VSMC-specific EP4 deletion exacerbates angiotensin II-induced aortic dissection by increasing vascular inflammation and blood pressure

Prostaglandin E2 (PGE2) plays an important role in vascular homeostasis. Its receptor, E-prostanoid receptor 4 (EP4) is essential for physiological remodeling of the ductus arteriosus (DA). However, the role of EP4 in pathological vascular remodeling remains largely unknown. We found that chronic angiotensin II (AngII) infusion of mice with vascular smooth muscle cell (VSMC)-specific EP4 gene knockout (VSMC-EP4^-/-) frequently developed aortic dissection (AD) with severe elastic fiber degradation and VSMC dedifferentiation. AngII-infused VSMC-EP4^-/- mice also displayed more profound vascular inflammation with increased monocyte chemoattractant protein-1 (MCP-1) expression, macrophage infiltration, matrix metalloproteinase-2 and -9 (MMP2/9) levels, NADPH oxidase 1 (NOX1) activity, and reactive oxygen species production. In addition, VSMC-EP4^-/- mice exhibited higher blood pressure under basal and AngII-infused conditions. Ex vivo and in vitro studies further revealed that VSMC-specific EP4 gene deficiency significantly increased AngII-elicited vasoconstriction of the mesenteric artery, likely by stimulating intracellular calcium release in VSMCs. Furthermore, EP4 gene ablation and EP4 blockade in cultured VSMCs were associated with a significant increase in MCP-1 and NOX1 expression and a marked reduction in α-SM actin (α-SMA), SM22α, and SM differentiation marker genes myosin heavy chain (SMMHC) levels and serum response factor (SRF) transcriptional activity. To summarize, the present study demonstrates that VSMC EP4 is critical for vascular homeostasis, and its dysfunction exacerbates AngII-induced pathological vascular remodeling. EP4 may therefore represent a potential therapeutic target for the treatment of AD.

Exogenous Vasohibin-2 Exacerbates Angiotensin II-Induced Ascending Aortic Dilation in Mice

Background: Chronic angiotensin II (AngII) infusion promotes ascending aortic dilation in C57BL/6J mice. Meanwhile, vasohibin-2 (VASH2) is an angiogenesis promoter in neovascularization under various pathologic conditions. The aim of this study was to investigate whether exogenous VASH2 influences chronic AngII-induced ascending aortic dilation.

Methods and Results: Eight–ten-week-old male C57BL/6J mice were injected with adenovirus (Ad) expressing either VASH2 or LacZ. One week after the injection, mice were infused with either AngII or saline s.c. for 3 weeks. Mice were divided into 4 groups: AngII+VASH2, AngII+LacZ, saline+VASH2, and saline+LacZ. Overexpression of VASH2 significantly increased AngII-induced intimal areas as well as the external diameter of the ascending aorta. In addition, VASH2 overexpression promoted ascending aortic medial elastin fragmentation in AngII-infused mice, which was associated with increased matrix metalloproteinase activity and medial smooth muscle cell (SMC) apoptosis. On western blot analysis, accumulation of apoptotic signaling proteins, p21 and p53 was increased in the AngII+VASH2 group. Furthermore, transfection of human aortic SMC with Ad VASH2 increased p21 and p53 protein abundance upon AngII stimulation. Positive TUNEL staining was also detected in the same group of the human aortic SMC.

Conclusions: Exogenous VASH2 exacerbates AngII-induced ascending aortic dilation in vivo, which is associated with increased medial apoptosis and elastin fragmentation.

Knockout of dihydrofolate reductase in mice induces hypertension and abdominal aortic aneurysm via mitochondrial dysfunction

Hypertension and abdominal aortic aneurysm (AAA) are severe cardiovascular diseases with incompletely defined molecular mechanisms. In the current study we generated dihydrofolate reductase (DHFR) knockout mice for the first time to examine its potential contribution to the development of hypertension and AAA, as well as the underlying molecular mechanisms. Whereas the homozygote knockout mice were embryonically lethal, the heterozygote knockout mice had global reduction in DHFR protein expression and activity. Angiotensin II infusion into these animals resulted in substantially exaggerated elevation in blood pressure and development of AAA, which was accompanied by excessive eNOS uncoupling activity (featured by significantly impaired tetrahydrobiopterin and nitric oxide bioavailability), vascular remodeling (MMP2 activation, medial elastin breakdown and adventitial fibrosis) and inflammation (macrophage infiltration). Importantly, scavenging of mitochondrial reactive oxygen species with Mito-Tempo in vivo completely abrogated development of hypertension and AAA in DHFR knockout mice, indicating a novel role of mitochondria in mediating hypertension and AAA downstream of DHFR deficiency-dependent eNOS uncoupling. These data for the first time demonstrate that targeting DHFR-deficiency driven mitochondrial dysfunction may represent an innovative therapeutic option for the treatment of AAA and hypertension.

Mast cell tryptase - Marker and maker of cardiovascular diseases

Mast cells are tissue-resident cells, which have been proposed to participate in various inflammatory diseases, among them the cardiovascular diseases (CVDs). For mast cells to be able to contribute to an inflammatory process, they need to be activated to exocytose their cytoplasmic secretory granules. The granules contain a vast array of highly bioactive effector molecules, the neutral protease tryptase being the most abundant protein among them. The released tryptase may act locally in the inflamed cardiac or vascular tissue, so contributing directly to the pathogenesis of CVDs. Moreover, a fraction of the released tryptase reaches the systemic circulation, thereby serving as a biomarker of mast cell activation. Actually, increased levels of circulating tryptase have been found to associate with CVDs. Here we review the biological relevance of the circulating tryptase as a biomarker of mast cell activity in CVDs, with special emphasis on the relationship between activation of mast cells in their tissue microenvironments and the pathophysiological pathways of CVDs. Based on the available in vitro and in vivo studies, we highlight the potential molecular mechanisms by which tryptase may contribute to the pathogenesis of CVDs. Finally, the synthetic and natural inhibitors of tryptase are reviewed for their potential utility as therapeutic agents in CVDs.

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.

A potential key mechanism in ascending aortic aneurysm development: Detection of a linear relationship between MMP-14/TIMP-2 ratio and active MMP-2

Objectives

Elevated matrix metalloproteinase-2 (MMP-2) tissue levels have been associated with ascending thoracic aortic aneurysm (aTAA). As MMP-2 activation is controlled by interactions among matrix metalloproteinase-14 (MMP-14), a tissue inhibitor of metalloproteinases-2 (TIMP-2) and Pro-MMP-2 in cell culture, this activation process might also play a role in aTAA.

Methods

Via gelatin zymography we analyzed tissue levels of MMP-2 isoforms (Pro-MMP-2, active MMP-2, total MMP-2) and via enzyme-linked immunosorbent assay (ELISA,) MMP-14,TIMP-2 and total MMP-2 tissue levels in N = 42 patients with aTAA. As controls, MMP-14 and TIMP-2 aortic tissue levels in N = 9 patients undergoing coronary artery bypass surgery were measured via ELISA, and levels of MMP-2 isoforms in N = 11 patients via gelatin zymography.

Results

Active MMP-2 was significantly higher in aTAA than in controls. Patients with aTAA exhibited significantly lower Pro-MMP-2 and TIMP-2 levels. Total MMP-2 and MMP-14 did not differ significantly between groups. Regression analysis revealed a linear relationship between TIMP-2 and the MMP-14/TIMP-2 ratio, as well as active MMP-2 in aTAA. Aneurysmatic tissue can be accurately distinguished from control aortic tissue (AUC = 1) by analyzing the active MMP-2/Pro-MMP-2 ratio with a cutoff value of 0.11, whereas MMP-14 and TIMP-2 roles are negligible in ROC analysis.

