Knockdown Of Toll-like Receptor Research Articles

Reovirus enhances cytotoxicity of natural killer cells against colorectal cancer via TLR3 pathway

BackgroundCetuximab has been approved for use for first-line treatment of patients with wild-type KRAS metastatic colorectal cancer (CRC). However, treatment with cetuximab has shown limited efficacy as a CRC monotherapy. In addition, natural killer (NK) cell function is known to be severely attenuated in cancer patients. The goal of this study was to develop a new strategy to enhance antibody-dependent cell-mediated cytotoxicity (ADCC) mediated by NK cells, in combination with cetuximab against CRC cells.MethodsEx vivo expanded NK cells were stimulated with reovirus, and reovirus-activated NK cells mediated ADCC assay were performed on CRC cells in combination with cetuximab. The synergistic antitumor effects of reovirus-activated NK cells and cetuximab were tested on DLD-1 tumor-bearing mice. Finally, Toll-like receptor 3 (TLR3) knockdown in NK cells, along with chemical blockade of TLR3/dsRNA complex, and inhibition of the TLR3 downstream signaling pathway, were performed to explore the mechanisms by which reovirus enhances NK cell cytotoxicity.ResultsWe first confirmed that exposure of NK cells to reovirus enhanced their cytotoxicity in a dose-dependent manner.We then investigated whether reovirus-activated NK cells exposed to cetuximab-bound CRC cells exhibited greater anti-tumor efficacy than either monotherapy. Co-culture of CRC cell lines with reovirus-activated NK cells indicated that NK cytotoxicity was significantly higher in combination with cetuximab, regardless of KRAS mutation status or EGFR expression level. We also found that reovirus activation of NK cells, in conjunction with cetuximab, resulted in significantly stronger anti-tumor efficacy.Finally, TLR3 knockdown, inhibition of TLR3/dsRNA complex or TBK1/IKKε demonstrated that activation of NK cells by reovirus was dependent on TLR3 and its downstream signaling pathway.ConclusionsThis study demonstrated that combination treatment of reovirus-activated NK cells with cetuximab synergistically enhances their anti-tumor cytotoxicity, suggesting a strong candidate strategy for clinical treatment of CRC.

Abstract 16966: A p53-Toll-Like Receptor 3-Bone Morphogenic Protein Interaction Regulates the Endothelial Phenotype and Function in Pulmonary Hypertension

Introduction: Pulmonary arterial hypertension (PAH) is characterized by complex remodeling of pulmonary arteries. In addition to impaired bone morphogenic protein (BMP) signaling, deficiency of the cell cycle regulator p53 has been implicated in PAH pathogenesis. Endothelial cells (ECs) from PAH patients have reduced levels of toll-like receptor 3 (TLR3), impairing EC function. This study investigated whether the p53, TLR3 and BMP pathways regulate endothelial phenotype and function in PAH. Methods: Human pulmonary artery ECs (PAECs) and rat CD117 + ECs were used. Knockdown experiments were carried out by targeting p53 and TLR3. Cells were further treated with the MDM2 antagonist Nutlin 3a, reducing p53 degradation, and with the TLR3 agonist Poly(I:C). Rats received CD117 + EC clones or SU5416 and were subjected to chronic hypoxia and then treated with Nutlin-3a, Poly(I:C) or vehicle. Results: We detected reduced p53 levels in PAECs from PAH patients. Clonal expansion of rat CD117 + ECs resulted in hyperproliferative cells with reduced p53 and TLR3 levels and evidence for histone methylation. Then, knockdown of p53 or TLR3 increased tube formation in surviving human and rat ECs. In addition, knockdown or activation of p53 indicated regulation of TLR3 mRNA by p53. TLR3 knockdown reduced expression of BMP2, whereas the TLR3 agonist Poly(I:C) induced BMP receptor 2 expression. Upstream, reduced p53 degradation by Nutlin 3a not only increased TLR3, but also BMP2 expression and increased BMP signaling in rat ECs. Interestingly, clonal selection resulted in EC clones with high BMP2 expression. TLR3 knockdown caused partial endothelial mesenchymal transition with increased expression of Snail, which was ameliorated by Poly(I:C). In vivo, Nutlin-3a treatment reduced PH while increasing TLR3 expression in rats. Poly(I:C) reduced PH and Smad2 phosphorylation in rats, and the protective effects were abolished in TRIF KO mice. Conclusion: The RNA receptor and p53 transcriptional target TLR3 regulates the BMP pathway in ECs and this interaction may explain some of the protective effects of TLR3 stimulation in PH. However as clonally selected ECs retain high BMP2 expression, differences between EC subpopulations can be suggested and are under investigation.

