Angiotensin II-induced abdominal aortic aneurysm occurs independently of the 5-lipoxygenase pathway in apolipoprotein E-deficient mice

Genetic association studies and pathological analysis of cardiovascular disease specimens implicate a role for the 5-lipoxygenase (5-LO)/leukotriene (LT) pathway in human cardiovascular disease. Previously, we had detected a role for this pathway in the incidence and severity of hyperlipidemic, cholate-containing, diet-induced aortic aneurysm in mice. The goal of the present study was to assess the importance of the 5-LO/LT pathway in angiotensin II (Ang II)-induced murine abdominal aortic aneurysm (AAA) formation. Mice with either genetic (5-LO(-/-)) or pharmacological (MK-0591) inhibition of the 5-LO pathway on an apolipoprotein E-deficient (apoE(-/-)) background were subjected to a normal chow diet with infusion of Ang II (500 ng/kg/min) for 28 days for assessment of AAA incidence and severity. Ang II-induced marked aortic wall remodeling with an incidence of 32, 29 and 40% AAA formation in 5-LO(-/-) apoE(-/-), 5-LO(+/+)apoE(-/-) and 5-LO(+/+)apoE(-/-) mice treated with FLAP inhibitor MK-0591, respectively, with no statistically significant differences in incidence or severity between groups. Abrogation of the 5-LO pathway in mice indicates a lack of role of leukotrienes in Ang II-induced AAA pathogenesis stressing the need for additional non-rodent AAA pre-clinical models to be tested.     

Three-dimensional microstructural changes in murine abdominal aortic aneurysms quantified using immunofluorescent array tomography

This study investigated the spatial and temporal remodeling of blood vessel wall microarchitecture and cellular morphology during abdominal aortic aneurysm (AAA) development using immunofluorescent array tomography (IAT), a high-resolution three-dimensional (3D) microscopy technology, in the murine model. Infrarenal aortas of C57BL6 mice (N=20) were evaluated at 0, 7, and 28 days after elastase or heat-inactivated elastase perfusion. Custom algorithms quantified volume fractions (VF) of elastin, smooth muscle cell (SMC) actin, and adventitial collagen type I, as well as elastin thickness, elastin fragmentation, non-adventitial wall thickness, and nuclei amount. The 3D renderings depicted elastin and collagen type I degradation and SMC morphological changes. Elastin VF decreased 37.5% (p<0.01), thickness decreased 48.9%, and fragmentation increased 449.7% (p<0.001) over 28 days. SMC actin VF decreased 78.3% (p<0.001) from days 0 to 7 and increased 139.7% (p<0.05) from days 7 to 28. Non-adventitial wall thickness increased 61.1%, medial nuclei amount increased 159.1% (p<0.01), and adventitial collagen type I VF decreased 64.1% (p<0.001) over 28 days. IAT and custom image analysis algorithms have enabled robust quantification of vessel wall content, microstructure, and organization to help elucidate the dynamics of vascular remodeling during AAA development.     

Synergistic effect of angiotensin II and nitric oxide synthase inhibitor in increasing aortic stiffness in mice

Although they are implicated on their own as risk factors for cardiovascular disease, the potential link between nitric oxide (NO) deficiency, ANG II, and vascular stiffening has not been tested before. We evaluated the role of chronic ANG II treatment and NO deficiency, alone and in combination, on aortic stiffness in mice and tested parameters contributing to increases in active or passive components of vascular stiffness, including blood pressure, vascular smooth muscle contractility, and extracellular matrix components. Untreated (control) mice and mice treated with a NO synthase (NOS) inhibitor [N(omega)-nitro-L-arginine methyl ester (L-NAME), 0.5 g/l] were implanted with osmotic minipumps delivering ANG II (500 ng.kg(-1).min(-1)) for 28 days. Aortic stiffness was then measured in vivo by pulse wave velocity (PWV) and ex vivo by load-strain analysis to obtain values of maximal passive stiffness (MPS). Blood pressure and aortic contractility ex vivo were measured. ANG II treatment or NOS inhibition with L-NAME did not independently increase vascular stiffness; however, the combined treatments worked synergistically to increase PWV and MPS. The combined treatments of ANG II + L-NAME also significantly increased aortic wall collagen content while decreasing elastin. These novel results suggest that NO deficiency and ANG II act synergistically to increase aortic stiffness in mice predominantly via changes in aortic wall collagen/elastin ratio.     