Conclusion

A larger amount of MMP-2 is activated in aTAA than in control aortic tissue–a factor that seems to be a central process in aneurysm development. When active MMP-2 exceeds 10% compared to Pro-MMP-2, we conclude that it originates from aneurysmatic tissue, which we regard as a starting point for further studies of aTAA biomarkers. The tissue's MMP-14/TIMP-2 ratio may regulate the degree of Pro-MMP-2 activation as a determining factor, while the enzymatic activities of MMP-14 and TIMP-2 do not seem to play a key role in aneurysm development.

Role of Noncoding RNAs in the Pathogenesis of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a local dilatation of the abdominal aortic vessel wall and is among the most challenging cardiovascular diseases as without urgent surgical intervention, ruptured AAA has a mortality rate of >80%. Most patients present acutely after aneurysm rupture or dissection from a previously asymptomatic condition and are managed by either surgery or endovascular repair. Patients usually are old and have other concurrent diseases and conditions, such as diabetes mellitus, obesity, and hypercholesterolemia making surgical intervention more difficult. Collectively, these issues have driven the search for alternative methods of diagnosing, monitoring, and treating AAA using therapeutics and less invasive approaches. Noncoding RNAs-short noncoding RNAs (microRNAs) and long-noncoding RNAs-are emerging as new fundamental regulators of gene expression. Researchers and clinicians are aiming at targeting these microRNAs and long noncoding RNAs and exploit their potential as clinical biomarkers and new therapeutic targets for AAAs. While the role of miRNAs in AAA is established, studies on long-noncoding RNAs are only beginning to emerge, suggesting their important yet unexplored role in vascular physiology and disease. Here, we review the role of noncoding RNAs and their target genes focusing on their role in AAA. We also discuss the animal models used for mechanistic understanding of AAA. Furthermore, we discuss the potential role of microRNAs and long noncoding RNAs as clinical biomarkers and therapeutics.

Neutrophil-to-Lymphocyte Ratio: A Comparative Study of Rupture to Nonruptured Infrarenal Abdominal Aortic Aneurysm

BACKGROUND

Neutrophil-to-lymphocyte ratio (NLR) has recently emerged as a useful predictor of cardiovascular risk and adverse outcomes. According to previous studies, an NLR >5 has the highest sensitivity and specificity for postoperative morbidity and mortality in cardiovascular disease. This study aims to evaluate the NLR in cases of infrarenal unruptured abdominal aortic aneurysm (uAAA) and ruptured abdominal aortic aneurysm (rAAA) and to assess the role of NLR as a prognostic marker of 30-day mortality in patients with uAAA and rAAA who underwent surgical repair.

METHODS

This retrospective cohort study examined 255 consecutive patients with intact or ruptured infrarenal AAA who underwent elective or urgent open repair surgery within our clinic in a 10-year period. Differences in prevalence were assessed using chi-squared calculations and values greater than 5 and a P-value less than 0.05 were considered significant. The averages were compared using the ANOVA parameter test when the Bartlett P-value was greater than 0.05.

RESULTS

The average NLR appeared to be significantly higher in the group of patients with rAAA (9.3 vs. 3.39, respectively P < 0001). Furthermore, NLR > 5 occurred in 77.6% of patients with rAAA but only 32.5% in patients with uAAA (odds ratio 5.085; 95% confidence interval [CI]: 3.0025-8.6145; P < 0000.1). In terms of the postoperative prognosis in patients with uAAA, mortality after 30 days postoperatively was considerably higher at 16.6% in patients with NLR >5 compared with 6% for patients with NLR < 5 (RR: 2.77; 95% CI: 1.020-7.55; P < 0.045). In the case of rAAA, mortality after 30 days was higher in patients with NLR >5 (61.44%) than those with NLR < 5 (45.83%). There was no relationship between NLR and length of hospital stay or between NLR and the maximum diameter of the AAA. There was also no difference in the NLR between genders or age groups.

CONCLUSIONS

The main findings of this study were the poor outcomes in terms of 30-day mortality for the patients presenting NLR values greater than 5 undergoing open surgical repair in both categories: infrarenal uAAA and rAAA. We also show that NLR is significantly higher among patients with rAAA and that an NLR >5 indicates a 5 times greater possibility of AAA being ruptured. We can use this easily determinable, broadly available, and inexpensive marker to identify high-risk patients, individually, or integrated into a risk-stratification system for patients diagnosed with AAA. This would help in the therapeutic management of AAA, including the avoidance of open surgery when there are prohibitive risks, instead opting for an endovascular approach.

Ginkgo biloba extracts prevent aortic rupture in angiotensin II-infused hypercholesterolemic mice

Abdominal aortic aneurysms (AAAs) are a chronic vascular disease characterized by pathological luminal dilation. Aortic rupture is the fatal consequence of AAAs. Ginkgo biloba extracts (GBEs), a natural herb extract widely used as food supplements, drugs, and cosmetics, has been reported to suppress development of calcium chloride-induced AAAs in mice. Calcium chloride-induced AAAs do not rupture, while angiotensin II (AngII)-induced AAAs in mice have high rate of aortic rupture, implicating potentially different mechanisms from calcium chloride-induced AAAs. This study aimed to determine whether GBE would improve aortic dilation and rupture rate of AngII-induced AAAs. Male apolipoprotein E (apoE) -/- mice were infused with AngII and administered either GBE or its major active ingredients, flavonoids and ginkgolides, individually or in combination. To determine the effects of GBE in mice with established AAAs, male apoE-/- mice were firstly infused with AngII for 28 days to develop AAAs, and then administered either GBE or vehicle in mice with established AAAs, which were continuously infused with AngII for another 56 days. GBE, but not the two major active components separately or synergistically, prevented aortic rupture, but not aortic dilation. The protection of GBE from aortic rupture was independent of systolic blood pressure, lipid, and inflammation. GBE also did not attenuate either aortic rupture or progressive aortic dilation in mice with established AAAs. GBE did not reduce the atherosclerotic lesion areas, either. In conclusion, GBE prevents aortic rupture in AngII-infused hypercholesterolemic mice, but only in the early phase of the disease development.

TLR4 and MMP2 polymorphisms and their associations with cardiovascular risk factors in susceptibility to aortic aneurysmal diseases

Background: Toll-like receptor 4 (TLR4) and matrix metalloproteinase 2 (MMP2) play important roles in aortic pathophysiology. We aimed to evaluate the contribution of TLR4 and MMP2 polymorphisms individually and complex interactions between gene and risk factors in susceptibility to aortic aneurysm (AA) and its subtypes. Methods: KASP method was adopted to detect TLR4rs11536889, rs1927914 and MMP2rs2285053 polymorphisms in 498 controls and 472 AA patients, including 212 abdominal AA (AAA) and 216 thoracic AA (TAA). Results: In the overall analysis, MMP2rs2285053 TC genotype was correlated with TAA risk (P = 0.047, OR = 1.487). Stratified analysis revealed an increased AA risk in males with TLR4rs1927914 TC genotype, while MMP2rs2285053 TC conferred an elevated AA risk in the subjects ≤60 years, and its TC genotype and dominant model were associated with TAA in the subjects ≤60 year. The interaction between TLR4rs1927914 and MMP2rs2285053 was associated with AAA risk (P _interaction = 0.028, OR = 2.913). Furthermore, significant interaction between TLR4rs11536889 and dyslipidemia was observed for TAA risk, while TLR4rs1927914 could interact with hypertension and diabetes to increase the risk of AA or its subtypes. Two-way interaction effect of TLR4rs1927914 and MMP2rs2285053 was enhanced by diabetes or dyslipidemia. Conclusion: TLR4 and MMP2 polymorphisms and their complex interactions with cardiovascular risk factors contributed to aortic aneurysmal diseases.

Inhibitory effects of cycloastragenol on abdominal aortic aneurysm and its related mechanisms

BACKGROUND AND PURPOSE

Abdominal aortic aneurysm (AAA) is a degenerative disease affecting human health, but there are no safe and effective medications for AAA therapy. Cycloastragenol (CAG), derived from Astragali Radix, has various pharmacological effects. However, whether CAG can protect against AAA remains elusive. In this study, we investigated whether CAG has an inhibitory effect on AAA and its related mechanism.

