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)

We investigated the effect of intratracheal (i.t.) lipopolysaccharide (LPS) on alveolar macrophage release of nitric oxide. Mice received i.t. LPS at doses ranging from 1 to 100 micrograms/100 g body weight and were killed at serial intervals for bronchoalveolar lavage. Control mice received i.t. phosphate-buffered saline. We found that after i.t. LPS, there was an early (1 to 3 days) influx of neutrophils followed by a later (5 to 7 days) influx of macrophages into the lungs. Alveolar macrophages lavaged from mice given i.t. LPS did not spontaneously release nitric oxide (measured as nitrite), but the capacity of these cells to release nitric oxide in vitro in response to interferon-gamma (IFN-gamma) or LPS was markedly upregulated. Alveolar macrophages lavaged from mice given i.t. LPS but not i.t. phosphate-buffered saline also expressed mRNA for inducible nitric oxide synthase as measured by semiquantitative reverse-transcription polymerase chain reaction. To investigate possible mechanisms for cellular priming for increased nitric oxide release after i.t. LPS, mice were depleted of CD4+ lymphocytes with an anti-CD4 antibody. Alveolar macrophages from CD4-depleted mice given i.t. LPS released significantly less nitric oxide in vitro in comparison to macrophages from nondepleted mice. Additional mice were treated with neutralizing doses of anti-tumor necrosis factor or anti-IFN-gamma antibody before i.t. LPS. Pretreatment with each cytokine antibody decreased but did not eliminate macrophage priming for nitric oxide release after i.t. LPS. We conclude that intratracheal LPS induces mRNA for nitric oxide synthase in alveolar macrophages, priming the cells for increased release of nitric oxide in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of nitric oxide release by macrophages after intratracheal lipopolysaccharide. 754 Dec 22

In the present studies, we analyzed the effects of acute endotoxemia on hepatocyte nitric oxide production and functional activity. Treatment of rats with 5 mg/kg of lipopolysaccharide (LPS), which induces acute endotoxemia, caused an increase in nitric oxide production in the liver, as measured by electron paramagnetic spin trapping, which was evident within 6 hours. This was associated with expression of inducible nitric oxide synthase (iNOS) messenger (m) RNA in hepatocytes and in sinusoidal cells throughout the liver lobule. Acute endotoxemia also caused alterations in hepatic structure, including hypertrophy, vacuolization, and chromosomal emargination, however these changes were not apparent for 24 to 48 hours. Hepatocytes isolated from endotoxemic rats released increased amounts of nitric oxide, measured by nitrite production, in response to interferon gamma (gamma-IFN) alone or in combination with LPS, tumor necrosis factor alpha, macrophage-colony stimulating factor, granulocyte/macrophage-colony stimulating factor, or hepatocyte growth factor. These results show that hepatocytes are sensitized by acute endotoxemia to respond to inflammatory mediators and growth factors. Increased nitrite production by hepatocytes was due to increased expression of iNOS mRNA and protein and was correlated with the time following induction of acute endotoxemia. Thus, cells isolated 48 hours after induction of acute endotoxemia released significantly more nitrite than cells recovered after 6 hours, a response that was not due to alterations in hepatocyte viability. Hepatocytes isolated from endotoxemic rats also exhibited a marked increase in proliferative capacity when compared with cells from control rats. Nitric oxide production by hepatocytes in vitro was associated with inhibition of cell growth and protein synthesis, which was reversed by the nitric oxide synthase inhibitor, NG-monomethyl-l-arginine (L-NMMA). Agarose gel electrophoresis showed extensive cytoplasmic DNA fragmentation in hepatocytes treated with LPS and gamma-IFN, a characteristic of apoptosis, which was also reversed by L-NMMA. These results, together with our findings that treatment of rats with an inhibitor of nitric oxide synthase partially reversed the structural alterations in the liver associated with acute endotoxemia suggest that nitric oxide may contribute to the pathophysiologic response to this bacterially derived toxin.
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PMID:Hepatic nitric oxide production following acute endotoxemia in rats is mediated by increased inducible nitric oxide synthase gene expression. 754 86

The ability of macrophages to kill some kinds of tumor cells is dependent upon the production of the free radical nitric oxide (NO) by the inducible enzyme NO synthase (iNOS; EC 1.14.13.39). Expression of the iNOS gene is induced by lipopolysaccharide (LPS) and augmented by interferon-gamma (IFN-gamma). Two regions of the iNOS promoter are known to regulate induction, a promoter proximal region I (RI) and a more distal region II (RII). Reconfiguration of RI within the iNOS regulatory region revealed its dependence upon native position and orientation for maximal activity, suggesting that it is a core promoter module, and further implicated the putative octamer element as a contributor to promoter activity. RII, however, functioned in a relatively orientation- and position-independent manner. Therefore, it had the characteristics of a classical enhancer element.
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PMID:A classical enhancer element responsive to both lipopolysaccharide and interferon-gamma augments induction of the iNOS gene in mouse macrophages. 754 63

