TLR4-MyD88 Signaling Pathway Research Articles

The activation of TLR4-MyD88 signaling promotes hepatic dysfunction and fibrotic changes in SD rats resulting from prolonged exposure to sodium arsenite

Arsenic, a poisonous metalloid element, is linked to liver diseases, but the exactmechanisms for this process are not yet to be completely elucidated. Toll like receptor 4 (TLR4), acting as a pathogenic pattern recognition receptor, plays a pivotal role in various inflammatory diseases via the myeloid differentiation factor 88 (MyD88) pathway. This study aims to investigate the involvement of the TLR4-MyD88 signaling pathway in liver injury induced by prolonged exposure to sodium arsenite (NaAsO2) in Sprague-Dawley rats. Our research findings demonstratethe activation of TLR4-MyD88 signaling pathway in long-term NaAsO2-exposed rat liver tissues, leading to a significant release of inflammatory factors, which suggests its potential involvement in the pathogenesis of NaAsO2-induced liver injury. We further administered lipopolysaccharide (LPS), a natural ligand of TLR4, and TAK-242, a specific inhibitor of TLR4, to rats in order to validate the specific involvement of the TLR4-MyD88 signaling pathway in NaAsO2-induced liver injury. The results showed that, 1 mg/kg.bw LPS treatment significantly activated TLR4-MyD88 signalling pathway and its mediated pro-inflammatory factors, leading to up-regulation of activation indicators in hepatic stellate cells (HSCs) as well as increased secretion levels of extracellular matrix (ECM) in the liver, and ultimately induced liver fibrosis and dysfunction in rats. Relevantly, subsequent administration of 0.5 mg/kg.bw TAK-242 significantly attenuated the expression levels of TLR4 and its associated proteins, mitigated collagen deposition, and partially improved liver fibrosis and dysfunction caused by NaAsO2 in rats. Our study fully confirms the pivotal role of the TLR4-MyD88 signaling in promoting liver injury induced by NaAsO2, thereby providing a novel molecular target for preventing and treating patients with arsenic poisoning-related liver injury.

The Role of the TLR4-MyD88 Signaling Pathway in the Immune Response of the Selected Scallop Strain “Hongmo No. 1” to Heat Stress

The innate immunity of marine bivalves is challenged upon exposure to heat stress, especially with increases in the frequency and intensity of heat waves. TLR4 serves a classical pattern recognition receptor in recognizing pathogenic microorganisms and activating immune responses. In this study, three genes, HMTLR4, HMMyD88 and HMTRAF6, were characterized as homologs of genes in the TLR4-MyD88 signaling pathway in the selected scallop strain “Hongmo No. 1”. According to RT-PCR, acute heat stress (32 °C) inhibited genes in the TLR4-MyD88 signaling pathway, and LPS stimulation-induced activation of TLR4-MyD88 signal transduction was also negatively affected at 32 °C. ELISA showed LPS-induced tumor necrosis factor alpha (TNF-α) or lysozyme (LZM) activity, but this was independent of temperature. RNA interference (RNAi) confirmed that HMTLR4 silencing suppressed the expression of its downstream gene, whether at 24 °C or at 32 °C. The level of TNF-α and the activity of LZM also decreased after injection with dsRNA, indicating a negative effect on the innate immunity of scallops. Additionally, acute heat stress affected the suppression of downstream gene expression when compared with that at 24 °C, which led us to the hypothesis that heat stress directly influences the downstream targets of HMTLR4. These results enrich the knowledge of scallop immunity under heat stress and can be beneficial for the genetic improvement of new scallop strains with higher thermotolerance.

Apigenin ameliorates diabetic neuropathy in rats by modulating the TLR4/MyD88 signaling pathway

