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S Moncada

Publications and source records attributed to S Moncada.

At least 145 records · Page 8Linked to original sources
PubMed1994

Effects of S-nitroso-glutathione in the human forearm circulation: evidence for selective inhibition of platelet activation.

OBJECTIVE: Nitric oxide (NO) is a vasodilator and inhibitor of platelet function. The clinical use of NO donors as inhibitors of platelet activation is limited by their concomitant hypotensive effect. S-nitroso-glutathione (GSNO) has a significant antiplatelet effect at doses that cause only a small decrease in blood pressure in rats. The aim of this study was to examine the antiplatelet and vasodilator properties of this nitrosothiol in the human forearm. METHODS: Forearm blood flow was measured by forearm occlusion plethysmography in five healthy males. Ex vivo platelet aggregation to ADP was performed in a platelet ionised calcium lumi-aggregometer. RESULTS: Intra-arterial infusion of GSNO (0.2, 1, and 5 nmol.min-1) resulted in inhibition of ADP (1-10 microM) induced platelet aggregation. This inhibition was submaximal for 0.2 and maximal for 1 and 5 nmol.min-1. However, the antiaggregatory effect observed at the lowest dose of GSNO was accompanied only by a threshold increase in forearm blood flow. CONCLUSIONS: These results show that GSNO is more effective as an inhibitor of platelet activation than as a vasodilator, suggesting that it is possible to achieve selective antiplatelet and potentially antithrombotic effects with NO donors.

Adenosine Diphosphate↗
PubMed1994

Association between biosynthesis of nitric oxide and changes in immunological and vascular parameters in patients treated with interleukin-2.

Hypotension is a dose-limiting side effect of interleukin-2 (IL-2) therapy. This may be due to increased biosynthesis of the potent vasodilator nitric oxide (NO) induced by cytokines such as tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), which are known to be generated during IL-2 therapy. We describe the relationship between NO biosynthesis and changes in immunological and vascular parameters during IL-2 therapy in 13 patients with metastatic cancer. Plasma concentrations of neopterin and nitrite plus nitrate (NOx) were higher in cancer patients prior to treatment compared with normal subjects (neopterin; 10.8 +/- 1.4 vs. 2.0 +/- 0.4 ng ml-1, P < 0.001: NOx; 45 +/- 6 vs. 28 +/- 2 microM, P < 0.005). Pretreatment TNF-alpha and IFN-gamma plasma concentrations were not significantly different in cancer patients from those in controls. During infusion of IL-2 (18 x 10(6) international units m-2 per day for 5 days) these parameters increased, reaching maximal concentrations at day 3 for IFN-gamma and day 5 for TNF-alpha, neopterin and NOx. The maximal induced NOx correlated with maximal TNF-alpha (r = 0.60, P < 0.04), IFN-gamma (r = 0.63, P < 0.02) and neopterin (r = 0.66, P < 0.01). As plasma NOx concentrations increased, systolic blood pressure fell, reaching a minimum at day 3 despite a continued rise in NOx concentrations. These changes were accompanied by a continuous increase in pulse rate throughout the infusion period. These findings indicate that induction of NO biosynthesis contributes to hypotension induced during IL-2 therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopterins↗
PubMed1994

Comparative pharmacology of analogues of S-nitroso-N-acetyl-DL-penicillamine on human platelets.

1. The effects of two new analogues of S-nitroso-N-acetyl-DL-penicillamine (SNAP), S-nitroso-N-formyl-DL-penicillamine (SNFP) and S-nitroso-DL-penicillamine (SNPL), on platelet function were examined in vitro. 2. SNAP and its analogues were potent inhibitors of platelet aggregation and inducers of disaggregation. 3. All compounds inhibited fibrinogen binding to platelets. 4. They also decreased the release of P-selectin from platelets. 5. Both inhibition of fibrinogen binding and release of P-selectin correlated with an increase in intraplatelet cyclic GMP concentrations. 6. At concentrations sufficient to inhibit platelet function and induce cyclic GMP formation (0.01-3 microM), the release of NO could be detected from SNPL but not from SNAP and SNFP. 7. Release of NO from all compounds was detected at concentrations > or = 10 microM. 8. Thus, the spontaneous release of NO from SNPL explains the actions of this compound on platelet function; however, platelet-mediated mechanisms may be involved in the release of NO from SNAP and SNFP.

Cyclic AMP↗
PubMed1994

Time-dependent enhancement or inhibition of endotoxin-induced vascular injury in rat intestine by nitric oxide synthase inhibitors.

