2009 — 2011 |
Castellano, Joseph |
F31Activity Code Description: To provide predoctoral individuals with supervised research training in specified health and health-related areas leading toward the research degree (e.g., Ph.D.). |
The Role of Human Apoe in Soluble Abeta Clearance Through the Ldlr in Vivo
DESCRIPTION (provided by applicant): The leading cause of dementia is Alzheimer's disease (AD), which is characterized by a progressive loss of cognitive function and memory, ultimately leading in death. It is estimated that over 5 million Americans currently suffer for AD, and the direct healthcare cost associated with AD and related dementias annually exceeds $145 billion. As the population ages over the next several decades, the health-care burden presented by AD will be staggering. Understanding the pathogenesis of this age-related disease is c critical to the development of effective therapies and is the primary motivation for this research proposal. Deposition of the Amyloidal (3 (A|3) peptide in the extracellular space of the brain constitutes one of the key pathological hallmarks of AD. Inheritance of apolipoprotein E4 (apoE4) is the major genetic risk factor for late-onset AD identified so far, while apoE2 inheritance appears to be protective. Toxic accumulation of the A(3 peptide is likely regulated by the rates of its production and its clearance from the interstitial fluid (ISF) of the brain;since apoE does not affect the synthesis of Ap, it likely regulates A|3 clearance from the ISF. Our group and others have shown that the binding between apoE and Ap influences Ap deposition and its clearance ifrom the brain. Abundant evidence indicates that the low density lipoprotein receptor (LDLR) is a major apoE receptor in the brain, likely providing an important clearance route for soluble Ap from the ISF. The process by which LDLR regulates Ap clearance in the context of human apoE isoforms remains poorly understood. My objective is to determine the role of LDLR in regulating human apoE-mediated clearance of Ap from the ISF. I hypothesize that apoE-mediated elimination of Ap from the ISF is facilitated by LDLR and follows a pattern that is isoform-dependent such that Ap clearance rate for apoE2 >apoE3 >apoE4. In Specific Aim 1,1 will use our in vivo microdialysis technique to directly assess Ap clearance in mice expressing each of the human apoE isoforms, comparing them to the same mice lacking LDLR. To complement this study, I will determine the AP half-life in the ISF of mice overexpressing LDLR and each of the human apoE isoforms. In Specific Aim 2,1 will analyze extracellular pools of Ap in mice overexpressing LDLR and each of the human apoE isoforms at ages prior to and after Ap deposition to assess LDLR's regulation of Ap levels in regions of the brain where deposits form. To assess the effect of LDLR on Ap deposition in the context of human apoE, I will quantify plaque load in brain sections from each of the groups of mice. The relevance of my proposed research plan to public health is that understanding the mechanisms by which LDLR and human apoE act to mediate Ap clearance will be critical to designing effective new therapies for AD.
