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H. Levkovitch–Verbin, R. Dardik, M. Kalev–Landoy, S. Kuulmann–Vander, S. Melamed; Simultaneous Changes in Mrna Levels of Pro–And Anti–Apoptotic Genes in Models of Glaucoma, Optic Nerve Transection and Secondary Degeneration in Rats . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1244.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate changes in retinal mRNA levels induced by complete optic nerve transection (ONT), elevated intraocular pressure (IOP) and partial ONT (a model for secondary degeneration) over time. Methods:We used a gene array of 96 marker genes associated with 18 signal transduction pathways to examine changes in RNA profiles of retinas taken from rats 6 hours after complete ONT. Seven genes were upregulated, confirmed by semi–quantitative RT–PCR analysis in 4 of them: Ei24 and Gadd45a (both associated with apoptosis induced via the p53 pathway), IAP–1 (inhibitor of apoptosis protein 1) and Cdk2 (cell cycle regulation and apoptosis). Levels of Gadd45a, IAP–1 and Cdk2 genes were then studied by quantitative RT–PCR in models of complete ONT, glaucoma (induced by the translimbal photocoagulation laser model) and secondary degeneration( induced by partial ONT of the superior area) over time. Results: Complete ONT model: 1 and 3 days after ONT, the significantly upregulated genes in the experimental eye were: the pro–apoptotic Gadd45a which was increased by 3.5±2.2– (p=0.04, n=8) and 3.24±0.71– (p=0.002, n=6) fold, respectively; the antiapoptotic IAP–1 by 2.8±0.3– (p=0.002, n=8) and 2.7±0.5– (p=0.007, n=6) fold, and Cdk2 by 2.1±0.5– (p=0.03, n=8) and 2.4±0.7– (p=0.03, n=6) fold. No change was detected at 3 hours. All gene levels returned to baseline at day14. Glaucoma model: 8 and 16 days and one month after IOP elevation, the significantly upregulated genes were: Gadd45a which was increased by 3.6±1.2– (p=0.008, n=9), 2.2±0.9– (p=0.03, n=9) and 2.9±1.7– (p=0.01, n=12) fold, respectively and IAP–1 by 1.9±0.2– (p=0.014, n=9), 2.7±0.54– (p=0.005, n=9) and 3.64± 0.76– (p=0.003, n=12) fold. No change was found at day 1. Interestingly, IOP elevation did not affect the level of Cdk2 at any time point. Partial ONT model: 14 days after partial ONT, there were increased Gadd45a levels in the inferior area (p=0.07, n=12), but there were no significantly increased levels of other genes in superior or inferior retinal areas at 3 or 14 days after injury. Conclusions:Both ONT and IOP elevation induced simultaneous upregulation of pro– and anti–apoptotic genes. IOP elevation–induced upregulation was slower and lasted longer. Cdk2 gene was upregulated only by ONT, indicating a possible different effect of the two procedures on cell cycle regulatory genes. Gadd45a may also be involved in secondary degeneration.
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