Protective Role Of Nitric Oxide Research Articles

Sodium chloride stress induces nitric oxide accumulation in root tips and oil body surface accompanying slower oleosin degradation in sunflower seedlings

Present work highlights the involvement of endogenous nitric oxide (NO) in sodium chloride (NaCl)-induced biochemical regulation of seedling growth in sunflower (Helianthus annuus L., cv. Morden). The growth response is dependent on NaCl concentration to which seedlings are exposed, they being tolerant to 40 mM NaCl and showing a reduction in extension growth at 120 mM NaCl. NaCl sensitivity of sunflower seedlings accompanies a fourfold increase in Na(+) /K(+) ratio in roots (as compared to that in cotyledons) and rapid transport of Na(+) to the cotyledons, thereby enhancing Na(+) /K(+) ratio in cotyledons as well. A transient increase in endogenous NO content, primarily contributed by putative NOS activity in roots of 4-day-old seedlings subjected to NaCl stress and the relative reduction in Na(+) /K(+) ratio after 4 days, indicates that NO regulates Na(+) accumulation, probably by affecting the associated transporter proteins. Root tips exhibit an early and transient enhanced expression of 4,5-diaminofluorescein diacetate (DAF-2DA) positive NO signal in the presence of 120 mM NaCl. Oil bodies from 2-day-old seedling cotyledons exhibit enhanced localization of NO signal in response to 120 mM NaCl treatment, coinciding with a greater retention of the principal oil body membrane proteins, i.e. oleosins. Abolition of DAF positive fluorescence by the application of specific NO scavenger [2-phenyl-4,4,5,5-tetramethyllimidazoline-1-oxyl-3-oxide (PTIO)] authenticates the presence of endogenous NO. These novel findings provide evidence for a possible protective role of NO during proteolytic degradation of oleosins prior to/accompanying lipolysis.

Protective roles of nitric oxide on antioxidant systems in tall fescue leaves under high-light stress

Nitric oxide (NO) is an important molecule involved in many physiological processes. In this study, the effect of NO on oxidative damage caused by high levels of light was investigated in tall fescue leaves. Tall fescue was developed in relative low light intensity (100
mol m-2 s-1) for 21 days and then transferred to high light (500
mol m-2 s-1). Tall fescue leaves was supplied with NO donor, sodium nitroprusside (SNP), before high-light treatment to determine the physiological mechanisms of NO on tall fescue tolerance to high-light stress. Treatment of tall fescue leaves with 100
M SNP before highlight stress resulted in alleviated light-induced electrolyte leakage, malondialdehyde and carbonyl contents in tall fescue leaves. The levels of H2O2 and superoxide radical ( ·- 2 O ) were reduced as well. Moreover, the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) increased in tall fescue in presence of SNP under high-light stress. This pattern was reversed by application of NO scavenger, 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) before light treatment. Pronounced increases of NO production were found in tall fescue leaves after exposure to high-light stress. The results suggested that high-light stress elevated NO level and that NO might act as a signalling molecule to enhance antioxidant enzyme activities, further protecting against injuries caused by high-light stress.

The role of nitric oxide synthesis induction and inhibition in regulation of blood neutrophil cell death during oxidative disbalance

Modeling oxidative stress in vitro with 5mM H2O2 has demonstrated a protective role of nitric oxide on realization of constitutional blood neutrophil cell death. The NO-synthase inductor L-arginine and the inhibitor of nitric oxide synthesis, L-NAME, influenced on the amount of annexin-positive cells, the content of Bax protein, reactive oxygen species, cyclic nucleotides, and calcium homeostasis in neutrophils under conditions realizing programmed death during oxidative stress in vitro and under acute inflammation. During oxidative stress L-arginine normalized the increased intracellular Ca2+ level and the cAMP/cGMP ratio due to increase of cGMP level, stabilized metabolism and prolonged neutrophil life. During acute inflammation NO induction was insufficient for limitation of Ca2+ release into cytosol and for onset of the apoptotic effect; blockade of NO synthesis deteriorated this situation by activating neutrophil apoptosis due to the sharp increase in Ca2+ content and reduction of cyclic nucleotides in cytosol. The protective effect of NO on neutrophil cell death during oxidative dysbalance is not associated with regulation of apoptotic protein Bax.

