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)

We describe here and partially characterize a Ca(2+)-independent phospholipase A2 that acts on phosphatidylinositol in normal human peripheral blood neutrophils. Neutrophils incubated with myo-[3H]inositol to form [3H]phosphatidylinositol and then stimulated with the calcium ionophore A23187 produced [3H]lysophosphatidylinositol. This deacylation was further characterized in cell sonicates by the specific release of [3H]arachidonic acid from exogenous [1-14C]stearoyl-2-[3H]arachidonyl-phosphatidylinositol. This phospholipase A2 is Ca2+ independent, retaining full activity in the presence of 10 mM EDTA, and is optimally active at alkaline pH (pH 9). A phosphatidylinositol-hydrolyzing phospholipase C activity was characterized by the production of [3H]-/[14C]-diglycerides. This phospholipase C activity is dependent on the presence of exogenous Ca2+ and is optimally active at neutral pH (pH 7.5). The lipoxygenase/cyclooxygenase inhibitors eicosatetraenoic acid and nordihydroguaiaretic acid and the calmodulin antagonist trifluoperazine were the only compounds tested that showed significant inhibition of phospholipase A2 activity. However, none of these phosphatidylinositol-hydrolyzing phospholipase A2 inhibitory compounds resulted in the accumulation of any radiolabeled diglyceride, monoglyceride, or phosphatidic acid intermediates. Following subcellular fractionation on sucrose density gradients, it was found that the plasma membrane-enriched fractions contained the highest specific activity for phospholipase A2; however, the cytosolic fraction contained a large part of the total phospholipase A2 activity. Furthermore, when neutrophils were first exposed to several agents, including lipopolysaccharide, phorbol myristate acetate, or N-formyl-methionyl-leucyl- phenylalanine, and then subfractionated, there was a significant translocation of the enzyme activity from the cytosolic fraction to the membrane-enriched fractions. These data suggest that this Ca(2+)-independent, phosphatidylinositol-hydrolyzing phospholipase A2 may play an important role in early cell activation, providing free arachidonic acid for subsequent metabolism into biologically active eicosanoids.
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PMID:Phosphatidylinositol hydrolysis by phospholipase A2 and C activities in human peripheral blood neutrophils. 146 38

The inhibitory effect of beta-alanyl-L-histidinato zinc (AHZ) on bone resorption in tissue culture was investigated. Calvaria were removed from weanling rats (3-week-old male) and cultured for periods up to 48 h in Dulbecco's modified Eagle medium (high glucose, 4.5%) supplemented with antibiotics and bovine serum albumin. The experimental cultures contained 10(-7) to 10(-4) mol/l AHZ. The bone-resorbing factors, parathyroid hormone (1-34) (PTH; 10(-7) mol/l), prostaglandin E2 (10(-5) mol/l), interleukin-1 alpha (IL1 alpha; 50 U/ml), and lipopolysaccharide (10 micrograms/ml), caused a significant decrease in bone calcium content. The decreases in bone calcium content induced by bone-resorbing factors were completely inhibited by the coexistence of AHZ (10(-6) to 10(-4) mol/l). Also, AHZ (10(-5) mol/l) completely inhibited the PTH (10(-7) mol/l) or IL1 alpha (50 U/ml)-induced increase in medium glucose consumption and lactic acid production by bone tissue. Furthermore, AHZ (10(-5) mol/l) fairly blocked both PTH (10(-7) mol/l)-increased acid phosphatase and decreased alkaline phosphatase activities of bone tissue. The inhibitory effect of AHZ (10(-5) mol/l) on PTH (10(-7) mol/l)-stimulated bone resorption was clearly prevented by the presence of 10(-4) mol/l dipicolinate, a chelator of zinc. However, zinc sulfate (10(-7) to 10(-4) mol/l) did not inhibit the PTH (10(-7) mol/l)-stimulated bone resorption in tissue culture. These findings indicate that AHZ had a direct inhibitory effect on bone resorption in vitro, and the AHZ effect was found in the chemical form of zinc-chelated dipeptide.
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PMID:Inhibitory effect of beta-alanyl-L-histidinato zinc on bone resorption in tissue culture. 146 76

