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)

Exposure of primary cultures of neonatal rat cortical astrocytes to bacterial lipopolysaccharide (LPS) results in the appearance of nitric oxide synthase (NOS) activity. The induction of NOS, which is blocked by actinomycin D, is directly related to the duration of exposure and dose of LPS, and a 2-hr pulse can induce enzyme activity. Cytosol from LPS-treated astrocyte cultures, but not from control cultures, produces a Ca(2+)-independent conversion of L-arginine to L-citrulline that can be completely blocked by the specific NOS inhibitor NG-monomethyl-L-arginine. The induced NOS activity exhibits an apparent Km of 16.5 microM for L-arginine and is dependent on NADPH, FAD, and tetrahydrobiopterin. LPS also induces NOS in C6 glioma cells and microglial cultures but not in cultured cortical neurons. The expression of NOS in astrocytes and microglial cells has been confirmed by immunocytochemical staining using an antibody to the inducible NOS of mouse macrophages and by histochemical staining for NADPH diaphorase activity. We conclude that glial cells of the central nervous system can express an inducible form of NOS similar to the inducible NOS of macrophages. Inducible NOS in glia may, by generating nitric oxide, contribute to the neuronal damage associated with cerebral ischemia and/or demyelinating diseases.
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PMID:Induction of calcium-independent nitric oxide synthase activity in primary rat glial cultures. 127 98

We studied the effect of focal cerebral ischemia on inducible (iNOS) and constitutive (cNOS) nitric oxide synthase enzymatic activities in the affected brain. The middle cerebral artery (MCA) was occluded in spontaneously hypertensive rats. Animals were killed 1, 2, 4, and 7 days later. cNOS and iNOS enzymatic activities were determined in the infarcted cortex using the assay of Bredt and Snyder. cNOS was assayed in the presence of calcium, whereas iNOS was assayed in the absence of calcium and in the presence of tetrahydrobiopterin. The validity of the iNOS assay was verified in rats treated with bacterial lipopolysaccharide. In these animals, the magnitude of the induction of iNOS enzymatic activity in lung, spleen, and brain paralleled the expression of iNOS mRNA, assessed by reverse-transcription polymerase chain reaction. After MCA occlusion, calcium-dependent (cNOS) activity was markedly reduced only in lesioned cerebral cortex at days 1-7 (p < 0.001; analysis of variance and Tukey's test). In contrast to cNOS, calcium-independent (iNOS) activity was induced substantially in the infarct (p < 0.005) but not in the contralateral intact cortex (p > 0.05). iNOS activity peaked at day 2 and was not different from baseline at day 7 (p > 0.05). No NADPH diaphorase-positive neurons were observed in the area of the lesion at days 1-7. Macrophages appeared at day 2 and invaded the infarcted tissue by day 7. At this time, numerous glial fibrillary acidic protein-positive astrocytes were observed within the lesion. The results suggest that the decline in calcium-dependent (cNOS) activity reflects loss of NOS neurons within the lesion.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Marked induction of calcium-independent nitric oxide synthase activity after focal cerebral ischemia. 752 24

Enhanced formation of nitric oxide (NO) by both the constitutive and the inducible isoforms of NO synthase (NOS) has been implicated in the pathophysiology of a variety of diseases, including circulatory shock. Non-isoform-selective inhibition of NO formation, however, may lead to side effects by inhibiting the constitutive isoform of NOS and, thus, the various physiological actions of NO. S-Methylisothiourea sulfate (SMT) is at least 10- to 30-fold more potent as an inhibitor of inducible NOS (iNOS) in immunostimulated cultured macrophages (EC50, 6 microM) and vascular smooth muscle cells (EC50, 2 microM) than NG-methyl-L-arginine (MeArg) or any other NOS inhibitor yet known. The effect of SMT on iNOS activity can be reversed by excess L-arginine in a concentration-dependent manner. SMT (up to 1 mM) does not inhibit the activity of xanthine oxidase, diaphorase, lactate dehydrogenase, monoamine oxidase, catalase, cytochrome P450, or superoxide dismutase. SMT is equipotent with MeArg in inhibiting the endothelial, constitutive isoform of NOS in vitro and causes increases in blood pressure similar to those produced by MeArg in normal rats. SMT, however, dose-dependently reverses (0.01-3 mg/kg) the hypotension and the vascular hyporeactivity to vasoconstrictor agents caused by endotoxin [bacterial lipopolysaccharide (LPS), 10 mg/kg, i.v.] in anesthetized rats. Moreover, therapeutic administration of SMT (5 mg/kg, i.p., given 2 hr after LPS, 10 mg/kg, i.p.) attenuates the rises in plasma alanine and aspartate aminotransferases, bilirubin, and creatinine and also prevents hypocalcaemia when measured 6 hr after administration of LPS. SMT (1 mg/kg, i.p.) improves 24-hr survival of mice treated with a high dose of LPS (60 mg/kg, i.p.). Thus, SMT is a potent and selective inhibitor of iNOS and exerts beneficial effects in rodent models of septic shock. SMT, therefore, may have considerable value in the therapy of circulatory shock of various etiologies and other pathophysiological conditions associated with induction of iNOS.
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PMID:Beneficial effects and improved survival in rodent models of septic shock with S-methylisothiourea sulfate, a potent and selective inhibitor of inducible nitric oxide synthase. 752 23

