PARKINSON’S DISEASE

Sankar Alagapan

Nov 23 2009

From A Manual of Diseases of the Nervous System: William Gowers

OVERVIEW

2

Molecular Mechanisms

PathophysiologySymptoms

Treatment Strategies

Disease Symptoms and Mechanisms

Introduction

INTRODUCTION• Neurodegenerative disease affecting movement,

cognition and other autonomic activities

• General age of onset of symptoms ~ 60 years

• Currently around 1.5 million people in the UnitedStates with Parkinson's disease (1 in 272)

• Medication costs for an individual person with PDaverage $2,500 a year, and therapeutic surgerycan cost up to $100,000 dollars per patient.

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HISTORY OF PARKINSON’S DISEASE

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• Kampavata - ancient Indian medical system ofAyurveda

• Shaking Palsy – Galen (AD 175)

• 1817: Description of Symptoms - JamesParkinson

• 1862: Coined the name- Jean-Martin Charcot

• 1919: Degeneration of Substantia NigraTretjakov

• 1968: First large scale results of treatment withL-Dopa Cotzias

• 1979: MPTP induced Parkinsonism - Davis et al,Langston

• 1997: PARK1 Gene Mutation was discovered -Polymeropoulus

SOME FAMOUS PARKINSONIAN PATIENTS

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CLINICAL FEATURES

• Motor Impairments– Tremor at rest

– Rigidity

– Akinesia (Bradykinesia)

– Postural Deformity

– Speech and swallowing disturbances

– Gait and Posture Disturbances

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Jankovic 2008

CLINICAL FEATURES

• Non Motor Impairments– Autonomic Dysfunction

• Orthostatic hypotension, sweating dysfunction, sphincter dysfunction and erectile dysfunction

– Cognitive and Neurobehavioral Abnormalities• Dementia, Depression, Executive Dysfunction

– Sleep Disorders• REM Behavior Disorder

– Sensory Abnormalities• Olfactory dysfunction, Paresthesia, Akathisia

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DIAGNOSIS

• Neurologic Examination– Unified Parkinson's Disease Rating Scale (UPDRS)

• Ioflupane – A radiological tracer for SPECT

• FDOPA and PET

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PATHOPHYSIOLOGY

• Loss of dopaminergic neurons in Substantia Nigra pars compacta and Locus Coeruleus

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Babraham Institute Piers Emsom Dopamine and Parkinson's DiseaseMadame Curie Bioscience Database

NEURODEGENERATION IN SN• Striatum – 80% of Dopaminergic neurons

– A9 group: Substantia Nigra pars compacta (SNpc)– A10: Ventral Tegmental Area (VTA)

• Neuromelanin in Midbrain DA Neurons– SNpc: 84 – 98%, VTA: 50%– Neuroprotective role in the normal brain by preferentially

sequestering pesticides, MPTP, Iron, etc.

• Vesicular Monoamine Transporter (VMAT)– VMAT2 helps incorporating cytoplasmic dopamine in

vesicles– VMAT2 expressed less in SNpc than in VTA

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NEURODEGENERATION IN SN• Dopamine Transporter (DAT)

– Neurotoxicity of MPTP by transporting MPP+

– Pattern of expression correlated with neuron loss

– DAT knockout mice resistant to MPTP neurotoxicity

• Calcium Binding Proteins– Calbindin D28K (CB), Calretinin (CR), and Parvalbumin(PV)

– Administration of 6-hydroxydopamine (6-OHDA) and MPTP results in degeneration of the CB-negative TH-positive neurons in the SNpc, but not the TH- and CB - positive neurons in the dorsal tier of the SNpc

• Mitochondrial DNA mutations

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NEURODEGENERATION SYMPTOMS

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Neocortex

Thalamus

Gpi/SNr

Hippocampus

Amygdala

Striatum

GPe

SNpc/VTA

Direct PathwayInDirect Pathway Globus Pallidus Internal Segment Suppression Theory

STN

NEURODEGENERATION SYMPTOMS

• Basal Ganglia Selection Theory:– Basal ganglia are involved in the selection of

motor programs

– Bradykinesia due to failure to select or engageappropriate motor programs

– Dyskinesia due to failure of basal ganglia tosuppress inappropriate motor programs

