Essential role for TIRAP in activation of the signalling cascade shared by TLR2 and TLR4

Signal transduction through Toll-like receptors (TLRs) originates from their intracellular Toll/interleukin-1 receptor (TIR) domain, which binds to MyD88, a common adaptor protein containing a TIR domain. Although cytokine production is completely abolished in MyD88-deficient mice, some responses to lipopolysaccharide (LPS), including the induction of interferon-inducible genes and the maturation of dendritic cells, are still observed. Another adaptor, TIRAP (also known as Mal), has been cloned as a molecule that specifically associates with TLR4 and thus may be responsible for the MyD88-independent response. Here we report that LPS-induced splenocyte proliferation and cytokine production are abolished in mice lacking TIRAP. As in MyD88-deficient mice, LPS activation of the nuclear factor NF-kappaB and mitogen-activated protein kinases is induced with delayed kinetics in TIRAP-deficient mice. Expression of interferon-inducible genes and the maturation of dendritic cells is observed in these mice; they also show defective response to TLR2 ligands, but not to stimuli that activate TLR3, TLR7 or TLR9. In contrast to previous suggestions, our results show that TIRAP is not specific to TLR4 signalling and does not participate in the MyD88-independent pathway. Instead, TIRAP has a crucial role in the MyD88-dependent signalling pathway shared by TLR2 and TLR4.     

二乙基亚硝胺诱导小鼠肝纤维化动态模型的建立及病理机制初探

摘要:目的 为 探 究 肝 纤 维 化 的 发 生 发 展 机 制 及 病 理 病 因 的 特 点, 本 研 究 通 过 建 立 二 乙 基 亚 硝 胺( diethylnitrosamine,DEN)诱导的肝纤维化动态小鼠模型,动态监测上述小鼠模型的血清生化指标,推断肝纤维化阶段。 方法 雄性 C57BL / 6 小鼠按梯度剂量每周 2 次腹腔注射 DEN,连续 8 周。 分别在第 2、4、6 和 8 周收集小鼠的血清和肝组织,通过检测相应血清生化指标、肝组织羟脯氨酸含量以及组织病理学检查监测和评估小鼠肝纤维化的发病进程。 采用 Western blot 检测 TGF-β1、α-SMA 和 TLR4 / MyD88 / NF-κB 信号通路相关蛋白以探究肝纤维化的发病机制。 结果 从第 4 周开始,与 对 照 组 相 比, DEN 诱 导 小 鼠 的 肝 功 能 相 关 血 清 生 化 指 标 ( AST、 ALT、 ALP、T-BIL、A / G 等)出现显著变化,且体质量出现明显下降。 肝脏指数出现明显下降,组织中羟脯氨酸含量均显著升高(P<0. 01) ,组织病理学结果显示 DEN 诱导组小鼠肝组织开始出现轻微胶原沉积。 Western blot 结果表明模型组小鼠肝组织中TGF-β1 和 α-SMA 表达显著上调,TLR4、MyD88、TRAF6 及细胞核 NF-κB p65 蛋白表达水平显著升高,细胞质 p65 NF-κB 表达显著下调。 结论 研究结果表明,肝纤维化的发生机制与肝损伤后激活 TLR4 / MyD88 / NF-κB 信号通路相关,而 TLR4 炎症通路的激活又进一步促进分泌 TGF-β1 并激活肝星状细胞从而导致大量细胞外基质沉积。 本研究表明,通过 DEN 诱导的小鼠肝纤维化发病机制可能与炎症相关,且可通过结合多个血清生化指标初步判断肝纤维化阶段。     