Nitric oxide (NO) produces rapid osteoclast detachment and contraction in vitro, and this effect is accompanied by a profound inhibition of bone resorption. Work by others has confirmed these findings in vivo: inhibition of NO synthase [NOS; L-arginine, NADPH: oxygen oxidoreductase (NO-forming), EC 1.14.13.39] in normal rats is followed by increased bone resorption reflected by a marked loss in bone mineral density. In our present study, immunocytochemistry and Northern blotting show the presence of the constitutive calcium-sensitive NOS isoform (cNOS) in normal rat osteoclasts and in the human preosteoclast cell line (FLG 29.1). The inducible NOS isoform (iNOS) was also clearly demonstrable in the rat cells especially after treatment with gamma interferon (IFN-gamma) and bacterial wall products [lipopolysaccharide (LPS)], while a basal level of transcript was detected in the untreated human preosteoclast line. However NADPH-diaphorase activity was intense only in neonatal rat osteoclasts attached to bone, perhaps reflecting either enhancement of cNOS activity by calcium or increased amounts of the inducible isoform in activated osteoclasts in situ compared with isolated neonatal rat osteoclasts. These actively resorb devitalized bone but the untreated cells contain relatively low levels of NOS; they are extremely sensitive to inhibition by NO. The iNOS inhibitor aminoguanidine markedly enhances in vitro resorption by activated NOS-rich chick osteoclasts and by normal rat osteoclasts treated with LPS or IFN-gamma. In contrast, the nonselective NOS inhibitor NG-monomethyl-L-arginine inhibits resorption by untreated neonatal rat osteoclasts. Thus, osteoclast function may require intermittent calcium-stimulated increases in NO production by cNOS against a basal inhibitory background activity of the iNOS isoform. However, bone resorption depends on precursor replication and on the activity of the mature cells, and we found that the NO donor 3-morpholinosydnonimine (SIN-1) (50 microM) profoundly depressed replication in the human preosteoclast line. Taken together, these results strongly suggest that NO maintains a central control of bone resorption in both avian and mammalian species by exerting a powerful tonic restraint of osteoclast numbers and activity. The presence of NOS in human cells implies a similar function in man and that conventional views of calcium homoeostasis and skeletal metabolism will need substantial revision. Since NO also influences behavior of the osteoblast, the bone-forming cell, in vitro, a similar effect in vivo might imply a general influence on bone remodeling.
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PMID:Bidirectional regulation of osteoclast function by nitric oxide synthase isoforms. 753 33

Atherosclerotic lesions contain monocytes/macrophages and vascular smooth muscle cells and thus may have an increased capacity for generation of nitric oxide by inducible nitric oxide synthase (NOS). We used three approaches (contractile responses, generation of L-citrulline from L-arginine, and staining with NADPH-diaphorase) to test the hypothesis that after administration of lipopolysaccharide (LPS) in vivo, generation of nitric oxide by inducible NOS is augmented in atherosclerotic arteries. New Zealand White (normal, n = 18) and Watanabe heritable hyperlipidemic (atherosclerotic, n = 21) rabbits were anesthetized and injected intravenously with vehicle or LPS. Contractile responsiveness of aortic segments was examined in vitro 4 hours after injection of LPS in vivo. There was a substantial (approximately fivefold) decrease in contractile sensitivity of aortas from LPS-treated atherosclerotic rabbits and a small (approximately twofold) decrease in normal rabbits. Incubation of aortic segments with aminoguanidine, which inhibits inducible NOS, restored contractile responsiveness after LPS treatment. In vitro assay of conversion of [14C]L-arginine to [14C]L-citrulline by aortic segments demonstrated marked (approximately fivefold) increase in calcium-independent conversion of [14C]L-arginine by LPS-treated atherosclerotic, but not normal, aortas. NADPH-diaphorase staining demonstrated positive cells only in the endothelium of normal rabbits and in the lesions and media of the atherosclerotic aortas in both vehicle- and LPS-treated rabbits. The general distribution of these NADPH-diaphorase-positive cells resembled that of smooth muscle cells and not macrophages. Thus, impairment of contractile responses, generation of L-citrulline, and staining with NADPH-diaphorase suggest that atherosclerotic arteries have increased capacity for generation of nitric oxide by inducible NOS.
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PMID:Evidence that expression of inducible nitric oxide synthase in response to endotoxin is augmented in atherosclerotic rabbits. 754 28

