Macrophage complexity in human atherosclerosis: opportunities for treatment?

Phytol from Scoparia dulcis prevents NF-κB-mediated inflammatory responses during macrophage polarization

Macrophages are primary immune cells that mediate a wide range of inflammatory diseases through their polarization potential. In this study, phytol isolated from Scoparia dulcis has been explored against 7-ketocholesterol and bacterial lipopolysaccharide-induced macrophage polarization in IC-21 cells. Isolated phytol has been characterized using GC-MS, TLC, HPTLC, FTIR, 1H-NMR, and HPLC analyses. The immunomodulatory effects of viable concentrations of phytol were tested on oxidative stress, arginase activity, nuclear and mitochondrial membrane potentials in IC-21 cells in addition to the modulation of calcium and lipids. Further, gene and protein expression of atherogenic markers were studied. Results showed that the isolated phytol at a viable concentration of 400 µg/ml effectively reduced the production of nitric oxide, superoxide anion (ROS generation), calcium and lipid accumulation, stabilized nuclear and mitochondrial membranes, and increased arginase activity. The atherogenic markers including iNOS, COX-2, IL-6, IL-1β, MMP-9, CD36, and NF-κB were significantly downregulated at the levels of gene and protein expression, while macrophage surface and nuclear receptor markers (CD206, CD163, and PPAR-γ) were significantly upregulated by phytol pre-treatment in macrophages. Therefore, the present pharmacognostic study supports the role of phytol isolated from Scoparia dulcis in preventing M2-M1 macrophage polarization under inflammatory conditions, making it a promising compound.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03924-9.

Advanced glycation endproducts in diabetes-related macrovascular complications: focus on methylglyoxal

Diabetes is associated with vascular injury and the onset of macrovascular complications. Advanced glycation endproducts (AGEs) and the AGE precursor methylglyoxal (MGO) have been identified as key players in establishing the relationship between diabetes and vascular injury. While most research has focused on the link between AGEs and vascular injury, less is known about the effects of MGO on vasculature. In this review, we focus on the mechanisms linking AGEs and MGO to the development of atherosclerosis. AGEs and MGO are involved in many stages of atherosclerosis progression. However, more research is needed to determine the exact mechanisms underlying these effects. Nevertheless, AGEs and MGO could represent valid therapeutic targets for the macrovascular complications of diabetes.

Macrophage polarization by potential nutraceutical compounds: A strategic approach to counteract inflammation in atherosclerosis

Chronic inflammation represents a main event in the onset and progression of atherosclerosis and is closely associated with oxidative stress in a sort of vicious circle that amplifies and sustains all stages of the disease. Key players of atherosclerosis are monocytes/macrophages. According to their pro- or anti-inflammatory phenotype and biological functions, lesional macrophages can release various mediators and enzymes, which in turn contribute to plaque progression and destabilization or, alternatively, lead to its resolution. Among the factors connected to atherosclerotic disease, lipid species carried by low density lipoproteins and pro-oxidant stimuli strongly promote inflammatory events in the vasculature, also by modulating the macrophage phenotyping. Therapies specifically aimed to balance macrophage inflammatory state are increasingly considered as powerful tools to counteract plaque formation and destabilization. In this connection, several molecules of natural origin have been recognized to be active mediators of diverse metabolic and signaling pathways regulating lipid homeostasis, redox state, and inflammation; they are, thus, considered as promising candidates to modulate macrophage responsiveness to pro-atherogenic stimuli. The current knowledge of the capability of nutraceuticals to target macrophage polarization and to counteract atherosclerotic lesion progression, based mainly on in vitro investigation, is summarized in the present review.

