Shunji Sugawara

Muramyldipeptide and diaminopimelic acid‐containing desmuramylpeptides in combination with chemically synthesized Toll‐like receptor agonists synergistically induced production of interleukin‐8 in a NOD2‐ and NOD1‐dependent manner, respectively, in human monocytic cells in culture

Two types of synthetic peptidoglycan fragments, diaminopimelic acid (DAP)‐containing desmuramylpeptides (DMP) and muramyldipeptide (MDP), induced secretion of interleukin (IL)‐8 in a dose‐dependent manner in human monocytic THP‐1 cells, although high concentrations of compounds are required as compared with chemically synthesized Toll‐like receptor (TLR) agonists mimicking bacterial components: TLR2 agonistic lipopeptide (Pam3CSSNA), TLR4 agonistic lipid A (LA‐15‐PP) and TLR9 agonistic bacterial CpG DNA. We found marked synergistic IL‐8 secretion induced by MDP or DAP‐containing DMP in combination with synthetic TLR agonists in THP‐1 cells. Suppression of the mRNA expression of nucleotide‐binding oligomerization domain (NOD)1 and NOD2 by RNA interference specifically inhibited the synergistic IL‐8 secretion induced by DMP and MDP with these TLR agonists respectively. In accordance with the above results, enhanced IL‐8 mRNA expression and the activation of nuclear factor (NF)‐κB induced by MDP or DMP in combination with synthetic TLR agonists were markedly suppressed in NOD2‐ and NOD1‐silenced cells respectively. These findings indicated that NOD2 and NOD1 are specifically responsible for the synergistic effects of MDP and DMP with TLR agonists, and suggested that in host innate immune responses to invading bacteria, combinatory dual signalling through extracellular TLRs and intracellular NODs might lead to the synergistic activation of host cells.

Identification of IL-18 and Th17 Cells in Salivary Glands of Patients with Sjögren's Syndrome, and Amplification of IL-17-Mediated Secretion of Inflammatory Cytokines from Salivary Gland Cells by IL-18

IL-18 is a proinflammatory cytokine and plays an important pathogenic role in inflammatory and autoimmune disorders. IL-17 is also a proinflammatory cytokine and IL-17-secreting Th17 cells are involved in autoimmunity. However, the pathological roles of IL-18 and Th17 cells in Sjögren’s syndrome (SS) remain to be elucidated. This study showed that the expression of IL-18 was detected in acinar cells, intraducts, and CD68+ macrophages in salivary glands of SS patients, but not in those of healthy subjects or patients with chronic graft-vs-host disease, by immunohistochemistry, and immunoblot analysis revealed that 24-kDa precursor form of IL-18 (proIL-18) and 18-kDa mature IL-18 were detected in SS salivary glands. The majority of the infiltrating cells in the salivary glands of SS patients were CD4+ T cells, and CD8+ T cells were infiltrated to a lesser extent. The predominant expression of IL-17 was found in infiltrating CD4+ T cells, whereas a small number of infiltrating CD8+ T cells expressed IL-17. Human salivary gland HSY and acinar AZA3 cells constitutively expressed proIL-18 and caspase-1, and a calcium ionophore A23187 induced the secretion of IL-18 from the cells. HSY and AZA3 cells expressed IL-18R and IL-17R on the cell surface, and IL-18 amplified the secretion of IL-6 and IL-8 that were induced by low amounts of IL-17. Primary salivary gland cells from normal subjects partially confirmed these findings. These results suggest that IL-18 and Th17 cells detected in the salivary glands in SS patients are associated with the pathogenesis of SS in the salivary glands.

Neutrophil Serine Proteinases Activate Human Nonepithelial Cells to Produce Inflammatory Cytokines Through Protease-Activated Receptor 2

1. Figs. 1B and 2A: Total RNAwas extracted from different cells, and cDNAwas prepared and analyzed for the expression of SLPI and PARs and GAPDH by RT-PCR. However, the patterns of GAPDH in these figures and those in the figures of The Journal of Immunology, 2002, 169: 4594–4603 and in Fig. 2A of Clinical and Diagnostic Laboratory Immunology, 2003, 10: 286–292 are the same. 2. Fig. 2B: Two panels of the expression of PAR-2 with HLE and Cat G are the same.

