The presence of white matter hyperintensities (WMH) and silent infarcts on magnetic resonance imaging is a common finding in elderly individuals. This subcortical ischemic vasculopathy is associated with age and cerebrovascular risk factors and can increase the risk of dementia, yet the contribution of subcortical vascular disease to the clinical profile and progression of Alzheimer’s disease patients is still relatively poorly understood. This study assessed the presence, severity and progression of WMH and lacunar infarcts and studied their relationship with measures of brain function and cognition in 64 patients with Alzheimer’s disease. Both a visual rating scale and volumetric tissue segmentation analysis were used to evaluate brain-behaviour relationships of WMH seen on T2-weighted and Proton Density MRI scans. In addition to describing the topographical distribution of WMH and lacunes, and examining sex differences, the volume and location of WMH were correlated with executive function, frontal lobe perfusion, and medial temporal lobe atrophy. The results confirm and extend previous findings suggesting that WMH are located primarily in the frontal and parietal regions and are associated with mild decline in tasks of executive function. WMH severity was not associated with a decrease in frontal lobe perfusion as measured by Single Photon Emission Computed Tomography. The investigation of different WMH subtypes revealed that lacunar infarcts were found most often within deep WMH. At one year follow-up, progression was seen in deep WMH, specifically in the frontal lobe and in lacunes found within the periventricular regions. Furthermore, progression in WMH was associated with a decline in cognition. Taken together, these studies indicate the utility of measuring WMH by subtype (periventricular and deep WMH and lacunes) in understanding progression patterns and brain-behavior relationships. Since, subcortical ischemic vasculopathy may be potentially preventable; this study underlines the need to study interventions that address risk factors for the development of small vessel cerebrovascular disease, which may be helpful in preventing disability in the elderly.

Alzheimer’s disease (AD), a progressive age-related neurodegenerative disorder is characterized by impairments in memory and cognitive functions. The two main pathogenic hallmarks associated with the progression of this multifactorial disease include accumulation of amyloid-beta (Aβ) plaques and the deterioration of the cholinergic system in the brain. Using cost-effective synthetic procedures, mono-, di-, and tri- substituted sym-triazine derivatives incorporating acetylcholine substrate analogues and aromatic phenyl moieties were synthesized for the targeted modulation of Aβ aggregation and acetylcholinesterase (AChE) activity. A subset of these sym-triazines demonstrated dual inhibition of Aβ fibrillization and AChE hydrolytic activity in vitro studies. These highly effective compounds were also shown to be well tolerated by differentiated human neuronal cells in cell viability tests. These novel compounds have the potential to undergo future in vivo pharmaceutical analysis and have a positive impact on the quality of life of the people living with this devastating disease and their caretakers.

There is evidence that the excitotoxin quinolinic acid (QUIN) synthesized through the kynurenine pathway (KP) by activated microglia may play a role in the pathogenesis of several major neuroinflammatory diseases and more particularly in Alzheimer??s disease (AD). The hypothesis of this project is QUIN affects the function and morphology of astrocytes. In this study I used human foetal astrocytes stimulated with AD associated cytokines including IFN-gamma, TNF-alpha, TGF-alpha and different concentrations of QUIN ranging from low physiological to high excitotoxic concentrations. I found that QUIN induces IL-1beta expression in human astrocytes and subsequently, contribute to the inflammatory cascade that is present in AD pathology. Glial fibrillary acid protein (GFAP) and vimentin protein expression were complementary in expression to each other after 24 hr stimulation with different QUIN doses. However, there were marked increases in GFAP levels and reduction in vimentin levels compared to controls with QUIN treatment indicating that QUIN can trigger astrogliosis in human astrocytes. Glutamine synthetase (GS) activity was used as a functional metabolic test for astrocytes and I found a dose-dependent inhibition of GS activity by QUIN. This inhibition was inversely correlated with iNOS expression whereby reduced GS activity is accompanied with an increase expression of iNOS in human astrocytes. These results suggest that reduction in GS activity can lead to accumulation of extracellular glutamate then leading to exacerbated excitotoxicity via NMDA receptor over-activation and ultimately neuronal death. PCR array results showed that at least four different pathways were activated with pathological concentration of QUIN including p38 MAPK that is associated with pro-inflammatory cytokine production, ERK/MAPK growth and differentiation that can modulate structural proteins, mitochondrial-induced apoptotic cascade and cell cycle control pathway. QUIN-induced astrogliosis and excitotoxicity could lead to glial scar formation and prevention of axonal growth thus exacerbation of neurodegeneration via synaptosomal NMDA receptor over-activation. All together, this study showed that, in the context of AD, QUIN is an important factor for astroglial activation, dysregulation and death, which can be mediated by the previously mentioned pathways.

