Glucose-induced oxidative stress in mesangial cells.
BACKGROUND
Hyperglycemia is a well-recognized pathogenic factor of long-term complications in diabetes mellitus. Hyperglycemia not only generates reactive oxygen species but also attenuates antioxidant mechanisms creating a state of oxidative stress.


METHODS
Porcine mesangial cells were cultured in high glucose (HG) for ten days to investigate the effects on the antioxidant defenses of the cell.


RESULTS
Mesangial cells cultured in HG conditions had significantly reduced levels of glutathione (GSH) compared with those grown in normal glucose (NG). The reduced GSH levels were accompanied by decreased gene expression of both subunits of gamma-glutamylcysteine synthetase (gamma-GCS), the rate-limiting enzyme in de novo synthesis of GSH. Elevated levels of intracellular malondialdehyde (MDA) were found in cells exposed to HG conditions. HG also caused elevated mRNA levels of the antioxidant enzymes CuZn superoxide dismutase (SOD) and MnSOD. These changes were accompanied by increased mRNA levels of extracellular matrix proteins (ECM), fibronectin (FN) and collagen IV (CIV). Addition of antioxidants to high glucose caused a significant reversal of FN and CIV gene expression; alpha-lipoic acid also up-regulated gamma-GCS gene expression and restored intracellular GSH and MDA levels.


CONCLUSIONS
The results demonstrate the existence of glucose-induced oxidative stress in mesangial cells as evidenced by elevated MDA and decreased GSH levels. The decreased levels of GSH are as a result of decreased mRNA expression of gamma-GCS within the cell. Antioxidants caused a significant reversal of FN and CIV gene expression, suggesting an etiological link between oxidative stress and increased ECM protein synthesis.
Catherwood
Mark A
MA
Department of Clinical Biochemistry, Queen's University of Belfast, Royal Group of Hospitals, Belfast, United Kingdom. mark.catherwood@bll.n-i.nhs.uk
Powell
Lesley A
LA
Anderson
Paul
P
McMaster
Dorothy
D
Sharpe
Peter C
PC
Trimble
Elisabeth R
ER
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002452:Cell Count; D002470:Cell Survival; D002478:Cells, Cultured; D002839:Chromans / Q000494:pharmacology; D003928:Diabetic Nephropathies / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D005920:Glomerular Mesangium / Q000166:cytology* / Q000201:enzymology*; D005947:Glucose / Q000494:pharmacology*; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics; D006861:Hydrogen Peroxide / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D013482:Superoxide Dismutase / Q000235:genetics; D013552:Swine
D000975:Antioxidants; D002839:Chromans; D016326:Extracellular Matrix Proteins; D016877:Oxidants; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D005947:Glucose; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid