Suppression of inducible nitric oxide synthase expression and nitric oxide production by macrolide antibiotics in sulfur mustard-exposed airway epithelial cells

Sulfur mustard, a vesicant chemical warfare agent, causes airway injury due to massive release of destructive enzymes and mediators of inflammation. Nitric oxide plays an important yet controversial role in inflammation. An impressive number of reports suggest that excessive amount of nitric oxide may promote inflammation-induced cell injury and death. Overproduction of nitric oxide is catalysed by up-regulated expression of the inducible isoform of nitric oxide synthase (iNOS). In this study, we used quantum dot-mediated immunocytochemistry to analyse iNOS expression and flow cytometry to analyse the intracellular nitric oxide production in sulfur mustard-exposed normal human small airway epithelial cells and bronchial/tracheal epithelial cells and studied the effect of four US Food and Drug Administration-approved macrolide antibiotics, namely, azithromycin, clarithromycin, erythromycin and roxithromycin. Exposure to 100 microM sulfur mustard significantly up-regulated iNOS expression and resulted in overproduction of nitric oxide in these cells. Addition of macrolide antibiotics to 100 microM in the medium reduced both iNOS expression and nitric oxide production to near normal level. Thus, the current study provides in vitro evidence of the immunomodulatory effects of macrolide antibiotics in sulfur mustard-exposed airway epithelial cells. These results suggest that macrolide antibiotics may serve as potential vesicant respiratory therapeutics through mechanisms independent of their antibacterial activity.     

Ethanol consumption increases the expression of endothelial nitric oxide synthase, inducible nitric oxide synthase and metalloproteinases in the rat kidney

Objectives The effects of longterm ethanol consumption on the levels of nitric oxide (NO) and the expression of endothelial NO synthase (eNOS), inducible NO synthase (iNOS) and metalloproteinase‐2 (MMP‐2) were studied in rat kidney. Methods Male Wistar rats were treated with 20% ethanol (v/v) for 6 weeks. Nitrite and nitrate generation was measured by chemiluminescence. Protein and mRNA levels of eNOS and iNOS were assessed by immunohistochemistry and quantitative real‐time polymerase chain reaction, respectively. MMP‐2 activity was determined by gelatin zymography. Histopathological changes in kidneys and indices of renal function (creatinine and urea) and tissue injury (mitochondrial respiration) were also investigated. Results Chronic ethanol consumption did not alter malondialdehyde levels in the kidney. Ethanol consumption induced a significant increase in renal nitrite and nitrate levels. Treatment with ethanol increased mRNA expression of both eNOS and iNOS. Immunohistochemical assays showed increased immunostaining for eNOS and iNOS after treatment with ethanol. Kidneys from ethanol‐treated rats showed increased activity of MMP‐2. Histopathological investigation of kidneys from ethanol‐treated animals revealed tubular necrosis. Indices of renal function and tissue injury were not altered in ethanol‐treated rats. Conclusions Ethanol consumption increased renal metalloproteinase expression/activity, which was accompanied by histopathological changes in the kidney and elevated NO generation. Since iNOS‐derived NO and MMPs contribute to progressive renal injury, the increased levels of NO and MMPs observed in ethanol‐treated rats might contribute to progressive renal damage.     

Luteolin inhibits LPS-stimulated inducible nitric oxide synthase expression in BV-2 microglial cells

Overproduction of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) acts as a neurotoxic effector in the central nervous system, resulting in neurodegenerative diseases. From the alcoholic extracts of Perilla frutescens, we have purified an inhibitor of NO production in lipopolysaccharide (LPS)-activated microglia by activity-guided purification. The active compound was identified as luteolin by spectral analysis. Luteolin inhibited the NO production in LPS-activated microglia in a dose-dependent manner (IC50=6.9 microM). Luteolin also suppressed the degradation of I-kappaB-alpha, the expression of protein and mRNA of iNOS in LPS-activated microglia as observed in Western blot analysis and RT-PCR experiments. Luteolin may have beneficial effects in the treatment of neuro-inflammatory diseases through the inhibition of iNOS expression.     

