Atherosclerosis In ApoE Null Mice Research Articles

Macrophage-restricted tyrosine phosphatase SHP2 is a novel anti-atherosclerotic regulator

Abstract Atherosclerosis is a main pathological basis for cardiovascular diseases. Macrophages, featured in phenotypic and functional plasticity, play critical roles in initiation, progression, and regression of atherosclerosis. Our previously studies have shown that protein tyrosine phosphatase SHP2 regulates macrophage polarization, the immune homeostasis mediated by the interactions between macrophages and epithelial cells in mouse lung and intestine, and a tumor-favorable immune microenvironment. However, a potential role of SHP2 in atherosclerotic macrophages remains unknown. The expression of SHP2 is increased in macrophages within human atherosclerotic plaques. SHP2 allosteric inhibitor and macrophage-specific SHP2 deletion worsened atherosclerosis in ApoE null mice. Total cholesterol and low-density lipoprotein were increased in SHP2 inefficient mice. SHP2 inefficiency promoted inflammatory M1 polarization and inhibited anti-inflammatory M2 polarization, which was ApoE-null-dependent. Less cholesterol accumulation was observed in SHP2 inefficient macrophages and cholesterol transporter CD 36 was downregulated. To further explore the underlying mechanism, RNA sequencing was performed using SHP2 deleted macrophages with or without oxLDL treatment. Taken together, our studies using SHP2 knockout mice and specific inhibitor suggest that SHP2 is a novel anti-atherosclerotic regulator in promoting inflammatory macrophage phenotype.

Endothelial-derived VWF, But Not Platelet-Derived, Exacerbates Atherosclerosis in Apoe-null Mice by Promoting Platelet and Leukocyte Adhesion

Hermansky-Pudlak syndrome (HPS) is a recessive disorder with bleeding diathesis, which has been linked to platelet granule defects. Both platelet granules and endothelial Weibel-Palade bodies (WPBs) are members of lysosome-related organelles (LROs) whose formation is regulated by HPS protein associated complexes such as BLOC (biogenesis of lysosome-related organelles complex) -1, -2, -3, AP-3 (adaptor protein complex-3) and HOPS (homotypic fusion and protein sorting complex). Von Willebrand factor (VWF) is critical to hemostasis, which is stored in a highly-multimerized form as tubules in the WPBs. In this study, we found the defective, but varying, release of VWF into plasma after desmopressin (DDAVP) stimulation in HPS1 (BLOC-3 subunit), HPS6 (BLOC-2 subunit), and HPS9 (BLOC-1 subunit) deficient mice. In particular, VWF tubulation, a critical step in VWF maturation, was impaired in HPS6 deficient WPBs. This likely reflects a defective endothelium, contributing to the bleeding tendency in HPS mice or patients. The differentially defective regulated release of VWF in these HPS mouse models suggests the need for precise HPS genotyping before DDAVP administration to HPS patients.

Effects of Chronic Whey Protein Supplementation on Atherosclerosis in ApoE-/- Mice.

Whey protein is associated with improvement of metabolic syndrome. This study aimed to evaluate effects of whey protein on atherosclerosis in ApoE-/- mice. Male ApoE-/- mice were fed with a high-fat/cholesterol diet (HFCD), or HFCD supplemented with 10% or 20% whey protein for 18 wk. At the end of experiment, serum lipid profiles and inflammatory cytokines were assayed. Livers were examined using HE staining and Oil Red O staining. Aortas were used for en face and cryosection analyses to observe aortic lesions. Western blotting analysis was used to assess relative protein expression of cholesterol metabolism in the liver and aorta. No significant differences were observed in body weight or food intake among the three groups. Liver examination demonstrated decreased lipid droplets and cholesterol content in the whey-protein-supplemented groups. En face lesion of the aorta revealed a 21.51% and 31.78% lesion reduction in the HFCD supplemented with 10% and 20% whey groups, respectively. Decreased lesion was also observed in cryosection analysis. Whey protein significantly increased the serum high-density lipoprotein cholesterol level by 46.43% and 67.86%. The 20% whey protein significantly decreased serum IL-6 (a proinflammatory cytokine) by 70.99% and increased serum IL-10 (an anti-inflammatory cytokine) by 83.35%. Whey protein potently decreased lipogenic enzymes (ACC and FAS) in the liver and NF-κB expression in the liver and aorta. Whey protein significantly increased protein expression of two major cholesterol transporters (ABCA1 and ABCG1) in the liver and aorta. Thus, chronic whey protein supplementation can improve HFCD-induced atherosclerosis in ApoE null mice by regulating circulating lipid and inflammatory cytokines and increasing expressions of ABCA1 and ABCG1.

