Community-based statins and advanced carotid plaque: Role of CD163 positive macrophages in lipoprotein-associated phospholipase A2 activity in atherosclerotic plaque

CD163+ Macrophages Induce Endothelial-to-Mesenchymal Transition in Atheroma

BACKGROUND

Cell phenotype switching is increasingly being recognized in atherosclerosis. However, our understanding of the exact stimuli for such cellular transformations and their significance for human atherosclerosis is still evolving. Intraplaque hemorrhage is thought to be a major contributor to plaque progression in part by stimulating the influx of CD163+ macrophages. Here, we explored the hypothesis that CD163+ macrophages cause plaque progression through the induction of proapoptotic endothelial-to-mesenchymal transition (EndMT) within the fibrous cap.

METHODS

Human coronary artery sections from CVPath's autopsy registry were selected for pathological analysis. Athero-prone ApoE-/- and ApoE-/-/CD163-/- mice were used for in vivo studies. Human peripheral blood mononuclear cell-induced macrophages and human aortic endothelial cells were used for in vitro experiments.

RESULTS

In 107 lesions with acute coronary plaque rupture, 55% had pathological evidence of intraplaque hemorrhage in nonculprit vessels/lesions. Thinner fibrous cap, greater CD163+ macrophage accumulation, and a larger number of CD31/FSP-1 (fibroblast specific protein-1) double-positive cells and TUNEL (terminal deoxynucleotidyl transferase-dUTP nick end labeling) positive cells in the fibrous cap were observed in nonculprit intraplaque hemorrhage lesions, as well as in culprit rupture sections versus nonculprit fibroatheroma sections. Human aortic endothelial cells cultured with supernatants from hemoglobin/haptoglobin-exposed macrophages showed that increased mesenchymal marker proteins (transgelin and FSP-1) while endothelial markers (VE-cadherin and CD31) were reduced, suggesting EndMT induction. Activation of NF-κB (nuclear factor kappa β) signaling by proinflammatory cytokines released from CD163+ macrophages directly regulated the expression of Snail, a critical transcription factor during EndMT induction. Western blot analysis for cleaved caspase-3 and microarray analysis of human aortic endothelial cells indicated that apoptosis was stimulated during CD163+ macrophage-induced EndMT. Additionally, CD163 deletion in athero-prone mice suggested that CD163 is required for EndMT and plaque progression. Using single-cell RNA sequencing from human carotid endarterectomy lesions, a population of EndMT was detected, which demonstrated significant upregulation of apoptosis-related genes.

CONCLUSIONS

CD163+ macrophages provoke EndMT, which may promote plaque progression through fibrous cap thinning.

Inflammatory Biomarkers to Predict Major Adverse Cardiovascular Events in Patients with Carotid Artery Stenosis

Background and Objectives: Inflammatory proteins and their prognostic value in patients with carotid artery stenosis (CAS) have not been adequately studied. Herein, we identified CAS-specific biomarkers from a large pool of inflammatory proteins and assessed the ability of these biomarkers to predict adverse events in individuals with CAS. Materials and Methods: Samples of blood were prospectively obtained from 336 individuals (290 with CAS and 46 without CAS). Plasma concentrations of 29 inflammatory proteins were determined at recruitment, and the patients were followed for 24 months. The outcome of interest was a major adverse cardiovascular event (MACE; composite of stroke, myocardial infarction, or death). The differences in plasma protein concentrations between patients with vs. without a 2-year MACE were determined using the independent t-test or Mann-Whitney U test to identify CAS-specific prognostic biomarkers. Kaplan-Meier and Cox proportional hazards analyses with adjustment for baseline demographic and clinical characteristics were performed to assess the prognostic value of differentially expressed inflammatory proteins in predicting a 2-year MACE in patients with CAS. Results: The mean age of the cohort was 68.8 (SD 10.2) years and 39% were female. The plasma concentrations of two inflammatory proteins were significantly higher in individuals with a 2-year MACE relative to those without a 2-year MACE: IL-6 (5.07 (SD 4.66) vs. 3.36 (SD 4.04) pg/mL, p = 0.03) and CD163 (233.825 (SD 230.306) vs. 159.673 (SD 175.669) pg/mL, p = 0.033). Over a follow-up period of 2 years, individuals with elevated levels of IL-6 were more likely to develop MACE (HR 1.269 (95% CI 1.122-1.639), p = 0.042). Similarly, over a 2-year period, patients with high levels of CD163 were more likely to develop MACE (HR 1.413 (95% CI 1.022-1.954), p = 0.036). Conclusions: The plasma levels of inflammatory proteins IL-6 and CD163 are independently associated with adverse outcomes in individuals with CAS. These CAS-specific prognostic biomarkers may assist in the risk stratification of patients at an elevated risk of a MACE and subsequently guide further vascular evaluation, specialist referrals, and aggressive medical/surgical management, thereby improving outcomes for patients with CAS.

