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)

Tumour necrosis factor (TNF) is synthesized initially as a membrane-bound precursor which is then cleaved to yield soluble, mature protein. The 26,000 MW TNF precursor isolated from the lysate of activated RAW 264.7 (mouse macrophage) cells by immunoprecipitation was used to identify pro-TNF cleavage enzyme in the same cells. A significant amount of mature protein was formed in samples containing Nonidet P-40 (NP-40)-lysed cells, whereas sonicated cells showed negligible activity. Most of the cleavage activity in macrophages was localized in the membrane/particulate fraction and remained largely insoluble after sonication or treatment with 2 mM EDTA/1 M NaCl, indicating that the enzyme is associated with the membrane/particulate fraction. The crude cleavage activity in membrane/particulate was partially inhibited by a spectrum of serine, cysteine and aspartate proteinase inhibitors, whereas secretion of TNF from activated macrophages was inhibited exclusively by serine and serine/cysteine proteinase inhibitors. This result suggested that, among heterogenous pro-TNF cleavage activities, the enzyme responsible for the processing of TNF is a serine proteinase. Pro-TNF cleavage activity was present in non-stimulated macrophages and decreased significantly 8 hr after lipopolysaccharide (LPS) stimulation, suggesting that it is negatively regulated after an initial burst of TNF synthesis.
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PMID:Pro-tumour necrosis factor cleavage enzyme in macrophage membrane/particulate. 824 55

Bacterial lipopolysaccharide (LPS) has been speculated to facilitate bacterial translocation by a mechanism involving physical disruption of the gut mucosal barrier. Polarized, cultured intestinal epithelial cells (Caco-2 cells) were used to study the effect of LPS on enterocyte structure, viability, and susceptibility to bacterial invasion. Varying concentrations of biologically active LPS were incubated with enterocytes for 1 and 16 hr. LPS had no noticeable effect on enterocyte viability or morphology, as measured by uptake of vital dyes, by distribution of cytoskeletal filamentous actin, and by visualization of subcellular ultrastructure. Transepithelial electrical resistance was similar in enterocyte cultures incubated with LPS for 1 hr, but there was a noticeable decrease after 16 hr, indicating a loss of epithelial integrity after prolonged exposure to LPS. The effect of LPS on bacterial uptake was studied using six strains of enteric bacteria with varying abilities to invade Caco-2 cells: Listeria monocytogenes, Salmonella typhimurium, Proteus mirabilis, Escherichia coli (2 strains), and Enterococcus faecalis. Electron microscopy showed enteric bacteria in intimate association with enterocyte apical microvilli, and internalized bacteria were consistently observed within cytoplasmic, membrane-bound vacuoles. Following a 1-hr incubation of individual strains of enteric bacteria with Caco-2 cells, numbers of viable intracellular bacteria varied significantly between individual bacterial strains, but numbers of intracellular bacteria were similar for each strain incubated with enterocytes exposed to 0, 10, and 100 micrograms LPS for 1 and 16 hr. Thus, although prolonged exposure to LPS might have some effect on enterocyte culture integrity (as measured by decreased electrical resistance), LPS had no discernible effect on enterocyte structure, viability, and susceptibility to bacterial invasion. These results suggested that LPS-induced bacterial translocation might not involve loss of epithelial viability, or facilitated entry of bacteria into intestinal epithelial cells.
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PMID:Effect of LPS on epithelial integrity and bacterial uptake in the polarized human enterocyte-like cell line Caco-2. 837 30

epsilon receptor modulating protein (epsilon RMP) was identified and purified in our previous studies as a murine T cell-derived soluble 17-kDa chymotryptic serine protease which suppresses avidity of binding between IgE and CD23 (low affinity Fc receptor for IgE) without decreasing the quantitative expression of the CD23 molecule. Some, but not all, of the other known soluble serine proteases showed epsilon RMP-like CD23-modulating activities. Further studies indicated that epsilon RMP exists not only as a soluble protein but also as a 36-kDa T-cell surface form. Both soluble and membrane-bound epsilon RMP can induce purified splenic B cells to secrete IgE in the presence of IL-4 even without lipopolysaccharide (LPS). In this study, therefore, we have tested effects of several known serine proteases on Ig production in vitro and have found that: (i) coculture of splenic B cells in the presence of LPS and IL-4 with serine proteases which have epsilon RMP-like substrate specificity, such as kallikrein and alpha-chymotrypsin, results in a significant increase of IgG1 and a slight increase of IgE secretion at low concentrations, and significant suppression at high concentrations in an isotype-selective manner; and (ii) the effects of these proteases are blocked by phenylmethylsulfonyl fluoride but not by indomethacin, suggesting that serine protease activity but not prostaglandin E2 is involved. The biological significance of the possible involvement of serine proteases on Ig class switching is discussed.
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PMID:Biphasic effect of kallikrein on IgE and IgG1 syntheses by LPS/IL-4-stimulated B cells. 842 28

