TRIF-dependent Signaling Pathways Of Toll-like Receptors Research Articles

Isobavachalcone suppresses the TRIF-dependent signaling pathway of Toll-like receptors.

Toll-like receptors (TLRs) are integral membrane-bound receptors that are central to innate and adaptive immune responses. They are known to activate a cascade of downstream signals to induce the secretion of inflammatory cytokines, chemokines, and type I interferons. Dysregulated activation of TLR signaling pathways can induce the activation of various transcription factors, such as nuclear factor kappa B (NF-κB) and interferon regulatory factor 3 (IRF3). TLRs act via MyD88- and TRIF-mediated pathways to induce inflammatory responses. To evaluate the therapeutic potential of isobavachalcone (IBC), a natural chalcone component of Angelica keiskei, we examined its effects on signal transduction via TLR signaling pathways. IBC inhibited the activation of NF-κB and IRF3 induced by TLR agonists and their target genes. IBC also inhibited the activation of NF-κB and IRF3 induced by overexpression of downstream signaling components of TLR signaling pathways. These results suggest that IBC can regulate both MyD88- and TRIF-dependent signaling pathways of TLRs, resulting in a dramatic increase of new therapeutic options for various inflammatory diseases involving TLRs.

Suppression of the TRIF-dependent signaling pathway of TLRs by epoxomicin.

Toll-like receptors (TLRs) can recognize specific signatures of invading microbial pathogens and activate a cascade of downstream signals to induce the secretion of inflammatory cytokines, chemokines, and type I interferons. The activation of TLRs triggers two downstream signaling pathways: the MyD88- and the TRIF-dependent pathways. To evaluate the therapeutic potential of epoxomicin, a member of the linear peptide α',β'-epoxyketone first isolated from an actinomycetes strain, we examined its effects on signal transduction via TLR signaling pathways. Epoxomicin inhibited the activation of NF-kB and IRF3 induced by TLR agonists, decreased the expression of interferon-inducible protein-10, and inhibited the activation of NF-kB and IRF3 induced by overexpression of downstream signaling components of TLR signaling pathways. These results suggest that epoxomicin can regulate both the MyD88- and TRIF-dependent signaling pathways of TLRs. Thus, it might have potential as a new therapeutic drug for a variety of inflammatory diseases.

Eicosapentaenoic acid suppresses TRIF-dependent signaling pathway of TLRs by targeting TBK1

Toll-like receptors (TLRs) induce an innate immune system. In general, there are two main pathways in TLRs: the myeloid differentiation primary response protein 88 (MyD88)-dependent and toll-interleukin-1 receptor domain-containing adapter-inducing interferon-β (TRIF)-dependent pathways. In this study, it has been investigated whether eicosapentaenoic acid (EPA), a polyunsaturated fatty acid (PUFA), and arachidic acid (ACA), a saturated fatty acid (SFA), can modulate the TLR signaling pathways. EPA suppressed the activation of interferon regulatory factor 3 (IRF3) and the expression of Interferon gamma-induced protein (IP-10) induced by Toll-like receptor 3 (TLR3) or TLR4 agonists by targeting TANK-binding kinase 1 (TBK1); however, ACA did not. These results demonstrate that EPA inhibits the TRIF-dependent signaling in the TLR3 and TLR4 pathways. The results raise the possibility that certain dietary PUFAs can modulate TLR-derived signaling and inflammatory target gene expression and can alter the susceptibility to microbial infection and chronic inflammatory diseases. Practical application Eicosapentaenoic acid (EPA) is a bioactive lipid that modulates inflammation and immunity. TLRs play a central role as initiators of the innate immune responses. EPA regulates TRIF-dependent pathways of TLRs by targeting TBK1. EPA may be a useful strategy to understand the mechanism of antiinflammatory activities.

Suppression of TLRs signaling pathways by 1-[5-methoxy-2-(2-nitrovinyl)phenyl]pyrrolidine

Toll-like receptors (TLRs) play significant roles in recognizing the pathogen-associated molecular patterns that induce innate immunity, and subsequently, acquired immunity. In general, TLRs have two downstream signaling pathways, the myeloid differential factor 88 (MyD88)-dependent and toll-interleukin-1 receptor domain-containing adapter-inducing interferon-β (TRIF)-dependent pathways, which lead to the activation of nuclear factor-kappa B (NF-κB) and interferon regulatory factor 3 (IRF3). 1-[5-methoxy-2-(2-nitrovinyl)phenyl]pyrrolidine (MNP) has been previously synthesized in our laboratory. To evaluate the therapeutic potential of MNP, its effect on signal transduction via the TLR signaling pathways was examined. MNP was shown to inhibit the activation of NF-κB and IRF3 induced by TLR agonists, as well as to inhibit the expression of cyclooxygenase-2, inducible nitric oxide synthase, and interferon inducible protein-10. MNP also inhibited the activation of NF-κB and IRF3 induced by the overexpression of downstream signaling components of the MyD88- or TRIF-dependent signaling pathways. These results suggest that MNP can modulate MyD88- and TRIF-dependent signaling pathways of TLRs, leading to decreased inflammatory gene expression.

