Synergistic activation of 2-deoxy-D-glucose uptake in rat and murine peritoneal macrophages by human macrophage colony-stimulating factor-stimulated coupling between transport and hexokinase activity and phorbol-dependent stimulation of pentose phosphate-shunt activity

Hexokinase translocation during neutrophil activation, chemotaxis, and phagocytosis: disruption by cytochalasin D, dexamethasone, and indomethacin

Neutrophils expend large amounts of energy to perform demanding cell functions. To better understand energy production and flow during cell activation, immunofluorescence microscopy was employed to determine the location of the key metabolic enzyme hexokinase during various conditions. Hexokinase is translocated from the neutrophil's cytosol to its periphery in response to N-formyl-methionyl-leucyl-phenylalanine (fMLP) and other activating stimuli, but not during exposure to the formyl peptide receptor antagonist N-tert-BOC-phe-leu-phe-leu-phe (Boc-PLPLP). Translocation was observed from 10(-6) to 10(-9)M fMLP. However, fMLP did not affect the intracellular distribution of lactate dehydrogenase. Hexokinase accumulated at the lamellipodium of cells exposured to an fMLP gradient whereas it localized to the phagosome after latex bead uptake. Thus, hexokinase is differentially translocated within cells depending upon the prevailing physiological conditions. Further studies noted that cytochalasin D, dexamethasone, and indomethacin blocked hexokinase translocation. Parallel regulation of reactive oxygen metabolite (ROM) production was shown. We speculate that hexokinase translocation participates in neutrophil activation.

The in vitro manipulation of carbohydrate metabolism: a new strategy for deciphering the cellular defence mechanisms against nitric oxide attack

This study was aimed at examining the effects of manipulating the carbohydrate source of the culture medium on the cellular sensitivity of epithelial cells to an oxidative attack. Our rationale was that substituting galactose for glucose in culture media would remove the protection afforded by glucose utilization in two major metabolic pathways, i.e. anaerobic glycolysis and/or the pentose phosphate pathway (PPP), which builds up cellular reducing power. Indeed, we show that the polarized human colonic epithelial cell line HT29-Cl.16E was sensitive to the deleterious effects of the NO donor PAPANONOate [3-(2-hydroxy-2-nitroso-1-propylhydrazino)-1-propanamine] only in galactose-containing medium. In such medium NO attack led to cytotoxic and apoptotic cell death, associated with formation of derivatives of NO auto-oxidation (collectively termed NOx) and peroxynitrite, leading to intracellular GSH depletion and nitrotyrosine formation. The addition of 2-deoxyglucose, a non-glycolytic substrate, to galactose-fed cells protected HT29-Cl. 16E cells from NO attack and maintained control GSH levels through its metabolic utilization in the PPP, as shown by (14)CO(2) production from 2-deoxy[1-(14)C]glucose. Therefore, increasing the availability of reducing equivalents without interfering with energy metabolism is able to prevent NO-induced cell injury. Finally, this background provides the conceptual framework for establishing nutritional manipulation of cellular metabolic pathways that could provide new means for (i) deciphering the mechanisms of cell injury by reactive nitrogen species and reactive oxygen species at the whole-cell level and (ii) establishing the hierarchy of intracellular defence mechanisms against these attacks.

Streptozotocin-induced diabetes increases fructose 2,6-biphosphate levels and glucose metabolism in thymus lymphocytes

Acute effect of streptozotocin-induced diabetes on several parameters of glucose metabolism was investigated in thymus lymphocytes (thymocytes). The cells from diabetics rats accumulated in vitro about 2-fold more fructose 2,6-bisphosphate (Fru-2, 6-P2) in the presence of increasing glucose concentration than cells from normal rats. An increased production of lactate was also observed. Phosphofructokinase-1 (PFK-1) and phosphofructokinase-2 (PFK-2) activities were enhanced in cells from diabetic rats compared with those from normal rats. [U-14C]glucose incorporation into glycogen was also increased in cells from diabetic rats and the 14CO2 liberation was lesser than in cells from normal animals. From these data it may be concluded that the response of thymocytes to streptozotocin-induced diabetes is similar to that observed in other extrahepatic tissues.

