Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.5.1.19 (NOS)
 7,285 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In glomerulonephritides, autacoids such as nitric oxide (NO), reactive oxygen species, and prostanoids are produced in increased amounts in response to cytokines such as interleukin-1 (IL-1). These autacoids influence the expression of glomerular injury by their direct as well as interactive actions. We studied the effect of hydrogen peroxide (H2O2) on NO production in rat mesangial cells. We demonstrate that transient exposure of mesangial cells to H2O2 prior to sustained exposure to IL-1 decreased extracellular accumulation of NO2/NO3 and cellular guanosine 3,'5'-cyclic monophosphate (cGMP) content. H2O2 markedly impaired inducible nitric oxide synthase (iNOS) activity induced by IL-1 directly measured by the conversion of L-[14C]arginine to L-[14C]citrulline. Such impairment in iNOS activity was accompanied by a parallel reduction in iNOS protein abundance but not by a reduced expression of iNOS mRNA. The inhibitory effect of H2O2 on NOS activity was further supported by peroxide-induced impairment in IL-1-driven, NO-dependent synthesis of prostaglandin E2. Our studies thus provide the first direct evidence of a posttranscriptional inhibitory effect of H2O2 on iNOS activity. Additionally, our studies uncover the existence of a previously unrecognized effect of H2O2 on the production of NO that may exert influence on the severity of glomerular injury during glomerular inflammation.
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PMID:Hydrogen peroxide downregulates IL-1-driven mesangial iNOS activity: implications for glomerulonephritis. 922 32

We have investigated the effect of N-(3-(aminomethyl)benzyl)acetamidine (1400W), a novel and highly selective inhibitor for inducible NOS (iNOS), on in vivo growth of solid tumors expressing iNOS. For the EMT6 murine mammary adenocarcinoma, in which iNOS is expressed in the tumor cells, continuous infusion of 1400W for 6 days at 10 or 12 mg/kg(-1)/h(-1) resulted in significant reduction in tumor weight (357 +/- 46 and 466 +/- 70 mg, respectively) compared with that of controls [726 +/- 65 (P < 0.001) and 796 +/- 88 mg (P < 0.02), respectively]. Reduced growth was also observed for a human tumor xenograft (colon adenocarcinoma DLD-1) genetically engineered to express iNOS constitutively and treated for 13 days with 6 mg/kg(-1)/h(-1) 1400W compared with controls (tumor weights 340 +/- 50 and 580 +/- 90 mg, respectively; P < 0.03). Growth of the parental DLD-1 clone was not altered with this treatment compared with that of controls (tumor weights 170 +/- 10 and 240 +/- 50 mg, respectively). Inhibition of iNOS in vivo was confirmed by decreases in plasma nitrite + nitrate concentrations in treated animals compared with that of controls (63-83% decreases for all experiments) and was supported by plasma and tumor concentrations of 1400W that were equivalent and 2.6-4.9 times higher than the EC50 previously reported for iNOS in a tissue assay. For the murine colon adenocarcinoma Colon 38, in which intratumoral macrophages are the predominant source of iNOS and which had high intratumoral arginine concentrations, 1400W treatment had no effect on growth or plasma nitrate + nitrate. Future studies with more potent selective iNOS inhibitors and a wider range of tumors may determine whether iNOS inhibitors could represent a novel approach to the treatment of cancer. These studies confirm that nitric oxide production in tumors plays a role in promoting their growth, rather than a role as a host defense mechanism in inhibiting growth.
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PMID:Selective inhibition of inducible nitric oxide synthase inhibits tumor growth in vivo: studies with 1400W, a novel inhibitor. 924 64

