HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 281, Issue 52, 39766-39775, December 29, 2006

This Article Full Text Full Text (PDF) All Versions of this Article: 281/52/39766    most recent M608268200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by O'Malley, Y. Articles by Sivitz, W. I. Search for Related Content PubMed PubMed Citation Articles by O'Malley, Y. Articles by Sivitz, W. I. Social Bookmarking                      What's this?

Reactive Oxygen and Targeted Antioxidant Administration in Endothelial Cell Mitochondria^*

From the Department of Internal Medicine, Division of Endocrinology and Metabolism and the College of Pharmacy, Division of Medicinal and Natural Products Chemistry, Iowa City Veterans Affairs Medical Center and the University of Iowa, Iowa City, Iowa 52242

We used fluorescent probes and EPR to study the mechanism(s) underlying reactive oxygen species (ROS) production by endothelial cell mitochondria and the action of mitoquinol, a mitochondria-targeted antioxidant. ROS measured by fluorescence resulted from complex I superoxide released to the matrix and converted to H₂O₂. In contrast, EPR largely detected superoxide generated at complex III and effluxed outward. ROS fluorescence by mitochondria fueled by the complex II substrate, succinate, was substantial but markedly inhibited by rotenone. Superoxide, detected by EPR, in succinate-fueled mitochondria was not inhibited by rotenone and likely derived from semiquinone formation at complex III. Mitoquinol decreased H₂O₂ fluorescence by succinate-fueled mitochondria but had little effect on the EPR signal for superoxide. This was not associated with a detectable decrease in membrane potential. Mitoquinol markedly enhanced ROS fluorescence in mitochondria fueled by the complex I substrates, glutamate and malate. Inhibitor studies suggested that this occurred in complex I, at one or more Q binding pockets. The above effects of mitoquinol were determined in mitochondria isolated and subsequently exposed to the targeted antioxidant. However, similar effects were observed in mitochondria after antecedent exposure to mitoquinol/mitoquinone in culture, suggesting that the agent is retained after isolation of the organelles. In conclusion, ROS production in bovine aortic endothelial cell mitochondria results largely from reverse transport to complex I and through the Q cycle in complex III. Mitoquinol blocks ROS from reverse electron transport but increases superoxide production derived from forward transport. These effects likely occur at one or more Q binding sites in complex I.

Received for publication, August 29, 2006

^* This work was supported by Veterans Affairs Medical Research Funds and National Institutes of Health Grant DK25295. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Dept. of Internal Medicine, Division of Endocrinology and Metabolism, The University of Iowa Hospitals and Clinics, 422GH, 200 Hawkins Drive, Iowa City, IA 52242. Tel.: 319-353-7812; Fax: 319-353-7850; E-mail: william-sivitz{at}uiowa.edu.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				S. M. Davidson and M. R. Duchen Endothelial Mitochondria: Contributing to Vascular Function and Disease Circ. Res., April 27, 2007; 100(8): 1128 - 1141. [Abstract] [Full Text] [PDF]