The salient role of microRNAs in atherogenesis

The effect of miR-223-3p on endothelial cells in coronary artery disease

Endothelial cell damage and dysfunction are crucial factors in the development and early stages of coronary artery disease (CAD) and apoptosis plays a significant role in this process. In this study, We aimed to simulate the CAD vascular microenvironment by treating endothelial cells with tumor necrosis factor alpha (TNF-α) to construct an endothelial cell apoptosis model. Our findings revealed that the TNF-α model resulted in increased micro-RNA 223-3p (miR-223-3p) mRNA and Bax protein expression, decreased kruppel-like factor 15 (KLF15) and Bcl-2 protein expression, and decreased cell viability. More importantly, in the TNF-α-induced endothelial cell apoptosis model, transfection with the miR-223-3p inhibitor reversed the effects of TNF-α on Bcl-2, Bax expression. We transfected miRNA-223-3p mimics or inhibitors into endothelial cells and assessed miR-223-3p levels using RT-PCR. Cell viability was detected using CCK8. Western blot technology was used to detect the expression of Bcl-2, Bax, and KLF15. In summary, this study demonstrates the role and possible mechanism of miR-223-3p in endothelial cells during CAD, suggesting that miR-223-3p may serve as a promising therapeutic target in CAD by regulating KLF15.

The role of miRNAs in the diagnosis of stable atherosclerosis of different arterial territories: A critical review

Atherosclerotic disease is a major cause of morbidity and mortality worldwide. Atherosclerosis may be present in different arterial territories and as a single- or multi-territorial disease. The different phenotypes of atherosclerosis are attributable only in part to acquired cardiovascular risk factors and genetic Mendelian inheritance. miRNAs, which regulate the gene expression at the post-transcriptional level, may also contribute to such heterogeneity. Numerous miRNAs participate in the pathophysiology of atherosclerosis by modulating endothelial function, smooth vascular cell function, vascular inflammation, and cholesterol homeostasis in the vessel, among other biological processes. Moreover, miRNAs are present in peripheral blood with high stability and have the potential to be used as non-invasive biomarkers for the diagnosis of atherosclerosis. However, the circulating miRNA profile may vary according to the involved arterial territory, considering that atherosclerosis expression, including the associated molecular phenotype, varies according to the affected arterial territory. In this review, we discuss the specific circulating miRNA profiles associated with atherosclerosis of different arterial territories, the common circulating miRNA profile of stable atherosclerosis irrespective of the involved arterial territory, and the circulating miRNA signature of multi-territorial atherosclerosis. miRNAs may consist of a simple non-invasive method for discriminating atherosclerosis of different arterial sites. The limitations of miRNA profiling for such clinical application are also discussed.

The Role of Inflammation in Cardiovascular Disease

Atherosclerosis is a chronic inflammatory disease, in which the immune system has a prominent role in its development and progression. Inflammation-induced endothelial dysfunction results in an increased permeability to lipoproteins and their subendothelial accumulation, leukocyte recruitment, and platelets activation. Recruited monocytes differentiate into macrophages which develop pro- or anti-inflammatory properties according to their microenvironment. Atheroma progression or healing is determined by the balance between these functional phenotypes. Macrophages and smooth muscle cells secrete inflammatory cytokines including interleukins IL-1β, IL-12, and IL-6. Within the arterial wall, low-density lipoprotein cholesterol undergoes an oxidation. Additionally, triglyceride-rich lipoproteins and remnant lipoproteins exert pro-inflammatory effects. Macrophages catabolize the oxidized lipoproteins and coalesce into a lipid-rich necrotic core, encapsulated by a collagen fibrous cap, leading to the formation of fibro-atheroma. In the conditions of chronic inflammation, macrophages exert a catabolic effect on the fibrous cap, resulting in a thin-cap fibro-atheroma which makes the plaque vulnerable. However, their morphology may change over time, shifting from high-risk lesions to more stable calcified plaques. In addition to conventional cardiovascular risk factors, an exposure to acute and chronic psychological stress may increase the risk of cardiovascular disease through inflammation mediated by an increased sympathetic output which results in the release of inflammatory cytokines. Inflammation is also the link between ageing and cardiovascular disease through increased clones of leukocytes in peripheral blood. Anti-inflammatory interventions specifically blocking the cytokine pathways reduce the risk of myocardial infarction and stroke, although they increase the risk of infections.

miR-351 promotes atherosclerosis in diabetes by inhibiting the ITGB3/PIK3R1/Akt pathway and induces endothelial cell injury and lipid accumulation

Background

The miR-351 gene is significantly upregulated in diabetic mice with atherosclerosis. However, the mechanism by which its presence is important for the overall disease has not been elucidated. Therefore, this study will investigate the mechanism of miR-351 in the process of diabetes mellitus with atherosclerosis through miR-351 gene knockout mice.

