Progression Of Atherosclerosis In Mice Research Articles

Role of ADAR2-mediated innate immune responses in vascular inflammation and atherosclerosis

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsche Forschungsgemeinschaft (DFG) Background Adenosine-to-inosine (A-to-I) RNA editing is an epitranscriptional regulator of RNA metabolism, catalyzed by the adenosine deaminases acting on RNA-1/-2 (ADAR1/2). Whether ADAR2 play a role in atherosclerotic processes remains elusive. Aim We examined the role of ADAR2 in vascular endothelial cell (EC) immunomodulatory responses and its biological relevance in murine and human atherosclerosis. Methods The role of ADAR2 in atherosclerosis was determined in a double ADAR2 and ApoE knockout mice fed with Western diet for 20 weeks. Three mouse genetic models (global and inducible vascular endothelial cell (iEC)-restricted ADAR2 and IL6ST knockout) were used to determine the role of ADAR2 in IL-6-related innate immunity. Expression levels of ADAR2 were measured in peripheral blood mononuclear cells derived from 533 individuals at risk for atherosclerotic vascular disease. Structural vascular measurements were used, including intima-media thickness (IMT), carotid wall maximum thickness (maxWT), and the number of atheromatous plaques by carotid and femoral artery ultrasonography as surrogate markers of subclinical arterial disease. Study participants were followed for major adverse cardiovascular events (MACE). Results Genetic ablation of ADAR2 resulted in a reduction of atherosclerotic plaque burden and necrotic core in the aorta and brachiocephalic trunk as well as reduced leukocyte infiltration in atherosclerotic plaques without affecting cholesterol levels in mice. Blood analysis revealed decreased pro-inflammatory cytokine levels including IL-6 after treatment of ADAR2/APOE KO mice compared to littermate control mice. Intravital imaging of IL-6-inflamed vascular endothelium showed that rolling and adhesion of leukocyte subsets to vascular wall were impaired by 2-fold in ADAR2-/- or iEC-ADAR2-/- KO mice. In vivo and ex vivo histological examination revealed that endothelial ADAR2 controls endothelial vascular adhesion molecule expression induced by gp130 signaling. ADAR2-deficient transcriptome revealed a selective upregulation of a conserved group of miRNAs targeting the IL6ST mRNA. Multilayered rescue studies including miR-inhibitors restored IL6ST levels after ADAR2 deficiency. In humans, increased ADAR2 expression was independently associated with the presence of CAD, higher C-reactive protein and mean carotid IMT after adjustment for traditional risk factors. Increased ADAR2 at baseline was prospectively associated with accelerated progression of subclinical atherosclerosis reflected by the increased number of carotid plaques at follow-up (OR=3.74, P<0.05). Finally, high ADAR2 levels were independently associated with higher MACE incidence across a median follow-up period of 54 months. Conclusion Posttranscriptional control of vascular inflammation by ADAR2 is integral for the development and progression of atherosclerosis in mice and humans. Our findings suggest that ADAR2 may serve as a promising therapeutic target for atherosclerosis.Role of ADAR2 in atherosclerosis

Hawthorn leaf flavonoids alleviate the deterioration of atherosclerosis by inhibiting SCAP-SREBP2-LDLR pathway through sPLA2-ⅡA signaling in macrophages in mice