Nitric oxide mitigates apoptosis in human endothelial cells induced by 9,10-phenanthrenequinone: Role of proteasomal function

It has been widely recognized that nitric oxide (NO) suppresses oxidative damage of endothelial cell, but little is known about its pathophysiological role in apoptotic induction by 9,10-phenanthrenequinone (9,10-PQ), a major quinone component in diesel exhaust particles. Here, we have investigated the change in NO level in human aortic endothelial cells and the effect of NO in each step of apoptotic signaling initiated by 9,10-PQ. Treatment with 9,10-PQ evoked a bell-shaped production of NO, which was presumably due to increase in an active form of endothelial NO synthase. Pretreatment with exogenous NO decreased the susceptibility of the cells to 9,10-PQ, and retrieved from apoptotic signaling (reactive oxygen species generation, glutathione depletion and caspase activation) induced during exposure to high concentrations of 9,10-PQ. In addition, inhibition of endogenous NO production augmented the toxicity of 9,10-PQ. Interestingly, the 9,10-PQ treatment resulted in marked decreases in the proteasomal activities, which were partially abrogated by NO and a cell-permeable cGMP analog. These results indicate that proteasomal dysfunction by oxidative stress participates in the 9,10-PQ-induced apoptotic signaling and is ameliorated by NO via a cGMP-dependent pathway, thereby suggesting the protective role of NO in vascular damage caused by 9,10-PQ.

Nitric Oxide-Mediated Toxicity in Paraquat-Exposed SH-SY5Y Cells: A Protective Role of 7-Nitroindazole

The precise mechanism underlying the role of nitric oxide (NO) or nitric oxide synthases (NOSs) in paraquat-mediated toxicity is yet to be fully elucidated. The importance of the NADPH-diaphorase activity of NOSs in paraquat toxicity, in addition to the production of NO, has previously been reported as a mechanism of toxicity. However, other studies have highlighted the toxicity of NO alone and, conversely a protective role of NO in paraquat-mediated toxicity has also been described. The goal of this study was to clarify the involvement of NO and NOS in paraquat-mediated toxicity in an SH-SY5Y cell system, and to evaluate the putative role of 7-nitroindazole as a protective agent in human neural cells. Our results indicate that the three previously described isoforms of NOS are expressed in SH-SY5Y cells, with the data showing that these synthases act as paraquat diaphorases. While this process could occur at the expense of NO production, NO alone does play a toxic role, with its production leading to the formation of the toxicant peroxynitrite. Although the efficacies of the different inhibitors tested cannot be directly compared because the various NOS forms were probably inhibited to differing extents, the results support the idea that endogenous and inducible NO is a neurotoxic mediator of the effects of paraquat. The NADPH-diaphorase activity of NOS and NO production are therefore factors implicated in the toxicity mediated by the herbicide paraquat.

Nitric oxide regulates TLR sensitivity and cytokine production by PDCA1+/Ly6C+ “inflammatory” dendritic cells and dendritic cell programming of Th1 immune responses. (90.28)

Abstract Studies using Nitric Oxide Synthase 2 knockout (NOS2 KO) mice have implicated nitric oxide (NO) in the control of Th1 T cells, autoreactive T cell and prevention of autoimmunity. We investigated whether the effect of NO on DCs might contribute to the NO-mediated control of Th1 immune responses. We found that GM-CSF and IL4-derived bone marrow DCs (GM/IL4-DCs) from NOS2 KO mice have enhanced survival and responsiveness to TLR signals compared to WT DCs. TLR stimuli induce a substantial up-regulation in NOS2 KO GM/IL4-DCs of a Ly6Ch DC subset characterized by: 1) high expression of co-stimulatory molecules and other maturation markers (CD86h/MHCIIh/PDCA1+); 2) a substantial increase in inflammatory cytokine production; and 3) decreased Mac3 expression compared to WT DCs. The DC subset dysregulated in the absence of NO resembles the recently described "inflammatory" DC. Furthermore, TLR-stimulated OVA-loaded, NOS2 KO GM/IL4-DCs compared to WT DCs induced increased IFNγ production of OTII CD4+ T cells either in vitro or in vivo. Our findings suggest that autocrine NO drives DC differentiation toward an "inflammatory" DC with a more macrophage phenotype and with lower co-stimulator/antigen-presenting capability and cytokine production, and thus toward a DC with less potential to activate Th1 immune responses. The [EC1]NO effects on DC programming of T cells may be crucial for the protective role of NO in autoimmune diseases. (Supported by NIH grants AI44257 and AI52203). [EC1]less potential for adaptive immunity, why would this be a good thing?

