DNA looping mediates cooperative transcription activation

Transcription factors respond to multilevel stimuli and co-occupy promoter regions of target genes to activate RNA polymerase (RNAP) in a cooperative manner. To decipher the molecular mechanism, here we report two cryo-electron microscopy structures of Anabaena transcription activation complexes (TACs): NtcA-TAC composed of RNAP holoenzyme, promoter and a global activator NtcA, and NtcA-NtcB-TAC comprising an extra context-specific regulator, NtcB. Structural analysis showed that NtcA binding makes the promoter DNA bend by ∼50°, which facilitates RNAP to contact NtcB at the distal upstream NtcB box. The sequential binding of NtcA and NtcB induces looping back of promoter DNA towards RNAP, enabling the assembly of a fully activated TAC bound with two activators. Together with biochemical assays, we propose a 'DNA looping' mechanism of cooperative transcription activation in bacteria.

The Impact of LY487379 or CDPPB on eNOS Expression in the Mouse Brain and the Effect of Joint Administration of Compounds with NO• Releasers on MK-801- or Scopolamine-Driven Cognitive Dysfunction in Mice

The role of endothelial nitric oxide synthase (eNOS) in the regulation of a variety of biological processes is well established, and its dysfunction contributes to brain pathologies, including schizophrenia or Alzheimer's disease (AD). Positive allosteric modulators (PAMs) of metabotropic glutamate (mGlu) receptors were shown to be effective procognitive compounds, but little is known about their impact on eNOS expression and stability. Here, we investigated the influence of the acute and chronic administration of LY487379 or CDPPB (mGlu2 and mGlu5 PAMs), on eNOS expression in the mouse brain and the effect of the joint administration of the ligands with nitric oxide (NO) releasers, spermineNONOate or DETANONOate, in different combinations of doses, on MK-801- or scopolamine-induced amnesia in the novel object recognition (NOR) test. Our results indicate that both compounds provoked eNOS monomer formation, and CDPPB at a dose of 5 mg/kg exaggerated the effect of MK-801 or scopolamine. The coadministration of spermineNONOate or DETANONOate enhanced the antiamnesic effect of CDPPB or LY487379. The best activity was observed for ineffective or moderate dose combinations. The results indicate that treatment with mGluR2 and mGluR5 PAMs may be burdened with the risk of promoting eNOS uncoupling through the induction of dimer dissociation. Administration of the lowest possible doses of the compounds with NO• donors, which themselves have procognitive efficacy, may be proposed for the treatment of schizophrenia or AD.

Kinetic study on the reaction of sodium nitrite with neurotransmitters secreted in the stomach

Nitroso-compounds are potentially mutagenic and carcinogenic compounds due to their ability to alkylate DNA bases. One of the most common sources of human exposure to nitroso-compounds is their formation in the acidic environment of the stomach by the reaction between electron-rich molecules present in the lumen and sodium nitrite ingested in the diet. To date, the formation of nitroso-compounds by the reaction of nitrite with food components has been investigated in depth, but little attention has been paid to substances secreted in the stomach, such as dopamine or serotonin, whose reaction products with nitrite have proven mutagenic properties. In this article, we present a kinetic study with UV-visible spectroscopy of the nitrosation reactions of both molecules, as well as of L-tyrosine, the amino-acid precursor of dopamine. We determined the kinetic parameters and reaction mechanisms for the reactions, studying the influence of the reactants concentration, pH, temperature, and ionic strength on the reaction rate. In all cases, the favoured reaction product was a stable nitroso-compound. Serotonin, the molecule whose product was the most mutagenic, underwent two consecutive nitrosation reactions. These findings suggest that additional biological research is needed to understand how this reaction alters the function of these neurotransmitters as well as the potentially toxic effects they may have once nitrosated.

The possibility of diagnosing intrauterine infection by the content of nitrite and non-thiolate nitroso compounds in maternal blood plasma

The aim of the study is to develop a method for early diagnosis of intrauterine infection (IUI). A study of markers of inflammation in the venous blood of 60 pregnant women was conducted. The study was followed by a retrospective assessment of the outcomes of pregnancies and childbirth. Of these, 33 patients with a gestation period of more than 37 weeks (full-term pregnancy) and, accordingly, 27 patients from whom the blood sample was taken at a period of less than 37 weeks - patients with the threat of premature birth (PB). PB is the main factor contributing to the development of IUI. 27 patients were diagnosed with premature rupture of the membranes (PROM). Of these, 15 are with the threat of PB. 8 of them had a diagnosed IUI. In all cases of diagnosed PROM, including those with IUI, the concentration of nitrite and nontiolate nitroso compounds (NO2-+RNO) in the mother's blood plasma was 2.3±1.2 µM, while normally it does not exceed 0.1 µM (p<0.001). Regardless of the duration of pregnancy. The use of antibiotics in the case of PROM contributed to the normalization of the concentration (NO2-+RNO). Therefore, increasing of this indicator is result of bacterial infection. Indications of other markers of inflammation: the number of leukocytes in venous blood and in a smear of vaginal contents, the level of C-RB did not significantly change in both PROM and IUI (p>0.1). Since the concentration index (NO2-+RNO) increased in almost all cases of PREM, unlike all other clinical and biochemical indicators used in modern medicine, there is an obvious sense of its use for the current monitoring of the health of pregnant women. But it is still impossible to say unequivocally about the possibility of monitoring the fetal health by concentration (NO2-+RNO) in the mother's blood.

Multi-DNA Adduct and Abasic Site Quantitation In Vivo by Nano-Liquid Chromatography/High-Resolution Orbitrap Tandem Mass Spectrometry: Methodology for Biomonitoring Colorectal DNA Damage

Epidemiological and mechanistic studies suggest that processed and red meat consumption and tobacco smoking are associated with colorectal cancer (CRC) risk. Several classes of carcinogens, including N-nitroso compounds (NOCs) in processed meats and heterocyclic aromatic amines (HAAs) and polycyclic aromatic hydrocarbons (PAHs) in grilled meats and tobacco smoke, undergo metabolism to reactive intermediates that may form mutation-inducing DNA adducts in the colorectum. Heme iron in red meat may contribute to oxidative DNA damage and endogenous NOC formation. However, the chemicals involved in colorectal DNA damage and the paradigms of CRC etiology remain unproven. There is a critical need to establish physicochemical methods for identifying and quantitating DNA damage induced by genotoxicants in the human colorectum. We established robust nano-liquid chromatography/high-resolution accurate mass Orbitrap tandem mass spectrometry (LC/HRAMS2) methods to measure DNA adducts of nine meat and tobacco-associated carcinogens and lipid peroxidation products in the liver, colon, and rectum of carcinogen-treated rats employing fresh-frozen and formalin-fixed paraffin-embedded (FFPE) tissues. Some NOCs form O6-carboxymethyl-2'-deoxyguanosine, O6-methyl-2'-deoxyguanosine, and unstable quaternary N-linked purine/pyrimidine adducts, which generate apurinic/apyrimidinic (AP) sites. AP sites were quantitated following derivatization with O-(pyridin-3-yl-methyl)hydroxylamine. DNA adduct quantitation was conducted with stable isotope-labeled internal standards, and method performance was validated for accuracy and reproducibility. Limits of quantitation ranged from 0.1 to 1.1 adducts per 108 bases using 3 μg of DNA. Adduct formation in animals ranged from ∼1 in 108 to ∼1 in 105 bases, occurring at comparable levels in fresh-frozen and FFPE specimens for most adducts. AP sites increased by 25- to 75-fold in the colorectum and liver, respectively. Endogenous lipid peroxide-derived 3-(2-deoxy-β-d-erythro-pentofuranosyl)pyrimido[1,2-α]purin-10(3H)-one (M1dG) and 6-oxo-M1dG adduct levels were not increased by carcinogen dosing but increased in FFPE tissues. Human biomonitoring studies can implement LC/HRAMS2 assays for DNA adducts and AP sites outlined in this work to advance our understanding of CRC etiology.

