Conversion of linoleic acid into arachidonic acid by cultured murine and human keratinocytes (original) (raw)
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Biochimica et biophysica acta, 1994
Keratinocytes require the essential fatty acid (FA), linoleic acid (LA), for the synthesis of stratum corneum membrane lipids. A plasma membrane-FA binding protein (PM-FABP), is postulated to mediate cellular FA-uptake in hepatocytes and several other tissues, but the mechanism whereby exogenous FA are taken up by keratinocytes has not been investigated. This study examines the uptake of LA and oleic acid (non-essential) in cultured human keratinocytes, in comparison to dermal fibroblasts and the human hepatoma cell line, HepG2. As previously reported for hepatocytes, FA-uptake in keratinocytes was curvilinear, with an initial (30 s) rapid cellular influx. The initial uptake component was temperature dependent, exhibited saturable kinetics and was significantly inhibited by pretreatment with trypsin. In contrast, fibroblast FA-uptake lacked an initial rapid uptake component, was relatively temperature insensitive, and was not inhibited by trypsin. Keratinocytes differed from both he...
In vivo conversion of linoleic acid to arachidonic acid in human adults
Prostaglandins, Leukotrienes and Essential Fatty Acids, 1999
Human adults are shown to be capable of conversion of linoleic acid (LA, 18:2 n-6) to arachidonic acid (AA, 20:4 n-6) in vivo. It is confirmed that they can also convert alpha-linolenic acid (LNA, 18:3 n-3) to eicosapentaenoic acid (EPA, 20:5 n-3) and to docosahexaenoic acid (DHA, 22:6 n-3) in vivo. The time course and the maximal response for these processes during the first week after a single dose of the 18-carbon precursor is described. A stable-isotope method in which the protons of the Cl 7 and Cl 8 carbons are substituted with deuterium atoms is used in order to provide for a safe method for the study of human metabolism. High sensitivity and selectivity of detection is assured with negative ion, gas chromatography/mass spectrometry analysis. It is clear that human adults on an ad lib diet carry out EFA metabolism in vivo.
Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 1986
Essential fatty acid-deficient rats were fed ethyl [U-'4C]arachidonate (308 dpm/nmol) and when a decrease in the transepidermal water loss was seen, the epidermal sphingolipids, acylglucosylceramide and acylceramide were isolated. [ "CjLinoleic acid (approx. 130 dpm/nmol) was present in both lipid classes, while the substrate was only detected in the former. These results intimate that' in vivo retroconversion of arachidonic to linoleic acid can be induced in the rat.
Arachidonic acid metabolism in HEL/30 murine epidermal Cell Line
Archives of Dermatological Research, 1988
The established mouse epidermis-derived cell line HEL/30 was incubated in the presence of 3H arachidonic acid (AA) for 1 h. After medium removal, cells were reincubated with fresh medium in the presence or absence of the calcium ionophore A23187 and tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA). The AA metabolites formed were extracted from cell-free medium and analyzed using TLC and HPLC. The distribution of the recovered radioactivity showed PGE2, 15-hydroxy-eicosatetraenoic acid (15-HETE), and leukotriene B4 (LTB4), as major products of AA metabolism. The presence of calcium ionophore A23187 increased the release of radioactivity, without affecting the profile of metabolites present in the medium. TPA elicited a preferential increase of cycloxygenase metabolism, this effect being reversed by indomethacin. 5,8,11,14-eicosatetraynoic acid (ETYA) almost completely inhibited LT and HETE formation in A23187 and TPA-treated cells. The results show that HEL/30 cells are able to metabolize AA via both cyclo-and lipoxygenase pathways and that these activities can be modified by chemical means. This cell line might be a suitable tool for studying the involvement of arachidonic acid cascade in cell response to exogenous stimuli.
Release of lipoxygenase products of arachidonic acid from freshly isolated human keratinocytes
Archives of Dermatological Research, 1984
Lipoxygenation of arachidonic acid (aa) has previously been shown to generate potent chemoattractants for neurophils, eosinophils, monocytes and fibroblasts , the most potent being 5(S), 12(R)-dihydroxyeicosa-6,14-cis-8,10 trans-tetraenoic acid (leukotriene B4, LTB4) and 5(S)-hydroxyeicosatetraenoic acid (5-HETE). Other monoHETEs [13] and co-oxidation products of LTB4 [5] are less potent chemoattractants.
