Expression of nitric oxide synthase in ulcerative colitis

Abstract. Nitric oxide (NO) is generated from L-arginine by a family of enzymes called the NO synthases. Previous investigators have proposed that the expression of this inducible enzyme (iNOS) may account for the characteristic vasodilatation, oedema and impairment of gut motility seen in active ulcerative colitis. Using a specific antibody to iNOS, we have investigated the distribution of this enzyme in colonic tissue from patients with histologically proven ulcerative colitis. Eight patients with ulcerative colitis expressed calcium-independent citrulline activity (9.96±2.34 pmol citrulline mg^-1 protein min^-1) and showed immunoreactivity to the iNOS antibody within the inflammatory infiltrate of the lamina propria, and also within the cytoplasm of the epithelial cells lining the colon. Five age-matched controls showed no calcium-independent citrulline activity (0.2 ±0.08 pmol citrulline mg^-1 protein min^-1) and no immunoreaction to the antibody. We conclude that this enzyme is present in colonic tissue including the epithelium from patients with active colitis. Inhibition of this enzyme may provide a novel therapeutic option for patients with active ulcerative colitis.     

一氧化氮合酶抑制剂对严重烧伤大鼠的作用研究

目的 :研究一氧化氮合酶 (NOS)抑制剂对严重烧伤大鼠体内一氧化氮 (NO)含量及 NOS表达的影响及其与预后的关系。方法 :复制大鼠重症烧伤模型 ,检测应用非选择性 NOS抑制剂 N 硝基 L 精氨酸甲酯(L NAME)和选择性诱生型 NOS(i NOS)抑制剂氨基胍 (AG)后大鼠血液中 NO代谢产物 (NO- 2 /NO- 3 )以及肺和十二指肠组织中神经型 NOS(n NOS) m RNA的表达水平 ,同时统计各组大鼠的存活率。结果 :烧伤后大鼠血液中 NO- 2 /NO- 3 含量明显增高 ,L NAME和 AG都能抑制 NO2 /NO- 3 的升高 ,L NAME作用更为明显 ;烧伤后 n NOS的 m RNA表达在肺和十二指肠中均有不同程度升高 ,AG和 L NAME使 n NOS表达增加 ,AG作用更为明显 ;L NAME组动物存活时间较对照组显著缩短 ,AG组动物存活时间明显延长。结论 :结构型NOS(c NOS)与 i NOS在烧伤休克病理生理过程中的作用明显不同 ,i NOS活性过度增高与烧伤休克发病关系密切     

Nitric oxide and inflammatory bowel diseases

Nitric oxide (NO) production, as detectable by indirect and direct methods, as well as the expression of inducible nitric oxide synthase (iNOS) in the intestinal mucosa appear to be enhanced in active ulcerative colitis and, when in excess, to play a proinflammatory role in the disease. Despite some conflicting data, there is evidence that NO production is also increased in Crohn's disease. Many inflammatory features of inflammatory bowel disease are in keeping with the physiological properties of NO, and toxic megacolon, a complication of chronic colitis characterized by acute colonic dilatation, is associated with an enhanced intestinal synthesis of NO.   The drugs currently used in the treatment of inflammatory bowel disease (steroids, salicylates) do not seem to exert substantial effects on intestinal NO synthesis. The possible therapeutic role of selective iNOS inhibitors is still under investigation     

生物喋呤对烫伤脓毒症大鼠一氧化氮合成的影响

目的：探讨生物喋呤BH4在金黄色葡萄球菌（简称金葡菌）脓毒症中的生物学效应，阐明BH4对一氧化氮（NO）诱生的调控作用。方法：76只Wistar大鼠随机分为正常对照组（n=10)、烫伤对照组（n=10)、烫伤后金葡菌感染组（n=40)和羟基嘧啶（DAHP）拮抗组（n=16)。无菌留取动物肝、肺组织采用RT－PCR方法检测三磷酸鸟苷环水解酶I（GTP－CHI）、诱生型一氧化氮合酶（iNOS)基因表达，同时测定组织中BH4和NO的水平。结果：烫伤后金葡菌感染组动物肝、肺组织中GTP－CHI基因表达明显上调，BH4产生显著增加，iNOS mRNA表达和NO的水平亦明显升高，DAHP组GTP－CHI基因表达上调和BH4合成NO的产生亦明显下降。结论：烫伤后金葡菌感染可诱导体内BH4的合成，BH4在基因和蛋白水平调控着iNOS所介导的NO大量生成，从而对金葡菌脓毒症的病理过程起促进作用。     

