Small Interfering RNA-Induced TLR3 Activation Inhibits Blood and Lymphatic Vessel Growth

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 106; no. 17; pp. 7137 - 7142
• Main Authors: Cho, Won Gil, Albuquerque, Romulo J. C., Kleinman, Mark E., Tarallo, Valeria, Greco, Adelaide, Nozaki, Miho, Green, Martha G., Baffi, Judit Z., Ambati, Balamurali K., De Falco, Massimo, Alexander, Jonathan S., Brunetti, Arturo, De Falco, Sandro, Ambati, Jayakrishna, Ferrara, Napoleone
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 28.04.2009; National Acad Sciences
• Subjects: Angiogenesis; Animals; Antibodies; Apoptosis; Biological Sciences; Blood; Blood vessels; Cell Proliferation; Cells; Cornea; Double stranded RNA; Endothelial cells; Endothelial Cells - cytology; Hindlimb - blood supply; Hindlimb - metabolism; Lymphatic system; Lymphatic vessels; Lymphatic Vessels - metabolism; Mice; Neovascularization, Physiologic; Phosphorylation; Proteins; Ribonucleic acid; RNA; RNA, Small Interfering - genetics; Rodents; Small interfering RNA; Tissues; Toll like receptors; Toll-Like Receptor 3 - genetics; Toll-Like Receptor 3 - metabolism; Vehicles
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0812317106

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.