1	Excitotoxicity in genetic disease David R. Lynch, M. D., Ph. D lynch@pharm.med.upenn.edu 215-590-2242
2	Pathogenesis of Huntington Disease
3	Glutamatergic transmission
4	Excitotoxicity
5	Diseases involving excitotoxicity Acute disorders- Stroke Epilepsy hypoglycemia Head trauma Chronic disorders- Hyperglycinemia Hyperammonemia HIV encephalopathy Huntington’s disease, etc.
6	CAG disease and excitotoxicity Why? CAG diseases are all essentially exclusively neuronal Exceptions- weight loss in HD, androgen insensitivity signs in Kennedy syndrome, neonatal SCA7 Excitotoxicity is a neuronal paradigm Depends on glutamate receptors which are exclusively neuronal It is essentially a positive feedback set up.
7	Huntington’s disease and excitotoxicity Original animal models of HD Injection of Kainic acid into striatum Leads to selective loss of medium spiny neurons, the same neuroanatomical pattern as HD Can be mimicked by a series of metabolic toxins (3 nitropropionic acid)
8	Pharmacology of the NMDA receptor
9	Synaptic localization of glutamate receptors NMDA – PSD95 AMPA- GRIP Metabotropic Homer
10	Synaptic localization of glutamate receptors
11	Glutamatergic transmission
12	Genetic contributors to excitotoxicity Agonists Receptors Uptake Downstream pathways
13	Genetic contributors to excitotoxicity Agonists Quinolinic acid By product of serotonin metabolism Agonist of glutamate site on NMDA receptor Kynurenic acid Agonist of glycine site on NMDA receptor Free radical scavenger Glycine Hyperglycinemia
14	Synaptic localization of glutamate receptors-relation to HD
15	Excitotoxicity as interpreted based on subtypes
16	NR1/2B currents are increased in cells transfected with mutant htt Peak current density increased in expanded htt but not wild type of control cells. Not seen with NR1/2A
17	Enhanced sensitivity of striatal NMDA receptors in HEK cells by expanded htt
18	Excitotoxicity as interpreted based on subtypes
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20	Increases not Clearly NR1/2B mediated in mature MSN Not ifenprodil sensitive Con G sensitive
21	Synaptic localization of glutamate receptors
22	Enhanced sensitivity of striatal NMDA receptors in HD
23	"In medium spiny neurons in..." In medium spiny neurons in culture, glutamate stimulated caspase activation. Bigger in mutant htt. In animals, wild type neurons half way between short htt and long htt.
24	Enhanced sensitivity of striatal NMDA receptors in HD-mechanisms
25	Excitotoxicity
26	Caspase activation required for Neurodegeneration in HD mice HD mice crossed with caspase 3 and caspase 6 deficient mice Leads to lack of caspase cleavage of htt.
27	"Nuclear translocation" Nuclear translocation delayed in Caspase 6 deficient mice Correlates with lack of toxicity in caspase deficient line.
28	Protease modification of Htt
29	Enhanced sensitivity of striatal NMDA receptors in HD-mechanisms
30	Synaptic localization of glutamate receptors
31	Glutamatergic transmission
32	Electron microscopy of glial httt aggregates
33	Accumulation htt aggregates in glial nuclei of HD mice
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35	"GLT-1 is decreased in astrocytes..." GLT-1 is decreased in astrocytes form HD mice. Glutamate uptake is similarly decreased.
36	"Htt mediated toxicity is ameliorated..." Htt mediated toxicity is ameliorated by co culture of neurons with glia, but blocked by glia infected with expanded htt. Effect seen in absence of MK801
37	Increased excitotoxicity in vitro with HD glia
38	Loss of glutamate uptake Increase susceptibility to glutamate Subsequent cell death Not disease specific for HD
39	Loss of glutamate uptake SCA7 Ugly disease Progressive ataxia ( cerebellar degeneration Blindness (retinal degeneration) CAG in Ataxin 7 protein Loss of glutamate uptake.
40	Pathogenesis of Huntington Disease
41	What dose this mean about study of disease from neuroscientific point of view Excitotoxicity not close to actual genetic mutation. However, it represents a viable method for treatment Study patients/animals in addition to genes.