Suppression of the TRIF-dependent signaling pathway of toll-like receptor by triptolide

Toll-like receptors (TLRs) recognize specific patterns derived from invading microbial pathogens. TLR activation by microbial components triggers the activation of myeloid differential factor 88 (MyD88)- and tollinterleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent downstream signaling pathways, leading to the activation of nuclear factor-κB (NF-κB) and interferon regulatory factor 3 (IRF3). Triptolide (TP), an active ingredient of Tripterygium wilfordii Hook. F, has been reported to have positive effects on autoimmune and inflammatory diseases. To evaluate the therapeutic potential of TP, its effect on signal transduction via the TRIF-dependent pathway of TLRs induced by lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (poly[I:C]) was examined. TP inhibited NF-κB and IRF3 activation and IRF3 phosphorylation induced by LPS or poly[I:C]. TP also inhibited interferon-inducible genes such as, interferon inducible protein-10. These results suggest that TP can modulate TRIF-dependent signaling pathways of TLRs, and will become promising drug candidates in TLRs-based therapy in the future.

Suppression of TRIF-dependent signaling pathway of toll-like receptors by (E)-1-(2-(2-nitrovinyl)phenyl)pyrrolidine

Toll-like receptors (TLRs) play an important role in the recognition of microbial pathogens and induce innate immune responses. The recognition of microbial components by TLRs triggers the activation of myeloid differential factor 88 (MyD88)- and toll-interleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent downstream signaling pathways. Previously, we synthesized (E)-1-(2-(2-nitrovinyl)phenyl)pyrrolidine (NVPP), which contains a nitrovinyl-phenyl and pyrrolidine. To evaluate the therapeutic potential of NVPP, its effect on signal transduction via the TRIF-dependent pathway of TLRs induced by lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (poly[I:C]) was examined. NVPP inhibited LPS or poly[I:C]-induced activation of nuclear factor-κB (NF-κB) and interferon regulatory factor 3 (IRF3), and the phosphorylation of IRF3, as well as inhibiting the activation of interferon-inducible genes such as interferon inducible protein-10 (IP-10). These results suggest that NVPP can modulate TRIF-dependent signaling pathways of TLRs, potentially resulting in effective therapeutics for chronic inflammatory diseases.

Suppression of TRIF-dependent signaling pathway of toll-like receptors by allyl isothiocyanate in RAW 264.7 macrophages

Toll-like receptors (TLR) play a significant role in the induction of innate immune responses that are essential for host defense against invading microbial pathogens. In general, TLRs have two major downstream signaling pathways: myeloid differential factor 88 (MyD88)-dependent and toll-interleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent pathways. Allyl isothiocyanate (AITC) found in cruciferous vegetables has an effect on treatment of many chronic diseases. However, the exact molecular targets of AITC are still unidentified. Here, it was investigated whether AITC can modulate TLR signaling pathways and what is the molecular target of AITC in TLRs signaling pathways. AITC suppressed the activation of nuclear factor-κB by lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (poly[I:C]), but not by macrophage-activating lipopeptide of 2kDa (MALP-2) or cytosine-phosphate-guanine dinucleotide (CpG DNA). AITC also suppressed the activation of interferon regulatory factor 3 (IRF3) and the expression of interferon inducible protein-10 (IP-10) induced by LPS or poly[I:C]. These results suggest that AITC can modulate TRIF-dependent signaling pathways of TLRs leading to decreased inflammatory gene expression.

