Regulatory T cells in human and angiotensin II-induced mouse abdominal aortic aneurysms

Unravelling CD4+ T cell diversity and tissue adaptation of Tregs in abdominal aortic aneurysms through single-cell sequencing

Immune cell infiltration is a significant pathological process in abdominal aortic aneurysms (AAA). T cells, particularly CD4+ T cells, are essential immune cells responsible for substantial infiltration of the aorta. Regulatory T cells (Tregs) in AAA have been identified as tissue-specific; however, the time, location, and mechanism of acquiring the tissue-specific phenotype are still unknown. Using single-cell RNA sequencing (scRNA-seq) on CD4+ T cells from the AAA aorta and spleen, we discovered heterogeneity among CD4+ T cells and identified activated, proliferating and developed aorta Tregs. These Tregs originate in the peripheral tissues and acquire the tissue-specific phenotype in the aorta. The identification of precursors for Tregs in AAA provides new insight into the pathogenesis of AAA.

Overview of multifunctional Tregs in cardiovascular disease: From insights into cellular functions to clinical implications

Regulatory T cells (Tregs) are crucial in regulating T-cell-mediated immune responses. Numerous studies have shown that dysfunction or decreased numbers of Tregs may be involved in inflammatory cardiovascular diseases (CVDs) such as atherosclerosis, hypertension, myocardial infarction, myocarditis, cardiomyopathy, valvular heart diseases, heart failure, and abdominal aortic aneurysm. Tregs can help to ameliorate CVDs by suppressing excessive inflammation through various mechanisms, including inhibition of T cells and B cells, inhibition of macrophage-induced inflammation, inhibition of dendritic cells and foam cell formation, and induction of anti-inflammatory macrophages. Enhancing or restoring the immunosuppressive activity of Tregs may thus serve as a fundamental immunotherapy to treat hypertension and CVDs. However, the precise molecular mechanisms underlying the Tregs-induced protection against hypertension and CVDs remain to be investigated. This review focuses on recent advances in our understanding of Tregs subsets and function in CVDs. In addition, we discuss promising strategies for using Tregs through various pharmacological approaches to treat hypertension and CVDs.

Recent advances in targeted therapy for inflammatory vascular diseases

Vascular diseases constitute a significant contributor to worldwide mortality rates, placing a substantial strain on healthcare systems and socio-economic aspects. They are closely associated with inflammatory responses, as sustained inflammation could impact endothelial function, the release of inflammatory mediators, and platelet activation, thus accelerating the progression of vascular diseases. Consequently, directing therapeutic efforts towards mitigating inflammation represents a crucial approach in the management of vascular diseases. Traditional anti-inflammatory medications may have extensive effects on multiple tissues and organs when absorbed through the bloodstream. Conversely, treatments targeting inflammatory vascular diseases, such as monoclonal antibodies, drug-eluting stents, and nano-drugs, can achieve more precise effects, including precise intervention, minimal non-specific effects, and prolonged efficacy. In addition, personalized therapy is an important development trend in targeted therapy for inflammatory vascular diseases. Leveraging advanced simulation algorithms and clinical trial data, treatment strategies are gradually being personalized based on patients' genetic, biomarker, and clinical profiles. It is expected that the application of precision medicine in the field of vascular diseases will have a broader future. In conclusion, targeting therapies offer enhanced safety and efficacy compared to conventional medications; investigating novel targeting therapies and promoting clinical transformation may be a promising direction in improving the prognosis of patients with inflammatory vascular diseases. This article reviews the pathogenesis of inflammatory vascular diseases and presents a comprehensive overview of the potential for targeted therapies in managing this condition.

Deciphering Abdominal Aortic Diseases Through T-Cell Clonal Repertoire of Perivascular Adipose Tissue

BACKGROUND

Recent studies suggest that immune-mediated inflammation of perivascular adipose tissue of abdominal aortic aneurysms (AAAs) contributes to disease development and progression. Whether the perivascular adipose tissue of AAA is characterized by a specific adaptive immune signature remains unknown.

METHODS AND RESULTS

To investigate this hypothesis, we sequenced the T-cell receptor β-chain in the perivascular adipose tissue of patients with AAA and compared it with patients with aortic occlusive disease, who share the former anatomical site of the lesion and risk factors but differ in pathogenic mechanisms. Our results demonstrate that patients with AAA have a lower repertoire diversity than those with aortic occlusive disease and significant differences in variable/joining gene segment usage. Furthermore, we identified a set of 7 public T-cell receptor β-chain clonotypes that distinguished AAA and aortic occlusive disease with very high accuracy. We also found that the T-cell receptor β-chain repertoire differentially characterizes small and large AAAs (aortic diameter<55 mm and ≥55 mm, respectively).

CONCLUSIONS

This work supports the hypothesis that T cell-mediated immunity is fundamental in AAA pathogenesis and opens up new clinical perspectives.

The future for the therapeutics of abdominal aortic aneurysm: engineered nanoparticles drug delivery for abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a severe cardiovascular disease with a high mortality rate. Several screening and diagnostic methods have been developed for AAA early diagnosis. Open surgery and endovascular aortic repair (EVAR) are clinically available for patients who meet the indications for surgery. However, for non-surgical patients, limited drugs exist to inhibit or reverse the progression of aneurysms due to the complex pathogenesis and biological structure of AAA, failing to accumulate precisely on the lesion to achieve sufficient concentrations. The recently developed nanotechnology offers a new strategy to address this problem by developing drug-carrying nanoparticles with enhanced water solubility and targeting capacity, prolonged duration, and reduced side effects. Despite the rising popularity, limited literature is available to highlight the progression of the field. Herein, in this review, we first discuss the pathogenesis of AAA, the methods of diagnosis and treatment that have been applied clinically, followed by the review of research progressions of constructing different drug-loaded nanoparticles for AAA treatment using engineered nanoparticles. In addition, the feasibility of extracellular vesicles (EVs) and EVs-based nanotechnology for AAA treatment in recent years are highlighted, together with the future perspective. We hope this review will provide a clear picture for the scientists and clinicians to find a new solution for AAA clinical management.

Comprehensive bioinformatics analysis revealed potential key genes and pathways underlying abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a permanent, asymptomatic segmental dilatation of the abdominal aorta, with a high mortality risk upon rupture. Identification of potential key genes and pathways may help to develop curative drugs for AAA. We conducted RNA-seq on abdominal aortic tissues from both AAA patients and normal individuals as a control group. Integrated bioinformatic analysis was subsequently performed to comprehensively reveal potential key genes and pathways. A total of 1148 differential expressed genes (DEGs) (631 up-regulated and 517 down-regulated) were identified in our study. Gene Ontology (GO) analysis revealed enrichment in terms related to extracellular matrix organization, while KEGG analysis indicated enrichment in hematopoietic cell lineage and ECM-receptor interaction. Protein-protein interaction (PPI) network analysis revealed several candidate key genes, and differential expression of 6 key genes (CXCL8, CCL2, PTGS2, SELL, CCR7, and CXCL1) was validated by Gene Expression Omnibus (GEO) datasets. Receiver operating characteristic curve (ROC) analysis demonstrated these genes' high discriminatory ability between AAA and normal tissues. Immunohistochemistry indicated that several key genes were highly expressed in AAA tissues. Single-cell RNA sequencing revealed differential distribution patterns of these identified key genes among various cell types. 26 potential drugs linked to our key genes were found through DGIdb. Overall, our study provides a comprehensive evaluation of potential key genes and pathways in AAA, which could pave the way for the development of curative pharmacological therapies.

