title: In vivo evidence for a role of toll-like receptor 4 in the development of intimal lesions.
abstract: BACKGROUND
  Inflammation plays an important role in atherogenesis. The toll-like receptor 4 (TLR4) is the receptor for bacterial lipopolysaccharides and also recognizes cellular fibronectin and heat shock protein 60, endogenous peptides that are produced in response to tissue injury. To explore a possible role for this receptor in arterial obstructive disease, we determined the expression of TLR4 in the atherosclerotic arterial wall, including adventitia, and studied the effect of adventitial TLR4 activation on neointima formation in a mouse model.
  
  
  RESULTS
  Localization of TLR4 was studied in human atherosclerotic coronary arteries by immunohistochemistry and detected in plaque and adventitia. In the adventitia, not all TLR4-positive cells colocalized with macrophages. In primary human adventitial fibroblasts, expression of TLR4 was demonstrated by immunofluorescence, Western blot, and reverse transcriptase-polymerase chain reaction. Adding lipopolysaccharide to these fibroblasts induced activation of NF-kappaB and an increase of mRNAs of various cytokines. The effect of adventitial stimulation of TLR4 was studied in a mouse model. A peri-adventitial cuff was placed around the femoral artery. Application of lipopolysaccharide between cuff and artery augmented neointima formation induced by the cuff (intimal area+/-SEM, 9134+/-1714 versus 2353+/-1076 microm(2), P<0.01). In TLR4-defective mice, application of cuff and lipopolysaccharide resulted in a smaller neointima than in wild-type mice (intimal area, 3859+/-904 microm(2), P=0.02 versus wild type).
  
  
  CONCLUSIONS
  A functional TLR4 is expressed in human adventitial fibroblasts and macrophages. Adventitial TLR4 activation augmented neointima formation in a mouse model. These results provide evidence for a link between the immune receptor TLR4 and intimal lesion formation.
authors.affiliation: Experimental Cardiology Laboratory, Heart Lung Center Utrecht, University Medical Center Utrecht, The Netherlands.
authors.forename: Aryan
authors.initials: A
authors.lastname: Vink
authors.forename: Arjan H
authors.initials: AH
authors.lastname: Schoneveld
authors.forename: Jelger J
authors.initials: JJ
authors.lastname: van der Meer
authors.forename: Ben J
authors.initials: BJ
authors.lastname: van Middelaar
authors.forename: Joost P G
authors.initials: JP
authors.lastname: Sluijter
authors.forename: Mirjam B
authors.initials: MB
authors.lastname: Smeets
authors.forename: Paul H A
authors.initials: PH
authors.lastname: Quax
authors.forename: Sai Kiang
authors.initials: SK
authors.lastname: Lim
authors.forename: Cornelius
authors.initials: C
authors.lastname: Borst
authors.forename: Gerard
authors.initials: G
authors.lastname: Pasterkamp
authors.forename: Dominique P V
authors.initials: DP
authors.lastname: de Kleijn
mesh_terms: D000818:Animals; D001161:Arteriosclerosis / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D003324:Coronary Artery Disease / Q000209:etiology / Q000378:metabolism; D003331:Coronary Vessels / Q000166:cytology / Q000378:metabolism; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics; D029721:Drosophila Proteins; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D017539:Tunica Intima / Q000166:cytology / Q000378:metabolism* / Q000473:pathology
chemical_list: D016207:Cytokines; D029721:Drosophila Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors