Nitric oxide protects against the cytotoxic effects of reactive oxygen species

Effects of the immune system on muscle regeneration

Muscle regeneration is a complex process orchestrated by multiple steps. Recent findings indicate that inflammatory responses could play central roles in bridging initial muscle injury responses and timely muscle injury reparation. The various types of immune cells and cytokines have crucial roles in muscle regeneration process. In this review, we provide an overview of the functions of acute inflammation in muscle regeneration.

Molsidomine decreases hyperoxia-induced lung injury in neonatal rats

BACKGROUND

The study's objective is to evaluate if Molsidomine (MOL), an anti-oxidant, anti-inflammatory, and anti-apoptotic drug, is effective in treating hyperoxic lung injury (HLI).

METHODS

The study consisted of four groups of neonatal rats characterized as the Control, Control+MOL, HLI, HLI + MOL groups. Near the end of the study, the lung tissue of the rats were evaluated with respect to apoptosis, histopathological damage, anti-oxidant and oxidant capacity as well as degree of inflammation.

RESULTS

Compared to the HLI group, malondialdehyde and total oxidant status levels in lung tissue were notably reduced in the HLI + MOL group. Furthermore, mean superoxide dismutase, glutathione peroxidase, and glutathione activities/levels in lung tissue were significantly higher in the HLI + MOL group as compared to the HLI group. Tumor necrosis factor-α and interleukin-1β elevations associated with hyperoxia were significantly reduced following MOL treatment. Median histopathological damage and mean alveolar macrophage numbers were found to be higher in the HLI and HLI + MOL groups when compared to the Control and Control+MOL groups. Both values were increased in the HLI group when compared to the HLI + MOL group.

CONCLUSIONS

Our research is the first to demonstrate that bronchopulmonary dysplasia may be prevented through the protective characteristics of MOL, an anti-inflammatory, anti-oxidant, and anti-apoptotic drug.

IMPACT

Molsidomine prophylaxis significantly decreased the level of oxidative stress markers. Molsidomine administration restored the activities of antioxidant enzymes. Molsidomine prophylaxis significantly reduced the levels of inflammatory cytokines. Molsidomine may provide a new and promising therapy for BPD in the future. Molsidomine prophylaxis decreased lung damage and macrophage infiltration in the tissue.

The Role of Innate and Adaptive Immune Cells in Skeletal Muscle Regeneration

Skeletal muscle regeneration is highly dependent on the inflammatory response. A wide variety of innate and adaptive immune cells orchestrate the complex process of muscle repair. This review provides information about the various types of immune cells and biomolecules that have been shown to mediate muscle regeneration following injury and degenerative diseases. Recently developed cell and drug-based immunomodulatory strategies are highlighted. An improved understanding of the immune response to injured and diseased skeletal muscle will be essential for the development of therapeutic strategies.

Molecular Mechanisms of Nitric Oxide in Cancer Progression, Signal Transduction, and Metabolism

SIGNIFICANCE

Cancer is a complex disease, which not only involves the tumor but its microenvironment comprising different immune cells as well. Nitric oxide (NO) plays specific roles within tumor cells and the microenvironment and determines the rate of cancer progression, therapy efficacy, and patient prognosis. Recent Advances: Key understanding of the processes leading to dysregulated NO flux within the tumor microenvironment over the past decade has provided better understanding of the dichotomous role of NO in cancer and its importance in shaping the immune landscape. It is becoming increasingly evident that nitric oxide synthase 2 (NOS2)-mediated NO/reactive nitrogen oxide species (RNS) are heavily involved in cancer progression and metastasis in different types of tumor. More recent studies have found that NO from NOS2⁺ macrophages is required for cancer immunotherapy to be effective.

CRITICAL ISSUES

NO/RNS, unlike other molecules, are unique in their ability to target a plethora of oncogenic pathways during cancer progression. In this review, we subcategorize the different levels of NO produced by cells and shed light on the context-dependent temporal effects on cancer signaling and metabolic shift in the tumor microenvironment.

FUTURE DIRECTIONS

Understanding the source of NO and its spaciotemporal profile within the tumor microenvironment could help improve efficacy of cancer immunotherapies by improving tumor infiltration of immune cells for better tumor clearance.

Skeletal muscle regeneration is modulated by inflammation

Skeletal muscle regeneration is a complex process orchestrated by multiple steps. Recent findings indicate that inflammatory responses could play central roles in bridging initial muscle injury responses and timely muscle injury reparation. The various types of immune cells and cytokines have crucial roles in muscle regeneration process. In this review, we briefly summarise the functions of acute inflammation in muscle regeneration.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Immune system is closely relevant to the muscle regeneration. Understanding the mechanisms of inflammation in muscle regeneration is therefore critical for the development of effective regenerative, and therapeutic strategies in muscular disorders. This review provides information for muscle regeneration research regarding the effects of inflammation on muscle regeneration.

Immunobiology of Nitric Oxide and Regulation of Inducible Nitric Oxide Synthase

Nitric oxide (NO) is a bioactive gas that has multiple roles in innate and adaptive immune responses. In macrophages, nitric oxide is produced by inducible nitric oxide synthase upon microbial and cytokine stimulation. It is needed for host defense against pathogens and for immune regulation. This review will summarize the role of NO and iNOS in inflammatory and immune responses and will discuss the regulatory mechanisms that control inducible nitric oxide synthase expression and activity.

Effects of graded levels of montmorillonite on performance, hematological parameters and bone mineralization in weaned pigs

The aim of this study was to investigate the effects of graded levels of montmorillonite, a constituent of clay, on performance, hematological parameters and bone mineralization in weaned pigs. One hundred and twenty, 35-d-old crossbred pigs (Duroc×Large White×Landrace, 10.50±1.20 kg) were used in a 28-d experiment and fed either an unsupplemented corn-soybean meal basal diet or similar diets supplemented with 0.5, 1.0, 2.5 or 5.0% montmorillonite added at the expense of wheat bran. Each treatment was replicated six times with four pigs (two barrows and two gilts) per replicate. Feed intake declined (linear and quadratic effect, p< 0.01) with increasing level of montmorillonite while feed conversion was improved (linear and quadratic effect, p<0.01). Daily gain was unaffected by dietary treatment. Plasma myeloperoxidase declined linearly (p = 0.03) with increasing dietary level of montmorillonite. Plasma malondialdehyde and nitric oxide levels were quadratically affected (p<0.01) by montmorillonite with increases observed for pigs fed the 0.5 and 1.0% levels which then declined for pigs fed the 2.5 and 5.0% treatments. In bone, the content of potassium, sodium, copper, iron, manganese and magnesium were decreased (linear and quadratic effect, p<0.01) in response to an increase of dietary montmorillonite. These results suggest that dietary inclusion of montmorillonite at levels as high as 5.0% does not result in overt toxicity but could induce potential oxidative damage and reduce bone mineralization in pigs.

