Date of Award
Open Access Dissertation
Melissa A. Moss
Alzheimer’s disease (AD) is characterized symptoms of cognitive impairment resulting from blood-brain barrier (BBB) breakdown and neuronal cell death. AD is associated with aggregated amyloid-β (Aβ) plaques deposited around brain vasculature and within the brain. Changes in the brain occur up to 20 years before symptoms arise; however, there is currently no pre-symptomatic detection method available for AD. An intact BBB requires tight junction proteins (TJs) that render relatively high transendothelial electrical resistance (TEER). AD-associated breakdown of the BBB correlates with vascular Aβ deposition, suggesting that aggregated, pathological Aβ can modulate TEER. We explore leveraging this cellular response for early disease diagnosis via detection of early Aβ aggregates.
Primary human brain microvascular endothelial cells (HBMVECs) were cultured on a suspended membrane and supplemented to mimic the BBB. Once TEER values reflected TJ formation, HBMVEC monolayers were treated with oligomeric Aβ at picomolar to nanomolar concentrations, and TEER was monitored. Oligomeric Aβ at picomolar and nanomolar concentrations, but not monomer, induced a reduction of TEER and disruption of TJs. These results demonstrate that pathogenic Aβ oligomers are uniquely responsible for inducing endothelial monolayer permeability. By reducing monolayer electrical resistance, this response can be detected at physiological concentrations. This response was further explored with the influence of oxidative stress. Cells were sensitized with low concentrations of hydrogen peroxide, and TEER was monitored following exposure to oligomeric Aβ. Inducing oxidative stress simultaneously with oligomeric Aβ treatment elicited a more pronounced decrease in TEER relative to oligomers alone. These results validate that introduction of physiologically active Aβ oligomers to a stress induced state can further decrease electrical resistance of an endothelial monolayer, while non-pathogenetic monomer remains inert.
Together, these results provide evidence that oligomers, the pathogenic form of Aβ, selectively break down the BBB. Translation of this experimental observation to a cell-based biosensor platform will lay the groundwork for the development of cost-effective, early AD detection.
Watson, B. E.(2023). Detecting Physiological Concentrations of Alzheimer’s Associated Amyloid-β Protein Utilizing a Cell-Based Response. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/7221