Adventitial lymphocytic inflammation in human coronary arteries with intimal atherosclerosis

Role of Epicardial Adipose Tissue in Cardiovascular Diseases: A Review

Simple Summary

Cardiovascular diseases (CVDs) are the leading causes of death worldwide. Epicardial adipose tissue (EAT) is one of the most important risk factors for cardiovascular events and a promising new therapeutic target in CVDs. Here, we summarize the currently available evidence regarding the role of EAT in the development of CVDs, including coronary artery disease, heart failure and atrial fibrillation; compile data regarding the association between EAT’s function and the course of COVID-19; and present new potential therapeutic possibilities, aiming at modifying EAT’s function. The development of novel therapies specifically targeting EAT could revolutionize the prognosis in CVDs.

Abstract

Cardiovascular diseases (CVDs) are the leading causes of death worldwide. Epicardial adipose tissue (EAT) is defined as a fat depot localized between the myocardial surface and the visceral layer of the pericardium and is a type of visceral fat. EAT is one of the most important risk factors for atherosclerosis and cardiovascular events and a promising new therapeutic target in CVDs. In health conditions, EAT has a protective function, including protection against hypothermia or mechanical stress, providing myocardial energy supply from free fatty acid and release of adiponectin. In patients with obesity, metabolic syndrome, or diabetes mellitus, EAT becomes a deleterious tissue promoting the development of CVDs. Previously, we showed an adverse modulation of gene expression in pericoronary adipose tissue in patients with coronary artery disease (CAD). Here, we summarize the currently available evidence regarding the role of EAT in the development of CVDs, including CAD, heart failure, and atrial fibrillation. Due to the rapid development of the COVID-19 pandemic, we also discuss data regarding the association between EAT and the course of COVID-19. Finally, we present the potential therapeutic possibilities aiming at modifying EAT’s function. The development of novel therapies specifically targeting EAT could revolutionize the prognosis in CVDs.

Exploring the Relationship of Perivascular Adipose Tissue Inflammation and the Development of Vascular Pathologies

Initially thought to only provide mechanical support for the underlying blood vessels, perivascular adipose tissue (PVAT) has now emerged as a regulator of vascular function. A healthy PVAT exerts anticontractile and anti-inflammatory actions on the underlying vasculature via the release of adipocytokines such as adiponectin, nitric oxide, and omentin. However, dysfunctional PVAT produces more proinflammatory adipocytokines such as leptin, resistin, interleukin- (IL-) 6, IL-1β, and tumor necrosis factor-alpha, thus inducing an inflammatory response that contributes to the pathogenesis of vascular diseases. In this review, current knowledge on the role of PVAT inflammation in the development of vascular pathologies such as atherosclerosis and hypertension was discussed.

Relationship between epicardial adipose tissue and coronary artery stenoses on computed tomography in patients scheduled for carotid artery revascularization

BACKGROUND

We aimed to clarify the relationship between epicardial adipose tissue (EAT) volume and the presence of severe stenoses (SS) on coronary computed tomography angiography (CTA) for risk stratification of the patients with carotid artery stenoses.

METHODS

We prospectively performed CTA for 125 consecutive patients (72.4 ± 8.1 years, 85% men) without a history of coronary artery disease (CAD), who were scheduled for carotid artery revascularization from 2014 to 2020. SS was defined as ≥70% luminal stenosis on CTA. EAT was quantified automatically as the total volume of tissue with -190 to -30 HU.

RESULTS

Of 125 patients, 76 had SS. Between the patients with and without SS, there were significant differences in coronary artery calcium score (CACS), left ventricular ejection fraction (LVEF), dyslipidemia, and EAT, despite no differences in carotid echocardiography findings. After adjustment for age, gender, and dyslipidemia, EAT was an independent factor associated with SS (p=0.011), as well as CACS and LVEF. The addition of EAT to a baseline model including age, gender, dyslipidemia, LVEF, and CACS achieved both net reclassification improvement (0.505, p=0.003) and integrated discrimination improvement (0.059, p=0.003).

