PR1P Stabilizes VEGF and Upregulates Its Signaling to Reduce Elastase-induced Murine Emphysema

Abstract

Emphysema is a progressive and fatal lung disease with no cure that is characterized by thinning, enlargement, and destruction of alveoli, leading to impaired gas exchange. Disease progression is due in part to dysregulation of VEGF (vascular endothelial growth factor) signaling in the lungs and increased lung-cell apoptosis. Here we asked whether PR1P (Prominin-1-derived peptide), a novel short peptide we designed that increases VEGF binding to endothelial cells, could be used to improve outcome in in vitro and in vivo models of emphysema. We used computer simulation and in vitro and in vivo studies to show that PR1P upregulated endogenous VEGF receptor-2 signaling by binding VEGF and preventing its proteolytic degradation. In so doing, PR1P mitigated toxin-induced lung-cell apoptosis, including from cigarette-smoke extract in vitro and from LPS in vivo in mice. Remarkably, inhaled PR1P led to significantly increased VEGF concentrations in murine lungs within 30 minutes that remained greater than twofold above that of control animals 24 hours later. Finally, inhaled PR1P reduced acute lung injury in 4-and 21-day elastase-induced murine emphysema models. Taken together, these results highlight the potential of PR1P as a novel therapeutic agent for the treatment of emphysema or other lung diseases characterized by VEGF signaling dysregulation.

The Prominin-1-Derived Peptide Improves Cardiac Function Following Ischemia

“…We next turned to molecular biology studies to determine the molecular mechanism by which PR1P augments recovery from myocardial ischemia caused by coronary artery ligation. We recently showed that PR1P bound VEGF, enhanced the prevalence of VEGF dimers (the active form of VEGF) and prevented VEGF degradation in vitro and in vivo in the lungs when delivered via inhalation [ 10 ]. We, therefore, investigated here whether systemically delivered PR1P similarly stabilized VEGF dimers within injured myocardium.…”

“…We have previously shown that PR1P, a small peptide derived from the extracellular domain of prominin-1 and which binds to VEGF and protects it from proteolytic degradation [ 9 , 10 ], augmented angiogenesis in multiple in vivo angiogenesis models and improved perfusion of threatened limbs in a murine hind limb ischemia model [ 9 ]. Additionally, PR1P has been shown to increase VEGF levels and signaling within lungs when delivered via inhalation [ 10 ] and to protect neurons [ 11 ] and lung cells [ 10 ] from apoptosis. We hypothesized here that PR1P would upregulate endogenous VEGF signaling within compromised heart tissue and improve outcome from myocardial infarction.…”

The Prominin-1 Derived Peptide Improves Cardiac Function Following Ischemia

“…Overexpression of an elastase inhibitor in mice in their model led to improvement in diastolic dysfunction at 4 days and improved cardiac performance at 28 days following coronary artery ligation suggesting that elastase inhibition suppresses inflammation associated cardiac dilatation and dysfunction after MI 39 . Importantly, PR1P does not inhibit elastase per se, but instead blocks its binding to VEGF 10 . As such, the effect of PR1P on the functional outcome in the ischemic myocardium may be due in part to its ability to prevent VEGF degradation by elastase and other proteases which might limit potential signaling effects of VEGF degradation products 40,41 Kurtagic et al showed that VEGF degradation product generated by elastase is a macrophage chemoattract 41 , and so reduced VEGF degradation product could in itself mitigate inflammation.…”

“…3). We recently showed that PR1P binding to VEGF prevented its degradation by proteases, including plasmin and elastase, naturally released by inflammatory cells during inflammation, and which compete with PR1P for binding sites within the VEGF heparin binding domain (HBD) 10 . PR1P binding to VEGF within ischemic zones of the myocardium likely similarly increases endogenous VEGF levels and signaling by preventing VEGF degradation by proteases released by inflammatory cells recruited into the heart following ischemia.…”

“…3B) at this same time period. We previously showed that PR1P significantly reduced retinal ganglion cell apoptosis in an optic nerve crush injury model 11 and prevented respiratory epithelial cell apoptosis from cigarette smoke extract invitro and from LPS in-vivo in mice 10 . Downstream VEGF signaling including the phosphorylation and activation of the protein kinase AKT has been shown to inhibit CM apoptosis [20][21][22] .…”