Antisense oligonucleotide targeting hepatic Serum Amyloid A limits the progression of angiotensin II-induced abdominal aortic aneurysm formation.

BACKGROUND AND AIMS: Obesity increases the risk for abdominal aortic aneurysms (AAA) in humans and enhances angiotensin II (AngII)-induced AAA formation in C57BL/6 mice. We reported that deficiency of Serum Amyloid A (SAA) significantly reduces AngII-induced inflammation and AAA in both hyperlipidemic apoE-deficient and obese C57BL/6 mice. The aim of this study is to investigate whether SAA plays a role in the progression of early AAA in obese C57BL/6 mice. METHODS: Male C57BL/6J mice were fed a high-fat diet (60% kcal as fat) throughout the study. After 4 months of diet, the mice were infused with AngII until the end of the study. Mice with at least a 25% increase in the luminal diameter of the abdominal aorta after 4 weeks of AngII infusion were stratified into 2 groups. The first group received a control antisense oligonucleotide (Ctr ASO), and the second group received ASO that suppresses SAA (SAA-ASO) until the end of the study. RESULTS: Plasma SAA levels were significantly reduced by the SAA ASO treatment. While mice that received the control ASO had continued aortic dilation throughout the AngII infusion periods, the mice that received SAA-ASO had a significant reduction in the progression of aortic dilation, which was associated with significant reductions in matrix metalloprotease activities, decreased macrophage infiltration and decreased elastin breaks in the abdominal aortas. CONCLUSIONS: We demonstrate for the first time that suppression of SAA protects obese C57BL/6 mice from the progression of AngII-induced AAA. Suppression of SAA may be a therapeutic approach to limit AAA progression.

Ferrostatin-1 inhibits ferroptosis of vascular smooth muscle cells and alleviates abdominal aortic aneurysm formation through activating the SLC7A11/GPX4 axis.

Ferroptosis, a type of iron-catalyzed necrosis, is responsible for vascular smooth muscle cell (VSMC) death and serves as a potential therapeutic target for alleviating aortic aneurysm. Here, our study explored the underlying mechanism of ferroptosis affecting VSMC functions and the resultant formation of AAA using its inhibitor Ferrostatin-1 (Fer-1). Microarray-based gene expression profiling was employed to identify differentially expressed genes related to AAA and ferroptosis. An AAA model was established by angiotensin II (Ang II) induction in apolipoprotein E-knockout (ApoE-/- ) mice, followed by injection of Fer-1 and RSL-3 (ferroptosis inducer). Then, the role of Fer-1 and RSL-3 in the ferroptosis of VSMCs and AAA formation was analyzed in Ang II-induced mice. Primary mouse VSMCs were cultured in vitro and treated with Ang II, Fer-1, sh-SLC7A11, or sh-GPX4 to assess the effect of Fer-1 via the SLC7A11/GPX axis. Bioinformatics analysis revealed that GPX4 was involved in the fibrosis formation of AAA, and there was an interaction between SLC7A11 and GPX4. In vitro assays showed that Fer-1 alleviated Ang II-induced ferroptosis of VSMCs and retard the consequent AAA formation. The mechanism was associated with activation of the SLC7A11/GPX4 pathway. Silencing of SLC7A11 or GPX4 could inhibit the ameliorating effect of Fer-1 on the ferroptosis of VSMCs. In vivo animal studies further demonstrated that Fer-1 inhibited Ang II-induced ferroptosis and vessel wall structural abnormalities in AAA mouse through activation of the SLC7A11/GPX4 pathway. Fer-1 may prevent AAA formation through activation of the SLC7A11/GPX4 pathway.

Doxycycline induces mitochondrial dysfunction in aortic smooth muscle cells.