Isolated rat Kupffer cells produced and released prostaglandin (PG) E2, 6-keto-PGF1 alpha, and thromboxane B2 (TXB2) in response to lipopolysaccharide (LPS) stimulation. This elevation of PGE2, 6-keto-PGF1 alpha and TXB2 in the medium was not observed when cells were cultured in the absence of extracellular calcium or in the presence of an extracellular calcium chelator, EGTA. An intracellular calcium antagonist, TMB-8, also suppressed the production of PGE2, 6-keto-PGF1 alpha and TXB2 in a concentration-dependent manner. The intra-cellular calcium concentration of Kupffer cells elevated early after the addition of LPS determined by the use of fura-2 and a fluorescence microscopy. Moreover, calmodulin inhibitors, W-7 and W-13, apparently inhibited the production of PGF2, 6-keto-PGF1 alpha and TXB2. All these results suggest that LPS-induced PG production by stimulated rat Kupffer cells may be regulated by a calcium-calmodulin pathway.
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PMID:Calcium-dependent prostaglandin biosynthesis by lipopolysaccharide-stimulated rat Kupffer cells. 147 77

MARCKS is a specific protein kinase C (PKC) substrate that binds both calmodulin and actin and is phosphorylated during phagocyte activation, neurosecretion, and growth factor-dependent mitogenesis. We report here on MacMARCKS, a MARCKS homolog, whose synthesis is dramatically increased in macrophages when these cells are exposed to bacterial lipopolysaccharide. We have purified rabbit MacMARCKS and cloned its cDNA from rabbit and mouse. The effector domains of MacMARCKS and MARCKS are nearly identical, and both proteins bind calmodulin in a phosphorylation-regulated manner. MacMARCKS and MARCKS also share a second, highly conserved region also found in the internalization domain of the mannose-6-phosphate receptor. Our data suggest the existence of a family of PKC substrates that are targeted to different subcellular locations and that function to integrate PKC and calcium/calmodulin-dependent signals in the control of the plastic actin cytoskeleton.
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PMID:MacMARCKS, a novel member of the MARCKS family of protein kinase C substrates. 151 35

When B cells are stimulated with lipopolysaccharide (LPS) they start to proliferate and mature into immunoglobulin (Ig)-secreting cells. Co-stimulation with F(ab')2 fragments of antibodies directed against the B cell antigen receptor leads to an inhibition of Ig secretion but not of proliferation. This effect can be mimicked by phorbol esters alone or by a combination of phorbol esters and the Ca2+ ionophore ionomycin, which activate protein kinase C. Here we report that co-stimulation with phorbol esters and ionomycin differentially affects a group of genes normally up-regulated during the course of LPS-dependent B cell activation. Thus, the mRNA coding for the membrane-bound form of IgM and the interleukin 2 receptor (55-kDa protein) continue to be expressed at the levels typical of LPS-stimulated cells, while the mRNA coding for the secreted form of IgM (mu S) and for the J chain are reduced. The loss of mu S mRNA is attributable to an altered processing behavior with respect to the mu precursor and/or a decreased stability of the mRNA itself.
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PMID:Regulation of immunoglobulin gene expression in normal lymphocytes. II. Mechanisms of down-regulation of immunoglobulin secretion after engagement of the B cell antigen receptor. 153 86

