Atherosclerotic Plaques In ApoE Research Articles

Carotid artery wall imaging using 7.0T magnetic resonance imaging with threedimensional DANTE-prepared FLASH in ApoE-/- mice

To explore the feasibility of three-dimensional (3D) vessel wall imaging of carotid atherosclerotic plaques in ApoE-/- mice using 7.0T magnetic resonance imaging (MRI) with delays alternating with nutations for tailored excitation (DANTE)-prepared fast low-angle shot (DANTE-FLASH) technique. Numerical simulations were performed for optimizing imaging parameters to maximize the wall-lumen contrast. Six ApoE-/- and three wild-type mice were scanned using a 7.0T MRI scanner with DANTE-FLASH and multi-slice 2D RARE coupled with inflow outflow saturation bands (2D-IOSBRARE). The wall signal-to-noise ratio (SNRwall), lumen SNR (SNRlumen), wall-lumen contrast-to-noise ratio (CNR), lumen area (LA), and wall area (WA) were compared between DANTE- FLASH and 2D-IOSB-RARE sequences. Linear regression analysis was performed to assess the correlation between the MRI measurements and histopathological measurements of LA and WA. Based on the simulation results, a flip angle of 15° and a train length of 150 were implemented in the live imaging study. Compared with 2D-IOSB-RARE, DANTE-FLASH provided a slightly reduced CNR (P < 0.001) but much improved slice resolution. The LA and WA measurements from the DANTE-FLASH and 2D-IOSB- RARE showed excellent agreement based on ICC analysis (LA: ICC=0.94, P < 0.001; WA: ICC=0.93, P < 0.001) and Bland-Altman plots. Strong correlations were observed between the MRI and histopathological measurements for both LA (P < 0.0001) and WA (P < 0.0001). As a 3D black-blood MR sequence, DANTE-FLASH provides isotropic high spatial resolution to allow reliable visualization and quantitative evaluation of the arteriosclerotic lesions within the carotid artery of ApoE-/- mice using a 7.0T MRI scanner.

Highly sensitive magnetic particle imaging of vulnerable atherosclerotic plaque with active myeloperoxidase-targeted nanoparticles.

Inflammation is a pivotal driver of atherosclerotic plaque progression and rupture and is a target for identifying vulnerable plaques. However, challenges arise with the current in vivo imaging modalities for differentiating vulnerable atherosclerotic plaques from stable plaques due to their low specificity and sensitivity. Herein, we aimed to develop a novel multimodal imaging platform that specifically targets and identifies high-risk plaques in vivo by detecting active myeloperoxidase (MPO), a potential inflammatory marker of vulnerable atherosclerotic plaque.Methods: A novel multimodal imaging agent, 5-HT-Fe3O4-Cy7 nanoparticles (5HFeC NPs), used for active MPO targeting, was designed by conjugating superparamagnetic iron oxide nanoparticles (SPIONs) with 5-hydroxytryptamine and cyanine 7 N-hydroxysuccinimide ester. The specificity and sensitivity of 5HFeC NPs were evaluated using magnetic particle imaging (MPI), fluorescence imaging (FLI), and computed tomographic angiography (CTA) in an ApoE-/- atherosclerosis mouse model. Treatment with 4-ABAH, an MPO inhibitor, was used to assess the monitoring ability of 5HFeC NPs.Results: 5HFeC NPs can sensitively differentiate and accurately localize vulnerable atherosclerotic plaques in ApoE-/- mice via MPI/FLI/CTA. High MPI and FLI signals were observed in atherosclerotic plaques within the abdominal aorta, which were histologically confirmed by multiple high-risk features of macrophage infiltration, neovascularization, and microcalcification. Inhibition of active MPO reduced accumulation of 5HFeC NPs in the abdominal aorta. Accumulation of 5HFeC NPs in plaques enabled quantitative evaluation of the severity of inflammation and monitoring of MPO activity.Conclusions: This multimodal MPI approach revealed that active MPO-targeted nanoparticles might serve as a method for detecting vulnerable atherosclerotic plaques and monitoring MPO activity.

Overexpression of long noncoding RNA ANRIL inhibits phenotypic switching of vascular smooth muscle cells to prevent atherosclerotic plaque development in vivo.

