John K. Robinson - US grants

These studies will explore the role of cholinergic and GABA-ergic projections originating in the media septum in modulating memory processes mediated by the hippocampus. Microinjections of cholinergic muscarinic receptor antagonists and GABA-A receptor agonists and antagonists into the medial septal area will be performed. The alternative hypotheses that these systems interact either synergistically or as opponent-processes in contributing to attentional or memory processes will be tested. Understanding septal-hippocampal cholinergic and GABA-ergic interactions may lead to novel pharmacotherapies for Alzheimer's disease by suggesting coadministration protocols for GABA-ergic and cholinergic drugs.

Galanin is a neuropeptide that play an important role in memory formation and may contribute to the cognitive deficits in Alzheimer's disease. Therefore, galanin receptor antagonists may be for drugs for treating memory loss in Alzheimer's disease. The goal of the proposed studies is to determine whether a novel non-peptide galanin receptor ligand, galnon, exhibits similar disruptive effects on memory in rats as galanin. In the initial experiments, galnon will be administered into the lateral ventricle and into the ventral hippocampus to establish a dose- response relationship and to determine the extent that the effects of galnon can be localized to the ventral hippocampus (Aim 1). Next, galanin antagonists will be co-administered with galnon into these sites to confirm that the performance disruption of the memory tasks is mediated by galanin receptors (Aim 2). Finally, the potential for galnon to cross the blood-brain barrier and produce effects on memory will be assessed by administering it systemically (Aim 3). Successful demonstration of mnemonic effects of galnon similar to those of galanin will lead to a comprehensive program to modify galnon's chemical structure to produce a galanin antagonist that crosses the blood-brain barrier, is stable in vivo, and that posses memory-enhancing properties.

DESCRIPTION (provided by applicant): Lifestyle factors, such as diet, exercise, cognitive enrichment, and social stimulation are related to the risk of acquiring Alzheimer's disease (AD) and the severity of the symptoms. Furthermore, in both clinical studies and in studies in transgenic mouse models of AD, these factors have also often been shown to improve aspects of the symptoms. However, standard rodent environmental enrichment paradigms are not well suited for teasing apart the potential therapeutic aspects, but a method for providing a progressively challenging, sustained and cognitive-specific training regimen to mice would be able to study the cognitive challenge specifically (hereafter referred to as Progressive Cognitive Stimulation or PCS). It is unknown how such a sustained complex cognitive challenge might impact specific cerebral amyloid pathologies, associated neuroinflammation, and performance on the potential for new learning. Furthermore, how this complex cognitive challenge compares to a classic methodology, home-cage environmental enrichment (EE), is likely to be very revealing of the relative impacts of task-specific (PCS) versus general environmental complexity (EE). Accordingly, the hypotheses of our proposal are 1) PCS may ameliorate cerebral pathologies and preserve spatial learning and memory performance, and 2) PCS and the classic EE approach will interact by acting on multiple aspects of pathology. To test these hypotheses, it will first be determined if PCS reduces cerebral amyloid associated pathologies and preserves spatial learning and memory ability in transgenic Tg-5xFAD mice. Next, it will be determined how PCS compares to home-cage EE to determine whether a combination of these methodologies is required to achieve maximal benefits and whether they have different impacts on pathology. A well-characterized transgenic mouse model will be employed to investigate the differential contributions of cerebral microvascular amyloid and parenchymal amyloid to impairments of standard and complex learning and memory tasks. The established Tg-5xFAD mouse is a model of early-onset and robust parenchymal amyloid accumulation. Tg-5xFAD mice exhibit plaque-associated neuroinflammation and develop behavioral impairments. These studies intend to address important and timely questions including: Does long term cognitive-specific stimulation, through PCS, provide protection from amyloid pathologies and preserve new learning of spatial tasks? Completion of these studies will provide valuable insight into how different cognitive interventions impact on amyloid pathologies.

? DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is a progressive neurodegenerative condition that is the sixth leading cause of death with a prevalence of every one in eight Americans of 65 and older in the United States. Presently, there are no effective pharmacological therapeutic agents to prevent or treat AD. In light of the present shortcomings, there is a growing call that a concerted effort be made to discover modifiable risk factors for dementia and exploit those already identified. To this point, epidemiological studies have shown that demographic and lifestyle factors such as cardiovascular exercise are related to a lower risk of developing cognitive impairments as one ages and in AD. Of the lifestyle factors, cardiovascular exercise is particularly promising since reports suggest that moderate, but positive, benefits are produced when cardiovascular exercise has been introduced as an intervention in clinical trials for older adults in early stages of mild cognitive impairment. Additionally, while many benefits of cardiovascular exercise as an intervention and/or preventative lifestyle factor towards AD pathology and cognitive impairments are possible, the age of onset, duration and intensity of exercise required for improved outcomes is largely unknown. In this case, animal studies designed to answer these key questions comprehensively and in a manner that will inform prospective human clinical trials would be highly advantageous. Indeed, several studies have shown benefits of exercise in mouse models of AD pathology. However, in all of these studies exercise was generally presented as a qualitative treatment solely contrasted with a sedentary control condition rather than as a quantitative, dimensional factor having potential dose-response properties. Thus, the overall hypothesis of this proposal is that specific cardiovascular exercise regimens can provide prevention and/or interventional benefits towards cognitive impairment in the presence of Aß pathologies and in normal aging. While earlier studies in humans and mouse models are encouraging, neither has systematically evaluated the beneficial effects of cardiovascular exercise based on age of onset, duration and intensity. Here, we plan to fill this critical void in the existing knowledge and determine the potential preventative and interventional benefits of varying levels of cardiovascular exercise on cognitive decline in normal aging mice and in two distinct mouse models of amyloid pathologies commonly associated with AD, with corresponding cognitive impairments. Presently, recruitments are underway for an NIH supported clinical trial to evaluate Cognitive Benefits of Aerobic Exercise Across the Age Span ://www.nia.nih.gov/alzheimers/clinical-trials/cognitive-benefits- aerobic-exercise-across-age-span. Therefore, our proposed studies are not only novel, but also very timely, and could provide invaluable translational information to further guide study design in human trials.