Ly-1+ B cells have been reported to produce a number of autoantibodies, and to be involved in the selection and regulation of the conventional B cell repertoire. It is not known if these B cells, which are found in high numbers in the peritoneum of normal adult mice, themselves can be regulated. In this study, we evaluated the sensitivity of peritoneal B cells (PBCs) versus conventional splenic B cells to regulation in a model system for tolerance. Normal splenic (conventional) or PBCs (containing both CD5+ and CD5- 'sister' cells) were cultured overnight with either F(ab')2 or intact IgG anti-mouse Ig, washed, and then challenged with fluorescein(FL)-coupled to Brucella abortus (BA), trimethylammonium (TMA)-BA or lipopolysaccharide (LPS), and the IgM responses to the FL and TMA haptens measured. In contrast to spleen cells, which exhibited up to a 90% reduction in anti-FL responsiveness, pretreated PBCs were mostly resistant to this form of tolerance regardless of challenge. The anti-TMA response of PBCs, which reflects the skewed VH11 usage by peritoneal CD5 B cells, was also resistant to tolerance. However, splenic TMA-specific B cells appeared to be sensitive to unresponsiveness induced by anti-Ig. Signaling studies show that PBCs have a blunted initial Ca2+ response, suggesting that the consequence of anti-Ig crosslinking may be defective in these cells. Furthermore, phorbal myristate acetate and/or ionomycin treatment of both PB and splenic B cells led to hyporesponsiveness to LPS challenge. This suggests that PBCs may be defective in a signalling pathway, perhaps involving protein kinase C activation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Can peritoneal B cells be rendered unresponsive? 154 May 46

Macrophage procoagulant activity is an important mediator of extravascular fibrin deposition at sites of infection and appears to contribute to the pathogenesis of several infectious disease processes. Previous studies have shown that the inflammatory mediator platelet-activating factor was able to prime macrophages for induction of procoagulant activity by bacterial lipopolysaccharide. The present studies were designed to examine the mechanism of this priming effect. Platelet-activating factor (100 nM) primed macrophages for procoagulant activity generation in response to endotoxin at concentrations as low as 100 ng/ml and also following exposure to Escherichia coli, Bacteroides fragilis, and Staphylococcus aureus. The priming effect occurred following a pretreatment with platelet-activating factor for as short as 1 min, suggesting a rapid activation event. Two different doses of the calcium ionophore ionomycin were used to mimic the peak and sustained effects of platelet-activating factor on cytoplasmic calcium levels (1 microM and 100 nM, respectively). Neither dose was able to mimic the priming effect. However, extracellular calcium was necessary for induction of procoagulant activity and the priming effect. By contrast, the protein kinase C agonist phorbol myristate acetate reproduced the priming phenomenon observed for platelet-activating factor. In further support of the concept that protein kinase C activation mediated the effect of platelet-activating factor, the specific protein kinase C inhibitor staurosporine reversed the ability of platelet-activating factor to augment induction of macrophage procoagulant activity by endotoxin. These data suggest mechanisms by which inflammatory mediators within the microenvironment of infection might modulate the host response to bacterial pathogens.
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PMID:Platelet-activating factor modulates endotoxin-induced macrophage procoagulant activity by a protein kinase C-dependent mechanism. 154 68

Mouse macrophages activated by interferon-gamma kill intracellular Leishmania by a process that depends on the generation of L-arginine-derived nitrogen oxidation products. Interferon-induced intracellular killing can be mimicked by exposure of macrophages to the Ca2+ ionophore A23187 in the presence of lipopolysaccharide. The mechanisms of this effect were therefore investigated. Destruction of the parasite was accompanied by accumulation of nitrite in the macrophage culture fluids. Leishmanicidal activity and nitrite production in cultures stimulated with ionophore A23187 and lipopolysaccharide were abrogated when cells were activated in medium containing arginase or the L-arginine analogues L-canavanine, guanidine or NG-monomethyl-L-arginine. L-Arginine was required during the lipopolysaccharide-induced triggering phase only. Indeed, macrophage priming with ionophore A23187 in L-arginine-depleted medium led to full microbicidal activity and nitrite generation provided that L-arginine was present during subsequent triggering by lipopolysaccharide. Addition of NG-monomethyl-L-arginine to ionophore-activated macrophages increased O2- production on phorbol myristate stimulation, while inhibiting glucose oxidation through the hexose monophosphate shunt pathway. Leishmanicidal activity and nitrite production were also inhibited when ionophore-treated cultures were incubated with excess iron, implying a role for iron as a defence mechanism against the toxicity of nitrogen derivatives. These results indicate that the ionophore-induced leishmanicidal activity occurs through a process similar to that evoked by interferon-gamma, i.e. the production of L-arginine-derived nitrogen oxidation products.
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PMID:Macrophage activation for intracellular killing as induced by a Ca2+ ionophore. Dependence on L-arginine-derived nitrogen oxidation products. 159 22

