Biology and clinical relevance of nitric oxide

NO Exchange for a Water Molecule Favorably Changes Iontophoretic Release of Ruthenium Complexes to the Skin

Ruthenium (Ru) complexes have been studied as promising anticancer agents. Ru nitrosyl complex (Ru-NO) is one which acts as a pro-drug for the release of nitric oxide (NO). The Ru-aqueous complex formed by the exchange of NO for a water molecule after NO release could also possess therapeutic effects. This study evaluates the influence of iontophoresis on enhancing the skin penetration of Ru-NO and Ru-aqueous and assesses its applicability as a tool in treating diverse skin diseases. Passive and iontophoretic (0.5 mA·cm⁻²) skin permeation of the complexes were performed for 4 h. The amount of Ru and NO in the stratum corneum (SC), viable epidermis (VE), and receptor solution was quantified while the influence of iontophoresis and irradiation on NO release from Ru-NO complex was also evaluated. Iontophoresis increased the amount of Ru-NO and Ru-aqueous recovered from the receptor solution by 15 and 400 times, respectively, as compared to passive permeation. Iontophoresis produced a higher accumulation of Ru-aqueous in the skin layers as compared to Ru-NO. At least 50% of Ru-NO penetrated the SC was stable after 4 h. The presence of Ru-NO in this skin layer suggests that further controlled release of NO can be achieved by photo-stimulation after iontophoresis.

Reperfusion Syndrome: Cellular Mechanisms of Microvascular Dysfunction and Potential Therapeutic Strategies

Reperfusion injury is the paradoxical and complex phenomenon of exacerbation of cellular dysfunction and increase in cell death after the restoration of blood flow to previously ischemic tissues. It involves biochemical and cellular changes causing oxidant production and complement activation, which culminates in an inflammatory response, mediated by neutrophil and platelet cell interactions with the endothelium and among the cells themselves. The mounted inflammatory response has both local and systemic manifestations. Despite improvements in imaging, interventional techniques, and pharmacological agents, morbidity from reperfusion remains high. Extensive research has furthered the understanding of the various pathophysiological mechanisms involved and the development of potential therapeutic strategies. Preconditioning has emerged as a powerful method of ameliorating ischemia reperfusion injury to the myocardium and in transplant surgery. More recently, postconditioning has been shown to provide a therapeutic counter to vasoocclusive emergencies. More research and well-designed trials are needed to bridge the gap between experimental evidence and clinical implementation.

Effect of Two Ginger Varieties on Arginase Activity in Hypercholesterolemic Rats

Recently, ginger has been used in traditional Chinese medicine as an herbal therapy for treating several cardiovascular diseases, however, information on its mechanism of action is limited. The present study assessed the effect of two ginger varieties (Zingiber officinale and Curcuma longa) on the arginase activity, atherogenic index, levels of liver thiobarbituric acid reactive substances (TBARSs), and plasma lipids in rats fed with a high-cholesterol (2%) diet for 14 days. Following the treatment period, it was found that feeding a high-cholesterol diet to rats caused significant (p < 0.05) increases in arginase activity, atherogenic index, levels of TBARS, total cholesterol (TC), triglycerides (TGs), and low-density lipoprotein cholesterol (LDL-C) with a concomitant decrease in high-density lipoprotein cholesterol (HDL-C). However, both ginger and turmeric (2% and 4%) caused significant (p < 0.05) decreases in arginase activity and the atherogenic index, and prevented hypercholesterolemia by decreasing the TC, TGs, and LDL-C while increasing the HDL-C when compared with the controls. In conclusion, dietary supplementation with both types of rhizomes (ginger and turmeric) inhibited arginase activity and prevented hypercholesterolemia in rats that received a high-cholesterol diet. Therefore, these activities of ginger and turmeric represent possible mechanisms underlying its use in herbal medicine to treat several cardiovascular diseases.

Lack of association of the iNOS gene polymorphism with risk of cancer: a systematic review and Meta-Analysis

In order to investigate the association between the iNOS gene polymorphisms and susceptibility to cancer, a search of English papers was done using Pubmed, the Cochrane Library, Embase, ISI Web of Science, Google (scholar) database, and all Chinese reports were conducted using CBMDisc, Chongqing VIP database, and CNKI database. A total of eight studies were included in this meta-analysis including 1,920 cases and 2,373 controls. The results indicated that the polymorphisms in iNOS gene (C150T(Ser(608) Leu) polymorphism and polymorphic (CCTTT)n repeats) had no association with cancer risk for all genetic models. This meta-analysis suggested that the polymorphisms in the iNOS gene were not associated with cancer risk.

Ventilation causes pulmonary vascular dilation and modulates the NOS and VEGF pathway on newborn rats with CDH

BACKGROUND/PURPOSE

Congenital diaphragmatic hernia (CDH) is a defect that presents high mortality because of pulmonary hypoplasia and hypertension. Mechanical ventilation changes signaling pathways, such as nitric oxide and VEGF in the pulmonary arterioles. We investigated the production of NOS2 and NOS3 and expression of VEGF and its receptors after ventilation in rat fetuses with CDH.

METHODS

CDH was induced by Nitrofen. The fetuses were divided into 6 groups: 1) control (C); 2) control ventilated (CV); 3) exposed to nitrofen (N-); 4) exposed to nitrofen ventilated (N-V), 5) CDH and 6) CDH ventilated (CDHV). Fetuses were harvested and ventilated. We assessed body weight (BW), total lung weight (TLW), TLW/BW ratio, the median pulmonary arteriolar wall thickness (MWT). We analyzed the expression of NOS2, NOS3, VEGF and its receptors by immunohistochemistry and Western blotting.

RESULTS

BW, TLW, and TLW/BW ratio were greater on C than on N- and CDH (p<0.05). The MWT was higher in CDH than in CDHV (p<0.001). CDHV showed increased expression of NOS3 (p<0.05) and VEGFR1 (p<0.05), but decreased expression of NOS2 (p<0.05) and VEGFR2 (p<0.001) compared to CDH.

CONCLUSION

Ventilation caused pulmonary vasodilation and changed the expression of NOS and VEGF receptors.

Visualization of nitric oxide production by individual platelets during adhesion in flowing blood

Nitric oxide (NO) exerts vasodilatatory, antiplatelet, antioxidant, and antiproliferative effects. Endothelium-derived NO has been shown to be of crucial importance in cardiovascular protection, whereas evidence that NO is synthesized by platelets and regulates platelet function is still controversial. By using a sensitive and specific fluorescent probe, 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM), we visualized NO production in individual platelets undergoing adhesion on a collagen substrate under flow conditions. NO production, monitored in real time, was dependent on the shear rates applied, increasing with the raising of the shear rates. Furthermore, NO production increased in the presence of l-arginine (nitric-oxide synthase [NOS] substrate), and it decreased in the presence of L-NG-monomethyl arginine (L-NMMA) (NOS inhibitor) but not of D-NG-monomethyl arginine (D-NMMA) (L-NMMA-inactive enantiomer). Platelet deposition, measured with mepacrine-labeled platelets, was inversely related to NO production. A correlation was evident between Ca(++) elevation and NO production, suggesting that platelet NO formation is triggered by intracytoplasmic Ca(++) elevation. Simultaneous measurement of NO and Ca(++) indicated that NO production in individual platelets is preceded by Ca(++) elevations, with a lag phase of 33 ± 9.5 s. Our studies provide the first direct demonstration of platelet NO production triggered by the interaction with an activating surface under flow and suggest that intraplatelet Ca(++) elevation elicits the production of NO which, in turn, modulates thrombus size.

Arginase inhibition restores endothelial function in diet-induced obesity

Arginase may play a major role in the regulation of vascular function in various cardiovascular disorders by impairing nitric oxide (NO) production. In the current study, we investigated whether supplementation of the arginase inhibitor N(ω)-hydroxy-nor-l-arginine (nor-NOHA) could restore endothelial function in an animal model of diet-induced obesity. Arginase 1 expression was significantly lower in the aorta of C57BL/6J mice fed a high-fat diet (HFD) supplemented with nor-NOHA (40mgkg(-1)/day) than in mice fed HFD without nor-NOHA. Arginase inhibition led to considerable increases in eNOS expression and NO levels and significant decreases in the levels of circulating ICAM-1. These findings were further confirmed by the results of siRNA-mediated knockdown of Arg in human umbilical vein endothelial cells. In conclusion, arginase inhibition can help restore dysregulated endothelial function by increasing the eNOS-dependent NO production in the endothelium, indicating that arginase could be a therapeutic target for correcting obesity-induced vascular endothelial dysfunction.

