TRIF is a regulator of TLR2-induced foam cell formation

  • Authors:
    • Bin Huang
    • Dae‑Weon Park
    • Suk‑Hwan Baek
  • View Affiliations

  • Published online on: August 19, 2016     https://doi.org/10.3892/mmr.2016.5647
  • Pages: 3329-3335
Metrics: Total Views: 0 (Spandidos Publications: | PMC Statistics: )
Total PDF Downloads: 0 (Spandidos Publications: | PMC Statistics: )


Abstract

The activation of toll-like receptor 2 (TLR2) stimulates foam cell formation, which is a key early event in the process of atherosclerosis. In the present study, the role of toll/interleukin-1 receptor-domain-containing adaptor-inducing interferon-β (TRIF) in TLR2-mediated foam cell formation was investigated, and the importance of monocyte chemoattractant protein‑1 (MCP‑1), tissue factor (TF) and lectin‑like oxidized low‑density lipoprotein receptor‑1 (Lox‑1) were examined. Treatment of Raw 264.7 cells with the TLR2 agonist. Pam3CSK4, increased the gene expression of TRIF in a time‑dependent manner (RT‑PCR). The induced gene expression of TRIF stimulated by TLR2 was not observed in TLR2‑knockout mice‑derived bone marrow‑derived macrophages (BMDMs). Pam3CSK4 increased the mRNA expression of TRIF in the wild‑type BMDMs, but not in the TLR2‑knockout BMDMs. Knockdown of the expression of TRIF using small interfering RNA decreased Pam3CSK4‑induced foam cell formation (combination of oil‑red O and hematoxylin staining), suggesting a role of TRIF. Stimulation of TLR2 increased the expression levels of various genes, which are known to control atherosclerosis, including MCP‑1, TF and Lox‑1. The knockdown of TRIF also attenuated the Pam3CSK4‑induced expression of these genes. In addition, a reduction in TRIF affected the Pam3CSK4‑induced protein expression of MCP‑1 (EIA). Taken together, the results of the present study suggested that TRIF regulated foam cell formation via regulation of the expression levels of MCP‑1, TF and Lox‑1.

Introduction

Atherosclerosis is a chronic inflammatory disorder in which metabolic and immune components interact to initiate and develop arterial lesions (1). Macrophages are the major immune cells in arterial lesions, which release various inflammatory cytokines and chemokines, are involved in foam cell formation and express pattern-recognition receptors, including, toll-like receptors (TLRs, which mediate innate and adaptive immune responses (2). There is substantial evidence that the stimulation of TLRs initiates and accelerates atherosclerosis (3). Of the TLRs involved in atherosclerosis, TLR2 and TLR4 have received the most investigation, and 11 and 13 of these receptors have been identified in humans and mice, respectively (4). However, the pathways that link TLRs with cytoplasmic adaptors, including toll/interleukin-1 receptor-domain-containing adaptor-inducing interferon-β (TRIF) in the process of atherosclerosis remain to be fully elucidated.

TLR signaling is controlled by four types of cytoplasmic adaptors, myeloid differentiation factor 88 (MyD88), TRIF, MyD88 adaptor-like (MAL) and TRIF-related adaptor molecule (TRAM). During TLR4 signaling, MyD88 and MAL are recruit for the first signaling pathway, leading to early nuclear factor-κB (NF-κB) activation and the induction of cytokine genes (5). By contrast, TRIF and TRAM are recruited for the second signaling pathway, which activates interferon regulatory factor (IRF)3, late NF-κB activation and induction of the interferon gene (6). Although TLR2 signaling also uses MyD88 and Mal in a similar manner to TLR4, the availability of TRIF remains to be elucidated. During TLR3 and TLR4 signaling, TRIF initiates a signaling pathway through TNF receptor associated factor (TRAF)3, TANK-binding kinase 1 and inhibitor of NF-κB-kinase complex, which mediates the direct phosphorylation of IRF3 and IRF7 (7).

