Nitric Oxide Toxicity Research Articles

Using metagenomics to reveal landscape scale patterns of denitrifiers in a montane forest ecosystem

Denitrificationis an important process in the nitrogen cycle of many soil ecosystems, but the relationships between process rates and the genotype of denitrifying microorganisms are poorly understood. Genotyping may identify denitrifiers with less than the full complement of nitrogen-oxide reductases, which might be crucial for denitrification in nitrogen-limited environments, such as in montane forest landscapes. Therefore, a metagenomics survey was undertaken using soils from the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, USA where steep elevation, vegetation, and soil gradients provide a complex landscape matrix to assess occurrence patterns of the genes involved in denitrification. DNA was extracted from soils taken from three soil horizons, at three elevations, in two watersheds. Metagenomic analysis of reads showed that the relative abundance of denitrification genes within a community did not differ across soil depths but did vary among elevation zones, with total denitrification reads in High Hardwood > Spruce Fir > Low Hardwood. Reads from nirS were extremely rare, which suggests that complete denitrification is uncommon across this forest landscape. The gene with the largest proportion of denitrification specific reads was the quinol-oxidizing nitric oxide reductase, qnor, which reduces toxic nitric oxide to nitrous oxide. The relative enrichment of specialized denitrification genes involved in intermediate reactions may indicate that environmental factors are selecting for a partial denitrification process, rather than complete denitrification. High Hardwood soils had the highest denitrification gene abundance and the greatest potential rate of denitrification, indicating that metagenomic information was consistent with the process measurements. Although little energy is generated from complete denitrification, due to the acidic soil conditions and low nitrate availability in HBEF soils, the denitrifier community appears to compensate by producing particular denitrification genes. In particular, qnor may help the community cope with toxic nitric oxide produced via chemodenitrification, making it a public good.

Cooperative Roles of Nitric Oxide-Metabolizing Enzymes To Counteract Nitrosative Stress in Enterohemorrhagic Escherichia coli.

Enterohemorrhagic Escherichia coli (EHEC) has at least three enzymes, NorV, Hmp, and Hcp, that act independently to lower the toxicity of nitric oxide (NO), a potent antimicrobial molecule. This study aimed to reveal the cooperative roles of these defensive enzymes in EHEC against nitrosative stress. Under anaerobic conditions, combined deletion of all three enzymes significantly increased the NO sensitivity of EHEC determined by the growth at late stationary phase; however, the expression of norV restored the NO resistance of EHEC. On the other hand, the growth of Δhmp mutant EHEC was inhibited after early stationary phase, indicating that NorV and Hmp play a cooperative role in anaerobic growth. Under microaerobic conditions, the growth of Δhmp mutant EHEC was inhibited by NO, indicating that Hmp is the enzyme that protects cells from NO stress under microaerobic conditions. When EHEC cells were exposed to a lower concentration of NO, the NO level in bacterial cells of Δhcp mutant EHEC was higher than those of the other EHEC mutants, suggesting that Hcp is effective at regulating NO levels only at a low concentration. These findings of a low level of NO in bacterial cells with hcp indicate that the NO consumption activity of Hcp was suppressed by Hmp at a low range of NO concentrations. Taken together, these results show that the cooperative effects of NO-metabolizing enzymes are regulated by the range of NO concentrations to which the EHEC cells are exposed.

Insights into the mechanism of nitric oxide reductase from a FeB -depleted variant.

A key step of denitrification, the reduction of toxic nitric oxide to nitrous oxide, is catalysed by cytochrome c-dependent NO reductase (cNOR). cNOR contains four redox-active cofactors: three hemes and a nonheme iron (FeB ). Heme b3 and FeB constitute the active site, but the specific mechanism of NO-binding events and reduction is under debate. Here, we used a recently constructed, fully folded and hemylated cNOR variant that lacks FeB to investigate the role of FeB during catalysis. We show that in the FeB -less cNOR, binding of both NO and O2 to heme b3 still occurs but further reduction is impaired, although to a lesser degree for O2 than for NO. Implications for the catalytic mechanisms of cNOR are discussed.

Nitric oxide signaling, metabolism and toxicity in nitrogen-fixing symbiosis.