Toll-like Receptors, NOD1, and NOD2 in Oral Epithelial Cells

Oral epithelium might be the first barrier against oral bacteria in periodontal tissue. We hypothesized that oral epithelium is endowed with innate immune receptors for bacterial components, which play roles in host defense against bacterial infection without being accompanied by excessive inflammatory responses. We found clear expression of Toll-like receptor (TLR)4 as well as TLR2, and strong expression of NOD1 and NOD2 in normal oral epithelial tissues by immunohistochemical analysis. We also showed that primary oral epithelial cells in culture expressed these molecules using PCR, flow cytometry, and immunostaining. In inflamed oral epithelium, cell-surface localizations of TLR2 and TLR4 were more clearly observed than in healthy tissue. Upon stimulation with synthetic ligands for these receptors, the expression of β-defensin 2 was markedly up-regulated. These findings indicate that these molecules in oral epithelial cells are functional receptors that induce antibacterial responses.

A simple method to eliminate the antigenicity of surface class I MHC molecules from the membrane of viable cells by acid treatment at pH 3

We describe here a simple, reproducible method which specifically eliminates the antigenicity of surface class I major histocompatibility complex (MHC) molecules by acid treatment at pH 3 from the membrane of viable cells. When fresh mononuclear cells (MNC) or established cultured cell lines were treated at 4 degrees C for 2 min with citric acid buffer at pH 3 containing 1% bovine serum albumin, the antigenicity of class I MHC molecules, but not those of class II MHC and the other non-MHC antigens, was eliminated from the surface membrane without significant cell death. This method was effective for both human and murine cells with various origins. Monoclonal and polyclonal antibodies were used to identify the expression of surface antigens in conjunction with immunofluorescence tests. The eliminated antigenicity of human class I MHC antigens (i.e., HLA-A,B,C) on MNC regenerated when cells were incubated in the medium at 37 degrees C for 10 h. The pretreatment of cells with emetine (10(-4) M), a protein synthesis inhibitor, was found to be effective in inhibiting this regeneration. The acid treatment method might be useful for future studies on the functional characterization of surface class I MHC antigens.

Chemically synthesized pathogen‐associated molecular patterns increase the expression of peptidoglycan recognition proteins via toll‐like receptors, NOD1 and NOD2 in human oral epithelial cells

Peptidoglycan recognition proteins (PGRPs), a novel family of pattern recognition molecules (PRMs) in innate immunity conserved from insects to mammals, recognize bacterial cell wall peptidoglycan (PGN) and are suggested to act as anti‐bacterial factors. In humans, four kinds of PGRPs (PGRP‐L, ‐Iα, ‐Iβ and ‐S) have been cloned and all four human PGRPs bind PGN. In this study, we examined the possible regulation of the expression of PGRPs in oral epithelial cells upon stimulation with chemically synthesized  pathogen‐associated  molecular patterns (PAMPs) in bacterial cell surface components: Escherichia coli‐type tryacyl lipopeptide (Pam3CSSNA), E. coli‐type lipid A (LA‐15‐PP), diaminopimelic acid containing desmuramyl peptide (γ‐ d‐glutamyl‐meso‐DAP; iE‐DAP), and muramyldipeptide (MDP). These synthetic PAMPs markedly upregulated the mRNA expression of the four PGRPs and cell surface expression of PGRP‐Iα and ‐Iβ, but did not induce either mRNA expression or secretion of inflammatory cytokines, in oral epithelial cells. Suppression of the expression of Toll‐like receptor (TLR)2, TLR4, nucleotide‐binding oligomerization domain (NOD)1 and NOD2 by RNA interference specifically inhibited the upregulation of PGRP mRNA expression induced by Pam3CSSNA, LA‐15‐PP, iE‐DAP and MDP respectively. These PAMPs definitely activated nuclear factor (NF)‐κB in the epithelial cells, and suppression of NF‐κB activation clearly prevented the induction of PGRP mRNA expression induced by these PAMPs in the cells. These findings suggested that bacterial PAMPs induced the expression of PGRPs, but not proinflammatory cytokines, in oral epithelial cells, and the PGRPs might be involved in host defence against bacterial invasion without accompanying inflammatory responses.

Proteolysis of human monocyte CD14 by cysteine proteinases (gingipains) from Porphyromonas gingivalis leading to lipopolysaccharide hyporesponsiveness.

