Lisa M. Savage - US grants

[unreadable] DESCRIPTION (provided by applicant): A considerable body of evidence has demonstrated an important role for cholinergic transmission in cognition, memory and behavioral state control. Like other amnestic or dementia-related disorders, diencephalic amnesia is accompanied by cholinergic dysfunction. Using an animal model of diencephalic amnesia we have documented cholinergic loss in the medial septum/diagonal band (MS/DB) and hypo-cholinergic output in the hippocampus that correlates with behavioral impairment, which can be alleviated by cholinomimetic drugs. These results can be attributed to 2 potentially orthogonal, mechanisms: (1) Cholinergic cell loss in the MS/DB region causes hypocholinergic output in the hippocampus during learning; (2) Lesions to thalamic and hypothalamic nuclei degrade neural activation in limbic regions and this is reflected in impaired ACh output during cognitive processing. The proposed research uses 2 rodent models of diencephalic amnesia to conduct a systems level analysis of the relationships between neuroantomical, neurochemical and behavioral dysfunctions seen in diencephalic amnesia. Aims: Using animal models we will: (A) Apply stereological microscopy techniques, in combination with immunocytochemistry, to fully document cholinergic cell loss in several important ascending cholinergic pathways; (B) Assess functional acetylcholine disruption by a novel application of in-vivo microdialysis/HPLC to assess ACh efflux during cognitive processing on a range of tasks and brain regions (hippocampus, amygdala, and dorsal striatum) connected to nuclei damaged in diencephalic amnesia; (C) Test whether hippocampal or septal administration of drugs that increase brain ACh levels will differentially lead to recovery of learning/memory function; (D) Map the functional diversity of diencephalic nuclei using discrete neurotoxin-induced lesions to determine if such lesions cause decreased ACh output in key memory structures. Significance: The neural mechanisms of diencephalic amnesia remain undetermined. Using in-vivo microdialysis on-line during cognitive testing in animal models of diencephalic amnesia is novel and will enhance our understanding of the interdependence between diencephalic and other limbic structures. Such experiments are critical to understanding the role of acetylcholine dysfunction in amnesia and thus the development of pharmacotherapeutics. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Cognitive and memory impairments associated with normal aging and neurodegenerative disease are emerging as one of our nation's greatest health concerns. Therapeutic exercise has emerged as a non- invasive technique to improve learning, memory and cognition in both healthy and neurologically compromised populations. We posit a novel position that exercise-induced improvements in learning and memory are driven by two factors: First, acute rises in brain derived neurotrophic factor (BDNF) enhance memory; and second, the protracted increases in neurotrophins lead to a selective rescue of basal forebrain cholinergic neurons that co-express nestin that ultimately produces an increase in synaptic efficacy. These enhancements intensify activity-related acetylcholine (ACh) release within the septohippocampal circuit and this is what produces the delayed improvements in learning after exercise. This work will advance the field by providing proof of principle for a new mechanistic theory for how exercise can lead to improved cognitive functioning based on the modulation of the cholinergic system. In this proposal we will determine whether sustained exercise-induced release of neurotrophins, in particular nerve growth factor (NGF), will rescue a select population of cholinergic forebrain neurons that co-express nestin from a hypotrophic quiescent state produced by thiamine deficiency in a rodent model of amnesia (AIM 1). In addition, we will demonstrate the exercise-facilitated improvements in activity-dependent release of BDNF and ACh are time-dependent and uniquely drive the enhancement of different cognitive processes. Moreover, exercise activation of TrkA or TrkB receptors selectively upregulate critical synaptic proteins involved in the distinct temporal profile of neurochemical release and behavioral improvement (AIM 2). Developing both behavioral and pharmacological therapeutic interventions for cognitive/memory disorders requires a greater understanding of how the pathological brain reacts and adapts differently from the healthy brain. Such critical pre-clinical information is needed to improve the development of therapeutic strategies that are effective for the recovery of cognitive functions.

