Ang II-infused Mice Research Articles

Suppression of angiotensin II-induced pathological changes in heart and kidney by the caveolin-1 scaffolding domain peptide.

Dysregulation of the renin-angiotensin system leads to systemic hypertension and maladaptive fibrosis in various organs. We showed recently that myocardial fibrosis and the loss of cardiac function in mice with transverse aortic constriction (TAC) could be averted by treatment with the caveolin-1 scaffolding domain (CSD) peptide. Here, we used angiotensin II (AngII) infusion (2.1 mg/kg/day for 2 wk) in mice as a second model to confirm and extend our observations on the beneficial effects of CSD on heart and kidney disease. AngII caused cardiac hypertrophy (increased heart weight to body weight ratio (HW/BW) and cardiomyocyte cross-sectional area); fibrosis in heart and kidney (increased levels of collagen I and heat shock protein-47 (HSP47)); and vascular leakage (increased levels of IgG in heart and kidney). Echocardiograms of AngII-infused mice showed increased left ventricular posterior wall thickness (pWTh) and isovolumic relaxation time (IVRT), and decreased ejection fraction (EF), stroke volume (SV), and cardiac output (CO). CSD treatment (i.p. injections, 50 μg/mouse/day) of AngII-infused mice significantly suppressed all of these pathological changes in fibrosis, hypertrophy, vascular leakage, and ventricular function. AngII infusion increased β1 and β3 integrin levels and activated Pyk2 in both heart and kidney. These changes were also suppressed by CSD. Finally, bone marrow cell (BMC) isolated from AngII-infused mice showed hyper-migration toward SDF1. When AngII-infused mice were treated with CSD, BMC migration was reduced to the basal level observed in cells from control mice. Importantly, CSD did not affect the AngII-induced increase in blood pressure (BP), indicating that the beneficial effects of CSD were not mediated via normalization of BP. These results strongly indicate that CSD suppresses AngII-induced pathological changes in mice, suggesting that CSD can be developed as a treatment for patients with hypertension and pressure overload-induced heart failure.

Early pathological characterization of murine dissecting abdominal aortic aneurysms.

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

Interleukin-12p35 knockout promotes macrophage differentiation, aggravates vascular dysfunction, and elevates blood pressure in angiotensin II-infused mice

Numerous studies have demonstrated that inflammation is involved in the progression of hypertension. Inflammatory cytokines interleukin (IL)-12 and IL-35 belong to the IL-12 cytokine family and share the same IL-12p35 subunit. Accumulating evidence has demonstrated that IL-12p35 knockout (IL-12p35 KO) leads to cardiovascular disease by regulating the inflammatory response. This study aimed to investigate whether IL-12p35 KO elevates blood pressure in a hypertension mouse model. Mice with angiotensin (Ang) II infusion showed marked aortic IL-12p35 expression; thus, aortic macrophages may be the main source of IL-12p35. Wild-type and IL-12p35 KO mice were infused with Ang II or saline. IL-12p35 KO promoted M1 macrophage differentiation, amplified the inflammatory response, aggravated vascular dysfunction, and elevated blood pressure in Ang II-treated mice. Then, some Ang II-infused mice were given phosphate buffer saline, mouse recombinant IL-12 (rIL-12), or rIL-35, and the results showed that rIL-12 but not rIL-35 treatment had an antihypertensive effect on Ang II-infused mice. In addition, detection of human plasma IL-12 levels in hypertensive patients and control subjects showed that IL-12 was significantly increased in hypertensive patients when compared with control subjects. In hypertensive patients, IL-12 levels were positively correlated with blood pressure. IL-12p35 KO amplifies the inflammatory response and promotes blood pressure elevation in Ang II-treated mice. In addition, IL-12, but not IL-35, plays a protective role in the Ang II-induced hypertension model. Thus, IL-12 may be a novel therapeutic agent for the prevention and treatment of clinical hypertension.

SGK1-FoxO1 Signaling Pathway Mediates Th17/Treg Imbalance and Target Organ Inflammation in Angiotensin II-Induced Hypertension.

