Lesions In apoE-deficient Mice Research Articles

TAT-beclin1 treatment accelerates the development of atherosclerotic lesions in ApoE-deficient mice.

The importance of autophagy in atherosclerosis has garnered significant attention regarding the potential applications of autophagy inducers. However, the impact of TAT-Beclin1, a peptide inducer of autophagy, on the development of atherosclerotic plaques remains unclear. Single-cell omics analysis indicates a notable reduction in GAPR1 levels within fibroblasts, stromal cells, and macrophages during atherosclerosis. Tat-beclin1 (T-B), an autophagy-inducing peptide derived from Beclin1, could selectively bind to GAPR1, relieving its inhibition on Beclin1 and thereby augmenting autophagosome formation. To investigate its impact on atherosclerosic plaque progression, we established the ApoE-/- mouse model of carotid atherosclerotic plaques. Surprisingly, intravenous administration of Tat-beclin1 dramatically accelerated the development of carotid artery plaques. Immunofluorescence analysis suggested that macrophage aggregation and autophagosome formation within atherosclerotic plaques were significantly increased upon T-B treatment. However, immunofluorescence and transmission electron microscopy (TEM) analysis revealed a reduction in autophagy flux through lysosomes. Invitro, the interaction between T-B and GAPR1 was confirmed in RAW264.7 cells, resulting in the increased accumulation of p62/SQSTM1 and LC3-II in the presence of ox-LDL. Additionally, T-B treatment elevated the protein levels of p62/SQSTM1, LC3-II, and cleaved caspase 1, along with the secretion of IL-1β in response to ox-LDL exposure. In summary, our study underscores that T-B treatment amplifies abnormal autophagy and inflammation, consequently exacerbating atherosclerotic plaque development in ApoE-/- mice.

Knockdown of Bcl-3 alleviates psoriasis and dyslipidemia comorbidity by regulating Akt pathway.

Psoriasis is considered as an inflammatory skin disease accompanied by dyslipidemia comorbidity. B-cell leukemia-3 (Bcl-3) belongs to IκB (inhibitor of nuclear factor kappa B [NF-κB]) family, and regulates inflammatory response through associating with NF-κB. The role of Bcl-3 in psoriasis was investigated in this study. Apolipoprotein E (ApoE)-deficient mice were treated with imiquimod to induce psoriasis and dyslipidemia. Mice were injected intradermally in the back with lentiviral particles encoding Bcl-3 small hairpin RNA (shRNA). Hematoxylin and eosin were used to detect pathological characteristics. The blood lipid levels were determined by automatic biochemical analyzer, and inflammation was assessed by enzyme-linked-immunosorbent serologic assay and real-time quantitative reverse transcription polymerase chain reaction. Bcl-3 was elevated in imiquimod-induced ApoE-deficient mice. Injection with lentiviral particles encoding Bcl-3 shRNA reduced Psoriasis area and severity index (PASI) score in ApoE-deficient psoriatic mice. Knockdown of Bcl-3 also ameliorated imiquimod-induced psoriasiform skin lesions in ApoE-deficient mice. Moreover, loss of Bcl-3 enhanced expression of loricrin, an epidermal barrier protein, reduced expression of proliferating cell nuclear antigen (PCNA) and lectin-like oxidized LDL (oxLDL) receptor-1 (LOX-1) in imiquimod-induced ApoE-deficient mice. The enhanced levels of blood lipid in ApoE-deficient mice were attenuated by silencing of Bcl-3 with increase of high-density lipoprotein, and reduction of total cholesterol, triglycerides, and low-density lipoprotein cholesterol. Knockdown of Bcl-3 attenuated imiquimod-induced decrease of transforming growth factor beta (TGF-β), and increase of Interleukin (IL)-17A, IL-23, IL-6, and tumor necrosis factor-α (TNF-α) in ApoE-deficient mice. Protein expression of phospho-Akt (p-Akt) and p-GSK3β in ApoE-deficient psoriatic mice was decreased by silencing of Bcl-3. Loss of Bcl-3 exerted anti-inflammatory effect on psoriasis and dyslipidemia comorbidity through inactivation of Akt/GSK3β pathway.

Crude α-Mangostin Suppresses the Development of Atherosclerotic Lesions in Apoe-Deficient Mice by a Possible M2 Macrophage-Mediated Mechanism.

