Atherosclerotic plaque disruption induced by stress and lipopolysaccharide in apolipoprotein E knockout mice

Research development on gut microbiota and vulnerable atherosclerotic plaque

The relationship between gut microbiota and its metabolites with cardiovascular disease (CVD) has been proven. In this review, we aim to conclude the potential mechanism of gut microbiota and its metabolites on inducing the formation of vulnerable atherosclerotic plaque, and to discuss the effect of intestinal metabolites, including trimethylamine-N-oxide (TMAO), lipopolysaccharide (LPS), phenylacetylglutamine (PAG), short-chain fatty acids (SCFAs) on plaque stability. Finally, we include the impact of gut microbiota and its metabolites on plaque stability, to propose a new therapeutic direction for coronary heart disease. Gut microbiota regulation intervenes the progress of arteriosclerosis, especially on coronary atherosclerosis, by avoiding or reducing the formation of vulnerable plaque, to lower the morbidity rate of myocardial infarction.

Hepatic steatosis and advanced hepatic fibrosis are independent predictors of long-term mortality in acute myocardial infarction

AIM

To examine the prevalence and prognosis of hepatic steatosis and fibrosis in post-acute myocardial infarction (AMI) patients.

METHODS

Patients presenting with AMI to a tertiary hospital were examined from 2014 to 2021. Hepatic steatosis and advanced hepatic fibrosis were determined using the Hepatic Steatosis Index and fibrosis-4 index, respectively. The primary outcome was all-cause mortality. Cox regression models identified determinants of mortality after adjustments and Kaplan-Meier curves were constructed for all-cause mortality, stratified by hepatic steatosis and advanced fibrosis.

RESULTS

Of 5765 patients included, 24.8% had hepatic steatosis, of whom 41.7% were diagnosed with advanced fibrosis. The median follow-up duration was 2.7 years. Patients with hepatic steatosis tended to be younger, female, with elevated body mass index and an increased metabolic burden of diabetes, hypertension and hyperlipidaemia. Patients with hepatic steatosis (24.6% vs. 20.9% mortality, P < .001) and advanced fibrosis (45.6% vs. 32.9% mortality, P < .001) had higher all-cause mortality rates compared with their respective counterparts. Hepatic steatosis (adjusted hazard ratio 1.364, 95% CI 1.145-1.625, P = .001) was associated with all-cause mortality after adjustment for confounders. Survival curves showed excess mortality in patients with hepatic steatosis compared with those without (P = .002).

CONCLUSIONS

Hepatic steatosis and advanced fibrosis have a substantial prevalence among patients with AMI. Both are associated with mortality, with an incrementally higher risk when advanced fibrosis ensues. Hepatic steatosis and fibrosis could help risk stratification of AMI patients beyond conventional risk factors.

Relationship between non-invasively detected liver fibrosis and in-hospital outcomes in patients with acute coronary syndrome undergoing PCI

BACKGROUND

Patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI) still experience a high rate of in-hospital complications. Liver fibrosis (LF) is a risk factor for mortality in the general population. We investigated whether the presence of LF detected by the validated fibrosis 4 (FIB-4) score may indicate ACS patients at higher risk of poor outcome.

METHODS

In the prospective ongoing REAl-world observationaL rEgistry of Acute Coronary Syndrome (REALE-ACS), LF was defined by a FIB-4 score > 3.25. We repeated the analysis using an APRI score > 0.7. The primary endpoint was in-hospital adverse events (AEs) including a composite of in-hospital cardiogenic shock, PEA/asystole, acute pulmonary edema and death.

RESULTS

A total of 469 consecutive ACS consecutive patients were enrolled. Overall, 21.1% of patients had a FIB-4 score > 3.25. Patients with LF were older, less frequently on P2Y12 inhibitors (p = 0.021) and admitted with higher serum levels of white blood cells (p < 0.001), neutrophils to lymphocytes ratio (p < 0.001), C-reactive protein (p = 0.013), hs-TnT (p < 0.001), creatine-kinase MB (p < 0.001), D-Dimer levels (p < 0.001). STEMI presentation and higher Killip class/GRACE score were more common in the LF group (p < 0.001). 71 patients experienced 110 AEs. At the multivariate analysis including clinical and laboratory risk factors, FIB-4 > 3.25 (OR 3.1, 95%CI 1.4-6.9), admission left ventricular ejection fraction% below median (OR 9.2, 95%CI 3.9-21.7) and Killip class ≥ II (OR 6.3, 95%CI 2.2-18.4) were the strongest independent predictors of in-hospital AEs. Similar results were obtained using the APRI score.

CONCLUSION

LF detected by FIB-4 score > 3.25 was associated with more severe ACS presentation and worse in-hospital AEs irrespective of clinical and laboratory variables.

Metformin Directly Binds to MMP-9 to Improve Plaque Stability

Vulnerable atherosclerotic plaque rupture is the principal mechanism that accounts for myocardial infarction and stroke. High matrix metalloproteinase-9 (MMP-9) expression and activity have been proven to lead to plaque instability. Metformin, a first-line treatment for type 2 diabetes, is beneficial to plaque vulnerability. However, the mechanism underlying its anti-atherogenic effect remains unclear. Molecular docking and surface plasmon resonance experiments showed that metformin directly interacts with MMP-9, and incubated MMP-9 overexpressing HEK293A cells with metformin (1 μmol·L^-1) significantly attenuates MMP-9's activity using zymography and MMP activity assays. Moreover, metformin treatment drives MMP-9 degradation. Next, we constructed a carotid artery atherosclerotic plaque model and administered consecutive 14-day metformin (200 mg·kg^-1·d^-1) treatment by intragastric gavage. Immunofluorescence staining of the right carotid common artery and serum MMP activity assay results showed that metformin treatment decreased local plaque MMP-9 protein level and circulating MMP-9 activity, respectively. Histochemical staining revealed that after metformin treatment, the collagen content in plaque was significantly preserved, and the plaque vulnerability index decreased. These findings suggested that metformin improved atherosclerotic plaque stability by directly binding to MMP-9 and driving its degradation.

