Targeting VE-PTP activates TIE2 and stabilizes the ocular vasculature
Jikui Shen, … , Kevin G. Peters, Peter A. Campochiaro
Jikui Shen, … , Kevin G. Peters, Peter A. Campochiaro
Published September 2, 2014
Citation Information: J Clin Invest. 2014;124(10):4564-4576. https://doi.org/10.1172/JCI74527.
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Research Article Vascular biology

Targeting VE-PTP activates TIE2 and stabilizes the ocular vasculature

Abstract

Retinal and choroidal neovascularization (NV) and vascular leakage contribute to visual impairment in several common ocular diseases. The angiopoietin/TIE2 (ANG/TIE2) pathway maintains vascular integrity, and negative regulators of this pathway are potential therapeutic targets for these diseases. Here, we demonstrated that vascular endothelial-protein tyrosine phosphatase (VE-PTP), which negatively regulates TIE2 activation, is upregulated in hypoxic vascular endothelial cells, particularly in retinal NV. Intraocular injection of an anti–VE-PTP antibody previously shown to activate TIE2 suppressed ocular NV. Furthermore, a small-molecule inhibitor of VE-PTP catalytic activity (AKB-9778) activated TIE2, enhanced ANG1-induced TIE2 activation, and stimulated phosphorylation of signaling molecules in the TIE2 pathway, including AKT, eNOS, and ERK. In mouse models of neovascular age-related macular degeneration, AKB-9778 induced phosphorylation of TIE2 and strongly suppressed NV. Ischemia-induced retinal NV, which is relevant to diabetic retinopathy, was accentuated by the induction of ANG2 but inhibited by AKB-9778, even in the presence of high levels of ANG2. AKB-9778 also blocked VEGF-induced leakage from dermal and retinal vessels and prevented exudative retinal detachments in double-transgenic mice with high expression of VEGF in photoreceptors. These data support targeting VE-PTP to stabilize retinal and choroidal blood vessels and suggest that this strategy has potential for patients with a wide variety of retinal and choroidal vascular diseases

Authors

Jikui Shen, Maike Frye, Bonnie L. Lee, Jessica L. Reinardy, Joseph M. McClung, Kun Ding, Masashi Kojima, Huiming Xia, Christopher Seidel, Raquel Lima e Silva, Aling Dong, Sean F. Hackett, Jiangxia Wang, Brian W. Howard, Dietmar Vestweber, Christopher D. Kontos, Kevin G. Peters, Peter A. Campochiaro

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Figure 6

AKB-9778 suppresses ischemia-induced retinal NV in the presence of high ANG2 levels.

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AKB-9778 suppresses ischemia-induced retinal NV in the presence of high ...
Tet-opsin-Ang2 mice were placed in 75% oxygen at P7, returned to room air at P12, and divided into 4 groups: Dox+/vehicle (n = 17) received daily s.c. Dox (50 mg/kg) and an intraocular injection of vehicle; Dox+/AKB-9778 (n = 21) received daily s.c. Dox and an intraocular injection of 5 μg AKB-9778; Dox–/vehicle (n = 10) received an intraocular injection of vehicle; Dox–/AKB-9778 (n = 10) received an intraocular injection of 5 μg AKB-9778. At P17, the Dox+/vehicle mice had severe NV (A) that was markedly reduced in the Dox+/AKB-9778 mice (B). The large vessels are hyaloid vessels, but all other green staining is NV. Compared with Dox–/vehicle mice (C), Dox–/AKB-9778 mice appeared to show less NV (D). Scale bar: 500 μm. The area of NV was significantly larger in Dox+/vehicle mice versus that in Dox–/vehicle mice (E) (*P < 0.001 by 1-way ANOVA with Bonferroni’s correction), indicating that ANG2 stimulated NV. The area of NV was significantly smaller in Dox+/AKB-9778 versus Dox+/vehicle mice (**P < 0.001 by 1-way ANOVA with Bonferroni’s correction), indicating that AKB-9778 suppressed NV in the presence of high levels of ANG2 and possibly less so in the absence of high ANG2 levels. In hypoxic HUVECs (incubated in 5% oxygen for 4 or 16 hours), there were marked reductions of ANG1-induced (500 ng/ml) TIE2 phosphorylation (F) and downstream signaling (G); however, AKB-9778 (5 μM) restored TIE2 phosphorylation (F) and downstream signaling (G), even in the presence of exogenous ANG2 (500 ng/ml). Antibodies recognizing the proteins regardless of phosphorylation status were used as loading controls. Similar results were obtained in 3 independent experiments.