Plasma nitrate as an index of nitric oxide formation in man: analyses of kinetics and confounding factors

Does apocynin increase liver regeneration in the partial hepatectomy model?

BACKGROUND

Hepayocyte loss may develop secondary to liver surgery and at this point liver regeneration plays a significant act in terms of liver reserve. The purpose of this research was to investigate the efficacy of apocynin on liver regeneration and preservation after partial hepatectomy in rats.

METHODS

A total of 32 rats, have been divided into 4 groups (n: 8) for hepatectomy model. Inflammatory and antiinflammatory parameters were measured from blood and liver tissue samples. In addition, the effects of apocynin were examined immunohistochemically and histopathologically from liver tissue.

RESULTS

In liver tissue samples, a significant difference has been found in glutathione peroxidase, total nitrite, catalase, oxidative stress index, total antioxidant and total oxidant status between sham and hepatectomy groups. A significant difference has been achieved between hepatectomy and posthepatectomy-Apocynin in terms of glutathione peroxidase and oxidative stress index. Total antioxidant status, oxidative stress index, and total oxidant status were significantly different only between the sham and the hepatectomy groups. Statistical differences were found between sham and hepatectomy groups and between hepatectomy and pre+post-hepatectomy-Apocynin groups in terms of serum glutathione, malondialdehyde, total nitrite, and L-Arginine. There were significant differences between the sham and hepatectomy groups, between hepatectomy and posthepatectomy-apocynin groups, between posthepatctomy-apocynin and pre+posthepatectomy-apocynin groups in terms of sinusoidal dilatation, intracytoplasmic vacuolization and glycogen loss (p < 0.001), in all histopathologic parameters except sinusoidal dilatation (p < 0.05). However, significant Ki-67 increases have been elaborated in hepatectomy, posthepatectomy-apocynin, and pre+posthepatectomy-apocynin groups compared to sham group (p < 0.001), in pre+posthepatectomy apocynin group compared to hepatectomy and posthepatectomy-apocynin groups (p < 0.001).

DISCUSSION

Histopathology, immunohistochemistry, and biochemistry results of this study revealed that apocynin has a protective effect on enhancing liver regeneration in partial hepatectomy cases in rats.

Simultaneous Pharmacokinetic Analysis of Nitrate and its Reduced Metabolite, Nitrite, Following Ingestion of Inorganic Nitrate in a Mixed Patient Population

PURPOSE

The pharmacokinetic properties of plasma NO₃^- and its reduced metabolite, NO₂^-, have been separately described, but there has been no reported attempt to simultaneously model their pharmacokinetics following NO₃^- ingestion. This report describes development of such a model from retrospective analyses of concentrations largely obtained from primary endpoint efficacy trials.

METHODS

Linear and non-linear mixed effects analyses were used to statistically define concentration dependency on time, dose, as well as patient and study variables, and to integrate NO₃^- and NO₂^- concentrations from studies conducted at different times, locations, patient groups, and several studies in which sample range was limited to a few hours. Published pharmacokinetic studies for both substances were used to supplement model development.

RESULTS

A population pharmacokinetic model relating NO₃^- and NO₂^- concentrations was developed. The model incorporated endogenous levels of the two entities, and determined these were not influenced by exogenous NO₃^- delivery. Covariate analysis revealed intersubject variability in NO₃^- exposure was partially described by body weight differences influencing volume of distribution. The model was applied to visualize exposure versus response (muscle contraction performance) in individual patients.

CONCLUSIONS

Extension of the present first-generation model, to ultimately optimize NO₃^- dose versus pharmacological effects, is warranted.

Protective effect of dexpanthenol against cisplatin-induced hepatotoxicity

The aim of the present study was to investigate the protective effect of dexpanthenol (Dexp) against cisplatin (Cis)-induced hepatotoxicity. Thirty-two Sprague Dawley rats were divided into four groups: Control group (n=8), Dexp group (n=8, 500 mg/kg/ip/daily single dose/3 days Dexp), Cis group (n=8, 7 mg/kg/ip/single dose Cis) and Cis+Dexp group (n=8, 500 mg/kg/ip/daily single dose/3 days Dexp +7 mg/kg/ip/single dose Cis). MDA, CAT, GSH, GSH-Px, TOS, TAS, OSI, Total Nitrit, IL-1β, IL-6 and TNF-α levels were analyzed in liver tissue samples. After paraffinization of liver tissue samples, histopathological (congestion, loss of glycogen, number of Kupffer cells) and immunohistochemical (caspase-3 expression) parameters were assessed on the paraffinized liver sections. GSH, TAS, TOS, OSI, Tot Nit, L-Arginine, ADMA and SDMA levels were measured in the serum samples. Statistically significant differences were found between the groups in terms of all liver tissue biochemical parameters, with the exception of IL-1β and TNF-α levels. GSH, CAT, GSH-Px, TAS and Tot Nit levels were significantly higher in the Cis+Dexp group compared to the Cis group, whereas MDA, TOS, OSI and IL-6 levels were higher in the Cis group. Similarly, serum GSH, TAS, Tot Nit levels were higher in the Cis+Dexp group whereas TOS, L-Arginine, ADMA and SDMA levels were higher in Cis group. There were statistically significant differences between Control and Cis groups in terms of congestion increase, increase of glycogen loss, increase of Kupffer cell number and increase of caspase-3 expression (P<0.001). There was a statistically significant difference between the Cis and the Cis+Dexp groups in terms of histopathologic parameters, with the exception of congestion (P<0.001). To conclude, histopathological, immunohistochemical, and biochemical results of this study demonstrated that Dexp has a protective effect against Cis-induced hepatotoxicity.

Mechanisms underlying blood pressure reduction by dietary inorganic nitrate

Nitric oxide (NO) importantly contributes to cardiovascular homeostasis by regulating blood flow and maintaining endothelial integrity. Conversely, reduced NO bioavailability is a central feature during natural ageing and in many cardiovascular disorders, including hypertension. The inorganic anions nitrate and nitrite are endogenously formed after oxidation of NO synthase (NOS)-derived NO and are also present in our daily diet. Knowledge accumulated over the past two decades has demonstrated that these anions can be recycled back to NO and other bioactive nitrogen oxides via serial reductions that involve oral commensal bacteria and various enzymatic systems. Intake of inorganic nitrate, which is predominantly found in green leafy vegetables and beets, has a variety of favourable cardiovascular effects. As hypertension is a major risk factor of morbidity and mortality worldwide, much attention has been paid to the blood pressure reducing effect of inorganic nitrate. Here, we describe how dietary nitrate, via stimulation of the nitrate-nitrite-NO pathway, affects various organ systems and discuss underlying mechanisms that may contribute to the observed blood pressure-lowering effect.

Effects of Dietary Inorganic Nitrate Supplementation on Exercise Performance in Patients With Heart Failure: Protocol for a Randomized, Placebo-Controlled, Cross-Over Trial

Background

Chronic heart failure is characterized by an inability of the heart to pump enough blood to meet the demands of the body, resulting in the hallmark symptom of exercise intolerance. Chronic underperfusion of the peripheral tissues and impaired nitric oxide bioavailability have been implicated as contributors to the decrease in exercise capacity in these patients. nitric oxide bioavailability has been identified as an important mediator of exercise tolerance in healthy individuals, but there are limited studies examining the effects in patients with chronic heart failure.

Objective

The proposed trial is designed to determine the effects of chronic inorganic nitrate supplementation on exercise tolerance in both patients with heart failure preserved ejection fraction (HFpEF) and heart failure reduced ejection fraction (HFrEF) and to determine whether there are any differential responses between the 2 cohorts. A secondary objective is to provide mechanistic insights into the 2 heart failure groups’ exercise responses to the nitrate supplementation.

Methods

Patients with chronic heart failure (15=HFpEF and 15=HFrEF) aged 40 to 85 years will be recruited. Following an initial screen cardiopulmonary exercise test, participants will be randomly allocated in a double-blind fashion to consume either a nitrate-rich beetroot juice (16 mmol nitrate/day) or a nitrate-depleted placebo (for 5 days). Participants will continue daily dosing until the completion of the 4 testing visits (maximal cardiopulmonary exercise test, submaximal exercise test with echocardiography, vascular function assessment, and vastus lateralis muscle biopsy). There will then be a 2-week washout period after which the participants will cross over to the other treatment and complete the same 4 testing visits.

Results

This study is funded by National Heart Foundation of Australia and Victoria University. Enrolment has commenced and the data collection is expected to be completed in mid 2018. The initial results are expected to be submitted for publication by the end of 2018.

Conclusions

If inorganic nitrate supplementation can improve exercise tolerance in patients with chronic heart failure, it has the potential to aid in further refining the treatment of patients in this population.

Trial Registration

Australian New Zealand Clinical Trials Registry ACTRN12615000906550; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=368912 (Archived by WebCite at http://www.webcitation.org/6xymLMiFK)

Combined Dietary Nitrate and Exercise Intervention in Peripheral Artery Disease: Protocol Rationale and Design

Background

Peripheral artery disease (PAD) is caused by atherosclerotic occlusions in the legs. It affects approximately 8-12 million people in the United States alone, one-third of whom suffer from intermittent claudication (IC), defined as ischemic leg pain that occurs with walking and improves with rest. Patients with IC suffer a markedly impaired quality of life and a high perception of disability. Improving pain-free walking time is a primary goal of rehabilitation in this population.