Several studies have focused on the role of MyD88 in atherosclerosis. Inactivation of MyD88 leads to a reduction in atherosclerosis mediated by reduced macrophage recruitment to the artery wall, which is associated with reduced chemokine levels (8). Additionally, Michelsen et al showed that apolipoprotein E−/−MyD88−/− mice exhibit reduced aortic atherosclerosis and reduced macrophage accumulation (9). However, the role of TRIF in atherosclerosis remains to be fully elucidated, although a previous study by Lundberg et al demonstrated that the deletion of TRIF from myeloid cells was sufficient to attenuate vessel inflammation and protect against atherosclerosis (1). However, the role of TRIF in foam cell formation mediated by TLR2 stimulation remains to be fully elucidated.

Considering the significant importance of foam cell formation in TLR2 signaling, we aimed to determine whether TRIF is induced by TLR2 stimulation and whether TRIF is involved in foam cell formation in macrophages and if so, to determine the molecular mechanisms involved. Taken together, these results suggested the importance of TRIF in TLR2 mediated foam cell formation via inflammatory mediators, including MCP-1.

Materials and methods

Materials

Pam3CSK4 and the mouse TLR1-9 agonist kit was purchased from InvivoGen (San Diego, CA, USA). TRIzol and small interfering (si)RNA (TRIF) were purchased from Invitrogen; Thermo Fisher Scientific, Inc., Waltham, MA, USA).

Animals

A total of 20 male 6-week-old C57BL6 wild-type (WT) mice (average weight) were purchased from Central Lab Animal (South Korea). TLR2 deficient (average weight, C57BL6 background, 6 weeks, male) mice were kindly provided by Dr SJ Lee (Seoul National University, South Korea). For the experiments, a total of 20 mice were used. The mice were housed in standard conditions (temperature at 25±2°C, relative humidity (55±5%), 12/12 h light-dark cycle, and free access to food and water). The mice were sacrificed by cervical dislocation. The study was conducted in accordance with the guidelines and protocols approved by the Institutional Animal Care and Use Committee of Yeungnam University College of Medicine (Daegu, South Korea, permit number: YUMC-AEC2011-007).

Cell culture

Raw 264.7 cell lines were purchased from the American Type Culture Collection (Manassas, VA, USA) and grown in Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal bovine serum, penicillin (100 U/ml) and streptomycin (100 μg/ml; GE Healthcare Life Sciences, Logan, UT, USA) at 37°C in a humidified atmosphere of 5% CO2 and 95% O2. After euthanasia, the mice were sprayed with 70% ethanol and the femurs were dissected using scissors, cutting through the tibia below the knee joints, and through the pelvic bone close to the hip joint. Muscles connected to the bone were removed using clean gauze, and the femurs were placed into a polypropylene tube containing sterile phosphate-buffered saline (PBS) on ice. In a tissue culture hood, the bones were placed in 70% ethanol for 1 min, washed in sterile DMEM and then both epiphyses were removed using sterile scissors and forceps. The bones were flushed with a syringe filled with DMEM to extrude bone marrow into a 15 ml sterile polypropylene tube. A 5 ml plastic pipette was used to gently homogenize the bone marrow. Primary bone marrow-derived monocytes were differentiated into bone marrow-derived macrophages (BMDMs) by incubation in DMEM supplemented with 10% L929 cell (ATCC, Manassas, VA, USA)-conditioned medium, as a source of macrophage colony-stimulating factor, for 5–7 days at 37°C in a humidified atmosphere of 5% CO2 and 95% O2. The macrophages were cultured in 35 mm diameter plates (or 6-well plates) (5×105/1.5ml medium) and then treated with Pam3CSK4 (100 ng/ml) for 2–6 h.

