Complement C5 plasma levels are associated to abdominal aortic aneurysm prevalence and progression

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Complemento II-CM

La Caixa

Aim

Previous human and experimental studies have suggested a role of complement activation in abdominal aortic aneurysm (AAA).  We recently described an increase in complement C5 levels in plasma of subjects with subclinical atherosclerosis (1). Our aim was to investigate the potential association of C5 with AAA presence and progression.

Material and methods

Tissue and tissue-conditioned media from AAA (thrombus and wall) or healthy samples were obtained from surgical repair or brain-deceased organ donors, respectively. Blood samples from 490 AAA patients (maximal aortic diameter ≥30 mm) were obtained within a population-based ultrasound-screening trial in Danish men and from 176 age-matched screened negative controls. C5 protein levels were assessed by immunohistochemistry and ELISA.

Results

High C5 positive immunostaining was observed in AAA thrombus and media, while the staining in healthy arteries was faint. C5 levels were higher in tissue-conditioned media from AAA thrombus and AAA media as compared to healthy arteries (7.1±1 vs 2.9 ±0.5 vs 1.2±0.2ug/ml, p<0.0001 for both). C5 plasma levels in AAA patients were higher than in controls (116±8 vs 61±7 ug/ml, P<0.001). AAA patients at the upper tertile of C5 at baseline had a 25% higher risk of needing surgical repair during the follow-up (Hazard Ratio=1.25, 95% confidence interval, 1.045;1.511, P<0.05).

Conclusions

C5 is associated to AAA presence and progression suggesting its potential use as a prognostic marker. Future studies are needed to clarify the pathogenic role of C5 in AAA.

P3114Protective effect of SOCS1-based therapy in experimental abdominal aortic aneurysm

Introduction

Abdominal aortic aneurysm (AAA) is a multifactorial vascular disease characterized by chronic inflammation, oxidative stress and proteolytic activity in the aortic wall, which contribute to extracellular matrix degradation and aortic dilation. Altered expression and activation of Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway have been implicated in several cardiovascular diseases including atherosclerosis and aneurysm formation. Suppressors of cytokine signaling (SOCS) are key negative regulators of JAK/STAT pathway and have been considered an attractive target for therapeutic intervention.

AIM

We hypothesize that SOCS1 protein could influence AAA development by inhibiting JAK activity and, consequently, STAT activation and target gene expression. Therefore, this study investigates the effect of a SOCS1-derived synthetic peptide in a rodent model of AAA and in cultured vascular smooth muscle cells (VSMC).

Methods

Experimental AAA was induced in C57BL/6 mice (males, 12 weeks old) by transient elastase perfusion of the aorta. Mice were randomly divided into control (vehicle, i.p.) and treatment (SOCS1 peptide, 3 mg/kg/day, i.p.) groups. Fourteen days after AAA induction, mice were sacrificed, and aorta segments were collected for histology (n=10/group) and mRNA and protein expression analysis (n=8/group).

Results

Compared to the AAA control group, SOCS1-treated mice exhibited a significant decrease in aortic diameter (68±6% vs. control; p<0.005) and aortic wall thickness, (67±3% vs. control; p<0.001). Histological analyses of aortic tissues showed a higher content of VSMC (α-actin) along with reduced leukocyte infiltration (macrophages, neutrophils and T-cells) and oxidative stress markers (superoxide anion and 8-hydroxyguanosine) in SOCS1-treated mice. SOCS1 therapy also attenuated the gene expression of inflammatory cytokines (CCL2, CCL5, TNF, IFNγ) and matrix metalloproteinases (MMP2, MMP9) in aortic lesions, and altered the expression levels of macrophage M1 (ArgII, iNOS) and M2 (ArgI, CD206) polarization markers. In vitro experiments in murine VSMC revealed that SOCS1 peptide prevented the expression of cytokines and chemokines induced by non-toxic dose of elastase (5 ug/ml, 24 hours). Effects of SOCS1 treatment were accompanied by a reduction in STAT1 and STAT3 phosphorylation and gene expression, both in AAA lesions and cultured VSMC.

Conclusion

Our results suggest that SOCS1 peptide presents protective effects in experimental AAA by suppressing JAK/STAT pathway-mediated inflammation.

Acknowledgement/Funding

MINECO-FEDER (SAF2015-63696-R), ISCII (FIS-FEDER PI17/01495), Spanish Society of Arteriosclerosis.

Association of ficolin-3 with abdominal aortic aneurysm presence and progression

Essentials Abdominal aortic aneurysm (AAA) is asymptomatic and its evolution unpredictable. To find novel potential biomarkers of AAA, microvesicles are an excellent source of biomarkers. Ficolin-3 is increased in microvesicles obtained from activated platelets and AAA tissue. Increased ficolin-3 plasma levels are associated with AAA presence and progression.

