Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The signaling pathway involved in protein kinase C (PKC) activation and role of PKC isoforms in lipopolysaccharide (LPS)-induced nitric oxide (NO) release were studied in primary cerebellar astrocytes. LPS caused a dose- and time-dependent increase in NO release and inducible NO synthase (iNOS) expression. The tyrosine kinase inhibitor, genestein, the phosphatidylcholine-phospholipase C inhibitor, D609, and the phosphatidate phosphodrolase inhibitor, propranolol, attenuated the LPS effects, whereas the PI-PLC inhibitor, U73122, had no effect. The PKC inhibitors (staurosporine, Ro 31-8220, Go 6976, and calphostin C) also inhibited LPS-induced NO release and iNOS expression. However, long term (24 h) pretreatment of cells with 12-O-tetradecanoyl phorbol-13-acetate (TPA) did not affect the LPS response. Previous results have shown that TPA-induced translocation, but not down-regulation, of PKCeta occurs in astrocytes (Chen, C. C., and Chen, W. C. (1996) Glia 17, 63-71), suggesting possible involvement of PKCeta in LPS-mediated effects. Treatment with antisense oligonucleotides for PKCeta or delta, another isoform abundantly expressed in astrocytes, demonstrated the involvement of PKCeta, but not delta, in LPS-mediated effects. Stimulation of cells for 1 h with LPS caused activation of nuclear factor (NF)-kB in the nuclei as detected by the formation of a NF-kB-specific DNA-protein complex; this effect was inhibited by genestein, D609, propranolol, or Ro 31-8220 or by PKCeta antisense oligonucleotides, but not by long term TPA treatment. These data suggest that in astrocytes, LPS might activate phosphatidylcholine-phospholipase C and phosphatidylcholine-phospholipase D through an upstream protein tyrosine kinase to induce PKC activation. Of the PKC isoforms present in these cells, only activation of PKCeta by LPS resulted in the stimulation of NF-kB-specific DNA-protein binding and then initiated the iNOS expression and NO release. This is further evidence demonstrating that different members of the PKC family within a single cell are involved in specific physiological responses.
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PMID:Protein kinase C eta mediates lipopolysaccharide-induced nitric-oxide synthase expression in primary astrocytes. 967 61

1. Neutrophil priming by agents such as tumour necrosis factor-alpha, granulocyte/macrophage colony-stimulating factor and lipopolysaccharide causes a dramatic increase in the response of these cells to an activating agent; this process has been shown to be critical for neutrophil-mediated tissue injury both in vitro and in vivo. 2. The principle consequence of priming, aside from a direct effect on cell polarization, deformability and integrin/selectin expression, is to permit secretagogue-induced superoxide anion generation, degranulation and lipid mediator (e.g. leukotriene B4 and arachidonic acid) release. It is now recognized that most priming agents also serve an additional function of delaying apoptosis and hence increasing the functional longevity of these cells at the inflamed site. 3. The potential mechanisms underlying priming are discussed; current data suggest a dissociation between priming and changes in receptor number and/or affinity, G-protein expression, phospholipase C and phospholipase A2 activation and changes in intracellular Ca2+ concentration. However, more recent studies support a key role for protein tyrosine phosphorylation and enhanced phospholipase D and phosphoinositide 3-kinase activity in neutrophil priming. 4. Recent work has also revealed the potential for neutrophils to spontaneously and fully 'de-prime' after an initial challenge with platelet-activating factor. This ability of neutrophils to undergo a complete cycle of priming-de-priming (and re-priming) reveals a previously unrecognized flexibility in the control of neutrophil behaviour at an inflamed site.
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PMID:Neutrophil priming: pathophysiological consequences and underlying mechanisms. 968 67