Nitric Oxide-based Possibilities for Pharmacotherapy

The goal of nitric oxide (NO) based pharmacotherapy is to reach proper homeostasis of NO metabolism in the target tissue where endogenous production of NO is either too weak or excessively increased. In addition to the classic NO-based therapy of cardiovascular conditions with nitrates, a variety of new therapeutic possibilities have emerged including sexual disorders, gastrointestinal system, immunology, tumour growth regulation and respiratory disorders. NO levels of target tissues can be affected directly by NO donors, or indirectly by increasing the level of L-arginine, a substrate of nitric oxide synthase (NOS). While increased production of NO by induceable NOS (iNOS) by, for example, cytokines does not at present seem therapeutically meaningful, increased NO production by constitutive NOS (cNOS) may be involved in the beneficial effects of ACE inhibitors or oestrogens. NO production may be pharmacologically decreased by inhibition of expression of iNOS by glucocorticoids while both cNOS and iNOS derived NO production is inhibited by administration of false substrates, for example L-NAME. Additionally, the respiratory system and related vessels can be reached directly and more selectively by inhalation of pure NO gas. Possible problems in administering NO and perhaps some NO-donors include the toxic nature of the compound itself whereby vital enzyme systems may be inhibited and tissue damaging radicals formed. Future prospects of NO-based pharmocotherapy may feature selective ligands to different NOS isoforms and tissue selective donors that release NO in a controlled fashion.     

八肽缩胆囊素对脂多糖诱导血管内皮细胞诱生型一氧化氮合酶表达变化的抑制作用

目的探讨八肽缩胆囊素（CCK-8）对脂多糖（LPS）诱导血管内皮细胞诱生型一氧化氯合酶（iNOS）表达变化的影响。方法培养人脐静脉内皮细胞株ECV-304细胞。用0．01、0．1和1mg／L LPS处理2～24h，用生理盐水、10mol／LCCK-8和0．1mg／L LPS＋10^-8、10^-7、10^-8mol／L CCK-8处理16h；用比色法检测培养液中一氧化氮（NO）含量、细胞NOS活性，免疫细胞化学及蛋白质免疫印迹法检测iNOS蛋白表达。结果与生理盐水处理的对照组比较，LPS诱导培养液NO含量增多、细胞NOS活性增高、iNOS蛋白表达上调；CCK-8剂量依赣性抑制LPS的上述效应。而单独作用对iNOS蛋白表达、NOS活性和NO含量均无明显影响。结论CCK-8可以明显抑制LPS引起ECV-304细胞iNOS蛋白表达上调。减少NO生成。     

肾血管性高血压对诱导型一氧化氮合酶表达及活性的影响

目的通过测定肾血管性高血压大鼠血管及肾组织诱导型一氧化氮合酶（iNOS）活性及表达的变化情况,探讨血压与iNOS间的关系。方法运用肾动脉不全结扎方法制备SD大鼠肾血管性高血压模型,并应用Greiss反应、L-精氨酸同位素标记法及Westernblot等分别测定一氧化氮的终产物——尿中NO     

