TLR2、TLR4、TLR5和TLR9在小鼠Hp感染模型中的表达

目的:研究BALB/c小鼠在幽门螺杆菌(Hp)感染前后和用抗生素治疗后胃黏膜组织中Toll样受体(TLR)2、TLR4、TLR5、TLR9、IL-1β的表达,探讨Toll样受体家族在Hp感染机制中的作用。方法:60只BALB/c小鼠随机分为3组,第1组不予处理(正常组),第2组予感染Hp(Hp感染组),第3组感染Hp后予抗生素治疗(抗生素治疗组)。RT-PCR和Western blotting法半定量检测小鼠胃内TLR2、TLR4、TLR5、TLR9、IL-1β的表达,Giemsa染色切片计数Hp定植数量,HE染色切片判断黏膜炎症水平。结果:(1)TLR5、TLR9在各组小鼠胃黏膜组织中均无表达。(2)TLR2在Hp感染组胃黏膜组织中表达(PCR:0.13±0.025;Western:1.32±0.27)高于抗生素治疗组(PCR:0.04±0.011;Western:0.43±0.08),正常组无表达。(3)TLR4在Hp感染组胃黏膜组织中表达(PCR:0.22±0.051;Western:0.72±0.17)高于抗生素治疗组(PCR:0.06±0.009;Western:0.21±0.04),正常组无表达。(4)IL-1β在Hp感染组胃黏膜组织中有表达(PCR:0.27±0.038;Western:0.58±0.14),抗生素治疗组和正常组无表达。结论:TLR2、TLR4可能参与了Hp的致病机制,TLR5、TLR9可能未参与Hp的致病机制。     

慢性阻塞性肺疾病患者外周血单个核细胞中TLR3、TLR7、TLR8及TLR9 mRNA的表达

目的观察慢性阻塞性肺疾病(COPD)患者外周血单个核细胞中TLR3、TLR7、TLR8及TLR9mRNA的表达。方法用密度梯度离心法分离COPD患者和健康人外周血单个核细胞后,提取总RNA并逆转录为cDNA,用实时定量PCR检测TLR3、TLR7、TLR8及TLR9mRNA的拷贝数。结果COPD患者外周血单个核细胞的TLR3和TLR9mRNA表达较正常健康人明显增高(P<0.05),而TLR7和TLR8mRNA的表达在COPD患者和正常健康人之间却无显著差异(P>0.05)。在COPD患者中,急性期和稳定期患者的TLR3、TLR7、TLR8和TLR9无显著差异(P>0.05)。结论TLR3和TLR9的升高可能是COPD患者对病毒敏感性增高的一个重要机制。     

慢性阻塞性肺疾病患者外周血单个核细胞中论著TLR3、TLR7、TLR8及TLR9 mRNA的表达

目的 观察慢性阻塞性肺疾病(COPD)患者外周血单个核细胞中TLR3、TLR7、TLR8及TLR9 mRNA的表达.方法 用密度梯度离心法分离COPD患者和健康人外周血单个核细胞后,提取总RNA并逆转录为cDNA,用实时定量PCR检测TLR3、TLR7、TLR8及TLR9 mRNA的拷贝数.结果 COPD患者外周血单个核细胞的TLR3和TLR9 mRNA表达较正常健康人明显增高(P＜0.05),而TLR7和TLR8 mRNA的表达在COPD患者和正常健康人之间却无显著差异(P＞0.05).在COPD患者中,急性期和稳定期患者的TLR3、TLR7、TLR8和TLR9无显著差异(P＞0.05). 结论TLR3和TLR9的升高可能是COPD患者对病毒敏感性增高的一个重要机制.     

