Atherosclerosis in the apolipoprotein-E-deficient mouse: a decade of progress

The Gut Microbiome as Therapeutic Target in Central Nervous System Diseases: Implications for Stroke

Research on commensal microbiota and its contribution to health and disease is a new and very dynamically developing field of biology and medicine. Recent experimental and clinical investigations underscore the importance of gut microbiota in the pathogenesis and course of stroke. Importantly, microbiota may influence the outcome of cerebral ischemia by modulating central nervous system antigen-specific immune responses. In this review we summarize studies linking gut microbiota with physiological function and disorders of the central nervous system. Based on these insights we speculate about targeting the gut microbiome in order to treat stroke.

Acrolein increases macrophage atherogenicity in association with gut microbiota remodeling in atherosclerotic mice: protective role for the polyphenol-rich pomegranate juice

The unsaturated aldehyde acrolein is pro-atherogenic, and the polyphenol-rich pomegranate juice (PJ), known for its anti-oxidative/anti-atherogenic properties, inhibits macrophage foam cell formation, the hallmark feature of early atherosclerosis. This study aimed to investigate two unexplored areas of acrolein atherogenicity: macrophage lipid metabolism and the gut microbiota composition. The protective effects of PJ against acrolein atherogenicity were also evaluated. Atherosclerotic apolipoprotein E-deficient (apoE^-/-) mice that were fed acrolein (3 mg/kg/day) for 1 month showed significant increases in serum and aortic cholesterol, triglycerides, and lipid peroxides. In peritoneal macrophages isolated from the mice and in J774A.1 cultured macrophages, acrolein exposure increased intracellular oxidative stress and stimulated cholesterol and triglyceride accumulation via enhanced rates of their biosynthesis and over-expression of key regulators of cellular lipid biosynthesis: sterol regulatory element-binding proteins (SREBPs), 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR), and diacylglycerol acyltransferase1 (DGAT1). Acrolein-fed mice demonstrated a major shift in the gut microbiota composition, including a significant phylum-level change in increased Firmicutes and decreased Bacteroidetes. At the family level, acrolein significantly increased the prevalence of Ruminococcaceae and Lachnospiraceae of which the Coprococcus genus was significantly and positively correlated with serum, aortic and macrophage lipid levels and peroxidation. The pro-atherogenic effects of acrolein on serum, aortas, macrophages, and the gut microbiota were substantially abolished by PJ. In conclusion, these findings provide novel mechanisms by which acrolein increases macrophage lipid accumulation and alters the gut microbiota composition in association with enhanced atherogenesis. Moreover, PJ was found as an effective strategy against acrolein atherogenicity.

Molecular Imaging of Vulnerable Atherosclerotic Plaques in Animal Models

Atherosclerosis is characterized by intimal plaques of the arterial vessels that develop slowly and, in some cases, may undergo spontaneous rupture with subsequent heart attack or stroke. Currently, noninvasive diagnostic tools are inadequate to screen atherosclerotic lesions at high risk of acute complications. Therefore, the attention of the scientific community has been focused on the use of molecular imaging for identifying vulnerable plaques. Genetically engineered murine models such as ApoE^−/− and ApoE^−/−Fbn1C1039G^+/− mice have been shown to be useful for testing new probes targeting biomarkers of relevant molecular processes for the characterization of vulnerable plaques, such as vascular endothelial growth factor receptor (VEGFR)-1, VEGFR-2, intercellular adhesion molecule (ICAM)-1, P-selectin, and integrins, and for the potential development of translational tools to identify high-risk patients who could benefit from early therapeutic interventions. This review summarizes the main animal models of vulnerable plaques, with an emphasis on genetically altered mice, and the state-of-the-art preclinical molecular imaging strategies.

Acceleration of atherogenesis in ApoE-/- mice exposed to acute or low-dose-rate ionizing radiation

There is epidemiological evidence for increased non-cancer mortality, primarily due to circulatory diseases after radiation exposure above 0.5 Sv. We evaluated the effects of chronic low-dose rate versus acute exposures in a murine model of spontaneous atherogenesis. Female ApoE-/- mice (60 days) were chronically irradiated for 300 days with gamma rays at two different dose rates (1 mGy/day; 20 mGy/day), with total accumulated doses of 0.3 or 6 Gy. For comparison, age-matched ApoE-/- females were acutely exposed to the same doses and sacrificed 300 days post-irradiation. Mice acutely exposed to 0.3 or 6 Gy showed increased atherogenesis compared to age-matched controls, and this effect was persistent. When the same doses were delivered at low dose rate over 300 days, we again observed a significant impact on global development of atherosclerosis, although at 0.3 Gy effects were limited to the descending thoracic aorta. Our data suggest that a moderate dose of 0.3 Gy can have persistent detrimental effects on the cardiovascular system, and that a high dose of 6 Gy poses high risks at both high and low dose rates. Our results were clearly nonlinear with dose, suggesting that lower doses may be more damaging than predicted by a linear dose response.

iPAD or PADi-'tablets' with therapeutic disease potential?

Over the last five years, a growing body of literature has strengthened the rationale for the involvement of PAD (protein arginine deiminase) enzymes in diverse diseases, through direct roles of citrullination in mechanisms such as neutrophil extracellular trap formation and immune complex formation. The recent development of inhibitors of the PAD family, coupled with the availability of mice genetically deficient in PAD2 or PAD4, has accelerated understanding of the role of these targets in varied disease models. This review surveys the recent literature to confirm the therapeutic potential of PAD inhibitors as a new class of drugs to treat human autoimmune disease.

Sex Difference in Coronary Endothelial Dysfunction in Apolipoprotein E Knockout Mouse: Role of NO and A2A Adenosine Receptor

OBJECTIVE

Sex plays an important role in the pathophysiology of cardiovascular diseases. This study aims to investigate how sex impacts on the coronary flow regulation during atherosclerosis.

METHODS

ApoE KO mouse fed with western diet were used for atherosclerosis model. Coronary RH and flow response were measured using Langendorff-perfused isolated hearts.

RESULTS

Coronary RH and A23187-induced NO-dependent flow increases were significantly reduced in female (by ~28% and 48%, respectively), but not in male atherosclerotic mice. However, SNP-induced coronary vasodilation remains intact in both sexes of ApoE KO mice. L-NAME (NOS inhibitor) reduced baseline flow and RH to a lesser extent in ApoE KO (by ~19% and 31%) vs. WT (~30% and 59%, respectively), and abolished the sex difference in RH. In contrast, SCH58261 (a selective A2A AR antagonist) reduced the baseline flow and RH to a greater extent in atherosclerotic mice, but did not affect the sex difference. Immunofluorescent staining of coronary arteries showed a similar A2A AR upregulation in both sexes of ApoE KO mice.

CONCLUSIONS

Our results suggest that during atherosclerosis, female mice are more susceptible to NO-dependent endothelial dysfunction and the upregulation of A2A AR may serve as a compensatory mechanism to counteract the compromised endothelial function.

(Second) Harmonic Disharmony: Nonlinear Microscopy Shines New Light on the Pathology of Atherosclerosis

There has been increasing interest in second harmonic generation (SHG) imaging approaches for the investigation of atherosclerosis due to the deep penetration and three-dimensional sectioning capabilities of the nonlinear optical microscope. Atherosclerosis involves remodeling or alteration of the collagenous framework in affected vessels. The disease is often characterized by excessive collagen deposition and altered collagen organization. SHG has the capability to accurately characterize collagen structure, which is an essential component in understanding atherosclerotic lesion development and progression. As a structure-based imaging modality, SHG is most impactful in atherosclerosis evaluation in conjunction with other, chemically specific nonlinear optics (NLO) techniques to identify additional components of the lesion. These include the use of coherent anti-Stokes Raman scattering and two-photon excitation fluorescence for studying atherosclerosis burden, and application of stimulated Raman scattering to image cholesterol crystals. However, very few NLO studies have attempted to quantitate differences in control versus atherosclerotic states or to correlate the application to clinical situations. This review highlights the potential of SHG imaging to directly and indirectly describe atherosclerosis as a pathological condition.