Sevoflurane prevents vulnerable plaque disruption in apolipoprotein E-knockout mice by increasing collagen deposition and inhibiting inflammation

BACKGROUND

Sevoflurane may reduce the occurrence of major adverse cardiovascular events (MACCEs) in surgical patients, although the mechanisms are poorly understood. We hypothesised that sevoflurane stabilises atherosclerotic plaques by inhibiting inflammation and enhancing prolyl-4-hydroxylase α1 (P4Hα1), the rate-limiting subunit for the P4H enzyme essential for collagen synthesis.

METHODS

We established a vulnerable arterial plaque model in apolipoprotein E-knockout mice (ApoE^-/-) fed a high-fat diet that underwent daily restraint/noise stress, with/without a single prior exposure to sevoflurane for 6 h (1-3%; n=30 per group). In vitro, smooth muscle cells (SMCs) were incubated with tumour necrosis factor-alpha in the presence/absence of sevoflurane. Immunohistochemistry, immunoblots, and mRNA concentrations were used to quantify the effect of sevoflurane on plaque formation, expression of inflammatory cytokines, P4Hα1, and collagen subtypes in atherosclerotic plaques or isolated SMCs.

RESULTS

In ApoE^-/- mice, inhalation of sevoflurane 1-3% for 6 h reduced the aortic plaque size by 8-29% in a dose-dependent manner, compared with control mice that underwent restraint stress alone (P<0.05); this was associated with reduced macrophage infiltration and lower lipid concentrations in plaques. Sevoflurane reduced gene transcription and protein expression levels of pro-inflammatory cytokines (≥69-75%; P<0.05) and matrix metalloproteinases (≥39-65%; P<0.05) at both gene transcription and protein levels, compared with controls. Sevoflurane dose dependently increased Types I and III collagen deposition through enhanced protein expression of P4Hα1, both in vivo and in vitro (0.7-3.3-fold change; P<0.05).

CONCLUSIONS

Sevoflurane dose dependently promotes plaque stabilisation and decreases the incidence of plaque disruption in ApoE^-/- mice by increasing collagen deposition and inhibiting inflammation. These mechanisms may contribute to sevoflurane reducing MACCE.

Effects of occlusal disharmony on cardiac fibrosis, myocyte apoptosis and myocyte oxidative DNA damage in mice

Occlusal disharmony leads to morphological changes in the hippocampus and osteopenia of the lumbar vertebra and long bones in mice, and causes stress. Various types of stress are associated with increased incidence of cardiovascular disease, but the relationship between occlusal disharmony and cardiovascular disease remain poorly understood. Therefore, in this work, we examined the effects of occlusal disharmony on cardiac homeostasis in bite-opening (BO) mice, in which a 0.7 mm space was introduced by cementing a suitable applicance onto the mandibular incisior. We first examined the effects of BO on the level of serum corticosterone, a key biomarker for stress, and on heart rate variability at 14 days after BO treatment, compared with baseline. BO treatment increased serum corticosterone levels by approximately 3.6-fold and the low frequency/high frequency ratio, an index of sympathetic nervous activity, was significantly increased by approximately 4-fold by the BO treatment. We then examined the effects of BO treatment on cardiac homeostasis in mice treated or not treated with the non-selective β-blocker propranolol for 2 weeks. Cardiac function was significantly decreased in the BO group compared to the control group, but propranolol ameliorated the dysfunction. Cardiac fibrosis, myocyte apoptosis and myocyte oxidative DNA damage were significantly increased in the BO group, but propranolol blocked these changes. The BO-induced cardiac dysfunction was associated with increased phospholamban phosphorylation at threonine-17 and serine-16, as well as inhibition of Akt/mTOR signaling and autophagic flux. These data suggest that occlusal disharmony might affect cardiac homeostasis via alteration of the autonomic nervous system.

Molecular markers relevant to myocardial injury following dental extraction in patients with or without coronary artery disease

Objectives

The aim of this study was to characterize biological changes following dental extractions in patients with and without coronary artery disease (CAD).

Materials and methods

Forty-five patients (36 males and 9 females) referred for dental extraction underwent treatment and provided blood samples before, immediately after, and 24 h after the procedure. A broad array of biomarkers was employed to assess myocardial injury (highly sensitive troponin T, hs-TnT), bacterial burden (LPS endotoxin activity), and systemic inflammation (CRP, fibrinogen, IFN-γ, IL-1β, IL-6, IL-8, IL-10, IL-12, and TNF-α).

Results

Dental extraction in patients with and without CAD was associated with rises in hs-TnT (p = 0.013), hs-CRP (p < 0.001), fibrinogen (p = 0.005), endotoxin activity (p < 0.001), IFN-γ (p < 0.001), IL-6 (p < 0.001), IL-8 (p = 0.011), and IL-12 (p < 0.001) at 24 h compared with immediately post procedure. Changes in systemic inflammation and endotoxin activity were more evident in those with hs-TnT rise.

Conclusions

Simple dental extractions may cause mild increase in hs-TnT, indicating minor myocardial injury in both patients with and without CAD. Acute systemic inflammation and endotoxemia could represent a possible link between invasive dental treatment and increased risk of acute cardiovascular events. These findings indicate that invasive dental treatment (as simple as a single dental extraction) may impact negatively on clinical outcomes in dental patients, especially those with CAD.