Dectin-1和TLR2/TLR3/TLR4受体在免疫缺陷小鼠侵袭性肺曲霉菌病的表达

目的本研究利用小鼠动物模型,探讨烟曲霉感染免疫缺陷小鼠TLR2/TLR3/TLR4对树突状细胞植物血凝素-1(Dectin-1)表达的影响。通过检测TLRs和CLRs受体在不同免疫状态下的表达,揭示介导侵袭性肺曲霉菌病(IPA)肺损伤的关键受体。方法小鼠随机分成四组,A组为正常对照组;B组为环磷酰胺免疫抑制+未接种烟曲霉菌;C组正常状态小鼠+烟曲霉菌接种;D组为IPA感染组,免疫抑制+烟曲霉菌接种。采用real-time PCR方法进行小鼠肺组织各个时相点的TLR2、TLR3、TLR4、Dectin-1和β-actin m RNA的表达,检测受体间的相互表达调控。结果正常状态感染组(C组N+AF),TLR4/TLR2、Dectin-1 m RNA比正常对照组表达上调;IPA模型组(D组CP+AF),Dectin-1和TLR4、TLR2 m RNA比正常状态感染组表达下调;但TLR3 m RNA 48 h、72 h表达没有明显不同(P>0.05)。病理切片模型组小鼠72 h可见较严重的出血和充血;96 h时肺内有菌丝,肺泡间隔增宽,支气管壁破坏。正常状态感染烟曲霉小鼠72 h可见充血,肺泡弹性纤维破坏。结论成功建立了小鼠IPA动物模型,Dectin-1受体表达下调可能是环磷酰胺免疫抑制引起IPA的机制之一。Dectin-1的表达可能是建立在TLR2/TLR4对烟曲霉早期识别的基础上,TLR3可能起协同作用。     

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.     

TLR4 signaling induces TLR2 expression in endothelial cells via neutrophil NADPH oxidase

Interactions of polymorphonuclear neutrophils (PMNs) with endothelial cells may contribute to the activation of endothelial cell responses involved in innate immunity. We explored a novel function of PMN NADPH oxidase in the mechanism of Toll-like receptor-2 (TLR2) upregulation induced by LPS-TLR4 signaling in endothelial cells. We showed that LPS induced TLR2 up-regulation through TLR4- and MyD88-dependent signaling. In neutropenic mice, the LPS-induced NF-kB activation and TLR2 expression were significantly reduced, and both responses were restored upon repletion by PMN obtained from WT mice but not by PMNs from NADPH oxidase gp91pho(-/-) mice. These findings were recapitulated in mouse lung vascular endothelial cells cocultured with PMNs, indicating that the augmented NF-kB activation and the resultant TLR2 upregulation in endothelial cells were secondary to oxidant signaling generated by PMN NADPH oxidase. The functional relevance of NADPH oxidase in mediating TLR4-induced TLR2 expression in endothelial cells was evident by markedly elevated and stable ICAM-1 expression as well as augmented PMN migration in response to sequential challenge with LPS and peptidoglycan. Thus, PMN NADPH oxidase-derived oxidant signaling is an important determinant of the cross talk between TLR4 and TLR2 and the control of endothelial cell activation.     

TLR4-induced IFN-gamma production increases TLR2 sensitivity and drives Gram-negative sepsis in mice

Gram-negative bacterial infection is a major cause of sepsis and septic shock. An important inducer of inflammation underlying both syndromes is the cellular recognition of bacterial products through pattern recognition receptors (PRRs), including Toll-like receptors (TLRs). We identified a novel antagonistic mAb (named 1A6) that recognizes the extracellular portion of the TLR4–MD-2 complex. If applied to mice before infection with clinical isolates of Salmonella enterica or Escherichia coli and subsequent antibiotic therapy, 1A6 prevented otherwise fatal shock, whereas application of 1A6 after infection was ineffective. In contrast, coapplication of 1A6 and an anti-TLR2 mAb up to 4 h after infection with Gram-negative bacteria, in combination with the start of antibiotic therapy (mimicking clinical conditions), provided robust protection. Consistent with our findings in mice, dual blockade of TLR2 and TLR4 inhibited TNF-α release from human peripheral blood mononuclear cells upon Gram-negative bacterial infection/antibiotic therapy. Both murine splenocytes and human PBMCs released IFN-γ in a TLR4-dependent manner, leading to enhanced surface TLR2 expression and sensitivity for TLR2 ligands. Our results implicate TLR2 as an important, TLR4-driven sensor of Gram-negative bacterial infection and provide a rationale for blockade of both TLRs, in addition to antibiotic therapy for the treatment of Gram-negative bacterial infection.     

