Stable Product Of Nitric Oxide Research Articles

Nitric oxide levels in patients with diabetes mellitus: A systematic review and meta-analysis

BackgroundAltered serum nitric oxide (NO) levels in patients with diabetes mellitus (DM) have been reported by different studies; however, results are still controversial. Until this date, no meta-analysis evaluated the association of NO levels with DM. Thus, this paper describes a meta-analysis conducted to evaluate if there is a relationship between NO levels and type 1 DM (T1DM) or type 2 DM (T2DM). MethodsA literature search was done to identify all studies that investigated NO levels between T1DM or T2DM patients (cases) and non-diabetic subjects (controls). Measurement of nitrate and nitrite (NOx – the stable NO products) were used to estimate NO concentrations because they closely reflect NO bioavailability. Weighted mean differences (WMD) of NOx levels between case and control samples were calculated for T1DM and T2DM groups. ResultsThirty studies were eligible for inclusion in the meta-analysis (8 in T1DM samples and 22 in T2DM samples). NOx levels were increased in European T1DM patients compared with controls [random effect model (REM) WMD = 8.55, 95% CI 2.88 – 14.21]. No other ethnicity was evaluated in T1DM studies. NOx levels were also increased in both European (REM WMD = 18.76, 95% CI 1.67 – 35.85) and Asian (REM WMD = 18.41, 95% CI 8.01 – 28.81) T2DM patients, but not in Latin American patients compared with controls. ConclusionsThis meta-analysis detected a significant increase in NOx levels in European T1DM patients as well as European and Asian T2DM patients. Further studies in other ethnicities are necessary to confirm these data.

Determination of Nitric Oxide-Derived Nitrite and Nitrate in Biological Samples by HPLC Coupled to Nitrite Oxidation

Nitrite and nitrate are main stable products of nitric oxide, a pivotal cellular signaling molecule, in biological fluids. Therefore, accurate measurement of the two ions is profoundly important. Nitrite is difficult to be determined for a larger number of interferences and unstable in the presence of oxygen. In this paper, a simple, cost-effective and accurate HPLC method for the determination of nitrite and nitrate was developed. On the basis of the reaction that nitrite is oxidized rapidly to nitrate with the addition of acidic potassium permanganate, the determination of nitrite and nitrate was achieved by the following strategy: each sample was injected twice for HPLC analysis, i.e. the first injection was to measure nitrate, and the second injection was to measure total nitrate including initial nitrate and the nitrate from the conversion of nitrite with the addition of acid potassium permanganate in the sample. The amount of nitrite can be calculated as difference between injections 2 and 1. The HPLC separation was performed on a reversed phase C18 column for 15 min. The mobile phase consisted of methanol–water (2:98 by volume); the water in the mobile phase contained 0.60 mM phosphate salt (potassium dihydrogen and disodium hydrogen phosphate) and 2.5 mM tetrabutylammonium perchlorate (TBAP). The UV wavelength was set at 210 nm. Additionally, we systemically investigated the effects of the concentration of phosphate salt and TBAP in the mobile phase, the pH of the mobile phase, and the amount of acidic potassium permanganate added to the sample on the separation efficacy. The results showed that the limits of detection (LOD) and the limit of quantitation (LOQ) were 0.075 and 0.25 μM for nitrate (containing the oxidized nitrite), respectively. The linear range was 1–800 μM. This developed approach was successfully applied to assay nitrite/nitrate levels in cell culture medium, cell lysate, rat plasma and urine.

Nitric Oxide: A New Biomarker of Doxorubicin Toxicity in Children?

