1. PARKINSON‘S DISEASE
Treatment and models

2. Parkinson‘s disease (PD) is the second most common neurodegenerative disorder after Alzheimer‘s disease.
It is characterized by the loss of substantia nigra pars compacta (SNpc) dopaminergic (DA) neurons.
Parkinson is affecting 1% of the population older than 50 years.
DEFINITION

3. Characteristic are also the presence of intraneuronal cytoplasmic inclusions, called Lewy Bodies (LBs).
PD is also called Paralysis agitans and Shaking palsy because it causes resting tremor, muscular rigidity and the loss of postural reflexes.
The sense and intellect remains quite normal.
DEFINITION

4. Is a neurotransmitter in the substantia nigra, caudate nucleus and putamen (basalganglia)
It is essential for a normal movement and transmit the signal between cortex and thalamus.
DOPAMINE
Neocortex
Basalganglia
Thalamus

6. DOPAMINE Development: Dopa Dopamine + CO2
MAO and COMT destroy Dopamine.
Dopamine cannot cross blood-brain-barrier.
DOPAMINE

7. Brain-blood-barrier

8. α-SYNUCLEIN 2 forms: α-syn:
Is a 140 amino acid protein, very abundant in the brain.
its exact function is not known yet.
It has a natural tendency to clump together to form insoluble aggregates (LBs, LNs) and this tendency is likely increased in the mutated form.
α-SYNUCLEIN

9. Detected immunohistochemically in LBs, LNs
Detected immunohistochemically in LBs, LNs. (LB Dementia, Parkinson‘s, Alzheimer‘s, NBIA1).
In Drosophila: similar perinuclear and neuritic filamentous inclusions like LBs & LNs.
Is the precursor protein of a nonamyloid-β-protein component (NAC) isolated from Alzheimer‘s plaques.
Induces selective and progressive
loss of DA neurons.
α-SYNUCLEIN

10. β-SYNUCLEIN β-syn: homologue to α-syn
Is not able to form insoluble LBs or LNs.
Aminoacids in the NAC region are absent
= nonamyloidogenic
This region (aa 73-83) is essential for the typical aggregations in the brain.
β-SYNUCLEIN

11. Selective Insolubility of α-syn in human Lewy Body diseases
- Parkinson‘s Disease
- Alzheimer‘s Disease
- LB Dementias
- Hallervorden – Spatz Disease (NBIA type1)
METHODS

12. Transgenic mice expressing human
α-syn
Wild type: [wt]
Point mutation: [A30P]- α-syn
Point mutation: [A53T]- α-syn
Promotor: THY1 (brain neuron-specific)
Investigation of solubility of „syns“ in human LB Diseases
transgenic animals expressing human [wt] and mutant [A30P]- α-syn, [A53T]- α-syn
METHODS

13. [wt] and mutant α-syn assembled into LB-like fibrils in transgenic Drosophila:
locomotor deficit became apparent with increasing age.
 2 missense mutations in the α-syn gene (rare)  dominantly inherited PD.
In transgenic mice:
somal and neuritic accumulations of [wt] and mutant α-syn were observed in transgenice mouse brain.
modest reduction of locomotor performance, due to age-dependent degeneration of neuromuscular junctions.
IMPLEMENTATION

14. IMPLEMENTATION α-syn and β-syn: both in synaptosomal
fractions of rodent + human brain.
α-syn: highly soluble in aqueous buffer
In case of LB diseases:
detergent- insoluble α-syn + aggregates
were found in urea extracts.
Human α-syn was detergent-insoluble in
transgenic mouse brains, but not
endogenous mouse α-syn and β-syn!
IMPLEMENTATION

16. IMPLEMENTATION β-syn: no aggregates in vitro (no 73-83)
Conclusion: specific accumulation of
detergent-insoluble α-syn in transgenic
mice recapitulates a pivotal feature of
human LB diseases.
IMPLEMENTATION

