• The Korean Journal of Physiology and Pharmacology
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• v.8 no.5
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• pp.253-257
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• 2004

Schwann cells play an important role in peripheral nerve regeneration. Upon neuronal injury, activated Schwann cells clean up the myelin debris by phagocytosis, and promote neuronal survival and axon outgrowth by secreting various neurotrophic factors. However, it is unclear how the nerve injury induces Schwann cell activation. Recently, it was reported that certain cytoplasmic molecules, which are secreted by cells undergoing necrotic cell death, induce immune cell activation via the toll-like receptors (TLRs). This suggests that the TLRs expressed on Schwann cells may recognize nerve damage by binding to the endogenous ligands secreted by the damaged nerve, thereby inducing Schwann cell activation. Accordingly, this study was undertaken to examine the expression and the function of the TLRs on primary Schwann cells and iSC, a rat Schwann cell line. The transcripts of TLR2, 3, 4, and 9 were detected on the primary Schwann cells as well as on iSC. The stimulation of iSC with poly (I : C), a synthetic ligand for the TLR3, induced the expression of $TNF-{\alpha}$ and RANTES. In addition, poly (I : C) stimulation induced the iNOS expression and nitric oxide secretion in iSC. These results suggest that the TLRs may be involved in the inflammatory activation of Schwann cells, which is observed during Wallerian degeneration after a peripheral nerve injury.

• Journal of Life Science
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• v.21 no.1
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• pp.36-43
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• 2011

Diabetes mellitus is associated with vascular complications. Diabetic patients exhibit high levels of glycated adducts in serum compared to non-diabetic individuals. The aim of this study was to investigate whether extracellular glycated albumin (GA) predisposes vascular smooth muscle cells (VSMCs) to pro-inflammatory phenotype. Exposure of rat aortic smooth muscle cells (AoSMCs) to GA not only enhanced interleukin-6 (IL-6) release but also activated promoter activity of the IL-6 gene. GA-induced IL-6 promoter activation was suppressed by dominant-negative forms of Toll-like receptor (TLR)-4 and myeloid differentiation factor 88 (MyD88), but not by dominant-negative-forms of TLR-2 and TIR-domain-containing adapter-inducing interferon-$\beta$ (TRIF). Extracellular signal-regulated kinase (ERK) inhibition and diphenyleneiodium (DPI) also attenuated IL-6 induction by GA. Mutation at the nuclear factor-${\kappa}B$ (NF-${\kappa}B$)-binding site in the IL-6 promoter region suppressed promoter activation in response to GA. The present study proposes that GA would contribute to inflammatory reaction in the stressed vasculature by inducing IL-6 in VSMCs, and that TLR-4, EKR, and NF-${\kappa}B$ play active roles in the process.

• Journal of Veterinary Science
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• v.24 no.1
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• pp.2.1-2.14
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• 2023

Background: Hypothermia is a crucial environmental factor that elevates the risk of cardiovascular disease, but the underlying effect is unclear. Objectives: This study examined the role of cold stress (CS) in cardiac injury and its underlying mechanisms. Methods: In this study, a chronic CS-induced myocardial injury model was used; mice were subjected to chronic CS (4℃) for three hours per day for three weeks. Results: CS could result in myocardial injury by inducing the levels of heat shock proteins 70 (HSP70), enhancing the generation of creatine phosphokinase-isoenzyme (CKMB) and malondialdehyde (MDA), increasing the contents of tumor necrosis factor-α (TNF-α), high mobility group box 1 (HMGB1) interleukin1b (IL-1β), IL-18, IL-6, and triggering the depletion of superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH). Multiple signaling pathways were activated by cold exposure, including pyroptosis-associated NOD-like receptor 3 (NLRP3)-regulated caspase-1-dependent/Gasdermin D (GSDMD), inflammation-related toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)-mediated nuclear factor kappa B (NF-κB), and mitogen-activated protein kinase (MAPK), as well as oxidative stressinvolved thioredoxin-1/thioredoxin-interacting protein (Txnip) signaling pathways, which play a pivotal role in myocardial injury resulting from hypothermia. Conclusions: These findings provide new insights into the increased risk of cardiovascular disease at extremely low temperatures.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.2
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• pp.267-272
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• 2017