Intestinal conversion of linoleic acid to arachidonic acid in the rat
The Journal of Nutritional Biochemistry, 1993
The arachidonic acid (C20:4, n-6) appearing in intestinal lymph during linoleic acid (C18:2, n-6) absorption may originate from enterocyte synthesis or from the liver either after secretion in biliary phospholipids at the same time dietary linoleic acid absorption occurs or via plasma. The radioactivity measured in the total bile collected during the 6 hours of linoleic acid absorption is too small to explain hepatic origin of the C20:4 detected by high performance liquid chromatography analysis of labeled fatty acids recovered in the lymph, in the intestinal mucosa, and the intestinal wall at the peak of linoleic acid intestinal absorption. This study confirms the probability that under in vivo conditions, during the absorption processes, rat intestine is able to convert dietary linoleic acid independent of liver desaturases and elongase activities. (J. Nutr. Biochem. 4:655-658, 1993.)
Incorporation of α-linolenic acid and linoleic acid into human respiratory epithelial cell lines
Lipids, 2001
Animal and human studies designed to examine the effects of α-linolenic acid (ALA) and linoleic acid (LA) supplementation on the fatty acid composition of plasma and tissues have demonstrated a marked difference in incorporation into phospholipids of these 18-carbon precursors of the longchain polyunsaturates. Whereas tissue phospholipid levels are linearly related to dietary ALA and LA, the levels of tissue LA can be 10-fold higher than tissue ALA even when dietary levels are equivalent. There is some dispute whether this disparity is due to ALA being more rapidly metabolized to its products or substantially oxidized by the liver, or whether LA but not ALA is readily incorporated into cellular phospholipids. We examined the level of incorporation of polyunsaturated fatty acids into human respiratory epithelial cell lines (A549, 16HBE) by determining the dose-dependent incorporation of ALA and LA as free fatty acid (5-150 µg FFA/mL). Cell membrane phospholipid ALA and LA were both increased up to ~20-30% total fatty acids, with a concomitant decrease predominantly in monounsaturated membrane fatty acids, before significant toxicity was observed (50 µg/mL). Our data support the concept that rather than any inherent inability by human cells to incorporate ALA into membrane phospholipids, the lack of ALA content in human and animal tissues in vivo is due to the rapid metabolism or oxidation of this fatty acid in the liver.
Production of arachidonic and linoleic acid metabolites by guinea pig tracheal epithelial cells
Inflammation, 1990
Pulmonary epithelial cells may be responsible for regulating airway smooth muscle function, in part by release of fatty acid-derived mediators. Incubation of isolated guinea pig tracheal epithelial cells with radiolabeled arachidonic acid (AA) leads to the production of 5-and 15-hydroxyeicosatetraenoic acid (5-and 15-HETE) and smaller amounts of leukotriene (LT) B 4 and C4 and 12-hydroxyheptadecatrienoic acid (HHT). Epithelial cells also are able to release linoleic acid (LA) metabolites. Incubation with radiolabeled linoleic acid leads to the formation of 9-and 13-hydroxyoctadecadienoic acid (9-and 13-HODE). The biological significance of these mediators produced by epithelial cells is discussed.
Journal of Investigative Dermatology, 1996
This study w a s focused on the characterization of the m etabolism of linoleic acid by human dermal fibroblas ts and the effect of interleukin-l on the biosynthesis of octadecanoids. Dermal fibroblasts untreated and tre ated with recombinant IL-lf3 were incubated with exogenous labeled linoleic acid. A combination of high performance liquid chromatography and gas chromatography-mass spectrometry was used as the analytic technique. We found that dermal fibroblasts convert linole ic a cid mainly into 13-hydroxy-9-cis,11trails-octadecadie noic acid (13-HODE) and 9-hydroxy-l 0-tralls,12-cis-octadecadienoic acid (9-HODE), 13(S)-HODE and 9(R)-HODE being the predominant enantiomers. IL-lf3 increased the formation of both 13-HODE and 9-HODE in a concentration-dependent manner with similar EC so values as for prostanoid formation. This effect of IL-lf3 on HODEs formation was concomitant with the expression of prostaglandin L in o leic acid (LA) is an esse nti al CiS-. POIYU. nsa turated fatty ac id and the precursor o f 13-and 9-hydro peroxyoctadecad ienoic (HPODE) acids, w hi ch in turn are redu ced to the corresp o ndin g hyd roxy-octadecadienoic (HODE) acids, th ese being the majo r oxygenated m etabolites of LA p ro du ced by cell s. HPO DEs and H O D Es have bee n fo und in high am o unts in ath eroscleroti c (Kiirm , 1992) and pso riati c lesio ns (Camp cf al.,1 983; Bae r el. ai, 1990, 1991) and have several biologic acti viti es in volved in the inflammatory response (B uchanan el ai, 1985; Yam aj a Se tty el ai, 1987; Iversen et ai , 199 1; K u cl ai, 1992). T he site of oxygen insertion on LA is primarily at the C9 or C 13 and is largely dependen t on th e cell type. In general, enzymatic oxidation