Reduced neuronal nitric oxide synthase is involved in ischemia-induced hippocampal neurogenesis by up-regulating inducible nitric oxide synthase expression

Nitric oxide (NO), a free radical with signaling functions in the CNS, is implicated in some developmental processes, including neuronal survival, precursor proliferation, and differentiation. However, neuronal nitric oxide synthase (nNOS) -derived NO and inducible nitric oxide synthase (iNOS) -derived NO play opposite role in regulating neurogenesis in the dentate gyrus after cerebral ischemia. In this study, we show that focal cerebral ischemia reduced nNOS expression and enzymatic activity in the hippocampus. Ischemia-induced cell proliferation in the dentate gyrus was augmented in the null mutant mice lacking nNOS gene (nNOS−/−) and in the rats receiving 7-nitroindazole, a selective nNOS inhibitor, after stroke. Inhibition of nNOS ameliorated ischemic injury, up-regulated iNOS expression, and enzymatic activity in the ischemic hippocampus. Inhibition of nNOS increased and iNOS inhibitor decreased cAMP response element-binding protein phosphorylation in the ipsilateral hippocampus in the late stage of stroke. Moreover, the effects of 7-nitroindazole on neurogenesis after ischemia disappeared in the null mutant mice lacking iNOS gene (iNOS−/−). These results suggest that reduced nNOS is involved in ischemia-induced hippocampal neurogenesis by up-regulating iNOS expression and cAMP response element-binding protein phosphorylation.     

诱导型一氧化氮合酶的激活与血压的关系

本实验旨在探讨诱导型一氧化氮合酶（iNOS)的激活与血压之间的关系,三组SD大鼠分别静脉输注不同浓度（0．3％,4％及8％）NaCl溶液以使其处于不同的血压水平,运用同位素标记的L－精氨酸转换成L－Citrulline 的转换率变化及Greiss反应,分别测定不同血压时iNOS的活性及NO的生成量,另四组大鼠包括正常Wistar,正常SD,高盐诱导的高血压（NaHR)及自发性高血压大鼠（SHR）,经测定血压后,取主动脉血管并以Western印迹印交法测定其iNOS蛋白水平,结果表明,血压较低时,SD大鼠iNOS活基本没有改变,而在输入4％和8％NaCl并处于较高血压水平的SD大鼠,其iNOS活性及NO生存均明显升高,。此外Western 印迹表明,两种高血压大鼠主动脉组织iNOS蛋白水平均较正常Wistar及正常SD大鼠高,密度扫描表明,NaHR及SHR主动脉组织iNOS蛋白分别较正常SD大鼠及正常Wistar大鼠升高149％及261％,这一结果提示,诱导型一氧化氮合酶是血液动力学调控的重要组成部分,尤其是在血压处于较高水平时,iNOS具有重要的代偿调节作用,除细胞因子,细菌产物等之外,血压也是调节iNOS表达及活性的重要因素之一。     

Triptolide inhibits cyclooxygenase-2 and inducible nitric oxide synthase expression in human colon cancer and leukemia cells

Triptolide (TP),a traditional Chinese medicine,has been reported to be effective in thetreatment of autoimmune diseases and exerting antineoplastic activity in several human tumor cell lines.Thisstudy investigates the antitumor effect of TP in human colon cancer cells (SW114) and myelocytic leukemia(K562),and elucidates the possible molecular mechanism involved.SW114 and K562 cells were treatedwith different doses of TP (0,5,10,20,or 50 ng/ml).The cell viability was assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT). Results demonstrated that TP inhibited the proliferation ofboth tumor cell lines in a dose-dependent manner.To further investigate its mechanisms,the productsprostaglandin E_2 (PGE2) and nitric oxide (NO) were measured by enzyme-linked immunosorbent assay(ELISA).Our data showed that TP strongly inhibited the production of NO and PGE_2. Consistent with theseresults,the expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) was up-regulatedboth at the mRNA level and the protein expression level,as shown by real-time RT-PCR and Westernblotting.These results indicated that the inhibition of the inflammatory factor COX-2 and iNOS activitycould be involved in the antitumor mechanisms of TP.     