Heroin modulates the expression of inducible nitric oxide synthase

The use of heroin (diacetylmorphine) is associated with a high incidence of infectious disease, and the immunologic alterations responsible for heroin-induced changes in resistance to infection have not been well characterized. The present study tests the hypothesis that expression of inducible nitric oxide synthase (iNOS) is modulated by the administration of heroin. The initial study using rats showed that heroin administration (0, 0.01, 0.1, or 1.0 mg/kg s.c.) results in a pronounced reduction in lipopolysaccharide (LPS)-induced expression of iNOS mRNA in spleen, lung, and liver tissue as measured by RT-PCR. Heroin also produced a reduction in the level of plasma nitrite/nitrate, the more stable end-product of nitric oxide degradation. In a subsequent study, administration of the opioid receptor antagonist, naltrexone (0.1 mg/kg) prior to the injection of heroin (1.0 mg/kg) blocked the heroin-induced reduction of iNOS expression and plasma nitrite/nitrate levels indicating that the effect is mediated via the opioid-receptor. This study provides the first evidence that heroin induces an alteration of iNOS expression, and suggests that a reduction in nitric oxide production may be involved in the increased incidence of infectious diseases amongst heroin users.     

Adenosine kinase inhibitor attenuates the expression of inducible nitric oxide synthase in glial cells

The present study demonstrates the anti-inflammatory effect of adenosine kinase inhibitor (ADKI) in glial cells. Treatment of glial cells with IC51, an ADKI, stimulated the extracellular adenosine release and reduced the LPS/IFNgamma-mediated production of NO, and induction of iNOS and TNF-alpha gene expression. The recovery of IC51-mediated inhibition of iNOS expression by adenosine transport inhibitor, S-(4-nitrobenzyl)-6-thioinosine (NBTI), and the inhibition of LPS/IFNgamma-induced iNOS gene expression by exogenous adenosine indicate a role for adenosine release in IC51-mediated iNOS expression. The rescue of IC51-mediated inhibition of iNOS expression by adenosine receptor antagonist for A2A, 8-(3-chlorostyryl)caffeine (CSC) and alloxazine for A2B, further supports a role for interaction of adenosine and its receptors in anti-inflammatory activity. The IC51-mediated induction of cAMP levels, downstream target of A2A and A2B, and inhibition of LPS/IFNgamma-induced expression of iNOS by forskolin, a cAMP activator, document a role for cAMP mediated pathway in anti-inflammatory activity of IC51. Taken together, these studies document that IC51-mediated inhibition of iNOS expression is through activation of adenosine receptors, which activates A2A and A2B resulting in increased cAMP levels following LPS/IFNgamma stimulation. Moreover, the lack of effect of IC51 or adenosine on NFkappaB DNA binding activity and its transactivity indicates that the inhibition of iNOS expression mediated by IC51 may be through an NFkappaB independent pathway.     

Chloroquine inhibits inducible nitric oxide synthase expression in murine peritoneal macrophages

Induction of inducible nitric oxide synthase in vivo or in vitro in response to stimuli is only temporary. However, chronic localized expression of inducible nitric oxide synthase in certain organs has been associated with the development of autoimmune diseases or chronic inflammatory diseases. Chloroquine is being used as an antiinflammatory drug, and its inhibitory effect on the synthesis of pro-inflammatory cytokines, such as tumour necrosis factor-alpha and interferon-gamma, has been reported. In this study, we examined whether chloroquine could inhibit nitric oxide synthesis in murine peritoneal macrophages stimulated with interferon-gamma and lipopolysaccharide. Although prolonged incubation of cells with high concentrations of chloroquine showed some cytotoxicity, the drug itself was not cytotoxic when macrophages were preincubated with chloroquine for 2 hr, washed and stimulated with interferon-gamma and lipopolysaccharide in the absence of chloroquine for another 48 hr. The nitric oxide production from stimulated macrophages was markedly reduced by chloroquine in a dose-dependent manner and induction of inducible nitric oxide synthase mRNA was also suppressed by chloroquine pretreatment. These results show that chloroquine inhibits the induction of inducible nitric oxide synthase from interferon-gamma and lipopolysaccharide-stimulated macrophages, thereby reducing nitric oxide synthesis.     

Chloroquine induces the expression of inducible nitric oxide synthase in C6 glioma cells.