Research Advance of Chinese Medicine in Treating Atherosclerosis: Focus on Lipoprotein-Associated Phospholipase A2

As a serious cardiovascular disease, atherosclerosis (AS) causes chronic inflammation and oxidative stress in the body and poses a threat to human health. Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a member of the phospholipase A2 (PLA2) family, and its elevated levels have been shown to contribute to AS. Lp-PLA2 is closely related to a variety of lipoproteins, and its role in promoting inflammatory responses and oxidative stress in AS is mainly achieved by hydrolyzing oxidized phosphatidylcholine (oxPC) to produce lysophosphatidylcholine (lysoPC). Moreover, macrophage apoptosis within plaque is promoted by localized Lp-PLA2 which also promotes plaque instability. This paper reviews those researches of Chinese medicine in treating AS via reducing Lp-PLA2 levels to guide future experimental studies and clinical applications related to AS.

CD163+ macrophages restrain vascular calcification, promoting the development of high-risk plaque

Vascular calcification (VC) is concomitant with atherosclerosis, yet it remains uncertain why rupture-prone high-risk plaques do not typically show extensive calcification. Intraplaque hemorrhage (IPH) deposits erythrocyte-derived cholesterol, enlarging the necrotic core and promoting high-risk plaque development. Pro-atherogenic CD163+ alternative macrophages engulf hemoglobin:haptoglobin (HH) complexes at IPH sites. However, their role in VC has never been examined to our knowledge. Here we show, in human arteries, the distribution of CD163+ macrophages correlated inversely with VC. In vitro experiments using vascular smooth muscle cells (VSMCs) cultured with HH-exposed human macrophage - M(Hb) - supernatant reduced calcification, while arteries from ApoE-/- CD163-/- mice showed greater VC. M(Hb) supernatant-exposed VSMCs showed activated NF-κB, while blocking NF-κB attenuated the anticalcific effect of M(Hb) on VSMCs. CD163+ macrophages altered VC through NF-κB-induced transcription of hyaluronan synthase (HAS), an enzyme that catalyzes the formation of the extracellular matrix glycosaminoglycan, hyaluronan, within VSMCs. M(Hb) supernatants enhanced HAS production in VSMCs, while knocking down HAS attenuated its anticalcific effect. NF-κB blockade in ApoE-/- mice reduced hyaluronan and increased VC. In human arteries, hyaluronan and HAS were increased in areas of CD163+ macrophage presence. Our findings highlight an important mechanism by which CD163+ macrophages inhibit VC through NF-κB-induced HAS augmentation and thus promote the high-risk plaque development.

Understanding the role of alternative macrophage phenotypes in human atherosclerosis

INTRODUCTION

Atherosclerosis-based ischemic heart disease is still the primary cause of death throughout the world. Over the past decades there has been no significant changes in the therapeutic approaches to atherosclerosis, which are mainly based on lipid lowering therapies and management of comorbid conditions such as diabetes and hypertension. The involvement of macrophages in atherosclerosis has been recognized for decades. More recently, a more detailed and sophisticated understanding of their various phenotypes and roles in the atherosclerotic process has been recognized. This new data is revealing how specific subtypes of macrophage-induced inflammation may have distinct effects on atherosclerosis progression and may provide new approaches for treatment, based upon targeting of specific macrophage subtypes.

AREAS COVERED

We will comprehensively review the spectrum of macrophage phenotypes and how they contribute to atherosclerotic plaque development and progression.

EXPERT OPINION

Various signals derived from atherosclerotic lesions drive macrophages into complex subsets with different gene expression profiles, phenotypes, and functions, not all of which are understood. Macrophage phenotypes include those that enhance, heal, and regress the atherosclerotic lesions though various mechanisms. Targeting of specific macrophage phenotypes may provide a promising and novel approach to prevent atherosclerosis progression.

