Early increased MT1-MMP expression and late MMP-2 and MMP-9 activity during Angiotensin II induced aneurysm formation

Administration of an antibody against apoptosis inhibitor of macrophage prevents aortic aneurysm progression in mice

Apoptosis inhibitor of macrophage (AIM) is known to induce apoptosis resistance in macrophages and to exacerbate chronic inflammation, leading to arteriosclerosis. The role of AIM in aortic aneurysm (AA) remains unknown. This study examined the effects of an anti-AIM antibody in preventing AA formation and progression. In apolipoprotein E-deficient mice, AA was induced by subcutaneous angiotensin II infusion. Mice were randomly divided into two groups: (i) AIM group; weekly anti-murine AIM monoclonal antibody injection (n = 10), and (ii) IgG group; anti-murine IgG antibody injection as control (n = 14). The AIM group, compared with the IgG group, exhibited reduced AA enlargement (aortic diameter at 4 weeks: 2.1 vs. 2.7 mm, respectively, p = 0.012); decreased loss of elastic lamellae construction; reduced expression levels of IL-6, TNF-α, and MCP-1; decreased numbers of AIM-positive cells and inflammatory M1 macrophages (AIM: 1.4 vs. 8.0%, respectively, p = 0.004; M1 macrophages: 24.5 vs. 55.7%, respectively, p = 0.017); and higher expression of caspase-3 in the aortic wall (22.8 vs. 10.5%, respectively, p = 0.019). Our results suggest that administration of an anti-AIM antibody mitigated AA progression by alleviating inflammation and promoting M1 macrophage apoptosis.

Serum Catestatin Concentrations Are Increased in Patients with Atrial Fibrillation

The autonomic nervous system is crucial in initiating and maintaining atrial fibrillation (AF). Catestatin is a multipurpose peptide that regulates cardiovascular systems and reduces harmful, excessive activity of the sympathetic nervous system by blocking the release of catecholamines. We aimed to determine whether serum catestatin concentrations are associated with AF severity, duration indices, and various clinical and laboratory indicators in these individuals to better define the clinical value of catestatin in patients with AF. The present single center study enrolled 73 participants with AF and 72 healthy age-matched controls. Serum catestatin concentrations were markedly higher in AF patients than controls (14.11 (10.21-26.02) ng/mL vs. 10.93 (5.70-20.01) ng/mL, p = 0.013). Furthermore, patients with a more severe form of AF had significantly higher serum catestatin (17.56 (12.80-40.35) vs. 10.98 (8.38-20.91) ng/mL, p = 0.001). Patients with higher CHA₂DS₂-VASc scores (17.58 (11.89-37.87) vs. 13.02 (8.47-22.75) ng/mL, p = 0.034) and higher NT-proBNP levels (17.58 (IQR 13.91-34.62) vs. 13.23 (IQR 9.04-22.61), p = 0.036) had significantly higher serum catestatin concentrations. Finally, AF duration correlated negatively with serum catestatin levels (r = -0.348, p = 0.003). The results of the present study implicate the promising role of catestatin in the intricate pathophysiology of AF, which should be explored in future research.

The Role of Matrix Metalloproteinase in Inflammation with a Focus on Infectious Diseases

Matrix metalloproteinases (MMPs) are involved in extracellular matrix remodeling through the degradation of extracellular matrix components and are also involved in the inflammatory response by regulating the pro-inflammatory cytokines TNF-α and IL-1β. Dysregulation in the inflammatory response and changes in the extracellular matrix by MMPs are related to the development of various diseases including lung and cardiovascular diseases. Therefore, numerous studies have been conducted to understand the role of MMPs in disease pathogenesis. MMPs are involved in the pathogenesis of infectious diseases through a dysregulation of the activity and expression of MMPs. In this review, we discuss the role of MMPs in infectious diseases and inflammatory responses. Furthermore, we present the potential of MMPs as therapeutic targets in infectious diseases.

Succinate: A Novel Mediator to Promote Atherosclerotic Lesion Progression

Succinate is an important intermediate product of mitochondrial energy metabolism. Recent studies revealed that beyond its known traditional metabolic functions, succinate plays important roles in signal transduction, immunity, inflammation, and posttranslational modification. Recent studies showed that patients and mouse models with cardiovascular disease have high levels of serum succinate and succinate accumulation. Atherosclerosis (As) is the pathological basis of cardiovascular and peripheral vascular diseases, such as coronary heart disease, cerebral infarction, and peripheral vascular disease, and is a major factor affecting human health. This article reviews the progression of succinate in As diseases and its underlying mechanisms.

Angiotensin II is a crucial factor in retinal aneurysm formation

Retinal arterial macroaneurysms are characterized by the acquired fusiform or saccular dilatations of the retinal artery. Angiotensin II (Ang II) is a major signal molecule of the renin-angiotensin system, which exerts a range of pathogenic actions that are relevant to retinal vascular abnormalities. We aimed to study the effect of Ang II on retinal vessels and explore its relationship with retinal aneurysmal disease. C57BL/6J male mice were administered Ang II at 1000 ng/kg/min for 28 days, and the mice given saline served as controls. The mice in the treatment group were treated once daily by gastric gavage of candesartan cilexetil (an antagonist of Ang II type 1 (AT1) receptor) at 100 mg/kg/day. The in vivo imaging of murine retinas was performed using fundus photography, optical coherence tomography, fluorescein angiography, and indocyanine green angiography at 7th, 14th, and 28th days of infusion. At the end of the infusion and treatment, the morphological changes were evaluated by histopathological examination and electron microscopy; the levels of related proteins in murine retinas were examined by antibody array and Western blot analyses. We found that Ang II infusion induced aneurysm formation in mice retina, which presented as either solitary aneurysms or retinal arterial beading. The aneurysm formation was often accompanied with vessel leakage. Moreover, Ang II infusion itself may result in increased vascular permeability and ganglion cell and inner plexiform layer thickening. The blockade of AT1 receptors by systemic administration of candesartan cilexetil alleviated the Ang II-induced retinal vasculopathy. The protein level analysis further showed that Ang II upregulated IL-1β, PDGFR-β, and MMP-9 expression, and the expression of IL-1β could be inhibited by AT1 receptor antagonist. Our study provides evidence that Ang II is a crucial factor in retinal aneurysm formation and vessel leakage. It is probably the combined effect of Ang II on vessel inflammatory response, pericyte function, and extracellular matrix remodeling that predisposes the retinal arterial wall to aneurysm formation and blood-retinal barrier breakdown.

TREM-1 orchestrates angiotensin II-induced monocyte trafficking and promotes experimental abdominal aortic aneurysm

The triggering receptor expressed on myeloid cells 1 (TREM-1) drives inflammatory responses in several cardiovascular diseases but its role in abdominal aortic aneurysm (AAA) remains unknown. Our objective was to explore the role of TREM-1 in a mouse model of angiotensin II-induced (AngII-induced) AAA. TREM-1 expression was detected in mouse aortic aneurysm and colocalized with macrophages. Trem1 gene deletion (Apoe-/-Trem1-/-), as well as TREM-1 pharmacological blockade with LR-12 peptide, limited both AAA development and severity. Trem1 gene deletion attenuated the inflammatory response in the aorta, with a reduction of Il1b, Tnfa, Mmp2, and Mmp9 mRNA expression, and led to a decreased macrophage content due to a reduction of Ly6Chi classical monocyte trafficking. Conversely, antibody-mediated TREM-1 stimulation exacerbated Ly6Chi monocyte aorta infiltration after AngII infusion through CD62L upregulation and promoted proinflammatory signature in the aorta, resulting in worsening AAA severity. AngII infusion stimulated TREM-1 expression and activation on Ly6Chi monocytes through AngII receptor type I (AT1R). In human AAA, TREM-1 was detected and TREM1 mRNA expression correlated with SELL mRNA expression. Finally, circulating levels of sTREM-1 were increased in patients with AAA when compared with patients without AAA. In conclusion, TREM-1 is involved in AAA pathophysiology and may represent a promising therapeutic target in humans.

