Department of Biochemistry, Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt.
Department of Oral Biology and Diagnostic Sciences, Dental College of Georgia, Augusta University, Augusta, GA 30912, USA.
Int J Mol Sci. 2023 Jan 5;24(2):1071. doi: 10.3390/ijms24021071.
Age-related macular degeneration (AMD) is a major cause of blindness. Recent studies have reported impaired glycolysis in AMD patients with a high lactate/pyruvate ratio. Elevated homocysteine (Hcy) (Hyperhomocysteinemia, HHcy) was observed in several clinical studies, reporting an association between HHcy and AMD. We established the effect of HHcy on barrier function, retinal pigment epithelium (RPE) structure, and induced choroidal neovascularization (CNV) in mice. We hypothesize that HHcy contributes to AMD by inducing a metabolic switch in the mitochondria, in which cells predominantly produce energy by the high rate of glycolysis, or "Warburg", effect. Increased glycolysis results in an increased production of lactate, cellular acidity, activation of angiogenesis, RPE barrier dysfunction, and CNV. Evaluation of cellular energy production under HHcy was assessed by seahorse analysis, immunofluorescence, and western blot experiments. The seahorse analysis evaluated the extracellular acidification rate (ECAR) as indicative of glycolysis. HHcy showed a significant increase in ECAR both in vivo using (Cystathionine β-synthase) and mice retinas and in vitro (Hcy-treated ARPE-19) compared to wild-type mice and RPE cells. Moreover, HHcy up-regulated glycolytic enzyme (Glucose transporter-1 (GlUT-1), lactate dehydrogenase (LDH), and hexokinase 1 (HK1)) in Hcy-treated ARPE-19 and primary RPE cells isolated from , , and mice retinas. Inhibition of GLUT-1 or blocking of N-methyl-D-aspartate receptors (NMDAR) reduced glycolysis in Hcy-treated RPE and improved albumin leakage and CNV induction in Hcy-injected mice eyes. The current study suggests that HHcy causes a metabolic switch in the RPE cells from mitochondrial respiration to glycolysis during AMD and confirms the involvement of NMDAR in this process. Therefore, targeting Glycolysis or NMDAR could be a novel therapeutic target for AMD.
年龄相关性黄斑变性（AMD）是导致失明的主要原因。最近的研究报告称，AMD 患者的糖酵解受损，乳酸/丙酮酸比值升高。几项临床研究中观察到同型半胱氨酸（Hcy）升高（高同型半胱氨酸血症，HHcy），报告 HHcy 与 AMD 之间存在关联。我们在小鼠中建立了 HHcy 对屏障功能、视网膜色素上皮（RPE）结构和诱导脉络膜新生血管（CNV）的影响。我们假设 HHcy 通过诱导线粒体中的代谢转换导致 AMD，其中细胞主要通过高糖酵解率或“Warburg”效应产生能量。糖酵解增加导致乳酸产量增加、细胞酸度增加、血管生成激活、RPE 屏障功能障碍和 CNV。通过 Seahorse 分析、免疫荧光和 Western blot 实验评估 HHcy 下的细胞能量产生。 Seahorse 分析评估细胞外酸化率（ECAR）作为糖酵解的指标。与野生型小鼠和 RPE 细胞相比，HHcy 在体内（使用胱硫醚 β-合酶）和 小鼠的视网膜以及体外（Hcy 处理的 ARPE-19）均显示 ECAR 显著增加。此外，HHcy 上调了 Hcy 处理的 ARPE-19 和从 、 、 小鼠视网膜分离的原代 RPE 细胞中的糖酵解酶（葡萄糖转运蛋白-1（GlUT-1）、乳酸脱氢酶（LDH）和己糖激酶 1（HK1））。抑制 GLUT-1 或阻断 N-甲基-D-天冬氨酸受体（NMDAR）可减少 Hcy 处理的 RPE 中的糖酵解，并改善 Hcy 注射小鼠眼睛中的白蛋白渗漏和 CNV 诱导。本研究表明，HHcy 在 AMD 期间导致 RPE 细胞从线粒体呼吸到糖酵解的代谢转换，并证实 NMDAR 参与了这一过程。因此，针对糖酵解或 NMDAR 可能成为 AMD 的新治疗靶点。