Innate immunity and intestinal microbiota in the development of Type 1 diabetes

Type 1 diabetes (T1D) is a debilitating autoimmune disease that results from T-cell-mediated destruction of insulin-producing beta-cells. Its incidence has increased during the past several decades in developed countries, suggesting that changes in the environment (including the human microbial environment) may influence disease pathogenesis. The incidence of spontaneous T1D in non-obese diabetic (NOD) mice can be affected by the microbial environment in the animal housing facility or by exposure to microbial stimuli, such as injection with mycobacteria or various microbial products. Here we show that specific pathogen-free NOD mice lacking MyD88 protein (an adaptor for multiple innate immune receptors that recognize microbial stimuli) do not develop T1D. The effect is dependent on commensal microbes because germ-free MyD88-negative NOD mice develop robust diabetes, whereas colonization of these germ-free MyD88-negative NOD mice with a defined microbial consortium (representing bacterial phyla normally present in human gut) attenuates T1D. We also find that MyD88 deficiency changes the composition of the distal gut microbiota, and that exposure to the microbiota of specific pathogen-free MyD88-negative NOD donors attenuates T1D in germ-free NOD recipients. Together, these findings indicate that interaction of the intestinal microbes with the innate immune system is a critical epigenetic factor modifying T1D predisposition.     

p53-induced inhibition of Hif-1 causes cardiac dysfunction during pressure overload

Cardiac hypertrophy occurs as an adaptive response to increased workload to maintain cardiac function. However, prolonged cardiac hypertrophy causes heart failure, and its mechanisms are largely unknown. Here we show that cardiac angiogenesis is crucially involved in the adaptive mechanism of cardiac hypertrophy and that p53 accumulation is essential for the transition from cardiac hypertrophy to heart failure. Pressure overload initially promoted vascular growth in the heart by hypoxia-inducible factor-1 (Hif-1)-dependent induction of angiogenic factors, and inhibition of angiogenesis prevented the development of cardiac hypertrophy and induced systolic dysfunction. Sustained pressure overload induced an accumulation of p53 that inhibited Hif-1 activity and thereby impaired cardiac angiogenesis and systolic function. Conversely, promoting cardiac angiogenesis by introducing angiogenic factors or by inhibiting p53 accumulation developed hypertrophy further and restored cardiac dysfunction under chronic pressure overload. These results indicate that the anti-angiogenic property of p53 may have a crucial function in the transition from cardiac hypertrophy to heart failure.     

基于网络药理学和分子对接研究太子参抗心肌缺血的作用机制

为了探究太子参抗心肌缺血的潜在作用机制,采用网络药理学方法对太子参的活性成分及心肌缺血的相关靶点进行预测,构建太子参抗心肌缺血的关键靶点网络,对其进行基因本体(gene ontology,GO)功能及Pathway富集分析,并将太子参活性成分与关键靶点进行分子对接验证。筛选获得太子参活性成分8个,对应的抗心肌缺血关键靶点50个。GO功能及Pathway富集分析显示：太子参抗心肌缺血主要参与细胞凋亡、血管新生及炎症反应等生物过程,涉及MyD88-independent TLR4 cascade（非依赖MyD88的TLR4信号传导通路）、MyD88:Mal cascade initiated on plasma membrane（MyD88：质膜上启动的MAL级联）及Activated TLR4 signalling（激活的TLR4信号通路）等,其中主要的作用靶点包括JUN、MAPK1、IKBKG、PTPN11、RELA等;分子对接验证蒲公英萜醇与关键靶点AKT1、IL6、MAPK1、TP53的结合性最好。该研究揭示了太子参通过多途径、多靶点抗心肌缺血的作用机制,为进一步研究其抗心肌缺血作用提供了基础。     

The adaptor molecule TIRAP provides signalling specificity for Toll-like receptors

Mammalian Toll-like receptors (TLRs) function as sensors of infection and induce the activation of innate and adaptive immune responses. Upon recognizing conserved pathogen-associated molecular products, TLRs activate host defence responses through their intracellular signalling domain, the Toll/interleukin-1 receptor (TIR) domain, and the downstream adaptor protein MyD88 (refs 1-3). Although members of the TLR and the interleukin-1 (IL-1) receptor families all signal through MyD88, the signalling pathways induced by individual receptors differ. TIRAP, an adaptor protein in the TLR signalling pathway, has been identified and shown to function downstream of TLR4 (refs 4, 5). Here we report the generation of mice deficient in the Tirap gene. TIRAP-deficient mice respond normally to the TLR5, TLR7 and TLR9 ligands, as well as to IL-1 and IL-18, but have defects in cytokine production and in activation of the nuclear factor NF-kappaB and mitogen-activated protein kinases in response to lipopolysaccharide, a ligand for TLR4. In addition, TIRAP-deficient mice are also impaired in their responses to ligands for TLR2, TLR1 and TLR6. Thus, TIRAP is differentially involved in signalling by members of the TLR family and may account for specificity in the downstream signalling of individual TLRs.     

