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Contrasting effects of thiol-modulating agents on endothelial NO bioactivity
1Evans Memorial Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
American Journal of Physiology. Cell Physiology
|July 10, 2001
Summary
Glutathione (GSH) depletion affects endothelial nitric oxide (NO) bioactivity differently depending on the method used. Thiol oxidation impairs NO production and eNOS activity, while other depletion methods show varied effects.
Area of Science:
- Biochemistry
- Cellular Biology
- Vascular Physiology
Background:
- Endothelium-derived nitric oxide (NO) is crucial for vascular homeostasis.
- NO bioactivity is sensitive to intracellular redox status, influenced by glutathione (GSH).
- Previous studies show conflicting results on the link between GSH and endothelial NO bioactivity.
Purpose of the Study:
- To define the role of intracellular glutathione (GSH) in modulating endothelial NO bioactivity.
- To investigate how different GSH depletion methods impact NO production and endothelial nitric oxide synthase (eNOS) activity.
Main Methods:
- Porcine aortic endothelial cells (PAECs) were treated with buthionine-(S,R)-sulfoximine (BSO), diamide, or 1-chloro-2,4-dinitrobenzene (CDNB) to deplete GSH.
- Endothelial NO bioactivity was measured by A-23187-induced cGMP accumulation.
- eNOS catalytic activity was assessed by L-[(3)H]arginine-to-L-[(3)H]citrulline conversion in intact cells, cell fractions, and purified eNOS.
Main Results:
- BSO-induced GSH depletion had no effect on NO bioactivity.
- Diamide oxidized thiols, inhibited cGMP accumulation, impaired response to exogenous NO, and reduced eNOS activity by ~75%, reversible by dithiothreitol.
- CDNB inhibited cGMP accumulation, impaired eNOS activity in PAECs, and inactivated NADPH, a cofactor for eNOS and glutathione reductase.
Conclusions:
- Thiol-modulating agents have pleiotropic effects on endothelial NO bioactivity.
- Diamide inhibits NO bioactivity via thiol oxidation of eNOS.
- CDNB impairs eNOS activity by inactivating NADPH, potentially resolving conflicting prior research.