Addition of aspirin to a fish oil-rich diet decreases inflammation and atherosclerosis in ApoE-null mice

Aspirin (ASA) is known to alter the production of potent inflammatory lipid mediators, but whether it interacts with omega-3 fatty acids (FAs) from fish oil to affect atherosclerosis has not been determined. The goal was to investigate the impact of a fish oil-enriched diet alone and in combination with ASA on the production of lipid mediators and atherosclerosis. ApoE−/− female mice were fed for 13weeks one of the four following diets: omega-3 FA deficient (OD), omega-3 FA rich (OR) (1.8g omega-3 FAs/kg·diet per day), omega-3 FA rich plus ASA (ORA) (0.1g ASA/kg·diet per day) or an omega-3 FA deficient plus ASA (ODA) with supplement levels equivalent to human doses. Plasma lipids, atherosclerosis, markers of inflammation, hepatic gene expression and aortic lipid mediators were determined. Hepatic omega-3 FAs were markedly higher in OR (9.9-fold) and ORA (7-fold) groups. Mice in both OR and ORA groups had 40% less plasma cholesterol in very low-density lipoprotein-cholesterol and low-density lipoprotein fractions, but aortic plaque area formation was only significantly lower in the ORA group (5.5%) compared to the OD group (2.5%). Plasma PCSK9 protein levels were approximately 70% lower in the OR and ORA groups. Proinflammatory aortic lipid mediators were 50%–70% lower in the ODA group than in the OD group and more than 50% lower in the ORA group. In summary, less aortic plaque lesions and aortic proinflammatory lipid mediators were observed in mice on the fish oil diet plus ASA vs. just the fish oil diet.

Leucine supplementation via drinking water reduces atherosclerotic lesions in apoE null mice.

Recent evidence suggests that the essential amino acid leucine may be involved in systemic cholesterol metabolism. In this study, we investigated the effects of leucine supplementation on the development of atherosclerosis in apoE null mice. ApoE null mice were fed with chow supplemented with leucine (1.5% w/v) in drinking water for 8 week. Aortic atherosclerotic lesions were examined using Oil Red O staining. Plasma lipoprotein-cholesterol levels were measured with fast protein liquid chromatography. Hepatic gene expression was detected using real-time PCR and Western blot analyses. Leucine supplementation resulted in 57.6% reduction of aortic atherosclerotic lesion area in apoE null mice, accompanied by 41.2% decrease of serum LDL-C levels and 40.2% increase of serum HDL-C levels. The body weight, food intake and blood glucose level were not affected by leucine supplementation. Furthermore, leucine supplementation increased the expression of Abcg5 and Abcg8 (that were involved in hepatic cholesterol efflux) by 1.28- and 0.86-fold, respectively, and significantly increased their protein levels. Leucine supplementation also increased the expression of Srebf1, Scd1 and Pgc1b (that were involved in hepatic triglyceride metabolism) by 3.73-, 1.35- and 1.71-fold, respectively. Consequently, leucine supplementation resulted in 51.77% reduction of liver cholesterol content and 2.2-fold increase of liver triglyceride content. Additionally, leucine supplementation did not affect the serum levels of IL-6, IFN-γ, TNF-α, IL-10 and IL-12, but markedly decreased the serum level of MCP-1. Leucine supplementation effectively attenuates atherosclerosis in apoE null mice by improving the plasma lipid profile and reducing systemic inflammation.

NG2 Proteoglycan Ablation Reduces Foam Cell Formation and Atherogenesis via Decreased Low-Density Lipoprotein Retention by Synthetic Smooth Muscle Cells.

