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W F Stenson

Publications and source records attributed to W F Stenson.

87 records · Page 5Linked to original sources
PubMed1983

Esterification of monohydroxyfatty acids into the lipids of a macrophage cell line.

Cells of a mouse macrophage-like tumor cell line, J774.2, were incubated with 0.6 microM radiolabeled mono- and di-hydroxyfatty acids. Monohydroxyfatty acid products of the neutrophil and platelet lipoxygenase pathways (5-HETE, 15-HETE, and 12-HETE) were rapidly taken up (42-64% of the counts cell associated at 1 min) and esterified into triglycerides and phospholipids. 5-HETE and 12-HETE were found in triglycerides and distributed among phospholipid classes while 50% of added 15-HETE was esterified into phosphatidyl inositol. Treatment of phospholipids from cells incubated with 5-HETE, 12-HETE, and 15-HETE with phospholipase A2 resulted in release of the respective monohydroxyfatty acid. HHT, a monohydroxyfatty acid product of the cyclooxygenase pathway, was taken up and esterified more slowly than the lipoxygenase products. In addition, HHT was not released when the phospholipids from cells incubated with HHT were treated with phospholipase A2. LTB4, a dihydroxyfatty acid product of neutrophil lipoxygenase, was not taken up by J774.2 cells. The unique patterns of uptake and intracellular distribution of the different monohydroxyfatty acids suggests that the enzymes involved in the esterification of these compounds have substrate specificity and may also relate to the specific biologic effects of these compounds.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1983

Glutathione depletion inhibits amylase release in guinea pig pancreatic acini.

Isolated guinea pig pancreatic acini were specifically depleted of glutathione by treatment with 2-cyclohexene-1-one (2-CHX-1). Untreated acini contained 4.3 +/- 0.6 micrograms of glutathione per milligram protein. Incubation with 1 mM 2-CHX-1 for 5 min at 37 degrees C depleted glutathione to 17% of control values; 5 mM 2-CHX-1 depleted glutathione to less than 4% of control values. Incubation with 2-CHX-1 also impaired the ability of the isolated acini to secrete amylase in response to stimulation with carbachol and the ionophore A23187. The depletion of glutathione and the inhibition of amylase secretion by 2-CHX-1 were both dose dependent and time dependent. Incubation of acini with 2 mM 2-CHX-1 for 15 min at 37 degrees C reduced glutathione levels to 6.6% of control and reduced carbachol-stimulated amylase release to 63% of control. Higher doses of 2-CHX-1 or longer incubations resulted in greater depletion of glutathione and greater inhibition of carbachol-induced amylase release. These data indicate that specific depletion of glutathione impairs the ability of isolated acini to secrete amylase in response to physiological and pharmacologic stimuli and suggest that glutathione has a role in stimulus-secretion coupling in the exocrine pancreas.

Amylases↗
PubMed1982

5,8,11,14-Eicosatetraynoic acid (ETYA) inhibits binding of N-formyl-methionyl-leucyl-phenylalanine (FLMP) to its receptor on human granulocytes. A note of caution.

Binding of two biochemically chemotactic factors, FMLP and C5a, to their respective receptors on human granulocytes produces a transient several-fold increase in cAMP. To determine if arachidonic acid metabolites were responsible for the increased cAMP concentrations, two inhibitors of arachidonic acid metabolism, indomethacin and ETYA, were incubated with granulocytes prior to FMLP or C5A. ETYA, but not indomethacin, inhibited both the cAMP and superoxide responses to a similar degree. However, the mechanism of this effect was found to be through inhibition of the binding of FMLP to its receptor rather than through inhibition of arachidonate metabolism.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1982

Metabolism of arachidonic acid by pancreatic acini: relation to amylase secretion.