Electroporation

The Raw 264.7 cells were cultured in 100 mm diameter dishes at 1×106 and grown overnight prior to electroporation using Amaxa Cel Line Nuclofector Kit V (VCA-1003, Lonza, Switzerland). Cell were harvested and a defined number of cells washed with PBS (2×106−4×106 cells per electroporation). The cells were pelleted by centrifugation (100 × g for 2 min) and resuspended in 100 μl of the electroporation solution provided with the kit. A total of 8 μl of the siRNA (150 pM) was added to the cell suspension and gently mixed. The cell-siRNA mix was transferred into the Amaxa electroporation cuvette, placed into the Nuclofector and electroporated as described by the manufacturer's instruction. Subsequently, 500 μl warm media was added to the cuvette, and the sample transfered to the plate and incubated at 37°C.

Reverse transcription-polymerase chain reaction (RT-PCR) and RT-quantitative PCR (RT-qPCR)

Total RNA was extracted from the cells using TRIzol reagent. First-strand cDNA was synthesized from 1 μg total RNA by employing random primers, oligo-dT and reverse transcriptase (Promega Corporation, Madison, WI, USA). The thermal cycling condition were as follows: 95°C for 5 min, 95°C for 1 min, 63°C for 1 min, and 72°C for 1 min, for 26–33 cycles, using a Bio-Rad C1000™ Thermal Cycler (Bio-Rad Laboratories, Inc., Hercules, CA, USA). A total of 10 μl of the final amplification product were electrophoresed on a 2% agarose gel containing SYBR® Safe DNA gel stain (Thermo Fisher Scientific, Inc.). The expression levels of TLR2, TRIF, MCP-1, LOX-1 and TF were normalized against the β-actin control and visualized using the Fuji Intelligent Dark Box LAS-3000 Image Reader (FujiFilm, Tokyo, Japan). Densitometric analysis was carried out using LAS-3000 Fujifilm Image Reader and Multi Gauge 3.0 software. The following primers were used for the RT-qPCR: TRIF, forward 5′-GTATGGGCCCTCTGACTGAT-3′ and reverse 5′-ATAGGTGTG GTCTTCCCTGC-3′; MCP-1, forward 5′-AGAGAGCCAGACGGGAGGAA-3′ and reverse 5′-GTCACACTGGTCACTCCTAC-3′; TF, forward 5′-CACTCATCATTGTGGGAGCAGTG-3′ and reverse 5′-CGCGACGGGGTGTTCTT-3′); Lox-1, orward 5′-AGGTCCTTGTCCACAAGACTGG-3′ and reverse 5′-ACGCCCCTGGTCTTAAAGAATTG-3′); and β-actin, forward 5′-TCCTTCGTTGCCGGTCCACA-3′ and reverse 5′-CGTCTCCGGACTCCATCACA-3′.

siRNA

Stealth control siRNA and gene-specific siRNA against the following target gene were designed using Block-IT Stealth RNAi designer (Invitrogen; Thermo Fisher Scientific, Inc.): TRIF, 5′-GGACAUACGUUACACUCCACCAACA-3′.

Oil-red O and hematoxylin staining for foam cell formation

For lipid uptake analysis, the macrophages were cultured in 6-well plates (5×105/well) and then treated with Pam3CSK4 (100 ng/ml) and low density lipoprotein LDL (50 μg/ml) for 24 h at 37°C in a humidified atmosphere of 5% CO2 and 95% O2. Prior to Oil-red O staining, the media were removed from the wells using a Pasteur pipette or by gently inverting the plate over a waste container, and then gently rinsing with phosphate-buffered saline. Subsequently, 10% formalin was added to each well for 1 h to fix the cells, following which each well was rinsed with distilled H2O. The wells were then rinsed with 60% isopropanol for 5 min, dried and stained with Oil-red O (Sigma-Aldrich, St. Louis, MO, USA) and hematoxylin. Intracellular lipid droplets were detected by light microscopy using a DIAPHOT 300 light microscope (Nikon Corporation, Tokyo, Japan). Images were captured with an AxioCam ICc I digital camera system (Carl Zeiss, Oberkochen, Germany).