Decrease in free-radical production with age in rat peritoneal macrophages

The respiratory-burst reaction has been studied in rat peritoneal macrophages of different ages (3, 12 and 24 months) using phorbol 12-myristate 13-acetate (PMA) to stimulate NADPH oxidase. Production of O2-. and H2O2 decreased with age (about 50 and 75% respectively); however, no difference in NADPH oxidase activity was found. NO. production was also reduced with age (40%). Furthermore, a progressive and significant decrease in the pentose phosphate flux was detected as a function of age in control and PMA-stimulated macrophages. The NADPH/NADP+ ratio decreased with age in control and PMA-stimulated macrophages. Glucose uptake was lower in middle-aged (12 months) and old (24 months) animals but no differences were found between these groups.

Effect of adrenaline and phorbol myristate acetate or bacterial lipopolysaccharide on stimulation of pathways of macrophage glucose, glutamine and O2 metabolism. Evidence for cyclic AMP-dependent protein kinase mediated inhibition of glucose-6-phosphate dehydrogenase and activation of NADP+-dependent 'malic' enzyme

Adrenaline has recently been shown to stimulate both glucose metabolism and H2O2 release by macrophages but the activity of the key pentose phosphate pathway enzyme, glucose-6-phosphate dehydrogenase (which generates the NADPH crucial for the reduction of molecular oxygen), was reduced under these conditions [Costa Rosa, Safi, Cury and Curi (1992) Biochem. Pharmacol. 44, 2235-2241]. We report here that adrenaline activates another NADPH-producing enzyme, NADP(+)-dependent 'malic' enzyme, while also inhibiting glucose-6-phosphate dehydrogenase, via cyclic AMP-dependent protein kinase (PKA) activation. Regulation of glucose-6-phosphate dehydrogenase activity by PKA has not been reported elsewhere. The sparing of some glucose from pentose phosphate pathway consumption may be important in the provision of glycerol 3-phosphate which in the macrophage may be required for new phospholipid synthesis. Glutamine oxidation was also stimulated by adrenaline thus providing increased substrate (malate) for NADP(+)-dependent 'malic' enzyme and therefore shifting some of the burden of NADPH production from glucose to glutamine metabolism. We also report a novel synergistic effect of adrenaline and some bacterial products and/or gamma-interferon in stimulating secretory and metabolic pathways in macrophages which may be a part of a larger network of signals that lead to enhanced macrophage activity.

Leukocyte subpopulation changes in rats with autotransplanted endometrium and the effect of danazol

PROBLEM

This study examines immune cell populations in rats with autotransplanted endometrium and determines the effect of danazol on leukocyte subsets.

METHODS

As an experimental model of endometriosis, an autologous endometrial segment was implanted in the rat peritoneum. We used flow cytometry to analyze lymphocyte subsets in the peripheral blood (PB) and peritoneal fluid (PF) of the following groups of rats: no treatment, sham operation, endometrial implantation, endometrial implantation treated with danazol, and normal rats treated with danazol.

RESULTS

The natural killer (NK) cell population was decreased in both the PB and PF of rats with autotransplanted endometrium. Moreover, NK cells increased in a dose-dependent manner following danazol administration. Surgery itself increased the number of peritoneal macrophages as compared with the untreated group. This elevation was suppressed partially by endometrium-implantation and was attenuated by subsequent administration of danazol in a dose-dependent fashion.

CONCLUSIONS

These data suggest that ectopic endometrial cells may release immunosuppressive factors. This is the first documentation that rats with autotransplanted endometrium show the same immunologic changes as humans with endometriosis, and establishes the utility of this model for the study of endometriosis.

