Dynamic T cell-APC interactions sustain chronic inflammation in atherosclerosis

The Role of Bacterial Extracellular Membrane Nanovesicles in Atherosclerosis: Unraveling a Potential Trigger

PURPOSE OF REVIEW

In this review, we explore the intriguing and evolving connections between bacterial extracellular membrane nanovesicles (BEMNs) and atherosclerosis development, highlighting the evidence on molecular mechanisms by which BEMNs can promote the athero-inflammatory process that is central to the progression of atherosclerosis.

RECENT FINDINGS

Atherosclerosis is a chronic inflammatory disease primarily driven by metabolic and lifestyle factors; however, some studies have suggested that bacterial infections may contribute to the development of both atherogenesis and inflammation in atherosclerotic lesions. In particular, the participation of BEMNs in atherosclerosis pathogenesis has attracted special attention. We provide some general insights into how the immune system responds to potential threats such as BEMNs during the development of atherosclerosis. A comprehensive understanding of contribution of BEMNs to atherosclerosis pathogenesis may lead to the development of targeted interventions for the prevention and treatment of the disease.

Targeting pro-inflammatory T cells as a novel therapeutic approach to potentially resolve atherosclerosis in humans

Atherosclerosis (AS), a leading cause of cardio-cerebrovascular disease worldwide, is driven by the accumulation of lipid contents and chronic inflammation. Traditional strategies primarily focus on lipid reduction to control AS progression, leaving residual inflammatory risks for major adverse cardiovascular events (MACEs). While anti-inflammatory therapies targeting innate immunity have reduced MACEs, many patients continue to face significant risks. Another key component in AS progression is adaptive immunity, but its potential role in preventing AS remains unclear. To investigate this, we conducted a retrospective cohort study on tumor patients with AS plaques. We found that anti-programmed cell death protein 1 (PD-1) monoclonal antibody (mAb) significantly reduces AS plaque size. With multi-omics single-cell analyses, we comprehensively characterized AS plaque-specific PD-1+ T cells, which are activated and pro-inflammatory. We demonstrated that anti-PD-1 mAb, when captured by myeloid-expressed Fc gamma receptors (FcγRs), interacts with PD-1 expressed on T cells. This interaction turns the anti-PD-1 mAb into a substitute PD-1 ligand, suppressing T-cell functions in the PD-1 ligands-deficient context of AS plaques. Further, we conducted a prospective cohort study on tumor patients treated with anti-PD-1 mAb with or without Fc-binding capability. Our analysis shows that anti-PD-1 mAb with Fc-binding capability effectively reduces AS plaque size, while anti-PD-1 mAb without Fc-binding capability does not. Our work suggests that T cell-targeting immunotherapy can be an effective strategy to resolve AS in humans.

Crosstalk between efferocytic myeloid cells and T-cells and its relevance to atherosclerosis

The interplay between myeloid cells and T-lymphocytes is critical to the regulation of host defense and inflammation resolution. Dysregulation of this interaction can contribute to the development of chronic inflammatory diseases. Important among these diseases is atherosclerosis, which refers to focal lesions in the arterial intima driven by elevated apolipoprotein B-containing lipoproteins, notably low-density lipoprotein (LDL), and characterized by the formation of a plaque composed of inflammatory immune cells, a collection of dead cells and lipids called the necrotic core, and a fibrous cap. As the disease progresses, the necrotic core expands, and the fibrous cap becomes thin, which increases the risk of plaque rupture or erosion. Plaque rupture leads to a rapid thrombotic response that can give rise to heart attack, stroke, or sudden death. With marked lowering of circulating LDL, however, plaques become more stable and cardiac risk is lowered-a process known as atherosclerosis regression. A critical aspect of both atherosclerosis progression and regression is the crosstalk between innate (myeloid cells) and adaptive (T-lymphocytes) immune cells. Myeloid cells are specialized at clearing apoptotic cells by a process called efferocytosis, which is necessary for inflammation resolution. In advanced disease, efferocytosis is impaired, leading to secondary necrosis of apoptotic cells, inflammation, and, most importantly, defective tissue resolution. In regression, efferocytosis is reawakened aiding in inflammation resolution and plaque stabilization. Here, we will explore how efferocytosing myeloid cells could affect T-cell function and vice versa through antigen presentation, secreted factors, and cell-cell contacts and how this cellular crosstalk may contribute to the progression or regression of atherosclerosis.

Association of Lipoprotein(a) with peri-coronary inflammation in persons with and without HIV infection

BACKGROUND

Persons with human immunodeficiency virus (HIV) (PWH) have an increased risk of developing cardiovascular disease (CVD) compared to persons without HIV (PWoH). Lipoprotein(a) [Lp(a)] is a known atherosclerotic risk factor in PWoH, but there are no studies investigating Lp(a) and peri-coronary inflammation.

OBJECTIVE

To investigate whether Lp(a) is associated with peri-coronary inflammation as assessed by the fat attenuation index (FAI) and activated monocytes and T lymphocytes in PWH and PWoH.

METHODS

We measured plasma levels of Lp(a) at study entry in 58 PWH and 21 PWoH without CVD and who had FAI measurements. Associations of Lp(a) with FAI values of the right coronary artery (RCA) and left anterior descending artery were evaluated using multivariable regression models adjusted for potential confounders. Correlations between Lp(a) levels and systemic inflammatory markers and immune cell subsets were examined.

RESULTS

Lp(a) was associated with greater peri-coronary inflammation among PWH compared to PWoH (β=1.73, P=0.019) in the RCA, in adjusted models. Significant correlations were observed with certain inflammatory markers (tumor necrosis factor receptor [TNFR]-I, b=0.295, P<0.001; TNFR-II, b=0.270, P=0.002; high-sensitivity C-reactive protein, b=0.195, P=0.028). Significant correlations were found between Lp(a) levels and several markers of monocyte activation: CD16 -CD163+ (b= -0.199, P=0.024), and CD16 -DR+ MFI (b= -0.179, P=0.042) and T cell subset CD38+CD4+ TEMRA (b= 0.177, P= 0.044).

CONCLUSIONS

Lp(a) was associated with greater peri-coronary inflammation in the RCA in PWH compared to PWoH, as well as with select systemic inflammatory markers and specific subsets of immune cells in peripheral circulation.

The role of immune cells in different stages of atherosclerosis

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of immune cells in the intima of arteries. Experimental and clinical evidence shows that both innate and adaptive immunity orchestrate the progression of atherosclerosis. The heterogeneous nature of immune cells within atherosclerosis lesions is important. Studies utilizing high-dimensional mass spectrometry and single-cell RNA sequencing of leukocytes from atherosclerotic lesions show the diversity and adaptability of these immune cell subtypes. Their migration, compositional changes, phenotypic alterations, and adaptive responses are key features throughout atherosclerosis progression. Understanding how these immune cells and their subtypes affect atherogenesis would help to develop novel therapeutic approaches that control atherosclerosis progression. Precise targeting of specific immune system components involved in atherosclerosis, rather than broad suppression of the immune system with anti-inflammatory agents, can more accurately regulate the progress of atherosclerosis with fewer side effects. In this review, we cover the most recent advances in the field of atherosclerosis to understand the role of various immune cells on its development. We focus on the complex network of immune cells and the interaction between the innate immune system and adaptive immune system.

Haplo-insufficiency of Profilin1 in vascular endothelial cells is beneficial but not sufficient to confer protection against experimentally induced atherosclerosis

Actin cytoskeleton plays an important role in various aspects of atherosclerosis, a key driver of ischemic heart disease. Actin-binding protein Profilin1 (Pfn1) is overexpressed in atherosclerotic plaques in human disease, and Pfn1, when partially depleted globally in all cell types, confers atheroprotection in vivo. This study investigates the impact of endothelial cell (EC)-specific partial loss of Pfn1 expression in atherosclerosis development. We utilized mice engineered for conditional heterozygous knockout of the Pfn1 gene in ECs, with atherosclerosis induced by depletion of hepatic LDL receptor by gene delivery of PCSK9 combined with high-cholesterol diet. Our studies show that partial depletion of EC Pfn1 has certain beneficial effects marked by dampening of select pro-atherogenic cytokines (CXCL10 and IL7) with concomitant reduction in cytotoxic T cell abundance but is not sufficient to reduce hyperlipidemia and confer atheroprotection in vivo. In light of these findings, we conclude that atheroprotective phenotype conferred by global Pfn1 haplo-insufficiency requires contributions of additional cell types that are relevant for atherosclerosis progression.