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.

Omentin attenuates angiotensin II-induced abdominal aortic aneurysm formation in apolipoprotein-E knockout mice

AIMS

Abdominal aortic aneurysm (AAA) is an increasing and life-threatening disease. Obesity contributes to an increased risk of AAA. Omentin is a circulating adipokine, which is downregulated in obese complications. Here we examined whether omentin could modulate angiotensin (Ang) II-induced AAA formation in apolipoprotein-E knockout (apoE-KO) mice.

METHODS AND RESULTS

ApoE-KO mice were crossed with transgenic mice expressing the human omentin gene in fat tissue (OMT-Tg mice) to generate ApoE-KO/OMT-Tg mice. ApoE-KO/OMT-Tg and apoE-KO mice were subjected to continuous Ang II infusion by using osmotic mini pumps. ApoE-KO/OMT-Tg mice exhibited a lower incidence of AAA formation and a reduced maximal diameter of AAA compared with apo-E KO mice. ApoE-KO/OMT-Tg mice showed attenuated disruption of medial elastic fibers in response to Ang II compared with apo-E KO mice. ApoE-KO/OMT-Tg mice also displayed reduced expression levels of matrix metalloproteinase (MMP) 9, MMP2 and pro-inflammatory genes in aortic walls compared with apo-E KO mice. Furthermore, systemic administration of omentin also attenuated AAA formation and disruption of medial elastic fibers in response to Ang II in apoE-KO mice. Treatment of human monocyte-derived macrophages with omentin protein attenuated expression of MMP9 and pro-inflammatory mediators, and MMP9 activation after stimulation with lipopolysaccharide (LPS). Treatment of human vascular smooth muscle cells with omentin protein reduced expression and activation of MMP2 after stimulation with tumor necrosis factor α. Omentin treatment increased phosphorylation levels of Akt in human macrophages and vascular smooth muscle cells. The suppressive effects of omentin on MMP9 and MMP2 expression were reversed by inhibition of integrin-αVβ3/PI3-kinase/Akt signaling in macrophages and vascular smooth muscle cells, respectively.

CONCLUSION

These data suggest that omentin acts as an adipokine that can attenuate Ang II-induced development of AAA through suppression of MMP9 and MMP2 expression and inflammatory response in the vascular wall.

Angiotensin II and leukocyte trafficking: New insights for an old vascular mediator. Role of redox-signaling pathways

Inflammation and activation of the immune system are key molecular and cellular events in the pathogenesis of cardiovascular diseases, including atherosclerosis, hypertension-induced target-organ damage, and abdominal aortic aneurysm. Angiotensin II (Ang-II) is the main effector peptide hormone of the renin-angiotensin system. Beyond its role as a potent vasoconstrictor and regulator of blood pressure and fluid homeostasis, Ang-II is intimately involved in the development of vascular lesions in cardiovascular diseases through the activation of different immune cells. The migration of leukocytes from circulation to the arterial subendothelial space is a crucial immune response in lesion development that is mediated through a sequential and coordinated cascade of leukocyte-endothelial cell adhesive interactions involving an array of cell adhesion molecules present on target leukocytes and endothelial cells and the generation and release of chemoattractants that activate and guide leukocytes to sites of emigration. In this review, we outline the key events of Ang-II participation in the leukocyte recruitment cascade, the underlying mechanisms implicated, and the corresponding redox-signaling pathways. We also address the use of inhibitor drugs targeting the effects of Ang-II in the context of leukocyte infiltration in these cardiovascular pathologies, and examine the clinical data supporting the relevance of blocking Ang-II-induced vascular inflammation.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Gene Expression in Intracranial Aneurysms-Comparison Analysis of Aneurysmal Walls and Extracranial Arteries with Real-Time Polymerase Chain Reaction and Immunohistochemistry

BACKGROUND

This study was aimed at evaluating the gene expression levels of 4 genes in the intracranial aneurysm wall and comparing them with extracranial arteries. The analysis was done using real-time polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC). Also, a correlation of the differential genetic expression was done with various patient clinical and radiologic factors.

METHODS

The quantitative assessment of ribonucleic acid levels was done with RT-PCR and was validated with IHC. The genes studied were collagen 1A2 (COL1A2), tissue inhibitor of metalloproteinase 4 (TIMP4), cathepsin B (CTSB), and alpha-1 antitrypsin (α-1 AT). The analysis was done on 24 aneurysm sacs and superficial temporal/occipital artery samples from patients undergoing surgical clipping.

RESULTS

The mean fold change of COL1A2 in the aneurysm sample was 8.89, that of TIMP4 was 10.16, that of CTSB was 1.02, and that of α-1 AT was 1.46 when compared with normal control vessel on PCR. On semiquantitative IHC, COL1A2 was 94.44%, α-1 AT was 77.8% overexpressed, CTSB was positive in 50%, and the expression of TIMP4 was 94.4% underexpressed in aneurysmal walls. There was no statistically significant correlation between patient profile and gene expression.

CONCLUSIONS

On RT-PCR and IHC analysis, COL1A2 and α-1 AT were overexpressed, CTSB was marginally overexpressed, and TIMP4 had equivocal expression in the aneurysmal sac when compared with the normal extracranial vessel. This is the first study of its kind in the Indian population with the largest sample size on live human patients.

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.

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.

Cilostazol Attenuates Angiotensin II-Induced Abdominal Aortic Aneurysms but Not Atherosclerosis in Apolipoprotein E-Deficient Mice

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a permanent dilation of the abdominal aorta associated with rupture, which frequently results in fatal consequences. AAA tissue is commonly characterized by localized structural deterioration accompanied with inflammation and profound accumulation of leukocytes, although the specific function of these cells is unknown. Cilostazol, a phosphodiesterase III inhibitor, is commonly used for patients with peripheral vascular disease or stroke because of its anti-platelet aggregation effect and anti-inflammatory effect, which is vasoprotective effect. In this study, we evaluated the effects of cilostazol on angiotensin II-induced AAA formation.

APPROACH AND RESULTS

Male apolipoprotein E-deficient mice were fed either normal diet or a diet containing cilostazol (0.1% wt/wt). After 1 week of diet consumption, mice were infused with angiotensin II (1000 ng/kg per minute) for 4 weeks. Angiotensin II infusion increased maximal diameters of abdominal aortas, whereas cilostazol administration significantly attenuated dilatation of abdominal aortas, thereby, reducing AAA incidence. Cilostazol also reduced macrophage accumulation, matrix metalloproteinases activation, and inflammatory gene expression in the aortic media. In cultured vascular endothelial cells, cilostazol reduced expression of inflammatory cytokines and adhesive molecules through activation of the cAMP-PKA (protein kinase A) pathway.

CONCLUSIONS

Cilostazol attenuated angiotensin II-induced AAA formation by its anti-inflammatory effect through phosphodiesterase III inhibition in the aortic wall. Cilostazol may be a promising new therapeutic option for AAAs.

Sex differences in abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a vascular disorder with a high case fatality rate in the instance of rupture. AAA is a multifactorial disease, and the etiology is still not fully understood. AAA is more likely to occur in men, but women have a greater risk of rupture and worse prognosis. Women are reportedly protected against AAA possibly by premenopausal levels of estrogen and are, on average, diagnosed at older ages than men. Here, we review the present body of research on AAA pathophysiology in humans, animal models, and cultured cells, with an emphasis on sex differences and sex steroid hormone signaling.

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.

Catestatin-A Novel Predictor of Left Ventricular Remodeling After Acute Myocardial Infarction

Catestatin was discovered as a potent inhibitor of catecholamine secretion and plays important roles in the cardiovascular system. Our previous study demonstrates a close relationship between catestatin levels and prognosis of ST-elevation myocardial infarction (STEMI). Using the same population, the goal of this study is to investigate the ability of catestatin to predict left ventricular (LV) remodeling in STEMI patients. 72 patients and 30 controls were included. Catestatin was sampled after admission to the emergency room (ER), at day3 (D3), and day7 (D7) after STEMI. Echocardiography was performed at D3 and after 65 months for evaluation of LVEDD, EF, IVS, LVPW, E, A, E’, E/A, and E/E’. The changes of these parameters from D3 to 65 months were used to reflect the changes of ventricular structure and function. We found that plasma catestatin levels at D3 were highly correlated with the changes of LVEDD, EF, E, A, E’, E/A, as well as E/E’. Patients with higher catestatin levels developed worse ventricular function during the follow-up period. Single-point catestatin was effective to predict LVEDD change. And concurrently increasing catestatin and NT-proBNP levels predicted the highest risk of LV remodeling. This study suggests an important prognostic information of catestatin on LV remodeling.