CSF-1 stimulates nucleoside transport in S1 macrophages

We have examined nucleoside transport (NT) in a cell line derived from primary day 7 murine bone marrow macrophages (S1 macrophages) in response to the macrophage growth factor, colony-stimulating factor 1 (CSF-1). Adenosine and uridine transport in quiescent S1 macrophages occurred primarily by two facilitated diffusional routes, one that was sensitive and one that was relatively resistant to the inhibitor nitrobenzylthioinosine (NBMPR). Addition of CSF-1 to quiescent cultures resulted in increased adenosine and uridine transport with biphasic kinetics with respect to the cell cycle. Basal NT activity was elevated (about twofold) within 15 min of CSF-1 addition, returned to near basal levels by 1 h, and then increased again (three- to fourfold) 8-12 h later, returning again to basal levels by 48 h post CSF-1 stimulation. We propose that the large increase in NT activity at 8-12 h corresponded with the time when cultures synchronously began to enter the S phase of the cell cycle. In addition to these changes in the absolute rates, the proportions of NBMPR-sensitive and NBMPR-insensitive transport also change after CSF-1 addition. Quiescent cultures exhibited primarily NBMPR-insensitive transport while logrithmically growing cultures exhibited primarily NBMPR-sensitive nucleoside transport activity. The increase in the NBMPR-sensitive component of the transport process paralleled a similar increase in the number of high-affinity NBMPR binding sites, suggesting that the mechanism for upregulating NBMPR-sensitive NT activity involves increases in the number of NBMPR-sensitive transporter sites. Interestingly, we were unable to detect Na(+)-dependent concentrative uptake of adenosine, uridine, or formycin-B either in the S1 macrophage cell line or in primary (day 7) murine macrophages. Thus these bone marrow derived macrophages did not display the characteristically large Na(+)-dependent transport systems observed by others in peritoneal macrophages, implying that these two populations of macrophages are, indeed, functionally distinct.

The relationship between sugar metabolism, transport and superoxide radical production in rat peritoneal macrophages

Dexamethasone inhibits sugar-dependent phorbol myristate acetate (PMA)-stimulated superoxide production and 2-deoxy-D-glucose (2-dGlc) transport in rat peritoneal macrophages (Rist, R.J., Jones, G.E. and Naftalin, R.J. (1991) Biochem. J. 278, 119-128; Rist, R.J. and Naftalin, R.J. (1991) Biochem J. 278, 129-135). Here it is shown that with glucose as a substrate, dexamethasone (0.1 microM) acts as a non-competitive inhibitor of PMA-induced superoxide production; decreasing the maximal rate of superoxide production (P < 0.001) without altering the Km. In contrast, with 2-dGlc as a substrate, dexamethasone shows competitive inhibition of PMA-stimulated superoxide production; increasing the Km of superoxide production, (P < 0.001) without altering the Vmax. The maximal rate of PMA-stimulated superoxide production with glucose as substrate is 10-12-fold in excess of the maximal rate with 2-dGlc as substrate. Diphenylene iodonium (DPI) is a non-competitive inhibitor of PMA-stimulated glucose-dependent superoxide production in macrophages, (Ki = 1-5 microM) and significantly reduces the activity of the PMA-induced hexose monophosphate shunt, (HMPS) (P < 0.01). However, DPI (1 microM) has no significant effect on the PMA-induced increase in 2-dGlc uptake, suggesting that the stimulus for HMPS activity and superoxide production is separate from the stimulus for hexose transport. A model is described which explains the observed differences in hexose transport and glucose- and 2-dGlc-dependent superoxide production in terms of the differences in metabolism of the two sugars. Accumulation of free 2-dGlc within the cytosol leads to saturation of hexokinase and hence, the effects of PMA and dexamethasone, which alter the coupling between hexokinase and the transporter, are only observed at low concentrations of 2-dGlc, where it is accumulated to sub-saturating levels. Since glucose is completely metabolized within the cell, PMA and dexamethasone increase and decrease, respectively, net uptake of sugar and superoxide production at all glucose concentrations.

Direct observation of hexokinase translocation in stimulated macrophages

1. Fluorescence imaging of antibodies was used to show that phorbol 12-myristate 13-acetate (PMA) induces a 4-fold increase in the amount of hexokinase relative to the control in the cortical shell of rat peritoneal macrophage cytosol adjacent to the plasma membrane, and a corresponding depletion in the amount of hexokinase in the central core of the cytosol. However, there was no significant PMA-dependent change in the distribution of glucose-6-phosphate dehydrogenase. 2. Cytochalasin D, an inhibitor of actin microfilament polymerization, prevented the PMA-induced hexokinase translocation and also reduced the PMA-dependent increases in 2-deoxy-D-glucose transport and glucose-dependent PMA-stimulated superoxide production. 3. PMA caused a contraction of the width of the cortical F-actin zone. Cytochalasin D caused some dispersal of F-actin within the cell, increasing the density of F-actin within the central cytosolic core and causing aggregation of the F-actin within the cortex. These data are consistent with the view that PMA induces attachment of hexokinase to microfilaments within the cortical zone adjacent to the cell membrane of macrophages, and cytochalasin D prevents this attachment. This is the first direct demonstration of the translocation of hexokinase to the plasma membrane in activated cells, and supports the view that enhanced hexokinase activity in the cortical region of the cytosol is an important early component of the macrophage activation process.