TLR3/TAK1 signalling regulates rhinovirus-induced interleukin-33 in bronchial smooth muscle cells.

BackgroundAsthma exacerbations are commonly associated with rhinovirus (RV) infection. Interleukin-33 (IL-33) plays an important role during exacerbation by enhancing Type 2 inflammation. Recently we showed that RV infects bronchial smooth muscle cells (BSMCs) triggering production of interferons and IL-33. Here we compared levels of RV-induced IL-33 in BSMCs from healthy and asthmatic subjects, and explored the involvement of pattern-recognition receptors (PRRs) and downstream signalling pathways in IL-33 expression.MethodBSMCs from healthy and severe and non-severe asthmatic patients were infected with RV1B or stimulated with the PRR agonists poly(I:C) (Toll-like receptor 3 (TLR3)), imiquimod (TLR7) and poly(I:C)/LyoVec (retinoic acid-inducible gene 1 (RIG-I)/melanoma differentiation-associated protein 5 (MDA5)). Knockdown of TLR3, RIG-I and MDA5 was performed, and inhibitors targeting TBK1, nuclear factor-κB (NF-κB) and transforming growth factor (TGF)-β-activated kinase 1 (TAK1) were used. Gene and protein expression were assessed.ResultsRV triggered IL-33 gene and protein expression in BSMCs. BSMCs from patients with non-severe asthma showed higher baseline and RV-induced IL-33 gene expression compared to cells from patients with severe asthma and healthy controls. Furthermore, RV-induced IL-33 expression in BSMCs from healthy and asthmatic individuals was attenuated by knockdown of TLR3. Inhibition of TAK1, but not NF-κB or TBK1, limited RV-induced IL-33. The cytokine secretion profile showed higher production of IL-33 in BSMCs from patients with non-severe asthma compared to healthy controls upon RV infection. In addition, BSMCs from patients with non-severe asthma had higher levels of RV-induced IL-8, TNF-α, IL-1β, IL-17A, IL-5 and IL-13.ConclusionRV infection caused higher levels of IL-33 and increased pro-inflammatory and Type 2 cytokine release in BSMCs from patients with non-severe asthma. RV-induced IL-33 expression was mainly regulated by TLR3 and downstream via TAK1. These signalling molecules represent potential therapeutic targets for treating asthma exacerbations.

ISG56 is involved in CXCL10 expression induced by TLR3 signaling in BEAS-2B bronchial epithelial cells

Purpose and aim of the study: Bronchial epithelial cells play an important role in immune response against viral infections. Toll-like receptor 3 (TLR3) is a pathogen recognition receptor that recognizes viral double-stranded RNA (dsRNA). Activation of TLR3 induces the expression of interferon (IFN)-β, and newly synthesized IFN-β exhibits anti-viral activity by upregulating the expression of IFN-stimulated genes (ISGs). ISG56 encodes a multifunctional protein with tetratricopeptide motifs and is involved in anti-viral reactions through various mechanisms. Expression of chemokines such as CXCL10, which induces leukocyte chemotaxis, is essential for defense against airway microbes. However, regulation of chemokine expression by ISG56 in bronchial epithelial cells has not been fully investigated. The aim of this study was to examine the expression of ISG56 and its role in CXCL10 production in BEAS-2B bronchial epithelial cells treated with dsRNA.Materials and methods: BEAS-2B bronchial epithelial cells were treated with polyinosinic-polycytidylic acid (poly IC), a synthetic TLR3 ligand. The mRNA and protein expression levels of ISG 56 were analyzed by quantitative reverse transcription polymerase chain reaction and western blotting. The effect of knocking down TLR3, IFN-β, and ISG56 was examined using RNA interference. The protein expression of CXCL10 in culture medium was measured using an enzyme-linked immunosorbent assay.Results: Poly IC induced ISG56 expression in a concentration- and time- dependent manner. RNA interference showed that ISG56 induction was inhibited by knockdown of TLR3 or IFN-β and that ISG 56 knockdown decreased CXCL10 expression.Conclusions: ISG56 was induced by poly IC through TLR3/IFN-β axis, and ISG56 may positively regulated CXCL10 expression in BEAS-2B cells. ISG56 may modulate anti-viral innate immunity, at least in part, by regulating the expression of CXCL10 in bronchial epithelial cells.