17. METHODS Antibodies (rat, mouse) against LB recognizing epitopes
Brain fractionating and Western Bloting
Generation and Characterization of transgenic mice
In vitro aggregation
of recombinant syns
METHODS

18. MODELS Drosophila: short generation time fully sequenced genome
vast array of genetic information
availability of huge number of stocks containing mutations in almost every genes
Complete control about the experiment
short life-span: investigations of age-dependent disorders (neurodegeneration)
expression of human α-syn-gene causes several characteristics of human PD:
MODELS

19. MODELS Late-onset progressive degeneration of subsets of DA neurons.
Develop filamentous protein aggregates rich in α-synuclein within cell bodies and neurites of DA neurons.
MODELS

20. CHAPERONES Heat shock proteins Up-regulated during stress response
Help to refold misfolded proteins
Auluck et al. – aggregation = disorder involving
protein misfolding.
 Boost the amount of chaperones in neurons
Expression of gene encoding human Hsp70 completely prevents late-onset loss of DA neurons (induced by human α-syn).
Decreasing endogenous chaperone activity accelerates the neuronal loss in PD flies.
CHAPERONES

21. CHAPERONES Human disease Prakinson‘s disease Linkage to specific genes
α-synuclein
Treatment
of human
disease
Treatment of
Prakinson‘s
disease
CHAPERONES
Fly model
of disease
Fly Prakinson‘s
disease
Fly genetics to
develop new
treatments
Chaperones

22. CHAPERONES Polyglutamine disease: same neuronal
degeneration (expanded polyglutamine stretches)
Abnormal polyglutamine proteins suppressed by Hsp70
 Coexpression of Hsp70 with α-syn
Normal numbers of DA neurons in aged flies
 control: β-galactosidase coexpressed with α-syn
50% loss of DA neurons in aged flies
(α-syn – concentration did not alter [immunoblot] )
Interaction between endogenous chaperone activity and α-synuclein.
CHAPERONES

23. CHAPERONES Influencing of α-syn confirmation?
α-syn interferes with chaperone‘s activity by sequestration?
Chaperones can „detoxify“ the protein aggregation in a more subtle way.
Risk factors may hamper normal activity of chaperones (smoking)
Inducing general stress response: (for treatment)
Increases production of chaperones
Advertantly protect neurons?
CHAPERONES

24. MEDICATIONS Main goal: increase dopamine level
Dopamine precursors: can cross blood-brain-barrier, changed to dopamine
i.e. Levodopa, Sinemet, Madopar
Dopamine agonists: act directly on dopamine receptors (D1, D2), replace dopamine
i.e. Apomorphine, Mirapex
Inhibitors of dopamine metabolism:
i.e. Selegiline, Eldepryl
MEDICATIONS

25. Blocking the reuptake of dopamine/ increasing the release of dopamine:
i.e. Symmetrel
COMT inhibitors (Catechol-O-methyltransferase): are taken with L-Dopa, slow the break down of it.
i.e. tolcapone, entacapone
Anticholinergics: act not directly on dopamine, help to decrease the activity of Ach, which is balancing neurotransmitter
i.e. trihexyphenidyl
MEDICATIONS

26. Pallidotomy: tiny hole drilled in the skull, electric probe is used to destroy a small part of the global pallidus to reduce dyskinesia
Deep brain stimulation (DBS): very thin electrode is implanted into the brain, small electric pulses are used to stimulate the brain , blocks signals that cause PD symptoms.
Stem cell therapy: stem cells are undifferentiated cells, can be manipulated to differentiate into dopamine producing neurons (still experimental stage)
TREATMENT

27. Neuron developed from stem cell

28. RESSOURCES Science #295: Auluck et al.
„Suppression of α.synuclein toxicity in a Drosophila model for Parkinson‘s disease“
Science #295: Helfand
„Chaperones take flight“
Am J Pathol #159: Kahle et al.
„Selective insolubility of alpha-synuclein in human Lewy body diseases is recapitulated in a transgenic mouse model“ …
RESSOURCES