Suppression of the TRIF-dependent signaling pathway of toll-like receptors by (E)-isopropyl 4-oxo-4-(2-oxopyrrolidin-1-yl)-2-butenoate

Toll-like receptors (TLRs) are pattern recognition receptors that recognize molecular structures derived from microbes and initiate innate immunity. TLRs have two downstream signaling pathways, the MyD88- and TRIF-dependent pathways. Dysregulated activation of TLRs is closely linked to increased risk of many chronic diseases. Previously, we synthesized fumaryl pyrrolidinone, (E)-isopropyl 4-oxo-4-(2-oxopyrrolidin-1- yl)-2-butenoate (IPOP), which contains a fumaric acid isopropyl ester and pyrrolidinone, and demonstrated that it inhibits the activation of nuclear factor kappa B by inhibiting the MyD88-dependent pathway of TLRs. However, the effect of IPOP on the TRIF-dependent pathway remains unknown. Here, we report the effect of IPOP on signal transduction via the TRIF-dependent pathway of TLRs. IPOP inhibited lipopolysaccharide- or polyinosinic-polycytidylic acid-induced interferon regulatory factor 3 activation, as well as interferon- inducible genes such as interferon inducible protein-10. These results suggest that IPOP can modulate the TRIF-dependent signaling pathway of TLRs, leading to decreased inflammatory gene expression.

Parthenolide inhibits TRIF-dependent signaling pathway of Toll-like receptors in RAW264.7 macrophages.

Toll-like receptors (TLRs) play an important role in induction of innate immune responses for host defense against invading microbial pathogens. Microbial component engagement of TLRs can trigger the activation of myeloid differential factor 88 (MyD88)- and toll-interleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent downstream signaling pathways. Parthenolide, an active ingredient of feverfew (Tanacetum parthenium), has been used for centuries to treat many chronic diseases. Parthenolide inhibits the MyD88-dependent pathway by inhibiting the activity of inhibitor-κB kinase. However, it is not known whether parthenolide inhibits the TRIF-dependent pathway. To evaluate the therapeutic potential of parthenolide, its effect on signal transduction via the TRIF-dependent pathway of TLRs induced by lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (poly [I:C]) was examined. Parthenolide inhibited nuclear factor-κB and interferon regulatory factor 3 activation induced by LPS or poly[I:C], and the LPS-induced phosphorylation of interferon regulatory factor 3 as well as interferon-inducible genes such as interferon inducible protein-10. These results suggest that parthenolide can modulate TRIF-dependent signaling pathways of TLRs, and may be the basis of effective therapeutics for chronic inflammatory diseases.

Suppression of the TRIF-dependent signaling pathway of toll-like receptors by 4-oxo-4-(2-oxo-oxazolidin-3-yl)-but-2-enoic acid ethyl ester

Toll-like receptors (TLRs) recognize molecular structures derived from microbes and initiate innate immunity. The stimulation of TLRs by microbial components triggers the activation of the myeloid differential factor 88 (MyD88)-dependent and toll-interleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent major downstream signaling pathways. Previously, we synthesized a fumaryl oxazolidinone derivative, 4-oxo-4-(2-oxo-oxazolidin-3-yl)-but-2-enoic acid ethyl ester (OSL07), and demonstrated that it inhibits activation of nuclear factor kappa B (NF-?B) by inhibiting the TLR MyD88-dependent pathway. However, the effect of OSL07 on the TRIFdependent pathway remained unknown. Here, we examined the effect of OSL07 on signal transduction via the TLR TRIF-dependent pathway. OSL07 inhibited lipopolysaccharide- or polyinosinic-polycytidylic acid-induced interferon regulatory factor 3 activation and phosphorylation as well as interferon-inducible genes such as interferon inducible protein-10. All the results suggest that OSL07 can modulate TRIF-dependent signaling pathway of TLRs leading to decreased inflammatory gene expression.

Isoliquiritigenin Suppresses the Toll−Interleukin-1 Receptor Domain-Containing Adapter Inducing Interferon-β (TRIF)-Dependent Signaling Pathway of Toll-Like Receptors by Targeting TBK1

Toll-like receptors (TLRs) play an important role in induction of innate immune responses. TLRs can trigger the activation of myeloid differential factor 88 (MyD88)- and Toll-interleukin-1 receptor domain-containing adapter inducing interferon-beta (TRIF)-dependent downstream signaling pathways. Expression of more than 70% of lipopolysaccharide (LPS)-induced target genes is mediated through a TRIF-dependent signaling pathway. To evaluate the therapeutic potential of isoliquiritigenin (ILG), we examined its effect on signal transduction via the TRIF-dependent pathway of TLRs. ILG inhibited interferon regulatory factor 3 activation induced by LPS or polyinosinic-polycytidylic acid, as well as interferon-inducible genes, such as interferon-inducible protein-10. ILG attenuated ligand-independent activation of IRF3 induced by TRIF or TBK1. Furthermore, ILG inhibited TBK1 kinase activity in vitro. Together, these results demonstrate that TBK1 is the molecular target of ILG, resulting in the downregulation of the TRIF-dependent signaling pathways of TLRs.

