UMLS:C0036690 - FACTA Search

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Query: UMLS:C0036690 (sepsis)
59,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effective treatment of sepsis and septic shock has remained elusive despite intense research efforts. The tools of molecular biology have been applied to the problem of sepsis in an attempt to design more rational, directed therapy. Cellular interactions with invading microorganisms begin a series of stimulation events within the cell. One of the important interactions is the binding of lipopolysaccharide (LPS) from gram-negative bacteria to the LPS binding protein, and then this complex binding to CD14 on monocytes. Cell stimulation occurs through activation of signal transduction pathways within the cell, many of which have been defined. These include the kinases that phosphorylate proteins, and phosphatases that dephosphorylate proteins. The next step after activation of the signal transduction pathways is stimulation of nuclear regulatory factors. One of the best characterized of these is nuclear regulatory factor kappa B (NF-kappa B), which is a trans activating element that binds to specific DNA nucleotide sequences to allow transcription of downstream elements. Many inflammatory mediators are located downstream of NF-kappa B so that activation of NF-kappa B causes upregulation of the inflammatory mediators. The cytokines have been identified as a group of mediators important in the pathogenesis of sepsis, because several studies have shown that higher levels are correlated with a worse outcome in patients. Additionally, in experimental animal models, inhibition of cytokines improves survival, and administration of exogenous, recombinant cytokines reproduces many of the pathophysiologic alterations observed in sepsis. Molecular biology has played a critical role in the understanding of sepsis by providing the tools to make the recombinant cytokines of sufficient purity and quantity for infusion into experimental animals. The cellular response for the production of cytokines occurs through classic protein chemistry, with the signal transduction inducing messenger RNA (mRNA) coding for the cytokines, which are then translated and secreted. The relative contribution of local versus systemic cytokine production is beginning to be appreciated, with several diseases showing substantially higher local cytokine levels. The cytokines exert their activity on other cells by binding to their specific cytokine receptors. These receptors are part of the immune response and may be shed from the cell surface. These soluble receptors bind to and inactivate the cytokines. Inhibition of cytokine activity has been hypothesized as a potential therapy for sepsis. This inhibition has been done with antibodies directed against either the cytokines themselves or their receptors. Naturally occurring cytokine inhibitors have been cloned and expressed by molecular biologists and used for treatment of sepsis and other diseases. Using molecular biology techniques, the murine antibodies have been "humanized" to reduce their immunogenicity. The measurement of cytokines is critically important to our understanding of their role in health and disease. Cytokines may be measured by either immunologic methods or biological assays. Molecular biology has made important contributions to our understanding of sepsis by precisely identifying some of the mediators and providing reagents for therapeutic use.
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PMID:Applied molecular biology of sepsis. 892 69

Exposure to endotoxin produces a state of macrophage hyporesponsiveness on subsequent stimulation. Monocytes in patients with septic shock demonstrate a similar hyporesponsiveness to endotoxin. The purpose of this study was to examine whether this state of hyporesponsiveness extends to other inflammatory stimuli and the relationship of this state to cell surface receptor expression and the release of anti-inflammatory cytokines. Twelve normal volunteers, 10 patients with severe sepsis, and 9 patients with septic shock were included in the study. Monocytes from each subject were isolated and stimulated with lipopolysaccharide (LPS), staphylococcal enterotoxin B (SEB), and phorbol myristate acetate (PMA). Tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) were measured in the supernatants by enzyme-linked immunosorbent assay (ELISA). Serum levels of transforming growth factor-beta1 (TGF-beta1), prostaglandin E2 (PGE2), and interleukin-10 (IL-10) were also measured by ELISA. The expression of monocyte CD14 and HLA-DR in whole blood were measured by flow cytometry. Patients with septic shock demonstrated significantly decreased TNF-alpha and IL-1beta release as compared with normal subjects in response to LPS. In response to SEB, patients with sepsis and patient with septic shock demonstrated significantly decreased release of TNF-alpha and IL-1beta. Significant decreases in TNF-alpha release were found in the patients with septic shock after PMA stimulation. There were no significant differences in the monocyte response to the different stimuli between patients with gram-positive sepsis and gram-negative sepsis. HLA-DR expression was significantly decreased in patients with septic shock (58 +/- 9 fluorescence units (flU)) as compared with normal subjects (102 +/- 14 flU) (p < 0.05). No differences in CD14 expression were observed. IL-10 levels were significantly increased in patients with sepsis (16 +/- 4 pg/ml) and in patients with septic shock (42 +/- 15 pg/ml) and were detectable in 1 normal subject. TGF-beta1 levels were decreased in patients with septic shock (25 +/- 6 pg/ml) as compared with those in normal subjects (37 +/- 2 pg/ml)(p < 0.05). PGE2 levels were significantly increased in patients with septic shock and patients with sepsis. These data are consistent with a more generalized monocyte hyporesponsiveness to bacterial toxins that may be related to altered cell surface receptor expression and the release of anti-inflammatory cytokines.
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PMID:Monocyte response to bacterial toxins, expression of cell surface receptors, and release of anti-inflammatory cytokines during sepsis. 896 Jun 43

