Inhibiting the Th17/IL-17A–Related Inflammatory Responses With Digoxin Confers Protection Against Experimental Abdominal Aortic Aneurysm

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.

Oxidative Stress and the Pathogenesis of Aortic Aneurysms

Aortic aneurysms are responsible for significant morbidity and mortality. Despite their clinical significance, there remain critical knowledge gaps in the pathogenesis of aneurysm disease and the mechanisms involved in aortic rupture. Recent studies have drawn attention to the role of reactive oxygen species (ROS) and their down-stream effectors in chronic cardiovascular diseases and specifically in the pathogenesis of aortic aneurysm formation. This review will discuss current mechanisms of ROS in mediating aortic aneurysms, the failure of endogenous antioxidant systems in chronic vascular diseases, and their relation to the development of aortic aneurysms.

Interleukin-17 plays a role in dental pulp inflammation mediated by zoledronic acid: a mechanism unrelated to the Th17 immune response?

OBJECTIVE

To evaluate the influence of RORγT inhibition by digoxin on inflammatory changes related to interleukin-17 (IL-17) in the pulp of rats treated with zoledronate (ZOL).

METHODOLOGY

Forty male Wistar rats were divided into a negative control group (NCG) treated with saline solution, a positive control group (PCG) treated with ZOL (0.20 mg/kg), and three groups treated with ZOL and co-treated with digoxin 1, 2, or 4 mg/kg (DG1, 2, and 4). After four intravenous administrations of ZOL or saline solution in a 70-day protocol, the right molars were evaluated by histomorphometry (number of blood vessels, blood vessels/µm2, cells/µm2, total blood vessel area, and average blood vessel area) and immunohistochemistry (IL-17, TNF-α, IL-6, and TGF-β). The Kruskal-Wallis/Dunn test was used for statistical analysis.

RESULTS

PCG showed an increase in total blood vessel area (p=0.008) and average blood vessel area (p=0.014), and digoxin treatment reversed these changes. DG4 showed a reduction in blood vessels/µm2 (p<0.001). In PCG odontoblasts, there was an increase in IL-17 (p=0.002) and TNF-α (p=0.002) immunostaining, and in DG4, these changes were reversed. Odontoblasts in the digoxin-treated groups also showed an increase in IL-6 immunostaining (p<0.001) and a reduction in TGF-β immunostaining (p=0.002), and all ZOL-treated groups showed an increase in IL-17 (p=0.011) and TNF-α (p=0.017) in non-odontoblasts cells.

CONCLUSION

ZOL induces TNF-α- and IL-17-dependent vasodilation and ectasia, and the classical Th17 response activation pathway does not seem to participate in this process.

An evidence update to explore molecular targets and protective mechanisms of apigenin against abdominal aortic aneurysms based on network pharmacology and experimental validation

Abdominal aortic aneurysms (AAA) is a life-threatening disease and the incidence of AAA is still on the rise in recent years. Numerous studies suggest that dietary moderate consumption of polyphenol exerts beneficial effects on cardiovascular disease. Apigenin (API) is a promising dietary polyphenol and possesses potent beneficial effects on our body. Although our previous study revealed protective effects of API on experimental AAA formation, up till now few studies were carried out to further investigate its involved molecular mechanisms. In the present study, network pharmacology combined molecular docking and experimental validation was used to explore API-related therapeutic targets and mechanisms in the treatment of AAA. Firstly, we collected 202 API-related therapeutic targets and 2475 AAA-related pathogenetic targets. After removing duplicates, a total of 68 potential therapeutic targets were obtained. Moreover, 5 targets with high degree including TNF, ACTB, INS, JUN, and MMP9 were identified as core targets of API for treating AAA. In addition, functional enrichment analysis indicated that API exerted pharmacological effects in AAA by affecting versatile mechanisms, including apoptosis, inflammation, blood fluid dynamics, and immune modulation. Molecular docking results further supported that API had strong affinity with the above core targets. Furthermore, protein level of core targets and related pathways were evaluated in a Cacl2-induced AAA model by using western blot and immunohistochemistry. The experimental validation results demonstrated that API significantly attenuated phosphorylation of JUN and protein level of predicted core targets. Taken together, based on network pharmacological and experimental validation, our study systematically explored associated core targets and potential therapeutic pathways of API for AAA treatment, which could supply valuable insights and theoretical basis for AAA treatment.

T cells in abdominal aortic aneurysm: immunomodulation and clinical application

Abdominal aortic aneurysm (AAA) is characterized by inflammatory cell infiltration, extracellular matrix (ECM) degradation, and vascular smooth muscle cell (SMC) dysfunction. The inflammatory cells involved in AAA mainly include immune cells including macrophages, neutrophils, T-lymphocytes and B lymphocytes and endothelial cells. As the blood vessel wall expands, more and more lymphocytes infiltrate into the outer membrane. It was found that more than 50% of lymphocytes in AAA tissues were CD3+ T cells, including CD4+, CD8+T cells, γδ T cells and regulatory T cells (Tregs). Due to the important role of T cells in inflammatory response, an increasing number of researchers have paid attention to the role of T cells in AAA and dug into the relevant mechanism. Therefore, this paper focuses on reviewing the immunoregulatory role of T cells in AAA and their role in immunotherapy, seeking potential targets for immunotherapy and putting forward future research directions.

Blood immunological profile of abdominal aortic aneurysm based on autoimmune injury

Abdominal aortic aneurysm (AAA) occupies a large part of aorta aneurysm, and if there's no timely intervention or treatment, the risks of rupture and death would rise sharply. With the depth of research in AAA, more and more evidence showed correlations between AAA and autoimmune injury. Currently, a variety of bioactive peptides and cells have been confirmed to be related with AAA progression. Despite the tremendous progress, more than half researches were sampling from lesion tissues, which would be difficult to obtain. Given that the intrusiveness and convenience, serological test take advantages in initial diagnosis. Here we review blood biomarkers associated with autoimmune injury work in AAA evolution, aiming to make a profile on blood immune substances of AAA and provide a thought for potential clinical practice.

Mechanisms and efficacy of metformin-mediated suppression of established experimental abdominal aortic aneurysms

Objective

Metformin treatment attenuates experimental abdominal aortic aneurysm (AAA) formation, as well as reduces clinical AAA diameter enlargement in patients with diabetes. The mechanisms of metformin-mediated aneurysm suppression, and its efficacy in suppressing established experimental aneurysms, remain uncertain.

Methods

Experimental AAAs were created in male C57BL/6J mice via intra-aortic infusion of porcine pancreatic elastase. Metformin alone (250 mg/kg), or metformin combined with the 5' AMP-activated protein kinase (AMPK) antagonist Compound C (10 mg/kg), were administered to respective mouse cohorts daily beginning 4 days following AAA induction. Further AAA cohorts received either the AMPK agonist AICA riboside (500 mg/kg) as positive, or vehicle (saline) as negative, controls. AAA progression in all groups was assessed via serial in vivo ultrasonography and histopathology at sacrifice. Cytokine-producing T cells and myeloid cellularity were determined by flow cytometric analyses.

