Activation of Angiopoietin-Tie2 Signaling Protects the Kidney from Ischemic Injury by Modulation of Endothelial-Specific Pathways

Abstract

Background Ischemia-reperfusion AKI (IR-AKI) is estimated to affect 2%-7% of all hospitalized patients. The significant morbidity and mortality associated with AKI indicates urgent need for effective treatments. Previous studies have shown activation of the vascular angiopoietin-Tie2 tyrosine kinase signaling pathway abrogates ischemia-reperfusion injury (IRI). We extended previous studies to (1) determine the molecular mechanism(s) underlying kidney injury and protection related to decreased or increased activation of Tie2, respectively, and (2) to test the hypothesis that deletion of the Tie2 inhibitory phosphatase vascular endothelial protein tyrosine phosphatase (VE-PTP) or injection of a new angiopoietin mimetic protects the kidney from IRI by common molecular mechanism(s).Methods Bilateral IR-AKI was performed in VE-PTP wild-type or knockout mice and in C57BL/6J mice treated with Hepta-ANG1 or vehicle. Histologic, immunostaining, and single-cell RNA sequencing analyses were performed. ResultsThe phosphatase VE-PTP, which negatively regulates the angiopoietin-Tie2 pathway, was upregulated in kidney endothelial cells after IRI, and genetic deletion of VE-PTP in mice protected the kidney from IR-AKI. Injection of Hepta-ANG1 potently activated Tie2 and protected the mouse kidney from IRI. Single-cell RNAseq analysis of kidneys from Hepta-ANG1-treated and vehicle-treated mice identified endothelial-specific gene signatures and emergence of a new glomerular endothelial subpopulation associated with improved kidney function. Overlap was found between endothelial-specific genes upregulated by Hepta-ANG1 treatment and those downregulated in HUVECs with constitutive FOXO1 activation, including Entpd1/ENTPD1 that modulates purinergic receptor signaling.Conclusions Our data support a key role of the endothelium in the development of IR-AKI, introduce Hepta-ANG1 as a putative new therapeutic biologic, and report a model to explain how IRI reduces Tie2 signaling and how Tie2 activation protects the kidney.

Tackling AKI

“…10 Rather, an alternative strategy to VEPTP inhibition, Tie2 activation (a substrate for VEPTP), was tested in IR using a Hepta-ANG1, a novel angiopoietin 1 mimetic, which binds to and activates Tie2. Treatment with Hepta-ANG1 protected against IR-induced renal injury, 9 decreasing mRNA expression of the renal tubular injury marker Kim1 and increasing the expression of the healthy proximal tubule marker Slc34a1 after IR. However, the magnitude of benefit on plasma creatinine with Hepta-Ang1 treatment was modest compared with that seen in the VE-PTPiKO model (approximately 14% reduction in plasma creatinine versus approximately 66% reduction, respectively).…”

“…In this article, the authors show that the VE-PTP protein was upregulated after bilateral renal IR in mice, remaining significantly elevated 7 days after injury. 9 This led the authors to hypothesize that VE-PTP inhibition could provide protective effects during IR-AKI.…”

“…IR injury resulted in a significant elevation in plasma creatinine (approximately 1.5 mg/dl) on day 1 after injury in littermate controls, whereas IR injury in VE-PTPiKO mice exhibited improved plasma creatinine (approximately 0.5 mg/dl). 9 Despite observing compelling renal protective effects in the VE-PTP knockout mice after IR injury, the authors could not directly explore the effect of pharmacological inhibition of VE-PTP because of limited in vivo bioavailability of pharmacological inhibitors of VE-PTP, such as AKB-9778 (razuprotafib). 10 Rather, an alternative strategy to VEPTP inhibition, Tie2 activation (a substrate for VEPTP), was tested in IRusing a Hepta-ANG1, a novel angiopoietin 1 mimetic, which binds to and activates Tie2.…”

“…IR injury resulted in a significant elevation in plasma creatinine (approximately 1.5 mg/dl) on day 1 after injury in littermate controls, whereas IR injury in VE-PTPiKO mice exhibited improved plasma creatinine (approximately 0.5 mg/dl). 9…”

“…7,8 The article by Li et al in this issue of JASN further explores the role of endothelial targets, vascular endothelial protein tyrosine phosphatase (VE-PTP) and Tie2, in ischemia reperfusion (IR)-induced AKI. 9 VE-PTP (protein tyrosine phosphatase receptor type B) functions as a negative regulator of Tie2 by regulating Tie2 phosphorylation, which is stimulated by angiopoietin 1. In this article, the authors show that the VE-PTP protein was upregulated after bilateral renal IR in mice, remaining significantly elevated 7 days after injury.…”