Deficiency of receptor-associated protein attenuates angiotensin II-induced atherosclerosis in hypercholesterolemic mice without influencing abdominal aortic aneurysms

ObjectiveReceptor-associated protein (RAP) was initially described as a regulator of low density lipoprotein receptor-related protein 1 (LRP1), but is now known to regulate many proteins. Since the direct effects of RAP on vascular pathologies have not been studied, this study determined whether RAP deficiency influenced angiotensin II (AngII)-induced atherosclerosis and abdominal aortic aneurysms (AAAs) in hypercholesterolemic mice.Methods and resultsMale LDL receptor ?/? mice that were either RAP +/+ or ?/? were infused with AngII (500 ng/kg/min) for 4 weeks while consuming a saturated fat-enriched diet. RAP deficiency had no effects on body weight or AngII-induced increases of systolic blood pressure. Despite increased plasma cholesterol concentrations, RAP deficiency reduced atherosclerotic lesion size in aortic arches, while having no effect on AngII-induced AAAs. RAP deficiency profoundly reduced LRP1 protein abundance in macrophages, but did not change its abundance in aortic smooth muscle cells. Also, RAP deficiency had no effects on mRNA abundance of LRP1 or lipoprotein lipase in macrophages. To determine whether RAP deficiency in leukocytes influenced AngII-induced atherosclerosis, irradiated male LDL receptor ?/? mice were repopulated with bone marrow-derived cells from either RAP +/+ or ?/? male mice. The chimeric mice were infused with AngII (500 ng/kg/min) for 4 weeks while fed the saturated fat-enriched diet. RAP deficiency in bone marrow-derived cells did not influence either plasma cholesterol concentrations or atherosclerotic lesion size.ConclusionsWhole body RAP deficiency attenuated atherosclerosis without influencing AAAs in hypercholesterolemic mice infused with AngII. The anti-atherogenic effect was not attributable to RAP deficiency in bone marrow-derived cells.     

Angiotensin II-induced TLR4 mediated abdominal aortic aneurysm in apolipoprotein E knockout mice is dependent on STAT3

Abdominal Aortic Aneurysm (AAA) is a major cause of mortality and morbidity in men over 65 years of age. Male apolipoprotein E knockout (ApoE^−/−) mice infused with angiotensin II (AngII) develop AAA. Although AngII stimulates both JAK/STAT and Toll-like receptor 4 (TLR4) signaling pathways, their involvement in AngII mediated AAA formation is unclear. Here we used the small molecule STAT3 inhibitor, S3I-201, the TLR4 inhibitor Eritoran and ApoE^−/−TLR4^−/− mice to evaluate the interaction between STAT3 and TLR4 signaling in AngII-induced AAA formation. ApoE^−/− mice infused for 28 days with AngII developed AAAs and increased STAT3 activation and TLR4 expression. Moreover, AngII increased macrophage infiltration and the ratio of M1 (pro-inflammatory)/M2 (healing) macrophages in aneurysmal tissue as early as 7–10 days after AngII infusion. STAT3 inhibition with S3I-201 decreased the incidence and severity of AngII-induced AAA formation and decreased MMP activity and the ratio of M1/M2 macrophages. Furthermore, AngII-mediated AAA formation, MMP secretion, STAT3 phosphorylation and the ratio of M1/M2 macrophages were markedly decreased in ApoE^−/−TLR4^−/− mice, and in Eritoran-treated ApoE^−/− mice. TLR4 and pSTAT3 levels were also increased in human aneurysmal tissue. These data support a role of pSTAT3 in TLR4 dependent AAA formation and possible therapeutic roles for TLR4 and/or STAT3 inhibition in AAA.     

