13-hydroxy-9-11-octadecadienoic-acid and Skin-Neoplasms

In contrast to other 12S-lipoxygenase (LOX) isoforms expressed in the skin of mice, epidermis-type (e) 12S-LOX was found to be transcriptionally down-regulated in the course of epidermal tumor development in NMRI mice. This may indicate that this enzyme is related to antitumorigenic rather than protumorigenic effects. To test this hypothesis, two transgenic mouse lines were generated that differentially expressed e12S-LOX under the control of the bovine keratin 6 promoter known to be constitutively up-regulated in mouse skin tumors. As compared with the wild-type, low transgene expression correlated with a decreased skin tumor response paralleled by an up-regulation of leukocyte-type 12S-LOX and an accumulation of the linoleic acid derivative 13S-hydroxyoctadecadienoic acid. In contrast, high transgene expression coincided with an increased tumor response paralleled by a strong keratin 6 promoter-driven up-regulation of the transgenic e12S-LOX and an accumulation of the arachidonic acid derivative 12S-hydroxyeicosatetraenoic acid as the predominant LOX product. These results indicate a complex interaction between different LOX isoforms and an opposite role of arachidonic acid and linoleic acid products in the modulation of skin carcinogenesis.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; 9,10-Dimethyl-1,2-benzanthracene; Animals; Arachidonate 12-Lipoxygenase; Carcinogens; Down-Regulation; Female; Gene Expression; Isoenzymes; Linoleic Acids; Male; Mice; Mice, Inbred DBA; Mice, Transgenic; Papilloma; RNA, Messenger; Skin; Skin Neoplasms; Tetradecanoylphorbol Acetate; Transgenes

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Animals; Chromatography, High Pressure Liquid; Hydroxyeicosatetraenoic Acids; Linoleic Acids; Linoleic Acids, Conjugated; Mice; Papilloma; Skin Neoplasms

Previous studies demonstrated a requirement for arachidonic acid metabolites in tumor development in mouse skin. The goal of this study was to determine whether the arachidonate content of epidermal phospholipids could be altered by increasing dietary levels of linoleate and whether specific metabolites of linoleate and arachidonate have dissimilar biological effects. In a series of tumor studies in which the quantity of dietary linoleate was incrementally increased, a slight reduction in phospholipid levels of arachidonate was observed that correlated with an increased phospholipid level of linoleate and a suppression in tumor yield. A comparison of the arachidonate lipoxygenase metabolite 12-hydroxyeicosatetraenoic acid (12-HETE) with the 13-hydroxyoctadecadienoic acid (13-HODE) lipoxygenase metabolite of linoleate revealed that 12-HETE has biological activities that mimic the phorbol ester tumor promoters, whereas 13-HODE has antithetical effects. Specifically, 12(S)-HETE enhanced the activation of protein kinase C by phorbol esters, mimicked phorbol ester-induced adhesion of keratinocytes to fibronectin and mimicked phorbol ester repression of expression of a differentiation-related gene, keratin-1. 13-HODE blocked 12-HETE-induced cell adhesion and prevented 12-HETE-induced suppression of keratin-1 expression. Overall, these studies suggest that arachidonate and linoleate have opposing functions in the epidermis, particularly with regard to events involved in tumor development.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Animals; Arachidonic Acid; Female; Hydroxyeicosatetraenoic Acids; Linoleic Acid; Linoleic Acids; Mice; Phospholipases A; Protein Kinase C; Skin Neoplasms

A method for determination of the lipoxygenase products of linoleic acid (9- and 13-hydroxyoctadecadienoic acid; 9-HODE, 13-HODE) and of arachidonic acid (5-, 8-, 9-, 11-, 12-, and 15-hydroxyeicosatetraenoic acid; 5-, 8-, 9-, 11-, 12-, and 15-HETE) is described. The method combines solid-phase extraction, derivatization to the corresponding fully hydrogenated methylester/trimethylsilylether derivatives and capillary gas chromatography coupled with electron impact mass spectrometry. Each regioisomeric HODE and HETE shows a unique pair of mass spectrometric fragment ions originating from fission of the fatty acid carbon chain at the hydroxylated position. The carboxyl-terminal fragment is used for quantification relative to a carboxyl-18O2-labeled analogue added as internal standard and the methyl-terminal fragment is monitored for confirmation. The assay can be extended for quantification of the complete hydroxylation profile of linoleic and arachidonic acid. Applications of this assay are demonstrated for the quantification of HODEs and HETEs in normal, hyperplastic, and neoplastic mouse epidermis. In mouse epidermis papilloma, the tissue levels of 8- and 12-HETE were found to be increased by one to two orders of magnitude compared to levels in normal epidermis.

Topics: Animals; Arachidonic Acids; Female; Gas Chromatography-Mass Spectrometry; Hydroxyeicosatetraenoic Acids; Hydroxylation; Hyperplasia; Linoleic Acids; Linoleic Acids, Conjugated; Lipoxygenase; Mice; Papilloma; Skin; Skin Neoplasms