Astrocyte response to Junín virus infection

In a previous study of experimental murine encephalitis induced by Junín virus (JV), an arenavirus, we showed increased expression of iNOS by unidentified cells, concomitant with the astrocyte reaction. The specific inhibition of iNOS was associated with greater mortality but lower astrocytosis, suggesting that the protective role of nitric oxide (NO) synthesized by iNOS was related to enhanced astrocyte activation, representing a beneficial cellular response to virus-induced central nervous system damage. In the present work, cultured astrocytes were used to study whether JV infection could trigger iNOS expression and assess its eventual relationship with viral replication, glial fibrilary acidic protein (GFAP) expression levels and the presence of apoptosis. We found that JV infection of astrocytes did not induce apoptosis but produced both increased iNOS synthesis, detected by immunocytochemistry and fluorescence activated cell sorting (FACS) analysis, and increased NO, which was indirectly measured by nitrite/nitrate levels. These changes occurred early relative to the increases in GFAP expression, as detected by immunocytochemistry, FACS analysis and RT-PCR. The fact that iNOS inhibition abolished enhanced GFAP expression in infected monolayers suggests that NO was directly involved. In addition, iNOS inhibition enhanced virus replication. Together with data from confocal microscopy, these results suggest that JV induces iNOS expression in infected astrocytes and that the resulting NO has an important role both in reducing viral replication and in enhancing subsequent astrocyte activation.

Protective role of exogenous nitric oxide against oxidative-stress induced by salt stress in barley ( Hordeum vulgare)

To probe into the potential of relieving the oxidative damage of salt stress, we investigated the protective role of nitric oxide on barley under salt stress. Salt stress resulted in increased ion leakage, lipid peroxidation and protein oxidation in barley leaves. Simultaneous treatments of barley leaves with 50 μM sodium nitroprusside, a nitric oxide donor, alleviated the damage of salt stress, reflected by decreased ion leakage, and malendialdehyde (MDA), carbonyl, and hydrogen peroxide content in barley leaves. The presence of the nitric oxide donor increased the activities of superoxide dismutases (SOD), ascorbate peroxidases (APX), and catalases (CAT). Meantime, sodium nitroprusside addition increased accumulation of ferritin at the protein level, indicating that nitric oxide directly regulated ferritin accumulation. These results suggested that nitric oxide can effectively protect seedlings from salt stress damage by enhancing activities of antioxidant enzymes to quench the excessive reactive oxygen species caused by salt stress and inducing the increase of ferritin accumulation to chelate larger number of ferrous ion. Information from this study can be used to improve soil management practices for sustainable use of salt-affected soils in the future.

Nitric oxide in inflammation and pain associated with osteoarthritis

Osteoarthritis (OA) is a degenerative disease involving chondrocytes, cartilage and other joint tissues, and has a number of underlying causes, including both biochemical and mechanical factors. Although proinflammatory factors including nitric oxide (NO) are associated with OA, there is recent evidence suggesting that NO and its redox derivatives may also play protective roles in the joint. However, the mechanisms that underlie the development and progression of OA are not completely understood. Experiments have demonstrated that NO plays a catabolic role in the development of OA and mediates the inflammatory response, is involved in the degradation of matrix metalloproteinases, inhibits the synthesis of both collagen and proteoglycans, and helps to mediate apoptosis. However, there is also evidence that in cultured chondrocytes the addition of exogenous NO may inhibit proinflammatory activation by preventing the nuclear localization of the transcription factor nuclear factor-κB, whereas the presence of peroxynitrite – a redox derivative of NO – appears to enhance the inflammatory response by sustaining the nuclear localization of nuclear factor-κB. In addition, under some conditions exogenous NO can stimulate collagen synthesis in cultured rat fibroblasts and human tendon cells. The protective roles of NO in multiple cell types, along with the opposing activities in cultured chondrocytes, suggest that NO may play additional protective roles in chondrocyte function. NO and its derivatives have a similarly complicated involvement in nociception and pain, which may contribute to the functional disability of OA. Further research may help to elucidate a potential role for NO-donating agents in the management of OA.

