Elevated tissue plasminogen activator in patients with screening-detected abdominal aortic aneurysm

Targeted proteomics and metabolomics for biomarker discovery in abdominal aortic aneurysm and post-EVAR sac volume

BACKGROUND AND AIMS

Abdominal aortic aneurysm (AAA) patients undergo uniform surveillance programs both leading up to, and following surgery. Circulating biomarkers could play a pivotal role in individualizing surveillance. We applied a multi-omics approach to identify relevant biomarkers and gain pathophysiological insights.

MATERIALS AND METHODS

In this cross-sectional study, 108 AAA patients and 200 post-endovascular aneurysm repair (post-EVAR) patients were separately investigated. We performed partial least squares regression and ingenuity pathway analysis on circulating concentrations of 96 proteins (92 Olink Cardiovascular-III panel, 4 ELISA-assays) and 199 metabolites (measured by LC-TQMS), and their associations with CT-based AAA/sac volume.

RESULTS

The median (25th-75th percentile) maximal diameter was 50.0 mm (46.0, 53.0) in the AAA group, and 55.4 mm (45.0, 64.2) in the post-EVAR group. Correcting for clinical characteristics in AAA patients, the aneurysm volume Z-score differed 0.068 (95 %CI: (0.042, 0.093)), 0.066 (0.047, 0.085) and -0.051 (-0.064, -0.038) per Z-score valine, leucine and uPA, respectively. After correcting for clinical characteristics and orthogonalization in the post-EVAR group, the sac volume Z-score differed 0.049 (0.034, 0.063) per Z-score TIMP-4, -0.050 (-0.064, -0.037) per Z-score LDL-receptor, -0.051 (-0.062, -0.040) per Z-score 1-OG/2-OG and -0.056 (-0.066, -0.045) per Z-score 1-LG/2-LG.

CONCLUSIONS

The branched-chain amino acids and uPA were related to AAA volume. For post-EVAR patients, LDL-receptor, monoacylglycerols and TIMP-4 are potential biomarkers for sac volume. Additionally, distinct markers for sac change were identified.

Intraluminal thrombus: Innocent bystander or factor in abdominal aortic aneurysm pathogenesis?

BACKGROUND

Abdominal aortic aneurysms (AAAs) represent a complex multifactorial hemodynamic, thrombotic, and inflammatory process that can ultimately result in aortic rupture and death. Despite improved screening and surgical management of AAAs, the mortality rates have remained high after rupture, and little progress has occurred in the development of nonoperative treatments. Intraluminal thrombus (ILT) is present in most AAAs and might be involved in AAA pathogenesis. The present review examined the latest clinical and experimental evidence for possible involvement of the ILT in AAA growth and rupture.

METHODS

A literature review was performed after a search of the PubMed database from 2012 to June 2020 using the terms "abdominal aortic aneurysm" and "intraluminal thrombus."

RESULTS

The structure, composition, and hemodynamics of ILT formation and propagation were reviewed in relation to the hemostatic and proteolytic factors favoring ILT deposition. The potential effects of the ILT on AAA wall degeneration and rupture, including a review of the current controversies regarding the position, thickness, and composition of ILT, are presented. Although initially potentially protective against increased wall stress, increasing evidence has shown that an increased volume and greater age of the ILT have direct detrimental effects on aortic wall integrity, which might predispose to an increased rupture risk.

CONCLUSIONS

ILT does not appear to be an innocent bystander in AAA pathophysiology. However, its exact role remains elusive and controversial. Despite computational evidence of a possible protective role of the ILT in reducing wall stress, increasing evidence has shown that the ILT promotes AAA wall degeneration in humans and in animal models. Further research, with large animal models and with more chronic ILT is crucial for a better understanding of the role of the ILT in AAAs and for the potential development of targeted therapies to slow or halt AAA progression.