Isolated guinea pig pancreatic acini were incubated with exogenous [14C]arachidonic acid (10 microM) at 37 degrees C for 3 min. The lipids were extracted and separated by thin-layer chromatography. Radiolabeled metabolites were identified by comigration with standards: 0.024% of the recovered radioactivity comigrated with prostaglandin E2 (PGE2), 0.016% comigrated with PGF2 alpha, 4.9% was incorporated into triglycerides, 1.8% was incorporated into phospholipids, and 93.2% remained as arachidonic acid. The synthesis of PGE2 and PGF2 alpha was inhibited by indomethacin (ID50, 30 nM). Simultaneous addition of carbachol or caerulein with the [14C]arachidonic acid did not alter the metabolism of the arachidonate. Further studies were done on the role of arachidonate metabolites in the secretion of amylase. Exogenously added PGE2 and PGF2 alpha (0.3-100 nM) did not induce amylase secretion from isolated acini. Incubation of isolated acini with indomethacin (0.1-28 microM) did not inhibit the release of amylase induced by carbachol or caerulein. From these data, we conclude that isolated guinea pig pancreatic acini are capable of converting a small percentage of exogenous arachidonate to PGE2 and PGF2 alpha. However, there is no evidence for a role of these compounds in stimulus-secretion coupling.

Amylases↗
PubMed1982

Sulfasalazine inhibits the synthesis of chemotactic lipids by neutrophils.

Neutrophils metabolize arachidonic acid through the liposygenase pathway to 5-hydroxy-6,8,11,14-eicosatetrenoic acid (5-HETE) and 5,12-dihydroxy-6,8,10,14-eicosatraenoic acid (5,12 diHETE). 5-HETE and 5,12diHETE are potent chemotactic agents and are thought to have important roles in the inflammatory response. In this study we demonstrate the sulfasalazine, at concentrations found in the stool of patients being treated for ulcerative colitis, blocks the synthesis of both 5-HETE and 5,12 diHETE by human neutrophils. A sulfasalazine metabolite, 5-aminosalicylate, also blocks the synthesis of 5,12 diHETE.

Aminosalicylic Acids↗
PubMed1981

Metabolism of exogenous arachidonic acid by murine macrophage-like tumor cell lines.

Murine macrophage-like cell lines, J774.2, P388D1, RAW264.7 and PU-5-1R, were incubated with exogenous arachidonic acid (AA). The major metabolites were identified by comigration with known standards in TLC and HPLC and by characteristic behavior following reduction. During a 30 min incubation J774.2 cells metabolized exogenous 14C-AA (10 microM) to PGE2 (14.8%), 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) (13.0%), thromboxane B2 (TXB2) (7.4%), PGD2 (4.4%) and PGF2 alpha (3.0%). The remainder was incorporated into phospholipids (39.0%), triglycerides (6.1%), and as yet unidentified metabolites (8.2%). No PGF1 alpha was found. Metabolism of exogenous AA was rapid, being less than 90% completed at 3.5 min. Metabolism of exogenous AA is not increased by the simultaneous addition of macrophage stimuli including the cation ionophore A-23187, particulate phagocytic stimuli and endotoxin. The synthesis of cyclooxygenase products was inhibited by low doses of indomethacin (ID50=0.6 microM) while the synthesis of TXB2 and HHT was selectively inhibited by benzylimidazole (ID50=9.5 microM). Identification of a probable lipoxygenase product is being pursued. The synthesis of this product is not inhibited by indomethacin and migrates with an Rf value close to 5,12-diHETE in TLC. P388D1 and RAW264.7 cells metabolize exogenous AA to the same products as J774.2, but in different proportions, while PU-5-1R does not produce cyclooxygenase metabolites to any appreciable extent.

Animals↗
PubMed1981

Inhibition of human polymorphonuclear leukocyte function by 2-cyclohexene-1-one. A role for glutathione in cell activation.

