Novel effects of nitric oxide

Inhibition of neuronal nitric oxide synthase prevents alterations in medial prefrontal cortex excitability induced by repeated cocaine administration

RATIONALE

The medial prefrontal cortex (mPFC), a forebrain region that regulates cognitive function and reward-motivated behaviors, has been implicated in the neuropathological mechanisms of drug addiction and withdrawal. In cocaine-abstinent human addicts, neuronal activity of the mPFC is increased in response to cocaine re-exposure or drug-associated cues. Additionally, repeated cocaine exposure alters the membrane properties and ion channel function of mPFC pyramidal neurons in drug-withdrawn rats, leading to an increased firing in response to excitatory stimuli. Nitric oxide (NO), a diffusible neuromodulator of neuronal excitability, may play a role in initiating and maintaining behavioral effects of psychostimulants. However, the role of NO in the mechanisms by which cocaine affects membrane excitability is not well clarified.

OBJECTIVES

In this study, we attempted to determine whether inhibition of neuronal nitric oxide synthase (nNOS) altered the changes induced by repeated cocaine exposure and withdrawal.

METHODS

Visualized whole-cell current clamp recordings in brain slices containing the mPFC of rats administered (once per day for 5 days) with either vehicle (10% Cremophor EL in saline 0.9%), cocaine (15 mg/kg, i.p.), or cocaine and the nNOS inhibitor 7-NI (50 mg/kg, i.p.) were employed.

RESULTS

We found that nNOS inhibition prevented cocaine sensitization and the increased membrane excitability of pyramidal cells, evidenced by an increased number of evoked spikes and reductions in inward rectification observed after short-term withdrawal from cocaine.

CONCLUSIONS

These findings suggest that NO plays an important role in chronic cocaine-induced deregulation of the mPFC activity that may contribute to the development of behavioral sensitization and cocaine withdrawal.

Dynamic ligand exchange in soluble guanylyl cyclase (sGC): implications for sGC regulation and desensitization

Accumulating evidence indicates that the functional properties of soluble guanylyl cyclase (sGC) are affected not only by the binding of NO but also by the NO:sGC ratio and a number of cellular factors, including GTP. In this study, we monitored the time-resolved transformations of sGC and sGC-NO complexes generated with stoichiometric or excess NO in the presence and absence of GTP. We demonstrate that the initial five-coordinate sGC-NO complex is highly activated by stoichiometric NO but is unstable and transforms into a five-coordinate sGC-2 state. This sGC-2 rebinds NO to form a low activity sGC-NO complex. The stability of the initial complex is greatly enhanced by GTP binding, binding of an additional NO molecule, or substitution of βHis-107. We propose that the transient nature of the sGC-NO complex, the formation of a desensitized sGC-2 state, and its transformation into a low activity sGC-NO adduct require βHis-107. We conclude that conformational changes leading to sGC desensitization may be prevented by GTP binding to the catalytic site or by binding of an additional NO molecule to the proximal side of the heme. The implications of these observations for cellular NO/cGMP signaling and the process of rapid desensitization of sGC are discussed in the context of the proposed model of sGC/NO interactions and dynamic transformations.

Nitric oxide accumulation in Arabidopsis is independent of NOA1 in the presence of sucrose

Nitric oxide signals diverse responses in animals and plants. Whereas nitric oxide synthesis mechanisms in animals are well understood, how nitric oxide is synthesized and regulated in plants remains controversial. NOA1 is a circularly permuted GTPase that is important for chloroplast function and is implicated in nitric oxide synthesis. However, the reported consequences of a null mutation in NOA1 are inconsistent. Whereas some studies indicate that the noa1 mutant has severe reductions in nitric oxide accumulation, others report that nitric oxide levels are indistinguishable between noa1 and the wild type. Here, we identify a correlation between the reported ability of noa1 to accumulate nitric oxide with growth on sucrose-supplemented media. We report that noa1 accumulates both basal and salicylic acid-induced nitric oxide only when grown on media containing sucrose. In contrast, nitric oxide accumulation in wild type is largely insensitive to sucrose supplementation. When grown in the absence of sucrose, noa1 has low fumarate, pale green leaves, slow growth and reduced chlorophyll content. These phenotypes are consistent with a defect in chloroplast-derived photosynthate production and are largely rescued by sucrose supplementation. We conclude that NOA1 has a primary role in chloroplast function and that its effects on the accumulation of nitric oxide are likely to be indirect.

Ascorbic acid and N-acetyl cysteine prevent uncoupling of nitric oxide synthase and increase tolerance to ischemia/reperfusion injury in diabetic rat heart

Oxidative stress may cause a loss of tetrahydrobiopterin (BH4), a co-factor of nitric oxide synthase (NOS), decrease the bioavailability of NO and aggravate ischemia/reperfusion (I/R) injury in diabetic heart. We hypothesized that ascorbic acid (AA) and N-acetyl cysteine (NAC) protect the diabetic heart from I/R injury by increasing BH4/dihydrobiopterin (BH2) ratio and inhibiting uncoupling of NOS. Diabetes mellitus was induced in rats by streptozotocin treatment, and the hearts were isolated and perfused. BH4 and BH4/BH2 ratio decreased in the diabetic heart associated with increased production of superoxide and nitrotyrosine (NT). Treatment with AA or NAC significantly increased BH4/BH2 ratio in the diabetic heart associated with decreased production of superoxide and NT and increased generation of nitrate plus nitrite (NOx). Pre-treatment with AA or NAC before 30 min ischemia followed by 120 min reperfusion improved left ventricular (LV) function and reduced infarct size in the diabetic but not non-diabetic hearts. The NOS inhibitor, L-NAME, inhibited the increase in the generation of superoxide, NT and NOx, but aggravated LV function and increased infarct size in the diabetic heart. L-NAME also abrogated the increase in NOx and improvement of LV function and the infarct size-limiting effect induced by AA or NAC in the diabetic heart. These results suggest that AA and NAC increase BH4/BH2 ratio and prevent NOS uncoupling in the diabetic heart. Resultant increase in the bioavailability of NO renders the diabetic heart toleratant to I/R injury.