Prognostic value of D-dimer and markers of coagulation for stratification of abdominal aortic aneurysm growth

Abdominal aortic aneurysm (AAA) is associated with high morbidity and mortality and is an established cause of unbalanced hemostasis. A number of hemostatic biomarkers have been associated with AAA; however, the utility of hemostatic biomarkers in AAA diagnosis and prognosis is unclear. The aim of the present study was to characterize the potential prognostic value of D-dimer and markers of altered hemostasis in a large cohort of patients with AAAs characterized by either fast or slow aneurysm growth (frequency matched for baseline diameter) and subaneurysmal dilations. We measured plasma concentrations of thrombin-antithrombin (TAT) complex, platelet factor 4 (PF4), and D-dimer in 352 patients with either fast-growing AAAs (>2 mm/y), slow-growing AAAs (<2 mm/y), subaneurysmal aortic dilations, or nonaneurysmal aortas. Plasma D-dimer and TAT were significantly elevated in both AAA and subaneurysmal dilation patients compared with controls. Individuals with D-dimer levels ≥500 ng/mL had 3.09 times the odds of subaneurysms, 6.23 times the odds of slow-growing AAAs, and 7.19 times the odds of fast-growing AAAs than individuals with D-dimer level <500 ng/mL. However, no differences in D-dimer concentration were noted between fast- and slow-growing aneurysms. Plasma D-dimer and TAT were strong independent predictors of AAA growth rate with multivariate analysis revealing a 500-ng/mL increase in D-dimer or 1-µg/mL increase in TAT led to additional 0.21-mm and 0.24-mm changes in aortic diameter per year, respectively. Rising levels of plasma TAT, in addition to D-dimer, may predict disease progression and aneurysm growth in patients with AAA or subaneurysmal dilation.

Tissue factor levels and the fibrinolytic system in thin and thick intraluminal thrombus and underlying walls of abdominal aortic aneurysms

BACKGROUND

The hemostatic system cooperates with proteolytic degradation in processes allowing abdominal aortic aneurysm (AAA) formation. In previous studies, it has been suggested that aneurysm rupture depends on intraluminal thrombus (ILT) thickness, which varies across each individual aneurysm. We hypothesized that hemostatic components differentially accumulate in AAA tissue in relation to ILT thickness. Thick (A1) and thin (B1) segments of ILTs and aneurysm wall sections A (adjacent to A1) and B (adjacent to B1) from one aneurysm sac were taken from 35 patients undergoing elective repair.

METHODS

Factor levels were measured using enzyme-linked immunosorbent assay of protein extract.

RESULTS

Tissue factor (TF) activities were significantly higher in thinner segments of AAA (B1 vs A1, P = .003; B vs A, P < .001; B vs A1, P < .001; B vs B1, P = .001). Significantly higher tissue plasminogen activator was found in thick thrombus-covered wall segments (A) than in B, A1, and B1 (P = .015, P < .001, and P < .001, respectively). Plasminogen concentrations were highest in ILT. Concentrations of α₂-antiplasmin in thin ILT adjacent walls (B) were higher compared with wall (A) adjacent to thick ILT (P = .021) and thick ILT (A1; P < .001). Significant correlations between levels of different factors were mostly found in thick ILT (A1). However, no correlations were found at B sites, except for a correlation between plasmin and TF activities (r = 0.55; P = .004).

CONCLUSIONS

These results suggest that higher TF activities are present in thinner AAA regions. These parameters and local fibrinolysis may be part of the processes leading to destruction of the aneurysm wall.

TGF-β1 Suppresses Plasmin and MMP Activity in Flexor Tendon Cells via PAI-1: Implications for Scarless Flexor Tendon Repair

Flexor tendon injuries caused by deep lacerations to the hands are a challenging problem as they often result in debilitating adhesions that prevent the movement of the afflicted fingers. Evidence exists that tendon adhesions as well as scarring throughout the body are largely precipitated by the pleiotropic growth factor, Transforming Growth Factor Beta 1(TGF-β1), but the effects of TGF-β1 are poorly understood in tendon healing. Using an in vitro model of tendon healing, we previously found that TGF-β1 causes gene expression changes in tenocytes that are consistent with scar tissue and adhesion formation, including upregulation of the anti-fibrinolytic protein, PAI-1. Therefore, we hypothesized that TGF-β1 contributes to scarring and adhesions by reducing the activity of proteases responsible for ECM degradation and remodeling, such as plasmin and MMPs, via upregulation of PAI-1. To test our hypothesis, we examined the effects of TGF-β1 on the protease activity of tendon cells. We found that flexor tendon tenocytes treated with TGF-β1 had significantly reduced levels of active MMP-2 and plasmin. Interestingly, the effects of TGF-β1 on protease activity were completely abolished in tendon cells from homozygous plasminogen activator inhibitor 1 (PAI-1) knockout (KO) mice, which are unable to express PAI-1. Our findings support the hypothesis that TGF-β1 induces PAI-1, which suppresses plasmin and plasmin-mediated MMP activity, and provide evidence that PAI-1 may be a novel therapeutic target for preventing adhesions and promoting a scarless, regenerative repair of flexor tendon injuries.

