Oxidative stress in the pathogenesis of thoracic aortic aneurysm: protective role of statin and angiotensin II type 1 receptor blocker

The Antioxidant/Nitric Oxide-Quenching Agent Cobinamide Prevents Aortic Disease in a Mouse Model of Marfan Syndrome

Major pathologic changes in the proximal aorta underlie the life-threatening aortic aneurysms and dissections in Marfan Syndrome; current treatments delay aneurysm development without addressing the primary pathology. Because excess oxidative stress and nitric oxide/protein kinase G signaling likely contribute to the aortopathy, we hypothesized that cobinamide, a strong antioxidant that can attenuate nitric oxide signaling, could be uniquely suited to prevent aortic disease. In a well-characterized mouse model of Marfan Syndrome, cobinamide dramatically reduced elastin breaks, prevented excess collagen deposition and smooth muscle cell apoptosis, and blocked DNA, lipid, and protein oxidation and excess nitric oxide/protein kinase G signaling in the ascending aorta. Consistent with preventing pathologic changes, cobinamide diminished aortic root dilation without affecting blood pressure. Cobinamide exhibited excellent safety and pharmacokinetic profiles indicating it could be a practical treatment. We conclude that cobinamide deserves further study as a disease-modifying treatment of Marfan Syndrome.

Combination of folic acid with nifedipine is completely effective in attenuating aortic aneurysm formation as a novel oral medication

Aortic aneurysms are prevalent and severe vascular diseases with high mortality from unpredicted ruptures, while the only treatment option is surgical correction of large aneurysms with considerable risk. We have shown that folic acid (FA) is highly effective in alleviating development of aneurysms although not sufficient to completely attenuate aneurysm formation. Here, we examined therapeutic effects on aneurysms of combining FA with Nifedipine as novel and potentially more effective oral medication. Oral administration with FA (15 mg/kg/day) significantly reduced incidence of AAA from 85.71% to 18.75% in Ang II-infused apolipoprotein E (apoE) null mice, while combination of FA with Nifedipine (1.5, 5.0 or 20 mg/kg/day) substantially and completely further reduced incidence of AAA to 12.5%, 11.76% and 0.00% respectively in a dose-dependent manner. The combinatory therapy substantially and completely further alleviated enlargement of abdominal aortas defined by ultrasound, vascular remodeling characterized by elastin degradation and adventitial hypertrophy, as well as aortic superoxide production and eNOS uncoupling activity also in a dose-dependent manner, with combination of FA with 20 mg/kg/day Nifedipine attenuating all of these features by 100% to control levels. Aortic NO and H4B bioavailabilities were also dose-dependently further improved by combining FA with Nifedipine. These data establish entirely innovative and robust therapeutic regime of FA combined with Nifedipine for the treatment of aortic aneurysms. The comminatory therapy can serve as a first-in-class and most effective oral medication for aortic aneurysms, which can be rapidly translated into clinical practice to revolutionize management of the devastating vascular diseases of aortic aneurysms known as silent killers.

Allopurinol blocks aortic aneurysm in a mouse model of Marfan syndrome via reducing aortic oxidative stress

BACKGROUND

Increasing evidence indicates that redox stress participates in MFS aortopathy, though its mechanistic contribution is little known. We reported elevated reactive oxygen species (ROS) formation and NADPH oxidase NOX4 upregulation in MFS patients and mouse aortae. Here we address the contribution of xanthine oxidoreductase (XOR), which catabolizes purines into uric acid and ROS in MFS aortopathy.

METHODS AND RESULTS

In aortic samples from MFS patients, XOR protein expression, revealed by immunohistochemistry, increased in both the tunicae intima and media of the dilated zone. In MFS mice (Fbn1^C1041G/+), aortic XOR mRNA transcripts and enzymatic activity of the oxidase form (XO) were augmented in the aorta of 3-month-old mice but not in older animals. The administration of the XOR inhibitor allopurinol (ALO) halted the progression of aortic root aneurysm in MFS mice. ALO administrated before the onset of the aneurysm prevented its subsequent development. ALO also inhibited MFS-associated endothelial dysfunction as well as elastic fiber fragmentation, nuclear translocation of pNRF2 and increased 3'-nitrotyrosine levels, and collagen maturation remodeling, all occurring in the tunica media. ALO reduced the MFS-associated large aortic production of H₂O₂, and NOX4 and MMP2 transcriptional overexpression.

CONCLUSIONS

Allopurinol interferes in aortic aneurysm progression acting as a potent antioxidant. This study strengthens the concept that redox stress is an important determinant of aortic aneurysm formation and progression in MFS and warrants the evaluation of ALO therapy in MFS patients.

Aortic Cellular Diversity and Quantitative Genome-Wide Association Study Trait Prioritization Through Single-Nuclear RNA Sequencing of the Aneurysmal Human Aorta

BACKGROUND

Mural cells in ascending aortic aneurysms undergo phenotypic changes that promote extracellular matrix destruction and structural weakening. To explore this biology, we analyzed the transcriptional features of thoracic aortic tissue.

METHODS

Single-nuclear RNA sequencing was performed on 13 samples from human donors, 6 with thoracic aortic aneurysm, and 7 without aneurysm. Individual transcriptomes were then clustered based on transcriptional profiles. Clusters were used for between-disease differential gene expression analyses, subcluster analysis, and analyzed for intersection with genetic aortic trait data.

RESULTS

We sequenced 71 689 nuclei from human thoracic aortas and identified 14 clusters, aligning with 11 cell types, predominantly vascular smooth muscle cells (VSMCs) consistent with aortic histology. With unbiased methodology, we found 7 vascular smooth muscle cell and 6 fibroblast subclusters. Differentially expressed genes analysis revealed a vascular smooth muscle cell group accounting for the majority of differential gene expression. Fibroblast populations in aneurysm exhibit distinct behavior with almost complete disappearance of quiescent fibroblasts. Differentially expressed genes were used to prioritize genes at aortic diameter and distensibility genome-wide association study loci highlighting the genes JUN, LTBP4 (latent transforming growth factor beta-binding protein 1), and IL34 (interleukin 34) in fibroblasts, ENTPD1, PDLIM5 (PDZ and LIM domain 5), ACTN4 (alpha-actinin-4), and GLRX in vascular smooth muscle cells, as well as LRP1 in macrophage populations.

CONCLUSIONS

Using nuclear RNA sequencing, we describe the cellular diversity of healthy and aneurysmal human ascending aorta. Sporadic aortic aneurysm is characterized by differential gene expression within known cellular classes rather than by the appearance of novel cellular forms. Single-nuclear RNA sequencing of aortic tissue can be used to prioritize genes at aortic trait loci.

NADPH Oxidases in Aortic Aneurysms

Abdominal aortic aneurysms (AAAs) are a progressive dilation of the infrarenal aorta and are characterized by inflammatory cell infiltration, smooth muscle cell migration and proliferation, and degradation of the extracellular matrix. Oxidative stress and the production of reactive oxygen species (ROS) have been shown to play roles in inflammatory cell infiltration, and smooth muscle cell migration and apoptosis in AAAs. In this review, we discuss the principles of nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase/NOX) signaling and activation. We also discuss the effects of some of the major mediators of NOX signaling in AAAs. Separately, we also discuss the influence of genetic or pharmacologic inhibitors of NADPH oxidases on experimental pre-clinical AAAs. Experimental evidence suggests that NADPH oxidases may be a promising future therapeutic target for developing pharmacologic treatment strategies for halting AAA progression or rupture prevention in the management of clinical AAAs.

Identification of a common polymorphism in COQ8B acting as a modifier of thoracic aortic aneurysm severity

Thoracic aortic aneurysm (TAA) predisposes to sudden, life-threatening aortic dissection. The factors that regulate interindividual variability in TAA severity are not well understood. Identifying a molecular basis for this variability has the potential to improve clinical risk stratification and advance mechanistic insight. We previously identified COQ8B, a gene important for biosynthesis of coenzyme Q, as a candidate genetic modifier of TAA severity. Here, we investigated the physiological role of COQ8B in human aortic smooth muscle cells (SMCs) and further tested its genetic association with TAA severity. We find COQ8B protein localizes to mitochondria in SMCs, and loss of mitochondrial COQ8B leads to increased oxidative stress, decreased mitochondrial respiration, and altered expression of SMC contractile genes. Oxidative stress and mitochondrial cristae defects were prevalent in the medial layer of human proximal aortic tissues in individuals with TAA, and COQ8B expression was decreased in TAA SMCs compared with controls. A common single nucleotide polymorphism (SNP) rs3865452 in COQ8B (c.521A>G [p.His174Arg]) was associated with decreased rate of aortic root dilation in young individuals with TAA. In addition, the SNP was less frequent in a second cohort of early-onset thoracic aortic dissection (TAD) cases compared with controls. COQ8B protein levels in aortic SMCs were increased in TAA individuals homozygous for rs3865452 compared with those homozygous for the reference allele. Thus, COQ8B is important for aortic SMC metabolism, which is dysregulated in TAA, and rs3865452 may decrease TAA severity by increasing the COQ8B level. Genotyping rs3865452 may be useful for clinical risk stratification and tailored aortopathy management.