It has been demonstrated that serum/glucocorticoid regulated kinase 1 (SGK1) and the downstream transcription factor forkhead box O1 (FoxO1) plays a critical role in the differentiation of T helper 17 cells/regulatory T cells (Th17/Treg). In the present study, we hypothesized that this SGK1-FoxO1 signaling pathway is involved in Th17/Treg imbalance and target organ damage in angiotensin II (AngII)-induced hypertensive mice. Results show that SGK1 inhibitor EMD638683 significantly reversed renal dysfunction and cardiac dysfunction in echocardiography as indicated by decreased blood urine nitrogen and serum creatinine in AngII-infused mice. Flow cytometric assay shows that there was significant Th17/Treg imbalance in spleen and in renal/cardiac infiltrating lymphocytes as indicated by the increased Th17 cells (CD4+-IL17A+ cells) and decreased Treg cells (CD4+-Foxp3+). Consistently, real-time PCR shows that Th17-related cytokines including IL-17A, IL-23, and tumor necrosis factor α (TNF-α) was increased and Treg-related cytokine IL-10 was decreased in renal and cardiac infiltrating lymphocytes in AngII-infused mice. Meanwhile, SGK1 protein level, as well as its phosphorylation and activity, was significantly increased in spleen in AngII-infused rats. Furthermore, it was found that splenic phosphorylated FoxO1 was significantly increased, whereas total FoxO1 in nuclear preparation was significantly decreased in AngII-infused mice, suggesting that increased FoxO1 phosphorylation initiate its translocation from cytoplasm to nucleus. Notably, all changes were significantly inhibited by the treatment of EMD638683. These results suggest that SGK1 was involved in Th17/Treg imbalance and target organ damage in AngII-induced hypertension.

90. Catechol-O-methyltransferase deficiency leads to hypersensitivity on the pressor response against angiotensin II

Catechol-O-methyltransferase (COMT) metabolizes 2-hydroxyestradiol into 2-methoxyestradiol (2-ME); COMT deficiency has been shown to be associated with hypertension in men. Preeclampsia is a disease associated with hypersensitivity of pressor response against angiotensin II (Ang II). Here, we found that COMT deficiency could explain the hypersensitivity of pressor response against Ang II in mice because of the lack of 2-ME-dependent suppression of angiotensin II receptor type 1 (AT1R). Male C57BL/6 mice were subjected to COMT inhibitor (COMTi: 25 mg/kg per day) or oil (control) for 4 weeks, with or without low-dose Ang II infusion (ANGII: 70 ng/kg per minute) for the last 3 weeks. The Ang II-infused mice were treated with 2-ME (10 ng/d) or vehicle for the last 1 week. We obtained the following experimental groups: control, ANGII, COMTi, COMTi + ANGII, and COMTi + ANGII + 2-ME. We performed similar experiments using the in vivo administration of small interfering RNA of COMT instead of COMTi. Neither ANGII nor COMTi exhibited significant alterations in systolic blood pressure. Compared with ANGII or COMTi, COMTi + ANGII displayed significantly higher systolic blood pressure, albuminuria, and glomerular endotheliosis; 2-ME normalized such alterations. Similar phenotypes were observed in COMT small interfering RNA-treated mice. In the aorta of COMT-deficient mice, AT1R expression was increased; 2-ME suppressed AT1R expression. The 2-ME exhibited peroxisome proliferator-activated receptor γ agonistic activity in vitro and ex vivo plasma from pregnant female mice as well. In vitro, 2-ME suppressed both basal and Ang II-induced AT1R levels in a peroxisome proliferator-activated receptor γ-dependent manner. The 2-ME is relevant to combat COMT deficiency-associated hypertensive disorders via suppression of AT1R by its peroxisome proliferator-activated receptor γ activity.

Administration of ubiquitin-activating enzyme UBA1 inhibitor PYR-41 attenuates angiotensin II-induced cardiac remodeling in mice

Pathological cardiac hypertrophy is the main risk factor for heart diseases. The ubiquitin-proteasome system (UPS) is the major intracellular protein degradation system involved in the development of cardiac hypertrophic remodeling. Ubiquitin-activating enzyme E1, a key component of the UPS, catalyzes the first step in ubiquitin conjugation to mark cellular proteins for degradation via proteasome. However, the functional role of E1 (UBA1) in regulation of hypertrophic remodeling in angiotensin II (Ang II)-infused mice remains unknown. In this study, male wild-type mice were treated with UBA1 inhibitor PYR-41 at two doses of 5 and 10 mg and infused with Ang II (1000 ng/kg/min) for 14 days. Systolic blood pressure was detected by using tail-cuff system. Cardiac function was assessed by echocardiography. Hypertrophic remodeling was analyzed examined by histological examinations. The expressions of genes and proteins were detected by quantitative real-time PCR and immunoblotting analysis. After 14 days, Ang II infusion significantly increased UBA1 expression at both mRNA and protein levels in the hearts. Furthermore, Ang II-infused mice showed a significant increase in systolic blood pressure compensatory cardiac function, hypertrophy, interstitial fibrosis, inflammation and oxidative stress compared with saline-treated controls, whereas these effects were dose-dependently attenuated in PYR-41-treated mice. These beneficial actions were associated mainly with inhibition of PTEN degradation and multiple downstream mediators (AKT, ERK1/2, STAT3, TGF-β/Smad2/3 and NF-kB(p65)). In conclusion, these results indicate that inhibition of UBA1 suppresses Ang II-induced hypertrophic remodeling, and suggest that administration of low dose PYR-41 may be a new potential therapeutic approach for treating hypertensive heart diseases.

