title: Chlamydial heat shock protein 60 activates macrophages and endothelial cells through Toll-like receptor 4 and MD2 in a MyD88-dependent pathway.
abstract: Active inflammation and NF-kappaB activation contribute fundamentally to atherogenesis and plaque disruption. Accumulating evidence has implicated specific infectious agents including Chlamydia pneumoniae in the progression of atherogenesis. Chlamydial heat shock protein 60 (cHSP60) has been implicated in the induction of deleterious immune responses in human chlamydial infections and has been found to colocalize with infiltrating macrophages in atheroma lesions. cHSP60 might stimulate, enhance, and maintain innate immune and inflammatory responses and contribute to atherogenesis. In this study, we investigated the signaling mechanism of cHSP60. Recombinant cHSP60 rapidly activated NF-kappaB in human microvascular endothelial cells (EC) and in mouse macrophages, and induced human IL-8 promoter activity in EC. The inflammatory effect of cHSP60 was heat labile, thus excluding a role of contaminating LPS, and was blocked by specific anti-chlamydial HSP60 mAb. In human vascular EC which express Toll-like receptor 4 (TLR4) mRNA and protein, nonsignaling TLR4 constructs that act as dominant negative blocked cHSP60-mediated NF-kappaB activation. Furthermore, an anti-TLR4 Ab abolished cHSP60-induced cellular activation, whereas a control Ab had no effect. In 293 cells, cHSP60-mediated NF-kappaB activation required both TLR4 and MD2. A dominant-negative MyD88 construct also inhibited cHSP60-induced NF-kappaB activation. Collectively, our results indicate that cHSP60 is a potent inducer of vascular EC and macrophage inflammatory responses, which are very relevant to atherogenesis. The inflammatory effects are mediated through the innate immune receptor complex TLR4-MD2 and proceeds via the MyD88-dependent signaling pathway. These findings may help elucidate the mechanisms by which chronic asymptomatic chlamydial infection contribute to atherogenesis.
authors.affiliation: Division of Pediatric Critical Care, Steven Spielberg Pediatric Research Center Cedars-Sinai Medical Center, University of California-Los Angeles School of Medicine, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA.
authors.forename: Yonca
authors.initials: Y
authors.lastname: Bulut
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Faure
authors.forename: Lisa
authors.initials: L
authors.lastname: Thomas
authors.forename: Hisae
authors.initials: H
authors.lastname: Karahashi
authors.forename: Kathrin S
authors.initials: KS
authors.lastname: Michelsen
authors.forename: Ozlem
authors.initials: O
authors.lastname: Equils
authors.forename: Sandra G
authors.initials: SG
authors.lastname: Morrison
authors.forename: Richard P
authors.initials: RP
authors.lastname: Morrison
authors.forename: Moshe
authors.initials: M
authors.lastname: Arditi
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000943:Antigens, Differentiation / Q000502:physiology*; D000954:Antigens, Surface / Q000502:physiology*; D002460:Cell Line; D002461:Cell Line, Transformed; D018834:Chaperonin 60 / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D002692:Chlamydia trachomatis / Q000235:genetics / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D029721:Drosophila Proteins; D004340:Drug Contamination; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics; D051218:Lymphocyte Antigen 96; D008262:Macrophage Activation / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011956:Receptors, Cell Surface / Q000502:physiology*; D011971:Receptors, Immunologic / Q000502:physiology*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000494:pharmacology; D015398:Signal Transduction / Q000276:immunology*; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000943:Antigens, Differentiation; D000954:Antigens, Surface; D018834:Chaperonin 60; D029721:Drosophila Proteins; C495377:LY96 protein, human; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; C507779:MYD88 protein, human; D008562:Membrane Glycoproteins; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D011994:Recombinant Proteins; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D008156:Luciferases