Diverse roles of macrophage polarization in aortic aneurysm: destruction and repair

Mesenchymal stromal cell-derived exosomes protect against abdominal aortic aneurysm formation through CD74 modulation of macrophage polarization in mice

BACKGROUND

Mesenchymal stromal cell (MSC)-derived exosomes (MSC-Exo) have been recognized for their significant role in regulating macrophage polarization, a process crucial to the pathogenesis of abdominal aortic aneurysm (AAA). However, the therapeutic effects of MSC-Exo on AAA remain largely unexplored. Therefore, this study aimed to investigate the functional and mechanistic aspects of MSC-Exo in the progression of AAA.

METHODS

The MSC-derived exosomes were characterized using Transmission Electron Microscopy, Nanoparticle Tracking Analysis, and Western blotting. An experimental mouse model of AAA was established through the administration of angiotensin II (Ang II) in male apoe-/- mice and calcium chloride (CaCl2) in male C57/B6 mice, with subsequent tail vein injection of exosomes to evaluate their efficacy against AAA. Macrophage polarization was assessed using immunofluorescence staining and WB analysis. Mechanistic analysis was performed using 4D Label-free Proteomics analysis.

RESULTS

We found that intravenous administration of MSC-Exo induced M2 polarization of macrophages within an inflammatory environment, effectively impeding AAA development in Ang II or CaCl2-induced AAA model. The therapeutic efficacy of MSC-Exo treatment was dependent on the presence of macrophages. Mechanistically, MSC-Exo suppressed the levels of cluster of differentiation 74 (CD74), modulating macrophage polarization through the TSC2-mTOR-AKT pathway. These findings highlight the potential of MSC-Exo as a therapeutic strategy for AAA by modulating macrophage polarization.

Macrophages in cardiovascular diseases: molecular mechanisms and therapeutic targets

The immune response holds a pivotal role in cardiovascular disease development. As multifunctional cells of the innate immune system, macrophages play an essential role in initial inflammatory response that occurs following cardiovascular injury, thereby inducing subsequent damage while also facilitating recovery. Meanwhile, the diverse phenotypes and phenotypic alterations of macrophages strongly associate with distinct types and severity of cardiovascular diseases, including coronary heart disease, valvular disease, myocarditis, cardiomyopathy, heart failure, atherosclerosis and aneurysm, which underscores the importance of investigating macrophage regulatory mechanisms within the context of specific diseases. Besides, recent strides in single-cell sequencing technologies have revealed macrophage heterogeneity, cell-cell interactions, and downstream mechanisms of therapeutic targets at a higher resolution, which brings new perspectives into macrophage-mediated mechanisms and potential therapeutic targets in cardiovascular diseases. Remarkably, myocardial fibrosis, a prevalent characteristic in most cardiac diseases, remains a formidable clinical challenge, necessitating a profound investigation into the impact of macrophages on myocardial fibrosis within the context of cardiac diseases. In this review, we systematically summarize the diverse phenotypic and functional plasticity of macrophages in regulatory mechanisms of cardiovascular diseases and unprecedented insights introduced by single-cell sequencing technologies, with a focus on different causes and characteristics of diseases, especially the relationship between inflammation and fibrosis in cardiac diseases (myocardial infarction, pressure overload, myocarditis, dilated cardiomyopathy, diabetic cardiomyopathy and cardiac aging) and the relationship between inflammation and vascular injury in vascular diseases (atherosclerosis and aneurysm). Finally, we also highlight the preclinical/clinical macrophage targeting strategies and translational implications.

Mechanism and clinical implication of gut dysbiosis in degenerative abdominal aortic aneurysm: A systematic review

The gut microbiome is the entirety of microorganisms and their genomes residing in the gut, characterised by diversity, stability, and resilience. Disrupted gut microbiome has been implicated in multiple disease entities. The aim of this paper is to summarise the rapidly evolving contemporary evidence of gut dysbiosis on the development and progression of abdominal aortic aneurysm (AAA), discuss possible mechanisms, and explore potential microbiota-targeted interventions and prognostic markers for AAA. A systematic literature search was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, using PubMed, ScienceDirect, Web of Science, Ovid, Embase. Search terms of "microbiome" OR "dysbiosis" OR "microorganism"; AND "aneurysm" OR "dilatation" OR "aorta" were used. Study endpoints included effects of microbiota on AAA formation, effects of specific type of bacteria and its metabolite on AAA formation, and pre- or post-treatment by novel small-molecules/inhibitors. From May to August 2023, a total of twelve animal studies and eight human studies were included. Akkermansia muciniphila, Lactobacillus acidophilus and species from the Bacteroidetes phylum were associated with lower AAA incidence in both animal and human studies, while Proteobacteria phylum, Campylobacter, Fusobacterium and Faecalibacterium prausnitzii were found to be in abundance in the AAA group and were associated with larger aneurysms. The diversity of gut microbiota was inversely correlated with AAA diameter. Three important mechanisms were identified: including trimethylamine N-oxide pathway, butyric acid pathway, and aberrant tryptophan metabolism. With our expanding knowledge of the downstream pathogenic mechanisms of gut dysbiosis, novel therapeutics such as short-chain fatty acids and spermidine, as well as prognostic biomarkers such as TMAO have yielded promising preclinical results. In conclusion, there is strong evidence corroborating the role of gut dysbiosis in the pathogenesis of AAA, wherein its therapeutic and prognostic potential deserves further exploration.

The role of transcription factors in the pathogenesis and therapeutic targeting of vascular diseases

Transcription factors (TFs) constitute an essential component of epigenetic regulation. They contribute to the progression of vascular diseases by regulating epigenetic gene expression in several vascular diseases. Recently, numerous regulatory mechanisms related to vascular pathology, ranging from general TFs that are continuously activated to histiocyte-specific TFs that are activated under specific circumstances, have been studied. TFs participate in the progression of vascular-related diseases by epigenetically regulating vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). The Krüppel-like family (KLF) TF family is widely recognized as the foremost regulator of vascular diseases. KLF11 prevents aneurysm progression by inhibiting the apoptosis of VSMCs and enhancing their contractile function. The presence of KLF4, another crucial member, suppresses the progression of atherosclerosis (AS) and pulmonary hypertension by attenuating the formation of VSMCs-derived foam cells, ameliorating endothelial dysfunction, and inducing vasodilatory effects. However, the mechanism underlying the regulation of the progression of vascular-related diseases by TFs has remained elusive. The present study categorized the TFs involved in vascular diseases and their regulatory mechanisms to shed light on the potential pathogenesis of vascular diseases, and provide novel insights into their diagnosis and treatment.