Overexpression of tissue factor induced atherothrombosis in apolipoprotein E-/- mice via both enhanced plaque thrombogenicity and plaque instability

The mechanisms leading to atherothrombosis from "vulnerable plaque" are more complex than initially proposed. We aimed to clarify whether plaque thrombogenicity is critical in atherothrombosis in mice. In a murine model of plaque destabilization, we enhanced plaque thrombogenicity by systemically overexpressing murine tissue factor (TF) by adenovirus-mediated gene transfer. The potential effects and mechanisms of TF on plaque destabilization were examined in cultured human aortic smooth muscle cells (HASMCs), RAW264.7 cells and human umbilical vein endothelial cells (HUVECs). To elucidate the TF noncoagulant effects on plaque destabilization, TF-overexpressed mice were treated with the protease-activated receptor 2 (PAR-2) antagonist ENMD-1068. In TF-overexpressing apolipoprotein (E)-deficient (ApoE-/-) mice, 67% (8 of 12) of carotid plaques exhibited plaque disruption and atherothrombosis. Moreover, 58% (7 of 12) showed plaque hemorrhage, including 1 due to plaque disruption, 4 neovascularization and 2 both. In contrast, only 17% (2 of 12) of control mice showed atherothrombosis, both with plaque hemorrhage but no neovascularization. On PCR, TF overexpression increased the expression of inflammatory factors. In cultured cells, the TF-FVIIa complex enhanced the expression of inflammatory factors and a vicious cycle of inflammation. Also, TF-FVIIa complex induced intra-plaque angiogenesis via PAR-2. ENMD-1068 treatment significantly inhibited the expression of inflammatory factors and neovascularization, and the incidence of intra-plaque hemorrhage decreased in TF-overexpressing mice. In conclusions, TF overexpression enhanced plaque thrombogenicity, which played a pivotal role in atherothrombosis in ApoE-/- mice. In addition, TF promoted plaque instability by activating inflammatory and proangiogenic effects via TF-FVIIa/PAR-2 signaling.

Rosuvastatin stabilizes atherosclerotic plaques by reducing CD40L overexpression-induced downregulation of P4Hα1 in ApoE-/- mice

Background Cluster of differentiation 40 ligand (CD40L) and rosuvastatin (RSV) affect atherosclerotic plaque stability, but little is known about their roles in extracellular matrix (ECM) production. We investigated the effects of CD40L and RSV on pre-existing advanced plaques. Methods and results Pre-existing advanced plaques were induced in apolipoprotein E-knockout (ApoE^-/-) mice by the surgical placement of carotid constrictive silastic collars. Two weeks after surgery, mice were divided into the following treatment groups: control, empty adenovirus, CD40L adenovirus, CD40L adenovirus + RSV, and RSV. Mice received adenovirus via two tail-vein injections (2 × 10⁹ pfu each) and/or RSV via intragastric administration (5 mg/kg; daily for 4 weeks). Mice in the CD40L adenovirus group exhibited increased plaque disruption rates, increased relative plaque macrophage and lipid content, reduced plaque collagen content, and increased local inflammation compared to the other treatment groups, but no significant differences in plaque area were observed among the groups. Notably, in the atherosclerotic plaques of the CD40L adenovirus group, both the mRNA and protein expression of prolyl-4-hydroxylase alpha 1 (P4Hα1) was significantly decreased, leading to a consequent decrease in the protein expression of collagen types I and III. Treatment with RSV decreased the serum levels of CD40L in a lipid-independent fashion and attenuated the effects of CD40L overexpression, particularly with respect to P4Hα1 downregulation. Conclusions CD40L destabilized advanced plaques in the carotid arteries of ApoE^-/- mice, in part by decreasing P4Hα1 expression, and consequently collagen expression. These destabilizing effects were attenuated by RSV.

The Role of Psychological Stress on Heart Autophagy in Mice With Heart Failure

OBJECTIVE

Psychological stress in chronic heart failure (CHF) is associated with systemic neurohormonal and immune system responses and increased mortality. Autophagy refers to the biological process of degradation and recycling of dysfunctional cellular components. We investigated the role of psychological stress on autophagy function in CHF mice.

METHODS

C57BL/6 mice underwent transverse aortic constriction, with or without combined acoustic and restraint stress, and cardiac function was assessed by echocardiography analysis. Serum corticosterone and angiotensin II (Ang II) were determined using enzyme-linked immunosorbent assay (ELISA). Autophagy and oxidative stress were measured with immunohistochemistry and quantitative polymerase chain reaction, and chloroquine and rapamycin were used to detect autophagy flux. In vivo, cardiomyocytes were cultured with or without Ang II or N-acetylcysteine, and autophagy and oxidative stress were also detected.

RESULTS

A 1-week stress exposure significantly increased serum levels of corticosterone and Ang II (p = .000), increased levels of oxidative stress, induced overt heart failure, and increased mortality (p = .002). Furthermore, stress exposure unregulated messenger RNA expression of Bcl-2-interacting coiled-coil protein 1 (10.891 [3.029] versus 4.754 [1.713], p = .001), cysteine-rich domain containing beclin-1 interacting (6.403 [1.813] versus 3.653 [0.441], p = .006), and autophagy 7 (111.696 [4.049] versus 6.189 [1.931], p = .017), increased expression of autophagosomal, and decreased clearance of autophagosomes. In vitro, Ang II significantly increased autophagy flux in cultured cardiomyocytes, which could be partly inhibited by N-acetylcysteine.

CONCLUSIONS

Psychological stress may contribute to the development of CHF by enhancing heart oxidative stress and impairing autophagy flux.

