NO在植物中的调控作用

一氧化氮(NO)是一种易扩散的生物活性分子,是生物体内重要的信号分子.植物细胞通过NO合酶、硝酸还原酶、或非生化反应途径产生NO.NO参与植物生长发育调控和对生物与非生物环境胁迫的应答反应,大量证据表明NO是植物防御反应中的关键信使,其信号转导机制也受到越来越多的关注.本文主要通过讨论NO的产生、对植物生长周期的影响、在植物代谢中的信号调节以及参与细胞凋亡来阐述NO在植物中的作用.     

一氧化氮参与炎症及自身免疫反应

一氧化氮(nitric oxide,NO)是一种无机气体。在生物体内有多种生理和毒性作用。哺乳动物体内多种细胞可产生NO,如内皮细胞、神经细胞、巨噬细胞、血小板等,其靶细胞也多种多样。NO在体内是通过一氧化氮合成酶(NOS)由L-精氨酸合成。NOS有原生酶和诱生酶两种。原生酶为钙依赖     

一氧化氮(NO)在微生物中的作用研究

一氧化氮(nitric oxide NO)是微生物中重要的生物活性分子,在细菌生长、生物被膜形成、细胞保护以及耐药性等方面均能发挥重要作用.研究表明,微生物能够感受外源NO的作用,也可以通过自身的一氧化氮合酶(NOS)以及硝化和反硝化过程产生NO,本文将对近年来有关微生物中NO作用的研究进行概述.     

一氧化氮对家榆种子老化的影响及其作用机制研究

以家榆种子为试材,采用种子活力检测技术、激光共聚焦显微镜技术、蛋白质S-亚硝基化检测技术,结合多种相关抑制剂的使用,研究了NO对种子老化的影响及其作用机制。结果表明:(1)外源NO可显著提升老化处理后种子的活力,NO清除剂cPTIO可降低老化处理后种子的活力,且此影响可被NO供体硝普钠所恢复。(2)硝酸还原酶底物亚硝酸钠、类一氧化氮合酶底物L-精氨酸(L-Arg)均可提高老化处理后种子的活力,2种酶的抑制剂可降低种子活力,且此影响可被NO供体硝普钠所恢复,即硝酸还原酶与类一氧化氮合酶可参与种子老化过程中NO的产生。(3)种子老化过程中NO首先在子叶中合成,随后在胚根尖部、生长点与下胚轴等部位出现,蛋白质S-亚硝基化水平与NO在种子中产生的时间特点一致。研究认为,NO可提高种子抗老化能力,种子内NO可通过硝酸还原酶途径和类一氧化氮合酶途径产生,且与种子蛋白质S-亚硝基化水平相关。     

NF-κB、PKC和PC-PLC在双歧杆菌的脂磷壁酸激活巨噬细胞产生NO中的作用

目的探索双歧杆菌的LTA激活巨噬细胞产生一氧化氮（NO）的信号途径。方法以LTA刺激大鼠腹腔巨噬细胞,用激光共聚焦显微镜定量测定其诱导型一氧化氮合酶（iNOS）的含量,以Griess试剂检测巨噬细胞产生NO的含量。结果LTA刺激组大鼠腹腔巨噬细胞iNOS和NO的含量明显高于对照组（P〈0.01）。以PDTC、Chelerythrine和D609分别预先孵育巨噬细胞,再以LTA刺激巨噬细胞,其产生iNOS和NO的量明显低于LTA刺激组（P〈0.01）。结论双歧杆菌的LTA可通过NF-κB、PKC和PC-PLC激活巨噬细胞,使之产生多量的iNOS以及NO。     

NO在植物中的调控作用

一氧化氮（NO）是一种易扩散的生物活性分子,是生物体内重要的信号分子。植物细胞通过NO合酶、硝酸还原酶、或非生化反应途径产生NO。NO参与植物生长发育调控和对生物与非生物环境胁迫的应答反应,大量证据表明NO是植物防御反应中的关键信使,其信号转导机制也受到越来越多的关注。本文主要通过讨论NO的产生、对植物生长周期的影响、在植物代谢中的信号调节以及参与细胞凋亡来阐述NO在植物中的作用。     

