Abstract
Purpose :
Retinal neovascularization is a major cause of blindness in ischemic retinopathy including retinopathy of prematurity (ROP) and proliferative diabetic retinopathy. Protein kinase RNA-like endoplasmic reticulum kinase (PERK) is one of branches of the endoplasmic reticulum (ER) stress which can be activated by distinct insults including hypoxia. This study was to investigate the role of PERK in ischemic retinopathy.
Methods :
Studies were performed in a mouse model of oxygen-induced retinopathy (OIR) by maintaining wild type mice in 70% oxygen from postnatal day (P)7 to P12 and room air from P12 to P17. GSK2606414, a potent and selective inhibitor targeting PERK, was orally administered (50 mg/kg, once daily) to OIR pups from P12 to P16. Retinas were collected at P17 for analysis of phospho-PERK by Western blot. Whole retinas were labeled with isolectin B4 and the vasculature was examined by fluorescence microscopy.
Results :
The level of p-PERK was significantly increased (1.9 fold) in OIR retinas compared to room air control retinas at P17, suggesting that PERK pathway was activated in OIR model. After treatment with GSK2606414, OIR-induced phosphorylation of PERK was blunted in comparison to vehicle treatment, indicating PERK pathway could be effectively blocked by its inhibitor. Importantly, inhibition of PERK manifested a 36% reduction of retinal neovascularization (NV) and a 13% decrease of avascular area (p<0.05) compared to vehicle treatment during OIR. Moreover, in GSK2606414-treated OIR mice, the density and the distribution of the endothelial tip cells was elevated 2.8-fold at the junction of the vascular and avascular retina, and both the number and the length of tip cell filopodia were dramatically increased at P17. Although GSK2606414 treatment did not affect OIR-induced upregulation of angiogenic molecules including VEGF, EPO, Dll4, FGF2 and angiopoietin 2, it markedly reduced upregulation of CD206 and CD86, markers for M2 macrophage/microglia that promotes pathological angiogenesis.
Conclusions :
These data indicate that PERK pathway is involved in the development of pathological angiogenesis likely by regulation of M2 macrophage/microglia during retinal ischemia. Pharmacological inhibition of PERK may provide a novel approach to alleviate aberrant retinal vascular formation and promote normal retinal vessel regrowth.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.