Browsing by Subject "Alzheimer's disease"
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Item AB affects apoE transcriptionally through the activation of B-AR, cAMP and AP-2(2009-09) Rossello, Ximena SerenellaTwo key players in the development of Alzheimer’s disease (AD) are amyloid beta protein (Aβ) and apolipoprotein E (apoE). We and others have reported that Aβ elevates apoE protein levels in astrocytes, which in turn could alter lipid trafficking and cell function. The mechanism for the Aβ-induced increase in apoE levels is not clearly understood. We propose that Aβ affects apoE transcriptionally through the activation of the beta-adrenergic receptor (βAR), cAMP and the activator protein 2 (AP-2). To test this hypothesis it was first determined if the stimulation of apoE protein levels by Aβ was triggered by an upregulation of apoE mRNA, in contrast to changes in secretion or degradation. The results show a time-dependent increase in apoE mRNA expression levels with peak expression reached after 1 hour of Aβ treatment. βAR antagonists were used to evaluate the involvement of the βAR. The antagonists significantly inhibited the Aβ-induced stimulation of apoE mRNA and protein levels. In order to further understand the mechanism behind these results we assessed cAMP role in the proposed Aβ-apoE pathway. This second messenger has been associated with AD and has been shown to elevate apoE message and secretion levels. The data shows an Aβ-dependent elevation in cAMP levels as well as an increase in apoE levels after dBcAMP treatment, confirming the activation of a cAMP-dependent pathway. In addition, I provide evidence that confirms the participation of the transcription factor AP-2, specifically that of AP-2β. AP-2 is known to be unregulated by cAMP and to bind to the apoE promoter. I report an increase in AP-2β translocation to the nucleus after both cAMP and Aβ treatment and confirm its participation in the activation of the apoE promoter. In conclusion, my work reveals a novel pathway for Aβ stimulation of apoE abundance in astrocytes involving βAR and the transcription factor AP-2β. These findings not only help clarify the relationship between Aβ and apoE but also help understand AD progression and possibly show a mechanism that could aid in the fight against this fast growing disease.Item Assessment of movement skills and perceptual judgent in atypical aging.(2012-08) Jor’dan, Azizah-JehanThis study investigated if individuals with either mild cognitive impairment (MCI) or early-stage Alzheimer’s disease (AD) exhibit higher levels of postural motion when engaged in a perceptually demanding visual task, compared to a similar group of typically aging individuals. Participants were well-characterized patients currently enrolled in the Minneapolis Veteran Affairs Medical Center’s, existing protocols for patients (Protocol-Cognitive Changes in Older Adults: A Minneapolis VA Medical Center Database [the GRECC Memory Loss Clinic database]) and normal controls (Protocol-Normative Changes in Older Adults). Fifty-nine volunteer participants enrolled from these protocols. Groups were assigned according to a consensus diagnosis of AD, MCI, and Normal. Twenty-five AD, 19 MCI and 15 Normal participated in the study. Participants completed a visual task comprising two conditions: a control condition (Inspection) - looking only within the perimeter of the blank (white board) target; and an experimental condition (Search) – which required counting the frequency of a designated letter within a text block of randomly presented alphabet letters. Postural motion was recorded as center of pressure (COP) in centimeters, in both the medial-lateral (ML) and anterior-posterior (AP) planes of motion, using a stable motion detecting platform. Results indicate that the AD group was less able to modulate postural motion in the ML plane (postural motion increased when switching from the Inspection task to the Search task); both the MCI and Normal group decreased their postural motion when switching from the Inspection task to the Search task. All groups, in the AP plane, were able to modulate their postural motion when engaged in the more demanding Search task, but the AD recorded significantly higher postural motion than the Normal group. There was no significant difference between the Normal and MCI group; or between the AD and MCI group in the AP plane. When groups were reclassified according to their current Mini-Mental State Exam (MMSE) scores, there was a significant difference between the “Low” MMSE group and the “High” MMSE group, in which the Low group increased their postural motion in the ML plane when engaged in the more demanding Search task. Consistent with the previous analysis, in the AP, all groups were able to reduce their postural motion when engaged in the more demanding Search task. However, both the “Low” and “Middle” MMSE groups, who