Piceatannol (PIC) is a natural hydroxylated analog of resveratrol (RSV), which is a polyphenol known to extend lifespan by stimulating sirtuins. The aim of this study was to investigate the effects of PIC and RSV on the toll-like receptor 4 (TLR4)-nuclear factor kappa B ($NF-{\kappa}B$) pathway in mouse hepatocytes and an obese/diabetic KK/HlJ mouse model. AML12 mouse hepatocytes in the absence or presence of palmitic acids (PA) were treated with PIC ($50{\mu}M$) or RSV ($50{\mu}M$). Male KK/HlJ mice at 20 weeks of age were divided into three subgroups as follows: 1) obese and diabetic control (KK), 2) KK_PIC, and 3) KK_RSV. PIC and RSV were administered orally at a dose of 10 mg/kg/d for 4 weeks. Four weeks of PIC and RSV treatment did not affect body weight or food intake in KK mice. Serum fasting blood glucose was significantly reduced in KK_PIC, and 2 h oral glucose tolerance test area under the curve was significantly reduced by PIC and RSV treatment in KK mice. PIC tended to improve homeostasis model assessment of the insulin resistance index (HOMA-IR) and HOMA beta-cells in diabetic KK mice. TLR4 and $NF-{\kappa}B$ were down-regulated by PIC and RSV treatments in hepatocytes in the absence or presence of PA. Insulin receptor, AMP-activated protein kinase, peroxisome proliferator-activated receptor gamma, nucleotide oligomerization domain-like receptor family pyrin domain-containing 3, interleukin-1, and $NF-{\kappa}B$ were altered in PIC-treated livers. Collectively, PIC and RSV inhibited the $TLR4-NF-{\kappa}B$ pathway, and PIC seems to be more effective than RSV in the regulation of analyzed targets, which are involved in insulin signaling and inflammation in vivo.

• The Korean Journal of Physiology and Pharmacology
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• v.25 no.3
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• pp.217-225
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• 2021

Neuropathic pain (NP) that contributes to the comorbidity between pain and depression is a clinical dilemma. Neuroinflammatory responses are known to have potentially important roles in the initiation of NP and depressive mood. In this study, we aimed to investigate the effects of paeoniflorin (PF) on NP-induced depression-like behaviors by targeting the hippocampal neuroinflammation through the toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) signaling pathway. We used a murine model of NP caused by unilateral sciatic nerve cuffing (Cuff). PF was injected intraperitoneally once a day for a total of 14 days. Pain and depression-like behavior changes were evaluated via behavioral tests. Pathological changes in the hippocampus of mice were observed by H&E staining. The levels of proinflammatory cytokines in the hippocampus were detected using ELISA. Activated microglia were measured by immunohistochemical staining. The TLR4/NF-κB signaling pathway-associated protein expression in the hippocampus was detected by western blotting. We found that the PF could significantly alleviate Cuff-induced hyperalgesia and depressive behaviors, lessen the pathological damage to the hippocampal cell, reduce proinflammatory cytokines levels, and inhibit microglial over-activation. Furthermore, PF downregulated the expression levels of TLR4/NF-κB signaling pathway-related proteins in the hippocampus. These results indicate that PF is an effective drug for improving the comorbidity between NP and depression.

• Molecules and Cells
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• v.45 no.4
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• pp.257-272
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• 2022

In addition to inducing apoptosis, caspase inhibition contributes to necroptosis and/or autophagy depending on the cell type and cellular context. In macrophages, necroptosis can be induced by co-treatment with Toll-like receptor (TLR) ligands (lipopolysaccharide [LPS] for TLR4 and polyinosinic-polycytidylic acid [poly I:C] for TLR3) and a cell-permeable pan-caspase inhibitor zVAD. Here, we elucidated the signaling pathways and molecular mechanisms of cell death. We showed that LPS/zVAD- and poly I:C/zVAD-induced cell death in bone marrow-derived macrophages (BMDMs) was inhibited by receptor-interacting protein kinase 1 (RIP1) inhibitor necrostatin-1 and autophagy inhibitor 3-methyladenine. Electron microscopic images displayed autophagosome/autolysosomes, and immunoblotting data revealed increased LC3II expression. Although zVAD did not affect LPS- or poly I:C-induced activation of IKK, JNK, and p38, it enhanced IRF3 and STAT1 activation as well as type I interferon (IFN) expression. In addition, zVAD inhibited ERK and Akt phosphorylation induced by LPS and poly I:C. Of note, zVAD-induced enhancement of the IRF3/IFN/STAT1 axis was abolished by necrostatin-1, while zVAD-induced inhibition of ERK and Akt was not. Our data further support the involvement of autocrine IFNs action in reactive oxygen species (ROS)-dependent necroptosis, LPS/zVAD-elicited ROS production was inhibited by necrostatin-1, neutralizing antibody of IFN receptor (IFNR) and JAK inhibitor AZD1480. Accordingly, both cell death and ROS production induced by TLR ligands plus zVAD were abrogated in STAT1 knockout macrophages. We conclude that enhanced TRIF-RIP1-dependent autocrine action of IFNβ, rather than inhibition of ERK or Akt, is involved in TLRs/zVAD-induced autophagic and necroptotic cell death via the JAK/STAT1/ROS pathway.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.15
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• pp.6145-6150
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• 2014