Ethnopharmacological relevanceHawthorn leaves are a combination of the dried leaves of the Rosaceae plants, i.e., Crataegus pinnatifida Bge. or Crataegus pinnatifida Bge. var. major N. E. Br., is primarily cultivated in East Asia, North America, and Europe. hawthorn leaf flavonoids (HLF) are the main part of extraction. The HLF have demonstrated potential in preventing hypertension, inflammation, hyperlipidemia, and atherosclerosis. However, the potential pharmacological mechanism behind its anti-atherosclerotic effect has yet to be explored. Aim of the studyThe in vivo and in vitro effects of HLF on lipid-mediated foam cell formation were investigated, with a specific focus on the levels of secreted phospholipase A2 type IIA (sPLA2-II A) in macrophage cells. Materials and methodsThe primary constituents of HLF were analyzed using ultra-high performance liquid chromatography and liquid chromatography-tandem mass spectrometry. In vivo, HLF, at concentrations of 5 mg/kg, 20 mg/kg, and 40 mg/kg, were administered to apolipoprotein E knockout mice (ApoE−/−) fed by high-fat diet (HFD) for 16 weeks. Aorta and serum samples were collected to identify lesion areas and lipids through mass spectrometry analysis to dissect the pathological process. RAW264.7 cells were incubated with oxidized low-density lipoprotein (ox-LDL) alone, or ox-LDL combined with different doses of HLF (100, 50, and 25 μg/ml), or ox-LDL plus 24-h sPLA2-IIA inhibitors, for cell biology analysis. Lipids and inflammatory cytokines were detected using biochemical analyzers and ELISA, while plaque size and collagen content of plaque were assessed by HE and the Masson staining of the aorta. The lipid deposition in macrophages was observed by Oil Red O staining. The expression of sPLA2-IIA and SCAP-SREBP2-LDLR was determined by RT-qPCR and Western blot analysis. ResultsThe chemical profile of HLF was studied using UPLC-Q-TOF-MS/MS, allowing the tentative identification of 20 compounds, comprising 1 phenolic acid, 9 flavonols and 10 flavones, including isovitexin, vitexin-4″-O-glucoside, quercetin-3-O-robibioside, rutin, vitexin-2″-O-rhamnoside, quercetin, etc. HLF decreased total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and non-high-density lipoprotein cholesterol (non-HDL-C) levels in ApoE−/− mice (P < 0.05), reduced ox-LDL uptake, inhibited level of inflammatory factors, such as IL-6, IL-8, TNF-α, and IL-1ꞵ (P < 0.001), and alleviated aortic plaques with a thicker fibrous cap. HLF effectively attenuated foam cell formation in ox-LDL-treated RAW264.7 macrophages, and reduced levels of intracellular TC, free cholesterol (FC), cholesteryl ester (CE), IL-6, TNF-α, and IL-1β (P < 0.001). In both in vivo and in vitro experiments, HLF significantly downregulated the expression of sPLA2-IIA, SCAP, SREBP2, LDLR, HMGCR, and LOX-1 (P < 0.05). Furthermore, sPLA2-IIA inhibitor effectively mitigated inflammatory release in RAW264.7 macrophages and regulated SCAP-SREBP2-LDLR signaling pathway by inhibiting sPLA2-IIA secretion (P < 0.05). ConclusionHLF exerted a protective effect against atherosclerosis through inhibiting sPLA2-IIA to diminish SCAP-SREBP2-LDLR signaling pathway, to reduce LDL uptake caused foam cell formation, and to slow down the progression of atherosclerosis in mice.

Finasteride delays atherosclerosis progression in mice and is associated with a reduction in plasma cholesterol in men

Finasteride is commonly prescribed to treat benign prostate hyperplasia and male-pattern baldness in cis men and, more recently, trans individuals. However, the effect of finasteride on cardiovascular disease remains elusive. We evaluated the role of finasteride on atherosclerosis using low-density lipoprotein (LDL) receptor-deficient (Ldlr−/−) mice. Next, we examined the relevance to humans by analyzing the data deposited between 2009 and 2016 in the National Health and Nutrition Examination Survey. We show that finasteride reduces total plasma cholesterol and delays the development of atherosclerosis in Ldlr−/− mice. Finasteride reduced monocytosis, monocyte recruitment to the lesion, macrophage lesion content, and necrotic core area, the latter of which is an indicator of plaque vulnerability in humans. RNA sequencing analysis revealed a downregulation of inflammatory pathways and an upregulation of bile acid metabolism, oxidative phosphorylation, and cholesterol pathways in the liver of mice taking finasteride. Men reporting the use of finasteride showed lower plasma levels of cholesterol and LDL-cholesterol than those not taking the drug. Our data unveil finasteride as a potential treatment to delay cardiovascular disease in people by improving the plasma lipid profile.

LncRNA MIR4697HG Alleviates Endothelial Cell Injury and Atherosclerosis Progression in Mice via the FUS/ANXA5 Axis.

Atherosclerosis (AS) manifests with arterial intimal injury, lipid deposition and chronic inflammation, which is a key pathogenic cause of cardio-cerebrovascular disorders. LncRNA MIR4697HG was downregulated in human advanced atherosclerotic plaques. This study probed the precise biological functions and downstream regulatory mechanisms of MIR4697HG during AS progression. MIR4697HG levels in atherosclerotic plaque tissues and normal arterial intima were measured by RT-qPCR. An injury model of human umbilical vein endothelial cells (HUVECs) was induced through treating with oxidative low-density lipoprotein (ox-LDL). MIR4697HG overexpression plasmids (pcDNA-MIR4697HG) was transfected into ox-LDL-treated HUVECs, and then cell viability, apoptosis, reactive oxygen species (ROS) level, oxidative stress marker protein malondialdehyde (MDA) level and superoxide dismutase (SOD) activity, and adhesion molecule intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) levels in HUVECs were determined. Moreover, the binding between MIR4697HG and fused in sarcoma (FUS) was checked with RNA pull-down assay. The interaction between FUS and annexin A5 (ANXA5) was gauged with Co-immunoprecipitation. Then MIR4697HG/FUS/ANXA5 axis mediated HUVEC functions were accessed with rescue experiments. Additionally, an AS model was established via feeding a high-fat diet for ApoE-/- mice, and lentivirus MIR4697HG overexpression vector (Lv-MIR4697HG) was injected into AS mice followed by detection of atherosclerotic plaque area in mice. MIR4697HG was downregulated in atherosclerotic plaque tissues and HUVECs stimulated by ox-LDL. MIR4697HG overexpression attenuated ox-LDL-induced HUVEC viability inhibition, apoptosis, oxidative stress and adhesion molecule release. Moreover, MIR4697HG bound with FUS and facilitated FUS expression in HUVECs. FUS knockdown abrogated the functions of lncRNA MIR4697HG overexpression in ox-LDL induced HUVEC injury. Besides, FUS could bind with ANXA5. FUS overexpression inhibited ox-LDL induced HUVEC injury, while ANXA5 knockdown reversed these effects. Additionally, Lv-MIR4697HG reduced atherosclerotic plaque area in ApoE-/- mice. LncRNA MIR4697HG mitigated ox-LDL-induced apoptosis, oxidative stress and adhesion molecule release in HUVECs and alleviated AS progression in mice through the FUS/ANXA5 axis.

