The role of advanced glycation end products in retinal microvascular leukostasis.

Abstract

PURPOSE:

A critical event in the pathogenesis of diabetic retinopathy is the inappropriate adherence of leukocytes to the retinal capillaries. Advanced glycation end-products (AGEs) are known to play a role in chronic inflammatory processes, and the authors postulated that these adducts may play a role in promoting pathogenic increases in proinflammatory pathways within the retinal microvasculature.

METHODS:

Retinal microvascular endothelial cells (RMECs) were treated with glycoaldehyde-modified albumin (AGE-Alb) or unmodified albumin (Alb). NFkappaB DNA binding was measured by electromobility shift assay (EMSA) and quantified with an ELISA: In addition, the effect of AGEs on leukocyte adhesion to endothelial cell monolayers was investigated. Further studies were performed in an attempt to confirm that this was AGE-induced adhesion by co-incubation of AGE-treated cells with soluble receptor for AGE (sRAGE). Parallel in vivo studies of nondiabetic mice assessed the effect of intraperitoneal delivery of AGE-Alb on ICAM-1 mRNA expression, NFkappaB DNA-binding activity, leukostasis, and blood-retinal barrier breakdown.

RESULTS:

Treatment with AGE-Alb significantly enhanced the DNA-binding activity of NFkappaB (P = 0.0045) in retinal endothelial cells (RMECs) and increased the adhesion of leukocytes to RMEC monolayers (P = 0.04). The latter was significantly reduced by co-incubation with sRAGE (P < 0.01). Mice infused with AGE-Alb demonstrated a 1.8-fold increase in ICAM-1 mRNA when compared with control animals (P < 0.001, n = 20) as early as 48 hours, and this response remained for 7 days of treatment. Quantification of retinal NFkappaB demonstrated a threefold increase with AGE-Alb infusion in comparison to control levels (AGE Alb versus Alb, 0.23 vs. 0.076, P < 0.001, n = 10 mice). AGE-Alb treatment of mice also caused a significant increase in leukostasis in the retina (AGE-Alb versus Alb, 6.89 vs. 2.53, n = 12, P < 0.05) and a statistically significant increase in breakdown of the blood-retinal barrier (AGE Alb versus Alb, 8.2 vs. 1.6 n = 10, P < 0.001).

CONCLUSIONS:

AGEs caused upregulation of NFkappaB in the retinal microvascular endothelium and an AGE-specific increase in leukocyte adhesion in vitro was also observed. In addition, increased leukocyte adherence in vivo was demonstrated that was accompanied by blood-retinal barrier dysfunction. These findings add further evidence to the thinking that AGEs may play an important role in the pathogenesis of diabetic retinopathy.

• Authors: Tara C B Moore, Jonathan E Moore, Yuichi Kaji, Norma Frizzell, Tomohiko Usui, Vasiliki Poulaki, Iain L Campbell, Alan W Stitt, Tom A Gardiner, Desmond B Archer, Anthony P Adamis
• Journal: Investigative ophthalmology & visual science (Invest Ophthalmol Vis Sci) Vol. 44 Issue 10 Pg. 4457-64 (Oct 2003) ISSN: 0146-0404 [Print] United States
• PMID: 14507893 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Glycation End Products, Advanced
• NF-kappa B
• RNA, Messenger
• Intercellular Adhesion Molecule-1
• DNA

Topics

• Animals
• Blood-Retinal Barrier (drug effects)
• Capillaries
• Capillary Permeability
• Cattle
• Cell Adhesion (drug effects)
• DNA (metabolism)
• Electrophoretic Mobility Shift Assay
• Endothelium, Vascular (metabolism)
• Enzyme-Linked Immunosorbent Assay
• Glycation End Products, Advanced (pharmacology)
• Humans
• Intercellular Adhesion Molecule-1 (genetics)
• Male
• Mice
• Mice, Inbred C57BL
• NF-kappa B (metabolism)
• Neutrophils (physiology)
• RNA, Messenger (metabolism)
• Retinal Vessels (metabolism)
• Reverse Transcriptase Polymerase Chain Reaction
• Up-Regulation