Various functions of human phagocytes are modulated by nitric oxide (NO). We transfected the human U937 monoblastoid cell line with an expression vector containing human endothelial NO synthase (eNOS) or murine inducible NOS (iNOS) cDNA to study the regulatory role of NO without the nonspecific effects associated with exogenous NO sources. Western blot confirmed expression of eNOS or iNOS in respectively transfected cells, but not in naive or empty-vector transfected cells. Transfectants expressing iNOS, a calcium-independent enzyme, but not eNOS, a calcium-dependent enzyme, spontaneously produced NO (P < .001). The NO release from iNOS-transfected cells, as measured by nitrite and nitrate accumulation and by cyclic guanosine monophosphate (cGMP) increases in rat reporter cells, was inhibitable (P < .01 for both) with N(omega)-methyl-L-arginine (L-NMA), a NOS inhibitor. The eNOS transfectants were shown to contain functional enzyme by the conversion of L-arginine to L-citrulline in fractionated cells (P = .0001) and by exposing intact cells to calcium ionophore using the cGMP reporter cell assay (P = .0001). After differentiation with phorbol-12-myristate-13-acetate (PMA), iNOS transfectants produced more tumor necrosis factor-alpha (TNF-alpha) (124.9 +/- 25.4 pg/5 x 10(5) cells per 24 hours) than did empty-vector transfected cells (21.9 +/- 1.9 pg/5 x 10(5) cells per 24 hours; P = .02). This effect was inhibited by 500 micromol/L L-NMA (54.4 +/- 3.1 pg/5 x 10(5) cells per 24 hours; P = .05). However, in the presence of high concentrations of lipopolysaccharide (1 microg/mL), which further increased NO production in iNOS transfected cells (P = .044), TNF-alpha production was similar comparing PMA-differentiated iNOS and empty-vector transfectants (12.2 +/- 0.8 and 13.1 +/- 1.7 ng/5 x 10(5) cells per 24 hours, respectively; P = .5). The results show that under certain conditions endogenously produced NO can upregulate TNF-alpha production in human phagocytes.
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PMID:Endogenously produced nitric oxide increases tumor necrosis factor-alpha production in transfected human U937 cells. 924 48

1. This study investigated the effects of low dose endotoxin (lipopolysaccharide, LPS) on (i) systemic haemodynamics, (ii) renal blood flow (RBF), (iii) renal cortical and medullary perfusion and (iv) renal function in the anaesthetized rat. We have also investigated the effects of nitric oxide (NO) synthase (NOS) inhibition with NG-methyl-L-arginine (L-NMMA) on the alterations in systemic and renal haemodynamics and renal function caused by endotoxin. 2. Infusion of low dose LPS (1 mg kg-1 over 30 min, n = 6) caused a late fall in mean arterial blood pressure (MAP, at 5 and 6 h after LPS), but did not cause an early (at 1-4 h after LPS) hypotension. The pressor effect of noradrenaline (NA, 1 microgram kg-1, i.v.) was significantly reduced at 1 to 6 h after LPS (vascular hyporeactivity). Infusion of L-NMMA (50 micrograms kg-1 min-1 commencing 60 min before LPS and continued throughout the experiment, n = 7) abolished the delayed hypotension and significantly attenuated the vascular hyporeactivity to NA (at 2-6 h). 3. Infusion of LPS (1 mg kg-1 over 30 min, n = 6) caused a rapid (within 2 h) decline in renal function (measured by inulin clearance) in the absence of a significant fall in MAP or renal blood flow (RBF). L-NMMA (n = 7) attenuated the impairment in renal function caused by LPS so that the inulin clearance in LPS-rats treated with L-NMMA was significantly greater than in LPS-rats treated with vehicle (control) at 3-6 h after infusion of LPS. 4. Endotoxaemia also caused a significant reduction in renal cortical, but not medullary perfusion (measured as Laser Doppler flux). Infusion of L-NMMA caused a significant further fall in cortical perfusion and a significant fall in medullary perfusion in the absence of changes in RBF. 5. Infusion of LPS resulted in a progressive increase in the plasma levels of nitrite/nitrate (an indicator of the formation of NO), so that the plasma concentration of nitrite/nitrate was significantly higher than baseline at 150 to 330 min after LPS. Infusion of L-NMMA attenuated the rise in the plasma concentration of nitrite/nitrate (at 270 and 330 min, P < 0.05) caused by LPS. 6. Thus, the renal dysfunction caused by injection of low dose of endotoxin in the rat occurs in the absence of significant falls in blood pressure or total renal blood flow. Inhibition of NOS activity with L-NMMA attenuates the renal dysfunction caused by endotoxin (without improving intrarenal haemodynamics), suggesting that an overproduction of NO may contribute to the development of renal injury and dysfunction by causing direct cytotoxic effects.
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PMID:Intrarenal haemodynamics and renal dysfunction in endotoxaemia: effects of nitric oxide synthase inhibition. 928 24

