Skip to main content

Advertisement

SpringerLink
Log in

The critical role of ABCG1 and PPARγ/LXRα signaling in TLR4 mediates inflammatory responses and lipid accumulation in vascular smooth muscle cells

  • Regular Article
  • Published:
Cell and Tissue Research Aims and scope Submit manuscript

Abstract

Toll-like receptor 4 (TLR4) plays critical roles in vascular inflammation, lipid accumulation and atherosclerosis development. However, the mechanisms underlying these processes are still not well established, especially in vascular smooth muscle cells (VSMCs). ATP-binding cassette transporter G1 (ABCG1) is one of the key genes mediating inflammation and cellular lipid accumulation. The function of TLR4 in regulating the expression of ABCG1 and the underlying molecular mechanisms remain to be elucidated. In this study, we cultured VSMCs from the thoracic aortas of mice and treated the cells with 50 μg/ml oxidized low-density lipoprotein (oxLDL) to activate TLR4 signaling. We observed that activating TLR4 with oxLDL induced inflammatory responses and lipid accumulation in VSMCs. The expression of peroxisome proliferator-activated receptor gamma (PPARγ), liver X receptor alpha (LXRα) and ABCG1 was inhibited by TLR4 activation. However, these effects could be reversed by knocking out TLR4. PPARγ activation by rosiglitazone rescued LXRα and ABCG1 expression and reduced TLR4-induced inflammation and lipid accumulation. Silencing PPARγ expression with a specific small interfering RNA (siRNA) inhibited LXRα and ABCG1 expression and, importantly, enhanced TLR4-induced inflammation and lipid accumulation. In conclusion, ABCG1 expression was down-regulated by TLR4, which induces inflammation and lipid accumulation in VSMCs via PPARγ/LXRα signaling. These findings indicate a novel molecular mechanism underlying TLR4-induced inflammation and lipid accumulation.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6

Similar content being viewed by others

Abbreviations

ABCG1:

ATP-binding cassette transporter G1

LXRα:

Liver X receptor alpha

oxLDL:

Oxidized low-density lipoprotein

PPARγ:

Peroxisome proliferator-activated receptor gamma

RSG:

Rosiglitazone

TLR4:

Toll-like receptor 4

VSMCs:

Vascular smooth muscle cells

References

  • Akiyama TE, Sakai S, Lambert G, Nicol CJ, Matsusue K, Pimprale S, Lee YH, Ricote M, Glass CK, Brewer HB Jr, Gonzalez FJ (2002) Conditional disruption of the peroxisome proliferator-activated receptor gamma gene in mice results in lowered expression of ABCA1, ABCG1, and apoE in macrophages and reduced cholesterol efflux. Mol Cell Biol 22:2607–2619

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  • Allahverdian S, Pannu PS, Francis GA (2012) Contribution of monocyte-derived macrophages and smooth muscle cells to arterial foam cell formation. Cardiovasc Res 95:165–172

    Article  CAS  PubMed  Google Scholar 

  • Bo QL, Chen YH, Yu Z, Fu L, Zhou Y, Zhang GB, Wang H, Zhang ZH, Xu DX (2016) Rosiglitazone pretreatment protects against lipopolysaccharide-induced fetal demise through inhibiting placental inflammation. Mol Cell Endocrinol 423:51–59

    Article  CAS  PubMed  Google Scholar 

  • Broad A, Kirby JA, Jones DE (2007) Toll-like receptor interactions: tolerance of MyD88-dependent cytokines but enhancement of MyD88-independent interferon-beta production. Immunology 120:103–111

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  • Bujold K, Rhainds D, Jossart C, Febbraio M, Marleau S, Ong H (2009) CD36-mediated cholesterol efflux is associated with PPARgamma activation via a MAPK-dependent COX-2 pathway in macrophages. Cardiovasc Res 83:457–464

    Article  CAS  PubMed  Google Scholar 

  • Chavez-Sanchez L, Madrid-Miller A, Chavez-Rueda K, Legorreta-Haquet MV, Tesoro-Cruz E, Blanco-Favela F (2010) Activation of TLR2 and TLR4 by minimally modified low-density lipoprotein in human macrophages and monocytes triggers the inflammatory response. Hum Immunol 71:737–744

    Article  CAS  PubMed  Google Scholar 

  • Chawla A, Barak Y, Nagy L, Liao D, Tontonoz P, Evans RM (2001a) PPAR-gamma dependent and independent effects on macrophage-gene expression in lipid metabolism and inflammation. Nat Med 7:48–52

    Article  CAS  PubMed  Google Scholar 

  • Chawla A, Boisvert WA, Lee CH, Laffitte BA, Barak Y, Joseph SB, Liao D, Nagy L, Edwards PA, Curtiss LK, Evans RM, Tontonoz P (2001b) A PPAR gamma-LXR-ABCA1 pathway in macrophages is involved in cholesterol efflux and atherogenesis. Mol Cell 7:161–171

