T1-weighted MRI of targeting atherosclerotic plaque based on CD40 expression on engulfed USPIO's cell surface

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of cholesterol within the arterial wall. Its progression can be monitored via magnetic resonance imaging (MRI). Ultrasmall Superparamagnetic Particles of Iron Oxide (USPIO) (<5 nm) have been employed as T1 contrast agents for MRI applications. In this study, we synthesized USPIO with an average surface carboxylation of approximately 5.28 nm and a zeta potential of -47.8 mV. These particles were phagocytosed by mouse aortic endothelial cells (USPIO-MAECs) and endothelial progenitor cells (USPIO-EPCs), suggesting that they can be utilized as potential contrast agent and delivery vehicle for the early detection of atherosclerosis. However, the mechanism by which this contrast agent is delivered to the plaque remains undetermined. Our results demonstrated that with increasing USPIO concentration during 10-100 μg ml-1, consistent change appeared in signal enhancement on T1-weighted MRI. Similarly, T1-weighted MRI of MAECs and EPCs treated with these concentrations exhibited a regular change in signal enhancement. Prussian blue staining of USPIO revealed substantial absorption into MAECs and EPCs after treatment with 50 μg ml-1USPIO for 24 h. The iron content in USPIO-EPCs was much higher (5 pg Fe/cell) than in USPIO-MAECs (0.8 pg Fe/cell). In order to substantiate our hypothesis that CD40 protein on the cell surface facilitates migration towards inflammatory cells, we utilized AuNPs-PEI (gold nanoparticles-polyethylenimine) carrying siRNACD40to knockout CD40 expression in MAECs. It has been documented that gold nanoparticle-oligonucleotide complexes could be employed as intracellular gene regulation agents for the control of protein level in cells. Our results confirmed that macrophages are more likely to bind to MAECs treated with AuNPs-PEI-siRNANC(control) for 72 h than to MAECs treated with AuNPs-PEI-siRNACD40(reduced CD40 expression), thus confirming CD40 targeting at the cellular level. When USPIO-MAECs and MAECs (control) were delivered to mice (high-fat-fed) via tail vein injection respectively, we observed a higher iron accumulation in plaques on blood vessels in high-fat-fed mice treated with USPIO-MAECs. We also demonstrated that USPIO-EPCs, when delivered to high-fat-fed mice via tail vein injection, could indeed label plaques by generating higher T1-weighted MRI signals 72 h post injection compared to controls (PBS, USPIO and EPCs alone). In conclusion, we synthesized a USPIO suitable for T1-weighted MRI. Our results have confirmed separately at the cellular and tissue andin vivolevel, that USPIO-MAECs or USPIO-EPCs are more accessible to atherosclerotic plaques in a mouse model. Furthermore, the high expression of CD40 on the cell surface is a key factor for targeting and USPIO-EPCs may have potential therapeutic effects.

Normoxic HIF-1α Stabilization Caused by Local Inflammatory Factors and Its Consequences in Human Coronary Artery Endothelial Cells

Knowledge about normoxic hypoxia-inducible factor (HIF)-1α stabilization is limited. We investigated normoxic HIF-1α stabilization and its consequences using live cell imaging, immunoblotting, Bio-Plex multiplex immunoassay, immunofluorescence staining, and barrier integrity assays. We demonstrate for the first time that IL-8 and M-CSF caused HIF-1α stabilization and translocation into the nucleus under normoxic conditions in both human coronary endothelial cells (HCAECs) and HIF-1α-mKate2-expressing HEK-293 cells. In line with the current literature, our data show significant normoxic HIF-1α stabilization caused by TNF-α, INF-γ, IL-1β, and IGF-I in both cell lines, as well. Treatment with a cocktail consisting of TNF-α, INF-γ, and IL-1β caused significantly stronger HIF-1α stabilization in comparison to single treatments. Interestingly, this cumulative effect was not observed during simultaneous treatment with IL-8, M-CSF, and IGF-I. Furthermore, we identified two different kinetics of HIF-1α stabilization under normoxic conditions. Our data demonstrate elevated protein levels of HIF-1α-related genes known to be involved in the development of atherosclerosis. Moreover, we demonstrate an endothelial barrier dysfunction in HCAECs upon our treatments and during normoxic HIF-1α stabilization comparable to that under hypoxia. This study expands the knowledge of normoxic HIF-1α stabilization and activation and its consequences on the endothelial secretome and barrier function. Our data imply an active role of HIF-1α in vivo in the vasculature in the absence of hypoxia.

