017] [Indexed: 12/27/2022]
Abstract
Neurodegeneration in Alzheimer's disease (AD) is extensively studied, and the involvement of astrocytes and other cell types in this process has been described. However, the responses of astrocytes themselves to amyloid β peptides ((Aβ; the widely accepted major toxic factor in AD) is less well understood. Here, we show that Aβ(1-42) is toxic to primary cultures of astrocytes. Toxicity does not involve disruption of astrocyte Ca2+ homeostasis, but instead occurs via formation of the toxic reactive species, peroxynitrite. Thus, Aβ(1-42) raises peroxynitrite levels in astrocytes, and Aβ(1-42) toxicity can be inhibited by antioxidants, or by inhibition of nitric oxide (NO) formation (reactive oxygen species (ROS) and NO combine to form peroxynitrite), or by a scavenger of peroxynitrite. Increased ROS levels observed following Aβ(1-42) application were derived from NADPH oxidase. Induction of haem oxygenase-1 (HO-1) protected astrocytes from Aβ(1-42) toxicity, and this protective effect was mimicked by application of the carbon monoxide (CO) releasing molecule CORM-2, suggesting HO-1 protection was attributable to its formation of CO. CO suppressed the rise of NADPH oxidase-derived ROS caused by Aβ(1-42). Under hypoxic conditions (0.5% O2, 48 h) HO-1 was induced in astrocytes and Aβ(1-42) toxicity was significantly reduced, an effect which was reversed by the specific HO-1 inhibitor, QC-15. Our data suggest that Aβ(1-42) is toxic to astrocytes, but that induction of HO-1 affords protection against this toxicity due to formation of CO. HO-1 induction, or CO donors, would appear to present attractive possible approaches to provide protection of both neuronal and non-neuronal cell types from the degenerative effects of AD in the central nervous system.
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Affiliation(s)
- Nishani T Hettiarachchi
- Division of Cardiovascular and Diabetes Research, LICAMM Faculty of Medicine and Health, University of Leeds, Leeds LS2 9JT, UK
| | - John P Boyle
- Division of Cardiovascular and Diabetes Research, LICAMM Faculty of Medicine and Health, University of Leeds, Leeds LS2 9JT, UK
| | - Mark L Dallas
- Reading School of Pharmacy, University of Reading, Reading, RG6 6UB, UK
| | - Moza M Al-Owais
- Division of Cardiovascular and Diabetes Research, LICAMM Faculty of Medicine and Health, University of Leeds, Leeds LS2 9JT, UK
| | - Jason L Scragg
- Division of Cardiovascular and Diabetes Research, LICAMM Faculty of Medicine and Health, University of Leeds, Leeds LS2 9JT, UK
| | - Chris Peers
- Division of Cardiovascular and Diabetes Research, LICAMM Faculty of Medicine and Health, University of Leeds, Leeds LS2 9JT, UK
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Korenić A, Boltze J, Deten A, Peters M, Andjus P, Radenović L. Astrocytic mitochondrial membrane hyperpolarization following extended oxygen and glucose deprivation. PLoS One 2014; 9:e90697. [PMID: 24587410 PMCID: PMC3938803 DOI: 10.1371/journal.pone.0090697] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 02/03/2014] [Indexed: 11/23/2022] Open
Abstract
Astrocytes can tolerate longer periods of oxygen and glucose deprivation (OGD) as compared to neurons. The reasons for this reduced vulnerability are not well understood. Particularly, changes in mitochondrial membrane potential (Δψm) in astrocytes, an indicator of the cellular redox state, have not been investigated during reperfusion after extended OGD exposure. Here, we subjected primary mouse astrocytes to glucose deprivation (GD), OGD and combinations of both conditions varying in duration and sequence. Changes in Δψm, visualized by change in the fluorescence of JC-1, were investigated within one hour after reconstitution of oxygen and glucose supply, intended to model in vivo reperfusion. In all experiments, astrocytes showed resilience to extended periods of OGD, which had little effect on Δψm during reperfusion, whereas GD caused a robust Δψm negativation. In case no Δψm negativation was observed after OGD, subsequent chemical oxygen deprivation (OD) induced by sodium azide caused depolarization, which, however, was significantly delayed as compared to normoxic group. When GD preceded OD for 12 h, Δψm hyperpolarization was induced by both GD and subsequent OD, but significant interaction between these conditions was not detected. However, when GD was extended to 48 h preceding OGD, hyperpolarization enhanced during reperfusion. This implicates synergistic effects of both conditions in that sequence. These findings provide novel information regarding the role of the two main substrates of electron transport chain (glucose and oxygen) and their hyperpolarizing effect on Δψm during substrate deprivation, thus shedding new light on mechanisms of astrocyte resilience to prolonged ischemic injury.