小鼠腹主动脉斑块模型建立的两种方法及超高场强磁共振成像的应用价值

目的 探讨建立腹主动脉粥样硬化斑块模型的方法及超高场强磁共振成像(MRI)在活体监测及量化小鼠腹主动脉粥样硬化斑块中的应用价值.方法 高脂饮食法小鼠腹主动脉粥样硬化斑块模型的建立及磁共振检测(高脂饮食组):选择3批10～12月龄apoE-/-小鼠13只、WT鼠3只高脂饮食喂养,分别于喂养前、喂养3个月、喂养6个月3个时期进行小鼠腹主动脉7.0 T磁共振活体扫描.血管紧张素Ⅱ(AngⅡ)灌注法小鼠腹主动脉粥样硬化斑块模型的建立及磁共振检测(AngⅡ灌注组):选用10只6月龄apoE-/-小鼠,分为AngⅡ1000 ng·kg-1·min-1组3只、AngⅡ500 ng·kg-1·min-1组3只(以上两组均在背部埋置AngⅡ缓释泵14 d)和对照组为4只(埋置生理盐水缓释泵),分别于灌注前后行磁共振扫描,选用FLASH T1WI黑血及MSME-T2WI-PDWI双回波序列.高脂饮食组依次在各时期扫描后分别处死3、5、5只小鼠,AngⅡ灌注组于装泵后14 d行磁共振扫描,然后处死本组小鼠,取处死小鼠的肾动脉段腹主动脉制作病理切片,进行苏木素-伊红(HE)染色、Masson胶原纤维(CME)染色.每只小鼠选5～7层肾动脉段腹主动脉病理图像及多对比MRI图像,分别测量外腔面积(VOA)、内腔面积(LA),计算管肇面积(VWA)并进行MRI与病理测量结果的相关性分析.结果 两种方法建立的小鼠模型,其腹主动脉MRI与病理切片均可见不稳定斑块形成.高脂饮食组随着高脂饮食时间的延长,斑块进展,VWA不断增加,3个时期VWA方差分析F=29.94(P<0.05),斑块信号于PDWI、T2WI逐渐增加,且不均匀.高脂饮食组MRI测量的斑块面积与病理测量的斑块面积有较高的-致性(高脂喂养前、喂养3和6个月3个时期r值分别为0.84、0.95、0.90).病理切片中斑块成分与磁共振显示信号一致,均表现为脂质成分增加,纤维成分减少.AngⅡ1000 ng·kg-1·min-1组AngⅡ灌注后斑块面积与灌注前比较差异有统计学意义(P=0.017),分别为(2.65±0.48)mm2和(1.21±0.21)mm2,部分小鼠可见夹层动脉瘤形成.AngⅡ500 ng·kg-1·min-1组灌注后斑块面积也比灌注前有所进展,面积分别为(1.01±0.17)mm2和(0.85±0.11)mm2,MRI测量的斑块面积与病理测量的斑块面积有较高的一致性(r值为0.93).结论 AngⅡ灌注显著加快动脉粥样硬化进展并促进腹主动脉夹层动脉瘤形成,长期高脂饮食亦可形成晚期斑块.超高场强MRI多种序列黑血技术的综合应用能显示小鼠腹主动脉粥样硬化斑块的进展,其检测分析斑块大小结果与病理表现基本一致,对斑块成分的判定亦有一定价值.     

Angiotensin II infusion alters vascular function in mouse resistance vessels: roles of O and endothelium

We hypothesized that prolonged angiotensin II (AngII) infusion would alter vascular reactivity by enhancing superoxide anion (O-.2) generation. Male C57BL/6 mice were infused with AngII at 400 ng/kg/min (n=16, AngII mice) or vehicle (n=16, sham mice) for 2 weeks via subcutaneous osmotic minipumps. Contraction and relaxation of mesenteric resistance vessels (MRVs) were assessed using a Mulvany-Halpern myograph. AngII infusion increased systolic blood pressure, MRV NADPH oxidase activity and expression of p22phox mRNA. Contraction to norepinephrine was unchanged, but AngII infusion increased contractile responses to AngII (41+/-5 vs. 10+/-4%, p<0.001) and endothelin-1 (ET-1; 95+/-10 vs. 70+/-9%, p<0.05), which was normalized by tempol (10(-4) M, a stable membrane-permeable superoxide dismutase mimetic) and ebselen [10(-5) M, a peroxynitrite (ONOO-) scavenger]. Endothelium removal enhanced MRV contraction to AngII and ET-1 in sham mice but blunted these contractile responses in AngII mice. Relaxation to ACh was impaired in AngII mice (60.1+/-8.8 vs. 83.2+/-3.5%, p<0.01), which normalized by tempol, whereas relaxation to sodium nitroprusside was similar in both groups. N-nitro-L-arginine (NNLA, a nitric oxide synthase inhibitor), partially inhibited acetylcholine relaxation of vessels from sham mice but not from AngII mice. The residual endothelium-dependent hyperpolarizing-factor-like relaxation was not different between groups. In conclusion,the AngII slow pressor response in mouse MRVs consisted of specific contractile hyperresponsiveness and impairment in the NO-mediated component of endothelium-dependent relaxation, which was mediated by O-.2 and ONOO- in the vascular smooth muscle cell.     