Background: Phenotypic switching of vascular smooth muscle cells (VSMCs) plays a key role in atherosclerosis. Long noncoding RNA ANRIL (lncRNA-ANRIL) is critical in vascular homeostasis. Metformin produces multiple beneficial effects in atherosclerosis. However, the underlying mechanisms need to be elucidated.Methods and Results: Metformin increased lncRNA-ANRIL expression and AMPK activity in cultured VSMCs, and inhibited the phenotypic switching of VSMCs to the synthetic phenotype induced by platelet-derived growth factor (PDGF). Overexpression of lncRNA-ANRIL inhibited phenotypic switching and reversed the reduction of AMPK activity in PDGF-treated VSMCs. While, gene knockdown of lncRNA-ANRIL by adenovirus or silence of AMPKγ through siRNA abolished AMPK activation induced by metformin in VSMCs. RNA-immunoprecipitation analysis indicated that the affinity of lncRNA-ANRIL to AMPKγ subunit was increased by metformin. In vivo, administration of metformin increased the levels of lncRNA-ANRIL, suppressed VSMC phenotypic switching, and prevented the development of atherosclerotic plaque in Apoe-/- mice fed with western diet. These protective effects of metformin were abolished by infecting Apoe-/- mice with adenovirus expressing lncRNA-ANRIL shRNA. The levels of AMPK phosphorylation, AMPK activity, and lncRNA-ANRIL expression were decreased in human atherosclerotic lesions. Conclusion: Metformin activates AMPK to suppress the formation of atherosclerotic plaque through upregulation of lncRNA-ANRIL.

Detection of somatic mosaicism of the GBP3 gene in carotid atherosclerosis plaque by droplet digital PCR

Background and Aims: Previously, we identified copy number loss (CNV) of 7-8 exons of GBP3 in patients with coronary artery disease by array-CGH (doi:10.1038/srep41268). Guanylate-binding proteins, including GBP3, may be involved in macrophage activation in atherosclerosis. The increased expression of the Gbp3 gene was detected in foam cells of atherosclerotic plaque in ApoE(-/-) mice on the Western diet. (doi:10.1161/JAHA.115.002663). The aim was an assessment of copy-number events (CNV) of the GBP3 gene in patients with carotid atherosclerosis.

Abstract 15364: Radiation Exposure of the Base of the Heart Accelerates Coronary Atherosclerosis

Introduction: Radiation therapy (RT) is used in the treatment of approximately 50% of cancer patients. Thoracic RT is commonly used in breast cancer, Hodgkin’s lymphoma, head and neck and lung cancers among others. Unfortunately, the benefits of RT are often out-weighed by the by-stander cardiovascular risks and associated non-relapse mortality in cancer survivors. Hence, the development of cardiovascular disease (CVD) in patients receiving RT remains an important clinical problem. The base of the heart has been shown to be dose-sensitive wherein basal irradiation is associated with lower patient survival in lung-cancer patients treated with curative-intent RT. Although the mechanisms for RT-induced CVD are poorly understood, direct injury to the coronary arteries endothelium has been implicated. Hypothesis and Results: We hypothesized that irradiation harms heart tissue differentially depending upon the specific region that receives radiation. In order to test this hypothesis, we irradiated different regions of the heart and measured the development of atherosclerotic plaques as compared to control unirradiated mice. Apolipoprotein E knockout (ApoE -/- ) mice were irradiated with 16Gy to the base, apex or to the whole heart. Our results demonstrate that the base of the heart has significantly greater sensitivity to irradiation as compared to the apex, and develops atherosclerotic lesions that are equivalent to those produced by whole heart irradiation at 20 weeks post-RT. In addition, a greater number of plaques are present in the base of the heart after whole heart and basal irradiation compared to unirradiated controls at 40 weeks post-RT. Atherosclerotic plaques with subendothelial macrophage foam cell accumulation and fibrin deposits were also observed at 20 and 40 weeks post basal or whole heart RT. Ongoing studies are testing the effect of high-fat diet on the development of differential RT-induced atherosclerotic plaques in ApoE -/- mice and their correlation with heart function. Conclusion: Our studies strengthen the argument for advanced RT techniques to shield the base of the heart from radiation exposure to minimize RT-induced CVD and improve the quality of life and survival of cancer patients receiving RT.

Magnetic mesoporous silica nanoparticles-aided dual MR/NIRF imaging to identify macrophage enrichment in atherosclerotic plaques

Active foamy macrophage enrichment drives atherosclerotic plaque initiation and evolution, and is the prominent target for precisely identifying vulnerable plaque. Precise imaging of high-risk plaque allows promotion of treatment and prevention of vascular pathema. However, current iron oxide (IO) nanoparticles-based magnetic resonance (MR) imaging of plaque is often limited by insufficient perfusion and nonspecific accumulation of peri-aortic lymph nodes. Besides that, intrinsic defects of MR also impede its use for accurately identifying plaque details. Herein, by conjugating with PP1 peptide, a novel magnetic mesoporous silica nanoparticle (PIMI) loaded with near-infrared fluorescence (NIRF) dye (IR820) was fabricated to specifically target and quantify macrophage enrichment of atherosclerotic plaque in ApoE−/− mice using dual MR/NIRF imaging. Biocompatibility experiments ulteriorly confirmed the high safety of PIMI nanoparticles in vivo, which lays the foundation of next-generation contrast agent for recognizing macrophage-rich plaque in the near future.