1. The effects of the nitric oxide (NO) synthase inhibitors, NG-nitro-L-arginine methyl ester (L-NAME) and NG-monomethyl-L-arginine (L-NMMA), on the vascular damage induced by the endotoxin, E. coli lipopolysaccharide (LPS), in the ileum and colon were investigated in the conscious rat over a 5 h period. 2. Administration of LPS (3 mg kg-1, i.v.) increased ileal and colonic vascular injury after a lag period of 2 h, as determined by the leakage of radiolabelled albumin. 3. Administration of L-NAME (1-5 mg kg-1, s.c.) concurrently with LPS, produced a dose-dependent increase in vascular albumin leakage in the intestinal tissues, when determined over a 5 h period. Vascular albumin leakage with LPS and L-NAME (5 mg kg-1) was substantially increased after 1 h, reached maximal levels 3 h after administration, and then slowly declined. 4. L-NMMA (50 mg kg-1, s.c.), likewise elevated intestinal albumin leakage when administered concurrently with LPS, but this reached maximal levels after 1 h and rapidly declined over the subsequent 2 h. 5. In control rats, in the absence of LPS challenge, neither L-NAME (5 mg kg-1, s.c.) nor L-NMMA (50 mg kg-1, s.c.) increased intestinal vascular leakage of albumin over a 5 h period. 6. By contrast, when L-NAME (1-5 mg kg-1, s.c.) or L-NMMA (12.5-50 mg kg-1, s.c.) was injected 3 h after LPS, a dose-dependent reduction in the LPS-provoked vascular albumin leakage was observed. 7 Pretreatment with L-arginine (300 mg kg-1, s.c.) 15 min prior to the NO synthase inhibitors, reversed either the potentiation or the inhibition by L-NAME (5 mg kg-1, s.c.) or L-NMMA (50 mg kg-1, s.c.) of the LPS-induced intestinal vascular damage.8. These findings indicate that initial suppression of the constitutive NO synthase by L-NAME orL-NMMA following challenge with LPS aggravates the acute vascular injury in the ileum and colon,suggesting a defensive role of NO. By contrast, the delayed administration of NO synthase inhibitors, ata time of known expression of the inducible NO synthase, provides protection against the subsequent damage to the intestinal vasculature.

Amino Acid Oxidoreductases↗
PubMed1994

Effect of nitric oxide gas on the generation of nitric oxide by isolated blood vessels: implications for inhalation therapy.

1. We have investigated, using rat aortic rings, whether exogenous nitric oxide (NO) gas affects the activity or expression of the inducible, Ca(2+)-independent NO synthase. 2. Incubation of rings with lipopolysaccharide (LPS, S. typhosa) for 6 h resulted in a gradual loss of tissue tone, a time-dependent reduction in constrictor response to phenylephrine and significant expression and activity of Ca(2+)-independent NO synthase. 3. Following incubation of LPS-treated rings with NO gas, the expression of inducible NO synthase mRNA was still observed, although the enzyme activity was significantly reduced and there was no reduction in the response to phenylephrine. 4. Therefore, NO gas can inhibit the action but not the induction of an NO synthase likely to play a role in inflammatory states such as adult respiratory distress syndrome (ARDS). 5. These observations may explain the rebound phenomenon observed in some ARDS patients following inhalation therapy with NO gas.

Amino Acid Oxidoreductases↗
PubMed1994

Interactions of constitutive nitric oxide with PAF and thromboxane on rat intestinal vascular integrity in acute endotoxaemia.

1. The involvement of endogenous platelet activating factor (PAF) and thromboxane A2 in the acute microvascular damage in the ileum and colon induced by the nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) following endotoxin administration was investigated in the rat over a 1 h period. 2. Administration of L-NAME (1-10 mg kg-1, s.c.) concurrently with E. coli lipopolysaccharide (LPS; 3 mg kg-1, i.v.) dose-dependently increased vascular permeability in the ileum and colon, as determined by the leakage of radiolabelled albumin, and caused macroscopic mucosal damage in the ileum determined 1 h later. Neither LPS administration nor L-NAME (5 mg kg-1) alone affected resting vascular permeability. 3. Infusion of phenylephrine (10 micrograms kg-1 min-1, i.v. for 1 h) caused an elevation in blood pressure similar to that found following L-NAME administration (5 mg kg-1, i.v. or s.c.), but did not increase intestinal vascular permeability, when administered with LPS (3 mg kg-1, i.v.). 4. The increased vascular permeability in the ileum and colon and macroscopic damage in the ileum, induced by L-NAME (5 mg kg-1, s.c.) and LPS (3 mg kg-1, i.v.) was dose-dependently inhibited following s.c. pretreatment (15 min before challenge) with the thromboxane synthase inhibitors, OKY 1581 (5-25 mg kg-1) or 1-benzyl-imidazole (1-50 mg kg-1), or with the thromboxane receptor antagonist, BM 13177 (0.2-2 mg kg-1). 5. Pretreatment with the cyclo-oxygenase inhibitor, indomethacin (2-5 mg kg-', s.c., 15 min before challenge) reduced the microvascular injury in the ileum and colon and macroscopic lesions in the ileum,observed after the concurrent administration of L-NAME and LPS.6. Pretreatment (15 min) with the PAF-receptor antagonists, WEB 2086 (0.5-1 mg kg-', s.c.) or BN52021 (2.5-10 mg kg-', s.c.) likewise attenuated this intestinal vascular injury.7. Combined administration of low doses of l-benzyl-imidazole (1 mg kg-') with WEB 2086(0.5 mg kg-')15 min before L-NAME and LPS challenge, abolished this vascular damage and macroscopic injury.8. These results suggest that PAF and thromboxane A2 are released acutely following challenge with a low dose of endotoxin. However, these mediators do not appear to injure the intestinal micro vascular bed unless NO synthase is concurrently inhibited. Such findings support the protective role of constitutively-formed NO, counteracting the injurious vascular actions of cytotoxic mediators released under pathological conditions.