雾化吸入氯胺酮对哮喘大鼠肺组织一氧化氮及一氧化氮合酶的影响

目的通过建立大鼠支气管哮喘模型,观察不同浓度氯胺酮对哮喘大鼠肺组织iNOS活性及NO含量的影响。方法SD大鼠随机分成对照组(N组)、哮喘模型组(A组)、不同浓度氯胺酮预处理组(分别为K1组、K2组)和地塞米松组(D组),每组8只。A组大鼠用卵白蛋白辅以百日咳杆菌菌苗和氢氧化铝为佐剂注射致敏,2周后雾化吸入卵蛋白激发哮喘;氯胺酮处理组大鼠用同样方法致敏,但在激发前分别给予雾化吸入氯胺酮25 g/L(K1组)和50 g/L(K2组);D组在激发前给予雾化吸入0.01%地塞米松;N组用生理盐水替代卵蛋白进行注射和吸入。每组分别测定其肺组织NO2-/NO3-水平、肺组织诱导型NOS(iNOS)和原生型NOS(cNOS)活性水平,并用免疫组织化学法观察iNOS在大鼠哮喘模型肺组织中的分布。结果A组肺组织中NO2-/NO3-和iNOS水平升高,iNOS和肺组织NO2-/NO3-水平呈高度正相关;K1、K2组肺组织中NO2-/NO3-和iNOS水平低于A组(P<0.05);D组肺组织中NO2-/NO3-和iNOS水平亦低于A组(P<0.05)。结论25 g/L或50 g/L的氯胺酮雾化吸入可抑制哮喘大鼠肺组织iNOS活性,降低NO含量,减轻大鼠肺部炎症。     

Cytokine-induced intestinal epithelial hyperpermeability: role of nitric oxide.

OBJECTIVE: Incubation of enterocytic monolayers with interferon (IFN)-gamma increases nitric oxide (NO) production and permeability, but NO synthesis inhibitors ameliorate the development of IFN-gamma-induced hyperpermeability. Induction of inducible nitric oxide synthase (iNOS), an isoform of the enzyme responsible for NO biosynthesis, is often enhanced by the synergistic effects of multiple cytokines. Moreover, many of the cytopathic effects of NO are mediated by peroxynitrite, which is produced by the reaction of NO with superoxide radical anion. In the present study, we sought to determine whether combinations of several proinflammatory cytokines, including IFN-gamma, interleukin-1beta, and tumor necrosis factor-alpha, have synergistic effects on the induction of iNOS expression and/or hyperpermeability to hydrophilic solutes in cultured enterocytic monolayers. We also assessed the effects of aminoguanidine (a relatively selective iNOS inhibitor), L-N(G)-monomethyl arginine (an isoform-nonselective NO synthase inhibitor), and Tiron (a superoxide radical anion scavenger) on the development of cytokine-induced hyperpermeability. DESIGN: Caco-2 monolayers were incubated under control conditions or with IFN-gamma, interleukin-1beta, or tumor necrosis factor-alpha alone, pairwise combinations of these cytokines, or all three cytokines together (cytomix; CM). iNOS messenger RNA (mRNA) expression was assessed using Northern blot analysis. The permeability of Caco-2 monolayers growing on permeable supports in bicameral chambers was assessed by measuring the apical-to-basolateral flux of fluorescein disulfonic acid. The concentration of nitrate plus nitrite in culture supernatants, an indirect measure of NO production, was determined using the Griess reaction. RESULTS: After 24 hrs of incubation, up-regulation of iNOS mRNA expression was evident only in cells exposed to IFN-gamma-containing formulations. Expression of iNOS mRNA was far greater in cells incubated with CM than in cells treated with IFN-gamma alone or either of the two-component IFN-gamma-containing cytokine combinations. Compared with IFN-gamma, CM resulted in a higher rate of NO production over 48 hrs of incubation. The permeability of Caco-2 monolayers increased by approximately six-fold and approximately 20-fold after incubation for 48 hrs with IFN-gamma alone and CM, respectively. The increase in permeability induced by incubation with CM was significantly ameliorated by the addition of aminoguanidine, L-N(G)-monomethyl arginine, or Tiron. CONCLUSIONS: IFN-gamma-containing combinations of cytokines are potent inducers of iNOS in cultured enterocytic monolayers. Peroxynitrite may be an important mediator of cytokine-induced gut epithelial hyperpermeability.     