Decomposition of 2,4,6-trinitrotoluene (TNT) and 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO) by Fe13O13 nanoparticle: density functional theory study

To obtain more insight into the mechanisms of the decomposition of energetic compounds, we performed a computational study of the interaction of Fe₁₃O₁₃ nanoparticles with two energetic molecules such as 2,4,6-trinitrotoluene (TNT) and 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO). The density functional theory using M06-2X, B3LYP, and BLYP density functionals was applied. We found that the reactivity of these molecules strongly depends on the place of adsorption (so-called top and bottom planes of Fe₁₃O₁₃). Namely, only the interaction with the bottom plane results in the thermodynamic characteristics of the decomposition that provide a medium reaction rate for the studied processes. Several pathways for such decomposition were found. One of them is the inter-complex oxygen transfer of nitro-group oxygen to Fe₁₃O₁₃. This pathway results in the formation of adsorbed nitroso compounds. The second pathway describes a more complex decomposition that includes the transfer of the nitro-group oxygen accompanied by the hydrogen transfer. In all cases, the interaction of energetic molecules with Fe₁₃O₁₃ nanoparticles takes place along with a barrier-less electron transfer from Fe₁₃O₁₃ to TNT or NTO species.

Long-Term Storage Stability and Nitric Oxide Release Behavior of (N-Acetyl-S-nitrosopenicillaminyl)-S-nitrosopenicillamine-Incorporated Silicone Rubber Coatings

Physical incorporation of nitric oxide (NO) releasing materials in biomedical grade polymer matrices to fabricate antimicrobial coatings and devices is an economically viable process. However, achieving long-term NO release with a minimum or no leaching of the NO donor from the polymer matrix is still a challenging task. Herein, (N-acetyl-S-nitrosopenicillaminyl)-S-nitrosopenicillamine (SNAP-SNAP), a penicillamine dipeptide NO-releasing molecule, is incorporated into a commercially available biomedical grade silicone rubber (SR) to fabricate a NO-releasing coating (SNAP-SNAP/SR). The storage stabilities of the SNAP-SNAP powder and SNAP-SNAP/SR coating were analyzed at different temperatures. The SNAP-SNAP/SR coatings with varying wt % of SNAP-SNAP showed a tunable and sustained NO release for up to 6 weeks. Further, S-nitroso-N-acetylpenicillamine (SNAP), a well-explored NO-releasing molecule, was incorporated into a biomedical grade silicone polymer to fabricate a NO-releasing coating (SNAP/SR) and a comparative analysis of the NO release and S-nitrosothiol (RSNO) leaching behavior of 10 wt % SNAP-SNAP/SR and 10 wt % SNAP/SR was studied. Interestingly, the 10 wt % SNAP-SNAP/SR coatings exhibited ∼36% higher NO release and 4 times less leaching of NO donors than the 10 wt % SNAP/SR coatings. Further, the 10 wt % SNAP-SNAP/SR coatings exhibited promising antibacterial properties against Staphylococcus aureus and Escherichia coli due to the persistent release of NO. The 10 wt % SNAP-SNAP/SR coatings were also found to be biocompatible against NIH 3T3 mouse fibroblast cells. These results corroborate the sustained stability and NO-releasing properties of the SNAP-SNAP in a silicone polymer matrix and demonstrate the potential for the SNAP-SNAP/SR polymer in the fabrication of long-term indwelling biomedical devices and implants to enhance biocompatibility and resist device-related infections.

Structure of New Ferroverdins Recruiting Unconventional Ferrous Iron Chelating Agents

Ferroverdins are ferrous iron (Fe²⁺)-nitrosophenolato complexes produced by a few Streptomyces species as a response to iron overload. Previously, three ferroverdins were identified: ferroverdin A, in which three molecules of p-vinylphenyl-3-nitroso-4-hydroxybenzoate (p-vinylphenyl-3,4-NHBA) are recruited to bind Fe²⁺, and Ferroverdin B and Ferroverdin C, in which one molecule of p-vinylphenyl-3,4-NHBA is substituted by hydroxy-p-vinylphenyl-3,4-NHBA, and by carboxy-p-vinylphenyl-3,4-NHBA, respectively. These molecules, especially ferroverdin B, are potent inhibitors of the human cholesteryl ester transfer protein (CETP) and therefore candidate hits for the development of drugs that increase the serum concentration of high-density lipoprotein cholesterol, thereby diminishing the risk of atherosclerotic cardiovascular disease. In this work, we used high-resolution mass spectrometry combined with tandem mass spectrometry to identify 43 novel ferroverdins from the cytosol of two Streptomyces lunaelactis species. For 13 of them (designated ferroverdins C2, C3, D, D2, D3, E, F, G, H, CD, DE, DF, and DG), we could elucidate their structure, and for the other 17 new ferroverdins, ambiguity remains for one of the three ligands. p-formylphenyl-3,4-NHBA, p-benzoic acid-3,4-NHBA, 3,4-NHBA, p-phenylpropionate-3,4-NHBA, and p-phenyacetate-3,4-NHBA were identified as new alternative chelators for Fe²⁺-binding, and two compounds (C3 and D3) are the first reported ferroverdins that do not recruit p-vinylphenyl-3,4-NHBA. Our work thus uncovered putative novel CETP inhibitors or ferroverdins with novel bioactivities.

Histology of Chemically Induced Mesotheliomas in Mrc-wistar Rats

Two peritoneal mesotheliomas were induced in rats during a carcinogenicity study of 1-nitroso-5,6-dihydrouracil (NO-DHU) injected intraperitoneally. A review of literature concerning experimental induction of such tumors indicated that they seldom produced with organic compounds and rarely occur spontaneously. In the present study, several reports of chemically induced mesotheliomas of the testes are analyzed and the diagnoses critically reviewed along with other differential diagnoses.

Nitrosourea-Induced Brain Tumors in the Rat. Comments on the Pathogenesis of Mixed and Polymorphic Gliomas

Mixed gliomas are among the most frequent of brain tumors induced by nitrosourea derivatives. In a personal collection of 300 experimental tumors 142 were gliomas. The characteristics of the various oncotypes are described, with special reference to mixed and polymorphic gliomas. Generally, gliomas develop from microtumors and polymorphic gliomas from isomorphic gliomas. For this reason mixed gliomas probably represent an intermediate stage of the transformation. The principal cellular components of mixed gliomas in order of frequency are: oligodendroglial, astrocytic, ependymal and sarcomatous. Some pathogenetic hypotheses are advanced to explain the changes observed in gliomas during their development.