Breaking tolerance: the autoimmune aspect of atherosclerosis

Atherosclerotic cardiovascular disease (ASCVD) is a chronic inflammatory disease of the arterial walls and is characterized by the accumulation of lipoproteins that are insufficiently cleared by phagocytes. Following the initiation of atherosclerosis, the pathological progression is accelerated by engagement of the adaptive immune system. Atherosclerosis triggers the breakdown of tolerance to self-components. This loss of tolerance is reflected in defective expression of immune checkpoint molecules, dysfunctional antigen presentation, and aberrations in T cell populations - most notably in regulatory T (Treg) cells - and in the production of autoantibodies. The breakdown of tolerance to self-proteins that is observed in ASCVD may be linked to the conversion of Treg cells to 'exTreg' cells because many Treg cells in ASCVD express T cell receptors that are specific for self-epitopes. Alternatively, or in addition, breakdown of tolerance may trigger the activation of naive T cells, resulting in the clonal expansion of T cell populations with pro-inflammatory and cytotoxic effector phenotypes. In this Perspective, we review the evidence that atherosclerosis is associated with a breakdown of tolerance to self-antigens, discuss possible immunological mechanisms and identify knowledge gaps to map out future research. Rational approaches aimed at re-establishing immune tolerance may become game changers in treating ASCVD and in preventing its downstream sequelae, which include heart attacks and strokes.

Haplo-insufficiency of Profilin1 in vascular endothelial cells is beneficial but not sufficient to confer protection against experimentally induced atherosclerosis

Actin cytoskeleton plays an important role in various aspects of atherosclerosis, a key driver of ischemic heart disease. Actin-binding protein Profilin1 (Pfn1) is overexpressed in atherosclerotic plaques in human disease, and Pfn1, when partially depleted globally in all cell types, confers atheroprotection in vivo . This study investigates the impact of endothelial cell (EC)-specific partial loss of Pfn1 expression in atherosclerosis development. We utilized mice engineered for conditional heterozygous knockout of the Pfn1 gene in ECs, with atherosclerosis induced by depletion of hepatic LDL receptor by gene delivery of PCSK9 combined with high-cholesterol diet. Our studies show that partial depletion of EC Pfn1 has certain beneficial effects marked by dampening of select pro-atherogenic cytokines (CXCL10 and IL7) with concomitant reduction in cytotoxic T cell abundance but is not sufficient to reduce hyperlipidemia and confer atheroprotection in vivo . In light of these findings, we conclude that atheroprotective phenotype conferred by global Pfn1 haplo-insufficiency requires contributions of additional cell types that are relevant for atherosclerosis progression.

The Evolving Role of Dendritic Cells in Atherosclerosis

Atherosclerosis, a major contributor to cardiovascular morbidity and mortality, is characterized by chronic inflammation of the arterial wall. This inflammatory process is initiated and maintained by both innate and adaptive immunity. Dendritic cells (DCs), which are antigen-presenting cells, play a crucial role in the development of atherosclerosis and consist of various subtypes with distinct functional abilities. Following the recognition and binding of antigens, DCs become potent activators of cellular responses, bridging the innate and adaptive immune systems. The modulation of specific DC subpopulations can have either pro-atherogenic or atheroprotective effects, highlighting the dual pro-inflammatory or tolerogenic roles of DCs. In this work, we provide a comprehensive overview of the evolving roles of DCs and their subtypes in the promotion or limitation of atherosclerosis development. Additionally, we explore antigen pulsing and pharmacological approaches to modulate the function of DCs in the context of atherosclerosis.

Clonally expanded memory CD8+ T cells accumulate in atherosclerotic plaques and are pro-atherogenic in aged mice

Aging is a strong risk factor for atherosclerosis and induces accumulation of memory CD8+ T cells in mice and humans. Biological changes that occur with aging lead to enhanced atherosclerosis, yet the role of aging on CD8+ T cells during atherogenesis is unclear. In this study, using femle mice, we found that depletion of CD8+ T cells attenuated atherogenesis in aged, but not young, animals. Furthermore, adoptive transfer of splenic CD8+ T cells from aged wild-type, but not young wild-type, donor mice significantly enhanced atherosclerosis in recipient mice lacking CD8+ T cells. We also characterized T cells in healthy and atherosclerotic young and aged mice by single-cell RNA sequencing. We found specific subsets of age-associated CD8+ T cells, including a Granzyme K+ effector memory subset, that accumulated and was clonally expanded within atherosclerotic plaques. These had transcriptomic signatures of T cell activation, migration, cytotoxicity and exhaustion. Overall, our study identified memory CD8+ T cells as therapeutic targets for atherosclerosis in aging.

Atherosclerosis and Its Related Laboratory Biomarkers

Atherosclerosis constitutes a persistent inflammatory ailment, serving as the predominant underlying condition for coronary artery disease (CAD), peripheral artery disease (PAD), and cerebrovascular disease. The progressive buildup of plaques within the walls of medium- and large-caliber arteries characterizes the atherosclerotic process. This accumulation results in significant narrowing that impedes blood flow, leading to critical tissue oxygen deficiency. Spontaneous blockage of thrombotic vessels can precipitate stroke and myocardial infarction, which are complications representing the primary global causes of mortality. Present-day models for predicting cardiovascular risk incorporate conventional risk factors to gauge the likelihood of cardiovascular events over a ten-year span. In recent times, researchers have identified serum biomarkers associated with an elevated risk of atherosclerotic events. Many of these biomarkers, whether used individually or in combination, have been integrated into risk prediction models to assess whether their inclusion enhances predictive accuracy. In this review, we have conducted a comprehensive analysis of the most recently published literature concerning serum biomarkers associated with atherosclerosis. We have explored the potential utility of incorporating these markers in guiding clinical decisions.

Fat and inflammation: adipocyte-myeloid cell crosstalk in atherosclerosis

Adipose tissue inflammation has been implicated in various chronic inflammatory diseases and cancer. Perivascular adipose tissue (PVAT) surrounds the aorta as an extra layer and was suggested to contribute to atherosclerosis development. PVAT regulates the function of endothelial and vascular smooth muscle cells in the aorta and represent a reservoir for various immune cells which may participate in aortic inflammation. Recent studies demonstrate that adipocytes also express various cytokine receptors and, therefore, may directly respond to inflammatory stimuli. Here we will summarize current knowledge on immune mechanisms regulating adipocyte activation and the crosstalk between myeloid cells and adipocytes in pathogenesis of atherosclerosis.

An update on inflammation in uveal melanoma

Uveal melanoma (UM) is the primary ocular cancer with upto 50% of patients dying from metastasis. Although rare, it is deadly as patients with metastatic UM seldom survive beyond 18 months after diagnosis. Chemotherapeutics have no proven efficacy, including immunotherapies that have been tried as current treatment options but produce marginal improvement in overall survival for UM patients. While therapeutics are low in efficacy, there is an urgent need to explore novel targets in the treatment of UM. This review provides an update on the contribution of inflammation to UM with a focus on exploring potential therapeutic targets related to the inflammatory tumour microenvironment. As a tumour promoting event, inflammation is one of the hallmarks of cancers. The presence of the inflammatory phenotype characterised by the abundance of immune mediators and proinflammatory cytokines surrounding UM tumours, is a potential area to explore novel therapeutic targets. Despite decades of investigation regarding the role UM tumour microenvironment has played, that of inflammation in UM progression remains poorly understood. With advancement of technologies, an understanding of the prognosis of UM has been accelerated. Excitingly, novel therapeutic targets related to the inflammatory tumour microenvironment have been identified and relevant studies are underway in their preliminary phases, illustrating optimistic results.