Protective role of nitric oxide during hydrogen peroxide-induced oxidative stress in tobacco plants

Nitric oxide, produced from exogenous NO donor, sodium nitroprusside, and hydrogen peroxide exerted antagonistic effects on tobacco leaves at micromolar concentrations but induced synergistic effects at millimolar concentrations. During H2O2-induced oxidative stress, low concentrations of NO inhibited lipid peroxidation, counteracted the fragmentation of total DNA, and prevented accumulation of soluble proteins in Nicotiana plumbaginifolia cells. When applied at high concentrations, NO induced the caspase-like activity, promoted degradation of DNA and soluble proteins, and reduced ATP synthesis. The results are consistent with the hypothesis that NO performs a dual role in plants, acting as antioxidant (scavenger of reactive oxygen species) and as a signaling messenger. There are grounds to believe that, irrespective of the mechanism involved, nitric oxide performs a protective role during oxidative stress in tobacco leaves, because even high concentrations of NO exerted no immediate toxic effect but induced the programmed cell death through the activation of caspase-like proteases.

Protective roles of nitric oxide on germination and antioxidant metabolism in wheat seeds under copper stress

Nitric oxide (NO) is a multifunctional gaseous signal in plant. In the present study, we found that pretreatment with NO could significantly improve wheat seeds germination and alleviate oxidative stress against copper toxicity. With the enhancement of copper stress, the germination percentage of wheat seeds decreased gradually. Pretreatment during wheat seed imbibition with sodium nitroprusside (SNP), an NO donor, could greatly reverse the inhibitory effect of the following copper stress to wheat seeds germination. SNP-pretreated seeds also tended to retain higher amylase activities than that of the control without SNP pretreatment. On the other hand, there was no apparent difference in the activities of esterase in wheat seeds pretreated with or without SNP. Further investigations showed that pretreatment with NO donor dramatically stimulated the activities of superoxide dismutase (SOD, EC 1.15.1.1) and catalase (CAT, EC 1.11.1.6), decreased the activities of lipoxygenases, sustained a lower level of malondialdehyde, and interfered with hydrogen peroxide (H2O2) excessive accumulation compared with the control, thereby enhancing the antioxidative capacity in wheat seeds under copper stress. In addition, the seed copper contents were not significant different between those pretreated with SNP and the controls, inferring that protective roles of NO was not responsible for preventing Cu uptake.

Protective role for nitric oxide during the endoplasmic reticulum stress response in pancreatic β-cells

Higher requirements for disulfide bond formation in professional secretory cells may affect intracellular redox homeostasis, particularly during an endoplasmic reticulum (ER) stress response. To assess this hypothesis, we investigated the effects of the ER stress response on the major redox couple (GSH/GSSG), endogenous ROS production, expression of genes involved in ER oxidative protein folding, general antioxidant defense, and thiol metabolism by use of the well-validated MIN6 beta-cell as a model and mouse islets. The data revealed that glucose concentration-dependent decreases in the GSH/GSSG ratio were further decreased significantly by ER-derived oxidative stress induced by inhibiting ER-associated degradation with the specific proteasome inhibitor lactacystin (10 microM) in mouse islets. Notably, minimal cell death was observed during 12-h treatments. This was likely attributed to the upregulation of genes encoding the rate limiting enzyme for glutathione synthesis (gamma-glutamylcysteine ligase), as well as genes involved in antioxidant defense (glutathione peroxidase, peroxiredoxin-1) and ER protein folding (Grp78/BiP, PDI, Ero1). Gene expression and reporter assays with a NO synthase inhibitor (Nomega-nitro-L-arginine methyl ester, 1-10 mM) indicated that endogenous NO production was essential for the upregulation of several ER stress-responsive genes. Specifically, gel shift analyses demonstrate NO-independent binding of the transcription factor NF-E2-related factor to the antioxidant response element Gclc-ARE4 in MIN6 cells. However, endogenous NO production was necessary for activation of Gclc-ARE4-driven reporter gene expression. Together, these data reveal a distinct protective role for NO during the ER stress response, which helps to dissipate ROS and promote beta-cell survival.

