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Lipidomics is a vast field of intracellular pathways of lipids and their biochemical functions. In analogy to genomics and proteomics it contributes to the overall comprehension of system biology. The field elucidates the role of lipids as a subset of the major biological components. Within this family of molecules, often referred to as metabolic lipidome, lipid mediators (LMs) are currently under detailed investigations. Being part of lipid signaling events, which are unique in a sense that they are produced “on demand” at the site of action, LMs fulfill important roles in receptor and enzyme regulated processes. Furthermore, LMs along with phospholipids (PL) are known to have pro- and anti-tumoral properties, and cancer cells exhibit aberrant LM and PL profiles. Typical cells that produce a broad variety of LMs are monocytes and macrophages, which also use these chemical mediators to influence the communication between monocytes and macrophages with cancer cells. As lipidomics research involves the identification and quantification of the thousands of cellular lipid molecular species and their interactions with other lipids, proteins, and other metabolites, comparably fast analytical techniques that detect the overall lipid composition of individual cells are highly advantageous. Several types of analytical methodologies are applied for characterization of the lipidome of cells. By far most commonly used is mass spectrometry in combination with separation techniques that can provide a profile of the variety of lipids present, as well as their identification. Similar information can be obtained utilizing NMR spectroscopy. Meanwhile also well established for profiling biological samples is Raman spectroscopy. As Raman micro-spectroscopy can be used to image individual cells and depict subcellular components based on their spectroscopic fingerprints, it appears as an ideal label-free technique to investigate intracellular alterations noninvasively. minute spectral changes, due to compositional alterations can be reproducibly detected. In this context Raman micro-spectroscopy has for instance been applied to typing of bacteria or the differentiation between cancerous and normal cells. Raman spectroscopy can provide an OMIC-like view of the chemical status of individual cells and metabolism and has been suggested for lipidomic profiling.(1,2) The obtained data sets of were subjected to common statistical data evaluation, such as hierarchical cluster (HCA) and principal component analysis (PCA), in order to relate spectroscopic alterations to the compositional changes associated with the presence of a cancerous environment. Here we present first results obtained from M1 and M2 macrophages cocultured in vitro with cancer cells in order to evaluate the potential of Raman spectroscopy for lipid profiling.
Acknowledgements:
Financial support from the Carl Zeiss Foundation is highly acknowledged.
References
1. Huang W, Spiers A. Consideration of Future Requirements for Raman Microbiology as an Examplar for the Ab Initio Development of Informatics Frameworks for Emergent OMICS Technologies OMICS: A Journal of Integrative Biology 2006;10:238-41.
2. Wu H, Volponi J, Oliver A, Parikh A, Simmons B, Singh S. In vivo lipidomics using single-cell Raman spectroscopy. Proc Natl Acad Sci USA 2011;108:3809-14.
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