ALS Flashcards
What is ALS?
a rapidly progressive and fatal neurodegenerative disease
What is the average age of onset of ALS?
55
What are the types of ALS?
Sporadic - 90-95%
Familial - 5%
Guamanian - Guam territories around pacific - due to diet?
What are clinical symptoms of ALS onset?
Limbs - weakness of grip, decreased dexterity, foot drop, leg stiffness, tripping
Throat - slurred speech, difficulty chewing or swallowing
What are the clinical limb symptoms of ALS onset?
weakness of grip, decreased dexterity, foot drop, leg stiffness, tripping
What are the clinical throat symptoms of ALS onset?
slurred speech, difficulty chewing or swallowing
What are the clinical symptoms of ALS progression?
Limbs - unable to hold objects, write, feed or toilet, walk or stand or turnover in bed
Throat - unable to speak, swallow food or saliva
Breathing - breathless with exertion or lying flat
Cognition - dementia is rare but subtle deficits are common
What are the clinical limb symptoms of ALS progression?
unable to hold objects, write, feed or toilet, walk or stand or turnover in bed
What are the clinical throat symptoms of ALS progression?
unable to speak, swallow food or saliva
What are the clinical breathing symptoms of ALS progression?
breathless with exertion or lying flat
What are the clinical cognitive symptoms of ALS progression?
dementia is rare but subtle deficits are common
What symptoms may occur as the disease progresses?
difficulty breathing
difficulty swallowing
paralysis
What is the cause of death in ALS?
usually respiratory failure around 22m from diagnosis
Where are UMN located?
motor cortex and travel down to the spinal cord
Where are LMN located?
Travel out of the spinal cord to the relative muscles
What are the premotor clinical signs of ALS?
planning and initiation of movements are difficult
What are the UMN clinical signs of ALS?
modest weakness, stiffness, spasticity, hyperreflexia, extensor plantar response
What are the LMN clinical signs of ALS?
major weakness, muscle wasting, fasiculation
WHat are the cognitive clinical signs of ALS?
subtle deficits in around 30% patients affecting verbal fluency and executive functions
What are the spare clinical signs of ALS?
sensation, eye movement, bladder and bowel function
How is ALS diagnosed?
it is a diagnosis of exclusion which normally occurs around 12 months after symptom onset
What causes the muscle wasting in ALS?
due to lack of use because of de-innervation
What is thought to contribute to the degeneration process of ALS?
build up of unwanted proteins
What contributes to the development of paralysis?
pyramidal MNs in the frontal lobe degenerate and die causing severe spasticity and mild weakness of the muscle groups
What are the gene mutations associated with familial ALS?
c9orf71, SOD1, FUS, TDP43
What are the gene mutations associated with sporadic ALS?
c9orf72
What role does TDP-43 play in MN degeneration?
accumulates in the cell body of MNs in 95% of MND cases
Where does TDP-43 normally reside?
in the nucleus where is processes gene transcripts
What does TDP-43stand for?
Transactivation response DNA-binding protein of 43kDa
What can be seen in chick spinal neurons that express TDP-43 mutant?
- a reduction of axonal length
- increased cell toxicity
- developmental delay
- apoptotic cells
Why are zebrafish useful to explore neurodegeneration?
zebrafish have a short life span
What are 20% of familial ALS cases caused by?
mutations in the protein Cu/Zn Superoxide dismutase
What is the most common mutation in SOD1?
ala->val
What is mutant SOD1 a key component of in ALS?
protein aggregates
What does SOD1 do normally?
converts superoxide radicals to hydrogen peroxide and oxygen
Where is SOD1 generally found?
cell cytosol, nucleus and mitochondrial membrane
How many mutations in SOD1 have been found in ALS?
more than 140
What suggests that SOD1 mutations in ALS are not due to lack of enzyme activity?
SOD1 KO mice do not develop ALS
What do mutations in SOD1 potentially do to the enzyme?
cause it to gain toxic function
What are the potential cellular mechanisms underlying ALS?
oxidative damage, accumulation of IC aggregates, mitochondrial dysfunction, glutamate excitotoxicity, growth factor deficiency, glial cell pathology, Ca dysregulation
What do mutations in SOD1 do to the Cu binding site?
cause Cu binding site to be exposed to aberrant substrates
Where have protein aggregates been found in ALS?
the MNs and glial cells
What have protein aggregates in ALS been shown to have?
misfolded SOD1 - mutated SOD1 has increased propensity for aggregation
Why may there be a protein build up in ALS?
due to mitochondria attempting to remove the protein however the normal function of the mitochondria is interfered with OR UPS getting clogged up with protein
What have histological studies of mitochondria shown in ALS?
swelling and other mitochondrial abnormalities
What has mutant SOD1 been directly associated with in sporadic ALS?
cytochrome C association with the inner mitochondrial membrane -> disrupts respiration
What has been found in terms of glutamate in sporadic ALS?
elevated glutamate levels in the CSF
Why is glutamate transport markedly reduced in ALS?
due to pronounced loss of glial glutamate transport EAAT2
What does mutant SOD1 do to glutamate transport?
selectively inactivates EAAT2
How can EAAT2 involvement be tested?
using anti-sense oligonucleotides to lower EAAT2 levels -> neuronal death
What growth factor is deficient in ALS?
vascular endothelial growth factor
What techniques slowed ALS onset and progression in mutant SOD1 mice?
overexpression of VEGF
ICV administration of VEGF
IM delivery of VEGF-expressing lentiviral vectors
What other growth factors also delay ALS onset and progression in SOD1 mutant mice?
