Dataset Information

Protecting P-glycoprotein at the blood-brain barrier from degradation in an Alzheimer's disease mouse model.

ABSTRACT:

Background

Failure to clear A? from the brain is partly responsible for A? brain accumulation in Alzheimer's disease (AD). A critical protein for clearing A? across the blood-brain barrier is the efflux transporter P-glycoprotein (P-gp). In AD, P-gp levels are reduced, which contributes to impaired A? brain clearance. However, the mechanism responsible for decreased P-gp levels is poorly understood and there are no strategies available to protect P-gp. We previously demonstrated in isolated brain capillaries ex vivo that human A?40 (hA?40) triggers P-gp degradation by activating the ubiquitin-proteasome pathway. In this pathway, hA?40 initiates P-gp ubiquitination, leading to internalization and proteasomal degradation of P-gp, which then results in decreased P-gp protein expression and transport activity levels. Here, we extend this line of research and present results from an in vivo study using a transgenic mouse model of AD (human amyloid precursor protein (hAPP)-overexpressing mice; Tg2576).

Methods

In our study, hAPP mice were treated with vehicle, nocodazole (NCZ, microtubule inhibitor to block P-gp internalization), or a combination of NCZ and the P-gp inhibitor cyclosporin A (CSA). We determined P-gp protein expression and transport activity levels in isolated mouse brain capillaries and A? levels in plasma and brain tissue.

Results

Treating hAPP mice with 5 mg/kg NCZ for 14 days increased P-gp levels to levels found in WT mice. Consistent with this, P-gp-mediated hA?42 transport in brain capillaries was increased in NCZ-treated hAPP mice compared to untreated hAPP mice. Importantly, NCZ treatment significantly lowered hA?40 and hA?42 brain levels in hAPP mice, whereas hA?40 and hA?42 levels in plasma remained unchanged.

Conclusions

These findings provide in vivo evidence that microtubule inhibition maintains P-gp protein expression and transport activity levels, which in turn helps to lower hA? brain levels in hAPP mice. Thus, protecting P-gp at the blood-brain barrier may provide a novel therapeutic strategy for AD and other A?-based pathologies.

SUBMITTER: Ding Y

PROVIDER: S-EPMC7937299 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:Focused ultrasound (FUS) is used to locally and transiently induce blood-brain barrier (BBB) permeability, allowing targeted drug delivery to the brain. The purpose of the current study is to evaluate the potential of Vasculotide to accelerate the recovery of the BBB following FUS disruption in the TgCRND8 mouse model of amyloidosis, characteristic of Alzheimer's disease (AD). Accelerating the restoration of the BBB post-FUS would represent an additional safety procedure, which could be beneficial for clinical applications. Methods: TgCRND8 mice and their non-transgenic littermates were treated with Vasculotide (250 ng, intraperitoneal) every 48 hours for 3 months. BBB permeability was induced using FUS, in presence of intravenously injected microbubbles, in TgCRND8 and non-transgenic mice, and confirmed at time 0 by MRI enhancement using the contrast agent gadolinium. BBB closure was assessed at 6, 12 and 20 hours by MRI. In a separate cohort of animals, BBB closure was assessed at 24-hours post-FUS using Evans blue injected intravenously and followed by histological evaluation. Results: Chronic Vasculotide administration significantly reduces the ultra-harmonic threshold required for FUS-induced BBB permeability in the TgCRND8 mice. In addition, Vasculotide treatment led to a faster restoration of the BBB following FUS in TgCRND8 mice. BBB closure after FUS is not significantly different between TgCRND8 and non-transgenic mice. BBB permeability was assessed by gadolinium up to 20-hours post-FUS, demonstrating 87% closure in Vasculotide treated TgCRND8 mice, as opposed to 52% in PBS treated TgCRND8 mice, 58% in PBS treated non-transgenic mice, and 74% in Vasculotide treated non-transgenic mice. In both TgCRND8 mice and non-transgenic littermates the BBB was impermeable to Evans blue dye at 24-hours post-FUS. Conclusion: Vasculotide reduces the pressure required for microbubble ultra-harmonic onset for FUS-induced BBB permeability and it accelerates BBB restoration in a mouse model of amyloidosis, suggesting its potential clinical utility to promote vascular health, plasticity and repair in AD.