A mouse model for human atherosclerosis: long-term histopathological study of lesion development in the aortic arch of apolipoprotein E-deficient (E0) mice

Elastin-specific MR probe for visualization and evaluation of an interleukin-1β targeted therapy for atherosclerosis

Atherosclerosis is a chronic inflammatory condition of the arteries and represents the primary cause of various cardiovascular diseases. Despite ongoing progress, finding effective anti-inflammatory therapeutic strategies for atherosclerosis remains a challenge. Here, we assessed the potential of molecular magnetic resonance imaging (MRI) to visualize the effects of 01BSUR, an anti-interleukin-1β monoclonal antibody, for treating atherosclerosis in a murine model. Male apolipoprotein E-deficient mice were divided into a therapy group (01BSUR, 2 × 0.3 mg/kg subcutaneously, n = 10) and control group (no treatment, n = 10) and received a high-fat diet for eight weeks. The plaque burden was assessed using an elastin-targeted gadolinium-based contrast probe (0.2 mmol/kg intravenously) on a 3 T MRI scanner. T1-weighted imaging showed a significantly lower contrast-to-noise (CNR) ratio in the 01BSUR group (pre: 3.93042664; post: 8.4007067) compared to the control group (pre: 3.70679168; post: 13.2982156) following administration of the elastin-specific MRI probe (p < 0.05). Histological examinations demonstrated a significant reduction in plaque size (p < 0.05) and a significant decrease in plaque elastin content (p < 0.05) in the treatment group compared to control animals. This study demonstrated that 01BSUR hinders the progression of atherosclerosis in a mouse model. Using an elastin-targeted MRI probe, we could quantify these therapeutic effects in MRI.

Development of physiologically-informed computational coronary artery plaques for use in virtual imaging trials

BACKGROUND

As a leading cause of death, worldwide, cardiovascular disease is of great clinical importance. Among cardiovascular diseases, coronary artery disease (CAD) is a key contributor, and it is the attributed cause of death for 10% of all deaths annually. The prevalence of CAD is commensurate with the rise in new medical imaging technologies intended to aid in its diagnosis and treatment. The necessary clinical trials required to validate and optimize these technologies require a large cohort of carefully controlled patients, considerable time to complete, and can be prohibitively expensive. A safer, faster, less expensive alternative is using virtual imaging trials (VITs), utilizing virtual patients or phantoms combined with accurate computer models of imaging devices.

PURPOSE

In this work, we develop realistic, physiologically-informed models for coronary plaques for application in cardiac imaging VITs.

METHODS

Histology images of plaques at micron-level resolution were used to train a deep convolutional generative adversarial network (DC-GAN) to create a library of anatomically variable plaque models with clinical anatomical realism. The stability of each plaque was evaluated by finite element analysis (FEA) in which plaque components and vessels were meshed as volumes, modeled as specialized tissues, and subjected to the range of normal coronary blood pressures. To demonstrate the utility of the plaque models, we combined them with the whole-body XCAT computational phantom to perform initial simulations comparing standard energy-integrating detector (EID) CT with photon-counting detector (PCD) CT.

RESULTS

Our results show the network is capable of generating realistic, anatomically variable plaques. Our simulation results provide an initial demonstration of the utility of the generated plaque models as targets to compare different imaging devices.

CONCLUSIONS

Vast, realistic, and variable CAD pathologies can be generated to incorporate into computational phantoms for VITs. There they can serve as a known truth from which to optimize and evaluate cardiac imaging technologies quantitatively.

Comprehensive Analysis of 1-Year-Old Female Apolipoprotein E-Deficient Mice Reveals Advanced Atherosclerosis with Vulnerable Plaque Characteristics

Apolipoprotein E-knockout (Apoe-/-) mice constitute the most widely employed animal model of atherosclerosis. Deletion of Apoe induces profound hypercholesterolemia and promotes the development of atherosclerosis. However, despite its widespread use, the Apoe-/- mouse model remains incompletely characterized, especially at late time points and advanced disease stages. Thus, it is unclear how late atherosclerotic plaques compare to earlier ones in terms of lipid deposition, calcification, macrophage accumulation, smooth muscle cell presence, or plaque necrosis. Additionally, it is unknown how cardiac function and hemodynamic parameters are affected at late disease stages. Here, we used a comprehensive analysis based on histology, fluorescence microscopy, and Doppler ultrasonography to show that in normal chow diet-fed Apoe-/- mice, atherosclerotic lesions at the level of the aortic valve evolve from a more cellular macrophage-rich phenotype at 26 weeks to an acellular, lipid-rich, and more necrotic phenotype at 52 weeks of age, also marked by enhanced lipid deposition and calcification. Coronary artery atherosclerotic lesions are sparse at 26 weeks but ubiquitous and extensive at 52 weeks; yet, left ventricular function was not significantly affected. These findings demonstrate that atherosclerosis in Apoe-/- mice is a highly dynamic process, with atherosclerotic plaques evolving over time. At late disease stages, histopathological characteristics of increased plaque vulnerability predominate in combination with frequent and extensive coronary artery lesions, which nevertheless may not necessarily result in impaired cardiac function.

Ethyl acetate extract of Caesalpinia sappan L. for the treatment of atherosclerosis in ApoE-/- mice and its mechanism

The ethyl acetate extract of Caesalpinia sappan L. is a traditional Chinese medicine extract commonly used in the treatment of atherosclerosis. However, the mechanism of its use in the treatment of AS is not yet clear, which seriously affects the wide-scale application of this drug. In this study, a combination of metabolomics and lipidomics was used to analyze cardiac tissue to obtain differential metabolites and differential lipid molecules, bioinformatic analysis was performed on the significantly different metabolites and subclass analysis, cluster analysis, and chain length and chain saturation analyses were performed on screened lipid molecules showing significant differences. A correlation network diagram of the screened differential metabolites and differential lipid molecules was constructed. Hematoxylin and eosin staining of thoracic aorta in rats confirmed its therapeutic effect. This study found that the ethyl acetate extract of C. sappan L. upregulates D-mannose through the lysosome pathway, enhances lysosomal function, mediates autophagy, and indirectly regulates the levels of lipid subtypes such as lysophosphatidylinositol and phosphatidylserine, thereby improving AS.

Endometriosis promotes atherosclerosis in a murine model

BACKGROUND

Epidemiologic studies have demonstrated an association between endometriosis and the subsequent development of cardiovascular disease. The direct effect of endometriosis on the progression of atherosclerotic, if any, has not been previously characterized. Endometriosis leads to systemic inflammation that could have consequences for cardiovascular health. Here, we reported the effects of endometriosis on the development of atherosclerosis in a murine model.

OBJECTIVE

This study aimed to determine the contribution of endometriosis in promoting cardiovascular disease in a murine model of endometriosis.

STUDY DESIGN

Endometriosis was induced in 18 apolipoprotein E-null mice, the standard murine model used to study atherosclerosis. Mice of the same strain were used as controls (n=18) and underwent sham surgery without inducing endometriosis. The formation of endometriotic lesions was confirmed after 25 weeks of induction. Atherosclerotic lesions were subjected to hematoxylin and eosin staining followed by measurement of the aortic root luminal area and wall thickness. The whole aorta was isolated, and Oil Red O staining was performed to quantify the lipid deposits or plaque formation; moreover, biochemical assays were carried out in serum to determine the levels of lipids and inflammatory-related cytokines.

RESULTS

Apolipoprotein E mice with endometriosis exhibited increased aortic atherosclerosis compared with controls as measured using Oil Red O staining (7.9% vs 3.1%, respectively; P=.0004). Mice with endometriosis showed a significant 50% decrease in the aortic luminal area compared with sham mice (0.85 mm² vs 1.46 mm²; P=.03) and a significant increase in aortic root wall thickness (0.22 mm vs 0.15 mm; P=.04). There was no difference in the lipoprotein profile (P<.05) between mice with endometriosis and sham mice. The serum levels of inflammatory cytokines interleukin 1 alpha, interleukin 6, interferon gamma, and vascular endothelial growth factor were significantly (P<.05)increased in the endometriosis mice.

CONCLUSION

Our study used a murine model to determine the effect of endometriosis on atherosclerosis. Inflammation-related cytokines interleukin 1 alpha, interleukin 6, interferon gamma, and vascular endothelial growth factor (angiogenic factor) released by endometriotic lesions may contribute to the increased cardiovascular risks in women with endometriosis. To reduce the risk of cardiovascular disease, early identification and treatment of endometriosis are essential. Future treatments targeting inflammatory cytokines may help reduce the long-term risk of cardiovascular disease in women with endometriosis.