Effects of graded levels of montmorillonite on performance, hematological parameters and bone mineralization in weaned pigs

The aim of this study was to investigate the effects of graded levels of montmorillonite, a constituent of clay, on performance, hematological parameters and bone mineralization in weaned pigs. One hundred and twenty, 35-d-old crossbred pigs (Duroc×Large White×Landrace, 10.50±1.20 kg) were used in a 28-d experiment and fed either an unsupplemented corn-soybean meal basal diet or similar diets supplemented with 0.5, 1.0, 2.5 or 5.0% montmorillonite added at the expense of wheat bran. Each treatment was replicated six times with four pigs (two barrows and two gilts) per replicate. Feed intake declined (linear and quadratic effect, p< 0.01) with increasing level of montmorillonite while feed conversion was improved (linear and quadratic effect, p<0.01). Daily gain was unaffected by dietary treatment. Plasma myeloperoxidase declined linearly (p = 0.03) with increasing dietary level of montmorillonite. Plasma malondialdehyde and nitric oxide levels were quadratically affected (p<0.01) by montmorillonite with increases observed for pigs fed the 0.5 and 1.0% levels which then declined for pigs fed the 2.5 and 5.0% treatments. In bone, the content of potassium, sodium, copper, iron, manganese and magnesium were decreased (linear and quadratic effect, p<0.01) in response to an increase of dietary montmorillonite. These results suggest that dietary inclusion of montmorillonite at levels as high as 5.0% does not result in overt toxicity but could induce potential oxidative damage and reduce bone mineralization in pigs.

The anti-apoptotic effect of regucalcin is mediated through multisignaling pathways

Regucalcin (RGN/SMP30) was originally discovered in 1978 as a calcium-binding protein that does not contain the EF-hand motif of as a calcium-binding domain. The name, regucalcin, was proposed for this calcium-binding protein, which can regulate various Ca²⁺-dependent enzymes activation in liver cells. The regucalcin gene is localized on the X chromosome, and its expression is mediated through many signaling factors. Regucalcin plays a pivotal role in regulation of intracellular calcium homeostasis in various cell types. Regucalcin also has a suppressive effect on various signaling pathways from the cytoplasm to nucleus in proliferating cells and regulates nuclear function in including deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) synthesis. Overexpression of endogenous regucalcin was found to suppress apoptosis in modeled rat hepatoma cells and normal rat kidney proximal epithelial NRK52 cells induced by various signaling factors. Suppressive effect of regucalcin on apoptosis is related to inhibition of nuclear Ca²⁺-activated DNA fragmentation, Ca²⁺/calmodulin-dependent nitric oxide synthase, caspase-3, Bax, cytochrome C, protein tyrosine kinase, protein tyrosine phosphatase in the cytoplasm and nucleus. Moreover, regucalcin stimulates Bcl-2 mRNA expression and depresses enhancement of caspase-3, Apaf-1 and Akt-1 mRNAs expression. This review discusses that regucalcin plays a pivotal role in rescue of apoptotic cell death, which is mediated through various signaling factors.

Pro-oxidative synergic bactericidal effect of NO: kinetics and inhibition by nitroxides

NO plays diverse roles in physiological and pathological processes, occasionally resulting in opposing effects, particularly in cells subjected to oxidative stress. NO mostly protects eukaryotes against oxidative injury, but was demonstrated to kill prokaryotes synergistically with H2O2. This could be a promising therapeutic avenue. However, recent conflicting findings were reported describing dramatic protective activity of NO. The previous studies of NO effects on prokaryotes applied a transient oxidative stress while arbitrarily checking the residual bacterial viability after 30 or 60min and ignoring the process kinetics. If NO-induced synergy and the oxidative stress are time-dependent, the elucidation of the cell killing kinetics is essential, particularly for survival curves exhibiting a "shoulder" sometimes reflecting sublethal damage as in the linear-quadratic survival models. We studied the kinetics of NO synergic effects on H2O2-induced killing of microbial pathogens. A synergic pro-oxidative activity toward gram-negative and gram-positive cells is demonstrated even at sub-μM/min flux of NO. For certain strains, the synergic effect progressively increased with the duration of cell exposure, and the linear-quadratic survival model best fit the observed survival data. In contrast to the failure of SOD to affect the bactericidal process, nitroxide SOD mimics abrogated the pro-oxidative synergy of NO/H2O2. These cell-permeative antioxidants, which hardly react with diamagnetic species and react neither with NO nor with H2O2, can detoxify redox-active transition metals and catalytically remove intracellular superoxide and nitrogen-derived reactive species such as (•)NO2 or peroxynitrite. The possible mechanism underlying the bactericidal NO synergy under oxidative stress and the potential therapeutic gain are discussed.

Biological nitric oxide signalling: chemistry and terminology

Biological nitrogen oxide signalling and stress is an area of extreme clinical, pharmacological, toxicological, biochemical and chemical research interest. The utility of nitric oxide and derived species as signalling agents is due to their novel and vast chemical interactions with a variety of biological targets. Herein, the chemistry associated with the interaction of the biologically relevant nitrogen oxide species with fundamental biochemical targets is discussed. Specifically, the chemical interactions of nitrogen oxides with nucleophiles (e.g. thiols), metals (e.g. hemeproteins) and paramagnetic species (e.g. dioxygen and superoxide) are addressed. Importantly, the terms associated with the mechanisms by which NO (and derived species) react with their respective biological targets have been defined by numerous past chemical studies. Thus, in order to assist researchers in referring to chemical processes associated with nitrogen oxide biology, the vernacular associated with these chemical interactions is addressed.