Objective: To determine the neuroprotective effects of apigenin against streptozotocin (STZ)-induced diabetic neuropathy (DN). Methods: To induce DN, Wistar rats (150-200 g) were administered with STZ (55 mg/kg, i.p.). Then they were randomly assigned to various groups, viz., normal, diabetic control, insulin (10 IU/kg, s.c.), apigenin (5, 10, and 20 mg/kg, p.o.), and insulin (10 IU/kg) plus apigenin (20 mg/kg, p.o.). Various behavioral, biochemical, and molecular markers [tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, IL-6, Toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), and nuclear factor erythroid 2-related factor 2 (Nrf2)] were assessed. Results: Apigenin (10 and 20 mg/kg, p.o.) substantially reduced plasma glucose levels, lipid profile, aspartate transaminase, alanine transaminase, glycated hemoglobin, and neural advanced glycation end products in STZ-induced DN rats (P<0.05). After apigenin intervention, STZ-induced changes in food and water intake, body weight, urine output, allodynia, hyperalgesia, and insulin levels were markedly improved (P<0.05). Neural antioxidant enzymes (superoxide dismutase and glutathione) and Na+K+ATPase activity were also considerably elevated (P<0.05) while the level of lipid peroxidation was diminished following apigenin therapy (P<0.05). Furthermore, apigenin markedly upregulated the Nrf2 mRNA level while downregulating the mRNA expressions of TNF-α and ILs and the protein expressions of TLR4 and MyD88 (P<0.05). STZ-induced histological abnormalities in the sciatic nerve were also improved by apigenin treatment. Conclusions: Apigenin exerts its neuroprotective effect by modulating the inflammatory and oxidative stress pathways via regulating the TLR4-MyD88 signaling pathway.

Acetylation at the O-6 position of t-Glc improved immunoactivity of α-1,6-glucan from longan by additionally activating Dectin-1 and CD14 receptors

Acetylation is an important approach to improve the bioactivity of polysaccharides; however, the mechanisms have not been fully understood. As a key component of longan for exerting health promoting function, longan polysaccharide was hypothesized may achieve elevated immunoregulatory activity after acetylation. A bioactive longan polysaccharide (LP) composed of (1 → 6)-α-d-glucan (84.1 %) and with an average Mw of 9.68 × 104 kDa was acetylated to different degree of substitutions (DS) in this study. Key structural changes responsible for improvement in immunoregulatory activity were identified, and underlying mechanisms were investigated. Acetylated LP (Ac-LP) with DS 0.37, 0.78 and 0.92 were obtained. Structural characterization identified the substitution of acetyl groups occurs at O-6 positions of t-Glc non-selectively, while the backbone structure was not apparently changed. This resulted in increased expression of cytokines (IL-10, IL-6 and TNF-α) and ROS production in RAW264.7 macrophages, indicating improved immune activity which is positively related to the DS of Ac-LP. This is attribute to additional cellular receptors for Ac-LP (CD14 and Dectin-1) apart from receptors for LP (TLR4 and Ca2+ receptors), as well as the relative higher protein expression of TLR4-MyD88 signaling pathways. These results would provide guidance for the utilization of acetylated polysaccharides with improved immunoactivity.

Retraction Statement.

Retraction Statement.

Structure Characterization, Immunological Activity, and Mechanism of a Polysaccharide From the Rhizome of Menispermum dauricum DC.

The purpose of this study was to investigate the structural characterization and immunological activity in vitro and in vivo of a polysaccharide from the rhizome of Menispermum dauricum. A new polysaccharide named MDP was isolated from the rhizome of Menispermum dauricum by hot water extraction, ethanol precipitation, anion-exchange, and gel-filtration chromatography. MDP was homogeneous and had a molecular weight of 6.16 ×103 Da, and it was an α-D-glucan containing a (1 → 6)-linked backbone, with a glucosyl residue at the C-3 position along the main chain. MDP exhibited immunological activity in vitro, which could significantly promote the proliferation and phagocytosis of RAW264.7 cells and the release of TNF-α and IL-6 factors. For immunological activity in vivo. MDP could significantly increase the thymus and spleen indices, enhance the macrophage function, increase the level of cytokine (IL-6 and TNF-α) and immunoglobulin IgM in the serum and regulate T lymphocyte subsets. Furthermore, MDP elevated the expression of the critical nodes in the TLR4-MyD88 signaling pathways in vivo. These results support the concept that MDP may exhibit immunological activity through TLR4-MyD88 signaling pathway in vivo.