Alcohol (EtOH) has been shown to suppress lipopolysaccharide (LPS)-induced nitric oxide (NO) generation and tumor necrosis factor (TNF) production in the lung in vivo. We have previously reported that EtOH suppressed gene expression for inducible nitric oxide synthase (iNOS) with a subsequent decrease in release of reactive nitrogen intermediates by alveolar macrophages and recruited lung neutrophils. We hypothesized that a similar mechanism may be involved in EtOH-induced suppression of LPS-stimulated TNF production. In contrast to what we found with iNOS, EtOH had no effect on TNF mRNA in alveolar macrophages or recruited lung neutrophils. However, immunoreactive and bioactive TNF was reduced by 72%. EtOH treatment resulted in an increased level of the membrane-bound 26-kDa form of TNF, which suggested that proteolytic cleavage of this prohormone was affected by EtOH. Experiments with t-butyl alcohol, a tertiary alcohol that is not metabolized to acetaldehyde, yielded similar results. Thus EtOH appears to be the active substance in suppression of TNF in the lung in vivo. Pretreatment with intratracheal interferon-gamma 24 h before intratracheal LPS increased TNF bioactivity partly due to increased TNF mRNA and by increasing TNF processing, as evidenced by a decrease in the 26-kDa TNF prohormone and an increase in immunoreactive and bioactive TNF.
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PMID:Differential effects of in vivo ethanol on LPS-induced TNF and nitric oxide production in the lung. 754 51

The decreased contraction amplitude of isolated cardiac myocytes from guinea pigs exposed to lipopolysaccharide (LPS) was reported to be partially reversed by nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase (NOS) [Brady, et al., Am. J. Physiol. 263 (Heart Circ. Physiol. 32): H1963-H1966, 1992]. We have tested the potential involvement of NO formation in LPS-induced cardiac depression in the intact heart. Isolated perfused hearts of LPS-treated guinea pigs (4 mg/kg 4 h before organ removal) displayed a greatly decreased left ventricular pressure (LVP) when compared with untreated controls (48 +/- 11 vs. 93 +/- 18 mmHg, n = 6 hearts each), whereas heart rate and coronary flow were similar. Perfusion of LPS-treated hearts with L-NMMA or L-NAME (100 microM each) at constant flow did not increase LVP (50 +/- 14 and 44 +/- 11, respectively, vs. 52 +/- 14 mmHg). However, coronary resistance increased significantly. There was no difference between LPS-treated and control hearts in venous adenosine release (104 +/- 58 vs. 133 +/- 86 pmol.min-1.g-1). Measurement of the activities of the induced (iNOS) and constitutive forms of NOS revealed that there was no difference in total NOS activity (237 +/- 82 vs. 181 +/- 97 fmol.min-1.mg protein-1. There was no measurable induction of iNOS in the LPS-treated hearts either. Finally, cardiac energy status was studied by 31P nuclear magnetic resonance spectroscopy. There was no difference between LPS-treated and control hearts in myocardial ATP, creatine phosphate, pH, and free ADP (59 +/- 20 vs. 50 +/- 27 microM).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Endotoxin-induced contractile dysfunction in guinea pig hearts is not mediated by nitric oxide. 754 61

Examination of the proliferative responses in vitro to mitogens (concanavalin A, phytohemagglutinin, lipopolysaccharide) of spleen cells recovered from C57BL/6 mice during blood-stage Plasmodium chabaudi AS infection revealed that the most severe suppression occurred during the first 14 days post infection, that is, during the acute phase of infection. Coincidently, inducible nitric oxide synthase gene expression was found to be up-regulated in the spleens of infected mice, and both splenic and peritoneal macrophages produced high levels of NO in vitro in response to stimulation with lipopolysaccharide (LPS). The roles of NO, a molecule recently found to mediate immunosuppression during parasitic infections, and of the well-recognized immunosuppressive molecule prostaglandin were, therefore, investigated in the suppression of proliferation to mitogens and specific antigen of spleen cells from 7- and 14-day P. chabaudi AS-infected mice. Addition of either 0.5 mM NG-monomethyl-L-arginine (L-NMMA) or 0.5 mM aminoguanidine (AG), inhibitors of NO synthase, or 10 micrograms/ml indomethacin (INDO), a prostaglandin inhibitor, partially but significantly abrogated the suppression in response to concanavalin A (Con A) and phytohemagglutinin (PHA). Only the addition of INDO significantly increased the responses to LPS. Addition of L-NMMA or AG in combination with INDO partially but significantly abrogated the suppression in response to Con A and completely abrogated the suppression in response to PHA. The addition of L-NMMA or AG also significantly increased proliferation in response to parasite antigen. The contribution of NO to suppression of lymphoproliferation was confirmed by adding 3-morpholino-sydnonimine-hydrochloride (SIN-1), a chemical generator of NO, to mitogen-stimulated splenocyte cultures prepared from normal mice. The mechanism of NO-mediated suppression was investigated in coculture experiments using spleen cells from normal mice and peritoneal macrophages from either normal or day 7 infected mice. The addition of 5-10 x 10(4) peritoneal macrophages from infected mice significantly and consistently suppressed Con A- or PHA-stimulated proliferation of normal splenocytes. Moreover, suppression correlated with production of NO and could be reversed by the addition of L-NMMA or AG. These results suggest that, in addition to prostaglandin, increased NO production by macrophages within the first 2 weeks after infection with P. chabaudi AS contributes to immunosuppression associated with blood-stage malaria.
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PMID:Role of macrophage-derived nitric oxide in suppression of lymphocyte proliferation during blood-stage malaria. 754 5