The antibiotic doxycycline is known to inhibit inflammation and was therefore considered as a therapeutic to prevent abdominal aortic aneurysm (AAA) growth. Yet mitochondrial dysfunction is a key-characteristic of clinical AAA disease. We hypothesize that doxycycline impairs mitochondrial function in the aorta and aortic smooth muscle cells (SMCs). Doxycycline induced mitonuclear imbalance, reduced proliferation and diminished expression of typical contractile smooth muscle cell (SMC) proteins. To understand the underlying mechanism, we studied krüppel-like factor 4 (KLF4). The expression of this transcription factor was enhanced in SMCs after doxycycline treatment. Knockdown of KLF4, however, did not affect the doxycycline-induced SMC phenotypic changes. Then we used the bioenergetics drug elamipretide (SS-31). Doxycycline-induced loss of SMC contractility markers was not rescued, but mitochondrial genes and mitochondrial connectivity improved upon elamipretide. Thus while doxycycline is anti-inflammatory, it also induces mitochondrial dysfunction in aortic SMCs and causes SMC phenotypic switching, potentially contributing to aortic aneurysm pathology. The drug elamipretide helps mitigate the harmful effects of doxycycline on mitochondrial function in aortic SMC, and may be of interest for treatment of aneurysm diseases with pre-existing mitochondrial dysfunction.

Inhibition of smooth muscle cell death by Angiotensin 1-7 protects against abdominal aortic aneurysm.

Abdominal aortic aneurysm (AAA) represents a debilitating vascular disease characterized by aortic dilatation and wall rupture if it remains untreated. We aimed to determine the effects of Ang 1-7 in a murine model of AAA and to investigate the molecular mechanisms involved. Eight- to 10-week-old apolipoprotein E-deficient mice (ApoEKO) were infused with Ang II (1.44 mg/kg/day, s.c.) and treated with Ang 1-7 (0.576 mg/kg/day, i.p.). Echocardiographic and histological analyses showed abdominal aortic dilatation and extracellular matrix remodeling in Ang II-infused mice. Treatment with Ang 1-7 led to suppression of Ang II-induced aortic dilatation in the abdominal aorta. The immunofluorescence imaging exhibited reduced smooth muscle cell (SMC) density in the abdominal aorta. The abdominal aortic SMCs from ApoEKO mice exhibited markedly increased apoptosis in response to Ang II. Ang 1-7 attenuated cell death, as evident by increased SMC density in the aorta and reduced annexin V/propidium iodide-positive cells in flow cytometric analysis. Gene expression analysis for contractile and synthetic phenotypes of abdominal SMCs showed preservation of contractile phenotype by Ang 1-7 treatment. Molecular analyses identified increased mitochondrial fission, elevated cellular and mitochondrial reactive oxygen species (ROS) levels, and apoptosis-associated proteins, including cytochrome c, in Ang II-treated aortic SMCs. Ang 1-7 mitigated Ang II-induced mitochondrial fission, ROS generation, and levels of pro-apoptotic proteins, resulting in decreased cell death of aortic SMCs. These results highlight a critical vasculo-protective role of Ang 1-7 in a degenerative aortic disease; increased Ang 1-7 activity may provide a promising therapeutic strategy against the progression of AAA.

The protective effects of pirfenidone in preventing abdominal aortic aneurysm formation.

Vascular endothelial growth factor (VEGF)-mediated angiogenesis participates in the initiation and progression of abdominal aortic aneurysm (AAA). Pirfenidone is a compound that has anti-inflammatory and antioxidant properties and suppresses angiogenesis. Pirfenidone targets the extracellular matrix (ECM) and has therapeutic effects on fibrotic diseases. Therefore, we speculated that pirfenidone might have meaningful therapeutic effects in AAA, and the current study was designed to investigate this capacity. An AAA model was constructed in mice using a long-term injection of angiotensin II (Ang II), followed by a 28-day administration of 200 mg/kg/day pirfenidone. Increased maximal external diameter of the abdominal artery, promoted levels of VEGF-A and its receptor VEGF-R2, upregulated matrix metallopeptidases (MMP)-2 and MMP-9, and elevated release of pro-inflammatory cytokines were observed in AAA mice, which were extremely repressed by 200 mg/kg pirfenidone. Human aortic endothelial cells (HAECs) were stimulated with Ang II for 1 day, in the presence or absence of pirfenidone (100 nM). Elevated expression of VEGF-A and VEGF-R2, facilitated proliferation, increased tube formation ability, and upregulated MMP-2 and MMP-9 were observed in Ang II-stimulated HAECs, all of which were significantly rescued by 100 nM pirfenidone. Finally, the elevated levels of myeloid differentiation primary response 88 and phosphorylated nuclear factor-kappa-B subunit p65 observed in Ang II-stimulated HAECs were repressed by pirfenidone. Collectively, pirfenidone alleviated AAA by inhibiting ECM degradation and ameliorating endothelial dysfunction.

