Free radical biology and medicine: it's a gas, man

1 Biodynamics Institute, Louisiana State University, Baton Rouge, Louisiana; 2 Department of Chemistry and Biochemistry, University of California, Los Angeles, California; 3 Department of Pharmacology, University of California at Los Angeles School of Medicine, Center for the Health Sciences, Los An...

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Published in:American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2006-09, Vol.291 (3), p.R491-R511
Main Authors: Pryor, William A, Houk, Kendall N, Foote, Christopher S, Fukuto, Jon M, Ignarro, Louis J, Squadrito, Giuseppe L, Davies, Kelvin J. A
Format: Article
Language:English
Subjects:
Free Radicals - chemistry
Free Radicals - metabolism
Humans
Oxygen - chemistry
Oxygen - metabolism
Superoxides - chemistry
Superoxides - metabolism
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Summary:1 Biodynamics Institute, Louisiana State University, Baton Rouge, Louisiana; 2 Department of Chemistry and Biochemistry, University of California, Los Angeles, California; 3 Department of Pharmacology, University of California at Los Angeles School of Medicine, Center for the Health Sciences, Los Angeles, California; 4 Department of Environmental Health Sciences, School of Public Health, University of Alabama at Birmingham, Birmingham, Alabama; and 5 Ethel Percy Andrus Gerontology Center and Division of Molecular and Computational Biology, University of Southern California, Los Angeles, California We review gases that can affect oxidative stress and that themselves may be radicals. We discuss O 2 toxicity, invoking superoxide, hydrogen peroxide, and the hydroxyl radical. We also discuss superoxide dismutase (SOD) and both ground-state, triplet oxygen ( 3 O 2 ), and the more energetic, reactive singlet oxygen ( 1 O 2 ). Nitric oxide ( · NO) is a free radical with cell signaling functions. Besides its role as a vasorelaxant, · NO and related species have other functions. Other endogenously produced gases include carbon monoxide (CO), carbon dioxide (CO 2 ), and hydrogen sulfide (H 2 S). Like · NO, these species impact free radical biochemistry. The coordinated regulation of these species suggests that they all are used in cell signaling. Nitric oxide, nitrogen dioxide, and the carbonate radical (CO 3 ·– ) react selectively at moderate rates with nonradicals, but react fast with a second radical. These reactions establish "cross talk" between reactive oxygen (ROS) and reactive nitrogen species (RNS). Some of these species can react to produce nitrated proteins and nitrolipids. It has been suggested that ozone is formed in vivo. However, the biomarkers that were used to probe for ozone reactions may be formed by non-ozone-dependent reactions. We discuss this fascinating problem in the section on ozone. Very low levels of ROS or RNS may be mitogenic, but very high levels cause an oxidative stress that can result in growth arrest (transient or permanent), apoptosis, or necrosis. Between these extremes, many of the gasses discussed in this review will induce transient adaptive responses in gene expression that enable cells and tissues to survive. Such adaptive mechanisms are thought to be of evolutionary importance. antioxidants; antioxidant defense and repair; nitric oxide; carbon dioxide; hydrogen sulfide; carbon monoxide; ozone; hydrogen peroxide; dissolved ga
ISSN:0363-6119
1522-1490
DOI:10.1152/ajpregu.00614.2005