Salidroside simultaneously reduces de novo lipogenesis and cholesterol biosynthesis to attenuate atherosclerosis in mice

Salidroside is a kind of phenylethanoid glycoside and widespread in the plants from Rhodiola and Ligustrum species. Our previous study has reported that salidroside can prevent atherosclerosis progression by ameliorating glyerolipid and glycerophospholipid metabolism in apoE-deficient (apoE-/-) mice. However, its effect on neutral lipids and underlying mechanism remains largely unclear. Here we investigated the molecular mechanism of salidroside action from the perspective of metabolic regulation by integrating metabonomics and transcriptomics pattern. The results showed that salidroside significantly reduced cholesterols, esterified cholesterols, fatty acids, unsaturated fatty acids and triacylclycerols biosynthesis in liver through down-regulating the genes expressions of sterol regulatory element-binding proteins (Srebf1 and Srebf2). The expressions of SREBPs targeted and downstream genes, such as the encoding genes of fatty acid synthase (Fasn), glycerol-3-phosphate acyltransferase (Gpam), stearoyl-CoA desaturase (Scd), 3-hydroxy-3-methylglutaryl-CoA reductase (Hmgcr), and proprotein convertase subtilisin/kexin type 9 (Pcsk9), were also inhibited after salidroside administration. ATP citrate lyase gene (Acly) that encodes an important enzyme producing acetyl-CoA for cholesterol and fatty acid biosynthesis significantly decreased after treatment as well. Moreover, one of ketone body products, 3-hydroxybutyrate, was significantly up-regulated in drug-treated group, indicating that fatty acid degradation was accelerated by salidroside at the same time. Our findings identify salidroside as a regulator of lipid homeostasis in atherosclerotic mice, suggesting its potential to be an alternative medicine for lowering the risks of atherosclerosis-related diseases.

Mouse models of atherosclerosis and their suitability for the study of myocardial infarction

Atherosclerotic plaques impair vascular function and can lead to arterial obstruction and tissue ischaemia. Rupture of an atherosclerotic plaque within a coronary artery can result in an acute myocardial infarction, which is responsible for significant morbidity and mortality worldwide. Prompt reperfusion can salvage some of the ischaemic territory, but ischaemia and reperfusion (IR) still causes substantial injury and is, therefore, a therapeutic target for further infarct limitation. Numerous cardioprotective strategies have been identified that can limit IR injury in animal models, but none have yet been translated effectively to patients. This disconnect prompts an urgent re-examination of the experimental models used to study IR. Since coronary atherosclerosis is the most prevalent morbidity in this patient population, and impairs coronary vessel function, it is potentially a major confounder in cardioprotective studies. Surprisingly, most studies suggest that atherosclerosis does not have a major impact on cardioprotection in mouse models. However, a major limitation of atherosclerotic animal models is that the plaques usually manifest in the aorta and proximal great vessels, and rarely in the coronary vessels. In this review, we examine the commonly used mouse models of atherosclerosis and their effect on coronary artery function and infarct size. We conclude that none of the commonly used strains of mice are ideal for this purpose; however, more recently developed mouse models of atherosclerosis fulfil the requirement for coronary artery lesions, plaque rupture and lipoprotein patterns resembling the human profile, and may enable the identification of therapeutic interventions more applicable in the clinical setting.

Assessment of Total-Body Atherosclerosis by PET/Computed Tomography

Atherosclerotic burden has become the focus of cardiovascular risk assessment. PET/computed tomography (CT) imaging with the tracers 18F-fluorodeoxyglucose and 18F-sodium fluoride shows arterial wall inflammation and microcalcification, respectively. Arterial uptake of both tracers is modestly age dependent. 18F-sodium fluoride uptake is consistently associated with risk factors and more easily measured in the heart. Because of extremely high sensitivity, ultrashort acquisition, and minimal radiation to the patient, total-body PET/CT provides unique opportunities for atherosclerosis imaging: disease screening and delayed and repeat imaging with global disease scoring and parametric imaging to better characterize the atherosclerosis of individual patients.

A Timing Effect of 17-β Estradiol on Atherosclerotic Lesion Development in Female ApoE-/- Mice

Differences in size or composition of existing plaques at the initiation of estrogen (E2) therapy may underpin evidence of increased risk of atherosclerosis-associated clinical sequelae. We investigated whether E2 had divergent effects on actively-growing versus established-advanced atherosclerotic lesions. Eight weeks of subcutaneous bi-weekly injections of 3 µg/g 17β-estradiol (n = 18) or vehicle control (n = 22) were administered to female Apolipoprotein null-mice aged 25- or 45 weeks old. Histological assessment of lesion size within the brachiocephalic artery was conducted. Lesion composition was also assessed with acellular, calcification and fibrosis areas measured and other cellular features (intimal thickening, foam cells, lipid pools and cholesterol) scored (0–3) for severity. The comparison showed increased lesion size and calcified area with advancing age but no effect of E2. However, subtle changes in composition were observed following E2. Within the younger group, E2 increased intima thickening and acceleration of calcification. In the older group, E2 increased the thickness of the lesion cap. Therefore, this study shows different effects of E2 depending on the underlying stage of lesion development at the time of initiation of treatment. These divergent changes help explain the controversy of the adverse effects of E2 treatment in cardiovascular disease.

Soyasaponins A1 and A2 exert anti-atherosclerotic functionalities by decreasing hypercholesterolemia and inflammation in high fat diet (HFD)-fed ApoE-/- mice

Atherosclerosis is a chronic inflammatory disease causing coronary heart attacks and strokes. Soyasaponins (SS), the phytochemicals naturally existing in soybeans and their products, have been shown to reduce hypercholesterolemia and inflammation, which are intimately related to the genesis and development of atherosclerosis. However, the anti-atherosclerotic functionality of soyasaponins remains unknown. The aim of this study was to investigate the effects of the supplementation of two types of soyasaponin monomers (A1 and A2) on atherosclerotic plaque formation, serum lipid profiles, and inflammation in ApoE gene knockout (ApoE-/-) mice. Sixty 5-week-old ApoE-/- male mice were fed with a high-fat diet (HFD) and intervened by SSA1 and SSA2 (10 and 20 μmol per kg BW, respectively) or simvastatin (10 μmol per kg BW) for 24 weeks. The atherosclerotic lesions in the aorta, aortic root, and innominate artery, lipid profile and inflammatory markers in serum, and TLR4/MyD88/NF-κB signaling in arterial tissues were determined. SSA1 and SSA2 decreased the plaque ratio in the aortic root and innominate artery but not in the entire aorta. In serum, SSA1 reduced TG, TC, and LDL-C but increased HDL-C; SSA2 decreased TC, TG, and LDL-C but did not affect HDL-C. Meanwhile, SSA1 increased TG, SSA2 increased TC, and both of them increased bile acids in the feces. SSA1 and SSA2 lowered TNF-α, MCP-1, and hs-crp in serum. Furthermore, SSA1 and SSA2 reduced the TLR4 and MyD88 expressions in the aorta and innominate artery and inhibited NF-κB p65 and IκBα phosphorylation in the aorta. These results suggest that SSA1 and SSA2 exert anti-atherosclerotic functionalities by decreasing hypercholesterolemia and inflammation in HFD-fed ApoE-/- mice.

Rapamycin-Loaded Biomimetic Nanoparticles Reverse Vascular Inflammation

Rationale:

Through localized delivery of rapamycin via a biomimetic drug delivery system, it is possible to reduce vascular inflammation and thus the progression of vascular disease.

Objective:

Use biomimetic nanoparticles to deliver rapamycin to the vessel wall to reduce inflammation in an in vivo model of atherosclerosis after a short dosing schedule.

Methods and Results:

Biomimetic nanoparticles (leukosomes) were synthesized using membrane proteins purified from activated J774 macrophages. Rapamycin-loaded nanoparticles were characterized using dynamic light scattering and were found to have a diameter of 108±2.3 nm, a surface charge of −15.4±14.4 mV, and a polydispersity index of 0.11 +/ 0.2. For in vivo studies, ApoE −/− mice were fed a high-fat diet for 12 weeks. Mice were injected with either PBS, free rapamycin (5 mg/kg), or rapamycin-loaded leukosomes (Leuko-Rapa; 5 mg/kg) once daily for 7 days. In mice treated with Leuko-Rapa, flow cytometry of disaggregated aortic tissue revealed fewer proliferating macrophages in the aorta (15.6±9.79 %) compared with untreated mice (30.2±13.34 %) and rapamycin alone (26.8±9.87 %). Decreased macrophage proliferation correlated with decreased levels of MCP (monocyte chemoattractant protein)-1 and IL (interleukin)-b1 in mice treated with Leuko-Rapa. Furthermore, Leuko-Rapa–treated mice also displayed significantly decreased MMP (matrix metalloproteinases) activity in the aorta (mean difference 2554±363.9, P =9.95122×10 −6 ). No significant changes in metabolic or inflammation markers observed in liver metabolic assays. Histological analysis showed improvements in lung morphology, with no alterations in heart, spleen, lung, or liver in Leuko-Rapa–treated mice.

Conclusions:

We showed that our biomimetic nanoparticles showed a decrease in proliferating macrophage population that was accompanied by the reduction of key proinflammatory cytokines and changes in plaque morphology. This proof-of-concept showed that our platform was capable of suppressing macrophage proliferation within the aorta after a short dosing schedule (7 days) and with a favorable toxicity profile. This treatment could be a promising intervention for the acute stabilization of late-stage plaques.

The roles of gut microbiota and circadian rhythm in the cardiovascular protective effects of polyphenols

Polyphenols are secondary metabolites of plants that have been widely studied for their health benefits as antioxidants. In the last decade, several clinical trials and epidemiological studies have shown that long‐term consumption of polyphenol‐rich diet protects against chronic diseases such as cancers and cardiovascular diseases. Current cardiovascular studies have also suggested an important role of gut microbiota and circadian rhythm in the pathogenesis metabolic and cardiovascular diseases. It is known that polyphenols can modulate the composition of core gut microbiota and interact with circadian clocks. In this article, we summarize recent findings, review the molecular mechanisms and the potential of polyphenols as dietary supplements for regulating gut microbiota and circadian rhythms, and discuss future research directions.

Linked Articles

This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc

Smooth muscle cell fate and plasticity in atherosclerosis

Current knowledge suggests that intimal smooth muscle cells (SMCs) in native atherosclerotic plaque derive mainly from the medial arterial layer. During this process, SMCs undergo complex structural and functional changes giving rise to a broad spectrum of phenotypes. Classically, intimal SMCs are described as dedifferentiated/synthetic SMCs, a phenotype characterized by reduced expression of contractile proteins. Intimal SMCs are considered to have a beneficial role by contributing to the fibrous cap and thereby stabilizing atherosclerotic plaque. However, intimal SMCs can lose their properties to such an extent that they become hard to identify, contribute significantly to the foam cell population, and acquire inflammatory-like cell features. This review highlights mechanisms of SMC plasticity in different stages of native atherosclerotic plaque formation, their potential for monoclonal or oligoclonal expansion, as well as recent findings demonstrating the underestimated deleterious role of SMCs in this disease.

Shear-Induced CCN1 Promotes Atheroprone Endothelial Phenotypes and Atherosclerosis

BACKGROUND

Atherosclerosis occurs preferentially at the blood vessels encountering blood flow turbulence. The matricellular protein CCN1 is induced in endothelial cells by disturbed flow, and is expressed in advanced atherosclerotic lesions in patients and in the Apoe^-/- mouse model. The role of CCN1 in atherosclerosis remains undefined.

METHODS

To assess the function of CCN1 in vivo, knock-in mice carrying the integrin α6β1-binding-defective mutant allele Ccn1-dm on the Apoe^-/- background were tested in an atherosclerosis model generated by carotid artery ligation. Additionally, CCN1-regulated functional phenotypes of human umbilical vein endothelial cells, or primary mouse aortic endothelial cells isolated from wild-type and Ccn1 ^dm/dm mice, were investigated in the in vitro shear stress experiments under unidirectional laminar shear stress (12 dyn/cm²) versus oscillatory shear stress (±5 dyn/cm²) conditions.

RESULTS

We found that Ccn1 expression was upregulated in the arterial endothelium 3 days after ligation before any detectable structural changes, and intensified with the progression of atherosclerotic lesions. Compared with Apoe^-/- controls, Ccn1 ^dm/dm/ Apoe^-/- mice were remarkably resistant to ligation-induced plaque formation (n=6). These mice exhibited lower oxidative stress, expression of endothelin-1 and monocyte chemoattractant protein-1, and monocyte homing. CCN1/α6β1 critically mediated flow-induced activation of the pleiotropic transcription factor nuclear factor-κB and therefore the induction of atheroprone gene expression in the mouse arterial endothelium after ligation (n=6), or in cultured human umbilical vein endothelial cells or primary mouse aortic endothelial cells exposed to oscillatory shear stress (n=3 in triplicate). Interestingly, the activation of nuclear factor-κB by CCN1/α6β1 signaling prompted more production of CCN1 and α6β1. Blocking CCN1-α6β1 binding by the Ccn1-dm mutation or by T1 peptide (derived from an α6β1-binding sequence of CCN1) disrupted the positive-feedback regulation between CCN1/α6β1 and nuclear factor-κB, and prevented flow-induced atheroprone phenotypic alterations in endothelial cells or atherosclerosis in mice.

CONCLUSIONS

These data demonstrate a causative role of CCN1 in atherosclerosis via modulating endothelial phenotypes. CCN1 binds to its receptor integrin α6β1 to activate nuclear factor-κB, thereby instigating a vicious circle to persistently promote atherogenesis. T1, a peptide antagonist selectively targeting CCN1-α6β1, can be further optimized for developing T1-mimetics to treat atherosclerosis.

Impact of Gut Microbiota and Diet on the Development of Atherosclerosis in Apoe-/- Mice

Objective- To investigate the effect of gut microbiota and diet on atherogenesis. Approach and Results- Here, we investigated the interaction between the gut microbiota and diet on atherosclerosis by feeding germ-free or conventionally raised Apoe-/- mice chow or Western diet alone or supplemented with choline (which is metabolized by the gut microbiota and host enzymes to trimethylamine N-oxide) for 12 weeks. We observed smaller aortic lesions and lower plasma cholesterol levels in conventionally raised mice compared with germ-free mice on a chow diet; these differences were not observed in mice on a Western diet. Choline supplementation increased plasma trimethylamine N-oxide levels in conventionally raised mice but not in germ-free mice. However, this treatment did not affect the size of aortic lesions or plasma cholesterol levels. Gut microbiota composition was analyzed by sequencing of 16S rRNA genes. As expected, the global community structure and relative abundance of many taxa differed between mice fed chow or a Western diet. Choline supplementation had minor effects on the community structure although the relative abundance of some taxa belonging to Clostridiales was altered. Conclusions- In conclusion, the impact of the gut microbiota on atherosclerosis is dietary dependent and is associated with plasma cholesterol levels. Furthermore, the microbiota was required for trimethylamine N-oxide production from dietary choline, but this process could not be linked to increased atherosclerosis in this model.

Apolipoprotein E favours the blunting by high-fat diet of prostacyclin receptor activation in the mouse aorta

BACKGROUND AND PURPOSE

NO-mediated, endothelium-dependent relaxations of isolated arteries are blunted by ageing and high-fat diets, as well as by apolipoprotein E deletion. The present study was designed to test the hypothesis that apolipoprotein E deletion impairs endothelium-dependent responses to prostacyclin (IP) receptor activation.

EXPERIMENTAL APPROACH

Five-week-old ApoE^+/+ and ApoE^-/- mice were fed normal chow or high-fat diet for 29 weeks. The aortae were isolated for the measurements of isometric tension in Halpern-Mulvany myographs. Levels of proteins were assessed by Western blotting and immunofluorescence, and cyclic nucleotide levels by elisa.

KEY RESULTS

The IP receptor agonist, iloprost, induced endothelium-, NO-synthase- and IP-dependent relaxations in aortae of young ApoE^+/+ mice. High-fat diet favoured activation of thromboxane receptors by iloprost, causing contraction. Apolipoprotein E was present in aortae of ApoE^+/+ mice, especially in endothelium. Its presence was augmented by high-fat diet. Its deletion potentiated iloprost-induced relaxations in aortae of young mice and prevented the blunting of this response by high-fat diet. Levels of cAMP were higher, but those of cGMP were lower in the aorta of ApoE^-/- than in ApoE^+/+ mice of the same age. The levels of IP receptor protein were not different between ApoE^+/+ and ApoE^-/- mice.

