Abstract
Purpose: :
To investigate the cellular localization and temporal accumulation of advanced lipoxidation end-products (ALEs) in the retina during early experimental diabetes. The ability of pyridoxamine (PM), an ALE inhibitor, to prevent ALE accumulation was also evaluated.
Methods: :
The specificity of antibodies directed against Nε-(3-formyl-3,4-dehydropiperidino)lysine (acrolein-derived ALE; FDP-lysine) and 4-hydroxy-2-nonenal histidine (HNE) adducts were assessed by western dot blot analysis and used for immunohistochemical staining of retinal sections from control (n=6), streptozotocin(STZ)-induced diabetic rats (n=6) and diabetic animals treated with pyridoxamine (1 g/l drinking water; n=5). Sections were examined using confocal microscopy and fluorescence intensities of different layers of the retina were semiquantitatively analysed.
Results: :
Levels of 4-HNE modified proteins were similar in the retinas of control and diabetic animals after 4-months of diabetes (p>0.05). By contrast, a progressive accumulation of FDP-lysine was observed within the ganglion cell and inner plexiform layers of diabetic rats between 2-4 months disease-duration (p<0.05 at 2-months, p<0.001 at 4-months). During diabetes, Müller cells are known to exhibit intense expression of glial fibrillary acidic protein (GFAP), which is almost completely downregulated in retinal astrocytes (Barber et al, IOVS, 2000, 41:3561-8). In diabetic rats, FDP-lysine colocalised extensively with GFAP suggesting that this adduct selectively accumulates in Müller cells during diabetes. PM protected diabetic rats of 4-months disease duration from Müller cell accumulation of FDP-lysine (p>0.05 versus controls).
Conclusions: :
Acrolein-derived ALEs accumulate preferentially in Müller cells during early diabetes. PM may prevent the accumulation of ALEs in the diabetic retina. Acrolein-derived ALEs might be one of the factors that contribute to the reactive gliosis reported in the early stages of diabetic retinopathy.
Keywords: diabetic retinopathy • oxidation/oxidative or free radical damage • Muller cells