recorded higher postural motion, differed significantly from the “High” MMSE group. The results extend previous findings with respect to the strength of the perception-action link in aging individuals who experience cognitive change. Deficits in cognitive function related to postural motion, indicate an ‘embodied’ relationship that may be a sensitive measure to early-stage dementia.Item Cellular And Molecular Mechanism Of Action Of The Amyloid-Beta Oligomer Abeta Star 56(2016-01) Amar, FatouAlzheimer’s disease (AD) is a progressive neurodegenerative disorder, with asymptomatic and symptomatic phases. Hallmark lesions of AD include extracellular deposits of fibrillar amyloid-β (A β) and intracellular Neurofibrillary tangle formations (NFTs). However, recent evidence seems to support soluble oligomeric forms of amyloid proteins as bioactive species in AD. Amyloid-β oligomers (Aβo), such as Aβ*56, Aβ dimers and trimers have been demonstrated to be synaptotoxic species in AD. In particular, one of these oligomers, Aβ*56, was found to cause cognitive decline in the AD mouse model Tg2576, despite the absence of plaques and neuronal loss. In addition, cross-sectional studies suggest its possible involvement in the asymptomatic or preclinical phase of AD. However, it is currently unclear how this specific oligomer (Aβ*56) influences cellular and molecular processes to lead to cognitive deficits. My thesis focused on how Aβ*56 is able to disrupt cognition at the cellular and molecular level. First, we demonstrate that Aβ*56 forms a complex with NMDA receptors (NMDARs) resulting in an aberrant increase in intracellular calcium driven by synaptic NMDARs and the specific activation of the Ca2+/calmodulin dependent protein kinase CaMKIIα. Active CaMKIIα induces selective pathological changes in tau in vivo and in vitro, involving hyperphosphorylation and missorting. Importantly, other forms of endogenous Aβ oligomers do not appear to trigger these effects. Furthermore, other kinases such as GSK3, Cdk5 and fyn are not modulated by Aβ*56 in vitro. Interestingly, CaMKII phosphorylation is elevated in brain tissue of aged individuals, correlating with Aβ*56 abundance. These findings indicate that distinct Aβ oligomers activate specific neuronal signaling pathways in a highly selective manner in vitro. By extrapolation, these observations may have important consequences relative to our understanding of the different stages of AD.Item Chronic stress induces cellular senescence: implications for aging and neurodegenerative disorders(2022-06) Lyons, CareyChronic stress can shorten lifespan and is a risk factor for a diverse range of aging-related diseases. Despite the consistency of this relationship, it remains unclear how stress might affect aging biology. An association between stress exposure and induction of a fundamental aging process such as cellular senescence has been proposed, but experimental evidence is lacking. A complicating factor in human and rodent stress research is the variability of stressors and stress responses themselves. This dissertation presents several studies interrogating the biological processes by which chronic stress may affect aging and disease risk, and probing the relevance of stressor type to these effects. The thesis starts with a review of existing literature supporting the hypothesis that chronic psychological stress can induce cellular senescence. Chapter 2 provides the first experimental evidence causally linking chronic stress with an increase in senescent cells. Moreover, it suggests that a social stress model (chronic subordination stress; CSS), and a nonsocial psychological stress model (restraint stress) despite both most prominently affecting the brain, may be biased towards different senescence pathways (p16 or p21 respectively) and brain regions (hippocampus and cortex). Spatial transcriptomic profiling of the brains of CSS-exposed mice implicates the DNA Damage Response and elevated Ras/Raf signaling as mediators of CSS-induced senescence. CSS-induced SNCs also appears to alter the local microenvironment via pathways including interleukin signaling, and changes to the extracellular matrix. They are also associated with elevated glutamatergic neurotransmission. However, a lifelong pharmacogenetic strategy to eliminate senescent cells was detrimental to healthspan and lifespan and further exacerbates CSS-induced deficits in those measures. With the CNS emerging as a key target of stress-induced SNC, Chapter 3 reviews the association between stress and Alzheimer’s disease, with an emphasis on rodent models. Chapter 4 demonstrates differential effects of CSS and restraint stress on a mouse model of tau pathology (PS19) – one of the hallmarks of Alzheimer’s disease (AD). Although our study found only minor detrimental effects of either model, CSS appears to affect some cognitive function via a tau-independent