Nitric oxide production, systemic inflammation and lipid metabolism in periodontitis patients: possible gender aspect

AIM

Nitric oxide (NO) plays a crucial role in vascular tone regulation and is involved in pathogenesis of periodontitis. In this cross-sectional study, we investigated the serum and saliva levels of NO metabolites in periodontal disease and their relationship with serum C-reactive protein (CRP) levels, lipids metabolism and periodontal disease severity.

MATERIAL AND METHODS

Serum and saliva were collected from non-smoking patients with generalized severe periodontitis (n = 89) and healthy controls (n = 56). Serum and salivary levels of NO metabolites, serum levels of high density lipoproteins (HDL), low density lipoproteins (LDL), triglycerides, cholesterol and CRP were measured. Data were analysed in whole population and in different gender groups.

RESULTS

Periodontitis patients exhibited significantly lower serum and saliva levels of NO metabolites and significantly higher LDL, cholesterol and CRP levels than control group. Similar findings were observed within male but not within female population. Serum NO metabolites levels exhibited significant negative correlation with CRP in whole population and in male population. Significant positive correlation of serum NO metabolite levels with HDL levels was observed in whole population.

CONCLUSION

NO production is reduced in periodontitis, especially in male population. Gender might be an important factor in assessing risk of cardiovascular disease in periodontitis.

Fungal contribution to nitrous oxide emissions from cattle impacted soils

Microscopic soil fungi isolated from arable, grassland and forest soils have been suggested as producers of nitrous oxide (N(2)O). The aim of this work was to screen the capabilities for N(2)O production of microscopic fungi originating in the pasture soils of a cattle overwintering area with three levels of cattle impact intensity. In total, 36 fungal species from 11 genera were isolated during a 2-year study, and production of N(2)O under laboratory conditions was confirmed in 23 species (64%). Species belonging to the genera Fusarium, Penicillium, Monographella, Acremonium, Gibberella, Eurotium, and Pseudallescheria were found to be the most potent N(2)O-producers. Different N(2)O production patterns and wide variations in production rates, ranging from 1 to 150 μg N(2)O-Nd(-1), were observed, resulting in the transformation of 0.2-18.4% of the initial NO(2)(-)-N present in the cultivation medium. The data revealed distinct soil fungal communities in the different sections of the cattle overwintering area, and indicate a significant effect of cattle overwintering on the composition of soil fungal consortia. These observations confirm the importance of soil fungi in total N(2)O fluxes from grazed grassland ecosystems.

Antidepressant-like effect of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol, a putative trace amine receptor ligand involves l-arginine-nitric oxide-cyclic guanosine monophosphate pathway

1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol is a novel putative trace amine receptor modulator hypothesized to be useful for treatment-resistant depression. In our previous study, we have demonstrated the antidepressant-like effect of this molecule in mouse forced swim and tail suspension tests and shown to act via modulating the levels of norepinephrine, serotonin and dopamine. The present study attempts to explore the involvement of l-arginine-nitric oxide-cyclic guanosine monophosphate pathway in the antidepressant-like effect of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol in the mouse forced swim test. The antidepressant-like action of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol (8 mg/kg, i.p) was reversed by pretreatment with L-arginine (750 mg/kg, i.p.), a nitric oxide precursor. In contrast, pretreatment with methylene blue (a soluble guanlyate cyclase inhibitor and nitric oxide synthase (NOS) inhibitor) or 7-nitroindazole (a specific neuronal NOS inhibitor) potentiated the antidepressant-like effect of sub-effective dose of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol (2mg/kg, i.p.) in this test model. Furthermore, the antidepressant-like effect of this molecule (8 mg/kg, i.p.) was reversed by sildenafil (5mg/kg, i.p.), a phosphodiesterase inhibitor. In conclusion, the antidepressant-like action of 1-(7-methoxy-2-methyl-1,2,3,4-tetrahydro-isoquinolin-4-YL)-cyclohexanol involved L-arginine-nitric oxide-cyclic guanosine monophospate signaling pathway.

Inducible nitric oxide synthase genetic polymorphism and risk of asbestosis

Asbestos, a known occupational pollutant, may upregulate the activity of inducible nitric oxide synthase (iNOS) and thus the production of nitric oxide (NO). This study investigated whether iNOS (CCTTT)_n polymorphism is associated with an increased asbestosis risk in exposed workers. The study cohort consisted of 262 cases with asbestosis and 265 controls with no asbestos-related disease. For each subject the cumulative asbestos exposure data were available. The number of CCTTT repeats was determined following PCR amplification of the iNOS promoter region. Logistic regression was performed to estimate asbestosis risk. The OR of asbestosis was 1.20 (95%  CI = 0.85–1.69) for the LL genotype compared to the combined SL and SS genotypes and 1.26 (95% CI = 0.86–1.85) for the LL genotype compared to the SL genotype. The results of this study are borderline significant and suggest a possible role of iNOS (CCTTT)_n polymorphism in the risk of asbestosis; however, further studies are needed.

Inducible nitric oxide synthase (iNOS) gene polymorphism and disease prevalence

Nitric oxide synthase gene is present on chromosome 17 and has been implicated in a wide variety of diseases. The nitric oxide synthase enzyme forms nitric oxide that besides being a signalling molecule plays an important role in host immune response. Inducible nitric oxide synthase expression is regulated at the level of transcription. Single-nucleotide polymorphisms, copy number variation and simple sequence repeat are important variations that have been reported in human genome. The presence of such variations in the regulatory region affects the level of gene product in the cell, while variation in the coding region influences the structure of proteins and its activity. This alteration in the level of gene product and the structure of the protein molecule might be responsible for the final outcome of genetic as well as infectious diseases. In the present manuscript, we review the role of inducible nitric oxide synthase (iNOS) gene polymorphisms in different diseases and populations. The iNOS gene with one pentanucleotide repeat, two single-nucleotide polymorphisms in promoter region and one polymorphism in exon 16 has been implicated in several diseases. We have also predicted several polymorphisms in the promoter region of iNOS computationally, which might affect the transcription factor binding site (TFBS) and hypothesize that these polymorphisms have some putative role in the outcome of disease(s).

Effect of oleocanthal and its derivatives on inflammatory response induced by lipopolysaccharide in a murine chondrocyte cell line

OBJECTIVE

In joint diseases, cartilage homeostasis is disrupted by mechanisms that are driven by combinations of biologic factors that vary according to the disease process. In osteoarthritis (OA), biomechanical stimuli predominate, with up-regulation of both catabolic and anabolic factors. Likewise, OA progression is characterized by increased nitric oxide (NO) production, which has been associated with cartilage degradation. Given the relevance of cartilage degenerative diseases in our society, the development of a novel pharmacologic intervention is a critically important public health goal. Recently, oleocanthal isolated from extra virgin olive oil was found to display nonsteroidal antiinflammatory drug activity similar to that of ibuprofen, a drug widely used in the therapeutic management of joint inflammatory diseases. We undertook this study to evaluate the effect of oleocanthal and its derivatives on the modulation of NO production in chondrocytes.

METHODS

Cultured ATDC-5 chondrocytes were tested with different doses of oleocanthal and its derivatives. Cell viability was evaluated using the MTT assay. Nitrite accumulation was determined in culture supernatant using the Griess reaction. Inducible NO synthase (NOS2) protein expression was examined using Western blotting analysis.

RESULTS

Oleocanthal and its derivatives decreased lipopolysaccharide-induced NOS2 synthesis in chondrocytes without significantly affecting cell viability at lower concentrations. Among the derivatives we examined, derivative 231 was the most interesting, since its inhibitory effect on NOS2 was devoid of cytotoxicity even at higher concentrations.

