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The effect of uric acid on homocysteine-induced endothelial dysfunction in bovine aortic endothelial cells
Ivana Papezikova1, Michaela Pekarova, Antonin Lojek
1Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czech Republic.
Insights
High uric acid levels impair nitric oxide (NO) production and increase superoxide generation in endothelial cells, suggesting a detrimental role in cardiovascular health.
Area of Science:
- Cardiovascular Science
- Endothelial Biology
- Oxidative Stress
Background:
- Elevated plasma uric acid is linked to cardiovascular disease risk and endothelial dysfunction.
- The precise role of uric acid in endothelial dysfunction remains debated, with possibilities including a causative factor, marker, or even antioxidant.
Purpose of the Study:
- To investigate the direct effects of uric acid on endothelial cells, both intact and those with homocysteine-induced dysfunction.
- To determine if uric acid influences nitric oxide (NO) production and superoxide generation in bovine aortic endothelial cells.
Main Methods:
- Bovine aortic endothelial cells were treated with varying concentrations of uric acid and homocysteine.
- Nitric oxide (NO) production, eNOS expression and phosphorylation, and superoxide generation were measured.
- Electrochemical methods, Western blotting, and fluorescence microscopy were employed.
Main Results:
- Homocysteine significantly reduced NO release; low-dose uric acid partially restored it, while higher doses were ineffective.
- Uric acid alone, in a dose-dependent manner, decreased NO release.
- Uric acid increased superoxide production in stimulated cells but did not affect eNOS expression or phosphorylation.
Conclusions:
- Uric acid diminishes NO bioavailability in endothelial cells.
- Uric acid enhances superoxide generation, contributing to oxidative stress.
- These findings suggest uric acid may play a detrimental role in endothelial dysfunction.
Objectives:
Elevated plasma uric acid indicates an increased risk of cardiovascular diseases associated with endothelial dysfunction. However, the role of uric acid in the pathogenesis of endothelial dysfunction is still a matter of debate. It is not clear whether uric acid is a real causative risk factor, an inert marker, or even a protective molecule with respect to its antioxidant properties. We have studied the effect of uric acid on intact endothelial cells as well as cells with homocysteine-induced endothelial dysfunction.
Design:
Bovine aortic endothelial cells were treated with uric acid (100 - 600 muM) and homocysteine (100 muM) or with uric acid only. After 24 hours, the cells were stimulated with 1 mug/ml of calcium ionophore A23187, and nitric oxide (NO) production was measured electrochemically with the use of a NO-sensitive microelectrode. The expression of endothelial nitric oxide synthase (eNOS) and eNOS phosphorylation at Ser1179 was estimated with the use of Western blotting. Interaction between NO and uric acid was measured with a NO electrode. Superoxide generation was measured with the use of the fluorescence dye MitoSox Red.
Results:
Homocysteine strongly diminished A23187-induced NO release. 100 muM uric acid slightly restored NO production; higher concentrations were ineffective. Interestingly, a dose-dependent decrease of NO release was observed in the cells treated only with uric acid. Uric acid did not scavenge NO and did not change eNOS protein expression or phosphorylation at Ser1179, but dose-dependently increased superoxide production in A23187-stimulated cells.
Conclusion:
In conclusion, uric acid decreased NO bioavailability and enhanced superoxide generation in A23187-stimulated bovine aortic endothelial cells.