Effects of slow, sustained, and rate-tunable nitric oxide donors on human aortic smooth muscle cells proliferation

Smooth muscle cell (SMC) proliferation has been accepted as a common event in the pathophysiology of vascular diseases, including atherogenesis and intimal hyperplasia. Delivery of the nitric oxide synthase (NOS) substrate l-arginine, pharmacological nitric oxide (NO) donors, NO gas or overexpression of NOS proteins can inhibit SMC proliferation and reduce the injury responses within the blood vessel wall. Although commercial development of NO donors that attempt to provide exogenous delivery of NO has accelerated over the last few years, none of the currently available products can provide controlled, sustained, time-tunable release of NO. Nitrosamine-based NO donors, prepared in our laboratory, present a unique and innovative alternative for possible treatments for long-term NO deficiency-related diseases, including atherosclerosis, asthma, erectile dysfunction, cancer, and neurodegenerative diseases. A family of secondary amines prepared via nucleophilic aromatic displacement reactions could be readily N-nitrosated to produce NO donors. NO release takes place in three distinct phases. During the initial phase, the release rate is extremely fast. In the second phase, the release is slower and the rate remains essentially the same during the final stage. These compounds inhibited up to 35% human aortic smooth muscle cell proliferation in a concentration-dependent manner.

Chronic ethanol consumption induces histopathological changes and increases nitric oxide generation in the rat liver

In the present work we evaluated the effect of ethanol consumption in histopathological liver changes and several biochemical biomarkers employed in the detection of hepatic dysfunction. Male Wistar rats were treated with ethanol 20% (vol/vol) for 6 weeks. Histopathological investigation of livers from ethanol-treated animals revealed steatosis. Indices of hepatic function (transaminases) and mitochondrial respiration were not altered in ethanol-treated rats. Chronic ethanol consumption did not alter malondialdehyde (MDA) levels in the liver. Ethanol consumption induced a significant increase on hepatic nitrite and nitrate levels. Treatment with ethanol increased both mRNA expression and immunostaining of iNOS, but not eNOS. Finally, ethanol consumption did not alter hepatic levels of metalloproteinase (MMP)-2 and MMP-9. We conclude that alterations on biochemical biomarkers (nitrite and nitrate levels) and histopathology occurred in ethanol-treated rats, supporting the practice of including both types of evaluation in toxicity studies to detect potential ethanol-related hepatic effects. In our model of ethanol consumption, histopathological liver changes were accompanied by elevation in nitrite and nitrate levels indicating increased nitric oxide (NO) generation. Since iNOS-derived NO contributes to hepatic injury, the increased levels of NO described in our study might contribute to a progressive hepatic damage. Therefore, increases in NO generation may be an early indicator of ethanol-induced liver damage.

Generation of guanine-thymidine cross-links in DNA by peroxynitrite/carbon dioxide

Nitrosoperoxycarbonate derived from the combination of carbon dioxide and peroxynitrite is an important chemical mediator of inflammation. In aqueous solutions, it rapidly decomposes to the reactive species CO(3)(•-) and (•)NO(2) radicals that are known to initiate the selective oxidation and nitration of guanine in DNA. We have previously demonstrated that the reactions of carbonate radical anions with guanine in 2'-deoxyoligoribonucleotides generate a previously unknown intrastrand cross-linked guanine-thymine product G*-T* with a covalent bond between the C8 (G*) and the thymine N3 (T*) atoms (Crean Nucleic Acids Res. 2008, 36, 742-755). In this work, we demonstrate that G*-T* cross-linked products are also formed when peroxynitrite (0.1 mM) reacts with native DNA in aqueous solutions (pH 7.5-7.7) containing 25 mM carbon dioxide/bicarbonate, in addition to the well-known nitration/oxidation products of guanine such as 8-nitroguanine (8-nitro-G), 5-guanidino-4-nitroimidazole (NIm), 8-oxo-7,8-dehydroguanine (8-oxo-G), and spiroiminodihydantoin (Sp). The yields of these products, after enzymatic digestion with P1 nuclease and alkaline phosphatase to the nucleotide level and reversed phase HPLC separation, were compared with those obtained with the uniformly, isotopically labeled (15)N,(13)C-labeled 2'-deoxy oligoribonucleotides 5'-dGpT and 5'-dGpCpT. The d(G*pT*) and d(G*-T*) cross-linked products derived from the di- and trioligonucleotides, respectively, were used as standards for identifying the analogous lesions in calf thymus DNA by isotope dilution LC-MS/MS methods in the selected reaction monitoring mode. The NIm and 8-nitro-G are the major products formed (∼0.05% each), and lesser amounts of 8-oxo-G (∼0.02%) and d(G*pT*) and d(G*-T*) enzymatic digestion products (∼0.002% each) were found. It is shown that the formation of d(G*pT*) enzyme digestion product can arise only from intrastrand cross-links, whereas d(G*-T*) can arise from both interstrand and intrastrand cross-linked products.

The effects of vitamin A supplementation to rats during gestation and lactation upon redox parameters: increased oxidative stress and redox modulation in mothers and their offspring

Vitamin A is an essential nutrient required in adequate amounts for reproduction and development. Subtle variations in the status of maternal nutrition may affect physiological and metabolic parameters in the fetus. Evidence suggests a key role for oxidative stress in these events. Literature is controversial about the effects of vitamin A supplementation. Here, we studied the effects of vitamin A supplementation on female Wistar rats during gestation and lactation on oxidative stress parameters of maternal and offspring tissues. Rats received daily doses of vitamin A at 2500, 12,500 and 25,000IU/kg. We observed an increase of oxidative damage markers in the reproductive tissues and plasma of dams. The activity of glutathione-S-transferase was modulated by vitamin A supplementation. It was found to be increased in the liver of dams and decreased in the kidneys of mothers and offspring. In pups, supplementation decreased the total antioxidant potential of the liver along with decreased superoxide dismutase/catalase activity ratio in the kidney. The levels of lipoperoxidation were increased in male offspring, but decreased in female pups. Collectively, the results suggest that excessive vitamin A intake during gestation and lactation might be toxic for mothers with adverse effects for the developing offspring.

