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S. Parameswaran, Y. Ding, S.J. Ryan, R. Kannan, D.R. Hinton; Regulation of Methionine Sulfoxide Reductases (Msrs) in a Murine Model of Hyperoxia–Hypoxia Induced Retinopathy . Invest. Ophthalmol. Vis. Sci. 2006;47(13):885.
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We previously showed regulation of Msrs in RPE cells with oxidative stress and silencing of MsrA rendered RPE more susceptible to apoptosis. In this study, we examined the effects of hyperoxia–hypoxia on regulation of Msrs in a mouse model of retinopathy of prematurity (ROP).
Human RPE of early passages (3–4) in 1% FBS were exposed to 100µM cobalt chloride (CoCl2) for 30 min. to 4h. Gene expression of MsrA and MsrB2 was determined by real–time PCR and protein expression of MsrA by western blot analysis. Retinal neovascularization was induced in a mouse model of hyperoxia–hypoxia induced retinopathy in neonatal pups of two strains (C57BL/6J and 129S3/SvIM). Dams and their litters were placed in a hyperoxic environment (75 ± 3% O2) on postnatal day 7 (P7) and returned to room air on postnatal day 12 (P12). In this model, all animals show retinal angiogenesis, peaking at postnatal day 17 (P17) and regressing by postnatal day 26 (P26). Gene expression of MsrA and MsrB2 was quantitated by real–time PCR at 0h, 6h, 24h, 48h, 72h and 96h after hyperoxia and after 0h (P12), 12, 24 (P13), 48 (P14), 96h (P16) and on days 5 (P17), 7 (P19), 9 (P21) and 11(P23) of hypoxia.
Hypoxia induced by CoCl2 in vitro from 30 min. to 4h (verified by the upregulation of HIF1α) increased MsrA and MsrB2 gene expression as compared to normoxic controls. In the in vivo model, MsrA and MsrB2 were upregulated during hyperoxia but values were significantly higher in 129S3/SvIM than C57BL/6J. During the hypoxic period, MsrA expression exhibited biphasic regulation; an increase up to 12h and a decrease thereafter to 48h in both strains. MsrA showed upregulation during the angiogenic phase and this trend was maintained during the entire period of angiogenesis in both strains. Interestingly, MsrB2 was down regulated in 129S3/SvIM as opposed to an increase in C57BL/6J. Both strains showed significant decrease in MsrA and MsrB2 during the vascular regression period (P19–P23).
Our data show that hyperoxia–hypoxia regulates MsrA and MsrB2 genes in the mouse ROP model. The regulation pattern varies between 129S3/SvIM (more angiogenic) and C57BL/6J (less angiogenic) mouse strains for both genes.
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