Serum Nitric Oxide Metabolites Research Articles

The Significance of Serum Nitric Oxide Levels in Behçet's Disease and Recurrent Aphthous Stomatitis

Behçet's disease (BD) is an inflammatory multisystem disorder characterized by recurrent oral and genital aphthous ulcers, arthritis, uveitis, and thrombophlebitis; it can involve several organs. However, recurrent aphthous stomatitis (RAS) can be seen without a confirmed diagnosis of BD. Moreover, there is no way of predicting whether a patient with RAS will develop BD. Nitric oxide (NO) is a free radical synthesized from L-arginine by one of the family of nitric oxide synthase (NOS) enzymes. Increased production of NO during several inflammatory and infectious processes has been recently postulated. Our aim was to investigate the serum NO levels in patients with active and inactive BD and RAS. Forty-six patients with BD, 30 patients with RAS and 30 healthy controls were enrolled in the study. The patients with BD were separated into two groups: clinically active (n = 24) and inactive (n = 22). A blood sample was collected from all subjects in order to determine their serum NO levels. In patients with active BD, higher serum levels of NO metabolite were found in comparison with patients with inactive BD, in patients with RAS, or healthy controls (p < 0.05). We also found higher serum NO metabolite levels in patients with RAS than in healthy controls (p < 0.05). In patients with inactive BD, statistically significant higher levels of serum NO levels were found in comparison with the control group (p < 0.05). However, we found no statistically significant difference between the patients with inactive BD and RAS, which indicated that inactive BD cannot be distinguished from RAS by serum NO levels. We conclude that serum NO levels may be an important marker for estimating the severity of BD. However, further studies are needed to confirm our findings.

Effects of magnesium sulfate on lipid peroxidation and blood pressure regulators in preeclampsia

Objectives: To investigate the status of lipid peroxidation and serum levels of several vasoactive substances in preeclamptic (PE) pregnant women before and during treatment with magnesium sulfate (MgSO 4). Design and methods: The study population included 16 PE women. Circulating levels of malondialdehyde (MDA), endothelin 1 (ET-1), nitric oxide (NO) metabolites, and calcitonin gene-related peptide (CGRP) were measured before (at admission) and during MgSO 4 treatment (at delivery and 24 h postpartum). Results: At admission systolic and diastolic blood pressures were 157 ± 3 mm Hg and 106 ± 2 mm Hg, respectively, and decreased significantly during treatment at delivery and 24 h postpartum ( P < 0.0001). Before treatment, serum MDA concentrations were 0.383 ± 0.037 μmol/L, and decreased significantly during MgSO 4 administration at delivery and 24 h postpartum ( P < 0.0001). In contrast, serum ET-1 levels at 24 h postpartum were significantly higher as compared with those observed before treatment (79 ± 3 versus 65 ± 2 pg/mL, P = 0.002). Serum NO metabolite concentrations were 26 ± 3 μmol/L, and no significant changes were observed during treatment. Serum levels of CGRP were 50 ± 3 pg/mL at admission, and increased significantly at partum ( P < 0.001). Serum ET-1 correlated negatively with NO metabolites before treatment ( r = −0.69, P = 0.002), but not during treatment. In contrast, ET-1 correlated positively with serum CGRP levels during treatment ( r = 0.73, P = 0.002 and r = 0.71, P = 0.002, at delivery and 24 h postpartum, respectively), but not before treatment. Conclusions: This study demonstrates that MgSO 4 administration to PE pregnant women induced significant changes in lipid peroxidation, production of ET-1 and CGRP.

Association of increased phagocytic NADPH oxidase-dependent superoxide production with diminished nitric oxide generation in essential hypertension.