DsRNA induction of microRNA-155 disrupt tight junction barrier by modulating claudins

BackgroundThe impaired barrier function of the airway epithelium due to RNA virus infection is closely related to the development and exacerbation of allergic airway inflammation.ObjectiveIn this study, we investigated the roles of microRNAs on the mechanisms of double-stranded RNA (dsRNA)-induced epithelial barrier dysfunction.Methods16HBE14o- human bronchial epithelial cells were grown to confluence on Transwell inserts and exposed to poly-I:C. We studied epithelial barrier function by measuring transepithelial electrical resistance and paracellular flux of fluorescent markers and structure of tight junctions by immunofluorescence microscopy.ResultsPoly-I:C treated 16HBE14o- cells increased paracellular permeability. Knockdown of Toll-like receptor 3 and TRIF abrogated these effects. The expression of microRNA-155 (miR-155) was increased by poly-I:C in dose-dependent manner. Transfection of mir155 mimics into 16HBE14o- cells increased permeability and inhibited tight junction formation. Transfection of miR-155 inhibitor suppressed poly-I:C-induced barrier disruption. Poly-I:C treatment significantly decreased the expression of claudin members—claudin-1, -3, -4, -5, -9, -11, -16, -18 and -19. Transfection of miR-155 mimics showed similar changing expression pattern of claudin members with those of poly-I:C treatment.ConclusionThese results suggest that RNA virus infection can impair the epithelial barrier disruption mechanism by down-regulation of claudin members through the induction of miR-155.

Induction of C‐C motif chemokine ligand 2 through Toll‐like receptor 3 signaling in human cerebral microvascular endothelial cell/D3 cells: possible regulation by nuclear factor‐κB

AbstractObjectiveC‐C motif chemokine ligand 2 (CCL2) is a potent chemokine that plays an important role in host defense and inflammatory diseases in the central nervous system. Toll‐like receptor 3 (TLR3) is a pattern recognition receptor that recognizes viral double‐stranded RNAs. In the present study, we examined whether a TLR3 agonist induces CCL2 expression in brain microvascular endothelial cells, and investigated the mechanism underlying upregulation of CCL2 expression through TLR3 signaling.MethodsA human brain microvascular endothelial cell line, human cerebral microvascular endothelial cell (hCMEC)/D3 was treated with a TLR3 agonist, polyinosinic‐polycytidylic acid (poly IC). The mRNA and protein expression of CCL2 were evaluated using real‐time reverse transcription polymerase chain reaction and enzyme‐linked immunosorbent assay, respectively. The role of TLR3 and nuclear factor‐κB (NF‐κB) were examined with RNA interference. We also examined the effect of pretreatment with an NF‐κB inhibitor, SN50, an interferon regulatory factor 3 inhibitor MR67307 and human type I interferon neutralizing antibody mixture on poly IC‐induced CCL2 expression.ResultsExpression of CCL2 was induced by poly IC. Poly IC‐induced CCL2 expression was decreased by knockdown of TLR3 or NF‐κB p65 and by pretreatment with SN50. Neither MR67307 nor human type I interferon neutralizing antibody mixture affected the CCL2 expression induced by poly IC.ConclusionsCCL2 expression was induced by poly IC through TLR3 signaling, and NF‐κB is involved in this reaction. CCL2 produced by human brain endothelial cells might induce the infiltration of monocytes followed by immune and inflammatory reactions in the brain, and could be involved in the pathogenesis of viral encephalitis.

Toll-like Receptor 3 Is a Therapeutic Target for Pulmonary Hypertension.

Pulmonary arterial hypertension (PAH) is characterized by vascular cell proliferation and endothelial cell apoptosis. TLR3 (Toll-like receptor 3) is a receptor for double-stranded RNA and has been recently implicated in vascular protection. To study the expression and role of TLR3 in PAH and to determine whether a TLR3 agonist reduces pulmonary hypertension in preclinical models. Lung tissue and endothelial cells from patients with PAH were investigated by polymerase chain reaction, immunofluorescence, and apoptosis assays. TLR3-/- and TLR3+/+ mice were exposed to chronic hypoxia and SU5416. Chronic hypoxia or chronic hypoxia/SU5416 rats were treated with the TLR3 agonist polyinosinic/polycytidylic acid (Poly[I:C]). TLR3 expression was reduced in PAH patient lung tissue and endothelial cells, and TLR3-/- mice exhibited more severe pulmonary hypertension following exposure to chronic hypoxia/SU5416. TLR3 knockdown promoted double-stranded RNA signaling via other intracellular RNA receptors in endothelial cells. This was associated with greater susceptibility to apoptosis, a known driver of pulmonary vascular remodeling. Poly(I:C) increased TLR3 expression via IL-10 in rat endothelial cells. In vivo, high-dose Poly(I:C) reduced pulmonary hypertension in both rat models in proof-of-principle experiments. In addition, Poly(I:C) also reduced right ventricular failure in established pulmonary hypertension. Our work identifies a novel role for TLR3 in PAH based on the findings that reduced expression of TLR3 contributes to endothelial apoptosis and pulmonary vascular remodeling.

