Apoptotic cell death and rupture of abdominal aortic aneurysm

Circular RNA circ_0021001 regulates miR-148b-3p/GREM1 axis to modulate proliferation and apoptosis of vascular smooth muscle cells

Intracranial aneurysm (IA) is an abnormal expression in the intracranial arteries, which is related to the growth and apoptosis of vascular smooth muscle cells (VSMCs). Circular RNA (circRNA) circ_0021001 (also named circARFIP2) has been identified to mediate the regulation of VSMCs proliferation. However, the molecular mechanism of circ_0021001 involved in VSMC dysfunction in IA is poorly defined. The expression levels of circ_0021001, microRNA-148b-3p (miR-148b-3p), and Gremlin 1 (GREM1) were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability, proliferation, cell cycle progression, and apoptosis were detected by Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), and flow cytometry assays. Protein levels of proliferating cell nuclear antigen (PCNA), p21, B-cell lymphoma-2 (Bcl-2), Bcl-2 related X protein (Bax), and GREM1 were examined by western blot assay. The binding relationship between miR-148b-3p and circ_0021001 or GREM1 was predicted by StarBase and then verified using a dual-luciferase reporter assay. The expression levels of circ_0021001 and GREM1 were increased, and that of miR-148b-3p was decreased in IA tissues and HUASMCs. Moreover, the downregulation of circ_0021001 could repress proliferation ability and induce apoptosis of HUASMCs. The mechanical analysis uncovered that circ_0021001 served as a sponge of miR-148b-3p to regulate GREM1 expression. Circ_0021001 silencing could suppress cell growth and induce apoptosis of HUASMCs partially through modulating the miR-148b-3p/GREM1, presented circ_0021001 as a promising therapeutic target for IA.

Development of pharmacotherapies for abdominal aortic aneurysms

The cardiovascular field is still searching for a treatment for abdominal aortic aneurysms (AAA). This inflammatory disease often goes undiagnosed until a late stage and associated rupture has a high mortality rate. No pharmacological treatment options are available. Three hallmark factors of AAA pathology include inflammation, extracellular matrix remodeling, and vascular smooth muscle dysfunction. Here we discuss drugs for AAA treatment that have been studied in clinical trials by examining the drug targets and data present for each drug's ability to regulate the aforementioned three hallmark pathways in AAA progression. Historically, drugs that were examined in interventional clinical trials for treatment of AAA were repurposed therapeutics. Novel treatments (biologics, small-molecule compounds etc.) have not been able to reach the clinic, stalling out in pre-clinical studies. Here we discuss the backgrounds of previous investigational drugs in hopes of better informing future development of potential therapeutics. Overall, the highlighted themes discussed here stress the importance of both centralized anti-inflammatory drug targets and rigor of translatability. Exceedingly few murine studies have examined an intervention-based drug treatment in halting further growth of an established AAA despite interventional treatment being the therapeutic approach taken to treat AAA in a clinical setting. Additionally, data suggest that a potentially successful drug target may be a central inflammatory biomarker. Specifically, one that can effectively modulate all three hallmark factors of AAA formation, not just inflammation. It is suggested that inhibiting PGE₂ formation with an mPGES-1 inhibitor is a leading drug target for AAA treatment to this end.

Role of Necroptosis and Immune Infiltration in Human Stanford Type A Aortic Dissection: Novel Insights from Bioinformatics Analyses

Background

Stanford type A aortic dissection (TAAD) is one of the most life-threatening cardiovascular emergencies with high mortality and morbidity, and necroptosis is a newly identified type of programmed cell death and contributes to the pathogenesis of various cardiovascular diseases. However, the role of necroptosis in TAAD has not been elucidated. This study was aimed at determining the role of necroptosis in TAAD using bioinformatics analyses.