Cannabidiol protects against acute aortic dissection by inhibiting macrophage infiltration and PMAIP1-induced vascular smooth muscle cell apoptosis

Acute aortic dissection (AAD) progresses rapidly and is associated with high mortality; therefore, there remains an urgent need for pharmacological agents that can protect against AAD. Herein, we examined the therapeutic effects of cannabidiol (CBD) in AAD by establishing a suitable mouse model. In addition, we performed human AAD single-cell RNA sequencing and mouse AAD bulk RNA sequencing to elucidate the potential underlying mechanism of CBD. Pathological assays and in vitro studies were performed to verify the results of the bioinformatic analysis and explore the pharmacological function of CBD. In a β-aminopropionitrile (BAPN)-induced AAD mouse model, CBD reduced AAD-associated morbidity and mortality, alleviated abnormal enlargement of the ascending aorta and aortic arch, and suppressed macrophage infiltration and vascular smooth muscle cell (VSMC) apoptosis. Bioinformatic analysis revealed that the pro-apoptotic gene PMAIP1 was highly expressed in human and mouse AAD samples, and CBD could inhibit Pmaip1 expression in AAD mice. Using human aortic VSMCs (HAVSMCs) co-cultured with M1 macrophages, we revealed that CBD alleviated HAVSMCs mitochondrial-dependent apoptosis by suppressing the BAPN-induced overexpression of PMAIP1 in M1 macrophages. PMAIP1 potentially mediates HAVSMCs apoptosis by regulating Bax and Bcl2 expression. Accordingly, CBD reduced AAD-associated morbidity and mortality and mitigated the progression of AAD in a mouse model. The CBD-induced effects were potentially mediated by suppressing macrophage infiltration and PMAIP1 (primarily expressed in macrophages)-induced VSMC apoptosis. Our findings offer novel insights into M1 macrophages and HAVSMCs interaction during AAD progression, highlighting the potential of CBD as a therapeutic candidate for AAD treatment.

Macrophage in Sporadic Thoracic Aortic Aneurysm and Dissection: Potential Therapeutic and Preventing Target

Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening cardiovascular disorder lacking effective clinical pharmacological therapies. The underlying molecular mechanisms of TAAD still remain elusive with participation of versatile cell types and components including endothelial cells (ECs), smooth muscle cells (SMCs), fibroblasts, immune cells, and the extracellular matrix (ECM). The main pathological features of TAAD include SMC dysfunction, phenotypic switching, and ECM degradation, which is closely associated with inflammation and immune cell infiltration. Among various types of immune cells, macrophages are a distinct participator in the formation and progression of TAAD. In this review, we first highlight the important role of inflammation and immune cell infiltration in TAAD. Furthermore, we discuss the role of macrophages in TAAD from the aspects of macrophage origination, classification, and functions. On the basis of experimental and clinical studies, we summarize key regulators of macrophages in TAAD. Finally, we review how targeting macrophages can reduce TAAD in murine models. A better understanding of the molecular and cellular mechanisms of TAAD may provide novel insights into preventing and treating the condition.

Targeted PERK inhibition with biomimetic nanoclusters confers preventative and interventional benefits to elastase-induced abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a progressive aortic dilatation, causing ∼80% mortality upon rupture. Currently, there is no approved drug therapy for AAA. Surgical repairs are invasive and risky and thus not recommended to patients with small AAAs which, however, account for ∼90% of the newly diagnosed cases. It is therefore a compelling unmet clinical need to discover effective non-invasive strategies to prevent or slow down AAA progression. We contend that the first AAA drug therapy will only arise through discoveries of both effective drug targets and innovative delivery methods. There is substantial evidence that degenerative smooth muscle cells (SMCs) orchestrate AAA pathogenesis and progression. In this study, we made an exciting finding that PERK, the endoplasmic reticulum (ER) stress Protein Kinase R-like ER Kinase, is a potent driver of SMC degeneration and hence a potential therapeutic target. Indeed, local knockdown of PERK in elastase-challenged aorta significantly attenuated AAA lesions in vivo. In parallel, we also conceived a biomimetic nanocluster (NC) design uniquely tailored to AAA-targeting drug delivery. This NC demonstrated excellent AAA homing via a platelet-derived biomembrane coating; and when loaded with a selective PERK inhibitor (PERKi, GSK2656157), the NC therapy conferred remarkable benefits in both preventing aneurysm development and halting the progression of pre-existing aneurysmal lesions in two distinct rodent models of AAA. In summary, our current study not only establishes a new intervention target for mitigating SMC degeneration and aneurysmal pathogenesis, but also provides a powerful tool to facilitate the development of effective drug therapy of AAA.

Signaling through the IL-6-STAT3 Pathway Promotes Proteolytically-Active Macrophage Accumulation Necessary for Development of Small AAA

INTRODUCTION

Elevated interleukin-6 (IL-6) plasma levels have been associated with abdominal aortic aneurysm (AAA), but whether this cytokine plays a causative role in the degenerative remodeling or represents an effect from the inflammatory cascades initiated by infiltrating leukocytes remained unclear. This project aims to demonstrate that within the aortic wall, signaling from IL-6 through the STAT3 transcription factor is necessary for infiltration of proteolytically-active macrophages and development of small AAA.

METHODS

Following measurement of baseline infrarenal aortic diameter (AoD, digital microscopy), C57Bl/6 and IL-6 knockout (IL-6KO) mice underwent AAA induction by application of peri-adventitial CaCl2 (0.5 M) +/- implantation of an osmotic mini-pump delivering IL-6 (4.36 µg/kg/day over 21 days). At the terminal procedure, AoDs were measured by digital microscopy and aortas harvested for immunoblot (pSTAT3/STAT3), matrix metalloproteinase (MMP) quantification, or flow cytometric analysis of macrophage content. Plasma was collected for cytokine analysis.

