Toll-Like Receptor 4 Mediated Oxidized Low-Density Lipoprotein-Induced Foam Cell Formation in Vascular Smooth Muscle Cells

Abstract Background: Oxidized low-density lipoprotein (oxLDL) induced a foam-cell like phenotype of the vascular smooth muscle cells (VSMCs), leading to the inflammatory responses incorporating Toll-like receptors (Tlrs)-mediated cellular alterations. We previously found that Tlr4 participated in inflammation response in VSMCs under oxLDL stimulation. However, the role of Tlr4 in foam-cell formation and underlying molecular pathways has not been comprehensively elucidated. This study aimed to investigate the role of Tlr4-mediated mechanisms in oxLDL induced foam-cell formation within VSMCs. Methods: After incubated with different dose of oxLDL, the lipid, reactive oxygen species (ROS) accumulation and foam-cell phenotype of the VSMCs were detected. The alteration of Tlr family, ROS and lipid accumulation regulators including the Src kinase, Nox2, Nox4, Mnsod and sirtuins were measured. Then the Tlr4 was knock down and underlying cellular change and altered molecules were detected. Results: We showed that oxLDL induced foam-cell like phenotype in VSMCs and led to lipid and ROS accumulation in a dose-dependent manner. OxLDL induced the strongest upregulation of Tlr4 in the Tlrs family and initiated change of Src activation, Nox2, Mnsod, sirt1 and sirt3 expression. The effect of oxLDL was abolished by Tlr4 knockdown. Furthermore, knocking down of Tlr4 reduced Src activation and led to restored Sirt1/Sirt3 expression. Moreover, inhibiting or knocking down the Src kinase diminished lipid accumulation in VSMCs under oxLDL treatment. And overexpression of Sirt1/3 relieved the oxLDL induced ROS accumulation and foam-cell phenotype in VSMCs.Conclusions: These results demonstrated that Tlr4 is a critical regulator in oxLDL induced foam cell formation of VSMCs via mediating Src kinase as well as Sirt1 and Sirt3. Beyond the role of Tlr4 in inflammation response of VSMCs, we provide an integrated mechanism about TLR4 in VSMCs phenotype transition under oxLDL stimulation.

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Toll-Like Receptor 4 Mediated Oxidized Low-Density Lipoprotein-Induced Foam Cell Formation in Vascular Smooth Muscle Cells via Src and Sirt1/3 Pathway

Mediators of Inflammation ◽

10.1155/2021/6639252 ◽

2021 ◽

Vol 2021 ◽

pp. 1-17

Author(s):

Zhongli Chen ◽

Qiqi Xue ◽

Lijuan Cao ◽

Yanpin Wang ◽

Yuanyuan Chen ◽

...

Keyword(s):

Foam Cell ◽

Low Density Lipoprotein ◽

Cell Formation ◽

Density Lipoprotein ◽

Foam Cell Formation ◽

Cell Phenotype ◽

Toll Like Receptor ◽

Oxidized Low Density Lipoprotein ◽

Kinase Activation ◽

Ros Accumulation

Oxidized low-density lipoprotein (oxLDL) induced a foam-cell-like phenotype of the vascular smooth muscle cells (VSMCs), leading to the inflammatory responses incorporating Toll-like receptor- (Tlr-) mediated cellular alterations. However, the role of Tlr4 in foam cell formation and underlying molecular pathways has not been comprehensively elucidated. To further investigate the mechanism, VSMCs were incubated with different doses of oxLDL, and then, the lipid, reactive oxygen species (ROS) accumulation, Tlr family genes, and the foam cell phenotype were explored. We observed that oxLDL induced foam cell-like phenotype in VSMCs and led to lipid and ROS accumulation in a dose-dependent manner. Furthermore, in the Tlr family, Tlr4 demonstrated the strongest upregulation under oxLDL stimulation. Simultaneously, oxLDL induced activation of Src, higher expression of Nox2, and lower expression of Mnsod, Sirt1, and Sirt3. By interfering the TLR4 expression, the phenotype alteration, lipid accumulation in VSMCs, and Src kinase activation induced by oxLDL were abolished. After interfering Src activation, the oxLDL-induced lipid accumulation and foam cell phenotype in VSMCs were also alleviated. Furthermore, the ROS accumulation, upregulated Nox2 expression, downregulated Sirt1, Sirt3, and Mnsod expression in VSMCs under oxLDL stimulation were also relieved after the knockdown of Tlr4. Additionally, overexpression of Sirt1 and Sirt3 ameliorated the ROS accumulation and foam cell-like marker expression in VSMCs. These results demonstrated that beyond its familiar role in regulating inflammation response, Tlr4 is a critical regulator in oxLDL-induced foam cell formation in VSMCs via regulating Src kinase activation as well as Sirt1 and Sirt3 expression.