Inhibited aortic aneurysm formation in BLT1-deficient mice

Leukotriene B(4) is a proinflammatory lipid mediator generated by the enzymes 5-lipoxygenase and leukotriene A(4) hydrolase. Leukotriene B(4) signals primarily through its high-affinity G protein-coupled receptor, BLT1, which is highly expressed on specific leukocyte subsets. Recent genetic studies in humans as well as knockout studies in mice have implicated the leukotriene synthesis pathway in several vascular pathologies. In this study, we tested the hypothesis that BLT1 is necessary for abdominal aortic aneurysm (AAA) formation, a major complication of atherosclerotic vascular disease. Chow-fed Apoe(-/-) and Apoe(-/-)/Blt1(-/-) mice were treated with a 4-wk infusion of angiotensin II (1000 ng/min/kg) beginning at 20 wk of age, in a well-established murine AAA model. We found a reduced incidence of AAA formation as well as concordant reductions in the maximum suprarenal/infrarenal diameter and total suprarenal/infrarenal area in the angiotensin II-treated Apoe(-/-)/Blt1(-/-) mice as compared with the Apoe(-/-) controls. Diminished AAA formation in BLT1-deficient mice was associated with significant reductions in mononuclear cell chemoattractants and leukocyte accumulation in the vessel wall, as well as striking reductions in the production of matrix metalloproteinases-2 and -9. Thus, we have shown that BLT1 contributes to the frequency and size of abdominal aortic aneurysms in mice and that BLT1 deletion in turn inhibits proinflammatory circuits and enzymes that modulate vessel wall integrity. These findings extend the role of BLT1 to a critical complication of vascular disease and underscore its potential as a target for intervention in modulating multiple pathologies related to atherosclerosis.     

ANG II increases TIMP-1 expression in rat aortic smooth muscle cells in vivo

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are involved in tissue remodeling processes. TIMP-1 is the main native inhibitor of MMPs and it contributes to the development of tissue fibrosis. It is known that ANG II plays a fundamental role in vascular remodeling. In this study, we investigated whether ANG II modulates TIMP-1 expression in rat aortic smooth muscle cells. In vitro, ANG II induces TIMP-1 mRNA expression in a dose-dependent manner. The maximal increase in TIMP-1 expression was present after 3 h of ANG II stimulation. The ANG II increase in TIMP-1 expression was mediated by the ANG type 1 receptors because it was blocked by losartan. The increase in TIMP-1 expression was present after the first ANG II treatment, whereas repeated treatments (3 and 5 times) did not modify TIMP-1 expression. In vivo, exogenous ANG II was administered to Sprague-Dawley rats (200 ng. kg(-1). min(-1) sc) for 6 and 25 days. Control rats received physiological saline. After treatment, systolic blood pressure was significantly higher (P < 0.01), whereas plasma renin activity was suppressed (P < 0.01), in ANG II-treated rats. ANG II increased TIMP-1 expression in the aorta of ANG II-treated rats both at the mRNA (P < 0.05) and protein levels as evaluated by Western blotting (P < 0.05) and/or immunohistochemistry. Neither histological modifications at the vascular wall nor differences in collagen content in the tunica media were present in both the ANG II- and saline-treated groups. Our data demonstrate that ANG II increases TIMP-1 expression in rat aortic smooth muscle cells. In vivo, both short- and long-term chronic ANG II treatments increase TIMP-1 expression in the rat aorta. TIMP-1 induction by ANG II in aortic smooth muscle cells occurs in the absence of histological changes at the vascular wall.     