Direct measurement of actual levels of nitric oxide (NO) in cell culture conditions using soluble NO donors

Applying soluble nitric oxide (NO) donors is the most widely used method to expose cells of interest to exogenous NO. Because of the complex equilibria that exist between components in culture media, the donor compound and NO itself, it is very challenging to predict the dose and duration of NO cells actually experience. To determine the actual level of NO experienced by cells exposed to soluble NO donors, we developed the CellNO Trap, a device that allows continuous, real-time monitoring of the level of NO adherent cells produce and/or experience in culture without the need to alter cell culturing procedures. Herein, we directly measured the level of NO that cells grown in the CellNO Trap experienced when soluble NO donors were added to solutions in culture wells and we characterized environmental conditions that effected the level of NO in in vitro culture conditions. Specifically, the dose and duration of NO generated by the soluble donors S-nitroso-N-acetylpenicillamine (SNAP), S-nitrosoglutathione (GSNO), S-nitrosocysteine (CysNO) and the diazeniumdiolate diethyltriamine (DETA/NO) were investigated in both phosphate buffered saline (PBS) and cell culture media. Other factors that were studied that potentially affect the ultimate NO level achieved with these donors included pH, presence of transition metals (ion species), redox level, presence of free thiol and relative volume of media. Then murine smooth muscle cell (MOVAS) with different NO donors but with the same effective concentration of available NO were examined and it was demonstrated that the cell proliferation ratio observed does not correlate with the half-lives of NO donors characterized in PBS, but does correlate well with the real-time NO profiles measured under the actual culture conditions. This data demonstrates the dynamic characteristic of the NO and NO donor in different biological systems and clearly illustrates the importance of tracking individual NO profiles under the actual biological conditions.

Kinetically-defined component actions in gene repression

Gene repression by transcription factors, and glucocorticoid receptors (GR) in particular, is a critical, but poorly understood, physiological response. Among the many unresolved questions is the difference between GR regulated induction and repression, and whether transcription cofactor action is the same in both. Because activity classifications based on changes in gene product level are mechanistically uninformative, we present a theory for gene repression in which the mechanisms of factor action are defined kinetically and are consistent for both gene repression and induction. The theory is generally applicable and amenable to predictions if the dose-response curve for gene repression is non-cooperative with a unit Hill coefficient, which is observed for GR-regulated repression of AP1LUC reporter induction by phorbol myristate acetate. The theory predicts the mechanism of GR and cofactors, and where they act with respect to each other, based on how each cofactor alters the plots of various kinetic parameters vs. cofactor. We show that the kinetically-defined mechanism of action of each of four factors (reporter gene, p160 coactivator TIF2, and two pharmaceuticals [NU6027 and phenanthroline]) is the same in GR-regulated repression and induction. What differs is the position of GR action. This insight should simplify clinical efforts to differentially modulate factor actions in gene induction vs. gene repression.

Differentially expressed proteins in nitric oxide-stimulated NIH/3T3 fibroblasts: implications for inhibiting cancer development

PURPOSE

Recent evidence shows that nitric oxide (NO) may exhibit both pro-cancer and anti-cancer activities. The present study aimed to determine the differentially expressed proteins in NO-treated NIH/3T3 fibroblasts in order to investigate whether NO induces proteins with pro-cancer or anti-cancer effects.

MATERIALS AND METHODS

The cells were treated with 300 μM of an NO donor 3,3-bis-(aminoethyl)-1-hydroxy-2-oxo-1-triazene (NOC-18) for 12 h. The changed protein patterns, which were separated by two-dimensional electrophoresis using pH gradients of 4-7, were conclusively identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis of the peptide digests.

RESULTS

Seventeen differentially expressed proteins were identified in NOC-18-treated cells. Nine proteins [vinculin protein, keratin 19, ubiquitous tropomodulin, F-actin capping protein (α1 subunit), tropomyosin 3, 26S proteasome-associated pad1 homolog, T-complex protein 1 (ε subunit) N(G)-dimethylarginine dimethylaminohydrolase, and heat shock protein 90] were increased and eight proteins (heat shock protein 70, glucosidase II, lamin B1, calreticulin, nucleophosmin 1, microtubule-associated protein retinitis pigmentosa/end binding family member 1, 150 kD oxygen-regulated protein precursor, and heat shock 70-related protein albino or pale green 2) were decreased by NOC-18 in the cells. Thirteen proteins are related to the suppression of cancer cell proliferation, invasion, and metastasis while two proteins (heat shock protein 90 and N(G)-dimethylarginine dimethylaminohydrolase) are related to carcinogenesis. The functions of 150 kD oxygen-regulated protein precursor and T-complex protein 1 (ε subunit) are unknown in relation to carcinogenesis.

CONCLUSION

Most proteins differentially expressed by NOC-18 are involved in inhibiting cancer development.

Renal effects of glucose transporter 4 in Nω-nitro-L-arginine/ /high salt-induced hypertensive rats

OBJECTIVES

The aim of study was to determine the renal effects of glucose transporter 4 (GLUT4) in a hypertensive nephropathy rat model.

BACKGROUND

GLUT4 has been implicated in insulin resistance and hypertension in several animal models; however its role in hypertensive nephropathy still remains unclear.

METHODS

Hypertensive nephropathy was induced by Nω-nitro-L-arginine (L-NNA), a nitric oxide (NO) synthase inhibitor, 100 mg/ml in drinking water and high salt (HS) diet (4 % NaCl), for 15 days in the presence of insulin, a GLUT 4 agonist (1 U/day) and indinavir, a GLUT4 inhibitor (80 mg/kg/day).

RESULTS

Decreased basal renal medullary and cortical blood flow was enhanced in LNNA/HS/indinavir group (p < 0.01) but attenuated (p < 0.05) by insulin. Proteinuria was increased (p < 0.01) in LNNA/HS/indinavir group but attenuated (p < 0.01) by insulin. Insulin-treated rats decreased urine NO (p < 0.01) and urine Na2+ (p < 0.01) compared to other treated animals. In indinavir-treated animals, urine Na2+ was increased by benzamil, an epithelial sodium channel (ENaC) inhibitor (p < 0.01) and hydrochlorothiazide, a sodium/chloride co-transporter (NCC) inhibitor (p < 0.05).

CONCLUSION

GLUT4 exerts a renoprotective role which may be related to increase NO production. The antinatriuretic effects of GLUT4 appear to be due to enhancement of ion transport activity of ENaC and NCC at the renal tubules (Fig. 9, Ref. 34).

Interactions between (+)-catechin and quercetin during their oxidation by nitrite under the conditions simulating the stomach

When foods that contain catechins and quercetin glycosides are ingested, quercetin glycosides are hydrolyzed to quercetin during mastication by hydrolytic enzymes derived from oral bacteria and the generated quercetin aglycone is mixed with catechins in saliva. The present study deals with the interactions between (+)-catechin and quercetin during their reactions with nitrous acid under the conditions simulating the gastric lumen. Nitrous acid reacted with (+)-catechin producing 6,8-dinitrosocatechin, and quercetin partially suppressed the dinitrosocatechin formation. Nitric oxide, which was produced by not only (+)-catechin/nitrous acid but also quercetin/nitrous acid systems, was used to produce 6,8-dinitrosocatechin. Furthermore, 6,8-dinitrosocatechin was oxidized by nitrous acid to the quinone form. The quinone formation was significantly suppressed by quercetin. Quercetin-dependent suppression of the above reactions accompanied the oxidation of quercetin, which was observed with the formation of 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone. Taking the above results into account, we proposed a possible mechanism of 6,8-dinitrosocatechin formation and discuss the importance of quercetin to prevent the quinone formation from 6,8-dinitrosocatechin in the gastric lumen, taking the interactions between quercetin and catechins into account.

