PROJECT SUMMARY Alzheimer’s Disease (AD) is a progressive neurodegenerative brain disorder that impairs memory and cognitive functions. It is the most common dementia among older adults over age 65 and it is estimated that more than 5.8 million Americans may have dementia caused by AD. While the pathogenesis of AD is unclear, abnormal deposits of amyloid-β (Aβ) plaques and hyperphosphorylated tau proteins throughout the brain are thought to play a role in neuroinflammation, synapse loss, and neuronal cell death. While Aβ appears to spread in a diffuse manner, phosphorylated tau proteins are hypothesized to propagate between synaptically connected neurons. Recent studies suggest that the presence of Aβ may increase the rate of propagation, potentially due to neuroinflammatory effects. In addition, neuroinflammation may directly induce or exacerbate Aβ and tau proteinopathies, thereby worsen neuroinflammation and leading to further loss of synapses and neurons, creating a vicious cycle that likely promotes disease progression. However, the exact mechanisms that underlie propagation phosphorylated tau and its interplay with neuroinflammation remain elusive. Distinguishing these complex factors from each other in vivo, where numerous confounding signals exist, is extremely challenging. There is, therefore, a need for new methodologies to bridge this gap for revealing the underlying mechanisms by which transport of aberrant proteins and neuroinflammation accelerate the progression of AD. In order to address this need, we will employ a microfluidic in vitro platform in combination with a novel tri-culture (primary neuron, astrocyte, microglia) rat model of neuroinflammation that have been developed as part of the PIs’ current R03 award. The microfluidic platform consists of two physically distinct culture chambers (e.g., primary and secondary), corresponding to proximal and distal anatomic regions interconnected by microchannels that allow synaptic connectivity between the two cultures. The immediate goal of this administrative supplement is to study the contribution of glial cells and inflammation to the transport of abnormal tau proteins. Specifically, we will (i) determine the influence of Aβ and phosphorylated human tau (expressed by transfected neurons) on neuroinflammation in the tri-culture model, and (ii) employ the microfluidic platform to decouple the influences of Aβ addition itself and the Aβ-triggered neuroinflammation on tau propagation along the axonal tracts connecting the two cultures maintained in the primary and secondary chambers. The pilot study described here is expected to (i) identify the influence of pathogenic conformations Aβ added to the culture and/or human tau expression by transfected neurons on neuroinflammation, (ii) decouple the influence of pathogenic Aβ itself or its corresponding neuroinflammatory cytokine profile on propagation of pathogenic tau via axonal tracts, and (iii) establish the foundation for future mecha...