Adolescent intermittent ethanol exposure produces Sex-Specific changes in BBB Permeability: A potential role for VEGFA

Abstract

Binge drinking that typically begins during adolescence can have long-lasting neurobehavioral consequences, including alterations in the central and peripheral immune systems. Central and peripheral inflammation disrupts blood–brain barrier (BBB) integrity and exacerbates pathology in diseases commonly associated with disturbed BBB function. Thus, the goal of the present studies was to determine long-lasting effects of adolescent intermittent ethanol (AIE) on BBB integrity. For AIE, male and female Sprague Dawley rats were repeatedly exposed to ethanol (4 g/kg, intragastrically) or water during adolescence between postnatal day (P) 30 and P50. In adulthood (∼P75), rats were challenged with fluorescein isothiocyanate (FITC)-tagged Dextran of varying molecular weights (4, 20, & 70 kDa) for assessment of BBB permeability using gross tissue fluorometry (Experiment 1). Experiment 2 extended these effects using immunofluorescence, adding an adult ethanol-exposed group to test for a specific developmental vulnerability. Finally, as a first test of hypothesized mechanism, Experiment 3 examined the effect of AIE on Vascular Endothelial Growth Factor A (VEGFA) and its co-localization with pericytes (identified through expression of platelet derived growth factor receptor beta (PDGFRβ), a key regulatory cell embedded within the BBB. Male, but not female, rats with a history of AIE showed significantly increased dextran permeability in the nucleus accumbens (NAc), cingulate prefrontal cortex (cPFC), and amygdala (AMG). Similar increases in dextran were observed in the hippocampus (HPC) and ventral tegmental area (VTA) of male rats with a history of AIE or equivalent ethanol exposure during adulthood. No changes in BBB permeability were evident in females. When VEGFa expression was examined, male rats exposed to AIE were challenged with 3.5 g/kg ethanol (i.p.) or vehicle acutely in adulthood to assess long-lasting versus acute actions of ethanol. Adult rats with a history of AIE showed significantly fewer total cells expressing VEGFa in the AMG and dHPC following the acute ethanol challenge in adulthood. They also showed a significant reduction in the number of PDGFRβ positive cells that also expressed VEGFa signal. The anatomical distribution of these effects corresponded with increased BBB permeability after AIE (i.e., differential effects in the PVN, AMG, and dHPC). These studies demonstrated sex-specific effects of AIE, with males, but not females, demonstrating long-term increases in BBB permeability that correlated with changes in VEGFa and PDGFRβ protein, two factors known to influence BBB permeability.