Oxidative stress has been implicated in the pathogenesis of hypertension and its complications through alterations in nitric oxide (NO) metabolism. This study was designed to investigate whether a relationship exists between phagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent superoxide anion (*O2-) production and NO generation in patients with essential hypertension. Superoxide production was assayed by chemiluminescence under baseline and stimulated conditions on mononuclear cells obtained from hypertensives (n=51) and normotensives (n=43). NO production was evaluated by determining serum NO metabolites, nitrate plus nitrite (NOx). Although there were no differences in baseline *O2- production between normotensives and hypertensives, the *O2- production in phorbol myristate acetate (PMA)-stimulated mononuclear cells was increased (P <0.05) in hypertensives compared with normotensives. The PMA-induced *O2- production was completely abolished by apocynin, a specific inhibitor of NADPH oxidase. Moreover, stimulation of *O2- production by angiotensin II and endothelin-1 was higher (P <0.05) in cells from hypertensives than in cells from normotensives. In addition, diminished (P <0.001) serum NOx was detected in hypertensives compared with normotensives. Interestingly, an inverse correlation (r=0.493, P <0.01) was found between *O2- production and NOx in hypertensives. Generation of *O2- mainly dependent on NADPH oxidase is abnormally enhanced in stimulated mononuclear cells from hypertensives. It is suggested that this alteration could be involved in the diminished NO production observed in these patients.

CSF nitric oxide metabolites are associated with activity and progression of multiple sclerosis

To investigate the relationship of CSF and the serum nitric oxide metabolites nitrite and nitrate (NOx) to disease activity and progression in patients with multiple sclerosis (MS). The study was divided into cross-sectional and follow-up. In the cross-sectional study, 20 patients with relapsing-remitting (RR), 21 with secondary progressive (SP), and 10 with primary progressive (PP) MS and 14 control subjects were included. Patients were assessed on clinical (Expanded Disability Status Scale [EDSS], Ambulation Index [AI], 9-Hole Peg Test [9-HPT]) and MRI measurements. In the follow-up study, 34 MS patients from the cross-sectional study agreed to be assessed again after an average of 3.0 +/- 0.5 years. NOx was measured using a vanadium-based assay. In the cross-sectional study, CSF NOx was raised in patients with RR-MS (p = 0.001) and PP-MS (p = 0.02) vs controls. Higher CSF NOx levels were found in patients with mild disability (AI < or = 6.0; EDSS < or = 4.0; Multiple Sclerosis Severity Score [MSSS] < or = 4.8) vs patients with advanced disease (AI > 6.0 [p = 0.002]; EDSS > 4.0 [p = 0.02]; MSSS > 4.8 [p = 0.01]). In the subgroup of patients having Gd-enhancing MRI lesions (n = 11), correlation between the volume of enhancement and CSF NOx was found (r = 0.74, p = 0.01). In the follow-up study, patients with disability progression had higher baseline CSF NOx levels than those who were stable on EDSS (p = 0.02) or AI (p = 0.03). A positive correlation was found between baseline CSF NOx and the change in MR T2-weighted lesion load (r = 0.4, p = 0.03). CSF nitrite and nitrate levels were increased in mildly disabled patients with MS and found to correlate with the volume of Gd-enhanced lesions on MRI. Raised baseline CSF NOx was associated with clinical and MRI progression in MS patients over 3-year follow-up.

Serum nitric oxide metabolite levels and the effect of antipsychotic therapy in schizophrenia

Recently it was proposed that nitric oxide metabolites (NO) may have a role in the pathophysiology of schizophrenia and major depressive disorders. The present study was performed to assess changes in serum nitric oxide metabolite levels in schizophrenic patients compared with healthy controls. Our secondary aim was to further evaluate the impact of psychopharmacologic treatment on circulating NO levels not assessed previously. Serum NO levels of patients with schizophrenia (n=20) before and after 6 weeks of treatment were compared with those of healthy controls (n=20). Severity of schizophrenia and response to treatment were assessed with positive and negative symptoms of schizophrenia. NO levels were estimated by Griess method in serum samples. In patients with schizophrenia, pre-treatment serum NO levels were higher than those of control subjects (39.15 +/- 18.24 vs. 25.40 +/- 5.83 micromol/L, p=0.036) and also of post-treatment values (34.41 +/- 16.35 vs. 25.40 +/- 5.83 micromol/L, p=0.049), respectively. However, no significant difference was found between serum NO levels in pre- and post-treatment values. Our findings of increased serum NO levels in schizophrenic patients confirmed the role of NO in the pathophysiology of schizophrenia. However, we found that antipsychotic drugs do not reveal significant effects on serum levels of NO in schizophrenia in a 6-week treatment regimen. Further studies with longer therapy periods may suggest some new clues for novel treatment strategies employing antioxidants and NOS inhibitors in schizophrenia.

