Role of tumor necrosis factor alpha in induction of murine CD14 gene expression by lipopolysaccharide.

We previously demonstrated CD14 gene expression in myeloid and epithelial cells of the mouse and showed that expression of the CD14 gene in both is modulated by lipopolysaccharide (LPS). Here we test the hypothesis that the induction of CD14 in these cells is an indirect effect of LPS, one mediated by tumor necrosis factor alpha (TNF-alpha). TNF-alpha induced a transient increase in levels of CD14 in plasma with a peak at 6 to 8 h, and this increase in levels of CD14 antigen in plasma was accompanied by increased levels of CD14 mRNA in lung, liver, and kidney. Moreover, in situ hybridization studies revealed that CD14 mRNA was induced in both myeloid cells and epithelial cells, the same cells that respond to LPS. Pretreatment of mice with anti-TNF antiserum reduced the LPS-mediated increase in levels of CD14 in plasma and significantly reduced the level of induction of CD14 mRNA in selected epithelial cells in the kidney and liver. The antiserum did not appear to block LPS-mediated induction in myeloid cells in the tissues examined. In C3H/HeJ mice, the epithelial response to LPS was markedly attenuated whereas the response to TNF-alpha was normal. Thus, regulation of CD14 gene expression by LPS differs in epithelial and myeloid cells, with the epithelial responses in kidney and liver being mediated, in part, by TNF-alpha.     

Membrane-anchored CD14 is important for induction of interleukin-8 by lipopolysaccharide and peptidoglycan in uroepithelial cells

We investigated the induction of interleukin-8 (IL-8) by bacterial lipopolysaccharide (LPS) and peptidoglycan (PGN) in the bladder cancer cell lines T24, 5637, UM-UC-3, and HT1197. T24 and 5637 cells strongly induced IL-8 after stimulation with LPS or PGN in a dose- and time-dependent manner, whereas UM-UC-3 and HT1197 cells did so very weakly. The expression of CD14 at the mRNA, total cellular protein, and cell surface protein levels differed among these cell lines, but the expression levels of Toll-like receptors 2 and 4 (TLR2 and TLR4) were not significantly different. The CD14 expression levels were found to correlate with the inducibility of IL-8 by LPS or PGN. Treatment of T24 and 5637 cells with phosphatidylinositol-specific phospholipase C to eliminate CD14 from the cell surface dramatically suppressed the induction of IL-8. On the other hand, UM-UC-3 cells transfected with CD14 cDNA expressed membrane-anchored CD14 and showed more efficient induction of IL-8 by LPS stimulation than untransfected controls. These results suggest that the presence of the membrane-anchored, but not the soluble, form of CD14 is a strong factor in IL-8 induction in bladder epithelial cells in response to bacterial components. The presence of the membrane-anchored form of CD14 may thus be a determinant for the inflammatory response of uroepithelial cells.     

Membrane-Anchored CD14 Is Important for Induction of Interleukin-8 by Lipopolysaccharide and Peptidoglycan in Uroepithelial Cells

We investigated the induction of interleukin-8 (IL-8) by bacterial lipopolysaccharide (LPS) and peptidoglycan (PGN) in the bladder cancer cell lines T24, 5637, UM-UC-3, and HT1197. T24 and 5637 cells strongly induced IL-8 after stimulation with LPS or PGN in a dose- and time-dependent manner, whereas UM-UC-3 and HT1197 cells did so very weakly. The expression of CD14 at the mRNA, total cellular protein, and cell surface protein levels differed among these cell lines, but the expression levels of Toll-like receptors 2 and 4 (TLR2 and TLR4) were not significantly different. The CD14 expression levels were found to correlate with the inducibility of IL-8 by LPS or PGN. Treatment of T24 and 5637 cells with phosphatidylinositol-specific phospholipase C to eliminate CD14 from the cell surface dramatically suppressed the induction of IL-8. On the other hand, UM-UC-3 cells transfected with CD14 cDNA expressed membrane-anchored CD14 and showed more efficent induction of IL-8 by LPS stimulation than untransfected controls. These results suggest that the presence of the membrane-anchored, but not the soluble, form of CD14 is a strong factor in IL-8 induction in bladder epithelial cells in response to bacterial components. The presence of the membrane-anchored form of CD14 may thus be a determinant for the inflammatory response of uroepithelial cells.     

