Proteomics-based Development of Biomarkers in Cardiovascular Disease

Cardiovascular disease remains a paramount focus of basic science and clinical investigation throughout the developed world, although the demographics have changed considerably in the later half of the 20th century. Atherosclerotic cardiovascular disease, especially ischemic heart disease, has emerged as the major concern, while rheumatic fever and its cardiac sequelae have been superseded by congenital heart disease. Understanding these disease states and their perturbations requires clarification of mechanistic changes in organ phenotype over time, the influence of genetic variations, and the effects of pharmacologic, surgical, and interventional treatment. These requirements have been addressed, in part, by genetic, biochemical, and system approaches. It is clear, however, that knowledge of the DNA sequence, although essential, is not sufficient. A more meaningful understanding of gene expression can be achieved through characterization of the products of that expression, the proteins that are the essential biological determinants of disease phenotype. The ultimate phenotype of cell, organ, and organism is reflected in the instantaneous proteomic profile; similarly changes in human states of health are the result of changes in the proteomes of individual patients over time in response to endogenous and/or external stimuli. The advent of novel proteomic approaches to investigate the complexity of human illness promises to shed new light on the pathogenesis of a broad range of cardiovascular diseases. These inferences are multifaceted and include the commonly recognized role of proteomics in characterizing biomarkers and biosignatures for the prognosis and diagnosis of disease, the capability of these technologies of revealing information regarding functional subproteomes of organelles and networks in the heart and vasculature, and the importance of proteomics in defining changes in these functional subproteomes to guide future therapy. The central focus of this review is to discuss the importance of proteomics as a non-biased tool for protein discovery. We explore the role of proteomics for hypothesis-driven research into cellular organelle status, and we discuss how this approach facilitates an understanding of the function of the cell in normal and diseased states. Lastly we present a review of proteomics as a tool for biomarker development and lay out a vision for how this technology promises to facilitate distinct biomarker development. Signal transduction pathways are an experimental challenge in the study of complex cell/organ systems. The proteins and the interactions between molecules and post-translational modifications must be studied to understand how inputs into a cell are processed to modulate the phenotype of an organ. Pharmacologic and genetic interventions provide mechanisms by which single molecules can be targeted, thus creating experimental lesions in a signaling pathway that yield insights into the function of its components. Recent investigations in which these types of perturbations have been melded with proteomic analyses of the networks and pathways have afforded novel descriptions of cardiac cell signaling not possible previously. Importantly the biomedical profession has available an invaluable resource of web-based two-dimensional electrophoretic maps annotated for healthy and diseased cardiac tissues (such as failing myocardium) in a number of extensively characterized species. These resources have recently been highlighted in a comprehensive review by McGregor and Dunn (1McGregor E. Dunn M.J. Proteomics of the heart: unraveling disease.Circ. Res. 2006; 98: 309-321Crossref PubMed Scopus (119) Google Scholar). The failing myocardium characteristically displays impaired sarcoplasmic reticulum calcium cycling. It is well established that phospholamban activity is inversely related to the capability of the SR 1The abbreviations used are: SR, sarcoplasmic reticulum; 2D, two-dimensional; PTM, post-translational modification; HSP, heat shock protein; PKC, protein kinase C; EC, endothelial cell; HUVEC, human umbilical vein endothelial cell; 2-DE, two-dimensional gel electrophoresis; SMC, smooth muscle cell; EPC, endothelial progenitor cell; CRP, C-reactive protein. to cycle calcium, and thus an understanding of how this protein modulates the SR subproteome is of critical importance in developing new therapeutic strategies that aim at modulating the performance of the failing heart at the molecular level. Chu et al. (2Chu G. Kerr J.P. Mitton B. Egnaczyk G.F. Vazquez J.A. Shen M. Kilby G.W. Stevenson T.I. Maggio J.E. Vockley J. Rapundalo S.T. Kranias E.G. Proteomic analysis of hyperdynamic mouse hearts with enhanced sarcoplasmic reticulum calcium cycling.FASEB J. 2004; 18: 1725-1727Crossref PubMed Scopus (24) Google Scholar) used classical 2D electrophoresis and mass spectrometry to examine protein changes in hearts phospholamban as with approach in proteins and in of These in of proteins by of phospholamban and are related to enhanced cardiac performance in the understanding of how this protein modulates the SR subproteome is of critical importance in therapeutic strategies that modulate performance of the failing heart at the molecular level. of genetic of individual molecules to proteomic signaling pathways et al. G. J.E. analysis of a mouse with J. 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