Consequences of total, hepatocyte or intestinal LDL receptor deficiency on dyslipidemia and atherosclerosis progression in mice

Consequences of total, hepatocyte or intestinal LDL receptor deficiency on dyslipidemia and atherosclerosis progression in mice

Abstract 398: Retinoic Acid Exposure Promotes Phenotypic Characteristics Of Alternative Activation In Macrophages

Introduction: Macrophages are key players in atherosclerosis. Classically-activated (M1) macrophages show a pro-inflammatory phenotype, whereas alternatively-activated (M2) are anti-inflammatory. The M1/M2 balance in atherosclerosis determines the fate of the lesions and strategies to increase M2-like macrophages entail promising therapeutic candidates. Retinoic acid (RA), the transcriptionally active form of vitamin A, delays atherosclerosis progression in mice and has been investigated as a modulator of macrophage polarization. Hypothesis: RA modulates macrophage polarization by inducing M2-like responses. Methods: Bone marrow-derived macrophages from three wild-type C57BL/6J mice were differentiated (M0) and stimulated with LPS/IFNγ (M1) or IL-4 (M2) for 24h, followed by 6h exposure to 1 μM RA or vehicle (DMSO). RNAseq and gene enrichment analysis were performed. Efferocytosis assays were performed by co-culture of apoptotic Jurkat cells with treated macrophages and subsequent analysis by flow cytometry. Autophagy flux and lysosomal protein breakdown rate were also analyzed. Results: RNAseq showed that RA induced changes in 1,485 genes in M2 macrophages, while 821 and 227 genes were significantly regulated in M0 and M1, respectively. Given the lower impact of RA on M1, we focused our subsequent analyses on M0 and M2. Arginase 1 , a well-known marker of M2 activation, was significantly upregulated by RA at both the mRNA and the protein levels in M0 and M2. Scavenger receptors pathway was regulated in M2 exposed to RA, and efferocytosis assays showed that this group had significantly the highest efferocytotic capacity. Autophagy and Lysosome pathways were also significantly over-represented in M2 treated with RA, although autophagy flux and protein breakdown rate were not differentially affected by RA in M2 or M0 macrophages. Conclusions: Transcriptomic analyses showed a higher response of M2 macrophages to RA, compared to M0 and M1. Functional assays revealed that RA increased efferocytosis in M2 macrophages, a hallmark of alternative activation. Our results suggest that RA skews macrophages' polarization and it might promote an M2-like phenotype, especially in macrophages exposed to IL4, enhancing alternative activation.

Abstract 10391: Elevated Plasma Branched-Chain Amino Acids Level Promotes Atherosclerosis Progression by Facilitating Macrophage Polarization Toward M1 Phenotype That Results in the Increase of Inflammation

