title: The role of TLR2 and 4-mediated inflammatory pathways in endothelial cells exposed to high glucose.
abstract: Postprandial hyperglycemia induces inflammation and endothelial dysfunction resulting in vascular complications in patients with diabetes. Toll-like receptors (TLRs) are central to the regulation of inflammatory responses through activation of nuclear factor-kappa B (NF-ĸB). This study examined the role of TLR2 and 4 in regulating inflammation and endothelial dysfunction when exposed to fluctuating glucose concentrations. HMEC-1 cells (a human microvascular endothelial cell line) were exposed to control (5 mM), 30 mM (high), fluctuating (5/30 mM) and 11.2 mM glucose (approximate glycaemic criteria for the diagnosis of diabetes mellitus) for 72 h. Cells were assessed for TLR2, 4, high mobility group box -1 (HMGB1), NF-ĸB, monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Fluctuating glucose concentrations maximally upregulated TLR4 but not TLR2 expression with increased NF-ĸB activation, IL-8 and ICAM-1 expression. HMGB1 was increased in the supernatants of cells exposed to 30 mM and 11.2 mM glucose compared to control. The addition of recombinant HMGB1 induced NF-ĸB activation and synthesis of proinflammatory cytokines and chemokines, which were prevented by TLR2 or 4 signalling inhibition. An additive effect when both TLR2 and 4 signalling pathways were inhibited was observed. However, only inhibition of TLR4 signalling suppressed the synthesis of MCP-1, IL-8 and ICAM-1. In vivo, streptozotocin-induced diabetic mice exhibited an increase in glomerular ICAM-1 which was not evident in TLR2(-/-) or TLR4(-/-) diabetic mice. Collectively, our results suggest that targeting the signalling pathway of TLR2 and 4 may be of therapeutic benefit in attenuating vascular inflammation in diabetic microangiopathy.
authors.affiliation: Renal Research Group, Kolling Institute of Medical Research, University of Sydney, Royal North Shore Hospital, St Leonards, New South Wales, Australia.
authors.forename: Harshini
authors.initials: H
authors.lastname: Mudaliar
authors.affiliation: Renal Research Group, Kolling Institute of Medical Research, University of Sydney, Royal North Shore Hospital, St Leonards, New South Wales, Australia.
authors.forename: Carol
authors.initials: C
authors.lastname: Pollock
authors.affiliation: Renal Medicine Royal Prince Alfred Hospital and Collaborative Transplant Research Group, University of Sydney, Camperdown, New South Wales, Australia.
authors.forename: Jin
authors.initials: J
authors.lastname: Ma
authors.affiliation: Renal Medicine Royal Prince Alfred Hospital and Collaborative Transplant Research Group, University of Sydney, Camperdown, New South Wales, Australia.
authors.forename: Huiling
authors.initials: H
authors.lastname: Wu
authors.affiliation: Renal Medicine Royal Prince Alfred Hospital and Collaborative Transplant Research Group, University of Sydney, Camperdown, New South Wales, Australia.
authors.forename: Steven
authors.initials: S
authors.lastname: Chadban
authors.affiliation: Renal Research Group, Kolling Institute of Medical Research, University of Sydney, Royal North Shore Hospital, St Leonards, New South Wales, Australia.
authors.forename: Usha
authors.initials: U
authors.lastname: Panchapakesan
mesh_terms: D000818:Animals; D002460:Cell Line; D003921:Diabetes Mellitus, Experimental / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D042783:Endothelial Cells / Q000276:immunology* / Q000473:pathology; D017353:Gene Deletion; D005947:Glucose / Q000276:immunology*; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000276:immunology / Q000473:pathology; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology; D008807:Mice, Inbred BALB C; D015398:Signal Transduction; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000276:immunology*
chemical_list: D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D018799:Intercellular Adhesion Molecule-1; D005947:Glucose