    Article  CAS  PubMed  Google Scholar 

  • Chen W, Lin YJ, Zhou XY, Chen H, Jin Y (2016) Rosiglitazone protects rat liver against acute liver injury associated with the NF-kappaB signaling pathway. Can J Physiol Pharmacol 94:28–34

    Article  CAS  PubMed  Google Scholar 

  • Collins T, Read MA, Neish AS, Whitley MZ, Thanos D, Maniatis T (1995) Transcriptional regulation of endothelial cell adhesion molecules: NF-kappa B and cytokine-inducible enhancers. FASEB J 9:899–909

    CAS  PubMed  Google Scholar 

  • Dubuquoy L, Jansson EA, Deeb S, Rakotobe S, Karoui M, Colombel JF, Auwerx J, Pettersson S, Desreumaux P (2003) Impaired expression of peroxisome proliferator-activated receptor gamma in ulcerative colitis. Gastroenterology 124:1265–1276

    Article  CAS  PubMed  Google Scholar 

  • Edfeldt K, Swedenborg J, Hansson GK, Yan ZQ (2002) Expression of toll-like receptors in human atherosclerotic lesions: a possible pathway for plaque activation. Circulation 105:1158–1161

    CAS  PubMed  Google Scholar 

  • Higashimori M, Tatro JB, Moore KJ, Mendelsohn ME, Galper JB, Beasley D (2011) Role of toll-like receptor 4 in intimal foam cell accumulation in apolipoprotein E-deficient mice. Arterioscler Thromb Vasc Biol 31:50–57

    Article  CAS  PubMed  Google Scholar 

  • Huang Q, Pope RM (2010) Toll-like receptor signaling: a potential link among rheumatoid arthritis, systemic lupus, and atherosclerosis. J Leukoc Biol 88:253–262

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  • Ji Y, Wang Z, Li Z, Liu J (2010) Modulation of LPS-mediated inflammation by fenofibrate via the TRIF-dependent TLR4 signaling pathway in vascular smooth muscle cells. Cell Physiol Biochem 25:631–640

    Article  CAS  PubMed  Google Scholar 

  • Jia SJ, Niu PP, Cong JZ, Zhang BK, Zhao M (2014) TLR4 signaling: a potential therapeutic target in ischemic coronary artery disease. Int Immunopharmacol 23:54–59

    Article  CAS  PubMed  Google Scholar 

  • Jiang C, Ting AT, Seed B (1998) PPAR-gamma agonists inhibit production of monocyte inflammatory cytokines. Nature 391:82–86

    Article  CAS  PubMed  Google Scholar 

  • Johnson JL (2014) Emerging regulators of vascular smooth muscle cell function in the development and progression of atherosclerosis. Cardiovasc Res 103:452–460

    Article  CAS  PubMed  Google Scholar 

  • Kennedy MA, Barrera GC, Nakamura K, Baldan A, Tarr P, Fishbein MC, Frank J, Francone OL, Edwards PA (2005) ABCG1 has a critical role in mediating cholesterol efflux to HDL and preventing cellular lipid accumulation. Cell Metab 1:121–131

    Article  CAS  PubMed  Google Scholar 

  • Kuo MY, Ou HC, Lee WJ, Kuo WW, Hwang LL, Song TY, Huang CY, Chiu TH, Tsai KL, Tsai CS, Sheu WH (2011) Ellagic acid inhibits oxidized low-density lipoprotein (OxLDL)-induced metalloproteinase (MMP) expression by modulating the protein kinase C-alpha/extracellular signal-regulated kinase/peroxisome proliferator-activated receptor gamma/nuclear factor-kappaB (PKC-alpha/ERK/PPAR-gamma/NF-kappaB) signaling pathway in endothelial cells. J Agric Food Chem 59:5100–5108

    Article  CAS  PubMed  Google Scholar 

  • Li AC, Binder CJ, Gutierrez A, Brown KK, Plotkin CR, Pattison JW, Valledor AF, Davis RA, Willson TM, Witztum JL, Palinski W, Glass CK (2004) Differential inhibition of macrophage foam-cell formation and atherosclerosis in mice by PPARalpha, beta/delta, and gamma. J Clin Invest 114:1564–1576

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  • McMurray HF, Parrott DP, Bowyer DE (1991) A standardised method of culturing aortic explants, suitable for the study of factors affecting the phenotypic modulation, migration and proliferation of aortic smooth muscle cells. Atherosclerosis 86:227–237

    Article  CAS  PubMed  Google Scholar 

  • Michelsen KS, Wong MH, Shah PK, Zhang W, Yano J, Doherty TM, Akira S, Rajavashisth TB, Arditi M (2004) 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 U S A 101:10679–10684