A combination of signals transmitted through the antigen receptor, membrane-bound cell interaction molecules and cytokine receptors induces B cell proliferation and differentiation into immunoglobulin-secreting or memory cells. It has recently been suggested by Turner et al. (Cell 1994. 77: 297) that the complex changes in gene activities accompanying high levels of immunoglobulin secretion are under the common control of a master regulator, Blimp-1 (B lymphocyte-induced maturation protein). We show here that in naive mouse B cells stimulated with lipopolysaccharide (LPS) alone (which leads to high IgM production), Blimp-1 is highly expressed, while cells co-stimulated with LPS and anti-mu F(ab')2 show low levels of Blimp-1 mRNA and no longer secrete Ig. I gamma 1 sterile transcripts are, however, up-regulated after receptor co-ligation. Addition of interleukin (IL)-2 and IL-5 to LPS + anti-mu F(ab')2-treated primary B cells led to up-regulation of Blimp-1 and IgM secretion. Transfection of a Blimp-1 expression vector also induced IgM secretion. The data indicate that Blimp-1 is an important regulator of immunoglobulin secretion by primary B cells, and suggest that its level of expression may determine the differentiation to Ig-secreting plasma cells or entrance and maintenance in the memory pool.
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PMID:Blimp-1 overcomes the block in IgM secretion in lipopolysaccharide/anti-mu F(ab')2-co-stimulated B lymphocytes. 856 78

The myeloid differentiation antigen CD14 acts as the major receptor for bacterial lipopolysaccharide (LPS). A soluble form of the protein (sCD14) is present in human serum which functions as a soluble LPS receptor. We have compared the isoform patterns of soluble CD14 derived from human serum and of the recombinant proteins produced by CHO cells transfected with either the wild-type CD14 gene or with a cDNA coding for a truncated protein which lacks the C-terminal 21 amino acids [sCD14-(1-335)-peptide]. Using SDS/PAGE, two dominant isoforms (53 and 50 kDa) and two minor forms (46 and 43 kDa) can be detected in serum as well as in the supernatants of both transfectants. sCD14 is a glycoprotein which carries N- and O-linked carbohydrates. The different isoforms of sCD14-(1-335)-peptide are due to differences in the content of N-linked sugars. However after the removal of N- and O-linked carbohydrates from serum- and CHO-derived wild-type proteins, two isoforms are still present. These results indicate that N-linked glycosylation contributes to but does not fully explain the different forms of soluble CD14. We further examined whether the mutation of individual N-linked glycosylation sites influences the expression of membrane-bound and soluble CD14 forms and the ability of the membrane-bound molecule to bind LPS. As with the wild-type proteins, the different isoforms of the soluble mutants are partially due to differences in N-linked glycosylation. A truncated mutant which lacks the two N-terminal glycosylation sites {[Asp18, Asp132]CD14-(1-335)peptide} does not give rise to multiple forms on SDS gels. Like CD14-(1-335)-peptide, this mutant is not expressed on the cell surface suggesting that a smaller isoform present in the wild-type preparations results from proteolytic cleavage of the membrane-bound molecule. N-linked carbohydrates do not seem to be important for the binding of LPS to membrane-bound CD14.
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PMID:The myeloid differentiation antigen CD14 is N- and O-glycosylated. Contribution of N-linked glycosylation to different soluble CD14 isoforms. 861 16

