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)

1. In this study, the abilities of PC12 cells to synthesize and degrade kinins were investigated. Kinin formation was assessed as kinin and kininogen content of cells and supernatants in serum-free incubations by use of a bradykinin-specific radioimmunoassay. Expression of kininogen mRNA was demonstrated by reverse-transcriptase PCR. Kinin degradation pathways of intact PC12 cells were characterized by identification of the kinin fragments generated from tritiated bradykinin either in the absence or presence of the angiotensin I-converting enzyme inhibitor ramiprilat. 2. Kinin immunoreactivity in the supernatant of PC12 cell cultures accumulated in a time-dependent fashion during incubations in serum-free media. This effect was solely due to de novo synthesis and release of kininogen (35 pg bradykinin h-1 mg-1 protein) since it could be suppressed by cycloheximide. Continuous synthesis of kininogen was a specific property of PC12 cells, as it was not observed in cultured macro- or microvascular endothelial cells. PC12 cells contained only minor amounts of stored kininogen. The rate of kininogen synthesis was not affected by ramiprilat, bacterial lipopolysaccharide, nerve growth factor or dexamethasone, but was stimulated 1.4 fold when cells were pretreated for 1 day with 1 microM desoxycorticosterone. 3. By use of cDNA probes specific for kininogen subtype mRNAs, expression of low-molecular-weight kininogen and T-kininogen in PC12 cells was confirmed. Expression of high molecular weight kininogen mRNA was also shown, though only at the lowest limit of detection of the assay. 4. Degradation of tritiated bradykinin by PC12 cells occurred with a half-life of 48 min resulting in the main fragments [1-7]- and [1-5]-bradykinin. The degradation rate of bradykinin decreased to 15% in the presence of ramiprilat (250 nM). Apart from angiotensin I-converting enzyme direct cleavage of bradykinin to [1-7]- and [1-5]-bradykinin still occurred under this condition as a result of additional kininase activities. 5. Along with previous findings of B2-receptor-mediated catecholamine release, these results now confirm the hypothesis that a cellular kinin system is expressed in PC12 cells. The presence of such a system may reflect a role of kinins as local neuromodulatory mediators in the peripheral sympathetic system.
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PMID:Synthesis of kininogen and degradation of bradykinin by PC12 cells. 942 2

Expression of neurotrophins in pure microglia cultured from embryonic rat brain and the effects of lipopolysaccharide (LPS) on the expression were investigated. In untreated cultures, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin (NT)-4/5 mRNAs were detected by use of reverse transcriptase-polymerase chain reaction but NT-3 mRNA was not. LPS stimulation caused a marked increase in BDNF mRNA expression in addition to a slight increment of the NT-4/5 mRNA level; however, the NGF mRNA level was not affected. LPS also increased BDNF-like immunoreactivity in cultured microglia, an action consistent with an elevation of BDNF mRNA. These results demonstrate that LPS stimulates synthesis of BDNF and probably NT-4/5, specific ligands for tyrosine kinase receptor TrkB, suggesting that activated microglia, which appear in the damaged brain, participate in neuronal regeneration via production of such neurotrophins.
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PMID:Lipopolysaccharide enhances synthesis of brain-derived neurotrophic factor in cultured rat microglia. 945 17

Microglia/brain macrophages activated in response to injury, infection, or inflammation of the central nervous system (CNS) mediate both neurotoxic and neurotrophic activities. Although the cytotoxic effects of microglia have been analyzed in detail, little is known about the signaling pathways involved in microglial neurotrophin expression. Using purified rat microglial cell cultures, the effects of inflammatory agents such as lipopolysaccharide (LPS) on microglial nerve growth factor (NGF) expression were studied. Application of LPS (0.1-100 ng/ml) induced a rapid (2-4 h), dose-dependent increase in NGF mRNA expression followed by enhanced release of NGF protein within 24 h. To determine whether the transcription factor NF-kappaB, known to be stimulated in activated microglia, is involved in inflammatory mediator-induced NGF expression, we used the NF-kappaB inhibitor pyrrolidine dithiocarbamate (PDTC). Addition of PDTC (100 microM) to microglia completely abolished LPS-induced NGF synthesis, suggesting a key role for NF-kappaB in microglial NGF expression by inflammatory mediators. In conclusion, NF-kappaB-controlled NGF expression by activated microglia appears to contribute to the cross-talk between the immune and nervous systems during inflammation in the CNS.
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PMID:NF-kappaB modulates lipopolysaccharide-induced microglial nerve growth factor expression. 951 72