Prevention of free fatty acid-induced lipid accumulation, oxidative stress, and cell death in primary hepatocyte cultures by a Gynostemma pentaphyllum extract

Hepatocytes of a primary cell culture that are exposed to high glucose, insulin, and linoleic (LA) acid concentration respond with lipid accumulation, oxidative stress up to cell death. Such alterations are typically found in patients with non-alcoholic fatty liver disease (NAFLD). We used this cellular model to study the effect of an ethanolic Gynostemma pentaphyllum (GP) extract in NAFLD. When hepatocytes were cultured in the presence of high insulin, glucose, and LA concentration the extract completely protected the cells from cell death. In parallel, the extract prevented accumulation of triglycerides (TGs) and cholesterol as well as oxidative stress. Our data further demonstrate that GP stimulates the production of nitric oxide (NO) in hepatocytes and affects the molecular composition of the mitochondrial phospholipid cardiolipin (CL). We conclude that GP is able to protect hepatocytes from cell death, lipid accumulation, and oxidative stress caused by diabetic-like metabolism and lipotoxicity. Therefore, GP could be beneficial for patients with diabetes mellitus and NAFLD.

Bone marrow-derived mesenchymal stem cells modulate BV2 microglia responses to lipopolysaccharide

The immunoregulatory properties of mesenchymal stem cells (MSC) have been demonstrated on a wide range of cells. Here, we describe the modulatory effects of mouse bone marrow-derived MSC on BV2 microglia proliferation rate, nitric oxide (NO) production and CD40 expression. Mouse bone marrow MSC were co-cultured with BV2 cells at various seeding density ratios and activated with lipopolysaccharide (LPS). We show that MSC exert an anti-proliferative effect on microglia and are potent producers of NO when stimulated by soluble factors released by LPS-activated BV2. MSC suppressed proliferation of both untreated and LPS-treated microglia in a dose-dependent manner, significantly reducing BV2 proliferation at seeding density ratios of 1:0.2 and 1:0.1 (p<.05). Co-culturing MSC with BV2 cells at different ratios revealed interesting dynamics in NO production. A high number of MSC significantly increases NO in co-cultures whilst a lower number reduces NO. The increased NO levels in co-cultures may be MSC-derived, as we also show that activated BV2 cells stimulate MSC to produce NO. Cell-cell interaction is not a requirement for this effect as soluble factors released by activated BV2 cells alone do stimulate MSC to produce high levels of NO. Although NO is implicated as a mediator for T cell proliferation, it does not appear to play a major role in the suppression of microglia proliferation. Additionally, MSC reduced the expression of the microglial co-stimulator molecule, CD40. Collectively, these regulatory effects of MSC on microglia offer insight into the potential moderating properties of MSC on inflammatory responses within the CNS.

Redox control of asthma: molecular mechanisms and therapeutic opportunities

An imbalance in reducing and oxidizing (redox) systems favoring a more oxidative environment is present in asthma and linked to the pathophysiology of the defining symptoms and signs including airflow limitation, hyper-reactivity, and airway remodeling. High levels of hydrogen peroxide, nitric oxide ((*)NO), and 15-F(2t)-isoprostane in exhaled breath, and excessive oxidative protein products in lung epithelial lining fluid, peripheral blood, and urine provide abundant evidence for pathologic oxidizing processes in asthma. Parallel studies document loss of reducing potential by nonenzymatic and enzymatic antioxidants. The essential first line antioxidant enzymes superoxide dismutases (SOD) and catalase are reduced in asthma as compared to healthy individuals, with lowest levels in those patients with the most severe asthma. Loss of SOD and catalase activity is related to oxidative modifications of the enzymes, while other antioxidant gene polymorphisms are linked to susceptibility to develop asthma. Monitoring of exhaled (*)NO has entered clinical practice because it is useful to optimize asthma care, and a wide array of other biochemical oxidative and nitrative biomarkers are currently being evaluated for asthma monitoring and phenotyping. Novel therapeutic strategies that target correction of redox abnormalities show promise for the treatment of asthma.

Exhaled nitric oxide in the diagnosis and management of asthma: clinical implications

Exhaled nitric oxide (eNO) used as an aid to the diagnosis and management of lung disease is receiving attention from pulmonary researchers and clinicians alike because it offers a noninvasive means to directly monitor airway inflammation. Research evidence suggests that eNO levels significantly increase in individuals with asthma before diagnosis, decrease with inhaled corticosteroid administration, and correlate with the number of eosinophils in induced sputum. These observations have been used to support an association between eNO levels and airway inflammation. This review presents an update on current opportunities regarding use of eNO in patient care, and more specifically on its potential usage for asthma diagnosis and monitoring. The review will also discuss factors that may complicate use of eNO as a diagnostic tool, including changes in disease severity, symptom response, and technical measurement issues. Regardless of the rapid, convenient, and noninvasive nature of this test, additional well-designed, long-term longitudinal studies are necessary to fully evaluate the clinical utility of eNO in asthma management.

Markers of lung disease in exhaled breath: nitric oxide

Management of airway inflammation requires proper monitoring and treatment to improve long-term outcomes. However, achieving this goal is difficult, as current methods have limitations. Although nitric oxide (NO) was first identified 200 years ago, its physiological importance was not recognized until the early 1980s. Many studies have established the role of NO as an essential messenger molecule in body systems. In addition, studies have demonstrated a significant relationship between changes in exhaled NO levels and other markers of airway inflammation. The technique used to measure NO in exhaled breath is noninvasive, reproducible, sensitive, and easy to perform. Consequently, there is growing interest in the use of exhaled NO in the management of asthma and other pulmonary conditions. The purpose of this review is to promote a basic understanding of the physiologic actions of NO, measurement techniques, and ways that research findings might translate to future application in clinical practice. Specifically, the article will review the role of exhaled NO in regard to its historical background, mechanisms of action, measurement techniques, and implications for clinical practice and research.

Peroxynitrite formation from the simultaneous reduction of nitrite and oxygen by xanthine oxidase

One electron reductions of oxygen and nitrite by xanthine oxidase form peroxynitrite. The nitrite and oxygen reducing activities of xanthine oxidase are regulated by oxygen with K(oxygen) 26 and 100 microM and K(nitrite) 1.0 and 1.1 mM with xanthine and NADH as donor substrates. Optimal peroxynitrite formation occurs at 70 microM oxygen with purine substrates. Kinetic parameters: V(max) approximately 50 nmol/min/mg and K(m) of 22, 36 and 70 microM for hypoxanthine, pterin and nitrite respectively. Peroxynitrite generation is inhibited by allopurinol, superoxide dismutase and diphenylene iodonium. A role for this enzyme activity can be found in the antibacterial activity of milk and circulating xanthine oxidase activity.