Septic shock is a cytokine-mediated process typically caused by a severe underlying infection. Toxins generated by the infecting organism trigger a cascade of events leading to hypotension, to multiple organ system failure, and frequently to death. Beyond supportive care, no effective therapy is available for the treatment of septic shock. Nitric oxide (NO) is a potent vasodilator generated late in the sepsis pathway leading to hypotension; therefore, NO represents a potential target for therapy. We have previously demonstrated that transforming growth factor (TGF) beta1 inhibits inducible NO synthase (iNOS) mRNA and NO production in vascular smooth muscle cells after its induction by cytokines critical in the sepsis cascade. Thus, we hypothesized that TGF-beta1 may inhibit iNOS gene expression in vivo and be beneficial in the treatment of septic shock. In a conscious rat model of septic shock produced by Salmonella typhosa lipopolysaccharide (LPS), TGF-beta1 markedly reduced iNOS mRNA and protein levels in several organs. In contrast, TGF-beta1 did not decrease endothelium-derived constitutive NOS mRNA in organs of rats receiving LPS. We also performed studies in anesthetized rats to evaluate the effect of TGF-beta1 on the hemodynamic compromise of septic shock; after an initial 25% decrease in mean arterial pressure, TGF-beta1 arrested LPS-induced hypotension and decreased mortality. A decrease in iNOS mRNA and protein levels in vascular smooth muscle cells was demonstrated by in situ hybridization and NADPH diaphorase staining in rats treated with TGF-beta1. Thus these studies suggest that TGF-beta1 inhibits iNOS in vivo and that TGF-beta1 may be of future benefit in the therapy of septic shock.
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PMID:Arrest of endotoxin-induced hypotension by transforming growth factor beta1. 870 Aug 84

Nitric oxide synthase (NOS) isoenzymes generate nitric oxide (NO), a sensitive multifunctional intercellular signal molecule. High NO levels are produced by an inducible NOS (iNOS) in activated macrophages in response to proinflammatory agents, many of which also regulate local bone metabolism. NO is a potent inhibitor of osteoclast bone resorption, whereas inhibitors of NOS promote bone resorption both in vitro and in vivo. The possibility that osteoclasts, like macrophages, express a regulated iNOS and produce NO as a potential autocrine signal following inflammatory stimulation was investigated in well-characterized avian marrow-derived osteoclast-like cells. NO production (reflected by medium nitrite levels) was markedly elevated in these cells by the proinflammatory agents lipopolysaccharide (LPS) and the synergistic action of IL-1 alpha, TNF alpha, and IFN gama. inhibitors of NOS activity (aminoguanidine, L-NAME) or iNOS induction (dexamethasone, TGF beta) reduced LPS-stimulated nitrite production. LPS also increased the NOS-associated diaphorase activity of these cells and their reactivity with anti-iNOS antibodies. RT-PCR cloning, using avian osteoclast-like cell RNA and human iNOS primers, yielded a novel 900 bp cDNA with high sequence homology (76%) to human, rat, and mouse iNOS genes. In probing osteoclast-like cell RNA with the PCR-derived iNOS cDNA, a 4.8 kb mRNA species was detected whose levels were greatly increased by LPS. Induction of iNOS mRNA by LPS, or by proinflammatory cytokines, occurred prior to the rise of medium nitrite in time course studies and was diminished by dexamethasone. Moreover, osteoclast-like cells demonstrated an upregulation of NO production and iNOS mRNA by IL-8 and IL-10, regulatory mechanism's not previously described. It is concluded that osteoclast-like cells express a novel iNOS that is upregulated by inflammatory mediators, leading to NO production. Therefore, NO may serve as both a paracrine and autocrine signal for modulating osteoclast bone resorption.
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PMID:Proinflammatory agents, IL-8 and IL-10, upregulate inducible nitric oxide synthase expression and nitric oxide production in avian osteoclast-like cells. 870 87

