期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：20
页码：7630-7635
DOI：10.1073/pnas.0401723101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have investigated in whole cells whether, at low oxygen concentrations ([O2]), endogenous nitric oxide (NO) modulates the redox state of the mitochondrial electron transport chain (ETC), and whether such an action has any signaling consequences. Using a polarographic-and-spectroscopic-coupled system, we monitored redox changes in the ETC cytochromes bH, cc1, and aa3 during cellular respiration. The rate of O2 consumption (VO2) remained constant until [O2] fell below 15 {micro}M, whereas the onset of reduction of cytochromes aa3, part of the terminal ETC enzyme cytochrome c oxidase, occurred at {approx}50 {micro}M O2. Incubation of the cells with an inhibitor of NO synthase lowered significantly (P < 0.05) the [O2] at which reduction of the cytochromes occurred. We also measured intracellular superoxide ([IMG]f1.gif" BORDER="0">) production at different [O2] and found there was no increase in [IMG]f1.gif" BORDER="0"> generation in control cells, or those treated with the NO synthase inhibitor, when incubated at 21% O2. However, after 30-min exposure of control cells to 3% O2, an increase in [IMG]f1.gif" BORDER="0"> generation was observed, accompanied by translocation to the nucleus of the transcription factor NF-{kappa}B. Both of these responses were diminished by NO synthase inhibition. Our results suggest that endogenous NO, by enhancing the reduction of ETC cytochromes, contributes to a mechanism by which cells maintain their VO2 at low [O2]. This, in turn, favors the release of [IMG]f1.gif" BORDER="0">, which initiates the transcriptional activation of NF-{kappa}B as an early signaling stress response.