Colchicine protects against the development of experimental abdominal aortic aneurysm.

Abdominal aortic aneurysm (AAA) is characterized by at least 1.5-fold enlargement of the infrarenal aorta, a ruptured AAA is life-threatening. Colchicine is a medicine used to treat gout and familial Mediterranean fever, and recently, it was approved to reduce the risk of cardiovascular events in adult patients with established atherosclerotic disease. With an AAA mice model created by treatment with porcine pancreatic elastase (PPE) and ß-aminopropionitrile (BAPN), this work was designed to explore whether colchicine could protect against the development of AAA. Here, we showed that colchicine could limit AAA formation, as evidenced by the decreased total aortic weight per body weight, AAA incidence, maximal abdominal aortic diameter and collagen deposition. We also found that colchicine could prevent the phenotypic switching of vascular smooth muscle cells from a contractile to synthetic state during AAA. In addition, it was demonstrated that colchicine was able to reduce vascular inflammation, oxidative stress, cell pyroptosis and immune cells infiltration to the aortic wall in the AAA mice model. Finally, it was proved that the protective action of colchicine against AAA formation was mainly mediated by preventing immune cells infiltration to the aortic wall. In summary, our findings demonstrated that colchicine could protect against the development of experimental AAA, providing a potential therapeutic strategy for AAA intervention in the clinic.

ANGPTL8 deletion attenuates abdominal aortic aneurysm formation in ApoE-/- mice.

Angiopoietin-like protein 8 (ANGPTL8) plays important roles in lipid metabolism, glucose metabolism, inflammation, and cell proliferation and migration. Clinical studies have indicated that circulating ANGPTL8 levels are increased in patients with thoracic aortic dissection (TAD). TAD shares several risk factors with abdominal aortic aneurysm (AAA). However, the role of ANGPTL8 in AAA pathogenesis has never been investigated. Here, we investigated the effect of ANGPTL8 knockout on AAA in ApoE-/- mice. ApoE-/-ANGPTL8-/- mice were generated by crossing ANGPTL8-/- and ApoE-/- mice. AAA was induced in ApoE-/- using perfusion of angiotensin II (AngII). ANGPTL8 was significantly up-regulated in AAA tissues of human and experimental mice. Knockout of ANGPTL8 significantly reduced AngII-induced AAA formation, elastin breaks, aortic inflammatory cytokines, matrix metalloproteinase expression, and smooth muscle cell apoptosis in ApoE-/- mice. Similarly, ANGPTL8 sh-RNA significantly reduced AngII-induced AAA formation in ApoE-/- mice. ANGPTL8 deficiency inhibited AAA formation, and ANGPTL8 may therefore be a potential therapeutic target for AAA.

Treatment With Small Molecule Inhibitors of Advanced Glycation End-Products Formation and Advanced Glycation End-Products-Mediated Collagen Cross-Linking Promotes Experimental Aortic Aneurysm Progression in Diabetic Mice.

Background Although diabetes attenuates abdominal aortic aneurysms (AAAs), the mechanisms by which diabetes suppresses AAAs remain incompletely understood. Accumulation of advanced glycation end- (AGEs) reduces extracellular matrix (ECM) degradation in diabetes. Because ECM degradation is critical for AAA pathogenesis, we investigated whether AGEs mediate experimental AAA suppression in diabetes by blocking AGE formation or disrupting AGE-ECM cross-linking using small molecule inhibitors. Methods and Results Male C57BL/6J mice were treated with streptozotocin and intra-aortic elastase infusion to induce diabetes and experimental AAAs, respectively. Aminoguanidine (AGE formation inhibitor, 200 mg/kg), alagebrium (AGE-ECM cross-linking disrupter, 20 mg/kg), or vehicle was administered daily to mice from the last day following streptozotocin injection. AAAs were assessed via serial aortic diameter measurements, histopathology, and in vitro medial elastolysis assays. Treatment with aminoguanidine, not alagebrium, diminished AGEs in diabetic AAAs. Treatment with both inhibitors enhanced aortic enlargement in diabetic mice as compared with vehicle treatment. Neither enhanced AAA enlargement in nondiabetic mice. AAA enhancement in diabetic mice by aminoguanidine or alagebrium treatment promoted elastin degradation, smooth muscle cell depletion, mural macrophage accumulation, and neoangiogenesis without affecting matrix metalloproteinases, C-C motif chemokine ligand 2, or serum glucose concentration. Additionally, treatment with both inhibitors reversed suppression of diabetic aortic medial elastolysis by porcine pancreatic elastase in vitro. Conclusions Inhibiting AGE formation or AGE-ECM cross-linking enhances experimental AAAs in diabetes. These findings support the hypothesis that AGEs attenuate experimental AAAs in diabetes. These findings underscore the potential translational value of enhanced ECM cross-linking as an inhibitory strategy for early AAA disease.