Differential hypertensive protease expression in the thoracic versus abdominal aorta

BACKGROUND

Hypertension (HTN), which is a major risk factor for cardiovascular morbidity and mortality, can drive pathologic remodeling of the macro- and microcirculation. Patterns of aortic pathology differ, however, suggesting regional heterogeneity of the pressure-sensitive protease systems triggering extracellular matrix remodeling in the thoracic (TA) and abdominal aortas (AA). This study tested the hypothesis that the expression of two major protease systems (matrix metalloproteinases [MMPs] and cathepsins) in the TA and AA would be differentially affected with HTN.

METHODS

Normotensive (BPN3) mice at 14-16 weeks of age underwent implantation of osmotic infusion pumps for 28-day angiotensin II (AngII) delivery (1.46 mg/kg/day; BPN3+AngII; n = 8) to induce HTN. The TA and AA were harvested to determine levels of MMP-2, MMP-9, and membrane type 1-MMP, and cathepsins S, K, and L were evaluated in age-matched BPN3 (n = 8) control and BPH2 spontaneously hypertensive mice (non-AngII pathway; n = 7). Blood pressure was monitored via CODA tail cuff plethysmography (Kent Scientific Corporation, Torrington, Conn). Quantitative real-time polymerase chain reaction and immunoblotting/zymography were used to measure MMP and cathepsin messenger RNA expression and protein abundance, respectively. Target protease values were compared within each aortic region via analysis of variance.

RESULTS

Following 28 days infusion, the BPN3+AngII mice had a 17% increase in systolic blood pressure, matching that of the BPH2 spontaneously hypertensive mice (both P < .05 vs BPN3). MMP-2 gene expression demonstrated an AngII-dependent increase in the TA (P < .05), but MMP-9 was not altered with HTN. Expression of tissue inhibitor of metalloproteinases-1 was markedly increased in TA of BPN3+AngII mice, but tissue inhibitor of metalloproteinases-2 demonstrated decreased expression in the AA of both hypertensive groups (P < .05). Only cathepsin K responded to AngII-induced HTN with significant elevation in the TA of those mice, but expression of cathepsin L and cystatin C was inhibited in AA of both hypertensive groups (P < .05). Apoptotic markers were not significantly elevated in any experimental group.

CONCLUSIONS

By using two different models of HTN, this study has identified pressure-dependent as well as AngII-dependent regional alterations in aortic gene expression of MMPs and cathepsins that may lead to differential remodeling responses in each of the aortic regions. Further studies will delineate mechanisms and may provide targeted therapies to attenuate down-stream aortic pathology based on demonstrated regional heterogeneity.

Regulation of membrane type-1 matrix metalloproteinase activity and intracellular localization in clinical thoracic aortic aneurysms

OBJECTIVE

Membrane type-1 matrix metalloproteinase (MT1-MMP) is elevated during thoracic aortic aneurysm (TAA) development in mouse models, and plays an important role in the activation of matrix metalloproteinase (MMP)-2 and the release of matrix- bound transforming growth factor-β. In this study, we tested the hypothesis that MT1-MMP is subject to protein kinase C (PKC)-mediated regulation, which alters intracellular trafficking and activity with TAAs.

METHODS

Levels of MMP-2, native and phosphorylated MT1-MMP, and PKC-δ were measured in aortic tissue from patients with small TAAs (<5 cm; n = 8) and large TAAs (>6.5 cm; n = 8), and compared with values measured in normal controls (n = 8). Cellular localization of green fluorescent protein (GFP)-tagged MT1-MMP was assessed in aortic fibroblasts isolated from control and 4-week TAA mice. The effects of PKC-mediated phosphorylation on MT1-MMP cellular localization and function (active MMP-2 vs phospo-Smad2 abundance) were assessed after treatment with a PKC activator (phorbol-12-myristate-13-acetate [PMA], 100 nM) with and without a PKC-δ-specific inhibitor (röttlerin, 3 μM).

RESULTS

Compared with controls, MT1-MMP abundance was increased in aortas from both TAA groups. Active MMP-2 was increased only in the large TAA group. The abundances of phosphorylated MT1-MMP and activated PKC-δ were enhanced in the small TAA group compared with the large TAA group. MT1-MMP was localized on the plasma membrane in aortic fibroblasts from control mice and in endosomes from TAA mice. Treatment with PMA induced MT1-MMP-GFP internalization, enhanced phospho-Smad2, and reduced MMP-2 activation, whereas röttlerin pretreatment inhibited these effects.

CONCLUSIONS

Phosphorylation of MT1-MMP mediates its activity through directing cellular localization, shifting its role from MMP-2 activation to intracellular signaling. Thus, targeted inhibition of MT1-MMP may have therapeutic relevance as an approach to attenuating TAA development.

2-Photon Characterization of Optical Proteolytic Beacons for Imaging Changes in Matrix-Metalloprotease Activity in a Mouse Model of Aneurysm

Abdominal aortic aneurysm is a multifactorial disease that is a leading cause of death in developed countries. Matrix-metalloproteases (MMPs) are part of the disease process, however, assessing their role in disease initiation and progression has been difficult and animal models have become essential. Combining Förster resonance energy transfer (FRET) proteolytic beacons activated in the presence of MMPs with 2-photon microscopy allows for a novel method of evaluating MMP activity within the extracellular matrix (ECM). Single and 2-photon spectra for proteolytic beacons were determined in vitro. Ex vivo experiments using the apolipoprotein E knockout angiotensin II-infused mouse model of aneurysm imaged ECM architecture simultaneously with the MMP-activated FRET beacons. 2-photon spectra of the two-color proteolytic beacons showed peaks for the individual fluorophores that enable imaging of MMP activity through proteolytic cleavage. Ex vivo imaging of the beacons within the ECM revealed both microstructure and MMP activity. 2-photon imaging of the beacons in aneurysmal tissue showed an increase in proteolytic cleavage within the ECM (p<0.001), thus indicating an increase in MMP activity. Our data suggest that FRET-based proteolytic beacons show promise in assessing MMP activity within the ECM and will therefore allow future studies to identify the heterogeneous distribution of simultaneous ECM remodeling and protease activity in aneurysmal disease.

Cigarette smoke-induced MMP2 and MMP9 secretion from aortic vascular smooth cells is mediated via the Jak/Stat pathway

It is hypothesized that cigarette smoke may increase MMP2 and MMP9 secretion through Jak/Stat pathway in the aorta, thereby facilitating abdominal aortic aneurysm (AAA) formation/progression in smokers. We observed through zymograms that treatment of male rat aortic vascular smooth muscle cells (RASMC) with an aqueous extract of cigarette smoke (CSE) for 24 hours resulted in a significant increase in pro-MMP9 (P = .005) and a modest increase in pro-MMP2 (P = .055) production. Western blot with protein extracts from CSE-treated RASMC showed up-regulation of pStat3, pJak2, and T-Jak2 and unchanged levels of T-Stat3. Transfection of RASMC with small interfering RNAs for Jak2, Stat3, or both Jak2 and Stat3 significantly reduced pro-MMP9 (P < .005) and pro-MMP2 (P < .05) in medium of CSE-treated RASMC compared with control small interfering RNA-transfected cells. Immunoprecipitation with total Jak2 antibody showed increased pStat3 and T-Stat3 in the cytoplasm and nucleus of CSE-treated RASMC. Immunofluorescence revealed increased presence of pJak2, T-Jak2, pStat3, and T-Stat3 in the cytoplasm and nucleus of the CSE-treated cells. Treatment of control human tissues with CSE resulted in pro-MMP9 secretion and up-regulation of the Jak/Stat proteins. In addition, AAA tissues showed more pJak2 and pStat3 than control human tissues. Therefore, inhibiting the Jak/Stat pathway could be a potential therapeutic approach in the treatment of AAA.