Introduction: Few studies have reported that whether elevated plasma branched-chain amino acids (BCAA) level is causally related to atherosclerosis (AS) and the mechanism involved. Methods: First, the plasma BCAA level of 258 atherosclerotic cardiovascular disease (ASCVD) patients and 188 normal people was measured. Second, plaque volume, stability and inflammation of AS mice were evaluated. Third, we assayed BCAA level, catabolism-promoting genes and inflammation in the circulating monocytes of ASCVD patients and abdominal macrophages of AS mice. Fourth, inflammation and macrophage polarization were evaluated in BCAA catabolic deficient RAW 264.7 cells. Finally, mitochondrial hydrogen peroxide (mtH 2 O 2 ), nuclear H 2 O 2 and High mobility group box 1 (HMGB1) levels in RAW 264.7 cells were measured and RAW 264.7 cells-overexpressing catalase targeted to mitochondria (MCAT), nucleus (NCAT) and HMGB1KD RAW 264.7 cells were built to detect their effect on macrophage polarization. Results: First, we found that plasma BCAA level was an independent risk factor of ASCVD. Second, we also found plasma BCAA level was elevated in AS mice, which led to the increase of plaque volume and instability, as well as inflammation. The growth of plaque instability was characterized by increased macrophage amounts and decreased smooth muscle cells (SMCs) and collagen contents. Conversely, when plasma BCAA level was lowered, the above phenomena could be reversed. Third, elevated plasma BCAA level resulting from BCAA catabolic defect occurred in the monocytes of ASCVD patients and the abdominal macrophages of AS mice, which increased inflammatory response by promoting the polarization of macrophages toward M1 phenotype. Fourth, elevated BCAA level-mediated macrophage polarization toward M1 phenotype was regulated by increasing mtH 2 O 2 level to induce secretion of HMGB1 by increasing nuclear H 2 O 2 level. Finally, the improvement of BCAA catabolism of macrophages alleviated AS progression in mice. Conclusions: Our data demonstrates that elevated plasma BCAA level is an independent risk factor of ASCVD and promotes AS progression, indicating that plasma BCAA level might be a therapeutic target for ASCVD.

Transfer of exosomal microRNA-203-3p from dendritic cells to bone marrow-derived macrophages reduces development of atherosclerosis by downregulating Ctss in mice.

Dendritic cell-derived exosomes have been proven to be efficient adjuvant options for anti-tumor vaccines in cancer immunotherapy. However, their potency in atherosclerosis remains unclear. Here we summarize the association of microRNA-203-3p (miR-203-3p) with dendritic cell-derived exosomes and atherosclerosis. Firstly, dendritic cell-derived exosomes and bone marrow-derived macrophages were isolated, after which expression of miR-203-3p and cathepsin S was determined. After the establishment of atherosclerosis mouse models, gain- and loss-of-function experiments were conducted for the analysis of effects of miR-203-3p and cathepsin S on foam-cell formation, lipid accumulation, collagen deposition and serum total cholesterol. The results found high expression of cathepsin S in atherosclerosis mice and downregulation of miR-203-3p in the serum of atherosclerosis patients and ox-LDL-simulated bone marrow-derived macrophages. Cathepsin S was the target gene of miR-203-3p. miR-203-3p transporting from exosomes to bone marrow-derived macrophages resulted in inhibition of cathepsin S expression and atherosclerosis-related phenotypes in bone marrow-derived macrophages, thus alleviating atherosclerosis in mice, and this process was found to involve the p38/MAPK signaling pathway. These findings provided evidence that the transfer of miR-203-3p by dendritic cell-derived exosomes targeted cathepsin S in bone marrow-derived macrophages to attenuate atherosclerosis progression in mice, serving as a promising clinical target for atherosclerosis.

Iron accumulation in macrophages promotes the formation of foam cells and development of atherosclerosis

BackgroundMacrophages that accumulate in atherosclerotic plaques contribute to progression of the lesions to more advanced and complex plaques. Although iron deposition was found in human atherosclerotic plaques, clinical and pre-clinical studies showed controversial results. Several epidemiological studies did not show the positive correlation between a systemic iron status and an incidence of cardiovascular diseases, suggesting that the iron involvement occurs locally, rather than systemically.ResultsTo determine the direct in vivo effect of iron accumulation in macrophages on the progression of atherosclerosis, we generated Apoe−/− mice with a macrophage-specific ferroportin (Fpn1) deficiency (Apoe−/−Fpn1LysM/LysM). Fpn1 deficiency in macrophages dramatically accelerated the progression of atherosclerosis in mice. Pathophysiological evidence showed elevated levels of reactive oxygen species, aggravated systemic inflammation, and altered plaque-lipid composition. Moreover, Fpn1 deficiency in macrophages significantly inhibited the expression of ABC transporters (ABCA1 and ABCG1) by decreasing the expression of the transcription factor LXRα, which reduced cholesterol efflux and therefore promoted foam cell formation and enhanced plaque formation. Iron chelation relieved the symptoms moderately in vivo, but drastically ex vivo.ConclusionsMacrophage iron content in plaques is a critical factor in progression of atherosclerosis. The interaction of iron and lipid metabolism takes place in macrophage-rich atherosclerotic plaques. And we also suggest that altering intracellular iron levels in macrophages by systemic iron chelation or dietary iron restriction may be a potential supplementary strategy to limit or even regress the progression of atherosclerosis.