mechanism. Lastly, Chapter 5 presents an unbiased analysis of the proteomic changes shared by mice exposed to lifelong CSS and AD patients. This work replicates the lack-of-effect of CSS on tau pathology, while demonstrating that most of the overlapping proteins were functionally associated with enhanced NMDA receptor mediated glutamatergic signaling, an excitotoxicity mechanism known to affect neurodegeneration. These findings support the association between stress and AD progression and provide valuable insight into potential early biomarkers and protein mediators of this relationship. The results of these studies provide novel insight into the mechanisms by which stress may affect aging and risk for neurodegenerative disease.Item Credible Subgroups: Identifying the Population that Benefits from Treatment(2017-05) Schnell, PatrickA single treatment may have a different effect on different patients. In particular, some patients may benefit from a given treatment while others do not. Often, some of the variation in effect among patients can often be explained by characteristics of those patients that are observable before treatment. Widespread acknowledgment of treatment effect variation due to observable patient characteristics has increased the health science community's interest in a broad field referred to as personalized or precision medicine. Among the aims of precision medicine are identifying the set of treatments that would benefit a given patient, and conversely, identifying the population of patients who would benefit from a given treatment. We treat the latter problem in the context of clinical trials run by treatment developers (e.g., pharmaceutical companies), with special attention paid to interactions between those developers and the relevant regulatory agencies (e.g., the US Food and Drug Administration). The primary difficulty in estimating the benefiting population in such settings is controlling the frequency with which at least one type of patient is incorrectly determined to benefit, and doing so in a way that does not render the approach excessively conservative. As a motivating application throughout this dissertation, we consider a battery of related clinical trials of treatments for Alzheimer's disease carried out by the pharmaceutical company AbbVie. These trials contain a small number of continuous and binary baseline patient characteristics that may influence the treatment effect. We apply standard and more novel regression models to the supplied data and develop methods of inference to accommodate the varied features of the datasets, such as nonlinear effects, multiple important endpoints, more than two treatments, and regions of the covariate space that are sparse in observations or lacking common support among treatment arms. We also discuss topics in practical implementation of these methods. Our approaches yield reliable and easily interpretable inferences regarding the population that benefits from treatment.Item Impact of the revised life review program on quality of life for residents with Alzheimer’s disease in South Taiwan’s long term care facilities.(2010-03) Lin, Li-jungQuality of life (QOL) is the goal for services to elders particularly those with Alzheimer's Disease (AD) for whom successful outcomes are likely to mean small improvements. There is no universal definition of QOL or consensus on what components constitute the phenomena. Therefore, it is difficult to compare efficacy of services or service providers, or to know whether or not QOL has been achieved. Lawton (1997) advocates for defining QOL as a multidimensional phenomenon that cannot be evaluated as a single entity nor measured by one instrument and that must be evaluated from subjective and objective perspectives. This study investigates the efficacy of a revised version of the life review program (LRP-TW) to influence improvement in the QOL of elders with mild to moderate AD in four long term care facilities in South Taiwan when QOL is construed as a multidimensional entity (i.e. SF-36, MMSE, and GDS). An experimental, repeated-measure design was employed with 34 residents in four facilities randomly assigned to experimental and control groups. The experimental group participated in the 10-week, bi-weekly, LRP-TW; the control group received the typical programs routinely delivered to the residents in each of the facilities. The LRP-TW, framed by continuity and developmental theories (Erikson, 1950; Atchley, 1989) and life review reminiscence (Butler, 1963), included life stage relevant activities reflective of the Taiwan culture of earlier times that correspond to the dates when the subjects would have been at each successive stage. Quantitative analyses of data revealed that objective and subjective indicators of QOL were significantly intercorrelated to each other, but the LRP-TW did not significantly affect the objective and subjective