2-cyclohexene-1-one and diethyl maleate specifically decrease reduced glutathione (GSH) levels in human polymorphonuclear leukocytes (PMN) by direct conjugation, and by interaction with the glutathione-s-transferase system. Using these two nontoxic reagents we have examined the effect of decreased GSH levels on five parameters of PMN activation: superoxide generation, release of the lysosomal enzymes lysozyme and beta-glucuronidase, and increases in the influx of Na+ and Ca2+. When PMN pretreated with 2-cyclohexene-1-one or diethyl maleate were incubated with formyl-methionyl-leucyl-phenylalanine (FMLP) or the proteolytic fragment of the fifth component membrane of complement, C5a, agents that interact with surface membrane receptors, increases in all five parameters were inhibited in a dose-dependent manner. For O-2 generation and lysosomal enzyme release the ID50 for 2-CHX-1 was 40--90 micrometers corresponding with a 30--50% decrease in intracellular GHS. In contrast stimulation of treated PMN by the divalent cation ionophore A23187 or 5-hydroxyeicosatetraenoic acid was much less sensitive to depressed GSH; the ID50 for 2-cyclohexene-1-one was 1 mM or greater, corresponding with an 80--90% decrease in GSH. The effect of lowered GSH was not the result of decreased binding of FMLP to surface receptors because [3H]-FMLP binding studies demonstrated a two- to three-fold increase in the number of available binding sites. These data indicate that normal GSH levels are necessary for the transduction of the activation signal from the exterior to the interior of the PMN, but once initiated the activation sequence proceeds normally despite markedly lowered intracellular GSH.

Calcium↗
PubMed1980

Monohydroxyeicosatetraenoic acids (HETEs) induce degranulation of human neutrophils.

5-S-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE), a lipoxygenase product in neurophils, and 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE), a lipoxygenase product in platelets, were prepared biosynthetically and incubated with purified human peripheral neutrophils. Both 5-HETE and 12-HETE at 5- to 10-microM concentrations induced degranulation of specific granules. Both 5-HETE and 12-HETE are chemotactic for neutrophils at these concentrations. Arachidonic acid, the metabolic precursor of 5-HETE and 12-HETE, did not induce degranulation. The calcium ionophore A23187 induces neutrophils degranulation and also activates arachidonic acid metabolism in neutrophils resulting in 5-HETE production. Both ionophore-induced 5-HETE production and ionophore-induced degranulation can be inhibited, with very similar inhibition curves, by 5,8,11,14-eicosatetraynoic acid, an inhibitor of arachidonate metabolism. We propose that the mechanism for 5-HETE- and 12-HETE-induced degranulation is an alteration in the fatty acid composition of membrane phospholipids.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1979

12-L-hydroxy-5,8,10,14-eicosatetraenoic acid, a chemotactic fatty acid, is incorporated into neutrophil phospholipids and triglyceride.

Platelets contain a lipoxygenase which converts arachidonic acid to 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) which has been shown to be chemotactic for human neutrophils and eosinophils. [14C]-12-HETE was biosynthesized, purified and incubated at a concentration of 1 micro M with human neutrophils. Lipids were extracted from the neutrophils and the media, and the radiolabeled products identified. 26 percent of the radiolabel was found in the cells after 30 min incubation, essentially all of it esterified into phospholipid and triglyceride. The radiolabeled phospholipids and triglycerides were transesterified and the liberated fatty acid was identified as [14C]-12-HETE. This is the first demonstration of direct alteration of membrane components by a chemotactic agent and may be an example of a more generalized mechanism for altering membrane characteristics.

Arachidonic Acids↗
PubMed1979

Metabolism of arachidonic acid in ionophore-stimulated neutrophils. Esterification of a hydroxylated metabolite into phospholipids.