Role of neuronal nitric oxide synthase in colonic distension-induced hyperalgesia in distal colon of neonatal maternal separated male rats

BACKGROUND

Nitric oxide (NO) is implicated in the pathogenesis of irritable bowel syndrome (IBS) but the underlying mechanism is unclear. Thus, the aim of the present study is to examine the role of NO synthase (NOS) expression in the distal colon of neonatal maternal separation (NMS) model rats employed in IBS studies.

METHODS

Male neonates of Sprague-Dawley rats were randomly assigned into NMS and normal control (N) groups. Rats of NMS group were subjected to 3 h daily maternal separation on postnatal day 2-21. Rats were administrated non-selective NOS inhibitor l-NAME (100 mg kg(-1) ), selective neuronal NOS (nNOS) inhibitor 7-NINA (10mgkg(-1) ), selective inducible NOS (iNOS) inhibitor, endothelial NOS (eNOS) inhibitor (10mgkg(-1) ) or Vehicle (Veh; distilled water) intraperitoneally 1h prior to the experiment for the test and control groups, respectively.

KEY RESULTS

The amount of NO was significantly higher in the NMS Veh rats compared with unseparated N rats. Western-blotting and real-time quantitative PCR studies showed that protein and mRNA expression of nNOS were higher in the NMS group than that in the N rats; whereas no significant change in iNOS and eNOS was found in either groups. Neonatal maternal separation Veh rats showed low pain threshold and increased electromyogram (EMG) activity in response to colonic distension stimuli. l-NAME and 7-Nitroindazole monosodium salt (7-NINA) increased pain threshold pressure and attenuated EMG activity in the NMS rats. In addition, l-NAME and 7-NINA substantially reduced oxidative marker malondialdehyde level in NMS rats.

CONCLUSIONS & INFERENCES

Neonatal maternal separation increased the NO generation by nNOS upregulation that interact with reactive oxygen species contributing to the visceral hypersensitivity in IBS.

In vitro inhibition of human and rat platelets by NO donors, nitrosoglutathione, sodium nitroprusside and SIN-1, through activation of cGMP-independent pathways

Three different NO donors, S-nitrosoglutathione (GSNO), sodium nitroprusside (SNP) and 3-morpholino-sydnonimine hydrochloride (SIN-1) were used in order to investigate mechanisms of platelet inhibition through cGMP-dependent and -independent pathways both in human and rat. To this purpose, we also evaluated to what extent cGMP-independent pathways were related with the entity of NO release from each drug. SNP, GSNO and SIN-1 (100 μM) effects on platelet aggregation, in the presence or absence of a soluble guanylate cyclase inhibitor (ODQ), on fibrinogen receptor (α(IIb)β(3)) binding to specific antibody (PAC-1), and on the entity of NO release from NO donors in human and rat platelet rich plasma (PRP) were measured. Inhibition of platelet aggregation (induced by ADP) resulted to be greater in human than in rat. GSNO was the most powerful inhibitor (IC(50) values, μM): (a) in human, GSNO=0.52±0.09, SNP=2.83 ± 0.53, SIN-1=2.98 ± 1.06; (b) in rat, GSNO = 28.4 ± 6.9, SNP = 265 ± 73, SIN-1=108 ± 85. GSNO action in both species was mediated by cGMP-independent mechanisms and characterized by the highest NO release in PRP. SIN-1 and SNP displayed mixed mechanisms of inhibition of platelet aggregation (cGMP-dependent and independent), except for SIN-1 in rat (cGMP-dependent), and respectively lower or nearly absent NO delivery. Conversely, all NO-donors prevalently inhibited PAC-1 binding to α(IIb)β(3) through cGMP-dependent pathways. A modest relationship between NO release from NO donors and cGMP-independent responses was found. Interestingly, the species difference in NO release from GSNO and inhibition by cGMP-independent mechanism was respectively attributed to S-nitrosylation of non-essential and essential protein SH groups.

The Composition and Metabolic Phenotype of Neisseria gonorrhoeae Biofilms

Neisseria gonorrhoeae has been shown to form biofilms during cervical infection. Thus, biofilm formation may play an important role in the infection of women. The ability of N. gonorrhoeae to form membrane blebs is crucial to biofilm formation. Blebs contain DNA and outer membrane structures, which have been shown to be major constituents of the biofilm matrix. The organism expresses a DNA thermonuclease that is involved in remodeling of the biofilm matrix. Comparison of the transcriptional profiles of gonococcal biofilms and planktonic runoff indicate that genes involved in anaerobic metabolism and oxidative stress tolerance are more highly expressed in biofilm. The expression of aniA, ccp, and norB, which encode nitrite reductase, cytochrome c peroxidase, and nitric oxide reductase respectively, is required for mature biofilm formation over glass and human cervical cells. In addition, anaerobic respiration occurs in the substratum of gonococcal biofilms and disruption of the norB gene required for anaerobic respiration, results in a severe biofilm attenuation phenotype. It has been demonstrated that accumulation of nitric oxide (NO) contributes to the phenotype of a norB mutant and can retard biofilm formation. However, NO can also enhance biofilm formation, and this is largely dependent on the concentration and donation rate or steady-state kinetics of NO. The majority of the genes involved in gonococcal oxidative stress tolerance are also required for normal biofilm formation, as mutations in the following genes result in attenuated biofilm formation over cervical cells and/or glass: oxyR, gor, prx, mntABC, trxB, and estD. Overall, biofilm formation appears to be an adaptation for coping with the environmental stresses present in the female genitourinary tract. Therefore, this review will discuss the studies, which describe the composition and metabolic phenotype of gonococcal biofilms.

Tumor necrosis factor alpha pathways develops liver apoptosis in type 1 diabetes mellitus

We analyzed the contribution of TNF-α intracellular pathway in the development of apoptosis in the liver of streptozotocin-induced diabetic rats. In liver tissue, diabetes promoted a significant increase of TNF-α/TNF-R1, and led to the activation of caspase-8, of nuclear factor kappa B (NFκB), and JNK signaling pathways. The activation of NFκB led to an induction of iNOS and consequent increase in NO production. As a consequence of such changes a significant increase of caspase-3 activity and of apoptotic index were observed in the liver of diabetic animals. Importantly, the treatment in vivo of diabetic rats with etanercept (TNF-α blocking antibody) or aminoguanidine (selective iNOS inhibitor) significantly attenuated the induction of apoptosis by reduction of caspase-3 activity. Overall, we demonstrated that in the diabetes enhances TNF-α in the liver, which may be a fundamental key leading to apoptotic cell death, through activation of caspase-8, NFκB and JNK pathways.