Low expression of miR-186-5p regulates cell apoptosis by targeting toll-like receptor 3 in high glucose-induced cardiomyocytes.

To investigate the effect and mechanism of microRNA-186-5p (miR-186-5p) on the apoptosis in high glucose (HG)-treated cardiomyocytes. Diabetic cardiomyopathy model was established in cardiomyocytes by stimulating with HG. The expressions of miR-186-5p and toll-like receptor 3 (TLR3) were detected by quantitative polymerase chain reaction or Western blot analysis, respectively. Apoptosis was detected in HG-treated cardiomyocytes by flow cytometry and Western blot analysis. The interaction between miR-186-5p and TLR3 was explored by bioinformatics analysis and luciferase activity assay. Results showed that miR-186-5p expression was downregulated in HG-treated cardiomyocytes and its overexpression reversed HG-induced apoptosis and cleaved caspase-3 protein expression. Moreover, TLR3 was indicated as a target of miR-186-5p and regulated by miR-186-5p. Knockdown of TLR3 suppressed HG-induced apoptosis and cleaved caspase-3 protein expression. Besides, restoration of TLR3 ablated the effect of miR-186-5p on cell apoptosis. Collectively, miR-186-5p attenuated HG-induced apoptosis by regulating TLR3 in cardiomyocytes, providing novel biomarker for treatment of diabetic cardiomyopathy.

Retinoic acid‐inducible gene‐I, melanoma differentiation‐associated gene 5 and C‐X‐C motif chemokine ligand 10 are induced by a Toll‐like receptor 3 agonist in human brain microvascular endothelial cells

AbstractObjectiveBrain microvascular endothelial cells (BMEC) are the major component of the blood–brain barrier, and play a critical role in protecting the brain from pathogens. Although Toll‐like receptor 3 (TLR3) is known as an important pattern‐recognition receptor against viral double‐stranded RNA, the downstream reactions of TLR3 in human BMEC are not fully characterized. The purpose of the present study was to investigate the role of TLR3 signaling in the expression of retinoic acid‐inducible gene‐I (RIG‐I), melanoma differentiation‐associated gene 5 (MDA5) and C‐X‐C motif chemokine ligand 10 (CXCL10) in human BMEC.MethodsThe hCMEC/D3 cells, a human BMEC cell line, were cultured and stimulated with polyinosinic‐polycytidylic acid, a synthetic TLR3 agonist. Quantitative real‐time reverse transcription polymerase chain reaction, western blotting and enzyme‐linked immunosorbent assay were used to examine the expression of interferon‐β, RIG‐I and CXCL10. RNA interference against TLR3, interferon‐β, RIG‐I or MDA5 was also carried out.ResultsExpression of RIG‐I, MDA5 and CXCL10 were induced by polyinosinic‐polycytidylic acid, and this was inhibited by knockdown of either TLR3 or interferon‐β. Knockdown of RIG‐I or MDA5 did not affect the CXCL10 expression in the early phase (4 h), but decreased the CXCL10 induction in the late phase (8 or 24 h).ConclusionsRIG‐I, MDA5 and CXCL10 are induced through TLR3 activation in hCMEC/D3 cells, and RIG‐I and MDA5 might function to enhance and/or prolong the reactions mediated by CXCL10. These molecules might play a distinct role in innate immune reactions against double‐stranded RNA viruses in human BMEC.

Crystallinity of Double-Stranded RNA-Antimicrobial Peptide Complexes Modulates Toll-Like Receptor 3-Mediated Inflammation.