CONCLUSIONS AND IMPLICATIONS

Iloprost induced an endothelium-dependent relaxation in the aorta of young healthy mice which involved both the cGMP and cAMP pathways. This response was blunted by prolonged exposure to a high-fat diet. Apolipoprotein E deletion potentiated relaxations to IP receptor activation, independently of age and diet.

The effect of zirconium doping of cerium dioxide nanoparticles on pulmonary and cardiovascular toxicity and biodistribution in mice after inhalation

Development and manufacture of nanomaterials is growing at an exponential rate, despite an incomplete understanding of how their physicochemical characteristics affect their potential toxicity. Redox activity has been suggested to be an important physicochemical property of nanomaterials to predict their biological activity. This study assessed the influence of redox activity by modification of cerium dioxide nanoparticles (CeO₂ NPs) via zirconium (Zr) doping on the biodistribution, pulmonary and cardiovascular effects in mice following inhalation. Healthy mice (C57BL/6 J), mice prone to cardiovascular disease (ApoE^-/-, western-diet fed) and a mouse model of neurological disease (5 × FAD) were exposed via nose-only inhalation to CeO₂ NPs with varying amounts of Zr-doping (0%, 27% or 78% Zr), or clean air, over a four-week period (4 mg/m³ for 3 h/day, 5 days/week). Effects were assessed four weeks post-exposure. In all three mouse models CeO₂ NP exposure had no major toxicological effects apart from some modest inflammatory histopathology in the lung, which was not related to the amount of Zr-doping. In ApoE^-/- mice CeO₂ did not change the size of atherosclerotic plaques, but there was a trend towards increased inflammatory cell content in relation to the Zr content of the CeO₂ NPs. These findings show that subacute inhalation of CeO₂ NPs causes minimal pulmonary and cardiovascular effect four weeks post-exposure and that Zr-doping of CeO₂ NPs has limited effect on these responses. Further studies with nanomaterials with a higher inherent toxicity or a broader range of redox activities are needed to fully assess the influence of redox activity on the toxicity of nanomaterials.

Crossroads between peripheral atherosclerosis, western-type diet and skeletal muscle pathophysiology: emphasis on apolipoprotein E deficiency and peripheral arterial disease

Atherosclerosis is a chronic inflammatory process that, in the presence of hyperlipidaemia, promotes the formation of atheromatous plaques in large vessels of the cardiovascular system. It also affects peripheral arteries with major implications for a number of other non-vascular tissues such as the skeletal muscle, the liver and the kidney. The aim of this review is to critically discuss and assimilate current knowledge on the impact of peripheral atherosclerosis and its implications on skeletal muscle homeostasis. Accumulating data suggests that manifestations of peripheral atherosclerosis in skeletal muscle originates in a combination of increased i)-oxidative stress, ii)-inflammation, iii)-mitochondrial deficits, iv)-altered myofibre morphology and fibrosis, v)-chronic ischemia followed by impaired oxygen supply, vi)-reduced capillary density, vii)- proteolysis and viii)-apoptosis. These structural, biochemical and pathophysiological alterations impact on skeletal muscle metabolic and physiologic homeostasis and its capacity to generate force, which further affects the individual's quality of life. Particular emphasis is given on two major areas representing basic and applied science respectively: a)-the abundant evidence from a well-recognised atherogenic model; the Apolipoprotein E deficient mouse and the role of a western-type diet and b)-on skeletal myopathy and oxidative stress-induced myofibre damage from human studies on peripheral arterial disease. A significant source of reactive oxygen species production and oxidative stress in cardiovascular disease is the family of NADPH oxidases that contribute to several pathologies. Finally, strategies targeting NADPH oxidases in skeletal muscle in an attempt to attenuate cellular oxidative stress are highlighted, providing a better understanding of the crossroads between peripheral atherosclerosis and skeletal muscle pathophysiology.

Pathological and molecular analyses of atherosclerotic lesions in ApoE-knockout mice

The establishment of consistent and reliable methods for the analysis of atherosclerosis molecular pathways and for testing the efficiency of new therapeutics is of utmost importance. Here, we fed ApoE-knockout (KO) mice with high-fat diet to for 16 weeks to induce atherosclerosis. Atherosclerotic lesions in mice were methodically investigated using pathologic analyses and molecular biology tools. These lesions were histopathologically classified into three categories: early, progressive, and combined lesions. Immunohistochemical analyses showed that both F4/80 (macrophage marker) and tenascin-C are expressed in these lesions. Real-time PCR analysis conducted using formalin-fixed paraffin-embedded tissues with atherosclerotic lesions demonstrated an increase in the levels of many inflammatory chemokines, including Cxcl16, while antibody arrays performed using frozen atherosclerotic tissue samples showed elevated TIMP-1 expression. Subsequent immunohistochemical analyses showed that the expression of CXCL16, TIMP-1, MMP-9, MMP-8, and LOX-1 is localized in the atherosclerotic lesions. We confirmed that the expression of these proteins is localized to atherosclerotic lesion, which suggests their roles in the development of the lesions in ApoE-KO mice. Therefore, this mouse model represents an appropriate tool for elucidating molecular mechanisms underlying the development of atherosclerosis, and a model for the evaluation of therapeutic efficiency of novel drugs.

Role of parnaparin in atherosclerosis

Atherosclerosis is characterized by a proliferation of vascular smooth muscle cells (VSMCs) and their migration to the intima, which induces thickening of the intima itself, but the mechanism remains poorly understood. Low molecular weight heparin (LMWH) inhibits the proliferation of VSMCs. Previous studies have shown that a LMWH, parnaparin (PNP), acts on the processes of atherogenesis and atheroprogression in experimental animal models. The aim of this study was to investigate the involvement of oxidative stress, inflammation and VSMCs in the regulation of vascular wall homeostasis. We also considered the possibility of restoring vascular pathological changes using PNP treatment. In order to evaluate vascular remodelling in this study we have analysed the morphological changes in aortas of an animal model of atherosclerosis, apolipoprotein E-deficient mice (ApoE-/-) fed with a normal or a western diet without treatment or treated with PNP. We also analysed, by immunohistochemistry, the expression of proteins linked to atherogenesis and atheroprogression - an enzyme involved in oxidative stress, iNOS, examples of inflammatory mediators, such as tumour necrosis factor alpha (TNF-α), interleukins 1 and 6 (IL-1 and IL-6), and markers of VSMC changes, in particular plasminogen activator inhibitor-1 and thrombospondin-1 (PAI-1 and TSP-1). Our results could suggest that PNP downregulates VSMC proliferation and migration, mediated by PAI-1 and TSP-1, and reduces inflammation and oxidative stress in vessels. These data suggested that LMWH, in particular PNP, could be a theoretically practical tool in the prevention of atherosclerotic vascular modification.

Deletion of calponin 2 in macrophages alters cytoskeleton-based functions and attenuates the development of atherosclerosis

Arterial atherosclerosis is an inflammatory disease. Macrophages play a major role in the pathogenesis and progression of atherosclerotic lesions. Modulation of macrophage function is a therapeutic target for the treatment of atherosclerosis. Calponin is an actin-filament-associated regulatory protein that inhibits the activity of myosin-ATPase and dynamics of the actin cytoskeleton. Encoded by the gene Cnn2, calponin isoform 2 is expressed at significant levels in macrophages. Deletion of calponin 2 increases macrophage migration and phagocytosis. In the present study, we investigated the effect of deletion of calponin 2 in macrophages on the pathogenesis and development of atherosclerosis. The results showed that macrophages isolated from Cnn2 knockout mice ingested a similar level of acetylated low-density lipoprotein (LDL) to that of wild type (WT) macrophages but the resulting foam cells had significantly less hindered velocity of migration. Systemic or myeloid cell-specific Cnn2 knockouts effectively attenuated the development of arterial atherosclerosis lesions with less macrophage infiltration in apolipoprotein E knockout mice. Consistently, calponin 2-null macrophages produced less pro-inflammatory cytokines than that of WT macrophages, and the up-regulation of pro-inflammatory cytokines in foam cells was also attenuated by the deletion of calponin 2. Calponin 2-null macrophages and foam cells have significantly weakened cell adhesion, indicating a role of cytoskeleton regulation in macrophage functions and inflammatory responses, and a novel therapeutic target for the treatment of arterial atherosclerosis.