Doxorubicin (DOX) has been used in the treatment of childhood cancers, but its usage is limited because of cardiotoxicity. There are many studies on the role of nitric oxide (NO) in several cardiac diseases. However, to the authors’ knowledge, no studies have investigated the plasma levels of total nitrite, a stable product of NO, in children that received DOX. The authors determined plasma total nitrite levels in 29 children who received DOX and investigated the correlations between these and other clinical and laboratory findings. All patients were in remission during the study period. Plasma total nitrite levels and cardiac functions were determined prospectively. The mean cumulative DOX dose was 310.0 ± 90.9 mg/m2. In echocardiographic evaluation, 3 patients (10.3%) had a pathological value for ejection fraction (EF) and/or fractional shortening (FS), whereas 11 patients (37.9%) had a threshold value. Total nitrite levels were higher in patients than in matched controls (75.24 ± 39.4 vs 43.14 ± 10.58 μmol/L, respectively, P < .001). It was also found to be higher in patients who had a pathological/threshold value of EF and FS than in patients who had a physiological value of EF and FS (92.35 ± 50.36 vs 59.26 ± 13.56 μmol/L, respectively, P = .038). A negative correlation was found between FS and plasma total nitrite level (r = −.42, P = .023). The authors speculate that increased NO may be a sign of subclinical cardiotoxicity of DOX.

Experimental evidence that phenylalanine is strongly associated to oxidative stress in adolescents and adults with phenylketonuria

Few studies have looked at optimal or acceptable serum phenylalanine levels in later life in patients with phenylketonuria (PKU). This study examined the oxidative stress status of adolescents and adults with PKU. Forty PKU patients aged over fifteen years were enrolled, and were compared with thirty age-matched controls. Oxidative stress markers, anti-oxidant enzyme activities in erythrocytes, and blood anti-oxidant levels were examined. Nitric oxide (NO) production was also examined as a measure of oxidative stress. Plasma thiobarbituric acid reactive species and serum malondialdehyde-modified LDL levels were significantly higher in PKU patients than control subjects, and correlated significantly with serum phenylalanine level ( P < 0.01). Plasma total anti-oxidant reactivity levels were significantly lower in the patient group, and correlated negatively with phenylalanine level ( P < 0.001). Erythrocyte superoxide dismutase and catalase activities were higher and correlated significantly with phenylalanine level ( P < 0.01). Glutathione peroxidase activity was lower and correlated negatively with phenylalanine level ( P < 0.001). The oxidative stress score calculated from these six parameters was significantly higher in patients with serum phenylalanine of 700–800 μmol/l. Plasma anti-oxidant substances, beta-carotene, and coenzyme Q 10 were also lower (P < 0.001), although the decreases did not correlate significantly with the phenylalanine level. Serum nitrite/nitrate levels, as stable NO products, were higher together with low serum asymmetric dimethylarginine, as an endogenous NO inhibitor. Oxidative stress status is closely linked with serum phenylalanine levels. Phenylalanine level in should be maintained PKU below 700–800 μmol/l even in adult patients.

Expression of the gene for inducible nitric oxide synthase in experimental glomerulonephritis in the rat.

Nitrite, a stable product of nitric oxide (NO), is synthesized in vitro by glomeruli in experimental glomerulonephritis. We have now studied the expression of the gene for inducible NO synthase (iNOS) in accelerated nephrotoxic nephritis (NTN). The purpose of the study was to confirm in vivo induction of iNOS in this model of immune complex disease, and to relate the onset of induction and the level of expression to pathogenic events in the model. Glomeruli from rats with NTN were isolated at 6 h, 24 h and 2, 4 and 7 days and total RNA extracted. RNA (10 micrograms) was reverse transcribed and polymerase chain reaction (PCR) was performed with primers homologous to rat vascular smooth muscle iNOS and rat beta actin. A 222-base PCR product corresponding to iNOS mRNA was present in all experimental animals. iNOS expression was also found in activated macrophages, neutrophils and IL-1-stimulated but not unstimulated mesangial cells. Quantitative competitive PCR was carried out on glomerular samples using a 514-bp mutant of a 735-bp PCR product. iNOS expression was present at low levels in normal glomeruli and was markedly enhanced at 6 h after the induction of glomerulonephritis and peaked at 24 h. Increased iNOS expression persisted to day 7. beta actin mRNA levels were similar in all glomerular specimens. This study demonstrates that there is in vivo induction of iNOS in immune complex glomerulonephritis, corresponding to the generation of nitrite we have previously reported. iNOS gene expression is detectable within 6 h of induction of NTN, indicating the onset of gene transcription is closely related to the initial formation of immune complexes.

