This powerpoint discusses the role of transition metals and amyloid plaque formation in Alzheimer’s disease (AD) and how metal ion chelators may be employed as therapeutic agents for AD. It describes the disorder, how it progresses and what happens to the brain tissue. Furthermore, within the presentation I describe a drug which chelates metals including a description about the chemical formulation of these drugs and how the drug can be preventative of AD.

1. The role of Transition Metals &
Reactive Oxygen Species (ROS)
in Alzheimer’s Disease(AD).
By Piril Erel
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Normal  Alzheimer’s

2. Content Pages:
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10.Production Of ROS Induced By Aβ
11.Chelating Properties
12.PBT2 detoxifies Aβ Plaques
13.The Healthy Synapse – a glance into the synaptic cleft
14.Alzheimer’s Disease – a glance into the synaptic cleft
15.PBT2 – a glance into the synaptic cleft
16.Trial Method For PBT2
17.Results From PBT2
18.Conclusion
19.Ending
20.References
1. Aims & Objective
2. What Is Alzheimer’s Disease?
3. Risk Factors Associated With AD
4. Metal Homeostasis In Alzheimer’s Disease
5. Pathophysiology of AD
6. The Role Of Transition Metals
7. Amyloid- β(Aβ) Protein Plaque Formation And
How It Links To Transition Metals
8. Aggregation Of Aβ Is Metal Dependent
9. Interactions Of Transition Metals With Amyloid – β
Protein (AβPP)

3. The main aim of this project is to investigate current research in Alzheimer’s Disease(AD)
including novel ways to treat this illness which currently does not have any known cure.
By doing this assignment I will introduce The Metal Hypothesis for AD and a novel drug called
PBT2 which I will discuss in detail.
Objectives:
Explain ‘The Metal Hypothesis’
Provide an insight in the dysfunctions of an AD-brain relating to the Metal Hypothesis
Describe Reduced Oxygen Species (ROS)
Discuss how the Metal Hypothesis integrates with ROS to cause AD
Detail of how PBT2 could be an effective drug for AD patients.
Aims & Objective
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4. Alzheimer’s Disease(AD) is a slow progressive and fatal neurodegenerative disease
which is indicated by memory and cognitive dysfunction. Despite increasing
knowledge of genetics, epidemiology and neuropathology AD is not treatable.
Currently, disease modifying drugs or existing therapies only offer short-term
symptomatic relief.
It affects 800,000 people in the UK alone and 36 million people world wide, (data
from 2010), this number approximately doubles every 20 years, and is estimated to
reach 66 million in 2030 and 115 million in 2050.[1] This pressures scientists to make
finding a long term pharmacotherapy a priority.
What Is Alzheimer’s Disease?
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5. Risk Factors:
1. Age:
a. 1/5 people over 65 will get Alzheimer’s Disease
b. Up to 50% over age 85 have AD
2. Family History:
a. Strong genetic component in most cases of AD
3. Other:
a. Gender (female; menopause?)
b. Stroke, Obesity, High Cholesterol
c. Diabetes
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Risk Factors Associated With AD

6. The brain is a specialized organ which uses key cellular processes to work efficiently,
these processes require a high concentration of transition metal ions such as zinc(Zn)
and copper(Cu).
Zn2+ & Cu2+ are required in neuronal activity within synapses
Due to the necessity of these metal ions, cells have a sophisticated system to maintain
metal-ion homeostasis.
Breakdown of these mechanisms alter the ionic balance and can result in a disease state
such as AD.
These metal ions are suggested to have two distinct roles in the pathophysiology of AD:
1. Aggregation of Aβ peptide plaques
2. Production of reactive oxygen species induced by Aβ.
Metal Homeostasis In Alzheimer’s
Disease
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7. Promotion of Aβ in the
brain, which is collected
over decades due to the
presence of raised Zn2+ &
Cu2+ concentrations.
Sequestration of copper
by Aβ, drives the
generation of reactive
oxygen species.
Excessive aggregates of
Aβ trap essential metals:
Zinc & Copper.
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Pathophysiology Of AD