Osteoclastogenesis through TLR/NOD signaling

Lipopolysaccharide (LPS) and muramyl dipeptide (MDP) are components of microbial cell walls that cause innate immune responses and inflammation. Toll-like receptor 4 (TLR4) is a receptor for LPS and transduces signals through myeloid differentiation factor 88 (MyD88), which plays essential roles in the TLR/IL-1R signaling and activates NF-kappaB and MAP kinase pathways to induce RANKL expression in osteoblasts. Osteoblasts express NOD2, an intracellular sensor for MDP, in response to LPS, IL-1 and TNF. NOD2 binds RIP2, a serine/threonine kinase which transduces NF-kappaB signaling. Thus MDP synergistically enhances osteoclast formation induced by LPS, IL-1 and TNF through RANK ligand up-regulation in osteoblasts. In summary, innate immune receptors, TLR4 and NOD2, recognize bacterial components on cell surfaces and inside cells, respectively, and these signals cross-talk to induce RANKL expression in osteoblasts, which results in enhancing osteoclast formation and function.     

TLR2和TLR4激动剂对人脐血CD34+细胞迁移能力的影响

本研究旨在探讨Toll样受体2(Toll-like receptors 2,TLR2)和TLR4激动剂对人脐血CD34+细胞迁移功能的影响及其机制.采用流式细胞术检测脐血CD34+细胞表面TLR2和TLR4的表达情况;用趋化实验和黏附实验观察PAM3CSK4(TLR2激动剂)和LPS(TLR4激动剂)对人脐血CD34+细胞的迁移活性和黏附活性的影响.结果表明:人脐血CD34+细胞表面表达TLR2(14.2±3.8)%和TLR4(19.6±4.1)%.与对照组相比,LPS可明显抑制SDF-1诱导的CD34+细胞的趋化作用(p<0.01),但LPS对CD34+细胞的黏附能力,以及PAM3CSK4对CD34+细胞的趋化和黏附能力均无明显影响.进一步研究显示,LPS对CD34+细胞表面CXCR4的表达无明显影响,但可明显抑制CD34+细胞的自发迁移作用(p<0.05).结论:TLR4的活化可显著降低SDF-1诱导CD34+细胞的趋化功能,这可能与其抑制CD34+细胞的自发迁移作用具有一定的关系.     

TLR2 和 TLR4 激动剂对人骨髓来源的间充质干细胞迁移能力的影响简

本研究探讨Toll样受体2（Toll-like receptors2,TLR2）和TLR4激动剂对人骨髓来源的间充质干细胞（mesenchymal stem cells,MSC）迁移能力的影响及其机制.采用流式细胞术检测MSC表面TLR2和TLR4的表达情况,应用趋化实验和黏附实验观察PAM3CSK4（TLR2激动剂）和LPS（TLR4激动剂）对人骨髓来源的MSC的趋化活性和黏附活性的影响.结果表明,人骨髓来源的MSC表面表达TLR2 （24.5±3.2）％和TLR4（91.3±5.2）％.与对照组相比,PAM3CSK4可明显抑制SDF-1诱导的MSC的趋化作用,并增强MSC的黏附作用;而LPS对MSC的趋化和黏附能力均无明显影响.进一步研究显示,PAM3CSK4可呈剂量依赖性抑制MSC的自发迁移作用,但对MSC表面CXCR4的表达无明显影响.结论：TLR2的活化可显著抑制MSC的迁移能力,这可能与其抑制MSC的自发迁移和增强MSC的黏附作用具有一定的关系.     

Increased Toll-Like Receptor (TLR) Activation and TLR Ligands in Recently Diagnosed Type 2 Diabetic Subjects

OBJECTIVE

Individuals with type 2 diabetes have a myriad of metabolic aberrations including increased inflammation, increasing their cardiovascular risk. Toll-like receptors (TLRs) and their ligands play a key role in insulin resistance and atherosclerosis. However, there is a paucity of data examining the expression and activity of TLRs in type 2 diabetes. Thus, in the present study, we examined TLR2 and TLR4 mRNA and protein expression, their ligands, and signaling in monocytes of recently diagnosed type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

TLR mRNA, protein expression, TLR ligands, and TLR signaling were measured in freshly isolated monocytes from healthy human control subjects (n = 23) and type 2 diabetic subjects (n = 23) using real-time RT-PCR, Western blot, and flow cytometric assays.

