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Updated: Jun 18, 2026

Detection of Nitric Oxide and Superoxide Radical Anion by Electron Paramagnetic Resonance Spectroscopy from Cells using Spin Traps
Published on: August 18, 2012
Reactive oxygen and nitrogen species regulate inducible nitric oxide synthase function shifting the balance of nitric
Jian Sun1, Lawrence J Druhan, Jay L Zweier
1The Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210-1252, USA.
Abstract:
Inducible NOS (iNOS) is induced in diseases associated with inflammation and oxidative stress, and questions remain regarding its regulation. We demonstrate that reactive oxygen/nitrogen species (ROS/RNS) dose-dependently regulate iNOS function. Tetrahydrobiopterin (BH4)-replete iNOS was exposed to increasing concentrations of ROS/RNS and activity was measured with and without subsequent BH4 addition. Peroxynitrite (ONOO(-)) produced the greatest change in NO generation rate, approximately 95% decrease, and BH4 only partially restored this loss of activity. Superoxide (O2(.-)) greatly decreased NO generation, however, BH4 addition restored this activity. Hydroxyl radical ((.)OH) mildly decreases NO generation in a BH4-dependent manner. iNOS was resistant to H2O2 with only slightly decreased NO generation with up to millimolar concentrations. In contrast to the inhibition of NO generation, ROS enhanced O2(.-) production from iNOS, while ONOO(-) had the opposite effect. Thus, ROS promote reversible iNOS uncoupling, while ONOO(-) induces irreversible enzyme inactivation and decreases both NO and O2(.-) production.
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