Angiotensin II injures the arterial wall causing increased aortic stiffening in apolipoprotein E-deficient mice

Cardiovascular diseases, such as atherosclerosis and hypertension, are associated with arterial stiffening. Previous studies showed that ANG II exacerbated atherosclerosis and induced hypertension and aneurysm formation in apolipoprotein E-deficient (apoE-KO) mice. The aim of the present study was to examine the effects of chronic treatment of ANG II on the arterial elastic properties in apoE-KO mice. We hypothesized that ANG II will injure the arterial wall resulting in increased arterial stiffening. Male apoE-KO mice were infused with either ANG II (1.44 mg. kg(-1). day(-1)) or vehicle (PBS) for 30 days. ANG II treatment accelerated atherosclerosis in the carotid artery by sixfold (P < 0.001) and increased blood pressure by 30% (P < 0.05). Additionally, our data demonstrated that ANG II increased arterial stiffening using both in vivo and in vitro methods. ANG II significantly increased pulse wave velocity by 36% (P < 0.01) and decreased arterial elasticity as demonstrated by a more than 900% increase in maximal stiffening (high strain Young's modulus) compared with vehicle (P < 0.05). These functional changes were correlated with morphological and biochemical changes as demonstrated by an increase in collagen content (60%), a decrease in elastin content (74%), and breaks in the internal elastic lamina in the aortic wall. In addition, endothelium-independent vasorelaxation to sodium nitroprusside was impaired in the aortic rings of ANG II-treated mice compared with vehicle. Thus, the present data indicate that ANG II injures the artery wall in multiple ways and arterial stiffening may be a common outcome of ANG II-induced arterial damage.     

In vivo imaging of macrophages during the early-stages of abdominal aortic aneurysm using high resolution MRI in ApoE mice

Background

Angiotensin II (ANG II) promotes vascular inflammation and induces abdominal aortic aneurysm (AAA) in hyperlipidemic apolipoprotein E knock-out (apoE^−/−) mice. The aim of the present study was to detect macrophage activities in an ANG II-induced early-stage AAA model using superparamagnetic iron oxide (SPIO) as a marker.

Methodology/Principal Findings

Twenty-six male apoE^−/− mice received saline or ANG II (1000 or 500 ng/kg/min) infusion for 14 days. All animals underwent MRI scanning following administration of SPIO with the exception of three mice in the 1000 ng ANG II group, which were scanned without SPIO administration. MR imaging was performed using black-blood T2 to proton density -weighted multi-spin multi-echo sequence. In vivo MRI measurement of SPIO uptake and abdominal aortic diameter were obtained. Prussian blue, CD68,α-SMC and MAC3 immunohistological stains were used for the detection of SPIO, macrophages and smooth muscle cells. ANG II infusion with 1000 ng/kg/min induced AAA in all of the apoE^−/− mice. ANG II infusion exhibited significantly higher degrees of SPIO uptake, which was detected using MRI as a distinct loss of signal intensity. The contrast-to-noise ratio value decreased in proportion to an increase in the number of iron-laden macrophages in the aneurysm. The aneurysmal vessel wall in both groups of ANG II treated mice contained more iron-positive macrophages than saline-treated mice. However, the presence of cells capable of phagocytosing haemosiderin in mural thrombi also induced low-signal-intensities via MRI imaging.

Conclusions/Significance

SPIO is taken up by macrophages in the shoulder and the outer layer of AAA. This alters the MRI signaling properties and can be used in imaging inflammation associated with AAA. It is important to compare images of the aorta before and after SPIO injection.     

Baicalein protects against the development of angiotensin II-induced abdominal aortic aneurysms by blocking JNK and p38 MAPK signaling

An abdominal aortic aneurysm(AAA) is a permanent, localized dilatation of the abdominal aorta. In western countries, the morbidity of AAA is approximately 8%. Currently, pharmacotherapies for AAA are limited. Here, we demonstrate that baicalein(BAI), the main component of the Chinese traditional drug "Huang Qin", attenuates the incidence and severity of AAA in Apoe儃/儃 mice infused with angiotensin II(AngII). Mechanically, BAI treatment decreases AngII-induced reactive oxygen species(ROS) production in the aortic wall. Moreover, BAI inhibits inflammatory cell accumulation in the aortas of mice infused with AngII. It also inhibits AngII-induced activation of matrix metalloproteinase 2(MMP-2) and MMP-9 to maintain elastin content in vivo. In addition, it blocks AngII cascade by downregulating angiotensin type 1 receptor(AT1R) and inhibiting mitogen-activated protein kinases(MAPKs). Taken together, our findings show that BAI is an effective agent for AAA prevention.     