Lifestyle choices play a significant role in the etiology of atherosclerosis. Male Apoe−/− mice that develop spontaneous atherosclerotic lesions were fed 0%, 0.3%, and 0.4% mangosteen extracts, composed largely of α-mangostin (MG), for 17 weeks. Body weight gains were significantly decreased in both MG-treated groups compared to the control, but the general condition remained good throughout the study. The levels of total cholesterol (decreased very-low-density lipoprotein in lipoprotein profile) and triglycerides decreased significantly in the MG-treated mice in conjunction with decreased hepatic HMG-CoA synthase and Fatty acid transporter. Additionally, increased serum lipoprotein lipase activity and histopathology further showed a significant reduction in atherosclerotic lesions at both levels of MG exposure. Real-time PCR analysis for macrophage indicators showed a significant elevation in the levels of Cd163, an M2 macrophage marker, in the lesions of mice receiving 0.4% MG. However, the levels of Nos2, associated with M1 macrophages, showed no change. In addition, quantitative immunohistochemical analysis of macrophage subtypes showed a tendency for increased M2 populations (CD68+/CD163+) in the lesions of mice given 0.4% MG. In further analysis of the cytokine-polarizing macrophage subtypes, the levels of Interleukin13 (Il13), associated with M2 polarization, were significantly elevated in lesions exposed to 0.4% MG. Thus, MG could suppress the development of atherosclerosis in Apoe−/− mice, possibly through an M2 macrophage-mediated mechanism.

LongShengZhi Capsule Reduces Established Atherosclerotic Lesions in apoE-Deficient Mice by Ameliorating Hepatic Lipid Metabolism and Inhibiting Inflammation.

Disorders of lipid metabolism and inflammation play an important role in atherosclerosis. LongShengZhi (LSZ) capsule, a Chinese herbal medicine, has been used for treatment of patients with vascular diseases for many years. In this article, we determined the effect of LSZ on the progression of established atherosclerotic lesions in apoE-deficient (apoE) mice. ApoE mice were prefed high-fat diet (HFD) for 8 weeks to induce atherosclerosis, then started with LSZ treatment contained in HFD for 10 weeks. Although LSZ had little effect on HFD-induced hypercholesterolemia, it substantially reduced en face and sinus aortic lesions. The reduction of lesions was associated with reduced macrophage/foam cell accumulation by activating ABCA1/ABCG1 expression. LSZ maintained the integrity of arterial wall by increasing collagen or smooth muscle cell content and inhibiting cell apoptosis. LSZ also attenuated HFD-induced fatty liver by down-regulating expression of lipogenic and cholesterol synthetic genes while activating expression of triglyceride catabolism genes. Moreover, LSZ demonstrated potent anti-inflammatory effects. In vivo, LSZ reduced serum TNF-α levels, infiltration of neutrophils, Kupffer cells, and expression of inflammatory cytokines in the liver. In vitro, it inhibited lipopolysaccharide or palmitate-induced expression of inflammatory cytokines in macrophages. Therefore, LSZ reduces atherosclerosis by ameliorating hepatic lipid metabolism and inhibiting inflammation.

Emerging Roles of Tumor Necrosis Factor-Stimulated Gene-6 in the Pathophysiology and Treatment of Atherosclerosis.

Tumor necrosis factor-stimulated gene-6 (TSG-6) is a 35-kDa glycoprotein that has been shown to exert anti-inflammatory effects in experimental models of arthritis, acute myocardial infarction, and acute cerebral infarction. Several lines of evidence have shed light on the pathophysiological roles of TSG-6 in atherosclerosis. TSG-6 suppresses inflammatory responses of endothelial cells, neutrophils, and macrophages as well as macrophage foam cell formation and vascular smooth muscle cell (VSMC) migration and proliferation. Exogenous TSG-6 infusion and endogenous TSG-6 attenuation with a neutralizing antibody for four weeks retards and accelerates, respectively, the development of aortic atherosclerotic lesions in ApoE-deficient mice. TSG-6 also decreases the macrophage/VSMC ratio (a marker of plaque instability) and promotes collagen fibers in atheromatous plaques. In patients with coronary artery disease (CAD), plasma TSG-6 levels are increased and TSG-6 is abundantly expressed in the fibrous cap within coronary atheromatous plaques, indicating that TSG-6 increases to counteract the progression of atherosclerosis and stabilize the plaque. These findings indicate that endogenous TSG-6 enhancement and exogenous TSG-6 replacement treatments are expected to emerge as new lines of therapy against atherosclerosis and related CAD. Therefore, this review provides support for the clinical utility of TSG-6 in the diagnosis and treatment of atherosclerotic cardiovascular diseases.

