Toll-like receptor 2 stimulation induces intimal hyperplasia and atherosclerotic lesion development.
BACKGROUND
Toll like receptors (Tlr) are essential in activation of the innate immune system. We recently described that peptidoglycan, an exogenous Tlr2 specific ligand, is present in human atherosclerotic plaques and associated with histological markers for plaque vulnerability. Also, endogenous Tlr2 ligands can be expressed in atherosclerotic tissues. Here, we determined whether Tlr2 stimulation promotes pro-inflammatory cytokine/chemokine production in vitro and augments neointima formation and development of atherosclerotic plaques in vivo.


RESULTS
We detected Tlr2 using Western blot and RT-PCR in human coronary arteries and primary adventitial fibroblasts. RNAse protection assay demonstrated significant induction of IL-1, IL-6, IL-8 and MCP-1 mRNA after Tlr2 stimulation in human adventitial fibroblasts in vitro. ELISA demonstrated induction of IL-6, IL-8 and MCP-1. In vivo application of Pam(3)Cys-SK(4), a synthetic Tlr2 ligand, on femoral arteries of C57BL/6 wild type (WT) mice using a peri-adventitial cuff, significantly enhanced neointima formation compared to control arteries. This increased inflammatory response was not observed in Tlr2 knockout (Tlr2-/-) mice. In ApoE knockout mice (ApoE-/-), application of the same Tlr2 ligand led to a significant increase in atherosclerotic plaque development.


CONCLUSIONS
Local arterial Tlr2 stimulation induced neointima and atherosclerotic plaque formation in mouse femoral arteries. Tlr2 stimulation may be an important mediator in arterial occlusive disease.
Schoneveld
A H
AH
Department of Cardiology, Experimental Cardiology Laboratory, UMC, Heidelberglaan 100, Room G02.523, 3584 CX Utrecht, The Netherlands.
Oude Nijhuis
M M
MM
van Middelaar
B
B
Laman
J D
JD
de Kleijn
D P V
DP
Pasterkamp
G
G
D000818:Animals; D001057:Apolipoproteins E / Q000235:genetics; D015153:Blotting, Western / Q000379:methods; D018932:Chemokine CCL2 / Q000032:analysis / Q000235:genetics; D003324:Coronary Artery Disease / Q000276:immunology*; D005347:Fibroblasts / Q000276:immunology; D006801:Humans; D007375:Interleukin-1 / Q000032:analysis / Q000235:genetics; D015850:Interleukin-6 / Q000032:analysis / Q000235:genetics; D016209:Interleukin-8 / Q000032:analysis / Q000235:genetics; D008024:Ligands; D008074:Lipoproteins / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009389:Neovascularization, Pathologic / Q000139:chemically induced; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; D017539:Tunica Intima / Q000187:drug effects* / Q000473:pathology
D001057:Apolipoproteins E; C111835:CCL2 protein, human; D018932:Chemokine CCL2; D007375:Interleukin-1; D015850:Interleukin-6; D016209:Interleukin-8; D008024:Ligands; D008074:Lipoproteins; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; C061108:N-palmitoyl-S-(2,3-bis(palmitoyloxy)propyl)cysteinyl-seryl-lysyl-lysyl-lysyl-lysine