Novel epoxides formed during the liver cytochrome P-450 oxidation of arachidonic acid

Chacos, N.; Falck, John R.; Wixtrom, C.; Capdevila, Jorge H.

doi:10.1016/0006-291x(82)91336-5

Cited by 143 publications

(35 citation statements)

References 11 publications

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“…However, bearing in mind the well characterised involvement of cytochrome P-450 in the metabolic activation of compounds to biologically reactive intermediates, one must attempt to evaluate the potential role of cytochrome P-452 in this hepatotoxicity. For example, Oliw et al [75] and Chacos et al [76] have recently demonstrated that cytochrome P-450 is involved in the metabolism of unsaturated fatty acids to form olefin epoxides which may be of pathophysiological importance. The mutagenicity of aromatic epoxides is well established, hence further work must be carried out to establish whether fatty acid metabolism at other sites leading to the formation of mutagenic products occurs with cytochrome P-452.…”

Section: Discussionmentioning

confidence: 99%

Multiple forms of hepatic cytochrome P-450. Purification, characterisation and comparison of a novel clofibrate-induced isozyme with other major forms of cytochrome P-450

et al. 1984

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In the present studies, a novel form of highly purified cytochrome P-450 (cytochrome P-452) isolated from the hepatic microsomes of clofibrate-pretreated rats has been compared to the major isozymes isolated from the hepatic microsomes of rats pretreated with phenobarbital (cytochrome P-450) and 2-naphthoflavone (cytochrome P-447) using a number of biochemical criteria.The results show that these three isozymes exhibit marked structural differences from each other as judged by a complete lack of immunochemical cross-reactivity between the isozymes and the heterologous rabbit serum antibodies using Ouchterlony double diffusion, and non-identity between the limited proteolytic digestion maps of the three isozymes obtained in the presence of chymotrypsin, papain and Staphylococcus aureus V, proteases. Furthermore, the three isozymes exhibited clear differences in their monomeric molecular weights determined on calibrated sodium dodecyl sulphate/polyacrylamide gel electrophoresis in gels of varying acrylamide concentration. Substantial differences were also observed in the substrate specificities of the isozymes, which were reflected in differences in the turnover rates and positional selectivities of the hemoproteins for some model substrates. In addition, the isozymes differed in their substrate binding affinities and their ability to interact with purified hepatic microsomal cytochrome b,, as judged using difference spectrophotometry. Finally, subtle differences were detected in the ultraviolet visible absorbance spectra of the hemoproteins in the ferric, ferrous, and carbonmonoxyferrous states.Taken collectively, the above data provides compelling evidence that fundamental differences exist between these cytochrome P-450 isozymes, further establishing the uniqueness of the major form of cytochrome P-450 induced by clofibrate pretreatment.Cytochrome P-450 is the terminal hemoprotein component of the hepatic microsomal electron-transfer chain which functions in the oxidation of a structurally diverse number of xenobiotics and endogenous compounds [I]. Considerable evidence has been presented in support of the existence of Much confusion exists regarding the terminology of cytochrome P-450 isozymes primarily because there is no uniform classification system which has been adopted to make unequivocal assignments of the similarity between isozymes isolated in different laboratories. Accordingly, the above three isozymes described in this paper have been classified according to the wavelength maxima of the ferrouscarbonmonoxy adducts. In the current paper, limited use is made of the term cytochrome P-450 in a general sense to collectively indicate all the cytochrome P-450 isozymes. Where appropriate, we make extended use of the term cytochrome P-450 to indicate that major isozyme induced by phenobarbital pretreatment in rat liver. This is regarded as necessary because to make a distinction for this latter isozyme and rename it would add further confusion to the literature. Similarly, throughout this paper, the terms c...

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Section: Discussionmentioning

confidence: 99%

Multiple forms of hepatic cytochrome P-450. Purification, characterisation and comparison of a novel clofibrate-induced isozyme with other major forms of cytochrome P-450

et al. 1984

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“…They further noted that pretreatment with indomethacin, a potent cyclooxygenase inhibitor, reduced the 5,6-EET-dependent tracheal smooth muscle relaxation (76). Whereas 5,6-EET is known to be a substrate for cyclooxygenase, resulting in 5,6-epoxy PGs (71,72), esterified fatty acids (such as 5,6-EET-Me) are poor substrates for this enzyme system (77). Further investigation is required to determine whether 5,6-EET is the biologically active arachidonic acid metabolite, or whether further metabolism by cyclooxygenase is necessary for optimal activity.…”

Section: Introductionmentioning

confidence: 99%

The rabbit pulmonary cytochrome P450 arachidonic acid metabolic pathway: characterization and significance.