Relationship of Placental and Serum Lipoprotein-Associated Phospholipase A2 Levels with Hypertensive Disorders of Pregnancy

Background

A series of studies has shown that lipoprotein-associated phospholipase A2 (Lp-PLA2) is closely associated with abnormal lipid metabolism and vascular endothelial cell injury, but its role in hypertensive disorders of pregnancy (HDP) remains unclear. This study aims to determine the relationship between placental and serum LP-PLA2 levels and HDP, and to provide a feasible method for predicting HDP.

Methods

The placental and serum Lp-PLA2 levels of 63 patients with HDP (20, 25, and 18 cases with gestational hypertension, mild preeclampsia, and severe preeclampsia, respectively) and 20 women with normal pregnancies (control group) were measured via a combination of tissue microarray and immunohistochemistry, real-time quantitative RT-PCR and enzyme-linked immunosorbent assay (ELISA).

Results

1) The gene and protein expression levels of placental LP-PLA2: the HDP group had significantly higher levels than those of the control group (P < 0.05). The mild preeclampsia group had significantly higher levels than those of the control group (P < 0.05); the severe preeclampsia group had significantly higher levels than those of the mild preeclampsia group (P < 0.05). 2) Serum levels of Lp-PLA2: the HDP group had significantly higher levels than those of the control group (P < 0.05). The Lp-PLA2 levels increased gradually with the progression of the HDP; there were significant differences in the four groups using pair-wise comparisons (P < 0.05). 3) Serum levels of LP-PLA2 were positively correlated with placental LP-PLA2 levels in the HDP group (r = 0.435, P < 0.05).

Conclusion

Elevated Lp-PLA2 levels may be associated with the occurrence of HDP, and changes of Lp-PLA2 levels in the maternal blood may be regarded as a monitoring indicator for this disease.

Search for Reliable Circulating Biomarkers to Predict Carotid Plaque Vulnerability

Atherosclerosis is responsible for 20% of ischemic strokes, and the plaques from the internal carotid artery the most frequently involved. Lipoproteins play a key role in carotid atherosclerosis since lipid accumulation contributes to plaque progression and chronic inflammation, both factors leading to plaque vulnerability. Carotid revascularization to prevent future vascular events is reasonable in some patients with high-grade carotid stenosis. However, the degree of stenosis alone is not sufficient to decide upon the best clinical management in some situations. In this context, it is essential to further characterize plaque vulnerability, according to specific characteristics (lipid-rich core, fibrous cap thinning, intraplaque hemorrhage). Although these features can be partly detected by imaging techniques, identifying carotid plaque vulnerability is still challenging. Therefore, the study of circulating biomarkers could provide adjunctive criteria to predict the risk of atherothrombotic stroke. In this regard, several molecules have been found altered, but reliable biomarkers have not been clearly established yet. The current review discusses the concept of vulnerable carotid plaque, and collects existing information about putative circulating biomarkers, being particularly focused on lipid-related and inflammatory molecules.

Association Between Plasma Lipoprotein-Associated Phospholipase A2 and Plaque Vulnerability in TIA Patients With Unilateral Middle Cerebral Artery Stenosis

Background: Plasma lipoprotein-associated phospholipase A2 (Lp-PLA2) has emerged as a novel biomarker for coronary atherosclerosis. However, the association between Lp-PLA2 and plaque vulnerability in atherosclerosis of cervicocerebral arteries remains poorly defined, especially for intracranial atherosclerotic stenosis (ICAS). We aimed to investigate the association between Lp-PLA2 and plaque vulnerability in transient ischemic attack (TIA) patients with unilateral middle cerebral artery stenoses (MCAs).

Methods: In this study, a total of 207 patients were enrolled from April 2017 to April 2020. Clinical data were collected, and MCA plaques were examined with high-resolution magnetic resonance imaging (HRMRI). Baseline characteristics of patients were collected during hospitalization. Statistical comparisons were performed using Pearson's chi-squared test, Mann–Whitney U test, and the Breslow–Day/Tarone's test for the determination of heterogeneity in different age strata. Multivariate binary logistic analysis was used to investigate the potential independent predictors that were highly correlated to plaque vulnerability.

Results: The results showed that a high Lp-PLA2 level (>221 ng/ml) was associated with plaque vulnerability in TIA patients with unilateral MCAs. High Lp-PLA2 was independently associated with plaque vulnerability in patients ≤ 60 years old [multivariate adjusted odds ratio (OR) = 9.854; 95% CI, 2.458–39.501] but not in patients >60 years old (multivariate adjusted OR = 1.901; 95% CI, 0.640–5.650). Predictors of plaque vulnerability in different age strata were also different.

