Adventitial inflammation and its interaction with intimal atherosclerotic lesions

Shenlian extract improves atherosclerosis by relieving adventitial inflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Shenlian (SL) extract, a Chinese medicinal compound mainly pointing at inflammation response of atherosclerosis, is composed of Salvia miltiorrhizae Bunge and Andrographis paniculata (Burm.f.) Nees. Salvia miltiorrhizae Bunge has been reported to activate blood to remove stasis, while another herb, Andrographis paniculata (Burm.f.) Nees, has been revealed to clear endogenous heat toxins. The anti-atherosclerotic effects of these two herbs have been reported closely relating to inflammation. However, from the point of view of adventitial inflammation, the in-depth study of SL extract in anti-atherosclerotic effects by relieving adventitial inflammation is still unknown.

AIM OF THE STUDY

To explore the effects of adventitial inflammation in atherosclerosis progression and if SL extract could reverse the process.

MATERIALS AND METHODS

A novel atherosclerosis model based on adventitial inflammation was established. High-fat diet-fed ApoE-/- mice were implanted a cotton thread soaked with LPS on the right common carotid artery (RCCA). Meanwhile, three time points were set (week 2, 4, and 12) to accurately evaluate the effect of SL extract on the whole process of atherosclerosis with adventitial inflammation. The pathological changes of phenotype transformation of VAFs, vascular cell proliferation and collagen synthesis were observed dynamically by immunohistochemistry (IHC), BrdU method and sirius red staining. Then primary VAFs were stimulated by LPS to mirror the process of adventitial inflammation in vitro. The VAFS phenotype conversion and its function alterations including proliferation, migration, inflammatory secretion was assessed. Finally, we established a co-culture model of activated VAFs and vascular smooth muscle cells (VSMCs) to observe the impacts of activated VAFs on phenotype transformation and migration of VSMCs.

RESULTS

SL extract improved atherosclerosis progression by reducing lipid content, adventitial inflammation and plaque formation. HE results showed sham-operated group (Sham) appeared light infiltrated inflammation only in adventitia at week 2, and the degree of inflammation infiltrated in model was more severe than that in Sham at week 2, 4, and 12. At week 12, the sham and model group showed evidently thickened media and intima. The phenotypic transformation, proliferation and migration of vascular adventitial fibroblasts (VAFs) as well as inflammatory secretion enhanced remarkably in vivo and vitro, but SL extract reversed these changes. Moreover, SL extract downregulated JAK2-STAT3-MMP2 signal pathway. The VSMCs transformed from contractile phenotype into synthetic phenotype and the migration of VSMCs increased after co-culture with activated VAFs. In contrast, SL extract could suppress theses effects.

CONCLUSIONS

Taken together, atherosclerotic inflammation could be a "outside-in" signaling. Adventitial inflammation not only accelerated intimal plaque formation in atherosclerosis, but also worsened the degree of vascular lesion. And SL extract improved atherosclerosis by relieving adventitial inflammation, and the underlying mechanisms could be associated with curbing phenotypic transformation, proliferation and migration of VAFs and VSMCs.

The effect of carotid sinus neurectomy for carotid restenosis: a study protocol for a double-blinded and randomized controlled trial

BACKGROUND

Patients undergoing carotid endarterectomy (CEA) have a high restenosis rate, which increases the risk of stroke, and there is still a lack of effective treatment for restenosis. The cause of stenosis is related to local inflammatory reactions. Some basic studies have shown that the inflammatory response causing arterial stenosis is closely related to the nerve axons distributed in its outer membrane, and that removal of the nerve is effective in reducing the inflammatory response to prevent arterial stenosis. Therefore, we propose to design a randomized controlled trial to study whether disconnecting the carotid sinus nerve during a CEA operation can reduce carotid arterial restenosis.

