Nitric oxide, a novel biologic messenger

Proteomic analysis of protein S-nitrosylation

Nitric oxide (NO) produces covalent PTMs of specific cysteine residues, a process known as S-nitrosylation. This route is dynamically regulated and is one of the major NO signalling pathways known to have strong and dynamic interactions with redox signalling. In agreement with this scenario, binding of NO to key cysteine groups can be linked to a broad range of physiological and pathological cellular events, such as smooth muscle relaxation, neurotransmission and neurodegeneration. The characterization of S-nitrosylated residues and the functional relevance of this protein modification are both essential information needed to understand the action of NO in living organisms. In this review, we focus on recent advances in this field and on state-of-the-art proteomic approaches which are aimed at characterizing the S-nitrosylome in different biological backgrounds.

Smokers Have Reduced Nitric Oxide Production by Conducting Airways but Normal Levels in the Alveoli

Air exhaled by cigarette smokers contains reduced amounts of nitric oxide (NO). Measurement of NO at different expiratory flow rates permits calculation of NO production by the conducting airways (Vaw(NO)) and alveolar concentration of NO (P(ALV)). An independent measurement of diffusing capacity of the alveolar compartment (D(LNO)) multiplied by P(ALV) allows calculation of NO production by the alveoli (V(LNO)). Twelve asymptomatic cigarette smokers and 22 age-matched nonsmokers had measurements of D(LNO) and expired NO at constant expiratory flow rates varying from 60 to 1500 ml/s. Vaw(NO) in smokers was only 22 +/- 11 nl/min (mean +/- standard deviation, SD) compared to 70 +/- 37 nl/min in nonsmokers (p < .0001). In contrast, V(LNO) showed no significant difference (smokers: 203 +/- 104 nl/min, nonsmokers: 209 +/- 74 nl/min, p = .86). These data show that the diminished NO expired by smokers results from diminished NO production by the tissues of the conducting airways but normal values produced by the alveoli.

Downregulation by lipopolysaccharide of Notch signaling, via nitric oxide

The Notch signaling pathway appears to perform an important function in inflammation. Here, we present evidence to suggest that lipopolysaccharide (LPS) suppresses Notch signaling via the direct modification of Notch by the nitration of tyrosine residues in macrophages. In the RAW264.7 macrophage cell line and in rat primary alveolar macrophages, LPS was found to inhibit Notch1 intracellular domain (Notch1-IC) transcription activity, which could then be rescued by treatment with N(G)-nitro-l-arginine, a nitric oxide synthase (NOS) inhibitor. Nitric oxide (NO), which was produced in cells that stably express endothelial NOS (eNOS) and brain NOS (bNOS), also induced the inhibition of Notch1 signaling. The NO-induced inhibition of Notch1 signaling remained unchanged after treatment with 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (ODQ), a guanylyl-cyclase inhibitor, and was not found to be mimicked by 8-bromo-cyclic GMP in the primary alveolar macrophages. With regards to the control of Notch signaling, NO appears to have a significant negative influence, via the nitration of Notch1-IC, on the binding that occurs between Notch1-IC and RBP-Jk, both in vitro and in vivo. By intrinsic fluorescence, we also determined that nitration could mediate conformational changes of Notch1-IC. The substitution of phenylalanine for tyrosine at residue 1905 in Notch1-IC abolished the nitration of Notch1-IC by LPS. Overall, our data suggest that an important relationship exists between LPS-mediated inflammation and the Notch1 signaling pathway, and that this relationship intimately involves the nitration of Notch1-IC tyrosine residues.

Protective mechanism of glycyrrhizin on acute liver injury induced by carbon tetrachloride in mice

Glycyrrhizin is the major active component extracted from licorice (Glycyrrhiza glabra) roots, one of the most widely used herbal preparations for the treatment of liver disorders. This study evaluated the potential beneficial effect of glycyrrhizin in a mouse model of carbon tetrachloride (CCl(4))-induced liver injury. The mice were treated intraperitoneally with CCl(4) (0.5 ml/kg). They received glycyrrhizin (50, 100, 200, 400 mg/kg) 24 h and 0.5 h before and 4 h after administering CCl(4). The serum activities of aminotransferase and the hepatic level of malondialdehyde were significantly higher 24 h after the CCl(4) treatment, while the concentration of reduced glutathione was lower. These changes were attenuated by glycyrrhizin. CCl(4) increased the level of circulating tumor necrosis factor-alpha markedly, which was reduced by glycyrrhizin. The levels of hepatic inducible nitric oxide synthase, cyclooxygenase-2, and heme oxygenase-1 protein expression were markedly higher after the CCl(4) treatment. Glycyrrhizin diminished these alterations for inducible nitric oxide and cyclooxygenase-2 but the protein expression of heme oxygenase-1 was further elevated by the treatment of glycyrrhizin. CCl(4) increased the level of tumor necrosis factor-alpha, inducible nitric oxide synthase, cyclooxygenase-2, and heme oxygenase-1 mRNA expressions. The mRNA expression of heme oxygenase-1 was augmented by the glycyrrhizin treatment, while glycyrrhizin attenuated the increase in tumor necrosis factor-alpha, inducible nitric oxide synthase, and cyclooxygenase-2 mRNA expressions. These results suggest that glycyrrhizin alleviates CCl(4)-induced liver injury, and this protection is likely due to the induction of heme oxygenase-1 and the downregulation of proinflammatory mediators.

The contribution of nitric oxide and interferon gamma to the regulation of the neuro-inflammation in experimental autoimmune encephalomyelitis

Nitric oxide (NO) is a key messenger involved in physiological functions including endothelium-dependent vascular relaxation, inhibition of platelet adhesion and aggregation and regulation of inflammatory and immune responses. Here we briefly introduce NO and its functions and then describe our work over the past several years examining the role of NO in EAE in both the rat and the mouse. We show that NO plays a significant role in determining the resistance or susceptibility to EAE in various strains and or sexes of animals. We demonstrate that NO down-regulates several aspects of CNS inflammation but also has a dual role in that it is required for inflammation in some situations.

Hydrogen sulfide attenuates myocardial ischemia-reperfusion injury by preservation of mitochondrial function

The recent discovery that hydrogen sulfide (H(2)S) is an endogenously produced gaseous second messenger capable of modulating many physiological processes, much like nitric oxide, prompted us to investigate the potential of H(2)S as a cardioprotective agent. In the current study, we demonstrate that the delivery of H(2)S at the time of reperfusion limits infarct size and preserves left ventricular (LV) function in an in vivo model of myocardial ischemia-reperfusion (MI-R). This observed cytoprotection is associated with an inhibition of myocardial inflammation and a preservation of both mitochondrial structure and function after I-R injury. Additionally, we show that modulation of endogenously produced H(2)S by cardiac-specific overexpression of cystathionine gamma-lyase (alpha-MHC-CGL-Tg mouse) significantly limits the extent of injury. These findings demonstrate that H(2)S may be of value in cytoprotection during the evolution of myocardial infarction and that either administration of H(2)S or the modulation of endogenous production may be of clinical benefit in ischemic disorders.

Exogenous nitric oxide triggers classic ischemic preconditioning by preventing intracellular Ca2+ overload in cardiomyocytes

The involvement of nitric oxide (NO) in the late phase of ischemic preconditioning is well established. However, the role of NO as a trigger or mediator of "classic preconditioning" remains to be determined. The present study was designed to investigate the effects of NO on calcium homeostasis in cultured newborn rat cardiomyocytes in normoxia and hypoxia. We found that treatment with the NO donor, sodium nitroprusside (SNP) induced a sustained elevation of intracellular calcium level ([Ca(2+)](i)) followed by a decrease to control levels. Elevation of extracellular calcium, which generally occurs during ischemia, caused an immediate increase in [Ca(2+)](i) and arrhythmia in cultures of newborn cardiomyocytes. Treatment with SNP decreased [Ca(2+)](i) to control levels and re-established synchronized beating of cardiomyocytes. A decrease in extracellular [Na(+)], which inhibits the Na(+)/Ca(2+) exchanger, did not prevent [Ca(2+)](i) reduction by SNP. In contrast, application of thapsigargin, an inhibitor of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a), increased [Ca(2+)](i), and in its presence, SNP did not reduce [Ca(2+)](i), indicating that Ca(2+) reduction is achieved via activation of SERCA2a. The results obtained suggest that activation of SERCA2a by SNP increases Ca(2+) uptake into the sarcoplasmic reticulum (SR) and prevents cytosolic Ca(2+) overload, which might explain the protective effect of SNP from hypoxic damage.