T-cell Cholesterol Accumulation, Aging, and Atherosclerosis

PURPOSE OF REVIEW

The majority of leukocytes in advanced human atherosclerotic plaques are T-cells. T-cell subsets exert pro- or anti-atherogenic effects largely via the cytokines they secrete. Tregulatory cells (Tregs) are anti-inflammatory, but may lose these properties during atherosclerosis, proposed to be downstream of cholesterol accumulation. Aged T-cells also accumulate cholesterol. The effects of T-cell cholesterol accumulation on T-cell fate and atherosclerosis are not uniform.

RECENT FINDINGS

T-cell cholesterol accumulation enhances differentiation into pro-atherogenic cytotoxic T-cells and boosts their killing capacity, depending on the localization and extent of cholesterol accumulation. Excessive cholesterol accumulation induces T-cell exhaustion or T-cell apoptosis, the latter decreasing atherosclerosis but impairing T-cell functionality in terms of killing capacity and proliferation. This may explain the compromised T-cell functionality in aged T-cells and T-cells from CVD patients. The extent of T-cell cholesterol accumulation and its cellular localization determine T-cell fate and downstream effects on atherosclerosis and T-cell functionality.

Transition Metal-Based Therapies for Inflammatory Diseases

Inflammatory disease (ID) is a general term that covers all diseases in which chronic inflammation performs as the major manifestation of pathogenesis. Traditional therapies based on the anti-inflammatory and immunosuppressive drugs are palliative with the short-term remission. The emergence of nanodrugs has been reported to solve the potential causes and prevent recurrences, thus holding great potential for the treatment of IDs. Among various nanomaterial systems, transition metal-based smart nanosystems (TMSNs) with unique electronic structures possess therapeutic advantages owing to their large surface area to volume ratio, high photothermal conversion efficiency, X-ray absorption capacity, and multiple catalytic enzyme activities. In this review, the rationale, design principle, and therapeutic mechanisms of TMSNs for treatments of various IDs are summarized. Specifically, TMSNs can not only be designed to scavenge danger signals, such as reactive oxygen and nitrogen species and cell-free DNA, but also can be engineered to block the mechanism of initiating inflammatory responses. In addition, TMSNs can be further applied as nanocarriers to deliver anti-inflammatory drugs. Finally, the opportunities and challenges of TMSNs are discussed, and the future directions of TMSN-based ID treatment for clinical applications are emphasized.

Advances in immunotherapy modalities for atherosclerosis

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. Atherosclerosis is the pathological basis of atherosclerotic cardiovascular disease (ASCVD). Atherosclerosis is now understood to be a long-term immune-mediated inflammatory condition brought on by a complicated chain of factors, including endothelial dysfunction, lipid deposits in the artery wall, and monocyte-derived macrophage infiltration, in which both innate immunity and adaptive immunity play an indispensable role. Recent studies have shown that atherosclerosis can be alleviated by inducing a protective immune response through certain auto-antigens or exogenous antigens. Some clinical trials have also demonstrated that atherosclerotic is associated with the presence of immune cells and immune factors in the body. Therefore, immunotherapy is expected to be a new preventive and curative measure for atherosclerosis. In this review, we provide a summary overview of recent progress in the research of immune mechanisms of atherosclerosis and targeted therapeutic pathways.

The emerging role of Th1 cells in atherosclerosis and its implications for therapy

Atherosclerosis is a chronic progressive inflammatory disease of the large and medium-sized artery walls. The molecular mechanisms regulating the onset and progression of atherosclerosis remain unclear. T cells, one of the most common immune cell types in atherosclerotic plaques, are increasingly recognized as a key mediator in the pathogenesis of atherosclerosis. Th1 cells are a subset of CD4⁺ T helper cells of the adaptive immune system, characterized by the expression of the transcription factor T-bet and secretion of cytokines such as IFN-γ. Converging evidence shows that Th1 cells play a key role in the onset and progression of atherosclerosis. Besides, Th1 is the central mediator to orchestrate the adaptive immune system. In this review, we aim to summarize the complex role of Th1 cells in atherosclerosis and propose novel preventative and therapeutic approaches targeting Th1 cell-associated specific cytokines and receptors to prevent atherogenesis.

Association Between Atherosclerosis-Related Cardiovascular Disease and Uveitis: A Systematic Review and Meta-Analysis

BACKGROUND

Uveitis is not only an intraocular inflammatory disease, but also an indicator of systemic inflammation. It is unclear whether uveitis can increase the risk of cardiovascular disease (CVD) through the atherosclerotic pathway.

METHODS

PubMed and Embase databases were searched until 5 September, 2022. Original studies investigating uveitis and cardiovascular events were selected. The random-effects model was used to calculate the difference of groups in pooled estimates.

RESULTS

A total of six observational studies that included mainly ankylosing spondylitis (AS) patients were included. Of these, three studies reported data on carotid plaques and carotid intima-media thickness (cIMT) and the other three studies provided data on atherosclerosis-related CVD. No significant difference was found in cIMT between uveitis and controls (MD = 0.01, 95% CI = -0.03-0.04, p = 0.66), consistent with the findings of carotid plaque incidence (OR = 1.30, 95% CI = 0.71-2.41, p = 0.39). However, uveitis was associated with a 1.49-fold increase in atherosclerosis-related CVD (HR = 1.49, 95% CI = 1.20-1.84, p = 0.0002).

CONCLUSIONS

Uveitis is a predictor of atherosclerosis-related CVD in AS patients. For autoimmune disease patients with uveitis, earlier screening of cardiovascular risk factors and the implementation of corresponding prevention strategies may be associated with a better prognosis.

Costimulatory and coinhibitory molecules of B7-CD28 family in cardiovascular atherosclerosis: A review

Accumulating evidence supports the active involvement of vascular inflammation in atherosclerosis pathogenesis. Vascular inflammatory events within atherosclerotic plaques are predominated by innate antigen-presenting cells (APCs), including dendritic cells, macrophages, and adaptive immune cells such as T lymphocytes. The interaction between APCs and T cells is essential for the initiation and progression of vascular inflammation during atherosclerosis formation. B7-CD28 family members that provide either costimulatory or coinhibitory signals to T cells are important mediators of the cross-talk between APCs and T cells. The balance of different functional members of the B7-CD28 family shapes T cell responses during inflammation. Recent studies from both mouse and preclinical models have shown that targeting costimulatory molecules on APCs and T cells may be effective in treating vascular inflammatory diseases, especially atherosclerosis. In this review, we summarize recent advances in understanding how APC and T cells are involved in the pathogenesis of atherosclerosis by focusing on B7-CD28 family members and provide insight into the immunotherapeutic potential of targeting B7-CD28 family members in atherosclerosis.

Heparanase: A Novel Therapeutic Target for the Treatment of Atherosclerosis

Cardiovascular disease (CVD) is the leading cause of death and disability worldwide, and its management places a huge burden on healthcare systems through hospitalisation and treatment. Atherosclerosis is a chronic inflammatory disease of the arterial wall resulting in the formation of lipid-rich, fibrotic plaques under the subendothelium and is a key contributor to the development of CVD. As such, a detailed understanding of the mechanisms involved in the development of atherosclerosis is urgently required for more effective disease treatment and prevention strategies. Heparanase is the only mammalian enzyme known to cleave heparan sulfate of heparan sulfate proteoglycans, which is a key component of the extracellular matrix and basement membrane. By cleaving heparan sulfate, heparanase contributes to the regulation of numerous physiological and pathological processes such as wound healing, inflammation, tumour angiogenesis, and cell migration. Recent evidence suggests a multifactorial role for heparanase in atherosclerosis by promoting underlying inflammatory processes giving rise to plaque formation, as well as regulating lesion stability. This review provides an up-to-date overview of the role of heparanase in physiological and pathological processes with a focus on the emerging role of the enzyme in atherosclerosis.