DPP4 inhibitor reduces portal hypertension in cirrhotic rats by normalizing arterial hypocontractility

AIMS

Dipeptidyl peptidase-4 inhibitor (DPP4i), a new antidiabetic agent, is reported to affect the progression of chronic liver diseases. The study aims to investigate the effects of DPP4i on contractile response, splanchnic hemodynamics, and portal pressure in cirrhotic rats.

MATERIALS AND METHODS

A rat model of carbon tetrachloride-induced cirrhosis was used in this study. Sixteen rats with cirrhosis were treated with DDP4i sitagliptin for 5 consecutive days. Portal and systemic pressures and portal blood flow were measured. Mesenteric arterioles were isolated, and concentration-response curves to norepinephrine (NE) were evaluated. The expression of NADPH oxidase (Nox)1, Nox2, Nox4, and soluble epoxide hydrolase (sEH) were detected. Reactive oxygen species (ROS) and epoxyeicosatrienoic acid (EET) levels in mesenteric arteries were also measured.

KEY FINDINGS

In cirrhotic rats, sitagliptin significantly reduced portal blood flow and portal pressure without effects on systemic pressure and reversed the decreased response of mesenteric arterioles to NE in an endothelium-dependent manner. Sitagliptin suppressed the increased Nox4 expression and ROS production. In vitro studies showed that Nox4 inhibitor enhanced arteriolar response to NE and reduced hydrogen peroxide (H2O2) level in cirrhotic rats. Sitagliptin also reduced EET levels and increased sEH expression of mesenteric vessels. Pre-incubation with sEH inhibitor in vitro reversed sitagliptin-induced augmentation of response to NE in cirrhotic rats.

SIGNIFICANCE

DPP4 inhibition by sitagliptin in vivo has beneficial effects on portal hypertension in cirrhotic rats through normalizing arterial hypocontractility. DDP4 inhibitor may be a novel strategy in the treatment of patients with cirrhosis and portal hypertension.

Artesunate Attenuated the Progression of Abdominal Aortic Aneurysm in a Mouse Model

BACKGROUND

The inflammatory reaction is an important mechanism of pathogenesis of abdominal aortic aneurysm (AAA). Artesunate (AS) has been found to have anti-inflammatory effects in cardiovascular disease. The purpose of this study was to investigate whether AS could inhibit the development of AAA.

MATERIALS AND METHODS

AngII infused ApoE (-/-) male mice were selected as AAA model. Mice were spilt into three groups, the experimental control group (AngII), the AS treatment group (AngII + AS) and the negative control group (Vehicle) with 14 in each group. Daily administration of AS (100 mg/kg/d) or vehicle performed 3 day before the perfusion. At the end of the 28-day experiment, animal ultrasound and electronic digital caliper were used to measure the diameter of abdominal aorta. Histologic assays were performed to observe the microstructure of the aorta wall. Immunofluorescence staining was performed to detect inflammatory cells, as well as the levels of matrix metalloproteinases (MMPs). The transcription of cytokines and adhesion molecules were investigated by real-time fluorescence quantitative PCR (qPCR). Western blotting was performed to determine whether the NF-κB pathway is involved in the mechanism.

RESULTS

While AS failed to reduce the incidence of AAA, AS effectively reduced the diameter of AAA independently of blood pressure effects. Immunofluorescence detection showed that AS effectively reduced the levels of CD45+ cells and MAC3+ macrophages as well as MMP-2 and MMP-9. qPCR revealed that AS reduced mRNA transcription levels of MMP-2, MMP-9, the cytokine IL-1β, TNF-α, adhesion molecules ICAM-1, VCAM-1. AS decreased the levels of NF-κB signaling pathway in aorta.

CONCLUSIONS

AS can attenuate the development of AAA in mice. The possible mechanism is anti-inflammation.

Risk reduction and pharmacological strategies to prevent progression of aortic aneurysms

INTRODUCTION

While size thresholds exist to determine when aortic aneurysms warrant surgical intervention, there is no consensus on how best to treat this disease before aneurysms reach the threshold for intervention. Since a landmark study in 1994 first suggested ß-blockers may be useful in preventing aortic aneurysm growth, there has been a surge in research investigating different pharmacologic therapies for aortic aneurysms - with very mixed results.

AREAS COVERED

We have reviewed the existing literature on medical therapies used for thoracic and abdominal aortic aneurysms in humans. These include ß-blockers, angiotensin II receptor blockers, and angiotensin-converting enzyme inhibitors as well as miscellaneous drugs such as tetracyclines, macrolides, statins, and anti-platelet medications.

EXPERT OPINION

While multiple classes of drugs have been explored for risk reduction in aneurysm disease, with few exceptions results have been disappointing with an abundance of contradictory findings. The vast majority of studies have been done in patients with abdominal aortic aneurysms or thoracic aortic aneurysm patients with Marfan Syndrome. There exists a striking gap in the literature when it comes to pharmacologic management of non-Marfan Syndrome patients with thoracic aortic aneurysms. Given the differences in pathogenesis, this is an important future direction for aortic aneurysm research.

Non-syndromic thoracic aortic aneurysm: cellular and molecular insights

Thoracic aortic aneurysm (TAA) develops silently and asymptomatically and is a major cause of mortality. TAA prevalence is greatly underestimated, it is usually diagnosed incidentally, and its treatment consists mainly of prophylactic surgery based on the aortic diameter. The lack of effective drugs and biological markers to identify and stratify TAAs by risk before visible symptoms results from scant knowledge of its pathophysiological mechanisms. Here we integrate the structural impairment affecting non-syndromic non-familial TAA with the main cellular and molecular changes described so far and consider how these changes are interconnected through specific pathways. The ultimate goal is to define much-needed novel markers of TAA, and so the potential of previously identified molecules to aid in early diagnosis/prognosis is also discussed. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Current pharmacological management of aortic aneurysm

ABSTRACT

Aortic aneurysm (AA) remains one of the primary causes of death worldwide. Of the major treatments, prophylactic operative repair is used for AA to avoid potential aortic dissection (AD) or rupture. To halt the development of AA and alleviate its progression into AD, pharmacological treatment has been investigated for years. Currently, β-adrenergic blocking agents, losartan, irbesartan, angiotensin-converting-enzyme inhibitors, statins, antiplatelet agents, doxycycline, and metformin have been investigated as potential candidates for preventing AA progression. However, the paradox between preclinical successes and clinical failures still exists, with no medical therapy currently available for ideally negating the disease progression. This review describes the current drugs used for pharmacological management of AA and their individual potential mechanisms. Preclinical models for drug screening and evaluation are also discussed to gain a better understanding of the underlying pathophysiology and ultimately find new therapeutic targets for AA.

Blood pressure-independent inhibition of Marfan aortic root widening by the angiotensin II receptor blocker valsartan

Marfan syndrome (MFS) is a genetic disorder that results in accelerated aortic root widening and aneurysm. However, management of MFS patients with blood pressure (BP)-lowering medications, such as angiotensin II (AngII) receptor blocker (ARB) losartan, continues to pose challenges due to their questionable efficacy at attenuating the rate of aortic root widening in patients. Herein we investigate the anti-aortic root widening effects of a sub-BP-lowering dose valsartan, an ARB previously linked to non-BP lowering anti-remodeling effects. Despite absence of BP-lowering effects, valsartan attenuated MFS aortic root widening by 75.9%, which was similar to a hypotensive dose of losartan (79.4%) when assessed by ultrasound echocardiography. Medial thickening, elastic fiber fragmentation, and phospho-ERK signaling were also inhibited to a similar degree with both treatments. Valsartan and losartan decreased vascular contractility ex vivo between 60% and 80%, in a nitric oxide (NO)-sensitive fashion. Valsartan increased acetylcholine (Ach)-induced vessel relaxation and phospho-eNOS levels in the aortic vessel supporting BP-independent activation of protective endothelial function, which is critical to ARB-mediated aortic root stability. This study supports the concept of achieving aortic root stability with valsartan in absence of BP-lowering effects, which may help address efficacy and compliance issues with losartan-based MFS patient management.