The effect of Misoprostol, a prostaglandin E1 analog, on apoptosis in ischemia-reperfusion-induced intestinal injury

The aim of this study was to investigate whether Misoprostol, a synthetic prostaglandin (PG) E1 analog, has any effect on the prevention of apoptosis in ischemia-reperfusion (I/R)-induced intestinal injury. Thirty adult male Wistar albino rats were divided into three groups: group I=sham operated+saline; group II=I/R+saline; and group III=I/R+Misoprostol. Misoprostol (50microg/kg/d) was administered as an intragastric meal for 3 days. The terminal ileum was collected for histological and biochemical investigations. Apoptotic cells were detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelled (TUNEL) reaction. Immunohistochemical analysis was performed to determine the distribution of inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS). Samples were also analyzed for malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). The number of TUNEL-positive cells was higher in group II when compared to the other two groups (p<0.05). In group III this value was higher when compared to group I, but lower than group II (p<0.05). iNOS immunoreactivity was not detected in ileum sections of group I animals, but moderate immunoreactivity was seen in group II and mild immunoreactivity in group III. The immunoreactivity of eNOS was moderate in ileum sections of all three groups. In ileum tissue, MDA was found to be higher in group II compared to group I (p<0.05), but there was no difference in group III. SOD was not different between groups I and III, but was significantly higher in group II (p<0.05). In our experimental model of I/R-induced intestinal injury, apoptosis is induced in enterocytes, whereas Misoprostol decreases enterocyte apoptosis in this experimental model. Our results indicate that Misoprostol may play a key role in the pathophysiologic events leading to failure of the intrinsic gut barrier defense mechanisms of intestinal epithelium.

A polymorphism in the inducible nitric oxide synthase gene is associated with tuberculosis

iNOS or NOS2 is a molecule that plays a key role in the immunological control of a broad spectrum of infectious agents. Investigation is hampered by difficulty in estimating in vivo production of nitric oxide (NO), but genetic studies provide a potential means of examining the relation between NO production and disease outcome. To better characterize the host genetic factors determining the susceptibility to TB, we evaluated the influence of two polymorphisms in the NOS2A gene on the risk of developing pulmonary TB in a Northwestern Colombian population, which is a moderately-high endemic area. One hundred and fourteen patients with TB and negative for human immunodeficiency virus, plus 304 healthy controls were examined for NOS2A CCTTT and TAAA polymorphisms. A total of 160 healthy controls mentioned before, underwent tuberculin skin test (TST). Analysis disclosed significant differences between patients and controls with NOS2A CCTTT polymorphism (P=0.0001, Pc=0.001, OR=0.4, and 95%CI=0.3-0.7) independent of TST status. When the NOS2A alleles were stratified into short (8-11) and long (12-16) repeats, significant differences with short repeats were observed between TB patients and all controls (P=0.005, OR=0.63, 95%CI=0.46-0.86). No individual association with NOS2A TAAA was detected. These results indicate that a polymorphism in the NOS2A gene influences the susceptibility to TB and suggest a role for NOS2A in the pathogenesis of mycobacterial infection.

Sensitive determination of nitric oxide in some rat tissues using polymer monolith microextraction coupled to high-performance liquid chromatography with fluorescence detection

A simple, sensitive, selective, and low-cost method is proposed for rapidly determining nitric oxide (NO) in some rat tissues. Polymer monolith microextraction (PMME) using a poly(methacrylic acid-ethylene glycol dimethacrylate) (MAA-EGDMA) monolithic column was combined with derivatization of NO using 1,3,5,7-tetramethyl-8-(3',4'-diaminophenyl)-difluoroboradiaza-s-indacene (TMDABODIPY), and this was used to analyze the derivatives of NO by high-performance liquid chromatography (HPLC) with fluorescence detection at lambda (ex)/lambda (em) = 498/507 nm. The baseline separation of TMDABODIPY and its NO derivative is performed under simple conditions in which a C(18) column is used and eluted with 50 mmol L(-1) ethanolamine and methanol. The conditions for the extraction of NO derivatives were optimized. The limit of detection of NO was 2 x 10(-12) mol L(-1) (S/N = 3). The linearity range of the method was 9 x 10(-11)-4.5 x 10(-8) mol L(-1). The interday and intraday relative standard deviations were less than 5%. The proposed method was successfully applied to the determination of NO levels in some rat tissue samples including heart, kidney, and liver with recoveries varying from 87.1 to 95.2%.

Recurrent headache as the main symptom of acquired cerebral toxoplasmosis in nonhuman immunodeficiency virus-infected subjects with no lymphadenopathy: the parasite may be responsible for the neurogenic inflammation postulated as a cause of different types of headaches

Headache and/or migraine, a common problem in pediatrics and internal medicine, affect about 5% to 10% children and adolescents, and nearly 30% of middle-aged women. Headache is also one of the most common clinical manifestations of acquired Toxoplasma gondii infection of the central nervous system (CNS) in immunosuppressed subjects. We present 11 apparently nonhuman immunodeficiency virus-infected children aged 7 to 17 years (8 girls, 3 boys) and 1 adult woman with recurrent severe headaches in whom latent chronic CNS T. gondii infection not manifested by enlarged peripheral lymph nodes typical for toxoplasmosis, was found. In 7 patients, the mean serum IgG Toxoplasma antibodies concentration was 189 +/- 85 (SD) IU/mL (range 89 to 300 IU/mL), and in 5 other subjects, the indirect fluorescent antibody test titer ranged from 1:40 to 1:5120 IU/mL (n= <1:10 IU/mL). Some of the patients suffered also from atopic dermatitis (AD) and were exposed to cat and/or other pet allergens, associated with an increased IL-4 and decreased IFN-gamma production. These cytokine irregularities caused limited control of cerebral toxoplasmosis probably because IL-4 down-regulated both the production of IFN-gamma and its activity, and stimulated production of a low NO-producing population of monocytes, which allowed cysts rupture, increased parasite multiplication and finally reactivation of T. gondii infection. The immune studies performed in 4 subjects showed a decreased percentage of T lymphocytes, increased total number of lymphocytes B and serum IgM concentration, and impaired phagocytosis. In addition, few of them had also urinary tract diseases known to produce IL-6 that can mediate immunosuppressive functions, involving induction of the anti-inflammatory cytokine IL-10. These disturbances probably resulted from the host protective immune reactions associated with the chronic latent CNS T. gondii infection/inflammation. This is consistent with significantly lower enzyme indoleamine 2,3-dioxygenase (IDO) activity reported in atopic than in nonatopic individuals, and an important role that IDO and tryptophan degradation pathways plays in both, the host resistance to T. gondii infection and its reactivation. Analysis of literature information on the subjects with different types of headaches caused by foods, medications, and other substances, may suggest that their clinical symptoms and changes in laboratory data result at least in part from interference of these factors with dietary tryptophan biotransformation pathways. Several of these agents caused headache attacks through enhancing NO production via the conversion of arginine to citrulline and NO by the inducible nitric oxide synthase enzyme, which results in the high-output pathway of NO synthesis. This increased production of NO is, however, quickly down-regulated by NO itself because this biomolecule can directly inactivate NOS, may inhibit Ia expression on IFN-gamma-activated macrophages, which would limit antigen-presenting capability, and block T-cell proliferation, thus decreasing the antitoxoplasmatic activity. Moreover, NO inhibits IDO activity, thereby suppressing kynurenine formation, and at least one member of the kynurenine pathway, 3-hydroxyanthranilic acid, has been shown to inhibit NOS enzyme activity, the expression of NOS mRNA, and activation of the inflammatory transcription factor, nuclear factor-kB. In addition, the anti-inflammatory cytokines IL-4 and IL-10, TGF-beta, and a cytokine known as macrophage deactivating factor, have been shown to directly modulate NO production, sometimes expressing synergistic activity. On the other hand, IL-4 and TGF-beta can suppress IDO activity in some cells, for example human monocytes and fibroblasts, which is consistent with metabolic pathways controlled by IDO being a significant contributor to the proinflammatory system. Also, it seems that idiopathic intracranial hypertension, pseudotumor cerebri, and aseptic meningitis, induced by various factors, may result from their interference with IDO and inducible nitric oxide synthase activities, endogenous NO level, and cytokine irregularities which finally affect former T. gondii status 2mo in the brain. All these biochemical disturbances caused by the CNS T. gondii infection/inflammation may also be responsible for the relationship found between neurologic symptoms, such as headache, vertigo, and syncope observed in apparently immunocompetent children and adolescents, and physical and psychiatric symptoms in adulthood. We therefore believe that tests for T. gondii should be performed obligatorily in apparently immunocompetent patients with different types of headaches, even if they have no enlarged peripheral lymph nodes. This may help to avoid overlooking this treatable cause of the CNS disease, markedly reduce costs of hospitalization, diagnosis and treatment, and eventually prevent developing serious neurologic and psychiatric disorders.

