• Toxicological Research
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• v.23 no.2
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• pp.97-105
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• 2007

Toll-like receptors (TLRs) playa crucial role in initiating and regulating innate and adaptive immune responses by detecting invading microbial pathogens. TLRs can also respond to non-microbial molecules derived from damaged tissue. Accumulating evidence suggests that deregulation of TLRs results in the dysfunction of immune system and ultimately increases the risk of many immune and inflammatory diseases including infectious diseases, allergy, and autoimmune diseases. Therefore, understanding how the immune system is controlled by TLRs will provide new insight to find the way to prevent or treat infectious diseases and immune disorders.

• Journal of Microbiology and Biotechnology
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• v.26 no.12
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• pp.2214-2223
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• 2016

Toll-like receptors (TLRs) can recognize conserved molecular patterns and initiate a wide range of innate and adaptive immune responses against invading infectious agents. The aim of this study was to assess the transcript profile of mink TLRs (mTLRs) in mink peripheral blood mononuclear cells (PBMCs) and a range of tissues, and to explore the potential role of mTLRs in the antiviral immune response process. The results indicated that the mTLR partial nucleotide sequences had a high degree of nucleotide identity with ferret sequences (95-98%). Phylogenetic analysis showed that mammalian TLRs grouped into five TLR families, with a closer relationship of the mTLRs with those of ferret than the other mammalian sequences. Moreover, all the mTLRs were ubiquitously expressed in lymphoid organs (spleen and lymph nodes) and PBMCs. Interestingly, the mTLR expression patterns in lung, uterus, and heart showed quite a lot of similarity. Another remarkable observation was the wide expression of mTLR1-3 mRNAs in all tissues. Among the analyzed tissues, skeletal muscle was revealed to being the lowest repertoire of mTLR expression. Additionally, mink PBMCs exposed to the canine distemper virus revealed significant upregulation of mTLR2, mTLR4, mTLR7, and mTLR8 mRNAs, indicating that mTLRs have a role in innate immunity in the mink. Collectively, our results are the first to establish the basic expression patterns of mTLRs and the relationship between mTLRs and a virus, which will contribute to better understanding of the evolution and the functions of mTLRs in the innate immune system in minks.

• Clinical and Experimental Pediatrics
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• v.53 no.12
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• pp.985-988
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• 2010

The innate immune response is the first line of defense against microbial infections. Innate immunity is made up of the surface barrier, cellular immunity and humoral immunity. In newborn, immunologic function and demands are different to adults. Neonatal innate immunity specifically suppresses Th1-type immune responses, and not Th2-type immune responses, which are enhanced. And the impaired response of macrophages is associated with the defective innate immunity in newborn period. Toll-like receptors (TLRs) play a key roles in the detection of invading pathogens and in the induction of innate immune responses. In newborn, the expression of TLRs is age dependent, so preterm has low expression of TLRs. Also, there are defects in signaling pathways downstream of TLRs. As a consequence, the defects of TLRs activity cause the susceptibility to infection in the neonatal period.

• Biomedical Science Letters
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• v.18 no.3
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• pp.181-192
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• 2012

Toll-like receptors (TLRs) induce innate immune responses that are essential for host defense against invading microbial pathogens. In general, TLRs have two major downstream signaling pathways; myeloid differential factor 88 (MyD88) and Toll/IL-1R domain-containing adaptor inducing IFN-${\beta}$ (TRIF) leading to the activation of NF-${\kappa}B$ and IRF3. Numerous studies demonstrated that certain phytochemicals possessing anti-inflammatory effects inhibit NF-${\kappa}B$ activation induced by pro-inflammatory stimuli including lipopolysaccharide and tumor necrosis factor-${\alpha}$ ($TNF{\alpha}$). However, the direct molecular targets for such anti-inflammatory phytochemicals are not fully identified. In this paper, we will discuss about the molecular targets of phytochemicals in TLRs signaling pathways. These results present a novel anti-inflammatory mechanism of phytochemicals in TLRs signaling.

• BMB Reports
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• v.44 no.7
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• pp.468-472
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• 2011

Toll-like receptors (TLRs) are pattern recognition receptors that recognize molecular structures derived from microbes and initiate innate immunity. TLRs have two downstream signaling pathways, the MyD88- and TRIF-dependent pathways. Dysregulated activation of TLRs is closely linked to increased risk of many chronic diseases. Previously, we synthesized fumaryl pyrrolidinone, (E)-isopropyl 4-oxo-4-(2-oxopyrrolidin-1-yl)-2-butenoate (IPOP), which contains a fumaric acid isopropyl ester and pyrrolidinone, and demonstrated that it inhibits the activation of nuclear factor kappa B by inhibiting the MyD88-dependent pathway of TLRs. However, the effect of IPOP on the TRIF-dependent pathway remains unknown. Here, we report the effect of IPOP on signal transduction via the TRIF-dependent pathway of TLRs. IPOP inhibited lipopolysaccharide- or polyinosinic-polycytidylic acidinduced interferon regulatory factor 3 activation, as well as interferon-inducible genes such as interferon inducible protein-10. These results suggest that IPOP can modulate the TRIF-dependent signaling pathway of TLRs, leading to decreased inflammatory gene expression.