The relationship between famine exposure during early life and ascending aorta dilatation in adults

The relationship between exposure to famine in early life and the risk of ascending aorta dilatation (AAD) in adulthood is still unclear; therefore, we aimed to examine the association in the Chinese population. We investigated the data of 2598 adults who were born between 1952 and 1964 in Guangdong, China. All enrolled subjects were categorised into five groups: not exposed to famine, exposed during fetal period, and exposed during early, mid or late childhood. AAD was assessed by cardiac ultrasound. Multivariate logistic regression and interaction tests were performed to estimate the OR and CI on the association between famine exposure and AAD. There were 2598 (943 male, mean age 58·3 ± 3·68 years) participants were enrolled, and 270 (10·4 %) subjects with AAD. We found that famine exposure (OR = 2·266, 95 % CI 1·477, 3·477, P = 0·013) was associated with elevated AAD after adjusting for multiple confounders. In addition, compared with the non-exposed group, the adjusted OR for famine exposure during fetal period, early, mid or late childhood were 1·374 (95 % CI 0·794, 2·364, P = 0·251), 1·976 (95 % CI 1·243, 3·181, P = 0·004), 1·929 (95 % CI 1·237, 3·058, P = 0·004) and 2·227 (95 % CI 1·433, 3·524, P < 0·001), respectively. Subgroup analysis showed that the effect of famine exposure on the association with AAD was more pronounced in female, current smokers, people with BMI ≥ 24 kg/m2 and hypertensive patients. We observed that exposure to famine during early life was linked to AAD in adulthood.

Targeting feed-forward signaling of TGFβ/NOX4/DHFR/eNOS uncoupling/TGFβ axis with anti-TGFβ and folic acid attenuates formation of aortic aneurysms: Novel mechanisms and therapeutics

In the present study we aimed to identify novel mechanisms and therapeutics for thoracic aortic aneurysm (TAA) in Fbn1^C1039G/+ Marfan Syndrome (MFS) mice. The expression of mature/active TGFβ and its downstream effector NOX4 were upregulated while tetrahydrobiopterin (H₄B) salvage enzyme dihydrofolate reductase (DHFR) was downregulated in Fbn1^C1039G/+ mice. In vivo treatment with anti-TGFβ completely attenuated NOX4 expression, restored DHFR protein abundance, reduced ROS production, recoupled eNOS and attenuated aneurysm formation. Intriguingly, oral administration with folic acid (FA) to recouple eNOS markedly alleviated expansion of aortic roots and abdominal aortas in Fbn1^C1039G/+ mice, which was attributed to substantially upregulated DHFR expression and activity in the endothelium to restore tissue and circulating levels of H₄B. Notably, circulating H₄B levels were accurately predictive of tissue H₄B bioavailability, and negatively associated with expansion of aortic roots, indicating a novel biomarker role of circulating H₄B for TAA. Furthermore, FA diet abrogated TGFβ and NOX4 expression, disrupting the feed-forward loop to inactivate TGFβ/NOX4/DHFR/eNOS uncoupling axis in vivo and in vitro, while PTIO, a NO scavenger, reversed this effect in cultured human aortic endothelial cells (HAECs). Besides, expression of the rate limiting H₄B synthetic enzyme GTP cyclohydrolase 1 (GTPCHI), was downregulated in Fbn1^C1039G/+ mice at baseline. In cultured HAECs, RNAi inhibition of fibrillin resulted in reduced GTPCHI expression, while this response was abrogated by anti-TGFβ, indicating TGFβ-dependent downregulation of GTPCHI in response to fibrillin deficiency. Taken together, our data for the first time reveal that uncoupled eNOS plays a central role in TAA formation, while anti-TGFβ and FA diet robustly abolish aneurysm formation via inactivation of a novel TGFβ/NOX4/DHFR/eNOS uncoupling/TGFβ feed-forward pathway. Correction of fibrillin deficiency is additionally beneficial via preservation of GTPCHI function.

Deficiency of peroxiredoxin 2 exacerbates angiotensin II-induced abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is an inflammatory vascular disease characterized by structural deterioration of the aorta caused by inflammation and oxidative stress, leading to aortic dilatation and rupture. Peroxiredoxin 2 (PRDX2), an antioxidant enzyme, has been reported as a potential negative regulator of inflammatory vascular diseases, and it has been identified as a protein that is increased in patients with ruptured AAA compared to patients with nonruptured AAA. In this study, we demonstrated that PRDX2 was a pivotal factor involved in the inhibition of AAA progression. PRDX2 levels were increased in AAA compared with those in normal aortas in both humans and mice. Ultrasound imaging revealed that the loss of PRDX2 accelerated the development of AAA in the early stages and increased AAA incidence in mice infused with angiotensin II (Ang II). Prdx2^−/− mice infused with Ang II exhibited increased aortic dilatation and maximal aortic diameter without a change in blood pressure. Structural deterioration of the aortas from Prdx2^−/− mice infused with Ang II was associated with increases in the degradation of elastin, oxidative stress, and intramural thrombi caused by microhemorrhages, immature neovessels, and the activation of matrix metalloproteinases compared to that observed in controls. Moreover, an increase in inflammatory responses, including the production of cell adhesion molecules and the accumulation of inflammatory cells and proinflammatory cytokines due to PRDX2 deficiency, accelerated Ang II-induced AAA progression. Our data confirm that PRDX2 plays a role as a negative regulator of the pathological process of AAA and suggest that increasing PRDX2 activity may be a novel strategy for the prevention and treatment of AAA.

An enzyme with antioxidant properties may provide a biomarker and therapeutic agent to help treat abdominal aortic aneurysm (AAA). AAA involves the structural deterioration of the aorta through chronic inflammation and oxidative stress, and can trigger life-threatening artery rupture. An antioxidant enzyme called peroxiredoxin 2 (PRDX2) is increased in patients with ruptures, but whether its role in AAA is beneficial or detrimental is unclear. Goo Taeg Oh at the Ewha Womans University in Seoul, Jong-Gil Park at the Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea, and co-workers examined the effect of PRDX2 on AAA progression. PRDX2 suppressed structural damage in mice, limiting artery dilation and protein degradation. Loss of PRDX2 accelerated AAA development. Measuring levels of PRDX2 may indicate AAA severity in patients, while boosting the enzyme could repair aortic damage.

Angiotensin I Infusion Reveals Differential Effects of Angiotensin-Converting Enzyme in Aortic Resident Cells on Aneurysm Formation

BACKGROUND

Angiotensin (Ang)I is cleaved by angiotensin-converting enzyme (ACE) to generate AngII. The purpose of this study was to determine the roles of ACE in endothelial and smooth muscle cells in aortic aneurysms.Methods and Results:AngI infusion led to thoracic and abdominal aortic aneurysms in low-density lipoprotein receptor-deficient mice, which were ablated by ACE inhibition. Endothelial or smooth muscle cell-specific ACE deletion resulted in reduction of AngI-induced thoracic, but not abdominal, aortic dilatation.

CONCLUSIONS

AngI infusion causes thoracic and abdominal aortic aneurysms in mice. ACE in aortic resident cells has differential effects on AngI-induced thoracic and abdominal aortic aneurysms.

Pro-Renin Receptor Overexpression Promotes Angiotensin II-Induced Abdominal Aortic Aneurysm Formation in Apolipoprotein E-Knockout Mice

The pro-renin receptor (PRR) is an important novel component of the renin-angiotensin (Ang) system that has multiple functions, which are not yet completely understood. In this study, we aimed to explore the effect of PRR on the formation of Ang II-induced abdominal aortic aneurysm (AAA) in apolipoprotein E-knockout mice. We used Ang II (1.44 mg/kg/day) infusion to induce AAA followed by a treatment of saline, telmisartan, no treatment, Ad-EGFP, Ad-PRR, or Ad-PRR plus telmisartan. The incidence of AAA was 35%, 60%, 65%, 90%, and 55% in the Telmisartan, Vehicle, Ad-EGFP, Ad-PRR, and Ad-PRR+Telmisartan groups, respectively. Compared with the Vehicle and Ad-EGFP groups, PRR overexpression markedly increased macrophage infiltration; levels of proinflammatory cytokines, including monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α); the expression and activity of MMP2 and MMP9; NOX2 and NOX4 protein and mRNA expression; nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity; extracellular-signal-regulated kinase (ERK) and P38MAPK expression; but decreased smooth muscle cells content in AAA. However, telmisartan reversed the adverse effects of PRR. In addition, ERK inhibitor PD98059 eliminated the acceleration of Ang II-induced AAA formation by PRR, and coadministration of telmisartan and PD98059 further abolished the adverse effects of PRR on Ang II-induced AAA formation. Thus, PRR plays an important role in the pathological development of AAA via both Ang II-dependent and Ang II-independent activation of ERK pathways. These results suggest that inhibition of PRR activation may be a promising approach to the treatment of AAA.