IGF-1 and GDNF
Why is there growing evidence of glial cell involvement in ALS?
astrocytic inclusions are early indicators of SOD1 mutant toxicity
astrocytes expressing mutant SOD1 secrete factors that are toxic to MNs
What are the potential secreted agents from astrocytes in ALS?
proinflammatory chemokines and cytokines i.e. TNFa
What potential reason is there for selective degeneration of MNs in ALS?
MNs are more susceptible to excitotocity
Why are MNs more susceptible to excitotoxicity?
recieve very strong glutamatergic signalling
express Ca permeable AMPA receptors
have a low Ca buffering capacity
lack of what AMPA subunit is associated with MNs?
GluR2 - normally regulates Ca permeability
What is expected to happen with GluR2 in mutant SOD1?
accelerates MN degeneration and shortens life span
What were some of the first ALS therapies targeted at?
glutamate excitotoxicity
What is Riluzole?
the only drug for ALS which extends life expectency by 2-3 months
What are the acute effects of Riluzole in animal models?
decreasing persistant Nav currents
potentiation of a Ca-dependent K current
inhibiting glutamate release
What is ceftriaxone?
an antibiotic
What are the effects of ceftriaxone in ALS animal models?
increases expression of EAAT2 prolonging survival and upregulating EAAT2 mRNA
What are heat shock proteins?
proteins involved in protein folding and degradation
What is found in heat shock proteins in ALS?
abnormalities that lead to MN degeneration
What is Arimoclomol?
an oral agent that increases expression of HSPs involved in neuroprotective mechanisms
Which agent was disappointing in clinical trials targetting mitochondrial function?
creatine
What does creatine do?
stimulates mitochondrial respiration and phosphocreatine synthesis
why is simple stem cell therapy not enough in ALS?
cells around the MNs are damaged too
How would stem cell therapy be approached in ALS?
directing stem cells to the damaged area and providing growth factors for the MNs and other ells
What experimental protocol showed mouse embryonic stem cells to be successfully transplanted into a chick embryo?
- mouse embryonic stem cells treated with a chemical cocktail (retinoic acid and sonic hedgehog)
- after 2 week take form of MNs and dependent on same growth factos
- when transplanted to chick spinal cord migrated to anterior horn where MNs reside
- transplanted axons make functional contact with muscle cells
What is required for stem cell therapy to be effective?
the new cells must differentiate into MNs and make the connections to the denervated muscle
What is a current drawback in stem cell therapy?
Thus far they can improve limb function but limited evidence to suggest that they can connect with all desired targets - in humans this is up to 3M away
What is a potential drawback in stem cell therapy?
immunogenicity
What more specific cells may be used in stem cell therapy?
neural progenitor cells
What is a specific gene that needs to be expressed in order to regenerate damaged MNs?
glial cell line derived neurotrophic factor (GDNF)
Where have rat models particularly thrived with stem cell therapy?
when there has been two injection points
- the MNs
- the muscle
slower disease progression and increased survival
What is the suggested result of stem cell therapy?
provides protection rather than replacing MNs by differentiating into different cells that produce growth factors that reduce toxic damage
What is the main cause of death in ALS?
respiratory failure
Why is the main cause of death in ALS important for considering new therapies?
if diaphragm function can be improved, death might be delayed
What is ACE-031?
a protein that inhibits negative regulators of muscle growth i.e. myostatin
What does CK-2017357 do?
activates fast skeletal muscle troponin complex by increasing sensitivity to Ca - increases muscle force
What results have been found with ACE-031 in clinical trials thus far?
subcutaneous treatment is well-tolerated and increases muscle mass and volume
What results have been found with CK-2017357 in clinical trials so far?
well tolerated and muscle strength and pulmonary function have increased
How might RNA be targeted in treating ALS?
use of anti-sense oligonucleotides and siRNAs to lower mutant mRNA
What is the purpose of using anti-sense oligonucleotides and siRNAs to target ALS?
slows disease progress and increases survival in SOD1 mutant mice
helps patients with familial SOD1 mutations
What is ISIS666311?
a RNA targeting treatment that silences SOD1 gene expression and has been successful in phase 1 clinical trial
What do mutations in VEGF correlate to in ALS?
lower levels of VEGF protein expression and thus 2x risk of ALS developing
What has been found with regards to VEGF in ALS patients?
lower levels of VEGF in the CSF
What normally occurs with VEGF mRNA in healthy patients?
binds with HuR which results in VEGF protein production for neuroprotection and O2 supply to MNs
What occurs with VEGF mRNA in ALS patients?
mutant SOD1 competes with HuR to binding mRNA and thus reduces VEGF and compromising neuroprotection and perfusion - MN degeneration
How might VEGF be targeted in therapy?
delivering recombinant VEGF intracerebroventricularly to provide degenerating MNs with increased neuroprotective survival - improved o2 supply
