High-mobility group box-1 protein activates inflammatory signaling pathway components and disrupts retinal vascular-barrier in the diabetic retina

Exp Eye Res. 2013 Feb;107:101-9. doi: 10.1016/j.exer.2012.12.009. Epub 2012 Dec 21.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Inflammatory Agents / pharmacology
  • Blood-Retinal Barrier / metabolism*
  • Blotting, Western
  • Diabetes Mellitus, Experimental / metabolism*
  • Diabetes Mellitus, Experimental / pathology
  • Diabetic Retinopathy / metabolism*
  • Diabetic Retinopathy / pathology
  • Electric Impedance
  • Endothelium, Vascular / metabolism
  • Enzyme-Linked Immunosorbent Assay
  • Glycyrrhizic Acid / pharmacology
  • HMGB1 Protein / antagonists & inhibitors
  • HMGB1 Protein / physiology*
  • Immunohistochemistry
  • Immunoprecipitation
  • Intercellular Adhesion Molecule-1 / metabolism
  • Intravitreal Injections
  • MAP Kinase Signaling System / physiology
  • Male
  • NF-kappa B / metabolism
  • Occludin / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptor for Advanced Glycation End Products
  • Receptors, Immunologic / metabolism
  • Signal Transduction / physiology*
  • Toll-Like Receptor 2 / metabolism

Substances

  • Anti-Inflammatory Agents
  • HMGB1 Protein
  • Hbp1 protein, rat
  • NF-kappa B
  • Occludin
  • Ocln protein, rat
  • Receptor for Advanced Glycation End Products
  • Receptors, Immunologic
  • Tlr2 protein, rat
  • Toll-Like Receptor 2
  • Intercellular Adhesion Molecule-1
  • Glycyrrhizic Acid