Analysis of the human lumbar cerebrospinal fluid proteome

Idiopathic low back pain has no known cause, and the molecular basis is unknown. Neuropeptidergic systems have been previously studied, and proteomics methods have been applied in this present study. Proteomics combines high-resolution two-dimensional (2-D) gel electrophoresis, high-sensitivity mass spectrometry, and continuously expanding protein databases. Proteomics offers a comprehensive, bird's-eye view to analyze, at a systems level, all of the proteins in cerebrospinal fluid (CSF) that might contribute to idiopathic low back pain. CSF contains a high salt concentration and low protein concentration. In order to obtain a high-quality 2-D pattern, several sample preparation methods were tested to remove salts - protein precipitation with either acetone or trichloroacetic acid/acetone, or sample treatment with a Bio-Spin column. More spots were visualized on the 2-D gel of human CSF, and a relatively high protein recovery was obtained when a Bio-Spin column was used to process a human CSF sample. Sixty-one protein spots, obtained from 2-D gels with a pH range of either 3-10 or 4-7, were identified by matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and MALDI-post-source decay (PSD)-MS. These 61 protein spots represent 22 proteins; six of those proteins were not annotated in any previously published 2-D maps. Those six proteins are PRO2619, pigment epithelium-derived factor, albumin homolog, kallikrein-6 precursor, DJ717I23.1, and AMBP protein precursor. These protein-mapping data will contribute to the database that will be used in the future to compare the proteomes obtained from the CSF of controls and low back pain patients, to characterize differentially expressed proteins, and to elucidate the biological markers for idiopathic low back pain.