Methods

The RNA sequencing dataset GSE153434 and the microarray dataset GSE52093 were obtained from Gene Expression Omnibus (GEO) database. Differentially expressed genes of necroptosis (NRDEGs) were identified based on differentially expressed genes (DEGs) and necroptosis gene set. Gene set enrichment analysis (GSEA) was applied to evaluate the gene enrichment signaling pathway in TAAD. The STRING database and Cytoscape software were used to establish and visualize protein-protein interaction (PPI) networks and identify the key functional modules of NRDEGs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of NRDEGs were also performed. Additionally, Spearman correlations were used to construct the necroptosis-related transcription factor-target genes regulatory network, immune infiltration patterns were analyzed using the ImmuCellAI algorithm, and the correlation between immune cell-type abundance and NRDEGs expression was investigated. The expression levels of NRDEGs and immune infiltration were additionally verified in the GSE52093 dataset.

Results

We found that the necroptosis pathway was considerably enriched and activated in TAAD samples. Overall, 25 NRDEGs were identified including MLKL, RIPK1, and FADD, and among them, 18 were verified in the validation set. Moreover, GO and KEGG enrichment analyses found that NRDEGs were primarily involved in the tumor necrosis factor signaling pathway, nucleotide-binding oligomerization domain-like receptor signaling pathway, and interleukin-17 signaling pathway. The imbalance of Th17/Treg cells was identified in the TAAD samples. Furthermore, correlation analysis indicated that expression of NRDEGs was positively associated with proinflammatory immune-cell infiltrations and negatively associated with anti-inflammatory or regulatory immune-cell infiltrations.

Conclusions

The present findings suggest that necroptosis phenomenon exists in TAAD and correlates with immune cell infiltration, which indicate necroptosis may promote the development of TAAD through activating immune infiltration and immune response. This study paves a new road to future investigation of the pathogenic mechanisms and therapeutic strategies for TAAD.

Programmed cell death in aortic aneurysm and dissection: A potential therapeutic target

Rupture of aortic aneurysm and dissection (AAD) remains a leading cause of death. Progressive smooth muscle cell (SMC) loss is a crucial feature of AAD that contributes to aortic dysfunction and degeneration, leading to aortic aneurysm, dissection, and, ultimately, rupture. Understanding the molecular mechanisms of SMC loss and identifying pathways that promote SMC death in AAD are critical for developing an effective pharmacologic therapy to prevent aortic destruction and disease progression. Cell death is controlled by programmed cell death pathways, including apoptosis, necroptosis, pyroptosis, and ferroptosis. Although these pathways share common stimuli and triggers, each type of programmed cell death has unique features and activation pathways. A growing body of evidence supports a critical role for programmed cell death in the pathogenesis of AAD, and inhibitors of various types of programmed cell death represent a promising therapeutic strategy. This review discusses the different types of programmed cell death pathways and their features, induction, contributions to AAD development, and therapeutic potential. We also highlight the clinical significance of programmed cell death for further studies.

Memory T cells of patients with abdominal aortic aneurysm differentially expressed micro RNAs 21, 92a, 146a, 155, 326 and 663 in response to Helicobacter pylori and Lactobacillus acidophilus

Regarding the role of micro RNAs (miRNA) in the proliferation and differentiation of T cells as well as the controversy around the role of bacteria in the pathogenesis of abdominal aortic aneurysm (AAA), the effects of Helicobacter pylori (Hp) and Lactobacillus acidophilus (La) were investigated in the induction of miRNAs and apoptosis in CD4+ memory T (Tem) cells of AAA patients and controls. Signature atherosclerosis miRNAs 21, 92a, 146a, 155, 326 and 663 were measured in the sera and tissues of AAA patients and control. PBMCs separately and in co-culture with HUVEC were treated with Hp-water-extract (HpWE) and La-conditioned-medium (LaCM). Apoptosis and miRNA levels were assessed in the isolated Tem by flowcytometry and real-time-PCR. In single-culture, HpWE increased apoptosis and miR-155 and LaCM decreased apoptosis and increased miR-21. In co-culture, apoptosis decreased in both groups in response to CagA+HpWE. Also, all miRNAs increased in patients Tem but in controls, only miR- 146a and 21 showed changes. Although, apoptosis was similar in Tem of patients and controls, the effects of Hp and La were different on the induction of apoptosis and miRNAs and also these bacteria showed different impacts in single and co-culture conditions. Beyond the direct effects of these bacteria on the pathogenesis of diseases, their effects on miRNAs expression may shed light on their roles in the development and the prevention of AAA.

