[Short-interfering RNAs Induce Retinal Degeneration via TLR3 and IRF3]
>>Molecular Therapy (2011); doi:10.1038/mt.2011.212 Short-interfering RNAs Induce Retinal Degeneration via TLR3 and IRF3 Mark E Kleinman 1, Hiroki Kaneko 1, Won Gil Cho 1, 2, Sami Dridi 1, Benjamin J Fowler 1, Alexander D Blandford 1, Romulo JC Albuquerque 1, Yoshio Hirano 1, Hiroko Terasaki 3, Mineo Kondo 4, Takashi Fujita 5, Balamurali K Ambati 6, 7, Valeria Tarallo 1, Bradley D Gelfand 1, Sasha Bogdanovich 1, Judit Z Baffi 1 and Jayakrishna Ambati 1, 8
1Department of Ophthalmology and Visual Sciences, University of Kentucky, Lexington, Kentucky, USA2Department of Anatomy, Yonsei University Wonju College of Medicine, Wonju City, Korea3Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan4Department of Ophthalmology, Mie University Graduate School of Medicine, Tsu, Japan5Department of Molecular Genetics, Institute for Virus Research, and Graduate School of Biostudies, Kyoto University, Kyoto, Japan6Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah School of Medicine, Salt Lake City, Utah, USA7Department of Ophthalmology, Veterans Affairs Salt Lake City Healthcare System, Salt Lake City, Utah, USA8Department of Physiology, University of Kentucky, Lexington, Kentucky, USA Correspondence: Jayakrishna Ambati, Department of Ophthalmology and Visual Sciences, University of Kentucky, 740 S. Limestone Street, Ste E302, Lexington, Kentucky 40536-0284, USA. E-mail: jamba2@email.uky.edu
M.E.K., H.K., and W.G.C. contributed equally to this work.
Received 24 July 2011; Accepted 12 September 2011; Published online 11 October 2011.
The discovery of sequence-specific gene silencing by endogenous double-stranded RNAs (dsRNA) has propelled synthetic short-interfering RNAs (siRNAs) to the forefront of targeted pharmaceutical engineering. The first clinical trials utilized 21-nucleotide (nt) siRNAs for the treatment of neovascular age-related macular degeneration (AMD). Surprisingly, these compounds were not formulated for cell permeation, which is required for bona fide RNA interference (RNAi). We showed that these “naked” siRNAs suppress neovascularization in mice not via RNAi but via sequence-independent activation of cell surface Toll-like receptor-3 (TLR3). Here, we demonstrate that noninternalized siRNAs induce retinal degeneration in mice by activating surface TLR3 on retinal pigmented epithelial cells. Cholesterol conjugated siRNAs capable of cell permeation and triggering RNAi also induce the same phenotype. Retinal degeneration was not observed after treatment with siRNAs shorter than 21-nts. Other cytosolic dsRNA sensors are not critical to this response. TLR3 activation triggers caspase-3-mediated apoptotic death of the retinal pigment epithelium (RPE) via nuclear translocation of interferon regulatory factor-3. While this unexpected adverse effect of siRNAs has implications for future clinical trials, these findings also introduce a new preclinical model of geographic atrophy (GA), a late stage of dry AMD that causes blindness in millions worldwide.<<
If this proves out, this is bad news for the field. Especially since eye diseases have been among the first targeted, on account of the relative ease of delivery. Although I kind of thought folks were moving towards siRNAIs of 21nts or less, anyway.
Cheers, Tuck |
