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Zongbo WEI, Xingjun Fan; Decreased levels of reduced glutathione in the lens and lens epithelial cells promote epithelial-mesenchymal transition (EMT) via activating Wnt signaling. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3185.
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© ARVO (1962-2015); The Authors (2016-present)
The hallmarks of posterior capsular opacification (PCO) are lens epithelial cell proliferation, migration, and transdifferentiation, with the involvement of growth factors and cytokine, such as TGF-β. The lens maintains unusually high level of glutathione (GSH), particularly in lens epithelial layer and outer cortex regions, while no GSH is present in intraocular lens (IOL). We hypothesize that the residue lens epithelial cells after cataract surgery lose its interaction with native lens GSH and are therefore exposed to oxidative stress conditions, which promotes epithelial-mesenchymal transition (EMT).
The protein levels of the EMT markers αSMA, vimentin and collagen 1 were determined in both wild type and glutathione biosynthesis deficiency (Gclc-/- or Gclm-/-) mice lenses. The EMT markers were also investigated in HLE-B3 cells, primary cultured pig lens epithelial cells (PLECs) and ex vivo mouse lens culture with or without the treatment of buthionine sulphoximine (BSO) or Dimethyl fumarate (DMF). In vivo tests were achieved by mouse lens anterior capsule puncture and mock cataract surgery models. The glutathione ethyl ester (GSH-EE) or N-acetylcysteine (NAC) was used both in vitro and in vivo as rescue effort to restore redox state. Wnt signaling cascades were titrated in both in vitro and in vivo models.
Our data indicated that there was a dramatic increase of αSMA in LEGSKO mice lenses compared to wild type mice (p<0.05). EMT markers, αSMA, vimentin and collagen1 were also significantly elevated in HLE-B3 cells and primary cultured pig lens epithelial cells (PLECs) under BSO treatment. Immunocytochemistry stain demonstrated remarkable elevation of αSMA expression in mouse lens epithelial explant culture after treatment with 500μM BSO compared to vehicle controls. Immunofluorescent (IF) staining of injured lens anterior capsule whole-mounts revealed high expression of EMT markers in LEGSKO mice vs. wild type mice lenses. In addition, either BSO or TGFβ induced EMT markers could be ameliorated by GSH-EE or NAC treatment. Mechanistic pathway analysis indicated the involvement of Wnt signaling cascades.
These results implicate that survival signaling pathways involved in oxidative stress adaptive response may play a critical role in residual epithelial cells transdifferentiation after cataract surgery.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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