title: 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.
abstract: An early component of atherogenesis is abnormal vascular smooth muscle cell (VSMC) proliferation. The presence of Chlamydia pneumoniae in many atherosclerotic lesions raises the possibility that this organism plays a causal role in atherogenesis. In this study, C pneumoniae elementary bodies (EBs) rapidly activated p44/p42 mitogen-activated protein kinases (MAPKs) and stimulated proliferation of VSMCs in vitro. Exposure of VSMCs derived from human saphenous vein to C pneumoniae EBs (3x10(7) inclusion forming units/mL) enhanced bromodeoxyuridine (BrdU) incorporation 12+/-3-fold. UV- and heat-inactivated C pneumoniae EBs also stimulated VSMC proliferation, indicating a role of direct stimulation by chlamydial antigens. However, the mitogenic activity of C pneumoniae was heat-labile, thus excluding a role of lipopolysaccharide. Chlamydial hsp60 (25 microg/mL) replicated the effect of C pneumoniae, stimulating BrdU incorporation 7+/-3-fold. Exposure to C pneumoniae or chlamydial hsp60 rapidly activated p44/p42 MAPK, within 5 to 10 minutes of exposure. In addition, PD98059 and U0126, which are two distinct inhibitors of upstream MAPK kinase 1/2 (MEK1/2), abolished the mitogenic effect of C pneumoniae and chlamydial hsp60. Toll-like receptors (TLRs) act as sensors for microbial antigens and can signal via the p44/p42 MAPK pathway. Human VSMCs were shown to express TLR4 mRNA and protein, and a TLR4 antagonist abolished chlamydial hsp60-induced VSMC proliferation and attenuated C pneumoniae-induced MAPK activation and VSMC proliferation. Together these results indicate that C pneumoniae and chlamydial hsp60 are potent inducers of human VSMC proliferation and that these effects are mediated, at least in part, by rapid TLR4-mediated activation of p44/p42 MAPK.
authors.affiliation: Department of Medicine, New England Medical Center Hospitals and Tufts University School of Medicine, Boston Medical Center, Boston, Massachusetts, USA.
authors.forename: S
authors.initials: S
authors.lastname: Sasu
authors.forename: D
authors.initials: D
authors.lastname: LaVerda
authors.forename: N
authors.initials: N
authors.lastname: Qureshi
authors.forename: D T
authors.initials: DT
authors.lastname: Golenbock
authors.forename: D
authors.initials: D
authors.lastname: Beasley
mesh_terms: D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D001973:Bromodeoxyuridine; D002070:Butadienes / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D018834:Chaperonin 60 / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D023521:Chlamydophila Infections / Q000378:metabolism; D016993:Chlamydophila pneumoniae / Q000378:metabolism; D029721:Drosophila Proteins; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006358:Hot Temperature; D006801:Humans; D008050:Lipid A / Q000031:analogs & derivatives / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology; D009570:Nitriles / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012501:Saphenous Vein; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
chemical_list: D001426:Bacterial Proteins; D002070:Butadienes; D018834:Chaperonin 60; D029721:Drosophila Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D008050:Lipid A; D008562:Membrane Glycoproteins; D009570:Nitriles; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; C113580:U 0126; C049596:diphosphoryl lipid A; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D001973:Bromodeoxyuridine; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one