The role of the inflammatory cytokine interleukin 1beta (IL-1beta) as potent agonist of the PMN respiratory burst signal transduction cascade has been described. We hypothesized that this phenomenon is self-limiting and that polymorphonuclear leukocyte (PMN)-derived reactive oxygen intermediates (ROI) might provide feedback regulation on the IL-1beta surface receptor (IL-1betaR)-G-protein-effector enzyme transducing tripartite complex that ultimately leads to NADPH oxidase activation. Therefore, we separately assessed either baseline or IL-1beta-induced activation of each member of the IL-1betaR-G-protein-phospholipase D (PLD) or IL-1betaR-G-protein-phospholipase C (PLC) signaling systems in the presence or absence of one of several specific ROI scavengers/antioxidants. Purified human PMN were lipopolysaccharide primed, adhered for 2 h, and stimulated with 100 ng/mL IL-1beta with or without 1% v/v dimethyl sulfoxide, 10 mM NaN3, 30 mM L-alanine, 200 U catalase, or 300 U superoxide dismutase (SOD). To validate the use of these antioxidants, the production of O2-, H2O2, hypochlorous acid, or myeloperoxidase (MPO) in the employed experimental model was confirmed in a separate set of experiments. The expression of IL-1betaR type I or II was assessed by binding with corresponding 125I-labeled monoclonal antibodies and corrected for nonspecific binding. PLD activation was assessed by measuring phosphatidyl ethanol formation in the presence of ethanol. PLC activation was determined by quantitative measurement of diacylglycerol. The level of Galpha stimulatory and inhibitory subunits was assessed by Western blotting. IL-1betaR type I expression was significantly up-regulated in the presence of catalase and SOD. PLD activation was increased by dimethyl sulfoxide and NaN3, and PLC activation was up-regulated by NaN3, L-alanine, SOD, and catalase. After 5 min of stimulation with IL-1beta, Gialpha expression was significantly down-regulated by NaN3 and SOD, whereas SOD had an up-regulating effect on the expression of Gs alpha. Increasing concentrations of externally added authentic MPO progressively down-regulated both PLD and PLC activity. Thus, PMN-derived ROI, in addition to their role as antibacterial/fungal agents, serve as second messengers in IL-1beta signal transduction, with MPO having the most ubiquitous role as a modulator of PMN second messenger pathways.
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PMID:The role of neutrophil-derived oxidants as second messengers in interleukin 1beta-stimulated cells. 968 92

Protein A of S. aureus exhibits a wide array of immunopotentiating activities. Since the role of nitric oxide (NO) in bioregulation has been well envisaged; we studied the effect of Protein A on NO production by immunocytes both in vivo and in vitro. Our data indicate that PA at a comparable dose of LPS (lipopolysaccharide) increases the NO levels in the serum of Swiss albino mice by about 12-fold from its basal level. The peak level is reached at about 12 hours after i.p. inoculation of PA. However, NO concentration returns to the basal value 15 hours posttreatment. Splenic lymphocytes and peritoneal macrophages showed appreciable increase in NO production when cultured with PA in vitro. Interestingly, inhibitors of tyrosine kinase, phospholipase C, and protein kinase C (PKC) inhibited NO production in splenic lymphocytes. Thus, it appears that these enzymes participate in the signaling cascade induced by PA, which culminates in the production of NO downstream of PKC. It is possible that PA-induced NO production may have relevance with the anti-tumor and anti-parasitic properties of PA, described earlier.
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PMID:Protein A induces NO production: involvement of tyrosine kinase, phospholipase C, and protein kinase C. 975 46

In this study, Escherichia coli lipopolysaccharide (LPS) dose-dependently (100-300 microg/ml) and time-dependently (10-60 min) inhibited platelet aggregation in human platelets stimulated by agonists. LPS also dose-dependently inhibited the phosphoinositide breakdown and the intracellular Ca+2 mobilization in human platelets stimulated by collagen. LPS (300 microg/ml) also significantly inhibited the thromboxane A2 formation stimulated by collagen in human platelets. Moreover, LPS (100-300 microg/ml) dose-dependently decreased the fluorescence of platelet membranes tagged with diphenylhexatrience. In addition, LPS (200 and 300 microg/ml) significantly increased the formation of cyclic GMP but not cyclic AMP in platelets. LPS (200 microg/ml) also significantly increased the production of nitrate within a 30 min incubation period. Rapid phosphorylation of a platelet protein of Mr 47,000, a marker of protein kinase C activation, was triggered by phorbol-12-13-dibutyrate (PDBu, 50 nM). This phosphorylation was markedly inhibited by LPS (200 microg/ml) within a 30 min incubation period. These results indicate that the antiplatelet activity of LPS may be involved in two important pathways. (1) LPS may induce conformational changes in the platelet membrane, leading to change in the activity of phospholipase C. (2) LPS also activated the formation of nitric oxide (NO)/cyclic GMP in human platelets, resulting in inhibition of platelet aggregation. Therefore, LPS-mediated alteration of platelet function may contribute to bleeding diathesis in septicaemic and endotoxaemic patients.
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PMID:Mechanisms involved in the antiplatelet activity of Escherichia coli lipopolysaccharide in human platelets. 979 85