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Affiliation(s)
- Andrej Korenić
- Centre for Laser Microscopy, Department of Physiology and Biochemistry, Faculty of Biology, University of Belgrade, Belgrade, Serbia
| | - Johannes Boltze
- Fraunhofer Institute for Cell Therapy and Immunology, Leipzig, Germany ; Translational Centre for Regenerative Medicine, University of Leipzig, Leipzig, Germany ; Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Alexander Deten
- Fraunhofer Institute for Cell Therapy and Immunology, Leipzig, Germany
| | - Myriam Peters
- Fraunhofer Institute for Cell Therapy and Immunology, Leipzig, Germany
| | - Pavle Andjus
- Centre for Laser Microscopy, Department of Physiology and Biochemistry, Faculty of Biology, University of Belgrade, Belgrade, Serbia
| | - Lidija Radenović
- Centre for Laser Microscopy, Department of Physiology and Biochemistry, Faculty of Biology, University of Belgrade, Belgrade, Serbia
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Boyle JP, Hettiarachchi NT, Wilkinson JA, Pearson HA, Scragg JL, Lendon C, Al-Owais MM, Kim CB, Myers DM, Warburton P, Peers C. Cellular consequences of the expression of Alzheimer's disease-causing presenilin 1 mutations in human neuroblastoma (SH-SY5Y) cells. Brain Res 2012; 1443:75-88. [DOI: 10.1016/j.brainres.2011.12.061] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 10/28/2011] [Accepted: 12/31/2011] [Indexed: 11/27/2022]
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Riches K, Hettiarachchi N, Porter K, Peers C. Hypoxic remodelling of Ca2+ stores does not alter human cardiac myofibroblast invasion. Biochem Biophys Res Commun 2010; 403:468-72. [DOI: 10.1016/j.bbrc.2010.11.060] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Accepted: 11/13/2010] [Indexed: 10/18/2022]
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7
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Liu Y, Kintner DB, Begum G, Algharabli J, Cengiz P, Shull GE, Liu XJ, Sun D. Endoplasmic reticulum Ca2+ signaling and mitochondrial Cyt c release in astrocytes following oxygen and glucose deprivation. J Neurochem 2010; 114:1436-46. [PMID: 20557423 DOI: 10.1111/j.1471-4159.2010.06862.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In the present study, we investigated changes of cytosolic Ca2+([Ca2+](cyt)), endoplasmic reticulum Ca2+([Ca2+](ER)) and mitochondrial Ca2+(Ca2+(m)) in astrocytes following oxygen/glucose deprivation and reoxygenation (OGD/REOX). Two hours OGD did not cause changes in [Ca2+](cyt), but led to a significant increase in [Ca2+](ER). The elevation in [Ca2+](ER) continued and reached a peak level (130 +/- 2 microM) by 90 min REOX. An abrupt release of Ca2+(ER) occurred during 1.5-2.5 h REOX, which was accompanied with a delayed and sustained rise in [Ca2+](cyt). Moreover, Ca2+(m) content was increased significantly within 15 min REOX followed by a secondary rise (approximately 4.5-fold) and a release of mitochondrial cytochrome c (Cyt c). Astrocytes exhibited translocation of Cyt c from mitochondria to endoplasmic reticulum (ER) and up regulation of ER stress protein p-eIF2alpha. Blocking Na+-K+-Cl(-) cotransporter isoform 1 activity, either by its potent inhibitor bumetanide or genetic ablation, abolished release of ER Ca2+, delayed rise in [Ca2+](cyt) and Ca2+(m). Inhibition of the reverse mode operation of the Na+/Ca2+ exchanger significantly attenuated OGD/REOX-mediated Cyt c release. In summary, this study illustrates that OGD/REOX triggers a time-dependent loss of Ca2+ homeostasis in cytosol and organelles (ER and mitochondria) in astrocytes. Collective stimulation of Na+-K+-Cl(-) cotransporter isoform 1 and reverse mode function of Na+/Ca2+ exchanger contributes to these changes.