Double-stranded RNA (dsRNA) induces production of pro-inflammatory cytokines in normal human epidermal keratinocytes (NHEK) by specific binding to endosomal Toll-like receptor-3 (TLR3). Recently, it has been shown that hyperactivation of TLR3 in psoriatic keratinocytes by dsRNA can occur in the presence of human antimicrobial peptide (AMP) LL37. Here, we combine synchrotron X-ray scattering, microscopy, computer simulations, and measurements of NHEK cytokine production to elucidate a previously unanticipated form of specific molecular pattern recognition. LL37 and similar α-helical AMPs can form pro-inflammatory nanocrystalline complexes with dsRNA that are recognized by TLR3 differently than dsRNA alone. dsRNA complexes that activate IL-6 production in NHEK and those that do not are both able to enter cells and co-localize with TLR3. However, the crystallinity of these AMP-dsRNA complexes, specifically the geometric spacing between parallel dsRNA and the repeat number of ordered dsRNA, strongly influences the level of TLR3 activation. Crystalline complexes that present dsRNA at a spacing that matches with the steric size of TLR3 can recruit and engage multiple TLR3 receptors, driving receptor clustering and immune amplification, whereas crystalline complexes that exhibit poor steric matching do not. Reverse-transcription quantitative PCR of IL-6 during siRNA knockdown of TLR3 confirms that cytokine production is due to TLR3: High levels of IL-6 transcription are observed for sterically matched complexes without TLR3 knockdown, whereas such activity is abrogated with TLR3 knockdown.

Expression of CCL5 is induced by polyinosinic : polycytidylic acid in cultured hCMEC/D3 human brain microvascular endothelial cells

AbstractObjectiveBrain microvascular endothelial cells are one of the cell types that form the blood–brain barrier, and play an important role in the defense system of the brain. Toll‐like receptor 3 (TLR3) is a pattern‐recognition receptor against double‐stranded RNA, and TLR3 signaling is important in antiviral innate immune reactions. However, TLR3 signaling in brain microvascular endothelial cells is not well understood. We aimed to investigate the role of TLR3 signaling in chemokine CCL5 production in human brain microvascular endothelial cells.MethodsThe hCMEC/D3 human brain microvascular endothelial cells were cultured, and treated with an authentic TLR3 agonist polyinosinic : polycytidylic acid. The expression of CCL5 was examined using quantitative real‐time reverse transcription polymerase chain reaction and enzyme‐linked immunosorbent assay. Involvement of TLR3, interferon (IFN)‐β, or IFN‐λ1, IFN‐regulatory factor 3 or nuclear factor‐κB p65 in this reaction was examined using RNA interference. Translocation of p65 into the nucleus was examined using immunofluorescence staining.ResultsTreatment of cells with polyinosinic : polycytidylic acid induced the expression of CCL5, IFN‐β and IFN‐λ1, and also the translocation of p65 into the nucleus. Knockdown of TLR3, IFN‐regulatory factor 3 or p65 inhibited the induction of these molecules, while knockdown of neither IFN‐β nor IFN‐λ1 affected the expression of CCL5.ConclusionsTLR3 activation by polyinosinic : polycytidylic acid induces the expression of CCL5 in cultured hCMEC/D3 cells, and IFN‐regulatory factor 3 and p65 are involved in this reaction. CCL5 induced by TLR3 signaling in brain microvascular endothelial cells might contribute to antiviral protective reactions and/or detrimental responses associated with viral infection in the brain.

US10, a novel Npro-interacting protein, inhibits classical swine fever virus replication.

Classical swine fever (CSF) is a severe, febrile and highly contagious disease caused by classical swine fever virus (CSFV) that has resulted in huge economic losses in the pig industry worldwide. CSFV Npro has been actively studied but remains incompletely understood. Few studies have investigated the cellular proteins that interact with Npro and their participation in viral replication. Here, the yeast two-hybrid (Y2H) system was employed to screen Npro-interacting proteins from a porcine alveolar macrophage (PAM) cDNA library, and a blast search of the NCBI database revealed that 15 cellular proteins interact with Npro. The interaction of Npro with ribosomal protein S20, also known as universal S10 (uS10), was further confirmed by co-immunoprecipitation and glutathione S-transferase pull-down assays. Furthermore, uS10 overexpression inhibited CSFV replication, whereas the knockdown of uS10 promoted CSFV replication in PAMs. In addition, Npro or CSFV reduced uS10 expression in PAMs in a proteasome-dependent manner, indicating that Npro-uS10 interaction might contribute to persistent CSFV replication. Our previous research showed that CSFV decreases Toll-like receptor 3 (TLR3) expression. The results showed that uS10 knockdown reduced TLR3 expression, and that uS10 overexpression increased TLR3 expression. Notably, uS10 knockdown did not promote CSFV replication following TLR3 overexpression. Conversely, uS10 overexpression did not inhibit CSFV replication following TLR3 knockdown. These results revealed that uS10 inhibits CSFV replication by modulating TLR3 expression. This work addresses a novel aspect of the regulation of the innate antiviral immune response during CSFV infection.