Circ_0020397 regulates the viability of vascular smooth muscle cells by up-regulating GREM1 expression via miR-502-5p in intracranial aneurysm

AIMS

Circ_0020397 has been found to be down-regulated in intracranial aneurysm (IA), and deregulation of circ_0020397 involved in the regulation of vascular smooth muscle cells (VSMCs) proliferation. However, the mechanism by which circ_0020397 implicates in VSMC dysfunction in IA remains vague.

MATERIALS AND METHODS

The expression of circ_0020397, miR-502-5p and Gremlin 1 (GREM1) was detected using quantitative real-time polymerase chain reaction. Cell viability was analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Protein levels of proliferating cell nuclear antigen (PCNA) and GREM1 were measured using western blot. The interaction between miR-502-5p and circ_0020397 or GREM1 was confirmed by dual-luciferase reporter, RNA pull-down and RNA immunoprecipitation assay.

KEY FINDINGS

Circ_0020397 or GREM1 expression was decreased in VSMCs isolated from IA patients, and overexpression of circ_0020397 or GREM1 promoted VSMC viability and elevated PCNA expression level, while inhibition of them showed opposite effects. MiR-502-5p was confirmed to directly bind to circ_0020397 or GREM1, and miR-502-5p reversed the effects of circ_0020397 on VSMC viability and PCNA level. Besides, miR-502-5p overexpression suppressed VSMC viability and reduced PCNA level, while these effects were attenuated by GREM1 up-regulation. Importantly, circ_0020397 could regulate GREM1 expression via miR-502-5p in VSMCs.

SIGNIFICANCE

Circ_0020397 played an important role in phenotypic modulation in IA by promoting VSMC viability via miR-502-5p/GREM1 axis, suggesting a novel insight into IA pathogenesis and new targets for IA molecular therapy.

Role of autophagy in aneurysm and dissection of the ascending aorta

Maintenance of physiologically balanced levels of autophagy is crucial for cellular homeostasis and in the normal vessel wall, balanced autophagy can be considered a cytoprotective mechanism that preserves endothelial function and prevents cardiovascular disease. Recent studies pointed out the importance of the modulation of the autophagic flux in the pathogenesis of aortic dissection and aneurysms of the ascending aorta. Notably, shear stress (and its receptor p62), IL-6, Rab7 and Atg5/IRE1α pathways of autophagy may be considered the novel super-selective therapeutic target for the preventive and postoperative treatment of aortic aneurysm and aortic dissection. This review intends to summarize current evidences in this field trying to enlighten new avenues for future researches.

Necrotic cell debris induces a NF-κB-driven inflammasome response in vascular smooth muscle cells derived from abdominal aortic aneurysms (AAA-SMC)

Abdominal aortic aneurysm (AAA) is a multi-factorial progressive vascular disease with life-threatening complications. Increasing evidence suggests that smooth muscle cell (SMC) dysfunction and cell death contribute to dilatation and rupture of the aorta by inducing an inflammatory response. The exact mechanism of this response however, is incompletely understood. We here investigated in vitro the capacity of autologous necrotic cell debris (CD) to induce inflammasome components and inflammatory mediators in aortic SMC (AAA-SMC) isolated from patients with AAA undergoing surgical repair. AAA-SMCs were additionally primed with Interferon- γ (IFN-γ) before treatment with CD in order to mimic the proinflammatory status caused by higher IFN-γ concentrations that have been demonstrated in the wall of AAAs. Real-time RT-PCR revealed that CD significantly increased NLRP3 and IL1B mRNA expression in different SMC cultures within 6 h of exposure. Priming of the AAA-SMC with IFN-γ significantly increased expression of NLRP3, AIM2, IFI16 and CASP1 mRNAs, whereas IL1B mRNA was reduced. Additional exposure of IFN-γ-primed AAA-SMC to CD for 6-24 h, further augmented expression of AIM2, NLRP3, and Caspase-1 protein levels. Analysis of the SMC supernatants by ELISA revealed CD-induced release of the senescence-associated cytokines IL-6 and MCP-1 in native and IFN-γ-primed SMC, whereas no secretion of Interleukin-(IL) 1α and IL-1β secretion were observed. Our results implicate a role of necrotic cell debris derived from dead neighboring cells in SMC dysfunction and in inflammatory response of AAA tissue.