Denitrosylation of S-nitrosylated OGT is triggered in LPS-stimulated innate immune response

O-linked N-acetylglucosaminyltransferase (OGT)-mediated protein O-GlcNAcylation has been revealing various aspects of functional significance in biological processes, such as cellular signaling and activation of immune system. We found that OGT is maintained as S-nitrosylated form in resting cells, and its denitrosylation is triggered in innate immune response of lipopolysaccharide (LPS)-treated macrophage cells. S-nitrosylation of OGT strongly inhibits its catalytic activity up to more than 80% of native OGT, and denitrosylation of OGT leads to protein hyper-O-GlcNAcylation. Furthermore, blockage of increased protein O-GlcNAcylation results in significant loss of nitric oxide and cytokine production. We propose that denitrosylation of S-nitrosylated OGT is a direct mechanism for upregulation of OGT activity by which immune defense is critically controlled in LPS-stimulated innate immune response.

Reversal of inducible nitric oxide synthase uncoupling unmasks tolerance to ischemia/reperfusion injury in the diabetic rat heart

The diabetic heart is known to be susceptible to ischemia/reperfusion (I/R) injury by increased oxidative stress. Although oxidative stress upregulates inducible nitric oxide (iNOS), the role of iNOS in I/R injury in the diabetic heart has been poorly understood. Because iNOS-derived nitric oxide (NO) plays a crucial role in cardioprotection against I/R injury, we hypothesized that inhibition of iNOS uncoupling would restore tolerance to I/R injury in the diabetic heart. The present study demonstrated that iNOS-derived superoxide generation was reduced, and that the NO bioavailability was increased, by treatment with the NOS-cofactor, tetrahydrobiopterin (BH4), before I/R in the hearts isolated from diabetic rats. This was associated with a reduction of infarct size and improvement of left ventricular (LV) function after I/R. The cardioprotective effect of BH4 was abrogated by treatment with a thiol reducing agent dithiothreitol (DTT), but not a NO-sensitive guanylyl cyclase inhibitor ODQ, suggesting that iNOS-derived NO-mediated cardioprotection occurs through protein S-nitrosylation but not cGMP-dependent signaling in the diabetic heart. Indeed, protein S-nitrosylation was increased by treatment with BH4 in the diabetic heart and was inhibited by DTT. These results suggest that the inhibition of iNOS uncoupling unmasks tolerance to I/R injury through enhanced protein S-nitrosylation in the diabetic rat heart.

Nitric oxide and cyclic nucleotides: their roles in junction dynamics and spermatogenesis

Spermatogenesis is a highly complicated process in which functional spermatozoa (haploid, 1n) are generated from primitive mitotic spermatogonia (diploid, 2n). This process involves the differentiation and transformation of several types of germ cells as spermatocytes and spermatids undergo meiosis and differentiation. Due to its sophistication and complexity, testis possesses intrinsic mechanisms to modulate and regulate different stages of germ cell development under the intimate and indirect cooperation with Sertoli and Leydig cells, respectively. Furthermore, developing germ cells must translocate from the basal to the apical (adluminal) compartment of the seminiferous epithelium. Thus, extensive junction restructuring must occur to assist germ cell movement. Within the seminiferous tubules, three principal types of junctions are found namely anchoring junctions, tight junctions, and gap junctions. Other less studied junctions are desmosome-like junctions and hemidesmosome junctions. With these varieties of junction types, testes are using different regulators to monitor junction turnover. Among the uncountable junction modulators, nitric oxide (NO) is a prominent candidate due to its versatility and extensive downstream network. NO is synthesized by nitric oxide synthase (NOS). Three traditional NOS, specified as endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS), and one testis-specific nNOS (TnNOS) are found in the testis. For these, eNOS and iNOS were recently shown to have putative junction regulation properties. More important, these two NOSs likely rely on the downstream soluble guanylyl cyclase/cGMP/protein kinase G signaling pathway to regulate the structural components at the tight junctions and adherens junctions in the testes. Apart from the involvement in junction regulation, NOS/NO also participates in controlling the levels of cytokines and hormones in the testes. On the other hand, NO is playing a unique role in modulating germ cell viability and development, and indirectly acting on some aspects of male infertility and testicular pathological conditions. Thus, NOS/NO bears an irreplaceable role in maintaining the homeostasis of the microenvironment in the seminiferous epithelium via its different downstream signaling pathways.

Nitric oxide/reactive oxygen species generation and nitroso/redox imbalance in heart failure: from molecular mechanisms to therapeutic implications

Adaptation of the heart to intrinsic and external stress involves complex modifications at the molecular and cellular levels that lead to tissue remodeling, functional and metabolic alterations, and finally to failure depending upon the nature, intensity, and chronicity of the stress. Reactive oxygen species (ROS) have long been considered as merely harmful entities, but their role as second messengers has gradually emerged. At the same time, our comprehension of the multifaceted role of nitric oxide (NO) and the related reactive nitrogen species (RNS) has been upgraded. The tight interlay between ROS and RNS suggests that their imbalance may implicate the impairment in physiological NO/redox-based signaling that contributes to the failing of the cardiovascular system. This review initially provides basic concepts on the role of nitroso/oxidative stress in the pathophysiology of heart failure with a particular focus on sources of ROS/RNS, their downstream targets, and endogenous modulators. Then, the role of NO/redox regulation of cardiomyocyte function, including calcium homeostasis, electrogenesis, and insulin signaling pathways, is described. Finally, an overview of old and emerging therapeutic opportunities in heart failure is presented, focusing on modulation of NO/redox mechanisms and discussing benefits and limitations.

