Excess NO Research Articles

Flame-Made Pt/K/Al2O3 for NO x Storage–Reduction (NSR) Catalysts

High surface area Pt/K/Al2O3 catalysts were prepared with a 2-nozzle flame spray method resulting in Pt clusters on γ-Al2O3 and amorphous K storage material as evidenced by Raman spectroscopy. The powders had a high NO x storage capacity and were regenerated fast in a model exhaust gas environment. From 300 to 400 °C no excess NO x was detected in the off gas during transition from fuel lean to fuel rich conditions, resulting in a highly effective NO x removal performance. Above 500 °C, the NSR activity was lost and not recovered at lower temperatures as K-compounds were partially crystallized on the catalyst.

Trifluoromethyl Fluoroformyl Trioxicarbonate, CF3OC(O)OOOC(O)F: The First Nonsymmetric Acyl Trioxide

This paper reports for the first time the synthesis and characterization of trifluoromethyl fluoroformyl trioxicarbonate, CF(3)OC(O)OOOC(O)F. The new trioxide is obtained from the gas-phase photolytic reaction of CF(3)C(O)OC(O)CF(3) and FC(O)C(O)F at 223-228 K. It is a very thermally labile molecule that decomposes at room temperature by rupture of either of the CF(3)OC(O)O-O-OC(O)F bonds. These bonds are nonequivalent, and a branching ratio of 0.8 for fragmentation through the CF(3)OC(O)OO-OC(O)F bond was obtained. Unambiguous identification was possible through reaction of the trioxide with an excess of NO(2). Potential-energy surfaces (PES) of the different rotamers were studied by the B3LYP/6-311+G* method, and analysis of the IR frequency of the possible mixture of rotamers agrees excellently with the experimental IR spectrum. This molecule is the first nonsymmetric acyl trioxide reported in the literature.

Paeoniflorin protects RAW 264.7 macrophages from LPS-induced cytotoxicity and genotoxicity

LPS is one of the major constituents of the outer membrane of Gram-negative bacteria. LPS-induced activation of macrophage results in the nitrite (NO) production and the secretion of a pro-inflammatory mediator such as PGE 2. Excessive NO reacts with the superoxide anion to generate a selective oxidant and nitrating agent, peroxynitrite, which interacts with biological molecules and damages the cell membranes of them, being able to result in the cell death. We evaluated the protective effects of paeoniflorin (PF) against LPS-induced toxicity by measuring its dose-dependent effects on cell viability in MTT assay, NO production in NO assay, PGE 2 production in prostaglandin E 2 (PGE 2) assay, and DNA damage in comet assay in LPS-treated RAW 264.7 macrophages. In the comet assay, we also analyzed tail length, tail DNA, and tail moment as the markers of DNA strand breaks. PF-treatment significantly protected RAW 264.7 macrophages against LPS-induced toxicity with the increase of viable cells, the decrease of NO and PGE 2, and the repair of DNA damage.

Noncatalytic Interactions between Glutathione S-Transferases and Nitroalkene Fatty Acids Modulate Nitroalkene-Mediated Activation of Peroxisomal Proliferator-Activated Receptor γ