Resident and elicited murine macrophages differ in expression of their glycomes and glycan-binding proteins

The pleiotropic functions of macrophages in immune defense, tissue repair, and maintenance of tissue homeostasis are supported by the heterogeneity in macrophage sub-populations that differ both in ontogeny and polarization. Although glycans and glycan-binding proteins (GBPs) are integral to macrophage function and may contribute to macrophage diversity, little is known about the factors governing their expression. Here, we provide a resource for characterizing the N-/O-glycomes of various murine peritoneal macrophage sub-populations, demonstrating that glycosylation primarily reflects developmental origin and, to a lesser degree, cellular polarization. Furthermore, comparative analysis of GBP-coding genes in resident and elicited macrophages indicated that GBP expression is consistent with specialized macrophage functions and correlates with specific types of displayed glycans. An integrated, semi-quantitative approach was used to confirm distinct expression patterns of glycans and their binding proteins across different macrophages. The data suggest that regulation of glycan-protein complexes may be central to macrophage residence and recruitment.

Two-photon excited fluorescence (TPEF) may be useful to identify macrophage subsets based on their metabolic activity and cellular responses in atherosclerotic plaques

BACKGROUND AND AIMS

Atherosclerosis is characterized by the formation of lipid plaques within the arterial wall. In such plaques, the massive and continuous recruitment of circulating monocyte-derived macrophages induces inflammation, leading to plaque destabilization and rupture. Plaque vulnerability is linked to the presence of (i) a large lipid core that contains necrotic, "foamy" macrophages (FMs), (ii) a thin fibrous cap that cannot limit the prothrombotic lipid core, and potentially (iii) an imbalance between inflammatory and immunoregulatory macrophages. These opposite macrophage functions rely on the use of different energy pathways (glycolysis and oxidative phosphorylation, respectively) that may lead to different levels of the auto-fluorescent cofactors nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD). We hypothesized that high-resolution two-photon excited autofluorescence (TPEF) imaging of these cofactors may be used to monitor the metabolic activity and cellular responses of macrophages in atherosclerotic plaques.

METHODS

Different models of human FMs were generated by exposure to acetylated or oxidized low-density lipoproteins (LDL), with/without human carotid extract (CE). Their phenotype and optical properties were compared with those of extremely polarized macrophages, inflammatory M1 (M_LPS+IFNγ) and immunoregulatory M2 (M_IL4+IL13).

RESULTS

These FM models displayed an intermediate phenotype with low levels of M1 and M2 "specific" markers. Moreover, the NADH and FAD autofluorescence profiles of FM_{oxLDL ± CE} cells were significantly distinct from those of M1 and M2 macrophages.

CONCLUSIONS

TPEF imaging may be useful to follow the metabolic activity and cellular responses of the different macrophage subtypes present in atherosclerotic plaques in order to detect vulnerable areas.

Ginsenoside Rg3 Alleviates ox-LDL Induced Endothelial Dysfunction and Prevents Atherosclerosis in ApoE-/- Mice by Regulating PPARγ/FAK Signaling Pathway

The initiation of atherosclerosis (AS) induced by dyslipidemia is accompanied by endothelial dysfunction, including decreased healing ability and increased recruitment of monocytes. Studies showed ginsenoside Rg3 has potential to treat diseases associated with endothelial dysfunction which can protects against antineoplastic drugs induced cardiotoxicity by repairing endothelial function, while the effect and mechanism of Rg3 on dyslipidemia induced endothelial dysfunction and AS are not clear. Therefore, we investigated the effects of Rg3 on oxidized low-density lipoprotein (ox-LDL) induced human umbilical vein endothelial cells (HUVECs) dysfunction and high-fat diets (HFD) induced atherosclerosis in ApoE^−/− mice, as well as the mechanism. For in vitro assay, Rg3 enhanced healing of HUVECs and inhibited human monocytes (THP-1) adhesion to HUVECs disturbed by ox-LDL, down-regulated focal adhesion kinase (FAK)-mediated expression of vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1); restrained the FAK-mediated non-adherent dependent pathway containing matrix metalloproteinase (MMP)-2/9 expression, activation of nuclear factor-kappa B (NF-κB), high mRNA levels of monocyte chemotactic protein 1 (MCP-1) and interleukin 6 (IL-6), besides Rg3 up-regulated peroxisome proliferators-activated receptor γ (PPARγ) in ox-LDL-stimulated HUVECs. GW9662, the PPARγ-specific inhibitor, can repressed the effects of Rg3 on ox-LDL-stimulated HUVECs. For in vivo assay, Rg3 significantly reduced atherosclerotic pathological changes in ApoE^−/− mice fed with HFD, up-regulated PPARγ, and inhibited activation FAK in aorta, thus inhibited expression of VCAM-1, ICAM-1 in intima. We conclude that Rg3 may protect endothelial cells and inhibit atherosclerosis by up-regulating PPARγ via repressing FAK-mediated pathways, indicating that Rg3 have good potential in preventing dyslipidemia induced atherosclerosis.

