Proteomic analysis of the abdominal aortic aneurysm wall

Insight in the (Phospho)proteome of Vascular Smooth Muscle Cells Derived From Patients With Abdominal Aortic Aneurysm Reveals Novel Disease Mechanisms

BACKGROUND

Abdominal aortic aneurysm (AAA) is characterized by weakening and dilatation of the aortic wall in the abdomen. The aim of this study was to gain insight into cell-specific mechanisms involved in AAA pathophysiology by analyzing the (phospho)proteome of vascular smooth muscle cells derived from patients with AAA compared with those of healthy donors.

METHODS

A (phospho)proteomics analysis based on tandem mass spectrometry was performed on vascular smooth muscle cells derived from patients with AAA (n=24) and healthy, control individuals (C-SMC, n=8). Following protein identification and quantification using MaxQuant, integrative inferred kinase activity analysis was used to calculate kinase activity scores.

RESULTS

Expression differences between vascular smooth muscle cells derived from patients with AAA and healthy, control individuals were predominantly found in proteins involved in ECM (extracellular matrix) remodeling (THSD4 [thrombospondin type-1 domain-containing protein 4] and ADAMTS1 [A disintegrin and metalloproteinase with thrombospondin motifs 1]), energy metabolism (GYS1 [glycogen synthase 1] and PCK2 [phosphoenolpyruvate carboxykinase 2, mitochondrial]), and contractility (CACNA2D1 [calcium voltage-dependent channel subunit α-2/δ-1] and TPM1 [tropomyosin α-1 chain]). Phosphorylation patterns on proteins related to actin cytoskeleton organization dominated the phosphoproteome of vascular smooth muscle cells derived from patients with AAA . Besides, phosphorylation changes on proteins related to energy metabolism (GYS1), contractility (PARVA [α-parvin], PPP1R12A [protein phosphatase 1 regulatory subunit 12A], and CALD1 [caldesmon 1]), and intracellular communication (GJA1 [gap junction α-1 protein]) were seen. Kinase activity of NUAK1 (NUAK family SNF1-like kinase 1), FYN (tyrosine-protein kinase Fyn), MAPK7 (mitogen-activated protein kinase 7), and STK10 (serine/threonine kinase 10) was different in vascular smooth muscle cells derived from patients with AAA compared with those from healthy, control individuals.

CONCLUSIONS

This study revealed changes in expression and phosphorylation levels of proteins involved in various processes responsible for AAA progression and development (eg, energy metabolism, ECM remodeling, actin cytoskeleton organization, contractility, intracellular communication, and cell adhesion). These newly identified proteins, phosphosites, and related kinases provide further insight into the underlying mechanism of vascular smooth muscle cell dysfunction within the aneurysmal wall. Our omics data thereby offer the opportunity to study the relevance, either as drug target or biomarker, of these proteins in AAA development.

Selective inhibition of soluble tumor necrosis factor signaling reduces abdominal aortic aneurysm progression

Background

Tumor necrosis factor (TNF) is pathologically elevated in human abdominal aortic aneurysms (AAA). Non-selective TNF inhibition-based therapeutics are approved for human use but have been linked to several side effects. Compounds that target the proinflammatory soluble form of TNF (solTNF) but preserve the immunomodulatory capabilities of the transmembrane form of TNF (tmTNF) may prevent these side effects. We hypothesize that inhibition of solTNF signaling prevents AAA expansion.

Methods

The effect of the selective solTNF inhibitor, XPro1595, and the non-selective TNF inhibitor, Etanercept (ETN) was examined in porcine pancreatic elastase (PPE) induced AAA mice, and findings with XPro1595 was confirmed in angiotensin II (ANGII) induced AAA in hyperlipidemic apolipoprotein E (Apoe) -/- mice.

Results

XPro1595 treatment significantly reduced AAA expansion in both models, and a similar trend (p = 0.06) was observed in PPE-induced AAA in ETN-treated mice. In the PPE aneurysm wall, XPro1595 improved elastin integrity scores. In aneurysms, mean TNFR1 levels reduced non-significantly (p = 0.07) by 50% after TNF inhibition, but the histological location in murine AAAs was unaffected and similar to that in human AAAs. Semi-quantification of infiltrating leucocytes, macrophages, T-cells, and neutrophils in the aneurysm wall were unaffected by TNF inhibition. XPro1595 increased systemic TNF levels, while ETN increased systemic IL-10 levels. In ANGII-induced AAA mice, XPro1595 increased systemic TNF and IL-5 levels. In early AAA development, proteomic analyses revealed that XPro1595 significantly upregulated ontology terms including "platelet aggregation" and "coagulation" related to the fibrinogen complex, from which several proteins were among the top regulated proteins. Downregulated ontology terms were associated with metabolic processes.

Conclusion

In conclusion, selective inhibition of solTNF signaling reduced aneurysm expansion in mice, supporting its potential as an attractive treatment option for AAA patients.

