5/2/13 Objectives
Glutamate: How to monitor and mediate its effects in Down Syndrome •
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Glutamate physiology Glutamate ac<vity in DS Symptoms of excess glutamate Measuring glutamate Agents that modulate glutamate Dr. Erica Peirson The Glutamate System
•  Glutamate is the major
excitatory neurotransmitter
in the central nervous
system.
•  Nearly 50% of the neurons
in the brain are believed to
use glutamate as their
neurotransmitter.
•  Glutamate is balanced with
GABA (main inhibitory
chemical transmitter)
•  Both neurotransmitters
influence almost every
other chemical transmitter
in the brain.
The Glutamate System
•  Glutamate acts via two classes of
receptors which are found on both
neuron and glial cells:
–  Ligand gated ion channels (Ionotropic
receptors):
–  G-protein coupled (Metabotropic
receptors).
Glutamate Receptors
Ionotropic Glutamate Receptors Metabotropi
c Ionotropic NMDA AMPA Metabotropic Kainate Group I Group II Group III ac<va<on inhibi<on inhibi<on mGluR1 mGluR5 mGluR2
mGluR3 mGluR4 mGluR6-­‐8 1 5/2/13 Glutamate Physiology
Glutamate Physiology
•  Glutamate binds with glutamate receptors on
postsynaptic neurons and open allowing Na+
and Ca+ to flow into the neuron
•  Glutamate must be removed quickly from
synaptic cleft or these channels will be left open.
•  Astrocytres, a type of glial cell, take up glutamate
via EAAT channels.
•  Once inside the astrocyte glutamate is converted
to glutamine which is transferred back to the
presynaptic neuron to be made into more
glutamate
Glutamate Physiology
Glutamate Physiology
Glutamate Physiology
Glutamate as Excitotoxin Channel Blockers
Mg2+
Memantine
Antagonists
Selfotel
MRZ 2/576
Ifenprodil (2B)
Zn2+
Modulators
Polyamines
Histamine
Agonists
Glutamate NMDA
Coagonist
Glycine D-serine
Parsons et al., Drug News Perspect 1995
•  Overstimulation of glutamate receptors causes
neurodegeneration and neuronal damage through
a process called excitotoxicity.
•  Excessive glutamate, or excitotoxins acting on the
same glutamate receptors, overactivate glutamate
receptors (specifically NMDARs), causing high
levels of calcium ions (Ca2+) to influx into the
postsynaptic cell.
•  High Ca2+ concentrations activate a cascade of
cell degradation processes involving proteases,
lipases, nitric oxide synthase, and a number of
enzymes that damage cell structures often to the
point of cell death
2 5/2/13 Glutamate as Excitotoxin Glutamate as Excitotoxin Schema<c illustra<on of some apopto<c pathways triggered by excessive NMDA receptor ac<vity. The cascade of steps leading to neuronal cell death include: 1) NMDA receptor (NMDA-­‐Rc) hyperac<va<on, 2) ac<va<on of the p38 MAPK-­‐MEF2C (transcrip<on factor) pathway (MEF2 is subsequently cleaved by caspases to form an endogenous dominant-­‐
interfering form that contributes to neuronal cell death),32 3) toxic effects of free radicals such as NO and reac<ve oxygen species (ROS), and 4) ac<va<on of apoptosis-­‐inducing enzymes including caspases. cyt c, cytochrome c. Stuart A. Lipton. Failures and Successes of NMDA Receptor Antagonists: Molecular Basis for the Use of Open-­‐Channel Blockers like Meman<ne in the Treatment of Acute and Chronic Neurologic Insults. NeuroRx. 2004 Glutamate as Excitotoxin Glutamate as Excitotoxin •  Excess calcium in cytoplasm of cell is taken up by mitochondria which inhibits produc<on of ATP (energy). Glutamate as Excitotoxin •  Damaged neurons activate
microglia that secrete proinflammatory cytokines,
reactive oxygen intermediates,
proteinases and complement
proteins, which are all
cytotoxic
•  Activated microglia and
glutamate released from
damage neurnos can create
domino effect that perpetuates
neurodegeneration
Glutamate as Excitotoxin •  Excess glutamate implicated in other neurodegenera<ve diseases –  Hun<ngton’s –  ALS –  MS –  AD –  Parkinson’s –  Epilepsy D Nguyen, et al. A new vicious cycle involving glutamate excitotoxicity, oxida<ve stress and mitochondrial dynamics. Cell Death Dis. 2011 3 5/2/13 Glutamate Homeostasis •  Elevated GABA levels in the presence of elevated glutamate levels is a normal compensatory mechanism of the body. •  Focusing on blocking GABA does not address the true underlying problem. Glutamate Homeostasis ate