Methamphetamine‐Induced Selective Dopaminergic Neurotoxicity Is Accompanied by an Increase in Striatal Nitrate in the Mouse

Exposure to high doses of methamphetamine (METH), a major drug of abuse, may cause neuronal damage. Previous studies have implicated the role of peroxynitrite, produced by nitric oxide (NO) and reactive oxygen species, in dopaminergic neurotoxicity produced by METH in mice. The present article was undertaken to investigate if a neurotoxic regimen of METH is associated with changes in tissue levels of nitrate and nitrite, which are the stable products of NO. Administration of METH (5 mg/kg x 3) to Swiss Webster mice resulted in marked depletion of dopamine (DA) and DA transporter (DAT) binding sites but no change in 5-hydroxytryptamine (5-HT) and 5-HT transporter (5-HTT) binding sites in the striatum, amygdala, frontal cortex, and hippocampus, suggesting that METH causes selective neurotoxicity to DA nerve terminals. The concentration of nitrate in the striatum was increased by about two-fold after METH administration; however, no changes in nitrate concentration were detected in other brain regions that endured dopaminergic neurotoxicity. These findings suggest that (a) a neurotoxic regimen of METH produces selective increase in NO in the striatum, which may generate toxic species such as peroxynitrite, and (b) toxins other than NO-related derivatives may mediate dopaminergic neurotoxicity in the amygdala and frontal cortex.

Adrenomedullin and total nitrite levels in children with familial Mediterranean fever

Familial Mediterranean fever (FMF) is the most frequent periodic syndrome characterised by recurrent attacks of polyserositis. However, recent studies revealed that there might be an ongoing subclinical inflammation between the attacks. As nitric oxide (NO) and adrenomedullin (AM) are both synthesised in the endothelium, and mediates many functions within immune system, we considered them to be an interesting target of investigation in FMF. Fifteen children with FMF receiving regular colchicine, ranging in age from 3 to 16 years, were investigated in comparison with 15 healthy age- and sex-matched controls. The mean age of the patients was 9.7 +/- 3.9 years. Total nitrite, a stable product of NO, was quantitated by means of the Griess reaction, while AM was measured by HPLC. Plasma-urinary AM and total nitrite levels were significantly higher in children with FMF. Plasma AM levels (pmol/mL) in patients and controls were 40.95 +/- 5.99 vs. 34.86 +/- 5.24, P < 0.05, and urinary AM excretion (pmol/mg creatinine) was 51.16 +/- 28.15 vs. 37.5 +/- 24.26, P < 0.05 respectively. Plasma total nitrite levels (micromol/L) in patients and controls were 44.80 +/- 10.36 vs. 32.13 +/- 9.28, P < 0.05, and urinary nitrite excretion (micromol/mg creatinine) was 2.24 +/- 1.71 vs. 1.09 +/- 0.96, P < 0.05 respectively. This study considered that AM and NO may have a role in the immuno-inflammatory process of FMF, although, whether these act to preserve, or protect against, further inflammatory injury is not clear. Our results further supports the hypothesis that these patients have subclinical inflammation between attacks.

Effects of caffeine on placental total nitrite concentration: A 21-day, vehicle-controlled study in rats

