Tau protein differentially affects Piezo1 and Kir2.1 channels in brain capillary endothelial cells

Accumulation of amyloid-β (Aβ) peptides and Tau proteins in the brain is a hallmark of neurodegeneration. Such build-up forms Aβ plaques and Tau neurofibrillary tangles, both of which are associated with synaptic loss, cognitive decline, and reduced cerebral blood flow in Alzheimer's disease (AD). Two ion channels in brain capillary endothelial cells (ECs)-the inwardly rectifying potassium channel Kir2.1 and the mechanosensitive channel Piezo1-are critical regulators of cerebral blood flow, and both display impaired activity in AD. Whether Aβ and Tau affect these channels remains incompletely understood. Using patch-clamp electrophysiology and freshly isolated mouse brain capillary ECs, we examined whether Aβ_1-40 or Tau-441 directly modulate Kir2.1 or Piezo1 function. Exogenously applied Aβ_1-40 (10-100 nM) and Tau-441 (10-50 nM) had minimal effect on Kir2.1 current density, indicating that the Kir2.1 deficits observed in AD are less likely caused by direct interactions with Aβ or Tau. In contrast, we previously demonstrated that nanomolar Aβ_1-40 enhanced Piezo1 function. We further show here that 50 nM Tau-441 significantly increased Piezo1 open probability, and this enhancement was abolished by the superoxide dismutase and catalase mimetic EUK-134. These data collectively suggest that altered Piezo1 function in neurodegenerative disease could involve a direct effect of Aβ peptides or Tau proteins and further suggest that acute exposure to these proteins minimally impacts Kir2.1 activity. These novel findings present a new pathway through which Tau proteins could impair neurovascular function during neurodegeneration.