Se-Jeong Park

Suppression of homodimerization of toll-like receptor 4 by isoliquiritigenin.

Toll-like receptors (TLRs) play important inductive roles in innate immune responses for host defense against invading microbial pathogens. Activation of TLR4 by lipopolysaccharide (LPS) induces dimerization of TLR4 and, subsequently, activation of downstream signaling pathways including nuclear factor-kappa B and interferon regulatory factor 3. TLR4 dimerization may be an early regulatory event in activating signaling pathways induced by LPS. Here, biochemical evidence is reported that isoliquiritigenin, one of the major ingredients derived from licorice root, inhibits LPS-induced TLR4 dimerization resulting in inhibition of nuclear factor-kappa B and interferon regulatory factor 3 activation, and cyclooxygenase-2 and inducible nitric oxide synthase expression. These results suggest that isoliquiritigenin modulates TLR-mediated signaling pathways at the receptor level. Furthermore, these results suggest that TLRs themselves may be important targets for the prevention of chronic inflammatory diseases.

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-β (TRIF)-dependent downstream signaling pathways. 6-Shoagol, an active ingredient of ginger, inhibits the MyD88-dependent signaling pathway by inhibiting inhibitor-κB kinase activity. Inhibitor-κB kinase is a key kinase in nuclear factor κB (NF-κB) 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.

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.

Costunolide inhibits cyclooxygenase-2 expression induced by toll-like receptor 3 or 4 agonist

Toll-like receptors (TLRs) play an important role in the induction of innate immune responses recognizing conserved microbial structural molecules. The microbial pathogens trigger the activation of two downstream signaling pathways of TLRs; myeloid differential factor 88 (MyD88)- and toll interleukin-1 receptor domain containing adapter inducing interferon-β (TRIF)-dependent pathways leading to the activation of nuclear factor-κB (NF-κB) and interferon regulatory factor 3 (IRF3). Saussureae Radix has been used for centuries to treat a variety of diseases. Costunolide, one of the active ingredients in Saussureae Radix, has been used to treat many chronic diseases. However, the mechanism of costunolide’s beneficial effects is largely unknown. Here, we report biochemical evidence that costunolide inhibits NF-κB activation and cyclooxygenase-2 expression induced by the TLR3 agonist polyriboinosinic polyribocytidylic acid (poly[I : C]) or the TLR4 agonist lipopolysaccharide (LPS). These results suggest that costunolide can modulate the immune responses regulated by TLR signaling pathways.

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-β (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-κB 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-κB 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.

Phenethyl isothiocyanate regulates inflammation through suppression of the TRIF-dependent signaling pathway of Toll-like receptors.

AIMS The aim of this study was to evaluate the therapeutic potential of the phenethyl isothiocyanate (PEITC) in Toll-like receptor (TLR) signaling pathways. MAIN METHODS To evaluate the cytotoxic nature of PEITC in RAW 264.7 cells, cytotoxicity was determined using the MTS cell viability assay. RAW264.7 cells were transfected with a nuclear factor-κB (NF-κB), interferon β (IFNβ) PRDIII-I, or interferon inducible protein-10 (IP-10) luciferase plasmid and then luciferase enzyme activities were determined by luciferase assay. The expression of inducible nitric oxide synthase (iNOS) and phosphorylation of interferon regulatory factor 3 (IRF3) were determined by Western blotting. The levels of IP-10 were determined with culture medium by using an IP-10 enzyme-linked immunosorbent assay (ELISA) kit. KEY FINDINGS PEITC suppressed the activation of IRF3 and the expression of IP-10 induced by lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (poly[I:C]). SIGNIFICANCE TLRs play an important role in the induction of innate immune responses for host defense against invading microbial pathogens. PEITC found in cruciferous vegetables has an effect on treatment of many chronic diseases. Our results suggest that beneficial effects of PEITC on chronic inflammatory diseases are mediated through modulation of Toll-interleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent signaling pathway of TLRs.

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.

TBK1-targeted suppression of TRIF-dependent signaling pathway of toll-like receptor 3 by auranofin

Toll-like receptors (TLRs) play an important role in induction of innate immune responses. The stimulation of TLRs by microbial components triggers two branches of downstream signaling pathways: myeloid differential factor 88 (MyD88)- and toll-interleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent signaling pathways. Auranofin, a sulfur-containing gold compound (Au[I]), has been widely used for the treatment of rheumatoid arthritis. Since dysregulation of TLRs can lead to severe systemic inflammatory and joint destructive process in rheumatoid arthritis, auranofin-mediated modulation of TLR activation may have therapeutic potential against such diseases. Previously, we demonstrated that auranofin suppressed TLR4 signaling pathway by inhibiting TLR4 dimerization induced by LPS. Here, we examined the effect of auranofin on signal transduction via the TRIF-dependent pathway induced by a TLR3 agonist. Auranofin inhibited nuclear factor-κB and interferon (IFN) regulatory factor 3 (IRF3) activation induced by polyinosinic-polycytidylic acid (poly[I:C]). Auranofin inhibited poly[I:C]-induced phosphorylation of IRF3 as well as IFN-inducible genes such as IFN inducible protein-10. Furthermore, auranofin inhibited TBK1 kinase activity in vitro. All the results suggest that auranofin suppress TLR signaling at multiple steps.

Inhibition of homodimerization of toll-like receptor 4 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 TLR4 by lipopolysaccharide (LPS) 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-κB) by inhibiting the MyD88-dependent pathway of TLRs. TLR4 and the downstream signaling components are good therapeutic targets for many chronic inflammatory diseases. Here, it is investigated whether OSL07 modulates TLR4 downstream signaling pathways and what anti-inflammatory target in TLR4 signaling is regulated by OSL07. OSL07 inhibited LPS-induced NF-κB and interferon regulatory factor 3 activation by targeting TLR4 dimerization. These results suggest that OSL07 can modulate TLR4 signaling pathway leading to decreased inflammatory gene expression.

Suppression of Toll-like receptor 2 or 4 agonist-induced cyclooxygenase-2 expression 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 including bacteria, viruses, yeast, and fungi, and regulate the activation of innate immunity. All TLR signaling pathways culminate in the activation of nuclear factor-kappaB (NF-kappaB) transcription factor leading to the induction of inflammatory gene products including cytokines and cyclooxygenase-2 (COX-2). In the present report, we demonstrate biochemical evidence that the fumaryl oxazolidinone derivative 4-Oxo-4-(2-oxo-oxazolidin-3-yl)-but-2-enoic acid ethyl ester (OSL07), which was previously synthesized in our laboratory, inhibits the NF-kappaB activation induced by TLR agonists and overexpression of downstream signaling components of TLRs, MyD88 and IKKbeta. OSL07 also inhibits TLR agonist-induced COX-2 expression. These results indicate that the anti-inflammatory effects of OSL07 are caused by the modulation of the immune responses regulated by TLR signaling pathways.