EXPERIMENTAL APPROACH

The AAA mouse model was induced by incubating the abdominal aorta with elastase. CAG was administered by gavage at different doses beginning on the same day or 14 days after inducing AAA to explore its preventive or therapeutic effects respectively. The preventive effects of CAG on AAA were verified in another AAA mouse model induced by angiotensin II in ApoE-/- mouse. In vitro experiments were implemented on rat vascular smooth muscle cells (VSMCs) stimulated by TNF-α.

KEY RESULTS

Compared to the control AAA model group, CAG (125 mg·kg-1 body weight day-1 ) reduced the incidence of AAA, the dilatation of aorta and elastin degradation in media in both mouse models of AAA. CAG suppressed the inflammation, oxidation, phenotype switch and apoptosis in TNF-α-stimulated VSMCs, ameliorated the expression and activity of MMPs and decreased the activation of the ERK/JNK signalling pathway. CAG also inhibited the degradation of elastin in TNF-α-stimulated VSMCs.

CONCLUSION AND IMPLICATIONS

CAG presents protective effects against AAA through down-regulation of the MAPK signalling pathways and thus attenuates inflammation, oxidation, VSMC phenotype switch and apoptosis and the expression of MMPs as well as increasing elastin biosynthesis.

Early pathological characterization of murine dissecting abdominal aortic aneurysms

We report here on the early pathology of a well-established murine model of dissecting abdominal aortic aneurysms (AAAs). Continuous infusion of angiotensin II (AngII) into apolipoprotein E-deficient mice induces the formation of aortic dissection and expansion at some point after implantation of miniosmotic pumps containing AngII. While this model has been studied extensively at a chronic stage, we investigated the early pathology of dissecting AAA formation at multiple scales. Using high-frequency ultrasound, we screened 12-week-old male mice daily for initial formation of these aneurysmal lesions between days 3 and 10 post-implantation. We euthanized animals on the day of diagnosis of a dissecting AAA or at day 10 if no aneurysmal lesion developed. Aortic expansion and reduced vessel wall strain occurred in animals regardless of whether a dissecting AAA developed by day 10. The aortas of mice that did not develop dissecting AAAs showed intermediate changes in morphology and biomechanical properties. RNA sequencing and gene expression analysis revealed multiple proinflammatory and matrix remodeling genes to be upregulated in the suprarenal aorta of AngII-infused mice as compared to saline-infused controls. Histology and immunohistochemistry confirmed that extracellular matrix remodeling and inflammatory cell infiltration, notably neutrophils and macrophages, occurred in AngII-infused mice with and without dissecting AAAs but not saline-infused controls. Understanding early disease processes is a critical step forward in translating experimental results in cardiovascular disease research. This work advances our understanding of this well-established murine model with applications for improving early diagnosis and therapy of acute aortic syndrome in humans.

Macrophage-derived netrin-1 promotes abdominal aortic aneurysm formation by activating MMP3 in vascular smooth muscle cells

Abdominal aortic aneurysms (AAA) are characterized by extensive extracellular matrix (ECM) fragmentation and inflammation. However, the mechanisms by which these events are coupled thereby fueling focal vascular damage are undefined. Here we report through single-cell RNA-sequencing of diseased aorta that the neuronal guidance cue netrin-1 can act at the interface of macrophage-driven injury and ECM degradation. Netrin-1 expression peaks in human and murine aneurysmal macrophages. Targeted deletion of netrin-1 in macrophages protects mice from developing AAA. Through its receptor neogenin-1, netrin-1 induces a robust intracellular calcium flux necessary for the transcriptional regulation and persistent catalytic activation of matrix metalloproteinase-3 (MMP3) by vascular smooth muscle cells. Deficiency in MMP3 reduces ECM damage and the susceptibility of mice to develop AAA. Here, we establish netrin-1 as a major signal that mediates the dynamic crosstalk between inflammation and chronic erosion of the ECM in AAA.

Abdominal aortic aneurysms (AAA) are characterized by extensive extracellular matrix degradation. Here Hadi et al. identify a netrin-1/neogenin-based crosstalk between macrophages and vascular smooth muscle cells (VSMCs), leading to the secretion of the matrix metalloproteinase MMP-3 by VSMCs and subsequent matrix degradation in AAA lesions.

Decreased mitochondrial respiration in aneurysmal aortas of Fibulin-4 mutant mice is linked to PGC1A regulation

Aim

Thoracic aortic aneurysms are a life-threatening condition often diagnosed too late. To discover novel robust biomarkers, we aimed to better understand the molecular mechanisms underlying aneurysm formation.

Methods and results

In Fibulin-4R/R mice, the extracellular matrix protein Fibulin-4 is 4-fold reduced, resulting in progressive ascending aneurysm formation and early death around 3 months of age. We performed proteomics and genomics studies on Fibulin-4R/R mouse aortas. Intriguingly, we observed alterations in mitochondrial protein composition in Fibulin-4R/R aortas. Consistently, functional studies in Fibulin-4R/R vascular smooth muscle cells (VSMCs) revealed lower oxygen consumption rates, but increased acidification rates. Yet, mitochondria in Fibulin-4R/R VSMCs showed no aberrant cytoplasmic localization. We found similar reduced mitochondrial respiration in Tgfbr-1M318R/+ VSMCs, a mouse model for Loeys-Dietz syndrome (LDS). Interestingly, also human fibroblasts from Marfan (FBN1) and LDS (TGFBR2 and SMAD3) patients showed lower oxygen consumption. While individual mitochondrial Complexes I-V activities were unaltered in Fibulin-4R/R heart and muscle, these tissues showed similar decreased oxygen consumption. Furthermore, aortas of aneurysmal Fibulin-4R/R mice displayed increased reactive oxygen species (ROS) levels. Consistent with these findings, gene expression analyses revealed dysregulation of metabolic pathways. Accordingly, blood ketone levels of Fibulin-4R/R mice were reduced and liver fatty acids were decreased, while liver glycogen was increased, indicating dysregulated metabolism at the organismal level. As predicted by gene expression analysis, the activity of PGC1α, a key regulator between mitochondrial function and organismal metabolism, was downregulated in Fibulin-4R/R VSMCs. Increased TGFβ reduced PGC1α levels, indicating involvement of TGFβ signalling in PGC1α regulation. Activation of PGC1α restored the decreased oxygen consumption in Fibulin-4R/R VSMCs and improved their reduced growth potential, emphasizing the importance of this key regulator.

Conclusion

Our data indicate altered mitochondrial function and metabolic dysregulation, leading to increased ROS levels and altered energy production, as a novel mechanism, which may contribute to thoracic aortic aneurysm formation.

VPO1 Modulates Vascular Smooth Muscle Cell Phenotypic Switch by Activating Extracellular Signal-regulated Kinase 1/2 (ERK 1/2) in Abdominal Aortic Aneurysms

Background Hydrogen peroxide (H2O2) is a critical molecular signal in the development of abdominal aortic aneurysm ( AAA ) formation. Vascular peroxidase 1 ( VPO 1) catalyzes the production of hypochlorous acid ( HOC l) from H2O2 and significantly enhances oxidative stress. The switch from a contractile phenotype to a synthetic one in vascular smooth muscle cells ( VSMC s) is driven by reactive oxygen species and is recognized as an early and important event in AAA formation. This study aims to determine if VPO 1 plays a critical role in the development of AAA by regulating VSMC phenotypic switch. Methods and Results VPO 1 is upregulated in human and elastase-induced mouse aneurysmal tissues compared with healthy control tissues. Additionally, KLF 4, a nuclear transcriptional factor, is upregulated in aneurysmatic tissues along with a concomitant downregulation of differentiated smooth muscle cell markers and an increase of synthetic phenotypic markers, indicating VSMC phenotypic switch in these diseased tissues. In cultured VSMC s from rat abdominal aorta, H2O2 treatment significantly increases VPO 1 expression and HOC l levels as well as VSMC phenotypic switch. In support of these findings, depletion of VPO 1 significantly attenuates the effects of H2O2 and HOC l treatment. Furthermore, HOC l treatment promotes VSMC phenotypic switch and ERK 1/2 phosphorylation. Pretreatment with U0126 (a specific inhibitor of ERK 1/2) significantly attenuates HOC l-induced VSMC phenotypic switch. Conclusions Our results demonstrate that VPO 1 modulates VSMC phenotypic switch through the H2O2/ VPO 1/ HOC l/ ERK 1/2 signaling pathway and plays a key role in the development of AAA . Our findings also implicate VPO 1 as a novel signaling node that mediates VSMC phenotypic switch and plays a key role in the development of AAA . Clinical Trial Registration URL : www.chictr.org.cn . Unique identifier: Chi CTR 1800016922.