The effect of tocopheryl phosphates (TPM) on the development of atherosclerosis in apolipoprotein‐E deficient mice

α-Tocopheryl phosphate (TP) is a naturally occurring form of vitamin E found in the body. In the present study we compared the ability of an α-TP mixture (TPM) against a standard vitamin E supplement, α-tocopherol acetate (TA) on the development of atherosclerotic lesions in ApoE-deficient mice. Mice were maintained on either a normal chow diet for 24weeks (Normal Diet), vs a group in which the final 8weeks of the 24-week period mice were placed on a high fat (21%), high cholesterol (0.15%) challenge diet (HFHC), to exacerbate atherosclerotic lesion development.. The difference in these two control groups established the extent of the diet-induced atherosclerotic lesion development. Mice in the various treatment groups received either TA (300mg/kg chow) or TPM (6.7-200mg/kg chow) for 24weeks, with TPM treatment resulting in dose-dependent significant reductions in atherosclerotic lesion formation and plasma levels of pro-inflammatory cytokines. TA-treated mice, with the tocopherol equivalent TPM dose (200mg/kg chow), showed no significant reduction in plasma lipid levels or evidence for aortic lesion regression. At this TPM equivalent TA dose, a 44% reduction in aortic lesion formation was observed. In addition, these TPM treated mice, also showed a marked reduction in aortic superoxide formation and decreased circulating plasma levels of known pro-inflammatory markers IL-6, MCP-1, IL-1β, IFN-γ and TNF-α. These findings indicate that TPM treatment slows progression of atherosclerotic lesions in ApoE-deficient mice with this effect potentially involving reduced oxidative stress and decreased inflammation.

Isolated Conglutin γ from Lupin, but not Phytate, Lowers Serum Cholesterol Without Influencing Vascular Lesion Development in the ApoE-deficient Mouse Model.

Conglutin γ and phytate are considered as potential biofunctional compounds of lupin protein isolate, but their impact on vascular health is unknown. This study aimed to investigate the effect of conglutin γ and phytate, respectively, on circulating levels of sterols, markers of cholesterol biosynthesis and minerals, and on the development and progression of aortic lesions in apoE-deficient mice. To this end, mice were fed a western diet with either casein (200 g/kg; served as a control), conglutin γ from L. angustifolius (200 g/kg) or casein (200 g/kg) supplemented with phytate (5 g/kg) for 16 weeks. Here we found that conglutin γ but not phytate was capable of reducing the circulating concentration of cholesterol. Plasma levels of desmosterol and lathosterol as markers of the cholesterol synthesis were not affected, and 7-dehydrocholesterol was even higher in mice fed conglutin γ than in mice fed casein or casein + phytate. All mice developed pronounced aortic lesions, but histological characterization of plaque area and composition showed no differences between the three groups of mice. Conclusively, conglutin γ exerts cholesterol-lowering effects but appears to have no anti-atherosclerotic properties in the apoE-deficient mice. Phytate neither affected plasma cholesterol nor aortic lesion development.

Inhibition of ERK1/2 and activation of LXR synergistically reduce atherosclerotic lesions in ApoE-deficient mice.

Activation of liver X receptor (LXR) inhibits atherosclerosis but induces hypertriglyceridemia. In vitro, it has been shown that mitogen-activated protein kinase kinase 1/2 (MEK1/2) inhibitor synergizes LXR ligand-induced macrophage ABCA1 expression and cholesterol efflux. In this study, we determined whether MEK1/2 (U0126) and LXR ligand (T0901317) can have a synergistic effect on the reduction of atherosclerosis while eliminating LXR ligand-induced fatty livers and hypertriglyceridemia. We also set out to identify the cellular mechanisms of the actions. Wild-type mice were used to determine the effect of U0126 on a high-fat diet or high-fat diet plus T0901317-induced transient dyslipidemia and liver injury. ApoE deficient (apoE(-/-)) mice or mice with advanced lesions were used to determine the effect of the combination of T0901317 and U0126 on atherosclerosis and hypertriglyceridemia. We found that U0126 protected animals against T0901317-induced transient or long-term hepatic lipid accumulation, liver injury, and hypertriglyceridemia. Meanwhile, the combination of T0901317 and U0126 inhibited the development of atherosclerosis in a synergistic manner and reduced advanced lesions. Mechanistically, in addition to synergistic induction of macrophage ABCA1 expression, the combination of U0126 and T0901317 maintained arterial wall integrity, inhibited macrophage accumulation in aortas and formation of macrophages/foam cells, and activated reverse cholesterol transport. The inhibition of T0901317-induced lipid accumulation by the combined U0126 might be attributed to inactivation of lipogenesis and activation of lipolysis/fatty acid oxidation pathways. Our study suggests that the combination of mitogen-activated protein kinase kinase 1/2 inhibitor and LXR ligand can function as a novel therapy to synergistically reduce atherosclerosis while eliminating LXR-induced deleterious effects.

Effect of Methyl-CpG binding domain protein 2 (MBD2) on AMD-like lesions in ApoE-deficient mice.