DOCK2 Deficiency Attenuates Abdominal Aortic Aneurysm Formation-Brief Report.

BACKGROUND: Abdominal aortic aneurysm (AAA) is a potentially lethal disease that lacks pharmacological treatment. Degradation of extracellular matrix proteins, especially elastin laminae, is the hallmark for AAA development. DOCK2 (dedicator of cytokinesis 2) has shown proinflammatory effects in several inflammatory diseases and acts as a novel mediator for vascular remodeling. However, the role of DOCK2 in AAA formation remains unknown. METHODS: Ang II (angiotensin II) infusion of ApoE-/- (apolipoprotein E deficient) mouse and topical elastase-induced AAA combined with DOCK2-/- (DOCK2 knockout) mouse models were used to study DOCK2 function in AAA formation/dissection. The relevance of DOCK2 to human AAA was examined using human aneurysm specimens. Elastin fragmentation in AAA lesion was observed by elastin staining. Elastin-degrading enzyme MMP (matrix metalloproteinase) activity was measured by in situ zymography. RESULTS: DOCK2 was robustly upregulated in AAA lesion of Ang II-infused ApoE-/- mice, elastase-treated mice, as well as human AAA lesions. DOCK2-/- significantly attenuated the Ang II-induced AAA formation/dissection or rupture in mice along with reduction of MCP-1 (monocyte chemoattractant protein-1) and MMP expression and activity. Accordingly, the elastin fragmentation observed in ApoE-/- mouse aorta infused with Ang II and elastase-treated aorta was significantly attenuated by DOCK2 deficiency. Moreover, DOCK2-/- decreased the prevalence and severity of aneurysm formation, as well as the elastin degradation observed in the topical elastase model. CONCLUSIONS: Our results indicate that DOCK2 is a novel regulator for AAA formation. DOCK2 regulates AAA development by promoting MCP-1 and MMP2 expression to incite vascular inflammation and elastin degradation.

Gut Microbiota-Derived Trimethylamine N-Oxide Contributes to Abdominal Aortic Aneurysm Through Inflammatory and Apoptotic Mechanisms.

BACKGROUND: Large-scale human and mechanistic mouse studies indicate a strong relationship between the microbiome-dependent metabolite trimethylamine N-oxide (TMAO) and several cardiometabolic diseases. This study aims to investigate the role of TMAO in the pathogenesis of abdominal aortic aneurysm (AAA) and target its parent microbes as a potential pharmacological intervention. METHODS: TMAO and choline metabolites were examined in plasma samples, with associated clinical data, from 2 independent patient cohorts (N=2129 total). Mice were fed a high-choline diet and underwent 2 murine AAA models, angiotensin II infusion in low-density lipoprotein receptor-deficient (Ldlr-/-) mice or topical porcine pancreatic elastase in C57BL/6J mice. Gut microbial production of TMAO was inhibited through broad-spectrum antibiotics, targeted inhibition of the gut microbial choline TMA lyase (CutC/D) with fluoromethylcholine, or the use of mice genetically deficient in flavin monooxygenase 3 (Fmo3-/-). Finally, RNA sequencing of in vitro human vascular smooth muscle cells and in vivo mouse aortas was used to investigate how TMAO affects AAA. RESULTS: Elevated TMAO was associated with increased AAA incidence and growth in both patient cohorts studied. Dietary choline supplementation augmented plasma TMAO and aortic diameter in both mouse models of AAA, which was suppressed with poorly absorbed oral broad-spectrum antibiotics. Treatment with fluoromethylcholine ablated TMAO production, attenuated choline-augmented aneurysm initiation, and halted progression of an established aneurysm model. In addition, Fmo3-/- mice had reduced plasma TMAO and aortic diameters and were protected from AAA rupture compared with wild-type mice. RNA sequencing and functional analyses revealed choline supplementation in mice or TMAO treatment of human vascular smooth muscle cells-augmented gene pathways associated with the endoplasmic reticulum stress response, specifically the endoplasmic reticulum stress kinase PERK. CONCLUSIONS: These results define a role for gut microbiota-generated TMAO in AAA formation through upregulation of endoplasmic reticulum stress-related pathways in the aortic wall. In addition, inhibition of microbiome-derived TMAO may serve as a novel therapeutic approach for AAA treatment where none currently exist.

