缺氧对巨噬细胞HMGB1释放的影响及其机制

目的观察缺氧对巨噬细胞高迁移率族蛋白B1(HMGB1)释放的诱导作用,并初步探讨其可能的机制。方法采用巨噬细胞株RAW264.7,观察缺氧培养不同时间对培养上清液中HMGB1含量、细胞HMGB1mRNA表达和HMGB1胞内分布的影响,及不同浓度N-乙酰半胱氨酸对HMGB1释放的抑制作用。HMGB1含量和HMGB1mRNA表达水平分别采用酶联免疫吸附试验、实时荧光定量PCR法检测。结果缺氧培养6h后HMGB1mRNA表达水平已显示增强(P0.05),缺氧培养12h后培养上清液中HMGB1含量明显升高(P0.01),且显示HMGB1核浆转移;N-乙酰半胱氨酸对缺氧培养HMGB1释放有剂量依赖性抑制作用。结论缺氧能诱导巨噬细胞释放HMGB1,其机制可能与胞内氧自由基产生有关。     

Tetrahydroabietic Acid,a Reduced Abietic Acid,Inhibits the Production of Inflammatory Mediators in RAW264.7 Macrophages Activated with Lipopolysaccharide

Abietic acid (AA), the main component of the rosin fraction of oleoresin synthesized by conifer species, has been reported to have anti-inflammatory effects. AA is a weak contact allergen; however, compounds resulting from its oxidation by air elicit stronger allergic response. Hydrogenation of the conjugated double bonds of AA, as in tetrahydroabietic acid (THAA), decreases its susceptibility to air oxidation and would thus reduce the allergenicity of AA. The aim of this study was to investigate whether THAA could exert anti-inflammatory effects to the same extent as AA in RAW264.7 macrophages activated with the endotoxin lipopolysaccharide (LPS). THAA and AA inhibited the production of nitric oxide (NO) and prostaglandin E₂ by suppressing the expression of inducible NO synthase and cyclooxygenase-2, respectively, in LPS-activated RAW264.7 macrophages. They also inhibited the LPS-induced production of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α. Both THAA and AA prevented the LPS-induced nuclear translocation of the nuclear factor-κB/p65 subunit, suggesting that THAA may inhibit the production of pro-inflammatory mediators through the same mechanism as AA. In comparison, the anti-inflammatory effects of THAA and AA were almost identical, indicating that THAA retains the anti-inflammatory activity of AA at least in LPS-activated RAW264.7 macrophages.     

HMGB1 signals through toll-like receptor (TLR) 4 and TLR2

In response to bacterial endotoxin (e.g., LPS) or endogenous proinflammatory cytokines (e.g., TNF and IL-1beta), innate immune cells release HMGB1, a late cytokine mediator of lethal endotoxemia and sepsis. The delayed kinetics of HMGB1 release makes it an attractive therapeutic target with a wider window of opportunity for the treatment of lethal systemic inflammation. However, the receptor(s) responsible for HMGB1-mediated production of proinflammatory cytokines has not been well characterized. Here we demonstrate that in human whole blood, neutralizing antibodies against Toll-like receptor 4 (TLR4, but not TLR2 or receptor for advanced glycation end product) dose-dependently attenuate HMGB1-induced IL-8 release. Similarly, in primary human macrophages, HMGB1-induced TNF release is dose-dependently inhibited by anti-TLR4 antibodies. In primary macrophages from knockout mice, HMGB1 activates significantly less TNF release in cells obtained from MyD88 and TLR4 knockout mice as compared with cells from TLR2 knockout and wild-type controls. However, in human embryonic kidney 293 cells transfected with TLR2 or TLR4, HMGB1 effectively induces IL-8 release only from TLR2 overexpressing cells. Consistently, anti-TLR2 antibodies dose-dependently attenuate HMGB1-induced IL-8 release in human embryonic kidney/TLR2-expressing cells and markedly reduce HMGB1 cell surface binding on murine macrophage-like RAW 264.7 cells. Taken together, our data suggest that there is a differential usage of TLR2 and TLR4 in HMGB1 signaling in primary cells and in established cell lines, adding complexity to studies of HMGB1 signaling which was not previously expected.     