Enzyme-linked immunosorbent assay (EIA)

The protein levels of MCP-1 in the cell culture supernatant were measured by EIA using a specific sandwich enzyme immunoassay (mouse CCL2/JE/MCP-1 DuoSet ELISA kit; DY479, R&D Systems, Inc., Minneapolis, MN, USA). Briefly, the cell culture supernatant was placed in a 96-well microtiter plate, which was coated with murine polyclonal antibody against mouse MCP-1. Following incubation at room temperature for 2 h and careful washes, HRP-conjugated polyclonal antibody against MCP-1 was added. Following incubation for 2 h at room temperature and repeated washes, color reagents were added. The optical density of each well was then measured at 450 nm using an EL800 universal microplate reader (Bio-Tek instruments, Inc., Winooski, VT, USA) using a 550 nm reference wavelength.

Statistical analysis

Results are expressed as the mean ± standard deviation of a minimum of 3 independent assays. Statistical significance was calculated by analysis of variance using GraphPad Prism software, version 5.01 (GraphPad. Inc., La Jolla, CA, USA). Groups were compared with two-way analysis of variance with a Bonferroni post-test. P<0.05 was considered to indicate a statistically significant difference.

Results

Gene expression of TRIF is induced by TLR activation

MyD88 and TRIF are well known adaptor proteins involved in TLR4 signaling, however, only MyD88 is involved in TLR2 signaling (10). The present study investigated whether the TLR2 agonist, Pam3CSK4, can induce the mRNA expression of TRIF in the Raw 264.7 macrophage cell line. The results revealed that Pam3CSK4 induced the mRNA expression of TRIF in a time-dependent manner (Fig. 1A). To demonstrate the general effect of TLRs on the expression of TRIF, other types of TLR agonist were assessed. All of the agonists examined (TLR1/2, TLR4, TLR5, TLR6/2 and TLR9) induced the gene expression of TRIF, with effects similar to those of the TLR2 agonist (Fig. 1B). These results suggested that the gene expression of TRIF by TLR agonists is a general characteristic shown in TLRs. Whether Pam3CSK4 affects the gene expression of TRIF was also determined in BMDMs. The gene expression of TRIF was induced by Pam3CSK4 in the BMDMs from the WT mice, however, its expression was not affected in the BMDMs from the TLR2-knockout mice (TLR2 KO; Fig. 1C).

TRIF is involved in TLR2-induced foam cell formation

Previous studies have suggested that TLRs is involved in the pathology of atherosclerosis (11,12). Among TLRs, TLR2 is also involved in the progression of atheroma. A previous study reported that TLR2 is a receptor for foam cell formation (13,14); therefore, the present study attempted to determine the role of TRIF in TLR2-mediated foam cell formation using the siRNA technique. Compared with the control siRNA-transfected cells, the TRIF-siRNA transfected cells showed decreased mRNA expression of TRIF. The TLR2-mediated foam cell formation also decreased in the TRIF siRNA-transfected cells, compared with the control cells (Fig. 2A and B). These results suggested that TRIF was an important adaptor for TLR2-mediated foam cell formation.

Inflammatory mediators are upregulated by TLR2 stimulation

TRIF is also likely to be important adaptor for TLR2-mediated foam cell formation. To identify genes associated with TRIF, the present study aimed to identify genes, which control foam cell formation. Chemokines are involved in the pathogenesis of atherosclerosis by promoting the directed migration of inflammatory cells. MCP-1 is a representative chemokine involved in foam cell formation (15). In the present study, treatment of the cells with Pam3CSK4 markedly increased the mRNA expression of MCP-1 in a time-dependent manner. TF is a major risk factor for atherosclerosis, and lectin-Lox-1 is also crucial in oxidized-LDL-mediated atherosclerosis (14,16). Therefore, the present study measured changes in the expression levels of these two genes following TLR2 stimulation. The expression levels of the two genes increased significantly, in a time-dependent manner, although the reaction time was marginally different for the expression of MCP-1 (Fig. 3A). The present study also confirmed whether these genes were dependent on TLR2 using KO mice-derived BMDMs. Whereas the expression levels of the genes were induced by Pam3CSK4 in the BMDMs from the WT mice, their expression levels remained unchanged in the BMDMs from the TLR2-knockout mice (Fig. 3B).

