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D. A. White, R. Malhotra, A. S. Lewin, M. P. Krebs, S. Kaushal; Treatment of Retinal Degeneration by mTOR Inhibition in the T17M Mouse Model of Rhodopsin Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2007;48(13):66.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the effectiveness of rapamycin, an mTOR inhibitor, for treatment of the retinal degeneration observed in the T17M mouse model of autosomal dominant retinitis pigmentosa (ADRP)
hT17M+ mice were treated with weekly intraperitoneal injections of rapamycin at a dose of 20 mg/kg. Subsequent litters from the same line were untreated and used as controls. Electroretinographic (ERG) measurements were taken of the treated litters at 3, 4, and 5 months of age. Outer nuclear layer (ONL) thickness was determined histologically on DAPI-stained frozen sections. Immunofluorescence staining was performed to visualize rhodopsin on retinal sections of hT17M+ and nontransgenic littermate mice. Rapamycin efficacy was monitored by Western blot analysis of eyecup lysates using phosphorylated S6 as a marker protein.
Intraperitoneal injection of rapamycin led to mTOR inhibition and consequent reduction of the phosphorylated S6 levels in mouse eyecup lysates. ERG analysis of hT17M+ mice treated with rapamycin revealed significant rescue of both a- and b-wave responses, compared to untreated hT17M+ mice, at 4 and 5 months of age. This rescue was confirmed at the histological level, where there was significant preservation of rod photoreceptor nuclei in treated hT17M+ mice compared to untreated hT17M+ mice. Immunofluorescent staining of retinal sections showed that opsin was mislocalized to the perinuclear layer of untreated hT17M+mutant mice.
We observe both functional and structural evidence of retinal preservation in hT17M+mutant mice treated with the mTOR inhibitor rapamycin. The observation that opsin was mislocalized to the perinuclear layer of untreated hT17M+ mice leads us to postulate that this treatment helps to relieve the burden of misfolded/mislocalized mutant opsin, possibly via an autophagic mechanism.
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