沙眼衣原体感染活化NOD1信号通路的研究

目的:探索沙眼衣原体(Chlamydia trachomatis,Ct)持续感染状态下,NOD1、IL-6及STAT3分子的表达情况和相互关系。方法:利用HeLa229细胞或STAT3基因沉默的HeLa229细胞,分别建立沙眼衣原体的急性感染和持续感染模型;应用Western Blot及ELISA等方法检测不同感染状态下STAT3及NOD1蛋白表达水平以及细胞因子IL-6的分泌水平。结果:HeLa229细胞在Ct感染状态下,STAT3和NOD1以及IL-6表达水平均升高,且于持续感染状态下的升高较急性感染状态下的升高更明显;沉默STAT3基因后,Ct感染的细胞NOD1及IL-6的表达水平下降明显。结论:HeLa229细胞在Ct持续感染状态下,STAT3能上调NOD1及IL-6表达水平,上述分子间存在NOD1-IL-6-STAT3正反馈信号通路。     

X射线对A549细胞DNA的损伤可能与JAK/STAT信号通路的激活有关

本研究旨在观察不同剂量X射线对A549细胞DNA的损伤和JAK/STAT信号通路激活水平之间的关系。分别用2、4、8Gy X射线对A549细胞进行照射后,用CCK8法检测A549细胞增殖情况,用酶联免疫法检测照射后不同时间点培养液上清中白介素6 (interleukin 6, IL-6)的含量,用免疫荧光染色法检测细胞IL-6受体(IL-6 receptor, IL-6R)和p53结合蛋白1 (p53 binding protein 1, 53BP1)的蛋白表达情况,用Western blot检测细胞JAK2、p-JAK2、STAT3和p-STAT3的蛋白表达水平。结果显示,和对照组相比,X射线照射可降低细胞增殖水平,上调53BP1表达,提高细胞培养液上清中IL-6含量,并上调IL-6R、JAK2、p-JAK2、STAT3和p-STAT3表达水平。X射线照射的上述作用存在一定的剂量依赖性。以上结果提示,X射线造成细胞DNA损伤的机制可能与JAK/STAT信号通路的激活有关。     

IL-6/STAT3报告基因系统的构建及抑制IL-6/STAT3信号通路的中药单体的筛选及验证

寻找可抑制IL-6/STAT3信号通路的活化从而抑制肿瘤的生长和恶化的中药单体化合物具有重要意义及发展前景。文中通过基因重组技术构建出一种含有STAT3增强子序列和NanoLuc(NLuc)报告基因序列的新表达载体,并进一步建立受STAT3调控并稳定表达NLuc荧光素酶的细胞系,利用该细胞系定量检测多种中药单体化合物对IL-6/STAT3信号通路的调控作用,并对抑制IL-6/STAT3信号通路的中药单体的效果进行验证。酶切鉴定及测序结果表明报告基因表达载体pQCXIP-STAT3-NLuc构建成功。STAT3转录因子的刺激物白细胞介素-6(IL-6)作用于所构建的稳定表达NLuc的细胞系后出现特异性荧光素酶反应,且作用效果呈良好的剂量依赖性,表明受STAT3调控稳定表达NLuc荧光素酶的细胞系构建成功。Western blotting及Real-time PCR实验结果表明所筛选的中药单体化合物石斛碱及粉防己碱可抑制IL-6/STAT3信号通路并显著下调其下游基因Bcl-2及Bcl-x的表达,且作用呈剂量依赖性。综上所述,文中构建了可高效检测STAT3转录活性的报告基因系统,并利用该系统成功地筛选出可抑制IL-6/STAT3信号通路的中药单体化合物,具有一定的理论和应用价值。     

