NO Synthase (no + synthase)

Distribution by Scientific Domains
Distribution within Medical Sciences

Kinds of NO Synthase

  • endothelial no synthase
  • inducible no synthase
  • neuronal no synthase

  • Terms modified by NO Synthase

  • no synthase activity
  • no synthase expression
  • no synthase inhibitor
  • no synthase inhibitor ng

  • Selected Abstracts


    Role of shear stress on nitrite and NOS protein content in different size conduit arteries of swine

    ACTA PHYSIOLOGICA, Issue 2 2009
    X. Guo
    Abstract Aim:, Inherent fundamental difference exists among arteries of different sizes. The purpose of this study was to evaluate the relation between regional difference of wall shear stress (WSS) in various sizes arteries and contents of nitrite and NO synthase (NOS) isoforms. Methods:, Five different conduit arteries in a wide range of diameter (1,8 mm) were examined in the hind limbs of 13 pigs. Blood flow rate and outer diameter were measured in vivo to determine WSS. Arterial tissues were harvested for the measurement of nitrite and NOS protein contents. The concentration of nitrite, a product of NO synthesis, was determined by high-performance liquid chromatography method. Western blot analysis was used to assess the protein contents of endothelial NOS (eNOS), inducible NOS (iNOS) and neuronal NOS (nNOS). Results:, Our data show that WSS increases with a decrease in artery diameter. Nitrite level increases with increasing WSS and hence decreases with artery diameter. The eNOS protein contents decrease with an increase in diameter. No significant difference for iNOS and nNOS protein contents was found with different artery diameter. A significant positive correlation between tissue nitrite and eNOS protein contents was also observed. Finally, the WSS-normalized eNOS is not significantly different in various size vessels. Conclusion:, Regional difference in blood flow has no effect on iNOS and nNOS protein contents in these conduit arteries. Regional difference in eNOS expression and nitrite contents may be related to the WSS-induced NO by the endothelium under normal physiological conditions. [source]


    Imidazoline-induced amplification of glucose- and carbachol-stimulated insulin release includes a marked suppression of islet nitric oxide generation in the mouse

    ACTA PHYSIOLOGICA, Issue 3 2009
    S. Meidute-Abaraviciene
    Abstract Aim:, The role of islet nitric oxide (NO) production in insulin-releasing mechanisms is unclear. We examined whether the beneficial effects of the imidazoline derivative RX 871024 (RX) on ,-cell function might be related to perturbations of islet NO production. Methods:, Experiments were performed with isolated islets or intact mice challenged with glucose or carbachol with or without RX treatment. Insulin was determined with radioimmunoassay, NO generation with high-performance liquid chromatography and expression of inducible NO synthase (iNOS) with confocal microscopy. Results:, RX treatment, in doses lacking effects on basal insulin, greatly amplified insulin release stimulated by the NO-generating secretagogues glucose and carbachol both in vitro and in vivo. RX also improved the glucose tolerance curve. Islets incubated at high glucose levels (20 mmol L,1) displayed increased NO production derived from both neuronal constitutive NO synthase (ncNOS) and iNOS. RX abrogated this glucose-induced NO production concomitant with amplification of insulin release. Confocal microscopy revealed abundant iNOS expression in , cells after incubation of islets at high but not low glucose levels. This was abolished after RX treatment. Similarly, islets cultured for 24 h at high glucose levels showed intense iNOS expression in , cells. This was abrogated with RX and followed by an amplified glucose-induced insulin release. Conclusion:, RX effectively counteracts the negative impact of ,-cell NO generation on insulin release stimulated by glucose and carbachol suggesting imidazoline compounds by virtue of NOS inhibitory properties being of potential therapeutic value for treatment of ,-cell dysfunction in hyperglycaemia and type 2 diabetes. [source]


    EndothelinA (ETA) and ETB receptor-mediated regulation of nitric oxide synthase 1 (NOS1) and NOS3 isoforms in the renal inner medulla

    ACTA PHYSIOLOGICA, Issue 4 2007
    J. C. Sullivan
    Abstract Aim:, Our laboratory and others have shown that endothelin (ET)-1 directly stimulates nitric oxide (NO) production in inner medullary collecting duct (IMCD) cells. The goal of this study was to determine which NO synthase (NOS) isoforms in IMCD are sensitive to ET-1, and the role of ETA and ETB receptor activation in vivo and in vitro. Methods:, NOS enzymatic activity and NOS isoform protein expression were examined in cultured IMCD-3 cells and isolated renal inner medulla. ETB receptor-deficient homozygous rats (sl/sl) have elevated levels of circulating ET-1 and lack a functional ETB signalling pathway in kidneys, and furthermore provides a unique model to study ETA receptor signalling in the renal inner medulla in vivo. Results:, Incubation of IMCD-3 cells with exogenous ET-1 (50 nm) resulted in ETA -dependent increased NOS1 protein expression in IMCD-3 cells with no effect on NOS2 or NOS3 expression. ETB receptor antagonism has no effect on NOS expression in IMCD-3 cells. Consistent with in vitro results, cytosolic NOS1 protein expression was significantly greater in the renal inner medulla of sl/sl rats compared with heterozygous (sl/+) controls, with no alteration in NOS3 expression. In contrast to protein expression data, NOS1- and NOS3-specific enzymatic activities decreased in the cytosolic fraction from the renal inner medulla of sl/sl compared with sl/+. Conclusion:, These results provide evidence that both ETA and ETB receptors regulate NOS isoform activity in the renal inner medulla and specifically support the hypothesis that ETA receptor activation increases NOS1 expression. [source]


    Role of Nitric Oxide in Pentylenetetrazol-Induced Seizures: Age-Dependent Effects in the Immature Rat