FGL1-LAG3 axis impairs IL-10-Producing regulatory T cells associated with Systemic lupus erythematosus disease activity

Background

Systemic Lupus Erythematosus (SLE) is a prototypic autoimmune disease, which is accompanied by liver damage. However, it remains unknown whether liver damage is associated with SLE progression.

Method

ology: HepG2 and L-02 cells were stimulated with cytokines, and FGL1 mRNA and protein expression levels were determined using Real-time PCR and ELISA, respectively. Regulatory T cells (Treg) isolated from healthy individuals as well as patients with SLE and SLE and liver damage (SLE-LD) were cultured with autologous effector CD4+T cells in the presence of a functional antibody or isotype control. The expression levels of LAG3, CD25, PD-1, CXCR5, ICOS and OX40 were evaluated by flow cytometry. FGL1, IL-10, IL-17a and IL-21 levels in serum or culture supernatants were quantified by ELISA.

Results

Patients with SLE-LD exhibits higher disease activity indices and anti-dsDNA antibody levels. Importantly, fibrinogen-like protein 1 (FGL1), a key factor released from the injured liver, is up-regulated in patients with SLE-LD and is associated with disease activity. FGL1 expression is induced by the inflammatory cytokine IL-6 signaling in hepatocytes. Higher expression of the FGL1 receptor lymphocyte activation gene 3 (LAG3) is detected in Treg cells from patients with SLE-LD. The FGL1-LAG3 signaling axis inhibits Treg cell proliferation and impairs the suppressive activity of Treg cells by limiting IL-10 secretion. Furthermore, FGL1-LAG3 signaling promotes the production of pathogenic IL-17a and IL-21 by CD4+T cells by reducing IL-10 level produced by Treg in patients with SLE.

Conclusions

The FGL1-LAG3 signal axis is a key mechanism that subverts the suppressive function of Treg cells. This may provide a new therapeutic target for SLE and SLE-induced liver damage.

Peripheral T-cell activation, Th17 cells, regulatory T-cells, and aortic aneurysm in people with HIV

Here, we investigate if peripheral T-cell activation and proportion of Th17 and T-regulatory cells (Tregs) are associated with aortic aneurysm or aortic diameter in people with HIV. Aorta was examined by computed tomography scans and T-cells by flow cytometry in 428 participants, and aortic aneurysm was found in 32 participants. None of the T-cell subsets were associated with aortic aneurysm, but activated T-cells and Tregs had opposite association to aorta diameter indicating an inverse impact.

Machine learning algorithms assisted identification of post-stroke depression associated biological features

Objectives

Post-stroke depression (PSD) is a common and serious psychiatric complication which hinders functional recovery and social participation of stroke patients. Stroke is characterized by dynamic changes in metabolism and hemodynamics, however, there is still a lack of metabolism-associated effective and reliable diagnostic markers and therapeutic targets for PSD. Our study was dedicated to the discovery of metabolism related diagnostic and therapeutic biomarkers for PSD.

Methods

Expression profiles of GSE140275, GSE122709, and GSE180470 were obtained from GEO database. Differentially expressed genes (DEGs) were detected in GSE140275 and GSE122709. Functional enrichment analysis was performed for DEGs in GSE140275. Weighted gene co-expression network analysis (WGCNA) was constructed in GSE122709 to identify key module genes. Moreover, correlation analysis was performed to obtain metabolism related genes. Interaction analysis of key module genes, metabolism related genes, and DEGs in GSE122709 was performed to obtain candidate hub genes. Two machine learning algorithms, least absolute shrinkage and selection operator (LASSO) and random forest, were used to identify signature genes. Expression of signature genes was validated in GSE140275, GSE122709, and GSE180470. Gene set enrichment analysis (GSEA) was applied on signature genes. Based on signature genes, a nomogram model was constructed in our PSD cohort (27 PSD patients vs. 54 controls). ROC curves were performed for the estimation of its diagnostic value. Finally, correlation analysis between expression of signature genes and several clinical traits was performed.

Results

Functional enrichment analysis indicated that DEGs in GSE140275 enriched in metabolism pathway. A total of 8,188 metabolism associated genes were identified by correlation analysis. WGCNA analysis was constructed to obtain 3,471 key module genes. A total of 557 candidate hub genes were identified by interaction analysis. Furthermore, two signature genes (SDHD and FERMT3) were selected using LASSO and random forest analysis. GSEA analysis found that two signature genes had major roles in depression. Subsequently, PSD cohort was collected for constructing a PSD diagnosis. Nomogram model showed good reliability and validity. AUC values of receiver operating characteristic (ROC) curve of SDHD and FERMT3 were 0.896 and 0.964. ROC curves showed that two signature genes played a significant role in diagnosis of PSD. Correlation analysis found that SDHD (r = 0.653, P &lt; 0.001) and FERM3 (r = 0.728, P &lt; 0.001) were positively related to the Hamilton Depression Rating Scale 17-item (HAMD) score.

Conclusion

A total of 557 metabolism associated candidate hub genes were obtained by interaction with DEGs in GSE122709, key modules genes, and metabolism related genes. Based on machine learning algorithms, two signature genes (SDHD and FERMT3) were identified, they were proved to be valuable therapeutic and diagnostic biomarkers for PSD. Early diagnosis and prevention of PSD were made possible by our findings.

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.

Comparative analysis of thoracic and abdominal aortic aneurysms across the segment and species at the single-cell level

Introduction: Aortic aneurysm is a life-threatening disease resulted from progressive dilatation of the aorta, which can be subdivided into thoracic and abdominal aortic aneurysms. Sustained subcutaneous angiotensin II infusion can induce aortic aneurysms in mice. However, the relevance of using angiotensin II induction model to study aneurysm disease and the degree of commonality between species remain elusive. Methods: We utilized scRNA-seq to infer aortic cell sub-structures and transcriptional profiles in clinical patient TAAs and AAAs, as well as mouse models of corresponding diseases (Ang II induction) and in healthy mouse aorta. Unbiased comparison between mice and humans explored the possible reasonability and utility of mouse Ang II-induced aortic aneurysm as a model for human aortic aneurysm diseases. Meanwhile, we performed comparative analysis of aortic aneurysms between TAA and AAA in both organisms. Results and Discussion: We demonstrated similarities and differences of changes in the components of human and mouse cell types, and our unbiased comparison between mouse and human identified well conserved subpopulations of SMCs and macrophages. Furthermore, the results of our comparative analyses suggested different biological functions and distinct potential pathogenic genes for thoracic and abdominal aortic aneurysms. MIF and SPP1 signaling networks participated in aortic aneurysm in both organisms. This study maps aortic aneurysm and offers opportunities for future researches to investigate the potential of subpopulations or marker genes as therapy targets.

Propionate Alleviates Abdominal Aortic Aneurysm by Modulating Colonic Regulatory T-Cell Expansion and Recirculation

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SCFAs alleviate the progression of AAA in both Ca₃(PO₄)₂- and elastase-induced mouse AAA models.

