Stress-induced dysfunction of neurovascular astrocytes in the prefrontal cortex contributes to sex-dependent deficits in cognition and behavior.

Astrocytes form an integral component of the neurovascular unit, ensheathing brain blood vessels with endfeet high in aquaporin-4 (AQP4) expression. These AQP4-rich endfeet facilitate interaction between the vascular endothelium, astrocytes, and neurons, and help stabilize vascular morphology. Studies using preclinical models of psychological stress and post-mortem tissue from patients with major depressive disorder (MDD) have reported reductions in AQP4, loss of astrocytic structures, and vascular impairment in the prefrontal cortex (PFC). Though compelling, the role of AQP4 in mediating stress-induced alterations in neurovascular function and behavior remains unclear. Here, we address this, alongside potential sex differences in chronic unpredictable stress (CUS) effects on astrocyte phenotype, blood-brain barrier integrity, and behavior. CUS led to more pronounced shifts in stress-coping behavior and working memory deficits in male- as compared to female mice. Following behavioral testing, astrocytes from the frontal cortex were isolated for gene expression analyses. We found that CUS increased transcripts associated with blood vessel maintenance in males, but either had no effect on- or decreased- these transcripts in females. Furthermore, CUS caused a reduction in vascular-localized AQP4 and elevated extravasation of a small fluorescent reporter (Dextran) in the PFC in males but not females. Studies showed that knockdown of AQP4 in the PFC is sufficient to disrupt astrocyte phenotype and increase behavioral susceptibility to a sub-chronic stressor in males yet has little effect on stress susceptibility in females. Our findings provide evidence that sex-specific alterations in astrocyte phenotype and neurovascular integrity in the PFC contribute to cognitive-behavioral consequences following stress.