Dee Shen¹, Kui Tian¹, Peter Banks², and Wayne F. Patton^1
1Enzo Life Sciences, Farmingdale, NY, USA
²BioTek Instruments, Winooski, VT 05404 USA

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INTRODUCTION

A seminal study by Sutcliffe et al. (2011) highlights unexpected results that the liver, and not the brain, may be the primary source of β-amyloid deposits in the brain associated with Alzheimer’s disease (1). In the cited study, scientists from the Scripps Research Institute and ModGene, LLC used a mouse model for Alzheimer’s disease to identify genes that influence the amount of β-amyloid accumulation in the brain. They identified three genes that protected mice from brain β-amyloid accumulation and deposition. One of the genes is known to encode Presenilin-2, a plasma membrane protein previously associated with the etiology of human Alzheimer’s disease. Presenilin-2, is a component of an enzyme complex involved in the generation of pathogenic β-amyloid peptide. Higher expression levels of Presenilin-2 in the liver (but not the brain) correlated with greater accumulation of β-amyloid in the brain and development of Alzheimer’s-like pathology in mice. As the blood-brain barrier weakens with age, exogenous β-amyloid produced in the liver may be able to circulate in the blood, infiltrate the brain by an ill-characterized heterophagic mechanism, supplement brain-produced β-amyloid, and hasten neurodegeneration.

It can be hypothesized that alterations of the liver’s degradative capabilities potentially contribute to β-amyloid levels in the brain. Using a β-amyloid degradation assay, Maarouf et al. (2018) demonstrated that β-amyloid degradation rates were lower in Alzheimer’s disease subjects when compared with non-demented control subjects (2). Looking further at the expression of potential β-amyloid-degrading enzymes, they showed that cathepsin D and insulin-degrading enzyme, but not neprysilin, were significantly down-regulated in Alzheimer’s disease subjects. Although lower β-amyloid degradation rates could be a consequence of the disease rather than a contributing cause, these results do highlight the need to further investigate the role of β-amyloid produced in tissues other than the brain in the pathogenesis of Alzheimer’s disease.

OBJECTIVES

• Develop a cell-based model of β-amyloid heterophagic accumulation, using a readily available neuroblastoma cell line.
• Develop a fluorescent assay to visualize β-amyloid aggregates formed within the cells.
• Screen for small molecule compounds that induce formation of aggregates within the cells.
• Screen for small molecule compounds that prevent accumulation of β-amyloid aggregates within the cells that prevent accumulation of β-amyloid aggregates.