Methods

In this study, miR-351^−/− C57BL/6 mice were first induced to form a type 2 diabetes mellitus model with atherosclerosis by STZ injection and a high-fat diet. Pathological tests (oil red O, HE, and Masson staining) combined with biochemical indices (TC, TG, LDL-C, HDL-C, TNF-α, hs-CRP, NO, SOD, MDA, CAT, and GSH-Px) were performed to evaluate the pathological degree of atherosclerosis in each group. Mouse aortic endothelial cells were treated with oxidized low-density lipoprotein (ox-LDL) and 30 mM glucose to establish a diabetic atherosclerosis cell model. Combined with cell oil red O staining and flow cytometry, the effects of silencing miR-351 on lipid accumulation and cell apoptosis in the diabetic atherosclerosis cell model were determined. Fluorescence in situ hybridization was used to detect the localization and transcription levels of miR-351 in cells. The target genes of miR-351 were predicted by bioinformatics and verified by dual-luciferase activity reporting. Western blotting was used to detect the expression levels of phosphorylated inosine 3-kinase regulatory subunit 1 (PIK3R1)/serine/threonine kinase 1 (Akt) and apoptosis-related proteins after transfection with integrin subunit β3 (ITGB3) small interfering ribonucleic acid (siRNA).

Results

The expression of the miR-351 gene was significantly increased in the high-fat wild-type (HWT) group, and its expression was significantly decreased in the knockout mice. Silencing miR-351 effectively alleviated atherosclerosis in mice. The levels of miR-351 expression, apoptosis, lipid accumulation, and oxidative stress in ox-LDL + high glucose-induced endothelial cells were significantly increased. These phenomena were effectively inhibited in lentivirus-infected miR-351-silenced cell lines. Bioinformatics predicted that miR-351-5p could directly target the ITGB3 gene. Transfection of ITGB3 siRNA reversed the downregulation of apoptosis, decreased oil accumulation, and decreased oxidative stress levels induced by miR-351 silencing. In addition, it inhibited the activation of the PIK3R1/Akt pathway.

Conclusion

Silencing miR-351 upregulates ITGB3 and activates the PIK3R1/Akt pathway, thereby exerting anti-apoptosis and protective effects on endothelial cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00547-9.

Inflammation: A New Look at an Old Problem

Pro-inflammatory stress is inherent in any cells that are subject to damage or threat of damage. It is defined by a number of universal components, including oxidative stress, cellular response to DNA damage, unfolded protein response to mitochondrial and endoplasmic reticulum stress, changes in autophagy, inflammasome formation, non-coding RNA response, formation of an inducible network of signaling pathways, and epigenetic changes. The presence of an inducible receptor and secretory phenotype in many cells is the cause of tissue pro-inflammatory stress. The key phenomenon determining the occurrence of a classical inflammatory focus is the microvascular inflammatory response (exudation, leukocyte migration to the alteration zone). This same reaction at the systemic level leads to the development of life-critical systemic inflammation. From this standpoint, we can characterize the common mechanisms of pathologies that differ in their clinical appearance. The division of inflammation into alternative variants has deep evolutionary roots. Evolutionary aspects of inflammation are also described in the review. The aim of the review is to provide theoretical arguments for the need for an up-to-date theory of the relationship between key human pathological processes based on the integrative role of the molecular mechanisms of cellular and tissue pro-inflammatory stress.

Circulating MicroRNA Responses to Postprandial Lipemia with or without Prior Exercise

Repeated exposure to a high-fat meal triggers inflammation and oxidative stress, contributing to the onset of cardiometabolic diseases. Regular exercise prevents cardiometabolic diseases and a prior bout of acute endurance exercise can counteract the detrimental cardiovascular effects of a subsequent high-fat meal. Circulating microRNAs (ci-miRs) are potential mediators of these vascular effects through regulation of gene expression at the posttranscriptional level. Therefore, we investigated the expression of ci-miRs related to vascular function (miR-21, miR-92a, miR-126, miR-146a, miR-150, miR-155, miR-181b, miR-221, miR-222) in plasma from healthy, recreationally to highly active, Caucasian adult men after a high-fat meal with (EX) and without (CON) a preceding bout of cycling exercise. Ci-miR-155 was the only ci-miR for which there was a significant interaction effect of high-fat meal and exercise (p=0.050). Ci-miR-155 significantly increased in the CON group at two (p=0.007) and four hours (p=0.010) after the high-fat meal test, whereas it significantly increased in the EX group only four hours after the meal (p=0.0004). There were significant main effects of the high-fat meal on ci-miR-21 (p=0.01), ci-miR-126 (p=0.02), ci-miR-146a (p=0.02), ci-miR-181b (p=0.02), and ci-miR-221 (p=0.008). Collectively, our results suggest that prior exercise does not prevent high-fat meal-induced increases in vascular-related ci-miRs.

