Growing evidence suggests the contribution of altered brain microcirculation to cognitive impairment and dementia observed in Alzheimer's disease (AD) and AD-related dementia (ADRD). Yet, the lack of approaches to image and investigate the function of the small cerebrovasculature has hampered our progress in understanding the pathological sequence of vascular cognitive impairment and dementia (VCID). The earliest signs of AD and VCID in patients and mouse models typically involve deficits in cerebral blood flow. Specifically, neurons lack energy reserves and thus rely on a “just-in-time” neurovascular coupling (NVC) strategy in which active regions signal to the microvasculature to locally dilate and increase local blood flow. Patients and mouse models of AD or CADASIL, a monogenic archetypal form of VCID, show an early deterioration in NVC. Our previous studies have identified a molecular defect at play in capillary endothelial cells: depletion of phospholipid PIP2 prevents Kir2.1 channels to act as sensors of increases in external K+ — a product of neuronal activity — and transduce this into a vasodilator electrical signal that rapidly propagates to upstream arterioles, driving vasodilation and local hyperemia. We further linked PIP2 depletion to a lower ATP/ADP ratio (i.e., phosphorylation potential) in CADASIL capillary endothelium. Our multidisciplinary team, with complementary expertise in cutting-edge imaging of brain microcirculation and bioenergetic approaches, will test the hypothesis that alterations in the extracellular matrix inhibit autocrine activation of the epidermal growth factor receptor (EGFR) leading to mitochondrial dysfunction and lower ATP production in CADASIL but also in presence on Aβ oligomers. We further propose to investigate this pathomechanism in humans using freshly isolated brain microvessels paired with spatial and single cell transcriptomics in human autopsy brain tissue. To attain this goal, we will engage a wide variety of novel, state-of-the-art experimental approaches using intact animals, native tissue, and freshly isolated cells, complemented by sophisticated multi-omics analysis. Aim 1 will investigate Aβ- induced metabolic impairment in capillary endothelial cells in cerebral amyloid angiopathy (CAA) and Alzheimer's disease (AD) over time. Using extracellular matrix disruptions characteristic of CADASIL as a framework, Aim 2 will elucidate the mechanism by which EGFR inhibition impairs mitochondrial function in capillary endothelium. Finally, Aim3 will create an integrated view of the pathological role of EGFR inhibition and endothelial energetic impairment in in AD/ADRD by investigating this pathway in CAA and AD. The proposed work has the potential to provide a paradigm-shifting view on how capillary endothelial cell energetics control neurovascular coupling, and as such, should provide the foundation for understanding VCID development that is necessary to identify novel efficacious therapeutic strate...