Urokinase-type plasminogen activator plays a critical role in angiotensin II-induced abdominal aortic aneurysm

We have previously demonstrated that urokinase-type plasminogen activator (uPA) is highly expressed in the aneurysmal segment of the abdominal aorta (AAA) in apolipoprotein E-deficient (apoE-/-) mice treated with angiotensin II (Ang II). In the present study, we tested the hypothesis that uPA is essential for AAA formation in this model. An osmotic minipump containing Ang II (1.44 mg/kg per day) was implanted subcutaneously into 7- to 11-month-old male mice for 1 month. Ang II induced AAA in 9 (90%) of 10 hyperlipidemic mice deficient in apoE (apoE-/-/uPA+/+ mice) but in only 2 (22%) of 9 mice deficient in both apoE and uPA (apoE-/-/uPA-/- mice) (P<0.05). Although the expansion of the suprarenal aorta was significantly less in apoE-/-/uPA-/- mice than in apoE-/-/uPA+/+ mice, the aortic diameters of the aorta immediately above or below the suprarenal aorta were similar between the 2 groups. Ang II induced AAA in 7 (39%) of 18 strain-matched wild-type C57 black/6J control mice. The incidence was significantly higher in atherosclerotic apoE-deficient (apoE-/-) mice, in which 8 (100%) of 8 mice developed AAA. Only 1 (4%) of 27 uPA-/- mice developed AAA after Ang II treatment. We conclude the following: (1) uPA plays an essential role in Ang II-induced AAA in mice with or without preexisting hyperlipidemia and atherosclerosis; (2) uPA deficiency does not affect the diameter of the nonaneurysmal portion of the aorta; and (3) atherosclerosis and/or hyperlipidemia promotes but is not essential for Ang II-induced AAA formation in this model.     

Abdominal aortic aneurysms: fresh insights from a novel animal model of the disease

Abdominal aortic aneurysms (AAA) have a high prevalence in aged populations and are responsible for a large number of deaths. Despite the widespread nature of the disease, relatively little is known regarding mechanisms for formation and progression of aortic aneurysms. In part, this lack of knowledge is attributable to a paucity of animal models for this disease. This review summarizes the available animal models of AAA and focuses on a novel model of reproducible AAA generated by infusion of angiotensin II (AngII) into mice rendered hyperlipidemic by the absence of either apolipoprotein E or low-density lipoprotein receptors. AAA generated by AngII infusion have many characteristics of the human disease including marked luminal expansions, perimedial remodeling, inflammation, thrombosis and a link to hyperlipidemia. As in the human disease, male mice are more susceptible to the development of AAA than females. The vascular pathology occurs from the effects of AngII at AT1 receptors present on bone marrow-derived cells. Studies are ongoing to define the mediators responsible for AngII-induced inflammation and degradation of the medial layer of the vascular wall. The AngII-induced model of AAA has the potential to provide novel insights into the underlying mechanisms of this disease and assist with the development of pharmacological therapies.     

Angiotensin II infusion induces site-specific intra-laminar hemorrhage in macrophage colony-stimulating factor-deficient mice

Angiotensin II (AngII) infusion promotes macrophage infiltration into the aortic wall resulting in several forms of vascular pathology. To determine the causal role of macrophages in these vascular diseases, we used osteopetrotic (op) male mice in which a natural mutation ablates production of M-CSF and results in severe depletion of monocytes. AngII infusion into apoE-/- mice resulted in increased atherosclerosis that was attenuated in op mice. AngII infusion in op mice unexpectedly produced grossly discernable thickening of the proximal thoracic aorta characterized by intra-mural hematoma. This pathology was also observed in apoE+/+ x op male mice, and therefore, independent of hyper-lipidemia. No perceptible structural properties of aortas from op mice could be discerned prior to AngII infusion. Regional effects in the contractile response to phenylephrine were noted in aortic rings with enhanced responsivity in the upper thoracic aortas of op mice compared to those from +/+ mice. No differences in contractile response were noted in aortic rings from the lower thorax. In conclusion, deficiency of M-CSF attenuated AngII-induced atherosclerosis but led to an unanticipated pathology of intra-laminar hemorrhage in the upper aortic regions.     

Estrogen inhibits cardiac hypertrophy: role of estrogen receptor-beta to inhibit calcineurin

Estrogen has been reported to prevent development of cardiac hypertrophy in female rodent models and in humans. However, the mechanisms of sex steroid action are incompletely understood. We determined the cellular effects by which 17beta-estradiol (E2) inhibits angiotensin II (AngII)-induced cardiac hypertrophy in vivo. Two weeks of angiotensin infusion in female mice resulted in marked hypertrophy of the left ventricle, exacerbated by the loss of ovarian steroid hormones from oophorectomy. Hypertrophy was 51% reversed by the administration of E2 (insertion of 0.1 mg/21-d-release tablets). The effects of E2 were mainly mediated by the estrogen receptor (ER) beta-isoform, because E2 had little effect in ERbeta-null mice but comparably inhibited AngII-induced hypertrophy in wild-type or ERalpha-null mice. AngII induced a switch of myosin heavy chain production from alpha to beta, but this was inhibited by E2 via ERbeta. AngII-induced ERK activation was also inhibited by E2 through the beta-receptor. E2 stimulated brain natriuretic peptide protein expression and substantially prevented ventricular interstitial cardiac fibrosis (collagen deposition) as induced by AngII. Importantly, E2 inhibited calcineurin activity that was stimulated by AngII, related to E2 stimulating the modulatory calcineurin-interacting protein (MCIP) 1 gene and protein expression. E2 acting mainly through ERbeta mitigates the important signaling by AngII that produces cardiac hypertrophy and fibrosis in female mice.     

Genetic deficiency of cyclooxygenase-2 attenuates abdominal aortic aneurysm formation in mice

OBJECTIVE: Abdominal aortic aneurysms (AAAs) are characterized by chronic inflammation which contributes to the remodeling and eventual weakening of the vessel wall. Increased cyclooxygenase-2 (COX-2) expression is detected in human aneurysmal tissue and is suggested to contribute to the disease. The aim of the current study was to define the role of COX-2 expression in the development of AAAs, using a model of the disease. METHODS: AAAs were induced in mice by chronic angiotensin II infusion, and were analyzed following 3, 7, 21 or 28 days of the infusion. AAA incidence and severity, together with the expression of inflammatory markers, were compared between abdominal aortas from COX-2-deficient mice and their wild-type littermate controls. RESULTS: The AAA incidence in COX-2 wild-type mice was 54% (13/24), whereas AAAs were not detected in COX-2-deficient mice (0/23) following 28 days of angiotensin II infusion. The genetic deficiency of COX-2 also resulted in a 73% and 90% reduction in AAA incidence following 7 and 21 days of angiotensin II infusion, respectively. In COX-2 wild-type mice, COX-2 mRNA expression in the abdominal aorta was induced by angiotensin II beginning 3 days following initiation of the infusion, which continued throughout progression of the disease. Abundant COX-2 protein expression was detected in medial smooth muscle cells adjacent to the AAAs. The deficiency of COX-2 significantly attenuated mRNA expression in the abdominal aorta of the macrophage marker CD68, and the inflammatory cell recruitment chemokines, monocyte chemotactic protein-1 and macrophage inflammatory protein-1alpha. CONCLUSIONS: Our findings suggest that increased COX-2 expression in smooth muscle cells of the abdominal aorta contributes to AAA formation in mice by enhancing inflammatory cell infiltration.     

Transiently heightened angiotensin II has distinct effects on atherosclerosis and aneurysm formation in hyperlipidemic mice

Experimentally sustained increase in angiotensin II (AngII) promotes tissue destruction in various cardiovascular disorders. We examined whether transiently heightened AngII affects subsequent atherosclerosis and aneurysm formation. AngII or saline was administered for 2 weeks to apolipoprotein E (apoE)-deficient mice. Mice were sacrificed at the end of the 2-week infusion or 6- or 14 weeks later. Short-term AngII did not affect atherosclerosis immediately following the infusion or 6 weeks later. By contrast, 14 weeks after infusion there was remarkably more atherosclerosis in previously AngII-exposed mice. Preceding the build up of atherosclerotic lesions, AngII-exposure increased mRNA expression and immunostaining of monocyte chemoattractant protein-1 (MCP-1) and its receptor, CCR2. This was followed by greater macrophage-positivity in AngII-exposed aortae. In contrast to the delayed effects on atherosclerosis, 20% of mice were found to have abdominal aneurysms at the end of AngII-exposure. This effect was not contingent on blood pressure. Moreover, despite amplification in atherosclerosis following AngII, no aneurysms were found 14 weeks later. Our studies reveal that even transient exposure to AngII primes the vessel for subsequent amplification of atherosclerosis which involves activation of MCP-1/CCR2 and influx of macrophages into the nascent atherosclerotic plaque. By contrast, transient AngII-exposure causes prompt aneurysm formation that does not parallel atherosclerosis and disappears even in the face of progressively greater atherosclerotic lesions.     

Relationship between aldosterone and progesterone in the human menstrual cycle

CONTEXT: Aldosterone levels increase during the luteal phase of the menstrual cycle. Prior studies examining relationships between aldosterone and female sex hormones did not control for sodium balance, a major determinant of aldosterone production. OBJECTIVES: The objectives of this study were 1) to compare aldosterone levels between menstrual phases among cycling women in high- and low-sodium balance; and 2) to examine the relationships between aldosterone and female sex hormones in women and the effects of sex hormones on rat zona glomerulosa (ZG) cell aldosterone production in vitro. SUBJECTS/INTERVENTIONS: Normotensive, premenopausal women were studied in low- and/or high-sodium balance. Urinary aldosterone, basal serum aldosterone, plasma renin activity (PRA), plasma angiotensin II (AngII), and serum aldosterone after AngII infusion were measured. Isolated rat ZG cells were treated with progesterone, estradiol, or both, and aldosterone was measured. RESULTS: In high-sodium balance, urinary aldosterone, basal serum aldosterone, and serum aldosterone response to infused AngII were significantly greater (P < 0.05) in the luteal vs. follicular phase. PRA, AngII, and potassium did not differ. Progesterone directly correlated with urinary aldosterone, basal serum aldosterone, and serum aldosterone response to infused AngII. Estradiol did not significantly correlate with aldosterone. In low-sodium balance, no significant differences in aldosterone levels between phases were found. In vitro, progesterone increased ZG cell aldosterone production (P < 0.01), whereas estradiol had no effect. CONCLUSIONS: In women, urinary and serum aldosterone levels are significantly higher during the luteal phase in high- but not low-sodium balance, whereas PRA and AngII do not differ between phases. Progesterone may directly contribute to increased luteal phase aldosterone production, independent of the renin-angiotensin system.     

Enhanced angiotensin II-mediated effects in fibroblasts of patients with familial hypercholesterolemia