阿托伐他汀对冠心病慢性心力衰竭患者的心功能和预后的影响

目的:观察阿托伐他汀对冠心病慢性充血性心力衰竭患者的心功能和预后的影响.方法:选取2004年1月～2008年6月江汉大学附属医院心内科病区冠心病慢性充血性心力衰竭患者132例,随机分成治疗组(67例)和对照组(65例).两组患者均行冠心病慢性充血性心力衰竭的常规基础治疗.治疗组在常规治疗的基础上,加用阿托伐他汀10mg,每晚一次.总疗程26周.治疗前后检测血脂全套、左室射血分数(LVEF)、C反应蛋白(CRP),观察所有患者治疗后两年的住院次数、住院总日数和病死率.结果:治疗组与对照组比较,治疗6个月后,血清总胆固醇(TC),低密度脂蛋白胆固醇(LDL-C),CRP均有不同程度降低,LVEF明显提高,治疗后两年的住院次数和总日数相对减少,差异无显著性;病死率明显降低,差异有非常显著性(P<0.01).结论:阿托伐他汀治疗能改善冠心病慢性心衰患者的心功能和预后.     

SUMO1-dependent modulation of SERCA2a in heart failure

The calcium-transporting ATPase ATP2A2, also known as SERCA2a, is a critical ATPase responsible for Ca(2+) re-uptake during excitation-contraction coupling. Impaired Ca(2+) uptake resulting from decreased expression and reduced activity of SERCA2a is a hallmark of heart failure. Accordingly, restoration of SERCA2a expression by gene transfer has proved to be effective in improving cardiac function in heart-failure patients, as well as in animal models. The small ubiquitin-related modifier (SUMO) can be conjugated to lysine residues of target proteins, and is involved in many cellular processes. Here we show that SERCA2a is SUMOylated at lysines 480 and 585 and that this SUMOylation is essential for preserving SERCA2a ATPase activity and stability in mouse and human cells. The levels of SUMO1 and the SUMOylation of SERCA2a itself were greatly reduced in failing hearts. SUMO1 restitution by adeno-associated-virus-mediated gene delivery maintained the protein abundance of SERCA2a and markedly improved cardiac function in mice with heart failure. This effect was comparable to SERCA2A gene delivery. Moreover, SUMO1 overexpression in isolated cardiomyocytes augmented contractility and accelerated Ca(2+) decay. Transgene-mediated SUMO1 overexpression rescued cardiac dysfunction induced by pressure overload concomitantly with increased SERCA2a function. By contrast, downregulation of SUMO1 using small hairpin RNA (shRNA) accelerated pressure-overload-induced deterioration of cardiac function and was accompanied by decreased SERCA2a function. However, knockdown of SERCA2a resulted in severe contractile dysfunction both in vitro and in vivo, which was not rescued by overexpression of SUMO1. Taken together, our data show that SUMOylation is a critical post-translational modification that regulates SERCA2a function, and provide a platform for the design of novel therapeutic strategies for heart failure.     

Recognition of double-stranded RNA and activation of NF-kappaB by Toll-like receptor 3

Toll-like receptors (TLRs) are a family of innate immune-recognition receptors that recognize molecular patterns associated with microbial pathogens, and induce antimicrobial immune responses. Double-stranded RNA (dsRNA) is a molecular pattern associated with viral infection, because it is produced by most viruses at some point during their replication. Here we show that mammalian TLR3 recognizes dsRNA, and that activation of the receptor induces the activation of NF-kappaB and the production of type I interferons (IFNs). TLR3-deficient (TLR3-/-) mice showed reduced responses to polyinosine-polycytidylic acid (poly(I:C)), resistance to the lethal effect of poly(I:C) when sensitized with d-galactosamine (d-GalN), and reduced production of inflammatory cytokines. MyD88 is an adaptor protein that is shared by all the known TLRs. When activated by poly(I:C), TLR3 induces cytokine production through a signalling pathway dependent on MyD88. Moreover, poly(I:C) can induce activation of NF-kappaB and mitogen-activated protein (MAP) kinases independently of MyD88, and cause dendritic cells to mature.     