A selective antagonist of prostaglandin E receptor subtype 4 attenuates abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a progressive disease that has an increasing prevalence with aging, but no effective pharmacological therapy to attenuate AAA progression is currently available. We reported that the prostaglandin E receptor EP4 plays roles in AAA progression. Here, we show the effect of CJ-42794, a selective EP4 antagonist, on AAA using two mouse models (angiotensin II- and CaCl2 -induced AAAs) and human aortic smooth muscle cells isolated from AAA tissue. Oral administration of CJ-42794 (0.2 mg/kg per day) for 4 weeks significantly decreased AAA formation in ApoE-/- mice infused with angiotensin II (1 μg/kg per min), in which elastic fiber degradation and activations of matrix metalloproteinase (MMP)-2 and MMP-9 were attenuated. Interleukin-6 (IL-6) proteins were highly expressed in the medial layer of angiotensin II-induced mouse AAA tissues, whereas this expression was significantly decreased in mice treated with CJ-42794. AAA formation induced by periaortic CaCl2 application in wild-type mice was also reduced by oral administration of CJ-42794 for 4 weeks. After oral administration of CJ-42794 beginning 2 weeks after periaortic CaCl2 application and continuing for an additional 4 weeks, the aortic diameter and elastic fiber degradation grade were significantly smaller in CJ-42794-treated mice than in untreated mice. Additionally, in smooth muscle cells isolated from human AAA tissues, stimulation of CJ-42794 inhibited PGE2 -induced IL-6 secretion in a dose-dependent manner and decreased PGE2 -induced MMP-2 activity. These data suggest that inhibition of EP4 has the potential to be a pharmacological strategy for attenuation of AAA progression.

Epithelial Heparan Sulfate Contributes to Alveolar Barrier Function and Is Shed during Lung Injury

The lung epithelial glycocalyx is a carbohydrate-enriched layer lining the pulmonary epithelial surface. Although epithelial glycocalyx visualization has been reported, its composition and function remain unknown. Using immunofluorescence and mass spectrometry, we identified heparan sulfate (HS) and chondroitin sulfate within the lung epithelial glycocalyx. In vivo selective enzymatic degradation of epithelial HS, but not chondroitin sulfate, increased lung permeability. Using mass spectrometry and gel electrophoresis approaches to determine the fate of epithelial HS during lung injury, we detected shedding of 20 saccharide-long or greater HS into BAL fluid in intratracheal LPS-treated mice. Furthermore, airspace HS in clinical samples from patients with acute respiratory distress syndrome correlated with indices of alveolar permeability, reflecting the clinical relevance of these findings. The length of HS shed during intratracheal LPS-induced injury (≥20 saccharides) suggests cleavage of the proteoglycan anchoring HS to the epithelial surface, rather than cleavage of HS itself. We used pharmacologic and transgenic animal approaches to determine that matrix metalloproteinases partially mediate HS shedding during intratracheal LPS-induced lung injury. Although there was a trend toward decreased alveolar permeability after treatment with the matrix metalloproteinase inhibitor, doxycycline, this did not reach statistical significance. These studies suggest that epithelial HS contributes to the lung epithelial barrier and its degradation is sufficient to increase lung permeability. The partial reduction of HS shedding achieved with doxycycline is not sufficient to rescue epithelial barrier function during intratracheal LPS-induced lung injury; however, whether complete attenuation of HS shedding is sufficient to rescue epithelial barrier function remains unknown.

The active participation of p22phox-214T/C in the formation of intracranial aneurysm and the suppressive potential of edaravone

Oxidative stress reactions play an important role in the pathogenesis of intracranial aneurysm (IA). p22phox is involved in the oxidative stress reaction, and it is a critical subunit of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. The present study investigated the association of genetic variants within the gene encoding p22phox‑214T/C with IA. The p22phox‑214T/C gene polymorphisms in 192 cases of IA and 112 controls were analyzed by polymerase chain reaction‑restriction fragment length polymorphism (PCR‑RFLP). The mRNA expression of NADPH oxidase was also analyzed by RT‑PCR. The results of RT‑PCR were validated by ELISA. In a rabbit model of elastase‑induced aneurysm, we used edaravone for anti‑oxidative stress treatment to observe the curative effects. In the clinical cases, a significant difference in p22phox‑214T/C allele frequencies in the IA group was observed compared with the control group (P<0.001). The expression level of NADPH oxidase was differed significantly between the IA group and the control group. In the rabbit model of elastase‑induced aneurysm, the success rate of the aneurysmal model in the edaravone group and the wound ulcer rate were lower than those in the control group. In addition, the diameter of the aneurysm was smaller than in the edaravone group than in the control group (3.26±0.13 mm vs. 3.85±0.07 mm), and the expression of matrix metalloproteinase‑9 (MMP‑9) was significantly lower than that in the control group (P<0.0001). Thus, these data suggest the active participation of p22phox‑214T/C in the formation of IA and the suppressive potential of edaravone against IA formation.

Precise Therapy for Thoracic Aortic Aneurysm in Marfan Syndrome: A Puzzle Nearing Its Solution

Marfan Syndrome (MFS) is a rare connective tissue disorder, resulting from mutations in the fibrillin-1 gene, characterized by pathologic phenotypes in multiple organs, the most detrimental of which affects the thoracic aorta. Indeed, thoracic aortic aneurysms (TAA), leading to acute dissection and rupture, are today the major cause of morbidity and mortality in adult MFS patients. Therefore, there is a compelling need for novel therapeutic strategies to delay TAA progression and counteract aortic dissection occurrence. Unfortunately, the wide phenotypic variability of MFS patients, together with the lack of a complete genotype-phenotype correlation, have represented until now a barrier hampering the conduction of translational studies aimed to predict disease prognosis and drug discovery. In this review, we will illustrate available therapeutic strategies to improve the health of MFS patients. Starting from gold standard surgical overtures and the description of the main pharmacological approaches, we will comprehensively review the state-of-the-art of in vivo MFS models and discuss recent clinical pharmacogenetic results. Finally, we will focus on induced pluripotent stem cells (iPSC) as a technology that, if integrated with preclinical research and pharmacogenetics, could contribute in determining the best therapeutic approach for each MFS patient on the base of individual differences. Finally, we will suggest the integration of preclinical studies, pharmacogenetics and iPSC technology as the most likely strategy to help solve the composite puzzle of precise medicine in this condition.

Correlation between MMP and TIMP levels and elastic moduli of ascending thoracic aortic aneurysms

OBJECTIVE

The objective of this preliminary investigation is to determine if there is a relation between the biological levels of matrix metalloproteinases and tissue inhibitor of matrix metalloproteinase (TIMP) and the elastic moduli of the ascending aortic wall in patients with ascending thoracic aortic aneurysms (ATAA).

METHODS

Circumferential specimens from twelve patients with ATAA were obtained from the greater curvature and their tensile properties (maximum elastic modulus) were tested uniaxially. The levels of MMP1, 2, 3, 8, and 9 as well as TIMP1 and 2 were determined in these aortic wall specimens using MMP/TIMP antibodies array.