Neuronal nitric oxide synthase (nNOS) catalyzes the oxidation of NG-hydroxy-L-arginine (NHA) by hydrogen peroxide. The amino acid products were characterized by high-performance liquid chromatography/mass spectrometry of the o-phthalaldehyde/2-mercaptoethanol derivatives and identified as citrulline and N delta-cyanoornithine (CN-orn). The assignment of CN-orn was confirmed by independent chemical synthesis and comparison of the properties of the enzyme-derived product with those of synthetic CN-orn. The inorganic products detected in the enzymatic reaction were NO2- and NO3-, presumably from oxidation of NO-. The reaction of H2O2 and NHA with nNOS was at least 10-fold slower than the reaction of NADPH, O2, and NHA (Vmax,app = 49 +/- 2 nmol min-1 mg-1 for the reactions with 10 microM added H4B). The reaction exhibited saturation kinetics with respect to hydrogen peroxide [K(m,app)(H2O2) = 10 +/- 1 mM for the reactions with 10 microM added H4B]. No H2O2-dependent reaction was observed with L-arginine as the amino acid substrate. The different products for the NADPH- and H2O2-dependent transformations of NHA are of mechanistic significance in the NOS reaction.
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PMID:Formation of N delta-cyanoornithine from NG-hydroxy-L-arginine and hydrogen peroxide by neuronal nitric oxide synthase: implications for mechanism. 939 65

The activity and protein expression of endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS) were investigated during the development of hypertension in spontaneously hypertensive rats (SHR). SHR and Wistar-Kyoto rats (WKY) were studied at three different ages: 4, 14 to 17, and 63 weeks of age. After treatment with saline or lipopolysaccharide (LPS, 10 mg/kg IV) for 3 hours, the aortas were removed for measurement of NOS activity and protein expression assay by [3H]-L-citrulline formation method and Western blot analysis, respectively. Plasma levels of nitrite/nitrate (NO2-/NO3-) and tumor necrosis factor-alpha (TNF-alpha) were also determined. At 14 to 17 weeks and 63 weeks, the basal activity and protein expression of eNOS in the aortas were significantly lower in SHR than in WKY. In addition, the aged WKY exhibited lower eNOS activity than that of adult WKY, but this change was not seen in SHR. By comparison, the basal activity and protein expression of iNOS were only observed in SHR of the 14-to-17-week group and in the 63-week group; SHR still exhibited higher activities, and these differences were further exaggerated by treatment with LPS. The basal and LPS-induced NO2-/NO3- and TNF-alpha levels in the plasma were also higher in the SHR except the 4-week group. After treatment with quinapril, the basal and LPS-induced expressions of iNOS in SHR were significantly attenuated. Our results demonstrated that alterations of activity and protein expression of eNOS and iNOS occurred in SHR. In addition, aging may reduce the activity of eNOS in WKY but not in SHR. The decline of eNOS activity and/or expression may contribute to the development of hypertension, whereas the increase of iNOS expression may be a consequence of the pathological state of vessels associated with hypertension in SHR. However, the augmented expression of iNOS in SHR was attenuated by antihypertensive therapy, suggesting that the abnormal expression of iNOS is associated with hypertension.
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PMID:Alterations of nitric oxide synthase expression with aging and hypertension in rats. 946 Dec 35