Adipokine omentin-1 enhances atherosclerotic plaque stability by binding to macrophage integrin receptor

Abstract Background Omentin-1 is a novel cytokine which is primarily released by epicardial adipose tissues, and the molecule structure analysis revealed that it contained a fibrinogen-like domain. Clinical studies considered that the expression of omentin-1 is tightly associated with the development of cardiovascular diseases. In this research, we sought to investigate the effect of omentin-1 on already-established atherosclerotic lesion in ApoE−/− mouse and find out the cellular receptor of omentin-1 in macrophages. Methods We investigated the effect of omentin-1 on the plaque phenotype by implanting the ALZET minipump (which can continuously inject omentin-1 solution into mice's jugular vein) in western diet-treated ApoE−/− mice. To validate the conjugation of omentin-1 to integrin receptor αvβ3 and αvβ5, we performed immunoprecipitation experiment. Confocal microscopy was used to verify the spatial co-localization of omentin-1 and integrin receptors. Results In vivo studies showed that the administration of omentin-1 increased the collagen content and the average fibrous cap thickness of atherosclerotic plaque in ApoE−/− mice. Omentin-1 mitigated the formation of necrotic cores within the plaque, and reduced the foam cell infiltration concomitantly. Immunohistochemistry analysis of the atherosclerotic lesion from the aorta of mice revealed that the intravenous infusion of omentin-1 can suppress expression of inflammatory cytokines in vivo. Immunoprecipitation experiment and confocal microscopy analysis confirmed the binding of omentin-1 to integrin receptor αvβ3 and αvβ5. To further study the mechanism by which omentin-1 had exerted its protective function, we used human myeloid leukemia mononuclear cell line (THP1) and oxidized low density lipoprotein (ox-LDL) to establish macrophage-derived foam cell model in vitro. Cell studies demonstrated that omentin-1 can attenuated the apoptosis and inflammatory cytokines secretion in ox-LDL-induced macrophages. Besides, omentin-1 can promote the phosphorylation of integrin-relevant signaling pathway in macrophage. After adding the cilengitide (inhibitor of integrin receptor αvβ3 and αvβ5) or intervening the expression of integrin subunit αv, the phenomenon induced by omentin-1 were potently suppressed. Moreover, flowcytometry analysis provided the evidence that omentin-1 had a negative effect on macrophage efferocytosis ability. Conclusions The administration of adipokine omentin-1 can inhibit the necrotic cores formation and pro-inflammatory cytokines expression within the atherosclerotic lesion. The mechanism might be the inhibition of apoptosis and the secretion of pro-inflammatory cytokines in macrophage by binding to integrin receptor αvβ3 and αvβ5. Effect of omentin-1 on AS plaques. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): National natural science foundation of China

Dynamic monitoring of active calcification in atherosclerosis by 18F-NaF PET imaging.

The objective was to dynamically monitor the progression of atherosclerotic plaques in ApoE-/- mice with 18F-NaF PET imaging. The ApoE-/- mice were used to develop atherosclerosis models, and the C57BL/6J mice were used as control. 18F-NaF PET was performed when the mice were 12, 20, and 30weeks of age. Serum lipids and lipoproteins profiles, inflammatory cytokines, and calcification factors were tested by ELISA. The lipid distribution, morphology, and calcification of plaque were evaluated by Oil Red O, HE, and alizarin red staining. The correlation between imaging and the extent of calcification was analyzed by Pearson correlation analysis. The uptake of 18F-NaF in the aorta was gradually increased with each weekly extension. Compared with the ApoE-/- mice at the age of 12weeks and 20weeks, the levels of lipoprotein, inflammatory cytokines, and calcification factors were higher at 30weeks. In Oil Red O, HE, and alizarin red staining, the extent of the lipid area and calcification increased with time. The correlation analysis showed that the uptake of 18F-NaF in the aorta was related to the extent of calcification. 18F-NaF may dynamically monitor the progression of atherosclerotic plaques and ongoing microcalcification formation.

