title: High-mobility group box-1 protein activates inflammatory signaling pathway components and disrupts retinal vascular-barrier in the diabetic retina.
abstract: Extracellular high-mobility group box-1 (HMGB-1) functions as a pro-inflammatory cytokine and exhibits angiogenic effects. The purpose of this study was to investigate the expression of HMGB-1 signaling pathway components in the retinas of diabetic rats and to examine the effect of intravitreal administration of HMGB-1 on the retinas of rats. The retinas of diabetic and intravitreally injected HMGB-1 rats were studied using immunohistochemistry, Western blotting, co-immunoprecipitation and enzyme-linked immunosorbent assay. The effect of HMGB-1 on retinal endothelial cell barrier function was evaluated using electrical cell-substrate impedance sensing system (ECIS). Diabetes induced significant upregulation of the expression of HMGB-1, receptor for advanced glycation end products (RAGE), ERK(1/2) and nuclear transcription factor Kappa B (NF-κB), whereas the expression of toll-like receptor 2 (TLR2) and occludin was significantly downregulated. Co-immunoprecipitation studies revealed significant increase in interaction between HMGB-1 and RAGE. HMGB-1 reduced transendothelial electrical resistance of bovine retinal endothelial cells. Intravitreal administration of HMGB-1 to normal rats induced significant upregulation of intercellular adhesion molecule-1 (ICAM-1), soluble intercellular adhesion molecule-1 (sICAM-1), HMGB-1, RAGE, ERK(1/2), and NF-κB, and significantly increased retinal vascular permeability, whereas the expression of TLR2 and occludin was downregulated. Oral administration of glycyrrhizin, a specific inhibitor of HMGB-1, attenuated diabetes-induced upregulation of HMGB-1 expression, NF-κB activation and downregulation of occludin expression. Our findings provide evidence that in the diabetic retina, HMGB-1 possibly interacts with RAGE and activates ERK(1/2) and NF-κB to generate an inflammatory response and disrupt retinal vascular barrier.
authors.affiliation: Department of Ophthalmology, College of Medicine, King Abdul Aziz University Hospital, King Saud University, P.O. Box 245, 11411 Riyadh, Saudi Arabia. mghulam@ksu.edu.sa
authors.forename: Ghulam
authors.initials: G
authors.lastname: Mohammad
authors.forename: Mohammad Mairaj
authors.initials: MM
authors.lastname: Siddiquei
authors.forename: Amira
authors.initials: A
authors.lastname: Othman
authors.forename: Mohamed
authors.initials: M
authors.lastname: Al-Shabrawey
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Abu El-Asrar
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D001813:Blood-Retinal Barrier / Q000378:metabolism*; D015153:Blotting, Western; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000473:pathology; D003930:Diabetic Retinopathy / Q000378:metabolism* / Q000473:pathology; D017097:Electric Impedance; D004730:Endothelium, Vascular / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D019695:Glycyrrhizic Acid / Q000494:pharmacology; D024243:HMGB1 Protein / Q000037:antagonists & inhibitors / Q000502:physiology*; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D058449:Intravitreal Injections; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D016328:NF-kappa B / Q000378:metabolism; D062793:Occludin / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051195:Toll-Like Receptor 2 / Q000378:metabolism
chemical_list: D000893:Anti-Inflammatory Agents; D024243:HMGB1 Protein; C104200:Hbp1 protein, rat; D016328:NF-kappa B; D062793:Occludin; C568987:Ocln protein, rat; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic; C495343:Tlr2 protein, rat; D051195:Toll-Like Receptor 2; D018799:Intercellular Adhesion Molecule-1; D019695:Glycyrrhizic Acid