Nitric oxide (NO) is produced by numerous different cell types, and it is an important regulator and mediator of many processes including smooth muscle relaxation, neurotransmission, and murine macrophage-mediated cytotoxicity for microbes and tumor cells. Although murine macrophages produce NO readily after activation, human monocytes and tissue macrophages have been reported to produce only low levels of NO in vitro. The purpose of this study was to determine if stimulated human mononuclear phagocytes produce inducible nitric oxide synthase (iNOS) mRNA, protein, and enzymatic activity. By reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, we show that human monocytes can be induced to express iNOS mRNA after treatment with lipopolysaccharide (LPS) and/or interferon-gamma (IFN-gamma). By immunofluorescence and immunoblot analyses, we show monocytes and peritoneal macrophages contain detectable levels of iNOS antigen after stimulations with cytokines in vitro. Control monocytes or those cultured with LPS and/or various cytokines have low levels of NOS functional activity as measured by the ability of cell extracts to convert L-arginine to L-citrulline, and they produce low levels of the NO catabolites nitrite and nitrate. Peritoneal macrophages have significantly enhanced nitrite/nitrate production and NOS activity after treatment with LPS and/or IFN-gamma, whereas monocyte nitrite/nitrate production and NOS activity are not altered by the treatments. Monocytes cultured with various live or heat-killed bacteria, fungi, or human immunodeficiency virus (HIV)-1 do not produce high levels of nitrite/nitrate. Antibodies against transforming growth factor-beta (TGF-beta), a factor known to inhibit iNOS expression and NO production in mouse macrophages, do not enhance NO production in human monocytes or macrophages. Biopterin, an obligate cofactor of iNOS enzymatic activity, is undetectable in freshly isolated or cultured human monocytes and peritoneal macrophages. However, replenishment of intracellular levels of tetrahydrobiopterin by culture with the cell-permeable, nontoxic precursor sepiapterin does not enhance the abilities of the human mononuclear phagocytes to produce NO in vitro. Mixing experiments show no evidence of a functional NOS inhibitor in human mononuclear phagocytes. Thus, we demonstrate that human mononuclear phagocytes can produce iNOS mRNA and protein, and (despite this) their abilities to generate NO are very low.
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PMID:Human mononuclear phagocyte inducible nitric oxide synthase (iNOS): analysis of iNOS mRNA, iNOS protein, biopterin, and nitric oxide production by blood monocytes and peritoneal macrophages. 754 98

1. Endotoxin E. Coli lipopolysaccharide (LPS)-treatment in conscious, restrained rats increased plasma and urinary prostaglandin (PG) and nitric oxide (NO) production. Inducible cyclo-oxygenase (COX-2) and nitric oxide synthase (iNOS) expression accounted for the LPS-induced PG and NO release since the glucocorticoid, dexamethasone inhibited both effects. Thus, LPS (4 mg kg-1) increased the plasma levels of nitrite/nitrate from 14 +/- 1 to 84 +/- 7 microM within 3 h and this rise was inhibited to 35 +/- 1 microM by dexamethasone. Levels of 6-keto PGF1 alpha in the plasma were below the detection limit of the assay (< 0.2 ng ml-1). However, 3 h after the injection of LPS these levels rose to 2.6 +/- 0.2 ng ml-1 and to 0.7 +/- 0.01 ng ml-1 after LPS in rats that received dexamethasone. 2. The induced enzymes were inhibited in vivo with selective COX and NOS inhibitors. Furthermore, NOS inhibitors, that did not affect COX activity in vitro markedly suppressed PG production in the LPS-treated animals. For instance, the LPS-induced increased in plasma nitrite/nitrate and 6-keto PGF1 alpha at 3 h was decreased to 18 +/- 2 microM and 0.5 +/- 0.02 ng ml-1, 23 +/- 1 microM and 0.7 +/- 0.01 ng ml-1, 29 +/- 2 microM and 1 +/- 0.01 ng ml-1 in rats treated with LPS in the presence of the NOS inhibitors NG-monomethyl-L-arginine, NG-nitro arginine methyl ester and aminoguanidine, respectively. 3. The intravenous infusion of the NO donors sodium nitroprusside (SNP) or glyceryl trinitrate (GTN)increased prostaglandin production in normal animals (for instance urinary PGE2 excretion was increased from 96 +/- 10 to 576 +/- 12 pg min-1 and 400 +/- 24 pg min-1 in the presence of GTN or SNP respectively).4. Proteinuria was measured in order to evaluate the roles of NO and PG in renal damage associated with the in vivo injection of LPS. Interestingly, dexamethasone and the NOS inhibitors attenuated proteinuria in the LPS-treated rats. The COX inhibitors had no effect. It therefore appears that NO and not PG contributes to the LPS-induced renal damage; these findings support the potential use of NOS inhibitors in the treatment of renal inflammation.5. This study demonstrates the regulatory contribution of NO on the in vivo production of prostanoids and suggests that in inflammatory diseases that are driven by both NO and the prostaglandins, NOS inhibitors may act to reduce inflammation by the dual inhibition of cytotoxic NO and pro-inflammatory PG.
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PMID:Regulation of prostaglandin production by nitric oxide; an in vivo analysis. 754 31

