• Journal of Veterinary Clinics
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• v.26 no.6
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• pp.520-523
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• 2009

The purporse of this study was to evaluate the quantitative differences in mRNA expression of TLR-2, -4, and -9 in normal equine eyes and eyes with equine recurrent uveitis (ERU). Normal equine eyes (n = 6) and eyes with naturally-occurring ERU (n = 6) were collected. Real time PCR assay was performed to compare mRNA expression of TLR-2, -4, and -9 between normal and ERU eyes. A significant up-regulation of TLR-2 and -9 mRNA in the ciliary body and TLR-2 mRNA in the iris was found in eyes with ERU compared to the mRNA levels in these same tissues of normal equine eyes. There were no remarkable differences observed in TLR-4 mRNA expression between normal eyes and eyes with ERU. The current data suggest the potential involvement of TLR-2 and -9 in the pathogenesis of ERU. However, further study is required to determine the role of TLRs in ERU.

• International Journal of Oral Biology
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• v.31 no.1
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• pp.1-6
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• 2006

The primary cause of periodontitis is plaque-associated anaerobic gram-negative bacteria. As shown in the patients with defects in the number or function of neutrophils, innate immunity plays an important role in resistance to bacterial infection and periodontitis. Toll-like receptor 4(TLR4) is one of the key receptors that recognize the molecular patterns of microbes and initiate innate immune response. To understand the role of TLR4 in the pathogenesis of periodontitis, we investigated whether Asp299Gly of TLR4 mutation is associated with periodontitis in Korean population. Subjects for this study included 90 healthy subjects and 98 periodontitis patients. The Asp299Gly mutation was screened by PCR-Restriction Fragment Length Polymorphism(RFLP) of genomic DNA from blood cells using a primer that creates a NcoI restriction site only in the mutant allele. The Asp299Gly mutation was not found in all subjects tested. Our results suggest that the Asp299Gly mutation of TLR4 is very rare in a Korean population. Further mutation screening may be required to determine the role of TLR4 in the pathogenesis of periodontitis.

• Reproductive and Developmental Biology
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• v.39 no.4
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• pp.105-115
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• 2015

Toll-like receptor 7 (TLR7) is critical for the triggering of innate immune response by recognizing the conserved molecular patterns of single-stranded RNA (ssRNA) viruses and mediated antigenic adaptive immunity. To understand how TLR7 distinguish pathogen-derived molecular patterns from the host self, it is essential to be able to identify TLR7 receptor interaction interfaces, such as active sites or R848-agonist binding sites. The functional interfaces of TLR7 can serve as targets for structure-based drug design in studying the TLR7 receptor's structure-function relationship. In contrast to mammalian TLR7, chicken TLR7 (chTLR7) is unknown for its important biological function. Therefore, it has been targeted to mediate contrasting evolutionary patterns of positive selection into non-synonymous SNPs across eleven species using TLR7 conservation patterns (evolutionary conserved and class-specific trace residues), where protein sequence differences to the TLR7 receptors of interest record mutation that have passed positive section across the species. In this study, we characterized the Lys609 residue on chTLR7-ECD homodimer interfaces to reflect the current tendency of evolving positive selection to be transfer into a stabilization direction of the R848-agonist/chTLR7-ECDs complex under the phylogenetically variable position across species and we suggest a potential indicator for contrasting evolutionary patterns of both the species TLR-ECDs.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.2
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• pp.145-153
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• 2018

