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Cytochrome P450 oxidoreductase participates in nitric oxide consumption by rat brain

By Catherine N. Hall, Robert G. Keynes and John Garthwaite

Abstract

In low nanomolar concentrations, NO (nitric oxide) functions as a transmitter in brain and other tissues, whereas near-micromolar NO concentrations are associated with toxicity and cell death. Control of the NO concentration, therefore, is critical for proper brain function, but, although its synthesis pathway is well-characterized, the major route of breakdown of NO in brain is unclear. Previous observations indicate that brain cells actively consume NO at a high rate. The mechanism of this consumption was pursued in the present study. NO consumption by a preparation of central glial cells was abolished by cell lysis and recovered by addition of NADPH. NADPH-dependent consumption of NO localized to cell membranes and was inhibited by proteinase K, indicating the involvement of a membrane-bound protein. Purification of this activity yielded CYPOR (cytochrome P450 oxidoreductase). Antibodies against CYPOR inhibited NO consumption by brain membranes and the amount of CYPOR in several cell types correlated with their rate of NO consumption. NO was also consumed by purified CYPOR but this activity was found to depend on the presence of the vitamin E analogue Trolox (6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid), included in the buffer as a precaution against inadvertent NO consumption by lipid peroxidation. In contrast, NO consumption by brain membranes was independent of Trolox. Hence, it appears that, during the purification process, CYPOR becomes separated from a partner needed for NO consumption. Cytochrome P450 inhibitors inhibited NO consumption by brain membranes, making these proteins likely candidates

Topics: Research Article
Publisher: Portland Press Ltd.
OAI identifier: oai:pubmedcentral.nih.gov:2662488
Provided by: PubMed Central
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    Citations

    1. (1999). 15-Lipoxygenase catalytically consumes nitric oxide and impairs activation of guanylate cyclase.
    2. (1997). A kinetic study of the one-electron oxidation of Trolox C by the hydroperoxidase activity of lipoxygenase.
    3. (1997). A tutorial on the diffusibility and reactivity of free nitric oxide.
    4. (1993). Autoxidation kinetics of aqueous nitric oxide.
    5. (2001). Catalytic consumption of nitric oxide by 12/15- lipoxygenase: inhibition of monocyte soluble guanylate cyclase activation.
    6. (2000). Catalytic consumption of nitric oxide by prostaglandin H synthase-1 regulates platelet function.
    7. (1998). Chemical biology of nitric oxide: Insights into regulatory, cytotoxic, and cytoprotective mechanisms of nitric oxide.
    8. (2008). Concepts of neural nitric oxide-mediated transmission.
    9. (2003). Constitutive and inducible levels of CYP1A1 and CYP1A2 in rat cerebral cortex and cerebellum.
    10. (2004). Consumption of nitric oxide by endothelial cells: evidence for the involvement of a NAD(P)H-, flavin- and heme-dependent dioxygenase reaction.
    11. (2003). CYP2D in the brain.
    12. (2005). Cytochrome P450: nature’s most versatile biological catalyst.
    13. (2001). Cytochromes P450 in brain: function and significance.
    14. (1977). Differential inhibitory effects of vitamin E and other antioxidants on prostaglandin synthetase, platelet aggregation and lipoxidase.
    15. (2002). Differential sensitivity of guanylyl cyclase and mitochondrial respiration to nitric oxide measured using clamped concentrations.
    16. (1997). Dynamic properties of nitric oxide release from parallel fibres in rat cerebellar slices.
    17. (2004). Electron transfer by diflavin reductases.
    18. (2005). Enzyme-selective effects of nitric oxide on affinity and maximum velocity of various rat cytochromes P450. Drug Metab.
    19. (1997). Evidence against the involvement of cytochrome P450 metabolites in endothelium-dependent hyperpolarization of the rat main mesenteric artery.
    20. (1974). Highly purified detergent-solubilized NADPH-cytochrome P-450 reductase from phenobarbital-induced rat liver microsomes.
    21. (2003). Human extrahepatic cytochromes P450: function in xenobiotic metabolism and tissue-selective chemical toxicity in the respiratory and gastrointestinal tracts.
    22. (1998). Importance of glucose-6-phosphate dehydrogenase activity for cell growth.
    23. (2006). Inactivation of nitric oxide by rat cerebellar slices.
    24. (2002). Inhibition of cytochromes P450 by antifungal imidazole derivatives. Drug Metab Dispos.
    25. (2004). Kinetics of a cellular nitric oxide/cGMP/phosphodiesterase-5 pathway.
    26. (2007). Mammalian cytochromes P450–importance of tissue specificity.
    27. (2005). Molecular properties of mammalian proteins that interact with cGMP: protein kinases, cation channels, phosphodiesterases, and multi-drug anion transporters.
    28. (1999). NADPH and heme redox modulate pulmonary artery relaxation and guanylate cyclase activation by NO.
    29. (1989). NADPH-dependent cytochrome P450 reductase. In Molecular Aspects of Monooxygenases and
    30. (1994). Nanomolar concentrations of nitric oxide reversibly inhibit synaptosomal respiration by competing with oxygen at cytochrome oxidase.
    31. (2002). Nitric oxide and cytochrome oxidase: substrate, inhibitor or effector? Trends Biochem.
    32. (2005). Nitric oxide consumption through lipid peroxidation in brain cell suspensions and homogenates.
    33. (2002). Nitric oxide inactivation in brain by a novel O2-dependent mechanism resulting in the formation of nitrate ions.
    34. (2004). Nitric oxide metabolism in mammalian cells: substrate and inhibitor profiles of a NADPH-cytochrome P450 oxidoreductase-coupled microsomal nitric oxide dioxygenase. Free Radical Biol.
    35. (1995). Nitric oxide synthases: properties and catalytic mechanism.
    36. (1996). Nitric oxide, superoxide, and peroxynitrite: the good, the bad, and ugly.
    37. (2005). Novel extrahepatic cytochrome P450s.
    38. (2003). Properties of NO-activated guanylyl cyclases expressed in cells.
    39. (2001). Regulation, function, and tissue-specific expression of cytochrome P450 CYP1B1.
    40. (2001). The shaping of nitric oxide signals by a cellular sink.
    41. (2005). Trans-synaptic signalling by nitric oxide.
    42. (2004). Update on mechanism and catalytic regulation in the NO synthases.
    43. (2003). Viral delivery of P450 reductase recapitulates the ability of constitutive overexpression of reductase enzymes to potentiate the activity of mitomycin C in human breast cancer xenografts.
    44. (2006). Vitamin E deficiency accelerates nitrate tolerance via a decrease in cardiac P450 expression and increased oxidative stress.

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