Aqueous or lipid components of atherosclerotic lesion increase macrophage oxidation and lipid accumulation

INTRODUCTION AND OBJECTIVE

Understanding the interactions among atherosclerotic plaque components and arterial macrophages, is essential for elucidating the mechanisms involved in the development of atherosclerosis. We assessed the effects of lesion extracts on macrophages.

METHODS

Mouse peritoneal macrophages from atherosclerotic normoglycemic or hyperglycemic apoE(-/-) mice were incubated with aortic aqueous or with aortic lipidic extracts (mAAE or mALE) derived from these mice. In parallel, J774A.1 cultured macrophages were incubated with increasing concentrations of extracts prepared from human carotid lesions: polar lesion aqueous extract (hLAE), nonpolar lesion lipid extract (hLLE), or with their combination. In all the above systems we performed analyses of macrophage oxidative status, cholesterol, and triglyceride metabolism.

RESULTS

Aqueous or lipid extracts from either mice aorta or from human carotid lesions significantly increased macrophage oxidative stress as determined by reactive oxygen species (ROS) analysis. In parallel, a compensatory increase in the cellular antioxidant paraoxonase2 (PON2) activity and in macrophage glutathione content were observed following incubation with all extracts. Macrophage triglyceride mass and triglyceride biosynthesis rate were both significantly increased following treatment with the lipid extracts, secondary to upregulation of DGAT1. All extracts decreased cholesterol biosynthesis rate, through downregulation of HMGCR, the rate limiting enzyme in cholesterol biosynthesis. The combination of the human lesion extracts had the most significant effects.

CONCLUSION

The present study demonstrates that atherosclerotic plaque constituents enhance macrophage cellular oxidative stress, and accumulation of cholesterol and triglycerides, as shown in both in vivo and in vitro model systems.

Transcriptional Profiling of Foam Cells Reveals Induction of Guanylate-Binding Proteins Following Western Diet Acceleration of Atherosclerosis in the Absence of Global Changes in Inflammation

Background

Foam cells are central to two major pathogenic processes in atherogenesis: cholesterol buildup in arteries and inflammation. The main underlying cause of cholesterol deposition in arteries is hypercholesterolemia. This study aimed to assess, in vivo, whether elevated plasma cholesterol also alters the inflammatory balance of foam cells.

Methods and Results

Apolipoprotein E–deficient mice were fed regular mouse chow through the study or were switched to a Western‐type diet (WD) 2 or 14 weeks before death. Consecutive sections of the aortic sinus were used for lesion quantification or to isolate RNA from foam cells by laser‐capture microdissection (LCM) for microarray and quantitative polymerase chain reaction analyses. WD feeding for 2 or 14 weeks significantly increased plasma cholesterol, but the size of atherosclerotic lesions increased only in the 14‐week WD group. Expression of more genes was affected in foam cells of mice under prolonged hypercholesterolemia than in mice fed WD for 2 weeks. However, most transcripts coding for inflammatory mediators remained unchanged in both WD groups. Among the main players in inflammatory or immune responses, chemokine (C‐X‐C motif) ligand 13 was induced in foam cells of mice under WD for 2 weeks. The interferon‐inducible GTPases, guanylate‐binding proteins (GBP)3 and GBP6, were induced in the 14‐week WD group, and other GBP family members were moderately increased.

Conclusions

Our results indicate that acceleration of atherosclerosis by hypercholesterolemia is not linked to global changes in the inflammatory balance of foam cells. However, induction of GBPs uncovers a novel family of immune modulators with a potential role in atherogenesis.

Noninvasive Molecular Imaging of Mouse Atherosclerosis

Molecular imaging offers great potential for noninvasive visualization and quantitation of the cellular and molecular components involved in atherosclerotic plaque stability. In this chapter, we review emerging molecular imaging modalities and approaches for quantitative, noninvasive detection of early biological processes in atherogenesis, including vascular endothelial permeability, endothelial adhesion molecule up-regulation, and macrophage accumulation, with special emphasis on mouse models. We also highlight a number of targeted imaging nanomaterials for assessment of advanced atherosclerotic plaques, including extracellular matrix degradation, proteolytic enzyme activity, and activated platelets using mouse models of atherosclerosis. The potential for clinical translation of molecular imaging nanomaterials for assessment of atherosclerotic plaque biology, together with multimodal approaches is also discussed.

Preclinical models of atherosclerosis. The future of Hybrid PET/MR technology for the early detection of vulnerable plaque

Cardiovascular diseases are the leading cause of death in developed countries. The aetiology is currently multifactorial, thus making them very difficult to prevent. Preclinical models of atherothrombotic diseases, including vulnerable plaque-associated complications, are now providing significant insights into pathologies like atherosclerosis, and in combination with the most recent advances in new non-invasive imaging technologies, they have become essential tools to evaluate new therapeutic strategies, with which can forecast and prevent plaque rupture. Positron emission tomography (PET)/computed tomography imaging is currently used for plaque visualisation in clinical and pre-clinical cardiovascular research, albeit with significant limitations. However, the combination of PET and magnetic resonance imaging (MRI) technologies is still the best option available today, as combined PET/MRI scans provide simultaneous data acquisition together with high quality anatomical information, sensitivity and lower radiation exposure for the patient. The coming years may represent a new era for the implementation of PET/MRI in clinical practice, but first, clinically efficient attenuation correction algorithms and research towards multimodal reagents and safety issues should be validated at the preclinical level.

Effects of BM-573 on Endothelial Dependent Relaxation and Increased Blood Pressure at Early Stages of Atherosclerosis

Endothelial dysfunction is considered to be an early event in atherosclerosis and plays a pivotal role in the development, progression and clinical complications of atherosclerosis. Previous studies have shown the beneficial effects of combined inhibition of thromboxane synthase and antagonism of thromboxane receptors by BM-573 on atherosclerosis; however our knowledge about the beneficial effects of BM-573 on endothelial function and increased blood pressure related to early stage of atherosclerosis is limited. In the present study, we investigated the effects of short-term (3 μM, 1 hour) and chronic (10 mg/L, 8 weeks) treatments with BM-573 on vasodilatory function, nitric oxide (NO) bioavailability, oxidative stress and systolic blood pressure in 15 weeks old apolipoprotein E-deficient (ApoE-KO) mice. ApoE-KO mice showed a reduced endothelium-derived relaxation. In addition, NO bioavailability was reduced and oxidative stress and blood pressure were increased in ApoE-KO mice versus wild-type mice. BM-573 treatments were able to improve the relaxation profile in ApoE-KO mice. Short-term effects of BM-573 were mainly mediated by an increased phosphorylation of both eNOS and Akt, whereas BM-573 in vivo treatment also reduced oxidative stress and restored NO bioavailability. In addition, chronic administration of BM-573 reduced systolic blood pressure in ApoE-KO mice. In conclusion, pharmacological modulation of TxA2 biosynthesis and biological activities by dual TP antagonism/TxAS inhibition with BM-573, already known to prevent plaque formation, has the potential to correct vasodilatory dysfunction at the early stages of atherosclerosis.

αVβ3 integrin-targeted microSPECT/CT imaging of inflamed atherosclerotic plaques in mice

Background

α_Vβ₃-integrin is expressed by activated endothelial cells and macrophages in atherosclerotic plaques and may represent a valuable marker of high-risk plaques. We evaluated ^99mTc-maraciclatide, an integrin-specific tracer, for imaging vascular inflammation in atherosclerotic lesions in mice.