Role of Hepatic Nitric Oxide Synthases in Rats with Thioacetamide-induced Acute Liver Failure and Encephalopathy

Hepatic encephalopathy is neuropsychiatric derangement secondary to hepatic decompensation or portal-systemic shunting. Nitric oxide (NO) synthase inhibition aggravates encephalopathy and increases mortality in rats with thioacetamide (TAA)-induced acute liver failure, suggesting a protective role of NO. This study investigated the roles of endothelium-derived constitutive NO synthase (eNOS) and inducible NOS (iNOS) in the liver of rats with fulminant hepatic failure and encephalopathy. Male Sprague-Dawley rats (300-350 g) were randomized to receive TAA 350 mg/kg/day, by intraperitoneal injection or normal saline for 3 days. Severity of encephalopathy was assessed with the Opto-Varimex animal activity meter. Plasma levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase, and bilirubin were measured. Hepatic iNOS and eNOS RNA and protein expressions were assessed by reverse transcription-polymerase chain reaction and Western blot analyses, respectively. The TAA group showed lower motor activity counts than the normal saline group. Hepatic eNOS, but not iNOS, mRNA and protein expressions were enhanced in the TAA group. In addition, hepatic eNOS mRNA expression was negatively correlated with total movement but positively correlated with ALT and AST. Protein expression of hepatic eNOS was positively correlated with ALT, AST and bilirubin. Upregulation of hepatic eNOS was observed in rats with TAA-induced fulminant hepatic failure and encephalopathy, which might play a regulatory role.

Inhaled nitrite treats experimental pulmonary arterial hypertension

INTRODUCTION: Pulmonary arterial hypertension (PAH) is a disease of pulmonary arteries characterized by proliferation and remodeling, resulting in an increase in vascular resistance and heart failure. The vasoregulatory and protective role of nitric oxide in PAH has been characterized. The purpose of these studies was to test the hypothesis that inhaled nitrite protects against/reverses PAH.

Endothelial nitric oxide synthase gene polymorphisms in patients with nontraumatic femoral head osteonecrosis

As endothelial nitric oxide synthase (eNOS) has beneficial effects on skeletal, vascular, and thrombotic systems, the association between nontraumatic femoral head osteonecrosis (FHON) and eNOS gene polymorphisms was investigated in Korean patients with FHON. Genomic DNA from 103 patients with nontraumatic FHON (idiopathic in 50, steroid-induced in 29, and alcohol abuse in 24) and 103 control subjects matched for gender and age (3-year range) was analyzed for the 27-bp repeat polymorphism in intron 4 and Glu298Asp polymorphism in exon 7. The frequencies of alleles and genotypes were compared between patients and control subjects. The frequency of 4a allele was significantly higher in total patients than control subjects [6.8% vs. 2.4%, p = 0.0345, odds ratio (OR) 2.931]. In subgroup analysis, the 4a allele significantly increased in patients with idiopathic FHON versus control subjects (9.0% vs. 2.4%, p = 0.0297, OR 3.976). The frequency of the 4a/b genotype in total patients (13.6% vs. 4.9%, p = 0.0302, OR 3.083) as well as patients with idiopathic FHON (18.0% vs. 4.9%, p = 0.0246, OR 4.302) was higher than control subjects. The distribution of Glu298Asp polymorphisms was not significantly different between patients and control subjects. Microstellate polymorphism in intron 4 of eNOS polymorphism was significantly associated with idiopathic FHON in Korean patients. Because 4a allele is associated with lower synthesis of eNOS, these results suggest that carrier state of 4a allele in intron 4 might be a genetic risk factor of FHON and could provide insight into the protective role of nitric oxide in the pathogenesis of FHON.