Obesity and hyperlipidemia are critical risk factors for atherosclerosis. Because ablation of NG2 proteoglycan in mice leads to hyperlipidemia and obesity, we investigated the impact of NG2 ablation on atherosclerosis in apoE null mice. Immunostaining indicates that NG2 expression in plaque, primarily by synthetic smooth muscle cells, increases during atherogenesis. NG2 ablation unexpectedly results in decreased (30%) plaque development, despite aggravated obesity and hyperlipidemia. Mechanistic studies reveal that NG2-positive plaque synthetic smooth muscle cells in culture can sequester low-density lipoprotein to enhance foam-cell formation, processes in which NG2 itself plays direct roles. In agreement with these observations, low-density lipoprotein retention and lipid accumulation in the NG2/ApoE knockout aorta is 30% less than that seen in the control aorta. These results indicate that synthetic smooth muscle cell-dependent low-density lipoprotein retention and foam cell formation outweigh obesity and hyperlipidemia in promoting mouse atherogenesis. Our study sheds new light on the role of synthetic smooth muscle cells during atherogenesis. Blocking plaque NG2 or altering synthetic smooth muscle cells function may be promising therapeutic strategies for atherosclerosis.

Abstract 626: Vascular Endothelial HSP60 and Von Willebrand Factor Induction Are Both Involved in Promoting Fatty-Streak Formation in ApoE Null Mice

Objectives: This study was designed to determine the murine atherosclerosis in ApoE null mice with inducible expression of human heat shock protein 60 (hHSP60) in vascular endothelium. Background: Autoimmunity to HSP60 may be involved in eliciting early atherosclerotic lesions. Most classical risk factors of atherosclerosis were previously shown in cell culture models to induce HSP60 expression in vascular ECs and in vivo particularly at regions predilected to lesions. However, it has not been demonstrated directly in an animal model whether HSP60 induction in ECs are capable of influencing lesion formation. Methods: We developed ApoE -/- ::Cdh5-CreER T2 ::G-Lox-HSP60 triple Tg mouse model with tamoxifen-induced hHSP60 expression in ECs. Eight week-old triple TG mice were fed by tamoxifen citrate-contained chow for 2 weeks, followed by high fat chow (HF) for additional 4 and 8 weeks before sacrificed for oil red staining for fatty streaks and IHC staining. Results: In tamoxifen-fed triple Tg mouse, vascular EC expression of hHSP60 increased fatty-streak formation and increased the severity of lesions in comparison with uninduced triple Tg or wildtype ApoE mouse. In triple Tg mouse, we found tamoxifen strongly induced HSP60 expression in ECs of the lesions and to a lesser degree in ECs of veins and other arterial regions not predilected to lesions. Concomitant VWF induction at ECs and subendothelial regions was observed at areas with increased HSP60 expression. Conclusions: hHSP60 induction at vascular ECs accelerates fatty-steak formation in ApoE null mice that may involve increasing local VWF expression.

Nutritional B vitamin deficiency alters the expression of key proteins associated with vascular smooth muscle cell proliferation and migration in the aorta of atherosclerotic apolipoprotein E null mice.

Low B vitamin status is linked with human vascular disease. We employed a proteomic and biochemical approach to determine whether nutritional folate deficiency and/or hyperhomocysteinemia altered metabolic processes linked with atherosclerosis in ApoE null mice. Animals were fed either a control fat (C; 4% w/w lard) or a high-fat [HF; 21% w/w lard and cholesterol (0/15% w/w)] diet with different B vitamin compositions for 16weeks. Aorta tissue was prepared and global protein expression, B vitamin, homocysteine and lipoprotein status measured. Changes in the expression of aorta proteins were detected in response to multiple B vitamin deficiency combined with a high-fat diet (P<0.05) and were strongly linked with lipoprotein concentrations measured directly in the aorta adventitia (P<0.001). Pathway analysis revealed treatment effects in the aorta-related primarily to cytoskeletal organisation, smooth muscle cell adhesion and invasiveness (e.g., fibrinogen, moesin, transgelin, vimentin). Combined B vitamin deficiency induced striking quantitative changes in the expression of aorta proteins in atherosclerotic ApoE null mice. Deregulated expression of these proteins is associated with human atherosclerosis. Cellular pathways altered by B vitamin status included cytoskeletal organisation, cell differentiation and migration, oxidative stress and chronic inflammation. These findings provide new insight into the molecular mechanisms through which B vitamin deficiency may accelerate atherosclerosis.