Modulation of homocysteine toxicity by S-nitrosothiol formation: a mechanistic approach

The metabolic conversion of homocysteine (HCYSH) to homocysteine thiolactone (HTL) has been reported as the major cause of HCYSH pathogenesis. It was hypothesized that inhibition of the thiol group of HCYSH by S-nitrosation will prevent its metabolic conversion to HTL. The kinetics, reaction dynamics, and mechanism of reaction of HCYSH and nitrous acid to produce S-nitrosohomocysteine (HCYSNO) was studied in mildly to highly acidic pHs. Transnitrosation of this non-protein-forming amino acid by S-nitrosoglutathione (GSNO) was also studied at physiological pH 7.4 in phosphate buffer. In both cases, HCYSNO formed quantitatively. Copper ions were found to play dual roles, catalyzing the rate of formation of HCYSNO as well as its rate of decomposition. In the presence of a transition-metal ions chelator, HCYSNO was very stable with a half-life of 198 h at pH 7.4. Nitrosation by nitrous acid occurred via the formation of more powerful nitrosating agents, nitrosonium cation (NO(+)) and dinitrogen trioxide (N(2)O(3)). In highly acidic environments, NO(+) was found to be the most effective nitrosating agent with a first-order dependence on nitrous acid. N(2)O(3) was the most relevant nitrosating agent in a mildly acidic environment with a second-order dependence on nitrous acid. The bimolecular rate constants for the direct reactions of HCYSH and nitrous acid, N(2)O(3), and NO(+) were 9.0 x 10(-2), 9.50 x 10(3), and 6.57 x 10(10) M(-1) s(-1), respectively. These rate constant values agreed with the electrophilic order of these nitrosating agents: HNO(2) < N(2)O(3) < NO(+). Transnitrosation of HCYSH by GSNO produced HCYSNO and other products including glutathione (reduced and oxidized) and homocysteine-glutathione mixed disulfide. A computer modeling involving eight reactions gave a good fit to the observed formation kinetics of HCYSNO. This study has shown that it is possible to modulate homocysteine toxicity by preventing its conversion to a more toxic HTL by S-nitrosation.

Nitric oxide changes distinct aspects of the glycophenotype of human neuroblastoma NB69 cells

It is an open question whether the presence of nitric oxide (NO) affects the cell glycophenotype. A panel of six plant lectins was used in this study to monitor distinct aspects of cell surface glycosylation under nitrosative stress. We determined that treating human neuroblastoma NB69 cells with the long-lived NO donor 2,2'-(hydroxynitrosohydrazono)bis-ethanimine (DETA/NO) and monitoring the non-apoptotic adherent cell population significantly increases the presentation of N-glycans as detected by concanavalin A. Examining fine-structural features, bisected N-glycans and branch-end tailoring including α2,6-sialylation were found to be enhanced. Confocal fluorescence microscopy and cell permeabilization experiments pointed to a major effect of NO on the extent of cell surface N-glycan presentation. We also show that NO increases the level of protein O-GlcNAcylation, a multifunctional post-translational modification. Our results thus establish the first evidence for NO as modulator of distinct aspects of cell glycosylation.

Oxidative stress, inflammation, and cancer: how are they linked?

Extensive research during the past 2 decades has revealed the mechanism by which continued oxidative stress can lead to chronic inflammation, which in turn could mediate most chronic diseases including cancer, diabetes, and cardiovascular, neurological, and pulmonary diseases. Oxidative stress can activate a variety of transcription factors including NF-κB, AP-1, p53, HIF-1α, PPAR-γ, β-catenin/Wnt, and Nrf2. Activation of these transcription factors can lead to the expression of over 500 different genes, including those for growth factors, inflammatory cytokines, chemokines, cell cycle regulatory molecules, and anti-inflammatory molecules. How oxidative stress activates inflammatory pathways leading to transformation of a normal cell to tumor cell, tumor cell survival, proliferation, chemoresistance, radioresistance, invasion, angiogenesis, and stem cell survival is the focus of this review. Overall, observations to date suggest that oxidative stress, chronic inflammation, and cancer are closely linked.

[The role of oxidative/nitrosative stress in pathogenesis of paracetamol-induced toxic hepatitis]

INTRODUCTION

Paracetamol is an effective analgesic/antipyretic drug when used at therapeutic doses. However, the overdose of paracetamol can cause severe liver injury and liver necrosis. The mechanism of paracetamol-induced liver injury is still not completely understood. Reactive metabolite formation, depletion of glutathione and alkylation of proteins are the triggers of inhibition of mitochondrial respiration, adenosine triphosphate depletion and mitochondrial oxidant stress leading to hepatocellular necrosis. ROLE OF OXIDATIVE STRESS IN PARACETAMOL-INDUCED LIVER INJURY: The importance of oxidative stress in paracetamol hepatotoxicity is controversial. Paracetamol-induced liver injury cause the formation of reactive oxygen species. The potent sources of reactive oxygen are mitochondria, neutrophils. Kupffer cells and the enzyme xatnine oxidase. Free radicals lead to lipid peroxidation, enzymatic inactivation and protein oxidation. ROLE OF MITOCHONDRIA IN PARACETAMOL-INDUCED OXIDATIVE STRESS: The production of mitochondrial reactive oxygen species is increased, and the glutathione content is decreased in paracetamol overdose. Oxidative stress in mitochondria leads to mitochondrial dysfunction with adenosine triphosphate depletion, increase mitochondrial permeability transition, deoxyribonucleic acid fragmentation which contribute to the development of hepatocellular necrosis in the liver after paracetamol overdose. ROLE OF KUPFFER CELLS IN PARACETAMOL-INDUCED LIVER INJURY: Paracetamol activates Kupffer cells, which then release numerous cytokines and signalling molecules, including nitric oxide and superoxide. Kupffer cells are important in peroxynitrite formation. On the other hand, the activated Kupffer cells release anti-inflammatory cytokines. ROLE OF NEUTROPHILS IN PARACETAMOL-INDUCED LIVER INJURY: Paracetamol-induced liver injury leads to the accumulation of neutrophils, which release lysosomal enzymes and generate superoxide anion radicals through the enzyme nicotinamide adenine dinucleotide phosphate oxidase. Hydrogen peroxide, which is influenced by the neutrophil-derived enzyme myeloperoxidase, generates hypochlorus acid as a potent oxidant. ROLE OF PEROXYNITRITE IN PARACETAMOL-INDUCED OXIDATIVE STRESS: Superoxide can react with nitric oxide to form peroxynitrite, as a potent oxidant. Nitrotyrosine is formed by the reaction of tyrosine with peroxynitrite in paracetamol hepatotoxicity.