RESULTS

Direct relations were found between MMP2 and the elastic modulus of the ascending aorta wall (R² = 0.52) and between MMP9 and TIMP1 (R² = 0.63). However, weak positive relation was found between MMP2 and TIMP2 (R² = 0.23). We found inverse relations between MMP3 and MMP8 levels and the elastic module. There were no relations between MMP1 and MMP9 levels and the elastic modulus of aortic wall.

CONCLUSIONS

This preliminary study looks at the relationship between the elastic modulii and the MMPs/TIMPs levels found in aortic wall specimens. Given that the value of the elastic moduli can be obtained non-invasively, a close relation might permit to infer the value of MMPs and TIMPs levels from the non-invasive determination of the elasticity of the aortic wall. By allowing the non-invasive determination of the mechanical and biological properties of the aorta in in-vivo, the method proposed here might improve the prediction of outcomes of ascending aortic aneurysms. This is a very preliminary study (small sample size) and the outcomes of this study cannot be used as final conclusions and should be verified in further studies with larger sample of patients.

Glucagon-Like peptide-1: A new therapeutic target to treat abdominal aortic aneurysm?

Recent antidiabetic drugs including GLP-1 receptor agonists and DPP-IV inhibitors have demonstrated protective effects in several cardiovascular diseases but their effect in abdominal aortic aneurysm (AAA) is far less known. AAA can be associated with extremely high rates of mortality and pharmacological treatments are still lacking underlining the real need to identify new therapeutic targets. The aim of this review was to summarize current knowledge on the role of GLP-1 pathway in AAA. A systematic literature review was performed and 6 relevant studies (2 clinical and 4 experimental) were included. Experimental studies demonstrated a protective effect of both GLP-1 receptor agonists and DPP-IV inhibitors through targeting the main pathophysiological mechanisms underlying AAA formation. The effects of these drugs in human AAA are still poorly known. In the limelight of clinical and experimental studies, we discuss current limits and future directions.

Associations between serum relaxin 2, aneurysm formation/size and severity of atherosclerosis: a preliminary prospective analysis

Serum relaxin 2 (RL2) is a pleiotropic hormone that acts on various organs and systems, particularly the cardiovascular system. Although RL2 seems to upregulate the synthesis of nitric monoxide (NO) and matrix metalloproteinase (MMP)-2 and -9, current literature on its role in atherosclerosis and aneurysm formation is scarce. The aim of this study was to investigate the levels of serum RL2 in patients with an arterial aneurysm as well as in atherosclerotic patients, and correlate them with the severity of their related vascular disease. A total of 53 subjects were enrolled in this study: 37 patients were scheduled to undergo surgery: 21 patients for different forms of atherosclerotic disease (ATH), 16 patients for an arterial aneurysm (AA), 6 patients for undergoing temporal artery biopsy (TAB), and 10 healthy blood donors (HBD) served as the control groups. RL2 was measured using enzymelinked immunosorbent assay. RL2 was significantly higher in AA patients compared to ATH (P<0.01), TAB (P<0.001) and HBD (P<0.01). No significant difference was found between the ATH and TAB groups (P>0.05). In addition, ATH and AA patients were further subdivided based on the severity of their disease. Serum RL2 was progressively increased in patients with arterial aneurysms, showing a positive relationship with the size of the aneurysmatic dilatation. By contrast, the RL2 level was inversely related to the severity of the atherosclerotic disease. Studies with a larger cohort incorporating a consistent study population are warranted to verify our results and shed light on the mechanistic background of these processes.

Gingival fibroblasts protect against experimental abdominal aortic aneurysm development and rupture through tissue inhibitor of metalloproteinase-1 production

Aims

Abdominal aortic aneurysm (AAA), frequently diagnosed in old patients, is characterized by chronic inflammation, vascular cell apoptosis and metalloproteinase-mediated extracellular matrix destruction. Despite improvement in the understanding of the pathophysiology of aortic aneurysm, no pharmacological treatment is yet available to limit dilatation and/or rupture. We previously reported that human gingival fibroblasts (GFs) can reduce carotid artery dilatation in a rabbit model of elastase-induced aneurysm. Here, we sought to investigate the mechanisms of GF-mediated vascular protection in two different models of aortic aneurysm growth and rupture in mice.

Methods and results

In vitro, mouse GFs proliferated and produced large amounts of anti-inflammatory cytokines and tissue inhibitor of metalloproteinase-1 (Timp-1). GFs deposited on the adventitia of abdominal aorta survived, proliferated, and organized as a layer structure. Furthermore, GFs locally produced Il-10, TGF-β, and Timp-1. In a mouse elastase-induced AAA model, GFs prevented both macrophage and lymphocyte accumulations, matrix degradation, and aneurysm growth. In an Angiotensin II/anti-TGF-β model of aneurysm rupture, GF cell-based treatment limited the extent of aortic dissection, prevented abdominal aortic rupture, and increased survival. Specific deletion of Timp-1 in GFs abolished the beneficial effect of cell therapy in both AAA mouse models.

Conclusions

GF cell-based therapy is a promising approach to inhibit aneurysm progression and rupture through local production of Timp-1.

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

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

Chinese Herbal Medicine as a Potential Treatment of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is an irreversible condition where the abdominal aorta is dilated leading to potentially fatal consequence of aortic rupture. Multiple mechanisms are involved in the development and progression of AAA, including chronic inflammation, oxidative stress, vascular smooth muscle (VSMC) apoptosis, immune cell infiltration and extracellular matrix (ECM) degradation. Currently surgical therapies, including minimally invasive endovascular aneurysm repair (EVAR), are the only viable interventions for AAAs. However, these treatments are not appropriate for the majority of AAAs, which measure <50 mm. Substantial effort has been invested to identify and develop pharmaceutical treatments such as statins and doxycycline for this potentially lethal condition but these interventions failed to offer a cure or to retard the progression of AAA. Chinese herbal medicine (CHM) has been used for the management of cardiovascular diseases for thousands of years in China and other Asian countries. The unique multi-component and multi-target property of CHMs makes it a potentially ideal therapy for multifactorial diseases such as AAA. In this review, we review the current scientific evidence to support the use of CHMs for the treatment of AAA. Mechanisms of action underlying the effects of CHMs on AAA are also discussed.

Early growth response factor-1 DNA enzyme 1 inhibits the formation of abdominal aortic aneurysm in rats

The aim of the present study was to characterize the effects of early growth response factor-1 DNA enzyme (EDRz) in a rat abdominal aortic aneurysm (AAA) model to determine the mechanism by which EDRz inhibits AAA and affects the formation of AAA by regulating the activity of matrix metalloproteinase (MMP)-2 and MMP-9. EDRz was transfected into the abdominal aorta of rats using the jetPRIME transfection reagent following infusion with elastase. Fluorescent microscopy, hematoxylin and eosin staining, ultrastructural analysis, reverse transcription-quantitative polymerase chain reaction, western blotting and immunohistochemical analysis were performed to characterize the response to EDRz. The EDRz group showed minimal aneurysm formation when compared with the control group, with significantly lower aortic diameter expansion (2.5±0.1 vs. 3.5±0.1 mm; P<0.05). Early growth response factor 1 (Egr-1) mRNA and protein levels were significantly decreased in the EDRz group, as expected. The decrease in Egr-1 was accompanied by decreases in the mRNA and protein levels of MMP-2 and MMP-9 (P<0.05). Transfection of the Egr-1 specific synthetic DNA enzyme EDRz significantly reduced AAA following elastase infusion in rats, at least in part due to the decreased expression of downstream MMP-2 and MMP-9.

Deletion of BMAL1 in Smooth Muscle Cells Protects Mice From Abdominal Aortic Aneurysms

OBJECTIVE

Abdominal aortic aneurysm (AAA) has high mortality rate when ruptured, but currently, there is no proven pharmacological therapy for AAA because of our poor understanding of its pathogenesis. The current study explored a novel role of smooth muscle cell (SMC) BMAL1 (brain and muscle Arnt-like protein-1)-a transcription factor known to regulate circadian rhythm-in AAA development.