The chemokine receptor CX3CR1 reduces renal injury in mice with angiotensin II-induced hypertension.

The role of CX3CR1, also known as fractalkine receptor, in hypertension is unknown. The present study determined the role of the fractalkine receptor CX3CR1 in hypertensive renal and cardiac injury. Expression of CX3CR1 was determined using CX3CR1GFP/+ mice that express a green fluorescent protein (GFP) reporter in CX3CR1+ cells. FACS analysis of leukocytes isolated from the kidney showed that 34% of CD45+ cells expressed CX3CR1. Dendritic cells were the majority of positive cells (67%) followed by macrophages (10%), NK cells (6%), and T cells (10%). With the use of confocal microscopy, the receptor was detected in the kidney only on infiltrating cells but not on resident renal cells. To evaluate the role of CX3CR1 in hypertensive end-organ injury, an aggravated model of hypertension was used. Unilateral nephrectomy was performed followed by infusion of angiotensin II (ANG II, 1.5 ng·g-1·min-1) and a high-salt diet in wild-type ( n = 15) and CX3CR1-deficient mice ( n = 18). CX3CR1 deficiency reduced the number of renal dendritic cells and increased the numbers of renal CD11b/F4/80+ macrophages and CD11b/Ly6G+ neutrophils in ANG II-infused mice. Surprisingly, CX3CR1-deficient mice exhibited increased albuminuria, glomerular injury, and reduced podocyte density in spite of similar levels of arterial hypertension. In contrast, cardiac damage as assessed by increased heart weight, cardiac fibrosis, and expression of fetal genes, and matrix components were not different between both genotypes. Our findings suggest that CX3CR1 exerts protective properties by modulating the invasion of inflammatory cells in hypertensive renal injury. CX3CR1 inhibition should be avoided in hypertension because it may promote hypertensive renal injury.

Abstract P198: WNK-SPAK-NKCC1 Cascade Activation Contributes to Worsened Brain Damage in Mice With Hypertension Co-Morbidity after Ischemic Stroke

Objectives: The WNK-SPAK/OSR1 kinase complex plays an important role in renal salt handling and pathogenesis of hypertension by regulating ion transporters and channels. Hypertension is the most common risk factor for stroke and stroke patients with hypertension comorbidity have worsened outcome with an increased risk of dependency or death. However, the mechanisms underlying the worsened ischemic stroke pathophysiology with hypertension comorbidity remain poorly defined. In this study, we investigated roles of the WNK-SPAK-NKCC1 signaling pathway in ischemic brain damage in mice with hypertension comorbidity. Methods: Hypertension was induced in C57BL/6j male mouse (12-15 weeks) by subcutaneous infusion of 1000 ng/kg/min angiotensin II (AngII, mini-osmotic pump) for two weeks. Permanent ischemic stroke was induced by permanent occlusion of the distal branches of the left middle cerebral artery (pd-MCAO). Brain tissues were harvested for immunoblot assessment of expression levels of NKCC1, SPAK/OSR1 or WNK1-4. Infarct volume and hemisphere swelling were determined by TTC staining, and behavioral deficits were analyzed by foot fault test, cylinder test and adhesive tape removal test. Results: pd-MCAO stimulated expression of WNK proteins (isoforms 1, 2, 4), total and phosphorylated SPAK/OSR1 and NKCC1 proteins in ischemic brains of the AngII-infused hypertensive mice compared to normotensive saline controls. In parallel with the increased activation of WNK-SPAK-NKCC1 signaling, hypertensive mice displayed significantly larger infarct volume and hemispheric swelling at 24 h after pd-MCAO compared to normotensive controls. Moreover, hypertensive mice exhibited a slow recovery of neurological function after ischemic stroke compared to normotensive counterparts as assessed by sensory-motor sensitive tests. Conclusions: These results suggest that activation of the WNK-SPAK-NKCC1 complex in hypertensive ischemic brains associates, at least in part, with the worsened brain damage and neurological deficits. Pharmacological inhibition of WNK-SPAK complex has therapeutic potentials for stroke therapy with hypertension comorbidity.