Expression levels of MCP-1, TF and Lox-1 are TRIF dependent

The present study used siRNA to confirm the role of TRIF in the expression of MCP-1, TF and Lox-1. The TRIF siRNA technique was found to be successful in downregulation its level of gene expression. With the downregulation in the level of TRIF, the gene expression levels of MCP-1, TF and Lox-1 were also markedly attenuated on examination of the Pam3CSK4-induced responses (Fig. 4A). To confirm the changes in MCP-1, the present study assessed the protein levels of MCP-1 using an EIA. Production of the MCP-1 protein increased ~3.5-fold in the supernatants of the control siRNA-transfected cells following TLR2 stimulation. However, the protein expression of MCP-1 was reduced to almost basal levels in the TRIF siRNA-transfected cells (Fig. 4B). These results suggested that TRIF was an important adaptor protein, which controlled foam cell formation via the production of MCP-1.

Discussion

The present study initially found that Pam3CSK4 treatment increased the gene expression of TRIF in macrophages, suggesting that TRIF contributed to TLR2 signaling. TLR2 has previously been shown to be regulated via a MyD88-dependent signaling pathway only. However, the present study found that the TRIF adaptor protein also appeared to be a regulator of TLR2-mediated foam cell formation. In addition, as TRIF controls the expression of MCP-1, TF and Lox-1, which are representative regulators of foam cell formation, the present study hypothesized that TRIF was also an important adaptor protein in TLR2-mediated foam cell formation, together with MyD88.

TLR signaling is divided into an MyD88-dependent pathway and an MyD88-independent signaling pathway (17). The MyD88-dependent signaling pathway is used by all TLRs, with the exception of TLR3. Signaling via the MyD88-dependent pathways leads to the activation of mitogen-activated protein kinase and the inhibitor of NF-κB (IκB) kinase complex, resulting in activation of activator protein (AP)-1 and NF-κB, respectively (18,19). By contrast, TLR3 is only present in the MyD88-independent pathway. TRIF is the predominant adaptor protein in the MyD88-independent pathway, and can associate with TRAF6 to activate AP-1 and NF-κB, as in the MyD88-dependent pathway. TRIF can also interact with TRAF3 and phosphoinositide 3-kinase, resulting in the activation of interferon regulatory factor (IRF)3 and IRF2, respectively (20,21). TLR4 uses MyD88 and TRIF as adaptor proteins (22,23).

Generally, TRIF is constantly expressed in macrophages to convey signals via the interaction with downstream proteins, inducing various functions through the activation of specific transcription factors. However, the results of the present study showed that TLR2 stimulation elevated the gene expression of TRIF itself. To date, few mechanisms have been shown to increase the gene expression levels of TRIF. In the present study, the gene expression levels of TRIF were upregulated by all the TLR agonists assessed, indicating that this may be a general observation in TLR signaling. Due to the TRIF antibody quality, the present study was only able to verify the increase in gene levels. Pam3CSK4 treatment increased the expression of TRIF, along with other inflammatory mediators, whereas the downregulation of TRIF by siRNA decreased foam cell formation and inflammatory mediators. Therefore, the changes in the levels of TRIF may be an essential factor stimulating foam cell formation. In addition, the downregulation of TRIF decreased the expression levels of MCP-1, TF and Lox-1, which regulate foam cell formation. These three genes are known to be important mediators involved in atherosclerosis through foam cell formation (1416).