Background: Nitric oxide (NO) is a potent vasodilator that might have an10 important role in the modulation of maternal and fetal vascular tone during pregnancy. The effects of caffeine intake on maternal and fetal hemodynamic properties during pregnancy have been investigated in several human and animal studies. However, based on a literature search, there has been no study of placental total nitrite (a stable product of NO) concentration (PTNC) in pregnant humans or rats given caffeine. Objective: The aim of this study was to assess the effects of caffeine intake 10 on PTNC in rats. Methods: This 21-day, vehicle-controlled study was conducted at the Department10 of Pharmacology, Gaziantep University Hospital, Gaziantep, Turkey. Female Wistar rats were randomly assigned; based on age and weight, to receive 25, 50, or 100 mg/kg QD caffeine or 50 mg/kg QD isotonic saline solution (vehicle; age-matched control group), intraperitoneally for 21 days. After euthanization of the rats and cesarean section, the numbers of fetuses and fetal deaths were counted. The lengths and weights of the fetuses in each study group were noted. PTNC in the rats was determined using the Greiss reaction. Results: This study included 26 rats (7, 7, and 6 rats in the groups receiving10 25, 50, and 100 mg/kg. d caffeine, respectively; 6 rats in the control group). The mean (SD) lengths of the fetuses of the rats given 25, 50, and 100 mg/kg · d caffeine (4.90 [0.15], 4.02 [0.27], and 3.45 [0.17] mm, respectively) were significantly less compared with controls (5.10 [0.18] mm) (all, P < 0.001), as were the mean (SD) weights of the fetuses of rats given caffeine (5.86 [0.24], 4.97 [0.59], and 3.41 [0.23] g, respectively) versus controls (6.18 [0.21] g) (all, P < 0.001). The mean (SD) PTNCs in rats given 25, 50, and 100 mg/kg. d caffeine (19.82 [1.97], 29.39 [2.07], and 45.51 [7.66] nmol/g, respectively) were significantly higher compared with controls (16.10 [2.12] nmol/g) (all, P < 0.001). Conclusions: The results of this study in rats suggest that caffeine intake 10 might increase NO production in the placenta. In addition, based on our findings and those from previous studies, we suggest that this increase might be an adaptive physiologic response to prevent undesirable effects of caffeine on vascular tone during pregnancy.

Adrenomedullin and total nitrite levels in children with acute rheumatic fever

Objective: To investigate the levels of adrenomedullin (AM) and total nitrite, a stable product of nitric oxide (NO), in children with acute rheumatic fever (ARF). Design and methods: Eleven children with ARF were investigated in comparison with 14 healthy controls. Adrenomedullin was detected by HPLC, while total nitrite was quantitated by the Griess reaction. Results: Plasma urinary AM and total nitrite levels were significantly higher in children with ARF, irrespective of whether they were in the acute or convalescent phase of disease. Plasma AM (pmol/mL) levels were 49.19 ± 3.23 in the acute phase, 44.52 ± 4.26 in the convalescent phase, 35.49 ± 3.43 in controls, and urinary AM excretion (pmol/mg creatinine) was 43.45 ± 18.40 in the acute phase, 32.38 ± 15.37 in the convalescent phase, and 24.84 ± 11.38 in controls. Plasma total nitrite levels (μmol/L) were 75.37 ± 13.13 in the acute phase, 59.81 ± 12.78 in the convalescent phase, and 41.09 ± 10.27 in controls. Urinary total nitrite excretion (μmol/mg creatinine) was 3.82 ± 1.56 in the acute phase, 2.15 ± 0.58 in the convalescent phase, and 1.33 ± 0.61 in controls. The differences were statistically significant for all ( P < 0.05). Conclusion: This study considered that AM and NO may have a role in the immunoinflammatory process of ARF.

Effects of cyclooxygenase inhibitors on nitric oxide production and survival in a mice model of sepsis