So Much Cholesterol: the unrecognized importance of smooth muscle cells in atherosclerotic foam cell formation

PURPOSE OF REVIEW

Smooth muscle cells (SMCs) form the thickened intimal layer in atherosclerosis-prone arteries in early life, and provide the initial site for retention and uptake of atherogenic lipoproteins. Here we review current knowledge regarding the importance of SMCs in the deposition of cholesterol in atherosclerotic plaque.

RECENT FINDINGS

SMCs were found to comprise at least 50% of total foam cells in human coronary artery atherosclerosis, and exhibit a selective loss of expression of the cholesterol efflux promoter ATP-binding cassette transporter A1. Cholesterol loading induced a loss of SMC gene expression and an increase in macrophage and proinflammatory marker expression by cultured mouse and human arterial SMCs, with reversal of these effects upon removal of the excess cholesterol. Mice engineered to track all cells of SMC lineage indicated that, at most, SMCs make up about one-third of total cells in atherosclerotic plaque in these animals.

SUMMARY

SMCs appear to be the origin of the majority of foam cells in human atherosclerotic plaque. Recent studies suggest a renaissance of research on the role of SMCs in atherosclerosis is needed to make the next leap forward in the prevention and treatment of this disease.

Lingonberries reduce atherosclerosis in Apoe(-/-) mice in association with altered gut microbiota composition and improved lipid profile

SCOPE

To investigate the efficacy of lingonberries in prevention of atherosclerosis, using atherosclerosis-prone Apoe(-/-) mice and to clarify whether effects were associated with changes in the gut microbiota, gut metabolites, and lipid metabolism.

METHODS AND RESULTS

Male Apoe(-/-) mice were fed either low-fat diet, high-fat diet, or high-fat diet with 44% lingonberries for 8 weeks. Blood lipid profiles, hepatic gene expression, atherosclerotic plaques in the aortic root region of the heart, bacterial 16S rRNA gene profiles, and cecal short-chain fatty acids (SCFAs) were analyzed. Triglyceride levels and amount of atherosclerotic plaques decreased in the group fed lingonberries in comparison to the high-fat group. Hepatic expression of the bile acid synthesis gene Cyp7a1 was significantly upregulated in the lingonberry group. Lingonberries increased the cecal relative abundance of bacterial genera Bacteroides, Parabacteroides and Clostridium. The cecal levels of total SCFAs were significantly lower in the lingonberry group, while the cecal proportion of propionic acid was higher in mice fed lingonberries.

CONCLUSION

Intake of lingonberries resulted in decreased triglyceridemia and reduced atherosclerosis. The altered gut microbiota composition and SCFA profile was associated with increased hepatic bile acid gene expression in mice fed lingonberries.

The hypotensive effect of acute and chronic AMP-activated protein kinase activation in normal and hyperlipidemic mice

AMP-activated protein kinase (AMPK) is present in the arterial wall and is activated in response to cellular stressors that raise AMP relative to ADP/ATP. Activation of AMPK in vivo lowers blood pressure but the influence of hyperlipidemia on this response has not been studied. ApoE^−/− mice on high fat diet for 6 weeks and age-matched controls were treated with the AMPK activator, AICAR daily for two weeks. Under anesthesia, the carotid artery was cannulated for blood pressure measurements. Aortic tissue was removed for in vitro functional experiments and AMPK activity was measured in artery homogenates by Western blotting. ApoE^−/− mice had significantly raised mean arterial pressure; chronic AICAR treatment normalized this but had no effect in normolipidemic mice, whereas acute administration of AICAR lowered mean arterial pressure in both groups. Chronic AICAR treatment increased phosphorylation of AMPK and its downstream target acetyl-CoA carboxylase in normolipidemic but not ApoE^−/− mice. In aortic rings, AMPK activation induced vasodilation and an anticontractile effect, which was attenuated in ApoE^−/− mice. This study demonstrates that hyperlipidemia dysregulates the AMPK pathway in the arterial wall but this effect can be reversed by AMPK activation, possibly through improving vessel compliance.

Detection of vulnerable atherosclerosis plaques with a dual-modal single-photon-emission computed tomography/magnetic resonance imaging probe targeting apoptotic macrophages

Atherosclerosis (AS), especially the vulnerable AS plaque rupture-induced acute obstructive vascular disease, is a leading cause of death. Accordingly, there is a need for an effective method to draw accurate predictions about AS progression and plaque vulnerability. Herein we report on an approach to constructing a hybrid nanoparticle system using a single-photon-emission computed tomography (SPECT)/magnetic resonance imaging (MRI) multimodal probe, aiming for a comprehensive evaluation of AS progression by achieving high sensitivity along with high resolution. Ultrasmall superparamagnetic iron oxide (USPIO) was covered by aminated poly(ethylene glycol) (PEG) and carboxylated PEG simultaneously and then functionalized with diethylenetriaminepentacetate acid for (99m)Tc coordination and subsequently Annexin V for targeting apoptotic macrophages abundant in vulnerable plaques. The in vivo accumulations of imaging probe reflected by SPECT and MRI were consistent and accurate in highlighting lesions. Intense radioactive signals detected by SPECT facilitated focus recognization and quantification, while USPIO-based T2-weighted MRI improved the focal localization and volumetry of AS plaques. For subsequent ex vivo planar images, targeting effects were further confirmed by immunohistochemistry, including CD-68 and TUNEL staining; meanwhile, the degree of concentration was proven to be statistically correlated with the Oil Red O staining results. In conclusion, these results indicated that the Annexin V-modified hybrid nanoparticle system specifically targeted the vulnerable AS plaques containing apoptotic macrophages and could be of great value in the invasively accurate detection of vulnerable plaques.

Animal models of diabetic macrovascular complications: key players in the development of new therapeutic approaches

Diabetes mellitus is a lifelong, incapacitating metabolic disease associated with chronic macrovascular complications (coronary heart disease, stroke, and peripheral vascular disease) and microvascular disorders leading to damage of the kidneys (nephropathy) and eyes (retinopathy). Based on the current trends, the rising prevalence of diabetes worldwide will lead to increased cardiovascular morbidity and mortality. Therefore, novel means to prevent and treat these complications are needed. Under the auspices of the IMI (Innovative Medicines Initiative), the SUMMIT (SUrrogate markers for Micro- and Macrovascular hard end points for Innovative diabetes Tools) consortium is working on the development of novel animal models that better replicate vascular complications of diabetes and on the characterization of the available models. In the past years, with the high level of genomic information available and more advanced molecular tools, a very large number of models has been created. Selecting the right model for a specific study is not a trivial task and will have an impact on the study results and their interpretation. This review gathers information on the available experimental animal models of diabetic macrovascular complications and evaluates their pros and cons for research purposes as well as for drug development.

ADAM-10 could mediate cleavage of N-cadherin promoting apoptosis in human atherosclerotic lesions leading to vulnerable plaque: a morphological and immunohistochemical study

Atherosclerosis remains a major cause of mortality. Whereas the histopathological progression of atherosclerotic lesions is well documented, much less is known about the development of unstable or vulnerable plaque, which can rupture leading to thrombus, luminal occlusion and infarct. Apoptosis in the fibrous cap, which is rich in vascular smooth muscle cells (VSMCs) and macrophages, and its subsequent weakening or erosion seems to be an important regulator of plaque stability. The aim of our study was to improve our knowledge on the biological mechanisms that cause plaque instability in order to develop new therapies to maintain atherosclerotic plaque stability and avoid its rupture. In our study, we collected surgical specimens from atherosclerotic plaques in the right or left internal carotid artery of 62 patients with evident clinical symptoms. Histopathology and histochemistry were performed on wax-embedded sections. Immunohistochemical localization of caspase-3, N-cadherin and ADAM-10 was undertaken in order to highlight links between apoptosis, as expressed by caspase-3 immunostaining, and possible roles of N-cadherin, a cell-cell junction protein in VSMCs and macrophages that provides a pro-survival signal reducing apoptosis, and ADAM-10, a "disintegrin and metalloproteases" that is able to cleave N-cadherin in glioblastomas. Our results showed that when apoptosis, expressed by caspase-3 immunostaining, increased in the fibrous cap, rich in VSMCs and macrophages, the expression of N-cadherin decreased. The decreased N-cadherin expression, in turn, was linked to increased ADAM-10 expression. This study shows that apoptotic events are probably involved in the vulnerability of atherosclerotic plaque.

