The Role Of Histone Deacetylase Inhibitors In Ameliorating Memory Dysfunction Of An Alzheimer's ...

136 Pages·2013·2.55 MB·English

THE ROLE OF HISTONE DEACETYLASE INHIBITORS IN AMELIORATING
MEMORY DYSFUNCTION OF AN ALZHEIMER’S DISEASE MOUSE MODEL

by
MARK KILGORE

J. DAVID SWEATT, COMMITTEE CHAIR
JOHN HABLITZ
ERIK ROBERSON
GAVIN RUMBAUGH
J. MICHAEL WYSS

A DISSERTATION
Submitted to the graduate faculty of The University of Alabama at Birmingham,
in partial fulfillment of the requirements for the degree of
Doctor of Philosophy
BIRMINGHAM, ALABAMA
2013
THE ROLE OF HISTONE DEACETYLASE INHIBITORS IN AMELIORATING
MEMORY DYSFUNCTION OF ALZHEIMER’S DISEASE

MARK KILGORE

NEUROSCIENCE GRADUATE PROGRAM

ABSTRACT

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by amyloid beta
(Aβ) plaques and neurofibrillary tangles, along with cognitive impairments that progress
to dementia and eventually death. The development of drug treatments that rescue
memory deficits could be a promising therapy given in the early stages of AD. In the
following studies, we tested the potential for systemic treatment with histone deacetylase
(HDAC) inhibitors to ameliorate cognitive deficits in a mouse model of AD. Using the
APPSwe/PS1ΔE9 mouse model of AD, we showed that giving HDAC inhibitors
systemically for 3 weeks reversed contextual memory deficits, stably maintained
memories over a 2-week period, and targeted Class I HDAC proteins. Additionally, we
found that the APPSwe/PS1ΔE9 memory deficit was not due to a deficit in hippocampal
long-term potentiation (LTP), but these mice did show reduction in hippocampal CA1
pyramidal spine density that was restored using an HDAC inhibitor. Finally, we tested
the ability of an isoform-selective HDAC inhibitor for HDAC3 and found that it had no
effect on restoring APPSwe/PS1ΔE9 contextual memory deficits, indicating that HDAC3
does not play a significant role in the formation of hippocampal-dependent long-term
memory.
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ACKNOWLEDGMENTS
First and foremost, I would like to thank Dr. David Sweatt for giving me to
opportunity to join his lab and believing in me. I thank you for allowing me to work on a
project which I know you hold close to your heart. Under your counsel, I was able to
accomplish many great things both personally and professionally. Secondly, I would like
to thank Dr. Gavin Rumbaugh who guided me through my first and second years as a
graduate student and took interest in both me and my project. You kick-started the
project and set it off in a direction that propelled us to where we are now today. Thank
you for giving me your time and knowledge both while you were at UAB and still while
you are at Scripps.
I would also like to thank Dr. Courtney Miller for her great teaching ability and
her time to show me many techniques which were the cornerstone of my research. I truly
believe that your knowledge and expertise paved the way for the consistent and
reproducible results I continually achieved. Although when things didn’t go as planned
or hoped, I always remembered your calm demeanor and hope that I can emulate that
both personally and professionally.
A very large thank you goes to Felecia Hester who somehow keeps up with
children (graduate students and post-docs) who though they are not her own, she treats
them as if they were. Thank you Felecia for everything you do. Thank you for being a
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great resource, always having an answer, and having a kind smile that always lets you
know that someone cares about you.
And last but not least, thank you to my family and friends who have supported me
over the past few years and have given me a break from science when it was desperately
needed!