Risk factor criteria.

The concept of the risk factor for chronic diseases, such as cardiovascular disorders, is derived from the application of epidemiological methods initially developed for infectious and nutritional deficiency diseases to chronic conditions to identify the factor(s) linked to the development of the chronic disease. Typically in infectious or nutritional deficiency conditions, a single causative agent or primary cause is identified. Thus, the cause of tuberculosis is the tubercle bacillus, and the cause of pellagra is niacin deficiency. However, for cardiovascular diseases, in which causes are usually complex and multifactorial, new concepts were required. For example, individuals with hypertension have a far greater risk for cardiovascular disease than those without hypertension, but many individuals with hypertension never have clinical sequelae, and many individuals with diagnosed cardiovascular diseases have no hypertension. One can also argue that many individuals who are exposed to the tubercle bacillus do not develop clinical tuberculosis, but the converse is not true; no one has tuberculosis without the tubercle bacillus. This provides a clear distinction between multifactorial diseases, such as coronary disease where the risk factor concept is paramount, and other health conditions. The initial application of the risk factor concept was well developed long before the term was coined. Early in the previous century, insurance companies noted that individuals with high blood pressure were at higher risk for premature mortality1 and therefore would be accepted for life insurance only on payment of an additional premium. Insurance companies also recognized the related risk factor of obesity, and imposed higher premiums on overweight clients. In this context, risk factors are used as predictors of disease and mortality. Surprisingly, insurance companies failed to recognize the enormous contribution of smoking to cardiovascular risk until later. Although the underlying concept had been widely discussed and applied, the term “risk factor” was …

Nitric oxide in ascitic fluid is an independent predictor of the development of renal impairment in patients with cirrhosis and spontaneous bacterial peritonitis.

Cirrhotic patients with spontaneous bacterial peritonitis show a marked activation of the cytokine cascade, and cytokines induce the synthesis of nitric oxide in vitro. Our aim was to assess whether patients with ascitic fluid infection show increased levels of nitric oxide, and whether this is related to the development of renal impairment. Retrospective analysis of prospectively collected specimens from 168 patients with cirrhosis and presence of sterile or infected ascitic fluid. Routine biochemical data together with nitric oxide metabolites, tumour necrosis factor and interleukin-6 were measured. Univariate and multivariate analyses were performed to identify factors related to the development of renal impairment. Patients with infected ascites showed increased serum and ascitic-fluid levels of nitric oxide metabolites and cytokines compared with patients with sterile ascites. A significant direct correlation was observed between serum and ascitic fluid nitric oxide metabolite levels. Multivariate analysis identified ascitic-fluid nitric oxide metabolites as an independent predictor of renal impairment. The increased serum and ascitic fluid nitric oxide found in patients with infected ascites might induce a deterioration of the increased peripheral vasodilation found in this setting, leading to the development of renal impairment in a series of patients with spontaneous bacterial peritonitis.

Serum nitric oxide in patients with acute coronary syndromes: correlation with the extent of myocardial ischemia and role of diabetes mellitus

