Proinflammatory phenotype of vascular smooth muscle cells: role of efficient Toll-like receptor 4 signaling.
Recent evidence supports a role of Toll-like receptor (TLR) signaling in the development of atherosclerotic lesions. In this study, we tested whether TLR4 signaling promotes a proinflammatory phenotype in human and mouse arterial smooth muscle cells (SMC), characterized by increased cytokine and chemokine synthesis and increased TLR expression. Human arterial SMC were found to express mRNA encoding TLR4 and the TLR4-associated molecules MD-2 and CD14 but not TLR2 mRNA. Mouse aortic SMC, on the other hand, expressed both TLR2 and TLR4 mRNA constitutively. Human SMC derived from the coronary artery, but not those from the pulmonary artery, were found to express cell surface-associated CD14. Low concentrations (ng/ml) of Escherichia coli LPS, the prototypical TLR4 agonist, markedly stimulated extracellular regulated kinase 1/2 (ERK1/2) activity, induced release of monocyte-chemoattractant protein-1 (MCP-1) and interleukin (IL)-6, and stimulated IL-1alpha expression in human aortic SMC, and exogenous CD14 enhanced these effects. Expression of a dominant negative form of TLR4 in human SMC attenuated LPS-induced ERK1/2 and MCP-1 release. LPS was a potent inducer of NF-kappaB activity, ERK1/2 phosphorylation, MCP-1 release, and TLR2 mRNA expression in wild-type mice but not in TLR4-signaling deficient mouse aortic SMC. These studies show that TLR4 signaling promotes a proinflammatory phenotype in vascular smooth muscle cells (VSMC) and suggest that VSMC may potentially play an active role in vascular inflammation via the release of chemokines, proinflammatory cytokines, and increased expression of TLR2.
Yang
Xin
X
Molecular Cardiology Research Institute and Department of Medicine, Tufts-New England Medical Ctr., Box 8486, 750 Washington St., Boston, MA 02111, USA.
Coriolan
Daniel
D
Murthy
Vanishree
V
Schultz
Kelly
K
Golenbock
Douglas T
DT
Beasley
Debbie
D
D000818:Animals; D000954:Antigens, Surface / Q000235:genetics; D001011:Aorta / Q000166:cytology; D002352:Carrier Proteins / Q000235:genetics; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D006801:Humans; D007375:Interleukin-1 / Q000096:biosynthesis; D015850:Interleukin-6 / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000235:genetics / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins / Q000235:genetics*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000235:genetics*; D015398:Signal Transduction / Q000276:immunology*; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014657:Vasculitis / Q000276:immunology / Q000503:physiopathology*
D000954:Antigens, Surface; C111835:CCL2 protein, human; D002352:Carrier Proteins; D018932:Chemokine CCL2; D007375:Interleukin-1; D015850:Interleukin-6; C495377:LY96 protein, human; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3