Role of inducible nitric-oxide synthase in regulation of whole-cell current in lung epithelial cells

Lung inflammation is associated with enhanced expression of proinflammatory cytokines and increased production of nitric oxide (NO) by inducible NO synthase (iNOS). To investigate the possible relationship between cytokine-induced expression of iNOS and epithelial ion channel function, we measured whole-cell current in A549 cells treated with a mixture of cytokines: tumor necrosis factor, interleukin-1 beta, and interferon-gamma for 12 h. Cytokines significantly increased the expression and activity of iNOS, and reduced generation of cGMP in response to stimulation with NO donor S-nitroso-glutathione (GSNO). Patch-clamp studies showed that 100 microM GSNO increased the whole-cell current from 11.2 +/- 1.8 to 19.6 +/- 2.7 pA/pF (n = 16) in control cells, but had no effect in cytokine-treated cells (n = 9). N-(3-(Aminomethyl)benzyl)acetamidine (1400W), a selective inhibitor of iNOS, restored activation of the current by GSNO in cytokine-treated cells, indicating a crucial role for iNOS in this process. Cells treated with cytokines showed increased levels of peroxynitrite (ONOO(-)), compared with the control, or cells that were treated with the cytokines and 1400W or superoxide dismutase/catalase. Treatment of cells with 100 microM ONOO(-) had no effect on the whole-cell current, but in contrast to untreated cells, subsequent application of GSNO did not activate the current. In conclusion, cytokine-induced expression of iNOS affects activation of the whole-cell current via NO/cGMP pathway, likely by increasing the generation of ONOO(-).     

The anti-inflammatory and protective role of interleukin-38 in inflammatory bowel disease

Interleukin (IL)-38 exerts an anti-inflammatory function by binding to several cytokine receptors, including the IL-36 receptor. In this study, we evaluated IL-38 expression in the inflamed mucosa of patients with inflammatory bowel disease (IBD) and investigated its functions. IL-38 mRNA expression in endoscopic biopsy samples was evaluated using quantitative PCR. IL-38 protein expression was analyzed using immunohistochemical technique. Dextran sulfate sodium-induced colitis was induced in C57BL/6 background IL-38KO mice. The IL-38 mRNA and protein expression were enhanced in the active mucosa of ulcerative colitis, but not in Crohn’s disease. The ratio of IL-36γ to IL-38 mRNA expression was significantly elevated in the active mucosa of UC patients. Immunofluorescence staining revealed that B cells are the major cellular source of IL-38 in the colonic mucosa. IL-38 dose-dependently suppressed the IL-36γ-induced mRNA expression of CXC chemokines (CXCL1, CXCL2, and CXCL8) in HT-29 and T84 cells. IL-38 inhibited the IL-36γ-induced activation of nuclear-factor kappa B (NF-κB) and mitogen-activated protein kinases in HT-29 cells. DSS-colitis was significantly exacerbated in IL-38KO mice compared to wild type mice. In conclusion, IL-38 may play an anti-inflammatory and protective role in the pathophysiology of IBD, in particular ulcerative colitis, through the suppression of IL-36-induced inflammatory responses.     

Inhibition of nitric oxide synthesis by aminoguanidine increases intestinal damage in the acute phase of rat TNB-colitis

The role of nitric oxide (NO) in the pathophysiology of inflammatory bowel diseases (IBD) is controversially discussed. The aim of the present study was to investigate the role of NO inhibition in the acute phase of rat 2,4,6-trinitrobenzenesulphonic acid (TNB)-colitis. To inhibit NO synthesis we used aminoguanidine (AG) as a selective inhibitor of inducible nitric oxide synthase (iNOS). TNB-colitis was induced in rats with and without pretreatment with AG (200 mg kg-1 body weight in the drinking water). The severity of colitis was observed over a period of 7 days. On days 1 and 2, AG reduced concentrations of plasma nitrate and nitrite as well as of portal 6-keto-prostaglandin 1alpha. AG pretreatment increased colonic damage and inflammatory response, assessed by colonic myeloperoxidase and serum lactate dehydrogenase activity, macroscopic damage score, tumour necrosis factor-alpha concentration in stool and colonic glutathione content. The AG-treated group showed a higher and prolonged nuclear factor kappaB (NF-kappaB)/Rel binding activity in the colon. We conclude that NOS inhibition by AG is not beneficial in acute intestinal inflammation. With regard to appropriate therapeutic strategies, NF-kappaB/Rel activation might be a more suitable target.     