A vascular biology network model focused on inflammatory processes to investigate atherogenesis and plaque instability

Background

Numerous inflammation-related pathways have been shown to play important roles in atherogenesis. Rapid and efficient assessment of the relative influence of each of those pathways is a challenge in the era of “omics” data generation. The aim of the present work was to develop a network model of inflammation-related molecular pathways underlying vascular disease to assess the degree of translatability of preclinical molecular data to the human clinical setting.

Methods

We constructed and evaluated the Vascular Inflammatory Processes Network (V-IPN), a model representing a collection of vascular processes modulated by inflammatory stimuli that lead to the development of atherosclerosis.

Results

Utilizing the V-IPN as a platform for biological discovery, we have identified key vascular processes and mechanisms captured by gene expression profiling data from four independent datasets from human endothelial cells (ECs) and human and murine intact vessels. Primary ECs in culture from multiple donors revealed a richer mapping of mechanisms identified by the V-IPN compared to an immortalized EC line. Furthermore, an evaluation of gene expression datasets from aortas of old ApoE^-/- mice (78 weeks) and human coronary arteries with advanced atherosclerotic lesions identified significant commonalities in the two species, as well as several mechanisms specific to human arteries that are consistent with the development of unstable atherosclerotic plaques.

Conclusions

We have generated a new biological network model of atherogenic processes that demonstrates the power of network analysis to advance integrative, systems biology-based knowledge of cross-species translatability, plaque development and potential mechanisms leading to plaque instability.

Bovine Peptic Casein Hydrolysate Ameliorates Cardiovascular Risk Factors in a Model of ApoE-deficient Mice but not Overweight, Mildly Hypercholesterolaemic Men

Associations have been shown between consumption of bovine dairy and decreased prevalence of metabolic related disorders. Milk peptides may promote both angiotensin-I- converting enzyme (ACE) inhibition for blood pressure (BP) lowering and insulin action for better glycaemic control. Less is known of other metabolic parameters. The aim of this study was to investigate effects of dairy peptic casein hydrolysate (CH) on markers of cardiovascular disease (CVD) risk in (1) an apolipoproteinE (ApoE) - deficient mouse model of high-fat fed hypercholesterolaem- ia, and, (2) a clinical study of moderate overweight and hypercholesterolaemia. In Trial 1, ApoE-deficient mice were supplemented with high dose CH (~1g/kg body weight) in a randomised, 9-wk, parallel design intervention, and blood and tissue samples harvested. In Trial 2, 24 mildly hypercholesterolaemic men were supplemented with lower dose CH (~0.1g/kg body weight, 10g/day, 3-wks) and matched whey protein control (WP, 10g/day, 3-wks) in a randomised, 9-wk, cross-over design intervention. Diets were separated by a 3-wk washout. Fasting blood and urine samples were collected, and blood pressure (BP) measured weekly. Clinical trial registration number, ACTRN 12611001013954. In ApoE-deficient mice, administration of CH significantly inhibited circulating total cholesterol concentrations by 37% (TC, P<0.01) and decreased aorta atherosclerotic lesion score by 25% (P<0.01). In the clinical study there were no significant differential effects of CH supplementation on CV markers, including serum lipids (TC, LDL-C, HDL-C, triglyceride), glucose and BP. Whilst high dose bovine peptic CH attenuated CVD risk in a murine ApoE deficient model of aggressive hypercholesterolaemia, no evidence of amelioration of risk by supplementation with a lower dose of CH in an overweight population of mildly hypercholesterolaemic men was found.

Atherosclerotic plaque identification by virtual histology intravascular ultrasound in a rabbit abdominal aorta model of vulnerable plaque

This study aimed to evaluate the utility of virtual histology intravascular ultrasound (VH-IVUS) for recognizing vulnerable plaque compared to histological pathological analysis. Four-month-old New Zealand rabbits ( n = 16) were randomly divided into two groups: one fed a high-fat diet and subjected to balloon injury (experimental, n = 10) and one fed a high-fat diet alone (control, n = 6). Blood lipid profiles of overnight-fasted rabbits were measured at week 2 (beginning of study) and week 12 (end of study). At week 12, experimental group rabbits underwent IVUS under anaesthesia. Rabbits were sacrificed and a 5-cm segment of the abdominal aorta was removed. Arterial sections were subjected to pathological and immunohistochemical analyses. Serum lipid levels increased in all rabbits fed with high-fat diet, with low-density lipid cholesterol (LDL-C) levels increasing the most. Levels of six biomarkers (high sensitivity C-reactive protein, matrix metalloproteinase-3, interleukin [IL]-1, IL-10, tumour necrosis factor-α, and oxidized [ox]-LDL) showed no differences between the two groups at week 2, but were higher in the experimental group at week 12. A total of 276 atherosclerotic plaques in the experimental group were analysed. VH-IVUS had sensitivities of 87% and 92% for detection of noncalcified and calcified thin-cap fibroatheromas, respectively. VH-IVUS correctly identified 85% and 89% of noncalcified and calcified fibroatheromas, respectively. For detection of pathological intimal thickening, VH-IVUS showed a sensitivity of 79% and positive predictive value of 78%. Linear regression analysis showed a strong correlation between histology and VH-IVUS for the percent area of fibrous fibro-fatty tissue, necrotic calcified tissue, and confluent necrotic core. The intra-observer and inter-observer variability of the intimal and medial-adventitial boundaries was low. Endothelial injury followed by a high-fat diet in rabbits is a viable method for inducing atheroma, and VH-IVUS is a feasible, reproducible, and valuable means of vulnerable plaque identification in vivo.

Polyphenols: benefits to the cardiovascular system in health and in aging

Numerous studies have demonstrated the importance of naturally occurring dietary polyphenols in promoting cardiovascular health and emphasized the significant role these compounds play in limiting the effects of cellular aging. Polyphenols such as resveratrol, epigallocatechin gallate (EGCG), and curcumin have been acknowledged for having beneficial effects on cardiovascular health, while some have also been shown to be protective in aging. This review highlights the literature surrounding this topic on the prominently studied and documented polyphenols as pertaining to cardiovascular health and aging.

LOX-1 deletion and macrophage trafficking in atherosclerosis

BACKGROUND

Atherosclerosis is associated with macrophage accumulation. LOX-1 has been shown to induce macrophage attachment, and its deletion (LOX-1 knockout, KO) reduces atherosclerosis in LDLr KO mice fed a high cholesterol diet. We examined differences in macrophage trafficking in age-matched wild type, LOX-1 KO, LDLr KO, and LDLr/LOX-1 double KO mice.

METHODS

Sections of aortas of mice fed high cholesterol diet were collected at weeks 0, 4, 8, 12 and 19 and analyzed by immunohistochemistry and flow cytometry.

RESULTS

In the LDLr KO mice aorta, CD68 positivity (macrophage accumulation) increased over time up to 12 weeks, and then the accumulation fell modestly but significantly. The periaortal fat and adventitia showed more CD68 positivity than the media and intima. This pattern was also evident in the non-atherosclerotic areas. Importantly, LOX-1 KO and LDLr-LOX-1 double KO mice showed diminished CD68 positivity in comparison to wild type and LDLR KO mice, respectively. Further, macrophages from LOX-1 KO mice revealed a marked reduction in migration (vs. macrophages from wild type mice) in in vitro migration assay.

CONCLUSIONS

LOX-1 deletion translates into reduction in macrophage trafficking in the aorta of LDLr KO mice. Most of the macrophage trafficking appears in the subadventitial regions.

Eplerenone reduced lesion size in early but not advanced atherosclerosis in apolipoprotein E-deficient mice

The beneficial effects of eplerenone, a specific mineralocorticoid receptor blocker, were previously demonstrated in early atherosclerosis (ATS). The aim of the present study was to evaluate the effect of eplerenone in advanced versus early ATS. Apolipoprotein E knockout mice aged 16 or 32 weeks were randomly divided into eplerenone (100 mg·kg·d) or vehicle treatment for 14 weeks. Eplerenone reduced atherosclerotic lesion size by 51% only in early ATS. In peritoneal macrophages obtained from these mice, eplerenone reduced messenger RNA expression of pro-inflammatory markers, interleukin 6, tumor necrosis factor α, monocyte chemotactic protein 1, and increased anti-inflammatory marker arginase 1 to a greater extent in early compared with advanced ATS. These changes correspond to macrophage polarization toward alternative inflammatory phenotype. Messenger RNA expression of the mineralocorticoid receptor and aldosterone synthase were also reduced by eplerenone to a greater extent in early ATS, and these might increase the sensitivity of macrophages to mineralocorticoid blockade in early ATS. The results of the present study point to the benefits of early initiation of treatment with eplerenone in reducing experimental ATS.

