Jennifer L. Bizon - US grants

The basal forebrain cholinergic system plays an important role in cognitive functions such as memory and attention [8-13, 48-49], and it is therefore of great concern that cholinergic cells are particularly vulnerable to injury-and age-related degeneration. Previous research describes nerve growth factor (NGF), obtained by cholinergic cells via retrograde transport from cortical targets, as the critical substance in maintaining the viability of cholinergic neurons. Recent findings in this laboratory and others, however, indicate a much more complex interaction between endogenous trophic factors and the survival of the cholinergic forebrain system. This laboratory has demonstrated the existence of high levels of mRNA for acidic fibroblast growth factor (aFGF) localized within the cholinergic cells of basal forebrain. This finding along with reports that aFGF has a potent ability to protect and restore the integrity of cholinergic cells [8] suggests that aFGF may act as an autocrine neurotrophic for cholinergic neurons. The proposed research will further characterize the distribution of aFGF and its potential role in the preservation of the cholinergic forebrain system. Specifically, the aims of this study are to determine: (1) whether cholinergic neurons which synthesize aFGF are also expressing the FGF receptor and would therefore be capable of responding to this protective factor, (2) the anatomical relationship between cholinergic neurons which express aFGF and those which are responsive to NGF; (3) if the expression of local trophic factors identified in the forebrain may help sustain the cholinergic cells following ablation of all distant trophic support via excitotoxic lesion; and (4) to test the hypothesis that loss of aFGF expression contributes to age-related degeneration of the basal forebrain cholinergic neurons. The proposed research should further our understanding of the endogenous trophic support available to the cholinergic cells of the forebrain and therefore enhance our ability to develop therapeutic strategies for combating the age-related degeneration of this important brain system.

The observation that neurogenesis occurs in the adult dentate gyrus has sparked much speculation regarding a role for this phenomenon in hippocampal mnemonic function. This hypothesis may extend to cognitive aging, an idea supported by reports of age-related declines in neurogenesis [2,3,4] and substantial evidence for cognitive deficits during aging in functions that depend on the hippocampal formation [1]. Yet, to date, there is little evidence that changes in the rate of proliferation, survival or differentiation of these newly generated cells has consequences for cognitive function associated with the hippocampus in either young or aged animals. The proposed experiments will directly examine an association between cognitive abilities and neurogenesis in a well characterized model of hippocampal aging. Specifically, young, middle-aged, and aged rats will be behaviorally characterized on the spatial version of the Morris water maze task and a delayed match-to-place task that will assess working memory (Specific Aim 1). These behaviorally characterized rats of different ages then will be evaluated for the rate of proliferation and survival of new cells in the hippocampus (Specific Aim 2). Those results will be compared to data obtained in the olfactory system in the same subjects (Specific Aim 3). Additional material and methods will be used to study the numbers of newly generated hippocampal cells that differentiate into neurons (Specific Aim 4). Each of these aspects of neurogenesis will be related to individual differences in cognitive aging.