Identification of a novel probiotic and its protective effects on NAFLD via modulating gut microbial community

Non-alcoholic fatty liver disease (NAFLD) is becoming the most common progressive liver diseases. Therapeutic strategy based on gut-liver axis and probiotics is a promising approach for the treatment of NAFLD. However, rare probiotics have been applied in NAFLD treatment, and the involved molecular mechanism is not entirely clear. We initially identified a novel functional probiotic, Lactobacillus kefiranofaciens ZW3, on the lipid deposition by a simple and rapid zebrafish model. Supplementation with ZW3 to the methionine and choline deficient (MCD) diet induced NAFLD rats could improve the liver impairments and reduce inflammation through TLR4-MyD88 and JNK signaling pathways. Moreover, ZW3 modulated gut microbiota by promoting relative abundance of Firmicutes and Lactobacillus, decreasing the abundance of Escherichia-Shigella and Bacteroides. Functional prediction of microbiome showed ZW3 presented potential enhancement on carbohydrate and lipid metabolism, cell process control and signal transduction processes, and reduced several human diseases. This present study identified a novel probiotic and its protective effects on NAFLD, and interpreted the interactions of ZW3 with the immune system and gut microbiota involved in gut-liver axis. © 2022 Society of Chemical Industry.

Effect of soya phosphatidylcholine and possible underlying mechanism on ischemia/reperfusion injury in isolated perfused rat heart: an experimental and computational study.

This study was designed to assess the effect of soya phosphatidylcholine (SPC) against ischemia/reperfusion (I/R) injury and the possible underlying mechanism using experimental and computational studies. I/R injury was induced by global ischemia for 30min followed by reperfusion for 120min. The perfusion of the SPC was performed for 10min before inducing global ischemia. In the mechanistic study, the involvement of specific cellular pathways was identified using various inhibitors such as ATP-dependent potassium channel (KATP) inhibitor (glibenclamide), protein kinase C (PKC) inhibitor (chelerythrine), non-selective nitric oxide synthase inhibitor (L-NAME), and endothelium remover (Triton X-100). The computational study of various ligands was performed on toll-like receptor 4 (TLR4) protein using AutoDock version 4.0. SPC (100 μM) significantly decreased the levels of cardiac damage markers and %infarction compared with the vehicle control (VC). Furthermore, cardiodynamics (indices of left ventricular contraction (dp/dtmax), indices of left ventricular relaxation (dp/dtmin), coronary flow, and antioxidant enzyme levels were significantly improved as compared with VC. This protective effect was attenuated by glibenclamide, chelerythrine, and Triton X-100, but it was not attenuated by L-NAME. The computational study showed a significant bonding affinity of SPC to the TLR4-MD2 complex. Thus, SPC reduced myocardial I/R injury in isolated perfused rat hearts, which might be governed by the KATP channel, PKC, endothelium response, and TLR4-MyD88 signaling pathway.

Maternal Neutrophil Depletion Fails to Avert Systemic Lipopolysaccharide-Induced Early Pregnancy Defects in Mice.

Maternal infection-induced early pregnancy complications arise from perturbation of the immune environment at the uterine early blastocyst implantation site (EBIS), yet the underlying mechanisms remain unclear. Here, we demonstrated in a mouse model that the progression of normal pregnancy from days 4 to 6 induced steady migration of leukocytes away from the uterine decidual stromal zone (DSZ) that surrounds the implanted blastocyst. Uterine macrophages were found to be CD206+ M2-polarized. While monocytes were nearly absent in the DSZ, DSZ cells were found to express monocyte marker protein Ly6C. Systemic endotoxic lipopolysaccharide (LPS) exposure on day 5 of pregnancy led to: (1) rapid (at 2 h) induction of neutrophil chemoattractants that promoted huge neutrophil infiltrations at the EBISs by 24 h; (2) rapid (at 2 h) elevation of mRNA levels of MyD88, but not Trif, modulated cytokines at the EBISs; and (3) dose-dependent EBIS defects by day 7 of pregnancy. Yet, elimination of maternal neutrophils using anti-Ly6G antibody prior to LPS exposure failed to avert LPS-induced EBIS defects allowing us to suggest that activation of Tlr4-MyD88 dependent inflammatory pathway is involved in LPS-induced defects at EBISs. Thus, blocking the activation of the Tlr4-MyD88 signaling pathway may be an interesting approach to prevent infection-induced pathology at EBISs.