Abstract 131: Microbiota-Derived Metabolite Propionate Protects From Hypertensive Cardiovascular Damage

Objective: Inflammation drives cardiovascular disease, anti-inflammatory approaches may be beneficial. Short-chain fatty acids (SCFA) are bacterial metabolites with anti-inflammatory properties affecting host immune homeostasis including regulatory T cells (Treg). We investigated effects of the SCFA propionate (administered in drinking water, NaCl as control) in two mouse models, namely hypertensive heart disease (wild-type NMRI (WT), angiotensin (Ang)II infusion 1.44 mg/kg/d s.c. for 14 days) and atherosclerosis (Apolipoprotein E knockout (ApoE), AngII infusion 0.72 mg/kg/d s.c. for 28 days), respectively. Results: Propionate attenuated cardiac hypertrophy and fibrosis in both models significantly. Susceptibility to cardiac ventricular arrhythmias was significantly reduced in propionate-treated WT mice. Aortic atherosclerotic lesion area was significantly reduced in propionate-treated ApoE (27.6±8 vs. 7.9±2.4%). Treatment reduced splenic effector memory (CD4+ CD44+ CD62L-) T cell frequencies (WT: 30.5±4.6 vs. 19.1±1.6; ApoE: 41.1±3.1 vs. 32.7±1.4%) and splenic Th17 cells (WT: 1.0±0.2 vs. 0.6±0.1; ApoE: 1.3±0.1 vs. 0.9±0.1%) in both models, indicating beneficial effects on systemic inflammation. Similarly, propionate reduced cardiac immune cell infiltration (CD4+, CD8+, F4/80+) in WT mice. Propionate improved vascular dysfunction and moderately reduced blood pressure in both models. Organ-protective actions of propionate (cardiac inflammation and fibrosis) were abrogated in Treg-depleted (antiCD25-treated) AngII-infused WT mice, suggesting a central role for Treg. To verify our findings in a human cohort, we re-analyzed clinical and metagenomic data from a recent randomized controlled trial investigating the effect of a 90-day synbiotic intervention in 84 subjects with metabolic syndrome including healthy controls. Interestingly, in synbiotic-treated subjects an increased capacity for SFCA production was significantly correlated to blood pressure reduction. Conclusion: Data underscore the importance of SCFA for cardiovascular health and suggest that lifestyle modifications leading to augmented SCFA production could be a beneficial non-pharmacological add-on strategy for cardiovascular disease.

Dioscin ameliorates cardiac hypertrophy through inhibition of the MAPK and Akt/GSK3β/mTOR pathways

Cardiac hypertrophy occurs in response to multiple stimuli and develops into congestive heart failure with morbidity and mortality. Dioscin exerts protective effects against tumor growth and ischemia/reperfusion injury. However, whether and how dioscin attenuates angiotensin II (AngII)-induced cardiac hypertrophy is still unknown. In the current study, we found that dioscin attenuated cardiac hypertrophy and restored the impaired cardiac function induced by AngII infusion in vivo. In addition, dioscin blocked the activation of the MAPK and Akt/GSK3β/mTOR pathways and nuclear accumulation of p-Akt1 in AngII-infused mice. In vitro, dioscin inhibited the activation of the MAPK and Akt/GSK3β/mTOR pathways and nuclear translocation of p-Akt1 and thus alleviated the hypertrophic growth. Our study demonstrated dioscin protects against AngII-induced cardiac hypertrophy via inhibition of the MAPK and Akt/GSK3β/mTOR pathways and is a potential therapeutic candidate.

Perivascular Adipose Tissue-Derived PDGF-D Contributes to Aortic Aneurysm Formation During Obesity.

Obesity increases the risk of vascular diseases, including aortic aneurysm (AA). Perivascular adipose tissue (PVAT) surrounding arteries are altered during obesity. However, the underlying mechanism of adipose tissue, especially PVAT, in the pathogenesis of AA is still unclear. Here we showed that angiotensin II (AngII) infusion increases the incidence of AA in leptin-deficient obese mice (ob/ob) and high-fat diet-induced obese mice with adventitial inflammation. Furthermore, transcriptome analysis revealed that platelet-derived growth factor-D (PDGF-D) was highly expressed in the PVAT of ob/ob mice. Therefore, we hypothesized that PDGF-D mediates adventitial inflammation, which provides a direct link between PVAT dysfunction and AA formation in AngII-infused obese mice. We found that PDGF-D promotes the proliferation, migration, and inflammatory factors expression in cultured adventitial fibroblasts. In addition, the inhibition of PDGF-D function significantly reduced the incidence of AA in AngII-infused obese mice. More importantly, adipocyte-specific PDGF-D transgenic mice are more susceptible to AA formation after AngII infusion accompanied by exaggerated adventitial inflammatory and fibrotic responses. Collectively, our findings reveal a notable role of PDGF-D in the AA formation during obesity, and modulation of this cytokine might be an exploitable treatment strategy for the condition.