• Molecules and Cells
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• v.38 no.1
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• pp.26-32
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• 2015

Toll-like receptors (TLR) 7 and 9 transduce a cellular signal through the MyD88-dependent pathway and induce the production of inflammatory mediators against microbial nucleotide components. The repeated stimulation of TLR4 leads to endotoxin tolerance, but the molecular mechanisms of tolerance induced through the costimulation of individual TLR has not yet been established, although endosomal TLRs share signaling pathways with TLR4. In the present study, mouse macrophages were simultaneously stimulated with the TLR7 agonist, gardiquimod (GDQ), and the TLR9 agonist, CpG ODN 1826, to examine the mechanism and effector functions of macrophage tolerance. Compared with individual stimulation, the costimulation of both TLRs reduced the secretion of TNF-${\alpha}$ and IL-6 through the delayed activation of the NF-${\kappa}B$ pathway; notably, IL-10 remained unchanged in costimulated macrophages. This tolerance reflected the early induction of suppressor of cytokine signaling-1 (SOCS-1), according to the detection of elevated TNF-${\alpha}$ secretion and restored NF-${\kappa}B$ signaling in response to the siRNA-mediated abrogation of SOCS-1 signaling. In addition, the restimulation of each TLRs using the same ligand significantly reduced the expression of both TLRs in endosomes. These findings revealed that the costimulation of TLR7 and TLR9 induced macrophage tolerance via SOCS-1, and the restimulation of each receptor or both TLR7 and TLR9 downregulated TLR expression through a negative feedback mechanisms that protects the host from excessive inflammatory responses. Moreover, the insufficient and impaired immune response in chronic viral infection might also reflect the repeated and simultaneous stimulation of those endosomal TLRs.

• Molecular & Cellular Toxicology
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• v.5 no.2
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• pp.141-146
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• 2009

Toll-like receptors (TLRs) induce innate immune responses by recognizing conserved microbial structural molecules. All TLR signaling pathways culminate in the activation of nuclear factor kappa-B (NF-$\kappa$B) leading to the induction of inflammatory gene products such as cyclooxygenase-2 (COX-2). Deregulated activation of TLRs can lead to the development of severe systemic inflammation. Divalent heavy metals, cadmium and mercury, have been used for thousands of years. While cadmium and mercury are clearly toxic to most mammalian organ systems, especially the immune system, their underlying toxic mechanism(s) remain unclear. Here, we report biochemical evidence that cadmium, but not mercury, inhibits NF-$\kappa$B activation and COX-2 expression induced by TLR2 or TLR4 agonists, while cadmium does not inhibit NF-$\kappa$B activation induced by the downstream signaling component of TLRs, MyD88. Thus, the target of cadmium to inhibit NF-$\kappa$B activation may be upstream of MyD88 including TLRs themselves, or events leading to TLR activation by agonists.

• Molecules and Cells
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• v.28 no.4
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• pp.365-368
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• 2009

Toll-like receptors (TLRs) play an important role in host defense by sensing invading microbial pathogens and initiating innate immune responses. The stimulation of TLRs by microbial components triggers the activation of myeloid differential factor 88 (MyD88)- and toll-interleukin-1 receptor domain-containing adapter inducing interferon-${\beta}$ (TRIF)-dependent downstream signaling pathways. Isoliquiritigenin (ILG), an active ingredient of Licorice, has been used for centuries to treat many chronic diseases. ILG inhibits the MyD88-dependent pathway by inhibiting the activity of inhibitor-${\kappa}B$ kinase. However, it is not known whether ILG inhibits the TRIF-dependent pathway. To evaluate the therapeutic potential of ILG, we examined its effect on signal transduction via the TRIF-dependent pathway of TLRs induced by several agonists. ILG inhibited nuclear factor-${\kappa}B$ and interferon regulatory factor 3 activation induced by lipopolysaccharide or polyinosinic-polycytidylic acid. ILG inhibited the lipopolysaccharide-induced phosphorylation of interferon regulatory factor 3 as well as interferon-inducible genes such as interferon inducible protein-10, and regulated activation of normal T-cell expressed and secreted (RANTES). These results suggest that ILG can modulate TRIF-dependent signaling pathways of TLRs, leading to decreased inflammatory gene expression.

• Biomedical Science Letters
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• v.25 no.1
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• pp.60-65
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• 2019

Toll-like receptors (TLRs) are one of the families of pattern recognition receptors (PRR) operating in the innate immunity. TLRs have the ability to recognize relatively conserved microbial components, which are generally referred to as pathogen-associated molecular patterns (PAMPs). The activation of TLRs signaling leads to the activation of $NF-{\kappa}B$ and the expression of pro-inflammatory gene products such as cytokines and inducible nitric oxide synthase (iNOS). To evaluate the therapeutic potential of pristimerin, which is a naturally occurring triterpenoid compound from Celastraceae plants, iNOS expression induced by MALP-2 (TLR2 and TLR6 agonist), Poly[I:C] (TLR3 agonist), or LPS (TLR4 agonist) were examined. Pristimerin suppressed the iNOS expression induced by MALP-2, Poly[I:C], or LPS. These results suggest that pristimerin can modulate TLRs signaling pathways leading to decreased inflammatory gene expression.

• Biomedical Science Letters
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• v.25 no.3
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• pp.267-274
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• 2019

Toll-like receptors (TLRs) are one of the families of pattern recognition receptors (PRR) to recognize pathogen-associated molecular patterns (PAMPs). PAMPs stimulate TLRs to initiate specific immunoactivity. The activation of TLRs signaling leads to the expression of pro-inflammatory gene products such as cytokines and inducible nitric oxide synthase (iNOS). To evaluate the therapeutic potential of dehydrocostus lactone (DHL), which is a natural sesquiterpene lactone derived from various medicinal plants, iNOS expression induced by LPS (TLR4 agonist), MALP-2 (TLR2 and TLR6 agonist), or Poly[I:C] (TLR3 agonist) were examined. DHL suppressed the iNOS expression induced by LPS, MALP-2, or Poly[I:C]. DHL also inhibited nitrite production induced by LPS, MALP-2, or Poly[I:C]. These results suggest that DHL can modulate TLRs signaling pathways resulting in anti-inflammatory effect.