Amelioration of sepsis by TIE2 activation–induced vascular protection

Abstract

Protection of endothelial integrity has been recognized as a frontline approach to alleviating sepsis progression, yet no effective agent for preserving endothelial integrity is available. Using an unusual anti-angiopoietin 2 (ANG2) antibody, ABTAA (ANG2-binding and TIE2-activating antibody), we show that activation of the endothelial receptor TIE2 protects the vasculature from septic damage and provides survival benefit in three sepsis mouse models. Upon binding to ANG2, ABTAA triggers clustering of ANG2, assembling an ABTAA/ANG2 complex that can subsequently bind and activate TIE2. Compared with a conventional ANG2-blocking antibody, ABTAA was highly effective in augmenting survival from sepsis by strengthening the endothelial glycocalyx, reducing cytokine storms, vascular leakage, and rarefaction, and mitigating organ damage. Together, our data advance the role of TIE2 activation in ameliorating sepsis progression and open a potential therapeutic avenue for sepsis to address the lack of sepsis-specific treatment.

All TIEd up: mechanisms of Schlemm’s canal maintenance

“…Taken together with previous studies, which have documented decreased AHO and reduced expression of PROX1 and VEGFR3 in aged SC (12,13), these data suggest that loss of TIE2 signaling underlies age-dependent deterioration of SC function. In line with these observations, intraocular injections of TIE2-activating ABTAA-ANGPT2 antibody complexes (19) promoted SC EC proliferation and PROX1 and KLF4 expression and decreased IOP in aged mice, indicating a potentially important therapeutic avenue for prevention and treatment of agerelated SC degeneration.…”

Tie1 controls angiopoietin function in vascular remodeling and inflammation

“…Recombinant ANG1, inhibition of ANG2 or increasing Tie2 activity by therapeutic antibodies or a small-molecule phosphatase inhibitor have vascular protective effects in acute inflammation and in sepsis (32,33,34,62,72,73), consistent with an agonist action of ANG1 and antagonistic action of ANG2. Reduced Tie2 protein and Tie2 and Ang1 mRNA levels have been reported in murine sepsis and systemic inflammation (56,74).…”

Impaired angiopoietin/Tie2 signaling compromises Schlemm’s canal integrity and induces glaucoma

“…In comparison with those of siControl-LECs, siTIE2-LECs displayed reduced mRNA and protein expression of KLF4, VE-cadherin, and PROX1 ( Figure 13, A-D). Moreover, when hDLECs were stimulated with a TIE2 agonistic antibody, ANGPT2-binding and TIE2-activating antibody (ABTAA) (41), TIE2 downstream signals such as AKT and ERK were activated ( Figure 13, E and F). Furthermore, ABTAA attenuated IFN-γ-induced reduction of PROX1 levels in hDLECs, and its effect was abolished by ERK inhibitor, but not AKT inhibitor, indicating that TIE2 activation contributed to upregulating or maintaining PROX1 levels through activation of ERK signaling ( Figure 13, G and H).…”

“…To evaluate the changes in PROX1 expression in hDLECs, cells were incubated with control siRNA or siTIE2 for 48 hours and harvested at 72 hours after the start of transfection. For immunoblot detection of TIE2 downstream signaling proteins, ERK, p-ERK (T202/Y204, p-ERK), AKT, and p-AKT (S473, p-AKT) hDLECs were incubated with a premixed solution containing 2 μg/ml human ANGPT2 (R&D systems) and 10 μg/ml ABTAA for 30 minutes without serum starvation as previously described (41). To examine changes in PROX1 expression by ABTAA treatment, hDLECs were treated with premix solutions containing IFN-γ (Peprotech) -as an inhibitor of PROX1-and 2 µg/ was performed using FastStart SYBR Green Master Mix (Roche) and S1000 Thermocycler (Bio-Rad) with the indicated primers (Supplemental Table 2).…”