Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Prolactin (PRL) induces cell proliferation and cell differentiation through the well-known mitogen-activated protein kinases (MAPKs) and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathways, depending on the cell line. MAPKs play a central role in signaling transduction mechanisms that transmit mitogenic or differentiation signals from an activated receptor to the intracellular machinery. All of the cytokine receptors that activate the JAK/STAT pathway also activate the MAPK pathway. The aim of the present study was to delineate the signal pathways implicated in IL-8 release by THP-1 cells, pretreated with PRL, after stimulation with either lipopolysaccharide (LPS) or porins from Salmonella enterica serovar Typhimurium. PRL activates the JAK2/STAT1-3 signaling pathway, while LPS or porins from S. enterica serovar Typhimurium does not induce any phosphorylation of this pathway. However, in THP-1 cells, the combination of PRL followed by either S. enterica serovar Typhimurium LPS or porins produced a greater MEK1-MEK2/MAPKs activation response than treatment with PRL alone. Similarly, PRL pretreatment of THP-1 cells resulted in an increase in IL-8 release in response to stimulation with either LPS or porins. This additive effect on IL-8 release was reduced when the cells were also treated with PD-098059, a selective inhibitor of the MEK1 activator and the MAPK cascade, or SB203580, a specific inhibitor of the p38 pathway, or AG490, a specific JAK/STAT pathway inhibitor, providing evidence that there are different signal pathways activated which have a cumulative effect.
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PMID:Prolactin modulates IL-8 production induced by porins or LPS through different signaling mechanisms. 1556 16

High levels of the triacylglycerol-rich lipoproteins, very low density lipoprotein (VLDL) and intermediate density lipoprotein (IDL) have been identified as independent risk factors for coronary heart disease, and inflammation is thought to contribute to atherosclerosis and its complications. To understand how dyslipidemia promotes inflammation, we have characterised the effects of VLDL treatment on production of tumor necrosis factor-alpha (TNF) by human monocyte-derived macrophages. VLDL strongly potentiated lipopolysaccharide (LPS)-induced expression of TNF mRNA and secretion of TNF protein. VLDL activated mitogen-activated protein kinase-ERK kinase 1/2 (MEK1/2), and potentiated LPS-induced MEK1/2 activation. The MEK1/2 inhibitor U0126 strongly diminished TNF expression, indicating that MEK1/2 plays a central role in the regulation of TNF expression. VLDL did not activate transcription factors NF-kappaB and PPAR-gamma, but it activated AP-1 at least as potently as LPS, and potentiated LPS-induced activation of AP-1. The inhibitor U0126 completely prevented this potentiation. Inhibition of AP-1 by decoy oligonucleotides abolished potentiation of TNF secretion by VLDL. In conclusion, VLDL treatment potentiates TNF expression in macrophages by activation of MEK1/2 and AP-1. These findings suggest that triacylglycerol-rich lipoproteins are involved in inflammatory processes associated with atherosclerosis.
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PMID:Very low density lipoprotein potentiates tumor necrosis factor-alpha expression in macrophages. 1577 38

The effects of anthocyanidins, the aglycon nucleuses of anthocyanins widely occurring in reddish fruits and vegetables, on the expression of cyclooxygenase-2 (COX-2) were investigated in lipopolysaccharide (LPS)-activated murine macrophage RAW264 cells. Of five anthocyanidins, delphinidin and cyanidin inhibited LPS-induced COX-2 expression, but pelargonidin, peonidin and malvidin did not. The structure-activity relationship suggest that the ortho-dihydroxyphenyl structure of anthocyanidins on the B-ring appears to be related with the inhibitory actions. Delphinidin, the most potent inhibitor, caused a dose-dependent inhibition of COX-2 expression at both mRNA and protein levels. Western blotting analysis indicated that delphinidin inhibited the degradation of IkappaB-alpha, nuclear translocation of p65 and CCAAT/enhancer-binding protein (C/EBP)delta and phosphorylation of c-Jun, but not CRE-binding protein (CREB). Moreover, delphinidin suppressed the activations of mitogen-activated protein kinase (MAPK) including c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and p38 kinase. MAPK inhibitors (U0126 for MEK1/2, SB203580 for p38 kinase and SP600125 for JNK) specifically blocked LPS-induced COX-2 expression. Thus, our results demonstrated that LPS-induced COX-2 expression by activating MAPK pathways and delphinidin suppressed COX-2 by blocking MAPK-mediated pathways with the attendant activation of nuclear factor-kappaB (NF-kappaB), activator protein-1 (AP-1) and C/EBPdelta. These findings provide the first molecular basis that anthocyanidins with ortho-dihydroxyphenyl structure may have anti-inflammatory properties through the inhibition of MAPK-mediated COX-2 expression.
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PMID:Anthocyanidins inhibit cyclooxygenase-2 expression in LPS-evoked macrophages: structure-activity relationship and molecular mechanisms involved. 1596 74