Proteomics applications in biomarker discovery and pathogenesis for abdominal aortic aneurysm

Introduction: Abdominal aortic aneurysm (AAA) is a common, complex, and life-threatening disease. Currently, the pathogenesis of AAA is not well understood. No biomarkers or specific drugs are available for AAA in clinical applications. Proteomics is a powerful tool in biomarker discovery, exploration of pathogenesis, and drug target identification.Areas covered: We review the application of mass spectrometry-based proteome analysis in AAA patients within the last ten years. Differentially expressed proteins associated with AAA were identified in multiple sample sources, including vascular tissue, intraluminal thrombus, tissue secretome, blood, and cells. Some potential disease biomarkers, pathogenic mechanisms, or therapeutic targets for AAA were discovered using proteome analysis. The challenges and prospects of proteomics applied to AAA are also discussed.Expert opinion: Since most of the previous proteomic studies used relatively small sample sizes, some promising biomarkers need to be validated in multicenter cohorts to accelerate their clinical application. With the rapid development of mass spectrometry technology, modification-specific proteomics and multi-omics research in the future will enhance our understanding of the pathogenesis of AAA and promote biomarker discovery and drug development for clinical translation.

Abdominal Aortic Aneurysms Growth Is Associated With High Concentrations of Plasma Proteins in the Intraluminal Thrombus and Diseased Arterial Tissue

Objective—

Porosity of the intraluminal thrombus (ILT) is believed to convey biologically active components from the bloodstream toward the aneurismal wall. Accumulation of molecules in the abdominal aortic aneurysmatic tissue may influence vascular protein turnover and regulate abdominal aortic aneurysm growth. We sought to identify proteins with concentrations in the ILT and the abdominal aortic aneurysm wall which associate with aneurysmal expansion rate.

Approach and Results—

Proteomic analysis by liquid chromatography tandem-mass spectrometry of separated wall and ILT samples was correlated with preoperative aneurysmal growth rate in 24 individuals operated electively for infrarenal abdominal aortic aneurysm. The median preoperative growth rate was 3.8 mm/y (interquartile range, 3) and the mean observational time was 3.3±1.7 years. Plasma components dominated the group of proteins with tissue concentrations, which correlate positively with growth rates ( P <0.001, Fisher exact test, both in the ILT and the wall). In contrast, in the wall and thrombus samples, ECM (extracellular matrix) proteins were significantly more prevalent in the group of proteins with negative correlations to growth rates ( P <0.05, Fisher exact test). Similarly, a long series of proteins, related to cellular functions correlated negatively to growth rates.

Conclusions—

When the preoperative aneurysmatic growth rate has been high, the concentration of many plasma proteins residing in the ILT and the aneurysmatic tissue is also high, compatible with the hypothesis of increased tissue porosity and accumulation of plasma components as a driver of aneurysm expansion. Moreover, many matrix and cellular proteins which are found in high concentrations in slower-growing aneurysms provides new knowledge about potential treatment targets.

Proteomic analysis in cardiovascular research

Advances in mass spectrometry technology and bioinformatics using clinical human samples have expanded quantitative proteomics in cardiovascular research. There are two major proteomic strategies: namely, "gel-based" or "gel-free" proteomics coupled with either "top-down" or "bottom-up" mass spectrometry. Both are introduced into the proteomic analysis using plasma or serum sample targeting 'biomarker" searches of aortic aneurysm and tissue samples, such as from the aneurysmal wall, calcific aortic valve, or myocardial tissue, investigating pathophysiological protein interactions and post-translational modifications. We summarize the proteomic studies that analyzed human samples taken during cardiovascular surgery to investigate disease processes, in order to better understand the system-wide changes behind known molecular factors and specific signaling pathways.

Glucagon-like peptide-1 prevented abdominal aortic aneurysm development in rats

PURPOSE

To demonstrate the protective effect of glucagon-like peptide 1 (GLP-1) signaling on the cardiovascular system, we conducted this study to show that the GLP-1 receptor analog (lixisenatide) could inhibit abdominal aortic aneurysm (AAA) development in rats.

METHODS

Lixisenatide was injected subcutaneously 7 days after aneurysm preparation. We evaluated reactive oxygen species (ROS) expression by dihydroethidium staining and 8-hydroxydeoxyguanosine (8-OHdG; the oxidation product of DNA) by immunohistochemical staining. We also analyzed the effect of GLP-1 signaling on the inflammatory response. Histopathological examination was done on day 28, and the AAA dilatation ratio was calculated.

RESULTS

On day 14, ROS expression and 8-OHdG-positive cells in the aneurysm walls were seen to have been significantly decreased by lixisenatide treatment. Western blot analysis showed decreased ERK expression. There was significantly reduced tumor necrosis factor-α mRNA expression in the aneurysm walls and CD68-positive cell infiltration in the aneurysm walls. On day 28, it was evident that the lixisenatide had dramatically reduced aneurysm development in the rats.

CONCLUSION

GLP-1 elevation inhibits AAA development in rats through its anti-oxidant and anti-inflammatory effects. Thus, GLP-1 could be a potent pharmacological target for AAA treatment.