Circadian profiling of the transcriptome in NIH/3T3 fibroblasts: comparison with rhythmic gene expression in SCN2.2 cells and the rat SCN

To screen for output signals that may distinguish the pacemaker in the mammalian suprachiasmatic nucleus (SCN) from peripheral-type oscillators in which the canonical clockworks are similarly regulated in a circadian manner, the rhythmic behavior of the transcriptome in forskolin-stimulated NIH/3T3 fibroblasts was analyzed and compared relative to SCN2.2 cells in vitro and the rat SCN. Similar to the circadian profiling of the SCN2.2 and rat SCN transcriptomes, NIH/3T3 fibroblasts exhibited circadian fluctuations in the expression of the core clock genes, Per2, Cry1, and Bmal1, and 323 functionally diverse transcripts, many of which regulate cellular communication. Overlap in rhythmic transcripts among NIH/3T3 fibroblasts, SCN2.2 cells, and the rat SCN was limited to these clock genes and four other genes that mediate fatty acid and lipid metabolism or function as nuclear factors. Compared with NIH/3T3 cells, circadian gene expression in SCN oscillators was more prevalent among genes mediating glucose metabolism and neurotransmission. Coupled with evidence for the rhythmic regulation of the inducible isoform of nitric oxide synthase (iNos) in SCN2.2 cells and the rat SCN but not in fibroblasts, studies examining the effects of a NOS inhibitor on metabolic rhythms in cocultures containing SCN2.2 cells and untreated NIH/3T3 cells suggest that the gaseous neurotransmitter nitric oxide may play a key role in SCN pacemaker function. This comparative analysis of circadian gene expression in SCN and non-SCN cells may have important implications in the selective analysis of circadian signals involved in the coupling of SCN oscillators and regulation of rhythmicity in downstream cells.

Nitrogen oxide interaction with copper complexes formed by small peptides belonging to the prion protein octa-repeat region

The interaction between NO and copper(II) complexes formed by peptides coming from the N-terminal prion protein octa-repeat region was studied. Aqueous solutions of the Cu-Ac-HGGG-NH(2) and the Cu-Ac-PHGGGWGQ-NH(2) systems around pH 7.5 were tested after the addition of NONOates as a source of NO. UV-Vis, room temperature and frozen solution EPR spectra showed the occurrence of copper(ii) reduction in all these complexes. The reduction of these complexes is probably mediated by the formation of a labile NO adduct, which, after re-oxidation, leads to a relatively stable NO(2)(-) adduct through the apical coordination along the void site of their square pyramidal structure. In fact, the most significant shifts in EPR magnetic parameters (g(||) and A(||) or g(iso) and A(iso)) as well as in the optical parameters (lambda(max) and epsilon(max)) gave a reason for geometrical changes of the copper coordination polyhedron from a distorted square pyramid to a pseudo-octahedron. The presence of oxygen in the aqueous solution hindered the reduction ability of NO towards copper, but it made it easier to return to the original species. In order to elucidate the possible mechanism of this interaction, the reduction of copper complexed by these ligands was followed by means of zinc powder addition. The further addition of nitrite to the solution containing reduced copper led to the conclusion that nitrite could easily form an adduct, which after re-oxidation presented the same spectral features of the species obtained when the NO interaction was followed. The complexity of this interaction could involve both an inner or an outer-sphere electron transfer mechanism.

Role of protein tyrosine phosphatases in the regulation of interferon-γ-induced macrophage nitric oxide generation: implication of ERK pathway and AP-1 activation

NO is a potent molecule involved in the cytotoxic events mediated by macrophages (MØ) against microorganisms. We reported previously that inhibition of MØ protein tyrosine phosphatases (PTPs) mediates a protective effect against Leishmania infection, which was NO-dependent. Herein, we show that the PTP inhibitors of the peroxovanadium (pV) class, bpV(phen) and bpV(pic), can similarly increase murine MØ IFN-gamma-induced NO generation. Using various second messenger (JAK2, MEK, Erk1/Erk2, and p38) antagonists, we found that the Erk1/Erk2 pathway was the principal pathway submitted to regulation by PTPs in the context of IFN-gamma-driven MØ activation and increase in NO production. We observed that bpV(phen) increases inducible NO synthase (iNOS) expression, resulting in enhanced NO production, whereas the bpV(pic) increase of NO production does not seem to result from a modulation of iNOS expression. Transcription factors STAT-1alpha and NF-kappaB, recognized for their importance in NO generation, were not affected by the pV treatment. However, AP-1 was strongly activated by bpV(phen) but not by bpV(pic). Collectively, our results suggest that increased IFN-gamma-induced NO production, observed after bpV(phen) treatment, involves the activation of the transcription factor AP-1 by Erk1/Erk2- and stress-activated protein kinase/JNK-dependent transduction mechanisms.

Capsaicin and nitric oxide synthase inhibitor interact to evoke a hypothermic synergy

The present study investigated the effect of a drug combination of capsaicin and L-NAME on hypothermia in rats. Capsaicin administration (0.1, 0.25, 0.5, 1 and 2mg/kg, i.m.) caused a significant hypothermia. L-NAME (50mg/kg, i.p.), a nonspecific nitric oxide synthase (NOS) inhibitor, was ineffective. For combined administration, progressively increasing doses of capsaicin (0.1, 0.25, 0.5, 1 and 2mg/kg, i.p.) were given with a non-hypothermic dose of L-NAME (50mg/kg, i.p.). Experiments revealed that L-NAME (50mg/kg, i.p.) enhanced the hypothermic response to capsaicin (0.25, 0.5, 1, and 2mg/kg, i.m.). Comparison of the graded dose-effect curves for capsaicin alone and capsaicin plus L-NAME revealed a significant difference (P<0.05), thus indicating synergy for the drug interaction. To determine if L-NAME acted centrally, a fixed dose of L-NAME (1mg/rat, i.c.v.) was given with graded doses of capsaicin (0.25, 0.5, 1, and 2mg/kg, i.m.). L-NAME (1mg/rat, i.c.v.) only enhanced the hypothermia at a single dose of capsaicin (0.5mg/kg, i.m.). The super-additive hypothermia produced by the concurrent administration of capsaicin and L-NAME (50mg/kg, i.p.) is the first evidence of synergy for a drug combination of capsaicin and a NOS inhibitor. The synergy is apparent only when L-NAME is given systemically, thus indicating that the inhibition of peripheral NO production enhances the hypothermic response to capsaicin.

Schistosoma mansoni: Use of a fluorescent indicator to detect nitric oxide and related species in living parasites

Nitric oxide (NO) is synthesized enzymatically by nitric oxide synthase (NOS). Several groups have previously presented evidence for NOS activity and immunoreactivity in several parasitic platyhelminths, including schistosomes. Here, we use 4,5-diaminofluorescein-2 diacetate (DAF-2 DA), a fluorescent indicator of NO, to detect NO in living schistosomes. In adult worms, DAF-2 fluorescence is found selectively in epithelial-like cells. Fluorescence increases when worms are incubated in L-arginine, the precursor of NO synthesis, and decreases dramatically in the presence of the NOS inhibitor N(G)-nitro-L-arginine methyl ester, indicating that predicted NO release may be NOS-dependent, and that enzymatic NO signaling pathways may play an important role in schistosome physiology.