RESULTS

IL-6 infusion significantly increased the plasma IL-6 levels in C57Bl/6 and IL-6KO animals. The C57Bl/6 + CaCl2 group developed AAA (AoD >50% above baseline) but IL-6KO + CaCl2 did not. In the IL-6KO + IL-6+CaCl2 group, AAA developed to match that of C57Bl/6 + CaCl2 mice. STAT3 activity was significantly increased in animals with advanced stages of dilation (>40% from baseline), compared to those with ectasia (≤25%). Although cytokine profiles did not support T-cells or neutrophils as being active contributors in this stage of aortic remodeling, changes in the profile of elaborated MMPs suggested macrophage activity with a trend toward alternatively activated pathways. Flow cytometry confirmed significantly increased macrophage abundance specifically in animals with upregulated STAT3 activity and advanced aortic dilation.

CONCLUSION

In this murine model of AAA, progressive dilation to development of true AAA was only accomplished when IL-6 signaling upregulated STAT3 activity to effect accumulation of proteolytically-active macrophages. This pathway warrants further investigation to identify potential therapeutic avenues to abrogate growth of small AAA.

Administration of anti-inflammatory M2 macrophages suppresses progression of angiotensin II-induced aortic aneurysm in mice

Aortic aneurysm (AA) is a vascular disorder characterized pathologically by inflammatory cell invasion and extracellular matrix (ECM) degradation. It is known that regulation of the balance between pro-inflammatory M1 macrophages (M1Ms) and anti-inflammatory M2 macrophages (M2Ms) plays a pivotal role in AA stabilization. We investigated the effects of M2M administration in an apolipoprotein E-deficient (apoE^-/-) mouse model in which AA was induced by angiotensin II (ATII) infusion. Mice received intraperitoneal administration of 1 million M2Ms 4 weeks after ATII infusion. Compared with a control group that was administered saline, the M2M group exhibited reduced AA expansion; decreased expression levels of interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α), and monocyte chemoattractant protein-1 (MCP-1); and a lower M1M/M2M ratio. Moreover, the M2M group exhibited upregulation of anti-inflammatory factors, including IL-4 and IL-10. PKH26-labeled M2Ms accounted for 6.5% of cells in the aneurysmal site and co-expressed CD206. Taken together, intraperitoneal administration of M2Ms inhibited AA expansion by reducing the inflammatory reaction via regulating the M1M/M2M ratio. This study shows that M2M administration might be useful for the treatment of AA.

HDL metabolism and functions impacting on cell cholesterol homeostasis are specifically altered in patients with abdominal aortic aneurysm

Background

The etiopathogenesis of abdominal aortic aneurysm (AAA) is still unclarified, but vascular inflammation and matrix metalloproteases activation have a recognized role in AAA development and progression. Circulating lipoproteins are involved in tissue inflammation and repair, particularly through the regulation of intracellular cholesterol, whose excess is associated to cell damage and proinflammatory activation. We analyzed lipoprotein metabolism and function in AAA and in control vasculopathic patients, to highlight possible non-atherosclerosis-related, specific abnormalities.

Methods

We measured fluorometrically serum esterified/total cholesterol ratio, as an index of lecithin-cholesterol acyltransferase (LCAT) activity, and cholesteryl ester transfer protein (CETP) activity in patients referred to vascular surgery either for AAA (n=30) or stenotic aortic/peripheral atherosclerosis (n=21) having similar burden of cardiovascular risk factors and disease. We measured high-density lipoprotein (HDL)-cholesterol efflux capacity (CEC), through the ATP-binding cassette G1 (ABCG1) and A1 (ABCA1) pathways and serum cell cholesterol loading capacity (CLC), by radioisotopic and fluorimetric methods, respectively.

Results

We found higher LCAT (+23%; p < 0.0001) and CETP (+49%; p < 0.0001) activity in AAA sera. HDL ABCG1-CEC was lower (−16%; p < 0.001) and ABCA1-CEC was higher (+31.7%; p < 0.0001) in AAA. Stratification suggests that smoking may partly contribute to these modifications. CEC and CETP activity correlated with CLC only in AAA.

Conclusions

We demonstrated that compared to patients with stenotic atherosclerosis, patients with AAA had altered HDL metabolism and functions involved in their anti-inflammatory and tissue repair activity, particularly through the ABCG1-related intracellular signaling. Clarifying the relevance of this mechanism for AAA evolution might help in developing new diagnostic parameters and therapeutic targets for the early management of this condition.

N1-Methyladenosine (m1A) Regulation Associated With the Pathogenesis of Abdominal Aortic Aneurysm Through YTHDF3 Modulating Macrophage Polarization

Objectives

This study aimed to identify key AAA-related m1A RNA methylation regulators and their association with immune infiltration in AAA. Furthermore, we aimed to explore the mechanism that m1A regulators modulate the functions of certain immune cells as well as the downstream target genes, participating in the progression of AAA.

Methods

Based on the gene expression profiles of the GSE47472 and GSE98278 datasets, differential expression analysis focusing on m1A regulators was performed on the combined dataset to identify differentially expressed m1A regulatory genes (DEMRGs). Additionally, CIBERSORT tool was utilized in the analysis of the immune infiltration landscape and its correlation with DEMRGs. Moreover, we validated the expression levels of DEMRGs in human AAA tissues by real-time quantitative PCR (RT-qPCR). Immunofluorescence (IF) staining was also applied in the validation of cellular localization of YTHDF3 in AAA tissues. Furthermore, we established LPS/IFN-γ induced M1 macrophages and ythdf3 knockdown macrophages in vitro, to explore the relationship between YTHDF3 and macrophage polarization. At last, RNA immunoprecipitation-sequencing (RIP-Seq) combined with PPI network analysis was used to predict the target genes of YTHDF3 in AAA progression.

