Abstract
Abstract: :
Purpose: AOP2, a unique member of the peroxiredoxins family, recently renamed as Peroxiredoxin 6 (Prdx6). The antioxidant and signaling properties of this bifunctional protein are attributed to its ability to remove H2O2. Our working hypothesis is that AOP2 by limiting reactive oxygen species (ROS) levels, controls the cellular integrity. Since localization pattern, expression levels and regulation of the bio–molecules are important to predict their biological importance, we investigated age– and development–associated changes in mRNA and protein expression, and the localization pattern of AOP2 in mouse eye, and hormonal effects on its regulation.Methods: Expression levels of AOP2 mRNA and protein in whole lenses isolated from balb/c mice (day 0, and 1–42 weeks–old) were measured using quantitative real–time PCR and western blot, respectively, and were localized using in–situ hybridization and immunohistochemistry with AOP2 specific probes. Comparative levels of peroxiredoxins (Prdxs) (1–6) mRNA and protein in mouse lens, retina and human lens epithelial cells (LEC), were also monitored. To assess the influence of dexamethasone, TGF ß1, TNFα on AOP2 expression, mLECs were exposed to various concentrations of these reagents for variable times. Results:Expression level of AOP2 was increased gradually in lenses from Day–0 to 12 week old mice. AOP2 was predominately localized in cytoplasm of LEC and cortical fibers of lens. However, nuclear fibers of 8 week old mice showed negative staining. Interestingly, in embryonic eyes (E14), AOP2 was present in whole fibers and LECs. There was little change in AOP2 expression during prenatal period, but marked increase in expression immediately after birth, and gradually increased up to 8 week and became static at 12 week postnatal days. In mouse lens and retina and human LEC, expression of AOP2 was higher than those of other members of Prdxs. Expression of protein and mRNA was induced in the presence of dexamethasone (10–8M) and TNFα (20ng/ml), while significantly reduced in presence of TGFß (10ng/ml). Conclusions: Our findings suggest that AOP2 is a major antioxidant in lens and provide a topographic basis for the understanding of the role of the AOP2 in lens development. The increased expression of AOP2 at birth may be important for antioxidant defense based on its peroxidase function.
Keywords: antioxidants • gene/expression • oxidation/oxidative or free radical damage