Ficus deltoidea suppresses endothelial activation, inflammation, monocytes adhesion and oxidative stress via NF-κB and eNOS pathways in stimulated human coronary artery endothelial cells

Background

Ficus deltoidea (FD) has been shown to have antidiabetic, anti-inflammatory, antinociceptive and antioxidant properties. However, its effects on key events in the pathogenesis of atherosclerosis are unknown.

Aim

To investigate the endothelial activation, inflammation, monocyte-endothelial cell binding and oxidative stress effects of four FD varieties.

Methods

Human coronary artery endothelial cells (HCAEC) were incubated with different concentrations of aqueous ethanolic extracts of FD var. trengganuensis (FDT), var. kunstleri (FDK), var. deltoidea (FDD) and var. intermedia (FDI), together with LPS. Protein and gene expression of vascular cell adhesion molecule-1 (VCAM-1), intercellular cell adhesion molecule-1 (ICAM-1), endothelial-leukocyte adhesion molecule-1 (E-selectin), interleukin-6 (IL-6), Nuclear factor-κB (NF-κB) p50 and p65 and endothelial nitric oxide synthase (eNOS) were measured using ELISA and QuantiGene plex, respectively. Adhesion of monocyte to HCAEC and formation of reactive oxygen species (ROS) were detected by Rose Bengal staining and 2′-7′-dichlorofluorescein diacetate (DCFH-DA) assay.

Results

FDK exhibited the highest inhibition of biomarkers in relation to endothelial activation and inflammation, second in reducing monocyte binding (17.3%) compared to other varieties. FDK (25.6%) was also the most potent at decreasing ROS production.

Conclusion

FD has anti-atherogenic effects, possibly mediated by NF-κB and eNOS pathways; with FDK being the most potent variety. It is potentially beneficial in mitigating atherogenesis.

Deletion of haematopoietic Dectin-2 or CARD9 does not protect from atherosclerosis development under hyperglycaemic conditions

BACKGROUND

C-type lectin receptors, including Dectin-2, are pattern recognition receptors on monocytes and macrophages that mainly recognize sugars and sugar-like structures present on fungi. Activation of C-type lectin receptors induces downstream CARD9 signalling, leading to the production of cytokines. We hypothesized that under hyperglycaemic conditions, as is the case in diabetes mellitus, glycosylated protein (sugar-like) structures activate C-type lectin receptors, leading to immune cell activation and increased atherosclerosis development.

METHODS

Low-density lipoprotein receptor-deficient mice were lethally irradiated and transplanted with bone marrow from control wild-type, Dectin-2^-/- or Card9^-/- mice. After 6 weeks of recovery, mice received streptozotocin injections (50 mg/g BW; 5 days) to induce hyperglycaemia. After an additional 2 weeks, mice were fed a Western-type diet (0.1% cholesterol) for 10 weeks.

RESULTS AND CONCLUSION

Deletion of haematopoietic Dectin-2 reduced the number of circulating Ly6C^hi monocytes, increased pro-inflammatory cytokine production, but did not affect atherosclerosis development. Deletion of haematopoietic CARD9 tended to reduce macrophage and collagen content in atherosclerotic lesions, again without influencing the lesion size. Deletion of haematopoietic Dectin-2 did not influence atherosclerosis development under hyperglycaemic conditions, despite some minor effects on inflammation. Deletion of haematopoietic CARD9 induced minor alterations in plaque composition under hyperglycaemic conditions, without affecting lesion size.