Changes in circulating microRNA and arterial stiffness following high-intensity interval and moderate intensity continuous exercise

High‐intensity interval (HII) exercise elicits distinct vascular responses compared to a matched dose of moderate intensity continuous (MOD) exercise. However, the acute effects of HII compared to MOD exercise on arterial stiffness are incompletely understood. Circulating microRNAs (ci‐miRs) may contribute to the vascular effects of exercise. We sought to determine exercise intensity‐dependent changes in ci‐miR potentially underlying changes in arterial stiffness. Ten young, healthy men underwent well‐matched, 30‐min HII and MOD exercise bouts. RT‐qPCR was used to determine the levels of seven vascular‐related ci‐miRs in serum obtained immediately before and after exercise. Arterial stiffness measures including carotid to femoral pulse wave velocity (cf‐PWV), carotid arterial compliance and β‐stiffness, and augmentation index (AIx and AIx75) were taken before, 10min after and 60min after exercise. Ci‐miR‐21‐5p, 126‐3p, 126‐5p, 150‐5p, 155‐5p, and 181b‐5p increased after HII exercise (p < .05), while ci‐miR‐150‐5p and 221‐3p increased after MOD exercise (p = .03 and 0.056). One hour after HII exercise, cf‐PWV trended toward being lower compared to baseline (p = .056) and was significantly lower compared to 60min after MOD exercise (p = .04). Carotid arterial compliance was increased 60min after HII exercise (p = .049) and was greater than 60min after MOD exercise (p = .02). AIx75 increased 10 min after both HII and MOD exercise (p < .05). There were significant correlations between some of the exercise‐induced changes in individual ci‐miRs and changes in cf‐PWV and AIx/AIx75. These results support the hypotheses that arterial stiffness and ci‐miRs are altered in an exercise intensity‐dependent manner, and ci‐miRs may contribute to changes in arterial stiffness.

Race-specific changes in endothelial inflammation and microRNA in response to an acute inflammatory stimulus

Both aberrant vascular reactivity to acute cardiovascular stress and epigenetic mechanisms such as microRNA (miR) may underlie the increased propensity for African Americans (AA) to develop cardiovascular disease. This study assessed racial differences in acute induced endothelial inflammation and related miRs. Cultured human umbilical vein endothelial cells (HUVECs) derived from AA and Caucasian Americans (CA) were exposed to influenza vaccine to determine changes in inflammatory markers, endothelial nitric oxide synthase (eNOS), and miR expression/release. Endothelial function [flow-mediated dilation (FMD)], circulating IL-6, and circulating miR were also measured in young, healthy AA and CA individuals before and after receiving the influenza vaccine. There were no significant racial differences in any parameters at baseline. The vaccine induced increases in IL-6 release (24%, P = 0.02) and ICAM-1 mRNA (40%, P = 0.03), as well as reduced eNOS mRNA (24%, P = 0.04) in AA HUVECs, but not in CA HUVECs (all P > 0.05). Intracellular levels of anti-inflammatory miR-221-3p and miR-222-3p increased specifically in CA HUVECs (72% and 53%, P = 0.04 and P = 0.06), whereas others did not change in either race. HUVEC secretion of several miRs decreased in both races, whereas the release of anti-inflammatory miR-150-5p was decreased only by AA cells (-30%, P = 0.03). In individuals of both races, circulating IL-6 increased approximately twofold 24 h after vaccination (both P < 0.01) and returned to baseline levels by 48 h, whereas FMD remained unchanged. Although macrovascular function was unaffected by acute inflammation in AA and CA individuals, AA endothelial cells exhibited increased susceptibility to acute inflammation and unique changes in related miR.NEW & NOTEWORTHY Used as an acute inflammatory stimulus, the influenza vaccine induced an inflammatory response and decreased eNOS gene expression in endothelial cells derived from African Americans, but not Caucasian Americans. Race-specific changes in intracellular expression and release of specific microRNAs also occurred and may contribute to an exaggerated inflammatory response in African Americans. In vivo, the vaccine caused similar systemic inflammation but had no effect on endothelial function or circulating microRNAs in individuals of either race.