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Affiliation(s)
- Yan Liu
- Department of Biological Sciences and Biotechnology, School of Medicine, Tsinghua University, Beijing, China
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Pozzan T, Rudolf R. Measurements of mitochondrial calcium in vivo. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1317-23. [DOI: 10.1016/j.bbabio.2008.11.012] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2008] [Revised: 11/20/2008] [Accepted: 11/21/2008] [Indexed: 12/21/2022]
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Peers C, Dallas ML, Boycott HE, Scragg JL, Pearson HA, Boyle JP. Hypoxia and Neurodegeneration. Ann N Y Acad Sci 2009; 1177:169-77. [DOI: 10.1111/j.1749-6632.2009.05026.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Mehta SL, Li PA. Neuroprotective role of mitochondrial uncoupling protein 2 in cerebral stroke. J Cereb Blood Flow Metab 2009; 29:1069-78. [PMID: 19240738 DOI: 10.1038/jcbfm.2009.4] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The uncoupling proteins (UCPs) are mitochondrial transporter proteins involved in proton conductance across inner mitochondrial membrane (IMM). UCP2, which is one of the members of this class of proteins, has a wide but restricted tissue distribution including brain. Its physiologic role according to emerging evidences, although still not clear, indicate that distribution of UCP2 may be related to regulation of mitochondria membrane potential (DeltaPsim), production of reactive oxygen species (ROS), preservation of calcium homeostasis, modulation of neuronal activity, and eventually inhibition of cellular damage. These factors are very important in determining the fate of neurons and damage progression in the brain during various neurodegenerative diseases including cerebral stroke. Recent evidence indicates that an increased expression and activity of UCP2 are well correlated with neuronal survival after stroke and trauma. This review briefly covers the present understanding of UCP2, which eventually may be beneficial to understand the precise role of UCP2 to develop strategy to identify its potential therapeutic application.
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Affiliation(s)
- Suresh L Mehta
- Department of Pharmaceutical Sciences, Biotechnical Research Institute and Technology Research Enterprise (BRITE), North Carolina Central University, Durham, North Carolina, USA.
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11
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Aley PK, Bauer CC, Dallas ML, Boyle JP, Porter KE, Peers C. Hypoxic Modulation of Ca2+ Signaling in Human Venous and Arterial Endothelial Cells. J Membr Biol 2009; 227:151-8. [DOI: 10.1007/s00232-008-9147-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2008] [Accepted: 12/04/2008] [Indexed: 10/21/2022]
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Boycott HE, Wilkinson JA, Boyle JP, Pearson HA, Peers C. Differential involvement of TNF alpha in hypoxic suppression of astrocyte glutamate transporters. Glia 2008; 56:998-1004. [PMID: 18381653 DOI: 10.1002/glia.20673] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Transporter-mediated glutamate uptake is a principal function of astrocytes. Our previous studies have shown that this process is compromised under hypoxic conditions through the NF-kappaB mediated inhibition of expression of the glutamate transporters EAAT-1 and EAAT-2. Here, we demonstrate that identical conditions of hypoxia (1% O(2), 24 h) lead to a dramatic increase in TNFalpha production from astrocytes without altering their viability. This hypoxia-evoked production of TNFalpha was prevented in the presence of any of three mechanistically distinct NF-kappaB inhibitors. Exogenous application of TNFalpha was without effect on EAAT-1 expression as determined by Western blotting, but mimicked the effects of hypoxia to suppress expression of EAAT-2. Furthermore thalidomide, which prevents TNFalpha production, was without effect on hypoxic suppression of EAAT-1 but prevented hypoxic suppression of EAAT-2. These data indicate that regulation of glutamate transporter expression in astrocytes by hypoxia is subtype specific. Regulation of both EAAT-1 and EAAT-2 is mediated by NF-kappaB, and this transcriptional regulator is also required for increased production of TNFalpha. However, while TNFalpha is essential for hypoxic suppression of EAAT-2, hypoxic modulation of EAAT-1 expression is unaffected by this cytokine.
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Affiliation(s)
- Hannah E Boycott
- Division of Cardiovascular and Neuronal Remodelling, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT, United Kingdom
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Canellada A, Ramirez BG, Minami T, Redondo JM, Cano E. Calcium/calcineurin signaling in primary cortical astrocyte cultures: Rcan1-4 and cyclooxygenase-2 as NFAT target genes. Glia 2008; 56:709-22. [PMID: 18293408 DOI: 10.1002/glia.20647] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The calcineurin/nuclear factor of activated T cells (NFAT) signaling pathway mediates important cell responses to calcium, but its activity and function in astrocytes have remained unclear. We show that primary cortical astrocyte cultures express the regulatory and catalytic subunits of the phosphatase calcineurin as well as the calcium-regulated NFAT family members (NFATc1, c2, c3, and c4). NFATs are activated by calcium-mobilizing agents in astrocytes, and this activation is blocked by the calcineurin inhibitor cyclosporine A. Microarray screening identified cyclooxygenase-2 (Cox-2), which is implicated in brain injury, and Rcan 1-4, an endogenous calcineurin inhibitor, as genes up-regulated by calcineurin-dependent calcium signals in astrocytes. Mobilization of intracellular calcium with ionophore potently augments the promoter activity and mRNA and protein expression of Rcan 1-4 and Cox-2 induced by combined treatment with phorbol esters. Moreover, Rcan 1-4 expression is efficiently induced by calcium mobilization alone. For both the genes, the calcium signal component is dependent on calcineurin and is replicated by exogenous expression of a constitutively active NFAT, strongly suggesting that the calcium-induced gene activation is mediated by NFATs. Finally, we report that calcineurin-dependent expression of Cox-2 and Rcan 1-4 is induced by physiological calcium mobilizing agents, such as thrombin, agonists of purinergic and glutamate receptors, and L-type voltage-gated calcium channels. These findings provide insights into calcium-initiated gene transcription in astrocytes, and have implications for the regulation of calcium responses in astrocytes.