Objective

The nitric oxide (NO)-PAD trial is designed to compare the effects that 12 weeks of supervised exercise training, in combination with a high inorganic nitrate-content (beetroot [BR] juice) beverage or placebo (PL) beverage, has on clinical outcomes of exercise and functional capacity in two groups of PAD+IC patients: exercise training plus beetroot (EX+BR) and exercise training plus placebo (EX+PL). The primary aims of this randomized controlled, double-blind pilot study are to determine group differences following 12 weeks of EX+BR versus EX+PL in the changes for (1) exercise capacity: pain-free walking time (claudication onset time, COT), peak walk time (PWT), and maximal exercise capacity (peak oxygen uptake, VO_2peak) during a maximal-graded cardiopulmonary exercise test (max CPX) and (2) functional capacity: 6-minute walk (6MW) distance. The secondary aims will provide mechanistic insights into the exercise outcome measures and will include (1) gastrocnemius muscle oxygenation during exercise via near-infrared spectroscopy (NIRS); (2) gastrocnemius muscle angiogenesis: capillaries per unit area and per muscle fiber, and relative fraction of type I, IIa, IIb, and IId/x fibers; and (3) vascular health/function via brachial artery flow-mediated dilation, lower-limb blood flow via plethysmography, and pulse wave velocity and reflection.

Methods

A total of 30 subjects between 40 and 80 years of age with PAD who are limited by IC will undergo exercise training 3 days per week for 12 weeks (ie, 36 sessions). They will be randomized to either the EX+BR or EX+PL group where participants will consume a beverage high in inorganic nitrate (4.2 mmol) or a low-nitrate placebo, respectively, 3 hours prior to each training session.

Results

Data collection from this study has been completed and is in the process of analysis and write-up. While the study is too underpowered—EX+BR, n=11; EX+PL, n=13—to determine between-group differences in the primary outcomes of COT, PWT, and 6MW, preliminary observations are promising with Cohen d effect sizes of medium to large.

Conclusions

Exercise training is currently the most effective therapy to increase functional capacity in PAD+IC. If the addition of inorganic nitrate to an exercise regimen elicits greater benefits, it may redefine the current standard of care for PAD+IC.

Trial Registration

ClinicalTrials.gov NCT01684930; https://clinicaltrials.gov/ct2/show/NCT01684930 (Archived by WebCite at http://www.webcitation.org/6raXFyEcP)

Modeling Disease Progression: Angiotensin II Indirectly Inhibits Nitric Oxide Production via ADMA Accumulation in Spontaneously Hypertensive Rats

Nitric oxide (NO) production impairment is involved in the onset and development of hypertension. Although NO production impairment in spontaneously hypertensive rat (SHR) has been reported in a variety of researches, the time course of this progressive procedure, as well as its relationship with asymmetric dimethylarginine (ADMA) and angiotensin II (Ang II), has not been quantified. The aim of this research is to establish a mechanism-based disease progression model to assess Ang II and ADMA's inhibition of NO production in SHR's disease progression with/without ramipril's intervention. SHR were randomly divided into three groups: one disease group (n = 8) and two treatment groups (n = 8 for each group): standard treatment group (receiving ramipril 2 mg/kg^*day) and intensive treatment group (receiving ramipril 10 mg/kg^*day). ADMA, Ang II, NO, and SBP were determined weekly. Intensive treatment with ramipril was found to have no further attenuation of plasma NO and ADMA than standard treatment beyond its significantly stronger antihypertensive effects. Four linked turnover models were developed to characterize the profiles of ADMA, Ang II, NO, and SBP during hypertensive disease progression with/without ramipril intervention. Our model described Ang II and ADMA's contribution to NO production impairment and their responses to ramipril treatment throughout the disease progression in SHR. Model simulations suggested that Ang II affected NO production mainly through inhibiting ADMA elimination rather than affecting nitric oxide synthase (NOS) directly.

Association of eNOS Gene Polymorphisms G894T and T-786C with Risk of Hepatorenal Syndrome

Background. There are no studies investigating the relationship between endothelial nitric oxide synthase (eNOS) gene polymorphisms and hepatorenal syndrome (HRS). Aim. The purpose of this study is to elucidate whether eNOS gene polymorphisms (G894T and T-786C) play a role in the development of type-2 HRS. Methods. This study was carried out in a group of 92 patients with cirrhosis (44 patients with type-2 HRS and 48 without HRS) and 50 healthy controls. Polymorphisms were determined by polymerase chain reaction (PCR) and melting curve analysis. Results. We did not find any significant difference in allele and genotype distributions of the eNOS -T-786C polymorphism among the groups (p = 0.440). However, the frequency of GT (40.9%) and TT (13.6%) genotypes and mutant allele T (34.1%) for the eNOS G894T polymorphism were significantly higher (p < 0.001 and p < 0.001, resp.) in the HRS group than in both the stable cirrhosis (14.6%, 4.2%, and 11.5%, resp.) and the control (22.0%, 2.0%, and 13.0%, resp.) groups. Conclusion. The occurrence of mutant genotypes (GT/TT) and mutant allele T in eNOS -G894T polymorphisms should be considered as a potential risk factor in cirrhotic patients with HRS.

Neuroprotection by combination of resveratrol and enriched environment against ischemic brain injury in rats

OBJECTIVES

Both resveratrol (RV) and enriched environment (EE) exert beneficial effects on neurological functional recovery after an ischemic brain injury.

METHODS

The neuroprotective effect of combined treatment of RV and EE was examined in a rat model of middle cerebral artery occlusion (MCAO), aiming to further promote neurological functional recovery.

RESULTS

The combined therapy of RV and EE clearly improved locomotor activity and behaviour examination, compared to the monotherapy of RV or EE alone. Stroke severity was also markedly ameliorated by the co-treatment. Mechanistic study revealed that the combined treatment reduced oxidative stress. Moreover, the detrimental ERK1/2 signalling upregulated by MCAO injury was markedly suppressed by the co-treatment, compared to RV or EE monotherapy.

DISCUSSION

Altogether, the combined therapy of RV and EE showed a clearly enhanced neuroprotective effect, compared to RV or EE monotherapy, which might be a new strategy for the treatment of ischemic brain injury.

Diagnostic Accuracy of Brain-derived Neurotrophic Factor and Nitric Oxide in Patients with Schizophrenia: A pilot study

Background

Brain-derived neurotrophic factor (BDNF) and nitric oxide (NO) play multiple roles in the developing and adult CNS. Since BDNF and NO metabolisms are dysregulated in schizophrenia, we measured these markers simultaneously in the blood of schizophrenics and assessed their diagnostic accuracy.

Methods

Thirty-eight patients with schizophrenia classified according to demographic characteristics, symptomatologyand therapy and 39 age- and gender-matched healthy controls were enrolled. BDNF was determined by the ELISA technique while the concentration of nitrite/nitrate (NO2−/NO3−) was measured by the colorimetric method.

Results

Serum BDNF levels were significantly lower (20.38±3.73 ng/mL, P = 1.339E-05), whilst plasma NO2−/NO3− concentrations were significantly higher (84.3 (72–121) μmol/L, P=4.357E-08) in patients with schizophrenia than in healthy controls (25.65±4.32 ng/mL; 60.9 (50–76) μmol/L, respectively). The lowest value of BDNF (18.14±3.26 ng/mL) and the highest NO2−/NO3− concentration (115.3 (80–138) μmol/L) were found in patients treated with second-generation antipsychotics (SGA). The patients diseased before the age of 24 and the patients suffering for up to one year had significantly lower serum BDNF levels than those diseased after the age of 24 and the patients who were ill longer than one year. Both BDNF and NO2−/NO3− showed good diagnostic accuracy, but BDNF had better ROC curve characteristics, especially in patients with negative symptomatology.

Conclusions

BDNF and nitrite/nitrate showed inverse changes in schizophrenic patients. The most pronounced changes were found in patients treated with second-generation antipsychotics. Although BDNF is not specific of schizophrenia, it may be a clinically useful biomarker for the diagnosis of patients expressing predominantly negative symptoms.

Acute Dietary Nitrate Intake Improves Muscle Contractile Function in Patients With Heart Failure: A Double-Blind, Placebo-Controlled, Randomized Trial

BACKGROUND

Skeletal muscle strength, velocity, and power are markedly reduced in patients with heart failure, which contributes to their impaired exercise capacity and lower quality of life. This muscle dysfunction may be partially because of decreased nitric oxide (NO) bioavailability. We therefore sought to determine whether ingestion of inorganic nitrate (NO3 (-)) would increase NO production and improve muscle function in patients with heart failure because of systolic dysfunction.

