The Potential Role of Kallistatin in the Development of Abdominal Aortic Aneurysm

Degree of expression of inflammatory proteins in the amniotic cavity, but not prior obstetric history, is associated with the risk severity for spontaneous preterm birth after rescue cerclage for cervical insufficiency

PROBLEM

To examine whether the severity of spontaneous preterm birth (SPTB) risk after rescue cerclage for acute cervical insufficiency (CI) is linked to the degree of inflammatory response in the amniotic fluid (AF) based on the concentrations of various inflammatory proteins and prior obstetric history.

METHOD OF STUDY

We conducted a retrospective cohort study of 65 singleton pregnant women (17-25 weeks) who underwent rescue cerclage following the diagnosis of acute CI and were subjected to amniocentesis. EN-RAGE, IL-6, IL-8, and IP-10 as inflammatory mediators and kallistatin, MMP-2/8, and uPA as extracellular matrix remodeling-related molecules were assayed in the AF using ELISA. The level of each inflammatory mediator was divided into quartiles.

RESULTS

Intra-amniotic inflammation (IAI; AF IL-6 level ≥2.6 ng/mL) was independently associated with SPTB after cerclage placement. The odds of SPTB at < 32 weeks, even after adjusting for confounders, increased significantly with each increasing quartile of baseline AF levels for each inflammatory mediator (p for trend < .05). Kaplan-Meier survival curves showed that the cerclage-to-delivery intervals were significantly shorter as the quartiles of AF EN-RAGE and MMP-8 increased (log-rank test, p < .01 each). Neither previous term birth nor prior PTB was associated with SPTB risk or cerclage-to-delivery interval after rescue cerclage. Multiparous women who experience CI after term birth showed significantly elevated levels of MMP-8 and reduced kallistatin levels in the AF.

CONCLUSION

In patients with CI, SPTB risk (especially risk severity) after rescue cerclage is associated with the degree of the inflammatory response in AF as well as the presence of IAI but not with prior obstetric history.

Dysregulations of Key Regulators of Angiogenesis and Inflammation in Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a chronic vascular disease caused by localized weakening and broadening of the abdominal aorta. AAA is a clearly underdiagnosed disease and is burdened with a high mortality rate (65-85%) from AAA rupture. Studies indicate that abnormal regulation of angiogenesis and inflammation contributes to progression and onset of this disease; however, dysregulations in the molecular pathways associated with this disease are not yet fully explained. Therefore, in our study, we aimed to identify dysregulations in the key regulators of angiogenesis and inflammation in patients with AAA in peripheral blood mononuclear cells (using qPCR) and plasma samples (using ELISA). Expression levels of ANGPT1, CXCL8, PDGFA, TGFB1, VEGFB, and VEGFC and plasma levels of TGF-alpha, TGF-beta 1, VEGF-A, and VEGF-C were found to be significantly altered in the AAA group compared to the control subjects without AAA. Associations between analyzed factors and risk factors or biochemical parameters were also explored. Any of the analyzed factors was associated with the size of the aneurysm. The presented study identified dysregulations in key angiogenesis- and inflammation-related factors potentially involved in AAA formation, giving new insight into the molecular pathways involved in the development of this disease and providing candidates for biomarkers that could serve as diagnostic or therapeutic targets.

The mechanism and therapy of aortic aneurysms

Aortic aneurysm is a chronic aortic disease affected by many factors. Although it is generally asymptomatic, it poses a significant threat to human life due to a high risk of rupture. Because of its strong concealment, it is difficult to diagnose the disease in the early stage. At present, there are no effective drugs for the treatment of aneurysms. Surgical intervention and endovascular treatment are the only therapies. Although current studies have discovered that inflammatory responses as well as the production and activation of various proteases promote aortic aneurysm, the specific mechanisms remain unclear. Researchers are further exploring the pathogenesis of aneurysms to find new targets for diagnosis and treatment. To better understand aortic aneurysm, this review elaborates on the discovery history of aortic aneurysm, main classification and clinical manifestations, related molecular mechanisms, clinical cohort studies and animal models, with the ultimate goal of providing insights into the treatment of this devastating disease. The underlying problem with aneurysm disease is weakening of the aortic wall, leading to progressive dilation. If not treated in time, the aortic aneurysm eventually ruptures. An aortic aneurysm is a local enlargement of an artery caused by a weakening of the aortic wall. The disease is usually asymptomatic but leads to high mortality due to the risk of artery rupture.