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Affiliation(s)
- Andrea Canellada
- Department of Vascular Biology and Inflammation. Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain
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Fletcher EL, Downie LE, Ly A, Ward MM, Batcha AH, Puthussery T, Yee P, Hatzopoulos KM. A review of the role of glial cells in understanding retinal disease. Clin Exp Optom 2008; 91:67-77. [PMID: 18045252 DOI: 10.1111/j.1444-0938.2007.00204.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Retinal vascular diseases such as diabetic retinopathy and retinopathy of prematurity are major causes of visual loss. Although the focus of a great deal of research has been on the aetiology of vascular growth, it is now emerging that anomalies in other retinal cell types, especially glial cells, occur very early in the course of the disease. Glial cells have major roles in every stage of disease, from the earliest subtle variations in neural function, to the development of epi-retinal membranes and tractional detachment. Therefore, having a firm understanding of the function of retinal glia is important in our understanding of retinal disease and is crucial for the development of new treatment strategies.
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Affiliation(s)
- Erica L Fletcher
- Department of Anatomy and Cell Biology, The University of Melbourne, Victoria, Australia.
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15
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Wilkinson JA, Scragg JL, Boyle JP, Nilius B, Peers C. H2O 2-stimulated Ca2+ influx via TRPM2 is not the sole determinant of subsequent cell death. Pflugers Arch 2007; 455:1141-51. [PMID: 18043941 DOI: 10.1007/s00424-007-0384-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Revised: 10/17/2007] [Accepted: 10/30/2007] [Indexed: 01/13/2023]
Abstract
Activation of transient receptor potential melastatin 2 (TRPM2), a non-selective, Ca(2+)-permeable cation channel, is implicated in cell death. Channel opening is stimulated by oxidative stress, a feature of numerous disease states. The wide expression profile of TRPM2 renders it a potentially significant therapeutic target in a variety of pathological settings including cardiovascular and neurodegenerative diseases. HEK293 cells transfected with human TRPM2 (HEK293/hTRPM2) were more vulnerable to H(2)O(2)-mediated cell death than untransfected controls in which H(2)O(2)-stimulated Ca(2+) influx was absent. Flufenamic acid partially reduced Ca(2+) influx in response to H(2)O(2) but had no effect on viability. N-(p-Amylcinnamoyl) anthranilic acid substantially attenuated Ca(2+) influx but did not alter viability. Poly(adenosine diphosphate ribose) polymerase inhibitors (N-(6-oxo-5,6-dihydro-phenanthridin-2-yl)-N,N-dimethylacetamide, 3,4-dihydro-5-[4-(1-piperidinyl)butoxy]-1(2H)-isoquinolinone and nicotinamide) reduced Ca(2+) influx and provided a degree of protection but also had some protective effects in untransfected controls. These data suggest H(2)O(2) triggers cell death in HEK293/hTRPM2 cells by a mechanism that is in part Ca(2+) independent, as blockade of channel opening (evidenced by suppression of Ca(2+) influx) did not correlate well with protection from cell death. Determining the underlying mechanisms of TRPM2 activation is pertinent in elucidating the relevance of this channel as a therapeutic target in neurodegenerative diseases and other pathologies associated with Ca(2+) dysregulation and oxidative stress.
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Abstract
Numerous cardiorespiratory disorders result in persistent systemic hypoxia, or at worst (as a consequence of stroke) deprive the brain of oxygen completely for a period of time. Patients suffering from such conditions are much more susceptible to the development of dementias such as AD (Alzheimer's disease). Until recently, the cellular and molecular basis for the predisposition to AD by systemic hypoxia has been completely unknown. However, emerging evidence suggests that pathological cellular remodelling caused by chronic hypoxia shows striking similarities to those observed in the central nervous system as a consequence of AD. Furthermore, prolonged hypoxia can induce formation of Abetas (amyloid beta peptides), the primary neurotoxic elements of AD, which accumulate over years to form the extracellular plaques that are the hallmark feature of the disease. Hypoxia can lead to paradoxical increases in mitochondrial ROS (reactive oxygen species) generation upstream of Abeta formation. The downstream consequences of prolonged hypoxia include remodelling of functional expression of voltage-gated calcium channels and disturbance of intracellular calcium homoeostasis via disrupted calcium buffering and inhibition of calcium extrusion mechanisms. These effects can be mimicked by application of exogenous Abeta and, crucially, appear to depend on Abeta formation. Current knowledge supports the concept that prevention of the deleterious effects of hypoxia may prove beneficial in slowing or preventing the onset of AD.