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

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

Abstract 710: Deficiency of IL12p40 Promotes Angiotensin II-Induced Abdominal Aortic Aneurysm

Introduction: Abdominal aortic aneurysm (AAA) is caused by the immune and inflammatory cell accumulation of the aortic wall, leading to enhanced inflammation and aneurysm formation. Our recent studies demonstrate that inhibition of Notch signaling attenuates AAA formation by shifting the macrophage balance towards anti-inflammatory (M2) phenotype. Using IL12p40 knockout (KO) mice, we investigated the direct effects of M2-like macrophages in the development of AAA. Methods and Results: Male (8-10 week-old) wild-type (WT) and IL12p40-KO mice (n=10) on C57BL/6 background were infused with angiotensin-II (AngII, 1,000 ng/kg/min) by implanting osmotic pumps subcutaneously for 28 days. Comparable increase in mean, systolic and diastolic arterial blood pressure was observed between WT and IL12p40-KO mice in response to AngII. Unexpectedly, AngII significantly increased the AAA-associated mortality (2/10) and luminal expansion (7/10) in IL12p40-KO mice as determined by transabdominal ultrasound. In addition, IL12p40-deficiency significantly increased aortic stiffness in the abdominal aortas in response to AngII than WT as measured by pulse wave velocity (PWV) and atomic force microscopy (AFM). Macroscopic and histological examination also showed that IL12p40-KO mice exhibited severe abdominal aortic lesion formation and increased maximal aortic width compared to WT mice. Increased elastin fragmentation and collagen deposition was detected in aorta of AngII-infused IL12p40-KO mice compared to AngII-infused WT mice. Further, there was no significant change in the total cholesterol, triglycerides and HDL-cholesterol levels in the serum of WT and IL12p40-KO mice treated with AngII. Importantly, bone marrow derived macrophages (BMDM) from IL12p40-KO mice showed increased mRNA expression of M2-markers (TGF-β1 and IL10) and decreased expression of M1-markers (iNOS and TNF-α) at basal level compared to WT BMDM. Conclusions: IL12p40 deficiency may promote the development of AAA, in part, by facilitating recruitment of M2-like macrophages and potentiating aortic-stiffness and fibrosis mediated by TGF-β1 and IL10. In summary, optimal M1/M2 balance rather than predominance of M2-phenotype may be prerequisite to prevent AAA formation.

Abstract 566: High-density Lipoprotein Inhibits Serum Amyloid a -Mediated Inflammasome Activation

Objectives: Interleukin-1beta (IL-1β) has been implicated in inflammatory diseases, including atherosclerosis and abdominal aortic aneurysm (AAA). Production of bioactive IL-1β is controlled by the inflammasome, a multi-protein complex that regulates caspase-1 activity. Serum Amyloid A (SAA) is an acute-phase protein whose levels in circulation is elevated in individuals with chronic inflammation. We previously reported that deficiency of SAA protects mice from angiotensin II (AngII)-induced AAA. Here we report that reduced AngII-induced AAA in SAA-deficient mice is accompanied by significant reductions in plasma IL-1β, indicating that SAA is required for inflammasome activation in AngII-infused mice. The objective of this study is to investigate mechanisms involved in SAA-mediated inflammasome activation. Methods/Results: SAA dose-dependently induced both caspase-1 activation and IL-1β secretion in J774 macrophage-like cells incubated with 0-25 μg/ml purified mouse SAA. The ability of SAA to induce IL-1β secretion was significantly reduced in bone marrow-derived macrophages deficient in NLRP3. A caspase-1inhibitor, Z-YVAD-FMK, significantly suppressed IL-1β secretion induced by SAA, whereas the P2X7-receptor antagonist, AA38079, had no effect. Inhibition of reactive oxygen species (ROS), cathepsin-B activation, and cellular potassium efflux by N-acetyl-L-cysteine, CA-074, and glyburide, respectively, blocked NLRP3 inflammasome activation by SAA. Pre-incubating SAA with HDL prior to cell treatments completely abrogated SAA-mediated inflammasome activation. In contrast, HDL did not alter inflammasome activation triggered by ATP. Conclusions: SAA-mediated NLRP3 inflammasome activation in macrophages is dependent on ROS generation, release of cathepsin-B, and potassium efflux, and is independent of the P2X7 receptor. Moreover, our data identify a novel mechanism by which HDL may exert cardioprotective effects.