measures of QOL. However, qualitative analyses of data revealed that the LRP-TW successfully applies a variety of leisure activities as tools to trigger each participant's past leisure experiences and related memories. The LRP-TW is promotable as a recreational therapy intervention in long term care facilities throughout Taiwan. Further study with a larger sample size and efficient measuring strategy continuing the search for reliable methods for measuring QOL as a multi-dimensional compound model are needed.Item INSULIN TRAFFICKING PERTURBATIONS AT THE BLOOD-BRAIN BARRIER IN ALZHEIMER’S DISEASE MODELS(2017-11) Sarma, VidurAlzheimer’s disease (AD) is recognized as a multifactorial disease and a major cause of dementia in the elderly. Pathological hallmarks of AD include brain amyloid beta (Aβ) deposits and intraneuronal tangles of hyperphosphorylated tau protein. Reduction of brain Aβ burden is widely considered as a viable therapeutic strategy for AD, and developing methods to promote brain Aβ clearance has been at the forefront of AD research. Recent clinical trials conducted in a small group of AD patients demonstrated the efficacy of intranasally-administered insulin in improving memory and reducing brain amyloid burden (Craft et al., 2012). Although the mechanism of insulin action is not clear, epidemiological studies have linked type 2 diabetes (T2DM), characterized by hyperinsulinemia and peripheral insulin resistance, with cognitive decline and amyloid burden in AD (Matsuzaki et al., 2010). One possibility is that hyperinsulinemia damages the cerebrovascular endothelium, referred to as the blood brain barrier (BBB). The BBB is a major signaling and material trafficking pathway between plasma and brain that not only delivers glucose and insulin to brain but also serves as the primary clearance portal for brain Aβ (Storck et al., 2016; Yuede et al., 2016). Hence, T2DM could augment AD pathology by inhibiting insulin delivery and disrupting brain Aβ clearance. Although, intranasal insulin may remedy the situation, this approach may limited, due to variable absorption of insulin into CNS. Moreover, insulin is a growth factor with multiple physiological targets; hence, chronic insulin therapy will have off-target effects. As a fundamental approach, critical insulin-responsive cellular and molecular pathways that facilitate Aβ trafficking should be identified. Only through elucidating these dysfunctions in AD/T2DM can novel therapeutic targets be rationally sought. In this work, the key questions concern the dynamics of insulin transport from systemic circulation into brain via the BBB and the disruption in insulin trafficking caused by Aβ peptides in AD brain. Importantly, molecular components in the insulin trafficking/signaling pathway that are disturbed by Aβ exposure were identified as well as the perturbed insulin delivery and brain insulin resistance. This new knowledge will facilitate the search for novel therapeutic targets for AD. I have been investigating mechanisms triggering insulin scarcity in AD brains by conducting kinetic biodistribution and SPECT/CT imaging assays in Aß peptide over-producing transgenic mice (APP/PS1), insulin resistant db/db (leptin receptor deficient) and aged WT mice. I analyzed plasma pharmacokinetic and dynamic brain uptake data by 3-compartmental analysis on SAAM© and discovered differences in distribution rate constants between WT and the insulin-resistant mouse groups. Upon simulating tissue distribution of a given dose of insulin in a 3-compartmental Stella© model with the estimated rate constants, I discovered that APP/PS1, db/db aged, and Aβ40/Aβ42 pre-treated WT mouse display higher plasma AUC and lower brain AUC levels of insulin, as compared to healthy, young WT mice. This led us to a hypothesis that Aß40 and Aß42 interfere with the transport of insulin into the brain parenchyma. Now, the appearance of systemic insulin in the brain parenchyma is contingent upon insulin receptors (IR) expressed by BBB endothelial cells. Therefore, I employed human cerebrovascular microendothelial cells (hCMEC) and over-expressed hCMEC monolayers with IR to investigate mechanistic interactions between Aß peptides and insulin transcytosis across the BBB. The processes involved in insulin transcytosis across BBB endothelial cells are postulated to operate in tandem with downstream signaling cascades. I studied variables in IR-mediated transport processes and correlated the results with shifts in phosphorylation of proteins expressed in downstream insulin signaling pathways, as a consequence of Aß peptide exposure. Through flow cytometry and radioactive Transwell© transport assays, I discovered that the IR-mediated uptake, permeability and exocytosis of insulin across hCMEC/D3 cells were significantly impaired by pre-exposure to Aβ40 and Aβ42. With help of FRAP/FLIP imaging analyses, I found that the half-life of