Cellular immunostaining of angiotensin-converting enzyme in human coronary atherosclerotic plaques

Macrophage niche imprinting as a determinant of macrophage identity and function

Macrophage niches are the anatomical locations within organs or tissues consisting of various cells, intercellular and extracellular matrix, transcription factors, and signaling molecules that interact to influence macrophage self-maintenance, phenotype, and behavior. The niche, besides physically supporting macrophages, imposes a tissue- and organ-specific identity on the residing and infiltrating monocytes and macrophages. In this review, we give examples of macrophage niches and the modes of communication between macrophages and surrounding cells. We also describe how macrophages, acting against their immune defensive nature, can create a hospitable niche for pathogens and cancer cells.

Comparison of fimasartan and amlodipine therapy on carotid atherosclerotic plaque inflammation

Background

The renin‐angiotensin system plays an important role in promoting atherosclerotic plaque inflammation, which may be inhibited by angiotension‐II receptor blockers.

Hypothesis

We investigated the effects of fimasartan and amlodipine therapy on carotid atherosclerotic plaque inflammation using ¹⁸F‐fluorodeoxyglucose (¹⁸FDG) positron emission tomography (PET) imaging.

Methods

Fifty patients with acute coronary syndrome (ACS) and at least one lesion with ¹⁸FDG uptake in the carotid artery (target‐to‐background ratio [TBR] ≥ 1.6) were randomly assigned to receive either fimasartan (60 mg once a day) or amlodipine (5 mg once a day). ¹⁸FDG PET examinations were performed in all patients at baseline and 6 months. The primary endpoint was the percent change in the index vessel TBR for the most diseased segment (MDS TBR).

Results

The two groups had similar baseline characteristics. At the 6‐month follow‐up, index vessel and aorta MDS TBR significantly decreased in both groups. However, the percent change in index vessel MDS TBR was similar between the two groups (−9.33 ± 14.2% vs −7.73 ± 19.1%, respectively, P = 0.9). No significant difference was found for the percent change in the whole vessel TBR for the index vessel between the two groups, with similar findings for changes in MDS TBR or whole vessel TBR for the aorta. Total cholesterol, low‐density lipoprotein cholesterol levels, and blood pressure improved to a similar degree in both groups.

Conclusions

Fimasartan and amlodipine reduce carotid atherosclerotic plaque inflammation similarly in patients with ACS, offering the same level of effectiveness.

ACE2 and ACE in acute and chronic rejection after human heart transplantation

OBJECTIVES

The authors sought to evaluate cardiac activity of angiotensin-converting enzyme (ACE) and ACE2 after heart transplantation (HT) and its relation with acute rejection (AR) and chronic allograft vasculopathy (CAV).

BACKGROUND

The renin-angiotensin system is altered in heart failure and HT. However, ACE and ACE2 activities in post-HT acute and chronic rejection have not been previously studied.

METHODS

HT patients (n = 45) were included when appropriate serial endomyocardial biopsies (EMB) and coronary angiography were available for analysis. In 21 patients, three post-HT time points were selected for CAV study in EMB tissue: basal (0-3 wks), second (2-3 months) and third (4-5 months). At 10 years post-HT, CAV was evaluated by coronary angiography (CA) and patients were grouped by degree of CAV: 0-1, non-CAV (n = 15) and 2-3, CAV (n = 6). For the AR study, 28 HT patients with evidence of one EMB rejection at grade 3 and two EMB grade 1A and/or 1B rejections were selected.

RESULTS

Post-HT, ACE2 activity was increased in the CAV group, compared to non-CAV. Patients with AR showed increased ACE, but not ACE2, activity.

CONCLUSIONS

Our results suggest that early post-HT cardiac ACE2 activity may have an important role in CAV development. In contrast, ACE activity was increased in AR. The renin-angiotensin system seems to be altered after HT and strategies to balance the system may be useful.