Relationship between plasma fibrinogen degradation products(FDP) and D-dimer levels and disease activity in rheumatoid arthritis: A STROBE compliant article

In this study, we aimed to investigate whether fibrinogen degradation products(FDP)and D-dimer could be used as serological indicators of rheumatoid arthritis(RA) activity, such as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and platelets (PLT). A total of 112 consecutive patients with RA between July 2018 and July 2020 were divided into moderate and high disease activity groups (disease activity score 28(DAS28) > 3.2, n = 60) and low disease activity and remission groups (DAS28≤3.2, n = 52). A total of 50 healthy volunteers were included in the control group, and FDP and D-dimer levels were compared across the three groups. The correlations of FDP and D-dimer levels with ESR, CRP, PLT, and DAS28 were analyzed. Analyses of the receiver operating characteristic(ROC) curves and area under the ROC curve (AUC) of FDP, D-dimer, ESR, CRP, and PLT levels were performed. FDP and D-dimer levels were significantly higher in the high-activity compared to the low-activity and remission (P < .001), and the control (P < .001). No significant differences in FDP and D-dimer were observed between the low-activity and remission and the control (P > .05). FDP and D-dimer levels were positively correlated with ESR, CRP, PLT, and DAS28 (all P < .001). The ROC curves showed that the FDP and D-dimer levels could be used to evaluate the RA activity (all P < .001). The AUC of FDP was significantly larger than that of PLT (P = .047). FDP and D-dimer can be used as supplementary serological indicators to assess RA activity, in addition to ESR, CRP, and PLT.

Crosstalk between dendritic cells and T lymphocytes during atherogenesis: Focus on antigen presentation and break of tolerance

Atherosclerosis is a chronic disease resulting from an impaired lipid and immune homeostasis, where the interaction between innate and adaptive immune cells leads to the promotion of atherosclerosis-associated immune-inflammatory response. Emerging evidence has suggested that this response presents similarities to the reactivity of effector immune cells toward self-epitopes, often as a consequence of a break of tolerance. In this context, dendritic cells, a heterogeneous population of antigen presenting cells, play a key role in instructing effector T cells to react against foreign antigens and T regulatory cells to maintain tolerance against self-antigens and/or to patrol for self-reactive effector T cells. Alterations in this delicate balance appears to contribute to atherogenesis. The aim of this review is to discuss different DC subsets, and their role in atherosclerosis as well as in T cell polarization. Moreover, we will discuss how loss of T cell tolerogenic phenotype participates to the immune-inflammatory response associated to atherosclerosis and how a better understanding of these mechanisms might result in designing immunomodulatory therapies targeting DC-T cell crosstalk for the treatment of atherosclerosis-related inflammation.

Immunodominant MHC-II (Major Histocompatibility Complex II) Restricted Epitopes in Human Apolipoprotein B

BACKGROUND

CD (cluster of differentiation) 4+ T-cell responses to APOB (apolipoprotein B) are well characterized in atherosclerotic mice and detectable in humans. CD4+ T cells recognize antigenic peptides displayed on highly polymorphic HLA (human leukocyte antigen)-II. Immunogenicity of individual APOB peptides is largely unknown in humans. Only 1 HLA-II-restricted epitope was validated using the DRB1*07:01-APOB3036-3050 tetramer. We hypothesized that human APOB may contain discrete immunodominant CD4+ T-cell epitopes that trigger atherosclerosis-related autoimmune responses in donors with diverse HLA alleles.

METHODS

We selected 20 APOB-derived peptides (APOB20) from an in silico screen and experimentally validated binding to the most commonly occurring human HLA-II alleles. We optimized a restimulation-based workflow to evaluate antigenicity of multiple candidate peptides in HLA-typed donors. This included activation-induced marker assay, intracellular cytokine staining, IFNγ (interferon gamma) enzyme-linked immunospot and cytometric bead array. High-throughput sequencing revealed TCR (T-cell receptor) clonalities of APOB-reactive CD4+ T cells.

RESULTS

Using stringent positive, negative, and crossover stimulation controls, we confirmed specificity of expansion-based protocols to detect CD4+ T cytokine responses to the APOB20 pool. Ex vivo assessment of AIM+CD4+ T cells revealed a statistically significant autoimmune response to APOB20 but not to a ubiquitously expressed negative control protein, actin. Resolution of CD4+ T responses to the level of individual peptides using IFNγ enzyme-linked immunospot led to the discovery of 6 immunodominant epitopes (APOB6) that triggered robust CD4+ T activation in most donors. APOB6-specific responding CD4+ T cells were enriched in unique expanded TCR clonotypes and preferentially expressed memory markers. Cytometric bead array analysis detected APOB6-induced secretion of both proinflammatory and regulatory cytokines. In clinical samples from patients with angiographically verified coronary artery disease, APOB6 stimulation induced higher activation and memory phenotypes and augmented secretion of proinflammatory cytokines TNF (tumor necrosis factor) and IFNγ, compared with patients with low coronary artery disease.

CONCLUSIONS

Using 3 cohorts, each with ≈20 donors, we discovered and validated 6 immunodominant, HLA-II-restricted APOB epitopes. The immune response to these APOB epitopes correlated with coronary artery disease severity.

A Bibliometric Analysis of Research on the Links Between Gut Microbiota and Atherosclerosis

Background

Emerging evidence has linked gut microbiota (GM) and its related metabolites to atherosclerosis (AS). This study aimed to analyze the evolution of GM in AS in the past decades, and provide valuable insights in this field.

Methods

Web of Science Core Collection (WoSCC) was applied to retrieve the publications related to GM in AS from their inception until 2 December 2021, and the data was analyzed in Microsoft Excel, Scimago Graphica, CiteSpace, and VOSviewer.

Results

In total, 560 documents were extracted from the WoSCC databases. The publications have shown rapid growth since 2008. China and Cleveland Clin were the most prolific country and institution, respectively. The journal with the most publications is Nutrients, and Nature was the most co-cited journal. Among 3556 related authors, Hazen, Stanley L., Tang, W. H. Wilson, and Wang, Zeneng were the top 3 contributing authors in this field. Aside from “gut microbiota,” “atherosclerosis,” the terms “TMAO,” “metabolite,” “obesity,” and “phosphatidylcholine” were frequently occurred in the abstract and title of articles. Burst detection of keywords indicated that “metabolic syndrome,” “acid,” and “bile acid” were hot topics in recent years. According to the co-citation analysis of references, the research focus in this area has changed over time, and recent researches focus on choline, hypertension, butyrate, and berberine.

Conclusion

Our study showed that the researches of GM in AS have been flourishing, and the content themes were constantly deepened. Human GM is critical to atherosclerotic diseases, and this hot topic is still worthy of more focus in the future.

A humanized β2 integrin knockin mouse reveals localized intra- and extravascular neutrophil integrin activation in vivo

β₂ integrins are leukocyte-specific adhesion molecules that are essential for leukocyte recruitment. The lack of tools for reporting β₂ integrin activation in mice hindered the study of β₂ integrin-related immune responses in vivo. Here, we generated a humanized β₂ integrin knockin mouse strain by targeting the human β₂ integrin coding sequence into the mouse Itgb2 locus to enable imaging of β₂ integrin activation using the KIM127 (extension) and mAb24 (high-affinity) reporter antibodies. Using a CXCL1-induced acute inflammation model, we show the local dynamics of β₂ integrin activation in arresting neutrophils in vivo in venules of the mouse cremaster muscle. Activated integrins are highly concentrated in a small area at the rear of arresting neutrophils in vivo. In a high-dose lipopolysaccharide model, we find that β₂ integrins are activated in association with elevated neutrophil adhesion in lung and liver. Thus, these mice enable studies of β₂ integrin activation in vivo.