AVE0991, a nonpeptide angiotensin-(1-7) mimic, inhibits angiotensin II-induced abdominal aortic aneurysm formation in apolipoprotein E knockout mice

AVE0991, a nonpeptide angiotensin-(1-7) mimic, has similar protective effects for cardiovascular system to Ang-(1-7). In this article, we aimed to explore the effects of AVE0991 and Ang-(1-7) on abdominal aortic aneurysm (AAA) induced by Ang II in apolipoprotein E knockout mice. The mice AAA model was established by Ang II infusion, and then mice received different treatment with saline, Ang II (1.44 mg/kg/day), different dose AVE0991 (0.58 or 1.16 μmol/kg/day), or Ang-(1-7) (400 ng/kg/min). The incidence of AAA was 76%, 48%, 28%, and 24% in the vehicle, the low-dose AVE0991, high-dose AVE0991, and the Ang-(1-7) group, respectively. In comparison with control group, AVE0991 and Ang-(1-7) treatment significantly increased smooth muscle cells and decreased macrophage accumulation, the expression levels of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor α (TNF-α), and the expression and activity of metalloproteinases 2 and 9 in mice AAA model or in human smooth muscle cells (hVSMCs). The therapeutic effects may be contributed to reduction of oxidative stress and downregulation of P38 and ERK1/2 signal pathways via Mas receptor activation, whereas the positive impacts were reversed by co-administration with the Mas antagonist A779 (400 ng/kg/min) and AVE0991 in Ang II-infused mice or in hVSMCs. Therefore, AVE0991 and Ang-(1-7) might be novel and promising interventions in the prevention and treatment of AAA. KEY MESSAGES: • AVE0991 dose-dependently inhibited Ang II-induced AAA formation in Apoe^-/- mice. • Ang-(1-7) played the same protective role as high-dose AVE0991. • Inhibition of Mas receptor with A779 could reverse the protective effect of AVE0991. • The therapeutic effects may be contributed to reduction of oxidative stress and downregulation of P38 and ERK1/2 signal pathways via Mas receptor activation.

Inflammation in thoracic aortic aneurysms

Mutations in extracellular matrix and smooth muscle cell contractile proteins predispose to thoracic aortic aneurysms in Marfan syndrome (MFS) and related disorders. These genetic alterations lead to a compromised extracellular matrix-smooth muscle cell contractile unit. The abnormal aortic tissue responds with defective mechanosensing under hemodynamic stress. Aberrant mechanosensing is associated with transforming growth factor-beta (TGF-β) hyperactivity, enhanced angiotensin-II (Ang-II) signaling, and perturbation of other cellular signaling pathways. The downstream consequences include enhanced proteolytic activity, expression of inflammatory cytokines and chemokines, infiltration of inflammatory cells in the aortic wall, vascular smooth muscle cell apoptosis, and medial degeneration. Mouse models highlight aortic inflammation as a contributing factor in the development of aortic aneurysms. Anti-inflammatory drugs and antioxidants can reduce aortic oxidative stress that prevents aggravation of aortic disease in MFS mice. Targeting TGF-β and Ang-II downstream signaling pathways such as ERK1/2, mTOR, PI3/Akt, P38/MAPK, and Rho kinase signaling attenuates disease pathogenesis. Aortic extracellular matrix degradation and medial degeneration were reduced upon inhibition of inflammatory cytokines and matrix metalloproteinases, but the latter lack specificity. Treating inflammation associated with aortic aneurysms in MFS and related disorders could prove to be beneficial in limiting disease pathogenesis.

Anatomically specific reactive oxygen species production participates in Marfan syndrome aneurysm formation

Marfan syndrome (MFS) is a connective tissue disorder that results in aortic root aneurysm formation. Reactive oxygen species (ROS) seem to play a role in aortic wall remodelling in MFS, although the mechanism remains unknown. MFS Fbn1^C1039G/+ mouse root/ascending (AS) and descending (DES) aortic samples were examined using DHE staining, lucigenin‐enhanced chemiluminescence (LGCL), Verhoeff's elastin‐Van Gieson staining (elastin breakdown) and in situ zymography for protease activity. Fbn1^C1039G/+ AS‐ or DES‐derived smooth muscle cells (SMC) were treated with anti‐TGF‐β antibody, angiotensin II (AngII), anti‐TGF‐β antibody + AngII, or isotype control. ROS were detected during early aneurysm formation in the Fbn1^C1039G/+ AS aorta, but absent in normal‐sized DES aorta. Fbn1^C1039G/+ mice treated with the unspecific NADPH oxidase inhibitor, apocynin reduced AS aneurysm formation, with attenuated elastin fragmentation. In situ zymography revealed apocynin treatment decreased protease activity. In vitro SMC studies showed Fbn1^C1039G/+‐derived AS SMC had increased NADPH activity compared to DES‐derived SMC. AS SMC NADPH activity increased with AngII treatment and appeared TGF‐β dependent. In conclusion, ROS play a role in MFS aneurysm development and correspond anatomically with aneurysmal aortic segments. ROS inhibition via apocynin treatment attenuates MFS aneurysm progression. AngII enhances ROS production in MFS AS SMCs and is likely TGF‐β dependent.

Aortic pathology from protein kinase G activation is prevented by an antioxidant vitamin B12 analog

People heterozygous for an activating mutation in protein kinase G1 (PRKG1, p.Arg177Gln) develop thoracic aortic aneurysms and dissections (TAAD) as young adults. Here we report that mice heterozygous for the mutation have a three-fold increase in basal protein kinase G (PKG) activity, and develop age-dependent aortic dilation. Prkg1^R177Q/+ aortas show increased smooth muscle cell apoptosis, elastin fiber breaks, and oxidative stress compared to aortas from wild type littermates. Transverse aortic constriction (TAC)—to increase wall stress in the ascending aorta—induces severe aortic pathology and mortality from aortic rupture in young mutant mice. The free radical-neutralizing vitamin B₁₂-analog cobinamide completely prevents age-related aortic wall degeneration, and the unrelated anti-oxidant N-acetylcysteine ameliorates TAC-induced pathology. Thus, increased basal PKG activity induces oxidative stress in the aorta, raising concern about the widespread clinical use of PKG-activating drugs. Cobinamide could be a treatment for aortic aneurysms where oxidative stress contributes to the disease, including Marfan syndrome.

Individuals carrying a gain-of-function mutation in PKG1 develop thoracic aortic aneurysms and dissections. Here Schwaerzer et al. show that mice carrying the same mutation recapitulate the human disease, and find that treatment with anti-oxidants including cobinamide, a vitamin B12 analog, prevents disease progression.

Hair whitening and obesity are independently related to ascending aorta dilatation in young-middle aged men

OBJECTIVE

Hair whitening (HW) is strongly linked with aging. Ascending aortic dilation (AAD) and HW share common etiologic factors. We investigated the association of HW with ascending aortic diameters.

METHODS

Our study included 93 male subjects aged below 50 years. All patients underwent echocardiography to measure ascending aortic diameter, in addition to routine biochemistry tests, physical examination, and thorough medical history. HW score (HWS) was defined according to the percentage of white hair (HWS 1: <25%; HWS 2: 25-50%; HWS 3: 50-75%; and HWS 4: 75-100).

RESULTS

Patients with highest HWS were older and had a higher percentage of hypertension (HT) and family history of HW. Moreover, this subgroup had increased ascending aortic diameter, higher serum uric acid, and lower total bilirubin concentrations. Multivariate analyses including age, HT, height, waist circumference, c-reactive protein, and family history of HW identified body weight and HWS as the independent predictors of ascending aortic diameter.

CONCLUSION

An independent association between the degree of HW and AAD exists in middle-aged men, which may depend on coexisting factors that enhance both pathologies rather than causality. We think that oxidative stress may be one of these stressors.

NADPH oxidase 1/4 inhibition attenuates the portal hypertensive syndrome via modulation of mesenteric angiogenesis and arterial hyporeactivity in rats

AIM

NADPH oxidase (NOX)-derived reactive oxygen species (ROS) plays key roles in the development of portal hypertension (PHT) and represents a potential therapeutic method. The objective of this study was to investigate whether pharmacological inhibition of NADPH oxidase activity could ameliorate PHT in rats.

METHOD

PHT model was established by partial portal vein ligation (PPVL). Rats were treated with 30 mg/kg GKT137831 (the most specific Nox1/4 inhibitor) or vehicle daily by gavage for 14 days beginning at the day of PPVL or sham operation (SO). Hemodynamics, severity of portal-systemic shunting, vascular contractility, vascular endothelial growth factor (VEGF), VEGFR-2, CD31, AKT, phospho-AKT (p-AKT, at Ser473), endothelial nitric oxide synthase (eNOS), and phospho-eNOS (p-eNOS, at Ser1177) expressions were evaluated. Nitric oxide (NO) production and oxidative stress in mesenteric arteries, and hydrogen peroxide (H2O2) in both mesenteric tissues and arteries were measured.