[Hepatoprotective effects of extracts and polysaccharides from seaweed]

Antioxidants of natural origin are considered as possible agents for prevention and treatment of liver diseases. Marine algae and in particular their extracts and obtained from them sulfated polysaccharides are significant sources of natural antioxidants. The recent data on the effect of the extracts and sulfated polysaccharides of seaweed on the functional activity of the liver with injuries induced by CCl4, some drugs (paracetamol, diclofenac), N-nitrosocompounds, aflatoxin are presented in the review. Particular attention is paid to the effect of sulfated polysaccharides and in particular fucoidans on the functional activity of the liver in patients with chronic viral hepatitis C. Fucoidan is highly safe and active not only as an antioxidant but also as an inhibitor of HCV replication, has antiinflammatory and immunomodulating effects. The data of the review allow to conclude that seaweed extracts and sulfated polysaccharides may be a basis for development of new generation drugs in the future for the treatment and prevention of liver diseases.

Decoupling of ammonium regulation and ntcA transcription in the diazotrophic marine cyanobacterium Trichodesmium sp. IMS101

Nitrogen (N) physiology in the marine cyanobacterium Trichodesmium IMS101 was studied along with transcript accumulation of the N-regulatory gene ntcA and of two of its target genes: napA (nitrate assimilation) and nifH (N(2) fixation). N(2) fixation was impaired in the presence of nitrite, nitrate and urea. Strain IMS101 was capable of growth on these combined N sources at <2 μM but growth rates declined at elevated concentrations. Assimilation of nitrate and urea was impaired in the presence of ammonium. Whereas ecologically relevant N concentrations (2-20 μM) suppressed growth and assimilation, much higher concentrations were required to affect transcript levels. Transcripts of nifH accumulated under nitrogen-fixing conditions; these transcript levels were maintained in the presence of nitrate (100 μM) and ammonium (20 μM). However, nifH transcript levels were below detection at ammonium concentrations >20 μM. napA mRNA was found at low levels in both N(2)-fixing and ammonium-utilizing filaments, and it accumulated in filaments grown with nitrate. The positive effect of nitrate on napA transcription was abolished by ammonium additions of >200 μM. This effect was restored upon addition of the glutamine synthetase inhibitor L-methionin-DL-sulfoximine. Surprisingly, ntcA transcript levels remained high in the presence of ammonium, even at elevated concentrations. These findings indicate that ammonium repression is decoupled from transcriptional activation of ntcA in Trichodesmium IMS101.

[Study on semi-synthetic transforming technology for the natural product of isocorydione]

Transforming technology for semi-synthesized isocorydione from the natural product ofisocorydine was studied. The factors affecting on the reaction yield were investigated. UV spectrophotometry was used to indicate the semi-synthesized yield of isocorydione. The optimum reaction conditions were determined as following: reacting for 12 h in the solution of sodium dihydrogen phosphate at pH 10, the temperature was 25 degrees C and the ratio of isocorydine to Fremy's radical was 1 : 2. Under the optimum conditions, the yield could reach up to 50.0%. The molecular structure of isocorydione was elucidated by X-ray single-crystal diffraction analysis for the first time.

Nitric oxide blocks cellular heme insertion into a broad range of heme proteins

Although the insertion of heme into proteins enables their function in bioenergetics, metabolism, and signaling, the mechanisms and regulation of this process are not fully understood. We developed a means to study cellular heme insertion into apo-protein targets over a 3-h period and then investigated how nitric oxide (NO) released from a chemical donor (NOC-18) might influence heme (protoporphyrin IX) insertion into seven targets that present a range of protein structures, heme ligation states, and functions (three NO synthases, two cytochrome P450's, catalase, and hemoglobin). NO blocked cellular heme insertion into all seven apo-protein targets. The inhibition occurred at relatively low (nM/min) fluxes of NO, was reversible, and did not involve changes in intracellular heme levels, activation of guanylate cyclase, or inhibition of mitochondrial ATP production. These aspects and the range of protein targets suggest that NO can act as a global inhibitor of heme insertion, possibly by inhibiting a common step in the process.

[The effect of nitric oxide on the proliferation and ALP activity of human dental pulp cells in vitro]

PURPOSE

To study the effect of nitric oxide on the biological characteristic of human dental pulp cells.

METHODS

The dental pulp cells were cultured with nitric oxide at different concentration of nitric oxide (10 micromol/L, 50 micromol/L, 100 micromol/L) by tissue explant. The effect of nitric oxide were studied with MTT assay and ALPase immunoassay. The data were statistically analyzed with SPSS13.0 software package.

RESULTS

NOC-18 suppressed the proliferation of pulp cells in a concentration-dependent manner.The pulp cells showed higher ALP activity and NOC-18 promoted the ALP activity in a concentration-dependent manner when cultured in mineralization-promoting medium.While NOC-18 did not affect the ALP activity of cells in the normal medium.

CONCLUSION

It is suggested that there is a significant effect of nitric oxide on dental pulp cells proliferation and ALP activity.

Cerebrospinal fluid, serum and plasma protein oxidation in Alzheimer's disease

OBJECTIVES

Many studies have shown differences in carbonylation and nitration of individual proteins in brain and body fluids of Alzheimer's disease (AD) patients. Therefore, we wanted to examine whether total levels of these oxidative stress markers of proteins were altered in AD.

PATIENTS AND METHODS

Total levels of carbonyls and nitrotyrosine in cerebrospinal fluid, serum and plasma were measured in 22 AD patients and 18 age-matched controls using commercially available enzyme immunoassay kits.

RESULTS

Protein carbonylation in cerebrospinal fluid did not differ between AD patients and controls but was decreased in APOE epsilon4 carriers as compared with non-carriers. Serum but not plasma levels of carbonyls tended to be decreased in AD patients as compared with aged controls. Nitrotyrosine concentrations did not differ between the groups. Surrogate cerebrospinal fluid markers for AD, beta-amyloid (1-42) and tau, correlated with blood carbonyl and nitrotyrosine levels.

CONCLUSIONS

According to these preliminary data, changes in oxidative metabolism related to the pathogenesis of AD cannot be detected as increased cerebrospinal fluid, serum or plasma protein carbonylation or nitration.