Bacterial lipopolysaccharide (LPS) plays a central role in the pathogenesis of gram-negative sepsis and shock. The glycosylphoshatidyl inositol (GPI) anchored glycoprotein CD14 on mononuclear cells binds LPS, especially in the presence of an LPS binding serum protein, activating the production of pro-inflammatory cytokines, i.e. TNF-alpha. However, since GPI anchorage to the cell membrane lacks the intracellular signalling capacity, the existence of at least a second receptor has been postulated. In attempt to identify additional LPS receptors, we used the human myelomonocytic cell line THP-1. This undifferentiated cell line did not respond to LPS in terms of TNF-alpha release, but when induced with 250 U/ml of IFN-gamma for 48 h, the cells released TNF-alpha (174 +/- 58.6 U/ml. L929 cell bioassay) in response to 10 vg/ml of E. coli 0111 LPS, in the absence of serum. Blockade of either HLA-DR or CD14 receptors with specific MAbs did not reduce the amount of cytokine released. However, when both the receptors were sequentially blocked involved on the effector cells a remarkable inhibition of TNF-alpha release was observed (8.6 +/- 1.4). It seems therefore, that HLA-DR receptor may be with CD14 in triggering TNF-alpha release by IFN-gamma, induced THP-1 cells.
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PMID:The release of tumor necrosis factor alpha (TNF-alpha) by interferon gamma (IFN-gamma) induced THP-1 cells stimulated with smooth lipopolysaccharide is inhibited by MAbs against HLA-DR and CD14 receptors on the effector cell. 903 62

Individuals with a consistently lower immune response may be more susceptible to infection but less prone to autoimmune disease or severe sepsis. The molecular mechanisms determining the low responder status are, however, unclear. We have screened 60 male donors for tumour necrosis factor (TNF) protein levels after stimulation of monocytes with lipopolysaccharide (LPS). Among these we identified three donors each that consistently had a level of less than 20% (low responders; LR) or of more than 80% (high responders; HR) of the maximum response seen in this population. Northern blot analysis of TNF mRNA after LPS stimulation revealed lower transcript levels in LR. Half life determination after actinomycin D blockade showed a similar decay rate for LR and HR and after blockade of degradation by cycloheximide treatment mRNA levels increased but LR remained lower compared to HR. These data indicate that the lower TNF mRNA levels in LR are not due to a more rapid mRNA degradation but rather a result of lower transcription. Transcripts for interleukin 6 (IL-6) were also low in LPS-stimulated monocytes of LR. Because expression of the LPS receptor CD14 was similar in LR and HR monocytes, our data suggest that differences in signal transduction account for the LR and HR phenotype.
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PMID:TNF gene expression in monocytes of low and high responder individuals. 912 9