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Propionate expands the pool of Tregs in the cLP and enhances the cell-intrinsic ability of cLP-Tregs to recirculate by downregulating CD69 expression on the surface of cLP-Tregs.

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Propionate facilitates the recirculation of cLP-Tregs from the cLP through colonic dLNs and circulating blood to the inflamed aneurysm to mitigate AAA.

Emerging evidence supports that intestinal microbial metabolite short-chain fatty acids (SCFAs) increase the pool of regulatory T cells (Tregs) in the colonic lamina propria (cLP) and protect against nonintestinal inflammatory diseases, such as atherosclerosis and post-infarction myocardial inflammation. However, whether and how SCFAs protect the inflamed aortas of subjects with abdominal aortic aneurysm (AAA) remains unclear. Here, the authors revealed the protective effect of SCFAs on AAA in mice and the expansion of Tregs in the cLP, and propionate exerted Treg-dependent protection against AAA by promoting the recirculation of cLP-Tregs through colonic draining lymph nodes (dLNs) to the inflamed aorta.

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.

Human abdominal aortic aneurysm (AAA): Evidence for an autoimmune antigen-driven disease

Abdominal aortic aneurism (AAA) is a complex immunological disease with a strong genetic component, and one of the ten leading causes of death of individuals 55-74 years old worldwide. Strong evidence has been accumulated suggesting that AAA is an autoimmune specific antigen-driven disease. Mononuclear cells infiltrating AAA lesions comprised of T and B lymphocytes and other cells expressing early-, intermediate- and late-activation antigens, and the presence of antigen-presenting cells have been documented, demonstrating an ongoing immune response. The three components of the trimolecular complex, T-cell receptor (TCR)/peptide (antigen)/HLA have been identified in AAA, and specifically: (i) clonal expansions of T-cell clones in AAA lesions; (ii) the association of AAA with particular HLA Class I and Class II; and (iii) self or nonself putative AAA-associated antigens. IgG autoantibodies recognizing proteins present in normal aortic tissue have been reported in patients with AAA. Molecular mimicry, defined as the sharing of antigenic epitopes between microorganisms (bacteria, viruses) and self antigens, maybe is responsible for T-cell responses and antibody production in AAA. Also, the frequency and the suppressor activity of CD4 + CD25 + FOXP3+ Tregs and the expression of FOXP3 transcripts and protein have been reported to be significantly impaired in AAA patients vs normal donors.

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.

Single-Cell Sequencing Analysis and Multiple Machine Learning Methods Identified G0S2 and HPSE as Novel Biomarkers for Abdominal Aortic Aneurysm

Identifying biomarkers for abdominal aortic aneurysms (AAA) is key to understanding their pathogenesis, developing novel targeted therapeutics, and possibly improving patients outcomes and risk of rupture. Here, we identified AAA biomarkers from public databases using single-cell RNA-sequencing, weighted co-expression network (WGCNA), and differential expression analyses. Additionally, we used the multiple machine learning methods to identify biomarkers that differentiated large AAA from small AAA. Biomarkers were validated using GEO datasets. CIBERSORT was used to assess immune cell infiltration into AAA tissues and investigate the relationship between biomarkers and infiltrating immune cells. Therefore, 288 differentially expressed genes (DEGs) were screened for AAA and normal samples. The identified DEGs were mostly related to inflammatory responses, lipids, and atherosclerosis. For the large and small AAA samples, 17 DEGs, mostly related to necroptosis, were screened. As biomarkers for AAA, G0/G1 switch 2 (G0S2) (Area under the curve [AUC] = 0.861, 0.875, and 0.911, in GSE57691, GSE47472, and GSE7284, respectively) and for large AAA, heparinase (HPSE) (AUC = 0.669 and 0.754, in GSE57691 and GSE98278, respectively) were identified and further verified by qRT-PCR. Immune cell infiltration analysis revealed that the AAA process may be mediated by T follicular helper (Tfh) cells and the large AAA process may also be mediated by Tfh cells, M1, and M2 macrophages. Additionally, G0S2 expression was associated with neutrophils, activated and resting mast cells, M0 and M1 macrophages, regulatory T cells (Tregs), resting dendritic cells, and resting CD4 memory T cells. Moreover, HPSE expression was associated with M0 and M1 macrophages, activated and resting mast cells, Tregs, and resting CD4 memory T cells. Additional, G0S2 may be an effective diagnostic biomarker for AAA, whereas HPSE may be used to confer risk of rupture in large AAAs. Immune cells play a role in the onset and progression of AAA, which may improve its diagnosis and treatment.

Trained Immunity in Perivascular Adipose Tissue of Abdominal Aortic Aneurysm—A Novel Concept for a Still Elusive Disease

Abdominal aortic aneurysm (AAA) is a chronic, life-threatening vascular disease whose only therapeutic option is a surgical repair to prevent vessel rupture. The lack of medical therapy results from an inadequate understanding of the etiopathogenesis of AAA. Many studies in animal and human models indicate a ‘short-circuiting’ of the regulation of the inflammatory-immune response as a major player in the AAA chronic process. In this regard, perivascular adipose tissue (PVAT) has received increasing interest because its dysfunction affects large arteries primarily through immune cell infiltration. Consistently, we have recently produced evidence that innate and adaptive immune cells present in the PVAT of AAAs contribute to sustaining a damaging inflammatory loop. However, it is still unclear how the complex crosstalk between adaptive and innate immunity can be self-sustaining. From our perspective, trained immunity may play a role in this crosstalk. Trained immunity is defined as a form of innate immune memory resulting in enhanced responsiveness to repeated triggers. Specific innate stimuli and epigenetic and metabolic reprogramming events induce and shape trained immunity in myeloid progenitor cells improving host defense, but also contributing to the progression of immune-mediated and chronic inflammatory diseases. Here we present this hypothesis with data from the literature and our observations to support it.

Functional Diversities of Regulatory T Cells in the Context of Cancer Immunotherapy

Regulatory T cells (Tregs) are a subset of CD4+ T cells with their immunosuppressive activities to block abnormal or excessive immune responses to self and non-autoantigens. Tregs express the transcription factor Foxp3, maintain the immune homeostasis, and prevent the initiation of anti-tumor immune effects in various ways as their mechanisms to modulate tumor development. Recognition of different phenotypes and functions of intratumoral Tregs has offered the possibilities to develop therapeutic strategies by selectively targeting Tregs in cancers with the aim of alleviating their immunosuppressive activities from anti-tumor immune responses. Several Treg-based immunotherapeutic approaches have emerged to target cytotoxic T lymphocyte antigen-4, glucocorticoid-induced tumor necrosis factor receptor, CD25, indoleamine-2, 3-dioxygenase-1, and cytokines. These immunotherapies have yielded encouraging outcomes from preclinical studies and early-phase clinical trials. Further, dual therapy or combined therapy has been approved to be better choices than single immunotherapy, radiotherapy, or chemotherapy. In this short review article, we discuss our current understanding of the immunologic characteristics of Tregs, including Treg differentiation, development, therapeutic efficacy, and future potential of Treg-related therapies among the general cancer therapy.