Unbiased identification of cysteine S-nitrosylation sites on proteins

Covalent addition of nitric oxide (NO) to Cys-sulfur in proteins, or S-nitrosylation, plays pervasive roles in the physiological and pathophysiological modulation of mammalian protein functions. Knowledge of the specific protein Cys residues that undergo NO addition in different biological settings is fundamental to understanding NO-mediated signal transduction. Here, we describe in detail an MS-based proteomic protocol for facile, high-throughput and unbiased discovery of SNO-Cys residues in proteins from complex biological samples. The approach, termed SNOSID (SNO-Cys site identification), can be used to identify endogenous and chemically induced S-nitrosylation sites in proteins from tissues or cells. Identified SNO-Cys sites may provide insights into novel mechanisms and proteins that mediate NO bioactivities in health and disease. SNOSID builds on the biotin-switch method for covalent addition of disulfide-linked biotin at S-nitrosylation sites on proteins. Biotinylated proteins are then subjected to trypsinolysis and the resulting biotin-tagged peptides are affinity-captured on streptavidin-agarose. After selective elution with beta-mercaptoethanol, the peptides are sequenced using nanoflow liquid chromatography tandem mass spectrometry (nLC-MS/MS). Validation that identified peptide ions as originating from authentic NO-Cys-containing precursor proteins can be provided by establishing that these peptide ions are absent from control samples where S-NO bonds were subjected to prior photolysis, using a UV transilluminator. The protocol requires approximately 2 days for sample processing, including the incubation time for proteolysis. An additional 1-2 days is needed for sample analysis by nLC-MS/MS and data analysis/interpretation.

S-nitrosylation of microtubule-associated protein 1B mediates nitric-oxide-induced axon retraction

Treatment of cultured vertebrate neurons with nitric oxide leads to growth-cone collapse, axon retraction and the reconfiguration of axonal microtubules. We show that the light chain of microtubule-associated protein (MAP) 1B is a substrate for S-nitrosylation in vivo, in cultured cells and in vitro. S-nitrosylation occurs at Cys 2457 in the COOH terminus. Nitrosylation of MAP1B leads to enhanced interaction with microtubules and correlates with the inhibition of neuroblastoma cell differentiation. We further show, in dorsal root ganglion neurons, that MAP1B is necessary for neuronal nitric oxide synthase control of growth-cone size, growth-cone collapse and axon retraction. These results reveal an S-nitrosylation-dependent signal-transduction pathway that is involved in regulation of the axonal cytoskeleton and identify MAP1B as a major component of this pathway. We propose that MAP1B acts by inhibiting a microtubule- and dynein-based mechanism that normally prevents axon retraction.

Substrate radical intermediates in soluble methane monooxygenase

EPR spin-trapping experiments were carried out using the three-component soluble methane monooxygenase (MMO). Spin-traps 5,5-dimethyl-1-pyrroline N-oxide (DMPO), alpha-4-pyridyl-1-oxide N-tert-butylnitrone (POBN), and nitrosobenzene (NOB) were used to investigate the possible formation of substrate radical intermediates during catalysis. In contrast to a previous report, the NADH-coupled oxidations of various substrates did not produce any trapped radical species when DMPO or POBN was present. However, radicals were detected by these traps when only the MMO reductase component and NADH were present. DMPO and POBN were found to be weak inhibitors of the MMO reaction. In contrast, NOB is a strong inhibitor for the MMO-catalyzed nitrobenzene oxidation reaction. When NOB was used as a spin-trap in the complete MMO system with or without substrate, EPR signals from an NOB radical were detected. We propose that a molecule of NOB acts simultaneously as a substrate and a spin-trap for MMO, yielding the long-lived radical and supporting a stepwise mechanism for MMO.

Role of thiamine thiol form in nitric oxide metabolism

In alkaline media the thiamine cyclic form is converted into a thiol form (pK(a) 9.2) with an opened thiazole ring. The thiamine thiol form releases nitric oxide from S-nitrosoglutathione (GSNO). Thiamine disulfide, mixed thiamine disulfide with glutathione, and nitric oxide are produced in the reaction. Free glutathione was recorded in small amounts. The concentration of formed nitric oxide agreed well with the concentration of degraded GSNO. The concentration of released nitric oxide was determined under anaerobic conditions spectrophotometrically by production of nitrosohemoglobin. In air, the release of nitric oxide was recorded by the production of nitrite or the oxidation of oxyhemoglobin to methemoglobin. The concentration of the thiol form in the body under physiological pH values (7.2-7.4) did not exceed 1.5-2.0%. We believe that due to the exchange reactions between the thiamine thiol form and S-nitrosocysteine protein residues, nitric oxide can be released and mixed thiamine-protein disulfides are formed. The mixed thiamine disulfides (including thiamine ester disulfides) as well as the thiamine disulfide form are quite easily reduced by low molecular weight thiols to form the thiamine cyclic form with a closed thiazole ring. A possible role of the thiamine thiol form in releasing deposited nitric oxide from low-molecular-weight S-nitrosothiols and protein S-nitrosothiols and in regulation of blood flow in the vascular bed is discussed.

S-nitrosothiol and S-nitrosoalbumin levels in pre-eclampsia plasma

The aetiology of pre-eclampsia still eludes researchers. Recently, the development of laboratory techniques to measure the levels of serum nitrosothiols, compounds that appear to play a role in signal transduction and stress responses, could be the driving force in the search for the exact cause of pre-eclampsia. We attempted to verify a new technique of estimating the levels of S-nitrosothiols and S-nitrosoalbumin in pre-eclampsia. The laboratory technique used as described previously could not identify these compounds. None the less, these nitrosothiols and nitrosoalbumin may be involved in the aetiology of pre-eclampsia.

Production of NA by endothelial NO-synthase: An in vitro versus in vivo study

Endothelial-derived relaxing factor (EDRF) is secreted by different endothelia in vivo. It is synthesised by endothelial NO-synthase (eNOS). Despite numerous works, its identity is not fully understood. Here the production of NA, a nitroso-arginine, which was shown to be synthesised by brain NO-synthase (bNOS), was studied in eNOS preparations. NA was quantified by reductive differential pulse voltammetry (RDPV) during its irreversible electrochemical transformation to N-hydroxy-arginine (NHA). Using microelectrodes, NA and nitrite were simultaneously measured in pure recombinant eNOS giving similar enzyme activity. NA was detected at the surface of human endothelial cells (HUVEC) and disappeared when D-arginine was introduced in the culture medium. NA production by endothelium tissue was studied in rat corpus cavernosum using voltammetric microelectrodes. NA concentration at the endothelium surface was linked to vasodilatation measured by laser Doppler induced by acetylcholine injection. LNMA ic injection induced NA disappearance. These preliminary new experiments suggested that NA could be the endogenous nitroso-compound presented early as EDRF.

Determination of diethanolamine in shampoo products containing fatty acid diethanolamides by liquid chromatography with a thermal energy analyzer

A liquid chromatography (LC) method using a thermal energy analyzer (TEA) is described for the determination of diethanolamine (DEA) in shampoo products containing fatty acid diethanolamides. DEA was converted to N-nitrosodiethanolamine (NDELA) by dissolving a portion of the product in 6M acetic acid and mixing with sodium nitrite for 1 h at room temperature. The reaction mixture was dried, dissolved in acetone, and analyzed for NDELA by LC-TEA. The recovery of DEA from 2 shampoo products at fortification levels of 25, 250, and 1000 ppm ranged from 70 to 105%. Twenty shampoo products were analyzed by this method, and 19 were found to contain DEA at levels ranging from 140 to 15 200 ppm.

