• The Korean Journal of Physiology and Pharmacology
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• 제19권5호
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• pp.461-465
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• 2015

Microglia, the resident macrophages in the central nervous system, can rapidly respond to pathological insults. Toll-like receptor 2 (TLR2) is a pattern recognition receptor that plays a fundamental role in pathogen recognition and activation of innate immunity. Although many previous studies have suggested that TLR2 contributes to microglial activation and subsequent pathogenesis following brain tissue injury, it is still unclear whether TLR2 has a role in microglia dynamics in the resting state or in immediate-early reaction to the injury in vivo. By using in vivo two-photon microscopy imaging and $Cx3cr1^{GFP/+}$ mouse line, we first monitored the motility of microglial processes (i.e. the rate of extension and retraction) in the somatosensory cortex of living TLR2-KO and WT mice; Microglial processes in TLR2-KO mice show the similar motility to that of WT mice. We further found that microglia rapidly extend their processes to the site of local tissue injury induced by a two-photon laser ablation and that such microglial response to the brain injury was similar between WT and TLR2-KO mice. These results indicate that there are no differences in the behavior of microglial processes between TLR2-KO mice and WT mice when microglia is in the resting state or encounters local injury. Thus, TLR2 might not be essential for immediate-early microglial response to brain tissue injury in vivo.

• Biomolecules & Therapeutics
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• 제18권3호
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• pp.271-279
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• 2010

Streptococcus pneumoniae is the major pathogen that frequently causes serious infections in children, the elderly and immunocompromised patients. S. pneumoniae is known to produce reactive oxygen species (ROS) and S. pneumoniae-produced ROS is considered to play a role in pneumococci pathogenesis. SIGN-R1 is the principal receptor of capsular polysaccharides (CPSs) of S. pneumoniae. However, there is a considerable lack of knowledge about the protective role of SIGN-R1 against S. pneumoniae-produced ROS in SIGN-$R1^+$ macrophages. While investigating the protective role of SIGN-R1 against ROS, we found that SIGN-R1 intimately bound to peroxiredoxin-1 (Prx-1), one of small antioxidant proteins in vitro and in vivo. This interaction was increased with ROS generation which was produced by stimulating SIGN-R1 with dextran, a polysaccharide ligand of SIGN-R1. Also, SIGN-R1 crosslinking with 22D1 anti-SIGN-R1 antibody increased Prx-1 in vitro or in vivo. These results suggested that SIGN-R1 stimulation with CPSs of S. pneumoniae increase the expression level of Prx-1 through ROS and its subsequent interaction to SIGN-R1, providing an important antioxidant role for the host protection against S. pneumoniae.

• Molecules and Cells
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• 제42권1호
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• pp.1-7
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• 2019

Macrophage is an important innate immune cell that not only initiates inflammatory responses, but also functions in tissue repair and anti-inflammatory responses. Regulating macrophage activity is thus critical to maintain immune homeostasis. Tyro3, Axl, and Mer are integral membrane proteins that constitute TAM family of receptor tyrosine kinases (RTKs). Growing evidence indicates that TAM family receptors play an important role in anti-inflammatory responses through modulating the function of macrophages. First, macrophages can recognize apoptotic bodies through interaction between TAM family receptors expressed on macrophages and their ligands attached to apoptotic bodies. Without TAM signaling, macrophages cannot clear up apoptotic cells, leading to broad inflammation due to over-activation of immune cells. Second, TAM signaling can prevent chronic activation of macrophages by attenuating inflammatory pathways through particular pattern recognition receptors and cytokine receptors. Third, TAM signaling can induce autophagy which is an important mechanism to inhibit NLRP3 inflammasome activation in macrophages. Fourth, TAM signaling can inhibit polarization of M1 macrophages. In this review, we will focus on mechanisms involved in how TAM family of RTKs can modulate function of macrophage associated with anti-inflammatory responses described above. We will also discuss several human diseases related to TAM signaling and potential therapeutic strategies of targeting TAM signaling.