Key ferroptosis-related genes in abdominal aortic aneurysm formation and rupture as determined by combining bioinformatics techniques

Objectives

Abdominal aortic aneurysm (AAA) is a cardiovascular disease with high mortality and pathogenesis closely related to various cell death types, e.g., autophagy, apoptosis and pyroptosis. However, the association between AAA and ferroptosis is unknown.

Methods

GSE57691 and GSE98278 dataset were obtained from the Gene Expression Omnibus database, and a ferroptosis-related gene (FRG) set was downloaded from the FerrDb database. These data were normalized, and ferroptosis-related differentially expressed genes (FDEGs, AAA vs. normal samples) were identified using the limma package in R. FRGs expression was analyzed by Gene Set Expression Analysis (GSEA), and FDEGs were analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes (KEGG) pathway enrichment analyses using the clusterProfiler package in R and ClueGO in Cytoscape. Protein–protein interaction networks were assembled using Cytoscape, and crucial FDEGs were identified using CytoHubba. Critical FDEG transcription factors (TFs) were predicted with iRegulon. FDEGs were verified in GSE98278 set, and key FDEGs in AAA (compared with normal samples) and ruptured AAA (RAAA; compared with AAA samples) were identified. Ferroptosis-related immune cell infiltration and correlations with key genes were analyzed by CIBERSORT. Key FEDGs were reverified in Ang II-induced AAA models of ApoE^–/– and CD57B/6J mice by immunofluorescence assay.

Results

In AAA and normal samples, 40 FDEGs were identified, and the expression of suppressive FRGs was significantly downregulated with GSEA. For FDEGs, the GO terms were response to oxidative stress and cellular response to external stimulus, and the KEGG pathways were the TNF and NOD-like receptor signaling pathways. IL6, ALB, CAV1, PTGS2, NOX4, PRDX6, GPX4, HSPA5, HSPB1, and NCF2 were the most enriched genes in the crucial gene cluster. CEBPG, NFAT5, SOX10, GTF2IRD1, STAT1, and RELA were potential TFs affecting these crucial genes. Ferroptosis-related immune cells involved in AAA formation were CD8+ T, naive CD4+ T, and regulatory T cells (Tregs); M0 and M2 macrophages; and eosinophils. Tregs were also involved in RAAA. GPX4, SLC2A1, and PEBP1 expression was downregulated in both the RAAA and AAA samples. GPX4 and PEBP1 were more important in AAA because they influenced ferroptosis-related immune cell infiltration, and SLC2A1 was more important in RAAA.

Conclusions

This is the first study to show that ferroptosis is crucial to AAA/RAAA formation. The TNF and NOD-like signaling pathways and ferroptosis-related immune cell infiltration play key roles in AAA/RAAA. GPX4 is a key ferroptosis-related gene in AAA. Ferroptosis and related genes might be promising targets in the treatment of AAA/RAAA.

Kallistatin limits abdominal aortic aneurysm by attenuating generation of reactive oxygen species and apoptosis

Inflammation, vascular smooth muscle cell apoptosis and oxidative stress are believed to play important roles in abdominal aortic aneurysm (AAA) pathogenesis. Human kallistatin (KAL; gene SERPINA4) is a serine proteinase inhibitor previously shown to inhibit inflammation, apoptosis and oxidative stress. The aim of this study was to investigate the role of KAL in AAA through studies in experimental mouse models and patients. Serum KAL concentration was negatively associated with the diagnosis and growth of human AAA. Transgenic overexpression of the human KAL gene (KS-Tg) or administration of recombinant human KAL (rhKAL) inhibited AAA in the calcium phosphate (CaPO₄) and subcutaneous angiotensin II (AngII) infusion mouse models. Upregulation of KAL in both models resulted in reduction in the severity of aortic elastin degradation, reduced markers of oxidative stress and less vascular smooth muscle apoptosis within the aorta. Administration of rhKAL to vascular smooth muscle cells incubated in the presence of AngII or in human AAA thrombus-conditioned media reduced apoptosis and downregulated markers of oxidative stress. These effects of KAL were associated with upregulation of Sirtuin 1 activity within the aortas of both KS-Tg mice and rodents receiving rhKAL. These results suggest KAL-Sirtuin 1 signalling limits aortic wall remodelling and aneurysm development through reductions in oxidative stress and vascular smooth muscle cell apoptosis. Upregulating KAL may be a novel therapeutic strategy for AAA.