Glutam ry)
to
(excita
GABA )
ory
(inhibit
Glutamate Homeostasis Glutamate
(excitatory)
GABA
(inhibitory)
Glutamate Homeostasis Glutamate
(excitatory)
GABA
(inhibitory)
Glutamate in DS Glutamate in DS “The up-­‐regula<on of mGluR5 was observed in DS…” “…the human GLUR5 gene, which is located on human chromosome 21q22.1…” 4 5/2/13 Glutamate in DS “…these results show that NMDA-­‐
induced calcium rise is altered in TgDyrk1A cerebellar neurons and indicate that calcium signaling is dysregulated in TgDyrk1A mice cerebella.” Measuring Glutamate •  Tes<ng glutamate is done non-­‐invasively with a urine test •  Test results are used as a guide for treatment, not diagnosis •  Assuming neurotransmiber levels and guessing appropriate interven<on is not helpful. •  All children with DS do not have the same biochemistry. •  Test, don’t guess Measuring Glutamate Symptoms of excess glutamate •
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Aggression Irritability Anxiety Poor Insomnia Seizures •
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Hyperac<vity Headaches/Migraines concentra<on/focus Nocturnal bed we`ng Areas of heightened intelligence Eosinophilia? Measuring Glutamate “Novel ELISAs for Screening of the Biogenic Amines…
can result in relevant informa<on on neurological processes, or pharmacological response to therapeu<c interven<on…” Measuring Glutamate •  Urinary neurotransmiber tes<ng objec<vely establishes the need for interven<on •  Guides therapeu<c decisions •  Qualita<vely assesses interven<on effec<veness Ballabh, P., et al. (2004). Neurobiological Disorders. 16:1-13.
5 5/2/13 Mitochondria Support Measuring Glutamate Peer-­‐review ar<cle provides comprehensive overview of validity & clinical applicability of urinary neurotransmiber tes<ng “During synap<c ac<vity, the clearance of neuronally released glutamate leads to an intracellular sodium concentra<on increase in astrocytes that is associated with significant metabolic cost.” Singh P, Mann KA, Mangat HK, Kaur G. Prolonged glutamate excitotoxicity: effects on mitochondrial an<oxidants and an<oxidant enzymes. Mol Cell Biochem. 2003 Mitochondria Support •
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Acety-­‐l-­‐carni<ne Ubiquinol (CoQ10) Liposomal glutathione An<oxidants D-­‐Ribose Glutamate Antagonists •
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Bacopa monnieri Gotu kola Ginkgo biloba St. John’s Wort Zinc •
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Magnesium B6 EGCG Curcumin Taurine Bacopa monnieri Gotu kola •  Neuroprotec<ve •  An<oxidant •  An<-­‐inflammatory •  Reduces SOD •  Nootropic •  Glutamate antagonist Chowdhuri DK, et al. Antistress effects of bacosides of Bacopa monnieri: modulation of Hsp70
expression,
superoxide dismutase and cytochrome P450 activity in rat brain. Phytother Res. (2002)
Hosamani R, Muralidhara. Neuroprotective efficacy of Bacopa monnieri against rotenone induced
stress and neurotoxicity in Drosophila melanogaster. Neurotoxicology. (2009)
oxidative
•  Neuroprotec<ve •  An<oxidant •  An<-­‐inflammatory •  Glutamate antagonist •  Raises glutathione •  Nootropic levels Anil Kumar, Samrita Dogra, Atish Prakash. Neuroprotective Effects of Centella asiatica against
Intracerebroventricular
Colchicine-Induced Cognitive Impairment and Oxidative Stress Int J Alzheimer
Dis. 2009
Lee MK,et al. Asiatic acid derivatives protect cultured cortical neurons from glutamate-induced
Khan R, Krishnakumar A, Paulose CS. Decreased glutamate receptor binding and NMDA R1 gene
expression in hippocampus of pilocarpine-induced epileptic rats: neuroprotective role of Bacopa
monnieri extract. Epilepsy Behav. (2008)
excitotoxicity. Res Commun Mol Pathol Pharmacol. 2000
Singh M, Murthy V, Ramassamy C. Modulation of hydrogen peroxide and acrolein-induced oxidative
stress, mitochondrial dysfunctions and redox regulated pathways by the Bacopa monniera extract:
potential implication in Alzheimer's disease. J Alzheimers Dis. 2010;21(1):229-47
Veerendra Kumar MH, Gupta YK. Effect of Centella asiatica on cognition and oxidative stress in an
intracerebroventricular streptozotocin model of Alzheimer's disease in rats. Clin Exp Pharmacol Physiol.