Protective Role for Smooth Muscle Cell Hepcidin in Abdominal Aortic Aneurysm.

BACKGROUND: Hepcidin is a liver-derived hormone that controls systemic iron homeostasis, by inhibiting the iron exporter ferroportin in the gut and spleen, respective sites of iron absorption and recycling. Hepcidin is also expressed ectopically in the context of cardiovascular disease. However, the precise role of ectopic hepcidin in underlying pathophysiology is unknown. In patients with abdominal aortic aneurysm (AAA), hepcidin is markedly induced in smooth muscle cells (SMCs) of the aneurysm wall and inversely correlated with the expression of LCN2 (lipocalin-2), a protein implicated in AAA pathology. In addition, plasma hepcidin levels were inversely correlated with aneurysm growth, suggesting hepcidin has a potential disease-modifying role. METHODS: To probe the role of SMC-derived hepcidin in the setting of AAA, we applied AngII (Angiotensin-II)-induced AAA model to mice harbouring an inducible, SMC-specific deletion of hepcidin. To determine whether SMC-derived hepcidin acted cell-autonomously, we also used mice harboring an inducible SMC-specific knock-in of hepcidin-resistant ferroportinC326Y. The involvement of LCN2 was established using a LCN2-neutralizing antibody. RESULTS: Mice with SMC-specific deletion of hepcidin or knock-in of hepcidin-resistant ferroportinC326Y had a heightened AAA phenotype compared with controls. In both models, SMCs exhibited raised ferroportin expression and reduced iron retention, accompanied by failure to suppress LCN2, impaired autophagy in SMCs, and greater aortic neutrophil infiltration. Pretreatment with LCN2-neutralizing antibody restored autophagy, reduced neutrophil infiltration, and prevented the heightened AAA phenotype. Finally, plasma hepcidin levels were consistently lower in mice with SMC-specific deletion of hepcidin than in controls, indicating that SMC-derived hepcidin contributes to the circulating pool in AAA. CONCLUSIONS: Hepcidin elevation in SMCs plays a protective role in the setting of AAA. These findings are the first demonstration of a protective rather than deleterious role for hepcidin in cardiovascular disease. They highlight the need to further explore the prognostic and therapeutic value of hepcidin outside disorders of iron homeostasis.

Targeting mitochondrial stress with Szeto-Schiller 31 prevents experimental abdominal aortic aneurysm: Crosstalk with endoplasmic reticulum stress.

BACKGROUND AND PURPOSE: Mitochondrial dysfunction and inflammation contribute to a myriad of cardiovascular diseases. Deleterious crosstalk of mitochondria and persistent endoplasmic reticulum (ER) stress triggers oxidative stress, which is involved in the development of vascular diseases. This study determined if inhibition of mitochondrial stress reduces aneurysm development in angiotensin II (Ang II)-infused apolipoprotein-E-deficient (ApoE-/- ) mice and its effect on ER stress. EXPERIMENTAL APPROACH: The mitochondria-targeted tetrapeptide, Szeto-Schiller 31 (SS31), ameliorated mitochondrial dysfunction and the enhanced expression of ER stress markers triggered by Ang II in ApoE-/- mice, and limited plasmatic and vascular reactive oxygen species (ROS) levels. Interestingly, SS31 improved survival, reduced the incidence and severity of abdominal aortic aneurysm (AAA), and the Ang II-induced increase in aortic diameter as evaluated by ultrasonography, resembling the response triggered by the classic ER stress inhibitors tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyrate (PBA). KEY RESULTS: Disorganization of the extracellular matrix, increased expression of metalloproteinases and pro-inflammatory markers and infiltration of immune cells induced by Ang II in the abdominal aorta were effectively reduced by SS31 and ER inhibitors. Further, C/EBP homologous protein (CHOP) deficiency in ApoE-/- mice attenuated Ang II-mediated increase in vascular diameter and incidence of AAA, suggesting its contribution to the favourable response induced by ER stress inhibition. CONCLUSIONS AND IMPLICATIONS: Our data demonstrate that inhibition of mitochondrial stress by SS31 limits AAA formation and increases survival through a reduction of vascular remodelling, inflammation and ROS, and support that attenuation of ER stress contributes to the favourable response elicited by SS31.