An intact endothelium releases nitric oxide (NO), which acts through cyclic GMP to mediate coronary dilatation, whereas a diseased endothelium releases less NO and more endothelin and poorly reduces the vasomotor tone. Release of NO is indirectly assessed by the measurement of NO synthase and the end product metabolites of NO (i.e. nitrites and nitrates). Diabetic patients (patients) with the potential of diabetic microangiopathy and endothelial dysfunction are theoretically expected to be poor secretors of NO. The aim of the present study is to correlate the serum level of NO in patients with acute coronary syndromes (ACS) (i.e. unstable angina, nonST segment elevation myocardial ischemia [NSTEMI], and ST segment elevation myocardial ischemia) in correlation with the extent of the total ischemic burden in relation to the presence or absence of diabetes mellitus. To achieve this aim we studied 59 patients, 20 diabetics and 39 nondiabetics (53 males, six females), with ACS (unstable angina in 20 patients, NSTEMI in five patients and acute myocardial ischemia in 34 patients). Before any therapeutic intervention, arterial blood samples were withdrawn to assess the serum NO metabolites level by the Griess reaction. Acute myocardial perfusion imaging with gated SPECT study was carried out by injecting 10 mci 99mTC SestaMIBI IV during chest pain with acquisition of the first set of SPECT images to asses the area of myocardium at risk (MAR), and to estimate of the initial ejection fraction. The second set was acquired 72 hours later to assess the extent of myocardial salvage achieved by different therapeutic modalities (PTCA, SK, etc.). A twenty-segment scoring system was applied for both sets of images to estimate the salvage index (SI): SI = [(MAR - second score) / MAR] × 100. A control group of 20 patients matched for age and sex were also studied.

Nitric oxide in ischemic heart disease. Defective production or impaired function?

Among the mediators released by coronary arterial endothelium, namely prostacyclin, endothelin, thrombomodulin, and so on, nitric oxide (NO) (i.e. endothelial-derived relaxing factor) has been the subject of our intense research. A biologic link between endothelial damage and atherosclerotic coronary arterial disease has been presumably related to decreased arterial bioavailability of NO through predisposing to leucocyte and platelet adhesion, vasoconstriction and smooth muscle cell proliferation. The present study is intended to re-evaluate the potential role of NO in the pathophysiology of coronary heart disease through assessing the serum NO metabolites (nitrites and nitrates) in 150 patients (patients) with ischemic heart disease (118 male, 32 female; mean age 53.4 ± 8.3 years, range 33–80 years). Of the latter, 77 patients (51.3%) had unstable angina (AP), and 73 (48.7%) had recent myocardial infarction (MI). Twenty subjects with normal coronary arteriography (15 male, 5 female; mean age 55.4 ± 4.5 years) served as a control group. Of the studied patients, 89 (59%) were smokers, 68 (45%) were diabetics, 60 (40%) were hypertensives and 63 (43%) were dyslipidemic. Following clinical evaluation including 12-lead ECG, all patients were subjected to routine laboratory testing (including liver and kidney functions, lipid profile, CBC, and random blood sugar). Specific laboratory tests included serum fibrinogen and plasma NO expressed as its metabolites, nitrites and nitrates (NOx), as measured by the Griess reaction. All patients and controls were subjected to diagnostic coronary arteriography with assessment of the extent of coronary disease (number of affected vessels) as well as the severity of stenosis (using the Gensini scoring system). Compared with the control group, ischemic patients had significantly lower levels of NOx (52.8 ± 7.3 vs 15.8 ± 7.3, P < 0.000) with a significantly lower level of NOx in the MI group compared with the AP group (22.1 ± 3.4 vs 9 ± 2.3, P < 0.000). No significant correlation either with the extent or the severity of coronary artery disease was shown. Furthermore, compared with nonsmokers, smokers with ischemic heart disease exhibited significantly lower levels of serum NOx (28.5 ± 14.2 vs 13.8 ± 10.3, P < 0.002). Other risk factors (dyslipidemia, hypertension, diabetes mellitus [DM]) in the ischemic group did not show any significant correlation with serum NOx level (P = 0.1, P = 0.09, P = 0.1, respectively). In conclusion, although NO plays a major role in mediating coronary arterial dilation under healthy condition, it is substantially defective in coronary arterial disease, yet the poor correlation with DM and dyslipidemia (diseases primarily characterized by endothelial dysfunction) would point to impaired NO function rather than just defective production.