CONCLUSION

This class of molecules shows potential as a therapeutic weapon for the treatment of inflammatory degenerative joint diseases.

Development of nitrosyl ruthenium complex-loaded lipid carriers for topical administration: improvement in skin stability and in nitric oxide release by visible light irradiation

The prominent nitric oxide (NO) donor [Ru(terpy)(bdqi)NO](PF(6))(3) has been synthesized and evaluated with respect to noteworthy biological effects due to its NO photorelease, including vascular relaxation and melanoma cell culture toxicity. The potential for delivering NO in therapeutic quantities is tenable since the nitrosyl ruthenium complex (NRC) must first reach the "target tissue" and then release the NO upon stimulus. In this context, NRC-loaded lipid carriers were developed and characterized to further explore its topical administration for applications such as skin cancer treatment. NRC-loaded solid lipid nanoparticles (SLN) and nanostructured lipid carriers were prepared via the microemulsification method, with average diameters of 275+/-15 nm and 211+/-31 nm and zeta potentials of -40.7+/-10.4 mV and -50.0+/-7.5 mV, respectively. In vitro kinetic studies of NRC release from nanoparticles showed sustained release of NRC from the lipid carriers and illustrated the influence of the release medium and the lyophilization process. Stability studies showed that NO is released from NRC as a function of temperature and time and due to skin contact. The encapsulation of NRC in SLN followed by its lyophilization, significantly improved the complex stability. Furthermore, of particular interest was the fact that in the NO photorelease study, the NO release from the NRC-loaded SLN was approximately twice that of just NRC in solution. NRC-loaded SLN performs well enough at releasing and protecting NO degradation in vitro that it is a promising carrier for topical delivery of NO.

Influence of inducible nitric oxide synthase polymorphisms in Japanese patients with non-alcoholic fatty liver disease

AIM

Genetic factors as well as environmental factors play an important role in the development of non-alcoholic fatty liver disease (NAFLD). Recently, inducible nitric oxide synthase (iNOS) was significantly higher in the severest form of non-alcoholic steatohepatitis (NASH), and nitric oxide (NO) has been determined to play an important role in the process of fibrosis in NASH. In this study, we investigated iNOS gene polymorphisms for associations with NAFLD.

METHODS

A total of 115 NAFLD patients, consisting of 65 patients with NASH and 50 patients with simple steatosis, in whom a positive diagnosis had been made by liver biopsy, and 435 healthy control subjects, were recruited into this study.

RESULTS

We investigated 10 single nucleotide polymorphisms (SNP) of the iNOS gene, one of which, rs1060822, had the lowest P-value in the allele frequency model (P = 0.00078) with an odds ratio (95% confidence interval) of 0.49 (0.32-0.75). Four SNP, rs2297510, rs2297511, rs2797512 and rs1060822, were significantly associated with NAFLD, even when the most conservative Bonferroni's correction was applied. Linkage disequilibrium analysis revealed that SNP rs1060822 and three other SNP, rs2297510, rs2297511 and rs2797512, were in the same block. We also investigated associations between rs1060822 genotypes and the fibrosis index, and the results of the analysis revealed an additive increase in the fibrosis index and intrahepatic iNOS mRNA expression in the patients with the T allele of rs1060822.

CONCLUSION

This is the first study to identify genetic variations in iNOS that may influence the risk of NAFLD and liver fibrosis in NAFLD.

Oral L-arginine protects against cyclosporine-induced hepatotoxicity in rats

Cyclosporine A (CyA) leads to liver injury, probably by causing the production of free radicals and resulting in nitric oxide (NO) deficiency. We evaluated CyA-mediated liver damage histopathologically to determine the possible beneficial effects of L-arginine (L-Arg). In this study, 7 groups of Sprague-Dawley rats; (1) Control group; (2) 0.9% NaCl group; (3) CyA group: 7.5mg/kg/day; (4) L-Arg group: 2g/lt/day; (5) l-NAME (N-nitro-L-arginine methyl ester) group: 5mg/100ml/day; (6) CyA+L-Arg group: L-Arg (2g/lt/day)+CyA (7.5mg/kg/day); and (7) CyA+L-NAME group: CyA (7.5mg/kg/day)+L-NAME (5mg/100ml/day) were included. At the end of the treatments, animals were killed and hepatic tissues were treated for morphological (hematoxylin and eosin) and biochemical (NO and malondialdehyde, MDA) analyses, and serum was processed for biochemical (alanine transaminase (ALT), aspartate transaminase (AST), bilirubin, alkaline phosphatase (ALP) and total protein) study. The results indicated that CyA-induced hepatotoxicity was characterized by sinusoidal dilatation, hepatocellular vacuolization, neutrophilic infiltration and hepatocellular necrosis. These findings were less pronounced in the CyA+L-Arg group than CyA alone group. L-NAME group showed moderate changes. The CyA+L-NAME (Group 7) had more severe changes. We found changes in tissue NO and MDA levels. We think that the tissue damage caused by CyA is mild and reversible at the period when biochemical parameters are just starting to become abnormal and that L-Arg may have a protective effect against CyA damage on liver.

Association between nitric oxide and oxidative stress in continuous ambulatory peritoneal dialysis patients with peritonitis

BACKGROUND

Peritonitis is a major complication in continuous ambulatory peritoneal dialysis (CAPD) patients, and the mechanisms involved in the pathology are important if the success rate of treatment strategies is to increase.

MATERIAL AND METHODS

A total of 50 CAPD patients (25 with 25 episodes of peritonitis and 25 with no clinical or laboratory signs of infection) were included in the study. Malondialdehyde (MDA) and nitric oxide (NO) metabolites in serum and dialysate effluents were determined.

RESULTS

The dialysate/serum (D/S) ratio of the NO metabolites and serum NO metabolite concentrations were significantly higher in the peritonitis group. Serum and dialysate MDA concentrations were also significantly higher in the peritonitis group. The D/S ratio of MDA was significantly higher in the control group.

CONCLUSIONS

Local peritoneal NO production and oxidative stress seem to increase in CAPD patients during the peritonitis attack.

Lack of association of the cyclooxygenase-2 and inducible nitric oxide synthase gene polymorphism with risk of cervical cancer in Korean population

Currently, many studies have shown that nitric oxide (NO) and prostaglandin (PG) are main inflammatory mediators involved in a variety of pathophysiological processes including inflammation and carcinogenesis. In this article, we explored the possible association of polymorphisms, of two representative inflammatory mediators, with the risk for cervical cancer. This study included 176 cases of histologically confirmed invasive cervical cancer, and 172 healthy controls. Allele frequency of 12 single-nucleotide polymorphisms (SNPs) of cyclooxygenase-2 (COX-2) and COX5 of the inducible nitric oxide synthase (iNOS) genes in 43 different normal populations were analyzed. We found that 14 of 17 showed a monomorphic or minimal minor allele frequency; therefore, we did not continue with additional analysis. Three SNPs (2 for COX-2, 1 for iNOS) were chosen for the study. Genotyping of three SNPs (SNP-rs5275 in the untranslated region of exon 10 and rs5277 in the coding region of exon 3 of COX-2, and iNOS Ser(608)Leu allele C/T polymorphism within exon 16 of the iNOS reductase domain) was performed. No significant increase was found in any of the genotypes of the COX-2 or iNOS in the cancer group. We investigated the possible correlation between the genotypes and the clinicopathologic parameters of cervical cancer. No significant association of the genotypes studied was found with respect to clinical stage, lymph node (LN) status, histologic type, or parametrial invasion. Our data did not reveal an association between COX-2 and iNOS polymorphisms with cervical cancer in Korean women.

Nitric oxide and nursing: a review

AIMS AND OBJECTIVES

This paper, therefore, aimed to review published literature in this area of pharmacological exploitation, to look at the therapeutic applications and clinical relevance and, by so doing, provide an accessible source for nurses to gain insight into the role of nitric oxide in the clinical setting.