    EPILEPSIA, Issue 4 2000
    Anne Pereira de Vasconcelos
    Summary: Purpose: Seizure susceptibility and consequences are highly age dependent. To understand the pathophysiologic mechanisms involved in seizures and their consequences during development, we investigated the role of nitric oxide (NO) in severe pentylenetetrazol (PTZ)-induced seizures in immature rats. Methods: Four cortical electrodes were implanted in 10-day-old (P10) and 21-day-old (P21) rats, and seizures were induced on the following day by repetitive injections of subconvulsive doses of PTZ. The effects of NG -nitro- l -arginine methyl ester (l -NAME; 10 mg/kg) and 7-nitroindazole (7NI; 40 mg/kg), two NO synthase (NOS) inhibitors, and l -arginine (l -arg; 300 mg/kg), the NOS substrate, were evaluated regarding the mean PTZ dose, seizure type and duration, and mortality rate. Results: At P10, the postseizure mortality rate increased from 18,29% for the rats receiving PTZ only to 100% and 89% for the rats receiving l -NAME and 7NI, respectively; whereas l -arg had no effect. Conversely, at P21, NOS inhibitors did not affect the 82,89% mortality rate induced by PTZ alone, whereas l -arg decreased the mortality rate to 29%. In addition, all NO-related drugs increased the duration of ictal activity at P10, whereas at P21, L -arg and L -NAME affected the first seizure type, producing clonic seizures with L -arg and tonic seizures with L -NAME. Conclusions: The relative natural protection of very immature rats (P10) against PTZ-induced deaths could be linked to a high availability of L -arg and, hence, endogenous NO. At P21, the modulation of seizure type by NO-related compounds may be related to the maturation of the brain circuitry, in particular the forebrain, which is involved in the expression of clonic seizures. [source]


    Asymmetric dimethylarginine (ADMA): the silent transition from an ,uraemic toxin' to a global cardiovascular risk molecule

    EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 2 2005
    D. Fliser
    Abstract Endothelial dysfunction as a result of reduced bioavailability of nitric oxide (NO) plays a central role in the process of atherosclerotic vascular disease. In endothelial cells NO is synthesized from the amino acid l -arginine by the action of the NO synthase (NOS), which can be blocked by endogenous inhibitors such as asymmetric dimethylarginine (ADMA). Acute systemic administration of ADMA to healthy subjects significantly reduces NO generation, and causes an increase in systemic vascular resistance and blood pressure. Increased plasma ADMA levels as a result of reduced renal excretion have been associated with atherosclerotic complications in patients with terminal renal failure. However, a significant relationship between ADMA and traditional cardiovascular risk factors such as advanced age, high blood pressure and serum LDL-cholesterol, has been documented even in individuals without manifest renal dysfunction. As a consequence, the metabolism of ADMA by the enzyme dimethylarginine dimethylaminohydrolase (DDAH) has come into the focus of cardiovascular research. It has been proposed that dysregulation of DDAH with consecutive increase in plasma ADMA concentration and chronic NOS inhibition is a common pathophysiological pathway in numerous clinical conditions. Thus, ADMA has emerged as a potential mediator of atherosclerotic complications in patients with coronary heart disease, peripheral vascular disease, stroke, etc., being the culprit and not only an innocent biochemical marker of the atherosclerotic disease process. [source]


    A role for nitric oxide in sensory-induced neurogenesis in an adult insect brain

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2005
    M. Cayre
    In the adult cricket, neurogenesis occurs in the mushroom bodies, the main integrative structures of the insect brain. Mushroom body neuroblast proliferation is modulated in response to environmental stimuli. However, the mechanisms underlying these effects remain unspecified. In the present study, we demonstrate that electrical stimulation of the antennal nerve mimics the effects of olfactory activation and increases mushroom body neurogenesis. The putative role of nitric oxide (NO) in this activity-regulated neurogenesis was then explored. In vivo and in vitro experiments demonstrate that NO synthase inhibition decreases, and NO donor application stimulates neuroblast proliferation. NADPH-d activity, anti- l -citrulline immunoreactivity, as well as in situ hybridization with a probe specific for Acheta NO synthase were used to localize NO-producing cells. Combining these three approaches we clearly establish that mushroom body interneurons synthesize NO. Furthermore, we demonstrate that experimental interventions known to upregulate neuroblast proliferation modulate NO production: rearing crickets in an enriched sensory environment induces an upregulation of Acheta NO synthase mRNA, and unilateral electrical stimulation of the antennal nerve results in increased l -citrulline immunoreactivity in the corresponding mushroom body. The present study demonstrates that neural activity modulates progenitor cell proliferation and regulates NO production in brain structures where neurogenesis occurs in the adult insect. Our results also demonstrate the stimulatory effect of NO on mushroom body neuroblast proliferation. Altogether, these data strongly suggest a key role for NO in environmentally induced neurogenesis. [source]


    The effects of nitric oxide on magnocellular neurons could involve multiple indirect cyclic GMP-dependent pathways

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003
    C. M. Vacher
    Abstract Nitric oxide (NO) is known to regulate the release of arginine-vasopressin (AVP) and oxytocin (OT) by the paraventricular nucleus (PVN) and the supraoptic nucleus (SON). The aim of the current study was to identify in these nuclei the NO-producing neurons and the NO-receptive cells in mice. The determination of NO-synthesizing neurons was performed by double immunohistochemistry for the neuronal form of NO synthase (NOS), and AVP or OT. Besides, we visualized the NO-receptive cells by detecting cyclic GMP (cGMP), the major second messenger for NO, by immunohistochemistry on hypothalamus slices. Neuronal NOS was exclusively colocalized with OT in the PVN and the SON, suggesting that NO is mainly synthesized by oxytocinergic neurons in mice. By contrast, cGMP was not observed in magnocellular neurons, but in GABA-, tyrosine hydroxylase- and glutamate-positive fibers, as well as in GFAP-stained cells. The cGMP-immunostaining was abolished by incubating brain slices with a NOS inhibitor (L-NAME). Consequently, we provide the first evidence that NO could regulate the release of AVP and OT indirectly by modulating the activity of the main afferents to magnocellular neurons rather than by acting directly on magnocellular neurons. Moreover, both the NADPH-diaphorase activity and the mean intensity of cGMP-immunofluorescence were increased in monoamine oxidase A knock-out mice (Tg8) compared to control mice (C3H) in both nuclei. This suggests that monoamines could enhance the production of NO, contributing by this way to the fine regulation of AVP and OT release and synthesis. [source]


    Neuronal nitric oxide synthase (nNOS) mRNA is down-regulated, and constitutive NOS enzymatic activity decreased, in thoracic dorsal root ganglia and spinal cord of the rat by a substance P N-terminal metabolite