Vascular Macrophages in Atherosclerosis

Atherosclerosis is the main pathological basis for the occurrence of most cardiovascular diseases, the leading global health threat, and a great burden for society. It has been well established that atherosclerosis is not only a metabolic disorder but also a chronic, sterile, and maladaptive inflammatory process encompassing both innate and adaptive immunity. Macrophages, the major immune cell population in atherosclerotic lesions, have been shown to play critical roles in all stages of atherosclerosis, including the initiation and progression of advanced atherosclerosis. Macrophages have emerged as a novel potential target for antiatherosclerosis therapy. In addition, the macrophage phenotype is greatly influenced by microenvironmental stimuli in the plaques and presents complex heterogeneity. This article reviews the functions of macrophages in different stages of atherosclerosis, as well as the phenotypes and functions of macrophage subsets. New treatment strategies based on macrophage-related inflammation are also discussed.

Role of Inflammatory Cell Subtypes in Heart Failure

Inflammation is a well-known feature of heart failure. Studies have shown that while some inflammation is required for repair during injury and is protective, prolonged inflammation leads to myocardial remodeling and apoptosis of cardiac myocytes. Various types of immune cells are implicated in myocardial inflammation and include neutrophils, macrophages, eosinophils, mast cells, natural killer cells, T cells, and B cells. Recent clinical trials have targeted inflammatory cascades as therapy for heart failure with limited success. A better understanding of the temporal course of the infiltration of the different immune cells and their contribution to the inflammatory process may improve the success for therapy. This brief review outlines the major cell types involved in heart failure, and some of their actions are summarized in the supplementary figure.

Ultramorphological analysis of plaque advancement and cholesterol crystal formation in Ldlr knockout mouse atherosclerosis

BACKGOUND AND AIMS

The low-density lipoprotein receptor-deficient (Ldlr^-/-) mouse has been utilized by cardiovascular researchers for more than two decades to study atherosclerosis. However, there has not yet been a systematic effort to document the ultrastructural changes that accompany the progression of atherosclerotic plaque in this model.

METHODS

Employing several different staining and microscopic techniques, including immunohistochemistry, as well as electron and polarized microscopy, we analyzed atherosclerotic lesion development in Ldlr^-/- mice fed an atherogenic diet over time.

RESULTS

Lipid-like deposits occurred in the subendothelial space after only one week of atherogenic diet. At two weeks, cholesterol crystals (CC) formed and increased thereafter. Lipid, CC, vascular smooth muscles cells, and collagen progressively increased over time, while after 4 weeks, relative macrophage content decreased. Accelerated accumulation of plate- and needle-shaped CC accompanied plaque core necrosis. Lastly, CC were surrounded by cholesterol microdomains, which co-localized with CC through all stages of atherosclerosis, indicating that the cholesterol microdomains may be a source of CC.

CONCLUSIONS

Here, we have documented, for the first time in a comprehensive way, atherosclerotic plaque morphology and composition from early to advanced stages in the Ldlr^-/- mouse, one of the most commonly used animal models utilized in atherosclerosis research.

MiR-652-3p inhibition enhances endothelial repair and reduces atherosclerosis by promoting Cyclin D2 expression

BACKGROUND

Atherosclerosis is a hyperlipidemia-induced condition affecting the arterial wall that damages healthy endothelial cell (EC) function, leading to enhanced risk of atherothrombotic events. Certain microRNAs regulate EC dysfunction in response to hyperlipidemia and may be suitable therapeutic targets to combat atherosclerosis.

METHODS

miRNA expression in human ECs was analyzed under various conditions to identify key microRNAs. High-cholesterol diet (HCD)-fed Mir652-/-Apoe-/- (Mir652-/-) mice and matching Mir652+/+Apoe-/- (Mir652+/+) mice were subjected to carotid injury to analyze the effects of miR-652 knockdown on endothelial repair. In silico analysis followed by in vitro and in vivo experiments were applied to identify miR-652's target gene Ccnd2 and investigate the pair's effects on ECs. miR-652-5p and miR-652-3p antagomir therapies were tested in Mir652+/+ mice under normal and HCD diet to assess their effect on endothelial repair.