Angiotensin-Converting Enzyme in Smooth Muscle Cells Promotes Atherosclerosis-Brief Report

OBJECTIVE

Angiotensin-converting enzyme (ACE) is present in many cell types of atherosclerotic lesions. This study determined whether ACE activity in endothelial and smooth muscle cells (SMCs), 2 major resident cell types of the aorta, contributes to hypercholesterolemia-induced atherosclerosis.

APPROACH AND RESULTS

All study mice were in low-density lipoprotein receptor(-/-) background. To determine the contribution of ACE on endothelial cells to atherosclerosis, female ACE floxed mice were bred to male Tie2-Cre transgenic mice. Endothelial cell-specific deletion of ACE significantly decreased serum ACE activity, but had no effect on systolic blood pressure and atherosclerosis. Because ACE protein is present on SMCs, the most abundant cell type of the aorta, we then determined whether ACE on SMCs contributes to atherosclerosis. ACE was depleted from SMCs by breeding female ACE floxed mice with male SM22-Cre transgenic mice. SMC-specific deficiency of ACE did not affect ACE activity in serum, but ablated its presence and activity in the aortic media. Although SMC-specific deficiency of ACE had no effect on systolic blood pressure, it significantly attenuated hypercholesterolemia-induced atherosclerosis in both male and female mice.

CONCLUSIONS

These studies provide direct evidence that ACE derived from endothelial cells does not play a critical role in atherosclerosis. Rather, SMC-derived ACE contributes to atherosclerosis, independent of circulating ACE activity and blood pressure.

Simvastatin Attenuates Oxidative Stress, NF-κB Activation, and Artery Calcification in LDLR-/- Mice Fed with High Fat Diet via Down-regulation of Tumor Necrosis Factor-α and TNF Receptor 1

Simvastatin (SIM) is anti-inflammatory. We used low density lipoprotein receptor knockout (LDLR-/-) mice and human aortic smooth muscle cells (HASMCs) as model systems to study the effect of SIM on arterial calcification and to explore the potential mechanisms contributing to this protective effect. High-fat diet (HFD) caused the LRLR -/- to develop dyslipidemia, diabetics, atherosclerosis and aortic smooth muscle calcification. SIM, N-acetyl cysteine (NAC, a ROS scavenger) and apocynin (APO, a NADPH oxidase inhibitor) did not significantly retard the development of dyslipidemia or diabetic. However, those treatments were still effective in attenuating the HFD-induced atherosclerosis and aortic smooth muscle calcification. These findings suggest that the protective effect of SIM against aortic calcification is not contributed by the cholesterol lowering effect. SIM, NAC and APO were found to attenuate the HFD induced elevation of serum TNF-α, soluble TNFR1 (sTNFR1), 3-nitro-tyrosine. We hypothesized that the pro-inflammatory cytokine, oxidative stress and TNFR1 played a role in inducing aortic calcification. We used HASMC to investigate the role of TNF-α, oxidative stress and TNFR1 in inducing aortic calcification and to elucidate the mechanism contributes the protective effect of SIM against aortic calcification. We demonstrated that treating HASMC with TNF-α induced cell Ca deposit and result in an increase in ALP, NADPH oxidase activity, NF-kB subunit p65, BMP2, MSX2, and RUNX2 expression. SIM suppressed the TNF-α induced activation of NADPH oxidase subunit p47, the above-mentioned bone markers and TNFR1 expression. Furthermore, p65, p47 and TNFR1 siRNAs inhibited the TNF-α-mediated stimulation of BMP-2, MSX2, RUNX2 expression. SIM, APO, and NAC either partially inhibit or completely block the TNF-α induced H2O2 or superoxide production. These results suggest that SIM may, independent of its cholesterol-lowering effect, suppresses the progression of vascular diseases through the inhibition of the inflammation mediators TNF-α and TNFR1.