Suppression of TLR4-MyD88 signaling pathway attenuated chronic mechanical pain in a rat model of endometriosis

BackgroundAs a classic innate immunity pathway, Toll-like receptor 4 (TLR4) signaling has been intensively investigated for its function of pathogen recognition. The receptor is located not only on immune cells but also on sensory neurons and spinal glia. Recent studies revealed the involvement of neuronal TLR4 in different types of pain. However, the specific role of TLR4 signaling in the pain symptom of endometriosis (EM) remains obscure.MethodsThe rat endometriosis model was established by transplanting uterine horn tissue into gastrocnemius. Western blotting and/or immunofluorescent staining were applied to detect high mobility group box 1 (HMGB1), TLR4, myeloid differentiation factor-88 adaptor protein (MyD88), and nuclear factor kappa-B-p65 (NF-κB-p65) expression, as well as the activation of astrocyte and microglia. The antagonist of TLR4 (LPS-RS-Ultra, LRU) and MyD88 homodimerization inhibitory peptide (MIP) were intrathecally administrated to assess the behavioral effects of blocking TLR4 signaling on endometriosis-related pain.ResultsMechanical hyperalgesia was observed at the graft site, while HMGB1 was upregulated in the implanted uterine tissue, dorsal root ganglion (DRG), and spinal dorsal horn (SDH). Compared with sham group, upregulated TLR4, MyD88, and phosphorylated NF-κB-p65 were detected in the DRG and SDH in EM rats. The activation of astrocytes and microglia in the SDH was also confirmed in EM rats. Intrathecal application of LRU and MIP alleviated mechanical pain on the graft site of EM rats, with decreased phosphorylation of NF-κB-p65 in the DRG and reduced activation of glia in the SDH.ConclusionsHMGB1-TLR4-MyD88 signaling pathway in the DRG and SDH may involve in endometriosis-related hyperpathia. Blockade of TLR4 and MyD88 might serve as a potential treatment for pain in endometriosis.

Extracellular histones stimulate collagen expression in vitro and promote liver fibrogenesis in a mouse model via the TLR4-MyD88 signaling pathway.

BACKGROUNDLiver fibrosis progressing to liver cirrhosis and hepatic carcinoma is very common and causes more than one million deaths annually. Fibrosis develops from recurrent liver injury but the molecular mechanisms are not fully understood. Recently, the TLR4-MyD88 signaling pathway has been reported to contribute to fibrosis. Extracellular histones are ligands of TLR4 but their roles in liver fibrosis have not been investigated.AIMTo investigate the roles and potential mechanisms of extracellular histones in liver fibrosis.METHODS In vitro, LX2 human hepatic stellate cells (HSCs) were treated with histones in the presence or absence of non-anticoagulant heparin (NAHP) for neutralizing histones or TLR4-blocking antibody. The resultant cellular expression of collagen I was detected using western blotting and immunofluorescent staining. In vivo, the CCl4-induced liver fibrosis model was generated in male 6-week-old ICR mice and in TLR4 or MyD88 knockout and parental mice. Circulating histones were detected and the effect of NAHP was evaluated.RESULTSExtracellular histones strongly stimulated LX2 cells to produce collagen I. Histone-enhanced collagen expression was significantly reduced by NAHP and TLR4-blocking antibody. In CCl4-treated wild type mice, circulating histones were dramatically increased and maintained high levels during the duration of fibrosis-induction. Injection of NAHP not only reduced alanine aminotransferase and liver injury scores, but also significantly reduced fibrogenesis. Since the TLR4-blocking antibody reduced histone-enhanced collagen I production in HSC, the CCl4 model with TLR4 and MyD88 knockout mice was used to demonstrate the roles of the TLR4-MyD88 signaling pathway in CCl4-induced liver fibrosis. The levels of liver fibrosis were indeed significantly reduced in knockout mice compared to wild type parental mice.CONCLUSIONExtracellular histones potentially enhance fibrogenesis via the TLR4–MyD88 signaling pathway and NAHP has therapeutic potential by detoxifying extracellular histones.

Immunomodulatory effects of a polysaccharide from Solanum nigrum Linne through TLR4-MyD88 signaling pathway

Solanum nigrum Linne polysaccharide (SNLP), an active ingredient from Solanum nigrum Linne, has been proposed to inhibit tumor growth and display immunomodulatory activity. However, the molecular mechanism related to immune regulation remains unclear. In the present study, a homogeneous polysaccharide (SNLP-1) was extracted, the immune effects and the underlying molecular mechanisms were investigated. The immunomodulatory activity assay in vitro showed that SNLP-1 promoted the release of NO and TNF-α and IL-6 secretion in macrophages. In tumor-bearing mice, SNLP-1 could improve immune function including increasing the spleen index, thymus index and inducing Th1 responses mediated by IL-2, IFN-γ, and TNF, as well as decreasing the tumor weight. Furthermore, SNLP-1 elevated the expression of the critical nodes in the TLR4-Myd88 signaling pathways in vitro and in vivo. These results indicated that TLR4-MyD88 signal pathway may be one of the signal pathways of immune regulation of SNLP-1.

