PROJECT SUMMARY/ABSTRACT Aging is one of the major risk factors for the development and progression of cerebrovascular, cardiovascular, and neurodegenerative diseases, contributing to long-term disability and mortality in the elderly. Aging- associated progressive structural and functional decline of vascular cells lead to vascular dysfunction such as decreased cerebral blood flow. While the vasculature is one of the most important targets of aging, it is not clear whether accumulating vascular pathologies or aging drives vascular dysfunction. The overall long-term goal of this project is to elucidate aging, and brain hypoperfusion-associated temporal changes in the cerebral vasculature. We will test the hypothesis that brain hypoperfusion exacerbates aging-associated compromised blood-brain-barrier integrity facilitated by mitochondrial dysfunction. To test our overall hypothesis, we proposed two specific aims. We will use young and old, male, and female mito-Dendra2 expressing and wild type mice in the proposed studies. Bilateral common carotid artery stenosis (BCAS) will be used to mimic cerebral hypoperfusion. The therapeutic potential of vascular mitochondria will be tested using a mitochondria targeted tetrapeptide. Two-photon microscopy will be used to determine how hypoperfusion exacerbates aging-associated BBB dysfunction in vivo, to map the brain vasculature, and vascular mitochondrial dynamics real time. Our studies will be complemented with immunofluorescence studies, discovery-based proteomics approach, and Western blot. The proposed research will reveal how aging and cerebral hypoperfusion affect endothelial mitochondria, and will elucidate mechanisms that might contribute to aging-related pathologies such as Alzheimer’s disease.