Double bond configuration of palmitoleate is critical for atheroprotection

ObjectiveSaturated and trans fat consumption is associated with increased cardiovascular disease (CVD) risk. Current dietary guidelines recommend low fat and significantly reduced trans fat intake. Full fat dairy can worsen dyslipidemia, but recent epidemiological studies show full-fat dairy consumption may reduce diabetes and CVD risk. This dairy paradox prompted a reassessment of the dietary guidelines. The beneficial metabolic effects in dairy have been claimed for a ruminant-derived, trans fatty acid, trans-C16:1n-7 or trans-palmitoleate (trans-PAO). A close relative, cis-PAO, is produced by de novo lipogenesis and mediates inter-organ crosstalk, improving insulin-sensitivity and alleviating atherosclerosis in mice. These findings suggest trans-PAO may be a useful substitute for full fat dairy, but a metabolic function for trans-PAO has not been shown to date. MethodsUsing lipidomics, we directly investigated trans-PAO's impact on plasma and tissue lipid profiles in a hypercholesterolemic atherosclerosis mouse model. Furthermore, we investigated trans-PAO's impact on hyperlipidemia-induced inflammation and atherosclerosis progression in these mice. ResultsOral trans-PAO supplementation led to significant incorporation of trans-PAO into major lipid species in plasma and tissues. Unlike cis-PAO, however, trans-PAO did not prevent organelle stress and inflammation in macrophages or atherosclerosis progression in mice. ConclusionsA significant, inverse correlation between circulating trans-PAO levels and diabetes incidence and cardiovascular mortality has been reported. Our findings show that trans-PAO can incorporate efficiently into the same pools that its cis counterpart is known to incorporate into. However, we found trans-PAO's anti-inflammatory and anti-atherosclerotic effects are muted due to its different structure from cis-PAO.

Alcohol Consumption in Combination with an Atherogenic Diet Increased Indices of Atherosclerosis in Apolipoprotein E/Low-Density Lipoprotein Receptor Double-Knockout Mice.

Alcohol abuse and adherence to atherogenic diet (AD; a low-carbohydrate-high-protein diet) have been positively associated with cardiovascular disease. In addition, it has been demonstrated clinically that dietary intake is increased on days when alcohol is consumed. Here, the additive effects of ethanol (EtOH) and AD on atherosclerosis, a major underlying cause of cardiovascular disease, were investigated in apolipoprotein E/low-density lipoprotein receptor double-knockout (KO) mice. The mechanisms, especially aortic oxidative stress damage, were highlighted. Twelve-week-old male KO mice on AD with or without EtOH treatment were bred for 4months. Age-matched male C57BL/6J mice on a standard chow diet without EtOH treatment served as controls. Analyses were conducted using ultrasound biomicroscopy, histopathological and fluorescence immunohistochemical examinations, Western blots, and polymerase chain reaction. KO mice on AD with EtOH treatment showed increases in aortic maximum intima media thickness, hypoechoic plaque formation, and mean Oil-Red-O content. These results were associated with enhanced ratio of aortic 8-hydroxy-2'-deoxyguanosine (8-OHdG)-immunopositive area to the metallothionein (MT) immunopositive area and suppression of AD-induced up-regulated aortic Mt1, Mt2, and upstream stimulatory factor 1 mRNA expressions. Moreover, 8-OHdG was expressed in the nuclei of CD31- and alpha smooth muscle actin-immunopositive cells, and the up-regulated mRNA expressions of aortic nitric oxide synthase 3 and platelet-derived growth factors were only observed in the KO mice on AD with EtOH treatment. Alcohol abuse and adherence to AD may promote the shift of aortic oxidative stress and antioxidative stress balance toward oxidative stress predominance and reduced antioxidative stress, which may be partly due to the decrease in MT at the cell biological level and down-regulation of Mt at the gene level, which in turn could play a role in the up-regulation of endothelial dysfunction-related and vascular smooth muscle cell proliferation-related gene expression and the progression of atherosclerosis in mice with hyperlipidemia.

