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。     

Equol inhibits nitric oxide production and inducible nitric oxide synthase gene expression through down-regulating the activation of Akt

In the present study, we report the inhibitory effect of equol on nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) gene expression in murine macrophages. In vivo administration of equol (i.p.) attenuated NO production by peritoneal adherent cells isolated from lipopolysaccharide (LPS)-treated mice. Equol dose-dependently inhibited the LPS-induced production of NO in isolated peritoneal adherent cells and RAW 264.7 cells. The mRNA expression of iNOS was also blocked by equol in LPS-stimulated RAW 264.7 cells. Further study demonstrated that the LPS-induced activation of Akt was suppressed by equol in RAW 264.7 cells while the activation of ERK, SAPK/JNK and p38 MAP kinase was not affected. Equol also blocked LPS-induced NF-kappaB activation. Moreover, the LPS-induced NO production and NF-kappaB activation was inhibited by LY294002, a specific inhibitor of phosphatidylinositol 3-kinase/Akt pathway, in RAW 264.7 cells. These results suggest that equol might inhibit NO production and iNOS gene expression, at least in part, by blocking Akt activation and subsequent down-regulation of NF-kappaB activity.     

A sesquiterpene lactone, costunolide, from Magnolia grandiflora inhibits NF-kappa B by targeting I kappa B phosphorylation

A sesquiterpene lactone, costunolide (CTN), was identified from Magnolia grandiflora together with parthenolide (PTN) by its strong inhibition of LPS-induced NF-kappa B activation. CTN, which showed more potent inhibition than PTN in the NF-kappa B activation, strongly suppressed nitric oxide (NO) production in LPS-stimulated RAW 264.7 cells. RT-PCR and Western blot analyses demonstrated that CTN suppressed the expression of iNOS mRNA and protein in a dose-dependent manner. CTN also significantly inhibited LPS-induced DNA-binding activity of NF-kappa B as well as the LPS-induced degradation of I kappa B-alpha and -beta. Furthermore, CTN inhibited LPS-induced phosphorylation of I kappa B-alpha. These findings support that CTN inhibits NO production by down-regulating iNOS expression, at least, in part through the inhibition of I kappa Bs' phosphorylation and degradation, which are essential for the activation of NF-kappa B.     

Inhibition of p38 and ERK MAP kinases blocks endotoxin-induced nitric oxide production and differentially modulates cytokine expression.

Mitogen-activated protein kinases (MAPKs) are thought to have a critical role in lipopolysaccharide (LPS)-induced immune responses but the molecular mechanisms underlying the mediation of these signaling are not clear. The roles of p38 and extracellular signal-regulated kinase (ERK) in the regulation of nitric oxide (NO) and proinflammatory cytokine expression in J774A.1 macrophages in response to LPS were examined. Specific inhibitors for p38 and ERK, SB203580 and PD98059, respectively, were used. LPS (30ng/ml) activated inducible nitric oxide synthase (iNOS), subsequent NO production, and gene expression for tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, and IL-12. Treatment of cultures with SB203580 increased LPS-induced reactive oxygen species (ROS) production, whereas both SB203580 and PD98059 decreased LPS-induced NO production. Concomitant decreases in the expression of iNOS mRNA and protein were detected. SB203580 and PD98059 decreased LPS-induced gene expression of IL-1beta and IL-6. SB203580 increased LPS-induced expression of TNF-alpha and IL-12; PD98059 had no effect on these cytokines. Results indicated that both p38 and ERK pathways are involved in LPS-stimulated NO synthesis and the expression of IL-1beta and IL-6. p38 signaling pathway is involved in LPS-induced ROS, TNF-alpha and IL-12 production.     

Anti-inflammatory activity of 20(S)-protopanaxadiol: enhanced heme oxygenase 1 expression in RAW 264.7 cells

20( S)-Protopanaxadiol (PPD) is one of the metabolites of ginsenosides from Panax ginseng. In this study, we demonstrate that PPD inhibits the increase in lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) expression through inactivation of nuclear factor-kappaB by preventing degradation of inhibitory factor-kappaBalpha. PPD also induces heme oxygenase 1 (HO-1) expression in RAW 264.7 cells, at the mRNA and protein levels, in the presence and absence of LPS. This effect is associated with suppression of LPS-induced nitric oxide (NO) production and iNOS expression. The HO-1 inducer hemin is associated with the suppression of LPS-induced NO production in a dose-dependent manner, and the HO-1 inhibitor tin protoporphyrin attenuates the inhibitory activity of PPD on LPS-induced NO production. These results provide evidence for the role of HO-1 in the inhibition of LPS-induced NO production by PPD.     

