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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aim of this study was to establish the effect of bacterial endotoxin lipopolysaccharide (LPS) on type II phospholipase A2 (PLA2) content and in vitro net PLA2 enzymatic activity in human choriodecidua. More particularly, the objective was to ascertain whether an increase in type II PLA2 tissue content and PLA2 enzymatic activity is associated with the previously documented stimulatory effect of LPS on prostaglandin E2 (PGE2) release from choriodecidua. Choriodecidua explants were incubated in RPMI 1640 (control) or RPMI 1640 containing LPS (0.1 ng/ml to 10 micrograms/ml) for up to 24 h. Under the incubation conditions utilized, LPS (1 microgram/ml) stimulated the release of PGE2 3-fold (p < 0.001, n = 4 tissues), in a time-dependent manner (p < 0.005). Tissue immunoreactive (ir)-type II PLA2 content and PLA2 enzymatic activity were determined by monoclonal antibody sandwich ELISA and radiolabeled enzyme assay procedures, respectively. The tissue content of type II PLA2 immunoreactivity in choriodecidua obtained from women (n = 7) at term but not in labor averaged 155 +/- 24 ng/ml DNA. PLA2 enzymatic activity average 29.8 +/- 5.1 pmol phosphatidylethanolamine (PE)/mg DNA/h. LPS at a concentration of 1 microgram/ml increased immunoreactive type II PLA2 tissue content by 180% of the control value (p < 0.05, n = 7) within 1 h of exposure and remained significantly elevated for 18 h when compared to controls (174% of control, p < 0.01, n = 7).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Bacterial endotoxin increases type II phospholipase A2 immunoreactive content and phospholipase A2 enzymatic activity in human choriodecidua. 816 24

Mononuclear cell invasion into the vascular-vessel wall is a very important initial step in the development of atherosclerotic lesions. Hypercholesterolemia leads to a marked adhesion of circulating blood monocytes to arterial endothelial cells in vivo, and minimally oxidized low-density lipoprotein enhances monocyte adhesion to endothelial cells in vitro. The activation of phospholipase A2 (PLA2) is also important in the oxidation of low-density lipoprotein by endothelial cells. In this study, we investigated the role of PLA2 activation in the adhesion of a leukemic monocyte cell line (THP-1 cells) to endothelial cells in vitro using an adhesion assay and a cell-ELISA technique. The treatment of human umbilical-cord-vein endothelial cells with PLA2 stimulators such as interleukin-1 beta, tumor necrosis factor and lipopolysaccharide all increased the adhesion of THP-1 cells to endothelial cells. Exogenous PLA2 also increased the adhesion of these cell types. The increased adhesion induced by these PLA2 stimulators, as well as PLA2 itself, was reversed by various inhibitors of the PLA2 reaction. A product of the PLA2 reaction, lysophosphatidylcholine, also increased cell adhesion. A cell-ELISA technique showed the enhanced expression of vascular-cell-adhesion-molecule 1 and intercellular-adhesion-molecule 1 to endothelial cells after treatment with PLA2 stimulators, PLA2 or lysophosphatidylcholine. These results suggest that the PLA2 reaction enhances monocyte adhesion to endothelial cells through the expression of cellular adhesion molecules.
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PMID:The phospholipase-A2 reaction leads to increased monocyte adhesion of endothelial cells via the expression of adhesion molecules. 822 14

Early accumulation of polymorphonuclear leukocytes (PMN) in the liver after in vivo exposure to Escherichia coli lipopolysaccharide (LPS) and concomitant in vitro phorbol myristate acetate (PMA)-stimulated superoxide anion (O2-) generation has recently been described in a rat model of endotoxemia. The purpose of this investigation was to study the role of phospholipase A2 (PLA2), arachidonic acid (AA), its metabolites, and protein kinase C (PKC) in the mechanism of PMA-stimulated O2- generation of liver infiltrated PMN as compared to circulating blood PMN. Rat PMN were isolated after a 1.5-h infusion of saline or LPS from the blood (SAL-PMN) or the liver (LPS-PMN), respectively. The following results were observed in both SAL-PMN and LPS-PMN: 1) Inhibitors of cyclooxygenase (indomethacin) and 5-lipoxygenase [eicosatetraynoic acid, WY 50,295 tromethamine and VZ 65, 4-(11-hydroxy-1,9-undecadiin)-brenzcatechin] pathways did not inhibit O2- generation; 2) the potent marine PLA2 inhibitor Manoalide inhibited O2- generation in a dose-dependent manner (IC50 = 0.5 microM); 3) exogenously added AA enhanced PMA-stimulated O2- generation in a time- and dose-dependent manner and partially reversed the effect of Manoalide in LPS-PMN; 4) staurosporine, a putative PKC inhibitor, blocked PMA-stimulated O2- generation completely in the absence of AA and 79% in the presence of AA. It was concluded that LPS-induced liver sequestration of PMN does not alter the role PLA2, AA and PKC play in PMA-stimulated O2- generation. These findings should have implications on the design of novel therapeutic approaches for the modulation of O2- release in the pathogenesis of LPS hepatotoxicity.
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PMID:Modulation of superoxide anion generation by manoalide, arachidonic acid and staurosporine in liver infiltrated neutrophils in a rat model of endotoxemia. 822 68