Dipeptidyl Peptidase-4 Inhibitor Decreases Abdominal Aortic Aneurysm Formation through GLP-1-Dependent Monocytic Activity in Mice

Abdominal aortic aneurysm (AAA) is a life-threatening situation affecting almost 10% of elders. There has been no effective medication for AAA other than surgical intervention. Dipeptidyl peptidase-4 (DPP-4) inhibitors have been shown to have a protective effect on cardiovascular disease. Whether DPP-4 inhibitors may be beneficial in the treatment of AAA is unclear. We investigated the effects of DPP-4 inhibitor sitagliptin on the angiotensin II (Ang II)-infused AAA formation in apoE-deficient (apoE^-/-) mice. Mice with induced AAA were treated with placebo or 2.5, 5 or 10 mg/kg/day sitagliptin. Ang II-infused apoE^-/- mice exhibited a 55.6% incidence of AAA formation, but treatment with sitagliptin decreased AAA formation. Specifically, administered sitagliptin in Ang II-infused mice exhibited decreased expansion of the suprarenal aorta, reduced elastin lamina degradation of the aorta, and diminished vascular inflammation by macrophage infiltration. Treatment with sitagliptin decreased gelatinolytic activity and apoptotic cells in aorta tissues. Sitaglipitn, additionally, was associated with increased levels of plasma active glucagon-like peptide-1 (GLP-1). In vitro studies, GLP-1 decreased reactive oxygen species (ROS) production, cell migration, and MMP-2 as well as MMP-9 activity in Ang II-stimulated monocytic cells. The results conclude that oral administration of sitagliptin can prevent abdominal aortic aneurysm formation in Ang II-infused apoE^-/-mice, at least in part, by increasing of GLP-1 activity, decreasing MMP-2 and MMP-9 production from macrophage infiltration. The results indicate that sitagliptin may have therapeutic potential in preventing the development of AAA.     

CCL7 contributes to angiotensin II-induced abdominal aortic aneurysm by promoting macrophage infiltration and pro-inflammatory phenotype

Chemokine C-C motif ligand 7 (CCL7), a member of CC chemokine subfamily, plays pivotal roles in numerous inflammatory diseases. Hyper-activation of inflammation is an important characteristic of abdominal aortic aneurysm (AAA). Therefore, in the present study, we aimed to determine the effect of CCL7 on AAA formation. CCL7 abundance in aortic tissue and macrophage infiltration were both increased in angiotensin II (Ang II)-induced AAA mice. Ex vivo, CCL7 promoted macrophage polarization towards M1 phenotype. This effect was reversed by the blockage of CCR1, a receptor of CCL7. CCL7 up-regulated JAK2/STAT1 protein level in macrophage, and CCL7-induced M1 activation was suppressed by JAK2/STAT1 pathway inhibition. To verify the effect of CCL7 on AAA in vivo, either CCL7-neutralizing antibody (CCL7-nAb) or vehicles were intraperitoneally injected 24 hours prior to Ang II infusion and subsequently every three days for 4 weeks. CCL7-nAb administration significantly attenuated Ang II-induced luminal and external dilation as well as pathological remodelling. Immunostaining showed that CCL7-nAb administration significantly decreased aneurysmal macrophage infiltration. In conclusion, CCL7 contributed to Ang II-induced AAA by promoting M1 phenotype of macrophage through CCR1/JAK2/STAT1 signalling pathway.     

Evolving anisotropy and degree of elastolytic insult in abdominal aortic aneurysms: Potential clinical relevance?