Aorta Regulatory T Cells with a Tissue-Specific Phenotype and Function Promote Tissue Repair through Tff1 in Abdominal Aortic Aneurysms

In addition to maintaining immune tolerance, Foxp3⁺ regulatory T cells (Tregs) perform specialized functions in tissue homeostasis and remodeling. However, whether Tregs in aortic aneurysms have a tissue-specific phenotype and function is unclear. Here, a special group of Tregs that potentially inhibit abdominal aortic aneurysm (AAA) progression are identified and functionally characterized. Aortic Tregs gradually increase during the process of AAA and are mainly recruited from peripheral circulation. Single-cell TCR sequencing and bulk RNA sequencing demonstrate their unique phenotype and highly expressed trefoil factor 1 (Tff1). Foxp3^cre/cre Tff1^flox/flox mice are used to clarify the role of Tff1 in AAA, suggesting that aortic Tregs secrete Tff1 to regulate smooth muscle cell (SMC) survival. In vitro experiments confirm that Tff1 inhibits SMC apoptosis through the extracellular signal-regulated kinase (ERK) 1/2 pathway. The findings reveal a tissue-specific phenotype and function of aortic Tregs and may provide a promising and novel approach for the prevention of AAA.

Pathogenic Tconvs promote inflammatory macrophage polarization through GM‐CSF and exacerbate abdominal aortic aneurysm formation

Abdominal aortic aneurysms (AAAs) elicit massive inflammatory leukocyte recruitment to the aorta. CD4⁺ T cells, which include regulatory T cells (Tregs) and conventional T cells (Tconvs), are involved in the progression of AAA. Tregs have been reported to limit AAA formation. However, the function and phenotype of the Tconvs found in AAAs remain poorly understood. We characterized aortic Tconvs by bulk RNA sequencing and discovered that Tconvs in aortic aneurysm highly expressed Cxcr6 and Csf2. Herein, we determined that the CXCR6/CXCL16 signaling axis controlled the recruitment of Tconvs to aortic aneurysms. Deficiency of granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), encoded by Csf2, markedly inhibited AAA formation and led to a decrease of inflammatory monocytes, due to a reduction of CCL2 expression. Conversely, the exogenous administration of GM‐CSF exacerbated inflammatory monocyte infiltration by upregulating CCL2 expression, resulting in worsened AAA formation. Mechanistically, GM‐CSF upregulated the expression of interferon regulatory factor 5 to promote M1‐like macrophage differentiation in aortic aneurysms. Importantly, we also demonstrated that the GM‐CSF produced by Tconvs enhanced the polarization of M1‐like macrophages and exacerbated AAA formation. Our findings revealed that GM‐CSF, which was predominantly derived from Tconvs in aortic aneurysms, played a pathogenic role in the progression of AAAs and may represent a potential target for AAA treatment.

AAA Revisited: A Comprehensive Review of Risk Factors, Management, and Hallmarks of Pathogenesis

Despite declining incidence and mortality rates in many countries, the abdominal aortic aneurysm (AAA) continues to represent a life-threatening cardiovascular condition with an overall prevalence of about 2-3% in the industrialized world. While the risk of AAA development is considerably higher for men of advanced age with a history of smoking, screening programs serve to detect the often asymptomatic condition and prevent aortic rupture with an associated death rate of up to 80%. This review summarizes the current knowledge on identified risk factors, the multifactorial process of pathogenesis, as well as the latest advances in medical treatment and surgical repair to provide a perspective for AAA management.

Curcumin nicotinate suppresses abdominal aortic aneurysm pyroptosis via lncRNA PVT1/miR-26a/KLF4 axis through regulating the PI3K/AKT signaling pathway

Abdominal aortic aneurysm (AAA) is a chronic dilated disease of the aorta that is characterized by chronic inflammation. Curcumin (Cur) is previously showed to attenuate AAA by inhibiting inflammatory response in ApoE -/- mice. Since Cur has the limitations of aqueous solubility and instability. Here, we focus on the role of curcumin nicotinate (CurTn), a Cur derivative is derived from Cur and nicotinate. An in vitro model of AAA was established by treating vascular smooth muscle cells (VSMCs) with II (Ang-II). Gene and protein expressions were examined by quantitative real-time PCR (qPCR) or western blotting. Cell migration and pyroptosis were determined by transwell assay and flow cytometry. The interaction between plasmacytoma variant translocation 1 (PVT1), miR-26a and krüppel-like factor 4 (KLF4) was predicted by online prediction tool and confirmed by luciferase reporter assay. CurTn reduced Ang-II-induced AAA-associated proteins, inflammatory cytokine expressions, and attenuated pyroptosis in VSMCs. PVT1 overexpression suppressed the inhibitory effect of CurTn on AngII-induced pyroptosis and inflammatory in VSMCs by sponging miR-26a. miR-26a directly targeted KLF4 and suppressed its expression, which eventually led to the deactivation of the PI3K/AKT signaling pathway. Besides, the regulatory effect of CurTn on pyroptosis of VSMCs induced by Ang-II was reversed through the PVT1/miR-26a/KLF4 pathway. In short, CurTn suppressed VSMCs pyroptosis and inflammation though mediation PVT1/miR-26a/KLF4 axis by regulating the PI3K/AKT signaling pathway, CurTn might consider as a potential therapeutic target in the treatment of AAA.

Rolipram Prevents the Formation of Abdominal Aortic Aneurysm (AAA) in Mice: PDE4B as a Target in AAA

Abdominal aortic aneurysm (AAA) is a common life-threatening condition characterized by exacerbated inflammation and the generation of reactive oxygen species. Pharmacological treatments to slow AAA progression or to prevent its rupture remain a challenge. Targeting phosphodiesterase 4 (PDE4) has been verified as an effective therapeutic strategy for an array of inflammatory conditions; however, no studies have assessed yet PDE4 in AAA. Here, we used angiotensin II (AngII)-infused apolipoprotein E deficient mice to study the involvement of the PDE4 subfamily in aneurysmal disease. PDE4B but not PDE4D was upregulated in inflammatory cells from both experimental and human AAA. The administration of the PDE4 selective inhibitor rolipram (3 mg/kg/day) to AngII-challenged mice (1000 ng/kg bodyweight/min) protected against AAA formation, limiting the progressive increase in the aortic diameter without affecting the blood pressure. The drug strongly attenuated the rise in vascular oxidative stress (superoxide anion) induced by AngII, and decreased the expression of inflammatory markers, as well as the recruitment of macrophages (MAC3+), lymphocytes (CD3+), and neutrophils (ELANE+) into the vessel wall. Rolipram also normalized the vascular MMP2 expression and MMP activity, preserving the elastin integrity and improving the vascular remodelling. These results point to PDE4B as a new therapeutic target for AAA.

Regulatory T Cells Accelerate the Repair Process of Renal Fibrosis by Regulating Mononuclear Macrophages

BACKGROUND

We aimed to investigate the mechanisms of renal fibrosis and explore the effect of CD4+CD25+Foxp3+ regulatory T cells (Treg) on renal fibrosis after the obstruction was removed.

METHODS

Fifty-five C57BL/6 mice were randomly divided into three groups: the unilateral ureteral obstruction (UUO) group, the relief for unilateral ureteral obstruction (RUUO) group, and the RUUO+Treg group. Renal fibrosis indexes of RUUO mice were evaluated using hematoxylin and eosin (HE) and, Masson staining and immunohistochemistry after CD4+CD25+Treg cells were injected into the tail vein at the moment of recanalization. We detected the levels of Treg, M1, and M2 markers by flow cytometry, and the levels of transforming growth factor (TGF)-β1, interleukin (IL)-1β, IL-6 and IL-10 using ELISA.

