Proteomic identification of differentially expressed proteins in aortic wall of patients with ruptured and nonruptured abdominal aortic aneurysms

ObjectiveTo compare the basic proteomic composition of abdominal aortic aneurysm (AAA) wall tissue in patients with nonruptured and ruptured aneurysms.MethodsA proteomic approach with two-dimensional gel electrophoresis (2D-PAGE) and mass spectrometry (MS) was used to identify differentially expressed proteins in AAA tissue from nine patients with nonruptured and eight patients with ruptured AAA. Computerized image analysis was used to detect protein spots. Differentially expressed protein spots were in-gel digested and identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Western blot analysis was used to confirm differential expression.ResultsSeven differentially expressed proteins were detected among 745 protein spots, selecting spots whose average relative volumes differed more than twofold between the nonruptured and the ruptured group. Four protein spots were up-regulated in the ruptured group, and three were down-regulated. Five of the spots were identified. Among the upregulated spots, No. 605 was identified as peroxiredoxin-2. The up-regulation was confirmed by Western blotting. No. 381 was identified as an actin fragment. Two spots, Nos. 719 and 499, could not be identified. Among the down-regulated protein spots, No. 130 contained two peptides; one reliably determined peptide, FEDGVLDPDYPR, is found in vitronectin. Another peptide, QIDNPDYK, was borderline significant and found in calreticulin. The down-regulation of vitronectin was confirmed by Western blotting. Spot Nos. 193 and 199 both contained peptides from albumin with actin also present in No. 199.ConclusionThe identified proteins suggest that the aortic wall of ruptured aneurysms responds to a stressful condition and that proteolytic degradation of the cytoskeleton and connective tissue may be part of the response.

Clinical RelevanceThe use of biomarkers in medicine lies in their ability to detect disease and to support diagnostic and therapeutic decisions. Proteins are the main functional outcomes of genes, so proteomics will lead biology and medicine beyond genomics. The identification, quantification, classification, and functional assignment of proteins will be essential to the full understanding of the molecular events of AAA progression. New research and novel understanding of the molecular basis of the disease reveal an abundance of exciting new biomarkers that present a promise for use in the everyday clinical practice. Consequently, the blood level of an ideal biomarker should have: high sensitivity (increased pathologically in the presence of the disease), high specificity (not increased in the absence of the disease), add information about the risk or prognosis, change in accordance with the clinical evolution, reflecting the current status of disease, be reproducible (as determined by the low coefficient of variation), and be easy and less expensive to determine. The identification of such biomarkers also causes identification of potential pathogenetic pathways, and may thus open possibilities for pharmacological inhibition of growth and provide a tool for monitoring this inhibition.