Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.3 (phospholipase C)
18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human blood monocytes were activated by bacterial lipopolysaccharide endotoxin (LPS) (10 ng/ml) for cytotoxicity of WEHI-164 mouse fibrosarcoma cells, determined by release of 51Cr from WEHI-164 tumour cells incubated with monocyte supernatants. The chemotactic peptide N-formylmethionyl-leucyl-phenylalanine (FMLP) augmented LPS-induced cytotoxicity but had no effect alone. FMLP but not LPS stimulated phospholipase C (PLC), determined by the release of [3H]inositol phosphates. Addition of tumour promoter and protein kinase C stimulant, phorbol-12-myristate-13-acetate (PMA) at concentrations of 3 x 10(-10) M to 3 x 10(-9) M, resulted in an augmentation of 30-200% in LPS-evoked cytotoxicity. The effects of FMLP and PMA, like the effect of LPS alone, were completely blocked by antibody to recombinant human tumour necrosis factor-alpha (TNF-alpha), indicating that cytotoxicity induced by LPS, FMLP, and PMA were due solely to TNF release. Concentrations of PMA greater than 3 x 10(-9) M caused inhibition of TNF release. Okadaic acid (20 ng/ml), an inhibitor of phosphatases I and IIa, augmented the effects of LPS and the stimulatory effects of low levels of PMA, suggesting that phosphorylation was important in the actions of both LPS and PMA. The effects of LPS and of low levels of PMA were augmented by the protein kinase C (PKC) inhibitors H-7 (10-30 microM), staurosporine (2-10 nM) and calphostin C (0.1 microM). Higher concentrations of the inhibitors prevented LPS-evoked TNF release and its augmentation by low levels of PMA. However, they did not prevent the inhibition by high levels of PMA. One possible explanation for the results is that different isozymes of PKC may mediate the stimulatory as compared to the inhibitory effects of PKC on TNF production.
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PMID:Paradoxical stimulation and inhibition by protein kinase C modulating agents of lipopolysaccharide evoked production of tumour necrosis factor in human monocytes. 162

Decay accelerating factor (DAF) is a cell-surface phosphatidylinositol-anchored protein that protects the cell from inadvertent complement attack by binding to and inactivating C3 and C5 convertases. We have measured DAF on human umbilical vein endothelial cells (HUVEC) by immunoradiometric assay after its removal by phosphatidylinositol-specific phospholipase C or Nonidet P-40 detergent extraction and have previously demonstrated that DAF synthesis can be stimulated by phorbol ester activation of protein kinase C. We now report that although stimulation (4-48 h) of HUVEC with various cytokines, including TNF, IL-1, and IFN-gamma, did not alter DAF levels, wheat germ agglutinin (WGA) (5-50 micrograms/ml), a lectin specific for binding N-acetyl neuraminic acid and N-acetyl glucosamine residues, increased DAF levels fivefold when incubated with HUVEC for 12 to 24 h. The lectins Con A and PHA also stimulated DAF expression twofold, whereas a number of others including Ulex europaeus, Bandeiraea simplicifolia lectin I, and Ricinus communis agglutinin I, which bind to endothelial cells, were inactive. The increase in DAF by WGA was inhibited by N-acetyl glucosamine (10-50 mM) but by neither N-acetyl neuraminic acid nor removal of surface N-acetyl neuraminic acid with neuraminidase. However, succinylated WGA, which has unaltered affinity for N-acetyl glucosamine but not longer binds N-acetyl neuraminic acid, was inactive. These data suggest that the binding of WGA to sugar residues alone is not sufficient to trigger DAF expression and that occupation of additional, specific sites are required. The increase in DAF levels on HUVEC was blocked by inhibitors of RNA and protein synthesis. We conclude that continuous occupation by WGA of specific binding sites on HUVEC triggers events leading to DAF synthesis. This unique, long term stimulation of endothelial cells by lectins may be relevant to cell:cell interactions at the endothelium.
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PMID:Wheat germ agglutinin and other selected lectins increase synthesis of decay-accelerating factor in human endothelial cells. 171 83

Recombinant human tumor necrosis factor (rh TNF) when administered intravenously together with the phospholipase C inhibitor tricyclodecan-9-yl-xanthogenate (D609) and lauric acid (C12), leads to the partial regression of various human tumor transplants in athymic mice. Extensive necrosis occurred after a single intravenous infusion, with no detectable side effects. TNF-mediated cytotoxicity was found to be correlated with the depletion of energy in HeLa cells. The activity of rh TNF was enhanced by the absence of glucose, while it was reduced by addition of extraneous ATP. In the presence of rh TNF, D609, and C12, cellular energy metabolism was almost completely switched to glycolysis. Under these conditions the cytocidal activity of rh TNF on HeLa cells was amplified at least 60-fold.
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PMID:Tumor necrosis factor induces necrosis of human carcinoma xenografts in the presence of tricyclodecan-9-yl-xanthogenate and lauric acid. 214 Oct 5