维生素D3诱导的U937细胞中CD14表达的实验研究

目的: 探讨维生素D3诱导U937细胞上CD14蛋白的表达及其对内毒素 (LPS)刺激的反应性。方法: 用0. 1μmol/LVitD3与U937细胞共同培养 24h诱导CD14基因的表达, 并观察U937细胞对不同浓度的LPS刺激不同时间的反应性。结果: VitD3能稳定诱导U937细胞表达CD14mRNA和CD14蛋白。经VitD3诱导的U937细胞对LPS刺激的敏感性显著增强, 表现为低浓度LPS刺激即能诱导该细胞核中NF -κB激活, 促进TNF- αmRNA的转录和表达, 并将表达的TNF α释放入培养上清中。结论: VitD3能诱导U937细胞中CD14基因和蛋白的表达, 并增加其对LPS刺激的反应性。     

Identification of two candidate innate immune genes by transcriptional profiling and RNA interference in mouse mammary gland epithelial cells stimulated with lipopolysaccharide

Mammary epithelial cells (MECs) play an important role in immune responses and inflammatory diseases such as mastitis, which is mainly attributed to the activation of Toll-like receptors and the release of cytokines. However, the overall change of gene expression and biological pathways of MECs to microbial factors stimulation remains unknown. Here, we analyzed the gene expression profile in mouse MECs treated with lipopolysaccharide (LPS) for 24?h. Microarray analysis revealed that about 1548 genes differentially expressed, these genes mainly involved in 346 gene ontology terms and 128 molecular pathways, and particularly, some innate immune-associated pathways were significant. By analyzing data for pathway relation network, we prioritized differentially expressed genes with respect to LPS. The importance of changes, indicating that RNA interference-mediated inhibition of two genes identified in this analysis, transforming growth factor beta 1 (Tgf-β1) and platelet-derived growth factor B (Pdgfb), reduced interleukin (IL)-6 and tumor necrosis factor α production respectively, in gene expression was verified. These findings delineate mouse MECs gene response patterns induced by LPS and identify Tgf-β1 and Pdgfb that have been closely related to innate immunity.     

Lipopolysaccharide (LPS) regulates TLR4 signal transduction in nasopharynx epithelial cell line 5-8F via NFkappaB and MAPKs signaling pathways

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.     

Lipopolysaccharide induces CXCL2/macrophage inflammatory protein-2 gene expression in enterocytes via NF-kappaB activation: independence from endogenous TNF-alpha and platelet-activating factor

CXCL2 (macrophage inflammatory protein-2 (MIP-2)), a critical chemokine for neutrophils, has been shown to be produced in the rat intestine in response to platelet-activating factor (PAF) and to mediate intestinal inflammation and injury. The intestinal epithelium, constantly exposed to bacterial products, is the first line of defence against micro-organisms. It has been reported that enterocytes produce proinflammatory mediators, including tumour necrosis factor (TNF) and PAF, and we showed that lipopolysaccharide (LPS) and TNF activate nuclear factor (NF)-kappaB in enterocytes. However, it remains elusive whether enterocytes release CXCL2 in response to LPS and TNF via a NF-kappaB-dependent pathway and whether this involves the endogenous production of TNF and PAF. In this study, we found that TNF and LPS markedly induced CXCL2 gene expression in IEC-6 cells, TNF within 30 min, peaking at 45 min, while LPS more slowly, peaking after 2 hr. TNF- and LPS- induced CXCL2 gene expression and protein release were completely blocked by pyrrolidine dithiocarbamate (PDTC) and helenalin, two potent NF-kappaB inhibitors. NEMO-binding domain peptide, a specific inhibitor of inhibitor protein kappaB kinase (IKK) activation, a major upstream kinase mediating NF-kappaB activation, significantly blocked CXCL2 gene expression and protein release induced by LPS. WEB2170 (PAF antagonist) and anti-TNF antibodies had no effect on LPS-induced CXCL2 expression. In conclusion, CXCL2 gene is expressed in enterocytes in response to both TNF and LPS. LPS-induced CXCL2 expression is dependent on NF-kappaB activation via the IKK pathway. The effect of LPS is independent of endogenous TNF and PAF.     