The important role of catestatin in cardiac remodeling

Catestatin (CST) was first discovered as a potent non-competitive and reversible inhibitor of catecholamine secretion. Recent reports on plasma CST level in heart diseases suggested a cardioprotective role for this peptide. Given that cardiac remodeling is the dominant pathologic process in cardiac dysfunction, we propose that CST participates in the regulation of concern pathways and contributes to the inhibition of cardiac remodeling. In this minireview, the potential mechanism of cardiac remodeling involving CST will be discussed from three aspects: hypertrophy, fibrosis, and apoptosis.

Phosphorylation of AKT and abdominal aortic aneurysm formation

It is hypothesized that differential AKT phosphorylation between sexes is important in abdominal aortic aneurysm (AAA) formation. Male C57BL/6 mice undergoing elastase treatment showed a typical AAA phenotype (80% over baseline, P < 0.001) and significantly increased phosphorylated AKT-308 (p308) and total-AKT (T-AKT) at day 14 compared with female mice. Elastase-treated Raw cells produced increased p308 and significant amounts of matrix metalloproteinase 9 (MMP-9), and these effects were suppressed by LY294002 treatment, a known AKT inhibitor. Male and female rat aortic smooth muscle cells treated with elastase for 1, 6, or 24 hours demonstrated that the p308/T-AKT and AKT-Ser-473/T-AKT ratios peaked at 6 hours and were significantly higher in the elastase-treated cells compared with controls. Similarly, male cells had higher phosphorylated AKT/T-AKT levels than female cells. LY294002 also inhibited elastase-induced p308 formation more in female smooth muscle cells than in males, and the corresponding cell media had less pro-MMP-9. AKT siRNA significantly decreased secretion of pro-MMP-9, as well as pro-MMP-2 and active MMP-2 from elastase-treated male rat aortic smooth muscle cells. IHC of male mice AAA aortas showed increased p308, AKT-Ser-473, and T-AKT compared with female mice. Aortas from male AAA patients had a significantly higher p308/T-AKT ratio than female AAA tissues. These data suggest that AKT phosphorylation is important in the upstream regulation of MMP activity, and that differential phosphorylation may be important in sex differences in AAA.

Hepatoprotective effects of loach (Misgurnus anguillicaudatus) lyophilized powder on dimethylnitrosamine-induced liver fibrosis in rats

This study investigates the hepatoprotective effects and the potential therapeutic mechanisms of loach (Misgurnus anguillicaudatus) lyophilized powder (MLP) on dimethylnitrosamine (DMN) induced liver fibrosis in rats. After treatment with MLP (50, 100, 200 mg/kg), alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin (Alb), total protein (TP) and hydroxyproline (Hyp) levels were detected, to assess the destruction of hepatocytes and the extent of liver fibrosis. Matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), hyaluronic acid (HA), Laminin (LN), procollagen type-III (PC-III), collagen type-IV (C-IV), and transforming growth factor-β₁ (TGF-β₁) contents in serum were all tested using ELISA kits. Alpha-smooth muscle actin (α-SMA) and the tissue inhibitor of metalloproteinase-1 (TIMP-1) protein contents and distribution were evaluated using western blot and immunohistochemical analysis. MLP significantly decreased the serum concentrations of ALT, AST, Hyp, HA, LN, PC-III, C-IV, MMP-2, TIMP-1, α-SMA and TGF-β₁, while increasing the contents of Alb and MMP-9. No significant changes on TP serum concentrations were observed. These results suggest that MLP has anti-hepatic fibrosis effects and its mechanism may be associated with the attenuation of extracellular matrix (ECM) synthesis, the acceleration of ECM degradation, inhibition of hepatic stellate cells (HSCs) activation and TGF-β₁ expression.

Vascular extracellular matrix in atherosclerosis

The extracellular matrix (ECM) is an essential component of the human body that is responsible for the proper function of various organs. Changes in the ECM have been implicated in the pathogenesis of several cardiovascular conditions including atherosclerosis, restenosis, and heart failure. Matrix components, such as collagens and noncollagenous proteins, influence the function and activity of vascular cells, particularly vascular smooth muscle cells and macrophages. Matrix proteins have been shown to be implicated in the development of atherosclerotic complications, such as plaque rupture, aneurysm formation, and calcification. ECM proteins control ECM remodeling through feedback signaling to matrix metalloproteinases (MMPs), which are the key players of ECM remodeling in both normal and pathological conditions. The production of MMPs is closely related to the development of an inflammatory response and is subjected to significant changes at different stages of atherosclerosis. Indeed, blood levels of circulating MMPs may be useful for the assessment of the inflammatory activity in atherosclerosis and the prediction of cardiovascular risk. The availability of a wide variety of low-molecular MMP inhibitors that can be conjugated with various labels provides a good perspective for specific targeting of MMPs and implementation of imaging techniques to visualize MMP activity in atherosclerotic plaques and, most interestingly, to monitor responses to antiatheroslerosis therapies. Finally, because of the crucial role of ECM in cardiovascular repair, the regenerative potential of ECM could be successfully used in constructing engineered scaffolds and vessels that mimic properties of the natural ECM and consist of the native ECM components or composite biomaterials. These scaffolds possess a great promise in vascular tissue engineering.

Role of the renin-angiotensin system on abdominal aortic aneurysms

BACKGROUND

Abdominal aortic aneurysm (AAA) is a complex degenerative disease, which leads to morbidity and mortality in a large portion of the elderly population. Current treatment options for AAA are quite limited as there is no proven indication for pharmacological therapy and surgery is recommended for AAA larger than 5·5 cm in luminal diameter. Thus, there is a great need to elucidate the underlying pathophysiological cellular and molecular mechanisms to develop effective therapies. In this narrative review, we will discuss recent findings concerning some potential molecular and clinical aspects of the renin-angiotensin system (RAS) in AAA pathophysiology.

MATERIALS AND METHODS

This narrative review is based on the material found on MEDLINE and PubMed up to April 2013. We looked for the terms 'angiotensin, AT1 receptor, ACE inhibitors' in combination with 'abdominal aortic aneurysm, pathophysiology, pathways'.

RESULTS

Several basic research and clinical studies have recently investigated the role of the RAS in AAA. In particular, the subcutaneous infusion of Angiotensin II has been shown to induce AAA in Apo56 knockout mice. On the other hand, the pharmacological treatments targeting this system have been shown as beneficial in AAA patients.

CONCLUSIONS

Emerging evidence suggests that RAS may act as a molecular and therapeutic target for treating AAA. However, several issues on the role of RAS and the protective activities of angiotensin-converting enzyme (ACE) inhibitors and Angiotensin 1 receptors blockers against AAA require further clarifications.

Cysteine protease cathepsins and matrix metalloproteinases in the development of abdominal aortic aneurysms

Both cysteine protease cathepsins and matrix metalloproteinases are implicated in the pathogenesis of abdominal aortic aneurysms (AAAs) in humans and animals. Blood and aortic tissues from humans or animals with AAAs contain much higher levels of these proteases, and often lower levels of their endogenous inhibitors, than do blood and aortic tissues from healthy subjects. Protease- and protease inhibitor-deficient mice and synthetic protease inhibitors have affirmed that cysteinyl cathepsins and matrix metalloproteinases both participate directly in AAA development in several experimental model systems. Here, we summarize our current understanding of how proteases contribute to the pathogenesis of AAA, and discuss whether proteases or their inhibitors may serve as diagnostic biomarkers or potential therapeutic targets for this common human arterial disease.