Results

Metformin limited established experimental AAA progression at 3 (-85%) and 10 (-68%) days following treatment initiation compared with saline control. Concurrent Compound C treatment reduced this effect by approximately 50%. In metformin-treated mice, reduced AAA progression was associated with relative elastin preservation, smooth muscle cell preservation, and reduced mural leukocyte infiltration and neoangiogenesis compared with vehicle control group. Metformin also resulted in reduced interferon-γ-, but not interleukin-10 or -17, producing splenic T cells in aneurysmal mice. Additionally, metformin therapy increased circulating and splenic inflammatory monocytes (CD11b⁺Ly-6C^high), but not neutrophils (CD11b⁺Ly-6G⁺), with no effect on respective bone marrow cell populations.

Conclusions

Metformin treatment suppresses existing experimental AAA progression in part via AMPK agonist activity, limiting interferon-γ-producing T cell differentiation while enhancing circulating and splenic inflammatory monocyte retention.

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.

Immune and inflammatory mechanisms of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a life-threatening cardiovascular disease. Immune-mediated infiltration and a destruction of the aortic wall during AAA development plays significant role in the pathogenesis of this disease. While various immune cells had been found in AAA, the mechanisms of their activation and function are still far from being understood. A better understanding of mechanisms regulating the development of aberrant immune cell activation in AAA is essential for the development of novel preventive and therapeutic approaches. In this review we summarize current knowledge about the role of immune cells in AAA and discuss how pathogenic immune cell activation is regulated in this disease.

Potential of Disease-Modifying Anti-Rheumatic Drugs to Limit Abdominal Aortic Aneurysm Growth

Inflammation is strongly implicated in the pathogenesis of abdominal aortic aneurysms (AAA). This review examined the potential role of biologic disease-modifying anti-rheumatic drugs (bDMARDs) as repurposed drugs for treating AAA. Published evidence from clinical and preclinical studies was examined. Findings from animal models suggested that a deficiency or inhibition of tumour necrosis factor-α (TNF-α) (standard mean difference (SMD): −8.37, 95% confidence interval (CI): −9.92, −6.82), interleukin (IL)-6 (SMD: −1.44, 95% CI: −2.85, −0.04) and IL-17 (SMD: −3.36, 95% CI: −4.21, −2.50) led to a significantly smaller AAA diameter compared to controls. Human AAA tissue samples had significantly increased TNF-α (SMD: 1.68, 95% CI: 0.87, 2.49), IL-1β (SMD: 1.93, 95% CI: 1.08, 2.79), IL-6 (SMD: 2.56, 95% CI: 1.79, 3.33) and IL-17 (SMD: 6.28, 95% CI: 3.57, 8.99) levels compared to non-AAA controls. In human serum, TNF-α (SMD: 1.11, 95% CI: 0.25, 1.97) and IL-6 (SMD: 1.42, 95% CI: 0.91, 1.92) levels were significantly elevated compared to non-AAA controls. These findings implicate TNF-α, IL-17 and IL-6 in AAA pathogenesis. Randomised controlled trials testing the value of bDMARDs in limiting AAA growth may be warranted.

Role of Extracellular Matrix and Inflammation in Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is one of the most dangerous cardiovascular diseases, occurring mainly in men over the age of 55 years. As it is asymptomatic, patients are diagnosed very late, usually when they suffer pain in the abdominal cavity. The late detection of AAA contributes to the high mortality rate. Many environmental, genetic, and molecular factors contribute to the development and subsequent rupture of AAA. Inflammation, apoptosis of smooth muscle cells, and degradation of the extracellular matrix in the AAA wall are believed to be the major molecular processes underlying AAA formation. Until now, no pharmacological treatment has been implemented to prevent the formation of AAA or to cure the disease. Therefore, it is important that patients are diagnosed at a very early stage of the disease. Biomarkers contribute to the assessment of the concentration level, which will help to determine the level and rate of AAA development. The potential biomarkers today include homocysteine, cathepsins, osteopontin, and osteoprotegerin. In this review, we describe the major aspects of molecular processes that take place in the aortic wall during AAA formation. In addition, biomarkers, the monitoring of which will contribute to the prompt diagnosis of AAA patients over the age of 55 years, are described.

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.

Statin therapy protects against abdominal aortic aneurysms by inducing the accumulation of regulatory T cells in ApoE-/- mice

CD4⁺CD25⁺ regulatory T cells (Tregs) have been shown to protect against abdominal aortic aneurysm (AAA) progression. Statins have immunomodulatory properties, and their effect on AAA partly depends on immune-related mechanisms. In this study, we aimed to explore whether there is an association between statins and Tregs in AAA progression. Sixty ApoE^-/- mice were randomly divided into four groups (n = 15 per group): A, saline group; B, control group; C, simvastatin group (intragastric administration of simvastatin); and D, PC61 group (simvastatin combined with an intraperitoneal injection of 100 μg CD25-depleting antibody PC61). After 2 weeks of simvastatin treatment, the mice received a continuous subcutaneous infusion of angiotensin II (Ang II; B, C, and D groups) or saline (A group) for 28 days. Simvastatin therapy for 6 weeks significantly decreased the incidence and severity of AAA and inhibited the apoptosis of smooth muscle cells and generation of reactive oxygen species, which was partly abolished after the injection of PC61 antibody. Importantly, simvastatin increased the number of Tregs and the levels of Treg-associated cytokines (TGF-β and IL-10) and decreased the level of IL-17 both in aortic tissues and serum. Interestingly, simvastatin attenuated Ang II-induced gut microbial dysbiosis, which might be associated with the accumulation of Tregs. In conclusion, simvastatin therapy prevented the development of AAA induced by Ang II in ApoE^-/- mice, which might be partly due to the induction of Treg accumulation. In addition, simvastatin regulated gut microbial dysbiosis, which might also be associated with Treg generation.

Fibrillin-1-regulated miR-122 has a critical role in thoracic aortic aneurysm formation

Thoracic aortic aneurysms (TAA) in Marfan syndrome, caused by fibrillin-1 mutations, are characterized by elevated cytokines and fragmentated elastic laminae in the aortic wall. This study explored whether and how specific fibrillin-1-regulated miRNAs mediate inflammatory cytokine expression and elastic laminae degradation in TAA. miRNA expression profiling at early and late TAA stages using a severe Marfan mouse model (Fbn1mgR/mgR) revealed a spectrum of differentially regulated miRNAs. Bioinformatic analyses predicted the involvement of these miRNAs in inflammatory and extracellular matrix-related pathways. We demonstrate that upregulation of pro-inflammatory cytokines and matrix metalloproteinases is a common characteristic of mouse and human TAA tissues. miR-122, the most downregulated miRNA in the aortae of 10-week-old Fbn1mgR/mgR mice, post-transcriptionally upregulated CCL2, IL-1β and MMP12. Similar data were obtained at 70 weeks of age using Fbn1C1041G/+ mice. Deficient fibrillin-1-smooth muscle cell interaction suppressed miR-122 levels. The marker for tissue hypoxia HIF-1α was upregulated in the aortic wall of Fbn1mgR/mgR mice, and miR-122 was reduced under hypoxic conditions in cell and organ cultures. Reduced miR-122 was partially rescued by HIF-1α inhibitors, digoxin and 2-methoxyestradiol in aortic smooth muscle cells. Digoxin-treated Fbn1mgR/mgR mice demonstrated elevated miR-122 and suppressed CCL2 and MMP12 levels in the ascending aortae, with reduced elastin fragmentation and aortic dilation. In summary, this study demonstrates that miR-122 in the aortic wall inhibits inflammatory responses and matrix remodeling, which is suppressed by deficient fibrillin-1-cell interaction and hypoxia in TAA.