Chloroquine, a well-known lysosomotropic agent, has long been used for the treatment of malaria and rheumatologic disorders. However, therapeutic doses of chloroquine are known to cause behavioral side effects. In the present study, we investigated whether chloroquine stimulates inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) synthesis in C6 glioma cells. Chloroquine caused dose-dependent increase in iNOS protein expression and NO production in C6 glioma cells. A tyrosine kinase inhibitor (genistein), a protein kinase C (PKC) inhibitor (Ro 31-8220), and a p38 mitogen-activated protein kinase (MAPK) inhibitor (SB 203580) all respectively suppressed chloroquine-induced iNOS expression and NO release from C6 glioma cells. Chloroquine activates p38 MAPK and stimulates PKC-alpha and -delta translocation from the cytosol to the membrane in C6 glioma cells. Chloroquine-stimulated p38 MAPK activation was blocked by genistein (20 microM), Ro 31-8220 (3 microM), and SB 203580 (10 microM). Incubation of lipopolysaccharide (LPS)-stimulated cells with chloroquine at non-toxic concentrations (10-100 microM) for 48 h increased iNOS expression, and led to a significant loss of adherent cells. Induction of DNA fragmentation in floating cells indicated that the C6 glioma cells were undergoing apoptosis. Taken together, our data suggest that chloroquine may activate tyrosine kinase and/or PKC to induce p38 MAPK activation, which in turn induces iNOS expression and NO production.     

芦荟大黄素对LPS诱导的RAW264.7细胞NO生成及iNOS表达的影响

目的观察芦荟大黄素(aloe-emodin)对脂多糖(LPS)诱导的RAW264.7细胞一氧化氮(NO)生成及诱生型一氧化氮合酶(iNOS)mRNA表达的作用。方法采用LPS诱导的RAW264.7细胞株建立细胞炎症反应模型。采用Griess试剂法测定NO释放量;采用硝普钠释放NO法测定NO自由基含量的变化;采用反转录聚合酶链反应(RT-PCR)分析iNOS mRNA表达改变。结果芦荟大黄素在0.69～2.50mg·L-1剂量范围内可抑制LPS诱导的RAW264.7细胞NO的释放,并呈剂量和时间依赖关系;芦荟大黄素在0.63～5.00mg·L-1剂量范围内可下调LPS诱导的RAW264.7细胞iNOS mRNA含量;而此范围内芦荟大黄素无直接清除NO自由基作用,不影响iNOS活性。结论芦荟大黄素可明显降低LPS诱导的RAW264.7细胞NO释放,呈时间和剂量依赖关系,此作用并非通过捕捉NO或抑制iNOS活性来实现,而是通过抑制iNOS mRNA表达发挥作用的。     

高糖抑制牛主动脉内皮细胞诱导型和结构型一氧化氮合酶的表达

目的:研究高糖对新生小牛主动脉内皮细胞(BAEC)一氧化氮合酶(NOS)表达的影响。方法:BAEC培养并传代于含正常葡萄糖(5.5mmol·L~(-1),NGBAEC),高糖(25 mmol·L~(-1),HG-BAEC)或高渗(葡萄糖5.5 甘露醇19.5 mmol·L~(-1),Mann-BAEC)的无酚红M1640培养基.Griess反应检测脂多糖(LPS)诱导的一氧化氮(NO)产生.Westem blot法检测结构型NOS(ecNOS)及诱导型NOS(iNOS)表达。结果:LPS(0.25-2 mg·L~(-1))剂量依赖性刺激BAEC产生NO,并在LPS 1 mg·L~(-1)达峰值。高糖显著抑制LPS诱导的NO产生(亚硝酸μmol·L~(-1):HG-BAEC 43±8,vs NG-BAEC 71±11,Mann-BAEC 70±9,n=4,P<0.01)。同样,与NG-和Mann-BAEC相比,HG-BAEC iNOS表达下降39.9％和39.3％,ecNOS表达下降28％和24％,而NG-与Mann-BAEC之间,LPS诱导的NO产量和iNOS和ecNOS的表达无差别。结论:高糖抑制BAEC NO的释放,与NOS的低表达有关。     

Selective inhibition of human inducible nitric oxide synthase by S-alkyl-L-isothiocitrulline-containing dipeptides