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0.87 |
2016 — 2019 |
Castellano, Joseph |
K99Activity Code Description: To support the initial phase of a Career/Research Transition award program that provides 1-2 years of mentored support for highly motivated, advanced postdoctoral research scientists. R00Activity Code Description: To support the second phase of a Career/Research Transition award program that provides 1 -3 years of independent research support (R00) contingent on securing an independent research position. Award recipients will be expected to compete successfully for independent R01 support from the NIH during the R00 research transition award period. |
Regulation of Hippocampal Plasticity and Learning and Memory by a Bloodborne Rejuvenation Factor
Aging is the major risk factor for Alzheimer?s disease (AD), leading to cellular and functional changes within the brain that culminate in dementia and cognitive decline. Lessening or reversing brain aging may delay Alzheimer?s disease onset or even protect against Alzheimer?s pathogenesis, having a large effect on quality of life and health burden imposed by AD. This proposal tests the hypothesis that young plasma reverses hippocampal decline in plasticity and learning/memory in the aged brain through regulation of transcriptional programs, including gene networks involving Alzheimer?s pathogenesis. TIMP2 is a key blood-borne factor enriched in young plasma that enhances hippocampal Activator-protein 1 (AP-1) and other plasticity markers, while reversing hippocampal cognitive decline in aged mice. Experiments will examine young plasma-mediated and TIMP2-mediated enhancement of AP-1, a transcriptional regulator of genes involved in hippocampal function, including MMPs that are intimately tied to amyloid-? metabolism. I will investigate the role of TIMP2 in mediating transcriptional changes in plasticity and Alzheimer?s-related genes in the aged hippocampus and the extent to which TIMP2 is a necessary factor for the beneficial effects conferred by young plasma. The mechanism by which TIMP2 improves hippocampal function, including its site of action, duration of its transcriptional control, and the effect of long-term increased TIMP2 activity on limiting cognitive decline in aged mice will be investigated. The results may inform therapies directed at restoring TIMP2 function as a treatment for Alzheimer?s disease. To fully characterize transcriptional changes induced by both young plasma and blood-borne TIMP2, Aim 1 will use next-generation sequencing methods (RNA-seq and ChIP-seq) in aged hippocampal tissue from mice treated systemically with young plasma, TIMP2, or control. ChIP-seq will be performed to identify all genes bound and regulated by AP-1 following treatment. Aim 2 assesses the necessity of TIMP2 for the cognitive improvements and transcriptional changes (identified in Aim 1) mediated by young plasma. Mice treated with young plasma will be compared to those receiving TIMP2-depleted (or KO) plasma or control. Aim 3 examines TIMP2?s site of action for improvements in aged hippocampal function (peripheral vs central) using a neutralization approach. The duration of TIMP2?s transcriptional regulation following treatment and the transcriptional and cognitive consequences of long-term peripheral TIMP2 expression using a viral-mediated approach will be pursued. Together, these aims critically assess the role of systemic TIMP2 in reversing hippocampal cognitive decline as a means to limit the impact of Alzheimer?s disease.
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1 |
2020 — 2021 |
Castellano, Joseph Michael |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Mechanisms of Timp2-Mediated Hippocampal Revitalization in Alzheimer's Disease @ Icahn School of Medicine At Mount Sinai
Project Summary/Abstract: Declining cognitive function is a hallmark feature of the aging process in the elderly population. Since aging is the major risk factor for many leading causes of death, including dementias such as Alzheimer's disease (AD), novel targets and strategies are needed as this population grows in the US and beyond. Though the conventional view has held that plasticity is limited in the aged brain, emerging data has challenged this notion, revealing that factors present within young blood are restorative for aged tissues throughout the body while suggesting links between the systemic environment and aging- and Alzheimer's- related changes in the brain. Aged mice sharing young blood via the parabiosis model or through plasma transfer exhibit improved synaptic plasticity, dendritic spine number, and cognitive performance, which led me to explore novel brain activities for systemic protein factors that may have relevance for AD. Our recently published work uncovered tissue inhibitor of metalloproteinases 2 (TIMP2), a protein enriched in developmentally-early human and young mouse plasma versus aged plasma that plays a surprisingly central role in regulating synaptic plasticity within the hippocampus. I showed that treatment with TIMP2 significantly revitalizes hippocampal function, as assessed by gene expression, long-term potentiation, and memory performance in hippocampal-dependent behavioral tasks. Moreover, removing TIMP2 from hippocampal slices dramatically reduced LTP and its loss in plasma ablated cognitive improvements conferred by young plasma. This work has nonetheless left many fundamental questions open related to TIMP2's function within the hippocampus, and its role in Alzheimer's disease remains unexplored. Recent work shows significantly reduced TIMP2 levels in AD patients with vascular changes in CSF and altered levels of TIMP2 target MMP2 in plasma; our preliminary data support a perturbation of TIMP2 metabolism in plasma in mouse models of AD pathology. We also find that TIMP2 expression decreases within dentate gyrus mossy cells important for the LTP response. In this work, we will probe the mechanism by which CNS TIMP2 directly regulates hippocampal function and the extent to which TIMP2 regulates hippocampal function in AD via changes in synaptic integrity as well as amyloid-? (A?)-dependent mechanisms. We hypothesize that TIMP2 regulates synaptic function in the normal hippocampus and is restorative in the context of AD pathology, primarily by acting to maintain synaptic integrity. We will address this hypothesis in three major aims: (1) To assess functional effects in mice in which hippocampal TIMP2 has been targeted and to evaluate the contribution of its source in mossy cells to plasticity, (2) to assess the role of canonical and putative TIMP2 targets within the hippocampus, (3) and to investigate the role of TIMP2 and related pathways in amyloid-independent and amyloid-dependent mechanisms of AD pathology. Our aims will interrogate the function of TIMP2, a novel molecule with pro- plasticity roles in the hippocampus, having implications for development and creation of AD therapies.