佛波酯对LPS／IFN-γ诱导的巨噬细胞活性氧产生的影响

目的研究佛波酯（PMA）对脂多糖／γ-干扰素（LPS／IFN-γ）诱导的巨噬细胞RAW264．7活性氧产生的影响。方法于实验前0、3、6、9、12、18h,用1μg／mL的LPS和100U／mL IFN-γ诱导处于对数生长期的RAW264．7细胞,采用蛋白质印迹技术检测细胞中一氧化氮合酶（iNOS）的表达;对经LPs／IFN-γ诱导12h的RAW264．7细胞加入终浓度为200ng／mL的PMA,应用激光共聚焦显微技术观察RAW264．7细胞中活性氧的产生。结果LPS／IFN-γ可使RAW264．7细胞的诱导型iNOS表达增加,同时PMA可刺激经LPS／IFN-γ诱导后的RAW264．7细胞产生呼吸爆发,细胞的荧光强度较未刺激组增强（P〈0．01）。结论PMA可促使经LPS／IFN-γ诱导的RAW264．7细胞产生大量活性氧。     

谷氨酰胺在体内/外对巨噬细胞炎症因子分泌的影响

目的 观察谷氨酰胺(Gln)在体内/外条件下对巨噬细胞炎症反应及热休克蛋白(HSP)表达的影响,探讨Gin在脓毒症时抑制体内炎症反应的机制.方法 实验 1:将培养的腹腔巨噬细胞株RAW264.7分为Gln 0、0.5和8 mmol/L 3组,分别于内毒素脂多糖(LPS)刺激后0、1、4、12和24 h收集细胞及上清液.实验2:45只昆明小鼠被随机均分为假手术(Sham)组、模型组、Gin组;采用盲肠结扎穿孔术(CLP)制备小鼠脓毒症模型,术后即刻从尾静脉注射Gin 0.75 g/kg(Gln组)或等量生理盐水(Sham组和模型组).6 h后采血,腹腔灌洗分离巨噬细胞.用酶联免疫吸附法(ELISA)检测细胞上清液、血清、巨噬细胞裂解液中肿瘤坏死因子-a(TNF-a)、白细胞介素-6(IL-6)、IL-10浓度;用蛋白质免疫印迹法检测巨噬细胞HSP72蛋白表达.结果 体外条件下Gin可显著促进RAW264.7细胞释放TNF-a,IL-6和IL-10,呈剂量和时间依赖性(P＜0.05或P＜0.01),LPS刺激4 h后,Gln 8 mmol/L组RAW264.7细胞HSP72表达显著增加(P均＜0.01).体内条件下,Gin组腹腔巨噬细胞TNF-a、IL-6含量均明显低于模型组(P＜0.01和P＜0.05),3组间IL-10含量比较差异无统计学意义;Gln组血清TNF-a浓度明显低于模型组(P＜0.05),两组血清IL-6、IL-10浓度差异无统计学意义;Gin组巨噬细胞HSP72表达较模型组和Sham组均显著升高(P均＜0.01).结论 Gin体外作用时可显著促进巨噬细胞释放TNF-a和IL-6,且该作用不能被HSP72表达所抑制.体内作用条件下Gln抑制腹腔巨噬细胞合成TNF-a和IL-6.体外和体内条件下Gln都可诱导巨噬细胞表达HSP72,提示HSP72表达可能不是Gln在脓毒症时抑制机体炎症反应的主要机制.     

Inhibition of macrophage activation and phagocytosis by a novel NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin.