In This Issue

HomeCirculation ResearchVol. 121, No. 9In This Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIn This Issue Ruth Williams Ruth WilliamsRuth Williams Search for more papers by this author Originally published13 Oct 2017https://doi.org/10.1161/RES.0000000000000178Circulation Research. 2017;121:1021LKB1 and Atherosclerosis (p 1047)Download figureDownload PowerPointThe kinase LKB1 slows foam cell formation and atherosclerosis progression in mice, report Liu et al.Atherosclerosis begins with the gradual accumulation of fatty deposits on blood vessel walls. Monocytes are recruited to the lesions where they convert to macrophages to phagocytose lipids in the lesions. Continued lipid uptake by the macrophages transforms them into foam cells, which is a critical step in plaque development. However, mechanisms underlying this transformation remain unclear. Liu and colleagues now show that the kinase LKB1, previously identified as having cardioprotective and anti-inflammatory effects, is a negative regulator of foam cell development. They found that, in mice prone to atherosclerosis, the levels of LKB1 in plaque macrophages decreases with disease progression. This decrease prevented LKB1-directed phosphorylation of scavenger receptor A (SRA)—a principle macrophage receptor responsible for lipid uptake and foam cell conversion. The team went on to show that LKB1-directed phosphorylation of SRA promotes the receptor’s degradation. They also found that atherogenesis was accelerated in atherosclerosis-prone mice with LKB1-lacking macrophages. As in mice, levels of LKB1 are also low in humans with atherosclerosis, suggesting the kinase may have a similar role in both mice and humans. Thus, boosting LKB1 levels in macrophages might be a new way to slow or prevent the progression of atherosclerosis.Endothelial TRPM2 in PMN Transmigration (p 1081)Download figureDownload PowerPointMittal et al examine the molecular details of neutrophil transmigration across the vascular endothelium.Neutrophils must exit the blood to get to sites of injury or infection, and they do this by squeezing through or between the endothelial cells—a process known as transmigration. Neutrophils generated reactive oxygen species (ROS) for killing bacteria, but recent evidence suggests ROS generation may also help neutrophils exit the blood. Indeed, exposure of endothelial cells in culture to the ROS hydrogen peroxide induces the opening of interendothelial junctions. And this process was shown to require calcium entry into endothelial cells via the cation channel TRPM2. Mittal and colleagues have now investigated this TRPM2-dependent mechanism in mice. The team engineered mice with endothelium-specific conditional deletion of TRPM2 and found that, when the mice were injected with bacterial toxin, the animals exhibited reduced inflammation (fewer neutrophils exiting the blood) compared with wild-type controls. Upon examining the molecular details of TRPM2-dependent transmigration, they found that neutrophil released ROS-induced production of ADPR, a TRPM2 activator, which was essential for the channel’s action. Together, these results suggest that, in cases of excessive inflammation, inhibition of TRPM2 might be an effective anti-inflammatory approach.CV Event Prediction by Machine Learning in MESA (p 1092)Download figureDownload PowerPointMachine learning strategy identifies clinical outcome predictors in large epidemiological study, report Ambale-Venkatesh et al.Epidemiological studies have led to the identification of several risk factors for cardiovascular disease, such as smoking, high blood pressure, and high cholesterol. But large epidemiological studies can provide many millions of data points from hundreds of variables, making the identification of other risk factors and outcome predictors a complex task. Ambale-Venkatesh and colleagues reasoned that the pattern recognition power of machine learning might make it an effective tool for mining such datasets. The team applied a machine learning technique to data from the Multi-Ethnic Study of Atherosclerosis (MESA), which includes 735 clinical variables (such as imaging, biomarkers, and questionnaires) from 6814 middle-aged to elderly individuals assessed over 12 years. They found that, compared with traditional data-mining approaches, machine learning predicted clinical outcomes with greater accuracy. It also identified nontraditional risk predictors, such as imaging scores, electrocardiography, and serum biomarkers for certain clinical outcomes, as opposed to more traditional predictors, such as ethnicity, gender, and medication use. The authors conclude that machine learning methods may be valuable for linking subclinical disease markers with outcomes in large cohort studies. Previous Back to top Next FiguresReferencesRelatedDetails October 13, 2017Vol 121, Issue 9 Advertisement Article InformationMetrics © 2017 American Heart Association, Inc.https://doi.org/10.1161/RES.0000000000000178 Originally publishedOctober 13, 2017 PDF download Advertisement

Effects of Astaxanthin on Reverse Cholesterol Transport and Atherosclerosis in Mice.

High plasma level of HDL-cholesterol (HDL-C) has been consistently associated with a decreased risk of atherosclerosis (AS); thus, HDL-C is considered to be an antiatherogenic lipoprotein. The development of novel therapies to enhance the atheroprotective properties of HDL may have the possibility of further reducing the residual AS risk. Reverse cholesterol transport (RCT) is believed to be a primary atheroprotective activity of HDL, which has been shown to promote the efflux of excess cholesterol from macrophage-derived foam cells via ATP-binding cassette transporter A1 (ABCA1), ATP-binding cassette transporter G1 (ABCG1), and scavenger receptor class B type I (SR-BI) and then transport it back to the liver for excretion into bile and eventually into the feces. In the current study, we investigated the effects of astaxanthin on RCT and AS progression in mice. The results showed that short- and long-term supplementation of astaxanthin promote RCT in C57BL/6J and ApoE−/− mice, respectively. Moreover, astaxanthin can relieve the plaque area of the aortic sinus and aortic cholesterol in mice. These findings suggest that astaxanthin is beneficial for boosting RCT and preventing the development of AS.

The trash piles up in vascular disease

Dying cells in the vessel wall block their own removal and drive atherosclerosis progression in mice.