Netrin-1 Monoclonal Antibody-Functionalized Nanoparticle Loaded with Metformin Prevents the Progression of Abdominal Aortic Aneurysms.

Background: Abdominal aortic aneurysms (AAAs) are a global health and economic burden. Therapeutic strategies to inhibit the progression of AAAs are currently lacking. Recently, the therapeutic effect of metformin on aneurysms has attracted considerable interest. However, the unfavorable pharmacokinetic properties of metformin limit its feasibility for AAA treatment. Methods and Results: We constructed a metformin-loaded netrin-1-responsive AAA-targeted nanoparticle (Tgt-NP-Met) for AAA management. Evaluation of the therapeutic effect of Tgt-NP-Met was performed by in vitro and in vivo experiments. Our results showed that the binding of netrin-1 monoclonal antibodies enhanced the AAA-targeting capability of nanoparticles (NPs). Moreover, Tgt-NP-Met administration prevented AAA development and reduced the aneurysm diameter in apolipoprotein E (ApoE)-deficient (ApoE-/-) mice that received continuous infusion of angiotensin II. Furthermore, metformin prevented AAA progression by inhibiting the transformation of vascular smooth muscle cells (VSMCs) from a contractile phenotype to a synthetic phenotype, which is mediated by macrophage infiltration and activation. Conclusion: Our findings identify metformin as a functional suppressor for macrophage-mediated phenotypic transformation of VSMCs and Tgt-NP-Met as an efficient therapeutic strategy for AAA management.

Group 2 Innate Lymphoid Cells Protect Mice from Abdominal Aortic Aneurysm Formation via IL5 and Eosinophils.

Development of abdominal aortic aneurysms (AAA) enhances lesion group-2 innate lymphoid cell (ILC2) accumulation and blood IL5. ILC2 deficiency in Rorafl/fl Il7rCre/+ mice or induced ILC2 depletion in Icosfl-DTR-fl/+ Cd4Cre/+ mice expedites AAA growth, increases lesion inflammation, but leads to systemic IL5 and eosinophil (EOS) deficiency. Mechanistic studies show that ILC2 protect mice from AAA formation via IL5 and EOS. IL5 or ILC2 from wild-type (WT) mice, but not ILC2 from Il5-/- mice induces EOS differentiation in bone-marrow cells from Rorafl/fl Il7rCre/+ mice. IL5, IL13, and EOS or ILC2 from WT mice, but not ILC2 from Il5-/- and Il13-/- mice block SMC apoptosis and promote SMC proliferation. EOS but not ILC2 from WT or Il5-/- mice block endothelial cell (EC) adhesion molecule expression, angiogenesis, dendritic cell differentiation, and Ly6Chi monocyte polarization. Reconstitution of WT EOS and ILC2 but not Il5-/- ILC2 slows AAA growth in Rorafl/fl Il7rCre/+ mice by increasing systemic EOS. Besides regulating SMC pathobiology, ILC2 play an indirect role in AAA protection via the IL5 and EOS mechanism.

Angiotensin II Type 1 Receptor Blocker Prevents Abdominal Aortic Aneurysm Progression in Osteoprotegerin-Deficient Mice via Upregulation of Angiotensin (1-7).