APPROACH AND RESULTS

SMC-selective deletion of BMAL1 potently protected mice from AAA induced by (1) MR (mineralocorticoid receptor) agonist deoxycorticosterone acetate or aldosterone plus high salt intake and (2) angiotensin II infusion in hypercholesterolemia mice. Aortic BMAL1 was upregulated by deoxycorticosterone acetate-salt, and deletion of BMAL1 in SMCs selectively upregulated TIMP4 (tissue inhibitor of metalloproteinase 4) and suppressed deoxycorticosterone acetate-salt-induced MMP (matrix metalloproteinase) activation and elastin breakages. Moreover, BMAL1 bound to the Timp4 promoter and suppressed Timp4 transcription.

CONCLUSIONS

These results reveal an important, but previously unexplored, role of SMC BMAL1 in AAA. Moreover, these results identify TIMP4 as a novel target of BMAL1, which may mediate the AAA protective effect of SMC BMAL1 deletion.

Relationship between inflammation and progression of an abdominal aortic aneurysm in a rabbit model based on 18F-FDG PET/CT imaging

OBJECTIVE

To explore the relationship between abdominal aortic aneurysm development and inflammation in the rabbit through the establishment of a rabbit infrarenal abdominal aortic aneurysm model and the use of 18F-FDG PET/CT imaging.

METHODS

Twenty male New Zealand rabbits were administered an elastase intracavity perfusion to induce an infrarenal abdominal aortic aneurysm model. Prior to surgery, the rabbits underwent abdominal aorta ultrasonic testing and blood collection from the ear veins. Of the original 20 rabbits, 10 rabbits were euthanized two weeks after the operation following ultrasonic testing, PET/CT scanning and blood collection, and their arterial tissue samples were prepared for pathological and immunohistochemical staining. The remaining 10 rabbits were euthanized four weeks after the operation following ultrasonic testing, PET/CT scanning and blood collection, and the arterial tissue samples were prepared for pathological and immunohistochemical staining.

RESULTS

Compared with the preoperative measurement, the maximum growth rate of the aneurysm diameter is 89.21 ± 0.02% (the absolute increase in diameter is 2.040 ± 0.376 mm) two weeks after the operation. Compared with the two-week postoperative value, the maximum growth rate of the aneurysm diameter is 15.8 ± 0.01% (the absolute increase in diameter is 0.684 ± 0.115 mm) four weeks after the operation. Compared with the preoperative values, the blood MMP-2 and MMP-9 levels significantly increase two weeks after surgery, P < 0.05. Compared with the two-week postoperative values, the blood MMP-2 and MMP-9 levels significantly decrease after four weeks post-surgery, P < 0.05. At two weeks after the operation, the SUVmax and the TBR of the 18F-FDG PET/CT of the AAA wall are 0.90 ± 0.03 and 1.19 ± 0.09, respectively. At four weeks after the operation, the SUVmax and the TBR of the 18F-FDG PET/CT of the AAA wall are 0.35 ± 0.05 and 1.15 ± 0.12, respectively. Compared with two weeks after the operation, the SUVmax significantly decreases at four weeks after the operation, P < 0.05. Compared with two weeks after the operation, there is no significant difference in the TBR at four weeks after the operation, P > 0.05. Immunohistochemical staining shows that the CD68-positive cell rate at four weeks after the operation significantly decreases ( P < 0.05) compared with the CD68-positive cell rate at two weeks after the operation.

CONCLUSION

In the early stages of abdominal aortic aneurysm development, the inflammatory response of the arterial wall is significant, the local metabolic activity is strengthened, the SUVmax value of 18F-FDG is high, and the abdominal aortic aneurysm diameter experiences rapid growth. In the later stages of abdominal aortic aneurysm development, the diameter continues to increase; however, there are decreases in the wall inflammatory response, the local metabolic activity, and the SUVmax value of 18F-FDG. Thus, inflammation plays an important role in the early development of abdominal aortic aneurysm.

Interleukin-3 stimulates matrix metalloproteinase 12 production from macrophages promoting thoracic aortic aneurysm/dissection

Thoracic aortic aneurysm and dissection (TAAD) is due to degeneration of the aorta and causes a high mortality rate, while molecular mechanisms for the development of TAAD are still not completely understood. In the present study, 3-aminopropionitrile (BAPN) treatment was used to induce TAAD mouse model. Through transcriptome analysis, we found the expression levels of genes associated with interleukin-3 (IL-3) signaling pathway were up-regulated during TAAD development in mouse, which were validated by real-time PCR. IL-3 positive cells were increased in TAAD mouse aortas, especially for smooth muscle cells (SMCs). IL-3 deficiency reduced BAPN-induced TAAD formation. We then examined the matrix metalloproteinases (MMPs) expression during TAAD formation in both wild-type and IL-3 deficient mice, showing that MMP12 were significantly down-regulated in IL-3 deficient aortas. Mechanistically, we found recombinant IL-3 could increase MMP12 production and activity from macrophages in vitro Silencing of IL-3 receptor β, which was mainly expressed in macrophages but not SMCs, diminished the activation of c-Jun N terminal kinase (JNK)/extracellular-regulated protein kinases 1/2 (ERK1/2)/AP-1 signals, and decreased MMP12 expression in IL-3 stimulated macrophages. Moreover, both circulating and aortic inflammation were decreased in IL-3 deficient aortas. Taken together, our results demonstrated that IL-3 stimulated the production of MMP12 from macrophages by a JNK- and ERK1/2-dependent AP-1 pathway, contributing to TAAD formation. Thus, the IL-3/IL-3Rβ/MMP12 signals activation may be an important pathological mechanism for progression of TAAD.

CD40L Deficiency Protects Against Aneurysm Formation

OBJECTIVE

The mechanisms underlying formation of arterial aneurysms remain incompletely understood. Because inflammation is a common feature during the progressive degeneration of the aortic wall, we studied the role of the costimulatory molecule CD40L, a major driver of inflammation, in aneurysm formation.

APPROACH AND RESULTS

Transcriptomics data obtained from human abdominal aortic aneurysms and normal aortas revealed increased abundance of both CD40L and CD40 in media of thrombus-free and thrombus-covered human abdominal aortic aneurysms samples. To further unravel the role of CD40L in aneurysm formation, apolipoprotein E-deficient (Apoe^-/-) and Cd40l^-/-Apoe^-/- mice were infused with angiotensin II for 7 and 28 days. Only a minority of Cd40l^-/-Apoe^-/- mice (33% and 17%) developed (dissecting) aneurysms compared with 75% and 67% of Apoe^-/- littermates after 7 and 28 days of infusion, respectively. Total vessel area of the aorta at the suprarenal level was 52% smaller in angiotensin II-infused Cd40l^-/-Apoe^-/- mice compared with that in angiotensin II-infused Apoe^-/- mice. Chimeric Apoe^-/- mice repopulated with Cd40l^-/-Apoe^-/- bone marrow afforded a similar protection against dissecting aneurysm formation. Moreover, lack of CD40L protected mice from fatal aneurysm rupture. T helper cell and macrophage accumulation in aneurysmal tissue was reduced in Cd40l^-/-Apoe^-/- mice with a concomitant decrease in expression of proinflammatory chemo- and cytokines. In addition, aneurysms of Cd40l^-/-Apoe^-/- mice displayed reduced abundance of matrix metalloproteinase-13 and an increase in tissue inhibitor of metalloproteinase-3 while activity of matrix metalloproteinase-2 and matrix metalloproteinase-9 was diminished.

CONCLUSIONS

Deficiency of (hematopoietic) CD40L protects against dissecting aneurysm formation and reduces the incidence of fatal rupture. This is associated with a decreased accumulation and activation of inflammatory cells and a dampened protease activity in the arterial wall.