Matrix metalloproteinases: inflammatory regulators of cell behaviors in vascular formation and remodeling

Abnormal angiogenesis and vascular remodeling contribute to pathogenesis of a number of disorders such as tumor, arthritis, atherosclerosis, restenosis, hypertension, and neurodegeneration. During angiogenesis and vascular remodeling, behaviors of stem/progenitor cells, endothelial cells (ECs), and vascular smooth muscle cells (VSMCs) and its interaction with extracellular matrix (ECM) play a critical role in the processes. Matrix metalloproteinases (MMPs), well-known inflammatory mediators are a family of zinc-dependent proteolytic enzymes that degrade various components of ECM and non-ECM molecules mediating tissue remodeling in both physiological and pathological processes. MMPs including MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-12, and MT1-MMP, are stimulated and activated by various stimuli in vascular tissues. Once activated, MMPs degrade ECM proteins or other related signal molecules to promote recruitment of stem/progenitor cells and facilitate migration and invasion of ECs and VSMCs. Moreover, vascular cell proliferation and apoptosis can also be regulated by MMPs via proteolytically cleaving and modulating bioactive molecules and relevant signaling pathways. Regarding the importance of vascular cells in abnormal angiogenesis and vascular remodeling, regulation of vascular cell behaviors through modulating expression and activation of MMPs shows therapeutic potential.

Progressive alterations in microstructural organization and biomechanical response in the ApoE mouse model of aneurysm

AAA is a complex disease that leads to a localized dilation of the infrarenal aorta that develops over years. Longitudinal information in humans has been difficult to obtain for this disease, therefore mouse models have become increasingly used to study the development of AAAs. The objective of this study was to determine any changes that occur in the biomechanical response and fiber microstructure in the ApoE^−/− AngII mouse model of aneurysm during disease progression. Adult ApoE^−/− AngII infused mice along with wild-type controls were taken at 14 and 28 d. Aortas were excised and tested simultaneously for biaxial mechanical response and ECM organization. Data sets were fit to a Fung-type constitutive model to give peak strains and stiffness values. Images from two photon microscopy were quantified in order to assess the preferred fiber alignment and degree of fiber orientation. Biomechanical results found significant differences that were present at 14 d had returned to normal by 28 d along with significant changes in fiber orientation and dispersion indicating remodeling occurring within the aneurysmal wall. This return of some of the normal biomechanical function, in addition the continuing changes that occur in the microstructure suggest a restorative response that occurs in the ApoE^−/− AngII infused model after the initial aneurysm formation.

Interleukin-5 is a potential mediator of angiotensin II-induced aneurysm formation in apolipoprotein E knockout mice

BACKGROUND

The aim of this study was to evaluate alterations in Th1 and Th2 cytokines during experimental abdominal aortic aneurysm (AAA) formation.

METHODS

AAAs were induced in apolipoprotein E null mice by infusing angiotensin II (Ang II, 1000 ng/kg/min). Aortic homogenates were assessed at 0, 7, 14, and 28 d (n = 11/time point) for select Th1 and Th2 cytokines by ELISA. Additional mice had co-administration of anti-IgG (n = 20) or anti-IL-5 (n = 20) and were assessed at 28 d for AAA. Aortic homogenates were assessed for MMP-2 and MMP-9 expression. Mouse aortic SMC (MASMC) and peritoneal-derived macrophages were treated with IL-5 (0-40 ng/mL), and cell extracts and media (0-48 h) were assessed for MMP-2 and MMP-9 expression.

RESULTS

Ang II infusion was associated with a 3.4-fold (P < 0.01) and 3.6-fold (P < 0.01) increase in IL-5 and IL-10 (respectively), and a 0.6-fold reduction in IL-6, by 7 d. Anti-IL-5, but not anti-IgG, ameliorated Ang II-induced AAA formation. Up-regulation of MMP-2 and MMP-9 was observed in aneurysmal aortas, but not in the aortas obtained from mice treated with anti-IL-5. IL-5 stimulation of MASMC increased MMP-2 and MMP-9 mRNA (2.1-fold and 2.7-fold, respectively, P < 0.01) and protein (1.6-fold and 1.9-fold, respectively, P < 0.01) by 24 h. IL-5 stimulation of macrophages did not alter MMP expression.

CONCLUSIONS

Ang II induces increased Th2 cytokines IL-5 and IL-10 early in the course of experimental AAA formation, and inhibition of IL-5 prevents AAA formation suggesting an important role. While IL-5 is capable of up-regulating MMP-2 and MMP-9 expression in MASMC, investigations into alternate roles in AAA formation is warranted.

Elevation of plasma high-density lipoproteins inhibits development of experimental abdominal aortic aneurysms

OBJECTIVE

Patients with abdominal aortic aneurysms have lower concentrations of high-density lipoproteins (HDLs), leading us to investigate whether increasing plasma HDLs could influence aneurysm formation.

METHODS AND RESULTS

Using the angiotensin II-induced hypercholesterolemic and the CaCl(2)-induced normocholesterolemic mouse model of AAA, we investigated the hypothesis that elevation of HDLs inhibits AAA. HDLs elevated before or at the time of AAA induction reduced AAA formation in both models but had no effect on early ruptures. Analysis of protein lysates from specific aortic segments demonstrated site-specific effects of HDLs on early signal transduction and cellular attrition. We found that HDLs reduced extracellular signal related kinases 1/2 activation in the suprarenal segment, while having no effect on p38 mitogen-associated protein kinase activation in any aortic segment and inhibiting c-Jun N-terminal kinase activation in all aortic segments. In addition, HDL elevation inhibited angiotensin II-induced apoptosis while inducing autophagy in the suprarenal segment of the aorta. Using Illumina gene array profiling we investigated the ability of HDL to modulate basal suprarenal aortic gene expression.

CONCLUSIONS

Increasing plasma HDLs inhibit experimental AAA formation, independent of hypercholesterolemia via reduced extracellular signal related kinases 1/2 activation and alteration of the balance of cellular attrition. HDLs modulate genes involved in matrix remodelling, cell migration, and proliferation.

Involvement of the renin-angiotensin system in abdominal and thoracic aortic aneurysms

Aortic aneurysms are relatively common maladies that may lead to the devastating consequence of aortic rupture. AAAs (abdominal aortic aneurysms) and TAAs (thoracic aortic aneurysms) are two common forms of aneurysmal diseases in humans that appear to have distinct pathologies and mechanisms. Despite this divergence, there are numerous and consistent demonstrations that overactivation of the RAS (renin-angiotensin system) promotes both AAAs and TAAs in animal models. For example, in mice, both AAAs and TAAs are formed during infusion of AngII (angiotensin II), the major bioactive peptide in the RAS. There are many proposed mechanisms by which the RAS initiates and perpetuates aortic aneurysms, including effects of AngII on a diverse array of cell types and mediators. These experimental findings are complemented in humans by genetic association studies and retrospective analyses of clinical data that generally support a role of the RAS in both AAAs and TAAs. Given the lack of a validated pharmacological therapy for any form of aortic aneurysm, there is a pressing need to determine whether the consistent findings on the role of the RAS in animal models are translatable to humans afflicted with these diseases. The present review compiles the recent literature that has shown the RAS as a critical component in the pathogenesis of aortic aneurysms.

The role of extracellular signal-related kinase during abdominal aortic aneurysm formation

BACKGROUND

It is hypothesized that activation of extracellular signal-related kinase (ERK) is critical in activating matrix metalloproteinases (MMPs) during abdominal aortic aneurysm (AAA) formation.

STUDY DESIGN

C57BL/6 male mice underwent either elastase or heat-inactivated elastase aortic perfusion (n = 9 per group). Mouse aortic smooth muscle cells were transfected with ERK-1 and 2 siRNA along with or without elastase treatment. Mouse and human aortic tissue were analyzed by Western blots, zymograms, and immunohistochemistry, and statistical analysis was done using Graphpad and Image J softwares.

