Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.14.13.39 (NO synthase)
 15,778 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A cytokine-mediated excessive increase in nitric oxide (NO) by macrophages or glial cells via an inducible isoform of NO synthase (iNOS) has been proposed to play an important role in demyelinating diseases. To further investigate the role of iNOS in demyelination, experimental allergic encephalomyelitis (EAE), a known animal model of multiple sclerosis (MS) in mice, was chosen in this study. A semiquantitative reverse transcriptase-polymerase chain reaction (RT/PCR) analysis revealed an increase in the mRNA levels of iNOS and cytokines known to induce iNOS or inflammatory cytokines (interleukin (IL)-1 alpha, IL-1 beta, IL-2, IL-6, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha and TNF-beta) in the spinal cord corresponding to the severity of the disease without significant change in the mRNA levels of immunoregulatory cytokines (IL-4, IL-10 and transforming growth factor (TGF)-beta) during the course of EAE. An immunohistochemical examination of the spinal cord using an iNOS-specific antibody showed iNOS-positive cells to be mainly inflammatory cells with a higher frequency of iNOS-positive cells at the peak of EAE than in the early phase. These iNOS-positive cells at the peak appeared to be composed of infiltrating macrophages and most of them were located in the necrotic area. These results suggested that cytokine-induced excessive NO via iNOS by macrophages caused tissue damage in the central nervous system in EAE.
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PMID:Expression of the inducible isoform of nitric oxide synthase in the central nervous system of mice correlates with the severity of actively induced experimental allergic encephalomyelitis. 749 86

Murine macrophages express high levels of nitric oxide synthase and produce large amounts of nitric oxide (NO) when stimulated with certain cytokines in the presence of a trace amount of lipopolysaccharide (LPS). The stimulatory cytokines include interleukin-1 (IL-1), interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and migration inhibitory factor. Activated macrophages are highly effective killers of intra- and extra-cellular pathogens. However, as excessive NO can lead to immunopathology (diabetes, graft-v.-host disease, EAE, liver cirrhosis, rheumatoid arthritis), NO production is necessarily under tight regulation. A number of cytokines, including IL-4, IL-10 and transforming growth factor-beta, can down regulate the induction of NO synthase in macrophages. In addition, macrophages exposed to LPS alone and then stimulated with a mix of IFN-gamma and LPS express significantly lower levels of NO synthase than cells stimulated without pre-exposure to LPS. Furthermore, NO can reduce the activity of NO synthase by feedback inhibition, and also inhibit the production of IFN-gamma by Th1 cells (thus turning off its own synthesis from upstream). The regulatory pathways involve tyrosine kinase and protein kinase C.
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PMID:The role of nitric oxide in parasitic diseases. 751 Jan

It has recently been appreciated that NO, a molecule previously known to play a physiologic role in blood pressure regulation, is a major effector molecule of macrophage cytotoxicity against a variety of microbial targets, including protozoan and helminth parasites. NO production by macrophages is arginine dependent and catalyzed by a cytokine-inducible form of the NO synthase. This activity is positively controlled by several up-regulatory stimuli (including IFN-gamma, TNF-alpha, IL-2) and negatively controlled by others (principally IL-10, IL-4, TGF-beta). Other cell types, such as endothelial cells and hepatocytes, display a similar capacity for NO production in response to cytokine stimulation. In murine models of leishmaniasis and schistosomiasis, in vivo NO synthesis correlates with protective immunity against infection. The effector molecule that plays a similar role in cell-mediated immunity in man has not yet been identified.
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PMID:NO as an effector molecule of parasite killing: modulation of its synthesis by cytokines. 752 Mar 38

C57BL/6 mice were vaccinated with irradiated cercariae of Schistosoma mansoni, and, at various times after challenge infection, total lung mRNA was isolated to assess the induction of several cytokines that previously had been shown in in vitro studies to be involved in the activation of macrophages and/or endothelial cells for nitric oxide (NO) production and killing of schistosomula. Vaccinated mice demonstrated a highly significant increase in IFN-gamma mRNA upon subsequent infection when compared with infected nonvaccinated controls. A similar, although less dramatic, increase in two other macrophage-activating cytokines, TNF-alpha and IL-2, also was observed. In contrast, although the Th2 cytokines IL-4, IL-5, IL-10, and IL-13 were elevated in challenged vaccinated animals, only IL-10 and IL-13 showed increases that were significant with respect to the mRNA levels observed in challenged controls. Neutralization of IFN-gamma reduced immunity in vaccinated animals and resulted in decreased IFN-gamma, IL-2, IL-10, TNF-alpha, and IL-12 p40 but markedly increased IL-4, IL-5, and IL-13 mRNA expression and serum IgE levels. Pulmonary NO synthase expression was elevated in immunized mice at a time at which immune elimination of schistosomula is believed to occur. Moreover, suppression of NO synthase activity with the inhibitor aminoguanidine reduced immunity, as measured by a 32 to 33% increase in worm burden. Together, these data support previous in vitro studies that suggest a role for NO in schistosomulum killing. Furthermore, the observation that the down-regulatory cytokines IL-4, IL-10, and IL-13 are induced together with IFN-gamma may provide an explanation for the failure of this vaccine to provide complete protection.
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PMID:Elevated expression of Th1 cytokines and nitric oxide synthase in the lungs of vaccinated mice after challenge infection with Schistosoma mansoni. 752 27