RESULT

Inhibition of NOX1/4 with GKT137831 significantly decreased cardiac index, increased portal flow resistance, reduced portal pressure (PP), portal blood flow, mesenteric angiogenesis and portal-systemic shunting (PSS) in PPVL rats. GKT137831 reduced the production of H2O2, down regulated mesenteric angiogenesis markers (CD31, vascular endothelial growth factor (VEGF) and VEGFR-2 expression. Compared with controls), the mesenteric artery contraction to norepinephrine (NE) was impaired in PPVL rats, which was reversed by exposure to GKT137831. In addition, GKT137831 markedly decrease NADPH oxidase activity and ROS production in mesenteric arteries, and reduced NO production by decreasing the level of phosphor-AKT and eNOS.

CONCLUSION

Inhibition of NOX1/4 decreased PP, ameliorated hyperdynamic circulation, mesenteric angiogenesis and arterial hyporesonse in portal hypertensive rats. Pharmacological inhibition of NOX1/4 activity may be a potential treatment for PHT-related complications.

Extracellular matrix in ascending aortic aneurysms and dissections - What we learn from decellularization and scanning electron microscopy

Pathological impairment of elastic fiber and other extracellular matrix (ECM) components are described for the aortic media of ascending thoracic aortic aneurysms (aTAA) but the exact pathological impairment of the structure and its degree still needs further investigations. To evaluate the quantity and quality of elastic fiber sheets and other ECM structures (e.g. collagen), cells were removed from different types of aneurysmal tissues (tricuspid aortic valve [TAV] associated-, bicuspid aortic valve [BAV] associated-aneurysmal tissue and acute aortic dissections [AAD]) using 2.5% sodium hydroxide (NaOH) and compared to decellularized control aortic tissue. Likewise, native tissue has been analysed. To evaluate the 2D- (histological evaluation, fluorescence- and auto-fluorescence based staining methods) and the 3D structure (scanning electron microscopic [SEM] examination) of the medial layer we first analysed for a successful decellularization. After proving for successful decellularization, we quantified the amount of elastic fiber sheets, elastin and other ECM components including collagen. Aside from clearly visible focal elastic fiber loss in TAV-aTAA tissue, decellularization resulted in reduction of elastic fiber auto-fluorescence properties, which is perhaps an indication from a disease-related qualitative impairment of elastic fibers, visible only after contact with the alkaline solution. Likewise, the loss of collagen amount in BAV-aTAA and TAV-aTAA tissue (compared to non-decellularized tissue) after contact with NaOH indicates a prior disease-associated impairment of collagen. Although the amount of ECM was not changed in type A dissection tissue, detailed electron microscopic evaluation revealed changes in ECM quality, which worsened after contact with alkaline solution but were not visible after histological analyses. Apart from the improved observation of the samples using electron microscopy, contact of aneurysmal and dissected tissue with the alkaline decellularization solution revealed potential disease related changes in ECM quality which can partly be connected to already published data, but have to be proven by further studies.

Proinflammatory Role of Angiotensin II in the Aorta of Normotensive Mice

Angiotensin II plays important functions in cardiovascular system mediating actions leading to inflammatory responses such as activation of VSMC in order to produce ROS, inflammatory cytokines, chemokines, and adhesion molecules. Changes in angiotensin II production could stimulate the recruitment and activation of myeloid cells initiating local inflammatory response without effect on BP. We aimed to verify if angiotensin II induces an inflammatory response in the aorta and if it correlates with variations in BP. C57Bl/6 mice treated with saline solution (0.9%, control group) or angiotensin II (30ng/kg, Ang II group) were used. BP and HR levels were measured. Immunohistochemistry for IL1-β, TGF-β, iNOS, CD45, and α-actin was performed in the aorta. BP and HR do not change. A biphasic response was observed both for IL1-β and TGF-β expression and also for the presence of CD45 positive cells, with an acute increase (between 30 and 60 minutes) and a second increase, between 24 and 48 hours. Positive staining for iNOS increased in the earlier period (30 minutes) in perivascular adipose tissue and in a longer period (48 hours) in tunica adventitia. Immunoblotting to α-actin showed no alterations, suggesting that the applied dose of angiotensin II does not alter the aortic VSMCs phenotype. The results suggest that angiotensin II, even at doses that do not alter BP, induces the expression of inflammatory markers and migration of inflammatory cells into the aorta of normotensive mice. Thus, angiotensin II may increase the propensity to develop a cardiovascular injury, even in normotensive individuals.

Potential Medication Treatment According to Pathological Mechanisms in Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a vascular disease with high mortality. Because of the lack of effective medications to stop or reverse the progression of AAA, surgical operation has become the most predominant recommendation of treatment for patients. There are many potential mechanisms, including inflammation, smooth muscle cell apoptosis, extracellular matrix degradation, oxidative stress, and so on, involving in AAA pathogenesis. According to those mechanisms, some potential therapeutic drugs have been proposed and tested in animal models and even in clinical trials. This review focuses on recent advances in both pathogenic mechanisms and potential pharmacologic therapies of AAA.

Oxidative Stress in Aortas of Patients with Advanced Occlusive and Aneurysmal Diseases

BACKGROUND

Aortoiliac occlusive disease (AOD) and abdominal aortic aneurysm (AAA) are very important cardiovascular diseases that present different aspects of pathophysiology; however, oxidative stress and inflammatory response seem be relevant in both of them. Our objective was to evaluate oxidative damage and degree of inflammatory infiltrate in aortas of patients surgically treated for AOD and AAA.

MATERIALS AND METHODS

Levels of reactive oxygen species (ROS), nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, and myeloperoxidase (MPO) expression as well as nitrite levels and superoxide dismutase (SOD) and catalase (CAT) activities were evaluated in aortas of patients with AOD (n = 16) or AAA (n = 14), while the control group was formed by cadaveric organ donors (n = 10). We also analyzed the degree of inflammatory infiltrate in these aortas.

RESULTS

There was an increase in ROS levels and NADPH oxidase activity in patients with AOD and AAA when compared with the control group, and the AOD group demonstrated higher ROS production and NADPH oxidase activity and also nitrite levels when compared with the AAA group (P < 0.001). On the other hand, an increase of SOD activity in the AOD group and CAT activity in the AAA group was observed. Inflammatory infiltrate and MPO expression were higher in the AOD group when compared with the control group (P < 0.05).

CONCLUSIONS

Oxidative stress is relevant in both AOD and AAA, though AOD presented higher ROS levels and NADPH activity. Increased activities of antioxidant enzymes may be a compensatory phenomenon which occurs in aortas of patients with AOD and AAA. Perhaps, a relationship between oxidative stress and degree of inflammatory infiltrate may exist in the pathophysiology of AOD and AAA.

Redox stress in Marfan syndrome: Dissecting the role of the NADPH oxidase NOX4 in aortic aneurysm

Marfan syndrome (MFS) is characterized by the formation of ascending aortic aneurysms resulting from altered assembly of extracellular matrix fibrillin-containing microfibrils and dysfunction of TGF-β signaling. Here we identify the molecular targets of redox stress in aortic aneurysms from MFS patients, and investigate the role of NOX4, whose expression is strongly induced by TGF-β, in aneurysm formation and progression in a murine model of MFS. Working models included aortae and cultured vascular smooth muscle cells (VSMC) from MFS patients, and a NOX4-deficient Marfan mouse model (Fbn1^C1039G/+-Nox4^-/-). Increased tyrosine nitration and reactive oxygen species levels were found in the tunica media of human aortic aneurysms and in cultured VSMC. Proteomic analysis identified nitrated and carbonylated proteins, which included smooth muscle α-actin (αSMA) and annexin A2. NOX4 immunostaining increased in the tunica media of human Marfan aorta and was transcriptionally overexpressed in VSMC. Fbn1^C1039G/+-Nox4^-/- mice aortas showed a reduction of fragmented elastic fibers, which was accompanied by an amelioration in the Marfan-associated enlargement of the aortic root. Increase in the contractile phenotype marker calponin in the tunica media of MFS mice aortas was abrogated in Fbn1^C1039G/+-Nox4^-/- mice. Endothelial dysfunction evaluated by myography in the Marfan ascending aorta was prevented by the absence of Nox4 or catalase-induced H₂O₂ decomposition. We conclude that redox stress occurs in MFS, whose targets are actin-based cytoskeleton members and regulators of extracellular matrix homeostasis. Likewise, NOX4 have an impact in the progression of the aortic dilation in MFS and in the structural organization of the aortic tunica media, the VSMC phenotypic modulation, and endothelial function.