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  • Moghimpour Bijani F, Vallejo JG, Rezaei N (2012) Toll-like receptor signaling pathways in cardiovascular diseases: challenges and opportunities. Int Rev Immunol 31:379–395

    Article  CAS  PubMed  Google Scholar 

  • Necela BM, Su W, Thompson EA (2008) Toll-like receptor 4 mediates cross-talk between peroxisome proliferator-activated receptor gamma and nuclear factor-kappaB in macrophages. Immunology 125:344–358

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  • Park Y, Pham TX, Lee J (2012) Lipopolysaccharide represses the expression of ATP-binding cassette transporter G1 and scavenger receptor class B, type I in murine macrophages. Inflamm Res 61:465–472

    Article  CAS  PubMed  Google Scholar 

  • Raines EW, Ferri N (2005) Thematic review series: the immune system and atherogenesis. Cytokines affecting endothelial and smooth muscle cells in vascular disease. J Lipid Res 46:1081–1092

    Article  CAS  PubMed  Google Scholar 

  • Rong JX, Shapiro M, Trogan E, Fisher EA (2003) Transdifferentiation of mouse aortic smooth muscle cells to a macrophage-like state after cholesterol loading. Proc Natl Acad Sci U S A 100:13531–13536

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  • Sabol SL, Brewer HB Jr, Santamarina-Fojo S (2005) The human ABCG1 gene: identification of LXR response elements that modulate expression in macrophages and liver. J Lipid Res 46:2151–2167

    Article  CAS  PubMed  Google Scholar 

  • Sasu S, LaVerda D, Qureshi N, Golenbock DT, Beasley D (2001) Chlamydia pneumoniae and chlamydial heat shock protein 60 stimulate proliferation of human vascular smooth muscle cells via toll-like receptor 4 and p44/p42 mitogen-activated protein kinase activation. Circ Res 89:244–250

    Article  CAS  PubMed  Google Scholar 

  • Thieringer R, Fenyk-Melody JE, Le Grand CB, Shelton BA, Detmers PA, Somers EP, Carbin L, Moller DE, Wright SD, Berger J (2000) Activation of peroxisome proliferator-activated receptor gamma does not inhibit IL-6 or TNF-alpha responses of macrophages to lipopolysaccharide in vitro or in vivo. J Immunol 164:1046–1054

    Article  CAS  PubMed  Google Scholar 

  • Thomassen MJ, Barna BP, Malur AG, Bonfield TL, Farver CF, Malur A, Dalrymple H, Kavuru MS, Febbraio M (2007) ABCG1 is deficient in alveolar macrophages of GM-CSF knockout mice and patients with pulmonary alveolar proteinosis. J Lipid Res 48:2762–2768

    Article  CAS  PubMed  Google Scholar 

  • Torocsik D, Barath M, Benko S, Szeles L, Dezso B, Poliska S, Hegyi Z, Homolya L, Szatmari I, Lanyi A, Nagy L (2010) Activation of liver X receptor sensitizes human dendritic cells to inflammatory stimuli. J Immunol 184:5456–5465

    Article  PubMed  Google Scholar 

  • Xu XH, Shah PK, Faure E, Equils O, Thomas L, Fishbein MC, Luthringer D, Xu XP, Rajavashisth TB, Yano J, Kaul S, Arditi M (2001) Toll-like receptor-4 is expressed by macrophages in murine and human lipid-rich atherosclerotic plaques and upregulated by oxidized LDL. Circulation 104:3103–3108

    Article  CAS  PubMed  Google Scholar 

  • Yang X, Coriolan D, Murthy V, Schultz K, Golenbock DT, Beasley D (2005) Proinflammatory phenotype of vascular smooth muscle cells: role of efficient Toll-like receptor 4 signaling. Am J Physiol Heart Circ Physiol 289:H1069–H1076

    Article  CAS  PubMed  Google Scholar 

  • Yang K, Zhang XJ, Cao LJ, Liu XH, Liu ZH, Wang XQ, Chen QJ, Lu L, Shen WF, Liu Y (2014) Toll-like receptor 4 mediates inflammatory cytokine secretion in smooth muscle cells induced by oxidized low-density lipoprotein. PLoS ONE 9, e95935

    Article  PubMed  PubMed Central  Google Scholar 

  • Yin YW, Liao SQ, Zhang MJ, Liu Y, Li BH, Zhou Y, Chen L, Gao CY, Li JC, Zhang LL (2015) TLR4-mediated inflammation promotes foam cell formation of vascular smooth muscle cell by upregulating ACAT1 expression. Cell Death Dis 6:1659

    Article  PubMed  PubMed Central  Google Scholar 

  • Yvan-Charvet L, Wang N, Tall AR (2010) Role of HDL, ABCA1, and ABCG1 transporters in cholesterol efflux and immune responses. Arterioscler Thromb Vasc Biol 30:139–143

    Article  CAS  PubMed  Google Scholar 

  • Zhang JY, Liu B, Wang YN, Zhang WN, Wang FJ (2014) Effect of rosuvastatin on OX40L and PPAR-gamma expression in human umbilical vein endothelial cells and atherosclerotic cerebral infarction patients. J Mol Neurosci 52:261–268

    Article  CAS  PubMed  Google Scholar 

Download references

Acknowledgments

The authors would like to thank Jianhong Mi, Yang Liu and Fangfang Li for their experimental support.