Immune mechanisms, including production of pro-inflammatory cytokines such as interleukin-1 (IL-1) and tumour necrosis factor (TNF), play an important role in early atherogenesis. The study of the mechanisms responsible for the increased cytokine production capacity of hypercholesterolemic hosts is therefore crucial for finding new strategies aimed to stop the development of atherosclerosis. We assessed the lipopolysaccharide (LPS)-induced cytokine production of macrophages from low-density lipoproteins (LDL)-receptor knock-out (LDLR-/-) mice, which have a seven- to ninefold higher plasma LDL concentration. Macrophages of LDLR-/- mice produced approximately twofold more IL-1alpha and IL-1beta in response to LPS when compared with macrophages of control mice (LDLR+/+). TNF-alpha synthesis was only slightly increased. Removal of CD14 by phospholipase C treatment of cells decreased cytokine production by 50% (IL-1) to 80% (TNF), but the differences between LDLR-/- and LDLR+/+ remained the same. In contrast, treatment of cells with anti-CD11c monoclonal antibody inhibited the IL-1alpha and IL-1beta production in LDLR-/- mice towards normal values, while no effect could be seen on TNF. In conclusion, LDLR-/- macrophages stimulated with LPS synthesize more IL-1alpha and IL-1beta than controls and this phenomenon is mediated by the CD11c/CD18 receptor.
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PMID:Increased interleukin-1alpha and interleukin-1beta production by macrophages of low-density lipoprotein receptor knock-out mice stimulated with lipopolysaccharide is CD11c/CD18-receptor mediated. 982 12

CD14 is a lipopolysaccharide (LPS) receptor distributed largely in macrophages, monocytes, and neutrophils; however, the role of CD14 in activation of Kupffer cells by LPS remains controversial. The purpose of this study was to determine if different methods used to isolate Kupffer cells affect CD14. Kupffer cells were isolated by collagenase (0.025%) or collagenase-Pronase (0.02%) perfusion and differential centrifugation using Percoll gradients and cultured for 24 h before experiments. CD14 mRNA was detected by RT-PCR from Kupffer cell total RNA as well as from peritoneal macrophages. Western blotting showed that Kupffer cells prepared with collagenase possess CD14; however, it was absent in cells obtained by collagenase-Pronase perfusion. Intracellular calcium in Kupffer cells prepared with collagenase was increased transiently to levels around 300 nM by addition of LPS with 5% rat serum, which contains LPS binding protein. This increase in intracellular calcium was totally serum dependent. Moreover, LPS-induced increases in intracellular calcium in Kupffer cells were blunted significantly (40% of controls) when cells were treated with phosphatidylinositol-specific phospholipase C, which cleaves CD14 from the plasma membrane. However, intracellular calcium did not increase when LPS was added to cells prepared by collagenase-Pronase perfusion even in the presence of serum. These cells were viable, however, because ATP increased intracellular calcium to the same levels as cells prepared with collagenase perfusion. Tumor necrosis factor-alpha (TNF-alpha) mRNA was increased in Kupffer cells prepared with collagenase perfusion 1 h after addition of LPS, an effect potentiated over twofold by serum; however, serum did not increase TNF-alpha mRNA in cells isolated via collagenase-Pronase perfusion. Moreover, treatment with Pronase rapidly decreased CD14 on mouse macrophages (RAW 264.7 cells) and Kupffer cells. These findings indicate that Pronase cleaves CD14 from Kupffer cells, whereas collagenase perfusion does not, providing an explanation for why Kupffer cells do not exhibit a CD14-mediated pathway when prepared with procedures using Pronase. It is concluded that Kupffer cells indeed contain a functional CD14 LPS receptor when prepared gently.
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PMID:Pronase destroys the lipopolysaccharide receptor CD14 on Kupffer cells. 1007 34