METHODS AND RESULTS

Using a double-blind, placebo-controlled, randomized crossover design, we determined the effects of dietary NO3 (-) in 9 patients with heart failure. After fasting overnight, subjects drank beetroot juice containing or devoid of 11.2 mmol of NO3 (-). Two hours later, muscle function was assessed using isokinetic dynamometry. Dietary NO3 (-) increased (P<0.05-0.001) breath NO by 35% to 50%. This was accompanied by 9% (P=0.07) and 11% (P<0.05) increases in peak knee extensor power at the 2 highest movement velocities tested (ie, 4.71 and 6.28 rad/s). Maximal power (calculated by fitting peak power data with a parabola) was therefore greater (ie, 4.74±0.41 versus 4.20±0.33 W/kg; P<0.05) after dietary NO3 (-) intake. Calculated maximal velocity of knee extension was also higher after NO3 (-) ingestion (ie, 12.48±0.95 versus 11.11±0.53 rad/s; P<0.05). Blood pressure was unchanged, and no adverse clinical events occurred.

CONCLUSIONS

In this pilot study, acute dietary NO3 (-) intake was well tolerated and enhanced NO bioavailability and muscle power in patients with systolic heart failure. Larger-scale studies should be conducted to determine whether the latter translates into an improved quality of life in this population.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01682356.

Endotoxin exposure and puberty in female rats: the role of nitric oxide and caspase-1 inhibition in neonates

Bacterial toxins are widespread in the environment as well as in the digestive system of humans and animals. Toxin from Gram-negative bacteria (endotoxin or lipopolysaccharide; LPS) has a life-long programming effect on reproduction in rats, but the mediators have not been well-documented, so we investigated the effects of LPS on the timing of puberty in female rats. Because the levels of nitric oxide (NO) and interleukin 1β (IL-1β) increase following injection of LPS, we injected neonates (post-natal day (pnd) 7) with LPS, with or without NO or IL-1β inhibitors. Half of the prepubescent (pnd 30) animals received an additional LPS injection. Vaginal opening, number of ovarian follicles, and serum anti-LPS antibodies were determined. A single LPS injection was sufficient to reduce the primordial follicle pool, but puberty was delayed when rats received 2 LPS injections (at pnd 7 and 30). NO or IL-1β inhibitors improved both of these parameters, suggesting that the early detrimental effects of LPS on puberty and primordial follicle pool are mediated by NO and IL-1β.

Is nitrate a good biomarker of the nitric oxide status? / Este ionul nitrat un bun biomarker al producţiei endogene de monoxid de azot?

A method of measuring in vivo nitric oxide (NO) levels is required to detect pathological conditions in which endogenous production is decreased or to identify agents able to release this biomolecule. Unfortunately, nitric oxide has a very short biological half-life and is very difficult to measure. Assay of the oxidative products’ of NO levels, nitrite (NO

Rabbits were used as experimental animals, a validated HPLC-UV/VIS method was used for speciation of nitrite and nitrate. The following substances were administered: blank; “negative blank”: phenyl-N-tert-butylnitrone (PBN); “positive blank” (nitroglycerin); nitrite.

PBN administration significantly increased nitrate and decreased nitrite levels, nitrite administration excessively increased nitrate levels, while nitroglycerin (1 mg/kg) significantly increased both nitrate and nitrite levels.

Results show that NOx test cannot be considered accurate in acute nitric oxide status testing. Nitrite alone should be used as an in vivo released nitric oxide marker.

Effect of acute dietary nitrate intake on maximal knee extensor speed and power in healthy men and women

Nitric oxide (NO) has been demonstrated to enhance the maximal shortening velocity and maximal power of rodent muscle. Dietary nitrate (NO3(-)) intake has been demonstrated to increase NO bioavailability in humans. We therefore hypothesized that acute dietary NO3(-) intake (in the form of a concentrated beetroot juice (BRJ) supplement) would improve muscle speed and power in humans. To test this hypothesis, healthy men and women (n = 12; age = 22-50 y) were studied using a randomized, double-blind, placebo-controlled crossover design. After an overnight fast, subjects ingested 140 mL of BRJ either containing or devoid of 11.2 mmol of NO3(-). After 2 h, knee extensor contractile function was assessed using a Biodex 4 isokinetic dynamometer. Breath NO levels were also measured periodically using a Niox Mino analyzer as a biomarker of whole-body NO production. No significant changes in breath NO were observed in the placebo trial, whereas breath NO rose by 61% (P < 0.001; effect size = 1.19) after dietary NO3(-) intake. This was accompanied by a 4% (P < 0.01; effect size = 0.74) increase in peak knee extensor power at the highest angular velocity tested (i.e., 6.28 rad/s). Calculated maximal knee extensor power was therefore greater (i.e., 7.90 ± 0.59 vs. 7.44 ± 0.53 W/kg; P < 0.05; effect size = 0.63) after dietary NO3(-) intake, as was the calculated maximal velocity (i.e., 14.5 ± 0.9 vs. 13.1 ± 0.8 rad/s; P < 0.05; effect size = 0.67). No differences in muscle function were observed during 50 consecutive knee extensions performed at 3.14 rad/s. We conclude that acute dietary NO3(-) intake increases whole-body NO production and muscle speed and power in healthy men and women.

Nitric oxide concentrations in gas emanating from the tails of obese rats

This study was undertaken to investigate the effects of oral L-arginine administration and exercising training on the NO concentration emanating from rat tail and NOx in plasma. Obese (fa/fa) Zucker rats (n = 22) were divided into four groups: (1) oral L-arginine administration (A) (n = 6), (2) exercise training (E), (3) exercise training + L-arginine administration (E + A) (n = 5), and (4) non-exercise training + non-L-arginine administration (N) (n = 6). The control (+/+) Zucker rats (n = 22) were also divided into the same four groups. The body weight of the E + A and the A groups was significantly lower than that of the N group. The NO concentration emitted from the tail was higher in the L-arginine (E + A and A) groups than in the non-L-arginine (E and N) groups in both obese and control rats. Exercise training did not affect the skin gas NO concentration in either obese or control rats. Plasma NOx concentrations in four obese rats were significantly higher than those observed in control rats. Exercise training did not influence the level of plasma NOx in obese or control rats. In conclusion, this study confirmed that L-arginine administration increases the skin gas NO concentration and obesity increases the plasma NOx level. The plasma NOx concentrations were not affected by L-arginine administration or exercise training in obese or control rats.

The effect of apricots on the experimental cataract model formed by sodium selenite

This study was designed in order to investigate whether sun dried apricots have a preventive effect on the experimental cataract model formed by sodium selenite in rats. Fifty-nine Spraque-Dawley rat pups were divided into three groups. Group 1 (control group) consisted of twenty rat pups, born from the rats nourished ad libitum. Group 2 consisted of 18 newborn rats, born from the rats nourished ad libitum with 10% sun dried natural apricots. Group 3 consisted of 21 newborn rats, born from the rats nourished ad libitum. Subcutaneous (30nmol/gr) sodium selenite injection was applied to all the newborn rats except the control group (Group 1) on postpartum day 10. Cataract development was graded by slit-lamp examination and photography. Encapsulated lenses were analyzed for reduced glutathione (GSH) and malondialdehyde (MDA), a marker of lipid per oxidation. Lenses were also analyzed for total nitrite (TN). The presence of oxidative stress in selenite cataract development and its prevention by sun dried apricots.

Normobaric hypoxia conditioning reduces blood pressure and normalizes nitric oxide synthesis in patients with arterial hypertension

OBJECTIVES

Insufficient production and/or increased decomposition of the potent endogenous vasodilator nitric oxide plays an important role in development and progression of arterial hypertension and its complications. One of the most effective means of stimulating endogenous nitric oxide synthesis is controlled adaptation to hypoxia. This study examined the effect of a 20-day, intermittent, normobaric intermittent hypoxia conditioning (IHC) program on blood pressure (BP) and nitric oxide production in patients with stage 1 arterial hypertension.

METHODS

The IHC sessions consisted of four to 10 cycles of alternating 3-min hypoxia (10% FIO2) and 3-min room air breathing. BP was monitored for 24 h before and after IHC, and nitric oxide synthesis was evaluated by 24-h urinary excretion of the stable nitric oxide metabolites nitrate and nitrite.

RESULTS

IHC increased nitric oxide synthesis and decreased BP in hypertensive patients to values similar to those of normotensive individuals. Significant inverse correlations were found between nitric oxide production and disease duration, SBP, and DBP. Moreover, IHC enhancement of nitric oxide synthesis was especially robust in patients with arterial hypertension of more than 5 years duration. The reduction in BP persisted for at least 3 months in 28 of 33 hypertensive patients.

CONCLUSION

IHC exerted a robust, persistent therapeutic effect and can be considered as an alternative, nonpharmacological treatment for patients with stage 1 arterial hypertension. The antihypertensive action of IHC is associated with normalization of nitric oxide production.