Interactions between legumes and rhizobia lead to the establishment of a symbiotic relationship characterized by the formation of a new organ, the nodule, which facilitates the fixation of atmospheric nitrogen (N2) by nitrogenase through the creation of a hypoxic environment. Significant amounts of nitric oxide (NO) accumulate at different stages of nodule development, suggesting that NO performs specific signaling and/or metabolic functions during symbiosis. NO, which regulates nodule gene expression, accumulates to high levels in hypoxic nodules. NO accumulation is considered to assist energy metabolism within the hypoxic environment of the nodule via a phytoglobin-NO-mediated respiration process. NO is a potent inhibitor of the activity of nitrogenase and other plant and bacterial enzymes, acting as a developmental signal in the induction of nodule senescence. Hence, key questions concern the relative importance of the signaling and metabolic functions of NO versus its toxic action and how NO levels are regulated to be compatible with nitrogen fixation functions. This review analyses these paradoxical roles of NO at various stages of symbiosis, and highlights the role of plant phytoglobins and bacterial hemoproteins in the control of NO accumulation.

Potential benefits and toxicity of nanoselenium and nitric oxide in peppermint

Taking account of nano-compounds and biofortification, this research was conducted to evaluate peppermint (Mentha x piperita L.) responses to nano-selenium (nSe; 0, 2, and 20 mg l-1) and/or nitric oxide (NO; 0 and 8 mg l-1). Significant increases in leaf length, and area, and shoot fresh mass were enhanced by the low level of nSe and/or NO, contrasted with the high dose. The inhibitory effects of the high dose of nSe on the growth-related characteristics were significantly mitigated by NO. The adverse impact of nSe20 on chlorophyll concentration was alleviated by NO. The individual and combined treatments of nSe2 led to the significant inductions in the activities of nitrate reductase and peroxidase, whereas nSe20 inhibited. The proline contents in the nSe and/or NO-treated plants were higher than in the control. The nSe and/or NO provoked stimulation in activities of phenylalanine ammonia lyase enzyme. The foliar applications of nSe and/or NO triggered the accumulations of soluble phenols. Interestingly, the toxicity of nSe at the high dose led to the severe cell destruction in the cortex layer of the basal stem, which was partially alleviated by NO. The simultaneous applications of these supplements may consider as an alternative strategy for fortifying and improving plant protection, regarding sustainable agriculture.

Rational design of novel irreversible inhibitors for human arginase

Parasites have developed a variety of strategies for invading hosts and escaping their immune response. A common mechanism by which parasites escape nitric oxide (NO) toxicity is the activation of host arginase. This activation leads to a depletion of l-arginine, which is the substrate for NO synthase, resulting in lower levels of NO and increased production of polyamines that are necessary for parasite growth and differentiation. For this reason, small molecule inhibitors for arginase show promise as new anti-parasitic chemotherapeutics. However, few arginase inhibitors have been reported. Here, we describe the discovery of novel irreversible arginase inhibitors, and their characterization using biochemical, kinetic, and structural studies. Importantly, we determined the site on human arginase that is labeled by one of the small molecule inhibitors. The tandem mass spectra data show that the inhibitor occupies the enzyme active site and forms a covalent bond with Thr135 of arginase. These findings pave the way for the development of more potent and selective irreversible arginase inhibitors.

Abstract WP322: Inhaled Nitric Oxide Augments Cerebral Blood Flow in Healthy Subjects

Introduction: Optimizing cerebral blood flow (CBF) is a cornerstone of clinical management for a number of neurologic disease states, most notably acute ischemic stroke. Transdermal nitric oxide donors are being investigated for acute stroke, though the effect of inhaled nitric oxide (iNO) on CBF remains largely unknown. Here we aim to quantify the cerebral hemodynamic response to iNO in healthy volunteers. Methods: Cerebral perfusion was measured during three doses of iNO (5ppm, 10ppm, and 20ppm) using the iNOMAX system (Mallinckrodt Pharmaceuticals) in 20 healthy volunteers. Continuous measurements of microvascular CBF were made with diffuse correlation spectroscopy (DCS), while middle cerebral artery mean flow velocity (MFV) was measured with transcranial Doppler. Cardiopulmonary status and nitric oxide toxicity (i.e. NO 2 ) were continuously monitored for safety. Results: Overall, iNO was safe and well tolerated. All subjects completed the protocol in its entirety. All 3 doses of iNO resulted in a small but statistically significant increase in microvascular CBF as compared to baseline (figure). No significant changes in MFV were identified (figure). During administration of iNO, there was no detrimental effect on blood pressure, nor was there any significant accumulation of toxic metabolites. Conclusions: iNO was safe and produced a small but significant increase in microvascular CBF in healthy volunteers. Future studies are warranted to determine the optimal dose of iNO and to explore the effect in acute ischemic stroke patients.