The SERPINA4 rs2070777 AA Genotype is Associated with an Increased Risk of Recurrent Miscarriage in a Southern Chinese Population

Background

Many inflammation-related gene polymorphisms are associated with susceptibility to recurrent miscarriage. SERPINA4 is involved in inflammation and is associated with susceptibility to a variety of diseases, but its relevance in recurrent miscarriage is unclear. Therefore, this study aimed to investigate the relationship between SERPINA4 gene polymorphisms and susceptibility to recurrent spontaneous abortion.

Methods

Two SERPINA4 polymorphisms were genotyped in 631 patients with recurrent miscarriage and 771 controls by TaqMan real-time polymerase chain reaction, and the strength of each association was evaluated through 95% confidence intervals (CIs) and odds ratios (ORs).

Results

The results showed that SERPINA4 rs2070777 AA genotypes were associated with an increased risk of recurrent miscarriage (AA vs AT/TT adjusted OR=1.409, 95% CI=1.032–1.924, P=0.0309), and we also found a significant association between the rs910352 T allele in the SERPINA4 gene and susceptibility to recurrent miscarriage (CT vs CC adjusted OR=1.579, 95% CI=1.252–1.992, P=0.0001; TT vs CC adjusted OR=1.524, 95% CI=1.134–2.049, P=0.0052). The combined analysis of two SNPs of the SERPINA4 gene revealed that carriers with one to two unfavorable genotypes were associated with a higher risk for recurrent miscarriage compared with individuals with no unfavorable genotypes (adjusted OR=1.257, 95% CI=1.019-1.550). Moreover, our study indicates that having one to two unfavorable genotypes is associated with an increased risk of recurrent miscarriage in women 35–40 years of age.

Conclusion

Our study suggests that SERPINA4 rs2070777AA genotypes might contribute to an increased risk of recurrent miscarriage in a southern Chinese population.

Kallistatin correlates with inflammation in abdominal aortic aneurysm and suppresses its formation in mice

Background

Kallistatin (KS), encoded by SERPINA4, was suggested to play a protective role in many cardiovascular diseases. However, its role in the pathogenesis of abdominal aortic aneurysm (AAA) remains unclear. The aim of this study was to examine the potential association of KS with AAA pathogenesis.

Methods

We examined KS (SERPINA4) expression in human AAA by PCR, immunohistochemistry, western blotting, and enzyme-linked immunosorbent assay (ELISA) and analyzed correlations between kallistain and clinical data. We then analyzed the effect of recombinant KS on AAA formation and the Wingless (Wnt) signaling pathway in a mouse AAA model developed by angiotensin II (AngII) infusion to apolipoprotein E-deficient (ApoE^-/-) mice.

Results

In AAA tissue samples, KS was significantly increased compared with samples from the control group (P<0.001, P<0.001, respectively). Clinically, decreased SERPINA4 expression in AAA tissue samples represented an increased rate of iliac artery aneurysm [odds ratio (OR): 0.017; P=0.040]. And decreased plasma KS level represented a high risk for rupture (OR: 0.837; P=0.034). KS inhibited AAA formation and blocked the Wnt signaling pathway in AngII-infused ApoE^-/- mice.

Conclusions

The present study demonstrates that aberrant changes in KS expression occur in AAA. KS plays an important anti-inflammatory role and showed important clinical correlations in AAA. Decreased KS (SERPINA4) level is a risk factor of AAA rupture. Our pre-clinical animal experiments indicate that treatment with recombination KS suppresses AngII-induced aortic aneurysm formation and might be a new target for the drug therapy of AAA.

Meprin-α (Mep1A) enhances TNF-α secretion by mast cells and aggravates abdominal aortic aneurysms

BACKGROUND AND PURPOSE

Abdominal aorticaneurysm (AAA) rupture is mainly due to elastic lamina degradation. As a metalloendopeptidase, meprin-α (Mep1A) critically modulates the activity of proteins and inflammatory cytokines in various diseases. Here, we sought to investigate the functional role of Mep1A in AAA formation and rupture.

EXPERIMENTAL APPROACH

AAA tissues were detected by using real-time PCR (RT-PCR), western blotting (WB), and immunohistochemistry. Further mechanistic studies used RT-PCR, WB, and enzyme-linked immunosorbent assays.