Zeldin¹,

et al. 1995

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Abstractacid -dihydroxyeicosatrienoic acid * hydroxyeicosatetraenoic acid Cytochrome P450 metabolizes arachidonic acid to several unique and biologically active compounds in rabbit liver and kidney. Microsomal fractions prepared from rabbit lung homogenates metabolized arachidonic acid through cytochrome P450 pathways, yielding cis-epoxyeicosatrienoic acids (EETs) and their hydration products, vic-dihydroxyeicosatrienoic acids, mid-chain cis-trans conjugated dienols, and 19-and 20-hydroxyeicosatetraenoic acids. Inhibition studies using polyclonal antibodies prepared against purified CYP2B4 demonstrated 100% inhibition of arachidonic acid epoxide formation. Purified CYP2B4, reconstituted in the presence of NADPH-cytochrome P450 reductase and cytochrome b5, metabolized arachidonic acid, producing primarily EETs. EETs were detected in lung homogenate using gas chromatography/mass spectroscopy, providing evidence for the in vivo pulmonary cytochrome P450 epoxidation of arachidonic acid. Chiral analysis of these lung EETs demonstrated a preference for the 14(R),15(S)-, 11(S),12(R)-, and 8(S),9(R)-EET enantiomers. Both EETs and vic-dihydroxyeicosatrienoic acids were detected in bronchoalveolar lavage fluid. At micromolar concentrations, methylated 5,6-EET and 8,9-EET significantly relaxed histamine-contracted guinea pig hilar bronchi in vitro. In contrast, 20-hydroxyeicosatetraenoic acid caused contraction to near maximal tension. We conclude that CYP2B4, an abundant rabbit lung cytochrome P450 enzyme, is the primary constitutive pulmonary arachidonic acid epoxygenase and that these locally produced, biologically active eicosanoids may be involved in maintaining homeostasis within the lung. (J. Clin. Invest. 1995. 95:2150-2160

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“…LTB4 was prepared from murine mastocytoma cells (6) and purified (7) as previously described. Epoxides and a diol derived from AA by cytochrome P450-dependent monooxygenase action (8)(9)(10) were a kind gift of Dr. J. Capdevila and Dr. N. Chacos (Dallas, TX). All compounds were diluted as stock solutions in ethanol with further dilutions in culture medium except for bradykinin (which was diluted directly in medium) and glucagon or BW755c (which were diluted in water).…”

Section: Introductionmentioning

confidence: 99%

“…The cell pellet was used for cell labeling with [3H]AA in the following manner. The cells were resuspended in 8-12 ml of calcium-free medium (Eagle's minimal essential medium with glucose 50 mg/dl) in the absence of any added proteins or serum, aliquoted into 2-4 plastic test tubes, and incubated with 2 #Ci/ ml of 5,6,8,9,11,12,14,15[3H]AA Ci/mmol; New England Nuclear, Boston, MA) at 370C in 5% CO2 and 95% air.…”

Section: Introductionmentioning

confidence: 99%

Lipoxygenase Pathway in Islet Endocrine Cells. OXIDATIVE METABOLISM OF ARACHIDONIC ACID PROMOTES INSULIN RELEASE

Metz¹,

VanRollins²,

Strife³

et al. 1983

J. Clin. Invest.

120

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A B S T R A C T Metabolism of arachidonic acid (AA) via the cyclooxygenase pathway reduces glucose-stimulated insulin release. However, metabolism of AA by the lipoxygenase pathway and the consequent effects on insulin secretion have not been simultaneously assessed in the endocrine islet. Both dispersed endocrine cell-enriched pancreatic cells of the neonatal rat, as well as intact islets of the adult rat, metabolized [3H]AA not only to cyclooxygenase products (prostaglandins E2, F2a, and prostacyclin) but also to the lipoxygenase product 12-hydroxyeicosatetraenoic acid (12-HETE). 12-HETE was identified by coelution with authentic tritiated or unlabeled 12-HETE using four high performance liquid chromatographic systems under eight mobile-phase conditions and its identity was confirmed by gas chromatography/mass spectrometry using selected ion monitoring. The predominant effect of exogenous AA (5 gg/ml) was to stimulate insulin release from pancreatic cells grown in monolayer. This effect was concentration-and time-dependent, and reversible. The effect of AA upon insulin release was potentiated by a cyclooxygenase inhibitor (indomethacin) and was prevented by either of two lipoxygenase inhibitors (5,8,11,14-

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Novel epoxides formed during the liver cytochrome P-450 oxidation of arachidonic acid

Cited by 143 publications

References 11 publications

Multiple forms of hepatic cytochrome P-450. Purification, characterisation and comparison of a novel clofibrate-induced isozyme with other major forms of cytochrome P-450

Multiple forms of hepatic cytochrome P-450. Purification, characterisation and comparison of a novel clofibrate-induced isozyme with other major forms of cytochrome P-450

The rabbit pulmonary cytochrome P450 arachidonic acid metabolic pathway: characterization and significance.

Lipoxygenase Pathway in Islet Endocrine Cells. OXIDATIVE METABOLISM OF ARACHIDONIC ACID PROMOTES INSULIN RELEASE

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