一氧化氮调节BAFF表达和T细胞非依赖的抗体应答

<正>已知天然免疫细胞产生的一氧化氮(NO)在T细胞免疫应答起着重要的调节作用,但它在B细胞体液免疫应答中的作用还不清楚。已有的研究提示,诱导性一氧化氮合酶(NOS2/iNOS)是正常的IgA抗体应答所必需的,然而,NOS2却能抑制病毒特异性的IgG2a的抗体应答反应。本文的研究人员利用NOS2敲除小鼠研究了T细胞依赖和T细胞非依赖的抗体应答中NO     

金黄色葡萄球菌对小鼠产生一氧化氮及一氧化氮合酶的影响

目的 :探讨金黄色葡萄球菌对小鼠产生一氧化氮 (NO)及一氧化氮合酶 (NOS)的影响 ,以进一步研究 NO及 NOS在抗感染免疫中的作用。方法 :将不同剂量的金黄色葡萄球菌注入小鼠腹腔 ,10 d后取小鼠血清和腹腔巨噬细胞培养上清 ,用硝酸还原酶法检测其 NO的含量 ,同时测定血清中 NOS的水平及抗金黄色葡萄球菌抗体的效价。结果 :金黄色葡萄球菌注射小鼠后 ,血清中 NO及 NOS的水平明显高于对照组 (P<0 .0 1) ,各组间两两比较亦差异有显著性 (P<0 .0 1)。腹腔巨噬细胞培养上清 NO的水平明显高于对照组 (P<0 .0 1) ,但不同剂量实验组之间差异无显著性 (P>0 .0 5)。结论 :金黄色葡萄球菌可引起小鼠血清中 NO、NOS升高 ,NO及 NOS可能在抗微生物感染免疫中起着重要的作用     

植物一氧化氮(NO)研究进展

一氧化氮(NO)是植物的重要生物活性分子,它参与植物生长发育的许多过程,如种子萌发、下胚轴伸长、叶扩展、根生长、侧根形成、细胞凋亡以及植物抗逆反应等。大量的证据表明,植物可以通过与动物NO合酶类似的酶产生NO。此外,植物还可通过硝酸还原酶产生NO。NO在植物中的信号传递途径仍不十分清楚,植物有可能采用与动物相类似的机制。由于植物的大多数生长发育现象都受到植物激素的调节和控制,NO与植物激素之间的关系也受到越来越多的关注。通过激素起作用可能是植物内源NO作用的机理之一。     

甲氨蝶呤诱导巨噬细胞M1极化促进骨肉瘤细胞凋亡的实验研究

目的:探讨甲氨蝶呤诱导巨噬细胞分化情况和分化后巨噬细胞对骨肉瘤细胞凋亡的影响。方法:采用甲氨蝶呤刺激小鼠单核巨噬细胞RAW264.7细胞24小时后,使用流式、免疫荧光等技术检测M1型巨噬细胞标志物CD86、诱导型一氧化氮合酶(Inducible nitric oxide synthase,i NOS)的表达量,并以脂多糖(Lipopolysaccharide, LPS)诱导巨噬细胞极化为阳性对照,未处理细胞为阴性对照,评估甲氨蝶呤的诱导效果。将经甲氨蝶呤刺激的巨噬细胞与骨肉瘤细胞K7共培养,使用流式技术检测骨肉瘤细胞K7凋亡程度。结果:一定剂量的甲氨蝶呤作用于小鼠单核巨噬细胞后,可以显著上调M1型巨噬细胞的标志物CD86、i NOS,上调程度与LPS组相当。与脂多糖诱导巨噬细胞极化类似,甲氨喋呤可以激活NF-κB。经甲氨蝶呤刺激后的巨噬细胞可以促进骨肉瘤细胞的凋亡。结论:甲氨蝶呤诱导向M1型分化的巨噬细胞可以促进骨肉瘤细胞的凋亡。     

Role of Nitric Oxide in the Progression of Pneumoconiosis

Conflicting evidence has been reported as to whether nitric oxide (NO) possesses anti-inflammatory or inflammatory properties. Data are presented indicating that in vitro or in vivo exposure to selected occupational dusts, i.e., crystalline silica, organic dust contaminated with endotoxin, or asbestos, results in upregulation of inducible nitric oxide synthase (iNOS) and the production of NO by alveolar macrophages and pulmonary epithelial cells. Nitric oxide production is associated temporally and anatomically with pulmonary damage, inflammation, and disease progression in response to occupational dusts. Blockage of inducible nitric oxide synthase by administration of NOS inhibitors or in iNOS knockout mice decreases the magnitude of injury and inflammation following in vivo exposure to silica, endotoxin, or asbestos. Therefore, NO may play an important role in the initiation and progression of pneumoconiosis.     