Previously, we designed and synthesized a new NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ). In the present research we looked into the effect of DHMEQ on the activation of macrophages, especially on the phagocytotic activity of cells of the mouse macrophage-like cell line RAW264.7. DHMEQ inhibited lipopolysaccharide (LPS)-induced NF-kappaB activation by inhibiting its nuclear translocation from the cytoplasm. It also inhibited the expression of inducible NO synthase (iNOS) and nitric oxide (NO) production induced by LPS and interferon-gamma. Using enzyme-linked immunosorbent assays (ELISAs) we showed DHMEQ to inhibit LPS-induced secretion of IL-6, IL-12, interleukin-1beta (IL-1beta), and TNF-alpha. Furthermore, DHMEQ also inhibited the phagocytosis of fluorescently labeled Escherichia coli by RAW264.7 cells treated with LPS or IL-1beta, thus being the first evidence for the involvement of NF-kappaB in the regulation of phagocytosis by use of this inhibitor. Deletion of p65 by siRNA also inhibited the phagocytosis. DHMEQ inhibited the LPS-induced but not IL-1beta-induced phagocytosis of glass beads, indicating that activation of not only NF-kappaB but also Toll-like receptor 4 (TLR-4) is essential for the phagocytosis of E. coli. Previously we found that DHMEQ inhibited type 2 collagen-induced rheumatoid arthritis and the growth of various human carcinomas in mice. It is thus likely that inhibition of macrophage activation is involved in the mechanism of these anti-inflammatory and antitumor activities of DHMEQ in mice.     

Delayed administration of D-Ala2-D-Leu5-enkephalin, a delta-opioid receptor agonist, improves survival in a rat model of sepsis

Sepsis is the major cause of death in intensive care units, despite enormous efforts in the development of antimicrobial therapies. Sepsis is mediated by early [e.g., tumor necrosis factor (TNF)-α and interleukin (IL)-1β] and late [e.g., high-mobility group box 1 protein (HMGB1)] proinflammatory cytokines. HMGB1, which is secreted into extracellular milieu by activated macrophages or passively released by destroyed macrophages, stimulates intensive inflammatory responses. D-Ala2-D-Leu5-enkephalin (DADLE), a synthetic δ-opioid receptor agonist, has been shown to protect rats from sepsis. Here we elucidated the mechanism for protective effect of DADLE against sepsis. Sepsis was established in Sprague-Dawley rats by means of cecal ligation and puncture (CLP). In this model, the serum levels of TNF-α and IL-1β were increased after 2-3 h, while those of HMGB1 were increased after 18 h. Administration of DADLE (5 mg/kg) concurrently with CLP improved survival, which was associated with the decreases in the serum levels of TNF-α, IL-1β and HMGB1. Importantly, DADLE administrated 4 h after CLP showed comparable protective effect as the concurrent administration, with decreased serum HMGB1 levels. Moreover, peritoneal macrophages isolated from rats were challenged with lipopolysaccharide (LPS). Concurrent or delayed DADLE administration at 10(-6) M suppressed the LPS-induced cell death. DADLE also suppressed the release of HMGB1 from macrophages that was induced by LPS, TNF-α or interferon-γ. In conclusion, DADLE protects rats from sepsis probably by decreasing the serum level of HMGB1. We propose DADLE as a candidate for septic shock therapy, even if it is administered after the onset of sepsis.     

Luteolin inhibits an endotoxin-stimulated phosphorylation cascade and proinflammatory cytokine production in macrophages

Flavonoids are naturally occurring polyphenolic compounds with a wide distribution throughout the plant kingdom. In the present study, we compared the ability of several flavonoids to modulate the production of proinflammatory molecules from lipopolysaccharide (LPS)-stimulated macrophages and investigated their mechanism(s) of action. Pretreatment of RAW 264.7 with luteolin, luteolin-7-glucoside, quercetin, and the isoflavonoid genistein inhibited both the LPS-stimulated TNF-alpha and interleukin-6 release, whereas eriodictyol and hesperetin only inhibited TNF-alpha release. From the compounds tested luteolin and quercetin were the most potent in inhibiting cytokine production with an IC(50) of less than 1 and 5 microM for TNF-alpha release, respectively. To determine the mechanisms by which flavonoids inhibit LPS signaling, we used luteolin and determined its ability to interfere with total protein tyrosine phosphorylation as well as Akt phosphorylation and nuclear factor-kappaB activation. Pretreatment of the cells with luteolin attenuated LPS-induced tyrosine phosphorylation of many discrete proteins. Moreover, luteolin inhibited LPS-induced phosphorylation of Akt. Treatment of macrophages with LPS resulted in increased IkappaB-alpha phosphorylation and reduced the levels of IkappaB-alpha. Pretreatment of cells with luteolin abolished the effects of LPS on IkappaB-alpha. To determine the functional relevance of the phosphorylation events observed with IkappaB-alpha, macrophages were transfected either with a control vector or a vector coding for the luciferase reporter gene under the control of kappaB cis-acting elements. Incubation of transfected RAW 264.7 cells with LPS increased luciferase activity in a luteolin-sensitive manner. We conclude that luteolin inhibits protein tyrosine phosphorylation, nuclear factor-kappaB-mediated gene expression and proinflammatory cytokine production in murine macrophages.     