Suppression of TRIF-dependent signaling pathway of Toll-like receptors by oak wood vinegar in RAW264.7 macrophages

Toll-like receptors (TLRs) play an important role in initiating innate immune responses. The stimulation of TLRs by microbial components triggers the activation of two downstream signaling pathways: myeloid differential factor 88 (MyD88)- and toll-interleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent signaling pathways. Wood vinegar (WV), a byproduct from charcoal production, has been evaluated for its various biological activities including anti-oxidant, anti-bacterial, and anti-inflammatory activities. To evaluate the therapeutic potential of WV, we examined its effect on signal transduction via the TRIF-dependent pathway of TLRs induced by TLR3 and TLR4 agonists. Oak wood vinegar (OWV) inhibited nuclear factor-κB and interferon regulatory factor 3 activation induced by lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (poly [I: C]). OWV also inhibited LPS- or poly[I:C]-induced interferon inducible protein-10 (IP-10). These results suggest that OWV can modulate TRIF-dependent signaling pathway of TLRs for anti-viral, anti-bacterial, and anti-inflammatory activities.

Suppression of the TRIF-dependent signaling pathway of toll-like receptors by isoliquiritigenin in RAW264.7 macrophages.

Toll-like receptors (TLRs) play an important role in host defense by sensing invading microbial pathogens and initiating innate immune responses. The stimulation of TLRs by microbial components triggers the activation of myeloid differential factor 88 (MyD88)- and toll-interleukin-1 receptor domain-containing adapter inducing interferon-beta (TRIF)-dependent downstream signaling pathways. Isoliquiritigen in (ILG), an active ingredient of Licorice, has been used for centuries to treat many chronic diseases. ILG inhibits the MyD88-dependent pathway by inhibiting the activity of inhibitor-kappaB kinase. However, it is not known whether ILG inhibits the TRIF-dependent pathway. To evaluate the therapeutic potential of ILG, we examined its effect on signal transduction via the TRIF-dependent pathway of TLRs induced by several agonists. ILG inhibited nuclear factor-kappaB and interferon regulatory factor 3 activation induced by lipopolysaccharide or polyinosinic-polycytidylic acid. ILG inhibited the lipopolysaccharide-induced phosphorylation of interferon regulatory factor 3 as well as interferon-inducible genes such as interferon inducible protein-10, and regulated activation of normal T-cell expressed and secreted (RANTES). These results suggest that ILG can modulate TRIF-dependent signaling pathways of TLRs, leading to decreased inflammatory gene expression.

TBK1-targeted suppression of TRIF-dependent signaling pathway of Toll-like receptors by 6-shogaol, an active component of ginger.

Toll-like receptors (TLRs) are primary sensors that detect a wide variety of microbial components involving induction of innate immune responses. After recognition of microbial components, TLRs trigger the activation of myeloid differential factor 88 (MyD88) and Toll-interleukin-1 (IL-1) receptor domain-containing adapter inducing interferon-beta (TRIF)-dependent downstream signaling pathways. 6-Shoagol, an active ingredient of ginger, inhibits the MyD88-dependent signaling pathway by inhibiting inhibitor-kappaB kinase activity. Inhibitor-kappaB kinase is a key kinase in nuclear factor kappaB (NF-kappaB) activation. However, it is not known whether 6-shogaol inhibits the TRIF-dependent signaling pathway. Our goal was to identify the molecular target of 6-shogaol in the TRIF-dependent pathway of TLRs. 6-Shogaol inhibited the activation of interferon-regulatory factor 3 (IRF3) induced by lipopolysaccharide (LPS) and by polyriboinosinic polyribocytidylic acid (poly[I:C]), overexpression of TRIF, TANK-binding kinase1 (TBK1), and IRF3. Furthermore, 6-shogaol inhibited TBK1 activity in vitro. Together, these results suggest that 6-shogaol inhibits the TRIF-dependent signaling pathway of TLRs by targeting TBK1, and, they imply that 6-shogaol can modulate TLR-derived immune/inflammatory target gene expression induced by microbial infection.

Guggulsterone suppresses the activation of transcription factor IRF3 induced by TLR3 or TLR4 agonists

Toll-like receptors (TLRs) are vital in the induction of innate immune responses. The microbial components trigger the activation of the myeloid differential factor 88 (MyD88)- and toll-interleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent downstream TLR signaling pathways. Guggulsterone, which has been used for centuries to treat many chronic diseases, inhibits the MyD88-dependent pathway by inhibiting the activity of inhibitor-κB kinase. However, it is not known whether guggulsterone inhibits the TRIF-dependent pathway. Presently, we sought to identify the molecular targets of guggulsterone in this pathway. Guggulsterone inhibited nuclear factor-κB and IRF3 activation induced by lipopolysaccharide or poly[I:C] and activation of IRF3 induced by the overexpression of TRIF, TBK1 or constitutively active IRF3. Guggulsterone also suppressed the lipopolysaccharide-induced phosphorylation of IRF3. These results suggest that guggulsterone can modulate both MyD88- and TRIF-dependent signaling pathways of TLRs leading to decreased inflammatory gene expression.