Evolution of Negative Cooperativity in Glutathione Transferase Enabled Preservation of Enzyme Function

Negative cooperativity in enzyme reactions, in which the first event makes subsequent events less favorable, is sometimes well understood at the molecular level, but its physiological role has often been obscure. Negative cooperativity occurs in human glutathione transferase (GST) GSTP1-1 when it binds and neutralizes a toxic nitric oxide adduct, the dinitrosyl-diglutathionyl iron complex (DNDGIC). However, the generality of this behavior across the divergent GST family and its evolutionary significance were unclear. To investigate, we studied 16 different GSTs, revealing that negative cooperativity is present only in more recently evolved GSTs, indicating evolutionary drift in this direction. In some variants, Hill coefficients were close to 0.5, the highest degree of negative cooperativity commonly observed (although smaller values of nH are theoretically possible). As DNDGIC is also a strong inhibitor of GSTs, we suggest negative cooperativity might have evolved to maintain a residual conjugating activity of GST against toxins even in the presence of high DNDGIC concentrations. Interestingly, two human isoenzymes that play a special protective role, safeguarding DNA from DNDGIC, display a classical half-of-the-sites interaction. Analysis of GST structures identified elements that could play a role in negative cooperativity in GSTs. Beside the well known lock-and-key and clasp motifs, other alternative structural interactions between subunits may be proposed for a few GSTs. Taken together, our findings suggest the evolution of self-preservation of enzyme function as a novel facility emerging from negative cooperativity.

Abstract B08: Metabolic adaption in inflammatory macrophages through the modulation of Fe-S cluster biogenesis factors

Abstract Macrophages are among the most abundant normal cells in the tumor microenvironment, and the mechanistic overlap in the metabolic changes in glycolytic cancer cells and inflammatory immune cells suggest that insights into the mechanisms underlying the metabolic changes could be useful in the treatment of both cancers and inflammatory diseases. Metabolic choices in immune cells are tightly linked to cell fate and function. Inflammatory immune cells, such as M1 macrophages and T-helper 17 cells, undergo a shift from OXPHOS to enhanced glucose uptake, glycolysis and the pentose phosphate pathway, whereas anti-inflammatory cells, such as M2 macrophages and regulatory T cells have lower glycolytic rates and higher levels of oxidative metabolism. The metabolic switch from OXPHOS to aerobic glycolysis (Warburg effect) in Toll-like receptor (TLR)-stimulated myeloid cells has been shown to result from the activation of glycolysis through the action of AKT and HIF-1α signaling, with mitochondrial respiration passively decreasing due to NF-kB mediated induction of inducible nitric oxide synthase (iNOS), which produces the toxic gas nitric oxide that damages the Fe-S cluster cofactors that are essential for mitochondrial electron transport. The results reported here indicate that the pro-inflammatory activation of macrophages also involved the active suppression of mitochondrial pyruvate catabolism and respiration through the down-regulation of several genes in the Fe-S cluster biogenesis pathway. A decrease in Fe-S cluster biogenesis/repair not only resulted in a decrease in the activities of Fe-S cluster dependent enzymes including the respiratory complexes I and II, mitochondrial and cytosolic aconitases, and ferrochelatase, but also reduced lipoylation in the E2 subunit of pyruvate dehydrogenase (PDH) complex, thereby inhibiting pyruvate catabolism through the TCA cycle. Inhibition of glycolytic metabolism limited the TLR-stimulated repression of Fe-S cluster biogenesis factors, consistent with a vital survival function of Fe-S cluster biogenesis in cells that depend on mitochondrial ATP production. Activation of AMPK, inhibition of mTOR, and inhibition of Nf-kB all resulted in reduced TLR-induced suppression of Fe-S cluster biogenesis factors. These results suggested that the regulation of Fe-S cluster biogenesis factors are highly sensitive to cellular metabolic needs and are subject to the regulation of metabolic regulators AMPK and mTOR and inflammation modulator Nf-kB. Our results suggested that, in addition to iNOS induction, repression of Fe-S cluster biogenesis/repair may serve to suppress OXPHOS to promote the production of mitochondrial ROS for host defense, and to drive prolonged glycolytic metabolism to produce ATP, NADPH, and biosynthetic precursors to meet the metabolic and anabolic demands of host defense. Citation Format: Wing-Hang Tong, Nunziata Maio, Tracey A. Rouault. Metabolic adaption in inflammatory macrophages through the modulation of Fe-S cluster biogenesis factors. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr B08.

