A Mechanism study toward understanding the protective effects of glutaredoxin 2 (Grx2) on light-induced retinal damage

Purpose: Glutaredoxin 2 (Grx2), located mainly in the mitochondria, is a glutathione-dependent oxidoreductase which is known to reduce S-glutathionylated proteins. In previous study, we have found that Grx2 could protect the retina from light-induced retinal degeneration. However, the molecular mechanisms that coordinate mitochondrial energy production with thiol-repair processes in the damaged retina remain largely unknown. To better understand the protective effects of Grx2 in the retina, our study was thus extended to analyze the full transcriptome changes of the retinal tissue in light-exposed Grx2 knockout (KO) mice. Methods: Wild type (WT) and Grx2 KO mice were exposed to white light at 12,000 lux for 1 hour after dark adaptation. The retinal damage was confirmed by the electroretinogram (ERG) recording and spectral domain optical coherence tomography (SD-OCT) measurement. Protein glutathionylation level was evaluated by Western Blot. We then compared the full transcriptome of the retinal tissue in WT and Grx2 KO mice by performed the whole transcriptome shotgun sequencing (RNA-seq). The gene network was analyzed using DESeq2 pathway analysis software and the selected genes of interest were further confirmed by real-time PCR and Western Blot. Results: Light-exposed Grx2 KO mice showed compromised visual function as indicated by severe loss of both a- and b-wave amplitudes and the thinning of the outer nuclear layer (ONL). Protein glutathionylation level was elevated in light-exposed Grx2 KO mice. We identified thousands of genes with statistical significant expression changes in light-exposed Grx2 KO mice and classified them into cellular processes and molecular pathways. Among these pathways, many genes that are related to complement activation and inflammation reaction were significantly upregulated. These genes include complement C3, C4a, C4B (C4B), Bcl-3, NF-kappa B, Jak3, and STAT3. Conclusions: Collectively, our results suggest that Grx2 could protect the retina from light-induced retinal degeneration. It plays an important role in regulating light-induced retinal inflammation which may be associated with its ability to reduce S-glutathionylated substrates.