lateral diffusion and exocytic recycling of IR in response to insulin was increased in presence of Aβ40 and Aβ42. With respect to hCMEC/D3 signal transduction downstream of IR, Western Blot analyses confirmed that Aβ40 and Aβ42 excessively activated the phosphorylation of the IR-β subunit at Tyr1162/1163 and decreased the phosphorylation of Akt at Ser 473. In addition, reverse-phase protein array (RPPA) assays revealed that phosphorylation of MAPK3 was increased whereas that of caveolin-1 was decreased due to Aβ40 and Aβ42 exposure. My results lead to conclude that Aβ peptides interfere with insulin signaling/trafficking at the BBB and reduce insulin availability in the AD brain. It is therefore imperative to rectify motifs which result in impaired insulin signaling at the BBB to improve its transport into the brain parenchyma.Item A Longitudinal Analysis of the Effects of the NYU Caregiver Intervention-Adult Child on Subjective Health(2020-11-10) Albers, Elizabeth, AObjective: The present study examined whether the NYU Caregiver Intervention for Adult Children (NYUCI-AC) influenced the subjective health of adult child family caregivers of persons with dementia. Methods: A randomized controlled trial, conducted between 2006 and 2012, compared outcomes among a psychosocial intervention group to usual care controls. One hundred and seven adult child caregivers of persons with dementia were included in the sample (n=54 assigned to the intervention group; n=53 assigned to the usual care control group). Participants were assessed up to eight times; every four months in the first year, then every six months afterwards. The current study focused on the effects of the NYUCI-AC on changes in self-rated health over the study period. Results: Growth curve models found that self-rated health among intervention group and control group caregivers did not differ over the study period. No effect of the intervention on self-rated health emerged over time after controlling for baseline differences in gender and satisfaction with social support. Conclusions: The NYUCI-AC is a multicomponent psychosocial intervention that provides counseling and support to adult child caregivers and did not alter subjective health over time.Item Microfabrication Approaches for Understanding the Role of Vascular Mechanics in Progressive Diseases(2016-08) Hald, EricVascular disease is a common cause of death that typically results from long-term alteration of vessel structure and function. The underlying mechanisms that lead to pathologic changes in the vasculature are largely unclear, especially in progressive diseases of the cerebral vessels. With the growing prevelance of blast traumatic brain injury in modern warfare, never before has investigation of cerebral vascular disease been more pertinent. Here, we focus on the development of microfabrication experimental approaches for probing the critical mechanical and biochemical pathways involved in progression of diseases, such as cerebral vasospasm, subarachnoid hemorrhage, and Alzheimer’s disease, that often result from TBI. First, we develop a microfluidic patterned deposition technique for studying functional mechanics in chronic vascular disease at the tissue scale. We modify substrate surfaces with genipin, a natural crosslinker, to extend culture times of in vitro vascular tissues that mimic native tissue structure and function. We successfully validate our technique, showing maintenance of patterned structural alignment and mechanical function over the course of two weeks. Lastly, we investigate the relationship between vascular disease and Alzheimer’s disease. Amyloid beta is a key precursor in the development of Alzheimer’s disease that accumulates in neuronal and cerebrovascular tissue and can result in neurodegeneration. During the development of cerebral amyloid angiopathy (CAA), which is present in over 80% of Alzheimer's disease cases, amyloid beta plaques form in the cerebral vessel walls and lead to severe attenuation of physiologic vasodilation. We measured the effect of amyloid beta treatment on vascular smooth muscle cell functional contractility using a single-cell traction force microscopy technique and developed a thin-walled arterial model for growth and remodeling response to mechanical perturbations. We found that amyloid beta induces a reduction in vascular smooth muscle cell mechanical output. We implemented this loss of function into a constrained mixture arterial model that suggests vessel growth and remodeling, in response to amyloid beta-mediated alteration of smooth muscle function, can lead to an inability of cerebral vessels to vasodilate. Our findings provide a possible explanation for the vascular injury and malfunction often associated with the development of neurodegeneration in Alzheimer’s disease.Item Personal Perspectives on Alzheimer’s Disease in Morocco(2017) Krueger, AllisonThe number