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2001
    Katalin J. Kovacs
    Abstract Nitric oxide (NO) in the spinal cord plays a role in sensory and autonomic activity. Pain induced by acetic acid in the abdominal stretch (writhing) assay and hyperalgesia associated with chronic pain are highly sensitive to NO synthase (NOS) inhibitors. Because substance P (SP) is released and up-regulated in some models of chronic pain, we hypothesized that an accumulation of SP metabolites may influence NOS expression and activity. To test this hypothesis, we examined the effect of intrathecally (i.t.) injected substance P (1-7) [SP(1-7)], the major metabolite of SP in the rat, on neuronal NOS (nNOS) mRNA in the thoracic and lumbar spinal cord, dorsal root ganglia (DRG) and on the corresponding constitutive NOS (cNOS) enzyme activity. Detected using quantitative RT-PCR, nNOS mRNA content in the thoracic spinal cord was decreased 6 h after injection of 5 µmol of SP(1-7) and returned to control 2 days later. In thoracic DRG, nNOS mRNA was reduced 48 h after SP(1-7). The cNOS enzymatic activity in thoracic spinal tissue was gradually decreased to a minimum at 72 h. Down-regulation of NOS by SP(1-7) in the thoracic area appears to be highly associated with capsaicin-sensitive primary afferent neurons. No similar changes in either parameter were measured in the lumbar area after SP(1-7). These data suggest that N-terminal SP fragments, which are known to cause long-term antinociception in the writhing assay, may do so by their ability to down-regulate NO synthesis along nociceptive pathways. [source]


    Exogenous nitric oxide causes potentiation of hippocampal synaptic transmission during low-frequency stimulation via the endogenous nitric oxide,cGMP pathway

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2001
    Christelle L. M. Bon
    Abstract Nitric oxide (NO) is a putative participant in synaptic plasticity and demonstrations that exogenous NO can elicit the same plastic changes have been taken to support such a role. The experiments, carried out on the CA1 region of rat hippocampal slices, were aimed at testing this interpretation. A major component of tetanus-induced long-term potentiation (LTP) was lost in response to l -nitroarginine, which inhibits NO synthase, and 1H -[1,2,4]oxadiazolo[4,3- a]quinoxalin-1-one (ODQ), which inhibits NO-sensitive soluble guanylyl cyclase (sGC). At 0.2 Hz afferent fibre stimulation, exogenous NO produced, concentration-dependently, a synaptic depression that reverted on washout to a persistent potentiation that occluded tetanus-induced LTP. The NO concentrations necessary (estimated in the 100-nm range), however, were mostly supramaximal for stimulating hippocampal slice sGC activity. Nevertheless the potentiation, but not the preceding depression, was blocked by ODQ. l -nitroarginine and an NMDA antagonist were similarly effective, indicating mediation by the endogenous NMDA receptor,NO synthase,sGC pathway. At a concentration normally too low to affect synaptic transmission but sufficient to stimulate sGC (estimated to be 50 nm), exogenous NO reversed the effect of l -nitroarginine and caused a potentiation which was blocked by ODQ. At a concentration inducing the depression/potentiation sequence, NO partially inhibited hippocampal slice oxygen consumption. It is concluded that, at physiological levels, exogenous NO can directly elicit a potentiation of synaptic transmission through sGC, provided that the synapses are suitably primed. At higher concentrations, NO inhibits mitochondrial respiration, which can result in an enduring synaptic potentiation due to secondary activation of the endogenous NO,cGMP pathway. [source]


    Effect of nitric oxide and NO synthase inhibition on nonquantal acetylcholine release in the rat diaphragm

    EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2000
    M. R. Mukhtarov
    Abstract After anticholinesterase treatment, the postsynaptic muscle membrane is depolarized by about 5 mV due to nonquantal release of acetylcholine (ACh) from the motor nerve terminal. This can be demonstrated by the hyperpolarization produced by the addition of curare (H-effect). The magnitude of the H-effect was decreased significantly to 3 mV when the nitric oxide (NO) donors, sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP) were applied to the muscle, or when NO production was elevated by adding l -arginine, but not d -arginine, as a substrate. The H-effect was increased to 8,9 mV by inhibition of NO synthase by l -nitroarginine methylester ( l -NAME), or by guanylyl cyclase inhibition by methylene blue and 1H-[1,2,4]oxidiazolo[4,3-a]quinoxalin-1-one (ODQ). ODQ increased the H-effect to 7.3 ± 0.2 mV and diminished the SNP-induced decrease of the H-effect when applied together with SNP. The effects of NO donors and l -arginine were eliminated by adding reduced haemoglobin, an extracellular NO scavenger. The present results, together with earlier evidence for the presence of NO synthase in muscle fibres, indicate that nonquantal release of ACh is modulated by NO production in the postsynaptic cell. [source]


    The effect of ultraviolet B irradiation on nitric oxide synthase expression in murine keratinocytes

    EXPERIMENTAL DERMATOLOGY, Issue 6 2000
    M. Sasaki
    Abstract: Nitric oxide (NO), which has several physiological functions in skin, is generated by NO synthase (NOS). NOS has at least three isoforms; endothelial NOS (eNOS), brain NOS (bNOS), and inducible NOS (iNOS). Ultraviolet B (UVB) irradiation has been reported to stimulate NO production in skin via induction or activation of NOS, however, the exact mechanism of NOS induction by UVB irradiation remains obscure. In this study, we investigated the direct effect of UVB on the expression of NOS isoforms in murine keratinocytes, and found a significant increase in NO production within 48 h. mRNA and protein expressions of bNOS were both enhanced by UVB irradiation in murine keratinocytes, whereas iNOS mRNA expression was suppressed at 4 and 12 h after UVB irradiation. These results suggest that the enhancement of NO production observed after UVB irradiation in murine keratinocytes may be explained in part by the upregulation of bNOS expression, but not iNOS expression. [source]


    Differential regulation of the nitric oxide,cGMP pathway exacerbates postischaemic heart injury in stroke-prone hypertensive rats