S-nitrosoalbumin-mediated relaxation is enhanced by ascorbate and copper: effects in pregnancy and preeclampsia plasma

S-nitrosoalbumin (SNO-Alb) is a major reservoir of releasable nitric oxide (NO) in plasma. In preeclampsia, a pregnancy-specific disorder associated with endothelial dysfunction, we previously found significant elevations in plasma SNO-Alb concentrations and decreased plasma ascorbate (Asc) levels. This increased SNO-Alb may result from low-plasma Asc if Asc, along with transition metals (eg, copper [Cu]) are necessary for release of NO from S-nitrosothiols. We propose that vasodilator effects of SNO-Alb, mediated by release of NO, are fully realized only when Asc/Cu availability is sufficient. Relaxation responses to SNO-Alb or the control reduced human serum albumin (SH-Alb), and responses to pooled plasma from normal or preeclamptic pregnancies were examined in isolated mouse arteries. Arteries preconstricted with phenylephrine were exposed to SNO-Alb or SH-Alb at physiologically relevant concentrations. When free Cu was added in excess (10 mumol/L), NO release was not dependent on Asc. However, when Cu was added at lower (physiological) levels, NO release was dependent on Asc. The addition of Asc and Cu to SNO-Alb stimulated vasodilatory responses in isolated arteries >90%, whereas no change in the SH-Alb (5%) response was observed. Preeclampsia plasma with higher levels of SNO-Alb caused arteries to relax 44.1+/-4.7%, whereas normal pregnancy plasma caused 11.9+/-4.2% relaxation (P=0.007). These data indicate that SNO-Alb alone or in plasma can act as a potent vasodilator, and that sufficient Asc/Cu promotes this action. We suggest that the higher circulating levels of SNO-Alb, in women with preeclampsia, reflect a deficiency in Asc/Cu-mediated release of NO from SNO-Alb.

The attenuation of hepatic microcirculatory alterations by exogenous substitution of nitric oxide by s-nitroso-human albumin after hemorrhagic shock in the rat

Hepatic microcirculatory disorders such as narrowing of sinusoids after hemorrhagic shock play a major role in the pathogenesis of organ failure. It is known that the balance of vasoactive mediators such as endothelin and nitric oxide (NO) regulate microvascular perfusion, including the diameter of hepatic sinusoids. The present study was designed to evaluate the role of exogenous substitution of NO by S-nitroso-albumin (S-NO-HSA) in the prevention of pathophysiological alterations of hepatic microcirculation. Anesthetized Sprague-Dawley rats were instrumented for invasive hemodynamic monitoring. Hemorrhagic shock was induced by bleeding to a mean arterial pressure (MAP) of 40 mmHg and was maintained for 60 min. Thereafter, the animals were resuscitated with shed blood and Ringer's solution. During the first hour of resuscitation, S-NO-HSA or pure HSA was infused continuously (10 micromol/kg/h) and hepatic microcirculation was detected by intravital epifluorescence microscopy either 5 or 24 h after the insult. Results were compared with a sham-treated group (n = 6-8 per group). Shock-induced microcirculatory narrowing of sinusoids was significantly reduced in the S-NO-HSA group compared with the HSA group both at 5 and 24 h (HSA: 9.3 +/- 0.2 microm; S-NO-HSA: 12.1 +/- 0.2 microm, P < 0.05). Sinusoidal perfusion was significantly higher in the S-NO-HSA group than in the HSA group (HSA: 50,934 +/- 1,382 microm3/s; S-NO-HSA: 78,120 +/- 2,348 microm3/s, P < 0.05). Reversible leukocyte adhesion to sinusoidal endothelium, an indicator of the inflammatory response, was significantly reduced in the S-NO-HAS-treated group. The findings of this study in a rat model of hemorrhagic shock suggest that NO substitution by S-NO-HSA during resuscitation attenuates both early and late hepatic microcirculatory disturbances as well as the increase in leukocyte adherence.

S-Nitroso Human Serum Albumin Improves Oxygen Metabolism during Reperfusion after Severe Myocardial Ischemia

Nitric oxide (NO) supplementation may modify myocardial oxygen consumption and vascular function after ischemia. We investigated the effects of the NO donor, S-nitroso human serum albumin (S-NO-HSA), on cardiac oxygen metabolism during controlled reperfusion on normothermic cardiopulmonary bypass after severe myocardial ischemia. Pigs randomly received either S-NO-HSA or human serum albumin prior to and throughout global myocardial ischemia. Myocardial oxygen utilization is impaired at the onset of reperfusion, which is not amenable to S-NO-HSA. However, NO supplementation during ongoing supply dependency of oxygen consumption eventually leads to greater myocardial oxygen delivery and consumption. In conjunction with a better washout of lactate, this indicates an improved capillary perfusion in the S-NO-HSA group during reperfusion, which results in a better contractile function post bypass.

Protective effect of keishi-bukuryo-gan and its constituent medicinal plants against nitric oxide donor-induced neuronal death in cultured cerebellar granule cells

Keishi-bukuryo-gan (Gui-Zhi-Fu-Ling-Wan) (KBG) is a traditional Chinese/Japanese medical (Kampo) formulation that has been administered to patients with "Oketsu" (blood stagnation) syndrome. In the process of neuronal cell death induced by brain ischemia, excessive generation of nitric oxide (NO) free radicals is implicated in the neurotoxicity. In the present study, we examined the protective effects of KBG and its constituent medicinal plants against NO donors, sodium nitroprusside (SNP) and 2,2'-(hydroxynitrosohydrazino)bis-ethanamine (NOC18)-induced neuronal death in cultured rat cerebellar granule cells (CGCs). MTT assay showed cell viability to be significantly increased by the addition of KBG extract (KBGE) (100 microg/ml), Cinnamomi Cortex extract (CCE) (3, 10 and 30 microg/ml), Paeoniae Radix extract (PRE) (100 microg/ml) and Moutan Cortex extract (MCE) (10 and 30 microg/ml) compared with exposure to SNP (30 microM, 24 h) only. Also, cell viability was significantly increased by the addition of KBGE (100 and 300 microg/ml), CCE (30 and 100 microg/ml), PRE (100 and 300 microg/ml) and MCE (30 and 100 microg/ml) compared with exposure to NOC 18 (100 microM, 48 h) only. Persicae Semen extract and Hoelen extract did not protect against NO donor-induced neuronal death. These results suggest that KBG has protective effect against NO-mediated neuronal death in cultured CGCs and that it is derived from Cinnamomi Cortex, Paeoniae Radix and Moutan Cortex.