Oxidized phospatidylcholine but not native phosphatidylcholine inhibits inducible nitric oxide synthase in RAW 264.7 macrophages

This study was designed to compare the effects of oxidized 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine (PAPC) and native PAPC on the inducible nitric oxide synthase (iNOS) in the macrophage cell line RAW 264.7. Macrophages stimulated by bacterial lipopolysaccharide (1 microg/ml) were incubated with increasing amounts of native or oxidized PAPC (oxPAPC, 10-20 microg/ml). Cells incubated with oxPAPC showed a dose-dependent inhibition of inducible nitric oxide synthesis, as well as reduced iNOS protein expression and mRNA levels. Additionally, chromatin immunoprecipitation assay revealed that oxPAPC reduced the interaction of the active NF-kappaB subunit p65 with the iNOS promoter region when compared to native PAPC.     

Antihypertensive effects of inducible nitric oxide synthase inhibition in experimental pre‐eclampsia

Upregulation of inducible nitric oxide synthase (iNOS) has been reported in both experimental and clinical hypertension. However, although pro‐inflammatory cytokines that up‐regulate iNOS contribute to pre‐eclampsia, no previous study has tested the hypothesis that a selective iNOS inhibitor (1400 W) could exert antihypertensive effects associated with decreased iNOS expression and nitrosative stress in pre‐eclampsia. This study examined the effects of 1400 W in the reduced uteroplacental perfusion pressure (RUPP) placental ischaemia animal model and in normal pregnant rats. Sham‐operated and RUPP rats were treated with daily vehicle or 1 mg/kg/day N‐[3‐(Aminomethyl) benzyl] acetamidine (1400 W) subcutaneously for 5 days. Plasma 8‐isoprostane levels, aortic reactive oxygen species (ROS) levels and nicotinamide adenine dinucleotide phosphate (NADPH)‐dependent ROS production were evaluated by ELISA, dihydroethidium fluorescence microscopy and lucigenin chemiluminescence respectively. Inducible nitric oxide synthase expression was assessed by western blotting analysis and aortic nitrotyrosine was evaluated by immunohistochemistry. Mean arterial blood pressure increased by ~30 mmHg in RUPP rats, and 1400 W attenuated this increase by ~50% (P < 0.05). While RUPP increased plasma 8‐isoprostane levels, aortic ROS levels, and NADPH‐dependent ROS production (P < 0.05), treatment with 1400 W blunted these alterations (P < 0.05). Moreover, while RUPP increased iNOS expression and aortic nitrotyrosine levels (P < 0.05), treatment with 1400 W blunted these alterations (P < 0.05). These results clearly implicate iNOS in the hypertension associated with RUPP. Our findings may suggest that iNOS inhibitors could be clinically useful in the therapy of pre‐eclampsia, especially in particular groups of patients genetically more prone to express higher levels of iNOS. This issue deserves further confirmation.     

Expression of inducible nitric oxide synthase in human cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) is an infectious disease caused by Leishmania parasite. The expression of inducible nitric oxide synthase (iNOS) and generation of nitric oxide in response to IFN-γ and TNF-α is important in control of infection. The aim of the study was to determine the expression of iNOS in the lesions of Leishmania tropica, and whether there was a correlation between the level of expression and the duration of the disease. Punch biopsy was performed from patients (n = 29) and iNOS immunohistochemical staining was applied. Expression of iNOS protein was detected 82.8% of patients. There was a strong expression with the duration of the disease less than 6 months (p < 0.002). These findings demonstrate that iNOS has a role in L. tropica especially during the early stages of the infection. (Mol Cell Biochem xxx: 147–149, 2005)     

Homocysteine stimulates inducible nitric oxide synthase expression in macrophages: Antagonizing effect of ginkgolides and bilobalide