Research Progress on the Injury Mechanism and the Protective Effect of Blood-Brain Barrier

The Blood-Brain Barrier (BBB) is important structure to maintaining the stabilization of central nervous system. It is composed of endothelial cell and tight junction, the basal lamina, astrocytic endfeet. BBB’s injuries is a important symbol when central nervous system generate lesion in cerebral ischemical reperfusion injury (CIRI), its’ the injury mechanism including that matrix metalloproteinases’ activity raise induce that basal lamina and extracellular matrix degradation, the augmentation of Aquaporin-4’s expression cause vasogenic edema, destruction of tight junction and decrease of related protein expression lead to raise of BBB permeability, the adhesion molecules and cytokines stimulate the inflammatory reaction, a lot of free radicals production and nitric oxide toxicity can pose the damage of endothelial cells and basal lamina. BBB’s protection mainly by reducing the change of BBB’s morphological structure; decreasing BBB’s permeability; reducing the harmful substances go into BBB; maintaining stabilize of central nervous system’s internal environment. Now the mechanism was constantly expounded that BBB’s injury, adjustment and repair, more and more medicines will be applied to the prevention and treatment of the BBB. In this paper, we will review about research progress on the injury mechanism of BBB and the protective effect of it.

Conditional regulation of Puf1p, Puf4p, and Puf5p activity altersYHB1mRNA stability for a rapid response to toxic nitric oxide stress in yeast

Puf proteins regulate mRNA degradation and translation through interactions with 3' untranslated regions (UTRs). Such regulation provides an efficient method to rapidly alter protein production during cellular stress. YHB1 encodes the only protein to detoxify nitric oxide in yeast. Here we show that YHB1 mRNA is destabilized by Puf1p, Puf4p, and Puf5p through two overlapping Puf recognition elements (PREs) in the YHB1 3' UTR. Overexpression of any of the three Pufs is sufficient to fully rescue wild-type decay in the absence of other Pufs, and overexpression of Puf4p or Puf5p can enhance the rate of wild-type decay. YHB1 mRNA decay stimulation by Puf proteins is also responsive to cellular stress. YHB1 mRNA is stabilized in galactose and high culture density, indicating inactivation of the Puf proteins. This condition-specific inactivation of Pufs is overcome by Puf overexpression, and Puf4p/Puf5p overexpression during nitric oxide exposure reduces the steady-state level of endogenous YHB1 mRNA, resulting in slow growth. Puf inactivation is not a result of altered expression or localization. Puf1p and Puf4p can bind target mRNA in inactivating conditions; however, Puf5p binding is reduced. This work demonstrates how multiple Puf proteins coordinately regulate YHB1 mRNA to protect cells from nitric oxide stress.

Super‐Reduced Mechanism of Nitric Oxide Reduction in Flavo‐Diiron NO Reductases

AbstractFlavo‐diiron nitric oxide reductases (FNORs) are non‐haem diiron proteins that protect anaerobic organisms against toxic nitric oxide by reducing it to nitrous oxide. The exact mechanism by which these enzymes operate is still unclear. Recent experimental evidence favors the diiron‐dinitrosyl mechanism involving [{FeNO}7]2 as a reactive intermediate in contrast to the previously suggested diiron‐mononitrosyl pathway. In this work a computational study of the diiron‐dinitrosyl, or the super‐reduced, mechanism has been undertaken and the key reactive intermediates have been identified. The two‐electron reduction of [{FeNO}7]2 to form [{FeNO}8]2 is confirmed as a key step for initiating the mechanism and leads to the instant formation of a hyponitrite adduct. The energy requirements for the formation of the intermediates competes well with the mono‐nitrosyl mechanism. This study provides an insight and a step forward towards gaining a better understanding of the mechanism of NO reduction by FNORs.