Accurately estimating patient-specific rupture risk remains a primary challenge in timing interventions for abdominal aortic aneurysms (AAAs). By re-analyzing published biaxial mechanical testing data from surgically repaired human AAAs, material anisotropy emerged as a potentially important determinant of patient-specific lesion progression. That is, based on a new classification scheme, we discovered that anisotropic aneurysmal specimens correlated with increased patient age at surgery when compared with more isotropic specimens (79.7 vs. 70.9 years, p<0.002), despite no significant difference in maximum diameter. Furthermore, using an idealized axisymmetric, finite-element growth and remodeling model of AAA progression, we found that both the initial axial extent of elastin loss and ongoing damage to elastin in the shoulder region of the AAA directly affected the degree of anisotropy as the lesion evolved, with more extensive insults increasing the anisotropy. This effect appeared to be mediated by alterations in axial loading and subsequent differences in orientation of deposited collagen fibers. While the observed increased age before surgical intervention may suggest a potential benefit of anisotropic remodeling, future biaxial tests coupled with pre-surgical data on expansion rates and detailed theoretical analyses of the biostability of a lesion as a function of anisotropy will be required to verify its clinical relevance to patient-specific rupture risk.     

Benzo[a]pyrene potentiates the pathogenesis of abdominal aortic aneurysms in apolipoprotein E knockout mice

The objective of this study was to determine the effect of benzo[a]pyrene (BaP), an abundant environmental polycyclic aromatic hydrocarbon compound, on the pathogenesis of abdominal aortic aneurysms (AAA). Earlier studies have shown that BaP promotes vasculopathy, including atherosclerosis, a predisposing factor for AAA development. In two experimental arms, 203 apolipoprotein E knockout (ApoE-/-) mice were evaluated in 4 groups: BaP, angiotensin II (AngII), BaP+AngII and control. Mice in the first arm were exposed to 5mg/kg/week of BaP for 42 days, and in the second arm to 0.71mg/kg daily for 60 days. In arm one, AAA incidence was higher in the BaP+AngII (14/28) versus AngII (8/27) group (p < 0.05), rupture (n=3) was observed only in BaP+AngII treated mice (p < 0.05). In the second arm, AAA incidence did not differ between AngII (17/30) and BaP+AngII (16/29) groups. However, intact AAA diameter was larger in the BaP+AngII (2.3 ± 0.1mm) versus AngII (1.9 ± 0.1mm) group (p < 0.05), but AAA rupture did not differ (p=NS). In both experimental arms, BaP+AngII mice showed increased expression of tumor necrosis factor alpha (TNF-α), cyclophilin A (Cyp A), and matrix metalloproteinase-9 (MMP9) (p < 0.05). No AAA occurred in control or BaP groups. These findings suggest the role of BaP exposure in potentiating AAA pathogenesis, which may have potential public health significance.     

Activation of AMP-activated protein kinase α2 by nicotine instigates formation of abdominal aortic aneurysms in mice in vivo

Smoking is the only modifiable risk factor that is associated with the development, expansion and rupture of abdominal aortic aneurysm (AAA). However, the causative link between cigarette smoke and AAA is unknown. Here we report a causative link between smoking and AAA in vivo. Acute infusion of angiotensin II (AngII) or nicotine, a major component of cigarette smoke, markedly increased the incidence of AAA in apolipoprotein E (apoE) knockout (Apoe(-/-)) mice and in mice deficient in both apoE and the AMP-activated kinase α1 subunit (AMPK-α1) (Apoe(-/-); Prkaa1(-/-) mice). In contrast, genetic deletion of AMPK-α2 (Apoe(-/-); Prkaa2(-/-) mice) ablated nicotine- or AngII-triggered AAA in vivo. Mechanistically, we found that both nicotine and AngII activated AMPK-α2 in cultured vascular smooth muscle cells (VSMCs), resulting in the phosphorylation of activator protein 2α (AP-2α) and consequent matrix metallopeptidase 2 (MMP2) gene expression. We conclude that smoking (through nicotine) instigates AAA through AMPK-α2–mediated AP-2α–dependent MMP2 expression in VSMCs.     