METHOD/DESIGN

This study is a randomized, double-blind, single-center study. We will recruit 276 patients, who will be randomly divided into the experimental group and the control group. Based on the standard CEA operation, the operator will search for the carotid sinus nerve on the surface of the internal carotid artery and will entirely transect it in the experimental group. Both groups will be guided with the same postoperative treatment and will be followed up every 3 months for 3 years after the operation. The main indices observed will be the carotid restenosis rate, incidence and nature of carotid plaque, and carotid blood flow velocity. Other indices will be arrhythmia, blood pressure variability, and biomarkers of atherosclerosis, such as blood lipids, hypersensitive C-reactive protein (hs-CRP), homocysteine, and total bilirubin.

DISCUSSION

It is expected that carotid sinus nerve transection will significantly reduce the occurrence of restenosis after CEA, decrease the incidence of ischemic stroke, and realize the effective primary prevention of stroke.

TRIAL REGISTRATION

ChiCTR2300073652. Registered on July 18, 2023.

Neuroimmune cardiovascular interfaces control atherosclerosis

Atherosclerotic plaques develop in the inner intimal layer of arteries and can cause heart attacks and strokes¹. As plaques lack innervation, the effects of neuronal control on atherosclerosis remain unclear. However, the immune system responds to plaques by forming leukocyte infiltrates in the outer connective tissue coat of arteries (the adventitia)^2-6. Here, because the peripheral nervous system uses the adventitia as its principal conduit to reach distant targets^7-9, we postulated that the peripheral nervous system may directly interact with diseased arteries. Unexpectedly, widespread neuroimmune cardiovascular interfaces (NICIs) arose in mouse and human atherosclerosis-diseased adventitia segments showed expanded axon networks, including growth cones at axon endings near immune cells and media smooth muscle cells. Mouse NICIs established a structural artery-brain circuit (ABC): abdominal adventitia nociceptive afferents^10-14 entered the central nervous system through spinal cord T₆-T₁₃ dorsal root ganglia and were traced to higher brain regions, including the parabrachial and central amygdala neurons; and sympathetic efferent neurons projected from medullary and hypothalamic neurons to the adventitia through spinal intermediolateral neurons and both coeliac and sympathetic chain ganglia. Moreover, ABC peripheral nervous system components were activated: splenic sympathetic and coeliac vagus nerve activities increased in parallel to disease progression, whereas coeliac ganglionectomy led to the disintegration of adventitial NICIs, reduced disease progression and enhanced plaque stability. Thus, the peripheral nervous system uses NICIs to assemble a structural ABC, and therapeutic intervention in the ABC attenuates atherosclerosis.

Differences in local immune cell landscape between Q fever and atherosclerotic abdominal aortic aneurysms identified by multiplex immunohistochemistry

Background:

Chronic Q fever is a zoonosis caused by the bacterium Coxiella burnetii which can manifest as infection of an abdominal aortic aneurysm (AAA). Antibiotic therapy often fails, resulting in severe morbidity and high mortality. Whereas previous studies have focused on inflammatory processes in blood, the aim of this study was to investigate local inflammation in aortic tissue.

Methods:

Multiplex immunohistochemistry was used to investigate local inflammation in Q fever AAAs compared to atherosclerotic AAAs in aorta tissue specimen. Two six-plex panels were used to study both the innate and adaptive immune systems.

Results:

Q fever AAAs and atherosclerotic AAAs contained similar numbers of CD68⁺ macrophages and CD3⁺ T cells. However, in Q fever AAAs, the number of CD68⁺CD206⁺ M2 macrophages was increased, while expression of GM-CSF was decreased compared to atherosclerotic AAAs. Furthermore, Q fever AAAs showed an increase in both the number of CD8⁺ cytotoxic T cells and CD3⁺CD8^-FoxP3⁺ regulatory T cells. Finally, Q fever AAAs did not contain any well-defined granulomas.