BACKGROUND

Nitric oxide is a chemical mediator fundamental in the maintenance of adequate tissue perfusion and effective cardiovascular function; a major endogenous regulator of vascular tone. The use of nitrates are well established as pharmacological agents but it is only recently that it has been recognized that they act as a source of nitric oxide. Although widely addressed within the medical literature, there appears to be a paucity of nursing literature that explores either its physiological action, or its relevance to nursing practice.

CONCLUSIONS

This literature review provides an overview of the use of nitric oxide and its implications for nursing practice and patient outcomes.

RELEVANCE TO CLINICAL PRACTICE

Knowledge of nitric oxide and its action is pertinent to nurses across diverse specialities. It helps in understanding the principles of many nitrogen-derived medications which nurses administer to their patients on a daily basis. In terms of oral medication, this is demonstrated by greater insights into the action of nitrates, the appreciation of surprising developments in medications such as sildenafil and the development of new drug opportunities such as nitric oxide-non-steroidal anti-inflammatory drugs. Equally, the use of inhaled nitric oxide therapy in adult and neonatal critical care units appears to be an increasingly valuable source of treatment. A particular research challenge is found in the attempt at nitric oxide inhibition in the management of septic shock. The authors argue that understanding such esoteric areas of therapeutic developments is increasingly to be part of the repertoire of knowledge and skills for nurses in the 21st century.

Effects of plasma nitric oxide levels on platelet activation in single donor apheresis and random donor concentrates

P-selectin is an useful marker to determine platelet activation and nitric oxide inhibits platelet activation, secretion, adhesion and aggregation. The aim of this study was to investigate the relationship between nitric oxide and P-selectin values in both single donor apheresis and random donor platelet concentrates. According to the results of this study, we found that the best platelet concentrate is freshly prepared single donor apheresis concentrate and it is important to prevent activation at the beginning of the donation. Nitric oxide, which is synthesized from platelets during the storage period, is not sufficient to prevent platelet activation.

Changes in pulmonary arteriole protein kinase cαexpression associated with supplementalL-arginine in broilers during cool temperature exposure

The present study was conducted to examine the effect of supplemental L-arginine on pulmonary arteriole protein kinase Calpha (PKCalpha) expression in broilers exposed to cool temperature, to investigate further the molecular mechanisms of supplemental L-arginine on modulating pulmonary vascular functions in hypertensive broilers. Broilers were subjected to sub-thermoneutral (cool) temperature to induce pulmonary hypertension syndrome (PHS), and an additional 10 g/kg L-arginine was added to the basal diet to evaluate the effects of supplemental L-arginine on PHS mortality, plasma nitric oxide (NO) production and pulmonary arterioles PKCalpha expression. Supplemental L-arginine reduced PHS mortality but did not affect right/total ventricle (RV/TV) ratios in clinically healthy birds. Birds fed additional L-arginine had increased plasma NO and decreased PKCalpha protein expression in pulmonary arterioles; NO production was negatively correlated with PKCalpha expression. These results demonstrated that supplemental L-arginine diminished PKCalpha expression in birds exposed to cool temperature. It is suggested that NO-induced loss of PKCalpha expression might be partially responsible for its effects on dilating pulmonary vasculature and inhibiting pulmonary vascular remodelling in vivo.

Serial measurements of peripheral vascular reactivity and exercise capacity in congestive heart failure and after heart transplantation

BACKGROUND

The regulation of nutritive blood flow to skeletal muscles during exercise seems to make an important contribution to exercise capacity. In congestive heart failure (CHF) this regulation seems to be impaired, with attenuated peripheral vasodilatory capacity. The results regarding improvement of peripheral vasoreactivity after heart transplantation (HTx) are conflicting, and the contribution of impaired peripheral vasoreactivity to the observed reduced exercise capacity among heart transplant recipients (HTR) has not been well elucidated. We therefore assessed the reversibility of impaired vasoreactivity in forearm and calf after HTx with relationship to exercise capacity.

METHODS AND RESULTS

The vasoreactivity of both forearm and calf was studied with venous occlusion plethysmography and related to exercise capacity in 64 patients with CHF and in 22 controls. Of these patients, 29 patients underwent HTx, and the same measurements were performed 10 days, 6 months and 1 year after HTx, and in a group of 15 HTR who had undergone HTx several years ago. Our main findings were (1) impaired resting blood flow in patients with CHF improved after HTx and even surpassed levels of controls; (2) peak forearm blood flow remained attenuated early after HTx, but normalized during the first year postoperatively; (3) both forearm and calf minimal resistance remained elevated after HTx; (4) vascular reactivity displays regional variations in forearm and calf both during CHF and after HTx; and (5) peripheral vascular reactivity relate to exercise performance in both patients with CHF and HTR, but the relationship seemed more pronounced in CHF.

CONCLUSION

With impaired vasoreactivity related to limited exercise capacity in CHF, improvement is evident after HTx, but both forearm and calf minimal resistance remains elevated. These findings suggest increased vasoconstrictor drive to both exercising and non-exercising muscles, possibly contributing to persistent physical limitation after HTx.

High serum TNF-alpha level in Type 2 diabetic patients with microangiopathy is associated with eNOS down-regulation and apoptosis in endothelial cells

A high dose of tumor necrosis factor (TNF)-alpha induces endothelial dysfunction and enhances apoptosis in vitro. The present study was conducted to examine whether incubating human umbilical vein endothelial cells (HUVECs) with serum from Type 2 diabetic patients complicated with retinopathy and/or microalbuminemia demonstrate endothelial dysfunction. Serum levels of TNF-alpha and vascular endothelial growth factor (VEGF) were elevated in diabetic patients. Plasma levels of TNF-alpha, two soluble TNF-alpha receptors (sTNFR), and VEGF were assessed in diabetic patients (CD, n=21) complicated with retinopathy and/or nephropathy, uncomplicated diabetic patients (UD, n=18), and in healthy normal participants (NS, n=16). In HUVECs incubated with patient's serum, endothelial constitutive nitric oxide synthase (eNOS) protein expressions were measured by Western blot analysis. Apoptosis in HUVECs was determined by optical microscopy, DNA fragmentation, and CPP32-like protease activity. Serum TNF-alpha, sTNFR-I, and asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NOS, in CD were significantly higher than in UD or NS. While, serum sTNFR-I and VEGF levels were significantly increased in the both diabetic patients, compared with those of NS, no difference was observed in the serum TNF-alpha, sTNFR-II, and ADMA levels between UD and NS. eNOS down-regulation and apoptosis were seen in HUVECs incubated with serum from CD for 24 h, but those observations were completely counteracted in the incubation by the addition of the antihuman TNF-alpha antibody. These results imply that eNOS down-regulation in CD is associated with high serum TNF-alpha levels despite of high serum of VEGF levels. Therefore, endothelial dysfunction in diabetic patients complicated with microangiopathy may, in part, be attributed to high serum TNF-alpha levels.

Plasma and urine nitric oxide levels in healthy Turkish children

Nitric oxide (NO) is an important messenger molecule with a wide range of actions in virtually all cell systems and organs. In kidneys it participates in glomerular and medullary hemodynamics, tubuloglomerular feed-back, renin secretion, and extracellular fluid balance. Although the role of NO in regulating renal function in adults is well-established, it has recently been suggested that NO has a more critical role in maintaining basal renal blood flow and glomerular filtration rate (GFR) in the developing kidney. NO is rapidly metabolized to the stable end products nitrite and nitrate, which are more slowly excreted into the urine. Thus these metabolites can be recommended as useful markers of endogenous NO synthase activity, despite limited data about age-related changes in in-vivo NO production. The aims of this study were to determine age-related normal reference values of serum and urinary NO metabolites and to assess the probable relationship between these metabolites and the GFR. Normal levels of NO end products in blood and urine of 296 healthy children (117 female, 179 male) between the ages of 0 and 16 were investigated, as was whether these values change with age. Serum and urinary nitrate levels did not differ according to sex. Serum nitrate levels are higher in younger children, especially in the newborn period, and decrease with age. Nitrate levels in urine are higher in younger children with a peak in infancy (1 month to 1 year) and decrease with age. It was demonstrated that this decrease in serum and urinary nitrate levels with age parallels the increase in GFR. In conclusion, urinary NO products may be an indirect marker of serum NO levels and NO might have an important regulatory function both in the maintenance of renal function and in the maturation of the developing kidneys.