2003
Mook-Jung I, Shin JE, Yun SH, Huh K, Koh JY, Park HK, Jew SS, Jung MW. Protective effects of
asiaticoside derivatives against beta-amyloid neurotoxicity. J Neurosci Res. 1999
Ramanathan M, Sivakumar S, Anand Vijayakumar PR, Saravanababu C, Rathinavel Pandian P.
Neuroprotective evaluation of standardized extracts of Centella asiatica in monosodium glutamate
treated rats. Indian J Exp Biol. 2007
6 5/2/13 Ginkgo biloba •  Neuroprotec<ve •  An<oxidant •  An<-­‐inflammatory •  Glutamate antagonist •  Nootropic •  GABA antagonist Mdzinarishvili A, Sumbria R, Lang D, Klein J. Ginkgo extract EGb761 confers neuroprotec<on by reduc<on of release in ischemic brain. J Pharm Pharm Sci. 2012. glutamate XM, “We conclude that, while antagonism of Li Z, Lin Gong PL, Du GH, Zeng FD. Effects of gingko biloba extract on glutamate-­‐induced [Ca2+]i changes in cultured cor<cal astrocytes aper hypoxia/reoxygena<on, H2O2 or L-­‐glutamate injury. Yao Xue Xue Bao. 2005 GABA(A) receptors may contribute to Chandrasekaran K, Mehrabian Z, Spinnewyn B, Chinopoulos C, Drieu K, Fiskum G. Bilobalide, a component of the Ginkgo biloba extract (EGb 761), protects against neuronal death in global brain ischemia and in glutamate-­‐
bilobalide'ʹs neuroprotective effects, induced excitotoxicity. Cell Mol Biol (Noisy-­‐le-­‐grand). 2002 Kiewert C, Kadditional mechanisms must be umar V, Hildmann O, Rueda M, Hartmann J, Naik RS, Klein J. Role of GABAergic antagonism in the neuroprotec<ve effects of bilobalide. Brain Res. 2007 postulated to fully explain bilobalide'ʹs actions.” Zinc Neuroprotec<ve Nootropic Glutamate antagonist Atsushi Takeda Insight into Glutamate Excitotoxicity from Synap<c Zinc Homeostasis. Int J Alzheimers Dis. 2011 Takeda A, Minami A, Seki Y, Oku N. Inhibitory func<on of zinc against excita<on of hippocampal glutamatergic neurons. Epilepsy Res. 2003 Amico-­‐Ruvio SA, Murthy SE, Smith TP, Popescu GK. Zinc effects on NMDA receptor ga<ng kine<cs. Biophys J. 2011 •
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* Also involved in ac<va<ng microglia Magnesium •  Neuroprotec<ve •  Nootropic •  Glutamate antagonist Anil Kumar, Samrita Dogra, Atish Prakash. Neuroprotective Effects of Centella asiatica against
Intracerebroventricular
Colchicine-Induced Cognitive Impairment and Oxidative Stress Int J Alzheimer
Dis. 2009
Lee MK,et al. Asiatic acid derivatives protect cultured cortical neurons from glutamate-induced
excitotoxicity. Res Commun Mol Pathol Pharmacol. 2000
Veerendra Kumar MH, Gupta YK. Effect of Centella asiatica on cognition and oxidative stress in an
intracerebroventricular streptozotocin model of Alzheimer's disease in rats. Clin Exp Pharmacol Physiol.
