Role of nitric oxide in gastrointestinal and hepatic function and disease

Reaction of a Co(III)-peroxo complex with nitric oxide: putative formation of a peroxynitrite intermediate

A Co(II) complex, [CoII(L)2(H2O)2](ClO4)2, 1, having a bidentate ligand L [L = bis(3,5-dimethylpyrazolyl)methane] has been synthesized. Complex 1 in acetonitrile solution at -40 °C, in the presence of H2O2 and NEt3, afforded the corresponding Co(III)-peroxo species, [CoIII(L)2(O22-)]+, as the transient intermediate 1a. Thermal instability precluded its isolation and further characterization. The addition of nitric oxide (NO) gas into the freshly prepared [CoIII(L)2(O22-)]+ in acetonitrile at -40 °C resulted in the corresponding Co(II)-nitrato complex, [CoII(L)2(NO3)](ClO4) (2). The reaction is proposed to proceed through a putative Co(II)-peroxynitrite intermediate 1b. It was evidenced by the characteristic phenol ring nitration reaction.

The role of human milk nutrients in preventing necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an intestinal disease that primarily impacts preterm infants. The pathophysiology of NEC involves a complex interplay of factors that result in a deleterious immune response, injury to the intestinal mucosa, and in its most severe form, irreversible intestinal necrosis. Treatments for NEC remain limited, but one of the most effective preventative strategies for NEC is the provision of breast milk feeds. In this review, we discuss mechanisms by which bioactive nutrients in breast milk impact neonatal intestinal physiology and the development of NEC. We also review experimental models of NEC that have been used to study the role of breast milk components in disease pathophysiology. These models are necessary to accelerate mechanistic research and improve outcomes for neonates with NEC.

Seasonal flexibility of the gut structure and physiology in Eremias multiocellata

Although gut seasonal plasticity has been extensively reported, studies on physiological flexibility, such as water-salt transportation and motility in reptiles, are limited. Therefore, this study investigated the intestinal histology and gene expression involved in water-salt transport (AQP1, AQP3, NCC, and NKCC2) and motility regulation (nNOS, CHRM2, and ADRB2) in desert-dwelling Eremias multiocellata during winter (hibernating period) and summer (active period). The results showed that mucosal thickness, the villus width and height, the enterocyte height of the small intestine, and the mucosal and submucosal thicknesses of the large intestine were greater in winter than in summer. However, submucosal thickness of the small intestine and muscularis thickness of the large intestine were lower in winter than in summer. Furthermore, AQP1, AQP3, NCC, nNOS, CHRM2, and ADRB2 expressions in the small intestine were higher in winter than in summer; AQP1, AQP3, and nNOS expressions in the large intestine were lower in winter than in summer, with the upregulation of NCC and CHRM2 expressions; no significant seasonal differences were found in intestinal NKCC2 expression. These results suggest that (i) intestinal water-salt transport activity is flexible during seasonal changes where AQP1, AQP3 and NCC play a vital role, (ii) the intestinal motilities are attenuated through the concerted regulation of nNOS, CHRM2, and ADRB2, and (iii) the physiological flexibility of the small and large intestine may be discrepant due to their functional differences. This study reveals the intestinal regulation and adaptation mechanisms in E. multiocellata in response to the hibernation season.

GLP-2 Regulation of Dietary Fat Absorption and Intestinal Chylomicron Production via Neuronal Nitric Oxide Synthase (nNOS) Signaling

Postprandial dyslipidemia is a metabolic condition commonly associated with insulin-resistant states, such as obesity and type 2 diabetes. It is characterized by the overproduction of intestinal chylomicron particles and excess atherogenic chylomicron remnants in circulation. We have previously shown that glucagon-like peptide 2 (GLP-2) augments dietary fat uptake and chylomicron production in insulin-resistant states; however, the underlying mechanisms remain unclear. Previous studies have implicated nitric oxide (NO) in the absorptive actions of GLP-2. In this study, we report a novel role for neuronal NO synthase (nNOS)-mediated NO generation in lipid uptake and chylomicron formation based on studies in C57BL/6J mice, nNOS-/- mice, and Syrian golden hamsters after intraduodenal and oral fat administration. GLP-2 treatment in wild-type (WT) mice significantly increased postprandial lipid accumulation and circulating apolipoprotein B48 protein levels, while these effects were abolished in nNOS-/- mice. nNOS inhibition in Syrian golden hamsters and protein kinase G (PKG) inhibition in WT mice also abrogated the effect of GLP-2 on postprandial lipid accumulation. These studies demonstrate a novel mechanism in which nNOS-generated NO is crucial for GLP-2-mediated lipid absorption and chylomicron production in both mouse and hamster models. Overall, our data implicate an nNOS-PKG-mediated pathway in GLP-2-mediated stimulation of dietary fat absorption and intestinal chylomicron production.

NO, CO and H2S: A Trinacrium of Bioactive Gases in the Brain

Oxygen and carbon dioxide are time honored gases that have direct bearing on almost all life forms, but over the past thirty years, and in large part due to the Nobel Prize Award in Medicine for the elucidation of nitric oxide (NO) as a bioactive gas, the research and medical communities now recognize other gases as critical for survival. In addition to NO, hydrogen sulfide (H₂S) and carbon monoxide (CO) have emerged as a triumvirate or Trinacrium of gases with analogous importance and that serve important homeostatic functions. Perhaps, one of the most intriguing aspects of these gases is the functional interaction between them, which is intimately linked by the enzyme systems that produce them. Despite the need to better understand NO, H₂S and CO biology, the notion that these are environmental pollutants remains ever present. For this reason, incorporating the concept of hormesis becomes imperative and must be included in discussions when considering developing new therapeutics that involve these gases. While there is now an enormous literature base for each of these gasotransmitters, we provide here an overview of their respective physiologic roles in the brain.

Nitric Oxide: From Gastric Motility to Gastric Dysmotility

It is known that nitric oxide (NO) plays a key physiological role in the control of gastrointestinal (GI) motor phenomena. In this respect, NO is considered as the main non-adrenergic, non-cholinergic (NANC) inhibitory neurotransmitter responsible for smooth muscle relaxation. Moreover, many substances (including hormones) have been reported to modulate NO production leading to changes in motor responses, further underlying the importance of this molecule in the control of GI motility. An impaired NO production/release has indeed been reported to be implicated in some GI dysmotility. In this article we wanted to focus on the influence of NO on gastric motility by summarizing knowledge regarding its role in both physiological and pathological conditions. The main role of NO on regulating gastric smooth muscle motor responses, with particular reference to NO synthases expression and signaling pathways, is discussed. A deeper knowledge of nitrergic mechanisms is important for a better understanding of their involvement in gastric pathophysiological conditions of hypo- or hyper-motility states and for future therapeutic approaches. A possible role of substances which, by interfering with NO production, could prove useful in managing such motor disorders has been advanced.