蒲公英多糖对溃疡性结肠炎大鼠IL-6/STAT3信号通路的影响

目的：观察蒲公英多糖对溃疡性结肠炎大鼠模型IL-6/STAT3信号通路的调控作用。方法：清洁级SD大鼠40只,雌雄各半,随机分为4组（n=10）：空白组、模型组、阳性对照组、蒲公英多糖组。采用2,4,6-三硝基苯磺酸（TNBS）诱导结肠炎大鼠模型,阳性对照组采用美沙拉嗪10 mg/kg·d灌胃,蒲公英多糖组采用蒲公英多糖10 mg/kg·d灌胃,治疗4周后处死,观察大鼠结肠粘膜病理改变,检测大鼠血清白介素-6（IL-6）含量、结肠髓过氧化物酶（MPO）、白介素-6受体（sIL-6Rα）、糖蛋白130（gp130）、转录活化因子3（STAT3）、IL-6 mRNA表达。结果：与正常组比较,模型组大鼠血清IL-6含量明显升高（P<0.01）,MPO阳性密度明显增高（P<0.01）,sIL-6Rα、gp130含量明显增高（P<0.01）,肠组织STAT3、IL-6 mRNA相对表达量明显增高（P<0.01）;与模型组比较蒲公英多糖组、美沙拉嗪组大鼠血清IL-6含量明显降低（P<0.01）,MPO阳性密度明显降低（P<0.01）,sIL-6Rα、gp130含量明显降低（P<0.01）,肠组织STAT3、IL-6 mRNA相对表达量与模型组比较明显降低（P<0.05）。结论：蒲公英多糖能够降低溃疡性结肠炎大鼠IL-6水平,下调IL-6/STAT3通路中sIL-6Rα、gp130蛋白表达量,进而下调大鼠肠组织STAT3、IL-6 mRNA的转录水平,缓解结肠组织的炎症状态,保护和修复粘膜组织,起到治疗溃疡性结肠炎的作用。     

STAT3基因沉默降低小鼠乳腺癌细胞的体外迁移能力

信号转导子与转录活化子3(STAT3)是一个具有信号转导和转录调控双重功能的转录因子,有文献报道STAT3在乳腺癌中的表达显著升高,并能促进乳腺癌的转移。为了深入探索STAT3在肿瘤发生发展中的作用和影响乳腺癌转移的分子机制,采用RNA干扰技术在小鼠乳腺癌细胞株4T1中沉默STAT3的表达。MTT实验结果显示STAT3沉默对4T1细胞的增殖能力没有影响;细胞迁移实验结果表明STAT3表达被沉默后4T1细胞的迁移能力明显被抑制;定量PCR结果显示,STAT3基因沉默后4T1细胞中VEGF和IL-6的mRNA水平下降,E-cadherin表达上升,mosin表达下降;信号通路检测显示STAT3基因表达沉默后MAPK的活化明显降低。研究表明STAT3在小鼠乳腺癌细胞的迁移过程中发挥重要作用,为以STAT3基因为靶向的治疗提供了一定的实验依据。     

小鼠Toll样受体3基因的克隆及真核表达

采用RT-PCR方法从小鼠巨噬细胞中克隆小鼠Toll样受体3(TLR3)基因,基因测序表明获得了小鼠全长TLR3cDNA,构建了真核表达质粒p3XFLAG-CMV-7.1-TLR3.重组质粒转染293T细胞,Western blotting检测蛋白表达,表达蛋白质的相对分子量与预计相符.采用TLR3的阳性刺激物poly(I∶C)刺激重组质粒转染的293T细胞,双荧光素酶报告基因系统检测发现能激活下游转录因子NF-κB的转录活性,并能诱导TLR3下游细胞因子IL-6和TNF-α的表达.小鼠TLR3基因的克隆和表达,为研究TLR3介导的信号通路及其在抗病毒免疫中的作用打下基础.     