Hyperhomocysteinemia is an independent risk factor for atherosclerotic diseases. Inducible nitric oxide synthase (iNOS) is mainly expressed in macrophages upon stimulation. Overproduction of nitric oxide (NO) by iNOS can exacerbate the development of atherosclerosis. Our previous studies demonstrated that the extract of ginkgo biloba leaves (EGb) inhibited the iNOS-mediated NO production in monocyte-derived macrophage. We also reported that homocysteine could stimulate monocyte chemoattractant protein-1 (MCP-1) expression in vascular cells causing enhanced monocyte chemotaxis. The objective of the present study was to investigate the effect of homocysteine on iNOS-mediated NO production in macrophages and the antagonizing effect of EGb. Human monocytic cell (THP-1)-derived macrophages were incubated with homocysteine for various time periods. Homocysteine at concentrations of 0.05–0.1 mM significantly stimulated NO production and iNOS activity in macrophages via increased expression of iNOS mRNA and protein. The increased iNOS expression was associated with activation of nuclear factor-kappa B (NF-B) arising from reduced expression of inhibitor protein (IB) mRNA as well as increased phosphorylation of IB protein in homocysteine-treated cells. EGb and its terpenoids (ginkgolide A, ginkgolide B and bilobalide) could antagonize the homocysteine effect on iNOS expression in macrophages via their antioxidant effect resulting in attenuation of NF-B activation. Taken together, our results have demonstrated that homocysteine, at pathophysiological concentrations, stimulates iNOS-mediated NO production in macrophages. EGb and its terpenoids can antagonize such stimulatory effect via antioxidation and attenuation of NF-B activation.     

The role of neutral sphingomyelinase produced ceramide in lipopolysaccharide-mediated expression of inducible nitric oxide synthase

Lipopolysaccharide (LPS) and interferon-gamma (IFN) treatment of C6 rat glioma cells increased the intracellular ceramide level and the expression of the inducible nitric oxide synthase (iNOS) gene. To delineate the possible role of ceramide in the induction of iNOS, we examined the source of intracellular ceramide and associated signal transduction pathway(s) with the use of inhibitors of intracellular ceramide generation. The inhibitor of neutral sphingomyelinase (3-O-methylsphingomyelin, MSM) inhibited the induction of iNOS, whereas inhibitor of acidic sphingomyelinase (SR33557) or that of ceramide de novo synthesis (fumonisin B1) had no effect on the induction of iNOS. MSM-mediated inhibition of iNOS induction was reversed by the supplementation of exogenous C8-ceramide, suggesting that ceramide production by neutral sphingomyelinase (nSMase) is a key mediator in the induction of iNOS. The MSM-mediated inhibition of iNOS gene expression correlated with the decrease in the activity of ras. Inhibition of co-transfected iNOS promoter activity by dominant negative ras supported the role of ras in the nSMase-dependent regulation of iNOS gene. NF-kappaB DNA binding activity and its transactivity were also reduced by MSM pretreatment, and were completely reversed by the supplementation of C8-ceramide. As the dominant negative ras also reduced NF-kappaB transactivity, NF-kappaB activation may be downstream of ras. Our results suggest that ceramide generated by nSMase may be a critical mediator in the regulation of iNOS gene expression via ras-mediated NF-kappaB activation under inflammatory conditions.     

