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。     

Inhibition of lipopolysaccharide-induced expression of inducible nitric oxide and cyclooxygenase-2 by chiisanoside via suppression of nuclear factor-kappaB activation in RAW 264.7 macrophage cells

In the present study, the effects of several triterpenes isolated from the leaves of Acanthopanax chiisanensis (Araliaceae), namely, chiisanoside, isochiisanoside, 22-hydroxychiisanoside and chiisanogenin (the aglycone of chiisanoside) were evaluated on lipopolysaccharide (LPS)-induced nitric oxide (NO) and prostaglandin E2 (PGE2) production by the RAW 264.7 macrophage cell line. Of the triterpenes tested, chiisanoside was found to most potently inhibit NO and PGE2 production. In addition, chiisanoside significantly reduced the release of inflammatory cytokines like TNF-alpha and IL-1beta. Consistent with these observations, the protein and mRNA expression levels of iNOS and COX-2 enzyme were found to be inhibited by chiisanoside in a concentration-dependent manner. Furthermore, chiisanoside inhibited the nuclear factor-kappaB (NF-kappaB) activation induced by LPS and this was associated with a reduction in p65 protein in the nucleus and with the phosphorylations of ERK1/2 and JNK MAP kinases. Taken together, our data indicate that the anti-inflammatory properties of chiisanoside might be the result from the inhibition of iNOS, COX-2, TNF-alpha and IL-1beta expression through the down-regulation of NF-kappaB binding activity.     

Chlorogenic acid inhibits lipopolysaccharide-induced cyclooxygenase-2 expression in RAW264.7 cells through suppressing NF-κB and JNK/AP-1 activation

Chlorogenic acid (CGA) is a naturally occurring phenolic acid in human diet. Data obtained from in vivo and in vitro experiments demonstrate that CGA mostly presents anti-oxidant and anti-carcinogenic activities. Here we show that CGA also inhibits lipopolysaccharide (LPS)-induced inflammatory response[AU1] in RAW 264.7 cells. Our results indicated that CGA significantly decreased LPS-induced up-regulation of cyclooxygenase (COX-2) at protein and mRNA levels in RAW 264.7 cells and as a result it inhibited prostaglandin E₂ (PGE₂) release from LPS-treated RAW 264.7 cells. In the further experiments, LPS-induced activation of nuclear factor-kappaB (NF-κB) and c-Jun N-terminal kinase (JNK)-c-Jun-activator protein (AP-1) pathway were suppressed significantly by CGA. In addition, CGA did not affect phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and p38. In conclusion, CGA suppresses LPS-induced COX-2 expression via attenuating the activation of NF-κB and JNK/AP-1 signaling pathways suggesting that CGA, the polyphenol compound in our food, could exert anti-inflammatory effects through inhibiting PGE₂ production.     

Inhibition of lipopolysaccharide-induced expression of inducible nitric oxide synthase and tumor necrosis factor-alpha by 2'-hydroxychalcone derivatives in RAW 264.7 cells

In cultures of the murine macrophage cell line RAW 264.7, effects of four 2'-hydroxychalcone derivatives, 2'-hydroxy-4'-methoxychalcone (compound 1), 2',4-dihydroxy-4'-methoxychalcone (compound 2), 2',4-dihydroxy-6'-methoxychalcone (compound 3) and 2'-hydroxy-4,4'-dimethoxychalcone (compound 4), on lipopolysaccharide (LPS)-induced production of nitric oxide (NO) and tumor necrosis factor (TNF)-alpha were examined. Compounds 1, 2 and 3 at 3-30microM inhibited the production with almost the same potency. Compound 4 showed no inhibitory activity. Compounds 1, 2 and 3 at 3-30microM inhibited the LPS-induced expression of inducible nitric oxide synthase (iNOS) and TNF-alpha mRNA. To clarify the mechanism involved, effects of compounds 1, 2 and 3 on the activation of nuclear factor (NF)-kappaB and activator protein-1 (AP-1) were examined. Both the LPS-induced activation of NF-kappaB and AP-1 were blocked by compounds 1, 2 and 3 at 3-30microM. Moreover, the three compounds at such concentrations inhibited the LPS-induced IkappaB degradation and the phosphorylation of c-jun N-terminal kinase (JNK) and c-jun. These findings suggest that the inhibition of the LPS-induced production of NO and TNF-alpha by the 2'-hydroxychalcone derivatives is due to the inhibition of NF-kappaB and AP-1 activations.     