Cytokines in Abdominal Aortic Aneurysm: Master Regulators With Clinical Application

Abdominal aortic aneurysm (AAA) is a potentially life-threatening disorder with a mostly asymptomatic course where the abdominal aorta is weakened and bulged. Cytokines play especially important roles (both positive and negative) among the molecular actors of AAA development. All the inflammatory cascades, extracellular matrix degradation and vascular smooth muscle cell apoptosis are driven by cytokines. Previous studies emphasize an altered expression and a changed epigenetic regulation of key cytokines in AAA tissue samples. Such cytokines as IL-6, IL-10, IL-12, IL-17, IL-33, IL-1β, TGF-β, TNF-α, IFN-γ, and CXCL10 seem to be crucial in AAA pathogenesis. Some data obtained in animal studies show a protective function of IL-10, IL-33, and canonical TGF-β signaling, as well as a dual role of IL-4, IFN-γ and CXCL10, while TNF-α, IL-1β, IL-6, IL-12/IL-23, IL-17, CCR2, CXCR2, CXCR4 and the TGF-β noncanonical pathway are believed to aggravate the disease. Altogether data highlight significance of cytokines as informative markers and predictors of AAA. Pathologic serum/plasma concentrations of IL-1β, IL-2, IL-6, TNF-α, IL-10, IL-8, IL-17, IFN-γ, and PDGF have been already found in AAA patients. Some of the changes correlate with the size of aneurysms. Moreover, the risk of AAA is associated with polymorphic variants of genes encoding cytokines and their receptors: CCR2 (rs1799864), CCR5 (Delta-32), IL6 (rs1800796 and rs1800795), IL6R (rs12133641), IL10 (rs1800896), TGFB1 (rs1800469), TGFBR1 (rs1626340), TGFBR2 (rs1036095, rs4522809, rs1078985), and TNFA (rs1800629). Finally, 5 single-nucleotide polymorphisms in gene coding latent TGF-β-binding protein (LTBP4) and an allelic variant of TGFB3 are related to a significantly slower AAA annual growth rate.

Interleukin 17, the double-edged sword in atherosclerosis

Cardiovascular diseases, including atherosclerosis, are the number one cause of death worldwide. These diseases have taken the place of pneumonia and other infectious diseases in the epidemiological charts. Thus, their importance should not be underestimated. Atherosclerosis is an inflammatory disease. Therefore, immunological signaling molecules and immune cells carry out a central role in its etiology. One of these signaling molecules is interleukin (IL)-17. This relatively newly discovered signaling molecule might have a dual role as acting both pro-atherogenic and anti-atherogenic depending on the situation. The majority of articles have discussed IL-17 and its action in atherosclerosis, and it may be a new target for the treatment of patients with this disease. In this review, the immunological basis of atherosclerosis with an emphasis on the role of IL-17 and a brief explanation of the role of IL-17 on atherosclerogenic disorders will be discussed.

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.

Digoxin targets low density lipoprotein receptor-related protein 4 and protects against osteoarthritis

OBJECTIVES

Dysregulated chondrocyte metabolism is closely associated with the pathogenesis of osteoarthritis (OA). Suppressing chondrocyte catabolism to restore cartilage homeostasis has been extensively explored, whereas far less effort has been invested toward enhancing chondrocyte anabolism. This study aimed to repurpose clinically approved drugs as potential stimulators of chondrocyte anabolism in treating OA.

METHODS

Screening of a Food and Drug Administration-approved drug library; Assays for examining the chondroprotective effects of digoxin in vitro; Assays for defining the therapeutic effects of digoxin using a surgically-induced OA model; A propensity-score matched cohort study using The Health Improvement Network to examine the relationship between digoxin use and the risk of joint OA-associated replacement among patients with atrial fibrillation; identification and characterisation of the binding of digoxin to low-density lipoprotein receptor-related protein 4 (LRP4); various assays, including use of CRISPR-Cas9 genome editing to delete LRP4 in human chondrocytes, for examining the dependence on LRP4 of digoxin regulation of chondrocytes.

RESULTS

Serial screenings led to the identification of ouabain and digoxin as stimulators of chondrocyte differentiation and anabolism. Ouabain and digoxin protected against OA and relieved OA-associated pain. The cohort study of 56 794 patients revealed that digoxin use was associated with reduced risk of OA-associated joint replacement. LRP4 was isolated as a novel target of digoxin, and deletion of LRP4 abolished digoxin's regulations of chondrocytes.

CONCLUSIONS

These findings not only provide new insights into the understanding of digoxin's chondroprotective action and underlying mechanisms, but also present new evidence for repurposing digoxin for OA.

An Experimental Study: Benefits of Digoxin on Hepatotoxicity Induced by Methotrexate Treatment

Purpose

The aim of the study is to examine the possible therapeutic effects of a known cardiac glycoside, digoxin, on a rat model of MTX-induced hepatotoxicity.

Methods

The study was conducted on twenty-four male rats. While eighteen rats received a single dose of 20 mg/kg MTX to obtain an injured liver model, six rats constituted the control group. Also, the eighteen liver toxicity model created rats were equally divided into two groups, one of which received digoxin 0.1 mg/kg/day digoxin (Group 1) and the other group (Group 2) was given saline (% 0.9NaCl) with a dose of 1 ml/kg/day for ten days. Following the trial, the rats were sacrificed to harvest blood and liver tissue samples to determine blood and tissue MDA, serum ALT, plasma TNF-α, TGF-β, IL-6, IL-1-Beta, and PTX3 levels.

Results

MTX's structural and functional hepatotoxicity was observable and evidenced by relatively worse histopathological scores and increased biochemical marker levels. Digoxin treatment significantly reduced the liver enzyme ALT, plasma TNF-α, TGF-β, PTX3, and MDA levels and decreased histological changes in the liver tissue with MTX-induced hepatotoxicity in the rat model.

Conclusion

We suggest that digoxin has an anti-inflammatory and antihepatotoxic effect on the MTX-induced liver injury model.

Translating mouse models of abdominal aortic aneurysm to the translational needs of vascular surgery

Introduction

Abdominal aortic aneurysm (AAA) is a condition that has considerable socioeconomic impact and an eventual rupture is associated with high mortality and morbidity. Despite decades of research, surgical repair remains the treatment of choice and no medical therapy is currently available. Animal models and, in particular, murine models, of AAA are a vital tool for experimental in vivo research. However, each of the different models has individual limitations and provide only partial mimicry of human disease. This narrative review addresses the translational potential of the available mouse models, highlighting unanswered questions from a clinical perspective. It is based on a thorough presentation of the available literature and more than a decade of personal experience, with most of the available models in experimental and translational AAA research.

Results

From all the models published, only the four inducible models, namely the angiotensin II model (AngII), the porcine pancreatic elastase perfusion model (PPE), the external periadventitial elastase application (ePPE), and the CaCl₂ model have been widely used by different independent research groups. Although the angiotensin II model provides features of dissection and aneurysm formation, the PPE model shows reliable features of human AAA, especially beyond day 7 after induction, but remains technically challenging. The translational value of ePPE as a model and the combination with β-aminopropionitrile to induce rupture and intraluminal thrombus formation is promising, but warrants further mechanistic insights. Finally, the external CaCl₂ application is known to produce inflammatory vascular wall thickening. Unmet translational research questions include the origin of AAA development, monitoring aneurysm growth, gender issues, and novel surgical therapies as well as novel nonsurgical therapies.