高压氧对脑缺血再灌注大鼠的海马诱导型一氧化氮合酶mRNA表达的影响

目的　观察高压氧对脑缺血再灌注大鼠的海马诱导型一氧化氮合酶信使核糖核酸 (iNOSmRNA)表达的影响。方法　将 5 4只大鼠随机分为脑缺血再灌注组 (IR组 )、脑缺血再灌注加高压氧处理组(HBO组 )和对照组 ,建立脑缺血再灌注大鼠动物模型。应用荧光定量逆转录 聚合酶链反应 (RT PCR )技术检测各组在再灌注 6h、2 4h、48h、96h时相点大鼠的海马iNOSmRNA表达。结果　再灌注各时相点的IR组和HBO组的海马iNOSmRNA表达均显著高于对照组 (均P <0 .0 1) ;HBO组大鼠再灌注 2 4h、48h、96h时海马iNOSmRNA表达均显著低于IR组 (P <0 .0 5 ,P <0 .0 1,P <0 .0 1)。结论　高压氧治疗可以显著抑制再灌注后大鼠海马iNOSmRNA表达 ,从而减少延迟性NO的产生 ,有助于减轻脑缺血再灌注损伤。     

人参皂甙对阿尔茨海默病治疗机制的实验研究

目的 研究人参皂甙对阿尔茨海默病(AD)相关β淀粉样蛋白(AB)诱导THP-1细胞表达诱导性一氧化氮合酶(iNOS)和一氧化氮的影响.方法 用免疫印迹法测定THP-1细胞iNOS表达,用Griess法测定细胞上清中一氧化氮的浓度.结果 模型组iNOS的表达明显高于对照组,与模型组比较,人参皂甙可明显减少THP-1细胞iNOS的表达和一氧化氮的产生.结论 人参皂甙可以抑制THP-1细胞iNOS的表达,进一步影响一氧化氮的产生而用于AD的治疗.     

Regulation of murine intestinal inflammation by reactive metabolites of oxygen and nitrogen: divergent roles of superoxide and nitric oxide.

Several reports have implicated reactive oxygen and nitrogen metabolites (RONS) in the initiation and/or progression of inflammatory bowel diseases (IBDs). We have investigated the role of three key RONS-metabolizing enzymes (inducible nitric oxide synthase [iNOS], superoxide dismutase [SOD], nicotinamide adenine dinucleotide phosphate [NADPH] oxidase) in a murine model of IBD. Mice genetically deficient ((-/-)) in either iNOS or the p47phox subunit of NADPH oxidase, transgenic (Tg) mice that overexpress SOD, and their respective wild-type (WT) littermates were fed dextran sulfate sodium (DSS) in drinking water for 7 days to induce colitis. In addition, the specific iNOS inhibitor 1400W was used in DSS-treated WT and p47phox(-/-) mice. WT mice responded to DSS feeding with progressive weight loss, bloody stools, elevated serum NO(X) and colonic mucosal injury with neutrophil infiltration. Both the onset and severity of colitis were significantly attenuated in iNOS(-/-) and 1400W-treated WT mice. While the responses to DSS did not differ between WT and p47phox(-/-) mice, enhanced protection was noted in 1400W-treated p47phox(-/-) mice. Interestingly, SOD(Tg) mice exhibited more severe colitis than their WT littermates. These findings reveal divergent roles for superoxide and iNOS-derived NO in intestinal inflammation.     