Chemical-induced, nonlethal, developmental model of dissecting aortic aneurysm

BACKGROUND: A chemical-induced, nonlethal, dissecting aortic aneurysm (DAA) is described following in utero exposure to semicarbazide, an inhibitor of the vascular enzyme semicarbazide sensitive amine oxidase (SSAO). METHODS: Sprague-Dawley rat dams were given semicarbazide (0.096-49.000 mg/kg/day) by IP injection on gestation days (GDs) 14-20, a period of rapid aortic development. Newborn rats (day 1) were killed and their thoracic organs were removed en bloc for near-serial cross sections and routine histopathology, Movat stain for elastin, and immunohistochemistry to differentiate cells involved in the evolution of the DAA. In subsequent experiments, pups from treated dams (0.096-6.125 mg/kg/day) were allowed to survive for 7 or 28 days. RESULTS: DAA occurred in nearly 100% of the rats at all doses except the lowest tested (1.530, 0.096 mg/kg/day). Dissections frequently extended to the carotids and, less frequently, to the abdominal aorta. Remodeling of vascular lesions proceeded by organization of collections of blood in vascular media (the "false lumen"), proliferation of vascular smooth muscle cells, fibrosis, and formation of irregular frayed elastic lamellae in healed vascular media. Biochemical quantitation and Western blot analysis of main extracellular matrix proteins on GD 20 showed no overt difference in expression of collagen type I, fibrillin-1, or elastin. CONCLUSION: This developmental model provides investigators an opportunity to explore the pathologic mechanisms of DAA and to examine the potential long-term effects of vascular remodeling of DAA.     

Group X secretory PLA2 in neutrophils plays a pathogenic role in abdominal aortic aneurysms in mice

Group X secretory PLA(2) (sPLA(2)-X) is expressed in neutrophils and plays a role in the pathogenesis of neutrophil-mediated tissue inflammation and injury. This study tested the hypothesis that sPLA(2)-X in neutrophils may contribute to the pathogenesis of abdominal aortic aneurysms (AAA) using sPLA(2)-X(-/-) mice. AAA was created by application of CaCl(2) to external surface of aorta. As a result, the aortas of sPLA(2)-X(-/-) mice had smaller diameters (percent increase from baseline; 24.8 ± 3.5% vs. 49.9 ± 9.1%, respectively; P < 0.01), a reduced grade of elastin degradation, and lower activities of elastase and gelatinase (26% and 19% lower, respectively) after CaCl(2) treatment compared with sPLA(2)-X(+/+) mice. In sPLA(2)-X(+/+) mice, immunofluorescence microscopic images showed that the immunoreactivity of sPLA(2)-X was detected only in neutrophils within aortic walls 3 days, 1, 2, and 6 wk after CaCl(2) treatment, whereas the immunoreactivity was not detected in macrophages or mast cells in aortic walls. sPLA(2)-X immunoreactivity also was colocalized in cells expressing matrix metalloproteinase (MMP)-9. Neutrophils isolated from sPLA(2)-X(-/-) mice had lower activities of elastase, gelatinase, and MMP-9 in response to stimuli compared with sPLA(2)-X(+/+) mice. The attenuated release of elastase and gelatinase from sPLA(2)-X(-/-) neutrophils was reversed by exogenous addition of mouse sPLA(2)-X protein. The adoptive transfer of sPLA(2)-X(+/+) neutrophils days 0 and 3 after CaCl(2) treatment reversed aortic diameters and elastin degradation grades in the lethally irradiated sPLA(2)-X(+/+) mice reconstituted with sPLA(2)-X(-/-) bone marrow to an extent similar to that seen in sPLA(2)-X(+/+) mice. In conclusion, sPLA(2)-X in neutrophils plays a pathogenic role in AAA in a mice model.     