Conclusion

New imaging techniques, experimental therapeutic alternatives, and endovascular treatment options provide a plethora of research topics to strengthen the individual features of currently available mouse models, creating the possibility of shedding new light on translational research questions.

MiR-191 as a Key Molecule in Aneurysmal Aortic Remodeling

Abdominal aortic aneurysms (AAA) are a complex disease with an unclear pathomechanism. A positive family history is emphasized as a significant risk factor, and a nonspecific model of inheritance suggests participation of epigenetic regulation in the pathogenesis of this disease. Past studies have implicated microRNAs in the development of AAA; therefore in this project, we measured miR-191 levels in AAA patients and compared them with a control group. We found that miR-191 levels were significantly elevated in aneurysmal patients, although this did not correlate with the available clinical data. We then developed an in vitro model where, using cells with an endothelial phenotype, we determined the effect of miR-191 on the transcriptome using RNA sequencing. Subsequent pathway analysis established that some of the perturbations mediated by miR-191 can be explained by several processes which have long been observed and described in literature as accompanying the development of abdominal aortic aneurysms.

Recombinant Interleukin-19 Suppresses the Formation and Progression of Experimental Abdominal Aortic Aneurysms

Background Interleukin-19 is an immunosuppressive cytokine produced by immune and nonimmune cells, but its role in abdominal aortic aneurysm (AAA) pathogenesis is not known. This study aimed to investigate interleukin-19 expression in, and influences on, the formation and progression of experimental AAAs. Methods and Results Human specimens were obtained at aneurysm repair surgery or from transplant donors. Experimental AAAs were created in 10- to 12-week-old male mice via intra-aortic elastase infusion. Influence and potential mechanisms of interleukin-19 treatment on AAAs were assessed via ultrasonography, histopathology, flow cytometry, and gene expression profiling. Immunohistochemistry revealed augmented interleukin-19 expression in both human and experimental AAAs. In mice, interleukin-19 treatment before AAA initiation via elastase infusion suppressed aneurysm formation and progression, with attenuation of medial elastin degradation, smooth-muscle depletion, leukocyte infiltration, neoangiogenesis, and matrix metalloproteinase 2 and 9 expression. Initiation of interleukin-19 treatment after AAA creation limited further aneurysmal degeneration. In additional experiments, interleukin-19 treatment inhibited murine macrophage recruitment following intraperitoneal thioglycolate injection. In classically or alternatively activated macrophages in vitro, interleukin-19 downregulated mRNA expression of inducible nitric oxide synthase, chemokine C-C motif ligand 2, and metalloproteinases 2 and 9 without apparent effect on cytokine-expressing helper or cytotoxic T-cell differentiation, nor regulatory T cellularity, in the aneurysmal aorta or spleen of interleukin-19-treated mice. Interleukin-19 also suppressed AAAs created via angiotensin II infusion in hyperlipidemic mice. Conclusions Based on human evidence and experimental modeling observations, interleukin-19 may influence the development and progression of AAAs.

Cardiac Glycosides as Immune System Modulators

Cardiac glycosides (CGs) are natural steroid compounds occurring both in plants and animals. They are known for long as cardiotonic agents commonly used for various cardiac diseases due to inhibition of Na⁺/K⁺-ATPase (NKA) pumping activity and modulating heart muscle contractility. However, recent studies show that the portfolio of diseases potentially treatable with CGs is much broader. Currently, CGs are mostly studied as anticancer agents. Their antiproliferative properties are based on the induction of multiple signaling pathways in an NKA signalosome complex. In addition, they are strongly connected to immunogenic cell death, a complex mechanism of induction of anticancer immune response. Moreover, CGs exert various immunomodulatory effects, the foremost of which are connected with suppressing the activity of T-helper cells or modulating transcription of many immune response genes by inhibiting nuclear factor kappa B. The resulting modulations of cytokine and chemokine levels and changes in immune cell ratios could be potentially useful in treating sundry autoimmune and inflammatory diseases. This review aims to summarize current knowledge in the field of immunomodulatory properties of CGs and emphasize the large area of potential clinical use of these compounds.

Sex-Based Differences Among Experimental Swine Abdominal Aortic aneurysms

BACKGROUND

Female sex protects against abdominal aortic aneurysms (AAAs); however, the mechanisms behind these sex-based differences remain unknown. The purpose of this study was to explore the role of sex and sex hormones in AAA formation among swine.

MATERIALS AND METHODS

Using a previous validated model, infrarenal AAA were surgically created in uncastrated male (n = 8), female (n = 5), and castrated male (n = 4) swine. Aortic dilation was measured on postoperative day 28 during the terminal procedure and compared to initial aortic diameter measured during the index procedure. Tissue was analyzed for immunohistochemistry, cytokine array, gelatin zymography, serum 17β-estradiol, and testosterone assay.

RESULTS

Uncastrated males had significantly larger maximal aortic dilation compared to castrated males (113.5% ± 11.4% versus 38.1% ± 4.5%, P = 0.0012). Females had significantly higher mean aortic dilation compared to castrated males (96.2% ± 7.5% versus 38.1% ± 4.5%, P = 0.0004). Aortic diameters between females and uncastrated males were not significantly different on day 28. Female swine had significantly higher concentrations of 17β-estradiol compared with uncastrated males (1590 ± 873.3 ng/mL versus 95.2 ± 2.3 ng/mL, P = 0.047), with no significant difference between females and castrated males. Uncastrated male AAA demonstrated significantly more elastin degradation compared with female and castrated males (P = 0.01 and <0 .01, respectively). No differences existed for T-cells or smooth muscle cells between groups. Multiple proinflammatory cytokines were elevated within uncastrated male aortic walls compared to females and castrated males.

CONCLUSIONS

Sex hormones, specifically 17β-estradiol and testosterone, influence experimental swine AAA formation as demonstrated by increased aneurysm size, collagen turnover, and elastolysis in uncastrated males in processes reflective of human disease.

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.

NSun2 regulates aneurysm formation by promoting autotaxin expression and T cell recruitment

Abdominal aortic aneurysm (AAA) is characterized by inflammatory cell infiltration and aggravated by hyperhomocysteinemia (HHcy). It is unknown whether the homocysteine (Hcy)-activated RNA methyltransferase NOP2/Sun domain family member 2 (NSun2) is associated with AAA. Here, we found that NSun2 deficiency significantly attenuated elastase-induced and HHcy-aggravated murine AAA with decreased T cell infiltration in the vessel walls. T cell labeling and adoptive transfer experiments confirmed that NSun2 deficiency inhibited the chemotaxis of vessels to T cells. RNA sequencing of endothelial cells showed that Hcy induced the accumulation of various metabolic enzymes of the phospholipid PC-LPC-LPA metabolic pathway, especially autotaxin (ATX). In the elastase-induced mouse model of AAA, ATX was specifically expressed in the endothelium and the plasma ATX concentration was upregulated and even higher in the HHcy group, which were decreased dramatically by NSun2 knockdown. In vitro Transwell experiments showed that ATX dose-dependently promoted T cell migration. HHcy may upregulate endothelial ATX expression and secretion and in turn recruit T cells into the vessel walls to induce vascular inflammation and consequently accelerate the pathogenesis of AAA. Mechanistically, secreted ATX interacted with T cells by binding to integrin α4, which subsequently activated downstream FAK/Src-RhoA signaling pathways and then induced T cell chemokinesis and adhesion. ATX overexpression in the vessel walls reversed the inhibited development of AAA in the NSun2-deficient mice. Therefore, NSun2 mediates the development of HHcy-aggravated AAA primarily by increasing endothelial ATX expression, secretion and T cell migration, which is a novel mechanism for HHcy-aggravated vascular inflammation and pathogenesis of AAA.