Differentiated PDGFRα-Positive Cells: A Novel In-Vitro Model for Functional Studies of Neuronal Nitric Oxide Synthase

It is evident that depletion of interstitial cells and dysfunction of nitric oxide (NO) pathways are key players in development of several gastrointestinal (GI) motility disorders such as diabetic gastroparesis (DGP). One of the main limitations of DGP research is the lack of isolation methods that are specific to interstitial cells, and therefore conducting functional studies is not feasible. The present study aims (i) to differentiate telomerase transformed mesenchymal stromal cells (iMSCs) into platelet-derived growth factor receptor-α-positive cells (PDGFRα-positive cells) using connective tissue growth factor (CTGF) and L-ascorbic acids; (ii) to investigate the effects of NO donor and inhibitor on the survival rate of differentiated PDGFRα-positive cells; and (iii) to evaluate the impact of increased glucose concentrations, mimicking diabetic hyperglycemia, on the gene expression of neuronal nitric oxide synthase (nNOS). A fibroblastic differentiation-induction medium supplemented with connective tissue growth factor was used to differentiate iMSCs into PDGFRα-positive cells. The medium was changed every day for 21 days to maintain the biological activity of the growth factors. Gene and protein expression, scanning electron and confocal microscopy, and flow cytometry analysis of several markers were conducted to confirm the differentiation process. Methyl tetrazolium cell viability, nitrite measurement assays, and immunostaining were used to investigate the effects of NO on PDGFRα-positive cells. The present study, for the first time, demonstrated the differentiation of iMSCs into PDGFRα-positive cells. The outcomes of the functional studies showed that SNAP (NO donor) increased the survival rate of differentiated PDGFRα-positive cells whereas LNNA (NO inhibitor) attenuated these effects. Further experimentations revealed that hyperglycemia produced a significant increase in expression of nNOS in PDGFRα-positive cells. Differentiation of iMSCs into PDGFRα-positive cells is a novel model to conduct functional studies and to investigate the involvement of NO pathways. This will help in identifying new therapeutic targets for treatment of DGP.

Influence between NO and CO in guinea pig stomach fundus

The interaction between carbon monoxide and nitric oxide and their role in modulation of stomach fundus excitability was studied. The presence and colocalization of heme oxygenase 1 (HO-1) and nitric oxide synthase (NOS) was verified in myentheric ganglia by immunohistochemistry. The role of inducible heme oxygenase isoenzyme was investigated after in vivo treatment of animals with CoCl2 (80 mg kg-1 b.w.) injected subcutaneously 24 hours before euthanasia. This treatment resulted in positive staining for the inducible isoform in stomach smooth muscle.

The effect of probiotics on ıntestinal motility in an experimental short bowel model

PURPOSE

To investigate the effect of probiotics on spontaneous contractions of smooth muscle isolated from jejunum and ileum of rat model.

METHODS

Four rat groups were created (n=8, in each) including control (Group 1), control+probiotic (Group 2), short bowel (Group 3), and short bowel+probiotic (Group 4). Groups 1 and 2 underwent sham operation, Groups 3 and 4 underwent massive bowel resection. Bifidobacterium Lactis was administered in Groups 2 and 4 daily (P.O.) for three weeks. On postoperative week 3, rats were sacrificed, and jejunum and ileum smooth muscle were isolated for organ bath. Muscle contraction changes were analyzed before and after addition of antagonists.

RESULTS

Short bowel group exhibited increased amplitude and frequency of spontaneous contractions. The addition of probiotics significantly decreased enhanced amplitude and frequency of bowel contraction in short bowel group and returned to control values. L-NNA increased amplitude and frequency of contractions in all groups. While indomethacin and nimesulide increased the amplitude in all groups, the frequency was only increased in jejunum. Hexamethonium and tetrodotoxin did not change the contraction characteristics in all groups.

CONCLUSION

We suggest that early use of probiotics may significantly regulate bowel motility, and accordingly improve absorption of nutrients in short bowel syndrome.

Amino Acids in Intestinal Physiology and Health

Dietary protein digestion is an efficient process resulting in the absorption of amino acids by epithelial cells, mainly in the jejunum. Some amino acids are extensively metabolized in enterocytes supporting their high energy demand and/or production of bioactive metabolites such as glutathione or nitric oxide. In contrast, other amino acids are mainly used as building blocks for the intense protein synthesis associated with the rapid epithelium renewal and mucin production. Several amino acids have been shown to support the intestinal barrier function and the intestinal endocrine function. In addition, amino acids are metabolized by the gut microbiota that use them for their own protein synthesis and in catabolic pathways releasing in the intestinal lumen numerous metabolites such as ammonia, hydrogen sulfide, branched-chain amino acids, polyamines, phenolic and indolic compounds. Some of them (e.g. hydrogen sulfide) disrupts epithelial energy metabolism and may participate in mucosal inflammation when present in excess, while others (e.g. indole derivatives) prevent gut barrier dysfunction or regulate enteroendocrine functions. Lastly, some recent data suggest that dietary amino acids might regulate the composition of the gut microbiota, but the relevance for the intestinal health remains to be determined. In summary, amino acid utilization by epithelial cells or by intestinal bacteria appears to play a pivotal regulator role for intestinal homeostasis. Thus, adequate dietary supply of amino acids represents a key determinant of gut health and functions.

Efficacy of SPM-NONOate following intrapulmonary delivery in promoting absorptions of poorly absorbed macromolecules in rats and the underling mechanism

This research aims to investigate the potential of N-[4-[1-(3-Aminopropyl)-2-hydroxy-2-nitrosohydrazino]butyl]-1,3-propanediamine (SPM-NONOate) for promoting the absorption of poorly absorbed macromolecules delivered by intrapulmonary route. Influence of SPM-NONOate on the drug absorption was characterized by using a series of fluorescein isothiocyanate-labeled dextrans (FDs) as affordable models of hydrophilic macromolecules with established tools for quantitative analysis. SPM-NONOate increased concentration-dependently within 1-10 mM the pulmonary absorptions of FDs in rats. Moreover, this promoting effect varied with the molecular weight of FDs, and the largest absorption enhancement effect was obtained for FD70. SPM-NONOate also showed promising enhancement potential on the absorption of some therapeutic peptides, where obvious hypoglycemic and hypocalcemic effects were observed after intrapulmonary delivery of insulin and calcitionin, respectively, with SPM-NONOate to rats. The safety of SPM-NONOate was confirmed based on measurement of some biological markers in bronchoalveolar lavage fluid (BALF) of rats. Additionally, mechanism underling the absorption enhancement action of SPM-NONOate was explored by combinatorial administration of FD4 and SPM-NONOate with various scavengers and generator to rat lungs. Results indicated that NO released from SPM-NONOate induced the enhancement in the drug absorption, and peroxynitrate, a NO metabolite, possibly participated in the absorption enhancing action of SPM-NONOate.

Maturation of Intestinal Oxygenation: A Review of Mechanisms and Clinical Implications for Preterm Neonates

Nutrient requirements of preterm neonates may be substantial, to support growth and maturation processes in the presence of challenging post-natal circumstances. This may be accompanied by substantial intestinal oxygen requirements. Preterm neonates may not be able to meet these oxygen requirements, due to a developmental delay in intestinal oxygenation regulation mechanisms. This review summarizes the available literature on post-natal maturation of intestinal oxygenation mechanisms and translates these changes into clinical observations and potential implications for preterm neonates. The different mechanisms that may be involved in regulation of intestinal oxygenation, regardless of post-natal age, are first discussed. The contribution of these mechanisms to intestinal oxygenation regulation is then evaluated in newborn and mature intestine. Finally, the course of clinical observations is used to translate these findings to potential implications for preterm neonates.

Intestinal gases: influence on gut disorders and the role of dietary manipulations

The inner workings of the intestines, in which the body and microbiome intersect to influence gut function and systemic health, remain elusive. Carbon dioxide, hydrogen, methane and hydrogen sulfide, as well as a variety of trace gases, are generated by the chemical interactions and microbiota within the gut. Profiling of these intestinal gases and their responses to dietary changes can reveal the products and functions of the gut microbiota and their influence on human health. Indeed, different tools for measuring these intestinal gases have been developed, including newly developed gas-sensing capsule technology. Gases can, according to their type, concentration and volume, induce or relieve abdominal symptoms, and might also have physiological, pathogenic and therapeutic effects. Thus, profiling and modulating intestinal gases could be powerful tools for disease prevention and/or therapy. As the interactions between the microbiota, chemical constituents and fermentative substrates of the gut are principally influenced by dietary intake, altering the diet, which, in turn, changes gas profiles, is the main therapeutic approach for gastrointestinal disorders. An improved understanding of the complex interactions within the intestines that generate gases will enhance our ability to prevent, diagnose, treat and monitor many gastrointestinal disorders.