Osteopontin is induced by nitric oxide in RAW 264.7 cells

Nitric oxide (NO) produced by macrophages is thought to contribute to various pathological conditions. Osteopontin (OPN) is a phosphorylated glycoprotein produced principally by macrophages. OPN inhibits inducible nitric oxide synthase (iNOS), which generates large amounts of NO production. However, the relationship between NO and endogenous OPN in activated macrophages has not yet been elucidated. We therefore examined expression of endogenous iNOS and OPN in a murine macrophage cell line, RAW 264.7 cells, by treating the cells with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma). Treatment of cells with LPS and IFN-gamma resulted in an increase of iNOS mRNA to maximum at 12 h after stimulation. In contrast, OPN mRNA was induced more slowly than iNOS mRNA. Induction of both iNOS and OPN mRNA in RAW 264.7 cells was markedly suppressed by addition of the specific iNOS inhibitor S-2-aminoethyl isothiourea dihydrobromide. The NOS inhibitor NG-methyl-L-arginine also suppressed induction of OPN mRNA but hardly affected iNOS mRNA expression. The NO-releasing agent spermine-NONOate but not peroxynitrite enhanced induction of OPN mRNA. These results suggest that NO directly up-regulates the endogenous OPN in macrophages stimulated with LPS and IFN-gamma. This up-regulation of endogenous OPN may represent a negative feedback system acting to reduce iNOS expression.     

Phagocytosis is regulated by nitric oxide in murine microglia.

Nitric oxide (NO) is produced by inducible nitric oxide synthase (iNOS) in activated microglia and has been shown to participate in host defense mechanisms. However, the role of NO produced by constitutive nitric oxide synthase (cNOS) in microglia is poorly understood. In this report, NO was found to regulate phagocytosis in murine BV-2 microglial cells as quantified by flow cytometry. Addition of NO-generating compounds caused impaired phagocytosis as compared to untreated microglia. The addition of nitric oxide synthase (NOS) inhibitors to microglial cells resulted in potentiation of phagocytosis, suggesting that constitutive NO was participating in the regulation of phagocytosis. The inverse correlation between NO production and phagocytosis was also observed when Alzheimer's beta-amyloid peptide was added. With beta-amyloid treatment, constitutive NO production decreased while phagocytosis increased. Cell extracts prepared from untreated microglia were found to contain both neuronal and endothelial NOS isoforms, but not the inducible form. The correlation of spontaneous NO production with attenuated phagocytosis suggests that constitutive NOS enzymes participate in microglial regulation.     

Chronic restraint stress aggravated arthritic joint swell of rats through regulating nitric oxide production

Stress-related hormone norepinephrine (NE) displayed diverse effects on immune system including macrophages, which influenced many kinds of inflammatory diseases. Nitric oxide (NO) from activated macrophages played an important role in inflammatory diseases. In this study, we investigated under chronic restraint stress how NE influenced the joint swell of Complete Freund's Adjuvant (CFA)-induced arthritis of rats and whether NE regulated macrophage's production of NO through influencing phosphorylation of protein kinases C (PKC). The results showed chronic restraint stress exacerbated paw swell of rats with arthritis. Inhibitor of inducible nitric oxide synthase, S-methylisothiourea (SMT), and 6-hydroxydopamine (6-OHDA) could counteract the effect of restraint stress on arthritis. NE, NO and endotoxin in plasma of rats underwent restraint were improved significantly. In vitro experiments, NE could promote macrophage to produce more NO and iNOS when macrophage was activated by lipopolysaccharide (LPS). This effect could be inhibited by α adrenergic antagonist phentolamine. Nevertheless, through α receptor NE could promote the phosphorylation of PKC and PKC inhibitor staurosporine could counteract NE's enhancive effect on production of NO and iNOS of macrophages. This study revealed that NE could exacerbate arthritic joint swell through promoting NO production, which was in α receptor dependent way through enhancing phosphorylation of PKC for NE to enhance the iNOS expression of activated macrophage.     