Abstract 15294: Activation of Mac-1 Integrin Prevents G-CSF Mediated Monocyte Mobilization and Atherosclerosis Severity in Hypercholesterolemic Mice

Background: Leukadherins (LA) are a novel family of Mac-1 agonists that increase cell adhesion and prevent leukocyte mobilization and tissue inflammation. This study brings new insights into how leukadherin LA1 protects hypercholesterolemic ApoE-null mice from excessive atherosclerosis development. Hypothesis: Activation of Mac-1 integrin with leukadherin LA1 retains monocytes in medullary and extramedullary centers and therefore, controls high fat diet induced monocytosis and atherosclerosis in ApoE-null mice. Methods and Results: Once daily administration of LA1 (10mg/kg) for 16 weeks significantly reduced atherosclerosis in the entire aorta and the aortic valve of high fat diet fed ApoE-null mice as determined by Sudan IV staining. The LA1 treatment had not effect on body weight or plasma lipid levels though it significantly reduced the number of circulating monocytes (Lin2- CD11c- CD11b+ by FACS). The remaining circulating monocytes in LA1-treated mice displayed low levels of Ly6C, a marker for inflammation. Interestingly, LA1 caused monocyte retention in the bone marrow (BM) and macrophages (F4/80+ by IHC) in the spleen of hypercholesterolemic mice, which account for the low numbers of monocytes seem in the circulation of these mice. On the other hand, the excessive number of BM monocytes didn’t compromise the number of hematopoietic (Lin- Sca+ c-Kit+) or myeloid (Lin- Sca- c-Kit+) progenitor cells. Finally, we assessed the effect of LA1 on systemic inflammatory mediators using multiplex immunoassay. The plasma levels of G-CSF, one of the main monocyte mobilization cytokines capable of promoting atherosclerosis in ApoE-null mice, were found reduced in a half in treated versus control mice. Conclusions: These data demonstrate that Mac-1 activation with LA1 significantly reduces atherosclerosis in hypercholesterolemic ApoE-null by impairing G-CSF mediated monocyte mobilization from medullary and extramedullary centers.

An extract from medical leech improve the function of endothelial cells in vitro and attenuates atherosclerosis in ApoE null mice by reducing macrophages in the lesions

AimMedicinal leech has been widely used as a traditional Chinese medicine in cardiovascular diseases. However, its pharmaceutical effect is not fully revealed. The goal of this study was to determine whether a leech extract has the effect of anti-atherosclerosis in ApoE −/− mice and the mechanism of this effect. Methods and resultsIn vivo experiments: ApoE −/− mice fed on high-cholesterol diet were separated into 5 groups. Control group was administrated with normal water; leech extract of low dose treatment group was given a leech extract of 0.02g/kg/d; leech extract of medium dose treatment group was given a leech extract of 0.1g/kg/d; leech extract of high dose treatment group was given a leech extract of 0.5g/kg/d; simvastatin group was given simvastatin of 10mg/kg/d. Leech extract significantly reduced atherosclerotic lesions in aortic root compared with control group. And the number of macrophage in or around the atherosclerosis plaque is significantly reduced in the leech extract groups compared with control group.In vitro experiments: human endothelial cell line, EA.hy926, was induced with TNF-α to perform endothelial dysfunction. Control group: EA.hy926 cells with no special treatment; TNF-α group: EA.hy926 cells were induced by 10ng/ml TNF-α for 6h; leech extract only group: EA.hy926 cells were treated with 200mg/ml leech extract only; leech extract and TNF-α group: 200mg/ml leech extract was applied before TNF-α induction. Protein and mRNA level were detected in each group, leech extract can decrease the expression of intercellular adhesion factor (ICAM-1) and monocyte chemotactic protein (MCP-1) compared with TNF-α group. Furthermore, it showed less adhesion and migration of THP-1 cells to EA.hy926 cells in the adhesion assay and transwell assay. The NF-κB translation to nucleus was blocked by leech extract in the NF-κB translocation assay. ConclusionsLeech extract could obviously attenuate the area of atherosclerosis lesion in ApoE −/− mice. And this effect is dose dependent. The effect is mainly a result of reduced invasion of monocyte in artery walls by blocking NF-κB translocation.