Conclusion: Lp-PLA2 levels may be correlated to plaque vulnerability in TIA patients with unilateral MCAs and might be a diagnostic biomarker for plaque vulnerability in this kind of patients, especially for ones aged ≤ 60 years old.

CD163+ macrophages are associated with a vulnerable plaque phenotype in human carotid plaques

Macrophages are a functionally heterogeneous group of immune cells abundant in atherosclerotic plaques. Macrophages expressing CD163 are associated with intraplaque hemorrhage and have previously been considered atheroprotective. However, in a recent study CD163-deficient atherosclerotic ApoE^-/- mice exhibited smaller and less complex plaques, suggesting a proatherogenic role of CD163. Previous smaller studies on CD163+ macrophages and plaque stability in humans have yielded diverging results. Here we assessed the association of CD163+ cells to plaque vulnerability in a large cohort of human carotid plaques. CD163 protein expression was analyzed by immunohistochemistry in 200 human carotid plaques removed by endarterectomy from 103 patients with and 93 patients without cerebrovascular symptoms. Furthermore, CD163 mRNA expression was analyzed in 66 of the plaques. Both protein and mRNA expression of CD163 was higher in plaques from symptomatic patients and in plaques with high vulnerability index. CD163+ macrophages were primarily found in shoulder regions and in the center of the plaques. The present data show that CD163 is associated with increased plaque vulnerability in human carotid plaques, supporting the notion that CD163+ macrophages could contribute to clinical events.

Targeting of CD163+ Macrophages in Inflammatory and Malignant Diseases

The macrophage is a key cell in the pro- and anti-inflammatory response including that of the inflammatory microenvironment of malignant tumors. Much current drug development in chronic inflammatory diseases and cancer therefore focuses on the macrophage as a target for immunotherapy. However, this strategy is complicated by the pleiotropic phenotype of the macrophage that is highly responsive to its microenvironment. The plasticity leads to numerous types of macrophages with rather different and, to some extent, opposing functionalities, as evident by the existence of macrophages with either stimulating or down-regulating effect on inflammation and tumor growth. The phenotypes are characterized by different surface markers and the present review describes recent progress in drug-targeting of the surface marker CD163 expressed in a subpopulation of macrophages. CD163 is an abundant endocytic receptor for multiple ligands, quantitatively important being the haptoglobin-hemoglobin complex. The microenvironment of inflammation and tumorigenesis is particular rich in CD163+ macrophages. The use of antibodies for directing anti-inflammatory (e.g., glucocorticoids) or tumoricidal (e.g., doxorubicin) drugs to CD163+ macrophages in animal models of inflammation and cancer has demonstrated a high efficacy of the conjugate drugs. This macrophage-targeting approach has a low toxicity profile that may highly improve the therapeutic window of many current drugs and drug candidates.

The Relationship Between the Level of Serum ESM-1 and Lp-PLA2 in Patients With Acute ST-Segment Elevation Myocardial Infarction

Acute ST‐segment elevation myocardial infarction (STEMI) is the most lethal coronary heart disease with vascular endothelium dysfunction and inflammation in the disease development process. Endothelial cell‐specific molecule 1 (ESM‐1) and lipoprotein‐associated phospholipase A2 (Lp‐PLA2) are important for the diagnosis and characterization of STEMI. To date, no studies have reported the correlation between ESM‐1 and Lp‐PLA2 levels in patients with STEMI, which may be an important predictor of the fatal disease. To measure the level of serum ESM‐1 and Lp‐PLA2, and to evaluate the relationship and the clinical significance of these two biomarkers in patients with acute STEMI, 37 inpatients with acute STEMI were sequentially enrolled in the research group and 24 study objects with normal coronary artery function were included in the control group. The measurement of the relative parameters was done by enzyme‐linked immunosorbent assay using blood samples taken from the median cubital vein while the inpatients were enrolled. The levels of serum SEM‐1 and Lp‐PLA2 were significantly higher in patients with acute STEMI than in study objects with normal coronary artery function (P < 0.05). A significant correlation of serum SEM‐1 and Lp‐PLA2 was observed, leading to close linearity (r² = 0.8131, P < 0.0001). In conclusion, the endothelium dysfunction factor ESM‐1 and inflammatory factor Lp‐PLA2 are significantly higher and correlated in patients with acute STEMI. These two factors could be novel and effective biomarkers for acute STEMI diagnosis and evaluation.

