Regulation of neovascularization by S-glutathionylation via the Wnt5a/sFlt-1 pathway

Abstract

S-glutathionylation occurs when reactive oxygen or nitrogen species react with protein-cysteine thiols. Glutaredoxin-1 (Glrx) is a cytosolic enzyme which enzymatically catalyses the reduction in S-glutathionylation, conferring reversible signalling function to proteins with redox-sensitive thiols. Glrx can regulate vascular hypertrophy and inflammation by regulating the activity of nuclear factor κB (NF-κB) and actin polymerization. Vascular endothelial growth factor (VEGF)-induced endothelial cell (EC) migration is inhibited by Glrx overexpression. In mice overexpressing Glrx, blood flow recovery, exercise function and capillary density were significantly attenuated after hindlimb ischaemia (HLI). Wnt5a and soluble Fms-like tyrosine kinase-1 (sFlt-1) were enhanced in the ischaemic-limb muscle and plasma respectively from Glrx transgenic (TG) mice. A Wnt5a/sFlt-1 pathway had been described in myeloid cells controlling retinal blood vessel development. Interestingly, a Wnt5a/sFlt-1 pathway was found also to play a role in EC to inhibit network formation. S-glutathionylation of NF-κB components inhibits its activation. Up-regulated Glrx stimulated the Wnt5a/sFlt-1 pathway through enhancing NF-κB signalling. These studies show a novel role for Glrx in post-ischaemic neovascularization, which could define a potential target for therapy of impaired angiogenesis in pathological conditions including diabetes.

Figure 1. Reactive protein thiolates undergo reversible or irreversible oxidation

Reactive oxygen species/ reactive nitrogen species (ROS/RNS) generate reversible intermediates including S-nitrosothiol (R-SNO) and sulfenic acid (R-SOH), which may become S-glutathionylated protein (R-SSG). R-SOH can be further oxidized to generate irreversible modifications such as sulfonic acid (R-SO₃H). ROS, reactive oxygen species; RNS, reactive nitrogen species; Glrx, Glutaredoxin; GSH, glutathione; Trx, thioredoxin.

Figure 2. Glutaredoxin system

R-SSG, S-glutathionylated protein; GR, glutathione reductase; Glrx, glutaredoxin-1, catalyze removal of GSH adducts in the presence of GSH and NADPH.

Figure 3. Enhanced endothelial Glrx increases NF-κB-dependent Wnt5a, upregulating the anti-angiogenic receptor sFlt-1

Glrx, Glutaredoxin; VEGF, vascular endothelial growth factor; sFlt-1, soluble fms-like tyrosine kinase-1 (VEGFR1); Wnt5a, wningless-type MMTC integration site family, member 5A; ROR2, receptor tyrosine kinase-like orphan receptor 2; –SSG, S-glutathionylation.