• Oscillator Theory

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PATHOPHYSIOLOGY

• Presence of Lewy Bodies– 1979 (Kosaka and

Mehraein)

• Lewy bodies stained strongly with antibodies of α – synuclein– 1997 (Spillantini et al)

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Spillantini et al 1997

α – SYNUCLEIN IN LEWY BODIES

• α-synuclein monomers become oligomers(protofibrils), which coalesce into fibrils and then aggregate into Lewy body inclusions

• Dysfunction of Ubiquitin ProteasomeSystem

• Neurotoxic vs Neuroprotective

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OXIDATIVE STRESS

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Nigral cells seem to be under a heightened state of oxidative stress

OXIDATIVE STRESS

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Nigral cells seem to be under a heightened state of oxidative stress

α – SYNUCLEIN AND OXIDATIVE STRESS

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EXCITOTOXICITY

• SNc neurons receive extensive glutamateinnervation from the cortex and thesubthalamic nucleus

• Dopamine lesions disinhibit the STN andincrease the firing rate of its excitatory outputneurons

• NMDA antagonists protect against dopaminecell loss resulting from MPP+ infusion into theSNc of rats

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CAUSATIVE FACTORS

• Neurotoxins:– MPTP, Rotetone, 6-OHDA etc

• Genetic Factors:– Mutations PARK1, PARK2, PARK5 etc.

• Neuroinflammation

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ANIMAL MODELS

• Pharmacological Induced Models– Reserpine– Alpha-methyl-para-tyrosine

• Toxin Induced Models– MPTP– Methamphetamine– Rotenone– 6 OHDA

• Genetic Models– PARK1– PARK2– PARK5

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PHARMACOLOGICAL INDUCED MODELS

• Resperine– First used by Carlsson (1950) in rabbits– Showed DA depletion in caudate and putamen

resulting in akinetic state– Led to use of Levodopa

• Alpha Methyl Para Tyrosine– Depletes Catecholamine by inhibiting Tyrosine

Hydroxylase

• Transient Effects, No Biochemical/Pathological Changes

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TOXIN INDUCED MODELS : MPTP• 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine

• Neurotoxicity and associated Parkinsonism discovered in 1979 – Davis et al.

• Drug abuse by 23 year old person lead to discovery

• Used in animal models to induce Parkinsoniansymptoms

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MPTP MECHANISM OF ACTION

24Dauer et al 2003

α – SYNUCLEIN AND MPTP

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OTHER TOXIN INDUCED MODELS• Rotenone:

– Naturally occurring lipophillic compound– Specific inhibitor of Mitochondrial complex I – Degeneration of a subset of nigrostriatal

dopaminergic neurons; the formation of cytoplasmicinclusions; and the development of parkinsonianmotor behavior

• 6 Hydroxydopamine (6 OHDA)– Accumulates in cytoplasm and produces ROS– Rapid degeneration of neurons when injected in SN– Progressive degeneration when injected in striatum

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GENETIC MODELS

• Generally mutations in the Ubiquitin Proteasome System

• Major: Genes coding Alpha-Synuclein, Parkin, UCH-L1, PINK1, DJ-1

27Moore 2005

GENETIC MODELS

• PARK1 (Italian and Greek families)– A30P and A53T substitution mutations in the gene

encoding alpha-synuclein or triplicate of the gene

– Proposed to cause misfolding or dysfunction of α-synuclein

• PARK5– Gene encoding UCHL1 (ubiquitin C terminal

hydrolase L1)

– Generates free Ubiquitin

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GENETIC MODELS

• PARK2 (Japanese Family)– Mutation in gene encoding protein Parkin, a E3

Ubiquitin Ligase

– Ubiquitin is added to proteins by Ligase to target them to Proteasome

– Absence of Lewy bodies in patients with homozygous deletion shows Parkin plays an important role in Lewy body formation

– Enable investigation of the ubiquitin-mediated protein degradation pathways

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GENETIC MODELS

30Moore 2005

MOLECULAR MECHANISMS

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NEUROINFLAMMATION

• Supported by Animal models– MPTP model ↑IL-1β and

↓NGF in striatum

– 6-OHDA model showed ↑TNFα in substantia nigra and striatum

• Produced from activated microglia– initially neuroprotective and

becomes neurotoxic later

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Apoptosis

TNFα, IL-1β, IL-6, IL-2,IL-4,

TGFα, TGF β1, TGF β2

BDNFNGF

Cytokines

Neurotrophins

TREATMENT STRATEGIES

• Drugs– L-Dopa and Dopamine Agonists

– MAO Inhibitors and COMT Inhibitors

• Gene therapy

• Surgical Interventions– Stem cell therapy

– Lesion surgeries and Deep Brain Stimulation

• Physiotherapy

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LEVODOPA

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Abbreviations:COMT - Catechol- O-methyltransferase