Measurement of in vivo nitric oxide synthesis in humans using stable isotopic methods: a systematic review

Stable isotopic methods are considered the "gold standard" for the measurement of rates of in vivo NO production. However, values reported for healthy human individuals differ by more than 1 order of magnitude. The reason for the apparent variability in NO production is unclear. The primary aim of this review was to evaluate and compare the rates of in vivo NO production in health and disease using stable isotope methods. Articles were retrieved using the PubMed electronic database. Information on concentrations, isotopic enrichments of fluxes, and conversion rates of molecules involved in the NO metabolic pathway was extracted from selected articles; 35 articles were included in the final analysis. Three protocols were identified, including the arginine-citrulline, the arginine-nitrate, and the oxygen-nitrate protocols. The arginine-citrulline protocol showed a wider variability compared to the arginine-nitrate and oxygen-nitrate protocols. The direction of the association between disease state and rate of NO production was essentially determined by the etiopathogenesis of the disorder (inflammatory, metabolic, vascular). Considerable variation in methodologies used to assess whole-body NO synthesis in humans exists. The precision of several aspects of the techniques and the validity of some assumptions made remain unknown, and there is a paucity of information about physiological rates of NO production from childhood over adolescence to old age.

Nitric oxide synthesis is reduced in subjects with type 2 diabetes and nephropathy

OBJECTIVE

Nitric oxide (NO) is a key metabolic and vascular regulator. Its production is stimulated by insulin. A reduced urinary excretion of NO products (NOx) is frequently found in type 2 diabetes, particularly in association with nephropathy. However, whether the decreased NOx excretion in type 2 diabetes is caused by a defective NOx production from arginine in response to hyperinsulinemia has never been studied.

RESEARCH DESIGN AND METHODS

We measured NOx fractional (FSR) and absolute (ASR) synthesis rates in type 2 diabetic patients with diabetic nephropathy and in control subjects, after l-[(15)N(2)-guanidino]-arginine infusion, and use of precursor-product relationships. The study was conducted both before and after an euglycemic hyperinsulinemic ( approximately 1,000-1,200 pmol/l) clamp.

RESULTS

In type 2 diabetes, NOx FSR was reduced both under basal (19.3 +/- 3.9% per day, vs. 22.9 +/- 4.5% per day in control subjects) and hyperinsulinemic states (24.0 +/- 5.6% per day, vs. 37.9 +/- 6.4% per day in control subjects; P < 0.03 by ANOVA). Similarly, in type 2 diabetes, NOx ASR was lower than in control subjects under both conditions (basal, 0.32 +/- 0.06 vs. 0.89 +/- 0.34 mol per day; hyperinsulinemia, 0.35 +/- 0.07 vs. 1.15 +/- 0.38 mol per day; P = 0.01 by ANOVA). In type 2 diabetes, the ability of insulin to stimulate both the FSR (4.7 +/- 3.2% per day) and the ASR (0.03 +/- 0.04 mol per day) of NOx was several-fold lower than that in control subjects (15.0 +/- 2.9% per day and 0.25 +/- 0.07 mol per day, P < 0.03 and P < 0.02, respectively). Also the fraction of arginine flux converted to NOx (basal, 0.22 +/- 0.05% vs. 0.65 +/- 0.25%; hyperinsulinemia, 0.32 +/- 0.06% vs. 1.03 +/- 0.33%) was sharply reduced in the patients (P < 0.01 by ANOVA).

CONCLUSIONS

In type 2 diabetic patients with nephropathy, intravascular NOx synthesis from arginine is decreased under both basal and hyperinsulinemic states. This defect extends the concept of insulin resistance to NO metabolism.

Clinical pharmacokinetics of the cyclooxygenase inhibiting nitric oxide donator (CINOD) AZD3582

The clinical pharmacokinetics of the COX-inhibiting nitric oxide donator (CINOD) AZD3582 and its metabolites, including naproxen, nitric oxide and nitrate, are summarized. AZD3582 has low aqueous solubility, moderate and passive intestinal permeability and is degraded by intestinal esterases. Its oral bioavailability (F) appears to be maximally a few per cent, and increases by several-fold after food intake. Ninety-four per cent or more of an AZD3582 dose is absorbed, of which at least 9–20% appears to be taken up as intact substance. AZD3582 has a predicted plasma protein binding degree of ∼ 0.1%, a half-life (t½) of 3 to 10 h and does not accumulate after repeated once- and twice-daily dosing. In patients AZD3582 does not provide a significantly better gastrointestinal (GI) side-effect profile than the highly permeable and locally irritating naproxen. Possible reasons for this include considerable GI uptake as naproxen, limited duration and extent of nitric oxide donation in the GI mucosa and the circulation, tolerance development (involving auto-inhibition of nitric oxide catalysing enzymes) and mucosal damage caused by nitric oxide. Blood pressure data suggest that nitric oxide is mainly donated within 3h. The uptake of naproxen is slightly slower and lower (≥ 94% relative GI uptake and 80–85% relative F) after AZD3582 administration compared with naproxen dosing. The naproxen t½ and trough steady-state concentrations after AZD3582 and naproxen dosing are similar. The average systemic nitrate exposure is approximately doubled after dosing of 375 to 750 mg AZD3582 twice daily.

Pre-clinical pharmacokinetics of the cyclooxygenase-inhibiting nitric oxide donor (CINOD) AZD3582

The pre-clinical pharmacokinetics of AZD3582 (4-(nitrooxy)butyl-(2S)-2-(6-methoxy-2-naphthyl) propanoate) and its primary metabolites (naproxen and nitrate) were evaluated. AZD3582 had intermediate and passive intestinal permeability (40 times lower than for naproxen), high systemic plasma clearance (CL), substantial gastrointestinal hydrolysis, intermediate volume of distribution (Vss; ≥3.4 L kg−1) and half-life (t1/2; 7 h), negligible plasma protein binding (∼0.1%), low/intermediate oral uptake (≥13% as intact substance) and low and varying oral bioavailability (mean 1.4% in minipigs and 3.9% in dogs). Following administration of therapeutically relevant oral doses, plasma concentrations of AZD3582 were very low (≤ 13 nM in minipigs and ≤442 nM in dogs; rat data not available) and varying, and accumulation was not apparent. The pharmacokinetics of AZD3582 did not show apparent dose-, time- or gender-related dependency. In blood and intestine, AZD3582 was hydrolysed to naproxen, nitrate and other metabolites. The rate of this conversion was higher in rats than in non-rodents, including man. Despite near-complete to complete uptake of the oral dose, AZD3582 administration resulted in a lower bioavailability (F) of total naproxen than naproxen administration: 55% and 85% relative bioavailability (Frel) in rats and minipigs, respectively. An increased distribution to metabolizing tissues of naproxen (as AZD3582), and thereby enhanced naproxen CL, is believed to be responsible. Following dosing of AZD3582 or naproxen, the t1/2 of naproxen was 5, 9–10 and &gt;40 h in rats, minipigs and dogs, respectively. The Vss and CL for naproxen were small. Plasma protein binding was extensive, and saturation was observed within the therapeutic dose and concentration range. Intake of food prolonged the systemic absorption of naproxen in the minipig. The pharmacokinetics of naproxen did not show apparent time- or gender-related dependency. Following oral dosing of [3H]-, [14C]- and [15N]-AZD3582, most [14C]- and [3H]-activity was excreted in urine and expired air, respectively. Seventeen per cent of [15N] was recovered in minipig urine as [15N]-nitrate. About 30% of [3H]-activity (naproxen and/or naproxen-related metabolites) was excreted in bile and re-absorbed. Concentrations of [14C]-activity (nitrooxy-butyl group and/or its metabolites) in milk were higher than in plasma and [3H]-activity in milk. [3H]- and [14C]-excretion data indicated that intact AZD3582 was not excreted in urine, bile or milk to a significant extent. There was no apparent consistency between tissue distribution of [14C]- and [3H]-activity in the rat, which suggests rapid and extensive metabolism of extravascularly distributed AZD3582. A substantial increase of plasma nitrate levels was found after single and repeated oral doses of AZD3582 in the minipig. No inhibition or induction of CYP450 was found.

Protective role of 27bp repeat polymorphism in intron 4 of eNOS gene in lacunar infarction

Association of the three potential endothelial nitric oxide synthase gene (eNOS) polymorphisms (T-786C in promoter region, G894T in exon 7 and tandem 27-bp repeats in intron 4) with an increased risk of lacunar infarction (LI) were investigated. Genotypes of 70 patients and 81 healthy controls were determined through PCR with or without RFLP. Flow-mediated dilatation (FMD) was performed to assess endothelial-dependent vasodilatation, whereas the endothelial-independent vasodilatation was assessed with nitroglycerin (NTG). Genotype distribution was significantly different between LI patients and controls for intron 4aa (alleles for four repeats), genotype frequency being 1.4% and 16.0%, respectively (odds ratio for additive effect, 0.47; 95% CI, 0.28-0.81; p=0.006). Haplotypes with the intron 4aa polymorphism were significantly higher in controls when compared with the LI group (p=0.001). Diminished FMD but normal NTG response confirmed that patients with LI have generalized endothelial dysfunction. Intron 4aa genotype of eNOS gene seems to be protective for isolated LI and the effect was potentiated by the absence of 786C polymorphism in any allele of the promoter region.