Methods

Apolipoprotein E-negative (ApoE^−/−) mice on a Western diet (n = 10) and normally fed adult C57BL/6 control mice (n = 4) were injected with ^99mTc-maraciclatide (51.8 ± 3.7 MBq). A blocking peptide was infused in three ApoE^−/− mice; this condition served as another control. After 90 min, the animals were imaged via single-photon emission computed tomography (SPECT). While maintained in the same position, the mice were transferred to computed tomography (CT) to obtain contrast-enhanced images of the aortic arch. Images from both modalities were fused, and signal was quantified in the aortic arch and in the vena cava for subtraction of blood-pool activity. The aorta was carefully dissected after imaging for gamma counting, autoradiography, and histology.

Results

Tracer uptake was significantly higher in ApoE^−/− mice than in both groups of control mice (1.56 ± 0.33 vs. 0.82 ± 0.24 vs. 0.98 ± 0.11, respectively; P = 0.006). Furthermore, higher tracer activity was detected via gamma counting in the aorta of hypercholesterolemic mice than in both groups of control mice (1.52 ± 0.43 vs. 0.78 ± 0.19 vs. 0.47 ± 0.31 ^99mTc-maraciclatide %ID/g, respectively; P = 0.018). Autoradiography showed significantly higher tracer uptake in the atherosclerotic aorta than in the control aorta (P = 0.026). Finally, in the atherosclerotic aorta, immunostaining indicated that the integrin signal came predominantly from macrophages and was correlated with the macrophage CD68 immunomarker (r = 0.73).

Conclusions

^99mTc-maraciclatide allows in vivo detection of inflamed atherosclerotic plaques in mice and may represent a non-invasive approach for identifying high-risk plaques in patients.

Short-term treatment with a 2-carba analog of cyclic phosphatidic acid induces lowering of plasma cholesterol levels in ApoE-deficient mice

Plasma cholesterol levels are associated with an increased risk of developing atherosclerosis. An elevated low-density lipoprotein cholesterol (LDL-C) level is a hallmark of hypercholesterolemia in metabolic syndrome. Our previous study suggested that when acetylated LDL (AC-LDL) was co-applied with a PPARγ agonist, rosiglitazone (ROSI), many oil red O-positive macrophages could be observed. However, addition of cyclic phosphatidic acid (cPA) to ROSI-stimulated macrophages completely abolished oil red O-stained cells, indicating that cPA inhibits PPARγ-regulated AC-LDL uptake. This study aimed to determine whether metabolically stabilized cPA, in the form of a carba-derivative of cPA (2ccPA), could reduce plasma cholesterol levels and affect the expression of genes related to atherosclerosis in apolipoprotein E-knockout (apoE(-/-)) mice. 2ccPA reduced LDL-C levels in these mice (n = 3) from 460 to 330 mg/ml, from 420 to 350 mg/ml, and 420 to 281 mg/ml under a western-type diet. 2ccPA also reduced expression of lipid metabolism-related genes, cytokines, and chemokines in ApoE-deficient mice on a high-fat diet. Taken together, these results suggest that 2ccPA governs anti-atherogenic activities in the carotid arteries of apoE-deficient mice.

Modulating the Gut Microbiota Improves Glucose Tolerance, Lipoprotein Profile and Atherosclerotic Plaque Development in ApoE-Deficient Mice

The importance of the gut microbiota (GM) in disease development has recently received increased attention, and numerous approaches have been made to better understand this important interplay. For example, metabolites derived from the GM have been shown to promote atherosclerosis, the underlying cause of cardiovascular disease (CVD), and to increase CVD risk factors. Popular interest in the role of the intestine in a variety of disease states has now resulted in a significant proportion of individuals without coeliac disease switching to gluten-free diets. The effect of gluten-free diets on atherosclerosis and cardiovascular risk factors is largely unknown. We therefore investigated the effect of a gluten-free high-fat cholesterol-rich diet, as compared to the same diet in which the gluten peptide gliadin had been added back, on atherosclerosis and several cardiovascular risk factors in apolipoprotein E-deficient (Apoe-/-) mice. The gluten-free diet transiently altered GM composition in these mice, as compared to the gliadin-supplemented diet, but did not alter body weights, glucose tolerance, insulin levels, plasma lipids, or atherosclerosis. In parallel, other Apoe-/- mice fed the same diets were treated with ampicillin, a broad-spectrum antibiotic known to affect GM composition. Ampicillin-treatment had a marked and sustained effect on GM composition, as expected. Furthermore, although ampicillin-treated mice were slightly heavier than controls, ampicillin-treatment transiently improved glucose tolerance both in the absence or presence of gliadin, reduced plasma LDL and VLDL cholesterol levels, and reduced aortic atherosclerotic lesion area. These results demonstrate that a gluten-free diet does not seem to have beneficial effects on atherosclerosis or several CVD risk factors in this mouse model, but that sustained alteration of GM composition with a broad-spectrum antibiotic has beneficial effects on CVD risk factors and atherosclerosis. These findings support the concept that altering the microbiota might provide novel treatment strategies for CVD.

Promoting brain health through exercise and diet in older adults: a physiological perspective

The rise in incidence of age-related cognitive impairment is a global health concern. Ageing is associated with a number of changes in the brain that, collectively, contribute to the declines in cognitive function observed in older adults. Structurally, the ageing brain atrophies as white and grey matter volumes decrease. Oxidative stress and inflammation promote endothelial dysfunction thereby hampering cerebral perfusion and thus delivery of energy substrates and nutrients. Further, the development of amyloid plaques and neurofibrillary tangles contributes to neuronal loss. Of interest, there are substantial inter-individual differences in the degree to which these physical and functional changes impact upon cognitive function as we grow older. This review describes how engaging in physical activity and cognitive activities and adhering to a Mediterranean style diet promote 'brain health'. From a physiological perspective, we discuss the effects of these modifiable lifestyle behaviours on the brain, and how some recent human trials are beginning to show some promise as to the effectiveness of lifestyle behaviours in combating cognitive impairment. Moreover, we propose that these lifestyle behaviours, through numerous mechanisms, serve to increase brain, cerebrovascular and cognitive reserve, thereby preserving and enhancing cognitive function for longer.

Genetic Dissection of Tissue-Specific Apolipoprotein E Function for Hypercholesterolemia and Diet-Induced Obesity

ApoE deficiency in mice (Apoe^−/−) results in severe hypercholesterolemia and atherosclerosis. In diet-induced obesity, Apoe^−/− display steatohepatitis but reduced accumulation of triacylglycerides and enhanced insulin sensitivity in white adipose tissue (WAT). Although the vast majority of apoE is expressed by hepatocytes apoE is also abundantly expressed in WAT. As liver and adipose tissue play important roles for metabolism, this study aims to outline functions of both hepatocyte- and adipocyte-derived apoE separately by investigating a novel mouse model of tissue-specific apoE deficiency. Therefore we generated transgenic mice carrying homozygous floxed Apoe alleles. Mice lacking apoE either in hepatocytes (Apoe^ΔHep) or in adipose tissue (Apoe^ΔAT) were fed experimental diets. Apoe^ΔHep exhibited slightly higher body weights, adiposity and liver weights on diabetogenic high fat diet (HFD). Accordingly, hepatic steatosis and markers of inflammation were more pronounced compared to controls. Hypercholesterolemia evoked by lipoprotein remnant accumulation was present in Apoe^ΔHep mice fed a Western type diet (WTD). Lipidation of VLDL particles and tissue uptake of VLDL were disturbed in Apoe^ΔHep while the plasma clearance rate remained unaltered. Apoe^ΔAT did not display any detectable phenotype, neither on HFD nor on WTD. In conclusion, our novel conditional apoE deletion model has proven here the role of hepatocyte apoE for VLDL production and diet-induced dyslipidemia. Specific deletion of apoE in adipocytes cannot reproduce the adipose phenotype of global Apoe^−/− mice, suggesting that apoE produced in other cell types than hepatocytes or adipocytes explains the lean and insulin-sensitive phenotype described for Apoe^−/− mice.

