Naringenin suppresses Toll-like receptor 2-mediated inflammatory responses through inhibition of receptor clustering on lipid rafts.

Toll-like receptors (TLRs) are important innate immune receptors that sometimes cause excessive inflammatory responses and a perpetuated inflammatory loop that can be involved in inflammatory and autoimmune diseases. TLR2 recognizes bacterial lipoproteins in association with TLR1 or TLR6, and triggers inflammatory responses through activation of the transcription factor NF-κB. Naringenin, a type of citrus flavonoid, has been shown to possess anti-inflammatory properties, but its detailed action against TLR2 remains to be fully elucidated.

Lipoprotein Extraction from Microbial Membrane and Lipoprotein/Lipopeptide Transfection into Mammalian Cells.

Microbial lipoproteins/lipopeptides are important virulence factors for periodontal diseases. The membrane lipoproteins from Mycoplasma salivarium or Tannerella forsythia can be easily extracted by exploiting a characteristic feature of Triton X-114: its aqueous nature at low temperatures (0-4 °C), which is absent at room temperature (25-37 °C). Transfection of these lipopeptides into macrophages was performed using the protein transfection reagent, PULSin.

Gasdermin D-independent release of interleukin-1β by living macrophages in response to mycoplasmal lipoproteins and lipopeptides.

Interleukin-1β (IL-1β) plays pivotal roles in controlling bacterial infections and is produced after the processing of pro-IL-1β by caspase-1, which is activated by the inflammasome. In addition, caspase-1 cleaves the cytosolic protein, gasdermin-D (GSDMD), whose N-terminal fragment subsequently forms a pore in the plasma membrane, leading to the pyroptic cell-death-mediated release of IL-1β. Living cells can also release IL-1β via GSDMD pores or other unconventional secretory pathways.

MyD88 signaling causes autoimmune sialadenitis through formation of high endothelial venules and upregulation of LTβ receptor-mediated signaling.

Autoimmune sialadenitis (AS), chronic inflammation of the salivary glands (SGs) with focal lymphocyte infiltration, appears in autoimmune diseases such as Sjӧgren's syndrome. The pathological role of MyD88-dependent innate immune signaling in autoimmune diseases including AS has been studied using mouse models, such as NOD mice. Although AS development in NOD mice was reported to be suppressed by Myd88 deficiency, its specific role remains unclear.

Differences in interleukin-1β release-inducing activity of Candida albicans toward dendritic cells and macrophages.

Objective: The purpose of this study is to elucidate differences in the mechanism of the IL-1β release-inducing activity of Candida albicans toward dendritic cells and macrophages because IL-1β is one of the proinflammatory cytokines which is crucial in host defense against candidiasis.

Design: Two C. albicans strains were used in this study.

Activation of nucleotide-binding domain-like receptor containing protein 3 inflammasome in dendritic cells and macrophages by Streptococcus sanguinis.

Streptococcus sanguinis is frequently isolated from the blood of patients with infective endocarditis and contributes to the pathology of this disease through induction of interleukin (IL)-1β responsible for the development of the disease. However, the mechanism of IL-1β induction remains unknown. In this study, S.

MyD88 deficiency alters expression of antimicrobial factors in mouse salivary glands.

The surfaces of oral mucosa are protected from infections by antimicrobial proteins and natural immunoglobulins that are constantly secreted in saliva, serving as principal innate immune defense in the oral cavity. MyD88 is an important adaptor protein for signal transduction downstream of Toll-like receptors and TACI, receptors for regulation of innate immunity and B cell responses, respectively. Although MyD88-mediated signaling has a regulatory role in the intestinal mucosal immunity, its specific role in the oral cavity has remained elusive.

Differences in recognition of wild-type and lipoprotein-deficient strains of oral Streptococci in vitro and in vivo.

Whole cells of wild-type strains of Streptococcus gordonii and Streptococcus mutans induced Toll-like receptor 2 (TLR2)-mediated nuclear factor-κB (NF-κB) activation, whereas those of lipoprotein (LP)-deficient strains did not. All strains upregulated the proliferation of TLR2(+/+) splenocytes more strongly than TLR2(-/-) splenocytes. However, significant differences were not observed between the cytokine-inducing activities of wild-type and LP-deficient strains toward TLR2(+/+) and TLR2(-/-) splenocytes.

Chlamydophila pneumoniae in human immortal Jurkat cells and primary lymphocytes uncontrolled by interferon-γ.

Lymphocytes are a potential host cell for Chlamydophila pneumoniae, although why the bacteria must hide in lymphocytes remains unknown. Meanwhile, interferon (IFN)-γ is a crucial factor for eliminating chlamydiae from infected cells through indoleamine 2,3-dioxygenase (IDO) expression, resulting in depletion of tryptophan. We therefore assessed if lymphocytes could work as a shelter for the bacteria to escape IFN-γ.

Regulation of Toll-like receptor signaling by NDP52-mediated selective autophagy is normally inactivated by A20.

Toll-like receptor (TLR) signaling is linked to autophagy that facilitates elimination of intracellular pathogens. However, it is largely unknown whether autophagy controls TLR signaling. Here, we report that poly(I:C) stimulation induces selective autophagic degradation of the TLR adaptor molecule TRIF and the signaling molecule TRAF6, which is revealed by gene silencing of the ubiquitin-editing enzyme A20.

