Lipoxygenbase-derived products of arachidonic acid mediate stimulation of hexose uptake in human polymorphonuclear leukocytes

Elevated levels of leukotriene B4 and leukotriene E4 in bronchoalveolar lavage fluid from patients with scleroderma lung disease

OBJECTIVE

The leukotrienes are a family of arachidonic acid-derived lipid mediators with proinflammatory and profibrotic properties. The aim of this study was to analyze the role of leukotriene B(4) (LTB(4)) and LTE(4) in the pathogenesis of scleroderma lung disease (SLD).

METHODS

Nineteen systemic sclerosis (SSc) patients with SLD, 11 SSc patients without SLD, and 10 healthy controls were studied. Bronchoalveolar lavage (BAL) fluid was obtained during routine bronchoscopy of the right middle lobe in all study subjects. Levels of LTB(4) and LTE(4) were measured using enzyme immunoassay kits.

RESULTS

Levels of LTB(4) and LTE(4) were significantly higher in SSc patients with SLD (251 +/- 170 pg/ml and 479 +/- 301 pg/ml, respectively), than those in patients without SLD (114 +/- 86 and 159 +/- 149 pg/ml) and those in normal controls (86 +/- 49 and 110 +/- 67 pg/ml). In the total group of patients with SSc, levels of both leukotrienes correlated positively with the total number of cells in the BAL fluid and correlated negatively with the forced vital capacity. After intravenous pulse therapy with cyclophosphamide in 6 patients, there was a significant reduction in the concentration of LTB(4) (from 380 +/- 196 pg/ml to 155 +/- 123 pg/ml) but no significant difference in the levels of LTE(4) (from 697 +/- 325 pg/ml to 418 +/- 140 pg/ml).

CONCLUSION

Our findings show that LTB(4) and LTE(4) levels are elevated in SSc patients with SLD and correlate with parameters of inflammation in the lungs. These results indicate that leukotrienes may contribute to the pathogenesis of SLD and may represent a new therapeutic target.

Bioactions of 5-hydroxyicosatetraenoate and its interaction with platelet-activating factor

In a variety of stimulated cells, platelet-activating factor (PAF) and numerous arachidonate derivatives are co-products that form as a consequence of receptor-mediated phospholipid mobilization. These lipid co-products produce a plethora of biological effects in a wide variety of cell systems. Furthermore, they often have a fascinating although less widely appreciated, interaction. 5-HETE, at submicromolar concentrations, exerts relatively few direct bioactions. It does, however, potently (16-160 nM) raise cytosolic free calcium [Ca2+]i and augment PAF-induced responses in human polymorphonuclear neutrophils (PMN) by as much as 100- to 1000-fold. 5-HETE acts on PMN by a structurally specific, stereospecific and pertussis toxin-inhibitable mechanism. In addition, PMN exposed to 5-HETE exhibit homologous but not heterologous desensitization. These findings suggest that 5-HETE, like PAF, may bind to its own specific plasmalemmal receptors to exert its unique set of bioactions. However, further investigation is required to demonstrate any putative 5-HETE receptors. Other potential mechanisms of 5-HETE-induced bioactions together with the possible effects of 5-HETE on PAF transduction mechanisms are also discussed.

The synthesis and molecular dynamics of phospholipids having hydroxylated fatty acids at the sn-2 position

We have devised a general method for the synthesis of phospholipids containing hydroxylated fatty acids and have utilized this methodology to synthesize two naturally occurring hydroxylated lecithins (i.e. 1-palmitoyl-2-[15(S)-hydroxy-5E, 8E,11E,13Z-eicosatetraenoyl]-sn-glycero-3-phosph ocholine (1-palm-2-15HETE PC) and 1-palmitoyl-2-[5-hydroxy-6Z,8E,11E, 14E-eicosatetraenoyl]-sn-glycero-3-phosphocholine (1-palm-2-5HETE PC]. After protection of the hydroxylated fatty acid as its t-butyldimethylsilyl derivative, the anhydride of the protected fatty acid was formed utilizing dicyclohexylcarbodiimide and subsequently was condensed with a regiospecific lysolecithin utilizing pyrrolidinopyridine as catalyst to form the protected hydroxylated lecithin. Finally, hydroxylated lecithins were formed after removal of the t-butyldimethylsilyl group with acetic acid. Electron spin resonance spectroscopy was utilized to interrogate the molecular dynamics of lipid bilayers comprised of mixtures of these hydroxylated lecithins and naturally occurring lecithins. Remarkably, the molecular dynamics of spin-labeled phospholipids in liposomes comprised of cholesterol and phosphatidylcholine were altered substantially after addition of only 3.5 mol% 1-palm-2-15HETE PC as assessed by the order parameter of 16-doxylstearoyl phosphatidylcholine.