The effects of selective ((5,5-dimethyl-3-(3-florophenyl)-4-(4-methylsulphonyl-2(5 H)-furanon); DFU) and ( N-(2-cyclohexyloxy-4-nitrophenyl)-methansulphonamide; NS 398)) or non-selective (diclophenac and proquazon) inducible cyclooxygenase (COX-2) inhibitors on the survival, nitrite (stable product of nitric oxide (NO) as an index for inducible NO synthase (iNOS) activity) and 6-keto-prostaglandin F 1α (6-keto-PGF 1α, stable product of prostacyclin as an index for COX-2 activity) production in serum, lungs, brain and/or kidney were investigated in endotoxin-induced sepsis model in mice. Endotoxin (10 mg kg −1, i.p.)-induced mortality was prevented by DFU, NS 398 and proquazon (0.1, 10 and 1 mg kg −1, respectively) and enhanced 2.6-fold with 0.1 mg kg −1 diclophenac. Endotoxin-induced increase in the serum levels of nitrite was only inhibited by 10 mg kg −1 diclophenac. Endotoxin caused a significant decrease only in the brain levels of nitrite without affecting 6-keto-PGF 1α levels in all tissues. The decreased levels of nitrite induced by endotoxin is further reduced by 0.1 mg kg −1 DFU and 1 and 10 mg kg −1 diclophenac while 10 mg kg −1 DFU and 1 mg kg −1 proquazon increased it. On the other hand, 1 mg kg −1 diclophenac and proquazon, and 10 mg kg −1 NS 398 increased the endotoxin-induced lung levels of 6-keto-PGF 1α. The results suggest that the COX inhibitors may have different effects on the survival and NO production depending on tissue and dose.

Time-Dependent Variations in Serum Nitrite, 6-Keto-Prostaglandin F1α and Thromboxane B2 Levels Induced by Lipopolysaccharide in Mice

Clinical features of certain immuno-inflammatory disorders exhibit time-dependent fluctuations, which could be related to circadian rhythmicity of proinflammatory mediator production. Many biologically active substances including nitric oxide (NO) and eicosanoids are released into the circulation in sepsis. Increased NO and eicosanoid levels have been reported to be responsible from death in septic shock. The aim of this study was to investigate the variations in the NO and eicosanoid production and mortality induced by bacterial endotoxin, lipopolysaccharide (LPS) injected either in the morning or in the evening. Experiments were performed on mice synchronised to 12 h light and 12 h dark (lights on at 09:00 h). Animals were injected intraperitoneally with LPS (10 mg/kg) at 09:00 (morning) and 21:00 h (evening) alone or in combination with aminoguanidine (NO synthase (NOS) inhibitor) (100 mg/kg) or indomethacin (cyclooxygenase (COX) inhibitor) (100 mg/kg). The serum was separated from blood samples obtained at nine different time points. Nitrite (stable product of NO), 6-keto-prostaglandin F1α (6-keto-PGF1α, stable product of prostacyclin) and thromboxane B2 (TxB2, stable product of thromboxane) concentrations in serum samples were measured. Serum nitrite levels showed a 24 h circadian rhythmicity depending on LPS injection time. Morning injection caused a peak after 15 h, while evening injection had two peaks after 9 and 18 h. The peak values obtained from morning and evening injections were significantly decreased by aminoguanidine and indomethacin. When LPS injected to mice in the morning and in the evening, it gradually increased the mortality rate within 24 h which could be abolished by aminoguanidine, but not indomethacin. Indomethacin-induced inhibition on LPS-induced nitrite levels was higher in the morning than in the evening. 6-keto-PGF1α and TxB2 levels were decreased by indomethacin when injected with LPS at both injection times, but not aminoguanidine. These results showed that there is an interaction between NO and eicosanoids, and LPS may produce different effects on NOS activity, but not eicosanoid production and mortality, depending on injection time in the experimental septic shock model in mice. Chronopharmacological manipulations of NOS and COX pathways and interactions between them could lead to novel therapeutic approaches for the treatment of septic shock.

Elevated vitreous nitric oxide levels in patients with proliferative diabetic retinopathy

