High glucose decreases intracellular glutathione concentrations and upregulates inducible nitric oxide synthase gene expression in intestinal epithelial cells.
Diabetes is associated with oxidative stress and increased concentrations of inflammatory cytokines. The aim of the study was to assess the effects of inflammatory cytokines and oxidative stress associated with increased glucose concentrations on inducible nitric oxide synthase (iNOS) promoter activity in intestinal epithelial cells. High-glucose (25 mmol/l) conditions reduced glutathione (GSH) concentrations in the human intestinal epithelial cell line, DLD-1. Addition of the antioxidant, alpha-lipoic acid, resulted in the restoration of GSH concentrations to normal. Upregulation of basal iNOS promoter activity was observed when cells were incubated in high glucose alone. This effect was significantly reduced by the addition of the antioxidant, alpha-lipoic acid, and completely blocked with inhibition of nuclear factor kappa B (NFkappaB) activity. Stimulation of cytokines (interleukin-1 beta, tumour necrosis factor-alpha, interferon-gamma) induced iNOS promoter activity in all conditions and this was accompanied by an increase in nitric oxide (NO) production. Inhibition of NFkappaB activity decreased, but did not completely inhibit, cytokine-induced iNOS promoter activity and subsequent production of NO. In conclusion, iNOS promoter activity induced by high concentrations of glucose is mediated in part through intracellular GSH and NFkappaB.
Powell
Lesley A
LA
Department of Clinical Biochemistry and Metabolic Medicine, Institute of Clinical Science, Queen's University Belfast, Grosvenor Road, Belfast BT12 6BJ, UK. l.powell@qub.ac.uk
Warpeha
Katherine M
KM
Xu
Weiming
W
Walker
Brian
B
Trimble
Elisabeth R
ER
D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D007422:Intestines / Q000166:cytology*; D009566:Nitrates / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000235:genetics* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects
D009566:Nitrates; D009573:Nitrites; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D005978:Glutathione; D005947:Glucose