    EXPERIMENTAL PHYSIOLOGY, Issue 1 2007
    Tetsuji Itoh
    Using a working perfused heart model, we investigated the hypothesis that alterations in the NO,cGMP pathway may exacerbate postischaemic mechanical dysfunction in the hypertrophied heart. Ischaemia for 25 min followed by reperfusion for 30 min produced marked cardiac mechanical dysfunction in both stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar Kyoto rats (WKY). Exogenous treatment with S -nitroso- N -acetyl- dl -penicillamine (SNAP), a NO donor, had beneficial effects on the cardiac dysfunction induced by ischaemia,reperfusion (I/R) in the WKY heart, but the cardioprotective effect of SNAP was eliminated by guanylyl cyclase inhibitor. Cardiac cGMP levels were increased by SNAP or ischaemia in WKY. In contrast, in SHRSP hearts, SNAP could not alleviate the cardiac dysfunction caused by I/R. Pre-ischaemia, the cardiac cGMP level was significantly higher in SHRSP than in WKY; however, no significant difference was found after SNAP and ischaemia. The myocardial Ca2+ -dependent NO synthase (NOS) activity increased at the end of ischaemia in WKY. Conversely, the Ca2+ -independent NOS activity and protein levels were upregulated by I/R in the SHRSP myocardium. In the SHRSP hearts, non-selective NOS and selective Ca2+ -independent NOS inhibitors or antioxidant treatment alleviated cardiac dysfunction caused by I/R. Moreover, mRNA expression and Western blotting analysis of cGMP-dependent protein kinase type I showed more deterioration of SHRSP hearts compared with WKY. These results suggest that: (1) the NO-dependent cardioprotective effect is depressed; and (2) overproduction of NO derived from Ca2+ -independent NOS contributes to postischaemic heart injury in the hypertrophied heart of hypertensive status. [source]


    NO synthase isoforms specifically modify peroxynitrite reactivity

    FEBS JOURNAL, Issue 19 2010
    Amandine Maréchal
    Nitric oxide synthases (NOSs) are multi-domain hemothiolate proteins that are the sole source of nitric oxide (NO) in mammals. NOSs can also be a source or a sink for peroxynitrite (PN), an oxidant that is suspected to be involved in numerous physiopathological processes. In a previous study, we showed that the oxygenase domain of the inducible NOS (iNOSoxy) reacts with PN and changes its oxidative reactivity [Maréchal A, Mattioli TA, Stuehr DJ & Santolini J (2007) J Biol Chem282, 14101,14112]. Here we report a similar analysis on two other NOS isoforms, neuronal NOS (nNOS) and a bacterial NOS-like protein (bsNOS). All NOSs accelerated PN decomposition, with accumulation of a similar heme intermediate. The kinetics of PN decomposition and heme transitions were comparable among NOSs. However, their effects on PN reactivity differ greatly. All isoforms suppressed PN two-electron oxidative activity, but iNOSoxy enhanced PN one-electron oxidation and nitration potencies, the oxygenase domain of nNOS (nNOSoxy) affected them minimally, and bsNOS abolished all PN reactivities. This led to the loss of both NOS and PN decomposition activities for nNOSoxy and iNOSoxy, which may be linked to the reported alterations in their electronic absorption spectra. Bacterial bsNOS was affected to a lesser extent by reaction with PN. We propose that these differences in PN reactivity among NOSs might arise from subtle differences in their heme pockets, and could reflect the physiological specificity of each NOS isoform, ranging from oxidative stress amplification (iNOS) to detoxification (bsNOS). [source]


    A pathway through interferon-, is the main pathway for induction of nitric oxide upon stimulation with bacterial lipopolysaccharide in mouse peritoneal cells

    FEBS JOURNAL, Issue 19 2003
    Motohiro Matsuura
    Production of nitric oxide (NO) in response to bacterial lipopolysaccharide (LPS) was investigated using cultures of mouse peritoneal exudate cells (PEC) and the macrophage cell line RAW264.7. In the presence of anti-(interferon-,) (IFN-,), NO production was markedly suppressed in the PEC culture but not in the RAW264.7 culture. In the PEC culture, LPS induced both IFN-, production and activation of IFN response factor-1, which leads to the gene expression of inducible NO synthase, but neither was induced in the culture of RAW264.7 cells. In addition to anti-(IFN-,), antibodies against interleukin (IL)-12 and IL-18 showed a suppressive effect on LPS-induced NO production in the PEC culture, and these antibodies in synergy showed strong suppression. Stimulation of the PEC culture with IL-12 or IL-18 induced production of IFN-, and NO, and these cytokines, in combination, exhibited marked synergism. Stimulation of the culture with IFN-, induced production of NO, but not IL-12. The macrophage population in the PEC, prepared as adherent cells, responded well to LPS for IL-12 production, but weakly for production of IFN-, and NO. The macrophages also responded well to IFN-, for NO production. For production of IFN-, by stimulation with LPS or IL-12 + IL-18, nonadherent cells were required in the PEC culture. Considering these results overall, the indirect pathway, through the production of intermediates (such as IFN-,-inducing cytokines and IFN-,) by the cooperation of macrophages with nonadherent cells, was revealed to play the main role in the LPS-induced NO production pathway, as opposed to the direct pathway requiring only a macrophage population. [source]


    Gastrointestinal effects of nonsteroidal anti-inflammatory drugs

    FUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 3 2003
    Brendan J. R. Whittle
    Abstract Non-steroidal anti-inflammatory drugs (NSAIDs) causes extensive damage to the gastrointestinal (GI) tract. The underlying mechanisms of gastric injury include topical irritant actions that disrupt the epithelial barrier, as well as the inhibition of cyclo-oxygenase (COX), which is predominantly the COX-1 isoform in the mucosa. This damage can be attenuated by antisecretory agents or by mucosal protective agents such as the synthetic prostanoids or nitric oxide (NO) donors. Compounds designed to attenuate topical irritancy, or have protective agents incorporated, such as NO-containing NSAIDs, the CINODs (cyclo-oxygenase-inhibiting NO-donating drugs) show reduced mucosal injury. NSAIDs also cause injury in the small intestine, which appears to result from initial COX inhibition, with subsequent translocation of indigenous bacteria, induction of NO synthase and production of the cytotoxic moiety, peroxynitrite. The COX-2 selective agents, the coxibs, which inhibit prostanoid biosynthesis at inflammatory sites, but not the endogenous protective prostanoids in the gut formed by COX-1, have proved so far to be a successful therapeutic approach to reducing NSAIDs GI damage. The clinical outcome of the use of the second generation of coxibs, and the newer NO NSAIDs is now awaited. [source]


    Phentolamine mesylate relaxes rabbit corpus cavernosum by a nonadrenergic, noncholinergic mechanism

    FUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 1 2001
    Subbarao Vemulapalli
    The contribution of NO-cGMP dependent pathway to phentolamine mesylate-evoked nonadrenergic, noncholinergic relaxation of rabbit corpus cavernosum was investigated in vitro. Stimulation of nonadrenergic, noncholinergic neurons of the rabbit corpus cavernosum elicited frequency-related relaxation that was significantly attenuated by L-NAME (NO synthase inhibitor) or ODQ (an inhibitor of guanylate cyclase). Moreover, tetrodotoxin, a sodium channel blocker, abolished the electrical field stimulation-induced relaxation of rabbit corpus cavernosum, suggesting that neuronal release of NO mediates relaxation to electrical field stimulation. Phentolamine mesylate (30 and 100 nM) dose-dependently enhanced electrical field stimulation-induced relaxation of the rabbit corpus cavernosum. Prazosin (30 ,M) and yohimbine (30 ,M) failed to affect phentolamine mesylate-mediated nonadrenergic, noncholinergic rabbit penile smooth muscle relaxation, suggesting that phentolamine relaxes rabbit corpus cavernosum independent of ,-adrenergic receptor blockade. In contrast, pretreatment of the rabbit cavernosal strips with L-NAME significantly-attenuated electrical field stimulation produced relaxations to phentolamine mesylate, suggesting that phentolamine mesylate relaxes rabbit corpus cavernosum by activating NO synthase. The data suggest that phentolamine mesylate relaxes nonadrenergic noncholinergic neurons of the rabbit corpus cavernosum by activating NO synthase and is independent of ,-adrenergic receptor blockade. [source]


    Long-term modulation of glucose utilization by IL-1, and TNF-, in astrocytes: Na+ pump activity as a potential target via distinct signaling mechanisms

    GLIA, Issue 1 2002
    Céline Véga
    Abstract Interleukin-1, (IL-1,) and tumor necrosis factor-, (TNF-,) markedly stimulate glucose utilization in primary cultures of mouse cortical astrocytes. The mechanism that gives rise to this effect, which takes place several hours after application of cytokine, has remained unclear. Experiments were conducted to identify the major signaling cascades involved in the metabolic action of cytokine. First, the selective IL-1 receptor antagonist (IL-1ra) prevents the effect of IL-1, on glucose utilization in a concentration-dependent manner, whereas it has no effect on the action of TNF-,. Then, using inhibitors of three classical signaling cascades known to be activated by cytokines, it appears that the PI3 kinase is essential for the effect of both IL-1, and TNF-,, whereas the action of IL-1, also requires activation of the MAP kinase pathway. Participation of a phospholipase C-dependent pathway does not appear critical for both IL-1, and TNF-,. Inhibition of NO synthase by L-NAME did not prevent the metabolic response to both IL-1, and TNF-,, indicating that nitric oxide is probably not involved. In contrast, the Na+/K+ ATPase inhibitor ouabain prevents the IL-1,- and TNF-,-stimulated 2-deoxyglucose (2DG) uptake. When treatment of astrocytes with a cytokine was followed 24 h later by an acute application of glutamate, a synergistic enhancement in glucose utilization was observed. This effect was greatly reduced by ouabain. These data suggest that Na+ pump activity is a common target for both the long-term metabolic action of cytokines promoted by the activation of distinct signaling pathways and the enhanced metabolic response to glutamate. GLIA 39:10,18, 2002. © 2002 Wiley-Liss, Inc. [source]


    Inducible nitric oxide synthase expression in laryngeal neoplasia: Correlation with angiogenesis

    HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 1 2002
    Alessandro Franchi MD
    Abstract Background The nitric oxide (NO) pathway plays a relevant role in angiogenesis and tumor progression in squamous cell carcinoma (SCC) of the head and neck. The aim of this study was to assess whether the NO pathway may be correlated with angiogenesis in the transition from laryngeal dysplasia to invasive carcinoma. Methods We investigated the expression of the inducible NO synthase (iNOS) in 26 laryngeal precancerous lesions and 35 squamous cell carcinomas with respect to microvessel density. In addition, we determined iNOS activity and cGMP levels in specimens from SCCs. Results There was a significant increase of iNOS levels detected immunohistochemically passing from hyperplastic/mild dysplastic to moderate/severe dysplastic lesions to SCC (p = .04). Accordingly, Northern and Western analyses demonstrated higher iNOS mRNA and protein levels in SCCs than dysplastic mucosa. iNOS expression was significantly correlated with microvessel counts both in the group of preneoplastic lesions (p = .02) and in the group of SCCs (p = .01). In addition, iNOS activity was correlated with iNOS immunohistochemical expression (p = .1) and was significantly associated with increased vascularization (p = .03) in SCCs. Similarly, iNOS expression was significantly correlated with cGMP levels in SCC (p = .02) and increased tumor vascularization correlated with higher cGMP levels (rs = .4; p = .01). Conclusions Our data indicate that the NO pathway may play a relevant role in the angiogenesis associated with the progression from laryngeal dysplasia to laryngeal SCC. © 2002 John Wiley & Sons, Inc. Head Neck 24: 16,23, 2002. [source]


    Nuclear factor-kappaB as a molecular target for migraine therapy.

    HEADACHE, Issue 4 2003
    U Reuter
    Ann Neurol. 2002;51:507-516. Nitric oxide (NO) generated from inducible NO synthase (iNOS) participates in immune and inflammatory responses in many tissues. The NO donor glyceryl trinitrate (GTN) provokes delayed migraine attacks when infused into migraineurs and also causes iNOS expression and delayed inflammation within rodent dura mater. Sodium nitroprusside, an NO donor as well, also increases iNOS expression. Because inflammation and iNOS are potential therapeutic targets, we examined transcriptional regulation of iNOS following GTN infusion and the consequences of its inhibition within dura mater. We show that intravenous GTN increases NO production within macrophages. L-N(6)-(1-iminoethyl)lysine, a selective iNOS inhibitor, attenuates the NO signal, emphasizing the importance of enzymatic activity to delayed NO production. iNOS expression is preceded by significant nuclear factor kappa B (NF-kappaB) activity, as reflected by a reduction in the inhibitory protein-kappa-Balpha (IkappaBalpha) and activation of NF-kappaB after GTN infusion. IkappaBalpha degradation, NF-kappaB activation, and iNOS expression were attenuated by parthenolide (3mg/kg), the active constituent of feverfew, an anti-inflammatory drug used for migraine treatment. These findings suggest that GTN promotes NF-kappaB activity and inflammation with a time course consistent with migraine attacks in susceptible individuals. We conclude, based on results with this animal model, that blockade of NF-kappaB activity provides a novel transcriptional target for the development of anti-migraine drugs. Comment: This paper suggesting the localization of NO production in dural macrophages as part of delayed inflammation may indicate proliferation and or recruitment of these cells in migraine. Could this also be a target for drug treatment? Specifically, is the genetic transcription that leads to nitric oxide generation such a target? To amend slightly the old advertising slogan, "when Michael Moskowitz talks, we all listen." DSM and SJT [source]