The in vitro development of cytotoxicity in response to granulocyte/macrophage-colony-stimulating factor or interferon gamma in the peripheral blood monocytes of patients with solid tumors: modulation by arachidonic acid metabolic inhibitors

The capacity of granulocyte/macrophage-colony-stimulating factor (GM-CSF) and interferon gamma (IFN gamma) to elicit monocyte cytotoxicity in vitro in the peripheral blood monocytes of patients with solid tumors was investigated. The cytotoxicity elicited by IFN gamma was significantly reduced in cancer patient monocytes compared to normal monocytes. The cytotoxicity elicited by GM-CSF, however, was comparable between cancer patient monocytes and normal monocytes, but was lower than that induced by IFN gamma. Indomethacin, a cyclooxygenase inhibitor, significantly augmented IFN gamma-elicited cytotoxicity in cancer patient monocytes, but not in normal monocytes. In contrast, indomethacin augmented GM-CSF-elicited cytotoxicity in both cancer patient monocytes and normal monocytes. Nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, was found to suppress cytotoxicity in response to IFN gamma and GM-CSF in both cancer patient monocytes and normal monocytes. The addition of leukotrienes to NDGA-treated cultures restored the development of cytotoxicity. Thus there are differences in the in vitro response of cancer patient monocytes and normal monocytes to distinct biological activators. Furthermore, these responses can be manipulated by agents that modulate arachidonic acid metabolism.

Effect of chemotactic factors on hexose transport in polymorphonuclear leucocytes

Transport of the nonmetabolizable glucose analogue, 3-O-methylglucose, was assessed in human polymorphonuclear leucocytes with or without the chemotactic peptide N-formylmethionylleucylphenylalanine (fMet-Leu-Phe). The peptide increased entry of labelled 3-O-methylglucose about 5-fold and the intracellular distribution space about 70%. The half-time of equilibration was 3 s in the treated cells. Similar effects were observed with zymosan-treated serum (containing the chemotactic factor C5a), with arachidonic acid, calcium ionophore A23187 and phorbol myristate acetate. However, the chemotactic protein, thrombin, had no effect, even though binding to high-affinity receptors was demonstrated. Km for zero-trans entry of 3-O-methylglucose was about 1 mM and fMet-Leu-Phe increased Vmax from 5 to about 25 amol.s-1.cell-1. Similar values were obtained from incubations for a few seconds with glucose and 2-deoxyglucose. The rate of 2-deoxyglucose uptake (8 min incubations) was limited by the transport step at substrate concentrations lower than approx. 0.1 mM, whereas the phosphorylation step became rate-limiting at higher concentrations. Thus, 2-deoxyglucose uptake can only be taken as a measure of transport at a tracer concentration. It is concluded that chemotactic factors can, but do not necessarily, increase the maximal transport velocity of hexoses entering the polymorphonuclear leucocyte via the glucose transporter.

Effects of nordihydroguaiaretic acid, phloretin, and phloridzin on the activity of adenylate cyclase, lipoxygenase and hexose transport, and growth of cultured keratinocytes

Compounds related to the flavonoid group of natural products may have potential as antipsoriatic drugs. The dihydrochalcone phloretin, its glycoside derivative phloridzin, and the structurally related compound nordihydroguaiaretic acid (NDGA) were selected for study. Phloretin and NDGA strongly inhibited keratinocyte growth but had no effect on isoproterenol-stimulated adenylate cyclase; phloridzin had no effect on growth but potentiated the response of the enzyme. None had any effect on phosphodiesterase. Neither phloretin or phoridzin inhibited lipoxygenase or, surprisingly, decreased deoxyglucose transport. Phloretin and NDGA should be considered antipsoriatic agents.

The effect of 5-hydroxyeicosatetraenoic acid on the proliferation of granulocyte progenitors and embryonic fibroblasts of the chick

The clonal proliferation of chicken granulocytic progenitors was inhibited 5-20-fold by the eicosanoid, 5-HETE, at 1.0 microM. Inhibition occurred at the lowest concentration measured (0.12 microM). This compound at 0.6 to 1.0 microM also inhibited the clonal proliferation of chick embryo fibroblasts by as much as 10-fold.