8. Metals are involved in essential biological functions but the
transport and utilization are generally controlled by their
chemistry making them physiologically useful and potentially able
to give rise to pathological miracles.
The levels of transition metals such as Cu, Fe and Zn in a healthy
brain neocortical parenchyma are still maintained at a high
concentration, however within an AD-affected brain these
concentrations are increased with the highest levels found within
amyloid plaque deposits[2].
Kenche et al stated that both the Zn2+ released from the
presynaptic terminals and Cu2+ released from the post-synaptic
terminals, following synapse stimulation, are pre-dominantly in a
‘free’ exchangeable form.
These ions, along with Aβ in the synaptic cleft results in an
inevitable interaction.
The Role Of Transition Metals
Pic – Reference:
Henryk Kozlowski, Marek Luczkowski, Maurizio Remelli, Daniel Valensin. (2012).
Copper, Zinc and iron in neurodegenerative diseases (Alzheimer's, Parkinsons's
and prion diseases). Metal Ion in Neurodegenerative Diseases. 256 (Fig. 3.), p1.
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9. Aβ is the main component of deposits found in the regions of the
brain involved with memory, emotions and intellectual function
of patients with AD[3].
Cherny et al, 1999 found that the use of promoting chelation of
metals in postmortem studies have shown that Zn2+ and Cu2+
mediate the precipitation of Aβ deposits in AD-brain tissue.
Studies show that the neuropil and amyloid plaques in AD-brains
have a high concentration of Cu and Zn, however we do not know
whether this is due to:
Abnormal activity of Cu (or Zn) homeostasis which initiates
Amyloid- β plaques.
Amyloid plaques having a high affinity to metal ions.
Amyloid plaques acting as metal sinks absorbing the ions into
their core [4].
Amyloid- β(Aβ) Protein Plaque Formation
And How It Links To Transition Metals
Pic2 - Reference:
AHAF (American Health Assistance Foundation). (). Amyloid
Plaques and Neurofibrillary Tangles.. Available:
http://pakmed.net/academic/age/alz/alz030.htm. Last accessed
14th Apr 2013.
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10. +
Zn2+/Cu2+
Aβ
Monomer
Oligomer Protofibril
β-
Amyloid
Fibril
Aggregation Of Aβ Is Metal Dependent
Non-
Pathogenic
Synaptic
Dysfunction
Membrane
Disruption
Inflammation
Subsequently research showed that Zn2+ & Cu2+ are required for the aggregation of Aβ.
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11. Aβ – Copper binding forms oxidative crosslinks between
monomers. The resulting cross-linked species are called
oligomers. Oligomers are very difficult for the brain to
clear and can eventually cause neuron death
Craddock et al, 2012 observed metal dyshomeostasis in
a AD-affected mouse model.
The interaction between Aβ and metals therefore
represents a mechanism of therapeutic intervention
that could both normalize metal homeostasis and
reduce the levels of toxic Aβ oligomers in the brain. *5+
Furthermore, Copper binding to A also generates ROS,
this binding causes a detrimental release of ROS.
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Interactions Of Transition Metals
With Amyloid - β Protein (AβPP)