Results

Eight DEMRGs were identified in our study, including YTHDC1, YTHDF1-3, RRP8, TRMT61A as up-regulated genes and FTO, ALKBH1 as down-regulated genes. The immune infiltration analysis showed these DEMRGs were positively correlated with activated mast cells, plasma cells and M1 macrophages in AAA. RT-qPCR analysis also verified the up-regulated expression levels of YTHDC1, YTHDF1, and YTHDF3 in human AAA tissues. Besides, IF staining result in AAA adventitia indicated the localization of YTHDF3 in macrophages. Moreover, our in-vitro experiments found that the knockdown of ythdf3 in M0 macrophages inhibits macrophage M1 polarization but promotes macrophage M2 polarization. Eventually, 30 key AAA-related target genes of YTHDF3 were predicted, including CD44, mTOR, ITGB1, STAT3, etc.

Conclusion

Our study reveals that m1A regulation is significantly associated with the pathogenesis of human AAA. The m1A “reader,” YTHDF3, may participate in the modulating of macrophage polarization that promotes aortic inflammation, and influence AAA progression by regulating the expression of its target genes.

Integrating Bulk Transcriptome and Single-Cell RNA Sequencing Data Reveals the Landscape of the Immune Microenvironment in Thoracic Aortic Aneurysms

Thoracic aortic aneurysm (TAA) is a life-threatening cardiovascular disease whose formation is reported to be associated with massive vascular inflammatory responses. To elucidate the roles of immune cell infiltration in the pathogenesis underlying TAA, we utilized multiple TAA datasets (microarray data and scRNA-seq data) and various immune-related algorithms (ssGSEA, CIBERSORT, and Seurat) to reveal the landscapes of the immune microenvironment in TAA. The results exhibited a significant increase in the infiltration of macrophages and T cells, which were mainly responsible for TAA formation among the immune cells. To further reveal the roles of immunocytes in TAA, we inferred the intercellular communications among the identified cells of aortic tissues. Notably, we found that in both normal aortic tissue and TAA tissue, the cells that interact most frequently are macrophages, endothelial cells (ECs), fibroblasts, and vascular smooth muscle cells (VSMCs). Among the cells, macrophages were the most prominent signal senders and receivers in TAA and normal aortic tissue. These findings suggest that macrophages play an important role in both the physiological and pathological conditions of the aorta. The present study provides a comprehensive evaluation of the immune cell composition and reveals the intercellular communication among aortic cells in human TAA tissues. These findings improve our understanding of TAA formation and progression and facilitate the development of effective medications to treat these conditions.

Single-Cell Sequencing of Immune Cells in Human Aortic Dissection Tissue Provides Insights Into Immune Cell Heterogeneity

Background

Inflammation plays an important role in the progression of sporadic aortic dissection (AD). Immune cells, especially macrophages, infiltrate the aorta and secrete inflammatory cytokines and matrix metalloproteinases to cause degradation of the extracellular matrix, thereby contributing to the pathogenesis of AD. However, the cellular heterogeneity within these immune cells has not been fully characterized.

Methods

We used single-cell RNA sequencing to profile the transcriptomes of all immune cells in AD tissue and normal aorta. Using magnetic-activated cell sorting gating on CD45, we obtained a higher resolution identification of the immune cell subsets in the aorta.

Results

We observed significant differences in the proportion of major immune cell subpopulations between AD and normal aorta tissues. Macrophages accounted for a higher percentage in the normal aorta, while the proportions of T cells, B cells and natural killer (NK) cells were all increased in AD tissues. Macrophage clusters that expanded in AD tissues originated primarily from circulating monocytes and expressed genes encoding proinflammatory cytokines and molecules involved in tissue repair. T and NK cells in AD tissues exhibited enhanced cytotoxic properties. A cluster of CD4⁺ T cells that had expanded in AD tissues was Th17-like and might contribute to the pathogenesis of AD. Cell–cell interaction analysis highlighted the increased communication between macrophages and T cells, which primarily regulated the costimulation of T cells.

Conclusions

Our study provides a comprehensive characterization of immune cells in the dissected aorta with an emphasis on the role of macrophages and T cells. The information from our study improves our understanding of immune mechanisms in AD formation and helps to identify additional useful targets for early diagnosis or therapy of AD.

Targeting macrophage TFEB-14-3-3 epsilon Interface by naringenin inhibits abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a lethal cardiovascular disease, and there is no proven drug treatment for this condition. In this study, by using the Connectivity Map (CMap) approach, we explored naringenin, a naturally occurring citrus flavonoid, as a putative agent for inhibiting AAA. We then validated the prediction with two independent mouse models of AAA, calcium phosphate (CaPO₄)-induced C57BL/6J mice and angiotensin II-infused ApoE^−/− mice. Naringenin effectively blocked the formation of AAAs and the progression of established AAAs. Transcription factor EB (TFEB) is the master regulator of lysosome biogenesis. Intriguingly, the protective role of naringenin on AAA was abolished by macrophage-specific TFEB depletion in mice. Unbiased interactomics, combined with isothermal titration calorimetry (ITC) and cellular thermal shift assays (CETSAs), further revealed that naringenin is directly bound to 14-3-3 epsilon blocked the TFEB-14-3-3 epsilon interaction, and therefore promoted TFEB nuclear translocation and activation. On one hand, naringenin activated lysosome-dependent inhibition of the NLRP3 inflammasome and repressed aneurysmal inflammation. On the other hand, naringenin induced TFEB-dependent transcriptional activation of GATA3, IRF4, and STAT6 and therefore promoted reparative M2 macrophage polarization. In summary, naturally derived naringenin or macrophage TFEB activation shows promising efficacy for the treatment of AAA.

