Thioredoxin-Interacting Protein Expression Is Required for VEGF-Mediated Angiogenic Signal in Endothelial Cells

Abstract

Thioredoxin-interacting protein (TXNIP) contributes to cellular redox-state homeostasis via binding and inhibiting thioredoxin (TRX). Increasing evidence suggests that cellular redox homeostasis regulates vascular endothelial growth factor (VEGF)-mediated signaling. This study aims to examine the redox-dependant role of TXNIP in regulating VEGF-mediated S-glutathionylation and angiogenic signaling. TXNIP-knockout mice (TKO) or wild-type (WT) treated with the reduced glutathione (GSH)-precursor, N-acetyl cysteine (WT-NAC, 500 mg/kg) were compared to WT using hypoxia-induced neovascularization model. In response to hypoxia, retinas from TKO and WT-NAC mice showed significant decreases in reparative revascularization and pathological neovascularization with similar VEGF expression compared with WT. VEGF failed to stimulate vascular sprouting from aortic rings of TKO compared to WT mice. TKO mice or WT+NAC experienced reductive stress as indicated by twofold increase in TRX reductase activity and fourfold increase in reduced-GSH levels compared with WT. In human microvascular endothelial (HME) cells, VEGF stimulated co-precipitation between vascular endothelial growth factor receptor 2 (VEGFR2) with low molecular weight protein tyrosine phosphatase (LMW-PTP). Silencing TXNIP expression blunted VEGF-induced oxidation of GSH and S-glutathionylation of the LMW-PTP in HME cells. These effects were associated with impaired VEGFR2 phosphorylation that culminated in inhibiting cell migration and tube formation. Overexpression of TXNIP restored VEGFR2 phosphorylation and cell migration in TKO-endothelial cells. TXNIP expression is required for VEGF-mediated VEGFR2 activation and angiogenic response in vivo and in vitro. TXNIP expression regulates VEGFR-2 phosphorylation via S-glutathionylation of LMW-PTP in endothelial cells. Our results provide novel mechanistic insight into modulating TXNIP expression as a potential therapeutic target in diseases characterized by aberrant angiogenesis.