MiR-135a represses oxidative stress and vascular inflammatory events via targeting toll-like receptor 4 in atherogenesis

Plenty of microRNAs have been identified as critical mediators in atherosclerosis progression, which is still a great threat to human health. Oxidative stress and inflammation have been implicated to contribute a lot to atherosclerosis development. MiR-135a is abnormally expressed in various cancer types, however its function in atherosclerosis is largely unexplored. Ox-LDL is commonly recognized as a crucial atherosclerosis regulator. In our current study, we observed ox-LDL was able to induce RAW264.7 cell apoptosis and meanwhile miR-135a was restrained by ox-LDL both dose-dependently and time- dependently. CD36 has been reported to participate in atherosclerosis process and miR-135a mimics can inhibit its expression while miR-135a inhibitors exhibited a reverse phenomenon. Meanwhile, miR-135a overexpression can suppress foam cell formation, TC, TG levels, and cell apoptosis induced by 20 µg/mL ox-LDL. Subsequently, it was found that miR-135a overexpression can inhibit oxidative stress by decreasing ROS, MDA levels, and increasing SOD levels. Reversely, miR-135a inhibition demonstrated an inhibitory effect in vitro. Apart from these, miR-135a can also modulate inflammation molecules including IL-6, IL-1β, and TNF-α. TLR4 was predicted as a target of miR-135a and the negative correlation between them was confirmed by dual-luciferase reporter assay in our study. This work improves our understanding of atherosclerosis events mediated by miR-135a/TLR4 and helps to develop new approaches for atherosclerosis.

Silencing of Non-POU-domain-containing octamer-binding protein stabilizes atherosclerotic plaque in apolipoprotein E-knockout mice via NF-κB signaling pathway

BACKGROUND

It remains unknown whether Non-POU-domain-containing octamer-binding protein (NonO) plays a causative role in plaque destabilization. We hypothesized that NonO gene silencing may stabilize atherosclerotic plaque by increasing P4Hα1 expression and inhibiting the inflammation.

METHODS AND RESULTS

Vulnerable atherosclerotic plaques were induced in ApoE-/- mice by high fat diet, perivascular collar placement and mental stress. Compared with normal carotid arteries, those contained vulnerable plaques had high NonO expression. In another in vivo experiment, mice contained vulnerable plaques were randomly divided into 5 groups to receive physiological saline, si-N.C-lentivirus (LV), si-NonO-LV, pGC-GFP-LV and NonO-LV, respectively. NonO overexpression increased while NonO silencing decreased the incidence of carotid plaque disruption. NonO overexpression enhanced macrophage infiltration and lipid deposition but reduced the content of vascular smooth muscle cells and collagen in plaques, leading to an increased plaque vulnerability index, whereas NonO silencing exhibited the opposite effect. In addition, NonO overexpression increased the expression of proinflammatory cytokines and matrix metalloproteinases and decreased the expression of P4Hα1 both in vivo and in vitro, whereas NonO silencing showed the contrary effect. NonO co-immunoprecipitated with NF-κB p65, and promoted its nuclear translocation and phosphorylation, and these effects were reversed by NonO silencing.

CONCLUSION

NonO may promote plaque destabilization and increase the incidence of plaque disruption in ApoE-/- mice by inducing the expression of inflammatory cytokines and matrix metalloproteinases and suppressing that of P4Hα1. The mechanism may involve the interaction of NonO with NF-κB leading to enhanced NF-κB nuclear translocation and phosphorylation.

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.

Quantification of Endothelial αvβ3 Expression with High-Frequency Ultrasound and Targeted Microbubbles: In Vitro and In Vivo Studies

Angiogenesis is a critical feature of plaque development in atherosclerosis and might play a key role in both the initiation and later rupture of plaques. The precursory molecular or cellular pro-angiogenic events that initiate plaque growth and that ultimately contribute to plaque instability, however, cannot be detected directly with any current diagnostic modality. This study was designed to investigate the feasibility of ultrasound molecular imaging of endothelial αvβ3 expression in vitro and in vivo using αvβ3-targeted ultrasound contrast agents (UCAs). In the in vitro study, αvβ3 expression was confirmed by immunofluorescence in a murine endothelial cell line and detected using the targeted UCA and ultrasound imaging at 18-MHz transmit frequency. In the in vivo study, expression of endothelial αvβ3 integrin in murine carotid artery vessels and microvessels of the salivary gland was quantified using targeted UCA and high-frequency ultrasound in seven animals. Our results indicated that endothelial αvβ3 expression was significantly higher in the carotid arterial wall containing atherosclerotic lesions than in arterial segments without any lesions. We also found that the salivary gland can be used as an internal positive control for successful binding of targeted UCA to αvβ3 integrin. In conclusion, αvβ3-targeted UCA allows non-invasive assessment of the expression levels of αvβ3 on the vascular endothelium and may provide potential insights into early atherosclerotic plaque detection and treatment monitoring.

Acute and chronic psychological stress as risk factors for cardiovascular disease: Insights gained from epidemiological, clinical and experimental studies

Cardiovascular disease (CVD) remains a leading cause of death worldwide and identification and therapeutic modulation of all its risk factors is necessary to ensure a lower burden on the patient and on society. The physiological response to acute and chronic stress exposure has long been recognized as a potent modulator of immune, endocrine and metabolic pathways, however its direct implications for cardiovascular disease development, progression and as a therapeutic target are not completely understood. More and more attention is given to the bidirectional interaction between psychological and physical health in relation to cardiovascular disease. With atherosclerosis being a chronic disease starting already at an early age the contribution of adverse early life events in affecting adult health risk behavior, health status and disease development is receiving increased attention. In addition, experimental research into the biological pathways involved in stress-induced cardiovascular complications show important roles for metabolic and immunologic maladaptation, resulting in increased disease development and progression. Here we provide a concise overview of human and experimental animal data linking chronic and acute stress to CVD risk and increased progression of the underlying disease atherosclerosis.

miR-223 Inhibits Lipid Deposition and Inflammation by Suppressing Toll-Like Receptor 4 Signaling in Macrophages