436-P: Characterization of Autoimmunity in the Acceleration of Atherosclerosis in Type 1 Diabetes

Hyperglycemia, hyperlipidemia and hypertension have been evaluated extensively as risk factors for cardiovascular disease (CVD) in people with type 1 diabetes (T1DM). However, the impact of autoimmunity in T1DM on CVD has not been determined. We have generated several mice models of atherosclerosis including ApoE-/-/NOD, ApoE-/-/NOD (congenic non diabetes and non-autoimmune), ApoE-/-/NOD (autoimmunity with insulitis, nondiabetes) and ApoE-/-/NOD autoimmune diabetic mice. All groups of mice have high plasma lipids but only ApoE-/-/NOD diabetic mice had hyperglycemia. However, ApoE-/-/NOD (insulitis and nondiabetes) and ApoE-/-/NOD (insulitis and diabetes) had high titers of autoantibodies to IA2 compared to control CongApoE-/-/NOD mice or nondiabetic ApoE-/-/NOD mice (P&amp;lt;0.0001). For the the severity of atherosclerosis, the presence of hyperglycemia in ApoE-/-/NOD-DM mice showed greater levels of lipid deposition in the descending aorta (22%) by en face assessment as compared to nondiabetic ApoE-/-/NOD mice (P&amp;lt;0.01). Similarly, we also observed in the macrophage content of the descending aorta, was greater in numbers in the ApoE-/-/NOD mice than in ApoE-/-/CongNOD mice (P&amp;lt;0.05) but less than in ApoE-/-/NOD-DM mice. FACS of the descending aorta showed the elevated CD3+/CD28- T-cells (CD4 and CD8) by 4.5 folds and decreased CD3+/CD28+ Treg cells by 46% at the atherosclerotic plaques of ApoE-/-/NOD mice, compared to those of CongApoE-/-/NOD mice. To further confirm the elevated infiltrate and accumulated CD3+ T-cells in vivo, we will investigate the levels of macrophages and CD3+ T-cells in the arterial wall of the coronary artery from the Medalists group T1D and autoimmunity with positive HLA DR3/4 risk alleles and autoantibodies and lacking monogenic diabetic variants, as compared to the group lacking HLA DR3/4 risk alleles and autoantibodies. These studies suggest that autoimmunity exacerbates atherosclerosis in T1D, independently and synergically hyperglycemia. Disclosure K. Park: None. Q. Li: None. H. Park: None. R. St-Louis: None. J. Fu: None. C. Rask-Madsen: None. E. Maddaloni: Consultant; Self; Merck KGaA. Speaker’s Bureau; Self; Abbott, AstraZeneca, Pikdare. H. Yokomizo: None. S. Kissler: None. A.H. Lichtman: None. G.L. King: Research Support; Self; Janssen Pharmaceuticals, Inc. Funding National Institutes of Health (R01DK053105); Thomas J. Beatson, Jr. Foundation

GYY4137 exhibits anti-atherosclerosis effect in apolipoprotein E (-/-) mice via PI3K/Akt and TLR4 signalling.

Hydrogen sulphide (H2 S) had been suggested to be involved in the pathogenesis of atherosclerosis, but the underlying molecular mechanisms are poorly understood. In this study, we aimed to investigate the anti-atherosclerosis effect of morpholin-4-ium-methoxyphenyl-morpholino-phosphinodithioate (GYY4137) in RAW264.7 cell-derived foam cells formation and in the atherosclerotic plaque of ApoE-/- mice fed with a high-fat diet, and study the underlying mechanisms of phosphatidylinositol 3-kinase (PI3K), serine/ threonine kinase (Akt) and Toll-like receptor 4 (TLR4) signalling pathway. In the ApoE-/- mice fed with a high-fat diet, daily GYY4137 administration for 8weeks effectively decreased carotid atherosclerotic plaque area and the volume of foam cells, regulated the lipid metabolism, down-regulated the pro-inflammatory cytokine levels and up-regulated the anti-inflammatory cytokines levels. Consistent with these findings, in the RAW264.7 cell-derived foam cells, GYY4137 ameliorated foam cell formation in vitro, and decreased the expression of pro-inflammatory cytokines. Furthermore, our studies showed that GYY4137 could activate the PI3K/Akt signalling pathway and consequently reduce the expression of TLR4 to be critical for foam cell formation, preventing atherosclerotic plaque formation and destabilization. LY294002, a PI3K inhibitor, could inhibit the phosphorylation of Akt and reduce the expression of TLR4, thus reduce the foam cell source and lipid volume in the unstable plaque tissue. Our results suggest that GYY4137 is an attractive novel therapeutic reagent for atherosclerosis diseases. This mechanism may be partially attributed to regulating the PI3K/Akt/TLR4 signalling pathway.