Activation with lipopolysaccharide induces macrophages to produce the enzymes arginase and nitric oxide (NO) synthase. Both enzymes use as a substrate the amino acid L-arginine, which can be either hydrolyzed by arginase to urea and ornithine or oxidized by NO synthase to NO and citrulline. NO is important in the bactericidal and cytotoxic activities of macrophages. An equivalent functional role of arginase and its products is not known. We tested the induction of arginase in bone marrow-derived macrophages by endogenous mediators that are known to induce NO synthase, such as interferon-gamma (IFN-gamma), or suppress the induction of this enzyme, such as interleukin (IL)-4, IL-10, and prostaglandin E2 (PGE2). We find that PGE2 and the TH2 cytokines IL-4 and IL-10 are potent inducers of arginase. In contrast, the TH1 cytokine IFN-gamma does not induce arginase. Simultaneous application of both types of mediators leads to reduced induction of both arginase and NO synthase. Exposure of macrophage cultures to inducers of NO synthase exhausts their ability to respond subsequently to inducers of arginase. Conversely, exposure of the cells to inducers of arginase exhausts their ability to respond subsequently to inducers of NO synthase. The results are consistent with a competition of both enzymes for their substrate, L-arginine, with a reciprocal inhibition in the induction of both enzymes, or a combination of both phenomena. The enzymes NO synthase and arginase appear to define two alternate functional states of macrophages, induced by TH1 and TH2 cytokines, respectively.
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PMID:Reciprocal regulation of the nitric oxide synthase/arginase balance in mouse bone marrow-derived macrophages by TH1 and TH2 cytokines. 753 72

Mice with a disruption of the IFN-gamma receptor alpha-chain gene (IFN-gamma R alpha o/o mice) were found to be significantly more sensitive than their wild-type counterparts to induction of the anti-CD3-induced disease syndrome. Specifically, when given a selected dose of anti-CD3 Ab, IFN-gamma R alpha o/o mice developed severe hypothermia and hypoglycemia, leading to 100% mortality within 72 h. In contrast, wild-type mice failed to develop overt pathologic manifestations and survived. Histologic examination revealed apoptosis in thymuses and spleens, which were significantly more pronounced in the mutant than in the wild-type mice, as confirmed by flow cytometric and DNA electrophoretic analysis. Apoptosis affected mainly CD4+CD8+ and CD4+CD8- thymocytes. Other histologic alterations were steatosis in livers, and erythrocyte extravasation and infiltration of apoptotic cells in lungs, all of which were exclusively observed in IFN-gamma R alpha o/o mice. Blood levels of TNF, IL-2, IL-6, and IL-10 were slightly more elevated in IFN-gamma R alpha o/o mice, but insufficiently so to explain increased disease severity. Thus, even more elevated cytokine levels in wild-type mice receiving high doses of anti-CD3 Ab were not associated with morbidity or apoptosis. Blood levels of IFN-gamma were barely detectable in anti-CD3-challenged wild-type mice, but were relatively high in the mutant mice. Increased susceptibility of IFN-gamma R alpha o/o mice was associated with impaired nitric oxide (NO) production, as indicated by significantly lower plasma nitrite levels and by more transient expression of spleen inducible NO synthase mRNA. Moreover, treatment of wild-type mice with the NO synthase inhibitor N-nitro-L-arginine methylester resulted in increased anti-CD3-induced morbidity and mortality. The data indicate that IFN-gamma R alpha o/o mice produce less NO and are therefore more sensitive than wild-type mice to the deleterious effect of anti-CD3 Ab.
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PMID:IFN-gamma receptor-deficient mice are hypersensitive to the anti-CD3-induced cytokine release syndrome and thymocyte apoptosis. Protective role of endogenous nitric oxide. 756 Oct 88