Mechanoresponsive Smad5 Enhances MiR-487a Processing to Promote Vascular Endothelial Proliferation in Response to Disturbed Flow

MicroRNAs (miRs) and bone morphogenetic protein receptor-specific Smads are mechano-responsive molecules that play vital roles in modulating endothelial cell (EC) functions in response to blood flow. However, the roles of interplay between these molecules in modulating EC functions under flows remain unclear. We elucidated the regulatory roles of the interplay between miR-487a and Smad5 in EC proliferation in response to different flow patterns. Microarray and quantitative RT-PCR showed that disturbed flow with low and oscillatory shear stress (OS, 0.5 ± 4 dynes/cm²) upregulates EC miR-487a in comparison to static controls and pulsatile shear stress (12 ± 4 dynes/cm²). MiR-487a expression was higher in ECs in the inner curvature (OS region) than the outer curvature of the rat aortic arch and thoracic aorta and also elevated in diseased human coronary arteries. MiR-487a expression was promoted by nuclear phospho-Smad5, which bound to primary-miR-487a to facilitate miR-487a processing. Algorithm prediction and luciferase reporter and argonaute 2-immunoprecipitation assays demonstrated that miR-487a binds to 3'UTR of CREB binding protein (CBP) and p53. Knockdown and overexpression of miR-487a decreased and increased, respectively, phospho-Rb and cyclin A expressions through CBP and p53. A BrdU incorporation assay showed that miR-487a enhanced EC proliferation under OS in vitro and in disturbed flow regions of experimentally stenosed rat abdominal aorta in vivo. These results demonstrate that disturbed flow with OS induces EC expression of miR-487a through its enhanced processing by activated-Smad5. MiR-487 inhibits its direct targets CBP and p53 to induce EC cycle progression and proliferation. Our findings suggest that EC miR-487 may serve as an important molecular target for intervention against disturbed flow-associated vascular disorders resulting from atherosclerosis.

MiR-520b inhibits endothelial activation by targeting NF-κB p65-VCAM1 axis

MiR-520b belongs to the miR-373/520 family, is expressed only in human and nonhuman primates. Previous reports indicated that the expression of miR-520b was repressed in human atherosclerotic plaque tissue compared with healthy vessels. However, the role of miR-520b in coronary artery disease still remains to be uncovered. In this study, we demonstrated that endothelial cells (ECs) in human atherosclerotic plaques expressed miR-520b and aimed to elucidate the impact of miR-520b on EC activation and inflammatory response. To determine the potential targets of miR-520b, we performed RNA-seq analysis by transfecting miR-520b mimics in ECs. The quantitative real-time PCR (qPCR) validation suggested that miR-520b over-expression reduced pro-inflammatory gene expression (e.g. ICAM1, VCAM1, SELE) while the inhibition of miR-520b induced their expression. By combining bioinformatics prediction and functional assays, we identified that RELA (Nuclear Factor-κB (NF-κB) Transcription Factor P65) was a direct target of miR-520b. Moreover, miR-520b mimics attenuated monocyte adhesion and monocyte trans-endothelial migration (the initial steps of atherosclerotic formation) in response to lipopolysaccharides (LPS) stimulation. Re-expression of a non-miR-targetable version of p65 could rescue the reduced monocyte cell attachment, suggesting that this process is NF-κB p65 dependent. MiR-520b reduced the abundance of NF-κB p65 in cytoplasmic fractions without corresponding increase in nuclear fractions, indicating that this regulation is independent of p65 translocation process. MiR-520b mimics attenuated the activity of VCAM-1 promoter, whereas miR-520b inhibitor activated its activity. However, miR-520b inhibitor had no effect on promoter activity containing the mutated NF-κB p65 binding sites, strongly demonstrating that the impact of miR-520b on VCAM1 gene is mediated by NF-κB p65. Thus, we concluded that miR-520b suppressed EC inflammation and the cross-talk between monocytes and ECs by down-regulating NF-κB p65-ICAM1/VCAM1 axis and might serve as a potential therapeutic target for EC dysfunction and atherosclerosis.

