Pharmaceutical Sciences and Ophthalmology, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045, USA.
Mol Pharm. 2013 Jun 3;10(6):2350-61. doi: 10.1021/mp3007133. Epub 2013 May 22.
Chronic hypoxia, a key stimulus for neovascularization, has been implicated in the pathology of proliferative diabetic retinopathy, retinopathy of prematurity, and wet age related macular degeneration. The aim of the present study was to determine the effect of chronic hypoxia on drug transporter mRNA expression and activity in ocular barriers. Sprague-Dawley rats were exposed to hypobaric hypoxia (PB = 380 mmHg) for 6 weeks, and neonatal calves were maintained under hypobaric hypoxia (PB = 445 mmHg) for 2 weeks. Age matched controls for rats, and calves were maintained at ambient altitude and normoxia. The effect of hypoxia on transporter expression was analyzed by qRT-PCR analysis of transporter mRNA expression in hypoxic and control rat choroid-retina. The effect of hypoxia on the activity of PEPT, OCT, ATB(0+), and MCT transporters was evaluated using in vitro transport studies of model transporter substrates across calf cornea and sclera-choroid-RPE (SCRPE). Quantitative gene expression analysis of 84 transporters in rat choroid-retina showed that 29 transporter genes were up regulated or down regulated by ≥1.5-fold in hypoxia. Nine ATP binding cassette (ABC) families of efflux transporters including MRP3, MRP4, MRP5, MRP6, MRP7, Abca17, Abc2, Abc3, and RGD1562128 were up-regulated. For solute carrier family transporters, 11 transporters including SLC10a1, SLC16a3, SLC22a7, SLC22a8, SLC29a1, SLC29a2, SLC2a1, SLC3a2, SLC5a4, SLC7a11, and SLC7a4 were up regulated, while 4 transporters including SLC22a2, SLC22a9, SLC28a1, and SLC7a9 were down-regulated in hypoxia. Of the three aquaporin (Aqp) water channels, Aqp-9 was down-regulated, and Aqp-1 was up-regulated during hypoxia. Gene expression analysis showed down regulation of OCT-1, OCT-2, and ATB(0+) and up regulation of MCT-3 in hypoxic rat choroid-retina, without any effect on the expression of PEPT-1 and PEPT-2. Functional activity assays of PEPT, OCT, ATB(0+), and MCT transporters in calf ocular tissues showed that PEPT, OCT, and ATB(0+) functional activity was down-regulated, whereas MCT functional activity was up-regulated in hypoxic cornea and SCRPE. Gene expression analysis of these transporters in rat tissues was consistent with the functional transport assays except for PEPT transporters. Chronic hypoxia results in significant alterations in the mRNA expression and functional activity of solute transporters in ocular tissues.
慢性缺氧是促进新生血管形成的关键刺激因素，与增殖性糖尿病视网膜病变、早产儿视网膜病变和湿性年龄相关性黄斑变性的病理学有关。本研究旨在确定慢性缺氧对眼屏障中药物转运体 mRNA 表达和活性的影响。将 Sprague-Dawley 大鼠暴露于低压缺氧（PB = 380 mmHg）6 周，将新生小牛维持在低压缺氧（PB = 445 mmHg）2 周。大鼠和小牛的年龄匹配对照在环境海拔和常氧下维持。通过 qRT-PCR 分析缺氧大鼠脉络膜-视网膜中转运体 mRNA 表达，分析缺氧对转运体表达的影响。通过体外转运研究模型转运体底物穿过小牛角膜和巩膜脉络膜-RPE（SCRPE），评估缺氧对 PEPT、OCT、ATB(0+)和 MCT 转运体活性的影响。定量基因表达分析大鼠脉络膜-视网膜中的 84 种转运体表明，29 种转运体基因的表达被上调或下调≥1.5 倍。9 种 ABC 家族外排转运体（MRP3、MRP4、MRP5、MRP6、MRP7、Abca17、Abc2、Abc3 和 RGD1562128）上调。对于溶质载体家族转运体，11 种转运体（SLC10a1、SLC16a3、SLC22a7、SLC22a8、SLC29a1、SLC29a2、SLC2a1、SLC3a2、SLC5a4、SLC7a11 和 SLC7a4）上调，而 4 种转运体（SLC22a2、SLC22a9、SLC28a1 和 SLC7a9）在缺氧时下调。在三种水通道蛋白（AQP）中，AQP-9 下调，AQP-1 上调。基因表达分析显示，缺氧大鼠脉络膜-视网膜中 OCT-1、OCT-2 和 ATB(0+)下调，MCT-3 上调，但 PEPT-1 和 PEPT-2 的表达无变化。在小牛眼组织中进行的 PEPT、OCT、ATB(0+)和 MCT 转运体的功能活性测定显示，PEPT、OCT 和 ATB(0+)的功能活性下调，而 MCT 的功能活性上调。在大鼠组织中的这些转运体的基因表达分析与功能转运测定一致，除了 PEPT 转运体。慢性缺氧导致眼组织中溶质转运体的 mRNA 表达和功能活性发生显著改变。
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