Licochalcone A attenuates abdominal aortic aneurysm induced by angiotensin II via regulating the miR-181b/SIRT1/HO-1 signaling

Licochalcone A (LA), a chalcone derived from liquorice, exhibits multiple biological activities, including anti-oxidation and anti-inflammation. This study aimed to investigate the role and underlying mechanism of LA in the abdominal aortic aneurysm (AAA). AAA model was established by continuous infusion of 1000 ng/kg/min of angiotensin II (AngII) in ApoE ^-/- mice for 4 weeks. At 7 days before AngII administration, 5 mg/kg/day or 10 mg/kg/day of LA was intraperitoneally administered to mice and continued for 4 weeks. The characteristics and quantification of AAAs were determined in situ. Real-time PCR or western blot was used to measure mRNA or protein levels of matrix metalloproteinase 2 and matrix metalloproteinase 9; pro-inflammatory cytokines tumor necrosis factor-α, interleukin-1β, and interleukin-6; apoptosis-related proteins Bax, Bcl-2, and active caspase-3; miR-181b; Sirtuin 1 (SIRT1); and heme oxygenase-1 (HO-1). Mouse-aorta-origin vascular smooth muscle (MOVAS) cells were used to confirm the involved pathways in vitro. We found LA administration dose-dependently reduced the incidence of AngII-induced AAA, aneurysm diameter enlargement, elastin degradation, matrix metalloproteinase production, pro-inflammatory cytokines and miR-181b expression, and vascular smooth muscle cell apoptosis. It elevated SIRT1 and HO-1 expression that was suppressed by AngII. AngII enhanced miR-181b but reduced SIRT1 and HO-1 expression in MOVAS cells. In AngII-stimulated MOVAS cells, downregulation of miR-181b significantly upregulated the expression of SIRT1 and HO-1, the effect of which was abrogated by SIRT1 siRNA. Collectively, LA could attenuate AngII-induced AAA by modulating the miR-181b/SIRT1/HO-1 signaling. LA might be a potential medical therapy for small AAA.     

Exercise modulates the aortic renin-angiotensin system independently of estrogen therapy in ovariectomized hypertensive rats

The renin-angiotensin-system is an important component of cardiovascular control and is up-regulated under various conditions, including hypertension and menopause. The aim of this study was to evaluate the effects of swimming training and estrogen therapy (ET) on angiotensin-II (ANG II)-induced vasoconstriction and angiotensin-(1-7) [ANG-(1-7)]-induced vasorelaxation in aortic rings from ovariectomized spontaneously hypertensive rats. Animals were divided into Sham (SH), Ovariectomized (OVX), Ovariectomized treated with E2 (OE2), Ovariectomized plus swimming (OSW) and Ovariectomized treated with E2 plus swimming (OE2 + SW) groups. ET entailed the administration of 5 μg of 17β-Estradiol three times per week. Swimming was undertaken for sixty minutes each day, five times per week. Both, training and ET were initiated seven days following ovariectomy. Forty-eight hours after the last treatment or training session, the animals’ systolic blood pressures were measured, and blood samples were collected to measure plasma ANG II and ANG-(1-7) levels via radioimmunoassay. In aortic rings, the vascular reactivity to ANG II and ANG-(1-7) was assessed. Expression of ANG-(1-7) in aortic wall was analyzed by immunohistochemistry. The results showed that both exercise and ET increased plasma ANG II levels despite attenuating systolic blood pressure. Ovariectomy increased constrictor responses to ANG II and decreased dilatory responses to ANG-(1-7), which were reversed by swimming independently of ET. Moreover, it was observed an apparent increase in ANG-(1-7) content in the aorta of the groups subjected to training and ET. Exercise training may play a cardioprotective role independently of ET and may be an alternative to ET in hypertensive postmenopausal women.     

The effects of nicotine administration on the pathophysiology of rat aortic wall

Abdominal aortic aneurysm (AAA) is the progressive dilation of the abdominal aorta. Nicotine is reported to be associated with the development and rupture of AAA, but the pathological effects of nicotine on normal rat aorta have not been determined. We investigated pathological changes in the aortic wall of rats caused by the administration of nicotine. Nicotine administration weakened the vascular wall, increased gelatinolytic activity and promoted the destruction of elastin and collagen in the rat abdominal aorta. There were no differences in the areas positive for matrix metalloproteinase (MMP)-2 and MMP-9 between the control and nicotine treated groups. The areas positive for MMP-12 in the nicotine group were significantly greater than for the control group. Gelatinolytic activity in the aortic wall was increased significantly in the nicotine group. Our findings suggest that MMP-12 is sensitive to nicotine exposure in rats.     