Glyceryl trinitrate, a nitric oxide donor, abrogates ferric nitrilotriacetate-induced oxidative stress and renal damage

Ferric nitrilotriacetate (Fe-NTA), a common water pollutant and a known renal carcinogen, acts through the generation of oxidative stress and hyperproliferative response. In the present study, we show that the nitric oxide (NO) generated by the administration of glyceryl trinitrate (GTN) affords protection against Fe-NTA-induced oxidative stress and proliferative response. Administration of Fe-NTA resulted in a significant (P<0.001) depletion of renal glutathione (GSH) content with concomitant increase in lipid peroxidation and elevated tissue damage marker release in serum. Parallel to these changes, Fe-NTA also caused down-regulation of GSH metabolizing enzymes including glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione-S-transferase and several fold induction in ornithine decarboxylase (ODC) activity and rate of DNA synthesis. Subsequent exogenous administration of GTN at doses of 3 and 6mg/kg body weight resulted in significant (P<0.001) recovery of GSH metabolizing enzymes and amelioration of tissue GSH content, in a dose-dependent manner. GTN administration also inhibited malondialdehyde (MDA) formation, induction of ODC activity, enhanced rate of DNA synthesis, and pathological deterioration in a dose-dependent fashion. Further, administration of NO inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), exacerbated Fe-NTA-induced oxidative tissue injury, hyperproliferative response, and pathological damage. Overall, the study suggests that NO administration subsequent to Fe-NTA affords protection against ROS-mediated damage induced by Fe-NTA.

Suppressive effect of endogenous regucalcin on nitric oxide synthase activity in cloned rat hepatoma H4-II-E cells overexpressing regucalcin

The role of endogenous regucalcin, which is a regulatory protein in calcium signaling, in the regulation of nitric oxide (NO) synthase activity in the cloned rat hepatoma H4-II-E cells was investigated. Hepatoma cells were cultured for 24-72 h in the presence of fetal bovine serum (FBS; 10%). NO synthase activity in the 5,500 g supernatant of cell homogenate was significantly increased by the addition of calcium chloride (10 microM) and calmodulin (2.5 microg/ml) in the enzyme reaction mixture. The presence of trifluoperazine (TFP; 50 microM), an antagonist of calmodulin, inhibited the effect of calcium (10 microM) addition in increasing NO synthase activity, indicating the existence of Ca(2+)/calmodulin-dependent NO synthase in hepatoma cells. NO synthase activity was significantly decreased by the addition of regucalcin (10(-8) or 10(-7) M) in the reaction mixture without or with Ca(2+)/calmodulin addition. The effect of regucalcin (10(-7) M) in decreasing NO synthase activity was also seen in the presence of TFP (50 microM) or EGTA (1 mM). The presence of anti-regucalcin monoclonal antibody (10-50 ng/ml) in the reaction mixture caused a significant elevation of NO synthase activity. NO synthase activity was significantly suppressed in the hepatoma cells (transfectants) overexpressing regucalcin. This decrease was completely abolished in the presence of anti-regucalcin monoclonal antibody (50 ng/ml) in the reaction mixture. Moreover, the effect of Ca(2+)/calmodulin addition in increasing NO synthase activity in the hepatoma cells (wild-type) was completely prevented in transfectants. The present study demonstrates that endogenous regucalcin has a suppressive effect on NO synthase activity in the cloned rat hepatoma H4-II-E cells.

Enzymology of the repair of free radicals-induced DNA damage

A number of intrinsic and extrinsic mutagens induce structural damage in cellular DNA. These DNA damages are cytotoxic, miscoding or both and are believed to be at the origin of cell lethality, tissue degeneration, ageing and cancer. In order to counteract immediately the deleterious effects of such lesions, leading to genomic instability, cells have evolved a number of DNA repair mechanisms including the direct reversal of the lesion, sanitation of the dNTPs pools, mismatch repair and several DNA excision pathways including the base excision repair (BER) nucleotide excision repair (NER) and the nucleotide incision repair (NIR). These repair pathways are universally present in living cells and extremely well conserved. This review is focused on the repair of lesions induced by free radicals and ionising radiation. The BER pathway removes most of these DNA lesions, although recently it was shown that other pathways would also be efficient in the removal of oxidised bases. In the BER pathway the process is initiated by a DNA glycosylase excising the modified and mismatched base by hydrolysis of the glycosidic bond between the base and the deoxyribose of the DNA, generating a free base and an abasic site (AP-site) which in turn is repaired since it is cytotoxic and mutagenic.

Mechanisms of the antioxidant effects of nitric oxide

The Janus face of nitric oxide (NO) has prompted a debate as to whether NO plays a deleterious or protective role in tissue injury. There are a number of reactive nitrogen oxide species, such as N2O3 and ONOO-, that can alter critical cellular components under high local concentrations of NO. However, NO can also abate the oxidation chemistry mediated by reactive oxygen species such as H2O2 and O2- that occurs at physiological levels of NO. In addition to the antioxidant chemistry, NO protects against cell death mediated by H2O2, alkylhydroperoxides, and xanthine oxidase. The attenuation of metal/peroxide oxidative chemistry, as well as lipid peroxidation, appears to be the major chemical mechanisms by which NO may limit oxidative injury to mammalian cells. In addition to these chemical and biochemical properties, NO can modulate cellular and physiological processes to limit oxidative injury, limiting processes such as leukocyte adhesion. This review will address these aspects of the chemical biology of this multifaceted free radical and explore the beneficial effect of NO against oxidative stress.