Exposure of neuronal PC12 cells, differentiated by nerve growth factor, to tumor necrosis factor-alpha (TNF-alpha) and bacterial lipopolysaccharide (LPS) resulted in de novo synthesis of inducible nitric oxide synthase (iNOS) mRNA and protein with an increase up to 24 h. Brain NOS expression was unaffected. The induction of iNOS in differentiated PC12 cells was associated with cell death characterized by features of apoptosis. The NOS inhibitors N-monomethylarginine, aminoguanidine, and 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine.HCl prevented TNF-alpha/LPS-induced cell death and DNA fragmentation, suggesting that the TNF-alpha/LPS-induced cell death is mediated by iNOS-derived NO. This hypothesis is supported by the finding that addition of L-arginine, which serves as a precursor and limiting factor of enzyme-derived NO production, potentiated TNF-alpha/LPS-induced loss of viability.
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PMID:Induction of nitric oxide synthase and nitric oxide-mediated apoptosis in neuronal PC12 cells after stimulation with tumor necrosis factor-alpha/lipopolysaccharide. 964 54

We reported previously that stem cell factor (SCF) is produced mainly by neurons and that its receptor (c-kitR), encoded by the protooncogene c-kit, is expressed in microglia, suggesting that SCF/c-kitR signaling may be involved in neuron-microglia interactions. We now report that SCF supports microglial survival in cultures, maintains them in process-bearing morphology, and inhibits microglial proliferation induced by colony stimulating factor-1. SCF potentiates microglial expression of the mRNAs of nerve growth factor, brain-derived neurotrophic factor and ciliary neurotrophic factor, and downregulates microglial expression of the inflammation-associated cytokines, tumor necrosis factor-a (TNF-alpha), and interleukin-1beta (IL-1beta). SCF potentiates lipopolysaccharide-stimulated, but attenuates interferon-gamma TFNalpha mediated expression of the mRNAs of IL-1beta and TNF-alpha. The SCF-induced expression of neurotrophin mRNAs is enhanced by the addition of lipopolysaccharide (LPS) but is reduced by IFNgamma. The interactions between SCF and LPS or IFNgamma in the regulation of inflammation-associated cytokine gene expression are accompanied by the differential regulation of c-kitR in microglia. These observations suggest that SCF/c-kitR signaling modulates microglial activity.
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PMID:Modulation of microglia by stem cell factor. 967 Sep 90

Although the physiological role of neurotrophins in neuronal development and survival has been extensively investigated, their role in glial cell physiology remains to be elucidated. In the present study, we investigated the effects of neurotrophins on cultured microglia from newborn rat brain. All of the neurotrophins tested nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4), increased the secretion of plasminogen and urokinase type-plasminogen activator and specific activity of acid phosphatase, but suppressed the release of constitutively-produced and lipopolysaccharide-stimulated nitric oxide (NO) from microglia. The reverse transcription-polymerase chain reaction, immunocytochemical staining, and Western blotting revealed that cultured microglia express Trk A, B, and C, and low-affinity NGF receptor, LNGFRp75. Neurotrophin was found to phosphorylate Trk A and B, and the neurotrophin-induced enhancement of plasminogen-secretion was suppressed by protein kinase inhibitor, K252a. Furthermore, neurotrophins caused an activation of transcription factor, NF-kappaB. These results indicate that the neurotrophin family regulate the function of microglia through Trk and/or LNGFRp75-mediated signal transduction.
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PMID:Neurotrophins regulate the function of cultured microglia. 977 79

Activated brain microglia play a pivotal role in inflammatory and degenerative disorders, mediating immune function and producing toxic and trophic agents. We previously reported that microglia express neurotrophins and that neurotrophin-3 (NT-3) increases microglial proliferation and phagocytosis, processes associated with cellular activation. However, mechanisms regulating responsiveness to NT-3 and expression of NT-3 in activated microglia remain undefined. To investigate mechanisms governing microglial responsiveness to neurotrophins, we determined whether microglia express trk C, the high-affinity receptor for NT-3, and whether the inflammatory agent lipopolysaccharide (LPS) regulates receptor expression. Trk C mRNA was expressed by unstimulated microglia, and both trk C mRNA and protein were dramatically increased by LPS. In contrast, expression of trk A, the high-affinity receptor for nerve growth factor (NGF), was down-regulated by LPS. Consequently, the same stimulus differentially influences responsiveness of microglia to distinct trophins. In addition, LPS induced microglial NT-3 expression, suggesting that increases in both the ligand and receptor modulate NT-3 effects on microglia. Regulation was specific, since brain-derived neurotrophic factor (BDNF) and NT-4/5 expression were unaltered by LPS. In sum, our findings raise the possibility that microglial NT-3 regulates their response to inflammation through autocrine mechanisms: LPS modulates both trk C and NT-3 which, in turn, regulate microglial function.
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PMID:Lipopolysaccharide differentially regulates microglial trk receptor and neurotrophin expression. 977 55

