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Flashcards in ND - L4 Deck (26):
1

Topics discussed?

pathways leading to neuronal dysfunction & memory loss
approaches to understanding the molecular & cellular biology in AD

2

pathways leading to neuronal dysfunction & memory loss?

Abeta
tau
inflammatory

3

Neurotoxic mechanisms associated with Abeta? (10)

direct reactive oxygen species generation
indirect oxidative stress
accumulation of intraneuronal Abeta
synaptic toxicity
aberrant cell signalling
inhibition of axonal transport
ER stress
inhibition of glutamate uptake
decreased cellular energy production
lack of trophic support

4

Direct reactive oxygen species generation?

Cu(OO) -O2--> Cu(I)+H2O2 --> Cu(II) + OH*

5

indirect oxidative stress?

NMDA type glutamate receptor modulation

6

accumulation of intraneuronal Abeta?

inhibits cell metabolism

7

synaptic toxicity?

NMDA receptor mediated
impairment of vesicle release
inhibition of vesicle trafficking to synapse o inhibition of endocytosis
modulation of extracellular environment

8

aberrant cell signalling?

Abeta can react with lots of receptors (eg. NMDA acetylcholine fyn kinase)
changes many aspects of cell function

9

inhibition of glutamate uptake?

Astrocytes regulate extracellular glutamate levels & protect neurons from too much

10

decreased cellular energy production?

maybe impaired glucose delivery (abeta affects mitochondria)

11

lack of trophic support from glia?

astrocytes protect neurons from oxidative stress
astrocytes provide nutrients and precursors for
important molecules such as precursors of antioxidant
molecules (eg Glutathione precursor cysteine)
astrocytes regulate levels of metals, co-factors etc
astrocytes secrete growth factors that maintain neurons
changes to astrocytes (eg activation) can result in loss of this support and neuronal dysfunction

12

What else does Abeta toxicity depend on? explain experiment

tau interaction with fyn kinase in neuronal dendrites

13

inflammation neurotoxicity?

resident microglia
invading monocytes
activated astrocytes
production of cytokines and reactive oxygen species that impair neurons
loss of trophic support for neurons
possibly a major role in secondary neurotoxic effects in AD

14

approaches to understanding the molecular & cellular biology in AD topics?

development of model systems
assays for neurotoxicity
identification of potential targets
cell models
animal models

15

What are some problems with synthetic Abeta peptides?

contamination with other toxic molecules
normal brain also contains Aβ
separation of different species
Aβ is very ‘sticky’ and aggregates easily
how do you keep it in the form it was purified in?

16

What is the name of a cell viability assay?

MTT/MTS

17

Advantages of MTT/MTS?

subtle measure of cell toxicity (small changes in cell energy levels can be assessed – more relevant to amyloid
toxicity than overt cell death)
rapid, simple assay (few steps) – easy to perform on large numbers of experiments
well known and reproducible

18

Disadvantages of MTT/MTS?

can't tell if healthy or dead
replicating --> increases measured viability
toxic to cells
not real time

19

Approaches to identify pathways in cell models?

knockdown of proteins (Fyn kinase)
inhibition of enzymes (calcineurin inhibitors)
analysis of protein changes induced by amyloid
measuring cell growth, function induced by amyloid

20

What have MTT/MTS assays of amyloid pepetide toxicity shown?

oligomeric forms toxic
mutation of His residues affects Cu binding (reduced toxicity)
mutation of Tyr10 also reduces toxicity

21

Optimum drugs for neurodegeneration are?

small
cross BBB
non-toxic
cleared quickly
highly specific
easy to make in large quantities

22

Topics of animal models?

AD 'like' mice
Tau mice
APP/Tau models

23

Types of AD 'like' mice?

Tg2576: human APP (mutations K595N/M596L) - aggressive onset AD

APP/PS1: APP double mutation and human mutant PS1 - more aggressive

24

Tau mice?

P301L: human Tau gene mutation
NFTs (dementia) but no amyloid deposits

25

What do APP/Tau models show?

changes to amyloid in AD are upstream on changes to tau (but tau critical for disease effects)

26

Other useful models?

knockout mice - compare deletions (most proteins redundant)
ex vivo tissue - brain slices
other animals