The differential effect of PGE(1) on d-galactosamine-induced nitrosative stress and cell death in primary culture of human hepatocytes

The pre-administration of PGE(1) reduced inducible nitric oxide synthase (NOS-2) expression and cell death induced by d-galactosamine (d-GalN) in cultured rat hepatocytes. The present study evaluated the role of nitric oxide (NO) during PGE(1) treatment in fully established d-GalN-induced cytotoxicity in cultured human hepatocytes. Human hepatocytes were isolated from liver resections by classic collagenase perfusion. PGE(1) (1 microM) was administered at 2 h before d-GalN (40 mM), or 2 or 10 h after d-GalN in cultured hepatocytes. The production of NO was inhibited by N-omega-nitroso-l-arginine methyl ester (l-NAME) (0.5 mM). Various parameters related to oxidative and nitrosative stress, mitochondrial dysfunction, NF-kappaB activation, NOS-2 expression and cell death were evaluated in hepatocytes. NO mediated mitochondrial disturbances, nitrosative stress and cell death in d-GalN-treated hepatocytes. The administration of PGE(1) 10 h after d-GalN enhanced NF-kappaB activation, NOS-2 expression and nitrosative stress. Although PGE(1) administered at 2 h before or 2h after d-GalN reduced apoptosis and necrosis, its administration 10 h after d-GalN had no beneficial effect on cell death. In conclusion, the administration of PGE(1) during advanced d-GalN cytotoxicity induced nitrosative stress and lost its cytoprotective properties in cultured human hepatocytes.

3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), a food-born carcinogenic heterocyclic amine, promotes nitric oxide production in murine macrophages

A heterocyclic amine, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) is one of the potent food-born dietary carcinogens derived mainly from burnt meat products. In the present study, we investigated the inductive effect of Trp-P-1 on nitric oxide (NO) production in murine macrophages since NO and its oxidized derivatives are directly involved in triggering mutagenesis and carcinogenesis. Our results show that Trp-P-1 induced mRNA expression of inducible NO synthase (iNOS) and NO production without co-stimulation in murine peritoneal macrophages and RAW 264.7 cells. Trp-P-1 further enhanced both iNOS mRNA expression and NO production, which were primarily induced by lipopolysaccharide (LPS). Electrophoretic mobility shift assay demonstrated that Trp-P-1, alone or in the presence of LPS, facilitated the DNA binding activity of the transcription factor NF-kappaB, and the trans-acting activity of the NF-kappaB was confirmative as determined by in vitro transfection and a luciferase reporter gene assay. Moreover, Trp-P-1 induced increasing intracellular reactive oxygen species (ROS), which play an important role in NF-kappaB activation. These results suggest that Trp-P-1 induces NO production mediated by an increased intracellular ROS, NF-kappaB activation, and subsequent iNOS gene expression.

Baclofen and NOS inhibitors interact to evoke synergistic hypothermia in rats

Our laboratory recently demonstrated that a drug combination of baclofen and L-NAME, a nonspecific nitric oxide synthase (NOS) inhibitor, evokes synergistic hypothermia in rats. These data are the first demonstration of synergy between a GABA agonist and NOS inhibitor. While the hypothermic synergy suggests a role for NOS in baclofen pharmacology, it is unclear whether the super-additive hypothermia is specific for baclofen and L-NAME or extends to drug combinations of baclofen and other NOS inhibitors. The site of action (central or peripheral) and isoforms of NOS that mediate the synergy are also unknown. Here, we confirm the hypothermic synergy with additional data and discuss potential mechanisms of the drug interaction. Baclofen (2.5, 3.5, 5 and 7.5 mg/kg, i.p.) was administered to rats by itself or with 7-nitroindazole (7-NI), a neuronal NOS inhibitor. 7-NI (10 mg/kg, i.p.) did not affect body temperature. For combined administration, 7-NI (10 mg/kg, i.p.) increased the relative potency of baclofen (F=18.9, P<0.05). The present data validate the hypothermic synergy caused by the drug combination of baclofen and L-NAME and implicate nNOS in the synergy. In a context broader than thermoregulation, NO production and transmission may play an important role in baclofen pharmacology.

Probing the differential effects of infrared light sources IR1072 and IR880 on human lymphocytes: evidence of selective cytoprotection by IR1072

Light therapy, both laser and LED, have been shown to provide clinical benefit in many therapeutic arenas. The effects of IR1072 and IR880 were investigated, using a range of single and multiple irradiation protocols, for their effect on freshly prepared human lymphocytes stimulated with phytohemagglutinin. Viable cell numbers remained significantly higher after irradiation with IR1072 and were significantly lower after IR880 irradiation compared to untreated controls, following a daily single irradiation over a 5-day period. Cell numbers were significantly higher after pre-treatment with IR1072 and exposure to UVA, compared to cells treated with UVA only. Cells irradiated twice on Day 3 post-harvest with various wavebands confirm on Day 5, an increase in % cell viability after IR1072, and IR1072 alternating with IR1268 irradiation, and a decrease in % cell viability after IR880 irradiation alone. Further, wavebands tested displayed no significant differences compared to the control. Cells were collected after exposure on Days 3 and 5 with IR1072 and IR880 treatments and protein levels were compared using quantitative immunoblotting probed with an anti-iNOS antibody. Following IR1072, but not IR880, treatment there was a 4.9+/-2.1-fold higher iNOS protein expression in treated cells compared to the control on Day 5 post-treatment.

An anti-ulcer drug, geranylgeranylacetone, suppresses inducible nitric oxide synthase in cultured vascular smooth muscle cells

OBJECTIVE

Geranylgeranylacetone (GGA) is commonly used as an anti-ulcer drug. If GGA affects inducible nitric oxide synthase (iNOS) in the vascular tissue, it could influence disease progression in coronary arteries. We investigated the effects of the anti-ulcer drug GGA on iNOS activity in vascular smooth muscle cells.

METHODS

We measured the production of nitrite, a stable metabolite of nitric oxide, in cultured rat vascular smooth muscle cells with the Griess reagent. iNOS protein and mRNA expressions were assayed by western blotting and northern blotting, respectively. The levels of nuclear factor (NF)-kappaB proteins in nuclear extracts were analyzed by gel retardation assay. Heat shock protein 70, a cytoprotective molecule, was evaluated by western blotting.

RESULTS

Incubation of cultures with interleukin-1beta for 24 h caused a significant increase in nitrite generation. Interleukin-1beta-induced nitrite production by vascular smooth muscle cells was significantly suppressed by GGA in a dose-dependent manner. GGA-suppressed nitrite production was accompanied by decreased iNOS mRNA and protein accumulations. GGA by itself did not modulate the basal level of nitrite production. Interleukin-1beta induced NF-kappaB activation in vascular smooth muscle cells, and the addition of GGA further inhibited this NF-kappaB activation. GGA itself induced heat shock protein 70 expression in a dose-dependent manner.

CONCLUSION

These findings demonstrated that GGA suppresses iNOS expression in cytokine-stimulated cultured vascular smooth muscle cells partially through the suppression of NF-kappaB activation, suggesting that GGA may modulate the pathophysiology of cardiovascular diseases including atherosclerosis. In addition, this effect may be associated with heat shock protein 70 production by GGA.

Changed Bcl:Bax ratio in endometrium of patients with unexplained infertility

Apoptosis has been shown to be an important regulator of endometrial function during the menstrual cycle and implantation. Recently, some possible implantation defects were identified in patients with unexplained infertility. In this study, we investigated the role of spontaneous apoptosis, which is regulated by death regulatory genes, such as Bcl-2, Bax, p53, and isoenzymes of nitric oxide synthases; eNOS and iNOS during the implantation window in women with unexplained infertility. Endometrial samples were evaluated from fertile (n=15) and unexplained-infertile women (n=15) during post-ovulatory 7th or 8th day of their menstrual cycles. Apoptotic cells were detected using the dUTP nick-end labelling assay and Bcl-2, Bax, p53, iNOS and eNOS were assessed immunohistochemically. Reduced apoptotic cells, weak immunoreactivity of p53 and strong immunoreactivity of Bcl-2 were observed in the unexplained-infertile group compared with the fertile group (p<0.001). Bax intensity was similar in both groups. While weak iNOS immunoreactivity was detected in both groups, moderately increased eNOS immunoreactivity was observed in infertile cases. Spontaneous apoptosis is reduced in the endometrium of unexplained-infertile women, and is associated with the changed Bcl-2:Bax ratio. This finding may be a contributing factor to defective implantation causing infertility in this group of patients.

