title: Hyperglycemia induces Toll-like receptor-2 and -4 expression and activity in human microvascular retinal endothelial cells: implications for diabetic retinopathy.
abstract: 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.
authors.affiliation: Laboratory for Atherosclerosis and Metabolic Research, Division of Endocrinology, Diabetes and Metabolism, Department of Pathology, University of California Davis Medical Center, Research Building 1, Room 3000, 4635 Second Avenue, Sacramento, CA 95817, USA.
authors.forename: Uthra
authors.initials: U
authors.lastname: Rajamani
authors.affiliation: Laboratory for Atherosclerosis and Metabolic Research, Division of Endocrinology, Diabetes and Metabolism, Department of Pathology, University of California Davis Medical Center, Research Building 1, Room 3000, 4635 Second Avenue, Sacramento, CA 95817, USA ; Veterans Affairs Medical Center, Mather, CA 95655, USA.
authors.forename: Ishwarlal
authors.identifier: 0000-0002-3255-2171
authors.initials: I
authors.lastname: Jialal
mesh_terms: D001786:Blood Glucose / Q000378:metabolism*; D002448:Cell Adhesion; D002478:Cells, Cultured; D018920:Coculture Techniques; D003930:Diabetic Retinopathy / Q000097:blood / Q000188:drug therapy / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D042783:Endothelial Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism; D007962:Leukocytes / Q000276:immunology / Q000378:metabolism; D055806:Microvessels / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012171:Retinal Vessels / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D015854:Up-Regulation
chemical_list: D001786:Blood Glucose; D018836:Inflammation Mediators; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D010455:Peptides; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4