Ex vivo effects of nonsteroidal antiinflammatory drugs on arachidonic acid metabolism in neutrophils from a reverse passive Arthus reaction

Rat neutrophils isolated from 4-h reverse passive Arthus reaction (RPAR) pleural exudates actively metabolize arachidonic acid via cyclooxygenase and lipoxygenase. Utilizing this system, the effect of oral doses of nonsteroidal antiinflammatory drugs on the ability of these cells to produce HHT, 5-HETE, and LTB from exogenously added arachidonic acid has been investigated. In vitro and ex vivo, indomethacin and timegadine inhibit cyclooxygenase activity in rat pleural neutrophils. In vitro, timegadine is a lipoxygenase as well as a cyclooxygenase inhibitor. This dual inhibition is confirmed by the observation that ex vivo timegadine inhibits the production of lipoxygenase as well as cyclooxygenase metabolites. While indomethacin, a cyclooxygenase inhibitor, primarily inhibits edema formation, the inhibition of both pathways of arachidonic acid metabolism by timegadine is reflected in the drug's ability to reduce cellular influx as well as edema formation in the RPAR pleural cavity inflammatory reaction.

Stimulation of glucose uptake by transforming growth factor beta: evidence for the requirement of epidermal growth factor-receptor activation

Transforming growth factor beta (TGF-beta), derived from human platelets, stimulates the uptake of 2-deoxy-glucose by cultured cell monolayers 2- to 4-fold. Stimulation can be detected as early as 30 min with as little as 0.1 ng of TGF-beta per ml and maximal effects can be obtained at 2 hr with 1 ng of the growth factor per ml. TGF-beta-induced stimulation of sugar uptake is enhanced by the co-addition of platelet-derived growth factor (10 ng/ml) or epidermal growth factor (EGF, 1 ng/ml). The NR-6 variant of mouse 3T3 cells, which lack EGF receptors, is not stimulated by TGF-beta. Antisera to EGF receptors that block 125I-labeled EGF binding also inhibit TGF-beta stimulation of 2-deoxyglucose uptake, although 125I-labeled TGF-beta binding remains unimpaired. In contrast, anti-sera to the EGF receptor, which do not block EGF binding, have no measurable effect on the TGF-beta-stimulated uptake of 2-deoxyglucose. We confirm that the receptor for TGF-beta is distinct from the receptor for EGF and we conclude that TGF-beta stimulation of 2-deoxyglucose uptake requires the co-activation of the EGF receptor kinase system.

Effect of 15-lipoxygenase-derived arachidonate metabolites on human neutrophil degranulation

Products of the 15-lipoxygenase pathway of arachidonate metabolism, prepared by techniques that effectively free them from contaminants, were examined for their ability to influence human neutrophil degranulation. 15(S)-Hydroxyicosatetraenoate [15(S)-HETE], 8(S),15(S)-dihydroxyicosatetraenoate, and 5(S),15(S)-dihydroxyicosatetraenoate did not directly stimulate this response, but 5(S),15(S)-dihydroxyicosatetraenoate (158-5000 nM) enhanced degranulation responses elicited by platelet-activating factor and its structural analogues. It had no such effect on the degranulation responses elicited by a tripeptide chemotactic factor, phorbol myristate acetate, leukotriene B4, or ionophore A23187. In many of these respects, the potentiating actions of 5,15-dihydroxyicosatetraenoate paralleled the actions of 5(S)-hydroxyicosatetraenoate. Indeed, these two metabolites had potentiating actions on platelet-activating factor that were non-additive and, under specific conditions, cross-desensitized each other. Based on the structural specificity demonstrated by these and other mono- and dihydroxyeicosatetraenoates in potentiating platelet-activating factor as well as their mutual cross-desensitizing actions, we suggest that 5-hydroxylated arachidonate metabolites act by a structurally specific receptor to potentiate human neutrophil responses to certain stimuli.

Relationship of cyclic-AMP levels in leukotriene B4-stimulated leukocytes to lysosomal enzyme release and the generation of superoxide anions

Leukotriene B4 stimulated the formation of cyclic AMP, the release of lysosomal enzyme and generation of superoxide anions by human leukocytes. Dose-response curves have shown that the enzyme release proceeded in parallel with increments in cyclic AMP, suggesting a linkage between cyclic AMP and leukotriene B4-induced leukocyte activation. However, preincubation of the cells with (5S,12S)-dihydroxy-6,8,10,14-eicosatetraenoic acid or leukotriene B4 resulted in a dose-dependent inhibition of leukotriene B4-induced degranulation, without causing parallel changes in the levels of cyclic AMP. Both dihydroxy acids also blocked leukotriene B4-induced superoxide anion generation. These results suggest that the leukocyte responses to leukotriene B4 and the concomitant cyclic-AMP increments may be merely coincidental. In addition, the present study further supports the suggestion that (5S,12S)-dihydroxy-6,8,10,14-eicosatetraenoic acid may modulate the action of leukotriene B4 in the leukocyte.