CONCLUSIONS

In patients with carotid stenoses, EAT is associated with CAD and is useful for additional risk stratification. Epicardial fat may have a specific role in the development of CAD in patients with suspected systemic atherosclerosis.

Atherosclerosis Pathways are Activated in Pericoronary Adipose Tissue of Patients with Coronary Artery Disease

PURPOSE

Perivascular release of inflammatory mediators may accelerate coronary lesion formation and contribute to plaque instability. Accordingly, we compared gene expression in pericoronary adipose tissue (PCAT) in patients with advanced coronary artery disease (CAD) and non-CAD controls.

PATIENTS AND METHODS

PCAT samples were collected during coronary bypass grafting from CAD patients (n = 21) and controls undergoing valve replacement surgery, with CAD excluded by coronary angiography (n = 19). Gene expression was measured by GeneChip™ Human Transcriptome Array 2.0. Obtained list of 1348 transcripts (2.0%) that passed the filter criteria was further analyzed by Ingenuity Pathway Analysis software, identifying 735 unique differentially expressed genes (DEGs).

RESULTS

Among the CAD patients, 416 (30.9%) transcripts were upregulated, and 932 (69.1%) were downregulated, compared to controls. The top upregulated genes were involved in inflammation and atherosclerosis (chemokines, interleukin-6, selectin E and low-density lipoprotein cholesterol (LDL-C) receptor), whereas the downregulated genes were involved in cardiac ischaemia and remodelling, platelet function and mitochondrial function (miR-3671, miR-4524a, multimerin, biglycan, tissue factor pathway inhibitor (TFPI), glucuronidases, miR-548, collagen type I, III, IV). Among the top upstream regulators, we identified molecules that have proinflammatory and atherosclerotic features (High Mobility Group Box 2 (HMGB2), platelet-derived growth platelet (PDGF) and evolutionarily conserved signaling intermediate in Toll pathways (ESCIT)). The activated pathway related to DEGs consisted of molecules with well-established role in the pathogenesis of atherosclerosis (TFPI, plasminogen activator, plasminogen activator, urokinase receptor (PLAUR), thrombomodulin). Moreover, we showed that 22 of the altered genes form a pro-atherogenic network.

CONCLUSION

Altered gene expression in PCAT of CAD patients, with genes upregulation and activation of pathway involved in inflammation and atherosclerosis, may be involved in CAD development and progression.

Adipose tissue macrophages as a therapeutic target in obesity-associated diseases

Obesity is an increasing problem in developed and developing countries. Individuals with obesity have a higher risk of several diseases, such as cardiovascular disease, increased risk of insulin resistance, type 2 diabetes, infertility, degenerative disorders, and also certain types of cancer. Adipose tissue (AT) is considered an extremely active endocrine organ, and the expansion of AT is accompanied by the infiltration of different types of immune cells, which induces a state of low-grade, chronic inflammation and metabolic dysregulation. Even though the exact mechanism of this low-grade inflammation is not fully understood, there is clear evidence that AT-infiltrating macrophages (ATMs) play a significant role in the pro-inflammatory state and dysregulated metabolism. ATMs represent the most abundant class of leukocytes in AT, constituting 5% of the cells in AT in individuals with normal weight. However, this percentage dramatically increases up to 50% in individuals with obesity, suggesting an important role of ATMs in obesity and its associated complications. In this review, we discuss current knowledge of the function of ATMs during steady-state and obesity and analyze its contribution to different obesity-associated diseases, highlighting the potential therapeutic target of ATMs in these pathological conditions.

Role of Inflammation in Vascular Disease-Related Perivascular Adipose Tissue Dysfunction

Perivascular adipose tissue (PVAT) is the connective tissue around most blood vessels throughout the body. It provides mechanical support and maintains vascular homeostasis in a paracrine/endocrine manner. Under physiological conditions, PVAT has anti-inflammatory effects, improves free fatty acid metabolism, and regulates vasodilation. In pathological conditions, PVAT is dysfunctional, secretes many anti-vasodilator factors, and participates in vascular inflammation through various cells and mediators; thus, it causes dysfunction involving vascular smooth muscle cells and endothelial cells. Inflammation is an important pathophysiological event in many vascular diseases, such as vascular aging, atherosclerosis, and hypertension. Therefore, the pro-inflammatory crosstalk between PVAT and blood vessels may comprise a novel therapeutic target for the prevention and treatment of vascular diseases. In this review, we summarize findings concerning PVAT function and inflammation in different pathophysiological backgrounds, focusing on the secretory functions of PVAT and the crosstalk between PVAT and vascular inflammation in terms of vascular aging, atherosclerosis, hypertension, diabetes mellitus, and other diseases. We also discuss anti-inflammatory treatment for potential vascular diseases involving PVAT.