[unreadable] DESCRIPTION (provided by applicant): Expectations of longevity have increased two-fold in the last century and it is estimated that upwards of 25% of people over age 65 exhibit some form of cognitive deficit. The term mild cognitive impairment (MCI) has been adopted to describe cognitive dysfunction that precedes or occurs in the absence of profound memory loss associated with devastating age-related conditions such as Alzheimer's disease (AD), but that can nevertheless severely compromise one's quality of life. Importantly, however, such cognitive decline is not an inevitable consequence of the aging process, as many people maintain mnemonic function on par with young adults well into advanced age. Among aged human and rodent populations, measures of basal forebrain cholinergic projection neuron integrity correlate with cognitive impairment, particularly in explicit/spatial memory. However, co-distributed GABAergic neurons, that comprise at least half of the projection from basal forebrain to cortical targets and that are implicated in the same mnemonic processes as cholinergic neurons, remain largely unstudied within the context of aging. Moreover, the mechanisms and timing of basal forebrain neuronal dysfunction as it relates to emergence of cognitive deficits across the lifespan is still unclear. In part, absence of such data has been due to a limited ability to detect cognitive deficits in rodents at ages preceding the latest stages of their lifespan. However, we have developed a novel rodent model of cognitive aging that reliably detects cognitive decline in some middle-aged and aged Fischer 344 rats while other rats at both ages perform as well as young cohorts. We hypothesize that combined deficiencies in cholinergic and GABAergic basal forebrain projection systems contribute to the emergence of age-related cognitive deficits. To test this hypothesis, we will evaluate the following measures in behaviorally-characterized young, middle-aged and aged rats: (i) integrity of cholinergic and GABAergic neuronal number, morphology, and phenotypic expression (using combined stereology/confocal microscopy) (ii) synaptic properties of cholinergic and GABAergic neurons in recordings from slices taken through basal forebrain, and (iii) muscarinic cholinergic and GABA(B) receptor expression and function in basal forebrain and its cortical target fields. Finally, we will treat middle-aged and aged rats with cholinergic and GABAergic drugs, both separately and in concert, to reverse age-related cognitive impairments. [unreadable] [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Accumulating evidence indicates that during normal aging, executive functions supported by the prefrontal cortex are among the earliest and most severely impaired cognitive abilities. Executive functions, which include attention, working memory, and cognitive flexibility, are essential to the successful guidance of adaptive behavior and to higher-order aspects of cognition such as decision making. Disruption of corticolimbic g- aminobutyric acid (GABA)ergic inhibitory circuits can have profound consequences for executive function, and preliminary data indicate that prefrontal cortical GABAergic systems are dysregulated in normal aging. Our long term goal is to understand how age-related alterations in forebrain inhibitory circuitry affect executive functions, and to identify potential therapeutic targets that can be exploited to improve cognition in aged individuals. Important to this goal, we have found that there are robust individual differences in the effects of normal aging on executive function, such that some aged subjects are impaired on an attentional set shifting test of cognitive flexibility whereas others are impaired on a delayed response test of working memory. Moreover, our preliminary data suggest that these distinct forms of executive dysfunction are linked to differences in patterns of GABAergic signaling. Building on our extensive preliminary data, the objective of this proposal is to determine how altered GABAergic signaling within the prefrontal cortex affects executive function and whether this signaling can be manipulated to attenuate age-related executive impairments. Our central hypothesis is that individual differences in prefrontal cortical GABAergic signaling underlie distinct forms of executive dysfunction within aging populations. The rationale for the proposed work is that by understanding how altered inhibitory signaling in prefrontal cortex contributes to different forms of executive dysfunction, we will be well-positioned to begin to develop intervention strategies that will allow tailored and more efficacious treatments for executive decline that accompanies aging. Using an integrative approach in which we combine behavioral assays with molecular, electrophysiological, anatomical, and pharmacological studies in Fischer 344 rats, we will test our central hypothesis by: 1) determining if individual differences in prefrontal cortical GABAergic signaling contribute to different forms of age-related executive dysfunction; 2) determining if compromised regulation and activation of prefrontal cortical interneurons contributes to age-related executive dysfunction; and 3) determining if altered GABAergic signaling and executive dysfunction in aging contribute to impairments in decision making. We will employ an innovative approach which both considers individual differences and employs the evaluation of multiple subcomponents of executive function. The findings from the proposed studies will be significant because the information gained will provide foundational knowledge necessary to develop tailored treatments for remediating executive decline and promoting quality of life and independence across the full lifespan.