Conclusions:

These findings demonstrate that despite the presence of pro-inflammatory effector cells, persistent local infection with C. burnetii is associated with an immune-suppressed microenvironment.

Funding:

This work was supported by SCAN consortium: European Research Area - CardioVascualar Diseases (ERA-CVD) grant [JTC2017-044] and TTW-NWO open technology grant [STW-14716].

OUP accepted manuscript

The vascular wall is comprised of distinct layers controlling angiogenesis, blood flow, vessel anchorage within organs, and cell and molecule transit between blood and tissues. Moreover, some blood vessels are home to essential stem-like cells, a classic example being the existence in the embryo of hemogenic endothelial cells at the origin of definitive hematopoiesis. In recent years, microvascular pericytes and adventitial perivascular cells were observed to include multi-lineage progenitor cells involved not only in organ turnover and regeneration but also in pathologic remodeling, including fibrosis and atherosclerosis. These perivascular mesodermal elements were identified as native forerunners of mesenchymal stem cells. We have presented in this brief review our current knowledge on vessel wall-associated tissue remodeling cells with respect to discriminating phenotypes, functional diversity in health and disease, and potential therapeutic interest.

Heterogeneous subpopulations of adventitial progenitor cells regulate vascular homeostasis and pathological vascular remodeling

Cardiovascular diseases are characterized by chronic vascular dysfunction and provoke pathological remodeling events such as neointima formation, atherosclerotic lesion development, and adventitial fibrosis. While lineage-tracing studies have shown that phenotypically modulated smooth muscle cells (SMCs) are the major cellular component of neointimal lesions, the cellular origins and microenvironmental signaling mechanisms that underlie remodeling along the adventitial vascular layer are not fully understood. However, a growing body of evidence supports a unique population of adventitial lineage-restricted progenitor cells expressing the stem cell marker, stem cell antigen-1 (Sca1; AdvSca1 cells) as important effectors of adventitial remodeling and suggests that they are at least partially responsible for subsequent pathological changes that occur in the media and intima. AdvSca1 cells are being studied in murine models of atherosclerosis, perivascular fibrosis, and neointima formation in response to acute vascular injury. Depending on the experimental conditions, AdvSca1 cells exhibit the capacity to differentiate into SMCs, endothelial cells, chondrocytes, adipocytes, and pro-remodeling cells such as myofibroblasts and macrophages. These data indicate that AdvSca1 cells may be a targetable cell population to influence the outcomes of pathologic vascular remodeling. Important questions remain regarding the origins of AdvSca1 cells and the essential signaling mechanisms and microenvironmental factors that regulate both maintenance of their stem-like, progenitor phenotype and their differentiation into lineage-specified cell types. Adding complexity to the story, recent data indicate that the collective population of adventitial progenitor cells is likely composed of several smaller, lineage-restricted subpopulations which are not fully defined by their transcriptomic profile and differentiation capabilities. The aim of this review is to outline the heterogeneity of Sca1+ adventitial progenitor cells, summarize their role in vascular homeostasis and remodeling, and comment on their translational relevance in humans.

Visualization of cardiovascular development, physiology and disease at the single-cell level: Opportunities and future challenges

Single-cell RNA sequencing (scRNA-seq), a method of transcriptome sequencing at the single-cell level, has recently emerged as a revolutionary technology in the field of biomedical research. Compared to conventional gene expression profiling in bulk, scRNA-seq resolves biological differences among individual cells and enables the identification of rare cell populations that are easily overlooked. This review introduces the method of scRNA-seq, summarizes its applications in the field of cardiovascular disease research, and discusses existing limitations and prospects for future applications.

