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)

Kupffer cells, a majority of the body's fixed macrophages, are a major site of bacterial lipopolysaccharide (LPS) metabolism and are mediators in the body's response to sepsis. Uptake of LPS is different in Kupffer cells than other macrophages. Signal transduction in other macrophages in response to LPS involves phosphorylation of proteins in the 50-60 kDa range. We hypothesized that Kupffer cells may have unique signal transduction pathways in response to LPS. Rat Kupffer cells were exposed to LPS (1 microgram/mL) for varying times ranging from 15 to 90 min. Cell lysates were Western blotted using an anti-phosphotyrosine antibody. The blots showed an increase in the amount of tyrosine phosphorylation on two proteins of 119 kDa and 83 kDa. The effects of varying LPS concentration (1 ng/mL-1 microgram/mL) showed an increasing amount of phosphorylation with increasing LPS concentration. To associate the importance of tyrosine phosphorylation in the response of Kupffer cells to LPS, the tyrosine kinase inhibitors, tyrphostin, lavendustin, and genisten were used to study the effects of inhibiting phosphorylation on TNF-alpha production. Kupffer cells were preincubated in the presence of the inhibitor and exposed to LPS (1 microgram/mL). TNF-alpha was measured in the conditioned media by ELISA. A 70% or greater decrease in TNF-alpha production was observed. When phagocytosis of latex beads by rat Kupffer cells was measured in vivo using intravital video microscopy, LPS treatment significantly increased uptake. This increase in phagocytosis was inhibited by tyrphostin. These results show what may be unique phosphorylation events in Kupffer cells that are related to LPS induced production of TNF-alpha.
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PMID:Tyrosine kinase activation in LPS stimulated rat Kupffer cells. 1035 46

The activation of the neutrophil respiratory burst is a two-step process involving an initial 'priming' phase followed by a 'triggering' event. The biochemical mechanisms which underlie these events are yet to be fully elucidated, but the evidence suggests a crucial role for stimulus-induced tyrosine phosphorylation. The enhanced tyrosine phosphorylation observed upon triggering primed cells may reflect an increase in tyrosine kinase activity or a reduction in the levels of the opposing phosphotyrosine phosphatases (PTPases). We have investigated the latter by examining the possibility that lipopolysaccharide (LPS)-induced priming of the neutrophil respiratory burst involves the suppression of cellular PTPase activity. Purified human neutrophils were incubated for 60 min with and without LPS. Priming of the respiratory burst was confirmed by fMet-Leu-Phe-induced cytochrome c reduction. The level of PTPase activity was assessed by dephosphorylation of [32P]RR-src peptide as substrate. Pretreatment of human neutrophils with 200 ng/ml LPS induced a 2.9 +/- 0.3 (mean +/- SEM, n = 3, P = 0.022) fold increase in the fMet-Leu-Phe-triggered respiratory burst. In the same cells, LPS did not induce a significant change in the total cellular PTPase activity (1.02 +/- 0.02-fold, mean +/- SEM, n = 3, P = 0.63). Similarly, stimulation of neutrophils with fMet-Leu-Phe or phorbol myristate acetate did not significantly affect the cellular PTPase activity (P = 0.94 and 0.68, respectively). Our results suggest that suppression of PTPase activity is not the mechanism underlying the priming and/or triggering of the neutrophil respiratory burst.
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PMID:Lipopolysaccharide-induced priming of the human neutrophil is not associated with a change in phosphotyrosine phosphatase activity. 1039 19

