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.
Cho
Won Gil
WG
Department of Ophthalmology and Visual Sciences, University of Kentucky, Lexington, KY 40536, USA.
Albuquerque
Romulo J C
RJ
Kleinman
Mark E
ME
Tarallo
Valeria
V
Greco
Adelaide
A
Nozaki
Miho
M
Green
Martha G
MG
Baffi
Judit Z
JZ
Ambati
Balamurali K
BK
De Falco
Massimo
M
Alexander
Jonathan S
JS
Brunetti
Arturo
A
De Falco
Sandro
S
Ambati
Jayakrishna
J
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