Target-Independent Suppression of Angiogenesis by siRNAs

  • Ambati, Jayakrishna (PI)

Grants and Contracts Details


RNA interference by small interfering RNAs (siRNAs) is rapidly b coming the tool of choice for in vitro and in vivo gene silencing and functional gen mics studies. Its power stems from ease of use, efficiency, and apparent target speci Icity has led to therapeutic investigations. However, recent investigations have un overed the ability of many siRNAs to trigger inflammation via toll like receptor (TL )-3 activation and interferon induction, independent of their designed target. Nonethe ess the first two human clinical trials of siRNAs were initiated in an ophthalmic dis ase: neovascular age-related macular degeneration (AMD), the leading cause ofblin ness among the elderly on three continents. We have made the surprising observation that numerous siRNAs ( 10) can suppress angiogenesis in an animal model of neovascular AMD in a target i dependent fashion. We found, using Tlr3-I -, IlIO-/-, III T1 -, Ifnarrl -, and Ifng-/- mice at an array of siRNAs targeted against non-mammalian genes, against tissue spe 'fic genes not expressed in the eye, against random sequences not found in nature and siRNAs that do not enter the RNA interference silencing complex all trigger TL 3 activation and induce IL-I 0 and IL-12 expression, thereby suppressing angiogene is by inhibiting inflammation and endothelial cell proliferation. We will test the ability of these non-targeted siRNAs to suppress 0 ular angiogenesis in TlrJ-1 - mice that will be rescued, through adenoviral vector med ated delivery, with wild-type TLR3 or TLR3 mutants recently discovered not to bind s·RNAs. These experiments will both confirm the role ofTLR3 in this paradoxical process and also guide development of small molecule agonists ofTLR3. We will a so test whether the ability of these non-targeted siRNAs to suppress angiogenesis is a lished in Il ]()-/- X Ill2-/- mice, as opposed to the partial suppression observed in the 'ngle knockout mice. These experiments will provide a mechanistic rationale for p rsuing the use IL- 10 and IL-12 as new anti-angiogenic strategies. We also will dete ine whether the absence of interferon induction and pro-inflammatory cytokine pro uction by these siRNAs despite TLR3 activation is due to proteolytic cleavage or i tracellular translocation of MAVS/IPS-liVISAICardif, a transducing protein ecently found to mediate TLR3-induced interferon induction in RNA viral infectionu. Collectively these experiments will provide novel information abO f t the in vivo immunology of the generic anti-inflammatory and anti-angiogenic ctivity of siRNAs. These studies are of great import both for design and interpretation of clinical trials of siRNAs in ocular angiogenesis, and are relevant to the 70 other dis ases driven by angiogenesis that affect over 500 million people worldwide.
Effective start/end date7/1/0712/31/13


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