MCP-1, which is also referred to as CCL2, is a small cytokine, which belongs to the CC chemokine family. MCP-1 is one of the key chemokines involved in the regulation of migration and infiltration of monocytes/macrophages (24,25). TF, which is the key initiator of the coagulation cascade, binds factor VIIa, resulting in activation of factor IX and factor X, ultimately leading to fibrin formation. TF is involved in the pathogenesis of atherosclerosis by promoting thrombus formation (26). Oxidized LDL is also crucial in the initiation and progression of atherosclerosis through a variety of mechanisms, including promoting foam cell generation and activating inflammatory processes (27). Lox-1, a type II membrane protein with a typical C-type lectin structure, has been identified as the predominant receptor for oxidized-LDL (28). Reported data have revealed that Lox-1 is important in atherosclerosis (16). On examination of these three factors, which are essential in atherosclerosis, their gene expression levels were reduced by TRIF knockdown, suggesting the presence of a direct association between TRIF and foam cell formation. Therefore, when the expression of TRIF is increased by TLR2 stimulation, inflammatory mediators, including MCP-1, produce and eventually promote the conversion of macrophages into foam cells. Therefore, the results of the present study showed that the reduction in expression levels of the above genes by TRIF knockdown was directly associated with foam cell formation.

The production of these three genes regulating foam cell formation is known to be regulated by the MyD88-dependent pathway in TLR signaling. However, the results of the present study showed that these three genes were regulated in a TLR2/TRIF-dependent manner. Associated reports have shown that the TLR4/TRIF pathway, in addition to the TLR4/MyD88 pathway, is also an important process (29). It was also previously reported that TRIF knockdown in differentiated neuronal cells decreases the expression of Lox-1 (30). TRIF-dependent pathways may be associated with TLR2 signaling, as it is with TLR-4 signaling. However, the role of the TRIF-dependent pathway in TLR2 signaling has received less investigation.

The results of the present study, which investigated macrophages from mice with TRIF knockdown, provided evidence supporting the connection between TRIF and TLR2 signaling in foam cell formation. The results of the present study indicated that Pam3CSK4 stimulated macrophage foam cell formation, and induced the expression levels of MCP-1, TF and Lox-1 in the context of an immune response to TLR2 via a TRIF-dependent pathway. In this regard, identification of TRIF as an important regulator of TLR2 signaling in macrophages may represent a possible therapeutic strategy for regulating inflammation and atherosclerosis.

Abbreviations:

TLR

toll-like receptor

MyD88

myeloid differentiation factor 88

NF-κB

nuclear factor-κB

IRF

interferon regulatory factor

MCP-1

monocyte chemoattractant protein-1

TRAF

tumor necrosis factor receptor-associated factor

BMDM

bone marrow-derived macrophage

siRNA

small interfering RNA

TF

tissue factor

Lox-1

lectin-like oxidized low-density lipoprotein receptor-1

LDL

low density lipoprotein

Acknowledgments

This study was supported by the 2013 Yeungnam University Research Grant (grant no. 213A061034).

References

1 

Lundberg AM, Ketelhuth DF, Johansson ME, Gerdes N, Liu S, Yamamoto M, Akira S and Hansson GK: Toll-like receptor 3 and 4 signalling through the TRIF and TRAM adaptors in haematopoietic cells promotes atherosclerosis. Cardiovasc Res. 99:364–373. 2013. View Article : Google Scholar : PubMed/NCBI

2 

Galkina E and Ley K: Immune and inflammatory mechanisms of atherosclerosis (*). Annu Rev Immunol. 27:165–197. 2009. View Article : Google Scholar

3 

Erridge C: The roles of toll-like receptors in atherosclerosis. J Innate Immun. 1:340–349. 2009. View Article : Google Scholar : PubMed/NCBI

4 

Akira S, Uematsu S and Takeuchi O: Pathogen recognition and innate immunity. Cell. 124:783–801. 2006. View Article : Google Scholar : PubMed/NCBI

5 

Verstrepen L, Bekaert T, Chau TL, Tavernier J, Chariot A and Beyaert R: TLR-4, IL-1R and TNF-R signaling to NF-kappaB: Variations on a common theme. Cell Mol Life Sci. 65:2964–2978. 2008. View Article : Google Scholar : PubMed/NCBI

6 

Mogensen TH: Pathogen recognition and inflammatory signaling in innate immune defenses. Clin Microbiol Rev. 22:240–273. 2009. View Article : Google Scholar : PubMed/NCBI

