Clinical Research Centre, School of Medicine, University College Dublin, Ireland.
Department of Ophthalmology, Mater Misericordiae University Hospital, Eccles Street, Dublin 7, Ireland.
Exp Eye Res. 2020 Dec;201:108349. doi: 10.1016/j.exer.2020.108349. Epub 2020 Nov 12.
Pseudoexfoliation syndrome (PXF) is the most common cause of secondary open angle glaucoma worldwide. Single nucleotide polymorphisms (SNPs) in the gene Lysyl oxidase like 1 (LOXL1) are strongly associated with the development of pseudoexfoliation glaucoma (PXFG). However, these SNPs are also present in 50-80% of the general population, suggestive of other factors being involved in the pathogenesis of PXFG. In this study, we aimed to investigate the influence of epigenetic regulation, specifically DNA methylation, on LOXL1 expression in PXFG using human tenons fibroblasts (HTFs), aqueous humour and serum samples from donors with and without PXFG. LOXL1 expression in HTFs was measured by qPCR and Western Blotting and LOXL1 concentration in aqueous humour was determined by ELISA. Global DNA methylation levels were quantified using an ELISA for 5-methylcytosine. MeDIP assays assessed the methylation status of the LOXL1 promoter region. Expression of methylation-associated enzymes (DNMT1, DNMT3a and MeCP2) were determined by qPCR and inhibited by 0.3 μM 5-azacytidine (5-aza). Results showed that LOXL1 expression was significantly decreased in PXFG HTFs compared with Control HTFs at gene (Fold change 0.37 ± 0.05, P < 0.01) level and showed a decrease, when measured at the protein level (Fold change 0.65 ± 0.42, P = 0.22), however this was not found to be significant. LOXL1 concentration was increased in the aqueous of PXFG patients compared with Controls (2.76 ± 0.78 vs. 1.79 ± 0.33 ng/ml, P < 0.01). Increased global methylation (56.07% ± 4.87% vs. 32.39% ± 4.29%, P < 0.01) was observed in PXFG HTFs compared with Control HTFs, as was expression of methylation-associated enzymes (DNMT1 1.58 ± 0.30, P < 0.05, DNMT3a 1.89 ± 0.24, P < 0.05, MeCP2 1.63 ± 0.30, P < 0.01). Methylation-associated enzymes were also increased when measured at protein level (DNMT1 5.70 ± 2.64, P = 0.04, DNMT3a 1.79 ± 1.55, P = 0.42, MeCP2 1.64 ± 1.33, P = 0.45). LOXL1 promoter methylation was increased in patients with PXFG compared to Control patients in both blood (3.98 ± 2.24, 2.10 ± 1.29, P < 0.05) and HTF cells (37.31 ± 22.0, 8.66 ± 10.40, P < 0.01). Treatment of PXFG HTFs with in 5-azacytidine increased LOXL1 expression when compared with untreated PXFG HTFs (Fold change 2.26 ± 0.67, P < 0.05). These data demonstrate that LOXL1 expression is altered in PXFG via DNA methylation and that reversal of these epigenetic changes may represent future potential therapeutic targets in the management of PXFG.
假性剥脱综合征(PXF)是全球最常见的继发性开角型青光眼的病因。赖氨酰氧化酶样 1(LOXL1)基因中的单核苷酸多态性(SNPs)与假性剥脱性青光眼(PXFG)的发展密切相关。然而,这些 SNPs 也存在于 50-80%的普通人群中,提示其他因素也参与了 PXFG 的发病机制。在这项研究中,我们旨在通过研究人Tenon 成纤维细胞(HTFs)、有和无 PXFG 供体的房水和血清样本,探讨表观遗传调控,特别是 DNA 甲基化对 LOXL1 表达的影响。通过 qPCR 和 Western Blotting 测量 HTFs 中的 LOXL1 表达,通过 ELISA 测量房水中的 LOXL1 浓度。使用 5-甲基胞嘧啶 ELISA 定量测量全基因组 DNA 甲基化水平。MeDIP 检测评估 LOXL1 启动子区域的甲基化状态。通过 qPCR 测定甲基化相关酶(DNMT1、DNMT3a 和 MeCP2)的表达,并通过 0.3μM 5-氮杂胞苷(5-aza)抑制。结果表明,与对照 HTFs 相比,PXFG HTFs 中的 LOXL1 表达在基因水平显著降低(Fold change 0.37±0.05,P<0.01),并且在蛋白水平上也呈下降趋势(Fold change 0.65±0.42,P=0.22),但这并没有显著差异。与对照组相比,PXFG 患者的房水中 LOXL1 浓度升高(2.76±0.78 vs. 1.79±0.33ng/ml,P<0.01)。与对照 HTFs 相比,PXFG HTFs 中观察到全基因组甲基化增加(56.07%±4.87% vs. 32.39%±4.29%,P<0.01),以及甲基化相关酶的表达增加(DNMT1 1.58±0.30,P<0.05,DNMT3a 1.89±0.24,P<0.05,MeCP2 1.63±0.30,P<0.01)。当在蛋白水平上测量时,甲基化相关酶的表达也增加(DNMT1 5.70±2.64,P=0.04,DNMT3a 1.79±1.55,P=0.42,MeCP2 1.64±1.33,P=0.45)。与对照患者相比,PXFG 患者的血液(3.98±2.24,2.10±1.29,P<0.05)和 HTF 细胞(37.31±22.0,8.66±10.40,P<0.01)中的 LOXL1 启动子甲基化增加。与未经处理的 PXFG HTFs 相比,用 5-氮杂胞苷处理 PXFG HTFs 增加了 LOXL1 的表达(Fold change 2.26±0.67,P<0.05)。这些数据表明,LOXL1 的表达在 PXFG 中通过 DNA 甲基化发生改变,逆转这些表观遗传变化可能代表了 PXFG 管理中未来潜在的治疗靶点。