The role of methyl-CpG binding domain protein 2 (MBD2) in an ApoE-deficient mouse model of age-related macular degeneration (AMD) was investigated. Eight-week-old Mbd2/ApoE double deficient (Mbd2(-/-) ApoE(-/-)) mice (n=12, 24 eyes, experimental group) and MBD2 (wt) ApoE(-/-) mice (n=12, 24 eyes, control group) were fed on Western-type diet for 4 months. The mice were sacrificed, and total serum cholesterol levels were analyzed and Bruch's membrane (BM) of the eyes was removed for ultrastructural observation by transmission electron microscopy. Moreover, intercellular adhesion molecule 1 (ICAM-1) immunoreactivities were evaluated by fluorescence microscopy in sections of the eyes in both groups for further understanding the function mechanism of MBD2. There was no significant difference in the total serum cholesterol levels between control group and experimental group (P>0.05). Transmission electron microscopy revealed that AMD-like lesions, various vacuoles accumulated on BM, notable outer collagenous layer deposits and dilated basal infoldings of retinal pigment epithelium (RPE) were seen in both groups, and the BM in control group was significantly thickened as compared with experimental group (P<0.05). Fluorescence micrographs exhibited the expression of ICAM-1 in choroid was higher in control group than in experimental group. We are led to conclude that MBD2 gene knockout may lead to accumulation of more deposits on the BM and influence the pathogenesis of AMD via triggering endothelial activation and inflammatory response in choroid, improving microcirculation, and reducing lipid deposition so as to inhibit the development of AMD-like lesions. Our study helps to provide a new therapeutic approach for the clinical treatment of AMD.

Abstract 551: The Dual Effect of Cigarette Smoke on Macrophage Abca1-dependent Cholesterol Efflux and Protease Production Leads to Decreased Collagen and Increased Necrosis in Plaques of ApoE Deficient Mice

Epidemiological evidence links smoking to an increase in the incidence and severity of cardiovascular disease. However, the molecular mechanisms responsible for susceptibility are unknown. The accumulation of lipids in macrophages induces an inflammatory response, with secretion of cytokines and proteases, and leads to necrosis and loss of collagen content within atherosclerotic lesions. Therefore, the effect of cigarette smoke on lipids in the atherosclerotic process and consequences was examined. Initial studies revealed that cigarette smoke attenuated cholesterol efflux. Subsequently, the end result of cigarette smoke exposure on atherosclerotic lesions in ApoE deficient mice demonstrated a significant increase in necrosis along with a dramatic decrease in the collagen content of lesions in ApoE deficient mice exposed to smoke for 20 weeks. Cigarette smoke extract (CSE) impaired the cholesterol efflux ability for ApoAI and correlated with ABCA1 loss and increased MMPs (9, 12, 13, in human THP-1 cells additionally MMP1 is increased), TLR4/Myd88 and TNFα expression in mouse bone marrow derived macrophages (BMdM) in vitro and in vivo in peritoneal macrophages elicited after 5 days of smoke exposure. Furthermore, by increasing ABCA1 expression with LXR agonist treatment the CSE-induced up regulation of MMPs (MMP-9 and 13) and TNFα was inhibited signifying a correlation between the cigarette smoke induced loss of ABC transporters and MMP induction. Moreover, BMDMs isolated from Cre-LysM-ABCA1 deficient mice displayed an increase in mRNA expression of MMPs (9, 12, 13) at a basal level, which was appreciably augmented with CSE as compared to control macrophages. The LXR induced decrease in MMPs and TNFα expression as well as decreased MMP-9 activity in macrophages was confirmed to be ABCA1-dependent since ABCA1 KO macrophages exposed to CSE did not exhibit this response. These findings establish that the effect of cigarette smoke on macrophage ABCA1-dependent cholesterol efflux impairment leads to both an increase in proteases and inflammatory cytokines and this combination of events is likely synergistic in ultimately generating a more vulnerable plaque through the increase in plaque necrosis and a decrease in collagen content.

Spirulina platensis and phycocyanobilin activate atheroprotective heme oxygenase-1: a possible implication for atherogenesis

Spirulina platensis, a water blue-green alga, has been associated with potent biological effects, which might have important relevance in atheroprotection. We investigated whether S. platensis or phycocyanobilin (PCB), its tetrapyrrolic chromophore, can activate atheroprotective heme oxygenase-1 (Hmox1), a key enzyme in the heme catabolic pathway responsible for generation of a potent antioxidant bilirubin, in endothelial cells and in a mouse model of atherosclerosis. In vitro experiments were performed on EA.hy926 endothelial cells exposed to extracts of S. platensis or PCB. In vivo studies were performed on ApoE-deficient mice fed a cholesterol diet and S. platensis. The effect of these treatments on Hmox1, as well as other markers of oxidative stress and endothelial dysfunction, was then investigated. Both S. platensis and PCB markedly upregulated Hmox1 in vitro, and a substantial overexpression of Hmox1 was found in aortic atherosclerotic lesions of ApoE-deficient mice fed S. platensis. In addition, S. platensis treatment led to a significant increase in Hmox1 promoter activity in the spleens of Hmox-luc transgenic mice. Furthermore, both S. platensis and PCB were able to modulate important markers of oxidative stress and endothelial dysfunction, such as eNOS, p22 NADPH oxidase subunit, and/or VCAM-1. Both S. platensis and PCB activate atheroprotective HMOX1 in endothelial cells and S. platensis increased the expression of Hmox1 in aortic atherosclerotic lesions in ApoE-deficient mice, and also in Hmox-luc transgenic mice beyond the lipid lowering effect. Therefore, activation of HMOX1 and the heme catabolic pathway may represent an important mechanism of this food supplement for the reduction of atherosclerotic disease.