A novel derivative for the assessment of urinary and salivary nitrate using gas chromatography/mass spectrometry

Previous gas chromatography/mass spectrometry (GC/MS) methods for determining nitrate in biological samples involve either hazardous chemicals or produce multiple isomers that can be difficult to quantitate. Modification of these methods, by the nitration of mesitylene instead of benzene and in the presence of trifluoroacetic anhydride rather than sulphuric acid, should enable simple isotopic quantitation for use in tracer studies, for example, in the measurement of nitric oxide production. Desiccated urine and saliva samples, in addition to aqueous labelled and unlabelled nitrate standards, were treated with trifluoroacetic anhydride and mesitylene at 70 degrees C for 1 h, cooled, then sequentially washed with deionised water and aqueous sodium bicarbonate. The solution of nitromesitylene in mesitylene was separated, dried and analysed by GC/MS. The full mass spectra exhibited abundant ions at m/z 165 and 166 corresponding to the unlabelled and labelled molecular species of nitromesitylene, respectively. Selected ion monitoring of these masses for a series of gravimetrically prepared standards indicated good agreement with isotopic enrichments in the range 0.0625-5 mole % excess, and at nitrate concentrations within the physiological range of 0.078-2 mmol/L. Derivatised samples were stable with respect to isotopic enrichments and nitrate concentrations at -20 degrees C for up to 21 days and exhibited excellent repeatability. Nitration of mesitylene proved to be a simple and rapid method for the measurement of isotope ratios in aqueous nitrates by GC/MS, which has applications in tracer studies and in concentration determinations by isotope dilution techniques for nitric oxide production.

Association of serum nitrate and nitrite levels with longitudinal assessments of disease activity and damage in systemic lupus erythematosus and lupus nephritis

OBJECTIVE

Reactive intermediate production is an essential component of the innate immune response that is induced during disease activity in murine lupus. This study was undertaken to determine whether a marker of systemic nitric oxide (NO) production correlates with prospectively studied disease activity in human systemic lupus erythematosus (SLE) and lupus nephritis patients.

METHODS

Eighty-three SLE patients and 40 control subjects were studied longitudinally. The SLE group included 23 patients with lupus nephritis documented by renal biopsy and 26 with a history of lupus nephritis. During each visit, following a 24-hour low-nitrate diet, traditional markers of disease activity and damage were determined. Serum nitrate plus nitrite (NOx) levels were determined by chemiluminescence detection.

RESULTS

NOx levels were higher in SLE patients than in controls during the first visit. In univariate longitudinal analyses, NOx levels were associated with SLE Disease Activity Index scores. In multivariate analyses, NOx levels were associated with serum levels of C3 and creatinine and the urinary protein:creatinine ratio. Among patients with lupus nephritis, those with proliferative lesions had higher NOx levels, and higher NOx levels were associated with accumulation of renal damage and lack of response to therapy.

CONCLUSION

This is the first study to prospectively demonstrate longitudinal associations between serum NOx levels and markers of SLE and lupus nephritis disease activity. The more pronounced association with proliferative lupus nephritis and with longitudinal response to lupus nephritis therapy provides a rationale for the study of reactive intermediates as biomarkers of disease activity and therapeutic targets in proliferative lupus nephritis.

Does pinealectomy affect the recovery rate after spinal cord injury?

Previous reports documented demonstrated that melatonin, a free radical scavenger, is important in protecting against oxidative stress-induced tissue damage after spinal cord injury (SCI). This study was undertaken to investigate the effects of pinealectomy (PX) and administration of exogenous melatonin after SCI in rats. These animals were randomized into six groups, each having 12 rats. Group 1 underwent laminectomy alone. Group 2 underwent laminectomy followed by SCI and received no medication. Group 3 underwent laminectomy followed by SCI and received melatonin. Group 4 underwent PX and laminectomy alone. Group 5 underwent PX and laminectomy followed by SCI and received no medication. Group 6 underwent PX and laminectomy followed by SCI and received melatonin. Melatonin (100 mg/kg) was given intraperitoneally immediately after trauma to the rats in the groups 3 and 6. PX caused a significant increase in the malondialdehyde (MDA), nitrite oxide (NO), glutathione (GSH), xanthine oxidase (XO) levels and decrease in GSH levels as compared with the control group. Trauma to the spinal cord results in significantly higher oxidative stress. Melatonin administration significantly reduced MDA, XO and NO levels, and increased GSH levels in the spinal cord after trauma. Exogenous melatonin treatment after trauma attenuated tissue lesion area and accelerated motor recovery rate. These findings suggest that reduction in endogenous melatonin after PX makes the rats more vulnerable to trauma and exogenous melatonin administration has an important neuroprotective effect on the level of the spinal cord.

Association of reactive oxygen and nitrogen intermediate and complement levels with apoptosis of peripheral blood mononuclear cells in lupus patients

OBJECTIVE

Both increased production of reactive oxygen and nitrogen intermediates (RONI) and reduced levels of complement may play a role in the increased apoptosis and reduced clearance of apoptotic cells in systemic lupus erythematosus (SLE). The objective of this study was to evaluate both processes in a parallel, prospective, longitudinal manner.

METHODS

Sixty-seven SLE patients were evaluated during multiple visits, and 31 healthy control subjects were evaluated once or twice. Clinical and laboratory features of SLE disease activity were determined, and blood was collected for measurement of serum nitrate plus nitrite (NOx) levels and for isolation of peripheral blood mononuclear cells (PBMCs). PBMCs were cultured with a nitric oxide (NO) donor and SLE or control plasma, with or without heat inactivation, cobra venom factor (CVF), or lipopolysaccharide plus interferon-gamma treatment. Cells were analyzed for apoptotic index (AI), cellular subsets, and RONI production.

RESULTS

The PBMC AI was associated with SLE and was inversely associated with complement levels over time. Changes in the AI with addition of a NO donor was longitudinally associated with serum NOx levels, and stimulation of SLE PBMCs led to parallel increases in RONI production and apoptosis. Addition of SLE plasma resulted in a greater PBMC AI, an effect that was increased with heat inactivation and was corrected with CVF treatment.

CONCLUSION

These data suggest that the greater AI observed in SLE PBMCs relates to increased PBMC RONI production and reduced complement levels. The longitudinal nature of these parallel associations within individuals suggests that these processes are dynamic and additive.

Acute effect of insulin on nitric oxide synthesis in humans: a precursor-product isotopic study

Nitric oxide (NO) is a key regulatory molecule with wide vascular, cellular, and metabolic effects. Insulin affects NO synthesis in vitro. No data exist on the acute effect of insulin on NO kinetics in vivo. By employing a precursor-product tracer method in humans, we have directly estimated the acute effect of insulin on intravascular NO(x) (i.e., the NO oxidation products) fractional (FSR) and absolute (ASR) synthesis rates in vivo. Nine healthy male volunteers were infused iv with L-[(15)N(2)-guanidino]arginine ([(15)N(2)]arginine) for 6 h. Timed measurements of (15)NO(x) and [(15)N(2)]arginine enrichments in whole blood were performed in the first 3 h in the fasting state and then following a 3-h euglycemic-hyperinsulinemic clamp (with plasma insulin raised to approximately 1,000 pmol/l). In the last 60 min of each experimental period, at approximately steady-state arginine enrichment, a linear increase of (15)NO(x) enrichment (mean r = 0.9) was detected in both experimental periods. In the fasting state, NO(x) FSR was 27.4 +/- 4.3%/day, whereas ASR was 0.97 +/- 0.36 mmol/day, accounting for 0.69 +/- 0.27% of arginine flux. Following hyperinsulinemia, both FSR and ASR of NO(x) increased (FSR by approximately 50%, to 42.4 +/- 6.7%/day, P < 0.005; ASR by approximately 25%, to 1.22 +/- 0.41 mmol/day, P = 0.002), despite a approximately 20-30% decrease of arginine flux and concentration. The fraction of arginine flux used for NO(x) synthesis was doubled, to 1.13 +/- 0.35% (P < 0.003). In conclusion, whole body NO(x) synthesis can be directly measured over a short observation time with stable isotope methods in humans. Insulin acutely stimulates NO(x) synthesis from arginine.

Whole body nitric oxide production is not decreased in patients with coronary atherosclerosis but is inversely related to plasma homocysteine

OBJECTIVE

Vascular endothelial nitric oxide (NO) biosynthesis is reported to be decreased in patients with atherosclerosis. The primary aim of the present study was to determine whether whole body NO production is decreased in patients with established coronary atherosclerosis (CA) as compared to healthy control (HC) subjects. As a secondary aim, we wished to ascertain whether whole body NO biosynthesis is inversely related to plasma homocysteine (Hcy) levels.

DESIGN

Whole body NO production was assessed by measuring the amount of [(15)N]-nitrate excreted in urine, following intravenous administration of L-[(15)N](2)-arginine.