In the present study, we found that S-nitroso-N-acetyl-DL-penicillamine, a spontaneous nitric oxide (NO) generator, dose-dependently inhibited basal nerve growth factor (NGF) release from mixed glial cells. To elucidate the function of endogenous NO in the regulation of NGF release, the mixed glial cells were stimulated with lipopolysaccharide (LPS) or LPS plus interferon-gamma (IFNgamma). The results showed that LPS alone induced NGF release and moderate NO production. However, costimulation with LPS plus IFNgamma greatly enhanced NO production but significantly suppressed LPS-induced NGF release. When N(G)-monomethyl-L-arginine, an NOS inhibitor, was added to the culture, the suppression of NGF release by IFNgamma was significantly reduced. Quantitative reverse transcription-polymerase chain reaction demonstrated S-nitroso-N-acetyl-DL-penicillamine was also able to inhibit the LPS-induced NGF mRNA expression. To understand the different contributions of astroglia and microglia to this phenomenon, both cell types were purified. We found purified astroglia produced high amounts of NGF but low amounts of NO. However, purified microglia produced a large amount of NO but very low amounts of NGF after stimulation with LPS or LPS plus IFNgamma. Our data also indicated the second messenger cyclic GMP, but not cyclic AMP, was able to inhibit basal NGF release. In vivo experiments confirmed that NGF protein level was significantly enhanced in rats treated with L-N(omega)-nitro-arginine methyl ester and in endothelial NO synthase mutant mice. Taken together, we conclude NO derived mainly from microglia down-regulates NGF release from astroglia at the transcriptional level by stimulating cyclic GMP pathway.
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PMID:Regulation of nerve growth factor release by nitric oxide through cyclic GMP pathway in cortical glial cells. 1041 53

Evidence for the role of the cannabimimetic fatty acid derivatives (CFADs), i.e. anandamide (arachidonoylethanolamide, AEA), 2-arachidonoylglycerol (2-AG) and palmitoylethanolamide (PEA), in the control of inflammation and of the proliferation of tumor cells is reviewed here. The biosynthesis of AEA, PEA, or 2-AG can be induced by stimulation with either Ca(2+) ionophores, lipopolysaccharide, or platelet activating factor in macrophages, and by ionomycin or antigen challenge in rat basophilic leukemia (RBL-2H3) cells (a widely used model for mast cells). These cells also inactivate CFADs through re-uptake and/or hydrolysis and/or esterification processes. AEA and PEA modulate cytokine and/or arachidonate release from macrophages in vitro, regulate serotonin secretion from RBL-2H3 cells, and are analgesic in some animal models of inflammatory pain. However, the involvement of endogenous CFADs and cannabinoid CB(1) and CB(2) receptors in these effects is still controversial. In human breast and prostate cancer cells, AEA and 2-AG, but not PEA, potently inhibit prolactin and/or nerve growth factor (NGF)-induced cell proliferation. Vanillyl-derivatives of anandamide, such as olvanil and arvanil, exhibit even higher anti-proliferative activity. These effects are due to suppression of the levels of the 100 kDa prolactin receptor or of the high affinity NGF receptors (trk), are mediated by CB(1)-like cannabinoid receptors, and are enhanced by other CFADs. Inhibition of adenylyl cyclase and activation of mitogen-activated protein kinase underlie the anti-mitogenic actions of AEA. The possibility that CFADs act as local inhibitors of the proliferation of human breast cancer is discussed here.
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PMID:Cannabimimetic fatty acid derivatives in cancer and inflammation. 1078 41

In this study, we examined the expression of nerve growth factor (NGF) and its receptors in mouse macrophages and the mechanisms involved in the effect of NGF on tumor necrosis factor (TNF)-alpha production. Macrophages expressed NGF and the NGF receptors TrkA and p75. Treatment of J744 cells or peritoneal macrophages with NGF induced a large increase in the production of TNF-alpha. In addition, NGF induced the secretion of nitric oxide in interferon-gamma-treated J774 cells or lipopolysaccharide-treated peritoneal macrophages. The induction of TNF-alpha production by NGF was blocked by K252a, an inhibitor of the TrkA receptor. NGF induced phosphorylation and activation of extracellular signal-regulated kinase, Erk1/Erk2 and c-Jun amino-terminal kinase, whereas it did not induce phosphorylation of p38 mitogen-activated protein kinase. Inhibition of the MAP kinase-Erk kinase pathway with PD 098059 decreased the secretion of TNF-alpha by NGF. Our results suggest that NGF has an important role in the activation of macrophages during inflammatory responses via activation of mitogen-activated protein kinases.
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PMID:Nerve growth factor regulates TNF-alpha production in mouse macrophages via MAP kinase activation. 1140 90


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