Animals↗
PubMed1994

Hormonal, renal, and metabolic alterations during hypertension induced by chronic inhibition of NO in rats.

The evolution of renal excretory function and circulating vasoactive systems was studied during progressive increases in blood pressure (BP) induced in rats by oral administration of NG-nitro-L-arginine methyl ester (L-NAME; 5-30 mg/100 ml) for 5 wk. L-NAME induced a stepped elevation (P < 0.05) in BP levels without changing creatinine clearance, urine flow, or sodium excretion rate along the study. Reductions (P < 0.05) in plasma renin activity and plasma aldosterone concentration were found only during treatment with 30 mg/100 ml of L-NAME. Plasma norepinephrine and epinephrine concentrations were elevated (P < 0.05) in the last week of the study. Plasma concentrations of endothelin-1 and urinary excretion of prostaglandin E2, 6-ketoprostaglandin F1 alpha, and thromboxane B2 were not significantly affected by L-NAME. Similarly, no changes in plasma concentrations of glucose, insulin, total cholesterol, or triglycerides were observed. In summary, during long-term administration of L-NAME, progressive increases in BP levels were observed without changes in either sodium excretion or enhanced circulating vasoconstrictor activity. Thus, it is likely that inhibition of synthesis of nitric oxide (NO) in the vasculature leads to an imbalance between the tonic relaxing action of NO and the influences of vasoconstrictor agents even when the latter remain at normal levels.

Aldosterone↗
PubMed1994

Differential induction of nitric oxide synthase in various organs of the mouse during endotoxaemia: role of TNF-alpha and IL-1-beta.

BALB/c mice injected intraperitoneally with bacterial lipopolysaccharide (LPS) developed lethal septic shock. This was accompanied by significantly elevated concentrations of nitrite and nitrate in the plasma and expression of high levels of nitric oxide (NO) synthase activity in the lungs, heart, spleen and peritoneal macrophages. Mice pretreated with anti-tumour necrosis factor-alpha (TNF-alpha) monoclonal antibody or anti-interleukin-1 beta (IL-1 beta) polyclonal antibody were protected, in a dose-dependent manner, from endotoxin-induced mortality. This effect was accompanied by a significant reduction in plasma levels of nitrite and nitrate. Antibody treatment also reduced the level of NO synthase activity in peritoneal macrophages, spleen and heart but had no effect on enzyme expression in the lung. These results demonstrate that TNF-alpha and IL-1 beta play an important role in the induction of NO following administration of LPS and in the development of endotoxin-induced shock. In addition, NO synthase activity is differentially expressed in various organs and this may not always require TNF-alpha and IL-1 beta.

Amino Acid Oxidoreductases↗
PubMed1994

Nitric oxide.

PHYSIOLOGICAL EFFECTS OF NITRIC OXIDE: The generation of nitric oxide by the vascular endothelium maintains a vasodilator tone that is essential for the regulation of blood flow and pressure. In the brain, nitric oxide acts as a mediator of cell-cell signalling. In the peripheral nervous system nitric oxide is also released from many nerves previously classified as non-adrenergic and non-cholinergic. Thus this simple gaseous molecule performs a wide variety of physiological functions. POTENTIAL FOR THERAPEUTIC MANIPULATIONS: Impaired production of nitric oxide can be countered by the administration of nitric oxide donors (in hypertension, atherosclerosis, gastrointestinal and genitourinary disorders) or by inhalation of nitric oxide gas (in chronic pulmonary hypertension or adult respiratory distress syndrome). The biggest challenge is to develop strategies that target the cytotoxic and damaging actions of nitric oxide without interfering with its essential protective functions.

Amino Acid Oxidoreductases↗
PubMed1994

[Nitric oxide and Hirschsprung's disease: a causal relation biochemically, immunohistochemically and functionally demonstrated].

