Johnathon Sturgis, Ke Jiang, Stephanie A Hagstrom, Maya Moorthy, Bonilha Vera L
Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA.
Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
bioRxiv. 2025 Jul 31:2025.07.30.667736. doi: 10.1101/2025.07.30.667736.
Retinal degenerative diseases, such as age-related macular degeneration (AMD), retinitis pigmentosa, and glaucoma, have been linked to mitochondrial dysfunction. However, the impact of mitochondrial DNA (mtDNA) mutation accumulation in the context of these retinopathies has yet to be thoroughly explored. Our previous studies focused on the retinal phenotype observed in the PolgD257A mutator mice (D257A), revealing the effects of aging and mtDNA mutation accumulation in the retina. We have reported that this model exhibited significant morphological and functional deficits in the retina by 6 months of age, with notable alterations in the retinal pigment epithelium (RPE) occurring as early as 3 months, including changes in the cristae density and reduction in length of mitochondria. This study investigated how mtDNA mutations affect the metabolic interaction between the retina and RPE in young (3 months) and old (12 months) wild-type (WT) and D257A mice. We assessed cellular energy production using freshly dissected retina samples from both groups through Seahorse analysis, immunofluorescence, and Western blot experiments. The analysis of aged D257A retina punches revealed significantly reduced basal and maximal mitochondrial respiration, along with increased mitochondrial reserve capacity compared to WT. However, glycolytic flux, measured as a function of extracellular acidification rate (ECAR), did not differ between WT and D257A mice. Both D257A retina and RPE exhibited decreased expression of essential electron transport proteins involved in oxidative phosphorylation. Additionally, we observed a reduction in the expression of glucose transporter 1 (GLUT-1) and lactate transporter (MCT1) at the apical surface of the RPE. Enzymes associated with glycolysis, including hexokinase II and lactate dehydrogenase A, were significantly lower in the aged D257A retina, while hexokinase I and pyruvate kinase 2 were upregulated in the RPE. These findings indicate that the accumulation of mtDNA mutations leads to impaired metabolism in both the retina and RPE. Furthermore, it suggests that glucose from the choroidal blood supply is being utilized by the RPE rather than being transported to the neural retina. Mitochondrial dysfunction in RPE promotes a glycolytic state in these cells, leading to reduced availability of metabolites and, consequently, diminished overall retinal function. These results are essential for advancing our understanding of the mechanisms underlying retinal degeneration and provide a new perspective on the role of mtDNA mutations in these diseases.
视网膜退行性疾病，如年龄相关性黄斑变性（AMD）、色素性视网膜炎和青光眼，已与线粒体功能障碍相关联。然而，在这些视网膜病变的背景下，线粒体DNA（mtDNA）突变积累的影响尚未得到充分探索。我们之前的研究聚焦于在PolgD257A突变小鼠（D257A）中观察到的视网膜表型，揭示了衰老和mtDNA突变积累在视网膜中的影响。我们已经报道，该模型在6月龄时视网膜出现显著的形态和功能缺陷，早在3个月时视网膜色素上皮（RPE）就出现明显改变，包括嵴密度变化和线粒体长度缩短。本研究调查了mtDNA突变如何影响年轻（3个月）和年老（12个月）野生型（WT）及D257A小鼠视网膜与RPE之间的代谢相互作用。我们通过海马分析、免疫荧光和蛋白质印迹实验，使用两组新鲜解剖的视网膜样本评估细胞能量产生。对老年D257A视网膜切片的分析显示，与WT相比，基础和最大线粒体呼吸显著降低，同时线粒体储备能力增加。然而，以细胞外酸化率（ECAR）衡量的糖酵解通量在WT和D257A小鼠之间没有差异。D257A视网膜和RPE中参与氧化磷酸化的必需电子传递蛋白的表达均降低。此外，我们观察到RPE顶端表面的葡萄糖转运蛋白1（GLUT-1）和乳酸转运蛋白（MCT1）表达减少。与糖酵解相关的酶，包括己糖激酶II和乳酸脱氢酶A，在老年D257A视网膜中显著降低，而己糖激酶I和丙酮酸激酶2在RPE中上调。这些发现表明，mtDNA突变的积累导致视网膜和RPE中的代谢受损。此外，这表明脉络膜血液供应中的葡萄糖被RPE利用，而不是被转运到神经视网膜。RPE中的线粒体功能障碍促进了这些细胞中的糖酵解状态，导致代谢物可用性降低，从而使整体视网膜功能受损。这些结果对于推进我们对视网膜变性潜在机制的理解至关重要，并为mtDNA突变在这些疾病中的作用提供了新的视角。
