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Early determinants of H2O2-induced endothelial dysfunction.
Beth M Boulden1, Julian D Widder, Jon C Allen
1Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30322, USA.
Free Radical Biology & Medicine
|August 10, 2006
Summary
Repeated exposure to hydrogen peroxide (H2O2) initially boosts nitric oxide (NO) but then reduces it. This early endothelial dysfunction stems from decreased tetrahydrobiopterin (BH4) and increased superoxide (O2*-) production.
Area of Science:
- Biochemistry
- Cell Biology
- Physiology
Background:
- Reactive oxygen species (ROS) can transiently activate endothelial nitric oxide synthase (eNOS), increasing nitric oxide (NO) production.
- However, prolonged or repeated ROS exposure leads to a decrease in NO production, indicating endothelial dysfunction.
- The early mechanisms driving this reduction in NO bioavailability are not fully understood.
Purpose of the Study:
- To investigate the early determinants of reduced nitric oxide (NO) production in endothelial cells following repeated hydrogen peroxide (H2O2) exposure.
- To identify key molecular players and pathways involved in H2O2-induced endothelial dysfunction.
Main Methods:
- Endothelial cells were exposed to H2O2.
- Nitric oxide (NO) production was measured electrochemically.
- Superoxide (O2*-) production and tetrahydrobiopterin (BH4) levels were quantified.
- Interventions included BH4 supplementation, scavenging of O2*- and peroxynitrite (ONOO-), and NADPH oxidase inhibition.
Main Results:
- Initial H2O2 exposure increased NO production, which then decreased over 30 minutes.
- This decrease was associated with a significant increase in O2*- production and a marked reduction in BH4 levels.
- Integrated NO production upon repeated H2O2 exposure was attenuated, confirming endothelial dysfunction.
- BH4 supplementation, O2*- or ONOO- scavenging, or NADPH oxidase inhibition prevented the dysfunction.
Conclusions:
- Early H2O2-induced endothelial dysfunction is characterized by decreased BH4 levels and increased O2*- production.
- The dysfunction is dependent on O2*-, ONOO-, and a functional NADPH oxidase.
- Repeated activation of NADPH oxidase by ROS may create a positive feedback loop promoting endothelial dysfunction.