OBJECTIVE: Familial hypercholesterolemia (FH) is characterized by a high incidence of coronary heart disease. Evidence suggests an important role for angiotensin II (AngII) in the fibrotic response to tissue injury, and in promoting myocardial hypertrophy via paracrine mechanisms mediated by fibroblasts. We sought to determine whether AngII promotes proliferative and pro-atherogenic responses in FH patients. METHODS: We used primary fibroblasts -- from five patients with heterozygous FH and five control subjects (C) -- to study AngII-induced cell growth, intracellular calcium fluxes, and expression/release of matrix components and pro-inflammatory peptides [transforming growth factor-beta1 (TGFbeta1) and endothelin-1 (ET-1)] and metalloproteinases involved in plaque remodeling and vulnerability. RESULTS: AngII stimulated cell replication (5.1 +/- 0.03 versus 3.2 +/- 0.04 cells/50 cells per well, P < 0.001), and induced a larger increase in intracellular calcium content in FH cells than in C cells, in a dose-dependent fashion (mean difference = 76 nmol/l, P < 0.001). Similarly, TGFbeta1 and ET-1 expression and release were potentiated (after 24-h incubation with 1 micromol/l AngII: TGFbeta1 was 190 +/- 12 in C and 376 +/- 9 pg/ml per 10(6) cells in FH, and ET-1 was 93 +/- 5 in C and 192 +/- 7 pmol/ml per 10(6) cells in FH; P < 0.001 for both). AngII-induced release of the metalloproteinases MMP-1 and MMP-2 was also increased in FH versus C cells (0.52 +/- 0.04 versus 0.36 +/- 0.05 and 24 +/- 4 versus 13 +/- 3 ng/mg protein with 1 micromol/l AngII). These enhanced responses were likely due to an increased angiotensin receptor 1 (AT1) expression in cells from FH patients induced by AngII, and were prevented by pretreating cells with the selective AT1 antagonist irbesartan. CONCLUSIONS: These findings show that some AngII-mediated pathways are enhanced in FH subjects irrespective of the presence of low-density lipoprotein (LDL), thus contributing to the development and progression of atherosclerosis in these patients.     

Mouse models of abdominal aortic aneurysms

Many mouse models of abdominal aortic aneurysms have been developed that use a diverse array of methods for producing the disease, including genetic manipulation and chemical induction. These models could provide insight into potential mechanisms in the development of this disease. Although experimental studies on abdominal aortic aneurysms (AAAs) have used a variety of mammalian and avian approaches, there is an increasing reliance on the use of mice. The models recapitulate some facets of the human disease including medial degeneration, inflammation, thrombus formation, and rupture. Most of the mouse models of AAA are evoked either by genetically defined approaches or by chemical means. The genetic approaches are spontaneous and engineered mutations. These include defects in extracellular matrix maturation, increased degradation of elastin and collagen, aberrant cholesterol homeostasis, and enhanced production of angiotensin peptides. The chemical approaches include the intraluminal infusion of elastase, periaortic incubations of calcium chloride, and subcutaneous infusion of AngII. A common feature of these models is the reduction of AAA incidence and severity by the prophylactic administration of matrix metalloproteinase (MMP) inhibitors or genetically engineered deficiencies of specific members of this proteolytic protein family. The validation of mouse models of AAAs will provide insight into the mechanisms of progression of the human disease.     

Interferon-beta attenuates angiotensin II-accelerated atherosclerosis and vascular remodeling in apolipoprotein E deficient mice

Atherosclerotic vascular disease is an inflammatory disease. Interferon-beta (IFN-beta) is an important immune modulator. However, the role of IFN-beta in atherosclerotic vascular disease is still not clear. The present study is designed to determine the effects of IFN-beta on atherosclerosis, abdominal aortic aneurysm (AAA) formation and proliferative vascular remodeling in apolipoprotein E (apoE) deficient mice. Six-month-old male apoE deficient mice fed a normal chow underwent ligation of the common left carotid artery, and were randomly assigned to receive either vehicle or angiotensin II (Ang II, 1.4 mg/kg daily) via a subcutaneously implanted osmotic infusion pump. The animals were further assigned to groups that were subjected to subcutaneous injection of vehicle or murine IFN-beta (10 MIU/kg, daily). Ang II increased atherosclerotic area in the non-ligated carotid artery and aortic arch, induced AAA, and exacerbated ligation-induced adventitial proliferation and neointimal hyperplasia characterized by smooth muscle cell (SMC) proliferation and macrophage infiltration in the ligated carotid artery. Co-treatment with IFN-beta, had no effects by itself, significantly attenuated Ang II-accelerated increase in the areas of neointima, adventitia, SMC and macrophage in the ligated carotid artery and suppressed Ang II-exacerbated atherosclerosis, but did not affect Ang II-induced AAA formation. These data indicate that IFN-beta can play a prominent anti-atherosclerosis, anti-inflammation, and anti-proliferation role of vasculoprotection.     

