Hyperglycemia Induces Toll-Like Receptor-2 and -4 Expression and Activity in Human Microvascular Retinal Endothelial Cells: Implications for Diabetic Retinopathy

• Published in: Journal of diabetes research 2014-01, Vol.2014 (2014), p.1-15
• Main Authors: Rajamani, Uthra, Jialal, Ishwarlal
• Format: Article
• Language: English
• Subjects: Blood Glucose - metabolism; Cell Adhesion; Cell adhesion & migration; Cells, Cultured; Chemokines; Coculture Techniques; Cytokines; Diabetes; Diabetic retinopathy; Diabetic Retinopathy - blood; Diabetic Retinopathy - drug therapy; Diabetic Retinopathy - genetics; Diabetic Retinopathy - immunology; Diabetic Retinopathy - metabolism; Endothelial Cells - drug effects; Endothelial Cells - immunology; Endothelial Cells - metabolism; Glucose; Humans; Hyperglycemia; Inflammation; Inflammation Mediators - metabolism; Kinases; Leukocytes - immunology; Leukocytes - metabolism; Microvessels - drug effects; Microvessels - immunology; Microvessels - metabolism; Myeloid Differentiation Factor 88 - metabolism; NF-kappa B - metabolism; Oxidative stress; Peptides - pharmacology; Proteins; Reactive oxygen species; Reactive Oxygen Species - metabolism; Retinal Vessels - drug effects; Retinal Vessels - immunology; Retinal Vessels - metabolism; RNA Interference; RNA, Messenger - metabolism; Toll-Like Receptor 2 - antagonists & inhibitors; Toll-Like Receptor 2 - genetics; Toll-Like Receptor 2 - metabolism; Toll-Like Receptor 4 - antagonists & inhibitors; Toll-Like Receptor 4 - genetics; Toll-Like Receptor 4 - metabolism; Transfection; Tumor necrosis factor-TNF; Up-Regulation
• ISSN: 2314-6745; 2314-6753
• DOI: 10.1155/2014/790902

Diabetic retinopathy (DR) causes visual impairment in working age adults and hyperglycemia-mediated inflammation is central in DR. Toll-like receptors (TLRs) play a key role in innate immune responses and inflammation. However, scanty data is available on their role in DR. Hence, in this study, we examined TLR2 and TLR4 mRNA and protein expression and activity in hyperglycemic human retinal endothelial cells (HMVRECs). HMVRECs were treated with hyperglycemia (HG) or euglycemia and mRNA and protein levels of TLR-2, TLR-4, MyD88, IRF3, and TRIF as well as NF-κB p65 activation were measured. IL-8, IL-1β, TNF-α and MCP-1, ICAM-1, and VCAM-1 as well as monocyte adhesion to HMVRECs were also assayed. HG (25 mM) significantly induced TLR2 and TLR4 mRNA and protein in HMVRECs. It also increased both MyD88 and non-MyD88 pathways, nuclear factor-κB (NF-κB), biomediators, and monocyte adhesion. This inflammation was attenuated by TLR-4 or TLR-2 inhibition, and dual inhibition by a TLR inhibitory peptide as well as TLR2 and 4 siRNA. Additionally, antioxidant treatment reduced TLR-2 and TLR4 expression and downstream inflammatory markers. Collectively, our novel data suggest that hyperglycemia induces TLR-2 and TLR-4 activation and downstream signaling mediating increased inflammation possibly via reactive oxygen species (ROS) and could contribute to DR.