Pharmacological characterization of 1-nitrosocyclohexyl acetate, a long-acting nitroxyl donor that shows vasorelaxant and antiaggregatory effects

Nitroxyl (HNO) donors have potential benefit in the treatment of heart failure and other cardiovascular diseases. 1-Nitrosocyclohexyl acetate (NCA), a new HNO donor, in contrast to the classic HNO donors Angeli's salt and isopropylamine NONOate, predominantly releases HNO and has a longer half-life. This study investigated the vasodilatative properties of NCA in isolated aortic rings and human platelets and its mechanism of action. NCA was applied on aortic rings isolated from wild-type mice and apolipoprotein E-deficient mice and in endothelial-denuded aortae. The mechanism of action of HNO was examined by applying NCA in the absence and presence of the HNO scavenger glutathione (GSH) and inhibitors of soluble guanylyl cyclase (sGC), adenylyl cyclase (AC), calcitonin gene-related peptide receptor (CGRP), and K(+) channels. NCA induced a concentration-dependent relaxation (EC(50), 4.4 µM). This response did not differ between all groups, indicating an endothelium-independent relaxation effect. The concentration-response was markedly decreased in the presence of excess GSH; the nitric oxide scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide had no effect. Inhibitors of sGC, CGRP, and voltage-dependent K(+) channels each significantly impaired the vasodilator response to NCA. In contrast, inhibitors of AC, ATP-sensitive K(+) channels, or high-conductance Ca(2+)-activated K(+) channels did not change the effects of NCA. NCA significantly reduced contractile response and platelet aggregation mediated by the thromboxane A(2) mimetic 9,11-dideoxy-11α,9α-epoxymethanoprostaglandin F(2)(α) in a cGMP-dependent manner. In summary, NCA shows vasoprotective effects and may have a promising profile as a therapeutic agent in vascular dysfunction, warranting further evaluation.

Aging and vascular dysfunction: beneficial melatonin effects

Aging is characterized by a progressive deterioration of physiological functions and metabolic processes. In aging and in diseases associated with the elderly, the loss of cells in vital structures or organs may be related to several factors. Sirtuin1 (SIRT1) is a member of the sirtuin family of protein deacetylases involved in life span extension; however, its involvement in the aging is not yet completely defined. Recently, melatonin, a pleiotropic molecule, shown to activate SIRT1 in primary neurons of young animals, as well as in aged neurons of a murine model of senescence. Melatonin is known to modulate oxidative stress-induced senescence and pro-survival pathways. We treated 6- and 15-week-old apolipoprotein E (APOE)-deficient mice (APOE 6w and 15w) with two melatonin formulations (FAST and RETARD) to evaluate their anti-aging effect. Morphological changes in vessels (aortic arch) of APOE mice were evaluated SIRT1, p53, endothelial nitric oxide synthase (eNOS), and endothelin-1 (ET-1) markers. We demonstrate that SIRT1 and eNOS decresed in APOE mice between 6 and 15 weeks and that aging induced an elevated expression of p53 and ET-1 in APOE animals. Melatonin improved the impairment of endothelial damage and reduced loss of SIRT1 and eNOS decreasing p53 and ET-1 expression. The RETARD melatonin preparation caused a greater improvement of vessel cytoarchitecture. In summary, we indicate that SIRT1-p53-eNOS axis as one of the important marker of advanced vascular dysfunctions linked to aging. Finally, we suggest that extended-release melatonin (RETARD) provides a more appropriate option for contrasting these dysfunctions compared with rapid release melatonin (FAST) administration.

Endothelial and vascular smooth muscle cell dysfunction mediated by cyclophylin A and the atheroprotective effects of melatonin

AIMS

This study evaluated the role of cyclophilin A (CyPA) in early phase of atherosclerosis and also examined the atheroprotective effects of melatonin due to its antioxidant properties.

MAIN METHODS

APOE null mice at 6 and 15weeks of age were treated with melatonin at a dose of 0.1mg/kg/day or 10mg/kg/day. We evaluated both histopathological alterations in endothelial and vascular smooth muscle cells by CyPA and rolling mononuclear cell expression during the early phase of atherosclerosis development.

KEY FINDINGS

Our study showed that CyPA expression increases and may modulate inflammatory cell adhesion and interleukin-6 expression inducing vascular smooth muscle cell migration and inflammatory cell extravasation in a time-dependent manner. Moreover, we observed an indirect atheroprotective effect of melatonin on vascular injury; it inhibited CyPA mediated inflammatory cell extravasation and oxidative stress.

SIGNIFICANCE

The melatonin treatment may represent a new atheroprotective approach that contributes to reducing the early phase of atherosclerosis involving the rolling of monocytes, their passage to subendothelial space and inhibition of CyPA expression.

Systemic and local ACTH produced during inflammatory states promotes osteochondrogenic mesenchymal cell differentiation contributing to the pathologic progression of calcified atherosclerosis

There are many well-known roles for the proopiomelanocortin (POMC) derived peptides and their receptors, the melanocortin receptors (MC-R). The focus here is on the evolving role of the melanocortin system in inflammation. Chronic inflammatory states such as those occurring in diabetes and obesity are associated with both a hyperactive hypothalamic-pituitary-adrenal (HPA) axis as well as increased incidence of atherosclerosis. An inflammation-induced hyperactive HPA axis along with increased leukocyte infiltration can lead to significant exposure to melanocortin peptides, particularly ACTH, in an inflamed vasculature. Mesenchymal progenitor cells are present throughout the vasculature, express receptors for the melanocortin peptides, and respond to ACTH with increased osteochondrogenic differentiation. Coupled to the increased exposure to ACTH during HPA hyperactivity is increased glucocorticoid (GC) exposure. GCs also promote chondrogenic differentiation of mesenchymal progenitors and increase their expression of MC-R as well as their expression of POMC and its cleavage products. It is hypothesized that during inflammatory states systemically produced ACTH and glucocorticoid as well as ACTH produced locally by macrophage and other immune cells, can influence and potentiate mesenchymal progenitor cell differentiation along the osteochondrogenic lineages. In turn the increase in osteochondrogenic matrix contributes to the pathophysiological progression of the calcified atherosclerotic plaque. The roles of the melanocortin system in inflammation and its resolution have just begun to be explored. Investigations into the ACTH-induced matrix changes among mesenchymal cell populations are warranted. ACTH signaling through the MC-R represents a new therapeutic target for the prevention and treatment of calcified atherosclerosis.

A new insight of mechanisms, diagnosis and treatment of diabetic cardiomyopathy

Diabetes mellitus is one of the most common chronic diseases across the world. Cardiovascular complication is the major morbidity and mortality among the diabetic patients. Diabetic cardiomyopathy, a new entity independent of coronary artery disease or hypertension, has been increasingly recognized by clinicians and epidemiologists. Cardiac dysfunction is the major characteristic of diabetic cardiomyopathy. For a better understanding of diabetic cardiomyopathy and necessary treatment strategy, several pathological mechanisms such as impaired calcium handling and increased oxidative stress, have been proposed through clinical and experimental observations. In this review, we will discuss the development of cardiac dysfunction, the mechanisms underlying diabetic cardiomyopathy, diagnostic methods, and treatment options.

In vivo fluorescence imaging of atherosclerotic plaques with activatable cell-penetrating peptides targeting thrombin activity

Thrombin and other coagulation enzymes have been shown to be important during atherosclerotic disease development. Study of these proteases is currently limited because of lack of robust molecular imaging agents for imaging protease activity in vivo. Activatable cell penetrating peptides (ACPPs) have been used to monitor MMP activity in tumors and, in principle, can be modified to detect other proteases. We have developed a probe that incorporates the peptide sequence DPRSFL from the proteinase activated receptor 1 (PAR-1) into an ACPP and shown that it is preferentially cleaved by purified thrombin. Active thrombin in serum cleaves DPRSFL-ACPP with >90% inhibition by lepirudin or argatroban. The DPRSFL-ACPP cleavage product accumulated in advanced atherosclerotic lesions in living mice, with 85% reduction in retention upon pre-injection of mice with hirudin. Uptake of the ACPP cleavage product was highest in plaques with histological features associated with more severe disease. Freshly resected human atheromas bathed in DPRSFL-ACPP retained 63% greater cleavage product compared to control ACPP. In conclusion, DPRSFL-ACPP can be used to study thrombin activity in coagulation and atherosclerosis with good spatial and temporal resolution. Thrombin-sensitive ACPPs may be developed into probes for early detection and intraoperative imaging of high risk atherosclerotic plaques.