Effect of Nitric Oxide on γ-Ray-Induced Micronucleus Frequency in RAW264.7 Cells

The effect of low-dose nitric oxide (NO) on gamma-ray-induced micronucleus (MN) frequency was investigated in RAW264.7 cells. Treatment of RAW264.7 cells with 0.25 mM sodium nitroprusside (SNP), a chemical NO donor, reduced the frequency of micronuclei induced by 5 Gy gamma rays by 43 to 45% between 3 and 12 h post-treatment. This effect was blocked by carboxy-PTIO, suggesting that NO may play a role in the reduction of radiation-induced MN frequency. To examine possible mechanisms underlying this effect, we first looked at changes in the antioxidant system after SNP treatment. A significant increase in intracellular glutathione (GSH) was seen in SNP-treated cells between 3 and 12 h post-treatment. Depletion of GSH with buthionine sulfoximine (BSO) increased the gamma-ray-induced increase in MN frequency. Detailed studies using various inducers of intracellular GSH suggested that GSH induction has a partial role in the reducing effect of NO on the gamma-ray-induced MN frequency. Next, the effect of NO on DNA repair and replication systems was examined. Wortmannin, an inhibitor of DNA-dependent protein kinase (DNA-PK), dose-dependently inhibited the reducing effect of NO, while caffeine, an inhibitor of ATM kinase and ATR kinase, did not. DNA-PK activity was increased by NO treatment. Etoposide, a topoisomerase II inhibitor, dose-dependently blocked the effect of NO in reducing the gamma-ray-induced MN frequency. These results suggest that the mechanisms of the effect of NO on the gamma-ray-induced MN frequency include elevation of GSH and up-regulation of DNA-PK activity for repairing double-strand breaks. NO may act as a signal for repair systems, e.g. for nonhomologous recombination and for the replication system in S phase, to reduce the MN frequency.

Differential expression of nitric oxide synthases in human scalp epidermal and hair follicle pigmentary units: implications for regulation of melanogenesis

BACKGROUND

Nitric oxide (NO) is a ubiquitous gaseous lipophilic molecule generated from the conversion of L-arginine to L-citrulline by the NO synthases (NOSs). Ultraviolet radiation (UVR)-induced NO production appears to stimulate epidermal melanogenesis. However, given their relative protection from UVR, it is unclear whether NO plays a similar role in hair bulb melanocytes.

OBJECTIVES

We aimed to identify the expression profiles of the NOS isoforms endothelial NOS (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS) and of phosphorylated eNOS and nitrotyrosine within the epidermal and follicular melanin units of normal human haired scalp during the hair growth cycle.

METHODS

This study employed single and double immunohistochemical and immunofluorescence staining techniques using haired scalp from 10 healthy individuals (six women and four men).

RESULTS

Melanocytes in the basal layer of the epidermis expressed eNOS, nNOS and nitrotyrosine. By contrast, melanogenically active melanocytes of the anagen hair bulb were wholly negative for these markers. However, other follicular melanocytes not actively involved in pigment production, including undifferentiated melanocytes located in the outer root sheath and melanocytes surviving the apoptosis-driven hair follicle (HF) regression during catagen/telogen, expressed eNOS, nNOS and nitrotyrosine. While iNOS was only weakly expressed in the basal layer of the human epidermis, it was highly expressed in keratinocytes of the inner root sheath (IRS), where it colocalized with trichohyalin, a differentiation-associated protein of the IRS that requires enzyme-catalysed conversion of arginine to citrulline.

CONCLUSIONS

The NOS isoforms and nitrotyrosine are differentially expressed in different cutaneous melanocyte subpopulations. Results of this study suggest a possible role for eNOS, nNOS, iNOS and nitrotyrosine in melanocyte biology, particularly with respect to melanogenesis and melanocyte survival during HF regression. Another example of possible NO involvement in HF biology is the postsynthetic modification of trichohyalin in differentiating keratinocytes of the IRS. These results suggest that NO may influence several aspects of HF biology.

Underlying mechanism of combined effect of methamphetamine and morphine on lethality in mice and therapeutic potential of cooling

An increase in polydrug abuse is a major problem worldwide. A previous study showed that coadministration of methamphetamine and morphine induced lethality in rodents and humans. However, the underlying mechanisms by which the lethality is increased by the coadministration of methamphetamine and morphine have not been fully understood. Therefore, the present study was designed to determine the mechanism of increased lethality induced by methamphetamine and morphine. Coadministered methamphetamine and morphine increased the lethality by more than 70% in BALB/c mice. Pretreatment with NMDA-receptor antagonists, such as MK-801 and 3-((R)-2-carboxypiperazin-4-yl) propyl-1-phosphonic acid (CPP), and benzamide [poly(ADP-ribose) polymerase (PARP) inhibitor] significantly attenuated the increased lethality induced by methamphetamine and morphine. Furthermore, the lethal effect induced by methamphetamine and morphine was completely attenuated by immediate cooling after the coadministration of methamphetamine and morphine. It has been reported that methamphetamine-induced neurotoxicity can be blocked by lowering the temperature, and this effect might be mediated by a reduction of release of free radicals. These results suggest that activation of NMDA receptors and PARP play an important role in the increased lethality induced by methamphetamine and morphine.

Potentiation by high potassium of lipopolysaccharide-induced nitric oxide production from cultured astrocytes

Uptake of K+ is an important role of astrocytes to maintain physiological lower extracellular K+ concentration in the CNS. In this study, the effect of high K+ concentration was examined on the cellular function of astrocytes from embryonic rat brain in primary culture. Nitric oxide (NO) production induced by lipopolysaccharide (LPS) was measured as an index of cellular function of astrocytes. Increasing KCl concentration to about 40 mM did not directly evoke NO production, but doubled the level of LPS (1 ng/ml)-induced NO production. K-gluconate showed a similar enhancing effect although the degree of enhancement was about half of that of KCl. Neither NaCl nor Na-gluconate showed any effect. The K(+)-channel blocker, 4-aminopyridine, but not tetraethylammonium or apamin, inhibited the enhancing effect of KCl. The LPS-induced iNOS protein expression determined by immunoblotting analysis was enhanced by high K+ treatment. The level of iNOS mRNA determined by real-time RT-PCR technique was also augmented by the presence of 40 mM KCl. These results indicate that the elevation of extracellular K+ concentration regulates astrocytic cell functions through a mechanism involving K(A)-type K(+)-channels and that potentiation of NO production by high K+ is due to the augmentation of iNOS mRNA and iNOS protein levels.

Exploration of the global antioxidant capacity of the stratum corneum by cyclic voltammetry

Cyclic voltammetry is proposed as a new method for evaluating the antioxidant capacity of skin based on the reducing properties of low molecular weight antioxidants (LMWA). Experiments were performed simply by recording the anodic current at 0.9 V/SCE of a platinum microelectrode placed directly on the epidermis surface without any gel or water. This method ensured a direct, rapid (less than 1 min), reliable (accuracy 12%) and non-invasive measurement of the global antioxidant capacity of the stratum corneum with a high spatiotemporal resolution. At the same time, the pH of the skin surface was determined by recording the cathodic current at 0 V/SCE. Based on an exploratory study involving nine volunteer subjects, the evolution of the amperometric response of the microelectrode with time revealed a periodic modification of the redox properties.

Kortikale Amaurosis und Status epilepticus bei akuter Porphyrie

The most common neurologic manifestations of acute intermittent porphyria (AIP) are autonomic visceral neuropathy, peripheral motor neuropathy, and CNS dysfunctions including seizures and neuropsychiatric disturbances. In rare instances, however, AIP patients have presented with acute cortical blindness. We present a 20-year-old woman who suffered her first attack of AIP. Following 1 week of abdominal pain, she was transferred from a surgical department because of sudden visual loss and deterioration of consciousness. On admission, she developed several generalized seizures. Magnetic resonance imaging showed bilateral DWI lesions occipitally and in the left anterior circulation. Cerebrospinal fluid, MR angiography, and duplex ultrasound were normal. On the following day, sedation and intubation became necessary because of a generalized status epilepticus. Analysis of porphyrinogens in blood, urine and stool showed significantly elevated values. Intravenous therapy with häm-arginate was initiated and antiepileptic therapy was changed to gagabentine. Under this therapeutical regime she remained stable and extubation was possible 48 h later.

