Journal Article

The Role of TLR2 and 4-Mediated Inflammatory Pathways in Endothelial Cells Exposed to High Glucose

Panchapakesan, Usha, Wu, Huiling, Pollock, Carol, Ma, Jin, Mudaliar, Harshini, Chadban, Steven

2014

Overview

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.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Activation / Adhesion / Animals / Biology and Life Sciences / Cell adhesion / Cell adhesion molecules / Cell Line / Chemokines / Complications / Cytokines / Diabetes mellitus / Diabetes Mellitus, Experimental - genetics / Diabetes Mellitus, Experimental - immunology / Diabetes Mellitus, Experimental - pathology / Diabetics / Endothelial cells / Endothelial Cells - immunology / Endothelial Cells - pathology / Endothelium / Exposure / Gene Deletion / Glucose / Glucose - immunology / Health aspects / High mobility group proteins / HMGB1 protein / Humans / Hyperglycemia / Immune system / Inflammation / Inflammation - genetics / Inflammation - immunology / Inflammation - pathology / Inhibition / Intercellular adhesion molecule 1 / Intercellular Adhesion Molecule-1 - immunology / Interleukin / Interleukin 8 / Medicine and Health Sciences / Mice / Mice, Inbred BALB C / Microvasculature / Monocyte chemoattractant protein / Monocyte chemoattractant protein 1 / NF-κB protein / Pathways / Proteins / Receptors / Signal Transduction / Signaling / Streptozocin / Synthesis / TLR2 protein / TLR4 protein / Toll-Like Receptor 2 - genetics / Toll-Like Receptor 2 - immunology / Toll-Like Receptor 4 - genetics / Toll-Like Receptor 4 - immunology / Toll-like receptors / Vascular cell adhesion molecule 1