Acute-on-chronic liver disease enhances phenylephrine-induced endothelial nitric oxide release in rat mesenteric resistance arteries through enhanced PKA, PI3K/AKT and cGMP signalling pathways

Acute-on-chronic liver disease is a clinical syndrome characterized by decompensated liver fibrosis, portal hypertension and splanchnic hyperdynamic circulation. We aimed to determine whether the alpha-1 agonist phenylephrine (Phe) facilitates endothelial nitric oxide (NO) release by mesenteric resistance arteries (MRA) in rats subjected to an experimental microsurgical obstructive liver cholestasis model (LC). Sham-operated (SO) and LC rats were maintained for eight postoperative weeks. Phe-induced vasoconstriction (in the presence/absence of the NO synthase –NOS- inhibitor L-NAME) and vasodilator response to NO donor DEA-NO were analysed. Phe-induced NO release was determined in the presence/absence of either H89 (protein kinase –PK- A inhibitor) or LY 294002 (PI3K inhibitor). PKA and PKG activities, alpha-1 adrenoceptor, endothelial NOS (eNOS), PI3K, AKT and soluble guanylate cyclase (sGC) subunit expressions, as well as eNOS and AKT phosphorylation, were determined. The results show that LC blunted Phe-induced vasoconstriction, and enhanced DEA-NO-induced vasodilation. L-NAME increased the Phe-induced contraction largely in LC animals. The Phe-induced NO release was greater in MRA from LC animals. Both H89 and LY 294002 reduced NO release in LC. Alpha-1 adrenoceptor, eNOS, PI3K and AKT expressions were unchanged, but sGC subunit expression, eNOS and AKT phosphorylation and the activities of PKA and PKG were higher in MRA from LC animals. In summary, these mechanisms may help maintaining splanchnic vasodilation and hypotension observed in decompensated LC.

Control and dysregulation of redox signalling in the gastrointestinal tract

Redox signalling in the gastrointestinal mucosa is held in an intricate balance. Potent microbicidal mechanisms can be used by infiltrating immune cells, such as neutrophils, to protect compromised mucosae from microbial infection through the generation of reactive oxygen species. Unchecked, collateral damage to the surrounding tissue from neutrophil-derived reactive oxygen species can be detrimental; thus, maintenance and restitution of a breached intestinal mucosal barrier are paramount to host survival. Redox reactions and redox signalling have been studied for decades with a primary focus on contributions to disease processes. Within the past decade, an upsurge of exciting findings have implicated subtoxic levels of oxidative stress in processes such as maintenance of mucosal homeostasis, the control of protective inflammation and even regulation of tissue wound healing. Resident gut microbial communities have been shown to trigger redox signalling within the mucosa, which expresses similar but distinct enzymes to phagocytes. At the fulcrum of this delicate balance is the colonic mucosal epithelium, and emerging evidence suggests that precise control of redox signalling by these barrier-forming cells may dictate the outcome of an inflammatory event. This Review will address both the spectrum and intensity of redox activity pertaining to host-immune and host-microbiota crosstalk during homeostasis and disease processes in the gastrointestinal tract.

Pathophysiological Mechanisms of Gastrointestinal Toxicity

Humans swallow a great variety and often large amounts of chemicals as nutrients, incidental food additives and contaminants, drugs, and inhaled particles and chemicals, thus exposing the gastrointestinal tract to many potentially toxic substances. It serves as a barrier in many cases to protect other components of the body from such substances and infections. Fortunately, the gastrointestinal tract is remarkably robust and generally is able to withstand multiple daily assaults by the chemicals to which it is exposed. Some chemicals, however, can affect one or more aspects of the gastrointestinal tract to produce abnormal events that reflect toxicity. It is the purpose of this chapter to evaluate the mechanisms by which toxic chemicals produce their deleterious effects and to determine the consequences of the toxicity on integrity of gastrointestinal structure and function. Probably because of the intrinsic ability of the gastrointestinal tract to resist toxic chemicals, there is a paucity of data regarding gastrointestinal toxicology. It is therefore necessary in many cases to extrapolate toxic mechanisms from infectious processes, inflammatory conditions, ischemia, and other insults in addition to more conventional chemical sources of toxicity.

H2 S-induced gastric fundus smooth muscle tension potentiation is mediated by the phosphoinositide 3-kinase/Akt/endothelial nitric oxide synthase pathway

NEW FINDINGS

What is the central question of this study? The present study investigated the relationship between H₂ S and NO in regulation of gastric fundus tension. What is the main finding and its importance? Endogenous or exogenous H₂ S and NO have opposite effects on fundus tension, and H₂ S-induced gastric fundus tension enhancements are mediated by inhibition of NO generation through the phosphoinositide 3-kinase/Akt pathway. These results are very important in exploring the mechanism of physiological accommodation and accommodation disorder. Hydrogen sulphide (H₂ S) is considered a new gasotransmitter, along with NO and CO. It was recently confirmed that H₂ S and NO play important roles in the regulation of gastrointestinal smooth muscle tension. The present study was designed to elucidate the interactions between H₂ S and NO with respect to the regulation of gastric fundus smooth muscle tension using Western blotting, physiological and electrochemical techniques. Real-time H₂ S and NO generation was detected in gastric smooth muscle tissue. NaHS, an H₂ S donor, enhanced fundus smooth muscle tension, whereas SNP, an NO donor, decreased fundus smooth muscle tension in a dose-dependent manner. NaHS-induced increases in fundus smooth muscle tension were suppressed by l-NAME, an NO synthase inhibitor. Aminooxyacetic acid (AOAA), a cystathionine β-synthase inhibitor, exerted inhibitory effects on fundus smooth muscle tension; these effects were also suppressed by l-NAME. Real-time NO generation was significantly potentiated by AOAA. Endothelial nitric oxide synthase (eNOS) phosphorylation at serine 1177 and Akt phosphorylation at serine 308 and threonine 473 were significantly inhibited by NaHS. LY294002, a phosphoinositide 3-kinase inhibitor, blocked these NaHS-mediated effects. However, eNOS phosphorylation at serine 1177 and Akt phosphorylation at serine 308 and threonine 473 were significantly potentiated by AOAA. Cystathionine β-synthase siRNA interference significantly increased eNOS phosphorylation at serine 1177 and Akt phosphorylation at serine 308 and threonine 473. Cystathionine β-synthase siRNA interference also increased total eNOS protein expression levels but did not significantly change total Akt kinase protein expression levels. These results suggest that H₂ S-induced enhancement of gastric fundus tension is mediated by inhibition of NO generation through the phosphoinositide 3-kinase/Akt pathway.

Arginine supplementation for prevention of necrotising enterocolitis in preterm infants

BACKGROUND

Decreased concentration of nitric oxide has been proposed as one of the possible cellular mechanisms of necrotising enterocolitis (NEC). Arginine can act as a substrate for production of nitric oxide in the tissues, and arginine supplementation may help to prevent NEC.

OBJECTIVES

To examine the effect of arginine supplementation (administered by any route) on the incidence of NEC in preterm neonates. To conduct subgroup analyses based on the dose of arginine and the gestational age of participants (≤ 32 weeks, > 32 weeks).

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 4), MEDLINE via PubMed (from 1966 to 12 May 2016), Embase (from 1980 to 12 May 2016) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; from 1982 to 12 May 2016). We also searched clinical trials databases, conference proceedings and reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials of arginine supplementation (administered orally or parenterally for at least seven days, in addition to what an infant may be receiving from an enteral or parenteral source) compared with placebo or no treatment.