1014 Regression of atherosclerosis in apolipoprotein-E deficient mice is feasible using high-dose angiotensin receptor blocker

Objectives: Clinical studies have suggested that renin-angiotensin inhibitors are effective for the prevention of atherosclerosis progression, but the results for regression of established lesions are equivocal. The aim of this study was to examine the effects of different doses of the angiotensin receptor blocker (ARB) candesartan on regression of atherosclerosis and lipid-induced nephropathy in apolipoprotein E (apoE)-deficient spontaneously hyperlipidemic (SHL) mice. Methods and results: Male SHL were given an atherogenic diet together with salt loading to induce atherosclerosis. The mice were then treated with various doses of candesartan (0-50 mg/kg/d) for 12 weeks. Treatment with high-dose ARB caused clear regression of atherosclerotic plaques in the aorta, which was not observed with normal-dose ARB. Biglycan and ACAT1 expression were significantly decreased, and aortic free cholesterol:cholesterol ester ratios were increased in these mice. Treatment of cultured THP-1 macrophages in vitro with candesartan resulted in a similar decrease in ACAT1 expression. In the kidney, glomerular lipid accumulation, mesangial expansion, and albuminuria were significantly regressed after the treatment with high-dose ARB, while biglycan and ACAT1 expressions were decreased. Conclusion: These results suggest that regression of established atherosclerosis lesions in ApoE-deficient mice is feasible using high-dose ARB, by mechanisms involving (i) a decrease in the lipid-retaining proteoglycan biglycan, and (ii) suppression of ACAT1 expression resulting in increased free cholesterol for lipid release.

OxLDL-targeted iron oxide nanoparticles for in vivo MRI detection of perivascular carotid collar induced atherosclerotic lesions in ApoE-deficient mice

Atherosclerotic disease is a leading cause of morbidity and mortality in developed countries, and oxidized LDL (OxLDL) plays a key role in the formation, rupture, and subsequent thrombus formation in atherosclerotic plaques. In the current study, anti-mouse OxLDL polyclonal antibody and nonspecific IgG antibody were conjugated to polyethylene glycol-coated ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, and a carotid perivascular collar model in apolipoprotein E-deficient mice was imaged at 7.0 Tesla MRI before contrast administration and at 8 h and 24 h after injection of 30 mg Fe/kg. The results showed MRI signal loss in the carotid atherosclerotic lesions after administration of targeted anti-OxLDL-USPIO at 8 h and 24 h, which is consistent with the presence of the nanoparticles in the lesions. Immunohistochemistry confirmed the colocalization of the OxLDL/macrophages and iron oxide nanoparticles. The nonspecific IgG-USPIO, unconjugated USPIO nanoparticles, and competitive inhibition groups had limited signal changes (p < 0.05). This report shows that anti-OxLDL-USPIO nanoparticles can be used to directly detect OxLDL and image atherosclerotic lesions within 24 h of nanoparticle administration and suggests a strategy for the therapeutic evaluation of atherosclerotic plaques in vivo.

Implantation of a Carotid Cuff for Triggering Shear-stress Induced Atherosclerosis in Mice

It is widely accepted that alterations in vascular shear stress trigger the expression of inflammatory genes in endothelial cells and thereby induce atherosclerosis (reviewed in 1 and 2). The role of shear stress has been extensively studied in vitro investigating the influence of flow dynamics on cultured endothelial cells 1,3,4 and in vivo in larger animals and humans 1,5,6,7,8. However, highly reproducible small animal models allowing systematic investigation of the influence of shear stress on plaque development are rare. Recently, Nam et al. 9 introduced a mouse model in which the ligation of branches of the carotid artery creates a region of low and oscillatory flow. Although this model causes endothelial dysfunction and rapid formation of atherosclerotic lesions in hyperlipidemic mice, it cannot be excluded that the observed inflammatory response is, at least in part, a consequence of endothelial and/or vessel damage due to ligation. In order to avoid such limitations, a shear stress modifying cuff has been developed based upon calculated fluid dynamics, whose cone shaped inner lumen was selected to create defined regions of low, high and oscillatory shear stress within the common carotid artery 10. By applying this model in Apolipoprotein E (ApoE) knockout mice fed a high cholesterol western type diet, vascular lesions develop upstream and downstream from the cuff. Their phenotype is correlated with the regional flow dynamics 11 as confirmed by in vivo Magnetic Resonance Imaging (MRI) 12: Low and laminar shear stress upstream of the cuff causes the formation of extensive plaques of a more vulnerable phenotype, whereas oscillatory shear stress downstream of the cuff induces stable atherosclerotic lesions 11. In those regions of high shear stress and high laminar flow within the cuff, typically no atherosclerotic plaques are observed. In conclusion, the shear stress-modifying cuff procedure is a reliable surgical approach to produce phenotypically different atherosclerotic lesions in ApoE-deficient mice.