PURPOSE: The aim of this study was to determine nitric oxide levels in the vitreous of patients with proliferative diabetic retinopathy. METHODS: Using the spectrophotometric method based on Griess reaction, we measured levels of nitrite, the stable product of nitric oxide, in the vitreous of 21 eyes of 21 patients who underwent vitrectomy for the treatment of proliferative diabetic retinopathy with tractional retinal detachment, prospectively. Three samples were excluded from the study because of blood contamination. The control group was made up of vitreous samples from 15 eyes of 15 normal cadavers and five eyes of five patients who were undergoing vitrectomy for macular hole surgery. RESULTS: Nitrite levels were 0.524 ± 0.27 μM and 0.383 ± 0.17 μM in the vitreous of patients with proliferative diabetic retinopathy of diabetes type I and type II, respectively. In 15 cadaver eyes and five vitreous samples from patients who underwent macular hole surgery, nitrite levels were below the detection limit (less than 0.08 μM). There was no significant difference between nitrite levels in patients with type I and type II diabetes ( P = .56), whereas there was a significant difference between diabetes groups and controls ( P < .00001). CONCLUSION: Vitreous nitric oxide levels are elevated in patients with proliferative diabetic retinopathy with tractional retinal detachment. Nitric oxide may play a role in the pathogenesis of proliferative diabetic retinopathy.

Upregulation of inducible nitric oxide synthase and nitric oxide occurs later than the onset of the hyperdynamic response during sepsis.

Polymicrobial sepsis is characterized by an early, hyperdynamic phase (i.e., 2-10 h after cecal ligation and puncture [CLP]) followed by a late, hypodynamic phase (16 h after CLP or later). Although nitric oxide (NO) plays an important role in the pathophysiologic response during sepsis, it remains unknown how early NO is upregulated after the onset of sepsis and which organs are responsible for producing the increased amount of NO. To study this, male rats were subjected to sepsis by CLP followed by fluid resuscitation. Blood samples were then taken at 2, 5, 10, or 20 h after CLP or sham operation. In additional groups of animals, the kidneys, small intestine, heart, liver, and lungs were harvested at 5 or 10 h after CLP. Plasma and tissue levels of nitrate and nitrite (NO3-/NO2-, stable products of NO) were determined by using a colorimetric assay. Inducible NO synthase (iNOS) mRNA was examined in various tissues harvested at 10 h after CLP by reverse transcription-polymerase chain reaction (RT-PCR) technique. The results indicate that plasma levels of NO3-/NO2- (mainly reflecting iNOS activity) did not increase at 2-5 h but were significantly elevated at 10-20 h after CLP. Tissue levels of NO3-/NO2- increased significantly in the kidneys, small intestines, heart, and liver at 10 h but not at 5 h after CLP. Similarly, iNOS gene expression was upregulated in the kidneys, small intestines, and liver. Thus, the above organs appear to be important sites responsible for producing the increased NO during sepsis. Because we previously showed that the hyperdynamic response occurs as early as 2 h after CLP and because iNOS-derived NO production is not upregulated earlier than 10 h after the onset of Sepsis, it appears that factors other than NO are responsible for producing the hyperdynamic response during sepsis.

Role of spinal muscarinic and nicotinic receptors in clonidine-induced nitric oxide release in a rat model of neuropathic pain

Intrathecal administration of α 2 adrenergic agonists, such as clonidine, is capable of alleviating neuropathic pain. Recent studies suggest that spinal nitric oxide (NO) mediates the analgesic effect of intrathecal clonidine. Furthermore, compared to nicotinic receptors, spinal muscarinic receptors play a greater role in the analgesic effect of intrathecal clonidine. In the present study, we tested a hypothesis that clonidine-evoked NO release is dependent primarily on muscarinic receptors in the spinal cord after nerve injury. A rat model of neuropathic pain was induced by ligation of the left L 5/L 6 spinal nerves. Using an in vitro spinal cord perfusion preparation, the effect of muscarinic and nicotinic receptor antagonists on clonidine-evoked nitrite (a stable product of NO) release was determined. Both muscarinic and nicotinic antagonists dose-dependently attenuated clonidine-elicited nitrite release. In spinal cords from the neuropathic rats, the inhibitory effect of muscarinic receptor antagonists (atropine and scopolamine) on clonidine-elicited nitrite release was more potent than that of nicotinic receptor antagonists (mecamylamine and hexamethonium). However, in spinal cords obtained from sham animals, the inhibitory effect of muscarinic and nicotinic antagonists did not differ significantly. These results indicate that muscarinic, as well as nicotinic, receptors mediate clonidine-induced NO release in the spinal cord. These data also suggest that after nerve injury, the cascade of activation of α 2 adrenergic receptors–muscarinic receptors–NO in the spinal cord likely plays a predominant role in the analgesic effect of intrathecal clonidine on neuropathic pain.