The study of t-PA, u-PA and PAI-1 genes polymorphisms in patients with abdominal aortic aneurysm

The most important feature of abdominal aortic aneurysm (AAA) pathogenesis is an enzymatic degradation of elastic lamellae and extracellular matrix proteins particularly with participation of matrix metalloproteinases. Plasmin, which is responsible for the dissolution of fibrin in blood vessels, plays also a key role in the cascade for activation of the metalloproteinases. The purpose of this study was to evaluate the influence of selected polymorphisms in genes coding for tissue plasminogen activator (−7351 C/T polymorphism), urokinase-type plasminogen activator (1788 C/T polymorphism) and plasminogen activator inhibitor 1 (−675 4G/5G and −844 G/A polymorphism) on the susceptibility to AAA. We performed a case–control study of 153 polish patients hospitalized due to AAA and compared them with matched healthy control subjects. The polymorphisms were ascertained through genotyping by polymerase chain reaction and restriction digestion of amplified fragments or through high-resolution melting analysis. In this study we have found lower frequency of wild-type GG genotype of the −844G/A PAI-1 polymorphism in cases than in controls, what may suggest the protective effect of this genotype for the risk of AAA development. None of the remaining polymorphisms tested were associated with AAA occurrence.

Increased PAI-1 in females compared with males is protective for abdominal aortic aneurysm formation in a rodent model

The serine proteases, along with their inhibitor plasmin activator inhibitor-1 (PAI-1), have been shown to play a role in abdominal aortic aneurysm (AAA) formation. The aim of this study is to determine if PAI-1 may be a protective factor for AAA formation and partially responsible for the gender difference observed in AAAs. Male and female wild-type (WT) C57BL/6 and PAI-1(-/-) mice 8-12 wk of age underwent aortic perfusion with porcine pancreatic elastase. Animals were harvested 14 days following perfusion and analyzed for phenotype, PAI-1 protein levels, and matrix metalloproteinase (MMP)-9 and -2 activity. WT males had an average increase in aortic diameter of 80%, whereas females only increased 32% (P < 0.001). PAI-1(-/-) males increased 204% and females 161%, significantly more than their WT counterparts (P < 0.001). Western blot revealed 61% higher PAI-1 protein levels in the WT females compared with the WT males (P = 0.01). Zymography revealed higher levels of pro-MMP-2 and active MMP-2 in the PAI-1(-/-) males and females compared with their WT counterparts. PAI-1(-/-) females had significantly higher serum plasmin levels compared with WT females (P = 0.003). In conclusion, WT female mice are protected from aneurysm formation and have higher levels of PAI-1 compared with males during experimental aneurysm formation. Additionally, both male and female PAI-1(-/-) animals develop significantly larger aneurysms than WT animals, correlating with higher pro- and active MMP-2 levels. These findings suggest that PAI-1 is protective for aneurysm formation in the elastase model of AAA and plays a role in the gender differences seen in AAA formation.

Treatment with simvastatin inhibits the formation of abdominal aortic aneurysms in rabbits

BACKGROUND

Abdominal aortic aneurysm (AAA) is a common and lethal disease. AAAs are associated with atherosclerosis, chronic inflammation, and extracellular matrix degradation. The aim of this study was to determine whether treatment with simvastatin can influence the development of experimental aortic aneurysms in a rabbit model.