DESCRIPTION (provided by applicant): Accumulating evidence indicates that during normal aging, executive functions supported by the prefrontal cortex are among the earliest and most severely impaired cognitive abilities. Executive functions, which include attention, working memory, and cognitive flexibility, are essential to the successful guidance of adaptive behavior and to higher-order aspects of cognition such as decision making. Disruption of corticolimbic g- aminobutyric acid (GABA)ergic inhibitory circuits can have profound consequences for executive function, and preliminary data indicate that prefrontal cortical GABAergic systems are dysregulated in normal aging. Our long term goal is to understand how age-related alterations in forebrain inhibitory circuitry affect executive functions, and to identify potential therapeutic targets that can be exploited to improve cognition in aged individuals. Important to this goal, we have found that there are robust individual differences in the effects of normal aging on executive function, such that some aged subjects are impaired on an attentional set shifting test of cognitive flexibility whereas others are impaired on a delayed response test of working memory. Moreover, our preliminary data suggest that these distinct forms of executive dysfunction are linked to differences in patterns of GABAergic signaling. Building on our extensive preliminary data, the objective of this proposal is to determine how altered GABAergic signaling within the prefrontal cortex affects executive function and whether this signaling can be manipulated to attenuate age-related executive impairments. Our central hypothesis is that individual differences in prefrontal cortical GABAergic signaling underlie distinct forms of executive dysfunction within aging populations. The rationale for the proposed work is that by understanding how altered inhibitory signaling in prefrontal cortex contributes to different forms of executive dysfunction, we will be well-positioned to begin to develop intervention strategies that will allow tailored and more efficacious treatments for executive decline that accompanies aging. Using an integrative approach in which we combine behavioral assays with molecular, electrophysiological, anatomical, and pharmacological studies in Fischer 344 rats, we will test our central hypothesis by: 1) determining if individual differences in prefrontal cortical GABAergic signaling contribute to different forms of age-related executive dysfunction; 2) determining if compromised regulation and activation of prefrontal cortical interneurons contributes to age-related executive dysfunction; and 3) determining if altered GABAergic signaling and executive dysfunction in aging contribute to impairments in decision making. We will employ an innovative approach which both considers individual differences and employs the evaluation of multiple subcomponents of executive function. The findings from the proposed studies will be significant because the information gained will provide foundational knowledge necessary to develop tailored treatments for remediating executive decline and promoting quality of life and independence across the full lifespan.

ABSTRACT Alzheimer's disease is a devastating and ultimately fatal neurodegenerative disorder that severely compromises normal cognition and behavior. Costs associated with caring for individuals suffering from AD now exceed 250 billion dollars annually and are expected to rise exponentially in the foreseeable future. Despite this staggering statistic, there exist few treatments and no cures for AD and related dementias. Significant advances in the treatment of AD will require scientists to cross traditional boundaries between disciplines. Indeed, there is increasing recognition that AD is pathologically, genetically, and/or clinically linked to a number of other dementing diseases. Moreover, it is clear that a fuller understanding of how primary risk factors and co- morbidities in AD influence disease progression could reveal novel targets for improving patient outcomes. The overarching goal of this proposal is to build upon outstanding infrastructure for neuroscience training and the vast expertise in AD research at the University of Florida to create a pre-doctoral training program that will foster the development of the next generation of AD researchers and equip them with the broad perspective and scientific skills necessary to make true advances in the treatment of this devastating and complex disease. Trainees for this program will be selected from a pool of outstanding students from diverse backgrounds who are admitted into one of two graduate programs?a biomedical science program and a clinical health psychology program. Trainees would benefit from (1) intensive mentorship in research concepts and methodology, scientific analysis and interpretation (2) opportunities to train and interact with world-class faculty who are leading authorities in the field of AD, aging and co-morbidities of this disease (3) diverse dissertation committees that include multiple mentors with distinct realms of expertise in order to promote broad-based and comprehensive training in AD research (4) assistance integrating large scale, open source data supported by NIA such as AMP- AD and ADNI into their own research (5) personalized mentorship in professional development including grant writing, oral presentations, and networking. Finally, this training program is designed to maximize interactions among trainees and training faculty that cross levels of analysis and to create a rigorous but supportive training environment that will prepare trainees for success in laboratory science and provide them with the knowledge and skills required to make a significant impact in advancing treatments for AD.