Toll-like receptors (TLRs) are expressed in immune and tumor cells and recognize pathogen-associated molecular patterns. Cervical cancer (CC) is directly linked to a persistent infection with high risk human papillomaviruses (HR-HPVs) and could be associated with alteration of TLRs expression. TLR9 plays a key role in the recognition of DNA viruses and better understanding of this signaling pathway in CC could lead to the development of novel immunotherapeutic approaches. The present study was undertaken to determine the level of TLR9 expression in cervical neoplasias from Tunisian women with 53 formalin-fixed and paraffin-embedded specimens, including 22 samples of invasive cervical carcinoma (ICC), 18 of cervical intraepithelial neoplasia (CIN), 7 of condyloma and 6 normal cervical tissues as control cases. Quantification of TLR9 expression was based on scoring four degrees of extent and intensity of immunostaining in squamous epithelial cells. TLR9 expression gradually increased from CIN1 (80% weak intensity) to CIN2 (83.3% moderate), CIN3 (57.1% strong) and ICC (100% very strong). It was absent in normal cervical tissue and weak in 71.4% of condyloma. The mean scores of TLR9 expression were compared using the Kruskall-Wallis test and there was a statistical significance between normal tissue and condyloma as well as between condyloma, CINs and ICC. These results suggest that TLR9 may play a role in progression of cervical neoplasia in Tunisian patients and could represent a useful biomarker for malignant transformation of cervical squamous cells.

• 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.

• Korean Journal of Agricultural Science
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• v.49 no.1
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• pp.11-18
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• 2022

A disrupted immune system during pregnancy is involved in pregnancy complications, such as spontaneous abortion, preeclampsia, and recurrent pregnancy loss. This study examined the role of toll-like receptor (TLR) 4 and ASC (apoptosis-associated speck-like protein containing a CARD [c-terminal caspase recruitment domain]) in pregnancy complications using a lipopolysaccharide (LPS)-induced miscarriage mice model. Incidences of miscarriage and embryonic resorption were examined at 9.5 days of pregnancy in wild-type (WT), ASC knockout (KO), and TLR4 KO mice after injecting them with LPS. The fetuses and placenta were obtained after sacrifice at 15.5 days of pregnancy. A significantly lower frequency of fetus absorption was found in TLR4 KO mice, whereas corresponding absorption outcomes were strongly induced in the WT and ASC KO mice upon an LPS injection. As expected, TLR4 KO mice were resistant to LPS-induced abortion. A histological analysis of the miscarried placenta showed increasing levels of the eosin staining of spongiotrophoblast cells without any obvious difference between WT and ASC KO mice. These results suggest that TLR4 KO mice are resistant to LPS, which affects pregnancy persistence, whereas WT and ASC KO mice show high miscarriage rates due to LPS. Moreover, the ASC adaptor is not directly involved in LPS-induced miscarriages, and the NLRP3 inflammasome can be activated by other proteins in the absence of ASC.

• The Korean Journal of Mycology
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• v.46 no.2
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• pp.161-176
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• 2018

Fungal ${\beta}$-glucan, known to have immunostimulatory and antitumor activities, can be recognized by host immune cells as one of the pathogen-associated molecular patterns (PAMPs). Although there are several reports on the diverse immunostimulatory activities of ${\beta}$-glucan, little is known about the intracellular signal transduction of ${\beta}$-glucan. Stimulation of RAW264.7 macrophage cells with ${\beta}$-glucan from Ganoderma lucidum induced the expressions of dectin-1, toll-like receptor 2 (TLR2), TLR4, and TLR6 at the transcription stage. Treatment with ${\beta}$-glucan also induced inflammatory mediators such as macrophage inflammatory proteins (MIP)-$1{\alpha}$, MIP-$1{\beta}$, MIP-$1{\gamma}$, interleukin (IL)-$1{\beta}$, and tumor necrosis factor (TNF)-${\alpha}$. Treatment of the cells with polymyxin B, an inhibitor of lipopolysaccharides (LPS), blocked the induction of inflammatory mediators in LPS- or ${\beta}$-glucan-stimulated systems. Pretreatment of the cells in our cell culture system with LY294002, a phosphoinositide 3-kinase (PI3K) inhibitor, or U0126, a mitogen-activated protein kinase/extracellular-signal-regulated kinase (MAPK/ERK) kinase (MEK)1/MEK2 inhibitor, led to a reduction in the induction of inflammatory mediators in a concentration-dependent manner. These results show that stimulation of the macrophage cells by ${\beta}$-glucan induced the expressions of both dectin-1 and TLRs. We also found that the PI3K/Akt and MEK pathways were involved in the induction of inflammatory mediators in macrophage cells during intracellular signal transduction of ${\beta}$-glucan.