    Nitric oxide suppresses transforming growth factor-,1,induced epithelial-to-mesenchymal transition and apoptosis in mouse hepatocytes,

    HEPATOLOGY, Issue 5 2009
    Xinchao Pan
    Nitric oxide (NO) is a multifunctional regulator that is implicated in various physiological and pathological processes. Here we report that administration of NO donor S-nitroso-N-acetylpenicillamine (SNAP) inhibited transforming growth factor-,1 (TGF-,1)-induced epithelial-to-mesenchymal transition (EMT) and apoptosis in mouse hepatocytes. Overexpression of inducible NO synthase (iNOS) by transfection of the iNOS-expressing vector, which increased NO production, also inhibited the TGF-,1-induced EMT and apoptosis in these cells. Treatment of cells with proinflammatory mediators, including tumor necrosis factor (TNF)-,, interleukin (IL)-1,, and interferon (IFN)-,, which increased the endogenous NO production, produced the same inhibitory effect. Furthermore, exogenous NO donor SNAP treatment caused a decrease in the intracellular adenosine triphosphate (ATP) levels. Consistently, depletion of intracellular ATP by mitochondrial uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) inhibited the TGF-,1-induced EMT and apoptosis, suggesting that an NO-induced decrease of ATP involved in the NO-mediated inhibition of TGF-,1-induced EMT and apoptosis. NO and FCCP also inhibited TGF-,1-induced STAT3 activation, suggesting that signal transducer and activator of transcription 3 inactivation is involved in the NO-induced effects on TGF-,1-induced EMT and apoptosis. Conclusion: Our study indicates that NO plays an important role in the inhibition of TGF-,1-induced EMT and apoptosis in mouse hepatocytes through the downregulation of intracellular ATP levels. The data provide an insight into the in vivo mechanisms on the function of NO during the processes of both EMT and apoptosis. (HEPATOLOGY 2009.) [source]


    Decreased hepatic nitric oxide production contributes to the development of rat sinusoidal obstruction syndrome

    HEPATOLOGY, Issue 4 2003
    Laurie D. Deleve M.D., Ph.D.
    This study examined the role of decreased nitric oxide (NO) in the microcirculatory obstruction of hepatic sinusoidal obstruction syndrome (SOS). SOS was induced in rats with monocrotaline. Monocrotaline caused hepatic vein NO to decrease by 30% at 24 hours and by 70% at 72 hours; this decrease persisted throughout late SOS. NG -nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase, exacerbated monocrotaline toxicity, whereas V-PYRRO/NO, a liver-selective NO donor prodrug, restored NO levels, preserved sinusoidal endothelial cell (SEC) integrity and sinusoidal perfusion as assessed by in vivo microscopy and electron microscopy, and prevented clinical and histologic evidence of SOS. NO production in vitro by SEC and Kupffer cells, the 2 major liver cell sources of NO, decreases largely in parallel with loss of cell viability after exposure to monocrotaline. Increased matrix metalloproteinase (MMP) activity increases early on in SOS and this increase in activity has been implicated in initiating SOS. Infusion of V-PYRRO-NO prevented the monocrotaline-induced increase in MMP-9. In conclusion, decreased hepatic NO production contributes to the development of SOS. Infusion of an NO donor preserves SEC integrity and prevents development of SOS. These findings show that a decrease in NO contributes to SOS by allowing up-regulation of MMP activity, loss of sinusoidal integrity, and subsequent disruption of sinusoidal perfusion. (Hepatology 2003;38:900,908). [source]


    Overexpression of inducible nitric oxide synthase and accumulation of 8-OHdG in nasopharyngeal carcinoma

    HISTOPATHOLOGY, Issue 2 2008
    Y Segawa
    Aims:, Nitric oxide (NO), produced by inducible NO synthase (iNOS), has been suggested to cause oxidative stress, leading to 8-hydroxydeoxyguanosine (8-OHdG) accumulation and subsequent transversion mutation of DNA. The aim was to evaluate iNOS expression and the status of oxidative stress in nasopharyngeal carcinoma (NPC). Methods and results:, Seventy-three cases of NPC were investigated to examine the immunohistochemical expression of iNOS, 8-OHdG and latent membrane protein-1 (LMP-1) and Epstein,Barr virus-encoded small RNA (EBER) expression using in situ hybridization. iNOS mRNA expression and p53 gene mutations were also assessed. Overexpression of iNOS, LMP-1 and EBER was observed in 62 (84.9%), 28 (38.4%) and 53 (72.6%) cases respectively. p53 gene mutation was found in 10 of 73 (13.7%) cases. Immunohistochemical iNOS expression was associated with the 8-OHdG labelling index, iNOS mRNA expression and p53 gene alteration (P < 0.0001, P = 0.016 and 0.0082 respectively). Conclusions:, Our present findings suggest that the expression of iNOS induces oxidative stress in NPC. Although the presence of p53 mutation was associated with iNOS overexpression, the type of acid,base change of p53 was transition, but not transversion, which suggests that the p53 gene is not the direct target of DNA damage by 8-OHdG accumulation. [source]


    Sulphasalazine inhibits macrophage activation: inhibitory effects on inducible nitric oxide synthase expression, interleukin-12 production and major histocompatibility complex II expression

    IMMUNOLOGY, Issue 4 2001
    György Haskó
    Summary The anti-inflammatory agent sulphasalazine is an important component of several treatment regimens in the therapy of ulcerative colitis, Crohn's disease and rheumatoid arthritis. Sulphasalazine has many immunomodulatory actions, including modulation of the function of a variety of cell types, such as lymphocytes, natural killer cells, epithelial cells and mast cells. However, the effect of this agent on macrophage (M,) function has not been characterized in detail. In the present study, we investigated the effect of sulphasalazine and two related compounds , sulphapyridine and 5-aminosalicylic acid , on M, activation induced by bacterial lipopolysaccharide (LPS) and interferon-, (IFN-,). In J774 M, stimulated with LPS (10 µg/ml) and IFN-, (100 U/ml), sulphasalazine (50,500 µm) suppressed nitric oxide (NO) production in a concentration-dependent manner. The expression of the inducible NO synthase (iNOS) was suppressed by sulphasalazine at 500 µm. Sulphasalazine inhibited the LPS/IFN-,-induced production of both interleukin-12 (IL-12) p40 and p70. The suppression of both NO and IL-12 production by sulphasalazine was superior to that by either sulphapyridine or 5-aminosalicylic acid. Although the combination of LPS and IFN-, induced a rapid expression of the active forms of p38 and p42/44 mitogen-activated protein kinases and c-Jun terminal kinase, sulphasalazine failed to interfere with the activation of any of these kinases. Finally, sulphasalazine suppressed the IFN-,-induced expression of major histocompatibility complex class II. These results demonstrate that the M, is an important target of the immunosuppressive effect of sulphasalazine. [source]