Febrigenic signaling to the brain does not involve nitric oxide

1. The involvement of peripheral nitric oxide (NO) in febrigenic signaling to the brain has been proposed because peripherally administered NO synthase (NOS) inhibitors attenuate lipopolysaccharide (LPS)-induced fever in rodents. However, how the unstable molecule of NO can reach the brain to trigger fever is unclear. It is also unclear whether NOS inhibitors attenuate fever by blocking febrigenic signaling or, alternatively, by suppressing thermogenesis in brown fat. 2. Male Wistar rats were chronically implanted with jugular catheters; their colonic and tail skin temperatures (T(c) and T(sk)) were monitored. 3. Study 1 was designed to determine whether the relatively stable, physiologically relevant forms of NO, that is, S-nitrosoalbumin (SNA) and S-nitrosoglutathione (SNG), are pyrogenic and whether they enhance LPS fever. At a neutral ambient temperature (T(a)) of 31 degrees C, afebrile or LPS (1 microg kg(-1), i.v.)-treated rats were infused i.v. with SNA (0.34 or 4.1 micromol kg(-1); the controls received NaNO(2) and albumin) or SNG (10 or 60 micromol kg(-1); the controls received glutathione). T(c) of SNA- or SNG-treated rats never exceeded that of the controls. 4. In Study 2, we tested whether the known fever-attenuating effect of the NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) at a subneutral T(a) (when fever is brought about by thermogenesis) also occurs at a neutral T(a) (when fever is brought about by skin vasoconstriction). At a subneutral T(a) of 24 degrees C, L-NAME (2.5 mg kg(-1), i.v.) attenuated LPS (10 microg kg(-1), i.v.) fever, presumably by inhibiting thermogenesis. At 31 degrees C, L-NAME enhanced LPS fever by augmenting skin vasoconstriction (T(sk) fall). 5. In summary, both SNA and SNG had no pyrogenic effect of their own and failed to enhance LPS fever; peripheral L-NAME attenuated only fever brought about by increased thermogenesis. It is concluded that NO is uninvolved in febrigenic signaling to the brain.

Enhanced S -Nitroso-Albumin Formation From Inhaled NO During Ischemia/Reperfusion

In the present study, we investigated whether inhaled nitric oxide (NO) was transported by plasma proteins, such as S -nitroso-albumin (SNO-Alb), in the feline circulation and whether this molecule delivers NO to the periphery under conditions of stress, specifically ischemia/reperfusion (I/R). A flow probe was interposed between the femoral and superior mesenteric artery for blood flow measurements, and a branch of the superior mesenteric vein was cannulated for arterial-venous sampling. In animals breathing room air, SNO-Alb was below detection level in arterial or venous blood. NO inhalation resulted in a significant arterial-venous gradient for SNO-Alb. Concomitant with this loss of SNO-Alb across the intestinal vasculature was an increase in nitrite (NO 2 − ). However, this release of NO was not sufficient to alter intestinal blood flow. I/R during NO inhalation caused a very large increase in arterial SNO-Alb that permitted a 5-fold increase in SNO-Alb consumption and significant generation of NO 2 − within the postischemic intestinal vasculature. The increased SNO-Alb consumption was sufficient to dramatically improve intestinal blood flow. The very large burst of arterial SNO-Alb during I/R was completely blocked by the administration of superoxide dismutase, suggesting that oxidative stress contributed to the increased SNO-Alb formation. Our data suggest that inhaled NO can increase nitrosothiol production and these molecules may be a functional NO delivery system during cardiovascular disease.

Rapid S-nitrosothiol metabolism by platelets and megakaryocytes

RSNOs (S-nitrosothiols) regulate platelet and megakaryocyte function, and may act in vivo as a nitric oxide reservoir. There is a discrepancy between the spontaneous rate of NO release from different RSNO compounds and their pharmacological effects, implying that target cells may mediate biological activity either by metabolism of RSNOs or by displaying cell surface receptors. In the present study, we sought evidence for rapid cell-mediated metabolism of RSNOs. Exposure of platelets to GSNO (S-nitrosoglutathione) for as little as 5 s inhibited thrombin-induced platelet aggregation by >95%; however, AlbSNO (S-nitrosoalbumin) was much less effective over these short time periods. Incubation of 1 μM GSNO or AlbSNO with platelets and megakaryocytes resulted in a 25–34% loss of RSNO recoverable from the supernatant (P<0.02) within 30 s. This rapid cell-mediated RSNO decay did not progress further over 5 min, and could not be accounted for by release of free NO. The γ-glutamyl transpeptidase inhibitor acivicin (100 μM) partially decreased GSNO decay, whereas the membrane-impermeable thiol-blocking agent 5,5´-dithiobis-(2-nitrobenzoic acid) (100 μM) completely blocked cell-mediated GSNO decay and partially blocked AlbSNO decay. Our results highlight differences between high- and low-molecular-mass RSNOs with regard to their rapid metabolism/uptake and subsequent cellular responses, and indicate a critical role for extracellular thiols in RSNO metabolism by platelets and megakaryocytes.

Nitric-oxide-induced Bax integration into the mitochondrial membrane commits MDA-MB-468 cells to apoptosis: essential role of Akt

We have previously reported that nitric oxide (NO) induces apoptosis in MDA-MB-468 cells through its action on the mitochondria and the release of cytochrome c. In this study, we investigated the critical events that must occur after which these cells are committed to apoptosis. We used the long-acting NO donor DETA-NONOate, which, at a concentration of 1 mM, releases NO in the range produced by activated macrophages. Depolarization of mitochondrial membrane potential (MMP) occurred at 4 h of DETA-NONOate treatment, which returned to control values and which was followed by another wave of depolarization at 24 h. There was a 2-fold increase of cytochrome c in the cytosol at 6 h, but it was not until 36 h that the level of cytochrome c was increased by 15-fold. Although the initial release of cytochrome c from the mitochondria could be inhibited by cyclosporin A or by bongkrekic acid, the later release continued even in its presence. We observed that the later release of cytochrome c at 36 h was independent of MMP depolarization but was dependent on Bax integration into the mitochondrial membrane, which committed the cells to apoptosis. We also observed a decline in the levels of cytosolic phospho-Akt at 16-24 h of DETA-NONOate treatment. We also conclude that decrease in phospho-Akt is an essential event upstream from Bax integration in MDA-MB-468 cells.

Modulation of NA-synthase activity in rat cortex using NA measurement with ultramicro carbon electrode following topical applications of pharmacological agents

The aim of the study was to document NA, the active product of brain NA-synthase known as NO-synthase in rat cortex. NA measurements in brain extracellular fluid were performed using an ultramicro carbon electrode (0.5-2 microm) with differential pulse voltammetry. The ultramicro carbon electrode was inserted at a fixed depth (125 microm) into the frontal cortex. A constant level of neuronal NA (0.66 mM) was found in rat cortex during a few hours in the basal state. Topical applications of competitive inhibitors of brain NO-synthase (L-NNA, L-NMA, D-arginine, 1 mg ml(-1)) and a NO-donor (SNAP, 1 mg ml(-1)) resulted in a complete disappearance of NA. Simultaneous in vivo measurements of L-NNA, an electroactive inhibitor (-1.2 V vs. Ag/AgCl), and NA (-1.66 V vs. Ag/AgCl) allowed the following of the diffusion of this neuronal specific inhibitor and the simultaneous inhibition of NA synthesis. Topical addition of acetylcholine (10 microM) produced a NA increase, while bradykinin, adenosine, and hydrogen peroxide (10 microM each) resulted in the disappearance of NA. Topical addition of radical oxygen species (ROS) scavengers (oxy-hemoglobin, methylen blue, ascorbic acid and cystein, l mg ml(-1)) had no influence on NA concentrations which remained at a constant level in brain cortex. These preliminary results indicated that NA is continuously produced at a high level by neurons. Acetylcholine and vasodilatators modulated neuronal NA synthesis after topical application, but ROS had no effect.