The Proatherogenic Effect of Chronic Nitric Oxide Synthesis Inhibition in ApoE-Null Mice Is Dependent on the Presence of PPARα

Inhibition of endothelial nitric oxide synthase (eNOS) accelerates atherosclerosis in ApoE-null mice by impairing the balance between angiotensin II (AII) and NO. Our previous data suggested a role for PPARα in the deleterious effect of the renin-angiotensin system (RAS). We tested the hypothesis that ApoE-null mice lacking PPARα (DKO mice) would be resistant to the proatherogenic effect of NOS inhibition. DKO mice fed a Western diet were immune to the 23% worsening in aortic sinus plaque area seen in the ApoE-null animals under 12 weeks of NOS inhibition with a subpressor dose of L-NAME, P = 0.002. This was accompanied by a doubling of reactive oxygen species (ROS-) generating aortic NADPH oxidase activity (a target of AII, which paralleled Nox1 expression) and by a 10-fold excess of the proatherogenic iNOS, P < 0.01. L-NAME also caused a doubling of aortic renin and angiotensinogen mRNA level in the ApoE-null mice but not in the DKO, and it upregulated eNOS in the DKO mice only. These data suggest that, in the ApoE-null mouse, PPARα contributes to the proatherogenic effect of unopposed RAS/AII action induced by L-NAME, an effect which is associated with Nox1 and iNOS induction, and is independent of blood pressure and serum lipids.

17β-Estradiol Suppresses the Macrophage Foam Cell Formation Associated with SOCS3

Evidence from clinical trials and animal experiments has shown that estrogen has anti-atherosclerotic effects when administered to young women or experimental animals. The mechanisms involve the modulation of vascular inflammation, growth factor expression, and oxidative stress injured arteries. However, whether estrogen modulates the foam cell formation in plaque remains unknown. Here, we investigated the effects of 17β-estradiol (E2) on cholesterol efflux in vivo and in vitro. ApoE null mice underwent an ovariectomy at 5(th) week of age and then were treated with E2 or vehicle for the following 8 weeks. Compared with the vehicle-treated mice, the serum total cholesterol level, atherosclerotic plaque size, and lipid deposits were decreased and meanwhile ATP-binding cassette transporter A1 (ABCA1) expression in the plaque was increased in mice with E2 treatment. E2 also increased suppressor of cytokine signaling 3 (SOCS3) expression in the atherosclerotic plaques and in RAW264.7 cells. In vitro, E2 treatment reversed janus kinase/signal transducers and activators of transcription (JAK/STAT)-inhibited ABCA1 expression in RAW264.7 cells but had no effect on ABCA1 expression in SOCS3 knockdown cells. SOCS3 overexpression elevated ABCA1 expression through the inhibition of JAK2/STAT3 phosphorylation. Finally, we also found that E2 enhanced the cholesterol efflux to apoA I in RAW264.7 cells. In summary, E2 reduces atherosclerosis in ApoE null mice associated with upregulating ABCA1 expression and modulating the cholesterol efflux, which are dependent on SOCS3 upregulation. These results provide new insight into the athero-protective effects of estrogen.

Intermedin ameliorates atherosclerosis in apoE null mice by modifying lipid profiles

Intermedin (IMD) is a recently discovered vasodilator peptide. We studied the role of IMD in the pathogenesis of atherosclerosis by investigating the ability of exogenous IMD to alter lipid profiles and ameliorate the development of atherogenic-diet induced atherosclerosis in ApoE−/− mice. Ten of eight-week-old male C57BL/6J mice were as control. Thirty of eight-week-old male ApoE−/− mice were fed with an atherogenic diet for 18 weeks. After feeding atherogenic diet for 12 weeks, the mice were equally and randomly divided into three groups. Normal saline was given in group A and C57BL/6J mice. Intermedin was given by mini osmotic pumps at the dosage of 100ng/kg/h and 500ng/kg/h in group B and group C respectively. After the treatment of IMD for 6 weeks, aortic ultrasonography of group C showed that IMD prevented the progression of atherosclerotic lesions and the increase of wall thickness in the aorta. Oil-red-O staining of the entire aorta and the atherosclerotic aortic root section showed 2 folds decrease atherogenic plaque (p<0.05). Serum lipid profiles were measured, compared with the group A, in group C TC and LDL-C levels were decreased by 86.32% and 89.68%, respectively (both p<0.05), meanwhile, HDL-C level was significantly increased by 74.82% (p<0.05). These data indicate that exogenous administration of IMD could prevent the progression of atherosclerotic plaque. The possible underlying mechanisms may relate to the improvement of lipid profiles.