Identification of MicroRNAs Dysregulated in CD14 Gene Silencing RAW264.7 Macrophage Cells

A cluster of differentiation antigen 14 (CD14) is involved in lipopolysaccharide (LPS)-induced proinflammatory cytokine release and LPS-induced septic shock. MicroRNAs (miRNAs) are short non-coding RNAs that are involved in the epigenetic regulation of cellular process and bacterial infection. Our previous study indicated that siRNA against CD14 effectively inhibited LPS-induced tumor necrosis factor alpha, chemokine (C-X-C motif) ligand 2, interleukin-6 release, and NO production. To identify miRNAs which are affected by CD14 gene silencing and dissect the mechanisms of the attenuating of LPS-induced damaging immune activation more clearly, based on the CD14 knockdown RAW264.7 macrophage cell line established in our previous study, miRNAs expression profiling of CD14 knockdown RAW264.7 cells were analyzed with miRNA microarray and validated by qRT-PCR, the potential targets were predicted and subjected to gene ontology (GO) pathway and biological processes analysis. We demonstrated for the first time that CD14 knockdown significantly changed the expression of 199a-3p, miR-199a-5p, and miR-21-5p in RAW264.7 cells, and significantly enriched GO terms in the predicted target genes of these miRNAs were apoptosis process, immune response, inflammatory response, innate immune response, anti-apoptosis, cytokine production, and cytokine-mediated signaling pathway. These findings may improve our understanding about functional mechanism of miRNAs in the attenuating of LPS-induced damaging immune activation more clearly.     

Identification of genes particularly sensitive to lipopolysaccharide (LPS) in human monocytes induced by wild-type versus LPS-deficient Neisseria meningitidis strains

Lipopolysaccharide (LPS) in the outer membrane of Neisseria meningitidis plays a dominant role as an inflammation-inducing molecule in meningococcal disease. We have used microarray analysis to study the global gene expression after exposure of human monocytes for 3 h to wild-type N. meningitidis (10(6)), LPS-deficient N. meningitidis (10(6) and 10(8)), and purified N. meningitidis LPS (1 ng [33 endotoxin units]/ml) to identify LPS-inducible genes. Wild-type N. meningitidis (10(6)) induced 4,689 differentially expressed genes, compared with 72 differentially expressed genes induced by 10(6) LPS-deficient N. meningitidis organisms. However, 10(8) LPS-deficient N. meningitidis organisms induced 3,905 genes, indicating a dose-response behavior of non-LPS cell wall molecules. A comparison of the gene expression patterns from 10(6) wild-type N. meningitidis and 10(8) LPS-deficient N. meningitidis organisms showed that 2,401 genes in human monocytes were not strictly LPS dependent. A list of "particularly LPS-sensitive" genes (2,288), differentially induced by 10(6) wild-type N. meningitidis but not by 10(8) LPS-deficient N. meningitidis organisms, showed an early expression of beta interferon (IFN-beta), most likely through the Toll-like receptor-MyD88-independent pathway. Subsequently, IFN-beta may activate the type I IFN signaling pathway, and an unknown number of IFN-beta-inducible genes, such as those for CXCL9, CXCL10, CXCL11, IFIT1, IFIT2, IFIT3, and IFIT5, are transcribed. Supporting this, human monocytes secreted significantly higher levels of CXCL10 and CXCL11 when stimulated by 10(6) wild-type N. meningitidis organisms than when stimulated by 10(8) LPS-deficient N. meningitidis organisms. Plasma CXCL10, but not CXCL11, was positively correlated (r = 0.67; P < 0.01) to LPS in patients (n = 24) with systemic meningococcal disease. Thus, new circulating biomarkers in meningococcal disease may be suggested through LPS-induced gene expression changes in human monocytes.     