Protective Effect of Oral L-arginine Supplementation on Cyclosporine Induced Nephropathy in Rats

BACKGROUND

One of the major adverse effects of long term cyclosporine A (CyA) administration is chronic nephrotoxicity. Several studies have suggested that alterations of the L-arginine (L-Arg) nitric oxide (NO) pathway may be involved in the pathogenesis of CyA-induced kidney damage.

AIM

We postulated that in vivo activation of L-Arg-NO pathway might have a beneficial effect on CyA-induced renal damage. Conditions of chronic NO enhancement was established with L-Arg supplementation and chronic NO blockade with N-nitro-L-Arg methyl ester (L-NAME). We tested the hypothesis that, if CyA administration alters intrarenal NO synthesis, then exogenous L-Arg supplementation could limit renal injury, on the contrary, L-NAME, a potent competitive inhibitor of NO synthesis, could enhance CyA nephrotoxicity. Harmful effect of NO blockade indirectly supports the beneficial effect of NO in a model of CyA nephrotoxicity.

METHODS

Rats were administered vehicle (VH), CyA (7.5 mg/kg/day), CyA + L-Arg (2g/kg/day), CyA + L-NAME (5 mg/100 ml/day), CyA + L-Arg + L-NAME, VH + L-Arg, VH + L-NAME and were sacrificed at the end of the experiment. Body weight, serum creatinine, blood urea nitrogen (BUN) and NO levels were determined. Tubular injury and interstitial fibrosis were evaluated semiquantitatively using scoring systems on paraffin sections stained with hematoxylin/eosin (H/E), Masson's trichromic and periodic acid-Schiff (PAS).

RESULTS

The CyA group developed marked renal injury, characterized by a significant increase in serum creatinine and BUN, and histopathological alterations including tubular dilatation, vacuolization, necrosis, interstitial cell infiltration and tubulointerstitial fibrosis. CyA reduced serum NO level. L-Arg treatment significantly enhanced NO biosynthesis and protected animals from CyA-induced kidney damage. In contrast L-NAME strikingly reduced serum NO level, and worsened biochemical and histopathological alterations.

CONCLUSION

Chronic CyA nephrotoxicity can be aggravated by NO blockade and ameliorated by NO enhancement suggesting that L-Arg supplementation may be protective in CyA nephrotoxicity.

Nitric Oxide and Skeletal Muscle Reperfusion Injury: Current Controversies (Research Review)

Nitric oxide (NO) has been implicated in a large number of disease processes, including ischemia-reperfusion injury following the restoration of oxygenated blood to previously ischemic muscle, which is a recognized significant complication of vascular surgery. Altered metabolism of NO is implicated in the endothelial dysfunction that forms part of the pathophysiology of ischemia-reperfusion injury. However, NO can demonstrate either protective or cytotoxic effects during reperfusion injury. The use of transgenic mice, either NO synthase (NOS) gene knockout animals, or animals that over-express NOS isoforms, along with direct NO measurements and NO donor or inhibitor studies, have all demonstrated a role for NO in skeletal muscle reperfusion injury. There appears to be an initial stimulation of NO production in the first 20-min of ischemia, with a gradual decline through early reperfusion and a second higher peak of NO commencing in the later stages of reperfusion. The absolute levels of NO in the reperfused tissue and its regulation by the subtle interplay with superoxide and the subsequent production of the highly toxic peroxynitrite anion, are important factors in determining whether NO, in the context of ischemia-reperfusion injury, has damaging or protective effects in the body.

Nitric oxide as inflammatory mediator in post-traumatic stress disorder (PTSD): evidence from an animal model

Post-traumatic stress disorder (PTSD) is a severe anxiety disorder that may develop after experiencing or witnessing a traumatic event. Recent clinical evidence has suggested the involvement of neurodegenerative pathology in the illness, particularly with brain imaging studies revealing a marked reduction in hippocampal volume. Of greater significance is that these anatomical changes appear to be positively correlated with the degree of cognitive deficit noted in these patients. Stress-induced increases in plasma cortisol have been implicated in this apparent atrophy. Although not definitive, clinical studies have observed a marked suppression of plasma cortisol in PTSD. The basis for hippocampal neurodegeneration and cognitive decline therefore remains unclear. Stress and glucocorticoids increase glutamate release, which is recognized as an important mediator of glucocorticoid-induced neurotoxicity. Recent preclinical studies have also noted that glutamate and nitric oxide (NO) play a causal role in anxiety-related behaviors. Because of the prominent role of NO in neuronal toxicity, cellular memory processes, and as a neuromodulator, nitrergic pathways may have an important role in stress-related hippocampal degenerative pathology and cognitive deficits seen in patients with PTSD. This paper reviews the preclinical evidence for involvement of the NO-pathway in PTSD, and emphasizes studies that have addressed these issues using time-dependent sensitization - a putative animal model of PTSD.

Expression of vasoactive mediators during mechanical ventilation in nitrofen-induced diaphragmatic hernia in rats

The high mortality in patients with congenital diaphragmatic hernia (CDH) has been attributed to pulmonary hypoplasia and persistent pulmonary hypertension (PPH). Endothelin-1 (ET-1), nitric oxide (NO), and calcitonin gene-related peptide (CGRP) have been reported to be important vasoactive mediators in the perinatal pulmonary circulation. The exact mechanism by which these vasoactive mediators interact to regulate the perinatal pulmonary vascular tone in CDH with PPH is not fully understood. We hypothesized that the altered pulmonary vascular reactivity in CDH is due to imbalance in vasoactive mediators. This study was designed to investigate mRNA expression of ET-1, eNOS, and CGRP in CDH lung in the perinatal period. A CDH model was induced in pregnant rats following administration of nitrofen. In control animals, the same dose of olive oil was given without nitrofen. Cesarean section was performed on day 21 of gestation. The newborn rats were intubated and ventilated, and ventilation was continued for 1-6 h. Left lungs were collected from both groups at 0, 1, and 6 h after ventilation (n=8 in each group). Reverse transcriptase-polymerase chain reaction on lung tissue was performed to evaluate the relative level of ET-1, eNOS, and CGRP mRNA expression. The results showed a significant increase in ET-1 mRNA in CDH lung at 1 and 6 h after ventilation compared with controls. In CDH lung, eNOS mRNA and CGRP mRNA levels were significantly increased at 1 h but were similar to control values at 6 h after ventilation. The increased expression of vasoconstrictor ET-1 mRNA and vasodilators eNOS mRNA and CGRP mRNA in the CDH lung at 1 h after ventilation suggests that pulmonary vascular tone is rapidly changing after birth. An imbalance in the production of vasoconstrictors and vasodilators by the CDH lung may contribute to high pulmonary vascular resistance.

Prevention of Contrast Media–induced Nephrotoxicity after Angiographic Procedures

Contrast medium-induced nephrotoxicity (ie, contrast nephrotoxicity [CN]) remains an important complication of angiographic procedures. If administration of iodinated contrast medium is deemed necessary in patients at high risk of CN, volume expansion should be offered and the lowest possible dose of nonionic isosmolar dimeric or nonionic low-osmolar monomeric contrast medium should be used. Prophylactic administration of fenoldopam or acetylcysteine has not offered consistent protection against CN. Intravenous acetylcysteine could be considered in emergency situations. Recently, sodium bicarbonate infusion has been shown to reduce the risk of CN. Hemofiltration for several hours before and after contrast medium injection may offer good protection against CN in patients with advanced renal disease. Prophylactic hemodialysis does not offer any protection against CN.

