A Multimodal Spectroscopic Imaging Method To Characterize the Metal and Macromolecular Content of Proteinaceous Aggregates ("Amyloid Plaques")

Biochemistry. 2017 Aug 15;56(32):4107-4116. doi: 10.1021/acs.biochem.7b00262. Epub 2017 Jul 18.

Abstract

Alzheimer's disease (AD) is a major international health and economic concern. A key pathological feature of AD is so-called "amyloid-β-plaques", or "Aβ-plaques", which are deposits of aggregated protein, enriched with the Aβ fragment of amyloid precursor protein. Despite their name, the deposits are not pure Aβ and have a heterogeneous, chemically complex composition that can include multiple proteins, lipids, and metal ions (Fe, Cu, or Zn). Despite extensive research, it is still uncertain whether Aβ-plaques are a cause or a consequence of AD pathology. Further characterization of the elemental and biochemical composition within and surrounding Aβ-plaques, and knowledge of how composition varies with disease state or progression, may provide important insight into the relationship between Aβ-plaques and AD pathology. With this aim in mind, herein we demonstrate a multimodal spectroscopic imaging workflow to better characterize the complex composition of Aβ-plaques. Our approach incorporates several spectroscopic imaging techniques, such as Fourier transform infrared spectroscopic imaging (FTIR), Raman microscopy, and X-ray fluorescence microscopy (XFM). While FTIR, Raman, and XFM have been used previously, mostly in isolation, to study Aβ-plaques, application of all three techniques, in combination with histology and fluorescence microscopy, has not been reported previously. We demonstrate that a multimodal workflow, incorporating all three methods on adjacent or serial tissue sections, can reveal substantial complementary information about the biochemical and elemental composition of Aβ-plaques. Information revealed by the method includes the relative content and distribution of aggregated protein, total lipid, lipid esters, cholesterol, and metals (Fe, Cu, or Zn).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alzheimer Disease / genetics
  • Alzheimer Disease / metabolism*
  • Alzheimer Disease / pathology
  • Amyloid beta-Peptides / genetics
  • Amyloid beta-Peptides / metabolism*
  • Animals
  • Metals / metabolism*
  • Mice
  • Mice, Transgenic
  • Protein Aggregation, Pathological / genetics
  • Protein Aggregation, Pathological / metabolism*
  • Protein Aggregation, Pathological / pathology
  • Spectrometry, X-Ray Emission
  • Spectroscopy, Fourier Transform Infrared
  • Spectrum Analysis, Raman

Substances

  • Amyloid beta-Peptides
  • Metals