RESULTS

Western blot and immunohistochemistry documented increased phospho-mitogen-activated protein kinase kinase-1/2 (pMEK-1/2; 153%, p = 0.270 by Western) and pERK (171%, p = 0.004 by Western blot) in the elastase perfused aortas. Male ERK-1(-/-) mice underwent elastase perfusion, and aortic diameter was determined at day 14. ERK-1(-/-) mice failed to develop AAA, and histologic analysis depicted intact collagen and elastin fibers in the aortas. Zymography of aortas of elastase-treated ERK-1(-/-) mice showed lower levels of proMMP2 (p < 0.005) and active MMP2 (p < 0.0001), as well as proMMP9 (p = 0.037) compared with C57BL/6 mice. siRNA transfection of ERK-1 and -2 significantly reduced formation of pro- and active MMP2 (p < 0.01 for both isoforms) in aortic smooth muscle cells treated with elastase in vitro. Human AAA tissue had significantly elevated levels of pMEK-1/2 (150%, p = 0.014) and pERK (159%, p = 0.013) compared with control tissues.

CONCLUSIONS

The MAPK (mitogen-activated protein kinase)/ERK pathway is an important modulator of MMPs during AAA formation. Targeting the ERK pathway by reagents that inhibit either the expression or phosphorylation of ERK isoforms could be a potential therapy to prevent AAA formation.

Calpain inhibition attenuates angiotensin II-induced abdominal aortic aneurysms and atherosclerosis in low-density lipoprotein receptor-deficient mice

Chronic infusion of angiotensin II (AngII) augments atherosclerosis and abdominal aortic aneurysm (AAA) formation in hypercholesterolemic mice. AngII-induced AAAs are associated with medial macrophage accumulation and matrix metalloproteinase (MMP) activation. Inhibition of calpain, a calcium-activated neutral cysteine protease, by overexpression of its endogenous inhibitor, calpastatin, attenuates AngII-induced leukocyte infiltration, perivascular inflammation, and MMP activation in mice. The purpose of this study was to define whether pharmacological inhibition of calpain influences AngII-induced AAAs in hypercholesterolemic mice. Male low-density lipoprotein receptor-/- mice were fed a fat-enriched diet and administered with either vehicle or a calpain-specific inhibitor, BDA-410 (30 mg/kg per day) for 5 weeks. After 1 week of feeding, mice were infused with AngII (1000 ng/kg per minute) for 4 weeks. AngII-infusion profoundly increased aortic calpain protein and activity. BDA-410 administration had no effect on plasma cholesterol concentrations or AngII-increased systolic blood pressure. Calpain inhibition significantly attenuated AngII-induced AAA formation and atherosclerosis development. BDA-410 administration attenuated activation of MMP12, proinflammatory cytokines (IL-6, monocyte chemoattractant protein-1), and macrophage infiltration into the aorta. BDA-410 administration significantly attenuated thioglycolate-elicited macrophage accumulation in the peritoneal cavity. We conclude that calpain inhibition using BDA-410 attenuated AngII-induced AAA formation and atherosclerosis development in low-density lipoprotein receptor-/- mice.

Candesartan, an angiotensin II type 1 receptor antagonist, inhibits pathological retinal neovascularization by downregulating VEGF receptor-2 expression

Several studies have examined the anti-angiogenic effects of angiotensin II type 1 (AT(1)) receptor antagonists; however, the mechanisms underlying these effects are currently unclear. In the present study, we examined the efficacy and the mechanism of candesartan, an AT(1) receptor antagonist, in suppressing pathological retinal neovascularization. We used an in vivo murine oxygen-induced retinopathy (OIR) model and also studied the in vitro proliferation and migration of human retinal microvascular endothelial cells (HRMECs) induced by vascular endothelial growth factor (VEGF)-A. The regulation of angiogenesis-associated genes such as hypoxia-inducible factor (HIF-1α), VEGF-A, VEGF receptor-1, and VEGF receptor-2 was evaluated with real-time RT-PCR in the OIR model. In the OIR model, candesartan suppressed the pathological neovascularization in a dose-dependent manner, but did not prevent the physiological angiogenesis. However, candesartan did not inhibit VEGF-A-induced proliferation or migration in HRMECs in the in vitro study. When administered interperitoneally in the OIR model, candesartan reduced the upregulation of VEGF receptor-2 in the retina, but had no effects in the other angiogenesis-related genes, such as HIF-1α, VEGF-A, and VEGF receptor-1. These findings indicate that candesartan inhibited the retinal pathological neovascularization, at least in part, by suppressing the expression of VEGF receptor-2, independent of VEGF signaling cascade. Therefore, candesartan may be a useful therapeutic target for the inhibition of retinal neovascularization that has a low risk of serious side effects.

Angiotensin-converting enzyme insertion/deletion polymorphism is a risk factor for thoracic aortic aneurysm in patients with bicuspid or tricuspid aortic valves

OBJECTIVE

The angiotensin-converting enzyme (ACE) is highly expressed in the aneurysmal vascular wall, in both animal models and human disease. Genetic variations in ACE could be crucial in determining the risk of thoracic aortic aneurysm (TAA). The aim of the present study was to examine the role of ACE insertion/deletion polymorphism on the risk of TAA in patients with bicuspid aortic valves or tricuspid aortic valves.

METHODS

We enrolled 216 patients (158 men; age, 58.9±14.9 years) with TAA, associated with bicuspid aortic valves (n=105) and tricuspid aortic valves (n=111) compared with 312 patients (252 men; age, 54.6±11.0 years) with angiographically proven coronary artery disease and 300 healthy controls (91 men; age, 40.4±10.5 years).

RESULTS

The genotype distribution of ACE insertion/deletion was significantly different between the patients with TAA compared with both the control group (P=.0005) and the coronary artery disease group (P=.03). The genotypes were not different between the control group and the coronary artery disease group (P=.3). Compared with the controls, both the bicuspid aortic valve patients (P=.0008) and tricuspid aortic valve patients (P<.0001) had a greater frequency of allele D. The aortic diameters were significantly different among the three genotypes (48.3±6.6, 45.3±8.9, 39.9±8.7 for the DD, DI, and II genotypes, respectively; P=.0002). A synergistic effect between the ACE D allele and hypertension was found for both an increased aortic diameter (P=.003) and the risk of TAA (P<.001). On multivariate logistic regression analysis, D allele (odds ratio, 3.0; 95% confidence interval, 1.1-8.1; P=.03) was a significant predictor of TAA.

CONCLUSIONS

ACE insertion/deletion polymorphism represents a genetic biomarker for TAA. These findings could have a significant effect on both the early detection and effective pharmacologic treatment of aortic disease.

Inhibition of the renin-angiotensin system downregulates tissue factor and vascular endothelial growth factor in human breast carcinoma cells

INTRODUCTION

The renin-angiotensin system (RAS) promotes angiogenesis and growth of neoplastic cells. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor AT1 blockers may protect against cancer. Tissue factor (TF), for its involvement in tumor growth, angiogenesis, and metastasis is considered a hallmark of cancer progression. In this study we evaluated whether RAS blockade modulates TF constitutive expression by the metastatic breast carcinoma MDA-MB-231 cell line.

MATERIALS AND METHODS

Cell TF activity was assessed by one stage clotting time, TF and VEGF antigens and mRNA levels by ELISA and RT-PCR, respectively. AT(1) was detected by flow-cytometry and angiotensin-II levels by EIA.

RESULTS

Captopril reduced in a concentration-dependent way both the strong constitutive TF activity (983.2±55.2 vs. 686.7±135.1U/5×10(5) cells with 10μg/ml captopril) and antigen (32.3±5.9 vs. 13.2±6.6ng/ml) in MDA-MB-231. Similar results were observed with enalapril. AT1 was present on cell membrane and losartan, a competitive inhibitor of AT1, reduced TF expression to a degree similar as that exerted by ACE inhibitors. Moreover, captopril and losartan downregulated the constitutive mRNA TF expression by ~35%. Similar results were observed with anti-AT1 and angiotensin II antibodies. In addition, the constitutive VEGF antigen and mRNA levels were reduced in the presence of captopril or losartan, and an anti-VEGF antibody downregulated cell TF activity by ~40%.