Various growth factors released by macrophages and other cell types modulate normal hematopoiesis. The physiological mechanisms whereby these molecules interact with specific target cells are ill defined. Eicosanoids, the products of fatty acid metabolism, are known to regulate cell proliferation and differentiation. The release of membrane-bound phospholipid by phospholipase-A2 (PLA-2) is the first critical step in the initiation of membrane remodeling and eventually eicosanoid synthesis. We report here data that demonstrates how various cytokines exhibit a marked hydrolytic activity mediated through PLA-2 against both [1-14C] oleic acid- and [1-14C] arachidonic acid-labeled Escherichia coli (micelle) substrates. PLA-2 extracts were prepared from neutrophils elicited by injecting rats ip with 8% glycogen. The rate of hydrolysis of free fatty acids from the phospholipid substrate was found to be linear, rapid, and pH dependent and was calculated to be 30 nmoles of phospholipid/hr/mg protein lysate. Cytokines (i.e., interleukin-1 [IL-1, human and murine recombinant, alpha], mouse lung cell-derived colony-stimulating factor [L-CSF], granulocyte-macrophage colony-stimulating factor [murine recombinant GM-CSF], tumor necrosis factor [murine recombinant TNF-alpha], and granulocyte colony-stimulating factor [human recombinant, G-CSF] all induced PLA-2 activity with the release of free fatty acids above basal levels. In contrast, lipopolysaccharide (LPS), interleukin-2, (IL-2, human recombinant), and macrophage colony-stimulating factor (M-CSF) did not significantly activate PLA-2 hydrolysis. The activation of this membrane-bound enzyme-substrate complex by these growth factors may serve as a mechanism whereby the appropriate target cells expressing receptors respond through either direct or secondary signals leading to the formation of free fatty acids with the eventual synthesis of prostanoid or lipoxygenase products, resulting in cellular proliferation and differentiation.
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PMID:The regulation of phospholipase-A2 (PLA-2) by cytokines expressing hematopoietic growth-stimulating properties. 865 Feb 56

Monocytes and macrophages express a glycosyl phosphatidylinositol (GPI)-anchored lipopolysaccharide (LPS) receptor on the cell surface which enables them to detect minute amounts of LPS released from Gram-negative bacteria. A soluble form of CD14 is also found free in serum, though its physiological function is unknown. the interaction of LPS with CD14 on the monocyte surface leads to an activation of the cells which is manifested in the sudden release of reactive oxygen species, a process referred to as an oxidative burst. In patients suffering from the condition known as paroxysmal nocturnal haemoglobinuria (PNH), the synthesis of GPI anchors is blocked in haematopoietic cells which are therefore unable to express GPI-linked proteins on their surface. In severe cases, over 90% of monocytes lack membrane-bound CD14, though normal levels of the soluble form of the receptor-sCD14-are found in the serum. Despite this lack of membrane-bound CD14, monocytes from PNH patients can respond to low concentrations of LPS. Here we show that the LPS-induced oxidative burst of these PNH monocytes requires a component present in serum. The serum-dependent activation can be inhibited by monoclonal antibodies to CD14, can be removed from the serum by passage over a matrix to which an anti-CD14 antibody has been bound, and the depleted serum can be reconstituted by the addition of either purified natural or purified recombinant soluble CD14. We conclude that an LPS-dependent oxidative burst in PNH monocytes can be mediated by soluble CD14.
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PMID:Human monocytes lacking the membrane-bound form of the bacterial lipopolysaccharide (LPS) receptor CD14 can mount an LPS-induced oxidative burst response mediated by a soluble form of CD14. 871 58

Helicobacter pylori and Porphyromonas gingivalis are gram-negative bacteria associated with chronic inflammatory diseases. These bacteria possess lipopolysaccharides (LPSs) that are able to activate human monocytes to produce tumor necrosis factor alpha but fail to activate human endothelial cells to express E-selectin. With Escherichia coli LPS, tumor necrosis factor alpha activation requires membrane-bound CD14 and E-selectin expression requires soluble CD14 (sCD14). Therefore, the ability of H. pylori and P. gingivalis LPSs to transfer to and bind sCD14 was examined by using immobilized recombinant sCD14 and human serum or recombinant LPS-binding protein (LBP). H. pylori and P. gingivalis LPSs were transferred to sCD14 when serum or LBP was present. However, the transfer of these LPSs to CD14 in serum was significantly slower than the transfer of E. coli LPS. Quantitation of the transfer rates by Michaelis-Menten kinetics yielded K(m) values of 6 and 0.1 nM for H. pylori and E. coli LPSs, respectively. The amount of P. gingivalis LPS required to obtain half-maximum binding to CD14 was approximately 10-fold greater than the amount of E. coli LPS required. The slower transfer rates displayed by these LPSs can be explained by the poor binding to LBP observed in direct binding assays. These results are consistent with the proportionately lower ability of these LPSs to activate monocytes compared with E. coli LPS. However, the ability of H. pylori and P. gingivalis LPSs to bind LBP and transfer to sCD14 demonstrates that the lack of endothelial cell CD14-dependent cell activation by these LPSs occurs distal to sCD14 binding.
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PMID:Helicobacter pylori and Porphyromonas gingivalis lipopolysaccharides are poorly transferred to recombinant soluble CD14. 875 5