Resident peritoneal macrophages synthesized and released eicosanoids when challenged by zymosan, a phagocytosable particle. Incubation of these cells with ethanol resulted in dose-dependent inhibition of arachidonic acid release and eicosanoid generation in response to zymosan. Ethanol affected the extent but not the ratio of eicosanoids released. When assayed in a cell-free system, endogenous phospholipase A2 activity was neither affected by the presence of ethanol in the incubation medium nor by preincubation of the cells with ethanol. Ethanol also inhibited arachidonic acid release in response to phorbol myristate acetate, a compound that, like zymosan, triggered a pertussis-toxin-sensitive response. When cells that had been previously treated with pertussis toxin were used, no further inhibitory effect of ethanol was seen in response to both zymosan and phorbol myristate acetate. On the other hand, ethanol had no effect on arachidonic acid release stimulated by ionophore A23187 or lipopolysaccharide, two compounds that triggered a pertussis-toxin-insensitive response. Moreover, ethanol was able to nearly abolish arachidonic acid release in response to fluoroaluminate, a direct activator of G-proteins. Altogether, the results of this study suggest that ethanol inhibits zymosan-stimulated eicosanoid production by interacting with a G-protein--or a G-protein-mediated process--that is critically involved in arachidonic acid mobilization.
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PMID:Ethanol inhibits zymosan-stimulated eicosanoid production in mouse peritoneal macrophages. 828 Jul 70

We tested the hypothesis that Kupffer cells modulate sinusoidal endothelial cell function in the liver. Rats were treated with Kupffer cell-depleting agents (gadolinium chloride and liposome-encapsulated dichloromethylene diphosphonate) or with inhibitors of phospholipase A2 or leukotriene A4 synthase (dexamethasone and diethylcarbamazine, respectively). Hyaluronan uptake by the isolated, perfused liver was measured as an index of the functional state of the sinusoidal endothelial cell. Plasma hyaluronan concentration was also determined. Three hours after Escherichia coli lipopolysaccharide administration (100 micrograms/100 gm body wt, intravenously) plasma hyaluronan levels were significantly increased (280% to 320%), whereas hepatic hyaluronan uptake was markedly decreased (approximately 76%). Pretreatment with gadolinium chloride (0.5 mg/100 gm body wt, intravenously, 21 hr before saline solution or lipopolysaccharide administration), liposome-encapsulated dichloromethylene diphosphonate (40 mumol/100 gm body wt, intravenously, 44 hr before saline solution or lipopolysaccharide injection), dexamethasone (40 micrograms/100 gm body wt, intravenously, 1 hr before saline solution or lipopolysaccharide administration) or diethylcarbamazine (repeated doses, 10 mg/100 gm body wt, intravenously, 1 hr before saline solution or lipopolysaccharide injection) counteracted the lipopolysaccharide inhibitory effect on hepatic hyaluronan uptake. With the exception of gadolinium chloride, all other agents also prevented the lipopolysaccharide-induced increase in plasma hyaluronan concentration. Gadolinium chloride only attenuated the lipopolysaccharide effect on plasma hyaluronan level. Taken together with earlier results from our laboratory, these data indicate that: (a) Kupffer cell activation by lipopolysaccharide results in suppression of hyaluronan uptake by sinusoidal endothelial cells and (b) such modulation of endothelial cell function is likely mediated by products of the lipoxygenase pathway of arachidonate metabolism.
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PMID:Modulation of hepatic sinusoidal endothelial cell function by Kupffer cells: an example of intercellular communication in the liver. 829 3

