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)

The effects of lipopolysaccharide (LPS) and/or inflammatory cytokines on the expression of inducible nitric oxide synthase (iNOS) were studied in mIMCD-3 cells, derived from the murine inner medullary collecting duct. Under basal conditions, the production of nitrite, a stable metabolite of NO, was negligible; however, incubation with tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IF-gamma) for 24 h resulted in a 12-fold increase in nitrite synthesis and the appearance of abundant iNOS mRNA and protein. The induction of nitrite production and iNOS mRNA was time dependent, requiring approximately 8 h for expression of significant levels of nitrite or iNOS mRNA. Coincubation with the transcription inhibitor actinomycin D or the translation inhibitor cycloheximide prevented the cytokine induction of iNOS mRNA and NO production, indicating that synthesis of intermediary proteins stimulated transcription of the iNOS gene. Nuclear run-on transcription demonstrated that the iNOS gene was transcriptionally inactive under basal conditions, but was markedly induced by TNF-alpha and IF-gamma. These results indicate that inflammatory cytokines stimulate NO production in mIMCD-3 cells by activating iNOS gene transcription in a process that requires new protein synthesis.
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PMID:Cytokines activate inducible nitric oxide synthase gene transcription in inner medullary collecting duct cells. 753 67

An inducible nitric oxide synthase has recently been described in proximal tubule epithelium. To investigate the effects of proximal tubule NO on Na+/K(+)-ATPase, we induced NO production in mouse proximal tubule epithelial cells by treatment with lipopolysaccharide (LPS) and interferon-gamma (IFN gamma) followed by determinations of ouabain-sensitive ATPase activity. Na+/K(+)-ATPase activity decreased after 4 h of LPS/IFN gamma treatment, reaching maximal inhibition after 24 h (34% reduction in activity). The inhibition of Na+/K(+)-ATPase activity by LPS/IFN gamma was prevented by simultaneous incubation with N omega-nitro L-arginine and markedly blunted by removal of L-arginine from the medium. The NO donors sodium nitroprusside and SIN-1 also inhibited Na+/K(+)-ATPase activity to a similar extent than LPS/IFN gamma. However, treatment with 8-pCPT-cGMP only modestly reduced Na+/K(+)-ATPase activity. Interestingly, superoxide dismutase prevented the inhibitory effects of NO on Na+/K(+)-ATPase activity, suggesting a role for peroxynitrite in this inhibition. We conclude that NO generated by mouse proximal tubule epithelial cell iNOS inhibits Na/K ATPase activity in an autocrine fashion and that this inhibition is accompanied by a reduction in Na-dependent solute transport.
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PMID:Autocrine inhibition of Na+/K(+)-ATPase by nitric oxide in mouse proximal tubule epithelial cells. 753 54

Mice deficient in inducible nitric oxide synthase (iNOS) were generated to test the idea that iNOS defends the host against infectious agents and tumor cells at the risk of contributing to tissue damage and shock. iNOS-/-mice failed to restrain the replication of Listeria monocytogenes in vivo or lymphoma cells in vitro. Bacterial endotoxic lipopolysaccharide (LPS) caused shock and death in anesthetized wild-type mice, but in iNOS-/-mice, the fall in central arterial blood pressure was markedly attenuated and early death averted. However, unanesthetized iNOS-/-mice suffered as much LPS-induced liver damage as wild type, and when primed with Propionobacterium acnes and challenged with LPS, they succumbed at the same rate as wild type. Thus, there exist both iNOS-dependent and iNOS-independent routes to LPS-induced hypotension and death.
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PMID:Altered responses to bacterial infection and endotoxic shock in mice lacking inducible nitric oxide synthase. 753 9