Antigen-Presenting Cell-Like Neutrophils Foster T Cell Response in Hyperlipidemic Patients and Atherosclerotic Mice

Neutrophils constitute abundant cellular components in atherosclerotic plaques. Most of the current studies are focused on the roles of granular proteins released by neutrophils in atherosclerosis. Here, we revealed a unique subset of neutrophils which exhibit the characteristics of antigen-presenting cell (APC) (which were called APC-like neutrophils afterwards) in atherosclerosis. The roles of APC-like neutrophils and relevant mechanisms were investigated in hyperlipidemic patients and atherosclerotic mice. Higher percentages of neutrophils and APC-like neutrophils were found in peripheral blood of hyperlipidemic patients than that of healthy donors. Meanwhile, we also identified higher infiltration of neutrophils and APC-like neutrophils in atherosclerotic mice. Ox-LDL induced Phorbol-12-myristate-13-acetate (PMA)-activated neutrophils to acquire the APC-like phenotype. Importantly, upon over-expression of APC-like markers, neutrophils acquired APC functions to promote the proliferation and interferon-γ production of CD3⁺ T cells via HLA-DR/CD80/CD86. In accordance with what found in vitro, positive correlation between neutrophils and CD3⁺ T cells was observed in hyperlipidemic patients. In conclusion, our work identifies a proinflammatory neutrophil subset in both hyperlipidemic patients and atherosclerotic mice. This unique phenotype of neutrophils could activate the adaptive immune response to promote atherosclerosis progression. Thus, this neutrophil subset may be a new target for immunotherapy of atherosclerosis.

Neoantigen Presentation and IFNγ Signaling on the Same Tumor-associated Macrophage are Necessary for CD4 T Cell-mediated Antitumor Activity in Mice

Tumor Associated Macrophages (TAMs) promote tumor survival, angiogenesis and metastases. Although they express MHC Class II molecules, little is known about their ability to present tumor antigens to tumor infiltrating CD4 T cells, nor what are the consequences of such presentation. To answer these questions, we used a C57/BL10 mouse tumor model where we subcutaneously implant a bladder carcinoma cell line naturally expressing the H-Y male antigen into female mice, making the H-Y antigen a de facto neoantigen. We found that TAMs indeed present tumor antigens to effector CD4 T cells and that such presentation is necessary for tumor rejection. As consequence of this interaction TAMs are re-educated to produce lower amounts of tumor promoting proteins and greater amounts of inflammatory proteins. The re-education process of the TAMs is transcriptionally characterized by an IFN-γ signature, including genes of known anti-viral and anti-bacterial functions. CD4 production of IFN-γ, and not TNF-α or CD40L, is required for the re-education process and tumor rejection. Furthermore, IFN-γ signaling on antigen presenting TAMs and not on bystander TAMs, is necessary for the anti-tumor effect. These data identify critical mechanisms of tumor rejection by CD4 T cells and underscores the importance of effector CD4 T cell-tissue macrophage interactions not only at the tumors site but potentially in other tissues.

MicroRNA profile of circulating CD4+ T cells in aged patients with atherosclerosis obliterans

Background

To evaluate the specificity of the expression patterns of microRNAs (miRNAs) in circulating CD4+ T cells in aged patients with atherosclerosis obliterans (ASO).

Methods

A comprehensive miRNA expression study was conducted using a miRNA microarray of CD4+ T cells isolated from peripheral blood mononuclear cells (PBMCs) of 33 patients with ASO and 24 healthy donors. A t test was used for statistical analysis, and the average linkage method was used for hierarchical clustering. The results were validated by qRT–PCR. Putative targeted pathways associated with validated miRNAs were predicted with the online software DIANA miRPath.

Results

We identified 44 miRNAs based on a cutoff value of a 1.3-fold change in expression between the two groups, with 18 miRNAs showing a false discovery rate (FDR) p value < 0.05. The qRT–PCR analysis validated differences in 12 miRNAs, and 6 miRNAs were proven to be differentially expressed among three age groups (age: 35–55 years; 56–75 years; 76–95 years): the miRNAs miR-21 (p: 0.0008; 0.0009; 0.0022), miR-29b (p: 0.453; < 0.0001; < 0.0001), and miR-374b (p: < 0.0001; < 0.0001; 0.2493) showed upregulated expression in patients with ASO, while miR-142-3p (p: < 0.0001; < 0.0001; < 0.0001), miR-142-5p (p: < 0.0001; < 0.0001; < 0.0001), and miR-150 (p: < 0.0001; < 0.0001; 0.0001) showed downregulated expression in patients with ASO. The validated miRNAs participated in CD4+ T cell activation, proliferation, and migration pathways.

Conclusions

Circulating CD4+ T cells in aged patients with ASO may show a distinct molecular signature. This is the first time that a distinctive, validated miRNA profile from circulating CD4+ T cells in atherosclerosis has been presented. This miRNA signature may be used to help elucidate the underlying mechanism of atherosclerosis. Further clinical studies and in-depth reports will contribute to identifying predictive and therapeutic targets in these patients with atherosclerosis.

Activated Platelets Upregulate β2 Integrin Mac-1 (CD11b/CD18) on Dendritic Cells, Which Mediates Heterotypic Cell-Cell Interaction

Recent evidence suggests interaction of platelets with dendritic cells (DCs), while the molecular mechanisms mediating this heterotypic cell cross-talk are largely unknown. We evaluated the role of integrin Mac-1 (αMβ2, CD11b/CD18) on DCs as a counterreceptor for platelet glycoprotein (GP) Ibα. In a dynamic coincubation model, we observed interaction of human platelets with monocyte-derived DCs, but also that platelet activation induced a sharp increase in heterotypic cell binding. Inhibition of CD11b or GPIbα led to significant reduction of DC adhesion to platelets in vitro independent of GPIIbIIIa, which we confirmed using platelets from Glanzmann thrombasthenia patients and transgenic mouse lines on C57BL/6 background (GPIbα^-/-, IL4R-GPIbα-tg, and muMac1 mice). In vivo, inhibition or genetic deletion of CD11b and GPIbα induced a significant reduction of platelet-mediated DC adhesion to the injured arterial wall. Interestingly, only intravascular antiCD11b inhibited DC recruitment, suggesting a dynamic DC-platelet interaction. Indeed, we could show that activated platelets induced CD11b upregulation on Mg²⁺-preactivated DCs, which was related to protein kinase B (Akt) and dependent on P-selectin and P-selectin glycoprotein ligand 1. Importantly, specific pharmacological targeting of the GPIbα-Mac-1 interaction site blocked DC-platelet interaction in vitro and in vivo. These results demonstrate that cross-talk of platelets with DCs is mediated by GPIbα and Mac-1, which is upregulated on DCs by activated platelets in a P-selectin glycoprotein ligand 1-dependent manner.

How the immune system shapes atherosclerosis: roles of innate and adaptive immunity

Atherosclerosis is the root cause of many cardiovascular diseases. Extensive research in preclinical models and emerging evidence in humans have established the crucial roles of the innate and adaptive immune systems in driving atherosclerosis-associated chronic inflammation in arterial blood vessels. New techniques have highlighted the enormous heterogeneity of leukocyte subsets in the arterial wall that have pro-inflammatory or regulatory roles in atherogenesis. Understanding the homing and activation pathways of these immune cells, their disease-associated dynamics and their regulation by microbial and metabolic factors will be crucial for the development of clinical interventions for atherosclerosis, including potentially vaccination-based therapeutic strategies. Here, we review key molecular mechanisms of immune cell activation implicated in modulating atherogenesis and provide an update on the contributions of innate and adaptive immune cell subsets in atherosclerosis.

The Effects of Porphyromonas gingivalis on Atherosclerosis-Related Cells

Atherosclerosis (AS), one of the most common types of cardiovascular disease, has initially been attributed to the accumulation of fats and fibrous materials. However, more and more researchers regarded it as a chronic inflammatory disease nowadays. Infective disease, such as periodontitis, is related to the risk of atherosclerosis. Porphyromonas gingivalis (P. gingivalis), one of the most common bacteria in stomatology, is usually discovered in atherosclerotic plaque in patients. Furthermore, it was reported that P. gingivalis can promote the progression of atherosclerosis. Elucidating the underlying mechanisms of P. gingivalis in atherosclerosis attracted attention, which is thought to be crucial to the therapy of atherosclerosis. Nevertheless, the pathogenesis of atherosclerosis is much complicated, and many kinds of cells participate in it. By summarizing existing studies, we find that P. gingivalis can influence the function of many cells in atherosclerosis. It can induce the dysfunction of endothelium, promote the formation of foam cells as well as the proliferation and calcification of vascular smooth muscle cells, and lead to the imbalance of regulatory T cells (Tregs) and T helper (Th) cells, ultimately promoting the occurrence and development of atherosclerosis. This article summarizes the specific mechanism of atherosclerosis caused by P. gingivalis. It sorts out the interaction between P. gingivalis and AS-related cells, which provides a new perspective for us to prevent or slow down the occurrence and development of AS by inhibiting periodontal pathogens.