PROJECT SUMMARY. The ability to make effective decisions is critical for managing finances, health care, and other activities of daily living necessary to maintain personal independence. Decision making is altered in both normal aging and in Alzheimer's disease (AD), albeit in different ways. Specifically, healthy older adults tend to make less impulsive and risky choices compared to young adults, whereas AD is associated with greater impulsivity and maladaptive risk taking relative to age-matched healthy controls. While distinct, these decision biases associated with aging and AD can both be maladaptive and have significant implications for life quality. Optimizing decision making could broadly benefit functional outcomes and promote independent living among older adults; however, development of interventions is currently hindered by a poor understanding of the neural mechanisms underlying maladaptive decision making in aging and AD. To begin to address this gap in knowledge, our labs have shown that aged rats, which lack overt AD pathology, exhibit reductions in impulsive and risky choice in a manner similar to that observed in aged humans. Moreover, preliminary data suggest that these age differences in decision making are mediated by the basolateral amygdala (BLA). The BLA is implicated in affective processing and is highly interconnected within decision-making circuits. Using in vivo optogenetic approaches in both young and aged rats, we have identified multiple, temporally distinct contributions of BLA to both impulsive and risky choice and shown these contributions of BLA to decision making change with age. The long-term goal of this research program is to determine the mechanisms by which decision making is altered in aging and AD. The immediate objective is to determine the effects of aging and early tau pathology on BLA function and its role in decision making. Our overarching hypothesis is that aging and tau pathology disrupt adaptive decision making through alterations in BLA excitatory and inhibitory dynamics. Aim 1 will determine how optogenetic activation and inhibition of BLA at discrete stages of the decision process influence aged rats' decision making. Parallel biochemical assays will evaluate the influence of age on BLA synaptic and excitatory/inhibitory signaling proteins in conjunction with decision making behavior. Aim 2 will address similar questions in conjunction with a virally-mediated approach that induces medial temporal lobe tau pathology in a manner that is anatomically relevant to early stage AD. Aim 3 will use optogenetic approaches to determine how aging alters the contributions of distinct BLA efferent circuits to decision making, and will use cellular electrophysiology to evaluate effects of aging on anatomically defined subsets of BLA efferent neurons. Completion of these experiments will reveal at the biochemical, cellular, and systems level how the BLA is influenced by aging and tau pathology, as well as how such alterations contribute to maladaptive decision making. The information will be significant because it will provide foundational knowledge that is critical for development of novel interventions to maximize decision quality in both normal aging and AD.

Title: Interactions of Perirhinal Tau Pathology and Aging in Cognitive Dysfunction Abstract: Intracellular inclusions comprised of tau proteins are among the earliest pathological features of Alzheimer's disease (AD), the most common age-associated neurodegenerative condition. Data show that tau inclusions initially emerge in the transentorhinal subregion (area 35) of perirhinal cortex by the fourth decade of life, twenty years prior to the typical AD diagnosis. The immediate consequences of this early area 35 tau pathology on cognition and disease progression, however, remain poorly understood. The long-term goal of this research is to develop sensitive cognitive assays for humans that provide a reliable index of early AD pathology. The primary objective of the current proposal is to develop a preclinical model that recapitulates many features of early AD using AAV technology to drive pathological tau burden in area 35 of young and aged rats. The secondary goal of this proposal is to establish behavioral assays as a biomarker for early detection and tracking of disease pathology in patient populations. These goals will be attained by testing the hypothesis that aging exacerbates tau burden in area 35 and that progressive pathology in this brain region is associated with performance on sensory discrimination tasks that utilize perceptual gradients to test stimulus discrimination abilities. The rationale for this this work is that because Alzheimer's disease develops against the backdrop of an aging brain, it is critical to elucidate how aging and pathological tau interact to influence disease mechanisms and cognitive outcomes associated with disease progression. This work is innovative because viral vector technology will be used to model the specific anatomical features of early Alzheimer's disease in conjunction with state-of-the-art cognitive assays that are highly sensitive to detecting behavioral dysfunction associated with aging and disease. The significance of the proposed experiments will be to establish the foundation for developing new diagnostic tools for AD that can facilitate early intervention and more effectively evaluate the efficacy of novel therapeutics before widespread neurodegeneration occurs.