CONCLUSIONS

These results could, at least in part, contribute to the discussion about the possible effects of ACE inhibitors and AT1 receptor antagonists in malignancy, and offer new clues to support their use for tumor control.

Prolonged infusion of angiotensin II in apoE(-/-) mice promotes macrophage recruitment with continued expansion of abdominal aortic aneurysm

Angiotensin II (AngII) infusion initiates abdominal aortic aneurysm (AAA) development due to medial disruption and results in luminal dilation and thrombus formation. The objective of this study was to determine whether AAA progressed during protracted AngII infusion. Male apoE(-/-) mice were infused with AngII using miniosmotic pumps. On day 27, suprarenal aortic luminal diameters were ultrasonically measured to identify mice exhibiting AAAs. Mice were designated to three groups with similar mean luminal dilation. Group 1 mice were sacrificed on day 28. Group 2 and 3 mice were subsequently infused with saline or AngII, respectively, for an additional 56 days. In Group 2, saline infusion-after the initial 28 days of AngII infusion-led to an immediate decrease in systolic blood pressure. Over the subsequent 56 days of saline infusion, there were no aneurysm-related deaths or significant changes in luminal diameter. In contrast, continuous AngII infusion in Group 3 maintained persistently increased systolic blood pressure, with aneurysmal rupture-associated deaths, increased luminal diameters, and tissue remodeling. Aortic aneurysmal segments that expanded during continuous AngII infusion exhibited macrophage accumulation in regions of medial disruption, predominantly on the adventitial aspect. Macrophages immunostained for CD206 more than for iNOS, consistent with an M2 phenotype. In conclusion, prolonged AngII infusion promotes AAA expansion, and is associated with enhanced rupture rates and increased macrophage infiltration.

Varespladib (A-002), a secretory phospholipase A2 inhibitor, reduces atherosclerosis and aneurysm formation in ApoE-/- mice

The family of secretory phospholipase A2 (sPLA2) enzymes has been associated with inflammatory diseases and tissue injury including atherosclerosis. A-001 is a novel inhibitor of sPLA2 enzymes discovered by structure-based drug design, and A-002 is the orally bioavailable prodrug currently in clinical development. A-001 inhibited human and mouse sPLA2 group IIA, V, and X enzymes with IC50 values in the low nM range. A-002 (1 mg/kg) led to high serum levels of A-001 and inhibited PLA2 activity in transgenic mice overexpressing human sPLA2 group IIA in C57BL/6J background. In addition, the effects of A-002 on atherosclerosis in 2 ApoE mouse models were evaluated using en face analysis. (1) In a high-fat diet model, A-002 (30 and 90 mg/kg twice a day for 16 weeks) reduced aortic atherosclerosis by 50% (P < 0.05). Plasma total cholesterol was decreased (P < 0.05) by 1 month and remained lowered throughout the study. (2) In an accelerated atherosclerosis model, with angiotensin II-induced aortic lesions and aneurysms, A-002 (30 mg/kg twice a day) reduced aortic atherosclerosis by approximately 40% (P < 0.05) and attenuated aneurysm formation (P = 0.0096). Thus, A-002 was effective at significantly decreasing total cholesterol, atherogenesis, and aneurysm formation in these 2 ApoE mouse models.

The prevalence and clinical impact of obesity in adults with Marfan syndrome

BACKGROUND

Patients with Marfan syndrome characteristically have an asthenic body habitus and are considered to be exempt from the obesity epidemic.

OBJECTIVE

To examine the prevalence and clinical impact of obesity in a cohort of adults with Marfan syndrome.

METHODS

Fifty outpatients (30 female) with a mean (+/- SD) age of 38+/-13 years were studied. Demographic variables including previously identified risk factors for aortic dissection were recorded. Body mass index (BMI) was determined and patients were classified as normal (BMI less than 25 kgm2), overweight (BMI 25 kgm2 to 29.9 kgm2) or obese (BMI 30 kgm2 or greater). Other cardiovascular risk factors were examined. An adverse clinical outcome was defined as either the attainment of surgical criteria for aortic root replacement or the presence of aortic dissection.

RESULTS

A family history of aortic dissection was present in 13 (26%) patients. In 23 (46%) patients, there was no known family history of Marfan syndrome. Mean BMI was 25.4+/-7.4 kgm2, with 18 (36%) patients having an elevated BMI. Positive smoking status was present in 15 (30%), hypertension in 13 (26%) and hyperlipidemia in 19 (38%) patients. Adverse clinical outcome was present in 27 (54%) patients. Logistic regression analysis revealed only index case (OR 44; P<0.001) and higher BMI (OR 1.2; P=0.04) to be significantly and independently associated with increased risk of adverse clinical outcome.

CONCLUSIONS

Obesity is common in adults with Marfan syndrome and is associated with an increased risk of aortic complications.

Alterations in membrane type-1 matrix metalloproteinase abundance after the induction of thoracic aortic aneurysm in a murine model

Thoracic aortic aneurysms (TAAs) develop as a result of dysregulated extracellular matrix remodeling mediated by several matrix metalloproteinases (MMPs). Membrane type-1 MMP (MT1-MMP) is the prototypical member of a unique family of membrane-bound MMPs, possessing multiple substrates and functions. The present study tested the hypothesis that MT1-MMP expression, abundance, and activity would be elevated during TAA development and that this protease is produced primarily by mesenchymal cells within the thoracic aorta. Descending thoracic aortas were harvested from C57BL/6J mice at multiple time points (2, 4, 8, and 16 wk, n = 15 each) post-TAA induction (0.5M CaCl(2), 15 min) and compared with reference controls (n = 15). The expression and abundance of MT1-MMP, MMP-2, and tissue inhibitor of metalloproteinase (TIMP)-2 were assessed by quantitative PCR and immunoblot analysis. MT1-MMP activity was determined by fluorescent peptide assay. MT1-MMP was localized within the aortic wall by immunohistochemistry. MT1-MMP abundance and localization in live animals (8 wk post-TAA induction vs. control) was determined by micro-ultrasound imaging with an MT1-MMP-targeted microbubble contrast agent. Aortic diameter was increased 172 +/- 7% at 16 wk post-TAA induction (P < 0.05). MT1-MMP and MMP-2 mRNA levels were elevated at 2 wk post-TAA induction (P < 0.05). MT1-MMP protein abundance increased progressively to a maximum of 178 +/- 26% at 16 wk post-TAA induction, whereas MMP-2 and TIMP-2 peaked at 2 wk post-TAA induction (526 +/- 93% and 376 +/- 48%, respectively, P < 0.05). MT1-MMP colocalized with fibroblasts, and MT1-MMP-targeted contrast binding was elevated in 8-wk TAA-induced mice versus control mice (217 +/- 53% vs. 81 +/- 8%, P < 0.05). In conclusion, these novel results suggest that MT1-MMP plays a dynamic multifunctional role in TAA development and, therefore, may provide a significant target for therapeutic strategies.

Loss of STAT1 is associated with increased aortic rupture in an experimental model of aortic dissection and aneurysm formation

BACKGROUND

Transcription factor signal transducer and activator of transcription (STAT) 1 has been linked to a variety of pathologic states involved with matrix remodeling, but its role in aortic pathology has not been previously described. The current study hypothesized that STAT1 regulates aneurysmal degeneration and its role was evaluated in human abdominal aortic aneurysm (AAA) and in a mouse model of aortic dissection.

METHODS

Apolipoprotein E knockout mice (ApoE-/-) or ApoE/STAT1 double knockout mice (ApoE/STAT1-/-) were infused with 1000 ng/kg/min of angiotensin II. Systolic blood pressure (SBP) was measured in the rodent tail. At sacrifice, aortic diameters and extent of aneurysm formation were measured by digital microscopy. STAT1 and phosphorylated-STAT1 protein levels were assessed in ApoE-/- mice at 0, 7, 14, and 28 days (n = 8/time point) by enzyme-linked immunosorbent assay. Histology was performed using hematoxylin and eosin (H&E) and Movat stains. Statistical analyses included chi(2) test, t test, and analysis of variance.