Effects of nitric oxide on red blood cell deformability

In addition to its known action on vascular smooth muscle, nitric oxide (NO) has been suggested to have cardiovascular effects via regulation of red blood cell (RBC) deformability. The present study was designed to further explore this possibility. Human RBCs in autologous plasma were incubated for 1 h with NO synthase (NOS) inhibitors [N(omega)-nitro-l-arginine methyl ester (l-NAME) and S-methylisothiourea], NO donors [sodium nitroprusside (SNP) and diethylenetriamine (DETA)-NONOate], an NO precursor (l-arginine), soluble guanylate cyclase inhibitors (1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one and methylene blue), and a potassium channel blocker [triethylammonium (TEA)]. After incubation, RBC deformability at various shear stresses was determined by ektacytometry. Both NOS inhibitors significantly reduced RBC deformability above a threshold concentration, whereas the NO donors increased deformability at optimal concentrations. NO donors, as well as the NO precursor l-arginine and the potassium blocker TEA, were able to reverse the effects of NOS inhibitors. Guanylate cyclase inhibition reduced RBC deformation, with both SNP and DETA-NONOate able to reverse this effect. These results thus indicate the importance of NO as a determinant of RBC mechanical behavior and suggest its regulatory role for normal RBC deformability.

FGF-2, NGF and IGF-1, but not BDNF, utilize a nitric oxide pathway to signal neurotrophic and neuroprotective effects against alcohol toxicity in cerebellar granule cell cultures

Neuronal death is a prominent neuropathological component of fetal alcohol syndrome (FAS). Identification of molecular agents and pathways that can ameliorate alcohol-induced cell loss offers possible therapeutic strategies for FAS and potential insight into its pathogenesis. This study investigated the effects of growth factors on cellular survival in alcohol-exposed cerebellar granule cell (CGC) cultures and examined the role of the nitric oxide (NO)-cGMP-PKG (cGMP-dependent protein kinase) pathway in the cell survival-promoting effects of these growth factors. Primary CGC cultures were exposed to 0 or 400 mg/dl ethanol, accompanied by either no growth factor or 30 ng/ml fibroblast growth factor-2 (FGF-2), nerve growth factor (NGF), insulin-like growth factor-1 (IGF-1), brain-derived neurotrophic factor (BDNF) or epidermal growth factor (EGF). Viable neurons were quantified after 1 day of exposure. Two distinct types of cell survival-promoting effects of growth factors were detectable: (1) a neurotrophic effect, in which the growth factors diminished the background death of neurons that occurred in alcohol-free cultures; and (2) a neuroprotective effect, in which the growth factors diminished alcohol-induced cell death. The various growth factors differed markedly in their patterns of cell survival promotion. While BDNF and FGF-2 exerted both a neurotrophic and a neuroprotective effect, IGF-1 had only a neurotrophic effect and did not protect against alcohol toxicity, and NGF had only a neuroprotective effect and did not diminish background cell death. EGF had neither a neurotrophic nor a neuroprotective effect. In order to determine the role of the NO-cGMP-PKG pathway in the cell survival-promoting effects mediated by growth factors, cultures were exposed to one of several pharmacological inhibitors of the pathway, including NAME, LY83583 and PKG inhibitor. The cell survival-promoting effects of FGF-2, NGF and IGF-1 were all substantially reduced by each of the pathway inhibitors. In contrast, neither the neurotrophic nor the neuroprotective effects of BDNF were altered by any of the pathway inhibitors. Thus, growth factors differ in their patterns of neurotrophic and neuroprotective effects, and they differ in their reliance on the NO-cGMP-PKG pathway. While FGF-2, NGF and IGF-1 all signal their survival-promoting effects through the NO-cGMP-PKG pathway, BDNF does not rely upon this pathway for signal transduction in CGC cultures.

Protective effect of a novel NO-donor on ischemia/reperfusion injury in a rat epigastric flap model

An altered metabolism of endothelial cell-derived nitric oxide has been implicated in the microvascular dysfunction associated with ischemia/reperfusion. The objective of this study was to examine whether S-nitroso human serum albumin, a novel nitric oxide-donor, improves flap viability and whether it influences edema formation after prolonged ischemia when administered prior to and in the initial phase of reperfusion. Denervated epigastric island skin flaps were elevated in 30 male Sprague Dawley rats, rendered ischemic for 8 hours, subsequently reperfused and further observed for either 3 hours (acute) or 7 days (chronic). In the sham rats (n = 6), skin flaps were elevated only. Starting 1 hour prior to reperfusion, S-nitroso human serum albumin (n = 12) or human serum albumin (n = 12) as placebo was infused systemically for 2 hours. In the chronic model, flap necrosis as well as viable flap size was evaluated after 7 days of reperfusion in six rats per group, comparing to sham rats. In the acute model, edema formation was evaluated after 3 hours of reperfusion in six rats per group. Administration of S-nitroso human serum albumin significantly decreased flap necrosis from 18.1 +/- 15.6% in the human serum albumin group to 2.1 +/- 1.5% in the S-nitroso human serum albumin group, which was similar to the sham group (2.5 +/- 4.2%). Viable flap size (sham 13.4 +/- 1.6 cm2) was also significantly improved in the S-nitroso human serum albumin group (10.1 +/- 1 cm2) versus the human serum albumin group (7.0 +/- 2.2 cm2). There was no significant difference between the groups regarding postischemic edema formation. These results show that administration of S-nitroso human serum albumin prior to and in the initial phase of reperfusion significantly improves flap viability after 7 days but does not influence early observable edema formation. These findings support the role of nitric oxide as an important mediator in the protection against skin flap ischemia/reperfusion injury.

Activity and expression of nitric oxide synthase in the hypertrophied rat bladder and the effect of nitric oxide on bladder smooth muscle growth

PURPOSE

We investigated the expression and activity of nitric oxide synthase (NOS) and the localization of cyclic guanosine monophosphate (cGMP) in hypertrophied rat bladder. We also examined whether nitric oxide (NO) has a growth inhibitory effect in bladder smooth muscle cells.

MATERIALS AND METHODS

The urethra was partly ligated and the bladder was removed 3 days, 3 or 6 weeks after obstruction. NOS activity was determined as the conversion of L-[14C]citrulline from L-[14C]arginine (Amersham Life Science, Solna, Sweden). Neuronal NOS (nNOS) expression was studied with Western blot analysis and immunohistochemistry. The expression of inducible NOS (iNOS) and cGMP was evaluated by immunohistochemistry. The effect of NO on isolated bladder smooth muscle cell growth was assessed as protein and DNA synthesis by [3H]-leucine and [3H]-thymidine (NEN Life Science Products, Zaventem, Belgium) incorporation, respectively.

RESULTS

Ca independent iNOS activity increased after short-term obstruction. Immunohistochemical studies in obstructed bladders demonstrated iNOS expression primarily in urothelial and inflammatory cells. Ca dependent nNOS activity decreased after obstruction, as confirmed by Western blot analysis. The cGMP immunoreactive cells were mainly found within the serosal layer of obstructed bladders. The NO donor DETA-NONOate (Alexis Biochemicals, Lausen, Switzerland) (300 microM.) reduced [3H]-leucine and [ H]-thymidine incorporation by a mean of 29% +/- 2% and 95% +/- 2%, respectively, in cultured bladder smooth muscle cells.

CONCLUSIONS

Bladder obstruction caused a small increase in iNOS activity and a decrease in nNOS activity. NO was found to have a growth inhibitory effect in bladder smooth muscle cells, suggesting that changes in NOS activity may influence the progress of bladder hypertrophy.