Sang-Il Ahn

Inhibition of homodimerization of toll-like receptor 4 by 6-shogaol

Toll-like receptors (TLRs) play a critical role in sensing microbial components and inducing innate immune and inflammatory responses by recognizing invading microbial pathogens. Lipopolysaccharide-induced dimerization of TLR4 is required for the activation of downstream signaling pathways including nuclear factor-kappa B (NF-κB). Therefore, TLR4 dimerization may be an early regulatory event in activating ligand-induced signaling pathways and induction of subsequent immune responses. Here, we report biochemical evidence that 6-shogaol, the most bioactive component of ginger, inhibits lipopolysaccharide-induced dimerization of TLR4 resulting in the inhibition of NF-κB activation and the expression of cyclooxygenase-2. Furthermore, we demonstrate that 6-shogaol can directly inhibit TLR-mediated signaling pathways at the receptor level. These results suggest that 6-shogaol can modulate TLR-mediated inflammatory responses, which may influence the risk of chronic inflammatory diseases.

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-beta (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-kappaB 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-kappaB 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.

Suppressive effects of 1-[4-fluoro-2-(2-nitrovinyl)phenyl]pyrrolidine on the Toll-like receptor signaling pathways.

When various pathogens invade a host, toll-like receptors (TLRs) play a significant role in recognizing the pathogen-associated molecular patterns carried by the pathogens to induce innate immune reaction, followed by acquired immunity reaction. 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. To evaluate the therapeutic potential of 1-[4-fluoro-2-(2-nitrovinyl)phenyl]pyrrolidine (FPP), previously synthesized in our laboratory, its effect on signal transduction via the TLR signaling pathways was examined. FPP inhibited the activation of nuclear factor-κB (NF-κB) and interferon regulatory factor 3 (IRF3) induced by TLR agonists, as well as inhibited the expression of cyclooxygenase-2, inducible nitric oxide synthase, and interferon inducible protein-10. FPP also inhibited the activation of NF-κB and IRF3 when induced by the overexpression of downstream signaling components of the TLRs. As a result, FPP has potential to become a new therapeutic drug for many inflammatory diseases.

Eupatorium makinoi suppresses toll-like receptor signaling pathways

ABSTRACT Toll-like receptors (TLRs) recognize microbial molecules that are widely presented by pathogens and initiate the innate immune system. TLR signaling is divided into two different signaling pathways, the myeloid differential factor 88 (MyD88)- and Toll/interleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent pathways. Eupatorium makinoi, a plant species in Asteraceae, is used for medicinal purposes in China, Korea, and Japan. Through our previous research, we found that an ethanol extract of E. makinoi (EEM) suppresses inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression. In this study, we investigated the effect of EEM on TLRs signaling pathways. EEM suppresses NF-κB activation and iNOS and COX-2 expressions induced by TLR2 or TLR4 agonists. Also, EEM suppresses the activation of interferon (IFNs) regulatory factor 3 (IRF3) induced by TLR3 or TLR4 agonists. All results indicate that EEM suppresses myeloid differentiation primary-response protein 88 (MyD88) and TRIF-dependent signaling pathways of TLRs and the expressions of target genes derived from the activation of TLRs GRAPHICAL ABSTRACT

Eupartoium makinoi suppresses lipopolysaccharide-induced inducible nitric oxide synthase and cyclooxygenase-2 expression

Inflammation is involved in numerous diseases including cancer. Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) play important roles in the development of certain inflammatory diseases. Eupatorium makinoi, which belongs to a family of Asteraceae plants, is used medicinally in East Asia. We investigated the effects of an ethanol extract of E. makinoi (EEM) on nuclear factor-kappa B (NF-κB) activation and the expression of iNOS and COX-2 with lipopolysaccharide (TLR4 agonist) in murine macrophages. EEM suppressed NF-κB activation and iNOS and COX-2 expression induced by LPS. These results suggest that EEM may regulate TLR4 signalling pathways and this may be a useful strategy for anti-inflammatory therapies.