Continuous infusion of a nonlethal dose of Escherichia coli lipopolysaccharide (LPS) into rats induced extravasation of mononuclear phagocytes into the liver and the priming of Kupffer cells for in vitro phorbol myristate acetate (PMA)-stimulated superoxide anion (O2-) release. The purpose of this investigation was to determine the role of protein kinase C (PKC), protein serine-threonine phosphatase(s) 1 and 2a, protein tyrosine kinase(s) and phosphatase(s), phospholipase A2 (PLA2), arachidonic acid (AA) and its cyclooxygenase (CO) and 5-lipoxygenase (5-LO) metabolites in the modulation of PMA-stimulated O2-generation in in vivo LPS-primed rat Kupffer cells. The following inhibitors blocked PMA-stimulated O2- generation in the absence (-AA) or presence of AA (+AA) (50 microM): 1) staurosporine, a putative PKC inhibitor (150 nM, 95% inhibition without AA, 88% inhibition with AA); 2) okadaic acid, a protein serine-threonine phosphatase inhibitor (2 microM, 65% inhibition with or without AA); 3) the marine PLA2 inhibitor manoalide (1 microM, 97.5% inhibition without AA, 75% with AA). In addition, it was observed that exogenously added AA enhanced PMA-stimulated O2- generation in a time- and dose-dependent manner (5-50 microM) and partially reversed the inhibitory effect of manoalide. The following inhibitors did not block PMA-stimulated O2- generation in the absence or presence of AA: 1) indomethacin, a CO inhibitor (1-100 microM) and WY-50,295M tromethamine, a novel 5-LO inhibitor (1-100 microM); 2) genistein, a protein tyrosine kinase inhibitor (1-100 microM); and 3) sodium orthovanadate (1-300 microM), a protein tyrosine phosphatase inhibitor. It was concluded that, in in vivo LPS-primed Kupffer cells, PMA-stimulated O2- generation is modulated by PKC, protein serine-threonine phosphatase(s), PLA2 and AA but not by protein tyrosine kinase(s) and phosphatase(s) and CO and 5-LO products. These findings could have implications on the design of novel therapeutic approaches for the modulation of enhanced O2- release by Kupffer cells in endotoxemia.
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PMID:Modulation of superoxide generation in in vivo lipopolysaccharide-primed Kupffer cells by staurosporine, okadaic acid, manoalide, arachidonic acid, genistein and sodium orthovanadate. 830 64

Previous studies have shown that: (a) platelet activating factor induces shock and intestinal injury, (b) exogenous platelet activating factor stimulates synthesis of endogenous platelet activating factor, and (c) tumour necrosis factor alpha and endotoxin synergise to induce shock and bowel injury in animals. These last two effects are largely mediated by platelet activating factor forming phospholipase A2 A2, a key enzyme for platelet activating factor synthesis, was examined in mouse intestine. It was found that tumour necrosis factor alpha and endotoxin synergise to stimulate platelet activating factor forming phospholipase A2 activity in the intestine, as well as platelet activating factor production, and these effects were blocked by pretreatment with platelet activating factor antagonists, SRI-63-441 and WEB 2086. In addition, exogenous platelet activating factor stimulates intestinal phospholipase A2 activity. These results show that tumour necrosis factor alpha and lipopolysaccharide synergistically activate the phospholipase A2 that participates in platelet activating factor formation, and this activation is largely mediated by endogenous platelet activating factor. Furthermore, platelet activating factor itself increases phospholipase A2 activity, suggesting that platelet activating factor induces its own synthesis, probably by phospholipase A2 activation.
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PMID:Tumour necrosis factor and endotoxin synergistically activate intestinal phospholipase A2 in mice. Role of endogenous platelet activating factor and effect of exogenous platelet activating factor. 830 72

A novel fluorescence assay for phospholipase A2 [Wilton (1990) Biochem. J. 266, 435-439] has been used to study the Group-II rat liver mitochondrial enzyme, and a number of novel properties of this enzyme were identified. (1) The enzyme activity was located in the liver macrophages (Kupffer cells) while negligible activity was associated with hepatocytes. (2) Although subcellular fractionation of whole liver confirmed the predominantly mitochondrial location of this enzyme activity, the analysis of the hepatocyte-free Kupffer-cell-enriched fraction revealed a different enzyme distribution, with the majority of activity being associated with the microsomal membrane fraction. (3) Bacterial endotoxin has been previously shown to be scavenged by Kupffer cells in rats. Treatment of rats with bacterial lipopolysaccharide (endotoxin) resulted in a dramatic time- and dose-dependent increase in liver phospholipase A2 activity. (4) It is known that injection of endotoxin into rodents results in elevated serum phospholipase A2 activity, while a similar phenomenon is seen in the condition of septic shock in man. The source of this serum enzyme was unknown. In this study perfusion of livers from rats pretreated with lipopolysaccharide with physiological saline demonstrated a 6-fold increase in phospholipase A2 activity in the perfusate compared with sham-treated controls, with only minor release of hepatic lipase. (5) Western-blot analysis confirmed an increased release of this Group-II phospholipase A2 into the perfusate of lipopolysaccharide-treated rats compared with sham-treated controls. These results suggest that liver Kupffer cells are a major source of the endotoxin-induced serum Group-II phospholipase A2 activity associated with bacterial infection and trauma.
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PMID:Rat liver mitochondrial phospholipase A2 is an endotoxin-stimulated membrane-associated enzyme of Kupffer cells which is released during liver perfusion. 832 56