ABCA7 is the closest homologue of ABCA1, which is established to play a key role in reverse cholesterol transport. ABCA1 deficiency causes Tangier disease and several ABCA1 modulations have been recently associated with Alzheimer’s disease. Prior research on ABCA7 focused on its role in macrophage lipid efflux and phagocytosis, however, tissue expression studies in mice revealed that ABCA7 is highly expressed in the brain. The function of ABCA7 in the brain is unknown and the purpose of this thesis was therefore to investigate the potential function of ABCA7 in the brain and the possible implications for Alzheimer’s disease. This was achieved by using in vitro models that transiently express ABCA7 and in vivo models including ABCA7 knockout (ABCA7 KO) mice and human APP transgenic (APPSwInd Tg) mice. ABCA7 was shown to potently stimulate cholesterol efflux from cells to extracellular apoE acceptors. Additionally, apoE expression was decreased by 20% in the brains of ABCA7 KO mice compared to wild type littermate controls and by 46% in ABCA7-deficient macrophages. In vitro models that stably express human APP protein demonstrated that the transient expression of ABCA7 increased intracellular APP targeting, which led to the inhibition of APP processing and a resultant decrease in the production of Aβ. In addition, ABCA7-deficient macrophages displayed impaired capacity to endocytose and degrade Aβ oligomers. Finally, in aged APPSwInd Tg mice where abundant amyloid plaques were present, ABCA7 expression was significantly decreased by 48%. Since cholesterol homeostasis modulates APP processing, the findings of this thesis suggest that ABCA7 may have a role in maintaining cellular cholesterol homeostasis via cholesterol efflux to apoE acceptors and possibly by regulating intracellular trafficking of specific membrane proteins. In summary, ABCA7 was clearly shown in this thesis to have an effect on Aβ generation, clearance and degradation. Furthermore, ABCA7 expression was also affected by Aβ deposition in the brain. Even though more work is required to further elucidate the exact function of ABCA7, the findings presented in this thesis provide the first clues to the function of ABCA7 in the brain.

The prevalence of chronic pain is known to increase with advancing age, with over 50% of community dwelling older adults (aged 65 years and over) and up to 80% of those residing in nursing homes estimated to be suffering some form of persistent or recurring pain complaint. In addition to a greater likelihood of pain, advancing age is associated with increased reports of pain interference. It is possible to ascribe age-related changes in pain report and impact to increased disease prevalence and severity in older people. However, there is also evidence that ageing has effects on pain perception, central pain processing, and plasticity of pain responses that are not explained by co-morbid disease. / The increased prevalence of chronic pain in older adults represents a major public health concern. As a result of increased life expectancy and the post-World War II baby boom, there will be a dramatic change in the demographic structure of our population over the coming decades, with older adults representing the fastest-growing segment of our communities. The proportion of the total population over the age of 65 in Australia has risen from 9% in 1976, to 12% in 2001, and is predicted to reach 16% by the year 2016. Pain that is undetected or under-treated can adversely affect quality of life for older adults, leading to diminished mood, impaired cognition, behavioural problems, as well as increased functional dependence. This in turn contributes to greater demands for daily personal care and a resultant increase in health-care costs. / Pain management is a particularly salient issue in the case of older adults with dementia, who are at increased risk of undetected pain on account of impaired cognition and communication skills. Indeed, clinical reports show that patients with Alzheimer’s disease (AD) are routinely administered fewer pain-relief medications compared with their cognitively-intact peers. Understandably, reports of reduced analgesia in AD have sparked considerable research interest, and over recent years there has been a marked increase in the number of studies aimed at better characterising the experience of pain in patients with AD. However, despite these efforts, the effects of neurodegeneration on pain processing, and the specific ways in which the disease process impacts on brain responses to noxious stimulation and the ensuing experience of pain have not been previously determined. / Improved management of pain is fundamental to the clinical care of older adults, particularly those with dementia. However, the potential to adequately counteract pro-nociceptive processes and facilitate endogenous inhibitory mechanisms in the treatment of ongoing pain in older adults will only become possible once the effects of ageing and age-related neurodegeneration on central pain processing are identified and described. The overarching goal of this thesis was therefore to improve current understanding of the ways in which normal ageing and Alzheimer’s disease impact on the perception and central nervous system processing of pain. The findings of this thesis provide valuable new insights into the impact of ageing and AD on the central mechanisms contributing to pain perception, and may therefore contribute toward better management and treatment of pain in this vulnerable and rapidly growing sector of our community. / Thesis outline: Chapter 2 provides a review of the background literature and rationale for the thesis. The chapter begins with a discussion of current understanding of pain as a multidimensional phenomenon shaped by sensory, emotional and cognitive components, and leads into a description of neural mechanisms of nociception, as well as the supraspinal processes involved in the elaboration of nociceptive signals into these aspects of pain. The impact of ageing on the structure and function of central nervous system regions underlying these processes are discussed, along with the findings from previous clinical and empirical data which suggest age-related changes in pain perception. Current understanding of the neuropathological and clinical aspects of AD is reviewed, with particular emphasis on potential ways in which the disease may impact on central nociceptive processing and the behavioural response to pain. This is followed by a review of the previous clinical and empirical literature examining pain perception in AD. Finally, the aims of the current thesis are outlined. / Chapter 3 describes the general methods which were employed in the subsequent empirical chapters in order to address the aims of the thesis. The equipment and psychophysical procedures used to assess pain perception in healthy young and older adults and patients with AD are described. The basic principals of magnetic resonance imaging (MRI) are then outlined, and the utility of structural and functional MRI for assessing age-related and disease-related changes to brain regions involved in pain perception and processing are discussed. The empirical studies which were undertaken to identify the impact of ageing and AD on central pain processing are presented in the next three chapters. / Chapter 4 begins with psychophysical studies comparing sensory and emotional responses to pain in healthy young and older adults, and follows with MRI investigations of age-related differences in brain volumetry and pain-related brain activity. Studies of pain sensitivity and pain-evoked brain activity in patients with AD compared with age-matched controls are presented in Chapter 5. Following on from these findings of AD-related differences in pain-evoked brain activation, the study described in Chapter 6 used functional connectivity analysis in order to assess the impact of AD on the functional integration of brain regions underlying the sensory, emotional, and cognitive aspects of pain. / The key findings presented in the preceding three chapters are summarized in a general discussion in Chapter 7. The implications of the findings, in terms of the clinical management of pain in older adults with and without Alzheimer’s disease are discussed. The opportunity is also taken to discuss some of the limitations of the present research, and finally, recommendations are made for future research directions.