Leptin is now recognized as a proinflammatory cytokine and thought to be a progressive factor for non-alcoholic steatohepatitis (NASH). Here we showed the effects of leptin on the production of TNF-alpha (tumor necrosis factor-alpha) by Kupffer cells (KCs) with signal transduction. Leptin enhanced TNF-alpha production accompanied by a dose-dependent increase of MAPK activity in lipopolysaccharide (LPS)-stimulated KCs. SB203580 and JNK inhibitor I, specific inhibitors of P38 and JNK, inhibited TNF-alpha production in KCs but PD98059, an inhibitor of the ERK pathway, did not affect TNF-alpha production by KCs. Recombinant constitutively active adenovirus (Ad)-MKK6 and-MKK7 increased TNF-alpha production in KCs with activation of P38 and JNK without any change by Ad-MEK1 delivery. On the other hand, KCs isolated from the Zucker rat (fa/fa), a leptin receptor-deficient rat, showed reduced production of TNF-alpha on stimulation with LPS. The delivery of Ad-MKK6 and-MKK7, but not Ad-MEK1, increased TNF-alpha production in KCs of Zucker rats with activation of P38 and JNK. Addition of leptin to normal rats increased LPS-induced hepatic TNF-alpha production in vivo and leptin receptor-deficient Zucker rats showed reduced hepatic TNF-alpha production on addition of LPS in vivo. These findings indicate that P38 and JNK pathways are involved in the signal transduction of leptin enhancement of LPS-induced TNF-alpha production.
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PMID:Leptin enhances TNF-alpha production via p38 and JNK MAPK in LPS-stimulated Kupffer cells. 1597 53

6-(Methylsulfinyl)hexyl isothiocyanate (6-MITC) is an active ingredient of Wasabi (Wasabia japonica (Miq.) Matsumura), which is a very popular pungent spice in Japan. To clarify the cellular signaling mechanism underlying the anti-inflammatory action of 6-MITC, we investigated the effects of 6-MITC on the expression of inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-activated murine macrophage RAW264 cells. 6-MITC showed a dose-dependent inhibition of LPS-induced nitric oxide (NO), iNOS mRNA and protein. LPS caused the c-Jun phosphorylation (a major component of AP-1) and IkappaB-alpha degradation. 6-MITC suppressed LPS-induced c-Jun phosphorylation, but did not inhibit IkappaB-alpha degradation. Cellular signaling analysis using MAPK-(U0126 for MEK1/2, SB203580 for p38 kinase and SP600125 for JNK) and Jak2-specific (AG490) inhibitors demonstrated that LPS stimulated iNOS expression via activating Jak2-mediated JNK, but not ERK and p38, pathway. 6-MITC suppressed iNOS expression through the inhibition of Jak2-mediated JNK signaling cascade with the attendant to AP-1 activation. In addition, the structure-activity study revealed that the inhibitory potency of methylsulfinyl isothiocyanates (MITCs) depended on the methyl chain length. These findings provide the molecular basis for the first time that 6-MITC is an effective agent to attenuate iNOS production.
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PMID:6-(Methylsulfinyl)hexyl isothiocyanate suppresses inducible nitric oxide synthase expression through the inhibition of Janus kinase 2-mediated JNK pathway in lipopolysaccharide-activated murine macrophages. 1613 49