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TABLE OF CONTENTS
Page
ABSTRACT ........................................................................................................................ ii
ACKNOWLEDGMENTS ................................................................................................. iii
LIST OF TABLES ............................................................................................................ vii
LIST OF FIGURES ......................................................................................................... viii
CHAPTER
I. INTRODUCTION .......................................................................................1
Alzheimer’s disease ...............................................................................1
Neurofibrillary Tangles ..................................................................1
Amyloid Hypothesis .......................................................................4
Mouse Models of AD ...................................................................10
Learning and Memory..........................................................................17
Hippocampal Long-term Memory Formation ..............................18
Hippocampal Long Term Potentiation .........................................21
Epigenetic Regulation of Long-term Memory Formation ...................23
Epigenetic Modifications .............................................................24
Histone Acetylation ......................................................................27
Histone Acetylation and LTM formation .....................................28
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HDAC Biology .............................................................................30
Inhibitors of HDACs ....................................................................33
HDAC Inhibitors and Memory .....................................................36
Non-Histone Targets of HDACs ..................................................37
Summary ..............................................................................................38
II. INHIBITORS OF CLASS I HISTONE DEACETYLASES REVERSE
CONTEXTUAL MEMORY DEFICITS IN A MOUSE MODEL OF
ALZHEIMER’S DISEASE .....................................................................43
III. CLASS I HISTONE DEACETYLASE INHIBITORS DO NOT
ENHANCE HIPPOCAMPAL LTP, BUT DO RESCUE SPINE DENSITY
DEFICITS IN A MOUSE MODEL OF ALZHEIMER’S DISEASE ......76
IV. Conclusions...............................................................................................102
V. General References ...................................................................................113
VI. Appendix: IRB/IACUC Approval Form .................................................127

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LIST OF TABLES
Table Page
1. IC50 Values of HDAC Inhibitors that Increase Memory Formation in
APPswe/PS1dE9 Mutant Mice ..............................................................................75

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LIST OF FIGURES
Figure Page
I. INTRODUCTION
1. The classic neuronal lesions of Alzhiemer’s disease demonstrated by the modified
Bielschowsky Silver Stain ...................................................................................................4
2. The hippocampus ..........................................................................................................19
3. Histone modifications regulate gene transcription .......................................................26
II. INHIBITORS OF CLASS I HISTONE DEACETYLASES REVERSE
CONTEXTUAL MEMORY DEFICITS IN A MOUSE MODEL OF
ALZHEIMER’S DISEASE
1. APPswe/PS1dE9 mice develop contextual memory deficits with age .......................69
2. Sodium Valproate treatment rescues contextual memory formation in
APPswe/PS1dE9 mutants ...........................................................................................70
3. Suberoylanilide hydroxamic acid (SAHA) rescues memory deficits in
APPswe/PS1dE9 mice ................................................................................................71
4. Sodium butyrate (NaB) rescues memory deficits in APPswe/PS1dE9 mice .............72
5. Sodium butyrate (NaB) treatment stabilizes newly consolidated memories in
APPswe/PS1dE9 mutants ...........................................................................................73
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6. Systemic injections of inhibitors of histone deacetylases (HDACi’s) cause elevations
in global histone acetylation .......................................................................................74

III. CLASS I HISTONE DEACETYLASE INHIBITORS DO NOT
ENHANCE HIPPOCAMPAL LTP, BUT DO RESCUE SPINE DENSITY
DEFICITS IN A MOUSE MODEL OF ALZHEIMER’S DISEASE
1. WT vs APPswe/PS1dE9 LTP ....................................................................................94
2. TSA enhances WT LTP..............................................................................................95
3. APPswe/PS1ΔE9 do not have enhanced LTP compared to WT ................................96
4. NaBu enhances LTP in WT control ...........................................................................97
5. NaBu does not enhance LTP in APPswe/PS1ΔE9 .....................................................98
6. Reduced spine density in APPswe/PS1dE9 is rescued by NaBu ...............................99
7. HDAC Protein levels from Tg and WT mice ...........................................................100
8. HDAC3-selective inhibitor does not rescue APPswe/PS1dE9 deficit .....................101

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I. INTRODUCTION

Alzheimer’s Disease
Alzheimer’s disease (AD) is characterized by severe memory impairment and
neuronal degeneration. AD is a progressive neurodegenerative disorder that gradually
causes loss of cognitive function in patients, and eventually leads to death (Cummings
and Cole, 2002). Early in the disease state, symptoms of AD present as an impairment in
episodic memory loss. As the disease progresses, memory loss symptoms become much
worse and are accompanied by neuronal loss found especially in the temporal and frontal
lobes (Braak et al., 1998). Usually, loss of executive function (planning, judgment)
occurs later in the disease course and often, patients are unaware of their memory
dysfunction (Cummings and Cole, 2002). Currently, diagnosis of AD consists of
postmortem identification of amyloid-beta (Aβ) plaques and neurofibrillary tangles in the
brain of patients who present with severe memory loss as described above (Arnold et al.,
1991, DSM-IV, 1994).

Neurofibrillary Tangles (NFTs)
Neurofibrillary tangles (NFTs) are intracellular, filamentous aggregates
comprised mostly of the microtubule-associated protein tau (Grundke-Iqbal et al., 1986).
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