Sequence- and target-independent angiogenesis suppression by siRNA via TLR3.

Clinical trials of small interfering RNA (siRNA) targeting vascular endothelial growth factor-A (VEGFA) or its receptor VEGFR1 (also called FLT1), in patients with blinding choroidal neovascularization (CNV) from age-related macular degeneration, are premised on gene silencing by means of intracellular RNA interference (RNAi). We show instead that CNV inhibition is a siRNA-class effect: 21-nucleotide or longer siRNAs targeting non-mammalian genes, non-expressed genes, non-genomic sequences, pro- and anti-angiogenic genes, and RNAi-incompetent siRNAs all suppressed CNV in mice comparably to siRNAs targeting Vegfa or Vegfr1 without off-target RNAi or interferon-alpha/beta activation. Non-targeted (against non-mammalian genes) and targeted (against Vegfa or Vegfr1) siRNA suppressed CNV via cell-surface toll-like receptor 3 (TLR3), its adaptor TRIF, and induction of interferon-gamma and interleukin-12. Non-targeted siRNA suppressed dermal neovascularization in mice as effectively as Vegfa siRNA. siRNA-induced inhibition of neovascularization required a minimum length of 21 nucleotides, a bridging necessity in a modelled 2:1 TLR3-RNA complex. Choroidal endothelial cells from people expressing the TLR3 coding variant 412FF were refractory to extracellular siRNA-induced cytotoxicity, facilitating individualized pharmacogenetic therapy. Multiple human endothelial cell types expressed surface TLR3, indicating that generic siRNAs might treat angiogenic disorders that affect 8% of the world's population, and that siRNAs might induce unanticipated vascular or immune effects.

Inhibition of laser-induced choroidal neovascularization by atorvastatin by downregulation of monocyte chemotactic protein-1 synthesis in mice.

PURPOSE: To determine the effect of atorvastatin, an HMG CoA reductase inhibitor, on experimental choroidal neovascularization (CNV) induced by laser photocoagulation in mice. METHODS: CNV was induced by laser photocoagulation in normal wild-type mice. The mice received either oral atorvastatin 10 (AS10 group) or 20 (AS20 group) mg/kg per day 3 days before and after laser application; 1 (AS1) and 2 (AS2) mg/kg per day were included in the measurement of the parameters of CNV volume and the expression of chemoattractant CC chemokine ligand 2/monocyte chemoattractant protein-1 (CCL2/MCP-1) and intracellular adhesion molecule (ICAM)-1. CNV responses were compared based on volume measurements 2 weeks after laser photocoagulation. Expression of vascular endothelial growth factor (VEGF), CCL2/MCP-1, and ICAM-1 in the RPE and choroid was quantified by ELISA 2 or 3 days after photocoagulation. Macrophage infiltration of the choroid was determined by flow cytometry. RESULTS: The mean CNV volume was significantly smaller in the AS1 (44.16 +/- 4.67 x 10(4) microm(3)), AS2 (36.49 +/- 4.64 x 10(4) microm(3)), AS10 (25.75 +/- 2.41 x 10(4) microm(3)), and AS20 (33.24 +/- 8.42 x 10(4) microm(3)) groups compared with control mice (64.21 +/- 2.27 x 10(4) microm(3); P = 0.0004, P < 0.0001, P < 0.0001, P < 0.0001, respectively). The mean VEGF and CCL2/MCP-1 protein levels decreased significantly (P = 0.001, P = 0.02, respectively) in the treated group compared with the control group. ICAM-1 expression did not differ significantly between the treated and control groups. The number of choroid-infiltrating macrophages decreased markedly in the treated group. CONCLUSIONS: Atorvastatin effectively inhibited laser-induced CNV in mice and was associated with downregulation of CCL2/MCP-1 and VEGF and reduced macrophage infiltration into the RPE/choroid.

Upregulation of VEGF in murine retina via monocyte recruitment after retinal scatter laser photocoagulation.

PURPOSE: This study was conducted to determine changes in the expression of vascular endothelial growth factor (VEGF) in murine retina after retinal scatter laser photocoagulation. METHODS: Photocoagulation (PHC) was performed on wild-type C57BL/6J mice using a diode laser, and the eyes were enucleated 1, 2, 3, 4, 7, and 14 days after laser treatment. VEGF and monocyte chemoattractant protein (MCP)-1 levels in the sensory retina and retinal pigmented epithelial (RPE) cells in both tissues were measured by ELISA. The VEGF mRNA was measured by real-time RT-PCR. Leukocyte infiltration into the RPE-choroid was determined by flow cytometry. VEGF comparisons between mice subjected to PHC and those treated with monocyte recruitment inhibitor (anti-MCP-1) were performed and statistically analyzed. The expression of VEGF and MCP-1 in the retina was determined by immunohistochemistry. RESULTS: VEGF protein levels significantly increased 1 day after PHC in both the RPE-choroid and the sensory retina. VEGF concentrations were maximum at day 3 after photocoagulation and stayed elevated until day 7. The number of choroid-infiltrating macrophages was markedly increased in mice with laser treatment compared with those without laser treatment. VEGF expression decreased after treatment with neutralized antibody to monocyte recruitment. We demonstrate that MCP-1 expression in the retina increased markedly after scatter laser photocoagulation by immunohistochemistry and ELISA. CONCLUSIONS: Retinal scatter laser photocoagulation induced upregulation of VEGF in the sensory retina and RPE-choroid at an early period. The authors speculate that the major source of VEGF in the retina after retinal scatter laser photocoagulation is the recruited monocytes.

Suppression of laser-induced choroidal neovascularization by nontargeted siRNA.

PURPOSE. To investigate the effect of nontargeted siRNAs on vascular leakage and vascular endothelial growth factor (VEGF)-A expression in the development of choroidal neovascularization (CNV). METHODS. Nontargeted siRNAs were 21-nt (nucleotides) siRNA-Luc (Luciferase) or 16-nt siRNA-Luc. Targeted 21-nt siRNA-Vegfa or phosphate-buffered saline (PBS) was used for comparison. Laser photocoagulation was used to induce CNV in wild-type C57BL/6J mice; 7 days later, vascular leakage was determined by fluorescein angiography, and CNV volumes were measured by confocal microscopy. Expression of VEGF-A in the retinal pigment epithelium (RPE)/choroid was quantified by ELISA 3 days after photocoagulation. RESULTS. Pathologically significant leakage developed in most of the 16nt-siRNA-Luc- or PBS-injected mice but in significantly fewer 21nt-siRNA-Luc- and 21nt-siRNA-Vegfa-injected mice (P = 0.0004, P = 0.0001, respectively). CNV volume in 21-nt siRNA-Luc- and 21nt-siRNA-Vegfa-injected eyes was significantly lower than in PBS-injected eyes (P = 0.0124, P = 0.0040, respectively). CNV volume was not suppressed by 16-nt siRNA-Luc injection (P = 0.7700). The mean VEGF protein level decreased significantly in the 21nt-siRNA-Luc- and 21nt-siRNA-Vegfa-injected eyes compared with PBS-injected eyes 3 days after laser photocoagulation (P = 0.0011, P = 0.0063, respectively). The 16nt-siRNA-Luc-injected eyes did not show VEGF-A suppression 3 days after laser photocoagulation (P = 0.3177). Between 21-nt siRNA-Luc- and 21nt-siRNA-Vegfa-injected eyes, there were no significant differences in CNV volume, the VEGF-A level, or pathologic leakage detected by fluorescein. CONCLUSIONS. These data suggest that nontarget 21nt-siRNA can suppress laser-induced choroidal neovascularization anatomically and functionally through VEGF suppression.