FINDINGS

miR-652-3p, which is upregulated in human and murine atherosclerotic plaques, suppresses expression of the endothelial repair gene Ccnd2, thereby enhancing atherosclerotic lesion formation. Post-denudation recovery of ECs was promoted in Mir652-/- mice due to enhanced EC proliferation attributable to de-repression of miR-652-3p's (but not miR-652-5p's) regulation of Ccnd2 expression. Under hyperlipidemic conditions at non-predilection sites, miR-652-3p produces anti-proliferative effects in ECs, such that Mir652-/- mice display reduced atherosclerotic progression. In contrast, neither miR-652-3p nor Ccnd2 displayed significant effects on the endothelium at predilection sites or under disturbed flow conditions. Administration of a miR-652-3p antagomir rescued the proliferation of ECs in vivo, thereby limiting atherosclerotic development.

INTERPRETATION

miR-652-3p blockade may be a potential therapeutic strategy against atherosclerosis.

Macrophages and Cardiovascular Health

Research during the last decade has generated numerous insights on the presence, phenotype, and function of myeloid cells in cardiovascular organs. Newer tools with improved detection sensitivities revealed sizable populations of tissue-resident macrophages in all major healthy tissues. The heart and blood vessels contain robust numbers of these cells; for instance, 8% of noncardiomyocytes in the heart are macrophages. This number and the cell's phenotype change dramatically in disease conditions. While steady-state macrophages are mostly monocyte independent, macrophages residing in the inflamed vascular wall and the diseased heart derive from hematopoietic organs. In this review, we will highlight signals that regulate macrophage supply and function, imaging applications that can detect changes in cell numbers and phenotype, and opportunities to modulate cardiovascular inflammation by targeting macrophage biology. We strive to provide a systems-wide picture, i.e., to focus not only on cardiovascular organs but also on tissues involved in regulating cell supply and phenotype, as well as comorbidities that promote cardiovascular disease. We will summarize current developments at the intersection of immunology, detection technology, and cardiovascular health.

Effects of Icariin on Atherosclerosis and Predicted Function Regulatory Network in ApoE Deficient Mice

Objective. Icariin plays a pivotal role in ameliorating atherosclerosis for animal models although its comprehensive biological role remains largely unexplored. This study aimed to fully understand the effects of icariin on atherosclerosis in high-fat diet-induced ApoE^-/- mice and investigate mRNA-miRNA regulation based on microarray and bioinformatics analysis. Methods. The areas of atherosclerotic lesions in en face aorta were evaluated. Microarray analysis was performed on atherosclerotic aortic tissues. The integrative analysis of mRNA and miRNA profiling was utilized to suggest specific functions of gene and supply an integrated and corresponding method to study the protective effect of icariin on atherosclerosis. Results. Icariin attenuated the development of atherosclerosis that the mean atherosclerotic lesion area was reduced by 5.8% (P < 0.05). Significant changes were observed in mRNA and miRNA expression patterns. Several miRNAs obtained from the miRNA-Gene-Network might play paramount part in antiatherosclerotic effect of icariin, such as mmu-miR-6931-5p, mmu-miR-3547-5p, mmu-miR-5107-5p, mmu-miR-6368, and mmu-miR-7118-5p. Specific miRNAs and GO terms associated with icariin in the pathogenesis of atherosclerosis were validated using GO analysis and miRNA-GO-Network. MiRNA-Pathway-Network indicated that icariin induced miRNAs mainly regulate the signaling pathways of PI3K/Akt signaling pathway, Ras signaling pathway, ErbB signaling pathway, and VEGF signaling pathway in aorta atherosclerotic lesion. Conclusions. Our data provides evidence that icariin is able to exhibit one antiatherosclerotic action by mediating multiple biological processes or cascades, suggesting the pleiotropic effects of icariin in atherosclerosis alleviation. The identified gene functional categories and pathways are potentially valuable targets for future development of RNA-guided gene regulation to fight disease.