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J. Petrash, S.-P. Huang; Elevation of Aldose Reductase in the Diabetic Eye. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2029.
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© ARVO (1962-2015); The Authors (2016-present)
Human aldose reductase (HAR, AKR1B1), a prototypical aldo-keto reductase, is thought to play an important role in the pathogenesis of diabetic cataract and retinopathy and is considered an attractive target for drugs to prevent diabetic eye disease. In addition to HAR, some human tissues have been reported to contain an aldose reductase-like enzyme (ALR-1) classified as AKR1B10 according to a systematic AKR nomenclature. The purpose of the current study was to examine expression levels of AKRs 1B1 and 1B10 in eyes from diabetic and nondiabetic tissue donors and in a tissue culture model.
Antibodies were prepared against recombinant AKR 1B1 as well as against synthetic peptides designed from sequences of 1B1 and 1B10. Expression of the respective enzymes was examined by immunohistochemical staining of fixed tissue sections. Quantitative comparisons between age-matched diabetic and nondiabetic tissues were carried out by real time PCR using mRNA extracted from cornea, lens, ciliary body, iris, and retina. Expression of 1B1 and 1B10 was examined by real time PCR and Western blotting using a human retina pigment epithelium cell line (ARPE-19).
Antibodies were shown to be specific against the targeted AKR by western blotting against recombinant enzymes purified from E. coli expression cultures. Both AKR1B1 and 1B10 were detected in the corneal epithelium and stroma and retinal plexiform layers at similar levels, whereas immunostaining for 1B1 was somewhat stronger in lens. qPCR showed that both genes are expressed throughout the eye, with 1B1 being considerably higher when transcript levels were normalized against actin. Transcript levels for 1B1 were similar in all tissues from donors with type 2 diabetes mellitus as compared to nondiabetic donors, except for retina. Approximately 2- to 3-fold higher levels of 1B1 mRNA were observed in the diabetic retina as compared to the nondiabetic comparison group. No influence of diabetes was found in the level of 1B10 transcripts measured in dissected eye tissues. Levels of 1B1 increased almost 100% when ARPE-19 cells were cultured in the presence of hyperosmolar media; however, 1B10 levels were unchanged under these conditions.
Two structurally similar aldo-keto reductases, AKRs 1B1 and 1B10, are found in tissues of the eye that are susceptible to diabetes. Although only 1B1 gene expression is elevated in diabetes, both enzymes are potently inhibited by clinically-relevant reductase inhibitors. Further studies are ongoing to evaluate whether multiple AKRs may be involved in the pathogenesis of diabetic eye disease.
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