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Glycine transporter GLYT1 is essential for glycine-mediated protection human intestinal epithelial cells against oxidative damage

Lookup NU author(s): Dr Alison Howard, Sajid Javed, Sarah Waring, Professor Dianne Ford, Professor Barry Hirst

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Abstract

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 sub-units, 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.


Publication metadata

Author(s): Howard A, Tahir I, Javed S, Waring SM, Ford D, Hirst BH

Publication type: Article

Journal: Journal of Physiology

Year: 2010

Volume: 588

Issue: 6

Pages: 995–1009

Print publication date: 01/02/2010

ISSN (print): 0022-3751

ISSN (electronic): 1469-7793

Publisher: Wiley-Blackwell Publishing Ltd.

URL: http://dx.doi.org/10.1113/jphysiol.2009.186262

DOI: 10.1113/jphysiol.2009.186262


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