Atherosclerosis and its complications rank as the leading cause of death with the hallmarks of lipid deposition and inflammatory response. MicroRNAs (miRNAs) have recently garnered increasing interests in cardiovascular disease. In this study, we investigated the function of miR-223 and the underlying mechanism in atherosclerosis. In the atherosclerotic ApoE^−/− mice models, an obvious increase of miR-223 was observed in aortic atherosclerotic lesions. In lipopolysaccharide (LPS) activated macrophages, its expression was decreased. The miR-223 overexpression significantly attenuated macrophage foam cell formation, lipid accumulation and pro-inflammatory cytokine production, which were reversed by anti-miR-223 inhibitor transfection. Mechanism assay corroborated that miR-223 negatively regulated the activation of the toll-like receptor 4 (TLR4)-nuclear factor-κB (NF-κB) pathway. Pretreatment with a specific inhibitor of NF-κB (pyrrolidinedithiocarbamate, PDTC) strikingly abrogated miR-223 silence-induced lipid deposition and inflammatory cytokine production. Furthermore, PI3K/AKT was activated by miR-223 up-regulation. Pretreatment with PI3K/AKT inhibitor LY294002 strikingly ameliorated the inhibitory effects of miR-223 on the activation of TLR4 and p65, concomitant with the increase in lipid deposition and inflammatory cytokine production. Together, these data indicate that miR-223 up-regulation might abrogate the development of atherosclerosis by blocking TLR4 signaling through activation of the PI3K/AKT pathway, and provides a promising therapeutic avenue for the treatment of atherosclerosis.

Chronic intermittent mental stress promotes atherosclerotic plaque vulnerability, myocardial infarction and sudden death in mice

Vulnerable atherosclerotic plaques are prone to plaque rupture leading to acute cardiovascular syndromes and death. Elucidating the risk of plaque rupture is important to define better therapeutic or preventive strategies. In the present study, we investigated the effect of chronic intermittent mental stress on atherosclerotic plaque stability and cardiovascular mortality in apolipoprotein E-deficient (ApoE(-/-)) mice with a heterozygous mutation in the fibrillin-1 gene (Fbn1(C1039G+/)(-)). This mouse model displays exacerbated atherosclerosis with spontaneous plaque ruptures, myocardial infarction and sudden death, when fed a Western-type diet (WD). Female ApoE(-/-)Fbn1(C1039G+/-) mice were fed a WD for up to 25 weeks. After 10 weeks WD, mice were divided in a control (n = 27) and mental stress (n = 29) group. The chronic intermittent mental stress protocol consisted of 3 triggers: water avoidance, damp bedding and restraint stress, in a randomly assigned order lasting 6 h every weekday for 15 weeks. Chronic intermittent mental stress resulted in a significant increase in the amount of macrophages in atherosclerotic plaques of the proximal ascending aorta, whereas type I collagen and fibrous cap thickness were decreased. The coronary arteries of mental stress-treated mice showed larger plaques, more stenosis, and an increased degree of perivascular fibrosis. Moreover, myocardial infarctions occurred more frequently in the mental stress group. As compared to the control group, the survival of stressed ApoE(-/-)Fbn1(C1039G+/-) mice decreased from 67% to 52% at 25 weeks WD, presumably due to myocardial infarctions. In conclusion, chronic intermittent mental stress promotes plaque instability, myocardial infarctions, and mortality of ApoE(-/-)Fbn1(C1039G+/-) mice.

Targeting blood thrombogenicity precipitates atherothrombotic events in a mouse model of plaque destabilization

Although some features of plaque instability can be observed in genetically modified mouse models, atherothrombosis induction in mice has been attested to be difficult. We sought to test the hypothesis that alterations in blood thrombogenicity might have an essential role in the development of atherothrombosis in ApoE-/- mice. In a mouse model of plaque destabilization established in our laboratory, we targeted blood thrombogenicity by systemically overexpressing murine prothrombin via adenovirus-mediated gene transfer. Systemic overexpression of prothrombin increased blood thrombogenicity, and remarkably, precipitated atherothrombotic events in 70% of the animals. The affected plaques displayed features of culprit lesions as seen in human coronary arteries, including fibrous cap disruption, luminal thrombosis, and plaque hemorrhage. Treatment with aspirin and clopidogrel substantially reduced the incidence of atherothrombosis in this model. Mechanistically, increased inflammation, apoptosis and upregulation of metalloproteinases contributed to the development of plaque destabilization and atherothrombosis. As conclusions, targeting blood thrombogenicity in mice can faithfully reproduce the process of atherothrombosis as occurring in human coronary vessels. Our results suggest that blood-plaque interactions are critical in the development of atherothrombosis in mice, substantiating the argument that changes in blood coagulation status may have a determinant role in the onset of acute coronary syndrome.

A rabbit model of spontaneous thrombosis induced by lipopolysaccharide

AIM

Inflammation plays a critical role in the development of atherosclerotic plaque, and lipopolysaccharide (LPS) is a potentially important source of inflammation. The aim of this study was to develop a rabbit model of spontaneous thrombosis mimicking the pathophysiological and morphological characteristics of atherosclerotic plaque in humans.

METHODS

The rabbits were randomized into four groups: group A (n=10) received a normal diet; group B (n=10) received a regular diet and weekly LPS injections (1 μg/kg, Escherichia coli); group C (n=15) received a cholesterol-enriched diet before and after sustaining a balloon injury to the right common carotid artery; and group D (n=15) was treated the same as group C in addition to receiving LPS injections. The morphological characteristics of the resulting lesions were evaluated using optical coherence tomography (OCT) and histology.

RESULTS

No significant atherosclerotic plaque was observed in groups A or B. Group D exhibited a higher incidence of spontaneous luminal thrombi than group C or B (60% vs. 20% vs. 10%, p<0.05). All of the thrombi detected with OCT were confirmed on histology. A good correlation between the fibrous cap thickness and thrombus arc was obtained on OCT and the histological evaluations.

CONCLUSIONS

A rabbit model of LPS-induced spontaneous thrombosis was developed in which OCT was used to follow changes in plaque morphology.