Inhibition of radiation induced nitration by curcumin and nicotinamide in mouse macrophages

Nitric oxide plays an important role in inflammation and carcinogenesis and has now been implicated as an important signaling molecule under normal physiological conditions also. Increased nitric oxide (NO) results in increased nitration of proteins at tyrosine, which can cause protein dysfunction or alterations in signal transduction pathways. Irradiation of Lipopolysaccharide (LPS) activated mouse peritoneal macrophages was found to increase NO production, inducible nitric oxide synthase (iNOS) expression and nitration of proteins. The increase in iNOS expression was very less when compared to increase in NO production, indicating the possibility of post-translational activation of iNOS by LPS and ionising radiation. The addition of curcumin, nicotinamide and Jun N-terminal kinase (JNK) inhibitor, SP 600125, reduced the levels of NO, iNOS expression and nitration of proteins in macrophages. Closer scrutiny of the inhibition pattern of these modulators revealed that although the JNK inhibitor did not result in significant decrease in iNOS expression it led to a significant decrease in NO production, implying the possible involvement of JNK in the regulation of iNOS activity. Curcumin and JNK inhibitor directly inhibited the nitration of proteins and JNK inhibitor and curcumin, when added together, did not show synergistic effect.

Treatment with 1,2,3,4-tetrahydroisoquinolone affects the levels of nitric oxide, S-nitrosothiols, glutathione and the enzymatic activity of γ-glutamyl transpeptidase in the dopaminergic structures of rat brain

Depletion of glutathione (GSH), nitrosative stress and chronic intoxication with some neurotoxins have been postulated to play a major role in the pathogenesis of Parkinson's disease. This study aimed to examine the effects of acute and chronic treatments with 1,2,3,4-tetrahydroisoquinoline (TIQ), an endo-/exogenous substance suspected of producing Parkinsonism in human, on the levels of nitric oxide (NO), S-nitrosothiols and glutathione (GSH) in the whole rat brain and in its dopaminergic structures. TIQ administered at a dose of 50 mg/kg i.p. significantly increased the tissue concentrations of NO and GSH in the substantia nigra (SN), striatum (STR) and cortex (CTX) of rats receiving this compound both acutely and chronically. Moreover, it decreased the level of oxidized glutathione (GSSG) and enhanced GSH:GSSG ratio affecting in this way the redox state of brain cells. TIQ also increased the level of S-nitrosothiols when measured in the whole rat brain and CTX, although it markedly decreased their level in the STR after both treatments. Inhibition of the constitutive NO synthase by l-NAME in the presence of TIQ caused decreases in GSH and S-nitrosothiol levels in the brain. The latter effect shows that the TIQ-mediated increases in GSH and S-nitrosothiol concentrations were dependent on the enhanced NO level. The above-described results suggest that TIQ can act as a modulator of GSH, NO and S-nitrosothiol levels but not as a parkinsonism-inducing agent in the rat brain.

Signal transduction underlying carbachol-induced PGE2 generation and cox-1 mRNA expression of rat brain

In this paper we have determined the different signal pathways involved in M(1) and M(3) muscarinic acetylcholine receptor (mAChR) dependent stimulation of cyclo-oxygenase 1 (cox-1) mRNA gene expression and PGE(2) production on rat cerebral frontal cortex. Carbachol stimulation of M(1) and M(3) mAChR exerts an increase in cox-1 mRNA gene expression without affecting cox-2 mRNA expression and increased PGE(2) generation. Besides, increased phosphoinositide (PI) turnover and stimulation of nitric oxide synthase (NOS) and cyclic GMP (cGMP) production. Inhibitors of phospholipase A(2) (PLA(2)), COX and phospholipase C (PLC), calcium/calmodulin (CaM), NOS and soluble guanylate cyclase prevent the carbachol effect. These results suggest that carbachol-activation of M(1) and M(3) mAChR increased PGE(2) release associated with an increased expression of cox-1 and NO-cGMP production. The mechanism appears to occur directly to PLC stimulation and indirectly to PLA(2) activation. These results may contribute to understand the effects and side effect of non-steroidal anti-inflammatory drugs in patients with cerebral degenerative diseases.

A double-blind, randomized, controlled study of oral pirfenidone for treatment of secondary progressive multiple sclerosis

Currently, there are no approved treatments for secondary progressive multiple sclerosis (MS) that stabilize or reverse the neurological disabilities associated with this disease. Oral pirfenidone was found to stabilize and overcome the disabilities in two published independent open-label studies in secondary progressive MS. This led us to study pirfenidone in a phase II double-blind, randomized and controlled, clinical trial in patients with advanced secondary progressive MS for 12 months. Forty-three patients met the eligibility criteria approved by the IRB and accepted by the FDA. Of these patients, 18 were randomly assigned to placebo and 25 patients to oral pirfenidone groups. All eligible patients were included in the statistical analysis of the data according to intention-to-treat principles. Some patients on oral pirfenidone manifested mild drug-related adverse effects, but it was well tolerated overall. By one month, pirfenidone significantly (P < 0.05) improved the Scripps Neurological Rating Scale (SNRS) scores, and scores remained significantly improved for 3, 6 and 12 months when compared to the baseline SNRS scores. In contrast, the SNRS scores of patients on oral placebo were not significantly improved at 1, 3, 6 or 12 months of the study, when compared with baseline scores. Oral pirfenidone significantly (P <0.04) reduced the incidence of relapses (27.8% on placebo versus 8.0% on pirfenidone). Furthermore, oral pirfenidone treatment was associated with a marked improvement in bladder dysfunction (40.0% on pirfenidone versus 16.7% on placebo). Expanded Disability Status Scale scores and MRI lesion count were not significantly different in the placebo and pirfenidone groups. These findings indicate a significant effect of pirfenidone on clinical disability and bladder function for secondary progressive MS patients. A major multicentre, double-blind, randomized, controlled trial is justified.

Correlations between neuronal nitric oxide synthase and muscarinic M3/M1 receptors in the rat retina

This study determined the different signal pathways involved in M1/M3 muscarinic acetylcholine receptor (mAChR) dependent stimulation of nitric oxide synthase (NOS) activity/cyclic GMP (cGMP) production and nNOS mRNA expression in rat retina. Exposure of the retina to different concentrations of carbachol caused an increase in NOS activity, cGMP production and phosphoinositol (PI) accumulation. The increase in NOS activity and cGMP content was blocked by L-NMMA and ODQ, respectively. Also, phospholipase C (PLC) and calcium/calmodulin (CaM) inhibition prevented the carbachol activation on NOS/cGMP pathways. Both, 4-DAMP and pirenzepine but not AF-DX 116 blocked the increase in NOS and cGMP induced by carbachol. Carbachol-stimulation of M1/M3 mAChR increased nNOS-mRNA levels associated with an increase of endogenous NO and cGMP production. The mechanism appears to occur secondarily to stimulation of PIs turnover via PLC. This triggers a cascade reaction involving CaM and soluble guanylate cyclase leading to NO and cGMP accumulation, that in turn, up regulates nNOS-mRNA gene expression. These results give novel insight into the mechanism involved in the regulation of nNOS-mRNA levels by mAChR activation of retina.

Nitric oxide and sleep

Nitric oxide (NO) is a biological messenger synthesized by three main isoforms of NO synthase (NOS): neuronal (nNOS, constitutive calcium dependent), endothelial (eNOS, constitutive, calcium dependent) and inducible (iNOS, calcium independent). NOS is distributed in the brain either in circumscribed neuronal sets or in sparse interneurons. Within the laterodorsal tegmentum (LDT), pedunculopontine tegmentum and dorsal raphe nucleus, NOS-containing neurons overlap neurons grouped according to their contribution to sleep mechanisms. The main target for NO is the soluble guanylate cyclase that triggers an overproduction of cyclic guanosine monophosphate. NO in neurons of the pontine tegmentum facilitates sleep (particularly rapid-eye-movement sleep), and NO contained within the LDT intervenes in modulating the discharge of the neurons through an auto-inhibitory process involving the co-synthesized neurotransmitters. Moreover, NO synthesized within cholinergic neurons of the basal forebrain, while under control of the LDT, may modulate the spectral components of the EEG instead of the amounts of different sleep states. Finally, impairment of NO production (e.g. neurodegeneration, iNOS induction) has identifiable effects, including ageing, neuropathologies and parasitaemia.

