权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Antioxidants transport via GLUT1 at the blood-retinal barrier

抗氧化剂通过 GLUT1 在血视网膜屏障上转运

基本信息

批准号：
15390046
负责人：
HOSOYA Ken-ichi
金额：
$ 8.45万
依托单位：
TOYAMA MEDICAL AND PHARMACEUTICAL UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

Vitamin C, which is an antioxidant in the body, plays a key role in protecting the retina from oxidative stress and is present in the retina at a high concentration compared with its presence in other organs. The purpose of study was to elucidate the mechanisms of vitamin C transport across the blood-retinal barrier (BRB) in vive and in vitro. [^<14>C]Dehydroascorbic acid (DHAA) and [^<14>C]ascorbic acid (AA) transport in the retina were examined using in vivo integration plot analysis in rats and the transport mechanism was characterized using a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB) as an in vitro model of the inner BRB. The apparent influx permeability clearance (CL) of [^<14>C]DHAA of the retina was about 38-fold greater than that of [^<14>C]AA, whereas there was no major difference in the heart. HPLC analysis revealed that most of the vitamin C accumulates in AA form in the retina. These results suggest that vitamin C is mainly transported … More in DHAA form across the BRB and accumulates in AA form in the rat retina. [^<14>C]DHAA uptake by TR-iBRB cells took place in an Na^+-independent and concentration-dependent manner with a Michaelis constant of 93.4 microM. This process was inhibited by facilitative glucose transporter (GLUT)s' substrates and inhibitors. [^<14>C]DHAA uptake was inhibited by glucose in a concentration-dependent manner with a 50% inhibition concentration of 5.56 mM. These results suggest that GLUTs are involved in DHAA transport at the inner BRB. To quantify GLUTS' gene levels at the inner BRB using a combination of magnetic isolation method for rat retinal vascular endothelial cells and real-time quantitative PCR analysis, GLUT1 expression was the largest of three GLUTs, whereas GLUT3 was not detected at the inner BRB. The expression of GLUT4 was 100-fold less than that of GLUT1, suggesting that GLUT1 is responsible for DHAA transport at the inner BRB. When glucose concentration in the blood was high as 20 mM in streptozotocin-induced diabetic rats, CL of [^<14>C]DHAA of the retina was inhibited by 31%. In conclusion, vitamin C is predominantly transported as DHAA via GLUT1 at the inner BRB and accumulates as AA in the retina. Hyperglycemia reduces the supply of the vitamin C to the retina. The physiological role of GLUT1 at the inner BRB appears to involve the supply of vitamin C as well as glucose from the circulating blood to the retina to protect the retina against oxidative stress. Less

维生素C是体内的一种抗氧化剂，在保护视网膜免受氧化应激方面起着关键作用，与其他器官相比，它在视网膜中的浓度很高。本研究的目的是在体内和体外研究维生素C通过血-视网膜屏障（BRB）的转运机制。在大鼠中使用体内整合图分析来检查[^<14>C]脱氢抗坏血酸（DHAA）和[^<14>C]抗坏血酸（AA）在视网膜中的转运，并且使用条件永生化大鼠视网膜毛细血管内皮细胞系（TR-iBRB）作为内部BRB的体外模型来表征转运机制。[^ C]DHAA在视网膜的表观内流渗透性清除率（CL）<14>约为[^ C]AA的38倍<14>，而在心脏中无显著差异。HPLC分析显示，大部分维生素C以AA形式积累在视网膜中。这些结果表明，维生素C主要通过 ...更多信息以DHAA形式穿过BRB并以AA形式在大鼠视网膜中积累。TR-iBRB<14>细胞对DHAA的摄取以非Na^+依赖性和浓度依赖性的方式进行，米氏常数为93.4 μ M。这一过程被促进性葡萄糖转运蛋白（GLUT）的底物和抑制剂抑制。葡萄<14>糖以浓度依赖性方式抑制DHAA的摄取，50%抑制浓度为5.56 mM。这些结果表明，GLUT参与了DHAA在内BRB的转运。为了定量GLUTS的基因水平在内部的BRB使用的大鼠视网膜血管内皮细胞的磁分离方法和实时定量PCR分析相结合，GLUT 1的表达是最大的三个GLUTs，而GLUT 3在内部的BRB没有检测到。GLUT 4的表达比GLUT 1的表达低100倍，表明GLUT 1负责DHAA在内部BRB的转运。在链脲佐菌素诱导的糖尿病大鼠中，当血液中的葡萄糖浓度高至20 mM时，视网膜的[^<14>C]DHAA的CL被抑制31%。总之，维生素C主要通过GLUT 1在内BRB处作为DHAA转运，并在视网膜中作为AA积累。维生素C缺乏症会减少视网膜的维生素C供应。GLUT 1在内BRB的生理作用似乎涉及从循环血液向视网膜供应维生素C以及葡萄糖，以保护视网膜免受氧化应激。少