B Lymphocytes and Macrophages in the Perivascular Adipose Tissue Are Associated With Coronary Atherosclerosis: An Autopsy Study

Background

Macrophages and T lymphocytes in the perivascular adipose tissue (PvAT) were previously linked to coronary artery disease. However, the role of these cells and B lymphocytes in the human PvAT adjacent to unstable atherosclerotic plaques has not been investigated. Moreover, previous studies were inconclusive on whether PvAT inflammation was restricted to the surroundings of the atheroma plaque.

Methods and Results

Coronary arteries were freshly dissected with the surrounding PvAT. Atherosclerotic plaques were classified according to the internationally accepted anatomopathological criteria. Immune cells in the PvAT were detected using immunohistochemistry and then quantified. We used linear and logistic regressions with robust standard errors, adjusted for possible confounding factors. In 246 atherosclerotic plaques (205 stable and 41 unstable plaques) from 82 participants (mean age=69.0±14.4 years; 50% men), the percentage of arterial obstruction was positively correlated with the densities of CD68⁺ macrophages (P=0.003) and CD20⁺ B lymphocytes (P=0.03) in the periplaque PvAT. The number of cells was greater in the periplaque PvAT than in the distal PvAT (macrophages, P<0.001; B lymphocytes, P=0.04). In addition, the density of macrophages in the periplaque PvAT was greater in the presence of unstable plaques (P=0.03) and was also greater near unstable plaques than in the distal PvAT (P=0.001). CD3⁺ T lymphocytes were not associated with percentage of obstruction and stable/unstable plaque composition.

Conclusions

The density of CD20⁺ B lymphocytes and CD68⁺ macrophages in periplaque PvAT was increased with plaque size, and the CD68⁺ macrophages were greater near unstable atherosclerotic plaques than near stable lesions. This inflammation was more intense in the periplaque PvAT than in the PvAT distal to the atherosclerotic plaques.

The impact of dapagliflozin on glucose excursions related to early proatherogenic derangement in the aortic wall

INTRODUCTION

Cardiovascular risk in the course of diabetes depends greatly on glycemic variability which is even more significant than chronic hyperglycemia. Optimal management of diabetes involves a multidisciplinary approach focused in particular on decreasing the risk of atherosclerosis. Therefore, our purpose was to evaluate the impact of dapagliflozin on glucose excursions and related proatherogenic changes in the aortic wall.

METHODS AND MATERIALS

Animal model of type 2 diabetes rich-fat/STZ rats was used. Wistar rats were randomized into 3 groups: dapagliflozin-treated with glucose excursions, placebo-treated with glucose excursions and placebo-treated with stable diabetes. Dapagliflozin was administered once a day, 1 mg/kg, for 8 consecutive weeks. Glucose levels were measured twice a week at fasting and postprandially. The samples of aortas were taken for histopathological and immunochemistry examinations at the end of the experiment. The derangement in the aortic wall and the distribution of CD68+ cells in the aorta were considered early signs of atherosclerosis.

RESULTS

Dapagliflozin reduced glucose excursion to the level characteristic for stable, well-controlled diabetes. It was related to a significant decrease in histopathological changes which were observed in the placebo-treated rats with glucose variability. Dapagliflozin significantly reduced also the accumulation of CD68+ macrophages in the aortic adventitia.

CONCLUSION

Dapagliflozin provides not only mere beneficial regulation of metabolic status with the depletion of glucose variability, but is also helpful in the prevention of early atherosclerosis related to the course of diabetes type 2.