Background Angiotensin II type 1 receptor blockers (ARBs) have been shown to limit the growth of abdominal aortic aneurysm (AAA), but their efficacy is controversial. This study aimed to investigate the molecular mechanism underlying the protective effect of ARBs against AAA progression. Methods and Results Olmesartan, an ARB, was administered to wild-type and osteoprotegerin-knockout (Opg-KO) mice starting 2 weeks before direct application of CaCl2 to aortas to induce AAA. The protective effect of olmesartan against AAA in wild-type and Opg-KO mice was compared at 6 weeks after AAA induction. Olmesartan prevented AAA progression in Opg-KO mice, including excessive aortic dilatation and collapse of tunica media, but not in wild-type mice. Deficiency of the Opg gene is known to cause excessive activation of the tumor necrosis factor-related apoptosis-inducing ligand-induced c-Jun N-terminal kinase/matrix metalloproteinase 9 pathway, resulting in prolonged AAA progression. Olmesartan attenuated the upregulation of phosphorylated c-Jun N-terminal kinase and matrix metalloproteinase 9 expression in the aortic wall of Opg-KO mice. In cultured vascular smooth muscle cells, tumor necrosis factor-related apoptosis-inducing ligand-induced c-Jun N-terminal kinase phosphorylation and matrix metalloproteinase 9 expression were inhibited by angiotensin (1-7), the circulating levels of which are increased by ARBs. Furthermore, administering an angiotensin (1-7) antagonist to Opg-KO mice diminished the protective effect of olmesartan against AAA progression. Conclusions Olmesartan prevented AAA progression in Opg-KO mice by upregulating angiotensin (1-7), suggesting that angiotensin (1-7) may be a key factor that mediates the protective effect of ARBs.

Interleukin-38 suppresses abdominal aortic aneurysm formation in mice by regulating macrophages in an IL1RL2-p38 pathway-dependent manner.

Macrophages play crucial roles in abdominal aortic aneurysm (AAA) formation through the inflammatory response and extracellular matrix degradation; therefore, regulating macrophages may suppress AAA formation. Interleukin-38 (IL-38) is a member of the IL-1 family, which binds to IL-36 receptor (IL1RL2) and has an anti-inflammation effect. Because macrophages express IL1RL2, we hypothesized that IL-38 suppresses AAA formation by controlling macrophages. We assessed a C57BL6/J mouse angiotensin II-induced AAA model with or without IL-38 treatment. RAW 264.7 cells were cultured with tumor necrosis factor-α and treated with or without IL-38. Because p38 has important roles in inflammation, we assessed p38 phosphorylation in vitro and in vivo. To clarify whether the IL-38 effect depends on the p38 pathway, we used SB203580 to inhibit p38 phosphorylation. IL1RL2+ macrophage accumulation along with matrix metalloproteinase (MMP)-2 and -9 expression was observed in mouse AAA. IL-38 reduced the incidence of AAA formation along with reduced M1 macrophage accumulation and MMP-2 and -9 expression in the AAA wall. Macrophage activities including inducible nitric oxide, MMP-2, and MMP-9 production and spindle-shaped changes were significantly suppressed by IL-38. Furthermore, we revealed that inhibition of p38 phosphorylation diminished the effects of IL-38 on regulating macrophages to reduce AAA incidence, indicating the protective effects of IL-38 depend on the p38 pathway. IL-38 plays protective roles against AAA formation through regulation of macrophage accumulation in the aortic wall and modulating the inflammatory phenotype. Using IL-38 may be a novel therapy for AAA patients.

Disulfiram protects against abdominal aortic aneurysm by ameliorating vascular smooth muscle cells pyroptosis.

PURPOSE: Recent studies demonstrated that pyroptosis is involved in abdominal aortic aneurysm (AAA) progression, suggesting a potential target for AAA treatment. This study aimed to identify if disulfiram could inhibit angiotensin II (Ang II)-induced vascular smooth muscle cells (VSMCs) damage, thereby exerting protective effects on AAA. METHODS: The AAA mouse model was established by continuous subcutaneous Ang II infusion for 28 days. Then aortic tissue of the mice was isolated and subjected to RNA sequencing, qRT-PCR, Western blotting, and immunofluorescence staining. To explore the therapeutic effect of disulfiram, mice were orally administered disulfiram (50 mg/kg/day) or vehicle for 28 days accompanied with Ang II infusion. Pathological changes in aortic tissues were measured using microultrasound imaging analysis and histopathological analysis. In addition, inflammatory response, pyroptosis, and oxidative stress damage were examined in mouse aortic vascular smooth muscle (MOVAS) cells stimulated with Ang II in vitro. RESULTS: The RNA sequencing and bioinformatic analysis results suggested that pyroptosis- and inflammation-related genes were significantly upregulated in AAA, consistent with the results of qRT-PCR and Western blotting. Most importantly, the therapeutic effect of disulfiram on AAA was identified in our study. First, disulfiram administration significantly attenuated Ang II-induced inflammation, pyroptosis, and oxidative stress in VSMCs, which is associated with the inhibition of the NF-κB-NLRP3 pathway. Second, in-vivo studies revealed that disulfiram treatment reduced AAA formation and significantly ameliorated collagen deposition and elastin degradation in the aortic wall. CONCLUSION: Our findings suggest that disulfiram has a novel protective effect against AAA by inhibiting Ang II-induced VSMCs pyroptosis.