Oleoylethanolamide stabilizes atherosclerotic plaque through regulating macrophage polarization via AMPK-PPARα pathway

BackgroundAtherosclerotic plaque rupture is the major trigger of acute cardiovascular risk events, and manipulation of M1/M2 macrophage homeostasis is an effective strategy for regulating atherosclerotic plaque stability. This study was aimed to illuminate the effects of oleoylethanolamide (OEA) on macrophage polarization and plaque stability. MethodsMacrophages derived from THP-1 were treated with OEA followed by LPS/IFN-γ, and the markers of M1, M2 macrophages were monitored by western blot, real-time PCR and immunofluorescence staining. The effect of OEA on macrophage polarization in the arch of aortic arteries was tested by immunofluorescence staining and western blot, and the plaque stability was completed by Masson’s trichrome and hematoxylin and eosin (HE) in apolipoprotein E (ApoE)−/− mice. ResultsOEA treatment enhanced the expression of two classic M2 macrophage markers, macrophage mannose receptor (CD206) and transforming growth factor (TGF-β), while the expression of iNOS (M1 macrophages) was decreased in THP-1-derived macrophages. Blocking of PPARα using siRNA and inhibition of AMP-activated protein kinase (AMPK) by its inhibitor compound C attenuated the OEA-induced expression of M2 macrophage markers. In addition, OEA significantly suppressed M1, promoted M2 macrophage polarization, increased collagen content and decreased necrotic core size in atherosclerotic plaques in ApoE−/− mice, which were linked with the expression of PPARα. ConclusionsOEA improved atherosclerotic plaque stability through regulating macrophage polarization via AMPK-PPARα pathway.

Endothelial to mesenchymal transition contributes to nicotine-induced atherosclerosis.

Rationale: Nicotine exposure via cigarette smoking is strongly associated with atherosclerosis. However, the underlying mechanisms remain poorly understood. The current study aimed to identify whether endothelial to mesenchymal transition (EndMT) contributes to nicotine-induced atherosclerosis.Methods: ApoE-/- mice were administered nicotine in their drinking water for 12 weeks. The effects of nicotine on EndMT were determined by immunostaining on aortic root and RNA analysis in aortic intima. In vitro nicotine-treated cell model was established on human aortic endothelial cells (HAECs). The effects of nicotine on the expression of EndMT-related markers, ERK1/2 and Snail were quantified by real-time PCR, western blot and immunofluorescent staining.Results: Nicotine treatment resulted in larger atherosclerotic plaques in ApoE-/- mice. The vascular endothelial cells from nicotine-treated mice showed mesenchymal phenotype, indicating EndMT. Moreover, nicotine-induced EndMT process was accompanied by cytoskeleton reorganization and impaired barrier function. The α7 nicotine acetylcholine receptor (α7nAChR) was highly expressed in HAECs and its antagonist could effectively relieve nicotine-induced EndMT and atherosclerotic lesions in mice. Further experiments revealed that ERK1/2 signaling was activated by nicotine, which led to the upregulation of Snail. Blocking ERK1/2 with inhibitor or silencing Snail by small interfering RNA efficiently preserved endothelial phenotype upon nicotine stimulation.Conclusion: Our study provides evidence that EndMT contributes to the pro-atherosclerotic property of nicotine. Nicotine induces EndMT through α7nAChR-ERK1/2-Snail signaling in endothelial cells. EndMT may be a therapeutic target for smoking-related endothelial dysfunction and cardiovascular disease.

Tacrolimus reduces atherosclerotic plaque formation in ApoE-/- mice by inhibiting NLRP3 inflammatory corpuscles.

Effect of tacrolimus on atherosclerotic plaques and its influence on Nod-like receptor protein 3 (NLRP3) inflammatory pathway were studied by establishing the mouse model of atherosclerosis. The mice were divided into 3 groups: C57BL/6 mouse group (WT group), ApoE−/− mouse group (ApoE−/− group) and ApoE−/− mouse + tacrolimus intervention group (ApoE−/− + Tac group). The area of atherosclerotic plaques and the pathological morphologic changes were observed. The NLRP3, interleukin-1β (IL-1β), IL-18, NLRP3 inflammatory corpuscles, pro-inflammatory factors IL-1β and IL-18 in the aorta were analyzed. The area of atherosclerotic plaques in ApoE−/− mice was increased significantly, and it was significantly reduced after tacrolimus intervention. After tacrolimus intervention, the arterial intima became obviously thinner and no obvious cholesterol crystals were observed. The macrophage infiltration in atherosclerotic plaques was significantly increased, and the content of smooth muscle cells was also increased. The levels of serum IL-1β, IL-18 and NLRP3 in ApoE−/− mice were significantly increased, and they remarkably declined after tacrolimus intervention. ROS content in atherosclerotic plaques was increased in ApoE−/− mice, and it remarkably declined after tacrolimus intervention. The protein content of NLRP3, ASC, Casp-1, IL-1β and IL-18 in the aorta in ApoE−/− mice was remarkably increased, and they were inhibited to some extent after tacrolimus intervention. In conclusion, it is speculated that tacrolimus may reduce the formation of AS through inhibiting ROS in macrophages and activation of NLRP3 inflammatory corpuscles and reducing the release of IL-1β and IL-18.