An intense suppression of splenic T cell proliferation to mitogens and to Ags from the parasite is characteristic of the acute phase of Trypanosoma cruzi infection in mice. The impairment of proliferation is coincident with high levels of IFN-gamma and nitrite and decreased production of IL-2 in the supernatants of spleen cell cultures from infected mice. Previous work demonstrated that suppression of proliferation is largely mediated by the population of adherent cells in the infected spleen. In this study we confirmed the active suppression exerted by these cells on Con A, anti-CD3, and parasite Ag-stimulated proliferation of CD4+ splenic T cells. Inasmuch as the high production of IFN-gamma and of nitrite were compatible with intense macrophage activation and nitric oxide (NO) production, we determined the effects of cytokines that regulate macrophage activation and of NO on the proliferation of spleen cells from infected mice. We show that spleen cell proliferation to Ag and to T cell polyclonal stimuli is increased by neutralizing mAbs to IFN-gamma, TNF-alpha and -beta, or by the inhibitor of NO synthase, NG-monomethyl-L-arginine, added to the cultures. The addition of rIL-2 or rIL-4 also contributed to suppression reversal, and the combined addition of rIL-2 and anti-IFN-gamma mAb further increased lymphocyte proliferation. Anti-IL-4, anti-IL-10, or anti-TGF-beta neutralizing mAbs did not modify suppressed proliferative responses, and the addition of rIL-10 or of rTGF-beta also did not recover cell proliferation. Thus, the suppression of proliferative responses in T. cruzi-infected mice resulted largely from increased NO production by macrophages activated by IFN-gamma and TNF allied to insufficient IL-2 to fully support in vitro growth of T lymphocytes.
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PMID:Cytokine and nitric oxide regulation of the immunosuppression in Trypanosoma cruzi infection. 756 Nov 3

Nitric oxide (NO) is an essential mediator for a variety of biological functions, including defence against a range of pathogens. However, excessive production of NO as a result of immunological stimulation, will lead to important immunopathologies. Therefore the production of NO is necessarily under tight regulation. The regulatory mechanisms so far known to control NO synthesis include cytokines (induction of NO synthase by IFN-gamma, TNF alpha, MIF and LPS, and down regulation by IL-4, IL-10 and TGF beta), feedback inhibition by NO itself, inhibition by pretreatment with LPS and glycoinositol-phospholipids and up regulation by lipophosphoglycan from the protozoa parasite, Leishmania major.
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PMID:Regulation of nitric oxide synthesis in infectious and autoimmune diseases. 773 95

Production of nitric oxide (NO) by macrophages is important for the killing of intracellular pathogens. IFN-gamma and LPS stimulate NO production by transcriptional up-regulation of inducible nitric oxide synthetase (iNOS). In the present study we used mice with a targeted disruption of the IFN regulatory factor-1 gene (IRF-1-/-) to investigate the importance of NO in the host immune response against Toxoplasma gondii, a major cause of infection in newborns and those with AIDS. IRF-1-/- mice were more susceptible to acute Toxoplasma infection, and treatment with either exogenous IFN-gamma or in vivo neutralization of endogenous IFN-gamma had little effect on their susceptibility to infection. However, administration of exogenous IL-12 was able to prolong survival even when IFN-gamma was depleted. An in vivo depletion study suggested that the mechanism of this protective response is mediated in part by CD4+ T cells. The administration of IL-12 could not overcome the inhibition of lymphoproliferative response in T. gondii-infected mice and treatment with N-monomethyl-L-arginine (L-NMMA), a nitric oxide synthase (iNOS) antagonist in vitro was unable to reverse the immunosuppression. In response to Toxoplasma infection, splenocytes from IRF-1-/- mice exhibited increased production of IL-10 as well as a 30-fold increase in its message expression. These studies indicate that NO may not be essential for host immunity to the parasite, and moreover that IL-12 appears to induce an IFN-gamma-independent mechanism of protection against this opportunistic pathogen.
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PMID:Production of nitric oxide (NO) is not essential for protection against acute Toxoplasma gondii infection in IRF-1-/- mice. 854 15

Leishmania major promastigotes were found to avoid activation of mouse bone marrow-derived macrophages (BMM0) in vitro for production of cytokines that are typically induced during infection with other intracellular pathogens. Coexposure of BMM0 to the parasite and other microbial stimuli resulted in complete inhibition of interleukin (IL) 12 (p40) mRNA induction and IL-12 release. In contrast, mRNA and protein levels for IL-1(alpha), IL-1(beta), tumor necrosis factor (TNF) alpha, and inducible NO synthase (iNOS) were only partially reduced, and signals for IL-10 and monocyte chemoattractant protein (MCP-1/JE) were enhanced. The parasite could provide a detectable trigger for TNF-alpha and iNOS in BMM0 primed with interferon (IFN) gamma, but still failed to induce IL-12. Thus IL-12 induction is selectively impaired after infection, whereas activation pathways for other monokine responses remain relatively intact. Selective and complete inhibition of IL-12(p40) induction was observed using BMM0 from either genetically susceptible or resistant mouse strains, as well as IL-10 knockout mice, and was obtained using promastigotes from cutaneous, visceral, and lipophosphoglycan-deficient strains of Leishmania. The impaired production of the major physiological inducer of IFN-gamma is suggested to underlie the relatively prolonged interval of parasite intracellular survival and replication that is typically associate with leishmanial infections, including those producing self-limiting disease.
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PMID:Leishmania promastigotes selectively inhibit interleukin 12 induction in bone marrow-derived macrophages from susceptible and resistant mice. 862 63


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