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Cytochrome P-450-dependent omega-oxidation of leukotriene B4 in rodent and human epidermis. 1989

H Mukhtar, and D P Bik, and T Ruzicka, and H F Merk, and D R Bickers
Department of Dermatology, University Hospitals, Case Western Reserve University, Cleveland, Ohio.

Leukotriene B4 (LTB4,5-12-dihydroxy 6,8,10,14-eicosatetraenoic acid), an enzyme-catalyzed oxidation product of arachidonic acid, is a major inflammatory mediator. Human polymorphonuclear leukocytes and rodent hepatic microsomes catabolize LTB4 to 20-OH-LTB4 and 20-COOH-LTB4, which is mediated by a cytochrome P-450 catalyzed reaction termed the LTB4 omega-hydroxylase. In this study we investigated the catabolism of LTB4 in rat, guinea pig, and human epidermis. The incubation of 3H-LTB4 (9 microM) for 60 min in the presence of oxygen, NADPH, and epidermal microsomes prepared from neonatal fat (3.0 mg) or adult guinea pig (2.6 mg) resulted in the formation of 20-OH-LTB4 and 20-COOH-LTB4. Metabolite identification was based on co-chromatography on high pressure liquid chromatography with highly purified reference standards. The formation of 20-OH-LTB4 and 20-COOH-LTB4 was accompanied by the disappearance of LTB4. The rate of formation of 20-OH-LTB4 was 9-12-fold higher than that of 20-COOH-LTB4. Product formation was negligible with boiled microsomes, required NADPH and oxygen, was linear with respect to incubation time and protein, and was maximal at pH 7.4. LTB4-omega-hydroxylase activity was inhibited (greater than 90%) by carbon monoxide or 2-diethylaminoethyl-2,2-diphenylvalerate hydrochloride (SKF-525A) (1 mM), whereas alpha-naphthoflavone produced only moderate (13%) or no effects. Topical application of 3-methylcholanthrene and other conventional inducers of epidermal monooxygenase activities to neonatal rats (100 mg/kg, single treatment) did not result in an increase in epidermal LTB4-omega-hydroxylase activity. The addition of 3H-LTB4 (30 nmoles) to primary human keratinocytes followed by incubation at 37 degrees C resulted in time-dependent disappearance of LTB4 and appearance of 20-OH-LTB4 and 20-COOH-LTB4 in the medium. These results suggest that LTB4 is catabolized by the cytochrome P-450-dependent enzyme system in rodent and human skin and that this may participate in modulating the effects of this proinflammatory lipid in this tissue.