SUBJECTS

19 CA and 13 HC.

RESULTS

Mean urinary [(15)N]-nitrate excretion was not different between the CA (113.1+/-13.9 nmol/mmol creatinine) and HC (129.9+/-15.4 nmol/mmol creatinine) groups, and was not different in CA subjects taking nitrates as compared to those not taking nitrates. Linear regression analysis revealed a strong inverse correlation between [(15)N]-nitrate excretion and plasma Hcy concentration (r=0.475, p=0.012). In contrast, no relationship was observed between [(15)N]-nitrate excretion and age, blood pressure (systolic or diastolic), plasma cholesterol (including subfractions), triglycerides or glucose.

CONCLUSIONS

Whole body NO production is inversely related to plasma Hcy, but is not related either to established coronary atherosclerosis or to the presence of other cardiovascular risk factors.

Central nervous system protection by resveratrol in streptozotocin-induced diabetic rats

The objective of the present study was to investigate the possible neuroprotective effect of resveratrol against streptozotocin-induced hyperglycaemia in the rat brain and medulla spinalis. Thirty adult male Wistar rats were divided into three groups as follows: control group, streptozotocin-induced diabetic-untreated group, and streptozotocin-induced diabetic resveratrol-treated group. Diabetes was induced by a single injection of streptozotocin (STZ) (60 mg/kg body weight). Three days after streptozotocin injection, resveratrol (10 mg/kg) was injected intraperiteonally daily over 6 weeks to the rats in the treatment group. Six weeks later, seven rats from each group were killed and the brain stem and cervical spinal cord were removed. The hippocampus, cortex, cerebellum, brain stem and spinal cord were dissected for biochemical studies (lipid peroxidation measuring malondialdehyde [MDA], xanthine oxidase [XO], nitric oxide [NO] and glutathione). MDA, XO and NO levels in hippocampus, cortex, cerebellum, brain stem and spinal cord in the streptozotocin-induced diabetic-untreated group increased significantly. Treatment with resveratrol significantly reduced MDA, XO and NO production and increased glutathione levels when compared to the streptozotocin-induced diabetic-untreated group. This study demonstrates that resveratrol is a potent neuroprotective agent against diabetic oxidative damage.

Serum, urinary, and salivary nitric oxide in rheumatoid arthritis: complexities of interpreting nitric oxide measures

Nitric oxide (NO) may play important roles in rheumatoid arthritis (RA). RA is an inflammatory disease involving joints and other systems including salivary glands. To assess NO production in RA patients, we compared levels of serum, urine, and salivary nitrite and nitrate (NOx) in patients with RA and normal subjects, and we examined the relationships of these measures to disease activity. Serum, urine, and NOx levels as well as renal creatinine, NOx clearance and fractional excretion rates were compared in 25 RA patients and 20 age- and gender-matched healthy controls. Subjects were hospitalized for 3 days and placed on a NOxrestricted diet. NOx was assayed using nitrate reductase and the Griess reagent. RA activity was assessed using standard clinical and laboratory measures. While consuming a restricted diet for 3 days to eliminate the effects of oral intake of NOx, 24 hour urinary NOx excretion decreased in both RA patients and healthy controls. Urine NOx levels at all time points were not significantly different between RA patients and normal subjects. Serum NOx levels also decreased during the 3 days of NOx restriction, but RA patients had higher serum NOx levels at all time points compared with the control group. Likewise, serum NOx/creatinine ratios were higher in RA patients than in controls. Although basal salivary flow rate and tear flow were lower in RA patients, salivary NOx levels did not differ between normal and RA subjects. While renal creatinine clearance was not different between the two groups, we found that RA patients had lower renal NOx clearance and lower renal NOx fractional excretion. After correction of p values for multiple comparisons, there were no significant relationships for the RA group between measures of disease activity and the urinary NOx, serum NOx, or urinary NOx clearance. Despite interest in the use of NO as a marker of disease activity, alterations in renal NOx clearance and fractional excretion in RA make it difficult to assess in vivo NO production even with strict dietary restriction of NOx intake.

Measurement of the NO metabolites, nitrite and nitrate, in human biological fluids by GC-MS

In this article we critically review the development and application of gas chromatography-mass spectrometry (GC-MS) techniques to the measurement of the nitric oxide (NO) metabolites, nitrite and nitrate, in human biological fluids. Our focus is on the issue of the fitness of any analytical strategy to its intended purpose and the validity of the analytical results generated. The accuracy, precision, recovery, selectivity and sensitivity of the various methods are evaluated and the potential pitfalls, both specific to the methods, and general to the area, are considered. Several examples of the applications of these techniques to clinical investigations of NO physiology are also critically evaluated.

Effects of resveratrol and methylprednisolone on biochemical, neurobehavioral and histopathological recovery after experimental spinal cord injury

AIM

To investigate the neuroprotective effect of resveratrol in an experimental spinal cord injury (SCI) model in rats.

METHODS

Male Wistar albino rats weighing 200-250 g were randomized into six groups. Weight-drop trauma was performed for SCI. Group 1 underwent laminectomy alone. Group 2 underwent laminectomy followed by SCI. Groups 3, 4, 5, and 6 underwent laminectomy followed by SCI and received resveratrol (100 mg/kg), methylprednisolone (MP) (30 mg/kg), resveratrol (100 mg/kg) plus MP (30 mg/kg), and ethanol (2%), respectively. The rats were divided into two subgroups for biochemical analysis (killed at 24 h after surgery) and for neurobehavioral and histopathological evaluation (killed at 6 weeks after surgery). Posttraumatic neurological recovery after surgery was recorded weekly.

RESULTS

Groups 3 and 5 revealed significantly lower malon-dialdehyde, nitric oxide, xanthine oxidase, and higher glutathione levels than group 4 (P<0.05). Neurological recovery rates were significantly better in groups 3 and 5 than group 4 (P<0.05). When spinal trauma size ratios were compared, there was no significant difference between treatment groups.

CONCLUSION

Resveratrol treatment revealed better biochemical recovery in the acute stage of trauma than MP treatment. Although resveratrol and combined treatment revealed better neurobehavioral recovery than MP treatment; resveratrol, MP, and combined treatment modalities improved histopathological recovery at the same level in the final stage of the experiment. Future studies involving different doses of resveratrol and different doses combinations with MP could promise better results as each drug has a different anti-oxidative mechanism of action.

Neuroprotection by resveratrol against traumatic brain injury in rats

Oxidative stress after traumatic brain injury may contribute to many of the pathophysiologic changes. Resveratrol, naturally present at high concentration in grape skin, seeds, and red wine, has significant antioxidant properties in a variety of in vitro and in vivo models. In this study, we investigate the effect of resveratrol on oxidative stress after traumatic brain injury in rat model.A total of 54 adult Wistar albino male rats weighing 250-300 g were used. The rats were allocated into three groups. The first group was control (sham-operated) group in which only a craniotomy was performed, the others were trauma and resveratrol groups. A 100 mg/kg single dose of resveratrol, freshly prepared by dissolving in 50% ethanol and diluted in physiological saline (2%), for resveratrol group, and 1 ml ethanol (2%) for trauma group, was administered intraperitoneally immediately after trauma. Weight-drop method was used for achieving head trauma. Then, all groups were separated into three subgroups for biochemical analysis, brain water content and histopathological assessment following trauma. Twenty-four hours after trauma brain water content and malondialdehyde (MDA), glutathione (GSH), nitric oxide (NO), xanthine oxidase (XO) levels of traumatic hemisphere were evaluated. Quantitative histopathological analysis was performed on 14th day postinjury. Trauma caused a significant increase in MDA, XO, NO levels and decrease in GSH level as compared to control group. Resveratrol administration significantly reduced MDA, XO and NO levels, increased GSH level, and also attenuated tissue lesion area. Our results indicate that treatment with resveratrol immediately after traumatic brain injury reduce oxidative stress and lesion volume. Future studies involving different doses and the dose-response relationship could promise better results.

The biology of nitric oxide and other reactive intermediates in systemic lupus erythematosus

Formation of reactive nitrogen and oxygen intermediates (RNI and ROI) is an essential part of the innate immune response. Markers of systemic RNI production are increased in the setting of systemic lupus erythematosus (SLE) activity. Several lines of evidence suggest mechanisms through which the activity of inducible nitric oxide synthase (iNOS) is pathogenic in SLE, including the ability of peroxynitrite (ONOO(-), a product of iNOS activity) to modify proteins, lipids, and DNA. These modifications can alter enzyme activity and may increase the immunogenicity of self antigens, leading to a break in immune tolerance. In humans, observational data suggest that overexpression of iNOS and increased production of ONOO(-) lead to glomerular and vascular pathology. Therapies designed to target iNOS activity or scavenge ROI and RNI are in development and may provide the means to reduce the pathogenic consequences of ROI and RNI in SLE.