The naturally occurring nitroalkenes, nitrolinoleic (NO(2)-LA) and nitrooleic (NO(2)-OA) acids, are among the most potent endogenous ligand activators of PPARgamma-dependent transcription. In order to understand mechanisms that regulate cellular response to these nitroalkenes, we previously demonstrated that glutathione conjugation of NO(2)-LA and MRP1-mediated efflux of the conjugates were associated with significant attenuation of PPARgamma activation by this nitroalkene [(2006) Biochemistry 45, 7889-7896]. Here we show that NO(2)-OA activation of PPARgamma is similarly affected by nonenzymatic conjugation and MRP1-mediated efflux. Moreover, the roles of glutathione S-transferases (GSTs) in the glutathione conjugation and bioactivities of NO(2)-LA and NO(2)-OA were investigated. While none of the GST isozymes tested (GSTA1-1, A4-4, M1a-1a, and P1a-1a) enhanced the rate of glutathione conjugation, expression of GSTA1-1, M1a-1a, or P1a-1a in MCF7 cells significantly reduced the magnitude of PPARgamma-dependent reporter gene transcription in response to NO(2)-LA and NO(2)-OA treatment, with GSTP1a-1a expression mediating the most potent inhibition of PPARgamma. Although these GSTs failed to catalyze nitroalkene conjugation with glutathione, the nitroalkenes were found to associate avidly with all four GST isozymes as indicated by their ability to inhibit GST activity with K(i)'s in the nanomolar range. Treatment of purified GSTP1a-1a with excess NO(2)-LA and NO(2)-OA resulted in the formation of covalent adducts between GSTP1a monomers and nitroalkenes, although separate experiments indicated that such covalent bond formation was not necessary for avid GST-nitroalkene interactions. These results suggest that GSTs can inhibit the activation of transcription by nitroalkenes via noncatalytic sequestration of these ligands, and their glutathione conjugates, away from their nuclear target, PPARgamma.

Effect of mutation of carboxyl side-chain amino acids near the heme on the midpoint potentials and ligand binding constants of nitrophorin 2 and its NO, histamine, and imidazole complexes.

Nitrophorins (NPs) are a group of NO-carrying heme proteins found in the saliva of a blood-sucking insect from tropical Central and South America, Rhodnius prolixus, the "kissing bug". NO is kept stable for long periods of time by binding it as an axial ligand to a ferriheme center. The fact that the nitrophorins are stabilized as Fe(III)-NO proteins is a unique property because most heme proteins are readily autoreduced by excess NO and bind NO to the Fe(II) heme irreversibly (K(d)s in the picomolar range). In contrast, the nitrophorins, as Fe(III) heme centers, have K(d)s in the micromolar to nanomolar range and thus allow NO to dissociate upon dilution following injection into the tissues of the victim. This NO can cause vasodilation and thereby allow more blood to be transported to the site of the wound. We prepared 13 site-directed mutants of three major nitrophorins, NP2, NP1, and NP4, to investigate the stabilization of the ferric-NO heme center and preservation of reversible binding that facilitates these proteins' NO storage, transport, and release functions. Of the mutations in which Glu and/or Asp were replaced by Ala, most of these carboxyls show a significant role stabilizing Fe(III)-NO over Fe(II)-NO, with buried E53 of NP2 or E55 of NP1 and NP4 being the most important and partially buried D29 of NP2 or D30 of NP4 being second in importance. The pK(a)s of the carboxyl groups studied vary significantly but all are largely deprotonated at pH 7.5 except E124.

Effect of Triterpene Acids of Eriobotrya japonica (Thunb.) Lindl. Leaf and MAPK Signal Transduction Pathway on Inducible Nitric Oxide Synthase Expression in Alveolar Macrophage of Chronic Bronchitis Rats

The goal of this study was to investigate the possible therapy mechanism of triterpene acids of Eriobotrya japonica (Thunb.) Lindl. Leaf (TAL) in alveolar macrophage (AM) of chronic bronchitis (CB) rats. CB model was established by injection of bacillus calmette guein (BCG) plus lipopolisacharide (LPS) in rats. TAL significantly inhibited the increased NO concentration, iNOS expression and phosphorylation of p38 MAPK in alveolar macrophages (AMs) of CB rats. Using in vivo test, we found that SB203580, a p38 MAPK inhibitor, (10 muM) significantly inhibited inducible nitric oxide synthase (iNOS) mRNA expression in AM. This data indicate that TAL highly decreases excessive iNOS expression and NO induction, and p38 MAPK signal transduction participates in iNOS expression and NO induction in AM of CB rats. The effect of TAL on iNOS expression in AM may be related to its inhibition of p38 MAPK signal transduction.

