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Xiaokun Han, Haibo Wang, M Elizabeth Hartnett; Inhibition of Uncoupling Protein 2 Promotes Physiologic Retinal Vascularization via Activation of GLUT1 and S6K1. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3448.
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© ARVO (1962-2015); The Authors (2016-present)
Retinopathy of prematurity is characterized by delayed physiologic retinal vascular development (PRVD) and increased intravitreal neovascularization. We found that increased retinal uncoupling protein 2 (UCP2), a regulator of cellular glucose metabolism, was associated with reduced blood glucose in rat pups in an oxygen-induced retinopathy (OIR) model compared to room air-raised pups. Since cellular glucose metabolism is important for retinal vascular development, we postulated that inhibition of UCP2 would facilitate PRVD and reduce the risk of ROP and addressed this hypothesis using a rat model of OIR.
Within 4-6 hours of birth, Sprague-Dawley dams and pups (male and female) were placed into an Oxycycler that cycled oxygen between 50% and 10% oxygen every 24 hours. Rat pups in the OIR model received intraperitoneal injections of genipin (10 mg/kg), an UCP2 inhibitor, or equal volumes of PBS every other day beginning at postnatal day 3 (p3) and extending through p13. At p14, pups were euthanized and PRVD determined by avascular retinal area/total retinal area (AVA) was assessed in isolectin-stained retinal flatmounts. Retinal VEGF was measured by ELISA. Human retinal microvascular endothelial cells (hRMVECs) transfected with UCP2 siRNA or control siRNA, or pretreated with genipin (5 µM) or DMSO, were then stimulated with VEGF (50 ng/ml) or PBS for 30 mins. After treatments, glucose uptake was determined by 2-NBDG-2-Deoxyglucose. GLUT1, a dominant isoform of glucose transporter in the retinal cells, and phosphorylated S6K1 (p-S6K1), a regulator for cell growth, were measured by western blots. Statistics were performed using two-tailed Student’s t-test and results were Mean ± SEM.
Compared to PBS-treated pups, genipin-treated pups had significantly less AVA (31.77±3.10 vs. PBS 45.52±4.61, p=0.03, n=13) and greater retinal VEGF protein (267±51.17 vs. PBS 181.31±12.18 pg/ml, p=0.02, n=6). Compared to control siRNA, GLUT1 protein and VEGF-induced p-S6K1 were increased in UCP2-transfected hRMVECs. Compared to control DMSO, glucose uptake was greater in hRMVECs treated with genipin (1.28±0.10 vs. DMSO 1.00±0.02, p=0.02, n=9).
Inhibition of UCP2 by genipin in the OIR model facilitated PRVD, potentially by increasing GLUT1 and VEGF-mediated S6K1 activation, which was found in cultured retinal endothelial cells.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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