Glycine transporter GLYT1 is essential for glycine-mediated protection of human intestinal epithelial cells against oxidative damage
Glycine transporter GLYT1 is essential for glycine-mediated protection of human intestinal epithelial cells against oxidative damage
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DOI：
10.1113/jphysiol.2009.186262
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发表时间：
2010-03-15
影响因子：
5.5
通讯作者：
Hirst, Barry H.
中科院分区：
文献类型：
--
作者：
Howard, Alison;Tahir, Imran;Hirst, Barry H.
甘氨酸保护哺乳动物肠道免受缺血再灌注（IR）损伤引起的氧化损伤，并预防或逆转实验诱导的结肠炎。然而，保护机制在很大程度上仍然未知。本研究的目的是直接证明甘氨酸介导的人肠上皮细胞的保护，并确定特定转运蛋白GLYT 1对甘氨酸摄取的要求。外源性甘氨酸保护人类肠道Caco-2和HCT-8细胞对氧化剂叔丁基氢过氧化物和减少细胞内活性氧的浓度，当应用之前，但不伴随着氧化挑战。氧化挑战前给予甘氨酸保留了细胞内谷胱甘肽浓度，但对甘氨酸摄取率没有影响。保护依赖于GLYT 1活性，被特定的GLYT 1抑制剂阻断，支持细胞内甘氨酸积累的要求。维持细胞内谷胱甘肽含量被认为是一种机制，通过这种机制，保护作用可能部分被介导。然而，表达的基因编码GLYT 1和谷胱甘肽合成酶谷氨酸-半胱氨酸连接酶，催化和修饰亚基，谷胱甘肽合成酶没有改变甘氨酸或叔丁基氢过氧化物，这表明转录调控不参与。这项工作证明了GLYT 1在肠道中的新作用，并表明肠上皮细胞直接响应氧化挑战，而不依赖于上皮外组织或功能，如神经元，血流或免疫反应进行抗氧化防御。甘氨酸的保护作用和维持上皮抗氧化防御表明它可能有益于治疗炎症性肠病。
Glycine protects mammalian intestine against oxidative damage caused by ischaemia-reperfusion (IR) injury and prevents or reverses experimentally-induced colitis. However the mechanism of protection remains largely unknown. The objectives of the current study were to demonstrate directly glycine-mediated protection of human intestinal epithelial cells and to determine the requirement for glycine uptake by the specific transporter GLYT1. Exogenous glycine protected human intestinal Caco-2 and HCT-8 cells against the oxidative agent tert-butylhydroperoxide and reduced the intracellular concentration of reactive oxygen species, when applied prior to but not concomitant with the oxidative challenge. Glycine given prior to oxidative challenge preserved intracellular glutathione concentration but had no effect on the rate of glycine uptake. Protection was dependent on GLYT1 activity, being blocked by a specific GLYT1 inhibitor, supporting a requirement for intracellular glycine accumulation. Maintained intracellular glutathione content is indicated as a mechanism through which the protective effect may in part be mediated. However expression of the genes encoding GLYT1 and the glutathione synthesising enzymes glutamate-cysteine ligase, both catalytic and modifier subunits, and glutathione synthetase was not altered by glycine or tert-butylhydroperoxide, suggesting transcriptional regulation is not involved. This work has demonstrated a novel role of GLYT1 in intestine and shown that intestinal epithelial cells respond directly to oxidative challenge without reliance on extra-epithelial tissues or functions such as neurone, blood-flow or immune responses for antioxidant defence. The protective actions of glycine and maintenance of epithelial antioxidant defences suggest it may be beneficial in treatment of inflammatory bowel disease.