SUMMARY

Background Abdominal aortic aneurysm (AAA) patients are usually asymptomatic and AAA evolution is unpredictable. Ficolin-3, mainly synthesized by the liver, is a molecule of the lectin complement-activation pathway involved in AAA pathophysiology. Objectives To define extra-hepatic sources of ficolin-3 in AAA and investigate the role of ficolin-3 as a biomarker of the presence and progression of AAA. Methods Microvesicles (exosomes and microparticles) were isolated from culture-conditioned medium of ADP-activated platelets, as well as from AAA tissue-conditioned medium (thrombus and wall). Ficolin-3 levels were analyzed by western-blot, real-time PCR, immunohistochemistry and ELISA. Results Increased ficolin-3 levels were observed in microvesicles isolated from activated platelets. Similarly, microvesicles released from AAA tissue display increased ficolin-3 levels as compared with those from healthy tissue. Moreover, ficolin-3 mRNA levels in the AAA wall were greatly increased compared with healthy aortic walls. Immunohistochemistry of AAA tissue demonstrated increased ficolin-3, whereas little staining was present in healthy walls. Finally, increased ficolin-3 levels were observed in AAA patients' plasma (n = 478) compared with control plasma (n = 176), which persisted after adjustment for risk factors (adjusted odds ratio [OR], 5.29; 95% confidence interval [CI], 3.27, 8.57)]. Moreover, a positive association of ficolin-3 with aortic diameter (Rho, 0.25) and need for surgical repair was observed, also after adjustment for potential confounding factors (adjusted hazard ratio, 1.55; 95% CI, 1.11, 2.15). Conclusions In addition to its hepatic expression, ficolin-3 may be released into the extracellular medium via microvesicles, by both activated cells and pathological AAA tissue. Ficolin-3 plasma levels are associated with the presence and progression of AAA, suggesting its potential role as a biomarker of AAA.

HDL and endothelial protection

High-density lipoproteins (HDLs) represent a family of particles characterized by the presence of apolipoprotein A-I (apoA-I) and by their ability to transport cholesterol from peripheral tissues back to the liver. In addition to this function, HDLs display pleiotropic effects including antioxidant, anti-apoptotic, anti-inflammatory, anti-thrombotic or anti-proteolytic properties that account for their protective action on endothelial cells. Vasodilatation via production of nitric oxide is also a hallmark of HDL action on endothelial cells. Endothelial cells express receptors for apoA-I and HDLs that mediate intracellular signalling and potentially participate in the internalization of these particles. In this review, we will detail the different effects of HDLs on the endothelium in normal and pathological conditions with a particular focus on the potential use of HDL therapy to restore endothelial function and integrity.

Increased levels of thioredoxin in patients with abdominal aortic aneurysms (AAAs). A potential link of oxidative stress with AAA evolution

OBJECTIVE

Oxidative stress is a main mechanism involved in vascular pathologies. Increased thioredoxin (TRX) levels have been observed in several oxidative stress-associated cardiovascular diseases. We aim to test the potential role of TRX as a biomarker of oxidative stress in abdominal aortic aneurysm (AAA).

METHODS

TRX levels were analysed in both AAA intraluminal thrombus (ILT) tissue and in tissue-conditioned media by immunohistochemistry, Western blot and ELISA. Moreover, serum TRX levels were assessed in AAA Caucasian patients by ELISA.

RESULTS

TRX was mainly localized in the luminal part of ILT in AAA. Compared with the abluminal layer, TRX release was increased in the luminal layer of the ILT of AAA (31+/-9 ng/ml vs. 9+/-3 ng/ml, p<0.05). The interest of this approach is that we can identify proteins potentially released into the blood compartment, which could serve as biomarkers of the pathology. In a training population, serum TRX levels were significantly increased in patients with AAA relative to healthy subjects (50+/-6 ng/ml vs. 26+/-3 ng/ml, p<0.05). These results were validated in a second independent group of patients. Moreover, a positive correlation between TRX and AAA size (rho=0.5, p<0.001) was observed. Finally, in AAA samples with follow-up, TRX was positively associated to aneurismal growth rate (rho=0.25, p=0.027).

CONCLUSIONS

TRX release is increased in the luminal part of AAA and TRX serum levels are increased in AAA patients compared with healthy subjects. TRX levels correlates with AAA size and expansion, suggesting its potential role as a biomarker of AAA evolution.

Plasma fingerprinting with GC-MS in acute coronary syndrome

New biomarkers of cardiovascular disease are needed to augment the information obtained from traditional indicators and to illuminate disease mechanisms. One of the approaches used in metabolomics/metabonomics for that purpose is metabolic fingerprinting aiming to profile large numbers of chemically diverse metabolites in an essentially nonselective way. In this study, gas chromatography-mass spectrometry was employed to evaluate the major metabolic changes in low molecular weight plasma metabolites of patients with acute coronary syndrome (n = 9) and with stable atherosclerosis (n = 10) vs healthy subjects without significant differences in age and sex (n = 10). Reproducible differences between cases and controls were obtained with pattern recognition techniques, and metabolites accounting for higher weight in the classification have been identified through their mass spectra. On this basis, it seems inherently plausible that even a simple metabolite profile might be able to offer improved clinical diagnosis and prognosis, but in addition, specific markers are being identified.