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, ∼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.
Original language | English (US) |
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Pages (from-to) | 130-137 |
Number of pages | 8 |
Journal | Archives of Biochemistry and Biophysics |
Volume | 494 |
Issue number | 2 |
DOIs | |
State | Published - Feb 2010 |
Externally published | Yes |
Keywords
- Dose-dependent
- Hydrogen peroxide
- Hydroxyl radical
- Inducible nitric oxide synthase
- Monomerization
- Nitric oxide
- Peroxynitrite
- Superoxide
- Tetrahydrobiopterin
- Uncoupling
ASJC Scopus subject areas
- Biochemistry
- Biophysics
- Molecular Biology