PROJECT SUMMARY MAIN 3 The Blood-Brain Barrier (BBB) plays an indispensable role in protecting the Central Nervous System (CNS) by restricting the ability of blood-borne pathogens, circulating immune cells, and macromolecules from passing into the brain parenchyma where these agents can exert a disruptive influence on CNS function. Recent studies have shown that BBB integrity waxes and wanes in response to psychological distress and immunological challenge, contributing to anxiety, depression, and even heightened suicidality. Importantly, human post-mortem studies showed BBB disruption among deceased males with Alcohol Use Disorder (AUD). Our lab recently revealed long-lasting effects of Adolescent Intermittent Ethanol (AIE) on BBB integrity that were sex-specific and brain region-selective. In males, AIE-induced BBB alterations were evident in early adulthood after a three-week period of forced abstinence, whereas females were largely unaffected. These findings call for comprehensive studies of sex-specific neurovascular dysfunction associated with AIE. One biological mechanism known to compensate for compromised BBB integrity is through increased deposition of Amyloid-b (Ab) protein in perivascular regions, which, as a “sticky” protein, attempts to seal the BBB and prevent enhanced permeability. Importantly, AIE has recently been shown to increase Ab(1-42) deposition and tau hyperphosphorylation in 3X transgenic mouse model of Alzheimer’s Disease (AD), exclusively in females when tested at 6-7 months of age. Consistent with this, we recently reported that long-term ethanol consumption later in life increased co-localization of Ab(1-42) in iba1+ cells (microglia) that were located in close proximity to the neurovasculature exclusively in female rats, and in the absence of transgenes that promote vulnerability to familial AD. Thus, emerging evidence suggests that chronic intermittent ethanol exposure produces distinctive patterns of neurovascular dysfunction in males and females, contributing to sex-specific outcomes later in life. The over-arching goal of this proposal, therefore, is to determine the sex-specific mechanisms by which AIE produces long-lasting changes in neurovascular integrity, with male-specific increases in BBB permeability and female-specific increases in Ab(1-42) deposition playing major roles in AIE-associated neurovascular dysfunction. Studies proposed in three Specific Aims will (i) fill critical gaps in our knowledge regarding natural development of the BBB during adolescence, (ii) provide new insight into reactivity of the BBB to acute ethanol challenge during adolescence and adulthood; (iii) establish distinct and separable paths of AIE-induced neurovascular dysfunction in male and female rats across adulthood; and (iv) test novel hypotheses regarding loss of BBB integrity as a harbinger of neurovascular dysfunction. These studies will provide much needed information about contributions of early life alcohol exposure to...