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

Our previous studies indicate that bacterial lipopolysaccharide (LPS) enhances natural killer (NK) cell-mediated cytotoxicity and increases intracellular calcium (Ca2+) in hepatocytes. Calmodulin (CAM) regulates Ca2(+)-ATPase activity, intracellular Ca2+, and is also implicated in NK cell-mediated cytolysis. In the present work, the effects of LPS and CAM on Ca2(+)-ATPase and intracellular Ca2+ in human NK cells were studied by a combined technique of immunogold electron microscopy and ultracytochemistry. Peripheral blood mononuclear cells were treated with 100 micrograms/ml E. coli (0111:B4) LPS and/or 5 micrograms/ml CAM in RPMI 1640 medium at 37 degrees C for 1 or 4 hr. NK cells labeled with monoclonal anti-Leu-11a (CD16) antibody and colloidal gold-conjugated anti-mouse IgG were processed for cytochemical localization of Ca2(+)-ATPase and Ca2+. Ca2(+)-ATPase was localized in the plasma membrane of NK cells, and its activity was suppressed by LPS but was enhanced by CAM. However, no apparent changes in the enzyme reaction were observed when cells were exposed to CAM concomitantly with LPS or stimulated with LPS before CAM. Apparent reduction of the enzyme reaction was observed when LPS stimulation was preceded by CAM. Ca2(+)-ATPase reaction in mitochondria was observed only in NK cells exposed to CAM. Computer image analysis showed no changes in the intracellular Ca2+ in NK cells treated with LPS for 1 hr, whereas a significant increase in Ca2+ was found in cells exposed to LPS for 4 hr. The intracellular Ca2+ significantly decreased in NK cells treated with CAM or with a combination of LPS and CAM as compared to that of controls (p less than 0.05). The results indicate that CAM is capable of blocking or reversing the inhibitory effect of LPS on Ca2(+)-ATPase, and suggest that in human NK cells the plasma membrane-associated Ca2(+)-ATPase is responsible for extrusion of intracellular Ca2+.
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PMID:Effects of bacterial lipopolysaccharide and calmodulin on Ca2(+)-ATPase and calcium in human natural killer cells, studied by a combined technique of immunoelectron microscopy and ultracytochemistry. 213 83

The mechanism(s) involved in the generation of free radicals in human leukocytes by phorbol myristate acetate (PMA), formyl-methionyl-leucyl-phenylalanine (FMP), lipopolysaccharide (LPS), arachidonic acid (AA), and recombinant-tumor necrosis factor-1-alpha (r-TNF-1 alpha) was investigated. Calmodulin antagonists, chlorpromazine and trifluoperazine, inhibited free radical generation in human leukocytes by these stimulants. Dexamethosone, an inhibitor of phospholipase A2, could also block free radical generation in human leukocytes induced by r-TNF 1 alpha. PMA, FMP, LPS and TNF can activate phospholipase A2 and induce the release of AA from the cell membrane lipid pool. AA induced free radical generation in human leukocytes can be inhibited by calmodulin antagonists. Hence, it is likely that calmodulin dependent events play a crucial role in the generation of free radicals by human leukocytes in response to various stimulants including TNF.
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PMID:Stimulation of free radical generation in human leukocytes by various agents including tumor necrosis factor is a calmodulin dependent process. 215 20

The mechanism(s) involved in the generation of free radicals in human leukocytes by cis-unsaturated fatty acids, gamma-linolenic acid (GLA), and arachidonic acid (AA), was investigated. Calmodulin antagonists, chlorpromazine and trifluoperazine, inhibited free radical generation by human leukocytes in vitro induced by GLA, AA PMA (Phorbol myristate acetate), formyl-methionyl-leucyl-phenylalanine (FMLP) and lipopolysaccharide (LPS). On the other hand, chloroquine, a phospholipase A2 inhibitor, and colchicine, a microtubule disrupting agent, were without any effect. When sub-optimal concentrations of GLA and AA were added together, leukocytes showed an additive effect on free radical generation. These results indicate that Calmodulin dependent event(s) play a significant role in the generation of free radicals by human leukocytes.
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PMID:Free radical generation in human leukocytes by CIS-unsaturated fatty acids is a calmodulin dependent process. 216 83