Abstract 110: Exogenous Vasohibin-2 Does Not Influence Angiotensin II-induced Abdominal Aortic Aneurysms Formation in Either Normolipidemic or Apolipoprotein E-Deficient Mice

Objective: Chronic angiotensin II (AngII) infusion promotes both ascending (TAAs) and abdominal aortic aneurysms (AAAs) in mice. Previously, we demonstrated that exogenous vasohibin-2 (VASH-2) exacerbated AngII-induced TAAs in normolipidemic mice. The purpose of this study was to examine whether exogenous VASH-2 influenced AngII-induced AAAs in mice. Methods and Results: In the initial study, male C57BL/6J mice (10 weeks old) were injected with VASH2 or LacZ expressing adenovirus (Ad; 7.5 x 109 vp/100 μ L) via tail vein at 2 week intervals. One week after the first injection, subcutaneous infusion of AngII (1,000 ng/kg/min) by mini osmotic pumps was initiated for 3 weeks. Consequently, mice were divided into 2 groups: AngII + Ad VASH2 in C57BL/6J mice (n=22) and AngII + Ad LacZ in C57BL/6J mice (n=21). VASH-2 overexpression had no effect on systolic blood pressure, heart rate, body weight, or serum total cholesterol concentrations. Exogenous VASH-2 did not affect ex vivo measurements of maximal diameters of abdominal aortas (AngII + Ad VASH2; 1.36 ± 0.39 mm, AngII + LacZ 1.34 ± 0.24 mm, n.s.) in AngII-infused mice. In a subsequent study, male apolipoprotein E-deficient (apoE-/-) mice (9 to 13 weeks old) were injected with VASH2 or LacZ as described for C57BL/6J mice. Consequently, mice were divided into 2 groups: AngII + Ad VASH2 in apoE-/- mice (n=14) and AngII + Ad LacZ in apoE-/- mice (n=14). Similarly, overexpression of VASH-2 had no effect on systolic blood pressure, heart rate, body weight, or serum total cholesterol concentrations in apoE-/- mice. Furthermore, exogenous VASH-2 did not affect ex vivo measurement of maximal diameter of abdominal aorta (AngII + Ad VASH2; 1.70 ± 0.61 mm, AngII + Ad LacZ; 1.61 ± 0.43 mm, n.s.) in AngII-infused apoE-/- mice. Conclusion: Despite our previous demonstration of the effects on TAA, exogenous VASH-2 did not influence AngII-induced AAA formation in either normolipidemic or apoE-/- mice.

Abstract 108: Lipopolysaccharide Fails to Augment Development of Angiotensin II-induced Abdominal Aortic Aneurysms in Mice

Background and objective: Our previous study demonstrated that deficiency of toll-like receptor 4 (TLR4) reduced angiotensin II (AngII)-induced abdominal aortic aneurysms (AAAs) in hypercholesterolemic mice. Lipopolysaccharide (LPS) is a well-known agonist of TLR4. Interaction of LPS and TLR4 promotes inflammation and augments hypercholesterolemia-induced atherosclerosis. The purpose of this study was to determine whether LPS augments AngII-induced AAAs. Methods and Results: Low-density lipoprotein (LDL) receptor -/- mice fed a Western diet develop hypercholesterolemia and have augmentation of AngII-induced AAAs. We found that LDL receptor -/- mice fed Western diet had increased LPS concentrations, as quantified by a Limulus Amebocyte lysate chromogenic endotoxin quantitation kit, compared to the same mice prior to Western diet feeding. To determine whether LPS plays a role on AngII-induced AAAs, 4 groups of male C57BL/6J mice, 10-week-old, were infused subcutaneously with: (1) Vehicle (N=5), (2) LPS (250 μ g/kg/day; N=10), (3) AngII (1,000 ng/kg/min; N=10), or (4) both AngII and LPS (N=10) through Alzet mini osmotic pumps for 28 days. Abdominal aortic expansion was monitored serially at 2 and 4 weeks of infusion using high frequency ultrasonography (Vevo 3100 system; FUJIFILM). Continuous luminal expansion was detected in both AngII-infused mice and mice co-infused with both AngII and LPS. These results were confirmed by ex vivo measurements of maximal outer diameters of suprarenal aortas after termination showing AngII infusion led to significant increase of abdominal aortic dilation, compared to vehicle or LPS infused mice. However, co-infusion of LPS with AngII did not augment AngII-induced AAAs. Conclusion: LPS has no effects on AngII-induced AAAs in normolipidemic mice.