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Affiliation(s)
- Chris Peers
- Faculty of Medicine, University of Leeds, Leeds LS2 9JT, UK.
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Boycott HE, Dallas M, Boyle JP, Pearson HA, Peers C. Hypoxia suppresses astrocyte glutamate transport independently of amyloid formation. Biochem Biophys Res Commun 2007; 364:100-4. [PMID: 17927959 DOI: 10.1016/j.bbrc.2007.09.102] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2007] [Accepted: 09/25/2007] [Indexed: 11/15/2022]
Abstract
Sustained hypoxia alters the expression of numerous proteins and predisposes individuals to Alzheimer's disease (AD). We have previously shown that hypoxia in vitro alters Ca2+ homeostasis in astrocytes and promotes increased production of amyloid beta peptides (Abeta) of AD. Indeed, alteration of Ca2+ homeostasis requires amyloid formation. Here, we show that electrogenic glutamate uptake by astrocytes is suppressed by hypoxia (1% O2, 24h) in a manner that is independent of amyloid beta peptide formation. Thus, hypoxic suppression of glutamate uptake and expression levels of glutamate transporter proteins EAAT1 and EAAT2 were not mimicked by exogenous application of amyloid beta peptide, or by prevention of endogenous amyloid peptide formation (using inhibitors of either beta or gamma secretase). Thus, dysfunction in glutamate homeostasis in hypoxic conditions is independent of Abeta production, but will likely contribute to neuronal damage and death associated with AD following hypoxic events.
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Affiliation(s)
- Hannah E Boycott
- School of Medicine, University of Leeds, Worsley Building, Leeds LS2 9JT, UK
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18
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Martín ED, Fernández M, Perea G, Pascual O, Haydon PG, Araque A, Ceña V. Adenosine released by astrocytes contributes to hypoxia-induced modulation of synaptic transmission. Glia 2007; 55:36-45. [PMID: 17004232 DOI: 10.1002/glia.20431] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Astrocytes play a critical role in brain homeostasis controlling the local environment in normal as well as in pathological conditions, such as during hypoxic/ischemic insult. Since astrocytes have recently been identified as a source for a wide variety of gliotransmitters that modulate synaptic activity, we investigated whether the hypoxia-induced excitatory synaptic depression might be mediated by adenosine release from astrocytes. We used electrophysiological and Ca2+ imaging techniques in hippocampal slices and transgenic mice, in which ATP released from astrocytes is specifically impaired, as well as chemiluminescent and fluorescence photometric Ca2+ techniques in purified cultured astrocytes. In hippocampal slices, hypoxia induced a transient depression of excitatory synaptic transmission mediated by activation of presynaptic A1 adenosine receptors. The glia-specific metabolic inhibitor fluorocitrate (FC) was as effective as the A1 adenosine receptor antagonist CPT in preventing the hypoxia-induced excitatory synaptic transmission reduction. Furthermore, FC abolished the extracellular adenosine concentration increase during hypoxia in astrocyte cultures. Several lines of evidence suggest that the increase of extracellular adenosine levels during hypoxia does not result from extracellular ATP or cAMP catabolism, and that astrocytes directly release adenosine in response to hypoxia. Adenosine release is negatively modulated by external or internal Ca2+ concentrations. Moreover, adenosine transport inhibitors did not modify the hypoxia-induced effects, suggesting that adenosine was not released by facilitated transport. We conclude that during hypoxia, astrocytes contribute to regulate the excitatory synaptic transmission through the release of adenosine, which acting on A1 adenosine receptors reduces presynaptic transmitter release. Therefore, adenosine release from astrocytes serves as a protective mechanism by down regulating the synaptic activity level during demanding conditions such as transient hypoxia.