Coronary Intimal Thickening Begins in Fetuses and Progresses in Pediatric Population and Adolescents to Atherosclerosis

The prevalence of coronary intimal thickening (IT) was assessed in fetuses and pediatric population. We studied the coronary arteries of 63 hearts obtained from fetuses, infants, children, and adolescents, deceased from noncardiac disease or trauma. Histomorphometric analysis, planimetry, and immunohistochemical studies were conducted. Intimal thickening consisted of proliferation of smooth muscle cells and scarce monocytes embedded in amorphous deposits within the internal elastic membrane (IEM). Intermingled lesions of intimal hyperplasia and parietal nonstenotic plaques were also observed. Intimal thickening was found in 10% of 20 fetuses, in 33.3% of 18 infants, 73.3% of 15 children, and 100% of 10 adolescents. A significant correlation (r = 0.671, P < 0.001) was found between the extent of IT and age. The IEM was duplicated or interrupted in 43% of patients, showing a positive correlation with the degree of IT (P = 0.01). Intimal thickening was predominantly found near bifurcation sites in the left anterior descending coronary artery (55.6%) and in zones free of bifurcation in the right coronary artery (75%). In conclusion, the prevalence and extension of IT lesions are higher at older ages within a young population. Intimal thickening may be regarded as the first event occurring in coronary preatherosclerosis, preceding lipid deposition.

Assessment of biomarkers of inflammation and premature atherosclerosis in adolescents with type-1 diabetes mellitus

Background Type-1 diabetes mellitus (T1DM) causes endothelial dysfunction and early atherosclerosis, which can result in premature coronary artery disease. The aim of this study was to determine the impact of glycemic control, vascular oxidative stress and inflammation on vascular health in adolescents with T1DM. Methods This was a cross-sectional study in adolescents with age- and sex-matched T1DM who were ≥12 years and were at least 2 years post-diagnosis. Recruitment was balanced to include individuals with hemoglobin A1c (HbA1c) ≤8.5% (n=27) or with HbA1c ≥9.5% (n=25). Biomarkers of inflammation were measured in the blood including C-reactive protein (CRP), interleukin-6 (IL-6), intercellular adhesion molecule-1 (ICAM-1), E-selectin, fibrinogen and tumor necrosis factor-α (TNF-α). Carotid intima media thickness (cIMT) and peripheral arterial tonometry (PAT) were assessed. Results Plasma E-selectin level was significantly different between the two groups with higher levels in the group with HbA1c ≥9.5% (65.0±27.7 ng/mL vs. 48.8±21.5 ng/mL, p=0.02). Though cIMT and PAT were not significantly different between the groups, Pearson correlation showed a significant direct relationship between rising HbA1c and mean right cIMT (p=0.02; r=0.37), PAT (p=0.03, r=0.31) and fibrinogen (p=0.03, r=0.03). Conclusions Elevated E-selectin level is an early marker of oxidative stress in T1DM patients with an elevated HbA1c level. Suboptimal glycemic control as evidenced by a rising HbA1c causes early atherosclerosis.

Identification of early atherosclerotic lesions in carotid arteries with quantitative characteristics measured by 3D MRI

PURPOSE

To evaluate the usefulness of quantitative characteristics of morphology and signal intensity of arterial wall measured by 3D multicontrast magnetic resonance vessel wall imaging (MRVWI) in identification of carotid early atherosclerosis (CEAS).

MATERIALS AND METHODS

In all, 61 older subjects (mean age 71.8 ± 5.6 years old; 25 males) without cardiovascular symptoms in the last 6 months were recruited. The carotid arteries without advanced plaque features on 3.0T MRI were included for analysis. Ultrasound imaging was used as a reference to identify CEAS. The morphological parameters including lumen area (LA), wall area (WA), wall thickness (WT), and normalized wall index (NWI = WA/[WA+LA] × 100%) and the signal intensity on 3.0T MR T₂ -weighted images (T₂ SI) of the carotid arterial wall were measured. Three regression models were built to identify CEAS with the following parameters: Model 1 with both morphological and T₂ SI parameters; Model 2 with T₂ SI parameters; and Model 3 with morphological parameters. All models were adjusted for age and sex. Area under the curve (AUC) was calculated to validate models.

RESULTS

Of the 86 carotid arteries without advanced plaques, 47 (54.7%) were found to have early plaques determined by ultrasound. Among three regression models, Model 1 showed the highest AUC values in identifying CEAS (left: AUC = 0.856, P < 0.001; right: AUC = 0.867, P < 0.001), followed by Model 2 (left: AUC = 0.843, P < 0.001; right: AUC = 0.798, P = 0.001), and Model 3 (left: AUC = 0.790, P = 0.002; right: AUC = 0.806, P < 0.001).

CONCLUSION

The combination of morphology and normalized T₂ SI of arterial wall measured by MRVWI is more effective than each characteristic alone in identification of CEAS. J. Magn. Reson. Imaging 2016;44:1270-1276.