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1 |
2021 |
Castellano, Joseph Michael |
RF1Activity Code Description: To support a discrete, specific, circumscribed project to be performed by the named investigator(s) in an area representing specific interest and competencies based on the mission of the agency, using standard peer review criteria. This is the multi-year funded equivalent of the R01 but can be used also for multi-year funding of other research project grants such as R03, R21 as appropriate. |
Mechanisms of Youth-Associated Blood-Borne Factors Regulating Cns Rejuvenation @ Icahn School of Medicine At Mount Sinai
Project Summary/Abstract: Novel approaches are needed to combat age-associated diseases of the brain, including Alzheimer?s disease (AD). Aging is the strongest risk factor for AD, yet we lack a detailed mechanistic understanding connecting normal aging to AD. Emerging data raise the possibility that neural plasticity can be revitalized in aged organisms. These studies demonstrate that factors present in young blood are restorative for aged tissues throughout the body, while suggesting links between the systemic environment and aging- and AD-related changes in the brain. Aged mice sharing young blood via parabiosis or those treated via plasma injections exhibit improved plasticity and improved cognitive performance. We provided evidence for specific youth-associated proteins, tissue inhibitor of metalloproteinases 2 (TIMP2) and colony-stimulating factor 2 (CSF2), that revitalize hippocampal function in aged mice when provided systemically. Conversely, several studies demonstrate that aged blood factors drive key aging phenotypes, including microgliosis and loss of neurogenesis, as well as hippocampus-dependent cognitive deficits, working in part through CCL11 and B2M. These studies leave fundamental questions open regarding the role of the systemic environment in aging and its link to AD through modulation of pathology. Recent work supports a role of blood-borne factors in modulating the state and function of the brain?s innate immune cells, microglia. Given this connection and data linking many AD risk genes to innate immune function, there is clear rationale to explore the link between aging and AD-related pathology through microglia. In preliminary studies, we find that exposure to young blood reduces microgliosis in the brains of aged mice, suggesting that young blood factors regulate microglia state in aging. In this proposal, we will rigorously address the role of youth-associated proteins in altering microglial gene expression and morphological profiles with the goal of clarifying the link between aging and AD pathomechanisms. We hypothesize that youth-associated factors rejuvenate microglia profiles in the aged brain and in the context of AD pathology. We will address this hypothesis in three major aims: (1) To determine the impact of systemic TIMP2 on microglia gene expression and morphology in aged mice; (2) to characterize the extent to which blood-borne brain rejuvenation is regulated by microglia function; and (3) to evaluate the impact of a combined systemic treatment of TIMP2 and CSF2 on age-associated vs. AD-associated changes in microglia profile and state. Our aims will interrogate the role of youth-associated blood-borne factors in regulating microglia using sophisticated approaches to rigorously define cellular and pathological regulation by the systemic environment, potentially opening novel avenues for AD therapy development.
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