of people affected with dementia worldwide is expected to increase dramatically in the coming decades. Alzheimer’s disease is the most common type of dementia, which is characterized by progressive memory loss and increasing behavioral changes throughout the course of the fatal disease. This growing healthcare concern affects not only those with the disease, but caregivers and family members as well. Understanding the unique challenges of affected families across cultures can be useful in providing culturally competent healthcare and providing support resources for patients and their families. This study investigated the major issues faced by families affected by Alzheimer’s disease in Morocco and the support resources available through a site visit, in-country library research, and semi-structured interviews to gain an in-depth understanding of the effects of the disease from multiple perspectives. Results indicate that there are at least four aging centers in Morocco, either in construction or already functioning, to provide caregiver support and education on Alzheimer's disease. Two out of three of the interview participants believe that Alzheimer's disease is not a major health priority on a national scale compared to other acute diseases.Item The Potential to Generate Exogenic Interneurons for Alzheimer’s Disease via Blastocyst Complementation(2022-12) Johnson, SetherAlzheimer’s disease (AD) currently affects millions of patients worldwide, and to date the development of effective therapies has been slow. In AD, numerous types of neural cells become dysfunctional and are susceptible to degeneration, leading to cognitive deficits. One particular cell type affected are GABAergic inhibitory interneurons. Normally, these cells function as modulators of neural circuits, and are associated with maintenance of network synchrony and oscillatory signaling important for memory encoding. Impairments in short term memory, electrophysiological abnormalities such as neural hyperactivity and epileptiform spikes, and loss of interneurons are seen in AD patients and AD mouse models. These observations suggest that degeneration and dysfunction of interneurons contributes to cognitive deficits in AD. Thus, restoring interneuron activity is one potential approach to treat AD. The generation of exogenic interneurons via blastocyst complementation is one promising method to generate these cells. In this method, interspecies chimeras are created by genetic editing in a host blastocyst, which establishes a developmental niche to be filled during expansion of the progeny of donor pluripotent stem cells (PSCs) injected into the blastocyst. Blastocyst complementation has several advantages compared to in-vitro directed differentiation of stem cells, namely that development occurs in an in-vivo context. Thus, progenitor cells are exposed to all the inductive cues needed for differentiation to the appropriate cell phenotype of interest, and therefore may more faithfully recapitulate the intended cell-type specific gene networks and biomolecular characteristics of those cells. Studies have shown that this technique can be applied for CNS tissues including specific brain regions. Specifically, previous work from the Low Lab at the University of Minnesota has shown that targeting the homeobox gene HHEX establishes a niche for the formation of various organs from donor cells including liver, pancreas, and brain (Ruiz-Estevez et al., 2021). HHEX may be a viable target gene for the generation of exogenic interneurons as previous work has indicated that knockout of HHEX impairs development of the medial ganglionic eminence (MGE), a developmental structure enriched in GABAergic interneuron progenitors (Martinez-Barbera et al., 2000). In addition, many studies have demonstrated that engraftment of MGE cells can reduce cognitive and electrophysiological deficits in AD mouse models. This suggests that the transplant of exogenic interneurons may be a feasible strategy to restore interneuron activity and reduce cognitive deficits in AD. While the generation of human-animal brain chimeras is controversial, recent surveys indicate the public is amenable to the concept for research and therapeutic use (Crane et al., 2020). Thus, future translation of this approach using human-porcine chimeras may provide exogenic human interneurons to treat AD patients. This thesis will describe the scientific background and rationale for exogenic interneuron generation by HHEX KO/blastocyst complementation as a potential approach to treat AD. It will also show preliminary analysis of HHEX KO/complemented mice, and show testing of a primary antibody for Lhx6 in wild type mouse tissue prior to the antibody being used to search for donor-derived interneuron progenitors in chimeras.Item Protein prenylation in the pathogenesis of Alzheimer’s Disease and its therapeutic potential(2021-06) Jeong, AngelaWith