DATA COLLECTION AND ANALYSIS

We assessed the methodological quality of trials by using information obtained from study reports and through personal communication with study authors. We extracted data on relevant outcomes and estimated and reported the effect size as risk ratio (RR), risk difference (RD) and mean difference (MD), as appropriate. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to assess the quality of evidence.

MAIN RESULTS

We identified three eligible studies that included a total of 285 neonates (140 received arginine) from three countries. We assessed the overall methodological quality of the included studies as good. We noted a statistically significant reduction in risk of development of NEC (any stage) among preterm neonates in the arginine group compared with the placebo group (RR 0.38, 95% confidence interval (CI) 0.23 to 0.64; I2 = 27%) (RD -0.19, 95% CI -0.28 to -0.10; I2 = 0%) and rated the quality of evidence as moderate. The number needed to treat for an additional beneficial outcome (NNTB) as required to prevent the development of NEC (any stage) was 6 (95% CI 4 to 10). Study results showed a statistically significant reduction in risk of development of NEC stage 1 (RR 0.37, 95% CI 0.15 to 0.90; I2 = 52%) (RD -0.07, 95% CI -0.14 to -0.01; I2 = 0%) and NEC stage 3 (RR 0.13, 95% CI 0.02 to 1.03; I2 = 0%) (RD -0.05, 95% CI -0.09 to -0.01; I2 = 89%) in the arginine group compared with the control group; the quality of evidence was moderate.Arginine supplementation was associated with a significant reduction in death related to NEC (RR 0.18, 95% CI 0.03 to 1.00; I2 = 0%) (RD -0.05, 95% CI -0.09 to -0.01; I2 = 87%). Results showed clinical heterogeneity in mortality rates. Mortality due to any cause was not significantly different between arginine and control or no treatment groups (RR 0.77, 95% CI 0.41 to 1.45; I2 = 42%) (RD -0.03, 95% CI -0.10 to 0.04; I2 = 79%). Investigators noted no significant side effects directly attributable to arginine, including hypotension or alterations in glucose homeostasis. Follow-up data from one trial revealed no statistically significant differences in adverse outcomes (cerebral palsy, cognitive delay, bilateral blindness or hearing loss requiring hearing aids) at 36 months. Limitations of the present findings include a relatively small overall sample size.

AUTHORS' CONCLUSIONS

Administration of arginine to preterm infants may prevent development of NEC. Because information was provided by three small trials that included 285 participants, the data are insufficient at present to support a practice recommendation. A multi-centre randomised controlled study that is focused on the incidence of NEC, particularly at more severe stages (2 and 3), is needed.

Immunostimulated Arginase II Expression in Intestinal Epithelial Cells Reduces Nitric Oxide Production and Apoptosis

Increased production of nitric oxide (NO) and subsequent local cytotoxicity to mucosal epithelial cells has been proposed as a putative mechanism involved in the development of necrotizing enterocolitis (NEC). Intestinal epithelial cells (IECs) metabolize L-arginine to either nitric oxide (NO) by NO synthase (NOS) or to L-ornithine and urea by arginase. L-ornithine is the first step in polyamine synthesis important for cell proliferation, while NO production can lead to apoptosis. We hypothesized that in IECs immunostimulation increases both NOS and arginase expression, and that arginase activity mitigates NO production and apoptosis. Rat intestinal epithelial cells (rIEC-6) were immunostimulated by either incubation with lipopolysaccharide (LPS) alone for 24 h or by incubation with conditioned media (CM) for 24 h. CM was obtained from RAW 264.7 cells (a macrophage cell line) treated with LPS (E. coli 0127:B8; 1 μg/ml) for 4 h. The rIEC-6 stimulated with LPS or with CM had significantly higher levels of inducible NOS (iNOS) protein, NO production, and arginase II protein than did the control cells. Direct LPS stimulation of rIEC-6 produced a less robust increase in iNOS expression and NO (represented as nitrite percent of control) than did CM stimulation. Inhibition of arginase using N^ω hydroxyl-L-arginine (NOHA) further increased stimulated NO production in rIEC-6. Viable cell numbers were significantly lower in CM stimulated cells after 24 h than in controls, and inhibition of arginase activity with NOHA resulted in a further significant decrease in viable cell numbers. We conclude that immunostimulated arginase expression of rIEC-6 cells tempers cytokine-induced iNOS-derived NO production and apoptosis.

Effects of nitric oxide modulating activities on development of enteric nervous system mediated gut motility in chick embryo model

The enteric nervous system (ENS) arises from the enteric neural crest-derived cells (ENCCs), and many molecules and biochemical processes may be involved in its development. This study examined the effects of modulating embryonic nitric oxide (NO) activity on the intestinal motility induced by ENS. One-hundred-and-twenty fertilized chicken eggs were assigned to three main groups and incubated at 37 degrees Centigrade and 60 percent humidity. The eggs were treated with NG-nitro-Larginine methyl ester (L-NAME), sodium nitroprusside (SNP), L-arginine (L-Arg) or vehicle from days 3 (1st group), 7 (2nd group) and 10 (3rd group) of incubation and continued up to day 18. On day 19, the embryos were sacrificed, the jejunal and colorectal segments were taken and the intestinal motility was assessed using isolated organ system. The intestinal motility was recorded normally and following cholinergic, adrenergic and non-adrenergic non-cholinergic (NANC) stimulations. The ENS structure was assessed by immunohistochemistry (IHC) using glial fibrillary acidic protein (GFAP). Rhythmic intestinal contractions were seen in all treatment groups, but inhibition of NO in the LNAME- treated embryos caused significant decrease (p less than 0.01) in the frequency and amplitude of the contraction. The responsiveness to adrenergic, cholinergic and NANC stimulations was also significantly decreased (p less than 0.05). The GFAP expression was significantly (p less than 0.05) reduced in the L-NAME-treated embryos. This study showed that the inhibition of NO caused a deficient development of the ENS, leading to a decrease in the frequency and amplitude of the intestinal contractions and reduced the responsiveness to adrenergic, cholinergic and NANC signalling.

Dominant role of interstitial cells of Cajal in nitrergic relaxation of murine lower oesophageal sphincter

Oesophageal achalasia is a disease known to result from reduced relaxation of the lower oesophageal sphincter (LES). Nitric oxide (NO) is one of the main inhibitory transmitters. NO-sensitive guanylyl cyclase (NO-GC) acts as the key target of NO and, by the generation of cGMP, mediates nitrergic relaxation in the LES. To date, the exact mechanism of nitrergic LES relaxation is still insufficiently elucidated. To clarify the role of NO-GC in LES relaxation, we used cell-specific knockout (KO) mouse lines for NO-GC. These include mice lacking NO-GC in smooth muscle cells (SMC-GCKO), in interstitial cells of Cajal (ICC-GCKO) and in both SMC/ICC (SMC/ICC-GCKO). We applied oesophageal manometry to study the functionality of LES in vivo. Isometric force studies were performed to monitor LES responsiveness to exogenous NO and electric field stimulation of intrinsic nerves in vitro. Cell-specific expression/deletion of NO-GC was monitored by immunohistochemistry. Swallowing-induced LES relaxation is strongly reduced by deletion of NO-GC in ICC. Basal LES tone is affected by NO-GC deletion in either SMC or ICC. Lack of NO-GC in both cells leads to a complete interruption of NO-induced relaxation and, therefore, to an achalasia-like phenotype similar to that seen in global GCKO mice. Our data indicate that regulation of basal LES tone is based on a dual mechanism mediated by NO-GC in SMC and ICC whereas swallow-induced LES relaxation is mainly regulated by nitrergic mechanisms in ICC.