Heterogeneous Photocatalysis with Nanoclusters of D10 Metal Ions Doped in Zeolites

Nanoclusters of d10 metal ions, including silver, gold, and copper ions anchored in the zeolite host, have been prepared and characterized using various spectroscopic techniques, including luminescence, Raman, and FT-EXAFS, along with theoretical calculations. Analyses indicate the formation of metal ion oligomers. The encapsulated oligomers in various zeolite hosts have been used to decompose toxic nitric oxide and pesticides into innocuous products. The properties of the various zeolites are identified and the catalytic role of parameters such as composition and pore diameter are investigated. The role of the d10 metal ion clusters in the catalytic reactions is discussed and kinetic mechanisms for the photocatalytic reactions are proposed.

The oxidation product (NO3−) of NO pollutant in flue gas used as a nitrogen source to improve microalgal biomass production and CO2 fixation

Oxydate of toxic nitric oxide pollutant in flue gas by UV/H2O2 was used as nitrogen source for microalgae culture to improve CO2 fixation efficiency by 112.8%.

Do β-Cells Generate Peroxynitrite in Response to Cytokine Treatment?

The purpose of this study was to determine the reactive species that is responsible for cytokine-mediated β-cell death. Inhibitors of inducible nitric oxide synthase prevent this death, and addition of exogenous nitric oxide using donors induces β-cell death. The reaction of nitric oxide with superoxide results in the generation of peroxynitrite, and this powerful oxidant has been suggested to be the mediator of β-cell death in response to cytokine treatment. Recently, coumarin-7-boronate has been developed as a probe for the selective detection of peroxynitrite. Using this reagent, we show that addition of the NADPH oxidase activator phorbol 12-myristate 13-acetate to nitric oxide-producing macrophages results in peroxynitrite generation. Using a similar approach, we demonstrate that cytokines fail to stimulate peroxynitrite generation by rat islets and insulinoma cells, either with or without phorbol 12-myristate 13-acetate treatment. When forced to produce superoxide using redox cyclers, this generation is associated with protection from nitric oxide toxicity. These findings indicate that: (i) nitric oxide is the likely mediator of the toxic effects of cytokines, (ii) β-cells do not produce peroxynitrite in response to cytokines, and (iii) when forced to produce superoxide, the scavenging of nitric oxide by superoxide is associated with protection of β-cells from nitric oxide-mediated toxicity.

Truncated Hemoglobin, HbN, Is Post-translationally Modified in Mycobacterium tuberculosis and Modulates Host-Pathogen Interactions during Intracellular Infection

Mycobacterium tuberculosis (Mtb) is a phenomenally successful human pathogen having evolved mechanisms that allow it to survive within the hazardous environment of macrophages and establish long term, persistent infection in the host against the control of cell-mediated immunity. One such mechanism is mediated by the truncated hemoglobin, HbN, of Mtb that displays a potent O2-dependent nitric oxide dioxygenase activity and protects its host from the toxicity of macrophage-generated nitric oxide (NO). Here we demonstrate for the first time that HbN is post-translationally modified by glycosylation in Mtb and remains localized on the cell membrane and the cell wall. The glycan linkage in the HbN was identified as mannose. The elevated expression of HbN in Mtb and M. smegmatis facilitated their entry within the macrophages as compared with isogenic control cells, and mutation in the glycan linkage of HbN disrupted this effect. Additionally, HbN-expressing cells exhibited higher survival within the THP-1 and mouse peritoneal macrophages, simultaneously increasing the intracellular level of proinflammatory cytokines IL-6 and TNF-α and suppressing the expression of co-stimulatory surface markers CD80 and CD86. These results, thus, suggest the involvement of HbN in modulating the host-pathogen interactions and immune system of the host apart from protecting the bacilli from nitrosative stress inside the activated macrophages, consequently driving cells toward increased infectivity and intracellular survival.