The microvascular endothelial cell (MVEC) is a major target of inflammatory cytokines overproduced in conditions such as sepsis and infectious diseases. We addressed the direct and indirect effects of tumor necrosis factor (TNF) on endothelial cells that can be relevant for the pathogenesis of septic shock, with particular attention to the acute respiratory distress syndrome (ARDS) and to cerebral malaria (CM). To identify functional and phenotypical changes occurring in MVEC during sepsis, we isolated these cells from the lungs of patients who died of ARDS. The constitutive expression of ICAM-1 and, to a lesser extent, VCAM-1, CD14, and TNFR2 were significantly increased on MVEC isolated from ARDS patients compared with control MVEC, whereas ELAM-1 and TNFR1 were not increased. We found that lung MVEC from ARDS patients present a procoagulant profile and a higher production capacity of interleukin-6 (IL-6) and IL-8 when compared with those from controls. As in pulmonary MVEC derived from ARDS patients, the only TNFR type found up-regulated in brain microvessels during CM was TNFR2. This increase in TNFR2 expression only occurred in CM-susceptible mice at the onset of the neurological syndrome. We therefore investigated the role of TNFR2 in the development of this brain pathology by comparing the incidence of CM in wild-type and TNF receptor knock-out mice. Unexpectedly, the genetic deficiency in TNFR2, but not in TNFR1, conferred protection against CM and its associated mortality. No ICAM-1 up-regulation was detected in the brain of Tnfr2 knockout mice, indicating a close correlation between protection against CM-associated brain damage, absence of TNFR2, and absence of ICAM-1 up-regulation in the brain. Our results in ARDS and CM indicate a specific up-regulation of TNFR2, but not of TNFR1, on lung and brain MVEC, respectively. This increased expression leads to a reduced sensitivity toward TNFR1-mediated phenomena, such as the sensitized TNF cytolytic activity on lung MVEC. In contrast, the sensitivity toward TNFR2-mediated effects, such as ICAM-1 induction by membrane-bound TNF, is increased on brain and lung MVEC expressing increased levels of TNFR2. Therefore, the ICAM-1-inducing effect, rather than the direct cytotoxicity of inflammatory cytokines, such as TNF, appears to be crucial in ARDS and CM-induced endothelial damage, and TNFR2 seems to play an important role in this activity in vivo.
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PMID:TNF receptors in the microvascular pathology of acute respiratory distress syndrome and cerebral malaria. 912 3

Endotoxin (lipopolysaccharide; LPS) and superantigens (exotoxins) have been identified as potent inducers of lethal shock. While endotoxin primarily interacts with CD14 receptors on macrophages, superantigens like the staphylococcal enterotoxin B (SEB) preferentially activate T cells. Both cell types are triggered to release pro-inflammatory cytokines that in turn induce lethal shock. We analyzed whether endotoxin and superantigen interact during the induction phase of lethal shock. We report that LPS and SEB operate synergistically. Lethal doses of both inducers were reduced 100-fold when given in combination. The induced serum levels of tumor necrosis factor, interleukin-6, and interferon-gamma (IFN-gamma) were elevated and remained high for a prolonged period. Moreover, synergistic action of LPS and SEB induced lethal toxic shock even without presensitization of mice with D-galactosamine (D-GalN). Opposed to D-GalN-pretreated mice, mice injected with LPS and SEB showed less liver damage, but rather apoptosis of epithelial cells in the bowel. Cyclosporin A and treatment with anti-IFN-gamma monoclonal antibody blocked the synergistic action of LPS and SEB, indicating that T cell-derived IFN-gamma is the mediator of the observed synergism. Concomitant injection of LPS and SEB had no influence on SEB-induced T cell deletion and anergy induction. Since Gram-positive and Gram-negative bacteria can be recovered from septic blood samples, the synergistic action of endotoxin and superantigens might be relevant during lethal septicemia.
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PMID:Superantigen and endotoxin synergize in the induction of lethal shock. 913 Jun 31

Interleukin(IL)-13, a cytokine produced by T helper 2 (Th2) cells, is a powerful inhibitor of macrophage functions, including surface expression of CD14 and production of IL-1 and tumor necrosis factor (TNF)-alpha. We tested the effects of recombinant mouse(m)IL-13 in a neonatal mouse model of endotoxin shock; this is a macrophage-dependent condition, which is a model of neonatal sepsis in humans. mIL-13 (0.5 microgram/mouse) dramatically reduced the lethal effects of lipopolysaccharide (LPS) if administered either 24 or 4 h prior to or concomitantly with LPS challenge. This action might be mediated by multiple modulatory activities of IL-13 on LPS-induced cytokine secretion since, relative to control animals, the mice treated with mIL-13 had eight times lower peak blood levels of TNF. The IL-1 beta levels were also decreased, whereas increased levels of IL-6 and IL-10 were observed at several time points after LPS challenge.
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PMID:Prevention of endotoxin-induced lethality in neonatal mice by interleukin-13. 920 14