Bacterial translocation up-regulates GTP-cyclohydrolase I in mesenteric vasculature of cirrhotic rats

In cirrhosis, arterial vasodilation and the associated hemodynamic disturbances are most prominent in the mesenteric circulation, and its severity has been linked to bacterial translocation (BT) and endotoxemia. Synthesis of nitric oxide (NO), the main vasodilator implicated, is dependent on the essential cofactor tetrahydrobiopterin (BH 4). The key enzyme involved in BH 4 synthesis is GTP-cyclohydrolase I (GTPCH-I), which is stimulated by endotoxin. Therefore, we investigated GTPCH-I activity and BH 4 biosynthesis in the mesenteric vasculature of cirrhotic rats with ascites, as well as their relationship with BT and endotoxemia, serum NO, and mean arterial pressure (MAP). GTPCH-I activity and BH 4 content in mesenteric vasculature was determined by high-performance liquid chromatography. BT was assessed by standard bacteriologic culture of mesenteric lymph nodes (MLNs). Serum endotoxin was measured by a kinetic turbidimetric limulus amebocyte lysate assay, and serum NO metabolite (NOx) concentrations were assessed by chemiluminescence. BT was associated with local lymphatic and systemic appearance of endotoxin and was accompanied by increases in serum NOx levels. GTPCH-I activity and BH 4 content in mesenteric vasculature were both increased in animals with BT and correlated significantly ( r = 0.69, P < .01). Both GTPCH-I activity and BH 4 levels significantly correlated with serum endotoxin and NOx levels ( r = 0.69 and 0.54, 0.81 and 0.53, P < .05). MAP (a marker of systemic vasodilatation) correlated with endotoxemia ( r = 0.58, P < .03) and with GTPCH-I activity ( r = 0.69, P < .01). In conclusion, in cirrhotic animals BT appears to lead to endotoxemia, stimulation of GTPCH-I, increased BH 4 synthesis, and further enhancement of vascular NO production that leads to aggravation of vasodilatation. (H epatology 2003;38:1508-1515.)

Bacterial translocation up-regulates GTP-cyclohydrolase I in mesenteric vasculature of cirrhotic rats.

In cirrhosis, arterial vasodilation and the associated hemodynamic disturbances are most prominent in the mesenteric circulation, and its severity has been linked to bacterial translocation (BT) and endotoxemia. Synthesis of nitric oxide (NO), the main vasodilator implicated, is dependent on the essential cofactor tetrahydrobiopterin (BH(4)). The key enzyme involved in BH(4) synthesis is GTP-cyclohydrolase I (GTPCH-I), which is stimulated by endotoxin. Therefore, we investigated GTPCH-I activity and BH(4) biosynthesis in the mesenteric vasculature of cirrhotic rats with ascites, as well as their relationship with BT and endotoxemia, serum NO, and mean arterial pressure (MAP). GTPCH-I activity and BH(4) content in mesenteric vasculature was determined by high-performance liquid chromatography. BT was assessed by standard bacteriologic culture of mesenteric lymph nodes (MLNs). Serum endotoxin was measured by a kinetic turbidimetric limulus amebocyte lysate assay, and serum NO metabolite (NOx) concentrations were assessed by chemiluminescence. BT was associated with local lymphatic and systemic appearance of endotoxin and was accompanied by increases in serum NOx levels. GTPCH-I activity and BH(4) content in mesenteric vasculature were both increased in animals with BT and correlated significantly (r = 0.69, P <.01). Both GTPCH-I activity and BH(4) levels significantly correlated with serum endotoxin and NOx levels (r = 0.69 and 0.54, 0.81 and 0.53, P <.05). MAP (a marker of systemic vasodilatation) correlated with endotoxemia (r = 0.58, P <.03) and with GTPCH-I activity (r = 0.69, P <.01). In conclusion, in cirrhotic animals BT appears to lead to endotoxemia, stimulation of GTPCH-I, increased BH(4) synthesis, and further enhancement of vascular NO production that leads to aggravation of vasodilatation.

Serum nitric oxide (NO) levels in systemic sclerosis patients: correlation between NO levels and clinical features.