Quantitative and kinetic TG-FTIR study of biomass residue pyrolysis: Dry distiller's grains with solubles (DDGS) and chicken manure

New energy policies all over the world are trying to tackle high oil prices and climate change by promoting the use of biomass to produce heat, electricity and liquid transportation fuels. In this paper we studied two different secondary fuels: dry distiller's grains with solubles (DDGS) and chicken manure. These materials have high content of nitrogen and ashes which limit their usage in thermal applications due to potential excessive NO x emissions and problems of slagging, fouling, corrosion and loss of fluidization. The fuels tested here were received from industrial partners. In order to reduce the ash content the fuels were pre-treated using water leaching pre-treatment. Pyrolysis of these fuels has been monitored through a TG-FTIR set-up. Quantification of the following volatile species was possible: CO, CO 2, CH 4, HCN, NH 3, HNCO, H 2O. The water leaching appeared to decrease the amount of ashes in both samples and remove some of the troublesome compounds like Cl, S and K. The DDGS thermogravimetric curve showed three main peaks at 280 °C, 330 °C and 402 °C with a total weight loss of around 79%wt a.r. (on an “as received” basis). NH 3 is the main N-compound released at low temperatures with a peak at 319 °C. HNCO and HCN were detected at higher temperatures of around 400 °C. Chicken manure reacted in four stages with peaks at 280 °C, 324 °C, 430 °C and 472 °C with a total average weight loss of 66%wt a.r. The main N-compound was HNCO, released at 430 °C. Ammonia was detected during the whole measurement, while HCN presented peaks of reactivity at 430 °C and 472 °C. Kinetic analysis was applied using a distributed activation energy method (DAEM) using discrete and Gaussian distributions and data for further modeling purposes were retrieved and presented.

THE EFFECT OF SUPEROXIDE DISMUTASE OVEREXPRESSION ON HEPATIC GLUCONEOGENESIS AND WHOLE-BODY GLUCOSE OXIDATION DURING RESUSCITATED NORMOTENSIVE MURINE SEPTIC SHOCK

Besides excess cytokine and NO production, enhanced oxygen radical formation was referred to contribute to the impaired hepatic gluconeogenesis during sepsis or endotoxemia. Therefore, we tested the hypothesis that genetic overexpression of the Cu/Zn-superoxide dismutase (SOD-1) may restore the sepsis-related lack of the norepinephrine-induced increase in hepatic gluconeogenesis and whole-body glucose oxidation. Anesthetized, ventilated, and instrumented wild-type control, and heterozygous and homozygous SOD-1-overexpressing mice received hydroxyethyl starch and norepinephrine to maintain normotensive hemodynamics measured at 18, 21, and 24 h after cecal ligation and puncture (CLP) or sham operation. Hepatic gluconeogenesis and whole-body glucose oxidation were calculated from liver tissue isotope and expiratory 13CO2 enrichments during continuous i.v. 1,2,3,4,5,6-13C6-glucose. Superior mesenteric artery and portal vein flows (ultrasound flow probes) and hepatic microcirculatory perfusion (Laser Doppler flowmetry) and O2 saturation (remission spectrophotometry) were comparable in the CLP and sham-operated animals, without any difference related to the mouse strain. Despite continuous i.v. norepinephrine necessary in the CLP mice, both glycemia and hepatic gluconeogenesis were similar, irrespective of the presence of sepsis and the genetic strain. Glucose oxidation rate progressively increased in the CLP groups, again without difference between the genetic strains. The surgery- and CLP-induced increase in liver cell oxidative DNA damage (tail moment in the comet assay) was less pronounced in the homozygous mice. Heterozygous nor homozygous SOD-1 overexpression did not improve the sepsis-related impairment of carbohydrate metabolism, possibly because of the lacking increase of the tissue catalase and the mitochondrial SOD activity, and the ongoing i.v. norepinephrine.

Effects of Sildenafil on Oxidative and Inflammatory Injuries of the Kidney in Streptozotocin-Induced Diabetic Rats

Background: Oxidative stress and inflammation are implicated in the pathogenesis of diabetic nephropathy. Because sildenafil citrate (Viagra®) has variable cardiovascular benefits, including antioxidative and immunomodulating effects, we investigated its influence on oxidative stress and inflammation in diabetic rat kidney. Methods: Streptozotocin-induced diabetic rats received sildenafil (3 mg/kg/day in drinking water) or not (undosed water) for 8 weeks and were compared to age-matched nondiabetic animals. We evaluated 8-hydroxydeoxyguanosine (8-OHdG; for oxidative DNA damage), inducible nitric oxide synthase (iNOS) and nitrotyrosine (for excessive NO production and peroxynitrite formation), and representative chemoattractants [monocyte chemotactic protein-1, MCP-1; for inflammation and monocyte/macrophage infiltrations (ED-1)] in the kidney. Results: Sildenafil-treated rats had a lower kidney-to-body weight ratio than untreated diabetic rats. Urinary albumin excretion in diabetic rats decreased significantly after sildenafil treatment without changes in systolic blood pressure. Sildenafil-treated rats had significantly lower urinary and renal cortical 8-OHdG levels than the nonsildenafil group. Sildenafil administration significantly attenuated the increased renal nitrotyrosine protein expression, positive iNOS and ED-1 staining in glomeruli and tubulointerstitium, and nitrotyrosine staining in tubulointerstitium. Cortical MCP-1 RNA expression in the sildenafil group was significantly lower than in the nonsildenafil group. Conclusions: Sildenafil treatment may attenuate renal damage by ameliorating oxidative and inflammatory injuries in diabetic rats.

Plant mitochondrial function during anaerobiosis.

Under hypoxic conditions, plant mitochondria preserve the capacity to oxidize external NADH, NADPH and tricarboxylic acid cycle substrates. Nitrite serves as an alternative electron acceptor at the level of cytochrome oxidase, with possibly complex III and the alternative oxidase also being involved. Nitric oxide is a significant product of the reaction, which has a high affinity for cytochrome c oxidase, inhibiting it. The excess NO is scavenged by hypoxically induced class 1 haemoglobin in the reaction involving ascorbate. By using nitrite, mitochondria retain a limited capacity for ATP synthesis. NADH, produced from glycolysis during anaerobiosis and oxidized in the mitochondrial electron transport chain, should shift the composition of metabolites formed during anaerobiosis with increased conversion of pyruvate to alanine and greater involvement of other transamination reactions, such as those involving gamma-aminobutyric acid formation. Anaerobic mitochondrial metabolism may have a more significant role than previously thought in alleviating the effects of anoxia on plant cells. There is a need to re-examine mitochondrial carbon and nitrogen metabolism under anoxia to establish the extent of this involvement.

Correction: Excessive Islet NO Generation in Type 2 Diabetic GK Rats Coincides with Abnormal Hormone Secretion and Is Counteracted by GLP-1

Correction: Excessive Islet NO Generation in Type 2 Diabetic GK Rats Coincides with Abnormal Hormone Secretion and Is Counteracted by GLP-1

Correction: Excessive Islet NO Generation in Type 2 Diabetic GK Rats Coincides with Abnormal Hormone Secretion and Is Counteracted by GLP-1

Correction: Excessive Islet NO Generation in Type 2 Diabetic GK Rats Coincides with Abnormal Hormone Secretion and Is Counteracted by GLP-1

Excessive Islet NO Generation in Type 2 Diabetic GK Rats Coincides with Abnormal Hormone Secretion and Is Counteracted by GLP-1

Excessive Islet NO Generation in Type 2 Diabetic GK Rats Coincides with Abnormal Hormone Secretion and Is Counteracted by GLP-1

Correction: Palmitate-Induced β-Cell Dysfunction Is Associated with Excessive NO Production and Is Reversed by Thiazolidinedione-Mediated Inhibition of GPR40 Transduction Mechanisms

Correction: Palmitate-Induced β-Cell Dysfunction Is Associated with Excessive NO Production and Is Reversed by Thiazolidinedione-Mediated Inhibition of GPR40 Transduction Mechanisms