Mal (MyD88-adapter-like) is required for Toll-like receptor-4 signal transduction.

The recognition of microbial pathogens by the innate immune system involves Toll-like receptors (TLRs), which recognize pathogen-associated molecular patterns. Different TLRs recognize different pathogen-associated molecular patterns, with TLR-4 mediating the response to lipopolysaccharide from Gram-negative bacteria. All TLRs have a Toll/IL-1 receptor (TIR) domain, which is responsible for signal transduction. MyD88 is one such protein that contains a TIR domain. It acts as an adapter, being involved in TLR-2, TLR-4 and TLR-9 signalling; however, our understanding of how TLR-4 signals is incomplete. Here we describe a protein, Mal (MyD88-adapter-like), which joins MyD88 as a cytoplasmic TIR-domain-containing protein in the human genome. Mal activates NF-kappaB, Jun amino-terminal kinase and extracellular signal-regulated kinase-1 and -2. Mal can form homodimers and can also form heterodimers with MyD88. Activation of NF-kappaB by Mal requires IRAK-2, but not IRAK, whereas MyD88 requires both IRAKs. Mal associates with IRAK-2 by means of its TIR domain. A dominant negative form of Mal inhibits NF-kappaB, which is activated by TLR-4 or lipopolysaccharide, but it does not inhibit NF-kappaB activation by IL-1RI or IL-18R. Mal associates with TLR-4. Mal is therefore an adapter in TLR-4 signal transduction.     

Oestrogen protects FKBP12.6 null mice from cardiac hypertrophy

FK506 binding proteins 12 and 12.6 (FKBP12 and FKBP12.6) are intracellular receptors for the immunosuppressant drug FK506 (ref. 1). The skeletal muscle ryanodine receptor (RyR1) is isolated as a hetero-oligomer with FKBP12 (ref. 2), whereas the cardiac ryanodine receptor (RyR2) more selectively associates with FKBP12.6 (refs 3, 4, 5). FKBP12 modulates Ca2+ release from the sarcoplasmic reticulum in skeletal muscle and developmental cardiac defects have been reported in FKBP12-deficient mice, but the role of FKBP12.6 in cardiac excitation-contraction coupling remains unclear. Here we show that disruption of the FKBP12.6 gene in mice results in cardiac hypertrophy in male mice, but not in females. Female hearts are normal, despite the fact that male and female knockout mice display similar dysregulation of Ca2+ release, seen as increases in the amplitude and duration of Ca2+ sparks and calcium-induced calcium release gain. Female FKBP12.6-null mice treated with tamoxifen, an oestrogen receptor antagonist, develop cardiac hypertrophy similar to that of male mice. We conclude that FKBP12.6 modulates cardiac excitation-contraction coupling and that oestrogen plays a protective role in the hypertrophic response of the heart to Ca2+ dysregulation.     