Protection of primary glial cells by grape seed proanthocyanidin extract against nitrosative/oxidative stress

Previous studies showed that proanthocyanidins provide potent protection against oxidative stress. Here we investigate the effects of grape seed proanthocyanidin extract (GSPE) as a novel natural antioxidant on the generation and fate of nitric oxide (NO) in rat primary glial cell cultures. GSPE treatment (50 mg/L) increased NO production (measured by NO(2-) assay) by stimulation of the inducible isoform of NOS. However, GSPE failed to affect the LPS/IFN-gamma-induced NO production or iNOS expression. Similar responses were found in the murine macrophage cell line RAW264.7. GSPE did not show any effect on dihydrodichlorofluorescein fluorescence (ROS marker with high sensitivity toward peroxynitrite) either in control or in LPS/IFN-gamma-induced glial cultures even in the presence of a superoxide generator (PMA). GSPE treatment alone had no effect on the basal glutathione (GSH) status in glial cultures. Whereas the microglial GSH level declined sharply after LPS/IFN-gamma treatment, the endogenous GSH pool was protected when such cultures were treated additionally with GSPE, although NO levels did not change. Glial cultures pretreated with GSPE showed higher tolerance toward application of hydrogen peroxide (H(2)O(2)) and tert-butylhydroperoxide. Furthermore, GSPE-pretreated glial cultures showed improved viability after H(2)O(2)-induced oxidative stress demonstrated by reduction in lactate dehydrogenase release or propidium iodide staining. We showed that, in addition to its antioxidative property, GSPE enhances low-level production of intracellular NO in primary rat astroglial cultures. Furthermore, GSPE pretreatment protects the microglial GSH pool during high output NO production and results in an elevation of the H(2)O(2) tolerance in astroglial cells.

Effects of nitric oxide on reactive oxygen species production and infarction size after brain reperfusion injury

OBJECTIVE

Deleterious effects of strokes may be ameliorated when thrombolysis (i.e., with recombinant tissue plasminogen activator) restores circulation. However, reperfusion injury, mediated by oxygen free radicals (reactive oxygen species [ROS]), may limit the benefits of recombinant tissue plasminogen activator treatment. We hypothesized that, during reperfusion, exogenous nitric oxide (NO) would reduce stroke size by quenching ROS.

METHODS

To investigate this hypothesis, we used two in vivo ischemia-reperfusion models, i.e., autologous cerebral embolism in rabbits and filament middle cerebral artery occlusion in rats. Using these models, we measured ROS levels (rabbit model) and stroke volumes (rat model) in response to transient ischemia, with and without intracarotid administration of ultrafast NO donor proline NO (proliNO).

RESULTS

In the rabbit cerebral embolism model, intracarotid administration of proliNO (10(-6) mol/L) (n = 6) during reperfusion decreased free radical levels from 538 +/- 86 nmol/L in the vehicle-treated group (n = 7) to 186 +/- 31 nmol/L (2,3'-dihydroxybenzoic acid; P < 0.001) and from 521 +/- 86 nmol/L (n = 7) to 201 +/- 39 nmol/L (2,5'-dihydroxybenzoic acid; P < 0.002). In the rat middle cerebral artery occlusion model, intracarotid administration of proliNO (10(-5) mol/L) (n = 10) during reperfusion reduced the brain infarction volume from 256 +/- 48 mm3 in the vehicle-treated group (n = 8) to 187 +/- 41 mm3 (P < 0.005). In both experimental groups, intracarotid infusion of proliNO did not affect regional cerebral blood flow, mean arterial blood pressure, or brain and body temperatures.

CONCLUSION

The beneficial effects of early restoration of cerebral circulation after cerebral ischemia were enhanced by intracarotid infusion of proliNO, most likely because of ROS scavenging by NO. These findings suggest the possibility of preventive treatment of reperfusion injury using NO donors.

Nitric oxide and peroxynitrite in postischemic myocardium

Alterations in the production of nitric oxide (NO.) are a critical factor in the injury that occurs in ischemic and reperfused myocardium; however, controversy remains regarding the alterations in NO. that occur and how these alterations cause tissue injury. As superoxide generation occurs during the early period of reperfusion, the cytotoxic oxidant peroxynitrite (ONOO-) could be formed; however, questions remain regarding ONOO- formation and its role in postischemic injury. Electron paramagnetic resonance spin trapping studies, using the NO. trap Fe(2+)-N-methyl-D-glucamine dithiocarbamate (Fe-MGD), and chemiluminescence studies, using the enhancer luminol, have been performed to measure the magnitude and time course of NO. and ONOO- formation in the normal and postischemic heart. Isolated rat hearts were subjected to control perfusion, or ischemia followed by reperfusion in the presence of Fe-MGD with electron paramagnetic resonance measurements performed on the effluent from these hearts. Whereas only trace signals were present prior to ischemia, prominent NO. adduct signals were seen during the first 2 min of reflow. The reperfusion associated increase in these NO. signals was abolished by nitric oxide synthase inhibition. In hearts perfused with luminol to detect ONOO- formation, a similar marked increase was seen during the first 2 min of reperfusion that was blocked by nitric oxide synthase inhibitors and by superoxide dismutase. Either NG-nitro-L-arginine methyl ester or superoxide dismutase treatment resulted in more than twofold higher recovery of contractile function than in untreated hearts. Immunohistology studies demonstrated that the ONOO(-)-mediated nitration product nitrotyrosine was formed in postischemic hearts, but not in normally perfused controls. Thus, NO. formation is increased during the early period of reperfusion and reacts with superoxide to form ONOO-, which results in protein nitration and myocardial injury.

Antioxidant status and nitric oxide in the malnutrition syndrome kwashiorkor

The pathophysiology of kwashiorkor, a severe edematous manifestation of malnutrition, is still poorly understood. The syndrome is, however, known to be associated with alterations in redox metabolism. To further elucidate the role of oxidative stress in kwashiorkor, we carried out a longitudinal study on the major blood antioxidants at the St. Joseph's Hospital, Jirapa, Ghana. All kwashiorkor patients (K) were followed up for 20 d. In comparison with local healthy controls (C), the plasma total antioxidant status was reduced to less than 50% in the patients (C, 0.87 +/- 0.21 mM; K, 0.40 +/- 0.20 mM; p<0.001). Similarly, the major plasma antioxidant albumin (C, 40.9 +/- 2.5 g/L; K, 19.1 +/- 7.4 g/L; p < 0.001) and erythrocyte glutathione (C, 2.39 +/- 0.28 mM; K, 1.01 +/- 0.33; p < 0.001) were decreased, whereas the levels of bilirubin and uric acid were not significantly altered. Nitrite and nitrate were found to be increased by a factor of 2 in kwashiorkor (C, 120 +/- 46 microM; K, 235 +/- 107 microM; p < 0.001). Over the observation period, the trends of albumin and glutathione levels were related to clinical outcome. These concentrations rose in patients who recovered and fell in patients who did not. Our study strongly supports the hypothesis that oxidative and nitrosative stress play a role in the pathophysiology of edematous malnutrition. Prophylactic and therapeutic strategies should aim at the careful correction of the reduced antioxidant status of the patients.