Vascular damage in systemic sclerosis (SSc) may be a factor in the abnormal regulation of several vasoactive agents. It has been well confirmed that plasma endothelin-1, as a vasoconstrictive factor, is elevated in patients with SSc. However, it is still controversial whether the levels of serum nitric oxide (NO), a strong vasodilator, are increased or decreased in SSc patients compared to healthy donors. In this study, we measured the levels of serum NO metabolites in SSc patients and determined the contribution of the excessive production of NO synthase (NOS)-2 by skin fibroblasts to NO synthesis. Serum NO levels of 45 patients with SSc were significantly higher than those of 20 healthy volunteers. In addition, some clinical features of SSc (the extent of skin fibrosis, short disease duration, and the complication of active fibrosing alveolitis) were all correlated positively with the levels of NO metabolites in SSc patients. To evaluate the levels of NOS-2 produced by skin fibroblasts, skin fibroblast cultures were established from SSc patients and healthy volunteers. Reverse transcription-polymerase chain reaction indicated that NOS-2 mRNA was spontaneously expressed in cultured fibroblasts derived from SSc patients, but not in those derived from healthy normal controls. Immunohistochemical staining also showed that NOS-2 proteins were detected in SSc fibroblasts but not in normal fibroblasts. The production of NO by cultured fibroblasts was visualized directly by a reagent (DAF-2 DA) used for the fluorescent detection of NO. Cultured SSc fibroblasts were capable of NO synthesis in culture media containing L-arginine, whereas normal fibroblasts (with no expression of NOS-2) did not synthesize detectable NO. These observations indicate that NO production is increased markedly in early-stage diffuse cutaneous SSc patients with active fibrosing alveolitis, and that constitutive NOS-2 expression in SSc fibroblasts may contribute to increased NO production.

Serum nitric oxide metabolites and E-selectin in preterm premature rupture of membranes.

Diseases with low-grade inflammation perturb endothelial function. We investigated whether preterm premature rupture of membranes (PPROM) is associated with endothelial dysfunction, as assessed by the levels of endothelium-derived nitric oxide metabolites (NOx) and E-selectin in maternal serum. The concentrations of NOx and E-selectin were measured in 32 pregnant women with PPROM and in 27 healthy gestational age-matched control women. The grade of inflammation was estimated by measuring serum C-reactive protein (CRP) and interleukin-6 (IL-6) concentrations. NOx and E-selectin concentrations were not different in PPROM patients as compared to controls. In 17 patients with PPROM, CRP rose above 12 mg/L. In this group, IL-6 concentration was significantly higher than among controls, but concentrations of NOx and E-selectin remained unaltered. There was a negative correlation between the levels of NOx, CRP and IL-6 and the interval from PPROM to delivery. The levels of NOx correlated positively with those of IL-6. PPROM, with or without CRP and IL-6 surges, does not affect endothelial function markedly, as judged from the unaltered concentrations of NOx and E-selectin in maternal serum.

Serum nitric oxide metabolites and E-selectin in preterm premature rupture of membranes

Serum nitric oxide metabolites and E-selectin in preterm premature rupture of membranes

Serum nitric oxide metabolites in patients with multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system characterized by myelin breakdown. The free radical nitric oxide (NO), which is considered to be a major metabolite in immune function and in autoimmune disorders, is among the possible mediators causing the inflammatory reactions in MS. Consequently, NO has been implicated in the pathogenesis of MS and its animal model experimental allergic encephalomyelitis (EAE). In this study, stable metabolites of NO (NO2−+NO3−) levels were determined in sera of MS patients (n=23) and control subjects (n=16). NO2−+NO3− levels were higher in MS patients when compared to control subjects. However, there was not any correlation with serum NO2−+NO3− values and clinical features of the disease such as duration of sickness, the time elapsed from the last attack and EDSS values. Our results imply that nitric oxide may be involved in the pathogenesis of MS although further studies are required to elucidate underlying mechanisms.

Serum inflammatory markers and clinical/MRI markers of disease progression in multiple sclerosis.