Orally supplemented L-arginine impairs amino acid absorption depending on dose in horses

The beneficial effect of L-arginine (L-Arg) supplementation, on the physiology of several species, has generated an interest in the use of L-Arg as a nutraceutical in horses, but dosage and absorption of orally supplemented L-Arg must be inferred from other species. The study objective was to determine the effect of 2 oral L-Arg doses on plasma arginine concentrations and the effect on absorption of other amino acids in mares. In Experiment 1, mares were blocked by age and breed and were fed L-Arg supplemented (supplemented with 0.025% BW L-Arg; n=6) or control (no supplement; n=6) concentrate on a single day with blood samples taken at 0, 0.5, 1, 2, 3, 4, and 5 h relative to feeding. In Experiment 2, mares (n=6) were used in a 3×3 Latin square design with L-Arg (0.0125% of BW), urea (0.0087% of BW), and control (no supplement) fed mixed into a grain concentrate as single meal with blood samples taken at 0, 1,2, 4, 6, 8,10, and 12 h relative to feeding. In Experiment 1, L-Arg supplementation increased (P<0.05) plasma L-Arg and ornthine concentrations and decreased (P<0.05) lysine and methionine concentrations compared with the control group. At 1 h post feeding, L-Arg mares had lower (P<0.05) plasma concentrations of histidine, glutamic acid, proline, isoleucine, threonine, phenylalanine, leucine, valine, alanine, and taurine. In Experiment 2, L-Arg supplementation increased (P<0.05) arginine and ornithine concentrations compared with urea and control; there was no difference among other amino acids. These experiments indicate that L-Argis absorbed and, dependent on the dose, alters the absorption of other amino acids in mares.

Arginine supplementation in prevention of necrotizing enterocolitis in the premature infant: an updated systematic review

BACKGROUND

Hypoxic-ischemic injury is thought to play a significant role in necrotizing enterocolitis (NEC). Nitric Oxide (NO) is the principal inhibitory neurotransmitter in the gut and is involved in regulation of mucosal blood flow and maintenance of mucosal integrity. NO is synthesized from L-arginine by NO synthases. Our primary objective was to determine the effectiveness of supplemental L-arginine versus placebo in prevention of NEC in preterm infants ≤ 34 weeks gestational age by systematic review of published randomized controlled trials (RCTs).

METHODS

This review included RCTs in which L-arginine was administered as a supplement to neonates to prevent NEC. Searches were conducted in OVID MEDLINE, EMBASE, PubMed, and CINAHL from their dates of inception to July, 2014. Inclusion criteria were informed parental consent, neonates born at ≤ 34 weeks gestation, and birth weight ≤ 1500 g. Exclusion criteria included neonates with severe congenital anomalies and inborn errors of metabolism. Incidence of NEC was the primary outcome measure. Whole data were analyzed by RevMan 5.1 (Update Software, Oxford, UK). Outcome data were analyzed to determine risk ratios, number needed to treat, confidence intervals, and test for overall effect.

RESULTS

Two trials including 425 neonates were eligible for this review. Of these, 235 neonates were included in the study. L-arginine had a 59% reduction in the incidence of stage II and III NEC (RR 0.41, 95% CI 0.20 to 0.85, NNT = 9) compared with placebo (P = 0.02). A similar finding was identified for all stages of NEC (60% reduction, RR 0.40, 95% CI 0.23 to 0.69, NNT = 5) (P = 0.001). At age 3 yrs, there was no significant difference between the 2 groups in terms of any neurodevelopmental disability (RR 0.65; 95% CI 0.23-1.83, P = 0.41).

CONCLUSIONS

L-arginine supplementation appears to be protective in prevention of NEC in preterm infants and without any significant impact on neurodevelopmental outcomes at 36 months of corrected age. With the addition of the results of one more study to the literature, an intriguing role for L-arginine supplementation continues to gain support. However, large multi-centre RCTs are needed before this can become common practice.

Carbon monoxide, hydrogen sulfide, and nitric oxide as signaling molecules in the gastrointestinal tract

Carbon monoxide (CO) and hydrogen sulfide (H2S) used to be thought of simply as lethal and (for H2S) smelly gaseous molecules; now they are known to have important signaling functions in the gastrointestinal tract. CO and H2S, which are produced in the gastrointestinal tract by different enzymes, regulate smooth muscle membrane potential and tone, transmit signals from enteric nerves, and can regulate the immune system. The pathways that produce nitric oxide, H2S, and CO interact; each can inhibit and potentiate the level and activity of the other. However, there are significant differences between these molecules, such as in half-lives; CO is more stable and therefore able to have effects distal to the site of production, whereas nitric oxide and H2S are short lived and act only close to sites of production. We review their signaling functions in the luminal gastrointestinal tract and discuss how their pathways interact. We also describe other physiological functions of CO and H2S and how they might be used as therapeutic agents.

Toward a better understanding of gastrointestinal nitrergic neuromuscular transmission

BACKGROUND

Nitric oxide (NO) is an important inhibitory neurotransmitter in the gastrointestinal (GI) tract. The majority of nitrergic effects are transduced by NO-sensitive guanylyl cyclase (NO-GC) as the receptor for NO, and, thus, mediated by cGMP-dependent mechanisms. Work carried out during the past years has demonstrated NO to be largely involved in GI smooth muscle relaxation and motility. However, detailed investigation of nitrergic signaling has turned out to be complicated as NO-GC was identified in several different GI cell types such as smooth muscle cells, interstitial cells of Cajal and fibroblast-like cells. With regards to nitrergic neurotransmission, special focus has been placed on the role of interstitial cells of Cajal using mutant mice with reduced populations of ICC. Recently, global and cell-specific knockout mice for enzymes participating in nitrergic signaling have been generated providing a suitable approach to further examine the role of NO-mediated signaling in GI smooth muscle.

PURPOSE

This review discusses the current knowledge on nitrergic mechanisms in gastrointestinal neuromuscular transmission with a focus on genetic models and outlines possible further investigations to gain better understanding on NO-mediated effects in the GI tract.

Effects of interleukin-10 gene deficiency on hepatic biochemical metabolism in mice

The aim of this study was to investigate the effect of interleukin-10 (IL-10) gene deficiency on mouse liver function. The experimental mice were divided into wild-type and IL-10 knockout groups. Serological biomarkers for liver functions were detected by the automatic biochemical analyzer AU5400. The pathological changes were assessed by the light microscope. The levels of inducible nitric oxide synthase (iNOS) and interleukin-1β (IL-1β) in liver tissues were determined by quantitative real-time PCR and enzyme-linked immunosorbent assay. Compared with the wild type, the serum levels of albumin (ALB), total protein, total bilirubin and direct bilirubin in IL-10-deficient mice were significantly decreased (P < 0.05). No obvious pathological changes including liver necrosis and inflammatory cell infiltration were found. The expression of iNOS and IL-1β genes, the serum levels of iNOS and IL-1β were significantly higher in IL-10-deficient mice than in wild-type mice (P < 0.05). The absence of IL-10 gene can significantly decrease serum ALB and bilirubin. The effect may be related to the upregulation of iNOS and IL-1β.

Manganese superoxide dismutase plays an important role in the inflammatory process and predicts disease severity and activity in patients with ulcerative colitis

The aim of this study was to investigate the expression pattern of manganese superoxide dismutase (MnSOD) in relation to inflammatory factors in ulcerative colitis (UC) and characterize this enzyme as a newly identified biomarker potentially linked to disease pathogenesis of UC. MnSOD expression was analyzed immunohistochemically in 48 formalin-fixed and paraffin-embedded specimens from patients with UC who had undergone endoscopical biopsy. MnSOD expression was observed in vascular endothelium, macrophages, and polymorphonuclear leukocytes within lamina propria of inflamed mucosa. The patients who did not express MnSOD tended to have stabilization of symptoms, but accompanied with status of inflammation. The MnSOD expression pattern was strongly correlated with disease type. MnSOD was expressed in polymorphonuclear leukocytes of all disease types, but cases of chronically counting and exacerbation type had particularly high frequency of immunopositive cells. MnSOD expression in macrophages was frequently observed in cases of symptom remaining type. The cases with MnSOD expression in the vascular endothelium showed a tendency to express in relapse-remission and exacerbation of symptoms. Immunohistochemical evaluation for MnSOD expression may be useful for predicting disease severity and activity in patients with UC.

Cell-specific deletion of nitric oxide-sensitive guanylyl cyclase reveals a dual pathway for nitrergic neuromuscular transmission in the murine fundus

BACKGROUND & AIMS

It is not clear how nitric oxide (NO) released from enteric neurons relaxes gastrointestinal (GI) smooth muscle. In analogy to the vascular system, NO might directly induce relaxation of smooth muscle cells (SMCs) by acting on its receptor, NO-sensitive guanylyl cyclase (NO-GC). Alternatively, intermediate cells, such as the interstitial cells of Cajal (ICCs), might detect nitrergic signals to indirectly regulate smooth muscle tone, and thereby regulate the motor function of the GI tract. We investigated the role of ICCs and SMCs in nitrergic relaxation using mice with cell-specific disruption of the gene encoding the β1 subunit of NO-GC (GUCY1B3).

METHODS

We created mice that lack NO-GC specifically in SMCs (SM-guanylyl cyclase knockout [GCKO]), ICCs (ICC-GCKO), or both (SM/ICC-GCKO). We investigated the effects of exogenous and endogenous NO on murine fundus using isometric force studies. Total gut transit time was measured to monitor the functional consequences of NO-GC deletion on GI motility in vivo.

RESULTS

NO-GC is expressed in ICC and SMC. Deletion of the NO receptor from SMCs incompletely reduced NO-induced fundus relaxation, which was hardly affected after ICC-specific deletion. Gut transit time did not change in SM-GCKO or ICC-GCKO mice compared with control mice. However, nitrergic relaxation was not observed in SM/ICC-GCKO mice, which had increased gut transit time compared with controls.

CONCLUSIONS

In mice, NO-GC is the only NO receptor to relax the fundus; deletion of NO-GC from the combination of SMCs and ICCs blocks nitrergic signaling. Therefore, ICCs and SMCs jointly mediate the relaxant effect of enteric NO.

Comparing beneficial effects of inhaled nitric oxide to L-arginine in necrotizing enterocolitis model in neonatal rats

OBJECTIVE

Necrotizing enterocolitis (NEC) is a common and devastating gastrointestinal condition of neonatal infants. The pathophysiology of NEC remains poorly understood. We tried to evaluate the effectiveness of inhaled NO compared to L-arginine usage in necrotizing enterocolitis model in rats.

MATERIAL-METHODS

46 newborn pups from 4 time-mated Sprague-Dawley pregnant rats were divided equally into 4 groups as follows: NEC (subjected to NEC), NEC + L-arginine, NEC + inhaled NO and control.

RESULTS

SOD, GSH-Px and NOx levels were significantly higher and MDA levels were significantly lower in NEC + inhaled NO group compared to NEC + L-arginine group. There was significantly lower intestinal injury and apoptosis index scoring in NEC + inhaled NO group compared to NEC + L-arginine group.

CONCLUSION

We think that inhaled NO can be used as a novel therapeutic agent like L-arginine in NEC, like using in pulmonary hypertention in newborns but much more studies are needed.

Endocannabinoids modulate non-adrenergic, non-cholinergic inhibitory neurotransmission in strips from the mouse gastric fundus

AIM

To investigate the effects of endocannabinoids on non-adrenergic, non-cholinergic (NANC) relaxant responses in gastric strips from mice.

METHODS

Gastric longitudinal strips from the fundus region were mounted in organ baths for isometric recording.

RESULTS

In carbachol-precontracted strips, electrical field stimulation (EFS) elicited tetrodotoxin (TTX)-sensitive fast nitrergic relaxant responses that were followed, at the highest stimulation frequency, by sustained relaxations. The latter were abolished by α-chymotrypsin. Anandamide caused a TTX-sensitive relaxation that was abolished by α-chymotrypsin but unaffected by the nitric oxide (NO) synthesis inhibitor, Nω-nitro-L-arginine (L-NNA). Anandamide reduced the amplitude of EFS-induced fast relaxations, whereas increased that of sustained ones. Relaxation to the nicotinic receptor agonist dimethylphenyl piperazinium iodide (DMPP) was decreased in amplitude by either anandamide or L-NNA, whereas, surprisingly, it was increased by α-chymotrypsin and abolished by L-NNA plus α-chymotrypsin. Relaxation to vasoactive intestinal polypeptide (VIP) was not influenced by anandamide or L-NNA and was abolished by α-chymotrypsin. Following VIP desensitization, fast relaxant responses to EFS were reduced and the sustained ones abolished. The CB1 receptor antagonist AM251 increased, only at the highest stimulation frequency, the amplitude of the EFS-induced fast relaxation and reduced the sustained one. AM251 increased the response to DMPP and abolished that to anandamide. The CB2 receptor antagonist AM630 had no effects.

CONCLUSION

These results indicate that endocannabinoids modulate, via prejunctional CB1 receptors, the NANC peptidergic neurotransmission that, in turn, affects the nitrergic one.

Nitric oxide-sensitive guanylyl cyclase is dispensable for nitrergic signaling and gut motility in mouse intestinal smooth muscle

BACKGROUND & AIMS

The nitric oxide-guanosine 3',5'-cyclic monophosphate (cGMP) signaling pathway has an important role in the control of smooth muscle tone. NO is produced by NO synthases and acts as a major inhibitory neurotransmitter in the gastrointestinal (GI) tract. The main target, NO-sensitive guanylyl cyclase (NO-GC), is stimulated by NO to produce the intracellular messenger cGMP. We investigated the role of NO-GC in nitrergic relaxation and GI motility.

METHODS

We tested relaxation of GI smooth muscle in mice that do not express NO-GC or mice with disruption of NO-GC specifically in smooth muscle cells. Different segments of the GI tract (fundus, lower esophageal sphincter, pyloric sphincter, and duodenum) were used in isometric force studies. NO donors and electrical field stimulation were used to assess nitrergic signaling. Whole-gut transit time was measured as an indicator of GI motility.

RESULTS

Mice that lack NO-GC do not have NO-induced relaxation of GI smooth muscle. Gut transit time was increased, resulting in GI dysfunction. Surprisingly, in mice that lack NO-GC specifically in smooth muscle, NO-induced relaxation was reduced only slightly, and whole-gut transit time was unchanged compared with wild-type mice.

CONCLUSIONS

Lack of NO-GC in smooth muscle cells does not impair NO-induced relaxation of GI tissues or GI motility. The NO receptor guanylyl cyclase in GI smooth muscle is therefore dispensable for nitrergic signaling in mice.

Nitric oxide activation of a potassium channel (BKCa) in feline lower esophageal sphincter

AIM: To assess the effect of nitric oxide (NO) on the large conductance potassium channel (BK_Ca) in isolated circular (CM) and sling (SM) muscle cells and muscle strips from the cat lower esophageal sphincter (LES) to determine its regulation of resting tone and relaxation.

METHODS: Freshly enzymatically-digested and isolated circular smooth muscle cells were prepared from each LES region. To study outward K⁺ currents, the perforated patch clamp technique was employed. To assess LES resting tone and relaxation, muscle strips were mounted in perfused organ baths.