MATERIALS AND METHODS

A total of 76 rabbits were randomized in four groups: in group I (n = 12), where the abdominal aortas were exposed to 0.9% NaCl, and in group II (n = 24), group III (n = 24) and group IV (n = 18), where the aortas were exposed to CaCl2 0.5 mol/L for 15 minutes after laparotomy. Group III received 2 mg/kg simvastatin daily starting 7 days before laparotomy, and in group IV, the daily treatment with simvastatin started 7 days after laparotomy. Animals were sacrificed at intervals of first, second, third, and fourth week to obtain measurements of aortic diameter and histological examination. Moreover, immunohistochemistry was used in order to examine the relative distribution of matrix metalloproteinases (MMPs) 2 and 9 (MMP-2 and MMP-9, respectively) and tissue inhibitor 1 of MMPs within the aortic aneurysms.

RESULTS

The increase of aortic diameter in animals of group I ranged from 4.6% to 7.6%; in group II, from 41% to 85% (P < 0.001 vs. group I); in group III, from 9% to 18% (group II vs. group III, P < 0.001); and in group IV; from 36% to 38%. Moreover, aortic specimens of group II presented a statistically significant increase in MMP-2 and MMP-9 immunoexpression compared with other groups (I, III, IV) (P < 0.05 for all comparisons), with the exception of animals of group IV at the end of second week. Immunoreactivity of tissue inhibitor 1 of MMPs was not statistically different among groups II, III, and IV.

CONCLUSIONS

Simvastatin may prove clinically significant in suppressing the development and expansion of AAAs and, thereby, in reducing the risk of rupture and the need for repair.

The association between serological markers for Chlamydophila pneumoniae and the development of abdominal aortic aneurysm

BACKGROUND

To investigate the association between serological markers for Chlamydophila pneumoniae (Cpn) and the development of abdominal aortic aneurysm (AAA) in a population-based case-control study.

METHODS

A screening for AAA among 65-75-year-old men and women was performed in a population with high prevalence of disease. Most of the subjects had undergone previous testing at the age of 60, including blood sampling. A total of 42 patients with AAA were compared with 100 age- and gender-matched controls with normal aortas. Cpn immunoglobulin A (IgA) and immunoglobulin G (IgG) antibodies present in plasma samples obtained at the time of screening (current) and in the past 5-15 (mean, 12) years (historical) were analyzed. Cpn antibody titers (<1/64, 1/64, 1/264, and 1/1024) were analyzed using the microimmunofluorescence technique.

RESULTS

No differences in current Cpn immunoglobulin A and IgG antibodies titers (p = 0.111 and 0.659), historical titers (p = 0.449 and 0.228), or titer change (delta) (p = 0.794 and 0.172) were observed between patients with AAA and controls. In all, 82% of the patients with AAA had a current Cpn IgG titer of 1/1024 as compared with the 70% of the control group. All 11 patients who had an aortic diameter of >40 mm reported having high current Cpn IgG titers. The fact that such a large proportion of the healthy population demonstrated an immune response against Cpn made it difficult to demonstrate possible effects of Cpn infection on AAA formation in a case-control study.

CONCLUSION

No significant associations were found between AAA detected by screening and Cpn antibody titer levels at the time of screening or during past screening at the age of 60.

Plasma tissue plasminogen activator and abdominal aortic aneurysm presence: a systematic review and meta-analysis

BACKGROUND

To summarize the present evidence for an association between circulating tissue plasminogen activator (tPA) levels and abdominal aortic aneurysm (AAA) presence, we performed a systematic review and meta-analysis of case-control studies that compared plasma tPA levels between patients with AAA and subjects without AAA.

METHODS

MEDLINE was searched to identify all case-control studies that compared plasma tPA levels between patients with AAA and subjects without AAA. For each study, data regarding plasma tPA levels in both the AAA and control groups were used to generate standardized mean differences and 95% confidence intervals. Study-specific estimates were combined using inverse variance-weighted average of logarithmic standardized mean differences in both fixed- and random-effects models.

RESULTS

Our search identified five eligible case-control studies, including data on 234 patients with AAA and 459 subjects without AAA. Pooled analysis of the five studies demonstrated nonsignificantly higher plasma tPA levels in the AAA group than those in the control group in fixed-effect models (standardized mean differences = 0.07; 95% confidence interval = -0.09-0.24; p = 0.40). There was minimal study heterogeneity of results (p = 0.05) and no evidence of significant publication bias (p = 0.3272).