血浆N末端脑利钠肽水平和心脏超声功能参数在评估临床心功能分级中的价值研究

目的探讨血浆N末端脑利钠肽(NT-proBNP)水平和心脏超声功能参数在评估临床心功能分级中的价值.方法选取慢性心力衰竭患者106例,入院次日清晨抽取患者空腹肘静脉血,采用酶联免疫法检测血浆NTproBNP水平,并对患者进行纽约心脏病协会(NYHA)心功能分级评定,之后进行心脏彩色多普勒超声检查.结果血浆NT-proBNP水平与心功能分级之间呈明显正相关(P0.01);左心室短轴缩短率、左心射血分数与心功能分级之间呈明显负相关(P0.01);左心室舒张末期内径、左心室收缩末期内径与心功能分级之间呈明显正相关(P0.01);不同心功能分级之间血浆NT-proBNP水平、各心脏超声功能参数均存在明显差异(P0.01);其中,心功能Ⅰ级和Ⅱ级,Ⅲ级和Ⅳ级之间差异均无统计学意义(P0.05),Ⅲ级与Ⅰ级、Ⅱ级,Ⅳ级与Ⅰ级、Ⅱ级之间差异均有显著统计学意义(P0.01);NT-proBNP联合心脏超声检查对不同心功能分级的诊断特异性和敏感性明显高于血浆NT-proBNP水平、心脏超声检查,差异具有统计学意义(P0.05).结论血浆NT-proBNP水平联合心脏超声功能参数能够客观准确地判断慢性心力衰竭患者的心功能情况,有助于指导临床对该类患者的治疗及判断预后.     

Pygo2转基因小鼠模型的建立及表型的初步分析

主要通过建立Pygo2转基因小鼠的模型对其表型进行初步分析.首先构建K14-2×flag-Pygo的转基因构件,经酶切、纯化后构建Pygo2转基因小鼠.出生后的仔鼠用PCR和Western方法检测基因型,并通过进一步的免疫组化验证Pygo2基因的表达.PCR检测获得7只转基因阳性鼠,6只Western检测为阳性.对转基因小鼠子代的胚胎和成体进行免疫组化证明,Pygo2基因在皮肤和乳腺组织中有过量表达.转基因小鼠的皮肤、乳腺以及鼠尾椎骨等组织出现了异常的表型.乳腺中有肿瘤组织的形成,且Pygo2在肿瘤中有大量表达.该模型的成功建立为进一步研究Pygo2的功能奠定了基础.     

Oxidative stress induces angiogenesis by activating TLR2 with novel endogenous ligands

Reciprocity of inflammation, oxidative stress and neovascularization is emerging as an important mechanism underlying numerous processes from tissue healing and remodelling to cancer progression. Whereas the mechanism of hypoxia-driven angiogenesis is well understood, the link between inflammation-induced oxidation and de novo blood vessel growth remains obscure. Here we show that the end products of lipid oxidation, ω-(2-carboxyethyl)pyrrole (CEP) and other related pyrroles, are generated during inflammation and wound healing and accumulate at high levels in ageing tissues in mice and in highly vascularized tumours in both murine and human melanoma. The molecular patterns of carboxyalkylpyrroles are recognized by Toll-like receptor 2 (TLR2), but not TLR4 or scavenger receptors on endothelial cells, leading to an angiogenic response that is independent of vascular endothelial growth factor. CEP promoted angiogenesis in hindlimb ischaemia and wound healing models through MyD88-dependent TLR2 signalling. Neutralization of endogenous carboxyalkylpyrroles impaired wound healing and tissue revascularization and diminished tumour angiogenesis. Both TLR2 and MyD88 are required for CEP-induced stimulation of Rac1 and endothelial migration. Taken together, these findings establish a new function of TLR2 as a sensor of oxidation-associated molecular patterns, providing a key link connecting inflammation, oxidative stress, innate immunity and angiogenesis.     

DNA损伤及氧化应激在放射性心脏损伤中的作用

 放射性心脏损伤（RIHD）是放射诱导的一种进行性加重的疾病,它几乎影响心脏所有结构,从而产生一系列心脏并发症。从早期的无症状到慢性心力衰竭,常需几年至十几年时间。近年来文献报道心脏在正常组织耐受剂量控制下,常规胸部放疗所致的心脏损伤,特别是迟发型心肌损伤问题日益突出。本文综述了DNA损伤及氧化应激在RIHD的发生发展中的作用,现有研究认为RIHD可使心脏僵硬度增加、心肌收缩及舒张功能下降,引起心肌电生理紊乱、心律失常、心功能不全甚至猝死。但目前尚缺乏对RIHD的有效治疗,其根本原因在于对RIHD的原因及发病机制尚未完全阐明。