7 

Ahmed S, Maratha A, Butt AQ, Shevlin E and Miggin SM: TRIF-mediated TLR3 and TLR4 signaling is negatively regulated by ADAM15. J Immunol. 190:2217–2228. 2013. View Article : Google Scholar : PubMed/NCBI

8 

Falck-Hansen M, Kassiteridi C and Monaco C: Toll-like receptors in atherosclerosis. Int J Mol Sci. 14:14008–14023. 2013. View Article : Google Scholar : PubMed/NCBI

9 

Michelsen KS, Wong MH, Shah PK, Zhang W, Yano J, Doherty TM, Akira S, Rajavashisth TB and Arditi M: Lack of toll-like receptor 4 or myeloid differentiation factor 88 reduces atherosclerosis and alters plaque phenotype in mice deficient in apolipoprotein E. Proc Natl Acad Sci USA. 101:10679–10684. 2004. View Article : Google Scholar : PubMed/NCBI

10 

Newton K and Dixit VM: Signaling in innate immunity and inflammation. Cold Spring Harb Perspect Biol. 4:a0060492012. View Article : Google Scholar : PubMed/NCBI

11 

Curtiss LK and Tobias PS: Emerging role of toll-like receptors in atherosclerosis. J Lipid Res. 50(Suppl): S340–S345. 2009. View Article : Google Scholar :

12 

Mann DL: The emerging role of innate immunity in the heart and vascular system: For whom the cell tolls. Circ Res. 108:1133–1145. 2011. View Article : Google Scholar : PubMed/NCBI

13 

Keyel PA, Tkacheva OA, Larregina AT and Salter RD: Coordinate stimulation of macrophages by microparticles and TLR ligands induces foam cell formation. J Immunol. 189:4621–4629. 2012. View Article : Google Scholar : PubMed/NCBI

14 

Park DW, Lyu JH, Kim JS, Chin H, Bae YS and Baek SH: Role of JAK2-STAT3 in TLR2-mediated tissue factor expression. J Cell Biochem. 114:1315–1321. 2013. View Article : Google Scholar

15 

Park DW, Baek K, Kim JR, Lee JJ, Ryu SH, Chin BR and Baek SH: Resveratrol inhibits foam cell formation via NADPH oxidase 1-mediated reactive oxygen species and monocyte chemotactic protein-1. Exp Mol Med. 41:171–179. 2009. View Article : Google Scholar : PubMed/NCBI

16 

Lee JG, Lim EJ, Park DW, Lee SH, Kim JR and Baek SH: A combination of Lox-1 and Nox1 regulates TLR9-mediated foam cell formation. Cell Signal. 20:2266–2275. 2008. View Article : Google Scholar : PubMed/NCBI

17 

Mitchell D, Yong M, Schroder W, Black M, Tirrell M and Olive C: Dual stimulation of MyD88-dependent toll-like receptors induces synergistically enhanced production of inflammatory cytokines in murine bone marrow-derived dendritic cells. J Infect Dis. 202:318–329. 2010. View Article : Google Scholar : PubMed/NCBI

18 

Dauphinee SM and Karsan A: Lipopolysaccharide signaling in endothelial cells. Lab Invest. 86:9–22. 2006. View Article : Google Scholar

19 

Oeckinghaus A, Hayden MS and Ghosh S: Crosstalk in NF-κB signaling pathways. Nat Immunol. 12:695–708. 2011. View Article : Google Scholar : PubMed/NCBI

20 

Honda K and Taniguchi T: IRFs: Master regulators of signalling by toll-like receptors and cytosolic pattern-recognition receptors. Nat Rev Immunol. 6:644–658. 2006. View Article : Google Scholar : PubMed/NCBI

21 

Randall RE and Goodbourn S: Interferons and viruses: An interplay between induction, signalling, antiviral responses and virus countermeasures. J Gen Virol. 89:1–47. 2008. View Article : Google Scholar