Nitric oxide contributes to resistance of the Brown Norway rat to experimental autoimmune encephalomyelitis

The Brown Norway (BN) rat is reported to be resistant to the induction of experimental autoimmune encephalomyelitis (EAE) and a number of mechanisms have been suggested to explain this resistance. In work reported here we provide evidence that such resistance in the BN rat can be accounted for, at least in part, by their ability to produce higher levels of nitric oxide (NO) than susceptible strains of rats. Spleen cells from the BN rat make significantly more NO following in vitro stimulation than do cells from the Lewis or PVG rat and following in vivo immunization using complete Freund's adjuvant (CFA) the BN rat makes substantially more NO than either susceptible strain. If carbonyl iron is used as adjuvant in vivo there is no increase in NO levels in the BN rat and they are rendered highly susceptible to EAE. Immunizing with CFA simultaneously with neuroantigen and carbonyl iron drives up NO levels and the resistance is restored. EAE produced using carbonyl iron is characterized by extensive macrophage/microglia presence in the central nervous system lesions of the BN rat yet the cytokine profile in the lymph nodes does not differ from that in the EAE Lewis rats.

Noradrenaline up-regulates the neuronal and the inducible nitric oxide synthase isoforms in magnocellular neurons of rat brain slices

Nitric oxide (NO) and noradrenaline (NA) are suggested to be implicated in the regulation of neuropeptide secretion in the supraoptic nuclei (SON) and the paraventricular nuclei (PVN) of the hypothalamus. Our study demonstrates short-term interactions between NA and the activity and expression of NO synthase (NOS) in magnocellular neurons, by using an ex vivo model of hypothalamic slices. In the SON as well as in the PVN, total NOS activity exhibited a time-dependant increase after an incubation with NA. In the SON, this increase of total NOS activity was in part the consequence of stimulation of the iNOS activity. Coimmunodetections showed that cells expressing the inducible form of NOS were not astrocytes but magnocellular neurons. Steady-state levels of iNOS and nNOS mRNA were dramatically enhanced by NA, particularly in the SON. Consequently, we provide new evidence that iNOS could play an important role in multiple physiological functions, including extracellular fluid balance, lactation, and parturition.

Distribution of nitric oxide synthase immunoreactivity in the mouse brain

Nitric oxide (NO) is a gaseous intercellular messenger with a wide range of neural functions. NO is synthesized by activation of different isoforms of nitric oxide synthases (NOS). At present NOS immunoreactivity has been described in mouse brain in restricted and definite areas and no detailed mapping studies have yet been reported for NOS immunoreactivity. We have studied the distribution of neuronal NOS-containing neurons in the brain of three months male mice, using a specific commercial polyclonal antibody against the neuronal isoform of nitric oxide synthase (nNOS). Neuronal cell bodies exhibiting nNOS immunoreactivity were found in several distinct nuclei throughout the brain. The neurons that were positively stained exhibited different intensities of reaction. In some brain areas (i.e., cortex, striatum, tegmental nuclei) neurons were intensely stained in a Golgi-like fashion. In other regions, immunoreactive cells are moderately stained (i.e., magnocellular nucleus of the posterior commissure, amygdaloid nucleus, interpeduncular nucleus, lateral periaqueductal gray) or weakly stained (i.e., vascular organ of the lamina terminalis, hippocampus, inferior colliculus, reticular nucleus). In the mouse, the NO-producing system appears well developed and widely diffused. In particular, nNOS immunoreactive neurons seem chiefly present in several sensory pathways like all the nuclei of the olfactory system, as well as in many regions of the lymbic system. These data suggest a widespread role for the NO system in the mouse nervous system.

Nitric oxide-cyclic GMP pathway with some emphasis on cavernosal contractility

Nitric oxide (NO) is formed from the conversion of L-arginine by nitric oxide synthase (NOS), which exists in three isoforms: neuronal (nNOS), endothelial (eNOS), and inducible (iNOS). nNOS is expressed in penile neurons innervating the corpus cavernosum, and eNOS protein expression has been identified primarily in both cavernosal smooth muscle and endothelium. NO is released from nerve endings and endothelial cells and stimulates the activity of soluble guanylate cyclase (sGC), leading to an increase in cyclic guanosine-3',5'-monophosphate (cGMP) and, finally, to calcium depletion from the cytosolic space and cavernous smooth muscle relaxation. The effects of cGMP are mediated by cGMP dependent protein kinases, cGMP-gated ion channels, and cGMP-regulated phosphodiesterases (PDE). Thus, cGMP effect depends on the expression of a cell-specific cGMP-receptor protein in a given cell type. Numerous systemic vasculature diseases that cause erectile dysfunction (ED) are highly associated with endothelial dysfunction, which has been shown to contribute to decreased erectile function in men and a number of animal models of penile erection. Based on the increasing knowledge of intracellular signal propagation in cavernous smooth muscle tone regulation, selective PDE inhibitors have recently been introduced in the treatment of ED. Phosphodiesterase 5 (PDE5) inactivates cGMP, which terminates NO-cGMP-mediated smooth muscle relaxation. Inhibition of PDE5 is expected to enhance penile erection by preventing cGMP degradation. Development of pharmacologic agents with this effect has closely paralleled the emerging science.

Effect of tetrahydrobiopterin on nitric oxide synthase-containing cells in the rat hippocampus

We have observed that tetrahydrobiopterin (BH4), a cofactor of nitric oxide synthase (NOS), acts as a self-protection factor against nitric oxide (NO) toxicity in PC12 cells. To further investigate the self-protection action of BH4 in vivo, the effect of deletion of endogenous BH4 on NO-producing cells was examined in the rat hippocampus. Following the peripheral infusion of 50 mM 2,4-diamino-6-hydroxypyrimidine (DAHP), an inhibitor of GTP cyclohydrolase I, using a miniosmotic pump for 14 days, BH4 content in the hippocampus decreased as compared with the control group administered with vehicle solution, which had no effect on brain BH4 content. When the rats were administered with 50 mM DAHP and 10 mM BH4, the DAHP-induced decrease in BH4 content was prevented. The extracellular concentration of NO metabolites remained unchanged following DAHP administration, suggesting that DAHP-induced decrease in BH4 content had no effect on NO production. The number of NOS-positive cells decreased following DAHP administration in the hippocampal regions, while the number of NOS-negative cells remained unchanged. The DAHP-induced decrease in the NOS-positive cell number was prevented by the administration of 10 mM BH4 and DAHP. These results suggest that endogenous BH4 may affect NOS-positive cell number in the rat hippocampus.

Ca2+, calmodulin and phospholipids regulate nitricoxide synthase activity in the rabbit submandibular gland

Nitric oxide (NO) plays an important role as an intra- and intercellular signaling molecule in mammalian tissues. In the submandibular gland, NO has been suggested to be involved in the regulation of secretion and in blood flow. NO is produced by activation of NO synthase (NOS). Here, we have investigated the regulation of NOS activity in the rabbit submandibular gland. NOS activity was detected in both the cytosolic and membrane fractions. Characteristics of NOS in the cytosolic and partially purified membrane fractions, such as Km values for l-arginine and EC(50) values for calmodulin and Ca(2+), were similar. A protein band that cross-reacted with anti-nNOS antibody was detected in both the cytosolic and membrane fractions. The membrane-fraction NOS activity increased 1.82-fold with treatment of Triton X-100, but the cytosolic-fraction NOS activity did not. The NOS activity was inhibited by phosphatidic acid (PA) and phosphatidylinositol 4,5-bisphosphate (PIP(2)). The inhibitory effects of phospholipids on the NOS activity were relieved by an increase in Ca(2+) concentrations. These results suggest that the Ca(2+)- and calmodulin-regulating enzyme nNOS occurs in cytosolic and membrane fractions, and PA and PIP(2) regulate the NOS activity in the membrane site by regulating the effect of Ca(2+) in the rabbit submandibular gland.