The aim of this study was to investigate the structure-activity relationship of S-alkyl-L-isothiocitrulline-containing dipeptides towards three partially purified recombinant human nitric oxide synthase (NOS) isozymes, as well as the effects of these compounds on cytokine-induced NO production by human DLD-1 cells. In an in vitro assay, S-methyl-L-isothiocitrulline (L-MIT) was slightly selective for human neuronal NOS (nNOS) over the inducible (iNOS) or endothelial (eNOS) isozyme, but the combination of a hydrophobic L-amino acid (L-Phe, L-Leu or L-Trp) with L-MIT dramatically altered the inhibition pattern to give selective iNOS inhibitors. Introduction of a hydroxy, nitro, amino or methoxy group at the para position of the aromatic ring of L-MIT-L-Phe (MILF) decreased the selectivity and inhibitory potency. A longer or larger S-alkyl group also decreased the selectivity and potency. Dixon analysis showed that all of the dipeptides were competitive inhibitors of the three isoforms of human NOS. The enzymatic time course curves indicated that MILF was a slow binding inhibitor of human iNOS. These results suggest that the human NOS isozymes have different-sized cavities in the binding site near the position to which the C-terminal of L-arginine binds, and the cavity of iNOS is hydrophobic. Interestingly, L-MIT-D-Phe (MIDF) showed little inhibitory activity or selectivity, suggesting that the cavity of human iNOS is located in a well-defined direction from the alpha carbon atom. NO production in cytokine-stimulated human DLD-1 cells was measured with a fluorescent indicator, DAF-FM. MILF, L-MIT-L-Trp(-CHO) (MILW) and L-MIT-L-Tyr (MILY) showed more potent activity than L-MIT in this whole-cell assay. Thus, S-alkyl-L-isothiocitrulline-containing dipeptides are selective inhibitors of human iNOS, and work efficiently in cell-based assay.     

Regulation of nitric oxide production in cultured human T84 intestinal epithelial cells by nuclear factor-kappa B-dependent induction of inducible nitric oxide synthase after exposure to bacterial endotoxin

BACKGROUND: Intestinal epithelium is consistently in contact with lipopolysaccharide (LPS) produced by intraluminal microbes. LPS induces nitric oxide production in many rodent cells, but in human cells it is very differently regulated. AIM: To test the hypothesis that exposure to LPS up-regulates nitric oxide synthesis in human intestinal epithelium. METHODS AND RESULTS: LPS induced nitric oxide synthesis in T84 cells in a time- and dose-dependent manner whereas detectable amounts of peroxynitrite were not produced. A novel selective inducible nitric oxide synthase (iNOS) inhibitor 1400 W potently inhibited LPS-induced nitric oxide synthesis in T84 cells while dexamethasone was relatively ineffective. Nitric oxide production was sensitive to cycloheximide, indicating that it was dependent on de novo protein synthesis. Nuclear factor-kappa B (NF-kappa B) inhibitor pyrrolidinedithiocarbamate abolished iNOS and nitric oxide production. Nitric oxide synthesis was also suppressed by genistein (tyrosine kinase inhibitor) and PD 98059 (p44/42 MAP kinase inhibitor) but enhanced by SB 203580 (p38 MAP kinase inhibitor). CONCLUSIONS: Intestinal epithelial cells express iNOS and produce nitric oxide in a nuclear factor-kappa B-dependent manner when exposed to LPS. The process is regulated by tyrosine kinases, and p44/42 and p38 MAP kinases. Because nitric oxide acts as an antimicrobial agent and immune modulator, these findings are implicated in the regulation of gut mucosal immunity.     

一氧化氮合成酶mRNA在正常大鼠肾组织中表达的研究

目的：探讨正常大鼠肾组织一氧化氮合成酶mRNA(NOSmRNA)表达的特点。方法 采用组织细胞原位杂交及图像分析技术,对正常大鼠肾组织中 NOS,NOSey NOSRNA表达的定位及含量进行了检测。同时测定肾组织NOS总活性。结果eNOS,nNOS及iNOS在正常肾组织中均有表达。eNOS和nNOS主要分布于肾小球及血管内皮,其中eNOS表达最丰富,髓质明显多于皮质。iNOS含量较低,且仅分布于皮质远,近曲小管上皮,结论 生理情况下,肾组织cNOS的表达量主要决定于eNOS的表达,其高表达对维持肾脏正常功能具有重要作用。     

Suppression of inducible nitric oxide synthase expression by diarylheptanoids from Alpinia officinarum

Six diarylheptanoids were isolated from the rhizome of Alpinia officinarum (Zingiberaceae) as inhibitors of nitric oxide (NO) production in the lipopolysaccharide-activated macrophage cell line RAW 264.7. A double bond at C-4 of the linker between two aromatic rings was found to be essential for activity. Furthermore, the active diarylheptanoids suppressed expression of the inducible NO synthase protein and mRNA. These results imply that the traditional use of Alpinia officinarum rhizome as anti-inflammatory drug may be explained, at least in part, by the inhibition of NO production in activated macrophages.