Abstract 304: Differential Effects of LRP1 in AngII-induced Ascending Aortic PathologiesBetween Male and Female Mice: Lack of Association With Elastin Fragmentation

Objective: Low-density lipoprotein receptor-related protein 1 (LRP1), a transmembrane protein, is important in maintaining elastin fiber integrity of the aortic wall. Smooth muscle cells (SMCs) of the ascending aorta are composed of the inner medial layers from the cardiac neural crest and the outer layers from the second heart field (SHF). LRP1 depletion in SMCs of male mice augments angiotensin II (AngII)-induced ascending aortic dilation and rupture attributed specifically to SMCs of SHF origin. The purpose of this study was to determine whether depletion of LRP1 in SHF-derived SMCs (SHF-SMC LRP1) has differential effects on AngII-induced aortic dilation, rupture, and elastin fragmentation between male and female mice. Methods and Results: Female LRP1 floxed mice were bred to male LRP1 floxed mice with Mef2c-Cre transgene to generate SHF-SMC LRP1 +/+ and -/- mice. Male and female mice at 12-14 weeks of age were infused with either saline or AngII (1,000 ng/kg/min) for 28 days (n = 12-31). Ascending aortic diameter (AoD) was measured by ultrasound, rupture was determined by necropsy, and elastin fragmentation was assessed by Movat’s staining. In male mice of both genotypes, AoD and elastin breaks were increased by AngII infusion, and AoD was positively correlated with elastin fragmentation (r 2 = 0.48, p < 0.001). SHF-SMC LRP1 deletion augmented aortic dilation, rupture rate, and elastin fragmentation in AngII-infused male mice. In females, AngII infusion increased AoD in SHF-SMC LRP1 -/- mice, but not in their wild type controls. AngII-induced elastin fragmentation did not differ between SHF-SMC LRP1 +/+ and -/- female mice, and no correlation between AoD and elastin fragmentation was detected (r 2 = 0.01, p = 0.88). Despite the extent of AngII-induced elastin fragmentation that was equivalent to that in males, aortic rupture is lower in female than in male LRP1 deleted mice (9 vs 38%, p = 0.02). Conclusion: In male mice, AngII infusion promotes dilation and rupture of ascending aorta that is augmented in SHF-SMC LRP1-/- mice and positively associated with elastin fragmentation. However, AngII only promotes ascending aortic dilation in female mice with SHF-SMC LRP1 deletion, despite elastin fragmentation being equivalent between SHF-SMC LRP1 +/+ and -/- mice.

Abstract 053: Differential Effects of LRP1 in AngII-induced Ascending Aortic PathologiesBetween Male and Female Mice: Lack of Association With Elastin Fragmentation

Objective: Low-density lipoprotein receptor-related protein 1 (LRP1), a transmembrane protein, is important in maintaining elastin fiber integrity of the aortic wall. Smooth muscle cells (SMCs) of the ascending aorta are composed of the inner medial layers from the cardiac neural crest and the outer layers from the second heart field (SHF). LRP1 depletion in SMCs of male mice augments angiotensin II (AngII)-induced ascending aortic dilation and rupture attributed specifically to SMCs of SHF origin. The purpose of this study was to determine whether depletion of LRP1 in SHF-derived SMCs (SHF-SMC LRP1) has differential effects on AngII-induced aortic dilation, rupture, and elastin fragmentation between male and female mice. Methods and Results: Female LRP1 floxed mice were bred to male LRP1 floxed mice with Mef2c-Cre transgene to generate SHF-SMC LRP1 +/+ and -/- mice. Male and female mice at 12-14 weeks of age were infused with either saline or AngII (1,000 ng/kg/min) for 28 days (n = 12-31). Ascending aortic diameter (AoD) was measured by ultrasound, rupture was determined by necropsy, and elastin fragmentation was assessed by Movat’s staining. In male mice of both genotypes, AoD and elastin breaks were increased by AngII infusion, and AoD was positively correlated with elastin fragmentation (r 2 = 0.48, p < 0.001). SHF-SMC LRP1 deletion augmented aortic dilation, rupture rate, and elastin fragmentation in AngII-infused male mice. In females, AngII infusion increased AoD in SHF-SMC LRP1 -/- mice, but not in their wild type controls. AngII-induced elastin fragmentation did not differ between SHF-SMC LRP1 +/+ and -/- female mice, and no correlation between AoD and elastin fragmentation was detected (r 2 = 0.01, p = 0.88). Despite the extent of AngII-induced elastin fragmentation that was equivalent to that in males, aortic rupture is lower in female than in male LRP1 deleted mice (9 vs 38%, p = 0.02). Conclusion: In male mice, AngII infusion promotes dilation and rupture of ascending aorta that is augmented in SHF-SMC LRP1-/- mice and positively associated with elastin fragmentation. However, AngII only promotes ascending aortic dilation in female mice with SHF-SMC LRP1 deletion, despite elastin fragmentation being equivalent between SHF-SMC LRP1 +/+ and -/- mice.

