ABSTRACT Endothelial cells (ECs), astrocytes and pericytes are integral components of the neurovascular unit (NVU) and play critical roles in blood brain barrier (BBB) formation and maintenance. These cells express uptake and efflux membrane transporters that regulate CNS penetration of molecules, therapeutic drugs and toxins. The function of the BBB and transporters is likely disrupted in many neurological disorders. Thus, development of tools to study NVU cells and their properties of BBB selective transport in vivo is a key priority in translational neuroscience research. We have discovered a unique set of small molecules that can be selectively transported into the cytoplasm of either ECs, pericytes or astrocytes with exquisite affinity and specificity. We have evidence that these molecules enter cells through membrane transporters, selectively expressed in each cell type. We hypothesize that these molecules could be adapted as probes for intravital animal and human imaging and also for cell-specific delivery of drugs. In this proposal, we aim to identify the precise mechanisms of probe membrane transport in vivo; establish the feasibility of using these molecules as cell-specific drug carriers or as radiopharmaceuticals for human imaging with positron emission tomography (PET) and finally test their in vivo properties in models of Alzheimer's disease and stroke. This project will improve our understanding of molecular transport mechanisms across the BBB and may transform the ability to selectively image and pharmacologically modulate cells of the NVU in health and disease.

NARRATIVE The blood brain barrier (BBB) is a very important structure that regulates the transport of many molecules that are critical for brain function and health. Endothelial cells, pericytes and astrocytes and critical cells in the formation and maintenance of the BBB and in the regulation of transport of molecules into the brain. However, there are very few tools to study these cells and transport mechanisms in vivo, especially in humans. We have discovered a group of molecules that we think can be used to develop probes to selectively deliver drugs and image these cells in animals and humans. In this proposal we will characterize in depth how these probes work and will do proof of principle experiments to determine their potential as cell specific probes in mice and humans. Finally, we will test the properties of the probes in Alzheimer's disease and stroke mouse models.