Neuroprotective effect of etomidate in the central nervous system of streptozotocin-induced diabetic rats

It is well known that hyperglycaemia due to diabetes mellitus leads to oxidative stress in the central nervous system. Oxidative stress plays important role in the pathogenesis of neurodegenerative changes. In the present study we investigated the possible neuroprotective effect of etomidate against streptozotocin-induced (STZ-induced) hyperglycaemia in the rat brain and spinal cord. A total of 40 rats were used in this study. Rats were divided into four groups: sham-control, diabetic, diabetic-etomidate treated and vehicle for etomidate treatment group. Diabetes mellitus was induced by a single injection of streptozotocin (60 mg/kg body weight). Three days after streptozotocin injection, etomidate (2 mg/kg) was injected intraperitoneally for etomidate group and lipid emulsion (10%) for vehicle group was injected with corresponding amount intraperitoneally every day for 6 weeks. Six weeks after streptozotocin injection, seven rats from each group were killed and brain, brain stem and cervical spinal cord were removed. The hippocampus, cortex, cerebellum, brain stem and spinal cord were dissected for the biochemical analysis (the level of malondialdehyde [MDA], total nitrite, reduced glutathione [GSH], and xanthine oxidase [XO] activity). STZ-induced diabetes resulted in significantly elevation of MDA, XO and nitrite levels in the hippocampus, cortex, cerebellum, brain stem and spinal cord of the rats (P < 0.05) while etomidate treatment provided significantly lower values (P < 0.05). This study demonstrated that etomidate have neuroprotective effect on the neuronal tissue against the diabetic oxidative damage.

Neuroprotective effect of mexiletine in the central nervous system of diabetic rats

Both experimental and clinical studies suggests that oxidative stress plays an important role in the pathogenesis of diabetes mellitus type 1 and type 2. Hyperglycaemia leads to free radical generation and causes neural degeneration. In the present study we investigated the possible neuroprotective effect of mexiletine against streptozotocin-induced hyperglycaemia in the rat brain and spinal cord. 30 adult male Wistar rats were divided into three groups: control, diabetic, and diabetic-mexiletine treated group. Diabetes mellitus was induced by a single injection of streptozotocin (60 mg/kg body weight). Mexiletine (50 mg/kg) was injected intraperitoneally every day for six weeks. After 6 weeks the brain, brain stem and cervical spinal cord of the rats were removed and the hippocampus, cortex, cerebellum, brain stem and spinal cord were dissected for biochemical analysis (the level of Malondialdehide [MDA], Nitric Oxide [NO], Reduced Glutathione [GSH], and Xanthine Oxidase [XO] activity). MDA, XO and NO levels in the hippocampus, cortex, cerebellum, brain stem and spinal cord of the diabetic group increased significantly, when compared with control and mexiletine groups (P < 0.05). GSH levels in the hippocampus, cortex, cerebellum, brain stem and spinal cord of the diabetic group decreased significantly when compared with control and mexiletine groups (P < 0.05). This study demonstrates that mexiletine protects the neuronal tissue against the diabetic oxidative damage.

Impaired plasma nitric oxide availability and extracellular superoxide dismutase activity in healthy humans with advancing age

This study is aimed to verify the modifications of extracellular superoxide dismutase (EC-SOD) activity and its potential involvement on the mechanism responsible for the impairment of plasma nitric oxide (NO) availability occurring with advancing age in healthy humans. For this purpose, plasma samples were drawn from 40 healthy men, aged 20-92 years, in fasting state and used for measurements of stable end-product nitrite/nitrate (NOx), as expression of NO availability, EC-SOD activity, thiobarbituric acid reactive substances (TBARS) as marker of lipid peroxidation, Trolox equivalent antioxidant capacity (TEAC) as a measure of plasma total antioxidant capacity, and in vitro susceptibility of low density lipoprotein (LDL) to copper-mediated oxidation, evaluated as lag time. As indicated by our results, advancing age was significantly related to decreased plasma values of NOx (r = -0.877, P < 0.001), EC-SOD activity (r = -0.888, P < 0.001), TEAC (r = -0.647, P < 0.001) and lag time (r = -0.621, P < 0.001) as well as to an increased plasma amount of TBARS (r = 0.858, P < 0.001). NOx plasma level resulted independently predicted by EC-SOD activity and age. EC-SOD activity, in turn, was determined by age and TEAC. Taken together, findings of the present study give further insight into the mechanism related to age-associated endothelial dysfunction, indicating that the decreased EC-SOD activity may be involved in the progressive reduction of plasma NO availability with advancing age through the age-related impairment of oxidant/antioxidant balance.

Lack of alteration of endogenous nitric oxide pathway during prolonged nitric oxide inhalation in intensive care unit patients

OBJECTIVE

To compare hemodynamic and gasometric variables and the plasma concentrations of nitric oxide metabolites (cyclic guanosine monophosphate and nitrate and nitrite), endothelin-1, and renin-angiotensin metabolites before and after the start of nitric oxide inhalation, after prolonged nitric oxide inhalation, and before and after nitric oxide withdrawal.

DESIGN

Prospective study.

SETTING

Surgical intensive care unit, university hospital.

SUBJECTS

Patients with acute lung injury and right ventricular failure.

INTERVENTIONS

Nitric oxide inhalation (10-12 ppm) during a median of 2.9 days (12 hrs to 6.5 days).

MEASUREMENTS AND MAIN RESULTS

The pulmonary vasodilator effects of inhaled nitric oxide improved arterial oxygenation in patients with acute lung injury (p < .05) and reduced right atrial pressure in patients with right ventricular dysfunction (p < .01). These beneficial effects lasted the whole period of prolonged inhaled nitric oxide therapy up to 6.5 days. However, when inhaled nitric oxide was withdrawn, pulmonary vasodilator effects rapidly disappeared, and Pao2/Fio2 ratio markedly deteriorated in all studied patients to return to pre-inhaled nitric oxide levels. Changes in plasma cyclic guanosine monophosphate and nitrate and nitrite paralleled those of pulmonary vasodilatory effects. An immediate increase in plasma cyclic guanosine monophosphate with a slightly delayed increase in plasma nitrate and nitrite was observed at inhaled nitric oxide start with no attenuation during the prolonged inhaled nitric oxide therapy. A marked decrease toward pre-inhaled nitric oxide levels was seen within hours of inhaled nitric oxide withdrawal. In addition, no alteration of plasma endothelin-1 or renin-angiotensin mediators was observed during or after inhaled nitric oxide therapy.

CONCLUSIONS

Our study showed a lack of attenuation in the beneficial effects of inhaled nitric oxide and a lack of alteration of endogenous nitric oxide, endothelin-1, and renin-angiotensin pathways during prolonged nitric oxide inhalation.

Origin of nitrite and nitrate in nasal and exhaled breath condensate and relation to nitric oxide formation

BACKGROUND

Raised concentrations of nitrate and nitrite have been found in exhaled breath condensate (EBC) in airway disease, and it has been postulated that this reflects increased nitric oxide (NO) metabolism. However, the chemical and anatomical origin of nitrate and nitrite in the airways has not yet been sufficiently studied.

METHODS

The fraction of exhaled NO at an exhalation flow rate of 50 ml/s (FE(NO)) and nitrite and nitrate in EBC, nasal condensate, and saliva were measured in 17 tracheostomised and 15 non-tracheostomised subjects, all of whom were non-smokers without respiratory disease. Tracheal and oral samples were taken from the tracheostomised subjects and nasal (during velum closure) and oral samples from the non-tracheostomised subjects. Measurements were performed before and after sodium nitrate ingestion (10 mg/kg) and use of antibacterial mouthwash (chlorhexidine 0.2%).

RESULTS

In tracheostomised subjects oral FE(NO) increased by 90% (p<0.01) while tracheal FE(NO) was not affected 60 minutes after nitrate ingestion. Oral EBC nitrite levels were increased 23-fold at 60 minutes (p<0.001) whereas the nitrite levels in tracheal EBC showed only a minor increase (fourfold, p<0.05). Nitrate was increased the same amount in oral and tracheal EBC at 60 minutes (2.5-fold, p<0.05). In non-tracheostomised subjects oral FE(NO) and EBC nitrite increased after nitrate ingestion and after chlorhexidine mouthwash they approached baseline levels again (p<0.001). Nasal NO, nitrate, and nitrite were not affected by nitrate intake or mouthwash. At baseline, mouthwash with deionised water did not affect nitrite in oral EBC or saliva, whereas significant reductions were seen after antibacterial mouthwash (p<0.05 and p<0.001, respectively).

CONCLUSIONS

Besides the salivary glands, plasma nitrate is taken up by the lower airways but not the nasal airways. Nitrate levels in EBC are thus influenced by dietary intake. Nitrate is reduced to nitrite by bacterial activity which takes place primarily in the oropharyngeal tract of healthy subjects. Only oropharyngeal nitrite seems to contribute to exhaled NO in non-inflamed airways, and there is also a substantial contribution of nitrite from the oropharyngeal tract during standard collection of EBC.