High fat diet induces adhesion of platelets to endothelium in two models of dyslipidemia

Cardiovascular diseases (CVD) represent about 30% of all global deaths. It is currently accepted that, in the atherogenic process, platelets play an important role, contributing to endothelial activation and modulation of the inflammatory phenomenon, promoting the beginning and formation of lesions and their subsequent thrombotic complications. The objective of the present work was to study using immunohistochemistry, the presence of platelets, monocytes/macrophages, and cell adhesion molecules (CD61, CD163, and CD54), in two stages of the atheromatous process. CF-1 mice fed a fat diet were used to obtain early stages of atheromatous process, denominated early stage of atherosclerosis, and ApoE(-/-) mice fed a fat diet were used to observe advanced stages of atherosclerosis. The CF-1 mice model presented immunostaining on endothelial surface for all three markers studied; the advanced atherosclerosis model in ApoE(-/-) mice also presented granular immunostaining on lesion thickness, for the same markers. These results suggest that platelets participate in atheromatous process from early stages to advance d stages. High fat diet induces adhesion of platelets to endothelial cells in vivo. These findings support studying the participation of platelets in the formation of atheromatous plate.

Psychological stress, vascular inflammation, and atherogenesis: potential roles of circulating cytokines

Cardiovascular disease is a major cause of morbidity and mortality worldwide. Epidemiological studies have clearly demonstrated that chronic psychosocial stress increases the risk of atherosclerotic cardiovascular disease and this may involve multiple mediators and regulating pathways, whereas the precise mechanisms underlying the effects of stress on development of atherosclerosis are not completely understood. In this mini review, we summarize current information from various animal studies suggesting that stress may promote atherogenesis by stimulating vascular inflammation via elevating the level of circulating proinflammatory cytokines (such as tumor necrosis factor α and interleukin 6). Although circulating cytokines can serve as reliable biomarkers of systemic inflammation, in light of the emerging evidence, we propose that these molecules may also have a causal role in mediating stress-triggered vascular inflammatory reaction and atherogenesis. Further studies are warranted to clarify whether targeting circulating cytokines may be an effective approach to reduce the detrimental effects of chronic stress.

Simvastatin increases Prolyl-4-Hydroxylase α1 expression in atherosclerotic plaque and ox-LDL-stimulated human aortic smooth muscle cells via p38 MAPK and ERK1/2 signaling

Prolyl-4-Hydroxylase α1 (P4Hα1) is essential for collagen synthesis but the effect of statin on P4Hα1 is unknown. We hypothesize that simvastatin may increase the expression of P4Hα1 in atherosclerotic plaques and ox-LDL-stimulated human aortic smooth muscle cells (HASMCs). In HASMCs, ox-LDL suppressed P4Hα1 expression significantly with peak value occurring at 50 ug/ml treated for 8h. Ox-LDL also inhibited the expression of type I and III collagen and increased the phosphorylation level of p38 MAPK and ERK1/2, but blockade or silencing of p38 and ERK1/2 inhibited the suppressive effect of ox-LDL on P4Hα1. Then HASMCs were stimulated with or without ox-LDL (50 ug/ml) for 8h after simvastatin pretreatment for 1h. Simvastatin significantly attenuated the suppressive effect of ox-LDL on P4Hα1 and collagen production by inhibiting ox-LDL uptake and the activation of p38 MAPK and ERK1/2. In apolipoprotein E-deficient mice, simvastatin and the inhibitors of p38 and ERK1/2 significantly increased the stability of the carotid plaques. We also found that simvastatin significantly increased the expression of P4Hα1 and collagen possibly due to decreased ox-LDL content and phosphorylation of p38 and ERK1/2 in plaques. Thus, simvastatin increases P4Hα1 and collagen expression in ox-LDL-stimulated HASMCs and atherosclerotic plaques via p38 MAPK and ERK1/2, thereby exerting a plaque stabilizing effect.

Effect of Testosterone on Inflammatory Markers in the Development of Early Atherogenesis in the Testicular-Feminized Mouse Model

BACKGROUND

Low levels of serum testosterone in men are associated with cardiovascular disease. Clinical studies show that testosterone replacement therapy (TRT) can improve symptoms of cardiovascular disease and reduce the inflammatory burden evident in atherosclerosis.

AIM

We used an in vivo animal model to determine whether testosterone influences mediators of vascular inflammation as part of its beneficial effects on atherogenesis.

METHODS

Testicular-feminized (Tfm) mice, which express low endogenous testosterone and a non-functional androgen receptor (AR), were used to assess the effect of androgen status on atheroma formation, serum lipids, and inflammatory mediators. Tfm mice were fed a high-cholesterol diet, received saline or physiological (TRT), and were compared to saline-treated XY littermates.

RESULTS

A total of 28 weeks of high-cholesterol diet caused fatty streak formation in the aortic root of XY littermates and Tfm mice, an effect significantly amplified in Tfm mice. Tfm mice on normal diet showed elevated serum tumor necrosis factor-α (TFN-α) and interleukin-6 compared to XY littermates. High-cholesterol diet induced increased monocyte chemoattractant protein-1 (MCP-1) in Tfm mice, and TFN-α and MCP-1 in XY littermates. TRT reduced fatty streak formation and serum interleukin-6 in Tfm mice but had no significant effects on lipid profiles. Monocyte/macrophage staining indicated local inflammation in aortic root fatty streak areas of all mice, with TRT reducing local inflammation through plaque reduction in Tfm mice. Fractalkine (CX₃CL1) and its receptor (CX₃CR1) were present in fatty streaks of all mice fed a high-cholesterol diet, independent of androgen status.

CONCLUSION

These results are consistent with AR-dependent and AR-independent anti-inflammatory actions of testosterone in atheroprotection, although the local anti-inflammatory mechanisms via which testosterone acts remain unknown.

Regulatory T cells prevent plaque disruption in apolipoprotein E-knockout mice

BACKGROUND

CD4(+)CD25(+) regulatory T cells (Tregs) have received considerable interest in atherogenesis. We hypothesized that Tregs treatment may dose-dependently stabilize atherosclerotic plaques by inhibiting inflammatory cytokine secretion and matrix metalloproteinases (MMPs) expression and enhancing P4Hα1 expression in atherosclerotic lesions.