To determine the role of intracellular calcium ([Ca2+]i) in the priming of monocytes (M phi) by bacterial lipopolysaccharide (LPS), the membrane expression of two functional proteins and phagocytosis and respiratory burst were examined by microfluorimetry. LPS induced a significant increase in HLA-DR and C3bi receptor (CR3) expression within 2 h of its addition to whole blood. The enhanced expression of both antigens by LPS was dose-dependent, with concentrations as low as 0.1 ng/ml producing a response. The involvement of [Ca2+]i was demonstrated by loading isolated M phi with the intracellular calcium chelator quin-2 or the inhibitor of intracellular calcium redistribution TMB-8 prior to addition of LPS. Both compounds inhibited the LPS-induced increase in HLA-DR and CR3 expression. No role for extracellular calcium, for calcium slow channel flux, or for the calcium-calmodulin complex in LPS priming was demonstrated when LPS was added in the presence of EGTA, trifluperazine (TFP), or verapamil. The addition of the calcium ionophores A23187 or ionomycin failed to increase expression of either antigen. Prior exposure to LPS primed M phi for enhanced phagocytosis and respiratory burst activity. These functions were inhibited by TMB-8, but not by TFP or verapamil. Addition of LPS to isolated M phi increased [Ca2+]i by 23% at 30 sec and 42% at 5 min, as measured by the calcium-sensitive, intracellular probe indo-1. These results suggest that intracellular Ca2+ mobilization is necessary, but not sufficient, for LPS-induced priming of human peripheral blood monocytes.
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PMID:Role of intracellular calcium in priming of human peripheral blood monocytes by bacterial lipopolysaccharide. 253 67

Human adherent monocytes stimulated with 1 microgram/ml pertussis toxin (PT) produced interleukin-1 (IL-1), as measured by thymocyte co-stimulation assay and enzyme-linked immunosorbent assay (ELISA), specific for IL-1 alpha and IL-1 beta. To clarify the role of protein kinase C (PKC) and calmodulin in IL-1 production, we investigated the effects of a PKC inhibitor, H-7, and a calmodulin antagonist, W-7 on PT- and lipopolysaccharide (LPS)-induced IL-1 production by monocytes. Addition of 10 microM and 20 microM H-7 to the culture medium markedly suppressed both PT- and LPS-induced IL-1 production. PT-induced IL-1 production was significantly suppressed by 5 microM and 10 microM W-7. However, LPS-induced IL-1 production was not suppressed by W-7 at the concentrations tested. When monocytes were labelled with Quin 2/AM, IL-1 production by monocytes stimulated with PT and LPS was markedly suppressed. These results indicate that different pathways are involved in the IL-1 production by PT and LPS; both calmodulin- and PKC-dependent processes are necessary for the IL-1 production induced by PT, whereas LPS-induced IL-1 production is dependent on the PKC. Inhibition of IL-1 production by interfering with intracellular Ca2+ trafficking in Quin 2/AM-loaded monocytes may be associated with the inhibition of PKC and calmodulin activity.
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PMID:Effect of protein kinase C inhibitor (H-7) and calmodulin antagonist (W-7) on pertussis toxin-induced IL-1 production by human adherent monocytes. Comparison with lipopolysaccharide as a stimulator of IL-1 production. 278 78

Hepatocellular injury was induced by exposure of primary cultures of rat hepatocytes to 4 mM D-galactosamine. The cell damage was very similar to that seen in vivo and in the isolated perfused rat liver, both in biochemical and in structural terms. The severity of the lesions caused by D-galactosamine was dependent on the age of the culture being treated. Less severe damage was found with older cultures. Since the primary metabolic effects of D-galactosamine were age-independent, the reduction in cell damage seems to be due to progressive cell dedifferentiation. Dexamethasone (1 microM) suppressed the full development of the injury, while 1 microM triiodo-L-thyronine enhanced it. A protection of hepatocytes by alpha 2-macroglobulin against the effects of D-galactosamine could be observed neither in vivo nor in vitro. Direct cytotoxic effects of endotoxin from Salmonella minnesota R 595 could be demonstrated only on hepatocytes in the early phases of primary culture using rather high doses of the purified lipopolysaccharide. It is unlikely that they play a major role in the hepatocellular injury seen following endotoxinemia in vivo. Lowering of extracellular Ca2+ concentration and additions of calcium/calmodulin inhibitors did not prevent cell injury after treatment with D-galactosamine. The results suggest that cell death is not due to an increased influx of Ca2+ into the cells.
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PMID:Toxicity of D-galactosamine for rat hepatocytes in monolayer culture. 285 29

The murine macrophage-like cell line J774.16 and peritoneal exudate cells elicited with thioglycollate or starch contain a major calmodulin (CaM)-binding protein (CaMBP) which is absent in trifluoperazine-resistant variants of J774, resident peritoneal macrophages and peritoneal macrophages elicited with concanavalin A, lipopolysaccharide, proteose peptone, or Bacillus Calmette-Guerin. Resident murine peritoneal cells maintained in tissue culture for 3 days begin to accumulate this protein, as do human peripheral blood monocytes after 7 days of culture. A specific competitive displacement radioimmunoassay was developed with the use of a rabbit antiserum raised to the partially purified CaM-binding protein and [125I]CaM covalently cross-linked to the principal CaM-binding protein in the preparation. The radioimmunoassay confirmed the unique cellular distribution of this protein, suggesting that it may be a marker for certain stages of macrophage differentiation. Monoclonal antibodies were prepared, and one of these was used to further purify the protein by immunoaffinity chromatography. A protein of Mr 50,000 to 60,000 was isolated. The protein could be selectively adsorbed to wheat germ agglutinin agarose and subsequently eluted with N-acetyl glucosamine. This property, plus the sensitivity of the protein to endoglycosidase F, led to the conclusion that it is a glycoprotein. The cellular distribution, subcellular localization, and evidence for glycosylation suggest that this protein may be a macrophage-specific receptor with a high affinity for Ca2+-CaM.
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PMID:Purification and distribution of a novel macrophage-specific calmodulin-binding glycoprotein. 298 Oct 93