The mechanism of tumour necrosis factor-mediated cytotoxicity was investigated by using various inhibitors of arachidonic acid metabolism. Phospholipase A2 inhibitors with different modes of action interfered with the cytotoxic action of TNF, whereas phospholipase C inhibitors did not. Neither cyclooxygenase nor lipoxygenase-blockers had a significant effect on TNF action. Experiments with scavengers of toxic oxygen radicals gave ambiguous results. The data obtained suggest the involvement of phospholipase A2 and arachidonic acid in the cytotoxic mechanism of TNF, but the exact role of these molecules is, however, still to be determined.
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PMID:Reduced tumour necrosis factor-induced cytotoxicity by inhibitors of the arachidonic acid metabolism. 312 40

Rabbit TNF has been purified 2000-fold by a series of salt precipitations, gel filtrations, ion exchange chromatography, and lectin affinity chromatography to a single species on SDS-polyacrylamide gel electrophoresis (SDS-PAGE). TNF activity could be recovered from nondenaturing gel systems and has been shown to be an alpha-globulin with an isoelectric point of 5.1. The m.w. was estimated to be 68,000 d by SDS-PAGE, 55,000 by gel filtration, and 52,000 by glycerol gradient centrifugation. TNF activity was stable over the pH range of 6 to 10 and was relatively heat stable, not being inactivated at 70 degrees C for 1 hr. TNF activity was pronase sensitive, but relatively trypsin resistant. Neuraminidase and phospholipase C treatment did not destroy TNF activity. Partially purified TNF was still capable of eliciting hemorrhagic necrosis in susceptible tumors. Crude TNF serum had an interferon titer of 3000 U, whereas the partially purified sample had a titer of <30 U.
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PMID:Purification and physico-chemical characterization of rabbit tumor necrosis factor. 699 83

Tumor necrosis factor alpha (TNF alpha), interleukin 1 beta (IL-1 beta), and endotoxin (LPS) are potent pro-inflammatory mediators which induce multiple and diverse biological responses in a wide variety of cell types. However, these pro-inflammatory mediators also have significant overlap and redundancy in their biological effects. This suggests that there is significant diversity in second messenger signal transduction systems induced by these stimuli to explain the diversity in biological responses, as well as significant redundancy. Here we show that one such second messenger common to several proinflammatory stimuli may be phosphatidic acid (PA). Intracellular PA species, which may have intracellular signaling functions, are rapidly induced in P388 monocytic leukemia cells by TNF alpha, IL-1 beta, or LPS. These PA species vary according to the bond type (i.e., sn-1 ester vs. ether vs. vinyl ether), acyl chain length, and the degree of saturation in the sn-1 and sn-2 positions. Although PA itself may have direct second messenger activities, many of the PA species induced are converted to diacylglycerol species (DG), which are structurally distinct from the DGs generated by phosphatidylcholine-specific phospholipase C (PC-PLC). Lisofylline [(R)-1-(5-hydroxyhexyl)-3,7-dimethylxanthine; LSF] selectively inhibits generation of selected species of PA in P388 cells induced by TNF alpha, IL-1 beta or LPS. TNF alpha-induced sphingomyelin hydrolysis, PLC-mediated PC hydrolysis, and DG kinase-mediated PA formation or TNF alpha-induced NF-kappa B activation and apoptosis are not inhibited by LSF. LSF has a marked protective effect in a variety of acute inflammatory animal models that may be due to inhibition of this shared second messenger pathway involving PA.
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PMID:Potential role for phosphatidic acid in mediating the inflammatory responses to TNF alpha and IL-1 beta. 770 34

Recent evidence demonstrates that the protein kinase C zeta (zeta PKC) isoform is required for the activation of nuclear factor kappa B (NF-kappa B) and mitogenic signaling in Xenopus oocytes and mammalian cells. The mechanism whereby zeta PKC regulates NF-kappa B most probably involves the activation of a putative I kappa B kinase of molecular mass approximately 50 kDa, which phosphorylates and inactivates I kappa B. Tumor necrosis factor alpha (TNF alpha) and interleukin-1, besides activating the phospholipase C-mediated breakdown of phosphatidylcholine, also generate ceramide, which is produced by stimulation of sphingomyelin hydrolysis. We show here that exogenous addition of sphingomyelinase (SMase) to NIH-3T3 fibroblasts transactivates a kappa B-dependent chloramphenicol acetyltransferase reporter plasmid, to an extent similar to that produced by TNF alpha or phosphatidylcholine/phospholipase C. More importantly, the ability of SMase to stimulate this parameter is severely impaired by transfection of a zeta PKC kinase-defective dominant negative mutant, which suggests a critical role of zeta PKC in SMase signaling. In keeping with this notion, we also demonstrate here that zeta PKC is activated in vitro by ceramide and in vivo by treatment of NIH-3T3 fibroblasts with SMase.
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PMID:Protein kinase C zeta isoform is critical for kappa B-dependent promoter activation by sphingomyelinase. 803 80