KEY RESULTS

Mep1A mediated AAA formation by regulating the mast cell (MC) secretion of TNF-α, which promoted matrix metalloproteinase (MMP) expression and apoptosis in smooth muscle cells (SMCs). Importantly, increased Mep1A expression was found in human AAA tissues and in angiotensin II-induced mouse AAA tissues. Mep1A deficiency reduced AAA formation and increased the survival rate of AAA mice. Pathological analysis showed that Mep1A deletion decreased elastic lamina degradation and SMC apoptosis in AAA tissues. Furthermore, Mep1A was expressed mainly in MCs, wherein it mediated TNF-α expression. Mep1A inhibitor actinonin significantly inhibited TNF-α secretion in MCs. TNF-α secreted by MCs enhanced MMP2 expression in SMCs and promoted SMC apoptosis.

CONCLUSION AND IMPLICATIONS

Taken together, these data suggest that Mep1A may be vital in AAA pathophysiology by regulating TNF-α production by MCs. Knocking out Mep1A significantly decreased AAA diameter and improved AAA stability in mice. Therefore, Mep1A is a potential new therapeutic target in the development of AAA.

Increased m6A methylation level is associated with the progression of human abdominal aortic aneurysm

Background

The role of N6-methyladenosine (m6A) modification in abdominal aortic aneurysm (AAA) has not been extensively studied. This study therefore aimed to investigate m6A RNA methylation and the expressions of the corresponding modulators in AAA.

Methods

A comparative study between AAA tissue samples (n=32) and healthy aortas (n=12) was performed using m6A methylation quantification for messenger RNA (mRNA) m6A status, quantitative polymerase chain reaction (qPCR), and western blot for the expressions of m6A modulators and immunohistochemistry (IHC) to detect locations of the modulators in AAA tissues.

Results

The m6A level significantly increased in AAA as compared to healthy aorta tissues. Among AAA patients, the high m6A level represented an even greater risk of AAA rupture as compared to non-ruptured AAA [odds ratio (OR), 1.370; 95% confidence interval (CI), 1.007-1.870]. The major N6-adenosine modulators, including YTHDF1, YTHDF3, FTO, and METTL14, are the main factors involved in aberrant m6A modification and the expression of both was significantly correlated to the proportion of m6A in total mRNA. Clinically, YTHDF3 represented an even greater risk of rupture (OR, 1.036; 95% CI, 1.001-1.072). Regarding the cellular location, METTL14 seemed to be associated with inflammatory infiltrates and neovascularization. Furthermore, a strong correlation was seen between FTO and aneurysmal smooth muscle cells (SMCs), YTHDF3, and macrophage infiltrate.

Conclusions

We were first to observe m6A modification in human AAA tissues. The results also reveal the important roles of m6A modulators, including YTHDF3, FTO, and METTL14, in the pathogenesis of human AAA and provide a new view on m6A modification in AAA. Our findings suggest a potential mechanism of epigenetic alterations in clinical AAA.

Stimulation of endothelial progenitor cells by microRNA-31a-5p to induce endothelialization in an aneurysm neck after coil embolization by modulating the Axin1-mediated β-catenin/vascular endothelial growth factor pathway

OBJECTIVE

Emerging evidence shows that frequent recurrence of intracranial aneurysms (IAs) after endovascular coiling is attributable to the lack of endothelialization across the aneurysm neck. Recently, much attention has been given to the role of microRNAs (miRs) in vascular disease, although their contributory role to IA is poorly understood.

METHODS

Adult male Sprague-Dawley rats were subjected to microsurgery to create a coiled embolization aneurysm model, and were injected with miR-31a-5p agomir or a negative control agomir via the tail vein at a dose of 10 mg/kg per week for 4 weeks after IA induction. H & E staining, scanning electron microscopy, and flow cytometry were performed to evaluate the effects of miR-31a-5p agomir on endothelialization and the number of circulating endothelial progenitor cells (EPCs). The effects of miR-31a-5p on the viability and functioning of EPCs were also determined using Cell Counting Kit-8, wound-healing assay, and tube formation assays.

RESULTS

The authors tested the ability of miR-31a-5p to promote EPC-induced endothelialization in a model of coiled embolization aneurysm. miR-31a-5p agomir improved endothelialization and elevated the number of circulating EPCs in the peripheral blood compared to a negative control agomir-treated group. In addition, the number of vWF- and KDR-positive cells in the aneurysm neck was increased in the miR-31a-5p agomir-treated group. Furthermore, upregulation of miR-31a-5p promoted EPC proliferation, migration, and tube formation and enhanced the expression of the proangiogenic factor vascular endothelial growth factor in vitro. Mechanistically, miR-31a-5p directly targeted the 3' untranslated region (3'UTR) of Axin1 messenger RNA and repressed its expression. Besides, miR-31a-5p exerted its effect on EPCs by regulating the Axin1-mediated Wnt/β-catenin pathway.