Nitric oxide induction as a novel immunoepidemiological target in malaria‐infected patients from endemic areas of the Islamic Republic of Iran

Objective. Malaria has been prevalent for a long time in Iran and continues to be a health problem despite substantial control programs. In addition to numerous cytokines, nitric oxide (NO) is thought to be a key molecule and a novel target of malaria immunopathology. Material and methods. The objective of this research was to measure reactive nitrogen intermediates (RNI) as stable metabolites of NO induction in plasma of malaria‐infected patients in Iran. In this study, 235 blood samples from malaria patients and 80 blood samples from healthy controls were randomly collected from different malarial endemic provinces of Iran, located in southeastern (Sistan & Balouchestan, Hormozgan, Kerman) and northwestern (Ardabil) areas. The involvement of NO in malaria patients has been investigated by statistical analysis of RNI values. Griess micro assay (GMA) was used during Plasmodium vivax, P. falciparum and mixed infections, in order to evaluate whether RNI changes are related to the provincial areas, parasite strains, clinical symptoms and age and gender parameters. Results. The results showed a significant increase of RNI level in malaria patients compared with the control groups of Ardabil (p<0.01), Sistan & Balouchestan, Hormozgan and Kerman (p<0.001) provinces. The level of RNI was higher in mixed plasmodial infection than in single infection. Conclusions. The high level of RNI was dependent on the type of infection, the plasmodia strain, the clinical symptoms, the age groups and the endemic provinces. Although, this study did not clarify the pathogenic and/or protective role of NO in malaria, our findings provide a novel immunoepidemiological aspect of basal NO production in patients with malaria in endemic areas in Iran.

A Possible Modulatory Role of Nitric Oxide in Paraquat-induced Lung Injury in Mice

The present study was undertaken to evaluate whether stimulation or inhibition of Nitric Oxide (NO) synthesis could affect lung toxicity induced by acute administration of paraquat (PQ) in mice. L-arginine (L-arg.), NG-nitro-L-arginine methyl ester (L-NAME) and aminoguanidine (AG) were employed as NO precursor, competitive and specific NO synthesis inhibitors, respectively. PQ was administered intraperitoneally to Swiss albino mice at a single dose of 50 mg kg -1 . L-arg. (700 mg kg -1 day-1), L-NAME (150 mg kg -1 day -1 ) or AG (100 mg kg -1 day -1 ) was given in drinking water of mice for 5 days before and one day after PQ administration. Appropriate controls were performed. PQ administratio n resulted in a pronounced elevation in lipid peroxides (157%) as well as decreased activity of alkaline phosphatase (ALP) (48%) and non-protein thiols (40%) in lung tissue compared to control non-treated mice as evidences of lung injury. Serum level of NO end products, nitrate and nitrite significantly elevated due to PQ administration (150%) as compared to control level. In mice given combined treatment of L-arg. and PQ, a remarkable rise in the serum level of nitrate and nitrite (140%) compared to the PQ group was observed. In addition, L-arg. ameliorated the increased level of lipid peroxides and non-protein thiols depletion as well as the decreased activity of ALP caused by PQ respectively. On the other hand, L-NAME and AG potentiated the deleterious effects of PQ on serum NO, lung lipid peroxides content, non-protein thiols content and alkaline phosphatase activity. In conclusion, PQ-induced lung injury in mice is alleviated by L-arg. but exacerbated by L-NAME and AG supplementati on. This could point out to a possible protective role of NO in PQ lung toxicity.

The protective roles of nitric oxide and superoxide dismutase in adriamycin-induced cardiotoxicity

Treatment with adriamycin (ADR) is associated with cardiotoxicity mediated through the generation of superoxide (O2*-). Because nitric oxide (*NO) reacts with O2*-, generating peroxynitrite, we hypothesized that decreased *NO production would lead to protection in acute cardiac injury. We investigated the role of decreased *NO levels in exacerbation of ADR-induced cardiotoxicity in vivo using iNOS (-/-) mice. Pathology, biochemical injury markers, and cardiac function were used to assess ADR-induced cardiac injury. Ultrastructural analysis demonstrated that iNOS (-/-) mice exhibited extensive cytoplasmic swelling and degeneration of mitochondria when compared to wildtype mice following treatment with ADR. Mice lacking iNOS exhibited a decrease in resting indices of cardiac function as well as an impairment in the positive inotropic actions of isoproterenol following treatment with ADR compared to nTg mice. Cardiac troponin, creatine phosphokinase, and lactate dehydrogenase levels were significantly increased after treatment in iNOS (-/-) mice as compared to controls and wildtype mice. These results indicate that a lack of *NO production by iNOS caused significantly enhanced cardiac injury. However, when iNOS (-/-) mice were crossed with manganese superoxide dismutase (MnSOD)-overexpressing animals, mitochondrial injury was ameliorated to the level of the wild type. These findings suggest that reduction of *NO levels mediated by ADR treatment leads to increased cardiac mitochondrial injury that can be attenuated by a compensatory increase in MnSOD.