Nitric Oxide in the Central Nervous System

The majority of the data on nitric oxide (NO) in the central nervous system (CNS) relies on histochemical and immunesohistochemical evidence concerning the distribution of the nitric oxide synthase (NOS), its inhibition by specific antagonists and its co-localization with the receptor enzyme guanylate cyclase (GC) in the same functional region. All three isoforms, endothelial (eNOS), neural (nNOS) and macrophage type inducible (iNOS), are of importance to the normal and pathological function of the CNS. In nNOS gene deleted mice eNOS seems to contribute to the maintanace of neuronal function. NO may contribute to synaptic plasticity as a retrograde mediator that is released by postsynaptic NMDA-receptor activation. Microglia contains membrane-bound inducible iNOS that may be important in host defence function. Glia and pericytes surrounding the blood vessels contain GC that is stimulated by NO released from endothelium and nerve endings. Excessive production of highly reactive NO may be responsible for the neurotoxicity mediated by NMDA receptors that contributes to the symptomatology of strokes and neurodegenerative diseases. Moreover, after initial stimulation by cytokines, large amounts of NO produced by iNOS in the microglia (brain-based macrophages) may cause cellular damage.     

Involvement of anti-inflammatory heme oxygenase-1 in the inhibitory effect of curcumin on the expression of pro-inflammatory inducible nitric oxide synthase in RAW264.7 macrophages

Curcumin, at high concentrations (>2 μM), inhibits the production of nitric oxide (NO) and the expression of inducible NO synthase (iNOS) through inactivation of nuclear factor (NF)-κB and, at low concentrations, induces the expression of heme oxygenase (HO)-1 in macrophages. Here, we demonstrated that curcumin at low concentrations (0.5–2 μM) can also inhibit NO production and iNOS expression in lipopolysaccharide (LPS)-activated RAW264.7 macrophages only when the cells were pretreated for at least 6 h with curcumin. Curcumin induced dose- and time-dependent HO-1 expression, and this was coincident with the inhibitory effects of low concentrations of curcumin on NO production and iNOS expression. Blockage of HO-1 activity or knockdown of HO-1 expression abolished the inhibitory effects of curcumin. Over-expression of HO-1 or exogenous addition of carbon monoxide, a byproduct derived from heme degradation, mimicked the inhibitory action of low concentrations of curcumin. Moreover, LPS-induced NF-κB was diminished in macrophages subjected to prolonged treatment with low concentrations of curcumin. Treatment with HO inhibitor abolished the inhibitory effect of curcumin on LPS-induced NF-κB activation. Collectively, we provide evidence to support the important role of HO-1 in inhibition of NO production and iNOS expression by curcumin even at low concentrations.     

肠系膜淋巴管结扎对失血性休克大鼠肺组织一氧化氮及其表达的影响

目的 观察结扎肠系膜淋巴管对不同时期重症失血性休克大鼠肺组织一氧化氮（NO）及其表达的影响，探讨肠淋巴途径在休克大鼠急性肺损伤（ALI）中的作用。方法 雄性Wistar大鼠78只，按随机数字表法分为假手术组（n=6）、休克组（n=42）和结扎组（n=30）。休克组与结扎组复制重症失血性休克模型，结扎组于休克复苏后行肠系膜淋巴管结扎术；休克组于休克后90min、输液复苏后0h，休克组及结扎组于输液复苏后1、3、6、12和24h各时间点处死大鼠，制备肺组织匀浆，检测NO及其合酶的变化；用逆转录-聚合酶链反应（RT—PCR）测定各组大鼠肺组织诱生型一氧化氮合酶（iNOS）．mRNA表达。结果 休克组大鼠复苏后3h肺组织NO含量、NOS活性及iNOSmRNA表达开始升高，复苏后6～12h持续在较高水平，均显著高于假手术组、休克后90min及复苏后0h（P〈0．05或P〈0．01）；结扎组仅于3h和6h增高，且结扎组复苏后6、12和24h肺组织NO含量、NOS活性以及iNOSmRNA表达均显著低于休克组相同时间点（P〈0．05或P〈0．01）。结论 肠系膜淋巴管结扎可降低重症失血性休克大鼠肺组织NO生成及iNOSmRNA表达，从而减轻肺损伤。