RESULTS

STAT1 messenger RNA and total protein were greater in human AAA vs non-AAA controls. In addition, aneurysms occurred in 8%, 50%, and 80% of ApoE-/- mice at 7, 14, and 28 days, respectively. Total STAT1 levels were not altered during the course of angiotensin II infusion. Phosphorylated STAT1 levels peaked at 7 days with a 1.4-fold increase over baseline (P < .05). Aneurysms occurred in 0%, 100%, and 100% of ApoE/STAT1-/- mice at 3, 5, and 28 days. In mice infused with angiotensin II for >3 days, aortic rupture occurred more frequently in ApoE/STAT-/- mice (53% vs 19%, P < .05) and at earlier time points (4.0 +/- 0.5 vs 9.2 +/- 0.77 days, P < .05) vs ApoE-/- mice. SBP did not differ between the groups during angiotensin II infusion. By 28 days, aneurysms were larger in ApoE/STAT1-/- mice compared with ApoE-/- mice (2.7 +/- 0.4 vs 1.9 +/- 0.1 mm, P < .05) and were more extensive. H&E and Movat stain did not reveal differences in aortic wall structural content at baseline between ApoE-/- and ApoE/STAT1-/- mice. Both groups demonstrated equal disorganization in the aneurysmal state.

CONCLUSIONS

Phosphorylated STAT1 is elevated during aneurysmal degeneration. Its loss is associated with a higher rate of acute aortic rupture and more extensive aneurysms in a mouse model of aortic dissection. Further investigation is necessary to determine whether these observations are secondary to an underlying aortic wall abnormality or alterations in vessel wall matrix remodeling.

Differential effects of mechanical and biological stimuli on matrix metalloproteinase promoter activation in the thoracic aorta

BACKGROUND

The effect of multiple integrated stimuli on vascular wall expression of matrix metalloproteinases (MMPs) remains unknown. Accordingly, this study examined the influence of the vasoactive peptide angiotensin II (Ang II) on wall tension-induced promoter activation of MMP-2, MMP-9, and membrane type-1 MMP (MT1-MMP).

METHODS AND RESULTS

Thoracic aortic rings harvested from transgenic reporter mice containing the MMP-2, MMP-9, or MT1-MMP promoter sequence fused to a reporter gene were subjected to 3 hours of wall tension at 70, 85, or 100 mm Hg, with or without 100 nM Ang II. Total RNA was harvested from the aortic rings, and reporter gene transcripts were quantified by quantitative real-time polymerase chain reaction to measure MMP promoter activity. MT1-MMP promoter activity was increased at both 85 and 100 mm Hg, compared with baseline tension of 70 mm Hg, whereas treatment with Ang II stimulated MT1-MMP promoter activity to the same degree at all tension levels (P<0.05). Elevated tension and Ang II displayed a potential synergistic enhancement of MMP-2 promoter activation at 85 and 100 mm Hg, whereas the same stimuli caused a decrease in MMP-9 promoter activity (P<0.05) at 100 mm Hg.

CONCLUSIONS

This study demonstrated that exposure to a relevant biological stimulus (Ang II) in the presence of elevated tension modulated MMP promoter activation. Furthermore, these data suggest that a mechanical-molecular set point exists for the induction of MMP promoter activation and that this set point can be adjusted up or down by a secondary biological stimulus. Together, these results may have significant clinical implications toward the regulation of hypertensive vascular remodeling.

Nitric oxide induces the progression of abdominal aortic aneurysms through the matrix metalloproteinase inducer EMMPRIN

Nitric Oxide (NO) is involved in the development and progression of abdominal aortic aneurysms (AAA). We found that inhibition of inducible NO synthase (iNOS) protects mice in an elastase-induced AAA model, significantly inhibiting the production of matrix metalloproteinase-13 (MMP-13). The extracellular MMP inducer (EMMPRIN; CD147) was increased in human AAA biopsies and in wild-type murine AAA but not in AAA from iNOS null mice. In cells overexpressing ectopic EMMPRIN, MMP-13 secretion was stimulated, whereas silencing of EMMPRIN by RNA interference led to significant inhibition of MMP-13 expression. In addition, elastase infusion of MMP-13 null mouse aortas induced a significant increase of EMMPRIN but reduced aortic dilatation when compared with wild-type mice, suggesting that NO-mediated AAA may be mediated through EMMPRIN induction of MMP-13. These findings were further verified in elastase-infused iNOS null mice, in which daily administration of NO caused a significant aortic dilatation and the expression of EMMPRIN and MMP-13. By contrast, in iNOS wild-type mice, pharmacological inhibition of iNOS by administration of 1400 W induced a reduction of aortic diameter and inhibition of MMP-13 and EMMPRIN expression when compared with control mice. Our results suggest that NO may regulate the development of AAA in part by inducing the expression of EMMPRIN and modulating the activity of MMP-13 in murine and human aneurysms.

Cyclophilin A enhances vascular oxidative stress and the development of angiotensin II-induced aortic aneurysms

Inflammation and oxidative stress are pathogenic mediators of many diseases, but therapeutic targets remain elusive. In the vasculature, abdominal aortic aneurysm (AAA) formation critically involves inflammaton and matrix degradation. Cyclophilin A (CyPA, encoded by Ppia) is highly expressed in vascular smooth muscle cells (VSMC), is secreted in response to reactive oxygen species (ROS), and promotes inflammation. Using the angiotensin II (AngII)-induced AAA model in Apoe^−/− mice, we show that Apoe^−/−Ppia^−/− mice were completely protected from AngII–induced AAA formation, in contrast to Apoe^−/−Ppia^+/+ mice. Apoe^−/−Ppia^−/− mice showed decreased inflammatory cytokine expression, elastic lamina degradation, and aortic expansion. These features were not altered by reconstitution of bone marrow cells from Ppia^+/+ mice. Mechanistic studies demonstrated that VSMC-derived intracellular and extracellular CyPA were required for ROS generation and matrix metalloproteinase-2 activation. These data define a novel role for CyPA in AAA formation and suggest CyPA is a new target for cardiovascular therapies.

Angiotensin II-induced hypertension regulates AT1 receptor subtypes and extracellular matrix turnover in mouse retinal pigment epithelium

Accumulation of specific deposits and extracellular molecules under the retinal pigment epithelium (RPE) has been previously observed in eyes with age-related macular degeneration (AMD) and may play a role in the pathogenesis of AMD. Even though age is the major determinant for developing AMD, clinical studies have revealed hypertension (HTN) as another systemic risk factor. Angiotensin II (Ang II) is considered the most important hormone associated with HTN. To evaluate the relationship of Ang II to AMD, we studied whether mouse RPE expresses functional Ang II receptor subtypes and whether HTN-induced Ang II regulates expression of these receptors as well as critical ECM molecules (MMP-2 and type IV collagen) involved in ECM turnover in RPE. We used 9-month-old C57BL/6 male mice infused with Ang II alone or Ang II in combination with the AT1 receptor antagonist candesartan or the AT2 receptor antagonist PD123319 for 4 weeks to determine whether HTN-associated Ang II was important for ECM regulation in RPE. We found that mouse RPE expressed both Ang II receptor subtypes at the mRNA and protein levels. Infusion with Ang II induced HTN and elevated plasma and ocular Ang II levels. Ang II also regulated AT1a and AT1b receptor mRNA expression, the intracellular concentration of calcium [Ca(2+)](i), MMP-2 activity, and type IV collagen accumulation. Concurrent administration of Ang II with the AT1 receptor blocker prevented the increase in blood pressure and rise in ocular Ang II levels, as well as the calcium and MMP-2 responses. In contrast, the type IV collagen response to Ang II was prevented by blockade of AT2 receptors, but not AT1 receptors. Plasma Ang II levels were not modified by the AT1 or AT2 receptor blockade. Since the effects of Ang II on MMP-2 and type IV collagen require inhibition of both Ang II receptor subtypes, these receptors may play a role as a potential therapeutic targets to prevent ECM turnover dysregulation in the RPE basement membrane, suggesting a pathogenic mechanism to explain the link between HTN and AMD.