MiR‐126a‐5p limits the formation of abdominal aortic aneurysm in mice and decreases ADAMTS‐4 expression

Abdominal aortic aneurysm (AAA) is a serious vascular disease featured by inflammatory infiltration in aortic wall, aortic dilatation and extracellular matrix (ECM) degradation. Dysregulation of microRNAs (miRNAs) is implicated in AAA progress. By profiling miRNA expression in mouse AAA tissues and control aortas, we noted that miR‐126a‐5p was down‐regulated by 18‐fold in AAA samples, which was further validated with real‐time qPCR. This study was performed to investigate miR‐126a‐5p's role in AAA formation. In vivo, a 28‐d infusion of 1 μg/kg/min Angiotensin (Ang) II was used to induce AAA formation in Apoe^‐/‐ mice. MiR‐126a‐5p (20 mg/kg; MIMAT0000137) or negative control (NC) agomirs were intravenously injected to mice on days 0, 7, 14 and 21 post‐Ang II infusion. Our data showed that miR‐126a‐5p overexpression significantly improved the survival and reduced aortic dilatation in Ang II‐infused mice. Elastic fragment and ECM degradation induced by Ang II were also ameliorated by miR‐126a‐5p. A strong up‐regulation of ADAM metallopeptidase with thrombospondin type 1 motif 4 (ADAMTS‐4), a secreted proteinase that regulates matrix degradation, was observed in smooth muscle cells (SMCs) of aortic tunica media, which was inhibited by miR‐126a‐5p. Dual‐luciferase results demonstrated ADAMTS‐4 as a new and valid target for miR‐126a‐5p. In vitro, human aortic SMCs (hASMCs) were stimulated by Ang II. Gain‐ and loss‐of‐function experiments further confirmed that miR‐126‐5p prevented Ang II‐induced ECM degradation, and reduced ADAMTS‐4 expression in hASMCs. In summary, our work demonstrates that miR‐126a‐5p limits experimental AAA formation and reduces ADAMTS‐4 expression in abdominal aortas.     

Chinese red yeast rice attenuates the development of angiotensin II-induced abdominal aortic aneurysm and atherosclerosis

ObjectiveAbdominal aortic aneurysm (AAA) is a chronic vascular disease characterized by medial degradation and inflammation. No medical approaches have been validated for treating AAA, and therapeutic options are limited to regular surveillance leading to surgical intervention. This study aimed to investigate whether administration of Chinese red yeast rice (Monascus purpureus; RYR) suppressed angiotensin II (AngII)-induced AAA and atherosclerosis.Methods and ResultsApolipoprotein E-deficient male mice fed a normal diet were administered either RYR extract (200 mg/kg/day) or vehicle by gavage for 1 week before initiating AngII infusion (1000 ng/kg/min) via subcutaneous osmotic pumps for 28 days. Red yeast rice extract administration significantly suppressed AngII-induced expansion of suprarenal diameter and area (P<.05). Furthermore, RYR extract significantly reduced atherosclerotic lesion areas in both the intima of aortic arches and cross sections of aortic roots (P<.05). These effects were associated with reductions of serum total cholesterol, intercellular adhesion molecule 1, vascular cell adhesion molecule 1, matrix metalloproteinase (MMP) 2 and increases of serum macrophage migration inhibitory factor, but no changes in serum interleukin (IL) 1α, IL-6, monocyte chemoattractant protein 1, MMP-9 and expression of MMP-2 and MMP-9 in aortic walls.ConclusionsThis study demonstrated that RYR extract administration suppressed AngII-induced AAA and atherosclerosis associated with regulating inflammation responses independent of lipid-lowering effects. Red yeast rice may have preventive potential for patients with AAA.