High glucose mediates prooxidant and antioxidant enzyme activities in coronary endothelial cells

Bayraktutan, Ulvi and Weidig, Pamela and McMaster, Dorothy and Ulker, Sibel (2004) High glucose mediates prooxidant and antioxidant enzyme activities in coronary endothelial cells. Diabetes Obesity and metabolism, 6 . pp. 432-441.

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Abstract

Objective: Excess levels of free radicals such as nitric oxide (NO) and superoxide anion (O2-)are associated with the pathogenesis of endothelial cell dysfunction in diabetes mellitus. This study was designed to investigate the underlying causes of oxidative stress in coronary microvascular endothelial cells (CMEC) exposed to hyperglycaemia.

Methods: CMEC were cultured under normal (5.5 mmol/L) or high glucose (22 mmol/L)concentrations for 7 days. The activity and expression (protein level) of eNOS, iNOS, NAD(P)H oxidase and antioxidant enzymes, namely, superoxide dismutase (SOD), catalase and glutahione peroxidase (GPx) were investigated by specific activity assays and Western analyses,respectively while the effects of hyperglycaemia on nitrite and O2 - generation were investigated

by Griess reaction and cytochrome C reduction assay, respectively.

Results: Hyperglycaemia did not alter eNOS or iNOS protein expressions and overall nitrite generation, an index of NO production. However, it significantly reduced the levels of intracellular antioxidant glutathione by 50% (p<0.05) and increased the protein expressions

and/or activities of p22-phox, a membrane-bound component of pro-oxidant NAD(P)H oxidase and antioxidant enzymes (p<0.05). Free radical-scavengers, namely, Tiron and MPG (0.1-1 mol/L) reduced hyperglycaemia-induced antioxidant enzyme activity and increased glutathione and nitrite generation to the levels observed in CMEC cultured in normoglycaemic medium (p<0.01). The differences in enzyme activity and expressions were independent of the increased osmolarity generated by high glucose levels as investigated by using equimolar concentrations of mannitol in parallel experiments.

Conclusions: These results suggest that hyperglycaemia-induced oxidative stress may arise in CMEC as a result of enhanced prooxidant enzyme activity and diminished generation of 3 antioxidant glutathione. By increasing the antioxidant enzyme capacity CMEC may protect themselves against free radical-induced cell damage in diabetic conditions.

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Item Type: Article
Schools/Departments: University of Nottingham UK Campus > Faculty of Medicine and Health Sciences > School of Medicine > Division of Medical Sciences and Graduate Entry Medicine
Depositing User: Sayers, Hazel
Date Deposited: 17 Apr 2007
Last Modified: 15 Aug 2013 07:37
URI: http://eprints.nottingham.ac.uk/id/eprint/483

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