RESULTS: (1) Electrophysiological recordings from isolated cells: (a) CM was more depolarized than SM (-39.7 ± 0.8mV vs -48.1 ± 1.6 mV, P < 0.001), and maximal outward current was similar (27.1 ± 1.5 pA/pF vs 25.7 ± 2.0 pA/pF, P > 0.05); (b) The NO donor sodium nitroprusside (SNP) increased outward currents only in CM (25.9 ± 1.9 to 46.7 ± 4.2 pA/pF, P < 0.001) but not SM (23.2 ± 3.1 to 27.0 ± 3.4 pA/pF, P > 0.05); (c) SNP added in the presence of the BK_Ca antagonist iberiotoxin (IbTX) produced no increase in the outward current in CM (17.0 ± 2.8 vs 13.7 ± 2.2, P > 0.05); and (d) L-NNA caused a small insignificant inhibition of outward K⁺ currents in both muscles; and (2) Muscle strip studies: (a) Blockade of the nerves with tetrodotoxin (TTX), or BK_Ca with IbTX had no significant effect on resting tone of either muscle; and (b) SNP reduced tone in both muscles, and was unaffected by the presence of TTX or IbTX.

CONCLUSION: Exogenous NO activates BK_Ca only in CM of the cat. However, as opposed to other species, exogenous NO-induced relaxation is predominantly by a non-BK_Ca mechanism, and endogenous NO has minimal effect on resting tone.

Investigation of relaxant effects of new agents affecting nitric oxide/cyclic guanosine monophosphate pathway on sheep oddi sphincter

OBJECTIVES

Nitric oxide (NO) is a potent nonadrenergic, noncholinergic mediator of gastrointestinal smooth muscle. We aimed to investigate the effects of new NO/cyclic guanosine monophosphate (cGMP) pathway-affecting agents at the sheep sphincter of Oddi (SO) in vitro.

METHODS

Sheep SO rings were mounted in organ baths and tested for isometric tension and cGMP levels in response to 3,3-bis(aminoethyl)-1-hydroxy-2-oxo-1-triazene; 3-morpholinosydnonimine hydrochloride (SIN-1); and BAY 41-2272 in the presence and absence of 1H-(1,2,4)oxadiazole(4,3-a)quinoxalin-1-one (ODQ).

RESULTS

3,3-bis(Aminoethyl)-1-hydroxy-2-oxo-1-triazene; SIN-1; and BAY 41-2272 relaxed SO rings in a concentration-dependent manner. These relaxations were significantly decreased in the presence of ODQ (P < 0.05). All agents significantly increased the cGMP levels compared with the control group (P < 0.05). The increased cGMP levels in the 3,3-bis(aminoethyl)-1-hydroxy-2-oxo-1-triazene- and BAY 41-2272-treated groups were significantly different from both control and carbachol groups (P < 0.05), whereas the increase in the SIN-1 group was significantly different from all groups (P < 0.05). The cGMP levels were significantly lower in the presence of ODQ compared with its absence (P < 0.05).

CONCLUSIONS

The relaxation of SO rings by these agents may be via increasing the levels of cGMP. The additional increase produced by SIN-1 may be the combined effects of NO generation and activation of guanylyl cyclase.

Ghrelin improves LPS-induced gastrointestinal motility disturbances: roles of NO and prostaglandin E2

Ghrelin, an important orexigenic peptide, exerts gastroprokinetic and anti-inflammatory effects. We investigated the role of ghrelin in LPS-induced gastrointestinal (GI) motility disturbances through NO and prostaglandin E2 pathways in mice. Ghrelin-containing cells and its receptor, growth hormone secretagogue receptor 1 (GHSR-1), were localized in the stomach and duodenum using an immunohistochemical method. The distribution of ghrelin-containing cells or GHSR-1 immunoreactivity in both the mucosal and the muscle layers was heterogeneous within both tissues. The i.p. administration of ghrelin (1-20 microg/kg) had no effect on gastric emptying but markedly increased the GI transit (GIT) in normal mice. LPS (20 mg/kg i.p.)-treated mice showed significant decreases in the gastric emptying and GIT. Ghrelin attenuated the LPS-induced delay in gastric emptying and GIT. We also performed immunohistochemical experiments on both tissues. Immunohistochemistry showed the presence of iNOS and cyclooxygenase 2 in both tissues of LPS-treated mice. Treatment of LPS-exposed mice with ghrelin (20 microg/kg) diminished the presence of iNOS but not cyclooxygenase 2 in both tissues. The effect of ghrelin on regulating LPS-induced GI motility disturbance was further found to be associated with a reduction in iNOS expression in the GI tract and plasma NO overproduction rather than regulation of neural or endothelial NO synthase expression in the GI tissue. In addition, ghrelin was found to elevate prostaglandin E2 levels in the GI tissue but showed no significant change in LPS-treated mice. These findings indicate that the action of ghrelin binding to GHSR-1 improves endotoxemia-induced GI motility disturbances mainly through down-regulating the NO pathway in the GI tract.

Neurodevelopmental outcomes of premature infants treated with l-arginine for prevention of necrotising enterocolitis

AIM

This study aimed to compare the long-term neurodevelopmental outcomes at 36 months adjusted age in preterm infants (birth weight < or = 1250 gm) who received supplementation with L-arginine during the first 28 days of life with controls.

METHODS

Surviving infants enrolled in a randomised control study of L-arginine supplementation were prospectively followed longitudinally to determine their neurodevelopmental outcomes at 36 months of adjusted age. Neurologic examination and neurodevelopmental assessments were performed by examiners who were unaware of the original treatment assignments.

RESULTS

A total of 132 children (95% of survivors) were evaluated at 36 months adjusted age. In the group given L-arginine, 5 of 61 (8.1%) had major neurodevelopmental disabilities, defined as the presence of one or more of cerebral palsy, cognitive delay (cognitive index <70), bilateral blindness or bilateral hearing loss requiring hearing aids as compared with 9 of 71 (12.6%) in the placebo group (relative risk, 0.64; 95 % confidence interval, 0.22-1.82; P= 0.40).

CONCLUSIONS

There is no increase in neurodevelopmental disability in preterm infants who received L-arginine supplementation.

Induced nitric oxide synthase as a major player in the oncogenic transformation of inflamed tissue

Nitric oxide (NO) is a free radical that is involved in the inflammatory process and carcinogenesis. There are four nitric oxide synthase enzymes involved in NO production: induced nitric oxide synthase (iNOS), endothelial NO synthase (eNOS), neural NO synthase (nNOS), and mitochondrial NOS. iNOS is an inducible and key enzyme in the inflamed tissue. Recent literatures indicate that NO as well as iNOS and eNOS can modulate cancer-related events including nitro-oxidative stress, apoptosis, cell cycle, angio-genesis, invasion, and metastasis. This chapter focuses on linking NO/iNOS/eNOS to inflammation and carcinogenesis from experimental evidence to potential targets on cancer prevention and treatment.

Heme oxygenase-1 protects interstitial cells of Cajal from oxidative stress and reverses diabetic gastroparesis

BACKGROUND & AIMS

Diabetic gastroparesis (delayed gastric emptying) is a well-recognized complication of diabetes that causes considerable morbidity and makes glucose control difficult. Interstitial cells of Cajal, which express the receptor tyrosine kinase Kit, are required for normal gastric emptying. We proposed that Kit expression is lost during diabetic gastroparesis due to increased levels of oxidative stress caused by low levels of heme oxygenase-1 (HO-1), an important cytoprotective molecule against oxidative injury.

METHODS

Gastric emptying was measured in nonobese diabetic mice and correlated with levels of HO-1 expression and activity. Endogenous HO-1 activity was increased by administration of hemin and inhibited by chromium mesoporphyrin.