Acute and subacute dermal toxicity of Break-Free CLP®: a weapons cleaning and maintenance compound

Break-Free CLP((R)) is a commercial cleaning, lubricating and preserving compound used in both the military and civilian sectors for maintenance of small- and large-caliber weapons. Like many commercial mixtures, there is very little information available on the toxicity of Break-Free CLP. Studies were conducted to characterize the biological effects of single or repeat dermal application of Break-Free CLP to the clipped backs of CD-1 mice. Break-Free CLP was applied neat, 50 microl three times of week for up to 2 weeks. Foci of epithelial ulceration were observed in skin sections from 22% of Break-Free CLP-treated animals in conjunction with markedly thickened epithelium suggesting that robust epithelial regeneration was occurring in these animals. Skin histopathology of Break-Free CLP-treated animals closely matched the histopathology from mice treated repeatedly with 2% croton oil in acetone (dermal irritation positive control). Serum alkaline phosphatase activity was significantly (P < 0.05) lower for mice treated with Break-Free CLP, 2% croton oil or 7,12-dimethylbenz[a]anthracene (DMBA) compared with negative and vehicle control mice. Skin nitric oxide (NO) levels were not significantly elevated for mice treated with Break-Free CLP but were significantly elevated for mice treated with dermal irritation positive control compound DMBA. The cumulative skin changes in Break-Free CLP-treated animals support conducting a subchronic dermal application study. The observed decreases in serum alkaline phosphatase activity suggest that future studies should include the liver and bone as possible target organs. Additionally, dermal penetration studies could provide key health risk assessment information for characterizing the potential health risks associated with chronic dermal exposure to Break-Free CLP.

Effect of nitric oxide on the development of nitrofen-induced fetal hypoplastic lung explants

BACKGROUND/PURPOSE

Nitric oxide (NO) is an important cell-signaling molecule, and its generators, nitric oxide synthases, are expressed temporospatially in fetal rat lung. Recently, NO has been reported to modulate branching of the fetal rat lung lobe in vitro. We designed this study to evaluate the effect of NO on the morphogenesis of hypoplastic lung using nitrofen-induced rat lung explant model.

METHODS

A hypoplastic fetal lung model and a normal control lung model were induced by feeding a pregnant rat with nitrofen (100 mg) or olive oil on day 9.5 of gestation, respectively. Fetal lungs were harvested on day 13.5 and placed in organ culture containing serum-free medium Dulbecco modified Eagle medium. An NO donor, DETA NONOate (DETA/NO), was added daily in the culture medium. The lung cultures were divided into 4 groups: group 1 (n = 8), normal controls without DETA/NO; group 2 (n = 22), normal controls with DETA/NO; group 3 (n = 13), hypoplastic lungs without DETA/NO; group 4 (n = 22), hypoplastic lungs with DETA/NO. The fetal lungs were incubated for 48 hours at 37 degrees C with 5% CO2. Lung bud count and area of the specimens were measured under computer-assisted digital tracings. The rate of increase in bud count and lung area was calculated as the ratio of each value at 48 hours minus each value at 0 hour, divided by the value at 0 hour.

RESULTS

The lung bud count was significantly increased in group 2 compared with group 1 at a concentration of 50 micromol/L DETA/NO (P < .05). In the nitrofen group, the lung bud count was significantly increased in group 4 compared with group 3 at 100 micromol/L DETA/NO added (P < .05). There was no significant difference in the rate of increase in whole lung area among the 4 groups. The peak increase rates of lung area and bud count were significantly lower in group 4 compared with group 2.

CONCLUSIONS

This study demonstrates that the NO donor, DETA/NO, promotes branching of the nitrofen-induced hypoplastic fetal lung explant. These data suggest that NO may modulate the development of the nitrofen-induced hypoplastic lung.

A novel genetic polymorphism of inducible nitric oxide synthase is associated with an increased risk of gastric cancer

AIM

Inducible nitric oxide synthase (iNOS) plays a central role in the pathway of reactive oxygen and nitrogen species metabolism when Helicobacter pylori (H pylori) infection occurs in humans. iNOS Ser(608)Leu allele, a novel genetic polymorphism (C/T) occurring within exon 16 of the iNOS reductase domain, may have a dramatic effect on the enzymatic activity. The aim of this study was to determine whether iNOS C/T polymorphism was associated with increased susceptibility to gastric cancer.

METHODS

We conducted a population based case-control study in a high gastric cancer incidence area, Yangzhong, China. Questionnaires from 93 patients with intestinal type gastric cancer (IGC), 50 with gastric cardia cancer (GCC) and 246 healthy controls were obtained between 1997 and 1998, and iNOS genotyping was carried out. Odds ratios (ORs), interaction index (gamma), and 95% confidence intervals for the combined effects of iNOS genotype and H pylori infection, cigarette smoking or alcohol drinking were estimated.

RESULTS

The frequency of (CT+TT) genotypes was higher in cases than in control group (24.48% vs 23.17%), but the difference was not statistically significant. After adjusting for age and gender, past cigarette smokers with (CT+TT) genotypes had a significantly increased risk of IGC (OR = 3.62, 95% CI: 1.23-10.64), while past alcohol drinkers with (CT+TT) genotypes had a significantly increased risk of GCC (OR = 3.33, 95% CI: 1.14-9.67). H pylori CagA negative subjects with (CT+TT) genotypes had a significantly increased risk of both IGC and GCC (OR = 2.19 and 3.52, respectively).

CONCLUSION

iNOS Ser(608)Leu allele may be a potential determinant of susceptibility to cigarette -alcohol induced gastric cancer, but larger studies are needed to confirm the observations.

Platelet-derived NO slows thrombus growth on a collagen type III surface

Nitric oxide (NO) is a free radical that plays an important role in modulating platelet adhesion and aggregation. Platelets are a source of vascular NO, but since erythrocytes avidly scavenge NO, the functional significance of platelet-derived NO is not clear. Our purpose was to determine if NO from platelets affects platelet thrombus formation in the presence of anticoagulated whole blood in an in vitro parallel plate flow system. We studied platelet adhesion and aggregation on a collagen type III surface in the presence of physiologically relevant fluid mechanical shear stress. We found that certain receptor mediated agonists (insulin and isoproterenol) caused a concentration dependent reduction in thrombus formation at a shear rate of 1000 s-1. This effect was mediated by NO since it was abolished in the presence of the NO inhibitor L-nitro-arginine-methyl-ester (L-NAME). As expected, at venous levels of shear rate (100 s-1) neither of the agonists had any effect on thrombus formation since platelet adhesion does not depend on activation at these low levels of shear. Interestingly, at a shear rate of 2000 s-1 the addition of L-NAME caused an increase in platelet coverage suggesting that shear, by itself, induces NO production by platelets. This is the first demonstration of shear stress causing platelets to produce an inhibitor of platelet activation. These results demonstrate that the development of a platelet thrombus is regulated in a complex way and that platelets produce functionally significant amounts of NO even in the presence of whole blood.

Impact of phototherapy on vasoactive mediators: NO and VEGF in the newborn

AIM

The objective of this study was to evaluate the effects of close and remote phototherapy on serum nitric oxide (NO) and vascular endothelial growth factor (VEGF) levels as well as on body temperature heart rate and blood pressure in neonates of different gestational ages.

PATIENTS AND METHOD

Term (gestational age > or = 37 weeks) and preterm neonates (GA < 37 weeks) with hyperbilirubinemia requiring phototherapy were included in the study. All patients except for the ones in incubators were randomized to receive either close phototherapy (15 cm above the patient) or remote phototherapy (30-45 cm above patient). Body temperature, heart rate and blood pressure were measured before treatment, six hours into treatment and one hour after cessation of treatment. Blood samples for NO and VEGF measurements were also taken at the same times.

RESULTS

Sixty-one term newborns and 37 preterm newborns were included in the study. Patients were distributed into four groups according to the dose of treatment together with gestational age, i.e. term close and remote photoherapy groups (n = 29, n = 32, respectively), preterm close and remote photoherapy groups (n=10, n=27, respectively). Body temperature increased significantly with phototherapy in all groups but was not at hyperthermia level. Heart rate increased in all groups except for term newborns in the remote phototherapy group and blood pressure decreased in term infants but was unchanged in preterms. None of these changes were at the level of tachycardia or hypotension for a newborn. Phototherapy did not result in elevation of NO or VEGF levels.

CONCLUSION

This study showed that in our group of patients close or remote phototherapy caused some body temperature, heart rate and blood pressure changes that were not clinically significant and did not result in increased levels of NO or VEGF, which are well known vasodilator mediators.