CONCLUSION

Overdose of paracetamol may produce severe liver injury with hepatocellular necrosis. The most important mechanisms of cell injury are metabolic activation of paracetamol, glutathione depletion, alkylation of proteins, especially mitochondrial proteins, and formation of reactive oxygen/nitrogen species.

Nitric oxide stimulates interleukin-6 production in skeletal myotubes

Strenuous exercise leads to the up-regulation of interleukin-6 (IL-6) production and enhanced nitric oxide (NO) release within the contracting skeletal muscles. In this study, we investigated whether NO regulates IL-6 production in C2C12 myotubes. These cells exhibited a concentration-dependent increase in IL-6 production upon stimulation with NO donors (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA-NONOate), (Z)-1-[N-(3-aminopropyl)-N-(n-propyl)amino]diazen-1-ium-1,2-diolate (PAPA-NONOate), and sodium nitroprusside (SNP). This treatment did not alter cGMP levels nor did the soluble guanylyl cyclase (sGC) inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one(ODQ), alter this response. The NO-independent sGC activator 5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]-pyrimidin-4-ylamine (BAY41-2272) and cyclic guanosine monophosphate (cGMP) analog 8Br-cGMP failed to induce IL-6 production. Upon exposure to NO donors, we observed an increase in Erk1/2 and p38 MAPK phosphorylation but not in SAPK/JNK. In addition, NO-induced IL-6 release was inhibited in a concentration-dependent fashion by the MEK1/2 inhibitor PD98059 and the p38 MAPK inhibitor SB203580 but not by the SAPK/JNK inhibitor SP600125. We conclude that NO-stimulated IL-6 production in differentiated C2C12 myotubes is cGMP-independent and mediated by activation of MAPK pathways.

Hemoglobin α and β are ubiquitous in the human lung, decline in idiopathic pulmonary fibrosis but not in COPD

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD) are disorders of the lung parenchyma. They share the common denominators of a progressive nature and poor prognosis. The goal was to use non-biased proteomics to discover new markers for these diseases.

METHODS

Proteomics of fibrotic vs. control lung tissue suggested decreased levels of several spots in the lung specimens of IPF patients, which were identified as Hemoglobin (Hb) α and β monomers and Hbα complexes. The Hbα and β monomers and complexes were investigated in more detail in normal lung and lung specimens of patients with IPF and COPD by immunohistochemistry, morphometry and mass spectrometry (MS).

RESULTS

Both Hb monomers, in normal lung, were expressed especially in the alveolar epithelium. Levels of Hbα and β monomers and complexes were reduced/lost in IPF but not in the COPD lungs when compared to control lung. MS-analyses revealed Hbα modification at cysteine105 (Cysα105), preventing formation of the Hbα complexes in the IPF lungs. Hbα and Hbβ were expressed as complexes and monomers in the lung tissues, but were secreted into the bronchoalveolar lavage fluid and/or induced sputum supernatants as complexes corresponding to the molecular weight of the Hb tetramer.

CONCLUSIONS

The abundant expression of the oxygen carrier molecule Hb in the normal lung epithelium and its decline in IPF lung are new findings. The loss of Hb complex formation in IPF warrants further studies and may be considered as a disease-specific modification.

Exposure to excess dissolved iron in vivo affects oxidative status in the bivalve Mya arenaria

The effect of in vivo Fe exposure on the oxidative metabolism of the bivalve Myaarenaria was studied. Fe was supplemented in natural seawater and resulted in a significant increase in the total Fe content in the bivalve digestive gland (DG) between 9 to 17days of exposure. Mortality of treated animals increased drastically after day 18. Oxidative stress conditions were characterized in DG through assessment of the generation of reactive oxygen species (ROS) and ascorbyl radical (A) content. Both parameters were affected following a biphasic profile showing significant increases by days 2 and 9 of Fe exposure. The content of 2-thiobarbituric acid reactive substances (TBARS) was significantly increased over control values by days 2, 9 and 17 of treatment. The labile Fe pool (LIP) in isolated DG was elevated over control values by day 7, and maintained this increase until day 17 of Fe exposure. The content of NO, assessed by EPR spin trapping, was 60% lower in DG of animals exposed for 2days to Fe than in control values, with no further changes. The biphasic profile of oxidative stress response to Fe exposure in DG suggests that at early stages of Fe supplementation the cellular control mechanisms, such as CAT activity, were operative to limit oxidative damage, but further Fe exposure overwhelmed these abilities. Moreover, the second phase could be understood as the consequence of the exhaustion of cellular protective systems that could also involve NO.

Nitric oxide: perspectives and emerging studies of a well known cytotoxin

The free radical nitric oxide (NO^•) is known to play a dual role in human physiology and pathophysiology. At low levels, NO^• can protect cells; however, at higher levels, NO^• is a known cytotoxin, having been implicated in tumor angiogenesis and progression. While the majority of research devoted to understanding the role of NO^• in cancer has to date been tissue-specific, we herein review underlying commonalities of NO^• which may well exist among tumors arising from a variety of different sites. We also discuss the role of NO^• in human physiology and pathophysiology, including the very important relationship between NO^• and the glutathione-transferases, a class of protective enzymes involved in cellular protection. The emerging role of NO^• in three main areas of epigenetics—DNA methylation, microRNAs, and histone modifications—is then discussed. Finally, we describe the recent development of a model cell line system in which human tumor cell lines were adapted to high NO^• (HNO) levels. We anticipate that these HNO cell lines will serve as a useful tool in the ongoing efforts to better understand the role of NO^• in cancer.