RESULTS

Type 2 diabetic subjects had significantly increased TLR2, TLR4 mRNA, and protein in monocytes compared with control subjects (P < 0.05). Increased TLR2 and TLR4 expression correlated with BMI, homeostasis model assessment–insulin resistance (HOMA-IR), glucose, A1C, N^ε-(carboxymethyl) lysine (CML), and free fatty acid (FFA). Ligands of TLR2 and TLR4, namely, HSP60, HSP70, HMGB1, endotoxin, and hyaluronan levels, were elevated in type 2 diabetic subjects and positively correlated with TLR2 and TLR4. Type 2 diabetic subjects showed increased MyD88, phosphorylated IRAK-1, Trif, TICAM-1, IRF-3, and NF-κB p65 expression in monocytes compared with control subjects. Furthermore, TLR-MyD88-NF-κB signaling resulted in elevated levels of cytokines (P < 0.05), but increased interleukin (IL)-1β, interferon (IFN)-γ, and endotoxin were not significant when adjusted for BMI.

CONCLUSIONS

In this comprehensive study, we make the novel observation that TLR2 and TLR4 expression and their ligands, signaling, and functional activation are increased in recently diagnosed type 2 diabetes and contribute to the proinflammatory state.Type 2 diabetes constitutes a group of metabolic aberrations including hyperglycemia, inflammation, and insulin resistance that increase the risk of cardiovascular disease (1). The mechanisms by which these metabolic abnormalities cause cardiovascular disease are not clear. Considerable evidence indicates that the harmful effects of elevated glucose are mediated by receptors leading to increased inflammation and oxidative stress (2,3). Recent studies demonstrating associations between elevated levels of circulating C-reactive protein, proinflammatory cytokines, and homeostasis model assessment–insulin resistance (HOMA-IR) suggest that inflammation is an important etiological factor in the development of both insulin resistance and type 2 diabetes (4). Moreover, inflammatory markers link the pathology of insulin resistance and type 2 diabetes. Activation of the innate immune system via toll-like receptors (TLRs) is implicated in the pathogenesis of insulin resistance, diabetes, and atherosclerosis (5–7). Complimentary genetic studies link TLR2 and TLR4 polymorphisms to type 2 diabetes, suggesting a casual relationship between TLR function and diabetes and its complications (8).TLRs are evolutionarily preserved pattern-recognition receptors (9), expressed on several cell types including monocytes, predominant cells of the innate immune system that are pivotal in diabetes and atherogenesis (10). TLRs play an important role in the activation and regulation of the innate immune system and inflammation (9). Each TLR family member recognizes a specific pathogen component, upon activation, triggers a signaling cascade leading to cytokine production and adaptive immune response (9). Among the TLRs, TLR2 and TLR4 play a critical role in the pathogenesis of insulin resistance, diabetes, and atherosclerosis in both clinical and experimental conditions (5–7,11). Ligands for TLR2 and TLR4 include high-mobility group B1 protein (HMGB1), heat shock protein (HSP) 60, HSP70, endotoxin, hyaluronan, advanced glycation end products, and extracellular matrix components (12). TLR2 and TLR4 bind to components of the gram-positive and -negative bacteria, respectively (12). TLR2 has broad ligand recognition specificity because of its ability to form heterodimers with TLR1, TLR6, and sometimes with CD14 and CD36 (13). TLR4 does not recognize endotoxin without the cofactor MD-2 (14). Collectively, these ligands and cofactors markedly increase TLR functionality and have not been studied in type 2 diabetes.TLR2 and TLR4 expression have been shown to be increased in conventional insulin resistance target tissues like skeletal muscle and adipose tissue of type 2 diabetic subjects (15,16). These important studies implicating TLRs in type 2 diabetes were derived using small sample size, and the association with respective TLR2/TLR4 ligands, cofactors, downstream signaling, and functional activation remains to be properly addressed. Moreover, systemic inflammation plays a significant role in the etiology and comorbidities of type 2 diabetes, and the role of TLR2 and TLR4 in this setting is not clear. Experimental evidence in mice demonstrates that TLR2 and TLR4 activation and downstream cytokine production lead to the development of diabetes (17,18). More recently, TLR4 has been indicated as a molecular link between free fatty acids (FFAs), inflammation, and the innate immune system (5). Also, Song et al. (19) reported increased TLR4 mRNA expression in differentiating adipose tissue of db/db mice.While these important observations from animal and human tissue data suggest a role for TLR2 and TLR4 in type 2 diabetes, it remains unknown whether alterations in TLR2 and TLR4 pathway activation contribute to systemic inflammation in diabetic human subjects. Therefore, the purpose of this study was to undertake a comprehensive analysis of TLR2 and TLR4 activation, ligands, cofactors, and downstream signaling in monocytes isolated from recently diagnosed patients with type 2 diabetes and matched control subjects.     