BIG1 controls macrophage pro-inflammatory responses through ARF3-mediated PI(4,5)P2 synthesis

Sepsis is caused by a dysregulated host inflammatory response to serious infections resulting in life-threatening organ dysfunction. The high morbidity and mortality make sepsis still a major clinical problem. Here, we investigated the roles of Brefeldin A-inhibited guanine nucleotide-exchange factor 1 (BIG1) in the pathogenesis process of sepsis and the underlying mechanisms. We found myeloid cell-specific BIG1 knockout (BIG1 cKO) significantly reduced the mortality and organ damage in LPS-induced and CLP-induced polymicrobial sepsis mouse model. The serum concentration and mRNA expression of pro-inflammatory cytokines including TNF-α, IL-6, IL-1β, and IL-12 were obviously decreased in BIG1 cKO mice. In bone marrow-derived macrophages or THP-1 cells, BIG1 deficiency caused an inhibited ARF3 activation, which reduced PI(4,5)P2 synthesis and the recruitment of TIRAP to the plasma membrane through inhibiting the activation of PIP5K induced by LPS, and eventually resulted in the inhibitory activity of TLR4-MyD88 signaling pathway. These results reveal a crucial new role of BIG1 in regulating macrophage inflammation responses, and provide evidence for BIG1 as a potential promising therapeutic target in sepsis.

TLR4-MyD88 signaling pathway is responsible for acute lung inflammation induced by reclaimed water

Previous research found that inhalation exposure of reclaimed water could cause severe pulmonary inflammation, and the endotoxin was proposed to be the key risk factor. To further support this view, the toxic effects of different reclaimed water induced by acute inhalation exposure were compared between wildtype C57BL/6J and TLR4 signaling pathway defect mice. It was found that reclaimed water with high levels of endotoxin could induce strong inflammation in wildtype mice, but not in Tlr4−/− and MyD88−/− mutants. The mixed bacterial culture from the reclaimed water showed very weak response in wildtype mice and no response in TLR4-signaling pathway deficient mice, which further suggested that the cell-bound endotoxins contribute little in the inflammation induced by reclaimed water. In addition, conditional knockout of the Tlr4 gene in myeloid cells resulted in a significant reduction of sensitivity to the reclaimed water in mutants, which indicates that myeloid cells play the most important role in the defensive immune system against the pollutants in the water. In general, this study demonstrated that the TLR4-MyD88 signaling pathway is responsible for the acute lung inflammation induced by reclaimed water, which excludes the possibility of other signaling pathway dependent inflammation inducers in reclaimed water.

A polysaccharide extracted from alfalfa activates splenic B cells by TLR4 and acts primarily via the MAPK/p38 pathway.

Alfalfa polysaccharide (APS) has been proposed to exhibit growth-promoting and immune-enhancing bodily functions in vivo. However, little is known about its downstream immunomodulatory and intrinsic molecular mechanisms. Herein, mouse splenic lymphocytes were isolated to characterize the immunomodulatory effects and molecular mechanisms of APS in vitro. The results demonstrated that APS selectively improved the cell viability and IgM production of B cells, but no effects on T cell viability or secretion of IL-2, IL-4 and IFN-γ were observed in vitro. The receptor blocking assay showed that TLR4 was the primary receptor involved in APS-mediated B cell activation, which was confirmed by the results obtained using C57BL/10ScNJ (TLR4 gene-deficient) mice. Moreover, APS activated the TLR4-MyD88 signaling pathway at the translational level by significantly increasing the protein expression of TLR4 and MyD88. Downstream pathway blocking assay demonstrated that both the MAPK and NF-κB pathways were involved in APS-induced B cell activation. Additionally, APS significantly enhanced the phosphorylation of p38, ERK, and JNK and activated the nuclear translocation of the NF-κB p65 subunit. Therefore, we concluded that APS specifically activates the immune functions of splenic B cells by TLR4, acting through the MAPK and NF-κB signaling pathways, and potently activates the p38 pathway.