We have previously reported that linomide, a quinoline-3-carboxamide, has antitumor effects against prostatic cancers in vivo through its ability to inhibit tumor angiogenesis. Subsequently, we reported that linomide inhibits several steps in the process of angiogenesis, including direct effects on endothelial cell proliferation and their chemotactic migration and invasion. Besides these direct effects, linomide's antiangiogenic activity also involves indirect effects secondary to inhibition of tumor infiltration of macrophages and their ability to secrete the angiogenic factor tumor necrosis factor-alpha (TNF-alpha). The current studies were conducted to gain insight into the mechanism by which linomide inhibits macrophage TNF-alpha secretion. The virally transformed RAW 264.7 mouse macrophage cell line was used as a model system. Chronic in vitro exposure (7 days) to 81-650 microM linomide is cytostatic to RAW cells. Such chronic exposure to linomide significantly decreased (P < 0.05) RAW cells' baseline ability to secrete TNF-alpha and also their ability to up-regulate TNF-alpha secretion in response to lipopolysaccharide (LPS) challenge. Ribonuclease protection assays demonstrated that linomide's ability to inhibit baseline and LPS-challenged TNF-alpha secretion is not functioning at the mRNA level, because steady-state levels of TNF-alpha mRNA do not change in response to linomide. Linomide's ability to inhibit TNF-alpha secretion is not associated with an increase in cell-associated TNF-alpha levels. Immunoprecipitation experiments demonstrated that linomide did not inhibit the normal proteolytic processing of the initial 26 kDa plasma membrane-bound TNF-alpha to the secreted 17 kDa soluble form. These results demonstrate that linomide inhibits TNF-alpha secretion by inhibition of the synthesis of the TNF-alpha protein. Linomide's ability to inhibit TNF-alpha protein synthesis is not due to an inhibition of general protein synthesis or secretion and is not mediated via a change in cyclic adenosine monophosphate levels.
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PMID:The antiangiogenic agent linomide inhibits tumor necrosis factor-alpha secretion via inhibition of its synthesis. 882 87

The intercellular adhesion molecule (ICAM) 1 is an Ig-like cell adhesion molecule expressed by several cell types, including leukocytes and endothelial cells. It can be induced in a cell-specific manner by several cytokines, for example, tumor necrosis factor-alpha, interleukin-1, and interferon-gamma, and inhibited by glucocorticoids. Its ligands are the membrane-bound integrin receptors LFA-1 and Mac-1 on leukocytes, CD43, the soluble molecule fibrinogen, the matrix factor hyaluronan, rhinoviruses, and Plasmodium falciparum malaria-infected erythrocytes. ICAM-1 expression is predominantly transcriptionally regulated. The ICAM-1 promoter contains several enhancer elements, among them a novel kappa B element which mediates effects of 12-O-tetradecanoylphorbol-13-acetate, interleukin-1, lipopolysaccharide, tumor necrosis factor-alpha, and glucocorticoids. Expression regulation is cell specific and depends on the availability of cytokine/hormone receptors, signal transduction pathways, transcription factors, and posttranscriptional modification. ICAM-1 plays a role in inflammatory processes and in the T-cell mediated host defense system. It functions as a costimulatory molecule on antigen-presenting cells to activate MHC class II restricted T-cells, and on other cell types in association with MHC class I to activate cytotoxic T-cells. ICAM-1 on endothelium plays an important role in migration of (activated) leukocytes to sites of inflammation. ICAM-1 is shed by the cell and detected in plasma as sICAM-1. Regulation and significance of sICAM-1 are as yet unclear, but sICAM-1 is increased in many pathological conditions. ICAM-1 may play a pathogenetic role in rhinovirus infections. Derangement of ICAM-1 expression probably contributes to the clinical manifestations of a variety of diseases, predominantly by interfering with normal immune function. Among these are malignancies (e.g., melanoma and lymphomas), many inflammatory disorders (e.g., asthma and autoimmune disorders), atherosclerosis, ischemia, certain neurological disorders, and allogeneic organ transplantation. Interference with ICAM-1 leukocyte interaction using mAbs, soluble ICAM-1, antisense ICAM-1 RNA, and in the case of melanoma mAb-coupled immunotoxin, may offer therapeutic possibilities in the future. Integration of knowledge concerning membrane-bound and soluble ICAM-1 into a single functional system is likely to contribute to elucidating the immunoregulatory function of ICAM-1 and its pathophysiological significance in various disease entities.
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PMID:Intercellular adhesion molecule-1. 883 67


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