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 3

AKB-9778 promotes TIE2 phosphorylation and activation of downstream signaling in HUVECs and enhances angiopoietin-induced TIE2 phosphorylation.

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AKB-9778 promotes TIE2 phosphorylation and activation of downstream sign...
HUVECs were left untreated or were treated with AKB-9778 alone or together with ANG1 or ANG2 (500 ng/ml) for 10 minutes. Cell lysates were immunoprecipitated (IP) with anti-TIE2 and immunoblotted sequentially for phosphotyrosine (p-Tyr) and TIE2, or they were probed with rabbit polyclonal antibodies against p-AKT, total AKT, p-ERK, total ERK, p-eNOS, or total eNOS. Incubation with AKB-9778 or ANG1 caused phosphorylation of TIE2 (A) and molecules in the TIE2 signaling pathway (B), which was markedly enhanced by coadministration of ANG1 with AKB-9778. Treatment with ANG2 caused no phosphorylation of TIE2 or downstream molecules, but there was strong phosphorylation with coadministration of ANG2 and AKB-9778, though less than was observed with ANG1 plus AKB-9778. (C)Knockdown of TIE2 in the EC-RF24 endothelial cell line (ECRF) with human TIE2-specific shRNA eliminated the ability of AKB-9778, with or without ANG1 or ANG2, to stimulate phosphorylation of AKT or ERK. (D) AKB-9778, ANG1, or a combination of both caused no detectable phosphorylation of VEGFR2, and AKB-9778 had no effect on phosphorylation of VEGFR2 induced by 25 ng/ml VEGF. MWr, relative molecular weight.