RESULTS

The tubular necrosis score, AO value of α-SMA (smooth muscle actin), and collagen area on the 3rd and 14th days post RUUO were up-regulated compared with the 7th day post RUUO (P<0.05). After injection of Treg via tail vein, the tubular necrosis score, AO value of α-SMA, TGF-β1 level, and collagen area in the RUUO+Treg group on the 14th day were down-regulated compared with the RUUO group (P<0.05). Moreover, Treg could transform M1 macrophages into M2 macrophages, manifesting as up-regulated expression of CD206 compared with the RUUO group (P<0.05). Treg could also down-regulate the secretion of IL-6 and IL-1β while up-regulating the secretion of IL-10 in vitro compared with the M1 group (P<0.05).

CONCLUSIONS

The kidney could deteriorate into a state of injury and fibrosis after the obstruction was removed, and Treg could effectively protect the kidney function.

Abdominal Aortic Aneurysm: Roles of Inflammatory Cells

Abdominal aortic aneurysms (AAAs) are local dilations of infrarenal segment of aortas. Molecular mechanisms underlying the pathogenesis of AAA remain not fully clear. However, inflammation has been considered as a central player in the development of AAA. In the past few decades, studies demonstrated a host of inflammatory cells, including T cells, macrophages, dendritic cells, neutrophils, B cells, and mast cells, etc. infiltrating into aortic walls, which implicated their crucial roles. In addition to direct cell contacts and cytokine or protease secretions, special structures like inflammasomes and neutrophil extracellular traps have been investigated to explore their functions in aneurysm formation. The above-mentioned inflammatory cells and associated structures may initiate and promote AAA expansion. Understanding their impacts and interaction networks formation is meaningful to develop new strategies of screening and pharmacological interventions for AAA. In this review, we aim to discuss the roles and mechanisms of these inflammatory cells in AAA pathogenesis.

Ex vivo expansion of regulatory T cells from abdominal aortic aneurysm patients inhibits aneurysm in humanized murine model

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a chronic inflammatory disease. Studies of human aneurysm tissue demonstrate dense inflammatory cell infiltrates with CD4+ T cells predominating. Regulatory T cells (Tregs) play an important role in inhibiting pro-inflammatory T cell proliferation, therefore, limiting collateral tissue destruction. The aim of this study was to investigate whether ex vivo augmentation of human Tregs attenuates aneurysm formation in humanized murine model of AAA.

METHODS

Circulating Treg population in AAA patients and age- and gender-matched controls were determined by real-time polymerase chain reaction and flow cytometry. To create humanized murine model of AAA, irradiated Rag1-deficient (Rag1-/-) mice, without mature T lymphocytes, at 7 weeks of age were given 5 × 106 of human CD4+ T cells intraperitoneally. Then the mice underwent CaCl2 aneurysm induction. Aortic diameters were measured before and at 6 weeks after aneurysm induction. Aortic tissue was collected for histology and protein extraction. Verhoeff-Van Gieson stain was used for staining elastic fiber. CD4+ T cells in the aortic tissue were detected by immunohistochemical staining.

RESULTS

In human peripheral blood mononuclear cells, the proportion of Tregs are decreased in AAA patients compared with matched control patients with significant vascular disease. We first validated the role of Tregs in the CaCl2 model of AAA. To determine the role of human T cells in AAA formation, Rag1-/- mice, resistant to CaCl2-aneurysm induction, were transplanted with human CD4+ T cells. Human CD4+ T cells were able to drive aneurysm formation in Rag1-/- mice. We show that ex vivo augmentation of human Tregs by interleukin-2 resulted in decreased aneurysm progression.

CONCLUSIONS

These data suggest that the ex vivo expansion of human Tregs may be a potential therapeutic strategy for inhibiting progression of AAA.

Patterns of immune infiltration in stable and raptured abdominal aortic aneurysms: A gene-expression-based retrospective study

BACKGROUND

Abdominal aortic aneurysm (AAA) is a disease characterized by weakening arterial wall and permanent expansion with high mortality once rupture, which was involved with immune system activation. However, owing to technical difficulties, previous research has limited the impact of one or limited immune cells on AAA.

METHODS

We analyzed the composition of immune cells using the CIBERSORT algorithm through transcriptome sequencing data from patients with stable (eAAA) and ruptured aneurysms (rAAA). The whole transcriptome sequencing data, including 17 patients with ruptured AAA and 31 patients with stable AAA were downloaded from Gene Expression Omnibus (GEO, GSE98278). After normalizing and data processing, five rAAA and seventeen eAAA patients entered the follow-up analysis. We performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis to identify several pathways that were significantly enriched in rAAA compared to eAAA tissues.

RESULTS

We demonstrated that the compositions of infiltrative immune cell in eAAA and rAAA were different. Naïve B cells, both resting and activated CD4+ memory T cells were found significantly higher in ruptured AAA, while memory B cells and activated mast cells were much less in ruptured AAA than that in stable AAA. Besides, PTX3 was significantly highly expressed in rAAA, which might be associated with the complement system and polarization of macrophages. Finally, differentially expressed genes and the related immune cells were mapped in a network to reveal the relationship between gene expression and infiltrative immune cells.

CONCLUSION

We identified the infiltrated immune cell profile of eAAA and rAAA patients, which might be the potential target of AAA treatment.

Cysteinyl cathepsins in cardiovascular diseases

Cysteinyl cathepsins are lysosomal/endosomal proteases that mediate bulk protein degradation in these intracellular acidic compartments. Yet, studies indicate that these proteases also appear in the nucleus, nuclear membrane, cytosol, plasma membrane, and extracellular space. Patients with cardiovascular diseases (CVD) show increased levels of cathepsins in the heart, aorta, and plasma. Plasma cathepsins often serve as biomarkers or risk factors of CVD. In aortic diseases, such as atherosclerosis and abdominal aneurysms, cathepsins play pathogenic roles, but many of the same cathepsins are cardioprotective in hypertensive, hypertrophic, and infarcted hearts. During the development of CVD, cathepsins are regulated by inflammatory cytokines, growth factors, hypertensive stimuli, oxidative stress, and many others. Cathepsin activities in inflammatory molecule activation, immunity, cell migration, cholesterol metabolism, neovascularization, cell death, cell signaling, and tissue fibrosis all contribute to CVD and are reviewed in this article in memory of Dr. Nobuhiko Katunuma for his contribution to the field.

Identification of crucial genes in abdominal aortic aneurysm by WGCNA

Background

Abdominal aortic aneurysm (AAA) is the full thickness dilation of the abdominal aorta. However, few effective medical therapies are available. Thus, elucidating the molecular mechanism of AAA pathogenesis and exploring the potential molecular target of medical therapies for AAA is of vital importance.

Methods

Three expression datasets (GSE7084, GSE47472 and GSE57691) were downloaded from the Gene Expression Omnibus (GEO). These datasets were merged and then normalized using the “sva” R package. Differential expressed gene (DEG) analysis and weighted gene co-expression network analysis (WGCNA) were conducted. We compared the co-expression patterns between AAA and normal conditions, and hub genes of each functional module were identified. DEGs were mapped to co-expression network under AAA condition and a DEG co-expression network was generated. Crucial genes were identified using molecular complex detection (MCODE) (a plugin in Cytoscape).