Functioning of Long Noncoding RNAs Expressed in Macrophage in the Development of Atherosclerosis

Chronic inflammation is part of the pathological process during atherosclerosis (AS). Due to the abundance of monocytes/macrophages within the arterial plaque, monocytes/macrophages have become a critical cellular target in AS studies. In recent decades, a number of long noncoding RNAs (lncRNAs) have been found to exert regulatory roles on the macrophage metabolism and macrophage plasticity, consequently promoting or suppressing atherosclerotic inflammation. In this review, we provide a comprehensive overview of lncRNAs in macrophage biology, highlighting the potential role of lncRNAs in AS based on recent findings, with the aim to identify disease biomarkers and future therapeutic interventions for AS.

Oxidized LDL Disrupts Metabolism and Inhibits Macrophage Survival by Activating a miR-9/Drp1/Mitochondrial Fission Signaling Pathway

Mitochondrial dysfunction is associated with macrophage damage, but the role of mitochondrial fission in macrophage cholesterol metabolism is not fully understood. In this study, we explored the influences of miR-9 and mitochondrial fission on macrophage viability and cholesterol metabolism. Macrophages were incubated with oxidized low-density lipoprotein (ox-LDL) in vitro, after which mitochondrial fission, cell viability, and cholesterol metabolism were examined using qPCR, ELISAs, and immunofluorescence. ox-LDL treatment significantly increased Drp1-associated mitochondrial fission. Transfection of Drp1 siRNA significantly reduced cell death, attenuated oxidative stress, and inhibited inflammatory responses in ox-LDL-treated macrophages. Interestingly, inhibition of Drp1-related mitochondrial fission also improved cholesterol metabolism by balancing the transcription of cholesterol influx/efflux enzymes. We also found that miR-9 was downregulated in ox-LDL-treated macrophages, and administration of a miR-9 mimic decreased Drp1 transcription and mitochondrial fission, as well as its effects. These results indicate that signaling via the novel miR-9/Drp1/mitochondrial fission axis is a key determinant of macrophage viability and cholesterol metabolism.

Non-hematopoietic erythropoietin-derived peptides for atheroprotection and treatment of cardiovascular diseases

Relevance: Cardiovascular diseases continue to be the leading cause of premature adult death.

Lipid profile and atherogenesis: Dislipidaemia leads to subsequent lipid accumulation and migration of immunocompetent cells into the vessel intima. Macrophages accumulate cholesterol forming foam cells – the morphological substrate of atherosclerosis in its initial stage.

Inflammation and atherogenesis: Pro-inflammatory factors provoke oxidative stress, vascular wall damage and foam cells formation.

Endothelial and mitochondrial dysfunction in the development of atherosclerosis: Endothelial mitochondria are some of the organelles most sensitive to oxidative stress. Damaged mitochondria produce excess superoxide and H2O2, which are the main factors of intracellular damage, further increasing endothelial dysfunction.

Short non-hematopoietic erythropoietin-based peptides as innovative atheroprotectors: Research in recent decades has shown that erythropoietin has a high cytoprotective activity, which is mainly associated with exposure to the mitochondrial link and has been confirmed in various experimental models. There is also a short-chain derivative, the 11-amino acid pyroglutamate helix B surface peptide (PHBSP), which selectively binds to the erythropoietin heterodymic receptor and reproduces its cytoprotective properties. This indicates the promising use of short-chain derivatives of erythropoietin for the treatment and prevention of atherosclerotic vascular injury. In the future, it is planned to study the PHBSP derivatives, the modification of which consists in adding RGD and PGP tripeptides with antiaggregant properties to the original 11-member peptide.

Physiologic blood flow is turbulent

Contemporary paradigm of peripheral and intracranial vascular hemodynamics considers physiologic blood flow to be laminar. Transition to turbulence is considered as a driving factor for numerous diseases such as atherosclerosis, stenosis and aneurysm. Recently, turbulent flow patterns were detected in intracranial aneurysm at Reynolds number below 400 both in vitro and in silico. Blood flow is multiharmonic with considerable frequency spectra and its transition to turbulence cannot be characterized by the current transition theory of monoharmonic pulsatile flow. Thus, we decided to explore the origins of such long-standing assumption of physiologic blood flow laminarity. Here, we hypothesize that the inherited dynamics of blood flow in main arteries dictate the existence of turbulence in physiologic conditions. To illustrate our hypothesis, we have used methods and tools from chaos theory, hydrodynamic stability theory and fluid dynamics to explore the existence of turbulence in physiologic blood flow. Our investigation shows that blood flow, both as described by the Navier–Stokes equation and in vivo, exhibits three major characteristics of turbulence. Womersley’s exact solution of the Navier–Stokes equation has been used with the flow waveforms from HaeMod database, to offer reproducible evidence for our findings, as well as evidence from Doppler ultrasound measurements from healthy volunteers who are some of the authors. We evidently show that physiologic blood flow is: (1) sensitive to initial conditions, (2) in global hydrodynamic instability and (3) undergoes kinetic energy cascade of non-Kolmogorov type. We propose a novel modification of the theory of vascular hemodynamics that calls for rethinking the hemodynamic–biologic links that govern physiologic and pathologic processes.