Adventitial tertiary lymphoid organ classification in human atherosclerosis

BACKGROUND

Atherosclerosis is a chronic inflammatory disease of the arterial wall. Adjacent to lamina intima lesion progression, a cellular compound develops in the lamina adventitia, defined as tertiary lymphoid organs (TLO) in mice. But in human system, it remains unknown whether these adventitial cellular accumulations represent these highly organized immunological structures.

PATIENTS AND METHODS

In this study, we investigated whether the adventitial cellular compounds represent TLOs in 72 human coronary artery samples by immunoenzyme staining.

RESULTS

The study showed that the adventitial cellular compound partly represented TLOs in human coronary arteries affected by atherogenesis in patients suffering from ischemic heart disease (56%) or a fatal myocardial infarction (100%), but not dilated cardiomyopathy. In addition, we established a classification for human TLOs, stage I-III, and showed that all stages were present in diseased coronary arteries. The stage of TLOs highly correlated with lesion size as well as plaque instability and rupture, and all patients with a myocardial infarction had stage III. Additionally, there were cellular infiltration and destruction of the lamina media, which were restricted to TLOs next to ruptured plaques in patients with a fatal myocardial infarction.

CONCLUSIONS

TLOs are present in patients with a coronary artery disease and highly correlated with lesion size, plaque instability, and rupture. Further studies are needed to investigate whether TLOs might be a specific diagnostic and drug target to modify plaque instability/rupture.

Perivascular Adipose Tissue Inflammation and Coronary Artery Disease: An Autopsy Study Protocol

Background

Perivascular adipose tissue (PAT) inflammation may have a role in coronary artery disease (CAD) pathophysiology. However, most evidence has come from samples obtained during surgical procedures that may imply in some limitations. Moreover, the role of B lymphocytes and inflammation in PAT that is adjacent to unstable atheroma plaques has not been investigated in humans using morphometric measurements.

Objective

The objective of this study is to investigate the inflammation in PAT, subcutaneous, and perirenal adipose tissues (SAT and PrAT) among chronic CAD, acute CAD, and control groups in an autopsy study.

Methods

Heart, SAT, and PrAT samples are collected from autopsied subjects in a general autopsy service, with the written informed consent of the next-of-kin (NOK). Sociodemographic and clinical data are obtained from a semistructure interview with the NOK. Coronary arteries are dissected and PAT are removed. Sections with the greatest arterial obstruction or unstable plaques, and the local with absence of atherosclerosis in all coronary arteries are sampled. PAT are represented adjacent to these fragments. Adipose tissues are fixed in 4% buffered paraformaldehyde solution and analyzed immunohistochemically for macrophages (CD68), macrophage polarization (CD11c for proinflammatory and CD206 for anti-inflammatory), B lymphocytes (CD20), and T lymphocytes (CD3). Slides will be scanned, and inflammatory cells will be quantified in 20 random fields. Participants will be categorized in CAD groups, after morphometric measurement of arterial obstruction and plaque composition analysis in accordance with American Heart Association classification. Three study groups will be investigated: acute CAD (at least one unstable plaque); chronic CAD (≥50% arterial obstruction); and controls (<50% arterial obstruction). Inflammatory cells in PAT, SAT, and PrAT will be counted and compared between groups using multivariate linear regression, adjusted for age, body mass index, hypertension, diabetes, alcohol use, and smoking.

Results

We present the methods of our study that was developed from 2 pilots. Currently, data collection and tissue processing are ongoing. Data collection, histology and immunochemistry procedures, and quantification of all inflammatory cells are expected to be concluded within 1 year.

Conclusions

This study will contribute for the understanding of the mechanisms of CAD pathophysiology because it will help to clarify the role of inflammation both in chronic and acute CAD.

Adipokines, diabetes and atherosclerosis: an inflammatory association

Cardiovascular diseases can be considered the most important cause of death in diabetic population and diabetes can in turn increase the risk of cardiovascular events. Inflammation process is currently recognized as responsible for the development and maintenance of diverse chronic diseases, including diabetes and atherosclerosis. Considering that adipose tissue is an important source of adipokines, which may present anti and proinflammatory effects, the aim of this review is to explore the role of the main adipokines in the pathophysiology of diabetes and atherosclerosis, highlighting the therapeutic options that could arise from the manipulation of these signaling pathways both in humans and in translational models.