Implantation of a Carotid Cuff for Triggering Shear-stress Induced Atherosclerosis in Mice

It is widely accepted that alterations in vascular shear stress trigger the expression of inflammatory genes in endothelial cells and thereby induce atherosclerosis (reviewed in (1) and (2)). The role of shear stress has been extensively studied in vitro investigating the influence of flow dynamics on cultured endothelial cells and in vivo in larger animals and humans. However, highly reproducible small animal models allowing systematic investigation of the influence of shear stress on plaque development are rare. Recently, Nam et al. introduced a mouse model in which the ligation of branches of the carotid artery creates a region of low and oscillatory flow. Although this model causes endothelial dysfunction and rapid formation of atherosclerotic lesions in hyperlipidemic mice, it cannot be excluded that the observed inflammatory response is, at least in part, a consequence of endothelial and/or vessel damage due to ligation. In order to avoid such limitations, a shear stress modifying cuff has been developed based upon calculated fluid dynamics, whose cone shaped inner lumen was selected to create defined regions of low, high and oscillatory shear stress within the common carotid artery. By applying this model in Apolipoprotein E (ApoE) knockout mice fed a high cholesterol western type diet, vascular lesions develop upstream and downstream from the cuff. Their phenotype is correlated with the regional flow dynamics as confirmed by in vivo Magnetic Resonance Imaging (MRI): Low and laminar shear stress upstream of the cuff causes the formation of extensive plaques of a more vulnerable phenotype, whereas oscillatory shear stress downstream of the cuff induces stable atherosclerotic lesions. In those regions of high shear stress and high laminar flow within the cuff, typically no atherosclerotic plaques are observed. In conclusion, the shear stress-modifying cuff procedure is a reliable surgical approach to produce phenotypically different atherosclerotic lesions in ApoE-deficient mice.

Regression of Atherosclerosis in Apolipoprotein E-Deficient Mice is Feasible Using High-Dose Angiotensin Receptor Blocker, Candesartan

Clinical studies have suggested that renin-angiotensin inhibitors are effective for the prevention of atherosclerosis progression, but the results for the regression of established lesions are equivocal. The aim of this study was to examine the effects of different doses of the angiotensin receptor blocker (ARB) candesartan on the regression of atherosclerosis and lipid-induced nephropathy in apolipoprotein E (apoE)-deficient spontaneously hyperlipidemic (SHL) mice. Male SHL were given an atherogenic diet together with salt loading to induce atherosclerosis. The mice were then treated with various doses of candesartan (0-50 mg/kg/d) for 12 weeks. Treatment with high-dose candesartan caused clear regression of atherosclerotic plaques in the aorta, which was not observed with normal-dose candesartan. Biglycan and ACAT1 expression were significantly decreased, and aortic free cholesterol: cholesterol ester ratios were increased in these mice. Treatment of cultured THP-1 macrophages in vitro with candesartan resulted in a similar decrease in ACAT1 expression. In the kidney, glomerular lipid accumulation, mesangial expansion, and albuminuria were significantly regressed after treatment with high-dose candesartan, while biglycan and ACAT1 expressions were decreased. These results suggest that regression of established atherosclerosis lesions in ApoE-deficient mice is feasible using high-dose candesartan, by mechanisms involving (i) a decrease in the lipid-retaining proteoglycan biglycan, and (ii) suppression of ACAT1 expression resulting in increased free cholesterol for lipid release.

Splenectomy Increases Atherosclerotic Lesions in Apolipoprotein E Deficient Mice

Atherosclerosis is an inflammatory immune disease associated with lipid accumulation in the intima layer of arteries. The spleen plays an important immune function, but its influence in development of atherosclerosis remains unclear. Evaluation of the role of the spleen in atherosclerosis is justified due to the high frequency of total splenectomies. In this work, the effect of splenectomy on the development of atherosclerosis in apolipoprotein E (ApoE) deficient mice was investigated. ApoE deficient mice were divided into a sham-operated control group (CT) and a splenectomized group (SP). Thirty days after surgery, animals were fed a high fat western diet. After 8 wk, mice were euthanized and their blood, heart, and aorta were subjected to analysis. Atherosclerotic lesion areas in the aortic root were stained with hematoxylin-eosin and quantified by morphometry. The atherosclerotic lesions in the thoracic and abdominal portions of aorta were determined by assessing the percentage of the luminal surface area stained by Sudan IV. Total serum cholesterol and anti-oxidized LDL antibodies were measured. Levels of total serum cholesterol did not vary significantly after splenectomy. Anti-oxidized LDL IgG antibodies were similar between groups. However, compared with the control group, lesions in the aortic root were significantly larger in splenectomized mice (P<0.01). These data were confirmed by the increase of atherosclerotic area in the thoracic and abdominal portions of aorta in splenectomized mice. These data indicate that splenectomy increases atherosclerotic lesions in ApoE deficient mice fed an atherogenic diet, suggesting an atheroprotector role of the spleen.