Suppression of inflammatory mediators by cruciferous vegetable-derived indole-3-carbinol and phenylethyl isothiocyanate in lipopolysaccharide-activated macrophages

This study was aimed to examine the effects of indole-3-carbinol (I3C) and beta-phenylethyl isothiocyanate (PEITC), bioactive components present in cruciferous vegetable, on the production of inflammatory mediators, including nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10), in lipopolysaccharide- (LPS-) stimulated RAW 264.7 macrophages. Possible mechanisms of the NO-inhibitory effects were also explored. The results indicated that I3C and PEITC inhibited NO production, and this suppression was associated with decreased production of TNF-alpha and IL-10 by activated macrophages. In addition, I3C suppressed NO production even after the inducible nitric oxide synthase (iNOS) protein had been produced, but such an inhibitory effect was not observed in cells treated with PEITC. Furthermore, both compounds reduced the NO contents generated from an NO donor in a cell-free condition, suggesting that the increased NO clearance may have contributed to the NO-inhibitory effects. In summary, both I3C and PEITC possessed antiinflammatory effects by inhibiting the productions of NO, TNF-alpha, and IL-10, although the NO-inhibitory effects may have involved in different mechanisms.

Anaerobic metabolism occurs in the substratum of gonococcal biofilms and may be sustained in part by nitric oxide

Neisseria gonorrhoeae is the etiologic agent of gonorrhea, which has been among the most frequently reported communicable diseases in the United States since 1960. Women frequently do not exhibit symptoms, which can lead to chronic infection. N. gonorrhoeae readily forms biofilms over abiotic surfaces, over primary and transformed cervical epithelial cells, and over cervical tissues in vivo. Biofilms are often associated with chronic infection, which suggests a link between biofilm formation and asymptomatic gonorrhea in women. Proteins involved in anaerobic metabolism and oxidative-stress tolerance are critical for normal biofilm formation of N. gonorrhoeae. Therefore, we examined the spatial profiles of anaerobic respiration in N. gonorrhoeae, using an aniA'-'gfp transcriptional fusion. Nitric oxide (NO) can elicit biofilm dispersal when present at sublethal concentrations in the surrounding medium. Some reports indicate that NO may also encourage biofilm formation at higher, potentially lethal concentrations. NO is produced by polymorphonuclear lymphocytes (PMNs) and cervical endothelial and epithelial cells. Thus, we also examined the effect of NO on N. gonorrhoeae biofilms. We found that anaerobic respiration occurs predominantly in the substratum of gonococcal biofilms and that expression of aniA is induced over time in biofilms. Treatment with high concentrations of a rapid-release NO donor prevents biofilm formation when supplied early in biofilm development but can also enhance biofilm formation once anaerobic respiration is initiated. NO treatment partially restores biofilm formation in an aniA::kan insertion mutant, which suggests that N. gonorrhoeae in biofilms may use NO as a substrate for anaerobic growth but prefer nitrite.

Anti-inflammatory activity and possible mechanism of extract from Mikania laevigata in carrageenan-induced peritonitis

Objectives

The aim was to test the potential use of an extract of Mikania laevigata (popularly known in Brazil as guaco), made from leaves harvested in different months of the year, on neutrophil migration after an inflammatory stimulus and investigate the underlying molecular mechanisms.

Methods

We examined the effect of guaco on vascular permeability and leucocyte function in carrageenan-induced peritonitis in mice.

Key findings

Our results demonstrated that guaco extract administered subcutaneously (3 mg/kg) decreased the vascular permeability and also leucocyte rolling and adhesion to the inflamed tissues by a mechanism dependent on nitric oxide. Specifically, inhibitors of nitric oxide synthase remarkably abrogated the guaco extract-mediated suppression of neutrophil migration to the inflammatory site. In addition, guaco extract-mediated suppression of neutrophil migration appeared to be dependent on the production of the cytokines interleukin-1β and tumour necrosis factor-α. One of the major constituents of the guaco extract, coumarin, was able to inhibit the neutrophil migration towards the inflammatory focus.

Conclusions

In conclusion the anti-inflammatory effect induced by guaco extract may be by inhibition of pro-inflammatory cytokine production at the inflammatory site.

Evaluation of the role of nitric oxide in acid sensing ion channel mediated cell death

Acid sensing ion channels (ASICs) are widely expressed in central and peripheral nervous system. They are involved in a variety of physiological and pathophysiological processes: synaptic transmission, learning and memory, pain perception, ischemia, etc. During ischemia, metabolic acidosis causes the drop of extracellular pH (pHe) which in turn activates ASICs. Activation of calcium permeable ASIC1a has been implicated in neuronal death. ASICs are modulated by several redox reagents, divalent cations and nitric oxide (NO). Although NO potentiates ASIC mediated currents, the physiological significance of such modulation has not been studied in detail. We have evaluated the role of endogenous NO in cell death at different pH, mediated by the activation of ASICs. At pH 6.1, death rates of ASIC1 expressing Neuro2A (N2A) cells are significantly higher in comparison to the cells that do not express ASICs. Amiloride, a blocker of ASICs protects the cell from acid-injury. Sodium nitroprusside, a potent NO donor not only increases the ASIC mediated currents but also increases cell death at low pH. L-Arg, the precursor of NO also potentiates ASICs in a pH dependent manner. L-Arg-induced NO production and potentiation of ASICs were observed at pHs 7.4, 7.2, 7.0 and 6.8. Lowering the pH below 6.8 did not result in significant production of NO or potentiation of ASICs upon L-Arg stimulation. Our results suggest that potentiation of ASICs by NO and subsequent cell death in vivo depends on the severity of acidosis. During mild and moderate acidosis, NO promotes cell death by potentiating ASICs, whereas this potentiation subsides in severe acidosis due to inhibition of NO synthase.