Interleukin 1 (IL-1) production by A/J (A) and C57BL/6J (B6) mouse peritoneal macrophages stimulated with lipopolysaccharide (LPS) was determined. Strain A macrophages produced low levels of soluble IL-1 bioactivity compared with B6 macrophages. This defect was not reversed by indomethacin, interferon-gamma, phorbol myristate acetate, or calcium ionophore A23187. In contrast, cytosolic IL-1 bioactivity was similar in LPS-stimulated A and B6 macrophages. Western blotting revealed that A macrophage supernatants contained lower levels of both 17-kd IL-1 alpha and 17-kd IL-1 beta but similar levels of tumor necrosis factor alpha compared with B6 macrophages. Cytosolic levels of 31-kd pro-IL-1 alpha and also 31-kd pro-IL-1 beta were similar in A and B6 macrophages. Oligonucleotide probing indicated that A and B6 macrophages contained similar levels of IL-1 alpha and also IL-1 beta mRNA. These findings indicate that LPS-stimulated A macrophage culture supernatants contain low levels of both IL-1 alpha and IL-1 beta compared with B6 macrophages and that these defects in IL-1 production are posttranscriptionally regulated.
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PMID:Defective lipopolysaccharide-induced production of both interleukin 1 alpha and interleukin 1 beta by A/J mouse macrophages is posttranscriptionally regulated. 161 93

Previous work has shown that renal metabolism of 25-dihydroxyvitamin D3 (25(OH)D3) to the active metabolite, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) is stimulated by prostaglandin E2 and inhibited by acetylsalicylate (aspirin). As prostaglandins are primary inflammatory mediators and synovial fluid macrophages are known to synthesise 1,25(OH)2D3 in vitro, the effects of prostaglandin E1, prostaglandin E2, and aspirin on the metabolism of 25(OH)D3 by cells cultured from synovial fluid of patients with inflammatory arthritis were investigated. Most cultures contained non-proliferating macrophages which formed 1,25(OH)2D3; however, two of 13 cultures contained colonies of rapidly proliferating fibroblast-like cells which formed 24,25(OH)2D3 (24,25(OH)2D3). Prostaglandin E1 and prostaglandin E2 (0.01-10 mumol/l) induced marked inhibition of 1,25(OH)2D3 synthesis (up to 94%) in a dose dependent manner after preincubations of 24 hours but not over straightforward six hour incubations. Exposure of macrophages to aspirin (1 mumol/l-1 mmol/l) for 24 hours did not affect 1,25(OH)2D3 synthesis unless the cells had been pretreated with lipopolysaccharides, in which instance 1 mM aspirin increased 1,25(OH)2D3 synthesis. Lipopolysaccharide is a macrophage activating factor which stimulates macrophages to form 1,25(OH)2D3, and it also induces prostaglandin synthesis which would be inhibited by aspirin. Taken together these results suggest that prostaglandin E1 and prostaglandin E2 synthesised by macrophages may act in an autocrine manner to attenuate the ability of macrophage activating factors, such as lipopolysaccharide, to stimulate 1,25(OH)2D3 synthesis. Prostaglandins synthesised by other inflammatory cells may also inhibit 1,25(OH)2D3 synthesis in a paracrine manner. In contrast, prostaglandin E2 and aspirin had limited effects on fibroblast 24,25(OH)2D3 synthesis. This study shows that the effects of prostaglandin E1, prostaglandin E2, and aspirin in macrophages contrast with those previously reported for the renal 25(OH)D3-1alpha-hydroxylase, where prostaglandin E2 stimulated and aspirin inhibited enzyme activity. These results further emphasise that synthesis of 1,25(OH)2D3 in non-renal sites is independently regulated, which is consistent with it having an immunological role at a local level rather than playing a part in systemic calcium homeostasis.
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PMID:Inhibition by prostaglandin E1 and E2 of 1,25-dihydroxyvitamin D3 synthesis by synovial fluid macrophages from arthritic joints. 161 28


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