脊髓水平iNOS在吗啡依赖大鼠戒断反应中的作用

目的:探讨脊髓水平诱导型一氧化氮合酶在吗啡依赖大鼠戒断反应中的作用。方法:健康雄性SD大鼠72只,体重200~250 g,吗啡剂量每次10 mg/kg,每日2次,隔日每次增加10 mg/kg,至第6天末次注射50 mg/kg,大鼠腹腔注射纳洛酮4 mg/kg建立吗啡依赖及戒断模型,在纳洛酮激发戒断前30 min鞘内注射iNOS特异性抑制剂氨基胍(AG)150μg。分为正常对照组、吗啡依赖组、吗啡戒断组、AG组。采用行为学(n=8)、免疫组织化学(n=6)和Western blot(n=4)方法观察鞘内应用iNOS特异性抑制剂氨基胍对吗啡依赖大鼠纳洛酮催促戒断反应和脊髓神经元iNOS表达的影响。结果:AG组戒断症状评分和戒断组促诱发痛评分均低于戒断组(P<0.05)。免疫组织化学和Western blot显示戒断组大鼠脊髓iNOS阳性神经元的数目和蛋白的表达增高,而AG组大鼠脊髓iNOS阳性神经元的数目和iNOS蛋白的表达低于戒断组(P<0.05)。结论:脊髓水平iNOS表达上调可能参与介导吗啡戒断反应。     

Neisseria meningitidis-induced death of cerebrovascular endothelium: mechanisms triggering transcriptional activation of inducible nitric oxide synthase

The intense host response to meningococcus reflects marked functional and morphological alterations in blood-brain barriers. We showed previously that mouse-derived cerebrovascular endothelium responded to meningococcal lysates with a robust nitric oxide (NO) response, resulting in the loss of cell viability. To understand how the NO synthase-2 gene in endothelium is activated by meningococcus, we investigated upstream roles for specific protein kinases. Using known kinase inhibitors, and measuring both mRNA expression and nitrite release, we found MAPK/ERK kinase (MEK)2, p38 kinase and phosphoinositide 3-kinase (but not MEK1 or phospholipase C) to be implicated in the NO synthase-2 response. Recruitment of these kinases by meningococcus did not depend on the prior release of the proinflammatory cytokines tumour necrosis factor alpha or interleukin-1beta from endothelium. These endothelial cells were found to express toll-like receptors (TLR) 2, 4 and 9 and antibodies directed against TLR 2 and 4 (but not TLR 9) blocked the NO synthase-2 response to meningococcus. Both meningococcus-induced translocation of nuclear factor-kB (NF-kB) and endothelial cell death were blocked by a known inhibitor of p38 kinase. Calpain inhibitor-1 blocked the NO synthase-2 response to meningococcus, which is further evidence of a role for NF-kB.     

Cellular and physiological upregulation of inducible nitric oxide synthase,arginase, and inducible cyclooxygenase in wound healing

Wound repair is regulated by overlapping cellular, physiological and biochemical events. Prostaglandins and nitric oxide have been a focus for inflammation research particularly since the discovery of their inducible isoforms nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Study of the cellular expression of iNOS and COX-2 and arginase which competes with iNOS for its substrate, in an in vivo model of wound healing could reveal important roles for these enzymes in the physiological progression of wound repair. Adult male rats received full thickness dermal wounds which were harvested at different times. Protein levels and activities of the enzymes were assessed by western blot and biochemical assays respectively. The cellular distribution and the colocalization were assessed by immunostaining. The protein levels and activities of iNOS, arginase, and COX-2 increased only during the inflammatory phase of wound. Immunocytochemistry showed that the three enzymes were coexpressed and the main cellular source was inflammatory cells mainly macrophages. iNOS was induced at the wound site and was the earliest to increase significantly (p < 0.05) for only up to 3 days postwounding. However, arginase and COX-2 significant ( p < 0.05) upregulation started at a later time points and continued for up to 14 days postwounding. Therefore iNOS, compared with arginase and COX-2, showed a temporal difference in expression during wound healing which could be explained by their products being required at different stages of the healing process. The coordinated expression of the three enzymes at different time points could account for the physiological progression of the healing process.     

