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Chunfeng Lu, Songhua Li, Minghao Jin; Activation of the Mixed Lineage Kinase Domain Like Protein-Mediated Necroptotic Pathway in Light-Induced Retinal Degeneration. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1287.
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Retinal degeneration triggered by photooxidative damage resembles many features of age-related macular degeneration, while the signaling pathways leading to photoreceptor death remain largely unknown. The purpose of this study was to investigate whether the necroptotic pathway contributes to degeneration of rods and cones in the photodamaged retinas.
Retinal photodamage was induced by exposing dark-adapted 129S2/Sv mice to 15000 lux white light for 0.5~3 hours. Degrees of rod and cone degeneration were evaluated by rhodopsin- immunohistochemistry and peanut agglutinin (PNA)-staining. Expression of receptor interacting protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like protein (MLKL) in the retinas was analyzed by immunoblot analysis. Activation of MLKL was assessed by detecting phosphorylation of MLKL. Correlation between photoreceptor degeneration and RIPK1 expression was determined by Spearman’s correlation analysis. Colocalization and interaction of necrosome proteins (RIPK1, RIPK3, and MLKL) were analyzed by immunohistochemistry and co-immunoprecipitation.
Intense light exposure caused degeneration of both rod and cone photoreceptors in a time-dependent manner. Photodamage also induced a time-dependent gradual increase of RIPK1 expression in the retinas. Spearman’s correlation analysis showed a negative correlation between numbers of PNA-positive cones and RIPK1 expression levels. The lengths of rod outer segments were also negatively correlated with RIPK1 expression levels. RIPK3 was significantly upregulated in the photodamaged retinas while MLKL expression levels in the photodamaged retinas were similar to those in non-photodamaged retinas. However, MLKL was strongly phosphorylated in the photodamaged retinas. Immunohistochemistry showed that both RIPK1 and RIPK3 were upregulated and were colocalized in photoreceptors of the photodamaged retinas. Consistent with these results, immunoprecipitation revealed that photodamage strongly promoted interaction of necrosome proteins in the retinas.
The RIPK-MLKL pathway was strongly activated in photoreceptors of photodamaged retinas, indicating that necroptosis contributed to rod and cone degeneration induced by intense light. This finding suggests that necrosome proteins are therapeutic targets to protect photoreceptors from photodamage.
This is a 2020 ARVO Annual Meeting abstract.
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