the unprecedented growth of senior population, Alzheimer’s disease (AD) has risen in prevalence to approximately 50 million people afflicted worldwide. While the molecular mechanisms underlying the AD pathogenesis have yet to be elucidated, emerging evidence suggests that a key posttranslational lipid modification of proteins, called prenylation, may play an important role in the pathogenesis of AD. Isoprenoids, including farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), are synthesized from mevalonate in the cholesterol biosynthesis pathway, and the attachment of these lipid prenyl groups is catalyzed by farnesyltransferase (FT) and geranylgeranyl transferases (GGTs), respectively. Once prenylated, proteins localize to cell membranes, where they interact with downstream effectors, and regulate various cellular processes. Multiple lines of evidence have shown that modulation of protein prenylation affects AD neuropathology. To investigate the contribution of each prenylation pathway to AD pathogenesis, our laboratory previously generated the transgenic AD model mice (APP/PS1) with systemic haplodeficiency of FT or GGT. While haplodeficiency of either FT or GGT reduced Aβ deposition and neuroinflammation, only FT haplodeficiency rescued cognitive deficits, suggesting distinct functions of the two prenylation pathways. To follow up on the previous work, my dissertation research is aimed to: 1) investigate the AD pathology-associated changes in prenylation; 2) elucidate the role of neuronal FT in the AD pathogenesis; 3) identify prenylation substrates involved in AD pathogenesis, which can be potentially targeted for therapeutic development. Studies with postmortem human brain tissue samples from two cohorts found that FT levels and the farnesylation of H-Ras were significantly elevated in the brains with AD. In line with this evidence from human samples, neuronal FT deletion attenuated memory impairment and mitigated the Aβ levels by reducing its production as well as normalizing the heightened mTORC1 activity in APP/PS1 mice. Finally, experiments employing a novel prenylomic profiling approach identified proteins whose prenylations were significantly upregulated in APP/PS1 mice compared to WT controls. Taken together, the findings from my dissertation research indicate that aberrant upregulation of protein farnesylation contributes to the pathogenic process of AD, and targeting protein farnesylation and/or downstream signaling pathways of farnesylated proteins may confer therapeutic benefits against AD.Item The Role of High-Density Lipoproteins and Related Pathways in Alzheimer’s Disease(2017-12) Hottman, DavidAlzheimer’s disease (AD) is the most prevalent age-related dementia and will place an increasingly demanding burden on our healthcare system as the population ages. It has been firmly established that high plasma levels of high-density lipoprotein (HDL) protect against cardiovascular disease and accumulating evidence indicates that the beneficial role of HDL extends to the central nervous system. There are several important biological mechanisms that regulate HDL generation and metabolism/function. One is through the cholesteryl ester transfer protein (CETP), which transports cholesterol esters and triglycerides between different lipoprotein particles. Loss-of-function mutations in CETP are associated with better cognition in aging. To investigate the role of CETP in AD, human CETP transgenic mice were crossed with an Alzheimer’s mouse model, followed by biochemical and behavioral analyses. The results showed that CETP-induced modest decrease in plasma HDL levels was insufficient to affect brain amyloid pathology, neuroinflammation, or memory function. Next, to explore the therapeutic potential of a cardiovascular protective, HDL-mimetic-peptide called D-apoJ[113-122], AD mice were treated with the peptide. This treatment robustly reduced brain amyloid pathology and improved memory function in AD mice. Further analyses showed that D-apoJ[113-122] exerted its beneficial effects through reduction of cerebral vascular amyloid deposition and clearance of brain amyloid to plasma. Finally, prenyltransferase-deficient mice were used to investigate the role of protein prenylation in synaptic function. Prenylation is an important posttranslational lipid modification process that attaches isoprenoids (the intermediates in the cholesterol biosynthesis pathway) to target proteins. Electrophysiological/histochemical experiments showed that systemic or forebrain-specific deficiency of one particular prenyltransferase, geranylgeranyltransferase-1, caused marked impairment in hippocampal synaptic plasticity and decrease in neuronal dendritic spine density. Further analyses indicated that reduction of prenylation of certain small GTPases, which rely on prenylation for proper cellular localization and function, underlies the detrimental