Angiopoietin-1 aggravates atherosclerosis by inhibiting cholesterol efflux and promoting inflammatory response

ObjectiveAngiopoietin-1 (Ang-1), a secreted protein, mainly regulates angiogenesis. Ang-1 has been shown to promote the development of atherosclerosis, whereas little is known about its effects on lipid metabolism and inflammation in this process. MethodAng-1 was transfected into ApoE−/− mice via lentiviral vector or incubated with THP-1 derived macrophages. Oil red O and HE staining were performed to measure the size of atherosclerotic plaques in ApoE−/− mice. Immunofluorescence was employed to show the expression of target proteins in aorta. [3H] labeled cholesterol was performed to examine the efficiency of cholesterol efflux and reverse cholesterol transport (RCT) both in vivo and vitro. Western blot and qPCR were used to quantify target proteins both in vivo and vitro. ELISA detected the levels of pro-inflammatory cytokines in mouse peritoneal macrophage. ResultsOur data showed that Ang-1 augmented atherosclerotic plaques formation and inhibited cholesterol efflux. The binding of Ang-1 to Tie2 resulted in downregulation of LXRα, ABCA1 and ABCG1 expression via inhibiting the translocation of TFE3 into nucleus. In addition, Ang-1 decreased serum HDL-C levels and reduced reverse cholesterol transport (RCT) in ApoE−/− mice. Furthermore, Ang-1 induced lipid accumulation followed by increasing TNF-α, IL-6, IL-1β，and MCP-1 produced by MPMs, as well as inducing M1 phenotype macrophage marker iNOS and CD86 expression in aorta of ApoE−/− mice. ConclusionAng-1 has an adverse effect on cholesterol efflux by decreasing the expression of ABCA1 and ABCG1 via Tie2/TFE3/LXRα pathway, thereby promoting inflammation and accelerating atherosclerosis progression.

Long noncoding RNA Chaer mediated Polycomb Repressor Complex 2 (PRC2) activity to promote atherosclerosis through mTOR signaling.

Recent studies highlighted long noncoding RNAs (lncRNAs) have been implicated in many biological processes and diseases. However, atherosclerosis is a major risk factor for cardiovascular disease, but the detailed mechanism of atherosclerosis progression remained unclear. In this study, we mainly focused on the role of lncRNA Chaer in atherosclerosis. RT-PCR was used to detect the expression of lncRNA Chaer in atherosclerosis patients and animal model. Moreover, the expression of Chaer in vascular smooth muscle cell dysfunction model was also measured. Proliferation ability was tested by CCK-8 and cyclin D1 assay, through loss- and gain-of-function approaches. Western-blot was used to measure the expression of H3 lysine 27 methylation, when Chaer was in different levels. RIP and ChIP assay discovered an interaction between Chaer and PRC2 through mTOR signaling. Here we identified a heart-enriched long non-coding RNA, named Cardiac Hypertrophy Associated Epigenetic Regulator (Chaer). We found that the Chaer was highly expressed in serum samples from 28 patients with atherosclerosis, compared with 28 healthy volunteers. Chaer was dramatically upregulated in atherosclerotic plaques of ApoE-/- mice. We also found that the expression of Chaer was upregulated in vascular smooth muscle cell injury model. Through loss- and gain-of-function approaches, we showed that Chaer promotes cell proliferation and induces apoptosis in vitro. Mechanistically, Chaer interacts with Polycomb Repressor Complex 2 (PRC2) through inhibiting histone H3 lysine 27 methylation. Further, this interaction is induced upon mTOR signaling pathway. According to the results, we found that lncRNA Chaer was closely related to the progression of atherosclerosis, which could be a previously uncharacterized lncRNA-dependent epigenetic checkpoint.

HHIPL1, a Gene at the 14q32 Coronary Artery Disease Locus, Positively Regulates Hedgehog Signaling and Promotes Atherosclerosis.