C3H apoE(-/-) mice have less atherosclerosis than C57BL apoE(-/-) mice despite having a more atherogenic serum lipid profile

Wild-type C57BL mice are known to be susceptible to diet-induced atherosclerosis, whilst C3H mice are resistant. We investigated the effect of these background strains on the hyperlipidaemia and atherosclerosis that develops in mice deficient in apolipoprotein E (apoE(-/-)). Male and female apoE(-/-) mice on C3H/HeNHsd (C3H) and C57BL/6J (C57) backgrounds were fed atherogenic Western diet for 12 weeks. Serum cholesterol and triglyceride concentrations were measured and atherosclerosis quantified in the aortic sinus. C3H apoE(-/-) mice fed normal diet had 1.5 2 fold higher serum cholesterol levels than C57 apoE(-/-) mice and 4-5 fold higher serum triglyceride concentrations. Feeding Western diet caused a 4-5 fold increase in serum cholesterol in all mice, but levels of triglyceride were either attenuated or were unaffected in C3H apoE(-/-) and C57 apoE(-/-) mice, respectively. C3H apoE(-/-) mice had approximately 2 fold higher serum cholesterol and 4 fold higher triglyceride concentrations than the C57 apoE(-/-) mice throughout the study. Serum triglyceride concentrations were 35-108% higher in male C3H apoE(-/-) than female C3H apoE(-/-) mice. Most of the lipids were present in the very low density lipoprotein (VLDL)/chylomicron fraction in both strains of mice whether they were fed normal or Western diet. Notwithstanding the lower plasma lipid concentrations, atherosclerotic lesion areas were more than 2-fold larger in C57 apoE(-/-) than in C3H apoE(-/-) mice (males 68 +/- 11 x 10(3) vs 30 +/- 6 x 10(3) females 102 +/- 12 x 10(3) vs 41 +/- 8 x 10(3) microm2. mean +/- SEM).     

Angiotensin II increases expression and secretion of cathepsin F in cultured human monocyte-derived macrophages: an angiotensin II type 2 receptor-mediated effect

Increasing evidence suggests that cathepsins and angiotensin II (AngII) participate in atherosclerosis, particularly in remodeling of the extracellular matrix of the inflamed arterial intima. Here, we show that AngII induces mRNA expression of cathepsin F, a member of the cysteine protease family, in human monocyte-derived macrophages. AngII did not affect the amount of intracellular cathepsin F protein, but significantly enhanced its secretion by the treated cells. The stimulatory effect of AngII was mediated by the AngII type 2 (AT(2)) receptor, as demonstrated by the ability of the AT(2)-receptor antagonist PD123319 to block the AngII-induced increase in cathepsin F secretion. Our present data demonstrate a novel proatherogenic role for AngII, namely its ability to enhance secretion of lysosomal cathepsin F by monocyte-derived macrophages.     

Valsartan impairs angiogenesis of mesenchymal stem cells through Akt pathway

Background

Angiotensin II (AngII) reportedly enhances stem cell proliferation, and type 1 angiotensin II receptor (AT1R) antagonists reduce angiogenesis in a rodent hindlimb ischemic model. Whether AT1R antagonists can alter the angiogenic activity of bone-marrow mesenchymal stem cells (BMSCs) is unknown. The purpose of this study is to investigate whether AT1R antagonists can alter the angiogenic activity of BMSCs and explore the potential mechanism for such an action.

Methods

Mouse BMSCs were isolated and treated with AngII, an AT1R antagonist, and a type 2 angiotensin II receptor (AT2R) antagonist. Angiogenic activity of BMSCs was detected by vascular endothelial growth factor (VEGF) secretion and tube formation of human umbilical vein endothelial cells (HUVECs). BMSCs isolated from enhanced green fluorescent protein (eGFP)-transgenic mice were allografted into ischemic hindlimbs in mice.