• Journal of Yeungnam Medical Science
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• 제30권1호
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• pp.10-16
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• 2013

Background: Toll-like receptors (TLRs) are well-known pattern recognition receptors. Among the 13 TLRs, TLR2 is the most known receptor for immune response. It activates mitogen-activated protein kinases (MAPKs), which are counterbalanced by MAPK phosphatases [MKPs or dual-specificity phosphatases (DUSPs)]. However, the regulatory mechanism of DUSPs is still unclear. In this study, the effect of a TLR2 ligand (TLR2L, Pam3CSK4) on DUSP4 expression in Raw264.7 cells was demonstrated. Methods: A Raw264.7 mouse macrophage cell line was cultured in Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum and 1% antibiotics (100 U/mL penicillin and 100 g/mL streptomycin) at $37^{\circ}C$ in 5% $CO_2$. TLR2L (Pam3CSK4)-mediated DUSP4 expressions were confirmed with RT-PCR and western blot analysis. In addition, the detection of reactive oxygen species (ROS) was measured with lucigenin assay. Results: Pam3CSK4 induced the expression of DUSP1, 2, 4, 5 and 16. The DUSP4 expression was also increased by TLR4 and 9 agonists (lipopolysaccharide and CpG ODN, respectively). Pam3CSK4 also induced ERK1/2 phosphorylation and ROS production, and the Pam3CSK4-induced DUSP4 expression was decreased by ERK1/2 (U0126) and ROS (DPI) inhibitors. U0126 suppressed the ROS production by Pam3CSK4. Conclusion: Pam3CSK4-mediated DUSP4 expression is regulated by ERK1/2 and ROS. This finding suggests the physiological importance of DUSP4 in TLR2-mediated immune response.

• 한국식품영양학회지
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• 제34권5호
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• pp.441-448
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• 2021

This study was designed to investigate the intracellular signaling pathways and immunoenhancing effect of macrophage activation by crude polysaccharides (CPP) extracted from citrus peels. CPP did not affect the cytotoxicity of RAW264.7 cells, but showed dose-dependent effects on cell viability. Also, CPP showed high production of chemokine (nitric oxide (NO)) and cytokines (interleukin (IL)-6 and tumor necrosis factor (TNF)-α). CPP increased IL-6, TNF-α, and inducible nitric oxide synthase (iNOS) mRNA expression dose-dependently. CPP also strongly induced the phosphorylation of the ERK, p38, and IκBα pathways in RAW 264.7 cells. In anti-pattern recognition receptors (PRRs) experiments, the effect of CPP on NO production was strongly suppressed by neutralizing toll-like receptor (TLR)2, TLR4, and Dectin1 antibodies, whereas IL-6 and TNF-α production by CPP was mainly suppressed by mannose receptor (MR). Therefore, these results suggest that CPP treatment-induced NO production was regulated by the ERK, p38, and NF-κB pathways through TLR2, TLR4, and Dectin1 receptors, whereas IL-6 and TNF-α production was primarily regulated by the ERK, p38, and NF-κB pathways through MR receptors.

• IMMUNE NETWORK
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• 제20권3호
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• pp.21.1-21.10
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• 2020

TLRs are pattern recognition receptors (PRRs) whose cytoplasmic signalling domain is similar to that of IL-1. The extracellular domain of TLRs serve as the binding site of pathogen associated molecular patterns. TLRs are found on both plasma and endosomal membranes and they mainly exert their function by activating genes which lead to production of inflammatory factors. The latest TLR to be discovered, TLR10 is a unique TLR which exhibit anti-inflammatory properties. TLR10 is found on the plasma membrane with other TLRs namely TLR1, TLR2, TLR4, TLR5 and TLR6. Studies have revealed that TLR10 is found on the same gene cluster with TLR1 and TLR6 and is also a coreceptor of TLR2. Up to date, TLR10 is the only TLR which exhibit anti-inflammatory property. Previously, TLR10 was thought to be an "orphan receptor" but much recent studies have identified ligands for TLR10. Currently there is no review article on TLR10 that has been published. In this narrative review, we are going to give an account of TLR10, its functions mainly as an anti-inflammatory PRR and its possible applications as a target in therapeutics.