Redox regulation of age-associated defects in generation and maintenance of T cell self-tolerance and immunity to foreign antigens

Thymic atrophy reduces naive T cell production and contributes to increased susceptibility to viral infection with age. Expression of tissue-restricted antigen (TRA) genes also declines with age and has been thought to increase autoimmune disease susceptibility. We find that diminished expression of a model TRA gene in aged thymic stromal cells correlates with impaired clonal deletion of cognate T cells recognizing an autoantigen involved in atherosclerosis. Clonal deletion in the polyclonal thymocyte population is also perturbed. Distinct age-associated defects in the generation of antigen-specific T cells include a conspicuous decline in generation of T cells recognizing an immunodominant influenza epitope. Increased catalase activity delays thymic atrophy, and here, we show that it mitigates declining production of influenza-specific T cells and their frequency in lung after infection, but does not reverse declines in TRA expression or efficient negative selection. These results reveal important considerations for strategies to restore thymic function.

Polymeric particle-based therapies for acute inflammatory diseases

Acute inflammation is essential for initiating and coordinating the body's response to injuries and infections. However, in acute inflammatory diseases, inflammation is not resolved but propagates further, which can ultimately lead to tissue damage such as in sepsis, acute respiratory distress syndrome and deep vein thrombosis. Currently, clinical protocols are limited to systemic steroidal treatments, fluids and antibiotics that focus on eradicating inflammation rather than modulating it. Strategies based on stem cell therapeutics and selective blocking of inflammatory molecules, despite showing great promise, still lack the scalability and specificity required to treat acute inflammation. By contrast, polymeric particle systems benefit from uniform manufacturing at large scales while preserving biocompatibility and versatility, thus providing an ideal platform for immune modulation. Here, we outline design aspects of polymeric particles including material, size, shape, deformability and surface modifications, providing a strategy for optimizing the targeting of acute inflammation.

Anti-inflammatory Strategies in Atherosclerosis

Atherosclerotic vascular disease and its related complications are the major cause of mortality in Western societies. Atherosclerosis is a chronic inflammatory disease of the arterial wall triggered by traditional and nontraditional risk factors and mediated by inflammatory and immune responses. Recent clinical trials provided compelling evidence corroborating that atherosclerosis is an inflammatory disease and demonstrated efficacy of anti-inflammatory interventions in reducing cardiovascular events and mortality. Traditional risk factors drive vascular inflammation, further justifying the instrumental role of intensified risk factor management in attenuating and preventing atherosclerotic disease and complications. Promising therapeutic approaches specifically related to inhibition of inflammation span traditional anti-inflammatory drugs, specific immunomodulation, and development of vaccination against atherosclerotic disease. Here, we review the inflammatory component in atherogenesis, the available evidence from clinical trials evaluating efficacy of therapeutic anti-inflammatory interventions in patients with high cardiovascular risk, and discuss potential future targets for anti-inflammatory or immune modulatory treatment in atherosclerotic cardiovascular disease.

Modulating Autoimmunity against LDL: Development of a Vaccine against Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall that leads to the build-up of occluding atherosclerotic plaques. Its clinical sequelae, myocardial infarction and stroke, represent the most frequent causes of death worldwide. Atherosclerosis is a multifactorial pathology that involves traditional risk factors and chronic low-grade inflammation in the atherosclerotic plaque and systemically. This process is accompanied by a strong autoimmune response that involves autoreactive T cells in lymph nodes and atherosclerotic plaques, as well as autoantibodies that recognize low-density lipoprotein (LDL) and its main protein component apolipoprotein B (ApoB). In the past 60 years, numerous preclinical observations have suggested that immunomodulatory vaccination with LDL, ApoB, or its peptides has the potential to specifically dampen autoimmunity, enhance tolerance to atherosclerosis-specific antigens, and protect from experimental atherosclerosis in mouse models. Here, we summarize and discuss mechanisms, challenges, and therapeutic opportunities of immunomodulatory vaccination and other strategies to enhance protective immunity in atherosclerosis.

Adaptive Immune Response Signaling Is Suppressed in Ly6Chigh Monocyte but Upregulated in Monocyte Subsets of ApoE-/- Mice — Functional Implication in Atherosclerosis

Rationale

Inflammatory monocyte (MC) subset differentiation is a major feature in tissue inflammatory and atherosclerosis. The underlying molecular mechanism remains unclear.

Objective

This study aims to explore molecule targets and signaling which determinate immunological features in MC subsets.

Methods and Results

Blood Ly6C^high and Ly6C^low MC subsets from control and ApoE^-/- mice were isolated by flow cytometry sorting and subjected for bulk high-throughput RNA-sequencing. Intensive bioinformatic studies were performed by analyzing transcriptome through four pairs of comparisons: A) Ly6C^high vs Ly6C^low in control mice; B) Ly6C^high vs Ly6C^low in ApoE^-/- mice; C) ApoE^-/- Ly6C^high vs control Ly6C^high MC; D) ApoE^-/- Ly6C^low vs control Ly6C^low MC. A total of 80 canonical pathways and 16 enriched pathways were recognized by top-down analysis using IPA and GSEA software, and further used for overlapping analysis. Immunological features and signaling were assessed on four selected functional groups, including MHCII, immune checkpoint, cytokine, and transcription factor (TF). Among the total 14578 significantly differentially expressed (SDE) genes identified though above four comparison, 1051 TF and 348 immunological genes were discovered. SDE immunological genes were matched with corresponding upstream SDE TF by IPA upstream analysis. Fourteen potential transcriptional axes were recognized to modulate immunological features in the Ly6C MC subset. Based on an intensive literature search, we found that the identified SDE immune checkpoint genes in Ly6C^high MC are associated with pro-inflammatory/atherogenic balance function. Immune checkpoint genes GITR, CTLA4, and CD96 were upregulated in Ly6C^low MC from all mice and presented anti-inflammatory/atherogenic features. Six cytokine genes, including Ccl2, Tnfsf14, Il1rn, Cxcl10, Ccl9, and Cxcl2, were upregulated in Ly6C^high MC from all mice and associated with pro-inflammatory/atherogenic feature. Cytokine receptor gene Il12rb2, Il1r1, Il27ra, Il5ra, Ngfr, Ccr7, and Cxcr5 were upregulated in Ly6C^low MC from all mice and presented anti-inflammatory/atherogenic features. MHCII genes (H2-Oa, H2-DMb2, H2-Ob, H2-Eb2, H2-Eb1, H2-Aa, and Cd74) were elevated in Ly6C^low MC from all mice. ApoE^-/- augmented pro-atherogenic/inflammatory and antigen-presenting cells (APC) feature in both subsets due to elevated expression of cytokine genes (Cxcl11, Cntf, Il24, Xcl, Ccr5, Mpl, and Acvr2a) and MHCII gene (H2-Aa and H2-Ea-ps). Finally, we modeled immunological gene expression changes and functional implications in MC differentiation and adaptive immune response for MC subsets from control and ApoE^-/- mice.

Conclusions

Ly6C^high MC presented pro-inflammatory/atherogenic features and lower APC potential. Ly6C^low MC displayed anti-inflammatory/atherogenic features and higher APC potential. ApoE^-/- confers upon both subsets with augmented pro-atherogenic/inflammatory function and APC potential.

Effects of fatty acids on T cell function: role in atherosclerosis

T cells are among the most common cell types present in atherosclerotic plaques and are increasingly being recognized as a central mediator in atherosclerosis development and progression. At the same time, triglycerides and fatty acids have re-emerged as crucial risk factors for atherosclerosis. Triglycerides and fatty acids are important components of the milieu to which the T cell is exposed from the circulation to the plaque, and increasing evidence shows that fatty acids influence T cell function. In this Review, we discuss the effects of fatty acids on four components of the T cell response - metabolism, activation, proliferation and polarization - and the influence of these changes on the pathogenesis of atherosclerosis. We also discuss how quiescent T cells can undergo a type of metabolic reprogramming induced by exposure to fatty acids in the circulation that influences the subsequent functions of T cells after activation, such as in atherosclerotic plaques.