Substance P augments nitric oxide production and gene expression in murine macrophages.

We investigated the effects of substance P (SP) on nitric oxide (NO) synthase activity in macrophages by measuring the production of nitrite and the expression of inducible NO synthase (iNOS) mRNA and protein. In LPS-activated macrophages, SP stimulated NO production in time and concentration dependent manners. These SP effects were blocked by a specific NK-1 receptor antagonist. Furthermore, SP stimulation increased the levels of both iNOS mRNA and iNOS protein. These results demonstrate that SP can increase LPS induced NO production in macrophages by augmenting the induction of iNOS expression. We also examined the role of SP on acute-cold stress induced altered production of NO by mouse peritoneal macrophages. SP enhanced the LPS-induced macrophages NO production from stressed mice relative to the non-stressed mice. These results suggest that SP may have an important modulatory role in production of NO by macrophages.     

Differential modulation of immunostimulant-triggered NO production by endoplasmic reticulum stress inducers in vascular smooth muscle cells

We investigated the effects of endoplasmic reticulum (ER) stress inducers thapsigargin (TG) and tunicamycin (Tm) on immunostimulant lipopolysaccharide/interferon (LPS/IFN)-induced expression of isoform of nitric oxide synthase (iNOS) and nitric oxide (NO) production in vascular smooth muscle cells. LPS/IFN-induced iNOS mRNA expression was markedly enhanced by TG, whereas iNOS mRNA expression was strongly attenuated by Tm. Similarly, production of iNOS protein was markedly upregulated by TG but virtually eliminated by Tm. LPS/IFN-induced guanosine triphosphate cyclohydrolase I mRNA expression was slightly reduced by TG and markedly inhibited by Tm. Similarly, LPS/IFN-mediated induction of cellular biopterin was modestly reduced by TG and markedly inhibited by Tm. TG modestly enhanced LPS/IFN-induced activation of NF-κB, whereas Tm had no effect on it. Cellular respiration was reduced by TG and Tm in a concentration-dependent manner, which was confirmed by apoptosis assay. Thus, TG and Tm-induced ER stress and differently modulated NO production through alterations in iNOS expression and activity independently of NF-κB activation and caused a similar degree of ER stress-induced apoptosis.     

Inhibition of lipopolysaccharide-induced expression of inducible nitric oxide synthase by phenolic (3E)-4-(2-hydroxyphenyl)but-3-en-2-one in RAW 264.7 macrophages

The large amount of nitric oxide (NO) produced by inducible NO synthase (iNOS) contributes to cellular injury in inflammatory disease. In the present study, a novel synthetic compound (3E)-4-(2-hydroxyphenyl)but-3-en-2-one (HPB) was found to inhibit lipopolysaccharide (LPS)-induced NO generation, but not through the inhibition of iNOS activity, in RAW 264.7 macrophages. Administration of HPB into mice also inhibited the LPS-induced increase in serum nitrite/nitrate levels. To evaluate the underlying mechanisms of HPB inhibition of NO generation, the expression of the iNOS gene in RAW 264.7 macrophages was examined. HPB abolished the LPS-induced expression of iNOS protein, iNOS mRNA and iNOS promoter activity in a similar concentration-dependent manner. LPS-induced nuclear factor-κB (NF-κB) DNA binding and NF-κB-dependent reporter gene activity were both significantly inhibited by HPB. This effect was mediated through the inhibition of inhibitory factor-κBα (IκBα) phosphorylation and degradation, and of p65 nuclear translocation. HPB had no effect on the LPS-induced phosphorylation of extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinases (MAPK), and c-Jun NH₂-terminal kinase (JNK). However, HPB suppressed the LPS-induced intracellular reactive oxygen species (ROS) production. These results indicate that HPB down-regulates iNOS gene expression probably through the inhibition of LPS-induced intracellular ROS production, which has been implicated in the activation of NF-κB.     