• 약학회지
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• 제52권1호
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• pp.73-78
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• 2008

Immune system can protect host attacking from a variety of microorganism and virus through innate and adaptive immunities. The innate immune system can be activated by recognition of conserved carbohydrates on the cell surface of pathogen resulting in protection, immunity regulation and inflammation. Immunostimulating and anti-tumor ${\beta}$-glucan, major cell wall component of many fungi, could be recognized as pathogen associated molecular pattern (PAMP) by C-type lectin such as pathogen recognition receptor (PRR) of host innate immunity cells. In spite of many studies of basidiomycetes ${\beta}$-glucan on immunostimulation, little is known about the precise mechanism as molecular-level. Among C-type lectins, dectin-1 was cloned and reported as a ${\beta}$-glucan receptor. In this report, we demonstrated induction of cytokine gene transcription by Ganoderma lucidum ${\beta}$-glucan in the absence or presence of lipopolysaccharide (LPS) by RT-PCR analysis. The expression of murine dectin-1 (MD-1) on RAW264.7 macrophage by RT-PCR showing both the full length, 757 bp $(MD-1{\alpha})$ and alternative spliced form, 620 bp $(MD-1{\beta})$. Both $MD-1{\alpha}$ and $MD-1{\beta}$ mRNAs were induced by ${\beta $-glucan both in the absence and presence of LPS. To explore expression of inflammatory cytokines by ${\beta}$-glucan, RAW264.7 cells were treated with ${\beta}$-glucan for 12 hours. As a result, the expressions of IL-1 IL-6, IL-l0 and $TNF-{\alpha}$ were increased by ${\beta}$-glucan treatment in a dose-dependent fashion. From these results, ${\beta}$-glucan induced transcriptions of dectin-1 and immune activating cytokine genes, indicating induction of immune allertness by expressing dectin-1 and secreting inflammatory cytokines.

• BMB Reports
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• 제46권7호
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• pp.376-381
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• 2013

It is unknown how soluble pattern-recognition receptors in blood, such as mannose-binding lectin (MBL) and ficolins, modulate mast cell-mediated inflammatory responses. We investigate how mouse MBL-A or ficolin-A regulate mouse bone marrow-derived mast cells (mBMMCs)-derived inflammatory response against bacterial lipopolysaccharide (LPS) stimulation. LPS-mediated pro-inflammatory cytokine productions on mBMMCs obtained from Toll-like receptor4 (TLR4)-deficient mice, TLR2-defficient mice, and their wildtype, were specifically attenuated by the addition of either mouse MBL-A or ficolin-A in a dose-dependent manner. However, the inhibitory effects by mouse MBL-A or ficolin-A were restored by the addition of mannose or N-acetylglucosamine, respectively. These results suggest that mouse MBL-A and ficolin-A bind to LPS via its carbohydrate-recognition domain and fibrinogen-like domain, respectively, whereby cytokine production by LPS-mediated TLR4 in mBMMCs appears to be down-regulated, indicating that mouse MBL and ficolin may have an inhibitory function toward mouse TLR4-mediated excessive inflammation on the mast cells.

• Mycobiology
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• 제48권1호
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• pp.1-8
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• 2020

Pentraxin 3 (PTX3) is a soluble pattern recognition receptor (PRR), which is produced by several kinds of cells, such as neutrophils, dendritic cells, macrophages, and epithelial cells. PTX3 is known to play an important protective effect against Aspergillus. Genetic linkage in gene-targeted mice and human PTX3 plays a non-redundant role in the immune protection against specific pathogens, especially Aspergillus. Recent studies have shown that the polymorphism of PTX3 is associated with increased susceptibility to invasive aspergillosis (IA). In this review, we provide an overview of these studies that underline the potential of PTX3 in diagnosis and therapy of IA.

• BMB Reports
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• 제50권2호
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• pp.55-57
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• 2017

Toll-like receptor 4 (TLR4) together with MD2, one of the key pattern recognition receptors for a pathogen-associated molecular pattern, activates innate immunity by recognizing lipopolysaccharide (LPS) of Gram-negative bacteria. Although LBP and CD14 catalyze LPS transfer to the TLR4/MD2 complex, the detail mechanisms underlying this dynamic LPS transfer remain elusive. Using negative-stain electron microscopy, we visualized the dynamic intermediate complexes during LPS transfer-LBP/LPS micelles and ternary CD14/LBP/LPS micelle complexes. We also reconstituted the entire cascade of LPS transfer to TLR4/MD2 in a total internal reflection fluorescence (TIRF) microscope for a single molecule fluorescence analysis. These analyses reveal longitudinal LBP binding to the surface of LPS micelles and multi-round binding/unbinding of CD14 to single LBP/LPS micelles via key charged residues on LBP and CD14. Finally, we reveal that a single LPS molecule bound to CD14 is transferred to TLR4/MD2 in a TLR4-dependent manner. These discoveries, which clarify the molecular mechanism of dynamic LPS transfer to TLR4/MD2 via LBP and CD14, provide novel insights into the initiation of innate immune responses.