Jeffrey N. Keller - US grants

The proteasome is found in all cells of the brain, and mediates the majority of overall protein degradation. In particular, the proteasome is responsible for mediating the degradation of most oxidized and damaged proteins in the brain. The proteasome is composed of multiple subunits, and degrades proteins through the coordinated efforts of at least 3 distinct proteolytic activities. Recently we have identified that there is a brain region specific impairment in the chymotrypsin-like activity of the proteasome, during normal brain aging. Recent studies from our laboratory indicate a possible role for decreased expression of heat shock proteins (HSP), and decreased expression of proteasome subunits, as a possible mechanism by which age-related proteasome inhibition occurs. Data in this proposal clearly demonstrate that inhibition of proteasome activity is sufficient to induce the accumulation of oxidized DNA in the brain, although the possible role of proteasome inhibition in mediating age-related increases in oxidative stress in the brain has not been determined previously. The focus of this proposal is to test the hypothesis that decreased expression of HSP, HSP associated proteins, and individual proteasome subunits in the brain directly contribute to age-related impairment of proteasome activity, which directly contributes to age-related increases in protein oxidation and DNA oxidation. The specific aims for testing this hypothesis are as follows: 1) To determine alterations in proteasome expression in the aging brain 2) To determine alterations in all proteasome proteolytic activities in the aging brain 3) To determine alterations in the expression of HSP, and HSP associated proteins, in the aging brain 4) To determine the mechanism by which proteasome activity is inhibited in the aging brain 5) To elucidate the role of proteasome inhibition in age-related increases in protein oxidation and DNA oxidation. Together, these studies will provide a basis for understanding proteasome biology in the brain, and elucidate the involvement of proteasome inhibition as a contributor to the deleterious effects associated with brain aging.

The receptor for advanced glycosylation end products (RAGE) has been implicated in mediating beta amyloid (A(3) toxicity and contributing to Alzheimer's disease (AD) pathogenesis, although the specifics on many aspects of RAGE biology and toxicity remain to be elucidated. Recent reports have demonstrated that, in contrast to the transmembrane RAGE receptor, the secreted or soluble forms of RAGE (sRAGE) are capable of suppressing several aspects of Ap pathogenesis in vivo. Pilot studies from our laboratory demonstrate that sRAGE suppresses the formation of assembled A(3 species and Ap -induced neurotoxicity, with sRAGE interacting with the oligomeric forms of Ap at higher apparent affinity than monomeric Ap. However, it is currently not known which regions of sRAGE are responsible for mediating each of these observations. The goal of this proposal is to test two related hypotheses. The first hypothesis is that increases in RAGE-ligand interactions occur during the progression of AD and in a transgenic mouse model of Ap pathogenesis, with oligomeric Ap representing a significant portion of the overall RAGE-ligand interactions. The second hypothesis is that sRAGE inhibits the formation of pathogenic p and the effects of pathogenic Ap, via specific and related domains within the sRAGE protein. The specific aims to test each of these hypotheses are as follows: 1) To define the alterations in RAGE-ligand interactions in AD and APP/PS-1 mice, 2) To elucidate the functional domains responsible for RAGE- Ap interactions, 3) To determine the mechanism by which sRAGE suppresses Ap-induced neurotoxicity, and 4) To determine the mechanism by which sRAGE suppresses Ap assembly and Ap deposition. Cumulatively, these data will advance the field by potentially identifying novel therapeutic strategies that could lead to eventual treatments for AD. Additionally, these findings will be critical in clarifying the current gaps that exist in our understanding of RAGE with Ap-assembly, Ap-deposition, and Ap-induced neurotoxicity.

? DESCRIPTION (provided by applicant): We are facing one of the most significant challenges of the 21st century; how to maintain brain health and prevent dementia in our rapidly aging population. Alzheimer's disease (AD) is the most common type of dementia. Currently, there is no treatment to prevent or cure AD. Mounting evidence indicates that late-onset AD is an age-related, multi-factorial disease(s), which has a complex genetic background and the onset and progression of AD are influenced to a large extent by modifiable factors such as cardiovascular risk factors and physical inactivity. However, at present, there is no direct evidence that reducing these modifiable risk factors prevents or slows AD. The overarching goal of this proposal is to conduct a rigorously designed randomized controlled phase II trial to determine the independent and combined effects of Intensive pharmacological Reduction of Vascular Risk factors (IRVR, blood pressure and lipids) and Exercise (Ex) on neurocognitive function in older adults at high risk of AD (primary outcome). Furthermore, we will determine the effects of these interventions on the neuroimaging, blood, and CSF biomarkers of AD (secondary outcomes). We will enroll 640 cognitively normal older adults age 65 to 79 with a family history (FH) of AD who have hypertension (SBP?140 mmHg) and dyslipidemia (according to the new 2013 ACC/AHA guidelines). They will be randomized into 2-yr interventions of IRVR (SBP?130mmHg, lowering lipids with atorvastatin), Ex, IRVR+Ex, and a control arm of standard care (a 2 x 2 factorial design). Aim 1: Determine the independent and combined effects of IRVR and Ex on neurocognitive function. Hypothesis: IRVR and Ex will improve global cognitive function, while IRVR+Ex will provide a greater benefit than either IRVR or Ex alone. Neurocognitive function will be measured using well-validated tests at baseline, 6, 12, 18, and 24 months to optimize study power using linear mixed effects models for analysis. Aim 2: Determine the independent and combined effects of IRVR and Ex on brain structural and neural network plasticity. Hypothesis: IRVR and Ex prevent or slow hippocampal and whole brain atrophy and improve brain default-mode network (DMN) functional connectivity, while IRVR+Ex will provide greater benefits than either IRVR or Ex alone. Changes in brain volume, structural and DMN functional connectivity will be measured using MRI at baseline, 12 and 24 months. Aim 3: Explore the underlying mechanisms by which IRVR, Ex and IRVR+Ex impact brain structure and function. Hypotheses: 1) IRVR and Ex reduce AD pathology as indicated by the changes in cerebrospinal fluid (CSF) A?42, tau and phosphorylated tau (p-tau), and CNS inflammation; 2) increases in brain perfusion and/or brain-derived neurotrophic factor (BDNF) mediate changes in brain structure and function; 3) IRVR+Ex will have greater impacts on improving AD biomarkers than either IRVR or Ex alone. Novel transcranial Doppler ultrasonography (TCD) methods will be used to assess cerebral autoregulation.