Resolving monocytes generated through TRAM deletion attenuate atherosclerosis

Polarization of low-grade inflammatory monocytes facilitates the pathogenesis of atherosclerosis. However, underlying mechanisms as well as approaches for resolving monocyte polarization conducive to the regression of atherosclerosis are not well established. In this report, we demonstrate that TRIF-related adaptor molecule (TRAM) mediated monocyte polarization in vivo and in vitro. TRAM controlled monocyte polarization through activating Src family kinase c-SRC, which not only induces STAT1/STAT5-regulated inflammatory mediators CCR2 and SIRP-α but also suppresses PPARγ-regulated resolving mediator CD200R. Enhanced PPARγ and Pex5 due to TRAM deficiency facilitated peroxisome homeostasis and reduction of cellular reactive oxygen species, further contributing to the establishment of a resolving monocyte phenotype. TRAM-deficient monocytes propagated the resolving phenotype to neighboring monocytes through CD200R-mediated intercellular communication. At the translational level, we show that TRAM-deficient mice were resistant to high-fat diet-induced pathogenesis of atherosclerosis. We further document that intravenous transfusion of TRAM-deficient resolving monocytes into atherosclerotic mice potently reduced the progression of atherosclerosis. Together, our data reveal that targeting TRAM may facilitate the effective generation of resolving monocytes conducive for the treatment of atherosclerosis.

Single cell analyses to understand the immune continuum in atherosclerosis

Atherosclerosis is initiated by the accumulation of lipids in the arterial wall that trigger a complex and poorly understood network of inflammatory processes. At the same time, recent clinical findings reveal that targeting specific immune alterations in patients with cardiovascular disease (CVD) represents a promising approach to preventing recurrent cardiovascular events. In order to achieve these tailored therapies, it is critical to resolve the heterogenous environment of the atherosclerotic lesion and decipher the complex structural and functional changes which immune cells undergo throughout disease progression. Recently, single-cell approaches including single cell mass cytometry by time of flight (CyTOF), single cell RNA sequencing (scRNA-seq) and Cellular Indexing of Transcriptomes and Epitopes by Sequencing (CITE-seq) have emerged as valuable tools in resolving cellular plasticity within atherosclerotic lesions. In this review, we will discuss the most important insights that have been gleaned from the application of these single-cell approaches to validated experimental models of atherosclerosis. Additionally, as clinical progress in treatment of the disease depends on the translation of discoveries to human tissues, we will also examine the challenges associated with the application of single-cell approaches to human vascular tissue and the discoveries made by the initial efforts in this direction. Finally, we will analyze the advantages and limitations of dissociative single-cell approaches and how novel in-situ technologies could advance the field by allowing for the investigation of individual cells while preserving the heterogenous architecture of the atherosclerotic lesion.

Beyond Self-Recycling: Cell-Specific Role of Autophagy in Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial vessel wall and underlies the development of cardiovascular diseases, such as myocardial infarction and ischemic stroke. As such, atherosclerosis stands as the leading cause of death and disability worldwide and intensive scientific efforts are made to investigate its complex pathophysiology, which involves the deregulation of crucial intracellular pathways and intricate interactions between diverse cell types. A growing body of evidence, including in vitro and in vivo studies involving cell-specific deletion of autophagy-related genes (ATGs), has unveiled the mechanistic relevance of cell-specific (endothelial, smooth-muscle, and myeloid cells) defective autophagy in the processes of atherogenesis. In this review, we underscore the recent insights on autophagy's cell-type-dependent role in atherosclerosis development and progression, featuring the relevance of canonical catabolic functions and emerging noncanonical mechanisms, and highlighting the potential therapeutic implications for prevention and treatment of atherosclerosis and its complications.

ApoB-Specific CD4+ T Cells in Mouse and Human Atherosclerosis

Atherosclerosis is a chronic inflammatory condition of the arterial wall that leads to the formation of vessel-occluding plaques within the subintimal space of middle-sized and larger arteries. While traditionally understood as a myeloid-driven lipid-storage disease, growing evidence suggests that the accumulation of low-density lipoprotein cholesterol (LDL-C) ignites an autoimmune response with CD4⁺ T-helper (T_H) cells that recognize self-peptides from Apolipoprotein B (ApoB), the core protein of LDL-C. These autoreactive CD4⁺ T cells home to the atherosclerotic plaque, clonally expand, instruct other cells in the plaque, and induce clinical plaque instability. Recent developments in detecting antigen-specific cells at the single cell level have demonstrated that ApoB-reactive CD4⁺ T cells exist in humans and mice. Their phenotypes and functions deviate from classical immunological concepts of distinct and terminally differentiated T_H immunity. Instead, ApoB-specific CD4⁺ T cells have a highly plastic phenotype, can acquire several, partially opposing and mixed transcriptional programs simultaneously, and transit from one T_H subset into another over time. In this review, we highlight adaptive immune mechanisms in atherosclerosis with a focus on CD4⁺ T cells, introduce novel technologies to detect ApoB-specific CD4⁺ T cells at the single cell level, and discuss the potential impact of ApoB-driven autoimmunity in atherosclerosis.

Inflammatory Cell Recruitment in Cardiovascular Disease

Atherosclerosis, the main underlying pathology for myocardial infarction and stroke, is a chronic inflammatory disease of middle-sized to large arteries that is initiated and maintained by leukocytes infiltrating into the subendothelial space. It is now clear that the accumulation of pro-inflammatory leukocytes drives progression of atherosclerosis, its clinical complications, and directly modulates tissue-healing in the infarcted heart after myocardial infarction. This inflammatory response is orchestrated by multiple soluble mediators that enhance inflammation systemically and locally, as well as by a multitude of partially tissue-specific molecules that regulate homing, adhesion, and transmigration of leukocytes. While numerous experimental studies in the mouse have refined our understanding of leukocyte accumulation from a conceptual perspective, only a few anti-leukocyte therapies have been directly validated in humans. Lack of tissue-tropism of targeted factors required for leukocyte accumulation and unspecific inhibition strategies remain the major challenges to ultimately translate therapies that modulate leukocytes accumulation into clinical practice. Here, we carefully describe receptor and ligand pairs that guide leukocyte accumulation into the atherosclerotic plaque and the infarcted myocardium, and comment on potential future medical therapies.

Comprehensive Analysis of the Immune Infiltrates and Aberrant Pathways Activation in Atherosclerotic Plaque

Atherosclerosis is the pathological basis of many cardiovascular and cerebrovascular diseases. The development of gene chip and high-throughput sequencing technologies revealed that the immune microenvironment of coronary artery disease (CAD) in high-risk populations played an important role in the formation and development of atherosclerotic plaques. Three gene expression datasets related to CAD were assessed using high-throughput profiling. CIBERSORT analysis revealed significant differences in five types of immune cells: activated dendritic cells (DCs), T follicular helper cells (Tfhs), resting CD4+ T cells, regulatory T cells (Tregs), and γδ T cells. Immune transcriptome analysis indicated higher levels of inflammatory markers (cytolytic activity, antigen presentation, chemokines, and cytokines) in the cases than in the controls. The level of activated DCs and the lipid clearance signaling score were negatively correlated. We observed a positive correlation between the fraction of Tfhs and lipid biosynthesis. Resting CD4+ T cells and the activity of pathways related to ossification in bone remodeling and glutathione synthesis showed a negative correlation. Gamma delta T cells negatively correlated with IL-23 signaling activity. GSEA revealed a close association with the inflammatory immune microenvironment. The present study revealed that CAD patients may have an inflammatory immune microenvironment and provides a timely update on anti-inflammatory therapies under current investigation.

P300/CBP Associated Factor (PCAF) Deficiency Enhances Diet-Induced Atherosclerosis in ApoE3*Leiden Mice via Systemic Inhibition of Regulatory T Cells

Background: Inflammatory stimuli induced by NF-kB drive atherosclerotic lesion formation. The epigenetic P300/CBP associated factor (PCAF) post-transcriptionally acetylates FoxP3, which is required for regulatory T-cell (Treg) differentiation and immune modulation. We hypothesize that PCAF deficiency affects atherosclerosis via regulation of regulatory Tregs.