Results

In our study, 6 and 10 gene modules were detected for the AAA and normal conditions, respectively, while 143 DEGs were screened. Compared to the normal condition, genes associated with immune response, inflammation and muscle contraction were clustered in three gene modules respectively under the AAA condition; the hub genes of the three modules were MAP4K1, NFIB and HPK1, respectively. A DEG co-expression network with 102 nodes and 303 edges was identified, and a hub gene cluster with 10 genes from the DEG co-expression network was detected. YIPF6, RABGAP1, ANKRD6, GPD1L, PGRMC2, HIGD1A, GMDS, MGP, SLC25A4 and FAM129A were in the cluster. The expression levels of these 10 genes showed potential diagnostic value.

Conclusion

Based on WGCNA, we detected 6 modules under the AAA condition and 10 modules in the normal condition. Hub genes of each module and hub gene clusters of the DEG co-expression network were identified. These genes may act as potential targets for medical therapy and diagnostic biomarkers. Further studies are needed to elucidate the detailed biological function of these genes in the pathogenesis of AAA.

T Cells Are Dominant Population in Human Abdominal Aortic Aneurysms and Their Infiltration in the Perivascular Tissue Correlates With Disease Severity

Abdominal Aortic Aneurysm (AAA) is a major cause of cardiovascular mortality. Adverse changes in vascular phenotype act in concert with chronic inflammation to promote AAA progression. Perivascular adipose tissue (PVAT) helps maintain vascular homeostasis but when inflamed and dysfunctional, can also promote vascular pathology. Previous studies suggested that PVAT may be an important site of vascular inflammation in AAA; however, a detailed assessment of leukocyte populations in human AAA, their anatomic location in the vessel wall and correlation to AAA size remain undefined. Accordingly, we performed in depth immunophenotyping of cells infiltrating the pathologically altered perivascular tissue (PVT) and vessel wall in AAA samples at the site of maximal dilatation (n = 51 patients). Flow cytometry revealed that T cells, rather than macrophages, are the major leukocyte subset in AAA and that their greatest accumulations occur in PVT. Both CD4⁺ and CD8⁺ T cell populations are highly activated in both compartments, with CD4⁺ T cells displaying the highest activation status within the AAA wall. Finally, we observed a positive relationship between T cell infiltration in PVT and AAA wall. Interestingly, only PVT T cell infiltration was strongly related to tertiles of AAA size. In summary, this study highlights an important role for PVT as a reservoir of T lymphocytes and potentially as a key site in modulating the underlying inflammation in AAA.

Systemic Upregulation of IL-10 (Interleukin-10) Using a Nonimmunogenic Vector Reduces Growth and Rate of Dissecting Abdominal Aortic Aneurysm

Objective- Recruitment of immunologic competent cells to the vessel wall is a crucial step in formation of abdominal aortic aneurysms (AAA). Innate immunity effectors (eg, macrophages), as well as mediators of adaptive immunity (eg, T cells), orchestrate a local vascular inflammatory response. IL-10 (interleukin-10) is an immune-regulatory cytokine with a crucial role in suppression of inflammatory processes. We hypothesized that an increase in systemic IL-10-levels would mitigate AAA progression. Approach and Results- Using a single intravenous injection protocol, we transfected an IL-10 transcribing nonimmunogenic minicircle vector into the Ang II (angiotensin II)-ApoE^-/- infusion mouse model of AAA. IL-10 minicircle transfection significantly reduced average aortic diameter measured via ultrasound at day 28 from 166.1±10.8% (control) to 131.0±5.8% (IL-10 transfected). Rates of dissecting AAA were reduced by IL-10 treatment, with an increase in freedom from dissecting AAA from 21.5% to 62.3%. Using flow cytometry of aortic tissue from minicircle IL-10-treated animals, we found a significantly higher percentage of CD4⁺/CD25⁺/Foxp3 (forkhead box P3)⁺ regulatory T cells, with fewer CD8⁺/GZMB⁺ (granzyme B) cytotoxic T cells. Furthermore, isolated aortic macrophages produced less TNF-α (tumor necrosis factor-α), more IL-10, and were more likely to be MRC1 (mannose receptor, C type 1)-positive alternatively activated macrophages. These results concurred with gene expression analysis of lipopolysaccharide-stimulated and Ang II-primed human peripheral blood mononuclear cells. Conclusions- Taken together, we provide an effective gene therapy approach to AAA in mice by enhancing antiinflammatory and dampening proinflammatory pathways through minicircle-induced augmentation of systemic IL-10 expression.

Clonally expanded alpha-chain T-cell receptor (TCR) transcripts are present in aneurysmal lesions of patients with Abdominal Aortic Aneurysm (AAA)

Abdominal aortic aneurysm (AAA) is a life-threatening immunological disease responsible for 1 to 2% of all deaths in 65 year old or older individuals. Although mononuclear cell infiltrates have been demonstrated in AAA lesions and autoimmunity may be responsible for the initiation and account for the propagation of the disease, the information available about the pathogenesis of AAA is limited. To examine whether AAA lesions from patients with AAA contain clonally expanded α-chain TCR transcripts, we amplified by the non-palindromic adaptor-PCR (NPA-PCR)/Vα-specific PCR and/or the Vα-specific PCR these α-chain TCR transcripts. The amplified transcripts were cloned and sequenced. Substantial proportions of identical α-chain TCR transcripts were identified in AAA lesions of 4 of 5 patients, demonstrating that clonally expanded T cells are present in these AAA lesions. These results were statistically significant by the bimodal distribution. Three of 5 of these patients were typed by DNA-based HLA-typing and all three expressed DRB1 alleles containing the DRβGln70 amino acid residue that has been demonstrated to be associated with AAA. All three patients exhibited clonally expanded T cells in AAA lesions. Four of the 5 patients with AAA who exhibited clonal expansions of α-chain TCR transcripts, also exhibited clonal expansions of β-chain TCR transcripts in AAA lesions, as we have demonstrated previously (J Immunol 192:4897, 2014). αβ TCR-expressing T cells infiltrating AAA lesions contain T-cell clones which have undergone proliferation and clonal expansion in vivo in response to as yet unidentified specific antigens that may be self or nonself. These results provide additional evidence supporting the hypothesis that AAA is a specific antigen-driven T-cell autoimmune disease.

Interleukin-10 promotes proliferation of vascular smooth muscle cells by inhibiting inflammation in rabbit abdominal aortic aneurysm

BACKGROUND

The formation and rupture of aneurysms is a reversible process involving the destruction and repair of smooth muscle cells, and the proliferation of vascular smooth muscle cells (VSMC) and inflammation play an important role. In our study, we investigated whether Interleukin-10 (IL-10) treatment delays and prevents the development of aneurysms, and the molecular mechanism whereby IL-10 could inhibit proliferation of VSMC by inhibiting inflammatory responses in abdominal aortic aneurysms.