Natural products as modulators of retinoic acid receptor-related orphan receptors (RORs)

Covering: 1994 to 2020 Retinoic acid receptor-related orphan receptors (RORs) belong to a subfamily of the nuclear receptor superfamily and possess prominent roles in circadian rhythm, metabolism, inflammation, and cancer. They have been subject of research for over two decades and represent attractive but challenging drug targets. Natural products were among the first identified ligands of RORs and continue to be of interest to this day. This review focuses on ligands and indirect modulators of RORs from natural sources and explores their roles in a therapeutic context.

Modulating Neuro-Immune-Induced Macrophage Polarization With Topiramate Attenuates Experimental Abdominal Aortic Aneurysm

The development of abdominal aortic aneurysm (AAA) is attributed to psychological and physical factors. Topiramate, which is an agonist of the GABA_A receptor, makes contributions to neuronal disease and is partially involved in immune regulation, may be effective upon abdominal aortic aneurysm progression. We used experimental abdominal aortic aneurysm models: Angiotensin II (Ang II)–induced ApoE^−/− male mice (Ang II/APOE model) in our study. In the Ang II/APOE model, all mice (n=64) were divided into four groups: sham group (PBS treatment), control group (Ang II treatment), low-dose group (Ang II + low-dose topiramate, 3 mg/day per mouse), and high-dose group (Ang II + high-dose topiramate, 6 mg/day per mouse). All treatments began on the day after surgery. Moreover, collected tissues and cultured cell were used for histology and biochemical examination. In vitro, the effects of topiramate on bone marrow-derived macrophage stimulated by LPS were investigated. Our data implied that topiramate treatment significantly promoted macrophages preservation and conversion of M1 to M2 macrophage phenotypes in vivo and in vitro. Accordingly, proinflammatory activities mediated by the M1 macrophages were decreased and the repair process mediated by M2 macrophages was enhanced. The low-dose and high-dose groups had abdominal aortic aneurysm incidences of 50% and 37.5%, respectively, compared with 75% in the control group. Topiramate, a promising drug for the psychological disease, that target neuro-immune-induced macrophage polarization may attenuate experimental abdominal aortic aneurysm progression.

Experimental abdominal aortic aneurysm growth is inhibited by blocking the JAK2/STAT3 pathway

BACKGROUND

The JAK/STAT pathway is a vital transcription signaling pathway that regulates gene expression and cellular activity. Our recently published study highlighted the role of IL-17A in abdominal aortic aneurysm (AAA) formation and rupture. IL-17A has been proven to upregulate vascular endothelial growth factor (VEGF) expression in some diseases. However, no study has demonstrated the relationships among JAK2/STAT3, IL-17A and VEGF. Therefore, we hypothesized that IL-17A may up-regulate VEGF expression via the JAK2/STAT3 signaling pathway to amplify the inflammatory response, exacerbate neovascularization, and accelerate AAA progression.

METHODS

To fully verify our hypothesis, two separate studies were performed: i) a study investigating the influence of JAK2/STAT3 on AAA formation and progression. ii) a study evaluating the relationship among IL-17A, JAK2/STAT3 and VEGF. Human tissues were collected from 7 AAA patients who underwent open surgery and 7 liver transplantation donors. All human aortic tissues were examined by histological and immunohistochemical staining, and Western blotting. Furthermore, mouse aortic tissues were also examined by histological and immunohistochemical staining and Western blotting, and the mouse aortic diameters were assessed by high-resolution Vevo 2100 microimaging system.

RESULTS

Among human aortic tissues, JAK2/STAT3, IL-17A and VEGF expression levels were higher in AAA tissues than in control tissues. Group treated with WP1066 (a selective JAK2/STAT3 pathway inhibitor), IL-17A, and VEGF groups had AAA incidences of 25%, 40%, and 65%, respectively, while the control group had an incidence of 75%. Histopathological analysis revealed that the IL-17A- and VEGF-related inflammatory responses were attenuated by WP1066. Thus, blocking the JAK2/STAT3 pathway with WP1066 attenuated experimental AAA progression. In addition, in study ii, we found that IL-17A siRNA seemed to attenuate the expression of IL-17A and VEGF in vivo study; treatment with VEGF siRNA decreased the expression of VEGF, while IL-17A expression remained high. In an in vitro study, rhIL-17A treatment increased JAK2/STAT3 and VEGF expression in macrophages in a dose-dependent manner.

CONCLUSION

Blocking the JAK2/STAT3 pathway with WP1066 (a JAK2/STAT3 specific inhibitor) attenuates experimental AAA progression. During AAA progression, IL-17A may influence the expression of VEGF via the JAK2/STAT3 signaling pathway. This potential mechanism may suggest a novel strategy for nonsurgical AAA treatment.

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.

Circular RNA microarray expression profile in 3,4-benzopyrene/angiotensin II-induced abdominal aortic aneurysm in mice

Abdominal aortic aneurysm (AAA) is an unpredictable but lethal disease that poses a therapeutic dilemma. Circular RNAs (circRNAs), whose functional roles as transcriptional regulators and microRNA (miRNA) sponges have been shown in former studies, are potential biomarkers for many diseases. AAA in male C57BL/6 J mice was induced by coadministration of angiotensin II (Ang II) and 3,4-benzopyrene (BaP). The circRNA expression profiling was performed using two samples from the control group and two samples from the AAA group. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to confirm the reliability of the microarray results. Among the 14 236 detected circRNAs, 413 showed obvious expression changes (fold change ≥ 2; P < 0.05) between the BaP/Ang II-induced AAA group and control group. Of the 413 that showed significant changes, 271 were upregulated, while the other 142 were downregulated. The expression levels of 10 circRNAs were validated by qRT-PCR. The interactions of the differentially expressed circRNAs with miRNAs were predicted. Immunofluorescence showed prominent vascular smooth muscle cell apoptosis in abdominal aortic tissues in the BaP/Ang II group. Furthermore, a circRNA-miRNA coexpression network based on six apoptosis-related circRNAs was built. The genes regulated by the network mapped to several pathways, including apoptosis, the IL-17 signaling pathway, and vascular endothelial growth factor signaling pathway, all of which are related to AAA formation. This study performed circRNA expression profiling in AAA and the results specifically predicted the regulatory role of circRNAs in AAA pathogenesis.

Digoxin Attenuates Receptor Activation of NF-κB Ligand-Induced Osteoclastogenesis in Macrophages

BACKGROUND

Even though hypoxia-inducible factor-1α (HIF-1α) is among the transcriptional factors demonstrated to contribute to the formation of abdominal aortic aneurysms (AAAs), the precise mechanism has been unclear. Digoxin is known as an inhibitor of HIF-1α, and shows a protective effect against the progression of AAAs.

OBJECTIVES

We tested the effect of digoxin on osteoclastogenesis (OCG) and examined the pathway through which digoxin exerts inhibition of HIF-1α.