Surfactant protein (SP) A and SP-D are involved in multiple immunomodulatory functions of innate host defense partly via their interaction with alveolar macrophages (AMs). In addition, both SP-A and SP-D bind to bacterial lipopolysaccharide (LPS). To investigate the functional significance of this interaction, we first tested the ability of SP-A and SP-D to enhance the binding of tritium-labeled Escherichia coli LPS to AMs. In contrast to SP-D, SP-A enhanced the binding of LPS by AMs in a time-, temperature-, and concentration-dependent manner. Coincubation with surfactant-like lipids did not affect the SP-A-mediated enhancement of LPS binding. At SP-A-to-LPS molar ratios of 1:2-1:3, the LPS binding by AMs reached 270% of control values. Second, we investigated the role of SP-A in regulating the degradation of LPS by AMs. In the presence of SP-A, deacylation of LPS by AMs increased by approximately 2.3-fold. Pretreatment of AMs with phosphatidylinositol-specific phospholipase C had no effect on the SP-A-enhanced LPS binding but did reduce the amount of serum-enhanced LPS binding by 50%, suggesting that a cell surface molecule distinct from CD14 mediates the effect of SP-A. Together the results for the first time provide direct evidence that SP-A enhances LPS binding and degradation by AMs.
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PMID:Surfactant protein A enhances the binding and deacylation of E. coli LPS by alveolar macrophages. 1007 Jan 20

Our previous study has demonstrated the potentiation by uridine triphosphate (UTP) of nitric oxide (NO) and prostaglandin E(2) (PGE(2)) production in lipopolysaccharide (LPS)-stimulated murine J774 macrophages. In this study, we found that the amount of interleukin-6 (IL-6) release in response to LPS stimulation was greatly enhanced in the presence of UTP. This enhancement exhibited concentration dependence and occurred after 8 h of treatment with LPS. RT-PCR analysis indicated that the steady-state level of IL-6 mRNA induced by LPS was apparently increased upon co-addition of UTP. The potentiation by UTP was inhibited by the treatment with U73122 (a phosphatidylinositol-phospholipase C inhibitor), BAPTA/AM (an intracellular Ca(2+) chelator), KN-93 (a selective inhibitor of calmodulin-dependent protein kinase) or PDTC (a nuclear factor kappaB inhibitor). To understand the cross-regulation among NO, PGE(2) and IL-6, all of which are dramatically induced after LPS stimulation, the effects of L-NAME (a nitric oxide synthase inhibitor), indomethacin (a cyclooxygenase inhibitor), NS-398 (a cycloxygenase-2 inhibitor) and IL-6 antibody were tested. The results revealed the positive regulation between PGE(2) and IL-6 synthesis because NS-398 and indomethacin inhibited LPS plus UTP-induced IL-6 release, and IL-6 antibody attenuated LPS plus UTP-induced PGE(2) release. Taken together these results reinforce the role of UTP as a regulatory element in inflamed sites by demonstrating the capacity of this nucleotide to potentiate LPS-induced release of inflammatory mediators.
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PMID:Potentiation of lipopolysaccharide-induced IL-6 release by uridine triphosphate in macrophages: cross-interaction with cyclooxygenase-2-dependent prostaglandin E(2) production. 1054 78

Inside the brain tissue, endothelins play numerous important biological roles. One of the targets, astrocytes, predominantly display endothelin receptor subtype B (ET(B)). On cultured primary rat astroglial cells, we analyzed the effect of IRL1620, a selective ET(B) receptor agonist, on the production of nitric oxide (NO) and the synthesis of interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha. We performed these experiments in the presence or absence of interferon-gamma (IFN-gamma) and/or lipopolysaccharide (LPS). IRL1620 decreases NO production under basal conditions and after IFN-gamma stimulation. However, during LPS-induced NO production, IRL1620 enhances this release. The basal IL-6 secretion and especially the LPS-induced synthesis are enhanced by the IRL1620 stimulation. The LPS-dependent TNF-alpha production is increased by the ET(B) stimulation. The IRL1620-induced decrease of basal NO production is not dependent on Ca2+ entry or on phospholipase C (PLC) activation, as shown by the use of LaCl3 and U73122, respectively. In the presence of LPS, the IRL1620 potentiation of NO production is inhibited by LaCl3 and U73122. The IRL1620-induced increase of IL-6 is dependent on PLC activation. These results suggest that endothelins can have dual effects depending on the costimulatory factors present. Endothelins thus have important immunomodulatory functions in the brain.
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PMID:Stimulation of endothelin B receptor modulates the inflammatory activation of rat astrocytes. 1064 11


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