22 

Guijarro-Muñoz I, Compte M, Álvarez-Cienfuegos A, Álvarez-Vallina L and Sanz L: Lipopolysaccharide activates toll-like receptor 4 (TLR4)-mediated NF-κB signaling pathway and proinflammatory response in human pericytes. J Biol Chem. 289:2457–2468. 2014. View Article : Google Scholar

23 

Weighardt H, Jusek G, Mages J, Lang R, Hoebe K, Beutler B and Holzmann B: Identification of a TLR4- and TRIF-dependent activation program of dendritic cells. Eur J Immunol. 34:558–564. 2004. View Article : Google Scholar : PubMed/NCBI

24 

Deshmane SL, Kremlev S, Amini S and Sawaya BE: Monocyte chemoattractant protein-1 (MCP-1): An overview. J Interferon Cytokine Res. 29:313–326. 2009. View Article : Google Scholar : PubMed/NCBI

25 

Kundu S, Roome T, Bhattacharjee A, Carnevale KA, Yakubenko VP, Zhang R, Hwang SH, Hammock BD and Cathcart MK: Metabolic products of soluble epoxide hydrolase are essential for monocyte chemotaxis to MCP-1 in vitro and in vivo. J Lipid Res. 54:436–447. 2013. View Article : Google Scholar :

26 

Steffel J, Luscher TF and Tanner FC: Tissue factor in cardiovascular diseases: Molecular mechanisms and clinical implications. Circulation. 113:722–731. 2006. View Article : Google Scholar : PubMed/NCBI

27 

Reiss AB and Cronstein BN: Regulation of foam cells by adenosine. Arterioscler Thromb Vasc Biol. 32:879–886. 2012. View Article : Google Scholar : PubMed/NCBI

28 

Murphy JE, Vohra RS, Dunn S, Holloway ZG, Monaco AP, Homer-Vanniasinkam S, Walker JH and Ponnambalam S: Oxidised LDL internalisation by the LOX-1 scavenger receptor is dependent on a novel cytoplasmic motif and is regulated by dynamin-2. J Cell Sci. 121:2136–2147. 2008. View Article : Google Scholar : PubMed/NCBI

29 

Xie H, Zhou H, Wang H, Chen D, Xia L, Wang T and Yan J: Anti-β(2)GPI/β(2)GPI induced TF and TNF-α expression in monocytes involving both TLR4/MyD88 and TLR4/TRIF signaling pathways. Mol Immunol. 53:246–254. 2013. View Article : Google Scholar

30 

Ding Z, Liu S, Wang X, Khaidakov M, Dai Y, Deng X, Fan Y, Xiang D and Mehta JL: Lectin-like ox-LDL receptor-1 (LOX-1)-toll-like receptor 4 (TLR4) interaction and autophagy in CATH.a differentiated cells exposed to angiotensin II. Mol Neurobiol. 51:623–632. 2015. View Article : Google Scholar

Related Articles

Journal Cover

October-2016
Volume 14 Issue 4

Print ISSN: 1791-2997
Online ISSN:1791-3004

Sign up for eToc alerts

Recommend to Library

Copy and paste a formatted citation
x
Spandidos Publications style
Huang B, Park DW and Baek SH: TRIF is a regulator of TLR2-induced foam cell formation. Mol Med Rep 14: 3329-3335, 2016
APA
Huang, B., Park, D., & Baek, S. (2016). TRIF is a regulator of TLR2-induced foam cell formation. Molecular Medicine Reports, 14, 3329-3335. https://doi.org/10.3892/mmr.2016.5647
MLA
Huang, B., Park, D., Baek, S."TRIF is a regulator of TLR2-induced foam cell formation". Molecular Medicine Reports 14.4 (2016): 3329-3335.
Chicago
Huang, B., Park, D., Baek, S."TRIF is a regulator of TLR2-induced foam cell formation". Molecular Medicine Reports 14, no. 4 (2016): 3329-3335. https://doi.org/10.3892/mmr.2016.5647