We have previously reported that a mixture of lipopolysaccharide and cytokines stimulates cultured rat pulmonary artery smooth muscle cells (RPASM) to express elevated levels of mRNA for inducible nitric oxide synthase (iNOS), and to produce large amounts of nitric oxide (NO). The current study tests the hypothesis that transforming growth factor-beta (TGF-beta) modulates this process. Accordingly, RPASM were treated with a mixture of LPS (10 micrograms/ml) and the cytokines interleukin-1 beta (5 U/ml), tumor necrosis factor-alpha (500 U/ml), and interferon-gamma (100 U/ml). In the absence of TGF-beta 1, NO production (indicated by colorimetric assay of cumulative nitrite levels at 24 h) was greatly increased, as previously observed. Under identical conditions, TGF-beta 1 caused a concentration-dependent decrease in NO production. The addition of neither excess L-arginine nor sepiapterin reversed the inhibition, indicating that the effect of TGF-beta 1 was not due to limitation of enzyme substrate or cofactor tetrahydrobiopterin, respectively. Northern and Western analyses showed that TGF-beta 1 reduced levels of iNOS mRNA and protein to baseline at all time points examined up to 24 h. Complete suppression of iNOS protein expression was evident even when TGF-beta 1 was added at postinduction time points. One mechanism of action of TGF-beta 1 was demonstrated in experiments in which degradation of iNOS protein was greatly increased by the addition of TGF-beta 1. These results demonstrate that TGF-beta 1 regulates production of NO in RPASM by inhibiting iNOS expression in part by increasing degradation of existing iNOS protein.
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PMID:TGF-beta regulates production of NO in pulmonary artery smooth muscle cells by inhibiting expression of NOS. 753 24

In view of studies showing that not only nitric oxide synthase (NOS) activity but arginase activity is induced in rodent macrophages by lipopolysaccharide (LPS), the objective of this study was to investigate the co-induction of these two enzymes and to ascertain whether common mechanisms are involved. RAW 264.7 cells were activated by 2 micrograms LPS/ml and incubated for up to 48 hr. Inducible NOS (iNOS) and inducible arginase II (AII) activities were monitored, respectively, by measuring NO2-/NO3- accumulation in cell culture media and formation of urea (as CO2) from L-arginine by cell lysates. AII activity increased linearly up to at least 48 hr, whereas NO2-/NO3- formation reached a plateau well before 48 hr. Immunoprecipitation experiments revealed that AII accounted for 90-100% of arginase activity in LPS-activated macrophages. The inhibitor of NF-kappa B activation, pyrrolidine dithiocarbamate, inhibited the induction of iNOS but not AII. Moreover, whereas IFN-gamma caused iNOS induction, AII induction was nearly abolished by IFN-gamma, perhaps by inhibiting transcription of the AII gene. These observations indicate that co-induction of iNOS and AII occurs by distinct transcriptional mechanisms, AII induction could diminish NO production by decreasing L-arginine availability, and IFN-gamma can prevent AII induction.
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PMID:Co-induction of arginase and nitric oxide synthase in murine macrophages activated by lipopolysaccharide. 753 53

We report here on the characterization of soluble and particulate forms of the inducible nitric oxide synthase in RAW 264.7 macrophage cells. Stimulation of these cells with E. coli lipopolysaccharide and interferon-gamma resulted in a significant induction of nitric oxide synthase activity with approximately 20% of the total activity localized to the cell membrane. Like the soluble enzyme form, the membrane-associated nitric oxide synthase activity was inhibited by NG-monomethyl-L-arginine and did not require the addition of calcium. Both protein forms were immunoreactive on Western blots with antibodies specifically recognizing the carboxyl terminus of the protein. In contrast, antibodies specific for the amino terminus recognized inducible nitric oxide synthase from the cytosol, but failed to recognize the membrane-associated protein. Thus, macrophage cells are capable of expressing two forms of the inducible nitric oxide synthase that are definable by an intracellular distribution that correlates to antigenic differences at the amino terminus.
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PMID:Particulate and soluble forms of the inducible nitric oxide synthase are distinguishable at the amino terminus in RAW 264.7 macrophage cells. 753 56