Health effects of carbon-containing particulate matter: focus on sources and recent research program results

Air pollution is a complex mixture of gas-, vapor-, and particulate-phase materials comprised of inorganic and organic species. Many of these components have been associated with adverse health effects in epidemiological and toxicological studies, including a broad spectrum of carbonaceous atmospheric components. This paper reviews recent literature on the health impacts of organic aerosols, with a focus on specific sources of organic material; it is not intended to be a comprehensive review of all the available literature. Specific emission sources reviewed include engine emissions, wood/biomass combustion emissions, biogenic emissions and secondary organic aerosol (SOA), resuspended road dust, tire and brake wear, and cooking emissions. In addition, recent findings from large toxicological and epidemiological research programs are reviewed in the context of organic PM, including SPHERES, NPACT, NERC, ACES, and TERESA. A review of the extant literature suggests that there are clear health impacts from emissions containing carbon-containing PM, but difficulty remains in apportioning responses to certain groupings of carbonaceous materials, such as organic and elemental carbon, condensed and gas phases, and primary and secondary material. More focused epidemiological and toxicological studies, including increased characterization of organic materials, would increase understanding of this issue.

Heterogeneity in vascular smooth muscle cell embryonic origin in relation to adult structure, physiology, and disease

Regional differences in vascular physiology and disease response exist throughout the vascular tree. While these differences in physiology and disease correspond to regional vascular environmental conditions, there is also compelling evidence that the embryonic origins of the smooth muscle inherent to the vessels may play a role. Here, we review what is known regarding the role of embryonic origin of vascular smooth muscle cells during vascular development. The focus of this review is to highlight the heterogeneity in the origins of vascular smooth muscle cells and the resulting regional physiologies of the vessels. Our goal is to stimulate future investigation into this area and provide a better understanding of vascular organogenesis and disease. .

Prediction of Response to Therapy for Autoimmune/Inflammatory Diseases Using an Activated Macrophage-Targeted Radioimaging Agent

The ability to select patients who will respond to therapy is especially acute for autoimmune/inflammatory diseases, where the costs of therapies can be high and the progressive damage associated with ineffective treatments can be irreversible. In this article we describe a clinical test that will rapidly predict the response of patients with an autoimmune/inflammatory disease to many commonly employed therapies. This test involves quantitative assessment of uptake of a folate receptor-targeted radioimaging agent ((99m)Tc-EC20) by a subset of inflammatory macrophages that accumulate at sites of inflammation. Murine models of four representative inflammatory diseases (rheumatoid arthritis, inflammatory bowel disease, pulmonary fibrosis, and atherosclerosis) show markedly decreased uptake of (99m)Tc-EC20 in inflamed lesions upon initiation of successful therapies, but no decrease in uptake upon administration of ineffective therapies, in both cases long before changes in clinical symptoms can be detected. This predictive capability should reduce costs and minimize morbidities associated with failed autoimmune/inflammatory disease therapies.

Multiscale investigation of USPIO nanoparticles in atherosclerotic plaques and their catabolism and storage in vivo

The storage and catabolism of Ultrasmall SuperParamagnetic Iron Oxide (USPIO) nanoparticles were analyzed through a multiscale approach combining Two Photon Laser Scanning Microscopy (TPLSM) and High-Resolution Transmission Electron Microscopy (HRTEM) at different times after intravenous injection in an atherosclerotic ApoE(-/-) mouse model. The atherosclerotic plaque features and the USPIO heterogeneous biodistribution were revealed down from organ's scale to subcellular level. The biotransformation of the nanoparticle iron oxide (maghemite) core into ferritin, the non-toxic form of iron storage, was demonstrated for the first time ex vivo in atherosclerotic plaques as well as in spleen, the iron storage organ. These results rely on an innovative spatial and structural investigation of USPIO's catabolism in cellular phagolysosomes. This study showed that these nanoparticles were stored as non-toxic iron compounds: maghemite oxide or ferritin, which is promising for MRI detection of atherosclerotic plaques in clinics using these USPIOs. From the Clinical Editor: Advance in nanotechnology has brought new contrast agents for clinical imaging. In this article, the authors investigated the use and biotransformation of Ultrasmall Super-paramagnetic Iron Oxide (USPIO) nanoparticles for analysis of atherosclerotic plagues in Two Photon Laser Scanning Microscopy (TPLSM) and High-Resolution Transmission Electron Microscopy (HRTEM). The biophysical data generated from this study could enable the possible use of these nanoparticles for the benefits of clinical patients.

Combined Plasma and Tissue Proteomic Study of Atherogenic Model Mouse: Approach To Elucidate Molecular Determinants in Atherosclerosis Development

Atherogenic cardiovascular diseases are the major cause of mortality. Prevention and prediction of incidents is important; however, biomarkers that directly reflect the disease progression remain poorly investigated. To elucidate molecular determinants of atherogenesis, proteomic approaches are advantageous by using model animals for comparing changes occurring systematically (bloodstream) and locally (lesion) in accordance with the disease progression stages. We conducted differential mass spectrometric analysis between apolipoprotein E deficient (apoED) and wild-type (wt) mice using the plasma and arterial tissue of both types of mice obtained at four pathognomonic time points of the disease. A total of 100 proteins in the plasma and 390 in the arterial tissues were continuously detected throughout the four time points; 29 were identified in common. Of those, 13 proteins in the plasma and 36 in the arterial tissues showed significant difference in abundance between the apoED and wt mice at certain time points. Importantly, we found that quantitative variation patterns regarding the pathognomonic time points did not always correspond between the plasma and arterial tissues, resulting in gaining insight into atherosclerotic plaque progression. These characteristic proteins were found to be components of inflammation, thrombus formation, and vascular remodeling, suggesting drastic and integrative alteration in accordance with atherosclerosis development.

Effects of Tomato and Soy Germ on Lipid Bioaccumulation and Atherosclerosis in ApoE-/- Mice

Dietary patterns with cardiovascular benefits have been recommended, but the relative contributions of individual foods and food components, alone or in combination, remain undefined. Male ApoE(-/-) mice were fed either a purified AIN-93G control diet, a Western diet (WD), or a WD with 10% tomato powder (TP), 2% soy germ (SG), or the combination, for 4 wk (n = 10 per group). Plasma total cholesterol and triglycerides were measured with enzymatic colorimetric kits, and serum amyloid A (SAA) was measured by ELISA. Liver lipids were extracted with chloroform:methanol, and triglycerides, free and esterified cholesterol measured with enzymatic colorimetric kits. Expression of Cyp27a1, Cyp7a1, Abcg5, and Abcg8 in the liver was determined by quantitative polymerase chain reaction. Sections of the aortic root and aorta were cut and stained with hematoxylin and eosin (H&E) to assess extent of atherosclerotic lesions. WD-fed animals had greater liver and adipose weights, plasma cholesterol and SAA, hepatic lipids, and atherosclerosis than AIN-93G animals. TP and SG did not decrease atherosclerosis as measured by H&E-stained sections of the aortic root, aortic arch, and descending aorta. The TP diets further increased plasma cholesterol, but also led to increased expression of the Abcg5/8 transporters involved in cholesterol efflux. Addition of SG alone to the WD attenuated WD-induced increases in plasma cholesterol, liver lipids, and gonadal adipose weight. The results of this study do not support the use of either TP or SG for reduction of atherosclerosis, but suggest some beneficial effects of SG on lipid metabolism in this model of cardiovascular disease.

