Regulation of Grxs in Cell Functions and Senescence in the Lens




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Purpose: Glutaredoxins (Grxs), a family of thiol transferases, can reverse protein glutathionylation using glutathione (GSH) as an electron donor. Therefore, it can regulate protein redox state and enzymatic activity. Specifically, Glutaredoxin 1 (Grx1) and Glutaredoxin 2 (Grx2) are predominantly localized in the cytoplasm and mitochondria, respectively. The Grx1/Grx2 double knockout (DKO) mice showed early onset of cataracts and were more sensitive to UV radiation, highlighting the importance of Grx1 and Grx2 in maintaining lens transparency. Lens epithelial cells (LECs) are crucial to lens transparency and functionality. Our current study is to explore novel roles of the Grxs in the lens using the Grx1-/-/Grx2-/- mouse model. Methods: We isolated LECs from the lenses of WT and DKO mice and conducted a range of in vitro experiments to study the effects of Grx depletion on the epithelial morphology, cell proliferation, cell death, and mitochondrial function of LECs. We also did lens tissue sectioning and hematoxylin and eosin (H&E) staining to visualize lens tissue. Results: Loss of Grx1/Grx2 led to stress fiber formation, cytoskeleton reorganization, and higher protein expression of mesenchymal markers (N-cadherin and vimentin) in LECs. The DKO LECs exhibited a lower proliferation rate and cell cycle arrest in comparison with WT LECs. Resistance to apoptosis and elevated levels of β-galactosidase activity of DKO LECs indicated that DKO LECs underwent cell senescence. DKO LECs also displayed compromised mitochondrial function, characterized by decreased ATP production, reduced expression levels of mitochondrial complexes III and IV, and increased proton leak. A compensatory metabolic shift towards glycolysis was observed in DKO LECs, indicating an adaptive response to Grx1 and Grx2 deficiencies. The HE staining data showed that the DKO mouse had aging lens epithelium characterized by less LEC density, remained flat in shape, and aligned less regularly. Conclusions: Our study demonstrates that the Grx1 and Grx2 DKO in LECs results in cytoskeletal reorganization, lower cell proliferation rate, cell cycle arrest, resistance to apoptosis, compromised mitochondrial function, and accelerated senescence. These findings underscore the importance of Grx1 and Grx2 in preventing LECs from undergoing premature aging.


Research Appreciation Day Winner - HSC College of Pharmacy, 2024 Pharmaceutical Science Research Award - 2nd Place