Molecular Profiling and Imaging of Peptides, Proteins and Drugs in Biological Tissue using Mass Spectrometry

Sammanfattning: Biological functions within cells and organisms are mainly carried out by the translational products; proteins and peptides. The analysis and characterization of these biomolecules are of great importance for the progress in disease research and biomarker and drug discovery. The term peptidomics was introduced to describe the comprehensive analysis of peptides (e.g. neuropeptides) in biological tissues. In this thesis, a peptidomics approach using nanoflow liquid chromatography coupled to electrospray mass spectrometry (MS) has been developed for detection, identification, and quantification of neuropeptides in different disease models. A thoroughly controlled sample preparation technique and targeted neuropeptide sequence collections have been used to improve sample quality and to increase the number of identified neuropeptides. In particular, neuropeptide changes in experimental models of Parkinson’s disease (PD), with or without L-DOPA treatment, and the effect of antidepressant treatment on neuropeptide expression have been investigated. Several novel, potentially bioactive, neuropeptides have been identified and a number of peptides derived from precursors such as secretogranin-1, preproenkephalin-B, and somatostatin have been found differentially expressed. Some of them represent novel findings, not previously associated with PD or treatment with antidepressants.In addition, MALDI imaging MS (IMS), a technology that permits detection and spatial distribution determination of endogenous compounds and/or administered drugs directly on tissue sections, has been used in both small protein and drug applications. MALDI IMS on tissue samples from experimental models of PD revealed differential expression patterns of two small proteins involved in calcium regulation, PEP-19 and FKBP-12. Biomolecular interaction analysis was performed on FKBP-12 using surface plasmon resonance together with MS and several potential binding partners were identified.In a second approach, MALDI IMS was used to study the distribution of the anticholinergic bronchodilator tiotropium in rat lung following inhalation of the drug. The distribution of the drug was monitored in both MS and MS/MS mode and the levels where linearly quantifiable in the range of 80 fmol – 5 pmol.Conclusively, in this thesis mass spectrometry based technologies have successfully been developed to detect, identify, and characterize small proteins, peptides, and drugs in various tissue samples.