The aim of this study was to assess whether mean serum levels of inflammatory markers when measured serially correlate with disease progression or putative MRI markers of axonal loss in a cohort of well-characterised multiple sclerosis (MS) patients. Serial serum levels of soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 (sICAM-1), nitric oxide metabolites nitrate and nitrite (NOx), C-reactive protein (CRP), neopterin and tumour necrosis factor alpha (TNF-alpha) were measured in 29 MS patients, 13 with a relapsing remitting (RR) and 16 with a secondary progressive (SP) course, who were participating in a phase II clinical trial of anti-CD4 therapy. Short-term whole blood stimulated TNF-alpha production was also measured. Patients were studied 12 times over an 18-month period. MRI variables included the number and volume of Gd-enhancing lesions and the change in T2-hyperintense, T1-hypointense lesions and cerebral volume between the baseline and exit studies. Disease progression required a sustained change in the EDSS. There was no correlation between mean levels of inflammatory markers over the study period and disease progression or changes in any of the MRI measures. However, mean sICAM-1 levels from the first 6 months of the study were higher in patients who progressed during the study than in those that did not (443 (SD439) vs. 235 (SD162) ng/mL, p=0.05). Mean levels of NOx were significantly higher in patients with RR MS than in patients with SP disease (59.1 micromol/L (SD 12.8) vs. 48.7 micromol/L (SD 11.9), p=0.02). Patients with either a single relapse or no relapse had significantly higher NOx levels than to patients with multiple relapses during the 18 month follow-up (59.0 micromol/L (SD 12.3) vs. 47.9 micromol/L (SD 12.0), p=0.02). The mean levels of the other inflammatory markers did not correlate with disease course or relapse-rate. Serum levels of many inflammatory markers do not correlate with short-term disease progression. Some of the data suggest that the effects of inflammation on disease progression are delayed. In addition raised levels of serum nitric oxide metabolites are associated with a lower number of clinical relapses and a non-progressive disease course. These findings, although preliminary, pose interesting questions on the role of nitric oxide in the pathogenesis of MS. Inducible NO production in the early stages of the disease may be beneficial.

Endogenous nitric oxide and endothelin-1 in persistent pulmonary hypertension of the newborn.

We studied changes in endogenous nitric oxide (NO) synthesis and endothelin-1 (ET-1) production in infants with persistent pulmonary hypertension of the newborn (PPHN). We determined concentrations of serum NO metabolites, i.e., nitrites and nitrates (NOx), and of plasma ET-1 in five infants with PPHN (PPHN group) and in 25 healthy full-term neonates (control group). In both groups, serum NOx concentrations increased over time and plasma ET-1 concentrations decreased with age. The differences in serum NOx concentrations between groups were not significant at < 12 h and 24 h of age; however, they were significantly higher in the PPHN group than in the control group at 5 days of age. The differences in plasma ET-1 concentrations between groups were not significant at 5 days of age, but were significantly higher in the PPHN group than in the control group at < 12 h and 24 h of age. Limited endogenous nitric oxide synthesis and elevated endogenous endothelin-1 production during the first few days of life may contribute to pulmonary hypertension in infants with persistent pulmonary hypertension of the newborn.

Attenuation of reperfusion injury by renal ischaemic preconditioning: the role of nitric oxide.

To determine the effect on nitric oxide (NO) release and renal NO synthase (endothelial, eNOS and inducible, iNOS) activity of renal ischaemia-reperfusion (I/R) in vivo in an animal model, and to examine the possible involvement of NO in ischaemic preconditioning (IP) of the kidney. In a right-nephrectomized rat model, 42 animals were randomized in four groups: controls; IP-only (4 min of ischaemia followed by 11 min of reperfusion, total of four cycles); renal warm ischaemia (45 min) and 6 h reperfusion; ischaemia (45 min) preceded by IP pretreatment. Serum NO metabolites were assayed 2 and 6 h after ischaemia or the control equivalent. NOS expression in the kidney was detected immuno-histochemically, and damage assessed morphologically in sections stained with haematoxylin and eosin. Kidney function was assessed by the levels of serum creatinine, urea and electrolytes. Compared with before ischaemia, the concentration of serum NO metabolites at 6 h was increased in the IP-only animals (P = 0. 016) and in the IP + I/R group (P = 0.002). There was greater eNOS expression in the IP-only group (P = 0.009) and in the IP + I/R group than in controls (P = 0.050). iNOS expression was greater in the IP-only animals than in the control group (P = 0.050). Histological assessment showed less evidence of cellular damage in IP + I/R animals than in the I/R-alone group (P = 0.020). Serum creatinine level was not significantly different between the IP-only group and the control. There were no differences after 2 h of reperfusion. Ischaemic preconditioning has a protective effect on renal structure and function, which may be produced by increased NO release arising from increased NOS expression by 6 h after reperfusion.