Role of Nitric Oxide on Motor Behavior

The present review paper describes results indicating the influence of nitric oxide (NO) on motor control. Our last studies showed that systemic injections of low doses of inhibitors of NO synthase (NOS), the enzyme responsible for NO formation, induce anxiolytic effects in the elevated plus maze whereas higher doses decrease maze exploration. Also, NOS inhibitors decrease locomotion and rearing in an open field arena. These results may involve motor effects of this compounds, since inhibitors of NOS, NG-nitro-L-arginine (L-NOARG), N(G)-nitro-L-arginine methylester (L-NAME), N(G)-monomethyl-L-arginine (L-NMMA), and 7-Nitroindazole (7-NIO), induced catalepsy in mice. This effect was also found in rats after systemic, intracebroventricular or intrastriatal administration. Acute administration of L-NOARG has an additive cataleptic effect with haloperidol, a dopamine D2 antagonist. The catalepsy is also potentiated by WAY 100135 (5-HT1a receptor antagonist), ketanserin (5HT2a and alfal adrenergic receptor antagonist), and ritanserin (5-HT2a and 5HT2c receptor antagonist). Atropine sulfate and biperiden, antimuscarinic drugs, block L-NOARG-induced catalepsy in mice. L-NOARG subchronic administration in mice induces rapid tolerance (3 days) to its cataleptic effects. It also produces cross-tolerance to haloperidol-induced catalepsy. After subchronic L-NOARG treatment there is an increase in the density NADPH-d positive neurons in the dorsal part of nucleus caudate-putamen, nucleus accumbens, and tegmental pedunculupontinus nucleus. In contrast, this treatment decreases NADPH-d neuronal number in the substantia nigra compacta. Considering these results we suggest that (i) NO may modulate motor behavior, probably by interfering with dopaminergic, serotonergic, and cholinergic neurotransmission in the striatum; (ii) Subchronic NO synthesis inhibition induces plastic changes in NO-producing neurons in brain areas related to motor control and causes cross-tolerance to the cataleptic effect of haloperidol, raising the possibility that such treatments could decrease motor side effects associated with antipsychotic medications. Finally, recent studies using experimental Parkinson's disease models suggest an interaction between NO system and neurodegenerative processes in the nigrostriatal pathway. It provides evidence of a protective role of NO. Together, our results indicate that NO may be a key participant on physiological and pathophysiological processes in the nigrostriatal system.

Beneficial effect of tetrahydrobiopterin on the survival of rats exposed to hepatic ischemia-reperfusion injury

Introduction The protective role of nitric oxide (NO) against hepatic ischemia-reperfusion (I/R) injury remains controversial. In this study we investigated the effect of tetrahydrobiopterin (BH4) on the survival of rats exposed to an hepatic I/R injury. Methods The rats were subjected to 100 minutes of 70% hepatic ischemia 30 minutes after administration of BH4 or saline. A specific inducible NO synthase (iNOS) blocker, 1400W, was used to evaluate endogenous iNOS. NOS protein measured the histological appearance of the liver by Western blotting, and survival was evaluated after reperfusion. Results The 1-week survival rate was 60% among the BH4 group and 10% for the saline group. The serum ALT and bilirubin values in the BH4 group were significantly lower than the saline group. Histological examination of the liver revealed only a small necrotic area in the BH4 group as opposed to massive necrosis and cell infiltration in the saline group. Injection of 1400W significantly decreased the prolongation of survival produced by BH4. Conclusions BH4 significantly improved the survival rate, the histological findings, and the liver function, thereby reducing liver failure. Western blotting showed a higher level of iNOS protein in the BH4 group than the saline group, 1400W suppressed this effect of BH4. Taken together, these observations suggest that NO derived from reactions driven by BH4-induced iNOS exerts a protective effect against reperfusion injury.