Macrophage-like P388D1 cells release [3H]arachidonic acid and produce prostaglandin E2 (PGE2) upon stimulation with bacterial lipopolysaccharide (LPS) and platelet-activating factor (PAF). To determine whether group II phospholipase A2 (PLA2) is involved in this release, we treated P388D1 cells with antisense inhibitors specific for group II PLA2 RNA. Treatment with oligonucleotide ASGII decreased PLA2 activity in P388D1 cell homogenates by approximately 60% and reduced the release of [3H]arachidonic acid and PGE2 from activated cells to nearly resting cell levels. The inhibition by antisense oligonucleotide ASGII was blocked when its sense complement, SGII, was included in the incubation mixture. Stably transfected P388D1 cells expressing an antisense construct for group II PLA2 also produced reduced quantities of PGE2 in response to LPS and PAF. These data suggest that prostaglandin production by activated P388D1 cells involves phospholipid hydrolysis by group II PLA2. Oligonucleotide ASGII also blocked the appearance of a heparin-releasable group II PLA2 in the culture supernatants of P388D1 cells. The disappearance of this protein correlated with reduced PGE2 production by activated cells, indicating that an extracellular heparin-associated pool of group II PLA2 is involved in prostaglandin production by P388D1 cells.
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PMID:Antisense inhibition of group II phospholipase A2 expression blocks the production of prostaglandin E2 by P388D1 cells. 840 42

The protein tyrosine kinase (PTK) inhibitor genistein has been demonstrated to inhibit platelet-activating factor-stimulated prostaglandin E2 (PGE2) production in lipopolysaccharide (LPS)-primed P388D1 macrophage-like cells (Glaser et al., J Biol Chem 265: 8658-8664, 1990). Therefore, the role of PTK in eicosanoid biosynthesis was investigated in murine resident peritoneal macrophages using genistein and tyrphostin-25, selective PTK inhibitors. Genistein, a competitive inhibitor of ATP binding on PTK, inhibited PGE2 production (IC50 = 20 microM) in response to zymosan, calcium ionophore A23187, and phorbol myristate acetate stimulation. Genistein also inhibited leukotriene C4 (LTC4) production in response to zymosan and calcium ionophore A23187 (IC50 = 10 and 15 microM, respectively) stimulation. Tyrphostin-25, a competitive inhibitor of substrate binding on PTK, inhibited zymosan-stimulated PGE2 and LTC4 production, IC50 = 20 and 7 microM, respectively. Neither genistein nor tyrophostin-25 had any effect on human synovial fluid phospholipase A2 (PLA2) activity in vitro or on cyclooxygenase activity in the intact macrophage; however, tyrphostin-25 did affect 5-lipoxygenase activity (determined from the metabolism of exogenously applied arachidonic acid). These results suggest PTK-mediated phosphorylation as a common event in the signal transduction mechanisms of different stimuli which activate PLA2 for arachidonic acid release and subsequent eicosanoid biosynthesis. Immunoblot analyses of zymosan-stimulated peritoneal exudate cells with the phosphotyrosine monoclonal antibody clone 4G10 demonstrated an increase in protein phosphotyrosine levels in eight major protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis: p59, 71, 76, 90, 100, 112, 125 and 150. Maximal phosphorylation of these protein substrates occurred after 1-2 min stimulation. Zymosan and LPS stimulation of peritoneal exudate cells produced similar patterns of protein tyrosine phosphorylation. Zymosan-stimulated tyrosine phosphorylation was inhibited by tyrphostin-25 in a concentration-dependent manner between 10 and 60 microM, demonstrating a similar concentration response between effects on tyrosine phosphorylation and eicosanoid biosynthesis in the murine peritoneal macrophage. The use of selective PTK inhibitors suggests a common role for PTK and tyrosine phosphorylation in eicosanoid biosynthesis in the murine peritoneal macrophage.
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PMID:Regulation of eicosanoid biosynthesis in the macrophage. Involvement of protein tyrosine phosphorylation and modulation by selective protein tyrosine kinase inhibitors. 844 70


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