Resveratrol Inhibits Growth of Experimental Abdominal Aortic Aneurysm Associated With Upregulation of Angiotensin-Converting Enzyme 2

Objective—

Recent evidence suggests an important role for angiotensin-converting enzyme 2 (ACE2) in limiting abdominal aortic aneurysm (AAA). This study examined the effect of ACE2 deficiency on AAA development and the efficacy of resveratrol to upregulate ACE2 in experimental AAA.

Approach and Results—

Ace2 deletion in apolipoprotein-deficient mice ( ApoE −/− Ace2 −/y ) resulted in increased aortic diameter and spontaneous aneurysm of the suprarenal aorta associated with increased expression of inflammation and proteolytic enzyme markers. In humans, serum ACE2 activity was negatively associated with AAA diagnosis. ACE2 expression was lower in infrarenal biopsies of patients with AAA than organ donors. AAA was more severe in ApoE −/− Ace2 −/y mice compared with controls in 2 experimental models. Resveratrol (0.05/100-g chow) inhibited growth of pre-established AAAs in ApoE −/− mice fed high-fat chow and infused with angiotensin II continuously for 56 days. Reduced suprarenal aorta dilatation in mice receiving resveratrol was associated with elevated serum ACE2 and increased suprarenal aorta tissue levels of ACE2 and sirtuin 1 activity. In addition, the relative phosphorylation of Akt and ERK (extracellular signal-regulated kinase) 1/2 within suprarenal aorta tissue and gene expression for nuclear factor of kappa light polypeptide gene enhancer in B cells 1, angiotensin type-1 receptor, and metallopeptidase 2 and 9 were significantly reduced. Upregulation of ACE2 in human aortic smooth muscle cells by resveratrol in vitro was sirtuin 1-dependent.

Conclusions—

This study provides experimental evidence of an important role for ACE2 in limiting AAA development and growth. Resveratrol upregulated ACE2 and inhibited AAA growth in a mouse model.

Vascular remodeling: A redox-modulated mechanism of vessel caliber regulation

Vascular remodeling, i.e. whole-vessel structural reshaping, determines lumen caliber in (patho)physiology. Here we review mechanisms underlying vessel remodeling, with emphasis in redox regulation. First, we discuss confusing terminology and focus on strictu sensu remodeling. Second, we propose a mechanobiological remodeling paradigm based on the concept of tensional homeostasis as a setpoint regulator. We first focus on shear-mediated models as prototypes of remodeling closely dominated by highly redox-sensitive endothelial function. More detailed discussions focus on mechanosensors, integrins, extracellular matrix, cytoskeleton and inflammatory pathways as potential of mechanisms potentially coupling tensional homeostasis to redox regulation. Further discussion of remodeling associated with atherosclerosis and injury repair highlights important aspects of redox vascular responses. While neointima formation has not shown consistent responsiveness to antioxidants, vessel remodeling has been more clearly responsive, indicating that despite the multilevel redox signaling pathways, there is a coordinated response of the whole vessel. Among mechanisms that may orchestrate redox pathways, we discuss roles of superoxide dismutase activity and extracellular protein disulfide isomerase. We then discuss redox modulation of aneurysms, a special case of expansive remodeling. We propose that the redox modulation of vascular remodeling may reflect (1) remodeling pathophysiology is dominated by a particularly redox-sensitive cell type, e.g., endothelial cells (2) redox pathways are temporospatially coordinated at an organ level across distinct cellular and acellular structures or (3) the tensional homeostasis setpoint is closely connected to redox signaling. The mechanobiological/redox model discussed here can be a basis for improved understanding of remodeling and helps clarifying mechanisms underlying prevalent hard-to-treat diseases.

Elevated oxidative stress in the aortic media of patients with bicuspid aortic valve

OBJECTIVE

Congenital bicuspid aortic valve (BAV) is distinctly associated with the development of ascending aortopathy in adulthood, portending risk of both ascending aortic aneurysm and dissection. Our previous work implicated deficiency in oxidative stress response as a mediator of the BAV-associated aortopathy. We hypothesize that reactive oxygen species generation invokes elevated local oxidative tissue damage in ascending aorta of patients with BAV.

METHODS

Ascending aortic specimens were obtained from patients undergoing elective aortic replacement and/or aortic valve replacement and during heart transplant operations. Levels of superoxide anion were measured via high-pressure liquid chromatography-based detection of 2-hydroxyethidium in aortic specimens. Lipid peroxidation and enzymatic activity of superoxide dismutase and peroxidase were quantified in aortic specimens.

RESULTS

Superoxide anion production was elevated in aortic specimens from patients with nonaneurysmal BAV (n = 59) compared with specimens from patients with the morphologically normal tricuspid aortic valve (TAV, n = 38). Total superoxide dismutase activity was similar among aortic specimens from patients with TAV versus BAV (n = 27 and 26, respectively), whereas peroxidase activity was increased in aortic specimens from patients with BAV compared with specimens from patients with TAV (n = 14 for both groups). Lipid peroxidation was elevated in aortic specimens from BAV patients compared with TAV patients (n = 14 and 11, respectively).

CONCLUSIONS

Superoxide anion accumulation and increased lipid peroxidation demonstrate that, despite increased peroxidase activity, the ascending aortopathy of patients with BAV involves oxidative stress. In addition, the absence of increased superoxide dismutase activity in BAV specimens indicates a deficiency in antioxidant defense. This suggests that the characteristic smooth muscle cell loss observed in BAV aortopathy may be a consequence of superoxide-mediated cell damage.

Inhibitory effects of doxycycline on the onset and progression of abdominal aortic aneurysm and its related mechanisms

The objective of this study was to investigate whether doxycycline (DOX) given at different doses and via different administration routes had protective or therapeutic effects on abdominal aortic aneurysm (AAA) induced by elastase in mice. Moreover, the anti-AAA mechanism of DOX was studied in TNF-α-stimulated vascular smooth muscle cell (VSMC) in vitro. For in vivo study, either daily administration of 30mg/kg of DOX by gavage or intraperitoneal injection of 15mg/kg DOX every other day for 14 days significantly prevented the development of AAA at its early stage. Further study showed that intraperitoneal injection of 15mg/kg DOX every other day for 7 times in total could also cure the established AAA. In vitro study showed that treating VSMCs with TNF-α together with DOX remarkably inhibited the expressions and activities of MMPs (MMP-2 and MMP-9), significantly suppressed the activation of protein kinase B (AKT) signaling pathway and mitogen-activated protein kinases (MAPKs) signal proteins, including extracellular signal-regulated kinase (ERK), c-Jun amino-terminal kinases (JNK) and p38, and downregulated mRNA levels of interleukin-6 (IL-6) and monocyte chemotactic protein 1 (MCP-1), and significantly upregulated mRNA levels of transforming growth factor beta (TGF-β), heme oxygenase 1 (HO-1) and superoxide dismutase 1 (SOD-1), indicating that DOX inhibits activities of MMPs through reducing oxidative stress, suppressing MAPKs and AKT signaling pathways and ameliorating inflammation in VSMCs, and therefore, exerts preventive as well as therapeutic effects on AAA.

The Role Matrix Metalloproteinases in the Production of Aortic Aneurysm

Matrix metalloproteinases (MMPs) have been implicated in the pathogenesis of aortic aneurysm because the histology of thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA) is characterized by the loss of smooth muscle cells in the aortic media and the destruction of extracellular matrix (ECM). Furthermore, AAA have evidence of inflammation and the cellular elements involved in inflammation such as macrophages can produce and/or activate MMPs This chapter focuses on human aortic aneurysm that are not due to specific known genetic causes because this type of aneurysm is the more common type. This chapter will also focus on MMP protein expression rather than on genetic data which may not necessarily translate to increased MMP protein expression. There are supporting data that certain MMPs are increased in the aortic wall. For TAA, it is most notably MMP-1, -9, -12, and -14 and MMP-2 when a bicuspid aortic valve is present. For AAA, it is MMP-1, -2, -3, -9, -12, and -13. The data are weaker or insufficient for the other MMPs. Several studies of gene polymorphisms support MMP-9 for TAA and MMP-3 for AAA as potentially important factors. The signaling pathways in the aorta that can lead to MMP activation include JNK, JAK/stat, osteopontin, and AMP-activated protein kinase alpha2. Substrates in the human vasculature for MMP-3, MMP-9, or MMP-14 include collagen, elastin, ECM glycoprotein, and proteoglycans. Confirmed and potential substrates for MMPs, maintain aortic size and function so that a reduction in their content relative to other components of the aortic wall may produce a failure to maintain aortic size leading to dilatation and aneurysm formation.