Superoxide production of human polymorphonuclear leukocytes stimulated by leukotriene B4

Leukotriene B4 stimulated a transient production of superoxide anions (O2-) by human polymorphonuclear leukocytes which continued for only about 1 min. The production was dependent on Ca2+ in the suspending medium and no production was observed without the addition of calcium. The concentrations of leukotriene B4 and calcium for the half-maximal production were about 1 microM and 200 microM, respectively. 8-(N,N,-Diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8), an intracellular calcium antagonist, did not inhibit the O2- production stimulated by leukotriene B4 in the presence of calcium, while N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), a calmodulin inhibitor, did. When leukotriene B4 was added to the cells treated with cytochalasin B, the production of O2- was biphasic: an initial rapid phase, followed by a slow one. The slow phase was also dependent on Ca2+ concentrations but it could be induced even without the addition of Ca2+ to the medium. The cells treated with both cytochalasin B and TMB-8 in Ca2+-free medium showed a negligible production of superoxide on addition of leukotriene B4, but the production appeared upon addition of CaCl2. These findings suggest that the superoxide production stimulated by leukotriene B4 is associated with the influx of Ca2+.

Generation of leukotrienes from human granulocytes by alveolysin from Bacillus alvei

We investigated the effect of alveolysin on human granulocytes. Alveolysin is an exoprotein produced by Bacillus alvei and belongs to the group of sulfhydryl-activated cytolysins. Other members of this group are streptolysin O and theta-toxin from Clostridium perfringens. It is demonstrated that alveolysin leads to leukotriene generation from human granulocytes, which exert chemotactic (leukotriene B4) and slow-reacting substance (leukotriene C4, D4, and E4) activity under sublytic concentrations.

12-0-tetradecanoylphorbol-13-acetate and concanavalin A enhance glucose uptake in thymocytes by different mechanisms

The effects of the tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA) and the plant lectin concanavalin A (Con A) on glucose uptake in murine thymocytes were studied. TPA induces a rapid dose-dependent increase in the uptake of 2-deoxyglucose and in the transport of 3-0-methylglucose. Con A also elicits a time- and dose-dependent enhancement of 2-deoxyglucose uptake. The effect of Con A, however, is less pronounced. The effect of combined treatment of thymocytes with Con A and TPA is not additive. Cytochalasin B completely inhibits the basal, as well as TPA- and Con A-enhanced, 2-deoxyglucose uptake. Dexamethasone markedly inhibits basal 2-deoxyglucose uptake, but is less inhibitory to enhanced 2-deoxyglucose uptake induced by TPA and Con A. The effect of TPA on 2-deoxyglucose uptake and 3-0-methylglucose transport is refractory to inhibition by isobutyl methyl xanthine, dibutyryl cyclic AMP, and ethyleneglycol tetraacetic acid. These agents markedly inhibit the enhancement of 2-deoxyglucose (2-DOG) uptake by Con A. p-Bromophenacyl bromide, an inhibitor of phospholipase A2, also selectively inhibits Con A enhancement of 2-DOG uptake. Taken together, the results suggest that Con A and TPA exert their stimulatory effect on glucose uptake by different activating mechanisms, but they may share a final common transport pathway.

Differential effects of anti-inflammatory drugs on lipoxygenase and cyclo-oxygenase activities of neutrophils from a reverse passive Arthus reaction

Rat neutrophils isolated from four-hour reverse passive Arthus reaction pleural exudates actively metabolize arachidonic acid. Production of 11-hydroxy- and 15-hydroxy-icosatetraenoic acid and 12-hydroxy-heptadecatrienoic acid is inhibited by indomethacin, benoxaprofen, BW 755C, piroxicam, ibuprofen, timegadine, and naproxen, suggesting that production of these arachidonic acid metabolites occurs at similar enzymic active sites. In addition, in the presence of the calcium inophore A23187 or the non-ionic detergent, BRIJ 56, rat neutrophils also produce the lipoxygenase products 5-hydroxy-icosatetraenoic acid and leukotriene B. The production of these metabolites is calcium dependent. Moreover, the calcium ionophore A23187 and BRIJ 56 synergistically act to augment the metabolism of exogenously added arachidonic acid via lipoxygenase. The formation of these metabolites is inhibited by BW 755C, benoxaprofen and timegadine but not by other non-steroidal anti-inflammatory drugs tested. In fact, at doses which inhibit cyclo-oxygenase activity, indomethacin, naproxen, and ibuprofen stimulate arachidonic acid metabolism via lipoxygenase.