Abstract 564: CD146 Deficiency Leads to Accelerated Atherosclerosis in Mice

Atherosclerosis is a chronic inflammatory disease of the large vessels and its progression is based in part on the continued recruitment of macrophages in the inflammatory wall. The well described role of CD146 in leukocyte infiltration in vitro suggests a role for this endothelial junction molecule in the early stages of the formation of atherosclerotic plaques. However, the involvement of CD146 in atherogenesis has not been elucidated. To investigate the role of CD146 deficiency in atherosclerosis, CD146 knocked-out (KO) mice were bred with ApoE KO mice. Mice were fed a high-fat Western diet for 24 weeks and were monitored for aortic wall thickness using high frequency ultrasound. After 24 weeks of diet, the arterial wall thickness was significantly higher in CD146 deficient mice (0.19±0.01mm vs 0.27±0.01mm; p=0.012) and there was a significant 47 % increase (p=0.015) in total aortic lesion area, evaluated by histological oil red O coloration. However, mice weights and total cholesterol plasma levels were similar between the two groups of mice. We detected a 2-fold increase in macrophage recruitment to the atherosclerotic plaque of the double KO mice compared with ApoE KO mice, suggesting that the atherosclerotic lesions in these mice were more inflammatory. In addition, CD146 deficient plaques contained significantly less smooth muscle cells (p=0.036) and could be more vulnerable. We observed a maladaptive immune response in double KO mice since the circulating neutrophils and monocytes were significantly increased (p=0.008 and p=0.015 respectively) in the absence of CD146 whereas circulating T lymphocytes were significantly decreased (p=0.026). In a similar way, splenocytes isolated from double KO mice contained significantly lower levels of T cells (p=0.002), suggesting a default of adaptive immunity in the absence of CD146 during atherosclerosis. Our results demonstrated the involvement of CD146 in the progression of atherosclerosis in mice. Our data also suggest that CD146 is involved in the regulation of adaptive immune response and its absence lead to an inflammatory phenotype, which could influence atherosclerosis plaque fate. Thus, CD146 should be considered as a potential target for protection against atherosclerosis.

Osteoglycin deficiency does not affect atherosclerosis in mice

Objective: The small leucine-rich proteoglycan Osteoglycin/Mimecan (OGN) is a component of the extracellular matrix, where it regulates collagen fibrillogenesis and cytokine availability. OGN is abundant in normal vessels and in atherosclerotic and restenotic lesions of rat, rabbit and human arteries. Osteoglycin-null mice show alterations in the thickness of collagen fibers of the cornea and the skin. In this work, we inspect the possible involvement of OGN in the atherosclerosis progression using a double knockout mouse model. Methods: In order to examine the progression of atherosclerosis in the absence of OGN, we developed double Apoe and Ogn knockout mice and performed a comparative histomorphological and immunofluorescence study of the atherosclerotic lesions of Apoe−/−Ogn−/− and Apoe−/−Ogn+/+ mice. Results: We demonstrate the presence of Ogn transcript in the aorta of wildtype mice, its absence in Ogn−/− mice, and the normal histomorphology of arteries of Ogn−/− mice. The composition of the extracellular matrix and also the cellular content and distribution were similar in atherosclerotic lesions of Apoe−/−Ogn−/− and Apoe−/−Ogn+/+ mice. Quantification of the lesion size revealed no significant differences between double and single knockout mice. The incidence, size and distribution of calcium deposits were similar in both groups of mice. Conclusions: The lack of the proteoglycan OGN does not affect the progression of atherosclerosis in mice. Possible causes for the absence of phenotype in the Apoe/Ogn double mutants are discussed.

P2Y13 receptor regulates HDL metabolism and atherosclerosis in vivo.

High-density lipoprotein (HDL) is known to protect against atherosclerosis by promoting the reverse cholesterol transport. A new pathway for the regulation of HDL-cholesterol (HDL-c) removal involving F1-ATPase and P2Y13 receptor (P2Y13R) was described in vitro, and recently in mice. However, the physiological role of F1-ATPase/P2Y13R pathway in the modulation of vascular pathology i.e. in the development of atherosclerotic plaques is still unknown. We designed a specific novel agonist (CT1007900) of the P2Y13R that caused stimulation of bile acid secretion associated with an increased uptake of HDL-c in the liver after single dosing in mice. Repeated dose administration in mice, for 2 weeks, stimulated the apoA-I synthesis and formation of small HDL particles. Plasma samples from the agonist-treated mice had high efflux capacity for mobilization of cholesterol in vitro compared to placebo group. In apoE−/− mice this agonist induced a decrease of atherosclerotic plaques in aortas and carotids. The specificity of P2Y13R pathway in those mice was assessed using adenovirus encoding P2Y13R-shRNA. These results demonstrate that P2Y13R plays a pivotal role in the HDL metabolism and could also be a useful therapeutic agent to decrease atherosclerosis. In this study, the up-regulation of HDL-c metabolism via activation of the P2Y13R using agonists could promote reverse cholesterol transport and promote inhibition of atherosclerosis progression in mice.