Gut microbiome dysbiosis contributes to abdominal aortic aneurysm by promoting neutrophil extracellular trap formation.

Abdominal aortic aneurysm (AAA) is an insidious and lethal vascular disease that lacks effective nonsurgical interventions. Gut microbiota dysbiosis plays key roles in many diseases, but its relationship with AAA has not been fully elucidated. Herein, we reveal significant abnormalities in the gut microbe composition of AAA patients and confirm that gut microbiota dysbiosis is an important cause of AAA. Specifically, R. intestinalis was significantly reduced in AAA patients. Using AAA mice, we show that R. intestinalis and its metabolite butyrate significantly reduce neutrophil infiltration and NOX2-dependent neutrophil extracellular trap formation, inflammation, and abnormal phenotypic switching of vascular smooth muscle cells in the aortic wall, thereby markedly alleviating AAA development. Our research uncovers the role and mechanism of the gut microbiota in AAA development and provides insights into AAA prophylaxis from a microecological perspective.

Vascular smooth muscle RhoA counteracts abdominal aortic aneurysm formation by modulating MAP4K4 activity.

Whether a small GTPase RhoA plays a role in the pathology of abdominal aortic aneurysm (AAA) has not been determined. We show here that RhoA expression is reduced in human AAA lesions, compared with normal areas. Furthermore, incidence of AAA formation is increased in vascular smooth muscle cell (VSMC)-specific RhoA conditional knockout (cKO) mice. The contractility of the aortic rings and VSMCs from RhoA cKO mice is reduced, and expression of genes related to the VSMC contractility is attenuated by loss of RhoA. RhoA depletion activates the mitogen-activated protein (MAP) kinase signaling, including MAP4K4, in the aorta and VSMCs. Inhibition of MAP4K4 activity by DMX-5804 decreases AAA formation. Set, a binding protein to active RhoA, functions as an activator of MAP4K4 by sequestering PP2A, an inhibitor of MAP4K4, in the absence of RhoA. In conclusion, RhoA counteracts AAA formation through inhibition of MAP4K4 in cooperation with Set.

Gut Microbiota Influence the Development of Abdominal Aortic Aneurysm by Suppressing Macrophage Accumulation in Mice.

BACKGROUND: Abdominal aortic aneurysm (AAA) is a life-threatening cardiovascular disease characterized by dilated abdominal aorta. Immune cells have been shown to contribute to the development of AAA, and that the gut microbiota is associated with numerous diseases, including cardiovascular diseases, by regulating immune systems or metabolic pathways of the host. However, the interaction between the gut microbiota and AAA remains unknown. METHODS: Apolipoprotein E-deficient male mice were fed a high-cholesterol diet and divided into three groups: the control group was maintained under normal water (control group), the oral AVNM group was maintained under drinking water supplemented with ampicillin, vancomycin, neomycin, and metronidazole, and the i.p. AVNM group was injected AVNM intraperitoneally. After 1 week of pretreatment with antibiotics, these mice were administrated Ang II via subcutaneous osmotic pumps for 4 weeks and euthanized to evaluate AAA formation. RESULTS: Depletion of gut microbiota by oral AVNM ameliorated the incidence of AAAs (control group: 58.9% versus oral AVNM group: 28.6% versus i.p. AVNM group: 75.0%, P = 0.0005) and prevented death due to ruptured aneurysms (control group: 11% versus oral AVNM group: 0% versus i.p. AVNM group: 15%). Oral AVNM suppressed monocyte storage in the spleen, but not in other organs. Despite possessing a higher level of cholesterol, recruitment of monocytes into the suprarenal aorta was suppressed in the oral AVNM group. In AVNM drinking mice, NOD1 ligand, a kind of PRR ligands, increased the development of AAAs and accumulation of macrophages in the aortae. CONCLUSIONS: The gut microbiota plays a critical role in AAA formation. Therefore, regulation of the microbiota or the immune system can be a therapeutic approach for AAA.