Focused Ultrasound-Induced Blood-Brain Barrier Opening Enhances GSK-3 Inhibitor Delivery for Amyloid-Beta Plaque Reduction.

Alzheimer's disease (AD) is a neurodegenerative disease that is the leading cause of age-related dementia. Currently, therapeutic agent delivery to the CNS is a valued approach for AD therapy. Unfortunately, the CNS penetration is greatly hampered by the blood-brain barrier (BBB). Focused-ultrasound (FUS) has been demonstrated to temporally open the BBB, thus promoting therapeutic agent delivery to the CNS. Recently, the BBB opening procedure was further reported to clear the deposited Aβ plaque due to microglia activation. In this study, we aimed to evaluate whether the use of FUS-induced BBB opening to enhance GSK-3 inhibitor delivery, which would bring additive effect of Aβ plaque clearance by FUS with the reduction of Aβ plaque synthesis by GSK-3 inhibitor in an AD mice model. FUS-induced BBB opening on APPswe/PSEN1-dE9 transgenic mice was performed unilaterally, with the contralateral hemisphere serving as a reference. GSK-3 level was confirmed by immunohistochemistry (IHC) and autoradiography (ARG) was also conducted to quantitatively confirm the Aβ plaque reduction. Results from IHC showed GSK-3 inhibitor effectively reduced GSK-3 activity up to 61.3% with the addition of FUS-BBB opening and confirming the proposed therapeutic route. ARG also showed significant Aβ-plaque reduction up to 31.5%. This study reveals the therapeutic potentials of ultrasound to AD treatment, and may provide a useful strategy for neurodegenerative disease treatment.

Introduction

Purpose Drug delivery with BBB opening

Study Objective To evaluate whether focused ultrasound-induced BBB opening enhances delivery of the GSK-3 inhibitor AR-A014418 to reduce Aβ synthesis and plaque load in an Alzheimer's disease mouse model.

Animal model / Human subject Mouse (Mus musculus), APPswe/PSEN1-dE9 transgenic, 12–14 months old, sex None; Mouse (Mus musculus), wild-type C57BL/6, age None, male; Mouse (Mus musculus), ICR (outbred), age None, sex None

Disease model Alzheimer's disease

MRI or image guidance method Stereotactic frame positioning to target the right hippocampus; contrast-enhanced MRI (Gd-DTPA) used post-FUS for confirmation/optimization

Targeted brain region(s) Hippocampus

Cargo name and characteristics AR-A014418 — small-molecule GSK-3 inhibitor (thiazole N-(4-methoxybenzyl)-N'-(5-nitro-1,3-thiazol-2-yl)urea), MW ≈ 308.3 Da; selective/potent GSK-3 inhibitor, administered intraperitoneally (21 μmol/kg) dissolved in 1% DMSO, weekly.

Route of administration Intraperitoneal (IP) injection

Outcomes and Safety

Summary of Outcomes Combined focused‑ultrasound (FUS)-induced BBB opening with systemic GSK‑3 inhibitor AR‑A014418 markedly downregulated GSK‑3 (up to 81.6% in cortex and 61.3% in hippocampus) and reduced amyloid‑β plaques (cortex: ~31–42%; hippocampus: ~26–40% depending on assay), whereas FUS alone or AR alone produced smaller reductions (FUS alone ~15% hippocampus; AR alone ~22–32%). FUS was applied unilaterally once weekly for 5 sessions to open the BBB and the combined AR+FUS regimen was the most successful.

Safety-related matter No adverse effects were reported in this study; prior literature cited indicates repeated FUS-BBB exposures did not pose additional hazard to brain tissue in healthy brains. The authors caution that peripheral effects of GSK-3 inhibition should be considered clinically but suggest these concerns may be manageable given localized CNS delivery via FUS to reduce systemic retention.

Brain Region

Ultrasound Parameters

Ultrasound instrument Focused ultrasound transducer (Imasonic, France); diameter = 60 mm; radius of curvature = 80 mm; frequency = 400 kHz

FUS Frequency 400 kHz

FUS Pressure 0 MPa; 0.41 MPa; 0.5 MPa

FUS Mode pulsed

Pulse duration 10 ms

Duration of a single FUS session 60 s

Focal Characteristics focal depth: None; focal length: 80 mm; aperture size: 60 mm

Treatment frequency Multiple sessions

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