PF4 antagonizes retinal neovascularization via inhibiting PRAS40 phosphorylation in a mouse model of oxygen-induced retinopathy

Biochim Biophys Acta Mol Basis Dis. 2020 Mar 1;1866(3):165604. doi: 10.1016/j.bbadis.2019.165604. Epub 2019 Nov 15.

Abstract

Retinal neovascularization (RNV) is a common pathology of blinding proliferative retinopathies. The current treatments to RNV, however, are hindered by limited efficacy, side effects, and drug resistance. A naturally-occurring cytokine in retina that is amicable to immune system and possesses robust anti-neovascular function would facilitate to overcome the hurdles. In this study, retinas from a mouse model of oxygen-induced retinopathy (OIR) underwent a protein array to screen the naturally-occurring cytokines that may antagonize RNV. Among the 62 angiogenesis-associated cytokines, platelet factor 4 (Pf4) stood out with the most prominent upregulation and statistical significance. Moreover, an intravitreal injection of mouse Pf4 demonstrated dramatic anti-vaso-obliteration and anti-neovascularization effects dose dependently in the OIR model; whereas human PF4 inhibited the proliferation, migration, and tubulogenesis of monkey retinal vascular endothelial cells treated with VEGF and TNF-α. These previously undescribed angiostatic effects of PF4 in OIR retinas and retinal vascular endothelial cells support translation of this naturally-occurring chemokine into a therapeutic modality to RNV supplementary to the anti-VEGFs. Mechanistically, a phosphorylation array and western blots indicated that downregulation of proline-rich Akt substrate of 40 kDa (Pras40) and its phosphorylation were necessary for Pf4's anti-neovascular effects in the OIR retinas. Indeed, overexpression of the wildtype Pras40 and the mutant version with deficient phosphorylation abolished and mimicked the Pf4's angiostatic effects in the OIR retinas, respectively. The similar effects were also observed in vitro. This study, for the first time, links PF4's anti-RNV function to an intracellular signaling molecule PRAS40 and its phosphorylation.

Keywords: Neovascularization; Oxygen-induced retinopathy; PF4; PRAS40; Proliferative retinopathy; Retinal ischemia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / antagonists & inhibitors*
  • Adult
  • Aged
  • Aged, 80 and over
  • Animals
  • Disease Models, Animal
  • Endothelial Cells / metabolism
  • Female
  • Humans
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Middle Aged
  • Oxygen / metabolism*
  • Phosphoproteins / antagonists & inhibitors*
  • Phosphorylation / physiology
  • Platelet Factor 4 / antagonists & inhibitors*
  • Retina / metabolism*
  • Retinal Neovascularization / metabolism*
  • Retinopathy of Prematurity / metabolism*
  • Signal Transduction / physiology
  • Vascular Endothelial Growth Factor A / metabolism

Substances

  • AKT1S1 protein, human
  • Adaptor Proteins, Signal Transducing
  • PF4 protein, human
  • Phosphoproteins
  • Vascular Endothelial Growth Factor A
  • proline-rich Akt substrate, 40 kDa protein, mouse
  • Platelet Factor 4
  • Oxygen