Targeted Proteomic Analysis of Patients with Ascending Thoracic Aortic Aneurysm

Abstract

Background: There is a need for clinical markers to aid in the detection of individuals at risk of harboring an ascending thoracic aneurysm (ATAA) or developing one in the future.

Objectives: To our knowledge, ATAA remains without a specific biomarker. This study aims to identify potential biomarkers for ATAA using targeted proteomic analysis.

Methods: In this study, 52 patients were divided into three groups depending on their ascending aorta diameter: 4.0-4.5 cm (N = 23), 4.6-5.0 cm (N = 20), and >5.0 cm (N = 9). A total of 30 controls were in-house populations ethnically matched to cases without known or visible ATAA-related symptoms and with no ATAA familial history. Before the debut of our study, all patients provided medical history and underwent physical examination. Diagnosis was confirmed by echocardiography and angio-computed tomography (CT) scans. Targeted-proteomic analysis was conducted to identify possible biomarkers for the diagnosis of ATAA.

Results: A Kruskal-Wallis test revealed that C-C motif chemokine ligand 5 (CCL5), defensin beta 1 (HBD1), intracellular adhesion molecule-1 (ICAM1), interleukin-8 (IL8), tumor necrosis factor alpha (TNFα) and transforming growth factor-beta 1 (TGFB1) expressions are significantly increased in ATAA patients in comparison to control subjects with physiological aorta diameter (p < 0.0001). The receiver-operating characteristic analysis showed that the area under the curve values for CCL5 (0.84), HBD1 (0.83) and ICAM1 (0.83) were superior to that of the other analyzed proteins.

Conclusions: CCL5, HBD1 and ICAM1 are very promising biomarkers with satisfying sensitivity and specificity that could be helpful in stratifying risk for the development of ATAA. These biomarkers may assist in the diagnosis and follow-up of patients at risk of developing ATAA. This retrospective study is very encouraging; however, further in-depth studies may be worthwhile to investigate the role of these biomarkers in the pathogenesis of ATAA.

Keywords: C-C motif chemokine ligand 5; ascending aortic thoracic aneurysm; biomarkers; defensin beta 1; intracellular adhesion molecule-1; proteomics.

Figure 1

Flowchart for study enrollment.

Figure 2

Angio-computed tomography of thoracic aortic aneurysm with electrocardiographic gating.

Figure 3

Evaluation of D-dimer in ATAA. (A) Violin plot of D-dimer levels in peripheral blood samples of ATAA patients depending on the aortic diameter. p-values annotated on the figure. * p < 0.05. (B) Pie chart illustrating the percentage of control subjects with normal or positive D-dimer. (C) Pie chart illustrating the percentage of ATAA patients with normal or positive D-dimer. Positive D-dimer was considered when >0.5 mg/L.

Figure 4

Statistically significant differences of serum MFI levels of CCL5 (A), HBD1 (B), ICAM1 (C), IL8 (D), TNFα (E) and TGFB1 (F) between control subjects and ATAA patients of different aortic diameter range. Distributions expressed in the form of violin plots. Comparisons of proteins’ MFI levels in serum that did not achieve statistical significance (p < 0.05) are not illustrated. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001. Significance was evaluated using Dunn’s multiple comparison test.

Figure 5

Receiver-operating characteristics curves for all ATAA patients versus all control subjects for each of the potential biomarkers. Receiver operator characteristic curve of D-dimer (A), CCL5 (B), HBD1 (C), ICAM1 (D), IL8 (E), TNFα (F) and TGFB1 (G) was plotted in ATAA patients. Diagnostic efficacy of these markers was determined. (H) Detailed information of ROC curves. AUC: area under the curve.

Figure 6

Statistically significant differences of serum MFI levels of CCL5 (A), HBD1 (B), ICAM1 (C), IL8 (D), TNFα (E) and TGFB1 (F) between patients suffering from other cardiovascular diseases (CVD) and ATAA patients of different aortic diameter range. Distributions expressed in the form of violin plots. Comparisons of proteins’ MFI levels in serum that did not achieve statistical significance (p < 0.05) are not illustrated. ** p < 0.01, *** p < 0.001, **** p < 0.0001. Significance was evaluated using Dunn’s multiple comparison test.

Figure 7

Schematic of our proposed model for the ascending thoracic aortic aneurysm (ATAA) formation. We suggest that long-term innate immune system activation through the release of the investigated proteins (CCL5, HBD1, ICAM1, IL8, TNFα, TGFB1) from neutrophils, dendritic cells, macrophages and vascular smooth muscle cells (VSMCs) occurs in ATAA. This activation results in a low-grade chronic inflammatory reaction that elicits disease instead of repair, resulting in chronic inflammation and in the development of ATAA.