Genome-wide association studies have identified chromosome 14q32 as a locus for coronary artery disease. The disease-associated variants fall in a hitherto uncharacterized gene called HHIPL1 (hedgehog interacting protein-like 1), which encodes a sequence homolog of an antagonist of hedgehog signaling. The function of HHIPL1 and its role in atherosclerosis are unknown. HHIPL1 cellular localization, interaction with sonic hedgehog (SHH), and influence on hedgehog signaling were tested. HHIPL1 expression was measured in coronary artery disease-relevant human cells, and protein localization was assessed in wild-type and Apoe-/- (apolipoprotein E deficient) mice. Human aortic smooth muscle cell phenotypes and hedgehog signaling were investigated after gene knockdown. Hhipl1-/- mice were generated and aortic smooth muscle cells collected for phenotypic analysis and assessment of hedgehog signaling activity. Hhipl1-/- mice were bred onto both the Apoe-/- and Ldlr-/- (low-density lipoprotein receptor deficient) knockout strains, and the extent of atherosclerosis was quantified after 12 weeks of high-fat diet. Cellular composition and collagen content of aortic plaques were assessed by immunohistochemistry. In vitro analyses revealed that HHIPL1 is a secreted protein that interacts with SHH and increases hedgehog signaling activity. HHIPL1 expression was detected in human smooth muscle cells and in smooth muscle within atherosclerotic plaques of Apoe-/- mice. The expression of Hhipl1 increased with disease progression in aortic roots of Apoe-/- mice. Proliferation and migration were reduced in Hhipl1 knockout mouse and HHIPL1 knockdown aortic smooth muscle cells, and hedgehog signaling was decreased in HHIPL1-deficient cells. Hhipl1 knockout caused a reduction of >50% in atherosclerosis burden on both Apoe-/- and Ldlr-/- knockout backgrounds, and lesions were characterized by reduced smooth muscle cell content. HHIPL1 is a secreted proatherogenic protein that enhances hedgehog signaling and regulates smooth muscle cell proliferation and migration. Inhibition of HHIPL1 protein function might offer a novel therapeutic strategy for coronary artery disease.

Silencing of junctional adhesion molecule-like protein attenuates atherogenesis and enhances plaque stability in ApoE-/- mice.

Background: Although junctional adhesion molecule-like protein (JAML) has recently been implicated in leukocyte recruitment during inflammation and wound repair, its role in atherosclerosis remains to be elucidated. Methods and results: First, we showed that JAML was strongly expressed in atherosclerotic plaques of cardiovascular patients. Similar results were obtained with atherosclerotic plaques of ApoE-/- mice. Co-immunofluorescence staining showed that JAML was mainly expressed in macrophages. Enhanced expression of JAML in cultured macrophages was observed following exposure of the cells to oxLDL. The functional role of JAML in atherosclerosis and macrophages function was assessed by interference of JAML with shRNA in vivo and siRNA in vitro Silencing of JAML in mice significantly attenuated atherosclerotic lesion formation, reduced necrotic core area, increased plaque fibrous cap thickness, decreased macrophages content and inflammation. In addition, histological staining showed that JAML deficiency promoted plaques to stable phenotype. In vitro, JAML siRNA treatment lowered the expression of inflammatory cytokines in macrophages treated with oxLDL. The mechanism by which JAML mediated the inflammatory responses may be related to the ERK/NF-κB activation. Conclusions: Our results demonstrated that therapeutic drugs which antagonize the function of JAML may be a potentially effective approach to attenuate atherogenesis and enhance plaque stability.

Aberrant MFN2 transcription facilitates homocysteine-induced VSMCs proliferation via the increased binding of c-Myc to DNMT1 in atherosclerosis.

It is well‐established that homocysteine (Hcy) is an independent risk factor for atherosclerosis. Hcy can promote vascular smooth muscle cell (VSMC) proliferation, it plays a key role in neointimal formation and thus contribute to arteriosclerosis. However, the molecular mechanism on VSMCs proliferation underlying atherosclerosis is not well elucidated. Mitofusin‐2 (MFN2) is an important transmembrane GTPase in the mitochondrial outer membrane and it can block cells in the G0/G1 stage of the cell cycle. To investigate the contribution of aberrant MFN2 transcription in Hcy‐induced VSMCs proliferation and the underlying mechanisms. Cell cycle analysis revealed a decreased proportion of VSMCs in G0/G1 and an increased proportion in S phase in atherosclerotic plaque of APOE−/− mice with hyperhomocystinaemia (HHcy) as well as in VSMCs exposed to Hcy in vitro. The DNA methylation level of MFN2 promoter was obviously increased in VSMCs treated with Hcy, leading to suppressed promoter activity and low expression of MFN2. In addition, we found that the expression of c‐Myc was increased in atherosclerotic plaque and VSMCs treated with Hcy. Further study showed that c‐Myc indirectly regulates MFN2 expression is duo to the binding of c‐Myc to DNMT1 promoter up‐regulates DNMT1 expression leading to DNA hypermethylation of MFN2 promoter, thereby inhibits MFN2 expression in VSMCs treated with Hcy. In conclusion, our study demonstrated that Hcy‐induced hypermethylation of MFN2 promoter inhibits the transcription of MFN2, leading to VSMCs proliferation in plaque formation, and the increased binding of c‐Myc to DNMT1 promoter is a new and relevant molecular mechanism.

