neurodegenerative Flashcards
Prion disease
Prion disease is rare type of neurovegetative disease caused by accumulation of misfolded proteins and loss of synapse
Spongiosis in prion disease
Spongiosis is a term for holes in brain tissue
scrapie prion disease
Affected animals and develops a loss of coordination, uncontrollable itch
BSE prion disease
a type found in cows, BSE was spread to other animals the number of cases was rapidly amplified when infected carcasses were processed into cattle feed.
CJD prion disease
most common human type that causes a lot of loss of brain tissue
Life expectancy is around 4 months
Symptoms of CJD prion disease
Symptoms include rapidly progressing dementia, development of movement disorders such as tremor and rigidity
vCJD prion disease
longer duration
only affected young people
prolonged neuropsychiatric syndrome
3 forms of prion disease
Sporadic prion disease - here an unknown stimulus results in the formation of PrPSc. The most common type.
Inherited, or familial, prion disease - results from a genetic abnormality in the Prnp gene, which encodes for the prion protein, resulting in formation of abnormal prion protein.
Acquired prion disease - the misfolded protein is taken in from an outside source; such as the development of variant Creutzfeldt-Jakob disease (vCJD) due to the ingestion of bovine prions or Kuru.
iatrogenic transfer prion disease
the accidental spread of prions between humans during medical or surgical treatment
PrPsc prion disease
PrPsc are misfolded protein
There is a cycle of proliferation, in which PrPSc accumulates and recruits PrPC
As the brain becomes depleted of PrPC, this stimulates synthesis of more, which in turn means more substrate for pathological conversion.
PrPC vs PrPsc
PrPc changes to PrPsc
two isoforms of PrP have identical primary structure but different secondary and tertiary structures.
PrPsc is harder to be broken down due to its stronger bonds
Prnp
Prnp codes for the PrP and knockout in mice still caused normal function in mice
Only impaired LTP and reduced after hyperpolarisation potentials.
PrP may have a role in modulation of neuronal excitability.
Can effect Prpsc conversion rate
treatment of Prion disease
Treatment only prolongs life a bit but still no cure
Whether in humans or animals, the disease is always fatal
Drug-DBM and trazodone
Largest risk factor of Alzheimer’s
Age
Dementia affects what
Issues occur with memory
What does dementia mini mental state test for
orientation, registration , attention, recall and language
Types of dementia
Alzheimer’s disease (AD): 50-75%
Vascular dementia (VD): 20%
Dementia with Lewy body (DLB): 15-20%
Frontotemporal dementia (FTD): 2%
Rare causes: Parkinson’s disease dementia (PDD), Huntington’s disease (HD), Prion disease, others.
Genetic risk factor of dementia
most cases are rare but can be inherited (<5%) e.g. mutations in the amyloid precursor protein (APP) and presenilin genes (PSEN1, PSEN2).
Dementia and cardiovascular disease
smoking and diabetes increase risk. Exercise decreases risk.
2 types of misled protein in dementia
Amyloid B plaques: used normally for synaptic function and BBB protection
Neurofibrillary Tangles: used normally for DNA protection and dendritic development
APP
APP has multiple cleavage sites to for different isomers
Once cleaved into its many forms, these have specific tissue expression and multiple functions including synapse regulation, synaptic plasticity and iron transport.
Non-amyloidogenic pathway
Used for neuroprotection,
Neurite outgrowth, Neural stem cell proliferation ,Enhances LTP
Use of a-secretase to snip parts of APP and amyloidogenic peptides release sAPPa
Amyloidogenic pathway
Mainly uses β-secretase in the brain(BACE1) to snip APP
Left with 3 products:
sAPPβ :Lacks most neuroprotective effects of sAPPα
Aβ:Varies in length, found in alzhiemer patients
AICD:Translocated to the nucleus & activates transcription of target genes such as p53, GSK3β & EGFR.
Treatment of dementia
have tried knocking out BACE1 but this leads to hypomyelination and caused seizures so acyetholinesterases are used
Amyloid B
play a central role in Alzheimer disease
Secondary structure - predominately alpha-helical but see global conformational rearrangement and formation of beta-sheet structure by fibrillization
Treatment in AD through Amyloid beta
Immunization(vaccination shows some help) via
BACE1 inhibitors
Aducanumab medication in Alzheimer’s
an antibody therapy that targets amyloid beta protein
Causes antibody to unbundle plaques or be to be engulfed by phagocytosis
Can lead to very bad effects and may decrease quality of life
Neurofibrillary tangles in Alzheimer’s
Occur from Tau proteins
Tau proteins is a family of microtubles associated proteins and promote stability of microtubule network
Disorder in Tau become hyperphosphorylated and form intraneuronal aggregates.
Tau microtubule binding
6 isoforms of Tau all with different binding sites
four microtubule-binding repeats(4R) promote microtubule construction(more likely to misfold)
three microtubule-binding repeats (3R)worse at promoting microtubule stability
synapse loss in AD
Synapse loss occurs with aging but with advancing AD synapses are disproportionately lost relative to neurons.
reduction in dendritic branch length and complexity
down regulation of postsynaptic proteins such as PSD-95
synaptic plasticity in AD
Synaptic plasticity fails with AD
Experiment done with mice cultured with higher temperature produced more synapses per area after 3 months
Astrocytes and microglia in AD
Astrocytes and microglia help to protect against Alzheimer’s
neuroprotective as it aims to clear cell debris, phagocytose dead cells, and release neurotrophic factors.
In later disease – persistence of damaging stimuli means microglia are chronically activated & release inflammatory cytokines that drive neurotoxicity and neurodegeneration
Types of astrocytes
A1 astrocytes are neurotoxic – they are stimulated by activated microglia release of (IL-1α), (C1q) and TNF-α. They can then activate β & γ secretase activity.They can also cause secretion of neurotoxins, loss of synaptogenesis and neuronal death
A2 astrocytes are neuroprotective – they upregulate several neuroprotective factors that promote synaptic repair
Genetic risk factor in AD
APOE ε4 allele is one of the highest risk factors
How is dopamine synthesised in basal ganglia
amino acid tyrosine is converted to L-dopa then L-dopa is decarboxylated to form dopamine.
Dopamine rich areas in the brain
localised to the substantia nigra and the ventral tegmental area in the midbrain
Dopamine pathways
mesocortical; mesolimbic; and the nigrostriatal pathway
Outline Basal ganglia structures
the striatum, which includes the caudate nucleus and the putamen,
the globus pallidus (GP) which is divided into two segments, the internal (GPi) and external parts (GPe),
subthalamic nucleus
substantia nigra
substantia nigra
divided into two parts, the reticular part (SNpr)-essential for movement coordination and initiation and the compact part (SNpc)-This region contains GABA-producing neurons. GABA is an inhibitory neurotransmitter that helps to regulate movement.
substantia nigra dysfunction causes which diseases
Parkinson’s disease, Huntington’s disease, and progressive supranuclear palsy
Basal ganglia
important in planning and modulation they switch pathways to determine motor program by using muscle tone, muscle length, speed, and strength of the movement by using the pyramidal system
Where do basal ganglia receive input
Caudate nucleus
Putamen
Nucleus accumbens