A change in inflammatory footprint precedes plaque instability: a systematic evaluation of cellular aspects of the adaptive immune response in human atherosclerosis

Background

Experimental studies characterize adaptive immune response as a critical factor in the progression and complications of atherosclerosis. Yet, it is unclear whether these observations translate to the human situation. This study systematically evaluates cellular components of the adaptive immune response in a biobank of human aortas covering the full spectrum of atherosclerotic disease.

Methods and Results

A systematic analysis was performed on 114 well‐characterized perirenal aortic specimens with immunostaining for T‐cell subsets (CD3/4/8/45RA/45RO/FoxP3) and the Th1/non‐Th1/Th17 ratio (CD4⁺T‐bet⁺/CD4⁺T‐bet⁻/CD4⁺/interleukin‐17⁺ double staining). CD20 and CD138 were used to identify B cells and plasma cells, while B‐cell maturation was evaluated by AID/CD21 staining and expression of lymphoid homeostatic CXCL13. Scattered CD4 and CD8 cells with a T memory subtype were found in normal aorta and early, nonprogressive lesions. The total number of T cells increases in progressive atherosclerotic lesions (≈1:5 CD4/CD8 T‐cell ratio). A further increase in medial and adventitial T cells is found upon progression to vulnerable lesions.

This critical stage is further hallmarked by de novo formation of adventitial lymphoidlike structures containing B cells and plasma cells, a process accompanied by transient expression of CXCL13. A dramatic reduction of T‐cell subsets, disappearance of lymphoid structures, and loss of CXCL13 expression characterize postruptured lesions. FoxP3 and Th17 T cells were minimally present throughout the atherosclerotic process.

Conclusions

Transient CXCL13 expression, restricted presence of B cells in human atherosclerosis, along with formation of nonfunctional extranodal lymphoid structures in the phase preceding plaque rupture, indicates a “critical” change in the inflammatory footprint before and during plaque destabilization.

Carotid hemodynamics is associated with monocyte count determined by serum homocysteine level in patients with essential hypertension

To examine the association between pulsatility index (PI) in the common carotid artery (CCA) as a marker of vascular resistance and cardiovascular risk factors, including serum homocysteine and inflammation, 67 hypertensive patients were enrolled. PI correlated with homocysteine and interleukin-6, monocyte count, gender, age and BMI, with monocyte count and age being independent determinants for PI. In turn, monocyte count correlated with homocysteine, tumor necrosis factor-alpha, and HDL-cholesterol, BMI, and gender, with HDL-cholesterol and homocysteine being independent determinants for monocyte count. These results indicated monocyte count determined by homocysteine is associated with arterial stiffness in hypertensive patients.

Epicardial adipose tissue predicts mortality in incident hemodialysis patients: a substudy of the Renagel in New Dialysis trial

BACKGROUND

Epicardial adipose tissue (EAT) has been described in the general population as an independent risk marker for incident coronary artery disease. In hemodialysis patients, it correlates with other markers of cardiovascular disease, but it is unknown if it is associated with adverse events.

METHODS

post hoc analysis of the Renagel in New Dialysis (RIND) patients study, a randomized trial of sevelamer versus calcium-based phosphate binders in 109 incident hemodialysis patients, followed for all-cause mortality for a median of 49.3 months. Patients underwent baseline cardiac computed tomography imaging within 120 days of dialysis initiation.

RESULTS

Baseline EAT measurements were available in 95 patients; EAT was positively correlated with age, body mass index, triglycerides, C-reactive protein, coronary artery calcium and aortic calcium, and negatively correlated with systolic and diastolic blood pressure, serum high density lipoprotein (HPL) cholesterol and serum phosphate (all P < 0.05). During follow-up, a total of 27 (28.4%) patients expired [mortality per 1000 patients/year: 95% confidence interval (95% CI) = 77 (64-94)]. Five-year survival rate was 44. 6% (95% CI: 21.1-65.7) and 71.2% (95% CI: 45.95-86.25) in patients with EAT above or below the median, respectively. Each 10 cc increase in EAT volume was associated with a significant 6% increase in the risk of death during follow-up [hazard ratio (HR): 1.060; 95% CI: 1.013-1.109; P-value = 0.012].