甲氨蝶呤对寻常型银屑病外周血TLR4及TLR9表达调控的研究

目的:研究甲氨蝶呤(MTX)对寻常型银屑病患者外周血Tol1样受体(TLR)4和TLR9表达的影响。方法:利用荧光定量聚合酶链反应法测定22例寻常型银屑病患者治疗前后外周血及20例正常对照者外周血中TLR4mRNA及TLR9mRNA的定量表达。结果:银屑病外周血中TLR4mRNA及TLR9mRNA的表达均高于正常对照者外周血的表达水平(t=11.26,P<0.001;t=8.39,P<0.001)。银屑病患者经过MTX治疗4w后,病情明显改善,外周血中TLR4mRNA及TLR9mRNA的表达水平低于患者治疗前的表达水平(t=3.49,P=0.0015;t=7.75,P<0.001),但与正常对照者的表达水平差异无统计学意义(t=1.76,P=0.0925;t=1.38,P=0.1741)。结论:TLR4及TLR9的表达增高与银屑病的发病有关。MTX能抑制寻常型银屑病外周血TLR4mRNA及TLR9mRNA的过度表达,这可能是MTX治疗银屑病的作用机制之一。     

TLR9 regulates Th1 responses and cooperates with TLR2 in mediating optimal resistance to Mycobacterium tuberculosis

To investigate the role of Toll-like receptor (TLR)9 in the immune response to mycobacteria as well as its cooperation with TLR2, a receptor known to be triggered by several major mycobacterial ligands, we analyzed the resistance of TLR9(-/-) as well as TLR2/9 double knockout mice to aerosol infection with Mycobacterium tuberculosis. Infected TLR9(-/-) but not TLR2(-/-) mice displayed defective mycobacteria-induced interleukin (IL)-12p40 and interferon (IFN)-gamma responses in vivo, but in common with TLR2(-/-) animals, the TLR9(-/-) mice exhibited only minor reductions in acute resistance to low dose pathogen challenge. When compared with either of the single TLR-deficient animals, TLR2/9(-/-) mice displayed markedly enhanced susceptibility to infection in association with combined defects in proinflammatory cytokine production in vitro, IFN-gamma recall responses ex vivo, and altered pulmonary pathology. Cooperation between TLR9 and TLR2 was also evident at the level of the in vitro response to live M. tuberculosis, where dendritic cells and macrophages from TLR2/9(-/-) mice exhibited a greater defect in IL-12 response than the equivalent cell populations from single TLR9-deficient animals. These findings reveal a previously unappreciated role for TLR9 in the host response to M. tuberculosis and illustrate TLR collaboration in host resistance to a major human pathogen.     

TLR signaling pathway in patients with sepsis

The pathogenesis of sepsis involves complex interaction between the host and the infecting microorganism. Bacterial recognition and signaling are essential functions of the cells of innate immune systems and drive a coordinated immune response. One of the more intriguing aspects of sepsis is the fact that the protective and damaging host response are part of the same process, that is, the inflammatory response that is aimed to control the infectious process also underscores many of the pathophysiological events of sepsis. The discovery of Toll-like receptors (TLRs) in humans, and the early recognition of TLR-4 as the receptor that signals LPS bioactivity were major breakthroughs not only in the field of sepsis but also in immunology as a whole. In this article, we aimed to review TLR expression and signaling in the context of sepsis. The results obtained by our group show that TLR and other cellular surface receptors may be differently regulated on mononuclear cells and neutrophils, and that they are dynamically modulated across the stages of sepsis. Toll-like receptor signaling gene expression in mononuclear cells is decreased in more severe forms of the disease. In contrast, up-regulated genes are seen along the clinical spectrum of sepsis in neutrophils.