Evaluation of Plaque Stability of Advanced Atherosclerotic Lesions in Apo E-Deficient Mice after Treatment with the Oral Factor Xa Inhibitor Rivaroxaban

Aim. Thrombin not only plays a central role in thrombus formation and platelet activation, but also in induction of inflammatory processes. Activated factor X (FXa) is traditionally known as an important player in the coagulation cascade responsible for thrombin generation. We assessed the hypothesis that rivaroxaban, a direct FXa inhibitor, attenuates plaque progression and promotes stability of advanced atherosclerotic lesions in an in vivo model. Methods and Results. Rivaroxaban (1 or 5 mg/kg body weight/day) or standard chow diet was administered for 26 weeks to apolipoprotein E-deficient mice (n = 20 per group) with already established atherosclerotic lesions. There was a nonsignificant reduction of lesion progression in the high-concentration group, compared to control mice. FXa inhibition with 5 mg Rivaroxaban/kg/day resulted in increased thickness of the protective fibrous caps (12.3 ± 3.8 μm versus 10.1 ± 2.7 μm; P < .05), as well as in fewer medial erosions and fewer lateral xanthomas, indicating plaque stabilizing properties. Real time-PCR from thoracic aortas revealed that rivaroxaban (5 mg/kg/day) treatment reduced mRNA expression of inflammatory mediators, such of IL-6, TNF-α, MCP-1, and Egr-1 (P < .05). Conclusions. Chronic administration of rivaroxaban does not affect lesion progression but downregulates expression of inflammatory mediators and promotes lesion stability in apolipoprotein E-deficient mice.

Atherosclerotic plaques induced by marble-burying behavior are stabilized by exercise training in experimental atherosclerosis

BackgroundWe assessed the hypothesis whether behavioral stress may affect the development of atherosclerosis and whether regular exercise training may influence the composition of atherosclerotic plaques in apolipoprotein (apo) E-deficient mice. MethodsAtherosclerosis was induced in apo E-deficient mice fed a high fat diet. Exercise training (45min swimming, 3 times/week) was conducted, and behavioral stress was provoked by glass marble-burying procedure. Mice were treated with marble-burying, marble-burying behavior plus swimming training, and swimming alone over 8weeks. ResultsExercise training decreased the atherosclerotic lesions, but marble-burying behavior increased the lesions. The plaques containing macrophage accumulation with intercellular adhesion molecule-1 (ICAM-1) expression associated with reduced collagen contents were induced in the mice treated with marble-burying. However, ICAM-1 expression was suppressed and collagen contents were reversed in the mice that received marble-burying behavior plus exercise training. In addition, exercise alone and concomitant exercise training reduced the superoxide production in aortic walls, shown by dihydroethidium staining, compared with that in mice with marble-burying behavior alone. There were no significant differences in the serum lipids profiles among the groups. ConclusionsBehavioral stress increased the atherosclerotic lesions and induced the adhesion molecule expression with superoxide production on the lesions in apo E-deficient mice. Exercise training may stabilize plaque lesions induced by marble-burying behavior in this animal model.

Response to Letter by Ryan et al Regarding Article, “Do Hemochromatosis Mutations Protect Against Iron-Mediated Atherogenesis?”