Results

The BMSCs constitutively expressed AT1Rs and AT2Rs. AngII treatment significantly increased VEGF secretion by BMSCs. Valsartan (AT1R antagonist) but not PD123319 (AT2R antagonist) treatment attenuated the AngII-induced promotion of VEGF synthesis by BMSCs. The AngII and AngII receptor antagonist control of angiogenic activity of BMSCs were confirmed by tube formation of HUVECs. AngII treatment promoted phosphorylated Ser473 Akt abundance in BMSCs. RNA interference of an isoform of AT1R, valsartan, and wortmannin treatments attenuated AngII-induced Akt phosphorylation. Allograft of BMSCs significantly increased blood flow and VEGF expression in the gastrocnemius muscles of ischemic hindlimbs, which was attenuated after valsartan treatment.

Conclusions

AT1R antagonists, via AT-1R/PI3K/Akt pathways, impair the AngII-induced promotion of angiogenic activity of mouse BMSCs.     

Efficacy of Simvastatin in Reducing Aortic Dilatation in Mouse Models of Abdominal Aortic Aneurysm

Purpose

Currently there is no effective drug therapy for abdominal aortic aneurysm (AAA). The aim of this study was to assess the ability of simvastatin to inhibit aortic dilatation in two mouse models.

Methods

AAAs were induced in two mice strains predisposed to atherosclerosis. Firstly, 11 weeks old male apolipoprotein E deficient (ApoE^?/?) mice were given vehicle control (n?=?27) or simvastatin (50 mg/kg/d, n?=?27) prior to being infused with angiotensin II (1 μg/kg/min) subcutaneously for 4 weeks. Secondly, 9 weeks old male low-density lipoprotein receptor deficient (LDLR^?/?) mice were fed a high fat diet, then given vehicle control (n?=?17) or simvastatin (50 mg/kg/d, n?=?18) and from 14 to 18 weeks of age infused with angiotensin II. Subsequently aortas were harvested, maximum suprarenal aortic diameter measured, aortic arch atheroma assessed by sudan IV staining and blood extracted to measure serum lipids. In the LDLR^?/? mice the suprarenal aortic diameter was also measured by ultrasound prior to aortic harvesting.

Results

In ApoE^?/? mice suprarenal aortic diameters were modestly smaller in animals receiving simvastatin without significant change despite reduction in macrophage infiltration. Aortic arch atheroma was substantially reduced in LDLR^?/? mice receiving simvastatin with borderline significant reduction in suprarenal aortic diameters. Simvastatin did not favourably modify serum lipids in either mouse model.

Conclusions

In this study involving two mouse models of AAA, simvastatin had limited efficacy in restricting aortic dilatation but substantial ability to reduce atheroma progression.     

Effect of macrophage-derived mouse ApoE, human ApoE3-Leiden, and human ApoE2 (Arg158-->Cys) on cholesterol levels and atherosclerosis in ApoE-deficient mice

The effect of monocyte/macrophage-derived wild-type mouse apolipoprotein E (apoE), human apoE3-Leiden, and human apoE2 on serum cholesterol levels and the development of atherosclerosis in apoE-deficient (apoe-/-) mice was investigated by using bone marrow transplantation (BMT). At 4 weeks after BMT, murine apoe+/+ bone marrow reduced serum cholesterol levels by 87% in apoe-/- mice, whereas macrophage-derived human apoE3-Leiden and human apoE2 induced a maximal, transient reduction of 35% and 48%, respectively. At 4 months after BMT, atherosclerosis was 23-fold (P<0.001) reduced in apoe+/+-->apoe-/- mice, whereas no significant reduction in apoE3-Leiden.apoe-/--->apoe-/- and apoE2.apoe-/--->apoe-/- mice could be demonstrated. A highly significant decrease in serum cholesterol levels (78% reduction) and atherosclerosis (21-fold, P<0. 001) was found in apoE3-Leiden.apoe-/- animals expressing high levels of apoE in multiple tissues, whereas apoE2 was ineffective even at high concentrations. Furthermore, in contrast to apoE-deficient macrophages, cholesterol efflux from apoE2 or apoE3-Leiden macrophages was not impaired. In conclusion, apoE3-Leiden as well as apoE2 are less effective in reducing cholesterol levels and atherosclerosis in apoe-/- animals, compared with apoe+/+, with apoE2相似文献