Propionibacterium acnes Recovered from Atherosclerotic Human Carotid Arteries Undergoes Biofilm Dispersion and Releases Lipolytic and Proteolytic Enzymes in Response to Norepinephrine Challenge In Vitro

In the present study, human atherosclerotic carotid arteries were examined following endarterectomy for the presence of the Gram-positive bacterium Propionibacterium acnes and its potential association with biofilm structures within the arterial wall. The P. acnes 16S rRNA gene was detectable in 4 of 15 carotid artery samples, and viable P. acnes was one among 10 different bacterial species recoverable in culture. Fluorescence in situ hybridization analysis of 5 additional atherosclerotic carotid arteries demonstrated biofilm bacteria within all samples, with P. acnes detectable in 4 samples. We also demonstrated that laboratory-grown cultures of P. acnes biofilms were susceptible to induction of a biofilm dispersion response when challenged with physiologically relevant levels of norepinephrine in the presence of iron-bound transferrin or with free iron. The production and release of lipolytic and proteolytic extracellular enzymes by P. acnes were shown to increase in iron-induced dispersed biofilms, and these dispersion-induced P. acnes VP1 biofilms showed increased expression of mRNAs for the triacylglycerol lipases PPA2105 and PPA1796 and the hyaluronate lyase PPA380 compared to that in untreated biofilms. These results demonstrate that P. acnes can infect the carotid arteries of humans with atherosclerosis as a component of multispecies biofilms and that dispersion is inducible for this organism, at least in vitro, with physiologically relevant levels of norepinephrine resulting in the production and release of degradative enzymes.

Practical assessment of the quantification of atherosclerotic lesions in apoE⁻/⁻ mice

Genetic manipulations have enabled the mouse to be widely used as an animal model for investigating the mechanisms of human atherosclerotic disease. However, there is no standard method for quantifying atherosclerotic lesions among different laboratories. The present study introduces a thorough and precise quantitative assessment of atherosclerotic lesions in mice. In the present study, 6‑week‑old apoE‑/‑ mice were fed either a chow diet or a high‑fat diet (HFD) for 12 weeks. Plasma lipid levels were measured every four weeks. Aortic atherosclerotic lesions were quantified and analyzed using an image analysis system. The aortic tree was isolated and stained with Oil Red O to measure the gross lesion area. The heart was removed and divided into sequential cross sections, which were then assessed for microscopic intimal lesions in the aortic root as follows: (1) Elastic van Gieson staining was performed to determine the area of the atherosclerotic lesion; (2) cross sections were stained with hematoxylin and eosin for histological analysis; and (3) cross sections were stained with Oil Red O and immunohistochemical staining for quantitative analysis of the cellular components within the lesions. ApoE‑/‑ mice fed with either the chow diet or HFD developed severe atherosclerosis in the aortic root, however, there were few lesions in the remainder of the aortic tree. Compared with the control group, the HFD apoE‑/‑ mice had increased plasma lipid levels and increases in the gross lesion area in the aortic tree, the microscopic lesion area in the aortic root and the number of macrophages, vascular smooth muscle cells and neutral lipids present within the lesions. HFD feeding in the apoE‑/‑ mice accelerated the development of atherosclerosis. The quantitative method described in the present study may be used to assist in future investigations of atherosclerosis in mice.

Specific targeting of atherosclerotic plaques in ApoE(-/-) mice using a new Camelid sdAb binding the vulnerable plaque marker LOX-1

PURPOSE

Molecular imaging has the potential to provide quantitative information about specific biological aspects of developing atherosclerotic lesions. This requires the generation of reliable, highly specific plaque tracers. This study reports a new camelid single-domain antibody fragment (sdAb) targeting the Lectin-like oxidized low-density lipoprotein receptor (LOX-1), a biomarker for the detection and molecular phenotyping of vulnerable atherosclerotic plaques.

PROCEDURES

A camelid sdAb was generated and selected for high affinity binding to LOX-1. Ex vivo biodistribution and in vivo single photon emission computed tomography (SPECT)/computed tomography (CT) imaging studies were performed in wild-type mice and in fat-fed atherosclerotic apolipoprotein E-deficient mice with (99m)Tc-labeled sdAbs. Gamma-counting and autoradiography analyses were performed on dissected aorta segments with different degrees of plaque burden. The specificity of the LOX-1-targeting sdAb was evaluated by blocking with unlabeled sdAb or by comparison with a nontargeting (99m)Tc-labeled control sdAb.

RESULTS

We generated a sdAb binding LOX-1 with a KD of 280 pM ± 62 pM affinity. After (99m)Tc-labeling, the tracer had radiochemical purity higher then 99 % and retained specificity in in vitro binding studies. Tracer blood clearance was fast with concomitant high kidney retention. At 3 h after injection, uptake in tissues other than plaques was low and not different than background, suggesting a restricted expression pattern of LOX-1. Conversely, uptake in aortic segments increased with plaque content and was due to specific LOX-1 binding. In vivo SPECT/CT imaging 160 min after injection in atherosclerotic mice confirmed specific targeting of LOX-1-expressing aortic plaques.

CONCLUSIONS

The LOX-sdAb specifically targets LOX-1-expressing atherosclerotic plaques within hours after injection. The possibility to image LOX-1 rapidly after administration combined with the favourable biodistribution of a sdAb are beneficial for molecular phenotyping of atherosclerotic plaques and the generation of a future prognostic tracer.

Chronic Internal Exposure to Low Dose 137Cs Induces Positive Impact on the Stability of Atherosclerotic Plaques by Reducing Inflammation in ApoE-/- Mice

After Chernobyl and Fukushima Daï Chi, two major nuclear accidents, large amounts of radionuclides were released in the environment, mostly caesium 137 (137Cs). Populations living in contaminated territories are chronically exposed to radionuclides by ingestion of contaminated food. However, questions still remain regarding the effects of low dose ionizing radiation exposure on the development and progression of cardiovascular diseases. We therefore investigated the effects of a chronic internal exposure to 137Cs on atherosclerosis in predisposed ApoE-/- mice. Mice were exposed daily to 0, 4, 20 or 100 kBq/l 137Cs in drinking water, corresponding to range of concentrations found in contaminated territories, for 6 or 9 months. We evaluated plaque size and phenotype, inflammatory profile, and oxidative stress status in different experimental groups. Results did not show any differences in atherosclerosis progression between mice exposed to 137Cs and unexposed controls. However, 137Cs exposed mice developed more stable plaques with decreased macrophage content, associated with reduced aortic expression of pro-inflammatory factors (CRP, TNFα, MCP-1, IFNγ) and adhesion molecules (ICAM-1, VCAM-1 and E-selectin). Lesions of mice exposed to 137Cs were also characterized by enhanced collagen and smooth muscle cell content, concurrent with reduced matrix metalloproteinase MMP8 and MMP13 expression. These results suggest that low dose chronic exposure of 137Cs in ApoE-/- mice enhances atherosclerotic lesion stability by inhibiting pro-inflammatory cytokine and MMP production, resulting in collagen-rich plaques with greater smooth muscle cell and less macrophage content.

Transcriptomic Changes in Zebrafish Embryos and Larvae Following Benzo[a]pyrene Exposure

Benzo[a]pyrene (BaP) is an environmentally relevant carcinogenic and endocrine disrupting compound that causes immediate, long-term, and multigenerational health deficits in mammals and fish. Previously, we found that BaP alters DNA methylation patterns in developing zebrafish, which may affect gene expression. Herein, we performed a genome-wide transcriptional analysis and discovered differential gene expression and splicing in developing zebrafish. Adult zebrafish were exposed to control or 42.0 ± 1.9 µg/l BaP for 7 days. Eggs were collected and raised in control conditions or continuously exposed to BaP until 3.3 and 96 h post-fertilization (hpf). RNA sequencing (RNA-Seq) was conducted on zebrafish embryos and larvae. Data were analyzed to identify differentially expressed (DE) genes (changed at the gene or transcript variant level) and genes with differential exon usage (DEU; changed at the exon level). At 3.3 hpf, BaP exposure resulted in 8 DE genes and 51 DEU genes. At 96 hpf, BaP exposure altered expression in 1153 DE genes and 159 DEU genes. Functional ontology analysis by Ingenuity Pathway Analysis revealed that many disease pathways, including organismal death, growth failure, abnormal morphology of embryonic tissue, congenital heart disease, and adverse neuritogenesis, were significantly enriched for the DE and DEU genes, providing novel insights on the mechanisms of action of BaP-induced developmental toxicities. Collectively, we discovered substantial transcriptomic changes at the gene, transcript variant, and exon levels in developing zebrafish after early life BaP waterborne exposure, and these changes may lead to long-term adverse physiological consequences.