HomeCirculation: Cardiovascular GeneticsVol. 3, No. 2Response to Letter by Ryan et al Regarding Article, “Do Hemochromatosis Mutations Protect Against Iron-Mediated Atherogenesis?” Free AccessResearch ArticlePDF/EPUBAboutView PDFSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBResponse to Letter by Ryan et al Regarding Article, “Do Hemochromatosis Mutations Protect Against Iron-Mediated Atherogenesis?” Jerome L. Sullivan Jerome L. SullivanJerome L. Sullivan Burnett School of Biomedical Sciences, University of Central Florida College of Medicine, Orlando, Fla Search for more papers by this author Originally published1 Apr 2010https://doi.org/10.1161/CIRCGENETICS.110.945212Circulation: Cardiovascular Genetics. 2010;3:e4Ryan et al1 propose another factor that may protect patients with hemochromatosis from atherosclerosis, namely, suppression of monocyte chemoattractant protein-1 (MCP-1). To know how much of the antiatherogenic effects of hemochromatosis mutations is due to this suppression will require additional investigation. Lawless et al2 report that MCP-1 is low with the C282Y variant but increased with H63D. This appears consistent with the hypothesis, because some H63D cases have higher hepcidin expression.3–5 In H63D, hepcidin normalized against ferritin is low, but the higher absolute hepcidin concentrations may allow higher macrophage iron in this variant. As noted in my study,6 there is a variable impact of genotype on hepcidin expression. Genotype of subjects in a study to test the hypothesis would need to be determined; however, testing the hypothesis would not rely directly on showing an association of genotype with disease. The hypothesis implies that protection against atherogenesis is inversely proportional to hepcidin expression. In an epidemiological study, the hypothesis suggests that among those with any 1 of the number of iron-overloading genotypes, protection against atherogenesis would be seen as a function of the degree of life-long hepcidin downregulation.In mice, the effects of Hfe−/− on atherogenesis on an ApoE−/− background may be informative on the question of the effects of Hfe loss and any changes in MCP-1 on atherogenesis. Loss of Hfe in mice increases their survival after infection with Salmonella typhimurium.7,8 Altered macrophage function associated with mutationally low macrophage iron may also lessen atherogenesis in Hfe−/−ApoE−/− double-knockout animals (nutritional iron depletion, sufficient to lessen macrophage iron, diminishes atherosclerosis in the ApoE−/− knockout mouse9). In Hfe knockouts, resting macrophages express MCP-1, and infection with S typhimurium increases macrophage MCP-1.7Hfe−/− mice are protected from S typhimurium despite the expression of MCP-1. Further study will be required to determine whether these animals exhibit some protection against atherosclerosis as well.DisclosuresNone. References 1 Ryan JD, Ryan E, Lawless M, Stolte J, Muckenthaler MU, Crowe J. Hepatic MCP-1 gene expression is suppressed in iron-loaded male C282Y homozygotes and correlates with hepcidin expression. Poster session presented at: International BioIron Society 2009 Meeting; June 7–11, 2009; Porto, Portugal. Am J Hematol. 2009; 84: E236–E375.CrossrefGoogle Scholar2 Lawless MW, White M, Mankan AK, Dwyer MJ, Norris S. Elevated MCP-1 serum levels are associated with the H63D mutation and not the C282Y mutation in hereditary hemochromatosis. Tissue Antigens. 2007; 70: 294–300.CrossrefMedlineGoogle Scholar3 Piperno A, Girelli D, Nemeth E, Trombini P, Bozzini C, Poggiali E, Phung Y, Ganz T, Camaschella C. Blunted hepcidin response to oral iron challenge in HFE-related hemochromatosis. Blood. 2007; 110: 4096–4100.CrossrefMedlineGoogle Scholar4 Bozzini C, Campostrini N, Trombini P, Nemeth E, Castagna A, Tenuti I, Corrocher R, Camaschella C, Ganz T, Olivieri O, Piperno A, Girelli D. Measurement of urinary hepcidin levels by SELDI-TOF-MS in HFE-hemochromatosis. Blood Cells Mol Dis. 2008; 40: 347–352.CrossrefMedlineGoogle Scholar5 Mast AE, Foster TM, Pinder HL, Beczkiewicz CA, Bellissimo DB, Murphy AT, Kovacevic S, Wroblewski VJ, Witcher DR. Behavioral, biochemical, and genetic analysis of iron metabolism in high-intensity blood donors. Transfusion. 2008; 48: 2197–2204.CrossrefMedlineGoogle Scholar6 Sullivan JL. Do hemochromatosis mutations protect against iron-mediated atherogenesis? Circ Cardiovasc Genet. 2009; 2: 652–657.LinkGoogle Scholar7 Nairz M, Theurl I, Schroll A, Theurl M, Fritsche G, Lindner E, Seifert M, Crouch ML, Hantke K, Akira S, Fang FC, Weiss G. Absence of functional Hfe protects mice from invasive Salmonella enterica serovar typhimurium infection via induction of lipocalin-2. Blood. 2009; 114: 3642–3651.CrossrefMedlineGoogle Scholar8 Wang L, Johnson EE, Shi HN, Walker WA, Wessling-Resnick M, Cherayil BJ. Attenuated inflammatory responses in hemochromatosis reveal a role for iron in the regulation of macrophage cytokine translation. J Immunol. 2008; 181: 2723–2731.CrossrefMedlineGoogle Scholar9 Lee TS, Shiao MS, Pan CC, Chau LY. Iron-deficient diet reduces atherosclerotic lesions in apoE-deficient mice. Circulation. 1999; 99: 1222–1229.CrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetails April 2010Vol 3, Issue 2 Advertisement Article InformationMetrics https://doi.org/10.1161/CIRCGENETICS.110.945212 Originally publishedApril 1, 2010 PDF download Advertisement SubjectsEpidemiologyGene Expression and RegulationGenetically Altered and Transgenic ModelsGeneticsGrowth Factors/CytokinesPathophysiology