Molecular and cellular targets of the MRI contrast agent P947 for atherosclerosis imaging

P947 (DOTA-Gd-peptide) was recently identified as an MRI contrast agent for the detection and characterization of the matrix metalloproteinases (MMP)-rich atherosclerotic plaques. Because this product displays a broad spectrum affinity for the MMP family, we hypothesized that it may also recognize other metalloproteinases overactivated in vulnerable atherosclerotic plaques. Therefore, this study aimed at describing, at the molecular and cellular level, the interactions between P947 and proteases of atherosclerotic plaques. Fluorimetric assays were used to measure the in vitro affinity of P947 toward recombinant and purified MMPs, angiotensin-converting enzyme (ACE), endothelin-converting enzyme (ECE-1), neutral endopeptidase (NEP), and both aminopeptidases A and N (APA and APN). Using similar fluorimetric assays associated with specific substrates, enzymatic activities were measured in vulnerable and stable plaques collected from human atherosclerotic carotid arteries. Ex vivo affinity of P947 for metalloproteinases in vulnerable lesions was subsequently determined. Interaction between P947 and major cell types present in atherosclerotic plaques was also investigated in different cell lines: PMA-1-differentiated THP-1 (macrophage), Ox-LDL-treated THP-1 (foam cell), Jurkat cell line (lymphocyte), and human umbilical vein endothelial cell (HUVEC, endothelial cell). Molecular targeting of P947 was confirmed by fluorimetry, ICP-MS, and in vitro MRI approaches. Potential application of P947 for detecting atherosclerotic plaques by in vivo MRI was tested in a rabbit model of atherosclerosis. In vitro, P947 displayed affinities for purified MMPs, ACE, ECE-1, NEP, APA, and APN in the micromolar range. Interestingly, MMPs, ACE, and APN exhibited higher activities in vulnerable plaques from human atherosclerotic carotid samples, as compared to stable plaques. ECE-1, NEP, and APA had either no activity or the same low activity in both vulnerable and stable plaques. P947 showed micromolar affinities for MMPs, ACE, and APN secreted by plaque samples. Moreover, P947 bound to THP-1 macrophages and THP-1 foam cells in a concentration-dependent manner and with a higher intensity than the control contrast agents DOTA-Gd or P1135 (DOTA-Gd coupled to a scrambled peptide). In THP-1 macrophages, P947 inhibited largely (70%) and almost completely (95%) MMP and APN activities, respectively, which strongly suggested an MMP- and APN-dependent binding of P947 to these cells. This enzyme-specific binding was confirmed with in vitro MRI. Indeed, the T1 value of THP-1 cells decreased from 2.094 s (macrophages w/o P947) to 2.004 s (macrophages with 1 mM of P947). In addition, the Gd content measured by ICP-MS was 11.01 ± 1.05 fg Gd/macrophage when cells were incubated in the presence of P947 and only 5.18 ± 0.43 fg Gd/macrophage with the control product P1135. The difference of Gd concentration between both contrast agents corresponded to a specific accumulation of 5.83 fg Gd/cell, which may be detected by MRI. MR imaging in the atherosclerosis rabbit model showed enhancement of the aortic wall after P947 injection with a significant increase of CNR values from 0.21 ± 0.02 (before injection) to 0.37 ± 0.07 (after injection), demonstrating the efficacy of the contrast agent to detect the atherosclerotic plaques in vivo. Taken together, these data suggest that P947 may be an interesting contrast agent for in vivo molecular MR imaging of MMPs, ACE, and APN activities present in vulnerable atherosclerotic plaques.

Monocyte angiotensin converting enzyme expression may be associated with atherosclerosis rather than arteriosclerosis in hemodialysis patients

BACKGROUND AND OBJECTIVES

Circulating monocytes can be divided into functionally distinct subpopulations according to their surface expression of CD14 and CD16. Monocytes with high-level expression of both antigens (CD14(++)CD16(+), Mo2 cells) are associated with cardiovascular morbidity and mortality in hemodialysis patients. These cells express angiotensin converting enzyme (ACE) on their surface. They are involved in the association of chronic inflammation and cardiovascular disease in kidney patients. Cardiovascular morbidity results from atherosclerosis (plaque-forming, vessel occluding disease) and arteriosclerosis (loss of arterial dampening function). It is unknown whether ACE-expressing proinflammatory monocytes are related to atherosclerosis, arteriosclerosis, or both.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

During baseline examination for a prospective study on monocyte ACE expression and mortality, 60 chronic hemodialysis patients of an academic outpatient center were screened for atherosclerosis by carotid artery ultrasound, for arteriosclerosis by pulse pressure measurement, and for ACE expression on Mo2 cells by flow cytometry.