转染HSP70基因对过氧化氢所致RAW264.7细胞损伤的影响

[目的]观察HSP70基因过表达是否能减轻过氧化氢所致的RAW264.7巨噬细胞损伤.[方法]用脂质体包裹重组质粒pcDNA3.1-HSP70导入RAW264.7细胞株,经G418筛选阳性克隆,用Western blot方法检测HSP70的表达情况;通过测定细胞存活率、LDH释放率,观察了HSP70基因过表达对过氧化氢所致RAW264.7细胞损伤的影响.[结果]获得了HSP70过表达的RAW264.7细胞系;HSP70过表达组细胞的存活率及LDH释放率与对照组比有明显差异.[结论]转染HSP70基因对过氧化氢所致RAW264.7细胞损伤有明显的保护作用.     

Geranylgeranylacetone ameliorates inflammatory response to lipopolysaccharide (LPS) in murine macrophages: inhibition of LPS binding to the cell surface

We investigated whether pretreatment with geranylgeranylacetone (GGA), a potent heat shock protein (HSP) inducer, could inhibit proinflammatory cytokine liberation and nitric oxide (NO) production in lipopolysaccharide (LPS)-treated murine macrophages. The levels of NO and tumor necrosis factor-alpha (TNF-alpha) released from murine macrophage RAW 264 cells were increased dose- and time-dependently following treatment with LPS (1 microg/ml). GGA (80 microM) treatment 2 h before LPS addition significantly suppressed TNF-alpha and NO productions at 12 h and 24 h after LPS, respectively, indicating that GGA inhibits activation of macrophages. However, replacement by fresh culture medium before LPS treatment abolished the inhibitory effect of GGA on NO production in LPS-treated cells. Furthermore, GGA inhibited both HSP70 and inducible NO synthase expressions induced by LPS treatment despite an HSP inducer. When it was examined whether GGA interacts with LPS and/or affects expression of Toll-like receptor 4 (TLR4) and CD14 on the cell surface, GGA inhibited the binding of LPS to the cell surface, while GGA did not affect TLR4 and CD14 expressions. These results indicate that GGA suppresses the binding of LPS to the cell surface of macrophages, resulting in inhibiting signal transduction downstream of TLR4.     

Inhibition of activation of nuclear factor kappaB is responsible for inhibition of inducible nitric oxide synthase expression by higenamine, an active component of aconite root.

Effects of higenamine on nitric oxide (NO) production and inducible NO synthase (iNOS) mRNA expression (RAW 264.7 cells), on vascular reactivity in vitro and in vivo (rats), and on survival rates (mice) and serum nitrite/nitrate levels (rats) were investigated by using last lipopolysaccharide (LPS) plus interferon (IFN)-gamma. Higenamine concentration-dependently inhibited NO production and inducible NO synthase mRNA in RAW 264.7 cells, in which the IC(50) was 53 microM. Higenamine (10 mg/kg i.p.) administered 90 min before LPS (5 mg/kg i.v.) prevented not only LPS-induced hypotension but also pressor response to norepinephrine (1 microgram/kg) in rats. Incubation of thoracic aorta with LPS (300 ng/ml) for 8 h in vitro resulted in suppression of the vasoconstrictor effects to phenylephrine, which was prevented by coincubation with higenamine. The survival rate to endotoxin in mice was significantly (P <.01) increased by the presence of higenamine in the LPS-treated group up to 48 h. Serum nitrite/nitrate levels were significantly (P <.05) reduced by higenamine in LPS-treated rats. Finally, higenamine inhibited the activation of nuclear factor kappaB in RAW 264.7 cells due to LPS + IFN-gamma by mobility shift assays. Taken together, these data strongly suggest that higenamine inhibits iNOS expression by inhibiting nuclear factor kappaB activation by LPS + IFN-gamma, which may be beneficial in inflammatory diseases in which enhanced formation of NO is the main causative factor. Furthermore, due to positive inotropic action, higenamine may be more effective in a condition where myocardial contractility is likely to depress, such as in septic shock and/or endotoxin-induced inflammatory disorders.     