Lipopolysaccharide and Its Analog Antagonists Display Differential Serum Factor Dependencies for Induction of Cytokine Genes in Murine Macrophages

Monocytes/macrophages play a central role in mediating the effects of lipopolysaccharide (LPS) derived from gram-negative bacteria by the production of proinflammatory mediators. Recently, it was shown that the expression of cytokine genes for tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and interferon-inducible protein-10 (IP-10) by murine macrophages in response to low concentrations of LPS is entirely CD14 dependent. In this report, we show that murine macrophages respond to low concentrations of LPS (≤2 ng/ml) in the complete absence of serum, leading to the induction of TNF-α and IL-1β genes. In contrast to the TNF-α and IL-1β genes, the IP-10 gene is poorly induced in the absence of serum. The addition of recombinant human soluble CD14 (rsCD14) had very little effect on the levels of serum-free, LPS-induced TNF-α, IL-1β, and IP-10 genes. In contrast, the addition of recombinant human LPS-binding protein (rLBP) had opposing effects on the LPS-induced TNF-α or IL-1β and IP-10 genes. rLBP inhibited LPS-induced TNF-α and IL-1β genes, while it reconstituted IP-10 gene expression to levels induced in the presence of serum. These results provide further evidence that the induction of TNF-α or IL-1β genes occurs via a pathway that is distinct from one that leads to the induction of the IP-10 gene and that the pathways diverge at the level of the initial interaction between LPS and cellular CD14. Additionally, the results presented here indicate that LPS structural analog antagonists Rhodobacter sphaeroides diphosphoryl lipid A and SDZ 880.431 are able to inhibit LPS-induced TNF-α and IL-1β in the absence of serum, while a synthetic analog of Rhodobacter capsulatus lipid A (B 975) requires both rsCD14 and rLBP to function as an inhibitor.     

Effects of Porphyromonas gingivalis and Escherichia coli lipopolysaccharides on mononuclear phagocytes.

The mononuclear phagocyte plays an important role in the regulation of microbe-induced inflammation, in part through its ability to secrete mediators, particularly cytokines, in response to microorganisms and their products. To evaluate the effects of the microbial flora associated with chronic adult periodontitis on cytokine induction, lipopolysaccharide (LPS) from the periodontopathogen Porphyromonas gingivalis was used to stimulate naive and phorbol ester-primed U937 monocytic cells, as well as elutriated human peripheral blood monocytes. We assessed the effect of this LPS, in comparison to that of LPS from Escherichia coli, on cell proliferation, cytokine induction, and surface expression of the LPS receptor CD14. P. gingivalis LPS stimulated proliferation of U937 cells at concentrations of greater than 1 ng/ml, while E. coli LPS inhibited proliferation. Phorbol myristic acid (PMA)-treated U937 cells and elutriated monocytes responded to E. coli LPS activation by producing tumor necrosis factor alpha (TNF-alpha) mRNA and protein; however, P. gingivalis LPS induced greater numbers of TNF-alpha mRNA-positive cells and higher (P < 0.05) levels of protein than did E. coli LPS. Both cell types expressed interleukin-1 beta (IL-1beta) mRNA and protein in response to either LPS treatment. Compared with E. coli LPS, P. gingivalis LPS induced significantly (P < 0.05) higher numbers of IL-1 mRNA-positive U937 cells and elutriated monocytes, as well as production of significantly more (P < 0.05) IL-1 protein by the monocytes. The PMA-treated U937 cells and the monocytes produced high levels of IL-1 receptor antagonist mRNA and protein which were only marginally affected by the LPS preparations. While E. coli LPS induced expression of CD 14 on the surface of PMA-primed U937 cells and monocytes, P. gingivalis LPS exhibited a significantly (P < 0.05) greater ability to enhance receptor levels. Our results indicate that P. gingivalis LPS can activate the mononuclear phagocyte for proliferation, cytokine production, and CD14 expression, providing evidence for the potential of this bacterial component to act as a critical regulatory factor in the chronic inflammatory response associated with periodontitis.     