The relationship between serum nitrate and endothelin-1 concentrations in preeclampsia

Recently it was suggested that abnormal endothelial function may contribute to the pathophysiological changes observed in preeclampsia (PE). Both nitric oxide (NO) and endothelin-1 (ET-1) are vasoactive substances produced by endothelial cells. NO is a vasodilator and has been believed to be decreased in PE. ET-1 is a vasoconstrictor and has been reported to be increased in PE. We simultaneously measured NO metabolites and ET-1 in sera from women with PE and investigated the correlation of NO and ET-1 concentrations. We obtained serum samples from 11 healthy nonpregnant (NP) women, 16 normotensive pregnant (NTP) women and 17 women with PE. In this study, the serum ET-1 level was assayed by the ET-1 RIA system, and serum NO metabolites were assayed by measuring nitrite (NO 2 −) and nitrate (NO 3 −) simultaneously in an HPLC-Griess reaction system. There was a significant correlation between NOx (nitrite + nitrate) and ET-1 in sera from all 44 women (NP, NTP and PE groups) (p<0.001). Nitrite and ET-1 in sera from each group were not significantly correlated. Nitrate and ET-1 in sera from the NP and NTP groups did not significantly correlate. However, there was a significant correlation between nitrate and ET-1 in sera from the PE group (p<0.05). The serum ET-1 and nitrate concentration in the PE group was significantly higher than in the NP and NTP groups (p<0.05 and p<0.001, respectively). These findings suggest that increased production of nitrate in PE may contribute to homeostatic vasodilation against vasoconstriction caused by a higher ET-1 concentration.

Nitric oxide metabolites in patients with asthma: induced sputum versus blood

Nitric oxide (NO) plays an important role in physiological regulation of the airways. The monitoring of airway inflammation has being observed in bronchial asthma directly, by sputum examination, and indirectly, by measurements in peripheral blood. To investigate the diagnostic value of these two methods, we compared NO metabolites in induced sputum and serum obtained in patients with asthma and control subjects. Hypertonic saline induced sputum and serum were obtained in 13 patients with asthma and 10 control subjects. NO metabolite level was assayed by using modified Griess reaction. Eosinophil cationic protein (ECP) was measured by fluoroimmunoassay, and detected interleukin (IL)-5 by a sandwich ELISA. The accuracy of the tests was measured by plotting the data in receiver operating characteristic (ROC) curves and comparing the area under the curve for NO metabolites. Asthmatic patients, compared with control subjects, had significantly higher NO metabolites in induced sputum (1252·5±203·3 moll −1 vs. 557·2±101±.5 mol l −1, P < 0·01) but not in serum. IL-5 in induced sputum was detected more frequently in patients with asthma than in control subjects [ 11 13 (84·6%) vs. 1 10 (10%), P < 0·01]. Asthmatic patients, compared with control subjects, had significantly higher ECP concentration in induced sputum (1270·0 ± 197·9 g 1 vs. 154·6 ± 47·4 g l −1, P < 0·01). There were significant positive correlations between NO metabolites in induced sputum and eosinophils, ECP in induced sputum ( r=0·58 P<0·05; r=0·64, P<0·01) in patients with asthma but not in serum. The area under the ROC curve showed that NO metabolites in induced sputum (0·78) are more accurate marker than NO metabolites in serum (0·53) ( P<0·05). These findings suggest that NO metabolites in induced sputum is a more valuable indicator to monitor asthmatic airway inflammation than those in serum.