SRPK1 gene silencing promotes vascular smooth muscle cell proliferation and vascular remodeling via inhibition of the PI3K/Akt signaling pathway in a rat model of intracranial aneurysms

OBJECTIVE

Intracranial aneurysm (IA) is a life threatening cerebrovascular disease characterized by phenotypic modulation of vascular smooth muscle cells (VSMCs) and loss of vessel cells. In addition to environmental factors, genetic factors have been proposed to be a critical factor in the onset and progression of IA. The present study investigates the effects of serine-arginine protein kinase 1 (SRPK1) on VSMC proliferation and apoptosis both in vivo and in vitro, as well as its role in vascular remodeling in vivo through PI3 K/Akt signaling in IA.

METHODS

Differentially expressed genes related to IA were initially identified using microarray analysis. Immunohistochemistry was conducted to determine SRPK1 expression in the vascular walls in IA and normal cerebral vascular walls. TUNEL staining were applied to observe cell apoptosis patterns of VSMCs. VSMC proliferation and apoptosis in vitro were detected by cell counting kit-8 (CCK8) assay and flow cytometry. The expressions of SRPK1, PI3 K/Akt signaling pathway- and apoptosis-related genes were evaluated by RT-qPCR and Western blot analysis.

RESULTS

Microarray data of GSE36791 and GSE54083 were analyzed to determine the selection of SRPK1 gene. The vascular walls in IA rat models produced high levels of SRPK1 expression and an activated PI3 K/Akt signaling pathway. VSMCs treated with siRNA-SRPK1 exhibited enhanced cell proliferation, repressed cell apoptosis, and increased vascular remodeling, all of which suggest the inhibition of the PI3 K/AKT pathway. Notably, PI3 K/AKT pathway reversed the effect of SRPK1 silencing.

CONCLUSION

Our results show that siRNA-mediated silencing of SRPK1 gene inhibits VSMC apoptosis, and increases VSMCs proliferation and vascular remodeling in IA via the PI3 K/Akt signaling pathway. Our findings provide a novel intervention target for the molecular treatment of IA.

Allergic Lung Inflammation Aggravates Angiotensin II-Induced Abdominal Aortic Aneurysms in Mice

OBJECTIVE

Asthma and abdominal aortic aneurysms (AAA) both involve inflammation. Patients with asthma have an increased risk of developing AAA or experiencing aortic rupture. This study tests the development of one disease on the progression of the other.

APPROACH AND RESULTS

Ovalbumin sensitization and challenge in mice led to the development of allergic lung inflammation (ALI). Subcutaneous infusion of angiotensin II into mice produced AAA. Simultaneous production of ALI in AAA mice doubled abdominal aortic diameter and increased macrophage and mast cell content, arterial media smooth muscle cell loss, cell proliferation, and angiogenesis in AAA lesions. ALI also increased plasma IgE, reduced plasma interleukin-5, and increased bronchioalveolar total inflammatory cell and eosinophil accumulation. Intraperitoneal administration of an anti-IgE antibody suppressed AAA lesion formation and reduced lesion inflammation, plasma IgE, and bronchioalveolar inflammation. Pre-establishment of ALI also increased AAA lesion size, lesion accumulation of macrophages and mast cells, media smooth muscle cell loss, and plasma IgE, reduced plasma interleukin-5, interleukin-13, and transforming growth factor-β, and increased bronchioalveolar inflammation. Consequent production of ALI also doubled lesion size of pre-established AAA and increased lesion mast cell and T-cell accumulation, media smooth muscle cell loss, lesion cell proliferation and apoptosis, plasma IgE, and bronchioalveolar inflammation. In periaortic CaCl2 injury-induced AAA in mice, production of ALI also increased AAA formation, lesion inflammation, plasma IgE, and bronchioalveolar inflammatory cell accumulation.