Functional Heterogeneity of Nadph Oxidases in Atherosclerotic and Aneurysmal Diseases

NADPH oxidases (NOX) are enzymes that catalyze the production of reactive oxygen species (ROS). Four species of NOX catalytic homologs (NOX1, NOX2, NOX4, and NOX5) are reportedly expressed in vascular tissues. The pro-atherogenic roles of NOX1, NOX2, and their organizer protein p47^phox were manifested, and it was noted that the hydrogen peroxide-generating enzyme NOX4 possesses atheroprotective effects. Loss of NOX1 or p47^phox appears to ameliorate murine aortic dissection and subsequent aneurysmal diseases; in contrast, the ablation of NOX2 exacerbates the aneurysmal diseases. It is possible that the loss of NOX2 activates inflammatory cascades in macrophages in the lesions. Roles of NOX5 in vascular functions are currently undetermined, owing to the absence of this enzyme in rodents and the limitation of the experimental procedure. Thus, it is possible that the NOX family of enzymes exhibits heterogeneity in the atherosclerotic diseases. In this aspect, subtype-selective NOX inhibitor may be promising when NOX systems serve as a molecular target for atherosclerotic and aneurysmal diseases.

Angiotensin II Induces an Increase in Matrix Metalloproteinase 2 Expression in Aortic Smooth Muscle Cells of Ascending Thoracic Aortic Aneurysms Through JNK, ERK1/2, and p38 MAPK Activation

In this study, we hypothesized that angiotensin II (Ang II) induces matrix metalloproteinase 2 (MMP-2) upregulation in aneurysmal smooth muscle cells (ASMCs) derived from ascending thoracic aortic aneurysms (ATAAs). We compared MMP-2 protein levels in ascending aortic specimens using Western blot and plasma concentrations by enzyme-linked immunosorbent assay between ATAA (n = 40) and coronary heart disease patients (n = 40). Additionally, the protein level of angiotensinogen (AGT) in the ascending aorta and the plasma concentration of Ang II were detected by Western blot and radioimmunoassay, respectively, in ATAA and coronary heart disease patients. In ATAA patients, Ang II and MMP-2 plasma levels were significantly increased (P < 0.05). Additionally, AGT and MMP-2 protein levels in the aorta of ATAA patients were higher (P < 0.01). Enhanced AGT suggested that the amount of Ang II in aneurysmal aorta specimens may be also increased, which was confirmed by immunofluorescent staining for Ang II. Moreover, we investigated the effect of Ang II on MMP-2 upregulation by ASMCs and determined the Ang II receptors and intracellular signaling pathways that are involved. Our results showed that treatment with Ang II significantly increased the expression of MMP-2 through the Ang II type 1 receptor (AT1R) and activated the 3 major mitogen-activated protein kinases (MAPKs), JNK, ERK1/2, and p38 MAPK. In conclusion, these results indicate that Ang II can induce MMP-2 expression elevation through AT1R and MAPK pathways in ASMCs and suggest that there is therapeutic potential for angiotensin receptor blocker drugs and MAPK inhibitors in the prevention and treatment of ATAAs.

Pathobiology of Idiopathic Ascending Aortic Aneurysms

The majority of ascending aortic aneurysms cannot be related to any specific etiology and should be qualified as idiopathic. The pathobiology of ascending aortic aneurysms remains incompletely understood. Data from direct study are still scarce and often limited because of patient heterogenicity. Currently available information suggests that destructive remodeling of the aortic wall, inflammation and angiogenesis, biomechanical wall stress, and molecular genetics are relevant mechanisms of idiopathic ascending aortic aneurysm formation and progression. Further understanding of these mechanisms will likely provide novel diagnostic, prognostic, and therapeutical tools for the clinician.

Increased Oxidative Stress and Xanthine Oxidase Activity in Human Ruptured Cerebral Aneurysms

Recent studies have suggested that oxidative stress may be involved in the development of arterial aneurysms. Xanthine oxidase is implicated in the generation of reactive oxygen species under pathological conditions in the cardiovascular system, and increased xanthine oxidase activity has been reported in human aortic aneurysms. We, therefore, studied the changes of xanthine oxidase activity and oxidative stress in human ruptured cerebral aneurysms. Six cerebral aneurysmal samples were obtained during surgery. Normal arteries of the similar size (one superficial temporal artery, four uterine arteries and three right gastroepiploic arteries) were used as controls. The xanthine oxidase activity was measured with a commercial assay kit, and its expression was localized by immunohistochemistry. The xanthine oxidase activity was significantly increased in aneurysms by 4.1 fold (P<0.05) compared to control arteries. This was accompanied by an elevated malondialdehyde (MDA) level (8.3±5.1 versus 2.9±0.7 nmol/g protein, mean ±SD, P<0.05), a marker of oxidative stress. Immunohistochemistry established that xanthine oxidase was mainly expressed in infiltrating inflammatory cells. Our study indicates that xanthine oxidase may have an important role in the increased oxidative stress in ruptured cerebral aneurysms. Further studies are needed to clarify the role of XO-derived reactive oxygen species in the development and rupture of cerebral aneurysms.

Local Application of Leptin Antagonist Attenuates Angiotensin II-Induced Ascending Aortic Aneurysm and Cardiac Remodeling

Background

Ascending thoracic aortic aneurysm (ATAA) is driven by angiotensin II (AngII) and contributes to the development of left ventricular (LV) remodeling through aortoventricular coupling. We previously showed that locally available leptin augments AngII‐induced abdominal aortic aneurysms in apolipoprotein E–deficient mice. We hypothesized that locally synthesized leptin mediates AngII‐induced ATAA.

Methods and Results

Following demonstration of leptin synthesis in samples of human ATAA associated with different etiologies, we modeled in situ leptin expression in apolipoprotein E–deficient mice by applying exogenous leptin on the surface of the ascending aorta. This treatment resulted in local aortic stiffening and dilation, LV hypertrophy, and thickening of aortic/mitral valve leaflets. Similar results were obtained in an AngII‐infusion ATAA mouse model. To test the dependence of AngII‐induced aortic and LV remodeling on leptin activity, a leptin antagonist was applied to the ascending aorta in AngII‐infused mice. Locally applied single low‐dose leptin antagonist moderated AngII‐induced ascending aortic dilation and protected mice from ATAA rupture. Furthermore, LV hypertrophy was attenuated and thickening of aortic valve leaflets was moderated. Last, analysis of human aortic valve stenosis leaflets revealed de novo leptin synthesis, whereas exogenous leptin stimulated proliferation and promoted mineralization of human valve interstitial cells in culture.

Conclusions

AngII‐induced ATAA is mediated by locally synthesized leptin. Aortoventricular hemodynamic coupling drives LV hypertrophy and promotes early aortic valve lesions, possibly mediated by valvular in situ leptin synthesis. Clinical implementation of local leptin antagonist therapy may attenuate AngII‐induced ATAA and moderate related LV hypertrophy and pre–aortic valve stenosis lesions.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov/. Unique identifier: NCT00449306.

Statin Use and Aneurysm Risk in Patients With Bicuspid Aortic Valve Disease

BACKGROUND

No medical therapy has been proven to prevent the progression of aortic dilatation in bicuspid aortic valve (BAV) disease, and prophylactic aortic surgery remains the mainstay of treatment.

HYPOTHESIS

Among patients with BAV disease who are referred for surgery, preoperative statin use is associated with decreased odds of ascending aortic dilatation.

METHODS

We reviewed all BAV patients who underwent aortic valve and/or aortic surgery at our center between April 2004 and December 2013. Aortic diameter (AD), defined as the maximum ascending aortic dimension, was determined by magnetic resonance imaging, computed tomography, or echocardiography. Patients were divided into 2 groups: maximal AD <4.5 cm or ≥4.5 cm. The association between preoperative statin use and aortic dilatation was assessed using multivariable logistic regression modeling.

RESULTS

Of 680 consecutive patients, 405 (60%) had AD <4.5 cm (mean age, 60 ± 14 years; 45% on statins), whereas 275 (40%) had AD ≥4.5 cm (mean age, 54 ± 13 years; 35% on statins) at the time of surgery. After adjusting for age, body surface area, sex, hypertension, aortic stenosis, severity of aortic regurgitation, and use of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and β-blockers, patients with AD ≥4.5 cm had 0.66× lower odds (95% confidence interval: 0.45-0.96) of being on preoperative statins compared with those with AD <4.5 cm (P = 0.029).

CONCLUSIONS

In a retrospective study of BAV patients referred for surgery, preoperative statin use was associated with lower odds of clinically significant ascending aortic dilatation.

Ortner's syndrome presenting as thoracic aortic aneurysm mimicking thoracic malignancy: a case report

Introduction

Ortner’s syndrome is defined as left recurrent laryngeal nerve palsy caused by a cardiovascular pathology. Here we report the case of a 68-year-old man who presented to our hospital with hoarseness, whose initial chest imaging mimicked a thoracic neoplastic process with left pleural effusion. The final diagnosis was Ortner’s syndrome due to the silent rupture of a thoracoabdominal aortic aneurysm. Diagnostic thoracentesis, before computed tomography, in resource-poor settings, may have resulted in an adverse outcome in our case.