Nitric oxide and angiogenesis

The steps required for new vessel growth are biologically complex and require coordinate regulation of contributing components, including modifications of cell--cell interactions, proliferation and migration of endothelial cells and matrix degradation. The observation that in vivo angiogenesis is accompanied by vasodilation, that many angiogenesis effectors possess vasodilating properties and that tumor vasculature is in a persistent state of vasodilation, support the existence of a molecular/biochemical link between vasodilation and angiogenesis. Several pieces of evidence converge in the indication of a role for nitric oxide (NO), the factor responsible for vasodilation, in physiological and pathological angiogenesis. Data originated in different labs indicate that NO can act both as an 'actor' of angiogenesis and as a 'director of angiogenesis', both functions being equally expressed during physiological and pathological processes. NO significantly contributes to the prosurvival/proangiogenic program of capillary endothelium by triggering and transducing cell growth and differentiation via endothelial-constitutive NO synthase (ec-NOS) activation, cyclic GMP (cGMP) elevation, mitogen activated kinase (MAPK) activation and fibroblast growth factor-2 (FGF-2) expression. Re-establishment of a balanced NO production in the central nervous system results in a reduction of cell damage during inflammatory and vascular diseases. Elevation of NOS activity in correlation with angiogenesis and tumor progression has been extensively reported in experimental and human tumors. In the brain, tumor expansion and edema formation are sensitive to NOS inhibition. On this basis, the nitric oxide pathway appears to be a promising target for consideration in pro- and anti-angiogenic therapeutic strategies. The use of NOS inhibitors seems appropriate to reduce edema, block angiogenesis and facilitate antitumor drug delivery.

Production of reactive oxygen species after reperfusion in vitro and in vivo: protective effect of nitric oxide

OBJECT

Thrombolytic treatments for ischemic stroke can restore circulation, but reperfusion injury, mediated by oxygen free radicals, can limit their utility. The authors hypothesized that, during reperfusion, nitric oxide (NO) provides cytoprotection against oxygen free radical species.

METHODS

Levels of NO and oxygen free radicals were determined in both reoxygenation in vitro and reperfusion in vivo models using an NO electrochemical probe and high-performance liquid chromatography with the 2,3- and 2,5-dihydroxybenzoic acid trapping method, before and after addition of the NO donor diethanolamine nitric oxide (DEA/NO). Reoxygenation after anoxia produced a twofold increase in NO release by human fetal astrocytes and cerebral endothelial cells (p < 0.005). In both cell lines, there was also a two- to threefold increase in oxygen free radical production (p < 0.005). In human fetal astrocytes and cerebral endothelial cells given a single dose of DEA/NO, free radical production dropped fivefold compared with peak ischemic levels (p < 0.001). In a study in which a rat global cerebral ischemia model was used, NO production in a vehicle-treated group increased 48 +/- 16% above baseline levels after reperfusion. After intravenous DEA/NO infusion, NO reached 1.6 times the concentration of the postischemic peak in vehicle-treated animals. In vehicle-treated animals during reperfusion, free radical production increased 4.5-fold over basal levels (p < 0.01). After intravenous DEA/NO infusion, free radical production dropped nearly 10-fold compared with peak levels in vehicle-treated animals (p < 0.006). The infarct volume in the vehicle-treated animals was 111 +/- 16.9 mm3; after DEA/NO infusion it was 64.8 +/- 23.4 mm3 (p < 0.01).

CONCLUSIONS

The beneficial effect of early restoration of cerebral circulation after cerebral ischemia is limited by reperfusion injury. These results indicate that NO release and oxygen free radical production increase during reperfusion, and suggest a possible early treatment of reperfusion injury using NO donors.

Nitric oxide effect on colonocyte metabolism: co-action of sulfides and peroxide

Luminal levels of nitric oxide/nitrite are high in colitis. Whether nitric oxide is injurious or protective to human colonocytes is unknown and the role of nitric oxide in the genesis of colitis unclear. The aims were to establish whether nitric oxide was injurious to oxidation of substrates (n-butyrate and D-glucose) in isolated human and rat colonocytes both alone and in the presence of hydrogen sulfide and hydrogen peroxide, agents implicated in cell damage of colitis. Nitric oxide generation from S-nitrosoglutathione was measured by nitrite appearance. Colonocytes were isolated and incubated with [1-14C] butyrate or [6-14C] glucose and 2.6 microM nitric oxide, 1.5 mM sodium hydrogen sulfide or 2.5 mM hydrogen peroxide. Acyl-CoA esters were measured by high performance liquid chromatography, 14CO2 radiochemically and lactate/ketones by enzymic methods. Results indicate that nitric oxide very significantly (p < .001) reduced acyl-CoA formation but did not impair 14CO2 generation. Peroxide and sulfide with nitric oxide resulted in significant reduction (p < 0.01) of substrate oxidation to CO2. Sulfide significantly stimulated release of nitric oxide from S-nitrosoglutathione. The principal conclusion is that nitric oxide diminishes CoA metabolism in colonocytes. CoA depletion has been observed in chronic human colitis for which a biochemical explanation has been lacking. For acute injurious action in human colonocytes nitric oxide requires co-action of peroxide and sulfide to impair oxidation of substrates in cells. From current observations treatment of colitis should aim to reduce simultaneously nitric oxide, peroxide and sulfide generation in the colon.

Superoxide enhances interleukin 1beta-mediated transcription of the hepatocyte-inducible nitric oxide synthase gene

BACKGROUND & AIMS

Exposure to oxidative stress, as in states of shock, ischemia-reperfusion injury, or sepsis, commonly initiates a complex cellular cascade of interlocking redox modulatory systems that detoxify electrophiles. In interleukin 1beta (IL-1beta)-treated rat hepatocytes, we have previously demonstrated that inducible nitric oxide synthase (iNOS) protein expression, steady-state iNOS messenger RNA (mRNA) levels, and NO synthesis are increased by oxidative stress induced by superoxide. The effect of hepatocellular redox state upon iNOS gene transcription has not been previously studied.