The subgranular zone (SGZ) of hippocampal dentate gyrus (HDG) is a primary site of adult neurogenesis. Toll-like receptors (TLRs), are involved in neural system development of Drosophila and innate immune response of mammals. TLR2 is expressed abundantly in neurogenic niches such as adult mammalian hippocampus. It regulates adult hippocampal neurogenesis. However, the role of TLR2 in adult neurogenesis is not well studied in global or focal cerebral ischemia. Therefore, this study aimed to investigate the role of TLR2 in adult neurogenesis after photochemically induced cerebral ischemia. At 7 days after photothrombotic ischemic injury, the number of bromodeoxyuridine (BrdU)-positive cells was increased in both TLR2 knock-out (KO) mice and wild-type (WT) mice. However, the increment rate of BrdU-positive cells was lower in TLR2 KO mice compared to that in WT mice. The number of doublecortin (DCX) and neuronal nuclei (NeuN)-positive cells in HDG was decreased after photothrombotic ischemia in TLR2 KO mice compared to that in WT mice. The survival rate of cells in HDG was decreased in TLR2 KO mice compared to that in WT mice. In contrast, the number of cleaved-caspase 3 (apoptotic marker) and the number of GFAP (glia marker)/BrdU double-positive cells in TLR2 KO mice were higher than that in WT mice. These results suggest that TLR2 can promote adult neurogenesis from neural stem cell of hippocampal dentate gyrus through increasing proliferation, differentiation, and survival from neural stem cells after ischemic injury of the brain.

• Molecules and Cells
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• v.25 no.2
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• pp.253-257
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• 2008

Acrolein is a highly electrophilic ${\alpha},{\beta}$-unsaturated aldehyde present in a number of environmental sources, especially cigarette smoke. It reacts strongly with the thiol groups of cysteine residues by Michael addition and has been reported to inhibit nuclear $factor-{\kappa}B$ ($NF-{\kappa}B$) activation by lipopolysaccharide (LPS). The mechanism by which it inhibits $NF-{\kappa}B$ is not clear. Toll-like receptors (TLRs) play a key role in sensing microbial components and inducing innate immune responses, and LPS-induced dimerization of TLR4 is required for activation of downstream signaling pathways. Thus, dimerization of TLR4 may be one of the first events involved in activating TLR4-mediated signaling pathways. Stimulation of TLR4 by LPS activates both myeloid differential factor 88 (MyD88)- and TIR domain-containing adapter inducing $IFN{\beta}$ (TRIF)-dependent signaling pathways leading to activation of $NF-{\kappa}B$ and IFN-regulatory factor 3 (IRF3). Acrolein inhibited $NF-{\kappa}B$ and IRF3 activation by LPS, but it did not inhibit $NF-{\kappa}B$ or IRF3 activation by MyD88, inhibitor ${\kappa}B$ kinase $(IKK){\beta}$, TRIF, or TNF-receptor-associated factor family member-associated $NF-{\kappa}B$ activator (TANK)-binding kinase 1 (TBK1). Acrolein inhibited LPS-induced dimerization of TLR4, which resulted in the down-regulation of $NF-{\kappa}B$ and IRF3 activation. These results suggest that activation of TLRs and subsequent immune/inflammatory responses induced by endogenous molecules or chronic infection can be modulated by certain chemicals with a structural motif that enables Michael addition.

• Clinical and Experimental Pediatrics
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• v.60 no.7
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• pp.208-215
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• 2017

Purpose: Activation of Toll-like receptor 2 (TLR2) present on circulating monocytes in patients with Kawasaki disease (KD) can lead to the production of proinflammatory cytokines and interleukin-10 (IL-10). We aimed to determine the association of the frequency of circulating TLR2+/ CD14+ monocytes (FTLR2%) with the outcomes of KD, as well as to compare FTLR2% to the usefulness of sIL-10. Methods: The FTLR2% in patients with KD was measured by flow cytometry. Serum levels of IL-10 (sIL-10) were determined in 31 patients with KD before the initial treatment with intravenous immunoglobulin (IVIG) and in 21 febrile controls by using enzyme-linked immunosorbent assay. Patients were classified as having coronary artery lesions (CALs) based on the maximal internal diameters of the proximal right coronary artery and proximal left anterior descending coronary artery one month after the initial diagnosis. Results: We found that FTLR2% greater than 92.62% predicted CALs with 80% sensitivity and 68.4% specificity, whereas FTLR2% more than 94.61% predicted IVIG resistance with 66.7% sensitivity and 71.4% specificity. Moreover, sIL-10 more than 15.52 pg/mL predicted CALs and IVIG resistance with 40% and 66.7% sensitivity, respectively, and 73.7% and 76.2% specificity, respectively. Conclusion: We showed that measuring FTLR2% before the initial treatment could be useful in predicting CAL development with better sensitivity than sIL-10 and with results comparable to sIL-10 results for the prediction of IVIG resistance in patients with KD. However, further studies are necessary to validate FTLR2% as a marker of prognosis and severity of KD.