Resveratrol inhibits hypertrophic scars formation by activating autophagy via the miR-4654/Rheb axis

Hypertrophic scars (HSs) are a type of pathological scar which are induced by surgery, burn injuries or trauma during the healing process. Due to the high recurrence rates and strong invasive properties, HSs have become a major clinical issue. Resveratrol has been identified as a potential agent to suppress scar formation; however, the underlying mechanism of action remains unclear. Therefore, the present study aimed to investigate the effect of resveratrol on HS-derived fibroblasts (HSFBs) in vitro. MTT assay was performed to evaluate cell viability following the resveratrol treatment. Western blot and RT-qPCR analysis was used to identify the expression levels and the relationship among autophagic markers, miR-4654 and resveratrol treatment. Finally, GFP-LC3 stable HSFBs cells were generated to further assess the effect of resveratrol. The results revealed that resveratrol significantly induced cell death in a dose-dependent manner and induced autophagy by downregulating the expression levels of Rheb in HSFBs. Notably, microRNA-4654 (miR-4654) was significantly decreased in the HSFBs and re-upregulated by resveratrol treatment dose-dependently. Through the bioinformatic analysis and luciferase assay, miR-4654 was identified to directly target Rheb. Transfection studies showed that miR-4654 negative correlated with Rheb expression, suggesting that the autophagic process may be altered by the miR-4654/Rheb axis under the control of resveratrol. In conclusion, the results of the present study suggested that resveratrol may promote autophagy by upregulating miR-4654, which in turn may suppress Rheb expression via directly binding to the 3′-untranslated region of Rheb. These findings provided a novel insight into the development of potential therapeutic targets for HSs.

What does computational fluid dynamics tell us about intracranial aneurysms? A meta-analysis and critical review

Despite the plethora of published studies on intracranial aneurysms (IAs) hemodynamic using computational fluid dynamics (CFD), limited progress has been made towards understanding the complex physics and biology underlying IA pathophysiology. Guided by 1733 published papers, we review and discuss the contemporary IA hemodynamics paradigm established through two decades of IA CFD simulations. We have traced the historical origins of simplified CFD models which impede the progress of comprehending IA pathology. We also delve into the debate concerning the Newtonian fluid assumption used to represent blood flow computationally. We evidently demonstrate that the Newtonian assumption, used in almost 90% of studies, might be insufficient to describe IA hemodynamics. In addition, some fundamental properties of the Navier-Stokes equation are revisited in supplementary material to highlight some widely spread misconceptions regarding wall shear stress (WSS) and its derivatives. Conclusively, our study draws a roadmap for next-generation IA CFD models to help researchers investigate the pathophysiology of IAs.

Epigenetic Mechanisms in Monocytes/Macrophages Regulate Inflammation in Cardiometabolic and Vascular Disease

Cardiometabolic and vascular disease, with their associated secondary complications, are the leading cause of morbidity and mortality in Western society. Chronic inflammation is a common theme that underlies initiation and progression of cardiovascular disease. In this regard, monocytes/macrophages are key players in the development of a chronic inflammatory state. Over the past decade, epigenetic modifications, such as DNA methylation and posttranslational histone processing, have emerged as important regulators of immune cell phenotypes. Accumulating studies reveal the importance of epigenetic enzymes in the dynamic regulation of key signaling pathways that alter monocyte/macrophage phenotypes in response to environmental stimuli. In this review, we highlight the current paradigms of monocyte/macrophage polarization and the emerging role of epigenetic modification in the regulation of monocyte/macrophage phenotype in obesity, diabetes mellitus, atherosclerosis, and abdominal aortic aneurysms.