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Abstract 3691: Deletion of Suppressor Of Cytokine Signaling-1 in a Murine Model of Atherosclerosis Results in a Lethal Systemic Inflammation

Circulation ◽

10.1161/circ.118.suppl_18.s_467-c ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Christina Grothusen ◽

Harald Schuett ◽

Stefan Lumpe ◽

Andre Bleich ◽

Silke Glage ◽

...

Keyword(s):

Foam Cell ◽

Low Density Lipoprotein ◽

Cell Formation ◽

Density Lipoprotein ◽

Foam Cell Formation ◽

Cytokine Signaling ◽

Suppressor Of Cytokine Signaling ◽

The Impact

Introduction: Atherosclerosis is a chronic inflammatory disease of the cardiovascular system which may result in myocardial infarction and sudden cardiac death. While the role of pro-inflammatory signaling pathways in atherogenesis has been well characterized, the impact of their negative regulators, e.g. suppressor of cytokine signaling (SOCS)-1 remains to be elucidated. Deficiency of SOCS-1 leads to death 3 weeks post-partum due to an overwhelming inflammation caused by an uncontrolled signalling of interferon-gamma (IFNγ). This phenotype can be rescued by generating recombination activating gene (rag)-2, SOCS-1 double knock out (KO) mice lacking mature lymphocytes, the major source of IFNγ. Since the role of SOCS-1 during atherogenesis is unknown, we investigated the impact of a systemic SOCS-1 deficiency in the low-density lipoprotein receptor (ldlr) KO model of atherosclerosis. Material and Methods: socs-1 −/− /rag-2 −/− deficient mice were crossed with ldlr-KO animals. Mice were kept under sterile conditions on a normal chow diet. For in-vitro analyses, murine socs-1 −/− macrophages were stimulated with native low density lipoprotein (nLDL) or oxidized (ox)LDL. SOCS-1 expression was determined by quantitative PCR and western blot. Foam cell formation was determined by Oil red O staining. Results: socs-1 −/− /rag-2 −/− /ldlr −/− mice were born according to mendelian law. Tripel-KO mice showed a reduced weight and size, were more sensitive to bacterial infections and died within 120 days (N=17). Histological analyses revealed a systemic, necrotic, inflammation in Tripel-KO mice. All other genotypes developed no phenotype. In-vitro observations revealed that SOCS-1 mRNA and protein is upregulated in response to stimulation with oxLDL but not with nLDL. Foam cell formation of socs-1 −/− macrophages was increased compared to controls. Conclusion: SOCS-1 seemingly controls critical steps of atherogenesis by modulating foam cell formation in response to stimulation with oxLDL. SOCS-1 deficiency in the ldlr-KO mouse leads to a lethal inflammation. These observations suggest a critical role for SOCS-1 in the regulation of early inflammatory responses in atherogenesis.