Combined effect of testosterone and apocynin on nitric oxide and superoxide production in PMA-differentiated THP-1 cells

Human inducible nitric oxide synthase (iNOS) is most readily observed in macrophages from patients with inflammatory diseases like atherosclerosis. The aim of the present study was to find out the combined effect of male sex hormone; testosterone and apocynin (NADPH oxidase inhibitor) on cytokine-induced iNOS production. THP-1 cells were differentiated into macrophages by phorbol myristate acetate (PMA). Expression of iNOS was induced by the addition of cytokine mixture? Testosterone was added at different concentrations (10(-6)-10(-12) M) with apocynin (1 mM). Testosterone (10(-8), 10(-10) M) inhibited NOx production in cytokine-added THP-1 cells which was further confirmed by quantikine assay of iNOS protein and RT-PCR analysis. Testosterone treatment decreased 40% of superoxide anion production. Testosterone showed inhibition of NADPH oxidase, especially expression of p67phox and p47phox (cytosol subunits). Addition of testosterone with apocynin further decreased the expression of p67phox and p47phox subunits of NADPH oxidase. The findings of the present study suggest that, testosterone; the male androgen plays an important role in the prevention of atherogenesis. Even though apocynin does not have any role on NO production, addition of apocynin together with testosterone is effective in suppressing iNOS activity.

Combined action of extracellular signal-regulated kinase and p38 kinase rescues Molt4 T cells from nitric oxide-induced apoptotic and necrotic cell death

The mechanisms that regulate nitric oxide (NO)-induced apoptosis, especially in T cell apoptosis, are largely uncharacterized. Here, we report that protection from NO-induced cell death by phorbol 12-myristate 13-acetate (PMA) is dependent on both p38 and extracellular signal-regulated kinase (ERK) activation. Exposure of Molt4 cells to NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP) induced both apoptotic and necrotic modes of cell death along with a sustained increase in p38 kinase phosphorylation. However, the p38 inhibitor SB202190 only slightly protected Molt4 cells from NO toxicity. In contrast, PMA rapidly phosphorylated both p38 kinase and ERK, and the phosphorylation statuses were not altered in the presence of SNAP. Interestingly, although each mitogen-activated protein kinase (MAPK) inhibitor by itself had only a modest effect, the combination of inhibitors for both MAPKs almost completely abolished the protective effect of PMA. Furthermore, dominant negative or catalytically inactive variants that modulate p38 and ERK mimicked the effects of MAPK inhibitors. We located the action of p38 and ERK upstream of the p53/mitochondrial membrane potential loss and caspases cascade. Together, these findings suggest that the PMA-induced activations of ERK and p38 kinase are parallel events that are both required for inhibition of NO-induced death of Molt4 cells.

Inducible activity of ginger rhizome (Zingiber offifinale Rosc.) on the mRNA expression of macrophage-inducible nitric oxide (NO) synthase and NO production in a macrophage cell line, RAW264.7 cells

We have investigated the effect of Zingiber offifinale Rosc. (ZOR) on macrophage-inducible nitric oxide (NO) synthase (macNOS) mRNA expression and NO production in RAW264.7 cells, a murine macrophage cell line; 100 microg/ml ZOR can induce macNOS mRNA expression, but induction effects at a dose below 10 microg/ml were weak or negligible. Kinetic studies showed that macNOS mRNA can be detected from 4 hours to 24 hours after dosing, with a peak at 8 hours. In accordance with the induction of macNOS mRNA expression, NO concentrations increased from 3.4 microM at 2 hours to almost 150 microM at 24 hours, reflecting a longer period of macNOS mRNA expression. The activity of ZOR can be considered to contribute, at least in part, to the beneficial effects of ZOR through the macNOS-mediated activation of the biodefense mechanism.

L-NAME (N omega-nitro-L-arginine methyl ester), a nitric-oxide synthase inhibitor, and WIN 55212-2 [4,5-dihydro-2-methyl-4(4-morpholinylmethyl)-1-(1-naphthalenyl-carbonyl)-6H-pyrrolo[3,2,1ij]quinolin-6-one], a cannabinoid agonist, interact to evoke synergistic hypothermia

Cannabinoids evoke profound hypothermia in rats by activating central CB(1) receptors. Nitric oxide (NO), a prominent second messenger in central and peripheral neurons, also plays a crucial role in thermoregulation, with previous studies suggesting pyretic and antipyretic functions. Dense nitric-oxide synthase (NOS) staining and CB(1) receptor immunoreactivity have been detected in regions of the hypothalamus that regulate body temperature, suggesting that intimate NO-cannabinoid associations may exist in the central nervous system. The present study investigated the effect of N(omega)-nitro-L-arginine methyl ester (L-NAME), a NO synthase inhibitor, on the hypothermic response to WIN 55212-2 [4,5-dihydro-2-methyl-4(4-morpholinylmethyl)-1-(1-naphthalenylcarbonyl)-6H-pyrrolo[3,2,1ij]quinolin-6-one], a selective cannabinoid agonist, in rats. WIN 55212-2 (1-5 mg/kg, i.m.) produced dose-dependent hypothermia that peaked 45 to 90 min post-injection. L-NAME (10-100 mg/kg, i.m.) by itself did not significantly alter body temperature. However, a nonhypothermic dose of L-NAME (50 mg/kg) potentiated the hypothermia caused by WIN 55212-2 (0.5-5 mg/kg). The augmentation was strongly synergistic, indicated by a 2.5-fold increase in the relative potency of WIN 55212-2. The inactive enantiomer of WIN 55212-2, WIN 55212-3 [S-(-)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazinyl]-(1-napthanlenyl) methanone mesylate] (5 mg/kg, i.m.), did not produce hypothermia in the absence or presence of L-NAME (50 mg/kg), confirming that cannabinoid receptors mediated the synergy. The present data are the first evidence that drug combinations of NOS blockers and cannabinoid agonists produce synergistic hypothermia. Thus, NO and cannabinoid systems may interact to induce superadditive hypothermia.

Elevated nitric oxide levels in childhood brain tumors

OBJECTIVES

One of the fundamental aspects of nitric oxide (NO) is the regulation of the inflammatory processes involved in neuronal apoptosis. Expressions of NO and NO synthase (NOS) are considered to be involved in brain tissue injuries and brain tumors. The purpose of our study was to investigate the roles of NO and inducible-form NOS (iNOS) in the pathogenesis of brain tumors.

METHODS

NO levels in the cerebrospinal fluid (CSF) of 36 brain tumor patients were detected utilizing the NO-chemiluminescence method. Deparaffinized tissue sections were immunostained for the presence of antibodies against iNOS and for apoptosis using the TUNEL stain. The results were compared with 10 control patients (with epilepsy and hydrocephalus).

CONCLUSIONS

Higher levels of NO and iNOS activities may induce immune responses and neurotoxicities. This preliminary study revealed elevated NO and NOS activities with an increased amount of apoptotic processes in brain tumor tissues, which may indicate the possible roles of NO in the formation of brain tumors.

Heat shock protein 90 as an endogenous protein enhancer of inducible nitric-oxide synthase

Nitric oxide (NO) generated by inducible NO synthase (iNOS) plays crucial roles in inflammation and host defense. With an intrinsically bound calmodulin, iNOS is fully active once expressed in cells. Thus, regulation of NO production from iNOS was thought to primarily occur at the enzyme transcriptional level. Here we show that NO synthesis from iNOS can be profoundly modulated by heat shock protein 90 (hsp90) through protein-protein interaction. To study whether hsp90 affects iNOS function, recombinant murine iNOS was purified from an Escherichia coli expression system by affinity chromatography. Hsp90, at physiological concentrations (10-500 nm), dose-dependently increased iNOS activity. This was a specific effect because neither denatured hsp90 nor irrelevant bovine serum albumin affected iNOS function. Overexpression of hsp90 enhanced NO production in iNOS-transfected cells. On the contrary, hsp90 inhibition dramatically decreased NO formation from iNOS in macrophages. Co-immunoprecipitation studies showed that hsp90 and iNOS associated with each other in cells. Overexpression of iNOS resulted in NO-mediated cellular injury. Hsp90 inhibition markedly attenuated NO formation and prevented cellular injury. These results demonstrated that hsp90 is an allosteric enhancer of iNOS. iNOS is coupled with hsp90 in cells, and this coupling facilitates NO synthesis. In light of the critical role of hsp90 in iNOS-mediated cytotoxic action, modulating the interaction between hsp90 and iNOS may be a new approach to intervene inflammation and immune response.