Epigenetic response of endothelial cells to different wall shear stress magnitudes: A report of new mechano-miRNAs

Endothelial cells (ECs) respond to flow stress via a variety of mechanisms, leading to various intracellular responses that can modulate the vessel wall and lead to diseases if the flow is disturbed. Mechano-microRNAs (miRNAs) are a subset of miRNAs in the ECs that are flow responsive. Mechano-miRNAs were shown to be related to atherosclerosis pathophysiology, and a number of them were identified as pathologic. Here, we exposed human carotid ECs to different wall shear stresses (WSS), high and low, and evaluated the response of miRNAs by microarray and quantitative polymerase chain reaction analysis. We discovered five new mechano-miRNAs that were not reported in that context previously to the best of our knowledge. Moreover, functional pathway analysis revealed that under low WSS conditions, several pathways regulating apoptosis are affected. In addition, KLF2 and KLF4, known atheroprotective genes, were downregulated under low WSS and upregulated under high WSS. KLF2 and VCAM1, both angiogenic, were upregulated under high WSS. NOS3, which is vascular protective, was also upregulated with higher WSS. On the contrary, ICAM-1 and E-selectin, both atherogenic and proinflammatory, were upregulated with high WSS. Collectively, the epigenetic landscape with the gene expression analysis reveals that low WSS is associated with a proapoptotic state, while high WSS is associated with a proliferative and proinflammatory state.

The role of microvesicles containing microRNAs in vascular endothelial dysfunction

Many studies have shown that endothelial dysfunction is associated with a variety of cardiovascular diseases. The endothelium is one of the primary targets of circulating microvesicles. Besides, microRNAs emerge as important regulators of endothelial cell function. As a delivery system of microRNAs, microvesicles play an active and important role in regulating vascular endothelial function. In recent years, some studies have shown that microvesicles containing microRNAs regulate the pathophysiological changes in vascular endothelium, such as cell apoptosis, proliferation, migration and inflammation. These studies have provided some clues for the possible roles of microvesicles and microRNAs in vascular endothelial dysfunction‐associated diseases, and opened the door towards discovering potential novel therapeutic targets. In this review, we provide an overview of the main characteristics of microvesicles and microRNAs, summarizing their potential role and mechanism in endothelial dysfunction, and discussing the clinical application and existing problems of microvesicles for better translational applications.

miR-125a-5p inhibits the expression of NLRP3 by targeting CCL4 in human vascular smooth muscle cells treated with ox-LDL

Recent findings have revealed that aberrant miR-125a-5p expression is involved in the development of atherosclerosis. The present study aimed to investigate the precise mechanism of microRNA (miR)-125a-5p in atherosclerosis. Human vascular smooth muscle cells (HVSMCs) were treated with 20 µg/ml oxidized low-density lipoprotein (ox-LDL) for 24 h and were employed as in vitro models of atherosclerosis. Reverse transcription quantitative (RT-qPCR) assays were used to detect miR-125a-5p levels. Immunofluorescence analysis was conducted to assess α-smooth muscle actin (α-SMA) expression. Western blotting and RT-qPCR assays were performed to measure the expression levels of NACHT, LRR and PYD domains-containing protein 3 (NLRP3), apoptosis associated speck-like protein (ASC), caspase-1, active interleukin (IL)-1β and C-C motif chemokine 4-like (CCL4). Furthermore, the association between miR-125a-5p and CCL4 was assessed using a double luciferase analysis. In addition, VSMCs were transfected with miR-125a-5p mimics (30 nM), miR-125a-5p inhibitor (100 nM) or small interfering RNA against CCL4 (si-CCL4, 50 pM), respectively to further investigate the function of miR-125a-5p in ox-LDL-treated HVSMCs. The present study found that the expression levels of miR-125a-5p were significantly downregulated in HVSMCs, whereas the expression levels of α-SMA, NLRP3, ASC, caspase-1, IL-1β and CCL4 were markedly upregulated following ox-LDL treatment. Overexpression of miR-125a-5p in the absence of ox-LDL treatment decreased NLRP3, IL-1β and CCL4 expression, whereas inhibition of miR-125a-5p exhibited the opposite effects. The results of double luciferase analysis confirmed that CCL4 was a direct target of miR-125a-5p. Moreover, transfection of si-CCL4 into HVSMCs significantly decreased the ox-LDL-induced expression of NLRP3, ASC, caspase-1 and IL-1β proteins. Taken collectively, the results of the present study suggested that miR-125a-5p could negatively regulate the NLRP3 inflammasome by targeting CCL4 in ox-LDL-treated HVSMCs. The data provide new insight to the inhibition of atherosclerosis progression.