Author information

Authors and Affiliations

  1. Department of Neurology, Institute of Surgery Research, Daping Hospital, Third Military Medical University, NO.10 Changjiang Branch Road, Yuzhong District, Chongqing, 400042, People’s Republic of China

    Xiaojie Cao, Lili Zhang, Lu Guo, Binghu Li, Yan Pi, Chunyan Long & Jingcheng Li

  2. Department of Neurology, Chengdu Military General Hospital, Chengdu, People’s Republic of China

    Xiaojie Cao & Qingsong Wang

  3. Department of Occupational Health, Faculty of Preventive Medicine, Third Military Medical University, NO.30 Gaotanyan Street, Shapingba District, Chongqing, 400038, People’s Republic of China

    Chunhai Chen, Qinlong Ma, Ping Deng, Gang Zhu, Lei Zhang, Zhengping Yu & Zhou Zhou

Authors
  1. Xiaojie Cao
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Lili Zhang
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Chunhai Chen
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Qingsong Wang
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Lu Guo
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Qinlong Ma
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Ping Deng
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. Gang Zhu
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. Binghu Li
    View author publications

    You can also search for this author in PubMed Google Scholar

  10. Yan Pi
    View author publications

    You can also search for this author in PubMed Google Scholar

  11. Chunyan Long
    View author publications

    You can also search for this author in PubMed Google Scholar

  12. Lei Zhang
    View author publications

    You can also search for this author in PubMed Google Scholar

  13. Zhengping Yu
    View author publications

    You can also search for this author in PubMed Google Scholar

  14. Zhou Zhou
    View author publications

    You can also search for this author in PubMed Google Scholar

  15. Jingcheng Li
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding authors

Correspondence to Zhou Zhou or Jingcheng Li.

Ethics declarations

Funding

This study was funded by the National Natural Science Foundation of China (number 81271282, 81400967) and the Natural Science Foundation Project of CQ CSTC (CSTC2012JJJQ10003).

Conflict of interest

None declared.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary Table S1

(DOC 34 kb)

Supplementary Figure 1

Identification of mice and primary VSMCs. a PCR identification of TLR4 KO mice. The 390-bp PCR products represent the WT TLR4 genotype, the 140-bp PCR products represent the mutant TLR4 genotype and both the 390-bp and 140-bp PCR products represent the heterozygous TLR4 genotype. b The first generation of cells came from thoracic aorta pieces cultured for 8 days and observed under an ordinary light microscope. Scale bar 200 μm. c Primary VSMC identification. Immunofluorescence images show the expression of α-SMA (green) and SM-22α (red) in VSMCs. Representative pictures of three independent experiments are shown. Scale bar 50 μm. (GIF 670 kb)

High Resolution (TIF 16481 kb)

Supplementary Figure 2

OxLDL stimulated TLR4 expression and promoted inflammatory responses, reversed by TLR4 deaficiency. a The images show TLR4 mRNA levels, which were normalized to β-actin mRNA levels (n = 3). b Representative immunoblotting and statistics data revealed the TLR4 protein expression in WT VSMCs (n = 3). The mRNA levels of TNF-α, IL-6, MCP-1 and VCAM-1 were detected via real-time PCR (c, n = 4). The data are represented as the fold change relative to the control and are presented as the mean ± SEM. *P < 0.05, **P < 0.01 compared with the untreated control group. (GIF 134 kb)

High Resolution (TIF 1818 kb)

Supplementary Figure 3

PPARγ-siRNA silencing efficiency. a The images show PPARγ mRNA levels, which were normalized to β-actin mRNA levels (n = 3). b Representative immunoblotting and statistics data revealed PPARγ expression in WT VSMCs (n = 3). The data are represented as the fold change relative to the control and are presented as the mean ± SEM. *P < 0.05, **P < 0.01 compared with the untreated control group. (GIF 46 kb)

High Resolution (TIF 1310 kb)

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Cao, X., Zhang, L., Chen, C. et al. The critical role of ABCG1 and PPARγ/LXRα signaling in TLR4 mediates inflammatory responses and lipid accumulation in vascular smooth muscle cells. Cell Tissue Res 368, 145–157 (2017). https://doi.org/10.1007/s00441-016-2518-3

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00441-016-2518-3

Keywords

Search

Navigation