Testing the Iron Hypothesis in a Mouse Model of Atherosclerosis

Hepcidin, the iron-regulatory hormone and acute phase reactant, is proposed to contribute to the pathogenesis of atherosclerosis by promoting iron accumulation in plaque macrophages, leading to increased oxidative stress and inflammation in the plaque (the "iron hypothesis"). Hepcidin and iron may thus represent modifiable risk factors in atherosclerosis. We measured hepcidin expression in Apoe(-/-) mice with varying diets and ages. To assess the role of macrophage iron in atherosclerosis, we generated Apoe(-/-) mice with macrophage-specific iron accumulation by introducing the ferroportin ffe mutation. Macrophage iron loading was also enhanced by intravenous iron injection. Contrary to the iron hypothesis, we found that hepatic hepcidin expression was not increased at any stage of the atherosclerosis progression in Apoe(-/-) or Apoe/ffe mice and that the atherosclerotic plaque size was not increased in mice with elevated macrophage iron. Our results strongly argue against any significant role of macrophage iron in atherosclerosis progression in mice.

Inhibition of endocannabinoid-degrading enzyme fatty acid amide hydrolase increases atherosclerotic plaque vulnerability in mice

The role of endocannabinoids such as anandamide during atherogenesis remains largely unknown. Fatty acid amide hydrolase (FAAH) represents the key enzyme in anandamide degradation, and its inhibition is associated with subsequent higher levels of anandamide. Here, we tested whether selective inhibition of FAAH influences the progression of atherosclerosis in mice. Selective inhibition of FAAH using URB597 resulted in significantly increased plasma levels of anandamide compared to control, as assessed by mass spectrometry experiments in mice. Apolipoprotein E-deficient (ApoE−/−) mice were fed a high-fat, cholesterol-rich diet to induce atherosclerotic conditions. Simultaneously, mice received either the pharmacological FAAH inhibitor URB597 1mg/kg body weight (n=28) or vehicle (n=25) via intraperitoneal injection three times a week. After eight weeks, mice were sacrificed, and experiments were performed. Vascular superoxide generation did not differ between both groups, as measured by L012 assay. To determine whether selective inhibition of FAAH affects atherosclerotic plaque inflammation, immunohistochemical staining of the aortic root was performed. Atherosclerotic plaque formation, vascular macrophage accumulation, as well as vascular T cell infiltration did not differ between both groups. Interestingly, neutrophil cell accumulation was significantly increased in mice receiving URB597 compared to control. Vascular collagen structures in atherosclerotic plaques were significantly diminished in mice treated with URB597 compared to control, as assessed by picro-sirius-red staining. This was accompanied by an increased aortic expression of matrix metalloproteinase-9, as determined by quantitative RT-PCR and western blot analysis. Inhibition of fatty acid amide hydrolase does not influence plaque size but increases plaque vulnerability in mice.

EP Receptors and Coxibs

Few chemical compounds have demonstrated a controversial association with a specific disease such as arachidonic acid with atherothrombosis. Arachidonic acid metabolism is deeply linked to atherothrombosis because compounds generated by this cascade, the eicosanoids, are key regulators of several pathophysiological processes critically involved in vessel homeostasis and blood clotting. After its release from membrane-bound phospholipids, arachidonic acid is metabolized by 4 main pathways: (1) prostaglandin (PG) endoperoxidase synthase, usually referred as cyclooxygenase (COX); (2) lipoxygenase; (3) P450 epoxygenase; and (4) nonenzymatic isoprostane biosynthesis1 (Figure 1). Among these pathways, cardiovascular research has mainly focused on COX-derived eicosanoids, usually called PGs. There are 2 main isoforms of COX, named COX-1 and COX-2, which are encoded by 2 separate genes. Whereas COX-1 is constitutively expressed in many tissues, the expression of COX-2 is induced by several proinflammatory cytokines and growth factors. In the vascular tree, COX-1 is expressed in endothelial cells and in vascular smooth muscle cells (VSMCs) both in healthy vessels and in atheromatous areas. On the contrary, COX-2 expression is evident in atherosclerotic regions, and several proatherosclerotic stimuli (ie, oxidized low-density lipoprotein, angiotensin II, advanced glycation elements)2 as well as vascular injury3 may increase its expression. Notably, COX-2 is highly expressed in macrophages located in the shoulder region of atherosclerotic plaques, both in mice4 and in humans.5 In macrophages, the expression of COX-2 has predominantly proinflammatory and proatherosclerotic effects, and selective deletion of COX-2 in macrophages significantly hampers the progression of atherosclerosis in mice.4,6 Figure 1. The cyclooxygenases pathway. ECs indicates endothelial cells; EP, PGE2 receptor; DP, PGD2 receptor; FP, PGF2α receptor; IP, prostacyclin receptor; …