effects in these mice, as observed in aged mouse brains. These results corroborate the critical role of protein prenylation in synaptic function during development and in the adult brain. Taken together, findings from this research provide novel insights into the role of HDL and related pathways in the pathogenesis of AD, and offer new avenues to develop effective therapies for AD.Item Trafficking of Amyloid beta protein at the Blood Brain Barrier: Novel Insights in Alzheimer's Disease Pathogenesis(2016-12) Sharda, NidhiAlzheimer’s disease (AD) is the most common form of dementia in elderly population. Unfortunately, the current treatment approaches for AD are symptomatic and do not interfere with the disease progression at any stage. The risk of AD increases with age; from 12 %, above 70 years of age, to 50 % beyond 80 years of age. Due to an improvement in average life span in many regions across the globe, AD is being recognized as a major socio-economic health problem that is expected to worsen in the near future. Also, with 99.6 % of current clinical trials failing in AD due to insufficient knowledge of the disease targets and lack of early diagnostic methods; detailed investigations into AD pathogenesis is critically important. Development of amyloid beta (Aβ) plaques in the brain is one of the primary pathological hallmarks of AD. Impaired clearance and not overproduction of toxic Aβ proteins leads to their accumulation and subsequent plaque formation in sporadic AD that accounts for more than 90 % of total AD cases. Blood brain barrier (BBB) is expected to be the primary clearance portal of Aβ from the brain. Being at the interface between brain and plasma, the BBB also maintains the dynamic equilibrium of brain and plasma Aβ pools. This equilibrium is believed to be perturbed in AD due to BBB dysfunction. However, the manifestations of BBB dysfunction and the precise mechanisms that may trigger it, are not clearly understood. Two major Aβ isoforms, Aβ40 and Aβ42, play a predominant role in AD pathogenesis. Aβ42 is believed to be pathological whereas Aβ40 is constitutively expressed and believed to have protective properties against neurological anomalies. Also, Aβ40 expression is 10- and 1.5- fold higher than Aβ42 in cerebral spinal fluid (CSF) and plasma, respectively. This ratio of Aβ42:Aβ40 increases in brain and decreases in plasma, respectively, during disease progression. However, the pathophysiological mechanisms driving this clinical observation is not known yet. In my thesis, I demonstrate distinct age dependent changes in the BBB permeability and plasma exposure of Aβ40 and Aβ42 at the BBB endothelium in wild type (WT) and AD-transgenic (APP,PS1) mice. Further, to investigate the pathophysiological mechanisms driving these observations, I conducted in-vitro studies in polarized hCMEC/D3 monolayers, a widely used BBB model, and demonstrated that Aβ40 and Aβ42 are internalized at the BBB endothelium via clathrin- and lipid raft-mediated endocytosis, respectively. This mechanistic difference offers an opportunity to the BBB to independently handle and modulate the clearances of Aβ40 and Aβ42. Also, in-vivo investigations coupled with quantitative modeling, have indicated that Aβ40 may accumulate more than Aβ42 at the BBB endothelium. This may decrease Aβ40 transcytosis at the BBB and increase the exposure of the BBB endothelium to the vasculotropic Aβ40. To investigate the mechanisms driving this observation, I tested the hypothesis published by our lab previously that the impaired transcytosis of Aβ40 at the BBB endothelium is due to the perturbed vesicular exocytosis. Also, synaptic transmission involving SNARE exocytosis machinery is known to be impaired in AD. Thus, I investigated the ability of Aβ40 and Aβ42 to perturb the SNARE exocytosis machinery at the BBB endothelium and in neurons, in comparison with tetanus neurotoxin, a well-established disruptor of the VAMP-2 mediated exocytosis. My findings reveal that Aβ40 and Aβ42 isoforms use VAMP-2 (vesicular SNARE) to exocytose at the BBB endothelium and neurons. Further, using fluorescence resonance energy transfer (FRET) and lifetime microscopy (FLIM), I have demonstrated that Aβ40 and Aβ42 interfere with the functioning of SNARE fusion between VAMP-2 and SNAP-25. Moreover, my findings suggest that Aβ40 may be more efficient than Aβ42 in perturbing this process, and consequently may interfere with its own exocytosis. In summary, my work provides evidence for the presence of distinct clearance mechanisms of Aβ40 and Aβ42 isoforms at the BBB endothelium. This novel assertion provides a framework to explain the disrupted clearance of Aβ, perturbed Aβ42:Aβ40 ratios and dysregulated transport of Aβ and other endogenous proteins at the BBB endothelium observed in AD patients. These findings could be applied to identify new drug targets to ameliorate BBB dysfunction in AD.