Cysteine proteinases (gingipains) elaborated from Porphyromonas gingivalis exhibit enzymatic activities against a broad range of host proteins and are considered key virulence factors in the onset and development of adult periodontitis and host defense evasion. In this study, we examined the ability of arginine-specific gingipains (high molecular mass Arg-specific gingipain (HRGP) and Arg-specific gingipain 2) and lysine-specific gingipain (KGP) to cleave monocyte CD14, the main receptor for bacterial cell surface components such as LPS. Binding of anti-CD14 mAb MY4 to human monocytes was almost completely abolished by 0.3 μM HRGP and KGP treatments for 15 min, and 1 μM RGP2 for 30 min. In contrast, the expressions of Toll-like receptor 4, and CD18, CD54, CD59, and HLA-A, -B, -C on monocytes were slightly increased and decreased, respectively, by 0.3 μM HRGP and KGP. This down-regulation resulted from direct proteolysis, because 1) gingipains eliminated MY4 binding even to fixed monocytes, and 2) CD14 fragments were detected in the extracellular medium by immunoblot analysis. Human rCD14 was degraded by all three gingipains, which confirmed that CD14 was a substrate for gingipains. TNF-α production by monocytes after HRGP and KGP treatments was decreased at 1 ng/ml, but not at 20 μg/ml LPS, indicating that gingipains inhibited a CD14-dependent cell activation. These results suggest that gingipains preferentially cleave monocyte CD14, resulting in attenuation of the cellular recognition of bacteria, and as a consequence sustain chronic inflammation.

Lipopolysaccharide promotes and augments metal allergies in mice, dependent on innate immunity and histidine decarboxylase.

Background Few adequate murine models exist for metal allergies, it being especially difficult to induce Ni allergy in mice.

Variation in CD4+ T and CD8+ T lymphocyte subpopulations in bovine mammary gland secretions during lactating and non-lactating periods.

Mammary gland secretions (MGS) of dairy cows at different stages of lactation were studied by immunofluorescence cytometry for T lymphocyte subpopulations using monoclonal antibodies. During early and late lactation, the mean ratio of CD4+/CD8+ T lymphocytes in the MGS was 0.5 and 0.8, respectively. A large proportion of the CD8+ cells coexpressed the activation molecule, ACT2. These results indicate that CD8+ ACT2+ cells constituted the major phenotype in the T lymphocytes throughout lactation. In the mammary gland of cows in which drying off was induced, however, the proportion of CD8+ ACT2+ cells decreased, resulting in the increase of the CD4+/ CD8+ ratio in the MGS. At the late non-lactation stage, the ratio reached a maximal level of 2.5-4.0, which was similar to or higher than that found in the peripheral blood. This selective increase of CD4+/CD8+ cell ratio correlated with an increase in the concentrations of total cells in the MGS. This high CD4+/CD8+ cell ratio during the drying off stage rapidly decreased just before parturition, correlating with the decrease in concentrations of total cells in the MGS, reaching the lowest level at early lactation. The cells isolated at the non-lactation stage produced the cytokines IL-2 and IL-4 at a level much higher than those of cells isolated at lactation stages, and the increases were correlated with the CD4+ T lymphocyte proportions.

Enhancement by galactosamine of lipopolysaccharide(LPS)-induced tumour necrosis factor production and lethality: its suppression by LPS pretreatment

D‐Galactosamine (GalN) depletes UTP primarily in the liver, resulting in decreased RNA synthesis in hepatocytes. Co‐injection of GalN and lipopolysaccharide (LPS) into mice produces fulminant hepatitis with severe hepatic congestion, resulting in rapid death. Although the underlying mechanism is uncertain, GalN enhances the sensitivity to tumour necrosis factor (TNF). Administration of uridine (a precursor of UTP) prior injection of either LPS itself or interleukin‐1 (IL‐1) reduces the lethality of GalN+LPS. The present study focused on the effects of these agents on TNF production. Intraperitoneal injection of GalN+LPS into mice greatly elevated serum TNF. Although large doses of LPS alone also greatly elevated serum TNF, LPS itself induced neither hepatic congestion nor rapid death. Administration of a macrophage depletor, liposomes encapsulated with dichloromethylene bisphosphonate, reduced both the TNF production and mortality induced by GalN+LPS. Uridine, when injected 0.5 h after the injection of GalN+LPS, reduced the production of TNF. Prior injection of LPS, but not of IL‐1, also reduced this TNF production. Serum from LPS‐injected mice reduced the TNF production induced by GalN+LPS, but it was less effective at reducing the lethality. Its ability to reduce TNF production was abolished by heat‐treatment. We hypothesize that a factor inhibiting TNF production by macrophages is produced by hepatocytes in response to LPS. Possibly, production of this hepatocyte‐derived TNF‐down‐regulator (TNF‐DRh) may be: (i) inhibited by GalN, causing over‐production of TNF by macrophages and (ii) stimulated by LPS‐pretreatment (and restored by uridine), causing reduced TNF production.