Low-Dose Calcitriol Decreases Aortic Renin, Blood Pressure, and Atherosclerosis in Apoe-Null Mice

To determine whether low-dose calcitriol attenuates atherosclerosis in apoE-null mice and, if so, through which predominant mechanism. Starting at the age of 6 weeks, mice received intraperitoneal injections of either 0.25 ng/g body weight of calcitriol or the vehicle, every other day for 8 weeks. Calcitriol treatment resulted in 35% reduction of atherosclerosis at the aortic sinus, and in a significant decrease in blood pressure. These effects were possibly mediated by downregulation of the renin-angiotensin system (RAS), as there was a 64% decrease in the aortic level of renin mRNA. None of the other components of the RAS or the prorenin receptor were affected by treatment. Low-dose calcitriol treatment did not modify the plasma level of monocyte chemoattractant protein-1, interferon γ, interleukin-4 and interleukin-10, which were similar in control and treated mice. Likewise, there was no difference in the percentage of splenic Foxp3+ regulatory T cells. Calcitriol treatment resulted in an unfavorable metabolic profile (glucose and lipids), as determined after a limited fast, a difference that disappeared after food was withheld for a longer time. At a relatively low dosage, calcitriol attenuates the development of atherosclerosis in apoE-null mice, most probably by down regulation of RAS, and not through immunomodulation; however, even at this low dose, calcitriol appears to elevate calcium and to have potentially adverse metabolic effects. Exploring the potential antiatherogenic effects of non-calcemic and safer analogues is therefore warranted.

Anti-inflammatory and anti-thrombotic intervention strategies using atorvastatin, clopidogrel and knock-down of CD40L do not modify radiation-induced atherosclerosis in ApoE null mice

Background and purposeWe previously showed that irradiating the carotid arteries of ApoE−/− mice accelerated the development of macrophage-rich, inflammatory and thrombotic atherosclerotic lesions. In this study we investigated the potential of anti-inflammatory (atorvastatin, CD40L knockout) and anti-thrombotic (clopidogrel) intervention strategies to inhibit radiation-induced atherosclerosis. Material and methodsApoE−/− mice were given 0 or 14Gy to the neck and the carotid arteries were harvested at 4 or 28weeks after irradiation. Atorvastatin (15mg/kg/day) or clopidogrel (20mg/kg/day) was given in the chow; control groups received regular chow. Clopidogrel inhibited platelet aggregation by 50%. CD40L−/−/ApoE−/− and ApoE−/− littermates were also given 0 or 14Gy to the neck and the carotid arteries were harvested after 30weeks. ResultsClopidogrel decreased MCP-1 expression in the carotid artery at 4weeks after irradiation. Expression of VCAM-1, ICAM-1, thrombomodulin, tissue factor and eNOS was unchanged in atorvastatin and clopidogrel-treated mice. Neither drug inhibited either age-related or radiation-induced atherosclerosis. Furthermore, loss of the inflammatory mediator CD40L did not influence the development of age-related and radiation-induced atherosclerosis. ConclusionsThe effects of radiation-induced atherosclerosis could not be circumvented by these specific anti-inflammatory and anti-coagulant therapies. This suggests that more effective drug combinations may be required to overcome the radiation stimulus, or that other underlying mechanistic pathways are involved compared to age-related atherosclerosis.

Differential effects of nutritional folic acid deficiency and moderate hyperhomocysteinemia on aortic plaque formation and genome-wide DNA methylation in vascular tissue from ApoE-/- mice