Nitric oxide (NO) is an important vasodilator that is produced by constitutive (cNOS) as well as inducible (iNOS) isoforms of nitric oxide synthase. The pore-forming hemolysin of Escherichia coli (HlyA), an important virulence factor in extraintestinal E. coli infections, was found to be a potent stimulator of NO liberation in isolated endothelial cells, and that it also causes thromboxane generation and related vasoconstriction in rabbit lungs. We investigated the effect of different concentrations of HlyA on pulmonary NO synthesis in buffer-perfused rabbit lungs. NO release into the alveolar as well as the intravascular compartment was monitored on-line by chemiluminescence detection of expired NO and by measurement of (peroxy-)nitrite/nitrate release into the perfusate. HlyA induced a pressor response and an immediate dose-dependent increase of exhalative and intravascular NO liberation, further enhanced by the addition of the NOS substrate L-arginine. The nonspecific NOS inhibitor N(G)-monomethyl-L-arginine (L-NMMA), but not the iNOS selective inhibitors aminoguanidine and 2-(2-aminoethyl)-2-thiopseudourea-dihydrobromide, blocked the HlyA-evoked NO liberation into both the alveolar and the intravascular compartments. Enhancement of NO formation (L-arginine) slightly reduced, and inhibition of NO synthesis (L-NMMA) amplified greatly, the HlyA-elicited vasoconstrictor response. Inhibition of the pressor response by a thromboxane receptor antagonist did not interfere with the exotoxin-elicited NO formation. We conclude (1) that marked NO biosynthesis occurs in this model of the septic lung, (2) that the signal transduction in response to HlyA proceeds via activation of cNOS directly related to exotoxin activity and not to secondary changes in shear stress, and (3) that this vasodilator release mitigates the HlyA-induced pulmonary vasoconstriction. These findings may have important implications for therapeutic approaches using NOS inhibitors in sepsis.
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PMID:Nitric oxide biosynthesis in an exotoxin-induced septic lung model: role of cNOS and impact on pulmonary hemodynamics. 947 64

Systemic bacterial lipopolysaccharides (LPS) induce inflammatory responses characteristic of sepsis. Instillation of LPS into rat bladder produces a localized inflammatory response similar to that seen in urinary tract infections (UTIs). Four hours after intravesical instillation of LPS, neutrophils infiltrate into the bladder, and mRNA for inducible nitric oxide synthase (iNOS) and the cytokines, interleukin (IL)-6 and IL-10, is detected in rat bladder but not in the kidney. Induction of iNOS protein is inferred because urinary nitrate and cGMP levels are increased 4 hr after LPS intravesical instillation and remain elevated for at least 24 hr. When LPS is injected intraperitoneally, iNOS and IL-6 mRNA are induced both in the bladder and in the kidney. These data are consistent with the effects of intravesical instillation of LPS remaining localized, iNOS activity increases in both particulate and soluble bladder fractions when measured 4 hr after intravesical instillation of LPS. The magnitude of these increases in iNOS activity in the bladder is not as great as when LPS is injected intraperitoneally. Intravesical instillation of LPS induces no increase in lung or kidney NOS activity. The localized inflammatory response produced by intravesical instillation of LPS demonstrates the importance of LPS as a mediator of the host response in UTIs and supports the use of urinary measurements of nitrate and cGMP in humans as indicative of the localized induction of iNOS in UTIs.
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PMID:Bladder instillation and intraperitoneal injection of Escherichia coli lipopolysaccharide up-regulate cytokines and iNOS in rat urinary bladder. 949 84