RESULTS

ACE expression on Mo2 monocytes was significantly higher in patients with severe compared with those with little or no carotid atherosclerosis. Mo2 ACE correlated with a score to semiquantify atherosclerosis and remained a significant predictor of carotid plaques in multivariate analysis including the other univariately associated variables of age, hemoglobin A1c, and albumin. Mo2 ACE was not related to pulse pressure.

CONCLUSIONS

ACE expression on Mo2, although being a known predictor of mortality and cardiovascular disease in end-stage renal disease patients, may act via enhancement of atherosclerosis rather than arteriosclerosis.

Circulating monocyte subpopulations with high expression of angiotensin-converting enzyme predict mortality in patients with end-stage renal disease

BACKGROUND

Circulating monocytes can be divided into distinct populations according to their expression of surface markers CD14 and CD16. In patients with chronic kidney disease (CKD), the cell fraction expressing high levels of CD14 and CD16 is expanded and the numbers of these cells are predictive for cardiovascular disease. The present pilot study describes the predictive role of a combined biomarker consisting of high numbers of CD14(++)CD16(+) cells together with high expression of angiotensin-converting enzyme (ACE) on these cells for mortality in CKD Stage V(D) (dialysis) patients.

METHODS

In a prospective observational study, monocyte subpopulations were enumerated and ACE expression was quantified in 74 CKD patients by flow cytometry. Patients were assigned to one of four groups according to monocyte population numbers and ACE expression below and above the respective medians and observed for mortality and cardiovascular events for 46 months.

RESULTS

Patients stratified to the 'high CD14(++)CD16(+), high ACE' group (n = 22) had a dramatically enhanced mortality of 70% at 2 years compared to all other patient groups (mortality 14.8%, HR 4.86 [95% CI 2.17-10.86, P < 0.0001]). Atherosclerosis-associated events predominated among the causes of death.

CONCLUSIONS

This study describes a new combined biomarker of monocyte subpopulation numbers together with high expression of ACE that has a striking predictive value for mortality of CKD patients. Further research into the pathophysiologic background of this observation is warranted.

New insights into target organ involvement in hypertension

Hypertension and its sequelae are complex processes. Optimization of the care of the hypertensive patient requires not only attention to the regulation of arterial pressure but also attention to blunting the hypertension-related processes that lead to vascular disease. It is clear that the regulation of these processes is much more complex than previously understood. Here several new insights into the pathogenesis of hypertension-related vascular disease have been explored. While this review is not exhaustive, it does serve to point out the varied nature of the biologic processes that must be taken into account and it points to new avenues for the development of therapeutic agents.

Quinaprilat-eluting stents do not attenuate intimal thickening following stenting in porcine coronary arteries

OBJECTIVE

Vascular injury increases angiotensin-converting enzyme (ACE) activity in the vessel wall, and experimental evidence suggests that high-dose oral ACE inhibition reduces intimal hyperplasia following balloon angioplasty. Local drug delivery can achieve high local concentrations which may be especially efficacious in inhibiting tissue growth following stent implantation. The aim of this study was to evaluate the angiographic and histomorphologic effects of quinaprilat-eluting stents in normal porcine coronary arteries.

METHODS

Ten pigs received phosphorylcholine-coated stents in each of the three major coronary arteries: one loaded with 780 microg quinaprilat, one with the solvent and one non-loaded control. Quantitative angiography was performed before and after stenting and at 4 weeks follow-up. At this time point the stented arteries were also analyzed using histology and morphometry.

