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A. Kasus-Jacobi, D. A. Thompson, M. A. Babizhayev, L. D. Marchette; New Insight Into the Function of the Leber Congenital Amaurosis-Causing Gene RDH12. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1647.
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We hypothesized that the role of the retinol dehydrogenase RDH12 is to protect photoreceptor cells from toxic short- and medium-chain aldehydes produced during oxidative stress. If not cleared, these aldehydes disrupt important cellular functions and lead to cell apoptosis. We investigated the ability of RDH12 to detoxify 4-hydroxynonenal (4-HNE), one of the most toxic products of lipid peroxidation, released in cells during situations of oxidative stress.
We compared the toxicity of 4-HNE in presence and absence of RDH12, in vitro, in cultured cells, and in vivo. The toxicity of 4-HNE was measured by quantification of 4-HNE-protein adducts and cell death. In vitro experiments were performed on microsomal fractions of retinas isolated from wild-type and Rdh12 knockout mouse and incubated with exogenous 4-HNE. Cultured HEK-293 cells were stably transfected with mouse or human Rdh12 cDNA, encoding the wild-type or a disease-causing mutant, and incubated with exogenous 4-HNE. Wild-type and Rdh12 knockout mice were subjected to bright light to induce the release of endogenous 4-HNE in photoreceptors.
We found that RDH12 is protective against the formation of 4-HNE-protein adducts in isolated retinal microsomes, cultured cells, and in retinas of mice subjected to bright light. The wild type RDH12 also significantly protects against 4-HNE-induced cell death in cultured cells. A mutation of RDH12 associated with Leber congenital amaurosis induces the loss of its protective function. Finally, as published before, RDH12 significantly protects against bright light-induced photoreceptor cell death in mouse retina.
The protective effect of RDH12 is most likely due to its ability to reduce 4-HNE to a non-toxic alcohol, preventing adducts formation and apoptosis. A defective clearance of 4-HNE and other toxic aldehydes could mediate the early onset vision loss and the retinal dystrophy associated with mutations in RDH12 in patients with Leber congenital amaurosis. If it is the case, an adapted strategy for treatment would be to use molecules such as carcinine that have the ability to enter the cells and scavenge toxic aldehydes.
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