6-(Methylsulfinyl)hexyl isothiocyanate (6-MITC) is a chemopreventive compound occurring in Wasabi (Wasabia japonica (Miq.) Matsumura), which is a very popular pungent spice in Japan. We investigated the effects of 6-MITC on the expression of cyclooxygenase-2 (COX-2) in lipopolysaccharide (LPS)-activated murine macrophage RAW264 cells. Treatment with 6-MITC suppressed LPS-mediated induction of COX-2 protein in a dose-dependent manner. Transfections with various COX-2 promoter reporter constructs revealed that the inhibitory effects of 6-MITC on COX-2 gene expression were directed by the core promoter elements including nuclear factor kappaB (NF-kappaB), CCAAT/enhancer-binding protein (C/EBP) and cyclic AMP-response element (CRE) sites. Western blotting analysis showed that 6-MITC inhibited LPS-induced activation of MAPK (ERK, p38 kinase and JNK) and transcriptional factors (CREB, c-Jun and C/EBPdelta) binding the core elements of COX-2 promoter, substantiating the involvement of these signal transduction pathways in the regulation of COX-2 expression by 6-MITC. Moreover, Western blotting experiments with MAPK-specific inhibitors (U0126 for MEK1/2, SB203580 for p38 kinase and SP600125 for JNK) demonstrated that 6-MITC suppressed LPS-induced COX-2 expression by blocking the activation of JNK-mediated AP-1 and ERK/p38 kinase-mediated CREB or C/EBPdelta. Finally, the structure-activity study revealed that the inhibitory potency of methylsulfinyl isothiocyanates (MITCs) depended on the methyl chain length. These findings demonstrate for the first time that 6-MITC is an effective agent to attenuate COX-2 production, and enhance our understanding of the anti-inflammation properties of 6-MITC.
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PMID:Inhibition of lipopolysaccharide-induced cyclooxygenase-2 transcription by 6-(methylsulfinyl) hexyl isothiocyanate, a chemopreventive compound from Wasabia japonica (Miq.) Matsumura, in mouse macrophages. 1625 55

Cytosolic phospholipase A2 (cPLA2) plays a pivotal role in mediating agonist-induced arachidonic acid (AA) release for prostaglandins (PG) synthesis induced by bacterial lipopolysaccharide (LPS) and cytokines. However, the intracellular signaling pathways mediating LPS-induced cPLA2 expression and PGE2 synthesis in canine tracheal smooth muscle cells (TSMCs) remains unknown. LPS-induced expression of cPLA2 and release of PGE2 was attenuated by inhibitors of tyrosine kinase (genistein), phosphatidylcholine-phospholipase C (D609), phosphatidylinositol-phospholipase C (U73122), PKC (GF109203X and staurosporine), removal of Ca2+ by BAPTA/AM plus EDTA, MEK1/2 (PD98059), p38 (SB202190), JNK (SP600125), and phosphatidylinositol 3-kinase (PI3-K; LY294002 and wortmannin). The involvement of MPAKs in LPS-induced responses was further confirmed by transfection of TSMCs with dominant negative mutants of ERK2 and p38. LPS-induced cPLA2 expression and PGE2 synthesis was inhibited by a selective NF-kappaB inhibitor (helenalin) and transfection with dominant negative mutants of NF-kappaB inducing kinase (NIK), IkappaB kinase (IKK)-alpha, and IKK-beta, consistent with that LPS-stimulated both IkappaB-alpha degradation and NF-kappaB translocation into nucleus in these cells. LPS-stimulated cPLA2 phosphorylation was inhibited by PD98059, GF109203X, and staurosporine, indicating the regulation by p42/p44 MAPK and PKC. Moreover, LPS-induced up-regulation of cPLA2 and COX-2 linked to PGE2 synthesis was inhibited by AACOCF3 (a selective cPLA2 inhibitor), implying the involvement of cPLA2 in these responses. These findings suggest that phosphorylation and expression of cPLA2 correlates with the release of PGE2 from LPS-challenged TSMCs, at least in part, mediated through MAPKs and NF-kappaB signaling pathways. LPS-mediated responses were modulated by PLC, Ca2+, PKC, tyrosine kinase, and PI3-K in TSMCs.
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PMID:Induction of cytosolic phospholipase A2 by lipopolysaccharide in canine tracheal smooth muscle cells: involvement of MAPKs and NF-kappaB pathways. 1627 65