In vivo inhibition of inducible nitric oxide and evaluation of the brain tissue damage induced by Toxocara canis larvae in experimentally infected mice

Nitric oxide (NO) is known to be produced by macrophages, endothelial cells and neurons and synthesized by an enzyme called nitric oxide synthase (NOS). Various effector mechanisms and infections can affect the NO production. Excessive amount of NO will lead to biochemical reactions, which cause toxic effects. In this study the role of NO has been evaluated in larval toxocarosis, which is a systemic parasite infection caused by T. canis larvae. Infection was established in the Balb/c mice with or without inducible NOS (iNOS) inhibition and the effects of infection and NOS inhibition were observed according to the results of SOD and LPx measurements in brain tissue and NADPH-diaphorase (NADP-d) histochemistry. Results of NADPH-d histochemistry indicate that iNOS inhibition has protective effect on the brains of infected mice and that larval T. canis infection could be related to oxidative stress, and NO production and iNOS inhibition can protect the tissue from damage in this infection.     

CAT2 arginine transporter deficiency significantly reduces iNOS-mediated NO production in astrocytes

We have previously demonstrated that genetic ablation of cationic amino acid transporter 2 (Cat2) significantly inhibits nitric oxide (NO) production by inducible nitric oxide synthase (iNOS) in activated macrophages. Here we report that iNOS activity is impaired by 84% in activated Cat2-deficient astrocytes. Cat2 ablation appears to reduce astrocyte NO synthesis by decreasing the uptake of the sole precursor, arginine, as well as by reducing the expression of iNOS following activation. Excessive or dysregulated NO production by activated astrocytes and other CNS cell types has been implicated in the pathogenesis of neurological disorders. Our results support the idea that manipulation of CAT2 transporter function might be useful for the therapeutic modulation of iNOS activity.     

Production of nitric oxide and self-nitration of proteins during monocyte differentiation to dendritic cells

Nitric oxide (NO) can stimulate dendritic cells to a more activated state. However, nitric oxide and peroxynitrites production by dendritic cells has been usually associated with pathological situations such as autoimmunity or inflammatory diseases. This study was designed to determine if dendritic cells obtained from healthy volunteers produce nitric oxide and peroxynitrites, which results in protein nitration. The expression of arginase II, but not arginase I, isoform was detected in monocytes and dendritic cells. There was higher inducible nitric oxide synthase (iNOS) protein expression and lower arginase activity both in immature and mature dendritic cells, compared to monocytes. This caused nitric oxide production, and maturation of dendritic cells which provoked a significative increase of nitrites and nitrates compared to immature dendritic cells. There was also peroxynitrites synthesis during monocyte differentiation as shown by the nitration of proteins. Immunoblot revealed a pattern of nitrated proteins in cell extracts obtained from monocytes and dendritic cells, however there were bands that appeared only in human dendritic cells, in particular an intense 90 kDa band. Nitric oxide production and nitrotyrosine formation could affect the antigen presentation and modify the immune response.     

Overexpression of the human inducible nitric oxide synthase gene enhances radiation-induced apoptosis in colorectal cancer cells via a caspase-dependent mechanism.

Nitric oxide (NO) has been reported to sensitize cancer cells to radiation. Since delivery of NO to tumors is limited in vivo by systemic toxicity of NO, we examined the potential of gene delivery of the human inducible nitric oxide synthase (iNOS) gene as a means of achieving high output NO production. We successfully transduced two colorectal cancer cell lines as evidenced by increased iNOS protein accumulation and nitrite production. We found that overexpression of iNOS enhanced the effects of radiation on apoptosis in both cell lines in a caspase-dependent fashion. Gene transfer of iNOS holds much promise as a potential radiosensitizer of cancer cells since it increases apoptosis in an additive manner with radiation.     

Regulation of nitric oxide production by arginine metabolic enzymes

Nitric oxide (NO) is synthesized from arginine by NO synthase (NOS), and the availability of arginine is one of the rate-limiting factors in cellular NO production. Citrulline, which is formed as a by-product of the NOS reaction, can be recycled to arginine by successive actions of argininosuccinate synthetase (AS) and argininosuccinate lyase (AL), forming the citrulline-NO cycle. AS and sometimes AL have been shown to be coinduced with inducible NOS (iNOS) in various cell types including activated macrophages, vascular smooth muscle cells, glial cells, neuronal PC12 cells, and pancreatic beta-cells. Cationic amino acid transporter (CAT)-2 is induced in activated macrophages but not in PC12 cells. On the other hand, arginase can downregulate NO production by decreasing intracellular arginine concentrations. iNOS and arginase activities are regulated reciprocally in macrophages by cytokines, and this may guarantee the efficient production of NO. In contrast, iNOS and arginase isoforms (type I and II) are coinduced in lipopolysaccharide (LPS)-activated macrophages. These results indicate that NO production is modulated by the uptake, recycling, and degradation of arginine.