Method: ApoE3^*Leiden (n = 13) and ApoE3^*LeidenxPCAF^−/− (n = 13) were fed a high-fat diet (HFD) containing 1.25% cholesterol. Systemic FoxP3⁺ T cells were measured every 4 weeks by flow cytometry (n = 6). After 5-months of HFD, mice were euthanized, and hearts and blood were collected. IL-6 and TNFα concentrations were measured in plasma to identify systemic inflammatory responses. Compositional and morphometrical analyses were performed on the atherosclerotic lesions in the aortic sinuses.

Results: After 5 months of HFD, plasma cholesterol concentrations were not different for ApoE3^*LeidenxPCAF^−/− compared to ApoE3^*Leiden mice. Expression of FoxP3 by systemic CD4⁺ T cells decreased 1.8 fold in ApoE3^*LeidenxPCAF^−/− after 5 months HFD and remained significantly reduced after 5 months of HFD. Systemic TNFα and IL-6 concentrations were comparable, whereas the atherosclerotic lesion size in ApoE3^*LeidenxPCAF^−/− mice was increased by 28% compared to ApoE3^*Leiden mice. In atherosclerotic lesions, no differences were observed in macrophage differentiation or VSMC content, although a small increase in collagen was identified.

Conclusion: Our data show that PCAF deficiency resulted in a decrease in circulatory FoxP3⁺ regulatory T cells and ameliorated atherosclerotic lesions with no differences in systemic inflammation or macrophage differentiation in the atherosclerotic lesions. This suggests that PCAF regulates atherosclerosis via modulation of FoxP3⁺ regulatory T cell differentiation.

T cell co-stimulator inducible co-stimulatory (ICOS) exerts potential anti-atherosclerotic roles through downregulation of vascular smooth muscle phagocytosis and proliferation

Background

Atherosclerosis (AS) is a chronic inflammatory disease. The role of the immune system in the etiology of the disease, particularly T cells, has been widely studied and is well established. T cell activation directly regulates co-signaling molecules present in immune synapses. Targeting one or several of these co-signaling molecules can inhibit T cell-mediated inflammation and delay or reduce AS. In recent years, this strategy has increasingly become a research focus. As such, we explored the role and therapeutic potential of the T cell co-stimulatory molecule inducible co-stimulatory (ICOS) in AS.

Methods

We compared the expression of ICOS in early AS lesions occurring in ApoE-deficient (ApoE-KO) rats fed a fat-diet and wild type (WT) rats fed the same diet. Eight-week old ApoE-KO and WT rats [ApoE-KO(0) and WT(0)] were fed a high-fat diet for 16 weeks [ApoE-KO(16) and WT(16)]. ICOS expression in aortic tissues was analyzed by quantitative real-time PCR, western blot, and confocal microscopy. The effect of ICOS overexpression in a transfected human T cell line on the phagocytosis and proliferation of co-cultured human aortic smooth muscle cells (HASMCs) was studied in vitro.

Results

Compared with WT(0), ApoE-KO(0), and WT(16) rats, ICOS expression in ApoE-KO(16) rats was significantly down-regulated both at the mRNA and protein levels. In vitro experiments indicated that ICOS overexpression reduces phagocytosis and proliferation by HASMCs, and may therefore produce an anti-atherosclerotic effect.

Conclusions

The immune synaptic co-signaling molecule ICOS has an anti-atherosclerotic effect through inhibition of HASMC phagocytosis and proliferation, and can be used to delay plaque formation during the early stages of AS.

Dooming Phagocyte Responses: Inflammatory Effects of Endogenous Oxidized Phospholipids

Endogenous oxidized phospholipids are produced during tissue stress and are responsible for sustaining inflammatory responses in immune as well as non-immune cells. Their local and systemic production and accumulation is associated with the etiology and progression of several inflammatory diseases, but the molecular mechanisms that underlie the biological activities of these oxidized phospholipids remain elusive. Increasing evidence highlights the ability of these stress mediators to modulate cellular metabolism and pro-inflammatory signaling in phagocytes, such as macrophages and dendritic cells, and to alter the activation and polarization of these cells. Because these immune cells serve a key role in maintaining tissue homeostasis and organ function, understanding how endogenous oxidized lipids reshape phagocyte biology and function is vital for designing clinical tools and interventions for preventing, slowing down, or resolving chronic inflammatory disorders that are driven by phagocyte dysfunction. Here, we discuss the metabolic and signaling processes elicited by endogenous oxidized lipids and outline new hypotheses and models to elucidate the impact of these lipids on phagocytes and inflammation.

CNS and peripheral immunity in cerebral ischemia: partition and interaction

Stroke elicits excessive immune activation in the injured brain tissue. This well-recognized neural inflammation in the brain is not just an intrinsic organ response but also a result of additional intricate interactions between infiltrating peripheral immune cells and the resident immune cells in the affected areas. Given that there is a finite number of immune cells in the organism at the time of stroke, the partitioned immune systems of the central nervous system (CNS) and periphery must appropriately distribute the limited pool of immune cells between the two domains, mounting a necessary post-stroke inflammatory response by supplying a sufficient number of immune cells into the brain while maintaining peripheral immunity. Stroke pathophysiology has mainly been neurocentric in focus, but understanding the distinct roles of the CNS and peripheral immunity in their concerted action against ischemic insults is crucial. This review will discuss stroke-induced influences of the peripheral immune system on CNS injury/repair and of neural inflammation on peripheral immunity, and how comorbidity influences each.

The effect of Toll-like receptor stimulation on the motility of regulatory T cells

Regulatory T cells (Tregs) have suppressive functions and play an important role in controlling inflammation and autoimmunity. The migratory capacity of Tregs determines their location and their location determines whether they inhibit the priming of naïve lymphocytes in lymphoid tissues or the effector phase of immune responses at inflamed sites. Tregs generated or expanded in vitro are currently being tested in clinics for the treatment of autoimmune disorders, however, little is known about the factors controlling their migration towards therapeutically relevant locations. In this study, we have modulated Treg dynamics using Toll-like receptor (TLR) agonists. Dynamic imaging with confocal and two-photon microscopy revealed that Tregs generated in vitro and stimulated with P3C (a TLR2 agonist) but not with R848 (a TLR7 agonist) or LPS (a TLR4 agonist) showed enhanced cell migration within splenic white pulp or draining lymph node when transferred into mice intravenously or into the footpad, respectively. In summary, our data demonstrate that Tregs are more motile in response to direct TLR stimulation in particular towards TLR2 signals. This may have implications for efficient clinical Treg induction protocols.

Heterogeneity of T Cells in Atherosclerosis Defined by Single-Cell RNA-Sequencing and Cytometry by Time of Flight

The infiltration and accumulation of pro- and anti-inflammatory leukocytes within the intimal layer of the arterial wall is a hallmark of developing and progressing atherosclerosis. While traditionally perceived as macrophage- and foam cell-dominated disease, it is now established that atherosclerosis is a partial autoimmune disease that involves the recognition of peptides from ApoB (apolipoprotein B), the core protein of LDL (low-density lipoprotein) cholesterol particles, by CD4⁺ T-helper cells and autoantibodies against LDL and ApoB. Autoimmunity in the atherosclerotic plaque has long been understood as a pathogenic T-helper type-1 driven response with proinflammatory cytokine secretion. Recent developments in high-parametric cell immunophenotyping by mass cytometry, single-cell RNA-sequencing, and in tools exploring antigen-specificity have established the existence of several unforeseen layers of T-cell diversity with mixed T_H1 and T regulatory cells transcriptional programs and unpredicted fates. These findings suggest that pathogenic ApoB-reactive T cells evolve from atheroprotective and immunosuppressive CD4⁺ T regulatory cells that lose their protective properties over time. Here, we discuss T-cell heterogeneity in atherosclerosis with a focus on plasticity, antigen-specificity, exhaustion, maturation, tissue residency, and its potential use in clinical prediction.