Extracellular traps derived from macrophages, mast cells, eosinophils and neutrophils are generated in a time-dependent manner during atherothrombosis

Extracellular traps generated by neutrophils contribute to thrombus progression in coronary atherosclerotic plaques. It is not known whether other inflammatory cell types in coronary atherosclerotic plaque or thrombus also release extracellular traps. We investigated their formation by macrophages, mast cells, and eosinophils in human coronary atherosclerosis, and in relation to the age of thrombus of myocardial infarction patients. Coronary arteries with thrombosed or intact plaques were retrieved from patients who died from myocardial infarction. In addition, thrombectomy specimens from patients with myocardial infarction were classified histologically as fresh, lytic or organised. Neutrophil and macrophage extracellular traps were identified using sequential triple immunostaining of CD68, myeloperoxidase, and citrullinated histone H3. Eosinophil and mast cell extracellular traps were visualised using double immunostaining for eosinophil major basic protein or tryptase, respectively, and citrullinated histone H3. Single‐ and double‐stained immunopositive cells in the plaque, adjacent adventitia, and thrombus were counted. All types of leucocyte‐derived extracellular traps were present in all thrombosed plaques, and in all types of the in vivo‐derived thrombi, but only to a much lower extent in intact plaques. Neutrophil traps, followed by macrophage traps, were the most prominent types in the autopsy series of atherothrombotic plaques, including the adventitia adjacent to thrombosed plaques. In contrast, macrophage traps were more numerous than neutrophil traps in intact plaques (lipid cores) and organised thrombi. Mast cell and eosinophil extracellular traps were also present, but sparse in all instances. In conclusion, not only neutrophils but also macrophages, eosinophils, and mast cells are sources of etosis involved in evolving coronary thrombosis. Neutrophil traps dominate numerically in early thrombosis and macrophage traps in late (organising) thrombosis, implying that together they span all the stages of thrombus progression and maturation. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

The role of infiltrating immune cells in dysfunctional adipose tissue

Adipose tissue (AT) dysfunction, characterized by loss of its homeostatic functions, is a hallmark of non-communicable diseases. It is characterized by chronic low-grade inflammation and is observed in obesity, metabolic disorders such as insulin resistance and diabetes. While classically it has been identified by increased cytokine or chemokine expression, such as increased MCP-1, RANTES, IL-6, interferon (IFN) gamma or TNFα, mechanistically, immune cell infiltration is a prominent feature of the dysfunctional AT. These immune cells include M1 and M2 macrophages, effector and memory T cells, IL-10 producing FoxP3+ T regulatory cells, natural killer and NKT cells and granulocytes. Immune composition varies, depending on the stage and the type of pathology. Infiltrating immune cells not only produce cytokines but also metalloproteinases, reactive oxygen species, and chemokines that participate in tissue remodelling, cell signalling, and regulation of immunity. The presence of inflammatory cells in AT affects adjacent tissues and organs. In blood vessels, perivascular AT inflammation leads to vascular remodelling, superoxide production, endothelial dysfunction with loss of nitric oxide (NO) bioavailability, contributing to vascular disease, atherosclerosis, and plaque instability. Dysfunctional AT also releases adipokines such as leptin, resistin, and visfatin that promote metabolic dysfunction, alter systemic homeostasis, sympathetic outflow, glucose handling, and insulin sensitivity. Anti-inflammatory and protective adiponectin is reduced. AT may also serve as an important reservoir and possible site of activation in autoimmune-mediated and inflammatory diseases. Thus, reciprocal regulation between immune cell infiltration and AT dysfunction is a promising future therapeutic target.

Adventitial Activation in the Pathogenesis of Injury-Induced Arterial Remodeling: Potential Implications in Transplant Vasculopathy

Transplant vasculopathy is one of the major causes of chronic rejection after solid organ transplantation. The pathogenic mechanisms of transplant vasculopathy are still poorly understood. Herein, we summarize current evidence suggesting that activation of the tunica adventitia may be involved in the pathogenesis of transplant vasculopathy. Adventitia is an early responder to various vascular injuries and plays an integral role in eliciting vascular inflammation and remodeling. Accumulation of macrophages in the adventitia promotes the development of vascular remodeling by releasing a variety of paracrine factors that have profound impacts on vascular mural cells. Targeting adventitial macrophages has been shown to be effective for repressing transplantation-induced arterial remodeling in animal models. Adventitia also fosters angiogenesis, and neovascularization of the adventitial layer may facilitate the transport of inflammatory cells through the arterial wall. Further investigations are warranted to clarify whether inhibiting adventitial oxidative stress and/or adventitial neovascularization are better strategies for preventing transplant vasculopathy.