MEK inhibition enhances efficacy of bacillus Calmette-Guérin on bladder cancer cells by reducing release of Toll-like receptor 2-activated antimicrobial peptides.

Bacillus Calmette-Guérin (BCG) is one of the standard treatment options for non-muscle-invasive bladder cancer. The details of the biological defense mechanisms against BCG remain unclear. Here, we investigated whether BCG-induced release of antimicrobial peptides (AMPs; e.g., human β-defensin-2, -3, and cathelicidin) is involved with mitogen-activated protein kinase (MAPK) pathways, and investigated the enhanced anticancer effect of BCG through the down-regulation of Toll-like receptors (TLRs) and MAPK pathways in bladder cancer cells. BCG-infected bladder cancer cells produced AMPs as a defense mechanism against BCG, which were reduced by MEK inhibitors by blocking phosphorylation of extracellular signal-regulated kinase (ERK1/2 or MEK) and c-Jun. MEK inhibitors enhanced inhibition of bladder cancer cell growth by decreased binding of c-Jun, p65 and Pol II to the activated protein-1 promoter. Knockdown of TLR2 and TLR4 reduced ERK phosphorylation. Knockdown of TLR 2 decreased release of AMPs, which was similar to the efficacy of MEK inhibitor on BCG-infected cells. BCG-infected bladder cancer cells were more prone to induction of AMP release following TLR2 activation via ERK and c-Jun pathway mediators. In conclusion, our data suggest that the BCG-induced release of AMPs in bladder cancer cells is a promising molecular target for enhancing the immunotherapeutic efficacy of BCG in bladder cancer patients.

740 Serum Amyloid A1 is induced by UV irradiation and detected by toll-like receptor 4 to cause skin inflammation

Cutaneous inflammation induced by UV irradiation has been well documented clinically. However, despite many previous efforts, it is not fully understood which molecules mediate this inflammatory response. Our recent study found that serum amyloid A1 (SAA1) was increased in UV-irradiated human skin. Since SAA1 has been reported to exert proinflammatory effect, this finding implicates SAA1 as a mediator in UV-induced cutaneous inflammation. Here, we demonstrated that the expression of SAA1 was increased by acute UV irradiation in mouse skin in vivo. Intradermal injection of recombinant mouse SAA1 caused inflammation and induced IL-1β and IL-6 in mouse skin in vivo. Correspondingly, treatment of recombinant human SAA1 (rhSAA1) induced IL-1β, IL-6, and IL-8 in primary normal human dermal fibroblasts (NHDFs). In addition, knockdown of Toll-like receptor 4 (TLR4) or blocking of NF-κB signaling pathway attenuated rhSAA1-induced proinflammatory cytokine expressions in NHDFs. Taken together, our data showed that SAA1 was produced by UV irradiation and induced inflammation in mouse skin in vivo and that SAA1 induced proinflammatory cytokines in NHDFs through TLR4/NF-κB signaling pathway. Therefore, our results suggest that SAA1 can be a potential mediator for UV irradiation-induced cutaneous inflammation.

Knockdown of toll-like receptor 4 signaling pathways ameliorate bone graft rejection in a mouse model of allograft transplantation

Non-union occurring in structural bone grafting is a major problem in allograft transplantation because of impaired interaction between the host and graft tissue. Activated toll-like receptor (TLR) induces inflammatory cytokines and chemokines and triggers cell-mediated immune responses. The TLR-mediated signal pathway is important for mediating allograft rejection. We evaluated the effects of local knockdown of the TLR4 signaling pathway in a mouse segmental femoral graft model. Allografts were coated with freeze-dried lentiviral vectors that encoded TLR4 and myeloid differentiation primary response gene 88 (MyD88) short-hairpin RNA (shRNA), which were individually transplanted into the mice. They were assessed morphologically, radiographically, and histologically for tissue remodeling. Union occurred in autografted but not in allografted mice at the graft and host junctions after 4 weeks. TLR4 and MyD88 expression was up-regulated in allografted mice. TLR4 and MyD88 shRNAs inhibited TLR4 and MyD88 expression, which led to better union in the grafted sites. More regulatory T-cells in the draining lymph nodes suggested inflammation suppression. Local inhibition of TLR4 and MyD88 might reduce immune responses and ameliorate allograft rejection.