DESCRIPTION (provided by applicant): Many alcoholics display moderate to severe cognitive dysfunction accompanied by brain pathology including cell loss and tissue shrinkage. A factor confounded with alcohol-related behaviors and alcohol consumption is poor nutrition. Specifically, many alcoholics are thiamine deficient. Thiamine is a vital nutrient that is criticalfor normal brain health and functioning. Thus, thiamine deficiency has emerged as a key factor underlying alcohol-induced brain damage. Thiamine deficiency in humans can lead to Wernicke encephalitis that can progress into Wernicke-Korsakoff syndrome and these disorders have a high prevalence among alcoholics. However, these disorders are commonly misdiagnosed, particularly in alcoholics. It is difficult, if not impossible, to disentangle the neurotoxic effecs of chronic alcohol consumption and thiamine deficiency in human patients. Therefore, animal models are critical for determining the exact contribution of alcohol- and thiamine deficiency-induced neurotoxicity, as well as the synergistic interaction of those factors, to brain and behavioral dysfunction. However, few such models have been developed, particularly pertaining to forebrain pathology and cortical-dependent behaviors. In this proposal, we use our recently developed translational animal model of chronic ethanol treatment (CET) combined with thiamine deficiency (TD) to determine both the independent actions of CET and TD as well as how these factors synergistically interact to affect neurotrophin adaptation, cognitive functioning and activation of the fronto-cortico-limbic network (AIM 1). We will determine whether basal forebrain cholinergic cell loss, altered cortical cellular structure and dysfunctional acetylcholin (ACh) release are critical mediators of alcohol-related cognitive impairment. Furthermore, we will determine whether exercise can restore behavior, cholinergic innervation, and behaviorally stimulated ACh efflux across the hippocampus and frontal cortex (AIM 2). The final AIM (3) will determine whether a moderate TD episode during CET leads to greater disruption of cytogenesis (neurogenesis in the hippocampus and gliogenesis in the frontal cortex). In addition, we will examine alternations in oligodendrocyte differentiation and myelin related proteins as a function of alcohol-related disease progression. This critical pre-clinical informatin is needed to improve the diagnostic criteria for alcohol-related neurological disorders and to develop therapeutic strategies that are effective for the recovery of cognitive functions after chronic alcohol addiction.

C7/8 UO1: Lisa Savage & Ryan Vetreno Recovery of Adolescent Alcohol Disruption of Basal Forebrain-Cortical Projection Circuits Project Summary Heavy alcohol consumption during adolescence is associated with persistent changes in brain structure, connectivity, and adult cortical-mediated cognitive function. Critical pathological changes consistently observed in rodent models of adolescent binge ethanol exposure (Adolescent Intermittent Ethanol; AIE) are a reduction of cortical nerve growth factor (NGF), suppression of the cholinergic phenotypes, and a long-term decrease in the number of functional cholinergic basal forebrain neurons (CBFNs). The cholinergic projection neurons within the nucleus basalis magnocellularis complex (NbM) provide acetylcholine (ACh) to the frontal cortex, including the medial prefrontal cortex (mPFC) and orbitofrontal cortex (OFC). Behaviorally-stimulated efflux of ACh in both the mPFC and OFC are blunted following AIE, and there is a loss of cognitive and behavioral flexibility. Our recent data demonstrate that AIE-induced loss of CBFNs is due to epigenetic silencing of cholinergic phenotypic markers, but exercise, potentially through a NGF mechanism, can reverse these epigenetic changes and rescue cholinergic neurons. This demonstrates that AIE is initially marked by a reduction of the expression of cholinergic neuronal phenotypes, rather than neuronal cell death. Thus, mechanisms should be explored to recover CFBN pathology following AIE. Our overarching hypothesis is that AIE-induced reductions of NGF in cortical projection sites leads to epigenetic silencing of cholinergic phenotypes with the NbM, retraction and/or dysfunctional re-innervation of the cortical-NbM cholinergic connectome, causing blunting of cortical cholinergic tone and cognitive dysfunction. However, appropriately timed NGF-based therapies (exercise, NGF gene therapy, CRISPR/dCas9-P300 editing) following AIE will reinvigorate cholinergic forebrain circuitry through the revitalization of cholinergic genes, which will rescue cortical ACh and recover AIE-induced impairments in cortical-dependent behaviors. Our goals are to map and rescue cholinergic forebrain and cortical circuit pathology seen following AIE (Aim 1), restore cognitive functioning by exercise, NGF-gene therapy, or selective chemogenetic stimulation of cholinergic neurons (Aim 2), and identify the central role of NGF deficits, through CRISPR/dCas9 editing, in AIE-induced epigenetic silencing of cholinergic phenotype genes (Aim 3). Mounting evidence supports the neuroprotective effects of NGF as a course to rescue vulnerable CBFNs undergoing neurodegeneration, and we have strong evidence that AIE-induced cholinergic pathology can be reversed. Understanding the mechanisms of cholinergic neuronal recovery will aid in the development of more effective therapies to treat cognitive dysfunction associated with alcohol-related brain damage and other neurodegenerative disorders.