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Affiliation(s)
- Eduardo D Martín
- Unidad Asociada Neurodeath, UCLM-CSIC, Departamento de Ciencias Médicas, Universidad de Castilla-La Mancha, Albacete, Spain
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19
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Boyle JP, Boycott HE, Khan A, Rapley H, Stanton C, Peers C. P2–039: Hypoxia–induced increase in amyloid–β peptide in cortical astrocytes does not depend on increased BACE–1 expression. Alzheimers Dement 2006. [DOI: 10.1016/j.jalz.2006.05.876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
| | | | - Ali Khan
- University of LeedsLeedsUnited Kingdom
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Peers C, Aley PK, Boyle JP, Porter KE, Pearson HA, Smith IF, Kemp PJ. Hypoxic regulation of Ca2+ signalling in astrocytes and endothelial cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2006; 580:185-90; discussion 351-9. [PMID: 16683717 DOI: 10.1007/0-387-31311-7_28] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Affiliation(s)
- Chris Peers
- Schools of Medicine, University of Leeds, UK
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21
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Atkinson L, Boyle JP, Pearson HA, Peers C. Chronic hypoxia inhibits Na+/Ca2+ exchanger expression in cortical astrocytes. Neuroreport 2006; 17:649-52. [PMID: 16603928 DOI: 10.1097/00001756-200604240-00018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Ca signalling is central to many diverse functions of astrocytes. Of the numerous proteins involved in Ca homeostasis, the Na(+)/Ca(2+) exchanger is of particular importance in signalling regulation. We have shown that Ca signaling is dramatically remodelled in astrocytes by periods of chronic hypoxia, in part by inhibition of Na(+)/Ca(2+) exchanger. Here, we demonstrate that bepridil-sensitive Ca extrusion (indicative of Na(+)/Ca(2+) exchanger activity) is suppressed following 24 h hypoxia (2.5 or 1% O2) owing to a loss of Na(+)/Ca(2+) exchanger expression, as determined using immunocytochemistry and Western blots. Hypoxic Na(+)/Ca(2+) exchanger 1 inhibition occurs at the level of transcription, as mRNA for Na(+)/Ca(2+) exchanger 1 was significantly suppressed by hypoxia. Our results show hypoxia perturbs Ca homeostasis in astrocytes via the suppression of Na(+)/Ca(2+) exchanger 1 expression.
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Affiliation(s)
- Lucy Atkinson
- Faculties of Medicine and Biological Sciences, University of Leeds, Leeds, UK
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22
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Aley PK, Murray HJ, Boyle JP, Pearson HA, Peers C. Hypoxia stimulates Ca2+ release from intracellular stores in astrocytes via cyclic ADP ribose-mediated activation of ryanodine receptors. Cell Calcium 2005; 39:95-100. [PMID: 16256194 DOI: 10.1016/j.ceca.2005.09.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Revised: 09/15/2005] [Accepted: 09/19/2005] [Indexed: 10/25/2022]
Abstract
The ability of O(2) levels to regulate Ca(2+) signalling in non-excitable cells is poorly understood, yet crucial to our understanding of Ca(2+)-dependent cell functions in physiological and pathological situations. Here, we demonstrate that hypoxia mobilizes Ca(2+) from an intracellular pool in primary cultures of cortical astrocytes. This pool can also be mobilized by bradykinin, which acts via phospholipase C and inositol trisphosphate production. By contrast, hypoxic Ca(2+) mobilization utilizes ryanodine receptors, which appear to be either present on the same intracellular pool, or on a separate but functionally coupled pool. Hypoxic activation of ryanodine receptors requires formation of cyclic ADP ribose, since hypoxic Ca(2+) mobilization was fully prevented by nicotinamide (which inhibits ADP ribosyl cyclase) or by 8-Br-cADP ribose, an antagonist of cyclic ADP ribose. Our results demonstrate for the first time the involvement of cyclic ADP ribose in hypoxic modulation of Ca(2+) signalling in the central nervous system, and suggest that this modulator of ryanodine receptors may play a key role in the function of astrocytes under conditions of fluctuating O(2) levels.
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Affiliation(s)
- Parvinder K Aley
- School of Medicine, Institute for Cardiovascular Research, University of Leeds, Leeds LS2 9JT, UK
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23
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Volterra A, Meldolesi J. Astrocytes, from brain glue to communication elements: the revolution continues. Nat Rev Neurosci 2005; 6:626-40. [PMID: 16025096 DOI: 10.1038/nrn1722] [Citation(s) in RCA: 1228] [Impact Index Per Article: 64.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
For decades, astrocytes have been considered to be non-excitable support cells of the brain. However, this view has changed radically during the past twenty years. The recent recognition that they are organized in separate territories and possess active properties--notably a competence for the regulated release of 'gliotransmitters', including glutamate--has enabled us to develop an understanding of previously unknown functions for astrocytes. Today, astrocytes are seen as local communication elements of the brain that can generate various regulatory signals and bridge structures (from neuronal to vascular) and networks that are otherwise disconnected from each other. Examples of their specific and essential roles in normal physiological processes have begun to accumulate, and the number of diseases known to involve defective astrocytes is increasing.
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Affiliation(s)
- Andrea Volterra
- Department of Cell Biology and Morphology, University of Lausanne, Rue du Bugnon 9, 1005 Lausanne, Switzerland.