Cycloastragenol Inhibits Experimental Abdominal Aortic Aneurysm Progression

The pathogenesis of abdominal aortic aneurysm involves vascular inflammation and elastin degradation. Astragalusradix contains cycloastragenol, which is known to be anti-inflammatory and to protect against elastin degradation. We hypothesized that cycloastragenol supplementation inhibits abdominal aortic aneurysm progression. Abdominal aortic aneurysm was induced in male rats by intraluminal elastase infusion in the infrarenal aorta and treated daily with cycloastragenol (125 mg/kg/day). Aortic expansion was followed weekly by ultrasound for 28 days. Changes in aneurysmal wall composition were analyzed by mRNA levels, histology, zymography and explorative proteomic analyses. At day 28, mean aneurysm diameter was 37% lower in the cycloastragenol group (p < 0.0001). In aneurysm cross sections, elastin content was insignificantly higher in the cycloastragenol group (10.5% ± 5.9% vs. 19.9% ± 16.8%, p = 0.20), with more preserved elastin lamellae structures (p = 0.0003) and without microcalcifications. Aneurysmal matrix metalloprotease-2 activity was reduced by the treatment (p = 0.022). Messenger RNA levels of inflammatory- and anti-oxidative markers did not differ between groups. Explorative proteomic analysis showed no difference in protein levels when adjusting for multiple testing. Among proteins displaying nominal regulation were fibulin-5 (p = 0.02), aquaporin-1 (p = 0.02) and prostacyclin synthase (p = 0.007). Cycloastragenol inhibits experimental abdominal aortic aneurysm progression. The suggested underlying mechanisms involve decreased matrix metalloprotease-2 activity and preservation of elastin and reduced calcification, thus, cycloastragenol could be considered for trial in abdominal aortic aneurysm patients.

Diabetes-Induced Changes in Macrophage Biology Might Lead to Reduced Risk for Abdominal Aortic Aneurysm Development

Type 2 diabetes patients are less likely to develop an abdominal aortic aneurysm (AAA). Since macrophages play a crucial role in AAA development, we hypothesized that this decrease in AAA risk in diabetic patients might be due to diabetes-induced changes in macrophage biology. To test this hypothesis, we treated primary macrophages obtained from healthy human volunteers with serum from non-diabetic vs. diabetic AAA patients and observed differences in extracellular acidification and the expression of genes involved in glycolysis and lipid oxidation. These results suggest an increase in metabolism in macrophages treated with serum from diabetic AAA patients. Since serum samples used did not differ in glucose content, these changes are not likely to be caused by differences in glycemia. Macrophage functions have been shown to be linked to their metabolism. In line with this, our data suggest that this increase in macrophage metabolism is accompanied by a shift towards an anti-inflammatory state. Together, these results support a model where diabetes-induced changes in metabolism in macrophages might lead to a reduced risk for AAA development.

Disturbed flow's impact on cellular changes indicative of vascular aneurysm initiation, expansion, and rupture: A pathological and methodological review

Aneurysms are malformations within the arterial vasculature brought on by the structural breakdown of the microarchitecture of the vessel wall, with aneurysms posing serious health risks in the event of their rupture. Blood flow within vessels is generally laminar with high, unidirectional wall shear stressors that modulate vascular endothelial cell functionality and regulate vascular smooth muscle cells. However, altered vascular geometry induced by bifurcations, significant curvature, stenosis, or clinical interventions can alter the flow, generating low stressor disturbed flow patterns. Disturbed flow is associated with altered cellular morphology, upregulated expression of proteins modulating inflammation, decreased regulation of vascular permeability, degraded extracellular matrix, and heightened cellular apoptosis. The understanding of the effects disturbed flow has on the cellular cascades which initiate aneurysms and promote their subsequent growth can further elucidate the nature of this complex pathology. This review summarizes the current knowledge about the disturbed flow and its relation to aneurysm pathology, the methods used to investigate these relations, as well as how such knowledge has impacted clinical treatment methodologies. This information can contribute to the understanding of the development, growth, and rupture of aneurysms and help develop novel research and aneurysmal treatment techniques.

Vascular Macrophages as Therapeutic Targets to Treat Intracranial Aneurysms

Aneurysmal subarachnoid hemorrhage (aSAH) is a highly fatal and morbid type of hemorrhagic strokes. Intracranial aneurysms (ICAs) rupture cause subarachnoid hemorrhage. ICAs formation, growth and rupture involves cellular and molecular inflammation. Macrophages orchestrate inflammation in the wall of ICAs. Macrophages generally polarize either into classical inflammatory (M1) or alternatively-activated anti-inflammatory (M2)-phenotype. Macrophage infiltration and polarization toward M1-phenotype increases the risk of aneurysm rupture. Strategies that deplete, inhibit infiltration, ameliorate macrophage inflammation or polarize to M2-type protect against ICAs rupture. However, clinical translational data is still lacking. This review summarizes the contribution of macrophage led inflammation in the aneurysm wall and discuss pharmacological strategies to modulate the macrophageal response during ICAs formation and rupture.

Targeting the Extracellular Matrix in Abdominal Aortic Aneurysms Using Molecular Imaging Insights

This review outlines recent preclinical and clinical advances in molecular imaging of abdominal aortic aneurysms (AAA) with a focus on molecular magnetic resonance imaging (MRI) of the extracellular matrix (ECM). In addition, developments in pharmacologic treatment of AAA targeting the ECM will be discussed and results from animal studies will be contrasted with clinical trials. Abdominal aortic aneurysm (AAA) is an often fatal disease without non-invasive pharmacologic treatment options. The ECM, with collagen type I and elastin as major components, is the key structural component of the aortic wall and is recognized as a target tissue for both initiation and the progression of AAA. Molecular imaging allows in vivo measurement and characterization of biological processes at the cellular and molecular level and sets forth to visualize molecular abnormalities at an early stage of disease, facilitating novel diagnostic and therapeutic pathways. By providing surrogate criteria for the in vivo evaluation of the effects of pharmacological therapies, molecular imaging techniques targeting the ECM can facilitate pharmacological drug development. In addition, molecular targets can also be used in theranostic approaches that have the potential for timely diagnosis and concurrent medical therapy. Recent successes in preclinical studies suggest future opportunities for clinical translation. However, further clinical studies are needed to validate the most promising molecular targets for human application.