METHODS

Using rat hepatocytes in primary culture, iNOS gene transcription was induced by IL-1beta. Oxidative stress was mediated by 1,2,3-benzenetriol (BZT), an autocatalytic source of superoxide. Nuclear run-on assays and transient transfection assays using the rat hepatocyte iNOS full-length promoter and deletion constructs were designed to isolate a cis-acting regulatory element. Specificity was confirmed by site-directed mutagenesis. Gel shift analysis determined the presence of a corresponding trans-acting regulatory factor.

RESULTS

In IL-1beta-treated cells, BZT increased iNOS gene transcription without altering mRNA half-life. An antioxidant-responsive element (ARE) was found in the iNOS promoter at base pair -1347, which conferred redox sensitivity. Gel shift analysis identified a corresponding nuclear protein capable of binding to ARE in IL-1beta- and BZT-treated rat hepatocytes.

CONCLUSIONS

An ARE in the rat hepatocyte iNOS promoter confers redox sensitivity and augments IL-1beta-mediated iNOS gene and protein expression in the setting of superoxide treatment.

Opposite effects of nitric oxide and nitroxyl on postischemic myocardial injury

Recent experimental evidence suggests that reactive nitrogen oxide species can contribute significantly to postischemic myocardial injury. The aim of the present study was to evaluate the role of two reactive nitrogen oxide species, nitroxyl (NO(-)) and nitric oxide (NO(.)), in myocardial ischemia and reperfusion injury. Rabbits were subjected to 45 min of regional myocardial ischemia followed by 180 min of reperfusion. Vehicle (0.9% NaCl), 1 micromol/kg S-nitrosoglutathione (GSNO) (an NO(.) donor), or 3 micromol/kg Angeli's salt (AS) (a source of NO(-)) were given i.v. 5 min before reperfusion. Treatment with GSNO markedly attenuated reperfusion injury, as evidenced by improved cardiac function, decreased plasma creatine kinase activity, reduced necrotic size, and decreased myocardial myeloperoxidase activity. In contrast, the administration of AS at a hemodynamically equieffective dose not only failed to attenuate but, rather, aggravated reperfusion injury, indicated by an increased left ventricular end diastolic pressure, myocardial creatine kinase release and necrotic size. Decomposed AS was without effect. Co-administration of AS with ferricyanide, a one-electron oxidant that converts NO(-) to NO(.), completely blocked the injurious effects of AS and exerted significant cardioprotective effects similar to those of GSNO. These results demonstrate that, although NO(.) is protective, NO(-) increases the tissue damage that occurs during ischemia/reperfusion and suggest that formation of nitroxyl may contribute to postischemic myocardial injury.

Enhancement of methylcholanthrene-induced neoplastic transformation in murine C3H 10T1/2 fibroblasts by antisense phosphorothioate oligodeoxynucleotide sequences

Antisense phosphorothioate oligodeoxynucleotides (ODNs) are increasingly used to target specific proteins for inhibition. Previous reports of antisense inhibition of the inducible nitric oxide synthase (iNOS) gene suggested its utility in defining the role of nitric oxide (NO) in carcinogenesis, as NO is mutagenic and chemical inhibitors of iNOS block neoplastic transformation in C3H 10T1/2 fibroblasts. Treatment with ODNs (0.025-25 microM) directed against 15mer sequences in the iNOS coding region decreased NO production consistent with a reduction of iNOS protein and iNOS mRNA, however, control ODNs (2.5 microM) also showed considerable nonspecific inhibition of NO synthesis. Treatment with both iNOS antisense and missense ODNs during the promotional phase of the C3H10T1/2 transformation assay significantly increased the number of neoplastic foci in 3-methylcholanthrene (MCA) treated cells which corresponded with the ability of the ODN to inhibit NO production. Enhanced neoplastic transformation and non-specific inhibition of NO synthesis resulting from exposure to antisense ODNs suggest limitations to their long-term use in humans at higher doses.

Hemodynamic effect of the nitroxide superoxide dismutase mimics

Reactive oxygen species play critical roles in a number of physiologic and pathologic processes. Nitroxides are stable free radical compounds that possess superoxide dismutase (SOD) mimetic activity and have been shown to protect against the toxicity of reactive oxygen species in vitro and in vivo. Tempol, a cell-permeable hydrophilic nitroxide, protects against oxidative stress and also is an in vitro and in vivo radioprotector. In the course of evaluating the pharmacology and toxicity of the nitroxides, Tempol and another nitroxide, 3-carbamoyl-PROXYL (3-CP), were administered intravenously in various concentrations to miniature swine. Tempol caused dose-related hypotension accompanied by reflex tachycardia and increased skin temperature. Invasive hemodynamic monitoring with Swan Ganz catheterization (SGC) confirmed the potent vasodilative effect of Tempol. However, 3-CP had no effect on porcine blood pressure. The hemodynamic effects of Tempol and 3-CP are discussed in the context of differential catalytic rate constants for superoxide disumation that may impact systemic nitric oxide (NO) levels and lead to vasodilation. These findings are consistent with a role for the superoxide ion in the modulation of blood pressure and have potential implications for the systemic use of nitroxides.

Role of superoxide anion in the fungicidal activity of murine peritoneal exudate macrophages against Penicillium marneffei

Penicillium marneffei is an important opportunistic fungal pathogen. The mechanisms of host defense against P. marneffei are not fully understood. In the present study, we, for the first time, investigated the role of superoxide anion (O2-) in the killing of two forms of P. marneffei, yeast cells and conidia, and the role of this killing mediator in the fungicidal activity of IFN-gamma-stimulated murine peritoneal macrophages. P. marneffei yeast cells were susceptible to the killing effect of activated macrophages and chemically generated O2, while conidia were not. These results suggested that O2- played some role in the fungicidal activity of macrophages. However, an oxygen radical scavenger, superoxide dismutase (SOD), did not suppress, but rather enhanced the fungicidal activity of IFN-gamma-stimulated macrophages against P. marneffei yeast cells. This inconsistency was explained by the release of insufficient concentrations of O2- by activated macrophages as compared with the amount of O2- necessary for the killing of yeast cells, which was predicted in a chemical generating system. On the other hand, SOD enhanced the production of nitric oxide (NO) by IFN-gamma-activated macrophages, and their increased fungicidal activity was significantly inhibited by N(G)-monomethyl-L-arginine (L-NMMA), a competitive inhibitor of NO synthase. Our results suggested that O2- does not function as the killing mediator of macrophages against P. marneffei, but rather plays an important role in the regulation of the NO-mediated killing system by suppressing NO production.