RESULTS

Repeated measures ANOVA yielded significantly smaller angiographic lumen in both quinaprilat and solvent groups: 2.62+/-0.31 and 2.65+/-0.31 mm, respectively versus control: 2.70+/-0.32 mm at follow-up, p<0.05. Histology confirmed this finding with an increment in intimal area (2.5+/-0.86 mm(2)) and thickness (0.57+/-0.29 mm) in the quinaprilat group; versus solvent (1.98+/-0.57 mm(2) 0.4+/-0.26 mm) and controls (1.92+/-0.50mm(2) and 0.41+/-0.18 mm).

CONCLUSION

Quinaprilat-eluting stents do not attenuate neointimal thickening following implantation in normal porcine coronary arteries, but rather show a tendency towards the opposite.

PPARdelta-mediated antiinflammatory mechanisms inhibit angiotensin II-accelerated atherosclerosis. Proc Natl Acad Sci U S A. 2008;105:4277-4282. [PMID: 18337495 DOI: 10.1073/pnas.0708647105]

Activation of the nuclear hormone receptor peroxisome proliferator-activated receptor delta (PPARdelta) has been shown to improve insulin resistance, adiposity, and plasma HDL levels. However, its antiatherogenic role remains controversial. Here we report atheroprotective effects of PPARdelta activation in a model of angiotensin II (AngII)-accelerated atherosclerosis, characterized by increased vascular inflammation related to repression of an antiinflammatory corepressor, B cell lymphoma-6 (Bcl-6), and the regulators of G protein-coupled signaling (RGS) proteins RGS4 and RGS5. In this model, administration of the PPARdelta agonist GW0742 (1 or 10 mg/kg) substantially attenuated AngII-accelerated atherosclerosis without altering blood pressure and increased vascular expression of Bcl-6, RGS4, and RGS5, which was associated with suppression of inflammatory and atherogenic gene expression in the artery. In vitro studies demonstrated similar changes in AngII-treated macrophages: PPARdelta activation increased both total and free Bcl-6 levels and inhibited AngII activation of MAP kinases, p38, and ERK1/2. These studies uncover crucial proinflammatory mechanisms of AngII and highlight actions of PPARdelta activation to inhibit AngII signaling, which is atheroprotective.

Long-term histological and immunohistochemical findings in human venous aorto-coronary bypass grafts

The aim of the present study was to analyse the long-term histology and immunohistochemistry of the plaque composition and cellular infiltration of SVGs (saphenous vein grafts) containing metallic stents. Percutaneous interventions in SVGs have a worse long-term clinical outcome compared with stenting of coronary arteries. Whether the pathological features of old degenerated SVGs condition the efficacy of drug-eluting stents is also unknown. Histology and immunohistochemistry of seven SVGs in the coronary circulation containing 12 metallic stents implanted 5 to 61 months before retrieval were analysed in patients undergoing a second aorto-coronary bypass surgery at a mean time of 11±6 years. The pathology of the old SVGs showed an important thrombotic and necrotic composition of the plaque, with plaque protrusion through the stent wires and a fragile media layer that could easily be damaged by stent placement with subsequent neointimal proliferation; indeed, stents with medial fracture had significantly greater mean neointimal thickness than those without (1.37±0.68 compared with 0.81±0.47 mm2; P<0.02). Neointimal inflammatory cell density correlated with increased neointimal thickness in patent vessels (r2=0.43, P<0.001). Immunostaining showed the total absence of ERs (oestrogen receptors), a poor cellular proliferative state as indicated by the presence of the Ki-67 marker, and persistent inflammation close to the stent wires as revealed by KP-1 and ACE (angiotensin-converting enzyme) immunostaining in most inflammatory cells in contact with the metal. These pathological findings may contribute to the more severe progression of disease and worse clinical outcome observed after conventional stented angioplasty of SVGs and might also interfere with the efficacy of drug-eluting stents in this specific atherosclerotic milieu.