[14C]Arachidonic acid incubated with human neutrophils was esterified into phospholipids and triglycerides. Stimulation of these labeled neutrophils with ionophore A23187 (2 microM) results in release of [14C]arachidonate from phospholipid and its metabolism to prostaglandin E2 and 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE), a lipoxygenase product. The released arachidonate is also metabolized to a polar lipid of unknown composition here disignated compound A. 5-HETE was found to be released into the medium and then taken up again by the cells. To determine its metabolic fate, [14C]5-HETE was prepared biosynthetically, purified, and incubated with stimulated, unlabeled neutrophils. Most of the radioactivity entered the cells and was esterified into phospholipids and triglycerides. The radiolabeled complex lipids were saponified, and the released fatty acids cochromatographed with authentic 5-HETE. The esterification of 5-HETE, a hydroxylated fatty acid, into membrane phospholipids may be an example of a more generalized mechanism for altering membrane characteristics.

Arachidonic Acids↗
PubMed1979

Formation of thromboxane B2 and hydroxyarachidonic acids in purified human lymphocytes in the presence and absence of PHA.

The metabolism of exogenous and endogenous [14C] arachidonc acid was studied in purified human peripheral blood lymphocytes carefully freed of contaminating platelets. Formation of products co-migrating in a number of different solvent systems with 5-hydroxyarachidonic acid (5-HETE), thromboxane B2 (TB2), prostaglandins and probably 12-hydroxyarachidonic acid (12-HETE) was demonstrated. In cells prelabeled with [14C] arachidonic acid, phytohemagglutinin (PHA) produced substantial (3.5- to 12-fold) increases in 5-HETE, 12-HETE, and TB2 radiolabeling. The metabolism of exogenous [14C] arachidonic acid was much less affected by PHA. Since PHA releases cell-bound arachidonic acid, it appears that the response involving endogenous label is due to increased availability of free arachidonic acid rather than induction of arachidonic acid-metabolizing enzymes. Various inhibitors of arachidonic acid metabolism exerted similar effects in lymphocytes to those described previously in other tissues providing a possible basis for interpreting their inhibitory effects on mitogenesis, described in the preceding paper.

Arachidonic Acids↗
PubMedDate not supplied

A comparison of effects of sulfasalazine and its metabolites on the metabolism of endogenous vs. exogenous arachidonic acid.

Sulfasalazine and, to a lesser extent, 5-aminosalicylic acid and N-acetyl-aminosalicylic acid, were found to block production of 5-hydroxy-6,8,11,14-eicosatetraenoic acid, leukotriene B4 (LTB4), and LTB4 stereoisomers from both exogenous and endogenous [14C]arachidonic acid (14C-AA) in ionophore A23187 (1 microgram/ml)-stimulated human neutrophils. Lipids were assessed by thin-layer chromatography and reverse-phase high-pressure lipid chromatography. Sulfasalazine blocked the synthesis of these metabolites from both exogenous and endogenous AA, but was more effective in blocking the metabolism of exogenous than endogenous AA. The IC50 for sulfasalazine in blocking the synthesis of LTB4 was 0.8 mM when exogenous AA was the substrate and 2.8 mM when endogenous AA was the substrate. N-Acetyl-aminosalicylic acid showed a similar pattern, but was less effective than sulfasalazine (IC50 for exogenous AA was 5.4 mM, and for endogenous AA was 8.0 mM). 5-Aminosalicylic acid had similar effects with an IC50 of 6.0 and 6.4 mM respectively. Sulfasalazine but not 5-aminosalicylic acid inhibited the incorporation of arachidonic acid into phospholipids and triglycerides. Sulfasalazine, but not its metabolites, inhibited the release of 14C-AA from membrane phospholipids in a dose-dependent manner (46.0% inhibition with 4 mM sulfasalazine). Sulfasalazine also blocked the metabolism of exogenously added LTB4 to 20-OH LTB4 and 20-COOH LTB4 with an IC50 of 2 mM. Our findings suggest that under physiologic conditions, with endogenous AA as a substrate, sulfasalazine acts as an inhibitor of lipoxygenase, of phospholipase A2 and of LTB4 metabolism, whereas 5-aminosalicylic acid and N-acetyl-aminosalicylic acid inhibit only lipoxygenase.

Aminosalicylic Acids↗