Interleukin 12p40 Deficiency Promotes Abdominal Aortic Aneurysm by Activating CCN2/MMP2 Pathways

Background Development of abdominal aortic aneurysm (AAA) is associated with proinflammatory cytokines including interleukin-12 (IL12). Deficiency of interleukin 12p40 (IL12p40) increases localized fibrotic events by promoting TGFβ2 (transforming growth factor β)-dependent anti-inflammatory response. Here, we determined whether IL12p40 deficiency in apolipoprotein E-/- mice attenuates the development of AAA by antagonizing proinflammatory response. Methods and Results Double knockout (DKO) mice were generated by crossbreeding IL12p40-/- mice with apolipoprotein E-/- mice (n=12). Aneurysmal studies were performed using angiotensin II (1 µg/kg/min; subcutaneous). Surprisingly, DKO mice did not prevent the development of AAA with angiotensin II infusion. Immunohistological analysis, however, showed distinct pathological features between apolipoprotein E-/- and DKO mice. Polymerase chain reaction (7 day) and cytokine arrays (28 day) of the aortic tissues from DKO mice showed significantly increased expression of cytokines related to anti-inflammatory response (interleukin 5 and interleukin 13), synthetic vascular smooth muscle cell phenotype (Activin receptor-like kinase-1 (ALK-1), artemin, and betacellulin) and T helper 17-associated response (4-1BB, interleukin-17e (Il17e) and Cd40 ligand (Cd-40L)). Indeed, DKO mice exhibited increased expression of the fibro-proteolytic pathway in the medial layer of aortae induced by cellular communication network factor 2 (CCN2) and Cd3+IL17+ cells compared with apolipoprotein E-/- mice. Laser capture microdissection showed predominant expression of CCN2/TGFβ2 in the medial layer of human AAA. Finally, Ccn2 haploinsufficiency in the mice showed decreased AAA incidence in response to elastase infusion, associated with decreased matrix metalloproteinase-2 expression. Conclusions Our study reveals novel roles for IL12p40 deficiency in inducing fibro-proteolytic activities in the aneurysmal mouse model. Mechanistically, these effects of IL12p40 deficiency are mediated by CCN2/matrix metalloproteinase-2 crosstalk in the medial layer of aneurysmal aortae.

GSK3 modulation in acute lung injury, myocarditis and polycystic kidney disease-related aneurysm

GSK3 are involved in different physical and pathological conditions and inflammatory regulated by macrophages contribute to significant mechanism. Infection stimuli may modulate GSK3 activity and influence host cell adaption, immune cells infiltration or cytokine expressions. To further address the role of GSK3 modulation in macrophages, the signal transduction of three major organs challenged by endotoxin, virus and genetic inherited factors are briefly introduced (lung injury, myocarditis and autosomal dominant polycystic kidney disease). As a result of pro-inflammatory and anti-inflammatory functions of GSK3 in different microenvironments and stages of macrophages (M1/M2), the rational resolution should be considered by adequately GSK3.

Macrophage Biology in Cardiovascular Diseases

Macrophages have a key functional role in the pathogenesis of various cardiovascular diseases, such as atherosclerosis and aortic aneurysms. Their accumulation within the vessel wall leads to sustained local inflammatory responses characterized by secretion of chemokines, cytokines, and matrix protein degrading enzymes. Here, we summarize some recent findings on macrophage contribution to cardiovascular disease. We focus on the origin, survival/death, and phenotypic switching of macrophages within vessel walls.

Mitochondrial metabolism in regulating macrophage polarization: an emerging regulator of metabolic inflammatory diseases

As a major type of immune cells with heterogeneity and plasticity, macrophages are classically divided into inflammatory (M1) and alternative/anti-inflammatory (M2) types and play a crucial role in the progress of the inflammatory diseases. Recent studies have shown that metabolism is an important determinant of macrophage phenotype. Mitochondria, one of the most important compartments involving cell metabolism, are closely associated with the regulation of cell functions. In most types of cell, mitochondrial oxidative phosphorylation (OXPHOS) is the primary mode of cellular energy production. However, mitochondrial OXPHOS is inhibited in activated M1 macrophages, rendering them unable to be converted into M2 phenotype. Thus, mitochondrial metabolism is a crucial regulator in macrophage functions. This review summarizes the roles of mitochondria in macrophage polarization and analyzes the molecular mechanisms underlying mitochondrial metabolism and function, which may provide new approaches for the treatment of metabolic inflammatory diseases.

Mechanism of TGF-β1 inhibiting Kupffer cell immune responses in cholestatic cirrhosis

Effect of exogenous transforming growth factor-β1 (TGF-β1) on cholestatic mice by inhibiting Kupffer cell immune responses in liver was investigated. To induce cholestasis, BALB/c mice received a sham operation (Mock group), or underwent a bile duct ligation (BDL group) and then were subcutaneously injected with TGF-β1 at multiple sites (TGF group). Liver functions were evaluated according to the levels of alanine aminotransferase (ALT), aspartate aminotransferase AST and γ-glutamyltranspeptidase (γ-GT) in serum samples. Expression of nuclear factor-κB (NF-κB), interleukin-6 (IL-6), IL-1β and tumor necrosis factor-α (TNF-α) was detected. Expression of inducible nitric oxide synthase (iNOS) and arginase-1 (Arg-1) in Kupffer cells (KCs) of the liver was detected. The isolated KCs were divided into control group, LPS group, TGF group and Galunisertib group and western blot analysis was used to detect the expression of NF-κB, IL-6, IL-1β, TNF-α, iNOS and Arg-1. The percentage of CD40, CD86, CD204 and CD206 as macrophage cell surface antigens were measured by flow cytometry. The indexes of liver function and liver fibrosis of the mice in the TGF group were significantly lower than those in the BDL group (P<0.05). The levels of IL-1β, IL-6 and TNF-α in the liver were lower than those in the BDL group, while the level of IL-10 was significantly increased (P<0.05). M2-type transformation occurred in liver Kupffer cells of mice in the TGF group. In cell experiments, TGF treatment downregulated the expression of IL-1β, IL-6, TNF-α and NF-κB, increased the expression of IL-10, and induced M2-type transformation in macrophages (P<0.05). In conclusion, TGF-ß1 diminished the progression of cholestasis in mice by inhibiting the inflammatory response of KCs and regulating KC polarization.