ABCA7 is the closest homologue of ABCA1, which is established to play a key role in reverse cholesterol transport. ABCA1 deficiency causes Tangier disease and several ABCA1 modulations have been recently associated with Alzheimer’s disease. Prior research on ABCA7 focused on its role in macrophage lipid efflux and phagocytosis, however, tissue expression studies in mice revealed that ABCA7 is highly expressed in the brain. The function of ABCA7 in the brain is unknown and the purpose of this thesis was therefore to investigate the potential function of ABCA7 in the brain and the possible implications for Alzheimer’s disease. This was achieved by using in vitro models that transiently express ABCA7 and in vivo models including ABCA7 knockout (ABCA7 KO) mice and human APP transgenic (APPSwInd Tg) mice. ABCA7 was shown to potently stimulate cholesterol efflux from cells to extracellular apoE acceptors. Additionally, apoE expression was decreased by 20% in the brains of ABCA7 KO mice compared to wild type littermate controls and by 46% in ABCA7-deficient macrophages. In vitro models that stably express human APP protein demonstrated that the transient expression of ABCA7 increased intracellular APP targeting, which led to the inhibition of APP processing and a resultant decrease in the production of Aβ. In addition, ABCA7-deficient macrophages displayed impaired capacity to endocytose and degrade Aβ oligomers. Finally, in aged APPSwInd Tg mice where abundant amyloid plaques were present, ABCA7 expression was significantly decreased by 48%. Since cholesterol homeostasis modulates APP processing, the findings of this thesis suggest that ABCA7 may have a role in maintaining cellular cholesterol homeostasis via cholesterol efflux to apoE acceptors and possibly by regulating intracellular trafficking of specific membrane proteins. In summary, ABCA7 was clearly shown in this thesis to have an effect on Aβ generation, clearance and degradation. Furthermore, ABCA7 expression was also affected by Aβ deposition in the brain. Even though more work is required to further elucidate the exact function of ABCA7, the findings presented in this thesis provide the first clues to the function of ABCA7 in the brain.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available online.

Thesis (PhD.)--Duquesne University, 2007. / Title from document title page. Abstract included in electronic submission form. Includes bibliographical references (p. 180-194) and index.

Thesis (M.S.)--Ohio University, 2002. / Title from PDF t.p.

Dissertation (Ph.D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.