CONCLUSIONS

This study suggests a pathological link between airway allergic disease and AAA. Production of one disease aggravates the progression of the other.

Autophagy in Vascular Disease

Autophagy is a reparative, life-sustaining process by which cytoplasmic components are sequestered in double-membrane vesicles and degraded on fusion with lysosomal compartments. Growing evidence reveals that basal autophagy is an essential in vivo process mediating proper vascular function. Moreover, autophagy is stimulated by many stress-related stimuli in the arterial wall to protect endothelial cells and smooth muscle cells against cell death and the initiation of vascular disease, in particular atherosclerosis. Basal autophagy is atheroprotective during early atherosclerosis but becomes dysfunctional in advanced atherosclerotic plaques. Little is known about autophagy in other vascular disorders, such as aneurysm formation, arterial aging, vascular stiffness, and chronic venous disease, even though autophagy is often impaired. This finding highlights the need for pharmacological interventions with compounds that stimulate the prosurvival effects of autophagy in the vasculature. A large number of animal studies and clinical trials have indicated that oral or stent-based delivery of the autophagy inducer rapamycin or derivatives thereof, collectively known as rapalogs, effectively inhibit the basic mechanisms that control growth and destabilization of atherosclerotic plaques. Other autophagy-inducing drugs, such as spermidine or add-on therapy with widely used antiatherogenic compounds, including statins and metformin, are potentially useful to prevent vascular disease with minimal adverse effects.

Enhanced Caspase Activity Contributes to Aortic Wall Remodeling and Early Aneurysm Development in a Murine Model of Marfan Syndrome

Objective—

Rupture and dissection of aortic root aneurysms remain the leading causes of death in patients with the Marfan syndrome, a hereditary connective tissue disorder that affects 1 in 5000 individuals worldwide. In the present study, we use a Marfan mouse model ( Fbn1 C1039G/+ ) to investigate the biological importance of apoptosis during aneurysm development in Marfan syndrome.

Approach and Results—

Using in vivo single-photon emission computed tomographic-imaging and ex vivo autoradiography for Tc99m-annexin, we discovered increased apoptosis in the Fbn1 C1039G/+ ascending aorta during early aneurysm development peaking at 4 weeks. Immunofluorescence colocalization studies identified smooth muscle cells (SMCs) as the apoptotic cell population. As biological proof of concept that early aortic wall apoptosis plays a role in aneurysm development in Marfan syndrome, Fbn1 C1039G/+ mice were treated daily from 2 to 6 weeks with either (1) a pan-caspase inhibitor, Q-V D -OPh (20 mg/kg), or (2) vehicle control intraperitoneally. Q-V D -OPh treatment led to a significant reduction in aneurysm size and decreased extracellular matrix degradation in the aortic wall compared with control mice. In vitro studies using Fbn1 C1039G/+ ascending SMCs showed that apoptotic SMCs have increased elastolytic potential compared with viable cells, mostly because of caspase activity. Moreover, in vitro (1) cell membrane isolation, (2) immunofluorescence staining, and (3) scanning electron microscopy studies illustrate that caspases are expressed on the exterior cell surface of apoptotic SMCs.

Conclusions—

Caspase inhibition attenuates aneurysm development in an Fbn1 C1039G/+ Marfan mouse model. Mechanistically, during apoptosis, caspases are expressed on the cell surface of SMCs and likely contribute to elastin degradation and aneurysm development in Marfan syndrome.