Imaging of small animal peripheral artery disease models: recent advancements and translational potential

Peripheral artery disease (PAD) is a broad disorder encompassing multiple forms of arterial disease outside of the heart. As such, PAD development is a multifactorial process with a variety of manifestations. For example, aneurysms are pathological expansions of an artery that can lead to rupture, while ischemic atherosclerosis reduces blood flow, increasing the risk of claudication, poor wound healing, limb amputation, and stroke. Current PAD treatment is often ineffective or associated with serious risks, largely because these disorders are commonly undiagnosed or misdiagnosed. Active areas of research are focused on detecting and characterizing deleterious arterial changes at early stages using non-invasive imaging strategies, such as ultrasound, as well as emerging technologies like photoacoustic imaging. Earlier disease detection and characterization could improve interventional strategies, leading to better prognosis in PAD patients. While rodents are being used to investigate PAD pathophysiology, imaging of these animal models has been underutilized. This review focuses on structural and molecular information and disease progression revealed by recent imaging efforts of aortic, cerebral, and peripheral vascular disease models in mice, rats, and rabbits. Effective translation to humans involves better understanding of underlying PAD pathophysiology to develop novel therapeutics and apply non-invasive imaging techniques in the clinic.

The enhanced expression of IL-17-secreting T cells during the early progression of atherosclerosis in ApoE-deficient mice fed on a western-type diet

Atherosclerosis is a chronic progressive inflammatory disorder and the leading cause of cardiovascular mortality. Here we assessed the dynamic changes of T-cell-derived cytokines, such as inteferon (IFN)-γ, interleukin (IL)-17 and IL-4, during the progression of atherosclerosis in apolipoprotein E-null (ApoE^−/−) mice, to understand the role of immune responses in different stages of atherosclerosis. Male ApoE^−/− mice were fed a high-fat, western-type diet (WD: 21% lipid, 1.5% cholesterol) after 5 weeks of age and were compared with C57BL/6 wild-type control mice fed a standard chow diet. Atherosclerotic lesions appeared in the aortic sinus of ApoE^−/− mice 4 weeks after WD and the lesions progressed and occupied >50% of the total sinus area 16 weeks after WD. Aortic IL-17 mRNA and protein expression started to increase in ApoE^−/− mice after 4 weeks on the WD and peaked at around 8–12 weeks on the WD. In terms of systemic expression of T-cell-derived cytokines, IL-17 production from splenocytes after anti-CD3/CD28 stimuli increased from 4 weeks on the WD, peaked at 12 weeks and returned to control levels at 16 weeks. The production of IFN-γ and IL-4 (Th1 and Th2 cytokines, respectively) from splenocytes was delayed compared with IL-17. Taken together, the present data indicate that Th17 cell response may be involved at an early stage in the development of atherosclerosis.

Xyloketal B attenuates atherosclerotic plaque formation and endothelial dysfunction in apolipoprotein e deficient mice

Our previous studies demonstrated that xyloketal B, a novel marine compound with a unique chemical structure, has strong antioxidant actions and can protect against endothelial injury in different cell types cultured in vitro and model organisms in vivo. The oxidative endothelial dysfunction and decrease in nitric oxide (NO) bioavailability are critical for the development of atherosclerotic lesion. We thus examined whether xyloketal B had an influence on the atherosclerotic plaque area in apolipoprotein E-deficient (apoE-/-) mice fed a high-fat diet and investigated the underlying mechanisms. We found in our present study that the administration of xyloketal B dose-dependently decreased the atherosclerotic plaque area both in the aortic sinus and throughout the aorta in apoE-/- mice fed a high-fat diet. In addition, xyloketal B markedly reduced the levels of vascular oxidative stress, as well as improving the impaired endothelium integrity and NO-dependent aortic vasorelaxation in atherosclerotic mice. Moreover, xyloketal B significantly changed the phosphorylation levels of endothelial nitric oxide synthase (eNOS) and Akt without altering the expression of total eNOS and Akt in cultured human umbilical vein endothelial cells (HUVECs). Here, it increased eNOS phosphorylation at the positive regulatory site of Ser-1177, while inhibiting phosphorylation at the negative regulatory site of Thr-495. Taken together, these findings indicate that xyloketal B has dramatic anti-atherosclerotic effects in vivo, which is partly due to its antioxidant features and/or improvement of endothelial function.

Corona-directed nucleic acid delivery into hepatic stellate cells for liver fibrosis therapy

Strategies to modify nanoparticles with biological ligands for targeted drug delivery in vivo have been widely studied but met with limited clinical success. A possible reason is that, in the blood circulation, serum proteins could rapidly form a layer of protein "corona" on the vehicle surface, which might block the modified ligands and hamper their targeting functions. We speculate that strategies for drug delivery can be designed based upon elegant control of the corona formation on the vehicle surfaces. In this study, we demonstrate a retinol-conjugated polyetherimine (RcP) nanoparticle system that selectively recruited the retinol binding protein 4 (RBP) in its corona components. RBP was found to bind retinol, and direct the antisense oligonucleotide (ASO)-laden RcP carrier to hepatic stellate cells (HSC), which play essential roles in the progression of hepatic fibrosis. In both mouse fibrosis models, induced by carbon tetrachloride (CCl4) and bile duct ligation (BDL), respectively, the ASO-laden RcP particles effectively suppressed the expression of type I collagen (collagen I), and consequently ameliorated hepatic fibrosis. Such findings suggest that this delivery system, designed to exploit the power of corona proteins, can serve as a promising tool for targeted delivery of therapeutic agents for the treatment of hepatic fibrosis.

Low-dose irradiation affects expression of inflammatory markers in the heart of ApoE -/- mice

Epidemiological studies indicate long-term risks of ionizing radiation on the heart, even at moderate doses. In this study, we investigated the inflammatory, thrombotic and fibrotic late responses of the heart after low-dose irradiation (IR) with specific emphasize on the dose rate. Hypercholesterolemic ApoE-deficient mice were sacrificed 3 and 6 months after total body irradiation (TBI) with 0.025, 0.05, 0.1, 0.5 or 2 Gy at low (1 mGy/min) or high dose rate (150 mGy/min). The expression of inflammatory and thrombotic markers was quantified in frozen heart sections (CD31, E-selectin, thrombomodulin, ICAM-1, VCAM-1, collagen IV, Thy-1, and CD45) and in plasma samples (IL6, KC, MCP-1, TNFα, INFγ, IL-1β, TGFβ, INFγ, IL-10, sICAM-1, sE-selectin, sVCAM-1 and fibrinogen) by fluorescence analysis and ELISA. We found that even very low irradiation doses induced adaptive late responses, such as increases of capillary density and changes in collagen IV and Thy-1 levels indicating compensatory regulation. Slight decreases of ICAM-1 levels and reduction of Thy 1 expression at 0.025–0.5 Gy indicate anti-inflammatory effects, whereas at the highest dose (2 Gy) increased VCAM-1 levels on the endocardium may represent a switch to a pro-inflammatory response. Plasma samples partially confirmed this pattern, showing a decrease of proinflammatory markers (sVCAM, sICAM) at 0.025–2.0 Gy. In contrast, an enhancement of MCP-1, TNFα and fibrinogen at 0.05–2.0 Gy indicated a proinflammatory and prothrombotic systemic response. Multivariate analysis also revealed significant age-dependent increases (KC, MCP-1, fibrinogen) and decreases (sICAM, sVCAM, sE-selectin) of plasma markers. This paper represents local and systemic effects of low-dose irradiation, including also age- and dose rate-dependent responses in the ApoE^-/- mouse model. These insights in the multiple inflammatory/thrombotic effects caused by low-dose irradiation might facilitate an individual evaluation and intervention of radiation related, long-term side effects but also give important implications for low dose anti-inflammatory radiotherapy.