Serum concentrations of nitric oxide, tumor necrosis factor (TNF)-alpha and TNF soluble receptors in women with overweight and obesity

The aims of the present study was to examine how overweight and obesity affect serum concentrations nitric oxide (NO) metabolites and to determine whether there is association between serum concentrations tumor necrosis factor (TNF)-alpha and TNF soluble receptors (sTNF-R) in subjects with overweight and obesity. The study groups involved 154 women: 102 obese (81 obese with body mass index [BMI] 30 to 40 kg/m2 and 21 obese with BMI > 40 kg/m2), 24 overweight patients, and 28 lean controls. Serum concentrations of NO metabolites and of TNF-alpha and its soluble receptors (sTNF-R1, sTNFR-2) were measured by enzyme-linked immunosorbent assay (ELISA) kits. Serum concentration of insulin was measured by radioimmunoassay (RIA). Plasma glucose, cholesterol, high-density lipoprotein (HDL)-cholesterol, and triglicerydes were determined by enzymatic procedure. Body composition was determined by impedance analysis using Bodystat (Douglas, British Isles). Serum concentrations of NO in the overweight group (35.1 +/- 12.1 micromol/L) and the obese groups with BMI 30 to 40 kg/m2 (32.8 +/- 9.3 micromol/L) and with BMI greater than 40 kg/m2 (33.3 +/- 8.5 micromol/L) were significantly higher when compared to controls (28.2 +/- 8.1 micromol/L): P < .05; P < .01, and P < .01, respectively. There was no difference in levels of NO between the overweight group and both obese groups. Serum concentration of TNF-alpha was also significantly higher in the group with overweight (6.5 +/- 3.1 pg/mL), in the obese group with BMI 30 to 40 kg/m2 (6.8 +/- 3.1 pg/mL), and in the obese group with BMI greater than 40 kg/m2 (7.4 +/- 2.6 pg/mL) when compared to controls (2.9 +/- 2.2 pg/mL): P < .00005; P < .00005, and P < .0000001, respectively. However, serum concentrations of sTNF-R1 and -R2 did not differ significantly between the overweight group, both obese groups, and controls. In conclusion, we observed increased serum concentrations of TNF-alpha and NO in overweight and obese women. It seems that there is an association between serum concentrations of TNF-alpha and NO; however, this relationship depends on the degree of obesity.

Thioredoxin restores nitric oxide-induced inhibition of protein kinase C activity in lung endothelial cells

We previously reported that exposure to exogenous nitric oxide (NO) causes diminished expression of thioredoxin/thioredoxin reductase, a critical component of the redox system that regulates the functions of redox-sensitive enzymes, receptors, and transcription factors. Here we examined the role of thioredoxin in NO-induced inhibition of protein kinase C (PKC) isoform(s) and potential interaction of PKC and thioredoxin in pulmonary artery endothelial cells (PAEC) in culture. Exposure to NO gas (8 ppm) significantly diminished the catalytic activity of the representative isoforms of the conventional, novel, and atypical PKCs alpha, epsilon, and zeta, respectively, in PAEC. Further examination of NO's effect on PKC-zeta revealed that NO-induced inhibition of the catalytic activity of PKC-zeta was time-dependent and regulated by a posttranscriptional mechanism. NO-induced loss of the catalytic activity of PKC-zeta was restored by incubation with the disulfide reducing agent dithiothreitol (DTT) as well as by purified thioredoxin or thioredoxin reductase. Confocal imaging studies revealed co-localization of PKC and thioredoxin in PAEC. These results indicate that: (1) NO-induced inhibition of PKC isoforms is associated with S-nitrosylation-mediated disulfide formation of active site thiols in PKC-zeta as the disulfide reducing agent DTT and/or the thioredoxin enzyme system restore PKC-zeta catalytic activity and (2) NO causes oxidation of endogenous thioredoxin as exogenous reduced thioredoxin or thioredoxin reductase are required to reduce thioredoxin and to restore the catalytic activity of PKC-zeta in PAEC.

Nitric oxide production by human peritoneal mesothelial cells

Nitric oxide (NO) has multiple actions, ranging from immunomodulation to regulation of vascular tone and capillary flow. Thus NO generation within the peritoneum could potentially affect peritoneal transport by increasing capillary vasodilatation, and regulate the response to bacterial invasion. Peritoneal mesothelial cells have a common embryological derivation with endothelial cells. As mesothelial cells are the predominant cell type lining the peritoneal cavity, they could potentially be a major source of locally produced nitric oxide. Nitric oxide was measured using the Griess reaction, as total nitrite and nitrate, in fresh unused and spent dialysate effluent (SPDE) from both healthy peritoneal dialysis patients, and during episodes of bacterial peritonitis. Whereas fresh CAPD dialysate was nitrite free (5 +/- 0.1 microM), SPDE from a standard 4 h day time exchange contained 10.2 +/- 0.6 microM/L/h, and that from the overnight dwell 9.1 +/- 0.7 microM/L/h. During an episode of peritonitis, dialysate nitrite and nitrate increased significantly from 9.0 +/- 1.0 microM/L/h, when not infected to 17.5 +/- 2.4, from the first CAPD bag drained at presentation, and 15.2 +/- 1.8 for the second and 16.0 +/- 2.5 for the third exchange (p<0.01). By the following day nitrite levels had returned to baseline, 7.0 +/- 1.0 microM/L/h. Human peritoneal mesothelial cells (HPMC) were cultured and found to produce nitric oxide (261 nmol/mg cell protein), which increased in a dose dependent manner with the addition of spent uninfected CAPD dialysate. The addition of L-arginine, a NO substrate resulted in a 10% increase in nitric oxide production, whereas the addition of the blocker L-NMMA produced a 10% reduction. RNA for inducible nitric oxide synthase (iNOS) was sought using northern blotting technique following combination stimulation with lipopolysaccharide and cytokines (IL-1beta, TNFalpha and gamma-INF, and/or spent dialysate from patients with bacterial peritonitis). However, we could not demonstrate RNA production for iNOS. Peritoneal mesothelial cells may be an important source of locally generated nitric oxide within the peritoneal cavity under basal conditions, but as they do not contain iNOS, the markedly increased NO production observed with episodes of acute bacterial peritonitis is more likely due to a combination of increased NO production by peritoneal macrophages and endothelial cells.

Inhibitors of nitric oxide synthesis block cold-induced thermogenesis in rats

N-nitro-arginine methyl ester (L-NAME), an unspecific nitric oxide synthase inhibitor, was administered to individually caged Sprague-Dawley rats exposed to cold (18 degrees C) and thermoneutral (30 degrees C) environmental temperatures during the active phase of the animals' circadian cycle. Unrestrained rats were administered intraperitoneal injections of 100 mg x kg-1 L-NAME or 1 mL x kg-1 saline. Telemetry was used to measure abdominal temperature. On a separate occasion, metabolic rate and evaporative water loss were measured using indirect calorimetery, before and after the injection of 100 mg x kg-1 L-NAME, in rats exposed to the two environments. Injection of L-NAME had no significant effect on body temperature, metabolic rate, or evaporative water loss in rats exposed to the 30 degrees C environment. In the 18 degrees C environment, L-NAME injection caused a prolonged fall in body temperature ( F(1,12) = 17.43, P = 0.001) and a significant decrease in metabolic rate (Student's t test, P = 0.001) and evaporative water loss (one-sample t test, P = 0.04). Therefore, the effects that systemic injection of L-NAME has on body temperature are dependent on environmental temperature, with nitric oxide synthase inhibition seemingly preventing the metabolic component of cold defence.

Inducible and endothelial constitutive nitric oxide synthase gene polymorphisms in Kawasaki disease

BACKGROUND

Nitric oxide (NO) is secreted by immune and vascular endothelial cells, and appears to play important roles in the pathophysiology of Kawasaki disease (KD). Thus, genetic variations in NO synthase (NOS) genes may be involved in the development of coronary artery lesions (CAL) in KD.