Polygonum cuspidatum, compared with baicalin and berberine, inhibits inducible nitric oxide synthase and cyclooxygenase-2 gene expressions in RAW 264.7 macrophages

Polygonum cuspidatum water extract (PCWE) was shown to be a potent inhibitor of lipopolysaccharide (LPS)-induced expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). PCWE was compared to baicalin isolated from Scutellaria baicalensis Georgi and berberine of Coptidis rhizoma and Phellodendri cortex, for their effects on LPS-induced nitric oxide (NO) production and iNOS and COX-2 gene expressions in RAW 264.7 macrophages. Both PCWE and the compounds inhibited LPS-induced NO production in a concentration-dependent manner without a cytotoxicity. The decrease in NO production was in parallel with the inhibition of LPS-induced iNOS gene expression by PCWE and the compounds. In contrast, iNOS enzyme activity was not inhibited by PCWE and two agents. In addition, only PCWE inhibited LPS-induced prostaglandin E2 (PGE2) production and COX-2 gene expression without affecting COX-2 enzyme activity, while baicalin or berberine did not. Furthermore, N-nitro-L-arginine (NLA) and N-nitro-L-arginine methyl ester (L-NAME) pretreatment enhanced LPS-induced iNOS protein expression, which was inhibited by these PCWE and two agents, although LPS-induced COX-2 protein expression was not affected by NLA and L-NAME. PCWE inhibited PGE2 production and COX-2 protein expression in NLA/LPS or L-NAME/LPS-co-treated RAW 264.7 cell, however, baicalin or berberine did not. From the results, it was concluded that co-treatment with NOS inhibitors and PCWE effectively blocks acute production of NO and inhibits expression of iNOS and COX-2 genes.     

Gigantol isolated from the whole plants of Cymbidium goeringii inhibits the LPS-induced iNOS and COX-2 expression via NF-kappaB inactivation in RAW 264.7 macrophages cells

During our efforts to find bioactive natural products with anti-inflammatory activity, we isolated gigantol from the whole plants of Cymbidium goeringii (Orchidaceae) by activity-guided chromatographic fractionation. Gigantol was found to have potent inhibitory effects on LPS-induced nitric oxide (NO) and prostaglandin E (2) (PGE (2)) production in RAW 264.7 cells. Consistent with these findings, gigantol suppressed the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the protein and mRNA levels in RAW 264.7 cells in a concentration-dependent manner. Our data also indicate that gigantol is a potent inhibitor of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) release and influenced the mRNA expression levels of these cytokines in a dose-dependent manner. Furthermore, a reporter gene assay for nuclear factor kappa B (NF-kappaB) and an electromobility shift assay (EMSA) demonstrated that gigantol effectively inhibited the activation of NF-kappaB, which is necessary for the expression of iNOS, COX-2, TNF-alpha, IL-1beta and IL-6. Thus, our studies suggest that gigantol inhibits LPS-induced iNOS and COX-2 expression by blocking NF- kappaB activation.     

Wogonin but not Nor-wogonin inhibits lipopolysaccharide and lipoteichoic acid-induced iNOS gene expression and NO production in macrophages

Wogonin (Wog; 5,7-dihydroxy-8-methoxy flavone) has been shown to effectively inhibit lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) gene expression and nitric oxide production in our previous study. In the present study, we found that Nor-wogonin (N-Wog; 5,7,8-trihydroxyl flavone), a structural analogue of Wog with an OH substitution at C8, performed different effect on LPS- or lipoteichoic acid (LTA)-induced iNOS gene expression and nitric oxide (NO) production in macrophages. Wog, but not N-Wog, significantly inhibits LPS- or LTA-induced NO production through suppressing iNOS gene expression at both protein and mRNA without affecting NO donor sodium nitroprusside-induced NO production, NOS enzyme activity, and cells viability. Activation of JNKs (not ERKs) via phosphorylation induction, and an increase in c-Jun (not c-Fos) protein expression were involved in LPS- and LTA-treated RAW264.7 cells, and those events were blocked by Wog, but not N-Wog, addition. Furthermore, 5,7-diOH flavone, but not 5-OH flavone, 7-OH flavone, 5-OH-7-OCH(3) flavone, significantly inhibits LPS-induced iNOS protein expression and NO production, and 7,8-diOCH(3) flavone performs more effective inhibitory activity on LPS-induced NO production and iNOS protein expression than 7-OCH(3)-8-OH flavone. These data suggest that OHs at both C5 and C7 are essential for NO inhibition of flavonoids, and OCH(3) at C8 may contribute to this activity, and suppression of JNKs-c-Jun activation is involved.