Photo-oxidative stress and neurodegenerative diseases studied by S-FTIRM

Infrared spectroscopy is a powerful technique in the study of condensed matter since the energy of electronic excitations and lattice vibrations fall in its range. The lattice vibrations are especially useful in soft condensed matter where the change is phonon modes signal conformational changes, oxidative stress or other bio-chemical processes in the living matter. Since the development of very bright infrared sources based on synchrotron radiation, the Fourier Transformed Infrared microscopy (S-FTIRM) enables the creation of a vibrational map of tissues, cells with a spatial resolution of few microns. This allows the localization of regions where structural/biochemical changes have happened. These maps carry quantitative information of the sample in contrast to simple fluorescence imaging.
We use this technique to perform an interdisciplinary research. We investigate topics of major interest in living matter such as oxidative stress and neurodegenerative diseases (Alzheimer, Huntington and multiple sclerosis).
These measurements will be performed at the newly created S-FTIRM facility of the Swiss Light Source (SLS) at Villigen.

 

1. Photo-oxidative stress in living cells

The basic principle of S-FTIRM is that the energy of atomic vibrations (measured in wavenumbers – image below) depends on the chemical bonding in which they participate and on the environment. Their change carries the signatures of a diseases. S-FTIRM has the ability to monitor the chemistry within an individual living cell without labels and with using low-photon energies. Thus, S-FTIRM yields a powerful tool for non-destructively probing bio-systems on a small size scale. The sample can be small but also heterogeneous, e.g. an individual living cell, microorganisms or larger biological systems, in which local biochemistry may have significant spatial variations.

 

  

 

Typical Fourier transformed infrared spectrum recorded for single cell over a 5×5 µm aperture. For the assignment of the vibrational modes see the text. (Courtesy L. Miller)

The force of S-FTIRSM is illustrated in the study of the consequences of the photo-oxidative stress of a single fibroblast cell exposed to visible light illumination in the presence of C60 derivate. The change of the intensity of the vibrational modes clearly indicates the biochemical changes upon oxidative stress.

 

   Single cell mapping of the functional group distribution for a non-treated (CTRL) fibroblast (top row) and exposed for 30min to OS (bottom row). (A) Optical image of a single cell. (B) Lipid distribution map (C) Protein distribution map resulting from the Amide I  (D) Asymmetric phosphate stretching distribution. (E) Ester distribution map illustrated by carbonyl ester group stretch. The concentrations of each component scale from blue (0) to red (max).

 

2. Neurodegenerative diseases

In particular, S-FTIRM, a method of infra-red mapping of protein conformation changes, is a sensitive tool to detect the distribution and changes in secondary structures of intra-cellular proteins [1].  Thus, this technique is sensitive for detection of protein-misfolding-caused diseases (such as Alzheimer or Creutzfeldt-Jakob diseases) by following protein conformational transitions (alpha-to-beta transitions) [2].   This transformation is the best followed by the shift of the amide I band, from 1650 cm-1 correspondind to the C=O vibrational band in alpha-helix to 1625 cm-1   in the case of the b-sheet [3, 4]. 

 

   The map of sample from the frontal loab of a patient died with Alzheimer diseas shows clearly the plaques of the amyloid proteins having beta-sheet formation. The left panel shows the principal of the map construction: the ratio of the peak intensities at 1625/1650 recorded in 5×5 µm window which is scaned through the tissue.

 

This research is performed in collaboration with  Dr. Lisa Miller and her group at the National Synchrotron Light Source, Brookhaven National Laboratory, USA.

 

References:
[1] Y. Mei, L. Miller, W. Gao, and R.A. Gross, “Imaging the Distribution and Secondary Structure of Immobilized Enzymes Using Infrared Microspectroscopy”, Biomacromolecules 4, pp. 70-74 (2003).
[2] L.M. Miller, P. Dumas, N. Jamin, J.L. Teillaud, J. Miklossy, and L. Forró, “Combining IR spectroscopy with fluorescence imaging in a single microscope: Biomedical applications using a synchrotron infrared source”, Rev. Sci. Instrum. 73, pp.1357- 1360 (2002).
[3] B. Vileno, “Oxidative stress on biomaterials: from molecules to cells”. PhD-thesis (Thesis Director: Prof. L. Forró), EPFL, Lausanne (2006).
[4] B. Vileno, S. Jeney, A. Sienkiewicz, P.M. Marcoux, L.M. Miller, and L. Forró, “Evidence of lipid peroxidation and protein phosphorylation in cells”, to be published (2009).
[5] M. Bonda et al., Synchrotron Infrared Microspectroscopy Detecting the Evolution of Huntington’s Disease Neuropathology and Suggesting Unique Correlates of Dysfunction in White versus Gray Brain Matter, Anal. Chem., 83, 7712–7720 (2011).