ApoAI-derived peptide increases glucose tolerance and prevents formation of atherosclerosis in mice

Aims/hypothesisFinding new treatment alternatives for individuals with diabetes with severe insulin resistance is highly desired. To identify novel mechanisms that improve glucose uptake in skeletal muscle, independently from insulin levels and signalling, we have explored the therapeutic potential of a short peptide sequence, RG54, derived from apolipoprotein A-I (ApoA-I).MethodsINS-1E rat clonal beta cells, C2C12 rat muscle myotubes and J774 mouse macrophages were used to study the impact of RG54 peptide on glucose-stimulated insulin secretion, glucose uptake and cholesterol efflux, respectively. GTTs were carried out on diet-induced insulin-resistant and Leprdb diabetic mouse models treated with RG54 peptide, and the impact of RG54 peptide on atherosclerosis was evaluated in Apoe−/− mice. Control mice received ApoA-I protein, liraglutide or NaCl.ResultsThe synthetic RG54 peptide induced glucose uptake in cultured muscle myotubes by a similar amount as insulin, and also primed pancreatic beta cells for improved glucose-stimulated insulin secretion. The findings were verified in diet-induced insulin-resistant and Leprdb diabetic mice, jointly confirming the physiological effect. The RG54 peptide also efficiently catalysed cholesterol efflux from macrophages and prevented the formation of atherosclerotic plaques in Apoe−/− mice.Conclusions/interpretationThe RG54 peptide exhibits good prospects for providing glucose control and reducing the risk of cardiovascular disease in individuals with severe insulin resistance.

Mir‐1976 Downregulation and Phosphorylation of LARP6 are Associated with Insulin‐like Growth Factor‐1 (IGF1)‐induced Collagen Upregulation in Vascular Smooth Muscle Cells

Collagen content in atherosclerotic plaque is a hallmark of plaque stability. We have shown that insulin‐like growth factor‐1 (IGF1) increased collagen content in atherosclerotic plaques of Apoe−/− mice. We have identified LARP6 (La Ribonucleoprotein Domain Family, Member 6), a collagen mRNA binding protein, as a mediator of IGF1‐dependent collagen I upregulation and increased mature fibril formation in smooth muscle cells (SMCs), however specific mechanisms have not been elucidated yet. A total of six micro RNAs (miRs), including miR‐1976, have been shown to bind to LARP6 mRNA. In fact, miR‐1976 mimic (20 nM) decreased LARP6 by 67% and reduced procollagen I by 85% (both are P&lt;0.05), indicating that miR‐1976 negatively regulates LARP6 expression. We found that IGF1 significantly downregulated miR‐1976 by 41±5% in SMCs after 3h of exposure. Moreover, miR‐1976 mimic inhibited IGF1‐induced LARP6 upregulation, suggesting that the downregulation of miR‐1976 mediates IGF1 upregulation of LARP6.It has been reported that LARP6 phosphorylation is critical for regulating translation of collagen polypeptides. To investigate whether IGF1 induces LARP6 phosphorylation, we assessed LARP6 electrophoretic mobility shift by SDS‐PAGE and immunoblotting. SMCs were serum‐starved and treated for 0–48h either with 10 ng/ml IGF1, or 2 ng/ml IFNy, or 2 ng/ml IL‐1b, or 2 ng/ml TNFa, or 10 ng/ml IL‐6. LARP6 protein was detected on immunoblots as a single 65kDa band in untreated SMCs. However, additional 67kDa LARP6 band was evident after 6h of cell treatment with IGF1 or with IL‐6. The density of 67kDa LARP6 band was gradually increased up to 18h of treatment. IGF1 and IL‐6 also increased expression levels of procollagen I and collagen I in a time‐dependent manner, with a peak at 18h. IFNy, IL‐1b, and TNFa did not induce 67kDa LARP6 band or increase in expression level of collagen in SMCs.Taken together, our data suggest that IGF1 promotes collagen expression by upregulating LARP6 levels via a downregulation of miR‐1976 and also by inducing phosphorylation of LARP6. Suggested mechanisms by which IGF1 induces collagen expression in vascular SMCs and thus potentially in atherosclerotic plaques would provide novel insights for a therapeutic approach increasing plaque stability.Support or Funding InformationNIH/NHLBI R01HL070241 (PD)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.