MATERIALS AND METHODS

RAW 264.7 macrophage cells were cultured and stimulated by soluble receptor activator of NF-κB ligand (sRANKL) with or without digoxin. First, we tested the effect of digoxin to attenuate macrophage activation, which led to OCG, characterized by tartrate-resistant acid phosphatase (TRAP)-positive macrophages (TPMs).

RESULTS

The activation of TPMs stimulated by sRANKL was attenuated by digoxin treatment. Furthermore, the receptor activator of NF-κB (RANK)/receptor activator of NF-κB ligand (RANKL) complex signaling pathway, which is stimulated by HIF-1α, was downregulated by digoxin treatment.

CONCLUSIONS

These results show that digoxin attenuates OCG. By inhibition of HIF-1α, digoxin decreases OCG through the downregulation of the RANK/RANKL signaling pathway. Therefore, digoxin is a potential candidate for medical treatment of AAAs.

Prophylactic digoxin treatment reduces IL-17 production in vivo in the neonatal calf and moderates RSV-associated disease

Respiratory syncytial virus (RSV) is a leading cause of morbidity and mortality in human infants. Bovine RSV infection of neonatal calves is pathologically and immunologically similar to RSV infection in infants, and is therefore a useful preclinical model for testing novel therapeutics. Treatment of severe RSV bronchiolitis relies on supportive care and may include use of bronchodilators and inhaled or systemic corticosteroids. Interleukin-17A (IL-17) is an inflammatory cytokine that plays an important role in neutrophil recruitment and activation. IL-17 is increased in children and rodents with severe RSV infection; and in calves with severe BRSV infection. It is currently unclear if IL-17 and Th17 immunity is beneficial or detrimental to the host during RSV infection. Digoxin was recently identified to selectively inhibit IL-17 production by antagonizing its transcription factor, retinoid-related orphan receptor γ t (RORγt). Digoxin inhibits RORγt binding to IL-17 and Th17 associated genes, and suppresses IL-17 production in vitro in human and murine leukocytes and in vivo in rodent models of autoimmune disease. We demonstrate here that in vitro and in vivo digoxin treatment also inhibits IL-17 production by bovine leukocytes. To determine the role of IL-17 in primary RSV infection, calves were treated prophylactically with digoxin and infected with BRSV. Digoxin treated calves demonstrated reduced signs of clinical illness after BRSV infection, and reduced lung pathology compared to untreated control calves. Digoxin treatment did not adversely affect virus shedding or lung viral burden, but had a significant impact on pulmonary inflammatory cytokine expression on day 10 post infection. Together, our results suggest that exacerbated expression of IL-17 has a negative impact on RSV disease, and that development of specific therapies targeting Th17 immunity may be a promising strategy to improve disease outcome during severe RSV infection.

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.

Ablation and Inhibition of the Immunoproteasome Catalytic Subunit LMP7 Attenuate Experimental Abdominal Aortic Aneurysm Formation in Mice

Low-molecular mass protein 7 (LMP7) is a proteolytic subunit of the immunoproteasome that is involved in regulating inflammatory responses. However, the role of LMP7 in the pathogenesis of abdominal aortic aneurysm (AAA) remains unknown. In this study, ApoE knockout (KO) or LMP7/ApoE double KO (dKO) mice were infused with angiotensin II (Ang II, 1000 ng/kg per minute) for up to 28 d. We found that LMP7 expression was significantly upregulated in AAA tissues from ApoE KO mice and human patients. Moreover, Ang II infusion markedly increased the incidence and severity of AAA in ApoE KO mice, which was considerably reduced in LMP7/ApoE dKO mice. Histological alterations, including aortic wall thickening, collagen deposition, elastin fragmentation, and vascular smooth muscle cell apoptosis in AAA tissue of ApoE KO mice, were also significantly attenuated in LMP7/ApoE dKO mice. Interestingly, LMP7/ApoE dKO mice showed a marked reduction of infiltration of CD3⁺ T cells, especially CD4⁺ T cells in AAA tissues compared with ApoE KO mice. Moreover, ablation of LMP7 substantially inhibited the differentiation of CD4⁺ T cells into Th1 and Th17 cells by reducing the activation of multiple transcriptional factors. We also investigated the effects of an LMP7-specific inhibitor PR-957 (also known as ONX 0914) on AAA formation in ApoE KO mice. PR-957 treatment could reduce the AAA incidence and severity. In conclusion, our results provide, to our knowledge, novel evidence that ablation or pharmacological inhibition of LMP7 attenuates Ang II-induced AAA formation, and LMP7 might be a novel therapeutic target for treating AAA in humans.

Characterization of CD4+ T Cell Subsets in Patients with Abdominal Aortic Aneurysms

BACKGROUND

The mediators produced by CD4+ T lymphocytes are involved in the pathogenesis of aneurysmal lesions in abdominal aortic aneurysm (AAA) patients. The aim of this study was to identify and characterize the CD4+ T cell subsets involved in human AAA.

METHODS

The CD4+ T cell subsets in 30 human aneurysmal lesions were determined using flow cytometry (FC) and immunohistochemistry (IHC). The peripheral blood mononuclear cells (PBMCs) from patients with AAA were also analyzed by FC and compared with control subjects.

RESULTS

Human aneurysmal lesions contained IFN-γ, IL-12p35, IL-4, IL-23p19, IL-17R, and IL-22 positive cells. PBMCs from AAA patients had higher expression levels of IFN-γ, TNF-α, IL-4, and IL-22 when compared to controls.

CONCLUSIONS

Our results show the presence of TH1, TH2, TH17, and TH22 subsets in aneurysmal lesions of AAA patients and suggest that these cells may be mainly activated in situ, where they can induce tissue degradation and contribute to the pathogenesis of AAA.

Structure-Based Design and Synthesis of Fluorene Derivatives as Novel RORγt Inverse Agonists

A new series of fluorene derivatives was designed and synthesized as novel retinoic acid receptor-related orphan receptor gamma t (RORγt) inverse agonists utilizing a molecular hybridization approach. The new compounds 10 - 15 were evaluated for their RORγt activity using biochemical FRET and cellular reporter gene assays. Moreover, the inhibitory activity of the fluorene derivatives 10 - 15 in mouse Th17 cell differentiation assay was assessed. The hybrid compound 15 that combines both fluorene and arylsulfone moieties displayed promising RORγt activity with IC₅₀ values of 68.6 and 99.5 nm in FRET and cellular assays, respectively. In addition, molecular modeling studies were employed to investigate potential binding mode of 15 to RORγt. These results render 15 a potential lead compound for development of therapeutics for Th17-driven autoimmune diseases.

Description of human AAA by cytokine and immune cell aberrations compared to risk-factor matched controls

BACKGROUND

The pathogenesis driving the formation of abdominal aortic aneurysms continues to be poorly understood. Therefore, we systemically define the cytokine and circulating immune cell environment observed in human abdominal aortic aneurysm compared with risk-factor matched controls.

METHODS

From 2015 to 2017, a total of 274 patients donated blood to the Indiana University Center for Aortic Disease. Absolute concentrations of circulating cytokines were determined, using enzyme-linked immunosorbent assays while the expression of circulating immune cell phenotypes were assayed via flow cytometric analysis.

