Aldose Reductase Inhibition Counteracts Diabetes-Induced Retinal Oxidative Injury, Glial Activation, and Apoptosis

Abstract

Purpose: To access the role for increased aldose reductase (AR) activity in oxidative injury, glial activation, and apoptosis in retinae of diabetic rats and high glucose-exposed cultured retinal pericytes and endothelial cells. Methods: Control (C) and STZ-diabetic (D) rats were treated with/without the AR inhibitor fidarestat (F, 16 mg/kg/g, for 10 wks after 2 wks without treatment). The rate of apoptosis was assessed in flat-mounted retinas by TUNEL assay with immunoperoxidase staining, and nitrotyrosine (NT), poly(ADP-ribose) [PAR, a marker of poly(ADP-ribose) polymerase activation] and glial fibrillary acidic protein (GFAP) expression in retinal sections by immunohistochemistry. Primary bovine retinal pericytes and endothelial cells were cultured in 5 mM or 30 mM glucose with/without F (10 microM) for 3-14 d. Apoptosis was assessed by TUNEL assay, NT and PAR by immunocytochemistry, and Bax and Bcl-2 expression by Western blot analyses. Results: The number of TUNEL-positive nuclei (Mean ± SEM) was increased ~4-fold in D (207 ± 33 vs 49 ± 4 in C, p < 0.01), and this increase was partially corrected in D+F (106 ± 34, p < 0.05 vs D). The apoptotic cell number increased with prolongation of exposure of both pericytes and endothelial cells to high glucose. F counteracted high glucose-induced apoptosis, and NT and PAR accumulation in both cell types. Antiapoptotic effect of F in high glucose-exposed retinal pericytes was not associated with inhibition of Bax or increase in Bcl-2 expression (endothelial cell studies are in progress). Conclusions: AR inhibition with fidarestat conteracts diabetes-associated retinal oxidative injury, glial activation, and apoptosis.