METHODS AND RESULTS

We established a vulnerable carotid plaque model in apolipoprotein E- knockout mice (ApoE-/-). Mice were divided into control, phosphate buffered saline (PBS), small-dose Tregs, moderate-dose Tregs, large-dose Tregs and PC groups. Histopathological analysis showed that the plaque disruption rate was 50%, 50%, 43.8%, 12.5%, 12.5% and 43.8% in the control, PBS, small-dose Tregs, moderate-dose Tregs, large-dose Tregs and PC groups. Tregs treatment resulted in a significant decrease in the relative contents of macrophages and lipids and a substantial increase in those of SMCs and collagen in the carotid plaque, leading to an almost 50% reduction of plaque vulnerability index. Furthermore, Tregs treatment decreased the expression of proinflammatory cytokines, MMP-2 and MMP-9 but increased the expression of P4Hα1 both in vivo and in vitro. Most of these therapeutic effects of Tregs were found to be mediated by transforming growth factor and interleukin-10.

CONCLUSION

Adoptive transfer of Tregs dose-dependently changed plaque composition to a stable plaque phenotype and lowered the incidence of plaque disruption in ApoE-/- mice. The major mechanisms involved reduced expression of inflammatory cytokines and MMP-2 and MMP-9, and enhanced expression of P4Hα1 in the carotid plaque. Tregs may provide a novel approach to the treatment of vulnerable plaques.

Th17 cells and IL-17 are involved in the disruption of vulnerable plaques triggered by short-term combination stimulation in apolipoprotein E-knockout mice

Considerable evidence indicates that type 1 T helper (Th1)- and Th17-mediated immune responses promote the formation of atherosclerotic plaques while that CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) have a protective effect. However, the functions of diverse CD4(+) lymphocyte subsets in plaque rupture remain poorly understood because of a shortage of satisfactory plaque rupture models. Here, we established a murine model of atherosclerotic plaque rupture using a high-fat diet and collar placement on the carotid artery, and triggered plaque rupture by short-term stimulation with a combination of lipopolysaccharide, phenylephrine injection and cold in apolipoprotein E-knockout (ApoE(-/-)) mice. We investigated the associations between Th1 cells, Th17 cells and Tregs and plaque rupture by PCR, flow cytometry, ELISA and immunohistochemistry. In total, 75% (18/24) of vulnerable plaques, but no stable plaques, showed rupture characteristics. The proportion of Th17 cells was increased among splenocytes after treatment, but the changes in the levels of Th1 cells and Tregs were not related to rupture. Furthermore, the treatment resulted in high levels of interleukin-17 (IL-17) in the serum and in the region of plaque rupture. In vitro, IL-17 increased the level of apoptosis, a major factor associated with plaque rupture, in cultured murine vascular smooth muscle cells. Th17 cells and IL-17 may be involved in the disruption of vulnerable plaques triggered by short-term stimulation with lipopolysaccharide, phenylephrine injection and cold in ApoE(-/-)mice.

Electrocardiographic features of patients with earthquake related posttraumatic stress disorder

AIM: To analyze electrocardiographic features of patients diagnosed with posttraumatic stress disorder (PTSD) after the Van-Erciş earthquake, with a shock measuring 7.2 on the Richter scale that took place in Turkey in October 2011.

METHODS: Surface electrocardiograms of 12 patients with PTSD admitted to Van Erciş State Hospital (Van, Turkey) from February 2012 to May 2012 were examined. Psychiatric interviews of the sex and age matched control subjects, who had experienced the earthquake, confirmed the absence of any known diagnosable psychiatric conditions in the control group.

RESULTS: A wide range of electrocardiogram (ECG) parameters, such as P-wave dispersion, QT dispersion, QT interval, Tpeak to Tend interval, intrinsicoid deflection durations and other traditional parameters were similar in both groups. There was no one with an abnormal P wave axis, short or long PR interval, long or short QT interval, negative T wave in lateral leads, abnormal T wave axis, abnormal left or right intrinsicoid deflection duration, low voltage, left bundle branch block, right bundle branch block, left posterior hemiblock, left or right axis deviation, left ventricular hypertrophy, right or left atrial enlargement and pathological q(Q) wave in either group.

CONCLUSION: The study showed no direct effect of earthquake related PTSD on surface ECG in young patients. So, we propose that PTSD has no direct effect on surface ECG but may cause electrocardiographic changes indirectly by triggering atherosclerosis and/or contributing to the ongoing atherosclerotic process.

Mouse models of atherosclerosis: explaining critical roles of lipid metabolism and inflammation

Atherosclerosis is the most common cause of death globally. It is a complex disease involving morphological and cellular changes in vascular walls. Studying molecular mechanism of the disease is hindered by disease complexity and lack of robust noninvasive diagnostics in human. Mouse models are the most popular animal models that allow researchers to study the mechanism of disease progression. In this review we discuss the advantage and development of mouse as a model for atherosclerotic research. Along with commonly used models, this review discusses strains that are used to study the role of two critical processes associated with the disease-lipid metabolism and inflammation.

Emotional stressors trigger cardiovascular events

AIMS

To describe the relation between emotional stress and cardiovascular events, and review the literature on the cardiovascular effects of emotional stress, in order to describe the relation, the underlying pathophysiology, and potential therapeutic implications.

MATERIALS AND METHODS

Targeted PUBMED searches were conducted to supplement the authors' existing database on this topic.

RESULTS

Cardiovascular events are a major cause of morbidity and mortality in the developed world. Cardiovascular events can be triggered by acute mental stress caused by events such as an earthquake, a televised high-drama soccer game, job strain or the death of a loved one. Acute mental stress increases sympathetic output, impairs endothelial function and creates a hypercoagulable state. These changes have the potential to rupture vulnerable plaque and precipitate intraluminal thrombosis, resulting in myocardial infarction or sudden death.