CONCLUSION

The results of our analysis suggest that plasma tPA levels may not be higher in patients with AAA than those in subjects without AAA. Higher plasma tPA levels may not be associated with AAA presence.

Markers of Proteolysis, Fibrinolysis, and Coagulation in Relation to Size and Growth Rate of Abdominal Aortic Aneurysms

We evaluated whether matrix metalloproteinases (MMPs) 2 and 9, their inhibitors, markers for fibrinolysis, and thrombin activation are associated with diameter and growth of abdominal aortic aneurysms (AAAs). Material and Methods: Matrix metalloproteinases 2 and 9, tissue inhibitor of MMPs (TIMP-1), serpine-1, tPa-serpine-1, and activated protein C— protein C inhibitor (APC-PCI) complex were analyzed in 353 patients with AAA grouped according to AAA size, and 219 gender- and age-matched healthy individuals. Follow-up of AAA growth for up to 7 years was possible in 178 of 353 patients. Results: At baseline, all groups of patients with AAA showed lower levels of MMP-2 and -9, and higher levels of TIMP-1, serpine-1, and t-Pa-serpine-1 than controls. Matrix metalloproteinase 2 correlated inversely and APC-PCI complex correlated directly with AAA diameter. We found no correlations between markers for proteolysis, fibrinolysis, coagulation, and yearly AAA growth. Conclusion: Matrix metalloproteinase 2 is lower and APC-PCI higher in patients with larger AAA, but the relevance of the markers for AAA growth is far from clarified.

Haemostatic and fibrinolytic factors in men with a small abdominal aortic aneurysm

BACKGROUND

: The presence of an abdominal aortic aneurysm (AAA) independently predicts cardiovascular disease (CVD) and its complications. Levels of plasma markers of fibrin turnover are raised in men with a large AAA (at least 5.5 cm) and predict CVD risk in healthy subjects. This study examined fibrin turnover in men with a small AAA.

METHODS

: Seventy-five men with a small AAA (30-55 mm) were compared with 90 controls matched for age, sex and race. Haemostatic and fibrinolytic parameters were assessed.

RESULTS

: Men with a small AAA had higher mean levels of fibrinogen (2.92 versus 2.59 g/l; P = 0.019), thrombin-antithrombin (TAT) complex (4.57 versus 1.89 ng/ml; P < 0.001), prothrombin F1 + 2 (1.13 versus 0.82 ng/ml; P = 0.004) and D-dimer (346.7 versus 120.2 ng/ml; P < 0.001). All markers correlated with maximum aortic diameter determined by ultrasonography. On multivariable regression the association between presence of an AAA and fibrinogen, TAT complex, prothrombin F1 + 2 and D-dimer levels remained significant after adjustment for confounding influences.

CONCLUSION

: Fibrin turnover was increased in these men with a small AAA, independently of concomitant CVD, conventional risk factors and inflammatory markers. Enhanced fibrin turnover may contribute to the risk of cardiac complications in this group.

Haemostatic markers in patients with abdominal aortic aneurysm and the impact of aneurysm size

INTRODUCTION

Abdominal aortic aneurysm is a common condition with high mortality when rupturing. However, the condition is also associated with nonaneurysmal cardiovascular mortality. A possible contributing mechanism for the thrombosis related cardiovascular mortality is an imbalance between the activation of the coagulation system and the fibrinolytic system. The aim of the present study was to investigate haemostatic markers in patients with nonruptured abdominal aortic aneurysm with special regard to the influence of aneurysm size and smoking habits.

METHODS

Seventy-eight patients with infrarenal aortic aneurysm and forty-one controls without aneurysm matched by age, gender and smoking habits were studied. Thrombin-antithrombin (TAT), prothrombin fragment 1+2 (F 1+2)--markers of thrombin generation, and von Willebrand factor antigen (vWFag)--considered as a reliable marker of endothelial dysfunction--were measured. Plasma levels of tissue plasminogen activator antigen (tPAag), and plasminogen activator inhibitor type 1 (PAI-1) were measured as markers of fibrinolytic activity. D-dimer, a marker of fibrin turnover, was also measured.

