Small interfering RNA-induced TLR3 activation inhibits blood and lymphatic vessel growth.
Neovascularization in response to tissue injury consists of the dual invasion of blood (hemangiogenesis) and lymphatic (lymphangiogenesis) vessels. We reported recently that 21-nt or longer small interfering RNAs (siRNAs) can suppress hemangiogenesis in mouse models of choroidal neovascularization and dermal wound healing independently of RNA interference by directly activating Toll-like receptor 3 (TLR3), a double-stranded RNA immune receptor, on the cell surface of blood endothelial cells. Here, we show that a 21-nt nontargeted siRNA suppresses both hemangiogenesis and lymphangiogenesis in mouse models of neovascularization induced by corneal sutures or hindlimb ischemia as efficiently as a 21-nt siRNA targeting vascular endothelial growth factor-A. In contrast, a 7-nt nontargeted siRNA, which is too short to activate TLR3, does not block hemangiogenesis or lymphangiogenesis in these models. Exposure to 21-nt siRNA, which we demonstrate is not internalized unless cell-permeating moieties are used, triggers phosphorylation of cell surface TLR3 on lymphatic endothelial cells and induces apoptosis. These findings introduce TLR3 activation as a method of jointly suppressing blood and lymphatic neovascularization and simultaneously raise new concerns about the undesirable effects of siRNAs on both circulatory systems.
Department of Ophthalmology and Visual Sciences, University of Kentucky, Lexington, KY 40536, USA.
Won Gil
WG
Cho
Romulo J C
RJ
Albuquerque
Mark E
ME
Kleinman
Valeria
V
Tarallo
Adelaide
A
Greco
Miho
M
Nozaki
Martha G
MG
Green
Judit Z
JZ
Baffi
Balamurali K
BK
Ambati
Massimo
M
De Falco
Jonathan S
JS
Alexander
Arturo
A
Brunetti
Sandro
S
De Falco
Jayakrishna
J
Ambati
D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D042783:Endothelial Cells / Q000166:cytology; D006614:Hindlimb / Q000098:blood supply / Q000378:metabolism; D042601:Lymphatic Vessels / Q000378:metabolism*; D051379:Mice; D018919:Neovascularization, Physiologic; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000235:genetics*; D051196:Toll-Like Receptor 3 / Q000235:genetics / Q000378:metabolism*
D034741:RNA, Small Interfering; C519703:TLR3 protein, mouse; D051196:Toll-Like Receptor 3