Heme oxygenase-1 deficiency exacerbates angiotensin II-induced aortic aneurysm in mice

Abdominal aortic aneurysm (AAA) is a chronic but often fatal disease in elderly population. Heme oxygenase-1 (HO-1) is a stress response protein with antioxidative and anti-inflammatory properties. HO-1 has been shown to protect against atherogenesis and arterial intimal thickening. Emerging evidences suggest that AAA and arterial occlusive disease have distinct pathogenic mechanisms. Thus, in this study we investigated the role of HO-1 in angiotensin II-induced AAA formation in HO-1^+/+apoE^−/− and HO-1^−/−apoE^−/− mice. We found that complete loss of HO-1 increased AAA incidence and rupture rate, and drastically increased aneurysmal area and severity, accompanied with severe elastin degradation and medial degeneration. Interestingly, we often observed not only AAA but also thoracic aortic aneurysm in HO-1^−/−apoE^−/− mice. Furthermore, reactive oxygen species levels, vascular smooth muscle cell (VSMC) loss, macrophage infiltration, matrix metalloproteinase (MMP) activity were markedly enhanced in the aneurysmal aortic wall in HO-1^−/−apoE^−/− mice. In addition, HO-1^−/−apoE^−/− VSMCs were more susceptible to oxidant-induced cell death and macrophages from HO-1^−/−apoE^−/− mice had aggravated responses to angiotensin II with substantial increases in inflammatory cytokine productions and MMP9 activity. Taken together, our results demonstrate the essential roles of HO-1 in suppressing the pathogenesis of AAA. Targeting HO-1 might be a promising therapeutic strategy for AAA.

Cysteinyl leukotriene receptor 1 antagonism prevents experimental abdominal aortic aneurysm

Cysteinyl-leukotrienes (cys-LTs) are lipid mediators involved in human inflammatory diseases, in particular asthma. We have previously identified cys-LTs in tissue specimens of human abdominal aortic aneurysm (AAA) and linked these mediators to increased metalloproteinase activity. Here we show in vivo that antagonism of the CysLT1 receptor by montelukast, an established antiasthma drug, protects against aneurysm in three mouse models of AAA at doses comparable to human medical practice. Together, these data support the role of cys-LTs in AAA and indicate a new potential therapeutic approach for treatment of this clinically silent and highly lethal disease.

Cysteinyl-leukotrienes (cys-LTs) are 5-lipoxygenase-derived lipid mediators involved in the pathogenesis and progression of inflammatory disorders, in particular asthma. We have previously found evidence linking these mediators to increased levels of proteolytic enzymes in tissue specimens of human abdominal aortic aneurysm (AAA). Here we show that antagonism of the CysLT1 receptor by montelukast, an established antiasthma drug, protects against a strong aorta dilatation (>50% increase = aneurysm) in a mouse model of CaCl₂-induced AAA at a dose comparable to human medical practice. Analysis of tissue extracts revealed that montelukast reduces the levels of matrix metalloproteinase-9 (MMP-9) and macrophage inflammatory protein-1α (MIP-1α) in the aortic wall. Furthermore, aneurysm progression was specifically mediated through CysLT1 signaling since a selective CysLT2 antagonist was without effect. A significantly reduced vessel dilatation is also observed when treatment with montelukast is started days after aneurysm induction, suggesting that the drug not only prevents but also stops and possibly reverts an already ongoing degenerative process. Moreover, montelukast reduced the incidence of aortic rupture and attenuated the AAA development in two additional independent models, i.e., angiotensin II- and porcine pancreatic elastase-induced AAA, respectively. Our results indicate that cys-LTs are involved in the pathogenesis of AAA and that antagonism of the CysLT1 receptor is a promising strategy for preventive and therapeutic treatment of this clinically silent and highly lethal disease.

Role of Macrophage Socs3 in the Pathogenesis of Aortic Dissection

BACKGROUND

Aortic dissection (AD) is a life-threatening medical emergency caused by the abrupt destruction of the intimomedial layer of the aortic walls. Given that previous studies have reported the involvement of proinflammatory cytokine interleukin-6 in AD pathogenesis, we investigated the role of signal transduction and activator of transcription 3 signaling, a downstream pathway of interleukin-6 in macrophages in pathogenesis of AD.

METHODS AND RESULTS

We characterized the pathological and molecular events triggered by aortic stress, which can lead to AD. Aortic stress on the suprarenal aorta because of infrarenal aorta stiffening and angiotensin II infusion for 1 week caused focal medial rupture at the branching point of the celiac trunk and superior mesenteric artery. This focal medial rupture healed in 6 weeks in wild-type (WT) mice, but progressed to AD in mice with macrophage-specific deletion of Socs3 gene (mSocs3-KO). mSocs3-KO mice showed premature activation of cell proliferation, an inflammatory response, and skewed differentiation of macrophages toward the tissue-destructive phenotype. Concomitantly, they showed aberrant phenotypic modulation of smooth muscle cells and transforming growth factor beta signaling, which are likely to participate in tissue repair. Human AD samples revealed signal transduction and activator of transcription 3 activation in adventitial macrophages adjacent to the site of tissue destruction.

CONCLUSIONS

These findings suggest that AD development is preceded by focal medial rupture, in which macrophage Socs3 maintains proper inflammatory response and differentiation of SMCs, thus promoting fibrotic healing to prevent tissue destruction and AD development. Understanding the sequence of the pathological and molecular events preceding AD development will help predict and prevent AD development and progression.

MicroRNAs as possible biomarkers for screening of aortic aneurysms: a systematic review and validation study

CONTEXT

There is an urgent need to identify non-invasive biomarkers for the early detection of aortic aneurysms, preceding a fatal event. The potential role for MicroRNAs (miRNAs) as diagnostic markers for aortic aneurysms was investigated through the present systematic review.

OBJECTIVE

To perform a comprehensive review on published studies examining the association of miRNAs with aortic aneurysms and further validate these results with plasma samples collected from thoracic aortic aneurysm (TAA) patients.

METHODS

The literature search was performed via numerous databases and articles were only included if they fulfilled the predefined eligibility criteria. The miRNAs reported three times or more with expression consistency were validated using plasma samples from TAA patients collected before and following surgery.

RESULTS

Twenty-four articles were selected from the literature search and 11 miRNAs were chosen for validation using our samples. The miRNAs which were further validated were found to follow the trend in the regulation pattern as with the majority of the published data. MiRNA hsa-miR-193a-5p was found to be significantly down-regulated in the plasma samples collected before the aneurysmal removal when compared with postsurgical serum samples.

CONCLUSIONS

Numerous miRNAs have been associated with aortic aneurysms, and specifically hsa-miR-193a-5p and hsa-miR-30b-5p; therefore they warrant further investigation as potential biomarkers. Registration: The protocol of the review was registered in Prospero Databases (ID: CRD42016039953).

Consideration of Sex Differences in Design and Reporting of Experimental Arterial Pathology Studies-Statement From ATVB Council

There are many differences in arterial diseases between men and women, including prevalence, clinical manifestations, treatments, and prognosis. The new policy of the National Institutes of Health, which requires the inclusion of sex as a biological variable for preclinical studies, aims to foster new mechanistic insights and to enhance our understanding of sex differences in human diseases. The purpose of this statement is to suggest guidelines for designing and reporting sex as a biological variable in animal models of atherosclerosis, thoracic and abdominal aortic aneurysms, and peripheral arterial disease. We briefly review sex differences of these human diseases and their animal models, followed by suggestions on experimental design and reporting of animal studies for these vascular pathologies.

