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A. Saadi, G. Wang, K. M. Qualls, A. Kasus-Jacobi, J. D. Ash; The Effect of Light on the Expression of Retinoid Cycle and Anti-Oxidative Stress Genes. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3522.
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The regeneration of visual chromophore 11-cis-retinaldehyde occurs in retinal pigmented epithelial cells and is dependent on an enzyme pathway called the retinoid cycle. We have observed that retinoid cycle genes can be regulated by light exposure. We designed this study to analyze light-dependent regulation of the visual cycle at the mRNA and protein level.
Six-week old Balb/c mice were exposed to 200 lux or 3000 lux of light for 4 hours. We then measured RNA and protein expression of retinoid cycle genes by Real-time-PCR and Western blots. We compared expression levels in light exposed animals to animals maintained in the dark. To determine if the effect was reversible we pre-exposed animals to light then placed them in the dark for 4 hours.
The retinoid cycle genes Rgr, Rdh5, Rdh8, Rpe65, Lrat, and Rdh12 showed an upregulation in gene expression upon exposure to normal lighting (200 lux) and bright light (3000 lux) at the RNA level. At the protein levels, all the proteins showed increase in expression when exposed to 3000 lux, but only RDH12 protein changed following 200 lux exposure. Normal and bright light exposure induced expression of anti-apoptotic genes such as Bcl2a1d, Parp14, and Grcc9 and oxidative stress genes such as Mt-1, Mt-2, Mthfd2, and Ahrr.
Our results suggest that light exposure results in increased expression of genes that are responsible for photo-isomerization which is necessary to maintain normal vision in the light. The increased expression of anti-oxidative stress genes suggests that normal light may regulate oxidative-stress defense pathways.
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