P6306Hyperlipidemia inhibits the protective effect of lisinopril after myocardial infarction via activation of dendritic cells

Abstract Background In clinical situation, patients with myocardial infarction (MI) usually suffered from hyperlipidemia, hypertension, renal dysfunction or diabetes as well and the interaction of those risk factors may affect the effectiveness of ACEI. Dendritic cell (DC) is a potent central immunoregulator that orchestrates various types of inflammatory cells in innate and adoptive immunity. The role of DCs in the inflammation of cardiovascular disease is a hotspot of international research. Purpose To investigate the improvement of cardiac remodeling and inflammatory immune response after MI via ACEI regulating DCs and explore that whether the protective effect of ACEI is under the circumstance of hyperlipidemia. Methods In vivo, MI mice models were created via coronary artery ligation. We detected the survival and left ventricular function on day 7 after MI. Tissue samples of the myocardium, spleen, bone marrow and peripheral blood were obtained and assessed for Ang2 concentration, inflammatory cytokines and DCs expression via immunohistochemistry, ELISA, flow cytometry and western blot. In vitro, we treated DCs with ox-LDL+AngIIfor 48 hours simulating the internal environment of MI in ApoE−/− mice to explore the mechanism involved in the DCs maturation and inflammation. Results Under the circumstance of hyperlipidemia, the cardioprotective effect of ACEI is attenuated through regulating DCs maturation and inflammation after MI, including survival rate (Figure 1) and left ventricular function. The number of DCs in cardiac tissue were increased in MI mice with hyperlipidemia (Figure 2), when compared with the WT group. The expression of the maturity phenotype related molecules, such as CD83, on the DCs in spleen were also increased in the ApoE−/− mice. Then, the expressions of inflammatory cytokines, such as IL-6 and TNF-α. In vitro, it was found that the immune maturation and inflammation of DCs could be further induced by ox-LDL on the basis of AngIItreatment, as indicated by the upregulation of CD83 and CD86, the expressions of cytokines and chemokines. Furthermore, ox-LDL could activate the toll-like receptor 4 (TLR4)-myeloid differentiation factor 88 (MyD88) signaling pathway, promoting the phosphorylation of interleukin-1 receptor associated kinase (IRAK)-4 and the nuclear transferring of nuclear factor-kappaB (NF-κB). Conclusion We proved ACEI reduces the recruitment of DCs to the infarct, leading to a higher survival rate and improved function and remodeling through decreased inflammation resulting from immune response after MI. However, this effect was inhibited under the circumstance of hyperlipidemia. TLR4-MyD88 signaling pathway might be the possible molecular mechanism involved in the immune maturation and inflammation of DCs induced by ox-LDL on the basis of AngII. Acknowledgement/Funding the Youth fund of the National Natural Science Foundation of China, Grant 81600280

MiR-216a-5p-containing exosomes suppress rTp17-induced inflammatory response by targeting TLR4.

Syphilis caused by Treponema pallidum (T. pallidum) infection is accompanied by inflammatory injury of tissue, and has a worldwide distribution and increasing incidence over the past decade. Tp17 has been reported to be a strong membrane immunogen, and was initially observed to play a role in inflammation during syphilis, reacting intensely with human syphilitic sera. We therefore used recombinant Tp17 (rTp17) as a stimulator in our study. Increasing evidence has demonstrated that microRNA (miRNA)-containing exosomes have emerged as a potential effective therapeutic target for many diseases. However, the biological functions and molecular mechanisms of miR-216a-5p in syphilis pathogenesis remain unknown. Our study first identified dramatically decreased miR-216a-5p in plasma of syphilis patients compared with the healthy control, which was negatively correlated with the expression of inflammatory cytokines, including IL-1β, IL-6, and TNF-α. Moreover, endothelial cells treated with miR-216a-5p-containing exosomes significantly attenuated the rTp17-induced inflammatory response. More importantly, we identified that miR-216a-5p could bind to the 3′-untranslated region (UTR) of Toll-like receptor (TLR) 4 (TLR4), and overexpression of TLR4 largely rescued the miR-216a-5p-mediated suppression of rTp17-induced inflammatory cytokine production and the TLR4-MYD88 signaling pathway. Thus, our results reveal a novel role of miR-216a-5p-containing exosomes in endothelial cells, implying a potential therapeutic target for inflammation in syphilis patients.