Differences in LPS-induced activation of bronchial epithelial cells (BEAS-2B) and type II-like pneumocytes (A-549)

Lipopolysaccharide (LPS) as a major component of the outer membrane of gram-negative bacteria stimulates various cells to initiate a signalling cascade which ultimately leads to cell activation and expression of immunoregulatory or inflammatory cytokines. The human respiratory epithelium is an important environmental interface, but differences in LPS-induced cell activation between bronchial and alveolar epithelial cells have not yet been investigated in detail. First, the expression of Toll-like receptors (TLRs), as pattern-recognition receptors, was investigated for the bronchial epithelial cells and type II-like pneumocytes, demonstrating that they fulfil the prerequisites for LPS signalling. Thereafter, the effects of LPS, soluble CD14 (sCD14) and LPS-binding protein (LBP) on the release of interleukin-6 (IL-6) and IL-8 were studied. In the presence of LPS, sCD14 induced a significant and concentration-dependent cytokine release in type II-like pneumocytes, whereas the response of bronchial epithelial cells to sCD14 stimulation was low, implicating sCD14-independent activation mechanisms. Furthermore, LBP revealed inhibitory effects on the activation of alveolar epithelial cells, which may represent a novel local defence mechanism during gram-negative infection. We conclude that distinct pathways exist for LPS-induced activation of bronchial and alveolar epithelial cells.     

Development of an inhaled endotoxin challenge protocol for characterizing evoked cell surface phenotype and genomic responses of airway cells in allergic individuals.

BACKGROUND: Environmental exposure to endotoxin is a known cause of exacerbation of asthma. Inhaled endotoxin protocols have been used to evaluate airway cell surface phenotypes associated with antigen presentation and innate immunity in healthy volunteers, but not in allergic volunteers. OBJECTIVES: To establish the safety of challenge with low-dose endotoxin (10,000 endotoxin units) (lipopolysaccharide [LPS]) inhalation in allergic individuals, to measure airway cell surface phenotypes associated with antigen presentation and innate immunity in induced sputum (IS) after LPS challenge, and to conduct gene expression profiling in IS cells to determine which host genetic networks are modified by LPS inhalation. METHODS: Induced sputum was obtained before and 6 hours after LPS inhalation in 10 allergic volunteers (8 with asthma and 2 with rhinitis). Flow cytometry was used to examine cell surface phenotypes on IS cells. Genomic expression was analyzed on a subset of IS samples (n = 10) using microarray and ingenuity pathway analysis. RESULTS: A total of 10,000 endotoxin units of LPS induced significant up-regulation of membrane CD14, CD11b, CD16, HLA-DR, CD86, and Fcepsilon receptor 1 on sputum phagocytes and increased expression of genes that influence antigen-presenting surface molecules (HLA-DR, chemokine ligand 2 or monocyte chemoattractant protein 1, v-rel reticuloendotheliosis viral oncogene homolog, prostaglandin-endoperoxide synthase 2 or cyclooxygenase 2, and transforming growth factor beta), immune activation (CD14, interleukin 1beta, and regulated upon activation, normal T cell expressed and secreted), and inflammation (intracellular adhesion molecule 1 and inhibitory kappaBalpha). Gene profiles for nuclear factor kappaB, interleukin 1, and tumor necrosis factor pathways were also significantly affected. CONCLUSIONS: Low-dose inhaled endotoxin challenge is safe in allergic individuals with mild to moderate disease. It enhances airway cell surface phenotypes and expression of genes associated with antigen presentation, innate immunity, and inflammation. Microarray with ingenuity pathway analysis can be successfully applied to sputum cells to characterize genetic responses to inhaled exacerbants.