    The effects of methylene blue on ovine post-pneumonectomy pulmonary oedema

    ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2010
    E. V. SUBOROV
    Background: We recently reported that post-pneumonectomy pulmonary oedema (PPO) occurs after ventilating the remaining lung with excessive tidal volumes. Studies in small animals have indicated that nitric oxide (NO) release increases in hyper-inflated lungs, but confirmatory evidence from larger animals is still lacking. We hypothesized that PPO could be prevented by methylene blue (MB), an inhibitor of NO synthase. Methods: Sheep were subjected to a right-sided pneumonectomy (PE) and randomly assigned to a protectively ventilated group ((PROTV group, n=7) with tidal volumes of 6 ml/kg at 20 inflations/min and a positive end-expiratory pressure (PEEP) of 2 cmH2O, and two groups undergoing ,injurious ventilation' (INJV) with tidal volumes of 12 ml/kg and zero end-expiratory pressure (ZEEP), a control group (INJV group, n=7) and a treatment group subjected to MB 1 h after PE (INJV+MB group, n=7). Haemodynamic variables, lung mechanics, blood gases and plasma nitrites and nitrates (NOx) were determined. Results: PE reduced pulmonary blood volume, extravascular lung water (EVLWI) and quasistatic lung compliance in all groups, in parallel with a rise in peak airway pressure (P<0.05). In the INJV group, pulmonary arterial pressure, EVLWI and pulmonary vascular permeability index increased and arterial oxygenation decreased towards cessation of the experiments. These changes were not antagonized by MB. Plasma NOx increased in all the groups compared with baseline, but with no intergroup difference. Conclusion: MB did not reduce PPO and accumulation of NOx in sheep subjected to ventilation with excessive tidal volumes and ZEEP. [source]


    Role of Inducible Nitric Oxide Synthase in Skeletal Adaptation to Acute Increases in Mechanical Loading,,

    JOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2002
    Makoto Watanuki M.D.
    Abstract To clarify the role of nitric oxide (NO) in regulation of bone metabolism in response to skeletal loading, we examined inducible NO synthase (iNOS) gene knockout mice in the tail-suspension model. Histomorphometric analyses of proximal tibias revealed that 7 days of tail suspension decreased the bone volume (BV/TV) and bone formation rate (BFR/BS) and increased the osteoclast surface (Oc.S/BS) in mice with all iNOS genotypes. Both iNOS+/+ and iNOS+/, mice responded to subsequent 14-day reloading, with increases in BV/TV and BFR/BS and a decrease in Oc.S/BS, whereas these responses were abolished in iNOS,/, mice. The osteoblasts flattened after tail suspension appeared cuboidal during subsequent reloading. Immunoreactivity for iNOS was detected in these osteoblasts and osteocytes by immunohistochemistry. These defective responses after reloading were rescued in iNOS,/, mice by treatment with an NO donor nitroglycerine (NG). Conversely, the responses in iNOS+/+ mice were inhibited by treatment with an NOS inhibitor aminoguanidine (AG). In bone marrow cell cultures, mineralized nodules derived from iNOS,/, mice after reloading were significantly reduced. Taken together, our results suggest that NO generated by iNOS in osteoblasts plays a critical role in adjusting bone turnover and increasing osteogenic activity in response to the acute increase in mechanical loading after tail suspension. [source]


    Downregulation of inducible nitric oxide synthetase by neurotrophin-3 in microglia

    JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2003
    Shun-Fen Tzeng
    Abstract Microglia activated after many neurological degeneration of the central nervous system (CNS) act as important regulators for neuropathogenesis in the injured CNS via producing proinflammatory mediators, such as nitric oxide (NO), TNF-,, and IL-1,. Neurotrophin-3 (NT-3) is a well-known trophic factor for neural survival, development, and plasticity. Activated microglia are NT-3-producing cells in the injured CNS, and express its receptor-TrkC. However, little is known about the effect of NT-3 on activated microglia. In this study, pre-treatment of a mouse microglial cell line, BV2, with NT-3 for 24 h indicated that NT-3 reduced the inducible form of NO synthase (iNOS), NO, and TNF-, in BV2 stimulated with lipopolysaccharide (LPS). NT-3 exerted less effect on the reduction of these proinflammatory mediators when it was added to BV2 cultures either simultaneously with LPS or post LPS treatment. These findings indicate that NT-3 may serve as an anti-inflammatory factor to suppress microglial activation. J. Cell. Biochem. 90: 227,233, 2003. © 2003 Wiley-Liss, Inc. [source]


    Downregulation of a rheumatoid arthritis-related antigen (RA-A47) by ra-a47 antisense oligonucleotides induces inflammatory factors in chondrocytes

    JOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2003
    Takako Hattori
    Previously we have shown that the expression of RA-A47 (rheumatoid arthritis-related antigen) which is identical to HSP47, a collagen-binding chaperon, is downregulated in chondrocytes by tumor necrosis factor , (TNF,). RA-A47 was also found on the surface of chondrocytes where it is recognized as an antigen in the serum of rheumatoid arthritis (RA) patients. Its translocation to the cell surface from endoplasmic reticulum membrane where it is normally located was also enhanced by TNF,. To understand the significance of RA-A47 downregulation in chondrocytes independent from other effects of TNF,, we used an antisense oligonucleotide approach and investigated the effect of this treatment on the expression of molecules related to matrix degradation and production of growth factors for chondrocytic, endothelial, and synovial cells. Here we show that treatment of rabbit chondrocyes and human chondrosarcoma cells HCS-2/8 by ra-a47 antisense S -oligonucleotides significantly reduced the expression of ra-a47 both at mRNA and protein level. Interestingly, this TNF,-independent RA-A47 downregulation was associated with a strong induction of matrix metalloproteinase (MMP)-9 mRNA and inducible NO synthase (iNOS) mRNA. The induction of active-type MMP-9 was further detected by gelatin zymography. Under the same conditions, the release of basic fibroblast growth factor (bFGF) and connective tissue growth factor (CTGF) from HCS-2/8 cells into the conditioned medium (CM) was strongly enhanced. These effects were not a result of TNF, upregulation, since the ra-a47 antisense oligonucleotide treatment did not enhance TNF, synthesis. These observations indicate that downregulation of RA-A47 induces TNF,-independent cartilage-degrading pathways involving iNOS and MMP-9. Furthermore, the stimulation of bFGF and CTGF release from chondrocytes may stimulate the proliferation of adjacent endothelial and/or synovial cells. J. Cell. Physiol. 197: 94,102, 2003© 2003 Wiley-Liss, Inc. [source]