Perivascular adipose tissue inflammation in vascular disease

Perivascular adipose tissue (PVAT) plays a critical role in the pathogenesis of cardiovascular disease. In vascular pathologies, perivascular adipose tissue increases in volume and becomes dysfunctional, with altered cellular composition and molecular characteristics. PVAT dysfunction is characterized by its inflammatory character, oxidative stress, diminished production of vaso-protective adipocyte-derived relaxing factors and increased production of paracrine factors such as resistin, leptin, cytokines (IL-6 and TNF-α) and chemokines [RANTES (CCL5) and MCP-1 (CCL2)]. These adipocyte-derived factors initiate and orchestrate inflammatory cell infiltration including primarily T cells, macrophages, dendritic cells, B cells and NK cells. Protective factors such as adiponectin can reduce NADPH oxidase superoxide production and increase NO bioavailability in the vessel wall, while inflammation (e.g. IFN-γ or IL-17) induces vascular oxidases and eNOS dysfunction in the endothelium, vascular smooth muscle cells and adventitial fibroblasts. All of these events link the dysfunctional perivascular fat to vascular dysfunction. These mechanisms are important in the context of a number of cardiovascular disorders including atherosclerosis, hypertension, diabetes and obesity. Inflammatory changes in PVAT's molecular and cellular responses are uniquely different from classical visceral or subcutaneous adipose tissue or from adventitia, emphasizing the unique structural and functional features of this adipose tissue compartment. Therefore, it is essential to develop techniques for monitoring the characteristics of PVAT and assessing its inflammation. This will lead to a better understanding of the early stages of vascular pathologies and the development of new therapeutic strategies focusing on perivascular adipose tissue.

LINKED ARTICLES

This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

Engineering nanomaterials to address cell-mediated inflammation in atherosclerosis

Atherosclerosis is an inflammatory disorder with a pathophysiology driven by both innate and adaptive immunity and a primary cause of cardiovascular disease (CVD) worldwide. Vascular inflammation and accumulation of foam cells and their products induce maturation of atheromas, or plaques, which can rupture by metalloprotease action, leading to ischemic stroke or myocardial infarction. Diverse immune cell populations participate in all stages of plaque maturation, many of which directly influence plaque stability and rupture via inflammatory mechanisms. Current clinical treatments for atherosclerosis focus on lowering serum levels of low-density lipoprotein (LDL) using therapeutics such as statins, administration of antithrombotic drugs, and surgical intervention. Strategies that address cell-mediated inflammation are lacking, and consequently have recently become an area of considerable research focus. Nanomaterials have emerged as highly advantageous tools for these studies, as they can be engineered to target specific inflammatory cell populations, deliver therapeutics of wide-ranging solubilities and enhance analytical methods that include imaging and proteomics. Furthermore, the highly phagocytic nature of antigen presenting cells (APCs), a diverse cell population central to the initiation of immune responses and inflammation, make them particularly amenable to targeting and modulation by nanoscale particulates. Nanomaterials have therefore become essential components of vaccine formulations and treatments for inflammation-driven pathologies like autoimmunity, and present novel opportunities for immunotherapeutic treatments of CVD. Here, we review recent progress in the design and use of nanomaterials for therapeutic assessment and treatment of atherosclerosis. We will focus on promising new approaches that utilize nanomaterials for cell-specific imaging, gene therapy and immunomodulation.