Products of inducible nitric oxide synthase (iNOS) are known to be involved in lung injury following intrapulmonary deposition of immunoglobulin G immune complexes (IgG-ICx). In the current studies rat alveolar macrophages stimulated in vitro with murine interferon gamma (IFN-gamma), tumor necrosis factor alpha, interleukin 1 alpha, (IL-1 alpha), lipopolysaccharide (LPS), or IgG-ICx immunostained for iNOS and produced nitrite/nitrate- (NO2-/NO3-) in a dose- and time-dependent manner requiring availability of L-arginine. Under the same conditions, IL-4 and IL-10 reduced NO2-/NO3- generation. Type II alveolar epithelial cells, which were obtained from normal rat lungs and stimulated in vitro with IgG-ICx, LPS, or IFN-gamma, also immunostained for iNOS and generated NO2-/NO3-. Special techniques of bronchoalveolar lavage (BAL) were used to retrieve alveolar macrophages and type II alveolar epithelial cells. Under these conditions, intrapulmonary deposition of LPS yielded BAL fluids containing increased amounts of NO2-/NO3- and macrophages that spontaneously released NO2-/NO3- and stained for iNOS. After intrapulmonary deposition of IgG both macrophages as well as type II cells (retrieved by BAL) spontaneously produced NO2-/NO3- and both cell types immunostained for iNOS (approximately 20% of all type II cells and 35% of all alveolar macrophages). Using dual fluorescence staining for cell identification, frozen sections of lung tissue after IgG immune complex deposition revealed iNOS in both alveolar macrophages and type II cells. Finally, in the immune complex model of alveolitis, the appearance of iNOS in macrophages as well as macrophage production in vitro of NO2-/NO3- was dependent on the in vivo availability of tumor necrosis factor alpha, IL-1, and IFN-gamma. These studies suggest a dual cell source for nitric oxide in inflamed lungs and the requirements for iNOS of several cytokines.
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PMID:Lung sources and cytokine requirements for in vivo expression of inducible nitric oxide synthase. 753 74

The present study characterizes mechanisms involved with the induction of nitric oxide (NO) production, nitric oxide synthase (NOS) enzymatic activity and mRNA expression in human articular chondrocytes. Activation of chondrocytes with lipopolysaccharide (LPS) or IL-1 resulted in time- and dose-dependent increases in iNOS mRNA followed by increased NOS enzymatic activity and NO release. The protein tyrosine kinase (PTK) inhibitors herbimycin A or genistein reduced IL-1 or LPS-induced NO release and NOS enzymatic activity. This was associated with inhibition of iNOS mRNA expression as determined by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. In contrast, inhibitors of protein kinase C (PKC) or protein kinase A (PKA) did not affect these responses. These results were confirmed in experiments with second messenger agonists where neither activation of PKC, nor increases in cyclic adenosine monophosphate (cAMP) or increased intracellular calcium levels were associated with the induction of iNOS mRNA or NO release. These results suggest that PKC, PKA and calcium-dependent signals are not required or sufficient for the stimulation of NO production. However, NO production is dependent on tyrosine kinases due to their role in the expression of iNOS mRNA.
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PMID:Tyrosine kinases are involved with the expression of inducible nitric oxide synthase in human articular chondrocytes. 753 12

Simultaneous incubation of primary rat bone-marrow-derived mononuclear phagocytes (BMMo) and tumor cells with gram-negative agents triggers within 24 h interferon gamma (IFN gamma)- and tumor necrosis factor (TNF alpha)-independent tumoricidal activity. On the other hand, BMMo that had been incubated for 24 h with gram-negative agents prior to re-exposure to the same agent had largely lost their ability to generate tumoricidal activity, although their ability to bind lipopolysaccharide (LPS) was not diminished. Parallel measurements of the kinetics of inducible nitric oxide synthase (iNOS), nitrite secretion, and tumoricidal activity triggered in primary BMMo by LPS revealed that these parameters take a coordinate course, reaching a peak within 24 h and then rapidly decaying. Down-regulation of expression of NOS protein and iNOS activity could be attributed neither to down-regulation of LPS receptors nor to L-arginine depletion.
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PMID:Coordinate up- and down-modulation of inducible nitric oxide synthase, nitric oxide production, and tumoricidal activity in rat bone-marrow-derived mononuclear phagocytes by lipopolysaccharide and gram-negative bacteria. 754 2

Production of nitric oxide (NO) can be stimulated by inflammatory cytokines and bacterial lipopolysaccharide (LPS) in mammalian cells via an inducible nitric oxide synthase (iNOS). Conversely, the transforming growth factor-beta s (TGF-beta s) suppress NO production by reducing iNOS expression. Production of NO leads to disparate consequences, some beneficial and some damaging to the host, depending on the cell and context in which iNOS is induced. The TGF-beta s counter these NO-mediated processes in macrophages, cardiac myocytes, smooth muscle cells, bone marrow cells, and retinal pigment epithelial cells. Autocrine or paracrine production of TGF-beta may thus serve as a physiological counterbalance for iNOS expression, a mechanism which may be subverted by pathogens and tumors for their own survival. A greater understanding of the mechanisms and consequences of NO and TGF-beta production may lead to effective therapeutic strategies in various diseases.
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PMID:Control of nitric oxide synthase expression by transforming growth factor-beta: implications for homeostasis. 754 59


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