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Role of Low Density Lipoprotein Oxidation in Foam Cell Formation

Free Radicals, Lipoproteins, and Membrane Lipids ◽

10.1007/978-1-4684-7427-5_19 ◽

1990 ◽

pp. 193-202 ◽

Cited By ~ 2

Author(s):

Urs P. Steinbrecher

Keyword(s):

Foam Cell ◽

Low Density Lipoprotein ◽

Cell Formation ◽

Density Lipoprotein ◽

Foam Cell Formation ◽

Low Density ◽

Lipoprotein Oxidation ◽

Low Density Lipoprotein Oxidation

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The Role of (Modified) Lipoproteins in Vascular Function: A Duet Between Monocytes and the Endothelium

Current Medicinal Chemistry ◽

10.2174/0929867325666180316121015 ◽

2019 ◽

Vol 26 (9) ◽

pp. 1594-1609 ◽

Cited By ~ 4

Author(s):

Johan G. Schnitzler ◽

Geesje M. Dallinga-Thie ◽

Jeffrey Kroon

Keyword(s):

Vascular Function ◽

Foam Cell ◽

Low Density Lipoprotein ◽

Cell Formation ◽

Density Lipoprotein ◽

Foam Cell Formation ◽

Peripheral Monocyte ◽

Remnant Cholesterol ◽

Modified Lipoproteins

Over the last century, many studies have demonstrated that low-density lipoprotein (LDL) is a key risk factor of cardiovascular diseases (CVD) related to atherosclerosis. Thus, for these CVD patients, LDL lowering agents are commonly used in the clinic to reduce the risk for CVD. LDL, upon modification, will develop distinct inflammatory and proatherogenic potential, leading to impaired endothelial integrity, influx of immune cells and subsequent increased foam cell formation. LDL can also directly affect peripheral monocyte composition, rendering them in a more favorable position to migrate and accumulate in the subendothelial space. It has become apparent that other lipoprotein particles, such as triglyceride- rich lipoproteins or remnants (TRL) and lipoprotein(a) [Lp(a)] may also impact on atherogenic pathways. Evidence is accumulating that Lp(a) can promote peripheral monocyte activation, eventually leading to increased transmigration through the endothelium. Similarly, remnant cholesterol has been identified to play a key role in endothelial dysfunction and monocyte behavior. In this review, we will discuss recent developments in understanding the role of different lipoproteins in the context of inflammation at both the level of the monocyte and the endothelium.

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ClC-3: A Novel Promising Therapeutic Target for Atherosclerosis

Journal of Cardiovascular Pharmacology and Therapeutics ◽

10.1177/10742484211023639 ◽

2021 ◽

pp. 107424842110236

Author(s):

Dun Niu ◽

Lanfang Li ◽

Zhizhong Xie

Keyword(s):

Therapeutic Target ◽

Chloride Channels ◽

Foam Cell ◽

Low Density Lipoprotein ◽

Cell Formation ◽

Density Lipoprotein ◽

Molecular Structures ◽

Foam Cell Formation ◽

Endothelium Dysfunction ◽

Atherosclerotic Process

Chloride channel 3 (ClC-3), a Cl−/H+ antiporter, has been well established as a member of volume-regulated chloride channels (VRCCs). ClC-3 may be a crucial mediator for activating inflammation-associated signaling pathways by regulating protein phosphorylation. A growing number of studies have indicated that ClC-3 overexpression plays a crucial role in mediating increased plasma low-density lipoprotein levels, vascular endothelium dysfunction, pro-inflammatory activation of macrophages, hyper-proliferation and hyper-migration of vascular smooth muscle cells (VSMCs), as well as oxidative stress and foam cell formation, which are the main factors responsible for atherosclerotic plaque formation in the arterial wall. In the present review, we summarize the molecular structures and classical functions of ClC-3. We further discuss its emerging role in the atherosclerotic process. In conclusion, we explore the potential role of ClC-3 as a therapeutic target for atherosclerosis.

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Protective Effect of Lusianthridin on Hemin-Induced Low-Density Lipoprotein Oxidation

Pharmaceuticals ◽

10.3390/ph14060567 ◽

2021 ◽

Vol 14 (6) ◽

pp. 567

Author(s):

Su Wutyi Thant ◽

Noppawan Phumala Morales ◽

Visarut Buranasudja ◽

Boonchoo Sritularak ◽

Rataya Luechapudiporn

Keyword(s):