Release of protein as well as activity of MMP-9 from unstable atherosclerotic plaques during percutaneous coronary intervention

OBJECTIVES

Few studies have investigated the composition of unstable coronary plaques in vivo in humans. The aims of this study were to investigate if substances released from plaques during percutaneous coronary intervention (PCI) under distal protection could give information about plaque composition and also indicate possible biomarkers in plasma that may be used to identify patients at risk.

METHODS AND RESULTS

Twenty patients with acute coronary syndromes undergoing PCI with distal protection were included. Plasma samples were taken before, during, and after the PCI in the aortic root, locally in the culprit vessel and intravenously. Plasma was analysed for possible markers of plaque instability. During PCI, local increases were observed for matrix metalloproteinase 9 (MMP-9), protein (P < 0.001) as well as activity (P < 0.001), interleukin 6 (IL-6; P < 0.01) and oxidized low-density lipoprotein (oxLDL; P = 0.01) in the culprit coronary artery. A systemic inflammatory response was also seen with increased levels of IL-10, MMP-3, serum amyloid A and C-reactive protein, but with no increase in MMP-9.

CONCLUSIONS

Our study shows that local sampling of blood under distal protection may be used to analyse coronary plaques and to identify biomarkers for unstable plaques. Our results suggest that MMP-9 is a potential biomarker, and that IL-6, MMP9 and possibly oxLDL are released from plaques.

Angiotensin-converting enzyme and vascular remodeling

Vascular remodeling is the result of a close interplay of changes in vascular tone and structure. In this review, the role of angiotension-converting enzyme (ACE) and the impact of ACE inhibition on vascular remodeling processes during vascular injury and restenosis, hypertension, atherosclerosis, and aneurysm formation are discussed. The role of ACE and angiotensin II (Ang II) in neointimal thickening has been firmly established by animal studies and is mediated by Ang II type 1 (AT(1)) receptor signaling events via monocyte chemoattractant protein-1 and NAD(P)H oxidase. ACE and Ang II are involved in the remodeling of large and resistance arteries during hypertension; here, cell proliferation and matrix remodeling are also regulated by signaling events downstream of the AT(1) receptor. In atherosclerosis, Ang II is involved in the inflammatory and tissue response, mediated by various signaling pathways downstream of the AT(1) receptor. Although ACE inhibition has been shown to inhibit atherosclerotic processes in experimental animal models, results of large clinical trials with ACE inhibitors were not conclusive. Remodeling of vessel dimensions and structure during aneurysm formation is counteracted by ACE inhibition. Here, a direct effect of ACE inhibitors on matrix metalloproteinase activity has to be considered as part of the working mechanism. The role of ACE2 in vascular remodeling has yet to be established; however, ACE2 has been shown to be associated with vascular changes in hypertension and atherosclerosis.

ACE phenotyping as a first step toward personalized medicine for ACE inhibitors. Why does ACE genotyping not predict the therapeutic efficacy of ACE inhibition?

Angiotensin (Ang)-converting enzyme (ACE) inhibitors are widely used for the treatment of cardiovascular diseases. Not all patients respond to ACE inhibitors, and it has been suggested that genetic variation might be a useful marker to predict the therapeutic efficacy of these drugs. In particular, the ACE insertion (I)/deletion (D) polymorphism has been investigated in this regard. Despite a decade of intensive research involving the genotyping of thousands of patients, we still do not know whether ACE genotyping helps in predicting the success of ACE inhibition. This review critically addresses the concept that predictive information on therapeutic efficacy of ACE inhibitors might be obtained based on ACE genotyping. It answers the following questions: Do higher ACE levels really result in higher Ang II levels? Is ACE the only converting enzyme in humans? Does ACE inhibition affect ACE expression? Why does ACE have 2 catalytically active domains? What is the relevance of ACE inhibitor-induced signaling through membrane-bound ACE? The review ends with the proposal that ACE phenotyping may prove to be a better first step toward personalized medicine for ACE inhibitors than ACE genotyping.