    Endothelial dysfunction in aged humans is related with oxidative stress and vascular inflammation

    AGING CELL, Issue 3 2009
    Leocadio Rodríguez-Mańas
    Summary Vascular endothelial dysfunction occurs during the human aging process, and it is considered as a crucial event in the development of many vasculopathies. We investigated the underlying mechanisms of this process, particularly those related with oxidative stress and inflammation, in the vasculature of subjects aged 18,91 years without cardiovascular disease or risk factors. In isolated mesenteric microvessels from these subjects, an age-dependent impairment of the endothelium-dependent relaxations to bradykinin was observed. Similar results were observed by plethysmography in the forearm blood flow in response to acetylcholine. In microvessels from subjects aged less than 60 years, most of the bradykinin-induced relaxation was due to nitric oxide release while the rest was sensitive to cyclooxygenase (COX) blockade. In microvessels from subjects older than 60 years, this COX-derived vasodilatation was lost but a COX-derived vasoconstriction occurred. Evidence for age-related vascular oxidant and inflammatory environment was observed, which could be related to the development of endothelial dysfunction. Indeed, aged microvessels showed superoxide anions (O2,) and peroxynitrite (ONOO,) formation, enhancement of NADPH oxidase and inducible NO synthase expression. Pharmacological interference of COX, thromboxane A2/prostaglandin H2 receptor, O2,, ONOO,, inducible NO synthase, and NADPH oxidase improved the age-related endothelial dysfunction. In situ vascular nuclear factor-,B activation was enhanced with age, which correlated with endothelial dysfunction. We conclude that the age-dependent endothelial dysfunction in human vessels is due to the combined effect of oxidative stress and vascular wall inflammation. [source]


    Simvastatin effects on portal-systemic collaterals of portal hypertensive rats

    JOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 8 2010
    Hui-Chun Huang
    Abstract Background and Aim:, Portal-systemic collateral vascular resistance and vasoconstrictor responsiveness are crucial in portal hypertension and variceal bleeding control. Statins enhance vasodilators production, but their influence on collaterals is unknown. This study aimed to survey the effect of simvastatin on collaterals. Methods:, Partially portal vein-ligated rats received oral simvastatin (20 mg/kg/day) or distilled water from ,2 to +7 day of ligation. After hemodynamic measurements on the eighth postoperative day, baseline perfusion pressure (i.e. an index of collateral vascular resistance) and arginine vasopressin (AVP, 0.1 nM,0.1 µM) responsiveness were evaluated with an in situ perfusion model for collateral vascular beds. RT-PCR of endothelial NO synthase (eNOS), inducible NOS (iNOS), cyclooxygenase-1 (COX-1), COX-2, thromboxane A2 synthase (TXA2 -S) and prostacyclin synthase genes was performed in parallel groups for splenorenal shunt (SRS), the most prominent intra-abdominal collateral vessel. To determine the acute effects of simvastatin, collateral AVP response was assessed with vehicle or simvastatin. SRS RT-PCR of eNOS, iNOS, COX-1, COX-2 and TXA2 -S, and measurements of perfusate nitrite/nitrate, 6-keto-PGF1, and TXB2 levels were performed in parallel groups without AVP. Results:, Acute simvastatin administration enhanced SRS eNOS expression and elevated perfusate nitrite/nitrate and 6-keto-PGF1, concentrations. Chronic simvastatin treatment reduced baseline collateral vascular resistance and portal pressure and enhanced SRS eNOS, COX-2 and TXA2 -S mRNA expression. Neither acute nor chronic simvastatin administration influenced collateral AVP responsiveness. Conclusion:, Simvastatin reduces portal-systemic collateral vascular resistance and portal pressure in portal hypertensive rats. This may be related to the enhanced portal-systemic collateral vascular NO and prostacyclin activities. [source]


    Detrimental effects of nitric oxide inhibition on hepatic encephalopathy in rats with thioacetamide-induced fulminant hepatic failure: Role of nitric oxide synthase isoforms

    JOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 7 2006
    Chi-Jen Chu
    Abstract Background:, Hepatic encephalopathy is a complex neuropsychiatric syndrome. A previous study showed that chronic nitric oxide (NO) inhibition aggravated the severity of encephalopathy in thioacetamide (TAA)-treated rats. The present study investigated the relative contribution of NO synthase (NOS) isoforms on the severity of hepatic encephalopathy in TAA-treated rats. Method:, Fulminant hepatic failure was induced in male Sprague-Dawley rats by intraperitoneal injection of TAA (350 mg/kg/day) for 3 days. Rats were divided into three groups to receive N, -nitro-L-arginine methyl ester (L-NAME, a non-selective NOS inhibitor, 25 mg/kg/day in tap water), L-canavanine (an inducible NOS inhibitor, 100 mg/kg/day via intraperitoneal injection) or normal saline (N/S) from 2 days prior to TAA administration and lasting for 5 days. Severity of encephalopathy was assessed by the counts of motor activity. Plasma levels of tumor necrosis factor-, (TNF- ,) were determined by enzyme-linked immunosorbent assay (ELISA), and total bilirubin, alanine aminotransferase (ALT) and creatinine were determined by colorimetric assay. Results:, Compared with L-canavanine or N/S-treated rats (0% and 4%, respectively), the mortality rate was significantly higher in rats receiving L-NAME administration (29%, P < 0.005). Inhibition of NO created detrimental effects on the counts of motor activities (P < 0.05). Rats treated with L-NAME had significantly higher plasma levels of total bilirubin, ALT, creatinine and TNF- , as compared with rats treated with L-canavanine or N/S (P < 0.01). Conclusion:, Chronic L-NAME administration, but not L-canavanine, had detrimental effects on the severity of hepatic damage and motor activities in TAA-treated rats. These results suggest that constitutive NOS activities play a major protective role in rats with fulminant hepatic failure. [source]