Monocyte-targeting supramolecular micellar assemblies: a molecular diagnostic tool for atherosclerosis

Atherosclerosis is a multifactorial inflammatory disease that can progress silently for decades and result in myocardial infarction, stroke, and death. Diagnostic imaging technologies have made great strides to define the degree of atherosclerotic plaque burden through the severity of arterial stenosis. However, current technologies cannot differentiate more lethal "vulnerable plaques," and are not sensitive enough for preventive medicine. Imaging early molecular markers and quantifying the extent of disease progression continues to be a major challenge in the field. To this end, monocyte-targeting, peptide amphiphile micelles (PAMs) are engineered through the incorporation of the chemokine receptor CCR2-binding motif of monocyte chemoattractant protein-1 (MCP-1) and MCP-1 PAMs are evaluated preclinically as diagnostic tools for atherosclerosis. Monocyte-targeting is desirable as the influx of monocytes is a marker of early lesions, accumulation of monocytes is linked to atherosclerosis progression, and rupture-prone plaques have higher numbers of monocytes. MCP-1 PAMs bind to monocytes in vitro, and MCP-1 PAMs detect and discriminate between early- and late-stage atherosclerotic aortas. Moreover, MCP-1 PAMs are found to be eliminated via renal clearance and the mononuclear phagocyte system (MPS) without adverse side effects. Thus, MCP-1 PAMs are a promising new class of diagnostic agents capable of monitoring the progression of atherosclerosis.

Synthesis of acid-stabilized iron oxide nanoparticles and comparison for targeting atherosclerotic plaques: evaluation by MRI, quantitative MPS, and TEM alternative to ambiguous Prussian blue iron staining

To further optimize citrate-stabilized VSOPs (very small iron oxide particles, developed for MR angiography) for identification of atherosclerotic plaques, we modified their surface during synthesis using eight other acids for electrostatic stabilization. This approach preserves effective production for clinical application. Five particles were suitable to be investigated in targeting plaques of apoE(-/-) mice. Accumulation was evaluated by ex vivo MRI, TEM, and quantitatively by magnetic particle spectroscopy (MPS). Citric- (VSOP), etidronic-, tartaric-, and malic-acid-coated particles accumulated in atherosclerotic plaques with highest accumulation for VSOP (0.2‰ of injected dose). Targets were phagolysosomes of macrophages and of altered endothelial cells. In vivo MRI with VSOP allowed for definite plaque identification. Prussian blue staining revealed abundant endogenous iron in plaques, indistinguishable from particle iron. In apoE(-/-) mice, VSOPs are still the best anionic iron oxide particles for imaging atherosclerotic plaques. MPS allows for quantification of superparamagnetic nanoparticles in such small specimens.

FROM THE CLINICAL EDITOR

The presence of vulnerable plaques in arteries is important for the prediction of acute coronary events. VSOP (very small iron oxide particles, developed for MR angiography) have been shown to be very sensitive in identifying atherosclerotic plaques. The authors studied here further modification to the surface of VSOP during synthesis and compared their efficacy.

DAMP, an acidotropic pH indicator, can be used as a tool to visualize non-esterified cholesterol in cells

Cholesterol-rich regions are attractive targets for studying metabolic disorders that involve accumulation of cholesterol. Despite efforts to develop probes for labelling cholesterol-rich regions in cells, few of these reagents have a low molecular weight. Previous studies have shown that the acidotropic pH indicator, N-{3-[(2,4-dinitrophenyl)amino]propyl}-N-(3-aminopropyl)methylamine dihydrochloride (DAMP), reacts with cholesterol-rich organelles, such as endocrine secretary granules from endocrine cells. In this study, we demonstrated that DAMP could react with free cholesterol in a dose-dependent manner, and DAMP was able to detect cholesterol-rich subcellular organelles. DAMP was sufficiently potent to detect free cholesterol-enriched organs, but was unable to detect atherosclerotic plaques primarily composed of esterified cholesterol. Taken together, these results demonstrate that DAMP facilitates the study of cholesterol-enriched lipid rafts and disorders which involve cholesterol accumulation.

Tri-band spectroscopic optical coherence tomography based on optical parametric amplification for lipid and vessel visualization

A tri-band spectroscopic optical coherence tomography (SOCT) system has been implemented for visualization of lipid and blood vessel distribution. The tri-band swept source, which covers output spectrum in 1.3, 1.5, and 1.6  μm wavelength windows, is based on a dual-band Fourier domain mode-locked laser and a fiber optical parametric amplifier. This tri-band SOCT can further differentiate materials, e.g., lipid and artery, qualitatively by contrasting attenuation coefficients difference within any two of these bands. Furthermore, ex vivo imaging of both porcine artery with artificial lipid plaque phantom and mice with coronary artery disease were demonstrated to showcase the capability of our SOCT.

Impact of Inhibiting Ileal Apical versus Basolateral Bile Acid Transport on Cholesterol Metabolism and Atherosclerosis in Mice

BACKGROUND

Bile acid sequestrants have been used for many years to treat hypercholesterolemia by increasing hepatic conversion of cholesterol to bile acids, thereby inducing hepatic LDL receptor expression and clearance of apoB-containing particles. In order to further understand the underlying molecular mechanisms linking gut-liver signaling and cholesterol homeostasis, mouse models defective in ileal apical membrane bile acid transport (Asbt-null) and ileal basolateral membrane bile acid transport (Ostα-null) were studied under basal and hypercholesterolemic conditions.

KEY MESSAGES

Hepatic conversion of cholesterol to bile acids is the major pathway for cholesterol catabolism and a major mechanism for cholesterol elimination. Blocking ileal apical membrane bile acid transport (Asbt-null mice) increases fecal bile acid excretion, hepatic Cyp7a1 expression, and the relative proportion of taurocholate in the bile acid pool, but decreases ileal FGF15 expression, bile acid pool size, and hepatic cholesterol content. In contrast, blocking ileal basolateral membrane bile acid transport (Ostα-null mice) increases ileal FGF15 expression, reduces hepatic Cyp7a1 expression, and increases the proportion of tauro-β-muricholic acid in the bile acid pool. In the hypercholesterolemic apoE-null background, plasma cholesterol levels and measurements of atherosclerosis were reduced in Asbt/apoE-null mice, but not in Ostα/apoE-null mice.

CONCLUSIONS

Blocking the intestinal absorption of bile acids at the apical versus basolateral membrane differentially affects bile acid and cholesterol metabolism, including the development of hypercholesterolemia-associated atherosclerosis. The molecular mechanism likely involves an altered regulation of ileal FGF15 expression.

Exopolysaccharide-producing probiotic Lactobacilli reduce serum cholesterol and modify enteric microbiota in ApoE-deficient mice

BACKGROUND

Probiotic bacteria have been associated with a reduction in cardiovascular disease risk, a leading cause of death and disability.

OBJECTIVES

The aim of this study was to assess the impact of dietary administration of exopolysaccharide-producing probiotic Lactobacillus cultures on lipid metabolism and gut microbiota in apolipoprotein E (apoE)-deficient mice.

METHODS

First, we examined lipid metabolism in response to dietary supplementation with recombinant β-glucan-producing Lactobacillus paracasei National Food Biotechnology Centre (NFBC) 338 expressing the glycosyltransferase (Gtf) gene from Pediococcus parvulus 2.6 (GTF), and naturally exopolysaccharide-producing Lactobacillus mucosae Dairy Product Culture Collection (DPC) 6426 (DPC 6426) compared with the non-β-glucan-producing isogenic control strain Lactobacillus paracasei NFBC 338 (PNZ) and placebo (15% wt:vol trehalose). Second, we examined the effects on the gut microbiota of dietary administration of DPC 6426 compared with placebo. Probiotic Lactobacillus strains at 1 × 10(9) colony-forming units/d per animal were administered to apoE(-/-) mice fed a high-fat (60% fat)/high-cholesterol (2% wt:wt) diet for 12 wk. At the end of the study, aortic plaque development and serum, liver, and fecal variables involved in lipid metabolism were analyzed, and culture-independent microbial analyses of cecal content were performed.