Cardiac and vascular phenotypes in the apolipoprotein E-deficient mouse

Cardiovascular death is frequently associated with atherosclerosis, a chronic multifactorial disease and a leading cause of death worldwide. Genetically engineered mouse models have proven useful for the study of the mechanisms underlying cardiovascular diseases. The apolipoprotein E-deficient mouse has been the most widely used animal model of atherosclerosis because it rapidly develops severe hypercholesterolemia and spontaneous atherosclerotic lesions similar to those observed in humans. In this review, we provide an overview of the cardiac and vascular phenotypes and discuss the interplay among nitric oxide, reactive oxygen species, aging and diet in the impairment of cardiovascular function in this mouse model.

Intravascular optical coherence tomography detection of atherosclerosis and inflammation in murine aorta

OBJECTIVE

The goal of this study was to evaluate the feasibility of imaging the aorta of apolipoprotein E-deficient (ApoE(-/-)) mice for the detection of atherosclerosis and macrophages using optical coherence tomography (OCT) compared with histology.

METHODS AND RESULTS

Atherosclerosis was induced by high-fat diet in 7-week-old ApoE(-/-) mice for 10 (n=7) and 22 (n=7) weeks. Nine-week-old ApoE(-/-) mice (n=7) fed a standard chow diet were used as controls. OCT images of a 10-mm descending aorta in situ were performed in 4 mice for each, and plaque and macrophages were determined at 0.5-mm intervals. Automated detection and quantification of macrophages were performed independently using a customized algorithm. Coregistered histological cross-sections were stained with hematoxylin-eosin, Mac-3, and von Kossa. Three mice in each group had en face OCT imaging to detect macrophages, which were compared with lipid-positive area with Sudan IV. OCT images were successfully acquired in all mice. OCT and histology were able to discriminate macrophages and plaque among the 3 groups and showed excellent correlation for (1) visual detection of plaque (r=0.98) and macrophages (r=0.93), (2) automated detection and quantification of macrophages by OCT versus Mac-3-positive area (r=0.92), and (3) en face OCT detection of macrophages versus Sudan IV-positive area (r=0.92).

CONCLUSIONS

Murine intra-aortic OCT is feasible and shows excellent correlation with histology for detection of atherosclerotic plaque and macrophages.

Interleukin-17A Deficiency Accelerates Unstable Atherosclerotic Plaque Formation in Apolipoprotein E-Deficient Mice

Objective—

Interleukin(IL)-17A, an inflammatory cytokine, has been implicated in atherosclerosis, in which inflammatory cells within atherosclerotic plaques express IL-17A. However, its role in the development of atheroscelrosis remains to be controversial.

Methods and Results—

To directly examine the role of IL-17A in atherosclerosis, we generated apolipoprotein E (ApoE)/IL-17A double-deficient (ApoE −/− IL-17A −/− ) mice. Mice were fed with high-fat diet (HFD) for either 8 or 16 weeks, both starting at ages of 6 to 8 weeks. We found that splenic CD4 + T-cells produced high amounts of IL-17A in ApoE −/− mice after HFD feeding for 8 weeks. Atherosclerosis was significantly accelerated in HFD-fed ApoE −/− IL-17A −/− mice compared with ApoE −/− mice. Splenic CD4 + T-cells of ApoE −/− IL-17A −/− mice after HFD feeding for 8 weeks, but not for 16 weeks, exhibited increased interferon gamma and decreased IL-5 production. Importantly, formation of vulnerable plaque as evidenced by reduced numbers of vascular smooth muscle cells and reduced type I collagen deposition in the plaque was detected in ApoE −/− IL-17A −/− mice after HFD feeding for 8 weeks.

Conclusion—

These results suggest that IL-17A regulates the early phase of atherosclerosis development after HFD feeding and plaque stability, at least partly if not all by modulating interferon gamma and IL-5 production from CD4 + T-cells.

Endothelial-specific Nox2 overexpression increases vascular superoxide and macrophage recruitment in ApoE⁻/⁻ mice

Aims

Vascular disease states are associated with endothelial dysfunction and increased production of reactive oxygen species derived from NADPH oxidases. However, it remains unclear whether a primary increase in superoxide production specifically in the endothelium alters the initiation or progression of atherosclerosis.

Methods and results

Mice overexpressing Nox2 specifically in the endothelium (Nox2-Tg) were crossed with ApoE^−/− mice to produce Nox2-Tg ApoE^−/− mice and ApoE^−/− littermates. Endothelial overexpression of Nox2 in ApoE^−/− mice did not alter blood pressure, but significantly increased vascular superoxide production compared with ApoE^−/− littermates, measured using both lucigenin chemiluminescence and 2-hydroxyethidium production (ApoE^−/−, 19.9 ± 6.3 vs. Nox2-Tg ApoE^−/−, 47.0 ± 7.0 nmol 2-hydroxyethidium/aorta, P< 0.05). Increased endothelial superoxide production increased endothelial levels of vascular cell adhesion protein 1 and enhanced macrophage recruitment in early lesions in the aortic roots of 9-week-old mice, indicating increased atherosclerotic plaque initiation. However, endothelial-specific Nox2 overexpression did not alter native or angiotensin II-driven atherosclerosis in either the aortic root or the descending aorta.

Conclusion

Endothelial-targeted Nox2 overexpression in ApoE^−/− mice is sufficient to increase vascular superoxide production and increase macrophage recruitment possible via activation of endothelial cells. However, this initial increase in macrophage recruitment did not alter the progression of atherosclerosis. These results indicate that Nox-mediated reactive oxygen species signalling has important cell-specific and distinct temporal roles in the initiation and progression of atherosclerosis.

Hypercholesterolemia promotes early renal dysfunction in apolipoprotein E-deficient mice

Background

Aging and dyslipidemia are processes which can lead to deleterious consequences to renal function. Therefore, the aim of this study was to determine the effects of both hypercholesterolemia and aging on renal function in mice.

Methods

Male hypercholesterolemic apolipoprotein E-deficient mice (ApoE, n = 13) and age-matched C57BL/6 control mice (C57, n = 15) were studied at 2 (young) and 8 (adult) month-old. At each time point, animals were placed in metabolic cages for 24 hours to urine volume and urinary creatinine quantification. Blood samples were collected for serum cholesterol, urea and creatinine measurements. Glomerular filtration rate (GFR) was estimated through creatinine clearance determination. Mesangial expansion was evaluated by Periodic Acid Schiff staining, renal fibrosis was determined through Masson's trichrome staining and neuronal nitric oxide synthase (nNOS) expression in the kidney was performed by Western Blotting. To statistical analysis two-way ANOVA followed by Fisher's post hoc test was used.

Results

Total plasma cholesterol was increased about 5-fold in ApoE mice at both time points compared to C57 animals. At 2-month-old, GFR was already markedly reduced in ApoE compared to C57 mice (187 ± 28 vs 358 ± 92 μL/min, p < 0.05). Adult C57 (-77%) and ApoE (-50%) mice also presented a significant reduction of GFR. In addition, serum urea was significantly increased in young ApoE animals compared to C57 mice (11 ± 1.3 vs 7 ± 0.9 mmol/L, p < 0.01). A significant mesangial expansion was observed at 2-month old ApoE mice compared to C57 mice (35 ± 0.6 vs 30 ± 0.9%, respectively, p < 0.05), which was aggravated at 8-month old animals (40 ± 3 and 35 ± 3%, respectively). Tubulointersticial fibrosis was augmented at both young (17 ± 2%, p < 0.05) and adult (20 ± 1%, p < 0.05) ApoE mice compared to respective C57 age controls (8 ± 1 and 12 ± 2%, respectively). The expression of nNOS was markedly reduced in a time-dependent manner in both strains.

Conclusions

These data show that both hypercholesterolemia and aging contribute to the loss of renal function in mice.