Muse Cells and Aortic Aneurysm

The aorta is a well-organized, multilayered structure comprising several cell types, namely, endothelial cells (ECs), vascular smooth muscle cells (VSMCs), and fibroblasts, as well as an extracellular matrix (ECM), which includes elastic and collagen fibers. Aortic aneurysms (AAs) are defined as progressive enlargements of the aorta that carries an incremental risk of rupture as the diameter increases over time. The destruction of the aortic wall tissue is triggered by atherosclerosis, inflammation, and oxidative stress, leading to the activation of matrix metalloproteinases (MMPs), and inflammatory cytokines and chemokines, resulting in the loss of the structural back bone of VSMCs, ECM, and ECs. To date, cell-based therapy has been applied to animal models using several types of cells, such as VSMCs, ECs, and mesenchymal stem cells (MSCs). Although these cells indeed deliver beneficial outcomes for AAs, particularly by paracrine and immunomodulatory effects, the attenuation of aneurysmal dilation with a robust tissue repair is insufficient. Meanwhile, multilineage-differentiating stress-enduring (Muse) cells are known to be endogenous non-tumorigenic pluripotent-like stem cells that are included as several percent of MSCs. Since Muse cells are pluripotent-like, they have the ability to differentiate into cells representative of all three germ layers from a single cell and to self-renew. Moreover, Muse cells are able to home to the site of damage following simple intravenous injection and repair the tissue by replenishing new functional cells through spontaneous differentiation into tissue-compatible cells. Given these unique properties, Muse cells are expected to provide an efficient therapeutic efficacy for AA by simple intravenous injection. In this chapter, we summarize several studies on Muse cell therapy for AA including our recent data, in comparison with other kinds of cell therapies.

Peptidyl-prolyl isomerase Pin1 deficiency attenuates angiotensin II-induced abdominal aortic aneurysm formation in ApoE-/- mice

Peptidyl-prolyl isomerase Pin1 has been reported to be associated with endothelial dysfunction. However, the role of smooth muscle Pin1 in the vascular system remains unclear. Here, we examined the potential function of Pin1 in smooth muscle cells (SMCs) and its contribution to abdominal aortic aneurysm (AAA) pathogenesis. The level of Pin1 expression was found to be elevated in human AAA tissues and mainly localized to SMCs. We constructed smooth muscle-specific Pin1 knockout mice to explore the role of this protein in AAA formation and to elucidate the underlying mechanisms. AAA formation and elastin degradation were hindered by Pin1 depletion in the angiotensin II-induced mouse model. Pin1 depletion reversed the angiotensin II-induced pro-inflammatory and synthetic SMC phenotype switching via the nuclear factor (NF)-κB p65/Klf4 axis. Moreover, Pin1 depletion inhibited the angiotensin II-induced matrix metalloprotease activities. Mechanically, Pin1 deficiency destabilized NF-κB p65 by promoting its polyubiquitylation. Further, we found STAT1/3 bound to the Pin1 promoter, revealing that activation of STAT1/3 was responsible for the increased expression of Pin1 under angiotensin II stimulation. Thus, these results suggest that Pin1 regulates pro-inflammatory and synthetic SMC phenotype switching and could be a novel therapeutic target to limit AAA pathogenesis.

IL-1β (Interleukin-1β) and TNF-α (Tumor Necrosis Factor-α) Impact Abdominal Aortic Aneurysm Formation by Differential Effects on Macrophage Polarization

OBJECTIVE

Abdominal aortic aneurysms are inflammatory in nature and are associated with some risk factors that also lead to atherosclerotic occlusive disease, most notably smoking. The purpose of our study was to identify differential cytokine expression in patients with abdominal aortic aneurysm and those with atherosclerotic occlusive disease. Based on this analysis, we further explored and compared the mechanism of action of IL (interleukin)-1β versus TNF-α (tumor necrosis factor-α) in abdominal aortic aneurysm formation.

APPROACH AND RESULTS

IL-1β was differentially expressed in human plasma with lower levels detected in patients with abdominal aortic aneurysm compared with matched atherosclerotic controls. We further explored its mechanism of action using a murine model and cell culture. Genetic deletion of IL-1β and IL-1R did not inhibit aneurysm formation or decrease MMP (matrix metalloproteinase) expression. The effects of IL-1β deletion on M1 macrophage polarization were compared with another proinflammatory cytokine, TNF-α. Bone marrow-derived macrophages from IL-1β^-/- and TNF-α^-/- mice were polarized to an M1 phenotype. TNF-α deletion, but not IL-1β deletion, inhibited M1 macrophage polarization. Infusion of M1 polarized TNF-α^-/- macrophages inhibited aortic diameter growth; no inhibitory effect was seen in mice infused with M1 polarized IL-1β^-/- macrophages.

CONCLUSIONS

Although IL-1β is a proinflammatory cytokine, its effects on aneurysm formation and macrophage polarization differ from TNF-α. The differential effects of IL-1β and TNF-α inhibition are related to M1/M2 macrophage polarization and this may account for the differences in clinical efficacy of IL-1β and TNF-α antibody therapies in management of inflammatory diseases.

Aortic Dissection and Aortic Aneurysms Associated with Fluoroquinolones: A Systematic Review and Meta-Analysis

BACKGROUND

Our objective was to evaluate the association between fluoroquinolone use and aortic dissection or aortic aneurysm in a systematic review and meta-analysis.

METHODS

We searched Medline, Embase, and Scopus from inception to February 15, 2017. We selected controlled studies for inclusion if they reported data on aortic dissection and aortic aneurysm associated with fluoroquinolones exposure versus no exposure. Data were extracted by 2 independent reviewers, with disagreements resolved through further discussion. We assessed the quality of studies using the Newcastle-Ottawa Scale for observational studies and the strength of evidence using the Grading of Recommendations Assessment, Development, and Evaluation approach. The odds ratios (ORs) from observational studies were pooled using the fixed-effect inverse variance method, and statistical heterogeneity was assessed using the I² statistic.

RESULTS

After a review of 714 citations, we included 2 observational studies in the meta-analysis. Current use of fluoroquinolones was associated with a statistically significantly increased risk of aortic dissection (OR, 2.79; 95% confidence interval [CI], 2.31-3.37; I² = 0%) and aortic aneurysm (OR, 2.25; 95% CI, 2.03-2.49; I² = 0%) in a fixed-effects meta-analysis. The unadjusted OR estimates and sensitivity analysis using a random-effects model showed similar results. We rated the strength of evidence to be of moderate quality. The number needed to treat to harm for aortic aneurysm for elderly patients aged more than 65 years who were current users of fluoroquinolones was estimated to be 618 (95% CI, 518-749).

CONCLUSIONS

Evidence from a small number of studies suggests that exposure to fluoroquinolones is consistently associated with a small but significantly increased risk of aortic dissection and aortic aneurysm.

A novel reproducible model of aortic aneurysm rupture

INTRODUCTION

Given the unknown biologic antecedents before aortic aneurysm rupture, the purpose of this study was to establish a reproducible model of aortic aneurysm rupture.

METHODS

We fed 7-week-old apolipoprotein E deficient mice a high-fat diet for 4 weeks and osmotic infusion pumps containing Angiotensin II were implanted. Angiotensin II was delivered continuously for 4 weeks at either 1,000 ng/kg/min (n = 25) or 2,000 ng/kg/min (n = 29). A third group (n = 14) were given Angiotensin II at 2,000 ng/kg/min and 0.2% β-aminopropionitrile dissolved in drinking water. Surviving mice were killed 28 days after pump placement, aortic diameters were measured, and molecular analyses were performed.

RESULTS

Survival at 28 days was significantly different among groups with 80% survival in the 1,000 ng/kg/min group, 52% in the 2,000 ng/kg/min group, and only 14% in the Angiotensin II/β-aminopropionitrile group (P = .0001). Concordantly, rupture rates were statistically different among groups (8% versus 38% versus 79%, P < .0001). Rates of abdominal aortic aneurysm were 48%, 55%, and 93%, respectively, with statistically higher rates in the Angiotensin II/β-aminopropionitrile group compared with both the 1,000 ng and 2,000 ng Angiotensin II groups (P = .006 and P = .0165, respectively). Rates of thoracic aortic aneurysm formation were 12%, 52%, and 79% in the 3 groups with a statistically higher rate in the Angiotensin II/β-aminopropionitrile group compared with 1,000 ng group (P < .0001).

CONCLUSIONS

A reproducible model of aortic aneurysm rupture was developed with a high incidence of abdominal and thoracic aortic aneurysm. This model should enable further studies investigating the pathogenesis of aortic rupture, as well as allow for targeted strategies to prevent human aortic aneurysm rupture.