Cornuside suppresses lipopolysaccharide-induced inflammatory mediators by inhibiting nuclear factor-kappa B activation in RAW 264.7 macrophages

Cornuside, a secoiridoid glucoside compound, was isolated from the fruit of Cornus officinalis SIEB. et ZUCC. Cornuside has been reported to possess immunomodulatory and anti-inflammatory activities. However, the effects and mechanism of action of cornuside in inflammation have not been fully characterized. The present study was therefore designed to examine whether cornuside suppresses inflammatory response in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. Cornuside significantly inhibited the LPS-induced production of nitric oxide, prostaglandin E(2), tumor necrosis factor-alpha, interleukin-6 (IL-6), and IL-1beta. The mRNA and protein expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were also decreased by cornuside. Furthermore, cornuside significantly attenuated the LPS-stimulated phosphorylation and degradation of inhibitory kappa B-alpha and the subsequent translocation of the p65 subunit of nuclear factor-kappa B (NF-κB) to the nucleus. Cornuside also reduced the phosphorylations of extracellular-signal-related kinase (ERK1/2), p38, and c-Jun N-terminal kinase (JNK1/2). These results suggest that the anti-inflammatory property of cornuside is related to the downregulations of iNOS and COX-2 due to NF-κB inhibition as well as the negative regulation of ERK1/2, p38, and JNK1/2 phosphorylations in RAW 264.7 cells.     

Triptolide inhibits murine-inducible nitric oxide synthase expression by down-regulating lipopolysaccharide-induced activity of nuclear factor-kappa B and c-Jun NH2-terminal kinase

Triptolide (PG490) is a natural, biologically active compound extracted from the Chinese herb Tripterygium wilfordii. It has been shown to possess potent anti-inflammatory and immunosuppressive properties. In Raw 264.7 cells stimulated with lipopolysaccharide (LPS) to mimic inflammation, triptolide inhibits nitric oxide (NO) production in a dose-dependent manner and abrogates inducible nitric oxide synthase (iNOS) gene expression. To investigate the mechanism by which triptolide inhibits murine iNOS gene expression, we examined activation of mitogen-activated protein kinases (MAP kinases) and nuclear factor-kappa B (NF-kappa B) in these cells. Addition of triptolide inhibited phosphorylation of c-Jun NH(2)-terminal kinase (JNK) but not that of extracellular signal-regulated kinase (ERK) or p38 mitogen-activated protein kinase. In addition, triptolide significantly inhibited the DNA binding activity of NF-kappa B. Taken together, these results suggest that triptolide acts to inhibit inflammation through inhibition of NO production and iNOS expression through blockade of NF-kappa B and JNK activation.     

Inhibition of inducible nitric oxide synthase and cyclooxygenase-2 expression by flavonoids isolated from Tanacetum microphyllum

Plant flavonoids show anti-inflammatory activity both in vitro and in vivo. Some flavonoids have been reported previously to inhibit nitric oxide (NO) and prostaglandin E2 (PGE2) production by suppressing inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression. The present study focuses on the effect of various naturally occurring flavonoids (santin, ermanin, centaureidin and 5,3'-dihydroxy-4'-methoxy-7-methoxycarbonylflavonol) on modulation of lipopolysaccharide (LPS)-induced iNOS and COX-2 expression in RAW 264.7 cells. Western blotting showed that all flavonoids suppressed the induction of both iNOS and COX-2. Ermanin and 5,3'-dihydroxy-4'-methoxy-7-methoxycarbonylflavonol were the most potent inhibitors. This study suggests that inhibition of iNOS and COX-2 expression by flavonoids may be one of the mechanisms responsible for their anti-inflammatory effects, and that they may be potential agents for use in the treatment of inflammatory diseases.     