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Lenart B, Kintner DB, Shull GE, Sun D. Na-K-Cl cotransporter-mediated intracellular Na+ accumulation affects Ca2+ signaling in astrocytes in an in vitro ischemic model. J Neurosci 2005; 24:9585-97. [PMID: 15509746 PMCID: PMC6730155 DOI: 10.1523/jneurosci.2569-04.2004] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Na-K-Cl cotransporter isoform 1 (NKCC1) plays an important role in maintenance of intracellular Na+, K+, and Cl- levels in astrocytes. We propose that NKCC1 may contribute to perturbations of ionic homeostasis in astrocytes under ischemic conditions. After 3-8 hr of oxygen and glucose deprivation (OGD), NKCC1-mediated 86Rb influx was significantly increased in astrocytes from NKCC1 wild-type (NKCC1+/+) and heterozygous mutant (NKCC1+/-) mice. Phosphorylated NKCC1 protein was increased in NKCC1+/+ astrocytes at 2 hr of OGD. Two hours of OGD and 1 hr of reoxygenation (OGD/REOX) triggered an 3.6-fold increase in intracellular Na+ concentration ([Na+]i) in NKCC1+/+ astrocytes. Inhibition of NKCC1 activity by bumetanide or ablation of the NKCC1 gene significantly attenuated the rise in [Na+]i. Moreover, NKCC1+/+ astrocytes swelled by 10-30% during 20-60 min of OGD. Either genetic ablation of NKCC1 or inhibition of NKCC1 by bumetanide-attenuated OGD-mediated swelling. An NKCC1-mediated increase in [Na+]i may subsequently affect Ca2+ signaling through the Na+/Ca2+ exchanger (NCX). A rise in [Ca2+]i was detected after OGD/REOX in the presence of a sarcoplasmic-endoplasmic reticulum (ER) Ca2+-ATPase inhibitor thapsigargin. Moreover, OGD/REOX led to a significant increase in Ca2+ release from ER Ca2+ stores. Furthermore, KB-R7943 (2-[2-[4(4-nitrobenzyloxy)phenyl]ethyl]isothiourea mesylate), an inhibitor of reverse-mode operation of NCX, abolished the OGD/REOX-induced enhancement in filling of ER Ca2+ stores. OGD/REOX-mediated Ca2+ accumulation in ER Ca2+ stores was absent when NKCC1 activity was ablated or pharmacologically inhibited. These findings imply that stimulation of NKCC1 activity leads to Na+ accumulation after OGD/REOX and that subsequent reverse-mode operation of NCX contributes to increased Ca2+ accumulation by intracellular Ca2+ stores.
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Affiliation(s)
- Brett Lenart
- Department of Neurosurgery, University of Wisconsin Medical School, Madison, Wisconsin 53792, USA
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25
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Koyama Y, Matsui S, Itoh S, Osakada M, Baba A, Matsuda T. The selective Na+-Ca2+ exchange inhibitor attenuates brain edema after radiofrequency lesion in rats. Eur J Pharmacol 2005; 489:193-6. [PMID: 15087242 DOI: 10.1016/j.ejphar.2004.03.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2003] [Revised: 02/12/2004] [Accepted: 03/05/2004] [Indexed: 11/21/2022]
Abstract
2-[4-[(2,5-Difluorophenyl)methoxy]phenoxy]-5-ethoxyaniline (SEA0400), a specific inhibitor of the Na+-Ca2+ exchanger, exerts cytoprotective action and reduces brain infarct volume after cerebral ischemia. We examined the effect of SEA0400 on vasogenic brain edema in rats. Histological observations showed that radiofrequency current caused brain infarct and extravasation of endogenous albumin in the brain. SEA0400 (3 and 10 mg/kg, i.v.) significantly suppressed the increase in brain water content with attenuation of Evans blue dye and sodium fluorescein extravasation after radiofrequency lesion. The findings suggest that the Na+-Ca2+ exchanger plays a role in vasogenic edema formation after radiofrequency lesion.
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Affiliation(s)
- Yutaka Koyama
- Laboratory of Medicinal Pharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, Osaka 565-0871, Japan
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26
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Smith IF, Boyle JP, Kang P, Rome S, Pearson HA, Peers C. Hypoxic regulation of Ca2+ signaling in cultured rat astrocytes. Glia 2005; 49:153-7. [PMID: 15390111 DOI: 10.1002/glia.20083] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Acute hypoxia modulates various cell processes, such as cell excitability, through the regulation of ion channel activity. Given the central role of Ca2+ signaling in the physiological functioning of astrocytes, we have investigated how acute hypoxia regulates such signaling, and compared results with those evoked by bradykinin (BK), an agonist whose ability to liberate Ca2+ from intracellular stores is well documented. In Ca2+-free perfusate, BK evoked rises of [Ca2+]i in all cells examined. Hypoxia produced smaller rises of [Ca2+]i in most cells, but always suppressed subsequent rises of [Ca2+]i induced by BK. Thapsigargin pre-treatment of cells prevented any rise of [Ca2+]i evoked by either BK or hypoxia. Restoration of Ca2+ to the perfusate following a period of acute hypoxia always evoked capacitative Ca2+ entry. During mitochondrial inhibition (due to exposure to carbonyl cyanide p-trifluromethoxyphenyl hydrazone (FCCP) and oligomycin), rises in [Ca2+]i (observed in Ca2+-free perfusate) evoked by hypoxia or by BK, were significantly enhanced, and hypoxia always evoked responses. Our data indicate that hypoxia triggers Ca2+ release from endoplasmic reticulum stores, efficiently buffered by mitochondria. Such liberation of Ca2+ is sufficient to trigger capacitative Ca2+ entry. These findings indicate that the local O2 level is a key determinant of astrocyte Ca2+ signaling, likely modulating Ca2+-dependent astrocyte functions in the central nervous system.
