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Incorporation of 15‐hydroxyeicosatrienoic acid in specific phospholipids of cultured human keratinocytes and psoriatic plaques
Author(s) -
Heitmann Jette,
Iversen Lars,
Kragballe Knud,
Ziboh Vincent A.
Publication year - 1995
Publication title -
experimental dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.108
H-Index - 96
eISSN - 1600-0625
pISSN - 0906-6705
DOI - 10.1111/j.1600-0625.1995.tb00225.x
Subject(s) - keratinocyte , chemistry , psoriasis , human skin , dermatology , biochemistry , biology , medicine , in vitro , genetics
15‐hydroxyeicosatrienoic acid, 15‐HETrE, the 15‐lipoxygenase product of dihomogammalinolenic acid (DGLA), can inhibit the biosynthesis of the proinflammatory eicosanoids leukotriene B 4 (LTB 4 ) and 12‐hydroxyeicosatctraenoic acid (12‐HETE). The purpose of the present study was to investigate the incorporation of [ I4 C] 15‐HETrE in specific membrane phospholipids of cultured human keratinocytes in vitro . [ I4 C] 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, [ I4 C]15‐HETrE showed selectivity for incorporation into phosphatidylinositol (PI). The mean proportion of [ I4 C] 15‐HETrE in the PI, phosphatidylcholin (PC) and phosphatidyle‐thanolamin (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 µM, 6.2 µM, 18.6 µM of 15‐HETrE (0.4 µg, 1, 2 µg and 3.6 µg 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 A 2 and identified by reverse phase and straight phase high preformance liquid chromatography. There was a dose‐dependent incorporation of 15‐HETrE into the specific phospholipids PI and PC. When expressed as ng 15‐HETrE/ug phospholipid phosphate, 15‐HETrE accumulated preferent‐ically in PI. After injection of the highest 15‐HETrE concentration, the mean amount of 15‐HETrE estcrified in PI and PC was 81.9 ng/µg PI phosphate and 19.4 ng/µg PC phosphate, respectively. This incorporation of 15‐HETrE incorporated into epidermal PLs was not accompanied by a clinical change of the treated psoriatic plaques. It remains to be determined whether higher 15‐HETrE incorporated might induce clinical improvement of psoriasis.