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Jihong Wu, Fengjuan Gao, Feng Gao, Yi Zhang, Xinghuai Sun; High pressure induces mtDNA damage and mutations and mitochondrial dysfunction in primary cultured retinal ganglion cells. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6021.
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© ARVO (1962-2015); The Authors (2016-present)
Cumulative mtDNA damage and mutations occurred in glaucoma and contributed to the progressive RGCs loss. However, the mechanisms of which trigger mtDNA damages in glaucoma are still unclear. This study is to investigate whether high pressure directly induced mtDNA damage and mutations of RGCs and the subsequent mitochondrial dysfunction.
The RGCs isolated from neonatal rat were cultured primarily, and exposed to 30 mmHg hydrostatic pressure using a closed, pressurized chamber equipped with a manometer. The cells were collected at 24, 48, 72, and 120 hrs after high pressure (HP) for analysis of mtDNA damage and mutations, mtDNA repair enzymes and mitochondrial function.
HP induced mtDNA damage as early as 24h after onset. The damage continued to increase and was significantly increased (>40%) at 72h. An increase in mtDNA mutation was observed when the duration of HP was extended beyond 48h, reaching levels 5.1-fold higher (p<0.01) than those of the control. mRNA levels of mtDNA repair/replication enzymes OGG1, MYH, and POLG in the RGCs were increased 11.2-fold (p<0.01), 6.3-fold (p<0.05), and 1.8-fold, respectively, at 12h of HP exposure. In contrast, the mitochondrial accumulation of OGG1, MYH, and POLG proteins was slightly increased at 48 h of HP exposure but was significantly decreased at 72h of HP exposure. Furthermore, we found no significant increase in ROS throughout the duration of the experiment, diminishing the possibility that ROS caused the mtDNA damage or mutation under HP conditions.mtDNA-encoded proteins ND5, ND6 and cytochrome b (subunits of complex I and III), were significantly decreased in the HP-treated RGCs. The activities of complex I and complex III were decreased by 22.6% (p<0.05) and 40.8% (p<0.01), respectively, at 120h after HP. A decrease in Δψm in HP-treated RGCs was detected. The MAPR in the cells under HP decreased in a time-dependent manner, with levels amounting to 67.9% of those in the control cells at 120h (p<0.05).
HP itself directly induced mtDNA damage and mutations of RGCs. HP resulted in the reduction in the activities of complex I and complex III, which might be due to the decreased expression of mtDNA-encoded proteins. Mitochondrial function in the RGCs decreased after HP.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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