Epigenetic landscapes suggest that genetic risk for intracranial aneurysm operates on the endothelium.
Poppenberg Kerry E,Jiang Kaiyu,Tso Michael K,Snyder Kenneth V,Siddiqui Adnan H,Kolega John,Jarvis James N,Meng Hui,Tutino Vincent M
BMC medical genomics
BACKGROUND:Genetics play an important role in intracranial aneurysm (IA) pathophysiology. Genome-wide association studies have identified several single nucleotide polymorphisms (SNPs) that are linked to IA but how they affect disease pathobiology remains poorly understood. We used Encyclopedia of DNA Elements (ENCODE) data to investigate the epigenetic landscapes surrounding genetic risk loci to determine if IA-associated SNPs affect functional elements that regulate gene expression and if those SNPs are most likely to impact a specific type of cells. METHODS:We mapped 16 highly significant IA-associated SNPs to linkage disequilibrium (LD) blocks within the human genome. Within these regions, we examined the presence of H3K4me1 and H3K27ac histone marks and CCCTC-binding factor (CTCF) and transcription-factor binding sites using chromatin immunoprecipitation-sequencing (ChIP-Seq) data. This analysis was conducted in several cell types relevant to endothelial (human umbilical vein endothelial cells [HUVECs]) and inflammatory (monocytes, neutrophils, and peripheral blood mononuclear cells [PBMCs]) biology. Gene ontology analysis was performed on genes within extended IA-risk regions to understand which biological processes could be affected by IA-risk SNPs. We also evaluated recently published data that showed differential methylation and differential ribonucleic acid (RNA) expression in IA to investigate the correlation between differentially regulated elements and the IA-risk LD blocks. RESULTS:The IA-associated LD blocks were statistically significantly enriched for H3K4me1 and/or H3K27ac marks (markers of enhancer function) in endothelial cells but not in immune cells. The IA-associated LD blocks also contained more binding sites for CTCF in endothelial cells than monocytes, although not statistically significant. Differentially methylated regions of DNA identified in IA tissue were also present in several IA-risk LD blocks, suggesting SNPs could affect this epigenetic machinery. Gene ontology analysis supports that genes affected by IA-risk SNPs are associated with extracellular matrix reorganization and endopeptidase activity. CONCLUSION:These findings suggest that known genetic alterations linked to IA risk act on endothelial cell function. These alterations do not correlate with IA-associated gene expression signatures of circulating blood cells, which suggests that such signatures are a secondary response reflecting the presence of IA rather than indicating risk for IA.
Patterns of immune infiltration in stable and raptured abdominal aortic aneurysms: A gene-expression-based retrospective study.
Lei Chuxiang,Yang Dan,Chen Siliang,Chen Wenlin,Sun Xiaoning,Wu Xiao,Chen Mengyin,Li Yuan,Zheng Yuehong
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.
Regulatory T cells protected against abdominal aortic aneurysm by suppression of the COX-2 expression.
Liu Bin,Kong Jing,An Guipeng,Zhang Kai,Qin Weidong,Meng Xiao
Journal of cellular and molecular medicine
CD4 CD25 regulatory T cells (Tregs) have been shown to protect against the development of abdominal aortic aneurysm (AAA). Cyclooxygenase-2 (COX-2), a pro-inflammatory protein, can convert arachidonic acid into prostaglandins (PGs). The present study was aimed to investigate the effect of Tregs on COX-2 expression in angiotension II (Ang II)-induced AAA in ApoE mice. Tregs were injected via tail vein in every 2 weeks. Ang II was continuously infused by a micropump for 28 days to induce AAA. In vivo, compared with the control group, adoptive transfer of Tregs significantly reduced the incidence of AAA, maximal diameter, and the mRNA and protein expression of COX-2 in mice. Immunofluorescence showed that Tregs treatment reduced COX-2 expression both in smooth muscle cells (SMCs) and macrophages in AAA. In vitro, the Western blot analysis showed that Tregs reduced Ang II-induced COX-2 expression in macrophages and SMCs. Meanwhile, ELISA showed that Tregs reduced Ang II-induced prostaglandin E (PGE ) secretion. Moreover, Tregs increased SMC viability and induced transition of macrophages phenotype from M1 to M2. In conclusion, Tregs treatment dramatically decreased the expression of COX-2 in vivo and in vitro, suggesting that Tregs could protect against AAA through inhibition of COX-2. The study may shed light on the immune treatment of AAA.