The regulation of macrophage lipoprotein lipase (LPL) by cytokines and lipopolysaccharide (LPS) is of potentially crucial importance in the pathogenesis of atherosclerosis and in the responses to endotoxin challenge. We show here that the reduction of LPL activity in J774.2 macrophages observed in the presence of interleukin (IL-1) and IL-11 was sensitive to herbimycin A, with the effect of LPS, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) on LPL activity being sensitive to both herbimycin A and wortmannin. The action of the inhibitors on the IFN-gamma-dependent reduction of LPL activity was mediated at the level of LPL mRNA metabolism, with translational and/or post-translational levels of regulation being involved in the action of all the other mediators tested. These observations suggest that both the tyrosine kinase and the phosphatidylinositol-3'-kinase signalling pathways are involved in the suppression of macrophage LPL expression by LPS and cytokines.
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PMID:Involvement of both the tyrosine kinase and the phosphatidylinositol-3' kinase signal transduction pathways in the regulation of lipoprotein lipase expression in J774.2 macrophages by cytokines and lipopolysaccharide. 1041 46

The effects of tyrphostin AG-556 (TYR), a tyrosine kinase inhibitor, were evaluated on shock induced by lipopolysaccharide (LPS) or group B streptococcus (GBS) in rats. Mortality and mean survival time were monitored. Plasma 6-keto prostaglandin F1alpha (6-keto PGF1alpha) was also measured at four hours after LPS injection. The effects of TYR on the production of 6-keto PGF1alpha thromboxane B2(TXB2) and nitrite (NO) from LPS or GBS stimulated in vitro peritoneal rat macrophage were also examined. Salmonella enteritidis LPS (12 mg/kg, i.v. ) (n=6) produced severe shock (100% mortality). Simultaneous treatment with TYR (n=6) significantly (p < 0.01) extended mean survival time and 33% of rats survived. Plasma 6-keto PGF1alpha concentrations were increased in LPS controls, whereas TYR (5 mg/kg) significantly (p < 0.05) decreased the production. Animals treated with GBS/D-galactosamine (n=9) also exhibited shock with 100% lethality and TYR again prolonged survival time (p < 0.05) with 55% of the animals surviving. To evaluate direct effects of TYR on mediator production induced by LPS or GBS, rat macrophages were stimulated with heat-killed GBS or LPS with or without TYR. Supernatants were collected at 24 h for determination of TXB2, 6-keto PGF1alpha and NO. All mediators measured were significantly increased (p < 0.05) with LPS or GBS. TYR inhibited (p < 0.05) the production of all mediators from macrophages induced by LPS or GBS. The decrease in eicosanoids was associated with a reduction of the content of cyclooxygenase-2 (COX-2) as determined by western blotting. Collectively, these results suggest that TYR ameliorates toxic shock induced by LPS or gram positive bacteria. This protection is associated with suppression of macrophage mediator production.
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PMID:Protective effect of tyrphostin AG-556 on shock induced by endotoxin or gram positive bacteria. 1044 90

C-type natriuretic peptide (CNP) is secreted by endothelial cells and has vasodilatory and antiproliferative activity against smooth muscle cells. Using defined laminar shear stress exposures of cultured bovine aortic endothelial cells, we investigated the regulation of CNP gene by PhosphorImaging the ratio of CNP mRNA to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA. A 6 h exposure to arterial shear stress of 25 dyn/cm2 caused a marked elevation (10.5 +/- 6.2-fold: n=10, p<0.001) of CNP/GAPDH mRNA ratio compared to stationary controls. Arterial shear stress was 2.6 times more potent than a venous level of shear stress of 4 dyn/cm2 in elevating the CNP/GAPDH mRNA ratio. After 6 h, CNP secretion by shear stressed BAEC was elevated over stationary controls by 3.1-fold (n=5, p<0.001) to a level of 34 +/- 7.5 pg/cm2 BAEC. Shear stress elevated CNP mRNA in the presence of L-NAME (400 microM) indicating that autocrine signaling through shear-induced NO production or guanylate cyclase activation was not involved. Similarly, the tyrosine kinase inhibitor genistein (10 microM), which can also block shear-induced NO production, had no effect on CNP mRNA induction by shear stress in BAEC. The intracellular calcium chelator BAPTA/AM (5 microM) attenuated the shear stress-induced CNP mRNA expression by 71%. Interestingly, dexamethasone (1 microM) potentiated by 2-fold the shear stress enhancement of CNP mRNA. Shear stress was a more potent inducer of CNP than either phorbol myristrate acetate or lipopolysaccharide. Hemodynamic shear stress may be an important physiological regulator of CNP expression with consequent effects on vasodilation and regulation of intimal hyperplasia.
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PMID:Shear stress induction of C-type natriuretic peptide (CNP) in endothelial cells is independent of NO autocrine signaling. 1046 26