GSK2593074A blocks progression of existing abdominal aortic dilation

Objective

Receptor interacting proteins kinase 1 and 3 (RIPK1 and RIPK3) have been shown to play essential roles in the pathogenesis of abdominal aortic aneurysms (AAAs) by mediating necroptosis and inflammation. We previously discovered a small molecular inhibitor GSK2593074A (GSK’074) that binds to both RIPK1 and RIPK3 with high affinity and prevents AAA formation in mice. In this study, we evaluated whether GSK’074 can attenuate progression of existing AAA in the calcium phosphate model.

Methods

C57BL6/J mice were subjected to the calcium phosphate model of aortic aneurysm generation. Mice were treated with either GSK’074 (4.65 mg/kg/day) or dimethylsulfoxide (DMSO) controls starting 7 days after aneurysm induction. Aneurysm growth was monitored via ultrasound imaging every 7 days until harvest on day 28. Harvested aortas were examined via immunohistochemistry. The impact of GSK’074 on vascular smooth muscle cells and macrophages were evaluated via flow cytometry and transwell migration assay.

Results

At the onset of treatment, mice in both the control (DMSO) and GSK’074 groups showed similar degree of aneurysmal expansion. The weekly ultrasound imaging showed a steady aneurysm growth in DMSO-treated mice. The aneurysm growth was attenuated by GSK’074 treatment. At humane killing, GSK’074-treated mice had significantly reduced progression in aortic diameter from baseline as compared with the DMSO-treated mice (83.2% ± 13.1% [standard error of the mean] vs 157.2% ± 32.0% [standard error of the mean]; P < .01). In addition, the GSK’074-treated group demonstrated reduced macrophages (F4/80, CD206, MHCII), less gelatinase activity, a higher level of smooth muscle cell-specific myosin heavy chain, and better organized elastin fibers within the aortic walls compared with DMSO controls. In vitro, GSK’074 inhibited necroptosis in mouse aortic smooth muscle cells; whereas, it was able to prevent macrophage migration without affecting Il1b and Tnf expression.

Conclusions

GSK’074 is able to attenuate aneurysm progression in the calcium phosphate model. The ability to inhibit both vascular smooth muscle cell necroptosis and macrophage migration makes GSK’074 an attractive drug candidate for pharmaceutical treatment of aortic aneurysms.

Previous clinical trials evaluating pharmaceutical treatments in blocking aneurysm progression have failed. However, most agents used in those trials focused on inhibiting only one mechanism that contributes to aneurysm pathogenesis. In this study, we found GSK’074 is able to attenuate aneurysm progression in the calcium phosphate model by inhibiting both vascular smooth muscle cell necroptosis and macrophage migration, which are both key processes in the pathogenesis of aneurysm progression. The ability of GSK’0474 to inhibit multiple key pathologic mechanisms makes it an attractive therapeutic candidate for aneurysm progression.

Estrogen receptor β upregulates CCL2 via NF-κB signaling in endometriotic stromal cells and recruits macrophages to promote the pathogenesis of endometriosis

STUDY QUESTION

How is the activation of estrogen receptor β (ERβ) in endometriotic stromal cells (ESCs) involved in macrophage recruitment to promote the pathogenesis of endometriosis?

SUMMARY ANSWER

ERβ modulates the production of C-C motif chemokine ligand 2 (CCL2) via nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling in ESCs and thus recruits macrophages to ectopic lesions to promote pathogenesis.

WHAT IS KNOWN ALREADY

Macrophages are mainly recruited to the peritoneal cavity to promote the pathogenesis of endometriosis. Recent studies have demonstrated that ERβ plays an important role in the progression of endometriosis through modulating apoptosis and inflammation.

STUDY DESIGN, SIZE, DURATION

An observational study consisting of 22 cases (women with endometriosis, diagnosed by laparoscopy and histological analysis) and 14 controls (without endometriosis) was carried out.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Tissues and stromal cells that were isolated from 22 patients with ovarian endometrioma and deeply infiltrating endometriosis were compared with tissues and stromal cells from 14 patients with normal cycling endometrium using immunohistochemistry, quantitative PCR, Western blot, cell migration assay and cloning formation assay. P values < 0.05 were considered significant, and experiments were repeated in at least three different cell preparations.

MAIN RESULTS AND THE ROLE OF CHANCE

We observed that accumulated macrophages were recruited to the ectopic milieu and mainly adopted an alternatively activated macrophage (M2) phenotype. To reveal the underlying mechanism for this, we conducted a series of experiments and found that high expression of ERβ led to the production of CCL2 via NF-κB signaling and macrophages were recruited to the ectopic milieu. An in vitro co-culture assay also suggested that the recruited macrophages in turn could promote the proliferation and clonogenic ability of ESCs. Overall, the activation of ERβ in ESCs is involved in macrophage recruitment via NF-κB/CCL2 signaling and subsequently appears to promote the pathogenesis of endometriosis.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Due to the limitations of obtaining surgical specimens, endometrioma tissues were collected mainly from women diagnosed with middle to late stage endometriosis. We identified the predominant presence of M2 macrophages in the samples used in our study, but the underlying mechanism of how recruited macrophages acquire the M2 phenotype is undefined.

WIDER IMPLICATIONS OF THE FINDINGS

This work provides novel insight into the mechanism by which ERβ may modulate macrophage infiltration and promote pathogenesis, which may provide a new therapeutic target for endometriosis.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Natural Science Foundation of China (81671430). The authors have no conflicts of interest.

Extracellular Vesicles as Therapeutic Agents for Cardiac Fibrosis

Heart disease remains an increasing major public health challenge in the United States and worldwide. A common end-organ feature in diseased hearts is myocardial fibrosis, which stiffens the heart and interferes with normal pump function, leading to pump failure. The development of cells for regenerative therapy has been met with many pitfalls on its path to clinical translation. Recognizing that regenerative cells secrete therapeutically bioactive vesicles has paved the way to circumvent many failures of cell therapy. In this review, we provide an overview of extracellular vesicles (EVs), with a focus on their utility as therapeutic agents for cardiac regeneration. We also highlight the engineering potential of EVs to enhance their therapeutic application.