Summary Psychological stress and hypothalamic-pituitary-adrenal (HPA) axis dysfunction play a role in many disorders including Alzheimer?s disease (AD), major depression, metabolic syndrome, and sarcopenia. Chronic high levels of stress and elevated corticosteroids are also hypothesized to act as ?accelerants? of many age-associated diseases and phenotypes. Further, numerous studies report an association between increased stress and HPA axis dysfunction with increased rates of cognitive decline and hippocampal and brain atrophy in late-life dementia. Our interest in the HPA axis stemmed from rodent model data implicating psychological stress, corticotropin-releasing hormone/factor (CRH/CRF), and corticosterone, as factors that impact amyloid and tau pathology and age-associated declines in cognitive function. Indeed, suppression of the HPA axis theoretically represents a unique therapeutic strategy in AD, as it has been implicated in regulating the underlying A? and tau proteinopathies and independently affecting, presumably through corticosteroid excess, brain atrophy and cognitive decline. Unfortunately, testing the role of HPA axis in AD and cognitive aging, has been hindered by the lack of small molecule therapeutics that effectively suppress HPA axis activation in humans. As an alternative to small molecule approaches, we have successfully developed a picomolar affinity IgG1 monoclonal antibody (mAb) targeting CRF (anti-CRF mAb, CTRND05) that dose-dependently blocks stress-induced increases in corticosterone, and can rapidly reverse select Cushingoid phenotypes in mice overexpressing CRF. Metabolic and immunologic studies reveal numerous effects consistent with long-lasting suppression of the HPA-axis; multi-organ transcriptomic studies shows robust regulation of numerous genes that may mediate the physiologic effects of CTRND05. We hypothesize that passive immunotherapy targeting CRF represents a novel, translatable, therapeutic approach to AD and possibly many other disorders. Through pleiotropic actions, anti-CRF immunotherapy may slow the development of A? and tau pathologies as well as brain atrophy and cognitive decline. In this proposal, we will systematically and rigorously evaluate the therapeutic potential of this anti-CRF immunotherapy in appropriate preclinical models and develop companion theragnostic biomarkers. As CRF is completely conserved between humans and mice, and is present at similar concentrations, positive results from these studies will provide the rationale for testing of a humanized high affinity anti- CRF mAb for therapeutic benefit in humans.

Summary Psychological stress and hypothalamic-pituitary-adrenal (HPA) axis dysfunction play a role in many disorders including Alzheimer?s disease (AD), major depression, metabolic syndrome, and sarcopenia. Chronic high levels of stress and elevated corticosteroids are also hypothesized to act as ?accelerants? of many age-associated diseases and phenotypes. Further, numerous studies report an association between increased stress and HPA axis dysfunction with increased rates of cognitive decline and hippocampal and brain atrophy in late-life dementia. Our interest in the HPA axis stemmed from rodent model data implicating psychological stress, corticotropin-releasing hormone/factor (CRH/CRF), and corticosterone, as factors that impact amyloid and tau pathology and age-associated declines in cognitive function. Indeed, suppression of the HPA axis theoretically represents a unique therapeutic strategy in AD, as it has been implicated in regulating the underlying A? and tau proteinopathies and independently affecting, presumably through corticosteroid excess, brain atrophy and cognitive decline. Unfortunately, testing the role of HPA axis in AD and cognitive aging, has been hindered by the lack of small molecule therapeutics that effectively suppress HPA axis activation in humans. As an alternative to small molecule approaches, we have successfully developed a picomolar affinity IgG1 monoclonal antibody (mAb) targeting CRF (anti-CRF mAb, CTRND05) that dose-dependently blocks stress-induced increases in corticosterone, and can rapidly reverse select Cushingoid phenotypes in mice overexpressing CRF. Metabolic and immunologic studies reveal numerous effects consistent with long-lasting suppression of the HPA-axis; multi-organ transcriptomic studies shows robust regulation of numerous genes that may mediate the physiologic effects of CTRND05. We hypothesize that passive immunotherapy targeting CRF represents a novel, translatable, therapeutic approach to AD and possibly many other disorders. Through pleiotropic actions, anti-CRF immunotherapy may slow the development of A? and tau pathologies as well as brain atrophy and cognitive decline. In this proposal, we will systematically and rigorously evaluate the therapeutic potential of this anti-CRF immunotherapy in appropriate preclinical models and develop companion theragnostic biomarkers. As CRF is completely conserved between humans and mice, and is present at similar concentrations, positive results from these studies will provide the rationale for testing of a humanized high affinity anti- CRF mAb for therapeutic benefit in humans.