12. The brain needs oxygen in order to synthesize the large quantities of ATP required.
This accounts for 20% of the body’s total basal oxygen consumption therefore generates high levels of reactive oxygen
species (ROS).
Exposure to ROS damages neurons in the brain.
Oxidative stress plays an important role in initiating AD through provoking cell signaling pathways. [4]
It represents an imbalance between the amount of ROS being produced and the ability of the body to detect and remove
these toxic substances.
This is due to cellular antioxidant defense mechanisms becoming overwhelmed by ROS causing macromolecular damage. ROS
may also result in harmful effects such as;
Damage of DNA.
Oxidation of polyunsaturated fatty acids.
Oxidation of amino acids in proteins.
Oxidatively inactivation of specific enzymes. [6]
Production Of Reactive Oxygen
Species Induced By Aβ
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13. In order for a drug to be used as a potential treatment for brain
disorders, it must possess certain characteristics which enable it to
pass the blood brain barrier(BBB) such as:
Low molecular weight
Poorly charged or not charged at all
Stable
Selectivity of certain metal ions
Low toxicity
Minimum side effects.[7]
Chelating Properties
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14. This recently discovered treatment shows rapid improvement in
cognition in mouse models of AD.
A Copper/Zinc Ionophore – it competes for metals but also
redistributes metals back into the cell as it transports ions across
the lipid bilayer.
PBT2 aids the clearance of Aβ aggregates in the brain by targeting
zinc and copper ions effectively it detoxifies the Aβ plaques.
PBT2 has a greater affinity for metal compared to Aβ’s affinity to
metal:
Aβ affinity for Zn is - Kd = 10-9
PBT2 affinity for Zn is - Kd =10-13
Metals are promiscuous, they can jump and bind to which ever is
stronger, so if a metal is bound to an Aβ plaque and PBT2 is present,
due to the 104x greater force, the metal will dissociate and bind to
the drug.
PBT2 provides a mechanism which shuttles metals away from Aβ
PBT2 detoxifies A plaques
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15. Zn2+ is exocytosed into the synaptic cleft in
concentrations of around 300 μM
Cu2+ is released post-synaptically following
activation of NMDA with Cu2+
concentrations around 15 μM in the
synaptic cleft.
Once cleavage of APP takes place, Aβ is
released into the synaptic cleft and it aids
lowering of zinc concentration by acting as
a sponge.
Aβ is further degraded by enzymes into
smaller monomers.[8]
The Healthy Synapse – a glance into
the synaptic cleft
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16. The decrease in ATP leads to a reduction
metal reuptake, causing the average
concentration of metals to rise over time.
Cu & Zn react with Aβ forming Aβ
oligomers and then, crucially, to Aβ
amyloid plaques
Aβ can bind up to 2.5 moles of metal ions
however the more metals it is bound to,
the more aggregated it becomes
Aβ oligomers are resistant to degradation.
Alzheimer’s Disease – a glance into
the synaptic cleft
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17. PBT2:
PBT2 taken orally crosses the blood brain barrier
and can be detected in the synaptic cleft.
PBT2 has a high affinity for metals
Chelation by PBT2 allows Zu & Cu to be removed
from Aβ
The advantage of PBT2 lies in the ionophoric
properties of the drug
Concentrations of the metal ions are reduced to
normal
Thus diverted from binding to Aβ,
This reduces precipitation, reduces covalent Aβ
oligomer formation and reduces toxic redox activity.
PBT2 – a glance into the synaptic
cleft
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18. Objectives For Phase IIa:
To test the safety and efficacy of PBT2 in patients with mild AD.
To monitor any changes in cognition after administration of PBT2 using
the Neuro-psychological Test Battery (NTB) which measures Executive
Function(EF).
PBT2 has undergone a 12 week Phase II trial in which the drug was orally
administered daily to 78 patients with mild AD who where randomly
allocated into either one of the 3 groups below:
Placebo
50mg and
250mg
It was a double-blind, randomized, placebo-controlled trial
Trial Method For PBT2
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19. Patients with a 250mg dose of PBT2 daily showed a significant increase in EF scores compared to the
placebo group.
250mg dose of PBT2 also showed a significant decrease in Aβ protein plaques.*9+
This shows promising results for PBT2 as a treatment drug for Alzheimer’s Disease. Phase IIb clinical
trials is currently underway this time scientists are evaluating the effect of PBT2 on:
Safety and tolerability
Brain metabolic activity
Brain volumes
Cognition
Functional abilities[10]
Results
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20. Through thorough research into this area, current drug trials target memory
deficit in early – moderate Alzheimer’s
However it is questionable whether this is too late.
Consideration of executive function and early treatment of AD; a cure may be
possible or at least consequences are more reversible.
PBT2 not only detoxifies the harmful Aβ plaques but also re-establishes
homeostasis of metals at a stage where neuronal death hasn’t yet occurred.
Clinical trials for PBT2 Phase IIb will hopefully provide promising results for
curing AD.
Conclusion
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21. Thank You For Listening & Watching,
Piril Erel
12004723
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22. 1. Nicole L Batsch, Mary S Mittelman. (2012). Overcoming The Stigma Of Dementia. Available:
www.alz.co.uk/research/WorldAlzheimerReport2012.pdf. Last accessed 2th Apr 2013.
2. Craig S. Atwood, Richard C. Scarpa, Xudong Huang, Robert D. Moir, Walton D. Jones, David P. Fairlie, Rudolph E. Tanzi and Ashley I.
Bush.. (2000). Characterization of Copper Interactions with Alzheimer Amyloid Beta Peptides: Identification of an Attomolar-Affinity
Copper Binding Site on Amyloid Beta1–42. Journal of Neurochemistry. 75 (No.3), 1219.
3. Martini, FH (2012). Fundamentals of Anatomy & Physiology. 9th ed. San Francisco: Pearson Education. 542.
4. Xiongwei Zhu, Bo Su, Xinglong Wang, Akihiko Nunomura, Paula I. Moreira, Hyoung-gon Lee, George Perry, Mark A. Smith, . (2008).
Oxidative Stress Signaling in Alzheimer's Disease. National Institute of Health. 5(6) (1), 525-532.
5. Daniel Kantor. (October 4, 2010). Alzheimer's Disease. Available: www.scripps.org/articles/3458-alzheimer-s-disease. Last accessed
15th Apr 2013.
6. Brooker, Robert J. (2011). Genetics: analysis and principles (4th ed.). McGraw-Hill Science.
7. Budimir, A. Metal Ions, Alzheimers Disease & Chelation Therapy. Acta Pharm.2011;61():1-14
8. Duce, JA et al. (2010). Biological Metals & Alzheimer's Disease: Implications for therapeutics and diagnostics. Progress in
Neurobiology. 92 (1-18), 4.
9. Faux, N.A et al. (2010). PBT2 Rapidly Improves Cognition in Alzheimer's Disease: Additional Phase II Analyses. Journal of Alzheimer's
Disease. 20 (1), 509-516.
10. Lannfelt, L and Prana Biotechnology. (2013). PBT2 Clinical Program. Available: www.pranabio.com/default.asp?contentID=625. Last
accessed 20th Apr 2013.
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References