Investigating the contributions and impact of neutrophil activity in a comorbid model of AD and VCID

Indiana University Indianapolis, Indianapolis IN

Investigators

Abstract

Project Summary/Abstract Alzheimer’s disease (AD) is the most common form of dementia often presenting with vascular contributions to cognitive impairment and dementia (VCID). Growing evidence has highlighted pathological contributions from an immune cell within the peripheral immune system: neutrophils. In cases of hyperhomocysteinemia (HHcy), a common risk factor for VCID, neutrophils cause vascular damage by oxidative stress and releasing products for matrix degradation as well as increasing blood hypercoagulability via release of neutrophil extracellular traps (NETs), any of which can be a confounding factor in current therapeutics. This proposal aims to investigate the mechanisms by which neutrophils are contributing to worsened cerebrovascular outcomes in AD and VCID, and the impact of depleting neutrophils on disease pathology to give a broader picture of immune-mediated neuropathologies. To answer these questions, we propose to examine the neutrophil response to APP, VCID, and APP-VCID comorbidities (Aim 1) and determine whether chronic depletion of neutrophils reduces neuropathology for each case (Aim 2). We hypothesize that mechanisms unique to each pathology will be additive while overlapping mechanisms across pathologies will be exacerbated. For Aim 1, cohorts of wild-type or Tg2576 mice will be placed on control diet or diet to induce HHcy. In vivo multiphoton microscopy imaging, flow cytometry, single- cell RNA sequencing, and intravascular labeling of leukocytes prior to tissue collection will be used to examine upregulated mechanisms. In Aim 2, mice from Aim 1 will be given isotype control antibody or murinized anti- Ly6G antibody for chronic neutrophil depletion at the start of diet to assess changes in physiological and cognitive outcomes. We will test the hypothesis that chronic depletion reduces the severity of comorbid disease pathology by longitudinal imaging using MRI, multiphoton imaging, and immunohistochemical assays for neuroinflammation and vascular damage. These aims will provide important information on an overlooked factor to vascular dementias. Achievement of these aims will aid in my own goals of becoming an independent researcher by improving my scientific knowledge of VCID and AD as well as supplement my available research skills in MRI, immunohistochemistry, and single-cell transcriptomics. To complete these aims, I have the resources at Indiana University – Indianapolis such as the Alzheimer’s Disease Research Center as part of the NIH, a program for developing new mouse models (MODEL-AD) to be used for investigating new treatments (TREAT- AD), as well as a well-equipped environment for dementia-related studies. My mentor, Dr. Wilcock, and mentoring committee will guide my professional development by providing assistance with my written and communicative skillsets as well as expanding upon my academic network. Overall, this proposal will provide both scientific and professional development training while adding important knowledge to the AD/VCID field.