BKCanitrosylation is associated with cerebral microvascular dysfunction in female5x-FADmice

Abstract

AbstractCerebral microvascular dysfunction and nitro-oxidative stress are present in patients with Alzheimer’s disease (AD) and may contribute to disease progression and severity. Large conductance Ca2+-activated K+channels (BKCa) play an essential role in vasodilatory responses and maintenance of myogenic tone in resistance arteries. BKCacan be modified in a pro-nitro-oxidative environment, resulting in decreased activity and vascular hyper-contractility, which can compromise cerebral blood flow regulation. We hypothesized that reductions in BKCafunction in cerebral arteries, as a consequence of nitro-oxidative stress, are associated with blunted neurovascular responses in the5x-FADmodel of AD. Using pressure myography, we observed that posterior communicating arteries (PComA) from 5 months-old female5x-FADmice showed higher spontaneous myogenic tone than wild-type (WT) littermates. Constriction to the BKCablocker iberiotoxin (30 nM) was smaller in5x-FADthan WT, suggesting lower basal BKCaactivity, which was independent of alterations in intracellular Ca2+transients or BKCamRNA expression. These vascular changes were associated with higher levels of oxidative stress in female5x-FADand a higher level of S-nitrosylation in the BKCaα-subunit. In females, pre-incubation of PComA from5x-FADwith the reducing agent DTT (10 µM) rescued iberiotoxin-induced contraction. Female5x-FADmice showed increased expression of iNOS mRNA, lower resting cortical perfusion atop the frontal cortex, and impaired neurovascular coupling responses. No significant differences between male5x-FADand WT were observed for all parameters above. These data suggest that the exacerbation in BKCaS-nitrosylation contributes to cerebrovascular and neurovascular impairments in female5x-FADmice.Significance StatementCerebral vascular dysfunction is increasingly recognized as a hallmark of Alzheimer’s disease and other dementias. Impaired microvascular regulation can lead to deficits in blood flow to the brain. An intrinsic property of the resistance vasculature is to constrict when pressurized (myogenic tone), generating a vasodilatory reserve. Detrimental over-constriction is prevented by vascular feedback mechanisms, including the opening of large-conductance Ca2+-activated K+channels (BKCa). Here, using a combination of molecular biology tools withex vivoandin vivovascular assessments, we show a novel mechanism associated with BKCadysfunction in the cerebral microvasculature of female5x-FADmice. We report increased BKCaS-nitrosylation linked to reduced activity and, consequently, higher basal myogenic tone. These changes were associated with lower perfusion of the frontal cortex and impaired neurovascular reactivity, suggesting that nitro-oxidative stress is an important mechanism of vascular dysfunction in Alzheimer’s disease.