Dominique P.V. de Kleijn, PhD
Laboratory of Experimental Cardiology, Vascular Biology
University Medical Center, Utrecht, The Netherlands
Toll-Like Receptor 4 and
VP Watch - August 21, 2002 - Volume 2, Issue 33
Toll-Like Receptor-4 Polymorhism and Atherogenesis
Kiechl et al., N. Eng. J. Med. 2002; 347:185-92
Asp299Gly Tlr-4 polymorphism attenuates receptor signaling
Attenuated Tlr-4 receptor signaling is
associated with decreased atherosclerosis
What is between Tlr-4 activation
Can animal models help us to identify a possible
Mouse models (I)
• Supporting: C3H mouse has a deficient Tlr-4
ApoE KO/C3H mouse gives less atherosclerotic
plaque compared to ApoE KO/B6 mouse. (Grimditch et al., 2000)
• Not supporting: C57Bl/10ScN has a deletion incl. the Tlr-4 gene
ApoE KO/ C57Bl/10ScN and ApoE KO/B6 do not differ in
arterial cholesterol levels. Plaque area not measured.
(Wright et al., 2000)
• Real Tlr-KO mouse models in comparable atherosclerotic
backgrounds are necessary to study Tlr-4 function in
Which cells express Tlr-4?
Bone marrow derived inflammatory cells like:
Role of Tlr-4 in bone marrow (BM) derived cells in
atherosclerotic mouse models (Shi et al., 2002; Van Eck et al., 2000)
Mouse models (I)
•Pointing to a major role of Tlr-4 in arterial wall cells
in primary human adventitial fibroblasts
Vink et al Circulation 2002 in press
Fibroblasts, Tlr-4 activation and
• LPS application in adventitia induces plaque formation in
hypercholesterolaemic rabbit model (Engelmann et al.
• Adventitial fibroblasts play a role in neointima formation
(Shi et al., 2000)
• LPS application stimulates migration of mouse embryonic
fibroblasts in in vitro assay (De Kleijn et al., 2002)
Mouse Femoral Cuff Model (III)
Gelatin ± LPS
Adventitial LPS Application
in Tlr-4 Deficient Balb/C
and wt Balb/C Mouse
Relative amount of neointima formation with and without LPS application in mouse cuff model
Balb/C Wildtype Balb/C Tlr-4 deficient
100 % 41 %
•Tlr-4 is involved in neointima formation
•Atherosclerosis might not be initiated only at the luminal
side but also at the advential side.
26 % 14 %
Vink et al., Circulation 2002 in press
as the soil for
Adventitial Tlr-4 activation
e.a. injury, infection, stress
e.a. shear stress, lipids, endothelial dysfunction and activation
? ? Direction of cell migration
Both luminal and adventitial side are important
Preclinical data pointed to a role of Tlr-4 in
Now, also clinical data show
that Tlr-4 is associated with atherosclerosis
(Kiechl et al., N. Eng. J. Med. 2002; 347:185- 92)
•What is the role of the adventitial endothelial cell?
•Does adventitial Tlr-4 activation affects the luminal endothelial cell?
•Is plaque matrix turn-over affected by Tlr-4 activation?
•Is plaque inflammation affected by Tlr-4 activation?
•Are their Tlr-4 antagonists?
•Can we use Tlr-4 as a (local) target of intervention?
•Should we target the adventitial layer?
de Kleijn DP, Smeets MB, Kemmeren PP, Lim SK, Van Middelaar BJ, Velema E, Schoneveld A,
Pasterkamp G, Borst C. Acute-phase protein haptoglobin is a cell migration factor involved in
arterial restructuring.FASEB J. 2002 Jul;16(9):1123-5.
Grimsditch DC, Penfold S, Latcham J, Vidgeon-Hart M, Groot PH, Benson GM.
C3H apoE(-/-) mice have less atherosclerosis than C57BL apoE(-/-) mice despite
having a more atherogenic serum lipid profile. Atherosclerosis. 2000 Aug;151(2):389-97.
Kiechl S, Lorenz E, Reindl M, Wiedermann CJ, Oberhollenzer F, Bonora E, Willeit J,
Schwartz DA. Toll-like receptor 4 polymorphisms and atherogenesis. N Engl J Med.
2002 Jul 18;347(3):185-92.
Li G, Chen SJ, Oparil S, et al. Direct in vivo evidence demonstrating neointimal migration of
adventitial fibroblasts after balloon injury of rat carotid arteries. Circulation 2000;101:1362-5.
Shi W, Wang X, Tangchitpiyanond K, Wong J, Shi Y, Lusis AJ. Atherosclerosis in
C3H/HeJ mice reconstituted with apolipoprotein E-null bone marrow. Arterioscler Thromb
Vasc Biol. 2002 Apr 1;22(4):650-5.
Van Eck M, Herijgers N, Vidgeon-Hart M, Pearce NJ, Hoogerbrugge PM, Groot PH,
Van Berkel TJ. Accelerated atherosclerosis in C57Bl/6 mice transplanted with Apo
E-deficient bone marrow. Atherosclerosis. 2000 May;150(1):71-80.
Vink A., Schoneveld, van der Meer J, Middelaar BJ. , Sluijter JPG, Smeets MB,
Quax PHA, Lim SK, Borst C, Pasterkamp G, De Kleijn, DPV. In Vivo Evidence
for a Role of Toll-like Receptor 4 in the Development of Intimal Lesions Circulation 2002 in press
Wright SD, Burton C, Hernandez M, Hassing H, Montenegro J, Mundt S, Patel S, Card DJ,
Hermanowski-Vosatka A, Bergstrom JD, Sparrow CP, Detmers PA, Chao YS. Infectious agents
are not necessary for murine atherogenesis. J Exp Med. 2000 Apr 17;191(8):1437-42.