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Affiliation(s)
- I F Smith
- Institute for Cardiovascular Research, University of Leeds, Leeds, United Kingdom
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27
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Smith IF, Boyle JP, Green KN, Pearson HA, Peers C. Hypoxic remodelling of Ca2+ mobilization in type I cortical astrocytes: involvement of ROS and pro-amyloidogenic APP processing. J Neurochem 2003; 88:869-77. [PMID: 14756807 DOI: 10.1046/j.1471-4159.2003.02212.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Chronic hypoxia (CH) alters Ca2+ homeostasis in various cells and may contribute to disturbed Ca2+ homeostasis of Alzheimer's disease. Here, we have employed microfluorimetric measurements of [Ca2+]i to investigate the mechanism underlying augmentation of Ca2+ signalling by chronic hypoxia in type I cortical astrocytes. Application of bradykinin evoked significantly larger rises of [Ca2+]i in hypoxic cells as compared with control cells. This augmentation was prevented fully by either melatonin (150 micro m) or ascorbic acid (200 micro m), indicating the involvement of reactive oxygen species. Given the association between hypoxia and increased production of amyloid beta peptides (AbetaPs) of Alzheimer's disease, we performed immunofluorescence studies to show that hypoxia caused a marked and consistent increased staining for AbetaPs and presenilin-1 (PS-1). Western blot experiments also confirmed that hypoxia increased PS-1 protein levels. Hypoxic increases of AbetaP production was prevented with inhibitors of either gamma- or beta-secretase. These inhibitors also partially prevented the augmentation of Ca2+ signalling in astrocytes. Our results indicate that chronic hypoxia enhances agonist-evoked rises of [Ca2+]i in cortical astrocytes, and that this can be prevented by antioxidants and appears to be associated with increased AbetaP formation.
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Affiliation(s)
- Ian F Smith
- Institute for Cardiovascular Research School of Biomedical Sciences, University of Leeds, Leeds, UK
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28
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Ouyang YB, Giffard RG. Programmed death phenomena: from organelle to organism. Ann N Y Acad Sci 2002; 45:371-9. [PMID: 15145551 DOI: 10.1016/j.neuint.2003.07.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2003] [Revised: 07/30/2003] [Accepted: 07/31/2003] [Indexed: 11/26/2022]
Abstract
Programmed death phenomena appear to be inherent not only in living cells (apoptosis), but also in subcellular organelles (e.g., self-elimination of mitochondria, called mitoptosis), organs (organoptosis), and even whole organisms (phenoptosis). In all these cases, the "Samurai law of biology"--it is better to die than to be wrong--seems to be operative. The operation of this law helps complicated living systems avoid the risk of ruin when a system of lower hierarchic position makes a significant mistake. Thus, mitoptosis purifies a cell from damaged and hence unwanted mitochondria; apoptosis purifies a tissue from unwanted cells; and phenoptosis purifies a community from unwanted individuals. Defense against reactive oxygen species (ROS) is probably one of the primary evolutionary functions of programmed death mechanisms. So far, it seems that ROS play a key role in the mito-, apo-, organo-, and phenoptoses, which is consistent with Harman's theory of aging. Here a concept is described that tries to unite Weismann's hypothesis of aging as an adaptive programmed death mechanism and the generally accepted alternative point of view that considers aging as an inevitable result of accumulation in an organism of occasional injuries. It is suggested that injury accumulation is monitored by a system(s) actuating a phenoptotic death program when the number of injuries reaches some critical level. The system(s) in question are organized in such a way that the lethal case appears to be a result of phenoptosis long before the occasional injuries make impossible the functioning of the organism. It is stressed that for humans these cruel regulations look like an atavism that, if overcome, might dramatically prolong the human life span.
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Affiliation(s)
- Yi-Bing Ouyang
- Department of Anesthesia, Grant Building S272, Stanford University School of Medicine, Stanford, CA 94305, USA
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