METHODS

The present study investigated the association of endothelial constitutive NOS (ecNOS) and inducible NOS (iNOS) gene polymorphisms with the development of CAL in KD in a Japanese population.

RESULTS

The genotype distributions of 27-bp tandem repeat polymorphism within intron 4 of ecNOS gene did not show any significant difference between controls and KD patients with or without CAL. In addition, there was no significant association between whole-allele distribution of iNOS gene promoter (penta-repeat CCTTT) polymorphism and KD with or without CAL.

CONCLUSION

These results did not support any association of ecNOS and iNOS gene polymorphisms to the development of CAL in KD patients in a Japanese population.

Amniotic levels of vascular endothelial growth factor and nitric oxide at the second trimester in Down's syndrome

OBJECTIVE

Since placentae in trisomy 21 show trophoblastic hypoplasia and hypovascularity, we investigated amniotic fluid vascular endothelial growth factor (VEGF) and nitric oxide (NO) in normal pregnancy and pregnancy complicated by trisomy 21. Furthermore, we investigated a possible role of NO in neurodegeneration of the brain in Down's syndrome.

METHODS

We retrospectively assessed NO and VEGF on mid-trimester amniotic fluid from 15 women who had fetal Down's syndrome, and compared the results with those of 15 controls matched for age and gestation.

RESULTS

In pregnancies complicated by trisomy 21, NO levels were significantly higher than in healthy controls (p < 0.001), whereas VEGF levels were significantly lower than in healthy controls (p < 0.05).

CONCLUSIONS

Our results suggest that the high levels of NO and the low levels of VEGF observed in the amniotic fluid of fetuses with Down's syndrome may be a sign of an imbalance of placental vascularization and altered endothelial function. Overproduction of NO could contribute to pathological cell death in the central nervous system, a process that has been demonstrated in many neurodegenerative diseases.

Is estradiol cardioprotection a nitric oxide-mediated effect?

BACKGROUND

Estradiol exerts a number of biological effects that support extensive observational data suggesting a protective role for estrogen in cardiovascular disease prevention. These include effects on lipid and carbohydrate metabolism, coagulation/fibrinolysis as well as a possible effect on vascular reactivity. It has been proposed that this might be mediated by vascular endothelial nitric oxide (NO) production. Accordingly, we designed complementary in-vivo and in-vitro studies to investigate this hypothesis further.

METHODS

Firstly, in a group of 10 healthy post-menopausal women, bilateral venous occlusion plethysmography was used to examine forearm vasoconstrictor responses to intrabrachial N(G)-monomethyl-l-arginine (l-NMMA; a substrate inhibitor of nitric oxide synthase) both before and after 4 weeks of treatment with transdermal 17beta-estradiol (E(2)) (80 microg/day). Secondly, we examined the direct effects of acute (24 h) and chronic (7 days) treatment with E(2) (10 pmol/l and 10 nmol/l) on endothelial nitric oxide synthase (eNOS) gene expression in cultured human aortic endothelial cells.

RESULTS

No significant differences were observed between the vasoconstrictor responses to l-NMMA (2, 4, 8 micromol/min) before and after E(2) treatment. Comparison of E(2)-treated endothelial cells with control cells showed no significant increase in eNOS mRNA expression following either acute or chronic estradiol treatment.

CONCLUSIONS

The present studies do not provide evidence for an eNOS-mediated cardioprotective response to estrogen and therefore suggest that additional mechanisms other than the endothelial NO system may have an important role in the cardiovascular effects of estrogen.

The effects of hormone replacement therapy on endothelial function in women with Turner's syndrome

OBJECTIVES

To examine the effect of hormone replacement therapy (HRT) on endothelial function of forearm resistance vessels in women with Turner's syndrome.

DESIGN

Subjects were studied on three occasions: on their usual HRT (study 1), then after 6 weeks off HRT (study 2) and finally after a further 6 weeks on HRT (study 3).

PATIENTS

Seven young women with Turner's syndrome were studied.

MEASUREMENTS

Forearm blood flow in response to intrabrachial infusion of bradykinin, 10, 30, 100 pmol/min (endothelium-dependent vasodilator), glyceryl trinitrate, 4, 8, 16 nmol/min (GTN; endothelium-independent vasodilator), noradrenaline, 60, 120, 240 pmol/min (NA, alpha-adrenergic receptor agonist) and NG-monomethyl-l-arginine, 1, 2, 4 micromol/min (L-NMMA; NO synthase inhibitor) was assessed by bilateral venous plethysmography.

RESULTS

The vasodilator response to bradykinin, expressed as the within-subject mean difference in area under the dose-response curve between study 2 and study 1, was significantly diminished (-744.2 +/- 287.2, P = 0.04) but improved 6 weeks after HRT recommencement. However, there was no significant change in response to GTN (between study 2 and study 1, 189.5 +/- 247.8, P = 0.47). The vasoconstrictor response to L-NMMA was also diminished in study 2 when compared to study 1 (-100.4 +/- 35.4, P = 0.039) and was restored after HRT was recommenced (between study 3 and study 2, 117.5 +/- 69.3, P = 0.17) whereas there was no significant difference in response to NA between study 2 and study 1 (76.7 +/- 50.6, P = 0.18) or study 3 and study 2 (-70.8 +/- 71.1, P = 0.38).

CONCLUSIONS

HRT improves endothelial function in women with Turner's syndrome.

Inducible nitric oxide synthase gene and diabetic retinopathy in Asian Indian patients

Nitric oxide, a signal transduction molecule, when modulated causes various diseases including diabetic retinopathy. In diabetes, allelic polymorphism of the inducible nitric oxide synthase (iNOS) gene is associated with retinopathy in the Northern Irish population. In the present study we investigated the Asian Indian population. One hundred and ninety-nine unrelated Asian Indian patients with 15 or more years of type 2 diabetes were divided into two groups: (a) diabetic retinopathy (DR) and (b) diabetic nonretinopathy (DNR) subjects. In these groups the pentanucleotide microsatellite repeat located 2.5 kb upstream of the transcription start site of the iNOS gene was amplified by polymerase chain reaction and analyzed. Eleven alleles, 175-225 bp, were identified. Allele 210 bp was significantly associated with retinopathy (p = 0.044). Individuals carrying this allele had twice the risk of developing retinopathy compared with those who did not carry this allele [odds ratio (OR) - 2.03; 95% CI 0.96-4.35]. Alleles 200 and 220 bp were also significantly associated with no retinopathy and no serious retinopathy complications, respectively. In the Asian Indian population, allele 210 bp of the iNOS gene is a high-risk allele for developing retinopathy and alleles 200 and 220 bp protect an individual from developing retinopathy or its complications.

Effect of JP-8 jet fuel on molecular and histological parameters related to acute skin irritation

Organic chemicals such as jet fuels and solvents can cause skin irritation after dermal exposure. The molecular responses to these chemicals resulting in acute irritation are not understood well enough to establish safe exposure limits. Male F-344 rats were dermally exposed to JP-8 jet fuel for 1 h using Hill Top Chambers. Whole skin samples were collected at 0, 1, 2, 4, and 6 h after the beginning of the exposures, homogenized, and analyzed for interleukin (IL)-1alpha and inducible nitric oxide synthase (iNOS) protein and nitrite levels. IL-1alpha levels (determined by ELISA) ranged from approximately 11 to 34% above the 0-h samples over the observed time period. At 1 and 2 h, significantly higher (p < 0.05) levels of IL-1alpha were detected when compared to the 0-h samples. Western blot analysis revealed significantly higher (p < 0.05) levels of iNOS at 4 and 6 h compared to 0-h samples. Increases in IL-1alpha and iNOS expression were also observed in the skin immunohistochemically. Nitrite concentrations in skin samples were measured to estimate nitric oxide production. Although nitrite concentrations in the skin increased approximately 6-27% above the 0-h samples over the observed time period, no significant changes in nitrite levels were detected. Pathological changes in the skin following JP-8 exposure were evaluated histologically. Increased numbers of granulocytes were observed infiltrating the skin at 2 h and were more prominent by 6 h. These data show that a 1-h exposure to JP-8 results in a local inflammatory response, which can be detected by changes in molecular and histological parameters.