The Impact of Nitric Oxide Toxicity on the Evolution of the Glutathione Transferase Superfamily: A PROPOSAL FOR AN EVOLUTIONARY DRIVING FORCE*

Glutathione transferases (GSTs) are protection enzymes capable of conjugating glutathione (GSH) to toxic compounds. During evolution an important catalytic cysteine residue involved in GSH activation was replaced by serine or, more recently, by tyrosine. The utility of these replacements represents an enigma because they yield no improvements in the affinity toward GSH or in its reactivity. Here we show that these changes better protect the cell from nitric oxide (NO) insults. In fact the dinitrosyl·diglutathionyl·iron complex (DNDGIC), which is formed spontaneously when NO enters the cell, is highly toxic when free in solution but completely harmless when bound to GSTs. By examining 42 different GSTs we discovered that only the more recently evolved Tyr-based GSTs display enough affinity for DNDGIC (KD < 10(-9) M) to sequester the complex efficiently. Ser-based GSTs and Cys-based GSTs show affinities 10(2)-10(4) times lower, not sufficient for this purpose. The NO sensitivity of bacteria that express only Cys-based GSTs could be related to the low or null affinity of their GSTs for DNDGIC. GSTs with the highest affinity (Tyr-based GSTs) are also over-represented in the perinuclear region of mammalian cells, possibly for nucleus protection. On the basis of these results we propose that GST evolution in higher organisms could be linked to the defense against NO.

Bioluminescent detection of peroxynitrite with a boronic acid-caged luciferin

Peroxynitrite, a highly reactive biological oxidant, is formed under pathophysiologic conditions from the diffusion-limited reaction of nitric oxide and superoxide radical anion. Peroxynitrite has been implicated as the mediator of nitric oxide toxicity in many diseases and as an important signaling disrupting molecule (L. Liaudet et al., Front. Biosci.14, 4809–4814, 2009) [1]. Biosensors effective at capturing peroxynitrite in a specific and fast enough manner for detection, along with readouts compatible with in vivo studies, are lacking. Here we report that the boronic acid-based bioluminescent system PCL-1 (peroxy-caged luciferin-1), previously reported as a chemoselective sensor for hydrogen peroxide (G.C. Van de Bittner et al., Proc. Natl. Acad. Sci. USA107, 21316–21321, 2010) [2], reacts with peroxynitrite stoichiometrically with a rate constant of 9.8±0.3×105M−1s−1 and a bioluminescence detection limit of 16nM, compared to values of 1.2±0.3M−1s−1 and 231nM for hydrogen peroxide. Further, we demonstrate bioluminescent detection of peroxynitrite in the presence of physiological competitors: carbon dioxide, glutathione, albumin, and catalase. We also demonstrate the utility of this method to assess peroxynitrite formation in mammalian cells by measuring peroxynitrite generated under normal culture conditions after stimulation of macrophages with bacterial endotoxin lipopolysaccharide. Thus, the PCL-1 method for measuring peroxynitrite generation shows superior selectivity over other oxidants under in vivo conditions.

Physiological, biochemical and molecular responses to a combination of drought and ozone in Medicago truncatula

Drought and tropospheric ozone are escalating climate change problems that can co-occur. In this study, we observed Medicago truncatula cultivar Jemalong that is sensitive to ozone and drought stress when applied singly, showed tolerance when subjected to a combined application of these stresses. Lowered stomatal conductance may be a vital tolerance mechanism to overcome combined ozone and drought. Sustained increases in both reduced ascorbate and glutathione in response to combined stress may play a role in lowering reactive oxygen species and nitric oxide toxicity. Transcriptome analysis indicated that genes associated with glucan metabolism, responses to temperature and light signalling may play a role in dampening ozone responses due to drought-induced stomatal closure during combined occurrence of these two stresses. Gene ontologies for jasmonic acid signalling and innate immunity were enriched among the 300 differentially expressed genes unique to combined stress. Differential expression of transcription factors associated with redox, defence signalling, jasmonate responses and chromatin modifications may be important for evoking novel gene networks during combined occurrence of drought and ozone. The alterations in redox milieu and distinct transcriptome changes in response to combined stress could aid in tweaking the metabolome and proteome to annul the detrimental effects of ozone and drought in Jemalong.

Asymmetric Production of Nitric Oxide in Mouse Primary Cortical Mixed Glial Cell Cultures Treated With Lipopolysaccharide

Activated glial cells produce many toxic molecules, including cytokines and nitric oxide (NO). There is evidence that excess NO production plays a key role in neuronal cell death. Previous research has demonstrated that cortical glial cells from the left and right cortices of the brain secrete cytokines asymmetrically. However, no evidence to date exists about whether glial cell-produced NO is produced asymmetrically as well. The results of this study show that NO production and inducible NO synthase gene expression are both significantly higher in the right hemisphere-derived mixed glial cell compared with cultures derived from the left.