UNLABELLED: Hirschsprung's disease may be due to impaired nonadrenergic-noncholinergic inhibitory input in the aganglionic segment of the colon. It has been suggested that nitric oxide (NO) might be the lacking neurotransmitter. Thus, our specific aims were to determine in ganglionic and aganglionic segments: 1. The activity of the NO synthetase (NO-S); 2. The location of this enzyme; and 3. The "in vitro" basal motor activity of the muscle strips and their responses to an NO donor and to an NO antagonist. METHODS: NO synthetase activity was quantified in samples of tissue from both aganglionic and ganglionic segments obtained during surgery in 6 patients with Hirschsprung's disease by the transformation of 14C-L-arginine into 14C-L-citrulline in tissue homogenates. Immunohistochemical staining of the tissues was performed using a polyclonal antibody raised against a peptide sequence of rat brain NO synthetase. Furthermore, in 2 patients we measured "in vitro" the tonic response of muscle strips to an exogenous NO donor (sodium nitroprusside) and to an NO antagonist (L-NAME). RESULTS: NOS activity was undetectable in every aganglionic segment whereas it was present in all ganglionic segments (0.49 +/- 0.09 pmol citrulina/mg.min; mean +/- SE). Immunohistochemically, NO-S was absent in the myenteric plexus of aganglionic segments and it was present in ganglionic segments. "In vitro" basal motor activity of ganglionic segments was normal, with presence of low-frequency contractions (LFC) and summation contraction (SC); in aganglionic segments SC were absent. Sodium nitroprusside induced a marked relaxation (90% from basal) in muscle strips, both aganglionic and ganglionic, precontracted with bethanocol.(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine↗
PubMed1993

Cloning, characterization, and expression of a cDNA encoding an inducible nitric oxide synthase from the human chondrocyte.

Incubation of human articular chondrocytes with interleukin 1 beta results in the time-dependent expression of nitric oxide (NO) synthase. We report here the isolation of a cDNA clone which encodes a protein of 1153 amino acids with a molecular mass of 131,213 Da and a calculated isoelectric point of 7.9. CHO cells transfected with a plasmid harboring this cDNA clone expressed NO synthase activity that was inhibited by some L-arginine analogues. The deduced amino acid sequence of the human chondrocyte inducible NO synthase shows 51% identity and 68% similarity with the endothelial NO synthase and 54% identity and 70% similarity with the neuronal NO synthase. The similarity (88%) between the human chondrocyte NO synthase cDNA sequence and that reported for the murine macrophage suggests that the inducible class of enzyme is conserved between different cell types and across species.

Amino Acid Oxidoreductases↗
PubMed1993

Cloning and expression of a rat neuronal nitric oxide synthase coding sequence in a baculovirus/insect cell system.

A DNA sequence encoding rat neuronal NO synthase (nNOS) was isolated and cloned into the baculovirus expression vector pVL1393 to generate pVLRBNOS. Transfection of Spodoptera frugiperda Sf-21 cells with the construct pVLRBNOS resulted in the synthesis of high levels of neuronal NO synthase. Analysis of the expression pattern revealed soluble, enzymatically active NO synthase in the cytoplasm of cell extracts. Active enzyme could also be purified from culture supernatants using 2'-5' ADP sepharose affinity chromatography. This enzyme was recognised by antibodies to the native nNOS and showed a similar degree of inhibition by arginine analogs as the native nNOS. The majority of the NOS synthesised had accumulated as insoluble "inclusion-body" material. The purification of recombinant nNOS from insect cells should facilitate characterisation of neuronal NO synthase.

Amino Acid Oxidoreductases↗
PubMed1993

[Significance of endogenous nitric oxide production for the effect of nitrates and in septic shock].

The endothelial relaxation factor postulated by Furchgott has been identified as the endogenous nitro-vasodilatator nitric oxide (nitrogen monoxide, NO). NO is derived from L-arginine and plays an important role in the regulation of circulation. In man, too, inhibitors of NO synthesis like L-NG monomethylarginine (L-NMMA) led to hypertension as well as to reduction of local blood flow. In vivo inhibition of NO synthesis leads to amplification of the effect and of the duration of the effect of nitrates. L-arginine/NO metabolism has also been detected in nonvascular tissues, i.e. from lungs, gastrointestinal tract and urogenital tract. The discovery of inducible nitric-oxide synthase activity in vascular smooth muscle cells, able to produce a great amount of NO, represents another important recent development. Important stimuli for the induction of this NO-synthase are cytokines that play possibly an important clinical role in the context of endotoxemic shock. Research over the last ten years has demonstrated that the L-arginine/NO system represents a central biological regulatory mechanism that plays an important role under physiologic and pathophysiologic conditions not only for the circulation but also in other organs.

Amino Acid Oxidoreductases↗