Toll-like receptors: Significance,ligands, signaling pathways,and functions in mammals

This review attempts to cover the implication of the toll-like receptors (TLRs) in controlling immune functions with emphasis on their significance, function, regulation and expression patterns. The tripartite TLRs are type I integral transmembrane receptors that are involved in recognition and conveying of pathogens to the immune system. These paralogs are located on cell surfaces or within endosomes. The TLRs are found to be functionally involved in the recognition of self and non-self-antigens, maturation of DCs and initiation of antigen-specific adaptive immune responses as they bridge the innate and adaptive immunity. Interestingly, they also have a significant role in immunotherapy and vaccination. Signals generated by TLRs are transduced through NFκB signaling and MAP kinases pathway to recruit pro-inflammatory cytokines and co-stimulatory molecules, which promote inflammatory responses. The excess production of these cytokines leads to grave systemic disorders like tumor growth and autoimmune disorders. Hence, regulation of the TLR signaling pathway is necessary to keep the host system safe. Many molecules like LPS, SOCS1, IRAK1, NFκB, and TRAF3 are involved in modulating the TLR pathways to induce appropriate response. Though quantification of these TLRs helps in correlating the magnitude of immune response exhibited by the animal, there are several internal, external, genetic and animal factors that affect their expression patterns. So it can be concluded that any identification based on those expression profiles may lead to improper diagnosis during certain conditions.     

Genetic polymorphisms in the Toll-like receptor signalling pathway in Helicobacter pylori infection and related gastric cancer

Background

Gastric cancer (GC) is a progressive process initiated by Helicobacter pylori-induced inflammation. Initial recognition of H. pylori involves Toll-like receptors (TLRs), central molecules in the host inflammatory response. Here, we investigated the association between novel polymorphisms in genes involved in the TLR signalling pathway, including TLR2, TLR4, LBP, MD-2, CD14 and TIRAP, and risk of H. pylori infection and related GC.

Methods

A case-control study comprising 310 ethnic Chinese individuals (87 non-cardia GC cases and 223 controls with functional dyspepsia) was conducted. Twenty-five polymorphisms were detected by MALDI-TOF mass spectrometry, PCR, PCR–RFLP and real-time PCR.

Results

Seven polymorphisms showed significant associations with GC (TLR4 rs11536889, TLR4 rs10759931, TLR4 rs1927911, TLR4 rs10116253, TLR4 rs10759932, TLR4 rs2149356 and CD14 −260 C/T). In multivariate analyses, TLR4 rs11536889 remained a risk factor for GC (OR: 3.58, 95% CI: 1.20–10.65). TLR4 rs10759932 decreased the risk of H. pylori infection (OR: 0.59, 95% CI: 0.41–0.86). Statistical analyses assessing the joint effect of H. pylori infection and the selected polymorphisms revealed strong associations with GC (TLR2, TLR4, MD-2, LBP and TIRAP polymorphisms).

Conclusions

Novel polymorphisms in TLR2, TLR4, MD-2, LBP, CD14 and TIRAP, genes encoding important molecules of the TLR signalling pathway, showed clear associations with H. pylori-related GC in Chinese.     

Total expression of HLA-G and TLR-9 in chronic lymphocytic leukemia patients

Suppressed immune status facilitates immune escape mechanisms that allow chronic lymphocytic leukemia cells to proliferate and expand. The expression of HLA-G could effectively inhibit the immune response. In immune response inhibitory signals follow activation of immune system which might be occur during bacterial or viral infection in CLL patients. In the current study we characterized two components of immune system, inhibitory molecule HLA-G with its receptor – CD85j and Toll-like receptor 9.     

Bacterial components regulate the expression of Toll-like receptor 4 on human mast cells

Objectives and design: The aim of this study was to investigate whether the exposure of mast cells (MCs) to bacterial components affects the expression of Toll-like receptor (TLR) 4, and to elucidate the behavior of MCs during the early response to infection. Materials: Two human MC lines, HMC-1 and LAD2, were employed. Messenger RNA expression was observed by RT and real-time PCR. TLR4 expression was determined by Western blotting. TNF-α secretion was analyzed with ELISA. The degranulation ratio was measured with betahexosaminidase assay. Results: Although bacterial components increased TLR4 mRNA, only lipopolysaccharide (LPS) augmented the TLR4 protein expression. LAD2 pre-treated with LPS for 8 h resulted in 2-fold increased TNF-α secretion on LPS restimulation. Conclusion: These results suggest that the exposure of MCs to LPS may reinforce the innate immune system due to up-regulation of MC TLR4, followed by increased TNF-α release. Received 20 April 2006; returned for revision 14 July 2006; accepted by G. Wallace 11 August 2006     

Theiler's virus infection induces TLR3‐dependent upregulation of TLR2 critical for proinflammatory cytokine production

Theiler's murine encephalomyelitis virus (TMEV) infection directly induces many proinflammatory genes, including type I interferon (IFN) and a variety of cytokine genes. These virus‐induced cytokines are a critical factor in developing TMEV‐induced demyelinating disease. We have previously reported that the major activation signal for the cytokine genes is mediated via TLR3. In this study, we describe that TLR2 is upregulated via TLR3 signal and cooperatively participates in the expression of IL‐6, IL‐1β, CCL2, and CCL5 genes following TMEV infection. The expression of these genes was significantly impaired in both TLR2‐deficient and TLR3‐deficient primary astrocytes. However, the induction of type I IFNs was not affected by TLR2 deficiency in the primary cells. TMEV infection led to TLR2‐mediated NF‐κB activation, but not IRF3 or IRF7 activation, critical for type I IFN production. More importantly, TLR3 was required for TMEV‐induced early TLR2 upregulation in primary astrocytes leading to the production of TLR2‐dependent cytokines such as IL‐6. Interestingly, soluble factor(s) produced via TLR2/3‐dependent signals appears to be partially associated with the downstream cytokine production. These results indicate that TMEV utilizes TLR3‐induced TLR2 to induce inflammatory cytokines, which are critical to the development of immune‐mediated demyelinating disease. © 2009 Wiley‐Liss, Inc.     

