Cross-Talk between Sirtuin 1 and the Proinflammatory Mediator High-Mobility Group Box-1 in the Regulation of Blood-Retinal Barrier Breakdown in Diabetic Retinopathy.

ABSTRACT

Purpose: High-mobility group box-1 (HMGB1) mediates inflammation and breakdown of blood-retinal barrier (BRB) in diabetic retina. Sirtuin-1 (SIRT1) has protective effects against inflammation and oxidative stress. The aim of this study was to investigate the interaction between HMGB1 and SIRT1 in regulating BRB breakdown in diabetic retina. Methods: BRB breakdown was assessed in vivo with fluorescein isothiocyanate-conjugated dextran. Vitreous samples from 47 proliferative diabetic retinopathy (PDR) and 19 nondiabetic patients, and epiretinal membranes from 13 patients with PDR were studied by enzyme-linked immunosorbent assay and immunohistochemistry. Retinas from 4-week diabetic rats and from normal rats intravitreally injected with HMGB1 were studied by spectrophotometric assay, Western blot analysis, and RT-PCR. We also studied the effect of the HMGB1 inhibitor glycyrrhizin and the SIRT1 activator resveratrol on diabetes-induced biochemical changes in the retina. Results: HMGB1 levels in vitreous samples from PDR patients were significantly higher than in nondiabetic controls, whereas SIRT1 levels were significantly lower in vitreous samples from patients with inactive PDR than those in patients with active PDR and nondiabetic controls. In epiretinal membranes, SIRT1 was expressed in vascular endothelial cells and stromal cells. Diabetes and intravitreal injection of HMGB1 in normal rats downregulated SIRT1expression, whereas glycyrrhizin and resveratrol normalized diabetes-induced downregulation of SIRT1. Resveratrol significantly attenuated diabetes-induced downregulation of occludin and upregulation of HMGB1 and receptor for advanced glycation end products in the retina and breakdown of BRB. Conclusions: Our findings suggest that a functional link between SIRT1 and HMGB1 is involved in regulating of BRB breakdown in diabetic retina.