2003
Mook-Jung I, Shin JE, Yun SH, Huh K, Koh JY, Park HK, Jew SS, Jung MW. Protective effects of
asiaticoside derivatives against beta-amyloid neurotoxicity. J Neurosci Res. 1999
Ramanathan M, Sivakumar S, Anand Vijayakumar PR, Saravanababu C, Rathinavel Pandian P.
Neuroprotective evaluation of standardized extracts of Centella asiatica in monosodium glutamate
treated rats. Indian J Exp Biol. 2007
EGCG •
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B6 Neuroprotec<ve An<-­‐inflammatory Nootropic Glutamate antagonist blind study, 89 children “In a double-­‐‑
Büyükokuroglu ME, Gepdiremen A, Taştekin A, Ors R. Pyridoxine may protect the cerebellar granular cells against glutamate-­‐induced toxicity. Int J Vitam Nutr Res. 2007 with Down'ʹs syndrome were given 5-­‐‑
Yang TT, Wang SJ. Pyridoxine inhibits depolariza<on-­‐evoked glutamate release in nerve terminals from rat hydroxytryptophan and pyridoxine cerebral cortex: a possible neuroprotec<ve mechanism? J Pharmacol Exp Ther. 2009 Dakshinamur< K, Sharma SK, Geiger JD. Neuroprotec<ve ac<ons of pyridoxine. Biochim Biophys Acta. 2003 hydrochloride in the first three years of Pueschel SM, Reed RB, Cronk CE, Goldstein BI. 5-­‐hydroxytryptophan and pyridoxine. Their effects in young life…these children showed consistently children with Down's syndrome. Am J Dis Child. 1980 higher levels of accomplishment.” •
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L-­‐theanine Blocks ac<va<on of microglial cells Neuroprotec<ve An<oxidant Supports mitochondria Jin S, Park M, Song JH. (-­‐)-­‐Epigallocatechin-­‐3-­‐gallate inhibits voltage-­‐gated proton currents in BV2 microglial cells. Eur J Pharmacol. 2013 Fu Y, Koo MW. EGCG protects HT-­‐22 cells against glutamate-­‐induced oxida<ve stress. Neurotox Res. 2006 Li C, et al. Green tea polyphenols control dysregulated glutamate dehydrogenase in transgenic mice by hijacking the ADP ac<va<on site. J Biol Chem. 2011 Orly Weinreb, Tamar Amit, Silvia Mandel, Moussa B. H. Youdim. Neuroprotec<ve molecular mechanisms of (−)-­‐
epigallocatechin-­‐3-­‐gallate: a reflec<ve outcome of its an<oxidant, iron chela<ng and neuritogenic proper<es. Genes Nutr. 2009 “EGCG strongly promoted mitochondrial biogenesis in DS cells.” Valen< D et al. Epigallocatechin-­‐3-­‐gallate prevents oxida<ve phosphoryla<on deficit and promotes mitochondrial biogenesis in human cells from subjects with Down's syndrome. Biochim Biophys Acta. 2013
7 5/2/13 Curcumin •
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Blocks microglial ac<va<on Glutamate antagonist Reduces neuroinflamma<on Blocks amyloid β protein An<oxidant Wang R, Li YB, Li YH, Xu Y, Wu HL, Li XJ. Curcumin protects against glutamate excitotoxicity in rat cerebral cor<cal neurons by increasing brain-­‐derived neurotrophic factor level and ac<va<ng TrkB. Brain Res. 2008 Lin TY, Lu CW, Huang SK, Wang SJ. Curcumin inhibits glutamate release from rat prefrontal nerve endings by affec<ng vesicle mobiliza<on. Int J Mol Sci. 2012 Lee HS, et al. Neuroprotec<ve effect of curcumin is mainly mediated by blockade of microglial cell ac<va<on. Pharmazie. 2007 Curcumin Popula<ons in India, who eat a diet high in turmeric, experienced a 4.4-­‐fold lower incidence of AD and drama<cally lower rates of colon cancer than those ea<ng a typical Western diet. S. K. Kulkarni, A. Dhir. An Overview of Curcumin in Neurological Disorders. Indian J Pharm Sci. 2010 Taurine MSG •  Avoid all hidden forms of MSG –  Hydrolyzed vegetable protein –  Yeast Extract –  Calcium caseinate –  et al •  Avoid all food and drink with aspartame Dr. Russell Blaylock 8