昆虫一氧化氮及其合酶的研究进展

一氧化氮作为一种重要的信息分子 ,参与调节昆虫嗅觉、视觉、机械感受、发育、机体防御及学习行为。该文从生理、生化、形态定位以及信号转导几方面综述了有关昆虫一氧化氮及其合酶的最新研究进展。     

Chronic stress induces the expression of inducible nitric oxide synthase in rat brain cortex

Long-term exposure to stress has detrimental effects on several brain functions in many species, including humans, and leads to neurodegenerative changes. However, the underlying neural mechanisms by which stress causes neurodegeneration are still unknown. We have investigated the role of endogenously released nitric oxide (NO) in this phenomenon and the possible induction of the inducible NO synthase (iNOS) isoform. In adult male rats, stress (immobilization for 6 h during 21 days) increases the activity of a calcium-independent NO synthase and induces the expression of iNOS in cortical neurons as seen by immunohistochemical and western blot analysis. Three weeks of repeated immobilization increases immunoreactivity for nitrotyrosine, a nitration product of peroxynitrite. Repeated stress causes accumulation of the NO metabolites NO2+ NO3- (NOx-) accumulation in cortex, and these changes occur in parallel with lactate dehydrogenase (LDH) release and impairment of glutamate uptake in synaptosomes. Administration of the selective iNOS inhibitor aminoguanidine (400 mg/kg i.p. daily from days 7 to 21 of stress) prevents NOx- accumulation in cortex, LDH release, and impairment of glutamate uptake in synaptosomes. Taken together, these findings indicate that a sustained overproduction of NO via iNOS expression may be responsible, at least in part, for some of the neurodegenerative changes caused by stress and support a possible neuroprotective role for specific iNOS inhibitors in this situation.     

Dehydroepiandrosterone inhibits lipopolysaccharide-induced nitric oxide production in BV-2 microglia

Levels of dehydroepiandrosterone (DHEA) and its sulfated derivative (DHEAS) decline during aging and reach even lower levels in Alzheimer's disease (AD). DHEA is known to exhibit a variety of functional activities in the CNS, including an increase of memory and learning, neurotrophic and neuroprotective effects, and the reduction of risk of age-related neurodegenerative disorders. However, the influence of DHEA on the immune functions of glial cells is poorly understood. In this study, we investigated the effect of DHEA on activated glia. The production of inducible nitric oxide synthase (iNOS) was studied in lipopolysaccharide (LPS)-stimulated BV-2 microglia, as a model of glial activation. The results showed that DHEA but not DHEAS significantly inhibited the production of nitrite in the LPS-stimulated BV-2 cell cultures. Pretreatment of BV-2 cells with DHEA reduced the LPS-induced iNOS mRNA and protein levels in a dose-dependent manner. The LPS-induced iNOS activity in BV-2 cells was decreased by the exposure of 100 microM DHEA. Moreover, DHEA suppressed iNOS gene expression in LPS-stimulated BV-2 cells did not require de novo synthesis of new proteins or destabilize of iNOS mRNA. Since DHEA is biosynthesized by astrocytes and neurons, our findings suggest that it might have an important regulatory function on microglia.     

Endogenous bacteria-triggered inducible nitric oxide synthase activation protects the ovariectomized rat stomach

Under experimental circumstances, ovariectomy attenuates gastric mucosal injury where nitric oxide (NO)-mediated pathways are involved. In this study, we have examined the changes in constitutive (cNOS) and inducible NO synthase (iNOS) enzyme activities (assessed by the citrulline assay), and the role of endogenous bacteria in ovariectomy-provoked mucosal defence. Gastric lesions were induced by indomethacin (50 mg/kg, s.c.) over a 4 h period in sham-operated and ovariectomized female Wistar rats. Groups of animals received the wide-spectrum antibiotic ampicillin (800 mg/kg/day, p.o., for 3 days), and others were injected with bacterial endotoxin (E. coli, 3 mg/kg, i.v., 5 h before autopsy). We found that ovariectomy increased iNOS and decreased cNOS activity (resulting an elevated total gastric NOS level), and protected the stomach, effects reversed by ampicillin treatment. In ovary-intact rats, administration of bacterial endotoxin enhanced gastric iNOS activity and reduced lesion-formation. These results suggest that ovariectomy improves gastric mucosal defence perhaps by endogenous bacteria-triggered induction of iNOS.