RESULTS

Human abdominal aortic aneurysm is characterized by a significant depletion of the antigen-specific, CD4⁺ Tr1 regulatory lymphocyte that corresponds to an upregulation of the antigen-specific, inflammatory Th17 cell. We found no differences in the incidence of Treg, B10, and myeloid-derived suppressor regulatory cells. Similarly, no disparities were noted in the following inflammatory cytokines: IL-1β, C-reactive protein, tumor necrosis factor α, interferon γ, and IL-23. However, significant upregulation of the inflammatory cytokines osteopontin, IL-6, and IL-17 were noted. Additionally, no changes were observed in the regulatory cytokines IL-2, IL-4, IL-13, TNF-stimulated gene 6 protein, and prostaglandin E2, but we did observe a significant decrease in the essential regulatory cytokine IL-10.

CONCLUSION

In this investigation, we systematically characterize the abdominal aortic aneurysm-immune environment and present preliminary evidence that faulty immune regulation may also contribute to aneurysm formation and growth.

A Typical Immune T/B Subset Profile Characterizes Bicuspid Aortic Valve: In an Old Status?

Bicuspid valve disease is associated with the development of thoracic aortic aneurysm. The molecular mechanisms underlying this association still need to be clarified. Here, we evaluated the circulating levels of T and B lymphocyte subsets associated with the development of vascular diseases in patients with bicuspid aortic valve or tricuspid aortic valve with and without thoracic aortic aneurysm. We unveiled that the circulating levels of the MAIT, CD4+IL−17A+, and NKT T cell subsets were significantly reduced in bicuspid valve disease cases, when compared to tricuspid aortic valve cases in either the presence or the absence of thoracic aortic aneurysm. Among patients with tricuspid aortic valve, these cells were higher in those also affected by thoracic aortic aneurysm. Similar data were obtained by examining CD19+ B cells, naïve B cells (IgD+CD27−), memory unswitched B cells (IgD+CD27+), memory switched B cells (IgD−CD27+), and double-negative B cells (DN) (IgD−CD27−). These cells resulted to be lower in subjects with bicuspid valve disease with respect to patients with tricuspid aortic valve. In whole, our data indicate that patients with bicuspid valve disease show a quantitative reduction of T and B lymphocyte cell subsets. Future studies are encouraged to understand the molecular mechanisms underlying this observation and its pathophysiological significance.

Imiquimod-Induced Psoriasis-Like Skin Lesions Do Not Accelerate Atherosclerosis in Low-Density Lipoprotein Receptor-Deficient Mice

Psoriasis is a chronic inflammatory skin disorder associated with several comorbidities, including atherosclerosis. Disease mechanisms that may affect both psoriasis and atherosclerosis include activation of T helper 1 and T helper 17 cells. Imiquimod application is an established mouse model of psoriasis-like skin inflammation. The cardiac glycoside digoxin inhibits the master transcription factor of T helper 17 differentiation, retinoid acid receptor-related orphan nuclear receptor γt, and attenuates IL-17-dependent pathologies in mice. We investigated whether cyclic imiquimod-induced psoriasis-like skin inflammation affects atherosclerosis in low-density lipoprotein receptor-deficient mice and whether digoxin modifies either disease. Topical imiquimod application increased ear thickness, keratinocyte proliferation, and accumulation of CD3⁺ T cells in the skin of low-density lipoprotein receptor-deficient mice. Also, imiquimod affected the mice systemically with induction of splenomegaly as well as increased plasma levels of IL-17A and serum amyloid A. Overall, imiquimod reduced atherosclerosis in the aortic arch en face, but it did not affect atherosclerosis in the aortic root. Digoxin significantly reduced the imiquimod-induced ear thickening, had divergent effects on imiquimod-induced systemic inflammation, and did not affect atherosclerosis. In conclusion, cyclic imiquimod applications can be used for long-term induction of psoriasis-like skin lesions, but they attenuate atherosclerosis in low-density lipoprotein-deficient mice. In this model, digoxin reduces skin inflammation, but it has no effect on atherosclerosis.

Hypoxia-inducible factor 1 in clinical and experimental aortic aneurysm disease

OBJECTIVE

Mural angiogenesis and macrophage accumulation are two pathologic hallmarks of abdominal aortic aneurysm (AAA) disease. The heterodimeric transcription factor hypoxia-inducible factor 1 (HIF-1) is an essential regulator of angiogenesis and macrophage function. In this study, we investigated HIF-1 expression and activity in clinical and experimental AAA disease.

METHODS

Human aortic samples were obtained from 24 AAA patients and six organ donors during open abdominal surgery. Experimental AAAs were created in 10-week-old male C57BL/6J mice by transient intra-aortic infusion of porcine pancreatic elastase (PPE). Expression of HIF-1α and its target gene messenger RNA (mRNA) levels were assessed in aneurysmal and control aortae. The HIF-1α inhibitors 2-methoxyestradiol and digoxin, the prolyl hydroxylase domain-containing protein (PHD) inhibitors cobalt chloride and JNJ-42041935, and the vehicle alone as control were administered daily to mice at varying time points beginning before or after PPE infusion. Influences on experimental AAA formation and progression were assessed by serial transabdominal ultrasound measurements of aortic diameter and histopathologic analysis at sacrifice.

RESULTS

The mRNA levels for HIF-1α, vascular endothelial growth factor A, glucose transporter 1, and matrix metalloproteinase 2 were significantly increased in both human and experimental aneurysm tissue. Tissue immunostaining detected more HIF-1α protein in both human and experimental aneurysmal aortae compared with respective control aortae. Treatment with either HIF-1α inhibitor, beginning before or after PPE infusion, prevented enlargement of experimental aneurysms. Both HIF-1α inhibition regimens attenuated medial elastin degradation, smooth muscle cell depletion, and mural angiogenesis and the accumulation of macrophages, T cells, and B cells. Whereas mRNA levels for PHD1 and PHD2 were elevated in experimental aneurysmal aortae, pharmacologic inhibition of PHDs had limited effect on experimental aneurysm progression.

CONCLUSIONS

Expression of HIF-1α and its target genes is increased in human and experimental AAAs. Treatment with HIF-1α inhibitors limits experimental AAA progression, with histologic evidence of attenuated mural leukocyte infiltration and angiogenesis. These findings underscore the potential significance of HIF-1α in aneurysm pathogenesis and as a target for pharmacologic suppression of AAA disease.

Grape-seed Polyphenols Play a Protective Role in Elastase-induced Abdominal Aortic Aneurysm in Mice

Abdominal aortic aneurysm (AAA) is a kind of disease characterized by aortic dilation, whose pathogenesis is linked to inflammation. This study aimed to determine whether grape-seed polyphenols (GSP) has anti-AAA effects and what mechanism is involved, thus to find a way to prevent occurrence and inhibit expansion of small AAA. In our study, AAA was induced by incubating the abdominal aorta of the mice with elastase, and GSP was administrated to the mice by gavage at different doses beginning on the day of the AAA inducement. In in vivo experiments, 800 mg/kg GSP could significantly reduce the incidence of AAA, the dilatation of aorta and elastin degradation in media, and dramatically decrease macrophage infiltration and activation and expression of matrix metalloproteinase (MMP) -2 and MMP-9 in the aorta, compared to the AAA model group. Meanwhile, 400 mg/kg GSP could also but not completely inhibit the occurrence and development of AAA. In in vitro experiments, GSP dose-dependently inhibited mRNA expression of interleukin (IL)-1β, IL-6 and monocyte chemoattractant protein-1 (MCP-1), and significantly inhibited expression and activity of MMP-2 and MMP-9, thus prevented elastin from degradation. In conclusion, GSP showed great anti-AAA effects and its mechanisms were related to inhibition of inflammation.