Double-stranded RNA upregulates the expression of inflammatory mediators in human aortic valve cells through the TLR3-TRIF-noncanonical NF-κB pathway.

Calcific aortic valve disease is a chronic inflammatory condition, and the inflammatory responses of aortic valve interstitial cells (AVICs) play a critical role in the disease progression. Double-stranded RNA (dsRNA) released from damaged or stressed cells is proinflammatory and may contribute to the mechanism of chronic inflammation observed in diseased aortic valves. The objective of this study is to determine the effect of dsRNA on AVIC inflammatory responses and the underlying mechanism. AVICs from normal human aortic valves were stimulated with polyinosinic-polycytidylic acid [poly(I:C)], a mimic of dsRNA. Poly(I:C) increased the production of IL-6, IL-8, monocyte chemoattractant protein-1, and ICAM-1. Poly(I:C) also induced robust activation of ERK1/2 and NF-κB. Knockdown of Toll-like receptor 3 (TLR3) or Toll-IL-1 receptor domain-containing adapter-inducing IFN-β (TRIF) suppressed ERK1/2 and NF-κB p65 phosphorylation and reduced inflammatory mediator production induced by poly(I:C). Inhibition of NF-κB, not ERK1/2, reduced inflammatory mediator production in AVICs exposed to poly(I:C). Interestingly, inhibition of NF-κB by prevention of p50 migration failed to suppress inflammatory mediator production. NF-κB p65 intranuclear translocation induced by the TLR4 agonist was reduced by inhibition of p50 migration; however, poly(I:C)-induced p65 translocation was not, although the p65/p50 heterodimer is present in AVICs. Poly(I:C) upregulates the production of multiple inflammatory mediators through the TLR3-TRIF-NF-κB pathway in human AVICs. The NF-κB activated by dsRNA appears not to be the canonical p65/p50 heterodimers.

CCL5 is induced by TLR 3 signaling in HuCCT1 human biliary epithelial cells: possible involvement in the pathogenesis of biliary atresia.

Biliary atresia (BA) is a disease of the newborn that is characterized by progressive, inflammatory and sclerosing cholangiopathy. Innate immune responses to viral components are thought to be involved in the pathogenesis of BA. It is also reported that some chemokines, such as CCL5, are possibly involved in the pathogenesis of experimental animal model of BA. We treated human biliary epithelial HuCCT1 cells with polyinosinic-polycytidylic acid (poly IC), an authentic double-stranded RNA (dsRNA) which mimics viral RNA, and analyzed the CCL5 expression by quantitative reverse transcription-PCR (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA). To examine the regulation mechanisms of CCL5, we subjected the cells to RNA interference (siRNA) against Toll-like receptor 3 (TLR3), interferon (IFN)-β, NF-κB p65 and IFN regulatory factor (IRF) 3. Immunohistochemical staining for CCL5 was also performed in tissues from patients with BA. Poly IC induced CCL5 expression in HuCCT1 cells. CCL5 expression induced by poly IC was inhibited by the knockdown of TLR3, p65 or IRF3, but it was not affected by knockdown of IFN-β. Immunohistochemical staining showed that CCL5 was strongly expressed in biliary epithelial cells of patients with BA. The current study suggests that TLR3 signaling induces CCL5 expression via NF-κB and IRF3 in bile duct cells, and this pathway may be involved in the pathogenesis of BA.

Staphylococcus aureus-derived membrane vesicles exacerbate skin inflammation in atopic dermatitis.