CONCLUSIONS

In this subanalysis of a randomized trial, EAT was an independent predictor of mortality in incident hemodialysis patients after ~4 years of follow-up. These hypothesis-generating findings will need confirmatory evidence.

Relation of vascular stiffness with epicardial and pericardial adipose tissues, and coronary atherosclerosis

OBJECTIVES

Increased measured vascular stiffness is an early marker of atherosclerosis and is associated with cardiovascular risk factors. Coronary artery calcium (CAC) and adipose tissues are accurate markers of overall burden of coronary atherosclerosis and metabolic status, respectively. We evaluated the relation of vascular stiffness with epicardial (EAT) and pericardial (PAT) adipose tissues, as well as the presence and severity of CAC.

METHODS

One hundred and eleven consecutive subjects, mean age 59 ± 11 years, 78% male, underwent 64-multidetector row cardiac computed tomography (MDCT) and their carotid-radial pulse wave velocity (PWV) was measured using SphygmoCor tonometry. EAT and total thoracic adipose tissue (TAT) volumes were measured using MDCT. PAT was calculated as TAT-EAT. The highest tertile of EAT (≥111 ml) and PAT (≥103 ml) were defined as significant adipose tissue depots.

RESULTS

PWV was moderately associated with EAT (r = 0.46, p < 0.001), and PAT (r = 0.41, p < 0.001). PWV increased proportionally with the severity of CAC from 0 to 400+. The relative risk of highest vs. lowest tertile of PWV was 3.03 (95% CI 1.22-7.51, p = 0.01) for significant EAT, 2.34 (95% CI 1.10-4.90, p = 0.02) for significant PAT and 2.46 (95% CI 1.13-3.14, p = 0.01) for significant CAC (CAC 100+) after adjustment for conventional cardiovascular risk factors. This relative risk was increased after combination of CAC 100+ with each significant adipose tissue.

CONCLUSIONS

Increased vascular stiffness is associated with increase in EAT, PAT and coronary atherosclerosis. EAT was associated with higher relative risk of PWV, compared with CAC, suggesting a role of adipose tissue in vascular stiffness.

Inflammation and atherosclerosis: direct versus indirect mechanisms

It is now widely accepted that the development of atherosclerotic lesions involves a chronic inflammatory response that includes both innate and adaptive immune mechanisms. However, it is still unclear precisely what induces the inflammatory response. Furthermore, inflammation within the blood vessel can be divided into direct mechanisms where the primary inflammatory events occur within the intima of the blood vessel and contribute to both the initiation and progression of the plaques and indirect mechanisms where inflammation at nonvascular sites can contribute to the progression of the lesions. The direct mechanisms include lipid deposition and modification, influx of lipoprotein associated factors and microparticles derived from many different cell types, and possibly bacterial and viral infection of vascular cells. Indirect mechanisms derive from inflammation related to autoimmune diseases, smoking, respiratory infection, and pollution exposure, and possibly periodontal disease and gastric infection. The mechanisms include secretion of cytokines and other inflammatory factors into the circulation with subsequent uptake into the plaques, egress and recruitment of activated inflammatory cells, formation of dysfunctional HDL and crossreactive autoantibodies.

Quantification of epicardial fat by computed tomography: why, when and how?

In the past decade, interest has grown in the relation between epicardial fat and cardiovascular disease. Several imaging modalities such as echocardiography, computed tomography, and magnetic resonance imaging can be used to quantify epicardial adipose tissue. Computed tomography provides high spatial resolution and true volume coverage of the heart; therefore, it constitutes an attractive approach to quantifying epicardial fat. An increasing body of evidence has been accumulated which shows a relation between epicardial fat volume and coronary atherosclerosis, cardiovascular outcomes, and even non-atherosclerotic heart disease such as atrial fibrillation. The association of increased epicardial fat volume with cardiac disease remains significant even after correction for weight, body mass index, and traditional cardiovascular risk factors. The mechanisms have not been reliably identified, but metabolic properties of epicardial fat may play a role. At the present time, epicardial fat quantification is not included in recommended algorithms for risk stratification. However, the available data are intriguing enough to warrant further research.