A high-throughput screening (HTS) assay for inhibitors of nitric oxide (NO) production by activated microglia was developed and used to compare the relative activities of various anti-inflammatory compounds and cell-permeable protein kinase inhibitors. BV-2 cells, an immortalized line that retains phenotypic features of microglia and produces NO in response to lipopolysaccharide (LPS), were used in the activation paradigm for the HTS assay. A characteristic feature of the compounds that were the most potent dose-dependent inhibitors of NO production is their ability to modulate serine/threonine protein kinases. The anti-inflammatory compound K252a, an inhibitor of calmodulin (CaM)-regulated protein kinases, had one of the highest potencies in the assay. Other classes of kinase inhibitors, including the protein kinase A inhibitor H-89, the mitogen activated protein kinase inhibitors PD98059 and SB203580, and the tyrosine kinase inhibitor genistein, were less potent and efficacious than K252a or the general serine/threonine/tyrosine kinase inhibitor staurosporine. K252a suppresses production of the inducible nitric-oxide synthase (iNOS). The inhibitory effect of K252a is not due to cell toxicity and does not correlate with inhibition of NFkappaB nuclear translocation. The mechanism of action appears to involve inhibition of phosphorylation of the transcription factor CREB, a protein whose activity is modulated by phosphorylation by CaM-dependent protein kinases. These data suggest that signal transduction pathways mediated by CaM-dependent protein kinases warrant future study as potential drug discovery targets.
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PMID:Screening in a cell-based assay for inhibitors of microglial nitric oxide production reveals calmodulin-regulated protein kinases as potential drug discovery targets. 1053 68

Tyrosine phosphorylation pathways are essential components of the process of macrophage activation and the resultant production of inflammatory mediators such as tumor necrosis factor (TNF) and nitric oxide (NO). Several lines of evidence suggest that members of the src family of protein tyrosine kinases play important roles in macrophage activation by gram-negative bacterial lipopolysaccharide (LPS) or the cytokine interferon-gamma (IFN-gamma), but targeted disruption of three members of the src family (hck, fgr, and lyn) in mice failed to demonstrate a requirement for these particular kinases in macrophage activation. We report that the pyrazolopyrimidine PP1, a src family-selective tyrosine kinase inhibitor, potently inhibits the production of TNF and inducible nitric oxide synthase (iNOS) in RAW 264.7 murine macrophages stimulated with LPS, rlFN-gamma, or LPS + rIFN-gamma. Furthermore, the tested concentrations of PP1 inhibit LPS- and rlFN-gamma-mediated tyrosine phosphorylation of the hck tyrosine kinase and its putative substrate, vav, but fail to block rlFN-gamma-mediated JAK2 tyrosine phosphorylation. These findings provide additional support for a model of macrophage activation involving one or more src-related kinases. Selective inhibitors of this signaling pathway should be studied in animal models of sepsis.
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PMID:The src family-selective tyrosine kinase inhibitor PP1 blocks LPS and IFN-gamma-mediated TNF and iNOS production in murine macrophages. 1056 9