C3H/HeJ mice are hyporesponsive to the biologic effects of bacterial lipopolysaccharide (LPS). The defect in the strain of mice is believed to be due to the expression of a mutant allele designated Lpsd at the chromosome four locus. The molecular basis of this hyporesponsiveness is not known, but it may result from some defective membrane signal transductions. To examine this possibility, we compared the abilities of interleukin 1 (IL-1) production by C3H/HeJ macrophages with those by C3H/He macrophages (LPS responsive) after stimulation with the calcium ionophore A23187 or phorbol myristate acetate (PMA). A23187 induced IL-1 production by C3H/He macrophages, but it did not induce IL-1 production by C3H/HeJ macrophages and neither did LPS. However, it had the ability to increase intracellular free Ca2+ in C3H/HeJ macrophages as well as in C3H/He macrophages, this being examined by the changes in cytosolic Ca2+ in the macrophages by using Quin 2. In contrast, PMA was able to induce IL-1 production by both C3H/He and C3H/HeJ macrophages without increasing intracellular Ca2+. Since polymyxin B did not inhibit A23187- or PMA-induced IL-1 production by C3H/He macrophages, these results are not due to the little amount of LPS in culture medium, but due to their own characteristics. A calmodulin antagonist W-7 effectively inhibited A23187-induced IL-1 production by C3H/He macrophages. However, it hardly inhibited LPS-induced IL-1 production except at high concentration, and it caused no inhibition of the PMA-stimulated one. These results suggest that the blocking sites expressed phenotypically by the Lpsd are shared by LPS- and A23187-stimulated cellular processes, although the actions of LPS and A23187 are different from each other. In addition to the direct study with LPS or lipid A, A23187 should provide another useful approach to clarify the molecular mechanisms of Lpsd defect in C3H/HeJ macrophages.
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PMID:Calcium ionophore A23187 does not stimulate lipopolysaccharide nonresponsive C3H/HeJ peritoneal macrophages to produce interleukin 1. 311 92

The effect of calmodulin inhibitors on synoviocyte phospholipase A2 activity was evaluated. Cells were incubated with [3H]arachidonic acid after 24 hours to label phospholipids. [3H]prostaglandin E2 synthesis was stimulated by Salmonella minnesota lipopolysaccharide (100 micrograms/ml). Trifluoperazine, 35 microM, reduced lipopolysaccharide-stimulated [3H]prostaglandin E2 synthesis by 50%. In sonicated suspensions of cells, calcium-dependent phospholipase A2 activity was inhibited by trifluoperazine 3-100 microM and by compound 48/80 (3 micrograms/ml). These agents inhibit calmodulin-dependent enzyme activity. The addition of calmodulin, 1 or 2.5 microM, to compound 48/80-treated suspensions reversed this inhibition in a dose-dependent manner. Agents which inhibit calmodulin-dependent enzymes can reversibly inhibit synoviocyte phospholipase A2 and thus prostaglandin E2 production.
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PMID:Effects of calmodulin inhibitors on rabbit synoviocyte phospholipase A2. 311 95

The effects of several calmodulin antagonists on the activation of RAW-264 macrophage-like cells for tumor cell killing were investigated. At concentrations ranging from 5 X 10(-8) to 5 X 10(-7) M, calmidazolium, trifluoperazine, chlorprothixene, chlorpromazine and W-13 inhibited the development of cytolytic activity, evoked in RAW-264 by treatment with lymphokine and lipopolysaccharide, in a dose-dependent manner. Since the order of the potency of these drugs against the activation of RAW-264 cells was much the same as their ability to inhibit calmodulin-dependent phosphodiestherase activity: calmidazolium greater than trifluoperazine greater than chlorprothixene greater than chlorpromazine greater than W-13, and because W-12, a nonactive analog of W-13, failed to inhibit the process of activation, we believe that the development of cytolytic activity in RAW-264 cells may be dependent on calmodulin. At micromolar concentrations, calmodulin antagonists (except calmidazolium) enhanced the process of activation. The enhancement of cytolytic activity was neither the result of the toxicity of these drugs nor related to their effects on intracellular calcium. It was entirely dependent on the presence of stimulants but occurred independently from the stage of macrophage activation, and most likely was due to the nonspecific interference of these agents with calmodulin-independent processes.
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PMID:The effect of calmodulin antagonists on the activation of RAW-264 macrophage-like cells for tumor cell killing. 375 42


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