Lipoprotein-Associated Phospholipase A2 is Linked with Poor Cardio-Metabolic Profile in Patients with Ischemic Stroke: A Study of Effects of Statins

Objectives

The objective of the study is to investigate the effects of statins on the lipoprotein-associated phospholipase A2 (Lp-PLA2) mass in patients with ischemic stroke.

Materials and Methods

A total number of 59 patient ages 43-69 years with cerebral stroke compared to 39 healthy controls that matching the age and body weight. The patients were divided into 32 patients on statins therapy assigned as statins users and 27 patients, not on statins therapy assigned as nonstatins users. Anthropometric and biochemical measurements were done including lipid profile and inflammatory biomarkers.

Results

Stroke patients on statins therapy showed a comparable low of Lp-PLA (29.82 ± 3.19 IU/mL) to nonstatins user stroke patients (15.58 ± 5.73 IU/mL). Lp-PLA2 mass levels were positively correlated with body mass index, blood pressure changes, total cholesterol, triglyceride, and very low-density lipoprotein and stroke risk (SR) percentage.

Conclusions

Patients on statins with ischemic stroke had low levels of Lp-PLA2 mass levels compared to nonstatins user with ischemic stroke. Lp-PLA2 mass levels were higher in men than women and correlated with lipid profile and SR in patients with ischemic stroke.

Lp-PLA2 as a promising predictor of comorbidities in patients with severe psoriasis

Objective: Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a well- known risk factor of atherosclerotic vascular diseases which are common comorbidities in psoriasis. The aim of this study was to evaluate serum Lp-PLA2 level in psoriatic patients and elucidate possible associations with disease activity, metabolic or inflammatory parameters and systemic treatment.Methods: We enrolled 33 patients with active plaque-type psoriasis and 11 healthy controls. Blood samples were collected before and after 3 months of systemic treatment with acitretin or methotrexate. Serum Lp-PLA2 level were evaluated by enzyme-linked immunosorbent assay.Results: Serum Lp-PLA2 level in patients with psoriasis did not statistically differ comparing to the control group (p = .2). However, in patients with severe psoriasis Lp-PLA2 was significantly higher than in the controls before and after treatment (p = .03, p = .01, respectively). The lipase did not correlate with BMI (p = .22); however, a statistical significance was noted between psoriatics with obesity compared to the controls (p = .03). No significant effect of systemic treatment combined (p = .5) nor separately with acitretin (p = .5) or methotrexate (p = .1) on the Lp-PLA2 level was found, despite clinical improvement.Conclusion: Lp-PLA2 assay might be helpful in assessment of the risk of cardiometabolic comorbidities development especially in patients with severe psoriasis and obesity.

CD163+ macrophages promote angiogenesis and vascular permeability accompanied by inflammation in atherosclerosis

Intake of hemoglobin by the hemoglobin-haptoglobin receptor CD163 leads to a distinct alternative non-foam cell antiinflammatory macrophage phenotype that was previously considered atheroprotective. Here, we reveal an unexpected but important pathogenic role for these macrophages in atherosclerosis. Using human atherosclerotic samples, cultured cells, and a mouse model of advanced atherosclerosis, we investigated the role of intraplaque hemorrhage on macrophage function with respect to angiogenesis, vascular permeability, inflammation, and plaque progression. In human atherosclerotic lesions, CD163+ macrophages were associated with plaque progression, microvascularity, and a high level of HIF1α and VEGF-A expression. We observed irregular vascular endothelial cadherin in intraplaque microvessels surrounded by CD163+ macrophages. Within these cells, activation of HIF1α via inhibition of prolyl hydroxylases promoted VEGF-mediated increases in intraplaque angiogenesis, vascular permeability, and inflammatory cell recruitment. CD163+ macrophages increased intraplaque endothelial VCAM expression and plaque inflammation. Subjects with homozygous minor alleles of the SNP rs7136716 had elevated microvessel density, increased expression of CD163 in ruptured coronary plaques, and a higher risk of myocardial infarction and coronary heart disease in population cohorts. Thus, our findings highlight a nonlipid-driven mechanism by which alternative macrophages promote plaque angiogenesis, leakiness, inflammation, and progression via the CD163/HIF1α/VEGF-A pathway.