Selenium suppresses the activation of transcription factor NF-κB and IRF3 induced by TLR3 or TLR4 agonists

Toll-like receptors (TLRs) play an important role in recognition of microbial components and induce innate immune responses by recognizing invading microbial pathogens leading to the activation of the adaptive immune responses. The microbial components trigger the activation of two downstream signaling pathways of TLRs; MyD88- and TRIF-dependent pathways leading to the expression of pro-inflammatory cytokines and type I interferons (IFNs). The MyD88- and TRIF-dependent pathways lead to the activation of NF-κB and IRF3 through the activation of IKK-β and TBK1, respectively. Selenium is an essential trace element nutrient possessing anticarcinogenic properties. Here, we attempted to identify the molecular targets of selenium in TLR signaling pathways. Selenium inhibited NF-κB activation induced by poly[I:C] (TLR3 agonist), LPS (TLR4 agonist) or overexpression of MyD88 or IKK-β which is the key kinase of MyD88-dependent signaling pathway. Selenium inhibited IRF3 activation induced by poly[I:C], LPS or the overexpression of TRIF or TBK1. Selenium also suppressed the expression of COX-2 and iNOS and the endogenous IFNβ mRNA induced by poly[I:C] or LPS. Therefore, our results suggest that selenium can modulate both MyD88- and TRIF-dependent signaling pathways of TLRs leading to decreased inflammatory gene expression.

Differential modulation of toll‐like receptor signaling pathways by selenium

Toll-like receptors (TLRs) play role in recognition of microbial components and induction of innate immunity. The microbial components activate signaling pathways of TLRs; MyD88- and TRIF-dependent pathways leading to activation of NF-κB and IRF3, respectively. Selenium is an essential trace element nutrient and is normal component of diets. Here, we attempted to identify the molecular targets of selenium in TLR signaling pathways. Selenium inhibited NF-κB activation induced by LPS, Poly[I:C] or overexpression of MyD88 or IKKβ because selenium was shown to inhibit the activity of IKKβ which is the key kinase in MyD88-dependent pathway of TLRs. However, it is not known whether selenium inhibits TRIF-dependent pathway. Selenium inhibited the activation of IFN regulatory factor 3 (IRF3) induced by LPS, poly[I:C], or the overexpression of TRIF or TBK1. These results suggest that selenium can modulate both MyD88- and TRIF-dependent signaling pathways of TLRs. Therefore, the results raise the possibility that selenium can modulate TLR-derived signaling and inflammatory target gene expression, and alter susceptibility to microbial infection and chronic inflammatory diseases.

Suppression of MyD88- and TRIF-dependent signaling pathways of toll-like receptor by (−)-epigallocatechin-3-gallate, a polyphenol component of green tea

Toll-like receptors (TLRs) play an important role in recognition of microbial components and induction of innate immunity. The microbial components trigger the activation of two downstream signaling pathways of TLRs; MyD88- and/or TRIF-dependent pathways leading to activation of NF-κB. (−)-Epigallocatechin-3-gallate (EGCG), a flavonoid found in green tea, is known to inhibit NF-κB activation induced by many pro-inflammatory stimuli. EGCG was shown to inhibit the activity of IKKβ which is the key kinase in the canonical pathway for NF-κB activation in MyD88-dependent pathway of TLRs. However, it is not known whether EGCG inhibits TRIF-dependent pathway through which more than 70% of lipopolysaccharide (LPS)-induced genes are regulated. Therefore, we attempted to identify the molecular target of EGCG in TRIF-dependent pathways of TLR3 and TLR4. EGCG inhibited the activation of IFN regulatory factor 3 (IRF3) induced by LPS, poly[I:C], or the overexpression of TRIF. The inhibition of IRF3 activation by EGCG was mediated through the suppression of the kinase activity of TBK1. However, EGCG did not inhibit activation of IRF3 induced by overexpression of constitutively active IRF3. These results suggest that the molecular target of EGCG is TBK1 in TRIF-dependent signaling pathways of TLR3 and TLR4. Therefore, our results suggest that green tea flavonoids can modulate both MyD88- and TRIF-dependent signaling pathways of TLRs and subsequent inflammatory target gene expression.