Alpha-synuclein (αS) acts as an alarmin to promote dendritic cell activation and proinflammatory immune response

Abstract Alpha-synuclein (αS) protein is involved in the development of neurodegenerative disorders including Parkinson’s disease. Recently, it has been shown that αS expression by enteric neurites in the inflamed tissues of the gut correlates with the degree of inflammation and αS is chemotactic for phagocytes. However, it is not clear whether αS plays any roles in immune responses. Here, we report that αS has potent immunopromoting activity. Treatment of human monocyte derived dendritic cells (Mo-DCs) by αS resulted in upregulation of costimulatory (CD80, CD83, & CD86) and MHC (HLA-ABC & HLA-DR) molecules and production of proinflammatory cytokines such as IL-12 and TNFα. αS activated NF-κB signaling pathways in DCs and conditioned DCs to potentiate Th1 and Th17 polarization of CD4+ T cells in an allogeneic MLR. αS also induced mouse bone marrow derived (BM)-DCs and macrophages in a Th1-polarizing and M1 direction, respectively. αS activation of APCs is mediated by the TLR4-MYD88 signaling pathways. In an in vivo setting, administration of αS induced the recruitment of APCs at the site of injection. Furthermore, αS enhanced the induction of OVA-specific antibody and T cell responses when mice were immunized with a mixture of OVA and αS. Based on the ability of αS to recruit APCs to the site of administration and to promote antigen-specific immune responses, αS can be considered an alarmin capable of promoting the development of innate and adaptive immune responses. Thus, αS, in addition to acting as an inducer of neurodegenerative diseases, exerts a potent previously unappreciated proinflammatory and immunostimulating effect.

Interleukin-1 receptor associated kinase (IRAK)-M -mediated type 2 microglia polarization ameliorates the severity of experimental autoimmune encephalomyelitis (EAE)

Toll-like receptor 4 (TLR4) play a key role in activating the innate immune system during pathogen recognition. In the pathogenesis of multiple sclerosis (MS), activated TLR4 together with myeloid differentiation primary response gene 88 (MyD88) produce an inflammatory microenvironment that promotes the differentiation of microglia into the M1 phenotype, who plays a key role in the pathogenesis of MS. Interleukin-1 receptor-associated kinase (IRAK)-M is specifically expressed in microglia in central nervous system (CNS) and act as a negative regulator of TLR4-MyD88 signaling pathway. Moreover, previous studies have shown that IRAK-M promotes the differentiation of type 2 microglia; however, its role in MS has not been explored. In the present study, we demonstrated that IRAK-M expression is elevated during EAE, and IRAK-M−/− mice significantly accelerated course and increased severity of disease, accompanied by a visible increase of the M1 microglia infiltrated. In conclusion, these data indicates that IRAK-M significantly improves EAE onset through down-regulation of the TLR4-MyD88 signaling pathway, which finally leads to differentiation of M2 phenotype in the microglia. Our study suggests that IRAK-M may be a potential therapeutic target for the treatment of MS.

Deferoxamine preconditioning activated hypoxia-inducible factor-1α and MyD88-dependent Toll-like receptor 4 signaling in intestinal stem cells

Background/PurposeToll-like receptors (TLRs) are important regulators of innate immunity, and TLR4 pathway can regulate the survival, migration, and differentiation of stem cells, including intestinal stem cells (ISCs). Deferoxamine (DFO), a hypoxia-mimic compound, can activate the proliferation of ISCs. In this study, we investigated the response of TLR4 signaling to DFO-induced hypoxia in cultured ISCs in vitro. MethodsAfter DFO treatment, the crypt organoid number was counted, and the expression levels of Lgr5, Hsp70, HMGB1, HIF-1α, TLR4, MyD88, TRIF, and TRAM in ISCs were examined using QPCR and Western blotting. The chemical inhibitors of different signaling molecules were then used to determine their role in DFO-induced change in ISCs. ResultsThe expression levels of Lgr5, HIF-1α, TLR4, MyD88, and TRIF in ISCs increased after DFO treatment, with peak expression of these molecules 6h after DFO treatment. In addition, DFO-induced gene expression of Lgr5 and HIF-1α was partially reversed by pretreatment with the inhibitor of TLR4 or MyD88, but not TRIF inhibitor. Inhibition of HIF-1α also resulted in partial downregulation of DFO-induced elevation of Lgr5 and TLR4. ConclusionsThese results demonstrated that DFO treatment activated HIF-1α and the TLR4-MyD88 signaling pathway, which might mediate the activation of ISCs.