Evidence for antiviral effect of nitric oxide. Inhibition of herpes simplex virus type 1 replication.

Nitric oxide (NO) has antimicrobial activity against a wide spectrum of infectious pathogens, but an antiviral effect has not been reported. The impact of NO, from endogenous and exogenous sources, on herpes simplex virus type 1 (HSV 1) replication was studied in vitro. HSV 1 replication in RAW 264.7 macrophages was reduced 1,806-fold in monolayers induced to make NO by activation with gamma IFN and LPS. A competitive and a noncompetitive inhibitor of nitric oxide synthetase substantially reduced the antiviral effect of activated RAW macrophages. S-nitroso-L-acetyl penicillamine (SNAP) is a donor of NO and was added to the media of infected monolayers to assess the antiviral properties of NO in the absence of gamma IFN and LPS. A single dose of S-nitroso-L-acetyl penicillamine 3 h after infection inhibited HSV 1 replication in Vero, HEp2, and RAW 264.7 cells in a dose-dependent manner. Neither virucidal nor cytocidal effects of NO were observed under conditions that inhibited HSV 1 replication. Nitric oxide had inhibitory effects, comparable to that of gamma IFN/LPS, on protein and DNA synthesis as well as on cell replication. This report demonstrates that, among its diverse properties, NO has an antiviral effect.     

Glabridin, an isoflavan from licorice root, inhibits inducible nitric-oxide synthase expression and improves survival of mice in experimental model of septic shock

(R)-4-(3,4-Dihydro-8,8-dimethyl)-2H,8H-benzo[1,2-b:3,4-b']dipyran-3yl)-1,3-benzenediol (glabridin), a flavonoid present in licorice extract, is known to have antimicrobial, anti-inflammatory, and cardiovascular protective activities. In the present study, we report the inhibitory effect of glabridin on nitric oxide (NO) production and inducible nitric oxide (iNOS) gene expression in murine macrophages. Glabridin attenuated lipopolysaccharide (LPS)-induced NO production in isolated mouse peritoneal macrophages and RAW 264.7 cells, a mouse macrophage-like cell line. Moreover, iNOS mRNA expression was also blocked by glabridin treatment in LPS-stimulated RAW 264.7 cells. Further study demonstrated that the LPS-induced nuclear factor (NF)-kappaB/Rel DNA binding activity and NF-kappaB/Rel-dependent reporter gene activity were significantly inhibited by glabridin in RAW 264.7 cells and that this effect was mediated through the inhibition of inhibitory factor-kappaB degradation and p65 nuclear translocation. Moreover, reactive oxygen species generation was also suppressed by glabridin treatment in RAW 264.7 cells. In contrast, the activity of mitogen-activated protein kinases was unaffected by glabridin treatment. In animal model, in vivo administration of glabridin increased the rate of survival of LPS-treated mice and inhibited LPS-induced increase in plasma concentrations of nitrite/nitrate and tumor necrosis factor-alpha. Collectively, these data suggest that glabridin inhibits NO production and iNOS gene expression by blocking NF-kappaB/Rel activation and that this effect was mediated, at least in part, by inhibiting reactive oxygen species generation. Furthermore, in vivo anti-inflammatory effect of glabridin suggests a possible therapeutic application of this agent in inflammatory diseases.