Antioxidant enzyme activities and total nitrite/nitrate levels in the collar model. Effect of nicardipine.

There is a large body of literature describing the causative role of oxidative stress mediated by increased levels of reactive oxygen species in the pathogenesis of cardiovascular disease such as atherosclerosis, hypertension, and restenosis after angioplasty. The positioning of a soft silicone collar around the rabbit carotid artery elicits intimal thickening. The findings from recent studies demonstrated that both intimal thickening and atherosclerosis lead to synthesis of inducible nitric oxide synthase, resulting in abundant amounts of nitric oxide. We investigated the effects of collaring and nicardipine treatment on the activities of antioxidant enzymes, superoxide dismutase and catalase, and total nitrite/nitrate levels, stable products of nitric oxide. Placing the collar increased the total nitrite/ nitrate levels and decreased superoxide dismutase activity in collared arteries. Treatment with nicardipine (20 mg/kg/day, s.c.) prevented enhanced nitric oxide degradation without affecting superoxide dismutase and catalase activities. Our results suggest that enhanced nitric oxide production and superoxide anion are generated in response to the collaring, resulting in oxidative stress within the segment in this model.

The hairy cell leukemia cell line Eskol spontaneously synthesizes tumor necrosis factor- α and nitric oxide

Tumor necrosis factor- α (TNF- α) and nitric oxide (NO) exert a wide array of immunoregulatory, partly related effects. We examined the production of these two mediators by the human hairy cell leukemia cell line Eskol. Combined cell lysate and supernatant of Eskol cells (0.5×10 6 cells ml −1) incubated for 18 h, contained a mean of 1.5 ng ml −1 TNF- α. This spontaneous TNF- α synthesis was enhanced by phorbol ester (PMA) and phytohemagglutinin (PHA) and decreased by dexamethasone. Nitrite, the stable product of NO, accumulated in the supernatant of Eskol cells after prolonged incubation. Maximal nitrite concentrations (range: 0.8–3.5 μM at 2×10 6 cells ml −1) were detected after 7 days of incubation. NO production was augmented by PHA and reduced by PMA. The inhibitors of NO synthase N G-monomethyl- l-arginine ( l-NMMA) and aminoguanidine decreased NO synthesis. Simultaneous activation with the proinflammatory cytokines, interferon- γ, interleukin-1 β and TNF- α, increased NO synthesis. These results suggest that NO production in Eskol cells results from inducible NO synthase activity. This is the first direct demonstration of NO formation in human lymphoid cells. The cell line, Eskol, may serve as a model to study regulation of TNF- α and NO synthesis in human B-cell leukemia.

Gut and Liver

To determine which organs produce the increased levels of nitric oxide (NO) seen after hemorrhage and resuscitation. Adult male rats underwent laparotomy (ie, trauma induced) and were bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximum bleedout volume was returned in the form of Ringer lactate. The rats were then resuscitated with Ringer lactate, 4 times the maximum bleedout volume for 1 hour. Sham-operated animals underwent only the surgical procedure. Plasma levels of nitrate/nitrite (NO3-/NO2-, stable products of NO) were measured by colorimetric assay at the maximum bleedout volume; at the end of hemorrhage; at the end of resuscitation; and 1.5, 4, 8, and 24 hours after resuscitation. In additional rats, the heart, liver, small intestine, kidneys, and spleen were harvested 4 hours after resuscitation for the measurement of NO3-/NO2- levels. Moreover, tissue perfusion was determined in the above-mentioned organs by radioactive microspheres 4 hours after resuscitation in other groups of animals. Plasma levels of NO3-/NO2- were similar to those of sham-operated animals during hemorrhage and at the end of resuscitation. One and a half hours after the end of resuscitation, however, NO production increased significantly. The peak levels of plasma NO3-/NO2- occurred at 4 hours, and the levels remained elevated even 24 hours after resuscitation. Tissue NO3-/NO2- levels were significantly increased in the liver, small intestine, and spleen 4 hours after resuscitation. In contrast, the levels of NO3-/NO2- were similar to those of sham-operated animals in the heart and kidneys at all times. Blood flow in the heart was maintained after hemorrhage, whereas hepatic, intestinal, splenic, and renal perfusion decreased significantly. The gut and liver seem to be the sites responsible for the increased NO production seen after trauma and hemorrhage. The overproduction of NO is most likely caused by up-regulation of inducible NO synthase. Thus, attempts to reduce NO production using specific inhibitors for inducible NO synthase might be helpful for improving hepatic and intestinal functions after trauma and hemorrhagic shock.