The human neuroblastoma cell line NB-39-nu expressed mRNA coding for inducible nitric oxide synthase (iNOS) following treatment with a combination of interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha). The level of iNOS mRNA peaked 24 h after stimulation and had declined by about 25% after 48 h. Trace levels of iNOS mRNA were detected after treatment with IFN-gamma alone, and its mRNA level was synergistically enhanced by simultaneous treatment with TNF-alpha. Neither bacterial lipopolysaccharide nor interleukin-1 beta (IL-1 beta) showed synergistic effects as great as that of TNF-alpha on iNOS gene expression. Dexamethasone inhibited the induction of iNOS mRNA by IFN-gamma and TNF-alpha. Induction of iNOS was confirmed by NADPH-diaphorase staining and by immunostaining with human iNOS-specific antibody.
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PMID:Nitric oxide synthase expression in human neuroblastoma cell line induced by cytokines. 872 59

Nitric oxide (NO) has been shown to play a significant role in inflammation. To clarify the role of NO in acute pancreatitis, we investigated the serum concentrations of NO chi (NO2- plus NO3-) and tumor necrosis factor-alpha (TNF-alpha) and the grade of pancreatitis in cerulein-induced pancreatitis in mice pretreated with lipopolysaccharide (LPS) or not. LPS pretreatment aggravated the cerulein pancreatitis in association with a transient increase in serum TNF-alpha, which was followed by a gradual elevation of serum NO chi. This elevation of serum NO chi concentration was inhibited by the NO synthase inhibitor NG-nitro-L-arginine (L-NNA). In addition, the activity of NADPH-diaphorase (NADPH-d), a marker for NO synthase, appeared in the peritoneal macrophages of LPS-pretreated mice after the induction of pancreatitis. No elevation of serum NO chi or appearance of NADPH-d activity in peritoneal cells was found in mice without LPS pretreatment. Administration of L-NNA enhanced the elevation of pancreatitis-induced serum amylase in mice untreated with LPS, while L-NNA inhibited the elevation in LPS-pretreated mice. The effects of L-NNA were reversed by the administration of L-arginine but were not affected by D-arginine. These results suggested that (a) inflammatory cells may not be fully activated to produce excessive NO in uncomplicated edematous pancreatitis, and (b) edematous pancreatitis may be aggravated by excessively produced NO if bacterial infection is complicated and inflammatory cells are activated to express inducible NO synthase.
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PMID:The role of nitric oxide in mouse cerulein-induced pancreatitis with and without lipopolysaccharide pretreatment. 892 22

We investigated the chemical and anatomical features of nitric oxide synthase (NOS)-containing neurons in the paraventricular and supraoptic nuclei in the rat hypothalamus using combinations of enzyme histochemistry, in situ hybridization and immuno-histochemistry. Neurons expressing NOS mRNA completely overlapped with NADPH-diaphorase-positive neurons. Topographical distribution of NOS was segregated from that of CRF-containing parvicellular neurons in the posterior paraventricular nucleus but overlapped with that of magnocellular neurons. In the paraventricular nucleus, 70% of oxytocin neurons contained NOS, which corresponded to one half of NOS neurons. About one third of vasopressin-immunoreactive neurons were NADPH-diaphorase-positive and the same proportion of NADPH-diaphorase-positive neurons were vasopressin-immunoreactive. In the supraoptic nucleus, 50% of oxytocin neurons were NADPH-diaphorase-positive, which corresponded to 40% of NOS neurons. About 25% of vasopressin neurons were NADPH-diaphorase-positive, and 30% of NADPH-diaphorase-positive neurons were vasopressin-immunoreactive. When NADPH-diaphorase histochemistry was performed first, subsequent immunostaining was markedly perturbed. Using fluoro-gold as a retrograde tracer, 4% of NADPH-diaphorase-positive neurons were shown to contribute to the descending projection to the spinal cord. About 40%-50% of NADPH-diaphorase-positive neurons exhibited Fos immunoreactivity after injection of lipopolysaccharide or hypertonic saline, while only 10%-15% of these neurons expressed Fos in response to immobilization or pain. Endogenous NO may be involved in the regulation of magnocellular functions, especially when the internal environment is disturbed.
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PMID:Nitric oxide synthase-containing magnocellular neurons of the rat hypothalamus synthesize oxytocin and vasopressin and express Fos following stress stimuli. 895 94


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