Determination of GSH, GSSG, and GSNO using HPLC with electrochemical detection

GSNO is an important intermediate in nitric oxide metabolism and mediates many ()NO-mediated signaling pathways through the post-translational modification of redox-sensitive proteins. The detection of GSNO in biological samples has been hampered by a lack of sensitive and simple assays. In this work, we describe the utilization of HPLC with electrochemical detection for the identification and quantification of GSNO in biological samples. GSNO requires a high potential (>700 mV) for its electrochemical detection, similar to that of GSSG. A simple isocratic HPLC system can be used to separate and simultaneously detect GSH, GSSG, and GSNO electrochemically. This HPLC system can be utilized to measure the redox profile of biological samples and applied for the measurement of GSNO reductase activity in cells. Proper sample preparation is essential in GSNO measurements, because artifactual formation of GSNO occurs in acidic conditions due to the reaction between GSH and nitrite. Treatment of samples with ammonium sulfamate or N-ethylmaleimide (NEM) can prevent the artifactual formation of GSNO and accurately detect GSNO in biological samples. Overall, the HPLC with electrochemical detection is a powerful tool to measure redox status in cells and tissues.

Pleiotropic vasoprotective effects of statins: the chicken or the egg?

Statins (3-hydroxy-3-methyl glutaryl coenzyme A [HMG-CoA] reductase inhibitors) are the most commonly used lipid-lowering drugs. Their main lipid-lowering effect is achieved by an increase in the expression of low-density lipoprotein cholesterol receptors associated with inhibition of cholesterol synthesis through inhibition of HMG-CoA reductase - the first and rate-limiting step in cholesterol synthesis. However, beyond cholesterol synthesis inhibition, inhibition of the HMG-CoA reductase affects as well the synthesis of other molecules with significant roles in different, yet often intercalating, metabolic pathways. On this basis, and supported by an increasing series of advocating epidemiological and experimental data, an extended dialogue has been established over the last few years regarding the nonlipid or "pleiotropic" actions of statins.

Central sensitization: a generator of pain hypersensitivity by central neural plasticity

Central sensitization represents an enhancement in the function of neurons and circuits in nociceptive pathways caused by increases in membrane excitability and synaptic efficacy as well as to reduced inhibition and is a manifestation of the remarkable plasticity of the somatosensory nervous system in response to activity, inflammation, and neural injury. The net effect of central sensitization is to recruit previously subthreshold synaptic inputs to nociceptive neurons, generating an increased or augmented action potential output: a state of facilitation, potentiation, augmentation, or amplification. Central sensitization is responsible for many of the temporal, spatial, and threshold changes in pain sensibility in acute and chronic clinical pain settings and exemplifies the fundamental contribution of the central nervous system to the generation of pain hypersensitivity. Because central sensitization results from changes in the properties of neurons in the central nervous system, the pain is no longer coupled, as acute nociceptive pain is, to the presence, intensity, or duration of noxious peripheral stimuli. Instead, central sensitization produces pain hypersensitivity by changing the sensory response elicited by normal inputs, including those that usually evoke innocuous sensations.

PERSPECTIVE

In this article, we review the major triggers that initiate and maintain central sensitization in healthy individuals in response to nociceptor input and in patients with inflammatory and neuropathic pain, emphasizing the fundamental contribution and multiple mechanisms of synaptic plasticity caused by changes in the density, nature, and properties of ionotropic and metabotropic glutamate receptors.

The role of nitric oxide in myocardial repair and remodeling

Nitric oxide (NO) plays a crucial role in many aspects of the pathophysiology of heart failure. NO is a double-edged sword; NO inhibits ischemia/reperfusion (I/R) injury, represses inflammation, and prevents left ventricular (LV) remodeling, whereas excess NO and co-existence of reactive oxygen species (ROS) with NO are injurious. The failing heart is exposed to not only oxidative stress by a plethora of humoral factors and inflammatory cells but also nitrosative stress. Activation of nitric oxide synthase (NOS) of any isoforms, [i.e., endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS)], concomitant with oxidative stress results in NOS uncoupling, leading to further oxidative/nitrosative stress. Indiscriminate removal of oxidative stress is not an effective means to prevent this detrimental process, because oxidative stress is necessary for an adaptive mechanism for cell survival against noxious stimuli. Therefore, removal of ROS in a site-specific manner or inhibition of the source of injurious ROS without affecting redox-sensitive survival signal transduction pathways represents a promising approach to elicit the beneficial effect of NO. Recent emerging pharmacological tools and regular exercise inhibit ROS generation in the proximity of NOSs, thereby increasing bioavailable NO and exerting cardioprotection against I/R injury and LV remodeling.

[Progress in portal hypertension]

In patients with portal hypertension due to cirrhosis, the mechanisms responsible for circulatory modifications are well-known. An elevation in intrahepatic vascular resistance related to a hepatic endothelin hyperproduction and an arterial nitric oxide (NO) hyperproduction. The presence and the degree of portal hypertension might be determined by the measurement of the hepatic venous pressure gradient but non-invasive technique as FibroTest or FibroScan might be useful to estimate the presence of severe portal hypertension. Numerous substances decrease portal pressure either by reducing hepatic vascular resistance or by reducing portal tributary blood flow. The combination of both types of substances is probably the best pharmacological treatment of portal hypertension but further hemodynamic and clinical studies are needed.

The role of nitric oxide in osteoarthritis

Elevated levels of markers of nitric oxide (NO) production are found in osteoarthritic joints suggesting that NO is involved in the pathogenesis of osteoarthritis (OA). In OA, NO mediates many of the destructive effects of interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF-alpha) in the cartilage, and inhibitors of NO synthesis have demonstrated retardation of clinical and histological signs and symptoms in experimentally induced OA and other forms of arthritis. As an important factor in cartilage, the regulation of inducible nitric oxide synthase (iNOS) expression and activity, and the effects of NO are reviewed, especially in relation to the pathogenesis of OA.

PRIMARY BIOMARKERS IN CEREBRAL SPINAL FLUID OBTAINED FROM PATIENTS WITH INFLUENZA-ASSOCIATED ENCEPHALOPATHY ANALYZED BY METABOLOMICS

In order to search for the specific biomarkers of patients with influenza-associated encephalopathy this article analyzed all metabolites in cerebrospinal fluid (CSF) by using metabolome analysis. In all metabolites, the peaks of two molecular weights, 246.0092 and 204.0611, were significantly higher than those in other diseases including influenza without convulsion (p < .05). The peak of a molecular weight 228.0247 in all of the patients except one was less than that in other patients. These results indicate that the new metabolites detected in CSF would be primary markers for the diagnosis of influenza-associated encephalopathy.