Targeting epigenetics and non-coding RNAs in atherosclerosis: from mechanisms to therapeutics

Atherosclerosis, the principal cause of cardiovascular death worldwide, is a pathological disease characterized by fibro-proliferation, chronic inflammation, lipid accumulation, and immune disorder in the vessel wall. As the atheromatous plaques develop into advanced stage, the vulnerable plaques are prone to rupture, which causes acute cardiovascular events, including ischemic stroke and myocardial infarction. Emerging evidence has suggested that atherosclerosis is also an epigenetic disease with the interplay of multiple epigenetic mechanisms. The epigenetic basis of atherosclerosis has transformed our knowledge of epigenetics from an important biological phenomenon to a burgeoning field in cardiovascular research. Here, we provide a systematic and up-to-date overview of the current knowledge of three distinct but interrelated epigenetic processes (including DNA methylation, histone methylation/acetylation, and non-coding RNAs), in atherosclerotic plaque development and instability. Mechanistic and conceptual advances in understanding the biological roles of various epigenetic modifiers in regulating gene expression and functions of endothelial cells (vascular homeostasis, leukocyte adhesion, endothelial-mesenchymal transition, angiogenesis, and mechanotransduction), smooth muscle cells (proliferation, migration, inflammation, hypertrophy, and phenotypic switch), and macrophages (differentiation, inflammation, foam cell formation, and polarization) are discussed. The inherently dynamic nature and reversibility of epigenetic regulation, enables the possibility of epigenetic therapy by targeting epigenetic "writers", "readers", and "erasers". Several Food Drug Administration-approved small-molecule epigenetic drugs show promise in pre-clinical studies for the treatment of atherosclerosis. Finally, we discuss potential therapeutic implications and challenges for future research involving cardiovascular epigenetics, with an aim to provide a translational perspective for identifying novel biomarkers of atherosclerosis, and transforming precision cardiovascular research and disease therapy in modern era of epigenetics.

MicroRNA-21 attenuates BDE-209-induced lipid accumulation in THP-1 macrophages by downregulating Toll-like receptor 4 expression

Growing evidence demonstrates a possible response of specific microRNA (miRNA) to environmental pollutant stimuli in multiple biological processes. We previously reported that a persistent organic pollutant, decabromodiphenyl ether (BDE-209), can enhance Toll-like receptor 4 (TLR4)-dependent lipid uptake in THP-1 macrophages; whether miRNAs are involved in this process remains unclear. In the present study, we investigated the levels of several miRNAs related to TLR4 signaling, including miRs-9, -21, -27b, -125b, -132, -146a, -147, -155, and -let-7e, in THP-1 macrophages after stimulation by BDE-209 and oxidized low-density lipoprotein. The results showed that the levels of miR-21 were significantly suppressed by BDE-209 at concentrations of 6.25, 12.5 and 25 μM, in a dose-dependent manner; whereas there was no significant changes for the other miRNAs investigated. Moreover, the suppression of miR-21 was accompanied by an upregulated TLR4 expression, at both mRNA and protein levels. Further analysis showed that the up-regulated TLR4 induced by BDE-209 was inhibited in macrophages transfected with miR-21 mimic; meanwhile opposite results were exhibited when an anti-miR-21 inhibitor was transfected to the macrophages. Additionally, transfection with miR-21 mimic effectively attenuated BDE-209-induced lipid accumulation in macrophages. Together, these data illustrate that miR-21 inhibits BDE-209-triggered lipid accumulation in macrophages through down-regulating TLR4 expression.

CD100 Effects in Macrophages and Its Roles in Atherosclerosis

CD100 or Sema4D is a protein from the semaphorin family with important roles in the vascular, nervous and immune systems. It may be found as a membrane bound dimer or as a soluble molecule originated by proteolytic cleavage. Produced by the majority of hematopoietic cells including B and T lymphocytes, natural killer and myeloid cells, as well as endothelial cells, CD100 exerts its actions by binding to different receptors depending on the cell type and on the organism. Cell-to-cell adhesion, angiogenesis, phagocytosis, T cell priming, and antibody production are examples of the many functions of this molecule. Of note, high CD100 serum levels has been found in inflammatory as well as in infectious diseases, but the roles of the protein in the pathogenesis of these diseases has still to be clarified. Macrophages are highly heterogeneous cells present in almost all tissues, which may change their functions in response to microenvironmental conditions. They are key players in the innate and adaptive immune responses and have decisive roles in sterile conditions but also in several diseases such as atherosclerosis, autoimmunity, tumorigenesis, and antitumor responses, among others. Although it is known that macrophages express CD100 and its receptors, few studies have focused on the role of this semaphorin in this cell type or in macrophage-associated diseases. The aim of this review is to critically revise the available data about CD100 and atherosclerosis, with special emphasis on its roles in macrophages and monocytes. We will also describe the few available data on treatments with anti-CD100 antibodies in different diseases. We hope that this review stimulates future studies on the effects of such an important molecule in a cell type with decisive roles in inflammatory diseases such as atherosclerosis.