Foam Cell ◽

Low Density Lipoprotein ◽

Cell Formation ◽

Density Lipoprotein ◽

Foam Cell Formation ◽

Raw 264.7 ◽

Low Density ◽

Lipoprotein Oxidation ◽

Raw 264.7 Macrophage Cells ◽

Low Density Lipoprotein Oxidation

Oxidation of low-density lipoprotein (LDL) plays a crucial role in the pathogenesis of atherosclerosis. Hemin (iron (III)-protoporphyrin IX) is a degradation product of hemoglobin that can be found in thalassemia patients. Hemin is a strong oxidant that can cause LDL oxidation and contributes to atherosclerosis in thalassemia patients. Lusianthridin from Dendrobium venustrum is a phenolic compound that possesses antioxidant activity. Hence, lusianthridin could be a promising compound to be used against hemin-induced oxidative stress. The major goal of this study is to evaluate the protective effect of lusianthridin on hemin-induced low-density lipoprotein oxidation (he-oxLDL). Here, various concentrations of lusianthridin (0.25, 0.5, 1, and 2 µM) were preincubated with LDL for 30 min, then 5 µM of hemin was added to initiate the oxidation, and oxidative parameters were measured at various times of incubation (0, 1, 3, 6, 12, 24 h). Lipid peroxidation of LDL was measured by thiobarbituric reactive substance (TBARs) assay and relative electrophoretic mobility (REM). The lipid composition of LDL was analyzed by using reverse-phase HPLC. Foam cell formation with he-oxLDL in RAW 264.7 macrophage cells was detected by Oil Red O staining. The results indicated that lusianthridin could inhibit TBARs formation, decrease REM, decrease oxidized lipid products, as well as preserve the level of cholesteryl arachidonate and cholesteryl linoleate. Moreover, He-oxLDL incubated with lusianthridin for 24 h can reduce the foam cell formation in RAW 264.7 macrophage cells. Taken together, lusianthridin could be a potential agent to be used to prevent atherosclerosis in thalassemia patients.

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Phagocytosis of lipase-aggregated low density lipoprotein promotes macrophage foam cell formation. Sequential morphological and biochemical events.

Arteriosclerosis and Thrombosis A Journal of Vascular Biology ◽

10.1161/01.atv.11.6.1643 ◽

1991 ◽

Vol 11 (6) ◽

pp. 1643-1651 ◽

Cited By ~ 37

Author(s):

J W Heinecke ◽

A G Suits ◽

M Aviram ◽

A Chait

Keyword(s):

Foam Cell ◽

Low Density Lipoprotein ◽

Cell Formation ◽

Density Lipoprotein ◽

Foam Cell Formation ◽

Low Density ◽

Macrophage Foam Cell

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Epac1 regulates cellular SUMOylation by promoting the formation of SUMO-activating nuclear condensates

10.1101/2022.01.12.476066 ◽

2022 ◽

Author(s):

Wenli Yang ◽

William G Robichaux ◽

Fang C Mei ◽

Wel Lin ◽

Li Li ◽

...

Keyword(s):

Molecular Mechanism ◽

Stress Responses ◽

Foam Cell ◽

Low Density Lipoprotein ◽

Cellular Stress ◽

Cell Formation ◽

Density Lipoprotein ◽

Foam Cell Formation ◽

Intracellular Camp ◽

Protein Sumoylation

Protein SUMOylation plays an essential role in maintaining cellular homeostasis when cells are under stress. However, precisely how SUMOylation is regulated, and a molecular mechanism linking cellular stress to SUMOylation remains elusive. Herein, we report that cAMP, a major stress-response second messenger, acts through Epac1 as a regulator of cellular SUMOylation. The Epac1-associated proteome is highly enriched with components of the SUMOylation pathway. Activation of Epac1 by intracellular cAMP triggers phase separation and the formation of nuclear condensates containing Epac1 and general components of the SUMOylation machinery to promote cellular SUMOylation. Furthermore, genetic knockout of Epac1 obliterates oxidized low-density lipoprotein induced cellular SUMOylation in macrophages, leading to suppression of foam cell formation. These results provide a direct nexus connecting two major cellular stress responses to define a molecular mechanism in which cAMP regulates the dynamics of cellular condensates to modulate protein SUMOylation.

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