Differential Proteomics Incorporating iTRAQ Labeling and Multi-dimensional Separations

Considerable effort is currently being expended to integrate newly developed “omics”-based approaches (proteomics, transcriptomics, and metabonomics) into preclinical safety evaluation workflows in the hope that more sensitive prediction of toxicology can be achieved as reported by Waters and Fostel (Nat. Rev. Genet. 5(12):936–948, 2004) and Craig et al. (J. Proteome Res. 5(7):1586–1601, 2006). Proteomic approaches are well placed to contribute to this effort as (a) proteins are the metabolically active products of genes and, as such, may provide more sensitive and direct predictive information on drug-induced liabilities and (b) they have the potential to determine tissue leakage markers in peripheral fluids. Here, we describe a workflow for proteomic semi-quantitative expression profiling of liver from rats treated with a known hepatotoxicant using a multiplexed isobaric labeling strategy and multi-dimensional liquid chromatography.