The Role of a Selective P2Y6 Receptor Antagonist, MRS2578, on the Formation of Angiotensin II-Induced Abdominal Aortic Aneurysms

Objective

The P2Y₆ receptor has been shown to be involved in many cardiovascular diseases, including hypertension and atherosclerosis. The study is aimed at exploring the role of the P2Y₆ receptor in Ang II-induced abdominal aortic aneurysm (AAA) formation in apolipoprotein E-deficient (apoE^−/−) mice by using its selective antagonist.

Methods

Male apoE^−/− mice were fed with high-fat diet and infused with angiotensin (Ang) II (1000 ng/kg/min) for 4 weeks to induce AAA or saline as controls. Mice were divided into four groups: normal saline (NS, placebo control) group (n = 8), Ang II+vehicle (Ang II) group (n = 14), Ang II-low dose MRS2578 (Ang II+MRS-16 mg) group (n = 14), and Ang II-high dose MRS2578 (Ang II+MRS-32 mg) group (n = 14). Daily intraperitoneal injection with vehicle or MRS2578 was pretreated one week before Ang II infusion. On postoperative day 10, aorta imaging of each group was taken by ultrasonography. After 4 weeks of Ang II infusion, the excised aortas were processed for diameter measurement and quantification of aneurysm severity and tissue characteristics; the blood samples were collected for measurement of the lipid profile and levels of cytokines. Verhoeff's Van Gieson (EVG) staining and immunochemistry staining were performed to evaluate disruption of the extracellular matrix (ECM) and infiltration of macrophages. Expression and activity of matrix metalloproteinases (MMPs) was measured by gelatin zymography.

Results

Treatment with MRS2578 made no significant difference in AAA formation, and maximal aortic diameter yet caused higher AAA rupture-induced mortality from 7% (Ang II) to 21.4% (Ang II+MRS-16 mg) or 42.9% (Ang II+MRS-32 mg), respectively (p < 0.05). Consistently, the severity of aneurysm tended to be more deteriorated in MRS2578-treated groups, especially the high-dosage group. The ratios of type III and IV aneurysm were much higher in the MRS2578-coadministered groups (p < 0.05). Furthermore, histological analyses showed that administration of MRS2578 significantly increased infiltration of macrophages, expression of monocyte chemotactic protein 1 (MCP-1) and vascular cell adhesion molecule-1 (VCAM-1), and activities of MMP-2 and MMP-9 followed by aggravating degradation elastin in vivo (p < 0.05). However, the multiple effects of MRS2578 on the development of AAA are independent of changes in systolic blood pressure and lipid profiles.

Conclusions

The present study demonstrated that administration of MRS2578 exacerbated the progression and rupture of experimental AAA through promoting proinflammatory response and MMP expression and activity, which indicated a crucial role of the P2Y₆ receptor in AAA development. Clinical Relevance. Purinergic P2Y receptors have attracted much attention since the P2Y₁₂ receptor antagonist had been successfully applied in clinical practice. Elucidating the underlying mechanisms of AAA and exploring potential therapeutic strategies are essential to prevent its progression and reduce the mortality rate.

Mesenchymal stem cell-derived conditioned medium attenuate angiotensin II-induced aortic aneurysm growth by modulating macrophage polarization

Mesenchymal stem cells (MSCs) exhibit therapeutic benefits on aortic aneurysm (AA); however, the molecular mechanisms are not fully understood. The current study aimed to investigate the therapeutic effects and potential mechanisms of murine bone marrow MSC (BM‐MSCs)–derived conditioned medium (MSCs‐CM) on angiotensin II (AngII)‐induced AA in apolipoprotein E‐deficient (apoE^−/−) mice. Murine BM‐MSCs, MSCs‐CM or control medium were intravenously administrated into AngII‐induced AA in apoE^−/− mice. Mice were sacrificed at 2 weeks after injection. BM‐MSCs and MSCs‐CM significantly attenuated matrix metalloproteinase (MMP)‐2 and MMP‐9 expression, aortic elastin degradation and AA growth at the site of AA. These treatments with BM‐MSCs and MSCs‐CM also decreased Ly6c^high monocytes in peripheral blood on day 7 and M1 macrophage infiltration in AA tissues on day 14, whereas they increased M2 macrophages. In addition, BM‐MSCs and MSCs‐CM reduced MCP‐1, IL‐1Ra and IL‐6 expression and increased IL‐10 expression in AA tissues. In vitro, peritoneal macrophages were co‐cultured with BM‐MSCs or fibroblasts as control in a transwell system. The mRNA and protein expression of M2 macrophage markers were evaluated. IL‐6 and IL‐1β were reduced, while IL‐10 was increased in the BM‐MSC systems. The mRNA and protein expression of M2 markers were up‐regulated in the BM‐MSC systems. Furthermore, high concentration of IGF1, VEGF and TGF‐β1 was detected in MSCs‐CM. Our results suggest that MSCs‐CM could prevent AA growth potentially through regulating macrophage polarization. These results may provide a new insight into the mechanisms of BM‐MSCs in the therapy of AA.

Interleukin-12 and -23 blockade mitigates elastase-induced abdominal aortic aneurysm

Macrophages play an important role in the inflammatory process that contributes to the development of abdominal aortic aneurysm (AAA). Studies of human and mouse AAA tissue reveal expanded populations of macrophages producing an abundance of pro-inflammatory cytokines, including TNF-α, IL-12p40 and high level of metalloprotease 9 (MMP-9) at the late stages of disease. Herein, we show that blockade of IL-12p40 in the early phase of aneurysm development suppresses macrophage expansion, inflammatory cytokine and MMP-9 production and mitigates AAA development. Since IL-12 and IL-23 are related cytokines that share the common p40 subunit, we also evaluate the effect of direct IL-23 blockade on the development of AAA. Specific IL-23p19 blockade prevents AAA progression with the same efficiency as IL-12p40 antagonism, suggesting that the efficacy of anti-IL-12p40 treatment may reflect IL-23 blockade. IL-12p40 and IL-23p19 are also abundantly expressed in human AAA tissue. Our findings have potential translational value since IL-12p40 and IL-23p19 antagonists already exist as FDA-approved therapeutics for various chronic inflammatory conditions.