Insulin resistance does not diminish eNOS expression, phosphorylation, or binding to HSP-90

Previously, using an animal model of syndrome X, the obese Zucker rat (OZR), we documented impaired endothelium-dependent vasodilation. The aim of this study was to determine whether reduced expression or altered posttranslational regulation of endothelial nitric oxide synthase (eNOS) underlies the vascular dysfunction in OZR rats. There was no significant difference in the relative abundance of eNOS in hearts, aortas, or skeletal muscle between lean Zucker rats (LZR) and OZR regardless of age. There was no difference in eNOS mRNA levels, as determined by real-time PCR, between LZR and OZR. The inability of insulin resistance to modulate eNOS expression was also documented in two additional in vivo models, the ob/ob mouse and the fructose-fed rat, and in vitro via adenoviral expression of protein tyrosine phosphatase 1B in endothelial cells. We next investigated whether changes in the acute posttranslational regulation of eNOS occurs with insulin resistance. Phosphorylation of eNOS at S632 (human S633) and T494 was not different between LZR and OZR; however, phosphorylation of S1176 was significantly enhanced in OZR. Phosphorylation of S1176 was not different in the ob/ob mouse or in fructose-fed rats. The association of heat shock protein 90 with eNOS, a key regulatory step controlling nitric oxide and aberrant O2−production, was not different between OZR and LZR. Taken together, these results suggest that changes in eNOS expression or posttranslation regulation do not underlie the vascular dysfunction seen with insulin resistance and that other mechanisms, such as altered localization, reduced availability of cofactors, substrates, and the elevated production of O2−, may be responsible.

New methods to evaluate endothelial function: A search for a marker of nitric oxide (NO) in vivo: re-evaluation of NOx in plasma and red blood cells and a trial to detect nitrosothiols

Although plasma NOx (NO(2)(-) and NO(3)(-)) has been used as an index of nitric oxide (NO) formation in vivo, many unreasonable results appeared even after active elimination of NOx contamination from laboratory ware. For example, plasma NOx concentrations did not increase during vasodilation mediated by the NO/cGMP pathway or after organ perfusion. A possible shift of NOx from plasma to erythrocytes (RBCs) as a cause of these phenomena has been excluded, leaving the destination of NOx (after leaving plasma) unknown. Kinetic analyses have revealed that steady state NOx concentrations in plasma and whole blood did not correlate with the NOx formation rate, but rather with the NOx elimination rate. Therefore, the supposition that the NO status is directly reflected by plasma NOx concentrations appears untenable. As nitrosothiols (R-SNOs), possible carriers of NO bioactivity, have been flagged as alternative indices of NO status in vivo, efforts have been made to detect these substances. When interference by ultrafiltration was eliminated, low molecular weight R-SNOs such as nitrosocystein and nitrosogluthathione were undetectable. However, a high-molecular weight R-SNO, nitrosoalbumin, was detected in human blood. Further research is required into the significance and practical use of nitrosoalbumin as a marker of NO in vivo.

Effects of 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS) and chlorpromazine on NO3- transport via anion exchanger in erythrocytes: inertness of DIDS in whole blood

We examined the effects of chlorpromazine on NO(3)(-) transport between erythrocytes (RBCs) and extracellular fluid. Chlorpromazine (10 microg/ml) did not influence NO(3)(-) movement in both whole blood and RBC suspension. Though an anion exchanger (AE1) inhibitor DIDS (4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid, 100 microM) did not alter NO(3)(-) movement in whole blood, it inhibited the movement in a concentration-dependent manner in the RBC suspension. The inhibition was abrogated by plasma and albumin concentration-dependently. Our results indicated that chlorpromazine had no effect on NO(3)(-) transport through AE1 and that the inertness of DIDS on AE1 in whole blood is due to interference by albumin in plasma.

Blood oxygen transport and endothelial dysfunction in patients with arterial hypertension

Disturbed nitric oxide (NO) synthesis leads to development of endothelial dysfunction that plays a significant role in the pathogenesis of arterial hypertension. The presence of various compounds of haemoglobin with NO can affect haemoglobin-oxygen affinity of the whole blood. Methaemoglobin and S-nitrosohaemoglobin increase it, whereas nitrosyl-haemoglobin decreases. The aim of this study was to investigate the blood oxygen transport indices and to assess the endothelial function in patients with arterial hypertension. The patients with mild hypertension had a 4.47% increased actual p50 (the blood pO(2) corresponding to its 50% oxygen saturation) (P<0.05), a diminished pO(2) (P<0.05), and a raised pCO(2) (P<0.01) as compared with the controls. The patients with severe hypertension had decreased pO(2) and pH, and actual p50 was reduced by 3.03% (P<0.05), which reflects a more pronounced oxyhaemoglobin dissociation curve shift leftwards. These changes can be assessed as a blood oxygen transport decompensation that enhanced tissue hypoxia. The results of our studies indicate that the endothelial dysfunction in patients with arterial hypertension leads to significant impairments in blood oxygen transport indices. The endothelium may be involved in development of the above blood oxygen transport impairments, since only sufficient amounts of NO maintain a normal blood flow and oxygen transport to tissues. The endothelial dysfunction leads to a disturbed production of different haemoglobin NO derivatives, which not only affects NO release at different sites of the arterial bed, but also haemoglobin-oxygen affinity and optimal blood oxygenation and deoxygenation in capillaries. These data support the notion that endothelial dysfunction may alter haemoglobin-oxygen affinity and tissue oxygen supply in vivo. Alternation of haemoglobin-oxygen supply may be involved in the pathogenesis of hypertension.

Implication of steady state concentrations of nitrite and nitrate metabolites of nitric oxide in plasma and whole blood in healthy human subjects

1. The aim of the present study was to determine whether the steady state NOx concentration reflects NOx formation in vivo. 2. A NO3- load study was performed after achieving NOx steady state. Chronological changes in NOx concentrations in plasma and whole blood samples from nine healthy subjects were determined by the HPLC-Griess system and NOx concentrations in erythrocytes were estimated as a possible NOx compartment influential in regulating plasma NOx concentrations. 3. Analysis was performed using the first-order one-compartment open model and the NOx formation rate was subsequently calculated. 4. The mean (+/-SEM) steady state NOx concentration of plasma (15.5 +/- 1.6 micromol/L), whole blood (12.8 +/- 1.2 micromol/L) and erythrocytes (11.9 +/- 0.7 micromol/L) did not correlate with the NOx formation rate in the compartments (0.50 +/- 0.05, 0.61 +/- 0.04 and 0.91 +/- 0.17 micromol/kg per h, respectively), whereas a significant correlation was found between the steady state NOx concentration and NOx elimination rate (Kel) in plasma (r=-0.69; P=0.04) and whole blood (r=-0.79; P=0.01). 5. Although there was no direct correlation between steady state NOx concentrations and serum creatinine levels, the correlation between half-life and serum creatinine levels was significant (plasma: r=0.60, P=0.02; whole blood: r=0.49, P=0.04). 6. Plasma NOx concentrations correlated significantly with erythrocyte NOx concentrations (r=0.92, P <0.01; erythrocyte NOx=0.66 x plasma NOx). 7. The results of the present study indicate that NOx does not accumulate excessively into erythrocytes at steady state and during a NO3- load and that the steady state NOx concentration in whole blood and plasma preferentially implies NOx elimination (mainly depending on renal function) rather than NOx formation.

Hypercholesterolemia impairs basal nitric oxide synthase turnover rate: a study investigating the conversion of l-[guanidino-15N2]-arginine to 15N-labeled nitrate by gas chromatography–mass spectrometry

Endothelial function is impaired in hypercholesterolemia and atherosclerosis, which is probably due to reduced biological activity of endothelium-derived nitric oxide (NO). NO is synthesized in functionally intact endothelium by oxidation of the terminal guanidino nitrogen atom(s) of the amino acid precursor, L-arginine. We applied stable isotope dilution techniques and gas chromatographic-mass spectrometric approaches to investigate metabolism of L-[guanidino-(15)N(2)]-arginine to (15)N-labeled nitrate in hypercholesterolemic rabbits and controls. After 4 weeks on control or 1% cholesterol-enriched diet, rabbits received 267 +/- 6 micromol of L-[guanidino-(15)N(2)]-arginine/kg of body weight via gastric cannulation. (15)N-isotope content of L-arginine in plasma and in platelet lysates increased 2h later in both groups, and almost returned to baseline until 24h. (15)N-isotope content of plasma nitrite and nitrate also increased in both groups at 2h, and had almost returned to natural content 24h later. (15)N-isotope content of urinary nitrate was significantly increased in control animals in urines collected from 0 to 12, 12 to 24, and had returned to baseline in the urine sample collected from 24 to 48 h. In the cholesterol group only a slight, insignificant elevation of (15)N-isotope content was observed for urinary nitrate. The extent of conversion of L-[guanidino-(15)N(2)]-arginine to (15)N-labeled nitrate was strongly and inversely correlated to plasma concentration of the endogenous NO synthase inhibitor, asymmetric dimethylarginine (ADMA), which was elevated in cholesterol-fed rabbits (R=0.77; p < 0.05). Our data show that baseline NO synthase turnover rate is reduced in rabbits during early hypercholesterolemia. Our study gives evidence that the mechanism of the impaired conversion of L-[guanidino-(15)N(2)]-arginine to (15)N-labeled nitrate most likely involves inhibition of NO synthase by ADMA, which is present in elevated concentrations in hypercholesterolemia.