ABSTRACT
ALDH3A1 (aldehyde dehydrogenase 3A1) is abundant in the mouse cornea but undetectable in the lens, and ALDH1A1 is present at lower (catalytic) levels in the cornea and lens. To test the hypothesis that ALDH3A1 and ALDH1A1 protect the anterior segment of the eye against environmentally induced oxidative damage, Aldh1a1(-/-)/Aldh3a1(-/-) double knock-out and Aldh1a1(-/-) and Aldh3a1(-/-) single knock-out mice were evaluated for biochemical changes and cataract formation (lens opacification). The Aldh1a1/Aldh3a1- and Aldh3a1-null mice develop cataracts in the anterior and posterior subcapsular regions as well as punctate opacities in the cortex by 1 month of age. The Aldh1a1-null mice also develop cataracts later in life (6-9 months of age). One- to three-month-old Aldh-null mice exposed to UVB exhibited accelerated anterior lens subcapsular opacification, which was more pronounced in Aldh3a1(-/-) and Aldh3a1(-/-)/Aldh1a1(-/-) mice compared with Aldh1a1(-/-) and wild type animals. Cataract formation was associated with decreased proteasomal activity, increased protein oxidation, increased GSH levels, and increased levels of 4-hydroxy-2-nonenal- and malondialdehyde-protein adducts. In conclusion, these findings support the hypothesis that corneal ALDH3A1 and lens ALDH1A1 protect the eye against cataract formation via nonenzymatic (light filtering) and enzymatic (detoxification) functions.
Subject(s)
Aldehyde Dehydrogenase/metabolism , Cataract/enzymology , Cornea/enzymology , Eye Proteins/metabolism , Lens, Crystalline/enzymology , Oxidative Stress , Aging/genetics , Aging/metabolism , Aging/pathology , Aldehyde Dehydrogenase/deficiency , Aldehyde Dehydrogenase 1 Family , Animals , Cataract/genetics , Cataract/pathology , Cornea/pathology , Eye Proteins/genetics , Glutathione/metabolism , Lens, Crystalline/pathology , Mice , Mice, Knockout , Oxidation-Reduction/radiation effects , Oxidative Stress/drug effects , Oxidative Stress/genetics , Phenotype , Proteasome Endopeptidase Complex/metabolism , Retinal Dehydrogenase , Ultraviolet Rays/adverse effectsABSTRACT
PURPOSE: To compare the abundance and spatial distribution of serum albumin in the mouse and bovine cornea. METHODS: Serum albumin from cornea was separated from transketolase by SDS-PAGE (+/-dithiothreitol [DTT]) and identified by peptide sequencing and immunoblot analyses. The fractional content of serum albumin was determined in water-soluble extracts of cornea by imaging analyses after SDS-PAGE. Serum albumin was localized in cornea by immunohistochemistry and by SDS-PAGE analyses of samples from separated epithelium and stroma. RESULTS: SDS-PAGE (-DTT) resolved mouse serum albumin and transketolase and indicated that serum albumin was 13% of the water-soluble protein in whole mouse corneas. By contrast, corneal epithelial fractions contained little (<1%) serum albumin. Immunohistochemistry indicated that mouse serum albumin was present throughout the stroma between collagen lamellae. Immunohistochemical analyses of bovine cornea yielded similar results. In addition, immunohistochemistry for serum albumin revealed positive staining in a small number of basal epithelial cells next to Bowman's membrane, and greater staining in the anterior-peripheral stroma as well as immediately adjacent to Descemet's membrane. CONCLUSIONS: Mouse and bovine cornea have a similar content and spatial distribution of serum albumin. The appreciable serum albumin in the cornea documented here and elsewhere raise the possibility that it contributes to the physiological or optical functions of the cornea. Moreover, serum albumin's ability to bind drugs suggests that mice corneas could be exploited to study drug-serum albumin interactions in vivo and to test the usefulness of serum albumin as a drug carrier for corneal disorders.
Subject(s)
Cornea/metabolism , Serum Albumin/metabolism , Amino Acid Sequence , Animals , Cattle , Electrophoresis, Polyacrylamide Gel , Fluorescent Antibody Technique , Immunoblotting , Mice , Microscopy, Confocal , Molecular Sequence Data , Sequence Homology, Amino Acid , Serum Albumin/chemistry , Serum Albumin, Bovine/chemistry , Serum Albumin, Bovine/metabolism , Transketolase/metabolismABSTRACT
We have constructed an ALDH3a1 null mouse to investigate the role of this enzyme that comprises nearly one-half of the total water-soluble protein in the mouse corneal epithelium. ALDH3a1-deficient mice are viable and fertile, have a corneal epithelium with a water-soluble protein content approximately half that of wild-type mice, and contain no ALDH3a1 as determined by zymograms and immunoblots. Despite the loss of protein content and ALDH3a1 activity, the ALDH3a1(-/-) mouse corneas appear indistinguishable from wild-type corneas when examined by histological analysis and electron microscopy and are transparent as determined by light and slit lamp microscopy. There is no evidence for a compensating protein or enzyme. Even though the function of ALDH3a1 in the mouse cornea remains unknown, our data indicate that its enzymatic activity is unnecessary for corneal clarity and maintenance, at least under laboratory conditions.