In this report, we demonstrate that a fetal mouse skin-derived dendritic cell line produces nitric oxide (NO) in response to the endotoxin [lipopolysaccharide (LPS)] and to cytokines [tumor necrosis factor-alpha (TNF-alpha) and granulocyte-macrophage colony-stimulating factor (GM-CSF)]. Expression of the inducible isoform of NO synthase (iNOS) was confirmed by immunofluorescence with an antibody against iNOS. The tyrosine kinase inhibitor genistein decreased LPS- and GM-CSF-induced nitrite (NO(-2)) production. The effect of LPS and cytokines on NO(-2) production was inhibited by the Janus kinase 2 (JAK2) inhibitor tyrphostin B42. The p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB-203580 also reduced the NO(-2) production evoked by LPS, TNF-alpha, or GM-CSF, but it was not as effective as tyrphostin B42. Inhibition of MAPK kinase with PD-098059 also slightly reduced the effect of TNF-alpha or GM-CSF on NO(-2) production. Immunocytochemistry studies revealed that the transcription factor nuclear factor-kappaB was translocated from the cytoplasm into the nuclei of fetal skin-derived dendritic cells (FSDC) stimulated with LPS, and this translocation was inhibited by tyrphostin B42. Our results show that JAK2 plays a major role in the induction of iNOS in FSDC.
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PMID:Involvement of JAK2 and MAPK on type II nitric oxide synthase expression in skin-derived dendritic cells. 1060 Jul 56

Adhesion of human monocytes (MOs) results in the rapid transcriptional activation of cytokine genes that are dependent on nuclear factor (NF)-kappaB. Several pathways leading to activation of NF-kappaB have been described, including those involving reactive oxygen intermediates (ROIs) and members of the mitogen-activated protein (MAP) kinase superfamily. To investigate the involvement of tyrosine phosphorylation (TP) and oxidant generation in interleukin (IL)-8 and GRO messenger RNA induction, MOs and human alveolar macrophages (AMs) were adhered to plastic or exposed to a particulate pollutant, residual oil fly ash (ROFA). Both stimuli caused rapid TP and ROI production in MOs and AMs. However, neither NF-kappaB translocation nor IL-8 gene induction occurred in adhered or ROFA-exposed AMs. Analysis of MAP kinase activation found phosphorylation of Jun amino-terminal kinase (JNK) and p38 in the AMs, but not of extracellular regulated kinase/MAP kinase (ERK/MAPK). AMs stimulated with lipopolysaccharide activated ERK/MAPK, in addition to JNK and p38, and showed translocation of NF-kappaB. In contrast to AMs, MO adhesion or exposure to ROFA particles in suspension rapidly activated p38, JNK, and ERK/MAPK, and activated NF-kappaB binding as well as IL-8 mRNA expression. Pretreatment with the tyrosine kinase inhibitors genistein or herbimycin A before adherence had no effect on transcriptional activation in MOs, whereas adherence and ROFA-induced oxidant generation was inhibited in both MOs and AMs. Taken together, these data indicate that NF-kappaB activation or generalized transcriptional activation of cytokine genes are independent of changes in oxidant stress imposed on phagocytes by adhesion. Furthermore, the data suggest that certain environmental responses in AMs may be uncoupled from activation of NF-kappaB.
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PMID:Adhesion and pollution particle-induced oxidant generation is neither necessary nor sufficient for cytokine induction in human alveolar macrophages. 1065 41

Nitric oxide synthase (NOS) is an enzyme which has a distinct cytokine-inducible isoform (iNOS). Many cytokine receptors have an intracellular tyrosine kinase domain. Here we have used two tyrosine kinase inhibitors (genistein and lavendustin A) to investigate the potential role of tyrosine kinase activation in the induction on both iNOS and fever caused by lipopolysaccharide (LPS) in rabbits. Direct administration of LPS into the organum vasculosum laminae terminalis (OVLT) increased iNOS expression. These increases paralleled the increase in deep body temperature in unanesthetized rabbits. Pretreatment with genistein or lavendustin A not only reduced the fever but also attenuated the iNOS expression in the OVLT following an intra-OVLT dose of LPS. These results suggest that tyrosine phosphorylation is part of the signal transduction mechanism that mediates the induction of both iNOS and fever elicited by LPS in the OVLT of rabbit brain.
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PMID:Involvement of tyrosine kinase in the pyrogenic fever exerted by NOS pathways in organum vasculosum laminae terminalis. 1067 Apr 30


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