METHODS

Models of rabbit abdominal aortic aneurysm (AAA) were established by elastin pressurization and perfusion, and recombinant IL-10 was used as a drug to intervene in treatment of the AAA model by rabbit ear vein injection. 1 week, 2 weeks and 4 weeks after establishing the AAA model, color Doppler ultrasound and H&E staining was used to observe the development of AAA. Western blotting and RT-qPCR were used to detect the gene expression of PCNA, OPN and α-SMA, Th1/Th2 cytokines were detected by RT-qPCR, Nf-kB and MCP-1 protein was analyzed by immunochemistry. Activation of Macrophage was analyzed by immunofluorescence.

RESULTS

Compared with the model group without any intervention, after treatment with IL-10, a decreased cell number was recorded and number of layers of smooth muscle cells in rabbit abdominal aortic aneurysms were significantly reduced, as was elastin breakage and smooth muscle cell degradation. The gene expression of PCNA and OPN, the mRNA expression of IFN-γ and TNF-α, and the protein expression of NF-kB and MCP-1 were elevated (P < 0.05), but α-SMA, IFN-γ, TNF-α, IL-4 and IL-13 were decreased (P < 0.05) in abdominal aortic aneurysm. The M2/M1 macrophage ratio increased significantly.

CONCLUSION

With treatment by IL-10, the development of rabbit abdominal aortic aneurysm was delayed. The molecular mechanism may have been that IL-10 treatment inhibits inflammation in aneurysm tissue by promoting the activation of M2 macrophages and altering Th1/Th2 cytokine production.Tthe inhibited inflammatory response promoted the proliferation and phenotypic transformation of VSMC.

IL (Interleukin)-33 Suppresses Abdominal Aortic Aneurysm by Enhancing Regulatory T-Cell Expansion and Activity

Objective- Inflammation occurs during the progression of abdominal aortic aneurysm (AAA). IL (interleukin)-33 is a pleiotropic cytokine with multiple immunomodulatory effects, yet its role in AAA remains unknown. Approach and Results- Immunoblot, immunohistochemistry, and immunofluorescent staining revealed increased IL-33 expression in adventitia fibroblasts from mouse AAA lesions. Daily intraperitoneal administration of recombinant IL-33 or transgenic IL-33 expression ameliorated periaorta CaPO4 injury- and aortic elastase exposure-induced AAA in mice, as demonstrated by blunted aortic expansion, reduced aortic wall elastica fragmentation, enhanced AAA lesion collagen deposition, attenuated T-cell and macrophage infiltration, reduced inflammatory cytokine production, skewed M2 macrophage polarization, and reduced lesion MMP (matrix metalloproteinase) expression and cell apoptosis. Flow cytometry analysis, immunostaining, and immunoblot analysis showed that exogenous IL-33 increased CD4+Foxp3+ regulatory T cells in spleens, blood, and aortas in periaorta CaPO4-treated mice. Yet, ST2 deficiency muted these IL-33 activities. Regulatory T cells from IL-33-treated mice also showed significantly stronger activities in suppressing smooth muscle cell inflammatory cytokine and chemokine expression, macrophage MMP expression, and in increasing M2 macrophage polarization than those from vehicle-treated mice. In contrast, IL-33 failed to prevent AAA and lost its beneficial activities in CaPO4-treated mice after selective depletion of regulatory T cells. Conclusions- Together, this study established a role of IL-33 in protecting mice from AAA formation by enhancing ST2-dependent aortic and systemic regulatory T-cell expansion and their immunosuppressive activities.

Sex Differences in Hypertension: Where We Have Been and Where We Are Going

While it has been known since the 1940s that men have greater increases in blood pressure (BP) compared with women, there have been intense efforts more recently to increase awareness that women are also at risk for developing hypertension and that cardiovascular diseases (CVDs) are the leading causes of death among both men and women in the United States. With the release of the 2017 Hypertension Clinical Guidelines, 46% of adults in the United States are now classified as hypertensive, and hypertension is the primary modifiable risk factor for the development of CVD. This increase in the prevalence of hypertension is reflected in an increase in prevalence among both men and women across all demographics, although there were greater increases in the prevalence of hypertension among men compared with women. As a result, the well-established gender difference in the prevalence of hypertension is even more pronounced and now extends into the sixth decade of life. The goals of this review are to (i) review the historical clinical trial data and hypertension guidelines from the perspective of both genders and then (ii) review the role of the renin-angiotensin system and T-cell activation in contributing to sex differences in BP control.

Modulation of Immune-Inflammatory Responses in Abdominal Aortic Aneurysm: Emerging Molecular Targets

Abdominal aortic aneurysm (AAA), a deadly vascular disease in human, is a chronic degenerative process of the abdominal aorta. In this process, inflammatory responses and immune system work efficiently by inflammatory cell attraction, proinflammatory factor secretion and subsequently MMP upregulation. Previous studies have demonstrated various inflammatory cell types in AAA of human and animals. The majority of cells, such as macrophages, CD4+ T cells, and B cells, play an important role in the diseased aortic wall through phenotypic modulation. Furthermore, immunoglobulins also greatly affect the functions and differentiation of immune cells in AAA. Recent evidence suggests that innate immune system, especially Toll-like receptors, chemokine receptors, and complements are involved in the progression of AAAs. We discussed the innate immune system, inflammatory cells, immunoglobulins, immune-mediated mechanisms, and key cytokines in the pathogenesis of AAA and particularly emphasis on a further trend and application of these interventions. This current understanding may offer new insights into the role of inflammation and immune response in AAA.

Ultraviolet B Exposure Inhibits Angiotensin II-Induced Abdominal Aortic Aneurysm Formation in Mice by Expanding CD4+Foxp3+ Regulatory T Cells

Background

Pathogenic immune responses are known to play an important role in abdominal aortic aneurysm (AAA) development. Ultraviolet B (UVB) irradiation has been demonstrated to have therapeutic potential not only for cutaneous diseases but also for systemic inflammatory diseases in mice by suppressing immunoinflammatory responses. We investigated the effect of UVB irradiation on experimental AAA.

Methods and Results

We used an angiotensin II–induced AAA model in apolipoprotein E–deficient mice fed a high‐cholesterol diet. Mice aged 10 weeks were irradiated with 5 kJ/m²UVB once weekly for 6 weeks (UVB‐irradiated, n=38; nonirradiated, n=42) and were euthanized for evaluation of AAA formation at 16 weeks. Overall, 93% of angiotensin II–infused mice developed AAA, with 60% mortality possibly because of aneurysm rupture. UVB irradiation significantly decreased the incidence (66%) and mortality (29%) of AAA (P=0.004 and P=0.006, respectively). UVB‐irradiated mice had significantly smaller diameter AAA (P=0.008) and fewer inflammatory cells in the aortic aneurysm tissue than nonirradiated mice, along with systemic expansion of CD4⁺Foxp3⁺ regulatory T cells and decreased effector CD4⁺CD44^highCD62L^low T cells in para‐aortic lymph nodes. Genetic depletion of regulatory T cells abrogated these beneficial effects of UVB treatment, demonstrating a critical role of regulatory T cells.

Conclusions

Our data suggest that UVB‐dependent expansion of regulatory T cells has beneficial effects on experimental AAA and may provide a novel strategy for the treatment of AAA.