Arctigenin inhibits lipopolysaccharide-induced iNOS expression in RAW264.7 cells through suppressing JAK-STAT signal pathway

Arctigenin has been demonstrated to have an anti-inflammatory function, but the precise mechanisms of its action remain to be fully defined. In the present study, we determined the effects of arctigenin on lipopolysaccharide (LPS)-induced production of proinflammatory mediators and the underlying mechanisms involved in RAW264.7 cells. Our results indicated that arctigenin exerted its anti-inflammatory effect by inhibiting ROS-dependent STAT signaling through its antioxidant activity. Arctigenin also significantly reduced the phosphorylation of STAT1 and STAT 3 as well as JAK2 in LPS-stimulated RAW264.7 cells. The inhibitions of STAT1 and STAT 3 by arctigenin prevented their translocation to the nucleus and consequently inhibited expression of iNOS, thereby suppressing the expression of inflammation-associated genes, such as IL-1β, IL-6 and MCP-1, whose promoters contain STAT-binding elements. However, COX-2 expression was slightly inhibited at higher drug concentrations (50 μM). Our data demonstrate that arctigenin inhibits iNOS expression via suppressing JAK-STAT signaling pathway in macrophages.     

Preventive effect of Ginkgo biloba extract (GBB) on the lipopolysaccharide-induced expressions of inducible nitric oxide synthase and cyclooxygenase-2 via suppression of nuclear factor-kappaB in RAW 264.7 cells

During our ongoing efforts to identify bioactive natural products with anti-inflammatory activity, we produced an extract from Ginkgo biloba (GBB) which contains higher levels of the active principles terpene and biflavonoid than EGb, the standard commercially available extract. In the present study, we examined and compared the effects of these two extracts on lipopolysaccharide (LPS)-induced nitric oxide (NO) and prostaglandin E2 (PGE2) production by the RAW 264.7 macrophage cell line. Our data indicate that GBB is a more potent inhibitor of NO and PGE2 production than EGb 761, and it also significantly decreased tumor necrosis factor (TNF)-alpha release. Consistent with these observations, the protein and mRNA expression levels of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) were found to be inhibited by GBB in a dose-dependent manner. Furthermore, GBB inhibited the LPS-induced DNA binding activity of nuclear factor-kappaB (NF-kappaB), which was associated with the prevention of IkappaB degradation, and subsequently with decreased p65 protein level in the nucleus. These results suggest that GBB inhibits LPS-induced iNOS, COX-2 and TNF-alpha expressions through the down-regulation of NF-kappaB-DNA binding activity.     

Rengyolone inhibits inducible nitric oxide synthase expression and nitric oxide production by down-regulation of NF-kappaB and p38 MAP kinase activity in LPS-stimulated RAW 264.7 cells

Nitric oxide (NO) is recognized as a mediator and regulator of inflammatory responses. Rengyolone, a cyclohexylethanoid isolated from the fruits of Forsythia koreana, exhibits anti-inflammatory activity with unknown mechanism. In this study, we found that rengyolone has a strong inhibitory effect on the production of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha). Rengyolone also inhibited inducible nitric oxide synthase (iNOS) gene expression and cyclooxygenase 2 (COX-2) by lipopolysaccharide (LPS). In order to explore the mechanism responsible for the inhibition of iNOS gene expression by rengyolone, we investigated its effect on LPS-induced nuclear factor-kappaB (NF-kappaB) activation. The LPS-induced DNA binding activity of NF-kappaB was significantly inhibited by rengyolone, and this effect was mediated through inhibition of the degradation of inhibitory factor-kappaBalpha and phosphorylation of p38 MAP kinase. Furthermore, rengyolone suppressed the expression of ICE protein in IL-1beta-treated D10S cells. Taken together, these results suggest that rengyolone attenuates the inflammation through inhibition of NO production and iNOS expression by blockade of NF-kappaB and p38 MAPK activation in LPS-stimulated RAW 264.7 cells.     

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.