Glucose- and phorbol myristate acetate-stimulated oxygen consumption and superoxide production in rat peritoneal macrophages is inhibited by dexamethasone

1. Rat peritoneal macrophages stimulated with phorbol 12-myristate 13-acetate (PMA) (40 nM) show an increase in the rate of oxygen consumption (measured with an O2 electrode) and the production of superoxide (measured by cytochrome c reduction), which are both dependent on the presence of exogenous glucose. There is a 1:1 correlation between the oxygen consumed and the superoxide produced over a range of glucose concentrations (0-10 mM). 2. Preincubation of macrophages with dexamethasone (1 microM) for 3 h significantly decreased the Vmax. for PMA-induced glucose-dependent oxygen consumption (P < 0.001) and glucose-dependent superoxide production (P < 0.001). However, dexamethasone did not significantly change the Km for glucose in either PMA-induced oxygen consumption or superoxide production. Dexamethasone is therefore a non-competitive inhibitor of PMA-stimulated glucose-dependent oxygen consumption (Ki = 0.83 +/- 0.09 microM) and superoxide generation (Ki = 0.87 +/- 0.09 microM). 3. The PMA-induced rate of oxygen consumption by macrophages was decreased at oxygen concentrations below approx. 15 microM. The Km of oxygen for PMA-induced oxygen consumption was 1.28 +/- 0.13 microM (n = 12), and this was not significantly different in the presence of dexamethasone; Km = 1.61 +/- 0.31 microM (n = 12). It is therefore concluded that in vivo macrophage superoxide production is not limited by external oxygen or glucose concentrations, even in hypoxic joints.

Augmented glucose use and pentose cycle activity in hepatic endothelial cells after in vivo endotoxemia

Glucose use and pentose cycle activity were determined in freshly isolated rat hepatic endothelial cells 3 hr after an intravenous injection of Escherichia coli lipopolysaccharide (0.1 mg/kg body weight), by use of [1-14C]glucose, [6-14C]glucose and [2-3H]glucose. Lipopolysaccharide treatment in vivo increased glucose use fivefold, whereas glucose oxidation in the pentose cycle was elevated from 0.2 to 1.5 nmol/hr/10(7) cells. In vitro incubation of endothelial cells from saline- and lipopolysaccharide-treated animals in the presence of phorbol 12-myristate 13-acetate (10(-6) mol/L) increased pentose cycle activity twofold and eightfold, respectively. Phorbol 12-myristate 13-acetate caused only a 40% to 60% increase in glycolysis in both groups. Addition of t-butyl hydroperoxide (0.5 mmol/L), a substrate for glutathione peroxidase, caused a 24-fold and 16-fold increase in the glucose flux through the pentose cycle in cells from saline- and lipopolysaccharide-treated rats, respectively. Oxidation of glucose through the Krebs cycle was also increased several-fold after t-butyl hydroperoxide administration. Depletion of cellular glutathione by N-ethylmaleimide (0.1 mmol/L) inhibited the phorbol 12-myristate 13-acetate-induced or t-butyl hydroperoxide-induced increase in the pentose cycle activity with no marked effects on glycolysis. Diphenyleneiodonium (0.1 mmol/L), an inhibitor of superoxide and nitric oxide synthesis inhibited the phorbol 12-myristate 13-acetate-induced increased pentose cycle activity with no effects on the t-butyl hydroperoxide-induced response.(ABSTRACT TRUNCATED AT 250 WORDS)

Up-regulation of glucose metabolism in Kupffer cells following infusion of tumour necrosis factor

