Drugs to treat neuro-degeneration Flashcards
What are neurodegenerative diseases?
these are incurable and debilitating conditions that result in the progressive degeneration or death of neurones (chronic)
Dead neurones in the adult CNS are replaced and their terminals can regenerate when their axons are interrupted. True or false
False
Pathological processes causing neuronal cell death can be described as having ____________ consequences.
irreversible
What has lead to the increase in research activity for neurodegenerative diseases ?
Incidence and social impact
What is the future of drug therapy in neurodegenerative disease?
Regenerative stem cell therapies to replace lost neurons
How are proteins in neurodegenerative diseases affected?
mis-folding of normal physiological proteins
mutated forms of physiological proteins
Briefly describe how mis-folded proteins are removed by intracellular degradation pathways
Chaperone proteins are produced; they binds to newly synthesised misfolded proteins and encourage them to fold correctly
Ubiquitination is also another intracellular process which marks proteins for degradation
What is a characteristic of mis-folded proteins ? What encourages this characteristic?
They tend to aggregate
This is because mis-folded proteins present hydrophobic surface residues; this promotes aggregation
Mis-folded proteins initially exist in what form?
Soluble oligomers
Mis-folded proteins later exist in what form?
insoluble aggregates
Insoluble aggregates of mis-folded proteins accumulate as ____________ intracellularly and extracellularly.
microscopic deposits
Insoluble aggregates are stable and resistant to proteolysis because…
Protective degradation mechanism is unable to cope
There is evidence that suggests that both soluble an insoluble aggregates may be neurotoxic. True or false
True
Excitotoxicity and free radical production lead to _________ and ___________.
Mitochondrial damage
Calcium overload
The NMDA receptor has a ____________ block.
magnesium
What are the glutamate receptors?
AMPA and NMDA receptors
What is the effect of an AMPA receptor on NMDA receptor in the presence of a strong stimulus ?
The magnesium block is displaced
Na+ and large Ca2+ ions can diffuse intracellularly via NMDA channel
Activation of glutamate receptors causes …
A calcium overload
Calcium influx
Calcium overloads affect many processes that are related to neurotoxicity. Give examples of instances where Ca2+ overloads affect neurotoxicity
-increased glutamate release from nerve terminals
-activation of proteases (e.g. calpains) and lipases which can cause membrane damage
-mitochondrial calcium overload stimulates the production of ROS
-activation of nitric oxide synthase which generates NO
-increased AA release and expression of COX results in the release of inflammatory mediators (PGs) and ROS as a byproduct of peroxidase activity of COX
What is the cyclooxygenase activity of COX enzyme ?
oxygenates AA to PGG2
What is the peroxidase activity of COX enzyme ?
reduces PGG2 to PGH2
What is the effect of free radicals on cells?
Damage mitochondria, membrane lipids, protein and DNA
What is produces when concentration of NO is high in the presence of ROS?
A highly reactive peroxynitrite free radical (ONOO-)
What is the effect of ROS on the mitochondria?
- inhibition of oxidative phosphorylation and reduced ATP synthesis which causes Ca2+ pump to stop working; this prevents Ca2+ sequestrations/extrusion mechanisms
- mitochondrial damage causes release of cytochrome C into cytosol initiating apoptosis
What is the potential effect of mitochondrial ROS such as superoxide?
O2- reacts with NO to form peroxynitrite (ONOO-)
What leads to neuronal cell death?
combination of excitotoxicity, calcium overload, free radicals, mitochondrial damage and oxidative stress
What is oxidative stress?
imbalance between the production of damaging ROS and antioxidant defences
Give examples of physiological antioxidant defences?
- superoxidde dismutase (SOD)
- catalase
- ascorbic acid
- glutathione (paracetamol?)
What neurological conditions have drugs available for treatment?
Parkinsons
Alzheimers
Huntingtons
Ischaemic brain damage
Neuropathic pain
What is parkinsons disease?
Progressive neurodegenerative disorder affecting the motor system
What are the cardinal signs of parkinsons disease?
Tremors: often begins in hand, foot and jaw
Rigidity (muscular): resistance to movement or short jerky movements
Bradykinesia: slow movement, loss of spontaneous/automatic movement
Postural instability: lack of balance and coordination
Describe briefly the pill-rolling tremor in hands observed in PD
- forefinger and thumb rub together (as if rolling a pill between them)
- slight wrist flexion and extension (up and down)
What is a shuffling gait?
- difficult to start walking
- in progress difficult to stop or change direction
What are the cognitive and psychiatric symptoms of PD ?
Depression and anxiety
Dementia
Behavioural problems
List some non-motor symptoms of PD?
Loss of sense of smell
Neuropathic pain
Problems with urination
Constipation
Postural hypotension
Excessive sweating
Swallowing difficulties
Drooling (sialorrhoea)
Sleeping disorders
What are the types of parkinsons disease?
Idiopathic PD
Familial PD
Vascular Parkinsonism
Drug induced Parkinsonism
Causes of idiopathic PD are unknown. What factors can affect idiopathic PD
genetic
environmental- exposure to pesticides, history of head injuries
How is early onset idiopathic PD described?
<50 years old
How is late onset idiopathic PD described?
> 50 years old
What known genes are implicated in familial PD?
LRRK2
PARK7
PINK1
PRKN
SNCA
Vascular parkinsonism can be caused by …
restricted blood supply to the brain
Mild stroke
Give an example of drug-induced parkinsonism
Antipsychotic drugs which block the action of dopamine
What proteins are implicated in alzheimers disease and what it the characteristic pathology?
Beta-amyloid- amyloid plaques
Tau protein- neurofibrillary tangles
What proteins are implicated in PD and what is the characteristic pathology?
alpha- synuclein - Lewy bodies
What proteins are implicated in Creuzfeldt-Jakob disease and what is the characteristic pathology ?
Prion protein- insoluble aggregates of prion protein
What proteins are implicated in Huntingtons disease and what is the characteristic pathology ?
Huntingtin- there are no gross lesions
What proteins are implicated in Motor Neuron disease and what is the characteristic pathology ?
Superoxide dimutase (antioxidant defence); loss of motor neurons