Skin colonization or infection with Staphylococcus aureus is known to trigger aggravation of atopic dermatitis (AD). However, the exact mechanisms by which S. aureus can worsen AD are unknown. We investigated whether and how S. aureus-derived membrane vesicles (MVs) contribute to worsening of AD. Immunohistochemical and immunoelectron microscopic analyses were performed to detect staphylococcal protein A (SPA) in the epidermis of AD lesions. HaCaT cells were treated with S. aureus MVs and were analysed for the expression of cytokine genes. Immunopathology and cytokine gene profiles were analysed after topical application of S. aureus MVs to AD-like skin lesions in a mouse model. The MV component SPA was detected in the keratinocytes as well as in the intercellular space of the epidermis of AD lesions colonized with S. aureus. Intact MVs from S. aureus delivered their components to keratinocytes and stimulated pro-inflammatory cytokine gene expression in vitro. A knock-down of Toll-like receptor 2 or nucleotide-binding oligomerization domain 2 using small interfering RNAs suppressed interleukin-8 gene expression. Topical application of intact S. aureus MVs to AD-like skin lesions in the mouse model induced massive infiltration of inflammatory cells and the resulting eczematous dermatitis. This inflammatory reaction was associated with a mixed Th1/Th2 immune response and enhanced expression of chemokine genes in AD-like skin lesions. This study showed the importance of S. aureus MVs as a potent mediator for worsening of AD among many exogenous worsening factors of AD. Thus, S. aureus MVs may be regarded as one of the therapeutic targets for the management of AD aggravation.

Serum amyloid A1 secreted from UV-irradiated keratinocytes induces matrix metalloproteinase-1 in fibroblasts through toll-like receptor 4.

Ultraviolet (UV) irradiation on skin triggers photoageing-related phenotypes such as formation of wrinkles. UV ray upregulates matrix metalloproteinase-1 (MMP-1), which in turn degrades extracellular matrix proteins, mostly collagens. Serum amyloid A1 (SAA1) is an acute-phase protein of which plasma concentration increases in response to inflammation. Although the expression of SAA1 in the skin was reported, its function in the skin is yet to be studied. In this research, we found that the expression of SAA1 was increased in acute UV-irradiated buttock skin and photoaged forearm skin in vivo. UV irradiation also increased SAA1 in normal human epidermal keratinocytes (NHEK), and treatment of recombinant human SAA1 (rhSAA1) induced MMP-1 in normal human dermal fibroblasts (NHDF) but not in NHEK. Next, we demonstrated that NHDF treated with UV-irradiated keratinocyte-conditioned media showed the increased MMP-1 expression; however, this increase of MMP-1 in NHDF was inhibited by knockdown of SAA1 in NHEK. In addition, knockdown of Toll-like receptor 4 (TLR4) inhibited rhSAA1-induced MMP-1 expression in NHDF. Taken together, our data showed that UV-induced SAA1 production in NHEK, and this secreted SAA1 induced MMP-1 expression in NHDF in a paracrine manner through TLR4 signalling pathway. Therefore, our results suggest that SAA1 can be a potential mediator for UV-induced MMP-1 expression in human skin.

Amyloid-beta mediates the receptor of advanced glycation end product-induced pro-inflammatory response via toll-like receptor 4 signaling pathway in retinal ganglion cell line RGC-5

Patients with diabetes mellitus have an increased risk of developing Alzheimer's disease. Amyloid-β, a product of amyloid precursor protein, is associated with neuro-inflammation in patients with Alzheimer's diseases. The correlation between amyloid-beta and advanced glycation end products, which accumulate in tissue of diabetic patients, is not clear. The aims of this study were to determine the effect of advanced glycation end product on the expression of amyloid precursor protein/amyloid-beta and associated pro-inflammatory responses in retinal ganglion cell line RGC-5. Treatment with advanced glycation end product produced upregulation of amyloid precursor protein and increased secretion of amyloid-β(1–40). Additionally, amyloid-β(1–40) induced toll-like receptor 4-dependent phosphorylation of tyrosine in myeloid differentiation primary response gene (88). We found that N-[N-(3,5-Difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester, a γ-secretase inhibitor, reduced the secretion of amyloid-β(1–40) and inhibited the advanced glycation end product-induced activation of myeloid differentiation primary response gene (88). Amyloid-β(1–40) induced the activation of NF-κB and the expression of TNFα mRNA. Knockdown of toll-like receptor 4 inhibited the amyloid-β(1–40)-induced phosphorylation of p65 in NF-κB. Additionally, the nuclear translocation of p65 and transcriptions of TNFα were inhibited by siRNA knockdown of receptor of advanced glycation end product or toll-like receptor 4. The advanced glycation end product-induced secretion of VEGF-A was also reduced by knockdown of toll-like receptor 4. Taken together, our data suggested that amyloid-β(1–40) mediates the interaction between receptor of advanced glycation end product and toll-like receptor 4. Inhibition of the toll-like receptor 4 is an effective method for suppressing the amyloid-β(1–40)-induced pro-inflammatory responses in RGC-5 cells.