RESULTS

Total cholesterol was reduced in serum (P < 0.001; ∼33-50%) and liver (P < 0.05; ∼30%) and serum triglyceride concentrations were reduced (P < 0.05; ∼15-25%) in mice supplemented with GTF or DPC 6426 compared with the PNZ or placebo group, respectively. In addition, dietary intervention with GTF led to increased amounts of fecal cholesterol excretion (P < 0.05) compared with all other groups. Compositional sequencing of the gut microbiota revealed a greater prevalence of Porphyromonadaceae (P = 0.001) and Prevotellaceae (P = 0.001) in the DPC 6426 group and lower proportions of Clostridiaceae (P < 0.05), Peptococcaceae (P < 0.001), and Staphylococcaceae (P < 0.01) compared with the placebo group.

CONCLUSION

Ingestion of exopolysaccharide-producing lactobacilli resulted in seemingly favorable improvements in lipid metabolism, which were associated with changes in the gut microbiota of mice.

Measurement of Endothelium-Dependent Vasodilation in Mice—Brief Report

Objective—

Endothelium-dependent, flow-mediated vasodilation after an increase in shear stress at the endothelial lining of conduit arteries during reactive hyperemia after ischemia is a fundamental principle of vascular physiology adapting blood flow to demand of supplied tissue. Flow-mediated vasodilation measurements have been performed in human studies and are of diagnostic and prognostic importance, but have been impossible because of technical limitations in transgenic mice to date, although these represent the most frequently used animal model in cardiovascular research.

Approach and Results—

Using high-frequency ultrasound, we visualized, quantified, and characterized for the first time endothelium-dependent dilation of the femoral artery after temporal ischemia of the lower part of the hindlimb and demonstrated that the signaling was almost exclusively dependent on stimulation of endothelial nitric oxide synthase, similar to acetylcholine, completely abolished after pharmacological or genetic inhibition of endothelial nitric oxide synthase and endothelial denudation, substantially impaired in mice of increasing age and cholesterol-fed ApoE knock outs and increased by the dietary polyphenol (−)-epicatechin. Intra- and interindividual variability were similar to the human methodology.

Conclusions—

The physiology of flow-mediated vasodilation in mice resembles that in humans underscoring the significance of this novel technology to noninvasively, serially, and reliably quantify flow-mediated vasodilation in transgenic mice.

Gal-geun-dang-gwi-tang improves diabetic vascular complication in apolipoprotein E KO mice fed a western diet

BACKGROUND

Gal-geun-dang-gwi-tang (GGDGT), an herbal medicine, is used to treat hypertension, stroke, and other inflammatory disorders in the clinical setting. Recently, GGDGT was recognized by the Korea Institute of Oriental Medicine. This study aimed to evaluate the effects of GGDGT in a diabetic atherosclerosis model using apolipoprotein E knockout (ApoE-/-) mice fed a Western diet.

METHODS

The mice were divided into four groups: control group, C57BL6J mice receiving a regular diet (RD); ApoE-/- group, ApoE-/- mice receiving a Western diet (WD); rosiglitazone group, ApoE-/- mice receiving rosiglitazone (WD + 10 mg · kg(-1) · day(-1)); GGDGT group, ApoE-/- mice receiving GGDGT (WD + 200 mg · kg(-1) · day(-1)).

RESULTS

Treatment with GGDGT significantly improved glucose tolerance and plasma lipid levels. In addition, GGDGT ameliorated acetylcholine-induced vascular relaxation of the aortic rings. Immunohistochemical staining showed that GGDGT suppressed intercellular adhesion molecule (ICAM)-1 expression; however, expression of endothelial nitric oxide synthase (eNOS) and insulin receptor substrate (IRS)-1 were restored in the thoracic aorta and skeletal muscle, respectively.

CONCLUSIONS

These findings suggest that GGDGT attenuates endothelial dysfunction via improvement of the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) signalling pathway and improves insulin sensitivity in diabetic atherosclerosis.

Velocity mapping of the aortic flow at 9.4 T in healthy mice and mice with induced heart failure using time-resolved three-dimensional phase-contrast MRI (4D PC MRI)

Objectives

In this study, we established and validated a time-resolved three-dimensional phase-contrast magnetic resonance imaging method (4D PC MRI) on a 9.4 T small-animal MRI system. Herein we present the feasibility of 4D PC MRI in terms of qualitative and quantitative flow pattern analysis in mice with transverse aortic constriction (TAC).

Materials and methods

4D PC FLASH images of a flow phantom and mouse heart were acquired at 9.4 T using a four-point phase-encoding scheme. The method was compared with slice-selective PC FLASH and ultrasound using Bland–Altman analysis. Advanced 3D streamlines were visualized utilizing Voreen volume-rendering software.

Results

In vitro, 4D PC MRI flow profiles showed the transition between laminar and turbulent flow with increasing velocities. In vivo, 4D PC MRI data of the ascending aorta and the pulmonary artery were confirmed by ultrasound, resulting in linear regressions of R² > 0.93. Magnitude- and direction-encoded streamlines differed substantially pre- and post-TAC surgery.

Conclusions

4D PC MRI is a feasible tool for in vivo velocity measurements on high-field small-animal scanners. Similar to clinical measurement, this method provides a complete spatially and temporally resolved dataset of the murine cardiovascular blood flow and allows for three-dimensional flow pattern analysis.

Electronic supplementary material

The online version of this article (doi:10.1007/s10334-014-0466-z) contains supplementary material, which is available to authorized users.

Late inflammatory and thrombotic changes in irradiated hearts of C57BL/6 wild-type and atherosclerosis-prone ApoE-deficient mice

BACKGROUND AND PURPOSE

Radiation-induced heart disease represents a late complication of thoracic radiotherapy. We investigated the inflammatory and thrombotic response after local heart irradiation in wild-type and atherosclerosis-prone mice.

MATERIAL AND METHODS

Atherosclerosis-prone ApoE(-/-) and C57BL/6 wild-type mice were sacrificed 20, 40, and 60 weeks after irradiation with 0.2, 2, 8, or 16 Gy. The expression of CD31, vascular cell adhesion molecule-1 (VCAM-1), thrombomodulin (TM), and CD45 were quantified by immunofluorescence staining of heart tissue sections.

RESULTS

Microvascular density decreased at 40 weeks after 16 Gy in C57BL/6 but not in ApoE(-/-) mice. CD31 expression declined in C57BL/6 mice at 40 weeks (8 Gy), but increased in ApoE(-/-) mice at 20 (2/8/16 Gy) and 60 weeks (16 Gy). Capillary area decreased in C57BL/6 at 40 weeks (8/16 Gy) but increased in ApoE(-/-) mice at 20 weeks (16 Gy). Endocardial VCAM-1 expression remained unchanged. TM-positive capillaries decreased at 40 weeks (8/16 Gy) in C57BL/6 and at 60 weeks (2/16 Gy) in ApoE(-/-) mice. Leukocyte infiltration transiently rose 40 weeks after 8 Gy (only ApoE(-/-)) and 16 Gy. After receiving a low irradiation dose of 0.2 Gy, no significant changes were observed in any of the mouse models.

CONCLUSION

This study demonstrated that local heart irradiation affects microvascular structure and induces inflammatory/thrombotic responses in mice in a dose- and time-dependent manner. Thereby, significant prothrombotic changes were found in both strains, although they were progressive in ApoE(-/-) mice only. Proinflammatory responses, like the increase of adhesion molecules and leukocyte infiltration, were more pronounced and occurred at lower doses in ApoE(-/-) vs. C57BL/6 mice. These findings indicate that metabolic risk factors, such as decreased ApoE lipoproteins, may lead to an enhanced proinflammatory and prothrombotic late response in locally irradiated hearts.