Prostaglandin E2 augments IL-10 signaling and function

In inflamed joints of rheumatoid arthritis, PGE(2) is highly expressed, and IL-10 and IL-6 are also abundant. PGE(2) is a well-known activator of the cAMP signaling pathway, and there is functional cross-talk between cAMP signaling and the Jak-STAT signaling pathway. In this study, we evaluated the modulating effect of PGE(2) on STAT signaling and its biological function induced by IL-10 and IL-6, and elucidated its mechanism in THP-1 cells. STAT phosphorylation was determined by Western blot, and gene expression was analyzed using real-time PCR. Pretreatment with PGE(2) significantly augmented IL-10-induced STAT3 and STAT1 phosphorylation, as well as suppressors of cytokine signaling 3 (SOCS3) and IL-1R antagonist gene expression. In contrast, PGE(2) suppressed IL-6-induced phosphorylation of STAT3 and STAT1. These PGE(2)-induced modulating effects were largely reversed by actinomycin D. Pretreatment with dibutyryl cAMP augmented IL-10-induced, but did not change IL-6-induced STAT3 phosphorylation. Misoprostol, an EP2/3/4 agonist, and butaprost, an EP2 agonist, augmented IL-10-induced STAT3 phosphorylation and SOCS3 gene expression, but sulprostone, an EP1/3 agonist, had no effect. H89, a protein kinase A inhibitor, and LY294002, a PI3K inhibitor, diminished PGE(2)-mediated augmentation of IL-10-induced STAT3 phosphorylation. In this study, we found that PGE(2) selectively regulates cytokine signaling via increased intracellular cAMP levels and de novo gene expression, and these modulating effects may be mediated through EP2 or EP4 receptors. PGE(2) may modulate immune responses by alteration of cytokine signaling in THP-1 cells.     

Both type I and II IFN induce insulin resistance by inducing different isoforms of SOCS expression in 3T3-L1 adipocytes

Although elevation of the blood glucose level is a causal adverse effect of treatment with interferon (IFN), the precise underlying molecular mechanism is largely unknown. We examined the effects of type I and type II IFN (IFN-β and IFN-γ) on insulin-induced metabolic signaling leading to glucose uptake in 3T3-L1 adipocytes. IFN-β suppressed insulin-induced tyrosine phosphorylation of IRS-1 without affecting its expression, whereas IFN-γ reduced both the protein level and tyrosine phosphorylation. Although both IFNs stimulated phosphorylation of STAT1 (at Tyr(701)) and STAT3 (at Tyr(705)) after treatment for 30 min, subsequent properties of induction of the SOCS isoform were different. IFN-β preferentially induced SOCS1 rather than SOCS3, whereas IFN-γ strongly induced SOCS3 expression alone. In addition, adenovirus-mediated overexpression of either SOCS1 or SOCS3 inhibited insulin-induced tyrosine phosphorylation of IRS-1, whereas the reduction of IRS-1 protein was observed only in SOCS3-expressed cells. Notably, IFN-β-induced SOCS1 expression and suppression of insulin-induced tyrosine phosphorylation of IRS-1 were attenuated by siRNA-mediated knockdown of STAT1. In contrast, adenovirus-mediated expression of a dominant-negative STAT3 (F-STAT3) attenuated IFN-γ-induced SOCS3 expression, reduction of IRS-1 protein, and suppression of insulin-induced glucose uptake but did not have any effect on the IFN-β-mediated SOCS1 expression and inhibition of insulin-induced glucose uptake. Interestingly, pretreatment of IFN-γ with IL-6 synergistically suppressed insulin signaling, even when IL-6 alone had no significant effect. These results indicate that type I and type II IFN induce insulin resistance by inducing distinct SOCS isoforms, and IL-6 synergistically augments IFN-γ-induced insulin resistance by potentiating STAT3-mediated SOCS3 induction in 3T3-L1 adipocytes.     

Modulation of TLR4 signaling by a novel adaptor protein signal-transducing adaptor protein-2 in macrophages

Signal-transducing adaptor protein-2 (STAP-2) is a recently identified adaptor protein that contains pleckstrin and Src homology 2-like domains as well as a YXXQ motif in its C-terminal region. Our previous studies have demonstrated that STAP-2 binds to STAT3 and STAT5, and regulates their signaling pathways. In the present study, STAP-2 was found to positively regulate LPS/TLR4-mediated signals in macrophages. Disruption of STAP-2 resulted in impaired LPS/TLR4-induced cytokine production and NF-kappaB activation. Conversely, overexpression of STAP-2 enhanced these LPS/TLR4-induced biological activities. STAP-2, particularly its Src homology 2-like domain, bound to both MyD88 and IkappaB kinase (IKK)-alphabeta, but not TNFR-associated factor 6 or IL-1R-associated kinase 1, and formed a functional complex composed of MyD88-STAP-2-IKK-alphabeta. These interactions augmented MyD88- and/or IKK-alphabeta-dependent signals, leading to enhancement of the NF-kappaB activity. These results demonstrate that STAP-2 may constitute an alternative LPS/TLR4 pathway for NF-kappaB activation instead of the TNFR-associated factor 6-IL-1R-associated kinase 1 pathway.     