Single-Cell RNA Sequencing Reveals Heterogeneity of Vascular Cells in Early Stage Murine Abdominal Aortic Aneurysm-Brief Report.
Yang Huan,Zhou Ting,Stranz Amelia,DeRoo Elise,Liu Bo
Arteriosclerosis, thrombosis, and vascular biology
OBJECTIVE:Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease characterized by smooth muscle cell depletion, ECM (extracellular matrix) degradation, and infiltration of immune cells. The cellular and molecular profiles that govern the heterogeneity of the AAA aorta are yet to be elucidated. Approach and Results: We performed single-cell RNA sequencing on mouse AAA tissues. AAA was induced in C57BL/6J mice by perivascular application of CaCl. Unbiased clustering identified 12 distinct populations of 8 cell types. Percentages of each population and gene expression were compared between sham and AAA tissue. Furthermore, we characterized the transcriptional profiles and potential functional features of populations in smooth muscle cells, fibroblasts, and macrophages and revealed the unique regulons in each cell type. CONCLUSIONS:Together, these data provide high-resolution insight into the complexity and heterogeneity of mouse AAA and indicate that populations within major cell types such as smooth muscle cells, fibroblasts, and macrophages may contribute differently to AAA pathogenesis. Graphic Abstract: A graphic abstract is available for this article.
Combining Bioinformatics Techniques to Study the Key Immune-Related Genes in Abdominal Aortic Aneurysm.
Nie Han,Qiu Jiacong,Wen Si,Zhou Weimin
Frontiers in genetics
Approximately 13,000 people die of an abdominal aortic aneurysm (AAA) every year. This study aimed to identify the immune response-related genes that play important roles in AAA using bioinformatics approaches. We downloaded the GSE57691 and GSE98278 datasets related to AAA from the Gene Expression Omnibus database, which included 80 AAA and 10 normal vascular samples. CIBERSORT was used to analyze the samples and detect the infiltration of 22 types of immune cells and their differences and correlations. The principal component analysis showed significant differences in the infiltration of immune cells between normal vascular and AAA samples. High proportions of CD4 T cells, activated mast cells, resting natural killer cells, and 12 other types of immune cells were found in normal vascular tissues, whereas high proportions of macrophages, CD8 T cells, resting mast cells, and six other types of immune cells were found in AAA tissues. In the selected samples, we identified 39 upregulated (involved in growth factor activity, hormone receptor binding, and cytokine receptor activity) and 133 downregulated genes (involved in T cell activation, cell chemotaxis, and regulation of immune response mediators). The key differentially expressed immune response-related genes were screened using the STRING database and Cytoscape software. Two downregulated genes, and , and three upregulated genes, , and , were identified by constructing a protein-protein interaction network. Functional enrichment of the differentially expressed genes was analyzed, and the expression of the five key genes in AAA samples was verified using quantitative polymerase chain reaction, which revealed that was downregulated in AAA, whereas , and were upregulated; there was no significant difference in PI3 expression. Our study shows that normal vascular and AAA samples can be distinguished via the infiltration of immune cells. Five genes, , and , may play important roles in the development, diagnosis, and treatment of AAA.
Modulation of Immune-Inflammatory Responses in Abdominal Aortic Aneurysm: Emerging Molecular Targets.
Li Hanrong,Bai Shuling,Ao Qiang,Wang Xiaohong,Tian Xiaohong,Li Xiang,Tong Hao,Hou Weijian,Fan Jun
Journal of immunology research
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.