Abstract
Steroidogenic acute regulatory protein facilitates the translocation of cholesterol to the inner mitochondrial membrane, thereby initiating steroidogenesis. At the inner mitochondrial membrane, cytochrome P450 side-chain cleavage enzyme converts cholesterol to pregnenolone, an oxidative process requiring electrons from NADPH. Pregnenolone then serves as the substrate for the formation of progesterone or dehydroepiandrosterone by downstream enzymes. Studies have shown that cigarette smoke (CS) influences steroid hormone levels. To better understand the underlying mechanisms, we used a mouse model to study the effects of chronic CS exposure on steroidogenesis. Through radioimmunoassay and metabolic conversion assays, we found that CS reduced progesterone and dehydroepiandrosterone without affecting cytochrome P450 side-chain cleavage enzyme or 3β-hydroxysteroid dehydrogenase 2 expression. However, CS did reduce expression of cytochrome c oxidase IV (COX IV), a component of the mitochondrial complex that serves as the last enzyme in the electron transport chain. Small interfering RNA-mediated COX IV knockdown indeed decreased progesterone synthesis in steroidogenic cells. In summary, COX IV likely plays a role in steroidogenesis, and passive smoking may negatively affect steroidogenesis by disrupting the electron transport chain.
Footnotes
This work was supported by the National Institutes of Health Eunice Kennedy Shriver National Institute of Child Health and Human Development [Grant R01-HD057876] (to H.S.B); a grant from Anderson Cancer Research Institute (to H.S.B.); and generous support from the Mercer University School of Medicine (to H.S.B.). Funding for the equipment in the Mass Spectrometry Facility at the University of Alberta is supported by the Canada Foundation for Innovation and Alberta Science and Research Investment Program.
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.111.182634.
↵ The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
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ABBREVIATIONS:
- OMM
- outer mitochondrial membrane
- 3βHSD2
- 3β-hydroxysteroid dehydrogenase 2
- P450
- cytochrome P450
- BisTris
- 2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol
- COX IV
- cytochrome c oxidase IV
- CS
- cigarette smoke
- DHEA
- dehydroepiandrosterone
- IMM
- inner mitochondrial membrane
- P450scc
- cytochrome P450 side-chain cleavage enzyme
- PAGE
- polyacrylamide gel electrophoresis
- RT
- retention time
- siRNA
- small interfering RNA
- StAR
- steroidogenic acute regulatory protein
- TLC
- thin-layer chromatography
- VDAC1
- voltage-dependent anion-selective channel protein 1.
- Received April 1, 2011.
- Accepted May 4, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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