IL-6 trans-signaling modulates TLR4-dependent inflammatory responses via STAT3

Innate immune responses triggered by the prototypical inflammatory stimulus LPS are mediated by TLR4 and involve the coordinated production of a multitude of inflammatory mediators, especially IL-6, which signals via the shared IL-6 cytokine family receptor subunit gp130. However, the exact role of IL-6, which can elicit either proinflammatory or anti-inflammatory responses, in the pathogenesis of TLR4-driven inflammatory disorders, as well as the identity of signaling pathways activated by IL-6 in a proinflammatory state, remain unclear. To define the contribution of gp130 signaling events to TLR4-driven inflammatory responses, we combined genetic and therapeutic approaches based on a series of gp130(F/F) knock-in mutant mice displaying hyperactivated IL-6-dependent JAK/STAT signaling in an experimental model of LPS/TLR4-mediated septic shock. The gp130(F/F) mice were markedly hypersensitive to LPS, which was associated with the specific upregulated production of IL-6, but not TNF-α. In gp130(F/F) mice, either genetic ablation of IL-6, Ab-mediated inhibition of IL-6R signaling or therapeutic blockade of IL-6 trans-signaling completely protected mice from LPS hypersensitivity. Furthermore, genetic reduction of STAT3 activity in gp130(F/F):Stat3(+/-) mice alleviated LPS hypersensitivity and reduced LPS-induced IL-6 production. Additional genetic approaches demonstrated that the TLR4/Mal pathway contributed to LPS hypersensitivity and increased IL-6 production in gp130(F/F) mice. Collectively, these data demonstrate for the first time, to our knowledge, that IL-6 trans-signaling via STAT3 is a critical modulator of LPS-driven proinflammatory responses through cross-talk regulation of the TLR4/Mal signaling pathway, and potentially implicate cross-talk between JAK/STAT and TLR pathways as a broader mechanism that regulates the severity of the host inflammatory response.     

IL-4 Suppresses the Responses to TLR7 and TLR9 Stimulation and Increases the Permissiveness to Retroviral Infection of Murine Conventional Dendritic Cells

Th2-inducing pathological conditions such as parasitic diseases increase susceptibility to viral infections through yet unclear mechanisms. We have previously reported that IL-4, a pivotal Th2 cytokine, suppresses the response of murine bone-marrow-derived conventional dendritic cells (cDCs) and splenic DCs to Type I interferons (IFNs). Here, we analyzed cDC responses to TLR7 and TLR9 ligands, R848 and CpGs, respectively. We found that IL-4 suppressed the gene expression of IFNβ and IFN-responsive genes (IRGs) upon TLR7 and TLR9 stimulation. IL-4 also inhibited IFN-dependent MHC Class I expression and amplification of IFN signaling pathways triggered upon TLR stimulation, as indicated by the suppression of IRF7 and STAT2. Moreover, IL-4 suppressed TLR7- and TLR9-induced cDC production of pro-inflammatory cytokines such as TNFα, IL-12p70 and IL-6 by inhibiting IFN-dependent and NFκB-dependent responses. IL-4 similarly suppressed TLR responses in splenic DCs. IL-4 inhibition of IRGs and pro-inflammatory cytokine production upon TLR7 and TLR9 stimulation was STAT6-dependent, since DCs from STAT6-KO mice were resistant to the IL-4 suppression. Analysis of SOCS molecules (SOCS1, −2 and −3) showed that IL-4 induces SOCS1 and SOCS2 in a STAT6 dependent manner and suggest that IL-4 suppression could be mediated by SOCS molecules, in particular SOCS2. IL-4 also decreased the IFN response and increased permissiveness to viral infection of cDCs exposed to a HIV-based lentivirus. Our results indicate that IL-4 modulates and counteracts pro-inflammatory stimulation induced by TLR7 and TLR9 and it may negatively affect responses against viruses and intracellular parasites.