Urotensin II promotes the production of LTC4 in rat aortic adventitial fibroblasts through NF-κB-5-LO pathway by p38 MAPK and ERK activations

Adventitia is the outer part of the arterial wall where the inflammatory response often occurs. Urotensin II (UII) is a potent vasoconstrictive peptide that also promotes the inflammatory process in patients with cardiovascular disease. Leukotriene C4 (LTC4), a lipid mediator, was recently found to play a role in the inflammatory process in the artery. We hypothesized that the adventitia is one of the resources of LTC4 and that UII may promote LTC4 production through the 5-LO (5-lipoxygenase) pathway in adventitial fibroblasts. Rat adventitial fibroblasts were isolated and incubated in serum-free medium with either UII alone or in combination with inhibitors of p38 MAPK, ERK, and UII receptors. The expression of 5-LO was detected using real-time polymerase chain reaction and Western blot. The translocation and binding activity of nuclear factor (NF)-κB were measured using immunofluorescence and electrophoretic mobility shift assay, respectively. The production of LTC4 was measured by enzyme-linked immunosorbent assay. The results indicated that: (1) adventitial fibroblasts were a source of LTC4 production; (2) UII increased the expression of the 5-LO mRNA and the protein by NF-κB activation through p38 MAPK and ERK pathways; and (3) UII promoted the LTC4 release in fibroblasts through the 5-LO pathway by p38 MAPK and ERK activations. The 5-LO pathway mediates LTC4 production, which may be a new mechanism in the pathogenesis of the vascular adventitial inflammation caused by UII.

Lymphocytes and the adventitial immune response in atherosclerosis

Although much of the research on atherosclerosis has focused on the intimal accumulation of lipids and inflammatory cells, there is an increasing amount of interest in the role of the adventitia in coordinating the immune response in atherosclerosis. In this review of the contributions of the adventitia and adventitial lymphocytes to the development of atherosclerosis, we discuss recent research on the formation and structural nature of adventitial immune aggregates, potential mechanisms of crosstalk between the intima, media, and adventitia, specific contributions of B lymphocytes and T lymphocytes, and the role of the vasa vasorum and surrounding perivascular adipose tissue. Furthermore, we highlight techniques for the imaging of lymphocytes in the vasculature.

Intraplaque haemorrhages as the trigger of plaque vulnerability

Atherothrombosis remains one of the main causes of morbidity and mortality in the western countries. Human atherothrombotic disease begins early in life in relation to circulating lipid retention in the inner vascular wall. Risk factors enhance the progression towards clinical expression: dyslipidaemia, diabetes, smoking, hypertension, ageing, etc. The evolution from the initial lipid retention in the arterial wall to clinical events is a continuum of increasingly complex biological processes. Current strategies to fight the consequences of atherothrombosis are orientated either towards the promotion of a healthy life style and preventive treatment of risk factors, or towards late interventional strategies. Despite this therapeutic arsenal, the incidence of clinical events remains dramatically high, dependent, at least in part, on the increasing frequency of type 2 diabetes and ageing. But some medical treatments, focusing only on prevention of the metabolic risk, have failed to reduce cardiovascular mortality, thus illustrating that our understanding of the pathophysiology of human atherothrombosis leading to clinical events remain incomplete. New paradigms are now emerging which may give rise to novel experimental strategies to improve therapeutic efficacy and prediction of disease progression. Recent studies strengthen the concept that the intraplaque neovascularization and bleeding (Figure 1, upper panel) are events that could play a major role in plaque progression and leucocyte infiltration, and may also serve as a measure of risk for the development of future events. The recent advances in our understanding of IntraPlaque Hemorrhage as a critical event in triggering acute clinical events have important implications for clinical research and possibly future clinical practice.