Correction: Palmitate-Induced β-Cell Dysfunction Is Associated with Excessive NO Production and Is Reversed by Thiazolidinedione-Mediated Inhibition of GPR40 Transduction Mechanisms

Correction: Palmitate-Induced β-Cell Dysfunction Is Associated with Excessive NO Production and Is Reversed by Thiazolidinedione-Mediated Inhibition of GPR40 Transduction Mechanisms

Excessive Islet NO Generation in Type 2 Diabetic GK Rats Coincides with Abnormal Hormone Secretion and Is Counteracted by GLP-1

BackgroundA distinctive feature of type 2 diabetes is inability of insulin-secreting β-cells to properly respond to elevated glucose eventually leading to β-cell failure. We have hypothesized that an abnormally increased NO production in the pancreatic islets might be an important factor in the pathogenesis of β-cell dysfunction.Principal FindingsWe show now that islets of type 2 spontaneous diabetes in GK rats display excessive NO generation associated with abnormal iNOS expression in insulin and glucagon cells, increased ncNOS activity, impaired glucose-stimulated insulin release, glucagon hypersecretion, and impaired glucose-induced glucagon suppression. Pharmacological blockade of islet NO production by the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) greatly improved hormone secretion from GK islets suggesting islet NOS activity being an important target to inactivate for amelioration of islet cell function. The incretin hormone GLP-1, which is used in clinical practice suppressed iNOS and ncNOS expression and activity with almost full restoration of insulin release and partial restoration of glucagon release. GLP-1 suppression of iNOS expression was reversed by PKA inhibition but unaffected by the proteasome inhibitor MG132. Injection of glucose plus GLP-1 in the diabetic rats showed that GLP-1 amplified the insulin response but induced a transient increase and then a poor depression of glucagon.ConclusionThe results suggest that abnormally increased NO production within islet cells is a significant player in the pathogenesis of type 2 diabetes being counteracted by GLP-1 through PKA-dependent, nonproteasomal mechanisms.

Palmitate-Induced β-Cell Dysfunction Is Associated with Excessive NO Production and Is Reversed by Thiazolidinedione-Mediated Inhibition of GPR40 Transduction Mechanisms

BackgroundType 2 diabetes often displays hyperlipidemia. We examined palmitate effects on pancreatic islet function in relation to FFA receptor GPR40, NO generation, insulin release, and the PPARγ agonistic thiazolidinedione, rosiglitazone.Principal FindingsRosiglitazone suppressed acute palmitate-stimulated GPR40-transduced PI hydrolysis in HEK293 cells and insulin release from MIN6c cells and mouse islets. Culturing islets 24 h with palmitate at 5 mmol/l glucose induced β-cell iNOS expression as revealed by confocal microscopy and increased the activities of ncNOS and iNOS associated with suppression of glucose-stimulated insulin response. Rosiglitazone reversed these effects. The expression of iNOS after high-glucose culturing was unaffected by rosiglitazone. Downregulation of GPR40 by antisense treatment abrogated GPR40 expression and suppressed palmitate-induced iNOS activity and insulin release.ConclusionWe conclude that, in addition to mediating acute FFA-stimulated insulin release, GPR40 is an important regulator of iNOS expression and dysfunctional insulin release during long-term exposure to FFA. The adverse effects of palmitate were counteracted by rosiglitazone at GPR40, suggesting that thiazolidinediones are beneficial for β-cell function in hyperlipidemic type 2 diabetes.

Molecular cloning and characterization of a cucumber MAP kinase gene in response to excess NO 3− and other abiotic stresses

Mitogen-activated protein kinases (MAPKs) play important roles in the transduction of extracellular signals to the intracellular targets in all eukaryotes. Here, a cucumber cDNA designated CsNMAPK, encoding a mitogen-activated protein kinase was isolated using RT-PCR, 3′ and 5′ RACE. The full-length cDNA sequence contains 1636 bp and an open reading frame (ORF) of 1113 bp, which encodes 370 amino acid residues. According to the phylogenetic analysis, CsNMAPK belongs to subgroup I MAPK in plants. Northern blot analysis revealed that CsNMAPK expressed differently in response to excess NO 3 −. And the CsNMAPK expression kinetics between a salt-resistant cultivar (Xintaimici) and a salt-sensitive cultivar (Shennongchunwu) was slightly different under 182 mmol L −1 NO 3 − treatment. The mRNA levels also increased after 24 h treatments with H 2O 2 and salicylic acid (SA), but decreased with abscisic acid (ABA) and low-temperature. However, there was no significant induction of CsNMAPK gene after 24 h drought and high-temperature treatments. Our results suggested that a MAP kinase cascade may function in excess NO 3 − and other abiotic stresses in cucumber.

Evaluation of the preventative effects exerted byLactobacillus fermentumin an experimental model of septic shock induced in mice

The preventative effects of the probiotic Lactobacillus fermentum CECT5716 were evaluated in the lipopolysaccharide (LPS) model of septic shock in mice. The probiotic was administered suspended in drinking water at the final concentration of 108 colony-forming units/ml for 2 weeks before the induction of an endotoxic shock by an intraperitoneal injection of LPS (400 microg/200 microl per mouse). Blood and different organs were collected after 24 h to evaluate the severity of the endotoxic shock and the preventative effects of the probiotic. L. fermentum reduced TNF-alpha levels in blood, which promotes the major alterations observed during septic shock, as well as the infiltration of activated neutrophils into the lungs. Furthermore, free radical overproduction and oxidative stress were associated with a significant decrease in hepatic glutathione levels in septic mice, and with an excessive NO production attributed to the induction of the inducible isoform of NO synthase (iNOS). In fact, hepatic glutathione levels were significantly increased in the group of mice receiving the probiotic, and the increased iNOS expression both in the colon and lungs was down-regulated in those mice treated with L. fermentum. Finally, pre-treatment with L. fermentum may also exert its protective action modulating the expression of different cytokines in splenocyte-derived T cells such us IL-2, IL-5, IL-6 or IL-10. In conclusion, pre-treatment with L. fermentum may exert its protective action against LPS-induced organ damage in mice by a combination of several actions including its antioxidant properties and by reduction of the synthesis of the pro-inflammatory TNF-alpha and IL-6.

Water quality implications of raising crop water productivity

Because of a growing and more affluent population, demand for agricultural products will increase rapidly over the coming decades, with serious implications for agricultural water demand. Symptoms of water scarcity are increasingly apparent, threatening ecosystem services and the sustainability of food production. Improved water productivity will reduce the additional water requirements in agriculture. However, there is a tradeoff between the quantity of water used in agriculture and the quality of return flow. Where yields are low due to limited nitrogen (N) and water supply, water productivity can be enhanced through higher fertilizer applications and improved water management. This limits the amount of additional water needed for increased food demand, thus leaving more water for environmental requirements. But it also increases the amount of nitrate (NO 3–N) leaching, thus adversely affecting the water quality of return flows. This paper quantifies the tradeoff between enhanced water productivity and NO 3–N leaching and shows the importance of the right management of water and N applications. Using the Decision Support System for Agro-technology Transfer (DSSAT) crop model, several scenarios combining different water and N application regimes are examined for maize ( Zea mays L.) in Gainesville, FL, USA. Without adequate water, nitrogen use efficiency (NUE) remains low, resulting in substantial NO 3–N leaching. Too much water leads to excessive NO 3–N leaching and lower water productivity. The lack of N is a cause of low water productivity but too much of it leads to lower NUE and higher losses. The paper concludes that increased NO 3–N leaching is an inevitable by-product of increased water productivity, but its adverse impacts can greatly be reduced by better management of water and N application. The paper briefly shows that leaching can be reduced and water productivity increased by split application of N-fertilizer. This implies that improved water and nutrient management at field- and scheme-level is a prerequisite to limit adverse impacts of agriculture on ecosystems, now and especially in the future.