RT Journal Article
SR Electronic
T1 TIME-DEPENDENT INHIBITION AND TETRAHYDROBIOPTERIN DEPLETION OF ENDOTHELIAL NITRIC-OXIDE SYNTHASE CAUSED BY CIGARETTES
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 131
OP 138
DO 10.1124/dmd.104.001891
VO 33
IS 1
A1 Ezra R. Lowe
A1 Andrew C. Everett
A1 Anthony J. Lee
A1 Miranda Lau
A1 Anwar Y. Dunbar
A1 Vladimir Berka
A1 Ah-lim Tsai
A1 Yoichi Osawa
YR 2005
UL http://dmd.aspetjournals.org/content/33/1/131.abstract
AB Smoking causes a dysfunction in endothelial nitric-oxide synthase (eNOS), which is ameliorated, in part, by administration of tetrahydrobiopterin (BH4). The exact mechanism by which the nitric oxide deficit occurs is unknown. We have previously shown that aqueous extracts of chemicals in cigarettes (CE) cause the suicide inactivation of neuronal NO synthase (nNOS) by interacting at the substrate-binding site. In the current study, we have found that CE directly inactivates eNOS by a process that is not affected by the natural substrate l-arginine and is distinct from the mechanism of inactivation of nNOS. We discovered that CE causes a time-, concentration-, and NADPH-dependent inactivation of eNOS in an in vitro system containing the purified enzyme, indicating a metabolic component to the inactivation. The CE-treated eNOS but not nNOS was nearly fully reactivated upon incubation with excess BH4, suggesting that BH4 depletion is a potential mechanism of inactivation. Moreover, in the presence of CE, eNOS catalyzed the oxidation of BH4 to dihydrobiopterin and biopterin by a process attenuated by high concentrations of superoxide dismutase but not catalase. We speculate that a redox active component in CE, perhaps a quinone compound, causes oxidative uncoupling of eNOS to form superoxide, which in turn oxidizes BH4. The discovery of a direct inactivation of eNOS by a compound(s) present in tobacco provides a basis not only for further study of the mechanisms responsible for the biological effects of tobacco but also a search for a potentially novel inactivator of eNOS. The American Society for Pharmacology and Experimental Therapeutics