Alterations of glucose metabolism and the oxidation of glutamine and palmitate were studied, by using specifically labelled substrates, in freshly isolated Kupffer cells and hepatic endothelial cells after infusion in vivo of human recombinant tumour necrosis factor-alpha (TNF; 7.5 x 10(5) IU/30 min per kg body wt., intravenously). Cells were incubated in a medium containing 5 mM-glucose, 0.4 mM-palmitate, 1 mM-lactate and 0.5 mM-glutamine. Administration of TNF in vivo increased glucose use in Kupffer cells by 70%. Glucose oxidation in the tricarboxylic acid cycle and flux in the Embden-Meyerhof (EM) pathway were elevated by 40 and 80% respectively. Treatment in vitro with 1 microM-phorbol 12-myristate 13-acetate (PMA) resulted in a similar percentage increase in glucose use by Kupffer cells prepared from either saline- or TNF-treated rats. However, PMA increased the activity of the hexose monophosphate shunt (HMS) by 3- and 10-fold in cells isolated from saline- or TNF-infused animals respectively. A phagocyte stimulus in vitro, opsonized zymosan, increased glucose use by 30% and doubled the flux through the HMS in Kupffer cells from saline-infused animals. The activity of the HMS in response to zymosan was increased by 400% after TNF treatment. In endothelial cells, basal glucose utilization was not altered by TNF treatment. PMA increased HMS activity in endothelial cells to a similar degree after saline or TNF infusion. Zymosan, however, increased HMS activity only in endothelial cells from TNF-treated rats. Oxidation of palmitate or glutamine was not affected by TNF treatment either under basal conditions or after challenge in vitro. Our data indicate that, after phagocytosis in vitro or protein kinase C activation, glucose use and flux through the HMS increase in Kupffer cells. This is accompanied by increased glycolytic flux, with no changes in glucose oxidation in the tricarboxylic acid cycle. After TNF exposure, followed by a secondary stimulus, the enhanced glucose use by Kupffer cells is primarily channelled through the HMS pathway. These data suggest that the increased glucose use in vivo by Kupffer cells found after immune-stimulated conditions may subserve primarily the increased need for NADPH and HMS intermediates.

Effects of macrophage colony-stimulating factor and phorbol myristate acetate on 2-D-deoxyglucose transport and superoxide production in rat peritoneal macrophages

2-D-Deoxyglucose (2-dGlc) uptake and accumulation into rat peritoneal macrophages was increased by colony-stimulating factor (mCSF) by stimulating the coupling between endofacial hexokinase activity and the sugar transporter. The evidence for this is as follows: (1) mCSF significantly decreased the Km for zero-trans uptake (P less than 0.05), without altering Vmax.; (2) the accumulation of free 2-dGlc was increased by mCSF (P less than 0.05); (3) mCSF retarded the rate of exit of accumulated free 2-dGlc. The mCSF-dependent increase in 2-dGlc uptake by macrophages was enhanced by preincubation of the cells in mCSF-free solution. The activity of the hexose monophosphate shunt (HMPS) measured by the differential uptake of 2-d[1-3H]Glc and 2-d[2,6-3H]Glc was not stimulated by mCSF. Also, in quiescent cells, superoxide production, as determined by cytochrome c reduction, was unaffected by mCSF. Phorbol myristate acetate (PMA; 40 nM) stimulated both the HMPS activity and superoxide production. Both these effects were dependent on the uptake of external sugar (2-dGlc). Incubation of the macrophages with mCSF enhanced the sugar transport and PMA-dependent stimulation of HMPS activity and superoxide production, indicating a role for mCSF in the 'priming' of macrophage functions. Both HMPS activity and superoxide production are entirely dependent on uptake of exogenous sugar, since the potent sugar-transport inhibitor cytochalasin B competitively inhibited 2-dGlc uptake, HMPS activity and superoxide generation in PMA-activated cells (Ki approximately 0.3 microM for all three processes). Over a wide range of 2-dGlc concentrations, 4 mol of superoxide were generated/mol of 2-dGlc metabolized in the HMPS pathway, indicating coupling between these processes. The Km of 2-d[2,6-3H]Glc uptake in PMA-treated cells was 0.45 +/- 0.07 mM, and Vmax. was 1.32 +/- 0.05 mumol.min-1.ml of cell water-1. It is evident that there is a large degree of slippage between HMPS activity and membrane-associated hexokinase activity, since the Km for HMPS activity was 0.06 +/- 0.02 mM and the Vmax. was 0.10 +/- 0.03 mumol.min-1.ml of cell water-1.