脂多糖刺激树突状细胞前后TLR2、3、4基因表达的检测

目的 检测脂多糖作用于树突状细胞前后TLR2、3、4基因的表达情况。方法 从外周血分离单核细胞，加入rhGM-CSF及rhIL-4，培养的第6天，实验组加入脂多糖刺激24h，对照组不加。分别提取细胞总RNA，行半定量RT-PCR，产物进行琼脂糖凝胶电泳分析。结果 单核细胞经GM-CSF及IL-4诱导7d后的DC表达较高水平TLR2、3、4。脂多糖刺激24h后，TLR2、3、4表达下降，TLR4几乎测不到。结论 树突状细胞在受脂多糖刺激前后TLRs的表达有显著变化，推测和它的功能成熟有关。     

ProtEx technology for the generation of novel therapeutic cancer vaccines

Therapeutic vaccines present an attractive alternative to conventional treatments for cancer. However, tumors have evolved various immune evasion mechanisms to modulate innate, adaptive, and regulatory immunity for survival. Therefore, successful vaccine formulations may require a non-toxic immunomodulator or adjuvant that not only induces/stimulates innate and adaptive tumor-specific immune responses, but also overcomes immune evasion mechanisms. Given the paramount role costimulation plays in modulating innate, adaptive, and regulatory immune responses, costimulatory ligands may serve as effective immunomodulating components of therapeutic cancer vaccines. Our laboratory has developed a novel technology designated as ProtEx^™ that allows for the generation of recombinant costimulatory ligands with potent immunomodulatory activities and the display of these molecules on the cell surface in a rapid and efficient manner as a practical and safe alternative to gene therapy for immunomodulation. Importantly, the costimulatory ligands not only function when displayed on tumor cells, but also as soluble proteins that can be used as immunomodulatory components of conventional vaccine formulations containing tumor-associated antigens (TAAs). We herein discuss the application of the ProtEx^™ technology to the development of effective cell-based as well as cell-free conventional therapeutic cancer vaccines.     

Cover Image,Volume 80, Issue 3

Primary dysmenorrhea affects the quality of life in young women, particularly school and work performance. This study investigated the mechanisms of penehyclidine hydrochloride (PHC) efficacy on a rat model of primary dysmenorrhea. The model was induced by injecting both estradiol benzoate and oxytocin. Different doses of PHC were administrated intraperitoneally following estradiol benzoate administration. Writhing scores were assessed, and pathological changes of the uterus were observed via hematoxylin and eosin staining. Western blot and real-time PCR were used to evaluate the expression level of the M₃ receptor, both TLR₃ and TLR₄ in uterine tissue, and the level of Ca²⁺ was measured in uterine tissues. Writhing scores significantly decreased in the PHC treatment group compared to model, and PHC alleviated the occurrence of edema or necrosis in the uteri compared to model group. PHC can decrease the M₃ receptor, TLR₃, TLR₄ expression, and the Ca²⁺ level compared to the model group. PHC is a potential candidate for the future treatment of primary dysmenorrhea due to its ability to attenuate muscarinic receptors and TLRs.

Visfatin as a therapeutic target for rheumatoid arthritis

Introduction: The rising prevalence of musculoskeletal pathologies in developed countries has caused a dramatic impact on social welfare. Amidst these musculoskeletal pathologies is Rheumatoid arthritis (RA), a chronic systemic autoimmune disease that mostly affects the synovium. RA metabolic-associated alterations, including distorted adipokine production, enhance RA inflammatory environment. Among the altered adipokines, visfatin is particularly involved in RA inflammation and catabolism and stands out as an essential enzyme linked to critical cell features.

Areas covered: We discuss the potential mechanism supporting the contribution of visfatin to RA and the association between RA and obesity. We discuss the repurposing of cancer-tested drugs to inhibit visfatin in the context of RA. Additionally, we address the possibility of combining these drugs with current RA therapy. Finally, we explore the future of visfatin as an RA biomarker or therapeutic target.

Expert opinion: Inhibition of visfatin has become an interesting therapeutic approach for RA pathology. Such a feat has already been attained in oncology using small molecule inhibitors, which suggest that a similar course of action would be worth pursuing in the RA context. Visfatin will become an important biomarker and therapeutic target for RA.     

Toll样受体和其他分子识别受体在固有免疫中的相互作用

Toll样受体（Toll-like receptors,TLRs）是参与非特异性免疫（天然免疫）的一类重要蛋白分子,也是连接非特异性免疫和特异性免疫的桥梁。TLRs是一类单次跨膜非催化性的蛋白,可以识别来源于微生物上具有保守结构的分子。当微生物突破机体的物理屏障,如皮肤、黏膜等时,TLRs可以通过识别这些微生物来激活机体的免疫应答反应。除此之外,机体还具有一些其他类型的分子识别模式受体,包括C型凝集素样受体、NOD样受体、视黄酸诱导基因Ⅰ样受体。这些受体都参与了机体免疫调节,它们之间相互作用,使之形成一张极为复杂而精密的网络体系。该综述主要阐明TLRs在机体免疫调节中的作用及其与其他分子识别受体在对病原体识别过程中的交叉相互作用。