UI MeSH Term Description Entries
D007633 Keratins A class of fibrous proteins or scleroproteins that represents the principal constituent of EPIDERMIS; HAIR; NAILS; horny tissues, and the organic matrix of tooth ENAMEL. Two major conformational groups have been characterized, alpha-keratin, whose peptide backbone forms a coiled-coil alpha helical structure consisting of TYPE I KERATIN and a TYPE II KERATIN, and beta-keratin, whose backbone forms a zigzag or pleated sheet structure. alpha-Keratins have been classified into at least 20 subtypes. In addition multiple isoforms of subtypes have been found which may be due to GENE DUPLICATION. Cytokeratin,Keratin Associated Protein,Keratin,Keratin-Associated Proteins,alpha-Keratin,Associated Protein, Keratin,Keratin Associated Proteins,Protein, Keratin Associated,alpha Keratin
D007975 Leukotriene B4 The major metabolite in neutrophil polymorphonuclear leukocytes. It stimulates polymorphonuclear cell function (degranulation, formation of oxygen-centered free radicals, arachidonic acid release, and metabolism). (From Dictionary of Prostaglandins and Related Compounds, 1990) 5,12-HETE,5,12-diHETE,LTB4,Leukotriene B,Leukotriene B-4,Leukotrienes B,5,12 HETE,5,12 diHETE,B-4, Leukotriene,Leukotriene B 4
D008861 Microsomes Artifactual vesicles formed from the endoplasmic reticulum when cells are disrupted. They are isolated by differential centrifugation and are composed of three structural features: rough vesicles, smooth vesicles, and ribosomes. Numerous enzyme activities are associated with the microsomal fraction. (Glick, Glossary of Biochemistry and Molecular Biology, 1990; from Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed) Microsome
D010084 Oxidation-Reduction A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471). Redox,Oxidation Reduction
D011919 Rats, Inbred Strains Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding. August Rats,Inbred Rat Strains,Inbred Strain of Rat,Inbred Strain of Rats,Inbred Strains of Rats,Rat, Inbred Strain,August Rat,Inbred Rat Strain,Inbred Strain Rat,Inbred Strain Rats,Inbred Strains Rat,Inbred Strains Rats,Rat Inbred Strain,Rat Inbred Strains,Rat Strain, Inbred,Rat Strains, Inbred,Rat, August,Rat, Inbred Strains,Rats Inbred Strain,Rats Inbred Strains,Rats, August,Rats, Inbred Strain,Strain Rat, Inbred,Strain Rats, Inbred,Strain, Inbred Rat,Strains, Inbred Rat
D003577 Cytochrome P-450 Enzyme System A superfamily of hundreds of closely related HEMEPROTEINS found throughout the phylogenetic spectrum, from animals, plants, fungi, to bacteria. They include numerous complex monooxygenases (MIXED FUNCTION OXYGENASES). In animals, these P-450 enzymes serve two major functions: (1) biosynthesis of steroids, fatty acids, and bile acids; (2) metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs (BIOTRANSFORMATION). They are classified, according to their sequence similarities rather than functions, into CYP gene families (>40% homology) and subfamilies (>59% homology). For example, enzymes from the CYP1, CYP2, and CYP3 gene families are responsible for most drug metabolism. Cytochrome P-450,Cytochrome P-450 Enzyme,Cytochrome P-450-Dependent Monooxygenase,P-450 Enzyme,P450 Enzyme,CYP450 Family,CYP450 Superfamily,Cytochrome P-450 Enzymes,Cytochrome P-450 Families,Cytochrome P-450 Monooxygenase,Cytochrome P-450 Oxygenase,Cytochrome P-450 Superfamily,Cytochrome P450,Cytochrome P450 Superfamily,Cytochrome p450 Families,P-450 Enzymes,P450 Enzymes,Cytochrome P 450,Cytochrome P 450 Dependent Monooxygenase,Cytochrome P 450 Enzyme,Cytochrome P 450 Enzyme System,Cytochrome P 450 Enzymes,Cytochrome P 450 Families,Cytochrome P 450 Monooxygenase,Cytochrome P 450 Oxygenase,Cytochrome P 450 Superfamily,Enzyme, Cytochrome P-450,Enzyme, P-450,Enzyme, P450,Enzymes, Cytochrome P-450,Enzymes, P-450,Enzymes, P450,Monooxygenase, Cytochrome P-450,Monooxygenase, Cytochrome P-450-Dependent,P 450 Enzyme,P 450 Enzymes,P-450 Enzyme, Cytochrome,P-450 Enzymes, Cytochrome,Superfamily, CYP450,Superfamily, Cytochrome P-450,Superfamily, Cytochrome P450
D004817 Epidermis The external, nonvascular layer of the skin. It is made up, from within outward, of five layers of EPITHELIUM: (1) basal layer (stratum basale epidermidis); (2) spinous layer (stratum spinosum epidermidis); (3) granular layer (stratum granulosum epidermidis); (4) clear layer (stratum lucidum epidermidis); and (5) horny layer (stratum corneum epidermidis).
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006899 Mixed Function Oxygenases Widely distributed enzymes that carry out oxidation-reduction reactions in which one atom of the oxygen molecule is incorporated into the organic substrate; the other oxygen atom is reduced and combined with hydrogen ions to form water. They are also known as monooxygenases or hydroxylases. These reactions require two substrates as reductants for each of the two oxygen atoms. There are different classes of monooxygenases depending on the type of hydrogen-providing cosubstrate (COENZYMES) required in the mixed-function oxidation. Hydroxylase,Hydroxylases,Mixed Function Oxidase,Mixed Function Oxygenase,Monooxygenase,Monooxygenases,Mixed Function Oxidases,Function Oxidase, Mixed,Function Oxygenase, Mixed,Oxidase, Mixed Function,Oxidases, Mixed Function,Oxygenase, Mixed Function,Oxygenases, Mixed Function
D000072470 Cytochrome P450 Family 4 A cytochrome P450 enzyme family that includes members which function in the metabolism of FATTY ACIDS, especially ARACHIDONIC ACIDS and their derivatives. CYP4 Enzymes,CYP4 Family

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