Alzheimer's Disease Flashcards
what is Alzheimer’s Disease
age related dementia - destroys brain cells -> prgressive decline of mental function
early AZ
poor short-term memory recall
language problems
depression
late AZ
long-term memory loss difficulty speaking confusion, disorientation anger, sadness, mood swings speech impairment difficulty swallowing/chewing
what does a PET brain scan show
shows Red strong bind - slectively to myloid plaques
what is the major cholinergic output of the CNS
basal forebrain
what role does the hippocampus play
short term memory
spatial navigation
what brain changes are associated with AZ
shrinkage of brain in cellular parts/language memory spaces
increase in ventricle fluid-filled region
what characteristic changes in neural cells are associated with AZ
senile plaques = diffuse extracellular deposits of B amyloid (AB) protien
neurofibrillary tangles = fibrous intracellular deposits hyperphosphorylated tau (paired helical filaments)
what is altered in AZ patients
cleavage pattern of amyloid precursor protein (APP)
normal cleavage: a + y secretases
abnormal cleavage: B + y secretases
the role of soluble APP
sAPP = transcriptional inhibtior of Lipoprotien Receptor 1 (LPR1)
LPR1 facilitates the endocytosis of a cholesterol-protein complex from the blood into neurons
- a deficit in LPR1 => increased cholesterol catabolism with associated abnormalities in synapse formation
why is soluble AB cytotoxic
AB can form ion channels in neuronal cell membranes
=may allow entry of excess Ca into neurons
cell death occurs by apoptosis
soluble peptide - based on the sequence of the pore forming region of the AB channel - blocks ion entry = prevents apoptosis
what do gene alteration increase likeliness of AZ
aggregation of AB is favoured by:
1. presence of ApoE4 variant of apolipoprotein E (component of chylomicrons / IDLs)
- mutations in the presenilin genes whose products - increase the activity of y-secretase
what is Tau
microtubule-associated protien = stabalises microtubules in neuronal processes
how is Tau altered
tau becomes hyperphosphorylated = inhibiting binding to microtubules
hyperphosphorylated tau forms insoluble aggregates
= may inhibit vesicular transport
mutations in tau = associated with early-onset AZ-like dementia
why does age = biggest risk factor
lower metabolism protein/cell repair GFs mitochondrial dysfunction free radicals
other possible contributing factors to AZ
low education severe head injury CVD obesity high blood pressure high cholesterol diabetes
what is AZ associated with and what is the evidence
loss of cholinergic neurons
a decrease in choline acetyltransferase activity of cortex and hippocampus in AZ patients
decreased density of cortical nicotinic cholinergic receptors
strategies for treating AZ
- agents that compensate hypofunction of the cholinergic system
- agents that interfere with metabolism of AB peptide
- agents that affect the process of formation of neurofibrillary tangles
- anti-inflammatory compounds
- agents that treat symptoms
AChE inhibitors
- GALANTAMINE (allosteric activator of nicotinic R)
- donepezil
- metrifonate-prodrug form of physostigmine
used to treat mild/moderate AZ
side effects: enhancement of Parasymp NS:
- nausea
- abdominal pain
- bradycardia
selective agonists of muscarinic/nicotinic receptors
fewer PNS effects
may lose effectiveness over time due to feedback reduction in receptor conc / reduced receptor response to ACh
agents that block excitotoxity
NMDA antagonist = block binding of glutamate
MEMANTINE - noncompetitive NMDA antagonist
a temporary improvement in cognitive function with moderate-severe AZ
potential treatment
Methylthioninium chloride = dissolves tau polymers
stem cell therapy
what do ApoE4 proteins do
lipoprotein complex - transport cholesterol/lipids through blood
what does ApoE2 cause
high risk of AZ
