8-11-14-eicosatrienoic-acid and 15-hydroxyeicosatrienoic-acid

A modification of the human monooxygenase system have been previously associated with the sudden infant death syndrome (SIDS): the hepatic CYP2C content was markedly enhanced and resulted from an activation of CYP2C gene transcription. To determine the possible consequence of the up-regulation of CYP2C in SIDS, we examined the metabolism of arachidonic acid (AA) an endogenous substrate of CYP2C involved in the physiologic regulation of vascular tone. The overall AA metabolism was extremely low during the fetal period and rose after birth to generate 14,15 epoxyeicosatrienoic acid (EET), 11,12 EET and the sum of 5,6 dihydroxyeicosatrienoic acid (diHETE)+omega/omega-1 hydroxy AA. In SIDS, the accumulation of CYP2C proteins was associated with a significant increase in the formation of 14,15 and 11,12 diHETE, which were shown to be supported by individually expressed CYP2C8 and 2C9 and HETE1 (presumably 15 HETE). This increase was markedly inhibited by addition of sulfaphenazole, a selective inhibitor of CYP2C9. So, we propose that the higher CYP2C content in SIDS stimulates the production of EETs and diHETEs and might have severe pathologic consequences in children.

Topics: 8,11,14-Eicosatrienoic Acid; Adult; Age Factors; Arachidonic Acid; Arachidonic Acids; Aryl Hydrocarbon Hydroxylases; Cytochrome P-450 CYP2C8; Cytochrome P-450 CYP2C9; Cytochrome P-450 Enzyme System; Humans; Hydroxyeicosatetraenoic Acids; Infant; Isoenzymes; Liver; Microsomes, Liver; NADP; Recombinant Proteins; Steroid 16-alpha-Hydroxylase; Steroid Hydroxylases; Sudden Infant Death; Up-Regulation

15-hydroxyeicosatrienoic acid, 15-HETrE, the 15-lipoxygenase product of dihomogammalinolenic acid (DGLA), can inhibit the biosynthesis of the proinflammatory eicosanoids leukotriene B4 (LTB4) and 12-hydroxyeicosatetraenoic acid (12-HETE). The purpose of the present study was to investigate the incorporation of [14C]15-HETrE in specific membrane phospholipids of cultured human keratinocytes in vitro. [14C]15-HETrE was rapidly incorporated into keratinocytes. When a plateau was reached after 3 hours, 15% of the added radioactivity was incorporated into lipids; 96.5% into phospholipids (PL) and 3.5% into neutral lipids (NL). Within the phospholipid classes, [14C]15-HETrE showed selectivity for incorporation into phosphatidylinositol (PI). The mean proportion of [14C]15-HETrE in the PI, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) was 83.2%, 8.5% and 8.3%, respectively. We then investigated the incorporation of 15-HETrE in epidermal phospholipids of psoriatic skin intralesionally injected with 15-HETrE. Four patients took part in the study. In each patient four identical plaques were injected with 0.65 ml of 2.0 microM, 6.2 microM, 18.6 microM of 15-HETrE (0.4 micrograms, 1, 2 micrograms and 3.6 micrograms respectively) or 0.65 ml of 0.88% NaCl twice a week. After 3 wk keratome biopsies were obtained from the treated plaques. Phospholipids extracted from the skin biopsies were separated into major classes by two-dimensional thin layer chromatography. 15-HETrE was then released from specific phospholipids after treatment with phospholipase A2 and identified by reverse phase and straight phase high performance liquid chromatography. There was a dose-dependent incorporation of 15-HETrE into the specific phospholipids PI and PC. When expressed as ng 15-HETrE/micrograms phospholipid phosphate, 15-HETrE accumulated preferentially in PI.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 8,11,14-Eicosatrienoic Acid; Anti-Inflammatory Agents, Non-Steroidal; Cells, Cultured; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Humans; Hydroxyeicosatetraenoic Acids; Injections, Intralesional; Keratinocytes; Phosphatidylcholines; Phosphatidylinositols; Phospholipases A; Phospholipases A2; Phospholipids; Psoriasis