During the past five years we observed many advances in the study of the polymer drug, "SMANCS". This first polymeric drug was approved by the Japanese Ministry of Health and Welfare in 1994 as a drug for primary liver cancer, in which the arterial injection of oily formulation in Lipiodol (a lipid contrast medium) is the standard procedure. The advantage of this tactic is the most extraordinary cancer targeting efficiency with the least systemic side effect and very prolonged slow release of SMANCS. The mechanism of tumor selective accumulation of SMANCS and polymeric drugs in general is discussed in view of the so called-EPR (enhanced permeability and retention) effect of solid tumor. The mode of action of SMANCS at the cellular level seems to accompany the generation of superoxide radical which damages DNA; strand break and modification of guaninine by 8-hydroxylguanine. Immunological potentiation involves either the cellular (M phi, T-cell, NK-cell) or molecular level (induction of cytokines, including interferon gamma). The in vivo effect of SMANCS is most pronounced in the tumor vessels where more concentrated SMANCS is accessible due to the EPR effect, and perhaps the generation of O2.-. Nitric oxide generated by both inducible form of NO synthase (iNOS) by the infiltrated macrophages and NOS of endothelial cells, and superoxide from SMANCS will readily react to form peroxynitrite (O2- + NO-->ONOO-), which is a very potent cytotoxic molecule and will damage (nitrate and oxidize) DNA and proteins. Thus, tissue damage and vascular injury or collapse will be the principle tumor toxic mechanism of SMANCS at tissue level. The dose of SMANCS (or grade I-IV tumor filling) and tumor regression parallel each other, and a profile of AFP-value and technical issues of SMANCS/Lipiodol administration intraarterially are also discussed.
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PMID:[Recent advances in research on SMANCS]. 951 80

Tetramethylpyrazine, an inhibitor of phosphodiesterase, has been widely used for treatment of cardiovascular diseases in China. Here, we investigate the effects of tetramethylpyrazine on hypotension, vascular hyporeactivity to norepinephrine (NE), release of tumor necrosis factor-alpha (TNF alpha) and nitric oxide (NO) in a rat model of circulatory shock induced by bacterial endotoxin (E. coli lipopolysaccharide, LPS). Male Wistar-Kyoto rats were anesthetized and instrumented for the measurement of mean arterial pressure (MAP) and heart rate (HR). Injection of LPS (10 mg/kg, i.v.) resulted in a fall in MAP and an increase of HR. In contrast, animals pretreated with tetramethylpyrazine (10 micrograms/kg, i.p. at 30 min prior to LPS) maintained a significantly higher MAP, but tachycardia was further enhanced at 60 min and 120 min when compared to rats given only LPS (LPS-rats). The pressor effect of NE (1 microgram/kg, i.v.) was also significantly reduced after treatment of rats with LPS. Similarly, the thoracic aorta obtained from rats after in vivo studies showed a significant reduction in the contractile responses elicited by NE (1 microM). Pretreatment of LPS-rats with tetramethylpyrazine partially, but significantly, prevented this LPS-induced hyporeactivity to NE in vivo and ex vivo. The injection of LPS resulted in a significant increase in the plasma TNF alpha level at 60 min, whereas the effect of LPS on the plasma nitrate (an indicator of NO formation) level increased in a time-dependent manner. This increment of both TNF alpha and nitrate levels induced by LPS was significantly reduced in LPS-rats pretreated with tetramethylpyrazine. The early hypotension caused by LPS was slightly, but significantly, prevented by pretreatment with tetramethylpyrazine, suggesting that tetramethylpyrazine affects the endothelial constitutive NOS (eNOS). This was examined by the effect of tetramethylpyrazine on acetylcholine (ACh, 1 microM)-induced relaxation in rats treated with tetramethylpyrazine for 4 h. However, tetramethylpyrazine had no significant effects on the ACh-induced relaxation, indicating that tetramethylpyrazine does not affect the activity of eNOS. Thus, tetramethylpyrazine attenuates the early hypotension and the delayed circulatory failure caused by endotoxin in the rat. These effects may be due to inhibition of the release of circulation factors and TNF alpha, which usually reveal synergism upon the induction of iNOS.
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PMID:Beneficial effects of tetramethylpyrazine, an active constituent of Chinese herbs, on rats with endotoxemia. 953 20


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