The oncoprotein kinase Tpl2 plays an essential role in macrophage activation by the bacterial component lipopolysaccharide (LPS). In response to LPS stimulation, Tpl2 phosphorylates a downstream kinase, MEK1, leading to the activation of ERK signaling pathway. Recent studies demonstrate that the NF-kappaB1 precursor protein p105 functions as an inhibitor of Tpl2 and that the LPS-stimulated Tpl2 activation requires p105 degradation. However, how p105 inhibits the signaling function of Tpl2 is not completely understood. We show here that p105 does not inhibit the intrinsic kinase activity of Tpl2. When complexed with p105, Tpl2 remains catalytically active and uses p105 as a substrate. However, the p105-bound Tpl2 is unable to phosphorylate its physiological target, MEK1. These findings suggest that p105 functions as a competitive inhibitor of Tpl2 that blocks its access by MEK1.
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PMID:Phosphorylation of NF-kappaB1/p105 by oncoprotein kinase Tpl2: implications for a novel mechanism of Tpl2 regulation. 1644 10

MNSFbeta is a ubiquitously expressed member of the ubiquitin-like family that has been implicated in various biological functions. Previous studies have demonstrated that MNSFbeta covalently binds to intracellular proapoptotic protein Bcl-G in mitogen-activated murine T cells. In this study, we further investigated the intracellular mechanism of action of MNSFbeta in macrophage cell line, Raw 264.7 cells. We present evidence that MNSFbeta.Bcl-G complex associates with ERKs in non-stimulated Raw 264.7. We found that MNSFbeta.Bcl-G directly bound to ERKs and inhibited ERK activation by MEK1. In Raw 264.7 cells treated with MNSFbeta small interfering RNA (siRNA) lipopolysaccharide (LPS)-induced ERK1/2 activation was enhanced and LPS-induced JNK and p38 activation was unaffected. SiRNA-mediated knockdown of MNSFbeta increased tumor necrosis factor alpha (TNFalpha) expression at mRNA and protein levels in LPS-stimulated Raw 264.7 cells. Finally, we found that transfection with MNSFbeta expression construct resulted in a significant inhibition of LPS-induced ERK activation and TNFalpha production. Co-transfection experiments with MNSFbeta and Bcl-G greatly enhanced this inhibition. Collectively, these findings indicate that MNSFbeta might be implicated in the macrophage response to LPS.
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PMID:The ubiquitin-like protein MNSFbeta regulates ERK-MAPK cascade. 1662 90

The lipopolysaccharide (LPS) of Gram-negative bacteria induces the expression of cytokines and proinflammatory genes via the TLR4 signaling pathway in diverse cell types. The purpose of the present study was to test the hypothesis that the nasopharynx epithelial cells (NECs) could recognize and respond to LPS. The underlying molecular mechanisms were further elucidated in the NEC line 5-8F for its ability to activate the NFkappaB and TNF-alpha reporter genes, in response to LPS. After LPS stimulation, the TNF-alpha promoter activity and the relevant production of TNF-alpha were significantly increased in 5-8F cells. Moreover, LPS activated NFkappaB p65, ERK1/2 and JNK1/2 and induced their translocation to the nucleus. Western blot analysis showed that the expression of NFkappaB p65, MEK1, ERK1/2, JNK1/2, phospho-ERK1/2 and phospho-JNK1/2 proteins also was increased in NEC 5-8F cells, following the LPS stimulation. Additionally, the expression of TLR1-6, MD2 and CD14 was examined by RT-PCR, and the CD14 expression was determined by flow cytometry analysis. We demonstrated that the expression of CD14, TLR4 and MD2 was crucial for the NEC responses to LPS. In conclusion, our results provide novel mechanisms for the response of nasopharnyx epithelial cells to LPS stimulation, through NFkappaB and MAPKs signaling pathways.
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PMID:Lipopolysaccharide (LPS) regulates TLR4 signal transduction in nasopharynx epithelial cell line 5-8F via NFkappaB and MAPKs signaling pathways. 1667 17


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