Previous studies have demonstrated that, like bacterial lipopolysaccharide (LPS), arabinofuranosyl-terminated lipoarabinomannan (AraLAM) from an attenuated strain of Mycobacterium induces potent early gene (c-fos, KC, JE and TNF-alpha) responses in murine macrophages, whereas extensively alpha-Manp capped LAM (ManLAM) from virulent M. tuberculosis do not. In this study we have extended analysis of the influence of mycobacterial LAM on macrophage function by demonstrating that AraLAM (but not ManLAM), like bacterial LPS, is a potent stimulator of inducible nitric oxide synthase (iNOS) expression independent of the autocrine activity of co-stimulated tumour necrosis factor-alpha (TNF-alpha) release. The inability of ManLAM to induce iNOS expression was not due to induction of the 'deactivating' cytokine interleukin-10 (IL-10). Indeed, like LPS, AraLAM was also a potent inducer of IL-10 expression. However, analysis of AraLAM- or LPS-induced responses in the presence of interferon-gamma (IFN-gamma) showed that, whereas IFN-gamma acts as a potent co-stimulus for iNOS, it completely inhibits the IL-10 response. Hence, the presence of IFN-gamma early in infection will have an important immunomodulatory role in determining the macrophage response. These results have important implications for the pathogenesis of virulent and avirulent mycobacteria in vivo.
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PMID:Opposing effects of interferon-gamma on iNOS and interleukin-10 expression in lipopolysaccharide- and mycobacterial lipoarabinomannan-stimulated macrophages. 754 44

Unlike large-vessel endothelial cells in cell culture, cardiac microvascular endothelial cells (CMEC) isolated from adult rat ventricular muscle exhibit little detectable constitutive nitric oxide (NO) synthase activity after isolation in vitro but respond to specific combinations of inflammatory mediators with an increase in inducible NO synthase (iNOS; type 2 NO synthase) activity. CMEC iNOS is induced by soluble inflammatory mediators in lipopolysaccharide-activated rat alveolar macrophage-conditioned medium at 24 hours, and this induction can be partially prevented by either interleukin-1 (IL-1) receptor antagonist or a polyclonal anti-rat tumor necrosis factor-alpha (TNF-alpha) antiserum. Interferon-gamma (IFN-gamma), which by itself does not induce iNOS in CMEC, potentiates and accelerates iNOS induction by IL-1 beta. Transforming growth factor-beta (TGF-beta) decreases iNOS activity, protein content, and mRNA abundance in IL-1 beta- and IFN-gamma-pretreated CMEC. To determine whether NO released by CMEC would affect myocyte contractile function in vitro, freshly isolated ARVM were allowed to settle onto confluent, serum-starved CMEC that had been pretreated for 24 hours with IL-1 beta, a cytokine that alone does not affect myocyte contractile function in vitro. Baseline contractile amplitude, at 2 Hz and 37 degrees C, of myocytes in heterotypic culture with IL-1 beta-pretreated CMEC was not different from that of myocytes in control, homotypic myocyte cultures. However, cocultured myocytes exhibited decreased contractile responsiveness to 2 nmol/L isoproterenol compared with control cells, and this could be reversed by the addition of 1 mmol/L NG-monomethyl-L-arginine, an inhibitor of NOS.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Contractile responsiveness of ventricular myocytes to isoproterenol is regulated by induction of nitric oxide synthase activity in cardiac microvascular endothelial cells in heterotypic primary culture. 754 25


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