? DESCRIPTION (provided by applicant): Cerebrovascular accumulation of the amyloid ß-protein (Aß), a condition known as cerebral amyloid angiopathy (CAA), is an important cause of vascular cognitive impairment (VCI) and a common pathological feature of patients with Alzheimer's disease (AD). In addition, several related familial CAA disorders result from mutations that reside within the Aß peptide sequence of AßPP gene including Dutch-type (E22Q) and Iowa- type (D23N). Evidence continues to accumulate indicating that cerebral microvascular amyloid can promote small vessel pathology, neuroinflammation and cognitive deficits in patients with AD and related CAA disorders. Previously, we generated unique transgenic mice that produce Dutch/Iowa CAA mutant human Aß in brain, designated Tg-SwDI, that develop early-onset and prominent subcortical fibrillar cerebral microvascular Aß deposition. Despite the value and unique insight that Tg-SwDI mice have provided in the study of subcortical small vessel CAA, associated pathologies and cognitive impairment there remains significant shortcomings with the use of this model. For example, in contrast to humans and higher animals, mice possess small brains with little white matter thus limiting neuroimaging capabilities and the study of important vascular mediated changes in these regions. In addition, the study of cognitive abilities in mice are much more restricted compared to higher species. Thus, there is an important need for better models to further our understanding of the impact of small vessel CAA on brain pathology and function. In light of the limitations of current mouse models, advances in the production of transgenic rats provide the opportunity to develop a more appropriate and reproducible species to model small vessel CAA. Thus, the overall hypothesis and aim of this exploratory R21 proposal is that the generation and characterization of novel transgenic rats will provide a superior model to study the impact of subcortical small vessel CAA on brain pathology and cognitive function. To accomplish this goal we propose to generate novel transgenic rats expressing Dutch/Iowa CAA mutant Aß in brain and subsequently 1) conduct temporal biochemical and pathological characterization; 2) determine the consequences of small vessel CAA on cognitive functions; and 3) perform neuroimaging studies to determine the impact of small vessel CAA on brain pathology using microMRI. Here, we take the unorthodox approach of submitting a multi-PI exploratory proposal that will bring together three collaborative investigators with distinct, but highly complimentary, expertise to generate and characterize novel transgenic rats for CAA. The investigators range in expertise from production of numerous transgenic mouse models and biochemical and pathological characterization (Dr. Van Nostrand), advanced behavioral and cognitive characterization of rodents (Dr. Robinson) and high-resolution neuroimaging morphometric analysis of rodent models (Dr. Benveniste). The aim of our group is to generate a superior model for the study of small vessel CAA and provide a much needed, more advanced and invaluable animal model of this condition to the research community for investigating pathogenic mechanisms and to evaluate potential diagnostic and therapeutic interventions with relevant cognitive and neuropathological endpoints.

Cerebrovascular accumulation of the amyloid b-protein (Ab), a condition known as cerebral amyloid angiopathy (CAA), is a common small vessel disease that is prevalent in the elderly, a prominent comorbidity of patients with Alzheimer?s disease (AD) and an important driver of vascular cognitive impairment and dementia (VCID). Despite the growing recognition of the contribution of CAA to dementia in AD and in VCID, there currently exists no effective therapeutic interventions for this condition. CAA can uniquely contribute to the cognitive decline in VCID and AD in several manners. For example, in response to deposited fibrillar Ab in CAA cognitive impairment is worsened by a chronic state of perivascular neuroinflammation and activation that is characterized by reactive astrocytes and activated microglia and endothelial cells that can produce thrombin, pro-inflammatory cytokines and chemokines, and reactive oxygen and nitrogen species. Also, the increase in perivascular expression and activation of certain proteolytic enzymes, including thrombin, can contribute to microinfarcts, disruption of vessel wall integrity and cerebral hemorrhage, all highly deleterious manifestations of the disease. Thus, perivascular neuroinflammation, vascular activation, thrombosis and hemorrhage associated with cerebral vascular amyloid can all be linked to thrombin, which represents a potential therapeutic target to treat CAA/VCID. Based on our preclinical work in AD mouse models we now propose to test the hypothesis that thrombin-mediated vascular activation, neuroinflammation and thrombosis is a central mechanism contributing to small vessel CAA pathology in the brain and that inhibiting thrombin will improve clinically relevant CAA pathological and VCID-associated endpoints. To test our hypothesis, we first propose to test if early and long-term administration of dabigatran is effective as a preventative treatment to reduce CAA pathology and associated VCID. Specifically, we will test if long term treatment with dabigatran reduces CAA, perivascular neuroinflammation, small vessel occlusions, cerebral microbleeds and improves cognitive performance in a novel and unique transgenic rat model of small vessel CAA. Second, we propose to test if administration of dabigatran during later stage disease is effective as an intervention to reduce CAA pathology and associated VCID. Specifically, we will test if shorter term treatment with dabigatran during later stages in the disease can lower CAA-related perivascular neuroinflammation, small vessel occlusions, cerebral microbleeds and improve cognitive performance in our transgenic rat model of small vessel CAA. Successful outcomes in these exploratory studies will pave the way for future studies to understand the precise beneficial mechanisms of dabigatran. This will complement our ongoing clinical studies of dabigatran treatment in early stage AD and could provide a needed therapeutic agent for CAA related vasculopathy and VCID.