Volume 51: 335-339, 2002

 

MINIREVIEW


The Role of Carbon Dioxide in Free Radical Reactions
of the Organism


A. VESELÁ, J. WILHELM

Department of Medical Chemistry and Biochemistry, Second Faculty of Medicine, Charles University, Center for Experimental Cardiovascular Research, Prague, Czech Republic


Received August 6, 2001
Accepted November 22, 2001


Summary
Carbon dioxide interacts both with reactive nitrogen species and reactive oxygen species. In the presence of superoxide, NO reacts to form peroxynitrite that reacts with CO2 to give nitrosoperoxycarbonate. This compound rearranges to nitrocarbonate which is prone to further reactions. In an aqueous environment, the most probable reaction is hydrolysis producing carbonate and nitrate. Thus the net effect of CO2 is scavenging of peroxynitrite and prevention of nitration and oxidative damage. However, in a nonpolar environment of membranes, nitrocarbonate undergoes other reactions leading to nitration of proteins and oxidative damage. When NO reacts with oxygen in the absence of superoxide, a nitrating species N2O3 is formed. CO2 interacts with N2O3 to produce a nitrosyl compound that, under physiological pH, is hydrolyzed to nitrous and carbonic acid. In this way, CO2 also prevents nitration reactions. CO2 protects superoxide dismutase against oxidative damage induced by hydrogen peroxide. However, in this reaction carbonate radicals are formed which can propagate the oxidative damage. It was found that hypercapnia in vivo protects against the damaging effects of ischemia or hypoxia. Several mechanisms have been suggested to explain the protective role of CO2 in vivo. The most significant appears to be stabilization of the iron-transferrin complex which prevents the involvement of iron ions in the initiation of free radical reactions.


Key words
CO2 · peroxynitrite · Free radicals · Oxidative damage · Hypercapnia


Reprint requests
Doc. Dr. J. Wilhelm, Department of Medical Chemistry and Biochemistry, Second Faculty of Medicine, Charles University, Plzeňská 221, 150 00 Prague 5, Czech Republic. E-mail:
jiri.wilhelm@lfmotol.cuni.cz


PHYSIOLOGICAL RESEARCH
© 2002 by the Institute of Physiology, Czech Academy of Sciences

ISSN 0862 - 8408

Issue 4