Effects of Interleukin 17 on the cardiovascular system

Cardiovascular diseases remain the leading cause of death worldwide and account for most of the premature mortality observed in chronic inflammatory diseases. Common mechanisms underlie these two types of disorders, where the contribution of Interleukin (IL)-17A, the founding member of the IL-17 family, is highly suspected. While the local effects of IL-17A in inflammatory disorders have been well described, those on the cardiovascular system remain less studied. This review focuses on the effects of IL-17 on the cardiovascular system both on isolated cells and in vivo. IL-17A acts on vessel and cardiac cells, leading to inflammation, coagulation and thrombosis. In vivo and clinical studies have shown its involvement in the pathogenesis of cardiovascular diseases including atherosclerosis and myocardial infarction that occur prematurely in chronic inflammatory disorders. As new therapeutic approaches are targeting the IL-17 pathway, this review should help to better understand their positive and negative outcomes on the cardio-vascular system.

Inhibition of the mTOR pathway in abdominal aortic aneurysm: implications of smooth muscle cell contractile phenotype, inflammation, and aneurysm expansion

The development of effective pharmacological treatment of abdominal aortic aneurysm (AAA) potentially offers great benefit to patients with preaneurysmal aortic dilation by slowing the expansion of aneurysms and reducing the need for surgery. To date, therapeutic targets for slowing aortic dilation have had low efficacy. Thus, in this study, we aim to elucidate possible mechanisms driving aneurysm progression to identify potential targets for pharmacological intervention. We demonstrate that mechanistic target of rapamycin (mTOR) signaling is overactivated in aortic smooth muscle cells (SMCs), which contributes to murine AAA. Rapamycin, a typical mTOR pathway inhibitor, dramatically limits the expansion of the abdominal aorta following intraluminal elastase perfusion. Furthermore, reduction of aortic diameter is achieved by inhibition of the mTOR pathway, which preserves and/or restores the contractile phenotype of SMCs and downregulates macrophage infiltration, matrix metalloproteinase expression, and inflammatory cytokine production. Taken together, these results highlight the important role of the mTOR cascade in aneurysm progression and the potential application of rapamycin as a therapeutic candidate for AAA.

NEW & NOTEWORTHY This study provides novel observations that mechanistic target of rapamycin (mTOR) signaling is overactivated in aortic smooth muscle cells and contributes to mouse abdominal aortic aneurysm (AAA) and that rapamycin protects against aneurysm development. Our data highlight the importance of preservation and/or restoration of the smooth muscle cell contractile phenotype and reduction of inflammation by mTOR inhibition in AAA.

Inhibition or deletion of angiotensin II type 1 receptor suppresses elastase-induced experimental abdominal aortic aneurysms

OBJECTIVE

Angiotensin (Ang) II type 1 receptor (AT1) activation is essential for the development of exogenous Ang II-induced abdominal aortic aneurysms (AAAs) in hyperlipidemic animals. Experimental data derived from this modeling system, however, provide limited insight into the role of endogenous Ang II in aneurysm pathogenesis. Consequently, the potential translational value of AT1 inhibition in clinical AAA disease management remains incompletely understood on the basis of the existing literature.

METHODS

AAAs were created in wild-type (WT) and AT1a knockout (KO) mice by intra-aortic infusion of porcine pancreatic elastase (PPE). WT mice were treated with the AT1 receptor antagonist telmisartan, 10 mg/kg/d in chow, or the peroxisome proliferator-activated receptor γ (PPARγ) antagonist GW9662, 3 mg/kg/d through oral gavage, beginning 1 week before or 3 days after PPE infusion. Influences on aneurysm progression as well as mechanistic insights into AT1-mediated pathogenic processes were determined using noninvasive ultrasound imaging, histopathology, aortic gene expression profiling, and flow cytometric analysis.

RESULTS

After PPE infusion, aortic enlargement was almost completely abrogated in AT1a KO mice compared with WT mice. As defined by a ≥50% increase in aortic diameter, no PPE-infused, AT1a KO mouse actually developed an AAA. On histologic evaluation, medial smooth muscle cellularity and elastic lamellae were preserved in AT1a KO mice compared with WT mice, with marked attenuation of mural angiogenesis and leukocyte infiltration. In WT mice, telmisartan administration effectively suppressed aneurysm pathogenesis after PPE infusion as well, regardless of whether treatment was initiated before or after aneurysm creation or continued for a limited or extended time. Telmisartan treatment was associated with reduced messenger RNA levels for CCL5 and matrix metalloproteinases 2 and 9 in aneurysmal aortae, with no apparent effect on PPARγ-regulated gene expression. Administration of the PPARγ antagonist GW9662 failed to "rescue" the aneurysm phenotype in telmisartan-treated, PPE-infused WT mice. Neither effector T-cell differentiation nor regulatory T-cell cellularity was affected by telmisartan treatment status.

CONCLUSIONS

Telmisartan effectively suppresses the progression of elastase-induced AAAs without apparent effect on PPARγ activation or T-cell differentiation. These findings reinforce the critical importance of endogenous AT1 activation in experimental AAA pathogenesis and reinforce the translational potential of AT1 inhibition in medical aneurysm disease management.

Cytokine amplification and macrophage effector functions in aortic inflammation and abdominal aortic aneurysm formation

On April 29, 2015, Son and colleagues published an article entitled "Granulocyte macrophage colony-stimulating factor (GM-CSF) is required for aortic dissection/intramural haematoma" in Nature Communications. The authors observed that the heterozygous Kruppel-like transcription factor 6 (KLF6) deficiency or absence of myeloid-specific KLF6 led to upregulation of macrophage GM-CSF expression, promoted the development of aortic hematoma/dissection, and stimulated abdominal aortic aneurysm (AAA) formation when the vessel wall was subjected to an inflammatory stimulus. The additional findings of increased adventitial fibrotic deposition, marked infiltration of macrophages, and increased expression of matrix metalloprotease-9 (MMP-9) and IL-6 were blocked with neutralizing GM-CSF antibodies, or recapitulated in normal mice with excess GM-CSF administration. The authors concluded that GM-CSF is a key regulatory molecule in the development of AAA and further suggested that activation of GM-CSF is independent of the transforming growth factor β (TGFβ)-Smad pathway associated with the Marfan aortic pathology. In this perspective, we expand on this mechanism, drawing from previous studies implicating a similar essential role for IL-6 signaling in macrophage activation, Th17 expansion and aortic dissections. We propose a sequential "two-hit" model of vascular inflammation involving initial vascular injury followed by recruitment of Ly6C(hi) macrophages. Aided by fibroblast interactions inflammatory macrophages produce amplification of IL-6 and GM-CSF expression that converge on a common, pathogenic Janus kinase (JAK)-signal transducers and activations of transcription 3 (STAT3) signaling pathway. This pathway stimulates effector functions of macrophages, promotes differentiation of Th17 lymphocytes and enhances matrix metalloproteinase expression, ultimately resulting in deterioration of vascular wall structural integrity. Further research evaluating the impact of interventions modulating this common JAK-STAT3 pathway may yield new therapeutic interventions for late stages of vascular expansion in inflammation driven aortic disease.