Low folate intake is associated with vascular disease. Causality has been attributed to hyperhomocysteinemia. However, human intervention trials have failed to show the benefit of homocysteine-lowering therapies. Alternatively, low folate may promote vascular disease by deregulating DNA methylation. We investigated whether folate could alter DNA methylation and atherosclerosis in ApoE null mice. Mice were fed one of six diets (n = 20 per group) for 16 weeks. Basal diets were either control (C; 4% lard) or high fat (HF; 21% lard and cholesterol, 0.15%) with different B-vitamin compositions: (1) folic acid and B-vitamin replete, (2) folic acid deficient (−F), (3) folic acid, B6 and B12 deficient (−F−B). −F diets decreased plasma (up to 85%; P < 0.05), whole blood (up to 70%; P < 0.05), and liver folate (up to 65%; P < 0.05) and hepatic SAM/SAH (up to 80%; P < 0.05). −F−B diets reduced plasma (up to 76%; P < 0.05), whole blood (up to 72%; P < 0.05), and liver B12 (up to 39%; P < 0.05) and hepatic SAM/SAH (up to 90%; P < 0.05). −F increased homocysteine 2-fold, while −F−B increased homocysteine 3.6- and 6.8-fold in the C and HF groups (P < 0.05). Plaque formation was increased 2-fold (P < 0.0001) in mice fed a HF diet. Feeding a HF–F diet increased lesion formation by 17% (P < 0.05). There was no change in 5-methyldeoxycytidine in liver or vascular tissue (aorta, periadventitial tissue and heart). These data suggest that atherogenesis is not associated with genome-wide epigenetic changes in this animal model.

Oral exposure to acrolein exacerbates atherosclerosis in apoE-null mice

BackgroundAcrolein is a dietary aldehyde that is present in high concentrations in alcoholic beverages and foods including cheese, donuts and coffee. It is also abundant in tobacco smoke, automobile exhaust and industrial waste and is generated in vivo during inflammation and oxidative stress. ObjectivesThe goal of this study was to examine the effects of dietary acrolein on atherosclerosis. MethodsEight-week-old male apoE-null mice were gavage-fed acrolein (2.5mg/kg/day) for 8 weeks. Atherosclerotic lesion formation and composition and plasma lipids and platelet factor 4 (PF4) levels were measured. Effects of acrolein and PF4 on endothelial cell function was measured in vitro. ResultsAcrolein feeding increased the concentration of cholesterol in the plasma. NMR analysis of the lipoproteins showed that acrolein feeding increased the abundance of small and medium VLDL particles. Acrolein feeding also increased atherosclerotic lesion formation in the aortic valve and the aortic arch. Immunohistochemical analysis showed increased macrophage accumulation in the lesions of acrolein-fed mice. Plasma PF4 levels and accumulation of PF4 in atherosclerotic lesions was increased in the acrolein-fed mice. Incubation of endothelial cells with the plasma of acrolein-fed mice augmented transmigration of monocytic cells, which was abolished by anti-PF4 antibody treatment. ConclusionsDietary exposure to acrolein exacerbates atherosclerosis in apoE-null mice. Consumption of foods and beverages rich in unsaturated aldehydes such as acrolein may be a contributing factor to the progression of atherosclerotic lesions.

NO-Donating Aspirin and Aspirin Partially Inhibit Age-Related Atherosclerosis but Not Radiation-Induced Atherosclerosis in ApoE Null Mice

BackgroundWe previously showed that irradiation to the carotid arteries of ApoE−/− mice accelerated the development of macrophage-rich, inflammatory atherosclerotic lesions, prone to intra-plaque hemorrhage. In this study we investigated the potential of anti-inflammatory and anti-coagulant intervention strategies to inhibit age-related and radiation-induced atherosclerosis.Methodology/Principal FindingsApoE−/− mice were given 0 or 14 Gy to the neck and the carotid arteries and aortic arches were harvested at 4 or 30 weeks after irradiation. Nitric oxide releasing aspirin (NCX 4016, 60 mg/kg/day) or aspirin (ASA, 30 or 300 mg/kg/day) were given continuously in the chow. High dose ASA effectively blocked platelet aggregation, while the low dose ASA or NCX 4016 had no significant effect on platelet aggregation. High dose ASA, but not NCX 4016, inhibited endothelial cell expression of VCAM-1 and thrombomodulin in the carotid arteries at 4 weeks after irradiation; eNOS and ICAM-1 levels were unchanged. After 30 weeks of follow-up, NCX 4016 significantly reduced the total number of lesions and the number of initial macrophage-rich lesions in the carotid arteries of unirradiated mice, but these effects were not seen in the brachiocephalic artery of the aortic arch (BCA). In contrast, high dose ASA lead to a decrease in the number of initial lesions in the BCA, but not in the carotid artery. Both high dose ASA and NCX 4016 reduced the collagen content of advanced lesions and increased the total plaque burden in the BCA of unirradiated mice. At 30 weeks after irradiation, neither NCX 4016 nor ASA significantly influenced the number or distribution of lesions, but high dose ASA lead to formation of collagen-rich “stable” advanced lesions in carotid arteries. The total plaque area of the irradiated BCA was increased after ASA, but the plaque burden was very low compared with the carotid artery.Conclusions/SignificanceThe development and characteristics of radiation-induced atherosclerosis varied between different arteries but could not be circumvented by anti-inflammatory and anti-coagulant therapies. This implicates other underlying mechanistic pathways compared to age-related atherosclerosis.

