Amyloid-β plaque reduction, endogenous antibody delivery and glial activation by brain-targeted, transcranial focused ultrasound

Exp Neurol. 2013 Oct;248:16-29. doi: 10.1016/j.expneurol.2013.05.008. Epub 2013 May 21.

Abstract

Noninvasive, targeted drug delivery to the brain can be achieved using transcranial focused ultrasound (FUS), which transiently increases the permeability of the blood-brain barrier (BBB) for localized delivery of therapeutics from the blood to the brain. Previously, we have demonstrated that FUS can deliver intravenously-administered antibodies to the brain of a mouse model of Alzheimer's disease (AD) and rapidly reduce plaques composed of amyloid-β peptides (Aβ). Here, we investigated two potential effects of transcranial FUS itself that could contribute to a reduction of plaque pathology, namely the delivery of endogenous antibodies to the brain and the activation of glial cells. We demonstrate that transcranial FUS application leads to a significant reduction in plaque burden four days after a single treatment in the TgCRND8 mouse model of AD and that endogenous antibodies are found bound to Aβ plaques. Immunohistochemical and western blot analyses showed an increase in endogenous immunoglobulins within the FUS-targeted cortex. Subsequently, microglia and astrocytes in FUS-treated cortical regions show signs of activation through increases in protein expression and changes in glial size, without changes in glial cell numbers. Enhanced activation of glia correlated with increased internalization of Aβ in microglia and astrocytes. Together these data demonstrate that FUS improved the bioavailability of endogenous antibodies and led to a temporal activation of glial cells, providing evidence towards antibody- and glia-dependent mechanisms of FUS-mediated plaque reduction.

Keywords: Alzheimer's disease; Amyloid-beta peptide; Astrocytes; Autoantibodies; Focused ultrasound; Immunoglobulin; Microglia; Transgenic mice.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alzheimer Disease / metabolism
  • Alzheimer Disease / pathology
  • Alzheimer Disease / therapy*
  • Amyloid beta-Peptides / genetics
  • Amyloid beta-Peptides / metabolism
  • Amyloid beta-Protein Precursor / genetics
  • Amyloid beta-Protein Precursor / metabolism
  • Animals
  • Blood-Brain Barrier / metabolism
  • Blood-Brain Barrier / pathology
  • Brain / metabolism
  • Brain / pathology
  • Female
  • Immunoglobulin G / metabolism*
  • Immunoglobulin M / metabolism*
  • Male
  • Mice
  • Mice, Transgenic
  • Neuroglia / metabolism
  • Neuroglia / pathology*
  • Plaque, Amyloid / genetics
  • Plaque, Amyloid / metabolism
  • Plaque, Amyloid / pathology*
  • Ultrasonography / methods*

Substances

  • Amyloid beta-Peptides
  • Amyloid beta-Protein Precursor
  • Immunoglobulin G
  • Immunoglobulin M