PROJECT SUMMARY: Older adults are the fastest-growing group of cannabis users in the US. Older adults use cannabis for a variety of reasons, including pain, insomnia, anxiety, and for recreation. Cannabis can, however, also exert robust effects on cognition. Almost all research on cannabis/cannabinoids and cognition has been conducted in young adults, and largely shows that acute administration impairs mnemonic and executive functions mediated by the medial temporal lobe and prefrontal cortex (which are also those most vulnerable to decline in aging and age- related neurodegenerative disease). In contrast, a few studies suggest that cannabinoids can exert distinct effects on the aged compared to the young brain, and preliminary data from our labs show that cannabis can actually enhance cognition selectively in aged rats. Indeed, cannabinoids have been proposed as potential treatments for the age-related neurodegenerative condition Alzheimer's disease (AD), and some preclinical research shows that cannabinoids can attenuate markers linked to AD pathology (e.g., neuroinflammation). Aging studies evaluating cannabis to date, however, are very limited and have not employed either cannabis itself or routes of administration that model those used most frequently by people (smoking and oral consumption). As such, it is unclear how cannabis, as it is actually used, affects cognitive decline and the synaptic dysfunction and AD-like pathology that contribute to cognitive impairments in older subjects. The long-term goal of our program is to determine how cannabis affects cognitive decline in aging and AD, and to determine the mechanisms of such effects. The objective of the current proposal is to model the two most common routes of human cannabis use (smoking and oral consumption) in well-characterized rat models of age-related cognitive decline, and to use these models to begin to elucidate effects of cannabis on behavioral and neurobiological dysfunction associated with aging and AD. Our overarching hypothesis is that cannabis can benefit cognition in aging by attenuating age-associated synaptic dysfunction, neuroinflammation, and tau pathology. Aim 1 will determine how acute cannabis affects performance in young adult and aged rats, as well as the synaptic mechanisms supporting effects of cannabis on cognition in aged subjects. Aim 2 will assess effects of chronic cannabis on cognition in young adult and aged rats, as well as on excitatory/inhibitory signaling and inflammatory markers linked to age-related cognitive impairments. Aim 3 will assess effects of chronic cannabis on AD-like tau pathology and cognition using a novel, targeted AAV-based approach in aged rats. The proposed experiments will be significant because they will provide foundational data concerning whether and how cannabis administration relevant for human consumption yields benefits for age-related cognitive decline and neuropathology.

PROJECT SUMMARY. One in three older adults exhibits some form of cognitive deficit, with 13% of individuals over age 65 meeting the clinical diagnosis of Alzheimer's disease (AD). Even in the absence of overt pathology, age-related cognitive dysfunction can be sufficiently severe as to disrupt instrumental activities of daily living and, consequently, the ability to maintain personal independence. In aging and AD, mnemonic functions supported by the hippocampus (HPC) and executive functions supported by the prefrontal cortex (PFC) are particularly vulnerable to decline. Both HPC and PFC undergo molecular and electrophysiological alterations with age that perturb the balance between excitatory and inhibitory (E/I) signaling necessary for optimal cognition. In addition, aberrant E/I signaling in aging increases susceptibility to AD neuropathology. Moreover, age-associated increases in peripheral inflammation can dysregulate E/I signaling, exacerbate AD pathology, and impair cognition. An ideal intervention for improving cognitive outcomes in aging would thus: 1) benefit multiple aspects of cognitive function with minimal side effects, 2) act to re-establish E/I homeostasis across the aged brain, 3) attenuate the accumulation of AD pathology that can worsen cognitive dysfunction, and 4) be readily translated across species. Electrical vagus nerve stimulation (VNS) has been used safely and effectively for 30 years to treat epilepsy and depression, and published and preliminary data show that it positively influences central nervous system E/I signaling. VNS also reduces pro-inflammatory cytokines in the periphery, as well as tau levels in AD patients. Most importantly, data in both animal and human subjects show that VNS enhances multiple forms of PFC- and HPC-dependent cognition that are compromised in aging. Despite these promising findings, VNS has not been rigorously evaluated as a potential treatment for age-associated cognitive decline. The objective of this proposal is to determine if chronic VNS mitigates deleterious neurobiological and inflammatory consequences of aging and improves cognitive function in aged subjects. Our rationale is that such studies will provide a foundation for use of VNS as a treatment for cognitive impairments in aging. Our overarching hypothesis is that chronic VNS will benefit cognition in aging by restoring E/I homeostasis, reducing inflammation, and protecting against AD- associated pathology. Aim 1 will determine whether VNS normalizes molecular and electrophysiological signatures of E/I dysregulation and reduces peripheral markers of inflammation in aging. Aim 2 will determine whether VNS remediates multiple forms of age-associated cognitive impairment. Aim 3 will use a targeted AAV- based approach to determine whether VNS protects against neuropathology and cognitive decline associated with AD-like tau pathology. These experiments will be significant as they will help to determine the utility of VNS as an intervention for treating cognitive decline in aging and AD.