Related Experiment Video
Updated: May 27, 2026
Intracerebroventricular Injection of Amyloid-β Peptides in Normal Mice to Acutely Induce Alzheimer-like Cognitive Deficits
Published on: March 16, 2016
Dynamic analysis of amyloid β-protein in behaving mice reveals opposing changes in ISF versus parenchymal Aβ during
Soyon Hong1, Omar Quintero-Monzon, Beth L Ostaszewski
1Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Abstract:
Growing evidence supports the hypothesis that soluble, diffusible forms of the amyloid β-peptide (Aβ) are pathogenically important in Alzheimer's disease (AD) and thus have both diagnostic and therapeutic salience. To learn more about the dynamics of soluble Aβ economy in vivo, we used microdialysis to sample the brain interstitial fluid (ISF), which contains the most soluble Aβ species in brain at steady state, in >40 wake, behaving APP transgenic mice before and during the process of Aβ plaque formation (age 3-28 months). Diffusible forms of Aβ, especially Aβ(42), declined significantly in ISF as mice underwent progressive parenchymal deposition of Aβ. Moreover, radiolabeled Aβ administered at physiological concentrations into ISF revealed a striking difference in the fate of soluble Aβ in plaque-rich (vs plaque-free) mice: it clears more rapidly from the ISF and becomes more associated with the TBS-extractable pool, suggesting that cerebral amyloid deposits can rapidly sequester soluble Aβ from the ISF. Likewise, acute γ-secretase inhibition in plaque-free mice showed a marked decline of Aβ(38), Aβ(40), and Aβ(42), whereas in plaque-rich mice, Aβ(42) declined significantly less. These results suggest that most of the Aβ(42) that populates the ISF in plaque-rich mice is derived not from new Aβ biosynthesis but rather from the large reservoir of less soluble Aβ(42) in brain parenchyma. Together, these and other findings herein illuminate the in vivo dynamics of soluble Aβ during the development of AD-type neuropathology and after γ-secretase inhibition and help explain the apparent paradox that CSF Aβ(42) levels fall as humans develop AD.
Insights
Soluble amyloid-beta (Aβ) forms, crucial in Alzheimer's disease (AD), decline in brain fluid as plaques form. Cerebral amyloid deposits sequester soluble Aβ, impacting diagnostic and therapeutic strategies for AD.
Area of Science:
- Neuroscience
- Biochemistry
- Pathology
Background:
- Soluble amyloid-beta (Aβ) species are increasingly recognized as critical players in Alzheimer's disease (AD) pathogenesis.
- Understanding the in vivo dynamics of soluble Aβ is essential for developing effective diagnostic and therapeutic interventions for AD.
Purpose of the Study:
- To investigate the dynamics of soluble Aβ in the brain interstitial fluid (ISF) during the development of Aβ plaque formation in a mouse model of AD.
- To explore the relationship between Aβ plaque deposition, soluble Aβ clearance, and the impact of γ-secretase inhibition on Aβ levels in vivo.
Main Methods:
- Microdialysis was employed to sample brain ISF in APP transgenic mice across a range of ages (3-28 months) to monitor soluble Aβ levels.
- Radiolabeled Aβ was administered into the ISF to track the clearance and sequestration of soluble Aβ in mice with and without Aβ plaques.
- Acute γ-secretase inhibition was performed in mice to assess its effect on soluble Aβ levels in different stages of plaque pathology.
Main Results:
- Soluble Aβ, particularly Aβ(42), significantly decreased in ISF as Aβ plaques progressively formed in the brain parenchyma.
- In plaque-rich mice, radiolabeled soluble Aβ cleared more rapidly from ISF and associated with insoluble pools, indicating sequestration by existing plaques.
- While γ-secretase inhibition reduced Aβ(38), Aβ(40), and Aβ(42) in plaque-free mice, Aβ(42) reduction was less pronounced in plaque-rich mice, suggesting a shift in Aβ(42) source.
Conclusions:
- Cerebral amyloid deposits act as a significant sink, sequestering soluble Aβ from the ISF.
- In advanced AD pathology, soluble Aβ(42) in ISF is largely replenished from parenchymal Aβ reservoirs rather than de novo synthesis.
- These findings illuminate the in vivo Aβ dynamics in AD and explain the observed decrease in cerebrospinal fluid (CSF) Aβ(42) levels during AD progression.
Related Concept Videos
01:23Alzheimer Disease ll: Pathophysiology
03:03Amyloid Fibrils
Amyloid deposits were observed as early as 1639 in the liver and the spleen. In 1854, Rudolph Virchow performed iodine staining, normally used to...
03:03Amyloid Fibrils
Amyloid deposits were observed as early as 1639 in the liver and the spleen. In 1854, Rudolph Virchow performed iodine staining, normally used to...