Case presentation

A 68-year-old Sri Lankan man was referred to us by an otolaryngologist for further evaluation of a suspected thoracic malignancy. His presenting symptom was hoarseness of three months duration. He had essential hypertension for the last four years and had a history of 25 pack-years of cigarettes smoking. His chest X-ray showed a left-sided mediastinal mass with mild to moderate pleural effusion. An ultrasound appeared to show an encysted pleural fluid collection. However, we proceeded with computed tomography before diagnostic thoracentesis. The diagnosis of Ortner’s syndrome was made after the computed tomography due to the silent rupture of his thoracoabdominal aortic aneurysm.

Conclusions

Hoarseness due to left recurrent laryngeal nerve palsy can be the presenting symptom of cardiovascular pathologies, Ortner’s syndrome. Silent rupture of thoracic aortic aneurysms can mimic that of thoracic malignancy, which is reported in literature. We illustrate the importance of a high degree of suspicion of cardiovascular pathology in order to avoid an adverse outcome following diagnostic thoracentesis.

Impaired glutathione redox system paradoxically suppresses angiotensin II-induced vascular remodeling

BACKGROUND

Angiotensin II (AII) plays a central role in vascular remodeling via oxidative stress. However, the interaction between AII and reduced glutathione (GSH) redox status in cardiovascular remodeling remains unknown.

METHODS

In vivo: The cuff-induced vascular injury model was applied to Sprague Dawley rats. Then we administered saline or a GSH inhibitor, buthionine sulfoximine (BSO, 30 mmol/L in drinking water) for a week, subsequently administered 4 more weeks by osmotic pump with saline or AII (200 ng/kg/minute) to the rats. In vitro: Incorporation of bromodeoxyuridine (BrdU) was measured to determine DNA synthesis in cultured rat vascular smooth muscle cells (VSMCs).

RESULTS

BSO reduced whole blood GSH levels. Systolic blood pressure was increased up to 215 ± 4 mmHg by AII at 4 weeks (p<0.01), which was not affected by BSO. Superoxide production in vascular wall was increased by AII and BSO alone, and was markedly enhanced by AII+BSO. The left ventricular weight to body weight ratio was significantly increased in AII and AII+BSO as compared to controls (2.52 ± 0.08, 2.50 ± 0.09 and 2.10 ± 0.07 mg/g respectively, p<0.05). Surprisingly, the co-treatment of BSO totally abolished these morphological changes. Although the vascular circumferential wall stress was well compensated in AII, significantly increased in AII+BSO. The anti-single-stranded DNA staining revealed increasing apoptotic cells in the neointima of injured arteries in BSO groups. BrdU incorporation in cultured VSMCs with AII was increased dose-dependently. Furthermore it was totally abolished by BSO and was reversed by GSH monoethyl ester.

CONCLUSIONS

We demonstrated that a vast oxidative stress in impaired GSH redox system totally abolished AII-induced vascular, not cardiac remodeling via enhancement of apoptosis in the neointima and suppression of cell growth in the media. The drastic suppression of remodeling may result in fragile vasculature intolerable to mechanical stress by AII.

Management of Aneurysmal Disease of the Aorta

Aneurysm of the aorta is largely a disease of the elderly. The incidence/prevalence of the disease has steadily increased in recent times, mainly because of the increase in awareness among patients/physicians and better imaging modalities. Early diagnosis and treatment of this disease holds the key to success and plays a part in prevention of catastrophic complications. With advancements in endovascular and surgical innovations, repair of aneurysmal disease has made significant progress, translating into better survival and long-term benefits. However, with significant morbidity and mortality associated with this disease, there is still a need for further research.

Endothelial cell-specific reactive oxygen species production increases susceptibility to aortic dissection

BACKGROUND

Increased production of reactive oxygen species (ROS) throughout the vascular wall is a feature of cardiovascular disease states, but therapeutic strategies remain limited by our incomplete understanding of the role and contribution of specific vascular cell ROS to disease pathogenesis. To investigate the specific role of endothelial cell (EC) ROS in the development of structural vascular disease, we generated a mouse model of endothelium-specific Nox2 overexpression and tested the susceptibility to aortic dissection after angiotensin II (Ang II) infusion.

METHODS AND RESULTS

A specific increase in endothelial ROS production in Nox2 transgenic mice was sufficient to cause Ang II-mediated aortic dissection, which was never observed in wild-type mice. Nox2 transgenic aortas had increased endothelial ROS production, endothelial vascular cell adhesion molecule-1 expression, matrix metalloproteinase activity, and CD45(+) inflammatory cell infiltration. Conditioned media from Nox2 transgenic ECs induced greater Erk1/2 phosphorylation in vascular smooth muscle cells compared with wild-type controls through secreted cyclophilin A (CypA). Nox2 transgenic ECs (but not vascular smooth muscle cells) and aortas had greater secretion of CypA both at baseline and in response to Ang II stimulation. Knockdown of CypA in ECs abolished the increase in vascular smooth muscle cell Erk1/2 phosphorylation conferred by EC conditioned media, and preincubation with CypA augmented Ang II-induced vascular smooth muscle cell ROS production.

CONCLUSIONS

These findings demonstrate a pivotal role for EC-derived ROS in the determination of the susceptibility of the aortic wall to Ang II-mediated aortic dissection. ROS-dependent CypA secretion by ECs is an important signaling mechanism through which EC ROS regulate susceptibility of structural components of the aortic wall to aortic dissection.

Overexpression of smooth muscle myosin heavy chain leads to activation of the unfolded protein response and autophagic turnover of thick filament-associated proteins in vascular smooth muscle cells

Duplications spanning nine genes at the genomic locus 16p13.1 predispose individuals to acute aortic dissections. The most likely candidate gene in this region leading to the predisposition for dissection is MYH11, which encodes smooth muscle myosin heavy chain (SM-MHC). The effects of increased expression of MYH11 on smooth muscle cell (SMC) phenotypes were explored using mouse aortic SMCs with transgenic overexpression of one isoform of SM-MHC. We found that these cells show increased expression of Myh11 and myosin filament-associated contractile genes at the message level when compared with control SMCs, but not at the protein level due to increased protein degradation. Increased expression of Myh11 resulted in endoplasmic reticulum (ER) stress in SMCs, which led to a paradoxical decrease of protein levels through increased autophagic degradation. An additional consequence of ER stress in SMCs was increased intracellular calcium ion concentration, resulting in increased contractile signaling and contraction. The increased signals for contraction further promote transcription of contractile genes, leading to a feedback loop of metabolic abnormalities in these SMCs. We suggest that overexpression of MYH11 can lead to increased ER stress and autophagy, findings that may be globally implicated in disease processes associated with genomic duplications.

Reactive oxygen species are involved in regulating hypocontractility of mesenteric artery to norepinephrine in cirrhotic rats with portal hypertension

Background: Oxidative stress is involved in the hypocontractility of visceral artery to vasoconstrictors and formation of hyperdynamic circulation in cirrhosis with portal hypertension. In the present study, we investigated the effect of reactive oxygen species (ROS) on the mesenteric artery contractility in CCl₄-induced cirrhotic rats, and the roles of G protein-coupled receptors (GPCRs) desensitization and RhoA /Rho associated coiled-coil forming protein kinase (ROCK) pathways.

Methods: The mesenteric artery contraction to norepinephrine (NE) was determined by vessel perfusion system following treatments with apocynin, tempol or PEG-catalase. The protein expression of α1 adrenergic receptor, β-arrestin-2, ROCK-1, moesin and p-moesin was measured by western blot. The interaction between α1 adrenergic receptor and β-arrestin-2 was assessed by co-immunoprecipitation.

Results: Pretreatment with apocynin or PEG-catalase in cirrhotic rats, the hydrogen peroxide level in the mesenteric arteriole was significantly decreased, and the dose-response curve of mesenteric arteriole to NE moved to the left with EC₅₀ decreased. There was no significant change for the expression of α1 adrenergic receptor. However, the protein expression of β-arrestin-2 and its affinity with α1 adrenergic receptor were significantly decreased. The ROCK-1 activity and anti- Y-27632 inhibition in cirrhotic rats increased significantly with the protein expression unchanged. Such effects were not observed in tempol-treated group.

Conclusion: The H₂O₂ decrease in mesenteric artery from rats with cirrhosis resulted in down regulation of the β-arrestin-2 expression and its binding ability with α1 adrenergic receptor, thereby affecting the agonist-induced ROCK activation and improving the contractile response in blood vessels.