Treatment of neonatal rat cardiomyocytes for 72 h in the presence of tumor necrosis factor alpha (TNF alpha) (10 U/ml) lead to a decrease in basal and alpha 1-adrenoceptor-induced formation of the calcium-mobilizing second messenger inositol trisphosphate (IP3) and its metabolites, IP2 and IP1, by 35 and 26%, respectively. The synthesis of phosphatidylinositol bisphosphate (PIP2), the substrate of PI-specific phospholipase C, was decreased by 45% following the TNF alpha (10 U/ml) exposure. Time courses of TNF alpha (10 U/ml)-induced alterations in rat cardiomyocytes showed a parallel decline of basal inositol phosphate formation and PIP2 synthesis suggesting that the decrease in inositol phosphate formation was due to the reduction in PIP2 synthesis. As the TNF alpha-induced decrease of PIP2 synthesis was associated with a decreased synthesis of the phospholipid phosphatidylinositol (PI), the precursor of PIP2, by 33%, the decreased availability of PIP2 is apparently, at least in part, the result of the decreased synthesis of PI. As an apparent functional consequence of the decrease in IP3 formation following the TNF alpha exposure, the alpha 1-adrenoceptor-mediated induction of arrhythmias by 100 mumol/l noradrenaline + 10 mumol/l timolol was abolished in TNF alpha-pretreated rat cardiomyocytes. To investigate one of the possible mechanisms of the TNF alpha-induced decrease of PIP2 formation, the effect of TNF alpha pretreatment on glycerol-3-phosphate dehydrogenase (GDH), a key enzyme of lipogenesis, was studied: Exposure of the rat cardiomyocytes for 72 h to TNF alpha induced a concentration-dependent decrease in GDH activity by maximally 55%.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Tumor necrosis factor alpha decreases inositol phosphate formation and phosphatidylinositol-bisphosphate (PIP2) synthesis in rat cardiomyocytes. 817 May 1

We have previously reported that LiCl increases considerably the cytotoxic activity of TNF towards some transformed cell lines such as L929. Here we show that treatment of these cell lines with the combination of TNF and LiCl leads to the prolonged accumulation of inositol monophosphate, inositol bisphosphate, and inositol trisphosphate, whereas treatment with TNF or LiCl alone did not. In contrast, both a LiCl-unresponsive TNF-sensitive cell line and TNF-resistant cell lines did not respond with increased accumulation of inositol phosphates (IPn) upon treatment with the combination of TNF and LiCl. Furthermore, the combination of TNF and LiCl induced a transient increase in cytidine diphosphate-diacylglycerol in L929 cells. Increased IPn and cytidine diphosphate-diacylglycerol accumulation preceded the onset of cell killing by approximately 1 h. TNF-mediated cytotoxicity and TNF-induced IPn accumulation were equally sensitive to inhibition by the phospholipase inhibitor neomycin and to stimulation by the protein kinase inhibitor staurosporine. Characterization of the inositol bisphosphate isomers by HPLC analysis revealed that the TNF + LiCl-induced increase in IPn levels was due to activation of a phospholipase C and not of a phospholipase D. In contrast to TNF, several other cytotoxic agents did not increase IPn production upon application in the presence of LiCl. The TNF + LiCl-induced increase in inositol triphosphate suggests a role for intracellular Ca2+ mobilization in TNF action. Moreover, several agents that lower the intracellular Ca2+ concentration inhibited TNF cytotoxicity. In conclusion, our data provide evidence that TNF cytotoxicity and its enhancement by LiCl are mediated by increased IPn accumulation resulting in Ca2+ mobilization.
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PMID:Enhancement of tumor necrosis factor cytotoxicity by lithium chloride is associated with increased inositol phosphate accumulation. 839 97

Fas antigen/Apo-1 (Fas) and the p55 tumor necrosis factor receptor (TNF-R) are two related cell surface molecules that induce apoptosis in susceptible cells. With regard to their cytoplasmic homology region, we investigated whether Fas like the TNF-R activates nuclear factor kappa B (NF-kappa B), using human SV80 fibroblasts transfected with the cDNA encoding human Fas. In this cell line Fas mobilizes the p50/p65 heterodimeric form of NF-kappa B and induces interleukin-6 (IL-6) production. Compared to NF-kappa B activation via the TNF-R differences in kinetics and signal intensity were observed. Peak activation occurred 2 hr after Fas compared to 1 hr after TNF-R stimulation. Furthermore, when equitoxic concentrations of anti-Fas antibody and TNF were applied, TNF triggered a stronger NF-kappa B response. Studies using inhibitors of signal transduction suggest that both receptors mediate NF-kappa B activation via similar routes: D609, an inhibitor of the phospatidylcholine-specific phospholipase C, had an inhibitory effect, while the protein kinase C inhibitor staurosporine had an enhancing effect on both Fas and TNF-R induced NF-kappa B mobilization. Interestingly, D609 had no influence on Fas and TNF-R mediated cytotoxicity arguing against an involvement of NF-kappa B in the cell death pathway triggered by these receptors. This is the first indication that Fas may activate genes via NF-kappa B and may thus in addition to its role as a cell death inducing receptor serve a much broader range of biological functions.
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PMID:Fas/Apo-1 activates nuclear factor kappa B and induces interleukin-6 production. 859 71


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