3-OMD - 3-O-methyldopa

AAAD - Aromatic amino acid

decarboxylase

MAO - Monoamine oxidase

DOPAC - 3,4-dioxyphenylacetic acid

HVA - Homovanillic acid

Loss of Dopamine Regulation

Substantial release of DA in pulsatile fashion

Motor Fluctuations

- Long Duration Response and Short Duration Response

- On-Off Effect

Dyskinesia

- Peak Dose Dyskinesia

- Biphasic Dyskinesia

- Square wave

- Yo-Yoing

LEVODOPA SIDE EFFECTS

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COMT Inhibitors

MAO Inhibitors

MAO INHIBITORS AND COMT INHIBITORS

• Selegiline and Rasagiline

• Neuroprotective nature, due to propargyl moiety, shown in vivo and in vitro

• Entacapone and Tolcapone

• Used in conjunction with levodopa and an AAAD inhibitor

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GENE THERAPY

• Genes to produce TH delivered virally (HSV) into striatum

• Genetically delivered AAADC using an AAV• Multiple genes – VMAT and TH

Dopamine Synthesis

• Viral vectors have been used to deliver GDNF to the striatum and SNc

• In vivo lentiviral delivery of a modified neurturin construct produced neuroprotection of rat nigrostriatal projections.

Neurotrophins

• Lentiviral delivery to increase expression of the normal Parkin gene in the substantia nigra of rats

• AAV carrier to deliver Hsp-70 to the substantia nigra of MPTP-treated mice

Parkin Gene

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LESION SURGERIES

• Early efforts focused onthe sensory roots ofspinal cord

• Focus then shifted tomotor cortex

• Subcortical nucleibecame areas ofinterest

• Pallidotomy andThalamotomy

38Clower 2002

LESION SURGERIES

39Clower 2002

LESION SURGERIES

40Clower 2002

DEEP BRAIN STIMULATION (DBS)

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Wikipedia Wired.com

Targets: Thalamus, GPi, STNStimulation parameters: Frequency of 135 to 185 Hz, pulse width of 60 to 120 μs, and amplitude of 1 to 3V

COMPLICATIONS ASSOCIATED WITH DBS

• Hemorrhage, ischemic lesions, seizures, infections, and misplaced leads

• Occurrence: ~ 5%

Surgical Procedures

• Electrode Failure, Lead breakage, cranial lead migration, Infection, Erosion, IPG Malfunction

• Occurrence: ~ 20%

DBS Hardware

• Eyelid apraxia, dystonic posturing, dysarthria, dyskinesia, limb and facial muscle spasms, depression, mood changes, visual disturbances, and pain

• Suicide rate of 4.6% in patients with DBS.

Stimulation

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STEM CELL THERAPY

• Hormonally induce stem cell differentiation intonigrostriatal dopaminergic neurons or theirprecursors and then to transplant them intopatients

• Embryonic stem cell (ESC) Neural Progenitorcells (NP)

• Human NPs grafted in striatum of Parkinsonianrats showed improvement of symptoms

• Results have also shown that mouse ESCdifferentiate into DA neurons in vivo

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PHYSIOTHERAPY

• Supplementary Therapy

• Help with movement, posture and balance

• Relieve muscle and joint stiffness and discomfort

• Exercises to maintain or improve muscle strength

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Neurotoxins and External AgentsGenetic FactorsNeuroinflammation

Molecular Mechanisms

PATHOPHYSIOLOGYLoss of Dopaminergic cells in the Substantia Nigra

SYMPTOMSMovement DisordersCognitive Decline

Cellular Level Manifestations

External Manifestations

Drugs, Gene therapy

Stem Cell Therapy

DBS, Physiotherapy

TREATMENT STRATEGIES

Complications and Side Effects

Oxidative Stress

??

PARKINSON’S DISEASE

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