RESULTS

In early stages of diabetes, HO-1 was up-regulated in gastric macrophages and remained up-regulated in all mice that were resistant to development of delayed gastric emptying. In contrast, HO-1 did not remain up-regulated in all the mice that developed delayed gastric emptying; expression of Kit and neuronal nitric oxide synthase decreased markedly in these mice. Loss of HO-1 up-regulation increased levels of reactive oxygen species. Induction of HO-1 by hemin decreased reactive oxygen species, rapidly restored Kit and neuronal nitric oxide synthase expression, and completely normalized gastric emptying in all mice. Inhibition of HO-1 activity in mice with normal gastric emptying caused a loss of Kit expression and development of diabetic gastroparesis.

CONCLUSIONS

Induction of the HO-1 pathway prevents and reverses cellular changes that lead to development of gastrointestinal complications of diabetes. Reagents that induce this pathway might therefore be developed as therapeutics.

Taurocholate-induced nitric oxide signaling and the ensuing production of reactive oxygen species lead to an increase in epithelial permeability in cultivated mouse gastric epithelium

We have here elucidated whether ulcerogenic agents affect the production of NO and reactive oxygen species (ROS). The ulcerogenic agents dose dependently induced NO and ROS production in mouse gastric epithelial cells. Taurocholate (TC, 5 mM) exposure did not affect cell viability, but it increased inducible nitric oxide synthase (iNOS) expression, NO production, ROS production, and epithelial permeability. Epithelial permeability was inhibited with NOS inhibitors or antioxidants. Oxidative stress induced by acetylsalicylic acid (ASA) and ethanol was not inhibited with NOS inhibitors. ASA induced ROS production even at low concentrations (1 mM), which did not affect cell viability. Ethanol-induced ROS production was linked to cell viability, suggesting direct oxidative stress caused by ethanol. Taurocholate-induced NO signaling and the ensuing production of ROS might contribute to initiation of defensive or adaptive cellular mechanisms. ASA-induced ROS signaling might have similar effects, whereas ethanol induced direct oxidative stress, having an influence on cell viability.

Pelvic nerve stimulation evokes nitric oxide mediated distal rectal relaxation in pigs

PURPOSE

Pelvic nerve stimulation evokes a complex motility response in the pig rectum with a proximal decrease and a distal increase in cross-sectional area. This study investigated whether the distal increase in the cross-sectional area is because of smooth muscle relaxation mediated by nitric oxide.

METHODS

The pelvic nerves were stimulated with cuff electrodes in ten chloralose-anesthetized minipigs. Pressure, volume, and cross-sectional areas at five positions in the rectum were obtained during stimulation to examine the effect of N(G)-nitro-L-arginine (an inhibitor of nitric oxide synthase) injection.

RESULTS

Stimulation evoked a median pressure decrease of 13 cm H(2)O (range, 0-27; P < 0.05; n = 10) in the anal canal, a pressure increase of 6 cm H(2)O (range,-15 to 30; P < 0.05; n = 10) in the rectum and a decrease of 39 mL (range, 30-63; P < 0.05; n = 6) in rectal volume. Rectal cross-sectional areas decreased 33 percent (range, 5-56; P < 0.02; n = 7) in the proximal part and increased 32 percent (range, 9-67; P < 0.02; n = 8) in the distal part. N(G)-nitro-L-arginine eliminated the increase in the distal rectal cross-sectional area (n = 5) and the decrease in anal canal pressure (n = 9) in all tested animals.

CONCLUSION

Pelvic nerve stimulation evokes distal rectal relaxation in pigs, sensitive to N(G)-nitro-L-arginine, which suggests that this smooth muscle response is mediated by nitric oxide.

The effect of nitric oxide, growth factors, and estrogen on gastric cell migration

BACKGROUND

To study gastric epithelial cell migration during nitric oxide (NO) and growth factor treatment, simulating inflammation and infection. Also, the effects of estrogen on migration of different malignant and nonmalignant gastric epithelial cell lines were explored.

MATERIAL AND METHODS

Isolated primary cultured rabbit gastric epithelial cells, rat gastric mucosal cells, human gastric adenocarcinoma cells, and human colon adenocarcinoma cells (WiDr) were cultured to confluency in appropriate media (5% CO2, 37 degrees C). The cells were treated by hepatocyte growth factor (HGF), transforming growth factor-alpha (TGF-alpha) and keratinocyte growth factor (KGF), with and without sodium nitroprusside (SNP, NO donor) or 17beta-estradiol. Caspase-3 activity and cell viability and migration speed after wounding were measured.

RESULTS

HGF was the most potent growth factor to stimulate migration. SNP dose-dependently decreased the speed of migration. HGF and TGF-alpha were able to overcome the SNP-induced inhibition of migration, whereas KGF was not. SNP also induced caspase-3 activity, which was inhibited by HGF and TGF-alpha. 17beta-estradiol decreased migration in all epithelial cells, but the decrease was more profound in malignant cell lines. HGF could overcome the estrogen retarded migration.

CONCLUSIONS

Growth factors can overcome NO-induced retardation of cell migration and inhibit NO-induced caspase-3 activity, which altogether might also have physiological significance in in vivo inflammation and in gastric cancer. The more profound decrease in migration speed of gastric adenocarcinoma cell line may suggest that estrogen might be one of the protective factor against female gastric adenocarcinoma before menopausal age.

Increased nitric oxide production during acute rejection in kidney transplantation: a useful marker to aid in the diagnosis of rejection

BACKGROUND

The diagnosis of acute rejection (AR) relies on biopsy (Bx), with all the noninvasive tests failing to show satisfactory predictive value. Nitric oxide (NO) has been shown to play a role in AR. The aim of this study is to analyze the relationship between NO and (1) biopsy-proven allograft rejection and (2) other reasons of allograft dysfunction.

PATIENTS AND METHODS

Fifty consecutive renal allograft recipients ages 23-72 yrs who were transplanted were prospectively recruited. Blood samples were collected for 3 months. Endogenous serum nitrate (SNO(3)) levels were measured with Griess reagent in 1178 samples. Biopsies were performed as clinically indicated. Tacrolimus levels, urinary cultures, and renal function tests were done as per unit protocol.

RESULTS

Fifty recipients (mean+/-SD age 45.2+/-2.18 yrs, 24 men and 6 women) underwent 68 biopsies. Forty-five Bx (66.2%) showed AR in 19 recipients (mean age 47+/-8) and 23 (33.8%) Bx in 13 recipients (mean age 43+/-12) showed no AR. SNO(3) in AR was (73+/-8.89 micromol/L) compared with negative Bx (45+/-4.5 micromol/L; P<0.05). There was also a significant difference in SNO(3) during AR and other causes of allograft dysfunction; delayed graft function (54+/-7.8 micromol/L), urinary tract infection (44+/-2.9 micromol/L), tacrolimus toxicity (51+/-2.86 micromol/L), and increase in serum creatinine (44+/-2.36 micromol/L).

CONCLUSION

There is a significant increase of serum nitrate with episodes of acute rejection compared with other causes of renal dysfunction. SNO(3) can therefore aid in the diagnosis of acute rejection.

Role of vasoactive substances on endometrial and ovarian function

In this review, it is proposed that the vasoactive agents endothelin (ET), nitric oxide (NO)/NO synthase (NOS) and carbon monoxide(CO)/heme oxygenase(HO) act directly on human endometrial functions and on ovarian functions in the normal menstrual cycle and in implantation periods. These vasoactive substances are likely to be important autocrine/paracrine factors that regulate a variety of physiological and pathological processes. The main actions of these agents are differentiation and implantation in the endometrial functions, and follicular growth, luteinization and atresia in the ovarian functions, in the tight connection between endometrial and ovarian systems during normal menstrual periods and during implantation (Reprod Med Biol 2007; 6: 157-164).