Arsenite Stimulates Poly(ADP-Ribosylation) by Generation of Nitric Oxide

Recent studies indicate that arsenic may generate reactive oxygen species to exert its toxicity. Because reactive oxygen species are known to induce poly(ADP-ribosylation), which is implicated in DNA repair, signal transduction, and apoptosis, we have investigated the effect of arsenite on poly(ADP-ribosylation). The results showed that arsenite treatment induced poly(ADP-ribosylation), NAD depletion, DNA strand breaks, and micronuclei in CHO-K1 cells. Increase of nitrite level, a stable product of nitric oxide, was also detected in medium of arsenite-treated cultures. S-methyl- l-thiocitrulline and Nω-nitro- l-arginine methyl ester, inhibitors of nitric oxide synthase, could suppress the arsenite-induced NAD depletion, DNA strand breaks, and micronuclei, whereas 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase, could enhance micronucleus production and NAD depletion in arsenite-treated cells. These results suggest that arsenite treatment may generate nitric oxide to damage DNA and which then stimulate poly(ADP-ribosylation). Because arsenite also induced DNA strand breaks and NAD depletion in bovine aortic endothelial cells, and these could also be suppressed by S-methyl- l-thiocitrulline, the induction of nitric oxide may be important to the etiology of arsenic-induced vascular disorders in humans.

The inhibitory effect of nitrite, a stable product of nitric oxide (NO) formation, on arginase

Macrophages contain arginase and an inducible NO synthase, demonstrated by using l-arginine, the common substrate, for production of both nitric oxide and urea. Arginase was inhibited by nitrite, the stable end product of NO. This inhibition was non-competitive, and could not be explained by the reaction of nitrite with arginine, or by the irreversible covalent modification of arginase, or by the removal of Mn 2+, a cofactor of arginase.

Renal nitric oxide synthases in transgenic sickle cell mice

The alpha H beta S [beta MDD] mouse is a useful model for studying renal functional abnormalities in sickle cell disease. We previously reported that these mice develop a urine concentrating defect when chronically exposed to a low oxygen environment. In the present study, we measured glomerular filtration rate (GFR), urinary excretion of NO2 s+ NO3, the stable products of nitric oxide (NO), and the abundance of endothelial constitutive nitric oxide synthase (NOS III) and inducible nitric oxide synthase (NOS II) in the kidneys by Western blot. Immunohistochemistry was also carried out. We found that GFR is significantly higher in the transgenic mice than in controls. The urinary NO2 + NO3/creatinine ratio was also higher. The Western blots revealed that both NOS III and NOS II are markedly increased in the kidneys of transgenic mice as compared to normal control mice. Immunohistochemistry localized NOS III reactivity in proximal convoluted cells in the cortex of control and alpha H beta S [beta MDD] mice. NOS II immunostaining was not seen in control mice but was clearly evident in glomeruli and distal nephron segments of the alpha H beta S [beta MDD] mice. These observations suggest that NOS II is induced in glomeruli and distal nephrons of the alpha H beta S [beta MDD] mice. An increase in synthesis of NO may occur in the glomeruli as a result of NOS II induction, and this may contribute to the hyperfiltration in these mice.