CONCLUSION

Therapies targeting this pathway can potentially prevent acute mental stressors from initiating plaque rupture. Limited evidence suggests that appropriately timed administration of beta-blockers, statins and aspirin might reduce the incidence of triggered myocardial infarctions. Stress management and transcendental meditation warrant further study.

Statins induce the accumulation of regulatory T cells in atherosclerotic plaque

CD4⁺CD25⁺ regulatory T cells (Tregs) mediate immune suppression and prevent autoimmune disorders. Recently, Tregs were found to present in atherosclerotic lesions and play an important role in the progression of atherosclerosis. Statins have immunomodulatory properties, and the effect of statins on atherosclerosis depends in part on their immunomodulatory mechanisms. We sought to determine whether statins exhibit an effect on Tregs in atherosclerotic plaques and in peripheral circulation of patients with acute coronary syndrome (ACS). In an in vivo experiment, we induced atherosclerotic plaques in apolipoprotein E-deficient (ApoE⁻/⁻) mice. The mice were randomly divided into two groups for 6-wk treatment: simvastatin (50 mg/kg/d) or vehicle (control). Simvastatin significantly increased the number of Tregs and the expression of Treg marker Foxp3 (Forkhead/winged helix transcription factor), transforming growth factor (TGF)-β and interleukin (IL)-10 in atherosclerotic plaques. Moreover, simvastatin played an important role in modulating the balance between antiinflammatory (Tregs and Th2 cells) and proinflammatory (Th17 and Th1 cells) subsets of T cells. In an in vitro experiment, peripheral blood mononuclear cells (PBMCs) were isolated from patients with ACS and incubated with simvastatin. After an incubation for 96 h, simvastatin significantly enhanced the frequency and functional suppressive properties of Tregs. Therefore, statin treatment may influence Tregs in atherosclerotic lesions. Furthermore, statins improved the quantity and suppressive function of Tregs in ACS patients.

Local gene silencing of monocyte chemoattractant protein-1 prevents vulnerable plaque disruption in apolipoprotein E-knockout mice

Monocyte chemoattractant protein-1 (MCP-1), a CC chemokine (CCL2), has been demonstrated to play important roles in atherosclerosis and becoming an important therapeutic target for atherosclerosis. The present study was undertaken to test the hypothesis that local RNAi of MCP-1 by site-specific delivery of adenovirus-mediated small hairpin RNA (shRNA) may enhance plaque stability and prevent plaque disruption in ApoE-/- mice. We designed an adenovirus-mediated shRNA against mouse MCP-1 (rAd5-MCP-1-shRNA). Male apolipoprotein E-knockout (ApoE-/-) mice (n = 120) were fed a high-fat diet and vulnerable plaques were induced by perivascular placement of constrictive collars around the carotid artery, intraperitoneal injection of lipopolysaccharide and stress stimulation. Mice were randomly divided into RNA interference (Ad-MCP-1i) group receiving local treatment of rAd5-MCP-1-shRNA suspension, Ad-EGFP group receiving treatment of rAd5-mediated negative shRNA and mock group receiving treatment of saline. Two weeks after treatment, plaque disruption rates were significantly lower in the Ad-MCP-1i group than in the Ad-EGFP group (13.3% vs. 60.0%, P = 0.01), and local MCP-1 expression was significantly inhibited in the Ad-MCP-1i group confirmed by immunostaining, qRT-PCR and western blot (P<0.001). Compared with the Ad-EGFP group, carotid plaques in the Ad-MCP-1i group showed increased levels of collagen and smooth muscle cells, and decreased levels of lipid and macrophages. The expression of inflammatory cytokines and activities of matrix metalloproteinases (MMPs) were lower in the Ad-MCP-1i group than in the Ad-EGFP group. In conclusion, site-specific delivery of adenoviral-mediated shRNA targeting mouse MCP-1 downregulated MCP-1 expression, turned a vulnerable plaque into a more stable plaque phenotype and prevented plaque disruption. A marked suppression of the local inflammatory cytokine expression may be the central mechanism involved.

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

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

Analysis of in situ and ex vivo αVβ3 integrin expression during experimental carotid atherogenesis

OBJECTIVE

Mural inflammation has been shown to contribute to the development of plaque, with the α(V)β(3) integrin highly expressed in atherosclerotic plaques. We herein examined α(V)β(3) integrin expression as a function of carotid atherosclerosis formation in the apolipoprotein E-deficient (apoE(-/-)) mouse.

METHODS AND RESULTS

Constrictive collars were placed around the left common carotid arteries of apo E(-/-) mice maintained on a high-fat diet (n = 14). Before and 21 days following collar placement, in vivo serial magnetic resonance imaging (MRI) measurements of the carotid aortic diameter were performed using a 7T magnetic resonance (MR) scanner. Near- infrared fluorescence (NIRF) imaging was performed (n = 6) using an in vivo imaging system 0-24 hours following administration of 1.0 nmol c(RGDyK)-Cy5.5 via the tail vein. A competition experiment was performed by the co-injection of a saturating dose of bicyclic RGD peptide H-Glu[cyclo(Arg-Gly-Asp-D-Tyr-Lys)]2 (n = 3). Following image acquisition and sacrifice at 24 hours after injection, carotid arteries were harvested for histological analyses. Neointima formation and arterial remodeling in the carotid arteries of apoE(-/-) mice were induced by the placement of a constrictive collar. Significantly greater fluorescent signals were obtained from constrictive collar left common carotid arteries as compared to uninvolved aortic segments in constrictive collar mice. Binding to stenotic lesions was efficiently blocked in competition experiments. Immunostaining confirmed the presence of mural α(V)β(3) integrin expression in macrophages in the neointima. Signal intensity increased in a macrophage density-dependent fashion in the stenotic segments.

CONCLUSION

Mural α(V)β(3) integrin expression, as determined using RGD-Cy5.5 near-infrared optical imaging, was increased in carotid arteries with constrictive collars in experimental mice. This expression can estimate the macrophage-bound inflammatory activity of atherosclerotic lesions.