Activation of the ROCK1 Branch of the Transforming Growth Factor-β Pathway Contributes to RAGE-Dependent Acceleration of Atherosclerosis in Diabetic ApoE-Null Mice

The multiligand RAGE (receptor for advanced glycation end products) contributes to atherosclerosis in apolipoprotein (Apo)E-null mice. To delineate the specific mechanisms by which RAGE accelerated atherosclerosis, we performed Affymetrix gene expression arrays on aortas of nondiabetic and diabetic ApoE-null mice expressing RAGE or devoid of RAGE at nine weeks of age, as this reflected a time point at which frank atherosclerotic lesions were not yet present, but that we would be able to identify the genes likely involved in diabetes- and RAGE-dependent atherogenesis. We report that there is very little overlap of the genes that are differentially expressed both in the onset of diabetes in ApoE-null mice, and in the effect of RAGE deletion in diabetic ApoE-null mice. Pathway-Express analysis revealed that the transforming growth factor-beta pathway and focal adhesion pathways might be expected to play a significant role in both the mechanism by which diabetes facilitates the formation of atherosclerotic plaques in ApoE-null mice, and the mechanism by which deletion of RAGE ameliorates this effect. Quantitative polymerase chain reaction studies, Western blotting, and confocal microscopy in aortic tissue and in primary cultures of murine aortic smooth muscle cells supported these findings. Taken together, our work suggests that RAGE-dependent acceleration of atherosclerosis in ApoE-null mice is dependent, at least in part, on the action of the ROCK1 (rho-associated protein kinase 1) branch of the transforming growth factor-beta pathway.

Insulin‐like growth factor I (IGF‐1) downregulates lipoprotein lipase and suppresses atherosclerotic foam cell formation in vivo and in vitro

We have shown that IGF‐1 decreases atherosclerosis in ApoE‐null mice. Lipoprotein lipase (LPL) increases the uptake of OxLDL by macrophages (MΦ), promoting foam cell formation and atherosclerosis development. To determine a potential effect of IGF‐1 on LPL and foam cell formation, we infused ApoE‐null mice with 1.5 mg/kg IGF‐1 or saline for 12w. IGF‐1 reduced aortic LPL mRNA levels by 31% (RT‐PCR) and serum LPL activity by 66% (fluorescence assay). This effect correlated with a 27% reduction in Oil Red‐positive lesion area and a 36% decrease in plaque MΦ (immunostaining with Mac‐3 a/b) suggesting that IGF‐1 reduced MΦ‐derived foam cell formation.Human blood monocyte‐derived MΦ were treated with 80 ug/ml OxLDL for 48h to stimulate formation of Oil Red‐positive "foam cells". OxLDL increased MΦ LPL mRNA levels and LPL activity &gt;5‐fold. Pre‐treatment with IGF‐1 (25 ng/ml, 24h) reversed OxLDL‐induced upregulation of LPL activity by 52% and decreased lipid uptake by 88%. Furthermore, adenovirus‐mediated overexpression of IGF1 receptor in MΦ prevented lipid uptake by 82% vs. control Ad‐GFP‐infected MΦ. Conversely, addition of exogenous LPL (5 ug/ml) stimulated DiI‐OxLDL binding by MΦ by 2.3‐fold and increased lipid uptake by 1.9‐fold (Oil Red‐staining). Liver X receptor (LXR) is a nuclear transcription factor regulating MΦ LPL expression. The LXR agonist 22R‐oxycholesterol (50 uM, 16h) increased LPL activity in MΦ &gt;2‐fold and IGF‐1 reversed this effect by 65%. In summary, our data indicate that IGF‐1 downregulates LPL in vivo and in vitro potentially via a LXR‐dependent mechanism and inhibits foam cell formation. This is the first report of an effect of IGF‐1 on cellular lipid internalization and these findings have major relevance for the understanding of mechanisms whereby IGF‐1 reduces atherosclerosis.