In vivo anti- and pro-tumour activities of the TLR2 ligand FSL-1.

TLR ligands as Th1 inducers have been investigated as potential anti-tumour agents. However, few attempts have been made to investigate the anti-tumour activity of TLR ligands as Th2 inducers. This study, therefore, was carried out to determine whether the TLR2 ligand FSL-1 as a Th2 inducers affects the growth of a QRsP tumour, a fibrosarcoma derived from the C57BL/6 (TLR2(+/+)) mouse in vivo.

Radiation-induced cancer cell repopulation: a possible mechanism implied by experiments using transplantable mouse-derived sarcoma cell line.

Purpose: Treatment with any cytotoxic agent can trigger surviving cells in a tumor to divide faster than before. This phenomenon is widely recognized as "repopulation". To better clarify the mechanism, gene expression profiling and pathological experiments were performed.

Regulation of MyD88 aggregation and the MyD88-dependent signaling pathway by sequestosome 1 and histone deacetylase 6.

MyD88 is an essential adaptor molecule for Toll-like receptors (TLRs) and interleukin (IL)-1 receptor. MyD88 is thought to be present as condensed forms or aggregated structures in the cytoplasm, although the reason has not yet been clear. Here, we show that endogenous MyD88 is present as small speckle-like condensed structures, formation of which depends on MyD88 dimerization.

The Toll-like receptor 2 (TLR2) ligand FSL-1 is internalized via the clathrin-dependent endocytic pathway triggered by CD14 and CD36 but not by TLR2.

Little is known of how Toll-like receptor (TLR) ligands are processed after recognition by TLRs. This study was therefore designed to investigate how the TLR2 ligand FSL-1 is processed in macrophages after recognition by TLR2. FSL-1 was internalized into the murine macrophage cell line, RAW264.

A role of the Ca2+ binding site of DC-SIGN in the phagocytosis of E. coli.

HEK293 cells stably expressing DC-SIGN (293/DC-SIGN) were examined for phagocytosis of Escherichia coli. 293/DC-SIGN stable transfectants were able to mediate phagocytosis of E. coli.

Regulation of MyD88-dependent signaling events by S nitrosylation retards toll-like receptor signal transduction and initiation of acute-phase immune responses.

Nitric oxide (NO) has been thought to regulate the immune system through S nitrosylation of the transcriptional factor NF-kappaB. However, regulatory effects of NO on innate immune responses are unclear. Here, we report that NO has a capability to control Toll-like receptor-mediated signaling through S nitrosylation.

Resveratrol modulates phagocytosis of bacteria through an NF-kappaB-dependent gene program.

Many studies have shown that the pharmacological effects of resveratrol, a phytoalexin polyphenolic compound, include protective effects against cancer and inflammation as well as enhancement of stress resistance. In this study, we examined whether resveratrol affected the phagocytosis of bacteria by macrophages and the activation of the transcription factor NF-kappaB after stimulation with or without the ligand FSL-1 for Toll-like receptor 2 (TLR2). Phagocytosis of Escherichia coli and of Staphylococcus aureus by THP-1 cells and RAW264.

Synthesis and characterization of a dipalmitoylated lipopeptide derived from paralogous lipoproteins of Mycoplasma pneumoniae.

Genomic analysis of Mycoplasma pneumoniae revealed the existence of a large number of putative lipoprotein genes compared with the numbers in other bacteria. However, the pathogenic roles of M. pneumoniae lipoproteins are still obscure.

The diacylated lipopeptide FSL-1 enhances phagocytosis of bacteria by macrophages through a Toll-like receptor 2-mediated signalling pathway.

A significant amount of evidence has been accumulated to show that Toll-like receptors (TLRs) function as sensors for microbial invasion. However, little is known about how signalling triggered by TLRs leads to the phagocytosis of pathogens. This study was designed to determine whether stimulation of TLR2 mainly with the lipopeptide FSL-1 plays a role in the phagocytosis of pathogens by macrophages.

Pathogen recognition by Toll-like receptor 2 activates Weibel-Palade body exocytosis in human aortic endothelial cells.

The endothelial cell-specific granule Weibel-Palade body releases vasoactive substances capable of modulating vascular inflammation. Although innate recognition of pathogens by Toll-like receptors (TLRs) is thought to play a crucial role in promotion of inflammatory responses, the molecular basis for early-phase responses of endothelial cells to bacterial pathogens has not fully been understood. We here report that human aortic endothelial cells respond to bacterial lipoteichoic acid (LTA) and synthetic bacterial lipopeptides, but not lipopolysaccharide or peptidoglycan, to induce Weibel-Palade body exocytosis, accompanied by release or externalization of the storage components von Willebrand factor and P-selectin.

The diacylated lipopeptide FSL-1 induces TLR2-mediated Th2 responses.

The diacylated lipopeptide FSL-1 enhanced the generation of IgG antibodies in TLR2(+/+) mice, but not in TLR2(-/-) mice, when administered together with hen egg lysozyme as an antigen. Escherichia coli lipopolysaccharide enhanced the generation of antigen-specific antibodies in both TLR2(-/-) and TLR2(+/+) mice. In TLR2(+/+) mice, the level of enhancement due to FSL-1 was similar to that caused by lipopolysaccharide.