Abstract 345: A Proteomic Study of Human and Mouse Plaques Supports Involvement of Proteolysis, Extracellular Matrix, and Cytoskeleton in Atherosclerotic Plaque Rupture

Abstract

Introduction: Atherosclerotic plaque rupture is the most common trigger of myocardial infarctions and strokes. The molecular mechanisms of plaque rupture are uncertain; accordingly, there are no specific interventions aimed at preventing plaque rupture. We used unbiased “shotgun” proteomics to identify proteins and pathways that are associated with human plaque rupture. We performed parallel proteomic analyses in a mouse model that develops plaque rupture. Methods: We used tandem mass spectrometry, performed on tissue extracts, to compare the proteomes of: 1) stable and unstable areas of human carotid plaques (n = 6); and 2) aortic arches of ApoE-null mice with (n = 6) or without (n = 6) macrophage-specific overexpression of urokinase plasminogen activator (uPA). Protein abundance was compared using the PepC statistical program, with correction for multiple comparisons. Gene ontology and pathway enrichment analysis were performed with DAVID. Results: Mass spectrometry detected a total of 1161 proteins in human plaque tissue. There were 150 proteins with increased abundance in the ruptured versus stable regions, including proteins involved in coagulation, inflammation, and proteolysis. 339 proteins were significantly decreased in ruptured areas, including smooth muscle-specific and extracellular matrix proteins. We identified 775 total proteins in the mouse aortas. 61 proteins with increased abundance in aortas of uPA-overexpressing mice included cytoskeletal proteins and proteases. 39 proteins with decreased abundance in aortas of uPA-overexpressing mice were predominantly extracellular matrix proteins. Gene ontology and pathway analysis revealed significant alterations in cytoskeletal proteins, extracellular matrix, and cell-adhesion in both human and mouse samples. Conclusion: We used shotgun proteomics to define alterations in proteomes of ruptured human plaques and of arterial tissue from a mouse model that develops plaque rupture. Specific proteolytic, cell-adhesion, and cytoskeletal organization networks are altered in unstable human plaques. The mouse model demonstrated remarkable similarity to these findings, supporting its use in investigating the molecular pathogenesis of plaque rupture.