Dimethylargininase, a nitric oxide regulatory protein, in Alzheimer disease

In this study, we show that dimethylargininase, a zinc protein involved in the regulation of nitric oxide synthase, is specifically elevated in neurons displaying cytoskeletal abnormalities and oxidative stress in Alzheimer disease (AD) while none of this enzyme was found in neurons in age-matched control cases. Seen in the context of earlier studies showing widespread nitric oxide related damage in AD and the role of dimethylargininase to activate nitric oxide synthetase, through catalytic removal of its endogenous inhibitors, these findings indicate major alterations in nitric oxide regulation in AD. Further, that low levels of zinc specifically inhibit dimethylargininase may provide a link between the numerous studies showing specific abnormalities in zinc and oxidative stress. Finally, our results provide additional evidence that oxidative stress- and nitric oxide-mediated events play important roles in the pathogenesis of AD.

Vasodilators in mechanical ventilation

Vasodilators that affect the pulmonary vasculature are appealing adjuncts in many cardiopulmonary conditions that require mechanical ventilation such as ARDS, COPD, PPHN, and cardiothoracic surgery. The adverse systemic effects of parenteral PGE1 and parenteral prostacyclin limit their usefulness in critically ill patients. Liposomal PGE1 has few systemic effects, but thus far has not resulted in a significant clinical benefit in patients with ARDS. Inhaled NO and aerosolized prostacyclin offer the advantage of selective pulmonary vasodilation with minimal systemic effects. Both agents decrease PAP and in many clinical situations improve oxygenation; however, the physiologic effects of inhaled NO and aerosolized prostacyclin have not convincingly led to improved clinical outcomes. Currently, use of vasodilators in mechanically ventilated patients remains investigational.

Modulation of leukocyte-endothelial interactions by reactive metabolites of oxygen and nitrogen: relevance to ischemic heart disease

Ischemia and reperfusion (I/R) are thought to play an important role in the pathophysiology of ischemic diseases of the heart. It is now well appreciated that leukocyte-endothelial cell interactions are important determinants for I/R-induced microvascular injury and dysfunction. There is a growing body of experimental data to suggest that reactive metabolites of oxygen and nitrogen are important physiological modulators of leukocyte-endothelial cell interactions. A number of investigators have demonstrated that I/R enhances oxidant production within the microcirculation resulting in increases in leukocyte adhesion and transendothelial cell migration. Several other studies have shown that exogenous nitric oxide (NO) donors may attenuate leukocyte and platelet adhesion and/or aggregation in a number of different inflammatory conditions including I/R. The objective of this review is to discuss the physiological chemistry of reactive metabolites of oxygen and nitrogen with special attention given to those interactions that may modulate leukocyte-endothelial cell interactions, provide an overview of the evidence implicating reactive metabolites of oxygen and nitrogen as modulators of leukocyte-endothelial cell interactions in vivo, and discuss how these mechanisms may be involved in the pathophysiology of ischemic heart disease.

Chemical biology of nitric oxide: Insights into regulatory, cytotoxic, and cytoprotective mechanisms of nitric oxide

There has been confusion as to what role(s) nitric oxide (NO) has in different physiological and pathophysiological mechanisms. Some studies imply that NO has cytotoxic properties and is the genesis of numerous diseases and degenerative states, whereas other reports suggest that NO prevents injurious conditions from developing and promotes events which return tissue to homeostasis. The primary determinant(s) of how NO affects biological systems centers on its chemistry. The chemistry of NO in biological systems is extensive and complex. To simplify this discussion, we have formulated the "chemical biology of NO" to describe the pertinent chemical reactions under specific biological conditions. The chemical biology of NO is divided into two major categories, direct and indirect. Direct effects are defined as those reactions fast enough to occur between NO and specific biological molecules. Indirect effects do not involve NO, but rather are mediated by reactive nitrogen oxide species (RNOS) formed from the reaction of NO either with oxygen or superoxide. RNOS formed from NO can mediate either nitrosative or oxidative stress. This report discusses various aspects of the chemical biology of NO relating to biological molecules such as guanylate cyclase, cytochrome P450, nitric oxide synthase, catalase, and DNA and explores the potential roles of NO in different biological events. Also, the implications of different chemical reactions of NO with cellular processes such as mitochondrial respiration, metal homeostasis, and lipid metabolism are discussed. Finally, a discussion of the chemical biology of NO in different cytotoxic mechanisms is presented.

Antimutagenic role of base-excision repair enzymes upon free radical-induced DNA damage

As a consequence of oxidative stress, reactive oxygen species are generated in the cells. They interact with DNA and induce various modifications. Among them, oxidised purines (such as C8-oxoguanine and purines whose imidazole ring is opened), oxidised pyrimidines (such as thymine and cytosine glycols, ring saturated and fragmented pyrimidines), ethenobases and hypoxanthine. These various lesions have either miscoding properties or are blocks for DNA and RNA polymerases during replication and transcription, respectively. Most of these lesions are repaired by the base excision pathway in which the first step is mediated by specific DNA glycosylases. We review the various glycosylases involved in the repair of oxidised bases in Escherichia coli. The Fpg protein (formamidopyrimidine-DNA glycosylase) contains a zinc finger and excises oxidised purines whereas the Nth protein excises oxidised pyrimidines. The Nei protein excises a comparable spectra of pyrimidines and is believed to act as a back up enzyme to the Nth protein. The hypoxanthine-DNA glycosylase excises hypoxanthine residue and is one of the various activities of the AlkA protein (including formyluracil and ethenopurines residues). The Nfo protein was shown to have a novel activity that incises 5' to an alpha-deoxyadenosine residue (the anomer of deoxyadenosine formed by gamma-irradiation). The mechanism of action of the Fpg and Nth proteins are discussed. The properties of the human counterpart of the Fpg and Nth proteins the hNth and OGG1 proteins, respectively are also reviewed.