High-mobility group box-1 and biomarkers of inflammation in the vitreous from patients with proliferative diabetic retinopathy

Abstract

Purpose: To measure levels of high-mobility group box -1 (HMGB1) and soluble receptor for advanced glycation end products (sRAGE) in the vitreous fluid from patients with proliferative diabetic retinopathy (PDR) and to correlate their levels with clinical disease activity and the levels of the inflammatory biomarkers monocyte chemoattractant protein-1 (MCP-1), soluble intercellular adhesion molecule-1 (sICAM-1), interleukin-1β (IL-1β), and granulocyte macrophage colony-stimulating factor (GM-CSF). In addition, we examined the expression of HMGB1 in the retinas of diabetic mice.

Methods: Vitreous samples from 29 PDR and 17 nondiabetic patients were studied by enzyme-linked immunosorbent assay. Retinas of mice were examined by immunofluorescence analysis and western blotting.

Results: HMGB1 was detected in all vitreous samples and sRAGE was detected in 5 PDR samples. IL-1β was detected in 3PDR samples and GM-CSF was not detected. Mean HMGB1 levels in PDR with active neovascularization were twofold and threefold higher than that in inactive PDR and nondiabetic patients, respectively. Mean HMGB1 levels in PDR patients with hemorrhage were significantly higher than those in PDR patients without hemorrhage and nondiabetic patients (p=0.0111). There were significant correlations between levels of HMGB1 and levels of MCP-1 (r=0.333, p=0.025) and sICAM-1 (r=0.548, p<0.001). HMGB1 expression was also upregulated in the retinas of diabetic mice.

Conclusions: Subclinical chronic inflammation might contribute to the progression of PDR.

Figure 1

Western-blotting analysis of high-mobility group box −1 (HMGB1) in mouse retina. There is a significant increase in the expression of HMGB1 in the retinas of diabetic mice (D) compared to the nondiabetic control (C). OD is optical density

Figure 2

Immunolocalization of high-mobility group box −1 (HMGB1) in control (upper row of panels) and diabetic (lower row of panels) retinas. Immunofluorescence using isolectin B4 as a vascular marker (red), a nuclear marker 4’,6-diamidino 2-phenylindole (DAPI), and HMGB1 antibody showed increased expression of HMGB1 in diabetic retina in comparison to the control. HMGB1 is localized mainly in ganglion cells (GC), inner nuclear layer (INL), and retinal vasculatures (arrows). Abbreviations: IPL represents inner plexiform layer; OPL represents outer plexiform layer; ONL represents outer nuclear layer.