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Thomas Holm, Leif Johnson, Line Kessel; Expression of oxidative markers in laser treated rat lenses. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2976. doi: https://doi.org/.
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The proposed use of non-invasive laser techniques to treat cataract have produced a need to determine the safety of the eye upon such treatment. We have here determined the altered expression of 7 proteins of the repair and protection mechanisms of the eye, as a response to laser treatment.
Eleven weeks old Brown Norway rats had their right lens treated with a 445nm laser using 40mW output for 30min. The left eye was used as control. Whole eyes were removed 2 days after laser treatment, fixed in 4% paraformaldehyde over night, and afterwards moved through PBS buffers with increasing sucrose concentration. Eyes were cryo sectioned at 10um and protein expression was visualized using immunohistochemistry on sections from the central part of the eye. Eyes were stained with antibodies for the transcription factors Nf-kB & Nrf2, enzyme subunits xCT & GCLc, the glutathione enzymes GSR & GPx1 and the heavy metal scavenger MT I&II. Enucleated lenses were removed after 2 days and homogenized using a rotor-homogenizer, and used for analysis of glutathione concentration as a response to laser treatment.
Of the two transcription factors, only Nf-κB showed increased expression in lens epithelium. The GSH transporter xCT and the GSH synthesising enzyme GCLc remained unaffected as did the GSH homeostasis enzymes Glutathione Reductase (GSR) and Glutathione Peroxidase 1 (GPx1). The heavy metal scavenger metallothionein (MT I&II) showed a marked increase in the lens epithelium. Glutathione analysis did not show a significant increase (p<0.1) in lenses 2 days after laser treatment.
The main response of the eye to the laser treatment is the activation of Nf-κB which in turn increase the expression of MT I&II. The response indicates that the eye is under oxidative stress during blue light irradiation since Nf-κB is primarily activated under oxidative stress. The lack of increased expression of GSH related proteins follow well the lack of significant increase in glutathione concentration.
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