gamma-tocopherol traps mutagenic electrophiles such as NO(X) and complements alpha-tocopherol: physiological implications

Christen, S; Woodall, AA; Shigenaga, MK; Southwell-Keely, PT; Duncan, MW; Ames, BN (1997). gamma-tocopherol traps mutagenic electrophiles such as NO(X) and complements alpha-tocopherol: physiological implications. Proceedings of the National Academy of Sciences of the United States of America - PNAS, 94(7), pp. 3217-22. Washington, D.C.: National Academy of Sciences NAS 10.1073/pnas.94.7.3217

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Peroxynitrite, a powerful mutagenic oxidant and nitrating species, is formed by the near diffusion-limited reaction of .NO and O2.- during activation of phagocytes. Chronic inflammation induced by phagocytes is a major contributor to cancer and other degenerative diseases. We examined how gamma-tocopherol (gammaT), the principal form of vitamin E in the United States diet, and alpha-tocopherol (alphaT), the major form in supplements, protect against peroxynitrite-induced lipid oxidation. Lipid hydroperoxide formation in liposomes (but not isolated low-density lipoprotein) exposed to peroxynitrite or the .NO and O2.- generator SIN-1 (3-morpholinosydnonimine) was inhibited more effectively by gammaT than alphaT. More importantly, nitration of gammaT at the nucleophilic 5-position, which proceeded in both liposomes and human low density lipoprotein at yields of approximately 50% and approximately 75%, respectively, was not affected by the presence of alphaT. These results suggest that despite alphaT's action as an antioxidant gammaT is required to effectively remove the peroxynitrite-derived nitrating species. We postulate that gammaT acts in vivo as a trap for membrane-soluble electrophilic nitrogen oxides and other electrophilic mutagens, forming stable carbon-centered adducts through the nucleophilic 5-position, which is blocked in alphaT. Because large doses of dietary alphaT displace gammaT in plasma and other tissues, the current wisdom of vitamin E supplementation with primarily alphaT should be reconsidered.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Service Sector > Institute for Infectious Diseases
UniBE Contributor:	Christen, Stephan
ISSN:	0027-8424
ISBN:	9096373
Publisher:	National Academy of Sciences NAS
Language:	English
Submitter:	Factscience Import
Date Deposited:	04 Oct 2013 14:56
Last Modified:	05 Dec 2022 14:17
Publisher DOI:	10.1073/pnas.94.7.3217
PubMed ID:	9096373
Web of Science ID:	A1997WR93000085
URI:	https://boris.unibe.ch/id/eprint/23698 (FactScience: 43500)