Although glycosylphosphatidyl-inositol (GPI) linked membrane proteins do not possess transmembrane or cytosolic sequences they elicit transmembrane signals. Using microscopic fluorescence imaging and resonance energy transfer (RET) techniques we have shown that certain pro-inflammatory GPI-linked membrane proteins can interact with leukocyte beta 2 integrins (complement receptor type 3 (CR3) and 4 (CR4) and the leukocyte function-associated antigen-1 (LFA-1)). For example, physical associations between CR3 and Fc gamma RIIIB, CR3 and urokinase receptors, and CR3 and CD14 (lipopolysaccharide receptor) have been found. Although Fc gamma RIIIB appears to be constitutively associated with CR3, urokinase receptors and CD14 associations with CR3 are influenced by their ligation status and cell function (e.g. adherence and locomotion). CR3-to-urokinase receptor interactions have been confirmed by immunoprecipitation techniques. Immunoprecipitation of CR3 from Brij-58 lysates after biotinylation of neutrophil membranes revealed proteins of M(r) = 40,000, 50,000, 74,000 and 120,000, in addition to bands corresponding to the integrin alpha and beta chains. Cell functions such as transmembrane signaling and superoxide release/priming have been linked to these interactions. Importantly, reagents that affect the lectin-like site of CR3, such as N-acetyl-D-glucosamine, alpha-methyl-D-mannoside and beta-glucan alter these interactions and, in parallel, leukocyte functions. Thus, the interactions of GPI-linked proteins and integrins can be highly dynamic events linked to cell activities. Our studies suggest that it may be possible to develop new drugs directed at the lectin-like site of beta 2 integrins that block GPI-linked protein-to-integrin coupling thereby controlling inflammatory cell processes including cell adherence, locomotion and activation. Such drugs may be useful in clinical conditions such as ischemia-reperfusion injury, sepsis, arthritis and others.
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PMID:Ectodomain interactions of leukocyte integrins and pro-inflammatory GPI-linked membrane proteins. 922 70

The rate of oxygen consumption in the human acute monocytic leukemia-derived cell line, Mono Mac 6, in response to lipopolysaccharide (LPS) in vitro was measured by electron paramagnetic resonance spectroscopy using an oxygen-sensitive spin-label, 4-oxo-2,2,6,6-tetramethylpiperidine-d16-1-oxyl (15N-PDT). Lipopolysaccharide impaired oxygen consumption in a dose-dependent manner which was shown to be mediated by mitochondrial dysfunction and could be augmented by pretreatment of the cells with interferon-gamma. Treatment of the cells with anti-CD14 monoclonal antibody failed to inhibit the LPS-induced effects on cellular respiration. These results suggest that LPS can directly reduce normal cellular oxygen consumption possibly via a CD14-independent pathway. This alteration of mitochondrial function by LPS may be responsible for the observed cell damage during sepsis.
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PMID:Lipopolysaccharide decreases oxygen consumption by Mono Mac 6 cells; an electron paramagnetic resonance oximetry study. 924 68

The accumulation of sCD14 shed from human monocytes in vivo might correlate with other inflammatory parameters and could be of importance in overcoming a sepsis situation. The development of the sCD14 titer in the supernatant of monocyte-enriched MNC cultures isolated from healthy volunteers was studied utilizing a commercially available sCD14 ELISA. These culture experiments revealed the prolonged liberation of sCD14 into the supernatant during a period of several days. A medium-exchange schedule of 2-3 days was found to be superior to a longer incubation period with respect to the sCD14 yield. PMA initially enhanced the CD14 shedding slightly, but after a few hours it strongly repressed the process. Such a reduction was also achieved by protein synthesis inhibitors (cycloheximide, actinomycin D). Additionally, we monitored the concentration of sCD14, CRP, IL-6 and IL-8 in human sera from healthy persons or patients suffering from severe burn injuries with or without sepsis. Our results indicate that sCD14 is strongly correlated with IL-6, but not with IL-8. sCD14 titers were higher in the group of patients with both burn injuries and sepsis. From experiments with monocyte-enriched MNC cultures isolated from healthy volunteers and medium supplemented with sera containing sCD14 as well as radiolabeled LPS, we conclude that the enhanced shedding of CD14 in vivo during sepsis is probably not able to reduce the binding of LPS to monocytes.
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PMID:Characteristics of CD14 shedding from human monocytes. Evidence for the competition of soluble CD14 (sCD14) with CD14 receptors for lipopolysaccharide (LPS) binding. 926 97

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