CXCL4 Plasma Levels Are Not Associated with the Extent of Coronary Artery Disease or with Coronary Plaque Morphology

BACKGROUND

CXCL4 is a platelet chemokine released at micromolar concentrations upon platelet activation. CXCL4 has been shown to promote atherogenesis by various mechanisms. However, data on CXCL4 plasma levels in patients with coronary artery disease are largely inconclusive. Computed coronary artery angiography (CCTA) represents an excellent tool to quantify and characterize coronary atherosclerotic plaques. We hypothesized that increased CXCL4 plasma levels may be associated with features of plaque instability resulting in adverse cardiovascular events. Specifically, we sought to determine whether CXCL4 levels are correlated with specific features of coronary artery disease including (1) plaque volume, (2) calcium score, (3) degree of stenosis, or (4) vascular remodeling.

METHODS AND RESULTS

CXCL4 plasma levels were measured by ELISA in 217 patients undergoing CCTA for suspected CAD (mean age 64.2 ± 9.4 years, 107 (49.3%) male). Mean CXCL4 plasma levels were 12.5 ± 4.6 ng/mL. There was no significant correlation between CXCL4 levels and any clinical or demographic parameters including cardiovascular risk factors. CXCL4 plasma levels did not differ between patient with or without coronary artery disease (CAD: 12.5 ± 4.5 ng/ml, no CAD: 12.5 ± 4.8 ng/ml). Neither univariate nor multivariate analysis showed an association between CXCL4 levels and plaque volume, total calcium score, degree of stenosis, or vascular remodeling. Subgroup analysis of patients with CAD as confirmed by CCTA did not show any association of CXCL4 levels with the extent of CAD.

CONCLUSIONS

While CXCL4 may be present and active within the arterial wall, local increase of CXCL4 may not translate into systemically elevated CXCL4 levels. Further studies will have to test whether CXCL4 may still represent a suitable therapeutic target in human atherosclerosis.

Coronary Atherosclerosis and Interventional Cardiology

The atherosclerotic process in coronary arteries begins with endothelial dysfunction and may provoke thrombotic total occlusion and myocardial infarction. In this state-of-the-art review, we discuss recent evidence of atheroslerosis, vulnerable plaque, and hemodynamic changes in the coronary tree, as well as the current techniques we implement in the catheterization lab to evaluate coronary stenosis. It is clear that atherosclerosis is a chronic inflammatory condition with several consequences in the coronary tree, however, we are able now to characterize the plaque and to select the appropriate treatment for many patients.

Adventitial Tertiary Lymphoid Organs as Potential Source of MicroRNA Biomarkers for Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is an inflammatory disease associated with marked changes in the cellular composition of the aortic wall. This study aims to identify microRNA (miRNA) expression in aneurysmal inflammatory cells isolated by laser microdissection from human tissue samples. The distribution of inflammatory cells (neutrophils, B and T lymphocytes, mast cells) was evaluated in human AAA biopsies. We observed in half of the samples that adventitial tertiary lymphoid organs (ATLOs) with a thickness from 0.5 to 2 mm were located exclusively in the adventitia. Out of the 850 miRNA that were screened by microarray in isolated ATLOs (n = 2), 164 miRNAs were detected in ATLOs. The three miRNAs (miR-15a-3p, miR-30a-5p and miR-489-3p) with the highest expression levels were chosen and their expression quantified by RT-PCR in isolated ATLOs (n = 4), M1 (n = 2) and M2 macrophages (n = 2) and entire aneurysmal biopsies (n = 3). Except for the miR-30a-5p, a similar modulation was found in ATLOs and the two subtypes of macrophages. The modulated miRNAs were then evaluated in the plasma of AAA patients for their potential as AAA biomarkers. Our data emphasize the potential of miR-15a-3p and miR-30a-5p as biomarkers of AAA but also as triggers of ATLO evolution. Further investigations will be required to evaluate their targets in order to better understand AAA pathophysiology.