CONCLUSIONS

Collectively, these results indicate that miR-31a-5p is an important regulator of EPC mobilization and endothelialization and may have a positive effect on aneurysm repair.

Is Abdominal Aortic Aneurysm Behavior after Endovascular Repair Associated with Aneurysm Wall Density on Computed Tomography Angiography?

Background and objectives: Abdominal aortic aneurysm (AAA) growth is unpredictable after the endovascular aneurysm repair (EVAR). Continuing aortic wall degradation and weakening due to hypoxia may have a role in post-EVAR aneurysm sac growth. We aimed to assess the association of aortic wall density on computed tomography angiography (CTA) with aneurysm growth following EVAR. Materials and Methods: A total of 78 patients were included in the study. The control group consisted of 39 randomly assigned patients without aortic pathology. Post-EVAR aneurysm sac volumes on CTA were measured twice during the follow-up period to estimate aneurysm sac behavior. A maximum AAA sac diameter, aortic wall and lumen densities in Hounsfield units (HU) on CTA were measured. A relative aortic wall density (the ratio of aortic wall to lumen densities) was calculated. A statistical data analysis was performed using standard methods. Results: An increase in the AAA sac volume was observed in 12 (30.8%) cases. Median relative aortic wall density on CTA scores in both the patient and the control group at the level of the diaphragm were similar: 0.15 (interquartile range (IQR), 0.11–0.18) and 0.16 (IQR 0.11–0.18), p = 0.5378, respectively. The median (IQR) relative aortic wall density score at the level of the maximum AAA diameter in the patient group was lower than at the level below renal arteries in the control group: 0.10 (0.07–0.12) and 0.17 (0.12–0.23), p < 0.0001, respectively. The median (IQR) relative growing AAA sac wall density score was lower than a relative stable/shrinking AAA sac wall density score: 0.09 (0.06–0.10) and 0.11 (0.09–0.13), p = 0.0096, respectively. Conclusions: A lower aortic aneurysm wall density on CTA may be associated with AAA growth after EVAR.

A Novel Bioabsorbable Sheet That Delivers NF-κB Decoy Oligonucleotide Restrains Abdominal Aortic Aneurysm Development in Rats

For the suppression of inflammation in the aneurysm development, we focused on inhibition of an important transcription factor, nuclear factor-kappa B (NF-κB), using a decoy strategy. We newly developed a novel bioabsorbable sheet that delivers NF-κB decoy oligodeoxynucleotide (ODN).We treated 5-week-old SD rats that were induced with abdominal aortic aneurysm (AAA) using 0.5 M CaCl₂ with an NF-κB decoy sheet. Four weeks after AAA induction, aortic tissue was excised for further examinations. We showed that this bioabsorbable sheet could deliver the decoy ODN into the target tissues and dissolve within a week. Treatment with the NF-κB decoy sheet reduced the aneurysm size compared with the controls. It also suppressed inflammation due to the effect of NF-κB decoy ODN. Immunohistochemistry revealed that the expression of CD31, CD4, and CD11b in the NF-κB decoy sheet group was significantly lower than in the control sheet group. The NF-κB decoy sheet was absorbed on the target tissue.We have revealed that the bioabsorbable sheet mediated decoy ODN is effective for transfection into target organs. We have also indicated that NF-κB decoy ODN transfection using this sheet has the potential to suppress the dilatation of aneurysm. The bioabsorbable sheet mediated transfection of the decoy ODN can be beneficial for the clinical treatment of AAA and other NF-κB-related cardiovascular diseases.

Thiol/disulphide homeostasis in thoracic aortic aneurysm and acute aortic syndrome

AIM

The aim of this study was to evaluate whether ranging values of thiol and disulphide herald a dilatation or impending acute aortic syndrome at thoracic aorta. Results/methodology: Study population consisted of patients with aortic aneurysm (n = 58), with acute aortic syndrome (n = 32) and without aortic aneurysm (control group; n = 61). A spectrophotometric method was used to determine thiol and disulphide. Native and total thiol levels were moderately correlated with maximal aortic diameter. At the end of 6 months, there was statistically significant increase in native, total thiol levels and decrease in disulfide and disulphide/native thiol ratio in operated group.

DISCUSSION/CONCLUSION

Lower thiol levels may be associated with the higher risk of aortic aneurysm development and may increase after surgical therapy.