• Toxicological Research
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• v.31 no.1
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• pp.11-16
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• 2015

Our body's immune system has defense mechanisms against pathogens such as viruses and bacteria. Immune responses are primarily initiated by the activation of toll-like receptors (TLRs). In particular, TLR4 is well-characterized and is known to be activated by gram-negative bacteria and tissue damage signals. TLR4 requires myeloid differentiation factor 2 (MD2) as a co-receptor to recognize its ligand, lipopolysaccharides (LPS), which is an extracellular membrane component of gram-negative bacteria. Gambogic acid is a xanthonoid isolated from brownish or orange resin extracted from Garcinia hanburyi. Its primary effect is tumor suppression. Since inflammatory responses are related to the development of cancer, we hypothesized that gambogic acid may regulate TLR4 activation. Our results demonstrated that gambogic acid decreased the expression of pro-inflammatory cytokines ($TNF-{\alpha}$, IL-6, IL-12, and $IL-1{\beta}$) in both mRNA and protein levels in bone marrow-derived primary macrophages after stimulation with LPS. Gambogic acid did not inhibit the activation of Interferon regulatory factor 3 (IRF3) induced by TBK1 overexpression in a luciferase reporter gene assay using IFN-${\beta}$-PRD III-I-luc. An in vitro kinase assay using recombinant TBK1 revealed that gambogic acid did not directly inhibit TBK1 kinase activity, and instead suppressed the binding of LPS to MD2, as determined by an in vitro binding assay and confocal microscopy analysis. Together, our results demonstrate that gambogic acid disrupts LPS interaction with the TLR4/MD2 complex, the novel mechanism by which it suppresses TLR4 activation.

• 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.

• Safety and Health at Work
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• v.13 no.1
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• pp.9-16
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• 2022

Background: The global shift toward greener societies demands new technologies and work operations in the waste-management sector. However, progressive industrial methods do not necessarily consider workers' health. This study characterized workers' exposure to bioaerosols and investigated the bioaerosols' potential to engage the immune system in vitro. Methods: Full shift personal aerosol sampling was conducted over three consecutive days. Dust load was analyzed by gravimetry, fungal and actinobacterial spores were analyzed by scanning electron microscopy, and endotoxin by limulus amebocyte lysate (LAL) assay. In vitro exposure of HEK cells to airborne dust samples was used to investigate the potential of inducing an inflammatory reaction. Results: The total dust exposure level exceeded the recommended occupational exposure limit (OEL) of 5.0 mg/m³ in 3 out of 15 samples. The inhalable endotoxin level exceeded the recommended exposure level by a 7-fold, whereas the fungal spore level exceeded the recommended exposure level by an 11-fold. Actinobacterial spores were identified in 8 out of 14 samples. In vitro experiments revealed significant TLR2 activation in 9 out of 14 samples vs. significant TLR4 activation in all samples. Conclusion: The present study showed that the dust samples contained potentially health-impairing endotoxin, fungi, and actinobacterial levels. Furthermore, the sampled dust contained microbial components capable of inducing TLR activation and thus have the potential to evoke an inflammatory response in exposed individuals.

• Journal of Microbiology and Biotechnology
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• v.29 no.10
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• pp.1506-1521
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• 2019

Tuberculosis, which is caused by Mycobacterium tuberculosis (Mtb), is among the most pressing worldwide problems. Mtb uniquely interacts with innate immune cells through various pattern recognition receptors. These interactions initiate several inflammatory pathways that play essential roles in controlling Mtb pathogenesis. Although the TLR signaling pathways have essential roles in numerous host's immune defense responses, the role of TLR signaling in the response to Mtb infection is still unclear. This review presents discussions on host-Mtb interactions in terms of Mtb-mediated TLR signaling. In addition, we highlight recent discoveries pertaining to these pathways that may help in new immunotherapeutic opportunities.