Chemiluminescence from mouse resident macrophages: characterization and modulation by arachidonate metabolites

Oxidative burst dependent chemiluminescence (CL), generated by mouse resident peritoneal and alveolar macrophages obtained by peritoneal and lung lavage, has been studied using a lumanol-dependent assay. Alveolar macrophages generated greater CL in response to opsonized zymosan (OpZ, 0.017-0.67 mg/ml) than did peritoneal cells, but the former were less sensitive to inhibition by joint cyclo-oxygenase/lipoxygenase inhibitors and superoxide dismutase. Responses of peritoneal macrophages to OpZ and calcium ionophore A23187 (0.1-0.5 microM) were small in comparison to responses of C. parvum-elicited cells, while FMLP (2-20 microM) was ineffective. Arachidonic acid alone (40-80 microM) generated slight CL from resident peritoneal macrophages. When added with OpZ (0.017 mg/ml), arachidonate (40 microM) initially enhanced, then inhibited CL, the inhibition being indomethacin (10 microM) sensitive. These data indicate that modulation of resident macrophage CL by arachidonate products differs somewhat from that reported for elicited macrophages.

Mechanism of arachidonic acid release in human polymorphonuclear leukocytes

Previous studies have demonstrated that [3H]arachidonic acid is released from prelabeled human neutrophil phospholipids when the cells are stimulated by calcium ionophore A23187 or by opsonized zymosan. Neither lysophospholipid generated by phospholipase A2 activity, diacylglycerol nor monoacylglycerol produced via phospholipase C/diacylglycerol lipase action have been identified following neutrophil challenge. The inability to detect any intermediates during the release of arachidonate is due to either rapid reacylation of lysophospholipid or conversion of diacylglycerol (monoacylglycerol) to cellular acylglycerols. The addition of exogenous [14C]fatty acid at the time of challenge was employed to determine the involvement of either phospholipase A2 or phospholipase C activities. Neutrophil stimulation with calcium ionophore A23187 resulted in an incorporation of exogenous [14C]arachidonate into phosphatidylinositol and phosphatidylcholine, those phospholipids which specifically release arachidonate. When the saturated fatty acid, [14C]stearate, replaced [14C]arachidonate, very little [14C]fatty acid was incorporated into any of the phospholipid species. Lipid phosphorus measurements revealed no significant mass change in any phospholipid class following ionophore challenge. Production of [14C]phosphatidic acid was not detected, as would be expected if diacylglycerol kinase and de novo phospholipid metabolism were significantly involved.

Granulocytes utilize different energy sources for movement and phagocytosis

Granulocytes depend on anaerobic glycolysis for the energy required for chemotaxis, phagocytosis, and microbial killing. Two potential sources of the needed glucose are available: exogenous glucose and intracellular glycogen. These studies demonstrate that chemotaxin-induced movement of granulocytes induces accelerated uptake of exogenous glucose while phagocytosis does not, presumably utilizing instead the relatively slow process of glycogenolysis. As measured by incorporation of extracellular radiolabeled hexoses [1-14C]glucose or [3H]deoxyglucose), the soluble chemotaxin-aggregants of granulocytes, nF-met-leu-phe, C5ades arg, bacterial filtrate, or arachidonic acid all augment transmembrane hexose uptake. This insulin-like activity closely parallels the dose-related effects of these agents on induction of granulocyte aggregation and chemotaxis. Insulin, itself, affects glucose transport minimally and mainly at supraphysiologic concentrations. In contrast, phagocytic stimuli fail to enhance hexose uptake at all, despite stimulating catabolism of glucose, which in turn is probably generated by glucogenolysis. these data show that granulocytes, whose motile function occurs in glucose-rich milieu, alter in tandem their cellular glucose uptake with their movement response. For phagocytosis, which often occurs in hypoglycotic, purulent exudates, granulocytes depend on stored energy supplies--probably glycogen. This coordination may be crucial in supporting granulocyte antimicrobial activity during acute inflammation.

