Human-brain ferritin studied by muon spin rotation: a pilot study

Area of Science:

• Biophysics
• Neuroscience
• Materials Science

Background:

• Ferritin is an iron-storage protein crucial for cellular iron homeostasis.
• Altered iron metabolism and ferritin composition are implicated in neurodegenerative diseases like Alzheimer's disease (AD).
• Understanding the mineral core of ferritin in AD is vital for elucidating disease mechanisms.

Purpose of the Study:

• To investigate the spin dynamics and mineral core composition of brain ferritin in Alzheimer's disease (AD) patients.
• To compare ferritin from AD patients with that from healthy controls and a reference sample.
• To explore potential correlations between ferritin's magnetic properties and AD.

Main Methods:

• Muon spin rotation spectroscopy was employed to probe the spin dynamics of ferritin.
• A model based on Néel theory of superparamagnetism was developed to interpret muon spin relaxation rates.
• Ferritin samples were isolated from the brains of AD patients and healthy controls, with horse-spleen ferritin used as a reference.

Main Results:

• Preliminary observations indicate differences in the mineral core composition of ferritin between AD patients and healthy controls.
• Healthy control ferritin cores are consistent with ferrihydrite.
• Ferritin from AD patients contains a crystalline phase with significantly larger magnetocrystalline anisotropy, potentially magnetite or maghemite.

Conclusions:

• The findings suggest altered iron mineral composition within brain ferritin in Alzheimer's disease.
• The increased magnetocrystalline anisotropy in AD ferritin may indicate a different iron storage state.
• Further research is needed to confirm the exact mineral phases and their role in AD pathogenesis.