Monocytes and macrophages in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a life-threatening disease associated with high morbidity, and high mortality in the event of aortic rupture. Major advances in open surgical and endovascular repair of AAA have been achieved during the past 2 decades. However, drug-based therapies are still lacking, highlighting a real need for better understanding of the molecular and cellular mechanisms involved in AAA formation and progression. The main pathological features of AAA include extracellular matrix remodelling associated with degeneration and loss of vascular smooth muscle cells and accumulation and activation of inflammatory cells. The inflammatory process has a crucial role in AAA and substantially influences many determinants of aortic wall remodelling. In this Review, we focus specifically on the involvement of monocytes and macrophages, summarizing current knowledge on the roles, origin, and functions of these cells in AAA development and its complications. Furthermore, we show and propose that distinct monocyte and macrophage subsets have critical and differential roles in initiation, progression, and healing of the aneurysmal process. On the basis of experimental and clinical studies, we review potential translational applications to detect, assess, and image macrophage subsets in AAA, and discuss the relevance of these applications for clinical practice.

Cathepsin S inhibition changes regulatory T-cell activity in regulating bladder cancer and immune cell proliferation and apoptosis

Regulatory T cells (Tregs) are immune suppressive cells, but their roles in tumor growth have been elusive, depending on tumor type or site. Our prior study demonstrated a role of cathepsin S (CatS) in reducing Treg immunosuppressive activity. Therefore, CatS inhibition in Tregs may exacerbate tumor growth. Using mouse bladder carcinoma MB49 cell subcutaneous implant tumor model, we detected no difference in tumor growth, whether mice were given saline- or CatS inhibitor-treated Tregs. However, mice that received inhibitor-treated Tregs had fewer splenic and tumor Tregs, and lower levels of tumor and splenic cell proliferation than mice that received saline-treated Tregs. In vitro, inhibitor-treated Tregs showed lower proliferation and higher apoptosis than saline-treated Tregs when cells were exposed to MB49. In contrast, both types of Tregs showed no difference in proliferation when they were co-cultured with normal splenocytes. Inhibitor-treated Tregs had less apoptosis in splenocytes, but more apoptosis in splenocytes with MB49 conditioned media than saline-treated Tregs. In turn, we detected less proliferation and more apoptosis of MB94 cells after co-culture with inhibitor-treated Tregs, compared with saline-treated Tregs. B220⁺ B-cell, CD4⁺ T-cell, and CD8⁺ T-cell proliferation and apoptosis were also lower in splenocytes co-cultured with inhibitor-treated Tregs than with saline-treated Tregs. Under the same conditions, the addition of cancer cell-conditioned media greatly increased CD8⁺ T-cell proliferation and reduced CD8⁺ T-cell apoptosis. These observations suggest that CatS inhibition of Tregs may reduce overall T-cell immunity under normal conditions, but enhance CD8⁺ T-cell immunity in the presence of cancer cells.

Elastin-Derived Peptides Promote Abdominal Aortic Aneurysm Formation by Modulating M1/M2 Macrophage Polarization

Abdominal aortic aneurysm is a dynamic vascular disease characterized by inflammatory cell invasion and extracellular matrix degradation. Damage to elastin in the extracellular matrix results in release of elastin-derived peptides (EDPs), which are chemotactic for inflammatory cells such as monocytes. Their effect on macrophage polarization is less well known. Proinflammatory M1 macrophages initially are recruited to sites of injury, but, if their effects are prolonged, they can lead to chronic inflammation that prevents normal tissue repair. Conversely, anti-inflammatory M2 macrophages reduce inflammation and aid in wound healing. Thus, a proper M1/M2 ratio is vital for tissue homeostasis. Abdominal aortic aneurysm tissue reveals a high M1/M2 ratio in which proinflammatory cells and their associated markers dominate. In the current study, in vitro treatment of bone marrow-derived macrophages with EDPs induced M1 macrophage polarization. By using C57BL/6 mice, Ab-mediated neutralization of EDPs reduced aortic dilation, matrix metalloproteinase activity, and proinflammatory cytokine expression at early and late time points after aneurysm induction. Furthermore, direct manipulation of the M1/M2 balance altered aortic dilation. Injection of M2-polarized macrophages reduced aortic dilation after aneurysm induction. EDPs promoted a proinflammatory environment in aortic tissue by inducing M1 polarization, and neutralization of EDPs attenuated aortic dilation. The M1/M2 imbalance is vital to aneurysm formation.

[Postoperative changes of Th17/Treg balance in patients with intracranial aneurysm rupture]

OBJECTIVE

To observe the dynamic changes of Th17/Treg balance in patients following surgical intervention for intracranial aneurysm rupture.

METHODS

The percentage of Th cells and the intracellular IL-17 level, Treg cell percentage and transforming growth factor -β1 (TGF-β1) levels were examined in 73 patients with rupture of aneurysms before and at 24 h, 72 h and 1 week after operation, with 62 patients with unruptured aneurysms and 65 healthy volunteers as the control. The correlations among the immune cells, cytokines and clinical characteristics of the patients (NIHSS, ADL and hospitalization stay) were analyzed.

RESULTS

Th17 percentage and intracellular IL-17 levels were significantly higher in the patients with ruptured and unruptured aneurysms than in the healthy volunteers, and were significantly higher in patients with ruptured aneurysms than in those with unruptured aneurysms. Treg cell percentage and TGF-β1 level were significantly lower in patients with aneurysms than in the healthy volunteers, and were lower in patients with ruptured aneurysms than in those with uruptured aneurysms (P<0.05). Patients with intracranial aneurysm rupture showed significantly increased Th17 cell percentage and IL-17 level but significantly lowered Treg cell percentage and TGF-β1 at 24 h following the surgery (P<0.05); these changes were reversed significantly at 72 h and 1 week after the surgery. Th17 cell percentage and IL-17 level were positively correlated with NIHSS and the length of postoperative hospital stay but inversely correlated with ADL; Treg cell percentage and TGF-β1 were inversely correlated with NIHSS and hospital stay but positively with ADL (P<0.05).

CONCLUSION

In patients with intracranial aneurysms, the systemic immune inflammatory response is highlighted by excessive Th17 cells and insufficient Treg cells, which are closely related with the outcomes of the patients following surgical intervention. Evaluation of Th17/Treg balance and the cytokine levels can help to assess the prognosis of patients with aneurysm rupture.

Inflammatory cell phenotypes in AAAs: their role and potential as targets for therapy

Abdominal aortic aneurysms (AAAs) are characterized by chronic inflammatory cell infiltration. AAA is typically an asymptomatic disease and caused ≈15 000 deaths annually in the United States. Previous studies have examined both human and murine aortic tissue for the presence of various inflammatory cell types. Studies show that in both human and experimental AAAs, prominent inflammatory cell infiltration, such as CD4(+) T cells and macrophages, occurs in the damaged aortic wall. These cells have the ability to undergo phenotypic modulation based on microenvironmental cues, potentially influencing disease progression. Proinflammatory CD4(+) T cells and classically activated macrophages dominate the landscape of aortic infiltrates. The skew to proinflammatory phenotypes alters disease progression and plays a role in causing chronic inflammation. The local cytokine production and presence of inflammatory mediators, such as extracellular matrix breakdown products, influence the uneven balance of the inflammatory infiltrate phenotypes. Understanding and developing new strategies that target the proinflammatory phenotype could provide useful therapeutic targets for a disease with no current pharmacological intervention.