Angiotensin II Promotes KV7.4 Channels Degradation Through Reduced Interaction With HSP90 (Heat Shock Protein 90).

Voltage-gated Kv7.4 channels have been implicated in vascular smooth muscle cells' activity because they modulate basal arterial contractility, mediate responses to endogenous vasorelaxants, and are downregulated in several arterial beds in different models of hypertension. Angiotensin II (Ang II) is a key player in hypertension that affects the expression of several classes of ion channels. In this study, we evaluated the effects of Ang II on the expression and function of vascular Kv7.4. Western blot and quantitative polymerase chain reaction revealed that in whole rat mesenteric artery, Ang II incubation for 1 to 7 hours decreased Kv7.4 protein expression without reducing transcript levels. Moreover, Ang II decreased XE991 (Kv7)-sensitive currents and attenuated membrane potential hyperpolarization and relaxation induced by the Kv7 activator ML213. Ang II also reduced Kv7.4 staining at the plasma membrane of vascular smooth muscle cells. Proteasome inhibition with MG132 prevented Ang II-induced decrease of Kv7.4 levels and counteracted the functional impairment of ML213-induced relaxation in myography experiments. Proximity ligation assays showed that Ang II impaired the interaction of Kv7.4 with the molecular chaperone HSP90 (heat shock protein 90), enhanced the interaction of Kv7.4 with the E3 ubiquitin ligase CHIP (C terminus of Hsp70-interacting protein), and increased Kv7.4 ubiquitination. Similar alterations were found in mesenteric vascular smooth muscle cells isolated from Ang II-infused mice. The effect of Ang II was emulated by 17-AAG (17-demethoxy-17-(2-propenylamino) geldanamycin) that inhibits HSP90 interactions with client proteins. These results show that Ang II downregulates Kv7.4 by altering protein stability through a decrease of its interaction with HSP90. This leads to the recruitment of CHIP and Kv7.4 ubiquitination and degradation via the proteasome.

The immunoproteasome subunit LMP10 mediates angiotensin II-induced retinopathy in mice

Inflammation has been implicated in a variety of retinal diseases. The immunoproteasome plays a critical role in controlling inflammatory responses, but whether activation of immunoproteasome contributes to angiotensin II (Ang II)-induced retinopathy remains unclear. Hypertensive retinopathy (HR) was induced by infusion of Ang II (3000 ng/kg/min) in wild-type (WT) and immunoproteasome subunit LMP10 knockout (KO) mice for 3 weeks. Changes in retinal morphology, vascular permeability, superoxide production and inflammation were examined by pathological staining. Our results showed that immunoproteasome subunit LMP10 expression and its trypsin-like activity were significantly upregulated in the retinas and serum of Ang II-infused mice and in the serum from patients with hypertensive retinopathy. Moreover, Ang II-infused WT mice showed an increase in the central retinal thickness, vascular permeability, reactive oxygen species (ROS) production and inflammation compared with saline controls, and these effects were significantly attenuated in LMP10 KO mice, but were aggravated in mice intravitreally injected with rAAV2-LMP10. Interestingly, administration of IKKβ specific inhibitor IMD-0354 remarkably blocked an Ang II-induced increase in vascular permeability, oxidative stress and inflammation during retinopathy. Mechanistically, Ang II-induced upregulation of LMP10 promoted PTEN degradation and activation of AKT/IKK signaling, which induced IkBα phosphorylation and subsequent degradation ultimately leading to activation of NF-kB target genes in retinopathy. Therefore, this study provided novel evidence demonstrating that LMP10 is a positive regulator of NF-kB signaling, which contributes to Ang II-induced retinopathy. Strategies for inhibiting LMP10 or IKKβ activity in the eye could serve as a novel therapeutic target for treating hypertensive retinopathy.