Role of stimulation of arachidonic acid release in the proliferative response of 3T3 mouse fibroblasts to platelet-derived growth factor

Human platelet-derived growth factor (PDGF) stimulates release of arachidonic acid from cellular phospholipids, synthesis and release of prostaglandins from the cell, and initiation of DNA synthesis in cultures of 3T3 Swiss mouse fibroblasts at similar concentrations with four independent preparations representing a million-fold range of purification. Stimulation of arachidonic acid and prostaglandin release is an early event (beginning within minutes) in the response to PDGF treatment. Incubating cells with PDGF at 4 degrees C followed by washing leads to activation of arachidonic acid release on warming the cells to 37 degrees C, consistent with binding of the factor to the cell surface. PDGF-stimulated arachidonic acid release, prostaglandin release, and initiation of DNA synthesis are all inhibited by phenylglyoxal at similar concentrations. These results suggest that activation of arachidonic acid release from phospholipids plays an essential role in the mechanism by which PDGF-stimulates the initiation of DNA synthesis in 3T3 cells. The stimulation of initiation of DNA synthesis by PDGF does not appear to be mediated by the synthesis of prostaglandins or other known arachidonic acid metabolites because neither indomethacin (a fatty acid cyclooxygenase inhibitor) nor phenidone (a lipoxygenase inhibitor) inhibit initiation of DNA synthesis at concentrations which inhibit arachidonic acid metabolism. Although the activation of arachidonic acid release by PDGF is a calcium-dependent process, a simple calcium flux appears unimportant to the mechanism of activation. Evidence was also obtained against an involvement of sodium fluxes or proteolytic activity in the mechanism of stimulating arachidonic acid release by PDGF or serum.

[New aspects of the blood flow-augmenting and insulin-like activity of muscle exercise: possible involvement of the kallikrein-kinin-prostaglandin system (author's transl)]

Adaptations of energy metabolism, as they occur during contractions of skeletal muscle besides by anaerobic glycolysis are achieved via changes in capillary blood flow providing substrates and oxygen for combustion. Since, initially, oxygen supply is restricted in the working muscle, glucose would seem to be the adequate fuel as it may be used anaerobically and yields more energy per mole of oxygen than fatty acids under such circumstances. Besides glucose, amino acids are also required for accelerated proteosynthesis according to the work load. Therefore, an enlargement of the capillary net has to be accompanied by an amplification of the action of insulin, which is often present in only small amounts, e.g., after an overnight fast. This aim is met in three ways: (1) enlargement of the capillary net with accelerated blood flow increasing the supply of insulin and the number of receptor sites for insulin binding; (2) accelerated transport of insulin through the capillary wall, providing more insulin in the interstitial space and at the plasma membranes; (3) a molecular mechanism directly involving the insulin-receptor-messenger complex, localized at the plasma membrane of the working muscle cell. These mechanisms resemble a self-regulatory process, set in motion by the release of metabolites from the working tissue. From recent studies there is accumulating evidence that kinins liberated from their precursors are involved as tissue hormones by carrying the signal across the interstitial space to the smooth muscle cells of the capillary vessels. Concomitantly, prostaglandins are released intracellularly to bring about, in cooperation with kinins, the various adaptive mechanisms. Amplifying systems of this kind may play a role not only in muscle but also in other tissues where adequate kinin or prostaglandin release would appear beneficial under several clinical conditions such as shock, coronary infarction, wound healing, etc.

The effect of free radical derived hydroxyeicosatetraenoic acids on hexose transport in the human polymorphonuclear leukocyte

The following racemic hydroxyicosatetraenoic acids were prepared and assayed for their ability to stimulate hexose transport in human polymorphonuclear leukocytes: 15-, 12-, 11-, 9-, 8-, and 5-hydroxyicosatetraenoic acids. The compounds were isolated from reduced, autoxidized arachidonic acid. The results demonstrate that only the 12- and 5-hydroxyicosatetraenoic acids are biologically active inducing half-maximal responses at 820 and 176 nM, respectively. Thus, the bioactions of hydroxicosatetraenoates ae crucially dependent upon the position of the hydroxy residue. Response to both hydroxyicosatetraenoates was effectively blocked by two inhibitors of arachidonic acid metabolism: nordihydroguaiaretic acid and indomethacin. A third arachidonic acid antimetabolite, 5, 8, 11, 14-eicosatetraynoic acid, completely inhibited the response to 12-HETE but caused only partial inhibition of the response to 5-HETE.