RESULTS

There were significantly higher levels of TAT and D-dimer in patients with abdominal aortic aneurysm. The highest level of TAT and D-dimer were detected in patients with large compared to small AAA.

CONCLUSIONS

The present data indicate a state of activated coagulation in patients with abdominal aortic aneurysm which is dependent by aneurysm size. The activated coagulation in AAA patients could contribute to an increased cardiovascular risk in patients also with small AAA. The possible impact of secondary prevention apart from smoking cessation has to be further evaluated and is maybe as important as finding patients at risk of rupture.

Gene expression analysis of a porcine native abdominal aortic aneurysm model

INTRODUCTION

We sought to characterize the gene expression patterns occurring during the development of aneurysms in the native porcine aorta.

METHODS

In Yorkshire swine, the infrarenal aorta was balloon dilated and infused with a solution of type I collagenase/pancreatic porcine elastase (16,000 U/1,000 U). Aneurysmal and control aortic samples were obtained at 1 (n = 3), 2 (n = 6), and 4 (n = 5) weeks following aneurysm induction. RNA was isolated, converted to biotin-modified antisense RNA and hybridized to porcine genome arrays. Aneurysmal and control gene intensities were compared using the 2-sample-for-means z-test. P < .01 was considered statistically significant.

RESULTS

Extracellular matrix remodeling genes that were upregulated in aneurysmal compared with control tissue included matrix metalloproteinase-1, -2, -3, and -9; MT-MMP; cathepsin-D, -H, -K, and -S; tissue inhibitor of metalloproteinase-1; and collagen I-alpha1 chain (P < .01). Elastin exhibited temporally downregulated gene expression (P < .01). Inflammatory genes that were upregulated included intercellular adhesion molecule-2, tumor necrosis factor-alpha, interleukin (IL)-1 beta, IL-10, chemokine receptor-4, and tissue plasminogen activator (P < .01). Atherosclerosis and cancer genes that were upregulated included apolipoprotein E, acyl-CoA binding protein, friend leukemia virus integration-1, and E26 transformation-specific sequence (P < .01).

CONCLUSION

The porcine model replicates the gene expression patterns that are observed during the development of aneurysms in human studies as well as in rodent models. The porcine model thereby represents a novel method to study the impact of endovascular, cell-based, and other therapeutic interventions on AAA pathophysiology.

Characterization of a site on PAI-1 that binds to vitronectin outside of the somatomedin B domain

Vitronectin and plasminogen activator inhibitor-1 (PAI-1) are proteins that interact in the circulatory system and pericellular region to regulate fibrinolysis, cell adhesion, and migration. The interactions between the two proteins have been attributed primarily to binding of the somatomedin B (SMB) domain, which comprises the N-terminal 44 residues of vitronectin, to the flexible joint region of PAI-1, including residues Arg-103, Met-112, and Gln-125 of PAI-1. A strategy for deletion mutagenesis that removes the SMB domain demonstrates that this mutant form of vitronectin retains PAI-1 binding (Schar, C. R., Blouse, G. E., Minor, K. M., and Peterson, C. B. (2008) J. Biol. Chem. 283, 10297-10309). In the current study, the complementary binding site on PAI-1 was mapped by testing for the ability of a battery of PAI-1 mutants to bind to the engineered vitronectin lacking the SMB domain. This approach identified a second, separate site for interaction between vitronectin and PAI-1. The binding of PAI-1 to this site was defined by a set of mutations in PAI-1 distinct from the mutations that disrupt binding to the SMB domain. Using the mutations in PAI-1 to map the second site suggested interactions between alpha-helices D and E in PAI-1 and a site in vitronectin outside of the SMB domain. The affinity of this second interaction exhibited a K(D) value approximately 100-fold higher than that of the PAI-1-somatomedin B interaction. In contrast to the PAI-1-somatomedin B binding, the second interaction had almost the same affinity for active and latent PAI-1. We hypothesize that, together, the two sites form an extended binding area that may promote assembly of higher order vitronectin-PAI-1 complexes.