Dexamethasone inhibits the hexose monophosphate shunt in activated rat peritoneal macrophages by reducing hexokinase-dependent sugar uptake

Dexamethasone decreases 2-D-deoxyglucose (2-dGlc) uptake and accumulation into rat peritoneal macrophages in vitro in a concentration- and time-dependent manner (Ki for 1 microM-dexamethasone after a 2 h exposure = 0.71 +/- 0.21 microM; Ki for 0.1 microM-dexamethasone after exposure for 4 h = 0.10 +/- 0.06 microM). The inhibition of 2-dGlc uptake is consistent with a decrease in the coupling between endofacial hexokinase activity and the sugar transporter. The evidence for this is: (1) the Km for zero-trans 2-dGlc uptake in quiescent macrophages was increased by dexamethasone, but there was no significant effect on the Vmax.; (2) dexamethasone increased the rate of exit of sugar from cells preloaded with 2-dGlc; (3). the free sugar accumulation within the cytosol of the cells above the external solution concentration was significantly decreased by dexamethasone. These effects of dexamethasone on 2-dGlc transport were antagonized by simultaneous exposure to the steroid RU 38486 (Ki = 0.04 +/- 0.01 microM; 4 h incubation). Although dexamethasone inhibited zero-trans uptake, the maximum rate of infinite-trans exchange uptake of 2-dGlc into cells preloaded with 3-O-methyl-D-glucose (40 mM) was unaltered by dexamethasone or RU 38486, indicating that the dexamethasone-dependent decrease in zero-trans uptake was not due to a change in the number of transporters in the plasma membrane. Dexamethasone also inhibited the phorbol myristate acetate-induced stimulation of hexose monophosphate shunt (HMPS) activity, and this was reversed by RU 38486. Cytochalasin B, the potent sugar-transport inhibitor, inhibited HMPS activity and 2-d[2,6-3H]Glc uptake equally, indicating a single site of action. By contrast, dexamethasone showed differential inhibition of HMPS activity and 2-d[2,6-3H]Glc uptake, suggesting that it not only acts by decreasing the coupling between hexokinase and sugar transport, but also at one or more additional points.

Uniporters and anion antiporters

The past year has seen a flurry of activity in the area of protein-mediated hexose uniport. Topics of interest covered here include: structure-function studies; the interaction of glucose carriers with glycolytic enzymes; regulation of cell surface glucose-carrier concentrations by insulin and the signalling mechanisms involved; and the role of the glucose-carrier isoform, GLUT2, in pancreatic beta-cell glucose-dependent insulin secretion. Nucleoside uniport and Glu-Asp antiport are also discussed briefly.

Characterization of functional receptors for vasoactive intestinal peptide (VIP) in rat peritoneal macrophages

Functional vasoactive intestinal peptide (VIP) receptors have been characterized in rat peritoneal macrophages. The binding depended on time, temperature and pH, and was reversible, saturable and specific. Scatchard analysis of binding data suggested the presence of two classes of binding sites: a class with high affinity (kd = 1.1 +/- 0.1 nM) and low capacity (11.1 +/- 1.5 fmol/10(6) cells), and a class with low affinity (kd = 71.6 +/- 10.2 nM) and high capacity (419.0 +/- 80.0 fmol/10(6) cells). Structural requirements of these receptors were studied with peptides structurally or not structurally related to VIP. Several peptides inhibited 125I-VIP binding to rat peritoneal macrophages with the following order of potency: VIP greater than rGRF greater than hGRF greater than PHI greater than secretin. Glucagon, insulin, somatostatin, pancreastatin and octapeptide of cholecystokinin (CCK 26-33) were ineffective. VIP induced an increase of cyclic AMP production. Half-maximal stimulation (ED50) was observed at 1.2 +/- 0.5 nM VIP, and maximal stimulation (3-fold above basal levels) was obtained between 0.1-1 microM. Properties of these binding sites strongly support the concept that VIP could behave as regulatory peptide on the macrophage function.