Suppression of Toll‐Like Receptor 4 Dimerization by 1‐[5‐Methoxy‐2‐(2‐nitrovinyl)phenyl]pyrrolidine

Toll‐like receptor 4 (TLR4) recognizes lipopolysaccharide (LPS) and triggers the activation of myeloid differention factor 88 (MyD88) and the Toll/interleukin‐1 receptor domain‐containing adapter, inducing interferon‐β (TRIF)‐dependent major downstream signaling pathways. To evaluate the therapeutic potential of 1‐[5‐methoxy‐2‐(2‐nitrovinyl)phenyl]pyrrolidine (MNP), previously synthesized in our laboratory, its effect on signal transduction via the TLR signaling pathways was examined. Here, we investigated whether MNP modulates the TLR4 signaling pathways and which anti‐inflammatory target in TLR4 signaling is regulated by MNP. MNP inhibited the activation of nuclear factor‐κB (NF‐κB) induced by LPS (TLR4 agonist), and it also inhibited the expression of cyclooxygenase‐2 and inducible nitric oxide synthase. MNP inhibited LPS‐induced NF‐κB activation by targeting TLR4 dimerization in addition to IKKβ. These results suggest that MNP can modulate the TLR4 signaling pathway at the receptor level to decrease inflammatory gene expression.

Suppression of the TRIF-dependent signaling pathway of Toll-like receptor by CDr10b in RAW264.7 macrophages

Toll-like receptors (TLRs) recognize distinct pathogen-associated molecular patterns and play a critical role in innate immune responses. TLR signaling pathways can be largely classified as either myeloid differential factor 88 (MyD88)- or toll-interleukin-1 receptor domain-containing adapter inducing interferon-β (TRIF)-dependent pathways. Compound of Designation red 10 binding (CDr10b) was synthesized to investigate its role in neuroinflammatory diseases. This study was conducted to determine whether CDr10b can affect TLR signaling pathways. CDr10b suppressed NF-κB activation as well as COX-2 and iNOS expression induced by TLR3 or TLR4 agonists. CDr10b also suppressed the activation of interferon regulatory factor 3 (IRF3) and the expression of interferon inducible protein-10 (IP-10) induced by TLR3 or TLR4 agonists. These results indicate that CDr10b can modulate the TRIF-dependent pathway of TLRs and has the potential to become a new therapeutic drug for chronic inflammatory diseases.

Carpesium abrotanoides extract inhibits inducible nitric oxide synthase expression induced by toll-like receptor agonists

Inflammation is a pathological and physiological process which is known to be involved in numerous diseases, while it is notable that a considerable proportion of chronic inflammatory diseases overlap with the development of cancer. One of the most important proteins for inflammatory responses is inducible nitric oxide synthase (iNOS). The present study investigated the effect of the extract of Carpesium abrotanoides L. (ECA) on inflammation by modulating iNOS expression induced by toll-like receptors (TLRs) agonists in murine macrophages. ECA suppressed iNOS expression induced by lipopolysaccharide (TLR4 agonist), macrophage-activating lipopeptide 2-kDa (TLR2 and TLR6 agonist), and polyriboinosinic polyribocytidylic acid (TLR3 agonist). All the results suggest that ECA can modulate TLR signaling pathways and subsequent chronic inflammatory responses.

CDr10b inhibits the expression of cyclooxygenase-2 and inducible nitric oxide synthase induced by lipopolysaccharide

The pathophysiological processes of inflammation can lead to a host of diseases, such as periodontitis, atherosclerosis, rheumatoid arthritis, and even cancer. The dysregulated inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) activation play important roles in the development of certain inflammatory diseases. Here, we investigated the effects of CDr10b which is originally developed for a microglia staining probe on inflammation, by modulating NF-κB activation and iNOS and COX-2 expression induced by lipopolysaccharide (LPS) in murine macrophages. The CDr10b suppressed NF-κB activation and iNOS and COX-2 expression induced by LPS. All the results suggest that CDr10b is a promising novel agent for the treatment of inflammatory diseases.

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.